JP2010145956A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten time taken until image formation can be carried out, by properly performing idle rotation processing for a photoreceptor and image stabilization processing. <P>SOLUTION: The printer includes: an engine control means for controlling an image forming process; and a main controller of which the starting time is later than that of the engine control means and which outputs data and an instruction required for image formation, to the engine control means. The engine control means determines whether the idle rotating processing for the photoreceptor is required or not (step S16) and whether the image stabilization processing is required or not (step S14). If the idle rotating processing for the photoreceptor is required, the idle rotation processing is performed for a given time determined based on the necessity or nonnecessity and type of the image stabilization process before the main controller is started (step S19). Thereafter, the predetermined image stabilization processing is performed following instruction given by the main controller (step S25). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus in which a toner image is formed using a photoconductor having an outer peripheral surface that circulates, and then the formed toner image is transferred and fixed on a recording sheet.

  2. Description of the Related Art Printers that form full-color images with yellow (Y), magenta (M), cyan (C), and black (K) toners are known as image forming apparatuses such as copying machines. This printer is usually provided with a toner image forming unit that forms a toner image with toner of each color of Y, M, C, and K, and the toner images of each color formed by each toner image forming unit are intermediate. After being transferred onto the transfer belt, the toner image on the intermediate transfer belt is transferred onto the recording sheet. The toner image transferred to the recording sheet is heat-fixed on the recording sheet by being heated and pressurized in the fixing unit.

  In each toner image forming unit, after the surface of the photosensitive drum is charged by a charger, an electrostatic latent image is formed by laser light emitted from the laser diode of the printer head to the photosensitive drum, and the formed electrostatic image is formed. The latent image is developed with toners of respective colors Y, M, C, and K by a developing device. The developing device is provided with a developing sleeve for adhering the toner to the photosensitive drum. By rotating the developing sleeve with a predetermined developing voltage applied, the toner on the surface of the developing sleeve is transferred to the photosensitive drum. The toner image is attached to the electrostatic latent image, thereby forming a toner image corresponding to the electrostatic latent image. The toner image on the photosensitive drum is transferred to the intermediate transfer belt, and the toner remaining on the photosensitive drum is removed by a cleaning member such as a cleaning blade.

  In such an image forming apparatus, since discharge products such as nitrogen oxides are generated due to discharge when the photosensitive drum is charged by the charger, when the stopped state in which the photosensitive drum is not rotationally driven continues for a long time, There is a possibility that the discharge product adheres to and accumulates on the surface of the photosensitive drum. When a developing operation is performed with the discharge product deposited on the surface of the photoconductive drum, the toner is not attached to the surface of the photoconductive drum due to the discharge product deposited on the surface of the photoconductive drum, and the toner image is white. There is a risk. In addition, when the developing operation is not performed for a long time, the toner in the developing device absorbs moisture to reduce resistance, and the density of the toner image transferred to the recording sheet is lowered, and the image quality changes such as image flow. May also occur.

  In Patent Document 1, cleaning is performed by driving the photosensitive drum and the developing device during a warm-up period for the fixing unit to raise the temperature to a predetermined temperature when the power is turned on, so that toner adheres to the photosensitive drum. A configuration for removal by a blade is disclosed. With such a configuration, the discharge product adhering to the photosensitive drum can be removed. Japanese Patent Laid-Open No. 2004-228561 has a configuration in which, prior to an image forming operation, the discharge sleeve deposited on the surface of the photosensitive drum is removed by rotating the developing sleeve in contact with a predetermined position on the surface of the photosensitive drum. It is disclosed.

  Without being limited to these configurations, for example, by rotating the photosensitive drum without performing the toner developing operation by the developing device, the discharge product attached to the surface of the photosensitive drum is removed by a cleaning blade provided in the developing device, etc. An idling process is also known which is removed by a cleaning member. In addition, when a change in image quality such as image flow occurs due to toner deterioration due to the drive stop state for a long time, the voltage applied to the charger for charging the surface of the photosensitive drum, the developing device An image stabilization process for adjusting a voltage applied to the developing sleeve is also known.

  The image stabilization process includes a color stabilization process executed for a black toner developer and a color developer, a monochrome stabilization process executed only for a black toner developer, and color development. Registration (color misregistration correction) performed only on the imager. In the color stabilization process, a maximum adhesion amount adjustment process that adjusts the maximum amount of toner that adheres to the surface of the photosensitive drum for each of the developing units Y, M, C, and K, and irradiation to the surface of the photosensitive drum Laser diode (LD) adjustment processing for adjusting the laser beam to be written, writing of each color from the amount of positional deviation of each pattern when the pattern of each color of Y, M, C, K is transferred onto the intermediate transfer belt A registration process for adjusting the timing and a gamma (γ) adjustment process for adjusting the gradation of the toner image of each color are sequentially executed. In the registration of the image stabilization process, only the above registration process is executed. In the monochrome stabilization process, each process other than the registration process in the color stabilization process is sequentially performed on the developing device for black toner. When such image stabilization processing is executed, the photosensitive drum is driven to rotate in each developing device, so that discharge products adhering to the photosensitive drum are also removed by a cleaning member such as a cleaning blade. . From this, when it is determined that the white spot of the toner image occurs due to the discharge product adhering to the photosensitive drum, only the image stabilization process is executed without executing the idling process of the photosensitive drum. Things are also done.

The image forming apparatus is provided with an engine control unit that controls an image forming operation in the main body of the image forming apparatus, and also processes an image data transmitted from a terminal device connected via a network such as a LAN, an engine A main controller is also provided for executing an image forming operation instruction or the like by the control unit. By providing an engine control unit for controlling the image forming operation and a main controller in charge of other control, it is possible to unify data management by the main controller, and it is easy to change programs. In the image stabilization process, the engine controller instructs the engine controller to start the image stabilization process, and the engine controller stabilizes the image based on test pattern data output from the main controller. Execute the process. Since the engine control unit and the main controller are configured by a computer, at the time of start-up, an initial operation is required to reach a steady state in which normal processing can be executed, and the start-up (start-up) is completed. During this time, a standby state in which normal processing cannot be performed is entered.
JP-A-6-149129 JP 7-121077 A

  In the image forming apparatus, if the rotation of the photosensitive drum continues for 8 hours (480 minutes) in a normal use environment, white spots are easily generated in the toner image. When the time is exceeded, an image stabilization process is performed to remove the discharge products adhering to the photosensitive drum. For example, in a general office, if the image forming apparatus is turned off at 9:00 pm and the image forming apparatus is turned on at 8:00 am the next day, the image forming apparatus is stopped for 8 hours or more. Therefore, since the rotation of the photosensitive drum has been stopped for 8 hours or more, the image stabilization process is executed.

  In the image forming apparatus including the engine control unit and the main controller, the operation according to each instruction cannot be executed until each start-up (start-up) is completed. In particular, since the main controller has a large amount of stored information, the time required for completing the activation is longer than the time required for completing the activation in the engine control unit. For this reason, the image stabilization process instructed to be executed by the main controller cannot be executed until the start of the main controller is completed. As a result, in a normal office, when the power is turned on at the start of business, a relatively long time is required until the image stabilization process is executed and finished, and the image forming apparatus can perform an image forming operation. There is a problem that time becomes long.

  In addition, since the color stabilization process as the image stabilization process usually requires a longer time than the idling process of the photosensitive drum, only white spots due to discharge products occur, and the toner image is deteriorated. In such a situation that does not occur, if an image stabilization process that is longer in execution time than the idle rotation process is executed instead of the idle rotation process, the time until the image forming operation becomes possible becomes longer. In the image stabilization process and the idling process, the cleaning member is in sliding contact with the photosensitive drum. Therefore, if these processes are executed for a long time, the life of the photosensitive drum may be reduced.

  The present invention has been made in view of such conventional problems, and an object of the present invention is to reduce the time until image formation becomes possible by appropriately performing idling rotation processing and image stabilization processing of the photoreceptor. An object of the present invention is to provide an image forming apparatus that can be shortened and that can suppress a reduction in the life of the photoreceptor.

  In order to achieve the above object, an image forming apparatus according to the present invention forms an electrostatic latent image by charging a surface of a photoconductor whose outer peripheral surface circulates with a charger and exposing the charged photoconductor. Then, after the toner image formed by developing the formed electrostatic latent image is transferred to a recording sheet, the toner image is thermally fixed by a fixing unit, and the surface of the photosensitive member after the toner image is transferred is cleaned by a cleaning member. An image forming apparatus for executing a forming process, the engine control means for controlling the image forming process, and the startup time longer than the engine control means, and data and instructions necessary for image formation to the engine control means A main controller that outputs the image, and the engine control means is configured to determine whether image stabilization processing involving rotation of the photosensitive member is necessary and idle rotation processing of the photosensitive member. A process necessity determining unit that determines whether or not, an idle rotation execution control unit that controls execution of the idle rotation process before the start of the main controller is completed when the idle rotation process is necessary, and the process An image stabilization process request unit that notifies the main controller of the image stabilization process determined to be necessary by the necessity determination unit, and the determined image based on an instruction from the main controller after the start of the main controller is completed. And an image stabilization process execution control unit that controls execution of the stabilization process.

  In the image forming apparatus of the present invention, the engine control means for controlling the image forming process determines whether or not a predetermined type of image stabilization processing is necessary and whether or not the photoreceptor is idling before the start of the main controller is completed. If the idle rotation process is necessary and the image stabilization process is not necessary to execute the idle rotation process based on the In addition, since the idling process time can be shortened in accordance with the image stabilization process time, it is possible to suppress a decrease in the life of the photoconductor.

Preferably, the engine control means further includes an idle rotation processing time determination unit that determines an execution time of the idle rotation process based on the determined execution time of the image stabilization process.
Preferably, the idle rotation processing time determination unit determines the execution time of the idle rotation processing as a predetermined time when the image stabilization processing is determined not to be necessary by the processing necessity determination unit. It is characterized by determining to.

Preferably, the idle rotation processing time determination unit is configured in advance to set the execution time of the idle rotation processing when the idle rotation processing and the image stabilization processing are determined to be necessary by the processing necessity determination unit. The time determined by subtracting the time required to execute the image stabilization process from the determined time is determined.
Preferably, the idle rotation processing time determination unit determines an execution time of the idle rotation processing as a time shorter than a time required for completing activation of the main controller.

Preferably, the processing necessity determination unit determines whether the image stabilization processing is necessary based on a relative humidity in the apparatus itself and a driving stop time of the photosensitive member.
Preferably, for each of the black photoconductor on which an image is formed with black toner, three color photoconductors on which images are formed with different color toners, and each of the black photoconductor and the color photoconductor An exposure unit that irradiates four laser beams for forming an electrostatic latent image, and the processing necessity determination unit performs color stabilization that is performed on all the photoconductors as the image stabilization processing. It is determined whether or not the blackening process and the black and white stabilization process executed for the black toner photoreceptor are necessary.

Preferably, when the processing necessity determination unit determines that neither the color stabilization processing nor the monochrome stabilization processing is necessary, registration as an image stabilization processing is performed based on the temperature in the exposure unit. It is characterized by determining whether or not it is necessary.
Preferably, the processing necessity determination unit determines whether the idling processing is necessary based on a relative humidity in the apparatus and a driving stop time of the photosensitive member.

  Preferably, the idle rotation processing time determination unit determines an execution time of the idle rotation processing to be shorter than a time required for warming up in the fixing unit.

  FIG. 1 is a schematic front view showing a schematic configuration of a tandem color digital printer (hereinafter simply referred to as “printer”) which is an embodiment of the image forming apparatus of the present invention. As shown in FIG. 1, this copier has a sheet supply unit A provided at the bottom and an image process unit B provided on the sheet supply unit A, and a network (for example, an in-house LAN). When a print execution instruction (print job) is received from a terminal device connected to), a toner image based on image data from the terminal device is supplied from the sheet supply unit A in the image processing unit B according to the instruction. Formed on the recording sheet.

  The image processing section B includes a conductive intermediate transfer belt 21 that is stretched horizontally in a substantially central portion of the printer and is disposed so as to be able to move in the direction indicated by an arrow X. Below the intermediate transfer belt 21, toner image formation for sequentially forming toner images on the intermediate transfer belt 21 with toner of each color of yellow (Y), magenta (M), cyan (C), and black (K). The units 10Y, 10M, 10C, and 10K are arranged in that order from the upstream side in the circumferential movement direction of the intermediate transfer belt 21. The intermediate transfer belt 21 is wound around a driven roller 22 disposed in the vicinity of the toner image forming unit 10Y and a driving roller 23 disposed in the vicinity of the toner image forming unit 10K. By being rotationally driven by a motor (not shown), it moves around in the direction indicated by arrow X.

  The toner image forming unit 10Y that forms a Y-color toner image is provided with a photosensitive drum 11Y disposed opposite to the intermediate transfer belt 21 and a charging device 12Y that charges the surface of the photosensitive drum 11Y. An electrostatic latent image is formed on the surface of the photosensitive drum 11Y charged by the charging device 12Y by laser light emitted from a print head (PH) 25 serving as exposure means. The print head 25 is provided below the driven roller 22. The toner image forming unit 10Y is further provided with a developing unit 13Y that develops the electrostatic latent image formed on the surface of the photoreceptor drum 11Y with Y-color toner. The developing device 13Y is provided with a developing sleeve 16Y for attaching the toner in the developing device 13Y to the electrostatic latent image formed on the surface of the photosensitive drum 11Y. The amount of toner attached to the electrostatic latent image Is adjusted by the developing voltage applied to the developing sleeve 16Y. The Y-color toner image on the surface of the photosensitive drum 11Y developed by the developing unit 13Y is intermediated by a primary transfer roller (not shown) disposed opposite to the photosensitive drum 11Y via the intermediate transfer belt 21. The image is transferred onto the transfer belt 21. The print head 25 is provided with a PH sensor 54 that detects the internal temperature.

  The other toner image forming units 10M, 10C, and 10K are similar to the toner image forming unit 10Y for Y color toner, and the photosensitive drums 11M, 11C, and 11K, the charging devices 12M, 12C, and 12K, the developing sleeve 16M, Developing units 13M, 13C, and 13K having 16C and 16K, respectively, are provided, and the print head 25 has images of M, C, and K colors on the respective surfaces of the photosensitive drums 11M, 11C, and 11K. Laser light is irradiated from laser diodes provided inside so that an electrostatic latent image corresponding to data is formed. The electrostatic latent images formed on the photosensitive drums 11M, 11C, and 11K are developed with toners of M, C, and K colors by the developing sleeves 16M, 16C, and 16K of the developing units 13M, 13C, and 13K, respectively. The developed toner images are then transferred to the photosensitive drums 11M, 11C, and 11K by a primary transfer roller (not shown) that faces the photosensitive drums 11M, 11C, and 11K via the intermediate transfer belt 21, respectively. The toner image is transferred onto the same area as the transferred area. As a result, a multiple image is formed on the intermediate transfer belt 21 in which toner images of each color of Y, M, C, and K are formed in the same region.

  In each of the toner image forming units 10Y, 10M, 10C, and 10K, after the toner images on the photosensitive drums 11Y, 11M, 11C, and 11K are transferred onto the intermediate transfer belt 21, the respective photosensitive drums 11Y. , 11M, 11C, and 11K are provided with cleaning blades 14Y, 14M, 14C, and 14K that remove deposits such as toner. On the photosensitive drums 11Y, 11M, 11C, and 11K, discharge products generated during charging by the charging devices 12Y, 12M, 12C, and 12K also adhere, but the cleaning blades 14Y, 14M, 14C, and 14K are The discharge products are also removed.

  Above the intermediate transfer belt 21, toner bottles 15Y, 15M, 15C, which store Y, M, C, and K toners supplied to the developing units of the image forming units 10Y, 10M, 10C, and 10K. Each of the toner bottles 15Y, 15M, 15C, and 15K is supplied with toner of each color, and is supplied to the developing devices 13Y, 13M, 13C, and 13K of the image forming units 10Y, 10M, 10C, and 10K. Is done.

  In the printer of this embodiment, it is possible to switch between a monochrome mode in which a monochrome image is formed using only K color toner and a color mode in which a color image is formed using four color toners of Y, M, C, and K. It has become. In the image forming operation in the color mode, the image forming units 10Y, 10M, 10C, and 10K are formed on the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11K that are rotationally driven at a predetermined peripheral speed. The toner images of each color Y, M, C, and K are multiple transferred onto the same area on the intermediate transfer belt 21. In the case of an image forming operation in the monochrome mode, for example, a K toner image formed by the selected K toner image forming unit 10 </ b> K is transferred onto a predetermined area on the intermediate transfer belt 21. A secondary transfer roller 24 is disposed so as to face the drive roller 23 that rotates the intermediate transfer belt 21 through the intermediate transfer belt 21, and the secondary transfer roller 24 and the drive roller 23 have a circumferential surface. A transfer nip N1 that forms a secondary transfer portion that transfers the toner image onto the recording sheet is formed between the circumferential transfer area of the intermediate transfer belt 21 along.

  The recording sheet supply unit A is provided on one side of the intermediate transfer belt 21 by supplying recording sheets stored in a recording sheet storage unit (not shown) one by one to the image processing unit B. The sheet is conveyed through a transfer nip into a sheet conveyance path 26 extending upward. The recording sheet passing through the sheet conveyance path 26 has a toner image transferred onto the intermediate transfer belt 21 while the recording sheet passes through the transfer nip N1 between the intermediate transfer belt 21 and the secondary transfer roller 24. Secondary transfer is performed on the recording sheet by the secondary transfer roller 24. The recording sheet that has passed through the transfer nip N1 is supplied to a fixing unit 41 provided above the transfer nip N1.

  The fixing unit 41 is configured, for example, by pressing a pressure roller 41b against a heating belt 41a that moves around, and a fixing nip N2 is formed therebetween. The recording sheet on which the toner image has been transferred is heat-fixed on the recording sheet by being heated and pressurized while passing through the fixing nip N2. A paper discharge tray 43 is provided above the toner bottles 15Y, 15M, 15C, and 15K provided in the image processing section B. The recording sheet thermally fixed by the fixing section 41 is placed on the paper discharge tray 43. To be discharged.

  Note that an IDC (image density control) sensor 51 for reading a test pattern formed on the intermediate transfer belt 21 is provided below the circumferential movement area of the intermediate transfer belt 21 near the drive roller 23. The IDC sensor 51 is provided to detect the toner density of the test pattern formed on the intermediate transfer belt 21. The IDC sensor 51 emits light toward the intermediate transfer belt 21 and is formed on the intermediate transfer belt 21. The reflected light from the test pattern is received. Further, a humidity sensor 52 and a temperature sensor 53 for detecting the humidity and temperature in the machine are provided in the vicinity of the IDC sensor 51, respectively.

  FIG. 2 is a block diagram showing the main part of the control system in the printer. The printer is sent from the terminal device and an engine control unit 121 that is a main control unit for controlling the toner image forming units 10Y, 10M, 10C, and 10K, the intermediate transfer belt 21, the print head 25, and the like in the image forming process unit B. A main controller 111 that performs image processing of image data and the like is provided. The engine control unit 121 is provided with an engine control CPU 122 that executes various controls, a RAM, a ROM (all not shown), and the like. The main controller (MFP controller) 111 is provided with a storage unit for storing various data, and it takes a relatively long time to initialize them. ) Is longer than the time required for startup (start-up completion) of the engine control CPU 122 in the engine control unit 121.

  The engine control unit 121 and the main controller 111 perform serial communication via the image bus 112, and image data input to the main controller 111 is sent to the engine control unit 121 via the image bus 112. Supplied. The engine control CPU 122 includes image stabilization sampling data output from the IDC sensor 51, in-machine humidity and temperature output from the humidity sensor 52 and the temperature sensor 53, and a print head (PH ) 25 internal temperatures are given respectively. The engine control unit 121 is connected to a nonvolatile memory 123 to which various data are written and read by the engine control CPU 122. The nonvolatile memory 123 stores the time when the photosensitive drums 11Y, 11M, 11C, and 11K are stopped, the time when the image stabilization process described later is executed, the time when the execution is completed, and the time when the image stabilization process is executed. In-machine humidity, in-machine temperature, and the like, which are environmental information, are written.

  The engine control CPU 122 of the engine control unit 121 uses the photoreceptors of the image forming units 10Y, 10M, 10C, and 10K based on the outputs of the humidity sensor 52 and the temperature sensor 53, the data written in the nonvolatile memory 123, and the like. Determination of the necessity of the idling process for rotating the drums 11Y, 11M, 11C, and 11K without performing the image forming operation, and the necessity of the image stabilization process for each of the image forming units 10Y, 10M, 10C, and 10K. Make a decision. The necessity of the idling process depends on the humidity inside the machine output from the humidity sensor 52 and the photosensitive drums 11Y, 11M obtained from the time when the photosensitive drums 11Y, 11M, 11C, 11K written in the nonvolatile memory 123 are stopped. , 11C, and 11K based on the continuous stop time. The necessity of the image stabilization process is as follows: the in-machine humidity output from the humidity sensor 52, the in-machine temperature output from the temperature sensor 53, and the internal temperature of the print head (PH) 25 output from the PH temperature sensor 54. The continuous stop time of the photoconductive drums 11Y, 11M, 11C, and 11K obtained from the time when the photoconductive drums 11Y, 11M, 11C, and 11K written in the non-volatile memory 123 are stopped, and the non-volatile memory 123 is written. Based on the in-machine environmental information (in-machine humidity and in-machine temperature) at the time of the previous image stabilization process, image stabilization of any kind of color stabilization process, monochrome stabilization process, and registration (color shift correction process) Whether or not to execute the process is determined.

  When the engine control CPU 122 determines that the idling process is necessary, the engine control CPU 122 idly rotates the photosensitive drums 11Y, 11M, 11C, and 11K in all the image forming units 10Y, 10M, 10C, and 10K for a predetermined time, and idly rotates. When the process ends, the end time is written in the nonvolatile memory 123. If the engine control CPU 122 determines that image stabilization processing is necessary, the engine stabilization CPU 122 performs color stabilization processing for stabilizing the image quality of the color image, and monochrome stabilization for stabilizing the image quality of the monochrome image. Process, registration for color misregistration correction, which kind of image stabilization processing is necessary or no image stabilization processing is necessary, and any kind of image stabilization processing Is required, the image stabilization process execution request is output to the main controller 111 together with the determined image stabilization process type. When the main controller 111 receives a request for image stabilization processing, the main controller 111 transmits an image stabilization processing command and pattern data corresponding to the received type of image stabilization processing to the engine control CPU 122. The engine control CPU 122 executes a predetermined type of image stabilization processing based on the received image stabilization processing command, and writes the end time in the nonvolatile memory 123 when the predetermined type of image stabilization processing ends.

  FIG. 3 is a table showing the conditions under which white spots in the image, which are the determination criteria for determining whether or not the idling process is necessary in the engine control CPU 122, occur. As shown in FIG. 3, the condition that white spots occur in the toner image formed on the recording sheet is based on the time when the photosensitive drum is continuously stopped and the relative humidity in the apparatus. That is, when the continuous stop time of the photosensitive drum is less than 480 minutes (8 hours), no white spot occurs in the image, and the continuous stop time of the photosensitive drum is 480 minutes (8 hours) or more and 960 minutes (16 If the relative humidity in the machine is 20% or more, white spots occur in the toner image, and the continuous stop time of the photosensitive drum is 960 minutes (16 hours) or more. In this case, white spots occur in the toner image regardless of the relative humidity in the machine. Therefore, in the engine control CPU 122, when the continuous stop time of the photosensitive drum is 480 minutes or more and less than 960 minutes and the relative humidity is 20% or more, and when the continuous stop time of the photosensitive drum is 960 minutes or more. In addition, it is determined that the idling process is necessary regardless of the relative humidity.

  FIG. 4 is a table showing image quality change occurrence conditions that serve as criteria for determining whether or not the image stabilization processing is necessary in the engine control CPU 122. As shown in FIG. 4, a change occurs in the image quality (toner density) of the toner image formed on the recording sheet based on the continuous stop time of the photosensitive drum and the relative humidity in the apparatus. That is, when the continuous stop time of the photosensitive drum is less than 480 minutes (8 hours), the image quality does not change, and the continuous stop time of the photosensitive drum is 480 minutes (8 hours) or more to ˜960 minutes ( Within the range of less than 16 hours, when the relative humidity in the apparatus becomes 19% or less or 80% or more, a change occurs that the toner density of the toner image becomes light. Even when the continuous stop time of the photosensitive drum is 960 minutes (16 hours) or longer, a change occurs in which the toner density of the toner image becomes light regardless of the relative humidity. Therefore, in the engine control CPU 122, the continuous stop time of the photosensitive drum is in the range of 480 minutes (8 hours) or more and less than 960 minutes (16 hours), and the relative humidity is less than 20% or 80% or more, and When the continuous stop time of the photosensitive drum is 960 minutes (16 hours) or longer, it is determined that the image stabilization process is necessary.

  From the above, when the continuous stop time of the photosensitive drum is 480 minutes (8 hours) or more and less than 960 minutes (16 hours), only a change in image quality occurs when the relative humidity is less than 20%, and 20% or more and 80 Even if the image quality is less than 80%, both the image quality change and the image quality are lost, and the continuous stop time of the photosensitive drum is 960 minutes (16 hours) or more, regardless of the relative humidity. Both image quality changes and white spots occur. The engine control CPU 122 starts activation (start-up) of the main controller 111 and the engine control unit 121, assuming that neither the idle rotation process nor the image stabilization process is necessary under the condition that no white spot and no change in image quality occur. Then, when the warm-up in the fixing device is started and the start-up (start-up) of the engine control unit 121 and the start-up (start-up) of the main controller 111 are completed, the warm-up is normally completed. Ready to operate. On the other hand, under the condition that only the white spot occurs, when the engine control CPU 122 is completely started up, the idling process is executed in parallel with the warming-up in the fixing unit 41, and the start-up of the main controller 111 is completed. When the rotation processing is finished and the main controller 111 is started up, the warm-up in the fixing unit 41 is usually finished, and the print operation is possible. On the condition that only the change in image quality occurs, when the engine control CPU 122 and the main controller 111 are activated, the engine control CPU 122 outputs an image stabilization processing execution request to the main controller 111, and the main controller 111 111 outputs an image stabilization processing command to the engine control CPU 122 in response to the image stabilization processing execution request, so that the engine control CPU 122 performs image stabilization processing based on the image data output from the main controller 111 and the like. When the image stabilization process is completed, the warm-up in the fixing unit 41 is completed, and the print operation is enabled. Furthermore, under conditions where both white spots and image quality changes occur, the engine control CPU 122 outputs an image stabilization processing execution request to the main controller 111 after the activation of the main controller 111 is completed. When the image stabilization process is executed by the image stabilization process command output from 111 to the engine control CPU 122 and ends, the warm-up in the fixing unit 41 is completed, and the print operation is enabled. In this case, white spots have occurred in the toner image, but since the image stabilization process is executed, the idling process is not executed.

  FIG. 5 is a table showing determination criteria for determining which kind of image stabilization processing, color stabilization processing, monochrome stabilization processing, or registration, is necessary in the image stabilization processing. Which type of image stabilization processing is executed is determined based on the absolute humidity in the machine, which is an index of the in-machine environment, and one of the color photosensitive drums (photosensitive drums 11Y, 11M, and 11C). Then, the rotation time of the photosensitive drum 11Y, which will be referred to as color PC hereinafter, and the photosensitive drum 11K for K (black) toner (hereinafter, the photosensitive drum 11K is referred to as KPC). This is based on the rotation stop time and the change in the internal temperature of the print head. The in-machine absolute humidity is calculated based on the in-machine temperature and the in-machine humidity detected by the temperature sensor 53 and the humidity sensor 54, respectively, and the absolute humidity is compared with the case where the previous image stabilization process was performed. If the change is greater than the preset range, the color stabilization process is executed regardless of the photosensitive drum stop time and the internal temperature change of the print head 25. If the change in absolute humidity is within a preset range, the image to be executed based on the color PC stop time, the KPC stop time, and the internal temperature change of the print head 25, respectively. The type of stabilization process is determined.

  When the change in absolute humidity in the machine is within the predetermined setting range (less than the setting range) since the last time image stabilization processing was executed, the color PC rotation stop time was set in advance. When the threshold value is exceeded, the color stabilization process is executed. When the color PC rotation stop time does not exceed the threshold value, but the KPC rotation stop time exceeds the preset threshold value, the monochrome stabilization process is executed. If the rotation stop time of each of the color PC and KPC does not exceed the threshold value, registration is executed if the internal temperature of the print head 25 has changed by 2 ° C. or more compared to the previous image stabilization process, and printing is performed. When the temperature change inside the head 25 is less than 2 ° C., none of the color stabilization process, the monochrome stabilization process, and the registration is executed.

The threshold value for the rotation stop time of the color PC and KPC is set to 8 hours because the image quality is likely to change as shown in FIG. 4 when the relative humidity in the machine is less than 20% and 80% or more. When the relative humidity in the apparatus is 20% to 80%, it is assumed that the image quality hardly changes, and the longer 16 hours is set.
FIG. 6 is a table for explaining specific processing of the image stabilization processing. When an image stabilization process execution request is output from the engine control CPU 121 to the main controller 111, an image stabilization process command is output from the main controller 111 to the engine control CPU 121. This also causes the engine control CPU 121 to perform color stabilization. Image stabilization processing of any one of image stabilization, monochrome stabilization, and registration is executed. Accordingly, the image stabilization process is not executed until an image stabilization process command is output from the main controller 111 to the engine control CPU 121 after the start-up (rise) of the main controller 111 is completed.

  In the case of color stabilization processing, first, adjustment processing of the IDC sensor 51 is performed as the first processing. In this case, the IDC sensor 51 irradiates light on the surface of the intermediate transfer belt 21 that circulates and adjusts the output of the IDC sensor 51 so that the amount of received light of the reflected light is constant. When the adjustment process of the IDC sensor 51 is completed, a toner maximum adhesion amount adjustment process in each of the image forming units 10Y, 10M, 10C, and 10K is performed as a second process. In the toner maximum adhesion amount adjustment process, each of the Y, M, C, and K toners adheres to the entire area of a predetermined area on the intermediate transfer belt 21 so that a “solid image” is formed at the maximum density. The image forming units 10Y, 10M, 10C, and 10K are driven. The “solid image” of each of the Y, M, C, and K toners formed on the intermediate transfer belt 21 is irradiated with light from the IDC sensor 51, and when the reflected light is received by the IDC sensor 51, the IDC sensor 51. Outputs sampling data corresponding to the amount of received light to the engine control CPU 121. The engine control CPU 121 detects the toner density of each “solid image” of Y, M, C, and K based on the image stabilization sampling data output from the IDC sensor 51, and the toner density in each “solid image”. In the image forming units 10Y, 10M, 10C, and 10K so that the charging voltage is applied to the chargers 12Y, 12M, 12C, and 12K and the developing sleeves provided in the developing units 13Y, 13M, 13C, and 13K. The development voltages applied to 14Y, 14M, 14C, and 14K are adjusted.

  Next, as a third process, a laser diode (LD) light amount adjustment process in the print head 25 is performed. In the LD light amount adjustment processing, the image forming units 10Y, 10M, 10C, and 10K are driven so that toner images having a predetermined line pattern are formed by all the image forming units 10Y, 10M, 10C, and 10K, respectively. In this case, by irradiating the surface of the photosensitive drums 11Y, 11M, 11C, and 11K with laser light at three levels of large, medium, and small, three types of line patterns are provided for each photosensitive drum. Are transferred onto the intermediate transfer belt 21. When the IDC sensor 51 receives the amount of reflected light from each line pattern transferred onto the intermediate transfer belt 21, it is emitted from the LD of the print head 25 based on the sampling data output from the IDC sensor 51. The amount of laser light is adjusted.

  When the LD light amount adjustment as the third process is completed, a registration (color misregistration correction) process is executed as the fourth process. In this case, each of the image forming units 10Y, 10M, 10C, 10C, 10C, 10C, 10C, 10C, 10C, 10C, 10C, 10C, 10C, 10C, 10C, 10C, and 10C is formed on the intermediate transfer belt 21 in parallel. By sampling data output by the IDC sensor 51 receiving the reflected light from the line pattern formed by the Y, M, C, and K toners formed on the intermediate transfer belt 21 when 10K is driven. Then, it is determined whether each line pattern is formed at a predetermined position without being displaced with respect to other line patterns. If any line pattern is misaligned, the main controller 111 calculates a correction amount necessary to eliminate the misalignment. Thereafter, based on the correction amount, Y, M, C, Each image data corresponding to K is corrected.

  Finally, as a fifth process, a gamma adjustment (γ adjustment) process is performed on the toner images formed by the image forming units 10Y, 10M, 10C, and 10K. In this γ adjustment process, the image forming units 10Y, 10M, 10C, and 10K are driven so that a toner image of a predetermined gradation is formed on the intermediate transfer belt 21 for each toner, and the respective toner images are driven. The gradation of the image data in the main controller 111 is corrected so as to correspond to this gradation. As described above, in the color stabilization process, it is necessary to execute all of the first process to the fifth process described above, and thus it usually takes 22 seconds.

  When the type of the image stabilization process is the monochrome stabilization process, the adjustment process of the IDC sensor 51 is performed as the first process, and the maximum toner adhesion amount adjustment process is performed as the second process, as in the color stabilization process. The toner maximum adhesion amount adjustment processing is performed only for the image forming unit 10K related to the black (K) color toner. Similarly, when the LD light amount adjustment process as the third process is executed only for the image forming unit 10K, the black toner formed by the image forming unit 10K as the fourth process without executing the registration. Image gamma adjustment processing is executed. In the case of monochrome stabilization processing, registration processing is not necessary. In the case of the monochrome stabilization process in which the first process to the fourth process are executed, a time of 10 (sec) is usually required.

Note that when the type of the image stabilization process is registration, only the registration process as the first process is executed. In this case, it usually takes 5 seconds.
FIG. 7 is a flowchart showing the contents of control by the engine control CPU 122. When the printer is turned on, the engine control CPU 122 and the main controller 111 start up (start up). When the engine control CPU 122 starts up (starts up), the engine control CPU 122 performs the control shown in FIG. To start. At this time, since the start (startup) is not completed in the main controller 111, the start processing (startup processing) is continuously executed. Note that the time from the completion of the activation of the engine control CPU 122 to the completion of the activation of the main controller 111 is, for example, 45 seconds.

  The engine control CPU 122 first executes a predetermined initial operation in the image processing unit B (step S11 in FIG. 7), and simultaneously with the start of this initial operation, the heating belt 41a so that the fixing unit 41 reaches a predetermined temperature. Heating (warming up) is started. As an initial operation, phase matching between the intermediate transfer belt 21 and each of the photosensitive drums 11Y, 11M, 11C, and 11K is usually performed. Next, the stop times of the color PC and KPC are calculated (S12). This stop time is calculated by reading the stop time of the photosensitive drum written in the nonvolatile memory 123 and comparing it with the current time. When the stop time of the color PC and KPC is calculated, the in-flight environment is read (step S13). Specifically, the detection results of the humidity sensor 51, the temperature sensor 52, and the PH temperature sensor 54 in the printer head 25 are read. Next, the necessity of image stabilization processing is determined based on the read in-machine environment (step S14).

  Whether or not the image stabilization process is necessary is determined based on the table shown in FIG. 5. Specifically, the absolute humidity is calculated from the detection results of the temperature sensor 52 and the humidity sensor 53 read in step S 13, and the previous time. When the change with respect to the absolute humidity when the image stabilization process is performed is not less than a predetermined range, the execution of the color stabilization process is determined. If the change in absolute humidity is within the predetermined range, if the color PC stop time calculated in step S12 is equal to or greater than the threshold, execution of the color stabilization process is determined. On the other hand, if the stop time of the color PC is not equal to or greater than the threshold, the monochrome stabilization process is performed if the stop time of the KPC is equal to or greater than the threshold (greater than the threshold set for the stop time of the color PC). Decide on execution. When execution of the color stabilization process is determined, the color stabilization process is executed for each of all the color image forming units 10Y, 10M, and 10C.

  Further, when the change in absolute humidity is within a predetermined range and the stop time of the color PC and KPC is not equal to or greater than the threshold value, neither the color stabilization process nor the monochrome stabilization process is executed. From the comparison of the detection result of the PH temperature sensor 54 read in step S13 (current temperature of the PH 25) with the detection result of the PH temperature sensor 54 in the previous image stabilization process read from the nonvolatile memory 123. Whether or not registration is necessary is determined based on the temperature change obtained by the above. In this case, when the temperature change of the PH temperature sensor 54 is 2 ° C. or higher, it is determined that registration is performed, and when it is lower than 2 ° C., it is determined that registration is not performed.

  When the necessity and type of the image stabilization process are determined, it is determined whether or not a condition for causing white spots in the toner image is satisfied (step S15). In this case, based on the relative humidity in the machine based on the detection result of the humidity sensor 52 read in step S13 and the stop time of the color PC and KPC acquired in step S12, the color shown in FIG. It is determined whether white toner occurs in the toner image in either PC or KPC. Then, based on the result of determination in step S15, it is determined whether the idling process of the photosensitive drum is necessary (step S16). If it is determined in step S15 that no white spots occur in the toner image and no idle rotation processing is required for either the color PC or KPC (“No” in step S16), the process proceeds to step S21. The main controller 111 is in a standby state until the activation is completed. If it is determined in step S15 that white spots are generated in the toner image and it is necessary to perform idling processing on one or both of the color PC and KPC (“Yes” in step S16), the idling time is determined. Control is executed (step S17). When it is determined that the idle rotation process is necessary in the color PC, the idle rotation process is executed for each of the photosensitive drums 11Y, 11M, and 11C that are the color PCs, and the idle rotation process is performed in the KPC. If it is determined that it is necessary, the idling process is executed only for the photosensitive drum 11K.

  FIG. 8 is a flowchart showing a subroutine of idling time determination control. In the idling time determination control, first, idling time Tpc is initialized and Tpc is reset to “0 second” (step S31 in FIG. 8). Next, in order to determine whether or not the execution of the image stabilization process is determined in step S14 of FIG. 7, it is first determined whether or not the execution of the color stabilization process is determined (step S32). If execution of the color stabilization process has been determined (“Yes” in step S32), the idling time Tpc is set to 0 seconds (step S33). That is, in the color stabilization process, the time required for the process is 22 seconds, and during that time, the photosensitive drum is rotated, and therefore, the removal of the adhering matter by the cleaning blade is also executed, and the white spots in the toner image are eliminated. Since the rotation of the photosensitive drum required for preventing the rotation of the photosensitive drum is executed for 20 seconds or more, the idle rotation control of the photosensitive drum is not particularly executed.

  If the color stabilization process is not executed (“No” in step S32), it is determined whether execution of the monochrome stabilization process is determined (step S34). If it is determined that the monochrome stabilization process is to be executed (“Yes” in step S34), the idling time Tpc is set to 10 seconds (step S35). The time required for the monochrome stabilization process is 10 seconds, and the photosensitive drum is rotated during that time. However, the photosensitive drum is rotated with respect to 20 seconds required to prevent white spots in the toner image. The rotation time is insufficient for 10 seconds. For this purpose, the photosensitive drum is idled for 10 seconds.

  If the monochrome stabilization process is not executed (“No” in step S34), it is determined whether execution of registration is determined (step S36). If execution of registration is determined (“Yes” in step S36), the idling time Tpc is set to 15 seconds (step S37). The time required for registration is 5 seconds, and the photosensitive drum rotates during that time, but the rotation time is 15 seconds shorter than the 20 seconds required to prevent white spots in the toner image. For this reason, the photosensitive drum is idled for 15 seconds. If registration is not executed (“No” in step S36), the photosensitive drum needs to be rotated for 20 seconds in order to eliminate white spots in the toner image. Tpc is set to 20 seconds (step S38).

  Thus, when the idling time Tpc of the photosensitive drum is set, it is determined whether the set idling time Tpc is longer than the time Tctr required for starting (starting up) the main controller 111. (Step S39). When the set idling time Tpc is longer than the activation time Tctr of the main controller 111 (“Yes” in step S39), the idling process of the photosensitive drum completes the activation of the main controller 111. Thus, a time obtained by subtracting the time Tprc necessary for executing the initial operation in the image processing section B from the start time Tctr is newly set as the idling time Tpc (step S40). When the set idling time Tpc is not longer than the activation time Tctr of the main controller 111 (“No” in step S39), the idling time Tpc is not changed. Thus, the idling time determination control ends, and the process proceeds to step S18 in the flowchart of FIG.

  In step S18 in the flowchart of FIG. 7, it is determined whether or not the idling process of the photosensitive drum is necessary in step S17 based on whether the set idling time Tpc is longer than “0”. When 0 second is set as the idling time Tpc (“No” in step S18), the process proceeds to step S21 and waits until the start of the main controller 111 is completed. On the other hand, when any one of 10 seconds, 15 seconds, and 20 seconds other than 0 seconds is set as the idling time Tpc (“Yes” in step S18), the idling time Tpc is set over the set idling time Tpc. The idle rotation process of the photosensitive drum is executed (step S19). Then, when the photosensitive drum is idly rotated for the set idling time Tpc, the current time at the end of idling processing is written as the idling end time for backup in the nonvolatile memory 123 (step S20). ). Thereafter, the main controller 111 is in a standby state until the activation is completed (step S21).

  When activation of the main controller 111 is completed, it is determined whether image stabilization processing is necessary (step S22). If image stabilization processing is necessary (“Yes” in step S22), the main controller 111 is informed. An image stabilization process execution request is notified (step S23), and the image stabilization process command and pattern data from the main controller 111 are received by the engine control CPU 122 (step S24). Stabilization processing is executed (step S25). When the image stabilization process is finished, the warm-up in the fixing unit 41 is also finished, and the fixing unit 41 is at a predetermined temperature, so that a printable state is entered.

  FIG. 9A shows an image forming apparatus according to the present embodiment, in which white spots occur in the toner image but no change in image quality, so that no image stabilization process is required, and the idling process of the photosensitive drum is performed. It is a time chart in the case of performing only. For example, in the office where the relative humidity is 50%, the printer is turned off at 9:00 pm and the power is turned on at 8:00 am the next day. This corresponds to the case where the printer is stopped for 11 hours until it is turned on. In this case, the idle rotation process of the photosensitive drum is set to 20 seconds as the time Tpc.

  When the printer is turned on, the engine control CPU 122 and the main controller 111 are started. When the engine control CPU 122 is started, the initial operation of the image processing unit B is executed and the warming in the fixing unit 41 is performed. Up starts. When the time Tprc elapses after the printer is turned on, the initial operation of the image processing unit B is completed, and the idling process of the photosensitive drum is executed over the time Tpc. The idling process time Tpc in this case is set to 20 seconds, and is shorter than the time Tctl (45 seconds) from when the power is turned on until the start of the main controller 111 is completed. The idling process is executed until the start-up is completed, and the deposits on the surface of the photosensitive drum are removed by the cleaning blade. When the idling process is completed, the main controller 111 is subsequently started up. At that point, the warm-up of the fixing unit 41 is also completed, and the printer is ready for printing. Accordingly, the time required from when the power supply is turned on to when the engine control CPU 122 and the main controller 111 are activated until the printable state is reached is the time (45 seconds) until the activation of the main controller 111 is completed.

  FIG. 9B shows that, in the image forming apparatus of the present embodiment, white spots occur in the toner image and the temperature in the printer head 25 has changed by 2 ° C. or more from the previous image stabilization process. 6 is a time chart in the case of executing idle rotation processing of a photosensitive drum and registration as image stabilization processing. In this case, 15 seconds is set as the set time Tpc of the idle rotation process of the photosensitive drum, and the initial operation of the image processing unit B is completed after the start of the engine control CPU 122 until the time Tprc elapses. Then, the idling process is executed for 15 seconds that is the set time Tpc. Thereafter, when 45 seconds as the time Tctl for starting the main controller 111 elapses, the start of the main controller 111 is completed, and registration is executed over a time Tstb (= 5 seconds). When the registration is completed, the print operation is enabled. Accordingly, the time from the completion of the activation of the engine control CPU 122 until the print operation is enabled is the time Tctl (= 45 seconds) until the activation of the main controller 111 is completed, and the time Tstb required for registration. (= 5 seconds) plus time (= 50 seconds).

  For comparison, FIG. 9C shows a time chart of processing executed when white spots occur in a toner image in a conventional printer. In the conventional printer, when the printer stop time has passed for 8 hours or more, the power is turned on after that, so that the color stabilization process is executed without executing the idling process. Therefore, in an office where the relative humidity is 50%, if the printer is turned off at 9 pm and the printer is stopped for 11 hours until the power is turned on at 8 am on the following day, When the engine control CPU 122 is turned on and startup is complete, a color stabilization process is executed. When a time Tctl (= 45 seconds) from when the printer power is turned on until the start of the main controller 111 is completed, the color stabilization process is executed for a time Tstb (= 22 seconds). Accordingly, the time from when the start of the engine control CPU 122 is completed until the printable state is reached is Tctl + Tstb = 45 + 22 = 67 (seconds). In contrast to such a conventional technique, in the case of the present embodiment shown in FIG. 9A, the time from when the power is turned on until printing becomes possible can be shortened over 22 seconds. In the case of the present embodiment shown in FIG. 9B, it is possible to shorten the time from the completion of the activation of the engine control CPU 122 to the ready state for printing for 17 seconds.

  In the printer of this embodiment, the printer power is turned on and the main controller 111 is not limited to the case where the engine control CPU 122 and the main controller 111 are activated when the printer power is turned on. When the engine control CPU 122 is turned off in the activated state, that is, when the sub switch is turned off while the printer power supply (main switch) is turned on, the printer is not operated for a predetermined time, and thus the sleep state. Even in such a case, control of the image stabilization process and the idling process is executed. A flowchart in this case is shown in FIG. In this case, almost the same processing as that in the flowchart shown in FIG. 7 is executed. However, since the main controller 111 is already started when the main controller 111 is started, the process of step S21 shown in FIG. There is no need to wait until the main controller 111 is activated, and this step S21 becomes unnecessary. Further, the “idle rotation time Tpc determination control” in step S17 in FIG. 7 is different only in steps S39 and S40 in the subroutine shown in FIG. 8, as shown in the subroutine in FIG. 11, and in step S39 in FIG. It is determined whether the total time of the set idle rotation time Tpc of the photosensitive drum and the determined time Tsb required for the image stabilization processing is longer than the warm-up time Twup in the fixing unit 41. When the total time (Tpc + Tsb) is longer than the warm-up time Twup (“Yes” in step S39), the idle rotation process of the photosensitive drum and the determined type of image stabilization process are performed in the fixing unit 41. A time obtained by subtracting the time Tsb required for the image stabilization processing of the determined type from the warming-up time Twup is newly set as the idle rotation time Tpc so that the warming-up time Twup ends before the completion (step S40). . If the total time (Tpc + Tsb) is not longer than the warm-up time Twup (“No” in step S39), the idling time Tpc is not changed. Other steps are the same as those in the subroutine shown in FIG.

  FIG. 12A shows a case where white spots occur in the toner image but the image quality changes when the engine control CPU 122 is turned off while the main controller 111 is activated after the printer is turned on. This is a time chart when only the idling process of the photosensitive drum is executed without executing the image stabilization process. Also in this case, as in the time chart shown in FIG. 9A, when the engine control CPU 122 is activated, the initial operation of the image processing unit B is executed, and when the time Tprc has elapsed since the engine control CPU 122 was activated, The idling process of the photosensitive drum is executed for a time Tpc (for example, 20 seconds). In this case, since the warming up of the fixing unit 41 has not yet been completed, the idling process is executed until the warming up of the fixing unit 41 is completed, and the deposit on the surface of the photosensitive drum is removed by the cleaning blade. The After the idling process is completed, the warm-up (WUP) of the fixing unit 41 is also completed, so that printing is possible.

  FIG. 12B shows a case where white spots are generated in the toner image and the inside of the printer head 25 when the engine control CPU 122 is turned off in a state where the printer is turned on and the main controller 111 is activated. 6 is a time chart in the case where the idle rotation process of the photosensitive drum and the registration as the image stabilization process are executed by the fact that the temperature is changed by 2 ° C. or more from the previous image stabilization process. In this case, when the time Tprc elapses after the initial operation of the image processing unit B ends after the engine control CPU 122 is activated, the idling process is performed for the set time Tpc, and thereafter, the time Tstb (= 5 Registration) over a period of seconds). After the registration is completed, the warm-up (WUP) of the fixing unit 41 is completed, and the print operation is enabled.

  In a conventional printer, when the printer controller is turned on and the main controller 111 is activated, and the engine control CPU 122 is turned off, a condition that causes white spots in the toner image is generated, thereby stabilizing the color. In the case of executing the conversion processing, as shown in the time chart of FIG. 12C, the initial operation and the color stabilization processing in the image processing section B are executed before the warm-up of the fixing section 41 is completed. It will be. In this case, as in the case of the present invention, the initial operation and the color stabilization process are completed before the warm-up (WUP) of the fixing unit 41 is completed. Since it is shorter than the rotation processing, it is possible to suppress the deterioration of the photosensitive drum, and it is possible to suppress a decrease in the life of the photosensitive drum.

  The image forming apparatus according to the present invention is not limited to a tandem color digital printer. For example, four developing devices are arranged around a rotating shaft, and these four developing devices are sequentially arranged as electrostatic latent images. A so-called four-cycle image forming apparatus that forms a full-color image facing the carrier may also be used. The present invention can be applied not only to a printer but also to a copying machine, a FAX, an MFP (Multiple Function Printer), and the like. In place of the photosensitive drum, a photosensitive belt may be used. Further, although the cleaning blade is used as a cleaning member for cleaning the surface of the photoreceptor, the present invention is not limited to this.

  In the present invention, the surface of the photosensitive drum is charged by a charger to form an electrostatic latent image, and the formed electrostatic latent image is developed with toner, transferred to a recording sheet and fixed, and the toner image is transferred. In the image forming apparatus that cleans the surface of the photoreceptor with the cleaning member, the idling process and the image stabilization process of the photoreceptor can be appropriately performed.

1 is a schematic diagram illustrating a schematic configuration of a tandem color digital printer which is an example of an image forming apparatus according to the present invention. 2 is a block diagram showing a main part of a control system in the printer. FIG. It is a table | surface which shows the conditions on which the white spot of the image used as the judgment reference for judging the necessity of an idling process occurs. It is a table | surface which shows the generation conditions of the image quality change used as the criterion for determining the necessity of an image stabilization process. It is a table | surface which shows the criteria for determining which kind of image stabilization process of the color stabilization process in an image stabilization process, a monochrome stabilization process, and a registration is required. It is a table | surface for demonstrating the specific process of an image stabilization process. It is a flowchart which shows the control content by engine control CPU. It is a flowchart which shows the subroutine of idling time determination control in that case. (A) is a time chart when only the idling process of the photosensitive drum is executed in the image forming apparatus of this embodiment, and (b) is the idling rotation of the photosensitive drum in the image forming apparatus of this embodiment. FIG. 6C is a time chart of processing executed under the condition that white spots occur in a toner image in a conventional printer, in the case of executing processing and registration as image stabilization processing. It is a flowchart which shows the control content by engine control CPU in case the engine control CPU122 is started from an OFF state in the state which the main controller was started. It is a flowchart which shows the subroutine of idling time determination control in that case. 10A is a time chart when only the idling process of the photosensitive drum is executed in the flowchart shown in FIG. 10, and FIG. 10B is an idling process of the photosensitive drum and the image in the flowchart shown in FIG. FIG. 6C is a time chart in the case of executing registration as a stabilization process, and FIG. 6C shows a white image on a toner image when the engine control CPU 122 is started from an off state with the main controller started in a conventional printer. It is a time chart of the process performed on the conditions which a loss | disappearance generate | occur | produces.

Explanation of symbols

A Sheet supply unit B Image processing unit 10Y, 10M, 10C, 10K Toner image forming unit 11Y, 11M, 11C, 11K Photosensitive drum 12Y, 12M, 12C, 12K Charging device 13Y, 13M, 13C, 13K Developer 14Y, 14M , 14C, 14K Cleaning blade 21 Intermediate transfer belt 25 Print head 41 Fixing unit 51 IDC sensor 52 Humidity sensor 53 Temperature sensor 54 PH temperature sensor 111 Main controller 121 Engine control unit 122 Engine control CPU

Claims (10)

It is formed by charging the surface of the photoconductor whose outer peripheral surface moves around with a charger, exposing the charged photoconductor to form an electrostatic latent image, and developing the formed electrostatic latent image. An image forming apparatus for performing an image forming process in which a toner image is transferred to a recording sheet and thermally fixed by a fixing unit, and the surface of the photoreceptor after the toner image is transferred is cleaned by a cleaning member.
Engine control means for controlling the image forming process; and a main controller that has a longer startup time than the engine control means and outputs data and instructions necessary for image formation to the engine control means,
The engine control means includes
A processing necessity determination unit that determines whether image stabilization processing involving rotation of the photoconductor and necessity of idling of the photoconductor are necessary;
When the idling process is necessary, the idling process execution control unit that controls the execution of the idling process before the start of the main controller is completed,
An image stabilization processing requesting unit for notifying the main controller of the image stabilization processing determined to be necessary by the processing necessity determination unit;
An image stabilization process execution control unit that controls execution of the determined image stabilization process based on an instruction from the main controller after completion of activation of the main controller;
An image forming apparatus comprising:   The engine control unit further includes an idle rotation processing time determination unit that determines an execution time of the idle rotation process based on the determined execution time of the image stabilization process. Image forming apparatus.   The idle rotation processing time determination unit determines an execution time of the idle rotation processing to be a predetermined time when the image stabilization processing is determined not to be necessary by the processing necessity determination unit. The image forming apparatus according to claim 2.   When the idling process and the image stabilization process are determined to be necessary by the processing necessity determination unit, the idling process time determination unit determines an execution time of the idling process from a preset time. 3. The image forming apparatus according to claim 2, wherein the time required to execute the image stabilization process is determined as a time obtained by subtracting.   The idle rotation processing time determination unit determines an execution time of the idle rotation processing to be a time shorter than a time required to complete activation of the main controller. Image forming apparatus.   6. The process necessity determination unit according to claim 1, wherein the necessity of the image stabilization process is determined based on a relative humidity within the apparatus and a drive stop time of the photosensitive member. The image forming apparatus according to claim 1. An electrostatic latent image is formed on the black photosensitive member on which an image is formed with black toner, three color photosensitive members on which images are formed with different color toners, and the black photosensitive member and the color photosensitive member, respectively. Exposure means for irradiating four laser beams for forming an image,
The processing necessity determination unit determines whether each of the color stabilization processing executed for all the photoconductors and the monochrome stabilization processing executed for the black toner photoconductor is performed as the image stabilization processing. The image forming apparatus according to claim 6, wherein the determination is made.   When the processing necessity determination unit determines that neither the color stabilization process nor the monochrome stabilization process is necessary, the necessity of registration as an image stabilization process based on the temperature in the exposure unit The image forming apparatus according to claim 7, wherein:   9. The process necessity determination unit according to claim 1, wherein the necessity determination unit determines whether the idling process is necessary based on a relative humidity in the apparatus and a drive stop time of the photosensitive member. The image forming apparatus according to claim 1.   The idle rotation processing time determination unit determines the execution time of the idle rotation processing as a time shorter than a time required for warming up in the fixing unit. Image forming apparatus.

Images