JP2004333617A - Charging device, transfer device, and image forming apparatus having charging device or transfer device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prolong the life of an image carrier and improve the image quality of an image forming apparatus by reducing a discharge in a minute gap between the image carrier and a charging member that is in contact with the image carrier, thereby preventing wear of the image carrier or sticking of discharge products to the image carrier. <P>SOLUTION: The charging device charges up an electrostatic latent image carrier 81 by using a cylinder member 16 as a charging electrode. The charging device includes: the cylinder member 16 formed of a flexible material that is resilient to force exerted from the outside of its face; and an attracting means 18 that is disposed within the cylinder member and applies force to a part that does not face the electrostatic latent image carrier 81 of the cylinder member, the force being exerted to attract the part toward the inside of the cylinder. By causing the force to act on the attracting means 18, the cylinder member 16 is brought into contact with the electrostatic latent image carrier 81. In addition, the cylinder member 16 is changed so as to have a curvature approximate to that of the electrostatic latent image carrier 81. Thus, the length β of the minute gap α between the cylinder member 16 that generates a discharge a and the electrostatic latent image carrier 81 is increased. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a charging device, a transfer device, and an image forming apparatus provided with the charging device or the transfer device, and more specifically, a charging device for applying a charge used to form an electrostatic latent image, A transfer device for transferring a visible image visualized corresponding to an electrostatic latent image, and an image of a copying machine, a printer, or the like using the electrophotographic method, including the charging device or the transfer device It relates to a forming apparatus.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an image forming apparatus used for an electrophotographic copying machine or a printer, a charging device is used in a series of processes including charging, developing, and cleaning of an image carrier such as a so-called photosensitive member. .
[0003]
Also, in the process of temporarily transferring the toner image formed on the image carrier to a transfer member such as an intermediate transfer member, or retransferring to a transfer member such as a recording medium to finally form an image, A transfer device using the same principle as a charging device is used similarly to a process of forming an image by directly transferring an image to a recording medium on a transfer target.
[0004]
A corotron has been widely used as a charging device for charging an image carrier.
[0005]
The corotron is effective as a means for uniformly charging the image carrier, but requires a high voltage power supply of several kilovolts to charge the image carrier to a predetermined potential. In addition, since ozone and nitrogen oxides are generated by corona discharge, it is not preferable from the viewpoint of causing deterioration of rubber parts and image carriers.
[0006]
Therefore, as a charging device replacing the corotron, various shapes of conductive members such as rollers, brushes, blades, films, and belts are brought into contact with the image carrier, and the image carrier is charged by applying a voltage to the conductive member. Contact type charging devices have been developed.
[0007]
FIG. 17 shows a charging device using a general charging roller. FIG. 17 is a schematic cross-sectional view for explaining an example of the charging device. In the drawing, reference numeral 50 denotes a metal core made of stainless steel, aluminum, or the like, and reference numeral 51 denotes a conductive rubber as a charging electrode or an elastic member such as a sponge. Reference numeral 81 denotes a photosensitive drum as an image carrier. N is a contact portion (nip portion) between the roller and the photosensitive drum. In this configuration, when the drum is rotated in a state where a voltage obtained by superimposing a DC voltage on an AC voltage is applied to the core metal 50 by the high-voltage AC power supply 6 and the DC power supply 8, the roller rotates according to the rotation and the roller 51 and the photosensitive drum are rotated. Discharge a is started in the minute gap α of 81, and the surface of the photosensitive drum 81 is charged.
[0008]
The conductive elastic member used for the elastic member 51 is, for example, a foamed member such as polystyrene, polyolefin, polyester, or polyamide, or a flexible member obtained by foaming EPDM or urethane, such as carbon or tin oxide. There is one in which conductive powder is dispersed.
[0009]
Generally, in an actual charging roller, a layer for preventing seepage of oil contained in elastic rubber, a layer for adjusting resistance and dielectric constant, a layer for protecting the surface from deterioration due to electric discharge, and the like are provided on the surface of the roller 51. Can be
[0010]
Further, as in Patent Document 1, a tube having a large tensile stress is provided on the surface of the elastic layer 51 for the purpose of suppressing set of the elastic layer when the elastic layer is left in a pressed state for a long time. It has also been suggested.
[0011]
These contact-type charging devices have the advantages that very little ozone or nitrogen oxides are generated and that a low voltage source is required as compared with a corotron. In addition, a method of charging an image carrier by applying a voltage obtained by superimposing a DC voltage on an oscillating voltage such as an AC voltage to these contact-type charging devices is excellent in charging uniformity, and in particular, a method in which a charging electrode and an image carrier are charged. It is possible to avoid abnormal charging caused by abnormal discharge. In addition, since it is difficult for dirt such as toner to adhere, and even if it adheres, poor charging hardly occurs due to its excellent charging ability, it is most often introduced to the market.
[0012]
However, in such a charger that applies an oscillating voltage, when the process speed of the image carrier is high, potential unevenness occurs due to a ripple component included in the oscillating voltage, and this causes image unevenness on the image carrier. Sometimes appeared.
[0013]
On the other hand, if the frequency of the oscillating voltage is increased to prevent this, bipolar discharges are repeated many times, and the image bearing member is easily worn and has a short life.
[0014]
In addition, since a bipolar discharge occurs in the minute gap between the image carrier and the charging member or the transfer-receiving member that comes into contact with the image carrier, a discharge product is generated although the amount is extremely small compared to the corotron. I do. The discharge products easily adhere to the image carrier, and may cause image defects such as image deletion.
[0015]
Further, in order to remove the discharge products adhered to the image carrier with a cleaner, measures such as rubbing the surface of the image carrier are required, which may cause a problem such as shortening of the life of the image carrier.
[0016]
In order to avoid the above-mentioned problem of the wear of the image carrier, a voltage waveform that gradually rises toward the peak of the amplitude and then sharply falls as a vibration voltage waveform with little damage to the image carrier is patented. Proposed in reference 2.
[0017]
However, the method is poor in theoretical grounds, and the reproducibility of the effect was poor in actual experiments.
[0018]
Further, for the purpose of avoiding the problem of wear of the image carrier, the roller-shaped power supply member and the support roller contact the image carrier during a predetermined nip region and move with the movement of the image carrier. Patent Document 3 proposes a contact-type charging device in which a belt-shaped electrically anisotropic functional member is disposed. According to this proposal, discharge occurs only between the roller-shaped power supply member and the belt-shaped electrically anisotropic functional member, and between the belt-shaped electric anisotropic functional member and the image carrier. No discharge occurs. It is described that this can reduce damage to the image carrier.
[0019]
However, the contents described in Patent Document 3 are limited to those in which charging to the image carrier is performed by injection of electric charge. In such an injection charging method, since the surface layer of the image carrier must be a conductor, there is a problem that it is difficult to control the electric conductivity and to cope with the adverse effect of increasing the thickness of the photosensitive layer. . In addition, due to the use of a support roller and a belt, the size of the apparatus cannot be avoided.
[0020]
On the other hand, contact-type charging devices using a tubular flexible member have been proposed in Patent Documents 4 and 5 for the purpose of suppressing charging unevenness.
[0021]
In Patent Document 4, a tubular flexible member is brought into contact with the surface of a photosensitive drum by a plurality of regulating members provided inside the tubular flexible member. In this contact-type charging device, since the curvature of the portion of the flexible member that contacts the photosensitive drum is small, the distance for forming the minute gap is longer than that of the above-described charging roller, and a long discharge time can be obtained. . As a result, charging unevenness can be reduced. Further, the flexible member has a small mass, and an electrostatic attraction force acts on the photosensitive drum, so that the flexible member comes into stable contact with the photosensitive drum, and is stable and uniform regardless of the axial length. It can be performed. Further, the flexible member rotates at substantially the same speed as the photosensitive drum due to the mechanical frictional force with the photosensitive drum, thereby increasing the apparent surface area, cleaning the discharge products due to the air flow, and contacting the photosensitive member with the photosensitive drum. It is described that a cleaning action can be expected, and poor charging due to adhesion of discharge products can be suppressed.
[0022]
However, in the contact-type charging device according to Patent Document 4, the tube-shaped flexible member is brought into contact with the photosensitive drum by two parallel rod-shaped regulating rods provided therein, and thus the shaft is attached to the surface of the photosensitive drum. If there is undulation in the direction, unevenness may occur in the discharge gap, resulting in uneven charging in the axial direction of the drum. In other words, in general, the aluminum cylinder, which is the substrate of the photosensitive drum, has irregularities (undulations) with a long period of several hundred microns and a period of several tens of microns due to the restriction of processing accuracy. However, even after the photoreceptor layer is provided on the surface, the undulation remains on the drum surface.
[0023]
In this case, since the tubular flexible member does not deform according to the undulation, unevenness occurs in the discharge gap in the axial direction, and as a result, uneven charging in the axial direction of the drum occurs. Further, if the regulating rod is thin, the deflection in the axial direction causes unevenness in the discharge gap in the axial direction, causing uneven charging. This could be improved by increasing the thickness of the regulating rod, but this resulted in an increase in the size of the charging device. In addition, when the number of regulating rods is small, the rotation of the flexible member in a portion where there is no regulating member becomes unstable, and noise due to vibration may be generated. In particular, when the photosensitive drum rotates at a high speed, the vibration causes resonance and is transmitted to a portion in contact with the drum, and as a result, the gap between the photosensitive drum and the photosensitive drum becomes unstable, and charging unevenness sometimes occurs.
[0024]
On the other hand, increasing the number of regulating members stabilizes the running property of the flexible member, but increases the size of the charging device and increases the cost. Furthermore, in order to maintain the uniformity of the gap in the axial direction of the photosensitive drum, it is necessary to adjust the axial direction of the regulating member with respect to the photosensitive drum axis with high precision, which has a point to be improved in terms of productivity. Was.
[0025]
On the other hand, in Patent Document 5, a rotating roller is included in a tube-shaped flexible member, the flexible member is directly in contact with the photosensitive drum by the rotating roller, and the tube-shaped flexible member is in contact with the photosensitive drum. A charging device is described in which a rotation restricting member for restricting the rotation radius of the flexible member is provided on the side opposite to the contact position. In this contact-type charging device, the flexible member and the photosensitive drum come into contact with each other at a stable predetermined contact pressure, and are charged at a contact portion with the photosensitive drum. Since the area contacted by the pressure is formed, it has a function of correcting uneven charging of the photoconductor by the area contacted by the minute contact pressure, and stable charging is achieved by increasing the area of the contact portion with the photoconductor. What is done is described.
[0026]
However, the charging device according to Patent Literature 5 performs charging at a contact portion between the flexible member and the photosensitive drum. Therefore, in order to perform stable charging, a small contact pressure is applied to both sides of a region having a charging function. In this case, it is necessary to form a wide contact area, and it is difficult to set parameters such as rigidity of the flexible member and pressing pressure. In addition, the larger the contact area between the flexible member and the photosensitive drum, the more the alternating current irrespective of the charging of the photoconductor is increased when a power supply obtained by superimposing an AC voltage on a DC voltage is used as a power supply. A large amount of power flows, and the power supply capacity must be increased, leading to an increase in the cost of the power supply. In addition, since the rotation regulating member slides on the charged surface of the flexible member, there is a problem that frictional heat is generated and the charged surface is deteriorated. Further, since the contact area between the rotation regulating member and the flexible member is large, the mechanical frictional force is large, and the rotation of the flexible member is not stabilized. In addition, since the rotation restricting member is disposed outside the flexible member, an increase in the size of the apparatus cannot be avoided.
[0027]
Further, as a problem common to Patent Documents 4 and 5, when the contact pressure becomes non-uniform in the axial direction due to an error in the outer diameter of the regulating member / rotating roller or variation in the pressing spring, the film is moved to one side. As a result, the edge portion is damaged and an image defect is generated.
[0028]
In particular, in Patent Document 5, the film sandwiched between the conductive elastic roller and the photosensitive member has a large thrust force, the film is moved to one side, and the contained elastic roller contacts the photosensitive member and causes leakage to the photosensitive member. There is a problem that image quality is adversely affected. Even if this problem is avoided by error management, the cost increases because the conductive elastic roller is used. Furthermore, there was a problem that charging was poor due to deterioration of the elastic material over time.
[Patent Document 1]
JP-A-7-44085
[Patent Document 2]
JP-A-10-198130
[Patent Document 3]
JP-A-2002-55511
[Patent Document 4]
Japanese Patent No. 3013769
[Patent Document 5]
JP-A-5-72869
[0029]
[Problems to be solved by the invention]
As described above, in the conventional charging device, there are still many points to be solved regarding discharge in a minute gap, and there is still room for improvement in stable and uniform charging and stable acquisition of high-quality images. Was left.
[0030]
Also, in the transfer device, there is still a point to be improved in view of stable and accurate transfer of a visible image such as toner.
[0031]
An object of the present invention is to reduce discharge in a minute gap between an image carrier that is a member to be charged and a member to be transferred that is a non-transfer member or a charging member that contacts the image carrier, An object of the present invention is to prevent the wear of the image carrier and the adhesion of discharge products to the image carrier to extend the life of the image carrier, and to improve the image quality of the image forming apparatus.
[0032]
[Means for Solving the Problems]
In order to achieve the above object, a first invention is a charging device for charging an electrostatic latent image carrier using a cylinder member as a charging electrode, and is a flexible device having elasticity against an external force. A cylinder member made of a material, and suction means for applying a force to draw in the direction inside the cylinder member to a portion of the cylinder member that does not face the electrostatic latent image carrier, which is located inside the cylinder member, By applying a force to the suction means, the cylinder member is brought into contact with the electrostatic latent image carrier, and is deformed to a curvature close to the electrostatic latent image carrier, so that the cylinder member and the cylinder member at which discharge occurs are statically affected. A charging device characterized in that the length of a minute gap with an electrostatic latent image carrier is increased.
[0033]
As a result, discharge can be generated for a long time in the minute gap portion, so that uniform charging and improvement in charging efficiency can be achieved.
[0034]
According to a second aspect of the present invention, in the first aspect, a shaft rotatable with respect to a central axis is installed inside the flexible cylinder member, and the cylinder member and the shaft are pliable. By using a plurality of wires of the same length that have a small elongation with respect to the pulling force, they are connected at a fixed period in the circumferential direction of the cylinder member and the shaft, and the shaft is pressed against the electrostatic latent image carrier, so that the image bearing member is pressed. By utilizing the tension generated in a wire located at a distance from the shaft with respect to the body as the suction means, a portion of the cylinder member that does not face the image carrier is drawn toward the inside of the cylinder. Device.
[0035]
Thus, the minute gap can be efficiently formed on the electrostatic latent image carrier side by the pressing force of the shaft.
[0036]
A third invention for achieving the above object is the second invention, wherein the diameter of the cylinder member in a cylindrical state (a state in which the cross section is circular) to which no force is applied is D, and the cylinder member in that state is D. On the other hand, when the distance between the cylinder member and the center position of the shaft is d when the shaft is moved to one side in the radial direction of the cylinder member so that the wire at one end is stretched, 0.01D <d <0.2D. In addition, the charging device determines the length of each wire between the shaft and the cylinder member.
[0037]
With such a configuration, the range of the optimal deformation amount caused by the cylinder being pressed against the electrostatic latent image carrier is clarified, and the fine gap can be formed more efficiently.
[0038]
According to a fourth aspect of the present invention, in the first aspect, a shaft rotatable with respect to a central axis is provided inside the flexible cylinder member, and the cylinder member and the shaft are pliable. By using a plurality of film materials of the same length that have a small elongation with respect to the pulling force, they are connected at a fixed cycle in the circumferential direction of the cylinder member and the shaft, and the shaft is pressed against the electrostatic latent image carrier, thereby forming an image. By using the tension generated in the film material located at a distance from the shaft with respect to the carrier as the suction means, a portion of the cylinder member that does not face the image carrier is drawn toward the inside of the cylinder. Device.
[0039]
With such a configuration, uniform minute gaps are formed in the axial direction of the cylinder member, thereby increasing the uniformity of charging, and reducing displacement and rotation unevenness due to a rotation difference between the cylinder member and the shaft. And more stable charging can be performed.
[0040]
A fifth aspect of the present invention for achieving the above object is the fourth aspect, wherein the diameter of the cylinder member in a cylindrical state (with a circular cross section) where no force is applied is D, and the diameter of the cylinder member in that state is D. When the distance between the cylinder member and the center position of the shaft is d when the shaft is moved to one side in the radial direction of the cylinder member so that the film material at one end is stretched, 0.01D <d <0.2D. , A charging device for determining the length of each film material between the shaft and the cylinder member.
[0041]
As a result, the minute gap can be formed more effectively over a desired length, so that the uniformity of charging can be further improved.
[0042]
According to a sixth aspect of the present invention, in the first aspect, a shaft rotatable with respect to a central axis is provided inside the flexible cylinder member, and the cylinder member and the shaft are pliable. An elastic roller having a smaller diameter than the cylinder member and a part of the shaft being connected to the cylinder member and the shaft at a constant period by using a plurality of wires having the same length and having a small elongation with respect to the pulling force. By installing the member and pressing the shaft against the electrostatic latent image carrier, the tension generated in the wire located farther from the shaft with respect to the image carrier is used as the suction means, so that the cylinder member The portion not facing the image carrier is drawn toward the inside of the cylinder, and the elastic roller member presses the portion where the cylinder member contacts the image carrier. A charging device designed to.
[0043]
With such a configuration, the stability of the contact portion can be further enhanced, so that stable charge can be applied.
[0044]
A seventh invention for achieving the above object is the first invention, wherein a shaft rotatable with respect to a central axis is provided inside the flexible cylinder member, and between the shaft and the cylinder member, In a certain range of expansion and contraction in the radial direction, it expands and contracts with a very small force irrespective of compression or tension, and has a characteristic that it does not extend more than a certain length even with a large force against a larger tensile deformation The diameter suppressing roller made of a functional material is fixedly arranged between the shaft and the diameter suppressing roller and between the diameter suppressing roller and the cylinder member, and the shaft is pressed against the electrostatic latent image carrier. By using the tension generated from the diameter suppression roller located farther than the shaft with respect to the image carrier from extending beyond a certain amount as the suction means, the cylinder The image bearing member not facing portions of the timber is a charging apparatus that draw in the direction of the interior of the cylinder.
[0045]
With such a configuration, the minute gap can be extended with a very simple configuration, and more stable charging can be performed.
[0046]
According to an eighth aspect of the present invention, in the first aspect, the flexible cylinder member is made of a soft magnetic material, and the flexible cylinder member is displaced from the center of the inside in a direction without the electrostatic latent image carrier. At the position, a magnet that extends in the shape of a rod in the axial direction of the cylinder member and whose both ends are supported is arranged, and the magnet is pressed against the electrostatic latent image carrier, whereby the magnetic attraction force acting between the magnet and the cylinder member is reduced. This charging device is configured to draw a portion of the cylinder member that does not face the image carrier in a direction toward the inside of the cylinder by using the suction member as a suction unit.
[0047]
With this configuration, the flexible cylinder member can be urged against the electrostatic image carrier by applying a desired pressing force with an extremely simple configuration, and the minute gap can be enlarged.
[0048]
A ninth invention for achieving the above object is the ninth invention according to the eighth invention, wherein the magnet has a smaller diameter than the cylinder member, has an axis parallel to the cylinder member, and both ends are rotatably fixed. The charging device is included in a non-magnetic cylindrical member.
[0049]
With such a configuration, the position of the flexible cylinder member can be regulated as desired, and more stable charging can be performed.
[0050]
A tenth invention for achieving the above object is the seventh invention, wherein a conductive elastic material, which is harder than the cylindrical diameter suppressing roller, is provided between the shaft and the diameter suppressing roller in the radial direction of the shaft. This is a charging device in which a pressing roller is disposed.
[0051]
Thereby, the position of the flexible member at the time of pressing can be more accurately regulated, and the stability of the contact portion can be further improved, so that the charging performance can be further improved.
[0052]
An eleventh invention for achieving the above object is a flexible tubular member which is capable of contacting a member to be charged, has at least its surface being conductive and has an autonomy so as to form an internal space in a free state, and The distance between the flexible tubular member and the center for rotating the flexible tubular member in a portion facing the charging member via the internal space is maintained within a desired distance range. And a member for urging the opposing portion toward the internal space.
[0053]
With such a configuration, the minute gap portion can be enlarged with a simpler configuration as compared with the related art, and the charging ability can be improved.
[0054]
According to a twelfth aspect of the present invention, in the eleventh aspect, the biasing member is a member that extends radially from a shaft disposed at the center for the rotation and is deformable. This is a charging device having a linear or planar member coupled to the inner surface of the flexible tubular member.
[0055]
With this, although the flexible tubular member is easily deformed, the arrangement is regulated in the opposite direction to the member to be charged, so that a more controlled minute gap can be easily formed. .
[0056]
According to a thirteenth invention for achieving the above object, in the eleventh invention, the biasing member has a porous member disposed in the internal space, and the porous member is easily compressed and deformed. This is a charging device that is a member having less tensile deformation.
[0057]
With such a configuration, a very simple configuration and easy manufacturing can be achieved, and the object can be achieved at lower cost.
[0058]
According to a fourteenth aspect of the present invention, in the eleventh aspect, the flexible tubular member has a magnetic body, and the biasing member is a magnetic force generating means disposed in the internal space. Is a charging device.
[0059]
With such a configuration, stable charging can be performed with a simple configuration.
[0060]
A fifteenth invention for achieving the above object is a transfer device for transferring toner held on an electrostatic latent image carrier using a cylinder member as a charging electrode, and has a resilience to an external force. A cylinder member made of a flexible material, and suction means for applying a force for attracting a portion of the cylinder member that is not opposed to the electrostatic latent image carrier toward the interior of the cylinder member. And a cylinder that generates a discharge by applying a force to the suction unit to cause the cylinder to contact the electrostatic latent image carrier and deform the cylinder member to a curvature close to the electrostatic latent image carrier. This is a transfer device in which the length of a minute gap between a member and an electrostatic latent image carrier is increased.
[0061]
As a result, a discharge can be generated in the minute gap portion for a long time, so that stable transfer and transfer efficiency can be improved.
[0062]
A sixteenth invention for achieving the above object is the fifteenth invention, wherein, in the flexible cylinder member, a shaft rotatable with respect to a central axis is installed inside the flexible cylinder member, and the cylinder member and the shaft are pliably pulled. By using a plurality of wires of the same length that have a small elongation with respect to the force, they are connected at a fixed period in the circumferential direction of the cylinder member and the shaft, and the shaft is pressed against the electrostatic latent image carrier, whereby the image carrier is A transfer member that uses a tension generated in a wire located farther from the shaft than the shaft as the suction means to draw a portion of the cylinder member that does not face the image carrier toward the inside of the cylinder. .
[0063]
Thus, a minute gap can be efficiently formed between the electrostatic latent image carrier and the electrostatic latent image carrier by the pressing force of the shaft.
[0064]
A seventeenth invention for achieving the above object is the sixteenth invention, wherein the diameter of the cylinder member in a cylindrical state (a state in which the cross section is circular) to which no force is applied is D, and the cylinder member in that state has one end. When the distance between the cylinder member and the center position of the shaft when the shaft is moved to one side in the radial direction of the cylinder member so that the wire is stretched is d, 0.01D <d <0.2D This is a transfer device in which the length of each wire between the and the cylinder member is determined.
[0065]
With such a configuration, the range of the optimal deformation amount caused by the cylinder being pressed against the electrostatic latent image carrier is clarified, and the fine gap can be formed more efficiently.
[0066]
According to an eighteenth aspect of the present invention, in the fifteenth aspect, a shaft rotatable with respect to a central axis is provided inside the flexible cylinder member, and the cylinder member and the shaft are pliablely pulled. By using a plurality of film materials of the same length that have a small elongation with respect to the force, the cylinder members and the shaft are connected at a constant period in the circumferential direction, and the shaft is pressed against the electrostatic latent image carrier, so that the image bearing is performed. A charging device that draws a portion of the cylinder member that does not face the image bearing member toward the inside of the cylinder by using the tension generated in the film material that is located farther from the body than the shaft as the suction unit; It is.
[0067]
With such a configuration, uniform minute gaps are formed in the axial direction of the cylinder member, thereby increasing the uniformity of charging and reducing displacement and uneven rotation due to a rotation difference between the cylinder member and the shaft. And more stable transfer can be performed.
[0068]
A nineteenth invention for achieving the above object is the invention according to the eighteenth invention, wherein the diameter of the cylinder member in a cylindrical state (with a circular cross section) to which no force is applied is D, and the cylinder member in that state has one end. When the distance between the cylinder member and the center position of the shaft is d when the shaft is moved to one side in the radial direction of the cylinder member so that the film material is stretched, 0.01D <d <0.2D, This is a transfer device in which the length of each film material between a shaft and a cylinder member is determined.
[0069]
As a result, the minute gap can be formed more effectively over a desired length, so that the transfer efficiency can be further improved.
[0070]
According to a twentieth aspect of the present invention, in the fifteenth aspect, a shaft rotatable with respect to a central axis is provided inside the flexible cylinder member, and the cylinder member and the shaft are pliablely pulled. An elastic roller member having a smaller diameter than the cylinder member and a part of the shaft being connected to the cylinder member and the shaft at a constant period by using a plurality of wires having the same length and having a small elongation with respect to the force. Is installed, and the shaft is pressed against the electrostatic latent image carrier, so that the tension generated in a wire located farther from the image carrier than the shaft is used as the suction means, so that the image of the cylinder member is formed. The portion not facing the carrier is drawn toward the inside of the cylinder, and the elastic roller member presses the portion where the cylinder member contacts the image carrier. A transfer device designed to.
[0071]
By adopting such a configuration, the stability of the contact portion can be further enhanced, so that stable transfer can be performed.
[0072]
According to a twenty-first invention for achieving the above object, in the fifteenth invention, a shaft rotatable around a central axis is installed inside the flexible cylinder member, and between the shaft and the cylinder member, In a certain range of expansion and contraction in the radial direction, it expands and contracts with a very small force irrespective of compression or tension, and has a characteristic that it does not extend more than a certain length even with a large force against a larger tensile deformation The diameter suppressing roller made of a functional material is fixedly arranged between the shaft and the diameter suppressing roller and between the diameter suppressing roller and the cylinder member, and the shaft is pressed against the electrostatic latent image carrier. By using the tension generated from the fact that the diameter suppressing roller positioned farther from the image carrier than the shaft does not extend beyond a certain amount as the suction means, The image bearing member not facing portion of the over member is a transfer apparatus that draw in the direction of the interior of the cylinder.
[0073]
With such a configuration, the minute gap can be extended with a very simple configuration, and more stable transfer can be performed.
[0074]
According to a twenty-second invention for achieving the above object, in the fifteenth invention, the flexible cylinder member is made of a soft magnetic material, and is shifted from a center of the inside thereof in a direction without the electrostatic latent image carrier. At the position, a magnet that extends in a rod shape in the axial direction of the cylinder member and whose both ends are supported is disposed, and the magnet is pressed against the electrostatic latent image carrier, thereby causing the magnetic attraction force acting between the magnet and the cylinder member to be increased. This is a transfer device in which a portion of the cylinder member that does not face the image carrier is drawn toward the inside of the cylinder by using as a suction unit.
[0075]
With this configuration, the flexible cylinder member can be urged against the electrostatic image carrier by applying a desired pressing force with an extremely simple configuration, and the minute gap can be enlarged.
[0076]
According to a twenty-third aspect of the present invention, in the twenty-second aspect, the magnet has a smaller diameter than the cylinder member, and has an axis parallel to the cylinder member and both ends rotatably fixed. Is a transfer device included in the non-magnetic cylindrical member.
[0077]
With such a configuration, it is possible to regulate the position of the flexible cylinder member as desired, and it is possible to perform more stable transfer.
[0078]
A twenty-fourth invention for achieving the above object is the twenty-first invention, wherein a conductive elastic material, which is harder than a cylindrical diameter suppressing roller, is provided between the shaft and the diameter suppressing roller in the radial direction of the shaft. This is a transfer device in which a pressing roller is disposed.
[0079]
Thereby, the position of the flexible member at the time of pressing can be more accurately regulated, and the stability of the contact portion can be further increased, so that the transfer performance can be further improved.
[0080]
A twenty-fifth invention for achieving the above object is a flexible tubular member which is capable of contacting a member to be transferred, has at least the surface thereof being conductive, and has a self-sustainability so as to form an internal space in a free state, and The distance between the flexible tubular member and the center for rotating the flexible tubular member in a portion facing the charging member via the internal space is maintained within a desired distance range. And a member for urging the opposing portion toward the internal space.
[0081]
With such a configuration, it is possible to enlarge the minute gap portion with a simpler configuration than in the related art, and it is possible to improve transfer performance.
[0082]
A twenty-sixth invention for achieving the above object is the twenty-fifth invention, wherein the urging member is a member that extends radially from an axis disposed at the center for the rotation and is deformable. A transfer device having a linear or planar member coupled to the inner surface of the flexible tubular member.
[0083]
With this, although the flexible tubular member is easily deformed, the arrangement is regulated in the opposite direction to the member to be charged, so that a more controlled minute gap can be easily formed. .
[0084]
According to a twenty-seventh aspect of the present invention, in the twenty-fifth aspect, the member for urging has a porous member disposed in the internal space, and the porous member is easily compressed and deformed. This is a transfer device that is a member with little tensile deformation.
[0085]
With such a configuration, a very simple configuration and easy manufacturing can be achieved, and the object can be achieved at lower cost.
[0086]
A twenty-eighth invention for achieving the above object is the twenty-fifth invention, wherein the flexible tubular member has a magnetic body, and the biasing member is a magnetic force generating member disposed in the internal space. It is a transfer device having means.
[0087]
With such a configuration, stable transfer can be performed with a simple configuration.
[0088]
A twenty-ninth aspect of the present invention for achieving the above object is a charging device according to any one of the first to fourteenth aspects, an electrostatic latent image carrier, and a charging device formed on the electrostatic latent image carrier. An image comprising: an exposure unit for forming an electrostatic latent image; and a developing unit for forming a visible image corresponding to the electrostatic latent image formed on the electrostatic latent image carrier. It is a forming device.
[0089]
This makes it possible to obtain stable image formation over a long period of time without a complicated configuration and without performing complicated control.
[0090]
A thirtieth invention for achieving the above object is a transfer device, a charging device, an electrostatic latent image carrier, and the electrostatic latent image carrier according to any one of the fifteenth to twenty-eighth inventions. Exposure means for forming an electrostatic latent image formed thereon, and a developing device for forming a visible image corresponding to the electrostatic latent image formed on the electrostatic latent image carrier And an image forming apparatus comprising:
[0091]
This makes it possible to obtain stable image formation over a long period of time without a complicated configuration and without performing complicated control.
[0092]
BEST MODE FOR CARRYING OUT THE INVENTION
[Example]
Hereinafter, the present invention will be described based on the illustrated embodiment. FIG. 2 is a schematic sectional view showing a preferred example of an image forming apparatus to which the charging device according to the present invention is applied.
[0093]
In FIG. 2, reference numeral 81 denotes a cylindrical photosensitive drum as an electrostatic latent image carrier. Around the photosensitive drum 81, a primary charger 82 as a charging device according to the present invention, a developing device 83, a transfer roller 84 and a cleaning device 85 are arranged. Of these image forming members, members excluding the transfer roller 84 are integrally formed as an image forming unit 86. The image forming unit 86 is detachable from the image forming apparatus main body 87, and when the contained toner is consumed, the unit 86 is replaced.
[0094]
After the photosensitive drum 81 is uniformly charged to a predetermined potential by a primary charger 82, the photosensitive drum 81 is irradiated with a semiconductor laser (not shown) and a laser beam 90 from a laser beam generator 89 containing a polygon rotating mirror 88. On the surface of 81, an electrostatic latent image corresponding to an image is formed at a predetermined position. The electrostatic latent image formed on the surface of the photosensitive drum 81 is developed by the developing device 83 to become a toner image. At this time, the laser beam 90 is used to write an image portion, and the toner having the same polarity as the surface potential of the photosensitive drum 81 charged by the primary charger 82 is used as the laser beam of the photosensitive drum 81. It is developed in the light irradiation part.
[0095]
The developing device 83 includes at least a developing roller 83a and a layer forming member 83b, and the inside of the developing device 83 is filled with a magnetic toner 83c. The magnetic toner 83c filled in the inside of the developing device 83 is attracted to the surface of the developing roller 83a by the magnetic force of the developing roller 83a, and is regulated to a predetermined layer thickness by the layer forming member 83b. Is charged. The toner adsorbed on the surface of the developing roller 83a and frictionally charged to a predetermined thickness and a predetermined polarity moves to a developing position close to the surface of the photosensitive drum 81 with the rotation of the developing roller 83a. The electrostatic latent image formed on the surface of the photosensitive drum 81 is developed by a toner layer.
[0096]
The toner image formed on the photosensitive drum 81 is transferred by transfer charging of a transfer roller 84 onto a transfer sheet 93 that is conveyed at a predetermined timing from a paper feed cassette 91 by a registration roller 92. After the transfer is completed, the transfer paper 93 onto which the toner image has been transferred is conveyed to the fixing device 95 by the conveyance belt 94, where the fixing process is performed, and is discharged outside the apparatus. In the fixing device 95, a transfer sheet 93 is inserted between a fixing roller 95a and a pressure roller 95b, and is fixed by heat and pressure.
[0097]
After the completion of the transfer step, the residual toner on the photosensitive drum 81 is cleaned by the blade 85a of the cleaning device 85 to prepare for the next image forming step. Then, when forming images continuously, the charging process by the primary charger 82 is continued, and all the above-described processes are repeated to output a plurality of continuous prints.
[0098]
(Example 1)
Next, the configuration of a first embodiment of the charging device according to the present invention will be described with reference to FIGS. 1, 3, and 4. FIG. The charging device according to this embodiment is used as the primary charger 82 (the same applies hereinafter).
[0099]
1A and 1B are schematic cross-sectional views when the charging device is cut along a plane perpendicular to the axis of the cylinder. FIG. 1A shows a state of the charger alone, and FIG. 1B shows a state of contacting the photosensitive drum 81. Show. FIG. 3 is an exploded perspective view of the charging device, and FIG. 4 is a schematic cross-sectional view taken along a plane passing through a center line of a cylinder axis in an assembled state.
[0100]
In the drawing, reference numeral 1 denotes a shaft serving as a rotating shaft, which is made of stainless steel, aluminum or the like, but may be made of another metal material or another material.
[0101]
Reference numeral 18 denotes a cylinder contact member, which includes an inner cylindrical portion 18a, an outer cylindrical portion 18c, and a connecting portion 18b connecting the inner cylindrical portion 18a and the outer cylindrical portion 18c.
[0102]
The inner diameter of the inner cylinder 18a is the same as the diameter of the shaft 1, and is made of plastic or the like. The outer cylinder 18c is made of a thin rigid flexible material such as vinyl chloride, and has an axial length substantially equal to that of the inner cylinder 18a. The connecting portion 18b is a wire made of a flexible and durable material such as a nylon thread or a carbon fiber, which has a small elongation with respect to a tensile force. The inner cylinder 18a and the outer cylinder 18c are connected to each other at regular intervals in the circumferential direction of the cylinder by connecting portions 18b having the same length (connected at 12 locations in the figure). The length of one connecting portion 18b is slightly longer than half of the difference between the inner diameter (diameter) of the outer cylinder 18c and the outer diameter (diameter) of the inner cylinder 18a (details will be described later).
[0103]
Reference numeral 16 denotes a thin cylinder member serving as a charging electrode, which is made of a conductive flexible material having a large shape restoring force (elasticity) against deformation in an out-of-plane direction, such as steel, nickel, or SUS. It is self-supporting so as to form a space, and its natural frequency is several tens Hz, preferably 100 Hz or more. As a specific example, it has been confirmed that a nickel material having a thickness of 20 to 50 μm and a Young's modulus of 100,000 to 300,000 MPa satisfies the present specification. Then, a high resistance coating may be provided on the surface of the cylinder member 16 as necessary. The inner diameter of the cylinder member 16 is the same as the outer diameter of the outer cylinder 18c.
[0104]
As shown in FIGS. 3 and 4, the shafts 1 are passed through the inner cylinders 18a of the plurality of cylinder contact members 18 arranged at equal intervals to fix them together. Then, it passes through the inside of the cylinder member 16 to fix the surface of the outer cylinder 18c and the cylinder 16 with an adhesive or the like, thereby forming a charging roller.
[0105]
Then, the charger 1 is formed by pressing the shaft 1 of the charging roller against the photosensitive drum 81 with a constant pressure in a rotatable state.
[0106]
The charging device according to this embodiment uses a cylinder member 16 made of a flexible cylinder as a charging electrode, and a cylinder contact member as a means for sucking a portion of the cylinder member that does not face the image carrier into the cylinder. The provision of 18 constitutes a charger.
[0107]
In the above configuration, the charging device according to this embodiment does not perform charging at the contact portion but charges the photosensitive member through the minute gap by the cylinder member 16 in the following manner. A charging device having high performance can be provided.
[0108]
That is, FIG. 1B shows a state in which the shaft 1 of the charging roller is pressed against the photosensitive drum. The connecting portion 18b, which is separated from the photosensitive drum 81 by a distance from the shaft 1, is pulled, and the tension causes the cylinder member 16 to contact the photosensitive drum. On the other hand, the connecting portion 18b closer to the photosensitive drum 81 than the shaft 1 is in a loose state. Since the cylinder member 16 has a high elasticity with respect to the out-of-plane force, the cylinder member 16 is deformed at the contact portion to a state close to the curvature of the photosensitive drum as shown in FIG.
[0109]
When the photosensitive drum 81 is rotated in this state, the charging roller rotates at substantially the same speed as the photosensitive drum 81 due to friction at the abutting portion (nip portion) N while maintaining this shape. The rotation is very stable because the cylinder member 16 is completely regulated by the cylinder contact member 18.
[0110]
Here, as shown in FIG. 1B, a voltage obtained by superimposing a DC voltage of −600 V on an AC voltage of, for example, 1500 to 2000 Vpp (peak-to-peak) and a frequency of 2000 Hz is applied to the cylinder member 16. 6 and a DC power supply 8. Then, the discharge a is started in the minute gap α between the cylinder member 16 and the photosensitive drum 81, and the surface of the photosensitive drum 81 is charged. As shown in FIG. 4, a voltage can be applied to the cylinder member 16 by providing a contact electrode 19 inside the cylinder member 16, but the shaft 1, the inner cylinder 18a constituting the cylinder contact member 18, and the connection By using a conductive material for the portion 18b and the outer cylinder 18c, it is also possible to apply the voltage from the end of the shaft 1.
[0111]
According to the charger having the above-described configuration, the portion N of the cylinder member 16 that contacts the photosensitive drum 81 is deformed along the surface of the photosensitive drum 81 and has a small curvature as described above. The discharge distance β and the discharge time longer than those of the charging member can be obtained. That is, when the photosensitive drum 1 is charged through the minute gap α, the discharge is generally performed within the range of the gap length of about 10 to 200 μm. In this embodiment, the cylinder member 16 and the photosensitive drum 81 are charged. , A long discharge distance β and a long discharge time can be obtained.
[0112]
On the other hand, as is apparent from the above description, the size of the charger of the present invention is determined by the diameter of the cylinder contact member 18, and the diameter is further determined by the diameter of the shaft 1 and the inner cylinder. The difference between the diameter of the outer cylinder 18a and the diameter of the outer cylinder 18c. Here, the diameter of the shaft may be any as long as the difference in displacement depending on the axial position with respect to the force for contacting the cylinder member 16 with the photosensitive drum 81 is small (the axial deflection of the shaft is small). It may be substantially the same as the shaft 50 of the conventional contact type charging roller. On the other hand, the difference between the diameters of the inner cylinder 18a and the outer cylinder 18c is such that the curvature of the portion N of the cylinder member 16 that contacts the photosensitive drum 81 is sufficiently close to the diameter of the photosensitive drum 81 as shown in FIG. However, any condition may be used as long as the inner cylinder 18a and the outer cylinder 18c are separated from each other. Obviously, it is easy to satisfy this condition. Therefore, according to this configuration, the charging device can be made smaller in size than a conventional charging roller using a flexible cylinder.
[0113]
Next, when the charging device of this embodiment is used, abnormal charging, which is triggered by abnormal discharge between the charging electrode and the image carrier, damage to the drum, and potential due to ripple components included in the oscillating voltage The result of unevenness will be described.
[0114]
FIG. 5 shows the magnitude of the abnormal charging that is triggered by the abnormal discharge between the charging electrode and the image carrier, compared with the conventional charging roller shown in FIG. 17, and is obtained by numerical simulation.
[0115]
The diameter of the drum is 30 mm, and a voltage obtained by superimposing an AC voltage on a DC voltage of -600 V as an applied voltage is used. The roller diameter of the conventional roller was 12 mm, and the roller of the present invention was such that the cylinder member 16 at the portion in contact with the photosensitive drum was deformed into a planar shape. An increase in the charge amount when an abnormal discharge occurs with respect to the charge amount when there is no abnormal discharge is indicated by a ratio (%) as charging unevenness.
[0116]
From this graph, it can be seen that according to the present invention, at an AC voltage of 1600 Vpp, a uniform charging property comparable to 2000 Vpp of a conventional charging roller can be achieved. This is because the discharge distance β and the discharge time of the charging roller of the present invention are long, and it is known that during the long discharge, charging unevenness due to abnormal discharge can be carefully repaired.
[0117]
Next, FIG. 6 shows the distribution of the amount of discharge exposure on the surface of the photosensitive drum when various AC voltages are applied. The drum diameter, the shape of the charging roller, and the voltage conditions are the same as in FIG. 5, and charging is performed from a state in which the charge on the surface of the photoconductor is completely removed. In FIG. 6, the abscissa represents the position on the drum surface by the gap length, which is indicated by changing the sign of the gap length on both sides of the nip. The distribution of the discharge exposure is expressed as a function of only the gap length between the charging roller and the photosensitive drum, and does not depend on the diameter of the charging roller. As a result, the discharge exposure distributions of the conventional roller and the roller of the present invention are the same, as shown in this graph. From this graph, the peak value of the discharge exposure amount is 900 μC / m by reducing the AC voltage from 2000 Vpp to 1600 Vpp. ² To 300 μC / m ² It can be seen that it can be reduced to about 1/3.
[0118]
Here, since the deterioration of the photosensitive drum surface due to the discharge is almost proportional to the peak value of the discharge exposure amount, the results of FIG. 5 and FIG. It can be seen that it can be reduced to 3. The present study was also conducted in an experiment in which an actual printout process was performed. As a result, it was found that the charging roller of the present invention can obtain an image of similar image quality with a lower AC voltage than the conventional charging roller. In addition, in the durability test of the same number of sheet passing drums, it was confirmed that the amount of wear of the drum was reduced to about 1/3.
[0119]
Further, under the same conditions as above, the potential unevenness caused by the ripple component included in the vibration voltage when the AC voltage was set to 1800 Vpp was calculated for the conventional roller and the charging roller of the present invention. Was found to be 5% with the charging roller of the present invention. This is due to the fact that the rate of change of the charge amount on the drum surface in the discharge region decreases due to the spread of the discharge region. Similar results have been obtained by experiments.
[0120]
Here, the length of the connection portion 18b will be described. The diameter of the cylinder member 16 in a cylindrical state (a state in which the cross section is circular) where no force is applied is D, and the shaft 1 is moved in the radial direction of the cylinder member 16 so that one end of the wire is stretched to the cylinder member 16 in that state The distance between the center position of the cylinder member 16 and the center position of the shaft 1 when it is moved to one side is d.
[0121]
According to the study by the inventor, when d <0.01D, the curvature of the portion of the cylinder member 16 that contacts the photosensitive drum 81 cannot be made sufficiently small, and as a result, the discharge distance cannot be lengthened.
[0122]
On the other hand, when 0.2D <d, it was found that the shape of the portion of the cylinder member 16 that abuts on the photosensitive drum 81 was excessively bent, so that traveling became extremely unstable.
[0123]
By determining the length of the connection portion 18b so as to be 0.01D <d <0.2D, the traveling as a roller is stabilized, and the curvature of the portion of the cylinder member 16 that abuts on the photosensitive drum 81 is sufficiently large. The charging device is deformed into a state close to the diameter of 81, and the discharge distance can be increased.
[0124]
Further, the thickness of the cylinder member 16 will be described. The inventor constructed the cylinder member 16 from a nickel material having a thickness of 30 μm and a Young's modulus of 200000 MPa. This thickness is mainly obtained from an experimental result that, when the cylinder member 16 is too thick, the cylinder member 16 is broken when the cylinder member 16 is rotated for a long time in a state of being in contact with the photosensitive drum 81. is there. That is, the elastic deformation of the cylinder member 16 at the contact portion with the photosensitive drum 81 generates a tensile stress at the inner peripheral portion. And it accumulates as metal fatigue, leading to fracture. Naturally, if the thickness is increased, the pressing force of the shaft 1 must be increased in order to sufficiently deform the cylinder member 16 at the contact portion. As a result, there is a problem that the damage to the surface of the photosensitive drum 81 increases. According to the study by the inventor, it has been found that a thickness of about 20 to 50 μm is appropriate.
[0125]
If there is a pinhole in the photosensitive layer of the photosensitive drum 81, an image may be disturbed due to concentration of discharge. However, by providing a high resistance coating on the surface of the cylinder member 16 as described above, the image may be distorted. Can be prevented.
[0126]
Further, since the charger of this configuration charges the photosensitive drum by discharging in a minute gap, there is no problem of conductivity on the surface of the photosensitive drum as in the case of injection charging. Further, since there is no sliding portion, troubles due to frictional heat and the like as described in Patent Document 5 described above do not occur.
[0127]
Further, here, the primary charger 82 in FIG. 2 has been described, but it goes without saying that the same effect can be obtained even when used as the transfer roller 84 (the same applies hereinafter).
[0128]
(Example 2)
Next, the configuration of a second embodiment of the charging device according to the present invention will be described with reference to FIGS.
[0129]
In the second embodiment, in particular, the configuration of the cylinder contact member is different from that of the first embodiment. The length in the axial direction is made equal to that of the cylinder member, and a film material is used instead of a wire as a connection part. Accordingly, the portion of the cylinder member made of the flexible cylinder that does not face the photosensitive drum is drawn toward the inside of the cylinder.
[0130]
FIG. 7 is an exploded perspective view of the charging device, and FIG. 8 is a schematic cross-sectional view taken along a plane passing through the center line of the cylinder axis in an assembled state.
[0131]
In the figure, reference numeral 2 denotes a shaft serving as a rotating shaft, which is made of a conductive material such as stainless steel or aluminum.
[0132]
Reference numeral 28 denotes a cylinder contact member, which includes an inner cylindrical portion 28a, an outer cylindrical portion 28c, and a connecting portion 28b connecting the inner cylindrical portion 28a and the outer cylindrical portion 28c.
[0133]
The inner diameter of the inner cylinder 28a is the same as the diameter of the shaft 2, the length in the axial direction is substantially the same as a cylinder member described later, and the material is made of plastic or the like. The outer cylinder 28c is made of a thin rigid flexible material such as thin vinyl chloride, and its axial length is substantially the same as that of the inner cylinder 28a. The connection portion 28b is a film material made of a flexible and durable material such as PET or polyimide, which has a small elongation with respect to a tensile force. The inner cylinder 28a and the outer cylinder 28c are connected to each other at a constant period in the circumferential direction of the cylinder by connecting portions 28b having the same length (12 points in the figure). The length of one connecting portion 28b in the radial direction is set to be slightly longer than half of the difference between the inner diameter of the outer cylinder 28c and the outer diameter of the inner cylinder 28a (details will be described later), and its width is approximately equal to the inner cylindrical portion 28a. And 28c in the axial direction.
[0134]
Reference numeral 16 denotes a cylinder member described by the same reference numerals in the first embodiment, and functions as a charging electrode. The inner diameter of the cylinder member 16 is the same as the outer diameter of the outer cylinder 18c.
[0135]
As shown in FIGS. 7 and 8, both are fixed to the inner cylinder 28a of the cylinder contact member 28 through the shaft 2. Then, the charging roller is formed by passing this through the inside of the cylinder member 16 and fixing the surface of the outer cylinder 28c and the cylinder 16 with an adhesive or the like. The shaft 2 and the cylinder member 16 are connected by a conductor wire 26 in advance.
[0136]
Then, a charging device is formed by pressing the photosensitive drum with a constant pressure in a rotatable state with the shaft of the charging roller.
[0137]
With the above configuration, schematic cross-sectional views taken along a plane perpendicular to the axis when pressed against the charging roller alone and the photosensitive drum are as shown in FIGS. 1A and 1B, respectively, as in the first embodiment. become.
[0138]
According to the configuration of this embodiment, similarly to the first embodiment, it is possible to provide a low-cost and stable charging device that charges the photosensitive member via the minute gap by the cylinder member 16. In other words, the connecting portion 28b of the portion away from the shaft 2 with respect to the photosensitive drum 81 is in a pulled state, and the tension causes the cylinder member 16 to contact the photosensitive drum. On the other hand, the connection portion 28b closer to the photosensitive drum 81 than the shaft 2 is in a loosened state. Since the cylinder member 16 has high elasticity against the out-of-plane force, the cylinder member 16 is deformed to a state close to the curvature of the photosensitive member as shown in FIG. When the photosensitive drum 81 is rotated in this state, the cylinder member 16 rotates at substantially the same speed as the photosensitive drum 81 due to friction at the contact portion while maintaining the cylinder shape.
[0139]
Here, a voltage obtained by superimposing a DC voltage of −600 V on an AC voltage of, for example, 1500 to 2000 Vpp (peak-to-peak) and a frequency of 2000 Hz is applied to the shaft 2 by the high-voltage AC power supply 6 and the DC power supply 8. Then, when a current flows through the cylinder member 16 through the conductor wire 26, discharge is started in a minute gap between the cylinder member 16 and the photosensitive drum 81, and the surface of the photosensitive drum 81 is charged.
[0140]
According to the charger of this configuration, as in the first embodiment, the portion of the cylinder member 16 that contacts the photosensitive drum 81 is deformed along the surface of the photosensitive drum 81 to reduce the curvature. As in the case of FIG. 1, the minute gap between the cylinder member 16 and the photosensitive drum 81 can be made long, and a longer discharge distance and discharge time can be obtained than in the conventional roller-shaped charging member shown in FIG. As a result, similarly to the first embodiment, it is possible to avoid abnormal charging caused by abnormal discharge between the charging electrode and the image carrier, to reduce the damage to the drum, and to further cause the ripple component included in the vibration voltage. A charging roller with less potential unevenness can be provided.
[0141]
As is clear from the above description, the size of the charger of the present invention is determined by the diameter of the cylinder contact member 28, and the diameter is further determined by the diameter of the shaft 2 and the inner cylinder 28a. And the diameter of the outer cylinder 28c. Here, the diameter of the shaft should be small as long as the shaft is not flexed in the axial direction with respect to the force for contacting the cylinder member 16 with the photosensitive drum 81, and is substantially the same as the shaft 50 of the conventional contact type charging roller shown in FIG. Is fine.
[0142]
On the other hand, the difference between the diameters of the inner cylinder 28a and the outer cylinder 28c is that even if the curvature of the portion of the cylinder member 16 that contacts the photosensitive drum 81 is sufficiently close to the diameter of the photosensitive drum 81, May be in a state of being separated from each other. Obviously, it is easy to satisfy this condition. Therefore, according to this configuration, the charging device can be made smaller in size than a conventional charging roller using a flexible cylinder.
[0143]
In the second embodiment, the uneven charging in the axial direction of the drum can be reduced as compared with the first embodiment. That is, the cylinder member 16 in the first embodiment is largely deformed along the surface of the photosensitive drum 81 as shown in FIG. At a portion away from the contact member 28, the shape becomes slightly circular. As a result, the gap length with the photosensitive drum 81 changes depending on the position of the drum in the axial direction, so that minute charging unevenness occurs. However, according to this embodiment, since the cylinder member 16 receives the force from the cylinder contact member 28 at any position evenly, the gap length does not vary in the axial direction of the drum. As a result, it is possible to provide a charging device with less charging unevenness in the drum axis direction as compared with the first embodiment.
[0144]
Regarding the radial length of the connection portion 28b, as described in Embodiment 1, the diameter of the cylinder member 16 in the cylindrical state (state in which the cross section is circular) where no force is applied is D, and in that state, When the distance between the center position of the cylinder member 16 and the center position of the shaft 2 when the shaft 2 is moved to one side in the radial direction of the cylinder member 16 so that the film material at one end is stretched with respect to the cylinder member 16 is d , 0.01D <d <0.2D.
[0145]
In this embodiment, the film has a shape having a surface along the direction of the central axis of the cylinder in the present embodiment, but in consideration of the thickness and rigidity of the film, as shown in FIG. A disk-shaped film 28b having a surface intersecting with the center axis (preferably a surface intersecting perpendicularly) may be used. That is, even if the above-mentioned film material in a state of being slackened in the radial direction, or a disk-shaped film made of a film material having a property of not extending beyond a certain value, a charging device with small charging unevenness could be provided as described above. .
[0146]
By making the film into a disk shape, the synchronization between the rotation of the shaft and the rotation of the cylinder is further improved.
[0147]
(Example 3)
FIGS. 9, 10, and 11 show a third embodiment of the present invention. FIG. 9 is a schematic sectional view when the charging device is cut along a plane perpendicular to the axis of the cylinder. FIG. 10 is an exploded perspective view of the charging device, and FIG. 11 is a schematic view of a surface passing through a center line of a cylinder shaft in an assembled state. FIG. The same parts as those in the first embodiment are denoted by the same reference numerals. In the third embodiment, a conductive shaft is used, and an elastic roller is provided between the plurality of cylinder contact members 18. Is different from the first embodiment.
[0148]
That is, in FIGS. 9, 10, and 11, reference numeral 2 denotes a shaft serving as a rotating shaft, which is made of a conductive material such as stainless steel or aluminum. Reference numeral 14 denotes a conductive elastic roller made of a conductive rubber, a conductive sponge, or the like, the outer diameter of which is about 1.1 to 1.5 times the shaft 2 and smaller than the inner diameter of the outer cylinder 18c. . The diameter of the hole 14 a of the elastic roller 14 is the same as the outer diameter of the shaft 2. Other members are the same as those in the first embodiment, and a description thereof will be omitted.
[0149]
As shown in FIGS. 10 and 11, a plurality of the cylinder contact members 18 and the elastic rollers 14 are alternately arranged, and the two are fixed to each other by passing the shaft 2 through the inner cylinder 18a and the hole 14a. Then, it passes through the inside of the cylinder member 16 to fix the surface of the outer cylinder 18c and the cylinder 16 with an adhesive or the like, thereby forming a charging roller.
[0150]
Then, the charging device is constituted by pressing the photosensitive drum with a constant pressure while rotating the shaft 2 of the charging roller.
[0151]
FIG. 9B shows a state in which the shaft 2 of the charging roller is pressed against the photosensitive drum. As in the first embodiment, since the cylinder member 16 has high elasticity against the out-of-plane force, the cylinder member 16 deforms to a state close to the curvature of the photosensitive drum 81 and comes into contact with the photosensitive drum 81. Further, in this embodiment, at the portion where the cylinder member 16 contacts the photosensitive drum, the elastic roller 14 contacts the cylinder member 16 and presses down, so that the cylinder member 16 is stably adhered to the photosensitive drum 81. You. That is, even when the surface shape of the photosensitive drum undulates in the axial direction of the drum, the cylinder member 16 is completely in close contact with the surface of the photosensitive drum 81, and a stable discharge gap α can be formed. .
[0152]
When the photosensitive drum 81 is rotated in this state, the charging roller rotates at substantially the same speed as the photosensitive drum 81 due to friction at the abutting portion thereof while maintaining this shape.
[0153]
Here, a voltage obtained by superimposing a DC voltage on an AC voltage similar to the above embodiment is applied to the shaft 2 by the high-voltage AC power supply 6 and the DC power supply 8. Then, when a current flows through the cylinder member 16 through the shaft 2 and the elastic roller 14, discharge is started in a minute gap between the cylinder member 16 and the photosensitive drum 81, and the surface of the photosensitive drum 81 is charged.
[0154]
According to the present embodiment, since a stable discharge gap α can be formed in the axial direction of the drum, it is possible to provide a charging device with less uneven charging in the axial direction of the photosensitive drum 81 than in the first embodiment.
[0155]
Here, when the cylinder member 16 is brought into contact with the photosensitive drum 81 as shown in FIG. 9B, the elastic roller 14 comes into contact with the cylinder member 16 with a slight nip width. They are determined to be in contact with each other, and can be easily determined from their geometric shapes.
[0156]
(Example 4)
Next, the configuration of a fourth embodiment of the charging device according to the present invention will be described with reference to FIGS. 12, 13, and 14. FIG. FIGS. 12A and 12B are schematic cross-sectional views when the charging roller is cut along a plane perpendicular to the axis of the cylinder. FIG. 12A shows a state of the charger alone, and FIG. 12B shows a state of contacting the photosensitive drum. . FIG. 13 is an exploded perspective view, and FIG. 14 is a schematic cross-sectional view taken along a plane passing through a center line of the assembled roller.
[0157]
In the figure, reference numeral 2 denotes a shaft serving as a rotating shaft, which is made of a conductive material such as stainless steel or aluminum.
[0158]
60 has a characteristic that it is compressed by a small force when a compressive force is applied in the radial direction, and does not extend more than a fixed length, for example, 1.01 to 1.2 times even with a large force against a tensile force. A roller (referred to as a diameter-suppressing roller) composed of a conductive functional material, for example, a cellulose-based conductive sponge obtained by filling cellulose with carbon black, a felt, a buffer material, or the like. A hole 60 a having the same diameter as the diameter of the shaft 2 is formed in the diameter suppressing roller 60.
[0159]
Reference numeral 16 denotes a cylinder member as the charging electrode described above, which is made of a flexible material. The inner diameter of the cylinder member 16 is the same as the outer diameter of the diameter suppressing roller 60.
[0160]
As shown in FIGS. 13 and 14, the shaft 2 is passed through the hole 60a of the diameter suppressing roller 60, and both are fixed with a conductive adhesive or the like. Then, the charging roller is formed by passing it through the inside of the cylinder member 16 and fixing the surface of the diameter suppressing roller 60 and the cylinder 16 in the same manner.
[0161]
Then, the charging device is configured by pressing the photosensitive drum with a constant pressure while rotating the shaft 1 of the charging roller.
[0162]
The present embodiment is characterized in that a diameter suppressing roller 60 is used as a suction unit for drawing a portion of the cylinder member 16 made of a flexible cylinder that does not face the photosensitive drum in a direction inside the cylinder.
[0163]
FIG. 12B shows a state in which the shaft 2 of the charging roller having the above configuration is pressed against the photosensitive drum. The diameter suppressing roller 60 at a portion away from the shaft 2 with respect to the photosensitive drum 81 is pulled and does not extend any further, and the cylinder member 16 comes into contact with the photosensitive drum 81 by this tension. On the other hand, the diameter suppressing roller 60 at a portion closer to the photosensitive drum 81 than the shaft 2 is in a compressed state. Since the cylinder member 16 has high elasticity against an out-of-plane force, the abutting portion is deformed to a state close to the curvature of the photosensitive drum as shown in FIG. At this time, since the diameter suppressing roller 60 in the compressed portion has a poor shape restoring force, the cylinder member 16 is mainly brought into contact with the photosensitive drum 81 by the tension of the diameter suppressing roller 60, and the deformation of the cylinder member 16 is reduced. This is almost the same as that shown in the first embodiment, and particularly, the curvature becomes small at the portion N in contact with the photosensitive drum 81. When the photosensitive drum 81 is rotated in this state, the cylinder member 16 rotates at substantially the same speed as the photosensitive drum 81 due to friction at the abutting portion thereof while substantially maintaining this shape.
[0164]
Here, a voltage obtained by superimposing a DC voltage on an AC voltage similar to the above embodiment is applied to the shaft 2 by the high-voltage AC power supply 6 and the DC power supply 8. Then, when a current flows through the cylinder member 16 via the shaft 2 and the diameter suppressing roller 60, discharge is started in a minute gap between the cylinder member 16 and the photosensitive drum 81, and the surface of the photosensitive drum 81 is charged.
[0165]
At this time, as described above, since the curvature of the cylinder member 16 at the portion in contact with the photosensitive drum 81 has a small curvature, the minute gap between the cylinder member 16 and the photosensitive drum 81 can be made long as in the first embodiment. And a longer discharge distance β and discharge time than the conventional roller-shaped charging member shown in FIG. As a result, similarly to the first embodiment, it is possible to avoid abnormal charging caused by abnormal discharge between the charging electrode and the image carrier, to reduce the damage to the drum, and to further cause the ripple component included in the vibration voltage. A charging roller with less potential unevenness can be provided.
[0166]
As is clear from the above description, the size of the charger of the present invention is determined by the diameter of the shaft 2 and the thickness of the diameter suppressing roller 60. Here, the diameter of the shaft is sufficient if the amount of deflection in the axial direction is small with respect to the force of contacting the cylinder member 16 with the photosensitive drum 81, and is substantially the same as the shaft 50 of the conventional contact-type charging roller shown in FIG. Is fine. On the other hand, the thickness of the diameter suppressing roller 60 may be any thickness as long as the curvature of the portion of the cylinder member 16 that contacts the photosensitive drum 81 can be sufficiently close to the diameter of the photosensitive drum 81. It is clear that the wall thickness is not so required to satisfy this condition. Therefore, according to this configuration, the charging device can be downsized as compared with a conventional charging roller using a flexible cylinder.
[0167]
Further, according to the present embodiment, the charging roller is constituted by the three members of the shaft 2, the diameter suppressing roller 60, and the cylinder member 16, so that a very simple and inexpensive charging roller can be provided as compared with the above embodiment. .
[0168]
Here, the difference between the present invention and the conventional charging roller described with reference to FIG. 17 will be clarified.
[0169]
First, the conventional charging roller shown in FIG. 17 obtains a contact pressure against the photosensitive drum 81 through a portion of the elastic member 51 facing the photosensitive drum 81 by applying a force to draw the core metal 50 toward the photosensitive drum. . On the other hand, in the present invention, by applying a pulling force to the shaft 2 in the direction of the photosensitive drum, a portion of the cylinder member 16 that is not opposed to the photosensitive drum 81 via the diameter suppressing roller 60 generates a pulling force toward the center of the cylinder, The contact pressure to the photosensitive drum is obtained by the deflection restoring force of the cylinder member 16. The bent shape of the main cylinder member 16 obtained in this manner produces the above-described effects. Due to such a difference in how the contact force is transmitted, the present invention has the following distinctive differences as compared with the conventional charging roller.
[0170]
First, the elastic member 51 in FIG. 17 which is a conventional technique is elastically deformed according to Hook's law against an external force regardless of compression / tension in a certain expansion / contraction range, such as foamable rubber. Used within elastic deformation. On the other hand, the functional material shown here expands and contracts with a very small force regardless of compression and tension within a certain range of expansion and contraction. (For example, about 1.2 times). In this case, in particular, in a state where the cylinder member 16 is extended to the limit length, a force for pulling the cylinder member 16 toward the center thereof is generated. Both are completely different in that they are used in the elastic / inelastic region.
[0171]
Further, as described in the related art, there is a conventional charging roller whose surface is covered with several layers different from the elastic member. However, the surface layer is provided for adjusting the resistance and permittivity of the roller, and has a poor shape restoring force as an elastic body against deformation in an out-of-plane direction. It takes time to recover. On the other hand, in the charging roller presented here, the surface is constituted by another member called a cylinder member, which is excellent in shape resilience (elasticity) against out-of-plane deformation, and is excellent in out-of-plane deformation. They are elastically deformed and recover their shapes instantly, and they are completely different.
[0172]
(Example 5)
Next, the configuration of a fifth embodiment of the charging device according to the present invention will be described with reference to FIG. This embodiment is characterized in that a magnet is used as a suction means for drawing a portion of a cylinder member made of a flexible cylinder that does not face the photosensitive drum in a direction toward the inside of the cylinder, and this is performed by magnetic attraction. 15A and 15B are schematic cross-sectional views when the charger is cut along a plane perpendicular to the axis of the cylinder. FIG. 15A shows a state of the charger alone, and FIG. 15B shows a state in which the charger is in contact with the photosensitive drum. FIG.
[0173]
In the figure, reference numeral 16 denotes a cylinder member as the above-mentioned charging electrode, which is made of a soft magnetic ferromagnetic material in addition to the condition of being a flexible conductor. Reference numeral 42 denotes a rigid cylindrical member (referred to as a non-magnetic cylindrical member) made of non-magnetic material such as aluminum. One end of the cylindrical member is disposed in contact with the cylinder member 16 and both ends thereof are rotatably fixed. ing. Numeral 40 denotes a T-shaped permanent magnet or electromagnet whose tip is a magnetic pole, and is disposed at a position near the side in contact with the cylinder member 16 inside the non-magnetic cylindrical member 42 as shown in the figure. . The non-magnetic cylindrical member 42 and the permanent magnet 40 have the same length as the cylinder member 16 and are fixed at both ends in the longitudinal direction. The charger of this embodiment has this configuration.
[0174]
Then, the charging device is configured by pressing the charging device against the photosensitive drum with a constant pressure.
[0175]
That is, as shown in FIG. 15B, the side of the cylinder member 16 that is not in contact with the non-magnetic cylindrical member 42 is pressed against the photosensitive drum 81. At this time, the portion of the cylinder member 16 that does not face the photosensitive drum 81 is attracted by the permanent magnet, and therefore does not separate from the non-magnetic cylindrical member 42. By this pressing, the curvature of the portion N of the cylinder member 16 that comes into contact with the photosensitive drum 81 is reduced, as shown in FIG. In this state, the electrode 44 is slidably pressed against the inner surface of the cylinder member 16.
[0176]
When the photosensitive drum 81 is rotated in this state, the charging roller rotates at substantially the same speed as the photosensitive drum 81 due to friction at the abutting portion thereof while maintaining this shape. At this time, the nonmagnetic cylindrical member 42 assists this driven rotation by its free rotation.
[0177]
Here, a voltage obtained by superimposing a DC voltage on an AC voltage similar to the above embodiment is applied to the electrode 44 by the high-voltage AC power supply 6 and the DC power supply 8. Then, when a current flows through the cylinder member 16, discharge is started in a minute gap between the cylinder member 16 and the photosensitive drum 81, and the surface of the photosensitive drum 81 is charged.
[0178]
As described above, the minute gap α between the cylinder member 16 and the photosensitive drum 81 obtained by the present charger is longer than that of the conventional charging roller shown in FIG. 17, thereby increasing the discharge distance β and the discharge time. Obtainable. As a result, it has a function of avoiding abnormal charging caused by abnormal discharge between the charging electrode and the image bearing member, has less damage to the drum, and further reduces potential unevenness due to a ripple component included in the vibration voltage. A small number of charging devices can be provided.
[0179]
(Example 6)
Next, the configuration of a sixth embodiment of the charging device according to the present invention will be described with reference to FIG. The sixth embodiment is characterized in that a hard elastic member is disposed between the shaft 2 and the diameter suppressing roller 60 in the fourth embodiment. 16A and 16B are schematic cross-sectional views when the charger is cut along a plane perpendicular to the axis of the cylinder. FIG. 16A shows a state of the charger alone, and FIG. 16B shows a state of contacting the photosensitive drum. FIG.
[0180]
In the figure, the same parts as those in FIG. 12 are denoted by the same reference numerals, and description thereof will be omitted. Reference numeral 64 denotes a roller (referred to as a pressing roller) made of a hard conductive elastic material such as conductive rubber having a cylindrical shape, and has the same axial length as the diameter suppressing roller 60. The main pressing roller 64 is positioned between the shaft 2 and the diameter suppressing roller 60 in the radial direction in a state where the end in the axial direction is aligned with the diameter suppressing roller 60, and the inner peripheral surface and the outer peripheral surface thereof are the shaft 2. And, it is fixed to the diameter suppressing roller 60 with a conductive adhesive or the like.
[0181]
Then, the charging device is constituted by pressing the photosensitive drum with a constant pressure while rotating the shaft 2 of the charging roller.
[0182]
FIG. 16B shows a state in which the shaft 2 of the charging roller is pressed against the photosensitive drum. Similarly to the fourth embodiment, the diameter suppressing roller 60 on the side closer to the photosensitive drum 81 with respect to the shaft 2 is compressed and deformed, and the diameter suppressing roller 60 on the far side extends to its limit. , And comes into contact with the photosensitive drum 81. At this time, the pressing roller 64 hardly deforms because its hardness is much higher than that of the diameter suppressing roller 60. Accordingly, in the present embodiment, in the portion N where the cylinder member 16 contacts the photosensitive drum, the pressing roller 64 presses the cylinder member 16 across the diameter suppressing roller 60, so that the cylinder member 16 is stabilized. And is brought into close contact with the photosensitive drum 81. In particular, even when the surface shape of the photosensitive drum undulates in the axial direction of the drum, the cylinder member 16 comes into close contact with the surface of the photosensitive drum 81, and a stable discharge gap α can be formed. .
[0183]
When the photosensitive drum 81 is rotated in this state, the charging roller rotates at substantially the same speed as the photosensitive drum 81 due to friction at the abutting portion thereof while maintaining this shape.
[0184]
Since a stable discharge gap can be formed in the axial direction of the drum in this manner, a charging device with less uneven charging in the axial direction of the photosensitive drum 81 than in the fourth embodiment can be provided.
[0185]
Here, the outer diameter of the pressing roller 64 is such that when the cylinder member 16 is brought into contact with the photosensitive drum 81 as shown in FIG. 16 is determined so as to have a slight nip width, and can be easily determined from its geometric shape.
[0186]
It should be noted that the present invention is not limited to the embodiment described in the above embodiment, and it is needless to say that the present invention can be appropriately modified and combined within the scope of the present invention.
[0187]
【The invention's effect】
As described in detail above, according to the present invention, instead of charging at the contact portion, the electrostatic latent image carrier is charged through the minute gap by the cylinder member made of a flexible material. A charging method, a charging device, a transfer device, and a charging method, which are relatively inexpensive, are relatively easy to manufacture, are relatively inexpensive, have less damage to the image carrier, have less charging unevenness, and do not cause problems such as generation of heat. An image forming apparatus can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of a charging roller according to a first embodiment of the present invention.
FIG. 2 is a configuration diagram illustrating an embodiment of an image forming apparatus to which the charging device according to the present invention is applied.
FIG. 3 is an exploded perspective view of the charging roller shown in FIG.
FIG. 4 is a schematic cross-sectional view of the charging roller shown in FIG. 1 in an assembled state.
FIG. 5 is a graph showing the voltage dependence of abnormal charging caused by abnormal discharge of the charging device according to the present invention.
FIG. 6 is a graph showing a discharge exposure amount on a photosensitive drum surface of the charging device according to the present invention.
FIG. 7 is an exploded perspective view of a charging roller according to Embodiment 2 of the present invention.
8 is a schematic cross-sectional view of the charging roller shown in FIG. 7 in an assembled state.
FIG. 9 is a schematic sectional view of a charging roller according to Embodiment 3 of the present invention.
FIG. 10 is an exploded perspective view of the charging roller shown in FIG.
11 is a schematic sectional view of the charging roller shown in FIG. 9 in an assembled state.
FIG. 12 is a schematic sectional view of a charging roller according to Embodiment 4 of the present invention.
FIG. 13 is an exploded perspective view of the charging roller shown in FIG.
14 is a schematic cross-sectional view of the charging roller shown in FIG. 12 in an assembled state.
FIG. 15 is a schematic sectional view of a charging roller according to Embodiment 5 of the present invention.
FIG. 16 is a schematic sectional view of a charging roller according to Embodiment 6 of the present invention.
FIG. 17 is a schematic sectional view of a conventional charging roller.
FIG. 18 is a perspective view of another configuration example of the cylinder contact member of the charging roller according to the second embodiment of the present invention.
[Explanation of symbols]
1.2: shaft, 6: high-voltage AC power supply, 8: DC power supply, 14.64: elastic roller, 16: cylinder member, 19/44: electrode, 18.28: cylinder contact member, 26: conductor wire, 40 : Permanent magnet, 42: non-magnetic cylindrical member, 60: diameter suppressing roller, 81: photosensitive drum

Claims (30)

A charging device that charges the electrostatic latent image carrier using a cylinder member as a charging electrode,
A cylinder member made of a flexible material having elasticity against an out-of-plane force;
Suction means for applying a force to draw in the direction of the inside of the cylinder member to a portion of the cylinder member that does not face the electrostatic latent image carrier, and applies a force to the suction means. By causing the cylinder member to contact the electrostatic latent image carrier and deforming it to a curvature close to that of the electrostatic latent image carrier, a discharge occurs between the cylinder member and the electrostatic latent image carrier. A charging device characterized in that the length of the minute gap is increased. A shaft rotatable with respect to a central axis is installed inside the flexible cylinder member, and the cylinder member and the shaft are formed using a plurality of wires of the same length that are supple and have a small elongation with respect to a pulling force. By connecting the cylinder member and the shaft in the circumferential direction at a constant period, and pressing the shaft against the electrostatic latent image carrier, the tension generated in the wire located farther from the shaft with respect to the image carrier is reduced. The charging device according to claim 1, wherein a portion of the cylinder member that does not face the image carrier is drawn toward the inside of the cylinder by using as a suction unit. The diameter of the cylinder member in a cylindrical state (a state of a circular section) where no force is applied is D, and the shaft is moved to one side in the radial direction of the cylinder member so that a wire at one end is stretched to the cylinder member in that state. When the distance between the cylinder member and the center position of the shaft is d, the length of each wire between the shaft and the cylinder member is determined so that 0.01D <d <0.2D. The charging device according to claim 2, wherein A shaft rotatable with respect to a central axis is installed inside the flexible cylinder member, and the cylinder member and the shaft are made of a plurality of film materials of the same length that are supple and have a small elongation with respect to a pulling force. Then, by connecting the cylinder member and the shaft in the circumferential direction at a constant period and pressing the shaft against the electrostatic latent image carrier, a tension generated in a film material located farther from the image carrier than the shaft is generated. 2. The charging device according to claim 1, wherein a portion of the cylinder member that does not face the image carrier is drawn toward the inside of the cylinder by using the suction member as the suction unit. D is the diameter of the cylinder member in a cylindrical state (with a circular cross section) where no force is applied, and the shaft is moved to one side in the radial direction of the cylinder member so that one end of the film material is stretched against the cylinder member in that state. When the distance between the cylinder member and the center position of the shaft is d, the length of each film material between the shaft and the cylinder member is determined so that 0.01D <d <0.2D. The charging device according to claim 4, wherein the charging device is a charging device. A shaft rotatable with respect to a central axis is installed inside the flexible cylinder member, and the cylinder member and the shaft are formed using a plurality of wires of the same length that are supple and have a small elongation with respect to a pulling force. By connecting the cylinder member and the shaft in the circumferential direction at a constant period, an elastic roller member having a smaller diameter than the cylinder member is installed on a part of the shaft, and the shaft is pressed against the electrostatic latent image carrier. By using the tension generated in the wire positioned farther than the shaft with respect to the image carrier as the suction means, the portion of the cylinder member that does not face the image carrier is drawn toward the inside of the cylinder, 2. The charging device according to claim 1, wherein an elastic roller member presses a portion where the cylinder member contacts the image carrier. Location. A shaft rotatable with respect to the central axis is installed inside the flexible cylinder member, and between the shaft and the cylinder member, in a certain range of expansion and contraction in the radial direction, regardless of compression and tension. It expands and contracts with an extremely small force, and with respect to a tensile deformation larger than that, a diameter suppressing roller made of a conductive functional material having a characteristic that it does not extend beyond a certain length even with a large force, a shaft and a diameter suppressing roller, The diameter suppressing roller and the cylinder member are configured to be fixedly disposed, respectively, and the shaft is pressed against the electrostatic latent image carrier, so that the diameter suppressing roller is located farther from the image carrier than the shaft. Is used as the suction means, and a portion of the cylinder member that does not face the image carrier is drawn toward the inside of the cylinder. The charging device according to claim 1, characterized in Rukoto. The flexible cylinder member is made of a soft magnetic material, and is extended in a rod shape in the axial direction of the cylinder member at a position displaced from the center of the inside in a direction without the electrostatic latent image carrier, and both ends thereof are supported. By disposing a magnet and pressing the magnet against the electrostatic latent image carrier, a magnetic attraction force acting between the magnet and the cylinder member is used as the attraction means, so that a portion of the cylinder member that does not face the image carrier. 2. The charging device according to claim 1, wherein the charging device is attracted toward the inside of the cylinder. The said magnet was smaller in diameter than the said cylinder member, the axis | shaft was parallel to the cylinder member, and the both ends were contained in the nonmagnetic cylindrical member fixed rotatably, The said claim characterized by the above-mentioned. 9. The charging device according to 8. 8. The pressing roller according to claim 7, wherein a pressing roller made of a conductive elastic material that is harder than the cylindrical diameter suppressing roller is disposed between the shaft and the diameter suppressing roller in the radial direction of the shaft. Charging device. A flexible tubular member capable of contacting with the member to be charged, having at least its surface being conductive and having an autonomy so as to form an internal space in a free state, and facing the member to be charged via the internal space; While the distance between the flexible tubular member and the center for rotating the flexible tubular member of the portion is kept within a desired distance range, the opposed portion is attached toward the internal space. And a member for energizing the charging device. The urging member may be a linear or planar member that extends radially from a shaft disposed at the center for the rotation and is deformable and coupled to the inner surface of the flexible tubular member. The charging device according to claim 11, further comprising a member. 12. The device according to claim 11, wherein the urging member has a porous member disposed in the internal space, and the porous member is a member that is easily compressed and has little tensile deformation. Charging device. 12. The charging device according to claim 11, wherein the flexible tubular member has a magnetic material, and the biasing member has a magnetic force generating unit disposed in the internal space. A transfer device that transfers the toner held on the electrostatic latent image carrier using a cylinder member as a charging electrode,
A cylinder member made of a flexible material having elasticity against an out-of-plane force;
A suction unit that is located inside the cylinder member and applies a force to draw in a direction inside the cylinder member to a portion of the cylinder member that does not face the electrostatic latent image carrier;
Discharge is generated by applying a force to the suction means so as to make contact with the electrostatic latent image carrier and deforming the cylinder member to a curvature close to the electrostatic latent image carrier. A transfer device wherein a length of a minute gap between a cylinder member and an electrostatic latent image carrier is increased. A shaft rotatable with respect to a central axis is installed inside the flexible cylinder member, and the cylinder member and the shaft are formed using a plurality of wires of the same length that are supple and have a small elongation with respect to a pulling force. By connecting the cylinder member and the shaft in the circumferential direction at a constant period, and pressing the shaft against the electrostatic latent image carrier, the tension generated in the wire located farther from the shaft with respect to the image carrier is reduced. 16. The transfer device according to claim 15, wherein a portion of the cylinder member that does not face the image carrier is drawn toward the inside of the cylinder by using the suction unit. The diameter of the cylinder member in a cylindrical state (a state of a circular section) where no force is applied is D, and the shaft is moved to one side in the radial direction of the cylinder member so that a wire at one end is stretched to the cylinder member in that state. When the distance between the cylinder member and the center position of the shaft is d, the length of each wire between the shaft and the cylinder member is determined so that 0.01D <d <0.2D. 17. The transfer device according to claim 16, wherein the transfer is performed. A shaft rotatable with respect to a central axis is installed inside the flexible cylinder member, and the cylinder member and the shaft are made of a plurality of film materials of the same length that are supple and have a small elongation with respect to a pulling force. Then, by connecting the cylinder member and the shaft in the circumferential direction at a constant period and pressing the shaft against the electrostatic latent image carrier, a tension generated in a film material located farther from the image carrier than the shaft is generated. 16. The transfer device according to claim 15, wherein a portion of the cylinder member, which does not face the image carrier, is drawn toward the inside of the cylinder by using the suction member as the suction unit. The diameter of the cylinder member in a cylindrical state (a state of a circular section) where no force is applied is D, and the shaft is moved to one side in the radial direction of the cylinder member so that a wire at one end is stretched to the cylinder member in that state. The length of each film material between the shaft and the cylinder member is determined so that 0.01D <d <0.2D, where d is the distance between the cylinder member and the center position of the shaft. 19. The transfer device according to claim 18, wherein: A shaft rotatable with respect to a central axis is installed inside the flexible cylinder member, and the cylinder member and the shaft are formed using a plurality of wires of the same length that are supple and have a small elongation with respect to a pulling force. By connecting the cylinder member and the shaft in the circumferential direction at a constant period, an elastic roller member having a smaller diameter than the cylinder member is installed on a part of the shaft, and the shaft is pressed against the electrostatic latent image carrier. By using the tension generated in the wire positioned farther than the shaft with respect to the image carrier as the suction means, the portion of the cylinder member that does not face the image carrier is drawn toward the inside of the cylinder, 16. The roller according to claim 15, wherein a portion where the cylinder member contacts the image carrier is pressed by an elastic roller member. Apparatus. A shaft rotatable with respect to the central axis is installed inside the flexible cylinder member, and between the shaft and the cylinder member, in a certain range of expansion and contraction in the radial direction, regardless of compression and tension. It expands and contracts with an extremely small force, and with respect to a tensile deformation larger than that, a diameter suppressing roller made of a conductive functional material having a characteristic that it does not extend beyond a certain length even with a large force, a shaft and a diameter suppressing roller, The diameter suppressing roller and the cylinder member are configured to be fixedly disposed, respectively, and the shaft is pressed against the electrostatic latent image carrier, so that the diameter suppressing roller is located farther from the image carrier than the shaft. Is used as the suction means, and a portion of the cylinder member that does not face the image carrier is drawn toward the inside of the cylinder. Transfer apparatus according to claim 15, characterized in Rukoto. The flexible cylinder member is made of a soft magnetic material, and is extended in a rod shape in the axial direction of the cylinder member at a position displaced from the center of the inside in a direction without the electrostatic latent image carrier, and both ends thereof are supported. By disposing a magnet and pressing the magnet against the electrostatic latent image carrier, a magnetic attraction force acting between the magnet and the cylinder member is used as the attraction means, so that a portion of the cylinder member not facing the image carrier. 16. The transfer apparatus according to claim 15, wherein the transfer device is drawn toward the inside of the cylinder. The said magnet was smaller in diameter than the said cylinder member, the axis | shaft was parallel to the cylinder member, and the both ends were contained in the nonmagnetic cylindrical member fixed rotatably, The said claim characterized by the above-mentioned. 23. The transfer device according to 22. 22. The pressing roller according to claim 21, wherein a pressing roller made of a conductive elastic material that is harder than the cylindrical diameter suppressing roller is disposed between the shaft and the diameter suppressing roller in the radial direction of the shaft. Transfer device. A flexible tubular member which is capable of contacting the member to be transferred and has a self-sustainability so that at least its surface is conductive and forms an internal space in a free state, and faces the member to be charged via the internal space. While the distance between the flexible tubular member and the center for rotating the flexible tubular member of the portion is kept within a desired distance range, the opposed portion is attached toward the internal space. And a member for energizing the transfer device. The urging member may be a linear or planar member that extends radially from a shaft disposed at the center for the rotation and is deformable and coupled to the inner surface of the flexible tubular member. The transfer device according to claim 25, further comprising a member. 26. The member according to claim 25, wherein the urging member has a porous member disposed in the internal space, and the porous member is a member that is easily compressed and has little tensile deformation. Transfer device. 26. The transfer device according to claim 25, wherein the flexible tubular member has a magnetic body, and the biasing member has a magnetic force generating unit disposed in the internal space. A charging device according to any one of claims 1 to 14, an electrostatic latent image carrier, and an exposure unit for forming an electrostatic latent image formed on the electrostatic latent image carrier. An image forming apparatus, comprising: a developing device for forming a visible image corresponding to the electrostatic latent image formed on the electrostatic latent image carrier. A transfer device according to any one of claims 15 to 28, a charging device, an electrostatic latent image carrier, and an electrostatic latent image formed on the electrostatic latent image carrier. An image forming apparatus comprising: an exposing unit; and a developing device for forming a visible image corresponding to the electrostatic latent image formed on the electrostatic latent image carrier.

Images