JP7043798B2 - Image forming device - Google Patents

Description

The present invention relates to an electrophotographic image forming apparatus.

Conventionally, an electrophotographic image forming apparatus forms an electrostatic latent image on the surface of a photoconductor drum and develops the electrostatic latent image to form an image.

Conventionally, an amorphous silicon photoconductor has been used as a photoconductor drum. Since this amorphous silicon photoconductor has excellent wear resistance, it has an advantage that the life of the photoconductor drum can be extended.

On the other hand, the amorphous silicon photoconductor has a drawback that so-called image flow is likely to occur. Here, the image flow means that the discharge product adhering to the surface of the photoconductor drum adsorbs moisture and the electric resistance on the surface of the photoconductor drum decreases, so that the electric charge on the surface of the photoconductor drum flows and is static. This is a phenomenon in which the boundary of an electric latent image is blurred. When such an image flow occurs, image defects are caused as a result. Image flow is likely to occur in the amorphous silicon photoconductor because the surface of the amorphous silicon photoconductor easily adsorbs moisture.

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

For example, Patent Document 1 discloses a technique for heating the surfaces of an intermediate transfer body and a photoconductor by convection of warm air from a heater means located below the intermediate transfer body.

Japanese Unexamined Patent Publication No. 2004-191790

However, in Patent Document 1, the manufacturing cost of the image forming apparatus may increase by adding a dedicated heater means for heating the surfaces of the intermediate transfer body and the photoconductor. Further, in Patent Document 1, a space for installing the heater means is required, which may lead to an increase in size of the image forming apparatus.

Therefore, 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.

The image forming apparatus according to the present invention limits the current flowing through the photoconductor drum on which an electrostatic latent image is formed, the light emitting element that irradiates the surface of the photoconductor drum with static electricity elimination light, and the light emitting element. A static eliminator equipped with a limiting resistance, and a control unit for executing a refresh control for removing water from the surface of the photoconductor drum when a predetermined condition is satisfied, and at the time of executing the refresh control. It is characterized in that the electric power input to the static eliminator is larger than the electric power input to the static eliminator at the time of executing normal printing.

The image forming apparatus is provided so as to be able to select between 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. The stop mode is selected and the predetermined conditions are satisfied. When the condition is satisfied, refresh printing may be executed in which the power applied to the static eliminator is larger than that at the time of normal printing.

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

The image forming apparatus further includes a charging member for charging the surface of the photoconductor drum and a developing member for developing an electrostatic latent image formed on the surface of the photoconductor drum, and the refresh control is performed by the refresh control. The processing includes a toner aging period in which the developing member forms a toner band on the surface of the photoconductor drum, and an energization aging period in which the charging member charges the surface of the photoconductor drum after the end of the toner aging period. During the toner aging period and the energization aging period, the power applied to the static eliminator may always be larger than that at the time of normal printing.

The image forming apparatus further includes a humidity sensor that detects 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 value. Is also good.

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

It is a schematic diagram which shows the image forming apparatus which concerns on one Embodiment of this invention. It is sectional drawing which shows the image formation part which concerns on one Embodiment of this invention. It is a perspective view which shows the static elimination apparatus which concerns on one Embodiment of this invention. It is a circuit diagram which shows the static elimination apparatus which concerns on one Embodiment of this invention. It is a block diagram which shows the control system of the image forming apparatus which concerns on one Embodiment of this invention. It is a timing chart which shows the refresh control in the image forming apparatus which concerns on one Embodiment of this invention. It is a flowchart which shows the control at the time of starting up the main power source in the image forming apparatus which concerns on one Embodiment of this invention. It is a graph which shows the result of Experiment 1. It is a graph which shows the result of Experiment 3.

Hereinafter, the image forming apparatus 1 according to the embodiment of the present invention will be described with reference to the drawings. The arrows Fr, Rr, L, R, U, and Lo appropriately attached to each figure 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, respectively.

First, the overall configuration of the image forming apparatus 1 will be described. The image forming apparatus 1 is, for example, a multifunction device having a printing function, a copying function, a fax function, and the like.

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

A paper S transport path P is provided on the right side of the apparatus main body 2. A paper feeding unit 10 is provided at the upstream end of the transport path P. A secondary transfer roller 11 is provided in the middle stream portion of the transport path P. A fixing device 12 is provided in the downstream portion of the transport 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 apparatus 8 (see the two-dot chain arrow in FIG. 1). This electrostatic latent image is developed into a toner image in each image forming unit 7. This toner image is primarily transferred from each image forming unit 7 to the intermediate transfer belt 5. As a result, a full-color toner image is formed on the intermediate transfer belt 5.

Further, the paper S taken out from the paper feed cassette 9 by the paper feed unit 10 is conveyed downstream along the transport path P and enters the nip region of the intermediate transfer belt 5 and the secondary transfer roller 11. The secondary transfer roller 11 secondary transfers the full-color toner image formed on the intermediate transfer belt 5 to the paper S. The paper S to which the toner image is secondarily transferred is conveyed further downstream on the transport path P and enters the fixing device 12. The fixing device 12 fixes the toner image on the paper S. The paper S on which the toner image is fixed is discharged onto the paper ejection tray 4.

Next, the image forming unit 7 will be described.

With reference to FIG. 2, the image forming unit 7 includes a photoconductor drum 14, a charging roller 15 (an example of a charging member) provided under the photoconductor drum 14, and a developing unit provided on the left side of the photoconductor drum 14. A roller 16 (an example of a developing member), a primary transfer roller 17 provided on the upper side of the photoconductor drum 14, a cleaning device 18 provided on the right side of the photoconductor drum 14, and an upper right side of the photoconductor drum 14 are provided. It is equipped with a static eliminator 19.

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

The photoconductor drum 14 includes a base material layer 21 and a photosensitive layer 22 that covers the outer periphery of the base material layer 21. The base material 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 portion 7 has a columnar shape. The charging roller 15 is rotatably provided. The charging roller 15 includes a core metal 24 and an elastic layer 25 that covers the outer periphery of the core metal 24. The core metal 24 is made of, for example, metal. The elastic layer 25 is formed of 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 photoconductor 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 peripheral surface of the developing roller 16 faces the surface of the photoconductor drum 14 with a gap. A plurality of non-rotatable magnetic poles (not shown) are housed inside the developing roller 16.

The primary transfer roller 17 of the image forming unit 7 sandwiches the intermediate transfer belt 5 together with the photoconductor drum 14. The primary transfer roller 17 is rotatably provided. The primary transfer roller 17 includes a core metal 27 and an elastic layer 28 that covers the outer periphery of the core metal 27. The core metal 27 is made of, for example, metal. The elastic layer 28 is formed of 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 housing 30, the seal member 31 fixed to the upper left portion of the housing 30, the rubbing roller 32 housed in the housing 30, and the lower left side of the rubbing roller 32. It is equipped with a blade 33.

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

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

The rubbing roller 32 of the cleaning device 18 is housed in the housing 30. The rubbing roller 32 is rotatably provided. The rubbing roller 32 is arranged on the downstream side of the sealing member 31 in the rotation direction of the photoconductor drum 14. The rubbing roller 32 includes a core metal 38 and an elastic layer 39 that covers the outer periphery of the core metal 38. The core metal 38 is made of, for example, metal. The elastic layer 39 is formed of an elastic material such as EPDM (ethylene propylene rubber).

The blade 33 of the cleaning device 18 is formed 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 arranged on the downstream side of the rubbing roller 32 in the rotation direction of the photoconductor drum 14. The tip of the blade 33 is in contact with the surface of the photoconductor drum 14.

The static elimination device 19 of the image forming unit 7 is arranged 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 static elimination device 19 is arranged on the downstream side of the primary transfer roller 17 and on the upstream side of the cleaning device 18 in the rotation direction of the photoconductor drum 14.

With reference to FIG. 3, the static elimination device 19 includes a substrate 41, a plurality of (for example, 18) 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. It is provided with a limiting resistor 43 and. The substrate 41 has a long flat plate shape in the front-rear direction. The plurality of light emitting elements 42 and the plurality of limiting resistors 43 are all arranged in a row along the front-rear direction. Each light emitting element 42 is composed of, for example, a chip-type LED (Light Emitting Diode). Each limiting resistance 43 is composed of, for example, a chip type resistance.

With reference to FIG. 4, one end of the static eliminator 19 is connected to the first power receiving terminal 46, and the other end of the static eliminator 19 is connected to the second power receiving terminal 47. The static elimination device 19 includes three static elimination units 48 connected in parallel with each other. Each static elimination unit 48 is composed of six light emitting elements 42 connected in series with each other and one limiting resistor 43 connected in series with the six light emitting elements 42. Each limiting resistor 43 is arranged on the upstream side of each light emitting element 42 in the direction in which current flows through each static elimination unit 48 (see arrow I in FIG. 4). Each limiting resistor 43 limits the current flowing through each light emitting element 42 and protects each light emitting element 42.

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

With reference to FIG. 5, the image forming apparatus 1 includes a control unit 51. The control unit 51 is composed 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 RAM (Random Access Memory) and a ROM (Read Only Memory). The storage unit 52 stores the threshold value Th of the humidity outside the machine.

The control unit 51 is connected to the display unit 53. The display unit 53 is composed 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 the 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 in accordance with 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 photoconductor drum 14, and rotates the photoconductor drum 14 based on a signal from the control unit 51.

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

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

The control unit 51 is connected to the power supply 59. The power supply 59 is connected to the power receiving terminals 46 and 47 of the static elimination device 19, and a voltage is applied between the 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 charge bias application unit 60. The charging bias applying unit 60 is connected to the charging roller 15, and applies a charging bias to the charging roller 15 based on a 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) is applied. The polarity of the primary transfer bias (forward bias) is opposite to the charging 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 the secondary transfer bias (forward bias) or the secondary transfer bias (reverse) is applied to the secondary transfer roller 11 based on the signal from the control unit 51. Bias) is applied. The polarity of the secondary transfer bias (forward bias) is opposite to the charging 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 transmits 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.

At the time of normal printing, the drum motor 55 rotates the photoconductor drum 14, so that the charging roller 15 is driven by the photoconductor drum 14 to rotate. Further, the charging bias applying unit 60 applies a charging bias to the charging roller 15. As a result, the charging roller 15 uniformly charges the surface of the photoconductor drum 14.

Further, when normal printing is executed, the exposure apparatus 8 exposes the surface of the charged photoconductor drum 14. As a result, an electrostatic latent image is formed on the surface of the photoconductor drum 14.

Further, when normal printing is executed, the developing motor 56 rotates the developing roller 16. Further, the development bias application unit 57 applies a development bias to the development roller 16. As a result, the toner T moves from the developing roller 16 to the surface of the photoconductor drum 14, the electrostatic latent image formed on the surface of the photoconductor drum 14 is developed, and the toner image is formed on the surface of the photoconductor drum 14. Toner. That is, the developing roller 16 develops the electrostatic latent image formed on the surface of the photoconductor drum 14.

Further, when normal printing is executed, 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. As a result, the toner image formed on the surface of the photoconductor drum 14 is primarily transferred to the intermediate transfer belt 5.

Further, when normal printing is executed, the secondary transfer bias application unit 62 applies the secondary transfer bias (forward bias) to the secondary transfer roller 11. As a result, the toner image primaryly transferred to the intermediate transfer belt 5 is secondarily transferred to the paper S.

Further, when normal printing is executed, the rubbing roller 32 of the cleaning device 18 rotates at a rotation speed different from that of the photoconductor drum 14, and rubs against the surface of the photoconductor drum 14. As a result, the surface of the photoconductor drum 14 is polished by the rubbing roller 32, and the residual toner T'(residual on the surface of the photoconductor drum 14 after the primary transfer) from the surface of the photoconductor drum 14 by the rubbing roller 32. Toner) is removed.

Further, when normal printing is executed, the photoconductor drum 14 rotates with respect to the blade 33 of the cleaning device 18. As a result, the surface of the photoconductor drum 14 is polished by the blade 33, and the residual toner T'is removed from the surface of the photoconductor drum 14 by the blade 33.

Further, when normal printing is executed, the power supply 59 applies a voltage between the power receiving terminals 46 and 47 of the static elimination device 19. As a result, each light emitting element 42 of the static elimination device 19 irradiates the surface of the photoconductor drum 14 with the static elimination light EL. When the static elimination light EL reaches the surface of the photoconductor drum 14, residual charges (charges remaining on the surface of the photoconductor drum 14 after the primary transfer) are removed from the surface of the photoconductor drum 14.

When the normal printing is executed, the electric power Pw1 [W] is input from the power supply 59 to the static elimination device 19. Along with this, a current of I1 [mA] flows through the static eliminator 19.

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

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

When the refresh control is executed, the belt motor 54 rotates the intermediate transfer belt 5 over the entire execution period P. Further, the drum motor 55 rotates the photoconductor drum 14 over the entire execution period P.

Further, when the refresh control is executed, 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 development bias application unit 57 applies the development bias to the development roller 16. As a result, the toner T moves from the developing roller 16 to the surface of the photoconductor drum 14 during the second period P2.

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

Further, when the refresh control is executed, the rubbing roller 32 of the cleaning device 18 rotates at a rotation speed different from that of the photoconductor drum 14 and rubs against the surface of the photoconductor drum 14 over the entire execution period P. As a result, the surface of the photoconductor drum 14 is polished by the rubbing roller 32, and the toner band is removed from the surface of the photoconductor drum 14 by the rubbing roller 32.

Further, when the refresh control is executed, the photoconductor drum 14 rotates with respect to the blade 33 of the cleaning device 18. As a result, the surface of the photoconductor drum 14 is polished by the blade 33, and the toner band is removed from the surface of the photoconductor drum 14 by the blade 33. When the toner band is removed from the surface of the photoconductor drum 14 as described above, the water adhering to the surface of the photoconductor drum 14 is also removed from the surface of the photoconductor drum 14 together with the toner band.

Further, when the refresh control is executed, the operation of the cooling fan 58 is stopped for the entire execution period P. This prevents the moist air outside the aircraft from being taken into the aircraft.

Further, when the refresh control is executed, the power supply 59 applies a voltage between the power receiving terminals 46 and 47 of the static elimination device 19 over the entire execution period P. As a result, each light emitting element 42 of the static elimination device 19 irradiates the surface of the photoconductor drum 14 with the static elimination light EL.

When the refresh control is executed, the power Pw2 [W] larger than the power Pw1 [W] input from the power supply 59 to the static eliminator 19 during the execution of normal printing during the entire execution period P is the power eliminator from the power supply 59. It is thrown into 19. Along with this, a current I2 [mA] larger than the current I1 [mA] flowing in the static eliminator 19 when normal printing is executed flows in the static eliminator 19. Therefore, a larger current flows through the limiting resistance 43 of each static elimination unit 48 of the static elimination device 19 than when normal printing is executed, and the calorific value of the limiting resistance 43 becomes larger than when normal printing is executed. Along with this, the surface of the photoconductor drum 14 is heated by the heat-generating limiting resistance 43.

Further, when the refresh control is executed, the charging roller 15 is driven by the photoconductor drum 14 to rotate over the entire execution period P. Further, during the fourth period P4, the charging bias applying unit 60 applies a charging bias to the charging roller 15. As a result, during the fourth period P4, the charging roller 15 uniformly charges the surface of the photoconductor drum 14.

Further, when the refresh control is executed, the primary transfer bias application unit 61 applies the primary transfer bias (reverse bias) to the primary transfer roller 17 over the entire execution period P. Further, the secondary transfer bias application unit 62 applies the secondary transfer bias (reverse bias) to the secondary transfer roller 11 over the entire period of the execution period P.

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

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

Next, in the image forming apparatus 1 configured as described above, an example of control at the time of starting up the main power supply will be described.

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

The control unit 51 determines whether or not the humidity H outside the machine detected by the humidity sensor 63 is equal to or higher than the threshold value 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 or not 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 executed. Therefore, the control unit 51 executes refresh control (step S106).

When the refresh control is completed, the control unit 51 determines whether or not the state in which image flow is likely to occur has been resolved (step S107). This determination is made, for example, based on 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 and executes 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 the printing of a predetermined number of sheets (for example, 100 sheets) is completed (step S108).

At the time of executing the refresh print, the electric power Pw2 [W] larger than the electric power Pw1 [W] applied from the power supply 59 to the static eliminator 19 at the time of executing the normal printing is input from the power supply 59 to the static eliminator 19. Along with this, a current I2 [mA] larger than the current I1 [mA] flowing in the static eliminator 19 when normal printing is executed flows in the static eliminator 19. Therefore, a larger current flows through the limiting resistance 43 of each static elimination unit 48 of the static elimination device 19 than when normal printing is executed, and the calorific value of the limiting resistance 43 becomes larger than when normal printing is executed. Along with this, the surface of the photoconductor drum 14 is heated by the heat-generating limiting resistance 43. Regarding other points, the method of executing refresh printing is the same as the method of executing normal printing, and thus the description thereof will be omitted. When the refresh printing is completed, the control unit 51 executes normal printing (step S104).

In the present embodiment, as described above, the electric power input to the static elimination device 19 when the refresh control is executed is larger than the electric power input to the static elimination device 19 when the normal printing is executed. This makes it possible to heat the surface of the photoconductor drum 14 by utilizing the heat generated by the limiting resistance 43 of the static elimination device 19 and remove water from the surface of the photoconductor drum 14. Along with this, it becomes possible to quickly eliminate the image flow.

Further, since the surface of the photoconductor drum 14 is heated by utilizing the heat generated by the limiting resistance 43 as described above, it is not necessary to add a dedicated heater for heating the surface of the photoconductor drum 14. Therefore, it is possible to prevent an increase in the manufacturing cost of the image forming apparatus 1 and an increase in the 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 charge burden due to power consumption in the heater.

Further, since the surface of the photoconductor drum 14 is heated by utilizing the heat generated by the limiting resistance 43 as described above, a dedicated resistance for heating the photoconductor drum 14 is provided on the back surface of the substrate 41 separately from the limiting resistance 43. It is possible to reduce the number of resistors required for the static eliminator 19 as compared to the case where it is mounted. Therefore, it is possible to simplify the configuration of the static eliminator 19 and reduce the manufacturing cost of the static eliminator 19.

Further, in the present embodiment, toner aging (an operation of forming a toner band on the surface of the photoconductor drum 14 and polishing the surface of the photoconductor drum 14 with a rubbing roller 32 or a blade 33) is performed when the refresh control is executed. Running. Such toner aging is advantageous for early elimination of image flow, but it consumes toner independently of printing, so if it is executed for a long period of time, the user's waiting time may increase. However, there is an adverse effect that wasteful toner consumption increases. In particular, image flow is likely to occur in the latter half of the durability of the image forming apparatus 1 (a state in which the image forming apparatus 1 is used to a considerable extent) or in a state in which the image forming apparatus 1 is left for a long period of time. 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, instead of using only toner aging to eliminate the image flow, the image flow is eliminated by using both the toner aging and the heat generated by the limiting resistance 43. ing. Therefore, it is possible to shorten the time required for refresh control as compared with the case where only toner aging is used. As a result, it is possible to shorten the waiting time of the user and suppress the consumption of toner due to toner aging.

Further, in the present embodiment, 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. This not only requests users who want to execute refresh control to eliminate image flow at an early stage, but also requests users who want to stop execution of refresh control to prolong the waiting time and suppress the increase in toner consumption. It will be possible to respond.

Further, in the present embodiment, when the stop mode is selected and a predetermined condition (humidity H ≧ threshold value Th) is satisfied, the power input to the static eliminator 19 is made larger than that at the time of normal printing. Is being executed. By adopting such a configuration, it is possible to quickly eliminate the image flow even when the stop mode is selected.

Further, the refresh printing is executed from the time when the stop mode is selected and the predetermined condition (humidity H ≧ threshold value Th) is satisfied until the 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 developing roller 16 forms a toner band on the surface of the photoconductor drum 14 in the second period P2 (an example of the toner aging period), and after the end of the second period P2, the charging roller 15 uses the photoconductor drum 14 to form a toner band. A fourth period P4 (an example of an energization aging period) for charging the surface of 14 is included, and during the second period P2 and the fourth period P4, the power input to the static eliminator 19 is normally printed. It is larger than when it was executed. By adopting such a configuration, it is possible to eliminate the image flow more reliably.

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

In this 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 in the machine.

In the present embodiment, the image forming apparatus 1 is a multifunction device. 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>
An experiment for demonstrating the effect of the present invention was conducted using the image forming apparatus 1 according to the present embodiment.

<Experimental conditions>
The details of the image forming apparatus 1 used in the experiment are as follows.
Linear velocity on the surface of the photoconductor drum 14: 250 [mm / sec]
Material of the photosensitive layer 22 of the photoconductor drum 14: Amorphous silicon Diameter of the photoconductor drum 14: 30 [mm]
Material of elastic layer 25 of charging roller 15: Epichlorohydrin rubber Diameter of charging roller 15: 9.5 [mm]
Charging potential of charging roller 15: +250 [V]
Material of blade 33: Urethane rubber Blade 33 thickness: 2.0 [mm]
JIS-A hardness of blade 33: 79 [°]
Repulsive elasticity 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, continuous printing was performed for 1 minute by changing the value of the current flowing through the static elimination device 19 (hereinafter referred to as "static elimination current Ie"), and the temperature of the limiting resistor 43 mounted on the upper surface of the substrate 41 was 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 result of Experiment 1 is shown in FIG.

As is clear from FIG. 8, the temperature of the limiting resistor 43 rises as the value of the static elimination current Ie increases. From this, it can be seen that the temperature of the limiting resistor 43 can be raised by increasing the power input from the power supply 59 to the static elimination device 19 and increasing the value of the static elimination current Ie.

<Experiment 2>
In Experiment 2, refresh control was executed by changing the value of the static elimination current Ie for the image forming apparatus 1 left in a high temperature and high humidity environment (temperature 32.5 [° C.], relative humidity 80 [%]) for 48 hours. Then, the number of times until the image flow was eliminated was measured. It should be noted that it was visually determined whether or not the image flow was eliminated.

In Experiment 2, the first period P1 to the fifth period P5 of the refresh control execution period P were 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 refresh control execution period P is
P = P1 + P2 + P3 + P4 + P5 = 59.875 [sec] ≈60 [sec]
Is. The results of Experiment 2 are shown in Table 1.

As is clear from Table 1, the larger the value of the static elimination current Ie, the smaller the number of times the refresh control is executed. From this, if the power applied from the power supply 59 to the static eliminator 19 is increased to increase the value of the static elimination current Ie, the heat generation of the limiting resistor 43 can be promoted and the moisture can be removed from the surface of the photoconductor drum 14. It can be seen that the refresh control can be executed less frequently.

The total execution time of the refresh control for each value of the static elimination current Ie is as follows.
When the static elimination current Ie = 0 [mA]: 60 [sec] x 10 [times] = 600 [sec]
When the static elimination current Ie = 20 [mA]: 60 [sec] x 8 [times] = 480 [sec]
When the static elimination current Ie = 40 [mA]: 60 [sec] x 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 reduces the waiting time of the user for refresh control. Can be shortened.

Further, for example, 125 [mg] of toner is used in one refresh control. Therefore, the total amount of toner used for each value of the static elimination current Ie is as follows.
When the static elimination current Ie = 0 [mA]: 125 [mg] x 10 [times] = 1250 [mg]
When the static elimination current Ie = 20 [mA]: 125 [mg] x 8 [times] = 1000 [mg]
When the static elimination current Ie = 40 [mA]: 125 [mg] x 4 [times] = 500 [mg]
Therefore, by increasing the value of the static elimination 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 static elimination current Ie of the image forming apparatus 1 left in a high temperature and high humidity environment (temperature 32.5 [° C.], relative humidity 80 [%]) for 48 hours without executing refresh control. Printing was performed by changing the value, and the image flow level for each number of prints was measured. The image flow level was measured visually. Table 2 shows the criteria for the image flow level.

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

As is clear from FIG. 9, the image flow is gradually eliminated by printing. Further, as is clear from FIG. 9, by increasing the value of the static elimination current Ie, the number of prints until the image flow is eliminated is reduced. From this, it can be seen that the image flow can be eliminated at an early stage by increasing the power input from the power supply 59 to the static elimination device 19 and increasing the value of the static elimination current Ie.

1 Image forming device 14 Photoreceptor drum 15 Charging roller (charging member)
16 Developing roller (developing member)
19 Static eliminator 42 Light emitting element 43 Limiting resistance 51 Control unit 63 Humidity sensor

Claims (4)

A photoconductor drum on which an electrostatic latent image is formed on the surface,
A static eliminator including a light emitting element that irradiates the surface of the photoconductor drum with static elimination light and a limiting resistor that limits the current flowing through the light emitting element.
Moisture is removed from the surface of the photoconductor drum so that an electrostatic latent image is not formed on the surface of the photoconductor drum and a toner band is formed on the surface of the photoconductor drum when a predetermined condition is satisfied. It is equipped with a control unit that executes refresh control to be removed.
The electric power input to the static eliminator when the refresh control is executed is made larger than the electric power input to the static eliminator when the normal printing is executed.
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.
When the stop mode is selected and the predetermined condition is satisfied, the image forming apparatus is characterized in that refresh printing is executed in which the power applied to the static eliminator is larger than that at the time of normal printing. .. The image forming apparatus according to claim 1, wherein the refresh printing is executed from the time when the stop mode is selected and the time when the predetermined condition is satisfied until the printing of a predetermined number of sheets is completed. A charging member that charges the surface of the photoconductor drum, and
Further, a developing member for developing an electrostatic latent image formed on the surface of the photoconductor drum is provided.
The refresh control is
The toner aging period in which the developing member forms a toner band on the surface of the photoconductor drum, and
After the end of the toner aging period, the charging member includes an energization aging period in which the surface of the photoconductor drum is charged.
The image forming apparatus according to claim 1 or 2, wherein during the toner aging period and the energization aging period, the electric power applied to the static elimination device is always larger than that at the time of normal printing. Further equipped with a humidity sensor that detects humidity inside or outside the aircraft,
The image forming apparatus according to any one of claims 1 to 3, 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 value.

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