JP2019070712A - Image forming apparatus, image density stabilization control method, and image density stabilization control program - Google Patents

Image forming apparatus, image density stabilization control method, and image density stabilization control program Download PDF

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JP2019070712A
JP2019070712A JP2017196104A JP2017196104A JP2019070712A JP 2019070712 A JP2019070712 A JP 2019070712A JP 2017196104 A JP2017196104 A JP 2017196104A JP 2017196104 A JP2017196104 A JP 2017196104A JP 2019070712 A JP2019070712 A JP 2019070712A
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image
density
stabilization control
unit
area
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泰浩 西村
Yasuhiro Nishimura
泰浩 西村
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シャープ株式会社
Sharp Corp
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Abstract

To provide an image forming apparatus that, in images in various density areas from a low density to a high density, performs appropriate image density stabilization control reflecting a user's usage state.SOLUTION: An image forming apparatus that forms an image in an electrophotographic system, and comprises: image carriers on each of which an electrostatic latent image is formed; developer carriers that each carry a developer; chargers that each apply a charging voltage to the image carrier; developing voltage application units that each apply a developing voltage to the developer carrier; a density area determination unit that determines the density area of the image on the basis of predetermined data; and an image density stabilization control unit that corrects the density of the image to be temporarily and substantially uniform on the basis of the density area determined by the density area determination unit.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an image forming apparatus, an image density stabilization control method, and an image density stabilization control program, and more specifically, an electrophotographic image forming apparatus and an image forming control method for an electrophotographic image forming apparatus. And an image density stabilization control program.
  In the electrophotographic image forming apparatus, the density of the printed image becomes unstable with the lapse of time after the start of printing due to the presence of the positive charge remaining after the charging of the photosensitive drum and the rotational shake due to the eccentricity of the photosensitive drum. Can be
Therefore, conventionally, an image forming apparatus having an image density stabilization control function has been developed which stabilizes the density of an image by correcting the charging voltage or the like of the photosensitive drum.
As such an image forming apparatus, in consideration of the image quality generally required in the market, an apparatus adapted to an image of lower density (highlight) than an image of high density is adopted.
  In addition, in the technology for improving the variation in image density due to the environment such as temperature and humidity, the correction LUT for input image density is used to output whether the change in density value can be easily confirmed whether it is an acceptable change amount for the user. The invention of an image forming apparatus for comparing and displaying the output density value in the case and the density value calculated by the setting LUT is also disclosed (for example, see Patent Document 1).
JP, 2013-026786, A
  However, in the conventional image density stabilization control method, the amount of correction differs depending on the density of the image to be corrected. Therefore, when the stabilization control of the image density is performed by adapting to a low density image, the high density image is The image quality may not be improved due to lack of correction amount.
  On the other hand, when the stabilization control of the image density is performed in conformity with the high density image, the correction amount is excessive for the low density image, the reverse correction is performed, and the image quality may be deteriorated.
As described above, although the printing result greatly varies depending on the density of the image to be corrected, the user largely varies as to which density image should be stabilized.
In addition, even if the user is the same, the image density area to be stabilized may change significantly depending on various factors such as the type of image data to be printed, the past printing result, print settings, environment such as humidity and temperature. .
Therefore, there has been a demand for an image forming apparatus that performs stabilization control of an appropriate image density reflecting the use situation of the user among images of various density regions from low density to high density.
  The present invention has been made in consideration of the above circumstances, and among the images of various density areas from low density to high density, the appropriate control for stabilizing the image density reflecting the use situation of the user An image density stabilization control method and an image density stabilization control program are provided.
The present invention relates to an image forming apparatus for forming an image by an electrophotographic method, wherein an image carrier on which an electrostatic latent image is formed, a developer carrier for carrying a developer, and a charging voltage for the image carrier. , A developing voltage applying unit applying a developing voltage to the developer carrier, a density area determining unit determining the density area of the image based on predetermined data, and the density area determining unit And an image density stabilization control unit for correcting the density of the image so as to be substantially uniform in time based on the density area determined by the above.
Further, the present invention is an image density stabilization control method of forming an image by an electrophotographic method, comprising: a density area determining step of determining a density area of the image according to a use condition of a user; And an image density stabilization control step of correcting the density of the image to be substantially uniform in time based on the density area determined in step b. Image density stabilization characterized in that the density area of the image is determined based on at least one of the density, the analysis result of the image data which is the origin of the image, and the density of the electrostatic latent image on the image carrier. Provide a control method.
Further, the present invention is an image density stabilization control program executed by an image forming apparatus for forming an image by an electrophotographic method, wherein a processor of the image forming apparatus controls the density of the image according to a use situation of a user. The density area determination step of determining the area and the image density stabilization control step of correcting the density of the image so as to be substantially uniform in time based on the density area determined in the density area determination step are executed. And the density area determining step is performed based on at least one of the image density selected by the user, the analysis result of the image data that is the basis of the image, and the density of the electrostatic latent image on the image carrier. An image density stabilization control program characterized by determining a density area of
  According to the present invention, of the images in various density regions from low density to high density, an image forming apparatus performing stabilization control of an appropriate image density reflecting the use situation of the user, an image density stabilization control method, and an image A concentration stabilization control program is realized.
FIG. 1 is a perspective view showing the appearance of a digital multi-function peripheral that is an embodiment of an image forming apparatus of the present invention. FIG. 2 is a cross-sectional view showing a mechanical configuration of a main body portion of the digital multi-functional peripheral shown in FIG. FIG. 2 is a block diagram showing a schematic configuration of the digital multi-functional peripheral shown in FIG. 6 is a flowchart showing processing of image density stabilization control of the digital multi-functional peripheral shown in FIG. 6 is a table summarizing the characteristics of four types of image density stabilization control of the digital multi-functional peripheral shown in FIG. 6 is a graph showing a change in image density, a grid bias and a change in development bias from the start of printing in the digital multi-functional peripheral shown in FIG. 6A to 6C show changes in image density, grid bias and development bias from the start of printing, respectively. 6 is a graph showing a change in image density, a change in grid bias, and a change in development bias from the start of printing when grid bias correction is performed so that a high density image is stabilized in the digital multi-functional peripheral shown in FIG. FIGS. 7A to 7C show changes in image density, grid bias and development bias, respectively, from the start of printing. 6 is a graph showing a change in image density from the start of printing, a change in grid bias, and a change in development bias when the grid bias is corrected so that a low density image is stabilized in the digital multi-functional peripheral shown in FIG. FIGS. 8A to 8C show changes in image density, grid bias and development bias, respectively, from the start of printing. 5 is a graph showing changes in image density distribution, grid bias and development bias for one rotation of the photosensitive drum from the start of printing. FIGS. 9A to 9C show changes in image density, grid bias and development bias, respectively, from the start of printing. 9 is a graph showing a change when grid bias correction is performed so that a high density image is stabilized in the digital multi-functional peripheral shown in FIG. FIGS. 10A to 10C show changes in image density, grid bias and development bias, respectively, from the start of printing. 6 is a graph showing a change in image density from the start of printing, a change in grid bias, and a change in development bias when the grid bias is corrected so that a low density image is stabilized in the digital multi-functional peripheral shown in FIG. FIGS. 11A to 11C show changes in image density, grid bias and development bias, respectively, from the start of printing. It is a graph which shows the change of the image density from the printing start, and the change of the laser power irradiated to a photosensitive drum. FIGS. 12A and 12B show the change in image density and laser power from the start of printing, respectively. FIG. 6 is a graph showing a change when the laser power is corrected so that an image with high density is stabilized in the digital multi-functional peripheral shown in FIG. FIGS. 13A and 13B show the change in image density and laser power from the start of printing, respectively. FIG. 6 is a graph showing a change when laser power correction is performed so that a low density image is stabilized in the digital multi-functional peripheral shown in FIG. FIGS. 14A and 14B show the change in image density and laser power from the start of printing, respectively. FIG. 6 is an explanatory view showing an example of a user selection screen by CMYK display displayed on a display operation unit. FIG. 13 is an explanatory diagram showing an example of a user selection screen by RGB display displayed on the display operation unit in the digital multi-functional peripheral according to the second embodiment. FIG. 14 is an explanatory view showing an example of a user selection screen by a preview screen displayed on the display operation unit in the digital multi-functional peripheral according to the third embodiment.
As mentioned above,
(1) The image forming apparatus according to the present invention is an image forming apparatus for forming an image by an electrophotographic method, which includes an image carrier on which an electrostatic latent image is formed, and a developer carrier for carrying a developer. A charger for applying a charging voltage to the image carrier, a developing voltage application unit for applying a developing voltage to the developer carrier, and a density area determination for determining a density area of the image based on predetermined data And an image density stabilization control section for correcting the density of the image to be substantially uniform in time based on the density area determined by the section and the density area determination section.
Further, the image density stabilization control method of the present invention is an image density stabilization control method for forming an image by an electrophotographic method, wherein the density area determination step of determining the density area of the image according to the use situation of the user And an image density stabilization control step of correcting the density of the image to be substantially uniform in time based on the density area determined in the density area determination step, and the density area determination step Determining a density area of the image based on at least one of the image density selected by the user, the analysis result of the image data that is the origin of the image, and the density of the electrostatic latent image on the image carrier. It features.
Further, the image density stabilization control program of the present invention is an image density stabilization control program executed by an image forming apparatus which forms an image by an electrophotographic method, and a use state of a user of the processor of the image forming apparatus. And an image density for correcting the density of the image so as to be substantially uniform based on the density area determined in the density area determining step of determining the density area of the image in accordance with the density area. Performing a stabilization control step, wherein the density area determination step includes at least one of an image density selected by a user, an analysis result of image data which is the basis of the image, and a density of an electrostatic latent image on an image carrier. In one embodiment, the density area of the image is determined.
In the present invention, the "image forming apparatus" is an MFP (Multifunctional Peripheral) including a copying machine having a copying (copy function) function such as a printer using an electrophotographic system for toner image formation and a function other than copying. Device, etc., which forms and outputs an image.
Further, "to correct the density of the image so that it becomes substantially uniform in time" is due to the influence of the presence of the residual positive charge generated inside the image carrier, the rotational blur due to the eccentricity of the image carrier, etc. After the start of image formation, the image density is corrected so as to be substantially uniform in time so that the density of the image does not decrease and the density unevenness does not occur.
Furthermore, preferred embodiments of the present invention will be described.
(2) The image processing apparatus further comprises a density area selecting unit for receiving selection of the image density by the user, wherein the density area determining unit determines the density area of the image based on the density selected by the image density selecting section. May be
  In this way, since the density area of the image is determined based on the density selected by the user, it is possible to realize an image forming apparatus that performs stabilization control of an appropriate image density reflecting the user's usage condition. .
  (3) An image data acquisition unit that acquires image data that is the source of the image, and an image data analysis unit that analyzes the image data are further provided, and the density region determination unit is acquired by the image data analysis unit. The density area of the image generated from the image data may be determined based on the analysis result of the image data.
  In this way, since the density area of the image is determined based on the analysis result of the image data acquired by the image data acquisition unit, the image formation for performing the stabilization control of the appropriate image density reflecting the use situation of the user The device can be realized.
  (4) The image forming apparatus further comprises a latent image density sensor for detecting the density of the electrostatic latent image on the image carrier, and the density area determination unit determines the density of the electrostatic latent image detected by the latent image density sensor. The density area of the image may be determined based on the above.
  In this way, since the density area of the image is determined based on the density of the electrostatic latent image detected by the latent image density sensor, the image is subjected to stabilization control of the appropriate image density reflecting the user's usage condition A forming device can be realized.
  (5) The image density stabilization control unit controls the charging device to control the charging voltage so that the density of the image in the density area determined by the density area determination unit becomes substantially uniform in time. It may be changed.
  In this way, the charging voltage is changed so that the density of the image in the density area determined by the density area determination unit becomes substantially uniform in time, so that the appropriate image density stability reflecting the user's use situation It is possible to realize an image forming apparatus that carries out image forming control.
  (6) The image density stabilization control unit controls the charger and the developing voltage application unit so that the density of the image of the density region determined by the density region determination unit becomes substantially uniform in time. As described above, the charging voltage and the developing voltage may be changed.
  In this way, the charging voltage and the developing voltage are changed so that the density of the image in the density area determined by the density area determination unit becomes substantially uniform in time, so that an appropriate image reflecting the user's usage condition It is possible to realize an image forming apparatus that performs density stabilization control.
  (7) The image forming apparatus further includes a charger cleaning unit that cleans the charger, and the image density stabilization control unit controls the charger cleaning unit according to the density area determined by the density area determining unit. By cleaning the charger at a predetermined timing, the density of the image may be corrected so as to be substantially uniform in time.
  In this way, by cleaning the charger at a predetermined timing according to the density area determined by the density area determination unit, the appropriate image density stabilization control reflecting the user's use situation is performed. An image forming apparatus can be realized.
  (8) The apparatus further comprises an optical scanning device for irradiating the image carrier with a laser for exposure, and the image density stabilization control unit controls the light scanning device to control the laser intensity to be irradiated to the image carrier. The density of the image of the density area determined by the density area determination unit may be corrected so as to be substantially uniform in time by changing.
  In this way, by changing the laser intensity to be irradiated to the image carrier so that the density of the image of the density area determined by the density area determination unit is stabilized, the appropriate use state reflecting the user It is possible to realize an image forming apparatus that performs stabilization control of image density.
  Hereinafter, the present invention will be described in more detail using the drawings. The following description is an exemplification in all respects, and should not be construed as limiting the present invention.
Embodiment 1
A digital multi-functional peripheral 1, which is an embodiment of the image forming apparatus of the present invention, will be described based on FIGS.
FIG. 1 is a perspective view showing the appearance of a digital multi-function peripheral 1 which is an embodiment of the image forming apparatus of the present invention. FIG. 2 is a cross-sectional view showing the mechanical configuration of the main body portion of the digital multi-functional peripheral 1 shown in FIG.
  The digital multifunction device 1 is a device such as an MFP (Multifunctional Peripheral: multifunction peripheral device) having digital processing of image data and having a copying function, a scanner function, and a facsimile function.
  As shown in FIG. 2, the digital multi-functional peripheral 1 includes an original conveying device 112 for conveying an original to a reading unit, an original reading device 111 for reading an original, and an image forming unit 102 for forming an image. The digital multi-functional peripheral 1 executes a scanner, print and copy job based on an instruction from a user accepted via the display operation unit 1071 or the physical operation unit 1072 or the communication unit 105 (see FIG. 3).
<Configuration of Digital MFP 1>
Here, the internal configuration of the digital multi-functional peripheral 1 shown in FIG. 2 will be briefly described.
In the digital multifunction peripheral 1, a color image using each color of black (K), cyan (C), magenta (M), and yellow (Y) is printed on a print sheet. Alternatively, a monochrome image using a single color (for example, black) is printed on the print sheet. Therefore, four developing devices 12, four photosensitive drums 13, four drum cleaning devices 14, and four chargers 15 are provided. In order to form four types of toner images corresponding to the respective colors, four image stations Pa, Pb, Pc, and Pd are configured in correspondence with black, cyan, magenta, and yellow, respectively.
  A toner image is formed in any of the image stations Pa, Pb, Pc, Pd as follows. The drum cleaning device 14 removes and collects residual toner on the surface of the photosensitive drum 13. Thereafter, the charger 15 uniformly charges the surface of the photosensitive drum 13 to a predetermined potential. Then, the light scanning device 11 exposes the uniformly charged surface to form an electrostatic latent image on the surface. Thereafter, the developing device 12 develops the electrostatic latent image. As a result, toner images of the respective colors are formed on the surfaces of the respective photosensitive drums 13.
  Further, the intermediate transfer belt 21 circumferentially moves in the arrow direction C. The belt cleaning device 22 removes and collects residual toner on the rotating intermediate transfer belt 21. The toner images of the respective colors on the surfaces of the respective photosensitive drums 13 are sequentially transferred to and superimposed on the intermediate transfer belt 21, and a color toner image is formed on the intermediate transfer belt 21.
  The print sheet is pulled out from any one of the four feeding trays 18 by the pickup roller 33, and is fed to the secondary transfer device 23 through the sheet conveyance path R1. Alternatively, the sheet is fed from the manual feed tray 19 by a pickup roller (not shown) and fed to the secondary transfer device 23 through the sheet conveyance path R1. A registration roller 34 is disposed in the sheet conveyance path R1 to temporarily stop the printing sheet and align the leading edge of the printing sheet. In addition, a conveyance roller 35 or the like is disposed which urges the conveyance of the print sheet. After temporarily stopping the print sheet, the registration roller 34 conveys the print sheet to the nip area between the intermediate transfer belt 21 and the transfer roller 23a in accordance with the transfer timing of the toner image.
  A nip area is formed between the transfer roller 23 a of the secondary transfer device 23 and the intermediate transfer belt 21. When the print sheet passes through the nip, a color toner image formed on the surface of the intermediate transfer belt 21 is transferred to the print sheet. After passing through the nip area, the print sheet is sandwiched between the heating roller 24 and the pressure roller 25 of the fixing device 17 to be heated and pressurized. The heating and pressing fix a color toner image on the printing sheet.
  The print sheet having passed through the fixing device 17 is discharged to the discharge tray 39a or 39b through the discharge roller 36a or 36b. The discharge destination of the print sheet is controlled by the control unit 100 described later, and the conveyance path is switched such that the print sheet is guided to any of the discharge trays 39a and 39b by a switching mechanism (not shown). The switching mechanism of the print sheet transport path is not shown in detail because it is well known in the technical field of the image forming apparatus.
Next, a schematic configuration of the digital multi-functional peripheral 1 will be described based on FIG.
FIG. 3 is a block diagram showing a schematic configuration of the digital multifunction peripheral 1 shown in FIG.
As shown in FIG. 3, the digital multi-functional peripheral 1 includes a control unit 100, an image reading unit 101, an image forming unit 102, a storage unit 103, an image processing unit 104, a communication unit 105, a paper feeding unit 106, a panel unit 107, and time counting. A unit 108 and an image density sensor 109 are provided.
Hereinafter, each component of the digital multi-functional peripheral 1 will be described.
The control unit 100 controls the digital multi-functional peripheral 1 in an integrated manner, and includes a CPU, a RAM, a ROM, various interface circuits, and the like.
The control unit 100 monitors and controls all loads such as detection of each sensor, a motor, a clutch, and a panel unit 107 in order to control the overall operation of the digital multi-functional peripheral 1.
  The image reading unit 101 is a part that detects and reads an original such as a card placed on an original placement table 191 or an original conveyed from an original tray, and generates image data.
  The image forming unit 102 is a unit that prints out the image data generated by the image processing unit 104 on a sheet.
A storage unit 103 is an element or storage medium that stores information necessary to realize various functions of the digital multi-functional peripheral 1, a control program, and the like. For example, a storage element such as a semiconductor element such as a RAM or a ROM, a hard disk, a flash storage unit, or an SSD is used.
The program and data may be held in different devices such that the area for holding data is a hard disk drive and the area for holding a program is a flash storage unit.
  The image processing unit 104 is a portion that converts an image of a document read by the image reading unit 101 into an appropriate electrical signal to generate image data. The image processing unit 1071 also processes image data input from the image reading unit 101 in accordance with an instruction from the display operation unit 1071 so as to be suitable for output such as enlargement and reduction. Further, it is a portion to associate a plurality of image data in accordance with a predetermined layout.
  A communication unit 105 communicates with a computer, a portable information terminal, an external information processing apparatus, a facsimile machine, etc. via a network etc., and transmits / receives various information such as e-mails and faxes to / from these external communication machines. It is.
  The sheet feeding unit 106 is a portion that conveys a sheet stored in a sheet feeding cassette and a manual feed tray to the image forming unit 102.
  The panel unit 107 is a unit provided with a liquid crystal display (Liquid Crystal Display), and includes a display operation unit 1071 and a physical operation unit 1072.
  A display operation unit 1071 is a part that displays various types of information and receives an instruction from the user by the touch panel function. The display operation unit 1071 is, for example, a CRT display, a liquid crystal display, an EL display, or the like, and is a display device such as a monitor or a line display for displaying electronic data such as a processing state of an operating system or application software. The control unit 100 displays the operation and status of the digital multi-functional peripheral 1 through the display operation unit 1071.
  The clock unit 108 is a part that measures time, and acquires time through, for example, a built-in clock or a network. The control unit 100 controls the charger cleaner (not shown) with reference to the time acquired by the timer unit 108 to clean the charger 15 at predetermined cleaning time intervals.
  The image density sensor 109 is a sensor that detects the image density from the density of the electrostatic latent image formed on the photosensitive drum 13.
<Image Density Stabilization Control of Digital MFP 1>
Next, image density stabilization control of the digital multi-function peripheral 1 according to the first embodiment of the present invention will be described based on FIG.
FIG. 4 is a flowchart showing processing of image density stabilization control of the digital multi-functional peripheral 1 shown in FIG.
  In step S11 of FIG. 4, the control unit 100 measures the density of the print image by the image density sensor 109, and stores the density measurement result in the storage unit 103 (step S11).
  In step S12, the control unit 100 analyzes the print data of the user in the past, and stores the density measurement result in the storage unit 103 (step S12).
  In step S13, the control unit 100 causes the storage unit 103 to store the image density result selected by the user according to the image density setting (step S13).
  Next, in step S20, the control unit 100 determines an image density area for which the user seeks stability based on the results of steps S11 to S13 (step S20).
  Next, in step S31, the control unit 100 selects periodic unevenness stabilization control based on the determination result of step S20 (step S31).
  Further, in step S32, the control unit 100 selects the 1-job image density stabilization control based on the determination result of step S20 (step S32).
  Next, in step S33, the control unit 100 selects stabilization control by developing potential correction based on the determination result of step S20 (step S33).
  Next, in step S34, the control unit 100 selects automatic charging cleaning based on the determination result of step S20 (step S34).
  The control unit 100 may select two or more stabilization controls among the stabilization controls in steps S31 to S34.
  Finally, in step S40, the control unit 100 reflects the selection result of the stabilization control on the image density stabilization correction control table, and stores the result in the storage unit 103 (step S40).
The control unit 100 corrects the image density based on the image density stabilization correction control table stored in the storage unit 103.
Here, Table 1 shows an example of the image density stabilization correction control table.
  Table 1 shows the correction start differential charging voltage, charging voltage (amplitude), exposure laser power and cleaning interval selected in four control methods: 1 Job stability, periodic unevenness stability, development potential stabilization and automatic charger cleaning. It shows that it varies depending on the image density (low density, medium density and high density).
FIG. 5 is a table summarizing the characteristics of four types of image density stabilization control of the digital multi-functional peripheral 1 shown in FIG.
From the top, there are four types of image density stabilization control in 1 Job: image density stabilization control, periodic unevenness stabilization control, development potential image density stabilization control, automatic charger cleaning.
FIG. 5 describes “correction target”, “degree of stabilization at low density”, “degree of stabilization at high density”, and “defect” regarding each image density stabilization control.
The correction target of the image density stabilization control in 1 Job is the charging voltage to the photosensitive drum 13. When the image density is low (at low density), the correction amount of the charging voltage is small and the image density is high (high At the time of density), the correction amount of the charging voltage is large.
Further, as a bad effect, for example, when the correction is made with the high density region correspondence table value (20 V in the example of Table 1), the correction of the low density portion becomes excessive.
The correction targets of the periodic unevenness stabilization control are the charging voltage and the developing voltage, and when the image density is low (at the time of low density), the correction amount of the charging voltage and the developing voltage is small and the image density is high (at the time of high density The correction amount of the charging voltage and the developing voltage is large, and the phase of the periodic change of the image density is inverted by 180 °.
Also, as a negative effect, for example, when the correction is made with the high density region correspondence table value (24 V in the example of Table 1), the phase of the density change in the low density portion is reversed.
The correction target of the stabilization control by the development potential correction is the laser power for irradiating the photosensitive drum 13, that is, the exposure amount. When the image density is low (at the time of low density), the correction amount of the laser power is small. Is high (at the time of high concentration), the correction amount of the laser power is large.
As a negative effect, when correction is performed using the high density region correspondence table value (12 μW in the example of Table 1), the correction of the low density portion becomes excessive.
The correction target of the automatic charger cleaning is the cleaning interval of the charger 15. When the image density is low (during low density), the cleaning interval is short and when the image density is high (high density), the cleaning interval is long.
Further, the disadvantage is that when the correction is made with the low density area correspondence table value (every 500 sheets in the example of Table 1), the cleaning interval becomes short and the downtime of the digital multi-functional peripheral 1 increases.
  Next, details of each image density stabilization control will be described.
<1 Job image density stabilization control>
The 1-Job image density stabilization control will be described based on FIGS. 6 to 8.
FIG. 6 is a graph showing changes in image density, grid bias and development bias from the start of printing in the digital multi-functional peripheral 1 shown in FIG. 6A to 6C show changes in image density, grid bias and development bias from the start of printing, respectively.
FIG. 7 is a graph showing a change when grid bias correction is performed so that a high density image is stabilized. FIGS. 7A to 7C show changes in image density, grid bias and development bias, respectively, from the start of printing.
FIG. 8 shows a change in image density, a change in grid bias, and a change in development bias from the start of printing when the grid bias is corrected so that a low density image is stabilized in the digital multi-functional peripheral 1 shown in FIG. It is a graph. FIGS. 8A to 8C show changes in image density, grid bias and development bias, respectively, from the start of printing.
Here, the horizontal axis in FIG. 6A indicates the elapsed time from the start of printing, the vertical axis indicates the height of the image density, and the horizontal axis in FIGS. 6B and 6C indicates the elapsed time from the start of printing The vertical axis represents the height of the bias. Moreover, all units are arbitrary units.
The same applies to FIGS. 7 and 8.
In the image formation, after the photosensitive drum 13 is charged, once it is left, residual positive charge may be generated inside the photosensitive drum 13.
Therefore, when charging next time, the negative charge is less likely to get on the photosensitive drum 13, causing a change in image density, and as shown in FIG. 6A, both the high density image and the low density image are generated. After printing starts, the image density decreases.
However, as shown in FIGS. 6B and 6C, it is assumed that the grid bias and the development bias are constant.
When the control unit 100 detects a decrease in image density due to the generation of the residual positive charge in the photosensitive drum 13 by the image density sensor 109, the control unit 100 prevents the decrease in the image density, Correction of the charging voltage.
Specifically, minus correction is performed to reduce the grid bias immediately after the start of printing, and the correction amount is changed in the high density area and the low density area.
When correcting the density change in the area where the image density is high, as shown in FIG. 7B, the negative correction is performed so that the grid bias immediately after the start of printing becomes low.
At this time, the correction amount is adjusted so that the high density image is stabilized.
As a result, as shown in FIG. 7A, the density change after the start of printing of the high density image is improved and stabilized.
On the other hand, for an image with a low density, the correction amount is excessive, so that a density change as seen from the density change of FIG. 6A is observed.
Next, when correcting the density change in the area where the image density is low, as shown in FIG. 8B, the negative correction is performed so that the grid bias immediately after the start of printing becomes low.
At this time, the correction amount is adjusted so that the low density image is stabilized.
As a result, as shown in FIG. 8A, the density change after the start of printing of the low density image is improved and stabilized.
On the other hand, in the case of an image having a high density, since the correction amount is insufficient, the density change is small from FIG. 6A, but the density change still remains.
  Note that which of the high density image and the low density image is to be corrected is determined based on the image density selected by the user or the analysis result of the print data in the past.
  In this way, the image of the target density is stabilized by correcting the grid bias according to which of the high density image and the low density image is stabilized. be able to.
<Non-uniform cycle stabilization control>
Next, periodic unevenness stabilization control will be described based on FIG. 9 to FIG.
FIG. 9 is a graph showing changes in image density distribution, grid bias and development bias for one rotation of the photosensitive drum 13 from the start of printing. FIGS. 9A to 9C show changes in image density, grid bias and development bias, respectively, from the start of printing.
FIG. 10 is a graph showing a change when the grid bias is corrected so that the high density image is stabilized in the digital multi-functional peripheral 1 shown in FIG. FIGS. 10A to 10C show changes in image density, grid bias and development bias, respectively, from the start of printing.
FIG. 11 shows a change in image density, a change in grid bias, and a change in development bias from the start of printing when the grid bias is corrected so that a low density image is stabilized in the digital multi-functional peripheral 1 shown in FIG. It is a graph. FIGS. 11A to 11C show changes in image density, grid bias and development bias, respectively, from the start of printing.
Here, the horizontal axis in FIG. 9A indicates the elapsed time from the start of printing, the vertical axis indicates the height of the image density, and the horizontal axis in FIGS. 9B and 9C indicates the elapsed time from the start of printing The vertical axis represents the height of the bias. Moreover, all units are arbitrary units.
The same applies to FIG. 10 and FIG.
  The periodic unevenness is a phenomenon in which unevenness occurs in the image density for one rotation of the photosensitive drum 13 due to the influence of rotational shake or the like due to the eccentricity of the photosensitive drum 13 or the like.
  As shown in FIG. 9A, in both the high density image and the low density image, a periodic change in the image density distribution due to periodic unevenness appears.
When the cycle density is detected by the image density sensor 109, the control unit 100 corrects the charging voltage of the photosensitive drum 13 in order to prevent the periodic change of the image density.
Specifically, as shown in FIGS. 10B and 10C, the grid bias and the development bias are corrected so as to periodically change with the passage of time.
At this time, the grid bias and the development bias are corrected so that the phase is exactly 180 ° inverted with the density change of the image in FIG. 9A, and the correction amount is adjusted so that the high density image is stabilized.
As a result, as shown in FIG. 10A, the periodic density change after printing of the high density image is improved and stabilized.
On the other hand, for an image with a low density, the correction amount is excessive, so that a periodic density change as seen from the density change of FIG. 9A can be seen.
Next, when correcting the density change in the area where the image density is low, as shown in FIG. 11B, the grid bias and the developing bias are corrected so as to periodically change with the passage of time.
At this time, the grid bias and developing bias are corrected so that the phase is exactly 180 ° inverted with the density change of the image, and the correction amount is adjusted smaller than that in FIG. 10B so that the low density image is stabilized. Do.
As a result, as shown in FIG. 11A, the density change after the start of printing of the low density image is improved and stabilized.
On the other hand, in the case of an image having a high density, since the correction amount is insufficient, the density change is small from FIG. 9A, but the density change still remains.
  Note that which of the high density image and the low density image is to be corrected is determined based on the image density selected by the user or the analysis result of the print data in the past.
<Stabilization control by developing potential correction>
Next, the stabilization control of the image density by the development potential correction will be described based on FIGS. 12 to 14.
FIG. 12 is a graph showing a change in image density from the start of printing and a change in laser power applied to the photosensitive drum 13. FIGS. 12A and 12B show the change in image density and laser power from the start of printing, respectively.
FIG. 13 is a graph showing a change when the laser power is corrected so that the high density image is stabilized in the digital multi-functional peripheral 1 shown in FIG. FIGS. 13A and 13B show the change in image density and laser power from the start of printing, respectively.
FIG. 14 is a graph showing a change when the laser power is corrected to stabilize the low density image in the digital multi-functional peripheral 1 shown in FIG. FIGS. 14A and 14B show the change in image density and laser power from the start of printing, respectively.
Here, the horizontal axis in FIG. 12A indicates the elapsed time from the start of printing, the vertical axis indicates the height of the image density, and the horizontal axis in FIG. 12B indicates the elapsed time from the start of printing Indicates the laser power. Moreover, all units are arbitrary units.
The same applies to FIGS. 13 and 14.
  As described in the image density stabilization control in 1 Job, generation of the residual positive charge inside the photosensitive drum 13 causes printing of both high density and low density images as shown in FIG. 12A. After the start, the image density decreases. At this time, as shown in FIG. 12B, the laser power is constant.
  For such a problem, when the control unit 100 detects a decrease in the image density due to the generation of the residual positive charge in the photosensitive drum 13 by the image density sensor 109, the control in place of the image density stabilization control within 1 Job is performed. Alternatively, in combination with image density stabilization control in 1 Job, stabilization control by development potential correction is performed.
  Specifically, minus correction is performed to reduce the laser power immediately after the start of printing, and the correction amount is changed in the area with high image density and the area with low density.
In the case of correcting the density change in the area where the image density is high, as shown in FIG. 13B, the negative correction is performed so that the laser power immediately after the start of printing becomes low.
At this time, the correction amount is adjusted so that the high density image is stabilized.
As a result, as shown in FIG. 13A, the density change after the start of printing of the high density image is improved and stabilized.
On the other hand, for an image with a low density, the correction amount is excessive, so that a density change as seen from the density change of FIG. 13A is observed.
Next, when correcting the density change in the area where the image density is low, as shown in FIG. 14B, the negative correction is performed so that the grid bias immediately after the start of printing becomes low.
At this time, the correction amount is adjusted so that the low density image is stabilized.
As a result, as shown in FIG. 13A, the density change after the start of printing of the low density image is improved and stabilized.
On the other hand, in the case of an image having a high density, since the correction amount is insufficient, the density change is small from FIG. 12A, but the density change still remains.
  Note that which of the high density image and the low density image is to be corrected is determined based on the image density selected by the user or the analysis result of the print data in the past.
<Automatic charge cleaning>
By performing the automatic cleaning operation of the charger 15 with the charger cleaner, it is possible to stabilize the image quality including the image density.
  For example, as shown in Table 2 below, the image quality and productivity of the digital multi-functional peripheral 1 are controlled by setting the cleaning time interval.
  Table 2 shows how many times the charger 15 should be cleaned for each of the low humidity environment, the normal humidity environment and the high humidity environment for each image quality priority setting, recommended setting and productivity priority setting.
  For example, in the image quality priority setting, cleaning of the charger 15 is executed once every 600 sheets in a low humidity environment.
However, if the automatic cleaning operation is frequently performed, the image quality is stabilized, but since the cleaning operation requires a certain time, the productivity of copying and printing of the digital multi-functional peripheral 1 is reduced.
Therefore, in order to solve such a problem, the cleaning operation of the charger 15 is performed at an appropriate time interval based on a predetermined setting according to whether the user gives priority to the image quality or the productivity. Do.
The automatic charging cleaning is performed when carrying out the cleaning control.
  As described above, by selecting the four types of image density stabilization control according to the characteristics, the digital multi-function peripheral 1 that performs appropriate image density correction control is realized.
  Next, an example of the selection of the image density by the user will be described based on FIG.
  FIG. 15 is an explanatory view showing an example of a user selection screen by CMYK display displayed on the display operation unit 1071. As shown in FIG.
As shown in FIG. 15, on the setting screen of image density, the control unit 100 causes the display operation unit 1071 to display a list of colors displayed in CMYK.
The user selects and touches the color to be stabilized out of the list of colors displayed on the display operation unit 1071.
For example, when the color of the Bk series in the top row of FIG. 15 is selected, the correction reflection destination is the Bk process condition.
Specifically, the control unit 100 stabilizes the image density with respect to the photosensitive drum 13, the developing device 12, and the charger 15 of the image station Pa corresponding to black according to the image density of the selected Bk series. Control control.
The same is true when other series of colors are selected.
  In this manner, the density area for which the user seeks stable image quality based on the density measurement result of the print image measured by the image density sensor 109, the density measurement result by analysis of the print data of the user in the past, and the image density result selected by the user. By performing optimal density stabilization control based on the determination result, to stabilize the appropriate image density that reflects the user's use situation among images of various density areas from low density to high density. A digital multi-functional peripheral 1 that performs control can be realized.
Second Embodiment
Next, an example of the selection of the image density by the user in the digital multi-functional peripheral 1 according to the second embodiment will be described based on FIG.
  FIG. 16 is an explanatory view showing an example of a user selection screen by RGB display displayed on the display operation unit 1071.
As shown in FIG. 16, on the setting screen of image density, the control unit 100 causes the display operation unit 1071 to display a list of colors displayed in RGB.
The user selects and touches the color to be stabilized out of the list of colors displayed on the display operation unit 1071.
For example, when the color of the R series in the top row of FIG. 16 is selected, the correction reflection destination is the MY process condition.
Specifically, control unit 100 causes image stations Pc and Pd corresponding to magenta and yellow to correspond to photosensitive drums 13, developing device 12 and charger 15, respectively, according to the image density of the selected MY series. , Stabilize control of image density.
The same is true when other series of colors are selected.
  In addition, it may be possible to set whether to display the setting screen in the CMYK display or the RGB display.
  In this way, among the images of various density areas from low density to high density, appropriate image density stabilization control reflecting the user's usage condition is reflected, reflecting the image of the optimum density desired by the user. It is possible to realize the digital multi-functional peripheral 1 to be performed.
Third Embodiment
Next, an example of selection of image density by the user in the digital multi-functional peripheral 1 according to the third embodiment will be described based on FIG.
As shown in FIG. 17, the control unit 100 may display a preview image of the input image on the display operation unit 1071 so that the user touches the image density to be stabilized.
For example, when a part of the preview image is touched, a circle is displayed at the touched position to indicate the selected image density to the user.
  In this way, referring to the preview screen, the image of the optimum density desired by the user is reflected, and among the images of various density regions from low density to high density, an appropriate image reflecting the user's usage situation It is possible to realize the digital multi-functional peripheral 1 that performs concentration stabilization control.
Embodiment 4
In the determination of the image quality / density area where the user seeks stability in step S20 of FIG. 4 of the first embodiment, the control unit 100 prioritizes the three results of steps S11 to S13 to be referred to for determination. Good.
  For example, the determination in step S20 may be performed after the priority order is determined in the order of the result of the user selection in step S13, the past print result in step S12, and the measurement result in step S11.
  In this way, among the images of various density regions from the low density to the high density, the appropriate image density stabilization control reflecting the user's usage condition is reflected, reflecting the density image that the user seeks to be stable. It is possible to realize the digital multi-functional peripheral 1 to be performed.
Fifth Embodiment
In the fifth embodiment, the image density correction value is calculated by direct calculation based on a predetermined calculation formula or the like based on the selected image density without using the image density stabilization correction control table as shown in Table 1. It may be carried out.
  In this way, the appropriate stabilization control is selected according to the use situation, so among the images of various density areas from low density to high density, the stabilization of the appropriate image density reflecting the use situation of the user It is possible to realize the digital multi-functional peripheral 1 that performs the integration control.
Preferred embodiments of the present invention also include combinations of any of the above-described plurality of embodiments.
Besides the embodiment described above, various modifications may be made to the present invention. Those variations are not to be construed as not falling within the scope of the present invention. The scope of the present invention should include the meanings equivalent to the scope of claims and all the modifications within the scope.
1: Digital MFP, 11: Optical scanning device, 12: Developing device, 13: Photosensitive drum, 14: Drum cleaning device, 15: Charger, 17: Fixing device, 18: Feeding tray, 19: Manual feeding tray, 21: Intermediate transfer belt, 22: Belt cleaning device, 23: Secondary transfer device, 23a: Transfer roller, 24: Heating roller, 25: Pressure roller, 33: Pickup roller, 34: Registration roller, 35: Conveying roller, 36a and 36b: discharge rollers 39a and 39b: discharge trays 100: control unit 101: image reading unit 102: image forming unit 103: storage unit 104: image processing unit 105: communication unit 106: supply Paper section, 107: Panel unit, 108: Timekeeping section, 1 9: image density sensor 111: document reader 112: document feeder 191: document platen 1071: display operation unit 1072: physical operation unit C: arrow direction Pa, Pb, Pc, Pd: image Station, R1: Sheet transport path

Claims (10)

  1. An image forming apparatus for forming an image by an electrophotographic method, comprising:
    An image carrier on which an electrostatic latent image is formed;
    A developer carrier that carries a developer;
    A charger for applying a charging voltage to the image carrier;
    A development voltage application unit that applies a development voltage to the developer carrier;
    The density of the image is corrected so that the density of the image becomes substantially uniform on the basis of the density area determination unit which determines the density area of the image according to the use condition of the user and the density area determined by the density area determination unit. And an image density stabilization control unit.
  2. It further comprises an image density selection unit that accepts the selection of the image density by the user,
    The image forming apparatus according to claim 1, wherein the density area determination unit determines the density area of the image based on the density selected by the image density selection unit.
  3. An image data acquisition unit that acquires image data that is the basis of the image;
    An image data analysis unit that analyzes the image data;
    The image forming apparatus according to claim 1, wherein the density area determination unit determines a density area of an image generated from the image data based on an analysis result of the image data obtained by the image data analysis unit. .
  4. It further comprises a latent image density sensor for detecting the density of the electrostatic latent image on the image carrier,
    The image forming apparatus according to any one of claims 1 to 3, wherein the density area determination unit determines the density area of the image based on the density of the electrostatic latent image detected by the latent image density sensor. .
  5.   The image density stabilization control unit controls the charger to change the charging voltage so that the density of the image of the density area determined by the density area determination unit becomes substantially uniform in time. The image forming apparatus according to any one of Items 1 to 4.
  6.   The image density stabilization control unit controls the charger and the development voltage application unit so that the density of the image of the density region determined by the density region determination unit becomes substantially uniform in time. The image forming apparatus according to any one of claims 1 to 4, wherein the charging voltage and the developing voltage are changed.
  7. The apparatus further comprises a charger cleaning unit for cleaning the charger.
    The image density stabilization control unit controls the charger cleaning unit to clean the charger at a predetermined timing according to the density area determined by the density area determination unit. The image forming apparatus according to any one of claims 1 to 6, wherein the image density is corrected so as to be substantially uniform in time.
  8. The apparatus further comprises an optical scanning device that irradiates the image carrier with a laser to perform exposure.
    The image density stabilization control unit controls the light scanning device to change the laser intensity to be irradiated to the image carrier, thereby the density of the image of the density region determined by the density region determining unit. The image forming apparatus according to any one of claims 1 to 7, wherein the image is corrected so as to be substantially uniform in time.
  9. An image density stabilization control method for forming an image by an electrophotographic method, comprising:
    A density area determining step of determining a density area of the image in accordance with a use condition of a user;
    And an image density stabilization control step of correcting the density of the image to be substantially uniform in time based on the density region determined in the density region determining step,
    The density area determination step is performed based on at least one of the image density selected by the user, the analysis result of the image data which is the origin of the image, and the density of the electrostatic latent image on the image carrier. An image density stabilization control method characterized by determining an area.
  10. An image density stabilization control program executed by an image forming apparatus that forms an image by an electrophotographic method, comprising:
    A processor of the image forming apparatus;
    A density area determining step of determining a density area of the image in accordance with a use condition of a user;
    Performing an image density stabilization control step of correcting the density of the image so as to be substantially uniform temporally on the basis of the density region determined in the density region determining step;
    The density area determination step is performed based on at least one of the image density selected by the user, the analysis result of the image data which is the origin of the image, and the density of the electrostatic latent image on the image carrier. An image density stabilization control program characterized by determining an area.
JP2017196104A 2017-10-06 2017-10-06 Image forming apparatus, image density stabilization control method, and image density stabilization control program Pending JP2019070712A (en)

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