JP2013182065A - Image forming apparatus and image forming program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrict a density change, compared to the case where a limited range of the amount of density correction is fixed.SOLUTION: An image forming apparatus comprises: image forming means configured to form a toner image corresponding to an image on a target transfer body; control means for controlling the image forming means so as to form a density control image with a predetermined density onto the target transfer body; a density sensor configured to detect the density of the density control image transferred onto the target transfer body; density correction means configured to correct density within a set limited range of an amount of correction so that the density of the density control image read by the density sensor reaches the predetermined density; and setting means configured to set the limited range of the amount of correction on the basis of the result of density correction performed by the density correction means in the past predetermined period.

Description

  The present invention relates to an image forming apparatus and an image forming program.

  According to Patent Document 1, a color image by a plurality of color toners is formed by performing charging, exposure, development by a plurality of developing units, and transfer to an image carrier a plurality of times in response to an image information signal. In the multicolor image forming apparatus to be formed, a storage unit provided inside each developing device for storing the total number of printed sheets, a density measuring unit for measuring the density of the toner image for density measurement, and measurement by the density measuring unit A multicolor comprising: an image density adjusting unit that controls an image forming condition according to a result; and a unit that adjusts an operation interval of the image density adjusting unit with reference to a total number of printed sheets stored in the storage unit An image forming apparatus is described.

  In Patent Document 2, prior to image formation, a plurality of density detection toner images visualized by changing image formation conditions are read by the density detection means, and the image formation is performed based on the read density data. An image forming apparatus having a control means for setting optimum image forming conditions is provided with a developing means that can be attached to and detached from the image forming apparatus main body, and the developing means is configured to control the image density. An image forming apparatus including a non-volatile memory storing at least a part of the data is described.

JP-A-10-186769 JP 2003-35979 A

  It is an object of the present invention to provide an image forming apparatus and an image forming program capable of suppressing density fluctuations as compared with a case where the limit range of the density correction amount is fixed.

  The image forming apparatus according to the first aspect of the present invention includes an image forming unit that forms a toner image corresponding to an image on the transfer target, and a density control image having a predetermined density formed on the transfer target. Control means for controlling the image forming means, a density sensor for detecting the density of the density control image transferred onto the transfer target, and the density of the density control image read by the density sensor Is based on the result of density correction performed by the density correction unit in the past predetermined period. Setting means for setting a limit width of the correction amount.

  According to a second aspect of the present invention, the setting means sets the limit width of the correction amount based on the length of time that has elapsed since the density correction performed previously by the density correction means.

  According to a third aspect of the present invention, the setting unit sets the limit amount of the correction amount so that the limit amount of the correction amount becomes smaller as the time elapsed from the density correction performed by the density correction unit last time becomes shorter. Set.

  According to a fourth aspect of the present invention, the setting unit sets a limit width of the correction amount based on a correction amount of density correction executed by the density correction unit in the predetermined period.

  According to a fifth aspect of the present invention, when the density correction direction executed by the density correction unit in the predetermined period alternately repeats an increasing direction and a decreasing direction, the setting unit sets the correction amount. The limit width of the correction amount is set so that the limit width is small.

  According to a sixth aspect of the invention, an image forming program causes a computer to function as the density correction unit and the setting unit of the image forming apparatus according to any one of the first to fifth aspects.

  According to the first and sixth aspects of the present invention, the density variation can be suppressed as compared with the case where the limit range of the density correction amount is fixed.

  According to the second and third aspects of the present invention, the density fluctuation is suppressed compared to the case where the limit range of the density correction correction amount is fixed regardless of the length of time elapsed since the previous density correction. Has the effect of being able to.

  According to the fourth and fifth aspects of the present invention, the density fluctuation is compared with the case where the limit range of the density correction correction amount is fixed regardless of the density correction correction amount executed in the past predetermined period. It has the effect that it can suppress.

1 is a diagram illustrating a schematic configuration of an image forming apparatus. FIG. 2 is a diagram illustrating a schematic configuration inside an image forming apparatus main body. 1 is a block diagram illustrating a configuration of a main part of an electric system of an image forming apparatus according to an embodiment. It is a flowchart which shows the flow of the density correction process which concerns on 1st Embodiment. It is a figure which shows an example of a correction coefficient. (A) is a figure for demonstrating the execution timing and correction amount of density correction which concern on 1st Embodiment, (B) is a figure which shows the density fluctuation | variation which concerns on 1st Embodiment. FIG. 6 is a diagram for explaining a charging potential, an exposure potential, a developing bias potential, and a differential potential. It is a flowchart which shows the flow of the density correction process which concerns on 1st Embodiment. (A) is a figure for demonstrating the execution timing and correction amount of density correction which concern on 1st Embodiment, (B) is a figure which shows the density fluctuation | variation which concerns on 1st Embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In the following, an embodiment in which the present invention is applied to an image forming apparatus having a copy function and a print (print) function will be described.

  (First embodiment)

  FIG. 1 shows a schematic configuration of an image forming apparatus 10 according to the present embodiment.

  The image forming apparatus 10 reads an image from a document placed at a reading position, acquires image information indicating the image, and image information acquired by the scanner 12, or based on image information acquired from the outside. An image is formed on the apparatus main body 14 that performs the forming process, a touch panel display (hereinafter referred to as “display”) 16 that displays an operation menu, a message, and the like and that is integrally provided with a transmissive touch panel on the surface. And a plurality of paper feed units 20 in which the paper P before forming an image is stored. The paper discharge unit 18 holds paper P (see also FIG. 2) discharged from the apparatus main body 14.

  Each paper feed unit 20 has a variable size of the paper P to be accommodated by adjusting the position of an internal partition member or the like. Each sheet feeding unit 20 accommodates a plurality of sheets P stacked.

  Note that the image forming apparatus 10 according to the present embodiment employs a pressure-sensitive touch panel as the touch panel, and forms an image when the user touches the display surface of the display 16 with a fingertip (touch operation). Various operations are instructed to the apparatus 10.

  Next, a schematic configuration inside the apparatus main body 14 will be described with reference to FIG.

  The apparatus main body 14 according to the present embodiment includes an image forming engine unit 22 that forms an image on a sheet P by an electrophotographic method.

  The image forming engine unit 22 according to the present embodiment includes four image forming units 24Y, 24M, 24C, and 24K. The image forming units 24 are arranged at predetermined intervals along the longitudinal direction of the intermediate transfer belt 26. The intermediate transfer belt 26 is wound around a plurality of winding rollers 28 and a roller 46A of a second transfer device 46 described later, and is formed in an endless belt shape that is conveyed in the direction of arrow E in FIG.

  The image forming unit 24Y corresponds to yellow (Y), the image forming unit 24M corresponds to magenta (M), the image forming unit 24C corresponds to cyan (C), and the image forming unit 24K corresponds to black (K). An image of each corresponding color is formed. In FIG. 2, an alphabet (Y / M / C / K) indicating a color corresponding to the end of the code is given, but in the following, this alphabet at the end of the code is omitted unless the color is particularly distinguished. I will explain.

  The image forming unit 24 is provided with a cylindrical photosensitive drum 30 that is rotationally driven at a predetermined rotational speed in the direction of arrow F in FIG.

  As shown in FIG. 2, a charger 36 that uniformly charges the surface of the photosensitive drum 30 is disposed around each photosensitive drum 30. Charging of the photosensitive drum 30 by the charger 36 is the first stage of a series of image forming processes. Further, a light beam based on a desired image is irradiated on the downstream side of the charger 36 along the rotation direction of each photosensitive drum 30 in the axial direction of the photosensitive drum 30 uniformly charged by the charger 36. An optical scanning device 38 for forming an electrostatic latent image is disposed on the photosensitive drum 30.

  Further, there are colors around the photosensitive drums 30 that are respectively responsible for the electrostatic latent images formed on the photosensitive drums 30 on the downstream side of the optical scanning device 38 along the rotation direction of the photosensitive drums 30. A developing device 40 is provided that develops each color image by developing with (yellow / magenta / cyan / black) toner. A contact point with the intermediate transfer belt 26 is located downstream of the developing unit 40, and a first transfer unit 42 is disposed. The first transfer device 42 is applied with a predetermined voltage to transfer the image on the photosensitive drum 30 to the intermediate transfer belt 26.

  Images of different colors formed on the respective photosensitive drums 30 are transferred onto the intermediate transfer belt 26 so as to overlap each other on the belt surface of the intermediate transfer belt 26 (in the same region). As a result, a color image is formed on the intermediate transfer belt 26.

  A density sensor 44 for detecting the density of the image is provided on the downstream side in the transport direction (the direction of arrow E in FIG. 2) from the transfer position of the image on the intermediate transfer belt 26 by the photosensitive drum 30K.

  A second transfer unit 46 including a pair of rollers 46A and 46B is disposed on the downstream side of the intermediate transfer belt 26 with respect to the density sensor 44 in the transport direction.

  The paper P stored in the paper supply unit 20 (see FIG. 1) is fed out one by one by the paper feed unit 48. The fed paper P is once conveyed to the alignment roll 52 via the paper conveyance path 50 and stopped, and the second transfer device is synchronized with the color image on the intermediate transfer belt 26 by the alignment roll 52. The second transfer unit 46 transfers the color image on the intermediate transfer belt 26 onto the paper P in a batch (secondary transfer). The sheet P on which the color image has been transferred is conveyed to a fixing device 54 where the image is fixed (heating, pressing, etc.). As a result, the image is fixed on the paper P, and a desired image is formed on the paper P. The paper P on which the image is formed is discharged to the discharge unit 18 via the discharge roll 56.

  Each photosensitive drum 30 is prepared for the next image forming process by removing residual toner and the like by the cleaning device 60 after the image transfer process is completed. In addition, residual toner, paper dust, and the like are removed from the intermediate transfer belt 26 by a belt cleaner 62 disposed downstream of the second transfer unit 46.

  Next, with reference to FIG. 3, the main configuration of the electrical system of the image forming apparatus 10 according to the present embodiment will be described.

  The image forming apparatus 10 includes a CPU (Central Processing Unit) 100 that controls the operation of the entire apparatus, a ROM (Read Only Memory) 102 as a storage medium in which various programs including a density correction amount calculation program to be described later are stored, and the like. A RAM (Random Access Memory) 104 that temporarily stores various data, a non-volatile memory 106 that stores various information including sheet-by-sheet interval information, which will be described later, and a display that controls the display of various information on the display 16 A control I / O 110 that detects a touch operation on the display 16 and a communication I / O that is connected to the network NET and transmits / receives information to / from an external terminal device (for example, a personal computer) via the network NET. F section 112 is provided.

  In addition, the image forming apparatus 10 controls the image forming control unit 114 that controls the image forming process performed by the image forming engine unit 22 described above, the sheet feeding unit 48, the alignment roll 52, and the discharge roll 56 to convey the sheet P. A conveyance control unit 116 for controlling the operation.

  The CPU 100, the ROM 102, the RAM 104, the nonvolatile memory 106, the display control unit 108, the operation input detection unit 110, the communication I / F unit 112, the image formation control unit 114, and the conveyance control unit 116 are mutually connected via the system bus BUS. It is connected. Therefore, the CPU 100 controls access to the ROM 102, RAM 104, and nonvolatile memory 106, displays various information such as operation screens and various messages on the display 16 via the display control unit 108, and a communication I / F unit. Control of transmission / reception of information to / from an external terminal device via 112, control of operation of the image formation engine unit 22 via the image formation control unit 114, and control of conveyance of the paper P via the conveyance control unit 116. Do each.

  Further, the CPU 100 grasps the operation content for the display 16 based on the operation information detected by the operation input detection unit 110, and the operation state of the image formation engine unit 22 based on various information derived by the image formation control unit 114. To figure out.

  Further, a density sensor 44 is further connected to the system bus BUS. Therefore, the CPU 100 grasps the density of the image detected by the density sensor 44.

  The image forming control unit 114 controls each image forming unit 24 (24Y, 24M, 24C, 24K) to form an image.

  Next, density correction processing will be described as an operation of the image forming apparatus 10 according to the present embodiment.

  FIG. 4 shows a flowchart showing the flow of processing of the density correction processing program executed by the CPU 100. Note that the program is stored in advance in the nonvolatile memory 106 as an example. The density correction process is the same for each color of Y, M, C, and K.

  The CPU 100 reads and executes a density correction processing program stored in the nonvolatile memory 106 at a predetermined timing. Note that the predetermined timing for executing the density correction processing is, for example, when the number of prints reaches a predetermined number before the print processing is started or after the print processing is completed. In this case, for example, when density correction processing is performed every time one printing process is completed, and when the number of printed sheets is different for each printing process, the density correction timing does not become a constant time interval. Even if the number of printed sheets is the same, the time required for the printing process varies depending on whether or not post-processing such as punching processing or stapling processing is performed depending on the printing processing, so the density correction timing does not become a fixed time interval. When the density correction timing is different as described above, the density correction cannot be performed properly if the correction amount of the density correction is constant.

  Therefore, in the present embodiment, the limit range of the correction amount is set based on the length of time that has elapsed since the previous density correction. Specifically, the correction amount limit width is set so that the correction amount limit width becomes smaller as the time elapsed since the previous density correction is shortened.

  Note that the CPU 100 stores the execution time in the nonvolatile memory 106 each time the density correction process shown in FIG. 4 is executed.

  First, in step 100, the time when the previous density correction was performed is read from the nonvolatile memory 106, and the elapsed time from the read time is calculated.

  In step 102, a density correction limit width is set according to the elapsed time. Specifically, for example, a predetermined normal correction amount limit width is in a range of ± TH, a correction coefficient corresponding to the elapsed time is a, and a corrected correction amount limit width is ± (TH × a). Set. FIG. 5 shows an example of the correction coefficient a. As shown in the figure, the correction coefficient a is set such that the correction coefficient becomes smaller as the elapsed time from the previous density correction becomes shorter. This is because if the time has not passed so much since the previous density correction, the developer characteristics have not changed so much, so if the limit of the correction amount is increased, it will be overcorrected. It is because it may become. In the example of FIG. 5, the correction coefficient a is 0.5 when the elapsed time from the previous density correction is 120 seconds or less, and the correction coefficient a is 0.1 when the elapsed time exceeds 120 seconds and 180 seconds or less. 7. The correction coefficient a is set to 1.0 when the time exceeds 180 seconds and 240 seconds or less, and the correction coefficient a when the time exceeds 240 seconds is set to 1.2.

  FIG. 6A shows an example of the setting of the correction coefficient a and the variation of the correction amount. FIG. 2B shows an example of density variation. As shown in FIG. 5A, when the operation of the image forming apparatus 10 is started from the time t1, the correction coefficient a is set to 1.0 and is set to the normal correction amount limit width TH. When the density correction is executed at the time t2, 180 seconds have passed since the time t1 when the previous density correction was executed. Therefore, as shown in FIG. 6, the correction coefficient a is set to 0.7. Is done. Next, when the density correction is executed at the time t3, 300 seconds have elapsed from the time t2 when the previous density correction was executed, so that the correction coefficient a is 1.2 as shown in FIG. Is set. Next, when the density correction is executed at the time t4, since 120 seconds have elapsed since the time t3 when the previous density correction was executed, the correction coefficient a is set to 0.5 as shown in FIG. Is set. Next, when density correction is executed at time t5, 240 seconds have passed since time t4 when the previous density correction was executed, so that the correction coefficient a is set to 1.0 as shown in FIG. Is set. Next, when the density correction is executed at the time t6, since 360 seconds have passed since the time t5 when the previous density correction was executed, the correction coefficient a is 1.0 as shown in FIG. Will remain.

  In step 104, the image forming control unit 114 is instructed to form a density control image on the intermediate transfer belt 26. As a result, the image formation control unit 114 controls the image formation engine unit 22 to form a density control image on the intermediate transfer body belt 26. This density control image is a solid image having a predetermined density (for example, 80%).

  In step 106, the density control image formed on the intermediate transfer belt 26 is read by the density sensor 44.

  In step 108, a correction amount for density correction is calculated based on the density difference between the density of the density control image read by the density sensor 44 and a predetermined density. As a density correction method, for example, there is a method of controlling the potential on the photosensitive drum 30.

  This will be specifically described below. As shown in FIG. 7, the surface potential of the photosensitive drum 30 is uniformly set to the charging potential VH by applying a charging voltage to the charger 36. When the photosensitive drum 30 uniformly charged by the charger 36 is irradiated with a light beam based on a desired image, the potential of the region irradiated with the light beam is an exposure potential VL corresponding to the exposure amount. Become. Then, by applying a developing bias voltage to the developing device 40, the potential of a developing roll (not shown) in the developing device 40 becomes the developing bias potential VB. By controlling the potential difference (development contrast) Vdev between the development bias potential VB and the exposure potential VL, the development amount is adjusted and the density is adjusted. The differential potential Vdev is changed by controlling at least one of a charging voltage applied to the charger 36, an exposure amount of the light beam irradiated by the optical scanning device 38, and a developing bias voltage applied to the developing device 40. . In this case, the correction amount of the difference potential Vdev according to the density difference between the density of the density control image read by the density sensor 44 and the predetermined density, that is, the density of the density control image read by the density sensor 44 is determined in advance. The correction amount of the differential potential Vdev is calculated so as to obtain a different density. The density correction may be performed by correcting the pixel value. In this case, the correction amount of the pixel value corresponding to the density difference between the density of the density control image read by the density sensor 44 and the predetermined density, that is, the density of the density control image read by the density sensor 44 is predetermined. The amount of correction of the pixel value that gives the density is calculated.

  In step 110, it is determined whether or not the correction amount calculated in step 108 is within the range of the limit width ± (TH × a) set in step 102. If the correction amount calculated in step 108 is within the range of the limit width ± (TH × a) set in step 102, the process proceeds to step 112. If it is out of the range, the process proceeds to step 114. To do.

  In step 112, density correction is executed with the correction amount calculated in step. On the other hand, in step 114, the correction amount is within the range of the correction amount limit width ± (TH × a) set in step 102, for example, the upper limit value + (TH × a) or the lower limit value− (TH × a). Change the correction amount and perform density correction.

  As described above, in this embodiment, the correction amount limit width is set so that the correction amount limit width becomes smaller as the time elapsed since the density correction performed last time becomes shorter.

  (Second Embodiment)

  Next, a second embodiment will be described. In addition, the same code | symbol is attached | subjected about the same part as 1st Embodiment, and the detailed description is abbreviate | omitted. Since the image forming apparatus according to the present embodiment is the same as that of the first embodiment, description thereof is omitted. Next, density correction processing will be described as an operation of the image forming apparatus 10 according to the present embodiment.

  FIG. 4 shows a flowchart showing the flow of processing of the density correction processing program executed by the CPU 100. Note that the program is stored in advance in the nonvolatile memory 106 as an example. The density correction process is the same for each color of Y, M, C, and K.

  The process of FIG. 8 differs from the process of FIG. 4 described in the first embodiment in the process of setting the correction amount limit width, that is, the processes of steps 100A and 102A. The other steps are the same as those in FIG. Each time the CPU 100 executes the density correction processing shown in FIG. 4, the CPU 100 stores the correction amount and time of the density correction performed in the nonvolatile memory 106.

  As shown in FIG. 8, in step 100A, the correction amount of the density correction amount executed in the past predetermined period is read from the nonvolatile memory 106.

  In step 102A, a density correction limit width is set based on the correction amount of the density correction amount executed in the past predetermined period. Specifically, for example, when the direction of density correction executed in a predetermined period in the past repeats alternately an increasing direction and a decreasing direction, the correction amount limit is set so that the correction amount limit width becomes small. Set the width.

  FIG. 9A shows an example of the setting of the correction coefficient a and the variation of the correction amount. FIG. 2B shows an example of density variation. As shown in FIG. 5A, when the operation of the image forming apparatus 10 is started from the time t1, the correction coefficient a is set to 1.0 and is set to the normal correction amount limit width TH. For example, when a past predetermined period has elapsed at time t5, the density correction direction is alternately repeated from the increasing direction to the decreasing direction and from the decreasing direction to the increasing direction in the period from t1 to t4. In this case, since the direction of density correction is frequently switched, it may be overcorrected. Therefore, as shown in FIG. 6A, at the time t5, the correction coefficient a is decreased from the normal 1.0 to 0.5. That is, the limit range of the correction amount is reduced.

  As described above, in this embodiment, when the direction of density correction in the past predetermined period alternately repeats the increasing direction and the decreasing direction, the correction amount Set the limit width.

  In this embodiment, the case where the density sensor 44 is provided on the intermediate transfer belt 26 has been described. However, the present invention is not limited to this. For example, each photoconductor drum 30 may be provided with a density sensor. Further, for example, the density control image may be transferred to the paper P, and the density of the image transferred onto the paper P may be detected by the scanner 12.

  4 and 8 according to the above embodiment are stored in advance in a nonvolatile memory 106, in addition to a form stored in advance in a storage element such as the ROM 102, an HDD (hardware Distributed in a storage device such as a disk drive, provided in a state stored in a computer-readable storage medium such as a CD-ROM or DVD-ROM, or wired or wireless communication means You may apply to a form etc.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Scanner 14 Apparatus main body 16 Display 18 Discharge part 20 Paper feed part 22 Image formation engine part 24 Image formation unit 26 Intermediate transfer body belt 30 Photosensitive drum 36 Charger 38 Optical scanning device 40 Developer 42 Transfer device 44 Density sensor 46 Transfer device 48 Paper feed portion 54 Fixing device 56 Discharge roll 60 Cleaning device

Claims (6)

Image forming means for forming a toner image corresponding to the image on the transfer member;
Control means for controlling the image forming means so that a density control image having a predetermined density is formed on the transfer member;
A density sensor that detects the density of the density control image transferred onto the transfer target;
Density correction means for correcting the density within a range of a set correction amount limit so that the density of the density control image read by the density sensor approaches the predetermined density;
Setting means for setting a limit width of the correction amount based on a result of density correction executed by the density correction means in a past predetermined period;
An image forming apparatus. The image forming apparatus according to claim 1, wherein the setting unit sets a limit width of the correction amount based on a length of time that has elapsed since the density correction performed previously by the density correction unit. The image according to claim 2, wherein the setting unit sets the correction amount limit width so that the correction amount limit width becomes smaller as the time elapsed from the density correction executed last time by the density correction unit becomes shorter. Forming equipment. The image forming apparatus according to claim 1, wherein the setting unit sets a limit range of the correction amount based on a correction amount of density correction executed by the density correction unit during the predetermined period. The setting means is configured such that when the direction of density correction performed by the density correction means in the predetermined period is alternately repeated in an increasing direction and a decreasing direction, the limit amount of the correction amount is reduced. The image forming apparatus according to claim 4, wherein a limit width of the correction amount is set. Computer
An image forming program for functioning as the density correcting unit and the setting unit of the image forming apparatus according to claim 1.

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