JP2004109151A - Charging device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charging device having a long service life and ensuring a gap between a charging roller and an image carrier with required accuracy at low cost, and to provide an image forming apparatus with the same. <P>SOLUTION: The charging device 110 has a charging roller 11 with recessed steps 10 in both ends and ring-shaped regulating members 13a, 13b fixed in the respective recessed steps 10, wherein fitting phase of the regulating member 13a at one end and the regulating member 13b at the other end are not coincident with each other. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a charging device provided with a charging roller for charging an image carrier such as a photoconductor, and an image forming apparatus such as a copying machine, a facsimile, or a printer having the same.
[0002]
[Prior art]
2. Description of the Related Art In an image forming apparatus such as a copying machine, a printer, or a facsimile, a toner image is formed and carried on a sheet-shaped recording medium by a transfer method or a direct method by an image forming process mechanism such as an electrophotographic method. Such an image forming process mechanism forms a toner image carried on a recording medium on an image carrier such as a photoreceptor. In one of the toner image forming processes, the image carrier is charged. The image forming process mechanism includes a charging device as a charging unit for performing the charging process.
[0003]
Conventionally, as a charging device, a charging device such as a scorotron which performs charging is mainly used, but this method has a problem that a large amount of discharge products such as ozone is generated. A charging device of a type that comes into contact with an image carrier has been widely used. In a charging device of this type, contamination such as toner adheres to a roller or the like with time, and if uneven charging occurs due to the adhesion of the stain, adversely affects image formation. This was a major factor in determining the life of the device.
[0004]
Therefore, as shown in [Patent Document 1], in a charging device using a roller, a film is attached to an end of the roller to reduce dirt on the roller, and a small gap is formed between the photoconductor and the roller. There has been proposed a technique for forming an image and suppressing adhesion of dirt. Further, as a technique for forming a gap by means other than a film, a technique has been proposed in which a step or a groove is provided at an end of a roller and a member for forming a gap is attached, as shown in [Patent Document 2]. On the other hand, as a material of the roller, an elastic member such as rubber or sponge is generally used, but a roller using a resin is also known as shown in [Patent Document 3].
[0005]
However, when the roller is made of rubber, it is difficult to perform machining with high precision by cutting, and there is a problem that the gap tends to fluctuate due to the environment due to large thermal expansion. On the other hand, a resin-made roller is high in hardness and easy to cut, but because of high hardness, when a film-shaped member is used as a member for forming a gap, this member is worn over time. There was a problem such as. When an organic photoreceptor is used as an image carrier, the photoreceptor may be damaged when a member forming a gap comes into contact. Therefore, in [Patent Document 2], a step or a groove is provided at the end of the roller so that the member forming the gap and the photoreceptor are not deteriorated and good durability is obtained, and the member forming the gap is thinned. A technique of using a thick elastic body has been proposed.
[0006]
[Patent Document 1]
JP 2001-194868 A [Patent Document 2]
JP 2002-55508 A [Patent Document 3]
JP-A-2002-55508
[Problems to be solved by the invention]
However, when a member having such a thickness is used, there is a problem in that a deviation in the thickness fluctuates the gap, and the fluctuation in the gap increases. In order to avoid this problem, it is conceivable to cut the member after attaching the member to the charging roller, but it is time-consuming, and the tube constituting the member may rotate during cutting. Yes, it is not appropriate because of high cost.
[0008]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a charging device that can provide a gap between a charging roller and an image carrier with required accuracy at low cost and has a long service life, and an image forming apparatus having the charging device.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 is a charging device including a charging roller having a concave step at both ends and a ring-shaped regulating member engaged with the step. The mounting phases of the above-mentioned regulating member and the regulating member at the other end are not coincident with each other.
[0010]
According to a second aspect of the present invention, in the charging device according to the first aspect, a phase of attachment of the regulating member at one end and the regulating member at the other end is shifted by 180 ° from each other. I do.
[0011]
The invention according to claim 3 is a charging device having a charging roller having concave steps at both ends and a ring-shaped restricting member engaged with the steps, wherein the restricting member is attached to each end by a plurality. The mounting phases of the restricting members at the respective ends are not coincident with each other.
[0012]
According to a fourth aspect of the present invention, in the charging device according to the third aspect, the phases of attachment of the adjacent regulating members at respective ends are shifted from each other by 180 °.
[0013]
According to a fifth aspect of the present invention, in the cleaning device according to the fourth aspect, any one of the regulating members at one end and one of the regulating members at the other end are attached. It is characterized in that the phases match.
[0014]
According to a sixth aspect of the present invention, in the charging device according to any one of the first to fifth aspects, a material of the charging roller is a resin containing an ion conductive material.
[0015]
According to a seventh aspect of the present invention, in the charging device according to any one of the first to sixth aspects, the material of the regulating member is a resin having heat shrinkability and lower hardness than the charging roller. Features.
[0016]
According to an eighth aspect of the present invention, there is provided an image forming apparatus comprising: the charging device according to any one of the first to seventh aspects; and an image carrier charged by the charging device. Is characterized in that the regulating member abuts and the charging roller does not contact.
[0017]
According to a ninth aspect of the present invention, in the image forming apparatus of the eighth aspect, the image carrier is an organic photoconductor having a protective layer containing a filler on the surface.
[0018]
According to a tenth aspect of the present invention, in the image forming apparatus according to the eighth or ninth aspect, at least the charging device and the image carrier are integrally detachable from the image forming device main body. .
[0019]
【Example】
FIG. 1 schematically shows an image forming apparatus to which the present invention is applied. The image forming apparatus may be any known one such as a copying machine, a facsimile, and a printer, but the image forming apparatus in this embodiment is a printer. Although the image forming apparatus of this embodiment forms a single color image, it may form a color image.
[0020]
The image forming apparatus 100 has a higher heat capacity than plain paper generally used for copying and the like, 90K paper such as OHP sheets, cards, and postcards, thick paper having a basis weight of about 100 g / m ² or more, and envelopes. Any of the large so-called special sheets can be used as a sheet-shaped recording medium for fixing a toner image. The size of the recording medium may be a size conforming to a general standard such as A4 size or A3 size, or may be a size out of the standard formed by cutting or the like.
[0021]
The image forming apparatus 100 is a photoconductive photosensitive drum (hereinafter, referred to as a “photosensitive member”) in which an organic photosensitive material or the like is applied to the surface of a cylindrical image carrier that is driven to rotate in the direction of arrow A. ) 101, a charging device 110 as charging means for uniformly charging the photosensitive member 101, and a laser beam 103 for forming a latent image corresponding to image information on the charged photosensitive member 101 to perform optical scanning. And an exposure device (not shown) as exposure means for performing the exposure.
[0022]
The image forming apparatus 100 also includes a developing device 104 that is a developing unit as a developing unit that develops a latent image on the photoconductor 101 after exposure, and a static eliminator that neutralizes the developed photoconductor 101 by emitting static electricity 105a. A transfer unit 105 for electrostatically transferring the toner image on the photoconductor 101 obtained by development by the developing device 104 to a sheet (not shown) which is a transfer material as a sheet-shaped recording medium that is brought into close contact with the photoconductor 101 And a registration roller 108 that conveys the sheet at a predetermined timing to a transfer area 107 which is a portion where the photoconductor 101 and the transfer device 109 are opposed to each other.
[0023]
The image forming apparatus 100 also separates the transfer sheet from the photoconductor 101 by a separating claw 111 as a sheet separating unit, and scrapes off the transfer residual toner remaining on the photoconductor 101 after transfer from the photoconductor 101. Accordingly, a cleaning device 106 as a cleaning unit that cleans the photoconductor 101, and a static elimination device 102 as a static elimination unit that emits static elimination light 102a to the photoconductor 101 before charging by the charging device 110, thereby eliminating static electricity from the photoconductor 101 And
[0024]
The image forming apparatus 100 also includes a paper feed tray (not shown) on which paper is loaded, a paper feed roller (not shown) serving as paper feeding means for feeding the paper loaded on the paper feed tray toward the registration roller 108, and a transfer device 109. And a fixing device (not shown) as fixing means for fixing the toner image on the sheet on which the toner image on the photosensitive member 101 is transferred. The sheet after fixing is discharged to the outside of the image forming apparatus 100.
[0025]
The developing roller 104a provided in the developing device 104 rotates in the direction B that moves in the same direction as the direction A at a position facing the photoconductor 101. The cleaning device 106 removes toner and fine paper powder remaining on the surface of the photoconductor 101 by the blade 106a. As the transfer means, a transfer charger, a transfer belt, or the like can be used instead of the transfer roller. The photoconductor is an OPC photoconductor having an outer diameter of φ30 mm, and a protective layer (not shown) having a thickness of 5 μm including a filler is formed on the surface. The charging device 110 and the photoreceptor 101 are integrally formed as a process cartridge so as to be detachable from the main body of the image forming apparatus 100.
[0026]
As shown in FIG. 2, the charging device 110 includes a charging roller 11 having concave steps 10 at both ends, and tubes 13 a and 13 b as ring-shaped regulating members fitted into the respective steps 10. ing. The charging roller 11 has an outer diameter φ of 12 mm, a core 14 having a shaft 15 serving as a center of rotation, and a resin layer 16 formed around the core 14 and containing ABS as a main component. I have. The tubes 13a and 13b are PFA tubes made by Gunze, each having a thickness of “10P” and a thickness of 300 μm.
[0027]
In order to make the gap between the resin layer 16 of the charging roller 11 and the photoreceptor 101, that is, the charging gap 50 μm, the step 10 is formed by a groove having a width of 8 mm and a depth of 250 μm, and the tube 13 is a heat-shrinkable tube. It was fitted into the groove by heating for 20 minutes in an atmosphere of 120 ° C. The resin layer 16 contains an ion conductive material. The tubes 13a and 13b are cut out from the same tube as described below, and a material having a hardness lower than the hardness of the resin layer 16 is selected.
[0028]
As shown in FIG. 2, the mounting phase of the tube 13 a fitted to one end of the charging roller 11 and the tube 13 b fitted to the other end of the charging roller 11 with respect to the charging roller 11. Are mismatched from each other, and their phases are shifted from each other by 180 °. The reason for shifting the phase in this manner is as follows.
[0029]
As shown in FIG. 3, the general heat-shrinkable tube 13 has a deviation of about ± 10% of the wall thickness of a general grade due to a slight shift between the center of the outer diameter and the center of the inner diameter. FIG. 3 exaggerates the situation. When there is a deviation in the wall thickness, the value of the wall thickness deviation becomes smaller as the wall thickness becomes smaller, but there is a problem in strength and durability, so that it is necessary to use a tube having a certain wall thickness. In this embodiment, since one long heat-shrinkable tube 13 is cut to a required length and used, the cut-out tubes 13a and 13b have the same thickness deviation. Therefore, marking or the like is performed on the heat-shrinkable tube 13 before cutting or the cut-off tubes 13a and 13b and assembled to the charging roller 11 to control the phase of the thickness variation.
[0030]
Here, if the phases of the tubes 13a 'and 13b' at both ends are aligned as shown in FIG. 7, the thin portions of the tubes 13a 'and 13b' come into contact with the photosensitive member 101 at the same time, so that charging is performed. The central portion of the roller 11 easily contacts the photoconductor 101. It is easy to come into contact at the center because the photoreceptor 101 and the charging roller 11 are both cut and processed so that the outer diameter of the center is larger than the end by several tens of μm. Due to the influence of slight deviation of the degree. If the phases of the tubes 13a and 13b at both ends are shifted by 180 ° as in the present embodiment shown in FIG. 2, the thin portion does not come into contact with the photoconductor at both ends at the same time. The likelihood of contact of 110 is reduced.
[0031]
Further, as shown in FIG. 4, a plurality of tubes 13a1, 13a2 and 13b1, 13b2 may be attached to each end, in other words, to one side, in this embodiment. In this case, the mounting phases of the tubes 13a1 and 13a2 do not coincide with each other, and the phases of the adjacent tubes 13a1 and 13a2 are shifted from each other by 180 °, and the mounting phases of the tubes 13b1 and 13b2 do not coincide with each other. The phases of the adjacent tubes 13b1 and 13b2 are shifted from each other by 180 °.
[0032]
One of the tubes 13a1 and 13a2 at one end and one of the tubes 13b1 and 13b2 at the other end have the same mounting phase with each other, and one of the tubes 13a1 and 13b2 has the same mounting phase. The mounting phase of the other tube 13a2 of the end tubes 13a1 and 13a2 and the other tube 13b2 of the other end tubes 13b1 and 13b2 match each other. If the end portions are attached in such a manner that the phases are different from each other, the gap is determined by the thicker one, so that it is considered that the same accuracy as when the thickness deviation is reduced by half is obtained. Further, it is considered that the gap is further stabilized by attaching two tubes to one side as in this embodiment and further controlling the phases of the tubes at both ends.
[0033]
In order to confirm the effect of attaching the tube and the effect of shifting the phase of the tube, such as the stability of the gap, the charging roller 11 and the photosensitive member 101 having the above-described configuration are used, and the heat applied by the above-described composition, thickness, and method is used. Using a shrink tube, (1) a roller with a 8 mm wide tube attached at a 180 ° phase shift on both ends, and (2) a 2 mm 4 mm tube attached on each side with a 180 ° phase shift on both ends. Is a roller with (3) a roller with a tube of 8 mm in width mounted with the phases of both ends aligned at 0 °, and (4) a roller with a PET tape of 8 mm in width and 50 μm in thickness (without groove 10). ) Was used to carry out the experiment. Of the above (1) to (4), (1) and (2) apply the present invention, and will be described below as Examples 1 and 2, respectively. Hereinafter, Comparative Examples 1 and 2 will be described.
[0034]
Five rollers were manufactured for Examples 1 and 2 and Comparative Example 1, and four rollers were manufactured for Comparative Example 2. The gap between the main body of the roller and the photoreceptor 101 was set at the front side of the machine (F) and at the center (C). , At three points on the back side (R) of the machine. The gap was measured using a laser scan micrometer LSM-600 manufactured by Mitutoyo. Details of the measurement method are described in Japan Hardcopy 2001 Transactions.
[0035]
As a result of the experiment, the maximum value and the minimum value of the charging gap of each roller are shown in FIG. 5, and the fluctuation width of the charging gap (difference between the maximum value and the minimum value) is shown in FIG. In the figure, “0 °” indicates Comparative Example 1, “180 °” indicates Example 1, “2” indicates Example 2, and “tape” indicates Comparative Example 2, respectively. In the case of Comparative Example 1, the photoconductor and the charging roller were in contact with each other at the center of all five, but under other conditions, the photoconductor 101 did not come into contact with the roller body. The variation width of the gap is 40 to 100 μm in Comparative Example 1, whereas it is reduced to 40 to 80 μm in Example 1 and 20 to 60 μm in Example 2. The tape of Comparative Example 2 has the best gap stability in the initial gap stability range of 15 to 40 μm.
[0036]
When the durability was confirmed by a paper passing test, the rollers of Examples 1 and 2 showed no damage to the tube and the photosensitive member 101 at the tube contact portion even after passing 150,000 sheets, and the rollers in the image area were not stained. The image was minor and there was no problem. With the roller of Comparative Example 1, there was no damage to the tube or the photosensitive member 101 in the tube contact portion after 100,000 sheets were passed, but toner and the like adhered to the roller near the center of the image area, and density unevenness occurred in the image. did. The toner of the roller of Comparative Example 2 began to adhere to the adhesive layer protruding from the end of the tape after passing 10,000 sheets, and the mass of the adhered toner gradually grew to be charged after 50,000 sheets. The gap became too wide, and density unevenness due to abnormal discharge appeared in the image. Further, a lot of scratches were generated on the surface of the photoconductor 101 at the tape or the tape contact portion.
[0037]
Thus, from experiments and paper passing tests, in terms of durability, the charging device using a tube has better performance than the tape, and the charging device provided with a phase shift is better when using a tube. The charging device 110 provided with one tube at one end and the charging device 110 provided with two tubes with respect to the variation width of the gap, the charging device 110 provided with two tubes fluctuates. It turned out that the width was small.
[0038]
In this embodiment, when image formation is started by a predetermined operation, the photosensitive member 101 is driven to rotate, and the photosensitive member 101 is rotated in the direction A by the charging operation of the charging device 110 by the above-described configuration. The exposure process by the developing device 103, the developing process by the developing device 104, the transferring process by the transferring device 109, the cleaning process by the cleaning device 106, the discharging process by the discharging device 102, and the next image forming cycle in which the charging device 110 is charged again. However, in the process of forming an image, since the phases of the tubes 13a and 13b or the tubes 13a1, 13a2, 13b1, and 13b2 are shifted as described above, the charging roller 110 and the photoconductor 101 are not in contact with each other, and the charging device is not charged. Scratch of the photoconductor 110 and the photoconductor 101 is prevented, and the deterioration is largely suppressed. Together are performed over time good image formation preventing density unevenness. Further, the charging device 110 and the photosensitive member 101 constitute a process cartridge and have a cartridge form. However, since the charging device 110 and the photosensitive member 101 have a long life, they need to be replaced less frequently. In this case, since the charging device 110 and the photosensitive member 101 are exchanged at the same time, the work can be easily performed.
[0039]
The charging device to which the present invention is applied and the image forming apparatus having the same have been described. However, the mounting phase of the regulating member may be shifted by 180 ° as long as it is suitable for charging. When a plurality of regulating members are provided at one end, not only two but also three or more regulating members may be provided. In the present embodiment, the charging device 110 and the photosensitive member 101 constitute a process cartridge. However, the charging device 110 and the photosensitive member 101 may be formed into a process cartridge including other members and means. Does not necessarily constitute a process cartridge.
[0040]
【The invention's effect】
The present invention relates to a charging device having a charging roller having a concave step at both ends and a ring-shaped restricting member engaged with the step, wherein the restricting member at one end and the ring at the other end are provided. Since the mounting phases of the regulating member and the regulating member are different from each other, it is necessary to obtain a gap between the charging roller and the image carrier with the required accuracy even when the regulating member having a thickness deviation is used. And a low-cost charging device can be provided.
[0041]
Assuming that the phase of attachment of the regulating member at one end and the regulating member at the other end is shifted by 180 ° from each other, the phase is shifted by 180 ° so that the charging roller is less likely to contact the image carrier. It is possible to provide a charging device capable of obtaining a gap between the charging roller and the image carrier with required accuracy at low cost.
[0042]
The present invention relates to a charging device having a charging roller having a concave step at both ends and a ring-shaped restricting member engaged with the step, wherein a plurality of restricting members are attached to each end, Since the mounting phases of the regulating members at the portions are not coincident with each other, the phase is shifted at each end, so that the gap between the charging roller and the image carrier is increased by the thicker regulating member at the portion facing the image carrier. It is possible to obtain a stable gap between the charging roller and the image carrier with the required accuracy, even if a regulating member having a thickness deviation is used, and a low-cost charging device can be obtained. Can be provided.
[0043]
Assuming that the phases of attachment of the adjacent regulating members at each end are shifted from each other by 180 °, the phase is shifted by 180 ° so that the charging roller is less likely to be in contact with the image bearing member, and the required accuracy is reduced at low cost. A charging device capable of providing a gap between the charging roller and the image carrier can be provided.
[0044]
If one of the regulating members at one end and one of the regulating members at the other end have the same mounting phase, the distance between the charging roller and the image carrier is reduced. A charging device with a more stable gap can be provided.
[0045]
If the material of the charging roller is a resin containing an ion conductive material, a charging device that can determine the shape of the charging roller with high accuracy can be provided.
[0046]
Assuming that the material of the regulating member is a resin having heat shrinkage and a hardness lower than that of the charging roller, the regulating member is attached to the charging roller by heat shrinkage, so that an adhesive is unnecessary, and production can be performed at low cost and easily. In addition to this, it is possible to provide a charging device that hardly causes damage to the image carrier and contributes to a longer life of the image carrier because the hardness of the regulating member is lower than the hardness of the charging roller.
[0047]
According to another aspect of the present invention, there is provided an image forming apparatus comprising: the charging device according to claim 1; and an image carrier charged by the charging device. And the charging roller is in non-contact, so that it is possible to provide an image forming apparatus that includes a charging device exhibiting the above-described effects, performs good charging over a long period of time, and can perform good image formation. .
[0048]
If the image carrier is an organic photoreceptor having a protective layer containing a filler on the surface, not only the charging device but also the image carrier is inexpensive, and the image formation can extend the life of the image carrier. An apparatus can be provided.
[0049]
If at least the charging device and the image carrier are detachable integrally with the image forming apparatus main body, the charging device and the image carrier have a longer life, so that the frequency of replacement is reduced, and Since the charging device and the image carrier are integrated, even when the user replaces the charging device and the image carrier, the work can be easily performed and the gap between the charging roller and the image carrier can be reduced. It is possible to provide an image forming apparatus which can have a good size, can perform good charging, and can perform good image formation thereby.
[Brief description of the drawings]
FIG. 1 is a side view schematically showing a charging device to which the present invention is applied and an image forming apparatus having the same.
FIG. 2 is a partially cutaway side sectional view of the charging device shown in FIG.
FIG. 3 is a front sectional view showing a tube used in the charging device shown in FIG. 2;
FIG. 4 is a partially cutaway side sectional view of another configuration example of the charging device.
FIG. 5 is a correlation diagram showing gaps between various rollers and an image carrier.
FIG. 6 is a correlation diagram showing a variation width of a gap between various rollers and an image carrier.
FIG. 7 is a partially broken side sectional view showing a comparative example of the charging device.
[Explanation of symbols]
REFERENCE SIGNS LIST 10 step 11 charging roller 13a regulating member 13a1 regulating member 13a2 regulating member 13b regulating member 13b1 regulating member 13b2 regulating member 100 image forming apparatus 101 image carrier 110 charging device

Claims (10)

In a charging device having a charging roller having a concave step at both ends and a ring-shaped restricting member engaged with the step, the charging device includes a restricting member at one end and a restricting member at the other end. A charging device, wherein the mounting phases are different from each other. 2. The charging device according to claim 1, wherein the phases of the mounting of the regulating member at one end and the regulating member at the other end are shifted from each other by 180 degrees. In a charging device having a charging roller having a concave step at both ends and a ring-shaped restricting member engaged with the step, a plurality of the restricting members are attached to each end, and at each end, A charging device, wherein the mounting phases of the regulating members do not match each other. The charging device according to claim 3, wherein adjacent control members are attached to each other at 180 ° in phase at each end. 5. The cleaning device according to claim 4, wherein any one of the regulating members at one end and one of the regulating members at the other end have the same mounting phase. Charging device. The charging device according to any one of claims 1 to 5, wherein a material of the charging roller is a resin containing an ion conductive material. The charging device according to any one of claims 1 to 6, wherein a material of the regulating member is a resin having heat shrinkability and lower hardness than the charging roller. 8. An image forming apparatus comprising: the charging device according to claim 1; and an image carrier charged by the charging device, wherein the regulating member contacts the image carrier, and An image forming apparatus, wherein the charging roller is non-contact. 9. The image forming apparatus according to claim 8, wherein the image carrier is an organic photoreceptor having a protective layer containing a filler on the surface. 10. The image forming apparatus according to claim 8, wherein at least the charging device and the image carrier are integrally detachable from an image forming apparatus main body.

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