JP5259306B2 - Image forming apparatus and image forming apparatus control method - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using an electrophotographic system such as a copying machine and a printer, and a control method for the image forming apparatus, and more particularly to an image forming apparatus having an image quality adjusting unit for stabilizing print image quality and an image The present invention relates to a method for controlling a forming apparatus.

  Conventionally, as an image forming apparatus that prints and prints out the results of various image processing performed on image data obtained by external reception or document reading, printer function, scanner function, facsimile function, copy function, etc. A so-called MFP (Multi Function Peripheral) that has various functions using network communication in addition to the basic functions is widely used.

  In such an image forming apparatus, the image quality changes depending on the usage environment such as temperature and humidity and the difference in the printed document. Therefore, in order to stabilize the print image quality, an image adjustment unit is provided to periodically adjust the image quality. To be implemented.

  However, periodically performing image quality adjustment by the image adjustment unit is an excellent technique in terms of maintaining the sharpness of a printed image, but when performing the adjustment operation, several tens of seconds to several minutes are performed. Since time is required, it is very troublesome for users who need urgency.

  In addition, when image quality adjustment is performed, a developer (toner) may be used to create a developed image such as a so-called toner patch on the photosensitive drum, and some developer is consumed. There is a problem that the amount of developer that can be used for a print job is reduced. Furthermore, even when image quality adjustment is performed, the image quality may be deteriorated due to factors outside the control range and detection by the image quality adjustment unit, and image quality may not be restored even when image quality adjustment is performed.

  Therefore, in order to solve the above-described problems, as an example of the related art, an image forming apparatus is disclosed that can obtain a print image with good reproducibility when a tendency that the print image is not faithfully reproduced with respect to the input image occurs. (See Patent Document 1).

Specifically, when the reproducibility of a print image deteriorates, the user reloads the print image into the image forming apparatus, compares the print image with the input image, and displays the data difference between the two on the operation panel. It has a configuration to let you.
JP 2002-287573 A

  However, the above-described conventional technology has a problem that the user needs to read the print image again, and that when the image quality adjustment at the normal time is executed, the operation time is required and the toner is consumed more than necessary.

  The present invention has been made in view of conventional problems, and does not interrupt a print job in image quality adjustment during a print job, consumes more toner than necessary, and is reproducible with respect to an input image. An object of the present invention is to provide an image forming apparatus and a method for controlling the image forming apparatus that can easily and reliably obtain a good print image.

An image forming apparatus and a method for controlling the image forming apparatus according to the present invention for solving the above-described problems are as follows.
The present invention includes a developing device that contains a developer containing toner for developing an electrostatic latent image formed on a photosensitive drum, and maintains a good image quality of an output image with respect to an input image. The image quality adjusting unit periodically adjusts the image forming conditions, and the image quality adjusting unit creates a toner patch on the photosensitive drum when the image forming environment changes before a print job, and The first image quality adjustment unit that adjusts the image quality based on the toner adhesion amount of the patch, and a detection sensor that optically reads a print image formed on the recording medium during the print job, and the print read by the detection sensor in the image forming apparatus to perform image quality adjustment includes a second image quality adjusting unit adjusting image quality based on the image density of the image, and corresponds to the input image as the image quality adjustment section, in order to perform the image quality adjustment That includes a conversion table set based imaging conditions dither values specified for each each color and gradation, if the number of image quality adjustment is printed from being executed reaches a predetermined number, the second image quality adjusting The image density of the input image is compared with the image density of the print image read by the detection sensor, and if there is a portion where the image density is different, the corresponding location on the conversion table is The conversion table is updated by calculating a dither value difference from a difference between an image density of an input image and an image density of a print image read by the detection sensor .

  Further, according to the present invention, as the configuration of the image quality adjustment unit, when the conversion table is updated, the value of the part on the converted conversion table where the same color is not updated is updated. It is preferable to calculate and update linearly in proportion to the result.

  In addition, according to the present invention, when a color whose conversion table has not been updated for a predetermined period is used at the time of image formation, the first image quality adjustment is performed before the image forming process is executed, that is, before the so-called print job. It is preferable to perform image quality adjustment by the unit and update the conversion table.

The present invention further includes an image quality adjustment step of periodically adjusting image formation conditions in order to maintain a good image quality of the output image with respect to the input image, and the image quality adjustment step is performed before the print job. A first image quality adjustment step of creating a toner patch on the photosensitive drum and adjusting the image quality based on the toner adhesion amount of the toner patch when there is a change, and formed on the recording medium during the print job. A second image quality adjustment step of optically reading the printed image and adjusting the image quality based on the image density of the read print image, and a method of controlling an image forming apparatus configured to perform image quality adjustment , as the image quality adjusting process, to set the image density on the basis of the conversion table set on the basis of the dither values specified for each each color and gradation of the image forming condition corresponding to the input image in order to perform the image quality adjustment Comprising a degree, if the number of sheets image quality adjustment is printed from being executed reaches a predetermined number, in the second image quality adjuster, image density of the printed image read by the image density of the input image and the sensor If there is a portion with a different image density, the difference between the image density of the input image and the image density of the print image read by the detection sensor is determined as a corresponding portion on the conversion table. And a step of calculating a dither value difference and updating the conversion table .

According to the present invention, a developing device that contains a developer containing toner for developing an electrostatic latent image formed on a photosensitive drum is provided, and a good image quality of an output image is maintained with respect to an input image. The image quality adjusting unit periodically adjusts the image forming conditions, and the image quality adjusting unit creates a toner patch on the photosensitive drum when there is a change in the image forming environment before the print job. A first image quality adjustment unit that adjusts the image quality based on the toner adhesion amount of the toner patch, and a detection sensor that optically reads a print image formed on a recording medium during a print job, and is read by the detection sensor. in the image forming apparatus to perform image quality adjustment includes a second image quality adjusting unit adjusting image quality based on the image density, the print image, the input image as the image quality adjustment section, in order to perform the image quality adjustment Comprising a conversion table to be set on the basis of the dither values defining the corresponding image forming condition for each each color and gradation, if the number of image quality adjustment is printed from being executed reaches a predetermined number, the second In the image quality adjustment unit, the image density of the input image is compared with the image density of the printed image read by the detection sensor. The input image and the print image are compared by calculating the dither value difference from the difference between the image density of the input image and the image density of the print image read by the detection sensor and updating the conversion table. Image quality adjustment during print jobs, without interrupting the print job and without consuming more toner than necessary, the input image is always reproducible. There printed image can be maintained, the image forming apparatus can be realized which can maintain the reproducibility of the high accuracy with respect to shade halftone.

  According to the present invention, as the configuration of the image quality adjustment unit, when the conversion table is updated, the value of the part where the same color on the conversion table that has been updated is not updated is updated. By linearly calculating and updating in proportion to the update result, it is possible to perform image quality adjustment by constantly updating the values in the conversion table regardless of any input by the user.

  Further, according to the present invention, when a color whose conversion table has not been updated for a predetermined period is used at the time of image formation, the first image before the image forming process is executed, that is, before the so-called print job. Image quality adjustment by the image quality adjustment unit, for example, by creating a toner patch of only one color and adjusting the image quality, and updating the conversion table, the value of the conversion table is always set regardless of what input is made by the user. The image quality can be adjusted by continuing to update.

Further, according to the present invention, includes an image quality adjustment process of adjusting the regular image forming condition in order to maintain good quality of the output image for the input image, the image quality adjustment process, image before printing job A first image quality adjustment step of creating a toner patch on the photosensitive drum and adjusting the image quality based on the toner adhesion amount of the toner patch when there is a change in the forming environment; and on the recording medium during the print job A second image quality adjustment step for optically reading the formed print image and adjusting the image quality based on the image density of the read print image, and a control method for the image forming apparatus configured to perform the image quality adjustment in the image-quality adjustment process, setting the image density on the basis of the conversion table set on the basis of the dither values specified for each each color and gradation of the image forming condition corresponding to the input image in order to perform the image quality adjustment To comprises the step, if the number of sheets image quality adjustment is printed from being executed reaches a predetermined number, the in the second image quality adjuster, image print image read by the sensor and the image density of the input image If there is a portion where the image density is different when compared with the density, the corresponding part on the conversion table is determined between the image density of the input image and the image density of the print image read by the detection sensor. By providing the step of calculating the dither value difference from the difference and updating the conversion table, the image quality adjustment can be performed by comparing the input image and the print image. The image forming apparatus control method can maintain a reproducible print image with respect to the input image without interrupting toner more than necessary. That.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The best embodiment of the present invention will be described in detail below with reference to the drawings.
FIG. 1 is an explanatory diagram showing an overall configuration of an image forming apparatus according to an embodiment of the present invention, and FIG. 2 is a block diagram showing an electrical configuration for adjusting image quality in the image forming apparatus.

  As shown in FIGS. 1 and 2, the image forming apparatus 100 according to the present embodiment includes a developing device 102 that contains a developer containing toner for developing an electrostatic latent image formed on the photosensitive drum 101. The image forming apparatus 100 includes an image quality adjusting unit 54a that periodically adjusts image forming conditions to maintain a good image quality of the output image with respect to the input image. As a configuration, a first image quality adjustment unit 54a1 that performs image quality adjustment based on the toner adhesion amount of a toner patch created on the photosensitive drum 101, and a print image formed on a recording medium during a print job are optically displayed. And a second image quality adjustment unit 54a2 that includes a detection sensor 155 that performs image quality adjustment based on the image density of the printed image read by the detection sensor 155. That.

First, the overall configuration of the image forming apparatus 100 will be described.
The image forming apparatus 100 according to the present embodiment forms multi-color and single-color images on a sheet based on read image data of a document or image data transmitted via a network or the like. Therefore, as shown in FIG. 1, the image forming apparatus 100 includes an exposure unit E, a photosensitive drum 101 (101a to 101d), a developing device 102 (102a to 102d), a charging roller 103 (103a to 103d), and a cleaning unit. 104 (104a to 104d), intermediate transfer belt 11, primary transfer roller 13 (13a to 13d), secondary transfer roller 14, fixing device 15, paper transport paths P1, P2, and P3, paper feed cassette 16, and manual paper feed tray 17 and a paper discharge tray 18 and the like. A document reading device 110 that optically reads an image of the document G by the CCD sensor 160 is disposed on the image forming apparatus 100.

  The image forming apparatus 100 corresponds to the hues of four colors of cyan (C), magenta (M), and yellow (Y), which are three subtractive primary colors obtained by color separation of black (K) and a color image. Image formation is performed in the image forming unit 55 (55a to 55d) using the image data.

  The image forming units 55a to 55d correspond to color images using each color. Accordingly, the developing device 102 (102a to 102d), the photosensitive drum 101 (101a to 101d), the charging roller 103 (103a to 103d), and the cleaning unit 104 (104a to 104d) generate four types of latent images corresponding to the respective colors. Four each are provided to form.

  The image forming units 55a to 55d have the same configuration. For example, the black image forming unit 55a includes a photosensitive drum 101a, a developing device 102a, a charging roller 103a, a primary transfer roller 13a, a cleaning unit 104a, and the like. . The image forming units 55 a to 55 d are arranged in a line in the moving direction (sub-scanning direction) of the intermediate transfer belt 11.

  The symbols a to d correspond to a for black, b for cyan, c for magenta, and d for yellow, and the above-mentioned means distinguished by these symbols constitute four image stations. Has been.

  In the present embodiment, as shown in FIG. 1, a temperature / humidity detection sensor 153 for detecting the atmospheric temperature and humidity in the image forming apparatus 100 is provided below these image forming units 55a to 55d. Note that the temperature / humidity detection sensor 153 may be provided at other locations in the apparatus as long as the ambient temperature and humidity in the apparatus can be detected.

  In the present embodiment, these image forming units 55a to 55d receive subsequent commands such as a print job from an external terminal even after a predetermined time has elapsed since the operation of the image forming units 55a to 55d ended. If not, the image forming units 55a to 55d are provided with a function of switching from the standby mode in which the image can be formed immediately to the image adjustment to the power saving mode in which the power supply to a part of the image forming units 55a to 55d is stopped. Further, when a subsequent command is received during the image adjustment period, the image forming units 55a to 55d are returned from the image adjustment to the standby mode.

  A detailed description of the operation of switching / returning to image adjustment of the image forming units 55a to 55d in the present embodiment will be described later.

  An exposure unit E, which is an exposure apparatus of this embodiment, includes a semiconductor laser, a polygon mirror 4, a first reflection mirror 7, a second reflection mirror 8, and the like (not shown), and each hue of black, cyan, magenta, and yellow. Each of the photosensitive drums 101a to 101d is irradiated with a light beam such as a laser beam modulated by the image data. On each of the photosensitive drums 101a to 101d, an electrostatic latent image is formed based on image data of each hue of black, cyan, magenta, and yellow.

  In the present embodiment, the exposure unit E is a method using a laser scanning unit (LSU) including a laser irradiation unit and a reflection mirror. For example, an EL or LED writing head in which light emitting elements are arranged in an array. You may use the thing of the method using.

  The photosensitive drum 101 is a substantially cylindrical image carrier disposed above the exposure unit E, and is controlled to rotate in a predetermined direction by a driving unit and a control unit (not shown). The photosensitive drum 101 is configured by forming a photoconductive layer on a base material. For example, a metal drum made of aluminum or the like is used as a base material, and a photoconductive layer such as amorphous silicon (a-Si), selenium (Se), or an organic photo semiconductor (OPC) is formed in a thin film on the outer peripheral surface thereof. ing. Note that the configuration of the photosensitive drum 101 is not particularly limited to the above-described configuration.

  The charging roller 103 is a contact-type charger that uniformly charges the surface of the photosensitive drum 101 to a predetermined potential. Instead of the charging roller 103, a contact type charger using a charging brush or a non-contact type charger using a charging wire may be used.

  The developing device 102 supplies toner to the surface of the photosensitive drum 101 on which the electrostatic latent image is formed, and develops the electrostatic latent image into a toner image. Each of the developing devices 102a to 102d contains toner of each hue of black, cyan, magenta, and yellow, and the electrostatic latent image of each hue formed on each of the photosensitive drums 101a to 101d is black, cyan. Then, the toner images are visualized as magenta and yellow toner images. The cleaning unit 104 removes and collects toner remaining on the surface of the photosensitive drum 101 after development and image transfer.

  The intermediate transfer belt 11 disposed above the photosensitive drum 101 is stretched between the driving roller 11a and the driven roller 11b to form a loop-shaped movement path. The outer peripheral surface of the intermediate transfer belt 11 faces the photosensitive drum 101d, the photosensitive drum 101c, the photosensitive drum 101b, and the photosensitive drum 101a in this order. Primary transfer rollers 13a to 13d are arranged at positions facing the respective photosensitive drums 101a to 101d with the intermediate transfer belt 11 interposed therebetween. Each of the positions where the intermediate transfer belt 11 faces the photosensitive drums 101a to 101d is a primary transfer position. The intermediate transfer belt 11 is formed endlessly with a film having a thickness of about 100 to 150 μm.

  The primary transfer rollers 13a to 13d have constant voltage control of a primary transfer bias opposite to the charging polarity of the toner in order to transfer the toner images carried on the surfaces of the photosensitive drums 101a to 101d onto the intermediate transfer belt 11. Applied. As a result, the toner images of the respective colors formed on the photosensitive drum 101 (101a to 101d) are sequentially superimposed on the outer peripheral surface of the intermediate transfer belt 11, and a full-color toner image is formed on the outer peripheral surface of the intermediate transfer belt 11. It is formed.

  However, when image data of only a part of the hues of yellow, magenta, cyan, and black is input, some of the four photosensitive drums 101a to 101d corresponding to the hue of the input image data. Only the photosensitive drum 101 forms an electrostatic latent image and a toner image. For example, when forming a monochrome image, an electrostatic latent image and a toner image are formed only on the photosensitive drum 101 a corresponding to the black hue, and only the black toner image is transferred to the outer peripheral surface of the intermediate transfer belt 11. Is done.

  Each of the primary transfer rollers 13a to 13d is configured by covering the surface of a shaft made of a metal (for example, stainless steel) having a diameter of 8 to 10 mm with a conductive elastic material (for example, EPDM, urethane foam, or the like). A high voltage is uniformly applied to the intermediate transfer belt 11 by the elastic material. In this embodiment, the primary transfer rollers 13a to 13d are used as the transfer electrodes, but brushes and the like can also be used.

  The toner image transferred to the outer peripheral surface of the intermediate transfer belt 11 at each primary transfer position is conveyed to a secondary transfer position that is a position facing the secondary transfer roller 14 by the rotation of the intermediate transfer belt 11. The secondary transfer roller 14 is pressed against the outer peripheral surface of the intermediate transfer belt 11 whose inner peripheral surface is in contact with the peripheral surface of the driving roller 11a at a predetermined nip pressure during image formation. In order to constantly obtain the nip pressure, either the secondary transfer roller 14 or the intermediate transfer belt drive roller 11a is made of a hard material such as metal, and the other is a soft material such as an elastic roller (elastic rubber roller or Foamed resin roller, etc.).

  When paper fed from the paper feed cassette 16 or the manual paper feed tray 17 passes between the secondary transfer roller 14 and the intermediate transfer belt 11, the secondary transfer roller 14 is charged with the toner charging polarity (-). Is applied with a high voltage of reverse polarity (+). As described above, the electrostatic latent images on the respective photoconductive drums 101 (101a to 101d) are visualized with toners corresponding to the respective hues to become toner images, and these toner images are transferred onto the intermediate transfer belt 11. Are stacked. Thereafter, the stacked toner images are moved to a contact position between the conveyed paper and the intermediate transfer belt 11 by the rotation of the intermediate transfer belt 11, and are transferred by the secondary transfer roller 14 disposed at this position. A toner image is transferred from the outer peripheral surface of the intermediate transfer belt 11 onto the sheet.

  The toner adhering to the intermediate transfer belt 11 due to the contact between the intermediate transfer belt 11 and the photosensitive drum 101 and the toner image remaining on the intermediate transfer belt 11 are not transferred when the toner image is transferred from the intermediate transfer belt 11 to the sheet. The toner that has been used becomes a cause of toner color mixing in the next step, and is therefore removed and collected by the intermediate transfer belt cleaning unit 12.

  The intermediate transfer belt cleaning unit 12 includes a cleaning blade as a cleaning member that contacts the intermediate transfer belt 11. The portion of the intermediate transfer belt 11 in contact with the cleaning blade is supported from the back side by an intermediate transfer belt driven roller 11b.

  The sheet on which the toner image is transferred as a visible image is guided to a fixing device 15 including a heating roller 15a and a pressure roller 15b, and passes between the heating roller 15a and the pressure roller 15b to be heated and pressed. Receive. As a result, the toner image that becomes a visible image is firmly fixed on the surface of the paper. The paper on which the toner image is fixed is discharged onto the paper discharge tray 18 by the paper discharge roller 18a.

  In the image forming apparatus 100, a substantially vertical direction for feeding the paper stored in the paper feed cassette 16 to the paper discharge tray 18 between the secondary transfer roller 14 and the intermediate transfer belt 11 and via the fixing device 15. Paper transport path P1 is provided.

  In the paper transport path P1, a pickup roller 16a that feeds the paper in the paper feed cassette 16 one by one into the paper transport path P1, a transport roller r10 that transports the fed paper upward, and the transported paper A registration roller 19 that guides between the secondary transfer roller 14 and the intermediate transfer belt 11 at a predetermined timing, and a paper discharge roller 18 a that discharges the paper to the paper discharge tray 18 are disposed.

  Further, inside the image forming apparatus 100, a sheet conveyance path P <b> 2 in which a pickup roller 17 a and a conveyance roller r <b> 10 are arranged is formed between the manual sheet feeding tray 17 and the registration roller 19. Further, a paper transport path P3 is formed between the paper discharge roller 18a and the upstream side of the registration roller 19 in the paper transport path P1.

  The paper discharge roller 18a is rotatable in both forward and reverse directions, and is used for forming a single-sided image for forming an image on one side of a sheet and for forming a second-side image in forming a double-sided image for forming an image on both sides of a sheet. Driven in the forward direction, the paper is discharged to the paper discharge tray 18.

  On the other hand, when the first side image is formed in the double-sided image formation, the paper discharge roller 18a is driven in the normal rotation direction until the rear end of the paper passes the fixing device 15, and then the rear end of the paper is sandwiched. Driven in the reverse direction, the paper is guided into the paper transport path P3. As a result, the paper on which the image is formed on only one side when the double-sided image is formed is guided to the paper transport path P1 with the front and back surfaces and the front and rear ends reversed.

  The registration roller 19 performs secondary transfer of paper fed from the paper feed cassette 16 or the manual paper feed tray 17 or transported via the paper transport path P3 at a timing synchronized with the rotation of the intermediate transfer belt 11. Guided between the roller 14 and the intermediate transfer belt 11. For this reason, the registration roller 19 stops rotating when the operation of the photosensitive drum 101 and the intermediate transfer belt 11 is started, and the sheet fed or conveyed prior to the rotation of the intermediate transfer belt 11 has the front end at the registration roller 19. The movement in the sheet conveyance path P1 is stopped in a state where the sheet 19 is in contact with the sheet 19. Thereafter, the registration roller 19 is a position where the secondary transfer roller 14 and the intermediate transfer belt 11 are in pressure contact with each other, at a timing when the front end portion of the sheet and the front end portion of the toner image formed on the intermediate transfer belt 11 face each other. Start spinning.

  Note that in all of the image forming units 55a to 55d, the primary transfer rollers 13a to 13d press the intermediate transfer belt 11 against all of the photosensitive drums 101a to 101d when full-color images are formed. On the other hand, during monochrome image formation in which image formation is performed only in the image forming unit 55a, only the primary transfer roller 13a is brought into pressure contact with the intermediate transfer belt 11 against the photosensitive drum 101a.

  Next, an electrical configuration for performing characteristic image adjustment in the image forming apparatus 100 according to the present embodiment will be described.

  As shown in FIG. 2, the image forming apparatus 100 according to the present embodiment performs image reading processing, image processing, image forming processing, recording medium (paper) transport processing, paper discharge processing, and the like in a ROM (Read Only Memory). ) In accordance with a program (routine) stored in advance 51, the central processing unit (CPU) 50 serving as a control unit of each component included in the image forming apparatus 100 uses a temporary storage unit such as a RAM (Random Access Memory) 52. To execute the process. Note that a storage unit such as an HDD (Hard Disk Drive) may be used instead of the ROM 51 and the RAM 52. Each process such as the image process may be configured by hardware.

  In the image forming apparatus 100, document image information transmitted from each terminal device connected to a communication network (not shown) is input to the image processing unit (routine) 54 of the CPU 50 via the communication processing unit 53. ing.

  The image processing unit 54 processes the document image information stored in the storage unit such as the RAM 52 into a print image suitable for printing (image formation on paper) by the above program.

  In the present embodiment, the image processing unit (routine) 54 includes a first image quality adjustment unit (routine) serving as an image quality adjustment unit 54a that adjusts a change in image quality of an output image such as a change in print image quality density or a change in color tone. ) 54a1 and a second image quality adjustment unit (routine) 54a2, and a conversion table 54a3 that defines image forming conditions corresponding to the input image for each color and each gradation in order to perform image quality adjustment.

  The predetermined amount setting unit 58 is provided with a storage unit 58a that stores a photosensitive member traveling distance (photosensitive member rotation time) that is a setting period in which image quality adjustment is performed according to a monochrome image or a color image, and the number of printed sheets.

  The image information for printing subjected to image processing by the image processing unit (routine) 54 is input to the image forming processing unit (routine) 55S. An image forming unit 55, a sheet conveying unit 56 for detecting and controlling various types of sheets in the sheet conveying paths P1 to P3, and the like, a sheet discharge unit 57 for performing various types of detection and control of sheets in the fixing device 15 and the sheet discharge roller 18a It is linked to a drive control unit 60 that controls each drive unit.

  The paper transported by the paper transporting unit 56 is transported by the paper transporting processing unit 56a, and a printing step for executing a printing process of image information in the image forming processing unit (routine) 55S, and then the printing process is performed. The paper is discharged to a paper discharge tray 18 which is a paper discharge unit by a paper discharge processing unit 57a after a fixing step executed on the paper by the fixing device 15. In the present embodiment, the fixing device 15 includes a heater 151 for adjusting the temperature of the surface of the heating roller 15a and the like, and a temperature detection sensor 152 for detecting the temperature of the fixing device 15 including the heating roller 15a. .

  Further, the image forming apparatus 100 includes a paper transport driving unit 62 that is a driving actuator such as the paper transport unit 56, the image forming unit 55, the fixing device 15, and the paper discharge unit 57, and print processing driving according to the set operating conditions. The operation of the unit 63, the fixing drive unit 64, the paper discharge drive unit 65, and the cleaner unit drive unit 66, that is, the operation synchronized with the instruction of the CPU 50 based on the program stored in the ROM 51 is performed by the control of the drive control unit 60. It has become.

  The image forming unit 55 is provided with a voltage application unit 55 </ b> A for applying a bias voltage to the photosensitive drum 101.

The paper conveyance drive unit 62 is a motor for driving the paper conveyance unit 56, specifically, the pickup rollers 16a and 17a and the registration rollers 19 on the above-described paper conveyance paths P1 and P2.
The print processing drive unit 63 is a drive motor for the photosensitive drum 101.
The fixing driving unit 64 is a driving motor for the heating roller 15 a and the pressure roller 15 b of the fixing device 15.
The paper discharge drive unit 65 is a drive motor such as a paper discharge roller 18a.
The cleaner unit driving unit 66 is a driving motor such as a brush roller provided in the cleaning unit 104. The drive motors of these drive units can be appropriately configured through a power transmission mechanism using the same or different motors as drive sources.

  Further, the CPU 50 is connected to a cumulative counter 59 having a storage unit 59a for recording the photosensitive body travel distance and the number of printed sheets corresponding to the monochrome image and the color image of the image forming apparatus 100. In the present embodiment, the monochrome and color photosensitive member travel distances and the number of printed sheets measured by the cumulative counter 59, and information such as the photosensitive member travel distance and the number of printed sheets set in the predetermined amount setting unit 58, Are compared by the comparison processing unit (routine) 70, and based on the result, the image quality adjustment for starting the image quality adjustment of the visible image by the first image quality adjusting unit (routine) 54a1 or the second image quality adjusting unit (routine) 54a2 is started. The adjustment start control processing unit (routine) 68 is controlled to operate.

Here, a specific operation of creating a patch image (toner patch) and performing image quality adjustment will be described with reference to the drawings.
FIG. 3 is a graph showing the relationship between the photosensitive drum surface potential and the charging roller applied voltage when securing the charging potential of the photosensitive drum in simple image adjustment, and FIG. 4 is a patch density and reflection density in high-definition image adjustment. It is a graph which shows the relationship.

  In the image forming apparatus 100, the surface potential on the photosensitive drum 101 can be changed by changing the voltage applied to the charging roller 103.

Specifically, as shown in FIG. 3, the surface potential of the photosensitive drum 101 increases as the voltage applied to the charging roller 103 increases. For example, the voltage applied to the charging roller 103 of the initial setting is −650V. On the other hand, the surface potential of the photosensitive drum 101 corresponding to the three applied voltages of −600 V, −650 V, and −700 V is read by a surface potential sensor (not shown) by swinging 50 V forward and backward. The read data is plotted, and a voltage applied to the charging roller 103 necessary for obtaining a target photosensitive drum surface potential of −630 V is obtained.
In this embodiment, as shown in FIG. 3, the voltage applied to the charging roller 103 is about −680V.

  First, in the image quality adjustment unit 54a, image adjustment for determining the solid image density is performed by the first image quality adjustment unit 54a1. This image quality adjustment operation is completed in a relatively short time (about 10 seconds).

  Next, image adjustment at a halftone level, that is, image quality adjustment for obtaining a target sensitivity curve (gamma characteristic) is performed. Based on the determined photoreceptor drum surface potential, a plurality of patch images (toner patches) having different image densities are created on the photoreceptor drum 101 or the intermediate transfer belt 11, and the image density is reflected by a reflection density sensor (not shown). (Reflection density) and plot the image density (toner adhesion amount) on the photosensitive drum 101 with respect to each patch density.

  Specifically, as shown in FIG. 4, if the measured value (solid line) is deviated from the target sensitivity curve (broken line), the laser output value is finely adjusted to approach the target. . This image quality adjustment operation takes time (about 60 seconds) to calculate from the plot because of the large number of image patches.

Next, the control operation of the image adjustment operation of the image forming apparatus according to the present embodiment will be described with reference to a flowchart.
FIG. 5 is a flowchart for explaining the control operation of the image quality adjustment operation of the image forming apparatus according to this embodiment.

  When the image quality adjustment operation is started in the image forming apparatus 100, first, image quality adjustment is performed by the first image quality adjustment unit 54a1.

  In the first image quality adjustment unit 54a1, it is determined whether or not the image forming environment has changed, such as when the power is turned on, a change in temperature and humidity, or immediately after replacement of consumables (step S1).

  If it is determined in step S1 that the image forming environment has changed, the first image quality adjustment unit 54a1 performs image quality adjustment by creating patch images (toner patches) for all colors (step S2). . In step S6, image quality adjustment is performed by the second image quality adjustment unit 54a2 in the print job immediately after that.

  On the other hand, if it is not determined in step S1 that the image forming environment has changed, the process proceeds to step S3, and it is determined whether or not a color for which the long-term conversion table 54a3 has not been updated is necessary for image formation.

  If it is determined in step S3 that a color for which the long-term conversion table 54a3 has not been updated is necessary for image formation, the first image quality adjustment unit 54a1 creates a patch image for only that one color. Image quality adjustment is performed (step S4). In step S6, image quality adjustment is performed by the second image quality adjustment unit 54a2 in the print job immediately after that.

  On the other hand, if it is determined in step S3 that the color for which the long-term conversion table 54a3 has not been updated is not necessary for image formation, the process proceeds to step S5, and the number of printed sheets from the previous image quality adjustment has reached the specified number. It is determined whether or not.

If it is determined in step S5 that the number of prints has reached the specified number, the process proceeds to step S6, and the image quality adjustment by the second image quality adjustment unit 54a2 is performed in the print job immediately after that. That is, image quality adjustment is performed without creating a patch image.
Thereby, it is possible to suppress consumption of toner more than necessary.

  On the other hand, if it is determined in step S5 that the number of printed sheets has not reached the specified number, the process ends without performing image quality adjustment.

  In the second image quality adjustment unit 54a2, the printed image is read by the detection sensor 155 (step S6), and the image density of the print image read by the detection sensor 155 is different from the image density of the input image. It is determined whether there is a portion that is present, that is, whether it is necessary to update the value of the conversion table 54a3 (step S7).

  In step S7, when there is no portion in which the image density of the print image read by the detection sensor 155 differs from that of the input image, and the input image and the output image match on the conversion table 54a3, the conversion table 54a3 is changed. Thus, the image quality adjustment determination ends.

  On the other hand, if it is determined in step S7 that there is a portion where the image density is different, that is, it is necessary to update the value of the conversion table 54a3, the image forming condition corresponding to the input image is set for each color and each gradation. Is calculated from the difference between the image density of the input image and the image density of the print image read by the detection sensor 155 on the conversion table 54a3 defined in (5) (step S8). Then, it is determined whether or not the values in the conversion table 54a3 are updated for all the gradations on the conversion table 54a3 (step S9).

  If it is determined in step S9 that the values in the conversion table 54a3 have been updated for all gradations on the conversion table 54a3, the image quality adjustment determination ends.

  On the other hand, when it is determined in step S9 that at least one of the conversion tables 54a3 has not been updated, that is, it is determined that the values of the conversion table 54a3 have not been updated for all the gradations on the conversion table 54a3. Updates and updates the value of the part that has not been updated linearly in proportion to the update result of the part that has been updated of the same color (step S10). Then, the image quality adjustment determination ends. In this way, image quality adjustment is performed by the image quality adjustment unit 54a.

Next, an example of the conversion table 54a3 used for image quality adjustment of the image forming apparatus 100 will be described.
FIG. 6 is an explanatory diagram showing the configuration of a conversion table used for image quality adjustment of the image forming apparatus of this embodiment.

  As shown in FIG. 6, the conversion table 54a3 used for image quality adjustment of the image forming apparatus 100 has 17 levels of A to Q in the range where the density of the patch image to be output (printed) ranges from 1 gradation to 255 gradations. The values are set for the four colors of black (K), cyan (C), magenta (M), and yellow (Y) so that the density gradually increases.

  FIG. 7 is a conversion table when the value changes in only one of the cyan densities in the conversion table of FIG.

  FIG. 8 is a conversion table when the maximum density and minimum density values of cyan density are fixed in the conversion table of FIG.

  FIG. 9 is a conversion table when the change amount of the value changed in the conversion table of FIG. 8 is linearly reflected on the density of other cyan.

  FIG. 10 is a conversion table when the amount of change of the value changed in the conversion table of FIG. 8 is linearly reflected on all values of other cyan densities.

  In this way, by using the conversion table 54a3, the density value can be easily set or updated in accordance with the density change.

Next, a modified example of the conversion table 54a3 described above will be described.
FIG. 11 is an explanatory diagram showing an example in which the values have changed in only two places in the conversion table of FIG.

  As shown in FIG. 11, this modification is a conversion table when the values change in only two of the cyan densities in the conversion table of FIG. 6.

  FIG. 12 is a conversion table when the maximum density and the minimum density values of the cyan densities are fixed in the conversion table of FIG.

  FIG. 13 is a conversion table when the change amount of the value changed in the conversion table of FIG. 12 is linearly reflected on the density of other cyan.

  FIG. 14 is a conversion table when the change amount of the value changed in the conversion table of FIG. 12 is linearly reflected on all values of other cyan densities.

Next, other modifications will be described.
FIG. 15 is an explanatory diagram showing an example in which the maximum density value is changed in the conversion table of FIG.

  As shown in FIG. 15, this modification is a conversion table when the conversion table of FIG. 6 changes by the highest density value among the cyan densities.

  FIG. 16 is a conversion table when the value of the minimum density which has not changed among the cyan densities in the conversion table of FIG. 15 is fixed.

  FIG. 17 is a conversion table when the change amount of the value changed in the conversion table of FIG. 16 is linearly reflected on other cyan densities.

  FIG. 18 is a conversion table when the change amount of the value changed in the conversion table of FIG. 17 is linearly reflected in all values of other cyan densities.

  In the conversion table 54a3 described above, the case where the density of cyan has been described has been described. However, the present invention is not limited to this, and other colors are similarly set and updated. Is possible.

  With the above-described configuration, according to the present embodiment, in the image forming apparatus 100, the image quality adjustment unit 54a performs the first image quality adjustment based on the toner adhesion amount of the patch image created on the photosensitive drum 101. Image quality adjustment unit 54a1 and a second image quality adjustment unit 54a2 that performs image quality adjustment based on the image density of the print image read by the detection sensor 155, thereby comparing the input image with the print image. Since adjustment can be performed, image quality adjustment can be performed without interrupting a print job without consuming more toner than necessary, and a print image with high reproducibility can be maintained for an input image at all times. .

  Further, according to the present embodiment, the second image quality adjustment unit 54a2 compares the image density of the input image with the image density of the print image read by the detection sensor, and updates the value of the conversion table 54a3. As a result, high-precision reproducibility can be maintained.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is configured as described above if the image forming apparatus has a function of adjusting image quality when performing image formation. The present invention is not limited to an image forming apparatus or a copying machine, and can be expanded to other image forming apparatuses.

  For example, in the above-described embodiment, the present invention has been described in accordance with an electrophotographic digital full-color multifunction peripheral as an image forming apparatus. The present invention can be similarly applied to other image forming methods / analog printers / facsimiles and the like.

  As described above, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims. That is, it is obvious for those skilled in the art that various changes or modifications can be conceived within the scope of the claims, and these naturally belong to the technical scope of the present invention. It is understood as a thing.

1 is an explanatory diagram showing an overall configuration of an image forming apparatus according to an embodiment of the present invention. 2 is a block diagram illustrating an electrical configuration for performing image quality adjustment in the image forming apparatus. FIG. 6 is a graph showing the relationship between the photosensitive drum surface potential and the charging roller applied voltage when securing the charged potential of the photosensitive drum in simple image adjustment. It is a graph which shows the relationship between the patch density and reflection density in high-definition image adjustment. 6 is a flowchart illustrating a control operation of an image quality adjustment operation of the image forming apparatus. It is explanatory drawing which shows the structure of the conversion table used for the image quality adjustment of the said image forming apparatus. It is explanatory drawing which shows an example which the value changed only in one place in the conversion table of FIG. It is explanatory drawing which shows an example which fixed the value of the highest density | concentration and the minimum density | concentration in the conversion table of FIG. It is explanatory drawing which shows an example which reflected the variation | change_quantity of the value which changed in the conversion table of FIG. 8 on another density | concentration linearly. It is explanatory drawing which shows the state which reflected the variation | change_quantity of the value changed in the conversion table of FIG. 8 on all the values of other density | concentration linearly. It is explanatory drawing which shows an example which the value changed only in two places in the conversion table of FIG. It is explanatory drawing which shows an example which fixed the value of the highest density | concentration and the minimum density | concentration in the conversion table of FIG. It is explanatory drawing which shows an example which reflected the variation | change_quantity of the value which changed in the conversion table of FIG. 12 on another density | concentration linearly. It is explanatory drawing which shows the state which reflected the variation | change_quantity of the value changed in the conversion table of FIG. 12 on all the values of other density | concentration linearly. It is explanatory drawing which shows an example which changed only the value of the highest density | concentration in the conversion table of FIG. It is explanatory drawing which shows an example which fixed the value of the minimum density which was not changed in the conversion table of FIG. It is explanatory drawing which shows an example which reflected the variation | change_quantity of the value which changed in the conversion table of FIG. 16 on another density | concentration linearly. It is explanatory drawing which shows the state which reflected the variation | change_quantity of the value changed in the conversion table of FIG. 17 on all the values of other density | concentration linearly.

Explanation of symbols

54 image processing unit 54a image quality adjusting unit 54a1 first image quality adjusting unit 54a2 second image quality adjusting unit 54a3 conversion table 55 image forming unit 55A voltage applying unit 55S image forming processing unit 58 predetermined amount setting unit 58a storage unit 59 cumulative counter 59a Storage unit 68 Image quality adjustment start control processing unit 70 Comparison processing unit 100 Image forming apparatus 101 Photosensitive drum 102 Developing device 155 Detection sensor

Claims (4)

A developing device containing a developer containing toner for developing the electrostatic latent image formed on the photosensitive drum, and periodically in order to maintain a good image quality of the output image with respect to the input image; An image quality adjustment unit that adjusts image formation conditions is provided , and the image quality adjustment unit creates a toner patch on the photosensitive drum when there is a change in the image formation environment before a print job and attaches toner to the toner patch. A first image quality adjustment unit that performs image quality adjustment based on the amount; and a detection sensor that optically reads a print image formed on a recording medium during a print job, and the image density of the print image read by the detection sensor A second image quality adjustment unit configured to perform image quality adjustment based on the image quality adjustment unit ,
Wherein as the image quality adjustment unit includes a conversion table for setting on the basis of the image forming condition corresponding to the input image to the dither values specified for each each color and gradation in order to perform the image quality adjustment,
When the number of printed sheets reaches the specified number after the image quality adjustment is executed, the second image quality adjustment unit compares the image density of the input image with the image density of the print image read by the detection sensor. If there is a portion having a different image density, the corresponding position on the conversion table is determined based on the difference between the image density of the input image and the image density of the print image read by the detection sensor. An image forming apparatus that calculates a difference and updates the conversion table . When the conversion table is updated, the image quality adjustment unit linearly changes the value of the portion of the conversion table that has been updated, that is not updated with the same color, in proportion to the update result of the updated portion. The image forming apparatus according to claim 1 , wherein the image forming apparatus calculates and updates the image forming apparatus. At the time of image formation, when a color whose conversion table has not been updated for a predetermined period is used, the image quality adjustment by the first image quality adjustment unit is performed before the image formation processing is executed, and the conversion table is the image forming apparatus according to claim 1 or 2, characterized in that update. An image quality adjustment process that periodically adjusts the image formation conditions in order to maintain a good image quality of the output image with respect to the input image, and the image quality adjustment process is performed when there is a change in the image formation environment before the print job In addition, a first image quality adjustment step of creating a toner patch on the photosensitive drum and adjusting the image quality based on the toner adhesion amount of the toner patch, and a print image formed on the recording medium during the print job are optically processed. And a second image quality adjustment step for adjusting the image quality based on the image density of the read print image, and a control method for the image forming apparatus configured to perform the image quality adjustment .
As the image quality adjusting process comprises as factory setting the image density on the basis of the conversion table set on the basis of the dither values specified for each each color and gradation of the image forming condition corresponding to the input image in order to perform the image quality adjustment ,
When the number of printed sheets reaches the specified number after the image quality adjustment is executed, the second image quality adjustment unit compares the image density of the input image with the image density of the print image read by the detection sensor. If there is a portion having a different image density, the corresponding position on the conversion table is determined based on the difference between the image density of the input image and the image density of the print image read by the detection sensor. A method for controlling an image forming apparatus, comprising: calculating a difference and updating the conversion table .

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