JP2017026878A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can prevent both image defects and cleaning failure.SOLUTION: An image forming apparatus comprises: a fur brush 6 that removes a toner on a surface of a photoconductor drum 1 after a toner image is transferred by a primary transfer roller 5, and rubs the surface of the photoconductor drum 1 to charge to have a potential with a polarity reverse to a polarity of a potential at which a toner image is developed; and a CPU 500 that changes a condition for the fur brush 6 to rub the surface of the photoconductor drum 1 according to an image forming condition stored in a memory 504.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an image forming apparatus such as an electrophotographic system.

  Conventionally, in the electrophotographic system, a colored toner is developed on an electrostatic latent image formed by charging and exposing the surface of an image carrier to form a visible image, and the toner image is transferred to a transfer paper or the like. The image is formed by fixing with a heat roll or the like. Untransferred toner, external additives, and discharge products remain on the surface of the image carrier after the transfer process. For this reason, it is necessary to remove them by a cleaning means prior to the image forming process.

  As a cleaning means for removing transfer residual toner and the like, various methods such as a method using a fur brush, a magnetic brush, and the like, and a method using an elastic cleaning blade are used. A means for scraping off the transfer residual toner by rubbing the image carrier with a cleaning blade is generally used because it is simple and inexpensive.

  With the recent increase in speed and image quality of image forming apparatuses, the toner to be used has become nearly spherical, and it has become difficult to ensure cleaning performance with only a cleaning blade. Therefore, there is a cleaning assisting unit that assists in removing the transfer residual toner. For example, a fur brush that comes into contact with the image carrier is disposed in front of the cleaning blade, and transfer residual toner before reaching the cleaning blade is removed with the fur brush. Since pre-cleaning can be performed with a fur brush, there is a technique for reducing the load of the cleaning blade and improving the cleaning performance.

  As a specific technique using a fur brush, in Patent Document 1, the rotation speed of a fur brush as charging auxiliary means is controlled slower than that of an image carrier during image formation, and the fur brush is used during non-image formation. Is rotated faster than that during image formation. In this way, a control for discharging the transfer residual toner in the fur brush is proposed. As a result, clogging of the fur brush can be prevented.

  In recent years, in order to extend the life of the image carrier, there is a thermosetting type image carrier whose surface is hardly scraped by irradiating the surface of the image carrier with an electron beam. If the surface of the image bearing member is difficult to scrape, damage such as chattering of the cleaning blade, reversal of the blade, chipping of the cleaning edge, and wear is likely to occur. Therefore, the role of a cleaning auxiliary member such as a fur brush for improving the cleaning performance has become important.

Japanese Patent Laid-Open No. 10-221925

  In Patent Document 1, the transfer residual toner in the fur brush is discharged to the image carrier by increasing the peripheral speed of the fur brush during non-image formation. However, in the fur brush in the initial state, there is no transfer residual toner in the fur brush, so only the number of times of rubbing with the image carrier increases.

  Depending on the material of the fur brush, if the number of times of rubbing with the image carrier increases, there is a problem that the image carrier is charged with a polarity opposite to the charged potential due to frictional charging with the fur brush. When the image carrier is charged with a reverse polarity, it becomes difficult to uniformly charge the charging means, and image unevenness occurs.

  Further, when the speed of the image forming apparatus is increased, the charging capability is required more as the image forming speed increases. For this reason, when the image carrier is charged to a polarity opposite to the charging potential by rubbing the fur brush, it is necessary to increase the charging ability for charging. In order to increase the charging capability, the apparatus configuration becomes complicated, such as providing a plurality of charging members, and it becomes difficult to reduce the size and cost of the apparatus. That is, if the image bearing member is charged to a polarity opposite to the charging potential by rubbing with a fur brush, it is difficult to increase the image forming speed.

  Furthermore, it is difficult to increase the speed of the image forming apparatus, and besides the unevenness of the image, it is different from the originally intended charging potential. There is a problem that a defective image occurs. However, if the frequency of rubbing between the fur brush and the image carrier is changed gradually, the role of the fur brush as a cleaning auxiliary member is impaired and the cleaning performance is deteriorated.

  Needless to say, the same problem arises in a cleaning auxiliary member that is not a fur brush but is in contact with the image carrier and is charged to a polarity opposite to the charging potential.

  SUMMARY An advantage of some aspects of the invention is to provide an image forming apparatus capable of achieving both prevention of image defects and prevention of cleaning defects.

  In order to achieve the above object, a typical configuration of an image forming apparatus according to the present invention includes an image carrier that carries a toner image, a charging unit that charges the image carrier, and the image that is charged by the charging unit. A latent image forming unit that forms an electrostatic latent image on the carrier, a developing unit that develops the electrostatic latent image formed on the image carrier by the latent image forming unit, and the image carrier by the developing unit. Image formation comprising: transfer means for transferring a developed toner image; cleaning means for cleaning toner on the image carrier after being transferred by the transfer means; and storage means for storing conditions for image formation In the apparatus, the cleaning unit is rubbed and the image carrier is charged to a potential having a polarity opposite to the potential polarity at which the toner image is developed, and the cleaning is performed according to the image forming conditions stored in the storage unit. Between the means and the image carrier Characterized in that it has a changing means for changing the conditions, the.

  According to the present invention, it is possible to achieve both prevention of image failure and prevention of cleaning failure.

1 is an explanatory cross-sectional view illustrating a configuration of an image forming apparatus according to the present invention. FIG. 3 is a cross-sectional explanatory view illustrating a configuration of a cleaning device of the image forming apparatus according to the present invention. FIG. 2 is a block diagram illustrating a configuration of a control system of the image forming apparatus according to the present invention. It is a cross-sectional explanatory view showing an example of a potential measuring means for measuring the potential of the image carrier. 6 is a flowchart illustrating an operation for changing a rubbing condition between the cleaning unit and the image carrier in the first embodiment of the image forming apparatus according to the present invention. It is a figure which shows the relationship between the cleaning performance with respect to the peripheral speed ratio of the peripheral speed of the cleaning means with respect to the peripheral speed of an image carrier, and the electric potential of an image carrier. It is a figure which shows the relationship between the idle speed of the cleaning means which consists of a new article and a durable product, the peripheral speed ratio of the peripheral speed of the cleaning means to the peripheral speed of the image carrier, and the potential of the image carrier. 12 is a flowchart illustrating an operation for changing a rubbing condition between a cleaning unit and an image carrier in a second embodiment of the image forming apparatus according to the present invention.

  An embodiment of an image forming apparatus according to the present invention will be specifically described with reference to the drawings.

  First, the configuration of the first embodiment of the image forming apparatus according to the present invention will be described with reference to FIGS.

<Image forming apparatus>
FIG. 1 is an explanatory cross-sectional view showing a configuration of an image forming apparatus according to the present invention. An image forming apparatus 13 shown in FIG. 1 includes photosensitive drums 1Y and 1Y serving as image carriers that carry toner images on image forming stations 14Y, 14M, 14C, and 14K for each color of yellow Y, magenta M, cyan C, and black K. 1M, 1C, 1K. For convenience of explanation, the photosensitive drums 1Y, 1M, 1C, and 1K may be described using the photosensitive drum 1 as a representative. The same applies to other image forming process means.

  Around each photosensitive drum 1, a charging roller 2 serving as a charging unit for uniformly charging the surface of the photosensitive drum 1 is provided. Further, a laser scanner 3 is provided as a latent image forming means for forming an electrostatic latent image by irradiating the surface of the photosensitive drum 1 uniformly charged by the charging roller 2 with a laser beam 3a corresponding to image information. Yes.

  Further, a developing device 4 is provided as developing means for supplying toner to the electrostatic latent image formed on the surface of the photosensitive drum 1 by the laser scanner 3 and developing the toner. Further, a primary transfer roller 5 is provided as primary transfer means for primary transfer of the toner image developed on the surface of the photosensitive drum 1 by the developing device 4 onto the outer peripheral surface of the intermediate transfer belt 8 as a transfer body.

  Further, a fur brush 6 made of a brush-like rotating body is provided as a cleaning means for cleaning residual toner remaining on the surface (on the image carrier) of the photosensitive drum 1 after the primary transfer by the primary transfer roller 5. ing. Further, a cleaning device 15 serving as a cleaning unit having the fur brush 6 and the cleaning blade 7 is provided.

  In the present embodiment, after the primary transfer, after the transfer residual toner remaining on the surface of the photosensitive drum 1 is scraped, a fur brush 6 that can be arbitrarily rotated as a brush-like rotating body that collects and holds the transfer residual toner. Is used. In the present embodiment, the fur brush 6 is used as a rotating body. However, a rotatable roll-shaped rotating body may be used.

  An intermediate transfer belt 8 is provided opposite to the surface of each photosensitive drum 1 so as to be rotatable in the clockwise direction in FIG. 1 by stretching rollers 8a, 8b, and 8c. A secondary transfer roller 10 serving as a secondary transfer unit is provided opposite to the outer peripheral surface of the intermediate transfer belt 8. The recording material 12 is conveyed to a secondary transfer nip portion where the outer peripheral surface of the intermediate transfer belt 8 and the secondary transfer roller 10 are in contact with each other by a conveying means (not shown).

<Image forming operation>
First, the surface of the photosensitive drum 1 that rotates counterclockwise in FIG. 1 is uniformly charged by a charging roller 2 to which a charging bias voltage is applied from a charging bias power source provided in a high-voltage power source 502 shown in FIG. The A laser beam 3 a corresponding to image information is scanned and exposed on the surface of the photosensitive drum 1 uniformly charged by the charging roller 2 to form an electrostatic latent image on the surface of the photosensitive drum 1. A toner (developer) is supplied from the developing device 4 to the electrostatic latent image formed on the surface of the photosensitive drum 1 and developed as a toner image.

  The toner image developed on the surface of each photosensitive drum 1 is applied with a primary transfer bias voltage to each primary transfer roller 5 from a primary transfer bias power source provided in a high voltage power source 502 shown in FIG. As a result, primary transfer is sequentially performed in a superimposed manner on the outer peripheral surface of the intermediate transfer belt 8 rotating in the clockwise direction in FIG.

  The toner image primarily transferred onto the outer peripheral surface of the intermediate transfer belt 8 is as follows. A primary transfer bias voltage is applied from the secondary transfer bias power source provided in the high voltage power source 502 shown in FIG. 3 to the secondary transfer roller 10 serving as a secondary transfer unit. As a result, secondary transfer is collectively performed on the recording material 12 conveyed to the secondary transfer nip portion where the outer peripheral surface of the intermediate transfer belt 8 and the secondary transfer roller 10 are in contact.

  The recording material 12 onto which the toner image has been secondarily transferred is conveyed to a fixing device 11 serving as a fixing unit, and is heated and passed while passing through a fixing nip portion between a fixing roller and a pressure roller provided in the fixing device 11. The toner image is thermally fixed to the recording material 12 by being pressurized.

  The transfer residual toner remaining on the outer peripheral surface of the intermediate transfer belt 8 after the secondary transfer is scraped and removed from the outer peripheral surface of the intermediate transfer belt 8 by a cleaning blade provided in a cleaning device 9 serving as a cleaning unit. Then, it is collected in a waste toner container.

<Developer>
The developer of this embodiment is configured as a two-component developer having a nonmagnetic toner and a magnetic carrier. The toner is triboelectrically charged to a negative polarity by rubbing with the magnetic carrier. The toner of this embodiment uses a toner having an average particle diameter of about 6 μm obtained by pulverizing and classifying a kneaded pigment in a resin binder mainly composed of polyester. The average charge amount of the toner attached to the exposed portion potential of the photosensitive drum 1 is about −30 μC / g.

<Image carrier>
The photosensitive drum 1 serving as an image carrier of the present embodiment has an organic photosensitive member made of negatively chargeable OPC (Organic Photo Conductor) having an axial length of 360 mm and an outer diameter of 84 mm. Configured. In the photosensitive drum 1, a photosensitive layer including a photoconductive layer mainly composed of an organic photoconductor is formed on a conductive substrate such as aluminum.

  OPC is generally configured by laminating a charge generation layer, a charge transport layer, and a surface protective layer made of an organic material on a metal substrate as a conductive substrate. For example, each layer can be formed using a material disclosed in JP-A-2005-43806. The photosensitive drum 1 normally rotates counterclockwise in FIG. 1 at a process speed (peripheral speed) of 300 mm / sec. The photosensitive drum 1 is rotationally driven by a motor 501 serving as a driving source that is driven and controlled by a CPU (Central Processing Unit) 500 serving as a control unit and a changing unit.

<Charging means>
The charging roller 2 serving as a charging unit of the present embodiment is a contact-type charging roller 2 that rotates in contact with the surface of the photosensitive drum 1. The surface of the photosensitive drum 1 is uniformly charged by utilizing a discharge phenomenon that occurs in a minute gap between the photosensitive drum 1 and the photosensitive drum 1. A charging bias voltage of a predetermined condition is applied to the conductive core metal of the charging roller 2.

  For example, the DC component (DC) bias applied to the charging roller 2 is set to −500 V, and the AC component (AC) bias is set to a peak-to-peak bias that is at least twice the discharge start voltage under the environmental conditions. As a result, the image forming area on the surface of the photosensitive drum 1 rotating counterclockwise in FIG. 1 is uniformly charged to about −500V. That is, the charging potential on the surface of the photosensitive drum 1 is negative (negative electrode) (negative) polarity, and the surface of the photosensitive drum 1 is charged on the negative (negative electrode) (negative) side.

  Note that the direct current component (DC) bias applied to the charging roller 2 during image formation is not limited to this value, and depends on the environmental conditions, the usage durability of the photosensitive drum 1 and the charging roller 2, and the like. It is appropriately set to a potential suitable for good image formation. In this embodiment, an example using the contact type charging roller 2 that contacts the surface of the photosensitive drum 1 will be described. However, other charging means such as a non-contact type charging roller 2 or a corona charger may be used. good.

<Latent image forming means>
The laser scanner 3 serving as a latent image forming unit of the present embodiment includes a semiconductor laser that performs image exposure on the surface of the photosensitive drum 1 uniformly charged by the charging roller 2 based on image information. The exposure potential on the surface of the photosensitive drum 1 irradiated with the laser beam 3a is -200V. In the present embodiment, an example in which a semiconductor laser is used as the image exposure unit will be described. However, another image exposure unit using an LED (Light Emitting Diode) or the like may be used.

<Potential measuring means>
FIG. 4 is a cross-sectional explanatory view showing a configuration of a potential measuring device 16 serving as a potential measuring means for measuring the surface potential of the photosensitive drum 1 serving as an image carrier. The potential measuring device 16 of the present embodiment measures the surface potential of the photosensitive drum 1 by a chopper type potential sensor.

  In the present embodiment, as a potential measuring means for measuring the surface potential of the photosensitive drum 1, a potential measuring device 16 including a chopper type potential sensor shown in FIG. 4 is used. As a result, the surface potential of the photosensitive drum 1 is measured after exposure by irradiating the surface of the photosensitive drum 1 uniformly charged by the charging roller 2 with the laser beam 3a by the laser scanner 3. Thereby, it can be confirmed whether the charging potential and the exposure potential on the surface of the photosensitive drum 1 are actually predetermined potentials.

  As shown in FIG. 4, the chopper-type potential sensor provided in the potential measuring device 16 includes a tuning fork vibrator 802 serving as a conductive vibrating object between the photosensitive drum 1 serving as a measurement object and the measurement electrode 801. Is arranged.

  The surface of the photosensitive drum 1 that is the object to be measured is increased or decreased by the tuning fork vibrator 802 that vibrates in the direction of the arrow A in FIG. Measure the electric field strength.

  It is also possible to measure the surface potential of the photosensitive drum 1 using a potential measuring means other than the chopper type potential sensor shown in FIG. For example, the measurement electrode 801 itself is physically vibrated by using a capacitance variation type potential sensor, and the electric field distribution between the measurement electrode 801 and the photosensitive drum 1 as a measurement object is changed to change the photosensitive drum 1. It is possible to measure the electric field strength of the surface of the film.

  In FIG. 4, the measurement electrode 801 receives lines of electric force 807 from the photosensitive drum 1 serving as a measurement object. The tuning fork vibrator 802 vibrates and chops electric lines of force 807 incident on the measurement electrode 801 from the photosensitive drum 1 as a measurement object in the direction of arrow A in FIG. The amplification element 803 amplifies the minute alternating current signal induced in the measurement electrode 801 by impedance conversion. The piezoelectric element 804 applies vibration to the tuning fork vibrator 802.

  Reference numeral 805 denotes a circuit board. Reference numeral 806 denotes a connection connector. Via the connector 806 and the circuit board 805, a drive signal to the piezoelectric element 804, a reception signal from the measurement electrode 801, a power source for driving these signals, and the like are input / output.

  As shown in FIG. 4, electric lines of force 807 are incident in the direction of arrow B from the surface of the photosensitive drum 1 serving as a measurement object toward the measurement electrode 801. The shield case 808 accommodates the circuit board 805. An amplifier element 803 serving as an impedance conversion circuit is mounted on the circuit board 805.

<Developing means>
As shown in FIG. 2, the developing device 4 serving as a developing means rotates a developer container 4a containing a two-component developer that is a mixture of non-magnetic toner and a magnetic carrier, and an opening of the developer container 4a. And a developing sleeve 4b serving as a developer carrying member provided as possible.

  In this embodiment, the axial length of the developing sleeve 4b is 325 mm. The developing sleeve 4b magnetically holds the developer in the developer container 4a by a magnet fixedly disposed therein, and a gap formed between the surface of the developing sleeve 4b and the surface of the photosensitive drum 1. The developer is transported to a developing unit composed of a part.

  The developing sleeve 4b is connected to a developing bias power source for applying a developing bias voltage in which a DC voltage of −400V and an AC voltage having a peak-to-peak voltage Vpp of 1600V are superimposed. By applying the developing bias voltage to the developing sleeve 4b, the toner is attached to the electrostatic latent image formed on the surface of the photosensitive drum 1, and the developing process is performed.

<Cleaning means>
FIG. 2 is an explanatory cross-sectional view illustrating the configuration of the cleaning device 15 serving as a cleaning unit. As shown in FIG. 2, each cleaning device 15 is provided with a fur brush 6 serving as a cleaning unit supported by a housing 20 so as to be rotatable in the clockwise direction of FIG. 2. The fur brush 6 according to the present embodiment serves as both a toner scraping unit that scrapes residual toner remaining on the surface of the photosensitive drum 1 after the primary transfer, and an image carrier polishing unit that polishes the surface of the photosensitive drum 1. ing. A cleaning blade 7 that contacts the surface of the photosensitive drum 1 is provided downstream of the fur brush 6 in the rotation direction of the photosensitive drum 1.

  Residues such as transfer residual toner remaining on the surface of the photosensitive drum 1 after the primary transfer are disturbed by the fur brush 6 to weaken the adhesion to the surface of the photosensitive drum 1. Thereafter, the cleaning blade 7 scrapes and removes the surface of the photosensitive drum 1 and collects it in a housing 20 that becomes a waste toner container.

  Residue such as transfer residual toner removed from the surface of the photosensitive drum 1 is once held between the fibers of the fur brush 6, and then the fur brush 6 is rotated by the clockwise rotation of the fur brush 6 in FIG. 2. It is carried to a contact position with the scraper 60 that is in contact with the outer peripheral surface of the.

  The fur brush 6 made of fibers is elastically deformed by contact between the tip of the scraper 60 and the outer peripheral surface of the fur brush 6. Residue such as transfer residual toner jumps out of the fur brush 6 due to the repulsive force of the fibers of the fur brush 6. And it falls to the vicinity of the conveyance spiral 61 which has the helical blade | wing provided in the lower part of this fur brush 6. FIG.

  Residue such as transfer residual toner that has dropped near the conveyance spiral 61 is conveyed in the axial direction of the photosensitive drum 1 by the spiral blades of the conveyance spiral 61 extending in the rotation axis direction of the photosensitive drum 1. Further, the toner is collected in a waste toner collection container (not shown) via a collection toner conveyance path (not shown).

  The cleaning blade 7 of this embodiment is made of urethane rubber, and the length of the cleaning blade 7 in the axial direction is 340 mm. The cleaning blade 7 is in contact with the surface of the photosensitive drum 1 with a predetermined contact pressure.

<Fur brush>
The fur brush 6 made of a brush-like rotating body is obtained by planting fibers on the rotating shaft 6a. It is manufactured by winding a cloth material in which fibers are implanted around the surface of a metal rotating shaft 6a having an outer diameter of 12 mm. The fiber of the fur brush 6 is a fiber in which 6 denier (weight per unit length) acrylic single fiber is bundled, and is implanted on the substrate at a flocking density of 50 kF / inch ² (flocking density per single fiber). It is a thing. The fiber length of the fur brush 6 is 4.5 mm.

  The fibrous acrylic employed as the fur brush 6 of this embodiment has a characteristic that it is easily charged negative (negative electrode) in the triboelectric charging series. Another fiber material applicable as the fur brush 6 may be polyester. The fur brush 6 is disposed at a position where the fur brush 6 enters about 0.5 mm with respect to the surface of the photosensitive drum 1, and the surface of the photosensitive drum 1 is rubbed while rotating in the forward direction with respect to the rotational direction of the photosensitive drum 1. To do.

  As the material of the fur brush 6, acrylic or polyester may be used as a charge series material that is easily charged to a polarity opposite to the charging potential of the toner and the photosensitive drum 1. The average charge amount of the transfer residual toner may be on the positive (positive electrode) side. This is an influence when the surface of the photosensitive drum 1 passes through the primary transfer roller 5. The average charge amount of the untransferred toner that has not been primarily transferred is greatly reduced, and the polarity may be reversed from negative (negative electrode) to positive (positive electrode).

  For this reason, the fur brush 6 having a charge series that tends to be negative (negative electrode) can easily collect the transfer residual toner or the like having a positive (positive electrode) polarity. Accordingly, there is an effect of assisting the cleaning operation by easily removing the transfer residual toner from the surface of the photosensitive drum 1.

  Further, there is an effect that the potential charged to the negative (negative electrode) on the surface of the photosensitive drum 1 by the contact of the fur brush 6 is gradually reduced in a direction to return to zero potential. From these effects, the material of the fur brush 6 is preferably acrylic or polyester.

  In addition, as the material of the fur brush 6, polytetrafluoroethylene (PTFE; polytetrafluoroethylene,), vinyl chloride or the like can be applied.

  As shown in FIG. 2, the scraper 60 is in contact with the outer surface of the fur brush 6 on the opposite side (the right side in FIG. 2) to the side facing the surface of the photosensitive drum 1 (the left side in FIG. 2). The transfer residual toner collected on the fur brush 6 by the repulsive force of the fiber of the fur brush 6 from the surface of the photosensitive drum 1 is ejected from the fur brush 6 by the scraper 60 in contact with the outer peripheral surface of the fur brush 6. As a result, the transfer residual toner collected by the fur brush 6 is less likely to clog the fibers of the fur brush 6.

  Further, when the cleaning device 15 is attached to the image forming apparatus 13, the metal rotating shaft 6 a of the fur brush 6 is attached so as to be in contact with the metal frame of the image forming apparatus 13. The photosensitive drum 1 and the fur brush 6 rotate in the directions of arrows a and b in FIG. As a result, the photosensitive drum 1 and the fur brush 6 rotate in the same direction at the contact nip portion between them.

  The fur brush 6 is a control means for driving and controlling the motor 501 serving as a drive source shown in FIG. 3, and can be arbitrarily rotated by a CPU 500 serving as a changing means. The fur brush 6 of the present embodiment is set so as to be able to rotate at a predetermined peripheral speed ratio (for example, 140%) with respect to the peripheral speed of the surface of the photosensitive drum 1.

<Characteristics of fur brush>
With the materials of the fur brush 6 and the photosensitive drum 1, the surface of the photosensitive drum 1 has a potential polarity at which the toner image is developed if the number of times of the rubbing of the fur brush 6 with respect to the surface of the photosensitive drum 1 is excessive. It will be charged to a reverse polarity potential. In the present embodiment, the positive polarity (positive electrode) in which the potential polarity at which the toner image on the surface of the photosensitive drum 1 is developed is opposite to the negative (negative electrode) is positive (positive electrode) charging. An example will be described.

  The surface of the photosensitive drum 1 is less likely to be positively (positively) charged when the fur brush 6 is in a new initial state. This is because when the fur brush 6 is new, there is no contamination due to the transfer residual toner and the fiber of the fur brush 6 has high rigidity. Further, the cleaning performance of the surface of the photosensitive drum 1 is higher when the fur brush 6 is in a new initial state.

  In the case of the initial fur brush 6 that is not soiled with the transfer residual toner, it is not necessary to rotate the fur brush 6 at a peripheral speed ratio of 140% with respect to the peripheral speed of the surface of the photosensitive drum 1. That is, since the new fur brush 6 in the initial state has sufficient cleaning performance, the cleaning performance will not be impaired even if the peripheral speed ratio of the surface of the photosensitive drum 1 is slower than 140%. .

  The inventor investigated the influence on the surface potential of the photosensitive drum 1 when the fur brush 6 in various states from the new initial state to the latter half of the durability was rubbed against the surface of the photosensitive drum 1. As a result, it was found that the surface of the photosensitive drum 1 is more likely to be positively (positively) charged as the transfer residual toner is clogged between the fibers of the fur brush 6.

  Similarly, when the cleaning performance of the fur brush 6 in various states is examined, the positive (positive electrode) charging potential V <b> 1 on the surface of the photosensitive drum 1 increases as the transfer residual toner becomes clogged between the fibers of the fur brush 6. I understood.

  It was also found that the positive (positive electrode) charging potential V1 on the surface of the photosensitive drum 1 increases as the ratio of the peripheral speed of the outer peripheral surface of the fur brush 6 to the peripheral speed of the surface of the photosensitive drum 1 decreases.

  The lower the positive (positive) charging potential V1 on the surface of the photosensitive drum 1, the stronger the rubbing force of the fur brush 6 against the surface of the photosensitive drum 1, and the higher the cleaning performance.

  Conversely, it was found that the higher the positive (positive) charging potential V1 on the surface of the photosensitive drum 1, the weaker the rubbing force of the fur brush 6 against the surface of the photosensitive drum 1 and the lower the cleaning performance.

  From the above, there is a correlation as shown in FIG. 6 between the positive (positive electrode) charging potential V1 on the surface of the photosensitive drum 1 and the cleaning performance, and these correlations are tabulated to form the image forming apparatus 13 shown in FIG. It is stored in a database 505 serving as a storage means provided in the inside.

  In order to prevent the positive (positive electrode) charging potential V1 on the surface of the photosensitive drum 1 from being lowered, toner is supplied to the fur brush 6 and the toner is forcibly clogged between the fibers of the fur brush 6 for photosensitivity. A method of reducing the rubbing force of the fur brush 6 against the surface of the drum 1 can be considered. Alternatively, the peripheral speed ratio of the outer peripheral surface of the fur brush 6 with respect to the peripheral speed of the surface of the photosensitive drum 1 may be reduced.

  When implementing these measures, the cleaning performance is performed within a range that does not impair the cleaning performance based on the correlation between the positive (positive electrode) charging potential V1 of the surface of the photosensitive drum 1 and the cleaning performance of the surface of the photosensitive drum 1. .

  How the surface of the photosensitive drum 1 is charged by rubbing with the fur brush 6 was determined by measuring as follows. As an environmental condition in which the image forming apparatus 13 is installed, an environmental condition in which the temperature is 20 ° C. and the humidity is 50% is considered. Under this environmental condition, the charging bias voltage applied to the charging roller 2 by the charging bias power source provided in the high voltage power source 502 shown in FIG. Further, the primary transfer bias voltage applied to the primary transfer roller 5 by the primary transfer bias power source similarly provided in the high voltage power source 502 is turned OFF. In addition, the operation of the laser scanner 3 or the like that affects the surface potential of the photosensitive drum 1 is also turned off.

  The cleaning device 15 performs the idle rotation of the photosensitive drum 1 for about 10 minutes in the same state as the normal image forming operation of the image forming device 13. The surface potential of the photosensitive drum 1 during idling was measured every second by the potential measuring device 16 shown in FIG. 4, and the surface potential of the photosensitive drum 1 after 10 minutes was measured.

  If the surface potential of the photosensitive drum 1 10 minutes after the start of idling of the photosensitive drum 1 is negative (negative electrode), it is determined that the polarity is the same as the negative (negative electrode) charging potential. It was determined that the effect of rubbing by the fur brush 6 was larger as the absolute value of the surface potential of the photosensitive drum 1 at that time was larger.

  On the other hand, if the surface potential of the photosensitive drum 1 10 minutes after the start of idling of the photosensitive drum 1 is on the plus (positive) side, it is determined that the polarity is opposite to the negative (negative) charging potential. The surface was judged to be positive (positive electrode) charged. Similarly, it was determined that the magnitude of the surface potential of the photosensitive drum 1 at that time was the magnitude of the influence of the rubbing of the fur brush 6.

<Control of rubbing condition of cleaning means>
Next, control of the rubbing condition of the fur brush 6 serving as a cleaning unit will be described with reference to FIGS. 3, 5, and 7. FIG. 3 is a block diagram showing the configuration of the control system of this embodiment. FIG. 5 is a flowchart showing how the ratio of the peripheral speed of the outer peripheral surface of the fur brush 6 to the peripheral speed of the surface of the photosensitive drum 1 is changed in accordance with the surface potential of the photosensitive drum 1. FIG. 7 is a diagram showing the relationship between the rotation time of the fur brush 6 (the idle rotation time of the photosensitive drum 1) and the positive (positive electrode) charging potential V1 on the surface of the photosensitive drum 1.

<Control system>
First, the configuration of the control system of this embodiment will be described with reference to FIG. In FIG. 3, the following members are connected to a CPU (Central Processing Unit) 500 serving as a control means. An environmental sensor 503 for detecting environmental conditions in which the potential measuring device 16 and the image forming apparatus 13 shown in FIG. 4 are installed is connected. In addition, a memory 504 serving as storage means for storing conditions for image formation is connected.

  In addition, the CPU 500 stores a table such as the durable number of the recording material 12 for each part and the peripheral speed ratio of the outer peripheral surface of the fur brush 6 to the peripheral speed of the surface of the photosensitive drum 1 according to the durable number of the recording material 12. A database 505 serving as a storage means is connected. In addition, a toner amount detection unit 506 serving as a toner amount detection unit is connected.

  The CPU 500 operates the image forming apparatus 13 in accordance with signals input in advance and stored in the database 505 and image formation input information. Therefore, the CPU 500 is connected to a motor 501 serving as a drive source for driving the photosensitive drum 1, the fur brush 6, the developing device 4, the intermediate transfer belt 8, and the like.

  Further, a high voltage power source 502 is connected to the CPU 500. The high-voltage power source 502 is provided with a charging bias power source that applies a charging bias voltage to the charging roller 2 during image formation. Further, a developing bias power source for applying a developing bias voltage to the developing sleeve 4b is provided. Further, a primary transfer bias power source for applying a primary transfer bias voltage to the primary transfer roller 5 is provided. Further, a secondary transfer bias power source for applying a secondary transfer bias voltage to the secondary transfer roller 10 is provided.

  As a result, the CPU 500 controls the motor 501 and the high-voltage power supply 502 in accordance with the image forming signal to apply the respective bias voltages to the charging roller 2, the developing device 4, the primary transfer roller 58, and the secondary transfer roller 10. An image forming operation can be performed.

  Next, drive control of the fur brush 6 will be described with reference to FIG. First, drive control of the fur brush 6 is started in step S1. The timing for carrying out the drive control of the fur brush 6 is as follows. In order to use the image forming apparatus 13, the power is turned on, and the image forming condition data stored in the memory 504 or the database 505 serving as a storage unit is referenced to perform a preparation operation for forming an image. At that time, the drive control of the fur brush 6 may be performed.

  Alternatively, it is known that when the fur brush 6 is in a new initial state, the surface of the photosensitive drum 1 is difficult to be positively (positively) charged by the rubbing of the fur brush 6. In this case, the image forming condition data stored in the memory 504 or the database 505 is referred to. The control timing may be changed according to the total number of rotations J0 of the fur brush 6 and the amount of toner remaining on the surface of the photosensitive drum 1 after the primary transfer arrives at the fur brush 6.

  For example, when the fur brush 6 is in a new initial state and the number of printed recording materials 12 is 10,000, the drive control of the fur brush 6 shown in FIG. Then, when the number of prints of the recording material 12 exceeds 10,000 and reaches 20000, the drive control of the fur brush 6 is performed every 2000 prints of the recording material 12. When the number of printed recording materials 12 exceeds 20000, the drive control of the fur brush 6 may be performed every 5000 printed recording materials 12.

  Note that the change in the rubbing condition between the fur brush 6 and the surface of the photosensitive drum 1 increases the number of times of rubbing between the fur brush 6 and the surface of the photosensitive drum 1 as the number of images formed on the recording material 12 increases. You can also make it. The number of friction between the fur brush 6 and the surface of the photosensitive drum 1 is proportional to the ratio of the peripheral speed of the fur brush 6 to the peripheral speed of the photosensitive drum 1. Therefore, the ratio of the peripheral speed of the fur brush 6 to the peripheral speed of the photosensitive drum 1 can be increased as the number of images formed on the recording material 12 increases. Further, as described above, the interval of the drive control timing for changing the peripheral speed ratio of the fur brush 6 with respect to the peripheral speed of the photosensitive drum 1 can be increased as the number of printed sheets of the recording material 12 increases.

  When the drive control of the fur brush 6 is started, the fur brush 6 and the photosensitive drum 1 are driven to rotate by the motor 501 without driving the charging roller 2, the intermediate transfer belt 8, the primary transfer roller 5, the developing device 4, and the like. A certain time (30 seconds in this embodiment) elapses after the fur brush 6 and the photosensitive drum 1 start to rotate. At that time, in step S2, the surface potential of the photosensitive drum 1 at that time is measured by the potential measuring device 16 shown in FIG. 4 arranged downstream of the laser scanner 3 shown in FIG. 2 in the rotation direction of the photosensitive drum 1. . In step S2, the charging potential V1 of the surface of the photosensitive drum 1 measured by the potential measuring device 16 shown in FIG. 4 is, for example, + 18V.

  Next, in step S3, the CPU 500 reads the threshold value V0 stored and stored in the database 505 in advance, and the charged potential on the surface of the photosensitive drum 1 measured by the potential measuring device 16 shown in FIG. V1 is compared with the threshold value V0. Although it depends on the configuration of the image forming apparatus 13, the threshold value V0 is set to + 10V in this embodiment. That is, when the positive (positive electrode) charging potential V1 potential on the surface of the photosensitive drum 1 is +10 V or less, no image defect occurs.

  In step S3, the charging potential V1 of the surface of the photosensitive drum 1 measured by the potential measuring device 16 shown in FIG. 4 and the threshold value V0 have the following equation (1). In this case, the charging potential V1 on the surface of the photosensitive drum 1 is not the positive (positive) charging potential V1 at which image unevenness occurs. For this reason, the process proceeds to step S4, the fur brush 6 is rotated at a peripheral speed ratio of 140% with respect to the peripheral speed of the surface of the photosensitive drum 1, and then the process proceeds to step S5 to finish the drive control of the fur brush 6.

[Equation 1]
V1 ≦ V0

  On the other hand, if the charging potential V1 of the surface of the photosensitive drum 1 measured by the potential measuring device 16 shown in FIG. 4 and the threshold value V0 are in the relationship of the following equation (2) in step S3, the process proceeds to step S6. .

[Equation 2]
V1> V0

  In step S6, the CPU 500 controls as follows according to the value of the charging potential V1 of the surface of the photosensitive drum 1 measured by the potential measuring device 16 shown in FIG. 4 and the threshold value V0. The positive (positive electrode) charging potential V1 of the surface of the photosensitive drum 1 shown in FIG. 6, the threshold value V0, and the peripheral speed ratio of the outer peripheral surface of the fur brush 6 to the peripheral speed of the surface of the photosensitive drum 1 are stored in the database 505 in advance. Refer to the table showing the relationship. Then, the ratio of the peripheral speed of the outer peripheral surface of the fur brush 6 to the peripheral speed of the surface of the photosensitive drum 1 is changed.

  The change in the peripheral speed ratio of the outer peripheral surface of the fur brush 6 with respect to the peripheral speed of the surface of the photosensitive drum 1 is the number of rotations of the fur brush 6 and the photosensitive drum 1 rotated by the motor 501 shown in FIG. Can be performed by controlling each of the above.

  In the present embodiment, the CPU 500 serving as the changing unit changes the rubbing condition between the fur brush 6 and the surface of the photosensitive drum 1 in accordance with the measurement result of the potential measuring device 16 shown in FIG.

  Then, the steps S2 to S3 are performed again at the peripheral speed ratio of the outer peripheral surface of the fur brush 6 to the peripheral speed of the surface of the photosensitive drum 1 changed in step S6. In step S3, the peripheral speed of the outer peripheral surface of the fur brush 6 with respect to the peripheral speed of the surface of the photosensitive drum 1 in step S6 until the charging potential V1 of the surface of the photosensitive drum 1 and the threshold value V0 satisfy the relationship of the above equation (1). The ratio change is performed repeatedly.

  The charging property by frictional charging caused by the rubbing of the surface of the photosensitive drum 1 by the fur brush 6 depends on environmental conditions such as temperature and humidity. For this reason, the threshold value V0 may be appropriately changed according to the detection result of the environmental sensor 503 that detects the environmental condition of the temperature and humidity of the place where the image forming apparatus 13 is installed. Environmental information such as temperature and humidity detected by the environmental sensor 503 is also sent to the CPU 500 and used for calculation control.

  In FIG. 5, the positive (positive) charging potential V <b> 1 on the surface of the photosensitive drum 1 is lowered by lowering the peripheral speed ratio of the outer peripheral surface of the fur brush 6 to the peripheral speed of the surface of the photosensitive drum 1. In addition to lowering the peripheral speed ratio of the outer peripheral surface of the fur brush 6 with respect to the peripheral speed of the surface of the photosensitive drum 1, toner may be forcibly supplied to the fur brush 6.

  Further, the ratio of the peripheral speed of the outer peripheral surface of the fur brush 6 to the peripheral speed of the surface of the photosensitive drum 1 adjusted in step S6 is adjusted in consideration of the cleaning performance shown in FIG. As a result, it is possible to realize both prevention of positive (positive) charging of the surface of the photosensitive drum 1 and ensuring of cleaning performance.

  Further, when the drive control of the fur brush 6 shown in FIG. 5 is performed, the measurement result by the potential measuring device 16 shown in FIG. 4 is determined in consideration of the signal from the high voltage power source 502 shown in FIG. Then, referring to the table stored in the database 505, the drive control result of the fur brush 6 shown in FIG. 5 is determined.

  FIG. 6 shows the relationship between the cleaning performance of the surface of the photosensitive drum 1 relative to the peripheral speed ratio of the outer peripheral surface of the fur brush 6 with respect to the peripheral speed of the surface of the photosensitive drum 1, and the positive (positive electrode) charging potential V1 of the surface of the photosensitive drum 1. Show. The positive (positive electrode) charging potential V1 on the surface of the photosensitive drum 1 is measured by the potential measuring device 16 shown in FIG. The cleaning performance of the surface of the photosensitive drum 1 was judged by measuring the number of passing particles such as toner on the surface of the photosensitive drum 1 passing through the cleaning blade 7 shown in FIG.

  In FIG. 6, the two vertical axes represent the positive (positive electrode) charging potential V <b> 1 on the surface of the photosensitive drum 1 and the cleaning performance of the surface of the photosensitive drum 1. As the cleaning performance of the surface of the photosensitive drum 1, the number of passing particles such as toner on the surface of the photosensitive drum 1 passing through the cleaning blade 7 shown in FIG. 2 is counted.

  The horizontal axis in FIG. 6 indicates the ratio of the peripheral speed of the outer peripheral surface of the fur brush 6 to the peripheral speed of the surface of the photosensitive drum 1. The ratio of the peripheral speed of the outer peripheral surface of the fur brush 6 to the peripheral speed of the surface of the photosensitive drum 1 is changed and checked under each condition. The positive (positive electrode) charging potential V1 of the surface of the photosensitive drum 1 and the cleaning performance are obtained. The compatible range is stored in the database 505 shown in FIG.

  As shown in FIG. 6, the fur brush 6 rubs against the photosensitive drum 1 as the peripheral speed of the outer peripheral surface of the fur brush 6 is higher than the peripheral speed of the surface of the photosensitive drum 1 (right side in FIG. 6). Therefore, as shown by a curve d in FIG. 6, the positive (positive electrode) charging potential V1 on the surface of the photosensitive drum 1 is increased.

  On the other hand, as the peripheral speed of the outer peripheral surface of the fur brush 6 is higher than the peripheral speed of the surface of the photosensitive drum 1 (right side in FIG. 6), as shown by the curve e in FIG. Will improve. When the peripheral speed of the outer peripheral surface of the fur brush 6 is slower than the peripheral speed of the surface of the photosensitive drum 1 (left side in FIG. 6), the ability to disturb the transfer residual toner on the surface of the photosensitive drum 1 is reduced and cleaning performance is improved. Will decline.

  In FIG. 6, the result of measuring the number of passing particles such as toner on the surface of the photosensitive drum 1 passing through the cleaning blade 7 was evaluated as the cleaning performance. Therefore, when the curve e rises in FIG. 6, it means that the cleaning performance is lowered, and when the curve e is lowered, it means that the cleaning performance is improved.

  For example, consider the case where the photosensitive drum 1, the fur brush 6 and the cleaning blade 7 are all new. When the peripheral speed ratio of the outer peripheral surface of the fur brush 6 with respect to the peripheral speed of the surface of the photosensitive drum 1 is 30% to 105%, the positive (positive) charging potential V1 on the surface of the photosensitive drum 1 and the cleaning performance can be compatible. I understood.

  FIG. 7 shows the relationship between the idling time of the fur brush 6 and the positive (positive electrode) charging potential V1 on the surface of the photosensitive drum 1. In FIG. 7, the vertical axis represents the positive (positive electrode) charging potential V <b> 1 on the surface of the photosensitive drum 1, and the horizontal axis represents the idling time of the fur brush 6. The conditions of the fur brush 6 plotted in FIG. 7 exemplify three kinds shown by the curves f, g, and h in FIG.

  A curve f shown in FIG. 7 is obtained by idling the peripheral speed of the outer peripheral surface of the new fur brush 6 at a peripheral speed ratio of 140% with respect to the peripheral speed of the surface of the photosensitive drum 1.

  A curve g shown in FIG. 7 is obtained by idly rotating the peripheral speed of the outer peripheral surface of the new fur brush 6 at a peripheral speed ratio of 100% with respect to the peripheral speed of the surface of the photosensitive drum 1.

  A curve h shown in FIG. 7 is obtained by idling the peripheral speed of the outer peripheral surface of the durable (old product) fur brush 6 at a peripheral speed ratio of 140% with respect to the peripheral speed of the surface of the photosensitive drum 1.

  In the curve f shown in FIG. 7, when the idling time of the fur brush 6 reaches 5 minutes, the positive (positive electrode) charging potential V1 on the surface of the photosensitive drum 1 exceeds + 50V. Therefore, the positive (positive electrode) charging potential V1 on the surface of the photosensitive drum 1 is high.

  A curve g shown in FIG. 7 indicates that the peripheral speed of the outer surface of the fur brush 6 indicated by the curve f is 140% to 100% of the peripheral speed of the surface of the photosensitive drum 1 in accordance with the control shown in FIG. A positive (positive electrode) charging potential V1 on the surface of the photosensitive drum 1 when the speed ratio is lowered is shown. In the curve g shown in FIG. 7, the positive (positive electrode) charging potential V1 on the surface of the photosensitive drum 1 is low and stable as compared with the curve f.

  A curve h shown in FIG. 7 is a durable (old product) fur brush 6, and therefore has a lower ability to positively (positively) charge the surface of the photosensitive drum 1 than a new fur brush 6. Therefore, the curve h shown in FIG. 7 shows the positive (positive) charging potential on the surface of the photosensitive drum 1 even if the peripheral speed ratio of the outer peripheral surface of the fur brush 6 to the peripheral speed of the surface of the photosensitive drum 1 remains 140%, which is the same as the curve f. V1 is low and stable.

  The positive (positive electrode) charging potential V1 on the surface of the photosensitive drum 1 may be measured for each sheet when an image is formed on the recording material 12. The positive (positive electrode) charging potential V1 on the surface of the photosensitive drum 1 can be measured at a timing such as during rotation after image formation is completed. Thereby, the positive (positive electrode) charging potential V1 on the surface of the photosensitive drum 1 can also be controlled to be a certain level or less.

  In other words, control is performed to change the peripheral speed ratio of the outer peripheral surface of the fur brush 6 to the peripheral speed of the surface of the photosensitive drum 1 so that the positive (positive electrode) charging potential V1 on the surface of the photosensitive drum 1 is stabilized below a certain level.

  In the present embodiment, the positive (positive electrode) charging potential V1 on the surface of the photosensitive drum 1 is an example measured by the potential measuring device 16 shown in FIG. For this reason, the provision of the potential measuring device 16 leads to an increase in size and cost of the image forming device 13.

  Since the positive (positive electrode) charging potential V1 on the surface of the photosensitive drum 1 is directly measured using the potential measuring device 16, the detection accuracy is good. In addition, in place of the potential measuring device 16, development is performed by supplying toner to the positive (positive) charging potential V 1 on the surface of the photosensitive drum 1. Then, the toner amount developed in the charged region of the positive (positive) charging potential V1 on the surface of the photosensitive drum 1 is detected by a toner amount detection unit 506 shown in FIG.

  The fur brush 6 slides on the surface of the photosensitive drum 1 and the surface of the photosensitive drum 1 is charged to a male potential opposite to the potential polarity at which the toner image is developed. The developing device 4 develops the charged potential. The toner amount of the developed toner image is detected by a toner amount detection unit 506 serving as a toner amount detection unit. The potential measuring unit of the present embodiment measures the surface potential of the photosensitive drum 1 based on the toner amount detected by the toner amount detecting unit 506 instead of the potential measuring device 16.

  Then, based on the detection result of the toner amount detection unit 506, the CPU 500 serving as a changing unit may perform control to change the peripheral speed ratio of the outer peripheral surface of the fur brush 6 with respect to the peripheral speed of the surface of the photosensitive drum 1.

  As the toner amount detection unit 506 shown in FIG. 3, for example, a patch that optically detects the density of a patch image developed by supplying toner to the positive (positive) charging potential V1 on the surface of the photosensitive drum 1. An image detection sensor can be applied. In addition, after fixing the toner image on the recording material 12, the toner image can be read with a scanner to measure the density.

  A positive (positive) charging potential V1 charged to a polarity opposite to the polarity of the charging potential on the developing side is detected by rubbing between the surface of the photosensitive drum 1 and the fur brush 6, and the photosensitive drum 1 is detected. The peripheral speed ratio of the outer peripheral surface of the fur brush 6 to the peripheral speed of the surface 1 is changed.

  The surface of the photosensitive drum 1 and the fur brush 6 are rubbed with each other in accordance with a positive (positive) charging potential V1 charged to a polarity opposite to the polarity of the charging potential on the developing side. The peripheral speed ratio of the outer peripheral surface of the fur brush 6 with respect to the peripheral speed of the surface of 1 is reduced. As a result, the surface potential of the photosensitive drum 1 can be prevented from being charged to a polarity opposite to the polarity of the charging potential on the developing side.

  That is, the surface potential of the photosensitive drum 1 is charged to a polarity opposite to the polarity of the charging potential on the developing side by rubbing of a cleaning member such as the fur brush 6. As a result, the surface potential of the photosensitive drum 1 becomes non-uniform. As a result, image defects such as image unevenness and white background fogging occur. In the present embodiment, this can be prevented and at the same time, the cleaning failure of the surface of the photosensitive drum 1 can be prevented. In addition, speeding up of image formation is facilitated.

  Next, the configuration of the second embodiment of the image forming apparatus according to the present invention will be described with reference to FIG. In addition, what was comprised similarly to the said 1st Embodiment attaches | subjects the same member name even if the same code | symbol or a code | symbol differs, and abbreviate | omits description.

  In the present embodiment, what is different from the first embodiment is a control flow for performing the rotation operation of the fur brush 6 shown in FIG. Therefore, the description which overlaps with the said 1st Embodiment is abbreviate | omitted. FIG. 8 is a flowchart showing a state in which the rotation operation of the fur brush 6 in the second embodiment of the image forming apparatus of this embodiment is controlled.

  In FIG. 8, the positive (positive electrode) charging potential V <b> 1 on the surface of the photosensitive drum 1 varies depending on the state F <b> 0 of the fur brush 6. As described above, the state F0 of the fur brush 6 changes when the image forming operation is repeated. Specifically, the state F0 change of the fur brush 6 varies depending on the rotation speed of the fur brush 6, the amount of toner entering between the fibers of the fur brush 6, and the charge amount of the toner.

  Further, the positive (positive electrode) charging potential V1 on the surface of the photosensitive drum 1 varies depending on the surface layer state and film thickness of the photosensitive drum 1.

  Therefore, in the present embodiment, the number of rotations of the fur brush 6 and the amount of toner reaching the fur brush 6 are integrated. Integration is performed by the data stored in the memory 504 serving as storage means for storing the image forming conditions of the image forming apparatus 13 shown in FIG.

  When the fur brush 6 and the surface of the photosensitive drum 1 are repeatedly rubbed, physical deformation and brush characteristics of the fur brush 6 change. For this reason, the change F0 of the fur brush 6 depends on the rotation speed of the fur brush 6.

  Further, the positive (positive electrode) chargeability of the surface of the photosensitive drum 1 varies depending on the presence or absence of toner between the fibers of the fur brush 6. Therefore, it is necessary to consider the amount of toner that reaches the fur brush 6 in addition to the rotation speed of the fur brush 6.

  The amount of toner reaching the fur brush 6 is calculated as follows. The transfer efficiency of the toner image measured at any time at the primary transfer nip between the surface of the photosensitive drum 1 and the surface of the primary transfer roller 5 which are in contact with each other via the intermediate transfer belt 8 shown in FIG. It is stored in the database 505 shown. Then, it is calculated by calculating the image information input at the time of image formation and the transfer efficiency stored in the database 505 shown in FIG.

  It is known that the toner charge amount changes when passing through the primary transfer roller 5. Therefore, the charge amount of the residual toner remaining on the surface of the photosensitive drum 1 when the transfer conditions such as the primary transfer bias voltage applied to the primary transfer roller 5 are changed is measured, and the storage means shown in FIG. 3 is obtained. Stored in the database 505.

  Based on the charge amount data of the residual toner remaining on the surface of the photosensitive drum 1 stored in the database 505, the following prediction can be made. Referring to transfer conditions such as a primary transfer bias voltage applied to the primary transfer roller 5 and image information to be printed, the amount of toner reaching the fur brush 6 and the charge amount of the toner are calculated and predicted. I can do it.

  When the toner reaching the fur brush 6 is calculated and predicted, if the toner distribution in the axial direction of the photosensitive drum 1 is also calculated, charging unevenness due to positive (positive electrode) charging on the surface of the photosensitive drum 1 will be caused. Can be prevented.

  On the other hand, it is known that the surface layer state of the photosensitive drum 1 that affects the positive (positive electrode) charging characteristics of the surface of the photosensitive drum 1 and the change in film thickness are related to the rotational speed of the photosensitive drum 1. For this reason, the CPU 500 accumulates the number of rotations of the photosensitive drum 1, and stores the total number of rotations N0 of the photosensitive drum 1 in the database 505 shown in FIG.

  The surface layer state and film thickness of the photosensitive drum 1 are predicted more accurately. For this purpose, charging conditions such as a charging bias voltage applied to the surface of the photosensitive drum 1 by the charging roller 2 shown in FIG. 2 are considered. Further, transfer conditions such as a primary transfer bias voltage applied to the primary transfer roller 5 are considered. Furthermore, it is desirable to consider the contact condition of the fur brush 6 and the cleaning blade 7 provided on the cleaning device 15 with the surface of the photosensitive drum 1.

  In this embodiment, the surface layer state and film thickness (photoconductor) state change of the photosensitive drum 1 uses only the total number N0 of rotation of the photosensitive drum 1 as a parameter for prediction calculation. Further, the change in the state F0 of the fur brush 6 uses the integrated value of the rotation speed of the fur brush 6 and the history of image information as parameters because the fur brush 6 is rotationally driven during image formation.

  FIG. 8 shows a flowchart for changing and controlling the ratio of the peripheral speed of the outer surface of the fur brush 6 to the peripheral speed of the surface of the photosensitive drum 1 for each number of recording materials 12 when forming an image on the recording material 12.

  In step S11 of FIG. 8, the control of the peripheral speed ratio of the outer peripheral surface of the fur brush 6 with respect to the peripheral speed of the surface of the photosensitive drum 1 is started. Next, in step S12, the CPU 500 refers to the total rotation number N0 of the photosensitive drum 1, the total rotation number J0 of the fur brush 6, and the image information L0 stored as needed in the database 505 shown in FIG. The database 505 is configured as a storage unit that stores conditions for image formation.

  Next, in step S13, the state F0 of the fur brush 6 is calculated from the image information L0 acquired by the CPU 500 in step S12 and the total rotation number J0 of the fur brush 6.

  In step S13, the state F0 of the fur brush 6 is calculated by a numerical value from 0% to 100% as to how much the positive (positive electrode) is charged by rubbing the surface of the photosensitive drum 1.

  In this embodiment, it is defined that the greater the value of the state F0 of the fur brush 6, the stronger the positive (positive) charging of the surface of the photosensitive drum 1 by the rubbing friction of the fur brush 6.

  The image information L0 is used to calculate the toner amount that the transfer residual toner remaining on the surface of the photosensitive drum 1 after the primary transfer reaches the fur brush 6 shown in FIG. 2 and the charge amount of the toner. In step S13, the state F0 of the fur brush 6 is calculated. At that time, the image information L0 uses the image information P printed on the X recording materials 12 immediately before the state F0 of the fur brush 6 is calculated. Furthermore, image information (including a control patch image) Q that has been flown up to the present after the fur brush 6 is replaced and used is used.

  The image information L0, P, Q here means not only normal image formation but also calculated including the amount of toner used for troubles such as images formed for control and jams (JAM). To do.

  Accordingly, an integration method based on the image information may be used, but the image information may be calculated based on a history of toner replenishment from a toner bottle (not shown) to the developing device 4 and the remaining amount of toner in the toner bottle.

  The image information P printed on the X recording materials 12 immediately before calculating the state F0 of the fur brush 6 is as follows. Even when the fur brush 6 is almost new, the control patch image formed on the surface of the photosensitive drum 1 is not transferred to the X recording materials 12 immediately before the state F0 of the fur brush 6 is calculated, and cleaning is performed. There is a case where the blade 7 collects. In addition, it is used to calculate the state F0 of the fur brush 6 on the assumption that a solid image is used with a low transfer efficiency and a large amount of toner reaches the fur brush 6.

  Therefore, the state F0 of the fur brush 6 takes into consideration the influence on the state F (P) of the fur brush 6 by the image that was flowed immediately before using the image information P and Q. Further, the influence on the state F (Q) of the fur brush 6 from when the fur brush 6 is replaced to the beginning of use is considered. Then, the above F (P) and F (Q) are calculated by the following formula 3 obtained by multiplying the coefficients α and β respectively. Note that F (P) and F (Q) in the following equation (3) are the changes in the outer diameter of the fur brush 6 due to the total number of rotations J0 (durability) of the fur brush 6 and the amount of toner that reaches the fur brush 6 ( Calculated from (image information).

[Equation 3]
F0 = α × F (P) + β × F (Q)

  Thereby, the state F0 of the fur brush 6 and the state of the surface of the photosensitive drum 1 are known. Further, the current peripheral speed (rotational speed) of the fur brush 6 is known. As a result, the positive (positive) charging potential V1 on the surface of the photosensitive drum 1 and the cleaning performance are calculated by using the table stored in the database 505 and predicted based on the number of rubbing between the fur brush 6 and the photosensitive drum 1. can do.

  That is, the setting range of the peripheral speed of the fur brush 6 that can achieve both the positive (positive electrode) charging potential V1 on the surface of the photosensitive drum 1 and the cleaning performance becomes clear. The respective threshold values N1, F2, and F1 shown in steps S14, S15, and S18 of FIG. 8 are set based on a setting range in which the positive (positive electrode) charging potential V1 on the surface of the photosensitive drum 1 and the cleaning performance can be compatible. Yes. The thresholds N1, F2, and F1 are appropriately changed according to the peripheral speed (rotational speed) of the fur brush 6.

  Next, in step S <b> 14, the CPU 500 compares whether or not the total rotation number N <b> 0 of the photosensitive drum 1 accumulated and stored in the database 505 at any time is greater than or equal to a preset threshold value N <b> 1. If the total number N0 of rotations of the photosensitive drum 1 is greater than or equal to the threshold N1 in step S14, the process proceeds to step S15.

  In step S15, the CPU 500 compares whether or not the state F0 of the fur brush 6 calculated by the equation 3 is equal to or less than a preset threshold value F2. In step S15, when the state F0 of the fur brush 6 is equal to or less than the threshold value F2, the CPU 500 determines that the possibility of positive (positive) charging of the surface of the photosensitive drum 1 due to the rubbing of the fur brush 6 is low. In step S16, the ratio of the peripheral speed of the outer peripheral surface of the fur brush 6 to the peripheral speed of the surface of the photosensitive drum 1 is not changed. Then, it progresses to step S17 and complete | finishes control.

  If the total rotation number N0 of the photosensitive drum 1 is less than the threshold value N1 in step S14, the process proceeds to step S18. In step S18, the CPU 500 determines whether or not the state F0 of the fur brush 6 is greater than or equal to a preset threshold value F1.

  The positive (positive) tendency of the surface of the photosensitive drum 1 varies depending on the surface state of the photosensitive drum 1. Therefore, the total number N0 of rotation of the photosensitive drum 1 is confirmed in the step S14. When the total number N0 of rotation of the photosensitive drum 1 is smaller than the threshold value N1, the surface of the photosensitive drum 1 tends to be positive (positive). Therefore, the threshold value F1 of the state F0 of the fur brush 6 is set in step S18 in accordance with the positive (positive) tendency of the surface of the photosensitive drum 1.

  On the other hand, when the total rotation number N0 of the photosensitive drum 1 is equal to or greater than the threshold value N1, the surface of the photosensitive drum 1 is difficult to be positive (positive). In consideration of the state, the threshold value F2 of the state F0 of the fur brush 6 is set in step S15. Since the threshold value F1 in step S18 is a threshold value in a state where the surface of the photosensitive drum 1 is likely to be positive (positive electrode), the allowable range for positive (positive electrode) of the fur brush 6 compared to the threshold value F2 in step S15. Becomes narrower. That is, a relationship of {threshold value F1 <threshold value F2} is set. Note that the tendency of the positive (positive electrode) surface of the photosensitive drum 1 to be greater in the initial stage differs depending on the surface layer of the photosensitive drum 1 and the material of the photosensitive layer.

  If the state F0 of the fur brush 6 is greater than or equal to the threshold value F1 in step S18, the process proceeds to step S19. In step S19, the CPU 500 refers to the table stored in the database 505 from the state of the photosensitive drum 1 and the fur brush 6 so that the peripheral speed (rotational speed) of the fur brush 6 becomes the optimum rotational speed. Change to

  Then, it progresses to said step S17 and complete | finishes control. If the state F0 of the fur brush 6 is larger than the threshold value F2 in step S15, the process proceeds to step S19, and the peripheral speed (rotational speed) of the fur brush 6 is referred to while referring to the table stored in the database 505. change. Then, it progresses to said step S17 and complete | finishes control.

  As in this embodiment, the following is predicted from the total rotation number N0 of the photosensitive drum 1, the rotation speed of the fur brush 6, the peripheral speed (rotational speed), and the image ratio. Under what conditions, the cleaning performance and the positive (positive) charging of the surface of the photosensitive drum 1 can be predicted. Thereby, the peripheral speed (rotational speed) of the fur brush 6 can be changed.

  In addition to changing the peripheral speed (rotational speed) of the fur brush 6, positive (positive) charging of the surface of the photosensitive drum 1 can be prevented by forcibly supplying toner to the fur brush 6.

  As described above, the method of preventing positive (positive electrode) charging on the surface of the photosensitive drum 1 may be properly used depending on the state of the image forming apparatus 13 and the usage situation.

  In the first embodiment, the potential measuring device 16 shown in FIG. 4, the patch image detection sensor, and the like are provided to measure the positive (positive) charging potential V <b> 1 on the surface of the photosensitive drum 1. In the present embodiment, the positive (positive) charging potential V1 on the surface of the photosensitive drum 1 is predicted without providing the potential measuring device 16 and the patch image detection sensor shown in FIG. 4, and the peripheral speed (rotational speed) of the fur brush 6 is estimated. ) Control can be optimized.

  As the control timing of the peripheral speed (rotational speed) of the fur brush 6, the state F0 of the fur brush 6 is calculated before or after the image formation, and the operation immediately after the calculation of the state F0 of the fur brush 6 is performed. The peripheral speed (rotational speed) of the fur brush 6 may be changed.

  The CPU 500 simply compares the state F0 of the fur brush 6 with the threshold values F1 and F2 by referring to the data in the table stored in the database 505. For this reason, it does not lead to a downtime of the image forming apparatus 13 and can be executed at short intervals.

<When changed from monochrome printing to color printing>
FIG. 1 shows a tandem type full-color image formation in which four color image forming stations 14Y, 14M, 14C, and 14K are arranged in a straight line along the stretching direction of the intermediate transfer belt 8 (the left-right direction in FIG. 1). Device 13. In such an image forming apparatus 13, the respective bias voltages are not applied to the charging roller 2 and the primary transfer roller 5 during monochrome printing such as black K color. Only the black K image forming station 14K performs the image forming operation with only the photosensitive drum 1 rotating idly.

  During black-and-white printing such as black K, the fur brush 6 and the photosensitive drum 1 continue to idle in the color image forming stations 14Y, 14M, and 14C.

  In this case, in step S13 of FIG. 8, the image information L0 acquired in step S12 is solid white and does not form an image in the color image forming stations 14Y, 14M, and 14C. For this reason, since there is no transfer residual toner remaining on the surface of each photosensitive drum 1 after the primary transfer, little transfer residual toner is supplied to each fur brush 6.

  For this reason, the CPU 500 detects that the toner entering between the fibers of the fur brush 6 has decreased, and the value of the state F0 of the fur brush 6 increases. That is, the CPU 500 determines that the positive (positive electrode) chargeability of the surface of the photosensitive drum 1 rubbed by the fur brush 6 during monochrome printing is increased. In step S19, the CPU 500 changes the peripheral speed (rotational speed) of the fur brush 6.

  That is, during monochrome printing, there is a high possibility that the surface of the photosensitive drum 1 is positively (positively) charged by the rubbing of the fur brush 6 in each of the color image forming stations 14Y, 14M, and 14C. For this reason, the peripheral speed (rotational speed) of the fur brush 6 is reduced. This prevents positive (positive electrode) charging of the surface of the photosensitive drum 1.

  On the other hand, monochrome printing is finished and color printing is started. At this time, if the peripheral speed (rotational speed) of the fur brush 6 is too low, the surface cleaning performance of the photosensitive drum 1 may be insufficient. For this reason, the control shown in FIG. 8 is performed again, and the change which raises the peripheral speed (rotational speed) of the fur brush 6 is implemented as needed.

  The tandem color image forming apparatus 13 moves so that the surface of each photosensitive drum 1 of the color image forming stations 14Y, 14M, and 14C is separated from the outer peripheral surface of the intermediate transfer belt 8 during monochrome printing. Some are provided with moving means. In this case, the color image forming stations 14Y, 14M, and 14C are stopped. For this reason, the above-described consideration is unnecessary, and the state F0 of the fur brush 6 may be appropriately determined according to the driving state of the fur brush 6 and the photosensitive drum 1.

<For monochrome printing>
In the color image forming stations 14Y, 14M, and 14C for monochrome printing such as black K, it is not necessary to apply the charging bias voltage to the charging rollers 2Y, 2M, and 2C. In that case, the surface potential of the photosensitive drum 1 is approximately 0V. For this reason, the surface of the photosensitive drum 1 is easily positively (positively) charged by the rubbing of the fur brush 6.

  Therefore, a small charging bias voltage is applied to the charging rollers 2Y, 2M, and 2C of the color image forming stations 14Y, 14M, and 14C during monochrome printing such as black K. As a result, the surface of the photosensitive drum 1 may be charged so as to have a small surface potential, although the surface potential is not as high as that during color printing.

  In steps S11 to S14 of FIG. 8 shown in the above-mentioned “change from monochrome printing to color printing”, the state F0 of the fur brush 6 is calculated from the image information L0 and the total number N0 of rotation of the photosensitive drum 1. Yes. In addition, the peripheral speed (rotational speed) of the fur brush 6 may be adjusted based on the setting of the charging bias voltage applied to the charging roller 2 that charges the surface of the photosensitive drum 1.

  According to the study by the present inventor, it has been found that as the absolute value of the surface potential of the photosensitive drum 1 is larger, the surface of the photosensitive drum 1 is less likely to be positively (positively) charged by the rubbing of the fur brush 6. Moreover, even if the photosensitive drum 1 has the same surface potential (for example, −100 V), the positive (positive electrode) on the surface of the photosensitive drum 1 when the fur brush 6 is rubbed by setting the charging bias voltage applied to the charging roller 2. It was also found that the charging potential V1 is different.

  As in this embodiment shown in FIG. 1, the peak-to-peak voltage Vpp is 800V as the AC component (AC) bias of the charging bias voltage applied to the contact charging type charging roller 2, and the surface potential of the photosensitive drum 1 is set to -100V. Consider the case of charging. Further, consider the case where the peak-to-peak voltage Vpp is 2000V as the AC component (AC) bias and the surface potential of the photosensitive drum 1 is charged to -100V.

  In this case, when the peak-to-peak voltage Vpp is 800 V as the AC component (AC) bias of the charging bias voltage applied to the charging roller 2, the surface of the photosensitive drum 1 is more likely to be positively (positively) charged due to the rubbing of the fur brush 6. I know that.

  Therefore, the peripheral speed (rotational speed) of the fur brush 6 may be changed based on the image information L0, the total rotation number J0 of the fur brush 6, and the total rotation number N0 of the photosensitive drum 1. Alternatively, the peripheral speed (rotational speed) of the fur brush 6 may be changed according to the AC component (AC) bias voltage of the charging bias voltage applied to the charging roller 2.

  The AC component (AC) bias voltage of the charging bias voltage applied to the charging roller 2 is a parameter having a correlation with the amount of discharge current from the charging roller 2. If the amount of discharge current from the charging roller 2 is small, the surface of the photosensitive drum 1 is likely to be positively (positively) charged by the rubbing of the fur brush 6.

  The charging roller 2 is not a contact charging method as in this embodiment, but a non-contact corona charging method is considered. When the amount of discharge current applied to the discharge electrode of the corona charger is reduced, the surface of the photosensitive drum 1 is easily positively (positively) charged by the rubbing of the fur brush 6.

  In consideration of these, during color printing, the alternating current component (AC) bias of the charging bias voltage applied to the charging roller 2 is as follows. With the peak-to-peak voltage Vpp applied at 2000V, a direct current component (DC) bias is applied to set the surface potential of the photosensitive drum 1 to −800V.

  On the other hand, in the color image forming stations 14Y, 14M, and 14C during monochrome printing, the AC component (AC) bias of each charging roller 2 is as follows. With the peak-to-peak voltage Vpp applied at 500V, a direct current component (DC) bias is applied to set the surface potential of the photosensitive drum 1 to -100V.

  The black K image forming station 14 </ b> K has the following AC component bias (AC) bias of the charging bias voltage applied to the charging roller 2. With the peak-to-peak voltage Vpp applied at 2000V, a direct current component (DC) bias is applied to set the surface potential of the photosensitive drum 1 to −800V.

  The color image forming stations 14Y, 14M, and 14C for monochrome printing do not perform image formation. For this reason, the AC component (AC) bias of the charging bias voltage applied to each charging roller 2 of the color image forming stations 14Y, 14M, and 14C during monochrome printing is as follows. The surface of the photosensitive drum 1 is charged by applying a peak-to-peak voltage Vpp that is 1/4 of the AC component (AC) bias of the charging bias voltage applied to each charging roller 2 during color printing.

  If the charging roller 2 is not a contact charging method but a non-contact corona charging method, the amount of discharge current applied to the discharge electrode of the corona charger is smaller in monochrome printing than in color printing.

  As described above, in the color image forming stations 14Y, 14M, and 14C during monochrome printing in which the surface of the photosensitive drum 1 is charged with a small amount of discharge current using the contact charging type charging roller 2, the following is performed. is there. The surface of each photosensitive drum 1 is easily positively (positively) charged by the rubbing of the fur brush 6.

  Therefore, a parameter corresponding to the amount of discharge current of the charging roller 2 is stored in the memory 504 and the database 505 in advance, and the peripheral speed (rotational speed) of the fur brush 6 is uniformly reduced during monochrome printing as compared with color printing. Control may be performed.

  Specifically, in the case of the contact charging type charging roller 2, the smaller the AC component (AC) bias or DC component (DC) bias of the charging bias voltage applied to the charging roller 2, the lower the fur brush 6. Control to lower the peripheral speed (rotational speed).

  Further, in the case of the non-contact corona charging method, control is performed to lower the peripheral speed (rotational speed) of the fur brush 6 as the amount of discharge current applied to the discharge electrode of the corona charger is smaller. In this case, the CPU 500 serving as the changing unit changes the rubbing condition between the fur brush 6 and the surface of the photosensitive drum 1 according to the amount of discharge generated by the charging bias applied to the corona charger serving as the charging unit.

  At the time of color printing, the ratio of the peripheral speed of the outer peripheral surface of the fur brush 6 to the peripheral speed of the surface of the photosensitive drum 1 is 120%. During monochrome printing, the peripheral speed (rotational speed) of the fur brush 6 may be controlled so that the ratio of the peripheral speed of the outer peripheral surface of the fur brush 6 to the peripheral speed of the surface of the photosensitive drum 1 becomes 100%.

  By reducing the amount of discharge current from each charging roller 2 of the color image forming stations 14Y, 14M, and 14C during monochrome printing, damage to each photosensitive drum 1 can be minimized. Furthermore, as described above, the surface of each photosensitive drum 1 can be prevented from being positively (positively) charged by rubbing with the fur brush 6.

<When color printing is changed to monochrome printing>
In the tandem type full-color image forming apparatus 13 shown in FIG. 1, during color printing, an image forming operation is performed in each of the color image forming stations 14Y, 14M, and 14C. For this reason, the peripheral speed (rotational speed) of the fur brush 6 may be changed according to the image information L0 for each of the image forming stations 14Y, 14M, and 14C. Depending on conditions, the fur brushes 6 of the image forming stations 14 for all colors may have the same peripheral speed (rotational speed).

  The case where the color printing is changed to the monochrome printing is as follows as in the case of “the case where the monochrome printing is changed to the color printing” described above. The fur brush 6 and the photosensitive drum 1 are kept in an idling state, and the transfer residual toner remaining on the surface of each photosensitive drum 1 after the primary transfer is not supplied between the fibers of the fur brush 6. For this reason, the positive (positive electrode) chargeability of the surface of the photosensitive drum 1 due to the rubbing of the fur brush 6 is increased.

  In accordance with the state F0 of the fur brush 6 during color printing, the peripheral speed (rotational speed) of the fur brush 6 is appropriately reduced during monochrome printing. During monochrome printing, the peripheral speed (rotational speed) of each fur brush 6 may be reduced uniformly. In addition to the case where the color printing is changed to the monochrome printing, the peripheral speed (rotational speed) of each fur brush 6 may be reduced uniformly when the monochrome printing is performed from the start of printing.

<When only the photosensitive drum 1 is replaced>
Although the fur brush 6 is in a durable state after repeated image formation, a case where only the photosensitive drum 1 is replaced when some trouble occurs or the life of the photosensitive drum 1 is reached will be described.

  When only the photosensitive drum 1 is replaced, when the data is retrieved from the table stored in the database 505 in step S12 of FIG. 8, the total number N0 of rotation of the photosensitive drum 1 is zero.

  Here, the photosensitive drum 1 itself has a characteristic that the surface of the photosensitive drum 1 is likely to be positively (positively) charged due to the rubbing of the fur brush 6. Therefore, in step S14 in FIG. 3, the CPU 500 refers to the data in the table stored in the database 505 to determine whether or not the photosensitive drum 1 is new.

  Thereby, the case where only the photosensitive drum 1 is replaced can be considered. In the new photosensitive drum 1, the peripheral speed ratio of the outer peripheral surface of the fur brush 6 with respect to the peripheral speed of the surface of the photosensitive drum 1 is reduced. Thereby, even when only the photosensitive drum 1 is replaced with a new one, it is possible to prevent the occurrence of positive (positive) charging on the surface of the photosensitive drum 1 due to the rubbing of the fur brush 6.

  As the durability of the photosensitive drum 1 progresses, the ratio of the peripheral speed of the outer peripheral surface of the fur brush 6 to the peripheral speed of the surface of the photosensitive drum 1 is increased. This makes it possible to achieve both prevention of positive (positive electrode) charging of the surface of the photosensitive drum 1 due to rubbing of the fur brush 6 and securing of cleaning performance.

<When forced toner consumption is executed>
For example, when images with a low image ratio such as a white solid image are continuously formed, the developing device 4 is idled and the developer stored in the developer container 4a is deteriorated. For this reason, when images with a low image ratio of a predetermined number of recording materials 12 are continuously formed, the developer stored in the developer container 4a of the developing device 4 may be forcibly consumed.

  When the toner forcibly consuming the developer contained in the developer container 4a of the developing device 4 is carried on the surface of the photosensitive drum 1 without being primarily transferred and reaches the cleaning device 15, a large amount of toner is absorbed by the fur brush 6 To reach.

  Alternatively, the amount of toner reaching the fur brush 6 may temporarily increase due to troubles such as continuous formation of a solid image and jam (JAM). In step S12 of FIG. 8, the image information P printed on the X recording materials 12 immediately before calculating the state F0 of the fur brush 6 among the image information L0 is considered. Further, the image information (including the control patch image) Q that has been flown up to the present after the fur brush 6 is replaced and used is considered. Then, the state F0 of the fur brush 6 is calculated in consideration of the image information P.

  Based on the state F0 of the fur brush 6, the CPU 500 determines whether or not the peripheral speed (rotational speed) of the fur brush 6 needs to be changed. Accordingly, it is possible to prevent both positive (positive) charging of the surface of the photosensitive drum 1 due to rubbing of the fur brush 6 and cleaning performance.

  According to the present embodiment, it is detected that the surface potential of the photosensitive drum 1 has been charged to a polarity opposite to the polarity of the charging potential on the developing side by rubbing the fur brush 6, and the fur relative to the peripheral speed of the surface of the photosensitive drum 1 is detected. The peripheral speed ratio of the outer peripheral surface of the brush 6 is changed.

  The outer peripheral surface of the fur brush 6 with respect to the peripheral speed of the surface of the photosensitive drum 1 in accordance with the charging potential V1 charged to a polarity opposite to the polarity of the charging potential on the developing side due to the rubbing of the fur brush 6. Reduce the peripheral speed ratio. As a result, the surface potential of the photosensitive drum 1 can be prevented from being charged to a polarity opposite to the polarity of the charging potential on the developing side.

  That is, the surface potential of the photosensitive drum 1 becomes non-uniform due to the charging potential V1 charged to a polarity opposite to the charging polarity on the developing side of the surface of the photosensitive drum 1 by rubbing of a cleaning member such as the fur brush 6. As a result, image defects such as image unevenness and white background fogging occur. It is possible to achieve both prevention of such image failure and prevention of cleaning failure. In addition, the image forming speed can be easily increased.

  In the present embodiment, the CPU 500 serving as the changing unit changes the rubbing condition between the fur brush 6 and the surface of the photosensitive drum 1 in accordance with the image forming conditions stored in the memory 504 serving as the storage unit and the database 505. Other configurations are the same as those in the first embodiment, and the same effects can be obtained.

  In each of the above embodiments, as an example of changing the rubbing condition between the fur brush 6 and the surface of the photosensitive drum 1, the ratio of the peripheral speed of the outer peripheral surface of the fur brush 6 to the peripheral speed of the surface of the photosensitive drum 1 is changed. An example to do was explained.

  In addition, the number of rubbing per unit time between the fur brush 6 and the surface of the photosensitive drum 1 is changed. Alternatively, the relative movement direction of the fur brush 6 and the surface of the photosensitive drum 1 is changed. Alternatively, the contact pressure between the fur brush 6 and the surface of the photosensitive drum 1 is changed. Alternatively, the amount of penetration of the fur brush 6 with respect to the surface of the photosensitive drum 1 is changed. The rubbing condition between the fur brush 6 and the surface of the photosensitive drum 1 can be changed by changing at least one of these.

1, 1Y, 1M, 1C, 1K ... photosensitive drum (image carrier)
5, 5Y, 5M, 5C, 5K ... Primary transfer roller (transfer means)
6, 6Y, 6M, 6C, 6K ... Fur brush (cleaning means)
500 ... CPU (change means)
504 ... Memory (storage means)

Claims (9)

An image carrier for carrying a toner image;
Charging means for charging the image carrier;
A latent image forming unit that forms an electrostatic latent image on the image carrier charged by the charging unit;
Developing means for developing the electrostatic latent image formed on the image carrier by the latent image forming means;
Transfer means for transferring the toner image developed on the image carrier by the developing means;
Cleaning means for cleaning toner on the image carrier after being transferred by the transfer means;
Storage means for storing conditions for image formation;
In an image forming apparatus having
The cleaning means rubs and the image carrier is charged to a potential opposite to the potential polarity at which the toner image is developed,
A changing unit that changes a rubbing condition between the cleaning unit and the image carrier in accordance with an image forming condition stored in the storage unit;
An image forming apparatus comprising: An image carrier for carrying a toner image;
Charging means for charging the image carrier;
A charging bias power source for applying a charging bias to the charging means;
A latent image forming unit that forms an electrostatic latent image on the image carrier charged by the charging unit;
Developing means for developing the electrostatic latent image formed on the image carrier by the latent image forming means;
Transfer means for transferring the toner image developed on the image carrier by the developing means;
Cleaning means for cleaning toner on the image carrier after being transferred by the transfer means;
In an image forming apparatus having
The cleaning means rubs and the image carrier is charged to a potential opposite to the potential polarity at which the toner image is developed,
A changing unit that changes a rubbing condition between the cleaning unit and the image carrier according to a discharge amount generated by a charging bias applied to the charging unit;
An image forming apparatus comprising: An image carrier for carrying a toner image;
Charging means for charging the image carrier;
A latent image forming unit that forms an electrostatic latent image on the image carrier charged by the charging unit;
A potential measuring means for measuring the potential of the image carrier;
Developing means for developing the electrostatic latent image formed on the image carrier by the latent image forming means;
Transfer means for transferring the toner image developed on the image carrier by the developing means;
Cleaning means for cleaning toner on the image carrier after being transferred by the transfer means;
In an image forming apparatus having
The cleaning means rubs and the image carrier is charged to a potential opposite to the potential polarity at which the toner image is developed,
According to the measurement result of the potential measuring means, changing means for changing the rubbing condition between the cleaning means and the image carrier;
An image forming apparatus comprising: The rubbing condition is
The number of times of rubbing per unit time between the cleaning unit and the image carrier, the relative moving direction of the cleaning unit and the image carrier, the contact pressure between the cleaning unit and the image carrier, the image The image forming apparatus according to claim 1, wherein the image forming apparatus is at least one of an amount of penetration of the cleaning unit with respect to the carrier. The change of the rubbing condition is
4. The image forming apparatus according to claim 1, wherein the number of times of rubbing between the cleaning unit and the image carrier is increased as the number of image forming sheets of the recording material increases.   The image forming apparatus according to claim 3, wherein the potential measuring unit measures the potential of the image carrier using a chopper-type potential sensor. The cleaning means rubs and the image carrier is charged to a potential opposite to the potential polarity at which the toner image is developed. The developed means develops the charged potential, and the image is developed. A toner amount detecting means for detecting the toner amount of the toner image;
The image forming apparatus according to claim 3, wherein the potential measuring unit measures the potential of the image carrier based on the toner amount detected by the toner amount detecting unit.   The image forming apparatus according to claim 1, wherein the cleaning unit is configured in a brush shape.   The image forming apparatus according to claim 1, wherein the cleaning unit is made of at least one material selected from polyester, acrylic, polytetrafluoroethylene, and vinyl chloride.