JP2016145916A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that allows an operator to more accurately grasp the remaining life of a photoreceptor according to the depth of recesses on the surface of the photoreceptor.SOLUTION: An image forming apparatus 100 comprises: a photoreceptor 1 that has a plurality of recesses each independently formed on the surface; a driving part 14 that drives to rotate the photoreceptor 1; a charging member 2; a power source E1 that applies a charging voltage; an exposure device 3; a developing device 4; a transfer device 12; and a control part 20. The control part 20 drives to rotate the photoreceptor 1 at a first speed in an image forming operation, and drives to rotate the photoreceptor 1 at a second speed different from the first speed in a test operation, and applies a charging voltage consisting only of a DC voltage to the charging member 2 to charge the photoreceptor 1, and thereby forming a test image.SELECTED DRAWING: Figure 12

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile apparatus using an electrophotographic system.

  As an electrophotographic photosensitive member (photosensitive member) used in an electrophotographic image forming apparatus, an organic material is used as a photoconductive substance (a charge generating substance or a charge transporting substance) because of low cost and high productivity. An organic photoreceptor having a photosensitive layer (organic photosensitive layer) provided on a support is widely used. In particular, rotatable drum type (cylindrical) photosensitive drums are widely used.

  As the organic photoreceptor, a photoreceptor having a laminated photosensitive layer is mainly used because of the advantages of high sensitivity and a variety of material designs. The laminated photosensitive layer includes a charge generation layer containing a photoconductive dye or a photoconductive pigment charge generation material, a charge transport layer containing a photoconductive polymer or a photoconductive low molecular weight compound charge transport material, Are stacked.

  By the way, an electrical external force, a mechanical external force, or both of them are directly applied to the surface of the photoreceptor in charging, exposure, development, transfer, and cleaning. For this reason, the photoreceptor is required to have durability against these external forces. Specifically, durability against the occurrence of scratches and wear on the surface due to these external forces, that is, scratch resistance and wear resistance are required. The following are known as techniques for improving the scratch resistance and wear resistance of the surface of the organic photoreceptor. A photoreceptor having a hardened layer using a curable resin as a binder resin as a surface layer. A photoreceptor having a charge transporting cured layer formed by curing and polymerizing a monomer having a carbon-carbon double bond and a charge transporting monomer having a carbon-carbon double bond by heat or light energy as a surface layer . A photoreceptor having a charge transporting cured layer formed by curing and polymerizing a hole transporting compound having a chain polymerizable functional group in the same molecule by the energy of an electron beam as a surface layer. Thus, in recent years, as a technique for improving the scratch resistance and abrasion resistance of the peripheral surface of the organic photoreceptor, there is a technique for increasing the mechanical strength of the surface layer using the surface layer of the photoreceptor as a cured layer.

  However, when an image is formed using a photoconductor having a high hardness, blurring of an electrostatic latent image called “image flow” tends to occur particularly in a high humidity environment. The cause of the image flow is considered as follows. That is, discharge products such as ozone and NOx are generated mainly by the charging means and adhere to the surface of the photoreceptor. The surface of the photosensitive member has a low surface friction coefficient μ and is hard, so that it is difficult to scrape, and the discharge product attached to the surface is difficult to be removed. Then, the discharge product that is difficult to remove attached to the surface absorbs moisture in a high humidity environment, lowers the charge holding ability of the surface of the photoreceptor, and generates blur of the electrostatic latent image. Therefore, particularly when the hardness of the photosensitive member is high, the attached discharge products are more difficult to be removed, and the image flow is likely to occur.

  As a countermeasure against image flow, a heater is generally installed in the vicinity of the photosensitive member or in the vicinity of the photosensitive member, and the surface of the photosensitive member is dried by raising the temperature of the surface of the photosensitive member. However, if an image is formed at a stage where the effects of these means cannot be obtained sufficiently, such as immediately after the power is turned on, an image flow may occur. In particular, in recent years, there are also devices that are not equipped with a heater from the viewpoint of energy saving.

  Therefore, Patent Document 1 describes a technique of using a photoconductor having a plurality of independent concave portions on the surface for the purpose of preventing image flow.

JP 2007-233357 A

  However, even if the photoconductor has a high hardness, the surface layer is gradually scraped by rubbing against the cleaning blade after a long period of use. Along with this, as shown in FIG. 21, in the photoreceptor having a concave portion on the surface, the depth of the concave portion is gradually reduced.

  With respect to image flow, it has been found that the deeper the concave portion, the higher the effect. When the concave portion becomes shallow as described above, there is a possibility that an image defect due to the image flow may occur. Therefore, when the depth of the concave portion is reduced due to the shaving of the photoconductor, it is desired to replace the photoconductor at an appropriate time.

  The reduction in the depth of the recess on the surface of the photoconductor can be determined by counting the number of image outputs performed using the photoconductor, counting the rotation time or charging time of the photoconductor, and reducing the wear amount of the photoconductor. Predict by predicting. However, in general, the depth of the concave portion on the surface of the photosensitive member is several μm at most, and it is difficult to accurately predict the small amount of wear of the photosensitive member that reduces the depth of the concave portion. Therefore, it is required to detect the decrease in the depth of the concave portion due to the shaving of the photoconductor directly and accurately to grasp the remaining life of the photoconductor more accurately.

  Accordingly, an object of the present invention is to provide an image forming apparatus capable of more accurately grasping the remaining life of the photoconductor according to the depth of the concave portion on the surface of the photoconductor.

  The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention provides a rotatable photosensitive member having a plurality of independent recesses formed on the surface thereof, a driving unit for rotationally driving the photosensitive member, and the photosensitive member disposed in contact with the photosensitive member. A charging member for charging the charging member, a power source for applying a charging voltage for charging the photosensitive member to the charging member, an exposure device for exposing the photosensitive member charged by the charging member to form an electrostatic image, and A developing device for developing an electrostatic image formed on the photoconductor by the exposure device with toner to form a toner image, and a transfer device for transferring the toner image formed on the photoconductor by the developing device to a transfer material An image forming operation for forming a toner image corresponding to arbitrary image information, transferring it to a transfer material and outputting it, and forming a test image for obtaining information relating to the remaining life of the photoconductor to form a transfer material on the transfer material Test motion that is transcribed and output And a control unit that executes the rotation of the photosensitive member at a first speed during the image forming operation and the photosensitive member during the test operation. An image characterized by being driven to rotate at a second speed different from the first speed and applying a charging voltage consisting only of a DC voltage to the charging member to charge the photoconductor to form the test image. Forming device.

  According to another aspect of the present invention, a rotatable photosensitive member having a plurality of independent recesses formed on a surface thereof, a driving unit that rotationally drives the photosensitive member, and the photosensitive member disposed in contact with the photosensitive member. A charging member that charges the body, a power source that applies a charging voltage for charging the photosensitive member to the charging member, and an exposure device that exposes the photosensitive member charged by the charging member to form an electrostatic image. A developing device for developing a toner image by developing an electrostatic image formed on the photosensitive member by the exposure device with toner, and a toner image formed on the photosensitive member by the developing device is transferred to a transfer target. A transfer device, a sensor for detecting the density of the toner image on the photosensitive member or the toner image on the transfer target, and a toner image corresponding to arbitrary image information, transferred to a transfer material and output Forming action and the feeling A control unit that forms a test image for obtaining information on the remaining life of the body and detects the density of the toner image of the test image by the sensor, and the control unit includes: During the image forming operation, the photosensitive member is rotationally driven at a first speed, and during the test operation, the photosensitive member is rotationally driven at a second speed different from the first speed, and the charging member. By applying a charging voltage consisting only of a DC voltage to the photoconductor, the photoconductor is charged to form the test image, and information indicating the remaining life of the photoconductor is reported based on the detection result of the test image by the sensor. An image forming apparatus is provided that outputs a signal for performing the above operation.

  According to the present invention, it is possible to more accurately grasp the remaining life of the photoconductor according to the depth of the concave portion on the surface of the photoconductor.

1 is a schematic sectional view of an image forming apparatus. It is a schematic diagram of an image forming unit. It is a photograph of the surface of the photoreceptor having a specific recess. FIG. 2 is a schematic cross-sectional view of a photoreceptor. It is a graph which shows an example of transition of the depth of the specific recessed part of the surface of a photoreceptor. FIG. 6 is an explanatory diagram for explaining a relationship between a rotation speed of a photoconductor and a level of horizontal streaks for each discharge pattern of a charging unit of the photoconductor. It is a schematic diagram which shows the example of the pattern of a test image. It is a block diagram which shows the control aspect which concerns on test operation. It is a timing chart figure which shows the sequence of test operation | movement. It is a schematic diagram which shows the example of the test image output by test operation | movement, and the test image for a comparison. It is a schematic diagram which shows the example of the condition of the horizontal stripe in the output test image. It is a schematic diagram which shows the example of the corresponding | compatible chart for judging the remaining lifetime of a photoreceptor. It is a schematic diagram of an optical sensor. It is a graph which shows an example of density | concentration level | step difference (DELTA) D of the test image detected with the optical sensor. It is a graph which shows an example of the relationship between density | concentration level | step difference (DELTA) D of a test image, and the remaining lifetime of a photoreceptor. It is a schematic diagram which shows the other example of the pattern of a test image. It is a block diagram which shows the control aspect which concerns on the other example of test operation. It is a timing chart figure which shows the sequence of the other example of test operation | movement. It is a schematic flowchart figure of test operation | movement and alerting | reporting operation | movement of remaining lifetime. It is a graph showing an example of the relationship between the DC voltage value and the charging potential of the photoreceptor in each of the DC charging method and the AC + DC charging method. FIG. 5 is a schematic diagram showing a decrease in the depth of a concave portion on the surface of a photoreceptor due to wear of the photoreceptor.

  The image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

Example 1
1. 1 is a schematic cross-sectional view of an image forming apparatus 100 according to an embodiment of the present invention. The image forming apparatus 100 according to the present exemplary embodiment is a tandem type laser beam printer that employs a contact charging method and an intermediate transfer method capable of forming a full-color image using an electrophotographic method.

  The image forming apparatus 100 includes first, second, third, and fourth image forming units SY, SM, SC, and SK as a plurality of image forming units. Each of the image forming units SY, SM, SC, and SK forms yellow (Y), magenta (M), cyan (C), and black (K) toner images, respectively. In this embodiment, the configurations and operations of the image forming units SY, SM, SC, and SK are substantially the same except that the color of the toner used is different. Therefore, hereinafter, unless there is a particular need for distinction, Y, M, C, and K at the end of a symbol representing an element for any color are omitted, and the elements will be described in a comprehensive manner.

  FIG. 2 is a schematic cross-sectional view showing the configuration of the image forming unit S in more detail. In this embodiment, the image forming unit S includes a photoconductor 1, a charging roller 2, an exposure device 3, a developing device 4, a primary transfer roller 5, and a photoconductor cleaning device 7 which will be described later.

  First, the image forming apparatus 100 includes a rotatable drum type (cylindrical) photosensitive member (photosensitive drum) 1 as an image carrier. In this embodiment, the photoconductor 1 is an organic photoconductor having a negative charging property, and a photocharge generation layer made of an organic material and a charge transport layer (on the surface of an aluminum cylinder (conductive substrate)) And a thickness of about 20 μm) in order from the bottom. Here, the surface layer of the photoreceptor 1 is a hardened layer using a curable resin as a binder resin. The photoreceptor 1 can be replaced when the surface layer is scraped due to wear due to use and it is determined that replacement is necessary by a test operation described later. The photoconductor 1 may be configured such that substantially only the photoconductor 1 can be detached and replaced with respect to the main body of the image forming apparatus 100 alone, or as a process cartridge or the like together with other process equipment. The main body may be detachable and replaceable. The process cartridge is a cartridge in which a photosensitive member and at least one of a charging unit, a developing unit, and a cleaning unit serving as a processing unit that acts on the photosensitive unit are integrally formed, and is attached to the apparatus main body of the image forming apparatus. Detachable.

  In this embodiment, as the curing treatment of the surface of the photoreceptor 1, a cured layer using a curable resin as the binder resin is used. However, the present invention is not limited to this. The following can be used as the hardened layer. A charge transporting cured layer formed by curing and polymerizing a monomer having a carbon-carbon double bond and a charge transporting monomer having a carbon-carbon double bond by heat or light energy. A charge transporting cured layer formed by curing and polymerizing a hole transporting compound having a chain polymerizable functional group in the same molecule by the energy of an electron beam.

  In this embodiment, the photosensitive member 1 has a length in the longitudinal direction (rotation axis direction) of 340 mm and an outer diameter of 30 mm, and is driven to rotate in the direction of the arrow R1 in the drawing around the center support shaft. In this embodiment, the photoreceptor 1 can rotate at a plurality of different rotational speeds. As shown in FIG. 8, the photosensitive member 1 is rotationally driven by the photosensitive member driving unit 14. The photoconductor drive unit 14 includes a motor 14 a as a drive source and a switching unit 14 b that switches the rotation speed of the photoconductor 1. As will be described in detail later, the switching unit 14b is configured to transfer the rotational speed of the photosensitive member 1 to a transfer material P by transferring an image corresponding to arbitrary image information to a transfer material P and during a test operation described later. Switch with. In this embodiment, the photoreceptor 1 is rotationally driven at a rotational speed (peripheral speed, process speed) of 300 mm / sec during normal image formation. In this embodiment, a flat portion and a plurality of concave portions are formed on the surface of the photosensitive member 1, and this will be described in detail later.

  Next, the image forming apparatus 100 includes a charging roller 2 that is a roller-type contact-type charging member as a charging unit that uniformly charges the surface of the photoreceptor 1. The charging roller 2 has a length in the longitudinal direction (rotation axis direction) of 330 mm and a diameter of 14 mm, and has a configuration in which a conductive rubber layer is formed on the outer periphery of a stainless steel core (core material). In the charging roller 2, both end portions of the cored bar in the longitudinal direction are rotatably held by bearing members, respectively, and are urged toward the photoreceptor 1 by a pressing spring. As a result, the charging roller 2 is brought into pressure contact with the surface of the photoreceptor 1 with a predetermined pressing force, and forms a charging nip that is a contact nip with the photoreceptor 1. The charging roller 2 is rotated in the direction of the arrow R3 in the figure following the rotation of the photosensitive member 1. The charging roller 2 charges the photosensitive member 1 by utilizing a discharge phenomenon that occurs in a small gap between the charging unit a and the photosensitive member 1. A charging voltage (charging bias) under a predetermined condition is applied to the charging roller 2 from a charging power supply (high voltage power supply) E1 as an application means via the cored bar. In this embodiment, the charging power source E1 is constituted by a DC power source and applies a charging voltage (charging DC voltage) consisting only of a DC voltage component to the charging roller 2. The charging DC voltage applied during image formation is appropriately set to a potential suitable for good image formation according to the environment and the repeated use status (amount used from the initial use) of the photosensitive member 1 and the charging roller 2. Is set.

  Here, in the case where the photosensitive member 1 is charged only with the charging direct current voltage, in order to make the surface of the photosensitive member 1 at the same charging potential as compared with the case where the charging alternating current voltage is superimposed, it is about twice. It is necessary to apply a charging DC voltage to the charging roller 2. FIG. 20 shows the relationship between the charging DC voltage value and the charging potential of the photosensitive member when the charging DC voltage and the charging AC voltage are superimposed (DC + AC charging method) and when only the charging DC voltage is used (DC charging method). An example of the relationship is shown.

  Next, the image forming apparatus 100 includes an exposure device 3 as an information writing unit (exposure unit) that forms an electrostatic latent image on the surface of the charged photoreceptor 1. In this embodiment, the exposure apparatus 3 is a laser beam scanner using a semiconductor laser. The exposure device 3 outputs a laser beam L that is modulated in response to an image signal sent to the image forming apparatus 100 from a host processing device (not shown) such as an image reading device or a personal computer. As a result, the surface of the rotating photoreceptor 1 that has been uniformly charged is subjected to laser scanning exposure (image exposure) at the exposure portion (exposure position) b. By this laser scanning exposure, the absolute value of the potential of the portion irradiated with the laser beam L on the surface of the photoreceptor 1 is lowered, and an electrostatic latent image (static image) corresponding to image information is formed on the surface of the rotating photoreceptor 1. Image) is formed sequentially.

  Next, the image forming apparatus 100 includes a developing device 4 as a developing unit that supplies toner to the electrostatic latent image on the photoreceptor 1 and develops the electrostatic latent image as a toner image (developer image). The developing device 4 develops the electrostatic latent image on the photoreceptor 1 by reversal development. That is, the exposed portion of the photosensitive member 1 whose absolute value of potential has been lowered by being exposed after being uniformly charged is charged to the same polarity as the charging polarity (negative polarity in this embodiment) of the photosensitive member 1. A toner image is formed by attaching the toner. The developing device 4 includes a rotatable developing sleeve 41 as a developer carrying member that carries the developer and conveys the developer to the developing portion c that is a portion facing the photoreceptor 1. The length of the developing sleeve 41 in the longitudinal direction (rotational axis direction) is 325 mm. In this embodiment, the developing sleeve 41 holds a magnetic brush made of a two-component developer composed of toner and carrier, and performs development while making contact with the photoreceptor 1 at the developing section c. A predetermined developing voltage (developing bias) is applied to the developing sleeve 41 from a developing power source (high voltage power source) E2 as an application means. In the present embodiment, the developing voltage is an oscillating voltage in which a DC voltage (developing DC voltage Vdc) and an AC voltage (developing AC voltage Vac) are superimposed. For example, the developing voltage is an oscillating voltage in which a predetermined DC voltage, a frequency of 8.0 kHz, a peak-to-peak voltage of 1.8 kV, and a rectangular wave AC voltage are superimposed. This DC voltage is appropriately set so as to have an appropriate fog removal potential difference with respect to the charging potential of the photosensitive member 1 in the developing section c. The fog removal potential difference is a potential difference between the charging potential of the photosensitive member 1 and the DC component of the developing voltage applied to the developing sleeve 41, and develops toner charged to a normal charging polarity (negative polarity in this embodiment). It is directed toward the sleeve 41 side.

  Next, the image forming apparatus 100 includes an intermediate transfer device 12 as a transfer device that transfers the toner image formed on the photoreceptor 1 to the transfer material P. The intermediate transfer device 12 is an intermediate transfer composed of an endless belt serving as an intermediate transfer member that is disposed so as to face each photoconductor 1 and temporarily holds and conveys the toner image from the photoconductor 1. It has a belt 6. The intermediate transfer belt 6 is wound around a plurality of stretching rollers and is stretched in a state where a predetermined tension is applied. The intermediate transfer belt 6 is rotationally driven in the direction of arrow R2 in the figure by a drive roller that is one of a plurality of stretching rollers. In this embodiment, the intermediate transfer belt 6 is driven to rotate in the primary transfer portion N1 so as to move in the same direction as the photoreceptor 1 at substantially the same speed. On the inner peripheral surface side of the intermediate transfer belt 6, primary transfer rollers 5 Y, 5 M, which are roller-shaped primary transfer members as primary transfer means, are disposed at positions facing the respective photoreceptors 1 Y, 1 M, 1 C, 1 K. 5C and 5K are arranged. The primary transfer roller 5 is urged (pressed) toward the photoreceptor 1 via the intermediate transfer belt 6, and a primary transfer portion (primary transfer nip) N1 where the intermediate transfer belt 6 and the photoreceptor 1 are in contact with each other. Form. Further, on the outer peripheral surface side of the intermediate transfer belt 6, a roller-like secondary transfer member serving as a secondary transfer unit is provided at a position facing a secondary transfer counter roller that is one of a plurality of stretching rollers. A secondary transfer roller 8 is disposed. The secondary transfer roller 8 is urged (pressed) toward the secondary transfer counter roller via the intermediate transfer belt 6, and a secondary transfer portion (secondary transfer portion) where the intermediate transfer belt 6 and the secondary transfer roller 8 come into contact with each other. Transfer nip) N2 is formed. Further, on the outer peripheral surface side of the intermediate transfer belt 6, as an intermediate transfer body cleaning unit, downstream of the secondary transfer portion N 2 and upstream of the most upstream primary transfer portion N 1 Y in the moving direction of the intermediate transfer belt 6. The belt cleaning device 11 is arranged. 1 is a pressure nip between the photoreceptor 1 and the intermediate transfer belt 6 formed by the primary transfer roller 5 being brought into pressure contact with the photoreceptor 1 through the intermediate transfer belt 6 with a predetermined pressing force. The primary transfer portion N1 is the transfer portion d in FIG.

  The toner image formed on the photoreceptor 1 is electrostatically transferred onto the intermediate transfer belt 6 that is rotationally driven in the arrow direction R2 in the figure by the action of the primary transfer roller 5 in the primary transfer portion N1. (Primary transfer). At this time, the primary transfer roller 5 receives a DC voltage having a polarity (positive in this embodiment) opposite to the normal charging polarity of the toner (charging polarity at the time of development) from a primary transfer power source E3 as an application unit. A primary transfer voltage (primary transfer bias) is applied. In this embodiment, a +600 V DC voltage is applied as the primary transfer voltage. For example, during full-color image formation, the primary transfer is performed such that the toner images of the respective colors formed by the image forming units SY, SM, SC, and SK are sequentially superimposed on the intermediate transfer belt 6 by the respective primary transfer units N1. Is done. As a result, a multi-toner image for a full-color image using four color toner images is obtained.

  Along with the progress of the primary transfer of the toner image to the intermediate transfer belt 6, a transfer material P such as recording paper is supplied from the transfer material transport mechanism (not shown) to the secondary transfer portion N2 at a predetermined control timing. The The toner image on the intermediate transfer belt 6 is electrostatically transferred onto the transfer material P that is nipped and conveyed by the secondary transfer roller 8 in the secondary transfer portion N2 by the action of the secondary transfer roller 8 ( Secondary transfer). At this time, the secondary transfer roller 8 is supplied with a secondary transfer voltage which is a DC voltage having a polarity opposite to the normal charging polarity of the toner (positive in this embodiment) from a secondary transfer power source as an application unit (not shown). (Secondary transfer bias) is applied. When a full color image is formed, the four color toner images on the intermediate transfer belt 6 are secondarily transferred onto the transfer material P all at once.

  The transfer material P onto which the toner image has been transferred through the secondary transfer portion N2 is separated from the surface of the intermediate transfer belt 6 and conveyed to a fixing device 9 as a fixing unit. In this embodiment, the fixing device 9 is a heat roller fixing device, and the transfer material P is subjected to a toner image fixing process by the fixing device 9 and is output as an image formed product (print, copy).

  Further, the primary transfer residual toner remaining on the surface of the photoconductor 1 after the primary transfer of the toner image is removed from the surface of the photoconductor 1 by the photoconductor cleaning device 7 and collected. The photoconductor cleaning device 7 scrapes and removes the primary transfer residual toner from the surface of the rotating photoconductor 1 by the cleaning blade 71 that contacts the photoconductor 1 in the cleaning unit e. In this embodiment, the cleaning blade 71 is a flat plate member made of urethane rubber, and the length of the photosensitive member 1 in the longitudinal direction (rotation axis direction) is 330 mm. The cleaning blade 71 is pressed against the photoreceptor 1 with a linear pressure of 30 gf / cm.

  The secondary transfer residual toner remaining on the surface of the intermediate transfer belt 6 after the secondary transfer of the toner image is removed from the surface of the intermediate transfer belt 6 by the belt cleaning device 11 and collected.

2. In this embodiment, a plurality of independent recesses are formed on the surface of the photoreceptor 1 in this embodiment. FIG. 3 is a photographic view of a region having a specific recess on the surface of the photoreceptor 1 as viewed from the normal direction of the surface of the photoreceptor 1. In the same photograph, a circular portion is a specific concave portion, and the other portion is a flat portion. The definition of these specific concave portions and flat portions will be described later.

  In addition, the shape of a specific recessed part is not limited to circular, Arbitrary shapes other than circular may be sufficient. For example, an ellipse or a polygon such as a square, a rectangle, a triangle, a quadrangle, a pentagon, and a hexagon can be used. Further, the arrangement is not limited to the shape arranged in alignment, and may be arranged at random.

  FIG. 4 is a schematic diagram of a cross-section in the longitudinal direction of the photoconductor 1 with respect to the region having the specific concave portion and the region having only the flat portion in the photoconductor 1. As shown in FIG. 4A, in the region having the specific recess, the specific recess is formed at a predetermined area ratio in the flat portion that occupies most of the surface of the photoreceptor 1. Due to the manufacturing method of the specific recess, a rim-shaped protrusion that is a non-recess and a non-flat portion may be formed around the specific recess. Further, among the specific recesses, a space at a height level on the surface (flat portion) of the photoreceptor 1 is defined as an opening. In addition, as shown in FIG. 4B, there is no specific recess or the above-mentioned rim-shaped protrusion in the region having only the flat portion.

The shape of the surface of the photoreceptor 1 in this embodiment will be described in more detail. The surface of the photoreceptor 1 at least in the image forming area (area used for forming a toner image of an image transferred and output to the transfer material P) has a plurality of depths 2 in a state before the photoreceptor 1 is used. Specific recesses having a diameter of 5 ± 0.2 μm and a maximum opening diameter of 20 μm to 80 μm are provided. Here, it is assumed that a square region having a side of 500 μm whose one side is parallel to the rotation direction of the photoconductor 1 is arranged at an arbitrary position on the surface of the photoconductor 1. At this time, the specific recess is provided on the surface of the photoreceptor 1 so that the area of the specific recess in the square region having a side of 500 μm is 7500 μm ² or more and 88000 μm ² or less. Further, a flat portion is provided on the surface of the photoreceptor 1 in addition to the specific recess. Here, it is assumed that a square region having a side of 500 μm whose one side is parallel to the rotation direction of the photoconductor 1 is arranged at an arbitrary position on the surface of the photoconductor 1. At this time, the flat portion is provided on the surface of the photoreceptor 1 so that the area of the flat portion in the square region having a side of 500 μm is 81000 μm ² or more and 240000 μm ² or less.

  Here, the definition of the specific concave portion and the flat portion in a square region having a side of 500 μm will be described. The specific concave portion or flat portion on the surface of the photoreceptor 1 can be observed using a microscope such as a laser microscope, an optical microscope, an electron microscope, or an atomic force microscope. First, the surface of the photoreceptor 1 is enlarged and observed with a microscope or the like. When the surface of the photoconductor 1 is a curved surface curved along the rotation direction, a cross-sectional profile of the curved surface is extracted and the curve is fitted. The cross-sectional profile is corrected so that the curve becomes a straight line, and a surface obtained by extending the obtained straight line in the longitudinal direction of the photoreceptor 1 is used as a reference surface. A region having an elevation difference within ± 0.2 μm from the obtained reference plane is defined as a flat portion in the square region having a side of 500 μm. A part located below the flat part is defined as a concave part. Regarding the depth and the longest diameter of the opening, the maximum distance from the flat portion to the bottom surface of the recess is the depth of the recess, and the cross section of the recess by the flat portion is the opening of the recess. The length of the longest line segment is the longest diameter of the opening of the recess.

  Of the recesses in the square area of 500 μm on one side, the depth determined as described above is in the range of 0.5 μm to 6 μm, and the longest diameter of the opening is in the range of 20 μm to 80 μm. This corresponds to a specific recess in a 500 μm square region.

  In this embodiment, substantially all of the plurality of recesses on the surface of the photoreceptor 1 are specified recesses, particularly the specified recesses having a depth of 2.5 ± 0.2 μm and a longest opening diameter of 20 μm to 80 μm. The depth and the longest diameter of the opening do not satisfy this condition is negligible. The surface of the photoreceptor 1 may have a recess whose depth and maximum opening diameter do not correspond to the specific recess, but it is preferable that a specific recess and a flat portion satisfying the above-described conditions be provided. In the following description, the depth of the concave portion on the surface of the photoreceptor 1 is represented by an average value in the image forming area. For example, the average value of the diameters of the recesses in an arbitrary 2 cm × 2 cm area in the image forming area of the photoreceptor 1 can be obtained and used.

  Here, the concave portion on the surface of the photoconductor 1 can be formed by a method of transferring a shape by pressing a mold having a predetermined shape against the surface of the photoconductor 1. For example, it can be formed by continuously pressing and pressing the mold on the surface (circumferential surface) of the photoconductor 1 while rotating the photoconductor 1 with a press-fitting shape transfer processing apparatus having a mold (mold). In addition, a method of forming a concave portion having a predetermined shape on the surface of the photosensitive member by laser irradiation is also known.

3. Suppression of image flow It has been found that the use of the photoreceptor 1 having a specific recess as in this embodiment dramatically improves the effect of suppressing image flow. Arranging the recesses sparsely suppresses abnormal vibration of the cleaning blade 71 from the photosensitive member 1 side, so-called chattering appropriately, creates a stable and good rubbing state, and reduces the pressure of the cleaning blade in the recesses. This increases the pressure on the other parts. In addition, among the non-concave portions where the pressure increases, the surface state is such that the causative substances of the image flow adhering to the surface of the photosensitive member 1 can be easily removed by increasing the number of flat portions that can be efficiently refreshed. Can be formed. It is considered that the effect of suppressing image flow is drastically improved by such a mechanism.

  However, as described above, when the depth of the specific concave portion is reduced, the chattering of the cleaning blade 71 is suppressed and a stable and good rubbing state is created, and the pressure of the cleaning blade on the concave portion is reduced. Any effect of increasing pressure on other parts is reduced. As a result, image flow is likely to occur. In order to effectively suppress the image flow, the depth of the specific recess in at least the image forming region of the photoreceptor 1 is preferably 1.0 μm or more, and more preferably 1.5 μm or more.

4). Suppression of the cleaning blade of the photoconductor and the abnormal noise By using the photoconductor 1 having the specific concave portion as in the present embodiment, the effect of suppressing the cleaning blade 71 from curling and abnormal noise can be dramatically improved. It turns out. The wobbling or abnormal noise of the cleaning blade 71 is an abnormal phenomenon that is likely to occur in a high-humidity environment when an image is formed using the photoconductor 1 having a particularly high hardness.

  That is, when the depth of the specific recess is reduced, the contact area between the cleaning blade 71 and the surface of the photosensitive member 1 is increased, the friction coefficient of the cleaning blade 71 is significantly increased, and the chatter phenomenon of the cleaning blade 71 becomes obvious. It is known. Then, the amplitude motion of the stick slip increases, and the photosensitive member 1 may resonate with the vibration of the cleaning blade 71 and generate an abnormal noise. Further, when the amplitude of the cleaning blade 71 is increased, the cleaning blade 71 may be reversed and the cleaning blade 71 may be bent. When the cleaning blade 71 is bent, the load on the photoconductor 1 is suddenly increased, and the image forming operation of the image forming apparatus 100 may be stopped.

  As in the case of image flow, it has been found that the deeper the recess, the higher the effect on the cleaning blade 71 as well as the wobbling and noise. If the concave portion becomes shallower, abnormal noise due to stick-slip of the cleaning blade 71 is likely to occur, and the probability that the cleaning blade 71 is swollen increases.

5. Setting of Depth of Recess In this example, as described above, the center of the depth of the specific recess was set to 2.5 μm. If the depth of the specific recess is greater than 3.5 μm, the gap between the cleaning blade 71 and the recess on the surface of the photoreceptor 1 is too large. For this reason, there is a possibility that the toner slips through the gap between the cleaning blade 71 and the concave portion of the surface of the photoreceptor 1 and stains the image due to poor cleaning. In addition, if the depth of the specific recess is less than 1.0 μm, there is a possibility that a phenomenon such as image flow, wobbling or abnormal noise of the cleaning blade 71 may occur. Therefore, the depth of the specific recess is most suitable about 2.5 μm.

6). Reducing Depth of Recess by Use of Photoreceptor When image formation is performed, the film thickness of the surface of the photoreceptor 1 is reduced by rubbing with a member (mainly the cleaning blade 71) that comes into contact. At this time, as shown in FIG. 21, in the region having the specific recess, the height level of the flat portion decreases, and therefore the depth from the flat portion to the specific recess relatively decreases. In addition, the height of the rim-shaped protrusion, which is a non-recessed portion and a non-flat portion, decreases with the rubbing. Incidentally, although the height level of the entire region (not shown) having only the flat portion is lowered as a whole, the surface shape remains flat.

  FIG. 5 is a graph showing the relationship of the depth of the specific concave portion with respect to the repeated use status (number of output images) of the photoreceptor 1. FIG. 5 shows that the depth of the specific concave portion decreases as the number of image outputs increases.

7). Expression of Horizontal Lines Horizontal lines (horizontal line image, horizontal line phenomenon) are stripe-like density unevenness appearing on an image along the longitudinal direction (main scanning direction) of the photosensitive member 1. The horizontal streak is not sufficiently charged with respect to the photosensitive member 1 in the gap between the photosensitive member 1 and the charging roller 2 in or near the charging nip, and the potential of the photosensitive member 1 reaches a desired potential. Is a phenomenon that is manifested by the occurrence of minute charging defects. Therefore, horizontal stripes are generally unlikely to occur in an image output using a charging voltage in which a charging DC voltage and a charging AC voltage are superimposed. On the other hand, horizontal stripes are likely to occur in an image output using a charging voltage consisting only of a charging DC voltage.

  More specifically, when an image is output using a charging voltage consisting only of a charging DC voltage, it is affected by a minute fluctuation of the gap size. For this reason, spark discharge is intermittently generated from the charging roller 2 to the photosensitive member 1, and a minute charging failure state is likely to occur, and for example, as shown in FIG. On the other hand, when output is performed using a charging voltage in which a charging DC voltage and a charging AC voltage are superimposed, the spark discharge is continuously in a very stable state in the gap between the photoreceptor 1 and the charging roller 2. . This is because AC discharge occurs. For this reason, the minute charging unevenness caused by the minute fluctuation of the gap size is immediately leveled, and the charging failure hardly occurs.

  Further, the unevenness of the surface of the photoreceptor 1 greatly affects the discharge state in the charging portion. Between the surface of the photoreceptor 1 and the charging roller 2, a gap is formed between the photoreceptor 1 and the charging roller 2 on the upstream side and the downstream side of the charging nip in the moving direction of the surface of the photoreceptor 1. Discharge regions (upstream discharge region and downstream discharge region) in which discharge occurs are present in regions where the upstream and downstream gaps are formed. When the DC charging method is adopted, even if the surface of the photoreceptor 1 is uneven, the discharge state in the downstream discharge region is controlled so that an abnormal image such as a horizontal stripe is not generated. That is, firstly, when the discharge state in the downstream discharge region is in a state of hardly discharging, the potential of the photosensitive member 1 is not disturbed by the discharge of the charging roller 2, and no abnormal image is generated. Second, when the discharge state in the downstream discharge region is in a stable discharge state, the discharge of the charging roller 2 does not disturb the potential of the photosensitive member 1, so that an abnormal image does not occur. .

  On the other hand, if the potential difference between the photosensitive member 1 and the charging roller 2 in the downstream discharge region is 10 to 20 V, the potential difference starts to start unstable discharge between the charging roller 2 and the photosensitive member 1, and the abnormality occurs. It is known that an abnormal discharge occurs and an abnormal image occurs. If there are irregularities on the surface of the photosensitive member 1 that cause a gap between the photosensitive member 1 and the charging roller 2 in the downstream discharge region in such an unstable discharge state, the starting point is the starting point. Unstable discharge starts and image defects such as horizontal streaks occur.

  There are the following two patterns as a system configuration for suppressing the occurrence of horizontal stripes. One is a system that does not generate discharge in the downstream discharge region as much as possible, such as using the photoconductor 1 in which dark decay of the surface potential hardly occurs. Here, the photoreceptor 1 in which the dark decay of the surface potential does not easily occur is, for example, the dielectric loss characteristics of the photoreceptor 1 in a frequency band corresponding to the time during which a portion of the surface of the photoreceptor 1 passes through the charging nip. For example, the photosensitive member 1 has a significantly small tan δ value. More specifically, in a system that does not generate a discharge in the downstream discharge region as much as possible, the potential difference between the photosensitive member 1 and the charging roller 2 in the downstream discharge region is set to be less than 10V. On the other hand, in the downstream discharge area, the photosensitive drum 1 having a large dark decay of the surface potential is used, or the charging roller 2 having a high electric resistance and the charging potential is difficult to move in the upstream discharge area. This is a system with a large discharge. More specifically, in a system in which the discharge in the downstream discharge region is large, the potential difference between the photoreceptor 1 and the charging roller 2 in the downstream discharge region is set to exceed 20V. Here, the photoreceptor 1 having a large dark decay of the surface potential has a dielectric loss characteristic tan δ of the photoreceptor 1 in a frequency band corresponding to a time during which a portion of the surface of the photoreceptor 1 passes through the charging nip, for example. For example, the photosensitive member 1 has a remarkably large value.

  By the way, in each system in which the occurrence of horizontal stripes is suppressed as described above, it is possible to intentionally generate horizontal stripes intentionally. Since the degree of occurrence of the horizontal stripe correlates with the unevenness of the surface of the photoconductor 1 as described above, that is, the depth of the concave portion of the surface of the photoconductor 1, It can be used to grasp the lifetime.

  In a system that does not generate a discharge in the downstream discharge region as much as possible, the rotational speed of the photosensitive member 1 is made slower than the normal rotational speed set so as not to generate a horizontal stripe. As a result, the amount of dark decay of the surface potential of the photoreceptor 1 during the passage through the charging nip increases, so that the discharge state in the downstream discharge region can be changed to a discharge state in which a horizontal stripe is generated. . In this case, more specifically, the rotational speed of the photosensitive member 1 is decreased so that the potential difference between the photosensitive member 1 and the charging roller 2 in the downstream discharge region is within a range of 10V to 20V.

  Further, in a system with a large discharge in the downstream discharge region, the rotational speed of the photoconductor 1 is set higher than the normal rotational speed set so as not to generate a horizontal stripe. As a result, the amount of dark decay of the surface potential of the photoreceptor 1 during the passage through the charging nip is reduced, so that the discharge state in the downstream discharge region can be changed to a discharge state in which horizontal streaks are generated. . In this case, more specifically, the rotational speed of the photoconductor 1 is increased so that the potential difference between the photoconductor 1 and the charging roller 2 in the downstream discharge region is within the range of 10V to 20V.

  FIG. 6 shows the relationship between the rotational speed of the photosensitive member 1 and the level of horizontal streaking in the above two systems. Note that the downstream discharge area is focused on because the discharge in the downstream discharge area finally affects the horizontal stripes on the image.

  That is, in the configuration in which an image is formed by the DC charging method, a horizontal streak does not occur at the rotational speed of the photoconductor 1 during normal image formation. However, the rotational speed of the photoconductor 1 is intentionally changed. As a result, a horizontal streak is likely to occur. Thereby, it is possible to detect the depth of the concave portion on the surface of the photoconductor 1 based on the level of occurrence of horizontal stripes and to grasp the remaining life of the photoconductor 1.

  As described above, when the dark decay amount of the surface potential of the photosensitive member 1 is large, the rotational speed of the photosensitive member 1 is intentionally made higher than that at the time of normal image formation, so The amount of discharge generated between the charging roller 2 is reduced. As a result, it is possible to intentionally make a state in which a horizontal streak that becomes a barometer of the remaining life of the photoreceptor 1 is likely to occur.

  On the contrary, when the dark attenuation amount of the photosensitive member 1 is small as described above, the rotational speed of the photosensitive member 1 is intentionally made slower than that at the time of normal image formation, so The amount of discharge generated with the charging roller 2 is increased. As a result, it is possible to intentionally make a state in which a horizontal streak that becomes a barometer of the remaining life of the photoreceptor 1 is likely to occur.

8). Test Image and Test Operation Next, a test image and a test operation for obtaining information related to the depth of the concave portion on the surface of the photoreceptor 1 in this embodiment will be described.

  In this embodiment, substantially the same test operation is performed for each of the first, second, third, and fourth image forming units SY, SM, SC, and SK in order to grasp the remaining life of the photosensitive member 1. Are sequentially performed sequentially at the same time by one instruction. In the following description, in order to avoid duplication, the description will be given focusing on one image forming unit S.

  In this embodiment, a system in which the discharge in the downstream discharge region is large, such as using the photoreceptor 1 having a large dark decay of the surface potential, will be described. In this case, the rotational speed of the photoconductor 1 in the test operation is faster than the rotational speed (herein also referred to as the first speed (or normal rotational speed)) during normal image formation (here, the second speed). Speed (or high rotation speed)).

  The test image is preferably a halftone image having a predetermined density from the viewpoint of easy confirmation of the occurrence of horizontal stripes. In this example, as a test image, a uniform halftone image was formed over the entire area of the A4 size image forming region as shown in FIG. However, the test image is not limited to this, and the test image is a part of the image forming area such as a patch in which a halftone image is formed only in a part of the A4 size as shown in FIG. It may be formed. Further, the test image may be a gradation pattern in which the level of horizontal streak generation in various density ranges can be confirmed as shown in FIG.

  The surface of the photoconductor 1 does not wear uniformly over the entire region in the main scanning direction, but wears unevenly according to the pressing force distribution of the cleaning blade 71, the pressing force distribution of the primary transfer roller 5, and the like. There is. Therefore, it is desirable that the test image is an image that can grasp the tendency of wear in the entire image forming area of the photoconductor 1 in the main scanning direction. For this purpose, test images are preferably formed at a plurality of locations such as at least the center and both ends of the image forming area in the main scanning direction of the photoconductor 1, and the entire area of the image forming area in the main scanning direction of the photoconductor 1. It is more preferable to form a test image on

  The test operation in the present embodiment will be described with reference to FIGS. FIG. 8 is a block diagram illustrating a schematic control mode of the image forming apparatus 100 related to the test operation, and FIG. 9 is a timing chart illustrating an operation sequence of each unit related to the test operation.

  The control unit 20 serving as a control unit provided in the image forming apparatus 100 includes a CPU 21 that is a central element that performs arithmetic processing, a memory 22 such as a ROM and RAM that are storage elements (storage units), and the like. The The RAM stores sensor detection results, calculation results, and the like, and the ROM stores control programs, data tables obtained in advance, and the like. In this embodiment, the control unit 20 comprehensively controls each unit of the image forming apparatus 100. In particular, in relation to the present embodiment, the control unit 20 includes a charging power source E1, a developing power source E2, a primary transfer power source E3, an operation unit 13 provided in the apparatus main body, a photoconductor driving unit 14, and a developing device. The drive unit 15, the exposure device 3, the fixing device 9 and the like are connected. In this embodiment, the control unit 20 executes a test operation (test image output mode) in response to an instruction from the operation unit 13 by an operator such as a service person or a user, and the test image is transferred to the transfer material P. The image is formed and output from the image forming apparatus 100.

  The control unit 20 shifts to a test operation (test image output mode) in response to an operator instruction by operating an operation button provided on the operation unit 13. Then, the control unit 20 instructs the switching unit 14b of the photoconductor driving unit 14 to switch the rotation speed of the photoconductor 1 to a high rotation speed, and starts the rotation of the photoconductor 1. In this embodiment, the rotation speed of the photosensitive member 1 is set to 300 mm / sec (normal rotation speed) during normal image formation and 450 mm / sec (high rotation speed) during the test operation. Then, the control unit 20 starts applying a charging DC voltage (-1200 V in this embodiment) from the charging power source E1 to the charging roller 2. Subsequently, the control unit 20 starts application of a development DC voltage (-450 V in this embodiment) from the development power source E2 to the development sleeve 41 of the development device 4, and immediately after that, the primary transfer power source E3 performs the primary transfer. Application of the primary transfer DC voltage (+700 V in this embodiment) to the roller 5 is started. Here, when the developing DC voltage is applied to the developing sleeve 41 in a state where the rotation of the developing sleeve 41 is not started, the toner existing between the photosensitive member 1 and the developing sleeve 41 is transferred to the photosensitive member 1 side. This is to suppress this. Subsequently, the control unit 20 causes the developing device driving unit 15 to start the rotation of the developing sleeve 41. The time from the start of applying the charging voltage to the charging roller 2 to the start of rotation of the developing sleeve 41 is about 1 second. This is because the photosensitive member 1 is rotated 2-3 times until the surface potential of the photosensitive member 1 is stabilized, and the charging portion a is passed 2-3 times. Next, immediately after the start of rotation of the developing sleeve 41, the control unit 20 starts application of a developing AC voltage (for example, a rectangular wave, a frequency of 10 kHz, 1.4 kVpp) from the developing power source E2 to the developing sleeve 41. Although development can be performed by applying only the development DC voltage, it is preferable to superimpose the development AC voltage in order to stabilize the density of the toner image. Next, the control unit 20 starts irradiation of laser light from the exposure device 3 to the photosensitive member 1. At this time, it is assumed that the exposure pattern by the laser beam corresponds to the test image pattern shown in FIG.

  In addition, after the exposure by the exposure apparatus 3 is completed, the control unit 20 applies the developing AC voltage, rotates the developing sleeve 41, applies the primary transfer DC voltage, and applies the developing DC voltage, contrary to the above procedure. Then, the application of the charging DC voltage is stopped in order. Further, the control unit 20 stops the rotation of the photoconductor 1 after the surface of the photoconductor 1 is sufficiently discharged. In order to neutralize the surface of the photoreceptor 1, light may be applied to the surface of the photoreceptor 1 using pre-exposure means.

  The toner image of the test image formed on the photoreceptor 1 is primarily transferred from the photoreceptor 1 to the intermediate transfer belt 6 and transferred from the intermediate transfer belt 6 to the transfer material P in the same manner as in the case of normal image formation. Then, the image is fixed on the transfer material P by the fixing device 9. Note that when the rotational speed of the photosensitive member 1 is switched to a high rotational speed, the rotational speed of the intermediate transfer belt 6 is correspondingly increased compared to that during normal image formation. In this manner, the operator can obtain an output product on which the test image indicating the information on the depth of the concave portion on the surface of the photoreceptor 1 is formed on the transfer material P.

9. FIG. 10A schematically shows an example of a test image output by rotating the photosensitive member 1 at a high rotational speed. In this case, the operator actually outputs a correspondence chart that is a reference image for associating the state of the horizontal streak in the test image prepared in advance with the remaining life of the photosensitive member 1 as shown in FIG. Compare the test images. In the correspondence chart of FIG. 12, the state of horizontal stripes is associated with the depth of the recesses on the surface of the photoconductor 1 and the remaining life of the photoconductor 1. The correspondence chart is provided by the provider of the image forming apparatus 100 by obtaining the relationship between the state of the horizontal stripe, the depth of the concave portion on the surface of the photoconductor 1 and the remaining life of the photoconductor 1 through an experiment or the like in advance. Can do. Then, the operator determines how many μm the depth of the concave portion on the surface of the photoconductor 1 at the time of outputting the test image, and how much the remaining life of the photoconductor 1 is. Can do.

  For example, when the horizontal streak generation level in the actually output test image is as shown in FIG. 11A, the depth of the recess on the surface of the photoreceptor 1 is 1. It can be understood that the remaining life of the photosensitive member 1 is about 0%. The level of horizontal streaks in the test image of FIG. 11A is relatively low. That is, as described above, when the depth of the concave portion on the surface of the photosensitive member 1 is 1.0 μm or less, there is a possibility that an image flow may occur, or the cleaning blade 71 may be twisted or generate abnormal noise. Therefore, in this case, the operator can grasp that the photoreceptor 1 should be replaced at an early stage.

  For example, when the level of horizontal streaks in the actually output test image is as shown in FIG. 11B, the depth of the concave portion on the surface of the photoreceptor 1 is determined from the corresponding chart in FIG. It is still about 2.0 μm, and it can be understood that the remaining life of the photoreceptor 1 is about 66%. The level of horizontal streaks in the test image of FIG. 11B is relatively high. In this case, the operator can grasp that it is not necessary to replace the photosensitive member 1 for a while.

  As described above, the remaining life of the photoconductor 1 can be grasped by confirming the information related to the depth of the concave portion on the surface of the photoconductor 1 by using the test image formed using the high rotation speed.

  FIG. 10B shows, as a modification, a test image (left side) output by rotating the photoconductor 1 at a high rotation speed and a comparison image output by driving the photoconductor 1 at a normal rotation speed. A test image (right side) is shown typically. These test images and comparative test images are continuously output at the same time in a test operation performed by one instruction. In this example, the test image and the comparative test image are formed on different transfer materials P and output. Further, the comparative test image is formed with the other conditions such as the density and pattern of the halftone being substantially the same as those of the test image except that the normal rotational speed is used as the rotational speed of the photoconductor 1. Is done. In this case, it is possible to detect streaky density unevenness caused by factors other than the horizontal streaks generated according to the concave portions on the surface of the photoreceptor 1. That is, since the comparative test image is output by rotating the photosensitive member 1 at a normal rotation speed, a horizontal stripe corresponding to the depth of the concave portion on the surface of the photosensitive member 1 hardly occurs. Therefore, streaky density unevenness generated corresponding to both the test image (left side) and the comparative test image (right side) occurs regardless of the depth of the concave portion on the surface of the photoreceptor 1. It can be judged that it is a thing. Therefore, when the test image is observed to determine the depth of the concave portion of the photoconductor 1 and the remaining life of the photoconductor 1, the test image and the corresponding chart are confirmed ignoring the stripe-like density unevenness. be able to. Thereby, the level of accuracy of the lifetime of the photosensitive member 1 grasped by the operator can be improved.

  Note that the output of the comparison test image can be performed following the output of the above-described test image in the test operation. However, the order in which the test image and the comparison test image are formed and output may be reversed, or may be formed and output on the same transfer material P if possible.

  As described above, in this embodiment, the image forming apparatus 100 includes the control unit 20 that executes the image forming operation and the test operation. In the image forming operation, a toner image corresponding to arbitrary image information is formed, transferred to the transfer material P, and output. In the test operation, a test image for obtaining information relating to the remaining life of the photoreceptor 1 is formed, transferred to the transfer material P, and output. Then, the controller 20 rotates the photosensitive member 1 at the first speed during the image forming operation. Further, the control unit 20 drives the photosensitive member 1 to rotate at a second speed different from the first speed during the test operation. At the same time, the control unit 20 applies a charging voltage consisting only of a DC voltage to the charging member 2 to charge the photoreceptor 1 to form a test image. Further, in the test operation, the control unit 20 further transfers a comparison test image formed on the transfer material P by rotating the photosensitive member 1 at the first speed and can be compared with the test image. Can be made.

  As described above, according to the present embodiment, it is possible to accurately detect the depth of the concave portion on the surface of the photosensitive member 1 that changes due to wear due to use, and to grasp the remaining life of the photosensitive member 1 more accurately. As a result, it is possible to suppress the occurrence of problems such as image flow, wobbling of the cleaning blade, and abnormal noise by replacing the photoconductor 1 at an appropriate time. Further, since the remaining life of the photoconductor 1 can be grasped more accurately, the necessity of replacing the photoconductor 1 early with a margin is reduced, and the life of the photoconductor 1 can be extended. Further, the remaining life of the photosensitive member 1 can be more accurately grasped by a simple method of changing the rotational speed of the photosensitive member 1 without changing the hardware configuration of the image forming device 100. It can also contribute to simplification.

Example 2
Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the first embodiment. Therefore, elements having the same functions or configurations as those of the first embodiment or corresponding to those of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In this embodiment, as in the first embodiment, in the test operation for grasping the remaining life of the photosensitive member 1, the photosensitive member 1 is rotationally driven at a high rotational speed as shown in FIG. 7A, for example. Output the test image. In addition, in the present embodiment, in a test operation, a correspondence chart, for example, a reference image as shown in FIG. 12 formed by rotating the photosensitive member 1 at a normal rotational speed is output. In the present embodiment, these test images and the corresponding chart are continuously output at the same time in a test operation performed by one instruction. The information of the correspondence chart is obtained in advance through experiments and stored in the memory 22 of the control unit 20.

  Thus, in this embodiment, the test image and the correspondence chart for the operator to determine the remaining life of the photoreceptor 1 are output at the same time in the test operation. That is, in the present embodiment, the control unit 20 can further relate the density unevenness and the remaining life of the photoconductor 1 formed by rotating the photoconductor 1 at the first speed in the test operation. Is transferred to the transfer material P and output. This eliminates the need for the operator to prepare and store or carry the corresponding chart in advance as in the first embodiment, and grasp the remaining life of the photoreceptor 1 using the corresponding chart output on the spot when necessary. Is possible.

  Since the corresponding chart is output by rotating the photosensitive member 1 at a normal rotation speed, a horizontal stripe corresponding to the depth of the concave portion on the surface of the photosensitive member 1 is hardly generated and can be used as a reference image. is there.

  Note that the operator may be able to select, for example, from the operation unit 13 whether to output the correspondence chart in the test operation. Further, as in the modification of the first embodiment, a comparative test image may be further output in the test operation.

  As described above, according to the present embodiment, the same effects as those of the first embodiment can be obtained, the trouble of storing or carrying the corresponding chart can be omitted, and the remaining life of the photoreceptor 1 can be grasped without delay when necessary. .

Example 3
Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the first embodiment. Therefore, elements having the same functions or configurations as those of the first embodiment or corresponding to those of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the present embodiment, density unevenness of a test image is detected using a sensor provided in the image forming apparatus 100, the remaining life of the photoconductor 1 is automatically detected by the image forming apparatus 100, and the detection result is notified. It can be so. In particular, in this embodiment, density unevenness of the toner image of the test image is detected on the intermediate transfer belt 6.

1. Optical Sensor In this embodiment, as shown in FIG. 1, an optical sensor 10 as a density detecting means is arranged so that the density of the toner image of the test image transferred onto the intermediate transfer belt 6 can be detected. . More specifically, the toner image in the image forming area on the intermediate transfer belt 6 at a position downstream of the most downstream primary transfer portion N1K and upstream of the secondary transfer portion N2 in the moving direction of the intermediate transfer belt 6. The optical sensor 10 is arranged so that the density of the light can be detected.

  FIG. 13A is a schematic configuration diagram of the optical sensor 10 in the present embodiment. The left-right direction in FIG. 13A is the main scanning direction (the direction substantially orthogonal to the moving direction of the intermediate transfer belt 6). The optical sensor 10 generally includes an optical system Q, an amplifier (AMP) 22, a peak detection circuit 24, a sample and hold circuit 26, an under peak detection circuit 28, and a sample and hold circuit 30. The optical system Q is configured to include an illumination optical system including a regular reflection LED 10a and a diffusion LED 10b, and a light receiving optical system including a lens 10c, a photodiode 10d, and a mask 10e. The regular reflection LED 10a is used to measure the density of a black toner image, and illuminates the toner image on the intermediate transfer belt 6 at an angle of 10 ° with respect to the normal of the surface of the intermediate transfer belt 6. The diffusion LED 10b is used for measuring the density of toner images of yellow, magenta, and cyan, and the angle of the toner image on the intermediate transfer belt 6 is 30 ° with respect to the normal of the surface of the intermediate transfer belt 6. Illuminate with. The light receiving optical system is disposed at an angle of 10 ° with respect to the normal of the surface of the intermediate transfer belt 6. Thereby, the illumination light by the regular reflection LED 10a can be received as the regular reflection on the surface of the intermediate transfer belt 6. Further, the light receiving optical system can receive only the diffused light from the toner without receiving the light that the illumination light from the diffusion LED 10b is specularly reflected by the surface of the intermediate transfer belt 6. As the lens 10c of the light receiving optical system, one having a diameter of 3 mm and a focal length of 6 mm is used, the distance from the surface of the intermediate transfer belt 6 to the lens and the distance from the lens to the photodiode are set to 12 mm, and the magnification of the optical system is 1x. A mask 10e that restricts the detection area of the sensor is provided immediately before the photodiode 10d. In this embodiment, the detection window of the mask 10e is a square of 1 mm × 1 mm. Portions other than the mask detection window are black to prevent stray light. With such an arrangement of the light receiving optical system, the detection area of the optical sensor 10 can be set to 1 mm × 1 mm which is substantially equal to the size of the detection window of the mask in both cases of regular reflection light and diffuse reflection light.

  When the optical image of the toner image on the intermediate transfer belt 6 is projected onto the light receiving surface of the photodiode 10d, the photodiode 10d outputs a current that changes according to the density of the optical image. The current output from the photodiode 10d is converted into current / voltage by the AMP 22 and then, as a sensor output signal, the control unit 20, the peak detection circuit 24, the under-peak detection circuit 28, and the two sample & hold circuits 26, 30 To be supplied. The peak detection circuit 24 detects the maximum position of the sensor output signal and supplies it to the sample and hold circuit 26 as a peak detection signal. The sample & hold circuit 26 holds the sensor output signal output from the AMP 22 using the peak detection signal output from the peak detection circuit 24 as a trigger. As a result, the maximum value of the sensor output signal is held and output to the control unit 20 as a hold signal. The control unit 20 calculates the image density based on the hold signal and controls the image density. The under peak detection circuit 28 detects the minimum position of the sensor output signal and supplies it to the sample and hold circuit 30 as an under peak detection signal. The sample and hold circuit 30 holds the sensor output signal output from the AMP 22 with the under peak detection signal output from the under peak detection circuit as a trigger. Thereby, the minimum value of the sensor output signal is held and output to the control unit 20 as an under-peak hold signal. The control unit 20 calculates the image density based on the hold signal and detects a horizontal stripe. Note that the AMP 22, the peak detection circuit 24, the under-peak detection circuit 28, and the sample and hold circuits 26 and 30 use general electric circuits, and a description thereof is omitted here.

  Further, the optical sensor 10 has a shutter 10f. FIG. 13B shows a configuration diagram of the shutter 10f. FIG. 13B is a view of the shutter 10f as seen from the LED / PD side. The shutter 10f is provided with a measurement window 10g and a reference plate 10h for obtaining a reference for the output voltage of the sensor. The optical sensor 10 includes a mechanism for moving the shutter 10f in the left-right direction in FIG. The shutter 10f is in such a position that the reference plate 10h is disposed on the light receiving system optical axis in a normally closed state, and the shutter 10f is opened only during measurement so that the measurement window 10g is disposed on the light receiving system optical axis. Move to.

2. Detection of Horizontal Streak and Calculation of Remaining Life FIG. 14 shows an output result obtained by converting an under-peak hold signal into an image density D when a horizontal stripe is generated. The image density D is shaken due to the occurrence of horizontal streaks in the test image formed on the intermediate transfer belt 6. Since the test image is formed with a constant density setting as a reference, a density step having a high density is generated protruding from the reference density level. Therefore, the control unit 20 calculates the density step ΔD from the reference density serving as the base. Further, information indicating the relationship between the density difference ΔD and the remaining lifetime of the photoreceptor 1 as shown in FIG. 15 is obtained in advance through experiments and stored in the memory 22 of the control unit 20. Thereby, the control unit 20 obtains the remaining life of the photoconductor 1 from the calculated density step ΔD using information indicating the relationship between the density step ΔD and the remaining life of the photoconductor 1 as shown in FIG. Can do. As information related to the density step ΔD obtained from the information indicating the relationship between the detection time (detection position) and the image density D as shown in FIG. 14, arbitrary information such as a maximum value, a minimum value, an average value, and the photoconductor 1 remaining lifetime can be related. In this embodiment, it is assumed that the maximum value of the density step ΔD obtained from the information indicating the relationship as shown in FIG. 14 and the remaining life of the photoreceptor 1 are related.

  In the present embodiment, the control unit 20 stores information indicating the obtained remaining life of the photoreceptor 1 in the memory 22. Then, the control unit 20 allows the operator to acquire information indicating the remaining life of the photosensitive member 1 by displaying it in response to the operator's request.

3. Test Image and Test Operation Next, a test image and a test operation for obtaining information related to the depth of the concave portion on the surface of the photoreceptor 1 in this embodiment will be described.

  In this embodiment, substantially the same test operation is performed for each of the first, second, third, and fourth image forming units SY, SM, SC, and SK in order to grasp the remaining life of the photosensitive member 1. Are sequentially performed sequentially at the same time by one instruction. In the following description, in order to avoid duplication, the description will be given focusing on one image forming unit S.

  As in the case of Example 1, the test image formed on the intermediate transfer belt 6 is preferably a halftone image having a predetermined density. In this embodiment, as shown in FIG. 16A, the test image has a width in the main scanning direction that can be detected by the optical sensor 10 and a uniform length corresponding to the circumference of the photoreceptor 1. Halftone images were formed. However, the present invention is not limited to this, and the test image is, for example, a plurality of patch-shaped halftone images formed in the sub-scanning direction (moving direction of the intermediate transfer belt 6) as shown in FIG. It may be. Thereby, toner consumption can be suppressed.

  In this embodiment, the optical sensor 10 is installed in a fixed state at the center in the main scanning direction. Therefore, the test image is formed at the center in the main scanning direction corresponding to the fixed position of the optical sensor 10.

  Here, as described in the first embodiment, the test image is desirably an image that can grasp the tendency of wear in the entire image forming area in the main scanning direction of the photosensitive member 1. For this purpose, for example, the optical sensor 10 is configured to be movable in the main scanning direction, or a plurality of optical sensors 10 are provided in the main scanning direction, so that the density difference ΔD can be detected at a plurality of positions in the main scanning direction, more preferably at the entire area. May be.

  The test operation in the present embodiment will be described with reference to FIGS. FIG. 17 is a block diagram illustrating a schematic control mode of the image forming apparatus 100 related to the test operation, and FIG. 18 is a timing chart illustrating an operation sequence of each unit related to the test operation.

  The control mode related to the test operation in the present embodiment is the same as that in the first embodiment. In particular, in terms of the relationship with the present embodiment, the control unit 20 further includes the optical sensor 10 and the intermediate transfer belt. A drive unit 16 is connected. The intermediate transfer belt drive unit 16 switches between a motor 16a as a drive source and a normal image forming time for forming an image to be output by transferring the rotation speed of the intermediate transfer belt 6 to the transfer material P and a test operation time. Part 16b. In this embodiment, the control unit 20 executes a test operation (photoreceptor remaining life detection mode) at a predetermined timing, detects the remaining life of the photoreceptor 1, and stores the detection result. Further, the control unit 20 displays information indicating the stored remaining life of the photoreceptor 1 in accordance with an instruction from the operator.

  When the main power supply of the image forming apparatus 100 is turned on or the image forming apparatus 100 returns from the sleep state, the control unit 20 shifts to a test operation (photoreceptor remaining life detection mode). Then, the control unit 20 instructs the switching unit 14b of the photoconductor driving unit 14 to switch the rotation speed of the photoconductor 1 to a high rotation speed, and starts the rotation of the photoconductor 1. At this time, the control unit 20 causes the switching unit 16b of the intermediate transfer belt driving unit 16 to increase the rotation speed of the intermediate transfer belt 6 in accordance with the rotation speed of the photosensitive member 1 as compared with that during normal image formation. The intermediate transfer belt 6 is started to rotate. Then, the control unit 20 starts application of a charging DC voltage from the charging power source E1 to the charging roller 2. Subsequently, the control unit 20 starts application of the development DC voltage from the development power supply E2 to the development sleeve 41 of the development device 4, and immediately thereafter, the primary transfer DC from the primary transfer power supply E3 to the primary transfer roller 5 is started. Start applying voltage. Subsequently, the control unit 20 causes the developing device driving unit 15 to start the rotation of the developing sleeve 41. Next, immediately after the start of rotation of the developing sleeve 41, the control unit 20 starts applying a developing AC voltage from the developing power source E <b> 2 to the developing sleeve 41. Next, the control unit 20 starts irradiation of laser light from the exposure device 3 to the photosensitive member 1. At this time, it is assumed that the exposure pattern by the laser beam corresponds to the test image pattern shown in FIG.

  In addition, after the exposure by the exposure apparatus 3 is completed, the control unit 20 applies the developing AC voltage, rotates the developing sleeve 41, applies the primary transfer DC voltage, and applies the developing DC voltage, contrary to the above procedure. Then, the application of the charging DC voltage is stopped in order. Further, the controller 20 stops the rotation of the photoconductor 1 after the surface of the photoconductor 1 is sufficiently discharged, and also stops the rotation of the intermediate transfer belt 6. In order to neutralize the surface of the photoreceptor 1, light may be applied to the surface of the photoreceptor 1 using pre-exposure means.

  The toner image of the test image formed on the photoreceptor 1 is transferred from the photoreceptor 1 to the intermediate transfer belt 6 in the same manner as in the case of normal image formation. Further, at the timing when the toner image of the test image transferred to the intermediate transfer belt 6 passes through the detection area by the optical sensor 10, the optical sensor 10 receives the specularly reflected light as described above. Then, the control unit 20 converts the light amount received by the optical sensor 10 into density information D, and calculates a density step ΔD that is a density step component of the density D. Further, the control unit 20 derives the remaining life of the photoconductor 1 from the calculated density step ΔD using information indicating the relationship between the density step ΔD and the remaining life of the photoconductor 1 as shown in FIG. Information indicating the remaining life of the photoreceptor 1 is stored in 22. The toner image of the test image on the intermediate transfer belt 6 is then removed from the intermediate transfer belt 6 by the belt cleaning device 11 and collected.

  FIG. 19A is a flowchart showing an outline of the procedure of the test operation. As described above, when the test operation is started, the control unit 20 sequentially starts the rotation of the photosensitive member 1 at a high rotation speed (S101), and the toner image of the test image is transferred to the intermediate transfer belt 6. Form (S102). Next, the control unit 20 causes the optical sensor 10 to detect the density of the toner image of the test image on the intermediate transfer belt 6 (S103), calculates the density step ΔD (S104), and obtains the remaining life of the photoreceptor 1. Save in the memory 22 (S105). Thereafter, the control unit 20 ends the test operation (S106). FIG. 19B is a flowchart showing an outline of an operation procedure for informing the remaining life of the photoreceptor 1. The control unit 20 reads information indicating the remaining life of the photosensitive member 1 stored in the memory 22 in response to an instruction by the operator operating an operation button provided on the operation unit 13 (S201). ). Then, the control unit 20 transmits information indicating the remaining life of the current photoreceptor 1 to the operation unit 13, and displays the remaining life of the current photoreceptor 1 on a display unit (display) provided in the operation unit 13. Information to be displayed is displayed (S203).

  Here, in the present embodiment, the timing for executing the test operation is the time when the main power supply is turned on and the time of return from the sleep state, but is not limited thereto. For example, the test operation may be executed at a predetermined timing set according to the cumulative number of image outputs of the image forming apparatus 100. However, since the wear of the photoconductor 1 does not change so much at the daily image output number level, the depth of the concave portion on the surface of the photoconductor 1 does not change so much. Therefore, as in the present embodiment, by performing the test operation only when the main power is turned on and when returning from the sleep mode, it is possible to sufficiently grasp the change in wear of the photosensitive member 1. In addition, since the test operation requires a certain time, if the test operation is executed too frequently, the productivity of the image forming apparatus 100 is lowered instead. Therefore, it is desirable to determine the timing for executing the test operation in view of the balance with the productivity of the image forming apparatus 100.

  Note that the information indicating the remaining life of the photosensitive member 1 is not limited to a numerical value such as “remaining life” to “%”. For example, “It is still possible to use enough”, “It is almost the end of life. ”,“ It has reached the end of its life. Replace it immediately. ”, Etc. Further, the method of notifying information indicating the remaining life of the photosensitive member 1 is not limited to display by characters, and may be any form such as lighting of a warning lamp or sound.

  Further, according to the present embodiment, the image forming apparatus 100 can automatically detect the remaining life of the photoreceptor 1. Therefore, the control unit 20 is not limited to displaying information indicating the remaining life of the photoreceptor 1 in accordance with an instruction from the operator, and automatically displays information indicating the remaining life of the photoreceptor 1 on the operation unit 13. Etc. For example, the control unit 20 can display information indicating the remaining life of the photosensitive member 1 on the operation unit 13 when the remaining life is less than a predetermined threshold value set in advance. In this case, a plurality of threshold values are provided stepwise in accordance with the remaining life level of the photosensitive member 1, and for example, the above-mentioned stepwise life warning can be displayed.

  Further, the information indicating the remaining life of the photosensitive member 1 is not limited to being displayed on the display unit of the operation unit 13 provided in the apparatus main body of the image forming apparatus 100. For example, when the image forming apparatus 100 is connected to a network, the control unit 20 sends information to a device that is communicably connected to the image forming apparatus 100 in a service station or the like automatically at a predetermined timing or according to an instruction. Can be sent. Thereby, for example, it is possible to determine whether or not the service person needs to be dispatched based on the information at the service station.

  As described above, in this embodiment, the image forming apparatus 100 uses the toner image on the intermediate transfer member as the transfer target as the sensor 10 that detects the density of the toner image on the photosensitive member or the toner image on the transfer target. An optical sensor for detecting the concentration of In addition, the image forming apparatus 100 includes a control unit 20 that forms a test image for obtaining information related to the remaining life of the photoreceptor 1 and executes a test operation in which the sensor 10 detects the toner image density of the test image. . Then, the controller 20 rotates the photosensitive member 1 at the first speed during the image forming operation. Further, the control unit 20 drives the photosensitive member 1 to rotate at a second speed different from the first speed during the test operation. At the same time, the control unit 20 applies a charging voltage consisting only of a DC voltage to the charging member 2 to charge the photoreceptor 1 to form a test image. Then, the control unit 20 outputs a signal for notifying information indicating the remaining life of the photoconductor 1 based on the detection result of the test image by the sensor 10. The control unit 20 can output a signal for notification to the storage unit that stores information indicating the remaining life of the photoreceptor 1. Further, the control unit 20 outputs a signal for notification to the operation unit 13 provided in the image forming apparatus 100 so that the operation unit 13 notifies the information indicating the remaining life of the photoreceptor 1. it can. In addition, the control unit 20 can output a signal for notification to a device connected to the image forming apparatus 100 so as to be communicable so that the device can notify information indicating the remaining life of the photosensitive member 1. .

  As described above, according to the present exemplary embodiment, the remaining life of the photosensitive member 1 can be more accurately grasped as in the first exemplary embodiment, and the operator can force the test image to be output when necessary without using the image forming apparatus. Information indicating the remaining lifetime of the photoreceptor 1 held at 100 can be quickly acquired.

Example 4
Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of the present embodiment are the same as those of the third embodiment. Accordingly, elements having the same functions or configurations as those of the third embodiment or corresponding to those of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the present embodiment, similarly to the modification of the first embodiment, the test image and the comparative test image are formed so as to be comparable in one test operation. The test image is formed by rotationally driving the photosensitive member 1 at a high rotational speed, and the comparative test image is formed by rotationally driving the photosensitive member 1 at a normal rotational speed. For example, the test image and the comparative test image can be continuously formed on the intermediate transfer belt 6. Based on the result of detecting the density of the toner image of the test image by the optical sensor 10 and the result of detecting the density of the toner image of the test image for comparison by the optical sensor 10, the remaining life of the photoreceptor 1 is detected. .

  In this embodiment, it can be evaluated that the density step generated in the test image is superimposed with the density step generated in the comparative test image. Therefore, in this embodiment, the remaining life of the photosensitive member 1 is obtained based on the difference in density step (which may be a maximum value, a minimum value, an average value, etc.) obtained for each image. it can. That is, the density step ΔD may be calculated by the following equation: ΔD = ΔD1−ΔD2. Here, ΔD1 is a density step in a test image formed by rotationally driving the photosensitive member 1 at a high rotational speed, and ΔD2 is a density step in a comparative test image formed by rotationally driving the photosensitive member 1 at a normal rotational speed. It is.

  As described above, in this embodiment, the control unit 20 notifies the information indicating the remaining life of the photoreceptor 1 based on the detection result of the test image by the sensor 10 and the detection result of the comparison test image by the sensor 10. The signal is output. In particular, in this embodiment, the control unit 20 obtains information related to density unevenness in the test image and the comparison test image based on the detection results of the test image and the comparison test image by the sensor 10. Then, the control unit 20 outputs a signal for informing information indicating the remaining life of the photoreceptor 1 based on the difference between the information related to the density unevenness in the test image and the information related to the density unevenness in the comparative test image. To do. In the present embodiment, the information related to density unevenness is the size of the density step generated with respect to the density serving as the reference of the test image.

  For example, as described in the modification of the first embodiment, the density unevenness existing in both the test image and the comparative test image is a horizontal stripe generated according to the depth of the concave portion of the photoreceptor 1. In some cases, it can be evaluated as not. In this case, the information indicating the relationship between the detection time (detection position) and the image density D obtained for each image as shown in FIG. 14 is compared, and other than the detection time (detection position) occurring in both images. Based on the density difference ΔD, the remaining life of the photoreceptor 1 can be obtained. Also in this case, the photosensitive member 1 is derived from the relationship between the density step ΔD and the remaining life of the photosensitive member 1 as shown in FIG. 15 based on the maximum value, the minimum value, the average value, etc. of the density step ΔD other than those to be excluded. Can be obtained.

  As described above, according to this embodiment, it is possible to automatically detect the life of the photoconductor 1 with higher accuracy.

Others While the present invention has been described with reference to specific embodiments, the present invention is not limited to the above-described embodiments.

  For example, in the above-described embodiment, a system having a large discharge in the downstream discharge region such as using a photoconductor having a large dark decay of the surface potential has been described. However, the present invention is not limited to this. The present invention can also be applied to a system that does not generate discharge in the downstream discharge region as much as possible, such as using a photoconductor that is less likely to cause dark decay of the surface potential. In this case, for example, the rotation speed (first speed) of the photoconductor during normal image formation is 300 mm / sec, and the rotation speed (second speed) of the photoconductor during the test operation is 100 mm / sec, which is slower than that. can do. That is, during a normal image forming operation, mainly due to discharge in the gap between the photosensitive member 1 and the charging member 2 downstream of the contact portion between the photosensitive member 1 and the charging member 2 in the moving direction of the surface of the photosensitive member 1. There is a system in which the photoreceptor 1 is charged to a predetermined charging potential. In this case, the second speed is higher than the first speed. On the other hand, in normal image formation, the second speed is slower than the first speed in a system in which the photoreceptor 1 is charged to a predetermined charging potential mainly by discharge in the upstream gap.

  In Examples 3 and 4, the density unevenness of the test image was detected on the intermediate transfer belt as the transfer target, but the present invention is not limited to this. You may make it detect the density nonuniformity of a test image on the photoconductor or the transfer material as a to-be-transferred body. When detecting density unevenness of the test image on the transfer material, the toner image on the transfer material may be detected in an unfixed state or in a state after being fixed.

  In the above-described embodiment, the case of the intermediate transfer type image forming apparatus has been described. However, the configuration of the image forming apparatus is not limited thereto. The image forming apparatus may be configured to directly transfer the toner image from the photosensitive member to the transfer material. For example, instead of the intermediate transfer member in the above-described embodiment, a transfer material carrier that carries and transports a transfer material is provided, and toner images are transferred from a plurality of photosensitive members to the transfer material carried on the transfer material carrier. Sequential transfer is well known in the art. As the transfer material carrier, a transfer material carrier belt similar to the intermediate transfer belt in the above-described embodiment is used. In this case, a transfer device that transfers the toner image from the photosensitive member to the transfer material is configured by the transfer material carrier, the transfer member that contacts the photosensitive member via the transfer material carrier. In such an image forming apparatus, when the density unevenness of the test image is detected by the optical sensor as in the third and fourth embodiments, the transfer on the photosensitive member, the transfer material carrier as the transfer target, and the transfer as the transfer target. It may be detected anywhere on the material. Further, the image forming apparatus is not limited to a color image forming apparatus, and may be a single color image forming apparatus such as a black single color.

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging roller 6 Intermediate transfer belt 20 Control part 31 Switching part 100 Image forming apparatus

Claims (12)

A rotatable photoreceptor having a plurality of independent recesses formed on the surface;
A drive unit that rotationally drives the photoreceptor;
A charging member disposed in contact with the photosensitive member and charging the photosensitive member;
A power source for applying a charging voltage for charging the photosensitive member to the charging member;
An exposure device that exposes the photoreceptor charged by the charging member to form an electrostatic image;
A developing device for developing the electrostatic image formed on the photosensitive member by the exposure device with toner to form a toner image;
A transfer device for transferring a toner image formed on the photoreceptor by the developing device to a transfer material;
An image forming operation for forming a toner image corresponding to arbitrary image information, transferring it to a transfer material and outputting it, and forming a test image for obtaining information relating to the remaining life of the photoconductor and transferring it to the transfer material A control unit that executes a test operation to be output
Have
The controller is
During the image forming operation, the photosensitive member is rotationally driven at a first speed,
During the test operation, the photoconductor is rotated at a second speed different from the first speed, and the photoconductor is charged by applying a charging voltage consisting only of a DC voltage to the charging member. An image forming apparatus for forming the test image.   In the test operation, the control unit further transfers a comparison test image, which is formed by rotationally driving the photoconductor at the first speed and is comparable to the test image, to a transfer material and outputs the transfer image. The image forming apparatus according to claim 1.   The control unit further includes a reference image formed by rotating and driving the photoconductor at the first speed in the test operation, and capable of associating the density unevenness state with the remaining life of the photoconductor. The image forming apparatus according to claim 1, wherein the image is transferred to a transfer material and output. A rotatable photoreceptor having a plurality of independent recesses formed on the surface;
A drive unit that rotationally drives the photoreceptor;
A charging member disposed in contact with the photosensitive member and charging the photosensitive member;
A power source for applying a charging voltage for charging the photosensitive member to the charging member;
An exposure device that exposes the photoreceptor charged by the charging member to form an electrostatic image;
A developing device for developing the electrostatic image formed on the photosensitive member by the exposure device with toner to form a toner image;
A transfer device for transferring a toner image formed on the photosensitive member by the developing device to a transfer target;
A sensor for detecting the density of the toner image on the photoconductor or the toner image on the transfer target;
An image forming operation for forming a toner image according to arbitrary image information, transferring it to a transfer material and outputting it, and forming a test image for obtaining information relating to the remaining life of the photoconductor, and forming the toner image of the test image A control unit that executes a test operation for detecting the concentration of
Have
The controller is
During the image forming operation, the photosensitive member is rotationally driven at a first speed,
During the test operation, the photoconductor is rotated at a second speed different from the first speed, and the photoconductor is charged by applying a charging voltage consisting only of a DC voltage to the charging member. An image forming apparatus comprising: forming a test image; and outputting a signal for informing information indicating a remaining life of the photoconductor based on a detection result of the test image by the sensor.   In the test operation, the controller further rotates the photoconductor at the first speed to form a comparison test image that can be compared with the test image, and sets the density of the toner image of the comparison test image. A signal for notifying the information indicating the remaining life of the photoconductor is output based on the detection result of the test image by the sensor and the detection result of the comparison test image by the sensor. The image forming apparatus according to claim 4.   The control unit obtains information related to density unevenness in the test image and the comparison test image based on detection results of the test image and the comparison test image by the sensor, and determines the density unevenness in the test image. The signal for informing the information indicating the remaining life of the photoconductor based on the difference between the information and the information on the density unevenness in the comparison test image is output. Image forming apparatus.   The image forming apparatus according to claim 6, wherein the information related to the density unevenness is a magnitude of a density step generated with respect to a density serving as a reference of the test image.   8. The image formation according to claim 4, wherein the control unit outputs the notification signal to a storage unit that stores information indicating a remaining life of the photoconductor. apparatus.   The control unit outputs a signal for the notification to an operation unit provided in the image forming apparatus, and causes the operation unit to notify information indicating a remaining life of the photoconductor. The image forming apparatus according to any one of 4 to 8.   The control unit outputs a signal for notification to a device connected to the image forming apparatus so as to be communicable, and causes the device to notify information indicating a remaining life of the photoconductor. Item 10. The image forming apparatus according to any one of Items 4 to 9.   During the image forming operation, the photosensitive member is mainly discharged by a discharge in the gap between the photosensitive member and the charging member on the downstream side of the contact portion between the photosensitive member and the charging member in the moving direction of the surface of the photosensitive member. The image forming apparatus according to claim 1, wherein the second speed is faster than the first speed.   During the image forming operation, the photosensitive member is mainly discharged by a discharge in the gap between the photosensitive member and the charging member upstream of the contact portion between the photosensitive member and the charging member in the moving direction of the surface of the photosensitive member. The image forming apparatus according to claim 1, wherein the second charging speed is slower than the first speed.