JP4454897B2 - Color image forming apparatus and method for controlling color image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to an electrophotographic color image forming apparatus such as a color printer and a color copying machine.And control method of color image forming apparatusAbout.
[0002]
[Prior art]
In recent years, color image forming apparatuses such as color printers and color copiers are required to improve the output image quality. In particular, the gradation of density and its stability greatly affect the quality of the image.
[0003]
However, in general, in an electrophotographic image forming apparatus, if there is a change in each part of the apparatus due to a change in environment or long-term use, the density of an obtained image will change. In particular, in the case of an electrophotographic color image forming apparatus, there is a possibility that the color balance may be lost even by a slight change in density, and therefore it is necessary to have means for always maintaining a constant density characteristic.
[0004]
Therefore, in order to obtain a constant density gradation characteristic even if fluctuations occur in each part of the apparatus, a density detection toner patch is prepared on the intermediate transfer member, the photosensitive member, or the transfer material carrier with the toner of each color, and its undetermined value. A method of stabilizing an image is widely used by detecting the density of a toner patch with a density detection sensor, and performing density control by applying feedback to process conditions such as exposure amount and development bias based on the detection result.
[0005]
However, density control using the above density sensor detects unfixed toner patches by forming them on an intermediate transfer member, a photosensitive member or a transfer material carrier. Can not.
[0006]
Therefore, the density of the patch image transferred / fixed on the transfer material can be adjusted to an original reading device such as an external flatbed scanner or a copying machine, or the density so that it can cope with changes in transferability and fixability to the transfer material. There is also a method in which density control is performed by detection with a sensor (hereinafter referred to as a color sensor) that detects the density of the toner patch on the transfer material provided separately from the sensor. However, this method has a demerit that the transfer material is wasted in every density control operation. That is, it is not very suitable for density control that is frequently performed.
[0007]
  Therefore, when the density control is performed using the toner patch on the transfer material, it is preferably used in combination with the density control using the unfixed patch described above. Applicant as an example of this techniqueHas already proposed several inventions. About one of themBriefly, the density of a toner patch after fixing formed on a transfer material is detected by a color sensor, and a target density gradation characteristic in image density control is calculated according to the detection result. In this method, image density control is performed using a density sensor so that characteristics can be obtained.
[0008]
  Also, RollA method of detecting the density of a toner patch after fixing formed on a sheet with a color sensor, correcting the density sensor according to the detection result, and performing image density controlHas also proposed.
[0009]
[Problems to be solved by the invention]
However, the above-described image density control method in the conventional color image forming apparatus has the following problems.
[0010]
First, in the conventional image density control, the density detection of the toner image after fixing by the color sensor and the density detection (density control) of the unfixed toner image by the density sensor are performed independently, so that the entire control is completed. It took a long time. In other words, there was no risk of discomfort to the user.
[0011]
Secondly, in the color image forming apparatus, there is a possibility that a density difference occurs in a short time, or a density difference also occurs due to a difference in image forming position (particularly, a position in the apparatus longitudinal direction). In this case, the above-described density difference is added to the difference between the density detection result by the color sensor and the density detection result by the density sensor, so that originally unnecessary correction control is performed. That is, the accuracy of density control is lowered.
[0012]
  The present invention has been made in view of the above-described circumstances, and can shorten the time for density control and can prevent a decrease in density control accuracy caused by temporal fluctuation and positional fluctuation of the detection toner patch density. Color image forming apparatusAnd control method of color image forming apparatusThe purpose is to provide.
[0013]
[Means for Solving the Problems]
This invention can solve the said subject by providing the following structure.
[0014]
  (1)A color image forming apparatus that corrects the gradation of image data using a gradation correction table that corrects the gradation of image data, and performs printing based on the corrected image data,First density detecting means for detecting the density of an unfixed detection toner image formed on the image carrier or the transfer material carrier, and fixing by fixing the unfixed detection toner image on the transfer material Second density detecting means for automatically detecting the density of the subsequent detection toner image before the transfer material is discharged to the paper discharge section;in frontDetection of the first concentration detection meansKnowledgeresultConcentration isTheThe detection result of the first density detection unit is corrected so that the unfixed detection toner image is fixed and corrected to the density detected by the second density detection unit.CorrectTeTableCalculateFirstCalculationMeans and said firstCalculationmeansCalculated byThe tableByThe firstCalculationOf the table by meansCalculationBy the first concentration detecting means whenCorrect the density,The calculation of the gradation correction table so that the corrected density becomes the target density is continued from the calculation of the table.Second to doCalculationAnd a color image forming apparatus.
  (2)A color image forming apparatus that corrects the gradation of image data using a gradation correction table that corrects the gradation of image data, and performs printing based on the corrected image data,First density detecting means for detecting the density of an unfixed detection toner image formed on the image carrier or the transfer material carrier, and fixing by fixing the unfixed detection toner image on the transfer material A second density detecting means outside the main body for detecting the density of the subsequent detection toner image, a means for fetching the detection result by the second density detecting means into the main body,in frontDetection of the first concentration detection meansKnowledgeresultConcentration isTheThe detection result of the first density detection unit is corrected so that the unfixed detection toner image is fixed and corrected to the density detected by the second density detection unit.CorrectTeTableCalculateFirstCalculationMeans and said firstCalculationmeansCalculated byThe tableByThe firstCalculationOf the table by meansCalculationBy the first concentration detecting means whenCorrect the density,The calculation of the gradation correction table so that the corrected density becomes the target density is continued from the calculation of the table.Second to doCalculationAnd a color image forming apparatus.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a color image forming apparatus and a control system for the apparatus according to the present invention will be described below.
[0027]
FIG. 1 is a cross-sectional view illustrating the overall configuration of a color image forming apparatus according to a first embodiment, FIG. 2 is an explanatory diagram illustrating the configuration of a density sensor, FIG. 3 is an explanatory diagram illustrating the configuration of a color sensor, and FIG. FIG. 5 is a flowchart showing the processing procedure of the image density control system in the first embodiment, FIG. 6 is an explanatory diagram showing a patch pattern used in the first embodiment, and FIG. FIG. 8 is a graph showing density gradation correction control, FIG. 9 is a block diagram showing a system configuration in the second embodiment, and FIG. 10 is an embodiment. FIG. 11 is a flowchart illustrating a processing procedure of the image density control system according to the third embodiment.
[0028]
Hereinafter, the present invention will be described in detail based on examples.
[0029]
Example 1
FIG. 1 is a cross-sectional view illustrating the overall configuration of the color image forming apparatus according to the first embodiment. As shown in the figure, this apparatus is a tandem color image forming apparatus that employs an intermediate transfer member 27 that is an example of an electrophotographic color image forming apparatus. The color image forming apparatus includes an image forming unit shown in FIG. 1 and an image processing unit (not shown).
[0030]
Hereinafter, the operation of the image forming unit in the electrophotographic color image forming apparatus will be described with reference to FIG. The image forming unit forms an electrostatic latent image with exposure light that is turned on based on the exposure time converted by the image processing unit, develops the electrostatic latent image to form a single color toner image, and converts the single color toner image A multi-color toner image is formed by superimposing, and the multi-color toner image is transferred to the transfer material 11 and the multi-color toner image on the transfer material 11 is fixed. Photoconductors (22Y, 22M, 22C, 22K) for each station, injection chargers (23Y, 23M, 23C, 23K) as primary charging means, toner cartridges (25Y, 25M, 25C, 25K), developing means (26Y, 26M, 26C, and 26K), an intermediate transfer member 27, a transfer roller 28, a cleaning unit 29, a fixing unit 30, a density sensor 41, and a color sensor 42.
[0031]
The photosensitive drums (photoconductors) 22Y, 22M, 22C, and 22K are configured by applying an organic optical conductive layer to the outer periphery of an aluminum cylinder, and are rotated by the driving force of a driving motor (not shown) being transmitted. Rotates the photosensitive drums 22Y, 22M, 22C, and 22K in the counterclockwise direction in the drawing according to the image forming operation.
[0032]
  As the primary charging means, yellow (Y), magenta for each stationT(M), cyan (C), and black (K) are provided with four injection chargers 23Y, 23M, 23C, and 23K for charging the photoreceptor, and each injection charger has a sleeve 23YS, 23MS, 23CS and 23KS are provided.
[0033]
Exposure light to the photosensitive drums 22Y, 22M, 22C, and 22K is sent from the scanner units 24Y, 24M, 24C, and 24K, and the electrostatic latent images are selectively exposed by exposing the surfaces of the photosensitive drums 22Y, 22M, 22C, and 22K. An image is formed.
[0034]
  As a developing means, in order to visualize the electrostatic latent image, yellow (Y), magentaT(M), cyan (C), and black (K) are provided with four developing devices 26Y, 26M, 26C, and 26K. Each developing device is provided with a sleeve 26YS, 26MS, 26CS, and 26KS. It has been. Each developing device is detachably attached.
[0035]
The intermediate transfer member 27 is in contact with the photosensitive drums 22Y, 22M, 22C, and 22K, and rotates clockwise when forming a color image. The intermediate transfer member 27 rotates in accordance with the rotation of the photosensitive drums 22Y, 22M, 22C, and 22K. The toner image is transferred. Thereafter, a transfer roller 28 (described later) comes into contact with the intermediate transfer member 27 to sandwich and convey the transfer material 11, and the multicolor toner image on the intermediate transfer member 27 is transferred to the transfer material 11.
[0036]
While the multi-color toner image is being transferred onto the transfer material 11, the transfer roller 28 contacts the transfer material 11 at the position 28a, and is separated from the position 28b after the printing process.
[0037]
The fixing unit 30 melts and fixes the transferred multi-color toner image while conveying the transfer material 11, and as shown in FIG. 1, the fixing roller 31 for heating the transfer material 11 and the transfer material 11 are fixed to the fixing roller. A pressure roller 32 is provided for pressure contact with 31. The fixing roller 31 and the pressure roller 32 are formed in a hollow shape, and heaters 33 and 34 are incorporated therein, respectively. In other words, the transfer material 11 holding the multicolor toner image is conveyed by the fixing roller 31 and the pressure roller 32 and is applied with heat and pressure to fix the toner on the surface of the transfer material 11.
[0038]
After the toner image is fixed, the transfer material 11 is discharged to a discharge tray (not shown) by a discharge roller (not shown), and the image forming operation is finished.
[0039]
The cleaning unit 29 cleans the toner remaining on the intermediate transfer member 27. The waste toner after the four-color multicolor toner image formed on the intermediate transfer member 27 is transferred to the transfer material 11 is: Stored in a cleaner container.
[0040]
The density sensor 41 is arranged toward the intermediate transfer body 27 in the color image forming apparatus of FIG. 1 and measures the density of the toner patch formed on the surface of the intermediate transfer body 27. An example of the configuration of the density sensor 41 is shown in FIG. An infrared light emitting element 51 such as an LED, a light receiving element 52 (52a, 52b) such as a photodiode or Cds, an IC (not shown) that processes received light data, and a holder (not shown) that accommodates these.
[0041]
The light receiving element 52 a detects the intensity of irregularly reflected light from the toner patch 64, and the light receiving element 52 b detects the intensity of regular reflected light from the toner patch 64. By detecting both the regular reflection light intensity and the irregular reflection light intensity, it is possible to detect the density of the toner patch 64 from a high density to a low density. An optical element such as a lens (not shown) may be used for coupling the light emitting element 51 and the light receiving element 52.
[0042]
The color sensor 42 is disposed toward the image forming surface of the transfer material 11 downstream from the fixing unit 30 in the transfer material conveyance path in the color image forming apparatus of FIG. 1, and after the fixing formed on the transfer material 11. The RGB output value of the color of the mixed color patch is detected. By disposing the image inside the color image forming apparatus, it becomes possible to automatically detect the fixed image before discharging it to the paper discharge unit.
[0043]
FIG. 3 shows an example of the configuration of the color sensor 42. The color sensor 42 includes a white LED 53 and a charge storage sensor 54a with an RGB on-chip filter. The white LED 53 is incident on the transfer material 11 on which the patch after fixing is formed at an angle of 45 degrees, and the intensity of diffuse reflected light in the 0 degree direction (vertical direction) is detected by the charge accumulation sensor 54a with an RGB on-chip filter. . The light receiving portion of the charge storage type sensor 54a with RGB on-chip filter is a pixel independent of RGB like 54b.
[0044]
The charge storage sensor 54a with RGB on-chip filter may be a photodiode. Several sets of three RGB pixels may be arranged. Further, a configuration in which the incident angle is 0 degree and the reflection angle is 45 degrees may be employed. Furthermore, you may comprise by LED which emits RGB three colors, and a sensor without a filter.
[0045]
As shown in FIG. 4, both the density sensor 41 and the color sensor 42 are arranged at the center position with respect to the longitudinal direction of the main body (the direction perpendicular to the transfer material conveyance direction). That is, they are arranged at the same position in the longitudinal direction. This arrangement is one of the features of the present invention. In this way, the patch density at the same position can be detected by the color sensor and the density sensor. That is, it is not affected by the positional density difference of the patch density (in this case, the density difference with respect to the position in the longitudinal direction).
[0046]
FIG. 5 is a flowchart showing the correction control of the density sensor and the image density control executed at the same time in this embodiment. The color sensor 42 is used for the control of this embodiment. That is, since a toner image fixed on a transfer material is required, it is preferable to reduce the execution frequency as much as possible. In the present embodiment, when the user desires to execute the correction control of the density sensor, it is performed by the user's manual operation.
[0047]
Hereinafter, the control flow will be described.
[0048]
First, in step S51, a patch pattern for sensor correction control and density control is formed on the intermediate transfer member 27.
[0049]
FIG. 6 shows a control patch pattern to be formed.
[0050]
The control patch patterns include yellow gradation patches 611, 612, 613, and 614, magenta gradation patches 621, 622, 623, and 624, cyan gradation patches 631, 632, 633, and 634, and black gradation patches. The total number is 641, 642, 643, 644. The gradation pattern printing rate (image data corresponding to the halftone patch) is 25% for patches 611, 621, 631, and 641, 50% for patches 612, 622, 632, and 642, and patches 613, 623, and 633. 643 is defined as 75%, and patches 614, 624, 634, and 644 are defined as 100%.
[0051]
Next, in step S52, the density sensor 41 detects the density of the toner patch formed in step S51.
[0052]
Next, in step S53, the transfer material is fed from the paper feed unit 21, and the control patch pattern on the intermediate transfer member is transferred to the transfer material by the transfer roller. Further, the patch pattern on the transfer material is fixed by the fixing unit 30.
[0053]
  Next, in step S54, stepSThe color sensor 42 detects the density of the toner patch fixed on the transfer material at 53.
[0054]
Here, the detected density detection result is a value that includes the effect of fluctuations in the transferability of the toner image onto the transfer material and fluctuations in the fixability, so compared with the case where unfixed toner is detected by the density sensor. High accuracy value.
[0055]
Next, in step S55, the output of the density sensor 41 is corrected. Hereinafter, the correction method of the density sensor 41 will be described with reference to FIG. In FIG. 7, the horizontal axis represents the detection result of the density sensor 41. The vertical axis represents the detection result of the color sensor 42. In the figure, the white circle point P indicates the detection result of step S54 (result of detection of the toner patch on the transfer material by the color sensor) and the detection result of step S52 (detection of the toner patch on the intermediate transfer material 27 by the density sensor). Result).
[0056]
The straight line A represents the case where the output of the density sensor is equal to the output of the color sensor, that is, the case where there is no measurement error of the density sensor (the color sensor detects the density on the transfer material, and thus the density detection accuracy is high. Therefore, it is considered that there is no measurement error of the color sensor). In the figure, the point P and the straight line A do not match. That is, a slight measurement error occurs in the density sensor.
[0057]
Next, a correction table (curve C in the figure) of the density sensor 41 is calculated. The correction table C is a curve that passes through the point P, and the gradation density that does not form a patch (the gradation between the patches) is calculated by performing spline interpolation between the origin and the point P. The correction table C is calculated for each color (yellow, magenta, cyan, black). The calculation of the correction table is executed by a main body CPU (not shown), and the calculated correction table C is stored in a main body memory (not shown) (nonvolatile memory is used in this embodiment).
[0058]
The above is the correction method of the density sensor 41.
[0059]
Next, in step S56, image density control is performed. The image density control performed in this embodiment is density gradation characteristic control for correcting the density gradation characteristic of the image. Hereinafter, density gradation characteristic control will be described with reference to FIG.
[0060]
In FIG. 8, the horizontal axis represents image data. The vertical axis represents the density detection result of the density sensor 41.
[0061]
P1, P2, P3, and P4 represent the results of detecting the toner patch on the intermediate transfer member by the density sensor 41. The detected density is a value after the correction by the correction table C calculated in step S55.
[0062]
Next, a straight line T represents a target density gradation characteristic for image density control. In this embodiment, the target density gradation characteristic T is determined so that the relationship between image data and density is proportional. A curve γ represents density gradation characteristics in a state where density control (tone correction control) is not performed. It should be noted that the density of the gradation in which no patch is formed was calculated by spline interpolation passing through the origin and P1, P2, P3, and P4.
[0063]
A curve D represents a gradation correction table calculated by this control, and is calculated by obtaining a symmetric point with respect to the target gradation characteristic T of the gradation characteristic γ before correction.
[0064]
The calculation of the gradation correction table D is executed by a main body CPU (not shown), and the calculated gradation correction table D is stored in a main body memory (not shown) (a non-volatile memory is used in this embodiment). Is done.
[0065]
When the print image is formed, the target gradation characteristics can be obtained by correcting the image data with the gradation correction table D.
[0066]
The above is the description of the correction control of the density sensor and the image density control executed at the same time in this embodiment.
[0067]
In the image forming apparatus, normal image density control is periodically performed using the density sensor 41 in addition to the above-described control. As a matter of course, the periodic image density control is a control using an unfixed patch, so that no transfer material is required. Further, in the color image forming apparatus of this embodiment, the periodic image density control is executed when the power is turned on, when the developing device or the photosensitive drum is replaced, or every predetermined number of prints. That is, it is executed when a change in density is predicted. At this time, the output of the density sensor is corrected every time by the correction table C already calculated. Further, the image density control method implemented here is the density gradation characteristic control described with reference to FIG. Accordingly, the tone correction table D is updated every time the periodic image density control is executed.
[0068]
When the transfer condition or the fixing condition is predicted to be changed (for example, when the intermediate transfer member or the fixing device is replaced, or when the installation location of the device, that is, the usage environment is changed), the user can use the density sensor described above. Correction control and image density control executed at the same time are executed, and the correction table C and gradation correction table D of the density sensor are updated.
[0069]
In this embodiment, the density sensor correction is performed in order to correct fluctuations in toner transfer property and fixing property to the transfer material. However, the output density of the color sensor is compared with the output density of the density sensor, and the target density is corrected. The density gradation characteristic T may be corrected.
[0070]
Furthermore, in this embodiment, the patches used for correction of the density sensor and the patches used for image density control are all common, but not all patches may be common. For example, when the number of patches necessary for image density control is larger than the number of patches necessary for correction of the density sensor, only a few patches for density sensor correction may be selected from the image density control patches. If at least one patch is common, the intended effect of the present invention can be obtained.
[0071]
Furthermore, in this embodiment, as a method of image density control, a plurality of patches are formed with a plurality of gradation patterns, engine density gradation characteristics are calculated from their density curves, and predetermined values are determined according to the calculation results. A method of calculating a gradation correction look-up table for obtaining the gradation characteristics is used. However, the density control method is not limited to this, and other methods may be used. For example, a plurality of predetermined pattern (halftone pattern, etc.) patches with different development conditions or charging conditions, etc., are formed on the intermediate transfer member, and the density of the patch pattern is detected to obtain a desired density. It is also possible to use a method for calculating the developing conditions and charging conditions.
[0072]
In this embodiment, the color image forming apparatus that detects the patch on the intermediate transfer member with the density sensor is taken as an example. However, the density sensor and the color sensor are arranged at the same longitudinal position, and the influence of the density difference in the longitudinal direction is affected. The technique of reducing is also effective in a color image forming apparatus in which a patch on a transfer material carrier such as a transfer belt is detected by a density sensor.
[0073]
As described above, in the present embodiment, fluctuation correction of toner transferability to the transfer material and fixability, that is, correction of the density sensor and image density control are performed at the same time. Therefore, compared to the case where the control is performed independently, the entire control is performed. The time required was shortened.
[0074]
Furthermore, by using a fixed patch and a non-fixed patch that are used for the correction of the density sensor, it is possible to accurately avoid the influence of density fluctuations that occur in a short period of time or density differences that occur due to differences in image formation positions. Density sensor correction was made possible. As a result, it was possible to provide a color image forming apparatus with improved accuracy of image density control and excellent density stability.
[0075]
(Example 2)
In this embodiment, when performing density sensor correction and density control using document reading means outside the apparatus (including a document reading device of a copying machine) or external density detection means, the time for density control is shortened. A method for preventing a decrease in density control accuracy caused by temporal variation and positional variation of the toner patch density for detection will be described.
[0076]
The present embodiment is an example in which the first embodiment is developed. The difference from the first embodiment is that a document reading means (including a document reading device of a copying machine) outside the apparatus or an external device is used instead of the color sensor. Only the portion using the density detecting means.
[0077]
FIG. 9 is a diagram illustrating a system configuration used in this embodiment, and includes a color image forming apparatus 1, a host computer 2 connected to the color image forming apparatus, and an external document reading apparatus 3.
[0078]
  The main configuration of the color image forming apparatus 1 is almost the same as that of the color image forming apparatus used in the first embodiment, and is different only in the absence of the color sensor 42. The document reading device 3 is a commercially available flat bed scanner and is a host computer.2Connected with.
[0079]
Next, the correction control of the density sensor and the image density control executed at the same time in this embodiment will be described with reference to the flowchart of FIG.
[0080]
Note that the document reader 3 is used for the control of this embodiment. That is, since a toner image fixed on a transfer material is required, it is preferable to reduce the execution frequency as much as possible. In the present embodiment, when the user desires to execute the correction control of the density sensor, it is performed by the user's manual operation.
[0081]
Hereinafter, the control flow will be described.
[0082]
First, in step S101, patch patterns for sensor correction control and density control are formed on the intermediate transfer member 27.
[0083]
As for the control patch pattern, the pattern of FIG. 6 is used as in the first embodiment.
[0084]
Next, in step S102, the density sensor 41 detects the density of the toner patch formed in step S101. Further, the detected density data is transmitted to the host computer 2.
[0085]
Next, in step S103, the transfer material is fed from the paper feed unit 21, and the control patch pattern on the intermediate transfer member is transferred to the transfer material by the transfer roller. Further, the patch pattern on the transfer material is fixed by the fixing unit 30. Thereafter, the transfer material on which the patch pattern is formed is discharged from the color image forming apparatus 1.
[0086]
Next, in step S104, the density of the patch pattern printed in step S103 is detected by the document reading device 3.
[0087]
The transfer material on which the patch pattern is printed is set on the document reading device 3 by the user.
[0088]
The detected density data is transmitted to the host computer 2.
[0089]
Next, in step S105, the output of the density sensor 42 is corrected. The sensor correction method is the same as that in the first embodiment, but the correction table C is calculated by the host computer 2.
[0090]
The calculated correction table C is transmitted from the host computer 2 to the color image forming apparatus 1 and stored in a main body memory (using a non-volatile memory in this embodiment) in the color image forming apparatus 1.
[0091]
The above is the correction method of the density sensor 41.
[0092]
Next, in step S106, image density control is performed. The image density control performed in this embodiment is density gradation characteristic control for correcting the density gradation characteristic of the image. The control method is the same as in the first embodiment.
[0093]
The above is the description of the correction control of the density sensor and the image density control executed at the same time in this embodiment.
[0094]
In the present embodiment, as in the first embodiment, normal image density control different from the above-described control is periodically performed using the density sensor 41. Needless to say, the gradation correction table D is updated each time periodic image density control is executed.
[0095]
When fluctuations in transfer conditions and fixing conditions are predicted, the user executes the above-described density sensor correction control and image density control executed simultaneously with the above-described density sensor correction table C and tone correction table D. Is updated.
[0096]
Further, in this embodiment, density sensor correction is performed in order to correct fluctuations in toner transfer properties and fixing properties to the transfer material. However, the output density of the document reader 3 is compared with the output density of the density sensor. The target density gradation characteristics may be corrected.
[0097]
Further, in this embodiment, as in the first embodiment, all patches of the patch used for correction of the density sensor and the patch used for image density control may not be common. If at least one patch is common, the intended effect of the present invention can be obtained.
[0098]
In this embodiment, an original reading device (flat bed scanner) is used as the external density detecting means. However, the external density detecting means is not limited to this. For example, a density measuring device that can be connected to a computer may be used, or a document reading device such as a copying machine may be used. As a matter of course, when the present invention is applied to a copying machine with an original reading device, the host computer 2 may not be provided.
[0099]
As described above, in this embodiment, even when the concentration detection means outside the apparatus is used, the time required for the entire control can be shortened. Furthermore, by using a fixed patch and a non-fixed patch that are used for the correction of the density sensor, it is possible to accurately avoid the influence of density fluctuations that occur in a short period of time or density differences that occur due to differences in image formation positions. Density sensor correction was made possible. As a result, it was possible to provide a color image forming apparatus with improved image density control accuracy and excellent density stability.
[0100]
(Example 3)
In this embodiment, a method will be described in which the same patch is detected by a color sensor and a density sensor, and the failure of each sensor is determined. It is to be noted that the present invention is preferably performed in combination with the first embodiment. Therefore, in this embodiment, an example in combination with the first embodiment will be described.
[0101]
FIG. 11 is a flowchart showing sensor failure determination control according to this embodiment.
[0102]
Hereinafter, the control of FIG. 11 will be described.
[0103]
In step S111, a toner patch is formed. The toner patch is formed on the intermediate transfer member, then transferred to the transfer material, and further fixed. Details are the same as in the first embodiment.
[0104]
In step S112, the color sensor and the density sensor detect the patch density.
[0105]
In step S113, it is determined whether there is an abnormality in the output value of the density sensor. It should be noted that the determination of abnormality is an abnormality when all patch outputs are zero.
[0106]
In step S114 and step S115, it is determined whether there is any abnormality in the output value of the color sensor. It should be noted that the determination of abnormality is an abnormality when all patch outputs are zero.
[0107]
If the output values of the color sensor and the density sensor are both normal, sensor correction control and image density control are executed in step S116.
[0108]
When only the output value of the density sensor is normal, it is determined that the color sensor is faulty. In this case, in step S117, only the image density control is performed without performing the sensor correction control.
[0109]
If only the output value of the color sensor is normal, it is determined in step S118 that the density sensor has failed. In this case, neither sensor correction control nor image density control is performed.
[0110]
If the output values of both the color sensor and the density sensor are abnormal, it is determined in step S119 that the image forming unit has failed.
[0111]
The above is the description of the sensor failure determination control according to the present embodiment.
[0112]
It should be noted that an optimal method may be determined in accordance with the color image forming apparatus to which the present invention is applied for the processing when the sensor failure is detected (the action of the user or the main body).
[0113]
In the color image forming apparatus used in the present embodiment, since the density sensor and the color sensor are set as service replacement parts, the failure of the sensor is displayed on the display panel, and the sensor failure has occurred to the user. Informs them to exchange services.
[0114]
The feature of this control is that the failure determination is performed by combining the output of the density sensor and the output of the color sensor, so that it is possible to clearly distinguish between the failure of the image forming unit and the failure of the sensor. Furthermore, since the patches used for determining the failure of the density sensor and the color sensor are shared, it is possible to reduce the time required for the failure determination control.
[0115]
Furthermore, since the patch used for sensor failure judgment and the patch used for image density control are common, the effect of further time reduction can be obtained.
[0116]
  As described above, in the present embodiment, the example of combination with the first embodiment has been described as an example in which the effect of the present invention can be maximized. However, the effect can be obtained even if the failure determination control of this sensor is performed alone. Of course.
  As described above, according to the present invention, correction of fluctuations in toner transfer property and fixing property to a transfer material, that is, correction of the density sensor and image density control are performed at the same time, which is compared with the case where the control is performed independently. As a result, the time required for the entire control could be shortened.
  Furthermore, by using a fixed patch and a non-fixed patch that are used for the correction of the density sensor, it is possible to accurately avoid the influence of density fluctuations that occur in a short period of time or density differences that occur due to differences in image formation positions. Density sensor correction was made possible. As a result, it was possible to provide a color image forming apparatus with improved image density control accuracy and excellent density stability.
  Even when density detection means outside the apparatus is used, the time required for the entire control can be shortened, and at the same time, density fluctuations occurring during a short period of time or density differences caused by differences in image formation positions can be reduced. Enables accurate density sensor correction that is not affected.
  In addition, since the failure determination is performed by combining the output of the density sensor and the output of the color sensor, it is possible to clearly distinguish between the failure of the image forming unit and the failure of the sensor. Furthermore, since the patches used for determining the failure of the density sensor and the color sensor are shared, it is possible to reduce the time required for the failure determination control.
[0117]
  As described above, according to the present invention, correction of fluctuations in toner transfer property and fixing property to a transfer material, that is, correction of the density sensor and image density control are performed at the same time. As a result, the time required for the entire control could be shortened.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating an overall configuration of a color image forming apparatus according to a first embodiment.
FIG. 2 is an explanatory diagram showing the configuration of a density sensor
FIG. 3 is an explanatory diagram showing a configuration of a color sensor.
[Fig. 4] Arrangement explanation of density sensor and color sensor
FIG. 5 is a flowchart illustrating a processing procedure of the image density control system according to the first exemplary embodiment.
FIG. 6 is an explanatory diagram showing patch patterns used in the first embodiment.
FIG. 7 is a graph showing the relationship between color sensor output / correction output and density sensor output.
FIG. 8 is a graph showing density gradation correction control.
FIG. 9 is a block diagram illustrating a system configuration according to the second embodiment.
FIG. 10 is a flowchart illustrating a processing procedure of the image density control system according to the second embodiment.
FIG. 11 is a flowchart illustrating a processing procedure of the image density control system according to the third embodiment.
[Explanation of symbols]
1 Color image forming device
2 Host computer
3 Document readingapparatus
11 Transfer material
22 Photoconductor (Photosensitive drum)
26 Developing means
27 Intermediate transfer member
30 FixationPart
41 Concentration sensor
42 Color sensor

Claims (6)

A color image forming apparatus that corrects the gradation of image data using a gradation correction table that corrects the gradation of image data, and performs printing based on the corrected image data,
First density detecting means for detecting the density of an unfixed detection toner image formed on the image carrier or the transfer material carrier;
Second density detection for automatically detecting the density of the detection toner image after fixing the unfixed detection toner image on the transfer material before the transfer material is discharged to the paper discharge unit. Means,
As is corrected concentration when it is detected by the pre-Symbol first concentration density is examined knowledge results of the sensing means to fix the detection toner image of the unfixed said second density detecting means, said first a first calculating means for calculating a ruthenate Buru to correct the detection result of the density detection means,
By the table the first calculation means has calculated, corrected concentration by the first density detecting means when the calculation of the table by the first calculating means is performed, the density after the correction target A color image forming apparatus comprising: a second calculation unit that performs the calculation of the gradation correction table so that the density becomes equal to the second calculation unit following the calculation of the table . A color image forming apparatus that corrects the gradation of image data using a gradation correction table that corrects the gradation of image data, and performs printing based on the corrected image data,
First density detecting means for detecting the density of an unfixed detection toner image formed on the image carrier or the transfer material carrier;
A second density detection means outside the main body for detecting the density of the detection toner image after fixing the unfixed detection toner image fixed on the transfer material;
Means for taking the detection result of the second concentration detection means into the main body;
As is corrected concentration when it is detected by the pre-Symbol first concentration density is examined knowledge results of the sensing means to fix the detection toner image of the unfixed said second density detecting means, said first a first calculating means for calculating a ruthenate Buru to correct the detection result of the density detection means,
By the table the first calculation means has calculated, corrected concentration by the first density detecting means when the calculation of the table by the first calculating means is performed, the density after the correction target A color image forming apparatus comprising: a second calculation unit that performs the calculation of the gradation correction table so that the density becomes equal to the second calculation unit following the calculation of the table . Based on the detection result by the first density detection means and the detection result by the second density detection means, it is determined whether one of the first density detection means or the second density detection means has failed. Has failure determination means,
Said first density detecting means is not failed by the failure judgment means, when the second concentration detection means is determined to have failed, without performing calculation by the first calculating means, said The second calculation means calculates the gradation correction table so that the density, which is the detection result of the unfixed detection toner image by the first density detection means , becomes a target density. The color image forming apparatus according to claim 1, wherein tone correction of image data is performed by a tone correction table . A control method of a color image forming apparatus that corrects the gradation of image data by a gradation correction table that corrects the gradation of image data, and performs printing based on the corrected image data,
A first density detection step of detecting a density of an unfixed detection toner image formed on the image carrier or the transfer material carrier by the first density detector;
The density of the detection toner image after fixing the unfixed detection toner image fixed on the transfer material by the second density detection means is automatically determined before the transfer material is discharged to the paper discharge unit. A second concentration detection step to detect
So as to correct the concentration when it is detected by the pre-Symbol first concentration density is examined knowledge results of the sensing means to fix the detection toner image of the unfixed said second density detecting means, said first a first calculation step of calculating a ruthenate Buru to correct the detection result of the density detection means,
By the table calculated in the first calculation step, the concentration of the first concentration detection step when the calculation of the table in the first calculation process is performed to correct the concentration after the correction target A method for controlling a color image forming apparatus , comprising: calculating a gradation correction table so that the density becomes equal to a second calculation step subsequent to the calculation of the table . A control method of a color image forming apparatus that corrects the gradation of image data by a gradation correction table that corrects the gradation of image data, and performs printing based on the corrected image data,
A first density detection step of detecting a density of an unfixed detection toner image formed on the image carrier or the transfer material carrier by the first density detector;
A second density detecting step for detecting the density of the detection toner image after fixing by fixing the unfixed detection toner image on the transfer material by a second density detecting means outside the main body;
Capturing the detection result in the second concentration detection step into the main body;
So as to correct the concentration when it is detected by the pre-Symbol first concentration density is examined knowledge results of the sensing means to fix the detection toner image of the unfixed said second density detecting means, said first a first calculation step of calculating a ruthenate Buru to correct the detection result of the density detection means,
By the table calculated in the first calculation step, the concentration of the first concentration detection step when the calculation of the table in the first calculation process is performed to correct the concentration after the correction target A method for controlling a color image forming apparatus , comprising: calculating a gradation correction table so that the density becomes equal to a second calculation step subsequent to the calculation of the table . Based on the detection result in the first concentration detection step and the detection result in the second concentration detection step, it is determined whether one of the first concentration detection means or the second concentration detection means has failed. Has a failure judgment process,
If it is determined that the first concentration detection means has not failed and the second concentration detection means has failed in the failure determination step, the calculation in the first calculation step is performed without performing the calculation. In the second calculation step, the gradation correction table is calculated so that the density that is the detection result of the unfixed detection toner image in the first density detection step becomes a target density, and the calculated 6. The method of controlling a color image forming apparatus according to claim 4, wherein gradation correction of image data is performed by a gradation correction table .

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