JP2014167524A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of suppressing the progress of wear of a photoreceptor due to the omission of a lubricant application mechanism, and effectively suppressing the occurrence of filming (silica filming).SOLUTION: There is provided an image forming apparatus that does not include lubricant application means for applying lubricant to an image carrier. The image forming apparatus uses a two-component developer having a toner and a carrier as a developer, controls an elastic power of the image carrier to be 42% or more, makes a short diameter/long diameter ratio of silica added to the developer 0.7 or less, and makes an absolute value of a surface potential of developing means higher than that of a surface potential of the image carrier in an image part, in which the potential of the image carrier is closer to the + side than that of the carrier.

Description

  The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile machine, and a multifunction machine including these.

  In general, this type of image forming apparatus electrically forms a latent image on the surface of a photoreceptor, and develops the formed latent image using a developer containing toner to form a developed image. After that, the developed image is transferred onto a recording medium via an intermediate transfer member or the like, and fixed by heating, pressing, or the like.

  However, due to the use of toner for a long period of time, the density of the fixed image changes in the formed image, and some toner particles adhere to non-image areas.

  Therefore, conventionally, a developer that suppresses uneven distribution of silica particles on the surface of toner particles has been proposed (Patent Document 1). This developer limits the average particle diameter, specific gravity, circularity, etc. of the silica particles in a developer having toner particles and silica particles adhering to the surface of the toner particles.

  Thus, if the uneven distribution of the silica particles is suppressed, the exposure of the toner particle surface is suppressed, the aggregation of the toner particles is suppressed, and the generation of the color point of the image can be suppressed.

  In general, an image forming apparatus is provided with a cleaning device because it is necessary to remove untransferred developer (untransferred toner), discharge products, and the like on a photoreceptor. However, there may be a filming phenomenon in which the external additive component released from the developer (toner) slips through the cleaning device and accumulates.

  The cleaning device is generally provided with a blade member that comes into pressure contact with the photoreceptor. However, fine scratches may occur on the surface of the photoreceptor due to the pressure contact of the blade. Such fine scratches become a portion where the above-described external additive components and untransferred toner are deposited, and if toner adheres from the scratch portion, condensation may occur and the filming phenomenon may be further promoted to cause poor cleaning. is there. The defective cleaning includes a problem that the background of the photoconductor is contaminated and an abnormal image with a remarkable background is obtained.

Further, on the surface of the photosensitive member that is in pressure contact with the cleaning blade, the blade in contact with the surface may vibrate, and abnormal noise such as chatter noise may be generated.
In particular, if the contact pressure of the cleaning blade against the surface of the photoreceptor, which is one of the factors that improve the cleaning performance by the cleaning blade, is increased, vibration due to friction between the blade tip and the surface of the photoreceptor increases. Vibration noise is likely to occur. Specifically, when a rubber blade such as polyurethane is used as the blade material, the frictional vibration at the blade tip increases by increasing the contact pressure of the blade. Furthermore, in a high temperature environment, a phenomenon occurs in which the rebound resilience of the blade increases, and the resonance at the blade contact position on the tourist body surface side is amplified, resulting in an uncomfortable combination of blade vibration and photoconductor resonance. Vibration sound is generated.

  Therefore, conventionally, by setting the softness on the surface of the photoconductor by setting the unilateral hardness and the elastic power on the surface of the photoconductor, it is possible to scrape the bottom of the deposited area stably and to perform cleaning. There is one that prevents the generation of abnormal noise due to frictional vibration of the blade (Patent Document 2).

  Conventionally, in order to suppress the cause of image quality defects (filming or the like), there is one that uses irregularly shaped silica fine particles instead of spherical shapes (Patent Document 3).

  By the way, in order to extend the life of the photoconductor, a lubricant may be applied to the photoconductor. However, since the lubricant application mechanism is relatively expensive, it is preferable not to have such a lubricant application mechanism. However, if the lubricant application mechanism is not provided, as described above, filming occurs and a problem arises that a whiteout image or the like occurs.

  When the linear pressure of the cleaning blade is increased in order to prevent the occurrence of filming, the wear of the photoconductor progresses even if the filming is improved, and the life of the photoconductor is shortened. For this reason, it can be proposed to set the softness on the surface of the photoconductor by setting the uniaxial hardness and the elastic power on the surface of the photoconductor as described in Patent Document 2 described above.

  However, the above-described Patent Document 2 does not specify a developer. That is, there is no description of silica that adheres to the toner surface and exhibits the function of imparting fluidity and chargeability. For this reason, the developer described in Patent Document 2 cannot exhibit stable fluidity and chargeability as a developer. For this reason, in the thing of patent document 2, even if a photoreceptor wear can suppress progress, generation | occurrence | production of filming cannot be suppressed effectively.

  That is, when silica is added to the toner, the silica attached to the surface of the photoreceptor is difficult to scrape if the silica is nearly circular. In addition, if the shape is an ellipse or an ellipse, the silica attached to the carrier of the toner is pulled in a direction in close contact with the carrier unless the potential on the surface of the photoreceptor and the potential on the surface of the developing roller are limited. It adheres to the surface in a lying state, and it is difficult to scrape off deposits on the surface of the photoreceptor.

  In Patent Document 1 and Patent Document 3, elliptical or elliptical silica is used, but in this case as well, the potential on the surface of the photoreceptor and the potential on the surface of the developing roller are not limited.

  In view of such circumstances, the present invention can suppress the progress of photoconductor wear due to the omission of the lubricant application mechanism, and can effectively suppress the occurrence of filming (silica filming). Is to provide.

  The image forming apparatus of the present invention includes an image carrier, a charging unit for charging the image carrier, a writing unit for forming an electrostatic latent image on the image carrier, and developing the electrostatic latent image with a developer. An image forming apparatus that includes a developing means for cleaning and a cleaning means for recovering a residual developer from the image carrier, and does not include a lubricant application means for applying a lubricant to the image carrier. In addition, a two-component developer having a toner and a carrier is used, the elastic power of the image carrier is 42% or more, and the minor axis / major axis ratio of silica added to the developer is 0.7 or less. In the image portion, the absolute value of the surface potential of the developing unit is higher than the surface potential of the image carrier, and the potential of the image carrier is on the positive side of the carrier.

  In the image forming apparatus of the present invention, the silica adhering to the image carrier can be easily removed by the developing means (developing roller), and the silica that has once passed through the cleaning means is difficult to re-enter the cleaning means side, so that the cleaning means side Silica entering into the film is reduced and filming is less likely to occur.

1 is an overall simplified view of an image forming apparatus according to an embodiment. FIG. 2 is a simplified diagram illustrating a relationship between a photosensitive member and a developing roller of the image forming apparatus illustrated in FIG. 1. FIG. 3 is an enlarged view of a main part of FIG. 2. It is sectional drawing of the image development apparatus of the image forming apparatus shown in the said FIG. It is a simplified diagram showing a magnetic field using a two-pole pumping magnet. It is an enlarged view showing the relationship between the photoconductor and the developer in the image area. FIG. 4 is an enlarged view showing a relationship between a photoconductor and a developer in a non-image area. It is a graph which shows the elastic power of the sample which investigated the presence or absence of generation | occurrence | production of filming.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention according to embodiments shown in the drawings will be described.

  FIG. 1 is a longitudinal side view schematically showing a color printer which is an image forming apparatus according to an embodiment of the present invention. In the main body case 2 of the color printer 1 according to the present embodiment, a printer engine 3, an optical writing device 4 as writing means for emitting a light beam, and a recording medium storage portion for storing a recording medium P as a transfer target. A paper feed cassette 5, a fixing device 6 for fixing the recording medium P on which the toner image is transferred, a waste toner collecting container 7 for collecting waste toner generated after the toner image is transferred, and the like.

  The printer engine 3 is a portion that forms a toner image and transfers the formed toner image to the recording medium P, and is an image carrier yellow (Y), cyan (C), magenta (M), black (K). Are provided with four photoconductors 8Y, 8C, 8M, and 8K, respectively. Further, the printer engine 3 includes a charging roller 9 for constituting a charging means (charging device) 30 disposed around each of the photoconductors 8Y, 8C, 8M, and 8K, and developing devices 10Y, 10C, and 10M as developing means. 10K, a cleaning unit 11, a primary transfer roller 12, an intermediate transfer belt 13 as an intermediate transfer member as an image carrier and a transfer target, a secondary transfer roller 14 as a transfer device, a belt cleaning unit 15 and the like. . Here, in the description of the present specification and drawings, the subscripts Y, C, M, and K indicate yellow, cyan, magenta, and black colors, respectively, and these subscripts are used as necessary. Omit.

Each of the photoconductors 8Y, 8C, 8M, and 8K is formed in a cylindrical shape, and a drive motor (not shown) is connected to the rotation shafts of these photoconductors 8Y, 8C, 8M, and 8K. As shown by the arrow by the driving force, it rotates around the center line. A photosensitive layer on which an electrostatic latent image is formed is provided on the outer peripheral surface of the photoreceptor 8. The charging roller 9 is disposed in contact with the outer peripheral surface of the photoconductor 8 or is disposed with a small gap from the outer peripheral surface of the photoconductor 8. When a voltage is applied to the charging roller 9 from a power supply unit (not shown), corona discharge is generated between the charging roller 9 and the photoconductor 8, and the photoconductors 8Y, 8C, 8M, 8K The outer peripheral surface is uniformly charged. The optical writing device 4 emits light beams LY, LC, LM, and LK corresponding to yellow, cyan, magenta, and black image data, and is uniformly charged with each photoconductor 8.
The outer peripheral surfaces of Y, 8C, 8M, and 8K are exposed. By this exposure, electrostatic latent images corresponding to the image data of the respective colors are formed on the outer peripheral surfaces of the photoreceptors 8Y, 8C, 8M, and 8K.

  The developing devices 10Y, 10C, 10M, and 10K contain yellow, cyan, magenta, and black toners, respectively, and the electrostatic latent images formed on the photoreceptors 8Y, 8C, 8M, and 8K have different colors. Supply toner. The supplied toner adheres to the electrostatic latent images corresponding to the image data of the respective colors formed on the outer peripheral surfaces of the photoreceptors 8Y, 8C, 8M, and 8K, and the photoreceptors 8Y, 8C, 8M, and 8K The electrostatic latent image on the outer peripheral surface is visualized as a toner image of each color.

  The intermediate transfer belt 13 is an endless loop belt formed of a resin film or rubber as a base, and is wound around a driving roller 16, an entrance roller 17, and a tension roller 18, and a driving motor (not shown). When the drive roller 16 connected to is rotated, it is rotated and transferred in the direction of arrow A. The entrance roller 17 and the tension roller 18 are driven to rotate by the frictional force with the intermediate transfer belt 13 as the intermediate transfer belt 13 rotates in the direction of arrow A.

  The primary transfer roller 12 is disposed on the inner peripheral surface side (inside of the loop) of the intermediate transfer belt 13, and a transfer voltage is applied to these primary transfer rollers 12, whereby each of the photoconductors 8Y, 8C, and 8M. , 8K toner image is transferred onto the intermediate transfer belt 13. The toner images formed on the photoconductors 8Y, 8C, 8M, and 8K are sequentially transferred and overlaid on the intermediate transfer belt 13, and four color toner images are stacked on the intermediate transfer belt 13 to form a color image. A toner image is formed.

  The cleaning unit 11 cleans the outer peripheral surface of each photoconductor 8 after the toner image is transferred to the intermediate transfer belt 13. By this cleaning, toner, paper dust, and the like remaining on the outer peripheral surface of the photoconductor 8 after the toner image is transferred to the intermediate transfer belt 13 are removed from the outer peripheral surface of the photoconductor 8 and collected as waste toner. .

  The color toner image formed on the intermediate transfer belt 13 is subjected to the secondary transfer at the timing when the recording medium P is fed by the registration roller 20 to the transfer position where the intermediate transfer belt 13 and the secondary transfer roller 14 are in contact with each other. When the transfer voltage is applied to the roller 14, the image is transferred to the recording medium P.

  The recording medium P is fed from the sheet feeding cassette 5 and is conveyed by the conveyance roller 19 and the registration roller 20, and is transferred to the fixing device 6 after the toner image is transferred. The recording medium P to which the toner image has been transferred is subjected to fixing processing by applying heat and pressure in the fixing device 6, and the toner image melted by this fixing processing is fixed to the recording medium P. The recording medium P for which the fixing process has been completed is discharged onto a discharge tray 21 formed on the upper surface of the main body case 2.

  The belt cleaning unit 15 cleans the outer peripheral surface of the intermediate transfer belt 13 after the color toner image is transferred to the recording medium P. By this cleaning, toner, paper dust, and the like remaining on the outer peripheral surface of the intermediate transfer belt 13 after the toner image is transferred are removed from the outer peripheral surface of the intermediate transfer belt 13 and collected as waste toner.

  Further, in the printer 1 according to this embodiment, a waste toner collecting device 7 is detachably disposed from the case main body 2 between an optical writing device 4 serving as writing means and a paper feed cassette 5. The waste toner collecting device 7 is a portion that stores waste toner collected by the cleaning units 11 and 15 from the cleaning units 11 and 15 and stores the thrown-in waste toner. The waste toner collecting device 7 is detachably attached to the main body case 2, and is removed from the main body case 2 when the waste toner in the waste toner collecting device 7 is almost full, so that the empty waste toner collecting device is removed. 7 is attached.

  The photosensitive member 8 that is a component of the printer engine 3, the charging roller 9, the developing means (developing device) 10 and the cleaning means 11 disposed around each photosensitive member 8 are unitized and housed in a case 22. Process cartridges 23 (23Y, 23C, 23M, and 23K) are formed. Each process cartridge 23 is detachably mounted in the main body case 2. Since the photosensitive member 8, the charging roller 9, the developing device 10, and the cleaning unit 11 are unitized as a process cartridge 23, replacement and maintenance work is facilitated, and the positional accuracy between the members is high. Therefore, the quality of the formed image can be improved. In this embodiment, the process cartridge 23 in which the photosensitive member 8, the charging roller 9, the developing device 10, and the cleaning unit 11 are unitized has been described as an example. However, there are various process cartridge configurations. For example, there is a unit in which at least one of the charging roller 9, the developing device 10, and the cleaning unit 11 and the photosensitive member 8 are housed in a case.

  The specific configuration of the process cartridge 23 of the present embodiment includes a cartridge case, a photosensitive member 8, a charging roller 9, a developing device 10, and a cleaning unit 11, as shown in FIG. The charging roller 9 uniformly charges the outer surface of the photoconductor 8.

The cleaning unit 11 includes a cleaning case 43 having an opening at a portion facing the photoconductor 8, and residual toner, carrier, and paper dust that are in contact with the photoconductor 8 and are untransferred toner as untransferred toner on the photoconductor 8. A cleaning blade 41 for scraping off and cleaning unnecessary deposits such as unnecessary deposits. The cleaning blade 41 is supported by a blade holder 44.

  The cleaning unit 11 includes a discharge screw 42 that is rotatably supported by the cleaning case 43. The cleaning unit 11 scrapes and removes unnecessary materials such as waste toner generated by the cleaning blade 41. 7 for transporting toward 7.

  In this case, the cleaning blade 41 includes a base material and a surface layer that covers at least the tip of the base material. The substrate of the cleaning blade 41 preferably has a high rebound resilience so that it can follow the eccentricity of the photosensitive member and minute undulations on the surface of the photosensitive member, and urethane rubber or the like is preferable. Moreover, it is preferable to make the hardness of the surface layer larger than the hardness of the substrate. The gap between the cleaning blade 41 and the photosensitive member 8 is preferably about 0.6 μm.

  The charging device 30 includes the charging roller 9 that rotates in contact with the surface of the photoreceptor 8 and a cleaning roller 32 that contacts the charging roller 9. The charging roller 9 is connected to a voltage application means (not shown) for applying a bias of an alternating current component to a direct current so as to charge the surface of the photoconductor 8 to a predetermined magnetic pole in a charging region facing the photoconductor 8. It has become.

  The developing device 10 includes a developing case 55 having an opening at a portion facing the photoconductor 8 and a developer carrying member disposed in close proximity to the photoconductor 8 so as to face the photoconductor 8 from the opening. The developing roller 51 has a developing blade 52 as a doctor as a regulating member that regulates the developer on the developing roller 51 to a certain height.

  Further, the developing device 10 is disposed below the developing case 55 so as to face each other, and is driven to rotate in opposite directions to stir the developer and supply the developer to the developing roller 51. A first conveying screw 53 and a second agitating screw 54 which are supply and stirring screws as conveying means, a partition wall 57 provided between the first conveying screw 53 and the second conveying screw 54, and a partition wall 57. It has the 1st storage chamber 58 and the 2nd storage chamber 59 which were partitioned off and each accommodated the 1st conveyance screw 53 and the 2nd conveyance screw 54. That is, the screw mechanism M is used for the developer conveying means.

  The developing roller 51 includes a magnet roller 51a serving as a magnetic field generating unit disposed therein, and a nonmagnetic developing sleeve 51b that includes the magnet roller 51a and is driven counterclockwise.

  The magnet roller 51a is magnetized with a plurality of magnetic poles. The plurality of magnetic poles form a magnetic field for causing the developing roller 51, specifically, the developing sleeve 51b, to carry the developer, and the toner in the developer carried on the developing sleeve 51b is transferred to the developing roller 51, specifically The developing sleeve 51b forms a magnetic field to be supplied to the photosensitive member 8 in the developing area DA facing the photosensitive member 8.

  An alternate long and short dash line indicates a magnetic force distribution formed by the plurality of magnetic poles. Due to the magnetic field formed by each magnetic pole, the developer on the surface of the developing sleeve 51b becomes a magnetic spike. In FIG. 4, each circle indicated by a broken line indicates the strength of the magnetic field from the center of the magnet roller 51a.

  In this case, the angle α formed by the line segment L2 connecting the center of the photosensitive member 8 and the center of the developing roller 51 and the half-width center line L2 of the magnetic field generated by the developing magnetic pole is preferably within ± 3 °. By the way, in FIG. 4, although the pumping pole is one pole, when the pumping pole is two poles, a magnetic field as shown in FIG. 5 will be formed.

  The elastic power of the photoconductor 8 as an image carrier is set to 42% or more. The elastic power is represented by the elastic deformation work × 100 / (plastic deformation work + elastic deformation work). In addition, as an upper limit of this elastic work rate, it is about 60%, for example. If the value of the elastic power exceeds 60%, tackiness is increased and the surface of the image carrier is easily contaminated, and problems such as filming are likely to occur.

  As shown in FIG. 2, the developer interposed between the photoreceptor 8 and the developing roller 51 is a two-component developer in which toner particles (toner) and magnetic particles (carrier) are mixed, and adheres to the toner surface. Silica is included to impart fluidity and chargeability. Further, the minor axis / major axis ratio of the silica is set to 0.7 or less to form the deformed silica. The lower limit of the minor axis / major axis ratio is, for example, 0.2. If the minor axis / major axis ratio of silica is less than 0.2, it is considered that the silica is too flat and a high transfer rate like a spherical toner cannot be obtained. Further, if the minor axis / major axis ratio of silica exceeds 0.7, it approximates a circle and does not constitute deformed silica.

  Further, silica has the same polarity as the toner, and a developer may be added with an additive that is charged with a polarity opposite to that of silica. For example, metal oxide is used as an external additive having a polarity opposite to that of the toner. By adding silica, the chargeability of the toner can be supplemented, and by adding the reverse polarity and additive to silica, the fluidity of the toner is enhanced, and the efficiency during development and transfer is increased.

The photosensitive member 8 at the time of non-image formation can have 0.001 mg / cm ² or more of toner. Here, the time of non-image formation is a state in which image formation is not performed. For example, after a toner image is transferred from the transfer belt 13 to the transfer paper, jamming occurs, and other density adjustment is performed on the transfer belt 13. For example, when an arbitrary pattern is drawn. When a jam occurs or density adjustment is performed, the amount of toner on the transfer belt 13 is larger than that in the case of normal background contamination.

Further, it is preferable that particles having a diameter of 30 μm or more do not adhere to the surface of the photoreceptor 8. Further, the developer pumping amount of the developing means (developing roller) is 30 mg / cm ² or more, and the developing gap between the photosensitive member 8 and the developing roller 51 is 0.4 μm or less. preferable.

  The direction of the magnetic field between the intermediate transfer member (intermediate transfer belt 13) and the photoconductor 8 is preferably the direction in which silica moves to the intermediate transfer member side. Further, it is preferable to provide a linear velocity difference between the intermediate transfer member (intermediate transfer belt 13) and the photosensitive member 8.

  In this image forming apparatus, in the image portion, the absolute value of the surface potential of the developing means (developing roller 51) is made higher than the surface potential of the image carrier (photoconductor 8), and the image carrier (photoconductor 8) is used. The potential is on the positive side with respect to the carrier. For example, the potential of the carrier can be −550V, and the potential of the photoconductor (OPC) 8 can be −50V.

  By setting in this way, as shown in FIG. 6, the deformed silica faces the direction in which it stands with respect to the carrier (that is, the major axis direction of the deformed silica is along the radial direction of the photoconductor 8). For this reason, the adhering matter adhering to the photoconductor 8 can be scraped off.

  By the way, in the non-image portion, the absolute value of the surface potential of the developing means (developing roller 51) is lower than the surface potential of the image carrier (photoconductor 8). At this time, the potential of the carrier 8 is more negative than the carrier. For example, the potential of the carrier is −550V, and the potential of the photoconductor (OPC) 8 is −700V. Here, the non-image portion refers to a region where there is no image in any region in the photosensitive member axial direction, and includes between recording media (paper). The area on the photoconductor other than the area (image portion) where the electrostatic latent image formed corresponding to the entire area of the original paper is present. A white image portion where no image is attached.

  In this case, as shown in FIG. 7, the deformed silica adhering on the photoconductor side of the carrier is oriented in the direction in which it is in close contact with the carrier (that is, the major axis direction of the deformed silica is along the outer diameter surface of the photoconductor 8). Become. For this reason, it becomes difficult to scrape off the adhered matter adhering to the photosensitive member 8.

  In the image forming apparatus configured as described above, by using a two-component developer using deformed silica, the deformed silica attached to the tip of the carrier or toner can collect the silica attached to the surface of the photoreceptor. it can. That is, by using a two-component developing device having a large elastic power and using deformed silica, silica adhering to the photoreceptor 8 can be efficiently removed. For this reason, the silica adhering to the photosensitive member is easily removed by the developing roller 51, so that it is difficult for the silica once passing through the blade 41 to re-enter the blade. Since silica entering the blade 41 is reduced, filming is less likely to occur. On the other hand, if the elastic power of the photoconductor 8 is less than 42%, the photoconductor does not repel the pressure of the magnetic spikes and absorbs the force, so that it adheres efficiently to the surface of the photoconductor. Silica cannot be recovered.

  In particular, in the image portion, the absolute value of the surface potential of the developing means (developing roller 51) is made higher than the surface potential of the image carrier (photosensitive member 8), and the potential of the image carrier 8 is more positive than the carrier. is there. For this reason, as shown in FIG. 6, the deformed silica faces the carrier (that is, the long diameter direction of the deformed silica is along the radial direction of the photoconductor 8). For this reason, the adhering matter adhering to the photoconductor 8 can be scraped stably.

  Since an external additive having a polarity opposite to that of silica is added, silica and an external additive having a polarity opposite to that of silica are likely to be aggregated. Since the amount of silica that enters the blade 41 alone is reduced, silica is less likely to adhere to the photoreceptor.

In addition, since the toner of 0.001 mg / cm ² or more is present on the photosensitive member 8 at the time of non-image formation, the toner base is charged to +. Since the toner comes together with the silica, the released silica is likely to adhere to the toner, so that the silica can be easily cleaned. Since the amount of silica that enters the blade 41 alone is reduced, silica is less likely to adhere to the photoreceptor.

  By using the screw mechanism M as the conveying means for supplying the developer to the developing means (developing apparatus 10), the shearing force applied to the toner is reduced, so that the stress applied to the toner is reduced and the liberation of silica can be suppressed. Since the amount of silica that enters the blade 41 is reduced, silica is less likely to adhere to the photoreceptor.

  By setting the surface of the image carrier (photoreceptor 8) so as not to contain particles having a diameter of 30 μm or more, the amount of silica entering the blade 41 is reduced, so that silica is less likely to adhere to the photoreceptor. On the other hand, when particles of 30 μm or more are contained on the surface of the image carrier, silica is easily caught.

If the pumping amount of the developing means (developing apparatus 10) is 30 mg / cm ² or more and the developing gap is 0.4 μm or less, silica adhering to the photoconductor can be easily collected by the carrier. Silica adhering to the photoreceptor can be reduced. For this reason, the amount of silica re-entering the blade 41 is reduced, and the silica is less likely to adhere to the photoreceptor 8. That is, when the development gap is wide, the scavenging effect is reduced, and when the pumping amount is large, the scavenging effect is increased. Here, the scavenging effect is a phenomenon in which a part of the toner adhering to the photoreceptor 8 during development is scraped again by the carrier in the development area.

  If the number of pumping poles of the developing means (developing apparatus 10) is one, it is possible to widen the developing gap to obtain the same pumping amount as compared with the two-pole pumping system. For this reason, since the stress applied to the toner is reduced, the liberation of silica can be suppressed. The amount of silica that enters the blade 41 is reduced, making it difficult for silica to adhere to the photoreceptor 8. Although a large amount of silica is attached to the carrier in the agitation unit, if the number of pumping poles is large, a stronger force is applied and the silica is not separated from the carrier. By setting the angle α to within ± 3 °, scavenging increases.

  If there is a difference in linear velocity between the transfer belt 13 and the photoconductor 8, silica moves to the transfer belt 13, so that the silica remaining on the photoconductor 8 is reduced. For this reason, the amount of silica entering the cleaning blade 41 is reduced, and silica is less likely to adhere to the photoreceptor.

  When the hardness of the blade surface is higher than that of the blade base material, the behavior of the edge is stabilized, so that silica can be easily damped without increasing the surface pressure of the blade 41. This makes it difficult for silica to pass through the blade 41 and makes it difficult for silica to adhere to the photoreceptor.

  If the distance between the blade 41 and the photosensitive member 8 is 0.6 μm or less, the behavior of the edge is stabilized, so that silica can be easily damped without increasing the surface pressure of the blade 41. For this reason, it becomes difficult for silica to pass through the blade 41 and silica hardly adheres to the photoreceptor 8.

  By using the charging roller 9 as the charging member, the amount of silica re-entering the blade 41 is reduced, so that the silica is difficult to adhere to the photoreceptor. By bringing the cleaning member (cleaning roller) 32 into contact with the charging roller 9, silica adhering to the charging roller 9 is prevented from being rubbed against the photoconductor 9 again. For this reason, since the amount of silica reattached to the photoreceptor 8 is reduced, the amount of silica re-entering the blade 41 is reduced, and the silica is less likely to adhere to the photoreceptor 8.

  Next, sample numbers of photoconductors 8 having different elastic powers are used. 1 to sample no. No. 6 was manufactured, and the occurrence of filming was examined on the photoconductor 8 using a developer to which deformed silica and circular silica were added.

  That is, sample No. In the case of using a developer in which deformed silica was added to Sample 1, sample No. 1 was used. In the case of using a developer in which circular silica is added to Sample 1, sample No. 1 is used. In the case of using a developer in which deformed silica is added to Sample 2, sample No. 2 was used. In the case of using a developer in which circular silica is added to Sample 2, sample No. 2 was used. In the case of using a developer in which deformed silica was added to Sample No. 3, Sample No. In the case where a developer in which circular silica was added to No. 3 was used, sample No. 3 was used. In the case of using a developer in which deformed silica is added to Sample 4, sample No. 4 was used. In the case of using a developer in which circular silica was added to No. 4, sample No. 4 was used. In the case of using a developer added with deformed silica in No. 5, sample no. In the case where a developer in which circular silica is added to No. 5 is used, sample no. In the case of using a developer in which deformed silica was added to No. 6, sample No. 6 was used. The case where a developer in which circular silica was added to No. 6 was used was examined.

  The irregular shaped silica is one having a minor axis / major axis ratio of 0.7 or less, and the circular silica is one having a minor axis / major axis ratio exceeding 0.7. In all cases, the absolute value of the surface potential of the developing roller 51 is made higher than the surface potential of the photoconductor 8, the carrier potential is set to -550V, and the potential of the photoconductor (OPC) 8 is set to -50V. .

  The result is Sample No. No. 6, the developer using the deformed silica was not filming. Regarding other samples, filming occurred regardless of whether the modified silica was added or the circular silica was added. That is, it is possible to suppress the occurrence of filming by combining a developer having a minor axis / major axis ratio of 0.7 or less and a deformed silica developer with a photosensitive member 8 having an elastic power of 42% or more. it can.

  In addition, this invention is not limited to the above-mentioned Example, Of course, a various change can be added in the range which does not deviate from the summary of this invention. Examples of the image forming apparatus according to the present invention include an electrophotographic copying machine, a laser beam printer, and a facsimile machine. By the way, when images with a low image area ratio are continuously formed, a portion having a high friction coefficient is generated on the surface of the carrier (photosensitive member surface), and such a portion is a core of filming. Kimono is easy to adhere. As a result, filming occurs and an abnormal image is generated. For this reason, it is preferable to perform the discharge mode periodically to scrape filming. In the discharge mode, generally, when image formation with a low image area ratio is continued, an image is formed on the image carrier between papers, and toner is consumed by cleaning without transferring to a recording medium. By replenishing the developing device with new toner for consumption, the replacement of the toner in the developing device is promoted, and the deterioration of the toner in the developing device over time is suppressed.

4 Writing means (optical writing device)
8 Image carrier (photoconductor)
9 Charging roller 10 Developing means (developing device)
11 Cleaning means 30 Charging means (charging device)
32 Cleaning roller 51 Developing roller M Screw mechanism

JP 2012-189960 A JP 2010-128187 A JP 2012-101953 A

Claims (14)

An image carrier, a charging unit for charging the image carrier, a writing unit for forming an electrostatic latent image on the image carrier, a developing unit for developing the electrostatic latent image with a developer, and the image carrier. An image forming apparatus comprising a cleaning means for recovering a residual developer from a body, and not provided with a lubricant applying means for applying a lubricant to the image carrier,
A two-component developer having a toner and a carrier is used as the developer, the elastic power of the image carrier is set to 42% or more, and the minor axis / major axis ratio of silica added to the developer is set to 0.1. 7 or less, and in the image portion, the absolute value of the surface potential of the developing means is higher than the surface potential of the image carrier, and the potential of the image carrier is on the positive side of the carrier. Forming equipment.   The image forming apparatus according to claim 1, wherein the developer contains an additive charged to have a polarity opposite to that of silica. The image forming apparatus according to claim 1, wherein 0.001 mg / cm ² or more of toner is present on the image carrier during non-image formation.   The image forming apparatus according to claim 1, further comprising a conveying unit that supplies the developer to the developing unit, and a screw mechanism is used for the conveying unit.   The image forming apparatus according to claim 1, wherein particles having a diameter of 30 μm or more are not attached to the surface of the image carrier. The developer pumping amount of the developing unit is 30 mg / cm ² or more, and the developing gap between the image carrier and the developing roller of the developing unit is 0.4 μm or less. The image forming apparatus according to claim 5.   The image forming apparatus according to claim 1, wherein the number of pumping electrodes of the developing unit is one.   An intermediate transfer member that temporarily transfers an image before transfer to the recording medium, and the direction of the electric field between the intermediate transfer member and the image carrier is such that silica moves toward the intermediate transfer member. The image forming apparatus according to claim 1, wherein the image forming apparatus is provided. 9. The image forming apparatus according to claim 8, wherein the intermediate transfer member is constituted by an intermediate transfer belt, and a linear velocity difference is provided between the intermediate transfer belt and a photoconductor as an image carrier.   The image forming apparatus according to claim 1, wherein the cleaning unit includes a cleaning blade, and the cleaning blade has a hardness of a surface layer larger than a hardness of a base material. .   The image forming apparatus according to claim 10, wherein a gap between the cleaning blade and the photoconductor as an image carrier is 0.6 μm or less.   The image forming apparatus according to claim 1, wherein a charging roller is used as the charging unit.   The image forming apparatus according to claim 12, further comprising a charging roller cleaning member that contacts the charging roller.   The image forming apparatus according to claim 13, wherein the charging roller cleaning member has a roller shape.

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