JP2014186208A - Cleaning device, transfer device including the same, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning device in which stable cleaning performance is maintained, even when the surface states of an image carrier and a cleaning member are changed due to long-term use and to provide a transfer device using the cleaning device and an image forming apparatus.SOLUTION: An intermediate transfer belt 141 carries a toner image comprising toner charged to a predetermined polarity on the surface thereof and is rotationally driven. A fur brush 146 comes into contact with the intermediate transfer belt 141 and is rotationally driven to clean the surface of the intermediate transfer belt 141. A bias application part for cleaning 51 applies a bias for cleaning having a polarity reverse to the polarity of the toner to the fur brush 146, during a cleaning period, that is, while the fur brush 146 cleans the intermediate transfer belt 141. An ammeter 52 detects a frictional current generated by friction between the fur brush 146 and the intermediate transfer belt 141. A bias control part for cleaning 32 adjusts a current for cleaning, according to the frictional current.

Description

  The present invention relates to a cleaning device that cleans an image carrier that carries a toner image, a transfer device including the same, and an image forming apparatus.

  2. Description of the Related Art Conventionally, an image forming apparatus such as a printer or a copier employing an electrophotographic system includes a photosensitive drum that carries an electrostatic latent image and a transfer device that transfers a toner image from the photosensitive drum to a sheet. . When an image composed of a plurality of colors typified by a full-color image is transferred to a sheet, the transfer device includes an intermediate transfer belt, a primary transfer member, and a secondary transfer member. The intermediate transfer belt is circulated so as to face the plurality of photosensitive drums, and a toner image is transferred from each photosensitive drum onto the intermediate transfer belt by a primary transfer voltage applied to the primary transfer member. Then, the toner image is collectively transferred from the intermediate transfer belt to the sheet by the secondary transfer voltage applied to the secondary transfer member.

  The transfer device as described above includes a belt cleaning device in order to collect toner remaining on the intermediate transfer belt after the secondary transfer. The belt cleaning device includes a cleaning member to which a cleaning bias is applied. The cleaning member rotates while contacting the intermediate transfer belt, and collects toner on the belt. Patent Document 1 discloses a technique in which the value of the cleaning bias applied to the cleaning member is changed according to the area of the toner image on the intermediate transfer belt.

JP 2011-112937 A

  In the technique described in Patent Document 1, the cleaning performance is improved by applying a larger cleaning bias to collect a large amount of residual toner. However, when the surface state of the intermediate transfer belt or the cleaning member changes with the use of the apparatus for a long time, the frictional charging characteristics between the two change. As a result, there is a problem that the friction current generated by the friction between the intermediate transfer belt and the cleaning member fluctuates the cleaning bias, and the cleaning performance becomes unstable.

  The present invention has been made in view of the above problems, and a cleaning device in which stable cleaning performance is maintained even when the surface state of an image carrier or a cleaning member changes due to long-term use, and It is an object of the present invention to provide a transfer device and an image forming apparatus to which this is applied.

  A cleaning device according to one aspect of the present invention includes a cleaning member that carries a toner image made of toner charged to a predetermined polarity on a surface and abuts on a rotationally driven image carrier, and cleans the surface, and the cleaning member Applies a cleaning bias having a polarity opposite to the polarity of the toner to the cleaning member during cleaning for cleaning the surface, and applies a predetermined cleaning current between the cleaning member and the image carrier. A current detection unit that detects a friction current generated by friction between the image carrier that is rotationally driven and the cleaning member during non-cleaning in which the cleaning bias is not applied to the cleaning member; A cleaning condition adjusting unit that adjusts a value of the cleaning bias or the cleaning current at the time of cleaning in accordance with the friction current detected by the current detection unit.

  According to this configuration, even when the surface state of the image carrier or the cleaning member changes as the cleaning device is used for a long time, the current detection unit causes the friction between the image carrier and the cleaning member. Detect current. Then, the cleaning condition adjustment unit adjusts the value of the cleaning bias or the cleaning current during cleaning according to the friction current detected by the current detection unit. For this reason, it is suppressed suitably that the cleaning performance of the cleaning member fluctuates due to generation or increase / decrease of the friction current.

  In the above configuration, the cleaning condition adjusting unit adjusts the cleaning current according to the friction current, and when the preset reference current of the cleaning current is Id and the friction current is Is, It is desirable that the cleaning condition adjustment unit adjusts the cleaning current Ic during the cleaning to Id + Is.

  According to this configuration, the cleaning current is stably maintained in a state where the influence of the friction current is preferably canceled out.

  In the above configuration, the cleaning member is preferably a brush roller that is driven to rotate and is formed of a conductive fur brush.

  According to this configuration, the surface of the image carrier is suitably cleaned by the fur brush. Further, even when a friction current is generated or when the friction current is increased or decreased due to a change in the surface property of the fur brush or the surface of the image carrier, fluctuations in the cleaning performance of the cleaning member are preferably suppressed. Is done.

  In the above configuration, the apparatus further includes a conductive recovery roller that contacts the brush roller and recovers the toner from the brush roller, and the bias application unit applies the cleaning bias to the brush roller via the recovery roller. It is desirable to apply.

  According to this configuration, the toner attached to the surface of the image carrier is suitably cleaned by the cleaning bias applied to the brush roller via the recovery roller. Further, the toner is stably recovered from the brush roller to the recovery roller.

  A transfer device according to another aspect of the present invention includes any of the cleaning devices described above, an intermediate transfer belt as the image carrier, and a transfer member that transfers the toner image from the intermediate transfer belt to a sheet. It is characterized by providing.

  According to this structure, it is suppressed suitably that the cleaning performance of the cleaning member fluctuates due to generation or increase / decrease of the friction current. Therefore, the surface of the intermediate transfer belt is stably cleaned, and the toner image is suitably transferred to the sheet.

  In the above configuration, the intermediate transfer belt is formed on a base material layer, an elastic layer disposed on the base material layer, the elastic layer, includes a filler therein, and the toner image is formed on a surface thereof. It is desirable to provide a coat layer to be supported.

  According to this configuration, if the elastic layer has irregularities, the irregularities may be formed on the surface of the coat layer due to the irregularities. In this case, the friction current between the surface of the intermediate transfer belt and the cleaning member is likely to change. Furthermore, when the filler is exposed from the surface of the intermediate transfer belt, the friction current is likely to fluctuate. Even in such a case, the cleaning condition adjustment unit adjusts the value of the cleaning current at the time of cleaning by the friction current detected by the current detection unit. For this reason, it is suppressed suitably that the cleaning performance of the cleaning member fluctuates due to generation or increase / decrease of the friction current.

  An image forming apparatus according to another aspect of the present invention, the cleaning device according to any one of the above, the image carrier that carries the toner image on a surface and is driven to rotate, and the toner image is transferred to a sheet. And a transfer member.

  According to this structure, it is suppressed suitably that the cleaning performance of the cleaning member fluctuates due to generation or increase / decrease of the friction current. Therefore, the surface of the image carrier is stably cleaned, and a toner image is suitably formed on the sheet.

  An image forming apparatus according to another aspect of the present invention is disposed opposite to the above-described transfer device and the intermediate transfer belt, carries a toner image on a peripheral surface, and holds the toner image on the intermediate transfer belt. And a photosensitive drum to be transferred.

  According to this structure, it is suppressed suitably that the cleaning performance of the cleaning member fluctuates due to generation or increase / decrease of the friction current. Therefore, the surface of the intermediate transfer belt is stably cleaned, and a toner image is suitably formed on the sheet.

  According to the present invention, even when the surface state of the image carrier or the cleaning member changes due to long-term use, a cleaning device that maintains stable cleaning performance, a transfer device to which the cleaning device is applied, and image formation An apparatus is provided.

1 is a cross-sectional view illustrating an internal structure of an image forming apparatus according to an embodiment of the present invention. It is typical sectional drawing which shows the periphery of the belt cleaning apparatus which concerns on embodiment of this invention. FIG. 2 is a schematic cross-sectional view showing a layer structure of an intermediate transfer belt according to an embodiment of the present invention. It is an electrical block diagram of the control part which concerns on embodiment of this invention. It is a timing chart which shows the control mode of the cleaning conditions in the embodiment of the present invention. It is a graph for demonstrating the reference current of the bias for cleaning in embodiment of this invention.

  Hereinafter, an image forming apparatus 10 according to an embodiment of the present disclosure will be described in detail with reference to the drawings. In this embodiment, a tandem color printer is illustrated as an example of an image forming apparatus. The image forming apparatus may be, for example, a copying machine, a facsimile machine, and a complex machine of these. The image forming apparatus may print a monochrome image.

  FIG. 1 is a cross-sectional view showing the internal structure of the image forming apparatus 10. The image forming apparatus 10 includes an apparatus main body 11 having a box-shaped housing structure. In the apparatus main body 11, a sheet feeding unit 12 that feeds the sheet P, an image forming unit 13 that forms a toner image to be transferred to the sheet P fed from the sheet feeding unit 12, and the toner image are primarily transferred. An intermediate transfer unit 14 (transfer device), a toner replenishing unit 15 that replenishes toner to the image forming unit 13, and a fixing unit 16 that performs a process of fixing an unfixed toner image formed on the sheet P to the sheet P. Decorated. Further, a discharge unit 17 that discharges the sheet P that has been subjected to the fixing process by the fixing unit 16 is provided on the upper portion of the apparatus main body 11.

  At an appropriate position on the upper surface of the apparatus main body 11, an unillustrated operation panel for inputting an output condition for the sheet P and the like is provided. This operation panel is provided with a power key, a touch panel for inputting output conditions, and various operation keys.

  In the apparatus main body 11, a sheet conveying path 111 extending in the vertical direction is further formed on the right side of the image forming unit 13. The sheet conveyance path 111 is provided with a conveyance roller pair 112 that conveys a sheet to an appropriate position. A registration roller pair 113 that corrects the skew of the sheet and feeds the sheet to a nip portion of secondary transfer described later at a predetermined timing is also provided on the upstream side of the nip portion in the sheet conveyance path 111. The sheet conveyance path 111 is a conveyance path that conveys the sheet P from the paper feeding unit 12 to the paper discharge unit 17 via the image forming unit 13 and the fixing unit 16.

  The paper feed unit 12 includes a paper feed tray 121, a pickup roller 122, and a paper feed roller pair 123. The sheet feeding tray 121 is detachably mounted at a lower position of the apparatus main body 11 and stores a sheet bundle P1 in which a plurality of sheets P are stacked. The pickup roller 122 feeds the uppermost sheet P of the sheet bundle P1 stored in the sheet feeding tray 121 one by one. The pair of paper feed rollers 123 sends out the sheet P fed out by the pickup roller 122 to the sheet conveyance path 111.

  The paper feeding unit 12 includes a manual paper feeding unit attached to the left side surface of the apparatus main body 11 shown in FIG. The manual paper feed unit includes a manual feed tray 124, a pickup roller 125, and a paper feed roller pair 126. The manual feed tray 124 is a tray on which the manually fed sheet P is placed, and is opened from the side surface of the apparatus main body 11 as shown in FIG. 1 when the sheet P is manually fed. The pickup roller 125 feeds out the sheet P placed on the manual feed tray 124. The pair of paper feed rollers 126 sends out the sheet P fed out by the pickup roller 125 to the sheet conveyance path 111.

  The image forming unit 13 forms a toner image to be transferred to the sheet P, and includes a plurality of image forming units that form toner images of different colors. As this image forming unit, in this embodiment, a magenta (M) color which is sequentially arranged from the upstream side to the downstream side in the rotation direction of the intermediate transfer belt 141 described later (from the left side to the right side in FIG. 1). A magenta unit 13M using a developer, a cyan unit 13C using a cyan (C) developer, a yellow unit 13Y using a yellow (Y) developer, and a black (Bk) developer are used. A black unit 13Bk is provided. Each unit 13M, 13C, 13Y, 13Bk includes a photosensitive drum 20, and a charging device 21, a developing device 23, a primary transfer roller 24, and a cleaning device 25 disposed around the photosensitive drum 20. An exposure device 22 common to the units 13M, 13C, 13Y, and 13Bk is disposed below the image forming unit.

  The photosensitive drum 20 is driven to rotate about its axis, and an electrostatic latent image and a toner image are formed on its peripheral surface. As this photosensitive drum 20, a photosensitive drum using an amorphous silicon (a-Si) material can be used. As shown in FIG. 1, the photosensitive drums 20 are arranged corresponding to the image forming units of the respective colors. The charging device 21 uniformly charges the surface of the photosensitive drum 20. As the charging device 21, a charging device using a contact charging method including a charging roller and a charging cleaning brush for removing toner attached to the charging roller can be used. The exposure device 22 has various optical system devices such as a light source, a polygon mirror, a reflection mirror, and a deflection mirror, and irradiates light that has been modulated based on image data onto the circumferential surface of the uniformly charged photoreceptor drum 20. Thus, an electrostatic latent image is formed.

  The developing device 23 supplies toner to the peripheral surface of the photosensitive drum 20 in order to develop the electrostatic latent image formed on the photosensitive drum 20. The developing device 23 is for a two-component developer composed of a toner and a carrier, and includes two stirring rollers 23A, a magnetic roller 23B, and a developing roller 23C. The stirring roller 23A circulates and conveys the two-component developer while stirring to charge the toner. A two-component developer layer is carried on the peripheral surface of the magnetic roller 23B, and toner formed by transferring toner to the peripheral surface of the developing roller 23C due to a potential difference between the magnetic roller 23B and the developing roller 23C. The layer is supported. The toner on the developing roller 23C is supplied to the peripheral surface of the photosensitive drum 20, and the electrostatic latent image is developed. In this embodiment, as an example, the toner has a characteristic of being charged to a positive polarity.

  The primary transfer roller 24 forms a primary transfer nip portion with the photosensitive drum 20 with the intermediate transfer belt 141 provided in the intermediate transfer unit 14 interposed therebetween, and a toner image on the photosensitive drum 20 is placed on the intermediate transfer belt 141. Primary transfer. As shown in FIG. 1, a primary transfer roller 24 is disposed to face the photosensitive drum 20 of each color. A primary transfer nip portion is formed between each photosensitive drum 20 and the primary transfer roller 24. In the present embodiment, the primary transfer roller 24 is composed of epichlorohydrin. Further, the outer diameter of the primary transfer roller 24 is 15 mm, and the resistance value is 1E + 6Ω when a voltage of 1000 V is applied. In the present embodiment, during the transfer operation, a transfer bias having a polarity opposite to the polarity of the toner is applied to the primary transfer roller 24 of each color with constant current control. Further, during a non-transfer operation different from the transfer operation, a transfer bias having the same polarity as the toner polarity is applied to the primary transfer roller 24 of each color with constant voltage control. The cleaning device 25 cleans the peripheral surface of the photosensitive drum 20 after the toner image is transferred.

  The intermediate transfer unit 14 is disposed in a space provided between the image forming unit 13 and the toner replenishing unit 15, and is rotatably supported by an intermediate transfer belt 141 (image carrier) and a unit frame (not shown). Drive roller 142 and driven roller 143. The intermediate transfer belt 141 is an endless belt-like rotating body, and is stretched between the driving roller 142 and the driven roller 143 so that the surface side thereof is in contact with the peripheral surface of each photosensitive drum 20. The intermediate transfer belt 141 carries on its surface a toner image made of toner charged to the predetermined polarity.

  A rotational driving force is applied to the driving roller 142, and the intermediate transfer belt 141 is driven to rotate by the rotation of the driving roller 142. In this embodiment, the drive roller 142 is composed of an aluminum three-headed pipe. In the vicinity of the driven roller 143, a belt cleaning device 144 for removing toner remaining on the surface of the intermediate transfer belt 141 is disposed.

  A secondary transfer roller 145 (transfer member) is disposed facing the drive roller 142. The secondary transfer roller 145 is pressed against the surface of the intermediate transfer belt 141 to form a secondary transfer nip portion. The toner image primarily transferred onto the intermediate transfer belt 141 is secondarily transferred to the sheet P supplied from the paper feeding unit 12 at the secondary transfer nip portion. In the present embodiment, the secondary transfer roller 145 is composed of epichlorohydrin. The outer diameter of the secondary transfer roller 145 is 20 mm, and the resistance value is 1E + 7Ω when a voltage of 1000 V is applied.

  The toner replenishing unit 15 stores toner used for image formation, and includes a magenta toner container 15M, a cyan toner container 15C, a yellow toner container 15Y, and a black toner container 15Bk in the present embodiment. These toner containers 15M, 15C, 15Y, and 15Bk respectively store replenishment toners for each color of MCYBk, and image forming units 13M, 13C, and 13C corresponding to each color of MCYBk from a toner discharge port 15H formed on the bottom surface of the container. The 13Y and 13Bk developing devices 23 are replenished with toner of each color through a toner conveying section (not shown).

  The fixing unit 16 includes a heating roller 161 having a heating source therein, a fixing roller 162 oriented with the heating roller 161, a fixing belt 163 stretched between the fixing roller 162 and the heating roller 161, and a fixing belt A pressure roller 164 which is disposed to face the fixing roller 162 via the H.163 and forms a fixing nip portion. The sheet P supplied to the fixing unit 16 is heated and pressurized by passing through the fixing nip portion. As a result, the toner image transferred to the sheet P at the secondary transfer nip is fixed to the sheet P.

  The paper discharge unit 17 is formed by recessing the top of the apparatus main body 11, and a paper discharge tray 171 for receiving the discharged sheet P is formed at the bottom of the concave portion. The sheet P on which the fixing process has been performed is discharged toward the discharge tray 151 via the sheet conveyance path 111 extending from the upper part of the fixing unit 16.

  Next, the belt cleaning device 144 (cleaning device) according to the present embodiment will be described in detail with reference to FIGS. 1 to 3. FIG. 2 is a schematic cross-sectional view showing the periphery of the belt cleaning device 144 of the intermediate transfer unit 14 inside the image forming apparatus 10. FIG. 3 is a cross-sectional view showing a layer structure in the thickness direction of the intermediate transfer belt 141.

  Referring to FIG. 2, the belt cleaning device 144 includes a fur brush 146 (cleaning member), a collection roller 147, and a blade 148.

  The fur brush 146 is disposed to face the driven roller 143 with the intermediate transfer belt 141 interposed therebetween. The fur brush 146 is a brush roller made of a conductive fur brush. The fur brush 146 is driven to rotate and cleans the surface of the intermediate transfer belt 141. In other embodiments, a fixed bar brush may be applied.

  The collection roller 147 contacts the fur brush 146 and collects the toner attached to the fur brush 146. The collection roller 147 is formed by disposing a conductive roller member around a shaft (not shown). The fur brush 146 and the collection roller 147 are rotationally driven in a direction indicated by an arrow in FIG. The blade 148 contacts the peripheral surface of the collection roller 147 and scrapes off the toner collected by the collection roller 147. The toner scraped off by the blade 148 is transported to a collection container (not shown) by a transport member 144R shown in FIG.

  Referring to FIG. 3, the above-described intermediate transfer belt 141 mainly has a three-layer structure. The intermediate transfer belt 141 includes a base material layer 141A, an elastic layer 141B, and a coat layer 141C. The base material layer 141 </ b> A corresponds to the lowermost layer of the intermediate transfer belt 141 and gives the intermediate transfer belt 141 a predetermined rigidity. The base material layer 141A is a hard resin layer. The elastic layer 141B is disposed on the base material layer 141A, corresponds to the intermediate layer of the intermediate transfer belt 141, and imparts elasticity to the intermediate transfer belt 141. Specifically, the primary transfer nip portion formed between the intermediate transfer belt 141 and the primary transfer roller 24 and the secondary transfer nip portion formed between the intermediate transfer belt 141 and the secondary transfer roller 145 are elastic. The intermediate transfer belt 141 is slightly compressed and deformed by the layer 141B. As a result, the nip portion is formed with a predetermined width in the circumferential direction of the intermediate transfer belt 141, and the transfer of the toner image is promoted. In the present embodiment, the elastic layer 141B is made of urethane rubber. For this reason, predetermined irregularities may be formed in the elastic layer 141B at the interface between the elastic layer 141B and the coat layer 141C. In other embodiments, the elastic layer 141B may be made of CR (chloroprene) rubber, NBR (nitrile) rubber, or the like. The coat layer 141C is formed on the elastic layer 141B and constitutes the uppermost layer of the intermediate transfer belt 141. The coat layer 141 </ b> C promotes toner retention on the intermediate transfer belt 141 and toner releasability from the intermediate transfer belt 141. The coat layer 141C is configured by containing (dispersing) a fluorine-based filler in a urethane binder. As described above, when predetermined irregularities are formed on the surface layer of the elastic layer 141B, irregularities are easily formed on the surface of the coat layer 141C disposed on the elastic layer 141B along the irregularities of the elastic layer 141B. . The unevenness formed on the surface of the coat layer 141C promotes the releasability of the toner layer transferred onto the intermediate transfer belt 141.

  Further, referring to FIG. 2, the belt cleaning device 144 includes a switch 50, a cleaning bias application unit 51 (bias application unit), and an ammeter 52 (current detection unit).

  The switch 50 switches the electrical connection destination to the recovery roller 147 between the cleaning bias applying unit 51 and the ammeter 52. The switch 50 is controlled by a cleaning bias controller 32 described later.

  The cleaning bias applying unit 51 is a high-voltage power source that applies a cleaning bias having a polarity opposite to the polarity of the toner to the fur brush 146 when the fur brush 146 cleans the surface of the intermediate transfer belt 141. By applying the cleaning bias, a predetermined cleaning current flows between the fur brush 146 and the intermediate transfer belt 141. Specifically, the cleaning bias applying unit 51 applies the cleaning bias to the fur brush 146 via the collection roller 147. The cleaning bias applying unit 51 applies a cleaning bias to the shaft of the collection roller 147, and a cleaning current flows between the roller member of the collection roller 147 and the fur brush 146. A predetermined potential difference is also formed between the fur brush 146 and the intermediate transfer belt 141, and the toner remaining on the intermediate transfer belt 141 is removed to the fur brush 146 side.

  The ammeter 52 is electrically connected to the recovery roller 147 as the switch 50 is switched. The ammeter 52 detects a friction current generated by friction between the intermediate transfer belt 141 that is rotationally driven and the fur brush 146 during non-cleaning when the cleaning bias is not applied to the fur brush 146. More specifically, the ammeter 52 detects the friction current via the collection roller 147.

  Next, the cleaning bias adjustment operation in the present embodiment will be described. FIG. 4 is an electrical block diagram of the control unit 30 provided in the image forming apparatus 10 according to the present embodiment. FIG. 5 is a flowchart when the cleaning bias control unit 32 described later adjusts the cleaning bias.

  The control unit 30 includes a CPU (Central Processing Unit), a ROM (Read Only Memory) that stores a control program, a RAM (Random Access Memory) that is used as a work area of the CPU, and the like. In addition, the cleaning bias applying unit 51, the driving roller 142, the fur brush 146, the recovery roller 147, and the ammeter 52 are electrically connected to the control unit 30. The control unit 30 functions to include a drive control unit 31, a cleaning bias control unit 32 (cleaning condition adjustment unit), and a storage unit 33 when the CPU executes a control program stored in the ROM.

  The drive control unit 31 controls a drive unit (not shown) to rotate the drive roller 142 of the intermediate transfer unit 14, the fur brush 146, and the recovery roller 147 of the belt cleaning device 144 in the directions indicated by the arrows in FIG.

  The cleaning bias control unit 32 controls the cleaning bias application unit 51 to apply a cleaning bias to the fur brush 146 via the collection roller 147. In the present embodiment, the cleaning bias control unit 32 controls the cleaning bias application unit 51 with constant current control. As described above, in the present embodiment, toner charged to positive polarity is used. Therefore, in order to collect the positive polarity toner remaining on the intermediate transfer belt 141, a negative polarity cleaning bias is applied to the fur brush 146.

  Further, the cleaning bias control unit 32 adjusts the value of the cleaning current of the cleaning bias at the time of cleaning based on the friction current detected by the ammeter 52. Specifically, when the preset reference current of the cleaning current is Id and the friction current is Is, the cleaning bias control unit 32 adjusts the cleaning current Ic at the time of cleaning to Id + Is.

  The storage unit 33 stores a preset reference current Id for the cleaning current. The reference current Id is referred to by the cleaning bias control unit 32, and the cleaning current Ic at the time of cleaning is determined.

  Referring to FIG. 5, when image forming operation is not performed in image forming apparatus 10, in other words, control unit 30 is in a state where intermediate transfer belt 141 is not cleaned by belt cleaning device 144. Then, the cleaning bias adjustment operation is started (step S1 in FIG. 5). This adjustment operation may be executed every time immediately before the image forming operation is executed, or may be executed every predetermined number of printed sheets or every predetermined waiting time. Furthermore, when the temperature around the image forming apparatus 10 changes, the adjustment operation may be executed according to the detection result of an environmental sensor (not shown) arranged inside or outside the apparatus main body 11.

  When the cleaning bias adjustment operation is started, the driving control unit 31 controls driving means (not shown), and the driving roller 142, the fur brush 146, and the collection roller 147 are rotationally driven (step S2). At this time, the cleaning bias control unit 32 controls the cleaning bias application unit 51 so that the cleaning bias is not applied to the collection roller 147 and the fur brush 146.

  When the intermediate transfer belt 141 and the fur brush 146 are rotated, the cleaning bias control unit 32 switches the switch 50 (FIG. 2), and then controls the ammeter 52 to detect the friction current Is (step S3). At this time, as described above, the cleaning bias applied by the cleaning bias applying unit 51 is not applied to the fur brush 146 and the collection roller 147. For this reason, the friction current Is generated by the friction between the intermediate transfer belt 141 and the fur brush 146 is detected by the ammeter 52 via the recovery roller 147.

  Next, the cleaning bias control unit 32 adjusts the cleaning current Ic according to the friction current Is detected by the ammeter 52. Specifically, the cleaning bias control unit 32 refers to the reference current Id of the cleaning current stored in the storage unit 33 in advance (Step S4).

  FIG. 6 is a graph schematically showing the reference current Id stored in the storage unit 33 in advance. FIG. 6A shows that different reference currents Id are stored depending on the environment (humidity) of the apparatus main body 11 of the image forming apparatus 10. This is because when the ambient humidity changes, the chargeability of the toner carried on the intermediate transfer belt 141 is different, and the toner recoverability by the fur brush 146 changes. FIG. 6B shows that different reference currents Id are stored depending on the printing speed of the image forming apparatus 10. When the printing speed is changed, the rotation speed of the intermediate transfer belt 141 is changed. That is, the time during which the fur brush 146 can collect the toner carried on the intermediate transfer belt 141 changes. For example, when the printing speed is increased, the time is shortened, so that it is necessary to quickly collect the toner with a larger cleaning current. FIG. 6C shows that different reference currents Id are stored in accordance with the image density of an image printed in the image forming apparatus 10. When the image density is high, when a toner image is transferred from the photosensitive drum 20 to the intermediate transfer belt 141, a transfer current value passing through the toner image per unit area is small. On the other hand, when the image density is low, when a toner image is transferred from the photosensitive drum 20 to the intermediate transfer belt 141, a transfer current value passing through the toner image per unit area becomes large. This is because the transfer current hardly flows between the photosensitive drum 20 and the intermediate transfer belt 141 in the background portion where no image exists, and the flow path of the transfer current tends to concentrate on the toner image. Therefore, as shown in FIG. 6C, paying attention to the fact that the toner charge remaining on the intermediate transfer belt 141 after the secondary transfer differs according to the image density, different reference currents Id are stored. Yes.

  As described above, the cleaning bias control unit 32 sets a suitable reference current Id in step S4 of FIG. 5 based on the environment around the image forming apparatus 10, the printing speed of the image forming apparatus 10, and the image density of the printed image. Reference is made from the storage unit 33. Then, the cleaning bias control unit 32 determines the latest cleaning current Ic by adding the detected friction current Is to the referenced reference current Id (step S5).

  At this time, when the polarity of the reference current Id and the polarity of the friction current Is are the same, the cleaning bias control unit 32 calculates the cleaning current Ic = Id + Is. Thereby, in the constant current control of the cleaning bias in the cleaning bias applying unit 51, the substantial cleaning current is suppressed from being reduced by the friction current Is. On the other hand, when the polarity of the reference current Id is opposite to the polarity of the friction current Is, the cleaning bias control unit 32 calculates the cleaning current Ic = Id + (− Is) (Is is an absolute value). Accordingly, in the constant current control of the cleaning bias in the cleaning bias applying unit 51, an excessive cleaning current is prevented from flowing in due to the friction current Is. Then, based on constant current control using the calculated cleaning current Ic as a target value, a cleaning bias is applied to the fur brush 146, and the toner on the intermediate transfer belt 141 is cleaned.

  As described above, according to the present embodiment, the ammeter 52 can perform the intermediate transfer even when the surface state of the intermediate transfer belt 141 or the fur brush 146 changes as the belt cleaning device 144 is used for a long time. A friction current Is between the belt 141 and the fur brush 146 is detected. The cleaning bias control unit 32 adjusts the value of the cleaning current Ic at the time of cleaning according to the friction current Is detected by the ammeter 52. For this reason, fluctuations in the cleaning performance of the fur brush 146 due to generation or increase / decrease of the friction current Is are preferably suppressed. In particular, the cleaning bias control unit 32 adjusts the cleaning current Ic during cleaning to Id + Is. For this reason, the cleaning current Ic is stably maintained in a state where the influence of the friction current Is is preferably canceled out. Therefore, the surface of the intermediate transfer belt 141 is stably cleaned, and the toner image is suitably transferred to the sheet.

  In the present embodiment, as described above, the intermediate transfer belt 141 includes the elastic layer 141B and the coat layer 141C. And coat layer 141C contains a filler inside. If the elastic layer 141B has irregularities, the irregularities may also be formed on the surface of the coat layer 141C by the irregularities. In this case, the frictional current Is between the surface of the intermediate transfer belt 141 and the fur brush 146 is likely to change due to, for example, a toner external additive buried in the unevenness. Furthermore, since the filler is exposed from the surface of the intermediate transfer belt 141, the friction current Is is likely to fluctuate. Even in such a case, the cleaning bias control unit 32 adjusts the value of the cleaning current Ic at the time of cleaning based on the latest friction current Is detected by the ammeter 52. For this reason, even under conditions where the friction current Is is likely to fluctuate, fluctuations in the cleaning performance of the fur brush 146 are preferably suppressed.

  As mentioned above, although one Embodiment of this invention was described in detail, this invention is not limited to this. The present invention can take, for example, the following modified embodiments.

  (1) In the above embodiment, the intermediate transfer belt 141 is used as the image carrier, but the present invention is not limited to this. The present invention may be applied to a cleaning device in which the photosensitive drum 20 is applied as an image carrier and the surface of the photosensitive drum 20 is cleaned.

  (2) In the above-described embodiment, the cleaning bias applying unit 51 is described as applying the cleaning bias to the fur brush 146 via the collection roller 147. However, the present invention is not limited thereto. It is not something. The cleaning bias applying unit 51 may apply the cleaning bias directly to the fur brush 146. Further, the cleaning bias control unit 32 may directly adjust the voltage value of the cleaning bias in accordance with the friction current Is. Even in this case, as a result, the cleaning current Ic is suitably adjusted.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 13 Image forming part 14 Intermediate transfer unit (transfer apparatus)
141 Intermediate transfer belt (image carrier)
141A Base material layer 141B Elastic layer 141C Coat layer 142 Drive roller 143 Driven roller 144 Belt cleaning device (cleaning device)
145 Secondary transfer roller (transfer member)
146 Fur brush (cleaning member, brush roller)
147 Collection roller 148 Blade 30 Control unit 31 Drive control unit 32 Cleaning bias control unit (cleaning condition adjustment unit)
33 Storage Unit 50 Switch 51 Cleaning Bias Application Unit (Bias Application Unit)
52 Ammeter (Current detector)

Claims (8)

A cleaning member that carries a toner image made of toner charged to a predetermined polarity on the surface and abuts on a rotationally driven image carrier, and cleans the surface;
When the cleaning member cleans the surface, a cleaning bias having a polarity opposite to the polarity of the toner is applied to the cleaning member, and a predetermined cleaning current is applied between the cleaning member and the image carrier. A bias application section to flow;
A current detection unit that detects a friction current generated by friction between the image carrier that is rotationally driven and the cleaning member at the time of non-cleaning in which the cleaning bias is not applied to the cleaning member;
A cleaning condition adjustment unit that adjusts the value of the cleaning bias or the cleaning current during the cleaning according to the friction current detected by the current detection unit;
A cleaning device comprising: The cleaning condition adjustment unit adjusts the cleaning current according to the friction current,
The cleaning condition adjustment unit adjusts the cleaning current Ic at the time of cleaning to Id + Is when the preset reference current of the cleaning current is Id and the friction current is Is. Item 4. The cleaning device according to Item 1.   The cleaning device according to claim 1, wherein the cleaning member is a brush roller that is driven to rotate and includes a conductive fur brush. A conductive recovery roller that contacts the brush roller and recovers the toner from the brush roller;
The cleaning apparatus according to claim 3, wherein the bias applying unit applies the cleaning bias to the brush roller through the recovery roller. A cleaning device according to any one of claims 1 to 4,
An intermediate transfer belt as the image carrier;
And a transfer member that transfers the toner image from the intermediate transfer belt to a sheet.   The intermediate transfer belt includes a base material layer, an elastic layer disposed on the base material layer, a coat layer formed on the elastic layer, including a filler inside, and carrying the toner image on the surface. The transfer apparatus according to claim 5, further comprising: A cleaning device according to any one of claims 1 to 4,
The image carrier that carries the toner image on its surface and is driven to rotate;
A transfer member for transferring the toner image to a sheet;
An image forming apparatus comprising: The transfer device according to claim 5 or 6,
A photoconductive drum disposed opposite to the intermediate transfer belt, carrying a toner image on a peripheral surface thereof, and transferring the toner image to the intermediate transfer belt;
An image forming apparatus comprising:

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