JP2005156706A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of stable image quality while preventing a toner leak although the apparatus is equipped with a rubbing roller as a cleaning means for an image carrier. <P>SOLUTION: Untransferred toner T transported on a photoreceptor drum 1 passes through a shield sheet 15 and moves toward the rubbing roller 7. Untransferred toner T transported on the rubbing roller 7 is rubbed off by a sheet member 113 and discharged getting over it. Untransferred toner T which is not rubbed off by the sheet member 13 passes through it and is circulated sticking on the rubbing roller 7 to be rubbed against the surface of the photoreceptor drum 1. The sheet member 13 sufficiently rubs excessive toner on the rubbing roller 7 so that no toner is deposited on the bottom of a cleaning container C below the rubbing roller 7, and sheet member 13 is pressed against the surface of the rubbing roller 7 with a prescribed sufficient pressing force to adjust the amount of toner on the rubbing roller 7. <P>COPYRIGHT: (C)2005,JPO&NCIPI

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 facsimile, or a printer using an electrophotographic process, and more particularly to an image forming apparatus provided with a cleaning unit that removes foreign matters adhering to the surface of an image carrier. is there.

  2. Description of the Related Art Conventionally, in such an image forming apparatus, a configuration of a cleaning unit that can prevent toner leakage due to edge chipping of a cleaning blade has been disclosed (for example, see Patent Document 1).

  Specifically, in a cleaning means comprising a cleaning blade for scraping off residual toner on the image carrier and a squee sheet for guiding the scraped residual toner to a cleaning container, a part of the cleaning member in the longitudinal direction of the image carrier is provided. The abutting sheet is provided in an exposed portion sandwiched between a portion where the cleaning blade and the image carrier abut and a portion where the squeeze sheet and the image carrier abut.

  With this configuration, the amount of residual toner once collected in the cleaning container can be reduced again on the surface of the image carrier at the exposed portion, and even if an edge defect occurs in the cleaning blade, the residual toner cleaning container It is possible to prevent leakage from toner (toner leakage).

  In addition, a configuration of an EP cartridge that can effectively prevent toner leakage even when a wavy state occurs in the shield plate is disclosed (for example, see Patent Document 2).

  Specifically, a drum-shaped latent image carrier, developing means for developing an electrostatic latent image formed on the latent image carrier with toner, and toner for collecting untransferred toner on the latent image carrier In the EP cartridge including the recovery means, the toner recovery means includes a cleaning blade that scrapes off the untransferred toner from the latent image carrier, a shield plate that receives the untransferred toner scraped off by the cleaning blade, and the shield plate And a waste toner delivery roller for feeding the untransferred toner received in step 1 to a waste toner box.

The surface portion of the shield plate that is in contact with the latent image carrier is arranged at a position that enters the lower side of the latent image carrier. According to these configurations, the toner scraped off by the cleaning blade can be always received by the shield plate even if a slight undulation state occurs on the shield plate, and toner leakage can be effectively prevented.
Japanese Patent Laid-Open No. 11-296037 JP 08-006474 A

  However, in the conventional configurations as described above, it is assumed that only a cleaning blade is provided as a cleaning unit for an image carrier (specifically, for example, a photosensitive drum), and a so-called rubbing roller is provided. The case is not considered. This rubbing roller rotates while being pressed against the photoconductive drum, and removes the deposits on the photoconductive drum, and has a structure in which toner is easily conveyed to the photoconductive drum side by the rotation. The above prior art is insufficient as a countermeasure against toner leakage.

  When the function of the rubbing roller is described again, the corona product generated by the corona discharge of the corona charger that charges the photosensitive member or transfers the toner image to the transfer member may adhere to the surface of the photosensitive member. However, it mainly removes such deposits. When the corona product adheres to the surface of the photoconductor, the surface resistance is lowered, the electrostatic latent image formed on the surface of the photoconductor is blurred, and adverse effects such as deterioration of the formed image quality occur. Such a corona product is removed by a rubbing roller to maintain good image quality.

  Specifically, an elastic roller made of silicon rubber or the like is pressed against the surface of the photoconductor and rotated to slide the photoconductor surface to remove the corona product. This method has a stable effect even when the photoreceptor is used for a long period of time. Also, a material such as paper or paper dust existing in the transfer area adheres to the surface of the photoreceptor or the toner is fixed or fused. It is an excellent method because it is also effective in removing cases.

  In the configuration using such a rubbing roller, the conventional technology as described above is not sufficient as a countermeasure against toner leakage, and also causes a problem when performing a so-called refresh mode in which the toner in the developing device is refreshed. In the refresh mode, for example, a solid black image is discarded so as to refresh the toner in the developing unit at a position between the sheets, that is, not transferred to the sheet, at the time of low density printing.

  In other words, in such a refresh mode, the old toner in the developing device is consumed without being transferred onto the paper, so the transfer efficiency to the paper is 0%, and a large amount of untransferred toner is conveyed to the rubbing roller portion. Come. Therefore, in order to discharge these toners to the waste toner box without dropping without dropping onto the paper, further countermeasures against toner leakage must be taken.

  However, the rubbing roller is originally provided to remove the deposits on the photosensitive drum, and the surface of the photosensitive drum is removed by using the abrasive component of the toner adhering to the surface of the rubbing roller. Since rubbing, it is necessary that an appropriate amount of toner adheres to the surface of the rubbing roller. For this reason, even if the toner on the rubbing roller is excessively scraped off, the rubbing on the surface of the photoconductive drum becomes insufficient, and a problem occurs due to the deposits remaining on the photoconductive drum.

  In particular, when the photosensitive drum is made of amorphous silicon, if ozone or NOx is adsorbed on the surface in addition to moisture, the toner is not surely placed on the photosensitive drum, so that the image flow due to this is remarkable. Become. Therefore, it is necessary to prevent toner leakage by scraping off excess toner while leaving an appropriate amount of toner on the rubbing roller.

  SUMMARY OF THE INVENTION In view of the above problems, the present invention provides image formation capable of maintaining stable image quality while preventing so-called toner leakage even in a configuration provided with a rubbing roller as a cleaning means for an image carrier. An object is to provide an apparatus.

  In order to achieve the above object, according to the present invention, there is provided an image forming apparatus that performs recording by transferring an image formed on an image carrier onto a sheet, and rotates while being pressed against the image carrier. An image forming apparatus provided with a rubbing roller for removing deposits on a carrier, characterized in that a sheet-like member is provided which is pressed against the rubbing roller and scrapes off excess toner on the rubbing roller. To do.

  Further, the toner amount on the rubbing roller is adjusted by switching the pressing state when the sheet-like member is pressed against the rubbing roller.

  Further, the pressing state is a pressing force. When there is a lot of excess toner on the rubbing roller, the pressing force is switched so that the excess toner is easily rubbed off by the sheet-like member. .

  Alternatively, the pressing state is an amount of extension from the nip portion (a dimension from the nip portion to the tip portion). Then, when there is a lot of excess toner on the rubbing roller, the amount of extension is reduced so that the excess toner is easily rubbed off by the sheet-like member. To do.

  According to the present invention, it is possible to provide an image forming apparatus capable of maintaining stable image quality while preventing so-called toner leakage even in a configuration including a rubbing roller as a cleaning unit for an image carrier. .

  Specifically, a sheet-like member that is pressed against the rubbing roller and scrapes off excess toner on the rubbing roller is provided. This makes it difficult for excess toner to accumulate on the lower side of the rubbing roller, thereby preventing so-called toner leakage.

  Further, the amount of toner on the rubbing roller is adjusted by switching the pressing state when the sheet-like member is pressed against the rubbing roller. This makes it difficult for excess toner to further accumulate on the lower side of the rubbing roller, and so-called toner leakage is reliably prevented.

  More specifically, the pressing force when the sheet-like member is pressed against the rubbing roller is switched. Thereby, the degree to which the toner on the rubbing roller is rubbed off by the sheet-like member can be switched.

  When there is a lot of excess toner on the rubbing roller, the pressing force is switched so that the excess toner is easily rubbed off by the sheet-like member. Thereby, even when a large amount of excess toner is generated in a case where the printing rate is high and the transfer efficiency is low as represented by the refresh mode, toner leakage is surely prevented.

  Alternatively, the amount of extension from the nip portion when the sheet-like member is pressed against the rubbing roller is switched. Thereby, the degree to which the toner on the rubbing roller is rubbed off by the sheet-like member can be switched.

  When there is a lot of excess toner on the rubbing roller, the amount of extension is reduced so that the excess toner is easily rubbed off by the sheet-like member. Thereby, even when a large amount of excess toner is generated in a case where the printing rate is high and the transfer efficiency is low as represented by the refresh mode, toner leakage is surely prevented.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present invention, first, a sheet-like member made of sheet metal or PET film or the like is pressed against the surface of the rubbing roller with its tip part slightly protruding from the nip portion, and excess toner on the rubbing roller is exposed to light. The amount of toner on the rubbing roller is adjusted so that it is not conveyed to the body drum portion.

  Secondly, the pressing force of the sheet-like member against the rubbing roller can be switched by a solenoid or the like, and in the refresh mode where a large amount of untransferred toner is generated, the sheet-like member is more strongly pressed against the rubbing roller, More toner is conveyed to the waste toner box, and the pressing force is weakened during normal printing so that toner leakage can be prevented while leaving proper toner on the surface of the rubbing roller.

  Further, the switching of the pressing force may be controlled based on the transfer efficiency estimated from the printing rate or the like, not the presence / absence of the refresh mode. Alternatively, as another method for controlling the amount of toner on the rubbing roller, the amount of extension of the sheet-like member from the nip portion may be switched depending on the presence or absence of the refresh mode or the transfer efficiency.

  FIG. 1 is a diagram schematically showing a schematic structure of an image forming apparatus of the present invention. In the figure, reference numeral 1 denotes a photosensitive drum made of, for example, amorphous silicon. Around the photosensitive drum 1, a main charger 2, an exposure device 3, a developing device 4, a transfer roller 5, a rubbing roller 7, a cleaning blade 6, and a static eliminator 8 are provided along the rotation direction. Yes. The rubbing roller 7 and the cleaning blade 6 are housed in a cleaning container C as a cleaning means. The material of the photosensitive drum is not limited to amorphous silicon, and OPC (Organic Photo Conductor) may be used.

  In the present invention, the photosensitive drum 1 made of amorphous silicon has a structure having a photosensitive layer 20 of amorphous silicon on a conductive substrate 12 as shown in FIG. The blocking layer 11, the amorphous silicon photoconductive layer 10, and the surface protective layer 9 are preferably used.

  The material for forming the photoconductive layer 10 in the photosensitive layer 20 is not particularly limited as long as it is amorphous silicon (a-Si). Preferred materials include a-Si, a-SiC, and a-SiO. , A-SiON and the like. Among these materials, a-SiC (amorphous silicon carbide) is particularly suitable as a photosensitive layer material because it has a particularly high resistance and can provide better charging ability, abrasion resistance, and environmental resistance.

  The above-described amorphous silicon photosensitive drum 1 is uniformly charged to the positive polarity by the main charger 2. As the main charger 2, a corona charger such as corotron or scorotron, a conductive roller, or the like is used. When the scorotron is used, the distance between the grid and the surface of the photosensitive drum 1 is preferably in the range of 0.4 to 0.8 mm. If this interval is too small, there is a risk of spark discharge, and if it is too large, it becomes difficult to perform charging effectively.

  After the main charging, the exposure device 3 performs image exposure by irradiating light such as laser light based on predetermined image information. By this light irradiation, the potential of the portion irradiated with light is lowered, and an electrostatic latent image is formed. The electrostatic latent image formed on the surface of the photoreceptor drum 1 is developed by the developing device 4 to form a toner image on the surface of the photoreceptor. Development by the developing device 4 may be performed by a regular development method or a reversal development method. When developing by the reversal development method, the light irradiation part by the image exposure becomes an image part, and the part not irradiated with light becomes a background part of the image. In normal development, the reverse pattern is obtained.

  As a developer used for development, a non-magnetic toner or a one-component developer composed of a magnetic toner in which magnetic powder is dispersed in a resin, a non-magnetic or magnetic toner and a magnetic carrier (for example, iron powder or ferrite) The developer is supplied to the surface of the photoreceptor by a known developing device 4 so that positively charged toner is obtained in the reverse development, and negatively charged toner is used in the normal development. Development is performed by adhering to the electrostatic latent image forming portion, and a toner image is formed.

  In the present invention, it is preferable that an abrasive is externally added to the toner regardless of whether a one-component developer or a two-component developer is used as the developer. That is, by using the toner to which an abrasive is externally added, the polishing action by the rubbing roller 7 described later is enhanced, and the water adhering to the surface of the photosensitive drum 1 can be effectively removed.

  The toner image formed as described above is transferred onto a sheet passing between the photosensitive drum 1 and the transfer roller 5 by the transfer roller 5 to which a transfer bias is applied. That is, the toner image is transferred from the surface of the photosensitive drum 1 to the surface of the sheet by an electric field formed between the photosensitive drum 1 and the transfer roller 5 by the transfer bias. Therefore, when the charging polarity of the toner image is positive (in the case of reversal development), a negative transfer bias is applied to the transfer roller 5, and when the charging polarity of the toner image is negative (in the case of regular development). A positive transfer bias is applied to the transfer roller 5.

  After the transfer of the toner image onto the paper by the transfer roller 5, the paper having the transferred toner image is introduced into a fixing device (not shown), and the toner image is fixed on the paper surface by heat and pressure. After that, it is discharged out of the device. On the other hand, after the transfer by the transfer roller 5 is completed, the photosensitive drum 1 is in frictional contact with the rubbing roller 7. As described above, the rubbing roller 7 can be rubbed and rotated with respect to the photosensitive drum 1 to remove moisture attached to the surface of the photosensitive drum 1 by the frictional contact. Therefore, as the rubbing roller 7, it is preferable to use a rubber roller such as EPDM in order to ensure a sufficient nip width (contact width) with the photosensitive drum 1.

  In order to effectively polish the surface of the photosensitive drum 1, the rubbing roller is preferably harder than, for example, the transfer roller 5 described above, and generally has a hardness of 55 to 65 ° (Asuka C). It is suitable to have. That is, by having such hardness, when the toner passes between the rubbing roller 7 and the photoreceptor drum 1, the photoreceptor (especially abrasive added to the toner) with the toner is used. The surface of the drum 1 is polished so that the attached water can be removed. If the hardness is smaller than the above range, it is difficult to effectively perform such polishing, and if the hardness is larger than the above range, it is difficult to secure a sufficient nip width necessary for polishing. It becomes difficult to perform polishing effectively.

  Furthermore, the rubber is preferably foamed rubber. That is, the use of the foam allows the toner functioning as an abrasive to be held on the surface of the roller and enables uniform and stable polishing. In this case, from the viewpoint of toner retention, the size of the foam cell is preferably about 100 to 300 μm. When magnetic toner is used as the toner, it is also effective in terms of toner retention to provide a magnet inside the rubbing roller 7. That is, since the magnetic toner can be adsorbed and held on the surface of the rubbing roller 7 by the magnetic force, moisture adhering to the surface of the photosensitive drum 1 due to wear can be effectively removed.

  After the photosensitive drum 1 comes into contact with the rubbing roller 7, the toner remaining on the surface of the photosensitive drum 1 is removed by the cleaning blade 6, and the residual charge is removed by the static eliminator 8. As the cleaning blade 6, a rubber blade made of polyurethane or the like is usually used in pressure contact with the surface of the photosensitive drum 1, but a fur brush or the like may be used as necessary. Further, as the static eliminator 8, an LED or the like is used, and the static elimination is performed by light irradiation. However, a charging roller, a corona charger, or the like may be used.

  FIG. 3 is a cross-sectional view schematically showing the vicinity of the cleaning container C of the image forming apparatus according to Embodiment 1 of the present invention. In the figure, the illustration of the cleaning blade is omitted. Further, the direction of arrow A in the figure is the rotational direction of the photosensitive drum 1, and the direction of arrow B is the rotational direction of the rubbing roller 7. In this embodiment, as shown in the figure, the sheet-like member 13 made of sheet metal, PET film or the like is placed on the side of the photosensitive drum 1 of the rubbing roller 7 with its tip part slightly protruding from the nip portion. Is pressed against the surface on the opposite side so that excess toner on the rubbing roller 7 is not conveyed to the photosensitive drum 1.

  Excess toner on the rubbing roller 7 scraped off by the sheet-like member 13 gets over the sheet-like member 13 and is guided to the adjacent discharge screw 14. Further, the rotation of the discharge screw 14 causes the toner to be conveyed in the direction perpendicular to the paper surface and carried into a waste toner box (not shown). On the other hand, a shield sheet 15 for preventing toner leakage from the cleaning container C is provided at the lower part of the rubbing roller 7 on the photosensitive drum 1 side, and the tip portion of the sheet is weakly applied to the surface of the photosensitive drum 1. In contact. Details will be described later. In the drawing, the photosensitive drum 1 and the rubbing roller 7 are drawn so as to overlap each other, but actually, the rubbing roller 7 is elastically deformed along the surface shape of the photosensitive drum 1. This also applies to FIG. 4 below.

  FIG. 4 is an enlarged cross-sectional view schematically showing the vicinity of the rubbing roller 7. In the figure, the sheet-like member 13 made of sheet metal or PET film has a bent shape with a substantially L-shaped cross section, and is composed of a rising portion 13a and a base portion 13b. The base portion 13b is fixed to the bottom surface of the cleaning container C, and the rising portion 13a rises from one end (left end in the drawing) of the base portion 13b. The rising portion 13a is pressed against the surface of the rubbing roller 7 on the side opposite to the photosensitive drum 1 side by an elastic force with the tip portion slightly protruding from the nip portion. The dimension from the nip part to the tip part is shown as D dimension.

  On the other hand, as described above, the shield sheet 15 for preventing toner leakage from the cleaning container C is provided at the lower part of the rubbing roller 7 on the photosensitive drum 1 side. It touches the surface with a weak force. A bracket 16 made of sheet metal or the like is provided below the cleaning container C. This has an inverted L-shaped bent shape with a wide cross section, and includes a rising portion 16a and a base portion 16b. The base portion 16b is fixed to the lower surface of the cleaning container C, and the rising portion 16a rises from one end (right end in the drawing) of the base portion 16b. The shield sheet 15 is attached to the outer surface of the rising portion 16a.

  In the above configuration, the untransferred toner T conveyed on the photosensitive drum 1 passes through the shield sheet 15 and then moves to the rubbing roller 7 side. The untransferred toner T remaining on the photosensitive drum 1 without shifting is scraped off by the cleaning blade 6 (not shown). Then, the untransferred toner T conveyed on the rubbing roller 7 is scraped off by the sheet-like member 13 and is guided to the discharge screw 14 (not shown) adjacent to the left side in the drawing.

  The untransferred toner T that has not been scraped off by the sheet-like member 13 circulates while passing through the toner T and remains attached to the rubbing roller 7 and is used for rubbing the surface of the photosensitive drum 1. Further, a part of the toner falls on the bottom surface of the cleaning container C below the rubbing roller 7 (more precisely, the upper surface of the base portion 13b of the sheet-like member 13) or the bracket 16. The dropped untransferred toner T is lifted and circulated again by the rubbing roller 7 and is also used for rubbing the surface of the photosensitive drum 1. The subsequent behavior of the untransferred toner T circulating on the rubbing roller 7 is the same as that of the untransferred toner T conveyed on the photosensitive drum 1.

  However, as the untransferred toner T that has fallen on the bottom surface of the cleaning container C gradually accumulates, it presses the shield sheet 15 from the inside, so the untransferred toner T gets over the shield sheet 15 and contacts the photosensitive drum 1. The untransferred toner T that has been transported on the photosensitive drum 1 falls without passing through the shield sheet 15 (collectively referred to as toner leakage). Call it.) Therefore, the toner on the rubbing roller 7 is sufficiently rubbed off by the sheet-like member 13 so that the toner does not accumulate on the bottom surface of the cleaning container C below the rubbing roller 7, and the amount of toner on the rubbing roller 7. It is necessary to adjust. Accordingly, the sheet-like member 13 is pressed against the surface of the rubbing roller 7 with an appropriate predetermined pressing force.

  FIG. 5 is an enlarged view schematically showing the vicinity of the rubbing roller 7 of the image forming apparatus according to Embodiment 2 of the present invention. In this embodiment, the pressing force of the sheet-like member 13 against the rubbing roller 7 can be switched. In the same figure, a sheet-like member 13 that is not bent is attached to the upper end portion of the flat lever member 17 and is pressed against the surface of the rubbing roller 7 with its tip portion slightly protruding from the nip portion. Yes.

  A rotation shaft 17a is provided at the lower end of the lever member 17, and is supported by a bearing on the cleaning container C side (not shown), for example, and the lever member 17 is indicated by an arrow E around the rotation shaft 17a. In addition, it is rotatable left and right, that is, in a direction away from and in proximity to the rubbing roller 7. Further, a pin 17b protrudes slightly above the center of the lever member 17 and extends in the same direction as the axial direction of the rotating shaft 17a, that is, in the direction perpendicular to the paper surface.

  The pin 17b is inserted through a hole 18ba opened at the tip of the plunger 18b of the solenoid 18. A rotating shaft 18a is provided at the lower end of the solenoid 18, which is supported by a bearing on the cleaning container C side (not shown), for example, and the solenoid 18 has left and right as shown by an arrow F around the rotating shaft 18a. It is freely rotatable. Reference numeral 18c denotes a compression coil spring which is fitted into the plunger 18b and biases the plunger 18b in a direction to push out the solenoid 18b.

  The plunger 18b is pulled or pushed out of the solenoid 18 as indicated by an arrow G when the solenoid 18 is energized ON / OFF. This figure shows a state where the plunger 18b is pushed out of the solenoid 18 by the compression coil spring 18c when the energization of the solenoid 18 is turned off. In this state, it is assumed that untransferred toner is not generated much during normal printing or the like, and the sheet-like member 13 is positioned so as to be pressed against the rubbing roller 7 with a relatively weak predetermined pressing force.

  When the printing rate is high and the transfer efficiency is low as represented by the refresh mode, a large amount of untransferred toner is generated. Therefore, at this time, when the solenoid 18 is energized, the plunger 18b is pulled into the solenoid 18 and the lever member 17 is rotated in the direction approaching the rubbing roller 7 (right rotation direction in the figure). Along with this, the solenoid 18 also rotates in the direction approaching the rubbing roller 7 (right rotation direction in the figure). Accordingly, the sheet-like member 13 is pressed against the rubbing roller 7 with a relatively strong predetermined pressing force so that the untransferred toner on the rubbing roller 7 is easily rubbed off, and a larger amount of untransferred toner becomes waste toner. It is transported to the box. Thereby, the toner amount on the rubbing roller 7 is adjusted.

  Note that the switching of the pressing force is not limited to the presence or absence of the refresh mode, but may be performed by estimating the magnitude of transfer efficiency from the printing rate. That is, when it is considered that the printing rate is high and the transfer efficiency is low and a large amount of untransferred toner is generated, the pressing force may be increased. In this embodiment, a solenoid is used for switching driving of the pressing force. However, the present invention is not limited to this, and other actuators such as a motor may be used. It may be finely controlled according to the amount of toner.

  FIG. 6 is an enlarged view schematically showing the vicinity of the rubbing roller 7 of the image forming apparatus according to Embodiment 3 of the present invention. In the present embodiment, the amount of extension of the sheet-like member 13 from the nip portion with respect to the rubbing roller 7 can be switched. In the same figure, a sheet-like member 13 that is not bent is attached to the upper end portion of the flat lever member 17 and is pressed against the surface of the rubbing roller 7 with its tip portion slightly protruding from the nip portion. Yes.

  Pins 17c and 17d project from the upper and lower ends of the lever member 17, respectively. These pins are inserted into, for example, long holes c and d on the cleaning container C (not shown), and the lever member 17 is indicated by an arrow H. Thus, it can move linearly up and down, that is, in the direction of approaching and moving away from the rubbing roller 7. A pin 17b protrudes slightly above the center of the lever member 17 and extends in the same direction as the axial direction of the pins 17c and 17d, that is, in the direction perpendicular to the paper surface.

  The pin 17b is inserted through a hole 18ba opened at the tip of the plunger 18b of the solenoid 18. A rotating shaft 18a is provided at the lower end of the solenoid 18, which is supported by a bearing on the cleaning container C side (not shown), for example, and the solenoid 18 has left and right as shown by an arrow F around the rotating shaft 18a. It is freely rotatable. Reference numeral 18c denotes a compression coil spring which is fitted into the plunger 18b and biases the plunger 18b in a direction to push out the solenoid 18b.

  The plunger 18b is pulled or pushed out of the solenoid 18 as indicated by an arrow G when the solenoid 18 is energized ON / OFF. This figure shows a state where the plunger 18b is pushed out of the solenoid 18 by the compression coil spring 18c when the energization of the solenoid 18 is turned off. This state assumes that untransferred toner is not generated much during normal printing or the like, and the amount of extension of the sheet-like member 13 from the nip portion with respect to the rubbing roller 7 (indicated by the D dimension) is relatively large. It is positioned so that

  When the printing rate is high and the transfer efficiency is low as represented by the refresh mode, a large amount of untransferred toner is generated. Therefore, at this time, when the energization of the solenoid 18 is turned on, the plunger 18 b is pulled into the solenoid 18 and the lever member 17 is lowered in a direction away from the rubbing roller 7. Along with this, the solenoid 18 also rotates in a direction away from the rubbing roller 7 (left rotation direction in the figure). Accordingly, the amount of extension of the sheet-like member 13 from the nip portion with respect to the rubbing roller 7 is made relatively small, and the untransferred toner on the rubbing roller 7 can easily get over the sheet-like member 13. A large amount of untransferred toner is conveyed to a waste toner box. Thereby, the toner amount on the rubbing roller 7 is adjusted.

  The extension amount switching is not limited to the presence / absence of the refresh mode, but may be performed by estimating the transfer efficiency from the printing rate. That is, when it is considered that the printing rate is high and the transfer efficiency is low and a large amount of untransferred toner is generated, the amount of extension may be controlled to be reduced. In this embodiment, the solenoid is used for switching the extension amount. However, the present invention is not limited to this, and other actuators such as a motor may be used. The amount may be finely controlled according to the amount of toner.

  The image carrier referred to in the claims corresponds to the photosensitive drum in the embodiment.

1 is a diagram schematically showing a schematic structure of an image forming apparatus of the present invention. FIG. 3 is a diagram schematically illustrating a layer cross-sectional structure of a photosensitive drum. FIG. 3 is a cross-sectional view schematically illustrating the vicinity of the cleaning container of the image forming apparatus according to the first embodiment. The expanded sectional view which shows typically the rubbing roller vicinity. FIG. 9 is an enlarged view schematically showing the vicinity of a rubbing roller of an image forming apparatus according to a second embodiment. FIG. 9 is an enlarged view schematically showing the vicinity of a rubbing roller of an image forming apparatus according to a third embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Main charger 3 Exposure device 4 Developing device 5 Transfer roller 6 Cleaning blade 7 Rub roller 8 Static eliminator 13 Sheet-like member 14 Discharge screw 15 Shield sheet 16 Bracket 17 Lever member 18 Solenoid C Cleaning container T Untransferred toner

Claims (6)

An image forming apparatus that performs recording by transferring an image formed on an image carrier onto a sheet,
In an image forming apparatus provided with a rubbing roller that rotates while being pressed against the image carrier and removes deposits on the image carrier,
An image forming apparatus, comprising: a sheet-like member that is pressed against the rubbing roller to rub off excess toner on the rubbing roller.   2. The image forming apparatus according to claim 1, wherein the toner amount on the rubbing roller is adjusted by switching a pressing state when the sheet-like member is pressed against the rubbing roller. .   The image forming apparatus according to claim 2, wherein the pressing state is a pressing force.   2. When the excessive toner on the rubbing roller is large, the pressing force is switched so that the excessive toner is easily rubbed off by the sheet-like member. The image forming apparatus according to 3.   The image forming apparatus according to claim 2, wherein the pressing state is an amount of extension from a nip portion.   The excess toner on the rubbing roller is switched so that the amount of extension is reduced so that the excess toner is easily rubbed off by the sheet-like member. Item 6. The image forming apparatus according to Item 5.

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