JP3850778B2 - Charging device and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a charging device that includes a charging roller and charges an image carrier such as a photosensitive member, and an image forming apparatus such as a copying machine, a facsimile, and a printer having the charging device.
[0002]
[Prior art]
In an image forming apparatus such as a copying machine, a printer, and a facsimile, a toner image is formed and supported on a sheet-like 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 photosensitive member. In one of the toner image forming steps, 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, a charging device using a charger method such as Scorotron has been the mainstream, but this method has a problem that a large amount of discharge products such as ozone is generated. The type of charging device that comes into contact with the image carrier has been widely used. In such a type of charging device, dirt such as toner adheres to the roller or the like over time, and if uneven charging causes uneven charging, image formation is adversely affected. This was a major factor in determining the lifetime of the device.
[0004]
Therefore, as shown in [Patent Document 1], in a charging device using a roller, a film is attached to the end of the roller in order to reduce contamination of the roller, and a small gap is formed between the photoreceptor and the roller. There has been proposed a technique for forming a film and suppressing the adhesion of dirt. In addition, as shown in [Patent Document 2], a technique has been proposed in which a step or a groove is provided at the end of a roller and a member for forming the gap is attached as a method of forming a gap using a film other than a film. On the other hand, an elastic member such as rubber or sponge is generally used as the material of the roller, but as shown in [Patent Document 3], a roller using a resin is also known.
[0005]
However, when the roller is rubber, there is a problem that it is difficult to process with high accuracy by cutting, and the thermal expansion is large, so that the gap is likely to vary depending on the environment. On the other hand, the resin roller has high hardness and is easy to cut, but because of its high hardness, if a film-like member is used as a member for forming a gap, this member will wear over time. There were problems such as. Further, when an organic photoconductor is used as the image carrier, the photoconductor may be damaged when a member forming a gap comes into contact therewith. 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 photoconductor are not deteriorated and good durability can be obtained. A technique of constituting with a thick elastic body has been proposed.
[0006]
[Patent Document 1]
JP 2001-194868 [Patent Document 2]
Japanese Patent Laid-Open No. 2002-55508 [Patent Document 3]
Japanese Patent Laid-Open No. 2002-55508
[Problems to be solved by the invention]
However, when such a thick member is used, there is a problem that the deviation of the thickness causes the gap to fluctuate and the gap fluctuates. In order to avoid this problem, it is conceivable to cut the member after attaching the member to the charging roller. However, it takes time and the tube constituting the member may rotate during cutting. Yes, and it is expensive, so it is not appropriate.
[0008]
SUMMARY OF THE INVENTION An object of the present invention is to provide a charging device having a long life and a gap between a charging roller and an image carrier having a required accuracy at a low cost, and an image forming apparatus having the charging device.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the invention described in 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, wherein the regulating member is The outer diameter center and the inner diameter center deviate from each other, and the thickness variation phase in the circumferential direction of the charging roller when attached to the charging roller is different from that of the regulating member at one end and the other. characterized in that between the regulating member of the end portion do not match each other.
[0010]
According to a second aspect of the present invention, in the charging device according to the first aspect, the thickness fluctuation phases are shifted from each other by 180 ^° .
[0011]
According to a third aspect of the present invention, there is provided a charging device including a charging roller having a concave step at both ends and a ring-shaped restricting member engaged with the step, wherein the restricting member includes an outer diameter center and an inner diameter center. A plurality of attachments at each end of the charging roller, and the phase of the wall thickness variation in the circumferential direction of the charging roller is mutually controlled by a plurality of regulating members attached to each end. It is characterized by disagreement.
[0012]
According to a fourth aspect of the present invention, in the charging device according to the third aspect , the thickness variation phases of the regulating members adjacent to each other are shifted from each other by 180 ^° .
[0013]
According to a fifth aspect of the present invention, in the charging device according to the fourth aspect, any one of the regulating members at one end and the one of the regulating members at the other end are the meat. It is characterized in that the phases of thickness fluctuations coincide.
[0014]
According to a sixth aspect of the present invention, in the charging device according to any one of the first to fifth aspects, the material of the charging roller is a resin containing an ionic 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]
The invention described in claim 8 is an image forming apparatus comprising the charging device according to any one of claims 1 to 7 and an image carrier charged by the charging device. Is characterized in that the regulating member abuts and the charging roller is non-contact.
[0017]
According to a ninth aspect of the present invention, in the image forming apparatus according to the eighth aspect, the image carrier is an organic photoreceptor 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 can be integrally attached to and detached from the main body of the image forming apparatus. .
[0019]
【Example】
FIG. 1 shows an outline of an image forming apparatus to which the present invention is applied. The image forming apparatus may be any known apparatus such as a copying machine, a facsimile machine, or a printer, but the image forming apparatus in this embodiment is a printer. The image forming apparatus of the present embodiment forms a single color image, but may form a color image.
[0020]
The image forming apparatus 100 has a heat capacity larger than that of plain paper such as plain paper generally used for copying, 90K paper such as an OHP sheet, card, postcard, thick paper equivalent to a basis weight of about 100 g / m ² or more, and envelope. Any large so-called special sheet can be used as a sheet-like recording medium for fixing a toner image. The size of the recording medium may be a size other than the standard that is formed by cutting or the like, in addition to the size that forms a general standard such as A4 size or A3 size.
[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 rotationally driven in the direction of arrow A. ) 101, a charging device 110 as a charging means for uniformly charging the photosensitive member 101, and a laser beam 103 that forms a latent image corresponding to image information on the charged photosensitive member 101 to emit light. And an exposure apparatus (not shown) as an exposure means to be performed.
[0022]
The image forming apparatus 100 also includes a developing device 104 serving as a developing unit that develops a latent image on the photoconductor 101 after exposure, and a static eliminator that discharges the photoconductor 101 after development by emitting a neutralizing light 105a. 105 and a transfer unit that electrostatically transfers a toner image on the photoconductor 101 obtained by development by the developing device 104 to a sheet (not shown) that is a transfer material as a sheet-like recording medium that is brought into close contact with the photoconductor 101. And a registration roller 108 that conveys a sheet to a transfer region 107 that is a portion where the photosensitive member 101 and the transfer device 109 face each other at a predetermined timing.
[0023]
The image forming apparatus 100 also scrapes the separation claw 111 as a sheet separating unit for separating the transferred paper from the photoconductor 101 and the transfer residual toner remaining on the photoconductor 101 after the transfer from the photoconductor 101. Accordingly, the cleaning device 106 as a cleaning unit that cleans the photosensitive member 101 and the neutralization device 102 as a neutralizing unit that emits the neutralizing light 102a to the photosensitive member 101 before charging by the charging device 110 to neutralize the photosensitive member 101. And have.
[0024]
The image forming apparatus 100 also includes a sheet feeding tray (not shown) on which sheets are stacked, a sheet feeding roller (not shown) serving as a sheet feeding unit that feeds sheets stacked on the sheet feeding tray toward the registration rollers 108, and a transfer device 109. And a fixing device (not shown) as fixing means for fixing the toner image on the sheet onto which the toner image on the photosensitive member 101 is transferred. The sheet after fixing is discharged outside the image forming apparatus 100.
[0025]
The developing roller 104 a provided in the developing device 104 rotates in the B direction that moves in the same direction as the A direction at a position facing the photoconductor 101. The cleaning device 106 removes toner remaining on the surface of the photoreceptor 101, fine paper dust, and the like by a 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 30 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 photosensitive member 101 are integrated into a process cartridge so that the charging device 110 and the photosensitive member 101 can be attached to and detached from the image forming apparatus 100 main body.
[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 a cored bar 14 having an outer diameter φ of 12 mm and a shaft 15 that forms the center of rotation, and a resin layer 16 mainly composed of ABS formed around the cored bar 14. Yes. The tubes 13a and 13b are Gunze PFA tubes, and “10P” having a thickness of 300 μm is used.
[0027]
In order to set the gap between the resin layer 16 of the charging roller 11 and the photosensitive member 101, that is, the charging gap to 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 inserted into the groove by heating for 20 minutes in an atmosphere of 120 ° C. The resin layer 16 contains an ionic conductive material. The tubes 13 a and 13 b are cut 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 phase of attachment of the tube 13 a fitted in one end of the charging roller 11 and the tube 13 b fitted in the other end of the charging roller 11 to the charging roller 11. Are inconsistent with each other and their phases are shifted by 180 ° from each other. The reason for shifting the phase in this way is as follows.
[0029]
As shown in FIG. 3, in a general heat shrinkable tube 13, there is a deviation of about ± 10% of the wall thickness in a general grade due to a slight deviation between the center of the outer diameter and the center of the inner diameter. FIG. 3 exaggerates the situation. If there is a deviation in the wall thickness, the thinner the wall thickness, the smaller the value of the wall thickness deviation. However, there is a problem in terms of strength and durability, so it is necessary to use a tube with some wall thickness. In the present embodiment, one long heat-shrinkable tube 13 is cut into a necessary length and used, so that the cut-out tubes 13a and 13b have a thickness deviation in the same manner. Therefore, marking or the like is performed on the heat-shrinkable tube 13 before being cut or the tubes 13a and 13b where the tubes are cut and assembled to the charging roller 11 to control the phase of wall thickness fluctuation.
[0030]
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 ′ are in contact with the photosensitive member 101 at the same time. It is easy to contact the photosensitive member 101 at the center of the roller 11. It is easy to make contact at the central portion because both the photosensitive member 101 and the charging roller 11 are cut, and the outer diameter of the central portion is several tens μm larger than the end portion, or the photosensitive member 101 and the charging roller 11 are parallel. This is due to the effects of slight deviations in 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 portions do not contact the photoconductor at both ends at the same time. The possibility of contact with 110 is reduced.
[0031]
Furthermore, as shown in FIG. 4, a plurality of tubes, that is, two tubes 13 a 1, 13 a 2, and 13 b 1, 13 b 2 in this embodiment may be attached to each end, in other words, one side. In this case, the mounting phases of the tubes 13a1 and 13a2 are inconsistent with each other, the phases of the adjacent tubes 13a1 and 13a2 are shifted by 180 ° from each other, and the mounting phases of the tubes 13b1 and 13b2 are inconsistent with each other. The phases of the adjacent tubes 13b1 and 13b2 are attached so as to be shifted from each other by 180 °.
[0032]
And one tube 13a1 of the tubes 13a1 and 13a2 at one end and one tube 13b1 of the tubes 13b1 and 13b2 at the other end are in phase with each other, and The current tube 13a2 of the end tubes 13a1 and 13a2 and the current tube 13b2 of the other end tubes 13b1 and 13b2 are in phase with each other. Thus, if it attaches to each edge part so that a phase may differ, since a gap is determined by the thicker one, it will be thought that the precision equivalent to the case where a thickness deviation is reduced by half is acquired. In addition, it is considered that the gap is more stable by attaching two tubes on each side as in this embodiment and managing the phase of the tubes at both ends.
[0033]
In order to confirm the effect of attaching the tube, such as the stability of the gap, and the effect of shifting the phase of the tube, the charging roller 11 and the photosensitive member 101 having the above-described configuration are used, and the heat attached by the above-described composition, thickness, and method. Using a shrinkable tube, (1) a roller with an 8 mm wide tube attached with a 180 ° phase shift at both ends, and (2) two 4 mm wide tubes on one side, with a phase shifted 180 °, (3) Roller with 8 mm wide tube with both ends aligned at 0 °, (4) Roller with 8 mm wide and 50 μm thick PET tape (no groove 10 formed) ) Was used to conduct the experiment. Of the above-mentioned (1) to (4), (1) and (2) are applied to the present invention and will be described below as Examples 1 and 2, respectively, and (3) and (4) are respectively Comparative examples 1 and 2 will be described below.
[0034]
For each of Examples 1 and 2 and Comparative Example 1, five rollers were prepared, and for Comparative Example 2, four rollers were prepared. The gap between the roller body and the photosensitive member 101 was set to the front side (F) and the center (C). , Measured at three points on the machine back side (R). For measurement of the gap, a laser scanning micrometer LSM-600 manufactured by Mitutoyo was used. Details of the measurement method are described in the Japan Hardcopy 2001 paper collection.
[0035]
As experimental results, the maximum value and the minimum value of the charging gap of each roller are shown in FIG. 5, and the fluctuation range 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. In the case of Comparative Example 1, the photoconductor and the charging roller were in contact with each other at the center portion, but the photoconductor 101 and the roller main body were not in contact under other conditions. Regarding the fluctuation range of the gap, it is 40 to 100 μm in Comparative Example 1, but is reduced to 40 to 80 μm in Example 1 and 20 to 60 μm in Example 2. The tape of Comparative Example 2 is most excellent in initial gap stability with a gap fluctuation range of 15 to 40 μm.
[0036]
When durability was confirmed by a paper passing test, the rollers of Examples 1 and 2 did not damage the tube or the photosensitive member 101 of the tube contact portion even after the passage of 150,000 sheets, and the rollers in the image area were also stained. There was no problem with the image. In the roller of Comparative Example 1, the tube and the photoconductor 101 at the tube contact portion were not damaged after passing 100,000 sheets. However, the toner adheres to the roller near the center of the image area, and density unevenness occurs in the image. did. In the roller of Comparative Example 2, the toner started to adhere to the adhesive layer protruding from the end of the tape after 10,000 sheets were passed, and the adhered toner mass gradually grew and charged after 50,000 sheets. The gap became too wide and density unevenness due to abnormal discharge appeared in the image. In addition, many rubbing scratches were generated on the surface of the photosensitive member 101 at the tape or tape contact portion.
[0037]
In this way, from the experiment and paper passing test, the charging device using the tube has better performance than the tape in terms of durability, and when the tube is used, the charging device provided with the phase shifted is better. Compared with the charging device 110 provided with one tube at one end and the charging device 110 provided with two tubes, the charging device 110 provided with two tubes fluctuates with respect to the variation width of the gap. I found that the width was small.
[0038]
In this embodiment, when image formation is started by a predetermined operation, the photosensitive member 101 is rotationally driven and the photosensitive member 101 is rotated in the A direction. 103, the developing process by the developing device 104, the transferring process by the transfer 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 charging by the charging device 110 is received again. However, in the image forming process, the charging roller 110 and the photosensitive member 101 are not in contact with each other because the phases of the tubes 13a and 13b or the tubes 13a1, 13a2, 13b1, and 13b2 are shifted as described above. 110 and the photoreceptor 101 are prevented from being scratched, and deterioration is greatly suppressed. Together are performed over time good image formation preventing density unevenness. The charging device 110 and the photosensitive member 101 constitute a process cartridge and are in the form of a cartridge. However, since the charging device 110 and the photosensitive member 101 have a long service life, the replacement frequency is low, and replacement is possible. In some cases, the charging device 110 and the photosensitive member 101 are replaced at the same time, so that the work can be easily performed.
[0039]
The charging device to which the present invention is applied and the image forming apparatus having the charging device have been described above. However, the phase of attaching the regulating member may be shifted by a phase different from 180 ° within a range suitable for charging. When a plurality of restricting members are provided at one end, not limited to two, but three or more restricting 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 as a process cartridge including other members and means. The process cartridge does not necessarily have to be configured.
[0040]
【The invention's effect】
The present invention provides 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 is displaced from the center of the outer diameter and the center of the inner diameter. The phase of the wall thickness variation in the circumferential direction of the charging roller when attached to the charging roller is inconsistent between the regulating member at one end and the regulating member at the other end. Therefore, even when a regulating member having a normal thickness deviation is used, a gap between the charging roller and the image carrier with a required accuracy can be obtained, and a low-cost charging device is provided. be able to.
[0041]
Assuming that the phase of the wall thickness fluctuation is 180 ^° from each other, the charging roller is less likely to come into contact with the image carrier by shifting the phase by 180 ^°. It is possible to provide a charging device capable of obtaining a gap between the two.
[0042]
The present invention provides 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 is displaced from the center of the outer diameter and the center of the inner diameter. The shape is a plurality, and is attached to each end of the charging roller, and the phase of wall thickness variation in the circumferential direction of the charging roller is inconsistent with each other by the plurality of regulating members attached to each end . The gap between the charging roller and the image carrier is determined by the thicker regulating member at a portion facing the image carrier by shifting the phase at each end, and a regulation member having a normal thickness deviation is used. Even if it is used, it is possible to obtain a stable gap between the charging roller and the image carrier with necessary accuracy, and to provide a low-cost charging device.
[0043]
If the phase of the thickness variation of the regulating member adjacent each end are shifted from each other by 180 ^°, the charging roller by shifting the phase 180 ^° are required at low cost hardly contacted by the image bearing member It is possible to provide a charging device capable of obtaining a gap between the charging roller and the image carrier with high accuracy.
[0044]
If the any one bract the thickness variation of the phase of any one the other end of the regulating member of the regulating member at one end are matched, the charging roller and the image bearing It is possible to provide a charging device that further stabilizes the gap between the body and the body.
[0045]
If the material of the charging roller is a resin containing an ionic conductive material, a charging device that can determine the shape of the charging roller with high accuracy can be provided.
[0046]
If the material of the regulating member is a resin having heat shrinkage and lower hardness than the charging roller, the regulating member is attached to the charging roller by thermal shrinkage, so no adhesive is required, and production is inexpensive and simple. In addition, since the hardness of the regulating member is lower than the hardness of the charging roller, the image bearing member is hardly damaged, and a charging device that contributes to extending the life of the image bearing member can be provided.
[0047]
The present invention is an image forming apparatus comprising the charging device according to any one of claims 1 to 7 and an image carrier to be charged by the charging device, wherein the regulating member includes the regulating member. Since the charging roller is in non-contact with the charging roller, it is possible to provide an image forming apparatus that includes the charging device that exhibits the above-described effects, can be charged well 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 image formation that can extend the life of the image carrier An apparatus can be provided.
[0049]
If at least the charging device and the image carrier can be integrally attached to and detached from the main body of the image forming apparatus, the charging device and the image carrier have a long life, and the replacement frequency is low. In addition, 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 be of a good size and can perform good charging and good image formation.
[Brief description of the drawings]
FIG. 1 is a side view schematically illustrating a charging device to which the present invention is applied and an image forming apparatus having the charging device.
2 is a partially broken 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 broken 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 fluctuation range of a gap between various rollers and an image carrier.
FIG. 7 is a partially broken side sectional view showing a comparative example of a charging device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Level | step 11 Charging roller 13a Control member 13a1 Control member 13a2 Control member 13b Control member 13b1 Control member 13b2 Control member 100 Image forming apparatus 101 Image carrier 110 Charging apparatus

Claims (10)

In a charging device having a charging roller having a concave step at both ends, and a ring-shaped regulating member engaged with the step,
The regulating member has a shape in which the center of the outer diameter is shifted from the center of the inner diameter, and the phase of the wall thickness variation in the circumferential direction of the charging roller when attached to the charging roller is the regulation of one end. A charging device, wherein the member and the regulating member at the other end are inconsistent with each other. The charging device according to claim 1 , wherein phases of the thickness fluctuations are shifted from each other by 180 ^° . In a charging device having a charging roller having a concave step at both ends, and a ring-shaped regulating member engaged with the step,
The regulating member has a shape in which the center of the outer diameter is shifted from the center of the inner diameter, and a plurality of the regulating members are attached to each end of the charging roller, and the phase of the wall thickness variation in the circumferential direction of the charging roller is A charging device characterized in that the plurality of restricting members attached to the part do not match each other. 4. The charging device according to claim 3 , wherein the thickness variation phases of the regulating members adjacent to each other are shifted from each other by 180 ^degrees . In the charging device according to claim 4, that any one bract the thickness variation of the phase of the regulating member of any one the other end of the regulating member at one end matches A charging device.   6. The charging device according to claim 1, wherein a material of the charging roller is a resin containing an ionic conductive material.   7. The charging device according to claim 1, wherein the 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 abuts on the image carrier. 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 a surface thereof.   10. The image forming apparatus according to claim 8, wherein at least the charging device and the image carrier are detachable integrally with the image forming apparatus main body.

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