JP6447252B2 - Image forming apparatus, image forming method, and program - Google Patents

Description

  The present invention relates to an image forming apparatus, an image forming method, and a program for forming an image by electrophotography. More specifically, the present invention relates to charging control in an image forming apparatus.

  2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus that forms a toner image on a photoreceptor, various controls have been proposed to prevent image quality degradation. For example, in Patent Document 1, as a configuration for dealing with density unevenness of an output image, a target potential corresponding to an environmental factor is prepared in advance, a charging voltage or an exposure amount corresponding to a detection result of an environmental sensor is set, A configuration is disclosed in which the toner supply amount is controlled by detecting the density of a patch formed based on the setting.

Japanese Patent Laid-Open No. 04-238368

  However, the conventional technique described above has the following problems. That is, residual charges, which are charges that have not reached the surface of the photoreceptor, exist inside the photoreceptor. This residual charge may cancel a part of the charge of the photosensitive member charged by the charging device, and may cause the surface potential of the photosensitive member to be lower than the target potential. This decrease in surface potential causes a decrease in image quality such as density difference and fogging. In a configuration having a plurality of photoconductors, the amount of decrease in surface potential varies among the individual photoconductors, and the problem of a difference in density between the photoconductors becomes significant.

  The present invention has been made to solve the problems of the above-described conventional apparatus. That is, an object of the present invention is to provide an image forming apparatus for forming an image by an electrophotographic method, and to provide a technique for suppressing deterioration in image quality due to variations in the surface potential of the photoreceptor.

  An image forming apparatus designed to solve this problem is a plurality of forming units that form toner images, and includes a photosensitive member, a charging device that charges the surface of the photosensitive member, and supplies toner to the photosensitive member. The forming section comprising: a toner supply device that performs transfer; a transfer device that transfers the toner on the photoconductor to a transfer material; and a contact member that contacts the photoconductor and collects the toner carried on the photoconductor A heat source and a control unit, wherein the control unit sets the absolute value of the charging voltage used for each charging device of the plurality of forming units to the absolute value of the target surface potential of the photoconductor. A value obtained by adding a correction voltage value corresponding to the absolute value of the residual charge, which is a charge existing on the photoconductor after passing through the charging device, is set to a larger value as the forming portion is farther from the heat source. Or for each charging device The absolute value of the charging current that can be used corresponds to the absolute value of the current value for setting the target surface potential of the photosensitive member to the absolute value of the residual charge that is the charge existing on the photosensitive member after passing through the charging device. The correction current value is a value obtained by adding the correction current values, and the correction current value is set to a larger value as the formation portion is farther from the heat source.

  The image forming apparatus disclosed in this specification includes a plurality of forming portions, and the absolute value of the charging voltage or the charging current used in the charging device of each forming portion corresponds to the target surface potential of the photoreceptor. A value obtained by adding a correction value corresponding to the absolute value of the residual charge, which is the charge existing in the photoconductor after passing through the charging device, is added to the value. Furthermore, the correction value to be added is increased as the formation portion is farther from the heat source.

  The lower the temperature of the photoconductor, the slower the moving speed of the residual charges moving inside the photoconductor. Therefore, there is a high possibility that the charge generated in the photoconductor does not reach the surface of the photoconductor until it reaches a position facing the charging device, and a part of the charge charged by the charging device is canceled by the subsequent arrival. Become. Further, it is presumed that as the distance of the photoconductor from the heat source increases, the temperature of the photoconductor is lower, and as a result, the moving speed of the residual charge is slower and the amount of decrease in the surface potential of the photoconductor is also estimated. In the image forming apparatus disclosed in this specification, the correction value to be added to the absolute value of the charging voltage or the absolute value of the charging current is increased as the charging device is farther from the heat source. Can be expected to reduce density variation between photoconductors.

  The heat source may include a fixing device that thermally fixes the toner image transferred to the sheet to the sheet, and a heater that heats the fixing device. Since the amount of heat generated from the heater of the fixing device is large, the present invention preferably operates by including the heater in the heat source.

  And an exposure device that forms an electrostatic latent image on the photoconductor using a light emitting unit and a polygon mirror that reflects the light emitted from the light emitting unit toward the photoconductor, and the control The charging voltage of the forming portion whose distance from the heater is farther than a threshold value is set to a value whose absolute value is larger than the charging voltage of the forming portion whose distance from the heater is closer than the threshold value; The absolute value of the charging voltage used for each charging device of the forming unit whose distance from the heater is farther than the threshold value may be set to a larger value as the forming unit is far from the motor for driving the polygon mirror. The motor that is the driving source of the polygon mirror generates heat even if it is not as high as the fixing device. Therefore, it is preferable to set the absolute value of the charging voltage based on the position of the motor of the polygon mirror if the distance from the heater of the fixing device is long and the position is not easily affected by the heat generated from the fixing device.

  Further, using a fixing device that thermally fixes the toner image transferred to the sheet to the sheet, a light emitting unit, and a polygon mirror that reflects light emitted from the light emitting unit toward the photoconductor, An exposure device that forms an electrostatic latent image on the photosensitive member, and the plurality of forming portions includes a first forming portion whose distance from the heater is closer than a first distance, and the heater. And a second forming unit whose distance from the motor that rotationally drives the polygon mirror is shorter than the second distance, and the control unit includes the second distance It is preferable that the charging voltage V2 of the forming portion is larger than the charging voltage V1 of the first forming portion. With this configuration, the first forming part is more susceptible to the heat of the heat source than the second forming part, and the temperature of the photoconductor is likely to be higher.

  In addition, the plurality of forming portions may have a distance from the heater that is longer than the first distance, a distance from a motor that rotationally drives the polygon mirror is closer to the second distance, and the second distance. A distance from the heater that is farther from the heater than the forming portion and a distance from the heater that is farther than the first distance and a distance from the motor that rotationally drives the polygon mirror are the second distance. And the control unit may make the charging voltage V4 of the fourth forming unit larger than the charging voltage V3 of the third forming unit. With this configuration, the third forming portion is more likely to have a higher temperature of the photoconductor than the fourth forming portion.

  In addition, the plurality of forming portions may have a distance from the heater that is longer than the first distance, a distance from a motor that rotationally drives the polygon mirror is closer to the second distance, and the second distance. A third forming unit that is farther from the heater than the forming unit is included, and the control unit may make the charging voltage V3 larger than the charging voltage V2. With this configuration, the second forming portion is more likely to have a higher temperature of the photoconductor than the third forming portion.

  The contact member may be a cleaning blade that removes toner on the photoconductor. In the configuration in which the cleaning blade is in contact with the photosensitive member, frictional heat is easily generated, and electric charges are easily generated in the organic layer of the photosensitive member. For this reason, the residual charge tends to increase, and the present invention works favorably.

  And a storage unit that stores a charging calculation formula that defines an absolute value of a charging voltage of each charging device of the plurality of forming units according to the cumulative number of printed sheets. The ratio of the amount of increase in the absolute value of the charging voltage to the amount of increase is different for each of the charging devices of the plurality of forming portions, and the ratio is a larger formula for the forming portion farther from the heat source, The control unit may set an absolute value of a charging voltage used for each charging device of the plurality of forming units by using the cumulative number of printed sheets and the plurality of charging arithmetic expressions stored in the storage unit. If the target surface potential is the same, the absolute value of the charging voltage is increased as the cumulative number of printed sheets increases. Further, in the formation portion that is far from the heat source and the temperature of the photoconductor is estimated to be low, the ratio of the increase in the absolute value of the charging voltage to the increase in the cumulative number of printed sheets is increased so that the density variation between the formation portions is reduced. Reduction can be expected.

  The charging device may include a wire and a grid circuit, and an absolute value of the charging voltage may be an absolute value of an applied voltage applied to the grid circuit. If it is a scorotron type charging device, the present invention works suitably.

  The image forming apparatus disclosed in the present specification may include a thermometer, and the control unit may set the correction voltage value to a larger value as the temperature obtained from the output value of the thermometer is lower. When the temperature obtained from the output value of the thermometer is low, it is estimated that the temperature of the photoconductor is also low. When the temperature of the photoconductor is low, it is preferable to increase the voltage value.

  In addition, the control unit performs a sheet number determination process for determining whether or not the continuous print sheet number is equal to or greater than a predetermined sheet number, and determines that the continuous print sheet number is equal to or greater than the predetermined sheet number in the sheet number determination process. Accordingly, the correction voltage value may be set to a smaller value than when the number of continuously printed sheets is less than a predetermined number. It is estimated that the temperature rises due to continuous printing. Therefore, it is desirable to reduce the correction voltage value when the number of continuously printed sheets exceeds a predetermined number.

  Further, the image forming apparatus disclosed in the present specification includes a thermometer, and the control unit determines whether or not the temperature is equal to or higher than a predetermined temperature based on an output value of the thermometer. And the absolute value of the charging voltage used for each charging device is changed to the absolute value of the target surface potential of the photoconductor in response to determining that the temperature is not equal to or higher than the predetermined temperature in the temperature determination process. The correction voltage value is added, and the absolute value of the charging voltage used for each charging device is determined as the target value of the photoconductor in response to the temperature determination process determining that the temperature is equal to or higher than a predetermined temperature. The absolute value of the surface potential is preferred. If the temperature is sufficiently high, the effect of residual charge is small. Therefore, if the temperature is equal to or higher than the predetermined temperature, the absolute value of the charging voltage may be the absolute value of the target surface potential of the photoreceptor.

  An image forming method for realizing the functions of the image forming apparatus, a computer program, and a computer-readable storage medium storing the computer program are also novel and useful.

  According to the present invention, it is an image forming apparatus that forms an image by an electrophotographic method, and a technique for suppressing a decrease in image quality due to variations in the surface potential of the photoreceptor is realized.

1 is a cross-sectional view illustrating a schematic configuration of a printer according to an embodiment. It is explanatory drawing which shows the photoconductor of a printer. FIG. 2 is a block diagram illustrating an electrical configuration of a printer. FIG. 6 is an explanatory diagram showing movement of electric charges inside a photoconductor. 6 is a flowchart illustrating a printing process procedure of a printer. 6 is a flowchart illustrating a procedure of charging control processing of the printer. It is a correction table which shows the example of the correction value for every process part. It is a correction table which shows the example of the correction value for every process part. It is a correction table which shows the example of the correction value for every process part.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of an image forming apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. In this embodiment, the present invention is applied to a printer having an image forming function.

  The printer 100 according to this embodiment is a color printer that forms a color image by an electrophotographic method. As shown in FIG. 1, the printer 100 includes a process unit 5, an exposure device 6, a transport belt 7, and a fixing device 8. The process unit 5 includes a black process unit 50K, a cyan process unit 50C, a magenta process unit 50M, and a yellow process unit 50Y along the traveling direction of the transport belt 7, and these are equally spaced. Are arranged side by side. Note that the arrangement order of the process parts of each color is not limited to the example shown in FIG. Each color process section 50K, 50C, 50M, 50Y is an example of a forming section. The exposure device 6 is an example of an exposure device, and the fixing device 8 is an example of a fixing device.

  As shown in FIG. 1, the black process unit 50 </ b> K includes a drum-shaped photoconductor 51, a charging device 52, a developing device 54, a transfer device 55, and a cleaner 56 disposed around the photoconductor 51. And have. The photoconductor 51 is an example of a photoconductor, the charging device 52 is an example of a charging device, the developing device 54 is an example of a toner supply device, the transfer device 55 is an example of a transfer device, and a cleaner. 56 is an example of a contact member. The other color process units 50C, 50M, and 50Y have the same configuration as the black process unit 50K except for the toner color.

  The photoconductor 51 of the printer 100 includes a metal core 511 and an organic photosensitive layer 512 formed around the metal core 511 as schematically shown in a part of the cross section in FIG. That is, the metal core 511 shown on the lower side in FIG. 2 is the central portion of the photoconductor 51, and the organic photosensitive layer 512 shown on the upper side in FIG. 2 is provided on the entire circumference on the surface side of the photoconductor 51. Yes. The metal core 511 is, for example, an aluminum pipe and is electrically grounded. In the organic photosensitive layer 512, a charge generating agent 513 and a charge transporting agent 514 are dispersed.

  In the printer 100 of this embodiment, as the organic photosensitive layer 512, for example, a charge generating agent 513 mainly composed of polycarbonates and mainly containing phthalocyanines, and charge transport mainly containing azoquinones and arylamines. And a material having a thickness of 30 μm in the radial direction of the photosensitive member 51 is used. The exemplified materials are not limited to these, and may be appropriately selected according to the type of toner. Details of the organic photosensitive layer 512 will be described later.

  The charging device 52 is a scorotron type charger provided with wires 521 and a grid 522, and charges the surface of the photoconductor 51 by discharging. As a result, the surface of the photoconductor 51 is almost uniformly charged. Hereinafter, the grid voltage applied to the grid 522 of the charging device 52 is referred to as a charging voltage. Further, a wire current that flows through the wire 521 of the charging device 52 is defined as a charging current. The wire 521 is an example of a wire, and the grid 522 is an example of a grid circuit.

  The developing device 54 stores toner, charges the toner, and supplies the toner to the developing roller 541. Further, the developing device 54 applies a predetermined voltage to the developing roller 541 and creates a potential difference between the potential of the developing roller 541 and the potential of the electrostatic latent image on the photosensitive member 51, thereby charging the charged toner to the photosensitive member. The electrostatic latent image on 51 is supplied. As a result, a toner image is formed on the photoreceptor 51. The transfer device 55 is disposed in parallel with the photosensitive member 51 with the conveyance belt 7 interposed therebetween. The transfer device 55 electrically draws the toner image on the photosensitive member 51 by passing a transfer current, and transfers it onto the sheet being conveyed by the conveyance belt 7.

  The cleaner 56 is a cleaning blade. One end of the cleaner 56 comes into contact with the photoconductor 51 and scrapes off the toner remaining on the photoconductor 51 after the transfer. The cleaner 56 is in contact with the rotation of the photoconductor 51 in the counter direction. For example, in FIG. 1, the photoconductor 51 is rotated in the clockwise direction in the drawing, and the cleaner 56 has a component opposite to the traveling direction of the surface of the photoconductor 51 at the contact point with the photoconductor 51. It is pressed in the direction of including.

  As shown in FIG. 1, the exposure device 6 is a laser exposure type exposure device. Inside the housing 60, a polygon mirror 61, a polygon motor 62, two laser diodes 63 and 64, and an fθ lens 65 are provided. , A plurality of reflecting mirrors 66 and a toric lens 68. 1, the laser diode 63 is arranged on the front side of the polygon mirror 61, and the laser diode 64 is arranged on the back side of the polygon mirror 61. The laser diodes 63 and 64 are an example of a light emitting unit, the polygon mirror 61 is an example of a polygon mirror, and the polygon motor 62 is an example of a motor.

  The polygon mirror 61 and the polygon motor 62 are coaxially located at positions closest to each other, and are both disposed above the process unit 5. The polygon mirror 61 has a regular hexagonal shape when viewed from above, and is rotated at a constant speed in one direction by a polygon motor 62 during image formation. Further, as shown in FIG. 1, the polygon mirror 61 and the polygon motor 62 of the printer 100 are positions between the process unit 50C and the process unit 50M, and in the direction orthogonal to the paper surface of FIG. It is arrange | positioned in the center position of the longitudinal direction.

  The laser diodes 63 and 64 emit laser light in a direction orthogonal to the paper surface of FIG. 1, and each laser light is incident on the polygon mirror 61. The laser diode 63 emits laser light from the front of the paper to the back, and the laser diode 64 emits laser light from the back of the paper to the front. As shown in FIG. 1, the laser light reflected by the polygon mirror 61 passes through the fθ lens 65, the reflection mirror 66, and the toric lens 68, and is irradiated on the photoreceptor 2.

  Further, the traveling direction of the reflected laser beam reflected by one surface of the polygon mirror 61 changes as the polygon mirror 61 rotates. That is, the laser light emitted in one direction from the laser diodes 63 and 64 scans the surface of the photosensitive member 51 in the axial direction by the polygon mirror 61. As a result, the photosensitive member 51 is exposed for one line in the axial direction, and an electrostatic latent image for one line is formed.

  The printer 100 further includes a paper feed tray 91 on which a sheet before toner image transfer is placed and a paper discharge tray 92 on which a sheet after image formation is placed. Further, the printer 100 is provided with a conveyance path 11 that is a path of a substantially S-shaped sheet, as indicated by a two-dot chain line in FIG. The printer 100 includes various rollers for conveying the sheet along the conveyance path 11. That is, the printer 100 conveys one of the sheets stored in the paper feed tray 91 along the conveyance path 11 using various rollers and the conveyance belt 7 and discharges the sheet to the paper discharge tray 92.

  The fixing device 8 includes a heating roller 81 and a pressure roller 82, and heat-fixes unfixed toner on the sheet to the sheet. The heating roller 81 includes a heater 811 for heating the heating roller 81 therein. The heater 811 is an example of a heater.

  As shown in FIG. 1, the fixing device 8 is disposed downstream of the process unit 5 and the conveyance belt 7 in the sheet conveyance direction. That is, among the color process units 50, the black color process unit 50 </ b> K arranged on the most upstream side is farthest from the fixing device 8. The other colors are, in order from the farthest from the fixing device 8, the cyan process unit 50C, the magenta process unit 50M, and the yellow process unit 50Y.

  Note that the printer 100 of this embodiment forms an image using a positively chargeable one-component toner. That is, the surface of the photoreceptor 51 is positively charged by the charging device 52 when printing is performed. Next, a part of the surface of the photoreceptor 51 is exposed by the exposure device 6, so that the potential of the part decreases. The toner contained in the developing device 54 is charged to the positive polarity by the developing device 54 and moves to a location where the potential of the photoconductor 51 is lowered.

  Further, when executing printing, the printer 100 takes out the sheets placed on the paper feed tray 91 one by one and conveys the sheets onto the conveyance belt 7. The transfer device 55 is set to a negative potential by the transfer current, and draws the toner on the photoreceptor 51 in synchronization with the conveyance of the sheet. As a result, the toner image is transferred to the sheet.

  When printing a color image, the printer 100 causes the process unit 5 to sequentially transfer the toner images of the respective colors formed on the photoconductor 51 on the sheet. When printing a monochrome image, the printer 100 operates only the black process unit 50K. Thereafter, the printer 100 conveys the sheet onto which the toner image has been transferred to the fixing device 8 and thermally fixes the toner image to the sheet. Then, the sheet after fixing is discharged to a discharge tray 92.

  Next, the electrical configuration of the printer 100 will be described. As shown in FIG. 3, the printer 100 according to this embodiment includes a controller 30 including a CPU 31, a ROM 32, a RAM 33, and an NVRAM (nonvolatile RAM) 34. The printer 100 includes a process unit 5, a network interface 37, a USB interface 38, an operation panel 40, and a thermometer 42, and these are electrically connected to the controller 30. Note that the controller 30 in FIG. 1 is a collective term for hardware used for controlling the printer 100 such as the CPU 31, and does not necessarily represent a single piece of hardware that actually exists in the printer 100.

  The ROM 32 stores firmware, which is a control program for controlling the printer 100, various settings, initial values, and the like. The RAM 33 is used as a work area from which various control programs are read or as a storage area for temporarily storing image data. The CPU 31 controls each component of the printer 100 while storing the processing result in the RAM 33 or the NVRAM 34 in accordance with a control program read from the ROM 32 and signals sent from various sensors. The CPU 31 is an example of a control unit. The controller 30 may be a control unit. The ROM 32 is an example of a storage unit.

  The network interface 37 is hardware for communicating with a device connected via a network using a LAN cable or the like. The USB interface 38 is hardware for communicating with a device connected via a USB cable or the like. The operation panel 40 is hardware that is responsible for displaying a notification to the user and receiving an instruction input by the user.

  The operation panel 40 includes, for example, a liquid crystal display and a button group including a start key, a stop key, a numeric keypad, and the like. The thermometer 42 measures the temperature of the surrounding environment of the printer 100 or the temperature inside the apparatus of the printer 100. The printer 100 can estimate the temperature of the photoconductor 51 based on the output value of the thermometer 42.

  Next, a charging voltage setting method in the printer 100 will be described. In the printer 100 according to the present embodiment, if there is a portion where the surface potential is partially lowered on the photoconductor 51 after charging and before exposure, the potential at the lowered portion has a small difference from the developing bias. On the other hand, since the charge amount of the charged toner varies, the toner having a large charge amount may move to a portion where the surface potential is lowered and is not an electrostatic latent image. If toner adheres to a portion of the surface of the photoconductor 51 other than the electrostatic latent image, for example, a fogged image in which the toner adheres to a white background portion may be formed, which may cause a reduction in image quality. There is. Therefore, in order to suppress deterioration in image quality, it is desirable that the surface potential of the photoconductor 51 at a position immediately before development is a stable potential with little variation. In particular, in color printing, it is desired that the surface potential of the photoconductor 51 of each color has little variation.

  As shown in FIG. 2, the photoreceptor 51 has an organic photosensitive layer 512 including a charge generating agent 513 and a charge transporting agent 514. The charge generating agent 513 receives energy such as light and heat and generates a positive charge and a negative charge. The generated charges are carried by the charge transfer agent 514 and move inside the organic photosensitive layer 512. That is, due to the potential difference between the surface of the photoconductor 51 and the metal core 511, the positive charge and the negative charge are separated separately and move to the center side and the surface side of the photoconductor 51, respectively.

  For example, in the state where the surface of the photoconductor 51 is at a positive potential with respect to the level of the metal core 511, the negative charge out of the generated charges is directed toward the surface of the photoconductor 51 as shown in FIG. The positive charge moves toward the metal core 511. The higher the surface potential of the photoconductor 51, the greater the force that attracts negative charges, and the movement speed of the negative charges is faster. When the negative charge reaches the surface of the photoconductor 51, it is combined with the positive charge on the surface of the photoconductor 51 to cancel the charge. As a result, the potential at that point decreases.

  Further, as described above, since the printer 100 of this embodiment uses positively charged toner, the charging device 52 charges the surface of the photoconductor 51 to the positive polarity. At the time of exposure, charges are generated in the organic photosensitive layer 512 by the energy of the laser beam generated from the exposure device 6. Since the surface of the photoconductor 51 has a positive potential due to the charging, negative charges out of the generated charges are attracted to the surface of the photoconductor 51 to lower the surface potential of the photoconductor 51 at that location. As a result, an electrostatic latent image is formed on the surface of the photoreceptor 51. Then, the developing device 54 develops the portion of the electrostatic latent image whose potential has been lowered with the positively charged toner.

  In the printer 100 of this embodiment, the cleaner 56 is in contact with the surface of the photoconductor 51 as described above. In particular, the printer 100 of this embodiment uses a contact type blade member as the cleaner 56, and presses the cleaner 56 against the surface of the photosensitive member 51. Therefore, frictional heat is generated at the contact point between the photoconductor 51 and the cleaner 56. Then, as shown in FIG. 4A, electric charge may be generated in the organic photosensitive layer 512 of the photoconductor 51 in response to the energy of this frictional heat.

  The electric charge generated at the contact point with the cleaner 56 also moves in the same manner as that caused by the exposure described above. That is, as shown in FIG. 4B, the negative charge among the generated charges moves toward the surface side of the positively charged photoreceptor 51. Further, the negative charge reaching the surface of the photoconductor 51 is combined with the positive charge on the surface of the photoconductor to offset the positive charge, as shown by being surrounded by a broken line in FIG. The potential of 51 is lowered. In the printer 100, of the residual charges that are generated in the organic photosensitive layer 512 and do not reach the surface of the photosensitive member, negative charges contribute to a decrease in the potential of the photosensitive member 51. Hereinafter, among the residual charges remaining inside the photoconductor 51, the charge having the opposite polarity to the charged polarity is simply referred to as “residual charge”.

  If the offset of the surface potential of the photoconductor 51 due to the residual charge occurs at a position after charging and before development, the print density may be affected. For example, as shown in FIG. 4C, when the residual charge reaches the surface of the photoconductor 51 at a position after charging, the potential of the photoconductor 51 at that location decreases. Note that the photosensitive member 51 in the portion shown in FIG. 4 is moved to the right in the drawing by rotation.

  The contact portion between the cleaner 56 and the photoconductor 51 in the printer 100 is a position after transfer and before charging. Of the charges generated by the frictional heat of the cleaner 56, the negative polarity charges may become residual charges in the charging range. If the moving speed of the residual charge in the organic photosensitive layer 512 is slow, the residual charge is likely to reach the surface of the photoreceptor 51 at the position after charging as described above. That is, there is a high possibility that the portion of the photoconductor 51 reaches the charging range by the charging device 52 before the residual charge reaches the surface of the photoconductor 51.

  In the printer 100, when the temperature of the photoconductor 51 is low, the movement speed of charges inside the photoconductor 51 tends to be slow. In particular, if there is a difference in the temperature of the photoconductor 51 for each color, there is a possibility that a difference in color will occur in the moving speed of the residual charge, and there will be a difference in color in the surface potential of the photoconductor 51 after charging. Since the printer 100 has a heat source such as the heater 811 of the fixing device 8 in the apparatus as described above, there is a possibility that a temperature difference occurs between the photoconductors 51 of the respective colors depending on the distance from the heat source of the photoconductor 51. is there.

  The printer 100 of this embodiment controls the charging voltage of each color so that the surface potential of the photoconductor 51 of each color is equal to or higher than a predetermined target surface potential even if the surface potential is offset by the residual charge after charging. Specifically, the temperature level between the photoconductors 51 is estimated based on the distance between the photoconductor 51 of each color and the heat source, and the charging voltage is set based on the estimation result. As a heat source, the heater 811 of the fixing device 8 is first mentioned. The polygon motor 62 also generates heat as it rotates at a high speed, although not as much as the heater 811. Therefore, the polygon motor 62 is also an example of a heat source.

  Next, as an example of performing the above-described charging control for each color, a printing process procedure for realizing the printing operation of the printer 100 will be described with reference to the flowchart of FIG. This print processing is executed by the CPU 31 when a print job is received.

  In the printing process, the printer 100 first acquires the temperature using the thermometer 42 (S101), and then starts warming up the fixing device 8 (S102). Further, based on the temperature acquired in S101, it is determined whether or not the temperature is equal to or higher than a predetermined temperature (S103). S103 is an example of a temperature determination process. The predetermined temperature is 40 ° C., for example. When it is determined that the acquired temperature is equal to or higher than the predetermined temperature (S103: YES), the printer 100 sets the charging voltage applied to each charging device 52 to a predetermined value (S104). The predetermined value is, for example, a voltage corresponding to the target surface potential of the photoreceptor 51.

  Then, the printer 100 determines whether or not the received print job is a color print job (S105). In response to determining that the job is a color print job (S105: YES), the printer 100 determines the charging voltage to be applied to each charging device 52 for all color process units 50K, 50C, 50M, and 50Y. The charging control process is executed (S106).

  Next, the charging control processing procedure for determining the charging voltage of the printer 100 will be described with reference to the flowchart of FIG. In the charging control process, the printer 100 first acquires a reference charging voltage (S201). The reference charging voltage is a charging voltage at which the surface potential of the photoconductor 51 becomes the target surface potential when a new photoconductor 51 having no residual charge is charged. The printer 100 determines the reference charging voltage based on, for example, the target surface potential of the photoreceptor 51, the print instruction setting, the environmental temperature and humidity, and the like. The reference charging voltage is a common value for each color.

  Then, the printer 100 reads from the ROM 32 a correction table that stores correction values set in advance according to the distance from the heat source (S202). For example, as shown in FIG. 7, the correction table is a table in which correction values for correcting the reference charging voltage and acquiring the charging voltage are stored for each process unit 50 of each color. The correction value for each color is determined as follows.

  In the printer 100 of this embodiment, the temperature level of the photoconductor 51 of the process unit 50 for each color can be estimated from the distance from the heater 811 and the distance from the polygon motor 62. As shown in FIG. 1, the fixing device 8 is downstream of the process unit 5 in the sheet conveyance direction. In other words, in the process unit 5, the color arranged on the upstream side in the sheet conveyance direction is farther from the fixing device 8. The process unit 5 that is farther from the fixing device 8 is less likely to receive heat from the heater 811, and thus the temperature of the photoconductor 51 is likely to be low. On the contrary, the process unit 5 that is closer to the fixing device 8 is more likely to receive heat from the heater 811, and thus the temperature of the photoconductor 51 is likely to be high.

  However, if the distance from the heater 811 exceeds a predetermined threshold, the influence of heat by the heater 811 is small. When the influence of heat from the heater 811 is small, the influence of heat from the polygon motor 62 cannot be ignored. That is, in the process units 50 in which the distance from the heater 811 exceeds a predetermined threshold value, the temperature of the photoconductor 51 is likely to be lower as the distance from the polygon motor 62 is longer. In the printer 100 of this embodiment, the threshold value is the distance between the heater 811 and the position between the process unit 50M and the process unit 50C.

  Of the two process units 50Y and 50M closer to the heater 811 than the threshold value, the process unit 50Y is closer to the heater 811 than the process unit 50M. For example, if the distance between the position between the process unit 50Y and the process unit 50M and the heater 811 is the first distance, the process unit 50Y is closer to the heater 811 than the first distance, and the process unit 50M The distance from the heater 811 is farther than the first distance. Therefore, it can be estimated that the temperature of the photoconductor 51 of the process unit 50M is lower than that of the photoconductor 51 of the process unit 50Y.

  Of the two process units 50C and 50K farther from the heater 811 than the threshold value, the process unit 50C is closer to the polygon motor 62 than the process unit 50K. For example, when the distance between the position between the process unit 50C and the process unit 50K and the polygon motor 62 is the second distance, the process unit 50C has a distance from the polygon motor 62 closer than the second distance. In 50K, the distance from the polygon motor 62 is longer than the second distance. Therefore, it can be estimated that the temperature of the photoconductor 51 of the process unit 50K is lower than that of the photoconductor 51 of the process unit 50C.

  The correction value for each color is a smaller value for a color estimated to have a higher temperature of the photoconductor 51. Specifically, as shown in FIG. 7, the correction value of the process unit 50M is larger than the correction value of the process unit 50Y. The correction value of the process unit 50K is larger than the correction value of the process unit 50C. The correction value of the process unit 50C is larger than the correction value of the process unit 50M. That is, the process unit 50Y is an example of a first formation unit, the process unit 50M is an example of a second formation unit, the process unit 50C is an example of a third formation unit, and the process unit 50K. Is an example of a fourth forming part.

  Note that the printer 100 may prepare a plurality of correction tables and use different correction tables depending on the temperature obtained from the output value of the thermometer 42. When the environmental temperature is low, there is a high possibility that the temperature of the photoconductor 51 is also low. Therefore, the printer 100 selects and uses a correction table in which a larger value is stored as a correction value as the environmental temperature is lower. In this way, the difference due to the environmental temperature due to the residual charge can be reduced.

  Unlike the present embodiment, in the printer having a configuration in which the threshold value is the distance between the position between the process unit 50Y and the process unit 50M and the heater 811, the correction value for each color is, for example, as shown in FIG. Thus, it is slightly different from the example of FIG. In the two process units 50M and 50C farther from the heater 811 than the threshold value, the distance from the polygon motor 62 is substantially equal. That is, the correction value of the process unit 50C is equal to the correction value of the process unit 50M.

  In some printers, the polygon mirror 61 and the polygon motor 62 are arranged above the process unit 50K farthest from the heater 811. In the printer having this configuration, when the threshold value is the same as that of the printer 100 of this embodiment, the correction values for the respective colors are as shown in FIG. 9, for example. In this case, of the two process units 50C and 50K farther from the heater 811 than the threshold value, the process unit 50K is closer to the polygon motor 62. For this reason, the correction value of the process unit 50K is smaller than the correction value of the process unit 50C.

The printer 100 sets the charging voltage of each process unit 50 to a value obtained by adding the correction value of the corresponding color acquired from the correction table read in S202 to the reference charging voltage acquired in S201 (S203). Since the reference charging voltage is a value common to each color, the charging voltage has a larger value as the correction value increases. That is, in the printer 100 according to the present embodiment, the charging voltage V1 of the process unit 50Y, the charging voltage V2 of the process unit 50M, the charging voltage V3 of the process unit 50C, and the charging voltage V4 of the process unit 50K are The relationship shown in 1) is obtained.
V1 <V2 <V3 <V4 (Formula 1)

  Next, the printer 100 further corrects the charging voltage of each color set in S203 with the cumulative number of printed sheets. This is because in the charging device 52, the surface potential of the photoconductor 51 when the same charging voltage is applied gradually decreases according to the cumulative number of printed sheets. Therefore, the printer 100 reads the cumulative number of prints of each color from the NVRAM 34 (S205). As will be described later, the printer 100 counts up the cumulative number of prints for each color and stores it in the NVRAM 34 every time printing is executed.

Further, the printer 100 reads the number correction formula for each color from the ROM 32 (S206). The number correction formula is a formula for obtaining the correction charging voltage VP using the charging voltage V obtained in S203 and the cumulative number of printed sheets P. The number correction formula is expressed by the following (Formula 2).
VP = V + (α × P) (Formula 2)
The sheet number correction formula is an example of a charging calculation formula. The coefficient α is an example of a ratio.

The coefficient α of the number correction formula differs for each color, and is larger as the process unit 50 is farther from the heat source. This is because the difference in the movement speed of the residual charge due to the temperature level becomes more prominent as the cumulative number of printed sheets increases. That is, αY that is the coefficient α of the process unit 50Y, αM that is the coefficient α of the process unit 50M, αC that is the coefficient α of the process unit 50C, and αK that is the coefficient α of the process unit 50K are expressed as The relationship shown in 3) is obtained.
αY <αM <αC <αK (Formula 3)

  Then, the printer 100 uses the charging voltage V of each color set in S203, the cumulative number of printed sheets of each color read in S205, and the correction number of each color read in S206, and the corrected charging voltage. Is stored in the RAM 33 (S207). Each coefficient α may be a predetermined value for each color, or may be determined by the printer 100 according to the cumulative number of printed sheets, print settings, and the like.

  The generation factors of charges that may become residual charges include, for example, the energy of laser light generated from the exposure apparatus 6 during exposure and the energy of frictional heat between the photoconductor 51 and the cleaner 56. The charge generated at any point becomes a residual charge when it remains in the photoreceptor 51 without being transported to the surface of the photoreceptor 51 within the charging range.

  On the other hand, it is not preferable to apply a charging voltage that is too large because the life of the printer 100 may be shortened. Therefore, the total value of each correction value to be added to the reference charging voltage includes a charge amount estimated to be generated by the exposure apparatus during exposure, a charge amount estimated to be generated by frictional heat between the photosensitive member 51 and the cleaner 56, and the like. It is advisable to set an upper limit based on it. Furthermore, the upper limit may be set to a larger value as the cumulative number of printed sheets increases. This is because the amount of charge estimated to be generated by frictional heat between the photoconductor 51 and the cleaner 56 is likely to increase according to the cumulative number of printed sheets. For example, if the cumulative number of printed sheets increases, the protective layer that protects the surface of the photoconductor 51 and the cleaner 56 is damaged, and if the frictional resistance increases, the frictional heat tends to increase, and the residual charge Is likely to increase.

  Returning to the printing process of FIG. 5, the printer 100 determines whether the warm-up is completed (S107). Here, the completion of the warm-up is determined by whether or not the fixing device 8 has reached a predetermined temperature. If it is determined that the warm-up has not been completed (S107: NO), the printer 100 continues the warm-up. On the other hand, in response to determining that the warm-up has been completed (S107: YES), the printer 100 reads the charging voltage stored in the RAM 33 or the like in the charging control process of S106 from the RAM 33 or the like, and uses the read charging voltage. The voltage is applied to the grid 522 of the charging device 52 (S108). Then, the printer 100 executes printing of one sheet (S109).

  Each time printing is executed, the printer 100 counts up the continuous print number and the cumulative print number for the colors used for printing and stores them in the NVRAM 34 (S110). Note that the printer 100 resets the continuous print number at the start of the print job. When the photoconductor 51 is replaced, the printer 100 resets the cumulative number of printed sheets of the corresponding color.

  Further, the printer 100 determines whether or not printing of the received print job is completed (S111). In response to determining that the printing has not ended (S111: NO), the printer 100 determines whether or not the number of continuously printed sheets has exceeded a predetermined number (S112). S112 is an example of the number determination process. The predetermined number is, for example, 100 sheets.

  In response to determining that the number of continuously printed sheets does not exceed the predetermined number (S112: NO), the printer 100 returns to S109 and prints another sheet with the same charging voltage. Note that the printer 100 applies a charging voltage only for a necessary period according to the progress of printing and the state of paper conveyance.

  In response to determining that the number of continuous prints exceeds the predetermined number (S112: YES), the printer 100 decreases the correction value (S113). In S113, for example, the printer 100 calculates a new correction value by subtracting a certain value from each of the previous correction values or by multiplying each of the previous correction values by a predetermined number less than one. . If printing is continuously performed, the temperature in the apparatus tends to rise because the fixing device 8 is kept in a heated state. As the temperature increases, the residual charge transport capability increases. Therefore, when the internal temperature rises above a certain level, it is desirable to correct the charging voltage by reducing the correction value. It should be noted that the correction value may be further reviewed every time the continuous printing number increases by a predetermined number.

  Note that the subtraction width of the correction value in S113 may be determined based on the balance of various effects on the residual charge amount due to continuous printing. In other words, in the printer 100, the subtraction width is determined based on how much the increase in the transport capability due to the temperature rise exceeds the increase in the amount of charge generated at the exposure location and the cleaning location due to continuous printing.

  Then, in response to determining that the print job has ended (S111: YES), the printer 100 ends the printing process.

  On the other hand, in response to determining that the received print job is not a color print job (S105: NO), the printer 100 determines a charging voltage to be applied to the charging device 52 of the process unit 50 of the color to be used (S105: NO). S115). For example, if the print instruction is for monochrome printing, the printer 100 executes the charging control process only for the black color.

  When the charging voltage is determined in S115, the printer 100 proceeds to S107 and executes printing using only the process unit 50 of the color to be used, as in the case of color printing. In this case, in S110, the number of continuous prints and the cumulative number of prints are counted up for only the colors to be used. When the print job is finished, the printing process is finished.

  If the temperature is equal to or higher than the predetermined temperature from the start of the print job, that is, if YES is determined in S103, the correction value is not used, and therefore the determination based on the continuous print number does not have to be executed. In this case, the printer 100 skips S112 and S113 without counting the number of continuous prints.

  As described above in detail, according to the printer 100 of this embodiment, a plurality of process units 50 are provided, and a charging voltage to be applied to the grid 522 of the charging device 52 is set for each process unit 50. In the printer 100, the charging voltage is set to a value that increases as the distance between the process unit 50 and a heat source such as the heater 811 increases, and the surface potential of the photoconductor 51 is charged. The value is set to a value equal to or higher than the target surface potential even if it is later canceled by the residual charge. As a result, the magnitude of heat received from the heat source for each color is different, so that the residual charge moving speed inside the photoconductor 51 is different, that is, the surface potential of the photoconductor 51 is lowered due to the residual charge. Even if the degree is different for each color, the variation in the surface potential of the photoconductor 51 can be suppressed. Therefore, it can be expected that image quality will be reduced.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, the present invention is not limited to a printer, and can be applied to any apparatus having an image forming function such as a copying machine, a scanner, and a FAX.

  For example, although the correction table and the number correction formula are stored in the ROM 32, they may be stored in the NVRAM 34. In addition, each numerical value of the correction value described in this embodiment is an example, and is not limited to the described value. Further, the number correction formula read in S206 is not limited to the one stored as a formula. For example, only the coefficient α of each color may be stored in the ROM 32 and used by applying to one equation.

  Further, for example, in the case of monochromatic printing, it is not necessary to take into account deterioration in image quality due to variations between the process units 50, and thus correction using correction values need not be performed. That is, S202 and S203 may be skipped.

  Further, for example, the correction based on the cumulative number of printed sheets in S205 to S207 may not be performed. That is, the charging voltage obtained in S203 may be used as the grid voltage.

  Further, for example, the correction value may not be subtracted from the continuous print number. That is, S112 and S113 are not necessary. In addition, for example, there is a high possibility that the residual charge will increase due to continuous printing due to various effects of continuous printing, that is, the relationship between the increase in transport capacity due to temperature rise and the increase in the amount of charge generated at the exposure and cleaning locations. In this case, the correction value may be increased in S113.

  In this embodiment, the grid voltage of the charging device 52 is controlled in accordance with the distance from the heat source. However, the wire current may be controlled. That is, when it is determined that the distance from the heat source is long, the wire current may be increased instead of increasing the grid voltage. Further, the present invention is not limited to the scorotron charging device, but can also be applied to a corotron charging device, a contact charging charging device using a charging roller, a charging brush, or the like.

  In the printer 100 of this embodiment, the photosensitive member 51 has a single-layer structure of the organic photosensitive layer 512 including the charge generating agent 513 and the charge transporting agent 514. However, the invention is not limited to this. For example, a two-layer structure having a transport layer including the charge transport material 514 and a generation layer including the charge generation agent 513 and the charge transport agent 514 from the metal core 511 side may be used. Further, for example, a structure of three or more layers including a surface layer may be used.

  Further, the contact member is not limited to the blade-like cleaner 56. However, if the cleaner 56 is a blade member, the residual charge in the charging range tends to be larger than in a printer having a cleaner using a roller member or a brush member. Therefore, the present invention is particularly useful in the printer 100 having the cleaner 56 made of the blade member.

  Further, the charging voltage may be controlled during the execution of the job. For example, the charging voltage may be lowered if the temperature in the apparatus rises beyond a predetermined range during job execution. For example, the charging control process may be executed for each printing.

  The processing disclosed in the embodiments may be executed by a single CPU, a plurality of CPUs, hardware such as an ASIC, or a combination thereof. Further, the processing disclosed in the embodiment can be realized in various modes such as a recording medium or a method recording a program for executing the processing.

6 Exposure Device 8 Fixing Device 811 Heater 31 CPU
42 Thermometer 51 Photoconductor 52 Charging Device 521 Wire 522 Grid 54 Developing Device 55 Transfer Device 56 Cleaner 61 Polygon Mirror 62 Polygon Motor 63, 64 Laser Diode 100 Printer

Claims (14)

A plurality of forming portions for forming a toner image,
A photoreceptor,
A charging device for charging the surface of the photoreceptor;
A toner supply device for supplying toner to the photoreceptor;
A transfer device for transferring the toner on the photoreceptor to a transfer material;
A contact member that contacts the photoreceptor and collects the toner carried on the photoreceptor;
The forming part comprising:
A heat source,
A control unit;
With
The controller is
The plurality of forming portions;
Correction corresponding to the absolute value of the residual charge, which is the charge existing in the photoconductor after passing through the charging device, with the absolute value of the charging voltage used for each charging device as the absolute value of the target surface potential of the photoconductor The value obtained by adding the voltage value, and the greater the distance from the heat source, the larger the correction voltage value,
Alternatively, the absolute value of the charging current used for each charging device is set to the absolute value of the current value for obtaining the target surface potential of the photosensitive member, and the residual charge that is present on the photosensitive member after passing through the charging device. An image forming apparatus characterized in that a correction current value corresponding to an absolute value of electric charge is added, and the correction current value is set to a larger value as the formation portion is farther from the heat source. The image forming apparatus according to claim 1,
A fixing device for thermally fixing the toner image transferred to the sheet to the sheet;
An image forming apparatus, wherein the heat source includes a heater for heating the fixing device. The image forming apparatus according to claim 2,
An exposure device that forms an electrostatic latent image on the photoconductor using a light emitting unit and a polygon mirror that reflects the light emitted from the light emitting unit toward the photoconductor;
The controller is
The charging voltage of the forming portion whose distance from the heater is farther than the threshold value is set to a value whose absolute value is larger than the charging voltage of the forming portion whose distance from the heater is closer than the threshold value,
Further, the absolute value of the charging voltage used for each charging device of the forming unit whose distance from the heater is farther than the threshold value is set to a larger value as the forming unit is far from the motor for driving the polygon mirror. An image forming apparatus. The image forming apparatus according to claim 1,
A fixing device for thermally fixing the toner image transferred to the sheet to the sheet;
An exposure device that forms an electrostatic latent image on the photoconductor using a light emitting unit and a polygon mirror that reflects light emitted from the light emitting unit toward the photoconductor;
With
In the plurality of forming portions,
A first forming portion whose distance from the heater is closer than the first distance;
A second forming portion having a distance from the heater that is longer than the first distance and a distance from a motor that rotationally drives the polygon mirror is closer than a second distance;
Is included,
The controller is
An image forming apparatus, wherein a charging voltage V2 of the second forming unit is set larger than a charging voltage V1 of the first forming unit. The image forming apparatus according to claim 4,
In the plurality of forming portions,
The distance from the heater is longer than the first distance, the distance from the motor that rotationally drives the polygon mirror is closer to the second distance, and the distance from the heater is more than the second forming portion. A distant third formation,
A fourth forming section having a distance from the heater that is longer than the first distance and a distance from the motor that rotationally drives the polygon mirror is longer than the second distance;
Is included,
The controller is
An image forming apparatus, wherein a charging voltage V4 of the fourth forming unit is set larger than a charging voltage V3 of the third forming unit. In the image forming apparatus according to claim 4 or 5,
In the plurality of forming portions,
The distance from the heater is longer than the first distance, the distance from the motor that rotationally drives the polygon mirror is closer to the second distance, and the distance from the heater is more than the second forming portion. A distant third formation is included,
The controller is
An image forming apparatus, wherein the charging voltage V3 is larger than the charging voltage V2. The image forming apparatus according to any one of claims 1 to 6,
The image forming apparatus according to claim 1, wherein the contact member is a cleaning blade that removes toner on the photoconductor. In the image forming apparatus according to any one of claims 1 to 7,
A storage unit for storing a charging calculation formula, which is an equation that defines an absolute value of a charging voltage of each charging device of the plurality of forming units according to the cumulative number of printed sheets;
The charging calculation formula is a formula in which the ratio of the increase amount of the charging voltage to the increase amount of the cumulative number of printed sheets is different for each charging device of the plurality of forming units, and the ratio is a distance from the heat source. The farther the formation part is, the larger the formula is,
The controller is
An absolute value of a charging voltage used for each charging device of the plurality of forming units is set using the cumulative number of printed sheets and the plurality of charging arithmetic expressions stored in the storage unit. . In the image forming apparatus according to any one of claims 1 to 8,
The charging device has a wire and a grid circuit,
The absolute value of the charging voltage is an absolute value of an applied voltage applied to the grid circuit. The image forming apparatus according to any one of claims 1 to 9,
Equipped with a thermometer,
The controller is
An image forming apparatus, wherein the correction voltage value is set to a larger value as the temperature obtained from the output value of the thermometer is lower. In the image forming apparatus according to any one of claims 1 to 10,
The controller is
A number determination process for determining whether or not the number of continuous prints is equal to or greater than a predetermined number;
The correction voltage value is set to a value smaller than that in the case where the continuous printing number is smaller than the predetermined number in response to the determination that the continuous printing number is equal to or larger than the predetermined number in the number determining process. Image forming apparatus. The image forming apparatus according to any one of claims 1 to 11,
Equipped with a thermometer,
The controller is
Based on the output value of the thermometer, a temperature determination process is performed to determine whether the temperature is equal to or higher than a predetermined temperature,
In response to determining that the temperature is not equal to or higher than the predetermined temperature in the temperature determination process, the absolute value of the charging voltage used for each charging device is changed to the absolute value of the target surface potential of the photoconductor. The absolute value of the charging voltage used for each charging device is determined as the absolute value of the target surface potential of the photoconductor in response to determining that the temperature is equal to or higher than the predetermined temperature in the temperature determination process. An image forming apparatus characterized by having a value. A plurality of forming portions for forming a toner image,
A photoreceptor,
A charging device for charging the surface of the photoreceptor;
A toner supply device for supplying toner to the photoreceptor;
A transfer device for transferring the toner on the photoreceptor to a transfer material;
A contact member that contacts the photoreceptor and collects the toner carried on the photoreceptor;
The forming part comprising:
A heat source,
An image forming method for an image forming apparatus comprising:
The plurality of forming portions;
Correction corresponding to the absolute value of the residual charge, which is the charge existing in the photoconductor after passing through the charging device, with the absolute value of the charging voltage used for each charging device as the absolute value of the target surface potential of the photoconductor The value obtained by adding the voltage value is set, and the correction voltage value is set to a larger value as the formation portion is farther from the heat source.
Alternatively, the absolute value of the charging current used for each charging device is set to the absolute value of the current value for obtaining the target surface potential of the photosensitive member, and the residual charge that is present on the photosensitive member after passing through the charging device. A setting step of setting the correction current value to a larger value as the formation portion farther away from the heat source is a value obtained by adding the correction current value corresponding to the absolute value of the charge;
An image forming method comprising: A plurality of forming portions for forming a toner image,
A photoreceptor,
A charging device for charging the surface of the photoreceptor;
A toner supply device for supplying toner to the photoreceptor;
A transfer device for transferring the toner on the photoreceptor to a transfer material;
A contact member that contacts the photoreceptor and collects the toner carried on the photoreceptor;
The forming part comprising:
A heat source,
In an image forming apparatus comprising
The plurality of forming portions;
Correction corresponding to the absolute value of the residual charge, which is the charge existing in the photoconductor after passing through the charging device, with the absolute value of the charging voltage used for each charging device as the absolute value of the target surface potential of the photoconductor The value obtained by adding the voltage value is set, and the correction voltage value is set to a larger value as the formation portion is farther from the heat source.
Alternatively, the absolute value of the charging current used for each charging device is set to the absolute value of the current value for obtaining the target surface potential of the photosensitive member, and the residual charge that is present on the photosensitive member after passing through the charging device. A setting process in which a correction current value corresponding to the absolute value of the electric charge is added, and the correction current value is set to a larger value as the formation portion is farther from the heat source.
A program characterized by having executed.

Images