JP2008151855A - Image forming device and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that gradation correction of color is performed even in a color copying machine or a printer of electrographic type or the like performing monochrome printing and copying only, and in the conventional technology, the copying machine or the printer performing job only using black toner consumes color toner since operation is performed while using much toner when gradation correction forms toner images (patches) on a photosensitive drum or the like. <P>SOLUTION: A color image forming device carries out a monochrome control mode performing gradation correction of black toner only and a color control mode performing gradation correction of the black toner and the color toner. At least either one of the first control mode or the second control mode can be set selectively to carry out the set control mode. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a color image forming apparatus that performs gradation correction.

  2. Description of the Related Art Conventionally, various controls that are not performed by a black and white copying machine or printer are performed on a color copying machine or printer such as an electrophotographic system (for example, Patent Document 1). When forming a color image, usually, toner images of four colors of yellow, magenta, cyan, and black are individually formed, and finally these are superimposed on a transfer material (for example, paper, transparent film). A full color image is obtained by mixing the toners. For this reason, the image quality differs significantly depending on the color balance of the toner images of the respective colors and the relative position accuracy. Various controls have been introduced to suppress the balance and position of these colors. For example, a feed-forward control in which a development contrast potential for obtaining optimum development characteristics based on environmental information such as temperature and humidity outside the image forming apparatus is set in advance, or a toner image (patch) is actually applied to a photosensitive drum or the like. The image quality is improved by gradation correction and the like by forming and detecting the density to self-diagnose the development characteristics and feed back to the image control parameters.

  In the above-described tone correction, patches and the like are actually formed and detected to update the setting of the image control parameter (change the image forming conditions by the image forming unit). In order to maintain image quality, this control is performed periodically such as when the power is turned on, when returning from sleep mode, or when a certain number of images are output.

  However, during the tone correction operation, an output job such as printing cannot be executed, and it takes time for tone correction itself. Therefore, if the job is executed at the time of job submission or job execution, the user job is completed. It takes time. Therefore, according to Japanese Patent Laid-Open No. 2005-173040, when warming up at power-on or when returning from sleep, it is confirmed whether there is a job, and if there is a job, simplified gradation correction is performed. Yes. Therefore, the control can be shortened as necessary while ensuring the image quality.

Further, according to Japanese Patent Laid-Open No. 2005-275378, the user sets the tolerance for the image quality, performs the normal gradation correction for a user with a narrow tolerance, and performs the gradation correction for a wide user. It is described that the control is performed in a short time or not. Therefore, an image can be output in a short time by the user's selection.
JP-A-5-322760 JP 2005-173040 A JP 2005-275378 A

  According to the above, it is possible to reduce start-up time and power consumption at the time of gradation correction by performing simplified gradation correction. For example, color such as black-and-white printing and electrophotography that only performs copying The color gradation correction also operates on the other copiers and printers.

  In the conventional technique, gradation correction is described as forming a toner image (patch) on a photosensitive drum or the like. In other words, it operates while using a lot of toner. Therefore, a multi-function device or printer that performs only a job that uses only black toner also has a problem of consuming color toner.

  An image forming unit capable of forming an image on a transfer material and capable of forming an image for gradation control; a detecting unit for detecting the density of the image for gradation control; and the gradation control unit immediately before image formation. An image is formed, an image forming condition is updated based on a detection result of the detecting unit with respect to the formed gradation control image, and an image is formed based on the updated image forming condition. And a control unit that controls gradation of an image to be formed. The control unit includes a monochrome control mode in which gradation correction is performed only for black toner, and the control unit includes black toner and color toner. And a color control mode for performing tone correction of at least one of the first control mode and the second control mode can be selectively set, and the set control mode can be selectively set. Is executed, and to, wherein the.

  According to the present invention, since there is an activation mode in which only the gradation correction of only black toner is performed, the amount of color toner used for gradation correction can be reduced as compared with a normal color image forming apparatus. Since there is an activation mode setting means for performing gradation correction only for black toner, the activation mode can be selected by the user.

  If only the black toner is not subjected to gradation correction, the intermediate transfer drum 13 is rotated four times in total, and the control time is reduced from 35 seconds to 20 seconds, which can be shortened by 15 seconds.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, what attached | subjected the same code | symbol in each drawing has the same structure or effect | action, The duplication description about these is abbreviate | omitted suitably.

  FIG. 1 shows an image forming apparatus according to Embodiment 1 as an example of an image forming apparatus according to the present invention. The image forming apparatus shown in FIG. 1 is an electrophotographic four-color full-color copying machine (hereinafter referred to as “image forming apparatus”) using an intermediate transfer member, and the figure schematically shows the schematic configuration thereof. It is.

  The outline of the configuration and operation of the entire image forming apparatus will be described with reference to FIG.

  The image forming apparatus shown in FIG. 1 includes a printer unit A that forms an image and a reader unit B that reads an image of a document.

  In the printer unit A, a drum-shaped electrophotographic photosensitive member (hereinafter referred to as “photosensitive drum”) 1 is disposed as an image carrier. The photosensitive drum is rotatably supported by the image forming apparatus main body M, and is rotationally driven at a predetermined process speed (circumferential speed) in the direction of arrow R1 by a driving unit (not shown).

  Various process devices are disposed around the photosensitive drum 1. That is, around the photosensitive drum 1, there are a primary charger (charging means) 2, an exposure device (exposure means) 3, a developing device (developing means) 4, a transfer device (transfer means) 5, and a cleaning device (cleaning means) 6. Is arranged. The primary charger (charging unit) 2 uniformly charges the surface of the photosensitive drum 1 along the rotation direction of the photosensitive drum 1. The exposure device (exposure unit) 3 irradiates the charged photosensitive drum 1 with a light image obtained by color-separating a color image or a light image corresponding thereto, thereby forming an electrostatic latent image of the image. The developing device (developing unit) 4 develops the electrostatic latent image on the photosensitive drum 1 as a toner image. The transfer device (transfer means) 5 transfers the toner image on the photosensitive drum 1. A cleaning device (cleaning means) 6 cleans the surface of the photosensitive drum 1.

  As the photosensitive drum 1, for example, an OPC photosensitive member in which an OPC (organic optical semiconductor) photosensitive layer is formed on the surface of a conductive aluminum substrate is used.

  The primary charger 2 has a charging roller in contact with the surface of the photosensitive drum 1 and a charging bias application power source (not shown) for applying a charging bias to the charging roller.

  The exposure device 3 includes a laser transmission device 11 that is on / off controlled according to image information and a reflection mirror 12 that guides the transmitted laser light to the surface of the photosensitive drum 1.

  The developing device 4 includes a fixed developing device 4A and a rotary developing device 4B. Among these, the fixed developing device 4A is constituted by a black developing device 4K in which a black developer is accommodated. The rotary developing unit 4B includes a rotatable rotary 4a and developer units 4Y, 4M, 4M, and 4M, which are mounted on the rotary unit 4a and store developer of yellow (Y), magenta (M), and cyan (C), respectively. 4C. The rotary developing device 4B is arranged at a developing portion (developing position) where the developing device of the color used for developing the electrostatic latent image on the photosensitive drum 1 is opposed to the surface of the photosensitive drum 1 by the rotation of the rotary 4a. Thus, toner is attached to the electrostatic latent image and developed as a toner image.

  The transfer device 5 includes an intermediate transfer drum 13 serving as an image carrier and an intermediate transfer member, and a primary transfer charger 14 disposed at a position corresponding to the photosensitive drum 1 in the intermediate transfer drum 13. A primary transfer portion T1 is formed between the photosensitive drum 1 and a position corresponding to the photosensitive drum 1 in the intermediate transfer drum 13. A secondary transfer roller 15 is disposed below the intermediate transfer drum 13. A transfer belt 17 is stretched around the secondary transfer roller 15 and the roller 16. A secondary transfer portion T <b> 2 is formed between the intermediate transfer drum 13 and the secondary transfer roller 15. A charger 18 for adjusting the potential of the toner image on the intermediate transfer drum 13 downstream of the primary transfer portion T1 and upstream of the secondary transfer portion T2 along the rotation direction of the intermediate transfer drum 13 (arrow R13 direction); There is a density detection sensor 19 that detects the density of the toner image on the intermediate transfer drum 13. The density detection sensor 19 is, for example, a reflective optical sensor, and is disposed so as to face the surface of the intermediate transfer drum 13. Further, a drum cleaner 23 for cleaning the surface of the intermediate transfer drum 13 is disposed on the downstream side of the secondary transfer portion T2 along the rotation direction of the intermediate transfer drum 13 and on the upstream side of the primary transfer portion T1. Yes.

  The cleaning device 6 has a cleaning blade 20 that removes residual toner remaining on the surface of the photosensitive drum 1 without being transferred to the intermediate transfer drum 13 during primary transfer. The cleaning device 6 shown in the figure is unitized together with the primary charger 2 described above. A registration roller 21 that supplies the secondary transfer portion T2 is disposed upstream of the secondary transfer portion T2 along the conveyance direction (arrow K direction) of the transfer material P as an image carrier. This is arranged such that the transfer material P conveyed from a paper feed cassette (not shown) that stores the transfer material P is aligned with the toner image on the intermediate transfer drum 13. Further, on the downstream side of the secondary transfer portion T2 along the transport direction of the transfer material P, a fixing device (fixing unit) 22 that heats and pressurizes the toner image on the transfer material P and fixes it on the transfer material P. Is arranged.

  The reader unit B includes an original table glass 31, a pressing plate 32, a light source 33, a reflection mirror 34, a lens 35, and a CCD 36.

  A document D is placed on the document table glass 31. The pressing plate 32 presses the document D against the document table glass 31. The light source 33 irradiates the document D. The reflection mirror 34 reflects the light irradiated from the light source 33 and reflected by the document D. The lens 35 forms an image of the reflected light from the reflection mirror 34. The CCD 36 receives light from the lens 35. The light emitted from the light source 33, reflected by the document D, reflected by the reflecting mirror 34, passed through the lens 35 and incident on the CCD 36 is subjected to various image processing by the image processing unit 37. . A reference numeral 38 in FIG. 1 is an operation panel provided on the upper surface of the image forming apparatus main body M.

  FIG. 2 shows a block diagram of the image processing unit 37. The image processing unit 37 includes an A / D conversion unit 41, a shading correction unit 42, a LOG conversion unit 443, a masking UCR unit 44, an LUT (look-up table) unit 45, and a pulse width modulation unit 46. A pattern generator 47 is connected to the pulse width modulation unit 46, a CPU 48 having a ROM 50 and a RAM 51 is connected to the LUT unit 45, and an external input I / F is connected to the LOG conversion unit 43. The image signal output from the image processing unit 37 is input to the laser driver 53 of the exposure apparatus 3, and the laser driver 53 performs on / off control of the laser transmission device in accordance with the image signal.

  An image forming operation of the image forming apparatus configured as described above will be briefly described. The photosensitive drum 1 is rotationally driven in the direction of arrow R1 at a predetermined process speed by a driving unit (not shown). The surface of the photosensitive drum 1 is uniformly charged to a predetermined polarity and potential by the primary charger 2. On the surface of the photosensitive drum 1 after charging, the exposure of the exposure device 3 based on the image information removes the charge of the light irradiation portion and forms an electrostatic latent image. This electrostatic latent image is developed as a yellow toner image by the first color (for example, yellow) developing device 4Y. This toner image is primarily transferred by the primary charger 14 to the intermediate transfer drum 13 at the primary transfer portion T1. After the toner image is transferred, the residual toner remaining on the surface of the photosensitive drum 1 is removed by the cleaning device 6 and used for image formation of the next color.

  The series of image forming processes described above, that is, charging, exposure, development, transfer (primary transfer), and cleaning are repeated for magenta, cyan, and black, which are three colors other than yellow. As a result, the four color toner images are superimposed on the intermediate transfer drum 13.

  The four color toner images on the intermediate transfer drum 13 reach the secondary transfer portion T <b> 2 by the rotation of the intermediate transfer drum 13. These toner images are secondarily transferred collectively by the secondary transfer roller 15 onto the transfer material P supplied to the secondary transfer portion T2 by the registration roller 21. The intermediate transfer drum 13 after the toner image transfer is not transferred onto the transfer material P, and residual toner remaining on the surface is removed by the drum cleaner 23. On the other hand, the transfer material P after the transfer of the toner image is heated and pressurized by the fixing device 22 to fix the toner image on the surface, and is then discharged outside the apparatus (outside the image forming apparatus main body M). As a result, the four-color full-color image formation on one transfer material P is completed.

  The image forming apparatus in the present embodiment performs image formation in the following order in order to maintain the image quality of a full-color image, particularly the color and gradation. A gradation patch (detection toner image), which is an image for gradation control, is created on the intermediate transfer drum 13, and a γ look-up table is created based on the information (image forming conditions are updated). To form an image.

  The gradation patch control for creating the γ look-up table is performed as follows.

  The gradation patch is formed by 8 patches for each color. The image signal level (0 to 255 level) for patch formation is determined in advance, and patch formation is performed based on the image signal. The patches of the respective colors are sequentially transferred to the intermediate transfer drum 13, and after the final color is transferred, are detected by the density detection sensor 19. The output voltage of the density detection sensor 19 is 0 to 5V. The output voltage is A / D converted so that the density 0 to 2.0 becomes 10 bits (0 to 1023 level).

  Based on this density information, a desired density gradation characteristic is maintained for each color by creating a γ look-up table, and the color balance when the colors are mixed is maintained.

  In the image forming apparatus of the present embodiment, the process speed of the photosensitive drum 1 is 117 mm / sec. The diameter of the photosensitive drum 1 is 62 mm, and the diameter of the intermediate transfer drum 13 is 186 mm. For the formation of gradation patches, the intermediate transfer drum 13 is rotated once for pre-stabilization processing (control) of the photosensitive drum 1 and the intermediate transfer drum 13, and the photosensitive drum is rotated five times for gradation patch formation and reading. 1. One rotation is performed for post-processing such as cleaning of the intermediate transfer drum 13. Therefore, the intermediate transfer drum 13 needs to be rotated a total of seven times, and the control time at this time is 35 seconds.

  By performing this control, the image density can be kept within a range of ± 0.05 with respect to the target density. On the other hand, when the control is not performed, the image is formed using the previously updated γ look-up table so that the range is about ± 0.20 at the worst. The information of the previously updated γ lookup table is stored in the RAM 51 as storage means (storage means), and image formation is executed using the previous γ lookup table in which the CPU 48 as the control means is stored.

  In the present invention, tone control refers to forming a patch immediately before image formation, updating the γ look-up table based on the formed patch, and forming an image using the updated γ look-up table.

  FIG. 3 shows a controller portion of the image forming apparatus of FIG.

  In FIG. 3, reference numeral 200 denotes the entire copying machine. The copying machine 200 includes a CPU (201) that executes software stored in a ROM (202) or a large-scale storage device (210) such as a hard disk, and the CPU (201) is connected to a system bus (213). Control each device collectively.

  Reference numeral 203 denotes a RAM which functions as a main memory, work area, and the like of the CPU (201). Reference numeral 205 denotes an external input controller (PANELC) which controls instruction inputs from various buttons provided on the copying machine or the touch panel (206). Reference numeral 207 denotes a display controller (DISPC), which controls the display of the display module (208) constituted by, for example, a liquid crystal display. A network interface card (NIC) 204 bi-directionally exchanges data with other network devices or file servers via the LAN (214). A is the same as A in FIG. 1 and B is the same as B in FIG. 1, and the engine and the controller are serially connected to perform communication. Reference numeral 211 denotes a non-volatile memory, which mainly has a function of storing an initial startup value and a counter value.

  The premise of the present invention has been outlined above, and a specific implementation method will be described below with reference to the drawings.

  First, a flow for setting the activation mode will be described with reference to FIGS. 4 to 6 and flowcharts FIG. 8, FIG. 11, and FIG.

  FIG. 4 is a diagram showing an example of a startup mode method selection screen displayed on the panel (206) of FIG. FIG. 5 is a diagram showing a series of manual activation mode setting selection screens displayed on the panel (206) of FIG. FIG. 6 is a series of diagrams showing a screen for inputting setting values in the automatic start mode setting displayed on the panel (206) of FIG. Flowchart FIG. 11 is a flowchart showing a series of flow for setting the activation mode. Flowchart FIG. 12 is a flowchart showing a series of flows for setting the manual activation mode. Flowchart FIG. 8 is a flowchart showing a series of flows for setting the automatic start mode.

  First, in S1101, a mode activation setting method is selected.

  In S1101, when the manual activation mode (402) is selected (Y in S1101), manual activation mode setting processing is performed in S1102.

  If the automatic startup mode (401) is selected in S1101 (N in S1101), automatic automatic mode setting processing is performed in S1103.

  The manual activation mode setting process (S1102) will be described.

  First, in S1201, the activation method is set to manual and stored in the nonvolatile memory (211) or the large-scale storage device (210).

  In step S1202, the activation mode is selected.

  When the monochrome mode (502) is selected in S1202 (Y in S1202), the startup mode is set to monochrome in S1203.

  In S1202, when the color mode (501) is selected (N in S1202), the activation mode is set to color in S1204.

  The automatic startup mode setting process (S1103) will be described.

  First, in S1301, the activation method is set to automatic and stored in the nonvolatile memory (211) or the large-scale storage device (210).

  In step S1302, a reference data period is set and stored in the nonvolatile memory (211) or the large-scale storage device (210). Here, the history period of the output data to be used as a reference when determining the mode activation is set at 601 and 602. Reference numeral 602 denotes a pull-down menu, and units such as time, date, week, month, and year can be selected as items.

  In step S1302, a color mode activation threshold value is set and stored in the nonvolatile memory (211) or the large-scale storage device (210). Here, the output rate condition value for starting in the color mode is set at 603. Therefore, when the color rate of the data output within the reference period set in 601 and 602 is equal to or greater than the percentage set in 603, the color mode is started.

  Next, actual activation will be described with reference to FIG. 7 and a flowchart of FIG. FIG. 7 is a diagram showing an example of the output history. Flowchart FIG. 9 is a flowchart showing a series of flow of gradation correction in the image forming apparatus.

  First, in S1401, the value of the activation method set in S1201 or S1301 is examined.

  If the activation method is manual in S1401 (Y in S1401), the activation mode value set in S1203 or S1204 is checked in S1402.

  In S1402, when the activation mode is monochrome (Y in S1402), only the black toner gradation correction is performed when the image forming apparatus is activated in S1403.

  If the activation mode is color in S1402 (N in S1402), both the black and color toner gradation corrections are performed when the image forming apparatus is activated in S1404.

  In S1401, if the activation method is automatic (N in S1401), the number of past output histories is compared with the set value of the activation mode in S1405. All past output histories are stored in the non-volatile memory (211) or the large-scale storage device (210) as the number of output sheets of date (701), color (702), and black and white (703) as shown in FIG. Yes. The history for the reference output data period set in S1302 is acquired. Then, it is checked whether the value of the number of color output divided by the total number of output is equal to or larger than the output rate condition value set in S1303.

  For example, if the activation time is 17:00 on June 22, 2006, the period set in S1302 is one month, and the value set in S1303 is 50%, the number of color output sheets is 15 and the total number of output sheets is 42. It does not exceed (S1406). Therefore, only the black toner gradation correction is performed as in S1403.

  For example, when the start time is 17:00 on June 22, 2006, the period set in S1302 is 1 hour, and the value set in S1303 is 50%, the number of color output sheets is 3 and the total number of output sheets is 3. The threshold value is exceeded (S1407). Therefore, tone correction of black and color toners is performed as in S1404.

  In S1403 or S1407, when only the black toner tone correction is performed, color toner tone correction is performed when a color job is received.

<Embodiment 2>
The configuration of the image forming apparatus according to the present embodiment is the same as that of the first embodiment. This embodiment is different from the above-described first embodiment in that it is at the time of return from sleep by job reception.

  A flow for returning from sleep by job reception will be described with reference to the flowchart of FIG. FIG. 10 is a flowchart showing a series of flow when returning from the free state by job reception.

  First, in step S1501, it is checked whether the received job is a color.

  If the received job is color in S1501 (Y in S1501), tone correction of black and color toner is performed in S1502.

  If the received job is not a color in S1501 (N in S1501), tone correction of black toner is performed in S1503.

  In step S1504, if normal startup processing is performed and step S1403 or S1406 is processed, the tone correction for black toner is performed in step S1503 and thus skipped. If the step of S1404 or S1407 is processed, the tone correction of the black toner is performed in S1503, and therefore only the tone correction of the color toner is performed.

2 is a diagram schematically showing an engine portion of the image forming apparatus according to Embodiment 1. FIG. 3 is a block diagram illustrating a configuration of an image processing unit according to Embodiment 1. FIG. 2 is a diagram schematically showing a controller portion of the image forming apparatus according to Embodiment 1. FIG. It is a schematic diagram which shows an example of a starting mode setting screen. It is a schematic diagram which shows an example of a manual starting mode setting screen. It is a schematic diagram which shows an example of an automatic starting mode setting screen. It is a figure which shows an example of an output history. It is the flowchart figure which showed a series of flows of automatic starting mode setting. FIG. 5 is a flowchart showing a series of gradation correction flows in the image forming apparatus. FIG. 6 is a flowchart showing a series of flows when returning from a free state by job reception. It is the flowchart figure which showed a series of flows of starting mode setting. It is the flowchart figure which showed a series of flows of manual starting mode setting.

Claims (3)

Form an image on the transfer material,
An image forming unit capable of forming an image for gradation control;
Detecting means for detecting the density of the image for gradation control;
The image for gradation control is formed immediately before the image formation, the image formation condition is updated based on the detection result of the detection unit for the formed gradation control image, and the image is based on the updated image formation condition. Control means for controlling the gradation of the image formed by the image forming means by forming
In a color image forming apparatus comprising:
The control means includes a black and white control mode for correcting gradation only for black toner,
The control means is capable of executing a color control mode for performing gradation correction of black toner and color toner,
At least one of the first control mode and the second control mode can be selectively set, and the set control mode is executed.
A color image forming apparatus. The color image forming apparatus according to claim 1,
Manual selection means for manually selecting the two modes;
Automatic selection means for automatically selecting the two modes;
The color image forming apparatus according to claim 1, comprising: The color image forming apparatus according to claim 2,
In the automatic selection means, as a decision to automatically switch the mode, a period setting means for setting a reference period of output history, a threshold setting means for setting a threshold for switching modes,
The color image forming apparatus according to claim 2, comprising:

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