JP5288260B2 - Cleaning device and image forming apparatus - Google Patents

Description

  The present invention relates to a cleaning device used in an image forming apparatus such as a copying machine, a facsimile machine, and a printer, and an image forming apparatus including the same.

  Conventionally, as a cleaning means for removing toner remaining on a photosensitive member after transfer of a toner image as a member to be cleaned, a blade cleaning type in which a rubber blade is brought into contact with the photosensitive member to remove the toner is known. ing. In the blade cleaning method, if the accuracy of adhesion between the blade and the surface of the photosensitive member is low, the toner slips and the cleaning property is liable to deteriorate. In order to prevent this, the blade is pressed against the photosensitive member with a strong contact pressure. However, when the blade is pressed against the photosensitive member with a strong contact pressure, the blade is turned over, causing streaky or strip-like cleaning failure, and it is difficult to maintain stable cleaning performance. Further, in the long term, the surface film scraping of the photoreceptor is promoted and the life of the photoreceptor is shortened.

  In recent years, there has been an increasing demand for higher image quality, and there is a tendency to reduce the particle size of toner. Furthermore, in order to reduce the toner manufacturing cost and improve the transfer rate, an image forming apparatus using a spherical toner formed from a pulverized (indeterminate) toner by a polymerization method or the like has been commercialized. When such a small particle diameter and spherical toner is used, it is known that the cleaning property is inferior to the pulverized toner in the blade cleaning method.

  Patent Document 1 discloses a cleaning method that has a good cleaning property even when cleaning a small particle size toner or a spherical toner and that suppresses mechanical rubbing that can reduce surface film abrasion of the photoreceptor. There are various electrostatic brush cleaning methods. The electrostatic brush cleaning method of Patent Document 1 includes a brush roller having conductive brush fibers so as to contact and rub against the surface of the photoreceptor, and further, a collection roller is arranged in contact with the brush fibers, and The toner is removed by a cleaning means comprising a rubber blade. At this time, a voltage is applied to both the collecting roller or the brush fiber and the collecting roller, and the toner is removed from the photoreceptor by electrostatic force in addition to the rubbing force by the brush. For this reason, the cleaning performance can be obtained even with respect to a small particle size toner or a spherical toner.

  As the recovery roller, one having a high resistance layer or an insulating layer on the surface is preferable. This is because if the surface of the collecting roller is conductive, charge is injected from the surface of the collecting roller to the toner on the brush roller at the contact portion between the collecting roller and the polarity of the toner with a low charge amount is reversed. Resulting in. The toner whose polarity is reversed does not move onto the collecting roller but remains on the brush roller. The toner remaining on the brush roller encounters the image carrier again by rotation, and adheres again to the image carrier to become cleaning residual toner, thereby degrading the cleaning performance on the image carrier. For this reason, in order to prevent charge injection from the collecting roller to the toner, it is preferable that the surface layer of the collecting roller has high resistance or insulation.

  Here, when the photosensitive member and the brush roller are in contact with each other, there is a possibility that the charge is injected from the brush roller to the toner on the photosensitive member and the polarity of the toner is reversed. When the polarity of the toner on the photoconductor is thus reversed, the toner cannot be removed from the photoconductor with a brush roller by electrostatic force. Further, even if the toner can be attached to the brush roller from the photosensitive member, there is a possibility that the charge is injected from the brush roller to the attached toner and the polarity of the toner is reversed. When the polarity of the toner adhering to the brush roller is reversed in this way, the toner is not collected by the collecting roller and continues to stay on the brush roller, and the cleaning performance is deteriorated. Therefore, by using the high resistance recovery roller to prevent the polarity of the toner adhering to the brush roller from being reversed and to prevent the toner from staying on the brush roller, the photoconductor can be cleaned well by the brush roller. You may not be able to. Therefore, not only the high resistance recovery roller is used, but the brush resistance of the brush roller is set to a high resistance to suppress the injection of electric charge from the brush roller to the toner adhering to the photosensitive member or the brush roller, and the polarity of the toner is reduced. It is conceivable to suppress the inversion.

However, the following problems can occur if the brush resistance of the brush roller is simply increased. In other words, when the brush resistance becomes high, the voltage applied to the brush roller necessary to clean the photosensitive member satisfactorily by electrostatic force becomes high. Further, as described above, in order to attach toner from the brush roller to the collection roller by an electrostatic force, it is necessary to apply a voltage higher than the voltage applied to the brush roller to the collection roller. For this reason, an expensive high-voltage power supply is required as a power supply for applying a voltage to the brush roller and the collection roller, and the brush and the collection roller surface are likely to be deteriorated because a high voltage is applied.
Therefore, the present applicant has proposed a cleaning device in which the brush resistance of the brush roller is set to 10 ⁵ [Ω] or more and 10 ⁷ [Ω] or less in Japanese Patent Application No. 2007-262918. In this way, by setting the brush resistance to a medium resistance, it is possible to suppress the charge injection into the toner and to clean the object to be cleaned, and to reduce the voltage applied to the brush roller and the recovery member.

Further, it has been found that when a high resistance recovery roller having a high resistance layer or an insulating layer on the surface is used, the surface potential of the recovery roller decreases with time.
As a result of intensive studies on the above problems, the present inventors have found the following. That is, when the recovery roller surface potential after the toner adhering to the recovery roller was removed with a rubber blade was measured, it was found that the recovery roller surface potential decreased as the amount of toner adhered per unit area of the recovery roller surface increased. It is. The reason for this has not been clarified yet, but when the charged toner adhering to the surface of the collecting roller is scraped off by the rubber blade, a peeling discharge occurs to give a negative charge to the high resistance layer or the insulating layer. End up. Alternatively, it is considered that the negative charge is given to the surface layer of the collecting roller due to toner adhesion, and the given charge remains even if the toner is scraped off by the rubber blade.

It has also been found that when the surface potential of the collecting roller decreases, the brush potential of the brush roller in contact with the collecting roller (hereinafter referred to as the surface potential of the brush roller) also decreases. The reason for this is not yet clear, but the present inventors consider the following three causes.
The first cause is as follows. As a result of the decrease in the potential of the collecting roller, the potential difference between the collecting roller and the brush roller decreases, and the toner having the opposite polarity to the polarity of the voltage applied to the brush roller attached to the brush roller is electrostatically moved to the collecting roller. This is because a large amount of toner remains on the brush roller. The polarity of the toner is opposite to the polarity of the voltage applied to the brush roller. As a result, when a large amount of toner remains on the brush roller, the surface potential of the brush roller is lowered due to the polarity of the toner.
The second cause is as follows. When the toner moves from the brush roller to the collecting roller, a peeling discharge occurs between the toner and the brush roller, and the electric charge having the same polarity as that of the toner is applied to the surface of the brush. Alternatively, the toner having the same polarity as the charged polarity of the toner is applied to the surface of the brush fiber due to the adhesion of the toner, and the charge having the same polarity as the charged polarity of the toner remains on the surface of the brush fiber even after the toner is removed by the collecting roller. Because.
The third cause is that the negative charge applied to the surface of the collecting roller moves to the brush.

  When the surface potential of the brush roller decreases, the potential difference between the photoconductor and the brush roller decreases, and the toner on the photoconductor cannot be moved electrostatically to the brush roller, resulting in poor cleaning.

  As described above, when the surface potential of the collecting roller is lowered, the surface potential of the brush roller in contact with the collecting roller is also lowered. The decrease in the surface potential of the collecting roller varies depending on the amount of toner attached to the collecting roller per unit area. The toner adhesion amount per unit area of the collecting roller is affected by the image area ratio of the image to be formed. That is, when an image having a high image area ratio is formed, a large amount of untransferred toner is generated, and the amount of toner adhering to the collection roller increases. Therefore, it is conceivable that the voltage applied to the brush roller is changed based on the image area ratio of the image to be formed to suppress a decrease in the surface potential of the brush roller.

However, it has been found through experiments by the present inventors that the higher the brush resistance of the brush roller, the greater the reduction in the brush surface potential when the surface potential of the collecting roller is lowered. The resistance of the brush varies widely, and for example, even if the brush roller is molded aiming at 10 ⁷ [Ω], it varies within a range of 10 ⁶ to 10 ⁸ [Ω]. As a result, even if the voltage applied to the brush roller is changed according to the image area ratio, the potential difference between the brush roller and the photosensitive member may become too large due to variations in brush resistance. As a result, charge injection into the toner on the photoconductor occurs, and the brush roller cannot be moved electrostatically. Alternatively, the potential difference between the brush roller and the photosensitive member may not be sufficiently recovered, and the toner on the photosensitive member may not be moved electrostatically to the brush roller. Therefore, even if the voltage applied to the brush roller is changed based on the image area ratio, there are cases where good cleaning properties cannot be obtained due to variations in the brush resistance of the brush roller.

  The present invention has been made in view of the above problems, and an object thereof is to provide a cleaning device and an image forming apparatus capable of satisfactorily cleaning toner on a member to be cleaned.

In order to achieve the above object, the invention according to claim 1 includes a surface-movable cleaning member that electrostatically moves and removes the powder on the surface-moving object to be cleaned on its own surface, and a resistance surface layer. A surface-movable recovery member that electrostatically moves and recovers the powder on the cleaning member to its own surface, and scrapes the powder on the recovery member by rubbing against the surface of the recovery member In the cleaning apparatus comprising: a removing member to be removed; a cleaning member voltage applying unit that applies a voltage to the cleaning member; and a recovery member voltage applying unit that applies a voltage to the recovery member. and surface potential measuring means for measuring, based on the measurement result of the surface potential measuring means, e Bei and control means for controlling the cleaning member voltage applying means, the resistance of the cleaning member , 10 ⁶ [Omega] or more, 10 ⁸ [Omega] or less, the surface resistance of the collecting member is, ^{10 10 [Ω} / □] or more and ^{10 13 [Ω} / □] or less, the cleaning member voltage The applying means applies a voltage having a polarity opposite to the charging polarity of the powder to the cleaning member, and the recovery member voltage applying means has a polarity opposite to the charging polarity of the powder and the cleaning member A voltage higher than the voltage applied to the recovery member is applied to the recovery member, and the control means causes the surface potential of the cleaning member to electrostatically move the powder on the object to be cleaned to the cleaning member. A cleaning apparatus that controls the cleaning member voltage application unit based on a measurement result of the surface potential measurement unit so that a target potential can be obtained .
Further, the invention of claim 2, in the cleaning device according to claim 1, the temperature and humidity detecting means for detecting the temperature and humidity in the apparatus is provided, based on the detection result of the previous SL temperature and humidity detecting means, the target potential Is set .
Further, the invention of claim 3 is the cleaning apparatus according to claim 1 or 2 , wherein the cleaning member is a brush in which conductive fibers are planted so as to extend from the outer periphery of the conductive metal core to the outside in the diameter direction. It is characterized by using a roller.
According to a fourth aspect of the present invention, in the cleaning device according to any one of the first to third aspects , the charging of the powder on the object to be cleaned is more upstream than the cleaning member in the surface movement direction of the object to be cleaned. It has a polarity control member for controlling the polarity.
Further, the invention of claim 5 is the cleaning apparatus according to claim 4 , wherein a conductive blade is used as the polarity control member, and the conductive blade is brought into contact with the surface of the object to be cleaned. Is.
The invention of claim 6 is the cleaning apparatus according to claim 4 , wherein a conductive brush is used as the polarity control member, and the conductive brush is brought into contact with the surface of the object to be cleaned. Is.
According to a seventh aspect of the present invention, there is provided an image carrier, a charging device that charges the image carrier, an exposure device that exposes the image carrier to form an electrostatic latent image, and the image carrier. A developing device that converts an electrostatic latent image into a toner image, a transfer device that transfers a toner image on the image carrier to a transfer material, and a cleaning device that removes transfer residual toner on the image carrier are provided. In the image forming apparatus, the cleaning device according to any one of claims 1 to 6 is used as the cleaning device.
According to an eighth aspect of the present invention, there is provided the image forming apparatus according to the seventh aspect , further comprising a plurality of developing devices that form toner images on the image carrier, and a plurality of toners formed on the image carrier. It is characterized in that images are superimposed to form a multicolor image.
According to a ninth aspect of the present invention, in the image forming apparatus according to the eighth aspect , each of the image forming apparatus includes a plurality of image carriers and a developing device that forms a toner image on the plurality of image carriers. A multicolor image is formed by superimposing toner images formed on a body.
According to a tenth aspect of the present invention, in the image forming apparatus according to the eighth or ninth aspect, the transfer device transfers a toner image to a transfer material via an intermediate transfer member, and the surface of the intermediate transfer member it is characterized in that using the cleaning device according to any one as an intermediate transfer member cleaning device for cleaning the residual toner of claims 1 to 6.

According to the present invention, since the cleaning member voltage applying unit is controlled based on the cleaning member surface potential measured by the surface potential measuring unit, the following effects can be obtained. That is, when the cleaning member surface potential measured by the surface potential measuring means is lower than the potential at which the powder on the object to be cleaned can be electrostatically moved to the cleaning member, the voltage value applied to the cleaning member is The cleaning member surface potential can be increased by increasing the cleaning member surface potential. As a result, a decrease in the surface potential of the cleaning member can be suppressed, and a decrease in potential difference between the cleaning member and the object to be cleaned can be suppressed. Therefore, good cleaning properties can be maintained. Further, when the cleaning member surface potential measured by the surface potential measuring means is higher than the potential at which charge injection does not occur with respect to the powder on the object to be cleaned, the cleaning member voltage is set so that the voltage value applied to the cleaning member is lowered. It becomes possible to lower the cleaning member surface potential by controlling the applying means. As a result, an increase in the surface potential of the cleaning member can be suppressed, and an increase in potential difference between the cleaning member and the object to be cleaned can be suppressed. As a result, in the region where the cleaning member electrostatically collects the powder adhering to the object to be cleaned, it is possible to suppress the charge injection into the powder and to suppress the reversal of the polarity of the powder. it can. As a result, the toner on the member to be cleaned can be electrostatically moved to the cleaning member satisfactorily.
Further, since the cleaning member voltage application unit is controlled based on the cleaning member surface potential measured by the surface potential measurement unit, the cleaning member surface potential is reliably applied even if the resistance of the cleaning member is different from the target resistance. The powder on the cleaning body can be maintained at a potential capable of electrostatically moving to the cleaning member.

1 is a schematic configuration diagram illustrating an entire printer according to a first embodiment. FIG. FIG. 2 is an enlarged schematic configuration diagram in the vicinity of an image forming unit. The schematic block diagram of a belt cleaning apparatus. 6 is a graph showing a charge amount distribution of a transfer residual toner remaining on an intermediate transfer belt after transfer, and a toner charge amount distribution after the toner has passed through a polarity control blade. The graph which shows the electrical resistance change by the environment of a polarity control blade. It is sectional drawing which shows an example of the brush fiber in an electroconductive brush. It is sectional drawing which shows another example in the brush fiber of the electroconductive brush. It is sectional drawing which shows another example (core-sheath structure) in the brush fiber of the electroconductive brush. It is sectional drawing which shows another example of the brush fiber of the core sheath structure in the same electroconductive brush. The schematic block diagram which shows the other example of a belt cleaning apparatus. The graph which shows the result of having investigated the electric potential of the cleaning brush and the electric potential of a SUS collection roller at the time of using a SUS collection roller as a collection roller. The graph which shows the result of having investigated the electric potential of a cleaning brush, and the electric potential of a high resistance collection roller when a high resistance collection roller is used as a collection roller. 6 is a graph showing a relationship between a potential difference between a collection roller surface and a brush tip in each collection roller and a toner collection rate. The graph which shows the relationship between cleaning remaining ID in each collection | recovery roller, and the collection roller applied voltage. The figure explaining the mode of resistance measurement of a collection roller. The graph which shows the relationship between the voltage applied to a cleaning brush, and cleaning property. FIG. 9 is a schematic configuration diagram of a belt cleaning device according to a first modification. FIG. 6 is a schematic configuration diagram of a belt cleaning device according to a second modification. The schematic block diagram of a process unit. 1 is a block diagram of the main part of a one-drum type full-color image forming apparatus. FIG. 10 is a schematic configuration diagram illustrating another example of a belt cleaning device according to a second modification.

[Embodiment 1]
Hereinafter, as a first embodiment of an image forming apparatus to which the present invention is applied, a so-called tandem type intermediate transfer type printer (hereinafter simply referred to as a printer) of an electrophotographic type will be described. As shown in FIG. 1, this printer has four process units 6Y, 6M, 6C, and 6K for generating toner images of yellow, magenta, cyan, and black (hereinafter referred to as Y, M, C, and K). It has. The four process units 6Y, 6M, 6C, and 6K have drum-shaped photoreceptors 1Y, 1M, 1C, and 1K, respectively. As shown in FIG. 2, the charging devices 2Y, M, C, and K, the developing devices 5Y, C, M, and K, and the photosensitive member cleaning devices 4Y and M are arranged around the photosensitive members 1Y, 1M, 1C, and 1K, respectively. , C, K, a static eliminator (not shown), and the like. The process units 6Y, 6M, 6C, and 6K use Y, M, C, and K toners of different colors, but have the same configuration. Further, below the process units 6Y, 6M, 6C, and 6K, there is an exposure device 7 that performs optical writing with a laser beam to form an electrostatic latent image on the photoreceptors 1Y, 1M, 1C, and 1K. Yes.

  In the printer of the present embodiment, the process units 6Y, 6M, 6C, and 6K are formed integrally as a process cartridge that can be attached to and detached from the apparatus body and replaced when the end of its service life is reached. Improvements can be made.

  Above the process units 6Y, 6M, 6C, and 6K, a transfer unit 17 having an intermediate transfer belt 8 as an image carrier is disposed. The intermediate transfer belt 8 is wound around a plurality of rollers such as a tension roller 14, a driving roller 12, support rollers 13, 15, and 16, and is driven to rotate counterclockwise in the drawing. In order to transfer the toner images formed on the photoreceptors 1Y, 1M, 1C, and 1K onto the intermediate transfer belt 8 at positions facing the photoreceptors 1Y, 1M, 1C, and 1K with the intermediate transfer belt 8 therebetween. Primary transfer rollers 9Y, 9M, 9C, and 9K are provided. Further, downstream of the primary transfer rollers 9Y, 9M, 9C, and 9K with respect to the rotation direction of the intermediate transfer belt 8, the toner image on the intermediate transfer belt 8 contacts the peripheral surface of the intermediate transfer belt 8 on the recording paper. A secondary transfer device having a secondary transfer roller 19 for transferring is provided. The secondary transfer device is not limited to the secondary transfer roller 19, and may be a secondary transfer belt that is stretched by several support rollers and a drive roller. The intermediate transfer belt 8 has a multilayer structure, and the base layer is made of, for example, a fluororesin, a PVD sheet, or a polyimide resin with little elongation, and the surface is covered with a smooth coat layer such as a fluororesin.

  Further, downstream of the secondary transfer roller 19, a belt cleaning device 10 that removes residual toner remaining on the intermediate transfer belt 8 after the transfer by the secondary transfer roller 19 is interposed via the intermediate transfer belt 8. It is provided so that it may oppose. The belt cleaning device 10 can be replaced integrally with the intermediate transfer body 8, but when the life setting is different from that of the intermediate transfer belt 8, the belt cleaning device 10 may be detachable alone.

  In FIG. 1, below the printer, a paper feed unit having a paper feed cassette 26 that houses the transfer paper P and a paper feed roller 27 that feeds the transfer paper P from the paper feed cassette 26 is provided. In addition, a registration roller 28 is provided on the upstream side of the secondary transfer roller 19 in the transfer direction of the transfer paper, and stops the transfer paper fed from the paper feed cassette 26 and sends it to the secondary transfer position. ing. On the other hand, a fixing device 20 is provided downstream from the secondary transfer position in the transfer sheet conveyance direction. Further, toner bottles 32Y, 32M, 32C, and 32K filled with new toner to be replenished to the developing devices 5Y, 5M, 5C, and 5K are located above the printer. The developing devices 5Y, 5M, 5C, and 5K are replenished.

  Next, the operation of the printer having the above configuration will be described. When a start switch (not shown) is pressed, the intermediate transfer unit 17 rotates and drives the drive roller 12 with a drive motor (not shown), and the other rollers 13, 14, 15, 16 are driven to rotate the intermediate transfer belt 8. Rotate. At the same time, the photosensitive units 1Y, M, C, and K are rotated by the process units 6Y, 6M, 6C, and 6K, and are uniformly charged by the charging rollers 2Y, 2M, 2C, and 3K, respectively, and then the exposure device 7 To form an electrostatic latent image. Each electrostatic latent image is developed by the developing devices 5Y, 5M, 5C, and 5K for the respective colors, and forms monochrome images of yellow, cyan, magenta, and black on the photoreceptors 1Y, 1M, 1C, and 1K. As the intermediate transfer belt 8 rotates, the monochrome images are sequentially transferred to form a composite color image on the intermediate transfer belt 8.

  On the other hand, in the paper feed unit, the paper feed roller 27 feeds the transfer paper P from the paper feed cassette 26 one by one, puts it in the paper feed path, and stops against the registration roller 28. Then, the registration roller 28 is rotated in synchronization with the composite color image on the intermediate transfer belt 8, the transfer paper is fed between the intermediate transfer belt 8 and the secondary transfer roller 19, and the color image is transferred onto the transfer paper. Transcript. The transfer paper after the transfer is sent to the fixing device 20, and the fixing device 20 applies heat and pressure to fix the image, and then is discharged. On the other hand, the photoconductors 1Y, 1M, 1C, and 1K after the primary transfer are subjected to the residual toner removal by the photoconductor cleaning devices 4Y, 4M, 4C, and 4K, and then are neutralized to prepare for the next image formation. Further, the intermediate transfer belt 8 after the secondary transfer is freed of residual toner by the belt cleaning device 10 and is ready for image formation by the tandem image forming device.

  The toner used in the printer preferably has a volume average particle diameter of 3 to 6 [μm] in order to reproduce minute dots of 600 dpi or more. Moreover, it is preferable that ratio (Dv / Dn) of a volume average particle diameter (Dv) and a number average particle diameter (Dn) exists in the range of 1.00-1.40. The closer (Dv / Dn) is to 1.00, the sharper the particle size distribution. With such a toner having a small particle size and a narrow particle size distribution, the toner charge amount distribution is uniform, a high-quality image with little background fogging can be obtained, and the electrostatic transfer method has a high transfer rate. can do.

  Next, the belt cleaning device 10 which is a characteristic part of the present embodiment will be described in detail. This belt cleaning device 10 is of an electrostatic cleaning type that has a good cleaning property even when cleaning toner having a small particle size or spheroidization, which is difficult with the conventional blade cleaning method.

  Here, problems of the conventional blade cleaning method will be described. As described above, in recent years, there has been an increasing demand for higher image quality, and the toner tends to have a smaller particle size. In addition, there is a tendency to use a spheroidized toner by a polymerization method or the like instead of a pulverized toner because of a demand for reduction in toner manufacturing cost and an improvement in transfer rate. The blade cleaning method, which has been used mainly as a means to remove the toner remaining on the image bearing member with the use of toner having a smaller particle size and spheroidization, is used for the accuracy of adhesion between the blade and the surface of the image bearing member. If it is low, the toner slips through and the cleaning property tends to be lowered. In order to prevent this, if the blade is pressed with a strong contact pressure, the blade is turned over, causing a so-called streak-like or belt-like cleaning failure, and it is difficult to keep stable cleaning performance. In addition, spherical toner can be cleaned by increasing the linear pressure to an extremely high level (specifically, linear pressure of 100 [gf / cm] or more). However, the life of the toner is extremely short due to wear of the cleaning blade or scratches on the belt. Become. The life of the cleaning blade (the life when the cleaning failure occurs due to shaving) is about 120K. When the linear pressure is 100 [gf / cm], the life of the cleaning blade is about 20K sheets. Further, it is well known that the blade cleaning property is inferior to the cleaning property for the pulverized (atypical) toner with respect to the spherical toner whose transferability is good.

  Therefore, the printer of the present embodiment employs the electrostatic cleaning type belt cleaning device 10. FIG. 3 is an enlarged view showing a schematic configuration of the belt cleaning device 10. The belt cleaning device 10 is in contact with a cleaning brush 521 as a cleaning member that removes toner from the intermediate transfer belt 8, a recovery roller 522 as a recovery member that recovers toner attached to the cleaning brush 521, and a recovery roller 522. A collecting blade 523 for scraping the collected toner and applying a charge to the surface of the collecting roller 522; a toner conveying coil 524 for conveying the collected toner to a waste toner tank (not shown) provided in the printer body; It has. As described above, the collection blade 523 has both a function as a removing member that removes toner from the surface of the collection roller 522 and a function as a charge supply unit that applies charges to the surface of the collection roller 522. The cleaning brush 521 is a brush roller that is driven to rotate about a brush rotation axis, and applies a voltage from a brush power supply 531 that is a cleaning member voltage application unit via a brush rotation shaft (core metal). Further, a voltage is applied to the collection roller 522 from a collection power source 532 serving as a collection member voltage application unit via a rotating shaft (core metal). The recovery blade 523 applies a voltage from the blade power source 533 via the support substrate. Further, on the upstream side in the rotation direction of the intermediate transfer belt 8 with respect to the position where the cleaning brush 521 removes the transfer residual toner on the intermediate transfer belt 8, polarity control is performed as a polarity control member for controlling the charge polarity of the transfer residual toner. A polarity control blade 520 to which a voltage is applied from the power source 530 is provided so as to contact the intermediate transfer belt 8 at a position facing the tension roller 14.

In the belt cleaning device 10 configured as described above, the toner on the intermediate transfer belt 8 is removed in the following four steps.
1. A polarity control blade 520 aligns the polarity of the toner on the intermediate transfer belt 8 with the normal charging polarity (here, negative polarity).
2. A voltage having a polarity opposite to that of the toner (here, positive polarity) is applied to the cleaning brush 521, and the toner on the intermediate transfer belt 8 is electrostatically moved onto the cleaning brush 521 (3A in FIG. 3).
3. A voltage having the same polarity as the cleaning brush 521 and a large absolute value is applied to the collecting roller 522, and the toner on the cleaning brush 521 is moved to the collecting roller 522 (3B in FIG. 3).
4). The toner on the collection roller 522 is scraped off by the collection blade 523.
Hereinafter, these steps will be described in detail.

  First, the charge amount of the toner that adheres to the intermediate transfer belt 8 and reaches the portion facing the belt cleaning device 10 and the charge amount of the toner after passing through the polarity control blade 520 will be described. Most of the toner on the intermediate transfer belt 8 before transfer is negatively charged. At the time of transfer, the toner on the intermediate transfer belt 8 is transferred to the transfer paper by the positive transfer bias applied to the secondary transfer roller 19, but most of the toner charged to positive polarity before transfer is intermediate as it is. It adheres to the transfer belt 8. Further, even if the toner is negatively charged before transfer, the charged polarity is shifted to the positive polarity side by receiving positive charge injection applied to the secondary transfer roller 19, and a part of the toner is positive. May be reversed.

  4A and 4B are graphs showing the charge amount distribution of the residual toner remaining on the intermediate transfer belt 8 after the transfer and the charge amount distribution of the toner after the toner has passed through the polarity control blade 520. FIG. is there. The charge amount distribution is obtained when an image is formed by the above printer based on the data obtained by measuring the charge amount Q of each toner and the particle size d of the toner with an E-spurt analyzer (EST-3) manufactured by Hosokawa Micron. 3 shows a Q / d (unit: fc / μm) distribution when several hundreds of toner remaining on the intermediate transfer belt is sampled. 4A shows a broad distribution in which positive polarity toner and negative polarity toner are mixed in half (hereinafter referred to as transfer residual toner A), and FIG. 4B shows that positive polarity toner is mixed. A broad distribution (hereinafter referred to as “transfer residual toner B”) mixed in a state larger than that of the negative polarity toner. FIG. 4C shows untransferred toner at the time of process control and the like, and most of the toner is negative polarity toner and has a sharp distribution.

  When the transfer residual toner A and the transfer residual toner B reach the position of the polarity control blade 520 by the rotation of the intermediate transfer belt 8, most of the toner is mechanically scraped off by the polarity control blade 520. Occurring and a part passes through the polarity control blade 520. The mechanically scraped toner naturally falls from the polarity control blade 520, is stored in the lower recovery unit of the belt cleaning device 10, and is recovered by the toner transport coil member 524 to a waste toner recovery unit (not shown). A voltage having the same polarity (negative polarity) as the charging polarity of the toner is applied to the polarity control blade 520, and when the toner passes through the toner polarity control blade 520, the toner is charged to the normal charging polarity (negative polarity). To do. FIGS. 4A and 4B show the charge amount distributions of the untransferred toner A and the untransferred toner B after passing through the polarity control blade 520 to which a voltage of −500 [V] is applied from the polarity control power source 530. FIG. As shown in FIGS. 4A and 4B, the charge amount distribution after passing differs depending on the charge amount distribution before passing through the polarity control blade 520, but both can be almost negative. In addition, the untransferred toner in FIG. 4C hardly changes or becomes slightly negative.

Further, a change in charge amount when the toner passes through the polarity control blade 520 will be described in detail.
As shown in FIG. 3, the polarity control blade 520 has a configuration in which a plate-like conductive elastic body is bonded on a support metal plate, and is brought into contact with the intermediate transfer belt 8 in the counter direction. The conductive elastic body imparts conductivity by kneading, for example, polyurethane rubber, carbon black, or an ionic conductive agent, and has an electric resistance of 2 × 10 ⁶ [Ω · cm] to 5 ×. 10 ⁷ [Ω · cm] is preferable. The thickness is preferably in the range of 1 to 3 [mm]. If the thickness is too thin, it becomes difficult to ensure the amount of pressing to the intermediate transfer belt 8 due to the surface of the intermediate transfer belt 8 and the waviness of the polarity control blade 520 itself. Hardness should just be in the range of 40-85 with a JIS-A hardness meter. The polarity control blade 520 does not clean the toner on the intermediate transfer belt 8 100%, and there is no problem even if the slip-through amount increases or decreases.
In this embodiment, the four types of polarity control blades 520 shown in Table 1 are used. Specifically, the electrical resistance is 10 ⁶ [Ω · cm], 10 ⁸ [Ω · cm], the thickness is 2.4 [mm], 2.8 [mm], and the free length is 7 [mm], 9 [mm]. , With a JIS-A hardness meter of 60-80, and a blade rebound resilience coefficient of 45%. FIG. 5 shows changes in electrical resistance depending on the environment of the polarity control blade 520 under the four conditions shown in Table 1.

  When toner is sandwiched between the polarity control blade 520 and the intermediate transfer belt 8, current flows into the toner due to the voltage applied to the polarity control blade 520, and the toner is charged with the same polarity as the applied voltage. It passes through the control blade 520. In addition, it is charged to the same polarity as the applied voltage by discharging or injecting electric charges at the entrance and exit of the fine gap formed by the intermediate transfer belt 8 and the polarity control blade 520. As a result, the toner has a negative charge amount distribution as shown in “after passing through the blade (application of current −40 μm)” in FIGS. 4A and 4B.

  Moreover, you may use a conductive brush as a polarity control member. When the conductive brush to which the voltage is applied and the toner on the photoreceptor come into contact, the charge amount of the toner changes according to the voltage value. The amount of change increases as the voltage increases. It has also been found by experiments by the inventors that the amount of change is greater as the conductive agent is exposed on the surface layer of the fiber. Since the phenomenon of changing the charge amount of the toner occurs even at a potential difference of about 200 [V], in addition to the phenomenon caused by the discharge, a circuit such as charging a capacitor can be formed and the charge is accumulated in the toner. (So-called charge injection). On the other hand, even if the voltage applied to the conductive brush as the polarity control member is higher than the discharge start voltage, it is possible to control the polarity of the toner by discharge. This is because the amount of the reversely charged toner increases because the bipolar ions generated by the toner adhere to the toner. 6 to 9 are sectional views of the raising of the conductive brush. 6 and 7 show the resistance values adjusted by dispersing a conductive agent in insulating fibers. FIG. 8 and FIG. 9 show the raising of the core-sheath structure in which the periphery of the conductive material is covered with insulating fibers. As shown in FIG. 6 and FIG. 7, the conductive brush having a raised brush in which the conductive agent in the fiber is dispersed to the fiber surface layer has an increased chance of direct contact between the conductive agent and the toner when contacting the toner. Charges easily flow into the toner from the conductive agent, and charge injection is more likely to occur than the conductive brushes having raised hairs shown in FIGS. As a result, the toner is more likely to be charged on the polarity side of the voltage applied to the conductive brush than the conductive brush having the raised brushes shown in FIGS. 8 and 9, which is preferable.

  Next, the electrostatic cleaning operation of the toner after passing through the polarity control blade 520 will be described. The transfer residual toner charged to the negative polarity having the normal charging polarity by the polarity control blade 520 is transferred to the position of the cleaning brush 521 by the rotation of the intermediate transfer belt 8. The cleaning brush 521 is supplied with a voltage having a polarity (positive polarity) opposite to the charging polarity of the toner from the brush power source 531, and the potential difference between the intermediate transfer belt 8 and the surface potential of the cleaning brush 521 at 3A in FIG. 3. The transfer residual toner charged to the negative polarity on the intermediate transfer belt 8 is electrostatically adsorbed and moved to the cleaning brush 521 by the electric field formed in the above.

  The collection roller 522 is provided in contact with the cleaning brush 521, and a positive voltage higher than that of the cleaning brush 521 is applied from the collection power source 532. The surface potential of the cleaning brush 521 and the collection roller are indicated by 3B in FIG. The toner that has moved onto the cleaning brush 521 is electrostatically adsorbed and moved onto the collection roller 522 by an electric field formed by a potential difference from the surface potential of 522.

The collection blade 523 is provided in contact with the collection roller 522, and scrapes off the toner on the collection roller 522. The toner scraped off is discharged out of the apparatus by the toner conveying coil 524 or returned to the developing device 5. The collection blade 523 has a function as a charge supply unit that supplies charges to the surface of the collection roller 522 so as to maintain the surface potential of the collection roller 522. The collection blade 523 collects the blade from the blade power source 533 via the support substrate. A positive voltage equal to or higher than the voltage applied to the core of the roller 522 is applied. Thereby, the surface potential of the collection roller 522 is stabilized. Further, the brush facing roller 508 that contacts the back surface of the intermediate transfer belt 8 and faces the cleaning brush 521 with the intermediate transfer belt 8 interposed therebetween has a volume resistance value equal to or higher than the volume resistance value of the intermediate transfer belt 8 on the surface. A resistance layer is provided. If the volume resistance value is close to insulation, the brush facing roller 508 cannot play the role of an electrode, so an extremely high resistance must be avoided. The resistance value of the resistance layer of the brush facing roller 508 needs to be set so that the cleaning electric field between the intermediate transfer belt 8 and the cleaning brush can be maintained and the brush current flowing from the cleaning brush to the intermediate transfer belt is lowered. Those of ⁶ to 10 ⁸ [Ω · cm] are suitable.
When the resistance value of the resistance layer required as the opposing roller of the polarity control blade 520 and the resistance value of the resistance layer required as the opposing roller of the cleaning brush are substantially the same value, as shown in FIG. In addition, the tension roller 14 that is the opposite roller of the polarity control blade 520 may also serve as the opposite roller of the cleaning brush. By configuring as shown in FIG. 10, the number of parts can be reduced, and space can be saved.

Specific configuration conditions of the cleaning brush 521, the collection roller 522, and the collection blade 523 used in the printer of this embodiment are as follows <Conditions for the cleaning brush 521>
Brush material: Conductive polyester (contains conductive carbon inside the fiber and the fiber surface is polyester, so-called core-sheath structure)
Brush resistance: 1 × 10 ⁷ [Ω] (applied voltage: 100 to 600 [V])
Brush shaft applied voltage: +1000 [V]
Brush flocking density: 10 [10,000 / inch ² ], fiber diameter of about 25 to 35 [μm], with brush tipping treatment Brush diameter: 16 [mm]
Amount of brush fiber biting into the collection roller: 1 [mm]
However, it is not limited to this.
However, the brush resistance is a value calculated by measuring the current value when a 1 [KV] voltage is applied with the brush roller facing the entire surface of the metal flat plate so as to bite the entire surface by 1 [mm]. .

<Conditions for Collection Roller 522>
Recovery roller mandrel applied voltage: +1400 [V]

<Conditions for Recovery Blade 523>
Conductive carbon-containing polyurethane rubber volume resistance: 1 × 10 ⁶ [Ω · cm] (measured at 25 ° C. and 50%)
Blade contact angle: 20 °
Blade thickness: 2.8 [mm]
Amount of blade biting into the collection roller: 0.6 [mm]
Applied voltage to recovery blade: +2400 [V]

The collection roller 522 is a high-resistance roller having a high-resistance resistance layer on the surface, in particular, in order to prevent the toner collection rate and reverse polarity injection into the toner. The advantage is large mainly in a high temperature and high humidity environment where reverse polarity charge injection into the toner is likely to occur. As the collection roller 522, a SUS metal core (φ16 [mm]) having PVDF with a thickness of 100 [μm] on the surface and an acrylic UV curable resin layer on the surface was used. As shown in FIG. 15, the roller resistance is such that the collecting roller 522 is fixed in a stationary state, and the resistance layer 522b and the rotating shaft are respectively used in a 10 [° C.] 15 [%] environment and a 32 [° C.] 80 [%] environment. A voltage of 1000 [V] is applied to the (core metal) 522a and a current is measured and calculated, and is 10 ¹² to 10 ¹³ [Ω · cm]. The same performance can be obtained not only by the collecting roller 522 used in the present embodiment, but also by covering the conductive cored bar with a high resistance elastic tube of about several [μm] to 100 [μm] or further with an insulating coating.

  The recovery roller 522 is a roller having a high resistance resistance layer on the surface, and the potential difference between the cleaning brush surface and the recovery roller surface can be made larger than that of the SUS (stainless steel) recovery roller. It explains using. FIG. 11 shows that in a 32 [° C.] 80 [%] environment, a SUS recovery roller is used, 500 [V] is applied to the brush shaft, and 550 [V] to 700 [V] is applied to the recovery roller shaft. The brush shaft potential, the brush tip potential, the collection roller shaft potential, the collection roller surface potential, and the potential difference (collection roller surface potential−brush tip potential) are shown. FIG. 12 shows a roller having a high-resistance resistance layer (hereinafter referred to as a high-resistance recovery roller) in a 32 [° C.] 80 [%] environment, and applying 500 [V] to the brush shaft, Brush shaft potential, brush tip potential, collection roller shaft potential, collection roller surface potential, potential difference (collection roller surface potential minus brush tip potential) when 500 [V] to 800 [V] is applied to the collection roller shaft, Is shown.

  When the SUS recovery roller is used, the brush tip potential approaches the recovery roller surface potential, and even if the recovery roller shaft applied voltage is increased, the potential difference between the two member surfaces does not increase.

Next, FIG. 13 shows a graph in which the horizontal axis indicates the potential difference between the brush tip potential and the recovery roller surface potential, and the vertical axis indicates the recovery rate. Here, the recovery rate means that an experimentally known toner amount (here, the toner amount per unit area [mg / cm ² ] is used for easy calculation) is adhered onto the photoreceptor 1 and the cleaning brush is used. In 521, the amount of toner collected on the collection roller 522 after cleaning (the amount of toner per unit area) is measured and calculated by Equation 1.

However, M / A is calculated from the toner mass per unit area [unit: [mg / cm ² ].

  As can be seen from FIG. 13, when the SUS collection roller is used as the collection roller 522, the collection rate is only 80%, whereas when the high resistance collection roller is used, there is a case where the collection rate is 100% or more. To do. Here, the reason why the collection rate exceeds 100 [%] is that the toner input is performed for 10 seconds, so that the toner collection of 100 [%] cannot be performed for the first few seconds by each rotation of the brush and the collection roller, and the brush Since the collecting roller 522 collects an amount of several tens [%] of the total amount of the toner collected next and the toner that is sequentially input, the collected amount exceeds the input amount. Because there are things.

  To summarize the results shown in FIGS. 11, 12, and 13 so far, even if the voltage applied to the collecting roller shaft is increased in order to improve the toner collecting performance from the brush, the toner in the case of the SUS collecting roller Although the recoverability does not increase, if the voltage applied to the recovery roller shaft is increased using a high resistance recovery roller, the potential difference between the brush tip and the recovery roller surface increases, and the toner recovery performance at the recovery roller 522 is improved. I understand. Therefore, it can be seen that the high resistance collection roller is better than the SUS collection roller in order to improve the toner collection performance.

  Further, the cleaning performance on the photosensitive member 1 in the case where the experiment shown in FIGS. 11 and 12 is performed is also better when the high resistance recovery roller is used as the recovery roller 522 than when the SUS recovery roller is used. It became. The result is shown in FIG.

  Note that the cleaning residual ID on the vertical axis in FIG. 14 is the following index. “Remaining cleaning ID” is obtained by transferring the toner on the intermediate transfer belt 8 after cleaning with the cleaning brush 521 with a scotch tape, pasting it on a white paper and measuring it with a spectrocolorimeter (X-Rite 938), while measuring the scotch. Only the tape is pasted on the same white paper and measured with a spectrocolorimeter. From the reflection density (ID: Image Density) of the toner, the tape and the white paper, the reflection density (ID) of the tape and the white paper with the scotch tape The value minus the minutes. There is a correlation between the ID and the number of toners, and the ID value increases as the number of toners increases. Therefore, the cleaning property can be determined by the ID. The smaller the cleaning residual ID, the better the cleaning performance.

  As shown in the figure, compared with the SUS collection roller, the high resistance collection roller has a large margin of applied voltage with respect to the cleaning residual ID when the collection roller applied voltage is increased, and cleaning is performed even when the applied voltage is increased. Good maintainability.

  The reason is as follows. When a positive voltage V1 is applied to the brush shaft and a positive voltage V2 (here, V2> V1) is applied to the collecting roller shaft, the negative toner adheres to the brush having a positive polarity. Then, it is collected by being attached to the collection roller 522 having a higher positive polarity and higher voltage than the cleaning brush 521. However, when the collection roller surface is made of metal (SUS steel), when the collection roller 522 comes into contact with the brush bristles and the toner adhering to the brush, electric charges are continuously supplied to the bristles and the brush adhering toner until the potential becomes the same as that of the collection roller surface. Try to. The speed (time) from when the SUS recovery roller surface gives charge to the brush and toner to when the charge is supplied again from the power source and the recovery roller surface becomes the same potential as the power source is high resistance recovery. Presumed to be faster than Roller. For this reason, the polarity of the toner attached to the brush is easier to reverse with the SUS recovery roller than with the high resistance recovery roller. When the polarity of the toner is reversed, the toner becomes positive and adheres to the brush having a low voltage even with the same positive polarity. Therefore, the positive toner is present in the brush, and the surface potential of the intermediate transfer belt 8 is on the negative polarity side with respect to the potential at the tip of the brush. Therefore, the toner adheres to the intermediate transfer belt 8 from the brush, resulting in poor cleaning. And output from the belt cleaning device 10. This causes problems such as charging device contamination.

On the other hand, in the case of a high resistance recovery roller having a high resistance layer of 10 ¹⁰ [Ω / □] or more, preferably 10 ¹⁰ [Ω / □] to 10 ¹³ [Ω / □] on the roller surface, the brush and the recovery roller Since the toner sandwiched between 522 is less likely to reverse the polarity, as a result, the cleaning failure due to the polarity-reversed toner hardly occurs.

As described above, in a high-temperature and high-humidity environment, the polarity of the toner sandwiched between the brush and the collection roller 522 when the surface of the collection roller is a high resistance layer (10 ¹⁰ [Ω · cm] or more) or an insulating layer. There is an advantage that is difficult to reverse.

FIG. 16 shows the results of examining the cleaning properties of the cleaning brushes 521 having the brush resistance R of 10 ⁵ , 10 ⁷ , 10 ⁹ [Ω]. The brush resistance is a value calculated by measuring a current value when a 1 [KV] voltage is applied with a brush roller facing the entire surface of a metal flat plate so as to bite 1 [mm]. . As shown in FIG. 16, when a cleaning brush having a brush resistance of 10 ⁹ [Ω] is used, cleaning cannot be performed unless 1200 [V] to 1500 [V] is applied to the brush rotation shaft (core metal). The power source 531 needs to be a high voltage power source. Further, it is necessary to apply a voltage higher than the voltage applied to the brush rotation shaft to the rotation shaft of the collection roller 522, and furthermore, a voltage obtained by adding a starting voltage to the collection blade rotation shaft is added to the collection blade 523. It is necessary to apply. As a result, the brush power source 531, the recovery power source 532, and the blade power source 533 need to be high cost high voltage power sources. On the other hand, when a cleaning brush with a brush resistance of 10 ⁵ [Ω] is used, the toner is charged to a positive polarity at a lower voltage than when a cleaning brush with a brush resistance of 10 ⁷ [Ω] is used. Reattached to the belt 8. For this reason, a cleaning brush with a brush resistance of 10 ⁵ [Ω] has a smaller cleaning margin than a cleaning brush with a brush resistance of 10 ⁷ [Ω]. Therefore, a cleaning brush having a brush resistance of 10 ⁷ [Ω] is most preferable. However, the brush resistance value may fluctuate due to variations in the production of brush fibers. To use a brush roller with a brush resistance of 10 ⁷ [Ω], the resistance of the roller is measured, and the brush resistance value falls within the standard value range. Since it must be sorted out, the inspection cost increases and the yield decreases. According to the study by the inventors, even 10 ⁶ [Ω] and 10 ⁸ [Ω] can be used because there is no problem in cleaning properties. Therefore, in this embodiment, a cleaning brush having a brush resistance of 10 ⁶ [Ω] to 10 ⁸ [Ω] is used. As a result, it is possible to suppress an increase in manufacturing cost and a decrease in yield, and a large margin for cleaning, and a voltage applied to each member (cleaning brush 521, recovery roller 522, recovery blade 523) can be suppressed to a low level. Can do.

  The raised brushes of the cleaning brush 521 are conductive brush fibers in which a resistance value is adjusted by dispersing a conductive agent in a base material as shown in FIGS. As a base material of the conductive brush fiber used for the cleaning brush 521, an insulating material such as nylon, polyester, or acrylic is generally used, and the same effect is obtained in any material. Carbon is often used as the conductive agent. Further, a “core-sheath structure” in which an insulator is provided on the surface and a conductive material is provided inside may be used. Representative fibers having a core-sheath structure are disclosed in JP-A-10-310974, JP-A-10-131035, JP-A-01-292116, JP-B-07-033637, JP-B-07-033606, and JP-B-03-064604.

  When the relationship between the brush tip potential in a low-temperature and low-humidity (10 [° C.] 15 [%]) environment and the cleaning residual ID on the intermediate transfer belt 8 is examined, the cleaning tip potential is 400 [V] to 1000 [V]. It was found that the ID was 0.01 or less, which was the target. It was also found that at high temperature and high humidity (32 [° C.] 80 [%]), the brush tip potential was 300 [V] to 500 [V] and the cleaning residual ID was 0.01 or less, which was favorable. This is because the amount of charge held by the toner varies depending on the temperature and humidity conditions. That is, in general, in a high-temperature and high-humidity environment, the amount of charge that the toner after passing through the polarity control blade is negatively charged is small. For this reason, if the positive charge injection from the brush to the toner occurs, it is easy to be positive. Increasing the voltage applied to the cleaning brush tends to inject charge from the brush to the toner. As a result, in a high-temperature and high-humidity environment, when the voltage value is increased, a large amount of toner is reversed to a positive polarity by charge injection from the brush, and the toner returns to the intermediate transfer belt 8 to increase the residual toner. Conceivable. Therefore, the upper limit value of the applied voltage at which the cleaning ID is 0.1 or less is lower in a high temperature and high humidity environment than in a low temperature and low humidity environment. Therefore, the brush tip potential with good cleaning properties in a low-temperature and low-humidity environment and a high-temperature and high-humidity environment is 400 [V] to 500 [V].

  However, it has been found that when a high resistance recovery roller is used as the recovery roller 522, the following problems occur in a low temperature and low humidity environment.

  The present inventors conducted a cleaning experiment in a low-temperature and low-humidity environment (10 [° C.] 15 [%]). After the toner adhered to the surface of the high-resistance recovery roller, the recovery roller after cleaning with the recovery blade 523 When the surface potential was measured, it was found that the recovery roller surface potential decreased. At the same time, when the brush tip potential of the cleaning brush 521 after passing through the contact portion with the collecting roller was measured using a surface potentiometer, it was found that the brush tip potential also fluctuated in units of several hundred volts.

The surface potential of the collecting roller and the potential of the brush tip were measured for 10 [s] using a surface potentiometer while inputting the toner. As a result, both potentials were reduced and the potential difference was reduced to about 30 [V]. On the other hand, when the surface potential of the collecting roller and the potential at the tip of the brush were measured for 2 [s] using a surface potentiometer while inputting the toner, the potential difference started, but the potential difference was still about 150 [V]. . In addition, when the surface potential of the collecting roller and the potential at the tip of the brush were measured for 10 [s] using a surface potentiometer without inputting toner, the potential was not decreased by several hundred volts. At this time, the M / A of the input toner is 0.1 [mg / cm ² ], and the Q / M (amount of charge per unit mass) is −5 [μC / g] to −11 [μC / g]. there were. Normally, the transfer residual toner remaining on the intermediate transfer belt 8 after the transfer is estimated to be approximately 0.02 [mg / cm ² ] to 0.08 [mg / cm ² ] although there are fluctuations. Set a little higher than this.

The cause of fluctuations in the brush tip potential and the recovery roller surface potential has not yet been clarified, but since there is a correlation between the presence of toner and the amount of toner M / A, the transfer of toner has some influence. That is certain. At present, when toner having a charge adhering to the surface of the collecting roller is scraped off by the collecting blade 523, a peeling discharge is generated, and a negative charge is given to the high resistance layer or the insulating layer. It is thought that the potential decreases. Alternatively, negative charge is applied to the surface layer of the collecting roller due to toner adhesion, and even if the toner is scraped off by the collecting blade 523, the charge applied to the surface layer of the collecting roller remains, so that the surface potential of the collecting roller 522 decreases. Is also possible. In addition, the following three reasons can be considered for the reduction of the brush surface potential. The first reason is that the potential difference between the recovery roller 522 and the cleaning brush 521 decreases as a result of the surface potential of the recovery roller 522 being lowered, and the toner adhering to the cleaning brush 521 is electrostatically moved to the recovery roller 522. Therefore, a lot of toner remains on the cleaning brush 521. The polarity of the toner is opposite to the polarity of the voltage applied to the cleaning brush 521. As a result, if a large amount of toner remains on the cleaning brush 521, it is considered that the surface potential of the cleaning brush 521 decreases due to the polarity of the toner. The second reason is that when the toner adhering to the cleaning brush 521 moves to the collecting roller, a peeling discharge occurs to give a negative charge to the brush fiber, or a negative charge is applied to the brush fiber due to the toner adhesion. As a result, the surface potential of the cleaning brush 521 is considered to decrease. However, the second reason is that the brush resistance is a medium resistance of 10 ⁶ to 10 ⁸ [Ω], and it is considered that some current flows through the brush fiber, so that a negative charge is applied to the brush fiber. As a result, it is unlikely that the brush tip potential will drop significantly. The third reason is considered that the negative charge applied to the surface of the collecting roller moves to the brush, and the tip potential of the cleaning brush 521 decreases. The present inventors consider that the first reason and the third reason are reasons for lowering the brush tip potential from the result that the tip potential of the cleaning brush is lowered when the surface potential of the recovery roller 522 is lowered.

  Thus, when the surface potential of the cleaning brush 521 decreases, the potential difference between the intermediate transfer belt 8 and the cleaning brush 521 decreases, and the toner on the intermediate transfer belt 8 can be electrostatically moved to the cleaning brush 521. It becomes impossible, and cleaning property will fall.

  Therefore, in the present embodiment, in order to give a charge to the surface of the high resistance recovery roller, a voltage is applied to the recovery blade that is in contact with the high resistance recovery roller to apply the charge to the surface of the recovery roller. The surface potential is suppressed from decreasing.

However, even when the electric charge on the surface of the collecting roller is applied to suppress the potential drop on the surface of the collecting roller, the potential of the cleaning brush 521 may be lowered. It was also found that the amount of decrease in the brush tip potential varies depending on the brush resistance. It was found that a high resistance cleaning brush with a brush resistance of 10 ⁸ [Ω] has a large decrease in brush tip potential with continuous use. The reason for this is not clear, but it is considered that when the brush resistance is large, the potential drop at the tip of the brush is large due to the high resistance when the fibers are formed of the same length of fiber. The brush resistance of the cleaning brush 521 varies greatly. For example, even if the brush roller is molded with the aim of 10 ⁷ [Ω], it varies within a range of 10 ⁶ to 10 ⁸ [Ω]. As a result, even if a predetermined voltage is applied to the brush roller, the brush tip potential may not be a desired potential.

  Therefore, in the belt cleaning device 10 of the present embodiment, a high resistance roller is used as the collection roller 522, and the usage environment may vary from low temperature and low humidity to high temperature and high humidity, and the resistance varies for each cleaning brush 521 during mass production. Even if there is, the following configuration is provided so that the tip potential of the cleaning brush can be maintained at a desired potential. That is, as shown in FIG. 3, a surface potential meter as surface potential measuring means for measuring the surface potential of the cleaning brush is provided. A control part controls the power supply for brushes based on the measurement result of the surface electrometer.

  As shown in FIG. 3, a metal plate 213 is disposed at a position where the brush tip is cut by 1 [mm] so as to contact the brush tip after contact with the collection roller over the entire axial direction. In the present embodiment, stainless steel is used as the metal plate 213, but the present invention is not limited to this as long as a process that does not cause alteration or rust is performed over a long period of time. Then, the probe 211 of the surface potentiometer 210 is placed at a 1 mm interval on the surface of another metal plate 212 that is connected to the metal plate 213 by a conducting wire to have the same potential, and the surface potential of the metal plate 212 is measured. In this embodiment, the metal plate 212 is regarded as the same potential as the brush surface potential, and the metal plate 212 is measured by the surface potentiometer 210. However, if the configuration is such that the surface potentiometer 210 can be arranged around the brush, the brush The probe 211 may be installed at a distance of 1 mm on the metal plate 213 in contact with the metal plate 213. However, since measurement cannot be performed accurately when toner adheres to the probe 211 of the surface potential meter 210, it is desirable to install the surface potential meter 210 at a position where it is difficult for toner to adhere.

  The operation when measuring the brush surface potential and maintaining the desired brush surface potential based on the value will be described below. As shown in FIG. 3, the image forming apparatus includes a control unit 200 including a CPU, a ROM, a RAM, an I / O interface, and the like. When image formation is started, a toner image is formed on the photosensitive member as described with reference to FIG. 2, and then the toner image is transferred onto the intermediate transfer belt 8, and then the toner image is transferred onto the transfer material. Printing is performed through the fixing device 20. When driving of the intermediate transfer belt 8 is started, a voltage Vb (hereinafter referred to as a reference voltage Vb) having the same value as a desired surface potential V3 (hereinafter referred to as a target potential V3) is first supplied from a brush power source 531 connected to the brush rotation shaft. At the same time, the cleaning brush 521 and the collection roller 522 also start to rotate. The brush surface potential V3 ′ after the cleaning brush 521 starts rotating is always detected by the surface potential meter 210. At each preset time t1, the detected surface potential value is input to the control unit 200, compared with the target potential V3, and the difference (V3′−V3) is calculated. The difference (V3′−V3) is added to the reference voltage Vb to determine the brush application voltage Vb ′, and the brush application voltage Vb ′ is switched after time t1 to time t2. After the time t1 after switching the brush application voltage Vb ′, the brush surface potential is detected in the same manner as described above, and the brush application voltage Vb ′ is switched after t2. This operation is repeated until the image formation is completed and the intermediate transfer belt 8 is stopped. The correction of the brush shaft applied voltage Vb ′ is repeated until the brush surface potential approaches the target potential V3. Note that the target potential V3 is set in a range of 400 [V] to 500 [V], which is a brush tip potential that has good cleaning properties in both a low temperature and low humidity environment and a high temperature and high humidity environment.

  Thereby, the potential difference between the cleaning brush 521 and the intermediate transfer belt 8 can be maintained at a potential difference at which the toner on the intermediate transfer belt 8 adheres to the cleaning brush 521 well. As a result, good cleaning properties can be maintained.

  Next, a modified example of the cleaning device will be described.

[Modification 1]
As described above, in a low temperature and low humidity environment, the brush tip potential with good cleaning properties is 400 [V] to 1000 [V]. Therefore, when the target potential V3 is set between 400 [V] and 500 [V] as described above, the cleaning performance margin is reduced in a low temperature and low humidity environment. Therefore, in a low-temperature and low-humidity environment, if the target potential V3 is set to about 700 [V], the margin for cleaning becomes large. On the other hand, in a high-temperature and high-humidity environment, the brush tip potential with good cleaning properties is 300 [V] to 500 [V], and if the target potential V3 is set to about 400 [V], the cleaning performance margin is sufficient. The degree is increasing. For this reason, in the belt cleaning apparatus 10A of the modified example, as shown in FIG. 17, a temperature / humidity sensor 220 serving as a temperature / humidity detecting means for detecting the temperature / humidity in the apparatus is provided in the belt cleaning apparatus 10A. Further, the charge amount of the toner input to the cleaning brush 521 under various temperature and humidity conditions is measured in advance, and an appropriate brush tip potential is determined for each case, and the determined brush potential is the ROM of the control unit 200. Is stored. While the main switch of the image forming apparatus is ON, the temperature and humidity are always detected by the temperature and humidity sensor 220.

  When driving of the intermediate transfer belt 8 is started, first, the detected value of the temperature / humidity sensor 220 is sent to the control unit 200, the target potential V3 corresponding to the detected temperature / humidity is selected, and the target selected first from the brush power source is selected. A reference voltage Vb having the same value as the potential V3 is applied to the brush rotation shaft. At the same time, the cleaning brush 521 and the collection roller 522 also start to rotate. Next, the brush tip potential V3 ′ after the start of rotation of the cleaning brush is always detected by the surface potential meter 210. At each preset time t1, the detected surface potential value is input to the control unit 200, compared with the target potential V3, and the difference (V3′−V3) is calculated. Then, the difference (V3′−V3) is added to the applied voltage Vb to determine the brush applied voltage Vb ′, and the brush applied voltage is switched after time t1 to time t2. After a time t1 after switching the brush application voltage Vb ′, the brush surface potential is detected by the surface potentiometer 210 as described above, and after t2, the brush application voltage Vb ′ is switched. This operation is repeated until the image formation is completed and the intermediate transfer belt 8 is stopped, and the correction of the brush application voltage Vb ′ is repeated until the target potential V3 is approached.

  When the temperature / humidity detected by the temperature / humidity sensor 220 after image formation starts, the target potential V3 is changed based on the temperature / humidity table held in the ROM of the control unit 200, and the brush surface potential is changed to the changed target potential V3. Thus, the brush application voltage Vb ′ is controlled.

  As described above, in the belt cleaning apparatus 10A according to the modified example, since the control is performed so that the optimum brush tip potential is matched to the temperature and humidity fluctuations, the margin of cleaning performance is increased, and more stable cleaning performance is obtained. be able to.

[Modification 2]
FIG. 18 is a schematic configuration diagram of a belt cleaning device 10B of Modification 2.
Since the polarity control blade 520 constantly rubs against the surface of the intermediate transfer belt 8, the intermediate transfer belt 8 is worn. For this reason, in the belt cleaning device 10B of the second modification, the surface of the intermediate transfer belt 8 is coated with a lubricant to protect the surface of the intermediate transfer belt 8. As shown in FIG. 18, a bar-like solid lubricant 601 obtained by solidifying the lubricant is brought into contact with the cleaning brush 521, and the lubricant is scraped off and applied to the surface of the intermediate transfer belt 8. The solid lubricant 601 is held by a holding member 602, and a pressure spring 603 that is a lubricant urging means is in contact with the holding member 602. The solid lubricant 601 is pressed against the cleaning brush 521 by the urging force of the pressure spring 603. When the cleaning brush 521 rotates, the solid lubricant 601 in contact with the cleaning brush 521 is rubbed, and the lubricant that has been scraped off and adhered to the cleaning brush 521 is applied to the surface of the intermediate transfer belt 8. Further, the leveling blade 604 for leveling and uniforming the lubricant applied to the surface of the intermediate transfer belt 8 is downstream of the surface of the intermediate transfer belt 8 with respect to the surface of the cleaning brush 521 in contact with the surface of the intermediate transfer belt 8. Is provided. The surface of the intermediate transfer belt 8 to which the lubricant has been applied is leveled by the leveling blade 604, and the lubricant on the surface of the intermediate transfer belt 8 is in a dense application state.

  In addition to the cleaning brush 521, a lubricant application brush may be provided. Since toner is always collected in the cleaning brush 521, when the lubricant is applied by the cleaning brush 521, the toner and the lubricant are mixed. As a result, there is a possibility that the toner once collected at the time of applying the lubricant is again adhered to the intermediate transfer belt 8. On the other hand, by providing a brush for applying the lubricant separately from the cleaning brush 521, it is possible to prevent the problem that the toner once collected at the time of applying the lubricant adheres again to the intermediate transfer belt 8.

  Moreover, as shown in FIG. 21, the structure which does not provide the leveling blade 604 may be sufficient.

[Embodiment 2]
Next, as a second embodiment, an example in which the present invention is applied to the photosensitive member cleaning device 4 of the photosensitive member 1 of the tandem intermediate transfer type printer of the first embodiment will be described.

  The process units 6Y, 6M, 6C, and 6K including the photoconductor cleaning devices 4Y, 4M, 4C, and 4K use Y, M, C, and K toners of different colors, but have the same configuration. Therefore, in the following description, the subscripts Y, M, C, and K are omitted. FIG. 19 is a schematic configuration diagram of a process unit 6 including the photoconductor cleaning device 4 according to the present embodiment. Similar to the belt cleaning device 10 described above, the photoconductor cleaning device 4 is of an electrostatic cleaning type that has good cleaning properties even with toner having a reduced particle size or spheroidization.

  As shown in FIG. 19, the photoconductor cleaning device 4 includes a polarity control blade 420 as a polarity control member for residual toner, a cleaning brush 421 as a cleaning member, and a recovery member that recovers toner attached to the cleaning brush 421. A collecting roller 422, a collecting blade 423 that contacts the collecting roller 422 and scrapes the collected toner, and applies a charge to the surface of the collecting roller 422, and a waste toner tank (not shown) provided in the printer main body. And a toner conveying coil 424 for conveying the collected toner. Thus, the collection blade 423 has both a function as a removing member that removes toner from the surface of the collection roller 422 and a function as a charge supply unit that applies charges to the surface of the collection roller 422. In addition, a polarity control power source 430 for applying a voltage to the polarity control blade 420, a brush power source 431 for applying a voltage to the cleaning brush 421, a recovery power source 432 for applying a voltage to the recovery roller 422, and a voltage to the recovery blade 423 are applied. And a blade power source 433.

  Further, the solid lubricant 441 obtained by solidifying the lubricant is brought into contact with the cleaning brush 421, and the lubricant is scraped off by rotation and applied to the surface of the photoreceptor 1. A bar-shaped solid lubricant 441 obtained by solidifying the lubricant is brought into contact with the cleaning brush 421, and the lubricant is scraped off by rotation to be applied to the surface of the photoreceptor 1. The solid lubricant 441 is held by a holding member 443, and a pressure spring 442 that is a lubricant urging means is in contact with the holding member 443. The solid lubricant 441 is pressed against the cleaning brush 421 by the urging force of the pressure spring 442. As a result, even if the solid lubricant 441 decreases with time, the solid lubricant 441 can be appropriately brought into contact with the cleaning brush 421 by the pressure of the pressure spring 442. Further, a leveling blade for leveling and uniforming the lubricant applied to the surface of the photoreceptor 1 may be provided. By applying a lubricant to the surface of the photoconductor 1, the coefficient of friction of the surface of the photoconductor is reduced, thereby improving the removability of transfer residual toner and preventing so-called filming in which the toner adheres to the surface of the photoconductor 1. be able to. In addition, the surface abrasion of the photoreceptor 1 can be reduced.

  The shielding member 444 is disposed such that a urethane rubber sheet having a thickness of 200 [μm] is attached to the casing of the photoconductor cleaning device 4 so that the amount of biting into the cleaning brush 421 is 1 [mm]. The pasting amount with the casing is 3 [mm], and the protruding amount is 7 [mm]. The material of the shielding member 444 is not limited to urethane rubber, and any material having insulating properties and flexibility may be used. Further, the thickness is not limited to 200 [μm] as long as the thickness is not wound by the brush rotation and is not splashed by the air flow by the brush rotation.

  In the photoconductor cleaning device 4 as well, the surface potential of the collecting roller is lowered in a low temperature and low humidity environment as in the belt cleaning device 10, and the brush tip potential of the cleaning brush is lowered. As a result, the potential difference between the photosensitive member 1 and the cleaning brush 421 decreases, and the toner on the photosensitive member cannot be moved electrostatically to the cleaning brush, which may cause a cleaning failure. Therefore, also in the photoconductor cleaning device 4, the brush tip potential is measured by the surface potential meter 451, and the brush power source 431 is controlled based on the measurement result.

  The operation when measuring the brush surface potential and maintaining the desired brush surface potential based on the value will be described below. When driving of the photosensitive member 1 is started, a voltage Vb (hereinafter referred to as a reference voltage Vb) having the same value as a desired surface potential V3 (hereinafter referred to as a target potential V3) is first supplied from a brush power source 431 connected to the brush rotation shaft. ), The cleaning brush 421 and the collection roller 422 also start to rotate. The brush surface potential V3 ′ after the cleaning brush 421 starts rotating is always detected by the surface potential meter 451. At each preset time t1, the detected surface potential value is input to the control unit 200, compared with the target potential V3, and the difference (V3′−V3) is calculated. The difference (V3′−V3) is added to the reference voltage Vb to determine the brush application voltage Vb ′, and the brush application voltage Vb ′ is switched after time t1 to time t2. After the time t1 after switching the brush application voltage Vb ′, the brush surface potential is detected in the same manner as described above, and the brush application voltage Vb ′ is switched after t2. This operation is repeated until the image formation is completed and the photosensitive member 1 is stopped, and the correction of the brush shaft applied voltage Vb ′ is repeatedly performed until the image becomes close to the ideal brush surface potential. The target potential V3 is a brush tip potential with good cleaning properties in both a low temperature and low humidity environment and a high temperature and high humidity environment.

  Thereby, the potential difference between the cleaning brush 421 and the photosensitive member 1 can be maintained at a potential difference at which the toner on the photosensitive member 1 adheres to the cleaning brush 421 satisfactorily. As a result, good cleaning properties can be maintained.

[Embodiment 3]
Next, as a third embodiment, the present invention is applied to a so-called one-drum type full-color image forming apparatus that forms a multicolor image with a photoconductor as one image carrier and a developing unit as a plurality of developing means. I will explain what I did.
In FIG. 20, a photosensitive member 101 as an image carrier, a writing optical unit, developing units 105C, 105M, 105Y, and 105K corresponding to cyan (C), magenta (M), yellow (Y), and black (K) colors. The intermediate transfer device 110, the paper transfer roller 103, a fixing device (not shown), and the like.

  The photoconductor 101 rotates counterclockwise as indicated by an arrow. Around the photoconductor belt cleaning device 104, the charge eliminating lamp 102, the charger 106, and the developing units 105C, 105M, 105Y, and 105K are arranged. The unit converts the color image data from the color scanner into an optical signal, performs optical writing corresponding to the image of the document, and forms an electrostatic latent image on the photoreceptor 101.

  The developing units 105C, 105M, 105Y, and 105K rotate to bring a developer head into contact with the surface of the photosensitive member 101 to develop the electrostatic latent image, and rotate to pump and stir the developer. Developer paddles, etc. The toner in each developing device is negatively charged in this example by stirring with a ferrite carrier, and each developing sleeve is charged with a negative DC voltage Vdc by a developing bias power source as a developing bias applying means (not shown). Is applied, or a developing bias of only a DC voltage is applied, and the developing sleeve is biased to a predetermined potential with respect to the metal substrate layer of the photoreceptor 101.

A toner image of each color is sequentially formed on the photoreceptor 101, and the formation order can be selected as appropriate.
The intermediate transfer device 110 includes an intermediate transfer belt 111, a belt cleaning device 113, and the like. The intermediate transfer belt 111 is stretched around a driving roller 112, a bias roller 115, a cleaning counter roller 116, a driven roller 114, and other driven rollers, and is driven and controlled by a driving motor (not shown).

By applying a primary transfer bias voltage to the bias roller 115, the toner image on the photoreceptor 101 is primarily transferred onto the intermediate transfer belt 111.
The primary transfer bias voltage is appropriately adjusted between 1000 [V] and 2000 [V] from the first color to the fourth color and applied.

The conditions of the printer 700 are as follows.
Photoreceptor potential: Image area: -80 to -130 [V]
Background: -500 to -700 [V]
Toner density: 5 to 10 [wt%] for each color
Toner charge amount (inside of developing device): each color −10 to −25 [μC / g]
Bias roller: Hydrin rubber roller coated with PFE tube, volume resistivity: 10 ⁹ [Ω · cm]
Intermediate transfer belt: Carbon-dispersed fluororesin ETFE (ethylene tetrafluoroethylene)
Further, the electric resistance of the intermediate transfer belt 111 is 10 ¹⁰ [Ω · cm] in volume resistivity and 10 ⁹ [Ω / □] in surface resistivity, and the belt cleaning device 113 of the intermediate transfer device 110 is shown in FIG. The belt cleaning apparatus shown in FIG. 18 or a belt cleaning apparatus that applies lubricant to the surface of the intermediate transfer belt 8 by using a cleaning brush as shown in FIGS. 18 and 21 is used.

  Further, a secondary transfer bias of AC voltage + DC voltage or DC voltage is applied to the paper transfer roller 103, and the superimposed toner images on the intermediate transfer belt 111 are collectively transferred onto the recording paper. The secondary transfer bias applied to the paper transfer roller 103 is 30 [μA].

  In the color copying machine having the above configuration, when an image forming cycle is started, first, the photosensitive member 101 is rotated counterclockwise as indicated by an arrow and the intermediate transfer belt 111 is rotated clockwise as indicated by an arrow by a drive motor (not shown). With the rotation of the intermediate transfer belt 111, K toner image formation, C toner image formation, M toner image formation, and Y toner image formation are performed, and finally they are superimposed on the intermediate transfer belt in the order of K, C, M, and Y. Thus, a toner image is formed.

  The K toner image formation is performed as follows. The charger 106 uniformly charges the photosensitive member 101 to about −700 [V] with negative charge by proximity roller charging. A semiconductor laser 107 indicated by an arrow performs raster exposure based on the K color image signal. When this raster image is exposed, a charge proportional to the exposure light amount disappears in the exposed portion of the photoreceptor 101 that is initially uniformly charged, and a K electrostatic latent image is formed. Then, when the negatively charged K toner on the K developing sleeve comes into contact with the K electrostatic latent image, the toner does not adhere to the remaining portion of the photoreceptor 101, and there is no charged portion, that is, exposure. K toner is attracted to the portion thus formed, and a K toner image similar to the electrostatic latent image is formed. The K toner image formed on the photoconductor 101 is transferred onto the surface of the intermediate transfer belt 111 that is driven at a constant speed in contact with the photoconductor 101 by the intermediate transfer device 110 as follows ( Hereinafter, the toner image transfer from the photosensitive member 101 to the intermediate transfer belt 111 is referred to as belt transfer).

  A primary transfer bias having a polarity opposite to that of the toner on the photoconductor 101, in this example, a positive polarity, is applied to the bias roller 115 by a power source (not shown), and an intermediate transfer belt portion wound around the bias roller 115 is a portion of the photoconductor 101. In contact with the surface, the intermediate transfer belt 111 rotates in the direction indicated by the arrow in FIG. 20 by the rotation of the driving roller 112 driven by a motor (not shown). The photosensitive member 101 and the intermediate transfer belt 111 are controlled to move in the same direction at the contact portion between them and to move at a constant speed. Since a voltage having a polarity opposite to that of the toner is applied to the bias roller 115, when the K toner image on the photoconductor reaches the primary transfer region which is a contact portion between the photoconductor 101 and the intermediate transfer belt 111, K The toner image is electrostatically drawn onto the surface of the intermediate transfer belt 111 and is primarily transferred onto the surface of the intermediate transfer belt 111.

  Some untransferred residual toner on the photoconductor 101 is cleaned by the photoconductor belt cleaning device 104 in preparation for reuse of the photoconductor 101. The collected toner is stored in a waste toner tank (not shown) via a collection pipe.

  When the photoconductor cleaning device 4 shown in FIG. 19 of the present invention is used for the photoconductor belt cleaning device 104, good cleaning properties can be obtained. The surface of the photoconductor 101 after the belt transfer is cleaned by the photoconductor belt cleaning device 104 and then uniformly discharged by the charge eliminating lamp 105.

  On the intermediate transfer belt 111, K, C, M, and Y toner images sequentially formed on the photosensitive member 101 are sequentially aligned on the same surface to form a four-color superimposed toner image. The four color toner images are collectively transferred onto the recording paper by the paper transfer roller 103. When the intermediate transfer belt cleaning device 10 shown in FIGS. 3 and 21 is used as the intermediate transfer belt cleaning device of this embodiment, good cleaning properties can be obtained.

  In the above, a voltage having the same polarity (negative polarity) as the charging polarity of the toner is applied to the polarity control blade 520, and a voltage having a polarity opposite to the charging polarity (positive polarity) of the toner is applied to the cleaning brush and the collecting roller. However, the reverse is also possible. That is, a positive voltage may be applied to the control blade 520 and a negative voltage may be applied to the cleaning brush and the collection roller.

  As described above, according to the cleaning apparatus of the present embodiment, the toner that is the powder on the intermediate transfer belt 8 that is the surface-moving object to be cleaned is a surface-movable cleaning member that electrostatically moves and removes the toner on its surface. A cleaning brush 521 is provided. Further, a recovery roller 522 is provided as a surface-movable recovery member that has a resistance surface layer and electrostatically moves the toner on the cleaning brush to its own surface for recovery. Further, a recovery blade 523 is provided as a removing member that slides on the surface of the recovery roller to scrape and remove the toner on the recovery roller. Further, a brush power source 531 serving as a cleaning member voltage applying unit that applies a voltage to the cleaning brush, and a recovery power source 532 serving as a recovery member voltage applying unit that applies a voltage to the recovery roller are provided. In addition, a surface potential meter serving as a surface potential measuring unit that measures the surface potential of the cleaning brush 521 is provided, and the control unit 200 serving as a control unit controls the brush power source 531 based on the measurement result of the surface potential meter. With this configuration, the brush power supply 531 can be controlled so that the surface potential of the cleaning brush becomes a potential at which the toner on the intermediate transfer belt 8 can electrostatically move to the cleaning brush. it can. Thus, the surface potential of the cleaning brush can be maintained at a potential at which the toner on the intermediate transfer belt 8 can electrostatically move to the cleaning brush, and good cleaning properties can be obtained.

  Further, according to the cleaning device of the first modification, the brush power source 531 is controlled based on the measurement result of the surface potentiometer and the detection result of the temperature / humidity sensor 220 serving as the temperature / humidity detection means. With this configuration, the surface potential of the cleaning brush can be set to an optimum potential for removing the toner on the intermediate transfer belt 8 even if the environment of the apparatus changes.

  In addition, by using a brush roller in which conductive fibers are planted so as to extend from the outer periphery of the conductive core bar to the outside in the diameter direction as a cleaning member, scraping with a brush at the same time as cleaning of the electrostatic transfer method The cleaning performance can be improved by performing the scraping method cleaning.

Further, since the brush resistance is set to 10 ⁶ [Ω] or more and 10 ⁸ [Ω] or less, the charge injection into the toner can be suppressed, and the photosensitive member 1 can be cleaned well, and the cleaning brush 521 and the recovery roller can be used. The voltage applied to 522 can be reduced, and energy saving and cost reduction can be achieved.

Further, since the resistance of the surface layer is set to 10 ¹⁰ [Ω / □] or more, it is possible to further suppress the reversal of the polarity of the toner sandwiched between the cleaning brush 521 and the collection roller 522 as described above. .

  In addition, a polarity control member that controls the charging polarity of the toner on the intermediate transfer belt is provided upstream of the cleaning brush 521. Thereby, the polarity of the toner on the intermediate transfer belt can be made uniform, and good electrostatic cleaning can be performed.

  Further, by using a conductive blade as the polarity control member, the polarity of the toner on the intermediate transfer belt can be made uniform with a simple configuration. Further, the toner on the intermediate transfer belt can be scraped off by the conductive blade by bringing the conductive blade into contact with the intermediate transfer belt. As a result, the amount of toner removed by the cleaning brush can be reduced. Therefore, the amount of toner adhering to the collecting roller can be reduced, and the reduction in the surface potential of the collecting roller in a low temperature and low humidity environment can be suppressed.

  Moreover, you may use a conductive brush as a polarity control member. By bringing the conductive brush into contact with the intermediate transfer belt, the toner on the intermediate transfer belt can be scraped off by the conductive brush. As a result, the amount of toner removed by the cleaning brush can be reduced. Therefore, the amount of toner adhering to the collecting roller can be reduced, and the reduction in the surface potential of the collecting roller in a low temperature and low humidity environment can be suppressed. Further, compared to a rubber conductive blade, wear can be suppressed and performance can be maintained over a long period of time.

  Further, by using the cleaning device of the present invention as a cleaning device for cleaning the photoreceptor 1 provided in the image forming apparatus, it is possible to satisfactorily clean the transfer residual toner on the photoreceptor 1. Thereby, high-quality image formation can be realized.

  In addition, according to the third embodiment, the cleaning device of the present invention is used as a cleaning device for removing the transfer residual toner on the photoconductor as an image carrier in the case of a one-drum type full-color image forming apparatus. The transfer residual toner on the body 1 can be cleaned well. Since the transfer residual toner on the photoconductor 1 can be cleaned well, it is possible to prevent the transfer residual toner on the photoconductor 1 from being mixed into the developing unit 105 of other colors, and to prevent color mixing. Can do. Thereby, high-quality image formation can be realized.

  According to the second embodiment, the cleaning device of the present invention is used as the photosensitive member cleaning device 4 for removing the transfer residual toner on the photosensitive member as the image carrier in the case of a tandem type full-color image forming apparatus. The transfer residual toner on each photoreceptor 1 can be cleaned well. Thereby, high-quality image formation can be realized.

  In addition, according to the first embodiment, by using the cleaning device of the present invention as the belt cleaning device 10 that cleans the intermediate transfer belt 8 that is an intermediate transfer member, the transfer residual toner on the intermediate transfer belt 8 is satisfactorily cleaned. can do. Since the transfer residual toner on the intermediate transfer belt 8 can be satisfactorily cleaned, the transfer residual toner on the intermediate transfer belt 8 can be prevented from adhering to the photoreceptor 1 of other colors, and color mixing can be prevented. be able to. Thereby, high-quality image formation can be realized.

DESCRIPTION OF SYMBOLS 1,101: Photoconductor 4, 104: Photoconductor cleaning device 8, 111: Intermediate transfer belt 10, 113: Belt cleaning device 210, 451: Surface potential meter 211: Probe 220: Temperature / humidity sensor 420, 520: Polarity control blade 421, 521: Cleaning brushes 422, 522: Collection rollers 423, 523: Collection blades 430, 530: Polarity control power sources 431, 531: Brush power sources 432, 532: Collection power sources 433, 533: Blade power sources 441, 601: Solid lubricants 442, 603: pressure springs 443, 602: holding member 444: shielding member 604: leveling blade

JP 2005-265907 A

Claims (10)

A surface-movable cleaning member that electrostatically moves and removes powder on the surface to be cleaned to its own surface; and
A surface-movable recovery member that has a resistance surface layer and electrostatically moves and recovers the powder on the cleaning member to its own surface;
A removal member that scrapes and removes powder on the recovery member by rubbing against the surface of the recovery member;
Cleaning member voltage applying means for applying a voltage to the cleaning member;
Recovery member voltage application means for applying a voltage to the recovery member;
In a cleaning device comprising:
Surface potential measuring means for measuring the cleaning member surface potential;
Based on the measurement result of the surface potential measuring means, Bei example and control means for controlling the cleaning member voltage applying means,
The resistance of the cleaning member is 10 ⁶ [Ω] or more and 10 ⁸ [Ω] or less,
The recovery member has a low surface resistance of 10 ¹⁰ [Ω / □] or more and 10 ¹³ [Ω / □] or less,
The cleaning member voltage application means applies a voltage having a polarity opposite to the charging polarity of the powder to the cleaning member,
The recovery member voltage applying means applies a voltage to the recovery member that is opposite in polarity to the charging polarity of the powder and higher than the voltage applied to the cleaning member,
The control means uses the measurement result of the surface potential measurement means so that the surface potential of the cleaning member becomes a target potential at which the powder on the object to be cleaned can electrostatically move to the cleaning member. And a cleaning device voltage application unit . The cleaning device according to 請 Motomeko 1,
A temperature / humidity detection means for detecting the temperature / humidity inside the device is provided ,
Based on the detection result of the previous SL temperature and humidity detecting means, a cleaning device and sets the target potential. The cleaning device according to claim 1 or 2 ,
A cleaning apparatus using a brush roller in which a conductive fiber is planted so as to extend from the outer periphery of the conductive metal core to the outside in the diameter direction as the cleaning member . The cleaning device according to any one 請 Motomeko 1 to 3,
A cleaning apparatus comprising a polarity control member for controlling a charging polarity of the powder on the object to be cleaned, upstream of the cleaning member in the surface movement direction of the object to be cleaned. The cleaning apparatus according to claim 4 .
As the polarity control member, using a conductive blade,
A cleaning device, wherein the conductive blade is brought into contact with the surface of an object to be cleaned. The cleaning apparatus according to claim 4 .
As the polarity control member, using a conductive brush,
A cleaning device, wherein the conductive brush is brought into contact with the surface of an object to be cleaned. An image carrier;
A charging device for charging the image carrier;
An exposure device that exposes the image carrier to form an electrostatic latent image;
A developing device for converting the electrostatic latent image on the image carrier into a toner image;
A transfer device for transferring a toner image on the image carrier to a transfer material;
In an image forming apparatus comprising a cleaning device that removes transfer residual toner on the image carrier,
An image forming apparatus characterized by using the cleaning device according to any one of claims 1 to 6 as the cleaning device. The image forming apparatus according to claim 7 .
A plurality of developing devices for forming toner images on the image carrier;
An image forming apparatus for forming a multicolor image by superimposing a plurality of toner images formed on the image carrier. The image forming apparatus according to claim 8 .
A plurality of image carriers;
Each having a developing device for forming a toner image on the plurality of image carriers;
An image forming apparatus for forming a multicolor image by superposing toner images formed on a plurality of image carriers. The image forming apparatus according to claim 8 or 9, wherein
The transfer device transfers a toner image to a transfer material via an intermediate transfer member,
An image forming apparatus characterized by using the cleaning device according to any one of claims 1 to 6 as an intermediate transfer member cleaning device for cleaning the residual toner of the intermediate transfer member surface.

Images