JP2004198805A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of stably maintaining a specified density gradation over a wide gradation area by changing the mode to form a toner patch in compliance with circumstances where the image forming apparatus is put. <P>SOLUTION: The image forming apparatus is equipped with a patch forming part 25 forming the toner patch for measurement in a prescribed mode set in advance on an image carrier, a density sensor 15 detecting the density of the toner patch formed by the patch forming part 25 at a prescribed detecting position, a patch state control part 45 setting the mode of the toner patch formed by the patch forming part 25 and also changing the set mode in compliance with the circumstances, and image condition control parts 41 to 44 adjusting an image forming condition to influence the density of a toner image formed on the image carrier 1 based on the detection result detected by the density sensor 15. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile, and more particularly, to an image forming apparatus that detects the density of a toner patch and adjusts image forming conditions based on the detection result.
[0002]
[Prior art]
Conventionally, in electrophotographic image forming apparatuses such as copiers and printers, since toner, which is a fine particle, is used, the image density is slightly affected by environmental changes and changes over time, and image density may fluctuate slightly. There is often a difference in image density depending on the machine used. For this reason, a predetermined number of toner patches of a predetermined density gradation are formed, the density is detected by a sensor, and the image forming conditions are adjusted by comparing the density with a target density, so that a predetermined density and gradation Is generally controlled.
[0003]
However, forming a toner patch consumes toner to increase running costs, increases the load on the cleaner to clean the toner patch, and reduces the number of times the toner patch is output to the minimum necessary to reduce productivity. There is a need to.
[0004]
Therefore, there is a method in which the density detection result of a toner patch is compared with a target density, and the cycle of outputting the toner patch is changed based on the comparison result (see Patent Document 1).
[0005]
However, even if the cycle for outputting the toner patch is changed, the number and density gradation of the toner patch to be output are fixed, so that the density and gradation other than the fixed density gradation change. There is a problem that can not deal with it.
[0006]
FIG. 1 is a diagram showing a gradation curve with the image density on the horizontal axis and the image density on the vertical axis using the toner density (TC) as a parameter when the shadow portion of the high density area is adjusted to the target density. is there.
[0007]
As can be seen from FIG. 1, in the highlighted portion of the low density region, the density is higher when the TC is high and lower when the TC is low, as compared with the case where the TC is medium.
[0008]
FIG. 2 is a diagram showing a gradation curve in which the image density is plotted on the horizontal axis and the image density is plotted on the vertical axis, with the change over time of the developer as a parameter when the shadow portion of the high density region is adjusted to the target density. .
[0009]
As can be seen from FIG. 2, in the highlighted portion of the low density region, when the developer deteriorates, the density increases. This is because the chargeability decreases as the developer deteriorates, and the amount of toner adhering to the photoconductor from the developing device increases.
[0010]
As described above, for example, even if the high-density area is adjusted to the target density by the high-density toner patch, the gradation may not match in the highlight portion of the low-density area. It is necessary to adjust the low-density area to the target density by the toner patch.
[0011]
Therefore, based on the characteristics of the gradation correction curve, the toner patch formation interval in the high-density area and the low-density area where the change is large is made smaller than the necessary interval by making it smaller than the medium density area where the change is almost constant. (Patent Document 2).
[0012]
[Patent Document 1]
Japanese Patent Application Laid-Open No. Hei 3-251878 (Examples, FIGS. 1 and 4)
[Patent Document 2]
JP-A-8-76527 (paragraph numbers 0052 to 0060, FIGS. 4 to 7)
[0013]
[Problems to be solved by the invention]
However, even if the toner patch formation interval is changed, the number of toner patches to be output and the density gradation are fixed, so that it is not possible to cope with a change in the gradation correction curve due to a change in the state of the image forming apparatus. In some cases, the characteristic unique to the image forming apparatus does not match the area where the toner patch is formed and the density is adjusted.
[0014]
FIG. 3 is a diagram illustrating a result of measuring a toner patch with a density sensor.
[0015]
In FIG. 3, the horizontal axis represents an image input signal converted into gradation, the vertical axis represents a detected density value of the toner patch, and the curve in the figure represents a detected value by the density sensor. Further, a black diamond indicates a case where the density sensor has a normal sensitivity, and a black square indicates a case where the density sensor has a darker sensitivity than usual.
[0016]
The degree of the characteristics of the density sensor varies depending on the time-dependent fluctuation and the environmental fluctuation, but generally the high-density region tends to be saturated. Therefore, even if toner patches are output at narrow intervals in a high-density region where saturation tends to be strong, the detection value of the density sensor hardly changes, and there is much waste.
[0017]
FIGS. 4 and 5 are diagrams showing the relationship between the image density and the image density when the temperature and humidity change, with the horizontal axis representing the image density and the vertical axis representing the image density.
[0018]
As shown in FIGS. 4 and 5, the density of the highlight portion, which is a low-density region, is higher in a low-temperature or low-humidity environment than in a normal environment, and is high in a high-temperature or high-humidity environment. Sometimes lower than in comparison.
[0019]
Therefore, when the environmental change is large, it is necessary to change the state of the toner patch in the highlight portion to sufficiently grasp the change in the gradation.
[0020]
FIG. 6 is a diagram showing a change in surface potential due to deterioration of the photoconductor.
[0021]
In FIG. 6, the horizontal axis indicates the rotation time of the photoconductor, and the vertical axis indicates the surface potential. The solid line in the figure indicates the case where the photoconductor is new, and the chain line indicates the case where the photoconductor has deteriorated. As shown in the figure, when the photoreceptor is deteriorated, the change in the surface potential becomes large, and it can be seen that uneven charging occurs. Therefore, density unevenness occurs depending on the formation position of the toner image on the photoconductor.
[0022]
FIG. 7 is a diagram illustrating a relationship between the image density formed on the paper and the charge amount of the developer.
[0023]
As shown in FIG. 7, when the image density increases, the amount of toner used increases, and the toner is not sufficiently stirred in the developing device, so that the charge amount decreases. For this reason, the amount of toner adhering to the photoconductor becomes larger than usual, and the density temporarily increases.
[0024]
FIG. 8 is a diagram illustrating the relationship between the time when the developer is left without stirring and the abscissa, and the amount of developer charge on the ordinate.
[0025]
As shown in FIG. 8, when the developer is left for a long time without stirring, the charge amount tends to decrease. Therefore, when an image is formed by using such a developer, the density Will be expensive.
[0026]
FIG. 9 is a diagram illustrating the relationship between the cumulative operation time of the developing device and the charge amount of the developer on the horizontal axis.
[0027]
As shown in FIG. 9, if the cumulative operation time of the developing device becomes longer, the charge amount becomes higher and the density of the formed image becomes lower. Therefore, it is necessary to set the image density of the toner patch to a higher density side. .
[0028]
In view of the above circumstances, the present invention is to change the manner in which a toner patch is formed according to the situation where an image forming apparatus is placed, and to stably maintain a predetermined density gradation over a wide gradation area. It is an object of the present invention to provide an image forming apparatus capable of performing the following.
[0029]
[Means for Solving the Problems]
The image forming apparatus of the present invention that achieves the above object forms a toner image on an image carrier, and finally transfers and fixes the toner image on a recording medium to form an image on the recording medium. In the image forming apparatus,
A patch forming unit for forming a toner patch for measurement in a predetermined manner set on the image carrier,
A density sensor for detecting the density of the toner patch formed by the patch forming unit at a predetermined detection position;
A patch mode control unit that sets the mode of the toner patch formed by the patch forming unit and changes the set mode according to the situation;
An image condition control unit that adjusts image forming conditions that affect the density of the toner image formed on the image carrier based on the detection result detected by the density sensor.
[0030]
As described above, the image forming apparatus includes a patch mode control unit that sets the mode of the toner patch formed by the patch forming unit and changes the set mode according to the situation, and is formed in a predetermined manner according to the situation. The density of the toner patch is detected and the image forming conditions are adjusted according to the situation where the image forming apparatus is placed, so that a predetermined density gradation can be stably maintained over a wide gradation area. It is.
[0031]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
(1st Embodiment)
FIG. 10 is a schematic configuration diagram illustrating the image forming apparatus according to the first embodiment.
[0032]
As shown in FIG. 10, the image forming apparatus according to the present embodiment sets an image processing unit 30 that performs image processing of an input image signal, an image forming unit 50 that forms an image on a sheet, and a mode of a toner patch. And a controller 40 that changes the mode according to the situation and adjusts the image forming conditions based on the detection result of the density of the toner patch thus formed.
[0033]
The image forming unit 50 includes four units 10Y, 10M, 10C, and 10K on which toner images of yellow (Y), magenta (M), cyan (C), and black (K) are formed, respectively. An intermediate transfer belt 20 that comes into contact with the four units and primary-transfers the toner image, and primary-transfers the toner images of each color formed on each of the four units 10Y, 10M, 10C, and 10K to the intermediate transfer belt 20 The primary transfer rolls 5Y, 5M, 5C, and 5K, the secondary transfer roll 6 that secondary-transfers the toner image primarily transferred on the intermediate transfer belt 20 to the paper P, and the paper P of a different type are stored. Three paper trays 12a, 12b, 12c, a transport roll 14 for transporting the paper P extracted from the paper trays 12a, 12b, 12c to a position where the secondary transfer roll 6 is arranged, And a fixing unit (not shown) is fixed on the sheet P by heating and pressing the toner image transferred to the paper P.
[0034]
Each unit 10 includes photosensitive drums 1Y, 1M, 1C, and 1K on which toner images are formed, chargers 2Y, 2M, 2C, and 2K that charge the photosensitive drums 1Y, 1M, 1C, and 1K, and a charged photosensitive drum. The drums 1Y, 1M, 1C, and 1K are subjected to image processing of image data input from the outside, and irradiated with exposure light modulated based on image signals separated into YMCK colors to form electrostatic latent images. Exposure section 3 applies YMCK toner of each color to the electrostatic latent image to form a toner image of each color, and agitates a developer in which toner and carrier are mixed to apply charged YMCK toner of each color. Developing units 4Y, 4M, 4C, and 4K for developing electrostatic latent images. It should be noted that there is a toner box 11 for storing toner of each color of YMCK, and the toner of each color is supplied to the developing machines 4Y, 4M, 4C and 4K at a predetermined timing. Further, each unit 10 is provided with a patch forming section for forming a toner patch for measurement of each color in a preset manner, and the intermediate transfer belt circulates more than the unit 10K for forming a K color toner image. On the downstream side in the direction A, there are provided a density sensor 15 for detecting the density of the toner patch on the intermediate transfer belt, a temperature sensor 16 for detecting the temperature in the image forming apparatus, and a humidity sensor 17 for detecting humidity. Each photosensitive drum 1 is provided with a potential sensor 18 for detecting a surface potential. Further, in the vicinity of the paper tray 12, there is provided a paper discrimination sensor 19 for discriminating the type of the paper that is extracted from the paper tray 12 and conveyed to the secondary transfer position.
[0035]
The intermediate transfer belt 20 is circulated in a direction indicated by an arrow A by being stretched around a driving roll 21 (not shown) for driving the belt, an opposing roll 22, and a tension roll 23 for applying tension to the belt.
[0036]
The image processing unit 30 includes an image data control unit 31 that creates a histogram for each image density based on the input image data, and an image pixel counter that counts the image density of each document or the average image density of a predetermined number of documents. 32.
[0037]
The control unit 40 includes a BCR voltage control unit 41 that adjusts a charging voltage, an LD light amount control unit 42 that adjusts an exposure light amount, and an adjustment that monitors toner consumption and supplies toner from the toner box 11 to the developing device 4. Control section 43 for performing a color correction, a gradation control section 44 for adjusting a gradation correction curve for forming a toner image at a predetermined density based on an input image signal, and an image affecting the density of the formed toner image. A patch mode control unit 45 for setting the mode of the toner patch for performing the feedback control of the forming condition in the patch forming unit 25 and changing the mode according to the situation; and a patch mode control unit. 45 has a memory 46 and a timer 47.
[0038]
Further, the image forming apparatus of the present embodiment includes a UI operation unit 26 as a user interface for manually adjusting the density gradation of an image, specifying an image mode, and specifying a paper type. .
[0039]
The input image signal is converted into an image signal for each YMCK color by the image processing unit 30 and modulated. When exposure light based on the image signal modulated from the exposure unit 3 is applied to the photosensitive drums 1Y, 1M, 1C, and 1K provided in the four units 10Y, 10M, 10C, and 10K, respectively, An electrostatic latent image is formed on each of the developing devices 4Y, 4M, 4C, and 4K, and a toner image of each color is formed. The toner images of each color are superimposed and transferred onto the intermediate transfer belt 20 by the primary transfer rolls 5Y, 5M, 5C, and 5K, and the toner image on the intermediate transfer belt 20 is transferred from the paper tray 12 by the secondary transfer roll 6. The image is transferred onto the sheet P conveyed by the conveying rolls 14 and further heated and pressed by a fixing device (not shown) to be fixed on the sheet P to form an image.
[0040]
At a predetermined timing, for example, when a density gradation adjustment instruction is given by the UI operation unit 26, the patch mode control unit 45 causes the patch forming unit 25 to form a toner patch in a predetermined mode set in advance. Then, the toner patch is detected by the density sensor 15, and the state of the toner patch to be formed next is changed according to the detection result and the situation where the image forming apparatus is placed, and the toner patch is detected by the density sensor. Based on the detection result, the BCR control unit 41, the LD light amount control unit 42, and the like adjust the density and correct the tone correction curve by the tone control unit 44, thereby optimizing the density and the tone.
[0041]
Although the image forming apparatus of the present embodiment has been described based on the tandem image forming apparatus using the intermediate transfer belt 20, the image forming apparatus does not need to be limited to the tandem structure, and has a plurality of cycles. It is not necessary to limit the present invention to the intermediate transfer belt 20, and an intermediate transfer member may be used. Further, the present invention is not limited to the intermediate transfer method, and may be applied to a method of directly transferring a recording medium carried on a paper transport belt or a recording medium transported by a roll.
[0042]
Hereinafter, a method in which the patch mode control unit 45 of the control unit 40 changes the mode of the toner patch to be formed by the patch forming unit 25 according to the situation will be described.
[0043]
FIG. 11A is a flowchart illustrating a mode in which the patch mode control unit of the control unit changes the image density of the toner patch in accordance with the density detection result of the toner patch.
[0044]
As shown in FIG. 11A, the patch mode control unit of the control unit has a density memory for storing a detection result detected by the density sensor, and performs a patch operation in accordance with the detection result stored in the density memory. The form of the toner patch to be formed on the forming unit is changed.
[0045]
The patch mode control unit monitors whether or not the timing for forming the toner patch has come (S-100), and when the timing has come, it causes the patch forming unit to form the toner patch (S-101). The toner patch is detected by the density sensor (S-102). If the detected toner patch is based on an image signal having an image density of 80% (S-103), the ratio of the detection value of the density sensor to the detection value of the reference plate is calculated and standardized, and the toner patch is detected. The detected RADCa, which is the concentration, is calculated (S-104). Then, a deviation .DELTA.RADCa, which is a difference between the calculated value and a target RADCa as the target density of the toner patch, is calculated (S-105). Based on the calculated deviation .DELTA. The amount of light emitted by the laser diode of one of the exposure devices is corrected (S-106) to obtain a predetermined density. Further, the patch mode control unit determines whether the magnitude of the deviation ΔRADCa is larger or smaller than 20 to set the image density PCin of the toner patch to be formed at the next timing (S-107). Then, the image density PCin of the next toner patch is changed to 20% (S-108). If the deviation is large, it is kept at 80% (S-109).
[0046]
On the other hand, if the detected toner patch is not based on the image signal having the image density of 80% (for example, the image density is 20%) (S-103), the ratio of the detection value of the density sensor to the detection value of the reference plate is calculated. Then, the detected RADCb, which is the density of the toner patch, is calculated (S-110). Then, a deviation ΔRADCb, which is a difference between the calculated value and a target RADCb, which is a target density of the toner patch, is calculated (S-111), and based on the calculated deviation ΔRADCb, the gradation control unit performs a gradation correction curve. Is corrected (S-112). Then, the patch mode control unit returns the image density of the image signal of the toner patch formed at the next timing to 80% (S-113).
[0047]
Here, the processing in (S-107) and (S-108, 109) is an example, and the processing in (S-108) is more finely set using a function according to the magnitude of the deviation ΔRADCa. Can be. Further, the processing in (S-107) can be determined based on past history or the like.
[0048]
FIG. 11B is a flowchart illustrating a mode of changing the image density of a toner patch when the patch mode control unit of the present embodiment forms a plurality of toner patches.
[0049]
As shown in FIG. 11B, the patch mode control unit monitors whether or not it is time to form a toner patch (S-200). Toner patches are formed at densities (10%, 25%, 40%, 60%, and 80%) (S-201), and toner patches having the five image densities are detected by a density sensor (S-202). The detection values of the toner patches of the five types of image densities, which are detected by the density sensor, are standardized by calculating the ratio with the detection values of the reference plate, and a detection RADC that is the density of the toner patches is calculated (S-203). Then, a deviation ΔRADC that is a difference between the calculated value and a target RADC that is a target density of the toner patch is calculated (S-204), and a gradation control unit is calculated from the relationship between the calculated deviation ΔRADC and the image density. Corrects the gradation correction curve (S-205). In addition, the patch mode control unit arranges the absolute values of the deviations ΔRADC of the plurality of toner patches in order of magnitude to set the image density PCin of the toner patch formed at the next timing, and sets the maximum absolute value of the deviation ΔRADC. A value is obtained (S-206), and a relationship between the maximum value and the minimum value of the absolute value of the deviation ΔRADC and each Cin number is obtained (S-207). Then, it is confirmed whether or not a flag indicating the change state of the image density is set (S-208). If the flag is not set, the image density of the toner patch to be formed next is maintained as it is (10%, 25%, 40%, 60%, 80%) (S-210), and the image density change flag is not set (S-211).
[0050]
On the other hand, when the flag is set, the magnitude of the maximum absolute value of the deviation ΔRADC is compared, and when it is determined that the difference is larger than 20, the toner patch to be formed next time is set in the same manner as when the flag is not set. Is maintained as it is (10%, 25%, 40%, 60%, 80%) (S-210). When it is determined that the absolute value of the deviation ΔRADC is larger than 20, the image density of the toner patch having the minimum deviation ΔRADC is determined, and the absolute value of the deviation ΔRADC is determined to be the maximum value. The image density is changed to the vicinity of the image density of the toner patch (S-212), and a flag indicating that the image density of the toner patch to be formed next is changed is set (S-213).
[0051]
As described above, when forming a plurality of toner patches, the image density of the toner patch having the smallest difference from the target density is changed, and the toner patch is moved to the vicinity of the image density of the toner patch having the largest difference from the target density. Thereby, the stability of the density gradation can be improved over a wide area.
[0052]
FIG. 12 is a diagram illustrating a sensitivity curve of the density sensor.
[0053]
In FIG. 12, the horizontal axis represents a value obtained by converting an input image signal into an image density, and the vertical axis represents a detection signal detected by the density sensor.
[0054]
The black diamonds in the figure represent the detected values of the density sensor in an ideal state, and the black squares represent the detected values in a certain state.
[0055]
As can be seen from the figure, the sensitivity of the density sensor tends to saturate the detection value in the high density region. Further, in an area where the density is extremely high due to the state of the density sensor, for example, an environmental temperature or a temporal change, a plurality of useless toner patches indicating a density higher than the target density may be formed.
[0056]
FIG. 13 is a flowchart illustrating a mode in which the patch mode control unit of the present embodiment detects the saturation tendency of the density sensor and changes the image density of the toner patch according to the detection result.
[0057]
In FIG. 13, when the power of the image forming apparatus is turned on immediately (S-300), the patch mode control unit sets the image density of the toner patch to 0% (0th toner patch), 10% ( Eleven types are set (1st toner patch), 20% (2nd toner patch), and 100% (10th toner patch) every 10% (S-301). Then, at the toner patch creation timing (S-302), toner patches of 11 types of image densities from the first toner patch to the tenth toner patch are formed in the patch forming unit (S-303). . Then, the density of the toner patches is detected by a density sensor (S-304), and the detection values of the toner patches of the 11 types of image densities by the density sensor are standardized by calculating the ratio with the detection value of the reference plate. The detected RADC that is the density of the toner patch is calculated (S-305). A deviation .DELTA.RADC that is a difference between the calculated 11 types of image density detection RADC and the respective target densities of the target RADC is obtained (S-306), and tone correction is performed using the obtained deviation .DELTA.RADC and the corresponding image density. The curve is corrected (S-307).
[0058]
Further, the patch mode control unit sets the toner patch number to ninth (S-308), and determines whether the ninth detected RADC is larger or smaller than the tenth detected RADC, and determines whether the ninth detected RADC is equal to the ninth detected RADC. It is determined whether the absolute value of the difference from the tenth detected RADC is larger or smaller than 5 (S-309).
[0059]
Hereinafter, the same determination is performed by sequentially setting the toner patch numbers to the younger numbers (S-310, 311). If the toner patch number determined to be small in the determination is only 9, the output of the density sensor is not saturated, and the image density of the toner patch to be formed next is not changed (S -313).
[0060]
On the other hand, if the toner patch number determined to be small in the determination is not only the number 9 but also a number smaller than the number 9, it is determined that the output of the density sensor is saturated, The image density of the toner patch is changed to reduce the ratio of the high density area (S-314). More specifically, the image densities of the eleventh to tenth toner patches are changed according to the image density of the toner patch with the smallest number determined to be saturated (S-315). (S-316).
[0061]
As described above, it is determined whether or not the density sensor is saturated based on the detected value of the density of each toner patch, and the toner patches in the saturated area are allocated outside the saturated area. be able to.
[0062]
Here, the change of the patch mode after (S-308) can be performed by other processing.
[0063]
FIG. 14 is a flowchart illustrating a mode in which the patch mode control unit of the present embodiment detects the tendency of saturation of the density sensor, and changes the number of toner patches according to the detection result.
[0064]
In FIG. 14, when the power of the image forming apparatus has just been turned on (S-350), the patch mode control unit sets the number of patches to 11 (S-351). Then, the timing for forming the toner patch is monitored (S-352), and when that timing is reached, the 0th to 10th toner patches are formed in the patch forming section with an image density obtained by multiplying the respective numbers by 10 times. (S-353).
[0065]
Here, in the present embodiment, the image density is set to 10 times the number, but is not limited to this.
[0066]
Then, the patch mode control unit detects the density of the toner patch formed by the patch forming unit with the density sensor (S-354), and determines the ratio of the detection value of the density sensor to the detection value of the reference plate to obtain a reference. The detected RADC, which is the density of the toner patch, is calculated (S-355). Next, a deviation ΔRADC which is a difference between the calculated detected RADC and a target RADC which is a density target value is calculated (S-356), and a tone correction curve is corrected by the obtained deviation ΔRADC and the corresponding image density. (S-357).
[0067]
Further, the patch mode control unit sets the toner patch number to No. 9 (S-358), and determines whether the ninth detected RADC is larger or smaller than the tenth detected RADC, and determines whether the ninth detected RADC is equal to the ninth detected RADC. It is determined whether the absolute value of the difference from the tenth detected RADC is larger or smaller than 5 (S-359).
[0068]
Hereinafter, the same determination is performed by sequentially setting the toner patch numbers to the youngest numbers (S-360, 361). If the toner patch number determined to be small in the determination is only No. 9 (S-362), the output of the density sensor is not saturated, and the image density of the toner patch to be formed next time is Are not changed (S-363).
[0069]
On the other hand, if the toner patch number determined to be small in the determination is not only the number 9 but also a number smaller than the number 9, it is determined that the output of the density sensor is saturated, The number of toner patches is changed to reduce the proportion of patches in the high density area (S-364). Specifically, 2 is added to the number of the toner patch with the smallest number determined to be saturated (S-365), and the added number is compared with 6 (S-366), 6 If smaller, the number is reduced to six (S-367). If larger than 6, the number is used as the number of toner patches to be formed next.
[0070]
As described above, it is determined whether or not the density sensor is saturated from the detected value of each toner patch density, and when the density sensor is saturated, the number of waste toner patches formed is reduced, so that it is possible to efficiently and accurately perform the process. It is possible to control image forming conditions.
[0071]
Next, a description will be given of how the state of the toner patch is changed when the density target value or the image forming condition is manually adjusted by the UI unit of the image forming apparatus according to the present embodiment.
[0072]
FIG. 15 is a diagram illustrating an example of a manual adjustment screen of the UI unit, and FIG. 16 is a diagram illustrating a situation where a point at which a toner patch is formed is changed when manual adjustment is performed.
[0073]
On the manual adjustment screen shown in FIGS. 15 and 16, a gradation correction curve is displayed with the image density (input image signal) as the horizontal axis and the image density (output image signal) as the vertical axis. In addition, points that can be manually adjusted (0, 64, 128, 192, 255; 255 correspond to Cin 100%) and points at which toner patches are formed are displayed. Are formed at points 0, 32, 64, 96, 128, 160, 192, 224 and 255. On the other hand, in FIG. 16, since the image density was manually adjusted at 64 points and the density was increased, the 32 points were set between 32 and 64 points in order to closely monitor the density in the vicinity. The image density of the toner patch is changed from 96 points to 64 and 96 points. .
[0074]
FIG. 17 is a flowchart illustrating a mode in which the image density on which the toner patch is formed is changed when the manual adjustment is changed.
[0075]
As shown in FIG. 17, manual adjustment is performed on the manual adjustment screen (S-1), and the patch mode control unit obtains information on the adjusted image density from the UI unit and determines the adjusted density area. (S-2) The image density of the toner patch at the next point is changed near the manually adjusted image density.
[0076]
Next, a description will be given of a change in the state of the toner patch when an environment change is detected by the environment sensor of the image forming apparatus of the present embodiment.
[0077]
FIG. 18 is a diagram illustrating a mode in which the patch mode control unit changes the image density of the toner patch according to the internal temperature detected by the temperature sensor.
[0078]
In FIG. 18, when the temperature inside the device is detected by the temperature sensor (S-400), the temperature difference Δtemp between the detected temperature inside the device and the temperature inside the device when the toner patch was formed last time is calculated (S-401). A magnitude comparison between the calculated temperature difference Δtemp and 5 ° C. is performed (S-402). If the temperature difference Δtemp is smaller than 5 ° C., the image density of the toner patch to be formed next is set to 80% (S-403). If the temperature difference Δtemp is greater than 5 ° C., the image density of the toner patch to be formed next is set to 20% (S-404), and the current in-machine temperature is set to the reference temperature at which the next temperature difference is calculated. Is set (S-405).
[0079]
FIG. 19 is a diagram illustrating a mode in which the patch mode control unit changes the image density of the toner patch in accordance with the in-machine humidity detected by the humidity sensor.
[0080]
In FIG. 19, when the humidity inside the device is detected by the humidity sensor (S-410), a humidity difference ΔHum between the detected inside humidity and the inside humidity when the toner patch was formed last time is calculated (S-411). Then, a magnitude comparison between the calculated humidity difference ΔHum and 15% is performed (S-412). If the humidity difference ΔHum is smaller than 15%, the image density of the toner patch to be formed next is set to 80% (S-413). If the humidity difference ΔHum is larger than 15%, the image density of the toner patch to be formed next is set to 20% (S-414), and the current in-machine humidity is set to the reference humidity at the time of calculating the next humidity difference. Is set (S-415).
[0081]
Next, a description will be given of a change in the state of the toner patch in the image forming apparatus according to the present embodiment when parts or consumables are replaced.
[0082]
FIG. 20 is a diagram illustrating image densities at respective image densities before and after replacement of the photoconductor.
[0083]
In FIG. 20, the horizontal axis represents image density, and the vertical axis represents image density. As can be seen from the figure, the image density after replacement of the photoconductor is lower in the highlight portion 2 than the image density before replacement of the photoconductor.
[0084]
Therefore, immediately after the replacement of the photoconductor, it is necessary to monitor the density of the highlight portion for a while.
[0085]
FIG. 21 is a diagram illustrating an aspect in which the image density is changed before and after the replacement of the photoconductor.
[0086]
In FIG. 21, the new or old state of the photoconductor is determined (S-500). For example, the operation time after the set button is pressed in exchange of the photoconductor is measured by a timer, so that the photoconductor is replaced. It is determined whether the state is shortly after or a state where a considerable time has elapsed (S-501). If the state has passed a considerable time, the image density is set to 80% (S-502). If the state is shortly after the replacement, the image density is set to 20% (S-503).
[0087]
FIG. 22 is a diagram illustrating a change in image density due to a decrease in film thickness on the surface of the photoconductor due to consumption of the photoconductor.
[0088]
In FIG. 22, the horizontal axis represents the image density and the vertical axis represents the image density, and the curve in the figure represents the gradation correction curve when the number of times of use of the photoconductor has increased to 100K cycles, 200K cycles, and 300K cycles. It shows.
[0089]
As can be seen from the figure, the density of the highlight portion gradually increases from the new state of the photoconductor as the number of times the photoconductor is used increases. When the photoconductor is in a new state, the density obtained when the image density is 40% is equivalent to the density obtained at an image density of 20% when 200 K cycles are used.
[0090]
FIG. 23 is a diagram illustrating a mode in which the patch mode control unit changes the image density of the toner patch based on the total number of rotations of the photoconductor.
[0091]
In FIG. 23, the patch mode control unit detects the total number of rotations of the photoconductor from the counter (S-510), divides the detected total number of rotations by 10,000, and subtracts from 20 to obtain the correction amount ΔPCin. It is calculated (S-511). Then, it is determined whether the correction amount ΔPCin is positive or negative (S-512). If the total number of rotations exceeds 200,000 (200K cycles) and the correction amount ΔPCin is negative, the image density PCin of the toner patch is set to 20% (S-513). If the total number of rotations is less than 200,000 (200K cycles) and the correction amount ΔPCin is positive, the image density PCin of the toner patch is set to an image density obtained by adding the correction amount ΔPCin to 20% (S-514). .
[0092]
As described above, when the total number of rotations is low, the image density is set near 40%, and when the total number of rotations is high, the image density approaches 20%. Image forming conditions can be adjusted.
[0093]
Here, the case where the deterioration state of the photoconductor is detected based on the number of rotations has been described. However, the detection may be performed by detecting the surface potential of the photoconductor with a sensor. Although the photoconductor has been described as an example here, the present invention can be similarly applied to a developing device, a transfer roll, a developer, and the like in addition to the photoconductor.
[0094]
Next, a case where the state of the toner patch is changed according to the type of the recording medium on which the image is formed will be described.
[0095]
If the image density is set in a low-density area when performing the density control with one toner patch, it becomes difficult to optimize the high-density area. Therefore, the image density is set in the high-density area. In general, the entire concentration control including the above is performed. However, in this method, since the gradation of the halftone becomes rough, the image quality is deteriorated unless the density in the halftone is optimized. Absent. On the other hand, there is a method of using a method of increasing the number of toner patches. However, if the number of toner patches is increased unnecessarily, productivity may decrease or toner consumption may increase. In this embodiment, the paper type is classified into plain paper, high-quality paper, and low-quality paper, and the state of the toner patch is changed according to the paper classification.
[0096]
24A and 24B are diagrams illustrating a paper selection screen in the UI unit. FIG. 24A is an example in which a paper type is selected for each tray, and FIG. This is an example of selection by a product name and a product number.
[0097]
24, a tray number and a paper type are displayed on a paper selection screen. In FIG. 24A, paper types such as plain paper and high-quality paper are displayed. In this case, product names such as P paper (65 gsmA4 of X company) and JD coated paper (103 gsmA3 of X company) are displayed. By moving the cursor based on the displayed paper, a predetermined paper type or the like is selected.
[0098]
FIG. 25 is a diagram illustrating a paper tray.
[0099]
There are three paper trays shown in FIG. 25, and the paper extracted from each paper tray is provided with a paper discrimination sensor at the position where the paper is extracted, and information such as the paper type detected by the paper discrimination sensor is provided. Is sent to the patch mode control unit.
[0100]
FIG. 26 is a flowchart illustrating a mode in which the patch mode control unit changes the image density of the toner patch based on information such as the paper type detected by the paper determination sensor.
[0101]
In FIG. 26, when the automatic image quality selection function button is pressed in the UI unit (S-600), a paper type is detected by a paper discrimination sensor or a paper selection unit by the UI unit (S-601). . When the patch state control unit obtains the information, it is determined whether or not the paper is high-quality paper (S-602). If the paper is high-quality paper, the image density of the toner patch is set to 40% (S-602). If it is not high-quality paper, the image density of the toner patch is set to 80% (S-603).
[0102]
FIG. 27 and FIG. 28 are diagrams showing a gradation correction curve in which the horizontal axis represents image density and the vertical axis represents image density.
[0103]
In FIG. 27, since the density is adjusted at the image density of 80%, the density is stable in the shadow part, but the density varies in the middle part where the image density is close to 40%. On the other hand, as shown in FIG. 28, in the high-quality paper, the image density of the toner patch is set to 40%, so that the density of the middle part is stabilized.
[0104]
In this way, the automatic image quality selection function normally performs density control to roughly match the entire gradation range with high-density toner patches, and increases the number of toner patches for high-quality paper where midtones are important. Instead, the density is adjusted according to the halftone by changing the image density, so that the density can be controlled according to the needs of the user. Even when high-quality paper is used, an image in which halftone is not emphasized can be formed by turning off the automatic image quality selection function.
[0105]
If formation of a plurality of toner patches is permitted, some of the toner patches can be moved to the halftone side or the highlight side.
[0106]
FIGS. 29 and 30 are diagrams illustrating an example of changing the image density of a toner patch when a plurality of toner patches are formed.
[0107]
29 and 30, the horizontal axis represents the image density, and the vertical axis represents the image density.
[0108]
In FIG. 29, the density is stable at the image densities of 20% and 80% where the toner patch is formed, but the variation is large in the halftone area.
[0109]
In this case, as shown in FIG. 30, by changing a toner patch having an image density of 80% to an image density of 50%, it is possible to stabilize the density of the entire gradation area by adjusting the density of the halftone.
[0110]
FIG. 31 is a diagram showing a sheet selection screen in the UI unit. FIG. 31A shows an example in which a sheet type is selected for each tray. FIG. This is an example of selection by a product name and a product number.
[0111]
31, a tray number and a paper type are displayed on a paper selection screen. In FIG. 31A, paper types such as plain paper and low-quality paper are displayed. In this case, a product name such as P paper (65 gsmA4 of X Company) or My Recycle 100 (67 gsmA3 of Y Company) is displayed. By moving the cursor based on the displayed paper, a predetermined paper type or the like is selected.
[0112]
FIG. 32 is a flowchart illustrating a mode in which the patch mode control unit changes the image density of the toner patch based on information such as the paper type detected by the paper determination sensor.
[0113]
In FIG. 32, the paper type and the like are detected by the paper discrimination sensor shown in FIG. When the patch state control unit obtains the information, it is determined whether or not the sheet is a low-quality sheet (S-612). The setting is made (S-614), and if the image is not a low-quality sheet, the setting is such that a toner patch having an image density of 50% is formed (S-613).
[0114]
FIG. 33 is a diagram illustrating a gradation correction curve in which the horizontal axis represents image density and the vertical axis represents image density.
[0115]
In FIG. 33, the toner patches are set to be formed at the image densities of 20%, 50%, and 80%, but the halftone patches having the image density of 50% are reduced. On the other hand, when a sheet other than the low-quality sheet is detected, the sheet is returned to its original state so that a halftone sheet having an image density of 50% is formed.
[0116]
In general, the number of toner patches is determined in consideration of toner consumption and productivity. Many. Therefore, the number of toner patches to be formed is excessive for low-quality paper. Therefore, the number of halftone toner patches is reduced. The number of toner patches to be reduced need not be limited to one, but may be plural.
[0117]
FIG. 34 is a diagram illustrating one effect obtained by reducing the number of toner patches.
[0118]
In FIG. 34, on the intermediate transfer belt, there is a non-image area between the image areas where the toner images are formed, and the toner patch is formed in the non-image formation area. Therefore, when the number of toner patches is reduced, the non-image forming area can be narrowed accordingly, and the productivity of image formation can be improved in some cases.
[0119]
Next, a case where the patch state control unit changes the state of the toner patch based on the image density counted by the image pixel counter will be described.
[0120]
FIG. 35 is a flowchart showing one mode of counting the image density of the document and changing the image density of the toner patch based on the result.
[0121]
As shown in FIG. 7, as the image density increases, the charge amount of the developer decreases. Therefore, the patch mode control unit changes the mode of the toner patch based on the image density counted by the image pixel counter.
[0122]
In FIG. 35, when the automatic image quality selection button is pressed in the UI unit (S-700), the image pixel counter counts the image density of the document (S-701). Then, a magnitude comparison between the counted image density and 30% is made (S-702), and when it is determined that the difference is less than 30%, the image density of the toner patch is set to 80% (S-703). . If it is determined that the density exceeds 30%, the image density of the toner patch is set to 40% (S-704).
[0123]
Here, the image density of each sheet to be printed is used, but the average image density of a predetermined number of prints may be used.
[0124]
FIG. 36 is a diagram showing a gradation correction curve when the image density is shown on the horizontal axis and the image density is shown on the vertical axis. FIG. 36 (a) shows a document having a high image density and a medium / low image density. 36B is a diagram showing a gradation correction curve of the original document, and FIG. 36B is a diagram showing a result of performing density adjustment by changing the image density of the toner patch.
[0125]
In FIG. 36, a solid line indicates a case where a document with a high image density is printed, and a broken line indicates a case where a document with a medium / low image density is printed. As shown in FIG. 36A, the density of the highlight portion is lower when printing a document with a high image density than when printing a document with a medium / low image density. The concentration is higher. Therefore, if the image density of the toner patch is changed to 40% and the densities of the highlight part and the middle part are matched, the density variation is eliminated as shown in FIG.
[0126]
As described above, when the density of all the gradations is set to be roughly adjusted by the toner patch of the high image density in the normal state, the density of the highlight portion is increased by the automatic image quality selection function. For a document having an image density, image forming conditions are automatically adjusted so as to lower the density of the highlight portion, so that the image density is optimized. However, when it is not necessary to emphasize the highlight part, the automatic image quality selection function can be set to OFF.
[0127]
FIG. 37 is a flowchart showing another mode of counting the image density of the document and changing the image density of the toner patch based on the result.
[0128]
In FIG. 37, when the automatic image quality selection button is pressed in the UI unit (S-710), the image pixel counter counts the image density (S-711). Then, a magnitude comparison between the counted image density and 30% is made (S-712), and when it is determined that it is less than 30%, a toner patch at an image density of 40% is not formed (S-713). . If it is determined that the image density exceeds 30%, a toner patch having an image density of 40% is formed (S-714).
[0129]
Here, the image density of each sheet to be printed is used, but the average image density of a predetermined number of prints may be used.
[0130]
FIG. 38 is a diagram showing a gradation correction curve when the horizontal axis represents the image density and the vertical axis represents the image density.
[0131]
In FIG. 38, a solid line indicates a case where a document with a high image density is printed, and a broken line indicates a case where a document with a medium / low image density is printed. As shown in the figure, the density of the highlighted area is higher when printing a document with a high image density than when printing a document with medium or low image density because the charge amount is lower. Has become. Therefore, by adding a toner patch having an image density of 40%, the densities of the highlight portion and the middle portion are adjusted.
[0132]
As described above, with respect to a document having a high image density, a toner patch having an image density of 40% is added, and image forming conditions are adjusted such that the density of a highlight portion is reduced based on a result of detecting the density. The concentration is optimized. However, when it is not necessary to emphasize the highlight part, the automatic image quality selection function can be set to OFF.
[0133]
Next, a mode in which the patch mode control unit changes the image density of the toner patch based on the non-energized time of the image forming apparatus measured by a timer will be described.
[0134]
FIG. 39 is a flowchart illustrating a mode in which the patch mode control unit changes the image density of the toner patch based on the non-operation time of the image forming apparatus.
[0135]
As shown in FIG. 8, when the developer is left without being stirred for a long time, the charge amount of the developer is reduced. Therefore, even if the printing operation is started thereafter, the density of the highlight portion is increased. Become.
[0136]
As shown in FIG. 39, the patch mode control unit monitors the non-energization time using a timer (S-750), and determines whether the non-energization time is 4 hours or more (S-751). If the non-energization time is less than 4 hours, the image density of the toner patch is set to 80% (S-752), and the toner patch creation counter is set to 0 (S-753). If the non-energization time is 4 hours or more, the toner patch creation counter is set to 20% if the toner patch creation counter is, for example, 2 or less (S-755), and one is set to the toner patch creation counter. It is added (S-756). If the toner patch creation counter is larger than 2, for example, the image density of the toner patch is set to 80% (S-757), and the toner patch creation counter is set to 0 (S-758).
[0137]
Here, in the present embodiment, when the operation is not performed for a long time, the image density of the toner patch is changed to the highlight portion side to optimize the density of the highlight portion, and thereafter, the image density is returned to the normal image density. . In this case, the return timing is determined based on the number of times of generation of the changed toner patch. However, the return timing may be set when the density of the highlight portion is optimized.
[0138]
FIG. 40 is a flowchart showing a timing at which the patch mode control unit returns the image density of the toner patch to the normal image density after changing the image density of the toner patch to the highlight unit side by the long-time operation of the developing device.
[0139]
As shown in FIG. 9, the charge amount of the developer increases with an increase in the cumulative operation time of the developing device. Therefore, the patch mode control unit uses a timer to calculate the cumulative time from when the developing device starts operating. T is monitored (S-760), and it is determined whether T has exceeded 10 minutes (S-761). When T exceeds 10 minutes, it is determined that the charge amount has sufficiently increased, and the image density of the toner patch is changed to 80% (S-763). Is determined to be insufficient, and the image density of the toner patch is kept at 20% (S-762).
[0140]
(Second embodiment)
The second embodiment is different from the first embodiment in that the control unit causes the patch forming unit to form a toner patch in a different manner, but is otherwise the same. Therefore, the operation of the different control unit will be described, and the description of the overall schematic configuration and the like of the common image forming apparatus is omitted.
[0141]
Hereinafter, the form of the toner patch that the control unit forms on the patch forming unit according to the situation will be described.
[0142]
FIG. 41 is a flowchart illustrating a mode in which the patch mode control unit of the control unit changes the image density of the toner patch according to the result of detecting the density of the toner patch.
[0143]
As shown in FIG. 41, the patch mode control unit of the control unit has a density memory for storing the detection result detected by the density sensor, and in accordance with the detection result stored in the density memory, Change the form of the toner patch to be formed.
[0144]
The patch mode control unit monitors whether or not the timing for forming the toner patch has come (S-100), and when the timing has come, causes the patch forming unit to form the toner patch (S-101). The toner patch is detected by the density sensor (S-102). If the detected toner patch is based on an image signal having an image density of 80% (S-103), the ratio of the detection value of the density sensor to the detection value of the reference plate is calculated and standardized, and the toner patch is detected. The detected RADCa, which is the concentration, is calculated (S-104). Then, a deviation .DELTA.RADCa, which is a difference between the calculated value and a target RADCa as the target density of the toner patch, is calculated (S-105). Based on the calculated deviation .DELTA. The amount of light emitted by the laser diode of one of the exposure devices is corrected (S-106) to obtain a predetermined density. Further, the patch mode control unit determines whether the magnitude of the deviation ΔRADCa is larger or smaller than 20 to set the image density PCin of the toner patch formed at the next timing (S-107). Using the deviation ΔRADCa, ΔPCin is obtained from the following equation (S-108a), and PCin is obtained (S-108b).
ΔPCin = 60−3 × | ΔRADCa | PCin = 80−ΔPCin
On the other hand, if the magnitude of the deviation ΔRADCa is larger than 20, ΔPCin is set to 0 (S-109a), and PCin is obtained from the above equation (S-109b).
[0145]
On the other hand, if the detected toner patch is not based on the image signal with the image density of 80% (S-103), the ratio of the detection value of the density sensor to the detection value of the reference plate is calculated and standardized, Detected RADCb, which is the concentration of, is calculated (S-110). Then, a deviation ΔRADCb which is a difference between the calculated value and a target RADCa which is a target density of the toner patch is calculated (S-111), and based on the calculated deviation ΔRADCb, the gradation control unit performs a gradation correction curve. Is corrected (S-112). Then, the patch mode control unit returns the image density of the image signal of the toner patch formed at the next timing to 80% (S-113).
[0146]
As described above, since the deviation ΔRADCa is smaller than 20, when the density of the toner patch is changed, if the density is calculated using a function, the image density of the toner patch to be formed next time is determined in accordance with the magnitude of the deviation ΔRADCa. Can be adjusted from 80% to 20%.
[0147]
FIG. 42 is a diagram showing a flowchart for determining the magnitude of the deviation ΔRADCa in (S-107) based on past data stored in the memory of the patch mode unit.
[0148]
The flowchart shown in FIG. 42 differs from that shown in FIG. 11 in (S-107), but is otherwise the same, and therefore, only the differences will be described.
[0149]
In FIG. 7, the patch mode control unit reads the past two deviation values and the current deviation value stored in the memory to set the image density of the toner patch formed at the next timing (S -107a) Average value of three deviation values ΔRADCa. Ave is calculated (S-107b). Then, the patch state control unit sets the deviation ΔRADCa. To set the image density PCin of the toner patch formed at the next timing. It is determined whether the size of Ave is larger or smaller than 20 (S-107c).
[0150]
By calculating the average of three times in this way, unexpected abnormal values can be removed, and an accurate situation can be grasped.
[0151]
Next, a case where the patch mode control unit of the present embodiment forms a plurality of toner patches will be described.
[0152]
FIG. 43 is a diagram showing a flowchart in which the patch mode control unit of the present embodiment detects the saturation tendency of the density sensor and changes the mode of the toner patch according to the detection result.
[0153]
In FIG. 43, immediately after the power of the image forming apparatus is turned on (S-300), the patch mode control unit sets the image density of the toner patch to 0% (0th toner patch), 10% ( Eleven types are set (1st toner patch), 20% (2nd toner patch), and 100% (10th toner patch) every 10% (S-301). Then, at the toner patch creation timing (S-302), toner patches of 11 types of image densities from the first toner patch to the tenth toner patch are formed in the patch forming unit (S-303). . Then, the density of the toner patches is detected by a density sensor (S-304), and the detection values of the toner patches of the 11 types of image densities by the density sensor are standardized by calculating the ratio with the detection value of the reference plate. The detected RADC that is the density of the toner patch is calculated (S-305). A deviation .DELTA.RADC that is a difference between the calculated 11 types of image density detection RADC and the respective target densities of the target RADC is obtained (S-306), and tone correction is performed using the obtained deviation .DELTA.RADC and the corresponding image density. The curve is corrected (S-307).
[0154]
Further, in this embodiment, the patch mode control unit sets the toner patch number to No. 10 (S-328), and determines whether the tenth detected RADC is 70 or less (S-329). ). When the toner patch number determined to be small in the determination is only No. 10 (S-332), since the output of the density sensor is not saturated, the image density of the toner patch to be formed next time is Is not changed (S-333).
[0155]
On the other hand, when it is determined that the number is small, the numbers are sequentially reduced to 0, and the determination is made up to 0 (S-330, 331). When the number is smaller than 9, the output of the density sensor is saturated. Then, the image density of the toner patch in the high-density area other than No. 10 is changed to reduce the ratio of the high-density area (S-334). Specifically, according to the image density (S-335) of the toner patch that is one younger than the youngest number determined to be saturated, the images of the ten types of toner patches from No. 0 to No. 9 The density is changed (S-336).
[0156]
As described above, it is determined whether or not the density sensor is saturated based on the detected value of the density of each toner patch, and the toner patches in the saturated area are allocated outside the saturated area. be able to.
Here, the change of the patch mode after (S-328) can be performed by another process.
[0157]
FIG. 44 is a diagram illustrating another flowchart in which the patch state control unit of the present embodiment detects the saturation tendency of the density sensor and changes the state of the toner patch according to the detection result.
[0158]
The flowchart shown in FIG. 44 is different from the flowchart shown in FIG. 14 in that the process following (S-328) for changing the state of the toner patch is different, but the other processes are common, and therefore the different portions will be described. I do.
[0159]
If the toner patch number determined to be small in the determination is only number 10, the output of the density sensor is not saturated, so the number of toner patches to be formed next is not changed (S-353). .
[0160]
On the other hand, if the toner patch number determined to be small in the determination is 9 or less, it is determined that the output of the density sensor is saturated, and the number of toner patches in the density area other than 10 is changed. Then, the ratio of the number of toner patches in the high density area is reduced (S-354). Specifically, 1 is added to the number k of the toner patch with the smallest number determined to be saturated (S-355), and the added number is compared with 6 (S-356). If the added number is 6 or more, the number is set, and if it is less than 6, it is set to 6 (S-357).
[0161]
As described above, even by reducing the number, it is possible to avoid generation of useless toner patches.
[0162]
Next, a description will be given of an embodiment in which the number of toner patches is increased when the detected value of the patch, the target density value, or the image forming condition is manually adjusted by the UI unit of the image forming apparatus of the present embodiment.
[0163]
FIG. 45 is a diagram illustrating a manual adjustment screen showing a situation where a point at which a toner patch is formed is added when manual adjustment is performed.
[0164]
On the manual adjustment screen shown in FIG. 45, a gradation correction curve is displayed with the image density (input image signal) on the horizontal axis and the image density (output image signal) on the vertical axis. In addition, it is formed at points (0, 64, 128, 192, 255) at which manual adjustment is possible and at points (0, 32, 64, 96, 128, 160, 192, 224, 255) where toner patches are formed. I have.
[0165]
Now, when the image density is manually adjusted at the point of 64 and the density is increased, a new density is set between the point of 32 and the point of 96% to closely monitor the density in the vicinity thereof. Add a toner patch with high image density.
[0166]
FIG. 46 is a flowchart showing a mode in which a toner patch is added when the density is changed by manual adjustment.
[0167]
As shown in FIG. 46, manual adjustment is performed on the manual adjustment screen (S-11), and the patch mode control unit obtains information on the adjusted image density from the UI unit and determines the adjusted density area. (S-12), a toner patch having a new image density is added near the manually adjusted image density (S-13).
[0168]
Next, a description will be given of a change in the state of the toner patch when an environment change is detected by the environment sensor of the image forming apparatus of the present embodiment.
[0169]
FIG. 47 is a flowchart illustrating a mode in which the patch mode control unit adds a new toner patch according to the internal temperature detected by the temperature sensor.
[0170]
In FIG. 47, when the temperature inside the device is detected by the temperature sensor (S-400), a temperature difference Δtemp between the detected temperature inside the device and the temperature inside the device when the toner patch was formed last time is calculated (S-401). A magnitude comparison between the calculated temperature difference Δtemp and 5 ° C. is performed (S-402). If the temperature difference Δtemp is smaller than 5 ° C., the image density of the toner patch to be formed next is maintained at 80% (S-406). If the temperature difference Δtemp is larger than 5 ° C., a toner patch having an image density of 20% is newly added next time (S-404), and the current in-machine temperature is set as a reference when the next temperature difference is calculated. The temperature is set (S-408).
[0171]
FIG. 48 is a flowchart illustrating a mode in which the patch mode control unit adds a new toner patch in accordance with the in-machine humidity detected by the humidity sensor.
[0172]
In FIG. 48, when the humidity inside the device is detected by the humidity sensor (S-410), a humidity difference ΔHum between the detected inside humidity and the inside humidity when the toner patch was formed last time is calculated (S-411). Then, a magnitude comparison between the calculated humidity difference ΔHum and 15% is performed (S-412). If the humidity difference ΔHum is smaller than 15%, the image density of the toner patch to be formed next is maintained at 80% (S-416). If the humidity difference ΔHum is larger than 15%, a toner patch having an image density of 20% is newly added next time (S-418), and the current in-machine humidity is used as a reference when the next humidity difference is calculated. The humidity is set (S-405).
[0173]
Next, a description will be given of a change in the state of the toner patch in the image forming apparatus according to the present embodiment when parts are replaced or the like.
[0174]
FIG. 49 is a flowchart showing a mode of changing the number of toner patches before and after the replacement of the photoconductor.
[0175]
The image density after replacement of the photoconductor is lower in the highlight portion than the image density before replacement of the photoconductor. Therefore, immediately after the replacement of the photoconductor, it is necessary to monitor the density of the highlight portion for a while.
[0176]
In FIG. 49, the new or old state of the photoconductor is determined (S-500). For example, the operation time after the set button is pressed in exchange of the photoconductor is measured by a timer, and the photoconductor is replaced. It is determined whether the state is shortly after or a state where a considerable time has elapsed (S-501). If the state has passed a considerable time, the image density is set to 80% (S-502). If it is in a state shortly after the replacement, a toner patch having an image density of 20% and an image density of 20% are additionally set (S-505).
[0177]
FIG. 50 is a diagram illustrating a mode in which the patch mode control unit changes the image density of the toner patch based on the total number of rotations of the photoconductor.
[0178]
It can be seen that the density of the highlight portion gradually increases from the new state of the photoconductor as the number of times the photoconductor is used increases.
[0179]
In FIG. 50, the patch mode control unit detects the total number of rotations of the photoconductor from the counter (S-520), adds 1 to an integer obtained by dividing the detected total number of rotations by 100,000, and creates a patch. The number Np is calculated (S-521). Then, a comparison is made between the number of created patches Np and 4 (S-522). If the number of created patches Np is 4 or less, the number is set as the number of toner patches to be created next time. If the number of patches Np exceeds 4, the next number of toner patches to be created is set to 4 (S-523).
[0180]
As described above, when the total number of rotations is low, the number of patches is small, and when the total number of rotations is high, the number of toner patches is set to 4, and the density of the highlight portion is finely detected, thereby efficiently adjusting the image forming conditions. can do.
[0181]
Next, a case where the state of the toner patch is changed according to the type of the recording medium on which the image is formed will be described.
[0182]
In the present embodiment, unlike the first embodiment, the paper type is set by a paper selection button provided on the paper tray. However, the type of paper set by the paper selection button and the manner in which the patch state control unit changes the image density of the toner patch are the same as those in the flowcharts shown in FIGS. The tray will be described.
[0183]
FIG. 51 is a diagram illustrating a paper tray of the image forming apparatus according to the present embodiment.
[0184]
The image forming apparatus illustrated in FIG. 51 includes an image forming unit on which a toner image is formed at an upper part, and a first paper tray, a second paper tray, and a third paper tray below the image forming unit. Each paper tray is provided with a paper selection button.
[0185]
The first paper tray of the paper tray shown in FIG. 51A can be set by selecting high quality paper and plain paper. The first paper tray of the paper tray shown in FIG. 51B can be set by selecting low-quality paper and plain paper.
[0186]
When, for example, high-quality paper is stored in the first paper tray and the high-quality paper selection button is pressed with the paper selection button, information indicating that high-quality paper has been set is sent to the patch mode control unit.
[0187]
The image forming apparatus according to the present exemplary embodiment includes an image density calculation unit that calculates a histogram for each image density of an image formed on a sheet based on an input image signal or an image signal obtained by reading a document. I have. Then, the patch mode control unit changes the image density or the number of the toner patches based on the histogram calculated by the image density calculation unit. This mode will be described.
[0188]
FIG. 52 is a flowchart showing a mode in which the patch mode controller changes the image density of the toner patch based on the histogram calculated by the image density calculator.
[0189]
In FIG. 52, the image density calculation unit calculates a histogram for each image density based on the input image signal (S-800). Then, the patch mode control unit determines whether there is an image density whose frequency (the number of pixels) exceeds a threshold value for changing the image density of the toner patch (S-801). The image density of the toner patch that has been set up to is maintained (S-802). If there is an image density exceeding the threshold value, a predetermined number n (for example, 2) of which the image density of the toner patch can be changed is read out (S-803), and the most frequently used number is determined based on the histogram. , The image density up to the n-th image density is extracted from the high image density, and the image density of the toner patch is set to the n-th image density (S-804).
[0190]
FIG. 53 is a schematic diagram illustrating the histogram calculated by the image density calculation unit and the image density extracted by the patch mode control unit when n = 2.
[0191]
In FIG. 53, the horizontal axis represents image density, and the vertical axis represents frequency.
[0192]
The solid line in the figure represents a histogram, and the broken line represents a threshold for changing the image density of the toner patch. As can be seen, there are peaks greater than the threshold at image densities of 20% and 80%.
[0193]
FIG. 54 is a diagram illustrating a case where the image density calculation unit calculates a histogram for each predetermined image density area.
[0194]
In FIG. 54, areas are set every 20% of the image density on the horizontal axis.
In this case, the patch mode control unit extracts an image density area having a peak larger than the threshold, and calculates a median value (20%) of each of the image density areas (10% to 30%) and (70% to 90%). , 80%) as the representative value and can be set as the image density.
[0195]
FIG. 55 is a diagram illustrating a case where the image density calculation unit calculates a histogram for each predetermined image density area.
[0196]
In FIG. 55, an area is set for every 20% of the image density on the horizontal axis.
Here, the patch mode control unit extracts the image density areas in which the average value of the frequency of each image density area is larger than the threshold value, and extracts the upper two image density areas (10% to 30%), (70% to 90%). %), The image density may be set as a central value (20%, 80%) as a representative value.
[0197]
FIG. 56 is a flowchart illustrating a mode in which the patch mode control unit allows the toner patch to be formed at a plurality of image densities for each image density area based on the histogram.
[0198]
In FIG. 56, the image density calculation unit calculates a histogram for each image density based on the input image signal (S-810). Then, the patch mode control unit determines whether there is an image density whose frequency (the number of pixels) exceeds the threshold value for changing the image density of the toner patch (S-811). The image density of the toner patch set up to is maintained (S-812). If there is an image density exceeding the threshold, the number of image density regions exceeding the threshold is calculated (S-813). Then, a comparison is made between the calculated number m of image density areas and the allowable number p of toner patches (S-814), and if the number m of image density areas is larger than the allowable number p, a higher rank based on the allowable number p is used. Is extracted (S-815), and when the number m of image density areas is equal to or smaller than the allowable number p, the calculated number m of image density areas is set as the number of toner patches for changing the image density ( S-816). Then, among the extracted image densities, the representative value of each image density area is set as the image density of the next toner patch in the order of the highest frequency (S-817).
[0199]
FIG. 57 is a diagram illustrating a case where the image density calculation unit calculates a histogram for each predetermined image density area.
[0200]
In FIG. 57, areas are set for every 20% of the image density on the horizontal axis.
[0201]
Here, the patch mode control unit extracts two (three in image density) image density regions exceeding the threshold value. However, since the allowable number p of toner patches is two, the upper two image density regions are extracted. The median (20%, 80%) of (10% to 30%) and (70% to 90%) is set as an image density as a representative value.
[0202]
FIG. 58 is a diagram illustrating a case where the image density calculation unit calculates a histogram for each predetermined image density area.
[0203]
In FIG. 55, an area is set for every 20% of the image density on the horizontal axis.
[0204]
Here, the patch mode control unit extracts the image density area in which the average value of the frequency of each image density area is larger than the threshold, and determines the median (20%) of the image density areas (10% to 30%). The image density can be set as a representative value.
[0205]
As described above, the histogram of the image density is calculated in advance based on the input image signal, and the toner patches are formed with the image density having a high frequency. Therefore, the density of the conspicuous gradation in the image formed on the paper is reduced. Next, a mode in which the patch mode control unit changes the image density of the toner patch based on the non-energization time of the image forming apparatus, which is measured by the timer, will be described. .
[0206]
FIG. 59 is a flowchart illustrating a mode in which the patch mode control unit changes the image density of the toner patch based on the non-operation time of the image forming apparatus.
[0207]
As shown in FIG. 8, when the developer is left without being stirred for a long time, the charge amount of the developer is reduced. Therefore, even if the printing operation is started thereafter, the density of the highlight portion is increased. Become.
[0208]
As shown in FIG. 59, the patch mode control unit monitors the non-energization time of the developing device using a timer (S-850), and determines whether the non-energization time is 4 hours or more (S-850). 851). If the non-energization time is less than 4 hours, it is considered that the charge amount of the developer has not decreased so much. Therefore, a toner patch having an image density of 20% is not set (S-852), and a toner patch is created. The counter is set to 0 (S-853). If the non-energization time is 4 hours or more, the toner patch creation counter is set to 20% if the toner patch creation counter is, for example, 2 or less (S-855), and one is set to the toner patch creation counter. It is added (S-856). If the toner patch creation counter is greater than 2, for example, the toner patch with the image density of 20% is not set (S-857), and the toner patch creation counter is set to 0 (S-858).
[0209]
In this embodiment, when the developing device is not operated for a long time, a toner patch having an image density of 20% is created, the density of the highlight portion is optimized, and the state is maintained. It is necessary to optimize even after the vessel starts operating.
[0210]
FIG. 60 is a flowchart showing the timing at which the patch state control unit returns the image density of the toner patch changed to the highlight unit side to the normal image density due to the long-term operation of the developing device.
[0211]
As shown in FIG. 9, the charge amount of the developer increases with an increase in the cumulative operation time of the developing device. Therefore, the patch mode control unit uses a timer to calculate the cumulative time from when the developing device starts operating. T is monitored (S-860), and it is determined whether T has exceeded 10 minutes (S-861). If T exceeds 10 minutes, it is determined that the charge amount has sufficiently increased, and the image density of the toner patch is changed to 80% (S-863). If T is less than 10 minutes, the image density is reduced. An 80% toner patch and a 20% image density toner patch are created (S-862).
[0212]
Next, a mode in which the patch mode control unit changes the number of toner patches created when the difference between the value detected by the density sensor and the target density is large will be described.
[0213]
FIG. 61 is a diagram showing a gradation correction curve in which the horizontal axis represents image density and the vertical axis represents image density.
[0214]
As shown in FIG. 61, when the difference between the target density and the value detected by the density sensor at a high image density, for example, when the image density is 80%, is large, it is considered that the shift often occurs in the entire gradation range.
[0215]
FIG. 62 is a flowchart showing a manner of changing patches when the number of toner patches to be created is small.
[0216]
In FIG. 62, when the patch mode control unit determines that it is time to create a toner patch (S-900), a predetermined toner patch is formed (S-901), and the density of the toner patch is measured by a density sensor. It is detected (S-902).
[0219]
In the case where the number of toner patches is one (S-903), the detected detection value is compared with the detection value from the reference plate, and the detected RADCa, which is the density based on the detection value, is calculated (S-904). ). Then, a deviation .DELTA.RADCa, which is a difference between the detected RADCa and the target density, is calculated (S-905). (S-906).
[0218]
Further, for forming the next toner patch, the patch state control unit compares the absolute value of the deviation ΔRADCa with 30 (S-907). The number is set to one, and the image density is set to 80% (S-908). When the deviation ΔRADCa is larger than 30, the number of toner patches is set to two, the image density is set to 80% and the image density is set to 40%, and the densities of the medium and low density areas are adjusted.
[0219]
On the other hand, when the number of toner patches is two (S-903), each detected value is compared with the detected value from the reference plate, and the detected RADCa and the detected RADCb, which are the densities based on the detected values, are compared. Is calculated (S-910). Then, a deviation ΔRADCa, which is a difference between the detected RADCa and the target concentration, and a deviation ΔRADCb, which is a difference between the detection RADCb and the target concentration, are calculated (S-911). Based on the deviation ΔRADCa, the LD light amount control unit The light amount of the laser which is one of the image forming conditions is corrected, and the gradation control unit corrects the gradation correction curve based on the deviation ΔRADCb (S-912). Then, it is set so that the number of toner patches is one and the image density is 80% (S-913).
[0220]
As described above, when the deviation from the target density is large, the number of toner patches is set to two, the image density is set to 80%, and the image density is set to 40%.
[0221]
FIG. 63 is a flowchart showing a manner of changing the image density when a plurality of toner patches are created.
[0222]
In FIG. 63, when the power is turned on (S-950), the number of toner patches is set to 5 (S-951). When the patch mode control unit determines that it is time to create a toner patch (S-952), the image density of the toner patch is determined by a predetermined formula according to the number of patches, and the image density of the toner patch is determined. To create a plurality of toner patches (S-953). Then, the densities of these toner patches are detected by a density sensor (S-954), and the detected detection value is compared with a detection value from a reference plate to calculate a detection RADC that is a density based on the detection value. (S-955). Then, a deviation ΔRADC that is a difference between the detected RADC and the target density is calculated (S-956), and based on the deviation ΔRADC, the LD light amount control unit corrects the laser light amount, which is one of the image forming conditions. (S-957).
[0223]
Further, for the next time a toner patch is formed, the patch mode control unit arranges the absolute values of the deviation ΔRADC in order of magnitude, and sets the maximum value ΔRADC. Max is obtained (S-958). Next, the maximum value ΔRADC. A comparison between Max and 10 is made, and if it is larger than 10, the number of toner patches is maintained as it is (S-959). On the other hand, the maximum value ΔRADC. If Max and 10 are smaller than 10, the number of toner patches created is reduced by one (S-960). If the reduced number is three or more, the number of toner patches reduced by one is maintained (S-960). If the reduced number is smaller than 3, the number of toner patches is set to 3 (S-962).
[0224]
As described above, when the deviation from the target density is large, the number of toner patches is maintained, and when the deviation is small, the number is reduced, so that the density can be adjusted efficiently.
[0225]
【The invention's effect】
As described above, according to the image forming apparatus of the present invention, according to various situations encountered by the image forming apparatus, the toner density can be changed in various ways, such as changing the image density and the number of toner patches to be created. Since the image is formed and the image forming conditions are adjusted based on the detection result, it is possible to efficiently and stably secure a target density over the entire gradation range.
[Brief description of the drawings]
FIG. 1 is a diagram showing a gradation curve with the image density on the horizontal axis and the image density on the vertical axis using the toner density (TC) as a parameter when the shadow portion of the high density area is adjusted to the target density. is there.
FIG. 2 is a diagram showing a gradation curve in which image density is plotted on the horizontal axis and image density is plotted on the vertical axis, using a temporal change of the developer as a parameter when a shadow portion of a high density region is adjusted to a target density. .
FIG. 3 is a diagram illustrating a result of measuring a toner patch with a density sensor.
FIG. 4 is a diagram illustrating the relationship between the image density and the image density when the temperature changes, with the horizontal axis representing the image density and the vertical axis representing the image density.
FIG. 5 is a diagram showing the relationship between the image density and the image density when the humidity changes, with the horizontal axis representing the image density and the vertical axis representing the image density.
FIG. 6 is a diagram showing a change in surface potential due to deterioration of a photoconductor.
FIG. 7 is a diagram illustrating a relationship between an image density formed on a sheet and a charge amount of a developer.
FIG. 8 is a diagram showing the relationship between the abscissa and the ordinate, where the abscissa represents the time during which the developer is left without stirring and the ordinate represents the charge amount of the developer.
FIG. 9 is a diagram illustrating the relationship between the cumulative operation time of the developing device and the vertical axis of the charge amount of the developer on the horizontal axis.
FIG. 10 is a schematic configuration diagram illustrating an image forming apparatus according to the first embodiment.
FIG. 11A is a flowchart illustrating a mode in which the patch mode control unit of the control unit changes the image density of the toner patch in accordance with the density detection result of the toner patch.
FIG. 11B is a flowchart illustrating a mode of changing the image density of a toner patch when the patch mode control unit according to the present embodiment forms a plurality of toner patches.
FIG. 12 is a diagram showing a sensitivity curve of a density sensor.
FIG. 13 is a flowchart illustrating a mode in which the patch mode control unit according to the present embodiment detects a saturation tendency of the density sensor and changes the image density of the toner patch according to the detection result.
FIG. 14 is a flowchart illustrating a mode in which the patch mode control unit of the present embodiment detects a saturation tendency of the density sensor and changes the number of toner patches according to the detection result.
FIG. 15 is a diagram illustrating a manual adjustment screen of the UI unit as an example.
FIG. 16 is a diagram illustrating a manual adjustment screen of a UI unit as an example.
FIG. 17 is a flowchart illustrating a mode in which the image density on which a toner patch is formed is changed when the manual adjustment is changed.
FIG. 18 is a diagram illustrating a mode in which the patch mode control unit changes the image density of the toner patch according to the in-machine temperature detected by the temperature sensor.
FIG. 19 is a diagram illustrating a mode in which the patch mode control unit changes the image density of the toner patch in accordance with the in-machine humidity detected by the humidity sensor.
FIG. 20 is a diagram illustrating image densities at respective image densities before and after replacement of a photoconductor.
FIG. 21 is a diagram illustrating a manner in which the image density is changed before and after the replacement of the photoconductor.
FIG. 22 is a diagram showing a change in image density due to a decrease in film thickness on the surface of the photoconductor due to consumption of the photoconductor.
FIG. 23 is a diagram illustrating a mode in which the patch mode control unit changes the image density of the toner patch according to the total number of rotations of the photoconductor.
FIG. 24 is a diagram illustrating a sheet selection screen in the UI unit.
FIG. 25 is a diagram illustrating a paper tray.
FIG. 26 is a flowchart illustrating a mode in which the patch mode control unit changes the image density of a toner patch based on information such as a paper type detected by a paper determination sensor.
FIG. 27 is a diagram showing a gradation correction curve in which the horizontal axis represents image density and the vertical axis represents image density.
FIG. 28 is a diagram showing a tone correction curve in which the horizontal axis represents image density and the vertical axis represents image density.
FIG. 29 is a diagram illustrating an example of changing the image density of a toner patch when a plurality of toner patches are formed.
FIG. 30 is a diagram illustrating an example of changing the image density of a toner patch when a plurality of toner patches are formed.
FIG. 31 is a diagram illustrating a paper selection screen in the UI unit.
FIG. 32 is a flowchart illustrating a mode in which the patch mode control unit changes the image density of a toner patch based on information such as a paper type detected by a paper determination sensor.
FIG. 33 is a diagram showing a gradation correction curve in which the horizontal axis represents image density and the vertical axis represents image density.
FIG. 34 is a diagram illustrating one effect obtained by reducing toner patches.
FIG. 35 is a flowchart showing one mode of counting the image density of a document and changing the image density of a toner patch based on the result.
FIG. 36 is a diagram showing a tone correction curve when the horizontal axis represents image density and the vertical axis represents image density.
FIG. 37 is a flowchart showing another mode of counting the image density of a document and changing the image density of the toner patch based on the result.
FIG. 38 is a diagram showing a tone correction curve when the horizontal axis represents image density and the vertical axis represents image density.
FIG. 39 is a flowchart illustrating a mode in which the patch mode control unit changes the image density of the toner patch based on the non-operation time of the image forming apparatus.
FIG. 40 is a flowchart showing a timing at which the patch mode control unit returns the image density of the toner patch to the normal image density after changing the image density of the toner patch to the highlight unit side due to the non-operation of the developing device for a long time.
FIG. 41 is a flowchart illustrating a mode in which the patch mode control unit of the control unit changes the image density of the toner patch in accordance with the density detection result of the toner patch.
FIG. 42 is a view showing a flowchart for performing the magnitude determination of the deviation ΔRADCa in (S-107) based on past data stored in the memory of the patch mode unit;
FIG. 43 is a diagram illustrating a flowchart in which the patch mode control unit according to the present embodiment detects the tendency of saturation of the density sensor and changes the mode of the toner patch according to the detection result.
FIG. 44 is a diagram illustrating another flowchart in which the patch mode control unit of the present embodiment detects the saturation tendency of the density sensor and changes the mode of the toner patch according to the detection result.
FIG. 45 is a diagram illustrating a manual adjustment screen showing a situation where a point at which a toner patch is formed is added when manual adjustment is performed.
FIG. 46 is a flowchart illustrating a mode in which a toner patch is added when the density is changed by manual adjustment.
FIG. 47 is a flowchart illustrating a mode in which the patch mode controller adds a new toner patch in accordance with the internal temperature detected by the temperature sensor.
FIG. 48 is a flowchart showing a mode in which the patch mode control unit adds a new toner patch in accordance with the in-machine humidity detected by the humidity sensor.
FIG. 49 is a flowchart showing a manner in which the number of toner patches is changed before and after replacement of a photoconductor.
FIG. 50 is a diagram illustrating a mode in which the patch mode control unit changes the image density of the toner patch according to the total number of rotations of the photoconductor.
FIG. 51 is a diagram illustrating a paper tray of the image forming apparatus according to the present embodiment.
FIG. 52 is a flowchart showing a mode in which the patch mode controller changes the image density of the toner patch based on the histogram calculated by the image density calculator.
FIG. 53 is a schematic diagram showing a histogram calculated by the image density calculation unit and an image density extracted by the patch mode control unit when n = 2.
FIG. 54 is a diagram illustrating a case where an image density calculation unit calculates a histogram for each predetermined image density area.
FIG. 55 is a diagram illustrating a case where an image density calculation unit calculates a histogram for each predetermined image density area.
FIG. 56 is a flowchart showing a mode in which the patch mode control unit allows forming a toner patch at a plurality of image densities for each image density area based on a histogram.
FIG. 57 is a diagram illustrating a case where an image density calculation unit calculates a histogram for each predetermined image density area.
FIG. 58 is a diagram illustrating a case where an image density calculation unit calculates a histogram for each predetermined image density area.
FIG. 59 is a flowchart illustrating a mode in which the patch mode control unit changes the image density of the toner patch based on the non-operation time of the image forming apparatus.
FIG. 60 is a flowchart showing a timing at which the patch mode control unit returns the image density of the toner patch changed to the highlight unit side to the normal image density due to the non-operation of the developing device for a long time.
FIG. 61 is a diagram showing a gradation correction curve in which the horizontal axis represents image density and the vertical axis represents image density.
FIG. 62 is a flowchart showing a manner of changing the image density when the number of toner patches to be created is small.
FIG. 63 is a flowchart showing a manner of changing the image density when a plurality of toner patches are created.
[Explanation of symbols]
1 Photoconductor drum
2 Charger
3 Exposure unit
4 Developing device
5 Primary transfer roll
6 Secondary transfer roll
10 units
11 Toner box
12 Paper tray
14 transport roll
15 Density sensor
16 Temperature sensor
17 Humidity sensor
19 Paper discrimination sensor
20 Intermediate transfer belt
21 Drive Roll
22 Counter roll
23 Tension roll
25 Patch formation unit
26 UI operation unit
30 Image processing unit
31 Image data control unit
32 image pixel counter
40 control unit
41 BCR control unit
42 LD light amount controller
43 TC control unit
44 Gradation control unit
45 Patch mode control unit
46 memory
47 timer
50 Image forming unit

Claims (16)

An image forming apparatus for forming a toner image on an image carrier, and finally transferring and fixing the toner image on a recording medium to form an image on the recording medium,
A patch forming unit for forming a toner patch for measurement in a predetermined manner set on the image carrier,
A density sensor for detecting the density of the toner patch formed by the patch forming unit at a predetermined detection position;
A patch mode control unit that sets the mode of the toner patch formed by the patch forming unit and changes the set mode according to the situation;
An image condition control unit that adjusts image forming conditions that affect the density of the toner image formed on the image carrier based on a detection result detected by the density sensor. Forming equipment. The image forming apparatus according to claim 1, wherein the patch state control unit changes an image density of the toner patch set in the patch forming unit according to a situation. 2. The image forming apparatus according to claim 1, wherein the patch mode control unit changes the number of the toner patches set in the patch forming unit according to a situation. The patch mode control unit compares the density detected by the density sensor with a target density, and changes the mode of the toner patch set in the patch forming unit according to the comparison result. The image forming apparatus according to claim 1. The patch state control unit has a density memory that stores a difference between the density detected by the density sensor and the target density, and according to a difference average size obtained by averaging the differences stored in the density memory, 2. The image forming apparatus according to claim 1, wherein an aspect of the toner patch set in the patch forming unit is changed. Equipped with a density adjustment unit that manually adjusts the density of the formed image,
The image forming apparatus according to claim 1, wherein the patch state control unit changes a state of the toner patch set in the patch forming unit in accordance with a command from the density adjustment unit. An environment sensor for detecting the temperature or humidity of the image forming apparatus is provided,
The image according to claim 1, wherein the patch state control unit changes the state of the toner patch set in the patch forming unit according to a temperature or humidity detected by the environment sensor. Forming equipment. The patch mode control unit includes a detection unit that detects that a part or a consumable that affects image forming conditions of the image forming apparatus has been replaced. The image forming apparatus according to claim 1, wherein an aspect of the toner patch set in a unit is changed. An operation state detection unit that detects an operation state of the image forming apparatus;
The image forming apparatus according to claim 1, wherein the patch state control unit changes a state of the toner patch set in the patch forming unit according to a detection result of the operation state detecting unit. . The image according to claim 9, wherein the image carrier rotates in a predetermined direction, and the operation state detection unit is a counter that counts a rotation number or a driving time of the image carrier. Forming equipment. A paper tray that stores the recording medium, and a determination unit that determines a type of the recording medium stored in the paper tray,
2. The patch mode control unit according to claim 1, wherein the patch mode control unit changes the mode of the toner patch set in the patch forming unit according to the type of the recording medium determined by the determination unit. Image forming device. An image density calculation unit that calculates an image density formed on a recording medium based on an input image signal or an image signal obtained by reading a document,
2. The patch state control unit according to claim 1, wherein the state of the toner patch set in the patch forming unit is changed according to the image density calculated by the image density calculation unit. Image forming device. The image density calculator is for obtaining a histogram for each predetermined image density of the input image signal,
2. The image forming apparatus according to claim 1, wherein the patch mode control unit changes the mode of the toner patch set in the patch forming unit to an image density having a high frequency in the histogram. . 14. The image forming apparatus according to claim 13, wherein the patch mode control unit obtains an average frequency averaged for each predetermined image density area, and compares the magnitude of the frequency based on the average frequency. The patch mode control unit compares the magnitude of the frequency for each predetermined image density area, and extracts a high-frequency image density exceeding a predetermined threshold value for each predetermined image density area. The image forming apparatus according to claim 13, wherein: The patch state control unit has a timer, and changes a state of the toner patch set in the patch forming unit according to an operation time or a non-energization time of the image forming apparatus measured by the timer. The image forming apparatus according to claim 1, wherein:

Images