JP3631673B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to paper dust removal in paper conveyance of an image forming apparatus.
[0002]
[Prior art]
In general, in an image forming apparatus such as a copying machine, transfer paper set in a paper feed unit such as a paper feed cassette is sent to a transfer paper transport path by a paper feed roller or the like, and transported on the transfer paper transport path An image is formed by being conveyed toward the image forming unit by a roller and a registration roller.
[0003]
In this case, when the transfer paper passes through various conveyance rollers such as a conveyance roller and a registration roller, paper dust is generated due to friction with these rollers.
[0004]
In the previous image forming unit, a cleaner for removing residual toner remaining on the photosensitive drum after transfer is provided. This cleaner collects the residual toner removed from the photosensitive drum and can use it again as a developing toner. Such a system is called a toner recycling system and is widely used in copying machines and the like.
[0005]
[Problems to be solved by the invention]
However, when such transfer paper with paper dust adhered is fed into the image forming section, the paper dust is transferred to the surface of the photosensitive drum, and between the cleaner blade and the photosensitive drum that removes residual toner from the photosensitive drum. The cleaner blade is damaged, and the cleaning blade is damaged, which causes the cleaning performance to deteriorate. Further, the filler contained in the paper powder stains the surface of the photosensitive drum, prevents proper formation of an electrostatic latent image on the photosensitive drum, and causes image deterioration. In the first-stage toner recycling system, when paper dust adheres to the photosensitive drum, the attached paper dust is returned to the developing unit together with the collected toner and mixed into the developer in the developing device. When paper dust is mixed into the developer, large paper dust is put in the gap to prevent normal frictional charging performed between the toner and the carrier in the developer or to restrict the developer on the developing roller to a predetermined amount. It may cause clogging and a large disturbance in the image.
[0006]
SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that can reliably remove paper dust contained in transfer paper on the upstream side of a transfer paper conveyance path from a transfer portion. It is aimed.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, the present inventors have focused on the relative permittivity of transfer paper and paper dust, and have completed an image forming apparatus capable of efficiently removing paper dust with a very simple configuration.
[0008]
That is, according to the first aspect of the present invention, a pair of paper transport rollers is arranged on a transfer paper transport path from the paper feed unit to the transfer unit, and the transfer surface side roller of the pair of paper transport rollers has a dielectric constant. An image forming apparatus comprising : a material having a rate of 4.0 or less; and a paper conveying roller on the opposite side to the paper conveying roller on the transfer surface side made of ethylene propylene rubber (EPDM) rubber. Device.
[0009]
In general, the dielectric constant of paper dust is about 4.0 to 10.0. According to the above configuration, the transfer surface roller of the pair of paper transport rollers has a relative dielectric constant of 4.0 or less and is smaller than the transfer paper. Therefore, when the transfer paper passes through the paper transport roller, When the paper transport roller and the paper powder contained in the transfer paper are rubbed, the paper powder is positively charged and the paper transport roller is negatively charged. For this reason, the paper powder having positive polarity is sucked by the roller on the transfer surface side having a negative polarity. Therefore, the paper dust is dissociated from the transfer paper and is adsorbed by the paper transport roller, and the paper dust adhering to the transfer paper can be surely removed before reaching the transfer section. Further, since the paper transport roller on the opposite side to the paper transport roller on the transfer surface side is made of ethylene propylene rubber, a sufficient paper transport force can be obtained.
[0010]
Here, the relative dielectric constant refers to the ratio between the dielectric constant of a certain material and the dielectric constant of vacuum, and the dielectric constant refers to a proportional constant between the electric flux density and the electric field.
[0011]
In addition, regarding triboelectric charging of materials, when a material with a low dielectric constant and a material with a high dielectric constant come into contact, the material with a high dielectric constant has a positive charge, and the material with a low dielectric constant has a negative charge. There is Coehn's law, which the present invention uses.
[0012]
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect of the present invention, the material on the transfer surface side of the pair of rollers is made of polyvinyl chloride.
[0013]
According to this configuration, since the relative dielectric constant of polyvinyl chloride is in the range of 3.0 to 3.3, it is sufficiently large relative to the relative dielectric constant of paper powder having a relative dielectric constant of 4.0 to 10.0. The difference can be ensured, so that the roller on the transfer surface side can be surely negatively charged and the paper dust can be triboelectrically charged to the positive polarity, and the paper dust adhering to the transfer paper can be surely removed. .
[0014]
According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, the roller on the transfer surface side of the pair of rollers is made of polyethylene.
[0015]
According to this configuration, since the relative dielectric constant of polyethylene is 2.3, a sufficiently large difference is ensured with respect to the relative dielectric constant of transfer paper and paper powder having a relative dielectric constant of 4.0 to 10.0. Accordingly, the roller on the transfer surface side can be more reliably negatively charged and the paper dust can be triboelectrically charged to the positive polarity, and the paper dust adhering to the transfer paper can be reliably removed.
[0016]
According to a fourth aspect of the present invention, in the image forming apparatus according to the first aspect, the material on the transfer surface side of the pair of rollers is made of a fluororesin.
[0017]
According to this configuration, since the relative permittivity of the fluororesin is 2.0, a sufficiently large difference is ensured with respect to the relative permittivity of the transfer paper and the paper dust having the relative permittivity of 4.0 to 10.0. As a result, the roller on the transfer surface side can be more reliably negatively charged and the paper dust can be triboelectrically charged to the positive polarity, and the paper dust adhering to the transfer paper can be reliably removed.
[0018]
According to a fifth aspect of the present invention, there is provided an image forming apparatus characterized in that a cleaning means is provided on the paper conveying roller on the transfer surface side in the previous period. With this configuration, it is possible to provide cleaning means on the roller on the transfer surface side and remove paper dust adsorbed on the roller.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is an overall sectional view of an embodiment in which an image forming apparatus according to the present invention is applied to a copying machine. The copying machine includes a paper feeding unit 10 disposed at a lower portion of the apparatus main body, a paper transporting unit 20 disposed above the paper feeding unit 10, and an image forming unit disposed above the paper transporting unit 20. 30, a fixing unit 40 disposed on the discharge side of the image forming unit 30, and an image reading unit 50 including the image forming unit 30 and optical members disposed above the fixing unit 40. Yes.
[0020]
The sheet feeding unit 10 sends a bundle of transfer sheets 15 stacked and loaded on the sheet feeding cassette 11 to the exit side of the sheet feeding cassette 11 by the rotation operation of the sheet feeding roller 12 having an arcuate outer peripheral part. It is designed to feed paper.
[0021]
The sheet conveying unit 20 conveys the transfer sheet 15 fed from the sheet feeding unit 10 toward the image forming unit 30 by the conveying roller pair 22 and the registration roller pair 23 via the reversing guide 21, and further the image forming unit 30. The transfer sheet 15 on which the image is formed in the fixing unit 40 is discharged onto the discharge tray 24 by the discharge roller pair 25. In the present embodiment, the registration roller pair 23 is configured as a paper conveying roller having a paper dust removing function. This point will be described later.
[0022]
The image forming unit 30 forms a predetermined toner image on the transfer paper 15 by an electrophotographic process. The image forming unit 30 has a photoconductive drum 31 having a photoconductivity supported rotatably and a photosensitive drum 31. A charger 32, an exposure device 33, a developing device 34, a transfer device 35, a cleaner 36, and a static eliminator 37 are provided around the rotation direction.
[0023]
The charger 32 includes a charging wire (not shown) to which a high voltage is applied, and applies a predetermined potential to the photosensitive drum 31 by corona discharge from the charging wire, and a positively charged single layer organic photoreceptor as a material. Is used. The exposure device 33 forms an electrostatic latent image on the surface of the photosensitive band drum 31 based on the image data of the original read by the image reading unit 50. The developing device 34 develops the electrostatic latent image with toner to form a toner image on the surface of the photosensitive drum 31. The transfer unit 35 is constituted by a transfer roller that is separated from the photosensitive drum 31 by a predetermined distance. The cleaner 36 removes toner remaining on the surface of the photosensitive drum after transfer. The static eliminator 37 removes residual charges on the surface of the photosensitive drum 31.
[0024]
The fixing unit 40 is disposed on the downstream side of the image forming unit 30 in the sheet conveying direction, and the transfer sheet 15 onto which the toner image is transferred in the image forming unit 30 is pressed against the heating roller 41 and the heating roller 41. The toner image is fixed on the transfer paper 15 by being sandwiched and heated by the roller 42.
[0025]
The image reading unit 50 reads the image information of the document by irradiating the document placed on the contact glass 51 with light from the exposure lamp 52.
[0026]
FIG. 2 is an enlarged explanatory view in the vicinity of a registration roller configured as a paper conveying roller having a paper dust removing function. As shown in this figure, the pair of registration rollers 23 is disposed upstream of the transfer sheet conveyance path from the image forming unit 30 and originally feeds the transfer sheet 15 to the transfer position (transfer unit) of the image forming unit 30. At the same time, it has a function of transferring the transfer paper 15 to the image forming unit 30 after aligning the leading edge of the transfer paper 15 when the transfer paper 15 is fed obliquely. The pair of registration rollers 23 includes a first registration roller 231 positioned on the surface (transfer surface) side on which the transfer sheet 15 faces the photosensitive drum 31 in the image forming unit 30 and the toner image is transferred. It consists of a second registration roller 232 located on the opposite side of the paper 15 and a cleaner 233 for removing paper dust adhering to the first registration roller from the roller.
[0027]
The first registration roller 231 is made of a cylindrical material of tetrafluoroethylene-fluoroalkyl vinyl ether copolymer (PFA), and the second registration roller 232 has a sufficiently large contact friction with the transfer paper 15. It is constituted by a cylindrical material of ethylene propylene (EPDM) rubber that can obtain force.
[0028]
The relative permittivity of the transfer paper 15 and the paper powder is in the range of 4.0 to 10.0, but PFA, which is the material of the first registration roller 231, has a relative permittivity of 2.1. When 15 passes the first registration roller 231, the first registration roller 231 is charged by friction between the transfer sheet 15 and paper dust. In this case, the first registration roller 231 is negatively charged, and the transfer paper 15 and paper dust are charged positively. This is because the material having a high relative permittivity and the material having a low relative permittivity are triboelectrically charged according to the above-mentioned Coehn's law. Is.
[0029]
Thus, when the paper dust and the first registration roller 231 are charged with opposite polarities, the paper dust is adsorbed by the first registration roller 231. Then, the paper dust adsorbed on the first registration roller 231 is removed by the cleaner 233. The cleaner 233 includes a brush roller 2331, a whip plate 2332, and a housing 2333. The brush roller 2331 is obtained by implanting polyester fiber, and is brought into contact with the first resist roller 231 while being rotated opposite to the paper, so that paper dust adheres to the brush roller 2331. The paper dust adhering to the brush roller 2331 is dropped by the hammering plate 2332 and stored in the housing 2333, and the paper dust adsorbed on the first registration roller 231 is removed.
[0030]
For this reason, the paper dust adhering to the transfer paper 15 is removed before being conveyed to the image forming unit 30, and the surface of the photosensitive drum 31 due to the filler contained in the paper powder can be prevented. It is possible to prevent the image quality of the image transferred to the image from being deteriorated. Further, since the paper dust is removed before being conveyed to the cleaner 36, it is possible to prevent the cleaning performance of the residual toner adhering to the photosensitive drum 31 from being lowered due to the suction of the paper dust to the cleaning flade.
[0031]
Further, there may be a case where sufficient friction cannot be obtained between the first registration roller 231 made of PFA and the transfer sheet 15, but this is because the second registration roller 232 is made of EPDM rubber. The registration roller 23 can obtain a sufficient sheet conveying force as a whole, and can also reliably function as the registration roller 23.
[0032]
If the material of the first registration roller 231 has a relative dielectric constant of 4.0 or less, it becomes lower than the relative dielectric constant of the paper powder, so that the paper powder can be removed by the above-described action. Therefore, the material of the first registration roller 231 is not limited to ethylene tetrafluoroethylene-fluoroalkyl vinyl ether copolymer (PFA), which is the material of the present embodiment, but vinyl chloride, polyethylene having a relative dielectric constant of 4.0 or less, or Other fluororesins other than PFA may be used.
[0033]
FIG. 3 shows the measurement experiment results of the recovered amount of paper dust when the first registration roller 231 is made of various materials. The second registration roller 232 was made of ethylene propylene (EPDM) rubber in any case. The numerical value in the column of the collected amount is paper dust detected by the cleaner unit 36 at the time of drum cleaning, and the lower this value indicates that the first registration roller 231 is removing more paper dust. .
[0034]
As shown in FIG. 3, when the material of the first registration roller 231 is polyacetal (PA), the amount of recovered paper dust is 39.9, and the amount of paper dust detected by the cleaner 36 from the other three materials is 39.9. It can be seen that the amount of paper dust is large and the performance of paper dust removal is poor. This is because the relative permittivity of polyacetal (PA) is 3.9 to 7.6, and the difference from the relative permittivity of paper powder 4.0 to 10.0 is less than that of the other three cases due to frictional charging. This is probably because the paper dust removing function of the present invention is not exhibited.
[0035]
On the other hand, in the other three materials shown in FIG. 3, the relative permittivity of each material is in the range of 2.0 to 3.3, and the relative permittivity is in the range of 4.0 to 10.0. The relative dielectric constant difference between the first registration roller 231 and the transfer sheet 15 is increased, and a larger electric field is formed between the first registration roller 231 and the transfer sheet 15 than the polyacetal (PA). A large amount of paper dust can be adsorbed to the first registration roller 231. Therefore, PFA having a relative dielectric constant of 2.1 has the largest amount of recovered paper dust, followed by the largest amount of recovered polyethylene paper powder having a relative dielectric constant of 2.3, and then the relative dielectric constant. However, the recovered amount of polyvinyl chloride paper dust is 3.0-3.3.
[0036]
Other fluorine resins other than PFA include ethylene tetrafluoride (PTFE, relative dielectric constant εr <2.1), tetrafluoroethylene-hexafluoropropylene copolymer resin (FEP, εr = 2.1), Tetrafluoroethylene-ethylene copolymer resin (ETFE, εr <2.1), tetrafluoroethylene-propylene copolymer rubber, ethylene trifluoride-ethylene copolymer resin (E-CTFE, εr = 2.3), An elastic body such as perfluoro fluorine rubber may be used.
[0037]
Although the embodiment in which the present invention is applied to a copying apparatus has been described above, the present invention is not limited to a copying machine but can be applied to various image forming apparatuses such as a facsimile machine and a printer.
[0038]
In the above-described embodiment, the second registration roller (the transfer side roller on the transfer surface) 232 is made of EPDM rubber. However, the first registration roller (the transfer surface side roller) and the transfer sheet 15 are given conveyance force. Various materials can be applied as long as the material can obtain a sufficient frictional force.
[0039]
In the above embodiment, polyester is used as the material of the brush roller, but other materials such as nylon, tetron, and wool may be used.
[0040]
Further, instead of the brush roller 2331 of the cleaner 233, an elastic blade such as rubber or film or a sponge may be directly pressed against the first registration roller 231 to remove paper dust by using the rotation of the roller. Moreover, you may remove the paper dust adhering to the 1st roller with a web.
[0041]
【The invention's effect】
As described above, according to the present invention, the relative permittivity of the transfer roller is arranged on the transfer paper transport path upstream of the image forming unit (transfer unit) on the transfer paper transport path. Since it is made of a lower material of 4.0 or less, when the transfer paper passes, the transfer paper and paper dust are charged positively and the paper conveying roller is charged negatively by frictional charging, so that the transfer paper passes from the transfer paper to the paper. The paper dust adhering to the transfer paper by the electric field formed toward the conveying roller can be adsorbed to the paper conveying roller and reliably removed. As a result, it is possible to prevent the transfer image from being deteriorated due to the filler contained in the paper dust adhering to the photoreceptor, and the cleaning performance from being deteriorated. Further, since the paper transport roller on the opposite side to the paper transport roller on the transfer surface side is made of ethylene propylene rubber, a sufficient paper transport force can be obtained.
[Brief description of the drawings]
FIG. 1 is an overall cross-sectional view of an embodiment in which an image forming apparatus according to the present invention is applied to a copying machine.
FIG. 2 is an enlarged explanatory view in the vicinity of a registration roller configured as a paper conveying roller having a paper dust removing function.
FIG. 3 is a measurement experiment result of a collected amount of paper dust when the first registration roller 231 is made of various materials.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Paper feed part 11 Paper feed cassette 12 Paper feed roller 15 Transfer paper 20 Paper conveyance part 21 Reverse guide 22 Carrying roller pair 23 Registration roller pair 231 First registration roller 232 Second registration roller 24 Discharge tray 25 Discharge roller pair 30 Image forming unit 31 Photosensitive drum 32 Charging device 33 Exposure device 34 Development device 35 Transfer device 36 Cleaner 37 Static eliminator 40 Fixing portion 41 Heating roller 42 Pressure roller 50 Image reading portion 51 Contact glass 52 Exposure lamp

Claims (5)

A pair of paper transport rollers is disposed on a transfer paper transport path from the paper feed unit to the transfer unit, and a material having a relative dielectric constant of 4.0 or less is used as a transfer surface side roller of the pair of paper transport rollers. An image forming apparatus , wherein the paper conveying roller on the opposite side to the paper conveying roller on the transfer surface side is made of ethylene propylene rubber . 2. The image forming apparatus according to claim 1, wherein the roller on the transfer surface side of the pair of rollers is made of polyvinyl chloride. 2. The image forming apparatus according to claim 1, wherein the roller on the transfer surface side of the pair of rollers is made of polyethylene. The image forming apparatus according to claim 1, wherein the roller on the transfer surface side of the pair of rollers is made of a fluororesin. The image forming apparatus according to claim 1, wherein a cleaning unit is provided on the paper conveying roller on the transfer surface side.

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