JP2014006399A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce malfunctions of an image forming apparatus and to improve the durability (lifetime) of the image forming apparatus.SOLUTION: In an image forming apparatus according to the invention in which an electrostatic latent image formed on the surface 1a of an image carrier 1 is developed with developer and imaged and the thus formed developer image is transferred to paper P, an electrostatic cleaning member 82 that electrostatically cleans off developer remaining on the surface of the image carrier is arranged upstream in the direction of rotation of the image carrier from a plate-like cleaning member 85 that cleans off developer remaining on the surface of the image carrier by coming into contact with the surface from a direction counter to the direction of rotation of the image carrier. Lubricant application means 9 is arranged downstream of the plate-like cleaning member 85 in the direction of rotation of the image carrier.

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a facsimile, a printer, a copying machine, and a multi-function machine having a plurality of functions as one, and more particularly, an image forming apparatus provided with an image carrier and a cleaning member for the image carrier Concerning improvement of durability.

  In an electrophotographic image forming apparatus, various means such as charging, exposure, development, transfer, static elimination, and cleaning are arranged around a belt-shaped or drum-shaped photoconductor serving as an image carrier. Then, the surface of the photoreceptor is uniformly charged by a charging means such as corona discharge, and an electrostatic latent image is formed by performing exposure corresponding to characters to be printed by the exposure means, and becomes a developer by the developing means. The electrostatic latent image is developed with toner to form an image. Thereafter, the toner image on the photosensitive member is transferred onto the intermediate transfer member by contact with the intermediate transfer member and bias application, and the toner image on the intermediate transfer member is transferred onto a sheet as a recording medium to transfer the toner. The toner image is fixed by heating and pressurizing the printed paper by the fixing means to complete the printing. After the transfer, the surface of the photoconductor is cleaned by removing the developer remaining in the cleaning unit, and the same process is repeated.

  In the image forming apparatus having the above-described configuration, it is required to extend the life of replacement parts such as a photoreceptor and a cleaning unit. Particularly in an image forming apparatus used in an industry that performs a large amount of printing such as a production printing business, the life of a replacement part greatly affects the cost per printing (CPP). The improvement of the life has a great effect on the running cost reduction.

  The key to improving the life of each of the cleaning means using a blade cleaning method made of an elastic member such as a photosensitive member and urethane rubber using a plate-like cleaning member is, in the case of the photosensitive member, a reduction in the wear rate of the surface layer of the photosensitive member. In the case of the cleaning means, the amount of wear on the edge of the cleaning member is reduced. The cleaning means using a plate-shaped cleaning member has a simple configuration, and a slight amount of toner is almost completely obtained by contacting the surface of the photosensitive member in the counter direction with respect to the rotational direction of the photosensitive member. It is widely adopted because it can be cleaned. The lifetime of the cleaning means using this cleaning member is determined by the amount of wear on the edge of the cleaning member that is in contact. As the amount of wear on the edge progresses, a large amount of toner cannot be damped, and slips downstream of the cleaning portion by the cleaning member in the rotation direction of the photosensitive member, resulting in a vertical streak image and an abnormal image. As an acceleration factor of edge wear, a large amount of toner is input to the edge of the cleaning member when a large amount of images having a high image area ratio are continuously printed. The additive (silica) slips through the cleaning member, and the edge of the cleaning member is damaged during the slipping, so that the cleaning member wears.

  As a method of reducing the progress of wear of the cleaning member, there is an optimization of the material prescription of the member, but basically it does not significantly change the physical properties of urethane rubber, so it can not dramatically improve the service life. Absent. As a method for dramatically reducing the progress of wear of the cleaning member, it is effective to prevent a large amount of toner from being input.

  Another problem that occurs when a large amount of toner is input to the edge of the cleaning member is that when the silica, which is the toner additive, passes through the cleaning member, the silica is exposed to mechanical stress from the cleaning member and is exposed to light. There is a phenomenon that sticks to the surface of the photoreceptor as it pierces the body and grows. Since the toner cannot be placed on the fixed portion, the portion becomes apparent as an abnormal image of white spots. Even for this problem, it is effective to reduce the amount of toner input to the cleaning member.

  As a countermeasure against such problems, conventionally, a lubricant such as zinc stearate is applied to the surface of the photoconductor with an application member, and a lubricant layer is formed on the surface of the photoconductor to protect it so that silica is not easily stuck. Prevents sticking. However, in this configuration, it is necessary to apply a large amount of lubricant when printing a large amount of a high image area ratio image, and there is a problem that the lifetime of the lubricant is lost. Further, the toner slipped from the cleaning member adheres to the application brush used as the lubricant application member, which promotes the scraping of zinc stearate, and this mechanism also causes a decrease in the life of the lubricant. .

  In addition, another concern about the large amount of toner input is that the scraping of the surface film of the photoreceptor proceeds. When the toner or toner additive slips through the edge of the cleaning member, it becomes an abrasive and scrapes the surface of the photoreceptor to reduce the life of the photoreceptor. On the other hand, it is conceivable to increase the film thickness of the photoconductor, but by making the film thick, residual charge remains on the photoconductor, and a desired photoconductor surface potential cannot be obtained, resulting in an image density. There is a problem that repeat fluctuations occur. From this point of view, the film thickness from the surface of the photoreceptor to the charge generation layer should be as thin as possible. Therefore, also for this problem, it is effective to prevent a large amount of toner from being input to the edge of the cleaning member.

  On the other hand, as another form of the cleaning means, there is an electrostatic cleaning system in which the toner is electrically cleaned by applying a bias to the brush member, instead of using a plate-shaped cleaning member. The advantages of this method are that it has a higher ability to collect toner than a plate-shaped cleaning member even when a large amount of toner is input, and it does not apply mechanical stress to the toner, so silica adheres to the surface of the photoreceptor. It is difficult to generate. Disadvantages of the electrostatic cleaning method are that it is impossible to collect a small amount of toner with different polarities, and it is necessary to arrange a plurality of brush members to collect toner of each polarity. The point which becomes expensive is mentioned.

  As a means to complement the disadvantages of the blade cleaning method and electrostatic cleaning brush method, a cleaning member composed of a single brush member that electrostatically cleans the toner upstream of the photosensitive member rotation direction, and a plate on the downstream side A configuration in which the respective cleaning members are arranged is conceivable. The aim of this configuration is that when a large amount of toner is input, most of the toner is cleaned by a brush member having a high recovery capability, and a small amount of toner with a different polarity is capable of completely cleaning a small amount of toner. By arranging a high plate-shaped cleaning member in contact with the photoconductor surface from the counter direction with respect to the photoconductor rotation direction and cleaning with the member, edge wear and photoconductor wear are significantly reduced. It is possible to prevent silica from sticking to the surface. Patent document 1 is mentioned as such a structure.

However, the configuration described in Patent Document 1 is not a perfect configuration, and a very small amount of untransferred toner is input when printing close to a blank image. Therefore, if these are collected by the brush member, the edge of the cleaning member No toner is input to the surface, and the cleaning member is likely to be caught. The cleaning member that comes into contact with the surface of the photoconductor from the counter direction has a high adhesion force between the surface of the photoconductor and the edge unless fine particles such as toner and toner additives are input, and the phenomenon of entrainment often occurs. . If the plate-shaped cleaning member is caught, it cannot normally be restored naturally, resulting in a failure of the device, and the reliability of the device is significantly reduced.
SUMMARY OF THE INVENTION An object of the present invention is to improve durability (life) with less occurrence of failures in an image forming apparatus.

  In order to achieve the above-described object, the electrostatic latent image formed on the surface of the image carrier according to the present invention is developed with a developer to form an image, and the formed developer image is transferred to a recording medium. In the image forming apparatus, the plate-shaped cleaning member that contacts the surface of the image carrier from the counter direction with respect to the rotation direction of the image carrier and cleans the developer remaining on the surface, and the image carrier rotates more than the cleaning member. And a brush-like electrostatic cleaning member that electrostatically cleans the developer staying on the surface of the image carrier, and a downstream side in the image carrier rotation direction of the plate-like cleaning member. It has the characteristic that it has the lubricant application means arrange | positioned.

  According to the present invention, the image carrier is disposed upstream of the plate-shaped cleaning member that cleans the developer staying on the surface in contact with the image carrier rotation direction from the counter direction. Since it has a brush-like electrostatic cleaning member that electrostatically cleans the developer residing on the surface of the body, and a lubricant application means disposed downstream of the plate-like cleaning member in the image carrier rotation direction. In addition, it is not necessary to increase the consumption of the lubricant to prevent the generation of silica, and it is possible to suppress the consumption to the minimum necessary for preventing the plate-like cleaning member from being caught. For this reason, it is possible to prevent the entrainment of the plate-like cleaning member, to improve the life of the lubricant application means by reducing the lubricant consumption by improving the margin for preventing silica sticking, and to improve the margin for preventing the progress of the film scraping of the photosensitive drum. The effect of improving the durability (life) of the lubricant application means by reducing the lubricant consumption can be obtained. That is, the occurrence of failure of the image forming apparatus is small, and durability (life) can be improved.

1 is a schematic configuration diagram showing a first embodiment of an image forming apparatus according to the present invention. The enlarged view which shows typically the cleaning state by a brush-shaped electrostatic cleaning member at the time of printing of the image of a high image area ratio. The enlarged view which shows typically the cleaning state by the plate-shaped cleaning member at the time of printing of the image of a high image area ratio. The enlarged view which shows typically the cleaning state by the brush-shaped electrostatic cleaning member and the plate-shaped cleaning member at the time of printing the image of a low image area ratio. FIG. 5 is a schematic configuration diagram illustrating a second embodiment of the image forming apparatus according to the present invention and a state before a non-imaged area on the image carrier reaches a brush-like electrostatic cleaning member. FIG. 3 is a schematic configuration diagram illustrating a state where a non-imaged region on the image carrier has reached a brush-like electrostatic cleaning member. FIG. 10 is a flock diagram of a configuration related to cleaning bias control performed in the second embodiment. The flowchart which shows the cleaning bias control processing content.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 is a schematic diagram showing a configuration of a high-speed full-color printer which is an embodiment of the image forming apparatus according to the present invention. The image forming apparatus includes a photosensitive drum 1 serving as an image carrier and various means such as charging, exposure, development, transfer, and cleaning. The image forming apparatus includes four sets of the photosensitive drum 1 and charging, exposing, developing, transferring, and cleaning means corresponding to yellow, magenta, cyan, and black colors. Since they have the same configuration, one of them will be described as a representative here.

  The photosensitive drum 1 is configured to be rotationally driven by a drive motor (not shown) in the direction of the arrow in the drawing. Around the photosensitive drum 1, a charging charger 2 as a charging unit, a developing unit 4, a transfer roller 6 as a primary transfer unit, a neutralizing lamp 7 as a neutralizing unit, a cleaning unit 8, and a lubricant applying unit 9 are arranged. Has been.

  The lubricant application means 9 is disposed between the lubricant 92 biased toward the photosensitive drum 1 by a spring 91 serving as a biasing means, and between the lubricant 92 and the photosensitive drum 1. An application brush 93 serving as an application member applied to the surface of the body drum 1 and a lubricant blade 94 for making the applied lubricant 92 uniform are provided. In this embodiment, the lubricant 92 is made of zinc stearate hardened in a block shape. As the lubricant 92, a known material other than zinc stearate may be used.

  The cleaning unit 8 mechanically writes off the transfer residual toner remaining on the photosensitive drum 1 and the electrostatic cleaning unit 80 that electrostatically cleans the transfer residual toner that becomes a developer remaining on the photosensitive drum 1. And a blade cleaning unit 81.

  The electrostatic cleaning unit 80 includes an electrostatic cleaning brush 82 serving as a brush-like cleaning member that electrostatically cleans the transfer residual toner when a cleaning bias is applied. The electrostatic cleaning brush 82 is rotatably supported by a stationary member such as a side plate (not shown), and a cleaning bias having a polarity opposite to that of the transfer residual toner (here, + polarity) is directly applied to a shaft portion thereof from a power source (not shown). It is comprised so that. The cleaning bias is not limited to the one that is directly applied to the electrostatic cleaning brush 82, but may be configured to be indirectly applied to the electrostatic cleaning brush 82.

  Around the electrostatic cleaning brush 82, a metal recovery roller 83 serving as a recovery member for electrostatically recovering the transfer residual toner cleaned from the photosensitive drum 1 from the electrostatic cleaning brush 82, and a contact with the recovery roller 83 A recovery blade 84 that removes the recovered toner from the recovery roller 83 is provided.

  The blade cleaning unit 81 is a cleaning blade 85 serving as a plate-like cleaning unit that removes transfer residual toner on the surface 1a of the photosensitive drum 1 by contacting the edge 85A from the counter direction with respect to the rotation direction of the photosensitive drum 1. Is attached to a side plate (not shown) via a bracket 86.

  In this embodiment, the electrostatic cleaning brush 82 is disposed upstream of the cleaning blade 85 in the rotation direction of the photosensitive drum, and the lubricant application unit 9 is disposed downstream of the cleaning blade 85 in the rotation direction of the photosensitive drum. ing.

  The photosensitive drum 1 is uniformly charged by corona discharge by a charging charger 2 serving as charging means. The uniformly charged photosensitive drum 1 is irradiated with laser light corresponding to an image to be printed with exposure light 3 from a writing device (not shown), whereby an electrostatic latent image is formed on the surface thereof. This electrostatic latent image is developed by the developing means 4 with toner as a developer supplied to the surface of the photosensitive drum 1a.

  The toner image on the surface 1 a of the photosensitive drum is applied by applying a primary transfer bias from the transfer roller 13 onto the intermediate transfer belt 5 serving as an intermediate transfer member disposed between the photosensitive drum 1 and the transfer roller 13. Transcribed. In the case of monochrome printing, a black toner image is transferred to the intermediate transfer belt 5 and transferred to a sheet serving as a recording medium in a secondary transfer unit (not shown). In the case of color printing, the toner images of the respective colors are transferred to the intermediate transfer belt 5 and are collectively transferred to a sheet serving as a recording medium in a secondary transfer unit (not shown).

  The photosensitive drum 1 after the transfer is reset by removing the remaining electrostatic potential due to light irradiation of the static elimination lamp 7. Further, the transfer residual toner is removed from the surface 1 a of the photosensitive drum 1 by the cleaning means 8. After removing the transfer residual toner, the surface of the photosensitive drum 1 is protected by applying the lubricant 92 to the surface 1a by the lubricant applying means 9.

  The situation when a large amount of images with a high image area ratio is printed in the configuration around the photosensitive drum described in FIG. 1 will be described. When an image having a high image area ratio is formed, the electrostatic latent image is developed on the photosensitive drum 1 with a large amount of toner, so that the transfer residual toner 100 after the toner is transferred to the intermediate transfer belt 5 or the like. Is also generated on the surface 1a of the photosensitive drum. A large amount of untransferred toner 100 is collected by an electrostatic cleaning brush 82 of the cleaning unit 8 as shown in FIG. Most of the transfer residual toner has a negative polarity, and most of the negative transfer residual toner 100 is recovered by being cleaned by the electrostatic cleaning brush 82 charged to the positive polarity. Since the contact pressure of the electrostatic cleaning brush 82 to the photosensitive drum 1 is low and the residual toner 100 is electrically collected, no mechanical stress is applied to the residual toner 100 and silica as a toner additive is separated. Thus, there is almost no phenomenon of sticking to the surface 1a of the photosensitive drum.

  A small amount of + polar residual transfer toner 100 passes through the electrostatic cleaning brush 82 and is input between the edge 85a of the cleaning blade 85 and the photosensitive drum surface 1a as shown in FIG. At this time, the toner input amount is almost recovered by the electrostatic cleaning brush 82 because it is disposed upstream of the cleaning blade 85 in the rotational direction of the photosensitive drum even when printing a large amount of high images. It will be slight. For this reason, the transfer residual toner 100 having a slight + polarity is easily scraped off by the edge 85a of the cleaning blade 85, and the surface 1a of the photosensitive drum can be cleaned. Further, since the amount of toner input is small, the damage (wear) of the edge 85a of the cleaning blade 85 is extremely small, and the transfer residual toner 100 that is stressed is also small, so that the edge 85a is worn and the surface of the photosensitive drum 1 is exposed. Silica sticking to 1a can also be prevented.

  On the other hand, a situation when an image with a low image area ratio that is close to a blank sheet is printed will be described below. Since the amount of toner used for development is small at the time of a low image, the transfer residual toner 100 becomes very small. As shown in FIG. 4, most of the untransferred toner 100 on the photosensitive drum surface 1a is collected when it reaches the electrostatic cleaning brush 82 as the photosensitive drum 1 rotates. The toner input amount is almost zero. For this reason, if the image drawing rate with a low image area rate continues, the possibility of the cleaning blade 85 being caught increases. However, as shown in FIG. 1, the lubricant 92 applied downstream from the cleaning blade 85 makes one round and reaches the edge 85 a of the cleaning blade 85, so that the fine particles of the lubricant 92 pass through the cleaning blade 85. By doing so, an excessive adhesion force between the photosensitive drum 1 and the cleaning blade 85 can be prevented, and the cleaning blade 85 can be prevented from being caught.

  According to such a configuration, the electrostatic cleaning brush 82 is disposed upstream of the cleaning blade 85 in the rotation direction of the photosensitive drum. The effect of preventing silica from sticking to the surface 1a of the photosensitive drum 1 due to a large amount of toner 100 input, and preventing the progress of film scraping of the photosensitive drum 1 due to a large amount of input of the transfer residual toner 100 can be obtained.

  By disposing the cleaning blade 85 downstream of the electrostatic cleaning brush 82 in the photosensitive drum rotation direction, it is not necessary to dispose a plurality of electrostatic cleaning brushes 82 as in the conventional configuration, and one electrostatic cleaning brush 82 is provided. Can be reduced.

  Since the lubricant applying means 9 is disposed downstream of the electrostatic cleaning brush 82 and the cleaning blade 85 in the rotation direction of the photosensitive drum, it is not necessary to increase the consumption amount of the lubricant 92 in order to prevent the generation of silica. It is possible to reduce the consumption to the minimum necessary for preventing the 85 from being caught. For this reason, it is possible to prevent the cleaning blade 85 from being caught, to improve the life of the lubricant application means 9 by reducing the lubricant consumption by improving the allowance for preventing silica sticking, and to improve the allowance for preventing the progress of film scraping of the photosensitive drum 1. The effect of improving the life of the lubricant application means 9 by reducing the lubricant consumption can be obtained.

According to the mechanism described above, the lifetime of each key part shown in FIG.
(Second Embodiment)
The second embodiment will be described with reference to FIGS. In the image forming apparatus shown in FIG. 1, in order to improve the function of the electrostatic cleaning unit 80, the transfer residual toner 100 that has been cleaned by the electrostatic cleaning brush 82 and adhered to the brush 82 is removed to It is necessary to strengthen the function to prepare for cleaning.

  The transfer residual toner 100 attached to the electrostatic cleaning brush 82 is electrically firmly attached because the cleaning bias (voltage) is applied to the electrostatic cleaning brush 82.

  Therefore, a metal recovery roller 83 such as SUS is provided so as to contact the electrostatic cleaning brush 82, and a voltage higher than the voltage applied to the electrostatic cleaning brush 82 from the power source 201 is supplied to the recovery roller 83. By applying from 202, the toner is transferred from the electrostatic cleaning brush 82 to the collection roller 83, and the electrostatic cleaning brush 82 is refreshed. The toner adhering to the collection roller 83 is scraped off by the collection blade 84 and dropped to the waste toner container.

  In such a configuration, it is difficult to refresh the brush cleanly while the electrostatic cleaning brush 82 makes one round, and a considerable amount of toner remains on the electrostatic cleaning brush 82. If the toner remains on the electrostatic cleaning brush 82, the ability to collect the transfer residual toner 100 originally attached to the photosensitive drum 1 is lowered, and the function as the electrostatic cleaning unit 80 is lowered.

  With respect to such a problem, in this embodiment, as shown in FIG. 5, a region A where toner is not attached in a non-image forming portion such as a sheet interval on the surface 1a of the photosensitive drum 1 is shown in FIG. The voltage applied to the electrostatic cleaning brush 82 is reduced or reduced to zero at the timing when it reaches the position facing the electrostatic cleaning unit 80, so that the transfer residual toner 100 remaining on the electrostatic cleaning brush 82 is attached. The adhesion force is reduced to facilitate collection on the collection roller 83. At this time, the electrostatic cleaning brush 82 has a reduced ability to collect the transfer residual toner 100 on the surface of the photosensitive drum. However, in this case, since there is almost no transfer residual toner 100 in the region A, there is no problem.

  Further, when the voltage of the electrostatic cleaning brush 82 is lowered, there may be a case where a phenomenon occurs in which the transfer residual toner 100 attached to the electrostatic cleaning brush 82 is slightly transferred back to the photosensitive drum 1. Further, since the cleaning blade 85 is disposed downstream of the rotation direction of the photosensitive drum, the reversely transferred toner can be scraped off and cleaned. There is no problem in this configuration. By performing voltage application control to the electrostatic cleaning brush 82 as described above, the function of the electrostatic cleaning unit 80 can be enhanced without any problems.

  As a form of voltage application control to the electrostatic cleaning brush 82, as shown in FIG. 7, a power source 201 and a collection roller for applying a cleaning bias to the electrostatic cleaning brush 82 to the control means 200 provided in the image forming apparatus. A power supply 202 for applying a cleaning bias to the line 83 is connected by wiring or the like, and information such as rotation information of the photosensitive drum 1 and paper feeding timing is input to the control unit 200. As shown in FIG. 8, the control means 200 controls the power supplies 201 and 202 so as to apply a preset cleaning bias to the electrostatic cleaning brush 82 and the collection roller 83, respectively. Next, the timing at which the region A where no toner adheres, such as between sheets, faces the electrostatic cleaning brush 82 is determined from the rotation information of the photosensitive drum 1 and information such as the sheet feeding timing. Specifically, it is determined whether or not the region A is opposed to the electrostatic cleaning brush 82, and in the case where it is opposed, this is achieved by controlling the power source 201 so that the cleaning bias is lower than that during cleaning. Can do.

DESCRIPTION OF SYMBOLS 1 Image carrier 1a Image carrier surface 9 Lubricant application means 82 Brush-like electrostatic cleaning member 85 Plate-like cleaning member 100 Residing developer

Japanese Patent No. 4597837

Claims (3)

In an image forming apparatus in which an electrostatic latent image formed on the surface of an image carrier is developed with a developer to form an image, and the formed developer image is transferred to a recording medium.
A plate-like cleaning member that contacts the surface of the image carrier from the counter direction with respect to the rotation direction of the image carrier and cleans the developer remaining on the surface;
A brush-shaped electrostatic cleaning member that is disposed upstream of the cleaning member in the rotation direction of the image carrier and electrostatically cleans the developer staying on the surface of the image carrier;
An image forming apparatus comprising: a lubricant application unit disposed downstream of the plate-shaped cleaning member in the rotation direction of the image carrier. In an image forming apparatus in which an electrostatic latent image formed on the surface of an image carrier is developed with a developer to form an image, and the formed developer image is transferred to a recording medium.
A plate-like cleaning member that contacts the surface of the image carrier from the counter direction with respect to the rotation direction of the image carrier and cleans the developer remaining on the surface;
The developer disposed on the upstream side of the plate-shaped cleaning member in the rotation direction of the image carrier and electrostatically cleans the developer staying on the surface of the image carrier by applying a voltage directly or indirectly. Having a brush-like electrostatic cleaning member,
The voltage applied to the brush-like cleaning member is reduced at a timing when a non-imaged area on the surface of the image carrier reaches a position facing the brush-like cleaning member. .   3. The image forming apparatus according to claim 2, wherein a lubricant application unit that applies a lubricant to the image carrier is disposed downstream of the cleaning member.

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