JP2012155284A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a structure which realizes reduction of variation in gloss level on a surface of an elastic intermediate transfer belt including an elastic layer and reduction an amount of toner consumption.SOLUTION: A value of a reflection light amount on an entire surface of an elastic intermediate transfer belt is measured with an optical sensor (S7). Based on the value of the reflection light amount measured, a gloss restoring toner image is determined which allows a more amount of toner to be provided on a portion where the reflection light amount is less (S8), and such toner image is formed for one round of the belt (S9). At this time, the toner image is transported to a belt cleaning unit and cleaned. This allows a more amount of toner to be supplied to a portion where reduction in gloss on the surface of the belt is larger, thus enabling restoration of the gloss through cleaning by the belt cleaning unit. Accordingly, the variation in gloss level is reduced. Further, this allows a less amount of toner to be provided on a portion where reduction in gloss is small, thus reducing an amount of toner consumption.

Description

  The present invention relates to an image forming apparatus such as a printer, a copying machine, a facsimile, or a multifunction machine using these using an electrophotographic system, an electrostatic recording system, or the like.

  In recent years, in an image forming apparatus using an electrostatic process, an intermediate transfer belt (intermediate transfer member) is widely used because of the need for high-quality images on a wide variety of papers. As the intermediate transfer belt, a resin belt typified by polyimide or the like is generally widely used because of its high image quality, long life, and high stability. Also, as a cleaning device for cleaning the intermediate transfer belt, a blade system having a high cleaning capability is widely used in consideration of the surface property of the resin belt (see Patent Document 1). The blade system is a structure in which the cleaning blade is brought into contact with the surface of the intermediate transfer belt to clean the toner and the like on the intermediate transfer belt.

  On the other hand, recently, the toner has been changed to a smaller particle size and a non-spherical toner shape due to further higher image quality and stabilization of the cleaning ability by the blade method. However, in the intermediate transfer belt made of resin, there is a problem of the hollowing out phenomenon that occurs at the time of transfer accompanying the change in toner. When the image is transferred, a large pressure is applied to the image, so that the toner undergoes stress deformation, the cohesive force between the toners increases, and a part of the image is not transferred onto the image carrier. This is a phenomenon that remains, particularly in characters and line images. In the case of a resin belt, since the pressure on the image at the time of transfer is large, this hollow-out phenomenon is particularly problematic.

  Therefore, in order to eliminate such a hollow-out phenomenon, an intermediate transfer belt using at least one elastic layer (hereinafter referred to as an elastic intermediate transfer belt) is employed instead of an intermediate transfer belt using resin. There is an example to do. Since the elastic intermediate transfer belt has at least one elastic layer in the layer structure, it is known that the elastic intermediate transfer belt is soft and the pressure acting on the toner in the transfer portion can be reduced, so that it is effective in the hollowing out phenomenon. In addition, since the secondary transfer section has good adhesion to paper, it not only improves transfer efficiency for general paper, but is also effective for transfer to thick paper and transfer to uneven paper. It is known that there is.

  In addition, when the intermediate transfer belt is new, the toner image is formed on the intermediate transfer belt during operations other than the image forming operation, and is cleaned by the cleaning device without being transferred to the transfer material at the secondary transfer portion. It is known (see Patent Document 2). In the case of this structure, the oxide film adhering to the belt surface at the time of a new article can be removed, and the surface state of the intermediate transfer belt can be made in the same manner as normal.

JP 2001-305878 A JP 2004-117597 A

  When the above-described elastic intermediate transfer belt having an elastic layer is cleaned by a blade method, toner, toner external additives, paper dust, and the like adhering to the belt surface cannot be sufficiently removed, and the belt surface state changes and the belt Surface gloss is likely to decrease. That is, a belt having an elastic layer is elastically deformed when the blade is brought into contact therewith, so that it is difficult for the blade to scrape off paper dust and other adhering matter, and the belt surface is rubbed with paper dust and the like. Decline is likely to occur.

  In particular, the change in the gloss of the belt surface varies depending on the toner density distribution of the formed image and whether or not the paper has passed the recording material surface. For this reason, when images with different toner concentrations are continuously formed in the direction (width direction) perpendicular to the toner image conveyance direction (travel direction) of the elastic intermediate transfer belt, the surface property of the elastic intermediate transfer belt is biased, that is, gloss A step will occur. This gloss level difference affects patch detection accuracy and transferability, particularly halftone uniformity, and ATVC control accuracy, which is transfer electric field control.

  It is conceivable to apply the structure described in Patent Document 2 to form a toner image having a uniform toner amount on the entire surface of the belt surface where image formation is possible, and to clean it. However, in this structure, the gloss on the belt surface can be recovered as a whole, but the gloss level difference generated on the belt surface cannot be eliminated. In addition, when a toner image for gloss recovery with a uniform toner amount is formed on the entire surface of the belt surface where image formation is possible, the toner is supplied to a portion where the gloss is not lowered, and more toner is consumed than necessary. I will end up measuring it.

  The present invention has been invented to realize a structure capable of reducing the gloss level difference on the surface of an intermediate transfer member having an elastic layer while suppressing toner consumption in view of the above circumstances.

  The present invention provides an image forming portion for forming a toner image, an intermediate transfer member having an elastic layer and carrying the toner image transferred from the image forming portion, and a toner image carried on the intermediate transfer member. An image forming apparatus comprising: a transfer unit that transfers to a recording material; and the intermediate transfer member that is positioned downstream of the transfer unit in the toner image conveyance direction and in contact with the surface of the intermediate transfer member. A cleaning blade that cleans the surface of the intermediate transfer member, a detection unit that detects a surface state of the intermediate transfer member when a toner image is not carried, and a gloss of the surface of the intermediate transfer member that can be derived from the detection result of the detection unit. The smaller the portion, the larger the toner amount, the gloss forming toner image is formed on the image forming unit, and the gloss restoring toner image carried on the intermediate transfer member is transferred to the recording material. In, and a control means for executing the gloss return mode for cleaning by the cleaning blade, in the image forming apparatus characterized by.

  According to the present invention, the smaller the gloss on the surface of the intermediate transfer body, the larger the toner amount of the gloss recovery toner image. Therefore, the smaller the gloss, the more the gloss can be recovered and the gloss level difference can be reduced. Further, since the toner amount is changed in accordance with the gloss, the toner consumption for reducing the gloss level difference can be suppressed.

1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of an intermediate transfer belt. The schematic diagram for demonstrating an optical sensor. The schematic diagram which shows the relationship between a patch and a sensor output. It is a figure explaining a belt cleaning apparatus, (A) is a schematic block diagram, (B) is an enlarged view which shows an operation state, (C) is the figure seen from the diagonally upper right of (A). The schematic structure perspective view which shows the installation state of an optical sensor. The control block diagram of 1st Embodiment. The figure which shows the relationship between the reduction degree of a belt reflected light amount, and a toner amount. The flowchart of control of 1st Embodiment. The schematic diagram for demonstrating arrangement | positioning of the optical sensor which concerns on the 2nd Embodiment of this invention. The control block diagram of 2nd Embodiment. (A) is a schematic diagram showing an example of an image formed by the image forming apparatus, and (B) is a diagram showing a relationship between the number of sheets passing through the image and a gloss value. The flowchart of control of 2nd Embodiment. The schematic diagram for demonstrating arrangement | positioning of the optical sensor which concerns on the 3rd Embodiment of this invention. The control block diagram of 3rd Embodiment. The flowchart of control of 3rd Embodiment. The schematic diagram of the image used in the experiment conducted in order to confirm the effect of this invention.

<First Embodiment>
A first embodiment of the present invention will be described with reference to FIGS. First, the image forming apparatus of this embodiment will be described with reference to FIG.

[Image forming apparatus]
The image forming apparatus of the present embodiment is a tandem system provided with four image forming stations (image forming units) as shown in FIG. In other words, a belt-like elastic intermediate transfer member as an intermediate transfer member, that is, an endless elastic intermediate transfer belt 181 is provided, and four image forming portions Pa, Pb, Pc, and Pd are arranged in series along the belt 181. It is arranged. These image forming portions Pa, Pb, Pc, and Pd are image forming portions for each color of yellow, magenta, cyan, and black, and the members constituting each image forming portion are given corresponding subscripts. ing. However, since the configuration of each image forming unit is the same, the following description omits the subscripts.

  The image forming unit P includes a drum-shaped electrophotographic photosensitive member (hereinafter referred to as a “photosensitive drum”) 101 that is an image carrier that is rotatably arranged. Around the photosensitive drum 101, process devices such as a primary charger 122, a developing device 123, and a cleaning device 112 are arranged. The developing devices 123a to 123d disposed in the image forming units Pa to Pd store yellow toner, magenta toner, cyan toner, and black toner, respectively.

  The surface of the photosensitive drum 101 is uniformly charged by the primary charger 122, and an image signal based on the corresponding color component of the document is projected from the exposure device 111 via a polygon mirror or the like to form an electrostatic latent image. .

  Next, toner is supplied from the developing device 123 and the electrostatic latent image is developed as a toner image. As the photosensitive drum 101 rotates, the toner image is conveyed to the primary transfer portion T1 where the photosensitive drum 101 and the elastic intermediate transfer belt 181 are in contact with each other. In the primary transfer portion T1, the first transfer bias is applied from the primary transfer member (first transfer unit), that is, the transfer roller 124 in this embodiment, and the toner image is transferred to the intermediate transfer belt 181. The elastic intermediate transfer belt 181 carrying the toner image is conveyed to the next image forming unit P, and by this time, the toner image similarly formed in the next image forming unit is formed in the previous image forming unit. Transferred onto the toner image.

  The toner images formed by the image forming units are superimposed and transferred onto the elastic intermediate transfer belt 181, and the belt 181 carries and transfers the transferred toner image. Thereafter, by this time, the recording material P sent out from the paper feed cassette 160 reaches the secondary transfer portion T2, and is transferred by the transfer bias applied to the secondary transfer member (second transfer means) 140 as the transfer means. The above four color toner images are transferred onto the recording material P. The recording material P to which the toner image is transferred is conveyed to the fixing unit 211. The fixing unit 211 fixes the toner image on the recording material P by heat and pressure. Such an image forming process is controlled by the control unit 300 serving as a control unit.

  Untransferred toner on the photosensitive drum that could not be transferred by the primary transfer member is cleaned by the drum cleaning device 112. Further, the transfer residual toner on the intermediate transfer belt 181 that could not be transferred by the secondary transfer member is scraped (cleaned) by the belt cleaning device 116 and used for the next image formation.

  Next, the configuration of each unit will be described sequentially. The photosensitive drum 101 as an image carrier is configured by applying an organic photoconductive layer (OPC) to the outer peripheral surface of an aluminum cylinder. Both ends of the photosensitive drum 101 are rotatably supported by flanges, and are driven to rotate in the counterclockwise direction in the figure by transmitting a driving force from a driving motor (not shown) to one end.

  The primary charger 122 is a conductive roller formed in a roller shape. The roller is brought into contact with the surface of the photosensitive drum 101, and a charging bias voltage is applied by a power source (not shown), so that the surface of the photosensitive drum 101 is primary. In this way, it is charged negatively. The charging bias is controlled to be turned on according to an image signal by a drive circuit (not shown).

  The developing device 123 includes a toner storage unit, a developing roller, and the like. The toner storage portions of the developing devices store black, cyan, magenta, and yellow toners having negative charge characteristics. In this embodiment, a two-component developer containing a nonmagnetic toner and a magnetic carrier is used. Accordingly, each color toner and carrier are stored in the toner storage portion and stirred while being transported by the transport screw, so that the toner is charged negatively and the carrier is charged positively. The developing roller is adjacent to the surface of the photosensitive drum 101 and is driven to rotate by a driving unit (not shown). A magnet is disposed in the developing roller, and the charged toner and carrier as described above are carried on the surface of the developing roller. The toner carried on the surface of the developing roller develops the electrostatic latent image on the surface of the photosensitive drum 101 by applying a developing bias voltage from a developing bias power source (not shown). Note that an external additive for improving the releasability of the toner is added to the developer.

  The elastic intermediate transfer belt 181 is wound around a driving roller 125, a tension roller 126, and a backup roller 129 as a support. Further, inside the intermediate transfer belt 181, transfer rollers 124a, 125b, 125c, and 125d, which are primary transfer members that are in contact with the intermediate transfer belt 181 so as to face the four photosensitive drums 101a, 101b, 101c, and 101d, are provided. They are arranged side by side. These transfer rollers are connected to a power supply for transfer bias (not shown), and a positive voltage is applied from the transfer roller. Due to this electric field, the intermediate transfer body 181 in contact with the photosensitive drum 101 is transferred to the intermediate transfer body 181 on the photosensitive drum 101. The negative color toner images are sequentially transferred to form a color image. Further, a home position detection seal for detecting the position of the intermediate transfer belt is affixed inside the intermediate transfer belt 181, and the position of the intermediate transfer belt is monitored by the belt home position detection sensor 201. In this embodiment, it is used to monitor the position of the amount of reflected light on the surface of the elastic intermediate transfer belt.

  The elastic intermediate transfer belt 181 is an endless belt composed of a plurality of layers having different elastic moduli of at least two layers. That is, as shown in FIG. 2, it has a three-layer structure of a resin layer 181a, an elastic layer 181b, and a surface layer 181c. Examples of the resin material constituting the resin layer 181a include polycarbonate, fluororesin (ETFE, PVDF), polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-butadiene copolymer, and styrene-vinyl chloride copolymer. Furthermore, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-acrylic acid). Butyl copolymer, styrene-octyl acrylate copolymer and styrene-phenyl acrylate copolymer), styrene-methacrylic acid ester copolymer (styrene-methyl methacrylate copolymer, styrene-methacrylic acid) Ethyl copolymers, and also styrene resins (styrene or styrene) such as styrene-phenyl methacrylate copolymer, styrene-α-methyl chloroacrylate copolymer, styrene-acrylonitrile-acrylate ester copolymer, etc. Monopolymer or copolymer containing a substituent). Furthermore, methyl methacrylate resin, butyl methacrylate 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. Furthermore, styrene-vinyl acetate copolymer, vinyl chloride-vinyl acetate copolymer, rosin-modified maleic acid resin, phenol resin, epoxy resin, polyester resin, polyester polyurethane resin, polyethylene, polypropylene, polybutadiene, and polyvinylidene chloride. Further, ionomer resins, polyurethane resins, silicone resins, ketone resins, ethylene-ethyl acrylate copolymers, xylene resins, polyvinyl butyral resins, polyamide resins, and polyimide resins. Furthermore, modified polyphenylene oxide resin, modified polycarbonate and the like can be mentioned, and one or more kinds selected from the group consisting of these can be used. However, it is not limited to the said material.

  The elastic material (elastic material rubber, elastomer) constituting the elastic layer 181b is butyl rubber, fluorine rubber, acrylic rubber, EPDM, NBR, acrylonitrile-butadiene-styrene rubber natural rubber, isoprene rubber, styrene-butadiene rubber. Further, butadiene rubber, ethylene-propylene rubber, ethylene-propylene terpolymer, chloroprene rubber, chlorosulfonated polyethylene, chlorinated polyethylene, urethane rubber, syndiotactic 1,2-polybutadiene, epichlorohydrin rubber. Furthermore, ricone rubber, fluorine rubber, polysulfide rubber, polynorbornene rubber, hydrogenated nitrile rubber. Furthermore, thermoplastic elastomers (for example, polystyrene, polyolefin, polyvinyl chloride, polyurethane, polyamide, polyurea, polyester, and fluororesin) can be used. And 1 type or 2 types or more chosen from the group which consists of these can be used. However, it is a matter of course that the material is not limited to the above materials.

  The material of the surface layer 181c is not particularly limited, but a material that increases the secondary transfer property by reducing the adhesion force of the toner to the surface of the intermediate transfer belt 181 is required. For example, one kind of resin material such as polyurethane, polyester, epoxy resin, elastic material (elastic material rubber, elastomer), butyl rubber, fluorine rubber, acrylic rubber, EPDM, NBR, acrylonitrile-butadiene-styrene rubber natural rubber, isoprene Rubber. Furthermore, elastic materials such as styrene-butadiene rubber, butadiene rubber, ethylene-propylene rubber, ethylene-propylene terpolymer, chloroprene rubber, chlorosulfonated polyethylene, chlorinated polyethylene, and urethane rubber can be used. Of these, two or more types can be used by dispersing one or more types of materials that reduce the surface energy and improve the lubricity, or have different particle sizes. Examples of the material for improving lubricity include powders and particles such as fluororesin, fluorine compound, fluorocarbon, titanium dioxide, and silicon carbide. Further, in order to perform blade cleaning, the surface of the intermediate transfer belt 181 is required to have wear resistance. You may use the belt which added the filler to the said material and raised abrasion property.

  A resistance value adjusting conductive agent is added to the resin layer 181a and the elastic layer 181b. The conductive agent for adjusting the resistance value is not particularly limited. For example, carbon black, graphite, metal powder such as aluminum and nickel, tin oxide, titanium oxide, antimony oxide, indium oxide, potassium titanate, antimony oxide-tin oxide Complex oxide (ATO). Furthermore, conductive metal oxides such as indium oxide-tin oxide composite oxide (ITO) can be used. The conductive metal oxide may be coated with insulating fine particles such as barium sulfate, magnesium silicate, and calcium carbonate. It is not limited to the conductive agent.

  In the elastic intermediate transfer belt according to this embodiment, the surface resistivity of the three layers is, for example, 12 Log · Ω / □ and the volume resistivity 9 Log · Ω · cm in order to maintain image quality. The surface ten-point average roughness is preferably 0.1 μm or more and 2.0 μm or less. Regarding the surface ten-point average roughness, when the blade cleaning exceeds 2.0 μm, the toner slips through the unevenness due to the roughness of the belt surface. On the other hand, when the thickness is 0.1 μm or less, the contact area between the cleaning blade and the belt is increased, adhesion is increased, and the cleaning blade is easily turned over.

  The elastic intermediate transfer belt 181 can be manufactured by, for example, a centrifugal molding method in which a material is poured into a rotating cylindrical mold to form a belt, a spray coating method in which a thin film is formed on the surface, and a cylindrical mold as a solution of the material. There is a dipping method in which it is soaked in the inside. Furthermore, there are a casting method for injecting into an inner mold and an outer mold, and a method for winding a compound around a cylindrical mold and performing vulcanization polishing. However, the present invention is not limited to this, and a belt is formed by combining a plurality of manufacturing methods. Can be manufactured.

  The color image carried on the intermediate transfer belt 181 in the primary transfer portion is further transferred to the recording material P by the secondary transfer roller 140 that is a secondary transfer member that contacts the intermediate transfer belt 181. The secondary transfer roller is connected to a power supply for transfer bias (not shown), and a positive voltage is applied from the transfer roller. Due to this electric field, the intermediate transfer belt is applied to the recording material P in contact with the intermediate transfer 181 belt. The negative polarity toner image on 181 is sequentially transferred to form a color image. The transfer electric field is determined by ATVC control. If there is a large gap between the surface of the belt on which ATVC control is performed and the surface of the belt on which the recording material is actually conveyed to the secondary transfer portion, the actual transfer electric field is different and desired transferability cannot be obtained. Therefore, the surface property of the belt needs to be substantially uniform within the same belt.

  Further, the secondary transfer roller 140 is configured to be selectively switchable between an operating state in contact with the elastic intermediate transfer belt 181 and a non-operating state separated from the elastic intermediate transfer belt 181. In the present embodiment, a solenoid that is a contact / separation mechanism that selectively contacts and separates from the elastic intermediate transfer belt 181 is used as the switching unit (not shown).

  In addition, an optical sensor 200 that is a detection unit that detects the surface state of the elastic intermediate transfer belt 181 is disposed opposite to the surface of the elastic intermediate transfer belt 181. In the present embodiment, as shown in FIG. 6 described later, a line sensor 200-1 in which a plurality of optical sensors are arranged is arranged. The optical sensor 200 will be described with reference to FIG. The optical sensor 200 includes a light emitting unit 200a and a light receiving unit 200b. When light emitted from the light emitting unit 200a is applied to the elastic intermediate transfer belt 181 and the position detection patch 200c formed on the belt 181, the reflected light enters the light receiving unit 200b and is photoelectrically converted. An output voltage corresponding to the amount of light is obtained. There is a lens 200d between the light emitting unit 200a and the light receiving unit 200b and an object to be detected such as the elastic intermediate transfer belt 181. The lens 200d is installed in order to converge the light in the light emitting unit 200a and efficiently receive the reflected light in the light receiving unit 200b.

  The optical sensor 200 has a configuration capable of adjusting the light amount based on the output voltage when the light amount reflected from the surface of the elastic intermediate transfer belt 181 is received by the light receiving unit 200b so as to obtain a certain appropriate output voltage. is there. The optical sensor 200 adjusts the amount of light so that the output voltage becomes a specified value by changing the amount of light because there is a change in the amount of light.

  This light amount adjustment is generally performed in a state where the position detection patch 200c is not provided on the elastic intermediate transfer belt 181, that is, on the surface of the elastic intermediate transfer belt 181. FIG. 3 shows an output waveform (analog) 200e when the position detection patch 200c is read after the light amount adjustment. The sensor output voltage on the surface of the elastic intermediate transfer belt is a specified value (for example, 5 V) after light amount adjustment from the output waveform value. In the case of a regular reflection type patch sensor, the output voltage when the position detection patch 200c is detected is lower than the output voltage on the surface of the elastic intermediate transfer belt, and is usually set to a threshold value 255 or less that can be digitized. The threshold value 255 and the output voltage are adjusted.

  The center of gravity of the rising and falling edges of the digitized output waveform 200f is taken and used as position detection data of the position detection patch 200c. The sensor output (waveform 200g) when the station 200 detects the yellow, magenta, cyan, and black position detection patch 200c is as shown in FIG. Since the reflectance of toner is different for each of yellow, magenta, cyan, and black, the output voltage at the time of patch detection is different for each color. This is because the reflectance changes depending on the color and density of the toner.

  Before adjusting the density of the position detection patch 200c for color misregistration correction, first, the light amount adjustment is performed while the surface of the elastic intermediate transfer belt 181 is being conveyed. When the output voltage reaches the specified value, the light amount is kept constant until the next light amount adjustment. The timing for adjusting the amount of light may be at the time of activation or every certain number of printed sheets. By reading an arbitrary toner patch with the optical sensor 200, not only the color misregistration of each color described above is corrected, but also the writing position on the recording material is detected, and the conveyance timing of the recording material at the secondary transfer unit is determined. It is used to do. The point on the belt where the light amount is adjusted and the point on the belt where the patch is actually applied are rarely the same, and therefore the surface property of the belt needs to be as small as possible within the same belt.

  Next, with reference to FIG. 5, the details of the belt cleaning unit 116 for residual toner remaining on the elastic intermediate transfer belt 181 after the secondary transfer will be described. The belt cleaning device 116 is located downstream of the secondary transfer roller 140 in the toner image conveyance direction (downstream in the rotation direction) of the elastic intermediate transfer belt 181. Then, the cleaning blade 116 a which is a blade-shaped cleaning member is brought into contact with the surface of the elastic intermediate transfer belt 181 to clean the surface of the belt 181.

  The cleaning blade 116a has, for example, a rubber hardness of 77 ° (JIS A), a rebound resilience of 45% (23 ° C.), a plate thickness of 2 mm, and a free length of 8 mm. For example, an elastic material such as polyurethane rubber can be used. . Further, the contact angle θ of the blade 116a is configured to be 0 ° or more and 25 ° or less when the direction of contact with the belt 181 is positive. In this embodiment, the rotation angle is 0 °, the contact angle is 25 °, and the total pressure against the transfer belt 181 is 0.8 kgf.

  Further, as shown in FIG. 5B, the belt cleaning device 116 is configured to be selectively switchable between an operating state and a non-operating state. The operating state is a state in which the blade 116a is brought into contact with the elastic intermediate transfer belt 181 to clean the surface of the belt 181 as the belt 181 is driven to rotate. The non-operating state is a state in which the cleaning of the surface of the elastic intermediate transfer belt 181 that is separated from the elastic intermediate transfer belt 181 is stopped. In this embodiment, a cam mechanism that is a contact / separation mechanism that selectively contacts and separates from the elastic intermediate transfer belt 181 is used as the switching unit.

  The cam mechanism includes a cam 116b that is rotationally driven by a motor 116i through a gear mechanism 116h, a swing plate 116d that contacts the cam 116 and swings about a fulcrum 116c by the rotation of the cam 116b, and a swing plate. And an intermediate member 116e for fixing the blade 116a. As shown in FIG. 5C, three cams 116a are arranged side by side on the rotating shaft, but this number is arbitrary. When the swing plate 116d is swung in the direction of the arrow in FIG. 5B by the rotation of the cam 116, the blade 116a comes into an operating state in which the blade 116a contacts the belt 181 as shown by the solid line in FIG. On the other hand, when the swing plate 116d swings to the position indicated by the broken line in FIG.

  In addition, a lubricant is applied in advance to a tip corner portion where the cleaning blade 116a contacts the elastic intermediate transfer belt 181. As this lubricant, for example, silicone resin particles having an average particle diameter of 3 μm having a spherical shape and a circularity of 0.93, and fluorinated graphite having an irregular shape, specifically, an average particle diameter of 2 μm having a scale shape are predetermined. Those mixed at a ratio of Examples of the silicone resin particles include Tospearl (trade name, manufactured by Toshiba Silicone). Further, as fluorinated graphite, for example, there is a trade name Cefbon (manufactured by Central Glass Co., Ltd.). The reason why the lubricant is applied in this manner is to improve the slipping property between the belt and the blade during the initial operation and to prevent turning. The coating width from the edge tip of the cleaning blade 116a was approximately 1 mm.

  The belt cleaning device 116 includes an accommodating portion 116f that accommodates deposits such as residual toner and paper dust removed by the cleaning blade 116a. A rotating screw 116g is disposed inside the accommodating portion 116f to convey adhered matter such as residual toner or paper dust to the outside of the cleaning device 116. Therefore, as shown in FIG. 5A, the toner cleaned in the operating state is accommodated in the accommodating portion 116f, and is conveyed and collected by the rotating screw 116g.

[Gloss recovery mode]
As described above, when the elastic intermediate transfer belt 181 having the elastic layer described above is cleaned by the blade type belt cleaning device 116, the gloss of the belt surface is likely to be reduced. In particular, since the fluctuation of the gloss on the belt surface varies depending on the toner density distribution of the image, the surface property of the elastic intermediate transfer belt is biased, that is, a gloss level difference occurs. In the present embodiment, the control unit 300 executes the gloss return mode in order to suppress such a gloss level difference. The gloss return mode will be described.

  First, in the gloss recovery mode, a gloss recovery toner image is formed in the image forming unit so that the toner amount increases as the gloss of the surface of the elastic intermediate transfer belt 181 that can be derived from the detection result of the optical sensor 200 decreases. That is, the entire surface of the belt 181 is detected by the optical sensor 200. Then, based on the amount of reflected light detected by the optical sensor 200, the control unit 300 controls the exposure device 111 and the like so that the toner amount increases as the reflected light amount on the surface of the belt 181 decreases. A gloss recovery toner image is formed thereon. The lower the amount of reflected light, the lower the gloss. Therefore, the controller 300 determines the supply amount and supply position of the toner so that a large amount of toner is supplied to the portion where the gloss is reduced.

  This gloss recovery toner image is transferred from the photosensitive drum 101 onto the elastic intermediate transfer belt 181. In the gloss return mode, the secondary transfer roller 140 is separated from the belt 181. For this reason, the gloss recovery toner image carried on the belt 181 passes through the secondary transfer portion and is cleaned by the belt cleaning device 116. Note that a bias in the direction opposite to the normal secondary transfer bias may be applied when the gloss return toner image passes through the secondary transfer portion T2 without separating the secondary transfer roller 140. As a result, the toner image carried on the belt 181 is not transferred to the secondary transfer roller 140 but is conveyed to the belt cleaning device 116 and cleaned.

  Further, such a gloss return mode is executed at the following timing. First, in the present embodiment, as shown in FIG. 7, the storage unit 301 is a storage unit that stores the maximum value of the amount of reflected light on the surface of the elastic intermediate transfer belt 181 detected by the optical sensor 200. The control unit 300 has a portion on the surface of the belt 181 where the amount of reflected light detected by the optical sensor 200 decreases by a predetermined value or more with respect to the maximum value of the amount of reflected light in the previous gloss recovery mode stored in the storage unit 301. If this is the case, execute the gross return mode.

  Hereinafter, such a gloss return mode will be described more specifically. In the present embodiment, as shown in FIG. 6, a plurality of optical sensors 200 are arranged side by side in a direction (width direction and longitudinal direction) orthogonal to the toner image transport direction (rotation direction) of the belt 181. Is used. The line sensor 200-1 can monitor the surface state (the amount of reflected light) of the elastic intermediate transfer belt 181 in all the width directions. For example, the line sensor 200-1 includes 60 to 70 optical sensors 200 arranged in the width direction.

  As shown in FIGS. 2 and 6, such a line sensor 200-1 is downstream in the rotation direction of the belt 181 of each image forming unit, upstream of the secondary transfer unit T 2, and in the entire width direction of the belt 181. They are arranged facing each other. Then, the reflected light amount value of the belt 181 when the toner image is not carried, that is, during non-image formation is measured. The amount of reflected light is measured with no toner image on the surface of the elastic intermediate transfer belt. Therefore, the belt cleaning device is operated on the elastic intermediate transfer belt and the developing sleeve is stopped (photosensitive drum). In a state separated from the elastic intermediate transfer belt).

  Next, it will be described with reference to FIGS. 7 to 9 along the flow of the gross return mode. As shown in FIG. 9, when the power is turned on or the sleep state ends, it is determined whether or not the elastic intermediate transfer belt 181 is new (S1). When the initial elastic intermediate transfer belt 181 is installed in the image forming apparatus, the amount of reflected light of the elastic intermediate transfer belt 181 is measured and stored in the storage unit 301 as an initial value (S2). On the other hand, if it is not the initial belt, the reflected light amount value stored in the storage unit 301 is referred to (S3).

  Thereafter, the amount of reflected light on the surface of the elastic intermediate transfer belt 181 is measured at the timing (S4) when the toner image is not formed on the elastic intermediate transfer belt 181 between the adjustment time before and after image formation and between the sheets (S5). . Such measurement may be performed every time, but may be performed, for example, at a timing when the number of formed images reaches a predetermined number (for example, 1000). The difference between the measured value and the above-mentioned reflected light amount initial value is monitored, and when the value is equal to or greater than a predetermined value X, the gloss return mode is activated. In this embodiment, assuming that the reflected light amount value of the initial elastic intermediate transfer belt is 100%, the gloss return mode is executed when one or more reflected light amount values reduced by 20% or more are confirmed in the width direction (S6). ). After the second time, as will be described later, when the reflected light amount value reduced by 20% or more from the maximum value (S13) of the reflected light amount value stored in the immediately preceding gloss return mode is confirmed in one or more places in the width direction, the gross amount is confirmed. The return mode is executed (S6). In the present embodiment, as a result of examination by the inventor through experiments and the like, the predetermined value is set to 20%, but it can be set arbitrarily.

  When it is confirmed that the reflected light quantity value has decreased by 20% or more from the initial value or the stored value, the reflected light quantity value for one circumference of the belt is measured while the belt home position detection sensor 201 monitors the circumferential position of the belt. The The belt reflected light amount values in the width direction at that time are stored together with the circumferential position obtained from the belt home position detection sensor 201 (S7). Note that the data stored here may be the data measured in S5. That is, S7 may be omitted and the data measured in S5 may be used. In any case, the density distribution of the gloss recovery toner image is determined (S8) from the relationship between the result and the predetermined amount of decrease in the reflected light amount and the toner band amount at that time (FIG. 8). The toner amount in FIG. 8 is converted with a single color solid image as FF.

The gloss recovery toner image whose density distribution has been determined is supplied for one round of the belt in accordance with the surface of the elastic intermediate transfer belt (S9). That is, the control unit 300 drives the image forming unit based on the determined density distribution to form a gloss return toner image. The toner used in the gloss recovery mode can be any color, but in this embodiment, a color with a large amount of toner for replenishment and a color with a small number of developer counters are used, and if the length of one belt is long, a plurality of colors are used. Is preferable. Further, the FF of a solid monochrome image in the present embodiment corresponds to a toner applied amount of 0.5 mg / cm ² .

  After the gloss return toner image is supplied, if the reflected light amount of the belt has been recovered (S10), the toner image supply is stopped and the process returns to the normal job (job) (S11). If the reflected light amount on the belt is reduced by 20% from the initial value or the recorded value even after the toner band is supplied (S10), a gloss return toner image is formed again for one round of the belt (S12), and the normal job Return to (S11). At that time, the maximum value of the reflected light amount value measured in S10 is stored for the next gloss return mode operation determination (S13). When the job is completed, it enters a standby or sleep state.

  In the gloss return mode, the secondary transfer roller 140 is separated from the elastic intermediate transfer belt 181, and the gloss return toner image is cleaned while being rubbed by the cleaning blade 116 a of the belt cleaning device 116. Toner, toner external additives, paper dust and the like adhering to the surface of the belt 181 are scraped off together with the toner when the toner is scraped off by the cleaning blade 116a.

  According to the present embodiment, the smaller the gloss on the surface of the elastic intermediate transfer belt 181, the greater the toner amount of the gloss recovery toner image. Therefore, the smaller the gloss, the more the gloss can be recovered and the gloss level difference is reduced. Can be reduced. Further, since the toner amount is changed in accordance with the gloss, the toner consumption for reducing the gloss level difference can be suppressed. That is, it is considered that a lot of toner, toner external additives, paper powder, and the like are attached to the portion where the gloss is lowered. For this reason, by supplying a large amount of toner to such a portion and facilitating the removal of such deposits, it is possible to restore the gloss and reduce the gloss level difference. On the other hand, since it is considered that there is little adhered matter in the portion where the gloss reduction is small, the amount of toner to be supplied can be reduced and the amount of toner consumed can be suppressed. In this embodiment, since the gloss level difference can be reduced in this manner, patch detection accuracy and transferability, in particular, halftone uniformity, and ATVC control accuracy that is transfer electric field control can be improved.

<Second Embodiment>
A second embodiment of the present invention will be described with reference to FIGS. In the first embodiment described above, in order to confirm the surface state of the elastic intermediate transfer belt, the reflected light amount values in the width direction on the elastic intermediate transfer belt are monitored. On the other hand, in this embodiment, as shown in FIG. 10, a plurality of optical sensors 200 (9 in this embodiment) are arranged in the width direction of the elastic intermediate transfer belt 181, and the surface state (reflection) of the belt 181. 9) is monitored. That is, in the case of the present embodiment, one optical sensor 200 is arranged for each of the areas obtained by dividing the surface of the belt 181 into nine parts in the width direction orthogonal to the toner image conveyance direction. Then, the reflected light amount value is measured at one location for each region.

  In the case of the present embodiment, as shown in FIG. 11, a video counter 302 as an integration unit integrates video count values based on image signals input from an original reading apparatus or an external terminal. That is, in the image forming mode in which the toner image carried on the elastic intermediate transfer belt 181 is transferred to the recording material, the video counter 302 integrates the output value for each pixel based on the input signal.

  Moreover, such an output value is memorize | stored in the memory | storage part 301 which is a 2nd memory | storage means. The storage unit 301 also associates the amount of reflected light measured by the optical sensor 200 over the entire surface of the belt 181 with the output value accumulated by the video counter 302 of the pixel corresponding to the measurement portion. Remember. That is, the amount of reflected light at each position is measured by the nine optical sensors 200 for one rotation of the belt, and the amount of reflected light at each position is stored in correspondence with the output value accumulated at the measured position. In this state, the measurement portion measured by the optical sensor 200 exists in a state where data of the measured reflected light amount value and the integrated output value correspond to each other over the entire circumference.

  On the other hand, in the non-measurement part where the optical sensor 200 is not arranged, there is data of the integrated output value, but there is no measurement value. In the present embodiment, the reflected light amount value of the part to be measured is predicted from the data of the measurement part. That is, the amount of reflected light on the surface of the all-elastic intermediate transfer belt is predicted from the integrated video count value (output value) at the nine points where the optical sensor 200 is disposed. Then, the gloss return mode operation timing, the supply amount and supply position of the gloss return toner image are determined.

  For this reason, the control unit 300 outputs an output value close to the output value of the pixel corresponding to the non-measurement portion among the output values stored in the storage unit 301 of the same region with respect to the reflected light amount of the non-measurement portion of each region described above. The gloss return mode is executed on the assumption that the amount of reflected light is stored in association with. That is, the output value integrated by the video counter 302 of the non-measurement part is compared with the output value integrated by the measurement part, and the data of the measurement part having the closest output value is selected. Then, the data of the selected measurement part is used as the reflected light amount value of the non-measurement part.

  More specific description will be given below. First, as shown in FIG. 10, the arrangement of the optical sensor 200 is at the positions (1) to (9). This is because the recording material, especially paper filler (talc, calcium carbonate, white clay, etc.) and paper dust adhere to the surface of the elastic intermediate transfer belt, which affects the surface properties of the belt. Have taken. For example, the middle sensor (5) can know the surface state of the belt based on the influence of whatever size of recording material is passed. On the contrary, the sensor (1) is only A3 size recording material, and can know the surface condition of the belt based on the effect of no paper when recording material smaller than A3 size is passed. As described above, with the arrangements (1) to (9), the influence of the recording material of A3, B4, A4R, B5, and postcard size and the influence of unevenness in the width direction of the elastic intermediate transfer belt can be obtained. You can know the surface condition of the belt based on this.

  Next, the influence of the toner concentration that affects the surface properties of the belt will be described. Changes in the gloss value of the elastic intermediate transfer belt when images having different toner densities in the width direction as shown in FIG. 12A are continuously printed using the image forming apparatus of FIG. 2 are shown in FIG. Shown in Thus, the influence on the surface of the elastic intermediate transfer belt varies greatly depending on the toner concentration. Therefore, in this embodiment, how much toner is formed on the surface of the elastic intermediate transfer belt is monitored using a video count method.

  This video count method will be described. A document image formed on a CCD sensor (not shown) is converted into an analog electric signal by the CCD sensor. The converted image information is input to an analog signal processing unit, sampled and held, dark level correction, etc., and then analog / digital converted (A / D conversion) by an A / D / SH processing unit. Further, shading correction is performed on the digitized signal. In the shading correction, correction for variation of each pixel of the CCD sensor and correction of variation in light quantity depending on the position based on the light distribution characteristics of the document illumination lamp are performed.

  Thereafter, an RGB line correction is performed in the RGB line correction unit. Since the light input to the RGB light receiving portions of the CCD sensor at a certain time is shifted on the original according to the positional relationship of the RGB light receiving portions, the RGB signals are synchronized here.

  Thereafter, an input masking process is performed by the input masking unit to convert luminance data into density data. Since the RGB value as it is output from the CCD sensor is affected by the color filter attached to the CCD sensor, the influence is corrected and converted to a pure RGB value.

  Thereafter, the image is scaled at a desired scaling factor in the scaling unit, and the scaled image data is sent to the image memory unit and stored therein. The stored image is first sent image data from the image memory unit to the γ correction unit. In the γ correction unit, a density corresponding to a desired output density is obtained from the original density data based on a look-up table (LUT) in consideration of the characteristics of the printer in order to obtain an output corresponding to the density value set in the operation unit. Convert to data. Next, the density data is sent to the binarization unit. The binarization unit converts an 8-bit multilevel signal into a binary signal. For example, a dither method, an error diffusion method, an improved error diffusion, or the like is used as this conversion method. The binarized data is sent to the video count unit, and binarized data is counted for each color image.

  Next, the details of the video counter are shown. The video counter counts output values for each color. The image signal for one color sent from the binarization unit counts the image signal for one image (pixel) by a 29-bit counter (each color) in parallel every 8 bits. These results are added by a 32-bit adder to obtain a video count for one image as 32-bit data.

  That is, the video count value is obtained by counting the number of image signals for one image in the image signal processing read from the reader unit in the image processing unit. Also, from this video count value, binarized data of density data obtained by the image processing unit is extracted, and the image density of the toner image formed on the intermediate transfer belt 181 is obtained.

  In the present embodiment, the integrated value of the video count value corresponding to the positions of the optical sensors (1) to (9) described above is stored in the storage unit 301 and used to predict the reflected light amount of the belt. Next, the gloss return mode will be described with reference to the flowchart of FIG. The flow of the present embodiment is different from the flow of the first embodiment (FIG. 9) in that S71 and S72 are inserted between S7 and S8. Since the other points are substantially the same as those in FIG. 9, S71 and S72 and the flow around them will be described.

  In S7, the amount of reflected light for one round of the belt is measured at the position where the optical sensor 200 is disposed. For example, the optical sensor 200 measures the circumference of the belt 1150 equally (approximately 10 mm intervals). The belt reflected light quantity value in the width direction at that time is stored together with the circumferential position obtained from the belt home position detection sensor 201. That is, 1150 pieces of measurement data are stored for one sensor.

  In the present embodiment, each optical sensor 200 is arranged with the presence or absence of paper as described above. Specifically, the region (1) is 128.5 to 165 mm from the center of the belt to the front. The area (2) is 105 to 128.5 mm. The area (3) is 91 to 105 mm in front. The area (4) is 74 to 91 mm in front. The area (5) is 0 to 74 mm in front. The area (6) is 74 to 91 mm in the back. The area (7) is 91 to 105 mm in the back. The area (8) is 105 to 128.5 mm at the back. The area (9) is 128.5 to 165 mm in the back. Based on the information of the optical sensor 200 arranged in each of these areas, the expected reflected light amount value of all the belts is calculated.

  As a method of calculating the expected reflected light amount value, the video count values of the measurement part and the non-measurement part are respectively read from the storage unit 301 (S71). Then, the reflected light amount value of the measurement portion having a video count value close to the video count value of the non-measurement portion is predicted to be the reflected light amount value of the non-measurement portion (S72). Thus, the reflected light amount value of the entire belt 181 can be obtained, and the density distribution of the gloss return toner image is determined based on the reflected light amount value (S8). The subsequent steps are the same as in the first embodiment.

  In the case of this embodiment configured as described above, the number of optical sensors 200 can be reduced as compared with the first embodiment, so that the cost can be reduced. Other structures and operations are the same as those in the first embodiment.

<Third Embodiment>
A third embodiment of the present invention will be described with reference to FIGS. In the second embodiment described above, in order to confirm the surface state of the elastic intermediate transfer belt, the reflected light amount value of the belt is monitored by nine optical sensors in the width direction on the elastic intermediate transfer belt. On the other hand, in the present embodiment, the optical sensor 200 is monitored at one point in the width direction of the elastic intermediate transfer belt 181, and the accumulated video count value of the one point portion, the recording material size, and the number of sheets to be passed are information. Then, the toner supply amount and supply position of the gloss return toner image are determined. The gross return mode is operated every predetermined job count. In this embodiment, for example, every 200 job counts.

  That is, the control unit 300 detects the size of the recording material and the number of sheets to be passed, and uses the value assumed as the amount of reflected light of the non-measurement portion in the area where the sensor is disposed, Correction is made so that the amount of reflected light becomes smaller as the number of sheets passing through the measurement portion is smaller. Note that the size of the recording material can be detected by user selection or automatic selection by the apparatus, and the number of sheets to be passed is detected by integrating signals from sensors that detect the passage of the recording material arranged in the recording material conveyance path. Is possible.

  In the present embodiment, as described above, one optical sensor 200 is disposed and the amount of reflected light on the surface of the elastic intermediate transfer belt 181 is measured. This optical sensor 200 is shown in (10) of FIG. It is arranged at the position. This is because the recording material, especially paper filler (talc, calcium carbonate, white clay, etc.) and paper dust adhere to the surface of the elastic intermediate transfer belt, which affects the surface properties of the belt. Have taken. The position of (10) can know the surface state of the belt based on the influence of whatever size of recording material is passed.

  Similarly to the second embodiment, the video count value (the integrated value of the output level of the digital image signal) corresponding to the position of the optical sensor 200 is stored in the storage unit 301. Further, in order to predict the surface property of the elastic intermediate transfer belt 181 in the width direction, the size of the recording material and the number of sheets to be passed are acquired by the control unit 300 and recorded in the storage unit 301 as shown in FIG.

  Next, the gloss return mode will be described with reference to the flowchart of FIG. In addition, S1-S3 of the flow of this embodiment is the same as the flow (FIG. 9) of the above-mentioned 1st Embodiment. In this embodiment, the gloss return mode is activated when the number of sheets to be passed becomes 200 from the initial state or when the previous gloss return mode was activated (S104). When the gloss return mode operation timing comes, the belt home position detection sensor 201 measures the reflected light amount value for one belt while monitoring the circumferential position of the belt. The belt reflected light amount value in the width direction at that time is stored together with the circumferential position obtained from the belt home position detection sensor 201 (S105). Next, similarly to S71 and S72 of the second embodiment, an expected reflected light amount value in the width direction is calculated using the integrated video count value. In the present embodiment, since there is one optical sensor, the entire range in the belt width direction is calculated using the optical sensor 200 arranged in (10) (S106, S107).

Next, the predicted reflected light amount value calculated above from the information on the size and number of recording materials is corrected using the following formulas (S108, S109).
α = A (optical sensor position) + {(Ps−Px) / Ps} × 25
α: Expected reflected light amount value after correction A (optical sensor position): Reflected light amount value at optical sensor position Ps: Number of sheets passed at optical sensor position Px: Number of sheets passed at position to be calculated

  Note that {(Ps−Px) / Ps} is the rate of decrease in the number of sheets that pass through the calculated position of the optical sensor, but this is multiplied by 25 because the reflected light amount of the belt decreases depending on the presence or absence of paper. This is because the ratio changes 25 times. Further, in the case of the present embodiment, the calculated position is, for example, a position that is divided into 1150 equal parts for one round of the belt and divided at intervals of 10 mm in the width direction. From the predicted reflected light amount value obtained above, the gloss return is determined from the relationship between the predetermined decrease in the reflected light amount value and the toner band amount at that time (FIG. 8), as in S8 and S9 of the first embodiment. The density distribution of the toner image is determined (S110). The toner image whose density distribution has been determined is supplied for one round of the belt in accordance with the surface of the elastic intermediate transfer belt (S111). After supplying the toner image, the process returns to the normal job (S112). When 200 sheets are further passed, the gloss return mode is activated.

  In the case of this embodiment configured as described above, the number of optical sensors 200 can be reduced as compared with the first and second embodiments, so that the cost can be further reduced. Other structures and operations are the same as those of the second embodiment.

<Other embodiments>
In each of the above-described embodiments, the tandem structure has been described. However, the present invention can also be applied to a one-drum structure having one photosensitive drum. Moreover, the above-described embodiments can be implemented in combination as appropriate. For example, the control for correcting in consideration of the presence or absence of paper in the third embodiment can also be applied to the first or second embodiment. In the third embodiment, the gloss return mode is performed every 200 sheets. However, as in the first and second embodiments, the relationship with the maximum reflected light amount value in the previous gloss return mode. The mode execution may be performed with

  Further, in each of the above-described embodiments, the structure using the optical sensor as the detection unit that detects the surface state of the belt 181 has been described. However, such a detection means is not limited to an optical sensor, and may be, for example, a value that detects a value related to the surface roughness of the belt 181. For example, if a roller is brought into contact with the belt 181 and the torque of the roller is detected, the surface roughness of the belt 181 can be detected. Since the gloss also changes depending on the surface roughness, the density distribution of the gloss return toner image can be derived from this point.

<Example>
Next, in order to confirm the effects of the first to third embodiments, in the image forming apparatus as shown in FIG. 2, when the respective controls of the above embodiments are turned on and when the controls are not turned on. Experiments were conducted to observe the surface state of the elastic intermediate transfer belt and to confirm the operation of the image forming apparatus. In this experiment, in the full-color mode, a process speed as a moving speed of the elastic intermediate transfer belt 181 was set to 150 mm / sec, and a paper passing test was repeatedly performed with a plain paper 100 continuous mode A4R feed. As the image, an image having a different toner density in the width direction as shown in FIG. 17 was used so that the gloss level difference of the belt is more likely to occur. The experimental environment was a high-temperature and high-humidity environment with a temperature of 30 ° C. and a humidity of 80 RH%, where the belt surface was likely to be adhered.

  The gloss value of the surface of the belt was measured with 35 points in the belt width direction and 20 points in the width direction using a handy GROSSMETER PG-1 manufactured by Nippon Denshoku Industries Co., Ltd., and the average value and standard deviation of all the gloss values were measured. Compared. The measurement was confirmed initially after passing 10,000 sheets, after passing 500,000 sheets, and after passing 1 million sheets. Table 1 shows the results of the above experiment. In Table 1, Example 1 corresponds to the configuration of the first embodiment, Example 2 corresponds to the configuration of the second embodiment, and Example 3 corresponds to the configuration of the third embodiment.

  Table 1 shows the average value of the gross value and the standard deviation value in parentheses. In general, the gloss value works well when it is 40 or more for reading by a sensor, and within 10 standard deviations for ensuring transferability and ATVC control accuracy. As shown in Table 1, the belt without any control has a large degree of gloss reduction, and the standard deviation value representing in-plane variation is considerably large at 16.2. On the other hand, it was confirmed that any of the devices in which the control of the present embodiment was added had a low degree of gloss reduction and a small in-plane variation.

  101a, 101b, 101c, 101d ... photosensitive drum, 111a, 111b, 111c, 111d ... exposure device, 116 ... belt cleaning device, 116a ... cleaning blade, 122a, 122b, 122c, 122d,. Primary charger, 123a, 123b, 123c, 123d ... developer, 181 ... elastic intermediate transfer belt (intermediate transfer member), 181b ... elastic layer, 140 ... secondary transfer roller (transfer means) ), 200 ... Optical sensor (detection means), 200-1 ... Line sensor (detection means), 300 ... Control section (control means), 301 ... Storage section (storage means, second Storage means), 302... Video counter (accumulation means), Pa, Pb, Pc, Pd... Image forming unit, P.

Claims (6)

An image forming unit for forming a toner image;
An intermediate transfer member having an elastic layer and carrying and conveying the toner image transferred from the image forming unit;
An image forming apparatus comprising: a transfer unit that transfers a toner image carried on the intermediate transfer member to a recording material;
A cleaning blade that is positioned downstream of the transfer means in the toner image conveyance direction of the intermediate transfer member and contacts the surface of the intermediate transfer member to clean the surface of the intermediate transfer member;
Detecting means for detecting a surface state of the intermediate transfer member in a state where a toner image is not carried;
A gloss recovery toner image is formed in the image forming unit so that the toner amount increases as the gloss of the surface of the intermediate transfer member, which can be derived from the detection result of the detection means, increases and is carried on the intermediate transfer member. Control means for executing a gloss return mode for cleaning the gloss recovery toner image by the cleaning blade without transferring the toner image to the recording material.
An image forming apparatus. The detection means is an optical sensor that irradiates light onto the surface of the intermediate transfer member and measures the amount of reflected light.
The control unit causes the image forming unit to form a toner image so that the toner amount increases in a portion where the amount of reflected light on the surface of the intermediate transfer member detected by the optical sensor is lower in the gloss return mode.
The image forming apparatus according to claim 1, wherein: Storage means for storing a maximum value of the amount of reflected light on the surface of the intermediate transfer body detected by the optical sensor in the gloss return mode;
The control unit is configured such that a portion where the reflected light amount detected by the optical sensor decreases by a predetermined value or more with respect to the maximum value of the reflected light amount in the previous gloss recovery mode stored by the storage unit is a surface of the intermediate transfer member. Executing the gross return mode if present
The image forming apparatus according to claim 2, wherein: Integration means for integrating output values for each pixel in an image forming mode in which the toner image carried on the intermediate transfer member is transferred to a recording material;
Second memory for storing the amount of reflected light measured by the optical sensor over the entire surface of the intermediate transfer member in the toner image conveying direction in association with the output value accumulated by the integrating means of the pixels corresponding to the measurement portion. Means,
The optical sensor is arranged one by one for each region obtained by dividing the surface of the intermediate transfer member into one or a plurality of regions in the width direction orthogonal to the toner image conveying direction,
The control unit is configured to calculate a reflected light amount of a non-measurement portion in which the optical sensor in the region is not disposed, out of output values stored by the second storage unit in the same region, of pixels corresponding to the non-measurement portion. Assuming that the amount of reflected light is stored in association with an output value close to the output value integrated by the integration means, the gloss return mode is executed.
The image forming apparatus according to claim 2, wherein the image forming apparatus is an image forming apparatus. The control means detects the size of the recording material and the number of sheets to be passed, and assumes the value assumed as the amount of reflected light of the non-measurement portion of the area, and passes the measurement portion in the area where the number of sheets to be passed of the non-measurement portion is the same. Correct so that the amount of reflected light is smaller as the number is smaller.
The image forming apparatus according to claim 4, wherein: The intermediate transfer member is an endless belt composed of a plurality of layers having different elastic moduli of at least two layers.
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

Images