JP2009008996A - Fixing device, image processor with the same, program, and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device capable of obtaining a satisfactory image free from image soil or the like, and also maintaining the life performance of a web, and to provide an electrophotographic image processor using the fixing device. <P>SOLUTION: The fixing device having a pair of rotatable fixing members has a cleaning member that cleans a fixing member. The cleaning member has a predetermined cleaning nip formed by a plurality of press members pressing the fixing member. The soiled state of the cleaning member, such as a web, is detected by a soil detecting section with high accuracy. On the basis of the result of the detection, the moving speed of the cleaning member is controlled. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fixing device and an image processing apparatus including the same.

  2. Description of the Related Art In recent years, electrophotographic image processing apparatuses have been widely used for copying machines, printers, facsimiles, multifunction machines, and the like. The electrophotographic image processing apparatus includes, for example, a photoconductor, a charging unit, an exposure unit, a developing unit, a transfer unit, and a fixing unit.

  The photosensitive member is a latent image forming member that forms an electrostatic latent image on the surface according to image information. The charging unit charges the surface of the photoreceptor. The exposure unit irradiates the charged photosensitive member surface with signal light to form an electrostatic latent image. The developing unit supplies toner to the electrostatic latent image on the surface of the photoreceptor to form a toner image. The transfer unit transfers the toner image on the surface of the photoreceptor to a recording medium. The fixing unit fixes the toner image on the recording medium to the recording medium to form an image.

  Here, as the fixing unit, a fixing device including a fixing roller and a pressure roller is generally used. The fixing roller is a roller member that has a heating means inside thereof and heats and melts the toner constituting the unfixed toner image on the recording medium to fix it on the recording medium. The pressure roller is provided so as to be in pressure contact with the fixing roller, and promotes fixing of the toner to the recording medium by pressing the toner against the recording medium when the toner is heated and melted by the fixing roller. The pressure contact portion between the fixing roller and the pressure roller is called a fixing nip portion. A recording medium carrying an unfixed toner image is introduced into the fixing nip so that the toner image carrying surface of the recording medium is in contact with the surface of the fixing roller, and the unfixed toner image is fixed to the recording medium by heating and pressing. .

  However, depending on fixing conditions such as temperature and pressure, environmental conditions such as temperature and humidity, or the type of recording medium, unfixed toner may adhere to the surface of the fixing roller during the fixing operation, and the surface of the fixing roller may be soiled. May end up.

  The toner once adhered to the fixing roller in this manner is fixed to the recording medium when the next recording medium passes through the fixing nip, and as a result, is recognized as image contamination. As described above, various measures have been taken in the past in order to prevent the occurrence of image smearing due to the toner adhering to the surface of the fixing roller.

  In conventional fixing devices, the toner adhering to the surface of the fixing roller is removed by bringing a cleaning web impregnated with oil for preventing toner adhesion (hereinafter simply referred to as “web” unless otherwise specified) into contact with the surface of the fixing roller. In addition, a toner adhesion preventing oil is applied to the surface of the fixing roller.

  As a specific example of using the web, for example, the fixing device 100 shown in FIG. FIG. 7 is a cross-sectional view schematically showing a configuration of the fixing device 100 using a web. The fixing device 100 includes a fixing roller 101, a pressure roller 102, and a cleaning device 103. The fixing roller 101 has heating means 101 a and 101 b inside, and is provided so as to be rotatable in the direction of an arrow 106. The pressure roller 102 is provided so as to be in pressure contact with the fixing roller 101 and to be rotatable in the direction of an arrow 107. A pressure-contact portion between the fixing roller 101 and the pressure roller 102 is a fixing nip portion 108.

  The recording medium 104 carrying the toner image 105 is introduced into the fixing nip portion 108 so that the toner image 105 contacts the surface of the fixing roller 101. The toner image 105 is heated and pressurized at the fixing nip portion 108 and fixed on the recording medium 104.

  The cleaning device 103 includes a web 109, a delivery roller 110, a winding roller 111, and a pressure roller 112. The web 109 is impregnated with oil. The feed roller 110 is rotatably provided and feeds the web 109 in the direction of the arrow 113. The take-up roller 111 is driven to rotate by a driving means (not shown) and is sent out in the direction of the arrow 113 from the feed roller 110 and then takes up the web 109 after coming into contact with the fixing roller 101. The pressure roller 112 is rotatably provided so as to be in pressure contact with the surface of the fixing roller 101 via the web 109.

  Accordingly, the web 109 is sandwiched between the fixing roller 101 and the pressure roller 112. Further, a pressure contact portion between the fixing roller 101 and the web 109 is a cleaning nip portion 114. The web 109 is fed from the feed roller 110 in the direction of the arrow 113, passes through the cleaning nip portion 114 and is taken up by the take-up roller 111, and the fixing roller 101 is passed when the web 109 passes through the cleaning nip portion 114. The toner adhering to the surface is removed and oil is applied to the surface of the fixing roller 101. The cleaning effect of the surface of the fixing roller 101 by the cleaning device 103 in the fixing device 100 is good.

  By the way, in recent years, the electrophotographic image processing apparatus has been increasingly reduced in size in particular, and the demand for higher speed has also increased. In order to sufficiently fix the toner on the recording medium, it is necessary to heat and press the toner and the recording medium for a predetermined time at a predetermined fixing temperature. For example, the downsizing of the apparatus generally reduces the diameter of the fixing roller. Therefore, the fixing nip width is reduced, and the heating time is shortened.

  Furthermore, since the small-diameter roller is weak against bending at the time of loading, the pressure at the fixing nip portion is also reduced. Thus, the downsizing of the apparatus may deteriorate the fixability.

  On the other hand, speeding up shortens the time during which the recording medium can be heated at the fixing nip. Therefore, it is generally necessary to maintain the fixing roller temperature at a higher temperature and within a predetermined temperature range. When the follow-up performance is lowered, the fixability is remarkably deteriorated, a large amount of toner is offset on the fixing roller, and the web is extremely stained. When the web is extremely dirty, not only the toner collecting performance of the web is remarkably lowered, but also the toner may be ejected from the web to the fixing roller as the stain progresses further. In order to prevent such performance degradation of the web, the web is impregnated with a larger amount of oil than the minimum required amount.

  However, there is a phenomenon that the oil impregnated in the web gradually moves toward the delivery roller side and accumulates due to capillary action. As a result, when the web is impregnated with a large amount of oil, as the web approaches the end of winding, the oil exceeds the amount of the web and oil leaks from the web, and oil streaks appear in the image There is a problem.

  Therefore, in order to perform sufficient cleaning and prevent oil streaks, the amount of oil impregnated into the web 109 is reduced, the feed amount is increased, and the thickness of the web 109 is reduced in order to prevent oil leakage from the web 109. There is also a way to increase it.

    However, these countermeasures increase the number of windings of the web 109 and increase the diameters of the feed roller 110 and the take-up roller 111, and the size of the apparatus cannot be avoided.

Therefore, as a technique for maintaining the cleaning performance and life performance without excessively increasing the amount of oil or the like, for example, in Patent Document 1, as shown in FIG. And the amount of web movement is controlled based on the detection result.
JP-A-10-97153

  By the way, in Patent Document 1, when it is determined by the web dirt detection unit 200 that there is a lot of dirt, the purpose is to prevent the cleaning performance from being deteriorated by increasing the moving amount of the web. Since the web is detected and judged after passing through the nip 114, the timing for controlling the web movement is more time-consuming than when the web is actually performing the cleaning operation at the cleaning nip. As a result, there is a problem that image contamination such as toner ejection cannot be completely prevented.

  Furthermore, in the configuration of Patent Document 1, since the optical sensor 200 is arranged in an oblique direction with respect to the web, the detection accuracy may be inferior.

  In view of the above problems, the present invention detects a dirty state of a cleaning member such as a web with higher accuracy, and controls a moving speed or the like based on the detection result, thereby obtaining a good image free from image contamination. At the same time, it is an object of the present invention to provide a fixing device capable of maintaining the life performance of the web and an electrophotographic image processing apparatus using the same.

  In order to achieve the above object, according to the present invention, a fixing device having a pair of rotatable fixing members includes a cleaning member for cleaning the fixing member, and the cleaning member is attached to the fixing member by a plurality of pressing members. Cleaning control that has a predetermined cleaning nip formed by pressing, and that is provided with a dirt detection unit that detects dirt on the cleaning member in the cleaning nip, and controls movement of the cleaning member based on a detection result by the dirt detection unit A part is provided.

  According to the above configuration, the dirt of the cleaning member in the region surrounded by the cleaning nip formed by the plurality of pressing members is detected by the dirt detector. The region surrounded by the cleaning nip is a region surrounded by the nip portion on the upstream side in the rotation direction and the nip portion on the downstream side when viewed from the fixing member. In a broad sense, the state of contamination of the cleaning member in the cleaning nip portion is detected.

  Then, it is determined whether the cleaning member is dirty in the cleaning nip. Based on the detection result, the cleaning member is remarkably dirty, and it is difficult to collect new toner. It is possible to predict a situation in which toner is ejected from the cleaning member to the fixing member.

  When the cleaning control unit determines that the contamination is detected based on the detection result of the contamination detection unit, it is possible to maintain the cleaning performance by instantaneously increasing the moving amount (winding amount) of the cleaning member. As a result, it is possible to prevent deterioration in image quality caused by the cleaning nip portion being extremely dirty and the toner ejecting to the fixing member, or the toner slipping through the cleaning member.

  In this case, the dirt detection unit can be an optical sensor. The optical sensor can reliably detect the contamination of the cleaning member, and it is possible to suppress deterioration in image quality due to the contamination of the cleaning member. Further, the optical sensor can be disposed substantially at right angles to the web constituting the cleaning member, and the detection accuracy is improved.

  Further, a plurality of dirt detection units can be provided in a direction perpendicular to the recording paper conveyance direction. According to this configuration, it is possible to dispose a plurality of dirt detection units in a direction perpendicular to the recording paper conveyance direction, and to control the movement of the cleaning member based on the detection results. It is possible to suppress the image quality degradation caused by it.

  In addition, the cleaning control unit can control the moving speed of the cleaning member based on the detection result of the dirt detection unit. According to this configuration, only when it is determined that the cleaning member is markedly contaminated, by increasing the moving speed of the cleaning member, it is possible to achieve both suppression of image degradation caused by the cleaning member contamination and an increase in the life of the cleaning member. It becomes possible.

  The cleaning control unit can forcibly wind up the cleaning member based on the detection result of the dirt detection unit. According to this configuration, only when it is determined that the cleaning member is markedly contaminated, the cleaning member is forcibly taken up to achieve both suppression of image deterioration caused by the cleaning member contamination and extension of the cleaning member life. It becomes possible.

  In addition, the present invention can provide a program for operating the fixing device as described above, and causing the computer to function as a cleaning control unit.

  Furthermore, the present invention can also provide a computer-readable recording medium on which the program is recorded.

  As described above, according to the present invention, a dirty image of a cleaning member such as a web is detected with higher accuracy, and a moving image or the like is controlled based on the detection result, thereby obtaining a good image free from image contamination. At the same time, the life performance of the cleaning member can be maintained.

  FIG. 1 is a cross-sectional view showing a schematic configuration of an image processing apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view showing a configuration of a main part (toner image forming unit) of the image processing apparatus shown in FIG. FIG. 3 is a cross-sectional view showing a schematic configuration of the fixing device according to the embodiment of the present invention.

  The image processing apparatus 1 is an electrophotographic image processing apparatus having a tandem configuration in which toner images of four colors of yellow, magenta, cyan, and black are sequentially superimposed and transferred. The image processing apparatus 1 includes a toner image forming unit 2, an intermediate transfer unit 3, a secondary transfer unit 4, a recording medium supply unit 5, a fixing device 6, and a scanner unit 7.

  The toner image forming unit 2 includes image forming units 10y, 10m, 10c, and 10b. The image forming units 10y, 10m, 10c, and 10b are arranged in a line in this order from the upstream side in the rotational driving direction (sub-scanning direction) of the intermediate transfer belt 21, which will be described later, that is, in the direction of the arrow 27, and input as digital signals or the like. An electrostatic latent image corresponding to the image information of each color is formed, toner of a color corresponding to the electrostatic latent image is supplied, and developed to form a toner image of each color.

  That is, the image forming unit 10y forms a toner image corresponding to yellow image information, the image forming unit 10m forms a toner image corresponding to magenta image information, and the image forming unit 10c includes cyan image information. The image forming unit 10b forms a toner image corresponding to black image information.

  The image forming unit 10y includes a photosensitive drum 11y, a charging roller 12y, an optical scanning unit 13, a developing device 14y, and a drum cleaner 15y.

  The photosensitive drum 11y is a roller-like member having a photosensitive layer on which an electrostatic latent image and thus a toner image is formed. Examples of the photosensitive drum 11y include those including a conductive substrate (not shown) and a photosensitive layer (not shown) formed on the surface of the conductive substrate.

  As the conductive substrate, a conductive substrate having a cylindrical shape, a columnar shape, a sheet shape or the like can be used, and among them, the cylindrical conductive substrate is preferable.

  Examples of the photosensitive layer include an organic photosensitive layer and an inorganic photosensitive layer. The organic photosensitive layer includes a laminate of a charge generation layer which is a resin layer containing a charge generation material and a charge transport layer which is a resin layer containing a charge transport material, and the charge generation material and the charge transport material in one resin layer And a resin layer containing. Examples of the inorganic photosensitive layer include a layer containing one or more selected from zinc oxide, selenium, amorphous silicon and the like. A base layer may be interposed between the conductive substrate and the photosensitive layer, and a surface layer (protective layer) for mainly protecting the photosensitive layer may be provided on the surface of the photosensitive layer.

  In the present embodiment, a photosensitive drum having a diameter of 30 mm including an aluminum base tube (conductive base) connected to the ground potential (GND) and an organic photosensitive layer having a thickness of 20 μm formed on the surface of the aluminum base tube. Is used. In the present embodiment, the photosensitive drum 11y is rotationally driven at a peripheral speed of 225 mm / s in the clockwise direction.

  The charging roller 12y is a roller-like member that is rotatably supported around an axis by a driving unit (not shown) and charges the surface of the photosensitive drum 11y to a predetermined polarity and potential. A power source (not shown) is connected to the charging roller 12y, and the surface of the photosensitive drum 11y is charged by discharging a voltage applied from the power source.

  In the present embodiment, a voltage of −1200 V is applied to the charging roller 12y, and the surface of the photosensitive drum 11y is charged to −600V. Instead of the charging roller 12y, a brush type charger, a charger type charger, a corona charger such as a scorotron, or the like can be used.

  The optical scanning unit 13 irradiates the charged surface of the photosensitive drum 11y with laser light 13y corresponding to yellow image information, and forms an electrostatic latent image corresponding to yellow image information on the surface of the photosensitive drum 11y. . A semiconductor laser or the like can be used for the optical scanning unit 13. In the present embodiment, an electrostatic latent image having an exposure potential of −70 V is formed on the surface of the photosensitive drum 11 y charged to −600 V.

  The developing device 14y includes a developing roller 17y, a developing blade 18y, a developing tank 19y, and stirring rollers 20y and 30y. The developing roller 17y carries the yellow toner 16y on its surface, and supplies the yellow toner 16y to the electrostatic latent image on the surface of the photosensitive drum 11y at a proximity portion (developing nip portion) between the developing roller 17y and the photosensitive drum 11y. To do. The developing roller 17y is supported by the developing tank 19y. A part of the developing roller 17y projects outward from an opening formed on the surface of the developing tank 19y facing the photosensitive drum 11y, and is close to the surface of the photosensitive drum 11y. It is a roller-shaped member that includes a fixed magnetic pole (not shown) and is rotatably driven around an axis. The developing roller 17y is driven to rotate in the direction opposite to that of the photosensitive drum 11y. Accordingly, in the developing nip portion, the developing roller 17y and the photosensitive drum 11y are rotationally driven in the same direction. In the present embodiment, the developing roller 17y rotates at a peripheral speed of 338 mm / s, which is 1.5 times the peripheral speed of the photosensitive drum 11y.

  Further, a power source (not shown) is connected to the developing roller 17y, and a DC voltage (developing voltage) is applied from the power source. As a result, the yellow toner 16y on the surface of the developing roller 17y is smoothly supplied to the electrostatic latent image. In the present embodiment, a developing voltage of −420 V is applied to the developing roller 17y. The yellow toner layer on the surface of the developing roller 17y comes into contact with the photosensitive drum 11y in the developing nip portion, and the yellow toner 16y is supplied to the electrostatic latent image.

  The developing blade 18y is a plate-like member having one end supported by the developing tank 19y and the other end provided to have a gap with the surface of the developing roller 17y, and uniformizes the yellow toner layer carried on the surface of the developing roller 17y ( Layer regulation).

  The developing tank 19y is a container-like member having an internal space with an opening formed on the surface facing the photosensitive drum 11y as described above. The developing tank 19y contains a developing roller 17y and stirring rollers 20y and 30y in its internal space, and stores yellow toner 16y. The developing tank 19y is replenished with yellow toner 16y from a toner cartridge (not shown) according to the consumption state of the yellow toner 16y. In the present embodiment, the developing tank 19y is filled with a magnetic carrier in advance. The yellow toner 16y supplied to the developing tank 19y is mixed with the magnetic carrier and used in the form of a yellow two-component developer, but is not limited thereto, and is also used in the form of a one-component developer containing only the yellow toner 16y. it can.

  The stirring rollers 20y and 30y are screw-like members that are supported so as to be rotatable around an axis in the internal space of the developing tank 19y. The stirring roller 20y is provided so as to be in pressure contact with the surface of the developing roller 17y. The agitating rollers 20y and 30y feed yellow toner 16y supplied from a toner cartridge (not shown) into the developing tank 19y to the periphery of the surface of the developing roller 17y by their rotational driving. According to the developing device 14y, the developer in a form in which the yellow toner 16y adheres to the magnetic carrier in the developing tank 19y is supplied to the surface of the developing roller 17y by the stirring rollers 20y and 30y, and a developer layer is formed on the surface. . The developer layer is made uniform by the developing blade 18y, and then yellow toner 16y is selectively supplied from the developer layer to the electrostatic latent image on the surface of the photosensitive drum 11y by using a potential difference or the like. A yellow toner image corresponding to the image information is formed.

  As described later, the drum cleaner 15y removes and collects the yellow toner 16y remaining on the surface of the photosensitive drum 11y after the yellow toner image on the surface of the photosensitive drum 11y is transferred to the intermediate transfer belt 21.

  According to the image forming unit 10y, the surface of the photosensitive drum 11y charged by the charging roller 12y is irradiated with signal light 13y corresponding to yellow image information from the optical scanning unit 13 to form an electrostatic latent image. Then, yellow toner 16y is supplied from the developing device 14y to the electrostatic latent image to develop the electrostatic latent image, thereby forming a yellow toner image. As will be described later, the yellow toner image is transferred to the intermediate transfer belt 21 that is pressed against the surface of the photosensitive drum 11y and is rotationally driven in the direction of an arrow 27.

  The yellow toner 16y remaining on the surface of the photosensitive drum 11y is removed and collected by the drum cleaner 15y. This image (toner image) forming operation is repeatedly executed. Since the image forming units 10m, 10c, and 10b have a structure corresponding to the image forming unit 10y except that magenta toner 16m, cyan toner 16c, or black toner 16b is used instead of the yellow toner 16y, the same reference numerals are used. In addition, “m” indicating magenta, “c” indicating cyan, and “b” indicating black are added to the end of each reference symbol, and description thereof is omitted.

  The toners 16y, 16m, 16c, and 16b (hereinafter collectively referred to as “toner 16” unless otherwise specified) contain a binder resin, a colorant, and a release agent. As the binder resin, those commonly used in this field can be used. For example, polystyrene, styrene-substituted homopolymer, styrene copolymer, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane Etc. Binder resin can be used individually by 1 type, or can use 2 or more types together. Among these binder resins, for color toners, a binder resin having a softening point of 100 to 150 ° C. and a glass transition point of 50 to 80 ° C. is preferable from the viewpoint of storage stability and durability. Polyester having a glass transition point is particularly preferred. Polyester exhibits high transparency in a softened or molten state. When the binder resin is polyester, when a multicolor toner image in which toner images of yellow, magenta, cyan and black are superimposed on each other is fixed on the recording medium 8, the polyester itself becomes transparent. Is obtained.

  As the colorant, pigments and dyes for toners conventionally used for electrophotographic image formation can be used. Examples of the pigment include azo pigments, benzimidazolone pigments, quinacridone pigments, phthalocyanine pigments, isoindolinone pigments, isoindoline pigments, dioxazine pigments, anthraquinone pigments, perylene pigments, and perinone pigments. , Organic pigments such as thioindigo pigments, quinophthalone pigments, metal complex pigments, inorganic pigments such as carbon black, titanium oxide, molybdenum red, chrome yellow, titanium yellow, chromium oxide, Berlin blue, metals such as aluminum powder Examples include powder. A pigment can be used individually by 1 type, or can use 2 or more types together.

  As the release agent, for example, wax can be used. As the wax, those commonly used in this field can be used, and examples thereof include polyethylene wax, polypropylene wax, and paraffin wax.

  In addition to the binder resin, the colorant, and the release agent, the toner 16 contains one or more general toner additives such as a charge control agent, a fluidity improver, a fixing accelerator, and a conductive agent. Can be contained. The toner 16 includes a pulverization method in which a colorant, a release agent, and the like are melt-kneaded and pulverized with a binder resin, a colorant, a release agent, a binder resin monomer, and the like are uniformly dispersed, and then a binder resin monomer. It can be produced according to a known method such as a suspension polymerization method for polymerizing a polymer, a binder resin particle, a colorant, a release agent and the like with an aggregating agent and heating the resulting fine particles of the aggregate. The volume average particle diameter of the toner 16 is not particularly limited, but is preferably 2 to 7 μm. When the volume average particle size of the toner 16 is less than 2 μm, the fluidity of the toner 16 is lowered, and during the developing operation, the supply, stirring and charging of the toner 16 become insufficient, the toner amount is insufficient, An increase or the like may occur, and a high-quality image may not be obtained. On the other hand, when the volume average particle diameter exceeds 7 μm, the toner particles having a large particle diameter that is difficult to be softened to the central portion increase, so that the fixability of the image to the recording medium 8 is lowered and the color of the image is deteriorated. In particular, in the case of fixing to OHP, the image becomes dark.

In the present embodiment, the toner 16 has the same configuration shown below except for the pigment. The toner 16 is a negatively chargeable insulating nonmagnetic toner having a glass transition point of 60 ° C., a softening point of 120 ° C., and a volume average particle size of 6 μm. A toner amount of 5 g / m ² is required to obtain an image density with a reflection density measurement value of 1.4 by X-Rite 310 using this toner. The toner 16 includes a polyester (binder resin) having a glass transition point of 60 ° C. and a softening point of 120 ° C., a low molecular weight polyethylene wax (release agent) having a glass transition point of 50 ° C. and a softening point of 70 ° C., and pigments of various colors. The content is 7% by weight of the total amount of the toner, the pigment content is 12% by weight of the total amount of the toner, and the balance is the binder resin polyester. The low molecular weight polyethylene wax contained in the toner 16 is a wax having a glass transition point and a softening point lower than that of the polyester of the binder resin.

  The intermediate transfer unit 3 includes an intermediate transfer belt 21, intermediate transfer rollers 22y, 22m, 22c, and 22b, support rollers 23, 24, and 25, and a belt cleaner 26. The intermediate transfer belt 21 is an endless belt-shaped toner image carrier that is stretched between support rollers 23, 24, and 25 to form a loop-shaped movement path. The intermediate transfer belt 21 includes photosensitive drums 11y, 11m, 11c, and 11b. It rotates in the direction of the arrow 27 at substantially the same peripheral speed. For the intermediate transfer belt 21, for example, a polyimide film having a thickness of 100 μm can be used. The material of the intermediate transfer belt 21 is not limited to polyimide, and films made of synthetic resins such as polycarbonate, polyamide, polyester, and polypropylene, and various rubbers can be used. In the film made of synthetic resin or various rubbers, a conductive material such as furnace black, thermal black, channel black, and graphite carbon is blended in order to adjust the electric resistance value as the intermediate transfer belt 21. The toner image carrying surface 21a of the intermediate transfer belt 21 is pressed against the photosensitive drums 11y, 11m, 11c, and 11b in this order from the upstream side in the rotational driving direction of the intermediate transfer belt 21. The positions where the intermediate transfer belt 21 is in pressure contact with the photosensitive drums 11y, 11m, 11c, and 11b are the intermediate transfer positions of the respective color toner images. Intermediate transfer rollers 22y, 22m, 22c, and 22b are disposed at positions facing the photosensitive drums 11y, 11m, 11c, and 11b with the intermediate transfer belt 21 interposed therebetween.

  The intermediate transfer rollers 22y, 22m, 22c, and 22b are opposed to the photosensitive drums 11y, 11m, 11c, and 11b through the intermediate transfer belt 21, and are opposite to the toner image carrying surface 21a of the intermediate transfer belt 21, respectively. It is a roller-like member provided in pressure contact and capable of being driven to rotate about its axis by driving means (not shown).

  For the intermediate transfer rollers 22y, 22m, 22c, and 22b, for example, a roller-shaped member including a metal shaft body and a conductive layer coated on the surface of the metal shaft body is used. The shaft body is formed of a metal such as stainless steel, for example. The diameter of the shaft body is not particularly limited, but is preferably 8 to 10 mm. The conductive layer is formed of a conductive elastic body or the like. As the conductive elastic body, those commonly used in this field can be used, and examples thereof include EPDM, foamed EPDM, foamed urethane and the like containing a conductive agent such as carbon black.

  A high voltage is uniformly applied to the intermediate transfer belt 21 by the conductive layer. The intermediate transfer rollers 22y, 22m, 22c, and 22b are opposite to the charging polarity of the toner in order to transfer the toner images formed on the surfaces of the photosensitive drums 11y, 11m, 11c, and 11b onto the intermediate transfer belt 21. A polar intermediate transfer bias is applied by constant voltage control. As a result, yellow, magenta, cyan, and black toner images formed on the photoconductive drums 11y, 11m, 11c, and 11b are sequentially superimposed and transferred onto the toner image carrying surface 21a of the intermediate transfer belt 21, thereby transferring a multicolor toner image. Is formed. However, when image information of only a part of yellow, magenta, cyan, and black is input, the image forming unit corresponding to the color of the input image information among the image forming units 10y, 10m, 10c, and 10b. Only a toner image is formed.

  The support rollers 23, 24, and 25 are rotatably provided around an axis by a drive unit (not shown), and the intermediate transfer belt 21 is stretched and rotated in the direction of an arrow 27. For the support rollers 23, 24, 25, for example, an aluminum cylindrical body (pipe-shaped roller) having a diameter of 30 mm and a wall thickness of 1 mm is used. The support roller 24 is pressed against a later-described secondary transfer roller 28 via the intermediate transfer belt 21 to form a secondary transfer nip portion, and is electrically grounded. The support roller 24 has a function of stretching the intermediate transfer belt 21 and a function of secondarily transferring the toner image on the intermediate transfer belt 21 to the recording medium 8.

  The belt cleaner 26 remains on the toner image carrying surface 21a after the toner image on the toner image carrying surface 21a (not shown) of the intermediate transfer belt 21 is transferred to the recording medium 8 in the secondary transfer fixing unit 4 described later. A member that removes toner, and is provided to face the support roller 25 with the intermediate transfer belt 21 interposed therebetween. The belt cleaner 26 includes a cleaning blade 26a and a toner storage container 26b. The cleaning blade 26a is a plate-like member that is pressed against the toner image carrying surface 21a of the intermediate transfer belt 21 by a pressing unit (not shown) and scrapes off residual toner on the toner image carrying surface 21a. For example, a blade made of a rubber material having elasticity (for example, urethane rubber) can be used as the cleaning blade 26a. The toner storage container 26b temporarily stores toner scraped off by the cleaning blade 26a.

  According to the intermediate transfer unit 3, the toner images formed on the photosensitive drums 11 y, 11 m, 11 c, and 11 b are superimposed and transferred onto a predetermined position of the toner image carrying surface 21 a of the intermediate transfer belt 21, and the toner image is transferred. It is formed. As will be described later, this toner image is secondarily transferred to the recording medium 8 at the secondary transfer nip portion. The toner, offset toner, paper dust, and the like remaining on the toner image carrying surface 21a of the intermediate transfer belt 21 after the secondary transfer are removed by the belt cleaner 26, and the toner image is transferred again to the toner image carrying surface 21a.

  The secondary transfer unit 4 includes a support roller 24 and a secondary transfer roller 28. The secondary transfer roller 28 is a roller-like member that is in pressure contact with the support roller 24 via the intermediate transfer belt 21 and is rotatably driven in the axial direction. The secondary transfer roller 28 includes, for example, a metal shaft body and a conductive layer coated on the surface of the metal shaft body. The metal shaft body is formed of a metal such as stainless steel, for example. The conductive layer is formed of a conductive elastic body or the like. As the conductive elastic body, those commonly used in this field can be used, and examples thereof include EPDM, foamed EPDM, foamed urethane and the like containing a conductive agent such as carbon black. A power supply (not shown) is connected to the secondary transfer roller 28, and a high voltage having a polarity opposite to the charging polarity of the toner 16 is uniformly applied. A pressure contact portion between the support roller 24, the intermediate transfer belt 21, and the secondary transfer roller 28 is a secondary transfer nip portion.

  According to the secondary transfer unit 4, the toner image on the intermediate transfer belt 21 is conveyed to the secondary transfer nip portion, and the recording medium 8 fed from a recording medium supply unit 5 (described later) is secondary-transferred in synchronization therewith. The toner image and the recording medium 8 are superposed at the secondary transfer nip portion, and the toner image is secondarily transferred to the recording medium 8. In this way, an unfixed toner image is carried on the recording medium 8. The recording medium 8 carrying the unfixed toner image is conveyed to the fixing device 6.

  The recording medium supply unit 5 includes a recording medium cassette 42, a pickup roller 43, and registration rollers 44a and 44b. The recording medium cassette 42 stores the recording medium 8. Examples of the recording medium 8 include plain paper, coated paper, color copy dedicated paper, OHP (overhead projector) film, and postcards. The size includes A4, A3, B5, B4, postcard size, and the like. The pickup roller 43 feeds the recording medium 8 to the transport path P one by one. The registration rollers 44a and 44b are a pair of roller-like members provided so as to be in pressure contact with each other, and are synchronized with the transfer of the multicolor toner image on the intermediate transfer belt 21 to the secondary transfer nip portion. The recording medium 8 is fed to the nip portion.

  According to the recording medium supply unit 5, the recording medium 8 stored in the recording medium cassette 42 is fed to the conveyance path P one by one by the pickup roller 43, and further, the secondary transfer nip by the registration rollers 44a and 44b. Sent to the department.

  A fixing device 6 shown in FIG. 3 includes a fixing roller 50, a pressure roller 60, and a cleaning device 70. The fixing roller 50 is a roller-like member that is rotatably supported by a support unit (not shown) and rotates at a predetermined speed in the direction of an arrow 56 by a drive unit (not shown). The fixing roller 50 heats and melts the toner 16 constituting the toner image carried on the recording medium 8 and fixes the toner 16 on the recording medium 8.

  In the present embodiment, a roller-like member including a cored bar 51, an elastic body layer 52, and a surface layer 53 is used as the fixing roller 50. As the metal forming the cored bar 51, a metal having high thermal conductivity can be used, and examples thereof include aluminum and iron. Examples of the shape of the core metal 51 include a cylindrical shape and a columnar shape, but a cylindrical shape with a small amount of heat released from the core metal 51 is preferable. The material constituting the elastic layer 52 is not particularly limited as long as it has rubber elasticity, but is preferably superior in heat resistance. Specific examples of such materials include silicone rubber, fluororubber, fluorosilicone rubber, and the like. Among these, silicone rubber having particularly excellent rubber elasticity is preferable. The material constituting the surface layer 53 is not particularly limited as long as it is excellent in heat resistance and durability and has weak adhesion to the toner 16. For example, PFA (tetrafluoroethylene and perfluoroalkyl vinyl ether copolymer) ), Fluororesin materials such as PTFE (polytetrafluoroethylene), fluororubber, and the like. In the present embodiment, the surface layer 53 is a PFA layer having a thickness of about 30 μm.

  Two heating units 54 are provided inside the fixing roller 50. This is because the start-up time from when the image processing apparatus 1 is turned on until the image can be formed is shortened, and the surface temperature of the fixing roller 50 is lowered due to the transfer of heat to the recording medium 8 when fixing the toner image. This is to prevent it. In the present embodiment, a halogen lamp is used for the heating unit 54.

  The pressure roller 60 is a roller-like member that is rotatably provided in a state of being pressed against the fixing roller 50 by a pressure mechanism (not shown) on the downstream side in the rotation direction of the fixing roller 50 with respect to the lowest vertical point of the fixing roller 50. It is. A pressure-contact portion between the fixing roller 50 and the pressure roller 60 is a fixing nip portion 55. The pressure roller 60 is rotated by the rotation of the fixing roller 50. The pressure roller 60 fixes the toner image on the recording medium 8 by pressing the toner 16 in a molten state against the recording medium 8 when the fixing roller 50 heat-fixes the toner image on the recording medium 8. Facilitate.

  In the present embodiment, a roller-like member having a diameter of 50 mm including a cored bar 61, an elastic body layer 62, and a surface layer 63 is used as the pressure roller 60. As a material for forming the cored bar 61, the elastic body layer 62, and the surface layer 63, the same metal or material as that for forming the cored bar 51, the elastic body layer 52, and the surface layer 53 of the fixing roller 50 can be used. Further, the shape of the cored bar 61 is the same as that of the fixing roller 50. A heating unit 64 is provided inside the pressure roller 60. This is because the start-up time from when the image processing apparatus 1 is turned on until the image can be formed is shortened, and the surface temperature of the pressure roller 60 is abrupt due to the transfer of heat to the recording medium 8 when fixing the toner image. This is to prevent a decrease or the like. In the present embodiment, a halogen lamp is used for the heating unit 64.

  The fixing device including the fixing roller 50 and the pressure roller 60 is controlled by a control unit (CPU (Central Processing Unit)) (not shown) that controls the entire operation of the image processing apparatus 1. When the control unit receives an image formation instruction, the control unit sends a control signal to a power source (not shown) that supplies power to the heating units 54 and 64 provided inside the fixing roller 50 and the pressure roller 60. The image forming instruction is input from an operation panel (not shown) provided on the upper surface in the vertical direction of the image processing apparatus 1 or an external device such as a computer connected to the image processing apparatus 1. Upon receipt of the control signal, the power supply supplies power to the fixing roller 50 and the pressure roller 60 to activate the heating units 54 and 64. The heating units 54 and 64 heat the surfaces of the fixing roller 50 and the pressure roller 60 so as to have respective set temperatures.

  When a temperature detection sensor (not shown) provided in the vicinity of the fixing roller 50 and the pressure roller 60 detects that the set temperature has been reached and the detection result is input to the control unit, the control unit drives the fixing roller 50 to rotate. A control signal is sent to a drive unit (not shown) to drive the fixing roller 50 in the direction of the arrow 55. Along with this, the pressure roller 60 is driven to rotate. In this state, the recording medium 8 carrying the unfixed toner image is conveyed from the secondary transfer portion 4 to the fixing nip portion, and the toner image is fixed to the recording medium 8 when the recording medium 8 passes through the fixing nip portion. The

  The cleaning device 70 includes a web 71, a delivery roller 76, a first pressure contact portion 72 that presses the web 71 against the surface of the fixing roller 50, a second pressure contact portion 73, and a winding roller 77. The 1st press-contact part 72 and the 2nd press-contact part 73 are roller-shaped members rotatably supported by the support means which is not shown in figure. The first pressure roller 72 and the second pressure roller 73 are arranged around the fixing roller 50 at a predetermined interval.

  The web 71 is provided by the first pressure roller 72 and the second pressure roller 73 so that the surfaces thereof are in pressure contact with the surface of the fixing roller 50. A pressure contact portion between the web 71 pressed by the first pressure roller 72 and the fixing roller 50 is a first cleaning nip portion 78, and a pressure contact portion between the web 71 pressed by the second pressure roller 73 and the fixing roller 50. Is the second cleaning nip 79. In the area between the two cleaning nips, although the pressure roller is not in contact with the fixing roller, the web 71 is in a state of being in contact with the fixing roller 50 and thus forms a pseudo nip portion. Hereinafter, it is referred to as a pseudo nip portion. The pseudo nip part is provided with a dirt detection part 200 for the purpose of detecting the dirt state of the web 71.

  As the dirt detection unit 200, for example, a reflective optical sensor including a general light emitting unit and a light receiving unit can be used. For the web 71, for example, a heat-resistant nonwoven fabric can be used. Although it does not restrict | limit especially as a heat-resistant nonwoven fabric, For example, the nonwoven fabric etc. which have a moderate softness | flexibility and mechanical strength including an aromatic polyamide fiber and the polyester fiber softened at high temperature are mentioned.

Such heat-resistant nonwoven fabrics are commercially available, and examples thereof include Nomex and Himeron (both are trade names). The thickness of the web 71 is not particularly limited, but is preferably 30 to 100 μm. In the present embodiment, a web having a thickness of 40 μm is used. The web 71 can be impregnated with oil. Oils commonly used in this field can be used as the oil, and examples thereof include silicone oils such as dimethyl silicone oil, amino-modified silicone oil, mercapto-modified silicone oil, and fluorine-modified silicone oil. In the present embodiment, a web 71 impregnated with silicone oil having a viscosity of about 0.01 m ² / s (10000 centistokes, 25 ° C.) is used.

  In this configuration, the dirt detection unit 200 is provided on the back side of the web, that is, on the side opposite to the toner collection surface. However, the web as described above is usually white or milky white, The thickness of the material is about several tens of μm. If the web collects toner and becomes dirty, the difference in optical density can be detected not only from the toner collection surface side, but also from the back surface. Therefore, also in this configuration, it is possible to sufficiently detect the web dirt state.

  The feed roller 76 is supported so as to be able to be driven and rotated around the axis, and the web 71 is wound around and held on the surface thereof. The take-up roller 77 is provided so as to be rotatable around the axis by the take-up roller driving unit 91 and winds the web 71 after contacting the fixing roller 50.

  According to the cleaning device 70, the web 71 fed out from the feeding roller 76 in the direction of the arrow 81 is stretched by the second pressure roller 73 and the first pressure roller 72, and the fixing roller 73 and 72 fixes the fixing roller. 50 is wound on the winding roller 77 after contacting the surface. The operation of the web 71 is controlled by a cleaning control unit 90 composed of a CPU.

  The cleaning control unit 90 detects that a predetermined number of recording media 8 have passed through the fixing nip portion 55 based on the number of rotations of the sensor, the fixing roller 50, and the like, and simultaneously writes pixel information and information from the web stain detection unit 200. Based on the above, a control signal is sent to a take-up roller drive unit 91 (here, a motor provided inside the main body of the image processing apparatus 1) that rotates the take-up roller 77.

  Upon receiving the control signal, the take-up roller driving unit 91 rotates the take-up roller 77 to take up the web 71 in the direction of the arrow 81 by a predetermined amount. Since the outer diameter of the take-up roller 77 is apparently increased by the take-up operation, correction is performed so that the take-up roller is always taken up by a predetermined amount, and a substantially constant take-up amount is obtained throughout the life of the web. Maintained.

  The pressure rollers 72 and 73 are roller-like members that are supported at both ends in the longitudinal direction so as to be driven and rotated by a bearing (not shown) and are pressed against the surface of the fixing roller 50 via a web 71 by a pressing means (not shown). .

  The pressure rollers 72 and 73 are driven to rotate together with the web 71 during the winding operation by the winding roller 77. For the pressure rollers 72 and 73, for example, a roller-shaped member including a metal core and an elastic layer 80 formed on the surface of the metal core is used. As an elastic material which comprises an elastic layer, heat resistant rubbers, such as silicone rubber, its foam etc. are mentioned, for example. The surface hardness of the elastic layer is not particularly limited, but is preferably 20 ° to 30 ° (Asker-c, Asker C hardness).

  Further, as shown in FIG. 4, the pressure roller 73 may be provided with a surface layer 80a in which the elastic layer of the pressure roller is covered with a material that is difficult to impregnate with oil. The material of the surface layer 80a may be any material that is excellent in heat resistance and difficult to penetrate oil. For example, PFA (copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether), PTFE (polytetrafluoroethylene), etc. Fluorine-based resin materials, fluorine rubber, polyimide and the like can be mentioned.

  The web 71 that is fed from the feed roller 76 in the direction of the arrow 81 and reaches the second cleaning nip 79 (pressure contact portion between the fixing roller 50 and the web 71) supplies oil to the surface of the fixing roller 50, The first cleaning nip portion 78 reliably collects the toner that has passed through without being collected. The web 71 that passes through the second cleaning nip portion 79 and the relay roller 75 and reaches the first cleaning nip portion 78 (pressure contact portion between the fixing roller 50 and the web 71) is attached to the surface of the fixing roller 50. Take in as much toner as possible.

  In FIG. 5, the web winding control will be described in more detail. First, the basic web feed speed is determined based on the written image information. For example, when the writing pixel amount (printing rate) per sheet is not more than a predetermined amount in A4 size, the web is wound up once per 10 sheets in terms of A4 paper. The pixel amount referred to here is, for example, a pixel amount corresponding to 50% in the A4 size. For example, from the image data input to each of the yellow, magenta, cyan, and black optical scanning units, the pixel amount is obtained by counting the number of pixels in which image information exists and dividing by the total number of pixels, and adding the respective results. It may be obtained by. In addition, the winding amount of the web per time is 0.5 mm.

  On the other hand, when the writing pixel amount is equal to or larger than the predetermined amount, the web is wound once every time five sheets are printed in terms of A4 paper. In this way, when fixing a high-print image by changing the winding speed depending on the pixel amount, the toner can pass through or be ejected by increasing the winding speed and improving the toner collecting ability of the web. Is suppressed.

  Based on such basic control, control is performed in consideration of the detection result of the dirt detection unit 200. That is, the dirt detection unit 200 provided between the first and second cleaning nips detects the web dirt condition, and the cleaning control unit 90 compares the detected value with the reference value, and the comparison result is obtained. Based on this, it is determined whether the web is dirty. If it is determined that the web is dirty, control is performed to further increase the winding speed. For example, when it is determined that the web is dirty by the stain determination under the condition where the pixel amount is 50% or more, the winding speed is further increased, for example, every time three sheets are printed, the sheet is wound once. Thus, the toner collecting ability by the web can be improved.

  Thus, by detecting the state of web contamination in the cleaning nip region and controlling the web winding speed based on the detection result, it is possible to obtain a good image free from toner slipping and jetting. Furthermore, since the amount of winding is increased only when necessary, the web life is not extremely shortened.

  Further, the ejection of toner from the web often occurs during the next printing after the fixing roller is heated in a standby state. If the fixing roller continues to be heated at the standby temperature, if the web is dirty, it is considered that the toner collected on the web once adheres to the fixing roller due to melting again, and is ejected. For such a problem, before and after the job operation ends and enters the standby state, preferably before the fixing roller completely stops and enters the standby state, the contamination detection unit performs the contamination determination and the contamination is detected. If it is determined, the web may be forcibly wound up at least so that the toner is not ejected from the web to the fixing roller. For example, there is no problem if it takes up several millimeters to 10 mm.

  FIG. 6 is a plan view of a cleaning unit of a fixing device according to another embodiment of the present invention. Since it is basically the same as the configuration of FIG. 3, detailed description thereof is omitted.

  A plurality (three in this embodiment) of dirt detectors 200a to 200c may be provided and controlled along the axial direction of the fixing roller 50 as shown in FIG. As a control method in the case where a plurality of dirt detection units 200 are provided, for example, the winding amount may be increased when one of them exceeds a determination reference value. In the case of this configuration, since the determination accuracy in the axial direction of the fixing roller 50 is increased, the contamination detection accuracy is improved, and a good image free from image contamination can be obtained.

  In the present embodiment, the configuration in which the cleaning device 70 is disposed on the surface of the fixing roller 50 has been described. However, the present invention is not limited thereto, and the cleaning device 70 may be disposed on the pressure roller 60 or both the fixing roller 50 and the pressure roller 60. Furthermore, the shape of the member to be cleaned is not limited to a roller shape, and there is no problem even if it is a belt shape.

  The fixing device according to the present embodiment includes a CPU (central processing unit) that executes instructions of a control program that realizes each function, a ROM (read only memory) that stores the program, and a RAM (random access memory) that expands the program. ), A storage device (recording medium) such as a memory for storing the program and various data. An object of the present invention is a recording medium in which a program code (execution format program, intermediate code program, source program) of a control program of a cleaning control unit, which is software that realizes the above-described functions, is recorded so as to be readable by a computer. This can be achieved by supplying the cleaning member control unit and reading and executing the program code recorded on the recording medium by the computer (or CPU or MPU).

  Examples of the recording medium include a tape system such as a magnetic tape and a cassette tape, a magnetic disk such as a floppy (registered trademark) disk / hard disk, and an optical disk such as a CD-ROM / MO / MD / DVD / CD-R. Card system such as IC card, IC card (including memory card) / optical card, or semiconductor memory system such as mask ROM / EPROM / EEPROM / flash ROM.

  Further, the image processing apparatus may be configured to be connectable to a communication network, and the program code may be supplied via the communication network. The communication network is not particularly limited. For example, the Internet, intranet, extranet, LAN, ISDN, VAN, CATV communication network, virtual private network, telephone line network, mobile communication network, satellite communication. A net or the like is available. Also, the transmission medium constituting the communication network is not particularly limited. For example, even in the case of wired such as IEEE 1394, USB, power line carrier, cable TV line, telephone line, ADSL line, etc., infrared rays such as IrDA and remote control, Bluetooth ( (Registered trademark), 802.11 wireless, HDR, mobile phone network, satellite line, terrestrial digital network, and the like can also be used. The present invention can also be realized in the form of a computer data signal embedded in a carrier wave in which the program code is embodied by electronic transmission.

Sectional drawing which shows schematic structure of the image processing apparatus which is embodiment of this invention 1 is an enlarged cross-sectional view of a toner image forming unit of the image processing apparatus shown in FIG. Sectional drawing which shows schematic structure of the fixing device which is embodiment of this invention Sectional drawing which shows schematic structure of the fixing apparatus which is another embodiment of this invention. 7 is a flowchart showing cleaning control of the fixing device according to the present invention. The top view of the cleaning apparatus which shows another embodiment of this invention Sectional view schematically showing a conventional fixing device Sectional drawing which shows schematic structure of the cleaning apparatus of the conventional fixing device

Explanation of symbols

50 Fixing roller 54 Heating part (halogen lamp)
55 fixing nip 60 pressure roller 70 cleaning device 71 web 72 first pressure roller 73 second pressure roller 76 delivery roller 77 take-up roller 78 first cleaning nip portion 79 second cleaning nip portion 90 cleaning control portion 91 Winding roller driving unit 200 Dirt detection unit (light sensor)

Claims (8)

  A fixing device having a pair of rotatable fixing members includes a cleaning member for cleaning the fixing member, and the cleaning member has a predetermined cleaning nip formed by pressing the fixing member with a plurality of pressing members. A fixing device is provided with a dirt detection unit for detecting dirt on the cleaning member in the cleaning nip, and a cleaning control unit for controlling the movement of the cleaning member based on a detection result by the dirt detection unit. .   The fixing device according to claim 1, wherein the stain detection unit is an optical sensor.   3. The fixing device according to claim 2, wherein a plurality of the contamination detection units are provided in a direction perpendicular to a conveyance direction of the recording paper passing through the fixing member.   The fixing device according to claim 1, wherein the cleaning control unit controls a moving speed of the cleaning member based on a detection result of the dirt detection unit.   The fixing device according to claim 1, wherein the cleaning control unit forcibly winds the cleaning member based on a detection result of the dirt detection unit.   An image processing apparatus comprising the fixing device according to claim 1.   A cleaning program for operating the fixing device according to claim 1, 4 or 5 for causing a computer to function as the cleaning control unit.   A computer-readable recording medium on which the cleaning program according to claim 7 is recorded.

Images