JP2008026447A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus wherein a failure where a residual toner after transfer passes through a gap between a cleaning blade and the surface of a photoreceptor drum is prevented, and charging fault due to toner deposition is prevented. <P>SOLUTION: Regarding the electrophotographic image forming apparatus A, equipped with a cleaning device 10 for scraping and removing the residual toner (t) after transfer on the surface of the photoreceptor drum 5 on the upstream side of an charger 6, the cleaning device 10 includes a cleaning housing 18, attached to the photoreceptor drum 5 so as to store the removed toner (t); and the cleaning blade 19, a base part thereof is fixed to the cleaning housing 18, and a tip free edge part 19a thereof is brought into contact with the surface of the photoreceptor drum 5 so as to scrape and remove the residual toner (t), after transfer. The cleaning blade 19 is constituted of a conductive member, and a voltage whose polarity is opposite to that of the toner (t) on the surface of the photoreceptor drum 5 is applied to the cleaning blade 19. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus including a cleaning device that scrapes and removes transfer residual toner on the surface of a photosensitive drum on the upstream side of a charger.

  Electrophotographic image forming apparatuses are widely used in image forming apparatuses such as copiers, facsimile machines, printers, or so-called multifunction machines having these functions. Among such image forming apparatuses, in the case of an image forming apparatus using a two-component (toner and carrier) developer, the surface of the photosensitive drum is uniformly charged with a corona charging type charger, and developed. In many cases, the toner remaining on the surface of the photosensitive drum after the transfer is scraped and removed by a blade type cleaning device. This blade type cleaning device is configured to scrape and remove the transfer residual toner on the surface of the photosensitive drum or the talc of the adhered paper by pressing the leading edge portion of the blade against the surface of the photosensitive drum. Part of the scraped toner or the like may float, move as the photosensitive drum rotates, and adhere to the charger grid, discharge wire, or needle electrode. For this reason, there is a problem that charging failure occurs on the surface of the photosensitive drum, and a defect occurs in image formation.

In Patent Document 1, in order to prevent the toner that has passed through the gap between the cleaning blade and the surface of the photosensitive drum from being hardened and reattached to the surface of the photosensitive drum, the cleaning blade has a two-layer structure. The surface (layer) on the downstream side of the rotation direction of the body drum is made of a conductive material, and a voltage having a polarity opposite to that of the toner is applied to the conductive material, so that the toner passing through the gap is adsorbed to the conductive material. A cleaning device is disclosed which is deposited (see column 0024 of the same patent document).
JP-A-7-181852

  The cleaning device disclosed in Patent Document 1 adsorbs and deposits toner passing through the gap between the cleaning blade and the surface of the photosensitive drum on the surface on the downstream side in the rotational direction of the photosensitive drum. Is to be removed by a service person during maintenance. However, the toner adsorbed and deposited on the surface on the downstream side in the rotation direction of the photosensitive drum in this way is removed by the service person during maintenance, but a part of it is released as the amount of accumulation increases. As described above, the concern of moving with the rotation of the photosensitive drum and adhering to the grid, discharge wire, needle electrode, etc. of the charger has not been wiped out.

  The present invention has been made in view of the above circumstances, and provides an image forming apparatus that prevents transfer residual toner and the like from slipping between the cleaning blade and the surface of the photosensitive drum, and does not cause charging failure due to toner adhesion. The purpose is to do.

  An image forming apparatus according to a first aspect of the present invention is an electrophotographic image forming apparatus provided with a cleaning device that scrapes and removes transfer residual toner on the surface of the photosensitive drum on the upstream side of the charger. Is attached to the photosensitive drum and contains the removed toner, a base is fixed to the cleaning casing, and the edge portion of the free end on the front side is brought into contact with the surface of the photosensitive drum. And a cleaning blade that scrapes and removes the transfer residual toner. The cleaning blade is made of a conductive member, and is applied with a voltage having a polarity opposite to that of the toner on the surface of the photosensitive drum.

  An image forming apparatus according to a second aspect of the present invention is an electrophotographic image forming apparatus provided with a cleaning device that scrapes and removes transfer residual toner on the surface of the photosensitive drum on the upstream side of the charger. Is attached to the photosensitive drum and contains the removed toner, a base is fixed to the cleaning casing, and the edge portion of the free end on the front side is brought into contact with the surface of the photosensitive drum. A cleaning blade that scrapes and removes transfer residual toner, and the cleaning blade includes a two-layer blade structure made of a conductive member, and an insulating layer interposed between the blade structures. The blade structure on the side is applied with a voltage having a polarity opposite to that of the toner on the surface of the photosensitive drum.

  In the second aspect of the invention, it is desirable that a voltage having the same polarity as the toner on the surface of the photosensitive drum is applied to the blade structure inside the cleaning casing. In these inventions, discharge means for discharging the stored toner to the waste toner box can be installed in the cleaning casing.

  In the image forming apparatus according to the first aspect, since the cleaning blade is made of a conductive member and a voltage having a polarity opposite to that of the toner on the surface of the photosensitive drum is applied, the cleaning blade adheres to the surface of the photosensitive drum. The residual toner and paper talc (hereinafter referred to as “toner” or the like) reaching the abutting portion of the toner is attracted to the cleaning blade, and the adhesion to the photosensitive drum is weakened. As a result, toner or the like does not slip through the cleaning blade while adhering to the surface of the photosensitive drum, and is scraped off by the edge of the cleaning blade. Is housed in a cleaning housing. When the amount of toner attracted to the cleaning blade is increased, it is released and stored in the cleaning casing. Accordingly, there is no toner that floats between the cleaning blade and the photosensitive drum between the cleaning device and the charger, and the toner moves downstream as the photosensitive drum rotates, and the charger There is no possibility of charging failure due to adhesion to the grid, discharge wire or needle electrode.

  In the image forming apparatus according to the second aspect of the invention, since a voltage having a polarity opposite to that of the toner is applied to the charger-side blade structure constituting the cleaning blade, it adheres to the surface of the photosensitive drum as described above. Thus, the toner that reaches the contact portion of the cleaning blade is subjected to a suction force toward the cleaning blade, and the adhesion force to the photosensitive drum is weakened. As a result, the toner or the like does not slip through the cleaning blade while adhering to the surface of the photosensitive drum, and is scraped off by the edge of the cleaning blade, and a part thereof is on the blade structure on the charger side. Although adhering by suction, the majority is accommodated in the cleaning housing. In this case, since another blade structure made of a conductive member exists inside the cleaning casing, it is possible to suppress the suctioned toner and the like from being collected in the edge portion. When a voltage of the same polarity as the toner is applied to the blade structure inside the cleaning case, a repulsive force acts on the toner or the like that is about to adhere to the blade structure on the charger side and collects at the edge. In this case, the toner is housed in the cleaning casing without being clogged, and the toner is more effectively prevented from clogging at the edge portion.

  In the above invention, if a discharge means for discharging the stored toner to the waste toner box is installed in the cleaning case, the stored toner in the cleaning case is sequentially discharged by operating the discharge means as appropriate. It is also possible to prevent the removed toner or the like from reattaching to the edge portion of the cleaning blade.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a schematic longitudinal sectional view showing an embodiment of an image forming apparatus according to the present invention, FIG. 2 is an enlarged conceptual view of the main part, FIG. 3 is an enlarged view of a portion X in FIG. 2, and FIG. It is a figure similar to FIG. 3 of a form.

  The image forming apparatus A shown in FIG. 1 is illustrated by taking a printer having an electrophotographic recording unit as an example. However, the image forming apparatus A is not limited to this, and is not limited to this. Needless to say, it may be a so-called multifunction machine or the like. In the figure, the apparatus main body 1 of the image forming apparatus A includes a recording paper (paper) feeding unit 2, an electrophotographic image recording unit 3, and a printed recording paper discharging unit 4 in this order. Layered in the height direction. The recording paper feeding unit 2 includes a detachable paper feeding cassette 2a capable of accumulating and storing a large number of recording papers, a separation paper feeding roller 2b installed at the front end in the paper feeding direction of the paper feeding cassette 2a, The separation pad 2c is elastically contacted with the peripheral surface of the separation sheet feeding roller 2b.

  The image recording unit 3 includes a corona charging type charger 6, an exposure unit 7 made up of an LED, a developing unit 8, a transfer roller (transfer unit) 9, and a residual toner cleaning device 10 around the photosensitive drum 5. The process units are arranged in this order, and the fixing device 11 on the downstream side thereof. These process units, except for the exposure device 7 and the transfer roller 9, develop the drum unit 50 including the photosensitive drum 5, the charger 6 and the residual toner removing device 10 together, the developer container, the stirrer, the developing roller, and the like. The drum unit 50 and the developer unit 80 are detachably attached to the apparatus main body 1 from the front side of the apparatus unit 1 or in a state where they are connected by some connecting means. Is done. It is also possible to make all the process parts except the exposure device 7 and the transfer roller 9 collectively a process unit. Here, the front side of the apparatus main body 1 refers to the front side of the sheet in FIG.

  The developing unit 80 shown in the figure is a developing unit using a two-component developer, and contains toner and a carrier in a developing unit housing 81 that also serves as a resin-molded developer container. The developer is supplied to the developing roller 85 biased by the supply paddle 84 while being stirred and transported by the stirring and transporting screws 82 and 83. A magnetic sensor 86 is attached to the outer surface of the developing device housing 81, and the toner concentration (mixing ratio of toner and carrier) in the developing device housing 81 is always detected. The toner hopper 12 is installed at a position away from the developing unit 80, and when the magnetic sensor 86 detects that the toner concentration in the developing unit housing 81 is lowered, the screw conveyor (pipe screw) 13 is moved. Thus, the toner is supplied into the developing device housing 81. In the toner hopper 12, an agitator 12a and a feeding screw 12b are disposed. The cleaning device 10 will be described later.

  On the downstream side of the fixing device 11, a switching gate 4a, a discharge roller pair 4b, and a discharge tray 4c are connected in series, and the discharge unit 4 is configured by these. A registration roller pair 14 is disposed in the vicinity of the upstream side of the process section, and the recording paper (paper) separated and fed out from the paper feed cassette 2a one by one by the action of the separation paper feed roller 2b and the separation pad 2c. Is registered by the registration roller pair 14 and introduced into the mating portion between the photosensitive drum 5 and the transfer roller 9. The surface of the photosensitive drum 5 is negatively charged by the charger 6 while rotating in the direction of the arrow in FIG. 2, and an optical image based on the image information is irradiated to the surface of the photosensitive drum 5 by the exposure device 7. An electrostatic latent image is formed on the surface of the photosensitive drum 5. This electrostatic latent image is formed by changing the potential of the light irradiated portion and maintaining the potential of other portions depending on the characteristics of the photoconductor on the surface of the photosensitive drum 5.

  The electrostatic latent image is successively developed by a developing device 8 to which a bias is applied, and reaches a matching portion between the photosensitive drum 5 and the transfer roller 9 as a toner image. During this development, toner is attracted to the photosensitive drum 5 due to a potential difference with the developing unit 8 at a portion where the potential has changed due to light irradiation, so that a black portion is formed. As a result, a black and white toner image based on the image information is formed. The registration roller pair 14 is rotationally driven under registration control so that the recording paper is introduced into the mating portion in synchronization with the toner image on the surface of the photosensitive drum 5.

  A bias is applied to the transfer roller 9, and the recording paper is nip-conveyed while being paired with the photosensitive drum 5 and being rotationally driven in the direction indicated by the arrow (with respect to the photosensitive drum 5). The toner image is transferred onto the recording paper. The toner remaining on the surface of the photosensitive drum 5 is removed and collected by the cleaning device 10. The recording paper onto which the toner image has been transferred is introduced into the fixing device 11 and fixed as a permanent image, and then the switching gate 4a is pushed up and discharged onto the discharge tray 4c through the discharge roller pair 4b. This series of recording paper feeds rises substantially vertically (vertically) immediately after feeding from the paper feed cassette 2a, and the discharge roller pair 4b makes a U-turn in a direction of about 180 degrees from the feed direction from the paper feed cassette 2a. This is done along the main feeding path P. With such a layout configuration, the entire apparatus can be made compact.

  The image forming apparatus A shown in the figure has a double-sided recording function, and circulates and joins the main feeding path P upstream of the registration roller pair 14 from the mounting position of the switching gate 4a of the main feeding path P. A reverse feeding path P1 is formed. The discharge roller pair 4b can be rotated forward and backward, and the reverse feed path P1 is provided with a pair of transport rollers 15 and 16, and when performing double-sided recording, single-sided recording was performed as described above. When the recording paper is conveyed along the main feed path P and the trailing edge of the recording paper reaches the discharge roller pair 4b, the discharge roller pair 4b temporarily stops and nips the trailing edge of the recording paper. Next, the discharge roller pair 4b is reversed, and the recording paper is conveyed from the rear end thereof by the conveying roller pairs 15 and 16 through the reverse feeding path P1, and joins the main feeding path P to reach the registration roller pair 14. It is registered by the registration roller pair 14 and is again introduced into the mating portion of the photosensitive drum 5 and the transfer roller 9 to record the back surface thereof. The recording paper recorded on both sides is then discharged onto the discharge tray 4c along the main feeding path P as described above.

  The image forming apparatus A shown in the figure is further provided with a manual paper feed function, and a manual feed tray 17 that can be opened and closed vertically is attached to the side of the apparatus main body 1. When not in use, the manual feed tray 17 is closed as shown by a two-dot chain line in FIG. 2, and can be opened and closed by a handle 17a. A separation feed roller 17b and a separation pad 17c are arranged in a resilient contact state at the front end of the manual feed tray 17, and a manual feed path P2 that joins the main feed path P is further downstream. It is connected continuously.

  When image recording is performed using the manual feed tray 17, the handle 17a is opened to open the manual feed tray 17, a recording paper is set thereon, and the manual feed roller 17b is operated by a start operation as appropriate. . The recording paper on the manual feed tray 17 is separated and fed out one by one by the action of the separation paper feed roller 17b and the separation pad 17c, is conveyed through the manual feed path P2, and joins the main feed path P. . Thereafter, the image is registered by the registration roller pair 14 and introduced into the mating portion between the photosensitive drum 5 and the transfer roller 9 to perform recording. When double-sided recording is performed on the manual recording sheet, the recording sheet is conveyed through the reverse feeding path P1 by the reverse rotation of the discharge roller pair 4b, and the back side recording is performed as described above. The recording paper on which recording has been completed is discharged onto the discharge tray 4c by the discharge roller pair 4b.

  Next, the cleaning device 10 incorporated in the image forming apparatus A will be described with reference to FIGS. The cleaning device 10 shown in the figure has a cleaning housing 18 constituting a part of a unit housing of the drum unit 50, a base portion fixed to the cleaning housing 18, and an edge portion 19a at the free end of the front side as a photosensitive drum 5. The cleaning blade 19 scrapes and removes toner and the like by being brought into contact with the surface and the discharging means 20 for the contained toner and the like installed in the cleaning casing 18. The cleaning casing 18 also serves as a storage container for removed toner and the like, and an opening 18 a formed on one side thereof is arranged along the surface of the photosensitive drum 5. A cleaning blade 19 is fixed to the edge of the opening 18a on the charger 6 side with its base portion. Further, a scooping sheet 21 for preventing leakage of stored toner or the like is attached to the edge of the opening 18a on the transfer unit 9 side. In the cleaning housing 18, a discharge means 20 including an impeller 20a and a discharge screw 20b is installed. The discharge screw 20b is connected to a waste toner conveying screw 23 (both shown in FIG. 1) leading to a waste toner box 22 attached to the front side of the toner hopper 12, and the toner contained in the cleaning case 18 is The impeller 20a, the discharge screw 20b, and the waste toner conveying screw 23 are operated to be discharged into the waste toner box 22 as needed.

  The cleaning blade 19 is made of, for example, a conductive member in which carbon black is dispersed in urethane sponge (urethane rubber), and an edge portion 19 a at the front free end thereof is rotated in the rotation direction with respect to the surface of the photosensitive drum 5. Elastically abuts in a state opposite to (counter state). A positive electrode voltage is applied to the cleaning blade 19 by the voltage applying means 24. Since the surface of the photosensitive drum 5 is negatively charged by the charger 6 as described above, the toner or the like has a negative polarity, so that the cleaning blade 19 has a polarity opposite to that of the toner or the like. Incidentally, in the case of the positive charging method, the voltage application of the cleaning blade 19 has a negative polarity.

  Thus, the sheet is fed to the mating portion between the photosensitive drum 5 and the transfer unit 9 and the toner image on the surface of the photosensitive drum 5 is transferred onto the sheet, and the surface of the photosensitive drum 5 is slightly changed. Transfer residual toner and talc, which is a component of the paper, are attached. When these adhering toners t reach the cleaning device 10 along with the rotation of the photosensitive drum 5, the edge portion 19 a of the cleaning blade 19 is in relative sliding contact with the surface of the photosensitive drum 5. The surface of the photosensitive drum 5 is scraped and removed. Since a voltage having a polarity opposite to that of the toner t is applied to the cleaning blade 19, the adhesion force to the surface of the photosensitive drum 5 is weakened and the toner t is likely to be released from the surface of the photosensitive drum 5. The scraping and removal are surely performed, and the toner or the like t does not slip through between the cleaning blade 19 and the surface of the photosensitive drum 5. Part of the scraped toner t and the like adheres to the cleaning blade 19 by the suction action, but most of the toner is accommodated in the cleaning casing 18. The toner t attached to the cleaning blade 19 is also released from the cleaning blade 19 and stored in the cleaning casing 18 as the amount thereof increases. The accommodated toner t is discharged to the waste toner box 22 as needed by the operation of the discharge means 20 and the like, and is appropriately processed.

  As described above, since the toner t does not slip between the cleaning blade 19 and the surface of the photosensitive drum 5, toner or the like accompanying the rotation of the photosensitive drum 5 is near the charger 6 on the downstream side. There is no floating, therefore, toner or the like does not adhere to the grid 6a of the charger 6, the discharge electrode (needle electrode in the illustrated example) 6b, etc., and charging failure does not occur.

  FIG. 4 shows a cleaning device 10 according to another embodiment, in which a cleaning blade 19 is laminated and integrated between a two-layer blade structure 19A, 19B made of a conductive member and the blade structure 19A, 19B. The blade structures 19A and 19B are made of a conductive member in which carbon black is dispersed in urethane sponge (urethane rubber) as described above. The insulating layer 19C is made of urethane sponge not containing carbon black and other insulating elastic materials. A positive polarity voltage is applied to the blade structure 19A on the charger 6 side by the voltage application means 24, and a negative voltage is applied to the blade structure 19B inside the cleaning casing 18 by the voltage application means 25. ing.

  Similarly to the above, when toner t or the like adhering to the surface of the photosensitive drum 5 after the transfer reaches the cleaning device 10 along with the rotation of the photosensitive drum 5, the edge portion 19 a of the cleaning blade 19 is placed on the surface of the photosensitive drum 5. Since they are in relative sliding contact with each other, they are scraped and removed from the surface of the photosensitive drum 5 by this action. Since a voltage having a polarity opposite to that of the toner t is applied to the blade structure 19A on the charger 6 side, the adhesion force of the toner t to the surface of the photosensitive drum 5 is weakened and the surface of the photosensitive drum 5 is reduced. And the scraping and removal are surely performed, so that the toner or the like t does not slip through between the cleaning blade 19 and the surface of the photosensitive drum 5. At this time, the toner t removed by scraping is accommodated in the cleaning casing 18, but a suction force to the blade structure 19 </ b> A acts on the toner t. However, since the voltage having the same polarity as that of the toner t is applied to the blade structure 19B located inside the cleaning casing 18 through the insulating layer 19C, the toner t that has been scraped off is repelled. Thus, it is accommodated in the cleaning casing 18 without accumulating in the edge portion 19a.

  Also in this embodiment, since toner or the like t does not slip between the cleaning blade 19 and the surface of the photosensitive drum 5, the photosensitive drum 5 is rotated in the vicinity of the charger 6 on the downstream side. There is no floating of toner or the like. Therefore, the toner or the like does not adhere to the grid 6a or the discharge electrode 6b of the charger 6, and charging failure does not occur. In addition, since toner or the like t does not accumulate in the edge portion 19a, toner clogging does not occur, and smooth rotation of the photosensitive drum 5 is maintained. Even when the voltage is not applied to the blade structure 19B located inside the cleaning housing 18, the conductive blade structure 19B and the blade structure 19A on the charger 6 side are laminated and integrated through the insulating layer 19C. Accordingly, accumulation of toner or the like t at the edge portion 19a is prevented. Since other configurations are the same as those of the above embodiment, common portions are denoted by the same reference numerals, and description thereof is omitted here.

  Although an example in which the charger is a corona charging method has been described, if there is a concern that charging failure due to floating toner may occur even in other charging method chargers, such charging can be achieved by applying the present invention. The problem of defects can be solved. Further, although a system using a two-component developer has been exemplified as the developing device, the present invention is not limited to this and can be applied to a single-component development system.

1 is a schematic longitudinal sectional view showing an embodiment of an image forming apparatus of the present invention. It is an expansion conceptual diagram of the principal part. It is an enlarged view of the X section in FIG. It is a figure similar to FIG. 3 of other embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 5 Photosensitive drum 6 Charging device 10 Cleaning apparatus 18 Cleaning housing | casing 19 Cleaning blade 19A Blade structure 19B Blade structure 19C Insulating layer 20 Discharge means 22 Waste toner box A Image forming apparatus t Toner etc.

Claims (4)

An electrophotographic image forming apparatus including a cleaning device that scrapes and removes transfer residual toner on the surface of the photosensitive drum on the upstream side of the charger,
The cleaning device is attached to the photosensitive drum and contains a cleaning housing for storing the removed toner, and a base is fixed to the cleaning housing, and an edge portion of a free end on the front side is brought into contact with the surface of the photosensitive drum. And a cleaning blade that scrapes and removes the transfer residual toner. The cleaning blade is made of a conductive member, and is applied with a voltage having a polarity opposite to that of the toner on the surface of the photosensitive drum. Forming equipment. An electrophotographic image forming apparatus including a cleaning device that scrapes and removes transfer residual toner on the surface of the photosensitive drum on the upstream side of the charger,
The cleaning device is attached to the photosensitive drum and contains a cleaning housing for storing the removed toner, and a base is fixed to the cleaning housing, and an edge portion of a free end on the front side is brought into contact with the surface of the photosensitive drum. A cleaning blade that scrapes and removes the transfer residual toner. The cleaning blade includes a two-layer blade structure made of a conductive member and an insulating layer interposed between the blade structures. An image forming apparatus, wherein a voltage having a polarity opposite to that of the toner on the surface of the photosensitive drum is applied to the blade structure on the charger side. The image forming apparatus according to claim 2.
The image forming apparatus according to claim 1, wherein a voltage having the same polarity as the toner on the surface of the photosensitive drum is applied to the blade structure inside the cleaning casing. The image forming apparatus according to any one of claims 1 to 3,
An image forming apparatus, wherein a discharge unit for discharging the stored toner to a waste toner box is installed in the cleaning casing.

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