JP2016048288A - Image forming apparatus, image forming method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique capable of achieving both the suppression of throughput of printing and the suppression of deterioration of image quality in an image forming apparatus that forms an image with toner.SOLUTION: A printer 100 comprises an image forming part 10 including a toner storage part 70; and a mark sensor 25. The printer 100 makes the image forming part 10 form a mark for correction and makes the mark sensor 25 read the mark to acquire mark data. When determining that the toner in the toner storage part 70 is not agitated for a long period of time, the printer 100 executes the formation of a mark and the acquisition of mark data twice, and determines whether or not the difference between the first mark data and the second mark data is in an allowable range. When it is determined to be in the allowable range, the printer 100 decides an adjustment value for image adjustment on the basis of the mark data of this time.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an image forming apparatus, an image forming method, and a program for forming an image using toner. More specifically, the technique relates to an operation for forming a correction mark and a toner stirring operation.

  Conventionally, in an image forming apparatus, correction processing for suppressing image positional deviation and density unevenness has been performed. As a procedure of the correction process, for example, in the case of misregistration correction, a misregistration correction mark is formed on the conveyance belt prior to the formation of an image to be printed, and the misalignment amount is determined based on the detection result of the mark. get. Then, the image formation timing is adjusted based on the acquired shift amount.

  Further, in an image forming apparatus that forms an image using toner, the toner in the developing device is agitated before the image is formed in order to stabilize the charge amount of the toner. For example, Japanese Patent Application Laid-Open No. H10-260707 discloses a document relating to toner agitation. Patent Document 1 discloses a technique for controlling the stirring time in accordance with the ratio of the toner and carrier replenishment amount.

JP 2011-128526 A

  However, the conventional technique described above has the following problems. That is, if a predetermined toner agitation time is secured, the toner may be agitated more than necessary when the charging is stable. Since the user waits for the toner stirring time before image formation, it is preferable that the stirring time is short. On the other hand, if the stirring time is too short, the image quality may be deteriorated.

  The present invention has been made to solve the above-described problems of the prior art. That is, an object of the present invention is to provide a technique for achieving both reduction in printing throughput and suppression of deterioration in image quality in an image forming apparatus that forms an image using toner.

  In order to solve this problem, an image forming apparatus includes a container that contains toner, a stirring unit that stirs the toner contained in the container, and a toner that is contained in the container. An image forming unit to be formed, a sensor, and a control unit, wherein the control unit forms a correction mark on the image forming unit and acquires mark data obtained by reading the mark with the sensor; , A period determination process for determining whether or not a non-stirring period, which is a period in which toner is not stirred in the stirring unit, and a period in which the non-stirring period is determined to be long in the period determining process Whether the difference between the mark data acquired in the first acquisition process and the mark data acquired in the second acquisition process is within an allowable range. Judge Determination that determines an adjustment value for image adjustment based on the mark data acquired in the current acquisition process when the difference determination process and the difference determination process determine that the difference is within the allowable range And processing.

  The image forming apparatus disclosed in this specification acquires mark data by forming and reading a correction mark. When it is determined that the non-agitating period in which the toner is not agitated is a long time, at least two acquisition processes are executed twice, and the difference between the first mark data and the second mark data is within an allowable range. It is judged whether it is in. If it is determined that it is within the allowable range, an adjustment value for image adjustment is determined based on the current mark data.

  If the non-stirring period is long, the amount of stirring is insufficient and there is a high possibility that appropriate mark data cannot be obtained. Therefore, in the image forming apparatus disclosed in this specification, when the non-stirring period is long, the acquisition process is executed at least twice, and the difference between the previous acquisition process and the current acquisition process is within an allowable range. Judge whether or not. If the difference is not within the allowable range, there is a high possibility that the charging is unstable, and it is unlikely that highly reliable mark data could be acquired. On the other hand, if the difference is within an allowable range, there is a high possibility that the charging is stable, and there is a high possibility that appropriate mark data with a small error from the user's print instruction can be acquired. Therefore, when the difference is within the allowable range, the adjustment value for image adjustment based on the mark data is determined, so that a highly reliable adjustment value can be obtained, which is preferable while suppressing a decrease in printing throughput. Image formation can be expected.

  In addition, when the mark is formed in the acquisition process, the toner is stirred in the stirring unit, and the control unit determines that the non-stirring period is long in the period determination process in the acquisition process. In this case, it is preferable that the sampling number of marks formed in this case is larger than the sampling number of marks formed when it is determined that the non-stirring period is not long. When it is determined that the non-stirring period is long, charging is more likely to be unstable than when the non-stirring period is not determined to be long. It is preferable to acquire the mark data.

  In addition, the image forming apparatus disclosed in the present specification includes an information storage unit that stores different information before and after the acquisition process, and the container includes the information storage unit before the acquisition process is executed. And an exchange storage unit for storing different information for the acquisition process, and when the mark is formed in the acquisition process, the toner is stirred in the stirring unit, and the control unit stores the information storage in the acquisition process. The number of marks sampled when the information before the acquisition process is stored in the storage unit is stored, and the information after the acquisition process is stored in the information storage unit In addition, the number may be larger than the number of mark samplings formed when the information before the acquisition process is stored in the exchange storage unit. In the case of the first acquisition process in the image forming apparatus, it is highly possible that the charging is more unstable than in the case of the first acquisition process in the container. Therefore, it is preferable to acquire the mark data with higher accuracy by increasing the number of samplings.

  Further, the image forming apparatus disclosed in the present specification includes an information storage unit that stores different information before and after the acquisition process is performed, and when the mark is formed in the acquisition process, the stirring unit In the acquisition process, the control unit detects a mark formed when information before the acquisition process is stored in the information storage unit. The number of samplings is formed when information after the acquisition process is executed is stored in the information storage unit, and the period from the previous power-off to the current power-on is longer than a predetermined time. It is better that the number of marks to be sampled is larger. In the case of the first acquisition process in the image forming apparatus, there is a high possibility that charging is unstable as compared with a case where the power-off period is long. Therefore, it is preferable to acquire the mark data with higher accuracy by increasing the number of samplings.

  In addition, the image forming apparatus disclosed in the present specification includes an information storage unit that stores different information before and after the acquisition process is performed, and the control unit is configured to store the information in the period determination process. When the information before the acquisition process is executed is stored in the storage unit and the acquisition process execution condition is satisfied, the non-agitation period may be determined to be long. In the first acquisition process in the image forming apparatus, the non-stirring period is not fixed. Therefore, it is preferable to consider that the non-stirring period is long.

  In the image forming apparatus disclosed in this specification, the container includes an exchange storage unit that stores different information before and after the acquisition process is performed, and the control unit determines the period determination. In the process, it is preferable to determine that the non-stirring period is long when the acquisition process execution condition is satisfied in a state where information before the acquisition process is stored in the exchange storage unit. If this is the first acquisition process after replacement of the container, the previous agitation time is unknown and the non-agitation period is not fixed. Therefore, it is preferable to consider that the non-stirring period is long.

  In the period determination process, the control unit may determine that the non-agitation period is long when the period from the previous power-off to the current power-on is longer than a predetermined time. When the period from the previous power-off to the current power-on is long, it is preferable to consider that the non-stirring period is long.

  Further, the image forming apparatus disclosed in the present specification has a plurality of containers, and different containers are provided for each color of toner, and the control unit displays a plurality of color marks in the acquisition process. It is good to form. When there are a plurality of containers, mark data can be acquired with higher accuracy by forming a mark using the color of each container and acquiring mark data corresponding to each color.

  The mark may be a density correction mark, and the control unit may have a different allowable range for each color in the difference determination process. The degree of conspicuous density unevenness differs for each toner color. Therefore, it is preferable to set an allowable range according to the toner characteristics.

  In addition, when there is a color for which the difference is determined to be outside the allowable range in the difference determination process, the control unit performs the acquisition process for the color again, and performs the previous acquisition process. It is preferable to execute a difference re-determination process for determining whether or not a difference between the acquired mark data and the mark data acquired in the current acquisition process is within the allowable range. For colors whose difference is within the allowable range, it is less necessary to calculate the difference again. Therefore, it is preferable to suppress the waste of toner by calculating the difference for colors whose difference is outside the allowable range.

  In the acquisition process, the control unit causes the image forming unit to form marks having different densities as marks for gamma correction, and obtains mark data for gamma correction obtained by reading the marks having different densities by the sensor. In the period determination process, when the period from the previous power-off to the current power-on is longer than a predetermined time, the non-agitation period is determined to be long and the gamma correction execution condition is satisfied. If it is, the predetermined time is preferably shorter than when the gamma correction execution condition is not satisfied. In the gamma correction, the accuracy of the correction value based on the mark data is likely to decrease due to the lack of charge amount. In addition, the gamma correction is performed fewer times than other corrections, and once an inappropriate correction value is obtained, it takes a long time to be corrected by the next execution. For this reason, when the gamma correction execution condition is satisfied, it is preferable to shorten the predetermined time to make it easier to execute the difference determination process.

  In the acquisition process, the control unit causes the image forming unit to form marks having different densities as marks for gamma correction, and obtains mark data for gamma correction obtained by reading the marks having different densities by the sensor. In the difference determination process, when the gamma correction execution condition is satisfied, the allowable range may be narrower than when the gamma correction execution condition is not satisfied. In the gamma correction, the accuracy of the correction value based on the mark data is likely to decrease due to the lack of charge amount. In addition, the gamma correction is performed fewer times than other corrections, and once an inappropriate correction value is obtained, it takes a long time to be corrected by the next execution. For this reason, when the gamma correction execution condition is satisfied, it is preferable to narrow the allowable range and strictly limit the use of the acquired mark data.

  A control 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, in an image forming apparatus that forms an image using toner, a technique for achieving both reduction in printing throughput and suppression of deterioration in image quality is realized.

1 is a block diagram illustrating an electrical configuration of a printer according to an embodiment. FIG. 2 is a cross-sectional view illustrating an internal configuration of the printer illustrated in FIG. 1. It is a schematic diagram which shows the structure of a developing device. It is a figure which shows arrangement | positioning of a mark sensor. It is a figure which shows the example of a density mark. 6 is a flowchart illustrating a procedure of density correction processing executed by a printer. It is explanatory drawing which shows the example of the kind of density mark. It is a flowchart which shows the procedure of a correction value determination process.

  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 that forms an image by electrophotography.

  As shown in FIG. 1, the printer 100 according to this embodiment includes a controller 30 having a CPU 31, a ROM 32, a RAM 33, an NVRAM (nonvolatile RAM) 34, and an ASIC 35. 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, and the ASIC 35 may be a control unit.

  Further, the printer 100 includes an image forming unit 10 that forms an image by an electrophotographic method, an operation unit 40 that receives an input operation from a user, and a communication interface (communication IF) 37 for connecting to an external device. These are controlled by the CPU 31.

  The communication interface 37 is hardware that enables communication with other devices. Specific examples of the communication interface 37 include a wired LAN interface, a wireless LAN interface, a serial communication interface, a parallel communication interface, and a facsimile interface. The printer 100 can receive a job for causing the image forming unit 10 to form an image from an external device via the communication interface 37.

  The operation unit 40 is provided on the exterior of the printer 100 and has various buttons for receiving input operations from the user, and a touch panel for displaying messages and setting contents. Examples of the various buttons include an execution button for causing the image forming unit 10 to form an image and a cancel button for inputting an instruction for canceling image formation. The operation unit 40 also accepts various inputs when the user touches the touch panel with a finger.

  Further, the printer 100 according to the present embodiment can form a color image. As will be described later, the image forming unit 10 includes toner storage units 70C, 70M, 70Y, and 70K for each color that can be individually attached to and detached from the printer 100. The toner storage units 70C, 70M, 70Y, and 70K include memories 701C, 701M, 701Y, and 701K, respectively. In the following, the Y, M, C, and K subscripts are omitted unless particularly distinguished. The controller 30 of the printer 100 can read and write information from and to the memory 701 of the toner storage unit 70 attached.

  The printer 100 also includes a cover 15 that is opened and closed when the toner container 70 is attached and detached, and an opening and closing sensor 16 that detects opening and closing of the cover. The open / close sensor 16 outputs different signals depending on whether the cover 15 is open or closed. The printer 100 can acquire the open / closed state of the cover 15 based on the output signal of the open / close sensor 16.

  Next, the configuration of the image forming unit 10 of the printer 100 will be described with reference to FIG. The image forming unit 10 forms a toner image by an electrophotographic method, transfers the toner image to a sheet, an exposure device 53 that irradiates the process unit 50 with light, and unfixed toner on the sheet. A fixing device 8 for fixing, a paper feed tray 91 for placing a sheet before image transfer, a paper discharge tray 92 for placing a sheet after image transfer, and a transport belt for transporting the sheet to a transfer position of the process unit 50 7.

  Further, in the printer 100, the sheet stored in the paper feed tray 91 located at the bottom passes through the paper feed roller 21, the registration roller 22, the process unit 50, and the fixing device 8, and passes through the paper discharge roller 26. As shown by a one-dot chain line in FIG. 2, a substantially S-shaped transport path 11 is provided so as to be guided to the paper discharge tray 92.

  The process unit 50 can form a color image, and process units corresponding to each color of cyan (C), magenta (M), yellow (Y), and black (K) are arranged in parallel. Specifically, a process unit 50C that forms an image of C color, a process unit 50M that forms an image of M color, a process unit 50Y that forms an image of Y color, and a process unit that forms an image of K color 50K. The process units 50 </ b> C, 50 </ b> M, 50 </ b> Y, and 50 </ b> K for each color are arranged along the conveyance belt 7 at equal intervals. The order of the process units is not limited to the example shown in FIG.

  The process unit 50K includes a drum-shaped photosensitive member 1, a charging device 2 that uniformly charges the surface of the photosensitive member 1, and a developing device 4 that develops the electrostatic latent image on the photosensitive member 1 with toner. , And a transfer device 5 that transfers the toner image on the photosensitive member 1 to a sheet or a conveyance belt 7. The photoreceptor 1 and the transfer device 5 are disposed in contact with the transport belt 7. The photosensitive member 1 is opposed to the transfer device 5 with the conveyance belt 7 interposed therebetween. The other process units 50C, 50M, and 50Y have the same configuration as the process unit 50K.

  Specifically, as illustrated in FIG. 3, the developing device 4 includes a developing unit 60 and a toner storage unit 70, and the space between both is connected through a supply port 69. In this embodiment, a nonmagnetic one-component toner is accommodated in the toner accommodating portion 70 as a developer. The toner container 70 is an example of a container. As described above, the toner container 70 is detachable from the printer 100. Only the toner container 70 may be attached or detached, the entire developing device 4 may be attached or detached, or a part of the developing device 4 including the toner container 70 may be attached or detached.

  The developing unit 60 includes a developing roller 61 that carries toner and conveys the toner toward the photoreceptor 1, and a toner supply roller that supplies toner to the developing roller 61 and scrapes off the toner on the developing roller 61. 62 and a regulating member 63 that regulates the thickness of the toner on the developing roller 61 and charges the toner.

  The toner storage unit 70 is provided with an agitator 71 as a member for stirring the toner. The agitator 71 is rotationally driven by a motor (not shown) and agitates the toner in the toner storage unit 70. The agitator 71 is an example of a stirring unit. A part of the agitated toner is discharged toward the developing unit 60 through the supply port 69.

  The toner discharged from the supply port 69 to the developing unit 60 is supplied to the developing roller 61 by the rotation of the toner supply roller 62, and at this time, the toner is frictionally charged between the toner supplying roller 62 and the developing roller 61. The toner supplied onto the developing roller 61 enters between the regulating member 63 and the developing roller 61 as the developing roller 61 rotates, and is thinned while being frictionally charged. Then, at a position facing the photoreceptor 1, a part of the toner moves onto the photoreceptor 1 and develops the electrostatic latent image formed on the photoreceptor 1.

  Returning to the description of the image forming unit 10 in FIG. 2, the surface of the photoreceptor 1 is uniformly charged by the charging device 2 in each of the process units 50C, 50M, 50Y, and 50K. Thereafter, exposure is performed with light from the exposure device 53, and an electrostatic latent image of an image to be formed is formed on the photoreceptor 1. Next, toner is supplied to the photoreceptor 1 via the developing device 4. Thereby, the electrostatic latent image on the photoreceptor 1 is visualized as a toner image.

  The image forming unit 10 takes out the sheets placed on the paper feed tray 91 one by one and conveys the sheets onto the conveyance belt 7. The toner image formed by the process unit 50 is transferred to the sheet. At this time, in color printing, toner images are formed by the process units 50C, 50M, 50Y, and 50K, and the toner images are superimposed on the sheet. On the other hand, in monochrome printing, a toner image is formed only by the process unit 50K and transferred to a sheet. Thereafter, the sheet on which the toner image is transferred is conveyed to the fixing device 8 and the toner image is thermally fixed to the sheet. Then, the sheet after fixing is discharged to a discharge tray 92.

  Further, the printer 100 performs correction processing so that density unevenness and positional deviation do not occur in images formed by the process units 50C, 50M, 50Y, and 50K. As a procedure for the correction process, correction marks are formed on the process units 50C, 50M, 50Y, and 50K, the marks are transferred onto the conveyance belt 7, and correction values are determined based on the detection results of the marks. To do. Therefore, the mark sensor 25 is disposed at a position downstream of the process units 50C, 50M, 50Y, and 50K in the traveling direction of the transport belt 7 and through which the sheet does not pass. The printer 100 detects the correction mark formed on the transport belt 7 by the mark sensor 25. The mark sensor 25 is an example of a sensor.

  Specifically, as shown in FIG. 4, the mark sensor 25 includes two sensors, a sensor 25R disposed on the right side in the width direction of the transport belt 7 and a sensor 25L disposed on the left side. Each of the sensors 25R and 25L is a reflective optical sensor in which a light emitting element 23 such as an LED and a light receiving element 24 such as a phototransistor are paired. The mark sensor 25 is configured to irradiate light from the oblique direction to the dotted frame E in FIG. 4 on the surface of the conveyor belt 7 by the light emitting element 23, and the light receiving element 24 receives the light. . The correction mark can be detected by the difference between the amount of light received when the correction mark 27 passes and the amount of light received directly from the conveyor belt 7. Note that the mark 27 in FIG. 4 is an example of a misalignment correction mark.

  The printer 100 acquires mark data corresponding to the current state at that time, based on the result of forming a correction mark and reading it with the mark sensor 25 when a correction processing execution condition described later is satisfied. Then, the printer 100 calculates a correction value for approaching an ideal image based on the acquired mark data. Further, the printer 100 executes image formation using the calculated correction value. Therefore, in order to form an appropriate image, it is required to acquire mark data that appropriately reflects the current situation.

  Next, various correction processes executed by the printer 100 will be described. The printer 100 according to this embodiment executes correction processing such as misregistration correction, development bias correction, and gamma correction. Note that these correction processes are merely examples, and the present invention is not limited to these.

  The misregistration correction is a dynamic image position misalignment caused by the eccentricity of the photosensitive member 1 or the conveyance roller, or a deviation in the pitch of the gear that rotationally drives them, or a misalignment of the mounting position of the photosensitive member 1 or the exposure device 53. This is a process for acquiring a correction value for adjusting a static image position shift caused by the above. In the misalignment correction, the printer 100 forms marks 27K, 27C, 27M, and 27Y as shown in FIG. For example, the long and narrow marks 27 are arranged side by side in the traveling direction of the conveyor belt 7 at the reading positions of the mark sensors 25R and 25L on both sides. The printer 100 reads the mark 27 with the mark sensor 25, calculates the interval between the marks 27, and acquires the periodic positional deviation amount and the positional deviation amount between colors. The correction value for adjusting the positional deviation is an example of an adjustment value for image adjustment.

  The printer 100 reads the position of each formed mark 27, specifically, the position of the leading edge side or the trailing edge side of each mark 27 in order to correct misalignment. The mark data for positional deviation correction is the position data of the mark 27. Since there is only one place for one mark 27 to be read, the number of sampled mark data for positional deviation correction corresponds to the number of marks 27 formed. As the number of marks 27 formed increases, the number of mark data samplings for correcting misalignment increases. The sampling number is the number of times each color mark is read in one correction process, and is the number of mark data that can be acquired for each color.

  The development bias correction is a process for acquiring a correction value for adjusting a deviation between the ideal density defined by the printer 100 and the density of the actually formed mark. In developing bias correction, the printer 100 forms, for example, 100% density marks 28K, 28C, 28M, and 28Y for each color, as shown in FIG. The printer 100 reads these marks 28 with the mark sensor 25, calculates the current density based on the amount of received light, and acquires density data. Then, a correction value of the developing bias for obtaining the current density close to the target density is acquired. For example, using a linear function of the density and the development bias value, the adjustment amount of the development bias value is calculated from the difference between the current density and the target density, and the calculated adjustment amount is acquired as the correction value of the development bias. . The mark data for developing bias correction is the density data of the mark 28. The correction value of the developing bias is an example of an adjustment value for image adjustment.

  As shown in FIG. 5, the development bias correction mark 28 is larger in the conveyance direction of the conveyance belt 7 than the misalignment correction mark 27. In developing bias correction, for example, the printer 100 reads a plurality of locations inside each mark 28 by causing the mark sensor 25 to read at predetermined time intervals, and acquires a plurality of density data for one mark. To do. If the reading interval is constant, the mark 28 having a larger size in the transport direction of the transport belt 7 has a larger sampling number of density data. The number of mark data sampling for developing bias correction increases as the size of each mark 28 in the transport direction of the transport belt 7 increases or as the number of marks 28 formed increases.

  It is also possible to correct the image density by correcting the exposure bias. Also when correcting the exposure bias, the printer 100 forms and reads the mark 28 and acquires the correction value of the exposure bias in the same manner as the correction of the development bias. The exposure bias correction value is an example of an adjustment value for image adjustment.

  The gamma correction is a process for correcting a deviation between an indicated density (indicated gradation) by an external computer and an output density of the printer 100 itself. In gamma correction, the printer 100 forms marks with a plurality of densities of, for example, 20%, 40%, 60%, 80%, and 100% for each color. These marks are read by the mark sensor 25, the actual density is calculated based on the amount of received light, and density data is acquired. Based on the relative relationship of the density of each mark, the density change characteristic of each color is specified. Then, a relative relationship table between the change characteristic and the gradation indicated by the external computer is created. The relative relationship table is an example of adjustment values for image adjustment.

  Similar to the development bias correction mark 28, the gamma correction mark is a mark having a certain area. That is, the printer 100 forms a plurality of density marks for each color as gamma correction marks. In the gamma correction, the printer 100 acquires a plurality of density data for one mark. If the reading frequency is constant, the greater the size of the transport belt 7 in the transport direction, the greater the number of density data samplings. The number of mark data samplings for gamma correction increases as the size of each mark increases or the number of marks formed increases.

  The printer 100 forms the development bias correction mark 28 and the gamma correction mark at the reading position of either the mark sensor 25R or 25L. These marks may be formed on both sides of the mark sensors 25R and 25L. However, in order to obtain appropriate mark data while suppressing the amount of toner used, it is preferable to form these marks only on one side.

  When the printer 100 receives a print job execution instruction, the printer 100 determines whether or not the conditions for executing each correction process are satisfied. If it is determined that the execution condition is satisfied, correction processing that satisfies the execution condition is executed prior to execution of the print job.

  In other words, the correction process is not executed immediately when the execution condition is satisfied, but is executed before the print job is executed when the print job execution condition is satisfied. Then, the printer 100 executes printing by correcting the operation of each unit with the correction value determined by the correction process. There are a plurality of correction processing execution conditions for each correction process. Execution conditions include, for example, cover open, power-on, user instruction input, printing more than a predetermined number of sheets, rotation amount of the agitator 71 is more than a threshold, continuous activation time is more than a threshold, environmental changes such as humidity and temperature, or the like This combination is applicable.

  In the printer 100, there are cases where both execution conditions for a plurality of correction processes are satisfied. When the execution conditions for a plurality of correction processes are satisfied and a plurality of correction processes are executed, the execution order is predetermined. Specifically, density correction such as development bias correction is first, and positional deviation correction and gamma correction are executed after density correction.

  For example, when the gamma correction execution condition is satisfied, the printer 100 also satisfies the development bias correction execution condition. Both the development bias correction and the gamma correction are density corrections that suppress density unevenness, and the development bias correction corrects density shifts in all gradations that are insufficient or excessive in density over all gradations. On the other hand, the gamma correction is a correction for correcting the density deviation for each gradation that is insufficient or excessive in density for each gradation and appropriately changing the density when the gradation is changed. If there is a density shift of all gradations, it is difficult to accurately detect a characteristic change for each gradation of density. Therefore, when executing gamma correction, development bias correction is executed before gamma correction.

  In addition, the positional deviation correction may satisfy the execution condition alone. However, if there is a deviation in the density of each mark, even if the mark is formed at the same image forming position, the amount of light received by the mark sensor 25 varies. For this reason, a deviation occurs in the mark detection position, making it difficult to detect the image forming position with high accuracy. Therefore, when both execution conditions of the positional deviation correction and the development bias correction are satisfied, the development bias correction is executed before the positional deviation correction.

  If the non-stirring period of the printer 100 is long, there is a high possibility that the toner charge amount is uneven and the density is highly likely to be uneven. For example, in the printer 100 in which the toner container 70 is set and shipped in advance, the toner in the toner container 70 may be exposed to the outside air during the storage period after manufacture. In particular, when the storage period after manufacturing the printer 100 is long, the toner tends to aggregate. Therefore, during the first operation after the main body is shipped, for example, it is necessary to perform toner agitation for a long period of time in order to reliably stabilize the charged state of the toner.

  In the printer 100 according to the present embodiment, when it is determined that the non-stirring period is long when the printing instruction is received, the density correction execution condition is satisfied. Prior to printing, the density is corrected by stirring the toner for a rather long time. However, when the density correction mark is formed in a state where the charged state of the toner is unstable, the density of the formed mark itself may be unstable. When the density of the mark is unstable, even if the correction value is determined based on the mark, the reliability of the determined correction value is low. Further, when other correction processing marks are formed based on the correction value, the reliability of the other correction processing is low.

  Therefore, when it is determined that the non-stirring period is long, the printer 100 according to the present embodiment executes the formation of the density correction mark twice and acquires the mark data for two times. Specifically, the process is executed in the order of mark formation → mark data acquisition → toner stirring → mark formation → mark data acquisition. The toner is also agitated during mark formation. Then, the difference between the mark data for two times is calculated, and it is determined whether or not the difference is within an allowable range.

  If stirring is insufficient at the time of the first mark formation, the charged state of the toner approaches a more stable state by stirring until the second mark formation, and the difference in mark data for the second time tends to be large. That is, when the difference between the mark data is large, it can be estimated that the toner is not sufficiently stirred at least once. That is, there is a high possibility that the charged state of the toner is not stable.

  On the other hand, if the charged state of the toner is stable, the difference in charge amount between the two mark formations is small, and the difference between the mark data for two times is small. That is, when the difference in mark data is small, it can be estimated that the charged state of the toner is stable and the reliability of the acquired mark data is high. Therefore, in the printer 100, when the difference between the mark data is not large, a correction value for density correction is determined based on the acquired mark data.

  Next, density correction processing which is a density correction correction value determination operation executed by the printer 100 will be described with reference to the flowchart of FIG. The density correction processing is, for example, development bias correction, and is executed by the CPU 31 when a print job is received in a state where the correction execution conditions are satisfied.

  In this density correction processing, first, it is determined whether or not the non-stirring period is long. As an example in which the non-stirring period is a long period, when the correction process is the first correction process after the printer 100 is shipped, when the correction process is the first correction process after at least one toner container 70 is replaced with a new one, This corresponds to the case where the elapsed time after execution of the previous correction process is long.

  Therefore, in the density correction process, the printer 100 first determines whether or not it is the first correction process after shipping the main body (S101). Whether or not the correction process is the first correction process after the main body is shipped can be determined by referring to the value of a flag that is set to ON when the correction process is executed. In this case, the printer 100 is configured to store the value of the flag in the NVRAM 34, and is shipped with the flag set to off. Then, the printer 100 sets the flag to ON after executing the correction process. That is, the value of the flag is different before and after the correction process is executed. Therefore, the printer 100 can determine whether it is before or after the first correction processing after the main body is shipped based on the value of the flag in the NVRAM 34. The NVRAM 34 in which the flag is stored is an example of an information storage unit.

  Then, in response to determining that it is the first correction process after the main body is shipped (S101: YES), the printer 100 sets the type of mark to be formed as the mark M1 with the largest number of samplings, and sets the difference threshold described later to the maximum. A difference threshold D1 having a narrow allowable range is set (S102). And the correction value determination process which is a process when it is judged that the non-stirring period is a long period is performed. The correction value determination process will be described later.

  The printer 100 includes a plurality of types of marks having different sampling numbers, such as a mark M1, a mark M2, and a mark M3 shown in FIG. In the density correction process, the larger the size of each mark to be formed and the larger the number of marks, the greater the number of samplings. That is, the mark M1 is used when the size of each mark is large and the number of marks is large, so that the number of sampling is the largest among the three types and the required accuracy is the highest. The mark M2 has the same size as each mark M3, but the number of marks is large, so the number of samples is less than the mark M1 and larger than the mark M3. The mark M3 has the smallest sampling number among the three types.

  Note that the number of samples is doubled when the size of each mark is doubled and when the number of marks is doubled at the same size, but the mark of each color is marked like mark M2. By repeating the above and doubling the number, it is preferable to eliminate the influence of the eccentricity of the photosensitive member 1 and the conveying belt 7 rather than doubling the size of each mark.

  The difference threshold is a threshold for determining an allowable range in which it can be determined that the charged state of the toner is stable as a difference between the mark data for two times. As described above, when the mark for density correction is formed twice and the mark data for two times is acquired, if the difference is less than the difference threshold, it is determined that the difference is small. The smaller the difference threshold, the narrower the allowable range. The difference threshold value D1 is smaller than any of other difference threshold values D2 and D3 described later.

  Note that the difference threshold value may be the same value for each color, or may be a different value for each color. When different values are set for the respective colors, the printer 100 stores the difference threshold value for each color and uses the difference threshold value corresponding to the color of the mark to be determined. In the printer 100, for example, a difference threshold value is determined in advance for each color according to the spectral reflectance characteristics of the toner, the sensitivity of the mark sensor 25, and the conspicuousness of density unevenness, and is stored in the ROM 32 or the NVRAM 34. The difference threshold is an example of the upper limit of the allowable range in the difference determination process.

  On the other hand, if it is determined that the correction process is not the first correction process after the main body is shipped (S101: NO), the printer 100 determines whether or not the gamma correction execution condition is satisfied (S104). As described above, when the density correction execution condition is satisfied, the gamma correction execution condition may also be satisfied. When the gamma correction execution condition is satisfied, high accuracy is also required for density correction in order to ensure the accuracy of gamma correction.

  Accordingly, in response to determining that the execution condition of gamma correction is satisfied (S104: YES), the printer 100 sets the type of the mark 28 to the mark M2 with a medium sampling number, and sets the difference threshold to a medium difference. The threshold value D2 is set, and the time threshold value is determined as the time threshold value T2 (S105). The time threshold value is a threshold value to be compared with an elapsed time described later, and is a criterion for determining whether or not the non-agitation period is a long time.

  On the other hand, in response to determining that the gamma correction execution condition is not satisfied (S104: NO), the printer 100 sets the type of the mark 28 to the mark M3 with the smallest number of samplings, and sets the difference threshold to the widest allowable range. The difference threshold value D3 is set, and the time threshold value is determined as the time threshold value T3 (S106). The difference threshold has a relationship of D1 ≦ D2 ≦ D3. The time threshold value has a relationship of T2 ≦ T3.

  Next, regardless of whether or not the gamma correction execution condition is satisfied, the printer 100 is the first correction process after the replacement of the toner storage unit 70 of at least one color of the developing device 4 with a new one. It is determined whether or not (S108). Therefore, for example, the printer 100 has formed an image using the toner in the mounted toner storage unit 70 based on the information in the memory 701 of each toner storage unit 70 shown in FIG. That is, it is determined whether or not this is the first correction process after replacement of a new product.

  Each toner storage unit 70 is shipped in a state where information indicating that the toner is new is stored in the memory 701. “New” means, for example, before the first correction process after shipment. For example, when the printer 100 detects that the cover 15 is closed → open → closed based on the output signal of the open / close sensor 16, the printer 100 determines that the toner storage unit 70 may be replaced. Information in the memory 701 is read. The read information is stored in the NVRAM 34, for example. If the opening / closing of the cover 15 is not detected, it can be determined that the toner storage unit 70 has not been replaced, so there is no need to read the memory 701 of the toner storage unit 70 each time printing is performed. However, since there is a possibility that the toner container 70 has been replaced while the power is off, it is preferable to read the memory 701 in the first correction process after the power is turned on.

  In step S <b> 108, the printer 100 acquires information from the NVRAM 34 and determines whether it is the first correction process after the replacement of the toner storage unit 70. Note that the printer 100 rewrites the information in the memory 701 and the information in the NVRAM 34 to information indicating that the correction processing has been performed after performing the first correction processing using the toner in the toner storage unit 70. That is, after the correction process is executed, the memory 701 stores information indicating that the first correction process has been executed. The memory 701 is an example of an exchange storage unit.

  Then, the printer 100 sets the mark type to the mark M2 (S109) in response to determining that it is the first correction process after the replacement of the toner container 70 (S108: YES). That is, the printer 100 increases the number of samplings of the mark 28 to a moderate level when there is a new toner container 70. Then, it is determined that the non-stirring period is long, and a correction value determination process described later is executed.

  On the other hand, when the printer 100 determines that it is not the first correction process after replacement (S108: NO), the printer 100 acquires the elapsed time after the previous toner agitation (S111). That is, the printer 100 does not change the number of samplings when there is no new toner container 70. The elapsed time is, for example, an elapsed time after execution of the previous correction process, an elapsed time after the previous printing execution, or an elapsed time after the previous rotation of the agitator 71. However, in the first correction process after the power is turned on, the printer 100 may set the elapsed time from the previous power-off to the current power-on. For example, the printer 100 stores the off time when the power is turned off, and acquires the elapsed time when the power is turned on.

  Then, the printer 100 determines whether or not the acquired elapsed time is greater than the time threshold set in S105 or S106 (S112). As described above, the time threshold is the time threshold T2 if the execution condition of the gamma correction is satisfied, and it is determined whether or not the acquired elapsed time is larger than the time threshold T2. If the gamma correction execution condition is not satisfied, the time threshold is the time threshold T3, and it is determined whether the acquired elapsed time is greater than the time threshold T3. If the elapsed time is greater than the time threshold, it is determined that the non-stirring period is long, and a correction value determination process described later is executed. S112 is an example of a period determination process.

  In other words, the printer 100 determines that the non-stirring period is long if it is the first correction process after shipment of the main body, if it is the first correction process after toner replacement, or if the elapsed time is long. To do. In the case of the first correction process after the main body is shipped, there is a possibility that toner aggregation has progressed or it is highly likely that the first agitation is performed, so the printer 100 regards the non-agitation period as a long period. Further, in the first toner container 70 after replacement, the toner stirring state is unknown, and the printer 100 regards the non-stirring period as a long period. Also, since the printer 100 does not perform toner agitation while the power is off, if the elapsed time from the previous power-off to the current power-on is long, the non-agitation period is regarded as a long time.

  Therefore, the printer 100 determines a correction value for determining an appropriate correction value after S102, after S109, or when it is determined that the elapsed time is greater than the time threshold (S112: YES). Processing is executed (S115).

  When the correction value determination process is started, both the type of mark to be formed and the difference threshold value to be used are determined. For example, in the case of correction processing for the first time after the main body is shipped, there is a high possibility that the toner charging state of all the toner storage units 70 is unstable. In the first correction process after shipment from the main body, after the density correction, another correction is executed using the acquired correction value. For this reason, in the first correction processing after the main body is shipped, the printer 100 forms a mark with a large number of samplings, narrows the allowable range, and acquires a correction value with particularly high reliability.

  If the execution condition for gamma correction is satisfied, the gamma correction is executed after the density correction processing. The gamma correction is performed less frequently than other corrections, and the correction value once determined is used for a long time. Therefore, when the gamma correction execution condition is satisfied, the printer 100 forms a mark with a larger number of samplings than when the gamma correction execution condition is not satisfied, narrows the allowable range, and performs density correction with high reliability. Get the correction value.

  In addition, in the first toner container 70 after the replacement, there is a high possibility that the charged state of the toner is unstable. Therefore, the printer 100 forms a mark with a large number of samplings and a correction value for highly reliable density correction To get. The printer 100 may increase the number of samplings even when it is determined that the elapsed time after the previous stirring is long.

  Next, the procedure of the correction value determination process will be described with reference to the flowchart of FIG. In the correction value determination process, the printer 100 first executes mark formation for each color and acquisition of density data (S201). That is, even if the non-stirring period is long, no special stirring time is provided before the mark is formed in S201, and the mark is formed early. The density data acquired in S201 is the first density data and is the first density data.

  When acquiring the density data, the printer 100 reads a plurality of positions of the formed mark with the mark sensor 25 and acquires a plurality of density values. The sampling number, which is the number of density values to be acquired, varies depending on the type of mark as described above. Then, the printer 100 calculates an average value by excluding a specific value from the plurality of density values. For example, the minimum density value and the maximum density value are excluded, and the average value of the other density values is used as the density data of this mark.

  Then, the printer 100 agitates the toner for a predetermined time (S202). Further, the printer 100 once again executes mark formation for each color and acquisition of density data (S204). In S204, the same shape and the same number of marks are formed under the same conditions as in S201, and the same number of samplings are performed. The same condition means, for example, that the mark is formed by setting the charging bias value, the developing bias value, and the exposure intensity to the same value. The density data acquired in S204 is second density data, and is second density data. S201 and S204 are an example of an acquisition process.

  Then, the printer 100 calculates a difference between the first density data and the second density data (S205). Furthermore, the printer 100 determines whether or not the calculated difference is smaller than the difference threshold (S206). The difference threshold is one of D1, D2 and D3 described above. S206 is an example of a difference determination process. Note that the printer 100 calculates a difference for each color in S205, and compares it with a corresponding difference threshold value for each color in S206.

  In response to determining that the difference is smaller than the difference threshold for all colors (S206: YES), the printer 100 determines a correction value for each color based on the second density data (S208), and correction value determination processing Exit. When the difference between the two density data is small, the charged state of the toner is stable, and it can be estimated that the density data is highly reliable. Therefore, the printer 100 determines a correction value based on the density data acquired for the second time, which is closer to the current state. S208 is an example of a determination process.

  On the other hand, when it is determined that there is a color whose difference is not smaller than the difference threshold (S206: NO), it can be estimated that the charged state of the toner of that color is not stable. Therefore, the printer 100 further agitates the toner for a predetermined time for at least the color whose difference is not small (S210). The stirring time in S210 may be the same as or different from the stirring time in S202.

  Then, the printer 100 executes mark formation and density data acquisition for the color having a large difference in S206 (S211). Then, the printer 100 calculates the difference between the density data acquired this time and the previous time, that is, the second density data, for the color having a large difference in S206 (S212). Then, the printer 100 determines whether or not the calculated difference is smaller than the difference threshold (S213). S213 is an example of a difference redetermination process.

  In response to determining that the difference is smaller than the difference threshold (S213: YES), the printer 100 determines a correction value based on the current density data (S215), and ends the correction value determination process. When the difference in density data becomes small, it can be estimated that the charged state of the toner is stable, and the correction value is determined based on the latest density data, so that a highly reliable correction value can be obtained. For the color whose difference between the first time and the second time is smaller than the difference threshold value, the correction value may be determined based on the density data acquired the second time without forming the mark again.

  On the other hand, if it is determined that the difference is not smaller than the difference threshold even in the re-formed mark (S213: NO), the printer 100 returns to S210 and repeats stirring, formation of the mark 28, and acquisition of density data. If the difference does not become small after repeating mark formation and density data acquisition a predetermined number of times, it is presumed that some problem has occurred, so an error message is displayed and the operation is stopped. Also good.

  After S208 or after S215, the printer 100 returns to the density correction process of FIG. 6. Since the printer 100 has determined the correction value in the correction value determination process of S115, the density correction process ends.

  On the other hand, if it is determined that the elapsed time is not greater than the time threshold (S112: NO), the printer 100 executes the formation of the mark 28 and the acquisition of density data once (S117). Then, the printer 100 determines a correction value based on the acquired density data (S118), and ends the density correction process. The mark formed in S117 is the type of mark determined in S105 or S106, and has a different sampling number depending on whether or not gamma correction is performed. In addition, the printer 100 stores the correction value determined in S118 in the NVRAM 34 or the like, and reads and uses the stored correction value in subsequent image formation.

  When the non-stirring period is not long, it can be assumed that the toner is sufficiently stirred and the charged state of the toner is stable. In other words, even if the formation of the mark 28 and the acquisition of density data are executed only once, there is a high possibility that highly reliable density data can be acquired. Therefore, in this case, since the mark is formed only once, compared to the case where the correction value determination process of S115 is executed, the amount of toner used is small, and the correction value can be determined early.

  As described above in detail, when it is determined that the non-agitation period is long, the printer 100 according to the present embodiment executes the process of forming the mark 28 and causing the mark sensor 25 to read it twice. Then, an adjustment value for image adjustment is determined in response to the difference between the first mark data and the second mark data not exceeding the difference threshold. If the non-stirring period is long, the charged state of the toner is likely to be unstable. Nevertheless, if the difference in mark data is small, it can be estimated that the charged state of the toner is stable, and the reliability of the acquired mark data is high. That is, when the difference in mark data is small, a highly reliable adjustment value can be acquired by determining an adjustment value for image adjustment based on the mark data. As a result, it is possible to expect both a reduction in printing throughput and a reduction in image quality.

  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 in an electrophotographic system, such as a copying machine, a multifunction machine, and a FAX apparatus.

  Further, in this embodiment, assuming that the toner is not agitated for a long time, the first determination after the main body shipment (S101), the toner storage unit 70 is new (S108), and the elapsed time is long (S112). Running. It is not necessary to perform all of these, and for example, at least one of these may be determined. Further, for example, it may be determined whether or not the period in which the toner is not agitated is a long period of time based on a determination different from these.

  Further, in this embodiment, the toner storage unit can be replaced for each color. However, the present invention can also be applied to a configuration in which the toner storage units for all colors are replaced together. In this embodiment, the cover 15 is provided with the opening / closing sensor 16 and the memory 701 of the toner storage unit 70 is read when the opening / closing of the cover is detected. For example, the memory 701 is stored regardless of whether the cover 15 is opened or closed. It may be read out. Further, in S108 of the present embodiment, it is determined that YES only when the attached toner storage unit 70 is new, but it may be determined as YES if it is the first after replacement regardless of whether or not it is new. Good.

  Further, for example, the present invention can be applied to the printer 100 including the toner storage unit 70 that does not have the memory 701. For example, if it is detected that the cover 15 is closed → open → closed based on an output signal from the open / close sensor 16 of the cover 15, it may be determined that the toner storage unit 70 has been replaced. When making a determination based on the output signal from the open / close sensor 16 or the like, it is preferable to determine that the toner storage unit 70 of all colors has been replaced because the replacement of the toner storage unit 70 cannot be determined.

  Further, in this embodiment, when there is at least one new toner container, mark formation is performed twice for all colors. For example, only twice for only toner in the new toner container 70. Yes, other colors may be set once. That is, the period determination process and the difference determination process may be executed for each color.

  In addition, for example, in the first case after shipping the main body, in the case of gamma correction, and after the replacement of the toner storage unit 70, the number of sampling of the mark 28 is increased. The adjustment value for image adjustment can be determined with high accuracy by acquiring mark data twice using the same mark 28 as in other cases and determining whether or not the difference is within an allowable range. . Further, although the difference threshold and the time threshold are set to different values depending on the presence or absence of gamma correction, they may be the same or only one of them may be different.

  Further, for example, as information stored in the flag of the NVRAM 34 or information stored in the memory 701 of the toner storage unit 70, for example, information in which predetermined information is written at the time of executing the correction process, execution of the first correction process This applies to information that is sometimes deleted. Alternatively, information on the number of executions of correction processing and the amount of stirring of the agitator 71 may be used.

  For example, when the period from the previous power-off to the current power-on is unknown, it may be determined that the elapsed time is long.

  For example, when the mark data difference is large, the mark formation and reading are executed again. For example, an error message may be displayed and the process may be terminated.

  Further, for example, when it is known that, among print images printed by the printer 100, the execution rate of printing only a monochrome image is higher than printing including a color image, for colors other than black, , The difference threshold may be increased to widen the allowable range.

  Further, in the present embodiment, when the execution conditions for a plurality of correction processes are satisfied, the development bias correction is preferentially executed, and the example in which the present invention is applied to the development bias correction has been described. However, the present invention is not limited to this, and other correction processes may be executed with priority. In that case, the present invention may be applied in a correction process executed with priority.

  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.

10 Image forming unit 25 Mark sensor 31 CPU
34 NVRAM
70 Toner container 71 Agitator 100 Printer 701 Memory

Claims (14)

A container for containing toner;
An agitation unit for agitating the toner contained in the container;
An image forming unit that forms an image using toner stored in the container;
A sensor,
A control unit;
With
The controller is
An acquisition process for forming a correction mark in the image forming unit and acquiring mark data obtained by reading the mark with the sensor;
A period determination process for determining whether a non-stirring period, which is a period in which the toner is not stirred in the stirring unit, is a long period;
When the non-agitation period is determined to be long in the period determination process, the acquisition process is executed twice, and the mark data acquired in the first acquisition process and the second acquisition process are performed. Difference determination processing for determining whether or not the difference from the mark data acquired in the above is within an allowable range;
A determination process for determining an adjustment value for image adjustment based on the mark data acquired in the current acquisition process when the difference determination process determines that the difference is within the allowable range;
An image forming apparatus characterized in that The image forming apparatus according to claim 1,
When the mark is formed in the acquisition process, the toner is stirred in the stirring unit,
The controller is
In the acquisition process, the number of mark samplings formed when the non-agitation period is determined to be long in the period determination process is formed when the non-agitation period is determined not to be long. An image forming apparatus characterized in that the number is larger than the sampling number of marks. The image forming apparatus according to claim 1,
An information storage unit for storing different information before and after the acquisition process is performed;
The container includes an exchange storage unit that stores different information before and after the acquisition process is performed,
When the mark is formed in the acquisition process, the toner is stirred in the stirring unit,
The controller is
In the acquisition process, the number of marks to be formed when the information before the acquisition process is stored in the information storage unit is determined by the number of mark samplings formed in the information storage unit. And the number of mark samplings formed when the information before the acquisition process is stored in the exchange storage unit is stored. An image forming apparatus. The image forming apparatus according to claim 1,
An information storage unit for storing different information before and after the acquisition process is performed;
When the mark is formed in the acquisition process, the toner is stirred in the stirring unit,
The controller is
In the acquisition process, the number of marks to be formed when the information before the acquisition process is stored in the information storage unit is determined by the number of mark samplings formed in the information storage unit. Is stored, and more than the number of marks sampled when the period from the previous power-off to the current power-on is longer than a predetermined time. Image forming apparatus. The image forming apparatus according to claim 1,
An information storage unit for storing different information before and after the acquisition process is performed;
The controller is
In the period determination process, the non-stirring period is determined to be long when the acquisition condition is satisfied in a state where the information before the acquisition process is stored in the information storage unit. An image forming apparatus. The image forming apparatus according to claim 1,
The container includes an exchange storage unit that stores different information before and after the acquisition process is performed,
The controller is
In the period determination process, the non-stirring period is determined to be long when the acquisition process execution condition is satisfied in a state where the information before the acquisition process is stored in the exchange storage unit. An image forming apparatus. The image forming apparatus according to claim 1,
The controller is
In the period determining process, the non-stirring period is determined to be a long period when the period from the previous power-off to the current power-on is longer than a predetermined time. In the image forming apparatus according to any one of claims 1 to 7,
There are a plurality of the containers, and different containers are provided for each color of toner,
The controller is
In the acquisition process, an image forming apparatus is characterized in that marks of a plurality of colors are formed. The image forming apparatus according to claim 8,
The mark is a density correction mark,
The controller is
In the difference determination process, the allowable range is different for each color. The image forming apparatus according to claim 9,
The controller is
If there is a color for which the difference is determined to be outside the allowable range in the difference determination process, the acquisition process is performed again for the color, and the mark data acquired in the previous acquisition process and the current time An image forming apparatus that executes a difference re-determination process for determining whether a difference from the mark data acquired in the acquisition process is within the allowable range. In the image forming apparatus according to any one of claims 1 to 10,
The controller is
In the acquisition process, marks having different densities are formed on the image forming unit as marks for gamma correction, and mark data for gamma correction obtained by reading each mark having different densities by the sensor;
In the period determining process, when the period from the previous power-off to the current power-on is longer than a predetermined time, it is determined that the non-stirring period is a long period and the gamma correction execution condition is satisfied. The image forming apparatus is characterized in that the predetermined time is shorter than when the gamma correction execution condition is not satisfied. The image forming apparatus according to any one of claims 1 to 11,
The controller is
In the acquisition process, marks having different densities are formed on the image forming unit as marks for gamma correction, and mark data for gamma correction obtained by reading each mark having different densities by the sensor;
In the difference determination process, the allowable range is narrower when a gamma correction execution condition is satisfied than when a gamma correction execution condition is not satisfied. In an image forming method of an image forming apparatus for forming an image using toner stored in a container,
An acquisition step of forming a correction mark and acquiring mark data obtained by reading the mark with a sensor;
A period determining step for determining whether or not a non-stirring period, which is a period during which the toner stored in the container is not stirred, when the execution condition of the acquisition step is satisfied;
When the non-stirring period is determined to be long in the period determination step, the acquisition step is executed twice, and the mark data acquired in the first acquisition step and the second acquisition step A difference determination step for determining whether or not the difference from the mark data acquired in the above is within an allowable range;
A determination step of determining an adjustment value for image adjustment based on the mark data acquired in the current acquisition step when it is determined in the difference determination step that the difference is within the allowable range;
An image forming method comprising: A container for containing toner;
An agitation unit for agitating the toner contained in the container;
An image forming unit that forms an image using toner stored in the container;
A sensor,
In an image forming apparatus comprising
An acquisition process for forming a correction mark in the image forming unit and acquiring mark data obtained by reading the mark with the sensor;
A period determination process for determining whether a non-stirring period, which is a period in which the toner is not stirred in the stirring unit, is a long period;
When the non-agitation period is determined to be long in the period determination process, the acquisition process is executed twice, and the mark data acquired in the first acquisition process and the second acquisition process are performed. Difference determination processing for determining whether or not the difference from the mark data acquired in the above is within an allowable range;
A determination process for determining an adjustment value for image adjustment based on the mark data acquired in the current acquisition process when the difference determination process determines that the difference is within the allowable range;
A program that executes

Images