JP2015184646A - image forming apparatus, image forming method, and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that forms images by using a toner, and a technology that achieves suppression of both a reduction in throughput of printing and a reduction in image quality.SOLUTION: A printer 100 determines whether or not a mark forming time, which is a time required for forming a mark for correction, falls within a pre-formation stirring time, which is a time for causing an agitator 71 in a toner storage part 70 to stir a toner before causing an image forming unit 10 to form images. The printer 100 causes the image forming unit 10 to form the mark for correction within the pre-formation stirring time provided that the mark forming time falls within the pre-formation stirring time.

Description

  The present invention relates to an image forming apparatus that forms an image using toner, an image forming method, and a storage medium. More specifically, the technique relates to a correction process for forming a 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, when the toner stirring operation and the correction process described above are performed prior to image formation, the time required for the correction process is waited before the image formation in addition to the time required for the stirring operation. As a result, the printing throughput decreases. On the other hand, if these are not executed, image quality will be degraded.

  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, and a control unit, and the control unit corrects within a stirring time before formation, which is a time for stirring the toner in the stirring unit before forming an image in the image forming unit. A determination process for determining whether or not a mark time, which is a time required for formation of a mark, is included, and the formation is performed on the condition that the mark time is determined to be within the stirring time before the formation in the determination process. A mark forming process for forming the mark on the image forming unit is performed within a pre-stirring time.

  The image forming apparatus disclosed in this specification determines whether or not the mark time required for forming the correction mark is within the agitation time before formation in which the toner is agitated before image formation. As the correction, for example, a positional deviation correction for adjusting the positional deviation of the image and a density correction for adjusting the density unevenness are applicable. Then, the mark is formed within the pre-formation stirring time on condition that the mark time is within the pre-formation stirring time.

  That is, in the image forming apparatus disclosed in this specification, if a correction mark can be formed within the stirring time before formation before image formation, the mark is formed within the stirring time before formation. As a result, toner agitation and mark formation are performed simultaneously. As a result, the image formation can be started earlier compared to the case where the formation of the mark is started after waiting for the stirring time before the formation.

  The mark time is a mark formation time that is a time for forming a mark in the image forming unit and a mark formation time that is for stirring the toner before the mark is formed in the image forming unit. Pre-stirring time may be included. Since there is an agitation time necessary for the formation of the mark even before the mark is formed, deterioration of the image quality of the mark is suppressed, and a highly accurate correction result can be expected.

  The agitation time before the mark formation differs depending on the type of the mark, and may be a time corresponding to the mark formed in the image forming unit. Since the required image quality varies depending on the content of correction, it is preferable to set an appropriate stirring time before forming each mark depending on the type of mark used for each correction.

  The types of marks include a gamma correction mark and a development bias correction mark. The agitation time before mark formation before the gamma correction mark is formed is the development bias correction mark. The stirring time before the mark formation before the mark is formed may be longer. The gamma correction mark is required to have high accuracy in the density of the mark. For this reason, it is preferable to stabilize the charge amount of the toner by making the stirring time before the mark formation longer than the mark for developing bias correction using only a specific density.

  The types of marks include a gamma correction mark and a misregistration correction mark. The stirring time before forming the mark before the gamma correction mark is formed is the misalignment correction mark. The stirring time before the mark formation before the mark is formed may be longer. The misregistration correction mark is correction for obtaining a correction value by detecting the edge of the mark, and accuracy of mark density is not required. For this reason, it is preferable to shorten the stirring time before forming the mark and increase the chance of forming the mark.

  The control unit may determine the start time of the mark time based on the end time of the pre-formation stirring time. That is, the control unit is configured such that the time length from the start of the pre-formation stirring time to the start of the mark time is longer than the time length from the end of the mark time to the end of the pre-formation stirring time. Good. According to this configuration, it is possible to secure a longer agitation time before mark formation, and an improvement in mark accuracy can be expected.

  The stirring time before formation is preferably longer as the non-stirring time, which is a continuous time during which the stirring portion is not stirred before the start of the stirring time before formation, is longer. The charge amount of the toner becomes unstable over time due to the discharge phenomenon. Therefore, it is preferable to sufficiently stir when the non-stirring time is long. Note that the non-stirring time can be acquired by storing the latest stirring completion time, for example. Also, it can be considered that the non-stirring time is long when a new article of the container is detected or immediately after the unpacking of the main body is detected.

  The pre-formation stirring time may vary depending on the required image quality of the image to be formed. The higher the required image quality, the more stable the charge amount of the toner. Therefore, it is preferable to set an appropriate stirring time depending on the required image quality.

  Further, the pre-formation stirring time may be different according to at least one of humidity and temperature. In the case of high temperature and high humidity, the charge amount of the toner tends to be lower than that in the case of low temperature and low humidity. Therefore, it is preferable to set an appropriate stirring time according to these environmental parameters.

  The control unit may execute the mark forming process when the correction execution condition is satisfied. By executing the mark formation process when the correction execution condition is satisfied, it is possible to reduce mark formation opportunities and suppress wasteful toner consumption.

  Moreover, the said control part is good to perform the change process which changes easily the execution condition of correction | amendment, when the length of the said stirring time before formation is longer than predetermined time. If the stirring time before formation is long, the possibility of forming a mark increases. Therefore, it is desirable to change the execution conditions of correction to increase the chances of mark formation.

  In addition, when performing a plurality of types of corrections, the control unit may set a time required for forming correction marks for all corrections to be executed as the mark time. By forming correction marks for all corrections to be executed, it is possible to obtain correction values with higher accuracy than when only some correction marks are to be formed. I can expect.

  The control unit may execute the gamma correction after other corrections when performing a plurality of types of correction including gamma correction. Gamma correction requires higher quality than other corrections. Therefore, when other correction execution conditions are also satisfied, it is preferable to execute the other correction first to ensure a longer stirring time.

  The control unit may execute the mark forming process when the image output unit forms an image to be output on a sheet. When only the mark is formed, it is difficult for the user to be dissatisfied even if the waiting time before the mark formation is long. Therefore, it is desirable that the operation of the present application is an operation for forming an image to be output on a sheet.

  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 that achieves 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. 6 is a flowchart showing a procedure of development preparation processing executed by a printer. It is a flowchart which shows the procedure of the correction process during stirring which a printer performs. It is a timing chart which shows the relationship between a some correction process and mark time. It is a timing chart which shows the relationship between stirring operation, specific stirring time, and mark time in case mark time is settled in specific stirring time.

  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 of this embodiment includes a controller 30 having a CPU 31, a ROM 32, a RAM 33, an NVRAM (Non Volatile RAM) 34, and an ASIC 35. The printer 100 also 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 37 for connecting to an external device. Be controlled. 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.

  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.

  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. A substantially S-shaped transport path 11 (a chain line in FIG. 2) 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. In the sheet conveyance direction, the process units 50C, 50M, 50Y, and 50K are arranged at equal intervals in this order from the downstream side. Note that the order of the process parts is not limited to this.

  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.

  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 printer 100 arranges the mark sensor 25 at a position downstream of the process units 50Y, 50M, 50C, and 50K and upstream of the fixing device 8 in the sheet conveyance direction. Then, the mark sensor 25 detects a correction mark formed on the conveyor belt 7.

  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 27 is determined by the difference between the amount of light received when the correction mark 27 (mark 27 in FIG. 4 is an example of a position deviation correction mark) and the amount of light received directly from the conveyor belt 7. Can be detected.

  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, 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, each color mark elongated in the main scanning direction is arranged side by side in the sub-scanning direction for each color. These marks are read by the mark sensor 25, the interval between the marks is calculated, and the amount of periodic displacement and the amount of displacement between colors are acquired.

  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 a mark with a predetermined density (for example, 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 a development bias correction value for obtaining an ideal density is obtained.

  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 a plurality of marks having different densities at predetermined density intervals (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 the density change characteristic of each color is specified from the relative density relation between the marks. Then, a relative relationship table between the change characteristic and the gradation indicated by the external computer is created.

  As described above, density correction for suppressing density unevenness includes development bias correction and gamma correction. Among them, 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.

  There are a plurality of correction process 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. For example, in the misregistration correction, there are an assumed misregistration amount and a point set for each factor causing misregistration, and each time a factor occurs, a point corresponding to the factor is added to the assumed misregistration amount. Then, the total point is regarded as the current positional deviation amount, and when the total point exceeds the execution threshold, it is determined that the execution condition for positional deviation correction is satisfied. Then, after the misalignment correction is performed, the total points are reset.

  When executing a print job, the printer 100 determines whether the execution conditions for each correction process are satisfied. If the execution condition is satisfied, correction processing that satisfies the execution condition is executed prior to execution of the print job. That is, the correction process is not performed immediately when the execution condition is satisfied, but is performed continuously with the print job when the execution condition of the print job is satisfied.

  If there is a deviation in the density of each mark, the amount of light received by the mark sensor 25 varies even if the marks are formed at the same image forming position. 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.

  Also in gamma correction, if the printer 100 itself has the above-described density shift of all gradations, it is difficult to accurately detect the characteristic change of each color density for each gradation. Therefore, when the gamma correction is executed, the development bias correction is also executed. That is, when the gamma correction execution condition is satisfied, the development bias correction execution condition is also satisfied. The development bias correction is executed before the gamma correction.

  The misregistration correction is a correction for acquiring a correction value by detecting the edge of the mark, and the misregistration correction mark is formed only with the maximum density. Therefore, the accuracy of density for each gradation of the mark is not required. Further, when the mark is formed, the mark itself cannot be formed at a desired density unless the charge amount of the toner is sufficiently secured. As a result, the credibility of the measurement result is low, and if gamma correction is performed based on the measurement result, the expression of light and shade tends to be inappropriate. For this reason, it is preferable that the gamma correction secures the toner charge amount by performing more toner agitation. Therefore, when both the execution conditions of the gamma correction and the positional deviation correction are satisfied, the toner is stirred during the positional deviation correction, and therefore the positional deviation correction is executed before the gamma correction.

Based on the combination of corrections described above, when each correction process satisfies the execution conditions at the same time, it is executed in the following priority order.
1. Development bias correction 2. Misalignment correction Gamma correction

  Next, toner agitation in the developing device 4 will be described. In order for the developing device 4 to stably develop the toner and develop the electrostatic latent image on the photoreceptor 1, it is desirable that the charge amount of the toner in the developing device 4 be a predetermined amount or more. Therefore, in the printer 100, when developing the developing device 4, it is necessary to agitate the toner stored in the toner storage unit 70 of the developing device 4 with the agitator 71 prior to the development. The stirring time required before the start of development is defined as the specific stirring time. This specific stirring time is an example of the stirring time before formation.

  As the specific stirring time described above increases, the possibility that the charge amount of the toner becomes a predetermined amount or more increases, but the start of image formation is delayed. Further, even if stirring is continued more than necessary, the mechanical stress on the toner increases, and the deterioration of the toner such as deformation of the toner particles and embedding of the external additive mixed in the toner proceeds. As a result, the charging characteristics of the toner are deteriorated. Therefore, the printer 100 according to the present embodiment stirs the toner for a specific stirring time at a stage where development is necessary. An appropriate specific stirring time is determined using at least one of the length of the non-stirring time during which the agitator 71 is not stirring, the deterioration state of the toner, and the image to be formed.

  FIG. 5 shows a procedure of development preparation processing, which is a preparatory operation before development performed by the printer 100. The development preparation process is executed by the CPU 31 when the print execution condition is satisfied, such as when a print job is received.

  In the development preparation process, the printer 100 first determines whether or not it is the first image formation after the main body is unpacked (S101). Whether or not it is the first image formation after unpacking the main body can be determined by referring to the value of a flag that is set to ON at the time of the first image formation, for example. 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, by setting the flag to ON after completion of the first image formation, it is possible to determine whether or not it is the first image formation after unpacking the main body based on the value of the flag.

  At the time of shipment, the printer 100 does not store various correction values. Alternatively, only correction values in the test environment before shipment are stored, and there is a possibility that the correction values are inappropriate in the current environment. For this reason, at the time of the first printing after the main body is unpacked, the printer 100 executes all the correction processes including the development bias correction, the positional deviation correction, and the gamma correction. Therefore, in order to form these correction marks in the image forming unit 10, all the execution conditions of the correction process are satisfied when the image is formed for the first time after unpacking the main body. As described above, the mark formation order is the order of development bias correction, positional deviation correction, and gamma correction.

  Further, the process units 50C, 50M, 50Y, and 50K may be shipped with the process units 50C, 50M, 50Y, and 50K attached, and the printer 100 may be used in any environment from when the process units are installed to when the user unpacks them. I can't guess what happened. That is, the toner charge amount decreases with time due to the discharge phenomenon. In addition to mechanical stress due to the agitator 71 and the toner supply roller 62, the toner deteriorates with changes in humidity and temperature when exposed to air for a long time. Therefore, the printer 100 cannot estimate the charge amount of the toner immediately after unpacking the main body. Even if correction processing is performed assuming that the toner is not charged, acquisition of an appropriate correction value cannot be expected depending on the deterioration state of the toner.

  Therefore, if it is the first image formation after the main body is unpacked (S101: YES), it is assumed that the toner is almost not charged and further deteriorated to some extent, and is set in the development preparation process. Among the stirring times, a specific stirring time A that is the longest time is set (S102). Thereby, in each correction process, acquisition of an appropriate correction value can be expected. In this embodiment, the initial value of the specific stirring time is 10 seconds, for example, the specific stirring time A is 30 seconds.

  If it is not the first image formation after the main body is unpacked (S101: NO), it is determined whether or not a new process part has been detected (S111). New article detection can be determined by, for example, detecting the position of the toner container 70 that is mechanically displaced between an unused state and a state where it has been used once. Even when a new product is detected, it is preferable to execute all corrections of development bias correction, misregistration correction, and gamma correction, so that the conditions for executing all correction processes are satisfied.

  If it is new, it is assumed that the toner is not charged. On the other hand, it is presumed that the toner has not deteriorated. Therefore, when a new process part is detected (S111: YES), the stirring time is longer than the initial value of the specific stirring time, and the specific stirring time is shorter than the specific stirring time A described above. B is set (S112). In this embodiment, for example, the specific stirring time B is 20 seconds.

When the specific stirring time A, the specific stirring time B, and the initial value (default value) of the specific stirring time are compared, the following relationship is obtained.
Specific stirring time A> Specific stirring time B> Initial value of specific stirring time

  If no new process part is detected (S111: NO), it is determined whether or not the execution condition of the gamma correction is satisfied (S121). In gamma correction, it is necessary to express the shading of the mark with high accuracy compared to other correction processes. In order to express the shading of the mark with high accuracy, it is necessary to ensure the toner charge amount appropriately. Therefore, when the gamma correction execution condition is satisfied (S121: YES), the specific stirring time B is set (S112).

  If the gamma correction execution condition is not satisfied (S121: NO), it is determined whether the non-stirring time, which is a continuous time during which the agitator 71 is not performing the stirring operation, is shorter than the first threshold time (S131). ). When the non-stirring time is shorter than the first threshold time (S131: YES), it can be estimated that stirring for the specific stirring time has been performed most recently and the toner charge amount is stable. For this reason, the specific stirring time is set to 0 (S132). In this case, image formation is started without stirring for a specific stirring time.

When the non-stirring time is not shorter than the first threshold time (S131: NO), the specific stirring time is calculated and set (S141). Specifically, the specific stirring time is proportional to the length of the non-stirring time as in the following formula (I).
Specific stirring time = α × length of non-stirring time (I)
α is a constant. That is, in S141, it sets so that specific stirring time may become long, so that the length of non-stirring time is long.

  Also, the amount of toner discharge and the amount of water in the toner container 70 differ depending on the temperature and humidity conditions, resulting in variations in the toner charge amount. Therefore, the environmental history may be reflected.

For example, the higher the humidity, the higher the humidity in the toner container. The higher the humidity in the toner container, the easier the toner particles adhere to each other, which can cause deterioration of the toner. As toner deterioration progresses, the variation in the charge amount of each toner increases, and it is necessary to lengthen the specific stirring time in order to secure a stable charge amount. Therefore, the humidity should be reflected in the length of the non-stirring time. Specifically, the humidity history during the non-stirring time may be quantified by integration as in the following formula (II).
Length of non-stirring time = β × ∫ (H · T) dt (II)

  In the formula (II), β is a correction coefficient. H is humidity and T is time. In addition, the average temperature or the average humidity during the non-stirring time may be acquired, and the acquired environmental information may be reflected in the length of the non-stirring time.

  Further, the longer the total stirring time of the agitator 71, the greater the mechanical stress on the toner. When mechanical stress is applied to the toner, deformation of the toner particles, embedding of the external additive mixed in the toner, and the like are likely to occur. That is, the longer the total stirring time, the easier the toner deteriorates. As the toner deterioration progresses, the charging characteristics of the toner worsen. Therefore, it is necessary to stabilize the charge amount by extending the stirring time. Therefore, the length of the non-stirring time may be weighted so that the specific stirring time becomes longer as the total rotation amount of the agitator 71 is larger.

  For the image printed on the sheet, the length of the non-stirring time may be weighted according to the time allowed as the waiting time until the printing starts. For example, when a print job is received via the communication IF 37, it is assumed that the user moves to the printer 100. Therefore, the time allowed as a waiting time until the start of printing is long. On the other hand, when receiving via the operation unit 40, it is assumed that the user is in front of the printer 100. Therefore, the time allowed for the waiting time until the start of printing is short. Therefore, when the time allowed as the waiting time until the start of printing is long based on the interface that has accepted the print job, the specific agitation time may be weighted.

  Further, the length of the non-stirring time may be weighted based on the required quality. That is, when printing in the high quality mode is required, it is necessary to further stabilize the charge amount of the toner. Therefore, you may add specific stirring time so that specific stirring time may become longer than non-high-quality mode.

  After S102, S112, S132, or S141, stirring by the agitator 71 is started (S151). After S151, an agitation correction process for forming correction marks as necessary during the specific agitation time is executed (S152).

  FIG. 6 shows the procedure of the correction process during stirring in S152. In the correction processing during stirring, first, it is determined whether or not the previously determined specific stirring time is longer than the second threshold time (S161). When the specific stirring time is longer than the second threshold time (S161: YES), the specific agitation time is changed so as to easily satisfy the execution condition of the correction process (S162). S162 is an example of a change process.

  When the specific stirring time is long, there is a high possibility that a correction mark can be formed during the specific stirring time. For this reason, the execution conditions of the correction process are easily satisfied, and the opportunities for executing the correction process are increased. As a method for easily satisfying the execution condition of the correction process, for example, when comparing the assumed positional deviation amount and the execution threshold as in the case of positional deviation correction, the execution threshold may be lowered. Alternatively, a certain amount of the assumed positional deviation amount may be added. Note that the change in S162 is temporary. Therefore, if the correction process during stirring is completed without executing the correction process, the changed value is restored.

  After S162, or when the specific stirring time is not longer than the second threshold time (S161: NO), it is determined whether or not the execution condition of the correction process is satisfied (S171). If the execution condition for the correction process is satisfied, the printer 100 changes the correction flag stored in the NVRAM 34 to ON. Then, after executing the correction process, the correction flag is changed to off. In S171, it is determined whether or not the execution condition of the correction process is satisfied depending on whether the correction flag is on or off. In S171, if any one of the positional deviation correction, the development bias correction, and the gamma correction satisfies the execution condition, it is determined that the correction processing execution condition is satisfied. If none of the conditions for executing the correction process is satisfied (S171: NO), the correction process during stirring is terminated without forming a mark.

  When at least one correction process execution condition is satisfied (S171: YES), a mark agitation time, which is the agitation time necessary for the correction mark, is calculated for the correction process that satisfies the execution condition. (S172). The agitation time for ensuring the quality of the mark is also required in forming the mark. The agitation time for the mark, which is ensured before the formation of the mark, separately from the specific agitation time for the print job determined earlier. Calculate The mark stirring time can be obtained by, for example, the above-described formula (I). However, the mark is an image that is not provided to the user, and it is sufficient that the minimum quality necessary for obtaining the correction value is ensured. Therefore, the required image quality is lower than the image printed on the sheet. That is, a smaller value is applied to the constant α.

  In addition, the positional deviation correction need only be able to determine the presence or absence of a mark, and does not need to accurately determine the density of the mark. Therefore, the misregistration correction does not have to have a high image quality as compared with the density correction such as the development bias correction and the gamma correction.

  Further, the gamma correction mark is set so that the toner consumption is larger and the execution opportunity is smaller than the development bias correction and misalignment correction marks. Therefore, it is predicted that the correction value once acquired is used for image formation many times. In addition, the accuracy of the density of the mark required for obtaining an accurate correction value is high. Therefore, for the mark for gamma correction, the value of α is changed so that the stirring time becomes longer even when compared with the development bias correction.

That is, the printer 100 changes the value of α so that the length of the mark stirring time corresponding to each correction mark satisfies the following relationship. The mark stirring time is an example of the stirring time before mark formation.
Gamma correction mark> Development bias correction mark> Misalignment correction mark

  After the mark agitation time is calculated in S172, a mark time that is the sum of the mark agitation time and the mark formation time that is the time for forming the mark in the image forming unit 10 is calculated (S173). ).

  When there are a plurality of correction processes satisfying the execution condition, the mark time is the time required for forming correction marks for all corrections to be executed. Specifically, when a plurality of correction processes are performed, the toner is stirred even during the mark time of the preceding correction process. Therefore, the stirring time necessary for the subsequent correction process is the difference between the mark time of the preceding correction process and the mark stirring time of the subsequent correction process.

  That is, as shown in FIG. 7A, when the mark time of the preceding correction process is longer than the mark agitation time of the subsequent correction process, while waiting for completion of mark formation of the preceding correction process. The mark agitation time for subsequent correction processing has elapsed. Thus, the mark formation for the subsequent correction process can be started immediately after the completion of the mark formation for the preceding correction process. Therefore, the mark time calculated in S173 is a time obtained by adding the mark formation time of the subsequent correction process to the mark time of the previous correction process.

  On the other hand, as shown in FIG. 7B, when the mark time of the preceding correction process is shorter than the mark agitation time for the subsequent correction process, the subsequent correction process waits for the difference time to elapse. Start mark formation. Therefore, the mark time calculated in S173 is the time obtained by adding the above-described difference time, the mark time of the preceding correction process, and the mark formation time of the subsequent correction process, that is, the mark time of the subsequent correction process. Become.

  After S173, it is determined whether the specific stirring time is longer than the mark time (S174). That is, it is determined whether or not the mark time is within the specific stirring time. S174 is an example of determination processing. If the specific stirring time is not longer than the mark time (S174: NO), the correction process during stirring is terminated without forming a mark.

  If the specific stirring time is longer than the mark time (S174: YES), the correction process that satisfies the execution condition can be completed within the specific stirring time. Therefore, the start timing of the correction process that satisfies the execution condition within the specific stirring time is determined (S181).

  Specifically, in S181, the start time of the mark time is determined based on the end time of the specific stirring time. That is, the longer the agitation time before mark formation, the more stable the image quality of the mark. Therefore, the start time of the mark time is determined so that the mark time is behind the specified stirring time.

  FIG. 8 shows the relationship between the stirring operation, the specific stirring time, and the mark time when the mark time falls within the specific stirring time. A period AB in FIG. 8 is a period from when the stirring operation is started in response to satisfying the printing execution condition until the rotation speed is stabilized. Further, a period DE in FIG. 8 is a margin that assumes an actual mark time variation. When no margin is provided, the period DE is not necessary. A period EF in FIG. 8 is a period for forming a print image.

  At the time of S181, the length of the mark time (period CD in FIG. 8) and the end timing of the specific stirring time (E in FIG. 8) are known. Therefore, a time that is traced back by the margin DE and the mark time CD from the end timing E of the specific stirring time is defined as a mark time start timing C. In this embodiment, when the difference between the specific stirring time length BE and the mark time length CD is greater than twice the margin DE, the time length from the start of the specific stirring time to the start of the mark time. BC becomes longer than the margin DE, that is, the time length DE from the end of the mark time to the end of the specific stirring time.

  After determining the start time of the mark time in S181, it is determined whether or not the start time of the mark time has been reached (S182). If the mark time start timing has not been reached (S182: NO), the process waits until the mark time start timing is reached. Then, when the mark timing start timing is reached (S182: YES), correction processing is started (S183). That is, the mark formation is started after waiting for the mark stirring time. Thereby, the stirring of the toner within the specific stirring time and the formation of the mark are performed in parallel. S183 is an example of a mark formation process. After S183, the agitation correction process is terminated.

  Returning to FIG. 5, after S152, it is determined whether or not stirring for the set specific stirring time is completed (S153). When the stirring for the specific stirring time is not completed (S153: NO), the process waits until the stirring for the specific stirring time is completed.

  When the stirring for the specific stirring time is completed (S153: YES), it is determined whether or not the execution condition of the correction process is satisfied (S154). In S154, although the execution condition of the correction process is satisfied at the start of the development preparation process, if the correction process is not executed during the correction process during stirring in S152, the execution condition of the correction process is satisfied. To be judged. In the correction process executed during the correction process during agitation in S152, the parameters for determining the execution condition of the correction process are initialized, so there is a high possibility that the execution condition of the correction process is not satisfied.

  If the execution condition for the correction process is satisfied (S154: YES), a mark is formed for the correction that satisfies the execution condition (S155). That is, in the printer 100, when the mark time does not fit within the specific stirring time, the mark is formed after the stirring for the specific stirring time is completed.

  When the execution condition of the correction process is not satisfied (S154: NO), or when the mark formation is completed in S155, formation of an image to be printed on the sheet is started (S156). That is, printing of the print job is started. Even after the specific agitation time has elapsed, the agitation operation continues with the image formation for printing, and therefore the end of the agitation operation is after completion of the image formation for printing. After S156, the development preparation process is terminated.

  As described above in detail, in the printer 100 according to the present embodiment, if the correction mark can be formed within the specific stirring time, the correction mark is formed within the specific stirring time. Thus, toner stirring and mark formation are simultaneously performed within the specific stirring time. As a result, the image formation based on the correction value obtained from the mark can be started earlier as compared with the case where the correction mark is formed after the specific stirring time has elapsed.

  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 image forming apparatus is not limited to a printer, but can be applied to any apparatus having a printing function, such as a copier, a FAX apparatus, or a multifunction machine. Further, the printer 100 according to the embodiment is a color printer and includes the process units 50C, 50M, 50Y, and 50K corresponding to the respective colors, but may be a monochrome printer including one process unit.

  In the embodiment, the specific agitation time is determined by a plurality of determinations of S101, S111, S121, and S131, but it is not necessary to make all of these determinations. That is, by performing at least one of these determinations, it can be expected to secure an appropriate specific stirring time as compared with a case where the specific stirring time is uniform.

  In the embodiment, the specific stirring time is variable according to the determination in S101, S111, S121, and S131. However, the specific stirring time may be fixed. Also, the stirring time for the mark is variable depending on the type of the mark, but may be fixed regardless of the type of the mark.

  In the embodiment, when the specific agitation time is long, the correction is performed so that the correction condition is easily satisfied.

  In the embodiment, if the mark time does not fit within the specified stirring time, the mark is formed after the stirring for the specified stirring time is completed, and an image to be printed on the sheet is formed after the mark is formed. However, printing may be prioritized, and after the stirring for a specific stirring time is completed, an image to be printed on the sheet may be formed, and the mark may be formed after the image is formed. In addition, it is not always necessary to form a mark. If the mark time does not fit within the specified stirring time, the mark is not formed in the development preparation process, and the preparation for development when the mark time falls within the specified stirring time. You may make it perform within a process.

  In the embodiment, in the correction process performed when the printing conditions are satisfied, the mark is formed within the specific stirring time for the print image, but another image is formed within the specific stirring time. For example, it is not limited to this. For example, as described above, the required mark agitation time differs depending on the type of mark, so it can also be applied to the case of forming a position correction mark within the agitation time required for the gamma correction mark. It is.

  If there is no relation between the printing conditions and the correction process, there is a possibility that the correction is performed a plurality of times even though printing is not performed. In such a case, the correction performed previously is useless. Further, when only the mark is formed, it is difficult for the user to be dissatisfied even if the waiting time before the mark is formed is long. Therefore, in order to suppress wasteful toner consumption, it is preferable to include the fact that the printing condition is satisfied in the execution condition of the correction process.

  Further, in the embodiment, when a plurality of correction processing execution conditions are satisfied, if correction marks for all corrections to be executed can be formed, the marks are formed within a specific stirring time. However, if some of the marks can be formed within the specified stirring time, the marks may be formed. In this case, the remaining marks may be formed prior to the formation of the image to be printed after the specific stirring time is completed, or may be formed after the image to be printed is formed.

  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.

1 Photosensitive member 4 Developing device 31 CPU
70 Toner container 71 Agitator 100 Printer

Claims (17)

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 control unit;
With
The controller is
It is determined whether or not a mark time, which is a time required for forming a correction mark, falls within a pre-formation stirring time that is a time for stirring the toner by the stirring unit before forming an image in the image forming unit. Judgment processing,
A mark forming process for forming the mark in the image forming unit within the pre-formation stirring time on condition that the mark time is determined to be within the pre-formation stirring time in the determination process;
An image forming apparatus characterized in that The image forming apparatus according to claim 1,
The mark time includes
A mark formation time which is a time for forming a mark in the image forming unit;
Agitation time before mark formation, which is a time for stirring the toner in the stirring unit before forming the mark in the image forming unit;
An image forming apparatus. The image forming apparatus according to claim 2,
The agitation time before the mark formation varies depending on the type of the mark and is a time corresponding to the mark to be formed in the image forming unit. The image forming apparatus according to claim 3,
There are two types of marks: gamma correction marks and development bias correction marks.
The image forming apparatus characterized in that the stirring time before mark formation before the mark for gamma correction is formed is longer than the stirring time before mark formation before the mark for correcting the development bias is formed. . The image forming apparatus according to claim 3 or 4, wherein:
There are two types of marks: gamma correction marks and misalignment correction marks.
The image forming apparatus characterized in that the stirring time before mark formation before the gamma correction mark is formed is longer than the stirring time before mark formation before the misalignment correction mark is formed. . The image forming apparatus according to any one of claims 1 to 5,
The controller is
An image forming apparatus, wherein the start time of the mark time is determined based on the end time of the pre-formation stirring time. The image forming apparatus according to any one of claims 1 to 6,
The controller is
An image formation characterized in that a time length from the start of the pre-formation stirring time to the start of the mark time is longer than a time length from the end of the mark time to the end of the pre-formation stirring time apparatus. In the image forming apparatus according to any one of claims 1 to 7,
The image forming apparatus, wherein the pre-formation stirring time is longer as the non-stirring time, which is a continuous time in which the stirring unit is not stirred before the start of the pre-formation stirring time, is longer. In the image forming apparatus according to any one of claims 1 to 8,
The image forming apparatus, wherein the pre-formation stirring time varies depending on a required image quality of an image to be formed. The image forming apparatus according to any one of claims 1 to 9,
The image forming apparatus, wherein the pre-formation stirring time varies depending on at least one of humidity and temperature. In the image forming apparatus according to any one of claims 1 to 10,
The controller is
An image forming apparatus that executes the mark forming process when a correction execution condition is satisfied. The image forming apparatus according to claim 11,
The controller is
An image forming apparatus, wherein when the pre-formation stirring time is longer than a predetermined time, a change process is executed to change the correction execution condition easily. The image forming apparatus according to any one of claims 1 to 12,
The controller is
An image forming apparatus characterized in that when a plurality of types of correction are executed, a time required for forming a correction mark for all corrections to be executed is set as the mark time. The image forming apparatus according to any one of claims 1 to 13,
The controller is
An image forming apparatus, wherein when performing a plurality of types of correction including gamma correction, the gamma correction is executed after other corrections. The image forming apparatus according to any one of claims 1 to 14,
The controller is
An image forming apparatus that executes the mark forming process when an image to be output on a sheet is formed in the image forming unit. In an image forming method of an image forming apparatus for forming an image using toner stored in a container,
A determination step of determining whether or not a mark time that is a time required for forming a correction mark is within a stirring time before forming that is a time for stirring the toner in the container before forming an image;
A mark forming step of forming the mark within the pre-formation stirring time, provided that the determination step determines that the mark time is within the pre-formation stirring time;
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;
In an image forming apparatus comprising
It is determined whether or not a mark time, which is a time required for forming a correction mark, falls within a pre-formation stirring time that is a time for stirring the toner by the stirring unit before forming an image in the image forming unit. Judgment processing,
A mark forming process for forming the mark in the image forming unit within the pre-formation stirring time on condition that the mark time is determined to be within the pre-formation stirring time in the determination process;
A storage medium for storing a program for executing the program.

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