JP2019086740A - Image forming apparatus - Google Patents

Abstract

To quickly cancel image deletion without causing an increase in manufacturing cost of an image forming apparatus and an increase in size of the image forming apparatus.SOLUTION: An image forming apparatus 1 according to the present invention comprises: photoreceptor drums 14 in each of which an electrostatic latent image is formed on its surface; static eliminators 19 each including light emitting elements that emit static eliminating light toward the surface of the photoreceptor drum 14 and limit resistors that limit a current flowing in the light emitting elements; and a control unit 51 that, when a predetermined condition is satisfied, executes refresh control of removing moisture from the surfaces of the photoreceptor drums 14. The image forming apparatus increases the power input to the static eliminators 19 during the execution of the refresh control compared with the power input to the static eliminators 19 during execution of normal printing.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an electrophotographic image forming apparatus.

  Conventionally, in an electrophotographic image forming apparatus, an electrostatic latent image is formed on the surface of a photosensitive drum, and the electrostatic latent image is developed to form an image.

  Conventionally, an amorphous silicon photoreceptor is used as a photoreceptor drum. The amorphous silicon photosensitive member is excellent in abrasion resistance, and has an advantage of enabling the life of the photosensitive drum to be extended.

  On the other hand, amorphous silicon photoreceptors have the disadvantage that so-called image flow is likely to occur. Here, with image flow, the discharge product attached to the surface of the photosensitive drum adsorbs moisture, and the electric resistance on the surface of the photosensitive drum decreases, so that the charge on the surface of the photosensitive drum flows and It is a phenomenon in which the boundary of the latent image is blurred. The occurrence of such an image flow results in an image defect. The image flow easily occurs on the amorphous silicon photosensitive member because the surface of the amorphous silicon photosensitive member tends to adsorb moisture.

  In order to eliminate such an image flow, it is required to remove the water adhering to the surface of the photosensitive drum. Therefore, conventionally, many techniques have been proposed for removing the water adhering to the surface of the photosensitive drum.

  For example, Patent Document 1 discloses a technique of heating the surfaces of an intermediate transfer member and a photosensitive member by convection of warm air from a heater unit located below the intermediate transfer member.

JP 2004-191790A

  However, in Patent Document 1, there is a possibility that the manufacturing cost of the image forming apparatus may increase by adding a dedicated heater unit for heating the surfaces of the intermediate transfer member and the photosensitive member. In addition, in Patent Document 1, a space for installing the heater means is required, which may lead to an increase in the size of the image forming apparatus.

  SUMMARY OF THE INVENTION An object of the present invention is to promptly eliminate the image flow without increasing the manufacturing cost of the image forming apparatus and increasing the size of the image forming apparatus.

  In the image forming apparatus according to the present invention, a photosensitive drum on which an electrostatic latent image is formed on the surface, a light emitting element for emitting static elimination light toward the surface of the photosensitive drum, and a current flowing to the light emitting element And a controller for performing a refresh control for removing water from the surface of the photosensitive drum when a predetermined condition is satisfied, and at the time of executing the refresh control. It is characterized in that the power supplied to the charge removing device is larger than the power supplied to the charge removing device at the time of normal printing.

  The image forming apparatus is provided so as to be selectable between an execution mode capable of executing the refresh control and a stop mode in which the execution of the refresh control is stopped, and the stop mode is selected and the predetermined condition is When satisfied, refresh printing may be performed in which the power supplied to the static eliminator is larger than that at the time of normal printing.

  The refresh printing may be performed from when the stop mode is selected and the predetermined condition is satisfied to when printing of a predetermined number of sheets is completed.

  The image forming apparatus further includes a charging member that charges the surface of the photosensitive drum, and a developing member that develops an electrostatic latent image formed on the surface of the photosensitive drum, and the refresh control The toner aging period in which the developing member forms a toner band on the surface of the photosensitive drum, and the electrical aging period in which the charging member charges the surface of the photosensitive drum after the toner aging period ends, During the toner aging period and during the current-flowing aging period, the power supplied to the static elimination device may be always larger than that during the execution of the normal printing.

  The image forming apparatus further includes a humidity sensor for detecting the humidity inside or outside the machine, and the control unit executes the refresh control when the humidity detected by the humidity sensor is equal to or higher than a predetermined threshold. Also good.

  According to the present invention, it is possible to promptly eliminate the image flow without increasing the manufacturing cost of the image forming apparatus and increasing the size of the image forming apparatus.

FIG. 1 is a schematic view showing an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing an image forming unit according to an embodiment of the present invention. It is a perspective view showing the static elimination device concerning one embodiment of the present invention. It is a circuit diagram showing the static elimination device concerning one embodiment of the present invention. FIG. 1 is a block diagram showing a control system of an image forming apparatus according to an embodiment of the present invention. 7 is a timing chart showing refresh control in the image forming apparatus according to the embodiment of the present invention. 7 is a flowchart showing control at start-up of the main power supply in the image forming apparatus according to an embodiment of the present invention. 7 is a graph showing the results of Experiment 1. 7 is a graph showing the results of Experiment 3.

  Hereinafter, an image forming apparatus 1 according to an embodiment of the present invention will be described with reference to the drawings. Arrows Fr, Rr, L, R, U, and Lo appropriately attached to the drawings respectively indicate the front side, the rear side, the left side, the right side, the upper side, and the lower side of the image forming apparatus 1.

  First, the entire configuration of the image forming apparatus 1 will be described. The image forming apparatus 1 is, for example, a multifunction peripheral having a print function, a copy function, a fax function, and the like in combination.

  As shown in FIG. 1, the image forming apparatus 1 includes a box-shaped apparatus main body 2. At an upper end portion of the apparatus body 2, an image reading apparatus 3 for reading an original image is provided. A sheet discharge tray 4 is provided on the top of the apparatus body 2. An intermediate transfer belt 5 is accommodated at a substantially central portion of the apparatus main body 2. The right end portion of the intermediate transfer belt 5 is wound around a driving roller 6. In the substantially central portion of the apparatus main body 2, four image forming units 7 are accommodated below the intermediate transfer belt 5. The four image forming units 7 correspond to black, cyan, magenta, and yellow toners, respectively. An exposure device 8 is accommodated in the lower portion of the apparatus body 2. At the lower end portion of the apparatus main body 2, a sheet feeding cassette 9 for storing the sheet S (recording medium) is accommodated.

  A conveyance path P for the sheet S is provided on the right side of the apparatus body 2. At the upstream end of the conveyance path P, a sheet feeding unit 10 is provided. A secondary transfer roller 11 is provided at a midstream portion of the conveyance path P. A fixing device 12 is provided downstream of the conveyance path P.

  Next, the operation of the image forming apparatus 1 will be described.

  First, an electrostatic latent image is formed in each image forming unit 7 by the light from the exposure device 8 (see the two-dot chain line arrow in FIG. 1). The electrostatic latent image is developed into a toner image in each image forming unit 7. The toner image is primarily transferred from each image forming unit 7 to the intermediate transfer belt 5. Thereby, a full color toner image is formed on the intermediate transfer belt 5.

  Further, the sheet S taken out of the sheet feeding cassette 9 by the sheet feeding unit 10 is conveyed to the downstream side of the conveyance path P and enters the nip region between the intermediate transfer belt 5 and the secondary transfer roller 11. The secondary transfer roller 11 secondarily transfers the full color toner image formed on the intermediate transfer belt 5 to the sheet S. The sheet S on which the toner image has been secondarily transferred is further transported to the downstream side of the transport path P and enters the fixing device 12. The fixing device 12 fixes the toner image on the sheet S. The sheet S on which the toner image is fixed is discharged onto the discharge tray 4.

  Next, the image forming unit 7 will be described.

  Referring to FIG. 2, the image forming unit 7 includes a photosensitive drum 14, a charging roller 15 (an example of a charging member) provided below the photosensitive drum 14, and a development provided on the left side of the photosensitive drum 14. The roller 16 (an example of a developing member), the primary transfer roller 17 provided on the upper side of the photosensitive drum 14, the cleaning device 18 provided on the right side of the photosensitive drum 14, and the upper right side of the photosensitive drum 14 And a static elimination device 19.

  The photosensitive drum 14 of the image forming unit 7 has a cylindrical shape. The photosensitive drum 14 is rotatably provided around a rotational axis X extending in the front-rear direction. That is, in the present embodiment, the front-rear direction is the rotational axis direction of the photosensitive drum 14. An arrow A in FIG. 2 indicates the rotation direction of the photosensitive drum 14.

  The photosensitive drum 14 includes a base material layer 21 and a photosensitive layer 22 covering the outer periphery of the base material layer 21. The base layer 21 is made of, for example, a metal and is electrically grounded. The photosensitive layer 22 is formed of, for example, amorphous silicon. Hereinafter, the surface of the photosensitive layer 22 is referred to as “the surface of the photosensitive drum 14”.

  The charging roller 15 of the image forming unit 7 has a cylindrical shape. The charging roller 15 is rotatably provided. The charging roller 15 includes a core 24 and an elastic layer 25 covering the outer periphery of the core 24. The cored bar 24 is made of, for example, metal. The elastic layer 25 is formed of, for example, an elastic material such as epichlorohydrin rubber and has conductivity. The outer peripheral surface of the elastic layer 25 is in contact with the surface of the photosensitive drum 14.

  The developing roller 16 of the image forming unit 7 has a cylindrical shape. The developing roller 16 is rotatably provided. The outer circumferential surface of the developing roller 16 is opposed to the surface of the photosensitive drum 14 with a gap. Inside the developing roller 16, a plurality of non-rotatable magnetic poles (not shown) are accommodated.

  The primary transfer roller 17 of the image forming unit 7 sandwiches the intermediate transfer belt 5 together with the photosensitive drum 14. The primary transfer roller 17 is rotatably provided. The primary transfer roller 17 includes a cored bar 27 and an elastic layer 28 covering the outer periphery of the cored bar 27. The cored bar 27 is made of, for example, metal. The elastic layer 28 is formed of, for example, an elastic material such as EPDM (ethylene-propylene rubber) and has conductivity.

  The cleaning device 18 of the image forming unit 7 is provided on the lower left side of the housing 30, the seal member 31 fixed to the upper left portion of the housing 30, the rubbing roller 32 accommodated in the housing 30, and And a blade 33.

  The housing 30 of the cleaning device 18 is opened toward the left side (the photosensitive drum 14 side), and has a substantially U-shaped cross section. The housing 30 is bent leftward from the lower end of the upper wall 35 extending in the left-right direction, the side wall 36 bent downward from the right end of the upper wall 35, and the lower end of the side wall 36 And a bottom wall 37. The left end portion of the upper wall 35 is opposed to the surface of the photosensitive drum 14 via a gap G.

  The seal member 31 of the cleaning device 18 is formed of, for example, a urethane sheet. The proximal end of the seal member 31 is fixed to the left end of the upper wall 35 of the housing 30. The tip of the seal member 31 is in contact with the surface of the photosensitive drum 14. The seal member 31 covers the gap G between the left end of the top wall 35 of the housing 30 and the surface of the photosensitive drum 14.

  The rubbing roller 32 of the cleaning device 18 is accommodated in the housing 30. The rubbing roller 32 is rotatably provided. The rubbing roller 32 is disposed downstream of the seal member 31 in the rotational direction of the photosensitive drum 14. The rubbing roller 32 includes a core 38 and an elastic layer 39 covering the outer periphery of the core 38. The cored bar 38 is made of, for example, metal. The elastic layer 39 is formed of, for example, an elastic material such as EPDM (ethylene-propylene rubber).

  The blade 33 of the cleaning device 18 is made of, for example, urethane rubber. The blade 33 is fixed to the left end of the bottom wall 37 of the housing 30. The blade 33 is disposed downstream of the rubbing roller 32 in the rotational direction of the photosensitive drum 14. The tip of the blade 33 is in contact with the surface of the photosensitive drum 14.

  The charge removing device 19 of the image forming unit 7 is disposed between the lower surface of the intermediate transfer belt 5 and the upper surface of the upper wall 35 of the housing 30 of the cleaning device 18. The charge removing device 19 is disposed downstream of the primary transfer roller 17 and upstream of the cleaning device 18 in the rotational direction of the photosensitive drum 14.

  Referring to FIG. 3, the static elimination device 19 includes a substrate 41, a plurality of (for example, eighteen) light emitting elements 42 mounted on the upper surface of the substrate 41, and a plurality (for example, 3) mounted on the upper surface of the substrate 41. And a limiting resistor 43). The substrate 41 has a flat plate shape that is long in the front-rear direction. The plurality of light emitting elements 42 and the plurality of limiting resistors 43 are all arranged in a line along the front-rear direction. Each light emitting element 42 is configured by, for example, a chip-type LED (Light Emitting Diode). Each limiting resistor 43 is configured by, for example, a chip-type resistor.

  Referring to FIG. 4, one end of charge removal device 19 is connected to first power reception terminal 46, and the other end of charge removal device 19 is connected to second power reception terminal 47. The static elimination device 19 includes three static elimination units 48 connected in parallel to one another. Each static elimination unit 48 is configured of six light emitting elements 42 connected in series with one another, and one limiting resistor 43 connected in series with the six light emitting elements 42. Each limiting resistor 43 is disposed upstream of each light emitting element 42 in the direction in which current flows in each of the charge removal units 48 (see arrow I in FIG. 4). Each limiting resistor 43 limits the current flowing to each light emitting element 42 and protects each light emitting element 42.

  Next, a control system of the image forming apparatus 1 will be described.

  Referring to FIG. 5, the image forming apparatus 1 includes a control unit 51. The control unit 51 is configured of, for example, a CPU (Central Processing Unit).

  The control unit 51 is connected to the storage unit 52. The storage unit 52 includes, for example, a random access memory (RAM) and a read only memory (ROM). The storage unit 52 stores the humidity threshold Th outside the aircraft.

  The control unit 51 is connected to the display unit 53. The display unit 53 is configured of, for example, an LCD (Liquid Crystal Display). The display unit 53 displays various screens (for example, an operation screen and an error display screen) based on a signal from the control unit 51.

  The control unit 51 is connected to the belt motor 54. The belt motor 54 is connected to the drive roller 6, and when the belt motor 54 rotates the drive roller 6 based on a signal from the control unit 51, the intermediate transfer belt 5 rotates following the rotation of the drive roller 6. Do. That is, the belt motor 54 rotates the intermediate transfer belt 5 based on the signal from the control unit 51.

  The control unit 51 is connected to the drum motor 55. The drum motor 55 is connected to the photosensitive drum 14 and rotates the photosensitive drum 14 based on a signal from the control unit 51.

  The controller 51 is connected to the developing motor 56. The developing motor 56 is connected to the developing roller 16, and rotates the developing roller 16 based on a signal from the control unit 51.

  The control unit 51 is connected to the developing bias applying unit 57. The development bias application unit 57 is connected to the development roller 16, and applies the development bias to the development roller 16 based on a signal from the control unit 51. The polarity of the developing bias is the same as the charging polarity of the toner.

  The control unit 51 is connected to the cooling fan 58. The cooling fan 58 operates based on a signal from the control unit 51 and takes in air outside the aircraft into the aircraft.

  The control unit 51 is connected to the power supply 59. The power source 59 is connected to each of the power receiving terminals 46 and 47 of the static elimination device 19, and applies a voltage between the respective power receiving terminals 46 and 47 of the static elimination device 19 based on the signal from the control unit 51.

  The control unit 51 is connected to the charging bias applying unit 60. The charging bias application unit 60 is connected to the charging roller 15, and applies the charging bias to the charging roller 15 based on the signal from the control unit 51. The polarity of the charging bias is the same as the charging polarity of the toner.

  The control unit 51 is connected to the primary transfer bias application unit 61. The primary transfer bias application unit 61 is connected to the primary transfer roller 17, and the primary transfer bias (forward bias) or the primary transfer bias (reverse) is applied to the primary transfer roller 17 based on the signal from the control unit 51. Bias). The polarity of the primary transfer bias (forward bias) is opposite to the charge polarity of the toner. The polarity of the primary transfer bias (reverse bias) is the same as the charging polarity of the toner.

  The control unit 51 is connected to the secondary transfer bias application unit 62. The secondary transfer bias application unit 62 is connected to the secondary transfer roller 11, and a secondary transfer bias (forward bias) or a secondary transfer bias (reverse) is applied to the secondary transfer roller 11 based on a signal from the control unit 51. Bias). The polarity of the secondary transfer bias (forward bias) is opposite to the charge polarity of the toner. The polarity of the secondary transfer bias (reverse bias) is the same as the charging polarity of the toner.

  The control unit 51 is connected to the humidity sensor 63. The humidity sensor 63 detects the humidity H outside the machine and sends it to the control unit 51.

  Next, an example of normal printing in the image forming apparatus 1 configured as described above will be described.

  When normal printing is performed, the drum motor 55 rotates the photosensitive drum 14 so that the charging roller 15 is driven to rotate by the photosensitive drum 14. Further, the charging bias application unit 60 applies a charging bias to the charging roller 15. Thereby, the charging roller 15 uniformly charges the surface of the photosensitive drum 14.

  Further, at the time of normal printing, the exposure device 8 exposes the charged surface of the photosensitive drum 14. Thereby, an electrostatic latent image is formed on the surface of the photosensitive drum 14.

  Further, at the time of normal printing, the developing motor 56 rotates the developing roller 16. Further, the developing bias applying unit 57 applies a developing bias to the developing roller 16. As a result, the toner T moves from the developing roller 16 to the surface of the photosensitive drum 14, the electrostatic latent image formed on the surface of the photosensitive drum 14 is developed, and a toner image is formed on the surface of the photosensitive drum 14. Ru. That is, the developing roller 16 develops the electrostatic latent image formed on the surface of the photosensitive drum 14.

  Further, at the time of normal printing, the belt motor 54 rotates the intermediate transfer belt 5. Further, the primary transfer bias application unit 61 applies a primary transfer bias (forward bias) to the primary transfer roller 17. Thus, the toner image formed on the surface of the photosensitive drum 14 is primarily transferred to the intermediate transfer belt 5.

  In addition, at the time of execution of normal printing, the secondary transfer bias application unit 62 applies a secondary transfer bias (forward bias) to the secondary transfer roller 11. Thus, the toner image primarily transferred to the intermediate transfer belt 5 is secondarily transferred to the sheet S.

  Further, when normal printing is performed, the rubbing roller 32 of the cleaning device 18 rotates at a rotational speed different from that of the photosensitive drum 14 and rubs against the surface of the photosensitive drum 14. Thereby, the surface of the photosensitive drum 14 is polished by the rubbing roller 32, and the residual toner T 'from the surface of the photosensitive drum 14 by the rubbing roller 32 remains on the surface of the photosensitive drum 14 after the primary transfer. Toner) is removed.

  Further, when the normal printing is performed, the photosensitive drum 14 rotates with respect to the blade 33 of the cleaning device 18. Thus, the surface of the photosensitive drum 14 is polished by the blade 33, and the residual toner T ′ is removed from the surface of the photosensitive drum 14 by the blade 33.

  Further, at the time of normal printing, the power supply 59 applies a voltage between the respective power receiving terminals 46 and 47 of the static elimination device 19. Thereby, each light emitting element 42 of the static eliminator 19 irradiates the surface of the photosensitive drum 14 with the static elimination light EL. When the static elimination light EL reaches the surface of the photosensitive drum 14, the residual charge (the charge remaining on the surface of the photosensitive drum 14 after the primary transfer) is removed from the surface of the photosensitive drum 14.

  When the normal printing is performed, the power Pw1 [W] is supplied from the power supply 59 to the static elimination device 19. Along with this, a current of I1 [mA] flows in the static elimination device 19.

  Next, an example of refresh control for removing water from the surface of the photosensitive drum 14 in the image forming apparatus 1 configured as described above will be described.

  Referring to FIG. 6, execution period P of the refresh control includes a first period P1 to a fifth period P5. Of the first period P1 to the fifth period P5, the second period P2 is an example of a toner aging period, and the fourth period P4 is an example of a power aging period.

  When the refresh control is performed, the belt motor 54 rotates the intermediate transfer belt 5 throughout the execution period P. In addition, the drum motor 55 rotates the photosensitive drum 14 throughout the execution period P.

  Further, at the time of execution of the refresh control, the developing motor 56 rotates the developing roller 16 from the beginning of the first period P1 to the middle of the third period P3. Further, during the second period P2, the developing bias applying unit 57 applies a developing bias to the developing roller 16. Thereby, the toner T is moved from the developing roller 16 to the surface of the photosensitive drum 14 during the second period P2.

  During the execution of the refresh control, the operation of the exposure device 8 is stopped throughout the execution period P, and an electrostatic latent image is not formed on the surface of the photosensitive drum 14. Therefore, when the toner T moves from the developing roller 16 to the surface of the photosensitive drum 14 as described above, a toner band (a band-like toner image continuous in the front-rear direction) is formed on the surface of the photosensitive drum 14.

  When the refresh control is performed, the rubbing roller 32 of the cleaning device 18 rotates at a rotational speed different from that of the photosensitive drum 14 and rubs against the surface of the photosensitive drum 14 throughout the execution period P. As a result, the surface of the photosensitive drum 14 is polished by the rubbing roller 32, and the toner band is removed from the surface of the photosensitive drum 14 by the rubbing roller 32.

  Further, at the time of execution of the refresh control, the photosensitive drum 14 rotates with respect to the blade 33 of the cleaning device 18. Thus, the surface of the photosensitive drum 14 is polished by the blade 33, and the toner band is removed from the surface of the photosensitive drum 14 by the blade 33. When the toner band is removed from the surface of the photosensitive drum 14 as described above, the moisture adhering to the surface of the photosensitive drum 14 is also removed from the surface of the photosensitive drum 14 together with the toner band.

  Further, when the refresh control is executed, the operation of the cooling fan 58 is stopped over the entire execution period P. This suppresses the intake of moist air outside the machine into the machine.

  Further, when the refresh control is performed, the power supply 59 applies a voltage between the respective power receiving terminals 46 and 47 of the static elimination device 19 throughout the execution period P. Thereby, each light emitting element 42 of the static eliminator 19 irradiates the surface of the photosensitive drum 14 with the static elimination light EL.

  During the execution of the refresh control, power Pw2 [W] larger than the power Pw1 [W] supplied from the power supply 59 to the static elimination device 19 at the time of normal printing execution is used from the power supply 59 over the entire execution period P. It is thrown into 19th. Along with this, a current I2 [mA] larger than the current I1 [mA] flowing to the static elimination device 19 at the time of normal printing flows to the static elimination device 19. Therefore, a larger current flows through the limiting resistor 43 of each static elimination unit 48 of the static elimination device 19 than when normal printing is performed, and the calorific value of the limiting resistor 43 becomes larger than when regular printing is performed. Along with this, the surface of the photosensitive drum 14 is heated by the generated limiting resistor 43.

  When the refresh control is performed, the charging roller 15 is driven to rotate by the photosensitive drum 14 over the entire execution period P. In addition, the charging bias application unit 60 applies a charging bias to the charging roller 15 during the fourth period P4. Thus, the charging roller 15 uniformly charges the surface of the photosensitive drum 14 during the fourth period P4.

  Further, at the time of executing the refresh control, the primary transfer bias application unit 61 applies a primary transfer bias (reverse bias) to the primary transfer roller 17 throughout the execution period P. In addition, the secondary transfer bias application unit 62 applies a secondary transfer bias (reverse bias) to the secondary transfer roller 11 throughout the execution period P.

  When the refresh control as described above is completed, the start operation for performing the normal printing is started.

  The image forming apparatus 1 according to the present embodiment is provided so as to be able to select an execution mode in which the refresh control can be performed and a stop mode in which the execution of the refresh control is stopped. For example, a mode selection screen is displayed when the user such as a user or a serviceman operates the display unit 53, and either the execution mode or the stop mode is selected when the operator operates the mode selection screen. It has become so.

  Next, in the image forming apparatus 1 configured as described above, an example of control when turning on the main power will be described.

  Referring to FIG. 7, when the main power supply of the image forming apparatus 1 is activated (step S101), the humidity sensor 63 detects the humidity H outside the apparatus and transmits it to the control unit 51 (step S102).

  The control unit 51 determines whether the external humidity H detected by the humidity sensor 63 is equal to or higher than the threshold Th stored in the storage unit 52 (step S103). If the determination in step S103 is No, the control unit 51 executes normal printing (step S104).

  On the other hand, if the determination in step S103 is YES, the control unit 51 determines whether the execution mode is selected (step S105). If the determination in step S105 is YES, the execution mode is selected, and refresh control can be performed. Therefore, the control unit 51 executes refresh control (step S106).

  When the refresh control ends, the control unit 51 determines whether the state in which the image flow is likely to occur has been eliminated (step S107). This determination is performed based on, for example, whether or not the value of the current flowing through the charging roller 15 is less than a predetermined threshold value. If the determination in step S107 is No, the control unit 51 returns to step S106 to execute refresh control again. On the other hand, if the determination in step S107 is YES, the control unit 51 executes normal printing (step S104).

  On the other hand, when the determination in step S105 is No, the stop mode is selected, and the execution of the refresh control is stopped. In this case, the control unit 51 executes refresh printing until printing of a predetermined number of sheets (for example, 100 sheets) is completed (step S108).

  When the refresh printing is performed, power Pw2 [W], which is larger than the power Pw1 [W] supplied from the power supply 59 to the charge removal apparatus 19 at the time of normal printing, is supplied from the power supply 59 to the charge removal apparatus 19. Along with this, a current I2 [mA] larger than the current I1 [mA] flowing to the static elimination device 19 at the time of normal printing flows to the static elimination device 19. Therefore, a larger current flows through the limiting resistor 43 of each static elimination unit 48 of the static elimination device 19 than when normal printing is performed, and the calorific value of the limiting resistor 43 becomes larger than when regular printing is performed. Along with this, the surface of the photosensitive drum 14 is heated by the generated limiting resistor 43. In the other points, the method of executing refresh printing is the same as the method of executing normal printing, and thus the description thereof is omitted. When the refresh printing is completed, the control unit 51 executes normal printing (step S104).

  In the present embodiment, as described above, the power supplied to the charge removing device 19 at the time of executing the refresh control is made larger than the power supplied to the charge removing device 19 at the time of performing the normal printing. As a result, it is possible to heat the surface of the photosensitive drum 14 using the heat generation of the limiting resistor 43 of the static elimination device 19 and to remove water from the surface of the photosensitive drum 14. Along with this, it is possible to quickly eliminate the image flow.

  Further, since the surface of the photosensitive drum 14 is heated using the heat generation of the limiting resistor 43 as described above, it is not necessary to add a dedicated heater for heating the surface of the photosensitive drum 14. Therefore, it is possible to prevent an increase in manufacturing cost of the image forming apparatus 1 and an increase in size of the image forming apparatus 1 due to the addition of the heater. In addition, it is possible to suppress an increase in the user's toll burden accompanying the power consumption in the heater.

  In addition, since the surface of the photosensitive drum 14 is heated using the heat generation of the limiting resistor 43 as described above, a dedicated resistance for heating the photosensitive drum 14 is provided on the back surface of the substrate 41 separately from the limiting resistor 43. It becomes possible to reduce the number of resistances required for the static elimination device 19 as compared to the case where it is mounted. Therefore, the configuration of the static eliminator 19 can be simplified, and the manufacturing cost of the static eliminator 19 can be reduced.

  Further, in the present embodiment, toner aging (operation of forming a toner band on the surface of the photosensitive drum 14 and polishing the surface of the photosensitive drum 14 with the rubbing roller 32 or the blade 33) at the time of executing refresh control Running. Although such toner aging is advantageous for the early elimination of the image flow, it consumes the toner regardless of the printing, so the user's waiting time becomes long when it is executed over a long period of time. There is an adverse effect that wasteful toner consumption increases. In particular, the image flow is likely to occur in the second half of the endurance of the image forming apparatus 1 (a state in which the image forming apparatus 1 is used to a considerable extent) or in a long standing condition of the image forming apparatus 1. Aging tends to be prolonged, and the above-mentioned adverse effects are likely to occur.

  On the other hand, in the present embodiment, as described above, not only the toner aging is used to eliminate the image flow but also the toner aging and the heat generation of the limiting resistor 43 are used to eliminate the image flow. ing. Therefore, compared to the case where only toner aging is used, the required time for refresh control can be shortened. As a result, it is possible to shorten the waiting time of the user and to suppress the consumption of toner due to toner aging.

  Further, in the present embodiment, the execution mode in which the refresh control can be executed and the stop mode in which the execution of the refresh control is stopped can be selected. As a result, not only the user's request to execute the refresh control and promptly eliminate the image flow, but also the user's request to stop the refresh control and suppress the increase of the waiting time and the increase of the toner consumption amount. It becomes possible to respond.

  Further, in the present embodiment, when the stop mode is selected and the predetermined condition (humidity H 閾 値 threshold value Th) is satisfied, refresh printing is performed in which the power input to the static elimination device 19 is larger than that in the normal printing. Is running. By adopting such a configuration, it is possible to promptly eliminate the image flow even when the stop mode is selected.

  Further, the refresh printing is executed from when the stop mode is selected and when the predetermined condition (humidity H ≧ threshold Th) is satisfied and printing of a predetermined number of sheets is completed. By adopting such a configuration, it is possible to easily determine the execution period of refresh printing.

  Further, in the refresh control, the charging roller 15 performs the refresh control after the second period P2 (an example of a toner aging period) in which the developing roller 16 forms a toner band on the surface of the photosensitive drum 14 and the second period P2. The fourth period P4 (an example of a current-flowing aging period) for charging the surface of 14 is included. During the second period P2 and the fourth period P4, the power supplied to the static elimination device 19 is normally printed at all times. It is bigger than at runtime. By adopting such a configuration, it is possible to more reliably eliminate the image flow.

  The control unit 51 also executes refresh control when the humidity detected by the humidity sensor 63 is equal to or higher than a predetermined threshold Th. By adopting such a configuration, it becomes possible to execute refresh control only when image flow is likely to occur, and execution of unnecessary refresh control prolongs the user's waiting time and increases toner consumption. Can be suppressed.

  In the present embodiment, the humidity sensor 63 detects the humidity outside the machine. On the other hand, in another different embodiment, the humidity sensor 63 may detect the humidity inside the machine.

  In the present embodiment, the image forming apparatus 1 is a multifunction peripheral. On the other hand, in another different embodiment, the image forming apparatus 1 may be a printer, a copier, a facsimile, or the like.

<Experiment>
The experiment for demonstrating the effect of this invention was conducted using the image forming apparatus 1 which concerns on this embodiment.

<Experimental conditions>
Details of the image forming apparatus 1 used in the experiment are as follows.
Linear velocity of the surface of the photosensitive drum 14: 250 [mm / sec]
Material of photosensitive layer 22 of photosensitive drum 14: Diameter of amorphous silicon photosensitive drum 14: 30 [mm]
Material of elastic layer 25 of charging roller 15: diameter of epichlorohydrin rubber charging roller 15: 9.5 [mm]
Charging potential of charging roller 15: +250 [V]
Material of blade 33: Thickness of urethane rubber blade 33: 2.0 [mm]
JIS-A hardness of blade 33: 79 [°]
Repulsive resilience of blade 33: 28% (measured in an environment of 23 ° C)
Young's modulus of blade 33: 11.4 [MPa]
Resistance value of limiting resistor 43: 470 [Ω]

<Experiment 1>
In Experiment 1, the value of the current (hereinafter referred to as "dielectricizing current Ie") flowing to the static eliminator 19 is changed to execute continuous printing for 1 minute, and the temperature of the limiting resistor 43 mounted on the upper surface of the substrate 41 is measured. did. The temperature at the time of the experiment was 25 ° C., and the humidity at the time of the experiment was 50%. The results of Experiment 1 are shown in FIG.

  As is clear from FIG. 8, the temperature of the limiting resistor 43 increases as the value of the static elimination current Ie increases. From this, it can be understood that the temperature of the limiting resistor 43 can be raised by increasing the power supplied from the power source 59 to the static eliminator 19 to increase the value of the static eliminator current Ie.

<Experiment 2>
In Experiment 2, the image forming apparatus 1 left in a high temperature and high humidity environment (temperature 32.5 [° C.], relative humidity 80 [%]) for 48 hours executes the refresh control by changing the value of the static elimination current Ie. And the number of times until the image flow was eliminated was measured. In addition, it was judged visually whether the image flow was eliminated.

In Experiment 2, the first period P1 to the fifth period P5 of the refresh control execution period P are set as follows.
First period P1: 400 [msec]
Second period P2: 475 [msec]
Third period P3: 2 [sec]
Fourth period P4: 50 [sec]
Fifth period P5: 7 [sec]
Therefore, the execution period P of refresh control is
P = P1 + P2 + P3 + P4 + P5 = 59.875 [sec] ≒ 60 [sec]
It is. The results of Experiment 2 are shown in Table 1.

  As apparent from Table 1, as the value of the static elimination current Ie increases, the number of times of execution of the refresh control decreases. From this, if the power supplied from the power source 59 to the charge removal apparatus 19 is increased to increase the value of the charge removal current Ie, heat generation of the limiting resistor 43 is promoted to remove moisture from the surface of the photosensitive drum 14 It can be seen that the number of refresh control executions can be reduced.

Further, the total execution time of the refresh control for each value of the static elimination current Ie is as follows.
In the case of static elimination current Ie = 0 [mA]: 60 [sec] × 10 [times] = 600 [sec]
In the case of static elimination current Ie = 20 [mA]: 60 [sec] × 8 [times] = 480 [sec]
In the case of charge removal current Ie = 40 [mA]: 60 [sec] × 4 [times] = 240 [sec]
Therefore, by increasing the value of the static elimination current Ie from 0 [mA] to 40 [mA], 360 [sec] (= 600 [sec]-240 [sec]) also waits for the user for refresh control. It can be shortened.

Also, for example, 125 mg toner is used in one refresh control. Accordingly, the total amount of toner used for each value of the static elimination current Ie is as follows.
In the case of static elimination current Ie = 0 [mA]: 125 [mg] × 10 [twice] = 1250 [mg]
In the case of static elimination current Ie = 20 [mA]: 125 [mg] × 8 [times] = 1000 [mg]
In the case of charge removal current Ie = 40 [mA]: 125 [mg] × 4 [times] = 500 [mg]
Therefore, by increasing the value of the discharging current Ie from 0 [mA] to 40 [mA], 750 [mg] (= 1250 [mg] -500 [mg]) is also the total amount of toner used for refresh control. Can be reduced.

<Experiment 3>
In Experiment 3, the image forming apparatus 1 left in a high temperature and high humidity environment (temperature 32.5 [° C.], relative humidity 80 [%]) for 48 hours is not subjected to the refresh control and is not The values were changed to execute printing, and the image flow level for each number of printed sheets was measured. In addition, the measurement of the image flow level was performed visually. The image flow level criteria are shown in Table 2.

As apparent from Table 2, the image flow level 4 is the best, and the image flow level 1 is the worst. The results of Experiment 3 are shown in FIG.

  As apparent from FIG. 9, the image flow is gradually eliminated by printing. Further, as apparent from FIG. 9, by increasing the value of the static elimination current Ie, the number of printed sheets until the image flow is eliminated is reduced. From this, it can be understood that the image flow can be eliminated early by increasing the power supplied from the power source 59 to the static eliminator 19 to increase the value of the static elimination current Ie.

1 image forming apparatus 14 photosensitive drum 15 charging roller (charging member)
16 Developing roller (developing member)
19 static elimination device 42 light emitting element 43 limiting resistance 51 control unit 63 humidity sensor

Claims (5)

A photosensitive drum on which an electrostatic latent image is formed;
A charge removing device comprising: a light emitting element for emitting a charge removing light toward the surface of the photosensitive drum; and a limiting resistor for limiting a current flowing to the light emitting element.
A control unit that executes refresh control to remove moisture from the surface of the photosensitive drum when a predetermined condition is satisfied;
An image forming apparatus, wherein the power supplied to the charge removal device at the time of execution of the refresh control is larger than the power supplied to the charge removal device at the time of execution of normal printing. An execution mode in which the refresh control can be executed and a stop mode in which the execution of the refresh control is stopped can be selected.
The present invention is characterized in that, when the stop mode is selected and the predetermined condition is satisfied, refresh printing is performed in which the power supplied to the static elimination device is larger than that at the time of normal printing. The image forming apparatus according to claim 1.   3. The image forming apparatus according to claim 2, wherein the refresh printing is performed from when the stop mode is selected and the predetermined condition is satisfied to when printing of a predetermined number of sheets is completed. A charging member for charging the surface of the photosensitive drum;
And a developing member for developing an electrostatic latent image formed on the surface of the photosensitive drum.
The refresh control is
A toner aging period in which the developing member forms a toner band on the surface of the photosensitive drum;
After the end of the toner aging period, an electrification aging period in which the charging member charges the surface of the photosensitive drum;
4. The method according to any one of claims 1 to 3, wherein during the toner aging period and during the electrification aging period, the power supplied to the charge removing device is always larger than that during the normal printing. Image forming device. It also has a humidity sensor that detects the humidity inside and outside the aircraft,
The image forming apparatus according to any one of claims 1 to 4, wherein the control unit executes the refresh control when the humidity detected by the humidity sensor is equal to or higher than a predetermined threshold.

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