JP2017187795A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device for preventing an erroneous detection of an image flow level even when using regenerated paper and imported paper containing a large amount of fillers independently of a use state and a use environment, capable of performing the detection of a correct image flow level and executing an image flow recovery action according to the image flow level.SOLUTION: When reaching the execution timing of the predetermined image flow recovery action, the control device forms a pattern image for image flow detection in the photoconductor drum (step S11), makes the pattern image for image flow detection read by a concentration sensor (step S13), and determines an image flow level from a detection result of the concentration sensor (step S15). When it is determined that an image flow recovery operation is necessary (Yes of step S16), a control part determines an image flow recovery operation execution time according to the image flow level (step S17), and makes the image flow recovery operation executed based on the determined image flow recovery operation time (step S18).SELECTED DRAWING: Figure 11

Description

  The present invention relates to an image forming apparatus that performs an image flow recovery operation for cleaning the surface of an image carrier to recover the image flow.

  Conventionally, in an electrophotographic image forming apparatus, a photosensitive drum is charged by a charging device, exposed by an exposure device, an electrostatic latent image is formed in accordance with the image data, and the electrostatic latent image is converted into toner by a developing device. Then, the toner image is transferred to a sheet and fixed, and image formation is performed. Here, in image formation, a phenomenon called image flow may occur.

  Here, the phenomenon called the above-described image flow will be described. The charging device charges the photosensitive drum by a discharge or the like with a relatively large voltage, and ozone or nitrogen oxides are generated by this high voltage discharge phenomenon and adhere to the surface of the photosensitive drum. The adhering ozone, nitrogen oxide, etc. oxidize the surface of the photosensitive drum to increase hydrophilicity.

  If moisture adheres to the surface of the photosensitive drum having increased hydrophilicity due to moisture or condensation in the air, the resistance of the surface of the photosensitive drum at the adhered portion decreases, and charging of the charging device occurs during image formation. The electric charge due to cannot be held on the surface of the photosensitive drum, and the potential cannot be maintained. As a result, an image that flows as a whole (image flow) is formed, which causes a reduction in image quality. This phenomenon is called image flow.

  When the image flow phenomenon as described above occurs, toner is attached to the photosensitive drum, and the photosensitive drum is polished by a blade or a rubbing roller to remove the attached ozone or nitrogen oxide, so-called aging. By this method, the cause of image flow is removed and a normal image is restored. The following configuration is known as a configuration for performing such a recovery operation.

  In Patent Document 1, a fixed pattern image for detecting image flow is developed on the surface of a photoconductor, the density is measured by a density sensor, and image flow occurs when the density is equal to or less than a set threshold value. In other words, a configuration is described in which the surface of the photosensitive member is recovered by the image flow recovery operation means.

  Japanese Patent Application Laid-Open No. 2005-228561 describes an image flow recovery operation in which toner is put on a photosensitive drum and rotated, and is polished by a cleaning member to clean the surface of the photosensitive drum. Before the image flow recovery operation, a pattern image for density detection is formed on the photosensitive drum, the pattern image is read by the detector, and the generation level of the image flow is determined from the read result. A configuration is described in which the image flow recovery operation time is changed according to the above.

  Patent Document 3 describes a configuration in which the friction resistance value of the photosensitive drum is detected based on the density of the toner image for density detection, and the AC voltage is reduced when a value larger than a predetermined friction resistance value is detected. Has been. According to this configuration, foreign matters such as discharge products can be prevented from adhering to the photosensitive drum, and an increase in the frictional resistance value can be suppressed, thereby preventing image flow.

JP 2004-126296 A JP 2010-32758 A JP 2010-60680 A

  However, in Patent Document 1, since the occurrence of image flow is determined only with a certain threshold value, even when a slight image flow occurs or when the threshold value is slightly exceeded, the image flow recovery operation for a certain time is performed. In some cases, the image flow recovery operation may be performed more than necessary. In other words, there is a problem that the image flow restoration operation cannot be performed in accordance with the level of occurrence of the image flow.

  On the other hand, in Patent Document 2, the aging operation time (image flow recovery operation time) is changed according to the occurrence level of the image flow and the apparatus stop time. However, since the pattern image for density detection is a solid image or a halftone, it is not considered that the density change characteristic of the image flow level changes depending on the pattern formation conditions of the pattern image. For example, in the case of a solid image or a halftone pattern image, it is difficult to distinguish from a density drop due to a decrease in developability due to durability or the like, and the density change with respect to a slight image flow is slow, so that a slight image flow is detected. I can't. Also, as the image flow level worsens, the density stops at once, and it is possible to detect a decrease in density due to the image flow, but at that level, the character image has reached a level where it cannot be decoded and the detection timing is It is almost too late, and the range that can be detected accurately is narrow. Also, in the case of pattern images such as horizontal ruled lines, there are line widths and line intervals that are easily affected by mechanical banding, etc., so it is difficult to distinguish them from density changes due to banding effects. The possibility of detection is high, and the image flow level cannot be detected with high accuracy.

  In addition, the use of recycled paper has been increasing year by year in response to increasing awareness of environmental issues in recent years. A large amount of filler is added to the recycled paper as compared with the conventional paper in order to improve the paper quality. Recently, paper imported from overseas has been widely used in the country. This imported paper contains more filler than domestic paper. In addition, these recycled and imported paper powders are easily charged negatively by sliding on the feeding and conveying unit during feeding and feeding, but both sides of the paper are strongly fed and conveyed. The amount of paper powder charged on the positive polarity side increases depending on the material used for conveyance. When these paper dusts reach between the transfer and the photosensitive drum, they are attracted to the photosensitive drum which is electrically charged to negative polarity. For this reason, paper dust tends to adhere to the photosensitive drums at the edge positions on both sides of the paper when the paper is passed, and it enters into recesses such as scratches on the photosensitive drum and fine grooves due to polishing during manufacturing, and images such as image flow Cause defects.

  Further, in Patent Document 3, with respect to the image flow caused by the paper dust as described above, the change in the frictional resistance value due to the paper dust of the paper adhering to the photosensitive drum, and the discharge product are exposed to light. A change in the frictional resistance value due to adhesion on the body drum is synthesized. Therefore, there is a high possibility of erroneous detection of the image flow level, and the image flow level cannot be detected with high accuracy. Further, since Patent Document 3 does not sufficiently consider paper dust affected by static electricity, it is not sufficient as a countermeasure against image defects caused by paper dust.

  The object of the present invention is to prevent erroneous detection of the image flow level and to accurately detect the image flow level even when recycled paper or imported paper containing a large amount of filler is used, regardless of the use state and use environment of the main body. The image flow recovery operation is executed in accordance with the image flow level.

  In order to achieve the above object, the present invention provides an image forming unit for forming a toner image on an image carrier, and a plurality of lines formed by the image forming unit on the image carrier in the rotation direction of the image carrier. Detecting means for detecting the density of the first toner image formed with a gap and the second toner image formed with a thicker line than the first toner image; and cleaning the image carrier. A cleaning unit; and a control unit that causes the cleaning unit to perform a cleaning operation for a time determined based on the detection results of the densities of the first and second toner images detected by the detection unit. To do.

  According to the present invention, regardless of the state of use of the main body and the usage environment, even if recycled paper or imported paper containing a large amount of filler is used as a recording material, erroneous detection of the image flow level is prevented, and an accurate image flow level is prevented. It is possible to perform detection and perform an image flow recovery operation according to the image flow level. This makes it possible to eliminate the image flow accurately even with a simple configuration, minimize the image flow recovery operation, reduce the toner consumption and power consumption, and shorten the waiting time of the user until printing is possible. It is possible to provide an image forming apparatus.

1 is a longitudinal sectional view of an image forming apparatus according to an embodiment of the present invention. It is a conceptual diagram of the charging device of the present invention. FIG. 3 is a diagram illustrating details of a general fixing device. It is a figure showing the layer structure of the photoconductor of this invention. It is a schematic block diagram of the concentration sensor of this invention. (A) It is a surrounding surface developed view of the photosensitive drum 1 of the present invention. (B) A pattern image diagram for image flow detection according to the present invention and definitions of P1 and P2. (A) It is a density transition at the time of image flow occurrence of the image flow detection pattern images P1 and P2. (B) An actual line enlarged image before occurrence of image flow (normal density). (C) An actual line enlarged image after the occurrence of image flow (at the time of maximum density). It is a solid line ratio by line width which is an embodiment of the present invention. It is a model diagram of toner on paper before and after banding of P1 and P2 of the present invention. (A) It is an example of table tb1 used when determining the image flow recovery operation execution time according to the output of the density sensor. (B) It is a figure which shows an example of the change of the output value of the density sensor of P1 and P2 according to an image flow level. 6 is a flowchart illustrating an example of image flow recovery operation control of the image forming apparatus main body T according to the embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, what attached | subjected the same code | symbol in each drawing has the same structure or effect | action, The duplication description about these was abbreviate | omitted suitably. Here, the device configuration, components, dimensions, materials, shapes, and other relative arrangements described in the following embodiments are within the scope of the present invention unless otherwise specified. It is not intended to limit only to them.

  FIG. 1 shows a schematic configuration of an image forming apparatus according to the first embodiment. In the present embodiment, a laser beam printer will be described as an example of the image forming apparatus.

  First, the configuration of the laser beam printer will be described with reference to FIG. This laser beam printer includes a photosensitive drum 1 as an image carrier having a photoconductive layer such as OPC or a-Si. The photosensitive drum 1 is rotatably supported by the apparatus main body T, and is driven to rotate at a predetermined speed in the direction of arrow A by a main motor (not shown). Around the photosensitive drum 1, a charging roller 2 as a charging device that uniformly charges the photosensitive drum 1 in almost the order along the rotation direction, and a laser scanner that is an exposure means for forming an electrostatic latent image. 3. A developing device 4 for visualizing the electrostatic latent image with toner, a transfer roller 5 serving as a transfer device for transferring the toner image on the photosensitive drum 1 to the recording material P, and the photosensitive drum 1 A cleaning device 6 is provided for collecting the remaining untransferred toner with a cleaning blade 6a.

  A cleaning brush rotating body 40 that cleans the surface of the charging roller 2 is pressed against the charging roller 2 with a predetermined pressure. The cleaning brush rotating body 40 has a brush body 43 made of a pile fabric, and is cleaned by pressing the charging roller 2 with a predetermined pressure and rotating by driving input from the charging roller 2.

  A feeding cassette 7 that stores the recording material P is disposed below the apparatus main body T, and a fixing device 8 is disposed above the photosensitive drum 1. A control unit 11 that controls an image forming operation and the like and a high-voltage power source unit 10 that applies a high voltage to the charging roller 2 and the developing device 4 are disposed on the back of the apparatus main body T. On the control unit 11, a main body CPU 11a that issues a command to execute an image forming operation and the like, a fixing CPU 11b that executes fixing temperature control and the like, and a memory 11c that stores programs and the like are mounted. Here, on the high-voltage power supply unit 10, a charging application power supply 10 a configured by a DC power supply and an AC power supply, a development application power supply 10 b configured by a DC power supply and an AC power supply, and positive and negative, respectively. And a transfer application power source 10c constituted by a direct current power source. The operation of the printer is realized by various CPUs on the control unit 11 reading necessary programs from the memory 11c and executing various controls.

  Next, the operation of the laser beam printer configured as described above will be described in the order of (1) charging, (2) exposure, (3) development, (4) transfer, (5) fixing, and (6) cleaning.

(1) Charging FIG. 2 shows details of the contact charging device in the image forming apparatus of this embodiment. The charging roller 2 that is in contact with the photosensitive drum 1 that is rotationally driven in the direction of arrow A by a main motor (not shown) with a predetermined pressure is rotationally driven in the direction of arrow B (see FIG. 1), and the high-voltage power supply unit 10 is charged. A predetermined DC voltage (DC charging method) or a voltage (AC + DC charging method) obtained by superimposing a predetermined DC voltage and a predetermined AC voltage is applied as a charging bias from the charging roller 2 through the metal shaft of the charging roller 2 from the power source 10a. . As a result, the surface of the photosensitive drum 1 that is rotationally driven at a predetermined speed is uniformly contact-charged to a predetermined polarity and potential (in the present embodiment, −500 to −800 V). In the present embodiment, the charging roller cleaning brush rotator 40 is also applied with a bias having the same polarity branched from the charging application power supply 10 a supplied to the charging roller 2. The bias applied to the charging roller cleaning brush rotator 40 may be the same as the high voltage power source applied to the charging roller 2 or may be a separate power source.

  The charging roller 2 is a conductive elastic roller having a roller shaft (conductive support, cored bar). The charging roller 2 rotatably supports both end portions of the roller shaft body via bearing members, and the roller axis is arranged substantially in parallel with the drum axis of the photosensitive drum 1 with respect to the photosensitive drum 1. They are arranged in contact with each other with a predetermined pressing force. In this embodiment, the charging roller 2 rotates following the rotation of the photosensitive drum 1. The charging roller 2 has a spring load (not shown) as a charging roller cleaning brush rotating body 40 composed of a brush 43 made of a pile fabric on a roller shaft (conductive support, core metal) (in this embodiment, One side 100-300 gf) is arranged with a predetermined pressing force. In this embodiment, the contact charging method using the charging roller 2 is adopted. However, the charging method is not limited to the contact charging method as long as the photosensitive drum 1 is charged to the negative polarity.

(2) Exposure The charged photosensitive drum 1 is subjected to image exposure on the surface by a laser scanner 3 as an exposure means based on the image information, and the charge of the exposed portion is removed to form an electrostatic latent image. Is done. In this embodiment, the exposure is performed by scanning exposure with a semiconductor laser (wavelength 780 nm). However, as long as the photosensitive drum 1 can be exposed, exposure using an LED array may be used instead of a semiconductor laser. Absent.

(3) Development The electrostatic latent image on the photosensitive drum 1 formed by exposure is developed by the developing device 4. The developing device 4 in this embodiment has a developing sleeve 4a having a predetermined surface roughness by coating the surface of an aluminum roller with blasting or carbon. The developing device 4 applies a developing bias (AC + DC charging system) in which a predetermined DC voltage and a predetermined AC voltage are superimposed on the developing sleeve 4 a from the developing application power source 10 b of the high-voltage power supply unit 10, thereby static electricity on the photosensitive drum 1. Toner is attached to the electrostatic latent image and developed as a toner image (visualization). The developing method in this embodiment is a one-component reversal jumping developing method using a one-component magnetic negative toner, but there is another method of developing in a contact state with respect to the photosensitive drum 1 (one-component contact development). In addition, a method in which a magnetic carrier is mixed with toner as a developer, the developer is conveyed by magnetic force, and developed in contact with the photosensitive drum 1 (two-component contact development), or the two components described above. There is a method of developing the developer in a non-contact state with respect to the photosensitive drum 1 (two-component non-contact development method), and any of them can be suitably used.

(4) Transfer The toner image developed on the photosensitive drum 1 is rotationally moved to the transfer roller 5 by the rotational driving of the photosensitive drum 1. In accordance with this timing, the recording material P stored in the feeding cassette 7 is conveyed by a feeding roller and a conveying roller (not shown), and is conveyed to a transfer nip portion N between the photosensitive drum 1 and the transfer roller 5. The Then, at a timing when the recording material P is conveyed to the transfer nip portion N, a predetermined DC voltage having a polarity opposite to that of the developer is applied to the transfer roller 5 from the transfer application power source 10c of the high-voltage power source unit 10, thereby the photosensitive drum 1 The toner images attached to the toner image are sequentially electrostatically transferred onto the recording material P (in this embodiment, since the toner has a negative polarity, a positive DC voltage (+1 to 5 KV) corresponding to the opposite polarity is applied to the transfer roller 5. ing). In this embodiment, a contact transfer roller system that contacts the photosensitive drum 1 is used, but in addition, a non-contact corona discharge transfer system that discharges by applying a high voltage of 20 to 30 KV to tungsten or gold wire, An intermediate transfer belt system in which a toner image is transferred to a transfer belt made of ITB and then transferred to a recording material P may be used. The transfer roller 5 in this embodiment is an ion conductive rubber roller in which a sponge rubber obtained by foaming a mixed rubber of NBR rubber (acrylonitrile butadiene rubber) and hydrin rubber is disposed on a metal roller shaft. An electronic conductive rubber roller in which carbon black is dispersed in rubber (ethylene-propylene-diene copolymer) may be used, and any of them can be suitably used.

(5) Fixing Next, the fixing device 8 will be described with reference to FIG. The recording material P electrostatically carrying the toner image is conveyed to the fixing device 8 along a conveyance guide (not shown). The fixing device 8 includes a fixing motor M2 that rotationally drives the fixing member 21 or the pressure member 22, a heating member 20 (a ceramic heater composed of a resistor and alumina) that is supported by the guide member 23 and heats the toner, A fixing member 21 (a fixing film made of a polyimide film having a thickness of 40 to 100 μm whose surface layer is coated with PFA or PTFE), which is a cylindrical rotating body containing the heating member 20, and the fixing member 21 are pressed and fixed. A pressure member 22 having elasticity in another fixing rotating body forming the nip portion N (a sponge rubber layer 22b obtained by foaming EPDM rubber, silicon rubber or fluoro rubber as a base layer on the rotating metal shaft 22a, silicon rubber, (Pressure roller constituted by a surface layer 22c formed of a heat-resistant resin such as fluoro rubber or fluoro resin) The made as main components. When the print signal is received, the fixing CPU 11b instructs the heating member 20 to set a predetermined temperature, and the fixing CPU 11b energizes the ceramic heater 20 until the thermistor 24 detects the predetermined temperature, so that the fixing nip N After heating and fixing the unfixed toner on the recording material P, the recording material P is discharged to a discharge tray (not shown) outside the apparatus. In this embodiment, an on-demand fixing method is used, but the present invention is not limited to this, and a heat roller method or an electromagnetic induction heating method may be used as long as the toner is fixed on the recording material P.

(6) Cleaning On the other hand, as shown in FIG. 1, after the toner image is transferred to the photosensitive drum 1, the toner or paper dust remaining on the surface of the photosensitive drum 1 without being transferred to the recording material P is removed from the cleaning blade of the cleaning device 6. It is removed by 6a. The toner collected in the cleaning device is discharged out of the apparatus by a collection toner conveyance screw (not shown) and conveyed into the collection toner box. The cleaning blade 6a in this embodiment is a blade cleaning device 6 using a casting type. The casting type is a type of cleaning blade that is molded into a desired shape by pouring a rubber material or the like into the mold. As a material of the rubber blade, for example, polyurethane, styrene-butadiene copolymer, chloroprene, butadiene rubber, ethylene-propylene-diene rubber, chlorosulfonated polyethylene rubber, fluorine rubber, silicon rubber, acrylic rubber are generally used. Any material having moderate elasticity and hardness, such as an elastomer such as nitrile rubber and chloroprene rubber, may be used. In particular, considering that the permanent set is small, a two-component thermosetting polyurethane material may be used. As the curing agent, general urethane curing agents such as 1,4-butanediol, 1,6-hexanediol, hydroquinone diethylol ether, bisphenol A, trimethylolpropane, and trimethylolethane can be used. The thickness of the strip-shaped rubber is usually 1.0 mm to 4 mm, preferably 1.5 mm to 2.0 mm. In this embodiment, a casting type cleaning blade is used, but the present invention is not limited to this. If the toner, paper powder, filler, etc. on the photosensitive drum can be removed, a plate-like adhesive type, A sandwiching type or a tip type cleaning blade may be used. Further, the cleaning blade is not particularly limited as long as it has a polishing effect.

  By repeating the above operations (1) to (6), image formation can be performed one after another.

  Hereinafter, the photosensitive drum 1 which is a functional material in the present embodiment will be described in detail.

(2) Photosensitive drum A schematic configuration of the photosensitive drum 1 used in this embodiment will be described with reference to FIG. However, the photosensitive drum is conscious of long life, and is not limited to this. The surface protective layer described this time may not be provided.

  The stacked photosensitive drum 1 used in this embodiment has a configuration in which a charge generation layer 54 containing a charge generation material and a charge transport layer 55 containing a charge transport material are stacked in order or in reverse order. Layers 54 + 55 are photosensitive layers. Further, it is possible to form a surface protective layer 56 on the photosensitive layer 53 or 54 + 55.

  Further, in order to optimize the film thickness of the electron transport layer, it is preferable to use the surface protective layer 56 in order to provide a width of the film thickness. It is sufficient that at least the surface layer of the photosensitive drum 1 contains a compound that can be polymerized or crosslinked and cured by heat, light such as visible light or ultraviolet light, and radiation.

  From the viewpoint of characteristics as a photoreceptor, particularly electrical characteristics such as residual potential and durability, a laminated photoreceptor drum is preferable. That is, a surface protective layer 56 is further formed on the functional separation type photoreceptor structure in which the charge generation layer 54 and the charge transport layer 55 are sequentially laminated, or on the photosensitive layer laminated in this functional separation type photoreceptor structure. The configuration is employed in this embodiment in order to extend the life of the photosensitive drum 1.

  As a method for curing the compound in the surface protective layer 56 in polymerization or crosslinking, the deterioration of the photoreceptor characteristics is small, the residual potential does not increase, and sufficient hardness can be exhibited. Used.

  The radiation used in generating the polymerization or crosslinking is preferably an electron beam or gamma ray. When using an electron beam of these, it is possible to use all types such as a scanning type, an electron curtain type, a broad beam type, a pulse type, and a laminar type as an accelerator.

  In the case of irradiating with an electron beam, in order to develop the electrical characteristics and durability performance of the photosensitive drum 1, the irradiation condition is preferably an acceleration voltage of 250 kV or less, and more preferably 150 kV or less. The irradiation dose is preferably in the range of 10 kJ / kg to 1000 kJ / kg, and more preferably in the range of 15 kJ / kg to 500 kJ / kg.

  When the acceleration voltage is larger than the upper limit of the above range, damage due to electron beam irradiation on the characteristics of the photoreceptor, so-called damage tends to increase. Further, if the irradiation dose is less than the lower limit of the above range, curing is likely to be insufficient. In addition, when the dose is large, the photoreceptor characteristics are likely to be deteriorated. From this viewpoint, the dose is preferably selected from the above range.

  In addition, as a compound for a surface layer that can be cured by polymerization or crosslinking, it is unsaturated in the molecule from the viewpoint of high reactivity, high reaction rate, and high hardness achieved after curing. Those containing a polymerizable functional group are preferred.

  Furthermore, among the molecules having an unsaturated polymerizable functional group in the molecule, compounds having an acrylic group, a methacryl group and a styrene group are particularly preferable.

  Moreover, the compound which has an unsaturated polymerizable functional group is divided roughly into a monomer and an oligomer by the repeating state of the structural unit. The monomer refers to a monomer having a relatively small molecular weight without repeating a structural unit having an unsaturated polymerizable functional group. On the other hand, an oligomer is a polymer having about 2 to 20 repeating units of a structural unit having an unsaturated polymerizable functional group. In addition, a so-called macronomer in which an unsaturated polymerizable functional group is bonded only to a terminal of a polymer or an oligomer can be used as a curable compound for a surface layer.

  In addition, it is more preferable that the compound having an unsaturated polymerizable functional group employs a charge transport compound in order to satisfy the charge transport function required for the surface layer. Among these charge transport compounds, an unsaturated polymerizable compound having a hole transport function is more preferable.

  As the support 51 of the photosensitive drum 1, any material having conductivity may be used. Specifically, for example, a metal such as aluminum, copper, chromium, nickel, zinc, and stainless steel, or an alloy of these metals formed into a drum or a sheet can be used. Moreover, what laminated metal foil, such as aluminum and copper, to the plastic film, and what vapor-deposited aluminum, indium oxide, tin oxide, etc. on the plastic film can be mentioned. Moreover, the metal which provided the conductive layer by apply | coating a conductive substance alone or with binder resin, a plastic film, paper, etc. can be mentioned.

  Further, an undercoat layer 52 having a barrier function and an adhesive function can be provided on the surface of the conductive support 51.

  The undercoat layer 52 is used to improve adhesion of the photosensitive layer 53 or 54 + 55, improve coating properties, protect the support 51, cover the support 51, improve charge injection from the support 51, or improve the sensitivity of the photosensitive layer 53 or 54 + 55. It is a layer formed for protection against electrical breakdown.

  As a material for the undercoat layer 52, polyvinyl alcohol, poly-N-vinylimidazole, polyethylene oxide, ethyl cellulose, ethylene-acrylic acid copolymer, casein, and polyamide can be used. Further, N-methoxymethylated 6 nylon, copolymer nylon, glue, gelatin and the like can be used. These materials are dissolved in a suitable solvent and applied to the surface of the support 51. And the film thickness of this undercoat layer 52 is 0.1-2 micrometers suitably.

  When the photoreceptor is the function separation type photoreceptor drum 1, the charge generation layer 54 and the charge transport layer 55 are laminated.

  Examples of the charge generation material used for the charge generation layer 54 include selenium-tellurium (Se-Te), pyripium, and thiapyrylium dyes. In addition, various central metals and crystal systems, specifically, for example, phthalocyanine compounds having crystal types such as α, β, γ, ε, and X type, anthanthrone pigments, dibenzpyrenequinone pigments, pyranthrone pigments, Mention may be made of trisazo pigments. Moreover, a disazo pigment, a monoazo pigment, an indigo pigment, a quinacridone pigment, an asymmetric quinocyanine pigment, a quinocyanine, an amorphous silicon, etc. can be mentioned.

  In the case of the function-separated type photosensitive drum 1, the charge generation layer 54 includes a charge generation material, 0.3 to 4 times the amount of binder resin and solvent, a homogenizer, ultrasonic dispersion, ball mill, vibration ball mill, sand mill. Disperse well by means such as attritor and roll mill. Then, the dispersion is applied and dried, or formed as a single composition film such as a vapor deposition film of a charge generation material. Here, the film thickness of the charge generation layer 54 is typically 5 μm or less, and preferably 0.1 to 2 μm.

  Examples of using binder resins include polymers and copolymers of vinyl compounds such as styrene, vinyl acetate, vinyl chloride, acrylic acid esters, methacrylic acid esters, vinylidene fluoride, and trifluoroethylene. Can do. Moreover, polyvinyl alcohol, polyvinyl acetal, polycarbonate, polyester, polysulfone, polyphenylene oxide, polyurethane, cellulose resin, phenol resin, melanin resin, silicon resin, epoxy resin, and the like can be given.

  The hole transporting compound having an unsaturated polymerizable functional group can be used as the charge transport layer 55 on the charge generation layer 54 described above. Alternatively, the charge transport layer 55 formed of the charge transport layer 55 and the binder resin can be formed on the charge generation layer 54 and then used as the surface protective layer 56.

  When a hole transporting compound is used as the surface protective layer 56, the charge transporting layer 55, which is the lower layer thereof, can select an appropriate charge transporting material from the above-described resin for charge generation layer and can be used together with an appropriate binder resin. Disperse or dissolve in solvent. Then, the solution can be formed by applying and drying by the above-mentioned known method.

  Examples of the charge transport material include a polymer compound having a heterocyclic ring or condensed polycyclic aromatic such as poly-N-vinylcarbazole and polystilanthracene. In addition, heterocyclic compounds such as pyrazoline, imidazole, oxador, triazole, or carbazole can be given. Moreover, low molecular compounds such as triarylamine derivatives such as triphenylamine, phenylresinamine derivatives, N-phenylcarbazole derivatives, stilbene derivatives, hydrazone derivatives, and the like can be given.

  If the weight of the charge transport material in the charge transport layer 55 is smaller than these ranges, the charge transport ability is lowered, and problems such as a decrease in sensitivity and an increase in residual potential occur. In this case, the thickness of the charge transport layer 55 in this example is in the range of 10 to 30 μm.

  In any case, the surface protective layer 56 is generally formed by applying a solution containing a hole transporting compound, followed by polymerization or curing reaction. It is also possible to form a surface layer using a material obtained by previously reacting a solution containing a hole transporting compound to obtain a cured product and then again dispersing or dissolving it in a solvent.

  Moreover, as a method for applying the above-mentioned solution, a dip coating method, a spray coating method, a curtain coating method, a spin coating, and the like are known. From the viewpoint of efficiency / productivity, the dip coating method is desirable as a method for applying the solution. It should be noted that other known film forming methods such as vapor deposition and plasma treatment can be appropriately selected.

  In the surface protective layer 56, conductive particles can be mixed. Examples of the conductive particles include metals, metal oxides, and carbon black.

  Specific examples of the metal as the conductive particles include aluminum, zinc, copper, chromium, nickel, stainless steel, and silver. Further, as the conductive particles, these metals can be used as plastic particles. Examples include those deposited on the surface.

  Specific examples of the metal oxide as the conductive particles include zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, and bismuth oxide. Further, indium oxide doped with tin, tin oxide doped with antimony, zirconium oxide doped with antimony, and the like can be given.

  These metal oxides can be used alone or in combination of two or more. In addition, when combining 2 or more types, it is also possible to just mix and it is also possible to give a solid solution or a melt | fusion.

  The average particle size of the conductive particles is preferably 0.3 μm or less, more preferably 0.1 μm or less, from the viewpoint of the transparency of the surface protective layer 56. Furthermore, in the conductive particle material described above, it is particularly preferable to use a metal oxide from the viewpoint of transparency.

The ratio of the conductive metal oxide particles in the surface protective layer 56 is one of the factors that directly determines the resistance of the surface protective layer. Therefore, the specific resistance of the protective layer is desirably in the range of 10 ⁸ to 10 ¹³ Ωm (10 ¹⁰ to 10 ¹⁵ Ωcm).

  The surface protective layer 56 can also contain fluorine atom-containing resin particles. Examples of the fluorine atom-containing resin particles include tetrafluoroethylene resin, trifluoroethylene resin, hexafluoroethylenepropylene resin, vinyl fluoride resin, vinylidene fluoride resin, difluorodiethylene chloride resin, and these A copolymer etc. are mentioned. And it is preferable to select at least one of these appropriately.

  And as said fluorine atom containing resin particle, especially tetrafluoroethylene resin and vinylidene fluoride resin are preferable. The molecular weight and particle size of the resin particles can be appropriately selected and are not necessarily limited to the molecular weight and particle size described above.

  The ratio of the fluorine atom-containing resin in the surface protective layer 56 is typically 5 to 40% by weight, and preferably 10 to 30% by weight with respect to the total mass of the surface layer. This is because when the proportion of the fluorine atom-containing resin particles is more than 40% by weight, the mechanical strength of the surface layer tends to be lowered, and when it is less than 5% by weight, the surface layer surface releasability and the surface layer are resistant to abrasion. This is because the wear and scratch resistance may be insufficient. In order to further improve dispersibility, binding properties and weather resistance, it is possible to add additives such as radical scavengers and antioxidants to the surface protective layer 56. The film thickness of the surface protective layer 56 is preferably in the range of 0.2 to 10 μm, and more preferably in the range of 1 to 5 μm.

(3) Toner In this example, the toner used for developing the electrostatic latent image includes a color component agent, a binder resin, an aliphatic hydrocarbon-aromatic hydrocarbon copolymer petroleum resin having 9 or more carbon atoms. In addition, a particle having a particle diameter of 7 μm formed of wax, magnetic agent or the like is used.

  Conventionally known resins can be used as the binder resin. For example, a polyester resin, a styrene resin, a styrene- (meth) acrylic resin, a styrene-butadiene resin, an epoxy resin, a polyurethane resin, and the like can be given. Such a polyester resin is synthesized from a polyol component and a polycarboxylic acid component by polycondensation. Examples of the polyol component used include ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3 butanediol, diethylene glycol, triethylene glycol, and 1,5-butanediol. Further, 1,6-hexanediol, neopentyl glycol, cyclohexanedimethanol, hydrogenated bisphenol A, bisphenol-A ethylene oxide adduct, bisphenol-A propylene oxide adduct, and the like can be given. Examples of the polycarboxylic acid component include maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, succinic acid, dodecenyl succinic acid, trimellitic acid, pyromellitic acid, and cyclohexanetricarboxylic acid. 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methylenecarboxypropanetetramethylenecarboxylic acid and their anhydrides Things.

  Further, the aliphatic hydrocarbon-aromatic hydrocarbon copolymer petroleum resin having 9 or more carbon atoms contained in the toner acts as a wax dispersion aid. For this reason, the dispersion of wax in the resin, the low-temperature fixability is maintained, the anti-offset property, the pulverization property, the image density decrease due to the charging deterioration due to the filming of the wax on the developing carrier, the filming on the image carrier The occurrence of image defects on the subject is remarkably improved. The same effect can be obtained when added to a magnetic developer.

  This aromatic hydrocarbon copolymerized petroleum resin is synthesized from diolefins and monoolefins contained in cracked oil fractions by-produced from ethylene plants that produce ethylene, propylene, etc. by steam cracking of petroleum. is there. A copolymer obtained by copolymerizing an aliphatic hydrocarbon monomer and an aromatic hydrocarbon monomer as described below is desirable. The aliphatic hydrocarbon monomer is at least one selected from isoprene, piperylene, 2-methyl-butene-1, and 2-methylbutene-2. The aromatic hydrocarbon monomer is at least one selected from vinyltoluene, α-methylstyrene, indene, and isopropenyltoluene.

  As the aromatic hydrocarbon monomer, it is more preferable to use a pure monomer having a high monomer purity because the coloring of the resin and the odor during heating can be kept low. The purity of the aromatic hydrocarbon monomer is 95% or more, more preferably 98% or more. The aromatic hydrocarbon monomer is a monomer having 9 or more carbon atoms. In the case of a copolymerized petroleum resin obtained from this monomer and an aliphatic hydrocarbon monomer, a binder resin compared to a copolymerized petroleum resin obtained from an aromatic hydrocarbon monomer having less than 9 carbon atoms and an aliphatic hydrocarbon monomer For example, compatibility with a polyester resin becomes higher. Furthermore, in order to satisfy the pulverization property and heat storage property of the toner, it is preferable that the aliphatic hydrocarbon copolymer having 9 or more carbon atoms has a large amount of aromatic hydrocarbon monomer. However, when the amount of the aromatic hydrocarbon monomer is too large, the dispersibility of the release agent is deteriorated. On the other hand, when there are too many aliphatic hydrocarbon monomers, heat preservation property etc. will fall. Therefore, the weight of the aromatic hydrocarbon monomer amount and the aliphatic hydrocarbon monomer amount is 99: 1 to 50:50, more preferably 98: 2 to 60:40, and still more preferably 98: 2 to 90:10. . The amount used is 2 to 50 parts by weight with respect to 100 parts by weight of the toner binder resin. More preferably, it is 3 to 30 parts by weight. When the amount of the petroleum resin is less than 2 parts by weight, there is no effect on the wax dispersion. When the amount exceeds 50 parts by weight, the toner tends to be excessively pulverized, and the particle size of the toner becomes small in the developing machine. Occurs, the image density becomes low, and the developability may be lowered.

  Furthermore, the fluidity of the toner can be improved by attaching fine powder as a surface treatment agent (external additive) to the surface of the toner. This is because hydrophobic silica or the like is used as such a fine powder. When hydrophobic silica is attached to the surface of the toner, not only the fluidity is improved, but also the cleaning property and charging property of the toner can be improved.

  Moreover, fine powder other than hydrophobic silica can also be used. For example, fine powders of oxides such as titanium oxide, alumina, cerium oxide, fatty acid metal salt, polyvinylidene fluoride, polystyrene, magnesium, zinc, aluminum, cobalt, iron, zirconium, manganese, chromium, cerium, strontium, tin, etc. It can be used. In addition, inorganic oxide fine powders that are complex metal oxides such as calcium titanate, magnesium titanate, strontium titanate, barium titanate, calcium zirconate, barium zirconate, barium stannate, calcium stannate are also available. It is. Examples of the carbonate compound include calcium carbonate, magnesium carbonate, and barium carbonate. Among these, hydrophobic silica is often used for color toners, and strontium titanate is often used for monochrome toners.

  The amount of the surface treatment agent used is usually 0.1 to 20% by mass with respect to 100 parts by mass of the toner.

  The effect is further increased by using the abrasive particles as a surface treatment agent. However, in this case, the mass should be 1% or less if it is limited to this abrasive. When the content is more than 1%, developability and density decrease are affected.

(4) Image Flow Level Detection Unit Next, the arrangement and configuration of the density sensor 9 as the detection unit according to the present embodiment and reading of the toner image will be described with reference to FIG.

  The density sensor 9 is provided for reading the toner image formed on the photosensitive drum 1 and detecting the density of the toner image. The density sensor 9 reads at least two types of pattern images P1 and P2 as toner images for image flow detection. In the present invention, the image flow level is accurately detected based on the reading results of at least two kinds of pattern images P1 and P2 for detecting the image flow, the toner is placed on the photosensitive drum 1, and the photosensitive drum is polished by the cleaning blade 6a. It is characterized in that the time of the image flow recovery operation for cleaning the surface of the drum 1 is determined according to the image flow level. The image data of the image flow detection pattern images P1 and P2 is stored in the memory 11c in the control unit 11, and is read and used before the image flow recovery operation is executed.

  For reading the image flow detection pattern images P1 and P2, the density sensor 9 can be provided between the developing device 4 and the transfer roller 5 in each image forming unit, for example, as shown in FIG.

  Next, a schematic configuration of the density sensor 9 will be described with reference to FIG. The density sensor 9 of the present embodiment has a light emitting unit 91 and light receiving units 92A and 92B, and the light emitting unit 91 irradiates the surface of the photosensitive drum 1. The light irradiated at this time is separated into P wave (light parallel to the incident surface) and S wave (light perpendicular to the incident surface) by the polarizing plate 95A, and only the P wave reaches the toner image on the photosensitive drum 1. . The light irradiated to the toner image is reflected again with P wave and S wave components and irradiated to the light receiving portions 92A and 92B. At the time of incidence, the light is again separated into P wave and S wave by the polarizing plate 95B. Light is received by receiving the light receiving parts 92A (S wave reflected light receiving part) and 92B (P wave reflected light receiving part). The light emitting unit 91 can be configured by a light emitting element such as an LED or a laser diode, and the light receiving units 92A and 92B can be configured by a light receiving element that outputs a current (voltage) by receiving light from a photodiode or a phototransistor.

  The outputs of the light receiving portions 92A and 92B are different in the intensity ratio of the P wave and the S wave when receiving the reflected light of the surface of the photosensitive drum 1 and when receiving the reflected light of the toner image. The output ratio is different. Even when the reflected light of the toner image is received, the output ratio of the light receiving portions 92A and 92B varies depending on the density of the read toner image due to the difference in the absorbance and reflectance of the P wave and S wave of the light. In order to calculate this output ratio, the outputs of the light receiving unit 92A and the light receiving unit 92B are input to the CPU 11a. Then, the CPU 11a calculates the output ratio of the light receiving units 92A and 92B.

  As described above, there is a corresponding relationship between the density of the toner image or the read toner amount and the output ratio of the light receiving units 92A and 92B. The relationship is acquired in advance through experiments or the like. In 11c, the correspondence between the density and the output ratio is stored as data, for example, in the form of a table. Then, density detection (during measurement), the outputs of the light receiving units 92A and 92B are received, and the CPU 11a disposed in the control unit 11 calculates the density of the toner image from the output of each light receiving unit 92 according to the toner amount. The density of the toner image can be detected.

  As shown in FIG. 5, a D / A conversion unit 93 that converts a digital signal of the CPU 11a into an analog signal can be provided to turn on / off the light emission of the light emitting unit 91 from the CPU 11a, adjust the light emission amount, and the like. . Also, an S-wave A / D converter 94A for converting the analog output of the light receiving unit 92A into a digital value can be provided so that the CPU 11a can handle it, and the analog output of the light receiving unit 92B is converted into a digital value. A P-wave A / D converter 94B can be provided.

  Next, the image flow detection pattern images P1 and P2 according to the present embodiment will be described with reference to FIG. 6A and 6B are diagrams showing examples of image flow detection pattern images P1 and P2 according to the present embodiment. FIG. 6A is a development view of the peripheral surface of the photosensitive drum 1, and FIG. It is an enlarged image figure of pattern images P1, P2.

  As shown in FIG. 6A, for example, the image flow detection pattern images P1 and P2 are arranged at substantially the center position in the main scanning direction of the photosensitive drum 1 and in the circumferential direction (sub-scanning direction) of the photosensitive drum 1. At least one round of the photosensitive drum 1 is formed. The reason why the image flow detection pattern images P1 and P2 need at least the length of one revolution of the photosensitive drum 1 is to reliably detect the occurrence of partial image flow. A density sensor 9 is arranged at a position for reading this image. The positions where the image flow detection pattern images P1 and P2 are formed and the position of the density sensor 9 are not limited to the center position, and can be set as appropriate in the main scanning direction (in the paper passing area). Further, the image flow detection pattern images P1 and P2 are not necessarily arranged adjacent to each other, but can be appropriately set in the main scanning direction, and the image density detection pattern image P1 can be set with the same density sensor 9 without using a plurality of density sensors. , P2 is formed, the image flow detection pattern image P1 is formed for one or more rounds at the same position on the photosensitive drum 1, and then the image flow detection pattern image P2 is formed for one or more rounds. The density may be read. In addition, the order in which the image flow detection pattern images P1 and P2 are formed at that time may be first.

  The width in the main scanning direction of the image flow detection pattern images P1 and P2 can be set to, for example, about 10 mm in accordance with the reading range of the density sensor 9. The length of the image flow detection pattern images P1 and P2 in the rotating direction is, for example, the same length as the peripheral length of the photosensitive drum 1 in order to confirm the occurrence of image flow over the entire circumference of the photosensitive drum 1. be able to. That is, the image flow detection pattern images P1 and P2 are formed in an area corresponding to at least one turn in the sheet passing area of the photosensitive drum. As a result, the image forming apparatus main body T is stopped for a long time, and ozone, nitrogen oxide, or the like adhering to a part of the surface of the photosensitive drum 1 adheres to cause an image flow in a part of the photosensitive drum 1. However, it is possible to detect the occurrence of part of the image flow.

  The image flow detection pattern images P1 and P2 are pattern images having different density changes when an image flow occurs. The image flow detection pattern image P <b> 1 is a first pattern image in which a plurality of lines are formed at intervals in the rotation direction of the photosensitive drum 1. On the other hand, the image flow detection pattern image P2 is a second pattern image in which a plurality of lines wider than the lines forming the image flow detection pattern image P1 are formed at intervals in the rotation direction of the photosensitive drum 1. is there.

  Specifically, for example, as shown in FIG. 6B, the image flow detection pattern image P1 is a fine line pattern, and the image flow detection pattern image P2 is a thick line pattern. In accordance with the reading range of the density sensor 9, for example, the line width a of the fine line pattern (P1) is set to 1 pixel or less of 600 dpi, the line interval b is set to a ≦ b <5a, and the line width c of the thick line pattern is set to 2a ≦ c <10a and the line interval d are in the range of c ≦ d <2c. If this relationship is satisfied, it is possible to prevent erroneous detection of a change in density due to density reduction due to lowering of developability, and to detect an image stream with high accuracy from a slight image stream.

  Further, it will be described that the line pattern can be distinguished from the image flow even when the density of the image flow detection pattern images P1 and P2 is changed due to banding or shock blur. FIG. 8 is an explanatory diagram of the line width at which the solid line ratio becomes a peak. FIG. 9 is a model diagram of toner on paper before and after banding of a fine line pattern and a thick line pattern.

  Since excessive toner is developed on the photosensitive drum 1 in a line image such as a character, generally, the density of the line image tends to be higher than the maximum density (solid density) of the surface image. This is because the amount of applied toner of a line image tends to be larger than the amount of applied toner of a solid image formed under the same image forming conditions. A ratio indicating how much the toner amount of the line image is larger than the toner amount of the solid image when the solid image and the line image are formed under the same image forming condition is called a solid line ratio. The solid line ratio is a ratio of the toner applied amount of the line image to the toner applied amount of the solid image.

  The factor that increases the solid line ratio is the edge effect of the developing electric field in the region of the line image within a predetermined width, which becomes noticeable in a line of several dots (5 dots line at 600 dpi in the image forming apparatus main body T). . As shown in FIG. 9, when the line width is large and the solid line ratio is large, the amount of toner loaded is large. Therefore, when affected by banding or the like, the toner layer collapses and the area occupied by the toner per unit area is large. spread. Conversely, when the line width is small and the solid line ratio is small, the toner amount is small and the toner layer is thin, so the toner does not spread even if affected by banding, etc. No change.

  As a result, when influenced by banding or the like, the density is high in the case of the thick line pattern P2 having a large solid line ratio, but the density is not greatly changed in the case of the thin line pattern P1 having a small solid line ratio compared to the thick line pattern P2. Therefore, it is not erroneously detected as an image flow.

  Next, an example of the order of the image flow level determination method will be described below.

  (1) Two types of horizontal ruled line pattern images P1 and P2 are formed in the center of the photosensitive drum 1 for one drum.

  (2) A density value is calculated from the density sensor output value of each pattern image.

  (3) A density profile for one rotation of the drum is created, and the maximum, minimum, and average values are acquired and compared with the normal density.

  (4) If the density average value for one round of the detection pattern 1 (thin line pattern image P1) is lower than the normal density, the minimum density value is selected.

  (5) If the density average value for one round of the detection pattern 2 (thick line pattern image P2) tends to increase from the normal density, the maximum density value is selected. If the density average value tends to decrease, the minimum density value is selected.

  (6) The portion selected in the above (4) and (5) is set as the worst point of image flow, and the image flow level is determined at that portion.

  As an example, the image flow level is determined based on the worst point of the image flow. However, the user can appropriately change the image flow level based on the average value of the image flow detection patterns on the photosensitive drum 1. It is possible.

  An example of the hardware configuration of the image forming apparatus main body T according to the embodiment of the present invention will be described with reference to FIG.

  As shown in FIG. 1, a control unit 11 is provided for controlling the operation of each unit and each member of the image forming apparatus main body T according to the present embodiment. The control unit 11 is connected to each unit of the image forming unit constituting the image forming apparatus main body T, and performs various controls such as rotation, charging, development, transfer, and fixing of the photosensitive drum 1 and the like.

  For example, the control unit 11 is provided with a main body CPU 11a, a fixing CPU 11b, and the like. The main body CPU 11a and the fixing CPU 11b are central processing units, issue control signals to each part of the image forming apparatus main body T based on a control program and data, receive signals from each part, and perform various calculations. The memory (storage unit) 11c is configured by combining volatile and non-volatile storage devices such as a ROM (Read Only Memory), a RAM (Random Access Memory), a HDD (Hard Disk Drive), and a flash ROM (not shown). The The memory (storage unit) 11c stores data such as control programs, control data, image data, and setting data.

  As described with reference to FIG. 5, the density sensor 9 is connected to the control unit 11, and the control unit 11 controls the light emission of the light emitting unit 91 of the density sensor 9, and the outputs of the light receiving units 92A and 92B. The main body CPU 11a calculates, for example, the density of the toner image read by the density sensor 9 with reference to data in the memory (storage unit) 11c.

  In the image forming apparatus main body T of the present embodiment, when the power is turned on, when the number of image formations reaches a fixed value, when a predetermined time has elapsed since the image forming apparatus main body T finished printing, etc. Thus, an image flow recovery operation for polishing and cleaning the photosensitive drum 1 with toner is performed. The program and data for the image flow recovery operation are stored in a memory (storage unit) 11c, and the control unit 11 performs the laser scanner 3, the photosensitive drum 1, The image flow recovery operation is performed by making full use of the developing device 4, the cleaning device 6, the fixing device 8, and the like.

  Specifically, the image flow recovery operation refers to a state in which a toner image having a constant density (for example, solid coating) is formed on the entire peripheral surface of the photosensitive drum 1, and the cleaning blade 6 a of the cleaning device 6 is applied to the photosensitive drum 1. The temperature control of the fixing device 8 is set to be kept at a predetermined set temperature (for example, 110 ° C.), the photosensitive drum 1 is rotated for a certain time, and the temperature of the fixing device 8 is controlled by the temperature control of the fixing device 8. 1 is polished while removing the water on the photosensitive drum 1 by heating the surface. That is, the toner is placed on the photosensitive drum 1 and polished by the cleaning blade 6a, and the surface of the photosensitive drum 1 is cleaned while removing moisture so that the discharge product does not adsorb moisture. The toner may contain a polishing component for effective polishing. By polishing the photosensitive drum 1, dirt on the photosensitive drum 1 such as attached discharge products and dust can be removed. Even if the discharge product cannot be completely removed by polishing with paper powder containing talc, the surface of the photosensitive drum 1 is warmed to remove moisture, so that adhesion of ozone, nitrogen oxides, etc. The image flow caused by such factors is eliminated.

  The image flow recovery operation itself has been conventionally performed by the image forming apparatus. However, the image forming apparatus main body T according to the present embodiment changes the density of the image flow detection pattern images P1 and P2 when the image flow occurs. By taking advantage of the above features, it is possible to prevent degradability of the developing device 4 from being deteriorated and erroneous detection of density changes due to mechanical banding, shock blur, etc. It is going to change time.

  FIG. 7A shows the characteristics of the density change when the image flow occurs in the image flow detection pattern images P1 and P2. The fine line pattern P1 has a weak electric field strength (edge effect) in the developing portion and a small solid line ratio, and therefore has high sensitivity to image flow, and the density linearly decreases from the normal density. On the other hand, the thick line pattern P2 has a stronger electric field strength (edge effect) than the thin line pattern P1, so that when the image flow level begins to deteriorate, the latent image gradually spreads more than the actual line width of FIG. 7B. It gets thicker. Then, as shown in FIG. 7C, the area on which the toner is placed increases, and the area occupied by the toner per unit area increases and the density increases. When the image flow is further deteriorated, the latent image spreads shallowly, so that the toner is not loaded and the density is decreased.

  The density change due to banding is often confused with the density change due to image flow in the case of a solid patch or the like, but the density of both the thin line pattern P1 that is less affected by banding and the thick line pattern P2 that is less affected by banding are detected. By comparing the density and the place where the density change occurs, the density change due to banding or the density change due to the image stream can be surely separated, so that an erroneous detection of the image stream level does not occur.

  The determination of the execution time of the image flow recovery operation of the image forming apparatus main body T according to the embodiment of the present invention will be described with reference to FIG. FIG. 10A is a table showing an example of a table tb1 used when determining the image flow level according to the output of the density sensor 9 and determining the image flow recovery operation execution time according to the image flow level. FIG. 10B is a diagram illustrating an example of a change in the output value of the density sensor of the pattern images P1 and P2 according to the image flow level.

  First, FIG. 10A will be described. FIG. 10A is a table used when determining the image flow recovery operation execution time based on the output of the density sensor 9 as described above. The table tb1 can be stored in the memory (storage unit) 11c.

  In this table tb1, the density sensor output values D1 and D2 are the results obtained by the operation of the main body CPU 11a with respect to the output of the density sensor 9, and the outputs of the light receiving units 92A and 92B of the density sensor 9 are output. The density values themselves of the pattern images P1 and P2 are calculated from the ratio.

  Here, the higher the degree of image flow, the lower the surface resistance on the photosensitive drum 1 so that the charge cannot be held, and the charge flows, and the potential difference between the portion where the toner is placed and the portion where the toner is not placed tends to decrease. appear. In other words, the charge of the portion where the charge is not canceled flows into the pixel where the charge is canceled by the laser light from the laser scanner 3. For example, when the photosensitive drum 1 is negatively charged, the potential of the pixel portion where the charge is canceled falls.

  As a result, the amount of toner to be deposited on the photosensitive drum 1 and the area on which the toner is deposited according to the image flow level show a unique tendency depending on the pattern images P1 and P2, and therefore the density also changes according to the image flow level. As an example, FIG. 10B shows the change in the output value of the density sensors P1 and P2 according to the image flow level.

  The density values corresponding to the output of the density sensor 9 are D1 and D2 in the table tb1. For example, if the density sensor output value D1 takes values from 0 to 1.5, 0 <(X1, X2, X3, X4, X5, X6) ≦ 1.5. If the density sensor output value D2 takes a value from 0 to 1.5, 0 <(Y1, X2, X3, Y4, Y5) ≦ 1.5. Therefore, for example, X1 = 0.25, X2 = 0.1, Y1 = 0.75, and Y2 = 0.85. The threshold values X and Y have a relationship of 0 <X1 <X2 <X3 <X4 <X5 <X6 <1.5, 0 <Y1 <Y2 <Y3 <Y4 <Y5 <Y6 <1.5.

  The image flow recovery operation execution time is determined by comparing the density sensor output value D1 with each of the threshold values X1 to X6 and the density sensor output value D2 with each of the threshold values Y1 to Y5, for example, by comparing the density sensor output value. It is determined by the values of D1 and D2. For example, if the density sensor output value D1 of the fine line pattern image P1 is X6 <D1 ≦ X5 and the density sensor output value Y1 of the thick line pattern image P2 is D2 ≦ Y5, as shown in FIG. The execution time is set to 120 seconds. Similarly, 60 seconds if X4 <D1 ≦ X3 = 0.9 and Y4 <D2 ≦ Y3, 20 seconds if X1 ≦ D1 <X2 and Y2 <D2 ≦ Y1, 0.6 ≦ D1 <X1 and Y1 <D2. If it is ≦ 0.4, it is determined as 10 seconds. If the output values of the density sensors of the fine line pattern image P1 and the thick line pattern image P2 do not fit in the table of FIG. 10A, the density change due to a decrease in developability or other factors due to mechanical banding, shock, etc. Therefore, it is possible to discriminate from density fluctuations due to image flow.

  Accordingly, as the image flow level is lighter, a desired toner density is obtained, the level of characters, fine line reproducibility, etc. is good, and the execution time of the image flow recovery operation is shortened compared with the case where the image flow level is heavy. The image flow level is shown in the leftmost column of the table tb1 in FIG. Note that FIG. 10A shows that the image flow becomes more severe as the number of levels increases. In FIG. 10A, the generation level of the image flow is divided into seven stages. However, by using a larger number of threshold values X, it is possible to perform multi-level level division, and the image flow recovery operation execution time. Can be further divided into multiple stages. Further, the image flow recovery operation execution time in this description is an example, and is set as appropriate.

  Next, an example of image flow recovery operation control of the image forming apparatus main body T according to the present embodiment will be described with reference to FIG. FIG. 11 is a flowchart showing an example of image flow recovery operation control of the image forming apparatus main body T according to the present embodiment. First, the start of FIG. 11 is determined in advance, for example, when a power is turned on or when returning from the sleep mode, when a certain number of sheets have been printed from the previous image flow recovery operation, an image flow recovery operation execution instruction is input by a service person who performs maintenance. This is a case where the execution timing of the image flow recovery operation is reached.

  First, the control unit 11 forms image flow detection pattern images P1 and P2 on the photosensitive drum 1 (step S11). That is, the control unit 11 performs density detection pattern images P1 and P2 (for example, a normal density 0.4 of P1, 0.4) on the photosensitive drum 1 before executing the image flow recovery operation. A normal concentration of P2 of 0.6) is formed. The density of the pattern images P1 and P2 formed on the photosensitive drum 1 is read by the density sensor 9.

  Then, the control unit 11 instructs the density sensor 9 to emit light (step S12), and causes the density sensor 9 to read the image flow detection pattern images P1 and P2 (step S13). The control unit 11 receives the read output from the density sensor 9 and calculates density sensor output values D1 and D2 (step S14). Next, the control unit 11 compares the density sensor output values D1 and D2 with the normal density value, and determines the image flow level from the density displacement from the normal density of the density sensor output values D1 and D2 (step S15). . Then, the necessity of the image flow recovery operation is confirmed (step S16). This is because when it is recognized from the output of the density sensor 9 and the density sensor output values D1 and D2 that no image flow has occurred, there is no need to perform an image flow recovery operation. For example, as described above, D1 is 0.4 and D2 is 0.6, or D1 and D2 are not density sensor output values corresponding to the table tb1 in FIG. If it is determined that it is not necessary to perform the image flow recovery operation (No in step S16), the process ends.

  On the other hand, when it is determined that the image flow recovery operation is necessary (Yes in Step S16), the control unit 11 determines the image flow recovery operation execution time from the table tb stored in the memory (storage unit) 11c (Step S16). S17). That is, the density sensor 9 reads the densities of the pattern images P1 and P2, and the control unit 11 determines the generation level of the image flow from the read result of the density sensor 9, and sets the image flow recovery operation execution time according to the generation level. Change. That is, the control unit 11 determines the surface state of the photosensitive drum from the detection result of the density sensor 9. As described above, the image flow recovery operation execution time is determined based on the density sensor output values D1 and D2. Then, based on the determined image flow recovery operation execution time, the control unit 11 causes each member to execute the image flow recovery operation (step S18).

  Next, the control unit 11 confirms the necessity of the image flow recovery operation again (step S19). For example, in order to eliminate complete image flow, the image flow recovery operation is executed more than once (for example, twice) automatically or when the image flow occurrence level is severe, or by input to the operation panel or the like If the setting is to be performed, if the set number of executions has not been reached, it is determined again that the image flow recovery operation is necessary (Yes in step S19), and the process returns to step S11. On the other hand, if the image flow recovery operation is not necessary again (No in step S19), the control relating to the image flow recovery operation is terminated, and the image forming apparatus main body T is again ready for printing.

  In this way, according to the present embodiment, the control unit 11 changes the image flow recovery operation time according to the detection result of the density sensor 9 serving as the detection means, so that the image can be reliably output according to the generation level of the image flow. The image flow recovery operation can be performed in the minimum necessary time to eliminate the flow. Conventionally, the image flow cannot be detected unless the density is reduced to a level that can be visually recognized by the user, or the level is such that the characters are faint and cannot be discriminated. Image flow can be detected. As a result, it is possible to perform an image flow recovery operation before the user sees the phenomenon of image flow. Conventionally, the image flow recovery operation has been performed for a certain period of time so that the generation level of the image flow can be eliminated even if it is severe. However, if the generation level of the image flow is low, the image flow recovery operation time is reduced. Therefore, the toner consumption and power consumption can be reduced, and the waiting time of the user before printing can be shortened. Accordingly, it is possible to provide an image forming apparatus (for example, the image forming apparatus main body T) with low running cost, convenience, and high productivity.

  An endurance test was performed by operating IR3045 (manufactured by Canon Inc.), which was modified to incorporate the concentration sensor 9 having the above-described configuration, with the examination software described above. In a high-temperature and high-humidity environment (30 ° C / 80%), an image with an applied toner amount of 0.025 g / A4 size was intermittently subjected to a sheet-passing image test (200K sheets), and the output paper images (50K, 100K, 150K, 200K sheets). It was very good, and both photographic images and text images were satisfactory on the image. Moreover, there was no image defect over a long period of time.

  Further, IR3045 (manufactured by Canon Inc.) having the above-mentioned main body modified is subjected to the above-described examination software with a toner loading amount of 0.025 g / A4 in a low-temperature and low-humidity environment (15 ° C./10%) and a normal environment (20 ° C./50%). A sheet passing image test (200K sheets) was conducted intermittently for one size image, and it was confirmed whether the printable time was extended due to erroneous detection of the image flow. Normally, the durability of printing in an environment where no image flow occurs does not extend the printable time. It was confirmed that there was no false detection of the image flow level due to density reduction due to deterioration in developability, density fluctuation due to banding, shock blur, etc.

  As described above, according to the present embodiment, it is possible to prevent erroneous detection of the image flow level even if recycled paper or imported paper containing a large amount of filler is used as a recording material, regardless of the use state and usage environment of the main body. An accurate image flow level is detected, and an image flow recovery operation corresponding to the image flow level can be executed. This makes it possible to eliminate the image flow accurately even with a simple configuration, minimize the image flow recovery operation, reduce the toner consumption and power consumption, and shorten the waiting time of the user until printing is possible. It is possible to provide an image forming apparatus.

  The embodiment of the present invention has been described above, but the scope of the present invention is not limited to this, and various modifications can be made without departing from the spirit of the invention.

P: Recording material T: Apparatus main body 1: Photoconductor drum 2 ... Charging roller 4 ... Developing apparatus 6 ... Cleaning apparatus 6a ... Cleaning blade 8 ... Fixing apparatus 9 ... Density sensor 10 ... High voltage power supply unit 11 ... Control unit 11a ... Main body CPU
11b: Fixing CPU
11c ... Memory 91 ... Light emitting part 92A, 92B ... Light receiving part 95A, 95B ... Polarizing plate

Claims (6)

An image forming unit for forming a toner image on the image carrier;
The image forming unit forms a first toner image formed on the image carrier with a plurality of lines spaced apart in the rotation direction of the image carrier, and a line thicker than the first toner image. Detection means for detecting the density of the second toner image;
Cleaning means for cleaning the image carrier;
Control means for causing the cleaning means to perform a cleaning operation for a time determined based on the detection results of the densities of the first and second toner images detected by the detection means;
An image forming apparatus comprising:   2. The image forming apparatus according to claim 1, wherein the second toner image has a pattern in which an edge effect of a developing portion by toner is stronger than that of the first toner image.   The control means determines a time for the cleaning means to perform the cleaning operation based on a difference between the density of the first and second toner images detected by the detection means and a reference density of each toner image. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. A storage unit for storing a table used when determining the execution time of the cleaning operation;
The said control means determines the execution time of the said cleaning operation | movement based on the table memorize | stored in the said memory | storage part from the detection result of the said detection means. The image forming apparatus described in 1.   The cleaning operation by the cleaning means is performed by forming the toner image on the image carrier and heating the fixing device that fixes the unfixed toner image on the recording material at a predetermined set temperature. The image forming apparatus according to claim 1, wherein the surface of the image carrier is cleaned by the cleaning unit by rotating a body.   6. The control device according to claim 1, wherein the control unit forms the first and second toner images in at least one area of the image carrier in the paper area. The image forming apparatus described in the item.