JP4976860B2 - Image forming apparatus - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile machine configured to be capable of color printing. The present invention relates to an image forming apparatus configured to be performed.

  An image forming apparatus for color printing irradiates light beams based on image information corresponding to each color sequentially on a peripheral surface of a photosensitive drum rotating around an axis, in which uniform charges are formed by a charger. To form an electrostatic latent image corresponding to each color, and by supplying toner from the developing device to the electrostatic latent image, a toner image of each color is sequentially formed on the peripheral surface of the photosensitive drum. Each time is formed, a color image is once formed on the surface of the intermediate transfer member by coating the surface of the intermediate transfer member that is rotating or rotating. The color image on the intermediate transfer member is transferred to a separately supplied sheet. The sheet after the transfer process is introduced into a fixing device, where the toner image is fixed by heating, and is then led to the outside.

  By the way, in such an image forming process, in order to form a uniform charge on the circumferential surface of the photosensitive drum, a high voltage is applied from a predetermined charger to the circumferential surface of the photosensitive drum. When this is applied, various discharge products such as ozone and nitrogen oxides caused by ozone are generated, and these discharge products adhere to the peripheral surface of the photosensitive drum. Various fillers contained in the paper also adhere to the peripheral surface of the photosensitive drum.

  When foreign matters such as discharge products, fillers, and residual toner adhere to the peripheral surface of the photoconductive drum, the electrical characteristics of the photoconductive drum change, thereby degrading image quality such as background fogging. Therefore, in order to eliminate such inconvenience, the cleaning device removes the foreign matter adhering to the circumferential surface of the photosensitive drum and the intermediate transfer member and cleans it.

  Incidentally, in recent years, smooth and tough amorphous silicon (hereinafter referred to as a-Si) has been used as a material for forming an image forming surface, and the a-Si is laminated on the peripheral surface of the photosensitive drum. -Si photosensitive drums are actively used. However, since a-Si is extremely hard, the peripheral surface of the a-Si photosensitive drum is difficult to be polished, and as a result, the a-Si photosensitive drum is likely to deposit foreign substances such as discharge products on the peripheral surface. Has difficulties.

  In addition, since a-Si has a hygroscopic property, a-Si on the peripheral surface of the photosensitive drum absorbs moisture in a high humidity environment such as in summer or rainy weather, and the a-Si layer is thereby formed. Due to the significant decrease in surface resistance, an image flow or the like occurs on the peripheral surface of the photosensitive drum, and as a result, there arises a disadvantage that an appropriate image cannot be formed.

  In order to eliminate such inconvenience, conventionally, a heater is provided inside the photosensitive drum, and the moisture absorbed by the a-Si layer is evaporated by heating the photosensitive drum with this heater. However, when a heater is employed, there are inconveniences that not only the part cost and energy cost increase, but also the start-up time of the apparatus is prolonged and usability is lowered.

  Therefore, in the invention of Patent Document 1, it is possible to set a refresh mode in which only the polishing process of the peripheral surface of the photosensitive drum is set in anticipation when the image forming process is not executed, and when this refresh mode is set. Then, toner is supplied from the developing device to the entire peripheral surface of the photosensitive drum, and this toner is used as an abrasive to perform a polishing process by a cleaning device. In this way, the photosensitive drum circumferential surface is intensively polished in the refresh mode without increasing the number of parts, so that effective cost effective cleaning of the photosensitive drum circumferential surface can be avoided while avoiding an increase in cost. Is done.

  However, in the case of an image forming apparatus for color printing, since the intermediate transfer member is always in contact with the peripheral surface of the photosensitive drum, the peripheral surface of the photosensitive drum is cleaned by the polishing process in the refresh mode. However, there is a problem that the moisture absorbed by the intermediate transfer member is transferred to the photosensitive drum.

Therefore, in order to solve such a problem, in the invention described in Patent Document 2, the toner for polishing the peripheral surface of the a-Si photosensitive drum is temporarily transferred to the intermediate transfer member, and this toner is transferred to the intermediate transfer member. Next, the toner on the intermediate transfer member is reversely returned to the peripheral surface of the a-Si photosensitive drum, and thereafter, the toner is used on the peripheral surface of the a-Si photosensitive drum by a conventional method. A polishing process is performed. By doing so, the transfer of moisture from the intermediate transfer member to the a-Si photosensitive drum is prevented.
Japanese Patent Laid-Open No. 11-3014 JP 2004-279902 A

  By the way, in the invention described in Patent Document 2, before executing the refresh mode, one of a plurality of developing devices each storing toner of each color is selected (in the embodiment, black toner is stored). (See paragraph [0042] of cited document 2)), the peripheral surface of the a-Si photosensitive drum is polished by toner from the selected developing device, and the intermediate transfer is performed. Water is removed from the body.

  However, the characteristics of the toner vary depending on the type (color) of the toner. Therefore, even when an arbitrarily selected toner is used, the peripheral surface of the a-Si photosensitive drum is polished and the moisture on the surface of the intermediate transfer member is removed. It is not always possible to effectively perform both processes simultaneously.

  The present invention has been made in view of such circumstances, and is applied to the refresh mode in consideration of the characteristics of the toner according to the type, thereby polishing the peripheral surface of the photosensitive drum and the surface of the intermediate transfer member. An object of the present invention is to provide an image forming apparatus capable of more effectively removing both moisture.

  According to the first aspect of the present invention, there is provided a photosensitive drum on which a toner image is formed on a peripheral surface, a plurality of developing devices for sequentially supplying each color toner and black toner to the peripheral surface of the photosensitive drum, and the photosensitive drum. An intermediate transfer member to which toner images sequentially formed on the peripheral surface of the photosensitive drum are transferred in an overlaid state, and the photosensitive drum is disposed so as to face the photosensitive drum via the intermediate transfer member. A transfer roller for transferring the toner on the surface to the surface of the intermediate transfer member, a rubbing means for rubbing the peripheral surface of the photosensitive drum, a cleaning means for cleaning the surface of the intermediate transfer member, the photosensitive drum, And a control unit that performs control to refresh the intermediate transfer member. The control unit supplies the black toner to the peripheral surface of the photosensitive drum as the refresh processing, and A first control for setting the color toner to the same charge as that of the toner image on the peripheral surface of the photosensitive drum, supplying the color toner to the peripheral surface of the photosensitive drum, and supplying the transfer roller to the peripheral surface of the photosensitive drum. The second control for setting the charge opposite to the charge of the toner image on the surface is performed.

  According to such a configuration, in the first control, the black toner is applied to the entire peripheral surface of the photosensitive drum in a state where the transfer roller is set to the same charge as that of the toner image formed on the peripheral surface of the photosensitive drum. Then, a solid image is formed with black toner. This solid image of black toner is not transferred from the peripheral surface of the photosensitive drum to the intermediate transfer member due to electrostatic repulsion. Accordingly, the black toner of the solid image on the circumferential surface of the photosensitive drum is removed from the circumferential surface of the photosensitive drum by rubbing with the rubbing means after passing through the intermediate transfer body. Since the black toner serves as an abrasive during the rubbing, the peripheral surface of the photosensitive drum is polished, so that foreign matters such as discharge products adhering to the peripheral surface are removed. The used black toner is collected from the peripheral surface of the photosensitive drum.

  Next, in the second control, color toner is transferred from the developing device to the peripheral surface of the photosensitive drum in a state where the transfer roller is set to a charge opposite to the charge of the toner image on the peripheral surface of the photosensitive drum by the control of the control unit. To be supplied. The water adhering to the surface of the intermediate transfer member is adsorbed by the color toner, and the surface of the intermediate transfer member becomes dry. Therefore, there is no inconvenience that moisture from the intermediate transfer member is transferred to the peripheral surface of the photosensitive drum that is in contact with the surface of the intermediate transfer member. The used color toner is collected from the surface of the intermediate transfer member by a cleaning means.

  Black toner is more abrasive than color toner, but color toner has higher water absorption than black toner, and there is a complementary relationship between black toner and color toner. Therefore, only the black toner is used for polishing the peripheral surface of the photosensitive drum, and only the color toner is used for water adsorption of the intermediate transfer member, thereby making the most of the properties of both toners. In this state, both the polishing process on the peripheral surface of the photosensitive drum and the moisture removal process on the surface of the intermediate transfer member are performed more reliably and efficiently than in the past.

  According to a second aspect of the invention, in the first aspect of the invention, the intermediate transfer member is an intermediate transfer belt stretched between a pair of support rollers so as to be capable of rotating.

  According to such a configuration, the intermediate transfer belt can be disposed in a flat state while securing a necessary area by being stretched between the pair of support rollers.

  According to the first aspect of the present invention, in the refresh process of the image forming apparatus, the black toner having a strong polishing force is employed for polishing the peripheral surface of the photosensitive drum, and the moisture of the intermediate transfer member is adsorbed. In this case, a color toner having a high moisture adsorptivity is used. For this reason, both the polishing process on the peripheral surface of the photosensitive drum and the moisture removal process on the surface of the intermediate transfer member are performed with only a predetermined color toner as in the past, while making the best use of the properties of the toner. Compared with the case where the polishing process on the peripheral surface of the photosensitive drum and the removal of moisture on the surface of the intermediate point vehicle body are performed, the process can be performed reliably and efficiently.

  According to the second aspect of the present invention, since the intermediate transfer belt that can be stretched in a flat state between the pair of support rollers is adopted as the intermediate transfer member, it contributes to the downsizing of the image forming apparatus. be able to.

  FIG. 1 is an external perspective view showing an embodiment of a printer (image forming apparatus) 10 capable of color printing according to the present invention. FIG. 1A shows a state in which a maintenance lid 112 is closed, FIG. 1B shows a state in which the maintenance lid 112 is opened, and FIG. 1C shows a state in which the maintenance lid 112 is opened and the toner container is removed. In FIG. 1, the XX direction is referred to as the left-right direction, and the YY direction is referred to as the front-rear direction. In particular, the -X direction is referred to as the left, the + X direction is referred to as the right, the -Y direction is referred to as the front, and the + Y direction is referred to as the rear.

  As shown in FIG. 1, a printer 10 according to the present embodiment is a so-called color machine configured to be capable of color printing, and will be described later for image forming processing in a printer main body 11 that has a substantially cubic shape in appearance. Various members are mounted. The printer main body 11 has a rounded shape as a whole, and is designed so as to give a visually friendly and compact impression to the user.

  The printer main body 11 is provided with a paper discharge tray 161 on the upper surface, a maintenance lid 112 is provided on the upper front surface facing the user, and a detachable paper cassette 121 is disposed below the maintenance lid 112. This makes it extremely easy to use in consideration of usability.

  The paper discharge tray 161 receives the paper P on which printing processing has been performed, and can receive the paper P discharged from a paper discharge port 162 formed facing the front at the rear of the upper surface of the printer main body 11. It has an inclined surface that is arcuate and slopes forward.

  The maintenance lid 112 is normally closed as shown in FIG. 1A, and is opened as shown in FIGS. 1B and 1C when the toner container 18 is replaced.

  The maintenance lid 112 is pivotally supported around a support shaft 122 a installed slightly above the sheet cassette 121 between the front positions of the pair of side plates 111 of the printer main body 11 so as to be rotatable forward and backward. The posture can be changed between a closed posture S1 in which the opening 110 is closed (FIG. 1A) and an open posture S2 in which the front opening 110 of the printer main body 11 is opened (FIG. 1B and FIG. 1C). It has become.

  The maintenance lid 112 is provided with a manual feed tray 122 that is pivotally supported around the support shaft 122a. The manual feed tray 122 is used when manually supplying the paper P for printing to the printer 10. The manual feed tray 122 is rotated clockwise around the support shaft 122a in a state in which the maintenance lid 112 is set in the closed posture S1 (indicated by a solid line in FIG. 1A), so that FIG. As indicated by a two-dot chain line in A), the maintenance lid 112 is pulled out.

  The toner container 18 includes a black container 18K filled with black toner, a cyan container 18C filled with cyan toner, a magenta container 18M filled with magenta toner, and a yellow container 18Y filled with yellow toner. Four types are adopted. The toner container 18 is arranged in the order of a black container 18K, a cyan container 18C, a magenta container 18M, and a yellow container 18Y from left to right facing the front opening 110 in the printer main body 11.

  Therefore, by opening the maintenance lid 112, the user faces the black to yellow containers 18K, 18C, 18M, and 18Y as shown in FIG. When the black to yellow containers 18K, 18C, 18M, and 18Y are removed from the printer main body 11 for replacement in this state, the state shown in FIG.

  The paper cassette 121 is for storing printing paper P, and is detachably attached to the printer main body 11. In the example shown in FIG. 1, the paper cassette 121 is provided in one stage, but is not limited to one stage, and may be two or more stages.

  FIG. 2 is a side sectional view illustrating an embodiment of the internal structure of the printer 10 shown in FIG. In addition, the direction display by Y in FIG. 2 is the same as that in FIG. 1 (−Y: forward, + Y: backward).

  As shown in FIG. 2, the printer 10 includes a paper feeding unit 12 that stores paper P to be subjected to color printing processing and feeds the paper P for printing processing, and a paper P sent from the paper feeding unit 12. An image forming unit 13 that transfers an image (toner image) formed by the image forming process to the paper P while conveying the toner, and a fixing that performs a fixing process on the toner image transferred to the paper P by the image forming unit 13 The printer main body 11 is equipped with a unit 14, a discharge destination switching unit 15 for switching the discharge destination of the paper P on which the fixing process has been performed by the fixing unit 14, and a paper discharge unit 16 for discharging the paper P for which the printing process has been completed. It is configured by being.

  The paper feed unit 12 includes the paper cassette 121 capable of storing a plurality of sheets P, which is detachably attached to a lower portion of the printer main body 11, and the manual feed used when manually feeding the sheets P. And a tray 122.

  A pickup roller 123 is provided at an upper position on the front side of each paper cassette 121, and the paper P stored in the paper cassette 121 is fed out one by one by the drive of the pickup roller 123 and sent toward the image forming unit 13. It is.

  The image forming unit 13 includes a photosensitive drum 131, a charging roller 132, an exposure device 133, a rotary developing device 20, a toner container 18, a transfer belt (intermediate transfer member) 134, and a primary transfer roller 135. , A secondary transfer roller 136, a drum cleaning device (sliding means) 30, and a belt cleaning device (cleaning means) 40.

  The photosensitive drum 131 has an electrostatic latent image formed on a peripheral surface thereof and a toner image formed along the electrostatic latent image, and has a shaft center extending in the left-right direction (a direction perpendicular to the paper surface of FIG. 2). It is possible to rotate.

  The charging roller 132 performs a charging process on the peripheral surface of the photosensitive drum 131 to form a uniform charge on the peripheral surface.

  The exposure device 133 forms an electrostatic latent image on the circumferential surface of the photosensitive drum 131 to which a uniform charge is applied by the charging roller 132 by irradiating the circumferential surface of the photosensitive drum 131 with laser light based on image information. It is.

  The rotary developing device 20 supplies toner to the peripheral surface of the photosensitive drum 131 on which the electrostatic latent image is formed by the exposure device 133 to form a toner image on the peripheral surface.

  The toner container 18 supplies toner to the rotary developing device 20.

  The transfer belt 134 is for transferring a toner image formed on the peripheral surface of the photosensitive drum 131.

  The primary transfer roller 135 electrostatically peels off the toner image on the photosensitive drum 131 and transfers it to the surface of the transfer belt 134.

  The secondary transfer roller 136 electrostatically peels off the toner image on the transfer belt 134 and transfers the toner image onto the paper P fed from the paper feeding unit 12.

  The drum cleaning device 30 cleans the peripheral surface of the photosensitive drum 131 after being transferred to the transfer belt 134.

  The belt cleaning device 40 performs a cleaning process on the surface of the transfer belt 134 after the transfer process on the paper P.

  In the present embodiment, the photosensitive drum 131 employs a so-called a-Si photosensitive drum in which an extremely smooth amorphous silicon layer that is tough and has excellent wear resistance is laminated on the peripheral surface. It is suitable for forming an image.

Each of the photosensitive drums 131 is supplied with toner as a developer from a corresponding developing device 22 described later while being rotated counterclockwise in FIG. Note that the developer includes a one-component system composed only of toner and a so-called two-component system composed of toner and carrier. The toner is a fine powder having a particle diameter of 6 to 12 μm in which an external additive such as a colorant, a charge control agent and wax is dispersed in a binder resin. On the other hand, the carrier is magnetic particles having a particle size of 60 to 200 μm such as magnetite (Fe ₃ O ₄ ), and is used for charging the toner. Incidentally, in the present embodiment, a one-component toner-only developer is used as the developer.

  The charging roller 132 is configured such that charges having a predetermined polarity are formed on the peripheral surface by a high voltage applied from a power source (not shown). Since the peripheral surface of the charging roller 132 is in contact with the peripheral surface of the photosensitive drum 131, uniform charges are formed on the peripheral surface of the photosensitive drum 131.

  The exposure device 133 irradiates the peripheral surface of the photosensitive drum 131 uniformly charged by the charging roller 132 with laser light based on image data input from a computer (not shown). An electrostatic latent image is formed on the peripheral surface of the photosensitive drum 131 by the laser beam irradiation of the exposure device 133. Then, the toner from the rotary developing device 20 is supplied to the electrostatic latent image formed on the peripheral surface of the photosensitive drum 131, so that a toner image is formed on the peripheral surface. Is transferred to the transfer belt 134.

  The rotary developing device 20 has a rotating frame body 21 formed in a circular shape in a side view (as viewed from a direction orthogonal to the paper surface of FIG. 2), and is mounted on the rotating frame body 21 at an equal pitch in the circumferential direction. Four developing devices 22 are provided. The rotating frame 21 is pivotally supported at a rear position of the photosensitive drum 131 so as to be rotatable about a frame shaft 211 disposed in parallel with the axis of the photosensitive drum 131 and at substantially the same height level. Has been. The rotating frame body 21 is equally divided into four sections in the circumferential direction by four partition plates 212 projecting radially from the frame body axis 211, and each section has a fan shape in a side view. Each developing unit 22 is mounted.

  The developing device 22 has an arcuate casing 210 that is fixed to the rotating frame 21 while being sandwiched between the partition plates 212. The developing unit 22 includes a black developing unit 22K filled with black toner, a cyan developing unit 22C filled with cyan toner, a magenta developing unit 22M filled with magenta toner, and a yellow toner. Four types of yellow developing device 22Y are employed.

  When forming a toner image with yellow toner on the peripheral surface of the photosensitive drum 131, the yellow developing unit 22 </ b> Y is set to a position facing the photosensitive drum 131 by the rotation of the rotary frame 21 around the frame axis 211. In this state, when the photosensitive drum 131 rotates around the drum center, yellow toner images are sequentially formed on the peripheral surface thereof. This yellow toner image is immediately transferred to the rotating transfer belt 134.

  The magenta, cyan, and black toner images are formed on the peripheral surface of the photosensitive drum 131 in the same manner as in the case of yellow, and the developing unit 22 filled with the target color toner is connected to the peripheral surface of the photosensitive drum 131. Opposed. The toner image of the next color is sequentially transferred onto the peripheral surface of the photosensitive drum 131 from which the toner image has disappeared by the transfer process to the transfer belt 134.

  Then, by appropriately synchronizing the rotation of the transfer belt 134 and the toner image forming operation of the photosensitive drum 131, a color image in which the toner of each color is applied is formed on the surface of the transfer belt 134. The color image is transferred to the paper P fed from the paper feeding unit 12 by the action of the secondary transfer roller 136, whereby color printing is performed on the paper P.

  A registration roller pair 124 is provided at a position immediately upstream of the secondary transfer roller 136, and the conveyance timing of the paper P sent from the paper feeding unit 12 to the image forming unit 13 is adjusted by the registration roller pair 124. Is done. The color image on the transfer belt 134 is transferred to an appropriate position on the paper P by adjusting the conveyance timing by the registration roller pair 124.

  The transfer belt 134 is driven by the primary transfer roller 135, an idle roller 134c provided slightly behind the primary transfer roller 135, and a drive motor (not shown) provided below the idle roller 134c. It is wound around a rotating drive roller 134a and a driven roller 134b disposed opposite to the drive roller 134a at a front position below the photosensitive drum 131.

  The driven roller 134b is urged in a direction away from the driving roller 134a by the urging force of an urging member 134d such as a coil spring, whereby the tension state of the transfer belt 134 is maintained. The secondary transfer roller 136 is disposed opposite to the drive roller 134a via the transfer belt 134 at a position directly below the drive roller 134a.

  A bias voltage for electrostatically peeling off the toner image on the transfer belt 134 is applied to the secondary transfer roller 136. Therefore, the toner image on the transfer belt 134 is transferred to the paper P passing between the transfer belt 134 and the secondary transfer roller 136.

  Between the driving roller 134a and the idle roller 134c, the belt cleaning device 40 for cleaning the surface of the transfer belt 134 after the transfer processing on the paper P is provided. The belt cleaning device 40 cleans the belt. The processed transfer belt 134 goes to the photosensitive drum 131 in order to receive the next transfer process.

  The fixing unit 14 performs a fixing process on the transfer image transferred to the paper P by the image forming unit 13. The fixing roller 141 is heated by an energizing heating element such as a halogen lamp, and the fixing roller 141 at the lower part. And a pressure roller 142 whose peripheral surface is pressed against and in contact with the peripheral surface of the fixing roller 141.

  The sheet P that has been transferred by the transfer belt 134 in the image forming unit 13 is guided to the circumference of the transfer belt 134 while being sandwiched between the transfer belt 134 and the secondary transfer roller 136, and is then fixed to the fixing unit 14. The toner image is fixed on the paper P by heating when passing between the fixing roller 141 and the pressure roller 142.

  The paper P after the fixing process is led to the paper discharge conveyance path 101 by driving the first discharge roller pair 143, and the paper discharge conveyance path 101 is raised by the forward drive of the second discharge roller pair 102, and the paper discharge outlet 162. The paper is discharged to a paper discharge tray 161 provided at the top of the printer main body 11.

  The discharge destination switching unit 15 is used when double-sided printing is performed on the paper P. The paper P once sent from the fixing unit 14 to the paper discharge conveyance path 101 after the one-side fixing process is completed. Is returned to the image forming unit 13 again with the front and back reversed.

  The discharge destination switching unit 15 includes a return roller 151 disposed opposite to a lower end portion of the paper discharge conveyance path 101 so that a peripheral surface of the lower portion of the first discharge roller pair 143 comes into contact with each other, and the return roller 151. And a return conveyance path 152 extending from the lower part of the sheet to the upstream side (front side in FIG. 2) of the registration roller pair 124 through the fixing unit 14.

  When performing double-sided printing on the paper P, the paper P after the fixing process for which single-sided printing has been completed is led out to the paper discharge conveyance path 101 until the trailing edge passes through the first discharge roller pair 143, and the second printing is continued. The discharge roller pair 102 is reversely driven. By doing so, it is guided to the drive of the return roller 151 on which single-sided printing is completed, and is sent back to the return transport path 152, and is directed to the registration roller pair 124 through the return transport path 152 with the front and back reversed. Thereafter, printing processing is performed on the back side of the paper P in the image forming unit 13.

  The toner container 18 supplies each color toner to the black developing unit 22K, cyan developing unit 22C, magenta developing unit 22M, and yellow developing unit 22Y of the rotary developing device 20, respectively. 4 units (black container 18K, cyan container 18C, magenta container 18M, and yellow container 18Y) corresponding to the black to yellow developing devices 22K, 22C, 22R, and 22Y. Adopted (see FIG. 1B).

  As shown in FIG. 1B, these four toner containers 18 are detachably mounted on a base 17 provided so as to extend in the left-right direction at a substantially middle position in front of the printer main body 11. Yes. Between each toner container 18 and the rotary developing device 20, a toner transfer mechanism for sending the toner in the toner container 18 to each developer 22 is provided. The details of the toner transfer mechanism will not be described.

  Hereinafter, the drum cleaning device 30 and the belt cleaning device 40 will be further described based on FIG. 3 with reference to FIGS. 1 and 2 as necessary. FIG. 3 is a partially enlarged view of FIG. 2 for explaining the rotary developing device 20, the drum cleaning device 30 and the belt cleaning device 40 in detail. Note that the direction indication by Y in FIG. 3 is the same as in FIG. 1 (−Y: forward, + Y: backward).

  As shown in FIG. 3, the rotary developing device 20 includes a pair of left and right support disks 23 concentric with the frame body shaft 211 and fixed to the printer main body 11 (in FIG. 3, the right side (the back side of the paper surface in FIG. 3). Side) only display). The rotating frame 21 is rotated around the frame axis 211 by driving a drive motor (not shown) provided in the printer body 11 while being concentrically sandwiched between the pair of support disks 23. To do.

  The four partition plates 212 are provided between the pair of support disks 23 so as to protrude from the frame shaft 211 in the radial direction evenly in the circumferential direction. Each of the developing units 22 (black developing unit 22K, cyan developing unit 22C, magenta developing unit 22M, and yellow developing unit 22Y) is mounted in each of the four sections partitioned by the partition plate 212.

  Each developing device 22 includes a circular receiving port 24 for receiving the developer replenished from the toner container 18 and a developing roller 25 for supplying the toner in the internal developer to the photosensitive drum 131. I have. The receiving port 24 is provided on the counterclockwise side of the outer surface of the developing device 22 (the portion corresponding to the circumference of the support disc 23) in a state where the developing device 22 is mounted on the rotating frame 21. On the other hand, the developing roller 25 is provided on the clockwise side of the outer surface of the developing device 22.

  The receiving port 24 is provided in a state where the black to yellow developing devices 22K, 22C, 22R, and 22Y are displaced in the left-right direction (direction perpendicular to the paper surface of FIG. 3). In the present embodiment, the receiving port 24 of the black developing device 22K is provided in the leftmost position, and then the receiving port 24 of the cyan developing device 22C is provided on the right side, and further on the right side, the magenta developing unit is provided. The receiving port 24 of the developing device 22M is provided, and the receiving port 24 of the yellow developing device 22Y is provided in the rightmost position.

  Such a receiving port 24 is blocked by a closing film 241. The closing film 241 is provided with a cross notch, and the developer is supplied into the developing device 22 in a state where the notch is pushed and expanded by a supply cylinder 182 described later.

  On the other hand, each of the toner containers 18 (FIG. 2) has a transport pipe 181 for transporting the internal developer toward the corresponding developing device 22. A supply cylinder 182 is provided at a position facing the receiving port 24 on the front end side (rear of FIG. 2) of each transport pipe 181.

  The replenishing cylinders 182 are arranged in parallel in the left-right direction (direction perpendicular to the paper surface of FIG. 3) at a position directly above the rotary developing device 20. In this embodiment, the leftmost of these supply cylinders 182 is the black supply cylinder communicating with the black container 18K, and the one adjacent to the right side is for cyan. A cyan supply cylinder that communicates with the container 18C, and further adjacent to the right side is a magenta supply cylinder that communicates with the magenta container 18M, and the rightmost supply cylinder is for yellow. This is a supply cylinder for yellow communicating with the container 18Y.

  Each of the supply cylinders 182 is configured to be lifted and lowered independently of the others by a lifting mechanism (not shown), and the opening at the tip is opened and closed by an opening / closing mechanism (not shown). . Accordingly, the supply cylinder 182 corresponding to the developing device 22 is lowered by the driving of the elevating mechanism in a state where the predetermined developing device 22 is positioned in a phase facing the photosensitive drum 131, thereby the supply cylinder 182. The front end of the closing film 241 pushes the notch of the closing film 241 correspondingly and enters the developing device 22. In this state, the opening at the tip of the supply cylinder 182 is opened by driving the opening / closing mechanism, whereby the developer fed from the toner container 18 is supplied into the developing device 22.

  The developing roller 25 is installed between the left and right wall surfaces in the rotary frame 21 in parallel with the photosensitive drum 131, and a peripheral surface of the developing roller 25 faces the peripheral surface of the photosensitive drum 131. It is made to rotate by driving. Then, the developing roller 25 is rotated in the clockwise direction in FIG. 5 around the axis while facing the photosensitive drum 131, so that the toner in the developer carried by the peripheral surface thereof is counterclockwise. Supplied to the circumferential surface of the photosensitive drum 131 rotating toward the surface.

  As shown in FIG. 3, a stirring member 251 such as a spiral feeder extending in the left-right direction is provided in the developing device 22, and the developer in the developing device 22 is developed while being stirred by the stirring member 251. The toner is conveyed toward the roller 25 and is supplied from the peripheral surface to the peripheral surface of the photosensitive drum 131 by driving the developing roller 25.

  As shown in FIG. 3, the drum cleaning device 30 includes a rubbing roller 32 that cleans a casing 31 that has a rectangular shape in a side view, with a peripheral surface slidingly in contact with the peripheral surface of the photosensitive drum 131, and A blade 33 that scrapes residual toner, discharge products, and the like transferred from the peripheral surface of the photosensitive drum 131 to the peripheral surface of the rubbing roller 32 by the sliding contact of the rubbing roller 32, and the residual scraped by the blade 33. A spiral feeder 34 for carrying toner and the like to a waste toner collecting container (not shown) is provided.

  The casing 31 is provided above the transfer belt 134 at a position immediately in front of the photosensitive drum 131. The casing 31 has a rear surface provided with an opening facing the peripheral surface of the photoconductive drum 131, and the rubbing roller 32 is in contact with the peripheral surface of the photoconductive drum 131 through the opening. Yes.

  The rubbing roller 32 includes a rubbing roller shaft 321 provided between the left and right side plates of the casing 31, and a rubbing roller body 322 that is concentrically and externally fitted to the rubbing roller shaft 321. ing. The rubbing roller body 322 is made of a synthetic resin material that can be elastically deformed and has excellent toughness.

  Such a rubbing roller 32 has a peripheral speed (approximately 210 mm / sec) faster than the peripheral speed (approximately 150 mm / sec) of the photosensitive drum 131 around the rubbing roller shaft 321 (see FIG. 3). In the example shown in (1), it is rotated clockwise). Then, as the rubbing roller 32 rotates, the a-Si layer on the peripheral surface of the photoconductive drum 131 is subjected to a polishing process via an abrasive (abrasive component in the toner), whereby the a-Si layer is removed. Residual toner and discharge products are removed.

  The blade 33 scrapes off foreign matters such as discharge products adhering to the peripheral surface of the rubbing roller 32, and is formed in a plate shape by an elastic material such as rubber. The blade 33 protrudes upward from a substantially central portion in the front-rear direction of the bottom plate of the casing 31, and an upper end thereof is in contact with the circumferential surface of the rubbing roller 32. Accordingly, the foreign matter scraped off from the peripheral surface of the rubbing roller 32 is dropped into a space in the casing 31 in front of the blade 33.

  The spiral feeder 34 is disposed in a space in front of the blade 33 in the casing 31 in parallel with the rubbing roller 32. The foreign matter scraped off from the peripheral surface of the rubbing roller 32 by the blade 33 and dropped into this space is collected in a collection bottle (not shown) provided at an appropriate position in the printer main body 11 (FIG. 1) by driving the spiral feeder 34. Is done.

  As shown in FIG. 3, the belt cleaning device 40 includes a brush 41 that wipes the surface of the transfer belt 134 on a casing 41 that has a triangular shape in a side view, and a voltage that applies a voltage to the brush roller 42. An application roller 43; a blade 44 for scraping waste toner adhering to the surface of the voltage application roller 43; and a spiral feeder 45 for transporting the waste toner scraped by the blade 44 to a waste toner collection container (not shown). Is constituted by being decorated.

  The casing 41 includes a top plate 411 whose rear portion is inclined downward toward the rear, a bottom plate 412 disposed opposite to the top plate 411 at a lower portion, and between the left and right ends of the top plate 411 and the bottom plate 412. And a pair of left and right side plates 413 installed. An opening for exposing the peripheral surface of the brush roller 42 is formed between the front edge of the top plate 411 and the front edge of the bottom plate 412.

  As shown in FIG. 3, the casing 41 is assembled to the printer main body 11, with the top plate 411 facing the front lower part of the rotary developing device 20, and the brush roller 42 on the drive roller 134a. The three-dimensional shape and the installation position are set so as to face the transfer belt 134.

  The brush roller 42 has a brush shaft 421 extending in the left-right direction (a direction orthogonal to the paper surface of FIG. 3), and a large number of metal hairs of the same length made of synthetic resin are uniformly planted on the peripheral surface of the brush shaft 421. And a fur brush 422 formed as a result. After the color image on the transfer belt 134 is transferred to the paper P, the brush roller 42 rotates on the surface of the transfer belt 134 that rotates clockwise while rotating counterclockwise in FIG. Thus, residual toner remaining on the surface of the transfer belt 134 is removed.

  An unillustrated solenoid member is provided in the vicinity of the belt cleaning device 40 in order to bring the brush roller 42 into and out of contact with the transfer belt 134. The belt cleaning device 40 can change the position between a contact position where the brush roller 42 contacts the transfer belt 134 and a separation position where the brush roller 42 is separated from the transfer belt 134 by forward / reverse driving of the solenoid member. Has been.

  The voltage application roller 43 removes the residual toner that the fur brush 422 of the brush roller 42 removes and holds from the surface of the transfer belt 134 with an electrostatic suction force. The surface is disposed in contact with the tip of the fur brush 422. The voltage application roller 43 includes a metal roller shaft 431 parallel to the brush shaft 421, and a synthetic resin roller body 432, which is a dielectric material that is externally fitted to the roller shaft 431 so as to be integrally rotatable. Yes.

  A high voltage from the power supply device is applied to the roller body 432 via the roller shaft 431, whereby a charge having a polarity opposite to the polarity of the residual toner is formed on the peripheral surface of the roller body 432. As a result, the residual toner adhering to the fur brush 422 is electrostatically adsorbed on the peripheral surface of the roller body 432, and the fur brush 422 is cleaned.

  In the casing 41, the blade 44 is erected slightly obliquely toward the peripheral surface of the voltage application roller 43 from a position slightly behind the central portion in the front-rear direction of the bottom plate 412. The blade 44 adheres to the peripheral surface of the roller main body 432 by the upper edge of the blade 44 being pressed against the peripheral surface of the roller main body 432 and the voltage application roller 43 rotating around the roller shaft 431 in the counterclockwise direction in FIG. The waste toner is scraped off. The scraped-off waste toner is temporarily stored in a waste toner storage space formed behind the blade 44 and then sent out to a waste toner collection container (not shown) by driving the spiral feeder 45.

  In the present invention, the image forming unit 13 removes foreign matters such as a normal mode in which a normal image forming process is performed, and residual toner and discharge products deposited and deposited on the peripheral surface of the photosensitive drum 131. The mode can be changed between a refresh mode in which the peripheral surface of the photosensitive drum 131 is refreshed.

  Such a mode is set for the following reason. That is, when the image forming unit 13 is in the normal mode in which normal image forming processing is being performed, residual toner remaining on the peripheral surface of the photosensitive drum 131 after the transfer processing of the toner image onto the paper P, or high voltage Is applied, foreign matter such as discharge products resulting from the discharge from the charging roller 132 is attached. These foreign matters are removed by a cleaning process by the drum cleaning device 30. Is accumulated on the peripheral surface of the photosensitive drum 131, the accumulated foreign matter cannot be removed from the photosensitive drum 131 by the normal cleaning process by the drum cleaning device 30.

  Therefore, in the present invention, in order to reliably remove foreign matter accumulated on the peripheral surface of the photosensitive drum 131, normal image forming processing is temporarily interrupted, and during this interruption, foreign matter removal on the peripheral surface of the photosensitive drum 131 is performed. The refresh mode is set only for the purpose, thereby ensuring the reliable removal of foreign matter from the peripheral surface of the photosensitive drum 131.

  In the present invention, in the refresh mode, moisture adhering to the surface of the transfer belt 134 is removed so that the moisture of the transfer belt 134 does not transfer to the peripheral surface of the photosensitive drum 131.

  In such a refresh mode, black toner is used as an abrasive, while color toner other than black toner (any one of cyan toner, magenta toner, and yellow toner) is used as a water absorbing agent. This is because black toner contains iron powder, which is a magnetic material, and this iron powder functions suitably as an abrasive, so that black toner is used as an abrasive. On the other hand, color toners contain more external additives such as silica and titanium oxide than black toners, and these external additives have high water absorption and therefore contain a large amount of such external additives. The color toner is used as a water absorbing material.

  Incidentally, the toner includes a toner prepared by pulverizing a raw material, and a polymerized toner produced by polymerizing while dispersing a colorant, an additive and the like and a predetermined monomer in a medium such as water. There is. While the particles of the pulverized toner have an irregular shape, the polymerized toner has a spherical shape. Therefore, when the toner is viewed from the viewpoint of the polishing process of the photosensitive drum 131 and the water absorption process of the transfer belt 134, the pulverized toner having an irregular shape and a large surface area is more suitable than the polymerization toner having a spherical shape and a small surface area. .

  Table 1 is a list summarizing superiority and inferiority in the use of such toners as abrasives and water absorbing materials.

  In this embodiment, black toner is used for polishing the peripheral surface of the photosensitive drum 131 and color toner is used for water absorption processing of the transfer belt 134 in accordance with such characteristics of the toner. Yes. Of the color toners, which of cyan toner, magenta toner, and yellow toner has the best water absorption performance differs depending on the manufacturer and brand of the actual toner used. Therefore, in actual use, it is preferable to test in advance which color toner has high water absorption and select based on the test result.

  4 and 5 are explanatory diagrams for explaining the processing mode in the image forming unit 13, FIG. 4 is a state in which the image forming unit 13 is set to the normal mode, and FIG. The state where the forming unit 13 is set to the refresh mode is shown. FIG. 5A shows the state of charge applied to the photosensitive drum 131 and the transfer belt 134 in the polishing process in the fresh mode, and FIG. 5B shows the photosensitive drum 131 and the photosensitive drum 131 in the moisture removing process in the fresh mode. The state of charge application to the transfer belt 134 is shown.

  First, as shown in these drawings, the printer main body 11 includes a power supply device 50 that supplies power transmitted from a commercial power source to various locations in the printer 10, and a control unit 60 that controls driving of the various locations in the printer 10. And are provided.

  The power supply device 50 functions as a function related to the processing mode (normal mode and refresh mode) in the image forming unit 13 by boosting the voltage from the commercial power supply to a predetermined value, the charging roller 132, the developing roller 25, and the primary transfer roller. 135 and the secondary transfer roller 136.

  The controller 60 applies a voltage to the charging roller 132, the developing roller 25, the primary transfer roller 135, and the secondary transfer roller 136 depending on whether the image forming unit 13 is in the normal mode or the refresh mode. Configured to control the amount.

  When the image forming unit 13 is set to the normal mode as shown in FIG. 4, a positive high voltage from the power supply device 50 is applied to the charging roller 132 under the control of the control unit 60. As a result, the a-Si layer 131 'on the peripheral surface of the photosensitive drum 131 rotating counterclockwise around the axis is uniformly charged to a high voltage plus. In this state, light based on image information is irradiated from the exposure apparatus 133 to the a-Si layer 131 ', thereby reducing the positive charging potential of the a-Si layer 131' (displayed by stippling in FIG. 4). An electrostatic latent image is formed on the a-Si layer 131 ′ by the portion where the potential is lowered.

  In this state, a positive voltage from the power supply device 50 is applied to the developing roller 25. Accordingly, the positively charged toner is supplied from the developing roller 25 rotating in the clockwise direction around the axis to the low potential portion (that is, the electrostatic latent image) of the peripheral surface of the photosensitive drum 131. As a result, a toner image along the electrostatic latent image (indicated by a circled + in FIG. 4) is formed on the a-Si layer 131 ′.

  On the other hand, a negative voltage from the power supply device 50 is applied to the primary transfer roller 135. Accordingly, when the photosensitive drum 131 rotates and the toner image on the a-Si layer 131 ′ reaches the position facing the primary transfer roller 135 via the transfer belt 134 that rotates in the clockwise direction, it is charged positively. The toner image is electrostatically attracted to the negative charge of the primary transfer roller 135, thereby being peeled off from the a-Si layer 131 ′ and transferred onto the surface of the transfer belt 134.

  Residual toner remaining in the a-Si layer 131 ′ after the transfer processing is rubbed against the rubbing roller 32 of the drum cleaning device 30 by the rotation around the axis of the photosensitive drum 131. Is removed.

  Such a transfer process of a series of toner images onto the transfer belt 134 is performed for the cyan developing unit 22C, the magenta developing unit 22M, the yellow developing unit 22Y, and the black developing unit 22K for each rotation of the transfer belt 134. As a result, a color image in which cyan toner, magenta toner, yellow toner, and black toner are overcoated is formed on the surface of the transfer belt 134.

  Incidentally, until a color image is formed on the surface of the transfer belt 134, the belt cleaning device 40 is separated from the transfer belt 134, so that an incomplete toner image is not removed from the transfer belt 134. Further, until a color image is formed on the surface of the transfer belt 134, no voltage is applied to the secondary transfer roller 136, so that the toner image on the transfer belt 134 is not peeled off.

  When a color image is formed on the surface of the transfer belt 134, a negative voltage is applied from the power supply device 50 to the secondary transfer roller 136, and the sheet P is transferred to the secondary transfer roller by the timing drive of the registration roller pair 124. It is fed toward 136 and the drive roller 134a. As a result, the positively charged color image on the surface of the transfer belt 134 is electrostatically peeled off from the transfer belt 134 and transferred to the paper P.

  At the same time, the belt cleaning device 40 is brought close to the transfer belt 134, and a negative voltage from the power supply device 50 is applied to the brush roller 42 via the voltage application roller 43, whereby the brush roller 42 is negatively charged. . Accordingly, residual toner remaining on the peripheral surface of the transfer belt 134 after the color image is transferred to the paper P is cleaned by the tip of the fur brush 422 of the brush roller 42 and electrostatically applied to the fur brush 422. The surface of the transfer belt 134 is cleaned by the adsorption. The residual toner adsorbed by the fur brush 422 is transferred to the peripheral surface of the roller body 432 of the voltage application roller 43, and is scraped off by the blade 44 by the counterclockwise rotation around the roller shaft 431 of the voltage application roller 43. Collected by the spiral feeder 45.

  In contrast, when the image forming unit 13 is set to the refresh mode, the polishing step shown in FIG. 5A (the control in this step is the first control according to the present invention) and FIG. The water removal process (the control in this process is the second control according to the present invention) shown in FIG. The polishing step is a step in which black toner is used as an abrasive and the surface of the a-Si layer 131 ′ is polished by the drum cleaning device 30. The moisture removal step is a step in which color toner other than black toner (for example, cyan toner) is used as a moisture adsorbent, and moisture on the surface of the transfer belt 134 is adsorbed to the cyan toner.

  In the polishing step, as shown in FIG. 5A, the developing roller 25 of the black developing device 22K is exposed to light by rotation around the frame shaft 211 of the rotary developing device 20 based on a control signal from the control unit 60. It faces the peripheral surface of the body drum 131. In this state, a uniform exposure process is performed on the entire peripheral surface of the photosensitive drum 131 from the exposure device 133, whereby a so-called solid electrostatic latent image is formed on the entire surface of the a-Si layer 131 '.

  In this state, rotation of the photosensitive drum 131 causes black toner to be supplied from the developing roller 25 of the black developing device 22K toward the solid electrostatic latent image on the a-Si layer 131 ′. A solid image is formed with black toner.

  At the same time, a positive voltage opposite to that in the normal mode is applied from the power supply device 50 to the primary transfer roller 135. Accordingly, when the black toner solid image reaches the primary transfer roller 135 due to the rotation of the photosensitive drum 131, the positively charged solid image repels the primary transfer roller 135 with a positive voltage. The image passes through the primary transfer roller 135 without being peeled off from the a-Si layer 131 ′ of the photosensitive drum 131 and reaches the drum cleaning device 30.

  Then, the black toner on the a-Si layer 131 ′ that has reached the drum cleaning device 30 is polished between the peripheral surfaces of the rubbing roller body 322 and the photosensitive drum 131 that are rotating in opposite directions while being in sliding contact with each other. It functions as an agent, thereby removing foreign matters such as residual toner and discharge products accumulated in the a-Si layer 131 '. The removed foreign matter is carried out and collected by driving the spiral feeder 34.

  This polishing process is stopped after the photosensitive drum 131 has been rotated a preset number of rotations, and the polishing process ends. Subsequently, the moisture removal process is started.

  In the moisture removing step, first, the rotary developing device 20 is rotated based on a control signal from the control unit 60, and the developing roller 25 of the cyan developing device 22C is moved to the photosensitive drum 131 as shown in FIG. It is opposed to the peripheral surface. In this state, a uniform exposure process is performed on the entire peripheral surface of the photosensitive drum 131 from the exposure device 133, thereby forming a solid electrostatic latent image with cyan toner on the entire surface of the a-Si layer 131 '. .

  Since cyan toner is supplied from the developing roller 25 of the cyan developing device 22C toward the solid electrostatic latent image on the a-Si layer 131 ′ of the rotating photosensitive drum 131, the circumference of the photosensitive drum 131 is increased. A solid image with cyan toner is formed on the surface.

  At the same time, a negative voltage similar to that in the normal mode is applied from the power supply device 50 to the primary transfer roller 135. Accordingly, when the solid image of cyan toner reaches the primary transfer roller 135 due to the rotation of the photosensitive drum 131, the solid image charged positively is electrostatically adsorbed to the primary transfer roller 135 having a negative potential and transferred. Transition to the surface of the belt 134.

  As a result, the surface of the transfer belt 134 is covered with a solid image of cyan toner, as shown in FIG. 5B. It is physically adsorbed by the pores and removed from the surface of the transfer belt 134.

  Then, the cyan toner adsorbing moisture on the transfer belt 134 is removed from the transfer belt 134 when it reaches the belt cleaning device 40 as in the normal mode described above.

  The moisture removing process is stopped when the transfer belt 134 reaches a preset number of turns. In this stop, first, the rotation of the developing roller 25 is stopped and the supply of cyan toner from the developing roller 25 to the peripheral surface of the photosensitive drum 131 is stopped. In this state, the transfer belt 134 is slightly more than one round. Circulated. In this way, when the water removal step is completed, no toner is present on the peripheral surface of the photosensitive drum 131 and the surface of the transfer belt 134.

  FIG. 6 is a block diagram for explaining drive control of the image forming unit 13 by the control unit 60 in the refresh mode. As shown in FIG. 6, the control unit 60 includes a CPU (central processing unit) 61 that is a so-called microcomputer and a ROM (read only memory) 62 that is a read-only storage device for the CPU 61. A random access memory (RAM) 63 is provided which is readable and writable with respect to the CPU 61 and stores temporary data during calculation.

  The CPU 61 determines whether or not to change the image forming process in the image forming unit 13 from the normal mode to the refresh mode, and whether or not to change the mode from the refresh mode to the normal mode when the refresh mode is set. A mode change discriminating unit 611 for discriminating and a control signal output unit 612 for outputting a control signal to the power supply device 50 based on the discrimination result by the mode change discriminating unit 611 are provided.

  In the present embodiment, a mode change key 115 is provided at an appropriate position of the printer main body 11, and when the mode change key 115 is operated, this operation information is input to the mode change determination unit 611. The mode change determination unit 611 determines that the mode change from the normal mode to the refresh mode is performed by inputting this operation information, and outputs a command signal to the control signal output unit 612. The control signal output unit 612 to which this command signal is input outputs a control signal to the power supply device 50, thereby starting a refresh mode.

  In addition, the printer main body 11 includes a rotation number sensor 64 that detects the number of rotations of the photosensitive drum 131 at an appropriate position in the vicinity of the photosensitive drum 131 and a rotation number sensor 65 that detects the number of rotations of the transfer belt 134. The detection results of the rotation number sensor 64 and the rotation number sensor 65 are input to the mode change determination unit 611.

  On the other hand, the ROM 62 stores the number of rotations (set number of rotations) of the photosensitive drum 131 in the polishing process and the number of rotations (set number of rotations) of the transfer belt 134 in the moisture removal process. The mode change discriminating unit 611 counts the number of detections every time a detection signal from the rotation number sensor 64 is input after the image forming unit 13 is changed to the refresh mode. Is compared with the set number of rotations stored in the ROM 62, and it is determined that the polishing process is completed when the count number becomes equal to the set number of rotations.

  The determination result of the mode change determination unit 611 is output to the control signal output unit 612 as a command signal. Upon receiving this signal, the control signal output unit 612 outputs a control signal for ending the polishing process toward the power supply device 50 and also outputs a control signal for starting the moisture removal process. As a result, the image forming unit 13 performs driving related to the moisture removing process, and the moisture of the transfer belt 134 is removed.

  When the moisture removal process is started, the mode change determination unit 611 counts the number of detections every time the detection signal from the circulation number sensor 65 is input, and the count number and the ROM 62 are stored each time the count is performed. The set number of laps is compared, and it is determined that the water removal process is completed when the count number becomes equal to the set number of laps.

  The determination result of the mode change determination unit 611 is output to the control signal output unit 612 as a command signal. Upon receiving this signal, the control signal output unit 612 outputs a control signal for ending the moisture removal process to the power supply device 50 and also outputs a control signal for returning the refresh mode to the original normal mode.

  The control signal output unit 612 outputs a predetermined drive signal from the power supply device 50 toward the power supply device 50. Upon receiving this control signal, the power supply device 50 supplies predetermined power to the charging roller 132, the rotary developing device 20, the drum cleaning device 30 and the belt cleaning device 40 in accordance with the contents of the control signal, thereby The refresh mode of the image forming unit 13 is executed.

  Specifically, when the control signal output unit 612 receives a refresh mode start command signal from the mode change determination unit 611, the control signal output unit 612 first executes a polishing process in the refresh mode. A control signal for outputting a drive signal to the photosensitive drum 131, the charging roller 132, the exposure device 133, and the drum cleaning device 30 is output to the device 50, and these are caused to perform predetermined driving.

  At the same time, the control signal output unit 612 causes the power supply device 50 to output a drive signal for causing the developing roller 25 of the black developing device 22K of the rotary developing device 20 to face the peripheral surface of the photosensitive drum 131. A control signal is output accordingly. Further, the control signal output unit 612 outputs a control signal for applying a positive voltage to the power supply device 50 toward the primary transfer roller 135.

  As a result, as shown in FIG. 5A, the black toner in the black developing device 22K is driven by the developing roller 25 in a state where the developing roller 25 of the black developing device 22K faces the peripheral surface of the photosensitive drum 131. Is supplied to the peripheral surface of the photosensitive drum 131 on which the solid electrostatic latent image is formed by light irradiation from the exposure device 133 while rotating around the axis, and the peripheral surface of the photosensitive drum 131 is added with black toner. A solid image charged is formed.

  This solid image passes through a position opposed to the primary transfer roller 135 by the rotation of the photosensitive drum 131, but since the positive voltage is applied to the primary transfer roller 135, the solid image is transferred to the transfer belt 134. It proceeds to the drum cleaning device 30 as it is.

  When the black toner solid image reaches the drum cleaning device 30, the a-Si layer 131 'of the photosensitive drum 131 functions as an abrasive by driving rotation of the rubbing roller 32 around the rubbing roller shaft 321. The toner is rubbed and polished to remove foreign matters such as residual toner and discharge products accumulated in the a-Si layer 131 '.

  In the rubbing process, no drive signal is output from the power supply device 50 to the drive roller 134a of the transfer belt 134. This is because, in the rubbing process, a solid image of black toner on the peripheral surface of the photosensitive drum 131 does not transfer to the transfer belt 134, and the transfer belt 134 does not function in the rubbing process. This is because there is no need to drive 134.

  Then, when a command signal (end signal) indicating that the rubbing process is completed is input from the mode change determination unit 611 to the control signal output unit 612, the control signal output unit 612 performs the water removal process in the refresh mode. In order to change to the process, a control signal for outputting a predetermined drive signal to the power supply device 50 toward the photosensitive drum 131, the charging roller 132, the exposure device 133, the drive roller 134a of the transfer belt 134, and the belt cleaning device 40 is provided. Output.

  At the same time, the control signal output unit 612 causes the power supply device 50 to output a drive signal for causing the developing roller 25 of the cyan developing device 22C of the rotary developing device 20 to face the peripheral surface of the photosensitive drum 131. A control signal is output accordingly. Further, the control signal output unit 612 outputs a control signal for applying a negative voltage toward the primary transfer roller 135 to the power supply device 50.

  As a result, as shown in FIG. 5B, the cyan toner in the cyan developing device 22C is driven by the developing roller 25 in a state where the developing roller 25 of the cyan developing device 22C faces the peripheral surface of the photosensitive drum 131. Is supplied to the peripheral surface of the photosensitive drum 131 on which a solid electrostatic latent image is formed by light irradiation from the exposure device 133, and a solid image positively charged with cyan toner is formed on the peripheral surface of the photosensitive drum 131. Is done.

  When the solid image reaches a position facing the primary transfer roller 135 due to the rotation of the photosensitive drum 131, a negative voltage is applied to the primary transfer roller 135, so that the solid image is transferred to the transfer belt 134. As a result, the entire surface of the transfer belt 134 is covered with cyan toner by the rotation of the driving roller 134a.

  The water adhering to the surface of the transfer belt 134 is adsorbed by the cyan toner that covers the surface and functions as a water absorbing agent, thereby removing the water from the transfer belt 134.

  Then, when the cyan toner covering the surface of the transfer belt 134 reaches the belt cleaning device 40 by the rotation of the transfer belt 134, the cyan toner is removed by the brush roller 423 by the driving rotation of the brush roller 42 of the belt cleaning device 40, and the transfer belt. The surface of 134 is sequentially cleaned and returned to the photosensitive drum 131. Even if the transfer belt 134 from which the moisture has been removed is brought into contact with the peripheral surface of the photosensitive drum 131 thereafter, the occurrence of inconvenience such as transfer of moisture from the transfer belt 134 to the photosensitive drum 131 is prevented.

  When the moisture removal process is completed by a predetermined number of rotations of the transfer belt 134 set in advance, a command signal to that effect is input from the mode change determination unit 611 to the control signal output unit 612. Since the control signal output unit 612 to which the command signal is input outputs a control signal for returning from the refresh mode to the normal mode to the related parts to the power supply device 50, the image forming unit 13 changes from the refresh mode to the normal mode. Returned to

  FIG. 7 is a flowchart for explaining control of the refresh mode by the control unit 60. First, whether or not the refresh mode is set in step S1 is determined by the mode change determination unit 611. When the refresh mode is set (YES in step S1), the polishing process that is the first half of the refresh mode is started. To do.

  In the polishing process, first, the photosensitive drum 131 is rotated (step S2), and then the light irradiation is performed over the entire peripheral surface of the photosensitive drum 131 by the exposure device 133 (step S3). A solid electrostatic latent image is formed on the peripheral surface of the body drum 131. Subsequently, based on the drive signal from the power supply device 50, the developing roller 25 of the black developing device 22K of the rotary developing device 20 faces the peripheral surface of the photosensitive drum 131 (step S4).

  Next, the developing device 22 is driven (step S5), and the black toner in the black developing device 22K is supplied to the peripheral surface of the photosensitive drum 131 by the driving rotation of the developing roller 25 thereby. As a result, a solid image of black toner is formed on the peripheral surface of the photosensitive drum 131.

  Subsequently, a positive voltage is applied to the primary transfer roller 135, and the belt cleaning device 40 is driven (step S7) while the primary transfer roller 135 is positively charged (step S6). As a result, the solid image of the black toner on the peripheral surface of the primary transfer roller 135 that has reached the primary transfer roller 135 by the rotation of the photosensitive drum 131 is positively charged, so that the primary image is positively charged. It repels the transfer roller 135, passes the primary transfer roller 135 as it is, and reaches the drum cleaning device 30.

  Then, the black toner on the circumferential surface of the photosensitive drum 131 that has reached the drum cleaning device 30 serves as an abrasive that polishes the circumferential surface of the photosensitive drum 131 by the rotation of the rubbing roller 32. The peripheral surface of 131 is cleaned.

  Next, in step S8, the mode change determination unit 611 determines whether or not the polishing process as described above has been completed. When the polishing process is completed (YES in step S8), the water removal process in step S9 and subsequent steps is performed. Starts.

  In the water removal step, first, the drum cleaning device 30 is stopped (step S9), and the rotary developing device 20 is continuously rotated by the drive signal from the power supply device 50 so that the developing roller 25 of the cyan developing device 22C is moved to the photosensitive drum. It faces the peripheral surface of 131 (step S10). Next, in this state, the primary transfer roller 135 and the drive roller 134a are simultaneously driven and rotated (step S11), whereby the transfer belt 134 starts rotating. In this state, the primary transfer roller 135 is negatively charged by applying a negative voltage (step S12). In this state, the belt cleaning device 40 is driven (step S13).

  Accordingly, the solid image positively charged with cyan toner on the circumferential surface of the primary transfer roller 135 that has reached the primary transfer roller 135 by the rotation of the photosensitive drum 131 is negatively charged via the transfer belt 134 to the primary transfer roller 135. Are transferred to the surface of the transfer belt 134. As a result, moisture present on the surface of the transfer belt 134 is adsorbed by the cyan toner that functions as an adsorbent, and moisture held by the transfer belt 134 is removed.

  Then, the solid image of cyan toner formed on the surface of the transfer belt 134 is removed and collected by the driving rotation of the brush roller 42 when it reaches the belt cleaning device 40.

  When the transfer belt 134 goes around a preset number of times, the mode change determination unit 611 determines that the moisture removal process has ended (step S14), and the series of refresh modes of the image forming unit 13 ends. When the series of refresh modes is completed, the image forming unit 13 returns to the original normal mode.

  As described in detail above, the printer 10 according to the present invention sequentially supplies the color drum and the black toner of each color to the photosensitive drum 131 on which the toner image is formed on the peripheral surface, and the peripheral surface of the photosensitive drum 131, respectively. A rotary developing device 20 having a plurality of developing devices 22, a transfer belt 134 onto which toner images sequentially formed on the peripheral surface of the photosensitive drum 131 are transferred in an overlaid state, and a photosensitive member via the transfer belt 134. A primary transfer roller 135 that is disposed to face the drum 131 and electrostatically transfers toner on the peripheral surface of the photosensitive drum 131 to the surface of the transfer belt 134, and a drum cleaning device 30 that rubs the peripheral surface of the photosensitive drum 131. And a belt cleaning device 40 that cleans the surface of the transfer belt 134.

  According to the post-processing apparatus 10 having such a configuration, when the printer 10 is set in the normal normal mode, the color toner and the black toner of each color are sequentially supplied from the developing unit 22 to the photosensitive drum 131, so A toner image of one color toner is formed on the peripheral surface of the photoconductive drum 131, and this toner image is transferred to the surface of the transfer belt 134 by the action of the primary transfer roller 135, and on the peripheral surface of the photoconductive drum 131. The toner image is formed and the toner image is transferred onto the transfer belt 134 one after another for another color toner, and finally the same processing is performed with the black toner. A color image in which each color toner and black toner are overcoated is formed. The color image on the transfer belt 134 is transferred to a separately supplied sheet.

  A toner of a certain color is supplied to the photosensitive drum 131 to form a toner image of that color on the peripheral surface of the photosensitive drum 131, and after the toner image is transferred to the transfer belt 134, Residual toner remaining on the peripheral surface is removed from the peripheral surface of the photosensitive drum 131 by the rubbing process by the drum cleaning device 30 and the color image formed on the transfer belt 134 is transferred to the sheet. The surface of the transfer belt 134 is cleaned by a cleaning process by the belt cleaning device 40.

  The printer 10 includes a control unit 60 that controls a predetermined refresh mode that is set to refresh the photosensitive drum 131 and the transfer belt 134.

  In the refresh mode, the control unit 60 supplies black toner to the circumferential surface of the photosensitive drum 131 and causes the primary transfer roller 135 to have the same charge as that of the toner image on the circumferential surface of the photosensitive drum 131 (in this embodiment, After the polishing of the peripheral surface of the photosensitive drum 131 by the drum cleaning device 30 using black toner as an abrasive is completed, the color toner is supplied to the peripheral surface of the photosensitive drum 131 and the primary Control is performed so that the transfer roller 135 is set to a charge opposite to the charge of the toner image on the circumferential surface of the photosensitive drum 131 (in this embodiment, a negative charge).

  Therefore, when the printer 10 is changed to the refresh mode, first, in the polishing process in the first half of the refresh mode, first, a toner image on which the primary transfer roller 135 is formed on the circumferential surface of the photosensitive drum 131 is controlled by the control unit 60. The black toner is supplied to the entire circumferential surface of the photosensitive drum 131 in a state where the charge is set to the same charge as that of the first charge to form a so-called solid image.

  The solid image of black toner does not move from the peripheral surface of the photosensitive drum 131 to the transfer belt 134 due to electrostatic repulsion. Accordingly, the black toner of the solid image on the circumferential surface of the photosensitive drum 131 is removed from the circumferential surface of the photosensitive drum 131 by rubbing with the rubbing roller 32 of the drum cleaning device 30 after passing the transfer belt 134. Since the peripheral surface of the photosensitive drum 131 is polished by the black toner acting as an abrasive during the rubbing, foreign matters such as residual toner and discharge products deposited and deposited on the peripheral surface are removed. Is done. The used black toner is collected from the peripheral surface of the photosensitive drum 131.

  Next, after the polishing process of the peripheral surface of the photosensitive drum 131 by the drum cleaning device 30 using black toner as an abrasive is completed, a water removal process which is the latter half of the refresh mode is executed in the image forming unit 13.

  In this moisture removal step, the development is performed in a state where the primary transfer roller 135 is set to a negative charge opposite to the charge of the toner image on the peripheral surface of the photosensitive drum 131 (a positive charge in the present embodiment) under the control of the control unit 60. Color toner (cyan toner in this embodiment) is supplied from the device 22 to the peripheral surface of the photosensitive drum 131.

  Therefore, the moisture adhering to the surface of the transfer belt 134 is adsorbed by the color toner that functions as a moisture adsorbent. As a result, the surface of the transfer belt 134 becomes dry. As a result, there is no inconvenience that moisture from the transfer belt 134 moves to the peripheral surface of the photosensitive drum 131 that is in contact with the surface of the transfer belt 134. The used color toner is collected from the surface of the transfer belt 134 by the belt cleaning device 40.

  Black toner is more abrasive than color toner, but color toner has higher water absorption than black toner, and there is a complementary relationship between black toner and color toner. Therefore, only the black toner is employed for polishing the peripheral surface of the photosensitive drum 131, and only the color toner is used for moisture adsorption of the transfer belt 134, thereby maximizing the properties of both toners. Both the polishing process of the peripheral surface of the photosensitive drum 131 and the moisture removal process of the surface of the transfer belt 134 can be reliably and efficiently performed in the state of being utilized.

  The present invention is not limited to the above embodiment, and includes the following contents.

  (1) In the above embodiment, the printer 10 is employed as the image forming apparatus. However, instead of the printer 10, a copying machine or a facsimile apparatus may be employed as the image forming apparatus.

  (2) In the above-described embodiment, the transfer belt 134 that circulates between the driving roller 134a and the driven roller 134b is employed as the intermediate transfer member. However, instead of the transfer belt 134, the intermediate belt that rotates about the axis is used. A transfer roller may be used.

  (3) In the above embodiment, difficult toner is used as the water adsorbent, but magenta toner or yellow toner may be used as the water adsorbent instead of the cyan toner. As to which color toner is adopted as the moisture adsorbent, it is only necessary to test the moisture adsorption performance of each color toner actually used and to exhibit the maximum performance.

  (4) In the above embodiment, the polishing step is first performed in the refresh mode, and the water removal step is subsequently performed. However, the present invention is particularly concerned with the order of the steps in the refresh mode. There is no limitation, and the polishing step may be performed after the moisture removing step is first performed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an external perspective view showing an embodiment of a printer capable of color printing according to the present invention, in which (A) is a state where a maintenance lid is closed, (B) is a state where a maintenance lid is opened, (C) shows a state where the maintenance lid is opened and the toner container is removed. It is explanatory drawing of the side sectional view which shows one Embodiment of the internal structure of the printer shown in FIG. FIG. 3 is a partially enlarged view of FIG. 2 for explaining the rotary developing device, the drum cleaning device, and the belt cleaning device in more detail. FIG. 7 is an explanatory diagram for explaining a processing mode in the image forming unit, and shows a state in which the image forming unit is set to a normal mode. 4 shows a state in which the image forming unit shown in FIG. 4 is set to the refresh mode. FIG. 4A shows a state in which charges are applied to the photosensitive drum and the transfer belt in the polishing process in the refresh mode, and FIG. The state of charge application to the photosensitive drum and the transfer belt in the water removal step in the mode is shown. It is a block diagram for explaining drive control of the image forming unit by the control unit in the refresh mode. It is a flowchart which shows the control flow of refresh mode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Printer 101 Paper discharge conveyance path 102 Discharge roller pair 11 Printer main body 110 Front opening 111 Side plate 112 Maintenance lid 115 Mode change key 12 Paper feed part 121 Paper cassette 122 Manual feed tray 122a Support shaft 123 Pickup roller 124 Registration roller pair 13 Image forming part 131 Photosensitive drum 131 ′ a-Si layer 132 Charging roller 133 Exposure device 134 Transfer belt (intermediate transfer member)
134a Drive roller 134b Driven roller 134c Idle roller 134d Biasing member 135 Primary transfer roller 136 Secondary transfer roller 14 Fixing unit 141 Fixing roller 142 Pressure roller 143 Discharge roller pair 15 Discharge destination switching unit 151 Return roller 152 Return conveyance path 16 Discharge Paper portion 161 Discharge tray 162 Discharge port 17 Base 18 Toner container 18K Black container 18C Cyan container 18M Magenta container 18Y Yellow container 181 Conveying pipe 182 Supply cylinder 20 Rotary developing device 21 Rotating frame 210 Arc shape Casing 211 Frame shaft 212 Partition plate 22 Developing device 22K Black developing device 22C Cyan developing device 22M Magenta developing device 22Y Yellow developing device 23 Support disk 24 Receiving port 241 Closing film 25 Image roller 251 agitating member 30 a drum cleaning device (rubbing means)
31 Casing 32 Rub roller 321 Rub roller shaft 322 Rub roller body 33 Blade 34 Spiral feeder 40 Belt cleaning device (cleaning means)
41 Casing 411 Top plate 412 Bottom plate 413 Side plate 42 Brush roller 421 Brush shaft 422 Far brush 43 Voltage application roller 431 Roller shaft 432 Roller body 44 Blade 45 Spiral feeder 50 Power supply device 60 Control unit 61 CPU 611 Mode change determination unit 612 Control signal output Part 62 ROM
63 RAM 64 Number-of-rotations sensor 65 Number-of-turns sensor P Paper S1 Closed posture S2 Opened posture

Claims (2)

A photosensitive drum on which a toner image is formed on the peripheral surface;
A plurality of developing devices for sequentially supplying each color toner and black toner to the circumferential surface of the photosensitive drum;
An intermediate transfer member to which toner images sequentially formed on the peripheral surface of the photosensitive drum are transferred in an overlaid state; and
A transfer roller disposed opposite to the photosensitive drum via the intermediate transfer body and electrostatically transferring toner on the peripheral surface of the photosensitive drum to the surface of the intermediate transfer body;
Rubbing means for rubbing the peripheral surface of the photosensitive drum;
Cleaning means for cleaning the surface of the intermediate transfer member;
A control unit that performs control to refresh the photosensitive drum and the intermediate transfer member,
The control unit supplies the black toner to the peripheral surface of the photosensitive drum as the refresh process, and sets the transfer roller to the same charge as the toner image on the peripheral surface of the photosensitive drum. And a second control for supplying the color toner to the circumferential surface of the photosensitive drum and setting the transfer roller to a charge opposite to the charge of the toner image on the circumferential surface of the photosensitive drum. An image forming apparatus.   The image forming apparatus according to claim 1, wherein the intermediate transfer member is an intermediate transfer belt stretched between a pair of support rollers so as to be able to circulate.

Images