JP2017161559A - Image forming apparatus, image density adjustment method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the accuracy in density adjustment even when an image defect is generated on a pattern image for density adjustment.SOLUTION: A color image forming apparatus 1 determines a sensitivity correction value of a density sensor 34 for a high-density image area and a non-image area on an intermediate transfer belt 41 formed by process cartridges 32C, 32M, 32Y, and 32K and stores as a high-density sensitivity correction value even in alignment processing and toner discharge processing not performed during density adjustment. The color image forming apparatus 1 forms a pattern image for density adjustment on the intermediate transfer belt 41 during density adjustment and performs density adjustment of the process cartridges 32C, 32M, 32Y, and 32K on the basis of a sensitivity correction value when the pattern image for density adjustment is read, and when the pattern image for density adjustment has an image defect, performs density adjustment by using the stored high-density sensitivity correction value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image forming apparatus, an image density adjustment method, and a program, and more particularly, to an electrophotographic image forming apparatus, an image density adjustment method, and a program for adjusting image density.

  2. Description of the Related Art An electrophotographic image forming apparatus such as a copying machine, a facsimile machine, or a printer uniformly charges a photosensitive member as a latent image carrier with a charger, and sensitizes a laser beam modulated based on image data from an exposure unit. Irradiate the body to form an electrostatic latent image. The image forming apparatus develops the electrostatic latent image with a developing unit and transfers it to a recording medium such as paper (hereinafter simply referred to as paper) at the transfer unit to form an image.

  In such an image forming apparatus, the image density may fluctuate due to the deterioration of the developing device, the toner characteristic fluctuation, etc., and the development unit is designed so that the image density is appropriate for such fluctuation. The image load output is adjusted (density adjustment).

  In the density adjustment, the image forming apparatus also forms a dark density patch when the density gradation pattern of each color is formed on an intermediate transfer belt, a recording medium (paper, etc.), and the reflection type of the dark density patch. The sensitivity correction value of the density sensor is calculated from the detection result of the density sensor. Then, the detection result of the density gradation pattern using this density sensor is corrected with the sensitivity correction value, the density gradation pattern color toner adhesion amount of each color is obtained, and the density adjustment of each color is performed.

  However, in the above-described conventional density adjustment method, if an image defect such as blurring occurs in a dark density patch generated at the time of density adjustment due to deterioration of the developing device or toner characteristic fluctuation, the sensitivity correction value is accurately obtained. Therefore, the calculation accuracy of the color toner adhesion amount is lowered. As a result, there is a problem that the accuracy of density adjustment is lowered.

  Conventionally, a powder concentration control for detecting a powder pattern formed on a detection target surface by an optical detection means disposed at a position facing the detection target surface and controlling the powder concentration based on the detection data In the method, a predetermined gradation pattern of powders having different adhesion amounts formed continuously on the surface to be detected is formed, and the detection data by the optical detection means for this or calculation processing data based thereon Among the acquired data, the accuracy of density control with a small number of patterns that can be obtained only by detection of a predetermined gradation pattern and is smaller than the predetermined gradation pattern is the accuracy of density control with a predetermined gradation pattern. A technique is disclosed that stores data necessary for maintaining the same level as in a memory and calls and uses the stored data as necessary when density control is performed with a small number of patterns. (See Patent Document 1).

  However, in the prior art described in the above publication, in powder density control, it can be obtained only by detecting a predetermined gradation pattern, and the accuracy of density control with a small number of patterns smaller than the predetermined gradation pattern. Is stored in the memory in order to keep the density equal to the accuracy of density control with a predetermined gradation pattern.When density control is performed with a small number of patterns, the stored data is called up and used as necessary. ing.

  However, when this technology is applied to density adjustment in electrophotographic image formation, it cannot cope with image defects such as blurring in a dark density patch generated during density adjustment. The correction value cannot be calculated accurately. As a result, there is a problem that the calculation accuracy of the color toner adhesion amount is lowered and the accuracy of density adjustment is lowered.

  Therefore, the present invention calculates the developer amount of the developer image of each color with high accuracy even when an image defect occurs in the density adjustment pattern image with high density for sensitivity correction value calculation formed at the time of density adjustment. The purpose is to improve the accuracy of density adjustment.

  In order to achieve the above object, an image forming apparatus according to claim 1 includes image forming means for a plurality of colors for forming a developer image on an intermediate transfer member or a recording medium conveyed in a predetermined conveying direction. The developer image is disposed at a predetermined position in the main scanning direction perpendicular to the transport direction of the intermediate transfer member or the recording medium, and the developer image is not applied to the intermediate transfer member or the recording medium by the image forming unit. Density detecting means for detecting the amount of reflected or transmitted light of the detection light irradiated to the forming area and the forming area as a non-forming area light quantity and a forming area light quantity, and the density detecting means from the non-forming area light quantity and the forming area light quantity A sensitivity correction value calculation means for calculating a sensitivity correction value of the image, and the density detection at the time of high density image formation in which the image forming means forms an image having a density higher than a predetermined level on the intermediate transfer member or the recording medium. A sensitivity correction value storage means for storing the sensitivity correction value calculated by the sensitivity correction value calculation means from the non-formation area light quantity detected by the means and the formation area light quantity as a high density sensitivity correction value; and the intermediate transfer member or the object to be covered. When the density adjustment pattern image of each color is formed on the recording medium by the image forming unit, the sensitivity correction value calculation unit detects the density adjustment pattern from the non-formation region light amount and the formation region light amount of the density adjustment pattern image. A density adjustment control means for calculating a sensitivity correction value, and a density correction sensitivity correction for performing density adjustment of the image forming means by comparing the density correction pattern detection sensitivity correction value with the high density sensitivity correction value. Sensitivity correction value setting means for setting a value, and each of the density adjustment pattern images detected by the density detection means based on the light amount of the formation area and the density adjustment sensitivity correction value. Developer amount calculating means for calculating the developer amount of the density adjustment pattern image, and density adjusting means for adjusting the developer image density by the image forming means based on the developer amount. It is characterized by.

  According to the present invention, even when an image defect occurs in a density adjustment pattern image having a high density for sensitivity correction value calculation formed at the time of density adjustment, the developer amount of each color developer image is calculated with high accuracy. Thus, the accuracy of density adjustment can be improved.

1 is a schematic configuration diagram of a color image forming apparatus to which an embodiment of the present invention is applied. FIG. 3 is a block diagram of a main part of the color image forming apparatus. Sectional drawing of a concentration sensor. The figure which shows an example of a density sensor and the pattern image for density adjustment. The figure which shows an example of a density sensor and an alignment pattern image. FIG. 6 is a diagram illustrating an example of a density sensor and a toner discharge pattern image. 1 is a functional block diagram of a color image forming apparatus. The flowchart which shows a registration / sensitivity correction value storage process. 10 is a flowchart illustrating toner discharge / sensitivity correction value storage processing. The flowchart which shows a density adjustment / sensitivity correction value storage process. 10 is a flowchart showing density adjustment / sensitivity correction value storage processing with image forming ability determination. The flowchart which shows the process of the head 11 continuing. The flowchart which shows the density | concentration adjustment / sensitivity correction value storage process in consideration of the generation | occurrence | production presence or absence of a density fluctuation factor.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, since the Example described below is a suitable Example of this invention, various technically preferable restrictions are attached | subjected, However, The range of this invention is unduly limited by the following description. However, not all the configurations described in the present embodiment are essential constituent elements of the present invention.

  1 to 13 are diagrams showing an embodiment of an image forming apparatus, an image density adjusting method, and a program according to the present invention. FIG. 1 is an embodiment of an image forming apparatus, an image density adjusting method, and a program according to the present invention. 1 is a schematic configuration diagram of a color image forming apparatus 1 to which an example is applied. In the following description, the color image forming apparatus 1 is described as performing print processing of print data of a print job received from outside via a network such as a LAN (Local Area Network). Or the like, and a printing process may be performed based on the image data from these image data input units.

  In FIG. 1, a color image forming apparatus 1 includes a main body housing 2 in which a paper feeding unit 10, a transport unit 20, a plotter unit 30, and the like are housed. 59 (see FIG. 2) and the like are provided.

  The paper supply unit 10 includes a paper supply tray 11, a paper supply roller 12, a separation pad (not shown), and the like, and a plurality of sheets (recording medium) P are stored in the paper supply tray 11. The paper feed unit 10 separates the paper P in the paper feed tray 11 one by one by the paper feed roller 12 and the separation pad, and sends the paper P to the transport unit 20.

  The conveyance unit 20 includes a registration roller 21, a secondary transfer roller 22, a fixing unit 23, a paper discharge roller 24, and the like, and also includes a plurality of conveyance rollers (not shown).

  The transport unit 20 transports the paper P sent out from the paper feed unit 10 to the registration rollers 21 and detects the paper P transported to the registration rollers 21 by a registration sensor (not shown). The color image forming apparatus 1 stops the conveyance of the temporary paper P by the registration roller 21 and then drives the registration roller 21 based on the detection result of the paper P by the registration sensor and the toner image formation status in the plotter unit 30. Control. In the color image forming apparatus 1, the registration roller 21 adjusts the timing of the paper P with the toner image formed by the plotter unit 30 and conveys the paper P to the secondary transfer roller 22. The transport unit 20 transports the paper P to the fixing unit 23 while transferring the color toner image formed by the plotter unit 30 onto the paper P transported from the registration roller 21 by the secondary transfer roller 22. The fixing unit 23 includes a fixing roller 23a and a pressure roller 23b. The fixing unit 23 heats and presses the paper P with the paper P sandwiched between the fixing roller 23a and the pressure roller 23b. The toner image is fixed on the paper P, and the paper P on which the fixing is completed is conveyed to the paper discharge roller 24.

  The transport unit 20 detects the paper P transported to the paper discharge roller 24 by a paper discharge sensor (not shown) and discharges the paper P onto the paper discharge tray 3 by the paper discharge roller 24.

  The plotter unit 30 includes an intermediate transfer unit 31, process cartridges 32C, 32M, 32Y, and 32K for each color of C (cyan), M (magenta), Y (yellow), and K (black), an exposure unit 33, and a density sensor 34. The intermediate transfer unit 31 includes an intermediate transfer belt 41, a secondary transfer drive roller 42, a tension roller 43, and CMYK transfer rollers 44Y, 44M, 44C, and the like. 44K etc. In the intermediate transfer unit 31, an intermediate transfer belt (intermediate transfer member) 41 formed in an endless belt-like ring shape is stretched between a secondary transfer driving roller 42 and a tension roller 43 that are stretched in a substantially horizontal direction. ing. The secondary transfer driving roller 42 is disposed in contact with the secondary transfer roller 22 with the intermediate transfer belt 41 interposed therebetween. Along with the intermediate transfer belt 41, CMYK process cartridges 32Y, 32M, 32C, and 32K are arranged. The process cartridges 32Y, 32M, 32C, and 32K include a charging roller, a developing / toner storage unit, and a cleaning unit that are not provided with reference numerals around the photosensitive members 45Y, 45M, 45C, and 45K that are driven to rotate clockwise in FIG. Are stored in a cartridge case (not shown). Each of the process cartridges 32Y, 32M, 32C, and 32K is in contact with the photoconductors 45Y, 45M, 45C, and 45K facing the transfer rollers 44Y, 44M, 44C, and 44K for each color with the intermediate transfer belt 41 interposed therebetween. In the state, it is housed and mounted in the main body housing 2 of the color image forming apparatus 1. In the plotter unit 30, the intermediate transfer belt 41 is conveyed between the photosensitive members 45Y, 45M, 45C, and 45K of the process cartridges 32Y, 32M, 32C, and 32K and the transfer rollers 44Y, 44M, 44C, and 44K.

  The exposure unit 33 includes a polygon motor, a polygon mirror, an Fθ lens, a laser diode, a mirror, and the like, although not denoted by reference numerals. The exposure unit 33 emits writing light for the process cartridges 32Y, 32M, 32C, and 32K of each color modulated based on the image data of each color from a laser diode to a polygon mirror that is rotationally driven by a polygon motor. The exposure unit 33 deflects the writing light in the main scanning direction by a polygon mirror, passes through an fθ lens, a mirror, and the like, and as shown by a one-dot chain line arrow in FIG. 1, each process cartridge 32Y, 32M, Irradiate uniformly charged photoreceptors 45Y, 45C, 45M, and 45K of 32C and 32K. The exposure unit 33 irradiates writing light to form electrostatic latent images on the photoconductors 45Y, 45C, 45M, and 45K of the respective colors.

  The plotter unit 30 rotates the photoconductors 45Y, 45C, 45M, and 45K on which the electrostatic latent images are formed in a clockwise direction, while supplying the toner of each color on the photoconductors 45Y, 45C, 45M, and 45K by the developing / toner storage unit. And the electrostatic latent image is developed to form a toner image (developer image). The plotter unit 30 sequentially superimposes and transfers the color toner images onto the intermediate transfer belt 41 by the transfer rollers 44Y, 44M, 44C, and 44K onto the photoreceptors 45Y, 45C, 45M, and 45K on which the toner images of the respective colors are formed. Form. The plotter unit 30 further rotates each of the photoconductors 45Y, 45C, 45M, and 45K, to which the toner image has been transferred, removes residual toner in the cleaning unit, and then charges again with a charging roller to be used for image formation. .

  The intermediate transfer belt 41 is driven to rotate counterclockwise by the secondary transfer driving roller 42, and is conveyed to the sheet P conveyed from the registration roller 21 between the secondary transfer driving roller 42 and the secondary transfer roller 22. Transfer the toner image.

  Further, the plotter unit 30 forms a pattern image on the intermediate transfer belt 41 and detects the pattern image by the density sensor 34 in order to perform a calibration process such as a predetermined color misregistration correction process and a density adjustment process. For example, a reflection type optical sensor is used as the density sensor 34. The position and density of the pattern image formed on the intermediate transfer belt 41 by the process cartridges 32Y, 32M, 32C, and 32K, and further, the intermediate transfer belt 41 are used. The density of the non-formal area where no image is formed is detected.

  Further, the plotter unit 30 is provided with a belt cleaning unit 35 on the outer peripheral surface on the right end side of the intermediate transfer belt 41. The belt cleaning unit 35 is connected to a waste toner box 36 disposed below the intermediate transfer belt 41 by a waste toner transfer hose (not shown).

  The plotter unit 30 removes the toner remaining on the intermediate transfer belt 41 after the transfer by the belt cleaning unit 35, conveys it to the waste toner box 36, and collects it.

  Further, the plotter unit 30 performs a toner discharge process for discharging the toner (developer) staying in the process cartridges 32Y, 32M, 32C, and 32K for a long time. That is, if the toner stays in the process cartridges 32Y, 32M, 32C, and 32K for a long period of time, the toner may deteriorate and development may not be possible. Therefore, the plotter unit 30 performs a toner discharge process for discharging the deteriorated toner out of the process cartridges 32Y, 32M, 32C, and 32K. In the toner discharge process, the plotter unit 30 forms an electrostatic latent image having a high density on the surface of the photoreceptors 45Y, 45C, 45M, and 45K using the toner to be discharged, transfers the latent image to the intermediate transfer belt 41, and performs belt cleaning. Collected by the unit 35. Therefore, the plotter unit 30 once forms an image with a high density on the intermediate transfer belt 41 in this toner discharge process.

  That is, the color image forming apparatus 1 forms a dark toner image on the intermediate transfer belt 41 during the position adjustment process and the toner discharge process in addition to the density adjustment process.

  Then, as described above, the color image forming apparatus 1 sequentially applies the toner images of the respective colors formed on the photoreceptors 45Y, 45C, 45M, and 45K onto the intermediate transfer belt 41 by the process cartridges 32Y, 32M, 32C, and 32K. A color toner image is formed by superimposing. The color image forming apparatus 1 forms an image on the paper P by transferring the toner image formed on the intermediate transfer belt 41 onto the paper P. The density of the toner image transferred onto the paper P is determined by the components Variation occurs due to deterioration of the environment and changes in environment (temperature, humidity, etc.).

  Therefore, the color image forming apparatus 1 performs a density adjustment process for adjusting the toner density in accordance with the number of toner image creation times (travel distances of the process cartridges 32Y, 32M, 32C, and 32K) and environmental changes. As the density adjustment processing, for example, the charging bias by the charging roller to the photoconductors 45Y, 45C, 45M, and 45K is kept constant, exposure is performed from the exposure unit 33, and the development bias of the development / toner storage unit is made variable. Thus, a density adjustment pattern image Pn (see FIG. 4) is formed, and this density adjustment pattern image is read by the density sensor 34. The color image forming apparatus 1 converts the output voltage value of the density sensor 34 into a toner density (the smaller the voltage, the higher the toner density). As will be described later, the color image forming apparatus 1 calculates a development bias so that the target toner density of the color image forming apparatus 1 is obtained, and performs density adjustment processing for setting as a development bias value of the development / toner storage unit. Thus, a toner image having a stable density is created.

  Further, in the color image forming apparatus 1, since the toner image has color shifts in the main scanning direction, the sub-scanning direction, and the oblique direction due to deterioration of parts and environmental (temperature / humidity) changes, the process cartridges 32Y, 32M, For example, four color strip-shaped alignment pattern images Pi (see FIG. 5) having different colors are formed on both sides of the intermediate transfer belt 41 in the main scanning direction by the 32C and 32K, and the alignment pattern image Pi. Is detected by the density sensor 34. Then, the color image forming apparatus 1 detects a positional deviation amount (color deviation amount) of the detected alignment pattern image Pi for each color. The color image forming apparatus 1 performs misregistration adjustment processing for correcting misregistration (color misregistration) by adjusting the optical writing timing or the like by the exposure unit 33 so that the misregistration amount becomes a predetermined value or less.

  Further, as described above, the color image forming apparatus 1 performs a toner discharge process for discharging the toner that stays in the process cartridges 32Y, 32M, 32C, and 32K for a long period of time. In this toner discharge process, the color image forming apparatus 1 applies the toner in the process cartridges 32Y, 32M, 32C, and 32K onto the intermediate transfer belt 41 to form a dark toner discharge pattern image Pt (see FIG. 6). Then, the toner discharge pattern image Pt is removed by the belt cleaning unit 35 and discharged to the waste toner box 36.

  In this embodiment, in the color image forming apparatus 1, the plotter unit 30 includes an intermediate transfer belt 41, and the toner images on the photoreceptors 45 Y, 45 C, 45 M, and 45 K are transferred onto the paper P via the intermediate transfer belt 41. Transcription. In the present invention, the plotter unit 30 of the color image forming apparatus 1 transfers the toner images of the respective colors on the photoconductors 45Y, 45C, 45M, and 45K directly and sequentially onto the paper P. Also good.

  The color image forming apparatus 1 has a control system configured as a block as shown in FIG. The color image forming apparatus 1 includes a CPU (Central Processing Unit) 51, a ROM (Read Only Memory) 52, a RAM (Random Access Memory) 53, an external I / F 54, an NVRAM (Nonvolatile Random Access Memory) 55, an I / O 56, an image. A processing IC 57, an operation I / F 58, an operation panel 59, the density sensor 34, and the like are provided, and each unit is connected by a system bus 60.

  The ROM 52 stores a basic program as the color image forming apparatus 1, a program of the image density adjustment method of the present invention, data necessary for executing these programs, and the like.

  The CPU 51 uses the RAM 53 as a work memory based on a program in the ROM 52 to control each unit of the color image forming apparatus 1 to execute processing as the color image forming apparatus 1, and an image density adjustment method to be described later Execute.

  The external I / F 54 is connected to an external device (not shown) such as a host computer via a network, a dedicated line, etc., and performs communication processing with the external device under the control of the CPU 51.

  The NVRAM 55 is a non-volatile memory, and stores various data that should be stored even when the color image forming apparatus 1 is powered off. The NVRAM 55 stores, for example, pattern data, density adjustment value, position correction value, toner elapsed time, and the like formed in the density adjustment process, the alignment process, and the toner discharge process under the control of the CPU 51.

  The NVRAM 55 also detects the detection result of the density sensor 34 detecting the density adjustment pattern image formed on the intermediate transfer belt 41 during the density adjustment process, and converts the toner density conversion information such as a conversion table or function for converting the toner density. I remember it.

  The image processing IC 57 performs image processing necessary for image formation by the plotter unit 30 on the image data to be printed (image formation target), and transmits the image data to the exposure unit 33. Further, the image processing IC 57 generates pattern image data to be formed in the density adjustment process, the alignment process, and the toner discharge process under the control of the CPU 51, and passes the pattern image data to the CPU 51.

  An operation panel 59 is connected to the operation I / F 58, and the operation I / F 58 exchanges signals between the CPU 51 and the operation panel 59.

  The operation panel 59 includes various operation keys, a display panel (for example, a liquid crystal panel) and the like. Various key operations necessary for giving an operation instruction to the color image forming apparatus 1 are performed from the operation keys on the operation panel 59, and the operation keys are operated on the display panel under the control of the CPU 51 via the operation I / F 58. Display and output contents and various information. In particular, the operation panel 59 notifies and outputs a predetermined warning under the control of the CPU 51.

  Various sensors such as the density sensor 34 are connected to the I / O 56, and a detection voltage from the sensor, particularly the density sensor 34, is passed to the CPU 51.

  As the density sensor 34, for example, a reflection type density sensor as shown in FIG. 3 is used. In the density sensor 34, a light emitting element 34b and a light receiving element 34c are accommodated in a case 34a. The light emitting element 34b is an LED (Light Emitting Diode) or the like, and the light receiving element 34c is a phototransistor or a photodiode. It is used. In the density sensor 34, the light receiving element 34c receives the reflected light of the detection light irradiated on the intermediate transfer belt 41 from the light emitting element 34b. The light receiving element 34c outputs a detection voltage Vs having a voltage corresponding to the amount of incident light. The density sensor 34 receives the reflected light of the detection light irradiated to the intermediate transfer belt 41 from the light emitting element 34b by the light receiving element 34c, and this reflected light is regular reflected light. That is, the surface of the intermediate transfer belt 41 has a sufficiently high gloss compared to the toner layer when the toner image is formed, and the detection light irradiated on the surface of the intermediate transfer belt 41 is almost regularly reflected. The On the other hand, the detection light applied to the toner layer is absorbed or diffused by the toner layer, and the ratio of regular reflection decreases. However, the ratio of regular reflection decreases as the toner density increases. . That is, the density sensor 34 uses the surface detection voltage Vsg when the reflected light on the surface (non-formation region) of the intermediate transfer belt 41 is detected and the toner image (formation region) formed on the surface of the intermediate transfer belt 41. The toner detection voltage Vsp when the reflected light is detected is output.

  Then, the density sensor 34 outputs the surface detection voltage Vsg and the toner detection voltage Vsp to the CPU 51 via the I / O 56.

  The CPU 51 determines the ratio Vr (Vr) of the surface detection voltage Vsg to the toner detection voltage Vsp when a dark density toner image (pattern image) is formed on the intermediate transfer belt 41 in the alignment process, toner discharge process and density adjustment process. = Vsp / Vsg). The CPU 51 stores the calculated high concentration detection voltage ratio Vr in the NVRAM 55 as a high concentration sensitivity correction value.

  As shown in FIGS. 4 to 6, the color image forming apparatus 1 detects an image in the non-image area of the intermediate transfer belt 41 in a state where the two density sensors 34 are aligned in the main scanning direction and separated by a predetermined distance. It is arranged at the position to do. In the present embodiment, two density sensors 34 are provided. However, the number may be any number as long as the intermediate transfer belt 41 and the toner image (pattern image) can be detected appropriately. For example, it may be one or three or more.

  FIG. 4 is a diagram illustrating a state in which the density adjustment pattern image Pn is formed on the pair of density sensors 34 and the intermediate transfer belt 41, and FIG. 5 is a diagram on the pair of density sensors 34 and the intermediate transfer belt 41. It is a figure which shows the state in which the pattern image Pi for alignment is formed. FIG. 6 is a diagram showing a state in which a toner discharge pattern image Pt is formed on the pair of density sensors 34 and the intermediate transfer belt 41. The original pattern data of the density adjustment pattern image Pn, the alignment pattern image Pi, and the toner discharge pattern image Pt is stored in the NVRAM 55 as described above.

  In FIGS. 4 to 6, as an example, the pattern images Pn, Pi, and Pt are detected using the two density sensors 34 that are evenly arranged on the left and right sides from the center of the image height.

  In the case of FIG. 4, in the density adjustment pattern image Pn, patch images having different densities are arranged at equal intervals in the sub-scanning direction, and the four color patch images of YMCK are a combination of YC and MK for each of the left and right colors. A pattern is formed. The color image forming apparatus 1 forms the density adjustment pattern image Pn in the non-image area on the intermediate transfer belt 41 by the plotter unit 30 at the timing of density adjustment processing, and the two density sensors 34 simultaneously The non-formation area and the formation area of the image on the transfer belt 41, that is, the density adjustment pattern image Pn is detected. The CPU 51 calculates the high concentration detection voltage ratio Vr based on the detection voltage of the concentration sensor 34 and stores the calculated high concentration detection voltage ratio Vr in the NVRAM 55.

  In the case of FIG. 5, the alignment pattern image Pi is a pattern image for aligning the overlapping positions of the YMCK color images, and is used for aligning the writing positions of the main scanning and the sub scanning with the reference color. It is a pattern image. The color image forming apparatus 1 forms the alignment pattern image Pi in the non-image area on the intermediate transfer belt 41 by the plotter unit 30 at the timing of the density adjustment processing, and simultaneously with the two density sensors 34 for a short time. In addition, the oblique pattern image Pi is detected, the amount of deviation in the sub-scanning direction, the pattern image Pi formed in the horizontal direction is detected, and the amount of deviation in the sub-scanning direction is detected. The CPU 51 calculates the high concentration detection voltage ratio Vr based on the detection voltage of the concentration sensor 34 and stores the calculated high concentration detection voltage ratio Vr in the NVRAM 55.

  In the case of FIG. 6, the toner discharge pattern image Pt is a pattern image having a sub-scanning length necessary for each color for refreshing each color toner. The color image forming apparatus 1 discharges the toner by forming the toner discharge pattern image Pt over the image area and the non-image area on the intermediate transfer belt 41 by the plotter unit 30 at the timing of the toner discharge process. Further, as will be described later, the color image forming apparatus 1 detects the toner discharge pattern image Pt simultaneously by the two density sensors 34 in a short time. The CPU 51 calculates the high concentration detection voltage ratio Vr based on the detection voltage of the concentration sensor 34 and stores the calculated high concentration detection voltage ratio Vr in the NVRAM 55.

  The CPU 51 stores the density adjustment pattern image Pn formed on the intermediate transfer belt 41 and the high density detection voltage ratio Vr when the density sensor 34 detects the non-formation area in the NVRAM 55 during the density adjustment process. Compared with the high concentration detection voltage ratio Vr. The CPU 51 determines the sensitivity correction value of the density sensor 34 based on the comparison result. That is, even if the surface of the intermediate transfer belt 41 (non-formation region) is irradiated with detection light having the same detection voltage from the density sensor 34, the surface state of the intermediate transfer belt 41 changes if the surface state changes due to durability deterioration or the like. The surface detection voltage Vsg on the surface also changes. On the other hand, the density sensor 34 can adjust the light emission amount of the detection light by adjusting the light emission voltage supplied to the light emitting element 34b.

  Then, the CPU 51 uses the determined sensitivity correction value and the high density detection voltage ratio Vr corrected by using the sensitivity corrected value and the toner density conversion information (high density sensitivity correction value) of the NVRAM 55 to adjust the density. The toner density of the density adjustment pattern image Pn is obtained.

  The color image forming apparatus 1 includes ROM, EEPROM (Electrically Erasable and Programmable Read Only Memory), EPROM, flash memory, flexible disk, CD-ROM (Compact Disc Read Only Memory), CD-RW (Compact Disc Rewritable), DVD ( A program for executing the image density adjustment method of the present invention recorded on a computer-readable recording medium such as a digital video disk (SD), a secure digital (SD) card, or an MO (Magneto-Optical Disc) is read into the ROM 52, NVRAM 55 Even when an image defect occurs in a dark density adjustment pattern image for sensitivity correction value calculation formed at the time of density adjustment, which will be described later, the developer amount of the developer image of each color with high accuracy And is constructed as an image forming apparatus that executes an image density adjustment method that improves the accuracy of density adjustment. There. The image density adjustment method program is a computer-executable program written in a legacy programming language such as an assembler, C, C ++, C #, Java (registered trademark), an object-oriented programming language, or the like. Can be stored and distributed.

  In the color image forming apparatus 1, the functional block as shown in FIG. 7 is constructed by introducing the program of the image density adjusting method. That is, the color image forming apparatus 1 has the above-described program introduced therein, and as shown in FIG. 7, the image forming unit 71, the density detecting unit 72, the sensitivity correction value calculating unit 73, the sensitivity correction value storage unit 74, the density An adjustment control unit 75, a sensitivity correction value setting unit 76, a developer amount calculation unit 77, a density adjustment unit 78, and a notification unit 79 are constructed.

  The image forming unit 71 is constructed by the plotter unit 30, in particular, the process cartridges 32C, 32M, 32Y, and 32K. ) Function as image forming means for a plurality of colors. Note that the image forming unit 71 may directly form a toner image on the paper P that is a recording medium.

  The density detector 72 is constructed by the density sensor 34. The density detection unit 72 is disposed at a predetermined position in the main scanning direction orthogonal to the conveyance direction of the intermediate transfer belt 41 and irradiates non-formation regions and formation regions of the toner image by the image forming unit 71 of the intermediate transfer belt 41. The reflected light amount of the detected light is detected as a non-formation region light amount and a formation region light amount. Here, the toner image non-formation region is a background portion of the intermediate transfer belt 41 where the toner image is not formed, and the formation region is a toner image portion. Therefore, the concentration detector 72 functions as a concentration detector. The density detection unit 72 is not limited to a reflection type that detects reflected light. When the intermediate transfer belt 41 is formed of a transmissive member, the density detection unit 72 is not formed so as to pass through a non-morphic region of the intermediate transfer belt 41. You may detect a region light quantity and the formation region light amount which permeate | transmitted the formation area.

  The sensitivity correction value calculation unit 73 is constructed by the CPU 51 and calculates the sensitivity correction value of the density detection unit 72 from the non-formation region light amount and the formation region light amount. Therefore, the sensitivity correction value calculation unit 73 functions as a sensitivity correction value calculation unit.

  The sensitivity correction value storage unit 74 is constructed by the NVRAM 55. The sensitivity correction value storage unit 74 detects the non-formation region light amount detected by the density detection unit 72 and the formation region when forming a high-density image in which the image forming unit 71 forms an image having a density higher than a predetermined level on the intermediate transfer belt 41. The sensitivity correction value calculated by the sensitivity correction value calculation unit 73 from the light amount is stored as a high density sensitivity correction value. Therefore, the sensitivity correction value storage unit 74 functions as a sensitivity correction value storage unit.

  The density adjustment control unit 75 is constructed by the CPU 51. The density adjustment control unit 75 causes the intermediate transfer belt 41 to form the density adjustment pattern image Pn of each color on the image forming unit 71, and the sensitivity is determined based on the non-formation region light amount and the formation region light amount of the density adjustment pattern image Pn. The correction value calculation unit 73 is made to calculate the sensitivity correction value at the time of density adjustment pattern detection. Therefore, the density adjustment control unit 75 functions as density adjustment control means.

  The sensitivity correction value setting unit 76 is constructed by the CPU 51. The sensitivity correction value setting unit 76 compares the sensitivity correction value at the time of density adjustment pattern detection with the high density sensitivity correction value of the sensitivity correction value storage unit 74, and performs density adjustment for performing density adjustment of the image forming unit 71. Set the sensitivity correction value. Therefore, the sensitivity correction value setting unit 76 functions as sensitivity correction value setting means.

  The developer amount calculation unit 77 is constructed by the CPU 51 and develops the density adjustment pattern image Pn of each color from the light amount of the density adjustment pattern image Pn detected by the density detection unit 72 and the density adjustment sensitivity correction value. The dosage is calculated. Therefore, the developer amount calculation unit 77 functions as a developer amount calculation unit.

  The density adjusting unit 78 is constructed by the CPU 51 and adjusts the toner image density (developer image density) by the image forming unit 71 based on the developer amount calculated by the developer amount calculating unit 77. Therefore, the density adjusting unit 78 functions as a density adjusting unit.

  The notification unit 79 is constructed by an operation panel 59, in particular, a display panel of the operation panel 59, and displays and outputs a predetermined warning. Therefore, the notification unit 79 functions as a notification unit.

  Next, the operation of this embodiment will be described. The color image forming apparatus 1 according to the present exemplary embodiment can accurately perform toner of each color toner image even when an image defect occurs in the density adjustment pattern image Pn having a high density for sensitivity correction value formation formed at the time of density adjustment. The amount is calculated to improve the accuracy of density adjustment.

  That is, the color image forming apparatus 1 forms the density adjustment pattern image Pn on the intermediate transfer belt 41 by the image forming unit 71 during the density adjustment process. In the color image forming apparatus 1, the density adjustment pattern image Pn and reflected light from the surface of the intermediate transfer belt 41 are detected by the density detection unit 72, and based on the detection result, the density adjustment of the toner image by the imaging unit 71 is performed. I do.

  However, if the density adjustment pattern image Pn has image defects such as fading or chipping, the density adjustment cannot be performed properly.

  Therefore, the color image forming apparatus 1 detects the sensitivity of the density detection unit 72 from the non-morphic area light quantity and the formation area light quantity at the time of image formation at the timing of forming a dark image other than the density adjustment pattern image Pn. Then, it is stored in the sensitivity correction value storage unit 74 as a high density sensitivity correction value. The color image forming apparatus 1 forms a density adjustment pattern image Pn at the time of density adjustment, and obtains the sensitivity correction value of the density detection unit 72 from the non-morphic area light amount detected by the density detection unit 72 and the formation region light amount. The density adjustment sensitivity correction value is obtained by comparison with the high density sensitivity correction value in the sensitivity correction value storage unit 74. By obtaining the density adjustment sensitivity correction value, the color image forming apparatus 1 can obtain an appropriate sensitivity correction value from the past sensitivity even if there is an image defect in the density adjustment pattern image Pn. Then, the color image forming apparatus 1 obtains the toner amount (developer amount) of the density adjustment pattern image Pn from the obtained sensitivity correction value and the light amount of the formation area detected by the density detection unit 72, and is formed by the image forming unit 71. Adjust the toner image density.

  The color image forming apparatus 1 employs the alignment processing timing shown in FIG. 8 and the toner discharge processing timing shown in FIG. 9 as the timing for forming a dark image, but the timing is limited to these timings. It is not a thing. Also, the density adjustment timing for adjusting the image density may be the timing for forming a dark image.

  The color image forming apparatus 1 calculates the sensitivity correction value of the density detection unit 72 from the detection results of the density detection unit 72 in the formation region and the non-formation region of the dark image formed at these timings. The sensitivity correction values are stored in the sensitivity correction value storage unit 74.

  That is, the color image forming apparatus 1 forms an alignment pattern image Pi as shown in FIG. 5 on the intermediate transfer belt 41 by the image forming unit 71 as shown in FIG. (Step S101).

  Next, the color image forming apparatus 1 detects the alignment pattern image Pi formed on the intermediate transfer belt 41 by the density detector 72 (step S102). Specifically, the density detector 72 outputs a toner detection voltage Vs corresponding to the amount of reflected light from the alignment pattern image Pi.

  The color image forming apparatus 1 calculates an alignment correction amount from the detection result (toner detection voltage Vs) of the density detection unit 72 of the alignment pattern image Pi, and stores it in the sensitivity correction value storage unit 74 (step S103). .

  Next, the color image forming apparatus 1 detects each density sensor from the toner detection voltage Vs output by the density detection unit 72 before and after the alignment pattern image Pi reaches the density detection unit 72, that is, immediately below the density sensor 34. A sensitivity correction value 34 is calculated (step S104). That is, the color image forming apparatus 1 calculates the ratio Vr as the sensitivity correction value from the surface detection voltage Vsg and the toner detection voltage Vsp. Since the alignment pattern image Pi is composed of a plurality of patches as shown in FIG. 5, the sensitivity correction value may be calculated from any of the patches, or may be calculated for all the patches. It is also possible to select the smallest value from the data and use it as the sensitivity correction value when performing density adjustment.

  In order to leave a history of sensitivity correction values for the past N times, the color image forming apparatus 1 stores the (N−i) previous result as the (N + 1−i) previous result, i is ( N-1) is repeated sequentially (i is 0 to N-1) (steps S105 to S107).

  When the color image forming apparatus 1 repeatedly performs processing and stores the latest N sensitivity correction values in the sensitivity correction value storage unit 74, the latest sensitivity correction value calculated this time is used as the previous sensitivity correction value to perform sensitivity correction. The data is stored in the value storage unit 74, and the alignment / sensitivity correction value storage process is terminated (step S108).

  The color image forming apparatus 1 does not repeat the process when the sensitivity correction value is not stored in the sensitivity correction value storage unit 74 in step S105. The color image forming apparatus 1 stores the sensitivity correction value calculated this time as the previous sensitivity correction value in the sensitivity correction value storage unit 74 and ends the alignment / sensitivity correction value storage process (step S108).

  Further, at the toner discharge processing timing, the color image forming apparatus 1 first calculates the toner discharge amount discharged in the toner discharge processing as shown in FIG. 9 (step S201). The color image forming apparatus 1 generates a toner discharge pattern in which the toner discharge amount becomes the calculated toner discharge amount. The color image forming apparatus 1 forms, for example, a toner discharge pattern image Pt as shown in FIG. 6 on the intermediate transfer belt 41 by the image forming unit 71 based on the generated toner discharge pattern (step S202). .

  Next, the color image forming apparatus 1 detects the toner discharge pattern image Pt formed on the intermediate transfer belt 41 by the density detector 72 (step S203). Specifically, the density detector 72 outputs a toner detection voltage Vs corresponding to the amount of reflected light from the toner discharge pattern image Pt.

  The color image forming apparatus 1 detects the sensitivity of each density sensor 34 from the toner detection voltage Vs output from the density detection unit 72 before and after the toner discharge pattern image Pt reaches the density detection unit 72, that is, immediately below the density sensor 34. A correction value is calculated (step S204). Also in this case, since the toner discharge pattern image Pt is composed of a plurality of patches as shown in FIG. 6, the sensitivity correction value may be calculated from any one of the patches, or all It is also possible to select the smallest value from the data calculated by the patch and use it as the sensitivity correction value when performing density adjustment.

  In order to leave a history of sensitivity correction values for the past N times, the color image forming apparatus 1 stores the (N−i) previous result as the (N + 1−i) previous result, i is ( N-1) is repeated sequentially (i is 0 to N-1) (steps S205 to S207).

  When the color image forming apparatus 1 repeatedly performs processing and stores the latest N sensitivity correction values in the sensitivity correction value storage unit 74, the latest sensitivity correction value calculated this time is used as the previous sensitivity correction value to perform sensitivity correction. The value is stored in the value storage unit 74, and the toner discharge / sensitivity correction value storage process is terminated (step S208).

  When the sensitivity correction value is not stored in the sensitivity correction value storage unit 74 in step S205, the color image forming apparatus 1 does not repeat the process. The color image forming apparatus 1 stores the sensitivity correction value calculated this time as the previous sensitivity correction value in the sensitivity correction value storage unit 74, and ends the toner discharge / sensitivity correction value storage process (step S208).

  Note that the sensitivity correction value stored in the alignment / sensitivity correction value storage process and the sensitivity correction value stored in the toner discharge / sensitivity correction value storage process are the history of the alignment process and the toner discharge process, respectively. It may be stored, or may be stored together as a history of sensitivity correction values.

  Then, as shown in FIG. 10, the color image forming apparatus 1 performs density adjustment / sensitivity correction value storage processing. That is, when the color image forming apparatus 1 comes to the density adjustment timing, as shown in FIG. 10, the image forming unit 71 causes the density adjustment pattern image (density adjustment gradation pattern image) Pn as shown in FIG. Are formed on the intermediate transfer belt 41 (step S301).

  Next, the color image forming apparatus 1 detects the density adjustment pattern image Pn formed on the intermediate transfer belt 41 by the density detection unit 72 (step S302). Specifically, the density detector 72 outputs a toner detection voltage Vs corresponding to the amount of reflected light from the density adjustment pattern image Pn.

  The color image forming apparatus 1 detects the sensitivity of each density sensor 34 from the toner detection voltage Vs output by the density detection unit 72 before and after the density adjustment pattern image Pn reaches the density detection unit 72, that is, immediately below the density sensor 34. A correction value is calculated (step S303). Also in this case, since the density adjustment pattern image Pn is composed of a plurality of patches as shown in FIG. 4, the sensitivity correction value may be calculated from any one of the patches, or all A sensitivity correction value may be selected by selecting the smallest value from the data calculated by the patch.

  When the color image forming apparatus 1 calculates the sensitivity correction value, the color image forming apparatus 1 acquires the previous sensitivity correction value stored in the sensitivity correction value storage unit 74 (step S304), and the calculated sensitivity correction value is the previous sensitivity. It is checked whether it is larger than the correction value (latest sensitivity correction value) (step S305).

  In step S305, when the calculated sensitivity correction value is larger than the previous sensitivity correction value (YES in step S305), the color image forming apparatus 1 uses the smaller one as the sensitivity correction value for density adjustment. The previous sensitivity correction value (latest sensitivity correction value) is set (step S306).

  In step S305, if the calculated sensitivity correction value is equal to or less than the previous sensitivity correction value (NO in step S305), the color image forming apparatus 1 uses the smaller one as the sensitivity correction value for density adjustment, or The latest calculated sensitivity correction value is set (step S307).

  After setting the sensitivity correction value, the color image forming apparatus 1 calculates the toner adhesion amount of the density adjustment pattern image Pn from the toner detection voltage Vs using the sensitivity correction value (step S308).

  The color image forming apparatus 1 determines the image forming unit 71, that is, the process cartridges 32C, 32M, and 32Y, based on the image forming load output when the density adjustment pattern image Pn that is a gradation image is generated and the toner adhesion amount. , 32K development characteristics are calculated (step S309).

  The color image forming apparatus 1 calculates an appropriate image forming load output from the calculated development characteristic and the target adhesion amount, sets it, and performs density adjustment processing (step S310).

  In order to leave a history of sensitivity correction values for the past N times, the color image forming apparatus 1 stores the (N−i) previous result as the (N + 1−i) previous result, i is ( N-1) is repeated sequentially (i is 0 to N-1) (steps S311 to S313).

  When the color image forming apparatus 1 repeatedly performs processing and stores the latest N sensitivity correction values in the sensitivity correction value storage unit 74, the latest sensitivity correction value calculated this time is used as the previous sensitivity correction value to perform sensitivity correction. The value is stored in the value storage unit 74, and the density adjustment / sensitivity correction value storage process is terminated (step S314).

  The color image forming apparatus 1 does not repeat the process when the sensitivity correction value is not stored in the sensitivity correction value storage unit 74 in step S311. The color image forming apparatus 1 stores the sensitivity correction value calculated this time as the previous sensitivity correction value in the sensitivity correction value storage unit 74, and ends the density adjustment / sensitivity correction value storage process (step S314).

  Accordingly, in the density adjustment process, even if the density adjustment pattern image Pn formed on the intermediate transfer belt 41 has a defect or the like, the past sensitivity correction value stored in the sensitivity correction value storage unit 74 is used to obtain high accuracy. The developer amount of each color developer image can be calculated. As a result, the accuracy of density adjustment can be improved.

  The color image forming apparatus 1 stops the density adjustment and the calculation of the sensitivity correction value when the image forming ability of the image forming unit 71, that is, the process cartridges 32C, 32M, 32Y, and 32K is reduced to a predetermined value or more. When the predetermined number of times is stopped, a warning may be output.

  That is, as shown in FIGS. 11 and 12, the color image forming apparatus 1 performs density adjustment / sensitivity correction value storage processing that involves image formation capability determination of the image forming unit 71, that is, the process cartridges 32C, 32M, 32Y, and 32K. I do. 11 and 12, the same step numbers are assigned to the same processing steps as those in FIG. 10, and the description thereof is omitted or simplified.

  First, the color image forming apparatus 1 acquires the latest sensitivity correction value stored in the sensitivity correction value storage unit 74 (step S401), and the latest sensitivity correction value is equal to or less than a preset sensitivity correction value upper limit. Is checked (step S402). That is, in the image forming unit 71 that is the process cartridge 32C, 32M, 32Y, or 32K, when the image forming ability deteriorates, the formed image becomes thin, the sensitivity correction value increases, and the density adjustment may fail. . Therefore, the color image forming apparatus 1 sets the upper limit of the sensitivity correction value indicating that the latest sensitivity correction value has deteriorated to the limit of the deterioration of the image forming capability of the image forming unit 71, and the latest sensitivity correction value is the sensitivity correction. It is checked whether the value is below the upper limit, that is, whether the degradation of the image forming ability is the limit.

  If the latest sensitivity correction value is equal to or less than the upper limit of the sensitivity correction value in step S402 (YES in step S402), the color image forming apparatus 1 performs the same density adjustment / sensitivity correction value storage processing as in FIG. (Steps S301 to S314) That is, in this case, the color image forming apparatus 1 determines that the image forming unit 71 has not deteriorated.

  When the density adjustment / sensitivity correction value storage process is performed, the color image forming apparatus 1 clears a density adjustment skip count, which will be described later, as shown in FIG. The process ends (step S403).

  If the latest sensitivity correction value exceeds the upper limit of sensitivity correction value in step S402 (NO in step S402), the color image forming apparatus 1 sets the density adjustment skip count to “1” as shown in FIG. "Is incremented (step S404). The number of density adjustment skips is counted by, for example, an internal counter. That is, in this case, the color image forming apparatus 1 first skips the density adjustment / sensitivity correction value storage process and increments the density adjustment skip count by “1”.

  The color image forming apparatus 1 checks whether the incremented density adjustment skip count exceeds a preset skip count upper limit (step S405). The upper limit of the number of skips is the number of times that it can be determined that the image forming unit 71 that is the process cartridge 32C, 32M, 32Y, or 32K has reached the limit.

  If the number of density adjustment skips is equal to or less than the number of skips in step S405 (NO in step S405), the color image forming apparatus 1 ends the density adjustment / sensitivity correction value storage process with image forming ability determination as it is. .

  In step S405, when the density adjustment skip count exceeds the skip count (YES in step S405), the color image forming apparatus 1 causes the notification section 79 to output a predetermined warning to generate an image forming capability. The density adjustment / sensitivity correction value storage process with determination ends (step S406).

  Accordingly, it is possible to prevent the image forming unit 71 that is the process cartridges 32C, 32M, 32Y, and 32K from performing an erroneous density adjustment when the image forming unit 71 is deteriorated, and to optimize the density adjustment. it can. Further, when the image forming unit 71 deteriorates, the density adjustment is stopped before the density adjustment pattern image Pn is created. Therefore, the density adjustment pattern image Pn is created to waste the toner. Can be prevented. Furthermore, if the image forming unit 71 that is the process cartridge 32C, 32M, 32Y, or 32K has exceeded the limit, a warning to that effect can be output, and appropriate correspondence to the image forming unit 71 is achieved. Can be achieved.

  Furthermore, as shown in FIG. 13, the color image forming apparatus 1 may perform density adjustment / sensitivity correction value storage processing in consideration of the presence or absence of density variation factors. In FIG. 13, the same processing steps as those in FIG. 10 are given the same step numbers, and the description thereof is omitted or simplified.

  In this case, the color image forming apparatus 1 first checks whether or not a density variation factor has occurred (step S501). The color image forming apparatus 1 determines whether or not this density variation factor has occurred, for example, by changes in the surrounding environment, changes in the travel distance of the process cartridges 32C, 32M, 32Y, and 32K, in particular, the photoreceptors 45Y, 45C, 45M, and 45K. Judgment is made based on whether the value is equal to or greater than a predetermined value.

  When a density variation factor is generated in step S501 (YES in step S501), the color image forming apparatus 1 performs the same density adjustment / sensitivity correction as in FIG. 10 as in FIG. Value storage processing is performed (steps S301 to S314).

  However, instead of step S305 in FIG. 10, the color image forming apparatus 1 performs, as step S502, processing for confirming whether or not the calculated sensitivity correction value is within a value determined to have no image loss. Run.

  If the calculated sensitivity correction value is within the range in step S502 (YES in step S502), the color image forming apparatus 1 sets the calculated sensitivity correction value as the density correction sensitivity correction value (step S502). S306).

  In step S502, if the calculated sensitivity correction value is out of range (NO in step S502), the color image forming apparatus 1 uses the latest sensitivity correction value in the sensitivity correction value storage unit 74 as the sensitivity for density adjustment. A correction value is set (step S307).

  That is, the color toner adhesion amount is calculated using the latest sensitivity correction value only when the density adjustment pattern image Pn is blurred and the calculated sensitivity correction value is not within the normal range.

  As described above, by performing the density adjustment / sensitivity correction value storage process only when the density variation factor occurs, it is possible to reduce useless density adjustment processing time, optimize the density adjustment process, and form a color image. The usability of the device 1 can be improved.

  If no density variation factor has occurred in step S501 (NO in step S501), the color image forming apparatus 1 forms a density adjustment pattern image Pn on the intermediate transfer belt 41 without a dark density patch. (Step S503).

  Next, the color image forming apparatus 1 detects the density adjustment pattern image Pn formed on the intermediate transfer belt 41 by the density detection unit 72 (step S504). The color image forming apparatus 1 performs the processes in step S503 and step S504 in order to perform the processes after step S308.

  After that, the color image forming apparatus 1 sets the latest sensitivity correction value in the sensitivity correction value storage unit 74 as the sensitivity correction value for density adjustment (step S307), proceeds to step S308, and performs the same processing as described above. Execute (Steps S308 to S314).

  As described above, the color image forming apparatus 1 according to the present exemplary embodiment includes a plurality of color image forming units (image forming units) that form toner images (developer images) on the intermediate transfer belt 41 that is transported in a predetermined transport direction. And a toner image non-formation region and a formation region by the image forming unit 71 on the intermediate transfer belt 41. A density detection unit (density detection means) 72 that detects the reflected light amount of the irradiated detection light as a non-formation region light amount and a formation region light amount, and the sensitivity of the density detection unit 72 based on the non-formation region light amount and the formation region light amount A sensitivity correction value calculation unit (sensitivity correction value calculation unit) 73 that calculates a correction value, and the density at the time of high density image formation in which the image forming unit 71 forms an image having a density higher than a predetermined level on the intermediate transfer belt 41. Detection unit Sensitivity correction value storage unit (sensitivity correction value storage means) 74 for storing the sensitivity correction value calculated by the sensitivity correction value calculation unit 73 from the non-formation region light amount detected by the detection unit 2 and the formation region light amount as a high density sensitivity correction value. The density adjustment pattern image Pn of each color is formed on the intermediate transfer belt 41 in the image forming unit 71, and the sensitivity correction value is calculated from the non-formation region light amount and the formation region light amount of the density adjustment pattern image Pn. A density adjustment control unit (density adjustment control means) 75 that causes the calculation unit 73 to calculate a sensitivity correction value at the time of density adjustment pattern detection, and the sensitivity correction value at the time of density adjustment pattern detection are compared with the high density sensitivity correction value. A sensitivity correction value setting unit (sensitivity correction value setting means) 76 for setting a density adjustment sensitivity correction value for adjusting the density of the image forming unit 71, and the density adjustment detected by the density detection unit 72. A developer amount calculation unit (developer amount calculation) that calculates the toner amount (developer amount) of the density adjustment pattern image Pn of each color based on the light amount of the formation area of the pattern image Pn and the sensitivity correction value for density adjustment Means) 77 and a density adjusting unit (density adjusting means) 78 for adjusting the toner image density (developer image density) by the image forming unit 71 based on the toner amount.

  Accordingly, in the density adjustment process, even if the density adjustment pattern image Pn formed on the intermediate transfer belt 41 has a defect or the like, the past sensitivity correction value stored in the sensitivity correction value storage unit 74 is used to obtain high accuracy. The developer amount of each color developer image can be calculated. As a result, the accuracy of density adjustment can be improved.

  In addition, the color image forming apparatus 1 of the present embodiment includes a plurality of color image forming processing steps for forming a toner image on the intermediate transfer belt 41 conveyed in a predetermined conveyance direction, and conveyance of the intermediate transfer belt 41. The amount of reflected or transmitted detection light applied to the non-formation region and the formation region of the toner image in the image forming process step on the intermediate transfer belt 41 is disposed at a predetermined position in the main scanning direction orthogonal to the direction. A density detection processing step for detecting a light amount as a non-formation region light amount and a formation region light amount, and a sensitivity correction value calculation processing step for calculating a sensitivity correction value in the density detection processing step from the non-formation region light amount and the formation region light amount Detected in the density detection processing step during high density image formation in which an image having a darkness of a predetermined level or more is formed on the intermediate transfer belt 41 in the image forming processing step. A sensitivity correction value storage processing step for storing the sensitivity correction value calculated in the sensitivity correction value calculation processing step from the non-formation region light amount and the formation region light amount in the sensitivity correction value storage unit 74 as a high density sensitivity correction value; The density adjustment pattern image Pn of each color is formed on the intermediate transfer belt 41 in the image forming process step, and the sensitivity correction value calculation process is performed from the non-formation region light amount and the formation region light amount of the density adjustment pattern image Pn. A density adjustment control processing step for calculating a sensitivity correction value at the time of density adjustment pattern detection in steps, and a density adjustment at the image forming processing step by comparing the sensitivity correction value at the time of density adjustment pattern detection with the high density sensitivity correction value. A sensitivity correction value setting process step for setting a density correction sensitivity correction value for performing the density adjustment, and the density adjustment detected in the density detection process step. A developer amount calculation processing step for calculating a toner amount of the density adjustment pattern image Pn of each color based on the light amount of the formation area of the pattern image Pn and the sensitivity correction value for density adjustment, and the process based on the toner amount. An image density adjustment method including a density adjustment process step of adjusting the toner image density in the image forming process step is executed.

  Accordingly, in the density adjustment process, even if the density adjustment pattern image Pn formed on the intermediate transfer belt 41 has a defect or the like, the past sensitivity correction value stored in the sensitivity correction value storage unit 74 is used to obtain high accuracy. The developer amount of each color developer image can be calculated. As a result, the accuracy of density adjustment can be improved.

  Further, in the color image forming apparatus 1 of the present embodiment, the control processor, the intermediate transfer belt 41 transported in a predetermined transport direction, an image forming process for a plurality of colors for forming a toner image, and the intermediate transfer belt 41 is disposed at a predetermined position in the main scanning direction orthogonal to the conveying direction of 41, and the reflected light quantity of the detection light applied to the non-formation area and the formation area of the toner image in the image forming process on the intermediate transfer belt 41 A non-formation area light amount and a formation area light quantity, a sensitivity correction value calculation process for calculating a sensitivity correction value in the density detection process from the non-formation area light quantity and the formation area light quantity, The sensitivity is determined from the non-formation area light quantity and the formation area light quantity detected by the density detection process when a high density image is formed on the intermediate transfer belt 41 by forming an image whose density is higher than a predetermined level by image processing. Sensitivity correction value storage processing for storing the sensitivity correction value calculated in the correction value calculation processing as a high density sensitivity correction value in the sensitivity correction value storage unit 74, and the density adjustment pattern image Pn for each color on the intermediate transfer belt 41. A density adjustment control process that is formed by an image forming process and calculates a sensitivity correction value at the time of density adjustment pattern detection by the sensitivity correction value calculation process from the non-formation area light quantity and the formation area light quantity of the density adjustment pattern image Pn; A sensitivity correction value setting process for setting a density correction sensitivity correction value for performing density adjustment in the image forming process by comparing the density adjustment pattern detection sensitivity correction value with the high density sensitivity correction value; The toner of the density adjustment pattern image Pn of each color based on the light amount of the formation area of the density adjustment pattern image Pn detected by the density detection process and the sensitivity adjustment value for density adjustment. A developer amount calculation processing for calculating the amount, are equipped with a program to be executed and the density adjustment process, the adjusting the toner image density at the image formation on the basis of the amount of toner.

  Accordingly, in the density adjustment process, even if the density adjustment pattern image Pn formed on the intermediate transfer belt 41 has a defect or the like, the past sensitivity correction value stored in the sensitivity correction value storage unit 74 is used to obtain high accuracy. The developer amount of each color developer image can be calculated. As a result, the accuracy of density adjustment can be improved.

  Further, in the color image forming apparatus 1 of the present embodiment, the sensitivity correction value storage unit 74 also stores the density adjustment pattern detection sensitivity correction value as the high density sensitivity correction value.

  Therefore, the density adjustment pattern detection sensitivity correction value when the density adjustment pattern image Pn is formed in the past is also used as the high density sensitivity correction value to obtain the density adjustment pattern image Pn formed on the intermediate transfer belt 41. Even if there is a defect or the like, the developer amount of the developer image of each color can be calculated with higher accuracy. As a result, the accuracy of density adjustment can be further improved.

  Further, in the color image forming apparatus 1 of the present embodiment, the sensitivity correction value setting unit 76 has the latest high density sensitivity correction value and the sensitivity correction value at the time of density adjustment pattern detection stored in the sensitivity correction value storage unit 74. And the smaller sensitivity correction value is set as the density adjustment sensitivity correction value.

  Therefore, it is possible to perform density adjustment using the sensitivity correction value based on the image with less deterioration as the density correction sensitivity correction value, and it is possible to further improve the density adjustment accuracy.

  Further, in the color image forming apparatus 1 of the present embodiment, the sensitivity correction value calculation unit 73 uses the light amount in the image forming region in the portion where the image defect is not generated as the light amount in the formation region. Is calculated.

  Therefore, it is possible to perform density adjustment using a sensitivity correction value based on an image having no image defect as the density correction sensitivity correction value, and the accuracy of density adjustment can be further improved.

  Further, in the color image forming apparatus 1 according to the present embodiment, the density adjustment control unit 75 has exceeded the upper limit of the sensitivity correction value where the high density sensitivity correction value of the sensitivity correction value storage unit 74 is a predetermined threshold value. Then, the formation of the density adjustment pattern image Pn by the image forming unit 71 and the calculation of the density correction pattern detection sensitivity correction value by the sensitivity correction value calculation unit 73 are stopped.

  Therefore, it is possible to improve the accuracy of the density correction pattern detection sensitivity correction value while suppressing consumption of toner for forming the useless density adjustment pattern image Pn.

  In addition, the color image forming apparatus 1 of the present embodiment further includes a notification unit (notification unit) 79 that notifies and outputs information, and the density adjustment control unit 75 forms the density adjustment pattern image Pn and the density. When the calculation of the adjustment pattern detection sensitivity correction value is stopped a predetermined number of times, the notification unit 79 is configured to output a predetermined warning.

  Therefore, it is possible to notify the user of an abnormality such as deterioration of the image forming unit 71 and to promptly respond to it, and to optimize the operation of the color image forming apparatus 1.

  Further, in the color image forming apparatus 1 according to the present embodiment, the density adjustment control unit 75 is configured to generate the density only when a factor that causes the density of the toner image by the image forming unit 71 to fluctuate beyond a predetermined value occurs. The adjustment pattern image Pn is formed and the sensitivity correction value is calculated when the density adjustment pattern is detected.

  Accordingly, it is possible to calculate the sensitivity correction value at the time of density adjustment processing and density adjustment pattern detection only when necessary, to save unnecessary toner consumption and processing time, and to improve the usability of the color image forming apparatus 1. Can do.

  Further, in the color image forming apparatus 1 of the present embodiment, the sensitivity correction value storage unit 74 uses the image position adjustment timing for each color as the timing for the high density image formation other than the formation of the density adjustment pattern image Pn. A developer discharge timing that is discharged after the image forming unit 71 forms a high-density image on the intermediate transfer belt 41 using long-term staying toner is used, and the high-density sensitivity correction value at the timing is stored.

  Therefore, the high density sensitivity correction value is obtained and stored in the sensitivity correction value storage unit 74 at the image alignment processing timing and toner discharge timing. As a result, even when there is a pixel defect or the like in the density adjustment pattern image Pn during the density adjustment process, the density adjustment can be performed using these high density sensitivity correction values in the sensitivity correction value storage unit 74. Processing can be performed appropriately.

  The invention made by the present inventor has been specifically described based on the preferred embodiments. However, the present invention is not limited to that described in the above embodiments, and various modifications can be made without departing from the scope of the invention. It goes without saying that it is possible.

DESCRIPTION OF SYMBOLS 1 Color image forming apparatus 2 Main body housing | casing 3 Paper discharge tray 10 Paper feed part 11 Paper feed tray 12 Paper feed roller 20 Transport part 21 Registration roller 22 Secondary transfer roller 23 Fixing part 23a Fixing roller 23b Pressure roller 24 Paper discharge roller 30 Plotter unit 31 Intermediate transfer unit 32C, 32M, 32Y, 32K Process cartridge 33 Exposure unit 34 Density sensor 35 Belt cleaning unit 36 Waste toner box 41 Intermediate transfer belt 42 Secondary transfer drive roller 43 Tension roller 44Y, 44M, 44C, 44K Transfer roller 45Y, 45M, 45C, 45K Photoconductor 51 CPU
52 ROM
53 RAM
54 External I / F
55 NVRAM
56 I / O
56 Image processing IC
58 Operation I / F
59 Operation Panel 71 Image Forming Unit 72 Density Detection Unit 73 Sensitivity Calculation Unit 74 High Density Sensitivity Storage Unit 75 Sensitivity Correction Value Calculation Unit 76 Developer Amount Calculation Unit 77 Density Adjustment Unit 78 Notification Unit P Paper Pn Density Adjustment Pattern Image Pi Position Pattern image for alignment Pt Toner discharge pattern image

JP 2004-354624 A

Claims (10)

A plurality of color image forming means for forming a developer image on an intermediate transfer member or a recording medium conveyed in a predetermined conveyance direction;
Non-formation of the developer image by the image forming means on the intermediate transfer member or the recording medium, which is disposed at a predetermined position in the main scanning direction orthogonal to the transport direction of the intermediate transfer member or the recording medium. Density detecting means for detecting the reflected light amount or transmitted light amount of the detection light applied to the region and the forming region as a non-forming region light amount and a forming region light amount;
Sensitivity correction value calculation means for calculating a sensitivity correction value of the density detection means from the non-formation area light quantity and the formation area light quantity;
From the non-formation region light amount and the formation region light amount detected by the concentration detection unit when forming a high density image in which the image forming unit forms an image having a density higher than a predetermined level on the intermediate transfer member or the recording medium. Sensitivity correction value storage means for storing the sensitivity correction value calculated by the sensitivity correction value calculation means as a high density sensitivity correction value;
The density adjustment pattern image of each color is formed on the intermediate transfer member or the recording medium by the image forming means, and the sensitivity correction value is calculated from the non-formation region light amount and the formation region light amount of the density adjustment pattern image. A density adjustment control means for causing the means to calculate a sensitivity correction value at the time of density adjustment pattern detection;
A sensitivity correction value setting means for setting a sensitivity correction value for density adjustment for performing density adjustment of the image forming means by comparing the sensitivity correction value at the time of density adjustment pattern detection with the high density sensitivity correction value;
A developer amount calculating means for calculating the developer amount of the density adjustment pattern image of each color based on the light amount of the forming area of the density adjustment pattern image detected by the density detection means and the sensitivity adjustment value for density adjustment; ,
Density adjusting means for adjusting the developer image density by the image forming means based on the developer amount;
An image forming apparatus comprising: The sensitivity correction value storage means includes
The image forming apparatus according to claim 1, wherein the density correction pattern detection sensitivity correction value is also stored as the high density sensitivity correction value. The sensitivity correction value setting means includes
The latest high density sensitivity correction value stored in the sensitivity correction value storage means is compared with the density correction pattern detection sensitivity correction value, and the smaller sensitivity correction value is set as the density adjustment sensitivity correction value. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The sensitivity correction value calculation means includes
4. The image according to claim 1, wherein the sensitivity correction value is calculated using a light amount in an image forming region of a portion where the image defect is not generated as the forming region light amount. 5. Forming equipment. The density adjustment control means includes:
When the high density sensitivity correction value of the sensitivity correction value storage means exceeds a predetermined threshold, the density adjustment pattern image is formed by the imaging means and the density adjustment pattern is detected by the sensitivity correction value calculation means. 5. The image forming apparatus according to claim 1, wherein the calculation of the sensitivity correction value is stopped. The image forming apparatus includes:
An informing means for informing and outputting information,
In addition,
The density adjustment control means includes:
6. The image formation according to claim 5, wherein when the formation of the density adjustment pattern image and the calculation of the density correction pattern detection sensitivity correction value are stopped a predetermined number of times, the notification means outputs a predetermined warning. apparatus. The density adjustment control means includes:
Only when a factor that causes the density of the developer image to fluctuate beyond a predetermined value is generated by the image forming means, the density adjustment pattern image is formed and the sensitivity correction value at the time of density adjustment pattern detection is calculated. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The sensitivity correction value storage means includes
As the timing for forming the high density image other than the formation of the density adjustment pattern image, the image forming means uses the image position adjustment timing of each color and a long-term staying developer to the intermediate transfer member or the recording medium. 8. The image forming apparatus according to claim 1, wherein a developer discharge timing that is discharged after forming a density image is adopted, and the high density sensitivity correction value at the timing is stored. . An image forming process step for a plurality of colors for forming a developer image on an intermediate transfer member or a recording medium conveyed in a predetermined conveyance direction;
The developer image is disposed at a predetermined position in the main scanning direction orthogonal to the transport direction of the intermediate transfer member or the recording medium, and the developer image in the image forming process step on the intermediate transfer member or the recording medium. A density detection processing step for detecting the reflected light amount or transmitted light amount of the detection light applied to the non-forming region and the forming region as a non-forming region light amount and a forming region light amount;
A sensitivity correction value calculation processing step for calculating a sensitivity correction value in the density detection processing step from the non-formation region light amount and the formation region light amount;
The non-formation region light amount and the formation region detected in the density detection processing step during high density image formation in which an image having a darkness of a predetermined level or more in the image forming processing step is formed on the intermediate transfer member or the recording medium. A sensitivity correction value storage processing step for storing the sensitivity correction value calculated in the sensitivity correction value calculation processing step from the light amount in the sensitivity correction value storage means as a high density sensitivity correction value;
A density adjustment pattern image of each color is formed on the intermediate transfer member or the recording medium in the image forming process step, and the sensitivity correction value is calculated from the non-formation region light amount and the formation region light amount of the density adjustment pattern image. A density adjustment control processing step for calculating a sensitivity correction value at the time of density adjustment pattern detection in the calculation processing step;
A sensitivity correction value setting process step for setting a density correction sensitivity correction value for performing density adjustment in the image forming process step by comparing the density correction pattern detection sensitivity correction value with the high density sensitivity correction value; ,
Developer amount calculation that calculates the developer amount of the density adjustment pattern image of each color based on the light amount of the formation area of the density adjustment pattern image detected in the density detection processing step and the sensitivity correction value for density adjustment Processing steps;
A density adjustment processing step for adjusting the developer image density in the image forming processing step based on the developer amount;
An image density adjustment method characterized by comprising: To the control processor,
An image forming process for a plurality of colors for forming a developer image on an intermediate transfer member or a recording medium conveyed in a predetermined conveyance direction;
The developer image is disposed at a predetermined position in the main scanning direction perpendicular to the transport direction of the intermediate transfer member or the recording medium, and the developer image is not removed in the image forming process on the intermediate transfer member or the recording medium. A density detection process for detecting the reflected light amount or transmitted light amount of the detection light applied to the formation region and the formation region as a non-formation region light amount and a formation region light amount;
A sensitivity correction value calculation process for calculating a sensitivity correction value in the density detection process from the non-formation region light amount and the formation region light amount;
From the non-formation area light quantity and the formation area light quantity detected by the density detection process at the time of high density image formation in which an image whose density is higher than a predetermined level by the image forming process is formed on the intermediate transfer member or the recording medium. A sensitivity correction value storage process for storing the sensitivity correction value calculated in the sensitivity correction value calculation process in the sensitivity correction value storage unit as a high density sensitivity correction value;
The density adjustment pattern image of each color is formed on the intermediate transfer member or the recording medium by the image forming process, and the sensitivity correction value is calculated from the non-formation region light amount and the formation region light amount of the density adjustment pattern image. A density adjustment control process for calculating a sensitivity correction value at the time of density adjustment pattern detection in the process;
A sensitivity correction value setting process for setting a density correction sensitivity correction value for performing density adjustment in the image forming process by comparing the density correction pattern detection sensitivity correction value with the high density sensitivity correction value;
A developer amount calculation process for calculating a developer amount of the density adjustment pattern image of each color based on the light amount of the formation area of the density adjustment pattern image detected in the density detection process and the sensitivity correction value for density adjustment. When,
A density adjustment process for adjusting the developer image density in the image forming process based on the developer amount;
A program characterized by having executed.

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