JP4961142B2 - Image forming apparatus - Google Patents

Description

The present invention relates to images forming device.

  Conventionally, in an electrophotographic image forming apparatus, an image carrier that is a member to be cleaned, such as an image carrier or an intermediate transfer member, is not adhered to the surface after a toner image is transferred to a recording member or another image carrier. Necessary transfer residual toner is removed by a cleaning device. As a cleaning member of this cleaning device, one using a cleaning blade is well known because it can generally be simplified in configuration and has excellent cleaning performance.

  Further, in order to meet the recent demand for higher image quality, an image forming apparatus using a nearly spherical toner (hereinafter referred to as “spherical toner”) formed by a polymerization method or the like is known. This spherical toner has characteristics such as higher transfer efficiency than conventional pulverized toner (unshaped toner), and is known to be able to meet the recent demand for higher image quality. However, as shown in FIG. 10, the spherical toner is dammed up by the cleaning blade 102, and then rolls by the frictional force with the photosensitive member 101 and slips through the cleaning blade 102, thereby deteriorating the cleaning performance.

  On the other hand, there is an electrostatic brush cleaning method as a cleaning method having a reliable cleaning property even when cleaning a small particle size toner or a spherical toner. FIG. 11 is a schematic configuration diagram of an electrostatic brush cleaning device. The electrostatic brush cleaning device 110 disposes the toner from the brush by disposing the conductive brush roller 111 so as to contact and rub against the surface of the photosensitive member 101 and repelling the toner adhering to the brush of the conductive brush roller 111. Flicker 112 is provided as a removing means. A voltage is applied to the conductive brush roller 111 from the power supply 113, and the toner is removed from the photosensitive member by an electrostatic force in addition to the rubbing force. For this reason, the cleaning performance can be obtained even with respect to a small particle size toner or a spherical toner.

  In general, in an image forming apparatus, a toner having a polarity opposite to that of a developed toner is applied in a transfer process to transfer the toner on the photoreceptor, so that the toner remaining on the photoreceptor after the transfer is the toner polarity after development. It is a mixture of the toner as it is and the toner charged to the opposite polarity. As a cleaning device for cleaning this bipolar mixture, a cleaning device 120 as shown in FIG. 12 has been proposed. That is, the first conductive brush roller 121 to which a positive voltage is applied and the second conductive brush roller 172 to which a negative voltage is applied are arranged and cleaned for each polarity toner.

  However, two conductive brush rollers 121 and 122 are arranged opposite to the photoconductor 101, and further, collecting devices 123 and 124 for collecting toner adhering to the respective brushes are arranged in the image forming apparatus. It is difficult to achieve the problem of miniaturization. Therefore, Patent Document 1 proposes a cleaning device that includes a conductive brush roller that cleans toner for each polarity toner without increasing the size. In the conductive brush roller of Patent Document 1, a positive bias is applied to a plurality of conductive nappings, and a negative bias is applied to the first region where the plurality of nappings have a positive potential and napping. Thus, the plurality of raised hairs are divided into second regions having a negative potential. Then, the brush roller divided into the positive and negative areas is rotated so that each of the brush rollers comes into contact with the surface of the photoconductor, and cleaning is performed for each polar toner from the surface of the photoconductor. Accordingly, it is only necessary to arrange one brush roller so as to face the image carrier, and this is advantageous in terms of downsizing.

JP 2005-157374 A

  In the electrostatic brush cleaner of Patent Document 1, the first region having a positive potential and the second region having a negative potential are configured by a plurality of raised portions that can be easily deformed. When the contact with the photosensitive member occurs, the raised hair is deformed, and the raised hair in the first region and the raised hair in the second region may come into contact with each other and leak. If the leakage occurs, the potentials of the first region and the second region decrease, and the transfer residual toner cannot be electrostatically adsorbed by the brush, resulting in a problem of defective cleaning. For this reason, it is conceivable that the raising is coated with an insulating member to prevent leakage even if the raising in the first region and the raising in the second region come into contact with each other. However, when the insulating coating disappears due to wear over time, the conductive portions of the brushed portions are exposed, and if the exposed portions are in contact with each other, there is a problem of leakage.

The present invention has been made in view of the above problems, and the object of the present invention is to reduce the size of the device and to include a first region having a positive potential and a second region having a negative potential. contact with and to provide the images forming apparatus that can be prevented from leaking.

To achieve the above object, the invention of claim 1 includes an image carrier, a charging device for charging the image carrier, a latent image forming device for forming an electrostatic latent image on the image carrier, Development device for developing toner by attaching toner to electrostatic latent image on image carrier, transfer device for transferring toner image on image carrier to transfer material, and cleaning device for cleaning image carrier The cleaning device has a first region having a positive potential and a second region having a negative potential on the surface, and is brought into contact with the image carrier for cleaning. A cleaning roller that forms a nip and electrostatically removes toner on the surface of the image carrier is provided. The toner has a shape factor SF-1 in the range of 100 to 150 and a particle size of 5 [μm. ] And 10 [μm] or less, and the image carrier and the above When the image carrier surface movement direction and the cleaning roller surface movement direction are the same in the region facing the cleaning roller, the linear velocity of the image carrier is Vd, and the linear velocity of the cleaning roller is Vc. 0.5 ≦ Vc / Vd ≦ 1.5, the cleaning nip width is set to 1 [mm] or less, and the pitch between the first region and the second region is set to 10 μm or more and 500 μm or less , The image carrier surface is configured to come into contact with the first region and the second region while passing through the cleaning nip, and an electric field formed between the first region and the second region. Then, the transfer residual toner on the surface of the image carrier is moved to a region having a potential opposite to the charged polarity of the toner, and is adhered to the region having a potential opposite to the charged polarity of the toner. It is characterized in that the removal from the surface.
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the cleaning device contacts the cleaning roller, blocks the toner adhering to the cleaning roller, and charges the toner on the surface of the cleaning roller. A scraper member is provided to face a region having a polarity different from the polarity.
According to a third aspect of the present invention, in the image forming apparatus of the second aspect, the scraper member is brought into contact with the cleaning roller so that one of the scraper member and the cleaning roller is elastically deformed. It is a feature.
According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the cleaning device includes a first electrode to which a positive bias is applied to the first region, and the second region. Is provided with a second electrode to which a negative bias is applied, and is electrically connected to a first power source that applies a positive bias to one end of the surface of the cleaning roller, and the positive electrode is connected to the first electrode. A first feeding electrode for feeding a bias and a second power source for applying a negative bias to the other end of the surface of the cleaning roller are electrically connected to feed the negative bias to the second electrode. The second power supply electrode is provided.
According to a fifth aspect of the present invention, in the image forming apparatus of the fourth aspect, the first electrode and the second electrode are formed by printing conductive ink on the surface of the cleaning roller by an ink jet method. It is a feature.
According to a sixth aspect of the present invention, in the image forming apparatus of the fourth aspect, the first electrode and the second electrode are formed by a photolithography method.

  According to the first to twelfth aspects of the present invention, the negatively charged toner on the surface of the image carrier is removed in the first region having the positive potential on the surface of the cleaning roller, and the negative potential on the surface of the cleaning roller is obtained. By removing the positively charged toner in the second region, it is possible to remove the bipolar toner on the surface of the photoreceptor with a single cleaning roller. Therefore, the apparatus can be reduced in size as compared with the case where two rollers to which positive and negative voltages are respectively applied are arranged. In addition, since the first region and the second region are formed on the surface of the cleaning roller, the first region and the second region are compared with those in which the first region and the second region are formed by a plurality of brushed brush brushes. Can be prevented from coming into contact with each other. Therefore, leakage caused by contact between the first region and the second region can be suppressed, a decrease in potential of the first region and the second region can be suppressed, and good cleaning performance can be maintained. Can do.

According to the onset bright, to remove the charged toner to the negative polarity of the image bearing member surface in the first region having a positive polarity of the potential of the cleaning roller surface, the second region having a negative potential of the cleaning roller surface By removing the positively charged toner, the bipolar toner on the surface of the photosensitive member can be removed with one cleaning roller. Therefore, the apparatus can be reduced in size as compared with the case where two rollers to which positive and negative voltages are respectively applied are arranged. In addition, since the first region and the second region are formed on the surface of the cleaning roller, the first region and the second region are compared with those in which the first region and the second region are formed by a plurality of brushed brush brushes. Can be prevented from coming into contact with each other. Therefore, leakage caused by contact between the first region and the second region can be suppressed, a decrease in potential of the first region and the second region can be suppressed, and good cleaning performance can be maintained. Can do.

  In the printer having the above configuration, the photosensitive member 1 whose surface is uniformly charged by the charging roller 2a of the charging device 2 forms an electrostatic latent image by the exposure device 3, and forms a toner image by the developing device 6. The toner image is transferred from the surface of the photoreceptor 1 to the transfer paper P conveyed from the paper feed tray 4 by the transfer device 5.

  Below the transfer device 5, a paper feed cassette 4 that stores a plurality of transfer papers P as recording bodies is disposed. The paper feed cassette 4 rotates the paper feed roller 4a pressed against the uppermost transfer paper P at a predetermined timing, and feeds the transfer paper P to the paper feed path. In the paper feed conveyance path, the transferred transfer paper P passes through the plurality of conveyance roller pairs 13 and then is sandwiched between the rollers of the registration roller pair 14 and stopped. The registration roller pair 14 faces the transfer nip between the transfer roller 12a and the photoconductor 1 at a timing at which the sandwiched transfer paper P can be superimposed on the toner image formed on the photoconductor 1 as described above. Send it out. As a result, the toner image on the photosensitive member 1 and the transfer paper P sent out by the registration roller pair 14 are brought into close contact with each other at the transfer nip. Then, it is electrostatically transferred onto the transfer paper P due to the influence of the transfer voltage.

  A paper transport belt 12 is wound around the transfer roller 12a, and the paper transport belt 12 is stretched between the transfer roller 12a and the drive roller 12b, and moves endlessly counterclockwise in the drawing. Further, a fixing device 9 and a discharge roller pair 10 are sequentially disposed on the left side of the paper conveying belt 12. The transfer paper P on which the above-described toner image has been electrostatically transferred is fed onto the paper transport belt 12 and then enters the fixing device 9. The transfer paper P that has entered the fixing device 9 is subjected to heat treatment and pressure treatment. As a result, the toner is thermally melted under pressure and the toner image is fixed on the transfer paper P. Then, the transfer paper P is discharged from the fixing device 9 to the paper discharge tray 15 through the paper discharge roller pair 10.

  The toner remaining on the photosensitive drum without being transferred is collected by the cleaning device 7.

  The photosensitive member 1, the developing device 6, the charging device 2, the cleaning device 7, and the like arranged around the photosensitive member 1 may be configured as a process cartridge. This process cartridge is detachable from the printer body. Therefore, when the life of a component housed in the process cartridge comes to an end or maintenance is necessary, the process cartridge may be replaced, and the convenience is improved.

  FIG. 2 is an enlarged configuration diagram showing the cleaning device 7. The cleaning device 7 includes a cleaning roller 71, a scraper member 73, and a transport unit 74. The cleaning roller 71 is brought into contact with the photoreceptor 1 to form a cleaning nip. The cleaning roller 71 is driven to rotate counterclockwise in the figure by driving means (not shown) so as to move in the same direction as the surface of the photoreceptor 1 at this nip. The plate-shaped scraper member 73 is disposed so that the edge at the tip thereof is brought into contact with the cleaning roller with a predetermined pressure. Further, the conveying means 74 is disposed below the scraper member 73 in the direction of gravity.

  FIG. 3 is a schematic configuration diagram of the cleaning roller 71. The cleaning roller 11 is formed with an elastic layer made of an elastic member such as foamed urethane rubber on a cylindrical metal core, and an insulating surface layer such as polyimide is formed on the elastic layer. The surface layer is provided with a plurality of first electrodes 71a to which a positive bias is applied and a plurality of second electrodes 71b to which a negative bias is applied. The first electrode 71a extends in the axial direction from a first connection electrode 71c provided at the left end of the cleaning roller 71 in the figure, and the second electrode 71b is provided at the right end of the cleaning roller 71 in the figure. The two connection electrodes 71d extend in the axial direction. The first electrode 71 a and the second electrode 71 b are arranged on the surface of the cleaning roller 71 so as to alternate. When a positive bias is applied to the first electrode 71a, the surface of the cleaning roller on which the first electrode is disposed becomes a first region 71e having a positive potential. In addition, when a negative bias is applied to the second electrode 71b, the surface of the cleaning roller on which the second electrode is disposed becomes a second region 71f having a negative potential. Then, by providing the first electrode and the second electrode alternately, as shown in FIG. 4, a strong electric field is formed between the first region 71e and the second region 71f. By the electric field formed between these regions, the transfer residual toner charged to the positive or negative polarity on the surface of the photoreceptor can be attracted to the cleaning roller 71 by being attracted to the first region 71e or the second region 71f.

  The first connection electrode 71c is in contact with a connection portion 701a of a first power source 701 that applies a positive bias to the first electrode 71a, and the second connection electrode 71d has a negative polarity with respect to the second electrode 71b. A connection portion 702a of the second power source 702 to which a bias is applied is in contact. The voltage applied to the first electrode 71a and the second electrode 71b is set to a voltage that does not discharge. In this embodiment, the electrode pitch is 100 [μm], a voltage of +500 [V] is applied to the first electrode 71a, and a voltage of −500 [V] is applied to the second electrode 71b. The first electrode 71a and the second electrode 71b do not have to be exposed from the surface of the cleaning roller 71, and a protective layer that covers the first electrode 71a and the second electrode 71b is provided on the surface layer of the cleaning roller 71. May be. By providing the protective layer, it is possible to suppress wear of the electrode due to frictional force with the scraper member 73 and the photoreceptor. Further, it is desirable to reduce the surface friction coefficient, for example, by forming the protective layer with a material having a low surface energy. Thereby, it can suppress that a protective layer wears out with the frictional force with the scraper member 73 or a photoconductor, or that dirt adheres to the surface. In addition, if the surface of the protective layer is triboelectrically charged, the electric field between the electrodes may be hindered. Therefore, the protective layer is preferably made of a high resistance conductive material. A material considering the triboelectric charging series of the protective layer may be used so that the non-charged toner or the weakly charged toner is frictionally charged to the negative polarity at the cleaning nip.

  The electrode on the surface layer of the cleaning roller can be formed by forming an electrode pattern on a thin flexible substrate made of polyimide or the like by a photolithography method and then performing an etching method to remove the metal film. Then, the surface layer on which the electrode is formed on the cleaning roller 71 can be formed by attaching the flexible substrate on which the electrode pattern is formed to the surface of the elastic layer. At this time, by sticking the electrode of the substrate on the surface of the elastic layer so as to be inside, the electrode is not exposed to the surface of the cleaning roller, and the electrode can be protected. By using a photolithography method, the electrodes can be made fine and the electrode pitch can be narrowed. Therefore, even if the linear velocity of the cleaning roller is not increased, the surface of the photoreceptor can be opposed to the first electrode and the second electrode in the process of passing the cleaning nip. Further, a strong electric field can be formed between the regions, and the toner can be captured by the electric field between the regions. Moreover, an electrode can also be formed on the surface of the cleaning roller by discharging conductive ink onto the surface of the surface layer by an inkjet method. Even if the electrodes are formed by the inkjet method, the electrodes can be made fine and the electrode pitch can be narrowed. In the cleaning device 7 of the present embodiment, it is preferable to form electrodes by an inkjet method. By using the inkjet method, the electrode can be directly formed on the surface of the cylindrical cleaning roller, and the cleaning roller 71 can be easily manufactured.

When the width of the electrode is wide and the electrode pitch is wide, the electric field between the regions becomes weak, and the influence of the electric field between the regions on the transfer residual toner on the surface of the photosensitive member becomes weak. When the electrode pitch is wide as described above, an electrostatic force that separates the transfer residual toner from the photoconductor acts on the transfer residual toner due to the electric field between the electrode and the photoconductor surface. Moves to the electrode side of the cleaning roller and is adsorbed. Since an intermolecular force or the like acts on the transfer residual toner with respect to the photoconductor, there is a large force for separating the transfer residual toner from the surface of the photoconductor. For this reason, when the transfer residual toner is removed from the surface of the photoconductor by an electric field between the electrode and the surface of the photoconductor, it is necessary to apply a large voltage to the electrode to increase the electric field.
On the other hand, as in this embodiment, when the electrode pitch is narrowed as a fine electrode, the electric field between the regions becomes strong, and the toner can be adsorbed to the cleaning roller by the electric field between the regions. Since the electric field between the first region 71e and the second region 71f is generated in the circumferential direction of the cleaning roller, the transfer residual toner on the surface of the photoconductor is caused by the electric field in the cleaning nip that contacts the surface of the cleaning roller. An electrostatic force that moves on the surface works. As a result, the transfer residual toner on the surface of the photosensitive member moves on the surface of the photosensitive member and adheres to a region having a potential different from the charged polarity of the transfer residual toner on the surface of the cleaning roller 71. In the apparatus of this embodiment, since spherical toner is used, it is easy to move the surface of the photoreceptor. For this reason, it is possible to move to a region having a potential different from the charged polarity of the transfer residual toner on the surface of the cleaning roller with a weak electric field as compared with the case of being separated from the photosensitive member and attached to the electrode of the cleaning roller. As a result, the voltage applied to the electrode can be weakened, and energy saving can be achieved. Further, the transfer residual toner is charged unevenly. For this reason, the weakly charged portion of the transfer residual toner may face the cleaning surface. Even in such a case, when the transfer residual toner rolls due to the action of the electric field between the regions, the strongly charged portion of the transfer residual toner faces the cleaning roller surface. As a result, the strongly charged portion of the transfer residual toner can be adsorbed on the electrode, and the transfer residual toner can be adsorbed on the surface of the cleaning roller with a strong electrostatic force.

  Next, the operation of the cleaning device 7 will be described in detail. When a print signal is input and an image forming operation is started, after the charging, writing, developing, and transferring steps, the transfer residual toner on the photosensitive member 1 is sent to a portion facing the cleaning device 7. In the transfer residual toner, in addition to the toner charged to the normal polarity (negative polarity) by being charged in the transfer step, the toner charged to the reverse polarity (positive polarity) or the non-charged toner is mixed. When the surface of the photoreceptor enters the cleaning nip region, negative transfer residual toner on the surface of the photoreceptor is between the first region 71e and the second region 71f on the surface of the cleaning roller 71 as shown in FIG. It is captured by the circumferential electric field formed in the cleaning roller. The negative transfer residual toner on the surface of the photoconductor moves under the influence of the electric field between the regions and moves between the photoconductor 1 and the cleaning roller 71 to the first region 71e having the positive potential and cleaning. It is electrostatically attracted to the first region 71e on the surface. On the other hand, the positive transfer residual toner on the surface of the photosensitive member moves while rolling between the photosensitive member 1 and the cleaning roller 71 to the second region 71f having a negative potential by the action of an electric field between the regions. The two regions 71f are electrostatically adsorbed. Further, the weakly charged transfer residual toner on the surface of the photosensitive member also rolls between the photosensitive member 1 and the cleaning roller 71 due to the action of a strong electric field between the regions, and frictionally charges to increase the charge amount to the first region 71e. Move and electrostatically attract to the cleaning roller 71. Further, the uncharged toner on the surface of the photosensitive member is frictionally charged before passing through the cleaning nip, and is electrostatically attracted to the cleaning roller 71. Thereby, the transfer residual toner on the surface of the photoreceptor is removed by the cleaning roller 71.

FIG. 5 is a view for explaining how the positive transfer residual toner electrostatically attracted to the second area 71 f on the surface of the cleaning roller 71 is removed by the scraper member 73. As shown in FIG. 5A, the positive transfer residual toner electrostatically attracted to the second region 71 f on the surface of the cleaning roller 71 is blocked by the scraper member 73. The positive transfer residual toner blocked by the scraper member 73 relatively moves on the surface of the cleaning roller as shown in FIG. Then, as shown in FIG. 5C, when the positive transfer residual toner blocked by the scraper member 73 faces the first region 71e having the positive potential on the surface of the cleaning roller 71, the positive transfer residual toner The transfer residual toner flies from the surface of the collecting roller with a repulsive force and is separated from the cleaning roller 71.
Similarly, the negative transfer residual toner adhering to the first area 71e on the surface of the cleaning roller 71 is blocked by the scraper member 73 and then relatively moves on the surface of the cleaning roller. Then, when facing the second region 71 e having a negative potential, it flies off the surface of the cleaning roller with a repulsive force and is detached from the cleaning roller 71. Thereby, the transfer residual toner is removed from the surface of the cleaning roller, and stable cleaning performance can be maintained.
The untransferred toner separated from the cleaning roller 71 falls to the transport unit 74 and is appropriately discharged out of the cleaning device 7 by the transport unit 74.

  Further, it is preferable that the scraper member 73 is brought into contact with the cleaning roller 71 so that at least one of the scraper member 73 and the cleaning roller 71 is elastically deformed. For example, when the scraper member 73 and the cleaning roller 71 are brought into contact with the cleaning roller 71 without being deformed, the scraper member 73 and the scraper member 73 as shown in FIG. There may be a gap between the surface of the cleaning roller. In such a case, the transfer residual toner adsorbed on the cleaning roller 71 may not be blocked by the scraper member 73 and may slip through the gap between the scraper member 73 and the cleaning roller 71. For this reason, as shown in FIG. 6B, the hardness of the scraper member 73 is lowered and elastically deformed so as to contact the cleaning roller 71. As a result, even if the scraper member 73 swells, the roller surface swells, or the eccentricity occurs, the scraper member 73 is elastically deformed to absorb these fluctuations and ensure the adhesion between the cleaning roller 71 and the scraper member 73. can do. Further, as shown in FIG. 6C, the same effect can be obtained even when the cleaning roller 71 is elastically deformed.

  Further, when the cleaning roller 71 has the same linear velocity as the photosensitive member 1, the contact position between the toner remaining on the photosensitive member and the cleaning roller 71 does not change until the cleaning roller 71 passes through the cleaning nip. Therefore, if the electrode to which a bias having the same polarity as the polarity of the transfer residual toner on the surface of the photoconductor is opposed at the entrance of the cleaning nip, the transfer residual toner on the surface of the photoconductor is not affected by the electric field of the electrode of the same polarity. However, it is not affected by the electric field between the regions. Therefore, the untransferred toner is not subjected to an electrostatic force that moves to an area of a different polarity on the surface of the cleaning roller due to an electric field between the areas. As a result, there is a possibility that the cleaning roller 71 cannot be electrostatically attracted and cannot be removed from the surface of the photoreceptor. Therefore, in the present embodiment, the cleaning roller 71 is made faster or slower than the linear velocity of the photosensitive member 1 so as to provide a linear velocity difference with the photosensitive member 1.

FIG. 7 is a diagram for explaining how the positive transfer residual toner is attracted to the cleaning roller 71 when the linear velocity of the cleaning roller 71 is made slower than the linear velocity of the photosensitive member to provide a linear velocity difference. . As shown in FIG. 7A, when the positive transfer residual toner on the surface of the photoreceptor faces the first electrode 71a to which a positive bias is applied, at the entrance of the cleaning nip, as shown in FIG. 7B. As described above, the transfer residual toner adhering to the surface of the photoconductor moves relatively upward on the surface of the cleaning roller 71 while rotating clockwise in the figure. Then, the untransferred toner on the surface of the photosensitive member is statically moved to the second region 71f having the negative potential on the upper side due to the influence of the electric field formed between the first region 71e and the second region 71f on the surface of the cleaning roller. It is attracted electrically and adheres to the second region 71f (FIG. 7C). Thereby, even if the polarity of the transfer residual toner on the surface of the photosensitive member at the entrance of the cleaning nip faces the first electrode having the same polarity, the toner can be reliably attracted to the cleaning roller 71 until it passes through the cleaning nip. .
In FIG. 7, the example in which the linear velocity of the cleaning roller 71 is made slower than the linear velocity of the photosensitive member has been described. However, the same effect can be obtained when the linear velocity of the cleaning roller 71 is made faster than the linear velocity of the photosensitive member 1. Can be obtained. In this case, the transfer residual toner relatively moves on the surface of the cleaning roller 71 downward in the figure, and is electrostatically attracted to the lower area in the figure.

  Further, the transfer residual toner once electrostatically attracted to the cleaning roller 71 is not mechanically moved on the surface of the cleaning roller due to the mechanical force due to the linear speed difference between the cleaning roller and the photosensitive member. The force is weaker than the electrostatic adsorption force by the electrodes. In the present embodiment, the mechanical force due to the difference in linear velocity is adjusted to be weaker than the electrostatic attraction force by the contact pressure of the cleaning roller to the photosensitive member. Further, it is preferable to reduce the elasticity of the surface of the cleaning roller so that the cleaning nip width does not become narrow as a result of the contact pressure of the cleaning roller to the photosensitive member decreasing.

  Further, a linear velocity difference between the photosensitive member 1 and the cleaning roller 71 so that the uncharged transfer residual toner on the photosensitive member is frictionally charged before it passes through the cleaning nip and can be electrostatically attracted to the cleaning roller 71, Set the cleaning nip width.

  If there is a slight linear velocity difference between the photosensitive member 1 and the cleaning roller 71, the transfer residual toner on the surface of the photosensitive member can be reliably affected by the electric field between the regions on the surface of the cleaning roller, and the transfer residual toner. It is possible to move to a region having a polarity different from the charged polarity of the toner and electrostatically attract the cleaning roller 71. However, in order to more reliably cause the transfer residual toner to be electrostatically attracted to the cleaning roller 71, the surface of the photoreceptor contacts the first region 71e and the second region 71f at least once while passing the cleaning nip. It is preferable. As a result, the transfer residual toner on the surface of the photosensitive member comes into contact with a region having a potential different from the charge polarity of the transfer residual toner until it passes through the cleaning nip. As a result, the transfer residual toner on the photoconductor can be electrostatically attracted to the cleaning roller 71 reliably.

  The distance between the first electrode 71a and the second electrode 71b (hereinafter referred to as electrode pitch) is preferably set at least equal to or greater than the particle size of the toner. The smaller the electrode pitch, the stronger the electric field between the regions and the stronger the force for electrostatically attracting the toner, which is preferable. However, as shown in FIG. 8A, when the electrode pitch L is smaller than the particle diameter of the toner, the toner on the photoreceptor is affected by the electric field between the plurality of regions. That is, of the cleaning roller surface area facing the transfer residual toner, the positive transfer residual is caused by the influence of the electric field X1 between the second area A located on the left side in the drawing and the first area B located substantially in the center. The toner is electrostatically moved to the left in the figure. At the same time, the positive electrode due to the influence of the electric field X2 between the second region C located on the right side in the drawing and the first region B located substantially in the center in the region of the surface of the cleaning roller facing the untransferred toner. The electrostatic transfer force acts on the right transfer residual toner in the figure. As a result, the forces that move the transfer residual toner electrostatically cancel each other. Therefore, the force for electrostatically moving the toner is weakened. For this reason, the electrode pitch L is preferably set to at least the particle size of the toner, as shown in FIG. As a result, the transfer residual toner is only affected by the electric field X3 between one region, and the effects of the electric field do not cancel each other. Therefore, the untransferred toner is moved by the electrostatic force that moves to the left in the drawing generated by the electric field between the regions, and is attracted to the second region 71f. In this embodiment, since toner having an average particle diameter of 5 to 10 [μm] is used, it is preferable that the electrode pitch L is at least 10 [μm] or more.

Further, as shown in FIG. 9, even when the electrode pitch L is wide, in order to contact the first electrode 71a and the second electrode 71b at least once while the surface of the photoreceptor passes through the cleaning nip, It is conceivable to increase the cleaning nip width or increase the linear velocity difference between the photosensitive member 1 and the cleaning roller 71. However, when the nip width is increased or the difference in linear velocity between the photosensitive member 1 and the cleaning roller 71 in the cleaning nip is increased, the transfer residual toner is caused by the progress of abrasion or friction due to the frictional force between the photosensitive member 1 and the cleaning roller 71. Additives and the like fall off and the filming on the surface of the photoreceptor is accelerated. In order to suppress such a problem, the linear velocity Vc of the cleaning roller 71 is preferably suppressed to 0.5 to 1.5 times the linear velocity Vd of the photosensitive member. Further, when the moving direction of the cleaning roller moves in the cleaning nip in the direction opposite to the moving direction of the photosensitive member, the transfer residual toner is caused by the progress of abrasion or friction due to the frictional force between the photosensitive member 1 and the cleaning roller 71 as described above. This may cause the film additive on the photosensitive member to fall off and accelerate the filming on the surface of the photosensitive member. Therefore, in the cleaning nip, the moving direction of the cleaning roller moves in the forward direction relative to the moving direction of the photosensitive member. Is preferred. If the diameter of the cleaning roller is increased, the cleaning nip width can be increased. However, if the diameter of the cleaning roller 71 is increased, the size of the apparatus is increased. For this reason, in order to suppress the enlargement of the apparatus, it is necessary to suppress the diameter of the cleaning roller to about 10 [mm]. When the diameter of the cleaning roller 71 is about 10 [mm], it is difficult to increase the cleaning nip width N by 1 [mm] or more. Therefore, in this embodiment, the nip width is set to 1 [mm] or less and (Vc (linear speed of the cleaning roller) / Vd (linear speed of the photosensitive member)) of 0.5 to 1.5. Therefore, in the present embodiment, the conditions for maximizing the electrode pitch L are when the nip width N is 1 [mm] and (Vc / vd) is 0.5 or 1.5.
The time t required for the surface of the photoreceptor to move from the cleaning nip entrance to the exit is t = N / vd. The distance y that the cleaning roller moves at this time t is Vc × t = (Vc / Vd) N. When the nip width N = 1 [mm] and (Vc / Vd) is 0.5, the moving distance y on the cleaning roller surface is 0.5 [mm]. That is, the surface of the cleaning roller moves by 0.5 [mm] while the surface of the photoconductor moves by 1 [mm] of the nip width. Therefore, if the inter-electrode pitch L is set to 0.5 [mm] or less, the surface of the photoreceptor can be brought into contact with the first electrode 71a and the second electrode 71b while passing through the cleaning nip. When (Vc / Vd) is 1.5, the surface of the cleaning roller moves 1.5 [mm] while the surface of the photoconductor moves 1 mm in nip width. That is, while the photosensitive member surface passes through the cleaning nip, the cleaning roller surface advances 0.5 [mm] ahead. Therefore, also in this case, if the inter-electrode pitch L is set to 0.5 [mm] or less, the surface of the photoreceptor can be brought into contact with the first electrode 71a and the second electrode 71b while passing through the cleaning nip. .

  Next, a toner that is preferably used in the image forming apparatus of the present embodiment will be described. In order to obtain a high-definition image, it is preferable that the particle size distribution of small particles is sharp. With a toner having a small particle size and a narrow particle size distribution, the toner charge amount distribution is uniform, a high-quality image with little background fogging can be obtained, and the transfer rate can be increased.

The toner shape factor SF-1 is preferably in the range of 100 to 150. Here, the shape factor SF-1 is a numerical value indicating the ratio of the roundness of the shape of the spherical material, and the square of the maximum length MXLNG of the elliptical shape formed by projecting the spherical material on a two-dimensional plane is defined as a graphic area AREA. Divided by and multiplied by 100π / 4.
That is, it is defined by the following equation (1).

When the value of SF-1 is 100, the shape of the toner becomes a true sphere, and becomes larger as the value of SF-1 increases. In general, when the shape of the toner is close to a sphere, the contact state between the toner and the toner or the toner and the photoconductor becomes point contact, so that the adsorption force between the toners is weakened and the fluidity is increased. The adsorption force between the toner and the photosensitive member is also weakened, and the transfer rate is increased. Therefore, the amount of toner removed by the cleaning device can be reduced. Accordingly, it is possible to extend the life of the cleaning device by using toner having a high degree of circularity with a shape factor SF-1 in the range of 100 to 150.

  Further, the toner used in this embodiment is prepared by the chemical synthesis method as described below. That is, a binder resin containing a modified polyester resin that can be urea-bonded in an organic solvent, a toner composition containing a colorant is dissolved or dispersed to form particles in an aqueous medium and a polyaddition reaction. It is obtained by removing the solvent from the dispersion, washing and drying. In addition, as a chemical synthesis method for increasing the average circularity and obtaining a so-called spherical toner, a known emulsion polymerization method, suspension polymerization method, dispersion polymerization method or the like may be used in addition to the above-described method. A toner obtained by spheroidizing treatment by heat treatment may be used.

  In this embodiment, the cleaning device of the present invention is applied to a monochrome image forming apparatus having one process cartridge, but the present invention is not limited to this. For example, the present invention can be applied to a color image forming apparatus in which four process cartridges of magenta, cyan, yellow, and black are arranged side by side to constitute a tandem image forming unit.

  Further, the present invention can be applied to an intermediate transfer type image forming apparatus that transfers a toner image on a photosensitive member to an intermediate transfer member and transfers the toner image on the intermediate transfer member to a transfer sheet. At this time, the cleaning device of the present invention can be applied not only as a cleaning device for cleaning the transfer residual toner attached on the photosensitive member but also as an intermediate transfer member cleaning device for cleaning the transfer residual toner attached on the intermediate transfer belt. . As the intermediate transfer member, in addition to a belt-shaped intermediate transfer belt, a drum-shaped intermediate transfer drum or the like can be used. The electrical characteristics (volume resistivity, surface resistivity, etc.), thickness, structure (single layer, double layer, multiple layers), material, material, etc. of the intermediate transfer member are appropriate depending on the imaging conditions. Can be selected and employed.

  In this embodiment, the cleaning roller is brought into contact with the photoconductor, but the cleaning roller may be disposed close to the photoconductor. Also in this case, the transfer residual toner on the surface of the photosensitive member is changed to the charge polarity of the transfer residual toner by the electric field between the first region having a positive potential on the surface of the cleaning roller and the second region having a negative potential. Attracts to the reverse polarity region. The transfer residual toner attracted by the influence of the electric field between the regions moves while rolling on the surface of the photosensitive member, and is adsorbed to a region having a polarity opposite to the charged polarity of the transfer residual toner. Thereby, the positive transfer residual toner and the negative transfer residual toner can be electrostatically adsorbed by one roller.

(1)
As described above, according to the cleaning device of the present embodiment, since the first region having the positive potential and the second region having the negative potential are provided on the surface of the cleaning roller, the first region and the second region are There is no leak due to contact. In addition, since the first region having a positive potential and the second region having a negative potential are provided on one roller, the negative transfer residual toner and the positive transfer residual toner are removed by one roller. can do. Therefore, the apparatus can be reduced in size as compared with the case where two rollers to which positive and negative voltages are respectively applied are arranged.
(2)
Further, the scraper member blocks the transfer residual toner adhering to the cleaning roller and opposes the region having a polarity different from the charged polarity of the toner on the surface of the cleaning roller. When the untransferred toner faces a region having a polarity different from the charging polarity of the toner on the surface of the cleaning roller, it flies off from the surface of the collecting roller by a repulsive force and is separated from the cleaning roller. Thereby, the transfer residual toner can be removed from the surface of the cleaning roller. Therefore, since the transfer residual toner is electrostatically removed from the cleaning roller, even the spherical toner, which is difficult to remove by mechanical removal residual toner from the cleaning roller such as scraping, can be satisfactorily removed. It can be removed from the surface.
(3)
Further, the scraper member is brought into contact with the cleaning roller so that one of the scraper member and the cleaning roller is elastically deformed. Accordingly, even if the position of contact with the scraper member varies due to eccentricity of the cleaning roller, the scraper member or the cleaning roller can be elastically deformed to absorb the variation. Accordingly, the scraper member is prevented from being separated from the cleaning roller, and the transfer residual toner that is electrostatically attracted to the cleaning roller can be satisfactorily blocked by the scraper member.
(4)
In addition, since a linear speed difference is generated between the photoconductor and the cleaning roller in the cleaning nip which is a contact area between the photoconductor and the cleaning roller, the transfer residual toner on the photoconductor passes through the cleaning nip. While passing, it can face different parts of the cleaning roller. As a result, the transfer residual toner on the photoconductor is affected by the electric field between the first region and the second region before passing through the cleaning nip, and the transfer residual toner is electrostatically applied to the cleaning roller. Can be attached to.
(5)
In addition, since the first and second regions and the surface of the photoconductor are in contact with each other at least once while the surface of the photoconductor passes through the cleaning nip, the negatively charged toner on the photoconductor The toner charged to the positive polarity can be surely removed by the cleaning roller.
(6)
Further, since the first region and the second region are alternately arranged at a pitch equal to or larger than the average particle diameter of the toner, the toner is not affected by the electric field between the plurality of regions. Therefore, it is possible to suppress the electrostatic force generated by the influence of the electric field between the regions from canceling each other and weakening the electrostatic force for moving the transfer residual toner to the region having the charged polarity and the different polarity potential of the transfer residual toner. .
(7)
In addition, the first electrode is disposed in the first region, and a positive bias is applied to the first electrode via the first connection electrode as the first power supply electrode provided at one end of the cleaning roller, thereby cleaning the first electrode. The first region of the roller can be a region having a positive potential. The second roller is disposed in the second region, and a negative bias is applied to the second electrode via a second connection electrode that is a second power feeding electrode provided at one end of the cleaning roller. The second region can be a region having a negative potential.
(8)
Moreover, the electrode pitch can be narrowed by using the first electrode and the second electrode as fine electrodes having a fine width in the width direction. As a result, the electric field between the electrodes is strengthened, and the transfer residual toner on the surface of the photoreceptor is electrostatically moved to the surface of the cleaning roller having a potential different from the charged polarity of the transfer residual toner due to the electric field between the electrodes. Can do. In addition, since the electrode pitch is narrowed, the first area and the second area on the surface of the cleaning roller are brought into contact with each other while the surface of the photoconductor passes through the cleaning nip even if the linear velocity difference between the photoconductor and the cleaning roller is small. The bipolar toner can be satisfactorily removed by the cleaning roller. In addition, since the difference in linear velocity between the photoconductor and the cleaning roller can be reduced, wear due to friction between the cleaning roller and the photoconductor can be suppressed.
(9)
Further, a fine electrode can be formed by ejecting conductive ink onto the surface of the cleaning roller by an inkjet method to form an electrode of the cleaning roller.
(10)
Further, by forming the electrodes of the cleaning roller by a photolithography method, a fine electrode can be formed and the pitch between the electrodes can be narrowed.
(11)
Further, according to the image forming apparatus of the present embodiment, by using the cleaning device 7 having the features (1) to (10), the device can be reduced in size and good cleaning performance can be obtained. it can.
(12)
A toner having a shape factor SF-1 in the range of 100 to 150 is used as a toner for forming a toner image. As a result, the amount of cleaning input is reduced, the margin is improved, and a high-quality image is obtained. In addition, the life of the cleaning device can be extended.

1 is a schematic configuration diagram illustrating an image forming apparatus according to an exemplary embodiment. FIG. 3 is an explanatory diagram of a cleaning device used in the image forming apparatus. Explanatory drawing of the cleaning roller of the cleaning device. The figure which shows the mode of the electric field on the surface of the cleaning roller. (A), (b), (c) is a figure which shows a mode that the scraper member of the cleaning apparatus removes the transfer residual toner adhering to the cleaning roller surface. (A), (b), (c) is a figure explaining the contact state of a scraper member and a cleaning roller. (A), (b), (c) is a diagram for explaining how to remove the transfer residual toner on the surface of the photosensitive member when the linear velocity of the cleaning roller is made slower than the linear velocity of the photosensitive member. (A) is a figure explaining the mode of the electric field which affects a toner when the electrode pitch L is smaller than the average particle diameter of a toner. FIG. 6B is a diagram illustrating a state of an electric field that affects the toner when the electrode pitch L is larger than the average particle diameter of the toner. The figure which shows the cleaning roller and photoconductor with a large electrode pitch L. The figure explaining a mode that spherical toner slips through a cleaning blade. The figure which shows an example of the conventional cleaning apparatus. The figure which shows the other example of the conventional cleaning apparatus.

Explanation of symbols

1: Photosensitive member 6: Developing device 7: Cleaning device 71: Brush roller 72: Collection roller 73: Scraper member 74: Conveying means

Claims (6)

An image carrier, a charging device for charging the image carrier, a latent image forming device for forming an electrostatic latent image on the image carrier, and a toner attached to the electrostatic latent image on the image carrier. In an image forming apparatus comprising: a developing device that visualizes; a transfer device that transfers a toner image on the image carrier to a transfer material; and a cleaning device that cleans the image carrier.
The cleaning device has a first region having a positive potential and a second region having a negative potential on a surface thereof, and is brought into contact with the image carrier to form a cleaning nip. A cleaning roller that electrostatically removes toner on the surface of
The toner has a shape factor SF-1 in the range of 100 to 150, a particle size of 5 [μm] or more and 10 [μm] or less,
In the facing region between the image carrier and the cleaning roller, the surface movement direction of the image carrier and the surface movement direction of the cleaning roller are the same direction, the linear velocity of the image carrier is Vd, and the line of the cleaning roller When the speed is Vc,
0.5 ≦ Vc / Vd ≦ 1.5,
The cleaning nip width is 1 [mm] or less,
The inter-region pitch between the first region and the second region is set to 10 μm or more and 500 μm or less ,
The image carrier surface is configured to contact the first area and the second area while passing through the cleaning nip,
Due to the electric field formed between the first region and the second region, the transfer residual toner on the surface of the image carrier is moved to a region having a potential opposite to the charged polarity of the toner. An image forming apparatus, wherein the image forming apparatus is attached to a region having a potential opposite to a charged polarity of toner and removed from the surface of the image carrier . The image forming apparatus according to claim 1.
The cleaning device includes a scraper member that contacts the cleaning roller, blocks the toner adhering to the cleaning roller, and opposes a region having a polarity different from the charged polarity of the toner on the surface of the cleaning roller. Image forming apparatus. The image forming apparatus according to claim 2.
An image forming apparatus, wherein the scraper member is brought into contact with the cleaning roller so that one of the scraper member and the cleaning roller is elastically deformed. The image forming apparatus according to any one of claims 1 to 3,
The cleaning device includes a first electrode to which a positive polarity bias is applied to the first region, a second electrode to which a negative polarity bias is applied to the second region, and one end side of the cleaning roller surface. A first power supply electrode for supplying a positive bias to the first power supply electrode for supplying the positive bias to the first electrode, and a negative polarity on the other end of the surface of the cleaning roller. An image forming apparatus comprising: a second power supply electrode that is electrically connected to a second power source that applies a bias, and that feeds the negative polarity bias to the second electrode. The image forming apparatus according to claim 4.
The image forming apparatus, wherein the first electrode and the second electrode are formed by printing conductive ink on a surface of the cleaning roller by an ink jet method. The image forming apparatus according to claim 4.
The image forming apparatus, wherein the first electrode and the second electrode are formed by a photolithography method.

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