JP2012088557A - Cleaning device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning device that sufficiently removes toner from a belt member against deterioration with age of a belt member and a cleaning member and environmental change, and sufficiently recovers toner on a cleaning member with the use of a recovery member, as well as an image forming apparatus.SOLUTION: Predetermined amount of current is flown between a cleaning brush roller and an intermediate transfer belt in predetermined timing, and voltage at the time is set as cleaning voltage. Predetermined amount of current is flown between a recovery roller and a cleaning brush roller in predetermined timing, and voltage at the time is set as recovery voltage.

Description

  The present invention relates to a cleaning device and an image forming apparatus.

  2. Description of the Related Art As an intermediate transfer belt cleaning device that cleans transfer residual toner on an intermediate transfer belt that is a bell and a member in an intermediate transfer type image forming apparatus, an apparatus that employs an electrostatic cleaning device is known.

  The electrostatic cleaning device includes a cleaning brush that is a cleaning member that rotates while contacting the intermediate transfer belt, a recovery roller that is a recovery member that rotates while contacting the cleaning brush, and a scraping blade that contacts the recovery roller. . A cleaning voltage having a polarity opposite to the normal charging polarity of the toner is applied to the cleaning brush. A recovery voltage having the same polarity as the cleaning voltage and a value larger than the cleaning voltage is applied to the recovery roller. Transfer residual toner, which is an adhering matter adhering to the surface of the intermediate transfer belt, is electrostatically transferred from the belt surface to the brush by the cleaning voltage while being scratched by the brush of the cleaning brush. Thereafter, after electrostatic transfer from the cleaning brush to the collecting roller, the scraping blade scrapes off the surface of the collecting roller.

  Conventionally, a constant cleaning voltage is applied to the cleaning brush roller, and a constant recovery voltage is also applied to the recovery roller. However, if the resistance change of the intermediate transfer belt occurs due to the environment or usage over time, the cleaning current flowing between the intermediate transfer belt and the cleaning brush roller is different from the optimum value for cleaning, and good cleaning cannot be performed. .

  Japanese Patent Application Laid-Open No. 2004-228561 describes a cleaning device including a constant current control unit that controls a current flowing between the cleaning brush and the intermediate transfer belt at the time of cleaning. By performing constant current control in this way, an optimum cleaning current can be supplied even if the resistance of the intermediate transfer belt varies due to the environment and usage over time, and a reduction in cleaning performance can be suppressed.

  However, the resistance change changes not only in the intermediate transfer belt but also in the cleaning brush depending on the environment and usage over time. Thus, when the resistance of the cleaning brush fluctuates, the recovery current flowing between the recovery roller and the cleaning brush is different from the optimum value for recovery, and the toner of the cleaning brush cannot be recovered to the recovery roller satisfactorily. The toner remaining on the cleaning brush is generated. If toner remains on the cleaning brush, when the cleaning brush rotates again to pass through the contact area with the intermediate transfer belt, the amount of new toner adhering to the brush fiber is reduced and the cleaning performance is reduced. There arises a problem that the residual toner is reattached to the intermediate transfer belt, resulting in poor cleaning.

  The present invention has been made in view of the above problems, and the object thereof is to remove toner from the belt member satisfactorily even with respect to changes with time and environmental changes of the belt member and cleaning member, and to improve the situation. It is an object of the present invention to provide a cleaning device and an image forming apparatus that can collect toner on a cleaning member with a collecting member.

In order to achieve the above object, the invention of claim 1 is characterized in that a cleaning voltage is applied, a cleaning member that electrostatically removes toner on the belt member while rotating, a recovery voltage is applied, and the cleaning member is applied. In a cleaning device including a collecting member that electrostatically collects the adhered toner from the cleaning member, the cleaning voltage is controlled so that an optimum cleaning current flows between the cleaning member and the belt member. In addition, there is provided control means for controlling a recovery voltage so that a recovery current optimum for recovery flows between the cleaning member and the recovery member.
According to a second aspect of the present invention, in the cleaning device of the first aspect, a predetermined current is allowed to flow between the cleaning member and the belt member at a predetermined timing, and the voltage at that time is detected by the voltage detection means. A cleaning voltage setting unit that detects and sets the detected voltage as a cleaning voltage, and a predetermined current is passed between the recovery member and the cleaning member at a predetermined timing, and the voltage at that time is detected by voltage detection. And a recovery voltage setting means for setting the detected recovery voltage as a recovery voltage. When the toner on the belt member is cleaned, the control means sets the cleaning voltage set by the cleaning voltage setting means. Applied to the cleaning member, the recovery voltage set by the recovery voltage setting means is applied to the recovery member. The one in which the features.
According to a third aspect of the present invention, in the cleaning device of the second aspect, the timing at which a predetermined current flows between the recovery member and the cleaning member is set in advance between the cleaning member and the belt member. It is characterized in that it is synchronized with the timing of flowing a predetermined current.
According to a fourth aspect of the present invention, in the cleaning device of the second or third aspect, the setting of the cleaning voltage and the setting of the recovery voltage are performed when the device is started.
According to a fifth aspect of the present invention, in the cleaning device according to any one of the second to fourth aspects, the cleaning member includes a plurality of cleaning portions each including the cleaning member and the recovery member, and the cleaning member is set when a cleaning voltage is set. And a current flowing between the belt member and the belt member.
According to a sixth aspect of the present invention, in the cleaning device of the fifth aspect, the three cleaning units are provided, the most upstream cleaning unit disposed at the most upstream in the belt member surface movement direction and the most downstream in the belt member surface movement direction. The polarity of the cleaning voltage of the most downstream cleaning unit arranged in the above and the polarity of the cleaning voltage of the middle cleaning unit arranged between the most upstream cleaning unit and the most downstream cleaning unit are different from each other. Is.
According to a seventh aspect of the present invention, in the cleaning device of the sixth aspect, the polarity of the cleaning voltage of the most upstream cleaning section and the most downstream cleaning section is opposite to the normal charging polarity of the toner. Is.
In the cleaning device according to any one of claims 2 to 7, the cleaning voltage setting means includes a cleaning voltage for cleaning the transfer residual toner and a cleaning for cleaning the untransferred toner image. The voltage is set.
The invention according to claim 9 is a toner image carried on the front surface of an endless belt member or a toner image carried on a recording member held on the front surface of the belt member. A belt device that conveys the belt member as the belt member moves endlessly, a toner image forming unit that forms a toner image on the front surface of the belt member or a recording member, and cleaning the toner on the belt member. An image forming apparatus including a cleaning unit uses the cleaning device according to any one of claims 1 to 8 as the cleaning unit.

According to the present invention, since the recovery voltage is controlled so that an optimal recovery current flows between the cleaning member and the recovery member, the optimal recovery current can be maintained even if the resistance of the cleaning member fluctuates. The toner on the cleaning member can be recovered well. As a result, it is possible to suppress toner from remaining on the cleaning brush, and it is possible to suppress defective cleaning.
In addition, since the cleaning voltage is controlled so that an optimum cleaning current flows between the cleaning member and the belt member, the optimum cleaning current can be maintained even if the resistance of the belt member fluctuates, which is favorable. Cleanability can be maintained.

1 is a schematic configuration diagram illustrating a main part of a printer according to an embodiment. FIG. 3 is an enlarged schematic configuration diagram in the vicinity of an intermediate transfer belt showing a gradation pattern and an optical sensor. FIG. 3 is an enlarged schematic view showing a chevron patch formed on the intermediate transfer belt. FIG. 2 is an enlarged configuration diagram illustrating a belt cleaning device of the printer and its surroundings in an enlarged manner. The timing chart of the applied voltage to the pre-cleaning brush roller of a pre-cleaning part, and the applied voltage to a pre-collection roller. The figure which shows VI (cleaning voltage-cleaning current) characteristic. The schematic diagram explaining the maximum diameter MXLNG and the planar area AREA of the projection image with respect to the two-dimensional plane of a toner particle. FIG. 4 is a schematic diagram for explaining a peripheral length PERI and a planar area AREA of a projected image with respect to a two-dimensional plane of toner particles. (A), (b), (c) is a figure which shows the shape of a toner typically, respectively. FIG. 2 is a schematic configuration diagram illustrating a main part of a tandem direct transfer type printer.

  Hereinafter, as an embodiment of an image forming apparatus to which the present invention is applied, a so-called tandem type intermediate transfer type printer (hereinafter simply referred to as a printer) will be described. First, the basic configuration of the printer will be described. FIG. 1 is a schematic configuration diagram showing a main part of the printer. The printer includes four process units 6Y, 6M, 6C, and 6K for generating toner images of yellow, magenta, cyan, and black (hereinafter referred to as Y, M, C, and K). The four process units 6Y, 6M, 6C, and 6K have drum-shaped photoreceptors 1Y, 1M, 1C, and 1K, respectively. Around the photoreceptors 1Y, 1M, 1C, and 1K, charging devices 2Y, 2M, 2C, and 3K, developing devices 5Y, 5C, 1M, and 1K, drum cleaning devices 4Y, 4M, 4C, and 1K, a static eliminator (not shown). ) Etc. The process units 6Y, 6M, 6C, and 6K use Y, M, C, and K toners of different colors, but have the same configuration. Above the process units 6Y, 6M, 6C, and 6K, there is an optical writing unit (not shown) for irradiating the surface of the photoreceptors 1Y, 1M, 1C, and 1K with laser light L to write an electrostatic latent image. It is arranged.

  Below the process units 6Y, 6M, 6C, and 6K, a transfer unit 7 is disposed as a belt device including an endless intermediate transfer belt 8 that is a belt member. In addition to the intermediate transfer belt 8, a plurality of stretching rollers disposed inside the loop, a secondary transfer roller 18, a tension roller 16, a belt cleaning device 100, a lubricant application device 200, and the like disposed outside the loop. have.

  Inside the loop of the intermediate transfer belt 8, four primary transfer rollers 9Y, 9M, 9C, 9K, a driven roller 10, a driving roller 11, a secondary transfer counter roller 12, and three counter rollers 13, 14 are provided. 15 and an application brush facing roller 17 are disposed. Each of these rollers functions as a stretching roller that stretches the intermediate transfer belt 8 around a part of its peripheral surface to stretch the belt. The counter roller 13, 14, 15 does not necessarily have to have a function of applying a constant tension, and may be driven to rotate as the intermediate transfer belt 8 rotates. The intermediate transfer belt 8 is moved endlessly in the clockwise direction in the drawing by the rotation of the driving roller 11 that is driven to rotate clockwise in the drawing by a driving means (not shown).

  The four primary transfer rollers 9Y, 9M, 9C, and 9K disposed inside the belt loop sandwich the intermediate transfer belt 8 between the photoreceptors 1Y, 1M, 1C, and 1K. As a result, primary transfer nips for Y, M, C, and K where the front surface of the intermediate transfer belt 8 and the photoreceptors 1Y, 1M, 1C, and 1K come into contact are formed. A primary transfer bias having a polarity opposite to that of the toner is applied to the primary transfer rollers 9Y, 9M, 9C, and 9K by a power source (not shown).

  Further, the intermediate transfer belt 8 is sandwiched between the secondary transfer counter roller 12 disposed inside the belt loop and the secondary transfer roller 18 disposed outside the belt loop. As a result, a secondary transfer nip where the front surface of the intermediate transfer belt 8 and the secondary transfer roller 18 abut is formed. A secondary transfer bias having a polarity opposite to that of the toner is applied to the secondary transfer roller 18 by a power source (not shown). The paper transfer belt is bridged by the secondary transfer roller, several supporting rollers, and a driving roller, and the intermediate transfer belt 8 and the paper transfer belt are placed between the secondary transfer roller 18 and the secondary transfer counter roller 12. It is good also as a structure inserted | pinched.

  Further, the three opposing rollers 13, 14, and 15 disposed on the inner side of the belt loop are connected to the cleaning brush rollers 101, 104, and 107 of the belt cleaning device 100 disposed on the outer side of the belt loop, and the intermediate transfer belt 8 is interposed therebetween. Is sandwiched. As a result, a cleaning nip is formed in which the front surface of the intermediate transfer belt 8 and the cleaning brush rollers 101, 104, and 107 come into contact with each other. The belt cleaning device 100 can be integrally replaced with the intermediate transfer belt 8. However, when the belt cleaning device 100 and the intermediate transfer belt 8 have different life settings, the belt cleaning device 100 is replaced with the intermediate transfer belt 8. May be independently detachable from the printer body. Details of the belt cleaning apparatus 100 will be described later.

  The printer includes a paper feed unit (not shown) having a paper feed cassette for storing the recording paper P and a paper feed roller for feeding the recording paper P from the paper feed cassette to the paper feed path. In addition, a registration roller pair (not shown) that receives the recording paper sent from the paper feeding unit and feeds it at a predetermined timing toward the secondary transfer nip is provided on the right side of the secondary transfer nip in the drawing. In addition, a fixing device (not shown) that receives the recording paper P sent out from the secondary transfer nip and fixes the toner image to the recording paper P is provided on the left side of the secondary transfer nip in the drawing. . Further, Y, M, C, and K toner supply devices (not shown) for supplying Y, M, C, and K toners to the developing devices 5Y, M, C, and K are provided as necessary.

  In recent years, in addition to plain paper that has been widely used as recording paper, special recording paper that is used for thermal transfer such as special paper having an uneven surface or iron print as a design has been increasingly used. When such special paper is used, transfer defects are more likely to occur when the toner image on the intermediate transfer belt 8 on which the color toners are superimposed is secondarily transferred onto the paper, as compared with conventional plain paper. Therefore, in the present printer, an elastic layer having low hardness is provided on the intermediate transfer belt 8 so that the toner layer and recording paper with poor smoothness can be deformed at the transfer nip portion. By providing the intermediate transfer belt 8 with an elastic layer having low hardness and making the intermediate transfer belt 8 elastic, the surface of the intermediate transfer belt 8 can be deformed following local irregularities. Thereby, without excessively increasing the transfer pressure with respect to the toner layer, good adhesion can be obtained, there is no loss of transfer of characters, and there is no transfer unevenness even on paper with poor smoothness, A transfer image having excellent uniformity can be obtained.

  In this printer, the intermediate transfer belt 8 includes at least a base layer, an elastic layer, and a surface coat layer.

  Examples of the material used for the elastic layer of the intermediate transfer belt 8 include elastic members such as elastic material rubber and elastomer. Specifically, butyl rubber, fluorine rubber, acrylic rubber, EPDM, NBR, acrylonitrile-butadiene-styrene. Rubber, natural rubber, isoprene rubber, styrene-butadiene rubber, butadiene rubber, urethane rubber, syndiotactic 1,2-polybutadiene, epichlorohydrin rubber, polysulfide rubber, polynorbornene rubber, thermoplastic elastomer (for example, polystyrene series) , Polyolefins, polyvinyl chlorides, polyurethanes, polyamides, polyureas, polyesters, fluororesins) and the like can be used. However, it is not limited to the said material.

  The thickness of the elastic layer depends on the hardness and the layer structure, but is preferably in the range of 0.07 to 0.5 [mm]. More preferably, the range of 0.25-0.5 [mm] is good. Further, if the thickness of the intermediate transfer belt 8 is as thin as 0.07 [mm] or less, the pressure on the toner on the intermediate transfer belt 8 at the secondary transfer nip portion becomes high, and transfer deficiency is likely to occur. The toner transfer rate decreases.

  The hardness of the elastic layer is preferably 10 ° ≦ HS ≦ 65 ° (JIS-A). Although the optimum hardness differs depending on the layer thickness of the intermediate transfer belt 8, if the hardness is lower than 10 ° JIS-A, transfer deficiency tends to occur. On the other hand, when the hardness is higher than 65 ° JIS-A, it is difficult to stretch the roller, and since it is stretched by long-term stretching, there is no durability and early replacement is necessary.

  The base layer of the intermediate transfer belt 8 is made of a resin with little elongation. Specifically, materials used for the base layer include polycarbonate, fluororesin (ETFE, PVDF, etc.), polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, Styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer) Styrene-octyl acrylate copolymer and styrene-phenyl acrylate copolymer), styrene-methacrylic acid ester copolymer (styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene) -Phenyl methacrylate copolymer, etc.), steel -Α-chloromethyl acrylate copolymer, styrene resin such as styrene-acrylonitrile-acrylate ester copolymer (monopolymer or copolymer containing styrene or styrene substitution product), methyl methacrylate resin, methacryl Acid butyl resin, ethyl acrylate resin, butyl acrylate resin, modified acrylic resin (silicone modified acrylic resin, vinyl chloride resin modified acrylic resin, acrylic / urethane resin, etc.), vinyl chloride resin, styrene-vinyl acetate copolymer, chloride Pinyl-vinyl acetate copolymer, rosin-modified maleic acid resin, phenol resin, epoxy resin, polyester resin, polyester polyurethane resin, polyethylene, polypropylene, polybutadiene, polyvinylidene chloride, ionomer resin, polyurethane resin, silicone Fat, ketone resins, ethylene - can be used ethyl acrylate copolymer, xylene resin and polyvinyl butyral resin, polyamide resin, one kind or two kinds or more selected from the group consisting of modified polyphenylene oxide resin. However, it is not limited to the said material.

  In addition, in order to prevent the elastic layer made of a rubber material having a large elongation from extending, a core layer made of a material such as a canvas may be provided between the base layer and the elastic layer. Examples of materials for preventing elongation used in the core layer include natural fibers such as cotton and silk, polyester fibers, nylon fibers, acrylic fibers, polyolefin fibers, polyvinyl alcohol fibers, polyvinyl chloride fibers, and polyvinylidene chloride fibers. , One or more selected from the group consisting of synthetic fibers such as polyurethane fiber, polyacetal fiber, polyfluoroethylene fiber and phenol fiber, inorganic fibers such as carbon fiber and glass fiber, and metal fibers such as iron fiber and copper fiber Threaded or woven fabric can be used. Of course, the material is not limited to the above. The above-described yarn may be twisted in any manner, such as one or a plurality of filaments twisted, one-twisted yarn, various twisted yarns, double yarn, or the like. Further, for example, fibers of a material selected from the above material group may be blended. Of course, the yarn can be used after being subjected to an appropriate conductive treatment. On the other hand, the woven fabric can be any woven fabric such as knitted weave, and of course, a woven fabric that has been woven can also be used and can be subjected to a conductive treatment.

  The coat layer on the surface of the intermediate transfer belt 8 is for coating the surface of the elastic layer, and is composed of a layer having good smoothness. The material used for the coating layer is not particularly limited, but generally, a material that increases the secondary transferability by reducing the amount of toner adhering to the surface of the intermediate transfer belt 8 is used. For example, one or more of polyurethane, polyester, epoxy resin, etc., or a material that reduces surface energy and increases lubricity, such as fluororesin, fluorine compound, fluorocarbon, titanium oxide, silicon carbide, etc. One type or two or more types, or those having different particle sizes as required can be dispersed and used. Further, it is also possible to use a material such as a fluorine-based rubber material in which a heat treatment is performed to form a fluorine layer on the surface and the surface energy is reduced.

  If necessary, the base layer, the elastic layer, or the coating layer is, for example, carbon black, graphite, metal powder such as aluminum or nickel, tin oxide, titanium oxide, antimony oxide, indium oxide, for the purpose of adjusting resistance. Conductive metal oxides such as potassium titanate, antimony oxide-tin oxide composite oxide (ATO), and indium oxide-tin oxide composite oxide (ITO) can be used. Here, the conductive metal oxide may be coated with insulating fine particles such as barium sulfate, magnesium silicate, and calcium carbonate. However, it is not limited to the said material.

  The surface of the intermediate transfer belt 8 is coated with a lubricant by a lubricant coating device 200 in order to protect the belt surface. The lubricant application device 200 is a coating that abuts on a surface of the intermediate transfer belt 8 with a solid lubricant 202 such as a zinc stearate lump and a lubricant powder that comes into contact with the solid lubricant and is scraped off from the solid lubricant by rotation. And a coating brush roller 201 as a member. The printer includes the lubricant application device 200, which may be appropriately provided depending on the toner to be used, the material of the intermediate transfer belt 8, and the surface friction coefficient.

  When image information is sent from a personal computer or the like, the printer rotates the drive roller 11 to move the intermediate transfer belt 8 endlessly. The stretching rollers other than the driving roller 11 are driven and rotated by the belt. At the same time, the photosensitive members 1Y, 1M, 1C, and 1K of the process units 6Y, 6M, 6C, and 6K are rotationally driven. Further, an electrostatic latent image is formed by irradiating the charged surface with laser light L while uniformly charging the surfaces of the photoreceptors 1Y, 1M, 1C, and 1K with the charging devices 2Y, 2M, 2C, and 2K. To do. The electrostatic latent images formed on the surfaces of the photoreceptors 1Y, 1M, 1C, and 1K are developed by the developing devices 5Y, 5M, 5C, and 5K, so that the Y, M on the photoreceptors 1Y, 1M, 1C, 1K are developed. , C, K toner images are obtained. The Y, M, C, and K toner images are primarily transferred while being superimposed on the front surface of the intermediate transfer belt 8 in the above-described primary transfer nips for Y, M, C, and K. As a result, a four-color superimposed toner image is formed on the front surface of the intermediate transfer belt 8.

  On the other hand, in a paper feed unit (not shown), the recording paper P is sent out from the paper feed cassette one by one by the paper feed roller and conveyed to the registration roller pair. Then, at a timing that can be synchronized with the four-color superimposed toner image on the intermediate transfer belt 8, the registration roller pair is driven to feed the recording paper P to the secondary transfer nip, and the four-color superimposed toner image on the belt is transferred. Batch transfer onto the recording paper P is performed. Thereby, a full-color image is formed on the surface of the recording paper P. The recording paper P after the formation of the full-color image is conveyed from the secondary transfer nip to a fixing device and subjected to a toner image fixing process.

  For the photoreceptors 1Y, M, C, and K after the Y, M, C, and K toner images are primarily transferred to the intermediate transfer belt 8, the remaining toner is cleaned by the drum cleaning devices 4Y, 4M, 4C, and 4K. Apply. Then, after neutralizing with a neutralizing lamp (not shown), it is uniformly charged with the charging devices 2Y, 2M, 2C, and 3K, and is ready for the next image formation. Further, the intermediate transfer belt 8 after the primary transfer to the recording paper P is subjected to a cleaning process for residual toner by the belt cleaning device 100.

  An optical sensor unit 150 is disposed on the right side of the K process unit 6K in the drawing so as to face the front surface of the intermediate transfer belt 8 with a predetermined gap. As shown in FIG. 2, the optical sensor unit 150 includes a Y optical sensor 151Y, a C optical sensor 151C, an M optical sensor 151M, and a K optical sensor 151K arranged in the width direction of the intermediate transfer belt 8. Each of these sensors is a reflection type photosensor, and reflects light emitted from a light emitting element (not shown) by a toner image on the front surface of the intermediate transfer belt 8 or the belt, and detects the amount of reflected light by a light receiving element (not shown). To do. A control unit (not shown) can detect the toner image on the intermediate transfer belt 8 or the image density (toner adhesion amount per unit area) based on the output voltage values from these sensors. .

In this printer, image density control for optimizing the image density of each color is executed when the power is turned on or every time a predetermined number of prints are performed.
In the image density control, first, gradation patterns Sk, Sm, Sc, and Sy of each color are automatically formed on the intermediate transfer belt 8 at positions facing the optical sensors 151Y, M, C, and K as shown in FIG. To do. The gradation pattern of each color is composed of 10 toner patches having an area of 2 [cm] × 2 [cm] having different image densities. The charging potentials of the photoreceptors 1Y, 1M, 1C, and 1K when creating the gradation patterns Sk, Sm, Sc, and Sy for each color are different from the uniform drum charging potential in the printing process and gradually increase in value. To do. Then, while forming a plurality of patch electrostatic latent images for forming a gradation pattern image on the photoreceptors 1Y, 1M, 1C, and 1K by scanning with laser light, they are used for Y, M, C, and K, respectively. Development is performed by the developing devices 5Y, M, C, and K. During this development, the value of the developing bias applied to the Y, M, C, and K developing rollers is gradually increased. By such development, gradation pattern images of Y, M, C, and K are formed on the photoreceptors 1Y, 1M, 1C, and 1K. These are primarily transferred so as to be arranged at a predetermined interval in the main scanning direction of the intermediate transfer belt 8. At this time, the toner adhesion amount of the toner patch in the gradation pattern of each color is about 0.1 [mg / cm ² ] at the minimum and 0.55 [mg / cm ² ] at the maximum, and the toner Q / d distribution When measured, it is almost aligned with the regular charging polarity.

  Each toner pattern (Sk, Sm, Sc, Sy) formed on the intermediate transfer belt 8 passes through a position facing the optical sensor 151 as the intermediate transfer belt 8 moves endlessly. At this time, the optical sensor 151 receives an amount of light corresponding to the toner adhesion amount per unit area with respect to the toner patch of each gradation pattern.

  Next, the adhesion amount of each color toner pattern in each toner patch is calculated from the output voltage of the optical sensor 151 when each color toner patch is detected and the adhesion amount conversion algorithm, and the image forming condition is based on the calculated adhesion amount. Adjust. Specifically, a function (y = ax + b) indicating a straight line graph is calculated by regression analysis based on the result of detecting the toner adhesion amount on the toner patch and the development potential when each toner patch is imaged. Then, an appropriate development bias value is calculated by substituting a target value of image density into this function, and development bias values for Y, M, C, and K are specified.

  The memory stores an image forming condition data table in which several tens of development bias values and appropriate drum charging potentials individually corresponding to the values are associated in advance. For each of the process units 6Y, 6M, 6C, and 6K, a developing bias value closest to the specified developing bias value is selected from the image forming condition table, and the drum charging potential associated therewith is specified.

The printer also performs color misregistration correction processing when the power is turned on or whenever a predetermined number of prints are performed. In this color misregistration amount correction process, Y, M, C, and K color toner images called chevron patches PV as shown in FIG. 3 are respectively provided at one end and the other end in the width direction of the intermediate transfer belt 8. An image for color misregistration detection is formed. As shown in FIG. 3, the chevron patch PV has a predetermined pitch in the belt moving direction, which is the sub-scanning direction, with the toner images of each color of Y, M, C, and K inclined by about 45 ° from the main scanning direction. Is a line pattern group arranged in. The amount of the chevron patch PV attached is about 0.3 [mg / cm ² ].

  By detecting each color toner image in the chevron patch PV formed at both ends in the width direction of the intermediate transfer belt 8, the position of each color toner image in the main scanning direction (photoconductor axial direction), the sub-scanning direction (belt movement) Direction) position, magnification error in the main scanning direction, and skew from the main scanning direction. The main scanning direction here refers to the direction in which the laser light is phased on the surface of the photosensitive member as it is reflected by the polygon mirror. For such Y, M, C toner images in the chevron patch PV, the optical sensor 151 reads the detection time difference from the K toner image. In the figure, the vertical direction of the paper surface corresponds to the main scanning direction, and after the Y, M, C, and K toner images are arranged in order from the left, the postures are different from those by 90 [°]. , Y toner images are further arranged. Based on the difference between the actual measurement value and the theoretical value of the detection time differences tyk, tmk, and tck with respect to K as the reference color, the shift amount in the sub-scanning direction of each color toner image, that is, the registration shift amount is obtained. Then, on the basis of the amount of registration deviation, the optical writing start timing for the photosensitive member 1 is corrected every other polygon mirror surface of the optical writing unit (not shown), that is, one scanning line pitch as one unit, and each color is corrected. To reduce the registration error of the toner image. Further, the inclination (skew) of each color toner image from the main scanning direction is obtained based on the difference in the amount of deviation in the sub-scanning direction between both ends of the belt. Based on the result, surface tilt correction of the optical system reflection mirror is performed to reduce skew of each color toner image. As described above, the color misregistration correction process is a process that corrects the optical writing start timing and surface tilt based on the detection timing of each toner image in the chevron patch PV to reduce registration deviation and skew deviation. By such a color misregistration correction process, it is possible to suppress the occurrence of color misregistration of an image due to a shift in the formation position of each color toner image with respect to the intermediate transfer belt 8 due to a temperature change or the like.

  Further, if the image forming operation with a low image area continues, the amount of old toner that stays in the developing device for a long time increases, so that the toner charging characteristics deteriorate and the image quality deteriorates when used for image formation (development capability decreases, Transferability decline). In order to prevent such old toner from staying in the developing device, the toner is discharged to a non-image area of the photosensitive member 1 at a fixed timing, and new toner is replenished to the developing device whose toner density has been lowered after the discharging to refresh the inside of the developing device. It has a refresh mode.

  A control unit (not shown) stores the toner consumption amount of each developing device 5Y, M, C, K and the operation time of each developing device 5Y, M, C, K, and at a predetermined timing, the developing device. Whether or not the toner consumption amount is equal to or less than the threshold value for the operation time of the predetermined period is checked for each developing device, and the refresh mode is executed for the developing device equal to or less than the threshold value.

When the refresh mode is executed, a toner consumption pattern having an area of 25 [mm] × 250 [mm] is created in the non-image forming area corresponding to the space between the sheets of the photoconductor and transferred to the intermediate transfer belt 8. The adhesion amount of the toner consumption pattern is determined based on the toner consumption amount with respect to the operation time of the developing device for a predetermined period, and the maximum adhesion amount per unit area may be about 1.2 [mg / cm ² ]. Further, when the toner Q / d distribution of the toner consumption pattern transferred to the intermediate transfer belt 8 is measured, it is almost aligned with the normal charging polarity.

  Each color gradation pattern, chevron patch, and toner consumption pattern formed on the intermediate transfer belt 8 are collected by the belt cleaning device 100. At this time, the belt cleaning device 100 must remove a large amount of toner from the intermediate transfer belt 8. However, in a conventional cleaning device including a polarity control unit and a brush roller, or a cleaning device including a brush roller that removes positive polarity toner and a brush roller that removes negative polarity toner, each color gradation pattern, Untransferred toner images such as chevron patches and toner consumption patterns could not be removed at once. In such a case, the toner on the intermediate transfer belt 8 that could not be cleaned may be transferred onto the recording paper during the next printing operation, resulting in an abnormal image.

  Therefore, in the belt cleaning device 100 of this printer, untransferred toner images that are transferred to the belt cleaning device 100 without being transferred to the recording paper P such as each color gradation pattern, chevron patch, and toner consumption pattern are removed at a time. Configured to be able to.

FIG. 4 is an enlarged configuration diagram showing the belt cleaning device 100 and its surroundings, which are characteristic points of the printer, in an enlarged manner.
In the figure, a belt cleaning device 100 includes a pre-cleaning unit 100a for roughly removing an untransferred toner image on the intermediate transfer belt 8, and a polarity opposite to a normal charging polarity (negative polarity) on the intermediate transfer belt 8. A reversely charged toner cleaning unit 100b that removes the toner charged to (positive polarity) and a regular charged toner cleaning unit 100c that removes the toner charged to the regular charge polarity on the intermediate transfer belt 8 are provided.

  The pre-cleaning unit 100a has a pre-cleaning brush roller 101 as a pre-cleaning member. Further, a pre-collecting roller 102 as a pre-collecting member that collects toner attached to the pre-cleaning brush roller 101, and a pre-scraping blade 103 as a pre-scraping member that contacts the pre-collecting roller 102 and scrapes the toner from the roller surface. have.

  Since most of the toner constituting the untransferred toner image is charged with a normal charging polarity (negative polarity), a voltage having a polarity (positive polarity) opposite to the normal charging polarity is applied to the pre-cleaning brush roller 101, The negative toner on the intermediate transfer belt 8 is electrostatically removed. Further, a positive polarity voltage larger than that of the pre-cleaning brush roller 101 is applied to the pre-collection roller 102.

  The reversely charged toner cleaning unit 100b is disposed on the downstream side of the pre-cleaning unit 100a in the moving direction of the intermediate transfer belt 8 and statically charges the reversely charged toner charged to the opposite polarity (positive polarity) to the normal charging polarity (negative polarity) of the toner. A reversely charged toner cleaning brush roller 104 is provided as a reversely charged toner cleaning member that is electrically removed. Further, the reversely charged toner collecting roller 105 as a reversely charged toner collecting member for collecting the reversely charged toner attached to the reversely charged toner cleaning brush roller 104, and abutting against the reversely charged toner collecting roller 105 and scraping the reversely charged toner from the roller surface. A reversely charged toner scraping blade 106 is provided as a reversely charged toner scraping member. A negative voltage is applied to the reversely charged toner cleaning brush roller 104, and a negative voltage greater than that of the reversely charged toner cleaning brush roller 104 is applied to the reversely charged toner recovery roller 105. Further, the reversely charged toner cleaning unit 100b applies a negative charge to the toner on the intermediate transfer belt 8 so that the charge polarity of the toner on the intermediate transfer belt 8 is aligned with the normal charge polarity (negative polarity). It also has a function as a control means.

  The normally charged toner cleaning unit 100c is disposed on the downstream side in the moving direction of the intermediate transfer belt 8 with respect to the reversely charged toner cleaning unit 100b, and serves as a normally charged toner cleaning member that electrostatically removes normally charged toner charged to a normally charged polarity. A regular charged toner cleaning brush roller 107 is provided. Further, the regular charged toner collecting roller 108 as a regular charged toner collecting member for collecting the regular charged toner attached to the regular charged toner cleaning brush roller 107 and the regular charged toner collecting roller 108 are abutted and scraped from the roller surface. A regular charged toner scraping blade 109 is provided as a regular charged toner scraping member. A positive voltage is applied to the normally charged toner cleaning brush roller 107, and a negative voltage greater than that of the normally charged toner cleaning brush roller 107 is applied to the normally charged toner recovery roller 108.

  Further, the belt cleaning device 100 is provided with a conveying screw 110 as a conveying means for conveying to a waste toner tank (not shown) provided in the image forming apparatus main body. In the belt cleaning device 100, the toner is removed to the waste toner tank (not shown) outside the belt cleaning device by the transport screw 110, but the toner removed from the waste toner case by providing the belt cleaning device 100 with a waste toner case. May be stored. The waste toner case is detachably attached to the belt cleaning device 100 so that the toner collected in the waste toner case 115 can be removed by removing the waste toner case 115 from the cleaning device 100 during maintenance or the like. To.

  Each of the cleaning brush rollers 101, 104, and 107 includes a metal rotary shaft member that is rotatably supported, and a brush portion that includes a plurality of raised brushes that are erected on the peripheral surface thereof. The diameter is φ15 to 16 [mm]. The raised nail has a two-layer core-sheath structure in which the inside is made of a conductive material such as conductive carbon and the surface portion is made of an insulating material such as polyester. As a result, the lead has substantially the same potential as the voltage applied to the cleaning brush roller, and the toner can be electrostatically attracted to the raised surface. As a result, the toner on the intermediate transfer belt 8 is electrostatically attached to the raised hair by the action of the voltage applied to the cleaning brush roller. Further, the raised brushes of the cleaning brush rollers 101, 104, and 107 may be composed of only conductive fibers instead of the two-layered core-sheath structure. Moreover, you may make it the so-called oblique hair planted in the attitude | position inclined with respect to the normal line direction of a rotating shaft member. Further, the raising of the pre-cleaning brush roller 101 and the regular charging toner cleaning brush roller 107 may be a core-sheath structure, and the raising of the reverse charging toner cleaning brush roller 104 may be composed of only conductive fibers. By forming the raising of the reversely charged toner cleaning brush roller 104 with only conductive fibers, charge injection from the reversely charged toner cleaning brush roller 104 to the toner is likely to occur. Therefore, the reversely charged toner cleaning brush roller 104 can satisfactorily align the toner on the intermediate transfer belt 8 with negative polarity. On the other hand, the brushing of the pre-cleaning brush roller 101 and the regular charging toner cleaning brush roller 107 has a core-sheath structure, so that charge injection into the toner can be suppressed, and the toner on the intermediate transfer belt 8 is charged positively. To suppress. Thereby, it is possible to prevent the pre-cleaning brush roller 101 and the normally charged toner cleaning brush roller 107 from generating toner that cannot be removed electrostatically.

  Further, each cleaning brush roller 101, 104, 107 bites into the intermediate transfer belt 8 by 1 [mm], and the brushing at the contact position by the driving means (not shown) is opposite to the moving direction of the intermediate transfer belt 8. Rotate to move in the direction (counter direction). By rotating the raised hair so as to move in the counter direction at the contact position, the linear velocity difference between the cleaning brush roller and the intermediate transfer belt 8 can be increased. This increases the probability of contact with the raised hair until a portion of the intermediate transfer belt 8 passes through the contact range with the cleaning brush roller, and the toner can be removed from the intermediate transfer belt 8 satisfactorily.

  In the belt cleaning apparatus 100, SUS rollers are used as the collecting rollers 102, 105, and 108. Each of the collection rollers 102, 105, and 108 is made of any material as long as it can perform the function of transferring the toner adhering to the cleaning brush roller from the brush to the collection roller by the potential gradient between the raised brush and the collection roller. It doesn't matter. For example, each of the collecting rollers 102, 105, and 108 is covered with a high resistance elastic tube of several [μm] to 100 [μm] on a conductive core metal or further coated with an insulating coating, and the roller resistance is set to log R = 12 to You may use what was 13 [(ohm)]. By using a SUS roller as each of the collection rollers 102, 105, 108, there is an advantage that the cost can be reduced, the applied voltage can be kept low, and the power can be saved. On the other hand, by setting the roller resistance to logR = 12 to 13 [Ω], the charge injection into the toner during the collection to the collection roller is suppressed, and the toner has the same polarity as the applied voltage of the collection roller. It can suppress that a recovery rate falls.

The conditions of the cleaning brush rollers 101, 104, and 107 are as follows.
・ Brush material: Conductive polyester (Contains conductive carbon inside the fiber, the fiber surface is polyester, so-called core-sheath structure)
・ Brush resistance: 10 ^6-8 [Ω]
・ Brush flocking density: 100,000 [lines / inch ² ]
・ Brush fiber diameter: about 25 to 35 [μm]
-Brush tipping treatment: None-Brush diameter φ: 15-16 [mm]
-Brush fiber biting amount into the intermediate transfer belt 8: 1 [mm]
The brush flocking density, brush resistance, fiber diameter, fiber type, and brush fiber biting amount can be optimized by the system and are not limited thereto. Examples of the types of fibers that can be used include nylon, acrylic, and polyester.

The conditions of each collection roller 102, 105, 108 are as follows.
・ Recovery roller core material: SUS
-Brush fiber biting amount into the collection roller: 1.5 [mm]
The collection roller material, brush fiber entrapment amount, and applied voltage can be optimized by the system, and are not limited thereto.

The conditions of each scraping blade 103, 106, 109 are as follows.
・ Blade contact angle: 20 °
・ Blade thickness: 0.1 [mm]
・ Blade biting amount into collection roller: 1.0 [mm]
The blade contact angle, the blade thickness, and the amount of biting into the collection roller can be optimized by the system, and are not limited thereto.

Next, the cleaning operation of the belt cleaning apparatus 100 will be described.
As shown in FIG. 4, the untransferred toner image and the untransferred toner image that have passed through the secondary transfer portion pass through an entrance seal (not shown) and are transferred to the position of the pre-cleaning brush roller 101 by the rotation of the intermediate transfer belt 8. A voltage having a polarity (positive polarity) opposite to the normal charging polarity of the toner is applied to the pre-cleaning brush roller 101, and an electric field formed by a potential difference between the intermediate transfer belt 8 and the surface potential of the pre-cleaning brush roller 101 The negatively charged toner on the intermediate transfer belt 8 is electrostatically attracted and moved to the pre-cleaning brush roller 101. The negative polarity toner that has moved to the pre-cleaning brush roller 101 is transported to a contact position with the pre-collection roller 102 to which a positive voltage having a larger value than that of the pre-cleaning brush roller 101 is applied. Then, the toner that has moved onto the pre-cleaning brush roller 101 is electrostatically adsorbed by the electric field formed by the potential difference between the surface potential of the pre-cleaning brush roller 101 and the surface potential of the pre-collecting roller 102, and the pre-collecting roller 102 The negative toner that has been moved upward and moved to the pre-collection roller 102 is scraped off from the surface of the collection roller by the pre-scraping blade 103. The toner scraped off by the pre-scraping blade 103 is discharged out of the apparatus by the transport screw 110.

  Next, the negative toner, the positive toner, and the positive transfer residual toner of the untransferred toner image on the intermediate transfer belt 8 that could not be removed by the pre-cleaning brush roller 101 are placed at the position of the reversely charged toner cleaning brush roller 104. Be transported. A voltage having the same polarity (negative polarity) as the normal charging polarity of the toner is applied to the reversely charged toner cleaning brush roller 104, and the polarity of the toner on the intermediate transfer belt 8 is made negative by charge injection or discharge. . Further, the positively charged toner that is not controlled to the negative polarity is attracted to the reversely charged toner cleaning brush roller 104 by the electric field formed by the potential difference between the intermediate transfer belt 8 and the surface potential of the reversely charged toner cleaning brush roller 104. To be removed. The positive polarity toner that has moved to the reversely charged toner cleaning brush roller 104 is transferred to a contact position with the reversely charged toner recovery roller 105 to which a negative polarity voltage larger than that of the reversely charged toner cleaning brush roller 104 is applied. The The toner that has moved onto the reversely charged toner cleaning brush roller 104 is electrostatically adsorbed by an electric field formed by the potential difference between the surface potential of the reversely charged toner cleaning brush roller 104 and the surface potential of the reversely charged toner recovery roller 105. Then, the toner is moved onto the reversely charged toner collecting roller 105. The positive toner moved to the reversely charged toner collecting roller 105 is scraped off from the surface of the collecting roller by the reversely charged toner scraping blade 106.

  Next, the toner shifted to the negative polarity by the reversely charged toner cleaning brush roller 104 and the negative polarity toner that could not be removed by the pre-cleaning brush roller 101 are transferred to the regular charged toner cleaning brush roller 107. The polarity of toner transferred to the normally charged toner cleaning brush roller 107 is controlled to be negative by the reversely charged toner cleaning brush roller 104. Further, the toner on the intermediate transfer belt 8 is almost removed by the pre-cleaning brush roller 101 and the reversely charged toner cleaning brush roller 104. Therefore, a very small amount of toner is transferred to the regular charged toner cleaning brush roller 107. The normal charge toner cleaning brush roller 107 is aligned with the negative polarity, and a very small amount of toner on the intermediate transfer belt 8 is applied with a voltage having a polarity (positive polarity) opposite to the normal charge polarity of the toner. The toner is electrostatically attached to the charged toner cleaning brush roller 107, collected by the regular charged toner collecting roller 108, and scraped off from the regular charged toner collecting roller 108 by the regular charged toner scraping blade 109.

  According to the belt cleaning apparatus 100, by providing the pre-cleaning brush roller 101, the negative-polarity toner that covers most of the untransferred toner image by the pre-cleaning brush roller 101 is roughly removed. As a result, the amount of toner input to the reversely charged toner cleaning brush roller 104 and the regular charged toner cleaning brush roller 107 can be reduced, and the remaining toner can be removed satisfactorily by these cleaning brush rollers 104 and 107. .

Next, features of the present embodiment will be described.
Conventionally, a constant cleaning voltage is applied to each of the cleaning brush rollers 101, 104, and 107 to remove the toner on the intermediate transfer belt 8. In addition, a constant recovery voltage is applied to each of the recovery rollers 102, 105, and 108 to recover the toner on the cleaning brush roller. However, when the temperature and humidity change depending on the environment, resistance changes of the intermediate transfer belt 8 and the cleaning brush roller occur, and the cleaning current flowing between the intermediate transfer belt and the cleaning brush roller differs from the optimum value for cleaning, Good cleaning is not possible. In addition, the recovery current flowing between the cleaning brush roller and the recovery roller is different from the optimal value for recovery, and good recovery cannot be performed. Further, when an endurance test of the intermediate transfer belt 8 and the cleaning brush roller was performed, it was found that resistance change occurred in both of them, and an optimal current did not flow due to this, and good cleaning and recovery could not be performed.

  Therefore, in the present embodiment, a voltage is set so that an appropriate current flows independently between the intermediate transfer belt 8 and the cleaning brush roller and between the cleaning brush roller and the collection roller. That is, an optimum current is passed between the intermediate transfer belt and the cleaning brush roller, and between the cleaning brush roller and the recovery roller, the voltage at that time is detected, and the voltage is changed to the cleaning voltage and the recovery voltage, thereby changing the environment. Even if the resistance of the intermediate transfer belt or the cleaning brush roller changes due to deterioration over time, good cleaning and recovery can always be performed.

  As shown in FIG. 4, the cleaning units 100a, 100b, and 100c include cleaning power supply units 130, 132, and 134 for applying a cleaning voltage to the cleaning brush rollers 101, 104, and 107, and recovery rollers 102, 105, and 108 includes recovery power supply units 131, 133, and 135 for applying a recovery power supply. Each of the cleaning power supply units 130, 132, and 134 includes power supplies 130a, 132a, and 134a, and voltage detection units 130b, 132b, and 134b for detecting a voltage. Further, each of the recovery power supply units 131, 133, and 135 also includes power supplies 131a, 133a, and 135a and voltage detection units 131b, 133b, and 135b for detecting the voltage.

  Each cleaning voltage and recovery voltage are set when the image forming apparatus is activated. Specifically, the cleaning voltage and the recovery voltage are determined at an arbitrary timing from the start of the image forming apparatus to the start of image formation. However, the timing for setting each cleaning voltage and recovery voltage is not limited to this, and it may be during a preparatory operation from the end of image formation to the start of the next image formation. In addition, a temperature / humidity sensor as an environment detection unit may be provided in the apparatus main body, and the cleaning voltage and the recovery voltage may be set based on the detection result of the temperature / humidity sensor. For example, a first threshold value that is a boundary value between a low-humidity environment and a medium-humidity environment and a second threshold value that is a boundary value between the medium-humidity environment and the high-humidity environment are provided. When the humidity changes across these thresholds, the cleaning voltage and the recovery voltage are set.

  First, the first cleaning voltage applied to the pre-cleaning brush roller 101 and the first recovery voltage applied to the pre-collection roller 102 are set. The intermediate transfer belt 8, the cleaning roller of each cleaning unit, and the collection roller are driven to rotate. Next, a control unit (not shown) controls the power supply 130a at a constant current so that a first cleaning current of 20 μA flows between the pre-cleaning brush roller 101 and the intermediate transfer belt, and the voltage at that time is detected by the voltage detection unit 130b. This is determined as the first cleaning voltage. Further, the power supply 131a is controlled at a constant current at the same timing, a first recovery current of 5 μA is caused to flow between the pre-recovery roller 102 and the pre-cleaning brush roller, and the voltage at that time is detected by the voltage detector 131b. Determined as recovery voltage.

  The first cleaning current is a value obtained by an experiment in advance, and a cleaning voltage value at which an optimum current for cleaning flows between the intermediate transfer belt 8 and the pre-cleaning brush roller 101 to which the transfer residual toner is attached is expressed as the transfer residual toner. This is the current value that flows between the pre-cleaning brush roller 101 and the intermediate transfer belt when it is applied to the non-pre-cleaning brush roller 101. In addition, the first recovery current is obtained when the recovery voltage value when an optimum current flows between the pre-cleaning brush and the recovery roller with the transfer residual toner attached is applied to the pre-recovery roller. This is the current value that flows between the pre-cleaning brush and the collecting roller.

  Next, a second cleaning voltage to be applied to the reversely charged toner cleaning brush roller 104 and a second recovery voltage to be applied to the reversely charged toner recovery roller are set. In the present embodiment, the portion where the first cleaning current flows on the intermediate transfer belt 8 passes through the cleaning nip of the reversely charged toner cleaning brush roller 104 and is applied to the reversely charged toner cleaning brush roller 104. A second cleaning voltage and a second recovery voltage to be applied to the reversely charged toner recovery roller are set. In this embodiment, the intermediate transfer belt rotates at 352 [mm / sec], and the distance between the pre-cleaning brush roller 101 and the reversely charged toner cleaning brush roller 104 is 20 [mm]. Therefore, the second cleaning voltage and the second recovery voltage are 20 [mm] ÷ 352 [mm / sec] = 0.06 [sec] after the voltage applied to the pre-cleaning brush roller 101 and the pre-collection roller 102 is determined. To decide. At this time, the first cleaning voltage and the first recovery voltage determined above are applied to the pre-cleaning brush roller 101 and the pre-recovery roller 102. By doing so, it is possible to determine the second cleaning voltage and the second recovery voltage in consideration of the influence of the electric charge applied to the intermediate transfer belt 8 from the pre-cleaning brush roller 101 and the pre-collection roller 102.

  When 0.06 [sec] has elapsed since the determination of the first cleaning voltage and the first recovery voltage, the power source 132a is controlled at a constant current, and the −40 μA first current between the reversely charged toner cleaning brush roller 104 and the intermediate transfer belt 8 is controlled. 2 Supply cleaning current. The voltage at that time is detected by the voltage detector 132b, and this is set as the second cleaning voltage. Further, the power source 133a is controlled at a constant current at the same timing, and a second recovery current of −5 μA is passed between the reversely charged toner recovery roller 105 and the reversely charged toner cleaning brush roller 104, and the voltage at that time is detected by the voltage detection unit 133b. This is determined as the second recovery voltage.

  The second cleaning current is also a value obtained in advance by experiments in the same manner as the first cleaning current. That is, when a cleaning voltage value when an optimum current flows between the intermediate transfer belt 8 to which the transfer residual toner adheres and the reversely charged toner cleaning brush roller 104 is applied to the reversely charged toner cleaning brush roller 104, the transfer is performed. This is a current value that flows between the intermediate transfer belt and the reversely charged toner cleaning brush roller in a state where there is no residual toner. The second recovery current is also a value obtained in advance by experiments in the same manner as the first recovery current.

  Next, the third cleaning voltage to be applied to the normally charged toner cleaning brush roller 107 and the third recovery voltage to be applied to the normally charged toner recovery roller 108 are determined. The third cleaning voltage and the second recovery voltage are determined when the location where the first and second cleaning currents flow on the intermediate transfer belt 8 passes through the cleaning nip of the normally charged toner cleaning brush roller 107. Do. In this embodiment, since the distance between the reversely charged toner cleaning brush roller 104 and the regular charged toner cleaning brush roller 107 is 20 [mm], 20 [mm] ÷ after the second cleaning voltage and the second recovery voltage are determined. The third cleaning voltage and the third recovery voltage are determined after 352 [mm / sec] = 0.06 [sec]. At this time, the voltage continues to be applied to the pre-cleaning brush roller and the pre-collecting roller, the reversely charged toner cleaning brush roller and the reversely charged toner collecting roller. By doing so, the effect of the charge applied to the intermediate transfer belt 8 from the pre-cleaning brush roller 101 and the pre-collecting roller 102 and the application from the reversely charged toner cleaning brush roller 104 and the reversely charged toner collecting roller 105 to the intermediate transfer belt 8 are achieved. The third cleaning voltage and the third recovery voltage can be determined in consideration of the influence of the generated charge.

  When 0.06 [sec] has elapsed since the determination of the second cleaning voltage and the second recovery voltage, the power source 134a is controlled at a constant current, and a third current of 5 μA is set between the normally charged toner cleaning brush roller 107 and the intermediate transfer belt 8. Apply cleaning current. The voltage at that time is detected by the voltage detector 134b and set as the third cleaning voltage. Further, the power source 135a is controlled at a constant current at the same timing, and a third recovery current of 5 μA is caused to flow between the normally charged toner recovery roller 108 and the normally charged toner cleaning brush roller 107, and the voltage at that time is detected by the voltage detector 135b. This is determined as the third recovery voltage.

  When the image forming operation is started, a control unit (not shown) performs cleaning by applying each set cleaning voltage and each recovery voltage to the corresponding cleaning brush roller and recovery roller.

  The third cleaning current and the third recovery current are values obtained in the same manner as the first cleaning current and the first recovery current.

  As described above, according to the belt cleaning apparatus 100, even when the resistance value of the intermediate transfer belt 8 or the cleaning brush roller changes due to environmental change or deterioration with time, the cleaning voltage optimum for cleaning, and It is possible to apply a recovery voltage optimum for recovery. However, the optimum values of the second and third cleaning currents and the second and third recovery currents differ depending on the configuration of the apparatus and the change in the rotation speed of the intermediate transfer belt 8, the pre-cleaning brush roller 101, and the pre-collecting roller 102. Therefore, the values of the second and third cleaning currents and the second and third recovery currents are not limited to the values described above.

  Further, as described above, the pre-cleaning unit 100a needs to remove about 90% of the untransferred toner image such as a toner pattern. When removing the untransferred toner image, the untransferred toner image on the intermediate transfer belt cannot be removed by the pre-cleaning brush roller even if the set first cleaning voltage is applied to the pre-cleaning brush roller. This is because a large amount of toner on the intermediate transfer belt becomes a resistance, so that an optimum cleaning current does not flow between the intermediate transfer belt and the pre-cleaning brush roller even if the first cleaning voltage set as described above is applied. . Therefore, in the pre-cleaning unit 100a, it is preferable to set a cleaning voltage for cleaning the untransferred toner image (hereinafter referred to as an untransferred cleaning voltage) and a recovery voltage at that time (hereinafter referred to as an untransferred recovery voltage). .

  Specifically, after determining the first cleaning voltage and the first recovery voltage in the same manner as described above, the control unit (not shown) causes a cleaning current of 80 μA to flow between the pre-cleaning brush roller 101 and the intermediate transfer belt 8. The power source 130a is controlled at a constant current. This 80 μA is a value obtained by experiments in advance, and when a cleaning voltage value when an optimum cleaning current flows when removing untransferred toner is applied to the cleaning brush roller when there is no untransferred toner image. The current value that flows between the cleaning brush and the intermediate transfer belt. Then, the voltage value when the cleaning current of 80 μA flows is detected by the voltage detector 130b, and the voltage value is determined as an untransferred cleaning voltage. Further, the power supply 131a is controlled at a constant current at the same timing so that a recovery current of 5 μA flows between the pre-cleaning brush roller 101 and the pre-recovery roller 102, and the voltage at that time is detected by the voltage detector 131b. This detected voltage value is determined as an untransferred recovery voltage.

FIG. 5 is a timing chart of the applied voltage to the pre-cleaning brush roller 101 of the pre-cleaning unit 100a and the applied voltage to the pre-collection roller 102.
As shown in the figure, when cleaning the toner consumption pattern as an untransferred toner image formed between papers, the pre-transfer cleaning voltage set as described above is applied to the pre-cleaning brush roller 101, and the pre-recovery roller 102 described above. Apply the untransferred recovery voltage set in step 1. In this way, by setting the cleaning voltage and the recovery voltage for removing the untransferred toner image that needs to clean a large amount of toner, it becomes possible to clean the untransferred toner image satisfactorily. Further, since most of the toner consumption pattern can be cleaned by the pre-cleaning brush roller 101, the untransferred toner image is removed in the cleaning unit located downstream from this, like the pre-cleaning unit 100a. Therefore, it is not necessary to apply a special cleaning voltage or recovery voltage. Therefore, when removing such an untransferred toner image, the second cleaning voltage is applied to the reversely charged toner cleaning brush roller, and the second recovery voltage is applied to the reversely charged toner recovery roller. A third cleaning voltage is applied to the regular charged toner cleaning brush roller, and a third recovery voltage is applied to the regular charged toner recovery roller.

For example, the amount of chevron patch PV deposited during the color misregistration correction process is about 0.3 [mg / cm ² ], and the maximum amount of toner consumption pattern deposited is 1.2 [mg / cm ² The amount of untransferred toner image attached varies. Therefore, the cleaning voltage applied to the pre-cleaning brush roller 101 may be varied according to the amount of untransferred toner image to be removed.

  In this case, first, when determining the cleaning voltage to be applied to the pre-cleaning brush roller 101, a plurality of different currents are supplied to the pre-cleaning brush roller 101, and the voltage detection unit 130b is used for each current value. Measure. A VI (cleaning voltage-cleaning current) characteristic as shown in FIG. 6 is obtained from the obtained measurement result. However, linear correction is performed at points other than the measurement point. At this time, a current of 5 μA which is optimum for collecting the toner on the pre-cleaning brush roller 101 is supplied to the pre-collecting roller 102, and the voltage value at that time is detected. From the obtained measurement results, the characteristics of the recovery voltage-cleaning voltage or the recovery voltage-cleaning current are obtained.

  The memory of the control unit stores a table in which the adhesion amount and the cleaning current value are associated with each other. When the untransferred toner image is removed, the cleaning current value is calculated from the adhesion amount and the table of the untransferred toner image. decide. Next, the cleaning voltage to be applied to the pre-cleaning brush roller 101 is determined from the cleaning current value and the VI characteristic shown in FIG. Further, the recovery voltage applied to the pre-recovery roller 102 is determined based on the cleaning current or the cleaning voltage. As a result, it is possible to satisfactorily clean any non-transferred toner image (toner pattern) with any attached amount.

  In the belt cleaning device of this embodiment, a cleaning voltage through which an optimum cleaning current flows when cleaning is determined in advance, and cleaning is performed by constant voltage control. This is because if the constant current control is performed so that an optimum cleaning current flows at the time of cleaning, immediately after the transfer residual toner or the untransferred toner image on the intermediate transfer belt enters the cleaning nip, due to the influence of the resistance of the toner, Cleaning current decreases. As described above, since the cleaning current decreases immediately after the untransferred toner or the untransferred toner image enters the cleaning nip, the toner input to the cleaning nip at the beginning may be defective in cleaning. In particular, when a large amount of toner such as an untransferred toner image adheres to the intermediate transfer belt, the amount of decrease in the cleaning current immediately after the input of the cleaning nip is large, so that defective cleaning tends to occur at the initial stage. On the other hand, as in the present embodiment, an initial cleaning failure does not occur by applying in advance a cleaning voltage through which an optimum cleaning current flows when cleaning.

  Further, the belt cleaning device 100 injects negative charge into the toner on the intermediate transfer belt 8 by the reversely charged toner cleaning brush roller 104, and sets the charge polarity of the toner passing through the regular charged toner cleaning brush roller 107 to the negative polarity. However, such polarity control may not necessarily be performed depending on toner conditions and image forming conditions. In the belt cleaning device 100, the normally charged toner cleaning unit 100c is provided on the most downstream side in the belt moving direction, but the reversely charged toner cleaning unit 100b may be provided on the most downstream side in the belt moving direction. In this case, the normal charge toner cleaning brush roller 107 injects positive charge into the toner on the intermediate transfer belt 8, and the polarity control is performed so that the charge polarity of the toner passing through the normal charge toner cleaning brush roller 107 is made positive. Alternatively, the polarity control may not be performed.

  In the belt cleaning device 100, the positively charged toner on the intermediate transfer belt 8 is removed by the reversely charged toner cleaning brush roller 104. However, the reversely charged toner cleaning unit 100b is changed to a polarity control unit so that the intermediate toner is removed. A configuration in which the positive toner on the transfer belt 8 is not removed may be employed. In this case, the toner on the intermediate transfer belt 8 that has passed through the pre-cleaning brush roller 101 is made to have a negative polarity by the polarity control unit and is sent to the normally charged toner cleaning brush roller 107 downstream in the belt moving direction from the polarity control unit. Be transported. Then, the negatively charged toner is removed by the normally charged toner cleaning brush roller 107. As a means for injecting negative charge into the toner on the intermediate transfer belt 8 in the polarity control unit, a conductive brush, a conductive blade, or the like may be used. Also, instead of aligning the charging polarity of the toner to negative polarity, arrange a cleaning brush roller to which a negative voltage is applied downstream of the polarity control unit in the belt moving direction so that it is aligned to positive polarity. A configuration in which toner having a positive polarity on the intermediate transfer belt is removed may be employed. Even in such a configuration, since the toner of the untransferred toner image is roughly removed from the intermediate transfer belt 8 by the pre-cleaning brush roller 101, the amount of toner transferred to the polarity control unit is reduced. Further, the amount of toner reattached from the pre-cleaning brush roller 101 to the intermediate transfer belt 8 is also reduced. Therefore, the polarity control unit can satisfactorily align the toner on the intermediate transfer belt 8 with one polarity. As a result, the toner on the intermediate transfer belt 8 can be satisfactorily electrostatically removed by the cleaning brush roller disposed downstream of the polarity control unit. Therefore, even if an untransferred toner image to which a large amount of toner is attached is input to the belt cleaning device 100, it can be satisfactorily cleaned.

Next, toner that is preferably used in the printer will be described.
The toner preferably used in this printer preferably has a volume average particle diameter of 3 to 6 [μm] in order to reproduce minute dots of 600 dpi or more. A toner having a ratio (Dv / Dn) of volume average particle diameter (Dv) to number average particle diameter (Dn) in the range of 1.00 to 1.40 is preferable. The closer (Dv / Dn) is to 1.00, the sharper the particle size distribution. With such a toner having a small particle size and a narrow particle size distribution, the toner charge amount distribution is uniform, a high-quality image with little background fogging can be obtained, and the electrostatic transfer method has a high transfer rate. can do.
The toner shape factor SF-1 is preferably in the range of 100 to 180, and the shape factor SF-2 is preferably in the range of 100 to 180. FIG. 7 is a diagram schematically showing the shape of the toner in order to explain the shape factor SF-1. The shape factor SF-1 indicates the ratio of the roundness of the toner shape and is represented by the following formula (1). This is a value obtained by dividing the square of the maximum length MXLNG of the shape formed by projecting the toner on a two-dimensional plane by the figure area AREA and multiplying by 100π / 4.
SF-1 = {(MXLNG) ² / AREA} × (100π / 4) (1)
When the value of SF-1 is 100, the shape of the toner becomes a true sphere, and becomes larger as the value of SF-1 increases.

FIG. 8 is a diagram schematically showing the shape of the toner in order to explain the shape factor SF-2. The shape factor SF-2 indicates the ratio of unevenness in the shape of the toner, and is represented by the following formula (2). A value obtained by dividing the square of the perimeter PERI of the figure formed by projecting the toner on the two-dimensional plane by the figure area AREA and multiplying by 100π / 4.
SF-2 = {(PERI) ² / AREA} × 100 / (4π) (2)
When the value of SF-2 is 100, there is no unevenness on the toner surface, and as the value of SF-2 increases, the unevenness of the toner surface becomes more prominent.

  Specifically, the shape factor is measured by taking a photograph of the toner with a scanning electron microscope (S-800: manufactured by Hitachi, Ltd.), introducing it into an image analyzer (LUSEX 3: manufactured by Nireco) and analyzing it. Calculated. When the shape of the toner is close to a spherical shape, the contact state between the toner and the toner or the toner and the photoconductor becomes a point contact, so that the adsorbing force between the toners becomes weak and the fluidity becomes high. The attraction force becomes weaker and the transfer rate becomes higher. If either of the shape factors SF-1 and SF-2 exceeds 180, the transfer rate is lowered, which is not preferable.

  In addition, a toner suitably used for a color printer is a toner material liquid in which at least a polyester prepolymer having a functional group containing a nitrogen atom, polyester, a colorant, and a release agent are dispersed in an organic solvent. Is a toner obtained by crosslinking and / or elongation reaction in an aqueous solvent. Hereinafter, the constituent material and the manufacturing method of the toner will be described.

(polyester)
The polyester is obtained by a polycondensation reaction between a polyhydric alcohol compound and a polycarboxylic acid compound.
Examples of the polyhydric alcohol compound (PO) include dihydric alcohol (DIO) and trihydric or higher polyhydric alcohol (TO). (DIO) alone or a mixture of (DIO) and a small amount of (TO) preferable. Examples of the dihydric alcohol (DIO) include alkylene glycol (ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, etc.); alkylene ether glycol (diethylene glycol) , Triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, etc.); alicyclic diols (1,4-cyclohexanedimethanol, hydrogenated bisphenol A, etc.); bisphenols (bisphenol A, bisphenol) F, bisphenol S, etc.); alkylene oxide (ethylene oxide, propylene oxide, butylene oxide, etc.) adduct of the above alicyclic diol; Alkylene oxide bisphenol (ethylene oxide, propylene oxide, butylene oxide, etc.), etc. adducts. Among them, preferred are alkylene glycols having 2 to 12 carbon atoms and alkylene oxide adducts of bisphenols, and particularly preferred are alkylene oxide adducts of bisphenols and alkylene glycols having 2 to 12 carbon atoms. It is a combined use. The trihydric or higher polyhydric alcohol (TO) includes 3 to 8 or higher polyhydric aliphatic alcohols (glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, sorbitol, etc.); trihydric or higher phenols (Trisphenol PA, phenol novolak, cresol novolak, etc.); and alkylene oxide adducts of the above trivalent or higher polyphenols.

  Examples of the polyvalent carboxylic acid (PC) include divalent carboxylic acid (DIC) and trivalent or higher polyvalent carboxylic acid (TC). (DIC) alone and (DIC) with a small amount of (TC) Mixtures are preferred. Divalent carboxylic acids (DIC) include alkylene dicarboxylic acids (succinic acid, adipic acid, sebacic acid, etc.); alkenylene dicarboxylic acids (maleic acid, fumaric acid, etc.); aromatic dicarboxylic acids (phthalic acid, isophthalic acid, terephthalic acid) And naphthalenedicarboxylic acid). Of these, preferred are alkenylene dicarboxylic acids having 4 to 20 carbon atoms and aromatic dicarboxylic acids having 8 to 20 carbon atoms. Examples of the trivalent or higher polyvalent carboxylic acid (TC) include aromatic polycarboxylic acids having 9 to 20 carbon atoms (such as trimellitic acid and pyromellitic acid). In addition, as polyhydric carboxylic acid (PC), you may make it react with polyhydric alcohol (PO) using the above-mentioned acid anhydride or lower alkyl ester (Methyl ester, ethyl ester, isopropyl ester, etc.).

  The ratio of the polyhydric alcohol (PO) to the polycarboxylic acid (PC) is usually 2/1 to 1/1, preferably as the equivalent ratio [OH] / [COOH] of the hydroxyl group [OH] and the carboxyl group [COOH]. Is 1.5 / 1 to 1/1, more preferably 1.3 / 1 to 1.02 / 1. The polycondensation reaction of polyhydric alcohol (PO) and polycarboxylic acid (PC) is performed at 150 to 280 ° C. in the presence of a known esterification catalyst such as tetrabutoxytitanate or dibutyltin oxide, while reducing the pressure as necessary. The produced water is distilled off to obtain a polyester having a hydroxyl group. The hydroxyl value of the polyester is preferably 5 or more, and the acid value of the polyester is usually 1 to 30, preferably 5 to 20. By giving an acid value, it tends to be negatively charged, and furthermore, when fixing to a recording paper, the affinity between the recording paper and the toner is good and the low-temperature fixability is improved. However, when the acid value exceeds 30, there is a tendency to deteriorate with respect to the stability of charging, particularly environmental fluctuation. The weight average molecular weight is 10,000 to 400,000, preferably 20,000 to 200,000. A weight average molecular weight of less than 10,000 is not preferable because offset resistance deteriorates. On the other hand, if it exceeds 400,000, the low-temperature fixability is deteriorated.

  In addition to the unmodified polyester obtained by the above polycondensation reaction, the polyester preferably contains a urea-modified polyester. The urea-modified polyester is obtained by reacting a terminal carboxyl group or hydroxyl group of the polyester obtained by the above polycondensation reaction with a polyvalent isocyanate compound (PIC) to obtain a polyester prepolymer (A) having an isocyanate group. It is obtained by cross-linking and / or extending the molecular chain by the reaction of the amine with amines. Examples of the polyvalent isocyanate compound (PIC) include aliphatic polyisocyanates (tetramethylene diisocyanate, hexamethylene diisocyanate, 2,6-isocyanatomethyl caproate, etc.); alicyclic polyisocyanates (isophorone diisocyanate, cyclohexylmethane diisocyanate, etc.) Aromatic diisocyanates (tolylene diisocyanate, diphenylmethane diisocyanate, etc.); araliphatic diisocyanates (α, α, α ′, α′-tetramethylxylylene diisocyanate, etc.); isocyanates; phenol derivatives, oximes, caprolactam And a combination of two or more of these. The ratio of the polyvalent isocyanate compound (PIC) is usually 5/1 to 1/1, preferably as an equivalent ratio [NCO] / [OH] of the isocyanate group [NCO] and the hydroxyl group [OH] of the polyester having a hydroxyl group. 4/1 to 1.2 / 1, more preferably 2.5 / 1 to 1.5 / 1. When [NCO] / [OH] exceeds 5/1, the low-temperature fixability deteriorates. When the molar ratio of [NCO] is less than 1/1, when a urea-modified polyester is used, the urea content in the ester becomes low and hot offset resistance deteriorates. The content of the polyvalent isocyanate compound (PIC) component in the polyester prepolymer (A) having an isocyanate group is usually 0.5 to 40 wt%, preferably 1 to 30 wt%, more preferably 2 to 20 wt%. . If it is less than 0.5 wt%, the hot offset resistance deteriorates, and it is disadvantageous in terms of both heat-resistant storage stability and low-temperature fixability. On the other hand, if it exceeds 40 wt%, the low-temperature fixability deteriorates. The number of isocyanate groups contained per molecule in the polyester prepolymer (A) having an isocyanate group is usually 1 or more, preferably 1.5 to 3 on average, more preferably 1.8 to 2 on average. Five. If it is less than 1 per molecule, the molecular weight of the urea-modified polyester will be low, and the hot offset resistance will deteriorate.

  Next, as amines (B) to be reacted with the polyester prepolymer (A), a divalent amine compound (B1), a trivalent or higher polyvalent amine compound (B2), an amino alcohol (B3), an amino mercaptan (B4) ), Amino acid (B5), and amino acid block of B1 to B5 (B6).

  Examples of the divalent amine compound (B1) include aromatic diamines (phenylenediamine, diethyltoluenediamine, 4,4′-diaminodiphenylmethane, etc.); alicyclic diamines (4,4′-diamino-3,3′-dimethyldicyclohexyl). Methane, diamine cyclohexane, isophorone diamine, etc.); and aliphatic diamines (ethylene diamine, tetramethylene diamine, hexamethylene diamine, etc.) and the like. Examples of the trivalent or higher polyvalent amine compound (B2) include diethylenetriamine and triethylenetetramine. Examples of amino alcohol (B3) include ethanolamine and hydroxyethylaniline. Examples of amino mercaptan (B4) include aminoethyl mercaptan and aminopropyl mercaptan. Examples of the amino acid (B5) include aminopropionic acid and aminocaproic acid. Examples of the compound (B6) obtained by blocking the amino group of B1 to B5 include ketimine compounds and oxazolidine compounds obtained from the amines of B1 to B5 and ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.). Among these amines (B), preferred are B1 and a mixture of B1 and a small amount of B2.

  The ratio of amines (B) is equivalent to the equivalent ratio [NCO] / [NHx] of isocyanate groups [NCO] in the polyester prepolymer (A) having isocyanate groups and amino groups [NHx] in amines (B). Is usually 1/2 to 2/1, preferably 1.5 / 1 to 1 / 1.5, more preferably 1.2 / 1 to 1 / 1.2. When [NCO] / [NHx] is more than 2/1 or less than 1/2, the molecular weight of the urea-modified polyester is lowered, and the hot offset resistance is deteriorated.

  The urea-modified polyester may contain a urethane bond together with a urea bond. The molar ratio of the urea bond content to the urethane bond content is usually 100/0 to 10/90, preferably 80/20 to 20/80, and more preferably 60/40 to 30/70. When the molar ratio of the urea bond is less than 10%, the hot offset resistance is deteriorated.

  The urea-modified polyester is produced by a one-shot method or the like. Polyhydric alcohol (PO) and polyvalent carboxylic acid (PC) are heated to 150-280 ° C. in the presence of a known esterification catalyst such as tetrabutoxytitanate, dibutyltin oxide, etc., and water produced while reducing the pressure as necessary. Distill off to obtain a polyester having a hydroxyl group. Subsequently, at 40-140 degreeC, this is made to react with polyvalent isocyanate (PIC), and the polyester prepolymer (A) which has an isocyanate group is obtained. Further, this (A) is reacted with amines (B) at 0 to 140 ° C. to obtain a urea-modified polyester.

  When reacting (PIC) and when reacting (A) and (B), a solvent may be used if necessary. Usable solvents include aromatic solvents (toluene, xylene, etc.); ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.); esters (ethyl acetate, etc.); amides (dimethylformamide, dimethylacetamide, etc.) and ethers And those inert to isocyanates (PIC), such as tetrahydrofuran (such as tetrahydrofuran).

  In addition, in the crosslinking and / or extension reaction between the polyester prepolymer (A) and the amines (B), a reaction terminator can be used as necessary to adjust the molecular weight of the resulting urea-modified polyester. Examples of the reaction terminator include monoamines (diethylamine, dibutylamine, butylamine, laurylamine, etc.), and those obtained by blocking them (ketimine compounds).

  The weight average molecular weight of the urea-modified polyester is usually 10,000 or more, preferably 20,000 to 10,000,000, and more preferably 30,000 to 1,000,000. If it is less than 10,000, the hot offset resistance deteriorates. The number average molecular weight of the urea-modified polyester or the like is not particularly limited when the above-mentioned unmodified polyester is used, and may be a number average molecular weight that can be easily obtained to obtain the weight average molecular weight. When the urea-modified polyester is used alone, its number average molecular weight is usually 2000-15000, preferably 2000-10000, more preferably 2000-8000. When it exceeds 20000, the low-temperature fixability and the glossiness when used in a full-color image forming apparatus are deteriorated.

  By using the unmodified polyester and the urea-modified polyester in combination, the low-temperature fixability and the glossiness when used in a full-color image forming apparatus are improved. Therefore, it is preferable to use the urea-modified polyester alone. The unmodified polyester may include a polyester modified with a chemical bond other than a urea bond.

  The unmodified polyester and the urea-modified polyester are preferably at least partially compatible with each other in terms of low-temperature fixability and hot offset resistance. Therefore, it is preferable that the unmodified polyester and the urea-modified polyester have a similar composition.

  The weight ratio of unmodified polyester to urea-modified polyester is usually 20/80 to 95/5, preferably 70/30 to 95/5, more preferably 75/25 to 95/5, and particularly preferably 80 /. 20-93 / 7. When the weight ratio of the urea-modified polyester is less than 5%, the hot offset resistance is deteriorated, and it is disadvantageous in terms of both heat-resistant storage stability and low-temperature fixability.

  The glass transition point (Tg) of the binder resin containing unmodified polyester and urea-modified polyester is usually 45 to 65 ° C, preferably 45 to 60 ° C. If it is less than 45 ° C., the heat resistance of the toner deteriorates, and if it exceeds 65 ° C., the low-temperature fixability becomes insufficient.

  In addition, since the urea-modified polyester is likely to be present on the surface of the obtained toner base particles, the heat-resistant storage stability tends to be good even when the glass transition point is low as compared with known polyester-based toners.

(Coloring agent)
As the colorant, all known dyes and pigments can be used. For example, carbon black, nigrosine dye, iron black, naphthol yellow S, Hansa yellow (10G, 5G, G), cadmium yellow, yellow iron oxide, ocher , Lead yellow, titanium yellow, polyazo yellow, oil yellow, Hansa yellow (GR1, RN, R), pigment yellow L, benzidine yellow (G, GR), permanent yellow (NCG), Vulcan fast yellow (5G, R) , Tartrazine rake, quinoline yellow rake, anthrazan yellow BGL, isoindolinone yellow, bengara, red lead, lead vermilion, cadmium red, cadmium mercurial red, antimon vermilion, permanent red 4R, para red, phissa red Parachlor ortho nitro Nirin Red, Resol Fast Scarlet G, Brilliant Fast Scarlet, Brilliant Carmine B, Permanent Red (F2R, F4R, FRL, FRLL, F4RH), Fast Scarlet VD, Belkan Fast Rubin B, Brilliant Scarlet G, Resol Rubin GX, Permanent Red F5R Brilliant Carmine 6B, Pigment Scarlet 3B, Bordeaux 5B, Toluidine Maroon, Permanent Bordeaux F2K, Helio Bordeaux BL, Bordeaux 10B, Bon Maroon Light, Bon Maroon Medium, Eosin Lake, Rhodamine Lake B, Rhodamine Lake Y, Alizarin Lake, Thioindigo Red B, thioindigo maroon, oil red, quinacridone red, pyrazolone red, Riazo Red, Chrome Vermillion, Benzidine Orange, Perinone Orange, Oil Orange, Cobalt Blue, Cerulean Blue, Alkaline Blue Lake, Peacock Blue Lake, Victoria Blue Lake, Metal Free Phthalocyanine Blue, Phthalocyanine Blue, Fast Sky Blue, Indanthrene Blue (RS, BC), indigo, ultramarine blue, bitumen, anthraquinone blue, fast violet B, methyl violet lake, cobalt purple, manganese purple, dioxane violet, anthraquinone violet, chrome green, zinc green, chromium oxide, pyridian, emerald green, pigment Green B, Naphthol Green B, Green Gold, Acid Green Lake, Malachite Green Lake, Phthalo Cyanine green, anthraquinone green, titanium oxide, zinc white, litbon and mixtures thereof can be used. The content of the colorant is usually 1 to 15% by weight, preferably 3 to 10% by weight, based on the toner.

  The colorant can also be used as a master batch combined with a resin. As a binder resin to be kneaded together with the production of the master batch or the master batch, a polymer of styrene such as polystyrene, poly-p-chlorostyrene, polyvinyl toluene or the like, or a copolymer of these and a vinyl compound, Polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, epoxy resin, epoxy polyol resin, polyurethane, polyamide, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, fat Aromatic or alicyclic hydrocarbon resins, aromatic petroleum resins, chlorinated paraffins, paraffin waxes and the like can be mentioned, and these can be used alone or in combination.

(Charge control agent)
Known charge control agents can be used, such as nigrosine dyes, triphenylmethane dyes, chromium-containing metal complex dyes, molybdate chelate pigments, rhodamine dyes, alkoxy amines, quaternary ammonium salts (fluorine-modified 4 Secondary ammonium salts or compounds, tungsten simple substances or compounds, fluorine activators, salicylic acid metal salts, and metal salts of salicylic acid derivatives. Specifically, Bontron 03 of a nigrosine dye, Bontron P-51 of a quaternary ammonium salt, Bontron S-34 of a metal-containing azo dye, E-82 of an oxynaphthoic acid metal complex, E-84 of a salicylic acid metal complex , Phenolic condensate E-89 (above, Orient Chemical Industries, Ltd.), quaternary ammonium salt molybdenum complex TP-302, TP-415 (above, Hodogaya Chemical Co., Ltd.), quaternary ammonium salt copy Charge PSYVP 2038, copy blue PR of triphenylmethane derivative, copy charge NEG VP2036 of quaternary ammonium salt, copy charge NX VP434 (manufactured by Hoechst), LR1-901, LR-147 which is a boron complex (manufactured by Nippon Carlit) ), Copper phthalocyanine, perylene, quinacridone, azo face , Sulfonate group, carboxyl group, and polymer compounds having a functional group such as quaternary ammonium salts. Of these, substances that control the negative polarity of the toner are particularly preferably used.

  The amount of charge control agent used is determined by the type of binder resin, the presence or absence of additives used as necessary, and the toner production method including the dispersion method, and is not uniquely limited. Preferably, it is used in the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin. The range of 0.2 to 5 parts by weight is preferable. When the amount exceeds 10 parts by weight, the chargeability of the toner is too high, the effect of the charge control agent is reduced, the electrostatic attraction with the developing roller is increased, the developer fluidity is lowered, and the image density is lowered. Invite.

(Release agent)
As a release agent, a low melting point wax having a melting point of 50 to 120 ° C. works more effectively as a release agent in the dispersion with the binder resin between the fixing roller and the toner interface. The effect on high temperature offset is exhibited without applying a release agent such as oil. Examples of such a wax component include the following. Examples of waxes and waxes include plant waxes such as carnauba wax, cotton wax, wood wax, rice wax, animal waxes such as beeswax and lanolin, mineral waxes such as ozokerite and cercin, and paraffin, microcrystalline, And petroleum waxes such as petrolatum. In addition to these natural waxes, synthetic hydrocarbon waxes such as Fischer-Tropsch wax and polyethylene wax, and synthetic waxes such as esters, ketones, and ethers can be used. Furthermore, fatty acid amides such as 12-hydroxystearic acid amide, stearic acid amide, phthalic anhydride imide, chlorinated hydrocarbon, and low molecular weight crystalline polymer resin, poly-n-stearyl methacrylate, poly-n- A crystalline polymer having a long alkyl group in the side chain such as a homopolymer or copolymer of polyacrylate such as lauryl methacrylate (for example, a copolymer of n-stearyl acrylate-ethyl methacrylate, etc.) can also be used. .

  The charge control agent and the release agent can be melt-kneaded together with the master batch and the binder resin, and of course, they may be added when dissolved and dispersed in the organic solvent.

(External additive)
Inorganic fine particles are preferably used as an external additive for assisting the fluidity, developability and chargeability of the toner particles. The primary particle diameter of the inorganic fine particles is preferably ⁵ × ¹⁰ -3~2 [μm], it is particularly preferably ⁵ × ¹⁰ -3~0.5 [μm]. Moreover, it is preferable that the specific surface area by BET method is 20-500 [m < ² > / g]. The use ratio of the inorganic fine particles is preferably 0.01 to 5 wt% of the toner, and particularly preferably 0.01 to 2.0 wt%. Specific examples of the inorganic fine particles include, for example, silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, tin oxide, quartz sand, clay, mica, wollastonite, diatomaceous earth. Examples include soil, chromium oxide, cerium oxide, bengara, antimony trioxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silicon carbide, and silicon nitride. Among these, as the fluidity imparting agent, it is preferable to use hydrophobic silica fine particles and hydrophobic titanium oxide fine particles in combination. In particular, when stirring and mixing are performed using particles having an average particle diameter of 5 × 10 ⁻⁴ μm or less, the electrostatic force and van der Waals force with the toner are remarkably improved. Even when stirring and mixing inside the developing device is performed to obtain a good image quality that does not cause the release of the fluidity imparting agent from the toner and does not generate firefly, etc., and further reduces the residual toner. It is done. Titanium oxide fine particles are excellent in environmental stability and image density stability, but have a tendency to deteriorate the charge rise characteristics. Therefore, if the amount of titanium oxide fine particles added is larger than the amount of silica fine particles added, this side effect is affected. It can be considered large. However, when the added amount of the hydrophobic silica fine particles and the hydrophobic titanium oxide fine particles is in the range of 0.3 to 1.5 wt%, the charge rising characteristics are not greatly impaired, and the desired charge rising characteristics can be obtained, that is, repeated copying. Stable image quality can be obtained even if

  Next, a toner manufacturing method will be described. Here, although a preferable manufacturing method is shown, it is not limited to this.

(Toner production method)
(1) A toner material solution is prepared by dispersing a colorant, unmodified polyester, a polyester prepolymer having an isocyanate group, and a release agent in an organic solvent.
The organic solvent is preferably volatile with a boiling point of less than 100 ° C. from the viewpoint of easy removal after toner base particle formation. Specifically, toluene, xylene, benzene, carbon tetrachloride, methylene chloride, 1,2-dichloroethane, 1,1,2-trichloroethane, trichloroethylene, chloroform, monochlorobenzene, dichloroethylidene, methyl acetate, ethyl acetate, methyl ethyl ketone, Methyl isobutyl ketone and the like can be used alone or in combination of two or more. In particular, aromatic solvents such as toluene and xylene and halogenated hydrocarbons such as methylene chloride, 1,2-dichloroethane, chloroform, and carbon tetrachloride are preferable. The usage-amount of an organic solvent is 0-300 weight part normally with respect to 100 weight part of polyester prepolymers, Preferably it is 0-100 weight part, More preferably, it is 25-70 weight part.

(2) The toner material liquid is emulsified in an aqueous medium in the presence of a surfactant and resin fine particles.
The aqueous medium may be water alone or an organic solvent such as alcohol (methanol, isopropyl alcohol, ethylene glycol, etc.), dimethylformamide, tetrahydrofuran, cellosolves (methyl cellosolve, etc.), lower ketones (acetone, methyl ethyl ketone, etc.). It may be included.

  The amount of the aqueous medium used relative to 100 parts by weight of the toner material liquid is usually 50 to 2000 parts by weight, preferably 100 to 1000 parts by weight. If the amount is less than 50 parts by weight, the dispersion state of the toner material liquid is poor, and toner particles having a predetermined particle diameter cannot be obtained. If it exceeds 20000 parts by weight, it is not economical.

Further, in order to improve the dispersion in the aqueous medium, a dispersant such as a surfactant and resin fine particles is appropriately added.
As surfactants, anionic surfactants such as alkylbenzene sulfonates, α-olefin sulfonates, phosphate esters, alkylamine salts, amino alcohol fatty acid derivatives, polyamine fatty acid derivatives, amine salt types such as imidazoline, Quaternary ammonium salt type cationic surfactants such as alkyltrimethylammonium salts, dialkyldimethylammonium salts, alkyldimethylbenzylammonium salts, pyridinium salts, alkylisoquinolinium salts, benzethonium chloride, fatty acid amide derivatives, polyhydric alcohols Nonionic surfactants such as derivatives, for example, amphoteric surfactants such as alanine, dodecyldi (aminoethyl) glycine, di (octylaminoethyl) glycine and N-alkyl-N, N-dimethylammonium betaine And the like.

  Further, by using a surfactant having a fluoroalkyl group, the effect can be obtained in a very small amount. Preferred anionic surfactants having a fluoroalkyl group include fluoroalkyl carboxylic acids having 2 to 10 carbon atoms and metal salts thereof, disodium perfluorooctanesulfonyl glutamate, 3- [ω-fluoroalkyl (C6-C11 ) Oxy] -1-alkyl (C3-C4) sodium sulfonate, 3- [ω-fluoroalkanoyl (C6-C8) -N-ethylamino] -1-propanesulfonic acid sodium, fluoroalkyl (C11-C20) carvone Acids and metal salts, perfluoroalkylcarboxylic acids (C7 to C13) and metal salts thereof, perfluoroalkyl (C4 to C12) sulfonic acids and metal salts thereof, perfluorooctanesulfonic acid diethanolamide, N-propyl-N- ( 2-Hydroxyethyl) Perful Olooctanesulfonamide, perfluoroalkyl (C6-C10) sulfonamidopropyltrimethylammonium salt, perfluoroalkyl (C6-C10) -N-ethylsulfonylglycine salt, monoperfluoroalkyl (C6-C16) ethyl phosphate, etc. Can be mentioned.

Product names include Surflon S-111, S-112, S-113 (Asahi Glass Co., Ltd.), Florard FC-93, FC-95, FC-98, FC-129 (Sumitomo 3M Co., Ltd.), Unidyne DS-101. DS-102 (manufactured by Daikin Industries), MegaFuck F-110, F-
120, F-113, F-191, F-812, F-833 (Dainippon Ink Co., Ltd.), Xtop EF-102, 103, 104, 105, 112, 123A, 123B, 306A, 501, 201, 204 (Manufactured by Tochem Products Co., Ltd.), Footent F-100, F150 (manufactured by Neos), and the like.

  In addition, examples of the cationic surfactant include aliphatic quaternary ammonium salts such as aliphatic primary, secondary or secondary amine acids having a fluoroalkyl group, and perfluoroalkyl (C6-C10) sulfonamidopropyltrimethylammonium salts. , Benzalkonium salt, benzethonium chloride, pyridinium salt, imidazolinium salt, trade names include Surflon S-121 (manufactured by Asahi Glass), Florard FC-135 (manufactured by Sumitomo 3M), Unidyne DS-202 (Daikin Industries) Manufactured), MegaFuck F-150, F-824 (Dainippon Ink Co., Ltd.), Xtop EF-132 (Tochem Products), Footgent F-300 (Neos), and the like.

  The resin fine particles are added to stabilize the toner base particles formed in the aqueous medium. For this reason, it is preferable to add so that the coverage existing on the surface of the toner base particles is in the range of 10 to 90%. For example, polymethyl methacrylate fine particles 1 [μm] and 3 [μm], polystyrene fine particles 0.5 [μm] and 2 [μm], poly (styrene-acrylonitrile) fine particles 1 [μm], trade name is PB- 200H (manufactured by Kao Corporation), SGP (manufactured by Sokensha), technopolymer SB (manufactured by Sekisui Chemical Co., Ltd.), SGP-3G (manufactured by Sokensha), micropearl (manufactured by Sekisui Fine Chemical Co., Ltd.) and the like. In addition, inorganic compound dispersants such as tricalcium phosphate, calcium carbonate, titanium oxide, colloidal silica, and hydroxyapatite can also be used.

  As a dispersant that can be used in combination with the above resin fine particles and inorganic compound dispersant, the dispersed droplets may be stabilized by a polymer protective colloid. For example, acrylic acid, methacrylic acid, α-cyanoacrylic acid, α-cyanomethacrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid or maleic anhydride and other (meth) acrylic monomers containing hydroxyl groups Bodies such as acrylic acid-β-hydroxyethyl, methacrylic acid-β-hydroxyethyl, acrylic acid-β-hydroxypropyl, methacrylic acid-β-hydroxypropyl, acrylic acid-γ-hydroxypropyl, methacrylic acid-γ-hydroxy Propyl, acrylic acid-3-chloro-2-hydroxypropyl, methacrylic acid-3-chloro-2-hydroxypropyl, diethylene glycol monoacrylate, diethylene glycol monomethacrylate, glycerol monoacrylate, glycerol monomethacrylate Luric acid esters, N-methylol acrylamide, N-methylol methacrylamide, etc., vinyl alcohol or ethers with vinyl alcohol, such as vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether, or compounds containing vinyl alcohol and a carboxyl group Esters such as vinyl acetate, vinyl propionate, vinyl butyrate, acrylamide, methacrylamide, diacetone acrylamide or their methylol compounds, acid chlorides such as acrylic acid chloride, methacrylic acid chloride, vinyl pyridine, vinyl pyrrolidone, vinyl Nitrogen compounds such as imidazole and ethyleneimine, or homopolymers or copolymers such as those having a heterocyclic ring thereof, polyoxyethylene, poly Xoxypropylene, polyoxyethylene alkylamine, polyoxypropylene alkylamine, polyoxyethylene alkylamide, polyoxypropylene alkylamide, polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl phenyl ether, polyoxyethylene stearyl phenyl ester, polyoxy Polyoxyethylenes such as ethylene nonylphenyl ester, celluloses such as methyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose can be used.

  The dispersion method is not particularly limited, and known equipment such as a low-speed shear method, a high-speed shear method, a friction method, a high-pressure jet method, and an ultrasonic wave can be applied. Among these, in order to make the particle size of the dispersion 2 to 20 [μm], a high-speed shearing method is preferable. When a high-speed shearing disperser is used, the number of rotations is not particularly limited, but is usually 1000 to 30000 [rpm], preferably 5000 to 20000 [rpm]. The dispersion time is not particularly limited, but in the case of a batch method, it is usually 0.1 to 5 minutes. The temperature during dispersion is usually 0 to 150 ° C. (under pressure), preferably 40 to 98 ° C.

(3) At the same time as the preparation of the emulsion, the amines (B) are added to cause a reaction with the polyester prepolymer (A) having an isocyanate group.
This reaction involves molecular chain crosslinking and / or elongation. The reaction time is selected depending on the reactivity between the isocyanate group structure of the polyester prepolymer (A) and the amines (B), but is usually 10 minutes to 40 hours, preferably 2 to 24 hours. The reaction temperature is generally 0 to 150 ° C, preferably 40 to 98 ° C. Moreover, a well-known catalyst can be used as needed. Specific examples include dibutyltin laurate and dioctyltin laurate.

(4) After completion of the reaction, the organic solvent is removed from the emulsified dispersion (reactant), washed and dried to obtain toner base particles.
In order to remove the organic solvent, the temperature of the entire system is gradually raised in a laminar stirring state, and after giving strong stirring in a certain temperature range, the solvent base is removed to produce spindle-shaped toner base particles. . Further, when an acid such as calcium phosphate salt or an alkali-soluble material is used as the dispersion stabilizer, the calcium phosphate salt is dissolved from the toner base particles by a method such as dissolving the calcium phosphate salt with an acid such as hydrochloric acid and washing with water. Remove. It can also be removed by operations such as enzymatic degradation.

(5) A charge control agent is injected into the toner base particles obtained above, and then inorganic fine particles such as silica fine particles and titanium oxide fine particles are externally added to obtain a toner. The injection of the charge control agent and the external addition of the inorganic fine particles are performed by a known method using a mixer or the like.

  Thereby, a toner having a small particle size and a sharp particle size distribution can be easily obtained. Furthermore, by giving strong agitation in the process of removing the organic solvent, the shape between the true spherical shape and the rugby ball shape can be controlled, and the surface morphology is also controlled between the smooth shape and the umeboshi shape. be able to.

  The toner has a substantially spherical shape and can be represented by the following shape rule. 9A, 9B, and 9C are diagrams schematically illustrating the shape of the toner. 9A, 9B, and 9C, when a substantially spherical toner is defined by a major axis r1, a minor axis r2, and a thickness r3 (where r1 ≧ r2 ≧ r3), the toner is defined. The ratio of the major axis to the minor axis (r2 / r1) (see FIG. 9B) is 0.5 to 1.0, and the ratio of the thickness to the minor axis (r3 / r2) (FIG. 9C )) Is preferably in the range of 0.7 to 1.0. When the ratio of the major axis to the minor axis (r2 / r1) is less than 0.5, the dot reproducibility and transfer efficiency are inferior because of being away from the true spherical shape, and high-quality image quality cannot be obtained. On the other hand, if the ratio of thickness to minor axis (r3 / r2) is less than 0.7, the shape is close to a flat shape, and a high transfer rate like a spherical toner cannot be obtained. In particular, when the ratio of the thickness to the minor axis (r3 / r2) is 1.0, the rotating body has a major axis as a rotation axis, and the fluidity of the toner can be improved.

Note that r1, r2, and r3 were measured with a scanning electron microscope (SEM) while changing the angle of field of view and taking pictures.

  Further, the cleaning device of the present invention can be applied not only to the belt cleaning device 100 that cleans the front surface of the intermediate transfer belt but also to the cleaning device 500 for the paper conveying belt 51 as shown in FIG. . As shown in FIG. 10, a paper transport belt 51 as a cleaning target used in an image forming apparatus of a tandem type direct transfer system comes into contact with the photoreceptors 1Y, 1M, 1C, 1K, and Y, M, C, A primary transfer nip for K is formed. Then, in the process of conveying the recording paper P from the left side to the right side in the figure along with its endless movement while holding the recording paper P on its surface, the primary transfer nip for Y, M, C, K is used. In order. As a result, the Y, M, C, and K toner images are superimposed and primarily transferred onto the recording paper P. Contamination such as toner adhering to the paper transport belt 51 after passing through the primary transfer nip for K is removed by the transport belt cleaning device 500. The optical sensor unit 150 is disposed so as to face the front surface of the paper transport belt 51 with a predetermined gap. Also in the printer shown in FIG. 10, image density control and positional deviation amount correction control are performed at a predetermined timing, a predetermined toner pattern (gradation pattern, chevron patch) is formed on the paper transport belt 51, and the optical sensor unit 150. Then, the toner pattern is detected, and a predetermined correction process is executed based on the detection result. A toner pattern which is an untransferred toner image detected by the optical sensor unit 150 is removed by the conveyor belt cleaning device 500. Thus, the paper transport belt 51 has a function as an image carrier that carries a toner image.

  By applying the cleaning device of the present invention to the transport belt cleaning device 500, the toner pattern formed on the paper transport belt 51 can be removed satisfactorily, and the back surface of the recording paper is prevented from being stained with toner. can do.

  As described above, according to the belt cleaning apparatus 100 of the present embodiment, the cleaning voltage is applied and the cleaning brush roller as the cleaning member that electrostatically removes the toner on the intermediate transfer belt 8 as the belt member while rotating, and the recovery voltage. And a recovery roller as a recovery member for electrostatically recovering toner adhering to the cleaning brush roller from the cleaning brush roller. Then, at a predetermined timing, a predetermined current is passed between the cleaning brush roller and the intermediate transfer belt, and the voltage at that time is set as the cleaning voltage. As a result, even when the resistance of the intermediate transfer belt fluctuates, the optimum cleaning current can be maintained, and good cleaning properties can be maintained. Further, at a predetermined timing, a predetermined current is passed between the collection roller and the cleaning brush roller, and the voltage at that time is set as the collection voltage. As a result, even when the resistance of the cleaning brush roller fluctuates, the optimum recovery current can be maintained, and the toner on the cleaning brush roller can be recovered satisfactorily. Thus, it is possible to suppress the generation of toner remaining on the cleaning brush roller, and it is possible to suppress the occurrence of defective cleaning.

  In addition, the set cleaning is performed by synchronizing the timing of flowing a predetermined current between the collection roller and the cleaning brush roller with the timing of flowing a predetermined current between the cleaning roller and the intermediate transfer belt. The recovery voltage can be set in consideration of the influence of the voltage, and the cleaning voltage can be set in consideration of the influence of the set recovery voltage.

  Further, the cleaning voltage and the collected voltage are set when the apparatus is started. By performing it at the start-up of an apparatus that has a high possibility that the environment has greatly changed compared to the previous use, it is possible to satisfactorily suppress poor cleaning.

  Since the amount of toner to be removed is different in each cleaning unit, the optimum current value flowing between the cleaning brush roller and the intermediate transfer belt is different in each cleaning unit. Therefore, by having a plurality of cleaning units each equipped with a cleaning brush roller and a collection roller, and setting the cleaning voltage, the current value flowing between the cleaning brush roller and the intermediate transfer belt can be made different for each cleaning unit. The optimum cleaning voltage can be set in each cleaning unit.

  In addition, the three cleaning units are provided, and a regular charging toner cleaning is provided as a pre-cleaning unit that is the most upstream cleaning unit disposed at the most upstream side in the intermediate transfer belt surface moving direction and a most downstream cleaning unit that is disposed at the most downstream side in the belt surface moving direction. And the polarity of the cleaning voltage of the reversely charged toner cleaning unit which is a middle cleaning unit disposed between the pre-cleaning unit and the regular charging cleaning unit. As a result, it is possible to inject a charge having a polarity opposite to the cleaning voltage of the normal charging toner cleaning unit to the toner that could not be removed by the pre-cleaning unit by reverse charging toner cleaning. It is possible to satisfactorily remove toner having a polarity opposite to the cleaning voltage of the toner cleaning unit.

  In addition, the polarity of the cleaning voltage of the pre-cleaning unit and the regular charging toner cleaning unit is opposite to the normal charging polarity of the toner, so that most of the untransferred toner images with normal charging polarity are removed by the pre-cleaning unit. The untransferred toner image can be roughly removed. As a result, the amount of toner input to the cleaning unit downstream from the pre-cleaning unit is reduced, and the remaining toner can be satisfactorily removed by the downstream cleaning unit. As a result, an untransferred toner image can be cleaned well.

  Further, a cleaning voltage for cleaning the transfer residual toner and a cleaning voltage for cleaning the untransferred toner image are set. Since the amount of toner to be removed differs between the untransferred toner and the untransferred toner image, the optimum cleaning voltage for cleaning the untransferred toner and the optimum cleaning voltage for cleaning the untransferred toner image are different. come. Therefore, by setting the cleaning voltage for cleaning the untransferred toner and the cleaning voltage for cleaning the untransferred toner image, both when cleaning the untransferred toner and when cleaning the untransferred toner image. Good cleaning properties can be obtained.

  In the image forming apparatus according to the present embodiment, the above-described belt cleaning apparatus is used as the belt cleaning apparatus, so that the toner on the intermediate transfer belt 8 can be satisfactorily cleaned, thereby realizing high-quality image formation. Can do.

4Y, M, C, K: Drum cleaning device 8: Intermediate transfer belts 13, 14, 15: Cleaning facing roller 51: Paper transport belt 100: Belt cleaning device 100a: Pre-cleaning unit 100b: Reversely charged toner cleaning unit 100c: Regular Charged toner cleaning unit 101: Pre-cleaning brush roller 102: Pre-collecting roller 103: Pre-scraping blade 104: Reversely charged toner cleaning brush roller 105: Reversely charged toner collecting roller 106: Reversely charged toner scraping blade 107: Regularly charged toner cleaning Brush roller 108: Regularly charged toner collecting roller 109: Regularly charged toner scraping blade 500: Conveyor belt cleaning device

JP 2005-316268 A

Claims (9)

A cleaning member that is applied with a cleaning voltage and electrostatically removes toner on the belt member while rotating;
In a cleaning apparatus comprising a recovery member to which a recovery voltage is applied and electrostatically recovers toner adhering to the cleaning member from the cleaning member.
The cleaning voltage is controlled so that an optimal cleaning current flows between the cleaning member and the belt member, and the recovery voltage is set so that an optimal recovery current flows between the cleaning member and the recovery member. A cleaning device comprising control means for controlling. The cleaning device according to claim 1.
Cleaning voltage setting means for causing a predetermined current to flow between the cleaning member and the belt member at a predetermined timing, detecting the voltage at that time with the voltage detection means, and setting the detected voltage as the cleaning voltage. When,
A recovery voltage setting in which a predetermined current is passed between the recovery member and the cleaning member at a predetermined timing, the voltage at that time is detected by the voltage detection means, and the detected recovery voltage is set as the recovery voltage. Means and
When the toner on the belt member is cleaned, the control means applies the cleaning voltage set by the cleaning voltage setting means to the cleaning member, and applies the recovery voltage set by the recovery voltage setting means to the recovery member. A cleaning device. The cleaning device according to claim 2.
The cleaning is characterized in that the timing at which a predetermined current flows between the recovery member and the cleaning member is synchronized with the timing at which a predetermined current flows between the cleaning member and the belt member. apparatus. The cleaning device according to claim 2 or 3,
The cleaning apparatus, wherein the cleaning voltage and the recovery voltage are set when the apparatus is started. The cleaning device according to any one of claims 2 to 4,
It has a plurality of cleaning parts including the cleaning member and the recovery member,
A cleaning device characterized in that when a cleaning voltage is set, a current value passed between the cleaning member and the belt member is made different in each cleaning unit. The cleaning device according to claim 5.
Three cleaning units are provided,
The polarity of the cleaning voltage of the most upstream cleaning unit disposed at the most upstream in the belt member surface moving direction and the most downstream cleaning unit disposed at the most downstream in the belt member surface moving direction, and the most upstream cleaning unit and the most downstream cleaning unit The cleaning device is characterized in that the polarity of the cleaning voltage of the middle-stage cleaning unit disposed between is different. The cleaning device according to claim 6.
A cleaning device, wherein the polarity of the cleaning voltage of the most upstream cleaning unit and the most downstream cleaning unit is opposite to the normal charging polarity of the toner. The cleaning device according to any one of claims 2 to 7,
The cleaning device, wherein the cleaning voltage setting means sets a cleaning voltage for cleaning the untransferred toner and a cleaning voltage for cleaning the untransferred toner image. For the endless movement of the belt member, the toner image carried on the front surface of the endless belt member or the toner image carried on the recording member held on the front surface of the belt member is used. A belt device to be conveyed along with,
Toner image forming means for forming a toner image on the front surface of the belt member or on the recording member;
An image forming apparatus comprising a cleaning unit that cleans the toner on the belt member.
An image forming apparatus using the cleaning device according to claim 1 as the cleaning unit.

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