JP2007086641A - Color image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color image forming apparatus designed so as to minimize times needed for density control and color shift correction control and consumption of consumable item even when a process cartridge is being replaced, and so as to ensure excellent usability. <P>SOLUTION: The color image forming apparatus includes a plurality of image forming means, a plurality of transfer means, a maximum density pattern forming means, a means for detecting light reflected from the pattern, a light emitting means, a density control means, a color shift correcting means, a process cartridge replacement detecting means, a density detection pattern forming means capable of altering a formation pattern according to the results of the replacement detecting means, and a color shift detection pattern forming means. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrophotographic color image forming apparatus, such as a color printer and a color copying machine.

  In an electrophotographic color image forming apparatus, images of different colors are sequentially transferred onto an intermediate transfer belt and collectively transferred onto a print paper, or images of different colors are sequentially applied onto a print paper held on a conveyance belt. Various methods for transferring the image have been proposed.

  In general, in an electrophotographic image forming apparatus, the characteristics vary depending on the use environment, the developing device, the number of printed sheets of the photoconductor, the sensitivity variation during the production of the photoconductor, the variation in the frictional charging characteristics during the production of the developer (toner) Therefore, the density characteristics of the printed image vary. Efforts to stabilize these changes and fluctuation characteristics are made every day, but it is not enough. In particular, in a color image forming apparatus, color reproduction is performed by superposing four toners of yellow, magenta, cyan, and black. Therefore, if the density of the developer of four colors, that is, the toner image is not accurately adjusted, it is good. Can not get a good color balance. Therefore, many color image forming apparatuses are equipped with an image density adjusting mechanism that automatically adjusts image forming conditions such as a charging potential, an exposure amount, and a developing bias. First, a toner image is formed on an image carrier or transfer material carrier under predetermined image forming conditions, and the density of the toner image is detected by an optical sensor composed of a light emitting element and a light receiving element. Then, means for matching the maximum density and halftone gradation characteristics of each color by feeding back to the process formation conditions such as high pressure conditions and laser power in accordance with the detected toner image density is used. The toner image formed on the image carrier or the transfer material carrier is collected in a waste toner container by the cleaning means.

  Similarly, in color misregistration correction control, there is a means for correcting by forming a resist detection patch on an intermediate transfer member or a transfer belt, reading the patch with an optical sensor, and feeding it back to an image writing position or the like. It is used.

  Performing image density control and color misregistration correction control as described above at the time of process cartridge replacement, every fixed number of prints, every fixed time, or when the environment changes, so that a stable color image (For example, refer patent document 1).

Image density control, color misregistration correction control, and the like are collectively referred to as “engine calibration” hereinafter.
JP 2003-167394 A

  However, in order to execute engine calibration such as image density control and color misregistration correction control, parts are consumed, such as toner consumption and photoconductor wear, although they are slight.

  Further, when executing the engine calibration, the printer, that is, the print engine needs to temporarily hold or stop the print command received from the user and shift to a special mode for realizing them. For this reason, from the viewpoint of usability, it is desired to reduce the execution frequency of the engine calibration and the execution time within a range where the print quality is not affected as much as possible.

  The present invention has been made paying attention to the above points. Even when a process cartridge is replaced, color image formation with excellent usability can be achieved by suppressing execution time and consumable consumption at the time of density control and color misregistration correction control as much as possible. An object is to provide an apparatus.

  In order to solve the above-described problems, a first invention according to the present application provides a plurality of latent image forming media and developing units that are detachable from the optical unit, or a single latent image forming medium and a plurality of removable developing units. And a plurality of transfer units that transfer the formed image onto an endless belt that passes through the image forming unit or onto a recording material that is conveyed while being held on the endless belt. Density detection pattern forming means for forming a predetermined density detection pattern on the latent image forming medium or the endless belt, light emitting means for irradiating the density detection pattern with light, the latent image forming medium or the endless Pattern regular reflection light detecting means for detecting regular reflection light of the density detection pattern formed on the belt, and the density formed on the latent image forming medium or the endless belt. Pattern diffuse reflection light detection means for detecting the diffuse reflection light of the detection pattern, and density control for controlling the image forming conditions based on the detection result of the density detection pattern of the pattern regular reflection light detection means and the pattern diffuse reflection light detection means In the color image forming apparatus having the means, when one or a plurality of the latent image forming media are replaced, a density detection pattern of a part of the colors including the replaced latent image forming media is generated instead of all the colors. It is characterized by performing density control.

According to a second aspect of the present application, there is provided an image forming unit including any one of a plurality of latent image forming media and developing units that can be attached to and detached from the optical unit, or a single latent image forming medium and a plurality of removable developing units. Means, a plurality of transfer means for transferring the formed image onto an endless belt passing through the image forming unit or onto a recording material conveyed while being held on the endless belt, and the latent image forming medium Or a pattern regular reflection light detection means for detecting regular reflection light of the color misregistration detection pattern formed on the endless belt and the latent image forming medium or the endless belt; Pattern diffuse reflection light detecting means for detecting diffuse reflection light of the color misregistration detection pattern formed on the latent image forming medium or the endless belt, and the pattern regular reflection light detection means In the color image forming apparatus having a color shift correcting means for controlling the amount of color shift or from the detection result of the pattern diffuse reflection light detecting means,
When one or more of the latent image forming media are replaced, color misregistration correction control is performed by generating a color misregistration detection pattern of only some colors including the replaced latent image forming media instead of all colors. It is characterized by.

  A third invention according to the present application is the color image forming apparatus according to the first invention or the second invention, wherein the density detection pattern and the color misregistration at the time of replacing a single color or a plurality of colors of the latent image forming medium. By arranging the pattern within one end of the endless belt at the same time, density control and color misregistration correction control are performed simultaneously.

  As mentioned above, although the detail was demonstrated about this invention, if this was further summarized, the said subject could be solved with the following structure.

(1) A plurality of removable image forming units each having a removable latent image forming medium and a developing unit;
A plurality of transfer means for detecting replacement of the image forming means, and a plurality of images formed on the endless belt passing through the image forming section or on a recording material conveyed while being held on the endless belt. Transfer means, density detection pattern forming means for forming a predetermined density detection pattern on the latent image forming medium or the endless belt, light emitting means for irradiating the density detection pattern with light, and the latent image forming medium Alternatively, pattern regular reflection light detecting means for detecting regular reflection light of the density detection pattern formed on the endless belt, and diffusion of the density detection pattern formed on the latent image forming medium or the endless belt. Pattern diffuse reflected light detecting means for detecting reflected light, density detection patterns of the pattern regular reflected light detecting means and the pattern diffuse reflected light detecting means In the color image forming apparatus having the density control means for controlling image forming conditions based on out results,
When it is detected by the replacement detection means that one or a plurality of the image forming means has been replaced, a density detection pattern for a part of the colors including the replaced image forming means is generated instead of all colors. A color image forming apparatus characterized by performing control.

  As described above, according to the first aspect of the present application, by controlling the density of only the replaced process cartridge, the consumption of toner other than the target process cartridge and the consumption of the developing device and the photoconductor are suppressed. Can do.

  According to the second aspect of the present application, by performing color misregistration correction control for only the replaced process cartridge, it is possible to suppress consumption of toner other than the target process cartridge and consumption of the developing device and the photosensitive member.

  According to the third aspect of the present application, an endless belt that performs density control and color misregistration correction control only for the replaced process cartridge and forms a toner image with the density control pattern and color misregistration correction control pattern of the corresponding color. By arranging within one round, density control and color misregistration correction control are performed simultaneously. By doing in this way, execution time can be significantly shortened compared with the case where density control and color misregistration correction control are performed separately.

  Hereinafter, the present invention will be described in detail based on the illustrated embodiments.

[First embodiment]
FIG. 2 is a cross-sectional view showing a schematic configuration of an electrophotographic method, that is, a color image forming apparatus using an electrophotographic process, such as a copying machine or a laser beam printer, which is an embodiment of the image forming apparatus of the present invention. FIG.

  In this embodiment, the color image forming apparatus has four independent color stations that execute an electrophotographic process, that is, image forming units PY, PM, PC, and PK arranged in a vertical row. In this embodiment, each image forming unit is formed into a cartridge and is detachable from the main body of the image forming apparatus.

  Each of the image forming units PY, PM, PC, and PK includes an image carrier 11, 12, 13, 14, chargers 21, 22, 23, 24, image exposure means 31, 32, 33, 34, a developer 41, 42, 43, 44 and cleaning devices 61, 62, 63, 64. A transfer belt 8 serving as a transfer material carrier is disposed along the image forming units PY, PM, PC, and PK. The transfer belt 8 adsorbs, for example, a transfer sheet 100 as a transfer material to the transfer belt 8 and conveys it to the image forming units PY, PM, PC, PK, and performs transfer. As a result, the full-color image is collectively transferred onto the transfer paper.

  In this embodiment, the image carriers 11, 12, 13, and 14 are rotary drum type electrophotographic photosensitive members (hereinafter referred to as “photosensitive drums”) that are used repeatedly, and are predetermined in the counterclockwise direction indicated by an arrow. It is rotationally driven at a peripheral speed (process speed) of. The photosensitive drums 11, 12, 13, and 14 are uniformly charged to a predetermined polarity and potential by a primary charging roller as the chargers 21, 22, 23, and 24 during the rotation process, and then the image exposure unit 31. , 32, 33, and 34, electrostatic latent images corresponding to the first to fourth color component images (for example, yellow, magenta, cyan, and black component images) of the target color image are formed. The The chargers 21, 22, 23, and 24 are DC contacts that perform charging by bringing a roller having an actual resistance of 1 × 10 6 Ω, to which a DC voltage of −1.2 kv is applied, into contact with the photosensitive drum at a total pressure of 9.8 N. This is a charging method, and the surface of the photosensitive drum is charged to -600V.

  The image exposure means 31, 32, 33, and 34 used in this embodiment are polygon scanners using laser diodes, and a laser beam modulated by an image signal is connected onto the photosensitive drums 11, 12, 13, and 14. To form an electrostatic latent image. Laser exposure is written from the position signal in the polygon scanner called BD for each scanning line in the main scanning direction (direction perpendicular to the progress of the transfer paper), and in the sub-scanning direction (transfer paper advance direction). By performing a predetermined time delay from the TOP signal starting from the switch in the road, each image forming unit PY, PM, PC, PK always performs exposure at the same position on the paper. Next, the electrostatic latent image is developed by the developing devices 41, 42, 43, and 44 of the respective image forming units PY, PM, PC, and PK. The developing devices 41, 42, 43, and 44 (yellow, magenta, cyan, and black) are rotated in the direction of the arrow in the drawing by a rotation driving device (not shown), and each developing device 41, 42, 43, and 44 is in the developing process. The photosensitive drums 11, 12, 13, and 14 are arranged to face each other. The toner (yellow, magenta, cyan, black) accommodated in each developing device 41, 42, 43, 44 is a so-called non-mag toner that does not contain a magnetic material, and is a contact one-component contact developing system. It is developed by.

  In this embodiment, each of the developing devices 41, 42, 43, and 44 uses the non-magnetic one-component contact developing method as described above, and has elastic rollers 41a, 42a, 43a, and 44a as developer carriers. . The elastic rollers 41a, 42a, 43a, and 44a rotate in the forward direction with respect to the photosensitive drums 11, 12, 13, and 14 at a peripheral speed that is 170% of the peripheral speed of the photosensitive drum, and can be changed by a controller signal. A voltage is applied to develop the latent image on the photosensitive drum. The transfer belt 8 is driven to rotate at the same peripheral speed as the photosensitive drums 11, 12, 13, and 14 in the direction indicated by the arrow. The transfer belt 8 is a 100 μm thick PVDF single-layer resin belt whose resistance is adjusted to 1 × 10 11 Ωcm, and the meandering and shifting of the belt are regulated by ribs (not shown) bonded to both sides of the back surface. As the transfer members 51, 52, 53, and 54, transfer rollers adjusted to a volume resistivity of 1 × 10 7 Ωcm are used, and contact the nip portions of the photosensitive drums 11, 12, 13, and 14 from the back surface of the transfer belt 8. ing.

  The transfer paper 100 is fed from a paper feed cassette (not shown in FIG. 2), passes through the registration rollers, and then contacts the transfer belt 8 at a position where the suction roller 7 is disposed via a transfer entrance guide. In this embodiment, the printer achieves the desired purpose by opening and closing only the front door for minimizing the ground contact area, replacing the image forming units PY, PM, PC, and PK formed in a cartridge, and jam processing. The image forming units PY, PM, PC, and PK are arranged vertically so that the main body is divided between the transfer belt 8 and the image forming units PY, PM, PC, and PK. From the above configuration, since the transfer paper 100 is conveyed upward against the gravity, it is necessary that the transfer paper 100 and the transfer belt 8 are sufficiently adsorbed. As described above, the suction roller 7 to which a bias is applied is provided near the contact point between the transfer paper 100 and the transfer belt 8, and a voltage of +1 KV is applied during image formation to apply a charge to the transfer paper. The suction conveyance force is generated.

  The transfer belt 8 is cleaned by providing a negative polarity bias to the transfer rollers 51, 52, 53, and 54 in a specially provided cleaning sequence without electrostatic cleaning. This is realized by collecting them on the photosensitive drums 11, 12, 13, and 14. The waste toner collected on the photosensitive drums 11, 12, 13, and 14 is collected by the cleaners 61, 62, 63, and 64 of the photosensitive drums 11, 12, 13, and 14. The suction roller 7 is formed by molding a solid rubber on a core metal having a diameter of 6 mm, and is configured such that a high pressure bias for suction can be applied to the core metal. Specifically, the suction roller 7 is a solid rubber roller having a diameter of 12 mm in which carbon black is dispersed in EPDM rubber for resistance adjustment. A resistance value is wound around the roller outer periphery with a metal foil having a width of 1 cm. The resistance value when a voltage of 500 V is applied between is adjusted to 1 × 10 5 Ω. The transfer paper 51 fed from a paper feed cassette (not shown) and obtained a suction force between the transfer inlet guide (not shown) and the suction roller 7 and the transfer belt 8 is transferred to the transfer roller 51. Enter the first color transfer station. In the transfer unit, the toner image is transferred from the photosensitive drum 11 of the first color by a transfer roller 51 as a transfer member provided on the back surface of the transfer belt. A DC bias of +1.5 kv is applied to the transfer rollers 51, 52, 53, and 54 together with each image forming unit from a high voltage power source. Thereafter, each time it passes through each image forming unit, toner images of different colors are transferred from the photosensitive drums 12, 13, 14 to the transfer paper 100 carried on the transfer belt 8, thereby creating a full color image. After the transfer of all colors is completed, the transfer paper 100 separated by the curvature from the rear end of the transfer belt 8 is fixed by a heat roller fixing device 9 and discharged outside the apparatus to obtain a final print.

  Next, image density control will be described.

  FIG. 2 shows the overall configuration of a color image forming apparatus for explaining the first embodiment of the present invention.

  In these color image forming apparatuses, density control is performed in order to accurately match the density of each color and obtain an image having a desired color. Specifically, the density control includes Dmax control for optimizing image forming conditions so that desired development characteristics of each color can be obtained, and a look-up table so that input image data and halftone image density have good linearity. Dhalf control is performed to change.

  FIG. 5 is a schematic diagram illustrating an example of a density detection pattern when executing Dmax control for all colors. In FIG. 5, 8 is an endless conveyance belt that also serves as a transfer belt, and sequentially conveys print paper to each color image forming unit, and 1 detects a density detection pattern formed on the conveyance belt 8. , An optical sensor provided in the center of the conveying belt 8 in the main scanning direction.

  Reference numerals 4101Y, 4102Y, 4103Y, and 4104Y are patch images of yellow toners having the same image pattern and different densities by changing the developing bias. Similarly, 4101M, 4102M, 4103M, 4104M, 4101C, 4102C, 4103C, 4104C, 4101K, 4102K, 4103K, and 4104K have the same image pattern and magenta, cyan, and black with different density by changing the development bias. This is a patch image. The arrow indicates the moving direction of the conveyor belt 8.

  FIG. 6 is a schematic diagram illustrating an example of a density detection pattern when executing Dhalf control for all colors. In FIG. 6, reference numeral 103 denotes an endless transfer belt that also serves as a conveyance belt for sequentially conveying print paper to each color image forming unit, and 1 detects a density detection pattern formed on the transfer belt 8. , An optical sensor provided at the center of the transfer belt 8 in the main scanning direction.

  Reference numerals 4201Y, 4202Y, 4203Y, and 4204Y are patch images of yellow toner that have the same developing bias and have different densities by changing the input image signal. 4201M, 4202M, 4203M, 4204M, 4201C, 4202C, 4203C, 4204C, 4201K, 4202K, 4203K, and 4204K are similarly developed biases are the same, and magenta, cyan, This is a black patch image. An arrow indicates the moving direction of the transfer belt 8.

  First, during Dmax control, an image is formed while switching the developing bias with the same image data (density detection pattern) at a predetermined density. Then, the specular reflection light detection output and the diffuse reflection light detection output are detected by the optical sensor 1, and a development bias value appropriate for desired development characteristics is obtained.

  Next, Dhalf control cancels the γ characteristic in order to prevent a natural image from being formed due to a shift in output density with respect to the input image signal due to the non-linear input characteristic (γ characteristic) peculiar to electrophotography. Image processing that keeps the input characteristics linear is performed. At the time of Dhalf control, the developing bias is fixed to a value optimized after Dmax control, and an image is formed with a plurality of image data. Then, the specular reflection light detection output and the diffuse reflection light detection output are detected by the optical sensor 1, and the image data input to the image forming apparatus that obtains a desired halftone density is converted by the controller of the image forming apparatus. The Dhalf control is performed after the image forming conditions are determined by the Dmax control.

  FIG. 7 is a flowchart for explaining a control method of density control. If there is a possibility that the process cartridge has been replaced, such as when the power is turned on or the CRG door (not shown) is opened or closed (step S10000), has the engine read the nonvolatile memory information on the process cartridge and replaced it? A check is made (step S10001). If there is an exchanged process cartridge, execution of density control is started (step S10002).

  When the execution of density control is started, initialization operations such as adjustment of the optical sensor 1 and reading of the optical sensor 1 on the belt surface in a state where there is no toner image are performed (step S10003).

  Next, a density detection pattern of the exchanged color among Y, M, C, and K is formed on the transport belt (step S10004). Since the image forming method is the same as that in printing described above, the description thereof is omitted.

  FIG. 10 is a schematic diagram showing an example of a density detection pattern when executing monochromatic DHALF control. In this embodiment, a pattern example when Cyan is exchanged is shown. Basically, the pattern is the same as that shown in FIG. 6, but a pattern other than the exchanged Cyan is not formed.

  After the density detection pattern is formed, the density detection pattern is detected by the optical sensor 1 shown in FIG.

  Based on the detected data, density control calculation is performed. In DMAX, an appropriate development bias value is calculated from a density pattern detection result for each toner by a processing unit (for example, CPU) (not shown). In DHALF, the non-linear input / output characteristics (γ characteristics) unique to electrophotography prevent the output density from deviating from the input image signal and prevent natural images from being formed. Data for image processing that keeps linear and obtains a desired halftone density is calculated (steps S10005 and S10006).

  After reading the density detection pattern, the toner image on the transfer belt 8 is cleaned by the above-described cleaning sequence to prepare for the next image formation (S10007).

  By adopting the configuration as described above, in this embodiment, it is possible to obtain a good image quality at all times while minimizing the toner consumption at the time of calibration forcing the user. A photographic device can be provided.

[Second Embodiment]
Only differences from the first embodiment will be described.

  In the first embodiment, density control is executed only for the color of the replaced process cartridge. In this embodiment, a color shift detection pattern is created only for the color of the process cartridge and the reference color that are replaced in the color shift correction control. Color misregistration correction control is performed.

  Uneven movement of multiple photosensitive drums and conveyor belts due to machine accuracy for each color in multiple image forming units, and relationship between the movement amount of the photosensitive drum outer peripheral surface and the conveyance belt at the transfer position of each image forming unit And the like occur in different colors for each color and do not match when the images are superimposed, resulting in a color shift (positional shift). In particular, in an apparatus having a plurality of image forming units having a laser scanner and a photosensitive drum, there is an error in the distance between the laser scanner and the photosensitive drum in each image forming unit. A difference occurs in the scanning width of the laser on the drum, and color misregistration occurs.

  An example of color misregistration is shown in FIG. 201 indicates an original image position, and 202 indicates an image position when color misregistration occurs. Also, (a), (b), and (c) are cases where there is a color shift in the scanning direction, but for the sake of explanation, two lines are drawn apart in the transport direction. (A) shows an inclination shift of the scanning line, which occurs when there is an inclination between the optical unit and the photosensitive drum. For example, the position is corrected in the direction of the arrow by adjusting the position of the optical unit or the photosensitive drum or the position of the lens. (B) shows color misregistration due to variations in scanning line width, and is caused by a difference in distance between the optical unit and the photosensitive drum. It tends to occur when the optical unit is a laser scanner. For example, the image frequency is finely adjusted (if the scanning width is long, the frequency is increased) and the length of the scanning line is changed to correct in the arrow direction. (C) shows the writing position error in the scanning direction. For example, if the optical unit is a laser scanner, it is corrected in the direction of the arrow by adjusting the writing start timing from the beam detection position. (D) shows the writing position error in the paper transport direction. For example, the correction is made in the direction of the arrow by adjusting the writing start timing of each color from the detection of the leading edge of the paper.

  In order to correct the color misregistration, a color misregistration detection pattern is formed for each color on the transfer belt 8 and detected by an optical sensor provided on the conveyance belt, and the color misregistration is detected and corrected. Perform correction control.

  FIG. 4 is a schematic diagram illustrating an example of a color misregistration detection pattern. Reference numeral 103 denotes an endless conveyance belt that also serves as a transfer belt, and sequentially conveys print paper to each color image forming unit. Reference numeral 107 denotes a transfer belt that detects a color misregistration detection pattern formed on the transfer belt 8. 8 is an optical sensor provided in the main scanning direction. Here, reference numerals 309 to 3019 denote patterns for detecting the amount of color misregistration in the paper conveyance direction and the scanning direction. The color misregistration detection pattern of 309 and 3011 is pattern 1, and the color misregistration detection pattern of 3013 and 3015 is pattern 2. , 3017 and 3019 are pattern 3 for detecting color misregistration. A, c, e, and g represent K as a reference color, and b, d, and f represent Y, M, and C as detected colors, respectively. An arrow indicates the moving direction of the transfer belt 8.

  According to the detection timing of each pattern, the amount of color misregistration for each color is calculated, corrected to a desired writing start timing, and color misregistration is reduced.

  FIG. 8 is a flowchart for explaining a control method of color misregistration correction control. If there is a possibility that the process cartridge has been replaced, such as when the power is turned on or the CRG door (not shown) is opened or closed, the engine reads the information in the nonvolatile memory on the process cartridge and checks whether it has been replaced (step S10010, S10011). If there is an exchanged process cartridge, execution of color misregistration correction control is started (step S10012). Since the control up to this point is the same as that in the density control of the first embodiment, the information in the density control may be used as it is when the control is continued from the density control.

  When the execution of the color misregistration correction control is started, initialization operations such as adjustment of the optical sensor 1 and reading of the optical sensor 1 on the belt surface in a state where there is no toner image are performed (step S10013).

  Next, a color misregistration correction pattern of the exchanged color of Y, M, C, and K and a predetermined reference color is formed on the transport belt (step S10014). If the color exchanged with the reference color is the same, a color shift pattern between the exchanged color and a predetermined sub-reference color is generated (step S10015).

FIG. 11 is a schematic diagram illustrating an example of a color misregistration detection pattern when executing a single color misregistration correction control. In this embodiment, a pattern example when Cyan is exchanged is shown. Basically, the pattern is the same as that shown in FIG. 6 except for the exchanged Cyan and the reference color Black.
After the color misregistration detection pattern is formed, the optical sensor 1 detects the timing of the color misregistration detection pattern from the specularly reflected light of the color misregistration detection pattern (step S10015), and an optimum writing start timing for each color by a processing unit (for example, CPU) not shown. Is calculated (step S10016).

  After reading the density detection pattern, the toner image on the transfer belt 8 is cleaned by the above-described cleaning sequence to prepare for the next image formation (step S10017).

  In the present invention, one optical sensor is provided, but the quantity is not limited to this.

  By adopting the configuration as described above, in this embodiment, it is possible to obtain a good image quality at all times while minimizing the toner consumption at the time of calibration forcing the user. A photographic device can be provided.

[Third embodiment]
Since the basic configuration and operation of the printer engine are the same as those in the first and second embodiments, only different points will be described.

  In the first and second embodiments, the color density control and the color misregistration correction control of the replaced process cartridge are individually executed. In this embodiment, the color density control pattern of the replaced process cartridge is changed to The detection pattern of the color misregistration correction control for the replaced process cartridge color and reference color is arranged within one rotation of the conveyor belt, and density control and color misregistration correction control are performed simultaneously.

  FIG. 9 is a flowchart for explaining the control method of this embodiment. If there is a possibility that the process cartridge has been replaced, such as when the power is turned on or the CRG door (not shown) is opened or closed, the engine reads the information in the nonvolatile memory on the process cartridge and checks whether it has been replaced (step S10020, S10021). If there is an exchanged process cartridge, execution of density control and color misregistration correction control (hereinafter referred to as calibration together) is started. (Step S10022).

  When execution of the calibration control is started, initialization operations such as adjustment of the optical sensor 1 and reading of the optical sensor 1 on the belt surface in a state where there is no toner image are performed (step S10023).

  Next, a color density control pattern of the replaced process cartridge among Y, M, C, and K and a detection pattern for color shift correction control of the replaced process cartridge color and reference color are formed on the transport belt (step). S10024).

  FIG. 1 is a schematic diagram showing an example of a detection pattern of this embodiment. In FIG. 1, reference numeral 1 denotes an optical sensor provided at the center of the transfer belt 8 in the main scanning direction for detecting a density detection pattern formed on the transfer belt 8. In this embodiment, a pattern example when Cyan is exchanged is shown. Reference numerals 199a to j and 1911a to j are color misregistration detection patterns, a, c, e, g, and j are black patterns that are reference colors, and b, d, f, h, and I are cyan patterns that are exchange colors. . 1901C to 1904C are Cyan density detection patterns. The contents of each pattern are the same as those in the first and second embodiments, but the pattern portions of the color not to be formed are packed and arranged within one turn of the transfer belt. By doing so, operations such as image formation, pattern detection, and cleaning during density control and color misregistration correction control can be performed simultaneously, and the effective time can be shortened.

  After the detection pattern is formed, the detection pattern is detected by the optical sensor 1 shown in FIG.

  Based on the detected data, density control calculation and color misregistration correction calculation are performed. Since each calculation is the same as in the first and second embodiments, a description thereof will be omitted.

  After reading the detection pattern, the toner image on the transfer belt 8 is cleaned by the above-described cleaning sequence to prepare for the next image formation.

  By adopting the configuration as described above, in this embodiment, the toner consumption during calibration imposed on the user is minimized, and the density waiting time and the color misregistration correction control are simultaneously executed, thereby minimizing the waiting time for calibration. In addition, it is possible to always obtain good image quality, and to provide an electrophotographic apparatus with high merchantability.

The figure explaining the calibration pattern which concerns on Example 3 of this invention. 1 is a diagram illustrating an entire image forming apparatus according to an embodiment of the present invention. The figure explaining the color shift which concerns on 2nd Example of this invention. The figure explaining the color shift detection pattern which concerns on 2nd Example of this invention. FIG. 6 is a diagram illustrating an example of a density detection pattern for Dmax control according to the first embodiment of the present invention. FIG. 6 is a diagram for explaining an example of a density detection pattern for Dhalf control according to the first embodiment of the present invention. Flowchart for explaining a control method of density control according to the first embodiment of the present invention. Flowchart for explaining a control method of color misregistration correction control according to the second embodiment of the present invention. Flowchart for explaining a control method of engine calibration control according to the third embodiment of the present invention. The figure explaining the density | concentration detection pattern of 1st Example of this invention The figure explaining the color shift detection pattern of 2nd Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical sensor 7 Adsorption roller 8 Transfer belt 9 Fixing device 11, 12, 13, 14 Photosensitive drum 21, 22, 23, 24 Charging roller 31, 32, 33, 34 Exposure device 41, 42, 43, 44 Developing device 51 , 52, 53, 54 Transfer rollers 61, 62, 63, 64 Cleaning device 101 Driving roller (stretching roller)
102, 103 Tension roller (stretching roller)
104 Secondary transfer roller

Claims (7)

A plurality of removable image forming means each having a removable latent image forming medium and a developing means;
A plurality of transfer means for detecting replacement of the image forming means, and a plurality of images formed on the endless belt passing through the image forming section or on a recording material conveyed while being held on the endless belt. Transfer means, density detection pattern forming means for forming a predetermined density detection pattern on the latent image forming medium or the endless belt, light emitting means for irradiating the density detection pattern with light, and the latent image forming medium Alternatively, pattern regular reflection light detecting means for detecting regular reflection light of the density detection pattern formed on the endless belt, and diffusion of the density detection pattern formed on the latent image forming medium or the endless belt. Pattern diffuse reflected light detecting means for detecting reflected light, density detection patterns of the pattern regular reflected light detecting means and the pattern diffuse reflected light detecting means In the color image forming apparatus having the density control means for controlling image forming conditions based on out results,
When it is detected by the replacement detection means that one or a plurality of the image forming means has been replaced, a density detection pattern for a part of the colors including the replaced image forming means is generated instead of all colors. A color image forming apparatus characterized by performing control.   2. The color image forming apparatus according to claim 1, wherein when one or more of the latent image forming media are replaced, a density detection pattern of only the color of the latent image forming medium replaced with a predetermined reference color is displayed. A color image forming apparatus characterized in that density control is performed.   3. The color image forming apparatus according to claim 1, wherein the image forming unit includes a non-volatile storage unit, and the replacement detection unit determines whether or not replacement is performed based on individual recognition information of the storage unit. A color image forming apparatus. A plurality of detachable image forming means each having a detachable latent image forming medium and a developing means, an exchange means for detecting exchange of the image forming means, and an endless image that passes the formed image through the image forming section A plurality of transfer means for transferring onto a belt-shaped belt or a recording material conveyed while being held on the endless belt; a predetermined color misregistration detection pattern forming means on the latent image forming medium or the endless belt; Pattern regular reflection light detecting means for detecting regular reflection light of the color misregistration detection pattern formed on the latent image forming medium or the endless belt, or the latent image forming medium or the endless belt formed on the endless belt. From the pattern diffuse reflection detection means for detecting the diffuse reflection light of the color misregistration detection pattern, and the detection result of the pattern regular reflection light detection means or the pattern diffuse reflection detection means In the color image forming apparatus having a color shift correcting means for controlling the displacement amount,
When the replacement detection unit detects that one or more of the image forming units are replaced, a color misregistration detection pattern for only a part of the colors including the replaced image forming unit is generated instead of all colors. A color image forming apparatus that performs color misregistration correction control.   5. The color image forming apparatus according to claim 4, wherein when one or a plurality of the latent image forming media are replaced, a color misregistration detection pattern for only the color of the latent image forming medium replaced with a predetermined reference color. A color image forming apparatus characterized in that color misregistration correction control is performed.   6. The color image forming apparatus according to claim 4, wherein the image forming unit includes a non-volatile storage unit, and the replacement detection unit determines whether or not replacement is performed based on individual recognition information of the storage unit. A color image forming apparatus.   7. The color image forming apparatus according to claim 1, wherein the density detection pattern and the color misregistration pattern at the time of replacement of a single color or a plurality of colors of latent image forming medium are simultaneously arranged within one end of the endless belt. A color image forming apparatus characterized in that density control and color misregistration correction control are performed simultaneously.