JP2002006697A - Tandem type full-color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tandem type full-color image forming device which is effectively suppressed from the deterioration of photoreceptor drums by discharge products by blowing air to the surfaces of the respective photoreceptor drums by using a common blast fan. SOLUTION: The tandem type full-color image forming device which is arranged with the plural photoreceptor drums 5 in juxtaposition on a transfer belt for transporting transfer paper and is arranged with corona chargers 7 for main electrostatic charge and developing devices packed with toners varying in colors from each other respectively around these photoreceptor drums is provided with a blast mechanism consisting of a main duct pipe 21 for storing the air from the blast fan 25 and plural branch duct pipes 22 communicating with this main duct pipe 21. The branch duct pipes respectively extend along the respective corona chargers 7 for main electrostatic charge and the air is blown onto the surfaces of the photoreceptor drums facing the respective corona charger for the main electrostatic charge by these branch duct pipes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a full-color image forming apparatus for forming a full-color image by an electrophotographic method, and more particularly, to a full-color image forming apparatus having a plurality of transfer belts for transferring transfer paper to a transfer area. The present invention relates to a tandem-type full-color image forming apparatus in which photosensitive drums are juxtaposed, and forms an image for each color on each photosensitive drum.

[0002]

2. Description of the Related Art At present, as an apparatus for forming an image by electrophotography such as a copying machine, a facsimile, a printer, etc., a color image forming apparatus capable of forming a full-color image as well as a monochrome image is commercially available. As such a color image forming apparatus, a tandem type full color image forming apparatus having a structure in which a plurality of photosensitive drums are arranged on a transfer belt for conveying a transfer sheet to a transfer area is known. The tandem type full-color image forming apparatus forms an image of each color for each photosensitive drum on a transfer belt, and forms a full-color image by transferring and superimposing these images on transfer paper conveyed by the transfer belt. It is to do.

[0003] Image formation on each photosensitive drum is performed by uniformly charging (main charging) the surface of the photosensitive drum to a predetermined polarity and irradiating the charged photosensitive drum surface with light to perform image exposure. An electrostatic latent image formed by light attenuation due to image exposure is developed with toner of each color filled in a developing device, and a toner image formed on a photosensitive drum is transferred by being conveyed on a transfer belt. This is done by transferring to paper.

In the above-described image formation, as a charging device for performing main charging, a corona charger and a roller-shaped contact charger are known. The corona charger charges the surface of the photosensitive drum by corona discharge. Discharge products such as ozone and NOx are generated, and these discharge products cause the photosensitive layer provided on the surface of the photosensitive drum to be charged. Is deteriorated. In order to avoid such a problem, a method is generally adopted in which discharge products are blown off by blowing air onto the surface of the photosensitive drum to prevent the discharge products from adhering to the surface of the photosensitive drum. I have. However, in a tandem-type full-color image forming apparatus, a plurality of photosensitive drums are provided, and image formation for each color is performed for each photosensitive drum.
In order to prevent the deterioration of the photosensitive drum due to discharge products by blowing air as described above, it is necessary to provide an air blowing mechanism for each of the plurality of photosensitive drums. Must be provided, resulting in an increase in the size of the apparatus and an increase in cost.
Therefore, in recent tandem-type full-color image forming apparatuses, a contact charger is often used as a main charger.

[0005]

However, the contact charger is a device that charges the surface of the photosensitive drum by bringing a conductive roller into contact with the photosensitive drum and applying a charging voltage having a predetermined polarity to the roller. Although it has an advantage that almost no discharge products such as ozone and NOx are generated, it has a problem that its life is short because it comes into contact with the photosensitive drum. Therefore, it is more advantageous to use a corona charger in terms of device life.

Accordingly, an object of the present invention is to provide a tandem type full-color image forming apparatus of the type in which an image is formed by main charging by a corona charger, in which the deterioration of a photosensitive drum due to a discharge product is effectively suppressed. To provide. Another object of the present invention is to provide a tandem type full-color image forming apparatus in which deterioration of a photosensitive drum due to a discharge product is effectively suppressed by blowing air to the surface of each photosensitive drum using a common blowing fan. Is to provide.

[0007]

According to the present invention, a plurality of photosensitive drums are juxtaposed on a transfer belt for transporting transfer paper, and a corona charger for main charging and a corona charger for main charging are provided around each photosensitive drum. In a tandem type full-color image forming apparatus in which developing units filled with toners of different colors are arranged, a main duct pipe for storing air from a blowing fan and a plurality of branch duct pipes communicating with the main duct pipe. And each of the branch duct pipes extends along each main charging corona charger, and the branch duct pipe causes the photosensitive drum surface facing each main charging corona charger. A tandem-type full-color image forming apparatus characterized in that air is blown thereon.

In the present invention, the main duct pipe connected to the blower fan is provided with a number of branch duct pipes corresponding to the number of photosensitive drums arranged on the transfer belt. Then, air is blown from the branch duct tube to the surface of each photosensitive drum. Therefore, 1
The air blower blows air to all the photoconductor drum surfaces, thereby effectively blowing off the discharge products generated by corona charging by the corona charger, and the photoconductors by the discharge products. The deterioration of the drum is effectively prevented. That is, according to the present invention, since a blowing fan is not provided for each photosensitive drum and air is blown to all the surfaces of the photosensitive drums by using one blowing fan, the apparatus is increased in size and cost is increased. Can be effectively avoided.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to specific examples shown in the accompanying drawings. FIG. 1 is a schematic side sectional view of a tandem-type full-color image forming apparatus of the present invention.
FIG. 2 is a diagram showing a planar structure of an air blowing device used in the image forming apparatus shown in FIG.

FIG. 1 shows a schematic structure of a tandem-type full-color image forming apparatus of the present invention. The apparatus includes a transfer belt 1 stretched between a pair of rollers. Transfer paper 2 filled in paper cassette
Are conveyed in the direction of the arrow in the figure and are discharged to a paper discharge cassette. On the transfer belt 1, a monochrome image forming area B, a cyan (blue) image forming area C, a magenta (red) image forming area M, and a yellow (yellow) image forming area Y are provided in this order from the right. In addition, a photosensitive drum 5 is arranged in each image forming area, and a transfer roller 6 is arranged below the transfer belt 1 so as to face each photosensitive drum. (Note that the arrangement order of the image forming areas is not particularly limited, and this arrangement can be appropriately changed.)

In each image forming area, around the photosensitive drum 5, a corona charger 7, an optical system 8 for image exposure, and a developing device specific to each image forming area are arranged in this order. I have. That is, in the monochrome image forming region B, the monochrome developing device 9B filled with black toner, in the cyan image forming region C, the cyan developing device 9C filled with cyan toner, and in the magenta image forming region M, magenta toner is filled. In the magenta developing device 9M and the yellow image forming area Y, a yellow developing device 9Y filled with yellow toner is provided. Further, although not shown, a static eliminator (not shown) and a cleaning device 1 are provided between the area where the transfer roller 6 is provided and the main charger 7.
0 is arranged.

The image forming cycle in each image forming area is
A description will be given taking the monochrome image forming area B as an example. First,
Main charging is performed by corona discharge by the corona charger 7, whereby the photosensitive drum 5 is uniformly charged to a predetermined polarity. Next, image exposure is performed by light irradiation from an optical system 7 such as an LED, and an electrostatic latent image is formed on the surface of the photosensitive drum 5. This electrostatic latent image is developed by the monochrome developing device 9B filled with black toner, and a toner image is formed on the surface of the photosensitive drum 5. The charge polarity of this toner image is the same as the charge polarity of the photosensitive drum 5 charged by the main charger 7 when developing by so-called reversal development, and when developing by so-called regular development. ,
The polarity is opposite to the charging polarity of the photosensitive drum 5. The toner image formed on the surface of the photosensitive drum 5 in this manner is transferred onto the transfer paper 2 conveyed on the transfer belt 1 in an area (transfer area) facing the transfer roller 6. This transfer is performed by applying a bias voltage having a polarity opposite to that of the toner image to the transfer roller 6. Further, instead of using the transfer roller 6, transfer can be performed by charging the back surface of the transfer paper 2 to a polarity opposite to that of the toner image using a corona charger. After the transfer is completed, the static eliminator and cleaning device 10 (not shown) removes the charge of the photosensitive drum 5 and cleans the toner remaining on the surface of the drum 5, and the next image forming cycle is performed.

As described above, in the monochrome image forming area B, a monochrome image composed of black toner is formed on the transfer paper 2, and similarly, in the cyan image forming area C, the cyan toner is formed on the transfer paper 2. In the magenta image forming region M, a red image formed of magenta toner is formed, and in the yellow image forming region Y, a yellow image formed of yellow toner is formed. That is, when forming a monochrome image, the above-described image forming cycle is executed only in the monochrome image forming area B, and a monochrome image is formed on the transfer paper 2. When a full-color image is formed, the above-described image forming cycle is executed in each of the image forming areas B, C, M, and Y.
The toner images of the respective colors are superimposed to form a full-color image on the transfer paper 2. The transfer paper 2 on which the above-described image is formed is discharged from the transfer belt 1 and introduced into the fixing device 11, where the image is fixed and discharged.

In the present invention, the tandem type full-color image forming apparatus having the above-described structure is provided with an air blowing device 2.
0 is provided, and air is blown onto the surface of the photosensitive drum 5 by the air blowing device 20, and a discharge product (eg, ozone, NOx, etc.) generated by corona discharge by the corona charger 7 is exposed. The photoconductor drum 5 is blown off from the surface of the body drum 5, and the deterioration of the photoconductor drum 5 due to these discharge products is effectively prevented.

FIG. 2 shows a schematic structure of the air blowing device 20.
And four branch duct pipes 2 connected to the main duct pipe 21
It consists of two. The main duct pipe 21 is a fan 2
5, and air from the blower fan 25 is blown into the pipe. This main duct pipe 2
As shown in FIG. 1, reference numeral 1 extends along the respective ends of the photosensitive drum 5 arranged on the transfer belt 1 over the entire area where the photosensitive drum 5 is provided.

Further, the branch duct pipe 22 is connected to the main duct pipe 2.
1 and communicates with the inner space of the main duct pipe 21. That is, the air blown into the main duct pipe 21 by the blower fan 25 is blown to each of the branch duct pipes 22. As shown in FIG. 1, the branch duct tubes 22 are provided along the upper surface of the corona charger 7 provided around each of the photosensitive drums 5, respectively. On the lower surface, openings 30 for blowing air are provided at regular intervals.

The corona charger 7 includes a corona wire 7
a has a structure stretched inside the shield wall 7b,
A discharge opening 7c is formed on the lower surface of the shield wall 7b, and a corona wire 7a is formed through the discharge opening 7c.
The main charging of the photosensitive drum 5 is performed by the corona discharge from the main body. According to the image forming apparatus of the present invention having the structure shown in FIG. 1, an opening 7d for introducing air is provided on the upper surface of the shield wall 7b.
Is formed, and the air from the branch duct pipe 22 is
The toner is introduced into the corona charger 7 through the opening 7d, and is sprayed on the surface of the photosensitive drum 5 through the discharge opening 7c. With such a structure, accumulation of discharge products such as ozone and NOx in the corona charger 7 is effectively prevented, and deterioration of the surface of the photosensitive drum 5 due to these discharge products is effectively prevented. It becomes possible.

In the present invention, the branch duct pipe 2
2 may not be disposed above the corona charger 7 but may be disposed upstream of the corona charger 7 in the rotation direction of the photosensitive drum 5. However, since various devices are arranged around the photoconductor drum 5, it is preferable to arrange the branch duct tube 22 above the corona charger 7 as shown in FIG. It is. It is also preferable to arrange the branch duct tube 22 above the corona charger 7 from the viewpoint of preventing the accumulation of discharge products in the corona charger 7. Further, fins or the like may be provided on the lower surface of the branch duct tube 22 in order to efficiently blow the air from the branch duct tube 22 onto the surface of the photosensitive drum 5. Further, in the present invention, it is preferable to increase the degree of sealing of the main duct pipe 21 and to make the main duct pipe 21 have such a shape that its cross-sectional area is equal throughout the longitudinal direction. By adopting such a shape, uniform air can be blown to all of the plurality of branch duct pipes 22 connected to the main duct pipe 21 at different positions.

[0019]

As described above, according to the present invention, air can be uniformly blown to each of the surfaces of a plurality of photosensitive drums by using one blower fan, and is generated by corona discharge by a corona charger. The deterioration of the photosensitive drum surface due to the discharge products can be effectively reduced. Further, in the present invention, it is not necessary to provide a blowing fan for each photosensitive drum, so that it is possible to effectively avoid an increase in size and cost of the apparatus.

[Brief description of the drawings]

FIG. 1 is a view showing a schematic structure of a tandem type full-color image forming apparatus of the present invention.

FIG. 2 is a diagram showing a planar structure of an air blowing device used in the image forming apparatus shown in FIG.

[Explanation of symbols]

 5: Photoreceptor drum 7: Corona charger 20: Air blowing device 21: Main duct tube 22: Branch duct tube 25: Ventilation fan

Claims (3)

[Claims] A plurality of photosensitive drums are arranged side by side on a transfer belt that conveys transfer paper.
In a tandem type full-color image forming apparatus in which a corona charger for main charging and a developing unit filled with toners of different colors are arranged, a main duct pipe for storing air from a blowing fan and a main duct pipe are connected. A plurality of branch duct pipes, and each of the branch duct pipes extends along each of the main charging corona chargers. A tandem-type full-color image forming apparatus wherein air is blown onto a photosensitive drum surface facing a container. 2. A photosensitive drum having a developing unit filled with black toner arranged around the photosensitive drum, a photosensitive drum having a yellow developing unit filled with yellow toner arranged around the photosensitive drum, and a magenta toner. And a photoreceptor drum around which a magenta developing device filled with C is filled, and a photoreceptor drum around which a cyan developing device filled with cyan toner is arranged, are arranged on a transfer belt.
5. A tandem-type full-color image forming apparatus according to item 1. 3. Each of the branch duct pipes is disposed above each charger, and air from the branch duct pipe is blown onto each photoreceptor drum surface through each corona charger. Item 2. A tandem-type full-color image forming apparatus according to Item 1.