JP4314749B2 - Charging apparatus and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a charging device of an electrophotographic image forming apparatus used for a copying machine, a printer, or the like.
[0002]
[Prior art]
Conventionally, in an electrophotographic image forming apparatus used for a copying machine, a printer, or the like, a charging device for performing charging and discharging has been widely used.
[0003]
In an electrophotographic image forming apparatus, the surface of a charge acceptor such as a photosensitive drum is charged by a charging device, an electrostatic latent image is formed by exposure, and a developer is attached to the electrostatic latent image. Is developed to obtain a developed image, and the developed image is transferred to a recording paper or the like and fixed, and an image is formed on the recording paper.
[0004]
The charging device used in such an image forming apparatus includes a non-contact charging method using corona discharge and a contact charging method using a charging roll.
[0005]
However, a non-contact charging device using corona discharge has a problem that ozone and the like are generated in large quantities, and a problem of space and cost. Therefore, a conductive member is arranged so as to come into contact with the surface of the charge receptor. A contact-type charging method has been developed in which a voltage is applied to a conductive member to generate a discharge in a minute gap in the vicinity of the contact portion for charging.
[0006]
However, a structure using a conductive elastic roll is likely to have a complicated structure, and it is difficult to secure a stable minute gap by increasing the adhesion to the charge receptor. In addition, although a contact using a conductive brush is easy to obtain uniform contact, image defects due to uneven charging are likely to occur. Further, those using blades are contaminated with residual toner and external additives, and image quality defects and abnormal discharge are likely to occur.
[0007]
On the other hand, JP-A-4-249270 discloses a contact charging device using a film-like member that is easy to obtain stable contact with a simple structure and is inexpensive.
[0008]
However, since the disclosed contact charging device performs charging while pressing the film-like member against the charge receptor, the film-like member vibrates, the charging voltage tends to become unstable, and foreign matter such as toner is present on the contact portion. Has a problem that the charging voltage becomes non-uniform.
[0009]
In order to solve this problem, there is a method of applying a DC voltage with an AC voltage superimposed on a film-like member, but cleaning failure due to an increase in the surface energy of the charge receptor, wear of the charge receptor, generation of charging noise A new problem of low charging efficiency occurs.
[0010]
Therefore, a conductive member formed in a cylindrical shape with a flexible film-like member is supported by being movably contacted with the peripheral surface of the support roller, and the film-like member is bent to be a charge receptor. JP-A-4-232777 and JP-A-5-72869 disclose a charging device to be brought into contact.
[0011]
According to this charging device, there is an advantage that frictional charging between the conductive member and the charge receptor is reduced, and charging failure due to vibration can be eliminated. In addition, since the conductive member rotates even if foreign matter adheres, it is possible to avoid the occurrence of vertical stripe-like image quality defects.
[0012]
[Problems to be solved by the invention]
However, the charging devices disclosed in JP-A-4-232777 and JP-A-5-72869, when used for a long period of time, cause charging failure, leading to deterioration in image quality. In particular, in an image forming apparatus of a cleanerless system in which the cleaner is not attached to the charge receptor, the charging device rubs against the charge receptor to which untransferred residual toner or discharge products are attached. There is a problem that foreign matter attachment is promoted and charging failure occurs.
[0013]
In order to remedy such problems, a technique of installing a cleaning pad such as a brush or sponge on the surface of the charging device to remove dirt is disclosed in Japanese Patent Laid-Open Nos. 8-137207 and 9-90841. Has been.
[0014]
However, the disclosed charging device uses a sponge or the like as a cleaning member and holds foreign substances in cells on the surface of the sponge or the like, and the number of formed cells is limited, and the cleaning capability is limited. For this reason, there is a problem in that charging failure occurs when used for a long period of time, leading to a reduction in image quality.
[0015]
Particularly in the image forming apparatus of the cleanerless system, the adhesion of the foreign matter on the surface of the charging device is promoted and it is easy to cause abnormal discharge, so that the charging device becomes unusable at an early stage or causes a streak-like image quality defect. There is a bug.
[0016]
Further, there is a fatal defect that the toner adheres to the surface of the conductive member when the charging device rubs against the charge receptor.
[0017]
In the above, the problems of the conventional charging device have been described. However, in terms of causing various problems when dirt adheres to the surface, a transfer device or a charge eliminating device that operates on the same principle as the charging device performs charge transfer. This is a common problem in the devices (hereinafter, these devices are referred to as charging devices).
[0018]
In view of the above circumstances, an object of the present invention is to provide a charging device that can reliably remove foreign substances adhering to the surface of a charging device by a cleaning unit and charge a charged object uniformly and stably.
[0019]
[Means for Solving the Problems]
A charging device according to a first aspect of the present invention that achieves the above object includes a contact charging member that contacts or approaches a charged body moving in a predetermined movement direction and charges the charged body to a predetermined potential, and the contact charging member In the charging device including the cleaning member for cleaning the first charging portion, the contact charging member includes a first cross-sectional portion having a predetermined first radius of curvature and a second having a second radius of curvature smaller than the first radius of curvature. A rod-like support having a cross-sectional shape having a cross-sectional portion extending in the width direction intersecting with the moving direction of the charged body, and surrounding the support around or in contact with the charged body. A tube-shaped charging film that charges the charged object while circulating, and charges the charged object in contact with or in proximity to the charged object at the first cross-section. Grayed member, a charging film circulating movement around the said support, the charged film is characterized in that for cleaning at a position passing through the second cross section of the support.
[0020]
Here, it is preferable that the cleaning member is a cleaning brush that brushes the surface of the charged film disposed at a position facing the second cross-sectional portion of the support.
[0021]
Moreover, it is preferable that the said cleaning brush is a rotatable brush roll formed by winding a brush sheet around the roll shaft surface.
[0022]
Moreover, it is preferable to provide a driving means for supplying a driving force in the rotational direction to the brush roll.
[0023]
Furthermore, it is also a preferable aspect that a driving means for driving the brush roll with a speed difference from the charged film is provided so that the brush roll slides on the charged film.
[0024]
A charging device according to a second aspect of the present invention that achieves the above object includes a contact charging member that contacts or approaches a charged body moving in a predetermined movement direction and charges the charged body to a predetermined potential, and the contact charging member The contact charging member includes a first cross-sectional portion having a predetermined first radius of curvature and a radius of curvature larger than the first radius of curvature or a flat second. A rod-like support having a cross-sectional shape having a cross-sectional portion and extending in the width direction intersecting the moving direction of the charged body, and surrounding the support around or in contact with the charged body. A tube-shaped charging film for charging the charged object while circulating, and charging the charged object in contact with or in proximity to the charged object at the first cross section. The cleaning member is charged film circulating movement around the said support, the charged film is characterized in that for cleaning at a position passing through the second cross section of the support.
[0025]
Here, it is preferable that the cleaning member is a cleaning blade that contacts the charged film at the second cross-sectional portion of the support to remove dirt on the surface of the charged film.
[0026]
Here, it is preferable that the charging device of the first invention and the second invention is provided with a driving means for supplying a driving force in the rotational direction to the charging film.
[0027]
In addition, driving means for driving the charged film of the charging device according to the first and second aspects of the invention with a speed difference from the charged body so as to slide on the charged body is provided. Is preferred.
[0028]
Furthermore, the cleaning member of the charging device according to the first and second aspects of the present invention is provided with a power supply mechanism capable of applying an electric bias to the cleaning member, and at least during the cleaning operation. Preferably, the charged film is biased and cleaned by applying a bias voltage to the conductive cleaning member.
[0029]
Here, an electrically insulating layer is provided on the surface of the support of the charging device according to the second aspect of the invention or the surface of the charged film in contact with the support, and the cleaning member having conductivity is configured to bias and clean the charged film. In addition, it is preferable that a predetermined bias voltage is applied to the charged film.
[0030]
A charging device according to a third aspect of the present invention that achieves the above object includes a contact charging member that contacts or approaches a charged body that moves in a predetermined moving direction, and charges the charged body to a predetermined potential, and the contact charging member In the charging device including a cleaning member for cleaning the charging member, the contact charging member is a rotating roll extending in a width direction intersecting a moving direction of the charged body, and the cleaning member is in contact with the rotating roll. A plurality of holes for taking in dirt are formed on the contact surface with the rotating roll that rotates or vibrates.
[0031]
Here, the cleaning member is preferably a cylindrical member that rotates or vibrates as the contact charging member rotates.
[0032]
The cleaning member is preferably a flat plate member that vibrates or is fixedly held as the contact charging member rotates.
[0033]
Furthermore, it is also a preferable aspect that the cleaning member is provided with a power source for applying a bias voltage for causing the cleaning member to perform bias cleaning.
[0034]
An image forming apparatus according to a first aspect of the present invention that achieves the above object is the image forming apparatus that forms a toner image, and transfers and fixes the toner image to the recording medium to form an image on the recording medium. A contact charging member that moves in a direction, contacts a charged object made of a recording medium or a member used in any process of image formation, and transfers the charge to and from the charged object; and the contact A charging device including a cleaning member for cleaning the charging member, wherein the contact charging member has a first cross-sectional portion having a predetermined first radius of curvature and a second radius of curvature smaller than the first radius of curvature. A rod-like support having a cross-sectional shape having a second cross-sectional portion extending in the width direction intersecting the moving direction of the charged body, and the support in contact with or in proximity to the charged body surrounding the support. A tube-shaped charging film that charges the charged object while circulating around the body, and charges the charged object in contact with or in proximity to the charged object at the first cross section. And the cleaning member cleans the charged film circulating around the support at a position where the charged film passes through the second cross-sectional portion of the support.
[0035]
An image forming apparatus according to a second aspect of the present invention that achieves the above object is the image forming apparatus for forming a toner image and transferring and fixing the toner image to the recording medium to form an image on the recording medium. A contact charging member that moves in a direction and contacts a charged object made of a recording medium or a member used in any process of image formation, and charges the charged object to a predetermined potential; and the contact charged member A charging device having a cleaning member for cleaning the first charging portion, wherein the contact charging member has a first cross-sectional portion having a predetermined first radius of curvature and a radius of curvature larger than the first radius of curvature or a flat first radius. A rod-like support having a cross-sectional shape having two cross-sectional portions and extending in the width direction intersecting the moving direction of the charged body, and surrounding or contacting the charged body. And a tube-like charged film that charges the charged object while circulating around the support, and the charged object is brought into contact with or close to the charged object at the first cross section. The cleaning member is for cleaning the charged film circulating around the support at a position where the charged film passes through the second cross-sectional portion of the support. Features.
[0036]
An image forming apparatus according to a third aspect of the present invention that achieves the above object is the image forming apparatus for forming a toner image and transferring and fixing the toner image on the recording medium to form an image on the recording medium. A contact charging member that moves in a direction and contacts a charged object made of a recording medium or a member used in any process of image formation, and charges the charged object to a predetermined potential; and the contact charged member In the charging device including a cleaning member for cleaning the charging member, the contact charging member is a rotating roll extending in a width direction intersecting a moving direction of the charged body, and the cleaning member is in contact with the rotating roll. A plurality of holes for taking in dirt are formed on the contact surface with the rotating roll that rotates or vibrates.
[0037]
DETAILED DESCRIPTION OF THE INVENTION
First, an embodiment of the charging device of the first invention will be described.
[0038]
FIG. 1 is a schematic configuration diagram of an image forming apparatus using the charging device according to the first embodiment of the first invention.
[0039]
The image forming apparatus shown in FIG. 1 includes a charge receptor 1 that rotates in the direction of arrow A, and the charging device 2 uniformly charges the surface of the charge receptor 1 while being in contact with the charge receptor 1. 3 irradiates the charged charge receptor 1 surface with exposure light to form an electrostatic latent image, and the developing device 4 develops the electrostatic latent image with toner to form a toner image. The toner image formed on the surface of the charge receptor 1 is transferred to the recording medium 5 conveyed in the direction of arrow B by the transfer device 6 at the position facing the charge receptor 1 with the recording medium 5 interposed therebetween, and fixed. An apparatus (not shown) heats and fixes the recording medium 5.
[0040]
The charge receptor 1 after the toner image is transferred to the recording medium 5 is neutralized by the neutralization lamp 7, and then the charging device 2 charges the charge receptor 1, and the same image forming process is repeated thereafter.
[0041]
The image forming apparatus described here is a cleanerless system that does not include a cleaner that cleans residual toner on the charge receptor, but is not necessarily limited thereto.
[0042]
FIG. 2 is a schematic configuration diagram showing the charging device according to the first embodiment of the first invention.
[0043]
As shown in FIG. 2, the charging device 2 includes a power supply electrode 10 to which a bias voltage is applied. Around the power supply electrode 10, a rod-shaped support member 11 has a circular cross-sectional portion 12 and a circular cross-section thereof. The egg-shaped cross section having a cross-sectional portion 13 having a smaller radius of curvature than that of the portion is formed. A tube-shaped charging film 15 covers the support member 11, and the charging film 15 is formed around the support member 11. The charge receptor 1 is contacted at a position passing through the circular cross section 12 of the egg shaped cross section of the support member 11.
[0044]
A cleaning brush 16 for brushing the charging film 15 is provided at a position passing through the cross section 13 having a small radius of curvature in the egg-shaped cross section of the support member 11, and the cleaning brush 16 is driven to rotate by a driving member (not shown) to be conductive. Rub the adhesive film 15.
[0045]
Seal members 17 are provided on both sides of the charging film 15 closer to the circular cross section 12 than a position passing through the cross section 13 having a small radius of curvature with which the cleaning brush 16 rubs. The foreign matter is scattered from the surface of the charge receptor 1.
[0046]
Here, the charging device does not necessarily need to be in contact with the charge acceptor, and may be disposed close to the charging device. In this case, when a voltage is applied to the power supply electrode 10, the charging film 15 rotates as the charge receptor 1 rotates due to electrostatic force generated between the charge receptor 1 and the charge film 15. In addition, since a minute gap is formed between the charge receptor 1 and the charging film 15, stable charging is performed as in the case of contact. Further, when the charging film 15 is disposed close to the charge receiver 1, the amount of toner attached to the charging film 15 can be reduced.
[0047]
Since the cross-section of the support member is egg-shaped and the circular cross-section 12 and the cross-section 13 having a small radius of curvature are provided, the charging parameter and the cleaning parameter can be optimized independently. That is, since the cleaning brush 16 is provided in the cross-sectional portion 13 having a small radius of curvature, the cleaning performance can be improved as compared with the case where the cleaning brush 16 is provided in a portion having the same curvature radius as the cross-sectional portion 12.
[0048]
The authors' experimental results that the cleaning performance is improved in this way will be described later.
[0049]
Here, the radius of curvature of the circular cross section 12 is set to 5 mm, and the radius of curvature of the cross section 13 having a small radius of curvature is set to 1.5 mm. However, the present invention is not limited to this.
[0050]
The material of the charging film 15 may be any material as long as it has semiconductivity. For example, polyester, polyamide, polyethylene, polycarbonate, polyolefin, polyurethane, polyvinylidene fluoride, polyimide, PEN, PEK, PES, PPS, PFA, PVdF, ETFE , CTFE resin, or synthetic rubber such as silicon rubber, ethylene propylene rubber, butyl rubber, acrylic rubber, urethane rubber, and nitrile rubber mixed with conductive powder such as carbon black, metal powder, metal oxide, etc. can do. Alternatively, a polar rubber such as epichlorohydrin rubber, chloroprene rubber, or EPDM rubber, or a semiconductive inorganic material such as amorphous silicon may be deposited on an insulating substrate by thin film or thick film deposition.
[0051]
However, polar rubber or the like has a strong adhesion and a rough surface, so that uniform charging can be obtained by coating the surface with a low adhesion material or the like. Further, when formed by vapor deposition of a thin film or thick film, since the hardness is large, it is preferable to dispose the charge acceptor in a non-contact manner.
[0052]
The volume resistance of the charging film 15 is 10 ² Spark discharge is likely to occur at Ω · cm or less, but 10 ¹¹ If it exceeds Ω · cm, dot-like charging failure is likely to occur. ^Three Ω · cm to 10 ^Ten It is preferable to use within the range of Ω · cm.
[0053]
In particular, in order to set the applied voltage of the charging device relatively low, or to suppress the potential fluctuation in a high-speed machine having a process speed of 150 mm / s or more, the volume resistance is set to 10%. ^Four Ω · cm to 10 ⁷ Most preferably, it is used within the range of Ω · cm.
[0054]
The voltage applied to the charging film 15 may be a DC voltage, or may be a DC voltage superimposed with an AC voltage that is at least twice the charging start voltage. However, since the DC voltage superimposed with the AC voltage increases the surface energy of the charge receptor and the charging device and adversely affects the charge receptor, it is preferable to apply only the DC voltage.
[0055]
In order to apply a voltage to the charging film 15, for example, power may be supplied from the support member 11 inside the charging film 15, or from the power supply electrode 10 that circumscribes or inscribes the charging film 15, or a cleaning brush. 16 may also be supplied.
[0056]
The thickness of the charging film 15 is preferably about 10 μm to 1 mm.
[0057]
When touching the charge receptor, it is preferable to touch it as softly as possible, so it is better to make it thin.However, if it is too thin, durability will be reduced.Considering the straightness of the charge receptor and the Young's modulus of the film material Thickness can be determined.
[0058]
Young's modulus is 500 kg / cm ² To 30000kg / cm ² It is preferably shaped to be 23,000 kg / cm, especially when low stress is required for the charge receptor. ² The following is desirable. In the case of non-contact arrangement with respect to the charge receptor, the Young's modulus is 500 kg / cm. ² To 10,000kg / cm ² In a soft film material, the straightness should be 2 mm or less, and the Young's modulus is 10,000 kg / cm. ² In the above hard film material, the straightness may be 1 mm or less, and more preferably 0.5 mm or less.
[0059]
The power supply electrode 10 may be made of a material having conductivity and sufficient hardness to work against the cleaning brush. For example, polyester, polyamide, polyethylene, polycarbonate, polyolefin, polyurethane, polyvinylidene fluoride, polyimide, PEN, PEK, PES, PPS, PFA, PVdF, ETFE, CTFE, etc., or synthetic rubber such as silicon rubber, ethylene propylene rubber, butyl rubber, acrylic rubber, urethane rubber, nitrile rubber, carbon black, metal powder, metal oxide What mixed electroconductive powders, such as a thing, can be used. Alternatively, a polar rubber such as epichlorohydrin rubber, chloroprene rubber, or EPDM rubber, or a semiconductive inorganic material such as amorphous silicon may be deposited on an insulating substrate by thin film or thick film deposition.
[0060]
However, since polar rubber and the like have strong adhesion and a rough surface, it is necessary to coat the surface with a low adhesion material or the like.
[0061]
Furthermore, it is not limited to the polymer material mentioned above, For example, metals, such as SUS, aluminum, brass, may be sufficient.
[0062]
The form of the power supply electrode 10 may be any form as long as it can contact the front surface or the back surface of the charging film 15, for example, a block body made of sponge, fiber, felt, rubber, non-woven fabric, foam, resin, metal or the like. Etc. are preferred.
[0063]
It is sufficient that the resistance value of the power supply electrode 10 is smaller than the resistance value of the charging film 15, but the smaller the resistance value, the better the resistance value when the change in the resistance value due to environmental changes and changes with time is taken into account. ^Three More preferably, it is Ω · cm or less.
[0064]
The material of the support member 11 may be any material that is insulative and can be molded into a required shape when the power supply electrode 10 is not used. For example, polyester, polyamide, polyethylene, polycarbonate, polyolefin, polyurethane, polyfluoride Resin such as vinylidene, polyimide, PEN, PEK, PES, PPS, PFA, PVdF, ETFE, CTFE, or synthetic rubber such as silicone rubber, EPDM, ethylene propylene rubber, butyl rubber, acrylic rubber, urethane rubber, nitrile rubber, etc. can do.
[0065]
In addition, when the power supply electrode 10 is also used, a material adjusted to obtain a predetermined resistance value by mixing conductive powder such as carbon black or metal powder into the above-described material may be used.
[0066]
The form of the support member 11 may be any form as long as it can contact the inner surface of the charging film 15, for example, a block body made of sponge, fiber, felt, rubber, nonwoven fabric, foam, resin, metal, or the like. Etc. are preferred.
[0067]
However, sufficient hardness is required when the cleaning brush 16 functions as an opposing member, and the material and configuration of the member of the cleaning brush 16, the pressing force, and the cross-sectional portion 13 of the support member 11 having a small radius of curvature. It is determined by the radius of curvature.
[0068]
The shape of the support member 11 is such that the radius of curvature of the circular cross section 12 at the position where the charging film 15 contacts the charge receptor 1 is 5 mm to 10 mm, and the cross section of the small radius of curvature at the position where the charging film 15 is cleaned. It shape | molds so that the curvature radius of 13 may be 1 mm to 2 mm.
[0069]
In order to suppress variations in charging performance in the rotation axis direction of the charging device, it is necessary to secure a margin at the nip portion. The radius of curvature 12 of the circular cross section is 4 mm or more when the paper is an A4 plate, and the A3 plate. In this case, it is necessary to be 5 mm or more.
[0070]
In addition, the range of the curvature radius of the cross-section part 13 of a small curvature radius is mentioned later.
[0071]
The cleaning brush 16 has a bundle of hairs, for example, spirally planted on the surface of a metal or a roll-shaped member having a strength equivalent to that of a metal, and the density of the planting is 3800 / cm. ² To 6200 / cm ² It is preferable that
[0072]
This is because if the flocking density is too low, the cleaning ability is insufficient, and if the flocking density is too high, toner accumulates in the hair inside the brush, and the charged film 15 is soiled by the accumulated toner.
[0073]
The hair material may be an insulating material that is easily charged to the same polarity as the toner, such as polypropylene, but is not limited thereto.
[0074]
The cleaning brush 16 may rotate in the same direction as the charging film 15 at the position where the charging film 15 is cleaned, or may rotate in the opposite direction to the charging film 15.
[0075]
When a voltage is applied to this charging device from a DC power supply to the feeding electrode 10, air is ionized in a minute gap formed in the vicinity of the charging region where the charging film 15 and the charge receptor 1 are close to or in contact with each other, and the DC power supply When the negative polarity side is connected to the power supply electrode, negative ions flow to the charge acceptor 1 side and charge the charge acceptor 1 negatively. Further, since the conductive film 15 is pulled in the moving direction of the charge receptor 1 by the application of voltage, the contact between the charged film 15 and the charge receptor 1 is stabilized and the resistance of the charged film 15 is sufficiently large so that the discharge is not caused. It is stable and does not lead to spark discharge. Furthermore, since the charging film 15 is semiconductive and it is possible to prevent an excessive current from flowing in the gap portion in the charging region, the charge receptor 1 can be charged uniformly.
[0076]
In this charging device, charging power is supplied from the feeding electrode 10 to the charging film 15 via the support member 11. However, the feeding electrode 10 is brought into contact with the surface of the charging film 15 to directly supply power to the charging film 15. It is also possible to supply
[0077]
In this case, an insulating layer may be formed on the inner surface of the charging film 15, or the support member 11 may be made of an insulating material.
[0078]
When the conductive support member 11 is brought close to the charge receptor 1, it is effective when there is a risk that the discharge current leaks.
[0079]
The cleaning brush 16 can also serve as the power supply electrode 10.
[0080]
It is also possible to stretch the charging film 15 with two or more rolls having different diameters to change the radius of curvature of the position close to or in contact with the charge receptor 1 or the position to be cleaned.
[0081]
Next, the results of testing the charge characteristics of the charge receptor using the charging device of this embodiment will be described.
[0082]
FIG. 3 is a schematic configuration diagram showing a test apparatus for testing charging characteristics using the charging apparatus according to the first embodiment of the first invention.
[0083]
The test apparatus shown in FIG. 3 has a drum-shaped charge receptor 1 that rotates in the direction of arrow A with a conductive substrate 9 grounded, and a surface potential sensor that detects the surface potential around the charge receptor 1. 20 and a surface potential meter 21 for displaying the surface potential detected by the surface potential sensor 20 and a charge eliminating lamp 7 for eliminating the surface charge of the charge receptor 1 are arranged, and the surface in the arrow A direction in which the charge receptor 1 rotates. The charging device 2 of the present embodiment is disposed on the upstream side of the potential sensor 20.
[0084]
In the charging device 2, the support member 11 is fixed so that the charging film 15 comes into contact with the charge receptor 1 at a position passing through the circular cross section 12 of the egg-shaped cross section of the support member 11. A DC power supply 22 is connected to the feeding electrode 10 of the charging device 2 so that the output voltage of the DC power supply 22 can be arbitrarily changed.
[0085]
Here, the charging film 15 is made of flexible PVdF, nylon, and polycarbonate having a thickness of 30 μm and 50 μm, each having a volume resistivity of 10 respectively. ^Five Ω · cm, 10 ⁷ A test was performed using a material formed so as to have Ω · cm.
[0086]
FIG. 4 is a diagram showing the results of testing charging characteristics with the test apparatus shown in FIG.
[0087]
In FIG. 4, the horizontal axis represents the applied voltage applied to the power supply electrode 10, and the vertical axis represents the surface potential of the charge receptor 1 detected by the surface potential sensor 20.
[0088]
The graph in the figure shows the result of measuring the surface potential of the charge receptor 1 when the DC voltage applied to the power supply electrode 10 is changed from 0V to minus 2000V.
[0089]
It was confirmed that when the DC voltage exceeds minus 550V, the surface potential increases linearly, and when the DC voltage is minus 2000V, the surface potential reaches about minus 1450V. In addition, no abnormal discharge occurred during this period, and the charging film 15 obtained good results for all the materials shown in FIG.
[0090]
Next, the results of testing the cleaning performance of the charging device of this embodiment will be described.
[0091]
In this performance test, the curvature radius in the cross section of the small curvature radius in the egg-shaped cross section of the supporting member of the charging device is changed to 1.0 mm, 1.5 mm, 2.0 mm, and 5.0 mm, and the A3 version The amount of toner adhering to the charging film of the charging device was measured after printing two, five, and ten half-tone images on a full-size sheet. The curvature radius of the circular cross section is 5.0 mm.
[0092]
The test apparatus has the same configuration as the image forming apparatus shown in FIG.
[0093]
The DC voltage applied to the charging device is minus 900V.
[0094]
The cleaning brush is made of insulating polypropylene fibers with a hair height of 2 mm on a metal shaft with a diameter of 8 mm, and the planting density is 4650 fibers / cm. ² Aligned so that the amount of interference with the surface of the charge receptor is 500 μm, and is rotated by a motor in the same direction as the charged film so that the rotation speed is 1.8 times that of the charged film. Driven.
[0095]
5 and 6 are diagrams showing test results of cleaning performance of the charging device according to the first embodiment of the first invention.
[0096]
FIG. 5 and FIG. 6 show the same test results by changing the parameters taken as parameters.
[0097]
FIG. 5 is a graph showing, as a parameter, the radius of curvature r at the cross section of the small curvature radius in the egg-shaped cross section of the support member.
[0098]
In FIG. 5, the horizontal axis represents the number of printed half-tone images, and the vertical axis represents the toner accumulation amount per unit area on the charged film. The amount of toner deposited was measured using a minute toner amount measurement method.
[0099]
The graph in the figure shows only the curvature radius at the cross section of the small curvature radius in the egg-shaped cross section of the support member, and the curvature radius r is 1.0 mm, 1.5 mm, 2.0 mm, and 5.0 mm, respectively. The toner accumulation amount of the charging device changed as described above is represented.
[0100]
As is apparent from this graph, in the charging device with the support member having a circular cross section and the curvature radius r of 5.0 mm, as the number of printed sheets increases, the toner adhering to the charging film cannot be sufficiently cleaned and the amount of accumulation gradually increases. However, each charging device having a cross-section of egg-shaped cross section with a small radius of curvature and a radius of curvature r of 2.0 mm, 1.5 mm, and 1.0 mm does not accumulate toner even when the number of printed sheets exceeds 5. It can be seen that it converges to a certain value.
[0101]
This is because when the toner is scraped off with a cleaning brush, the toner is charged when the toner moves from a part having a small radius of curvature to a part having a large radius of curvature in the egg-shaped cross section, compared to the case where the toner moves laterally in a circular section. This is probably because the film is easily separated from the film.
[0102]
FIG. 6 is a graph showing the number of printed half-tone images as a parameter.
[0103]
In FIG. 6, the horizontal axis represents the curvature radius r of the cross section of the small curvature radius in the egg-shaped cross section of the support member, and the vertical axis represents the amount of toner adhering to the chargeable film.
[0104]
The graph in the figure represents the toner accumulation amount of the charging device after printing two, five, and ten full-tone images of A3 size paper.
[0105]
As is apparent from this graph, regardless of the number of prints, the toner accumulation amount becomes the minimum when the radius of curvature r of the cross section of the small radius of curvature of the elastic member is 1.5 mm, and the radius of curvature r is 1.0 mm. Sometimes it can be seen that it has increased.
[0106]
This is because, around the egg-shaped cross section of the support member for cleaning the charging film, the periphery of the cross section of the small curvature radius vibrates due to the deflection caused by the rotation of the cleaning brush, and the contact pressure between the brush and the charging film varies. This is presumably because toner is deposited on the surface of the charged film in a streak pattern in the direction of the rotation axis.
[0107]
This vibration can be solved by increasing the hardness of the support member. However, if the hardness is increased too much, the charge receptor may be damaged, or the charged film may be broken at the cross section of the small radius of curvature. The radius of curvature r is considered to be a practical limit of around 1.0 mm.
[0108]
Next, a second embodiment of the charging device according to the first invention will be described.
[0109]
FIG. 7 is a schematic configuration diagram showing a charging device according to a second embodiment of the first invention.
[0110]
Compared with the first embodiment, the second embodiment includes a drive source that rotates the charging film at a higher speed than the rotation speed of the charge receptor, and the cleaning brush rotates in the opposite direction to the charging film. However, the other components are the same, and the same components are denoted by the same reference numerals, and only the differences will be described.
[0111]
In FIG. 7, a cleaning brush 16 for cleaning a conductive film 15 is provided in the vicinity of a cross-section portion 13 having a small radius of curvature in the egg-shaped cross section of the support member material 11, and the cleaning brush 16 is charged by a driving member (not shown). The charging film 15 is rubbed and rubbed by being rotated in the opposite direction.
[0112]
A driving source 18 for forcibly driving the charging film 15 is provided between the position where the charging film 15 contacts the charge receptor 1 and the position where the seal member 17 seals the toner.
[0113]
By providing this drive source 18, the charging film 15 can be smoothly rotated and the cleaning performance of the cleaning brush 16 can be enhanced even when the cleaning brush 16 receives a rotational force in the reverse direction.
[0114]
Since the drive source 18 is provided downstream of the cleaning brush 16 in the rotation direction of the charging film 15, contamination by toner can be prevented and the load applied to the charging film 15 can be dispersed.
[0115]
Next, an embodiment of the charging device of the second invention will be described.
[0116]
FIG. 8 is a schematic configuration diagram showing a charging device according to an embodiment of the second invention.
[0117]
Compared with the first embodiment of the first invention, the charging device of the second invention has a semicircular cross section of the support member and a flat part (or a large radius of curvature), and the flat part has The difference is that the cleaning member is provided and the drive source that rotates the charging film at a speed higher than the rotation speed of the charge receptor is different.
[0118]
Therefore, the same components as those of the first embodiment of the first invention shown in FIG. 2 are denoted by the same reference numerals, and only the differences will be described.
[0119]
The charging device 2 shown in FIG. 8 has a power supply electrode 10 to which a bias voltage is applied. A support member 11 having a semicircular cross section is formed around the power supply electrode 10, and the support member 11 has a semicircular shape. The periphery of the cross section is covered with a tube-shaped charging film 15.
[0120]
The support member 11 has a flat portion 19, and the charging film 15 is higher than the rotational speed of the charge receptor 1 at a position in contact with the charging film near the boundary between the flat portion 19 and the semicircular cross-sectional portion 12. A drive source 18 that rotates at a speed is provided, and the charge film 15 rotates around the semicircular cross section of the support member 11 and receives charge at a position passing through the semicircular cross section 12 of the cross section of the support member 11. In contact with the body 1.
[0121]
Further, in the vicinity of the flat portion 19 of the cross section of the support member 11, there are a cleaning blade 25 for cleaning the charging film 15 and a seal for sealing the toner and the like cleaned by the cleaning blade 25 from being scattered on the surface of the charge receptor 1. The member 17 is provided at a position facing the cleaning blade 25 on the flat portion 19.
[0122]
Here, it is preferable that the semicircular cross-sectional portion 12 of the support member 11 in the vicinity of the position where the charging film 15 approaches or contacts the charge receptor 1 has a curvature radius of 5 mm to 10 mm.
[0123]
In addition, the flat portion 19 of the support member 11 where the cleaning blade 25 is disposed is preferably formed so as to have a large curvature radius portion with a curvature radius of 30 mm or more in order to stably perform cleaning. More preferably, the radius of curvature is 40 mm or more.
[0124]
Next, test results comparing the cleaning performance of three charging devices having different cleaning methods described in the two embodiments of the first invention and the second embodiment of the invention will be described.
[0125]
9 and 10 are graphs showing the results of the cleaning performance test.
[0126]
In this performance comparison test, the cross section with a small curvature radius of the egg-shaped cross section of the support member is 1.5 mm, the circular cross section is 5.0 mm, and the cleaning brush is disposed at a position passing through the small curvature section. , A type 1 charging device (described in the first embodiment of the first invention) in which the cleaning brush rotates in the same direction as the charging film at a speed 1.8 times the rotation speed of the charging film, type 1 Type 2 charging device (described in the second embodiment of the first invention) in which the cleaning brush rotates in the reverse direction at the same speed as the charging film, and the support member has a semicircular cross section Type 3 charging device having a radius of curvature of 5.0 mm, a cleaning blade disposed on a flat portion of a support member, and a charging film rotating at a high speed by a driving source (Embodiment of the second invention) As described above, and as a comparative example, among the type 1 charging devices, the charging device of comparative example 1 from which the cleaning brush is removed and the cleaning brush are provided but the driving member is not provided, so the driven member is driven by the charging film. For each of the rotating charging devices of Comparative Example 2, the transition of the accumulated toner amount during continuous operation and the rising state of the charging potential due to the accumulated toner were confirmed.
[0127]
The cleaning blade used in Type 3 was a standard setting of a urethane material having a thickness of 2 mm, a free length of 8 mm, an abutting angle of 22 degrees, and an interference amount of 1 mm with the charging film.
[0128]
The test apparatus has the same configuration as the image forming apparatus shown in FIG. 1 with respect to the amount of accumulated toner, and the test apparatus has the same configuration as the test apparatus shown in FIG. Therefore, the configuration diagram and the description thereof are omitted here.
[0129]
FIG. 9 is a graph showing the amount of toner deposited on the charged film when the image forming apparatus is continuously operated.
[0130]
In FIG. 9, the horizontal axis represents the number of full-tone half-tone images printed on A3 size paper, and the vertical axis represents the amount of toner deposited on the charged film. The amount of toner deposited was measured using a minute toner amount measurement method.
[0131]
The graphs in the figure show the results when two sheets, five sheets, and ten sheets are printed for each of the charging devices of types 1 to 3 having different cleaning methods and the charging devices of comparative example 1 and comparative example 2, respectively. The measurement result of the amount of accumulated toner is shown.
[0132]
As is apparent from the graph, in the charging devices of Comparative Example 1 and Comparative Example 2, the amount of accumulated toner rapidly increases as the number of printed sheets increases.
[0133]
On the other hand, in the type 1 to 3 charging devices, even when the number of printed sheets exceeds 5, the amount of adhered toner is kept low within a certain value.
[0134]
FIG. 10 is a graph showing a situation in which the charge potential of the charge receptor is increased by the adhered toner when the image forming apparatus is continuously operated.
[0135]
In FIG. 10, the horizontal axis represents the number of printed half-tone images of A3 size paper, and the vertical axis represents the charge potential of the charge receptor.
[0136]
The graph in the figure shows the charge acceptance when printing two, five, and ten sheets for each of the charging devices of types 1 to 3 having different cleaning methods and the charging devices of Comparative Example 1 and Comparative Example 2. The measurement result of the charged potential of the body is shown.
[0137]
As is apparent from this graph, in the charging devices of Comparative Example 1 and Comparative Example 2, when the number of printed sheets increases, the charging potential rises proportionally, and even though the number of printed sheets is only 10 sheets, V potential rises.
[0138]
This is presumably because abnormal discharge occurs when the amount of toner deposited on the charged film increases as shown in FIG.
[0139]
On the other hand, in the type 1 to type 3 charging devices, the amount of accumulated toner is suppressed to a low level that does not cause a problem.
[0140]
Next, based on the above performance test results, a running test was performed on the type 1 to type 3 charging devices to confirm the maintainability.
[0141]
When the rising limit of the charging potential was set to 10 V, the limit number of printed sheets of A3 size paper was 500 sheets for Type 1, 1000 sheets for Type 2, and 3000 sheets for Type 3.
[0142]
In a cleanerless system using a conventional charging device and equipped with a pseudo cleaner called a refresher, the limit number of prints is several tens under the same conditions. Considering the sacrifice of print productivity, this is extremely effective.
[0143]
The charging device of the present invention may be integrated with, for example, a toner cartridge and supported detachably on the image forming apparatus. Thus, by collecting the used cartridge and replacing only the charging film, the charging device can be recycled, which contributes to cost reduction.
[0144]
Next, an embodiment of the charging device of the third invention will be described.
[0145]
FIG. 11 is a schematic configuration diagram of an image forming apparatus using the charging device according to the first embodiment of the third invention.
[0146]
The image forming apparatus shown in FIG. 11 includes a charge receptor 30 that rotates, and a charging device 32 that includes a cleaning member 31 is applied with a bias voltage from a power source 33 and is close to or in contact with the charge receptor 30. The surface of the charge receptor 30 is uniformly charged.
[0147]
The exposure device 34 irradiates the charged charge receptor 30 with exposure light to form an electrostatic latent image, and the developing device 35 develops the electrostatic latent image with toner to form a toner image.
[0148]
The toner image formed on the surface of the charge receptor 30 is transferred to the recording medium 39 conveyed from the paper feed tray 37 by the conveying roll 38 by the transfer device 36 located opposite to the charge receptor 30 across the recording medium. The image is transferred, heated by the fixing device 40 and fixed on the recording medium 39.
[0149]
The toner remaining on the charge receptor 30 after the toner image is transferred to the recording medium 39 is cleaned by the cleaner 41, and the charge remaining on the charge receptor 30 is discharged by the charge removal lamp 42.
[0150]
The charge acceptor 30 is charged again by the charging device 32 after static elimination, and the same image forming process is repeated thereafter.
[0151]
Here, the cleaner 41 for cleaning the charge receptor 30 is provided, but the present invention is not limited to this, and a cleanerless system may be used.
[0152]
FIG. 12 is a schematic configuration diagram showing the charging device according to the first embodiment of the third invention.
[0153]
The charging device 32 includes a conductive rotary roll 32a, a power supply electrode 32b that applies a bias voltage to the rotary roll 32a, and a power source 33 connected to the power supply electrode 32b, and a charge receptor that rotates in a fixed direction A. It is rotatably supported at a position in contact with 30.
[0154]
Further, a cleaning member 31 is provided on the outer peripheral surface of the rotary roll 32a, and this cleaning member 31 is held by a holding member 43 so as to lightly contact the outer peripheral surface of the rotary roll 32a.
[0155]
The charge receptor 30 has a structure in which a photoconductive layer 30b is laminated on a cylindrical conductor substrate 30a. The conductor substrate 30a is electrically grounded 30c, and is transferred close to or in contact with a charging device 32 to which a bias voltage is applied. In this configuration, discharge is generated in a minute gap near the position to charge the surface of the charge receptor 30.
[0156]
Here, in the charging device, the rotary roll 32a is composed of a conductive roll-shaped member, but it is not always necessary to be in the form of a roll, and may be in the form of a tube or as shown in FIG. 2 or FIG. The charging device in the first embodiment may have an egg-shaped cross section.
[0157]
Although not shown, the power supply electrode 32b is configured such that both ends thereof are held by a holding member such as a bearing and a pressing member such as a spring and do not move except in the vertical direction. The rotating roll 32a is connected to the power supply electrode 32b. The pressing force lightly presses against the charge receptor 30 side, and a frictional force is generated between the rotating roll 32a and the charge receiving member 30 by the pressing force. When the charge receiving 30 rotates, the rotating roll 32a is driven by the frictional force. Although it is configured to rotate, it may be configured to rotate by a drive source.
[0158]
Here, the rotating roll 32a mixes an ionic conductive agent in epichlorohydrin rubber and has a volume resistivity of 10. ^Five It is adjusted to be Ω · cm and is formed into a φ14 mm rubber roll. Also, the power supply electrode 32b serves as a power supply to the rotary roll 32a and a holding member for the rotary roll 32a. It is configured to be slightly longer than the length of the rotary roll 32a in the longitudinal direction, and a charging voltage is applied from bearings holding both ends thereof.
[0159]
However, the rotating roll 32a is not limited to this, and the same material as the material of the charging film described in the first embodiment of the first invention shown in FIG. 2 can be used.
[0160]
Moreover, although the power supply 33 which can apply the direct voltage of a constant voltage is connected to the rotary roll 32a, you may connect the power supply which can apply the voltage which superimposed alternating current on direct current | flow.
[0161]
In such a charging device 32, when a predetermined voltage is applied from the DC power source 33 to the rotating roll 32a via the conductive power supply electrode 32b, the charging apparatus 32 is formed in the vicinity of the contact portion between the rotating roll 32a and the charge receptor 30. Air ionization occurs in the minute gaps.
[0162]
If the negative polarity side of the power source 33 is connected to the power supply electrode 32b, negative ions or electrons flow toward the charge acceptor 30 and are charged, and the positive ions reach the rotary roll 32a and are neutralized.
[0163]
Moreover, the rotating roll 32a is pulled in the moving direction of the charge receptor 30 by applying a voltage, and the contact between the rotating roll 32a and the charge receptor 30 is stabilized.
[0164]
Since the rotating roll 32a has a sufficiently large resistance, the discharge is stabilized and spark discharge is not caused. Further, by using a semiconductive member for the rotating roll 32a, it is possible to prevent an excessive current from flowing in any part of the gap, and the charge receptor 30 can be charged uniformly. is there.
[0165]
On the other hand, since the rotating roll 32a is rotated by the frictional force with the charge receptor 30, if the frictional force is small, the rotating roller 32a loses the pressure of the cleaning member 31, and the rotation may become unstable or stop. Therefore, the pressing force of the rotating roll 32a is increased to some extent, or the non-image area at the end of the charge receptor 30 and the surface roughness of the rotating roll 32a are roughened, or a highly adhesive material is used. A rotational force can be obtained.
[0166]
However, in a cleanerless image forming apparatus that does not include a cleaner that removes residual toner from the charge receptor 30, a large amount of toner may be present at the contact portion between the rotary roll 32 a and the charge receptor 30. Slip easily occurs depending on the diameter. In this case, if the external driving source is provided in the charging device 32, stable rotation can be obtained.
[0167]
Next, the cleaning operation of the cleaning member 31 will be described.
[0168]
Most of the toner remaining on the charge receptor 30 without being transferred by the transfer device 36 is cleaned by the cleaner 41. However, it is difficult to remove completely, especially in a low-temperature and low-humidity environment, since some of the toner and external additives pass through the cleaner 41, most of them adhere to the surface of the rotary roll 32a. End up.
[0169]
In general, since the residual toner is charged with a positive polarity, a voltage is applied, and the residual toner is very easily attached to the negatively charged rotating roll 32a.
[0170]
However, since the cleaning member 31 of this embodiment (described in detail in FIG. 13) is provided with a large number of through holes, the toner adhering to the surface of the rotary roll 32a is scraped off at the edge portions of the through holes, The toner can be taken into the cleaning member 31.
[0171]
Further, if a voltage is applied to the cleaning member 31 so that a predetermined potential difference is generated between the rotary roller 32a, the cleaned toner adheres to the periphery and the inner wall of the hole of the cleaning member 31 and is taken into the interior. The toner does not contaminate the rotary roll 32a again.
[0172]
In the present embodiment, both ends of the cleaning member 31 are held by the holding member 43. However, the holding member 43 is not limited to this configuration, and may be a configuration that holds the cleaning member 31 in the entire longitudinal direction or a configuration that is formed in a shaft shape inside the cleaning member 31.
[0173]
Here, the cleaning member 31 is held so as to rotate, but may be configured so as to vibrate.
Further, the cleaning member 31 may be formed of a conductive member so that a voltage is applied.
[0174]
FIG. 13 is a schematic perspective view of a cylindrical cleaning member shown as an example used in the first embodiment.
[0175]
As shown in FIG. 13, the cleaning member 31 is formed of a thin cylinder having a large number of through holes 45 on the surface.
[0176]
Here, the diameter of the through hole can be arbitrarily set according to the diameter of the toner stored in the developing device.
[0177]
For example, when the toner diameter is 5 to 6 μm, the diameter can be 10 μm.
[0178]
The cleaning member 31 has a volume resistivity of 10 by mixing carbon in polycarbonate resin. ^Five A tube adjusted to be Ω · cm and formed into a thin cylinder with a thickness of 200 μm and φ10 mm is used, and through-holes with a diameter of 50 μm and a pitch of 100 μm are uniformly formed on the surface.
[0179]
As the material of the cleaning member 31, the same material as that described as the charging film material according to the first embodiment of the first invention can be used.
[0180]
Although not shown here, the holding member that holds the cleaning member 31 is formed of a conductive resin, and is configured to be applied with a cleaning voltage divided from a DC power source.
FIG. 14 is a schematic perspective view of a cylindrical cleaning member shown as another example used in the first embodiment.
[0181]
As shown in FIG. 14, the cleaning member 31 may constitute a mesh tube 47 in which a single yarn or a plurality of yarns that are bundled or twisted are knitted into a mesh shape and subjected to cylinder folding.
[0182]
The yarn used in such a structure may be conductive or insulating, and fibers such as rayon, polyester, teflon, acrylic, nylon, cupra, aramid, wool, silk, etc., and a conductive agent mixed in these fibers. A conductive yarn, a metal wire, nylon teg, or the like can be used. In addition, weaving can be made by plain weaving, twill weaving, tube folding, or the like.
[0183]
Next, the results of testing the charge characteristics of the charge receptor using the charging device of this embodiment will be described.
[0184]
Since the test apparatus for which the charging characteristics have been tested has the same configuration as the test apparatus shown in FIG. 3 except for the charging apparatus, the drawing is omitted and the test environment will be described.
[0185]
The charging device includes the charging device 32 of the present embodiment shown in FIG. 12, the power supply electrode 32 b is configured in a roll shape, and the conductive rotating roll 32 a is a roll so as to contact the surface of the charge receptor 30. Both ends are supported by a holding member such as a bearing and a pressing member such as a spring, and a power source 33 is connected to the roll so that a DC charging voltage is applied.
[0186]
The power source 33 can arbitrarily change the output voltage, and the surface potential of the charge acceptor 30 that changes as the applied voltage increases or decreases is measured with a surface potentiometer.
[0187]
Furthermore, the cylindrical cleaning member 31 shown in FIG. 13 is disposed in the charging device 32, and a DC voltage minus 300 V divided from the power source 33 is applied.
[0188]
The rotating roll 32a used for the charging device 32 is mixed with an ionic conductive agent in epichlorohydrin rubber and has a volume resistivity of 10. ^Five A rubber roll adjusted to Ω · cm was used.
[0189]
The cleaning member 23 has a volume resistivity of 10 by mixing carbon in polycarbonate resin. ^Five A tube adjusted to Ω · cm and formed into a thin cylinder of φ10 mm, a tube with a thickness of 200 μm, PVdF and nylon having a volume resistivity of 10 ^Five A 50 μm and 100 μm thick flexible film tube formed into a thin cylinder with a diameter of 10 mm is formed so as to be Ω · cm, and 50 μm and 100 μm in thickness with an insulating polycarbonate resin molded into a thin cylinder with a diameter of 10 mm. Each molded flexible film tube was tested.
[0190]
As the test results, the same good results as shown in FIG. 4 were obtained for all the cleaning members using the above-described materials.
[0191]
That is, when the surface potential of the charge receptor was measured when a DC voltage of 0 V to -2000 V was applied from the DC power supply, the surface potential of the charge receptor began to rise rapidly from the applied voltage of about -550 V, and -2000 V It was confirmed that the voltage reached approximately -1450 V at an applied voltage of 1, and during this time, no abnormal discharge was observed due to the charging device.
[0192]
Therefore, it was shown that the charging device provided with the cleaning member of the present embodiment can perform uniform charging without uneven charging potential.
[0193]
Next, a test of the cleaning performance of the cleaning member used in the charging device of this embodiment will be described.
[0194]
The test was configured as an image forming apparatus of the cleanerless system shown in FIG. 11 for each cleaning member formed so that the through hole area ratio was 7%, 23%, 40%, 84%, and 97%. Made in the environment.
[0195]
The test method is to remove the charging device cleaning member, print 10 black images with 100% black toner density, attach the cleaning member to the charging device, and determine the amount of toner and the toner capture rate taken by the cleaning member. It was.
[0196]
FIG. 15 is a diagram illustrating a toner capture rate at which the cleaning member takes in toner when the area ratio of the through holes formed in the cleaning member is changed.
[0197]
In FIG. 15, the horizontal axis represents the area ratio of the through holes, and the vertical axis represents the ratio (toner capture ratio) of the toner amount taken in by the cleaning member out of the toner amount adhering to the rotating roll.
[0198]
As is apparent from the figure, the toner capture rate increases as the number of through holes is increased and the area ratio of the holes increases, and the toner capture rate becomes extremely high especially when the area ratio occupied by the through holes exceeds 80%. I understood it.
[0199]
When the area ratio occupied by the through-holes increases, the edge portion that scrapes off the toner adhering to the outer peripheral surface of the rotating roll increases, which is considered to increase the toner capture rate.
[0200]
As described above, the cleaning member shown in this embodiment has a large toner removing effect even under a condition where a large amount of toner adheres to the charging device, and the area ratio occupied by the through holes is increased to about 80%. The toner capture rate can be 90% or more.
[0201]
By adjusting the size of the cleaning member, the cleaning member can be used without replacing it during the lifetime of the image forming apparatus.
[0202]
Next, the results of running tests using the image forming apparatus shown in FIG. 11 will be described.
[0203]
As a sustainability test, a running test for forming 10,000 prints was conducted, and changes in the images were confirmed. After printing 10000 prints, troubles caused by so-called foreign matter adhesion, such as density reduction and black streak, did not occur. In addition, toner adhesion to the outer peripheral surface of the rotating roll was hardly observed.
[0204]
For comparison, the same test was performed with the cleaning member removed from the charging device. As a result, fogging gradually occurred in the white image portion from the time when about 1000 sheets were printed, and black stripes were generated when 3000 sheets were printed. Became prominent.
[0205]
The outer peripheral surface of the rotating roll when 3000 sheets were printed was covered with toner or an external additive, and remarkable foreign matter adhesion was observed on the charge receptor at the position corresponding to the black streaks appearing on the print.
[0206]
From the above results, it is clear that the cleaning member according to the present invention functions effectively and prevents the toner and the like from adhering to the rotating roll.
[0207]
Next, the cleaner of the image forming apparatus shown in FIG. 11 was removed to constitute an image forming apparatus of a cleanerless system, and the image quality was confirmed by a similar running test.
[0208]
In addition to the charging device used in the present embodiment, as a comparative example, the same test was performed on a charging device having a configuration in which the cleaning member was removed.
[0209]
As a result, in the initial stage, prints with the same image quality were obtained both when the charging device of this embodiment was used and when the charging device of the comparative example was used. In the image forming apparatus using the charging device of the example, fogging gradually occurred in the white image portion, and after printing 100 sheets, vertical streak-like image quality defects and charging defects occurred.
[0210]
This is presumably because foreign matters such as toner adhered to the outer peripheral surface of the charging electrode and partially accumulated in a streak shape.
[0211]
On the other hand, when the charging device of the present embodiment was used, an image quality that was the same as that of the initial printing could be obtained even after printing 1000 sheets.
[0212]
Therefore, it has been clarified that the charging device according to the first embodiment of the third invention can be suitably used also in an image forming apparatus of a cleanerless system in which a cleaner is not provided for a charge receptor.
[0213]
From the above results, in order to maintain the charging potential uniformly over a long period of time, a cleaning member having a large number of through holes formed on the surface is brought into contact with the outer peripheral surface of the rotating roll, and the toner adhering to the outer peripheral surface of the rotating roll is removed. It has been proved that the configuration according to the present invention in which the outer peripheral surface of the rotating roll is always refreshed while being captured is very effective.
[0214]
Next, a charging device according to a second embodiment of the charging device of the third invention will be described.
[0215]
In the second embodiment, the configuration of the charging device is the same as that in the first embodiment, but the cleaning member used in the charging device is different in the form of a flat plate. Therefore, only the difference will be described.
[0216]
FIG. 16 is a schematic perspective view of a flat plate-like cleaning member shown as an example used in the second embodiment.
[0217]
The cleaning member 31 shown in FIG. 16 is a flat plate member 46, which is configured to form the same material as that of the cleaning member shown in the first embodiment into a sheet shape and contact with a rotating roll.
[0218]
As shown in the figure, the flat plate member 46 is provided with a plurality of rows of through holes 45 in the process direction B, and the through holes 45 arranged in the process direction B are formed by shifting the through holes from each other. Since one of the through holes 45 is fixed and held in contact with the outer peripheral surface of the toner, the toner adhering to the surface of the rotating roll can be removed evenly.
[0219]
Such a configuration eliminates the need for a cleaning member rotation mechanism, which is effective for cost reduction and size reduction.
[0220]
The flat plate member 46 may be configured to vibrate so as to reciprocate at a right angle or a certain angle to the process direction.
[0221]
Also in this embodiment, it was confirmed that good charging characteristics, a toner capture rate, and a running test result can be obtained as in the charging device in the first embodiment.
[0222]
Next, an embodiment of the image forming apparatus of the first invention will be described.
[0223]
FIG. 17 is a schematic configuration diagram of an image forming apparatus showing an embodiment of the first invention.
[0224]
In the present embodiment, the charge receptor and the paper correspond to the charged object.
[0225]
The image forming apparatus shown in FIG. 17 includes a charge receptor 50 that rotates in the direction of arrow A, and the surface of the charge receptor 50 is uniformly charged while the first charging device 51 is in contact with the charge receptor 50. The second charging device 55 in the position facing the charge receptor 50 with the paper sandwiched between the toner image developed by the developing device 53 with the toner formed by the exposure device 52 and the toner is developed in the direction of arrow B. Transfer to the moving paper. The charge receptor 50 after the toner image is transferred to the sheet is neutralized by the third charging device 59.
[0226]
The first charging device 51, the second charging device 55, and the third charging device 59 are similar to the embodiment of the charging device of the first invention shown in FIG. In the periphery of the feeding electrode 64, a rod-shaped support member 63 forms an egg-shaped cross section having a circular cross section and a cross section having a small curvature radius smaller than that of the circular cross section, A tube-shaped charged film 61 covers the support member 63, and the charged film 61 passes through a circular cross section of the egg-shaped cross section of the support member 63 while rotating around the support member 63. In contact with the charge acceptor 50 in position.
[0227]
A cleaning brush 62 for brushing the charging film 61 is provided at a position passing through a cross section having a small radius of curvature in the egg-shaped cross section of the support member 63. The cleaning brush 62 is driven to rotate by a driving member (not shown) and charged film. 61 is rubbed.
[0228]
The charging device which is an embodiment of the charging device of the first invention can charge the charge receptor 50 without causing abnormal discharge even if the charge receptor 50 is dirty, so that the first and second charging devices It is also preferable. In addition, the charging device which is an embodiment of the charging device of the first invention is suitable as the second charging device because it has a longer lifetime than the charge eliminating lamp.
[0229]
In the present embodiment, the charging device according to the first embodiment is applied to all charging devices. However, the charging device is not necessarily applied to all charging devices.
[0230]
Here, an example of an image forming apparatus that directly transfers a recording medium has been described. However, for example, an image forming apparatus that uses an intermediate transfer belt described in FIG. 18 or an image forming apparatus that uses an intermediate transfer drum is used. It can be applied to the charging device.
[0231]
Next, an embodiment of the image forming apparatus of the second invention will be described.
[0232]
FIG. 18 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment of the second invention.
[0233]
In this embodiment, the charge receptor, the intermediate transfer belt, and the paper correspond to the charged body.
[0234]
In FIG. 18, four charge receptors 50 rotating in a predetermined direction are arranged in series. A first charging device 51 comes into contact with each charge acceptor 50 to uniformly charge the charge acceptor 50, and an exposure device 52 irradiates the charge acceptor 50 with exposure light to form an electrostatic latent image. . The charge receiver 50 on which the electrostatic latent image is formed is developed with toner by the developing device 53 to form a toner image.
[0235]
The intermediate transfer belt 65 that circulates contacts each charge receptor 50 to form a nip portion, and the toner image formed on each charge receptor 50 is a second charging device 55 arranged at each primary transfer position. Primary transfer.
[0236]
The toner image on the intermediate transfer belt 65 that has been primarily transferred is secondarily transferred onto the sheet conveyed from the sheet tray 58 by the fourth charging device 56 disposed at the secondary transfer position, and the toner image on the sheet is transferred. The image is heated and pressurized by the fixing device 57 and fixed on the paper to form a fixed image.
[0237]
Each charge receptor 50 to which the toner image has been primarily transferred has its residual charge removed by the third charging device 59 and is prepared for the next image forming process to be charged by the first charging device 51. The intermediate transfer belt 65 on which the toner image has been secondarily transferred is cleaned with toner remaining on the intermediate transfer belt 65 by the fifth charging device 60 to prepare for the next secondary transfer process.
[0238]
Here, as the first to fifth charging devices, the charging device which is the embodiment of the charging device of the second invention described with reference to FIG. 8 is used.
[0239]
The charging device according to the embodiment of the charging device of the second invention can charge the charge receptor 50 and the intermediate transfer belt 65 without causing abnormal discharge even if the charge receptor 50 and the intermediate transfer 65 belt are dirty. Therefore, it is suitable as the first, second and fourth charging devices. In addition, the charging device which is an embodiment of the charging device of the second invention is suitable as the third charging device because it has a longer lifetime than the charge eliminating lamp, and is less likely to damage the intermediate transfer belt than the cleaner. It is also suitable as a fifth charging device.
[0240]
In the present embodiment, the charging device according to the first embodiment is applied to all charging devices. However, the charging device is not necessarily applied to all charging devices.
[0241]
Although the image forming apparatus using the intermediate transfer belt has been described here, an intermediate transfer drum may be used instead of the intermediate transfer belt. Further, the image forming apparatus of the second invention can be applied not only to the method using the intermediate transfer member but also to the image forming apparatus described in FIG.
[0242]
Next, an embodiment of the image forming apparatus of the third invention will be described.
[0243]
FIG. 19 is a schematic configuration diagram of an image forming apparatus showing an embodiment of the third invention.
[0244]
In the present embodiment, the charge receptor and the paper correspond to the charged object.
[0245]
The image forming apparatus shown in FIG. 19 includes a charge receptor 50 that rotates and moves, and the first charging device 51 uniformly charges the surface of the charge receptor 50 while approaching or in contact with the charge receptor 50. The exposure device 52 irradiates the uniformly charged surface of the charge receptor 50 with exposure light to form an electrostatic latent image, and the developing device 53 develops the electrostatic latent image with toner to form a toner image. Let
[0246]
The toner image formed on the surface of the charge receiver 50 is conveyed from the paper feed tray 58 by the conveyance roll 76 by the second charging device 55 located opposite the charge receptor 50 and the paper 54. 54, and is heated by the fixing device 57 to be fixed on the paper 54.
[0247]
The toner remaining on the charge receiver 50 after the toner image is transferred to the paper 54 is cleaned by the cleaner 75, and the charge remaining on the charge receiver 50 is discharged by the third charging device 59. .
[0248]
Here, the third charging device 59 can also be used as the cleaner 75.
[0249]
The charge acceptor 50 is charged again by the first charging device 51 after static elimination, and the same image forming process is repeated thereafter.
[0250]
The first, second, and third charging devices include a conductive rotary roll 70a, a power supply electrode 70b that applies a bias voltage to the rotary roll 70a, and a power source 73 connected to the power supply electrode 70b. It is rotatably supported at a position in contact with the charge receptor 50 that rotates in the direction. Further, a cleaning member 71 is provided on the outer peripheral surface of the rotary roll 70a, and this cleaning member 71 is held by a holding member 72 so as to be in light contact with the outer peripheral surface of the rotary roll 70a.
[0251]
Here, as the first, second and third charging devices, a charging device which is an embodiment of the charging device according to the third invention is used, and the cleaning member 71 has a third charging device according to the third invention. The cylindrical member or flat plate member described in the first embodiment or the second embodiment is used.
[0252]
Therefore, the charging device of this embodiment is suitable as the first and second charging devices because the charge acceptor 50 can be charged without causing abnormal discharge even if the charge acceptor 50 is dirty. Moreover, the charging device which is an embodiment of the charging device of the third invention is suitable as the third charging device because it has a longer lifetime than the charge eliminating lamp.
[0253]
In the present embodiment, the charging device according to the first embodiment is applied to all charging devices. However, the charging device is not necessarily applied to all charging devices.
[0254]
In this embodiment, an example of an image forming apparatus that directly transfers a recording medium has been described. However, for example, an image forming apparatus that uses an intermediate transfer belt described with reference to FIG. 18 or an image forming apparatus that uses an intermediate transfer drum. Can be applied to all charging devices.
[0255]
【The invention's effect】
As described above, the charging devices of the first and second inventions can optimize the cleaning parameters of the charging device independently of the charging parameters, and the charging devices of the third invention. The apparatus can maintain a stable charging performance for a long period of time because it can contact the charging electrode of a wide shape and reliably take in the foreign matter inside the cleaning member to refresh the surface of the charging electrode. Furthermore, since the image forming apparatus according to the first, second and third inventions uses the above-described charging device as a charging device or a transfer device, it is possible to provide a good image with stable charging performance over a long period of time. it can. In particular, this effect does not change even when a cleaner is not provided on the charge receptor, so that the charging performance in an image forming apparatus such as a cleaner-less can be dramatically improved. Further, these charging devices can be suitably used not only as a transfer device or a charging device of an image forming apparatus, but also as a low-cost and long-life static eliminator, or as a cleaner that does not damage a belt or the like. .
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus using a charging device according to a first embodiment of the first invention.
FIG. 2 is a schematic configuration diagram illustrating a charging device according to a first embodiment of the first invention.
FIG. 3 is a schematic configuration diagram showing a test apparatus for testing charging characteristics using the charging apparatus according to the first embodiment of the first invention.
4 is a diagram showing a result of testing charging characteristics with the charging device shown in FIG. 3; FIG.
FIG. 5 is a diagram illustrating a cleaning performance test result of the charging device according to the first embodiment of the first invention;
FIG. 6 is a diagram illustrating a cleaning performance test result of the charging device according to the first embodiment of the first invention;
FIG. 7 is a schematic configuration diagram showing a charging device according to a second embodiment of the first invention.
FIG. 8 is a schematic configuration diagram illustrating a charging device according to an embodiment of the second invention.
FIG. 9 is a graph showing the results of a cleaning performance test.
FIG. 10 is a graph showing the results of a cleaning performance test.
FIG. 11 is a schematic configuration diagram of an image forming apparatus using the charging device according to the first embodiment of the third invention.
FIG. 12 is a schematic configuration diagram illustrating a charging device according to a first embodiment of the third invention.
FIG. 13 is a schematic perspective view of a cylindrical cleaning member shown as an example used in the first embodiment.
FIG. 14 is a schematic perspective view of a cylindrical cleaning member shown as another example used in the first embodiment.
FIG. 15 is a diagram illustrating a toner capture rate at which a cleaning member takes in toner.
FIG. 16 is a schematic perspective view of a flat plate-shaped cleaning member shown as an example used in the second embodiment.
FIG. 17 is a schematic configuration diagram of an image forming apparatus showing an embodiment of the first invention.
FIG. 18 is a schematic configuration diagram showing an image forming apparatus according to an embodiment of the second invention.
FIG. 19 is a schematic configuration diagram of an image forming apparatus showing an embodiment of a third invention.
[Explanation of symbols]
1,30,50 charge acceptor
2,32 Charging device
3,34,52 Exposure equipment
4, 45, 53 Development device
5,39 Recording medium
6,36 Transfer device
7,42 Static elimination lamp
10 cored bar
11, 63 support member
12 Circular cross section
13 Cross section of small radius of curvature
15 Charged film
16 Cleaning brush
17 Seal member
18 Drive source
19 Flats
20 Surface potential sensor
21 Surface potential meter
22 DC power supply
25 Cleaning blade
30a Conductor board
30b Photoconductive layer
30c grounding
32a, 70a Rotating roll
32b, 64, 70b Feed electrode
33,73 power supply
37, 58 Paper tray
38 Transport roll
40, 57 fixing device
41,75 cleaner
43, 73 Holding member
45 Through hole
46 Flat plate member
47 mesh tube
51 First charging device
54 paper
55 Third Charging Device
56 Fourth charging device
59 Second charging device
60 fifth charging device
61 Charged film
62, 71 Cleaning member
65 Intermediate transfer belt

Claims (5)

In a charging device including a contact charging member that transfers charge to and from a charged body that contacts or approaches the charged body that moves in a predetermined movement direction, and a cleaning member that cleans the contact charging member ,
The contact charging member has a cross-sectional shape having a first cross-sectional portion having a predetermined first radius of curvature and a second cross-sectional portion having a second radius of curvature smaller than the first radius of curvature. A rod-like support extending in the width direction intersecting the moving direction of the body, and a tube shape surrounding the support and charging the charged object while circulating around the support in contact with or in proximity to the charged object And charging the charged object in contact with or in proximity to the charged object at the first cross-sectional portion,
The cleaning member is disposed at a position opposite to the second cross-sectional portion of the support, and the surface of the charged film is brushed at a position where the charged film passes through the second cross-sectional portion of the support. A charging device characterized by being a cleaning brush . 2. The charging device according to claim 1, further comprising driving means for driving the charged film with a speed difference from the charged body so that the charged film slides on the charged body. The cleaning member is conductive and includes a power supply mechanism capable of applying an electrical bias to the cleaning member, and applying a bias voltage to the conductive cleaning member at least during a cleaning operation. 2. The charging device according to claim 1, wherein the charged film is biased and cleaned. An electrically insulating layer is provided on at least the surface of the support or on the surface of the charged film that contacts the support, and the conductive cleaning member biases and cleans the charged film and has a predetermined bias on the charged film. The charging device according to claim 3, wherein a voltage is applied. In an image forming apparatus that forms a toner image and forms an image on the recording medium by transferring and fixing the toner image to the recording medium.
  A contact charging member that moves in a predetermined moving direction and that is in contact with or in proximity to a member to be used in any process of image formation or a charged member made of a recording medium; A charging device comprising a cleaning member for cleaning the contact charging member,
  The contact charging member has a cross-sectional shape having a first cross-sectional portion having a predetermined first radius of curvature and a second cross-sectional portion having a second radius of curvature smaller than the first radius of curvature. A rod-like support extending in the width direction intersecting the moving direction of the charged body, and a tube surrounding the support and charging the charged body while circulating around the support in contact with or in proximity to the charged body A charged film having a shape, and charging the charged object in contact with or in proximity to the charged object at the first cross-sectional portion,
  The cleaning member is disposed at a position opposite to the second cross-sectional portion of the support, and the surface of the charged film is brushed at a position where the charged film passes through the second cross-sectional portion of the support. An image forming apparatus comprising a cleaning brush.

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