JP6465697B2 - Image forming apparatus - Google Patents

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.

  2. Description of the Related Art Conventionally, as an electrophotographic photosensitive member (hereinafter also simply referred to as “photosensitive member”) used in an electrophotographic image forming apparatus, an organic photosensitive member has been widely used because of its low cost and high productivity. This is configured by providing a photosensitive layer (organic photosensitive layer) using an organic material as a photoconductive substance (charge generating substance or charge transporting substance) on a support. 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. A charge generation layer containing a charge generation material such as a photoconductive dye or a photoconductive pigment and a charge transport layer containing a charge transfer material such as a photoconductive polymer or a photoconductive low molecular weight compound are laminated. Configured.

  Since electric external force and / or mechanical external force is directly applied to the surface of the photoconductor in charging, exposure, development, transfer, and cleaning, the photoconductor 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 techniques 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 wear resistance of the peripheral surface of the organic photoreceptor, a technique has been established in which the surface layer of the photoreceptor is a hardened layer, thereby increasing the mechanical strength of the surface layer. ing.

  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. 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 of the photoconductor absorbs moisture in a high humidity environment, reduces the charge retention capability of the surface of the photoconductor, and generates blurring of the electrostatic latent image. Therefore, in particular, when the hardness of the photoconductor is high, discharge products adhering to the surface of the photoconductor become more difficult to be removed, and image flow is likely to occur.

  As a countermeasure against image flow, it is common to install a heater inside or near the photoconductor, and dry the surface of the photoconductor by increasing the temperature of the surface of the photoconductor. Corresponding to the flow leads to an increase in power consumption.

  Therefore, in Patent Document 1, it is proposed to determine whether or not to operate the heater by detecting the load torque of the motor generated when the photosensitive member is rotationally driven for the purpose of reducing power consumption.

JP 2005-173021 A

  However, the load torque of the motor that is generated when the photosensitive member is rotationally driven varies depending on the state of wear of the cleaning blade and the surface state of the photosensitive member, in addition to the adhesion of the discharge product that causes the image flow. For this reason, it is difficult to determine the image flow only with the load torque, and there remains a problem in terms of reducing power consumption by precise control of the heater.

  Therefore, an object of the present invention is to enable timely and sufficient operations to suppress image flow generated by absorbing discharge products adhering to a photoreceptor, and to reduce power consumption while suppressing image flow. It is an object of the present invention to provide an image forming apparatus capable of further reducing the above.

  The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention relates to a movable photosensitive member, a charging unit that charges the photosensitive member, an exposure unit that exposes the charged photosensitive member to form an electrostatic image, and a toner on the electrostatic image. A developing unit for supplying the toner, a transfer unit for transferring a toner image from the photosensitive member to the transfer target at the transfer unit, and a cleaning unit downstream of the transfer unit in the moving direction of the photosensitive member and contacting the photosensitive member. In an image forming apparatus, comprising: a cleaning member that removes toner from a photoconductor; a heating unit that heats the photoconductor; and a drive unit that drives the photoconductor; a detection unit that detects a driving torque of the drive unit; A predetermined toner image is formed on the photoconductor, the predetermined toner image reaches the cleaning unit, and an area on the photoconductor on which the predetermined toner image is formed passes through the cleaning unit. A detecting operation for detecting the driving torque of the driving means by the detecting means is performed, and the photosensitive member is driven by the cleaning member based on the driving torque detected in the detecting operation. A control unit that selects and executes one of a plurality of operation settings for performing at least one of a rubbing operation for rubbing or a heating operation for heating the photosensitive member by the heating unit. Forming device.

  According to the present invention, it is possible to perform a necessary and sufficient operation in a timely manner to suppress the image flow generated due to moisture absorption of the discharge product attached to the photosensitive member, and to further reduce the power consumption while suppressing the image flow. Reduction becomes possible.

1 is a cross-sectional configuration diagram of an image forming apparatus. It is a graph which shows the relationship between the number of image outputs, and the abrasion amount of a cleaning blade. It is a graph showing the relationship between the amount of wear of the cleaning blade and the driving torque when toner is interposed. 3 is a block diagram illustrating a control mode of a main part of the image forming apparatus. FIG. It is a flowchart figure which concerns on the abrasion detection operation | movement of a cleaning blade. FIG. 6 is a flowchart according to image flow recovery operation 1; It is a graph showing the relationship between the amount of wear of the cleaning blade and the driving torque when toner is interposed. It is a flowchart figure which concerns on the other example of the abrasion detection operation | movement of a cleaning blade. FIG. 5 is a schematic diagram for explaining the behavior of a cleaning blade when toner is interposed.

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

[Example 1]
1. Configuration of Image Forming Apparatus FIG. 1 is a cross-sectional configuration diagram of an image forming apparatus 10 according to an embodiment of the present invention. The image forming apparatus 10 according to the present exemplary embodiment is an electrophotographic laser beam printer that employs a contact charging method.

  As shown in FIG. 1, an image forming apparatus 10 includes a photosensitive drum 1 which is a rotatable drum type (cylindrical) electrophotographic photosensitive member (photosensitive member) as an image carrier. In this embodiment, the photosensitive drum 1 is an organic photoreceptor having a negative charging property, and a photocharge generation layer made of an organic material and a charge transport layer (on a surface of an aluminum cylinder (conductive drum base)) A thickness of about 20 μm). Here, the surface layer of the photosensitive drum 1 is a hardened layer using a curable resin as a binder resin. In this embodiment, a hardened layer using a curable resin is used as the surface hardening process of the photosensitive drum 1, but the present invention is not limited to this, and the following may be used. 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 drum 1 has a length in the rotation axis direction of 340 mm, an outer diameter of 30 mm, and a process speed (peripheral speed) of 300 mm / second centered on the central support shaft as indicated by an arrow R1 in FIG. It is rotationally driven in the direction (counterclockwise). The photosensitive drum 1 is rotationally driven by a drive motor 15 (FIG. 4) as drive means. As will be described later, the drive torque of the drive motor 15 can be detected by a torque detection circuit 13 (FIG. 4) as a torque detection means. As the torque detection means, a publicly available means can be arbitrarily used.

  As shown in FIG. 1, the image forming apparatus 10 includes a charging roller 2 as a contact-type charging unit that uniformly charges the surface of a rotating photosensitive drum 1. The charging roller 2 has a length of 330 mm in the rotation axis direction and a diameter of 14 mm, and is configured by forming a conductive rubber layer on the outer periphery of a stainless steel core. The charging roller 2 has both ends of the core metal held rotatably by bearing members, and is urged toward the photosensitive drum 1 by a pressing spring to have a predetermined pressing force against the surface of the photosensitive drum 1. It is in pressure contact. As a result, the charging roller 2 is rotated in the direction of the arrow R2 in FIG. 1 (clockwise) following the rotation of the photosensitive drum 1 (peripheral speed is 300 mm / second). The charging roller 2 charges the surface of the photosensitive drum 1 using a discharge phenomenon that occurs in a small gap between the charging roller a and the photosensitive drum 1. A charging voltage (charging bias) of a predetermined condition is applied to the core of the charging roller 2 from the charging power source PS1. In this embodiment, the charging power source PS1 includes a DC power source and an AC power source, and a vibration in which a DC voltage (charging DC voltage) and an AC voltage (charging AC voltage) are superimposed on the charging roller 2 as a charging voltage. Apply voltage. For example, the charging DC voltage is set to −500 V, and the peak-to-peak voltage value of the charging AC voltage is set to at least twice the discharge start voltage when only the charging DC voltage is applied in the environment. As a result, immediately after passing through the charging portion a, the image forming area (area where the toner image can be formed) of the rotating photosensitive drum 1 is uniformly charged to about −500V. Note that the charging DC voltage applied during image formation is not limited to the above value, and may be good depending on the environment and the usage status (repeated usage) of the photosensitive drum 1 and the charging roller 2. It is appropriately set to a potential suitable for image formation.

  As shown in FIG. 1, the image forming apparatus 10 performs exposure as exposure means (information writing means, latent image forming means) that forms an electrostatic latent image (electrostatic image) on the surface of the charged photosensitive drum 1. A device 3 is included. 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 modulated in accordance with an image signal sent from the host processing device such as an image reading device (not shown) to the image forming device 10. Then, the surface of the rotating photosensitive drum 1 that has been uniformly charged is subjected to laser scanning exposure (image exposure) at an exposure portion (exposure position) b. By this laser scanning exposure, the absolute value of the potential of the portion irradiated with the laser light L on the surface of the photosensitive drum 1 is lowered. Then, electrostatic latent images corresponding to image information are sequentially formed on the surface of the rotating photosensitive drum 1.

  As shown in FIG. 1, the image forming apparatus 10 supplies toner to the electrostatic latent image on the photosensitive drum 1, and develops (visualizes) the electrostatic latent image as a toner image (developer image). A developing device 4 is included. The developing device 4 includes a developing container 42 that contains a developer, and a rotatable developing sleeve 41 as a developer carrying member that is disposed to face the photosensitive drum 1 in an opening of the developing container. The developing container 42 contains a two-component developer mainly composed of toner (nonmagnetic toner particles) and a carrier (magnetic carrier particles) as a developer, and supplies the developer sleeve 41 with the two-component developer. The length of the developing sleeve 41 in the rotation axis direction is 325 mm. In the present embodiment, the developing sleeve 41 holds a magnetic brush made of a two-component developer composed of toner and a carrier, and this is applied to the photosensitive drum 1 at a developing portion c that is a facing portion between the developing sleeve 41 and the photosensitive drum 1. Develop while in contact. In this embodiment, as the toner, a toner having an average particle diameter of about 6 μm obtained by pulverizing and classifying a resin binder mainly composed of polyester and kneading a pigment is used. Further, the average charge amount of the toner adhering to the photosensitive drum 1 is about −30 μC / g. A predetermined developing voltage (developing bias) is applied to the developing sleeve 41 from the developing power source PS2. In the present embodiment, the development voltage is an oscillating voltage obtained by superimposing a DC voltage (development DC voltage) Vdc and an AC voltage (development AC voltage) Vac. For example, the development AC voltage has a frequency of 8.0 kHz, a peak-to-peak voltage of 1.8 kV, and a rectangular wave. The development DC voltage is appropriately set so as to have an appropriate fog removal potential with respect to the potential of the photosensitive drum 1 in the development section c. Here, the fog removal potential is a potential difference between the non-image portion potential (dark portion potential) on the photosensitive drum 1 and the development DC voltage.

  As shown in FIG. 1, the image forming apparatus 10 includes a transfer roller 5 as a contact-type transfer unit. The transfer roller 5 is pressed against the photosensitive drum 1 with a predetermined pressing force to form a pressure nip with the photosensitive drum 1. This pressure nip is the transfer portion d. A recording material P such as paper or a plastic sheet as a transfer medium is fed to the transfer portion d from a feeding device (not shown) at a predetermined control timing. The recording material P fed to the transfer part d is nipped and conveyed between the rotating photosensitive drum 1 and the transfer roller 5. In the meantime, a positive transfer voltage (transfer bias) having a polarity opposite to the negative polarity, which is the charge polarity (normal charge polarity) of the toner at the time of development, is applied to the transfer roller 5 from the transfer power source PS3. In this embodiment, the transfer voltage is + 600V. Thus, the toner image on the photosensitive drum 1 is sequentially electrostatically transferred onto the surface of the recording material P that is nipped and conveyed between the photosensitive drum 1 and the transfer roller 5 in the transfer portion d.

  The configuration of the image forming apparatus is not limited to the configuration in which the toner image is directly transferred from the photosensitive drum to the recording material. The toner image may be transferred from the photosensitive drum 1 to an intermediate transfer member that temporarily holds and conveys the toner image, and then transferred from the intermediate transfer member to a recording material.

  The recording material P onto which the toner image has been transferred through the transfer portion d is sequentially separated from the surface of the photosensitive drum 1 and conveyed to the fixing device 6. In this embodiment, the fixing device 6 is a heat roller fixing device. The recording material P is subjected to the fixing process of the toner image by the fixing device 6, and is output to the outside of the main body of the image forming device 10 as an image formed product (print, copy).

  The toner (transfer residual toner) remaining on the surface of the photosensitive drum 1 after the transfer of the toner image onto the transfer paper P in the transfer portion d is removed and collected from the surface of the photosensitive drum 1 by the cleaning device 7 in the cleaning portion e. The The cleaning device 7 includes a cleaning blade 71 as a cleaning member, and a collected toner container 72 that stores transfer residual toner removed from the surface of the photosensitive drum 1 by the cleaning blade 71. The cleaning blade 71 of this embodiment is formed of urethane rubber as an elastic material. The cleaning blade 71 is a flat plate having a predetermined thickness and having a predetermined length in a longitudinal direction arranged along the rotational axis direction of the photosensitive drum 1 and a short direction perpendicular to the longitudinal direction. Shaped. The cleaning blade 71 has one end (fixed end) in the short direction supported by the collected toner container 72, and the other end (free end) on the photosensitive drum 1 side is on the surface of the photosensitive drum 1. Abutted. This contact portion (nip with the photosensitive drum 1) is the cleaning portion e. Further, the cleaning blade 71 is located on the upstream side in the movement direction of the surface of the photosensitive drum 1 with respect to the free end side relative to the fixed end side, so that the free end faces the upstream side in the movement direction. Abuts on the surface (counter direction). The length in the longitudinal direction (axial direction) of the cleaning blade 71 is 330 mm. The cleaning blade 71 is pressed against the photosensitive drum 1 with a linear pressure of 30 gf / cm.

  As shown in FIG. 1, the image forming apparatus 10 includes an atmospheric heater (hereinafter, also simply referred to as “heater”) 12 as a heating unit for controlling the temperature of the surface of the photosensitive drum 1. The heater 12 is disposed above the photosensitive drum 1 and at a position close to the exposure device 3. The heater 12 is heated by a heater power supply G (FIG. 4). In addition, a thermo switch having a bimetal structure is attached to the heater 12, and the circuit is shut off when the temperature in the vicinity of the heater 12 exceeds the upper limit of the set temperature. In this embodiment, the temperature of the heater 12 is controlled within a range of 50 ± 2 ° C. (target temperature), and the amount of heat generated is 40 W.

  The driving of the image forming apparatus 10, power supplies PS1PS2, PS3, G output, image information processing, ON / OFF of the heater 12, and the like are controlled by the control unit 110 (FIG. 4). The control mode will be described later.

2. Operation Sequence The image forming apparatus 10 performs a series of image output operations (jobs) for forming and outputting an image on a single or a plurality of recording materials P, which is started by one start instruction (print signal). The image output operation generally includes an image forming process (printing process), a pre-rotation process, a paper-to-paper (inter-image) process when images are formed on a plurality of recording materials P, and a post-rotation process. The image forming process is a period for forming an electrostatic latent image, forming a toner image, and transferring a toner image of an image that is actually formed and output on the recording material P. Say. The pre-rotation process is a period for performing a preparatory operation before the image forming process from when the start instruction is input until the actual image formation is started. The inter-sheet process is a period corresponding to the interval between the recording material P and the recording material P when the image forming process is continuously performed on the plurality of recording materials P. The post-rotation process is a period during which an organizing operation (preparation operation) after the image forming process is performed. The non-image forming period is a period other than the image forming time, and includes the pre-rotation process, the sheet-interval process, the post-rotation process, and preparations when the image forming apparatus 10 is turned on or returned from the sleep state. This includes the operation during the previous multi-rotation process. When the post-rotation process is completed, the rotational driving of the photosensitive drum 1 is stopped, and the image forming apparatus 10 is kept in a standby state until the next start instruction is input. Further, when the standby state continues for a predetermined time or more, the sleep state is entered. In a state where the main power supply is OFF, power supply to almost all elements of the image forming apparatus 10 is turned OFF. In the sleep state, power supply to almost all elements of the image forming apparatus 10 is turned off so as to suppress power consumption more than in the normal standby state. However, the control unit 110 receives a start instruction and starts a job. Is maintained in a state where When a start instruction is input when returning from the sleep state or when the main power is turned on, the pre-rotation process is performed following the pre-multi-rotation process.

3. Image Flow Countermeasures Using a Cleaning Blade Conventionally, as an image flow countermeasure that does not rely on the heater 12, removal of discharge products by the cleaning blade 71 can be mentioned. This is to prevent image flow by driving the photosensitive drum 1 to cause the photosensitive drum 1 and the cleaning blade 71 to rub against each other and to peel off the discharge products adhering to the surface. At this time, it is preferable that the discharge is not caused in the charging roller 2 and the transfer roller 5 and no discharge product is generated. Further, if the photosensitive drum 1 is rubbed with the cleaning blade 71 after the toner is supplied to the cleaning blade 71 (cleaning unit e), the abrasive added to the toner accumulates on the edge of the cleaning blade 71, so The effect of rubbing is increased. The toner can be supplied to the cleaning blade 71 by conveying the toner supplied from the developing device 4 to the photosensitive drum 1 by the rotation of the photosensitive drum 1.

  However, it has been found that the removal of discharge products by the cleaning blade 71 is less effective at the end of the lifetime of the cleaning blade 71. As shown in FIG. 2, the edge of the cleaning blade 71 advances according to the amount of repeated use. When the edge is worn, the nip between the photosensitive drum 1 and the cleaning blade 71 increases and the peak pressure decreases, so that the polishing force of the cleaning blade 71 decreases.

  Table 1 shows the wear amount of the cleaning blade 71 and the rank of image flow in the driving time. This is an evaluation of how much the image flow has been recovered within a predetermined driving time from the state where the image flow has occurred and the character (Iroha) image has disappeared. At the time of evaluation, the character image, fine line (2L3S), and HT are used. When the character image disappears, XX, when the character image is read and the fine line is broken, X, and the fine line is not broken, but the HT is uneven. When there was, it was set as (triangle | delta), and when there was no unevenness in HT, it was set as (circle).

  When the cleaning blade 71 is not worn, the image flow can be quickly eliminated. However, as wear progresses, the driving time required to eliminate the image flow increases. Further, when the wear progresses to a certain extent, it cannot be eliminated only by driving the photosensitive drum 1. As described above, if the amount of repeated use of the cleaning blade 71 increases, the image flow cannot be eliminated only by rubbing the photosensitive drum 1 by the cleaning blade 71, and the heater 12 needs to be operated.

4). As described above, the operation of the heater 12 is required to eliminate the image flow after the repeated use amount increases. From the viewpoint of energy saving (reduction of power consumption), the heater 12 is It is desirable to stop until just before image flow occurs. Therefore, if the wear of the cleaning blade 71 can be detected, the ON / OFF timing of the heater 12 can be optimized.

  Usually, the driving torque of the photosensitive drum 1 and the cleaning blade 71 is a change in surface shape due to discharge products and carrier marks (such as scratches generated when the carrier contacts the photosensitive drum 1) attached to the photosensitive drum 1, It is affected by wear. Therefore, it is not possible to detect the precise wear of the cleaning blade 71 simply by detecting the driving torque of the photosensitive drum 1.

  On the other hand, as shown in FIG. 9, in the state where the toner is interposed between the photosensitive drum 1 and the cleaning blade 71, the intervening toner and the external additive separated from the toner roll while rolling. Exists between. Therefore, the contact area of the cleaning blade 71 with the photosensitive drum 1 is reduced. As a result, when the intervening toner exceeds a certain amount, the influence of the friction of the photosensitive drum 1 can be almost eliminated, so that the state of the cleaning hood 7 can be determined from the driving torque. FIG. 9A shows a state where no toner is interposed between the photosensitive drum 1 and the cleaning blade 71, and FIG. 9B shows a state where the toner is interposed.

  As shown in FIG. 3, when the cleaning blade 71 is worn, the driving torque in a state where toner is interposed between the photosensitive drum 1 and the cleaning blade 71 (hereinafter also referred to as “toner-mediated driving torque”). Decrease. This is because as the wear of the cleaning blade 71 progresses, the phenomenon that the toner slips through the cleaning blade 71 occurs due to the decrease in the peak pressure described above, and the contact area between the photosensitive drum 1 and the cleaning blade 71 is further reduced. is there. FIG. 3 also shows the image flow recovery time in Table 1.

  As described above, if the amount of wear of the cleaning blade 71 and the driving time of the photosensitive drum 1 until the image flow is recovered are obtained in advance, the threshold T0 of the toner-mediated driving torque T that requires the use of the heater 12 is determined. be able to. In this embodiment, the image flow recovery operation (sliding operation) by driving the photosensitive drum 1 is set to 60 seconds, and when the driving is longer than that, the image flow recovery by driving the photosensitive drum 1 is not performed, but the heater 12 Is turned ON to recover the image flow (heating operation). Accordingly, the threshold T0 (about 1.35 kgf · cm in this embodiment) of the driving torque during toner intervention is determined from the amount of wear of the cleaning blade 71 that can recover the image flow by driving the photosensitive drum 1 for 60 seconds.

  Here, when the amount of toner supplied to the cleaning blade 71 at the time of detecting the driving torque at the time of toner intervention is not constant, the amount of toner that passes through the cleaning blade 71 changes, so that the driving torque at the time of toner intervention changes. For this reason, in order to accurately detect the wear of the cleaning blade 71, it is desirable to change the contrast in accordance with the repetitive usage amount and the charge amount of the toner that changes depending on the environment. Here, the contrast is a potential difference between the image portion potential (bright portion potential) on the photosensitive drum 1 and the development DC voltage. In this embodiment, the charging DC voltage is set so that the density on the photosensitive drum 1 of the predetermined toner image (toner band) formed on the photosensitive drum 1 by the wear detection operation of the cleaning blade 71 is 1.20 in reflection density. The development DC voltage and the light emission amount of the exposure device 3 are set as appropriate.

  The width of the toner supplied to the cleaning blade 71 in the main scanning direction should be wide. This is because as the amount of toner present between the photosensitive drum 1 and the cleaning blade 71 increases, the influence of the photosensitive drum 1 can be eliminated. In this embodiment, a toner band having a maximum width of 310 mm that can be imaged by the exposure device 3 is formed on the photosensitive drum 1 and supplied to the cleaning blade 71. The length of the toner band in the rotation direction of the photosensitive drum 1 can be set as appropriate so that the drive torque can be detected by the torque detection circuit 13 with a desired accuracy. The length of the toner band in the rotation direction of the photosensitive drum 1 is usually shorter than the circumferential length of the photosensitive drum 1, but may be longer than the circumferential length of the photosensitive drum 1.

  Here, a predetermined toner image (toner band) formed on the photosensitive drum 1 by the developing unit c needs to pass through the transfer unit d and be supplied to the cleaning unit e. In this embodiment, since the transfer voltage is OFF during the wear detection operation of the cleaning blade 71, the toner image passes through the transfer portion d and is supplied to the cleaning portion e. As a means for allowing the toner image to pass through the transfer portion d, the transfer roller 5 may be separated from the photosensitive drum 1 or a voltage having a polarity opposite to that at the time of image formation may be applied to the transfer roller 5.

  In this embodiment, an example of digital development using the exposure device 3 will be described. However, only the development DC voltage applied to the development sleeve 41 with respect to the surface potential formed on the photosensitive drum 1 by the charging roller 2 is described. Alternatively, analog development for adjusting the density may be used.

5. Wear Detection Operation of Cleaning Blade 71 In this embodiment, the image forming apparatus 10 can perform the wear detection operation of the cleaning blade 71 using the above-described detection method. In this embodiment, the wear detection operation of the cleaning blade 71 is performed during the post-rotation process. This is because, depending on the detection result, it is desired to operate the heater 12 during standby or when the main power supply is turned off (heat generation, lighting), and there is a possibility that the effect of eliminating the image flow by the heater 12 cannot be sufficiently exhibited during the pre-rotation process. Because there is.

  In this embodiment, the wear of the cleaning blade 71 is detected when the humidity (relative humidity in this embodiment) H in the main body of the image forming apparatus 10 measured by the environmental sensor 14 described later exceeds a threshold value H0. Perform the action. This is because even if the discharge product adheres to the photosensitive drum 1, the amount of water absorbed by the discharge product is small if the moisture in the air is small, so that the latent image is less likely to be blurred. In this embodiment, the threshold value H0 of the humidity H is set to 50%.

  FIG. 4 is a block diagram illustrating a control mode of a main part of the image forming apparatus 10 according to the present exemplary embodiment. In FIG. 4, illustrations of parts not related to the wear detection operation of the cleaning blade 71 and the later-described image flow recovery operation in the image forming apparatus 10 are omitted.

  The controller 110 controls the driving of the photosensitive drum 1 and can detect the driving torque of the photosensitive drum 1 by commanding the torque detection circuit 13. In addition, the control unit 110 can control the power supply PS1 that applies a charging voltage to the charging roller 2, and can charge the photosensitive drum 1 to a predetermined potential in the charging unit a. Further, the control unit 110 can adjust the light amount of the exposure device 3 and form an electrostatic latent image on the photosensitive drum 1. Further, the control unit 110 can control the power supply PS2 that applies a development voltage to the development sleeve 41, and can form a toner image on the photosensitive drum 1 in the development unit c. The control unit 110 also includes information on the temperature and humidity in the apparatus main body of the image forming apparatus 10 and the ambient temperature and humidity detected by the environment sensor (temperature / humidity sensor) 14 as environment detection means. Is entered. Further, the control unit 110 has a built-in storage unit, and wear detection operation and image flow recovery operation of the cleaning blade 71 such as the number of formed images, average image duty (average image ratio), temperature inside and outside the apparatus main body, and humidity. It is possible to store information related to

  Here, the average image duty is an average value of the image ratio (printing rate) of the formed image, and the image ratio when the maximum density image is formed over the entire area of the image forming area is assumed to be 100%. Averaged for multiple images over time. For example, the average value of the image ratios of all the images formed from the new developer to the present, or the average value of the image ratios for the most recent predetermined number of images may be used.

  FIG. 5 is a flowchart of the wear detection operation of the cleaning blade 71.

  First, when the image formation is completed and the post-rotation process is started (S101), the control unit 110 measures the humidity H using the environmental sensor 14 (S102), and determines whether the humidity H is equal to or less than the threshold value H0. (S103). If the threshold value H0 or less (Yes in S103), the control unit 110 determines that no image flow occurs because there is little moisture adsorbed on the discharge product, and the wear detection operation of the cleaning blade 71 is not performed. The process ends. On the other hand, when the threshold value H0 is exceeded (No in S103), the control unit 110 determines that image flow occurs because there is a lot of moisture adsorbed on the discharge product, and performs the wear detection operation of the cleaning blade 71. In other words, the control unit 110 measures the temperature and humidity in the apparatus main body of the image forming apparatus 10 using the environment sensor 14, the charging DC voltage recorded in advance corresponding to the temperature and humidity, and the light amount of the exposure apparatus 3. The development DC voltage is output (S104). As information for adjusting charging conditions, exposure conditions, and development conditions when forming a toner band, information on at least one of temperature and humidity may be used, or instead of or in addition to the above-described information. Information on the average image Duty may be used. As a result, a toner band having a predetermined density is formed on the photosensitive drum 1 and supplied to the cleaning blade 71.

  Next, the control unit 110 measures the driving torque T at the time of toner intervention using the torque detection circuit 13, and determines whether or not the driving torque T at the time of toner intervention is equal to or greater than a threshold value (first threshold value) T0 (S105). . Then, if it is equal to or greater than the threshold value T0 (Yes in S105), the control unit 110 determines that wear of the cleaning blade 71 has not progressed and sets execution of an image flow recovery operation 1 described later (S106). . When the setting of the image flow recovery operation 1 is completed, the control unit 110 ends the wear detection operation of the cleaning blade 71. On the other hand, when the value is less than the threshold value T0 (No in S105), the control unit 110 determines that the cleaning blade 71 is worn, and the discharge product cannot be removed even when the photosensitive drum 1 is driven. It is set to execute the image flow recovery operation 2 (S107). When the setting of the image flow recovery operation 2 is completed, the control unit 110 ends the wear detection operation of the cleaning blade 71. Here, the processing of S104 to S107 is the wear detection operation of the cleaning blade 71.

6). Image Flow Recovery Operation Next, the image flow recovery operation will be described.

  First, in this embodiment, as the image flow recovery operation 1, an operation of driving the photosensitive drum 1 and sliding the photosensitive drum 1 with the cleaning blade 71 can be performed. When the photosensitive drum 1 is driven, voltage is not applied to the charging roller 2, the transfer roller 5 and the like so that an image flow hardly occurs, and an image is formed after an image forming signal is input. The driving time of the photosensitive drum 1 until this is extended. The image flow is generated when the discharge product on the surface of the photosensitive drum 1 which is a causative substance adsorbs moisture, but the discharge product on the surface of the photosensitive drum 1 is removed by the cleaning blade 71 in the image flow recovery operation. For this reason, it is difficult for image flow to occur. Further, the surface temperature of the photosensitive drum 1 increases due to the rubbing with the cleaning blade 71, and even if the discharge product remains, it becomes difficult to adsorb moisture, so that it is more difficult for image flow to occur. . The image flow recovery operation 1 is performed at the time of return from the sleep state or before multiple rotations when the main power is turned on.

  FIG. 6 is a flowchart of the image flow recovery operation 1. First, when the pre-multi-rotation process starts when returning from the sleep state or when the main power is turned on (S201), the control unit 110 measures the humidity H using the environmental sensor 14 (S202), and the humidity H is equal to or less than the threshold value H0. It is determined whether or not (S203). Then, if the threshold value H0 or less (Yes in S203), the control unit 110 determines that image flow does not occur because there is little moisture adsorbed on the discharge product, and performs processing without performing the image flow recovery operation 1. finish. On the other hand, when the threshold value H0 is exceeded (No in S203), the control unit 110 determines that image flow occurs due to the large amount of moisture adsorbed on the discharge product, and performs the image flow recovery operation 1. That is, the control unit 110 outputs a predetermined charging DC voltage, a light amount of the exposure device 3, and a development DC voltage, forms a toner band having a predetermined density on the photosensitive drum 1, and supplies the toner band to the cleaning blade 71 (S204). . This toner band may be the same as the toner band in the wear detection operation of the cleaning blade 71. However, here, since the toner band is formed in order to use the polishing action of the external additive of the toner, it is not required to control the density accurately like the toner band in the wear detection operation of the cleaning blade 71. You may form with the fixed constant defined. In addition, since the transfer voltage is OFF in the image flow recovery operation 1, the toner image passes through the transfer portion d and is supplied to the cleaning portion e. Thereafter, the control unit 110 drives the photosensitive drum 1 for a predetermined time, and performs a process of removing discharge products from the surface of the photosensitive drum 1 by rubbing with the cleaning blade 71 (S205). Then, when the predetermined time has passed, the control unit 110 stops driving the photosensitive drum 1 and ends the image flow recovery operation 1. Here, the processing of S204 and S205 is referred to as image flow recovery operation 1.

  As described above, when the image flow processing operation 1 is performed, the pre-multi-rotation process includes the pre-multi-rotation process for the time required for the toner band formation and the time for the subsequent rotation of the photosensitive drum 1 for a predetermined time. Will be extended. The predetermined time for driving the photosensitive drum 1 can be changed according to the amount of wear of the cleaning blade 71 indicated by the drive torque during toner intervention detected in the wear detection operation of the cleaning blade 71 (for example, 30 seconds, 60 seconds). ). That is, the control unit 110 requires the relationship between the drive torque and the wear amount obtained in advance as shown in FIG. 3, and the relationship between the wear amount and the drive time required for image flow recovery as shown in Table 1. Driving time can be obtained. Further, the predetermined time may be a predetermined fixed time that can sufficiently recover the image flow even with the wear amount corresponding to the above-described threshold value T0 for selecting the image flow recovery operation 1 (for example, 60 seconds).

  Next, in this embodiment, as the image flow recovery operation 2, an operation can be performed in which the heater 12 is operated so that the discharge product does not adsorb moisture. The image flow recovery operation 2 is performed at the time of the next standby state (including the sleep state) or when the main power is turned off when the image flow recovery operation 2 is set to be performed by the wear detection operation of the cleaning blade 71. The operation of the heater 12 by the image flow recovery operation 2 is performed when it is determined that the environment around the image forming apparatus 10 detected by the environment sensor 14 is high humidity when the execution timing arrives (for example, the above-described operation). It may be performed only when H0 is exceeded.

  By the way, it is possible to suppress the image flow by always performing the image flow recovery operation when turning on the main power or returning from the sleep state without performing the wear detection operation of the cleaning blade 71 as in the present embodiment. It is. However, in this case, since the control time after the main power supply is turned on or after returning from the sleep state becomes long, the productivity is impaired, or the amount of shaving of the photosensitive drum 1 by driving increases, and the photosensitive drum There is a possibility that the lifetime of 1 may be impaired. Further, when the heater 12 is used, power consumption increases. For this reason, as in the present embodiment, it is desirable that the image flow recovery operation be performed only when there is a possibility of image flow.

  As described above, the image forming apparatus 10 according to the present exemplary embodiment includes the movable photoreceptor 1, the charging unit 2 that charges the photoreceptor, and the exposure unit 3 that exposes the charged photoreceptor 1 to form an electrostatic image. And developing means 4 for supplying toner to the electrostatic image. Further, the image forming apparatus 10 includes a transfer unit 5 that transfers a toner image from the photosensitive member 1 to the transfer target P at the transfer unit d, and a cleaning unit e that is downstream of the transfer unit d in the moving direction of the photosensitive member 1. 1 and a cleaning member 71 for removing toner from the photoreceptor 1. Further, the image forming apparatus 10 includes a heating unit 12 that heats the photoconductor 1 and a driving unit 15 that drives the photoconductor 1. The image forming apparatus 10 further includes a detecting unit 13 that detects the driving torque of the driving unit 15 and a control unit 110 as described below. The control unit 110 forms a predetermined toner image on the photosensitive member 1, causes the toner image to reach the cleaning unit d, and the region on the photosensitive member on which the toner image is formed passes through the cleaning unit d. A detection operation for detecting the drive torque of the drive means by the detection means is executed. Further, the control unit 110 drives the photosensitive member based on the driving torque detected by the detecting operation and rubs the photosensitive member 1 with the cleaning member 71 or the heating operation that heats the photosensitive member with the heating unit 15. One of a plurality of operation settings for performing at least one of the above is selected and executed.

  In the present embodiment, the control unit 110 performs only the rubbing operation when the detected driving torque is equal to or higher than the first threshold value, and at least performs the heating operation when the detected driving torque is lower than the first threshold value. In particular, in the present embodiment, the control unit 110 performs only the heating operation when the detected drive torque is less than the first threshold value. Moreover, the control part 110 can perform detection operation, when the humidity of environment is more than predetermined humidity. In addition, the control unit 110 can execute an operation selected from a plurality of operation settings when the environmental humidity is equal to or higher than a predetermined humidity. In this embodiment, in the rubbing operation, after the toner is supplied from the developing unit 4 to the cleaning unit d via the photosensitive member 1, the photosensitive member 1 is driven for a predetermined time. Further, the control unit 110 is based on at least one of an average image ratio of images formed by the image forming apparatus 10, the number of images formed by the image forming apparatus 10, and at least one of temperature and humidity. The following adjustments can be made. That is, the potential difference between the potential of the image portion in the electrostatic image of the predetermined toner image on the photoconductor and the voltage applied to the developing means 4 is set so that the density of the predetermined toner image (toner band) approaches the predetermined density. Can be adjusted.

7). As described above, in the present embodiment, the wear state of the cleaning blade 71 is accurately detected by detecting the driving torque during toner intervention. If it is determined that there is a risk of image flow, the image flow recovery operation corresponding to the wear state of the cleaning blade 71 is executed out of a plurality of image flow recovery operations that are set. Suppresses the occurrence. As a result, an optimal image flow recovery operation can be selected in accordance with the usage status (repeated usage amount) of the cleaning blade 71. Therefore, it is possible to achieve both a reduction in downtime (a period during which an image output operation cannot be performed) and power consumption, and good image formation in which no image flow occurs over a long period of time. That is, in this embodiment, the wear state of the cleaning blade 71 is determined by detecting the driving torque when the toner is present. Then, when the wear of the cleaning blade 71 is not progressing, the image flow countermeasure by the cleaning blade 71 is selected, and when the cleaning blade 71 is being worn, the image flow countermeasure by the heater 12 is selected. Thereby, the heater 12 can be operated at an appropriate timing, and both reduction in power consumption and prevention of image flow can be achieved. Thus, by determining the wear state of the cleaning blade 71, the heater 12 is more accurately controlled, and not only the image flow in the latter half of the lifetime of the cleaning blade 71 is suppressed, but also the power consumption is further reduced. Can be planned.

[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, in the image forming apparatus according to the present embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus according to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

1. Outline In the first embodiment, two operations, the image flow recovery operation 1 by driving the photosensitive drum 1 (sliding with the cleaning blade 7) and the image flow recovery operation 2 by the heater 12, are the threshold value of the drive torque T at the time of toner intervention. It was switched to T0. On the other hand, the power consumption can be further reduced by combining these two operations.

  As shown in Table 1, when the amount of wear of the cleaning blade 71 exceeds 12 μm, it is necessary to drive the photosensitive drum 1 for about 90 seconds to recover the image flow. At this time, if the operation is performed with the output of the heater 12 lowered, the driving time of the photosensitive drum 1 until the recovery of the image flow can be reduced.

  As shown in FIG. 7, when the driving torque T at the time of toner intervention falls below the first threshold value T0, if the operation is performed with the output of the heater 12 lowered, the driving torque T at the time of toner intervention reaches the second threshold value T1. It can be seen that the image flow is restored when the drum 1 is driven for 60 seconds. The second threshold T1 is smaller than the first threshold T0.

  In other words, in the first embodiment, when the driving torque T during toner intervention falls below the first threshold value T0, the heater 12 operates at the normal output (maximum output). In contrast, in this embodiment, the image flow recovery operation by driving the photosensitive drum 1 and the image flow recovery operation by the heater 12 are combined. More specifically, when the toner-mediated driving torque T falls below the first threshold value T0, the image flow recovery operation 2 is performed by operating the heater 12 at a low output until the driving torque T falls below the second threshold value T1. In addition to this, the image flow recovery operation 1 is performed and the photosensitive drum 1 is rubbed with the cleaning blade 71. In this embodiment, the image flow recovery operation 1 is combined with the image flow recovery operation 1 at a low output. Thereby, the total power consumption is reduced while suppressing the image flow.

2. Cleaning Blade Wear Detection Operation FIG. 8 is a flowchart of the wear detection operation of the cleaning blade 71.

  First, when the image formation is completed and the post-rotation process is started (S301), the control unit 110 measures the humidity H using the environmental sensor 14 (S302), and determines whether the humidity H is equal to or less than the threshold value H0. (S303). Then, if the threshold value H0 or less (Yes in S303), the control unit 110 determines that image flow does not occur because the amount of moisture adsorbed on the discharge product is small, and does not perform the wear detection operation of the cleaning blade 71. The process ends. On the other hand, when the threshold value H0 is exceeded (No in S203), the control unit 110 determines that an image flow is generated due to the large amount of moisture adsorbed on the discharge product, and performs the wear detection operation of the cleaning blade 71. In other words, the control unit 110 measures the temperature and humidity in the apparatus main body of the image forming apparatus 10 using the environment sensor 14, the charging DC voltage recorded in advance corresponding to the temperature and humidity, and the light amount of the exposure apparatus 3. Then, the development DC voltage is output (S304). As a result, a toner band having a predetermined density is formed on the photosensitive drum 1 and supplied to the cleaning blade 71. Next, the controller 110 uses the torque detection circuit 13 to measure the driving torque T during toner intervention, and determines whether the driving torque T during toner intervention is equal to or greater than a first threshold T0 (S305).

  Then, if it is equal to or greater than the first threshold value T0 (Yes in S305), the control unit 110 determines that the cleaning blade 71 is not worn and sets execution of the image flow recovery operation 1 (S306). . When the setting of the image flow recovery operation 1 is completed, the control unit 110 ends the wear detection operation of the cleaning blade 71. In addition, when it is less than the first threshold value T0 (No in S305), the control unit 110 determines whether or not the toner intervention driving torque T is equal to or greater than the second threshold value T1 (S307). When the control unit 110 is equal to or greater than the second threshold value T1 (Yes in S307), the wear of the cleaning blade 71 is progressing, but within 60 seconds if the heater 12 is operating even at a normal output or less. It is determined that the image flow can be suppressed by driving the photosensitive drum 1. Then, it is set to execute the image flow recovery operation 3 (S308). When the setting of the image flow recovery operation 3 is finished, the wear detection operation of the cleaning blade 71 is finished. In addition, when the control unit 110 is less than the second threshold value T1 (No in S307), the cleaning blade 71 is worn, and it is determined that the discharge product cannot be removed even if the photosensitive drum 1 is driven. Execution of the image flow recovery operation 2 is set (S309). When the setting of the image flow recovery operation 2 is completed, the control unit 110 ends the wear detection operation of the cleaning blade 71. Here, the processing of S304 to S309 is the wear detection operation of the cleaning blade 71.

3. Image Flow Recovery Operation Next, the image flow recovery operation will be described. Since the image flow recovery operation 1 and the image flow recovery operation 2 in the present embodiment are the same as those in the first embodiment, description thereof will be omitted, and the image flow recovery operation 3 will be described.

  The image flow recovery operation 3 is a combination of an operation similar to the image flow recovery operation 2 and an operation similar to the image flow recovery operation 1. However, in the image flow recovery operation 3, in the same operation as the image flow recovery operation 2, the heater 12 operates at a lower output than the normal output in the image flow recovery operation 2 at the time of sleep or when the main power is turned off. In this embodiment, the temperature control range of the heater 12 is changed, and the normal temperature control range in the image flow recovery operation 2 is 50 ± 2 ° C. However, in the image flow recovery operation 3, the temperature control range is 40 ± 2 ° C. ℃. On the other hand, in the image flow recovery operation 3, the operation of sliding the photosensitive drum 1 with the cleaning blade 71 by driving the photosensitive drum 1 performed in the previous multi-rotation process is the same as the image flow recovery operation 1 in the first embodiment.

  As described above, in this embodiment, the control unit 110 causes only the heating operation to be performed when the drive torque detected in the detection operation is less than the first threshold and less than the second threshold smaller than the first threshold. In addition, when the temperature is less than the first threshold and greater than or equal to the second threshold, the rubbing operation and the heating operation at a target temperature lower than the target temperature when only the heating operation is performed are performed.

4). As described above, in this embodiment, the image flow recovery operation 3 is performed by combining the rubbing of the photosensitive drum 1 by the cleaning blade 71 and the heating by the heater 12, thereby further reducing power consumption. Is possible.

[Others]
As mentioned above, although this invention was demonstrated according to the specific Example, this invention is not limited to the above-mentioned Example.

  For example, in the above-described embodiment, an external heating type heating unit that heats the photosensitive member from the outside is used as a heating unit that heats the photosensitive member. However, an internal heating type heating unit that heats the photosensitive member from the inside may be used. Good.

  Further, the photosensitive member is not limited to a drum shape, and may be a belt shape, for example.

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 12 Atmosphere heater 13 Torque detection circuit 71 Cleaning blade 110 Control part

Claims (8)

Movable photoconductor, charging means for charging the photoconductor, exposure means for exposing the charged photoconductor to form an electrostatic image, developing means for supplying toner to the electrostatic image, transfer A transfer unit that transfers a toner image from the photoconductor to a transfer body at a portion, and a cleaning unit that contacts the photoconductor and removes toner from the photoconductor at a cleaning unit downstream of the transfer unit in the moving direction of the photoconductor In an image forming apparatus comprising: a member; a heating unit that heats the photosensitive member; and a driving unit that drives the photosensitive member.
Detecting means for detecting a driving torque of the driving means;
When a predetermined toner image is formed on the photosensitive member, the predetermined toner image reaches the cleaning unit, and an area on the photosensitive member on which the predetermined toner image is formed passes through the cleaning unit. A detection operation for detecting the drive torque of the drive means by the detection means is executed, the photoconductor is driven based on the drive torque detected in the detection operation, and the photoconductor is rubbed with the cleaning member. A controller that selects and executes one of a plurality of operation settings for performing at least one of a rubbing operation or a heating operation for heating the photosensitive member by the heating unit;
An image forming apparatus comprising:   The control unit performs only the rubbing operation of the rubbing operation and the heating operation when the driving torque detected in the detecting operation is equal to or greater than a first threshold value, and when the driving torque is less than the first threshold value. The image forming apparatus according to claim 1, wherein at least the heating operation is performed among the rubbing operation and the heating operation.   3. The control unit according to claim 2, wherein when the driving torque detected in the detection operation is less than the first threshold value, only the heating operation of the rubbing operation and the heating operation is performed. The image forming apparatus described.   When the driving torque detected in the detection operation is less than the first threshold value and less than a second threshold value that is less than the first threshold value, only the heating operation of the rubbing operation and the heating operation is performed. And when the temperature is less than the first threshold and greater than or equal to the second threshold, the heating operation is performed at a target temperature lower than the target temperature when only the rubbing operation and the heating operation are performed. The image forming apparatus according to claim 2.   The image forming apparatus according to claim 1, wherein the control unit causes the detection operation to be executed when an environmental humidity is equal to or higher than a predetermined humidity.   The image forming apparatus according to claim 1, wherein the control unit causes an operation selected from the plurality of operation settings to be executed when an environmental humidity is equal to or higher than a predetermined humidity.   7. The rubbing operation, wherein the photosensitive member is driven for a predetermined time after toner is supplied from the developing unit to the cleaning unit via the photosensitive member. The image forming apparatus according to one item.   The control unit is configured to determine the predetermined image based on at least one of an average image ratio of images formed by the image forming apparatus, the number of images formed by the image forming apparatus, and at least one of temperature and humidity. Adjusting the potential difference between the potential of the image portion of the electrostatic image of the predetermined toner image on the photoconductor and the voltage applied to the developing means so that the density of the toner image approaches a predetermined density. The image forming apparatus according to any one of claims 1 to 6.

Images