JP5966981B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  As a conventional technique described in the publication, an endless intermediate transfer member to which a toner image formed on an image carrier is transferred, a lubricant applied on the intermediate transfer member, and the lubricant is transferred to the intermediate transfer member. An image forming apparatus comprising: a lubricant application member applied to a member; and a transfer device that transfers a toner image on the intermediate transfer member to a recording medium. Of the region on the intermediate transfer member, the transfer device and the intermediate transfer An image forming apparatus is described in which the amount of lubricant applied in a contact area where a member is in direct contact can be changed with respect to the amount of lubricant applied in a non-contact area where the transfer device and the intermediate transfer member are not in direct contact. (See Patent Document 1).

  In addition, as a conventional technique described in other publications, in a secondary transfer type image forming apparatus, a secondary transfer bias to be supplied when performing a secondary transfer all at once on the transfer material is constant after the secondary transfer is completed. The secondary transfer bias is supplied to a secondary transfer roller disposed on the color image holding surface side of the intermediate transfer member, and the secondary transfer roller is supplied with the secondary transfer bias after completion of the secondary transfer. An image forming apparatus that is rotationally driven at a speed different from the peripheral speed of the intermediate transfer member is described (see Patent Document 2).

  Furthermore, as a prior art described in other publications, a resin particle body and silica particles attached to the surface of the resin particle body, the volume average particle diameter is 80 nm or more and 300 nm or less, and the particle size distribution index is 1.10 or more and 1 .40 or less, primary particles having an average circularity of 0.70 or more and 0.92 or less, a circularity distribution index of 1.05 or more and 1.50 or less, and a circularity of 0.95 or more There are resin particles containing silica particles having a ratio of 10% by number or less (see Patent Document 3).

JP 2011-180346 A Japanese Patent Laid-Open No. 04-296784 JP 2012-149190 A

  An object of the present invention is to provide an image forming apparatus that suppresses the occurrence of poor cleaning in a transfer unit.

According to the first aspect of the present invention, the toner image is transferred to the transfer body by sandwiching a transfer body that is divided into a plurality of types between the holding body that holds the toner image and the holding body. Generated by a discharge between the holding body and the transfer means corresponding to the type of the transfer object determined by the determination means. When the amount of discharge products to be predicted is large and the amount of discharge products is predicted to be larger than when a predetermined standard is used, the discharge product attached to the transfer unit is attached to the transfer unit. comprising a adhesion reducing means for reducing the force application, and a removal means for removing the discharge product adhered to the transfer unit, the adhesion reducing means is in contact with the surface and lubricant block of the transfer unit cleaning Have a brush When the surface of the transfer unit is provided with a lubricant supply unit for supplying a lubricant, and the discharge product is generated more than the reference in accordance with the type of the transfer target determined by the determination unit. When predicting, before the toner image is transferred to the transfer target, the time during which the cleaning brush contacts the surface of the transfer unit is increased, the rotation speed of the cleaning brush is increased, or the lubricant block is In the image forming apparatus, the amount of the lubricant supplied to the transfer unit by the lubricant supply unit is increased by an increase in load on the cleaning brush .
According to a second aspect of the present invention, the adhesion reduction means predicts that the discharge product is generated more frequently than the reference, depending on the type of the transfer object determined by the determination means. In this case, after the transfer unit transfers the toner image to the transfer target body, the holding body and the transfer unit are rubbed with each other with a difference in the moving speeds on the surfaces facing each other. The image forming apparatus according to claim 1, wherein an adhesion force of the discharge product attached to the transfer unit is reduced.
According to a third aspect of the present invention, the determination unit includes a resistance measurement unit that measures an electrical resistance between the holding unit between which the transfer target is sandwiched and the transfer unit, and the resistance measurement unit performs measurement. by the said electrical resistance, which is an image forming apparatus according to claim 1 or 2, characterized in that to determine the type of the material to be transferred.
According to a fourth aspect of the present invention, the toner image held by the holder is composed of a toner including a toner main body and a different type of external additive, and is added to the toner image transferred to the transfer target. The discharge product includes other toner images that are not transferred to the transfer body, and the adhesion reduction means is more suitable for the discharge product than in the case of using the reference according to the type of the transfer body determined by the determination means. When the amount of toner that forms the other toner image that is not transferred to the transfer target is increased, and the toner is removed from the transfer unit by the removing unit, The additive according to any one of claims 1 to 3 , wherein the discharge product adhering to the transfer means is polished to reduce the adhesion force of the discharge product attached to the transfer means. Image form described It is a device.
According to a fifth aspect of the present invention, the toner image is transferred to the transfer target body by sandwiching a transfer target that is divided into a plurality of types between the holding body that holds the toner image and the support body. Transfer means, a transfer electric field supply means for supplying a transfer voltage to the transfer means, and the transfer voltage supplied by the transfer electric field supply means is higher than a predetermined reference voltage. comprising a adhesion reducing means for reducing the adhesion to the transfer means of the discharge products adhering to the transfer unit, and a removal means for removing the discharge product adhered to the transfer unit, the adhesion force reduction The means includes a cleaning brush that comes into contact with the surface of the transfer means and the lubricant block, and includes a lubricant supply unit that supplies the lubricant to the surface of the transfer means, for transfer supplied by the transfer electric field supply means. The voltage of When the voltage is higher than the reference voltage, an increase in the time during which the cleaning brush contacts the surface of the transfer unit before transferring the toner image to the transfer target, an increase in the number of rotations of the cleaning brush, or the lubrication In the image forming apparatus, the amount of the lubricant supplied from the lubricant supply unit to the transfer unit is increased by increasing the load on the cleaning brush .

According to the first aspect of the present invention, it is possible to suppress the occurrence of defective cleaning in the transfer means as compared with the case where this configuration is not used.
According to the second aspect of the present invention, compared to the case where this configuration is not used, it is possible to reduce the adhesion force of the discharge product attached on the image carrier in addition to the transfer means.
According to the third aspect of the present invention, it is possible to automate the discrimination of the paper type as compared with the case where this configuration is not used.
According to the invention of claim 4 , it is not necessary to change the hardware configuration of the image forming apparatus as compared with the case where this configuration is not used.
According to the fifth aspect of the present invention, it is possible to suppress the occurrence of a cleaning failure in the transfer unit as compared with the case where this configuration is not used.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus to which a first exemplary embodiment is applied. It is an enlarged view of the secondary transfer part in FIG. FIG. 4 is a diagram illustrating an example of a toner image on an intermediate transfer belt in the first embodiment. It is a figure which shows an example of the wear cross section seen in the discharge current and the cleaning blade in the paper passing part RP and the non-paper passing part RN of the secondary transfer roll. Secondary transfer is performed according to the period (time) in which the secondary transfer roll and the cleaning brush are in contact with each other corresponding to the type of paper P (P type) or the resistance value R (secondary transfer part resistance R) of the secondary transfer part. It is a timing chart in the case of controlling the quantity of the lubricant supplied to a roll. The amount of lubricant supplied to the secondary transfer roll according to the rotational speed r of the cleaning brush of the roll cleaner corresponding to the type (P type) of the paper P or the resistance value R (secondary transfer portion resistance R) of the secondary transfer portion. It is a timing chart in the case of controlling. Lubrication supplied to the secondary transfer roll by the load L of the lubricant block on the cleaning brush of the roll cleaner corresponding to the type of paper P (P type) or the resistance value R (secondary transfer portion resistance R) of the secondary transfer portion. It is a timing chart in the case of controlling the quantity of an agent. It is a figure which shows an example of the relationship between the abrasion cross-sectional area in the non-sheet passing part RN of a cleaning blade, and the number of processed sheets when changing the load of the lubricant block with respect to the cleaning brush. Differences in the respective moving speeds on the surface where the secondary transfer roll and the intermediate transfer belt face each other (corresponding to the type (P type) of the paper P or the resistance value R (secondary transfer portion resistance R) of the secondary transfer portion ( 6 is a timing chart in the case of removing discharge products attached to the secondary transfer roll by providing a (speed difference). FIG. 10 is a diagram illustrating an example of a toner image on an intermediate transfer belt according to a third embodiment. It is a figure which shows the evaluation result of generation | occurrence | production of the cleaning blade and cleaning property. It is a schematic block diagram which shows an example of the image forming apparatus with which 4th Embodiment is applied.

(First embodiment)
[Image forming apparatus 1]
FIG. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus 1 to which the first exemplary embodiment is applied. An image forming apparatus 1 shown in FIG. 1 is generally an image forming apparatus based on a tandem type intermediate transfer method, and a plurality of image forming units 2Y, 2M, 2C, and 2K on which toner images of respective color components are formed by an electrophotographic method. The primary transfer unit 10 and the intermediate transfer belt for sequentially transferring (primary transfer) toner images of respective colors (components) formed by the image forming units 2Y, 2M, 2C, and 2K to an intermediate transfer belt 15 as an example of a holding body. The secondary transfer unit 20 transfers the toner image transferred onto the toner 15 (the toner image on which the toner images of the respective colors are superimposed) onto a sheet P as an example of a transfer target (secondary transfer). A fixing unit 60 for fixing the toner image on the paper P is provided. The image forming control unit 80 controls the operation of each device (each unit), and a user interface unit (UI unit) 85 that receives an operation-related instruction from the user and displays a message to the user. Yes.
Note that the image forming units 2Y, 2M, 2C, and 2K are referred to as image forming units 2 when they are not distinguished from each other.

Each of the image forming units 2Y, 2M, 2C, and 2K has an electrostatic latent image on the photosensitive drum 11 around the photosensitive drum 11 that rotates in the direction of arrow A. The charger 12 charges the photosensitive drum 11. A laser exposure device 13 (exposure beam is indicated by a symbol Bm in the figure), a developing device 14 that accommodates toner of each color and visualizes the electrostatic latent image on the photosensitive drum 11 with the toner, a photosensitive member For electrophotography, such as a primary transfer roll 16 that transfers toner images of each color formed on the drum 11 to the intermediate transfer belt 15 in the primary transfer unit 10, and a drum cleaner 17 that removes toner remaining on the photosensitive drum 11. Devices are arranged sequentially. These image forming units 2Y, 2M, 2C, and 2K are arranged in the order of yellow (Y), magenta (M), cyan (C), and black (K) from the upstream side of the intermediate transfer belt 15.
In the following description, it is assumed that the charging polarity of the toner is negative (negative) as an example.

The intermediate transfer belt 15 is constituted by a film-like endless belt in which an appropriate amount of an antistatic agent such as carbon black is contained in a resin such as polyimide or polyamide. And the volume resistivity is formed so that it may become 10 < ⁶ > -10 < ¹⁴ > (omega | ohm) cm, The thickness is comprised by about 0.1 mm, for example. The intermediate transfer belt 15 is circulated and driven (rotated) at a predetermined speed in the direction of arrow B shown in FIG. 1 by various rolls. The various rolls include a drive roll 31 that is driven by a motor (not shown) having excellent constant speed and rotates the intermediate transfer belt 15, and an intermediate transfer belt that extends linearly along the arrangement direction of the photosensitive drums 11. 15, a support roll 32 that supports the intermediate transfer belt 15, a tension roll 33 that functions as a correction roll that applies tension to the intermediate transfer belt 15 and prevents the intermediate transfer belt 15 from meandering, a backup roll 25 provided in the secondary transfer unit 20, an intermediate A cleaning backup roll 34 provided opposite to the intermediate transfer belt cleaner 35 that scrapes off the toner remaining on the transfer belt 15 is provided.

The primary transfer unit 10 includes a photosensitive drum 11 and a primary transfer roll 16 that are arranged so as to face each other with the intermediate transfer belt 15 interposed therebetween. The primary transfer roll 16 includes a shaft and a sponge layer as an elastic body layer fixed around the shaft. The shaft is a cylindrical bar made of metal such as iron or SUS. The sponge layer is a sponge-like cylindrical roll formed of a blend rubber of NBR, SBR, and EPDM containing a conductive agent such as carbon black and having a volume resistivity of 10 ⁷ to 10 ⁹ Ωcm. The primary transfer roll 16 is pressed against the photosensitive drum 11 with the intermediate transfer belt 15 interposed therebetween.
Further, a positive voltage (primary transfer bias) having a polarity opposite to the charging polarity (negative) of the toner is applied to the primary transfer roll 16. As a result, the toner images on the respective photosensitive drums 11 are sequentially electrostatically attracted to the intermediate transfer belt 15, and the toner images are transferred (primary transfer) onto the intermediate transfer belt 15.

The secondary transfer unit 20 includes a backup roll 25 disposed so as to face each other with the intermediate transfer belt 15 interposed therebetween, and a secondary transfer roll 22 as an example of a transfer unit. The secondary transfer roll 22 is disposed on the toner image holding surface side of the intermediate transfer belt 15 and is grounded. The backup roll 25 is arranged so that a metal power supply roll 26 is in contact therewith.
The secondary transfer roll 22 is pressed against the backup roll 25 with the intermediate transfer belt 15 interposed therebetween.

The power supply roll 26 is connected to a secondary transfer power source 27 as an example of a transfer electric field supply unit via a resistance measurement unit 28 that detects an electrical resistance (hereinafter referred to as resistance) of the secondary transfer unit 20. Yes. When the secondary transfer power supply 27 supplies a negative voltage to the power supply roll 26, the voltage is applied to the backup roll 25. As a result, a negative secondary transfer electric field (secondary transfer bias) is formed in the secondary transfer portion 20 (between the secondary transfer roll 22 and the backup roll 25).
In this state, when the paper P is conveyed to the secondary transfer unit 20, an image forming toner image composed of toner having negative charging characteristics (image forming toner images 101a and 101b in FIG. 3 described later). Is electrostatically attracted and transferred (secondary transfer) onto the paper P.
The secondary transfer bias is an electric field formed between the secondary transfer roll 22 and the backup roll 25 with the intermediate transfer belt 15 in between. However, when the secondary transfer power supply 27 supplies the secondary transfer bias. write.

  The resistance measuring unit 28 detects the resistance value R of the secondary transfer unit 20 by measuring the current flowing from the secondary transfer power source 27 to the power supply roll 26.

  The backup roll 25 is composed of a tube of EPDM and NBR blend rubber with carbon dispersed on the surface, and EPDM rubber on the inside. And it is formed so that the surface resistivity may be 6.5 log ohms, and hardness is set as 75 degrees (Asker C), for example.

On the other hand, the secondary transfer roll 22 is composed of a shaft, an elastic layer fixed in order around the shaft, and a release layer. The shaft is a cylindrical bar made of a metal such as aluminum, iron, or SUS. The elastic layer is a sponge-like cylindrical roll formed of a blend rubber of NBR, SBR and EPDM containing a conductive agent such as carbon black and having a volume resistivity of 10 ⁷ to 10 ⁹ Ωcm. The release layer is formed of fluororesin, fluororubber, or the like and covers the surface of the elastic layer. As the release layer, a fluororesin having good release properties is preferable. The surface resistivity is, for example, 6.5 log Ω, and the hardness is, for example, 75 ° (Asker C).

A roll cleaner 40 that removes toner adhering to the secondary transfer roll 22 is provided. The roll cleaner 40 is a cleaning brush 41 disposed in contact with the secondary transfer roll 22 so as to be rotatable, and cleaning as an example of a removing unit provided further downstream of the cleaning brush 41 in the rotation direction of the secondary transfer roll 22. A blade 42 is provided. The roll cleaner 40 is disposed so as to come into contact with the cleaning brush 41, and includes a lubricant block 43 that holds a lubricant supplied to the cleaning brush 41, a cleaning brush 41, a cleaning blade 42, and a cleaner block that houses the lubricant block 43. A housing 44, a support member 45 that fixes and supports the cleaning blade 42 to the cleaner housing 44, and a load setting member 46 that sets a force (load) for pressing the lubricant block 43 against the cleaning brush 41 are provided. One end of the load setting member 46 is fixed to the cleaner housing 44, and the other end is fixed to the lubricant block 43. The load is applied to the cleaning brush 41.
Further, the cleaner housing 44 is provided with a storage portion 47 for storing waste toner.
The cleaning brush 41, the cleaning blade 42, and the lubricant block 43 are examples of the lubricant supply unit.

The cleaning brush 41 has a hair bundle spirally planted on the surface of a shaft made of metal or the like. The bristles are made of insulating polypropylene that is easily charged to the same charge polarity (negative) as the toner.
The cleaning brush 41 is rotated by a motor 48 (see FIG. 2 described later) connected to the shaft.

Since the lubricant block 43 is disposed so as to contact the cleaning brush 41, the lubricant held by the lubricant block 43 is supplied to the cleaning brush 41. As the cleaning brush 41 rotates, the lubricant supplied to the cleaning brush 41 is supplied onto the secondary transfer roll 22.
The amount of lubricant supplied onto the secondary transfer roll 22 is determined based on the time during which the cleaning brush 41 is rotating in contact with the secondary transfer roll 22, the number of rotations of the cleaning brush 41, and the cleaning brush 41 from the lubricant block 43. It is controlled by the supply amount of lubricant. The amount of lubricant supplied to the cleaning brush 41 is determined by the force (load) that the load setting member 46 presses the lubricant block 43 against the cleaning brush 41, so that the tip of the cleaning brush 41 moves from the surface of the lubricant block 43 to the inside. It can be set according to the amount of bite.
The lubricant is obtained by pressing and compacting fine powders of metal-containing fatty acids such as zinc stearate and calcium stearate to form a block shape or the like.

  The lubricant reduces friction between the secondary transfer roll 22 and the cleaning blade 42, and suppresses curling (mekure) of the cleaning blade 42. The wobbling of the cleaning blade 42 will be described in detail later.

The cleaning blade 42 is a long plate-like member made of an elastic material such as urethane rubber. When viewed in a cross-section in the short direction, one of the square corners (ridges) is provided so as to contact the counter direction with respect to the rotation direction of the secondary transfer roll 22 (arrow C direction). Therefore, as the secondary transfer roll 22 rotates, the toner adhering to the secondary transfer roll 22 is scraped off by one corner of the cleaning blade 42.
The support member 45 fixes the cleaning blade 42 to the cleaner housing 44 so that the cleaning blade 42 contacts the secondary transfer roll 22 with a predetermined pressure (contact pressure).
The toner scraped off by the cleaning blade 42 falls into the accumulation portion 47 in the cleaner housing 44 and is accumulated as waste toner.

  Further, on the downstream side of the secondary transfer portion 20 of the intermediate transfer belt 15, intermediate transfer that removes toner and paper powder remaining on the intermediate transfer belt 15 after the secondary transfer and cleans the surface of the intermediate transfer belt 15. A belt cleaner 35 is provided. On the other hand, on the upstream side of the Y image forming unit 2Y, a reference sensor (home position sensor) 81 that generates a reference signal serving as a reference for taking image forming timings in the image forming units 2Y, 2M, 2C, and 2K. It is arranged. Further, an image density sensor 82 for adjusting image quality is disposed downstream of the K image forming unit 2K.

The reference sensor 81 recognizes a predetermined mark provided on the back side of the intermediate transfer belt 15 and generates a reference signal. Each image forming unit 2Y, 2M, 2C, 2K is configured to start image formation according to an instruction from the image formation control unit 80 based on the recognition of the reference signal.
On the other hand, the image density sensor 82 detects a density control toner image (toner patch) (a density control toner image 102 in FIG. 3 described later). The image forming control unit 80 adjusts the operating conditions of the image forming units 2Y, 2M, 2C, and 2K based on the detection result of the density control toner image detected by the image density sensor 82, and the image forming toner image. The density of the image forming toner images 101a and 101b in FIG. 3 to be described later is adjusted.

  Furthermore, in the image forming apparatus 1 according to the present embodiment, a paper storage unit 50 that stores the paper P, a pickup roll 51 that picks up and transports the paper P stored in the paper storage unit 50 at a predetermined timing, and a pickup After the secondary transfer by the secondary transfer roll 22, the secondary transfer roll 22 transports the paper roll 52 transported by the roll 51, the paper transport path 53 that feeds the paper P transported by the transport roll 52 to the secondary transfer unit 20. A conveyance belt 55 that conveys the conveyed paper P to the fixing unit 60 and a fixing entrance guide 56 that guides the paper P to the fixing unit 60 are provided.

  The fixing unit 60 includes a heating roll 61 containing a heating source such as a halogen lamp, and a pressure roll 62 pressed against the heating roll 61. Fixing is performed by passing the paper P on which the toner image is transferred between the heating roll 61 and the pressure roll 62.

  In the image forming apparatus 1 according to the first embodiment, in addition to the image forming toner image secondarily transferred to the paper P, a density control toner image (toner patch) and the like are formed. Note that the image forming toner image, the density control toner image, and the like are referred to as a toner image when they are not distinguished from each other.

Next, a basic image forming process of the image forming apparatus 1 in the first embodiment will be described. Here, an image forming process using an image forming toner image will be described.
In the image forming apparatus 1 shown in FIG. 1, image data output from an image reading device (not shown) or a personal computer (PC) (not shown) is subjected to predetermined image processing by an image processing device (not shown). Thereafter, the image forming operation is executed by the image forming units 2Y, 2M, 2C, and 2K. In the image processing apparatus, predetermined images such as shading correction, position shift correction, brightness / color space conversion, gamma correction, frame deletion, color editing, moving editing, and other various image editing are applied to the input image data. Processing is performed. The image data subjected to the image processing is converted into color material gradation data of four colors Y, M, C, and K, and is output to the laser exposure unit 13 via the image formation control unit 80.

  The laser exposure unit 13 irradiates the photosensitive drums 11 of the image forming units 2Y, 2M, 2C, and 2K with, for example, an exposure beam Bm emitted from a semiconductor laser according to the input color material gradation data. . In each of the photosensitive drums 11 of the image forming units 2Y, 2M, 2C, and 2K, the surface is charged by the charger 12, and then the surface is scanned and exposed by the laser exposure unit 13 to form an electrostatic latent image. The formed electrostatic latent images are developed as image forming toner images of Y, M, C, and K by the developing devices 14 of the image forming units 2Y, 2M, 2C, and 2K.

  The image forming toner images of the respective colors formed on the photosensitive drums 11 of the image forming units 2Y, 2M, 2C, and 2K are transferred to the primary transfer unit 10 where the photosensitive drums 11 and the intermediate transfer belt 15 are in contact with each other. The image is transferred onto the intermediate transfer belt 15. More specifically, in the primary transfer unit 10, a positive voltage (primary transfer bias) having a polarity opposite to the charging polarity (negative) of the image forming toner is supplied from the primary transfer roll 16 to the base material of the intermediate transfer belt 15. Then, primary transfer is performed in which the image forming toner image is sequentially superimposed on the surface of the intermediate transfer belt 15.

  The image forming toner images of the respective colors are sequentially primary-transferred onto the surface of the intermediate transfer belt 15 to form an image forming toner image in which the image forming toner images of the respective colors are superimposed and conveyed to the secondary transfer unit 20. Is done. The pickup roll 51 rotates in accordance with the timing at which the superimposed image forming toner image is conveyed to the secondary transfer unit 20, and the paper P having a predetermined size is supplied from the paper storage unit 50. The paper P supplied by the pickup roll 51 is transported by the transport roll 52, and reaches the secondary transfer unit 20 through the paper transport path 53. Before the sheet P reaches the secondary transfer unit 20, the conveyance of the sheet P is temporarily stopped, and a registration roll (not shown) is aligned with the movement timing of the intermediate transfer belt 15 on which the superimposed image forming toner image is held. ) Rotates, the position of the paper P and the position of the superimposed image forming toner image are aligned.

In the secondary transfer unit 20, the secondary transfer roll 22 is pressed against the backup roll 25 via the intermediate transfer belt 15. At this time, the sheet P conveyed at the same timing is sandwiched between the intermediate transfer belt 15 and the secondary transfer roll 22. At this time, a negative voltage (secondary transfer bias) having the same polarity as the charging polarity (negative) of the toner is supplied from the secondary transfer power supply 27 to the backup roll 25 via the power supply roll 26. Then, a secondary transfer bias is formed between the secondary transfer roll 22 and the backup roll 25, and the superimposed image forming toner images held on the intermediate transfer belt 15 are collectively transferred onto the paper P. Secondary transfer is performed.
Note that the secondary transfer bias is, for example, −12 kV.

  Thereafter, the paper P on which the superimposed image forming toner image has been transferred is provided on the downstream side of the secondary transfer roll 22 in the paper conveyance direction in a state of being peeled from the intermediate transfer belt 15 by the secondary transfer roll 22. It is conveyed to the conveyor belt 55. The conveyance belt 55 conveys the paper P to the fixing unit 60 in accordance with the conveyance speed in the fixing unit 60. The unfixed image forming toner image on the paper P conveyed to the fixing unit 60 is fixed on the paper P by being subjected to a fixing process by heat and pressure by the fixing unit 60 and becomes a fixed image. The paper P on which the fixed image is formed is conveyed to a paper discharge storage unit (not shown) provided in the discharge unit of the image forming apparatus 1.

After the transfer onto the paper P is completed, the toner remaining on the intermediate transfer belt 15 is conveyed as the intermediate transfer belt 15 moves, and is removed from the intermediate transfer belt 15 by the intermediate transfer belt cleaner 35.
Then, the toner attached to the secondary transfer roll 22 is removed from the secondary transfer roll 22 by the roll cleaner 40.

[Wrapping of the cleaning blade 42 of the roll cleaner 40]
The turning of the cleaning blade 42 of the roll cleaner 40 will be described.
FIG. 2 is an enlarged view of the secondary transfer unit 20 in FIG. FIG. 2A shows the intermediate transfer belt 15, the backup roll 25, the roll cleaner 40, and the paper P with the secondary transfer roll 22 in FIG. 1 as the center. 2B and 2C are views in which the secondary transfer roll 22 side is viewed in the width direction of the secondary transfer roll 22 from the direction indicated by the arrow IIBC in FIG. FIG. 2B shows the relationship among the intermediate transfer belt 15, the secondary transfer roll 22, the cleaning blade 42 of the roll cleaner 40, and the paper P. FIG. 2C shows the relationship between the intermediate transfer belt 15, the secondary transfer roll 22, the cleaning brush 41 of the roll cleaner 40, and the paper P.

  As shown in FIG. 2A, the secondary transfer roll 22 and the backup roll 25 are in contact with each other with the intermediate transfer belt 15 interposed therebetween to form a nip portion N. When a transfer bias is applied between the secondary transfer roll 22 and the backup roll 25 and the paper P is supplied to the nip portion N, the image forming toner image on the intermediate transfer belt 15 is transferred to the paper P.

  The cleaning blade 42 of the roll cleaner 40 is a long plate-like member, and one square corner which is a cross section in the short side direction is in contact with the secondary transfer roll 22. This angle is in contact with the direction (counter direction) facing the rotation direction of the secondary transfer roll 22 (a state indicated by a solid line). Here, the portion of the cleaning blade 42 that contacts the secondary transfer roll 22 is referred to as the tip portion of the cleaning blade 42.

  However, if the tip of the cleaning blade 42 loses the rotational force of the secondary transfer roll 22, the tip of the cleaning blade 42 is rolled and moves downstream in the rotation direction of the secondary transfer roll 22 (β indicated by a broken line). State). This state is referred to as a state where the cleaning blade 42 is rolled.

When the cleaning blade 42 of the roll cleaner 40 is in contact with the secondary transfer roll 22 shown in the state of α, the tip of the cleaning blade 42 is in contact with the rotation direction of the secondary transfer roll 22 in the counter direction. ing. For this reason, the tip of the cleaning blade 42 prevents the rotation of the secondary transfer roll 22, so that it is in close contact with the surface of the secondary transfer roll 22 and between the tip of the cleaning blade 42 and the surface of the secondary transfer roll 22. It is difficult for gaps (voids) to occur in
Therefore, the cleaning blade 42 can remove the toner adhering to the secondary transfer roll 22.

On the other hand, when the cleaning blade 42 of the roll cleaner 40 is swollen as shown in the state of β, the tip of the cleaning blade 42 does not disturb the rotation of the secondary transfer roll 22 and the secondary transfer roll 22. It will be in the state dragged by the rotation of. Then, the contact between the cleaning blade 42 and the secondary transfer roll 22 becomes poor, and a gap is generated between the cleaning blade 42 and the secondary transfer roll 22.
If a gap is generated between the cleaning blade 42 and the secondary transfer roll 22, the cleaning blade 42 cannot remove the toner attached to the secondary transfer roll 22, and the toner remains attached on the secondary transfer roll 22. Become. In this state, when the paper P passes through the secondary transfer portion 20 (nip portion N), the toner that remains on the secondary transfer roll 22 and remains unremoved moves to the back surface of the paper P and becomes dirty. . That is, a cleaning failure of the secondary transfer roll 22 occurs.
In this manner, the cleaning blade 42 of the roll cleaner 40 is swept to cause a cleaning failure of the secondary transfer roll 22.

As described above, the cleaning blade 42 is bent when the tip of the cleaning blade 42 loses the rotational force of the secondary transfer roll 22.
Therefore, in order to suppress the wobbling of the cleaning blade 42, a lubricant is supplied onto the secondary transfer roll 22 via the cleaning brush 41 to reduce friction between the cleaning blade 42 and the secondary transfer roll 22. Yes.
However, as will be described later, even if the lubricant is supplied to the secondary transfer roll 22, the cleaning blade 42 may be wrinkled.

  Next, with reference to FIG. 2B, the relationship between the intermediate transfer belt 15, the secondary transfer roll 22, the cleaning blade 42 of the roll cleaner 40, and the paper P as viewed from the direction indicated by the arrow IIBC in FIG. To do. Here, as an example, the width Wbe of the intermediate transfer belt 15 is set to be larger than the width Wro of the secondary transfer roll 22, and the secondary transfer roll 22 is set within the width Wbe of the intermediate transfer belt 15. The width Wbr of the cleaning blade 42 is set larger than the width Wro of the secondary transfer roll 22.

In FIG. 2B, the paper P is supplied to the central portions of the intermediate transfer belt 15 and the secondary transfer roll 22. That is, an image forming toner image (image forming toner images 101a and 101b in FIG. 3 described later) is formed at the center in the width direction of the intermediate transfer belt 15. Since the width of the paper P is narrower than the width of the secondary transfer roll 22, the secondary transfer roll 22 is divided into a paper passing portion RP through which the paper P passes and a non-paper passing portion RN through which the paper P does not pass.
Note that the portion of the cleaning blade 42 facing the paper passing portion RP of the secondary transfer roll 22 at the tip portion is cleaned, and the portion of the cleaning blade 42 facing the non-paper passing portion RN of the secondary transfer roll 22 is cleaned. This is referred to as a non-sheet passing portion RN of the blade 42 (see FIG. 2B).

In the paper passing portion RP, the intermediate transfer belt 15 and the secondary transfer roll 22 face each other with the paper P interposed therebetween. In the non-paper passing portion RN, the paper P does not exist. The transfer roll 22 comes into contact.
Since both end portions of the secondary transfer roll 22 may be deformed, the toner on which the toner image is formed is excluded from the region corresponding to the both end portions of the secondary transfer roll 22 on the intermediate transfer belt 15. Set as the image forming region RT.

  Note that the width Wbe of the intermediate transfer belt 15, the width Wro of the secondary transfer roll 22, and the width Wbr of the cleaning blade 42 do not have to have the relationship shown in FIG. For example, the width Wro of the secondary transfer roll 22 may be the largest. Further, the width Wbr of the cleaning blade 42 may be the largest. In this case, the toner image forming area RT on the intermediate transfer belt 15 may be set in a range where the toner attached to the secondary transfer roll 22 is removed by the cleaning blade 42.

Next, the relationship among the intermediate transfer belt 15, the secondary transfer roll 22, the cleaning brush 41 of the roll cleaner 40, and the paper P viewed from the direction indicated by the arrow IIBC will be described with reference to FIG. Here, as an example, the width Wbu of the cleaning brush 41 is set larger than the width Wro of the secondary transfer roll 22. Therefore, the lubricant is applied to the entire surface of the secondary transfer roll 22.
The cleaning brush 41 is rotated around the shaft by a motor 48 connected to the shaft of the cleaning brush 41.

  Note that the width Wbu of the cleaning brush 41 may not be the relationship shown in FIG. 2C, and the width Wbu of the cleaning brush 41 may be set smaller than the width Wro of the secondary transfer roll 22. In this case, the toner image forming region RT on the intermediate transfer belt 15 is within a range (width Wbr) where the toner attached to the secondary transfer roll 22 is removed by the cleaning blade 42, and the lubricant is removed by the cleaning brush 41. Is set within the range (width Wbu) in which the power is supplied.

[Toner image]
FIG. 3 is a diagram illustrating an example of a toner image on the intermediate transfer belt 15 according to the first embodiment. FIG. 3 shows a part of the surface of the intermediate transfer belt 15 as viewed from the secondary transfer roll 22 side in the secondary transfer unit 20. The intermediate transfer belt 15 moves in the arrow B direction. When the image forming apparatus 1 corresponds to, for example, A3 Nobi (329 mm × 483 mm or the like) paper P, the width of the toner image forming region RT on the intermediate transfer belt 15 is set larger than 329 mm, for example, 380 mm.

  As shown in FIG. 3, in addition to the image forming toner images 101a and 101b that are secondarily transferred to the paper P, the intermediate transfer belt 15 is density control provided between the image forming toner images 101a and 101b (gap). The toner image 102 is held.

  The image forming toner images 101a and 101b are provided on the intermediate transfer belt 15 in the center in the width direction. The image forming toner image 101a and the image forming toner image 101b have different sizes. In other words, the image forming toner image 101a is expressed smaller in width and length than the image forming toner image 101b, and the corresponding paper P has a different size. For example, the image forming toner image 101a corresponds to the A4 size (210 mm × 297 mm) paper P, and the image forming toner image 101b corresponds to the A3 size (297 mm × 420 mm) paper P. When the image forming toner images 101a and 101b are not distinguished from each other, they are referred to as image forming toner images 101.

As shown in FIGS. 2B and 2C, in the secondary transfer roll 22, a portion through which the paper P passes is a paper passing portion RP, and both sides thereof are non-paper passing portions RN. Therefore, as shown in FIG. 3, when the size of the paper P is different, the width of the paper passing portion RP and the width of the non-paper passing portion RN in the secondary transfer roll 22 are different. That is, as shown in FIG. 3, the image forming toner image 101a has a sheet passing portion RPa and a non-sheet passing portion RNa, and the image forming toner image 101b has a sheet passing portion RPb and a non-sheet passing portion RNb. Become. Here, when the paper passing portions RPa and RPb are not distinguished from each other, they are indicated as the paper passing portion RP, and when the non-paper passing portions RNa and RNb are not distinguished from each other, they are indicated as the non-paper passing portions RN.
2 and 3, the image forming toner images 101a and 101b are provided in the center of the toner image forming region RT on the intermediate transfer belt 15, but one end portion in the width direction of the toner image forming region RT. It may be provided close to the side.

The density control toner image 102 has a configuration that can be read by the image density sensor 82 for image quality adjustment.
Note that the density control toner image 102 does not have to be provided between successive image forming toner images 101, and may be provided when density control is required.

Next, referring to FIG. 3, the electric field (bias) applied by the secondary transfer power source 27 between the secondary transfer roll 22 and the backup roll 25 will be described.
When the image forming toner images 101 a and 101 b transferred to the paper P pass through the secondary transfer unit 20, the secondary transfer power source 27 backs up the secondary transfer bias that is a negative voltage via the power supply roll 26. Supply to roll 25. Accordingly, a secondary transfer bias is formed between the backup roll 25 and the secondary transfer roll 22 with the intermediate transfer belt 15 interposed therebetween.

For the image forming toner images 101a and 101b, a sheet P having a size corresponding to each of the image forming toner images 101a and 101b is supplied between the intermediate transfer belt 15 and the secondary transfer roll 22 (nip portion N of the secondary transfer unit 20). Therefore, the secondary transfer bias, which is a negative voltage, works to press the negatively charged toner constituting the image forming toner images 101a and 101b on the intermediate transfer belt 15 against the paper P side.
That is, the image forming toner images 101a and 101b are transferred to the paper P during the period in which the secondary transfer bias is applied.

When the density control toner image 102 passes through the secondary transfer unit 20, the secondary transfer power supply 27 supplies a positive voltage to the backup roll 25, so that the toner constituting the density control toner image 102 is intermediate. You may press against the transfer belt 15 side. As a result, the density control toner image 102 remains on the intermediate transfer belt 15.
Further, a negative voltage similar to the secondary transfer bias may be supplied to the backup roll 25 when the density control toner image 102 passes through the secondary transfer unit 20. As a result, the toner constituting the density control toner image 102 is pressed against the secondary transfer roll 22, and is transferred (attached) onto the secondary transfer roll 22.
Furthermore, when the density control toner image 102 passes through the secondary transfer unit 20, it is not necessary to supply a voltage. As a result, a part of the toner constituting the density control toner image 102 remains on the intermediate transfer belt 15 and the other part moves (attaches) on the secondary transfer roll 22.

[Generation of Discharge in Secondary Transfer Section 20]
The discharge generated in the secondary transfer unit 20 will be described.
As shown in FIGS. 2B and 2C, in the secondary transfer unit 20, the intermediate transfer belt 15, the secondary transfer roll 22, and the backup roll 25 face each other at a short distance. Then, a secondary transfer bias is supplied with the intermediate transfer belt 15 sandwiched between the secondary transfer roll 22 and the backup roll 25. The secondary transfer bias is as high as -12 kV, for example.

  FIG. 4 is a diagram illustrating an example of the discharge current in the sheet passing portion RP and the non-sheet passing portion RN of the secondary transfer roll 22 and the wear cross-sectional area seen in the cleaning blade 42. FIG. 4A shows an example of a simulation result of the discharge current in the sheet passing portion RP and the non-sheet passing portion RN of the secondary transfer roll 22, and FIG. 4B shows the wear cross-sectional area found in the cleaning blade 42. An example of an actual measurement value is shown.

In the simulation result shown in FIG. 4A, the discharge current of the paper passing portion RP is a sheet P between the secondary transfer roll 22 and the intermediate transfer belt 15 as in the paper passing portion RP shown in FIG. The discharge current of the non-sheet passing portion RN was obtained with the secondary transfer roll 22 and the intermediate transfer belt 15 in contact with each other as in the non-sheet passing portion RN shown in FIG.
Since the paper P has a high electrical resistance (hereinafter referred to as resistance), the paper passing portion RP in which the paper P is interposed has a smaller discharge current than the non-paper passing portion RN in which the paper P is not interposed.

  When discharge occurs, discharge products such as nitrogen oxide (NOx) adhere to the secondary transfer roll 22 and the intermediate transfer belt 15. The surface energy of the secondary transfer roll 22 increases due to the adhesion of these discharge products, so that the contact friction between the secondary transfer roll 22 and the cleaning blade 42 of the roll cleaner 40 increases, and the cleaning blade 42 wears. To increase.

Next, actual measurement values of the wear cross-sectional area of the cleaning blade 42 shown in FIG. The wear cross section is obtained by observing the cross section of the tip of the cleaning blade 42 with a laser microscope (manufactured by Keyence Corporation: VK-9500) and integrating the cross section lost due to wear within a predetermined range of the length of the tip. And asked.
FIG. 4B shows the case where the number of processed sheets P is 5.5k, 80k, and 515k. In any number of processed sheets, the wear cross-sectional area of the cleaning blade 42 is larger in the non-sheet passing portion RN than in the sheet passing portion RP. Further, as the number of processed sheets increases, the wear cross-sectional area of both the sheet passing portion RP and the non-sheet passing portion RN increases exponentially.
As described above, when the size of the paper P is changed, the widths of the paper passing portion RP and the non-paper passing portion RN change accordingly. The non-sheet passing portion RN corresponding to the size of the paper P is a region having a large wear cross-sectional area.

  The amount of the discharge product adhering on the secondary transfer roll 22 is considered to be proportional to the discharge current shown in FIG. The discharge current is larger in the non-sheet passing portion RN on the secondary transfer roll 22 than in the sheet passing portion RP. Therefore, it seems that the non-sheet passing portion RN of the cleaning blade 42 wears faster than the sheet passing portion RP, and the wear cross-sectional area is large.

As the surface energy of the secondary transfer roll 22 increases due to the attachment of the discharge product on the secondary transfer roll 22, the contact friction between the secondary transfer roll 22 and the tip of the cleaning blade 42 of the roll cleaner 40 is reduced. To increase. Then, the tip of the cleaning blade 42 loses the rotating force of the secondary transfer roll 22 and the cleaning blade 42 is bent.
Since the contact friction between the secondary transfer roll 22 and the tip of the cleaning blade 42 of the roll cleaner 40 is large at the non-sheet passing portion RN, the cleaning blade 42 shown in FIG. β may occur not only in the entire cleaning blade 42 but also in a part of the cleaning blade 42, for example, one end or both ends of the non-sheet passing portion RN.

  The ease of occurrence of discharge in the non-sheet passing portion RN varies depending on the type of the paper P and the like. For example, the thicker the paper P, the easier it is to discharge in the non-sheet passing portion RN. That is, the resistance value in the thickness direction of the paper P is larger as the paper P is thicker. Therefore, in order to set the flowing current value to a predetermined value, the voltage supplied by the secondary transfer power supply 27 is set higher than a predetermined reference voltage. Then, as the paper P is thicker, the voltage between the intermediate transfer belt 15 and the secondary transfer roll 22 is increased, and discharge is more likely to occur in the non-sheet passing portion RN. That is, the thicker the paper P, the easier it is to discharge in the non-sheet passing portion RN.

In the above description, the ease of occurrence of discharge in the non-sheet passing portion RN has been described using the thickness of the paper P. However, the resistance value R of the secondary transfer unit 20 that varies depending on the type of the paper P may be described. That is, the larger the resistance value R of the secondary transfer unit 20, the easier it is to generate a discharge in the non-sheet passing portion RN.
In addition to the above thickness, the types of paper P include basis weight (density), surface treatment (plain paper, coated paper, art paper), and the like. Further, although the paper P is used, any medium that can transfer an image may be used, and a plastic film or the like may be used. Even in this case, the paper P may be distinguished as the type. Then, the image formation control unit 80 may hold the relationship between the type of the paper P and the ease of occurrence of discharge or the resistance value R as a table.

The resistance value R of the secondary transfer unit 20 is detected by a resistance measurement unit 28 provided between the power supply roll 26 and the secondary transfer power supply 27, and the type of the paper P is determined and transmitted to the image formation control unit 80. Is done. For example, the resistance measuring unit 28 calculates the resistance value R of the secondary transfer unit 20 from the current value that flows when the secondary transfer power source 27 supplies the secondary transfer bias and the voltage output from the secondary transfer power source 27. That's fine. Then, the type of the paper P may be determined from the resistance value R.
Then, the image formation control unit 80 predicts the ease of occurrence of discharge in the secondary transfer unit 20 from the type of the paper P determined by the resistance measurement unit 28.
The image formation control unit 80 determines the type of the paper P from the resistance value R measured by the resistance measurement unit 28, and determines the ease of occurrence of discharge in the secondary transfer unit 20 from the determined type of the paper P. It may be predicted. In this case, the resistance measurement unit 28 and the image formation control unit 80 are examples of a determination unit.

As described above, the cleaning failure of the secondary transfer roll 22 is caused by the cleaning blade 42 of the roll cleaner 40. The cleaning blade 42 is swollen because the discharge product due to the discharge generated in the non-sheet passing portion RN adheres to the secondary transfer roll 22 and the surface energy of the secondary transfer roll 22 increases. This is because the contact friction between the roll cleaner 40 and the cleaning blade 42 increases.
Therefore, even if the discharge product adheres to the secondary transfer roll 22 due to discharge, if the cleaning blade 42 can easily remove it, it is considered that the wear of the tip of the cleaning blade 42 is suppressed. In addition, the occurrence of wobbling of the cleaning blade 42 of the roll cleaner 40 and the cleaning failure that stains the back surface of the paper P are suppressed.

Therefore, the adhesion force of the discharge organisms generated by the discharge generated in the non-sheet passing portion RN to the secondary transfer roll 22 is reduced and is easily removed by the cleaning blade 42. That is, even if a discharge occurs in the secondary transfer unit 20 and the discharge product adheres to the secondary transfer roll 22, the attached discharge product may be easily removed.
In the first embodiment, in order to make it easier to remove the discharge products adhering to the secondary transfer roll 22, the image formation control unit 80 is configured to store the discharge products compared to a predetermined reference. When it is predicted that the amount of occurrence will be large, control is performed so that the supply amount of the lubricant on the secondary transfer roll 22 is increased. Then, a lubricant is interposed between the secondary transfer roll 22 and the discharge product to reduce the adhesion force of the discharge product attached to the secondary transfer roll 22, and it is easy to remove (easy to remove) by the cleaning blade 42. To do.
The amount of lubricant supplied from the cleaning brush 41 to the secondary transfer roll 22 is such that the longer the period (time) in which the secondary transfer roll 22 and the cleaning brush 41 are in contact, the greater the number of rotations of the cleaning brush 41. The larger r is, the larger the depth at which the tip of the cleaning brush 41 bites into the inside from the surface of the lubricant block 43 is larger.

FIG. 5 shows a period in which the secondary transfer roll 22 and the cleaning brush 41 are in contact with each other corresponding to the type of paper P (P type) or the resistance value R (secondary transfer portion resistance R) of the secondary transfer portion 20. 6 is a timing chart in the case of controlling the amount of lubricant supplied to the secondary transfer roll 22 by (time). Here, the paper P is the paper P1 and the paper P2, and the paper P2 is thicker than the paper P1. Note that the resistance value R of the secondary transfer unit 20 is the resistance value R1 for the paper P1, and the resistance value R2 for the paper P2, and the resistance value R2 is larger than the resistance value R1 (R1 <R2). .
Here, it is assumed that the rotational speed r of the cleaning brush 41 is the rotational speed r1 while the intermediate transfer belt 15 and the secondary transfer roll 22 are rotating. The cleaning brush 41 may be rotated following the rotation of the secondary transfer roll 22 without being driven by the motor 48.

In FIG. 5, it is assumed that time elapses in alphabetical order (a, b, c,...). FIG. 5A shows a case where the image forming toner image 101 is continuously transferred to a plurality of sheets P1. The image forming toner image 101 is transferred to the plurality of sheets P1 in the period tr1 after the period tr0 has elapsed. For example, after the lapse of the period tr0 from the time a to the time b, the image forming toner image 101 is transferred to the paper P1 in the period tr1 from the time b to the time c. Further, after a period tr0 from time c to time d has elapsed, the image forming toner image 101 is transferred to the next sheet P1.
Here, the period tr0 is an interval provided for transferring the image forming toner images 101 to a plurality of sheets P1 continuously.
In this case, the amount of the lubricant supplied to the secondary transfer roll 22 is an amount that can easily remove the discharge product adhering to the secondary transfer roll 22. Here, the case where the image forming toner image 101 is continuously transferred onto a plurality of sheets P1 is a reference.

Next, FIG. 5B shows a case where the image forming toner images 101 are transferred to a plurality of sheets P2 following the sheet P1. Similarly to FIG. 5A, after the elapse of the period tr0 from the time a to the time b, the image forming toner image 101 is transferred to the paper P1 in the period tr1 from the time b to the time c. Next, after the period tr0 from the time c to the time d has elapsed, and further after the period tr2 from the time d to the time e has elapsed, the image forming toner image 101 on the paper P2 in the period tr1 from the time e to the time h Is transcribed. Further, in the period tr1 from time j to time m after the lapse of the period tr0 and the period tr2, the image forming toner image 101 is formed on the paper P2.
That is, when the image forming toner image 101 is transferred to the paper P2 having a thickness larger than that of the paper P1, the period tr2 is provided after the period tr0 before the image forming toner image 101 is transferred to the paper P2. The lubricant is supplied to the secondary transfer roll 22.

FIG. 5C shows a case where the image forming toner image 101 is transferred to the paper P1 following the paper P1 and the paper P2. In this case, the process is the same as that shown in FIG. Then, in the period tr1 from the time i to the time l when the period tr0 has elapsed from the time h, the image forming toner image 101 is formed on the paper P1.
That is, when the sheet P2 is shifted to the sheet P1, the image forming toner image 101 is transferred to the sheet P1 after the lapse of the period tr0 without providing the period tr2.

That is, when the image forming toner image 101 is transferred onto the paper P2 that is thicker than the paper P1, the period tr2 is provided before the image forming toner image 101 is transferred onto the paper P2, and the secondary transfer roll 22 is provided with the period tr2. A lot of lubricant is supplied.
Therefore, the amount of lubricant on the secondary transfer roll 22 is increased before the transfer to the paper P2 where discharge is likely to occur because it is thicker than the paper P1, and the discharge product is on the lubricant on the secondary transfer roll 22. To adhere to. In this way, even if more discharge products are generated in the paper P2 than in the case of the paper P1, more lubricant is provided between the secondary transfer roll 22 and the discharge products than in the case of the paper P1. By interposing it, the adhesion of the discharge product is reduced and the cleaning blade 42 facilitates removal.
Moreover, since the supply amount of the lubricant is increased only when it is predicted that the discharge is likely to occur and the generation of the discharge product is large, it is possible to suppress the supply of the lubricant from being excessive.

Here, when it is predicted that discharge is likely to occur and a large amount of discharge products are generated, a time for applying the lubricant is provided before transferring the image forming toner image 101 to the paper P, and the secondary transfer roll The amount of lubricant on 22 is increased. As a result, even if a lot of discharge products are generated and adhere to the secondary transfer roll 22, the amount of lubricant supplied onto the secondary transfer roll 22 is large. The adhesion force to the surface 22 is reduced and is easily removed by the cleaning blade 42.
That is, the period tr2 is a lubricant supply additional period that is added to increase the amount of lubricant supplied onto the secondary transfer roll 22 when it is predicted that many discharge products are generated.

  In this case, the image formation control unit 80 receives the notification that the paper P1 is changed to the paper P2 from the UI unit 85, and controls to provide a lubricant supply additional period (period tr2) at time d. . Here, the UI unit 85 is an example of a determination unit.

  A method of controlling the amount of lubricant supplied to the secondary transfer roll 22 according to the rotation time of the cleaning brush 41 of the roll cleaner 40 corresponding to the type (P type) of the paper P or the resistance value R of the secondary transfer unit 20 In the case of the paper P2 that is thicker than the paper P1, the lubricant supply additional period (period tr2) is provided in order to increase the amount of lubricant, so that the time required for image formation is longer than that of the paper P1.

  5 shows the case of the paper P1 (resistance value R1) and the paper P2 (resistance value R2). However, the lubricant supply additional period depends on the type of the paper P or the resistance value R of the secondary transfer unit 20. The length of (period tr2) may be changed.

Next, another method of increasing the supply amount of the lubricant on the secondary transfer roll 22 when it is predicted that the generation of discharge products is larger than the case of using as a reference will be described.
Here, a method for controlling the amount of lubricant supplied to the secondary transfer roll 22 by controlling the rotational speed r of the cleaning brush 41 will be described.

FIG. 6 shows the secondary transfer roll according to the rotation speed r of the cleaning brush 41 of the roll cleaner 40 corresponding to the type (P type) of the paper P or the resistance value R (secondary transfer portion resistance R) of the secondary transfer portion 20. 22 is a timing chart in the case of controlling the amount of lubricant to be supplied to 22. The time axis here is the same as in FIG.
Here, the cleaning brush 41 is rotated by the motor 48, and the rotation speed r is controlled by the image formation control unit 80.

FIG. 6A shows a case where the image forming toner image 101 is transferred continuously to a plurality of sheets P1. Similarly to FIG. 5A, the image forming toner images 101 are continuously transferred to a plurality of sheets P1 in the period tr1 with the period tr0 interposed therebetween. In this case, in the period tr0 and the period tr1, the cleaning brush 41 rotates at the rotation speed r1.
That is, when the image forming toner image 101 is transferred to the paper P1, the cleaning brush 41 rotates at the rotation speed r1 and supplies the lubricant to the secondary transfer roll 22.
In this case, the amount of the lubricant supplied to the secondary transfer roll 22 is an amount that can easily remove the discharge product adhering to the secondary transfer roll 22. In this case as well, the case where the image forming toner image 101 is continuously transferred onto a plurality of sheets P1 is used as a reference.

Next, in FIG. 6B, the image forming toner image 101 is transferred to the paper P1, the image forming toner image 101 is subsequently transferred to the paper P2 thicker than the paper P1, and the image forming toner image is continuously transferred to the paper P1. A case where 101 is transferred is shown. When transfer of the image forming toner image 101 to the paper P2 starts at time d, the cleaning brush 41 is changed from the rotational speed r1 to the rotational speed r2 (r2> r1) which is larger than the rotational speed r1. Thereby, the supply amount of the lubricant to the secondary transfer roll 22 is increased.
When the transfer of the image forming toner image 101 onto the paper P2 is completed at time f, the cleaning brush 41 is decreased from the rotational speed r2 to the rotational speed r1. As a result, the amount of lubricant supplied to the secondary transfer roll 22 is reduced.

In this case, upon receiving notification from the UI unit 85 that the sheet P1 has been changed to the sheet P2, the image formation control unit 80 increases the rotation number of the cleaning brush 41 from the rotation number r1 to the rotation number r2 at time d. You may control as follows. Note that when the image forming toner image 101 is continuously transferred to a plurality of sheets P2, the cleaning brush 41 may be maintained at the rotation speed r2. Here, the UI unit 85 is an example of a determination unit.
The image formation control unit 80 receives the resistance value R of the secondary transfer unit 20 from the resistance measurement unit 28, and when the resistance value R2 is higher than the resistance value R1 for the paper P1 (time d), the cleaning is performed. The brush 41 may be controlled to increase from the rotational speed r1 to the rotational speed r2. Then, when the resistance value R1 is lower than the resistance value R2 for the paper P2 (time f), the cleaning brush 41 may be controlled to decrease from the rotational speed r2 to the rotational speed r1. Here, the resistance measurement unit 28 is an example of a determination unit.

That is, when it is predicted that the discharge is likely to occur and the generation of the discharge product is large, when the image forming toner image 101 is transferred to the paper P, the rotational speed r of the cleaning brush 41 is increased to increase the secondary image. The amount of lubricant supplied onto the transfer roll 22 is increased. As a result, even if a large amount of discharge products are generated and adhere to the secondary transfer roll 22, the adhesion of the discharge products that adhere to the secondary transfer roll 22 is reduced and can be easily removed by the cleaning blade 42. ing.
Moreover, since the supply amount of the lubricant is increased only when it is predicted that the discharge is likely to occur and the generation of the discharge product is large, it is possible to suppress the supply of the lubricant from being excessive.

  In the method of controlling the supply amount of the lubricant by the rotation speed r of the cleaning brush 41 corresponding to the type (P type) of the paper P or the resistance value R of the secondary transfer unit 20, the type of the paper P or the secondary transfer unit Even if the resistance value R of 20 is different, the time required for image formation is the sum of the period tr0 and the period tr1, and there is no difference.

6 shows a method of switching the rotation speed r of the cleaning brush 41 in two stages in two cases of the paper P1 (resistance value R1) and the paper P2 (resistance value R2). The rotational speed r of the cleaning brush 41 may be changed in two steps or continuously according to the resistance value R of the next transfer unit 20.
Further, the rotation speed r of the cleaning brush 41 may be controlled to be changed by the voltage output from the secondary transfer power supply 27 to supply the secondary transfer bias.

Next, still another method for controlling so as to increase the amount of lubricant supplied onto the secondary transfer roll 22 when it is predicted that many discharge products are generated will be described.
Here, a method will be described in which the image formation control unit 80 controls the amount of lubricant supplied to the secondary transfer roll 22 by controlling the load L of the lubricant block 43 to the cleaning brush 41.
The lubricant block 43 is applied with a load L to the cleaning brush 41 by a load setting member 46. The load L is set by the image formation control unit 80.

FIG. 7 shows the load L of the lubricant block 43 on the cleaning brush 41 of the roll cleaner 40 corresponding to the type (P type) of the paper P or the resistance value R (secondary transfer portion resistance R) of the secondary transfer portion 20. 6 is a timing chart for controlling the amount of lubricant supplied to the secondary transfer roll 22; The time axis here is the same as in FIG.
Here, while the intermediate transfer belt 15 and the secondary transfer roll 22 are rotating, the cleaning brush 41 is also rotating at a predetermined rotation speed r1. The cleaning brush 41 may be rotated by the rotation of the secondary transfer roll 22 without being driven by the motor 48.

FIG. 7A shows a case where the image forming toner image 101 is continuously transferred to a plurality of sheets P1. As in FIG. 4A, the image forming toner images 101 are continuously transferred to a plurality of sheets P1 in the period tr1 with the period tr0 interposed therebetween. In this case, in the period tr0 and the period tr1, the lubricant block 43 is pressed against the cleaning brush 41 with the load L1.
In this case, the amount of the lubricant supplied to the secondary transfer roll 22 is an amount that can easily remove the discharge product adhering to the secondary transfer roll 22. In this case as well, the case where the image forming toner image 101 is continuously transferred onto a plurality of sheets P1 is used as a reference.

Next, in FIG. 7B, the image forming toner image 101 is transferred to the paper P1, the image forming toner image 101 is subsequently transferred to the paper P2 thicker than the paper P1, and the image forming toner is further transferred to the paper P1. The case where the image 101 is transferred is shown. When transfer of the image forming toner image 101 to the paper P2 starts at time d, the load L1 of the lubricant block 43 with respect to the cleaning brush 41 is changed to a load L2 (L2> L1) larger than the load L1. Thereby, the supply amount of the lubricant to the secondary transfer roll 22 is increased.
When the transfer of the image forming toner image 101 onto the paper P2 is completed at time f, the load L2 of the lubricant block 43 with respect to the cleaning brush 41 is changed to the load L1. As a result, the amount of lubricant supplied to the secondary transfer roll 22 is reduced.
In this case, in addition to the cleaning brush 41, the cleaning blade 42, and the lubricant block 43, the load setting member 46 is an example of a lubricant supply unit.

Then, the image formation control unit 80 receives a notification from the UI unit 85 that the sheet P1 has been changed to the sheet P2, and increases the load L1 of the lubricant block 43 to the cleaning brush 41 to the load L2 at time d. You may control to. Note that when the image forming toner image 101 is continuously transferred to a plurality of sheets P2, the load for pressing the cleaning brush 41 may be maintained at the load L2. Here, the UI unit 85 is an example of a determination unit.
The image formation control unit 80 receives the resistance value R of the secondary transfer unit 20 from the resistance measurement unit 28, and when the resistance value R2 is higher than the resistance value R1 for the paper P1 (time d), the cleaning is performed. Control may be performed so that the load L1 of the lubricant block 43 with respect to the brush 41 is increased to the load L2. Then, when the resistance value R1 is lower than the resistance value R2 with respect to the paper P2 (time f), the load L2 of the lubricant block 43 with respect to the cleaning brush 41 may be controlled to be reduced to the load L1. Here, the resistance measurement unit 28 is an example of a determination unit.

  In the method of controlling the supply amount of the lubricant by the load L of the lubricant block 43 with respect to the cleaning brush 41 corresponding to the type (P type) of the paper P or the resistance value R of the secondary transfer unit 20, Even if the resistance value R of the secondary transfer unit 20 is different, the time required for image formation is the sum of the period tr0 and the period tr1, and there is no difference.

FIG. 8 is a diagram illustrating an example of the relationship between the wear cross-sectional area in the non-sheet passing portion RN of the cleaning blade 42 and the number of processed sheets when the load L of the lubricant block 43 with respect to the cleaning brush 41 is changed. Here, the load L2 is twice the load L1. The paper P is A4 size.
As the number of processed sheets increases, the wear cross-sectional area of the non-sheet passing portion RN of the cleaning blade 42 increases. Then, compared to the case of the load L1, in the case of the load L2, which is twice the load L1, the wear cross-sectional area of the non-sheet passing portion RN of the cleaning blade 42 becomes small.

That is, the image formation control unit 80 increases the load L of the lubricant block 43 with respect to the cleaning brush 41 when the discharge is likely to occur and it is predicted that the discharge product is generated more than the reference. The amount of lubricant supplied onto the secondary transfer roll 22 is controlled to increase. As a result, even if many discharge products are generated and adhere to the secondary transfer roll 22, the amount of lubricant supplied onto the secondary transfer roll 22 is large, so that it adheres to the secondary transfer roll 22. The adhesion force of the discharge product is reduced and the cleaning blade 42 facilitates removal.
Moreover, since the supply amount of the lubricant is increased only when it is predicted that the discharge is likely to occur and the generation of the discharge product is large, it is possible to suppress the supply of the lubricant from being excessive.

7 shows a case where the load L of the lubricant block 43 to the cleaning brush 41 is changed in two stages in the case of the paper P1 (resistance value R1) and the paper P2 (resistance value R2). The load L of the lubricant block 43 with respect to the cleaning brush 41 may be changed in two or more steps or continuously according to the type or the resistance value R of the secondary transfer unit 20.
Further, the load L of the lubricant block 43 with respect to the cleaning brush 41 may be changed by the voltage output for supplying the secondary transfer bias from the secondary transfer power source 27.

Further, in the first embodiment, when it is expected that many discharge products are generated, a method of supplying a large amount of lubricant on the secondary transfer roll 22 by providing a lubricant application additional period in advance, and cleaning Although the method of increasing the rotation speed r of the brush 41 and the method of increasing the load for pressing the lubricant block 43 against the cleaning brush 41 have been shown, some or all of these may be used in combination.
In the first embodiment, the image formation control unit 80 and the lubricant supply unit are an example of an adhesion reducing unit.

(Second Embodiment)
In the first embodiment, in order to facilitate the removal of the discharge products adhering to the secondary transfer roll 22, the image formation control unit 80 predicts that the generation of discharge products is larger than that in the case of using as a reference. In this case, the lubricant is interposed between the secondary transfer roll 22 and the discharge product by controlling the supply amount of the lubricant on the secondary transfer roll 22 to be increased. Thereby, the adhesion force of the discharge product adhering to the secondary transfer roll 22 is reduced, and it is easy to remove (easy to remove) by the cleaning blade 42.
In the second embodiment, in the nip portion N where the secondary transfer roll 22 and the intermediate transfer belt 15 are in contact, the difference (speed) between the movement speeds of the surfaces of the secondary transfer roll 22 and the intermediate transfer belt 15 facing each other. Difference) and rubbing each other to reduce the adhesive force of the discharge products adhering to the secondary transfer roll 22, and the discharge products adhering to the secondary transfer roll 22 can be easily removed by the cleaning blade 42. To do.
Since other configurations are the same as those of the first embodiment, different portions will be described, and description of similar portions will be omitted.

  FIG. 9 shows each of the secondary transfer roll 22 and the intermediate transfer belt 15 facing each other corresponding to the type (P type) of the paper P or the resistance value R (secondary transfer unit resistance R) of the secondary transfer unit 20. 6 is a timing chart in the case of providing a surface moving speed difference (speed difference) and removing discharge products adhering to the secondary transfer roll 22; In FIG. 9, the time axis is the same as in FIG.

FIG. 9A shows a case where the image forming toner images 101 are continuously transferred onto a plurality of sheets P1, as in the case of FIG. 5A. The image forming toner image 101 is transferred to the plurality of sheets P1 in the period tr1 after the period tr0 has elapsed. Here, there is no period in which a difference (speed difference) between the movement speeds of the surfaces of the secondary transfer roll 22 and the intermediate transfer belt 15 facing each other is provided.
In this case, the lubricant supplied to the secondary transfer roll 22 is an amount that can easily remove the discharge product adhering to the secondary transfer roll 22. In this case as well, the case where the image forming toner image 101 is continuously transferred onto a plurality of sheets P1 is used as a reference.

Next, FIG. 9B shows a case where the image forming toner images 101 are transferred to a plurality of sheets P2 following the sheet P1, as in the case of FIG. 5B. After the elapse of the period tr0 from the time a to the time b, the image forming toner image 101 is transferred to the paper P1 in the period tr1 from the time b to the time c. Next, after a period tr0 from time c to time d elapses, the image forming toner image 101 is further transferred to the paper P2 in a period tr1 from time d to time f. Then, at the time f, in the period tr3 from the time f to the time h after the transfer of the image forming toner image 101 to the paper P2, the respective surfaces on which the secondary transfer roll 22 and the intermediate transfer belt 15 face each other. The moving speed difference (speed difference) is provided (“+”). Next, at time h, the speed difference between the secondary transfer roll 22 and the intermediate transfer belt 15 is set to “0”. The image forming toner image 101 is formed on the paper P2 in the period tr1 from the time i to the time l after the period tr0 from the time h to the time i. Then, in the period tr3 from the time 1 to the time m, a difference (speed difference) between the moving speeds of the respective surfaces where the secondary transfer roll 22 and the intermediate transfer belt 15 face each other is provided again ("+").
That is, when the image forming toner image 101 is transferred to the paper P2 having a thickness larger than that of the paper P1, the secondary transfer roll 22 and the intermediate transfer belt are transferred after the image forming toner image 101 is transferred to the paper P2. 15 is provided with a period tr3 in which a difference in speed (speed difference) between the surfaces facing each other is provided.

FIG. 9C shows a case where the image forming toner image 101 is transferred to the paper P1 following the paper P1 and the paper P2, as in FIG. 5C. In this case, the process is the same as in FIG. 9B until time h. Then, in the period tr1 from the time i to the time l when the period tr0 has elapsed from the time h, the image forming toner image 101 is formed on the paper P1. After that, the period tr3 in which the difference (speed difference) between the movement speeds of the surfaces of the secondary transfer roll 22 and the intermediate transfer belt 15 facing each other is not provided.
That is, after the transition to the paper P1, the period tr3 in which the difference (speed difference) between the moving speeds of the surfaces of the secondary transfer roll 22 and the intermediate transfer belt 15 facing each other is not provided.

When the image forming toner image 101 is transferred onto the paper P2 that is thicker than the paper P1, the image forming toner image 101 is transferred onto the paper P2, and then the secondary transfer roll 22, the intermediate transfer belt 15, and the like. A period tr3 in which there is a difference in moving speed (speed difference) between the surfaces facing each other is provided, and the secondary transfer roll 22 and the intermediate transfer belt 15 rub against each other, so that the discharge generated on the secondary transfer roll 22 is generated. The adhesion force of the object is reduced and the cleaning blade 42 facilitates the removal.
A period tr3 in which a difference in speed (speed difference) between the surfaces of the secondary transfer roll 22 and the intermediate transfer belt 15 facing each other is provided is a secondary transfer when it is predicted that many discharge products are generated. This is a discharge product removal period in which the discharge products attached on the roll 22 are removed.
Here, the adhesion force of the discharge product adhered on the intermediate transfer belt 15 can also be reduced.
Here, the image forming control unit 80, the intermediate transfer belt 15, and the secondary transfer roll 22 are examples of the adhesion reducing means.

In this case, the image formation control unit 80 receives a notification from the UI unit 85 that the sheet P1 has been changed to the sheet P2, and ends the transfer of the image forming toner image 101 to the sheet P2 (FIG. 9 ( It may be controlled to insert a discharge product removal period (period tr3 in FIG. 9B) at time f of b). Here, the UI unit 85 is an example of a determination unit.
Further, the image formation control unit 80 receives the resistance value R of the secondary transfer unit 20 from the resistance measurement unit 28, and when the resistance value R2 is higher than the resistance value R1 with respect to the paper P1 (time d or the like), It may be controlled to insert a discharge product removal period (period tr3) at a timing (time f or the like) when the high resistance value R2 ends. Here, the resistance measurement unit 28 is an example of a determination unit.

In FIG. 9, the discharge product removal period (period tr <b> 3) is not provided for the paper P <b> 1, but the type of the paper P or the secondary transfer unit 20 is used when any paper P is used. A discharge product removal period having a length corresponding to the resistance value R may be provided.
Further, the length of the discharge product removal period may be changed according to the voltage output from the secondary transfer power supply 27 to supply the secondary transfer bias.

  Note that the second embodiment and the first embodiment may be used in combination.

(Third embodiment)
In the first embodiment, by controlling the amount of lubricant supplied onto the secondary transfer roll 22, the adhesion of the discharge product that adheres to the secondary transfer roll 22 is reduced, and the cleaning blade 42 Easy to remove.
In the second embodiment, the secondary transfer roll 22 and the intermediate transfer belt 15 are provided with a difference in speed (speed difference) between the surfaces of the secondary transfer roll 22 and the intermediate transfer belt 15 facing each other. The adhesion of the discharge product adhered to the secondary transfer roll 22 was reduced, and the discharge product adhered on the secondary transfer roll 22 was easily removed by the cleaning blade 42.
In the third embodiment, an image forming toner image 101 is formed with toner having an irregularly shaped external additive, and is formed on the intermediate transfer belt 15 corresponding to the non-sheet passing portion RN of the secondary transfer roll 22. A toner image (toner band) is provided in a band shape. When the toner of the toner image (toner band) provided on the non-sheet passing portion RN adheres to the secondary transfer roll 22 and is removed by the cleaning blade 42 of the roll cleaner 40, the surface of the secondary transfer roll 22 It acts as an abrasive that polishes the toner, reduces the adhesion of the discharge product adhering to the secondary transfer roll 22, and facilitates removal by the cleaning blade 42.
Since other configurations are the same as those of the first embodiment, different portions will be described, and description of similar portions will be omitted.

[Toner image]
FIG. 10 is a diagram illustrating an example of a toner image on the intermediate transfer belt 15 according to the third embodiment. Similar to FIG. 3 in the first embodiment, FIG. 10 shows a part of the surface of the intermediate transfer belt 15 as viewed from the secondary transfer roll 22 side in the secondary transfer unit 20. The intermediate transfer belt 15 moves in the arrow B direction.
As shown in FIG. 10, the intermediate transfer belt 15 is a density control toner provided between (image gaps) the image forming toner images 101 a and 101 b and the image forming toner images 101 a and 101 b that are secondarily transferred to the paper P. The end portion toner images 103 a and 103 b as examples of other toner images provided as toner bands are held at both ends of the image 102 and the intermediate transfer belt 15 in the width direction.
Since the intermediate transfer belt 15, the image forming toner images 101a and 101b, and the density control toner image 102 are the same as those in the first embodiment, description thereof is omitted.

The edge toner images 103 a and 103 b are provided at both ends in the width direction of the intermediate transfer belt 15 so as to face the non-sheet passing portion RN of the secondary transfer roll 22. The end toner image 103a is provided outside the image forming toner image 101a, and the end toner image 103b is provided outside the image forming toner image 101b.
In FIG. 10, the end toner images 103 a and 103 b having the same shape are provided symmetrically with respect to the center in the width direction of the intermediate transfer belt 15. This is because the image forming toner images 101 a and 101 b are provided at the center in the width direction of the intermediate transfer belt 15.
As an example, the end toner images 103a and 103b are discretely provided with respect to the moving direction of the intermediate transfer belt 15 (the direction of the arrow B). The reason why they are provided discretely is to reduce toner consumption.

The widths of the edge toner images 103a and 103b in the width direction of the intermediate transfer belt 15 correspond to the widths of the image forming toner images 101a and 101b, respectively. The image forming toner image 101a corresponding to the A4 size paper P is narrower in the width direction of the intermediate transfer belt 15 than the image forming toner image 101b on the A3 size paper P. Therefore, the width in the width direction of the intermediate transfer belt 15 of the end toner image 103a corresponding to the image forming toner image 101a is equal to the width in the width direction of the end toner image 103b corresponding to the image forming toner image 101b. Widely set.
That is, the edge toner images 103a and 103b are provided so as to cover an area on the intermediate transfer belt 15 that is not occupied by the image forming toner image 101.
Note that when the edge toner images 103a and 103b are not distinguished from each other, they are referred to as edge toner images 103.

  When the image forming toner image 101 is provided at one end in the width direction of the intermediate transfer belt 15, the end toner image 103 is provided at the other end in the width direction of the intermediate transfer belt 15. What is necessary is just to provide.

On the other hand, the toner that forms the toner image includes a toner body and an external additive attached to the surface of the toner body. The “toner main body” refers to a toner obtained by removing an external additive.
The external additive has a volume average particle size of 70 nm to 400 nm and an average circularity of 0.5 to 0.9. Here, since the average circularity deviates from 1 (circle) and is less than 1, the external additive is referred to as an atypical external additive.

As an atypical external additive, when the charging polarity of the toner body is negative, it has the same charging polarity and is easily negatively charged. For example, silica is used when the charging polarity of the toner body is positive. For example, cerium oxide and strontium titanate can be used which have the same charging polarity and are easily charged to a positive polarity.
When the toner main body and the external additive have the same charging polarity, the toner main body and the external additive are simultaneously charged and easily transferred together without being separated.

  Here, since the charging characteristic of the toner is described as being negative, it is preferable to use silica that is easily negatively charged as the atypical external additive. Therefore, here, silica particles in which the external additive is composed of silica will be described as an example.

Next, an example in the third embodiment will be described. The silica particles may be silica, that is, particles containing SiO ₂ as a main component, and may be crystalline or amorphous. Moreover, the particle | grains manufactured from silicon compounds, such as water glass and alkoxysilane, may be sufficient, and the particle | grains obtained by grind | pulverizing quartz may be sufficient.
Here, the occurrence of wrinkling of the cleaning blade 42 and the cleaning performance were evaluated with a toner using five types of silica particles A to E as external additives.

[Method for producing silica particles]
Next, a method for producing silica particles A to E will be described.
-Silica particle A-
To a 1.5 L glass reaction vessel equipped with a stirrer, a dropping nozzle, and a thermometer, 300 g of methanol and 47.7 g of 10% ammonia (NH ₄ OH) water were added and mixed to obtain an alkali catalyst solution. The amount of catalyst in this alkaline catalyst solution, that is, the amount of NH ₃ (NH ₃ / (NH ₃ + methanol + water)) was 0.72 mol / L.
After adjusting the alkali catalyst solution to 25 ° C., 450 g of tetramethoxysilane (Si (OCH ₃ ) ₄ ) and 270 g of 4.44% ammonia water are supplied per minute while stirring. The flow rate was adjusted so that the amount of NH ₃ was 0.24 mol with respect to 1 mol of the total supply amount, and at the same time, addition was started, and dropwise addition was performed over 60 minutes to obtain a suspension of silica particles. However, the supply amount of tetramethoxysilane was 0.0021 mol / (mol · min) with respect to the number of moles of alcohol in the alkali catalyst solution.
Thereafter, 225 g of the solvent was distilled off by heating distillation, and 225 g of pure water was added, followed by drying with a freeze dryer to obtain atypical hydrophilic silica particles having a volume average particle size of 67 nm and a circularity of 0.92. .
Furthermore, 12 g of hexamethyldisilazane was added to 35 g of atypical hydrophilic silica particles, and the mixture was reacted at 150 ° C. for 2 hours to hydrophobize the silica particles to obtain hydrophobic silica particles (silica particles A). .

-Silica particles B-
To a 1.5 L glass reaction vessel equipped with a stirrer, a dropping nozzle and a thermometer, 300 g of methanol and 47.8 g of 10% aqueous ammonia were added and mixed to obtain an alkali catalyst solution. The amount of catalyst in this alkaline catalyst solution, that is, the amount of NH ₃ (NH ₃ / (NH ₃ + methanol + water)) was 0.72 mol / L.
After adjusting this alkali catalyst solution to 25 ° C., 450 g of tetramethoxysilane and 270 g of 4.44% ammonia water are added to 1 mol of the total amount of tetramethoxysilane supplied per minute while stirring. Then, the flow rate was adjusted so that the amount of NH ₃ was 0.24 mol, and at the same time, addition was started, and dropwise addition was performed over 60 minutes to obtain a suspension of silica particles. However, the supply amount of tetramethoxysilane was 0.0028 mol / (mol · min) with respect to the number of moles of alcohol in the alkali catalyst solution.
Thereafter, 225 g of the solvent was distilled off by heating distillation and 225 g of pure water was added, followed by drying with a freeze dryer to obtain atypical hydrophilic silica particles having a volume average particle size of 72 nm and a circularity of 0.89. .
Furthermore, 12 g of hexamethyldisilazane was added to 35 g of atypical hydrophilic silica particles and reacted at 150 ° C. for 2 hours to hydrophobize the silica particles to obtain hydrophobic silica particles (silica particles B). .

-Silica particles C-
To a 1.5 L glass reaction vessel equipped with a stirrer, a dropping nozzle and a thermometer, 300 g of methanol and 49.6 g of 10% ammonia water were added and mixed to obtain an alkali catalyst solution. The amount of catalyst in the alkaline catalyst solution, that is, the amount of NH ₃ (NH ₃ / (NH ₃ + methanol + water)) was 0.75 mol / L.
After adjusting this alkali catalyst solution to 25 ° C., 450 g of tetramethoxysilane and 270 g of 4.44% ammonia water are added to 1 mol of the total amount of tetramethoxysilane supplied per minute while stirring. Then, the flow rate was adjusted so that the amount of NH ₃ was 0.24 mol, and at the same time, addition was started, and dropwise addition was performed over 60 minutes to obtain a suspension of silica particles. However, the supply amount of tetramethoxysilane was 0.0050 mol / (mol · min) with respect to the number of moles of alcohol in the alkali catalyst solution.
Thereafter, 225 g of the solvent was distilled off by heating distillation and 225 g of pure water was added, followed by drying with a freeze dryer to obtain atypical hydrophilic silica particles having a volume average particle size of 150 nm and a circularity of 0.75. .
Furthermore, 7 g of hexamethyldisilazane was added to 35 g of atypical hydrophilic silica particles and reacted at 150 ° C. for 2 hours to hydrophobize the silica particles to obtain hydrophobic silica particles (silica particles C). .

-Silica particles D-
To a 1.5 L glass reaction vessel equipped with a stirrer, a dropping nozzle and a thermometer, 300 g of methanol and 55.2 g of 10% ammonia water were added and mixed to obtain an alkali catalyst solution. The amount of catalyst in this alkaline catalyst solution, that is, the amount of NH ₃ (NH ₃ / (NH ₃ + methanol + water)) was 0.82 mol / L.
After adjusting this alkali catalyst solution to 25 ° C., 450 g of tetramethoxysilane and 270 g of 4.44% ammonia water are added to 1 mol of the total amount of tetramethoxysilane supplied per minute while stirring. Then, the flow rate was adjusted so that the amount of NH ₃ was 0.24 mol, and at the same time, addition was started, and dropwise addition was performed over 60 minutes to obtain a suspension of silica particles. However, the supply amount of tetramethoxysilane was 0.0066 mol / (mol · min) with respect to the number of moles of alcohol in the alkali catalyst solution.
Thereafter, 225 g of the solvent was distilled off by heating distillation and 225 g of pure water was added, followed by drying with a freeze dryer to obtain atypical hydrophilic silica particles having a volume average particle size of 391 nm and a circularity of 0.52. .
Furthermore, 4 g of hexamethyldisilazane was added to 35 g of atypical hydrophilic silica particles and reacted at 150 ° C. for 2 hours to hydrophobize the silica particles to obtain hydrophobic silica particles (silica particles D). .

-Silica particles E-
To a 1.5 L glass reaction vessel equipped with a stirrer, a dropping nozzle, and a thermometer, 300 g of methanol and 55.8 g of 10% ammonia water were added and mixed to obtain an alkali catalyst solution. The amount of catalyst in this alkaline catalyst solution, that is, the amount of NH ₃ (NH ₃ / (NH ₃ + methanol + water)) was 0.82 mol / L.
After adjusting this alkali catalyst solution to 25 ° C., 450 g of tetramethoxysilane and 270 g of 4.44% ammonia water are added to 1 mol of the total amount of tetramethoxysilane supplied per minute while stirring. Then, the flow rate was adjusted so that the amount of NH ₃ was 0.24 mol, and at the same time, addition was started, and dropwise addition was performed over 60 minutes to obtain a suspension of silica particles. However, the supply amount of tetramethoxysilane was 0.0098 mol / (mol · min) with respect to the number of moles of alcohol in the alkali catalyst solution.
Thereafter, 225 g of the solvent was distilled off by heating distillation and 225 g of pure water was added, followed by drying with a freeze dryer to obtain atypical hydrophilic silica particles having a volume average particle size of 415 nm and a circularity of 0.46. .
Furthermore, 4 g of hexamethyldisilazane was added to 35 g of atypical hydrophilic silica particles and reacted at 150 ° C. for 2 hours to hydrophobize the silica particles to obtain hydrophobic silica particles (silica particles E). .

[Toner production method]
A method for producing toner using silica particles A to E will be described.
To a toner body for a printing system (700 Digital Color Press: manufactured by Fuji Xerox Co., Ltd.), 1.2 parts of any one of the aforementioned silica particles A to E and 1 part of rutile titanium oxide (volume average particle diameter 20 nm) In addition, blending was performed for 10 minutes at a peripheral speed of 32 m / s using a Henschel mixer, and then coarse particles were removed using a sieve having an opening of 45 μm to obtain toner particles.
Further, 100 parts of a carrier for a printing system (700 Digital Color Press: manufactured by Fuji Xerox Co., Ltd.) and 8 parts of the toner particles were mixed with a V blender, and sieved through a 500 μm mesh to prepare a toner.

Here, how to obtain the circularity and volume average particle diameter of the silica particles A to E will be described.
[Circularity]
The circularity is determined by mixing and dispersing silica particles A to E in iron powder or resin particles (polyester, weight average molecular weight Mw = 50000) having a particle diameter of 100 μm, and 100 primary particles of external additives on the iron powder or resin particles. Is observed with a scanning electron microscope (SEM), and is calculated from the projected area and the perimeter by Equation (1).
Here, 50% circularity in the cumulative frequency of the obtained circularity was defined as circularity.
Circularity = 4π × projection area / (perimeter) ²

[Volume average particle diameter]
The volume average particle size is obtained by mixing and dispersing silica particles A to E in iron powder or resin particles (polyester, weight average molecular weight Mw = 50000) having a particle size of 100 μm, and primary particles of external additives on the iron powder or resin particles. One hundred pieces were observed with an SEM, and the 50% diameter (D50v) in the cumulative frequency of equivalent circle diameters was calculated and used as the volume average particle diameter.

[Evaluation of cleaning blade 42 wobbling and cleaning]
FIG. 11 is a diagram illustrating the occurrence of wobbling of the cleaning blade 42 and the evaluation results of the cleaning performance. In FIG. 11, the five types of silica particles A to E used as the toner external additive and the presence / absence of the edge toner image 103 in the non-sheet passing portion RN are combined to generate the wrinkle of the cleaning blade 42 and The cleaning property was evaluated.

Example 1 uses a toner having silica particles B with a circularity of 0.89 and a volume average particle size of 72 nm as an external additive, and forms an end toner image 103 on a non-sheet passing portion RN (with toner band). In Example 2, a toner having silica particles C having a circularity of 0.75 and a volume average particle diameter of 150 nm as an external additive was used, and an end toner image 103 was formed on the non-sheet passing portion RN (toner band). In Example 3, in Example 3, a toner having silica particles D having a circularity of 0.52 and a volume average particle diameter of 391 nm as an external additive was used, and an end toner image 103 was formed on the non-sheet passing portion RN ( This is the case with a toner band.
Comparative Example 1 uses a toner having silica particles A having a circularity of 0.92 and a volume average particle size of 67 nm as an external additive, and forms a toner image 103 for the end portion on the non-sheet passing portion RN (with toner band). In Comparative Example 2, the toner having the circularity of 0.46 and the volume average particle diameter of 415 nm as the external additive was used, and the edge toner image 103 was formed on the non-sheet passing portion RN (toner band). In the case of Comparative Example 3, a toner using silica particles C having a circularity of 0.75 and a volume average particle size of 150 nm as an external additive is used, and the edge toner image 103 is not formed on the non-sheet passing portion RN ( This is the case with no toner band.
That is, Examples 1 to 3 and Comparative Examples 1 and 2 are different in the degree of circularity and volume average particle diameter of the silica particles, but both form the edge toner image 103 in the non-sheet passing portion RN (toner With band). On the other hand, Comparative Example 3 uses silica particles C as an external additive as in Example 2, but Comparative Example 3 has no toner band formed in the non-sheet passing portion RN (no toner band). In the second embodiment, a toner band is formed in the non-sheet passing portion RN (with toner band).
In addition, in FIG. 11, it arranges so that circularity may become small in order of the comparative example 1, Examples 1-3, and the comparative example 2. FIG.

The cleaning blade 42 was swung in a test environment of 28 ° C. and 80% RH. The paper P used is A4 size coated paper having a basis weight of 200 g / m ² . The image dot area ratio (Cin) of the toner image is 0.5% for each color of YMCK. The contact pressure of the cleaning blade 42 to the secondary transfer roll 22 is 29.4 kPa.
A toner image was formed on 3000 sheets of paper P, and the occurrence of wobbling in the cleaning blade 42 was examined.

  The evaluation is “◯” when the cleaning blade 42 does not wrinkle, “Δ” when the cleaning blade 42 wrinkles between 2000 and 3000 sheets, and the cleaning blade 42 between 500 and 2000 sheets. The case where the wrinkle occurred was “X”, and the case where the cleaning blade 42 was wrinkled with less than 500 sheets was “XX”.

The cleaning property was performed in a test environment of 10 ° C. and 20% RH. The paper P used is A4 size coated paper having a basis weight of 200 g / m ² . The image dot area ratio (Cin) of the toner image is 8% in each of YMCK. The contact pressure of the cleaning blade 42 to the secondary transfer roll 22 is 29.4 kPa. Under these conditions, after forming a toner image on 200,000 sheets of paper P, and after forming a toner image on 100,000 sheets of paper P and after forming a toner image on 200,000 sheets of paper P, an A3 size sheet P was inserted, and the presence or absence of stains on the back surface of the A3 size paper P outside the A4 size area was examined.
In the evaluation, “◯” indicates that the back surface of the A3 size paper P is not stained, “Δ” indicates that there is a slight stain, and “x” indicates that there is a stain.

As shown in FIG. 11, in the first to third embodiments, the cleaning blade 42 does not distort, and after any toner image is formed on 100,000 sheets and 200,000 sheets of A4 size paper P. The back side of the A3 size paper P was not stained.
However, the silica particles B (circularity 0.89) to D (circularity 0.52), which are external additives used in the toners used in Examples 1 to 3, are larger than the circularity 0.92; That is, in Comparative Example 1 using silica particles A that are close to a circle, the cleaning blade 42 is bent (less than 500 sheets) and a toner image is formed on 100,000 sheets of paper P. The back side of the paper P was dirty.
The silica particles E having a small degree of circularity of 0.46, that is, a large degree of irregularity, than the silica particles B (circularity of 0.89) to D (circularity of 0.52) used in Examples 1 to 3. In Comparative Example 2 in which the cleaning blade 42 is bent between 500 and 2000 sheets ("x"), a toner image is formed on 100,000 sheets of paper P, and then the back surface of the A3 sheet is stained. (“×”).

  Further, when the edge toner image 103 is provided in the non-sheet passing portion RN, the cleaning blade 42 is not bent, and even after the toner image is formed on the 200,000 sheets of paper P, the A3 size paper P Even when the same silica particles C as in Example 2 with no dirt on the back surface are used, as shown in Comparative Example 3, if the edge toner image 103 is not provided in the non-sheet passing part RN, the cleaning blade 42 A wrinkle occurred between 500 and 2000 sheets ("x"), and after forming a toner image on 100,000 sheets of paper P, there was a slight stain on the back surface of the A3 size paper P ("△"). ). After the toner image was formed on 200,000 sheets of paper P, the back surface of the A3 size paper P was soiled ("x").

  As described above, the toner has an unusual external additive having a volume average particle diameter of 70 nm or more and 400 nm or less and a circularity of 0.5 or more and less than 0.9, and a non-paper passing portion. When the edge toner image 103 (toner band) is provided on the RN, the occurrence of wobbling of the cleaning blade 42 is suppressed, and the backside contamination is also suppressed in the formation of toner images on 200,000 sheets of paper P.

This is because the toner of the edge toner image 103 (toner band) provided in the non-sheet passing portion RN adheres to the secondary transfer roll 22 and is removed by the cleaning blade 42 of the roll cleaner 40. This is because it acts as an abrasive for polishing the surface of the secondary transfer roll 22, reduces the adhesion of the discharge product adhering to the secondary transfer roll 22, and facilitates removal by the cleaning blade 42.
Here, the image formation control unit 80 is an example of an adhesive force reduction unit.

  Therefore, the image formation control unit 80 increases the area occupied by the toner of the edge toner image 103 (toner band) provided in the non-sheet passing portion RN when predicting that the generation of discharge products is large. Thus, the amount of toner acting as an abrasive for polishing the surface of the secondary transfer roll 22 may be controlled so that the discharge product can be easily removed (easy to peel off).

When the image formation control unit 80 predicts that many discharge products are likely to be generated from the type of the paper P from the UI unit 85 and the image processed image data, the edge toner image 103 (toner band) The toner amount may be controlled according to the area occupied by the toner.
By doing so, the amount of toner used in the edge toner image 103 (toner band) can be suppressed.
Further, the temperature and humidity of the environment in which the image forming apparatus 1 is installed are monitored, and the end portions are taken into consideration, for example, the difference in the occurrence of discharge and the difference in the ease of removal of the discharge product from the secondary transfer roll 22. The toner amount of the toner image 103 (toner band) may be further controlled.
Further, it is only necessary to change the toner and the toner image, and it is not necessary to change the hardware configuration of the image forming apparatus 1.

  Note that the third embodiment may be used in combination with one or both of the first embodiment and the second embodiment.

(Fourth embodiment)
[Image forming apparatus 1]
The image forming apparatus 1 according to the first to third embodiments is an image forming apparatus using a tandem intermediate transfer system, and includes a secondary transfer unit 20 using a secondary transfer roll 22. It was. The image forming apparatus 1 according to the fourth embodiment is an image forming apparatus using a tandem direct transfer method.

FIG. 12 is a schematic configuration diagram illustrating an example of the image forming apparatus 1 to which the fourth exemplary embodiment is applied. The same parts as those of the first embodiment are denoted by the same reference numerals, description thereof is omitted, and different parts will be described.
The image forming apparatus 1 according to the fourth embodiment is similar to the image forming apparatus 1 according to the first embodiment shown in FIG. 1. Each image forming unit 2Y, 2M, 2C, 2K, fixing unit 60, image forming A control unit 80 is provided.
Each of the image forming units 2Y, 2M, 2C, and 2K of the image forming apparatus 1 according to the second embodiment is a photosensitive as another example of the holding body of each of the image forming units 2Y, 2M, 2C, and 2K. A transfer unit 70 is provided as another example of transfer means for sequentially transferring the toner images of the respective colors (components) formed on the body drum 11 onto the paper P transported by the transfer transport belt 71.

  The transfer conveyance belt 71 is made of the same material as the intermediate transfer belt 15 in the first embodiment, and is circulated (rotated) at a predetermined speed in the direction of arrow D shown in FIG. 7 by various rolls. . As these various rolls, a driving roll 72 that is driven by a motor (not shown) having excellent constant speed to rotate the transfer conveyance belt 71, and a transfer conveyance belt that extends linearly along the direction in which the photosensitive drums 11 are arranged. 71, a support roll 73 that supports 71, a tension roll 74 that functions as a correction roll that applies tension to the transfer conveyance belt 71 and prevents the transfer conveyance belt 71 from meandering, a backup roll 75 provided in the transfer unit 70, and a transfer conveyance belt A cleaning backup roll 76 provided to face the belt cleaner 90 that scrapes off the toner on 71 is disposed.

The transfer unit 70 includes a photosensitive drum 11 and a backup roll 75 that are arranged to face each other with the transfer conveyance belt 71 interposed therebetween. The backup roll 75 includes a shaft and a sponge layer as an elastic body layer fixed around the shaft. The shaft is a cylindrical bar made of metal such as iron or SUS. The sponge layer is a sponge-like cylindrical roll formed of a blend rubber of NBR, SBR, and EPDM containing a conductive agent such as carbon black and having a volume resistivity of 10 ⁷ to 10 ⁹ Ωcm. The backup roll 75 is pressed against the photosensitive drum 11 with the transfer conveyance belt 71 interposed therebetween.
Further, a positive voltage (transfer bias) having a polarity opposite to the charging polarity (negative) of the toner is applied to the backup roll 75 via the resistance measuring unit 78 that detects the resistance of the transfer unit 70. It is supplied by a transfer power source 77 as an example. As a result, the toner images on the respective photosensitive drums 11 are sequentially electrostatically attracted to the paper P on the transfer / conveying belt 71, and the toner images are transferred to the paper P.

A belt cleaner 90 that removes the toner adhering to the transfer conveyance belt 71 is provided. Similar to the image forming apparatus 1 according to the first embodiment, the belt cleaner 90 is more than the cleaning brush 91 and the cleaning brush 91 that are disposed in contact with the transfer conveyance belt 71 on the downstream side of the transfer unit 70 so as to be rotatable. Further, a cleaning blade 92 provided on the downstream side in the moving direction of the transfer conveyance belt 71 is provided. The belt cleaner 90 is disposed so as to come into contact with the cleaning brush 91, and contains a lubricant block 93 that holds the lubricant supplied to the cleaning brush 91, a cleaning brush 91, a cleaning blade 92, and a lubricant block 93. A housing 94, a support member 95 for fixing and supporting the cleaning blade 92 to the cleaner housing 94, and a load setting member 96 for setting a force (load) for pressing the lubricant block 93 against the cleaning brush 91 are provided. One end of the load setting member 96 is fixed to the cleaner housing 94 and the other end is fixed to the lubricant block 93, and the load is applied to the cleaning brush 91.
Further, the cleaner housing 94 includes a storage unit 97 that stores waste toner.
Each member of the belt cleaner 90 is the same as each member of the roll cleaner 40 according to the first embodiment (the number is in the 40s), and the description thereof is omitted.

  The basic image forming process of the image forming apparatus 1 in the fourth embodiment is the same as that in the first embodiment except for the transfer unit 70. Also in the fourth embodiment, each of the image forming units 2Y, 2M, 2C, and 2K includes the image forming toner image 101 and the density control toner image 102 as shown in FIG. 3 in the first embodiment. Form.

  In the transfer unit 70, the backup roll 75 is pressed against the photosensitive drum 11 via the transfer conveyance belt 71. The sheet P conveyed to the transfer unit 70 at the same timing is sandwiched between the photosensitive drum 11 and the transfer conveyance belt 71. At that time, a positive voltage (transfer bias) having a polarity opposite to the charging polarity (negative) of the toner is supplied to the backup roll 75 from a transfer power source (not shown). Then, a transfer bias is formed between the photosensitive drum 11 and the backup roll 75 with the transfer conveyance belt 71 interposed therebetween, and the image forming toner image 101 held on the photosensitive drum 11 is transferred onto the paper P. The

The paper P onto which the image forming toner images respectively formed by the image forming units 2Y, 2M, 2C, and 2K are sequentially transferred is conveyed to the fixing unit 60.
The toner attached to the transfer conveyance belt 71 is removed by the belt cleaner 90.

  Similar to the secondary transfer unit 20 of the first embodiment, when a discharge is generated by the transfer bias applied in the transfer unit 70, the discharge product adheres to the transfer conveyance belt 71.

Therefore, as described in the first embodiment, the amount of lubricant supplied onto the transfer conveyance belt 71 is controlled by the type (P type) of the paper P or the resistance value R of the transfer unit 70. That is, when it is expected that many discharge products are generated, a lubricant application additional period is provided in advance, and a large amount of lubricant is supplied onto the transfer conveyance belt 71, whereby the discharge products are transferred to the transfer conveyance belt 71. You may apply the method of reducing the adhesive force of.
Further, when it is expected that many discharge products are generated, the number of rotations r of the cleaning brush 91 is increased, and a large amount of lubricant is supplied onto the transfer / conveying belt 71, whereby the transfer / conveying belt for the discharge products is supplied. A method of reducing the adhesive force to 71 may be applied.
In these methods, the cleaning brush 91, the cleaning blade 92, and the lubricant block 93 are other examples of the lubricant supply unit.
Further, in the case where it is expected that many discharge products are generated, by increasing the load for pressing the lubricant block 93 against the cleaning brush 91 and supplying a large amount of lubricant onto the transfer conveyance belt 71, A method of reducing the adhesion force of the discharge product to the transfer conveyance belt 71 may be applied.
In this method, the cleaning brush 91, the cleaning blade 92, the lubricant block 93, and the load setting member 96 are other examples of the lubricant supply unit.
The image formation control unit 80 and the lubricant supply unit are examples of the adhesion reducing unit.

  Further, as described in the second embodiment, when it is expected that a large amount of discharge products are generated, after the transfer of the image forming toner image 101 to the paper P is completed, the photosensitive drum 11 is completed. A difference (speed difference) is provided in the moving speeds of the surfaces facing the transfer conveyance belt 71 and the photosensitive drum 11 and the transfer conveyance belt 71 rub against each other, and the discharge product adhered on the transfer conveyance belt 71. You may apply the method of reducing the adhesive force of. In this method, the image formation control unit 80, the intermediate transfer belt 15, and the secondary transfer roll 22 are examples of the adhesion reducing means.

Furthermore, as described in the third embodiment, the toner including the atypical external additive is used, and the end toner image 103 (toner band) is provided, and the non-sheet passing portion RN of the transfer conveyance belt 71 is provided. When the toner adhering to the toner is removed by the cleaning blade 92, a method of reducing the adhesion force by polishing the discharge product adhering on the transfer conveyance belt 71 with a different type external additive may be applied. In this method, the image formation control unit 80 is an example of an adhesion reducing unit.
Also, some or all of the above methods may be used in combination.

Then, the image forming control unit 80 receives the notification that the paper P is changed from the UI unit 85, and the photosensitive drum 11 and the transfer conveyance belt 71 face each other by the amount of lubricant supplied onto the transfer conveyance belt 71. You may control the difference (speed difference) of the moving speed of each surface. Here, the UI unit 85 is an example of a determination unit.
Further, the image formation control unit 80 receives the resistance value R of the transfer unit 70 from the resistance measurement unit 78 provided between the transfer power source 77 and the backup roll 75, detects a change in the resistance value R, and transfers the transfer. The amount of lubricant supplied onto the belt 71 and the difference in speed (speed difference) between the surfaces of the photosensitive drum 11 and the transfer conveyance belt 71 facing each other may be controlled. Here, the resistance measurement unit 28 is an example of a determination unit.

  Therefore, even in the image forming apparatus using the direct transfer method, the occurrence of wobbling of the cleaning blade 92 of the belt cleaner 90 and the cleaning failure that stains the back surface of the paper P are suppressed.

  In this embodiment, the toner is described as having a negative polarity. However, when a positive polarity toner is used, the polarities of the transfer bias and the non-transfer bias may be reversed.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 2, 2Y, 2M, 2C, 2K ... Image forming unit, 10 ... Primary transfer part, 11 ... Photosensitive drum, 12 ... Charger, 13 ... Laser exposure device, 14 ... Developing device, 15 ... Intermediate transfer belt, 16 ... primary transfer roll, 17 ... drum cleaner, 20 ... secondary transfer section, 22 ... secondary transfer roll, 25 ... backup roll, 26 ... power supply roll, 27 ... secondary transfer power supply, 40 ... roll cleaner 41, 91 ... Cleaning brush, 42, 92 ... Cleaning blade, 43, 93 ... Lubricant block, 44, 94 ... Cleaner housing, 45, 95 ... Support member, 46, 96 ... Load setting member, 50 ... Paper container , 60 ... fixing unit, 70 ... transfer unit, 71 ... transfer conveyance belt, 80 ... image formation control unit, 81 ... reference sensor, 82 ... image density sensor, 85 ... UI unit, 90 ... Rutokurina, 101 or 101a, 101b ... image forming toner images, 102 ... density control toner image, 103, 103a, 103b ... end toner image, P ... paper

Claims (5)

A holder for holding a toner image;
A transfer means for transferring the toner image to the transfer target body with a transfer target divided into a plurality of types between the holding body and the transfer body;
Discrimination means for discriminating the type of the transfer object;
Corresponding to the type of the transferred object determined by the determining means, the amount of discharge products generated by the discharge between the holding body and the transferring means is predicted and used as a predetermined reference An adhesion force reducing means for reducing the adhesion force of the discharge product adhering to the transfer means to the transfer means when it is predicted that there are more discharge products than
And a removing means for removing the discharge product adhered to the transfer unit,
The adhesion reducing means is
It has a cleaning brush that comes into contact with the surface of the transfer means and the lubricant block, and includes a lubricant supply part that supplies a lubricant to the surface of the transfer means,
Before the toner image is transferred to the transfer object when it is predicted that the discharge product is generated more than the reference according to the type of the transfer object determined by the determination unit. In this case, when the cleaning brush is in contact with the surface of the transfer means, the number of rotations of the cleaning brush is increased, or the load on the lubricant block is increased by the lubricant supply unit, the lubricant supply unit causes the transfer means to move. An image forming apparatus characterized in that the amount of the lubricant supplied to the toner is increased . In the case where the adhesion reducing means predicts that the generation of the discharge product is larger than the reference based on the type of the transfer object determined by the determination means, After the toner image is transferred to the transfer object, the holding member and the transfer unit adhere to the transfer unit by rubbing each other with a difference in the moving speed on the surface where the holding unit and the transfer unit face each other. The image forming apparatus according to claim 1, wherein the adhesion force is reduced. The discriminating unit includes a resistance measuring unit that measures an electrical resistance between the holding body and the transfer unit between which the transfer target body is sandwiched, and the transfer target is measured by the electric resistance measured by the resistance measurement unit. the image forming apparatus according to claim 1 or 2, characterized in that to determine the type of the body. The toner image held by the holder is composed of toner including a toner main body and a different type of external additive, and in addition to the toner image transferred to the transfer target, the toner image is not transferred to the transfer target. Including toner images
The adhesion reducing means applies to the transfer object when it is predicted that the discharge product is generated more than the reference according to the type of the transfer object determined by the determination means. The amount of toner that forms the other toner image that is not transferred is increased, and when the toner is removed from the transfer unit by the removing unit, the discharge product adhered to the transfer unit is polished by the external additive. , an image forming apparatus according to any one of claims 1 to 3, characterized in that to reduce the adhesion force to adhere to the transfer means of the discharge products. A holder for holding a toner image;
A transfer means for transferring the toner image to the transfer target body with a transfer target divided into a plurality of types between the holding body and the transfer body;
A transfer electric field supply means for supplying a voltage for transfer to the transfer means;
Adhesion reduction for reducing the adhesion of the discharge product adhering to the transfer means to the transfer means when the voltage for transfer supplied by the transfer electric field supply means is higher than a predetermined reference voltage Means,
And a removing means for removing the discharge product adhered to the transfer unit,
The adhesion reducing means is
It has a cleaning brush that comes into contact with the surface of the transfer means and the lubricant block, and includes a lubricant supply part that supplies a lubricant to the surface of the transfer means,
When the voltage for transfer supplied by the transfer electric field supply means is higher than the reference voltage, the cleaning brush is in contact with the surface of the transfer means before transferring the toner image to the transfer target. The lubricant supply unit increases the amount of the lubricant supplied to the transfer means by increasing, increasing the rotation speed of the cleaning brush, or increasing the load of the lubricant block on the cleaning brush. An image forming apparatus.

Images