KR100542350B1 - Color image forming apparatus - Google Patents

Abstract

A color image forming apparatus is provided. The color image forming apparatus includes a photosensitive member provided to form an electrostatic latent image corresponding to image information input from the outside, a developing unit provided to supply a predetermined developer to the photosensitive member to visualize the electrostatic latent image, and a visible image from the photosensitive member. The transfer belt provided to form an image by overlapping the resultant, the paper transfer roller provided to transfer the image on the transfer belt to the paper, and the paper transfer roller in the process of driving the transfer belt and transferring the image to the paper. And a paper transfer backup roller provided to give each other, wherein the paper transfer roller and the paper transfer backup roller are arranged at a predetermined angle to each other.

Image Forming Device

Description

Color image forming apparatus

1 is a configuration diagram schematically showing the main part of the color conversion apparatus to which the present invention is applied;

2 is an enlarged view of a portion A of FIG. 1;

3 is a view of the two rollers shown in FIG.

4 and 5 are diagrams showing a state where the paper passes between the two rollers shown in FIG.

<Description of the symbols for the main parts of the drawings>

40: first photosensitive member 42: second photosensitive member

44: third photosensitive member 46: fourth photosensitive member

50: first cleaning blade 52: second cleaning blade

54: third cleaning blade 56: fourth cleaning blade

60: first developing unit 62: second developing unit

64: third development unit 66: fourth development unit

70: transfer belt 72: paper transfer backup roller

74: driver roller 76: paper transfer roller

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus. More particularly, an image is printed on a paper using a paper roll roller, a paper back up roller, and a transfer belt interposed between two rollers. A color image forming apparatus of an electrostatic pressure transfer method for transferring.

In general, a color image forming apparatus refers to a device that transfers an image signal in the form of a visible image on a paper, which is a print medium, according to a digital signal input from a computer or a scanner. This includes color laser printers, color digital copiers, and multifunction devices.

Such a color image forming apparatus supplies a photosensitive member on which a predetermined electrostatic latent image is formed, and a developer of various colors such as yellow, magenta, cyan, and black on the photosensitive member. A developing unit for visualizing a latent image, a transfer belt for sequentially superimposing images of various colors developed on the photosensitive body in contact with the photosensitive member, a belt transfer roller for transferring the image developed on the photosensitive member to the transfer belt; A paper transfer roller which transfers images superimposed on the transfer belt to various colors on the paper, a paper transfer roller which supports the paper transfer roller so that the paper transfer roller can press the paper at a predetermined pressure, and a paper transfer backup roller. Do not use a voltage supply power supply for generating a predetermined electrostatic force on the paper, and a fixing unit for permanently fixing an image already transferred onto the paper by heating and pressing the paper. This will print the desired image on the paper.

That is, the conventional color image forming apparatus sequentially superimposes the image developed on the photosensitive member on the photosensitive member by using a belt transfer roller, and then forms between the paper transfer roller and the paper transfer backup roller abutting on both sides of the transfer belt ( Hereinafter, an image forming operation is performed by passing the paper through a 'transfer nip portion'. The image superimposed on the transfer belt is transferred to the paper passing through the transfer nip as it is due to the pressure between the paper transfer roller and the transfer belt and the electrostatic force generated in the paper transfer backup roller.

On the other hand, the force applied to the entire area where the paper transfer roller and the transfer belt are in contact is relatively weakly applied at about 3 kgf. Therefore, the transfer of the image superimposed on the transfer belt to the paper can be regarded as the transfer of the electrostatic force generated in the paper transfer backup roller rather than the transfer caused by the pressure generated by such a force. Therefore, in the case of a dry color image forming apparatus using a dry developer, the efficiency of transferring images superimposed on the transfer belt to a paper is sufficient because the amount of toner jumped by the electrostatic force is hereinafter referred to as 'transfer efficiency'. Will appear relatively high. However, in the case of the wet color image forming apparatus using the wet developer, the transfer efficiency of the image is relatively low as about 80% because the amount of toner jumped by the electrostatic force is very low.

Therefore, the following two methods are used to increase the transfer efficiency as described above. First, the applicant filed with Korean Patent No. 10-2002-0007027 in order to supply a larger amount of the wet developer to compensate for the lack of the toner to be jumped, or to improve the adhesion between the paper transfer roller and the transfer belt. As described above, a large force of about 40 kgf or more is applied to the total area where the paper transfer roller and the transfer belt contact each other.

However, when more of the wet developer is supplied, the replacement cycle of the wet developer is very short, and a lot of costs are used.

In addition, when a large force of about 40kgf or more is applied to the entire area where the paper transfer roller and the transfer belt contact each other, the transfer efficiency can be substantially increased even though a small amount of developer is used. When a sheet enters or the paper is discharged from the transfer nip, a banding problem occurs in which a thick band-shaped image is further formed on the paper. That is, when a large force of about 40 kgf or more is applied to the entire area where the paper transfer roller and the transfer belt are in contact with each other, the speed of the paper passing through the transfer nip becomes the leading edge of the paper when entering or exiting the transfer nip. The phenomenon of instantaneous change due to the thickness is generated. In this case, a problem arises in that the paper is further formed with a thick band-shaped image due to the impact at this time.

Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide a color image forming apparatus which improves the roller angle of the transfer nip to minimize the impact generated when the paper passes through the transfer nip. have.

The color image forming apparatus of the present invention for achieving the above object is provided with a photosensitive member provided to form an electrostatic latent image corresponding to image information input from the outside, and to supply a predetermined developer to the photosensitive member to visualize the electrostatic latent image. A developing unit, a transfer belt provided to form an image by superimposing and transferring the result visualized from the photosensitive member, a paper transfer roller provided to transfer an image on the transfer belt to paper, and a transfer belt driven to transfer an image onto paper. And a paper transfer backup roller provided to support the paper transfer roller in the process, wherein the paper transfer roller and the paper transfer backup roller are arranged at a predetermined angle to each other.

Here, it is preferable that the center point of the paper transfer roller and the center point of the paper transfer backup roller cross each other.

The shifted angle between the paper transfer roller and the paper transfer backup roller is preferably 3 ° to 7 °.

Hereinafter, a preferred embodiment of the color image forming apparatus according to the present invention will be described in detail with reference to FIGS. 1 to 5.

 As shown in the drawing, the color image forming apparatus according to the present invention has a plurality of electrostatic latent images each formed according to the color configuration of the original image corresponding to predetermined image information (hereinafter, referred to as "original") input from the outside. A photosensitive member portion 55 including photosensitive members 40, 42, 44, and 46, a developing unit portion 65 for developing such electrostatic latent images, and a developed result superimposed from the photosensitive member portion 55, i. The transfer part 90 which transfers a color image to the sheet | seat 50 is provided.

The photosensitive member portion 55 is provided with the first to fourth photosensitive members 40, 42, 44, 46 spaced apart from each other at appropriate intervals, and the photosensitive members 40 are disposed around the photosensitive members 40, 42, 44, 46. Charging of the first to fourth cleaning blades 50, 52, 54, 56 and the photosensitive members 40, 42, 44, 46 to clean the surfaces of the 42, 44, 46. An antistatic device (not shown) to neutralize the state, a charging device (not shown) to charge the surface of the neutralized photoconductors 40, 42, 44, 46 prior to forming the electrostatic latent image, and the charged photosensitive members 40, 42, 44, 46) includes an optical scanning unit (not shown) for scanning light onto a surface to form a predetermined electrostatic latent image. Here, the first to fourth photosensitive members 40, 42, 44, and 46 are all photosensitive drums, and the black photosensitive member 40 in which an electrostatic latent image corresponding to the black image is formed in the color image of the original, respectively, is formed. A magenta photosensitive member 42 having an electrostatic latent image corresponding to the magenta image, a yellow photosensitive member 44 having an electrostatic latent image corresponding to the yellow image, and a cyan photosensitive member having an electrostatic latent image corresponding to the cyan image (46).

The developing unit 65 is provided below the photosensitive member 55 and includes first to fourth developing units 60, 62 that correspond one-to-one with the first to fourth photosensitive members 40, 42, 44, and 46. And 64, 66, and a development cartridge (not shown) for supplying a predetermined developer to these developing units 60, 62, 64, 66. In this case, the first to fourth developing units 60, 62, 64, and 66 are first to fourth developing rollers provided to contact the first to fourth photosensitive members 40, 42, 44, and 46, respectively. Color developers necessary for developing a predetermined electrostatic latent image on the first to fourth photosensitive bodies 40, 42, 44, and 46 through 60a, 62a, 64a, and 66a, that is, black ink (Ink), magenta ink, and yellow ink. And cyan ink. Accordingly, the electrostatic latent images formed on the first to fourth photosensitive members 40, 42, 44, and 46 are developed and visualized by these color developers.

The transfer unit 90 is configured to circulate on a closed loop and contacts the first to fourth photoconductors 40, 42, 44, and 46 on each of the photoconductors 40, 42, 44, 46. The transfer belt 70, which can sequentially superimpose the developed images of various colors, and the photosensitive bodies 40, 42, 44, and 46 are placed in rolling contact with the photosensitive members 40 with the transfer belt 970 interposed therebetween. First to fourth belt transfer rollers 78, 80, 82, 84 for transferring the image developed on the 42, 44, 46 to the transfer belt 70, and the respective photosensitive members 40, 42, 44, The first to fourth belt transfer rollers 78, 80, 82, and 84 are developed on the respective photosensitive members 40, 42, 44 and 46 so that the developed image on the 46 may be transferred to the transfer belt 70. The first to fourth charging power sources 78a, 80a, 82a, and 84a, which are charged to the opposite state of the charged image, and are provided on the outside of the transfer belt 70, and are superimposed on the transfer belt 70 in various colors. Paper transfer roll which transfers an image to paper 50 76 and the inner side of the transfer belt 70 to correspond to the paper transfer roller 76 so that the paper transfer roller 76 can press the paper 50 at a predetermined pressure. A voltage supply power supply 72a which generates a predetermined electrostatic force on the paper transfer backup roller 72 to support the paper transfer backup roller 72 and the image transfer backup roller 72 so that an image superimposed on the transfer belt 70 can be transferred onto the paper 50. And a driver roller 74 for circulating the transfer belt 70 while maintaining the transfer belt 70 in a predetermined shape suitable for transfer.

Here, the paper transfer roller 76 is grounded and is configured to be subjected to a constant pressing force, which is made of a material having a hardness of about 40-50 degrees. The paper transfer backup roller 72 serves to drive the transfer belt 70 together with the driver roller 74 in addition to supporting the paper transfer roller 76 and is composed of a hard cutting material. In addition, the voltage supply power supply 72a supplies a voltage of about 2.4 to 3.2 kV so that a predetermined electrostatic force is generated in the paper transfer backup roller 72 when the transfer is started.

On the other hand, the paper transfer roller 76 and the paper transfer backup roller 72 are arranged to abut on both sides of the transfer belt 70 via the transfer belt 70 as described above, and then, that is, the transfer nip between them. The image forming operation is performed by passing the paper 50 through the portion, wherein the paper transfer roller 76 and the paper transfer backup roller 72 are not arranged in parallel with each other, but as shown in FIG. 3. The angle is shifted. At this time, it is preferable that the paper transfer roller 76 and the paper transfer backup roller 72 are arranged so that their respective center points are shifted from each other by a predetermined angle. In this case, the shifted angle is preferably maintained at about 3 ° to 7 °. In addition, it is preferable that the mutually displaced angle between the paper transfer roller 76 and the paper transfer backup roller 72 be changed so as to be changeable according to the paper 50 supplied to the image forming apparatus.

Hereinafter, the operation and effects of the color image forming apparatus according to the present invention will be described in detail.

First, the surfaces of the first to fourth photoconductors 40, 42, 44, 46 are charged by a charging device.

Thereafter, the optical scanning unit scans light on the surfaces of each of the photosensitive members 40, 42, 44, and 46 to form a predetermined electrostatic latent image on the photosensitive members 40, 42, 44, and 46. In the black photosensitive member 40, an electrostatic latent image corresponding to the black image is formed in the color image of the above-described original, and magenta, yellow, and cyan photosensitive members 42, 44, and 46 are respectively magenta-imaged in the above-described color image of the original. An electrostatic latent image corresponding to a yellow cyan image is formed.

Thereafter, the first to fourth developing units 60, 62, 64, and 66 are first to fourth developing rollers provided to contact the first to fourth photosensitive members 40, 42, 44, and 46, respectively. The electrostatic latent images formed on the photosensitive members 40, 42, 44, 46 are developed by supplying predetermined color developers to the photosensitive members 40, 42, 44, 46 through 60a, 62a, 64a, 66a. .

Subsequently, the first to fourth belt transfer rollers 78, 80, 82, and 84 installed in rolling contact with the photosensitive members 40, 42, 44, and 46 with the transfer belt 70 interposed therebetween are closed loops. The image developed on each of the photosensitive members 40, 42, 44, 46 is transferred to the transfer belt 70 circulated to the transfer belt 70. On the transfer belt 70 circulated thereon, images of various colors are sequentially superimposed to finally form a desired color image.

Subsequently, the transfer belt 70 having the final color image formed thereon continues to be circulated by driving the driver roller 74 and the paper transfer backup roller 72, and the paper transfer roller 76 through which the paper 50 passes. It passes between the paper transfer backup rollers 72, that is, the transfer nip portion. Therefore, the final color image formed on the transfer belt 70 is transferred to the paper 50 as it is due to the pressure between the paper transfer roller 76 and the transfer belt 70 and a predetermined electrostatic force generated in the paper transfer backup roller 72. Will be.

At this time, in the case of the wet color image forming apparatus, a large force of about 40 kgf or more is applied to the entire area where the paper transfer roller 76 and the transfer belt 70 abut to increase the transfer efficiency to the paper 50. When the paper passes through the transfer nip where a force is applied, a banding phenomenon occurs due to the instantaneous speed change when paper enters or exits due to the thickness of the leading end of the paper. In the case of the color image forming apparatus according to the present invention, Since the paper transfer roller 76 constituting the nip portion and the paper transfer backup roller 72 are arranged at a predetermined angle to each other, the paper 50 entering and exiting the transfer nip portion enters or exits at the same time as before. It is not discharged at once, but gradually enters or is gradually discharged from a part of the tip portion as shown in FIGS. 4 and 5. Therefore, in the transfer nip portion of the color image forming apparatus according to the present invention, the phenomenon in which the speed does not change instantaneously when the paper 50 enters or exits is not generated. Therefore, all the conventional banding problems caused by this speed change are solved.

While the present invention has been described with reference to the specific embodiments shown, it is merely exemplary, and those skilled in the art will understand that various modifications and variations can be made therefrom. Therefore, the scope of the present invention should be defined by the appended claims and their equivalents.

As described above, in the color image forming apparatus according to the present invention, since the paper transfer roller and the paper transfer backup roller constituting the transfer nip are arranged at a mutually offset angle, the paper entering and exiting the transfer nip portion As is conventional, the tip portion is not entered at once or discharged at once, but gradually enters or is gradually discharged from a portion of the tip portion. Therefore, in the transfer nip of the color image forming apparatus according to the present invention, a phenomenon in which the speed does not change instantaneously when paper is entered or discharged is not generated. Therefore, all the conventional banding problems caused by this speed change have an effect to be solved.

Claims (3)

A photosensitive member provided to form an electrostatic latent image corresponding to image information input from the outside; A developing unit provided to visualize the electrostatic latent image by supplying a predetermined developer to the photosensitive member; A transfer belt provided to form an image by superimposing the visualized result from the photosensitive member; A paper transfer roller provided to transfer the image on the transfer belt to paper; And a paper transfer backup roller provided to support the paper transfer roller in the process of driving the transfer belt and transferring the image onto the paper. And the paper transfer roller and the paper transfer backup roller are arranged at a predetermined angle to each other. The color image forming apparatus according to claim 1, wherein a center point of the paper transfer roller and a center point of the paper transfer backup roller cross each other. The color image forming apparatus according to claim 2, wherein a shifted angle between the paper transfer roller and the paper transfer backup roller is 3 ° to 7 °.

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