JP2002154699A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely remove paper powder sticking to transfer paper on the upstream side of an image forming part. SOLUTION: Among a pair of regist rollers 23, the first regist roller 231 for contacting with the transfer object surface side of the transfer paper is composed of a construction material having a specific dielectric constant of 4.0 or less. When the transfer paper 15 passes through these regist roller pairs 23, the first regist roller 231 electrifies the paper powder included in the transfer paper as negative polarity to positive polarity by friction, and shakes down the paper powder sticking to the first regist roller 231 by a cleaner 233 after attracting the paper powder electrified to the positive polarity to the first regist roller 231, and can remove the paper powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to paper dust removal in paper transport of an image forming apparatus.

[0002]

2. Description of the Related Art Generally, in an image forming apparatus such as a copying machine, a transfer sheet set in a sheet feeding unit such as a sheet cassette is sent out to a transfer sheet conveying path by a sheet feeding roller or the like. The sheet is conveyed toward the image forming unit by a conveying roller, a registration roller, and the like arranged on the image forming apparatus to form an image.

Further, the image forming section is provided with a cleaner for removing residual toner remaining on the photoreceptor after transfer. The cleaner collects the residual toner removed from the photoreceptor, 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.

[0004]

However, when the transfer sheet passes through various transport rollers such as a feed roller, a transport roller, and a registration roller, paper dust is generated due to friction with these rollers. When the transfer paper to which the paper dust has adhered is sent to the image forming unit, the paper dust is transferred to the surface of the photoconductor, and gets caught between the photoconductor and a cleaner blade that removes residual toner from the photoconductor. As a result, the cleaner blade is damaged, which causes a reduction in cleaning performance. Further, the filler contained in the paper dust stains the surface of the photoconductor drum, hinders formation of an appropriate electrostatic latent image on the photoconductor drum, and causes image deterioration.

In the toner recycling system, when paper dust adheres to the photosensitive drum, the adhered paper dust is returned to the developing device together with the collected toner and mixed with the developer in the developing device, and the toner and the carrier in the developer are mixed. Normal friction charging performed between the developing roller and the gap for regulating the amount of the developer on the developing roller to a predetermined amount is clogged with large paper dust, thereby causing a large disturbance in an image. .

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides an image forming apparatus capable of reliably removing paper dust generated from transfer paper upstream of a transfer section on a transfer paper transport path. It is intended to be.

[0007]

In order to solve the above-mentioned problems, the present inventors pay attention to the relative permittivity of transfer paper and paper dust, and can remove paper dust efficiently with a very simple configuration. The image forming apparatus was completed.

That is, according to the first aspect of the present invention, a pair of paper transport rollers are disposed on a transfer paper transport path from a paper feed unit to a transfer unit, and the roller on the transfer surface side of the pair of paper transport rollers is provided. Is formed of a material having a relative dielectric constant of 4.0 or less.

Generally, the relative dielectric constant of paper dust is about 4.0 to 10.0 in consideration of the influence of temperature and humidity. According to the above configuration, the roller on the transfer surface side of the pair of paper transport rollers has a relative dielectric constant of 4.0 or less and is smaller than the transfer paper, so that when the transfer paper passes through the paper transport rollers. When the paper transport roller and the paper powder contained in the transfer paper rub against each other, the paper powder is charged to a positive polarity and the paper transport roller is charged to a negative polarity. Therefore, the paper powder having the positive polarity is sucked by the roller on the transfer surface side having the negative polarity. Accordingly, the paper dust is dissociated from the transfer paper and is attracted to the paper transport roller, so that the paper dust adhering to the transfer paper can be reliably removed before reaching the transfer section.

Here, the relative permittivity refers to the ratio between the permittivity of a material and the permittivity of vacuum, and the permittivity refers to the proportionality constant between the electric flux density and the electric field.

Further, regarding the triboelectric charging of a substance, generally, when a substance having a low dielectric constant contacts a substance having a high dielectric constant, the substance having a high dielectric constant takes on a positive charge, and the substance having a low dielectric constant takes a negative charge. There is Coehn's law, which takes advantage of this.

According to a second aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein a material of the roller on the transfer surface side of the pair of rollers is made of polyvinyl chloride.

According to this configuration, since the relative permittivity of polyvinyl chloride is in the range of 3.0 to 3.3, the relative permittivity is 4.0.
It is possible to ensure a sufficiently large difference with respect to the relative permittivity of the paper dust of 0 to 10.0, thereby ensuring that the roller on the transfer surface side is negatively charged and the paper dust is frictionally charged to the positive polarity. Thus, paper dust adhering to the transfer paper can be reliably removed.

According to a third aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein the roller on the transfer surface side of the pair of rollers is made of polyethylene.

According to this configuration, since the relative dielectric constant of polyethylene is 2.3, there is a sufficiently large difference between the relative dielectric constants of transfer paper and paper dust having a relative dielectric constant 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 frictionally charged to the positive polarity, and the paper dust attached to the transfer paper can be reliably removed.

According to a fourth aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein the roller on the transfer surface side of the pair of rollers is made of fluororesin.

According to this configuration, since the relative permittivity of the fluororesin is approximately 2.0, the relative permittivity is 4.0 to 10.0.
A sufficiently large difference can be secured with respect to the relative dielectric constants of the transfer paper and the paper dust, thereby making it possible to more reliably charge the roller on the transfer surface side to the negative polarity and to frictionally charge the paper dust to the positive polarity. Thus, paper dust attached to the transfer paper can be reliably removed.

According to a fifth aspect of the present invention, there is provided a cleaning device for removing paper dust adsorbed by the paper transport roller on the transfer surface side from the roller.
5. The image forming apparatus according to any one of 4. With this configuration, a cleaning unit is provided on the roller on the transfer surface side, and the paper dust adsorbed on the roller can be removed.

The cleaning means is preferably a brush type in which a brush roller is provided which is brought into contact with the transport roller while rotating and opposed thereto, thereby removing paper dust adsorbed on the transport roller.

[0020]

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 sheet feeding unit 10 disposed at a lower portion of the apparatus main body, a sheet conveying unit 20 disposed above the sheet feeding unit 10, and an image forming unit disposed above the sheet conveying 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 an optical system member disposed above the image forming unit 30 and the fixing unit 40. I have.

The paper supply unit 10 sends out a bundle of transfer papers 15 stacked and mounted on the paper supply cassette 11 to the outlet side of the paper supply cassette 11 by rotating a paper supply roller 12 having an arcuate outer peripheral portion. The paper is fed to the unit 20.

The paper transport section 20 transports the transfer paper 15 fed from the paper feed section 10 to the image forming section 30 by a transport roller pair 22 and a registration roller pair 23 via a reversing guide 21 and further transfers the image. The transfer paper 15 on which an image has been formed in the forming unit 30 to the fixing unit 40 is discharged onto a discharge tray 24 by a discharge roller pair 25. In the present embodiment, the registration roller pair 23
Is configured as a paper transport roller having a paper dust removing function. This will be described later.

The image forming section 30 forms a predetermined toner image on the transfer paper 15 by an electrophotographic process, has rotatable and rotatably supported photoconductive, positively charged single-layer organic photoreceptor. And a charger 3 around the photosensitive drum 31 along the rotation direction thereof.
2, an exposure unit 33, a development unit 34, a transfer unit 35, a cleaner 36, and a static eliminator 37.

The charger 32 is provided with a charging wire (not shown) to which a high voltage is applied, and gives a predetermined potential to the photosensitive drum 31 by corona discharge from the charging wire. Use an organic photoreceptor.
The exposing device 33 forms an electrostatic latent image on the surface of the photosensitive belt drum 31 based on image data of a document 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 configured by a transfer roller separated from the photosensitive drum 31 by a predetermined distance. The cleaner 36 removes the toner remaining on the surface of the photosensitive drum after the transfer. The static eliminator 37 removes residual charges on the surface of the photosensitive drum 31.

The fixing section 40 is disposed downstream of the image forming section 30 in the sheet conveying direction, and transfers the transfer sheet 15 on which the toner image has been transferred in the image forming section 30 to a heating roller 41.
The toner image is fixed on the transfer paper 15 by heating by sandwiching the pressure roller 42 pressed against the heating roller 41.

The image reading section 50 includes a contact glass 51
The original placed above is irradiated with light from an exposure lamp 52 to read image information of the original.

FIG. 2 is an enlarged explanatory view showing the vicinity of a registration roller configured as a paper transport roller having a paper dust removing function. As shown in FIG.
Reference numeral 3 is disposed upstream of the transfer path of the image forming unit 30 on the transfer paper transport path. Originally, the timing of feeding the transfer paper 15 to the transfer position (transfer unit) of the image forming unit 30 is intended.
When the transfer paper 15 is fed obliquely, the transfer paper 15 has a function of aligning the leading edge of the transfer paper and then transferring it to the image forming unit 30. This pair of registration rollers 23
Are opposed to the photosensitive drum 31 in the image forming unit 30 and the first registration roller 231 is located on the surface (transfer surface) on which the toner image is transferred, and the first registration roller 231 is located on the opposite side with the transfer paper 15 interposed therebetween. The second registration roller 232 and a cleaner 233 for removing paper dust adhering to the first registration roller from the roller.

The first registration roller 231 has at least a surface layer thereof made of a cylindrical material of ethylene tetrafluoroethylene-fluoroalkyl vinyl ether copolymer (PFA). It is composed of a cylindrical material of ethylene propylene (EPDM) rubber capable of obtaining a sufficiently large contact friction force between the rubber material and the rubber material.

The relative permittivity of the transfer paper 15 and the paper dust is 4.
0 to 10.0, but the first registration roller 2
The PFA 31 is a material having a relative dielectric constant of 2.1. Therefore, when the transfer paper 15 passes through the first registration roller 231, the first registration roller 231 due to friction with the transfer paper 15 and paper dust. Will be charged. In this case, the first registration roller 231 is negatively charged, and the transfer paper 15 and the paper powder are positively charged. This is based on the above-described Coehn's law, when a material having a high relative dielectric constant and a material having a low relative dielectric constant are frictionally charged, a material having a high relative dielectric constant is charged to a positive polarity and a material having a low relative dielectric constant is charged to a negative polarity. Things.

When the paper dust and the first registration roller 231 are charged to opposite polarities in this way, the paper dust is attracted to the first registration roller 231. The paper dust adsorbed by the first registration roller 231 is removed by the cleaner 233.
Removed by. The cleaner 233 includes a brush roller 2331, a beating plate 2332, and the housing 2
333. The brush roller 2331 is formed by implanting polyester fibers, and the first registration roller 2
31 and the brush roller 23
Paper powder will adhere to 31. Brush roller 233
The paper dust adhering to 1 is dropped by a beater plate 2332, collected in the housing 2333, and the paper dust adsorbed on the first registration roller 231 is removed.

For this reason, the paper dust adhering to the transfer paper 15 is removed before being conveyed to the image forming unit 30, so that the surface of the photosensitive drum 31 can be prevented from being stained by the filler contained in the paper dust. It is possible to prevent the image quality of the image transferred to the transfer paper 15 from deteriorating. 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 attached to the photosensitive drum 31 from being lowered due to the adsorption of the paper dust to the cleaning blade.

In some cases, sufficient friction cannot be obtained between the first registration roller 231 made of PFA and the transfer sheet 15, but the second registration roller 232 is made of EPDM rubber. Therefore, the registration roller 23 can obtain a sufficient paper conveyance force as a whole,
The function as the registration roller 23 can also be reliably performed.

The effect of triboelectric charging due to the difference in the relative dielectric constant between two contacting substances is remarkable. For example, two contacting substances are charged to a polarity different from the polarity to be charged before and after the contact. However, when both substances come into contact, a substance having a large relative dielectric constant is charged to a positive polarity and a substance having a small relative dielectric constant is charged to a negative polarity regardless of the past charging history. Therefore, as in the present embodiment, the material of the first registration roller 321 is changed to a tetrafluoroethylene-fluoroalkyl vinyl ether copolymer having a relative dielectric constant smaller than that of paper powder.
By selecting (PFA), it is ensured that the paper powder after contact and the first resist roller are negative even after contact, even if both are charged to polarities different from the polarities to be charged before and after contact. The paper dust is triboelectrically charged, and the paper dust is attracted to the first registration roller, so that the deterioration of the image due to the mixing of the paper dust into the photosensitive drum 15 can be prevented.

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 dust, so that the paper dust can be removed by the above operation. Therefore, the first registration roller 231
Is not limited to the tetrafluoroethylene-fluoroalkylvinylether copolymer (PFA) which is the material of the present embodiment, but also has a relative dielectric constant of 4.0 or less, such as vinyl chloride, polyethylene, or a fluororesin other than PFA. It may be.

FIG. 3 shows the results of an experiment for measuring the amount of recovered 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 each case. The numerical value in the collection amount column is the paper dust detected by the cleaner unit 36 during drum cleaning, and a lower value indicates that the first resist roller 231 removes more paper dust. .

As shown in FIG. 3, when the material of the first registration roller 231 is polyacetal (PA), the recovered amount of paper dust is 39.9, and the other three materials are detected by the cleaner 36. It can be seen that the amount of paper dust is large and the performance of paper dust removal is inferior. This is the polyacetal (P
The relative permittivity of A) is 3.9 to 7.6, and the difference from the relative permittivity of paper powder of 4.0 to 10.0 is smaller than that of the other three cases. It is considered that the removal function was not exhibited.

On the other hand, in the other three materials shown in FIG. 3, the relative dielectric constant of each material is in the range of 2.0 to 3.3, and the relative dielectric constant is in the range of 4.0 to 10.0. The difference in the relative dielectric constant from a certain paper powder is large, and the amount of charge charged by friction is larger than that of polyacetal (PA), so that more paper powder can be attracted to the first registration roller 231. Accordingly, PFA having a relative dielectric constant of 2.1 has the largest amount of recovered paper dust, followed by polyethylene having a relative dielectric constant of 2.3 which has the largest amount of recovered paper dust. Is 3.
The collection amount of paper powder of polyvinyl chloride of 0 to 3.3 is increasing.

Further, as another fluorine resin other than PFA,
Ethylene tetrafluoride (PTFE, relative permittivity εr <2.1), ethylene tetrafluoride-hexafluoropropylene copolymer resin (FEP,
εr = 2.1), tetrafluoroethylene-ethylene copolymer resin
(ETFE, εr <2.1), tetrafluoroethylene-
Elastic bodies such as propylene copolymer rubber, ethylene trifluoride-ethylene copolymer resin (E-CTFE, εr = 2.3), and perfluoro fluorine rubber may be used.

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 apparatus and a printer.

In the above embodiment, the second registration roller (roller on the transfer side of the transfer surface) 232 is made of EPDM rubber, but the first registration roller (roller on the transfer surface side) is formed of EPDM rubber.
At the same time, various materials can be applied as long as the material can provide a sufficient frictional force for applying a transfer force to the transfer paper 15.

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.

The brush roller 2 of the cleaner 233
Instead of 331, an elastic blade or sponge such as rubber or film may be directly pressed against the first registration roller 231 to remove paper dust by using the rotation of the roller.
Further, paper dust adhering to the first roller may be removed by a web.

In the above embodiment, the material of the photosensitive drum 31 is a positively charged single-layer organic photosensitive member. However, other than this material, an a-Si photosensitive member or a negatively charged laminated organic photosensitive member may be used. Does not affect the above-mentioned paper dust removing action.

In the above-described embodiment, the photosensitive drum 31 is used as the photosensitive member of the image forming section 30, but the use of the photosensitive belt does not affect the above-described paper dust removing action.

[0045]

As described above, according to the present invention, the relative permittivity of the transfer paper provided on the transfer paper transport path on the transfer paper transport path located upstream of the image forming section (transfer section) on the transfer paper transport path is increased. Since the transfer paper and the paper dust are made of a material of 4.0 or less, when the transfer paper passes, the paper dust is charged to the positive polarity by the frictional charging when the transfer paper passes, and the paper transport roller is charged to the negative polarity, and the transfer paper By adsorbing the paper dust adhering to the paper transport roller and removing the adsorbed paper dust by the cleaning means, the paper dust can be reliably removed before the transfer sheet is sent to the image forming section.

Further, the effect of triboelectric charging due to the difference in the relative dielectric constant between two materials in contact with each other is remarkable. When both materials come into contact with each other, a material having a large relative dielectric constant has a positive dielectric constant regardless of the past charging history. A substance having a small ratio is charged to a negative polarity. Therefore, when the material of the transport roller is made of a material having a relative dielectric constant different from that of the paper powder as in the present invention, the two materials are frictionally charged to different polarities and the paper powder can be reliably removed.

As a result, it is possible to prevent the transfer image from deteriorating due to the filler contained in the paper dust adhering to the photoreceptor and the cleaning performance from deteriorating.

[Brief description of the drawings]

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.

FIG. 2 is an enlarged explanatory view near a registration roller configured as a paper transport roller having a paper dust removing function.

FIG. 3 shows the results of an experiment for measuring the amount of collected paper dust when the first registration roller 231 is made of various materials.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 paper feed unit 11 paper feed cassette 12 paper feed roller 15 transfer paper 20 paper transport unit 21 inversion guide 22 transport 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 Photoreceptor drum 32 Charger 33 Exposure unit 34 Developing unit 35 Transfer unit 36 Cleaner 37 Static eliminator 40 Fixing unit 41 Heating roller 42 Pressure roller 50 Image reading unit 51 Contact glass 52 Exposure lamp

Claims (5)

[Claims] A pair of paper transport rollers are disposed on a transfer paper transport path from a paper feed section to a transfer section, and a roller having a relative dielectric constant of 4 between the pair of paper transport rollers on the transfer surface side. .
An image forming apparatus comprising: a material of 0 or less. 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. 3. 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. 4. The image forming apparatus according to claim 1, wherein the roller on the transfer surface side of the pair of rollers is made of fluororesin. 5. The image forming apparatus according to claim 1, further comprising a cleaning unit that removes, from the roller, the paper transporting roller on the transfer surface side, the paper dust adsorbed by the roller.