Image forming apparatus

Abstract

To provide a technique to execute image density control at an appropriate timing in an image forming apparatus in which a plurality of cartridges with different lives can be simultaneously mounted.SOLUTION: Provided is an image forming apparatus in which a plurality of cartridges can be simultaneously mounted, each having an image carrier on which an electrostatic latent image is formed and a developer carrier forming a developer image from the electrostatic latent image, wherein the cartridges have respective lives set thereto. The image forming apparatus comprises: an intermediate transfer body to which the developer images from the plurality of cartridges are transferred; detection means that outputs information related to reflected light from the developer images on the intermediate transfer body; and a control unit. The control unit performs image density control on the basis of an image data value and the information related to the reflected light, and when a first cartridge to which the first life is set and a second cartridge to which the second life different from the first life is set are simultaneously mounted, increases the frequency of the image density control.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] Conventionally, as an image forming apparatus such as a laser beam printer, an in-line color type image forming apparatus having a configuration in which a plurality of photosensitive drums as image carriers are arranged in the rotation direction of an intermediate transfer body is known. In such an image forming apparatus, a process cartridge type is generally adopted in which an image carrier, a developing means, and a toner container are integrated as a process cartridge, which is detachably attached to the main body of the image forming apparatus. Furthermore, such an image forming apparatus may be provided with process cartridges with a plurality of life settings. A user selects and purchases any one of the process cartridges with the respective life settings based on the price or the like, and installs it in the image forming apparatus. Furthermore, at that time, it may be possible to install a process cartridge with a different life depending on the color.

[0003] In such an image forming apparatus, it is possible to adjust the color tone by controlling the image density (calibration) according to the degree of use of the process cartridge.Patent Document 1 (JP 2003-270901 A) proposes suppressing the change in image density accompanying an increase in the number of prints by controlling the image density based on the result of density detection in an image forming apparatus using a process cartridge capable of color printing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2003-270901 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above-mentioned conventional configuration, when process cartridges with different life settings are installed in the same image forming apparatus, the color tone may not match between the cartridges. This is because the timing of image density control of the process cartridges differs according to the life setting, and therefore when process cartridges with different life settings are installed at the same time, the timing of image density control is shifted.

[0006] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a technique for executing image density control at an appropriate timing in an image forming apparatus capable of simultaneously mounting a plurality of cartridges having different life spans. [Means for solving the problem]

[0007] The present invention employs the following configuration. an image carrier on whose surface an electrostatic latent image is formed by exposure based on image data; and a developer carrier on which the electrostatic latent image is developed with a developer to form a developer image; an image forming apparatus capable of simultaneously mounting a plurality of cartridges each having a developer storage chamber, wherein each of the plurality of cartridges has a usable life set; an intermediate transfer body onto which the developer images formed by the plurality of cartridges are transferred; a detection means for irradiating the developer image transferred to the intermediate transfer body with light, detecting reflected light, and outputting information regarding the reflected light; A control unit; Equipped with The control unit is an image density control is performed to control an image density when the developer image is formed based on a value of the image data and information about the reflected light; When a first cartridge having a first lifespan set and a second cartridge having a second lifespan set different from the first lifespan are simultaneously mounted in the image forming device, the image density control is performed more frequently than when only the second cartridge is mounted. The image forming apparatus is characterized in that:

[0008] The present invention also employs the following configuration. An image forming apparatus capable of detachably mounting a plurality of cartridges, each of which has an image carrier on whose surface an electrostatic latent image is formed by exposure based on image data, a developer carrier which develops the electrostatic latent image with a developer to form a developer image, and a storage chamber which stores the developer, wherein each of the plurality of cartridges has a set usable life; an intermediate transfer body onto which the developer images formed by the plurality of cartridges are transferred; a detection means for irradiating the developer image transferred to the intermediate transfer body with light, detecting reflected light, and outputting information regarding the reflected light; A control unit; Equipped with The control unit is an image density control is performed to control an image density when the developer image is formed based on the value of the image data and information about the reflected light; When a first cartridge having a first lifespan set and a second cartridge having a second lifespan set different from the first lifespan are simultaneously mounted in the image forming device, the image density control is performed at both a first frequency determined for performing the image density control on the first cartridge and a second frequency determined for performing the image density control on the second cartridge. The image forming apparatus is characterized in that: Effect of the Invention

[0009] According to the present invention, it is possible to provide a technique for executing image density control at an appropriate timing in an image forming apparatus into which a plurality of cartridges having different life spans can be simultaneously installed. [Brief description of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view of a schematic configuration of an image forming apparatus according to a first embodiment of the present invention; [Diagram 2] 1 is a cross-sectional view showing a schematic configuration of a developing device and a process cartridge according to a first embodiment of the present invention; [Diagram 3] FIG. 1 is a diagram showing a control block of an image forming apparatus according to a first embodiment. [Figure 4] Concentration sensor configuration diagram [Diagram 5] Concentration sensor characteristics [Figure 6] Illustrative diagram of normalization correction of density sensor output [Figure 7] Flowchart of image density control method [Figure 8] Diagram of patch pattern on intermediate transfer belt [Figure 9] Image tone control diagram [Figure 10] Graph showing the change in gamma curve [Figure 11] Timing chart showing an example of image density control [Figure 12] 11 is a timing chart showing another example of image density control. [Figure 13] Timing chart showing an example of image density control in the second embodiment [Figure 14] Timing chart showing an example of image density control according to the third embodiment DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] A preferred embodiment of the present invention will be described in detail below with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative positions, etc. of the components described in the embodiment are not intended to limit the scope of the present invention to those alone. Furthermore, the materials, shapes, etc. of the members once described in the following description are the same as those described initially, unless otherwise specified. Well-known or publicly known technologies in the relevant technical field can be applied to configurations and processes not particularly shown or described. Furthermore, duplicated descriptions may be omitted.

[0012] [Example 1] First, the overall configuration of an electrophotographic image forming apparatus 100 will be described with reference to the schematic cross-sectional view of Fig. 1. The image forming apparatus 100 of this embodiment is a full-color laser printer that employs an in-line system and an intermediate transfer system. The image forming apparatus 100 can form a full-color image on a recording material 12 (e.g., recording paper) according to image information. The image information is input to the image forming apparatus main body 110 from a host device such as a personal computer (PC 120) communicably connected to the image forming apparatus main body 110 or an image reading device connected to the image forming apparatus main body 110.

[0013] The image forming apparatus 100 has a plurality of image forming sections, namely, first, second, third and fourth image forming sections SY, SM, SC and SK for forming images of each color of yellow (Y), magenta (M), cyan (C) and black (K), respectively. In this embodiment, the first to fourth image forming sections SY, SM, SC and SK are arranged in a line along the intermediate transfer belt 31. The image forming section S includes a primary transfer roller 32 and a process cartridge 7.

[0014] In this embodiment, the configurations and operations of the first to fourth image forming units are substantially the same except for the colors of the images they form. Therefore, unless a distinction is particularly required, the suffixes Y, M, C, and K given to the reference numerals to indicate that the element is provided for one of the colors will be omitted and a general description will be given.

[0015] In this embodiment, the image forming apparatus 100 has, as a plurality of image carriers, four photosensitive drums 1 arranged along an intermediate transfer belt 31. Fig. 2 is a schematic cross-sectional view of the process cartridge 7 in the longitudinal direction (rotation axis direction) of the photosensitive drums 1. The four photosensitive drums 1 have the same configuration. Fig. 3 is a block diagram showing a control block of the image forming apparatus 100.

[0016] The photosensitive drum 1 is rotated in the direction of the arrow A (clockwise direction in the figure) by a driving source 140 as a driving means. Around the photosensitive drum 1, a charging roller 2 (charging member) is arranged as a charging means for uniformly charging the surface of the photosensitive drum 1. Also, around the photosensitive drum 1, a developing roller 17 and a cleaning blade 6 are arranged. The developing roller 17 is a developing means for developing an electrostatic latent image into a toner image, and constitutes a developing unit 4 as a developing device. The cleaning blade 6 is a cleaning means for removing toner (transfer residual toner) remaining on the surface of the photosensitive drum 1 after transfer. The cleaning blade 6 abuts against the surface of the photosensitive drum 1, and this abutting portion is a contact portion. The process cartridge 7 will be described in more detail later. The recording material 12 is loaded on a recording material holding portion 44, and is transported along a transport path R by a pickup roller to reach between the secondary transfer roller 33 and the secondary transfer opposing roller 38.

[0017] In this embodiment, a photosensitive drum 1 and a charging roller as a process means acting on the photosensitive drum 1 are provided. The roller 2, developing unit 4, and cleaning blade 6 are integrally formed into a cartridge to form the process cartridge 7. The process cartridge 7 is detachably attached to the image forming apparatus 100. In this embodiment, the process cartridges 7 for each color have the same shape in terms of main components. The process cartridges 7 for each color differ in that they each contain toner of the respective colors, yellow (Y), magenta (M), cyan (C), and blank (K), respectively.

[0018] [Process cartridge] Next, the overall configuration of the process cartridge 7 that can be mounted in the image forming apparatus 100 of this embodiment will be described. In this embodiment, the basic configuration and operation of the process cartridges 7 for each color are the same except for the type (color) of developer contained therein. The process cartridge 7 has a photosensitive unit 13 equipped with a photosensitive drum 1 and the like, and a developing unit 4 equipped with a developing roller 17 and the like.

[0019] The photosensitive unit 13 has a cleaning frame 14 as a frame that supports various elements in the photosensitive unit 13. The photosensitive drum 1 is rotatably attached to the cleaning frame 14 via a bearing (not shown). The driving force of a driving motor as a driving source 140 is transmitted to the photosensitive unit 13, thereby rotating the photosensitive drum 1 in the direction of arrow A (clockwise direction) in accordance with the image forming operation. In this embodiment, an organic photosensitive body is used as the photosensitive drum 1, which is the center of the image forming process, in which the outer peripheral surface of an aluminum cylinder is coated with a functional film, an undercoat layer, a carrier generating layer, and a carrier transport layer, in that order.

[0020] In addition, a cleaning blade 6 and a charging roller 2 are arranged in the photosensitive unit 13 so as to contact the peripheral surface of the photosensitive drum 1. The residual toner removed from the surface of the photosensitive drum 1 by the cleaning blade 6 falls by gravity and is contained in a cleaning frame 14.

[0021] The charging roller 2, which is a charging means, is rotated by pressing a roller portion made of conductive rubber against the photosensitive drum 1. Here, a predetermined DC voltage is applied to the core metal of the charging roller 2 from the charging power source 142d in the charging process, and a uniform dark area potential (Vd) is formed on the surface of the photosensitive drum 1. The spot pattern of the laser light emitted from the above-mentioned scanner unit 30 in response to image data exposes the photosensitive drum 1, and the exposed area loses surface charge due to carriers from the carrier generation layer, lowering the potential. As a result, an electrostatic latent image is formed on the photosensitive drum 1, with the exposed area at a predetermined light area potential (Vl) and the unexposed area at a predetermined dark area potential (Vd).

[0022] On the other hand, the developing unit 4 includes a developing roller 17 (developer carrier), a developing blade 19, a toner supply roller 18 (supply means), toner 15, and a toner storage chamber 16 for storing the toner 15. The toner 15 in this embodiment is a non-magnetic one-component spherical toner that is charged negatively as the normal polarity and has a particle size of 7 μm. In addition, silica particles having a particle size of 20 nm are added to the surface of the toner 15 as a toner external additive (external particles).

[0023] The developing blade 19 is in counter contact with the developing roller 17, and regulates the coating amount of the toner supplied by the toner supply roller 18 and imparts an electric charge. The developing blade 19 is made of a thin plate-like member, and generates a contact pressure by utilizing the spring elasticity of the thin plate, and its surface comes into contact with the toner 15 and the developing roller 17. The toner 15 is frictionally charged by the rubbing between the developing blade 19 and the developing roller 17, and is given an electric charge while at the same time regulating the layer thickness. In this embodiment, a predetermined voltage is applied to the developing blade 19 from a blade bias power supply to stabilize the toner coat.

[0024] The developing roller 17 and the photosensitive drum 1 rotate so that their surfaces move in the same direction at the opposing portion N1 (contact portion) (the photosensitive drum 1 is indicated by an arrow A, and the developing roller 17 is indicated by an arrow G). In this embodiment, the toner 15 negatively charged by friction with respect to a predetermined DC voltage applied from the developing power source 142f at the opposing portion N1 in contact with the photosensitive drum 1 transfers only to the bright potential portion due to the potential difference, thereby visualizing the electrostatic latent image.

[0025] The toner supply roller 18 is disposed on the peripheral surface of the developing roller 17, forming a predetermined nip portion N2. The toner supply roller 18 rotates in the direction of the arrow E (counterclockwise in the figure). In this embodiment, the toner supply roller 18 is an elastic sponge roller having a foam formed on the outer periphery of a conductive core metal. The toner supply roller 18 and the developing roller 17 are in contact with each other with a predetermined penetration amount, and rotate so as to move in opposite directions to each other at the nip portion N2. This rotational action allows the toner supply roller 18 to supply toner to the developing roller 17 and scrape off the residual toner remaining on the developing roller 17.

[0026] A toner stirring member 20 is provided in the toner storage chamber 16. The toner stirring member 20 includes a sheet-like member that rotates in the direction of the arrow H, stirs the toner 15 stored in the toner storage chamber 16, and transports the toner 15 toward the top of the toner supply roller 18. In this embodiment, the developing roller 17 and the toner supply roller 18 both have an outer diameter of φ20, and the intrusion amount of the toner supply roller 18 into the developing roller 17 is set to 1.5 mm. In this embodiment, a predetermined DC bias is applied from the developing power source 142f to the developing roller 17, and in the developing section contacting the photosensitive drum 1, the toner is transferred only to the bright potential portion due to the potential difference, thereby visualizing the electrostatic latent image.

[0027] The process cartridge 7 is provided with a memory m made of a non-volatile memory or the like. The memory m stores information related to the determination of the frequency at which the controller 72 performs image density control. Here, examples of information related to the determination of the frequency at which the image density control is performed include the nominal life, the toner loading amount, at least one of the roughness and hardness of the charging roller 2, information on the layer structure of the charging roller 2, at least one of the roughness and hardness of the developing roller 17, at least one of the material of the surface layer of the photosensitive drum 1, the film thickness, and the susceptibility to photodegradation. The frequency of calibration itself, which is preset for the cartridge, may also be stored. The memory m is configured to be able to communicate with the controller 72 as the control unit of the image forming apparatus 100 shown in FIG. 1 in a non-contact manner or by contact via an electrical contact. That is, the controller 72 is able to read information from the memory m and write information to the memory m. Although the memory m is attached to the photosensitive unit 13 in FIG. 2, it may be attached to the developing unit 4. In addition, a memory m may be attached to both the photosensitive unit 13 and the developing unit 4. In this case, the memory m on the photosensitive unit 13 side stores information about the photosensitive drum 1 and the charging roller 2, and the memory m on the developing unit 4 side stores information about the developing roller 17 and the toner 15.

[0028] In this embodiment, there are a plurality of cartridges with different life settings for the process cartridges 7 of each color. Here, the life of the process cartridge 7 is a numerical value that indicates the section in which the cartridge can be used, and is typically set according to the capacity of the toner. When the life is set by the number of prints, the life may be set to the number of printable sheets when a typical image is printed using the toner contained in the process cartridge 7, or a numerical value with some margin may be set as the life. Furthermore, the life is typically expressed in the number of printable sheets of recording material, but it may also be expressed in other units based on the time the process cartridge 7 was used, such as the number of days or hours used. The process cartridge 7 has a nominal life set by the manufacturer. Here, a relatively short-lived process cartridge 7 with a nominal life of 10,000 sheets and a relatively long-lived process cartridge with a nominal life of 50,000 sheets are set. There are two types: Ridge 7 and Ridge 8.

[0029] 1, the image forming apparatus 100 includes a scanner unit 30 as an exposure means (exposure device) that irradiates a laser onto the photosensitive drums 1 based on image information to form an electrostatic latent image. The image forming apparatus 100 further includes an intermediate transfer belt 31 that faces the four photosensitive drums 1 and serves as an intermediate transfer body for transferring the toner images on the photosensitive drums 1 to a recording material 12.

[0030] As shown in FIG. 1, an intermediate transfer belt 31 formed of an endless belt contacts all the photosensitive drums 1 and rotates (moves) in the direction of arrow B (counterclockwise in the figure). The intermediate transfer belt 31 is stretched around a driving roller 37, a secondary transfer opposing roller 38, and a driven roller (not shown) as a plurality of supporting members. On the inner peripheral surface side of the intermediate transfer belt 31, four primary transfer rollers 32 as primary transfer means (transfer members) are arranged side by side so as to face each photosensitive drum 1. A bias of a polarity opposite to the normal charging polarity of the toner is applied to the primary transfer rollers 32 from a primary transfer bias power source. As a result, the toner image on the photosensitive drum 1 is transferred onto the intermediate transfer belt.

[0031] Further, a secondary transfer roller 33 serving as a secondary transfer means is disposed at a position facing the secondary transfer opposing roller 38 on the outer peripheral surface side of the intermediate transfer belt 31. A bias having a polarity opposite to the normal charging polarity of the toner is applied to the secondary transfer roller 33 from a secondary transfer bias power source. As a result, the toner image on the intermediate transfer belt 31 is transferred to the recording material 12.

[0032] As shown in FIG. 3, the image forming apparatus 100 includes a power supply 142. The power supply 142 functions as the above-mentioned primary transfer bias power supply and secondary transfer bias power supply, and as a blade bias power supply described later, according to instructions from the controller 72. In the example of FIG. 3, one power supply 142 functions to serve as a primary transfer bias power supply 142a, a secondary transfer bias power supply 142b, a blade bias power supply 142c, a charging power supply 142d that applies a voltage to the charging roller 2, a supply power supply 142e that applies a voltage to the toner supply roller 18, and a developing power supply 142f that applies a voltage to the developing roller 17. However, the power supply configuration is not limited to this, and a separate power supply device may be provided for each member.

[0033] When forming an image, first, the surface of the photosensitive drum 1 is uniformly charged by the charging roller 2. Next, an electrostatic latent image in accordance with the image information is formed on the photosensitive drum 1 by a laser beam corresponding to the image information emitted from the scanner unit 30. Next, a developer is supplied to the electrostatic latent image by the developing unit 4, and the electrostatic latent image is developed on the photosensitive drum as a toner image (developer image). Next, the developed toner image is transferred (primary transfer) onto the intermediate transfer belt 31 by the action of the primary transfer roller 32.

[0034] For example, when a full-color image is formed, the above-mentioned process is performed in sequence in the first to fourth image forming stations SY, SM, SC, and SK, and a four-color toner image is formed by superimposing the toner images of each color on the intermediate transfer belt 31. After that, the four-color toner images on the intermediate transfer belt 31 are secondarily transferred collectively onto the recording material 12. Furthermore, the fixing device 34 applies heat and pressure to the recording material 12, thereby fixing the toner image onto the recording material 12.

[0035] Incidentally, the primary transfer residual toner remaining on the photosensitive drum 1 after the primary transfer process is removed and collected by a cleaning blade 6. In addition, the secondary transfer residual toner remaining on the intermediate transfer belt 31 after the secondary transfer process is cleaned by an intermediate transfer belt cleaning device (not shown).

[0036] 3, the image forming apparatus 100 includes a controller 72. The controller 72 is an information processing device including computational resources such as a CPU 73, a ROM 74, and a RAM 75, and functions as a control unit that operates according to a program and instructions given via a PC 120 or a touch panel of the image forming apparatus main body 110. The controller 72 controls each of the components in the image forming apparatus, such as a drive source 140 such as a motor, a power source 142, a scanner unit 30, and a density sensor 41.

[0037] The image forming apparatus 100 of this embodiment includes a density sensor 41 as a detection means. The density sensor 41 is an optical sensor for detecting the amount of toner, and is used for image density control as calibration. The density sensor 41 is disposed to face the intermediate transfer belt 31 as shown in FIG. 1. The density sensor 41 measures reflected light intensity information corresponding to the density of a toner patch formed on the surface of the intermediate transfer belt 31. An example of the configuration of the density sensor 41 is shown in FIG. 4. The density sensor 41 has a light emitting element 51, a light receiving element 52 (a first light receiving element 52a, a second light receiving element 52b), and a processing circuit (not shown) such as an IC for processing received light data, and these are accommodated in a holder. The density sensor 41 is configured to be able to transmit and receive information to and from a controller 72. For the light emitting element 51, an infrared light emitting element such as an LED can be used. For the light receiving element 52, a photodiode, a Cds cell, or the like can be used.

[0038] The light emitting element 51 irradiates light toward the intermediate transfer belt 31. The first light receiving element 52a detects the intensity of specularly reflected light from the toner patch 64, and the second light receiving element 52b detects the intensity of diffusely reflected light from the toner patch 64. By detecting both the intensity of specularly reflected light and the intensity of diffusely reflected light, it is possible to detect the density of the toner patch 64, ranging from high density to low density. Note that an optical element such as a lens (not shown) may be used to couple the light emitting element 51 and the light receiving element 52.

[0039] In this embodiment, the intermediate transfer belt 31 is a single-layer resin belt made of polyimide with a circumference of 880 mm. An appropriate amount of carbon particles is dispersed in the resin to adjust the resistance of the belt, and the surface color is black. Furthermore, the surface of the intermediate transfer belt 31 is highly smooth and glossy, with a gloss level of approximately 100% (measured with a gloss meter IG-320 manufactured by Horiba, Ltd.).

[0040] When the surface of the intermediate transfer belt 31 is exposed (toner amount is 0), the density sensor 41 mainly detects reflected light through the first light receiving element 52a. This is because the surface of the intermediate transfer belt 31 is glossy, as described above. On the other hand, when a toner image is formed on the intermediate transfer belt 31, the specular reflection output gradually decreases as the density of the toner image (toner amount) increases. This is because the toner covers the surface of the intermediate transfer belt 31, reducing the specular reflection light from the belt surface.

[0041] FIG. 5 is a diagram showing the relationship between the detection value of the density sensor 41 and the toner amount. Here, the detection value corresponding to the regular reflection output is shown. In the figure, the vertical axis represents the output value voltage of the density sensor 41, and the horizontal axis represents the image density (corresponding to the toner amount). The density sensor 41 used in this embodiment has a maximum output value voltage of 5V. In the image forming apparatus 100 of this embodiment, the output value of the density sensor 41 is corrected using the output value (base output value) of the intermediate transfer belt 31 in a state where there is no toner. Specifically, the output value of the toner patch is normalized by the base output value of the intermediate transfer body (the output value when the image density is 0 in FIG. 5). (toner patch output / base output). The sensor output characteristics after normalization are shown in FIG. 6. By performing normalization, a similar correction is possible even when the gloss of the intermediate transfer belt 31 is reduced due to dirt, scratches, etc.

[0042] The above-described method of normalizing and correcting the toner patch output with the background output is a known method. This is used in many color image forming apparatuses on the market. Any existing configuration for detecting density can be used as the density sensor 41. The wavelength of the light is not limited to infrared light.

[0043] <Image Density Control Operation Common to All Examples> Next, the image density control in each embodiment will be described with reference to the flowchart of FIG. The image density control in the image forming apparatus 100 of the present invention is image gradation control for adjusting the density gradation characteristics of the image. Each step of the flow is executed by the controller 72 with reference to the output value of the density sensor 41 and the like.

[0044] [Image density control] The image density control can be performed at any timing, and may be performed periodically or when a change in image density is expected. In this embodiment, the timing of the image density control is appropriately controlled even when multiple process cartridges with different life spans are installed. First, in step S101, a background measurement of the intermediate transfer belt 31, that is, a density measurement in a state where no toner is placed thereon, is performed. At this time, the controller 72 rotates the intermediate transfer belt 31 by the drive source 140 so that predetermined measurement positions on the intermediate transfer belt 31 that are the subject of density measurement are sequentially brought within the measurement range of the density sensor 41. The measurement positions and the number of points are the same as those of the toner patch used for image density control.

[0045] 8 shows a patch pattern formed on the intermediate transfer belt 31. Along the moving direction (arrow F) of the intermediate transfer belt 31, a plurality of 8 mm square patches 88 are arranged at 2 mm intervals at positions corresponding to the portion where the density sensor 41 is arranged. The patches 88 include a yellow patch 88Y, a magenta patch 88M, a cyan patch 88C, and a black patch 88K. Each of the color patches 88Y to 88K includes eight patches with eight different image printing rates (density gradients) (hereinafter, simply referred to as Y1 to Y8, M1 to M8, C1 to C8, and K1 to K8). As a result, a total of 32 patches 88 are formed on the intermediate transfer belt 31.

[0046] The correspondence between each patch 88 and the printing rate (gradation) is set as follows: Y1, M1, C1, K1 = 12.5%; Y2, M2, C2, K2 = 25%, Y3, M3, C3, K3 = 37.5%; Y4, M4, C4, K4 = 50%, Y5, M5, C5, K5 = 62.5%; Y6, M6, C6, K6 = 75%, Y7, M7, C7, K7 = 87.5%, Y8, M8, C8, K8 = 100%.

[0047] The base measurement of the intermediate transfer belt 31 is performed on the locations where the above-mentioned 32 patches 88 are to be formed, before the patches 88 are formed. For example, the base measurement may be performed one revolution before the patches 88 are formed. As will be described later, each patch 88 may be printed in only one color to perform monochrome image density control.

[0048] 7, in step S102, the controller 72 rotates the intermediate transfer belt 31 by the drive source 140 of the image forming apparatus 100, and sequentially moves each patch forming position to a position facing the image forming unit. Then, the controller 72 controls the image forming unit to form the toner patch 88 on the intermediate transfer belt 31 as described in FIG.

[0049] Then, in step S103, the controller 72 detects the amount of reflected light from the toner patch 88 by using the density sensor 41, while the positions where the patches are formed on the intermediate transfer belt 31 are successively brought within the measurement range of the density sensor 41. Then, in step S104, the controller 72 calculates the density of the toner patch 88. At this time, first, the output value of the density of the toner patch 88 is normalized by the background output value of the intermediate transfer belt 31 (toner output / background output). Such normalization of the patch output is performed for all the patches 88 by using the background output value acquired at the position corresponding to the patch. Next, the controller 72 converts the normalized value into a density value by a density conversion table. The density conversion table is stored in advance in the ROM 74.

[0050] Next, in step S105, the controller 72 performs image gradation control (gradation correction). This image gradation control will be described with reference to Fig. 9. Note that only the gradation correction of cyan will be described here, but correction is also performed in the same manner for magenta, yellow, and black.

[0051] 9, the horizontal axis represents image data (e.g., pixel value %), and the vertical axis represents density detection values ​​(values ​​after normalization correction of output voltages) of the density sensor 41. Also, circles in the figure represent the detected density values ​​of the density sensor 41 for each patch C1, C2, C3, C4, C5, C6, C7, and C8. A curve γ passing through each point C1 to C8 represents density gradation characteristics in a state where density control (gradation correction control) is not performed. Note that, for image densities at gradations where no patches are formed, the controller 72 calculates image data values ​​by performing spline interpolation so as to pass through the origin and each point C1 to C8.

[0052] Next, the straight line T represents the target density gradation characteristic of the image density control. In this embodiment, the target gradation characteristic T is determined so that the relationship between image data and density is proportional. Note that the gradation characteristic is not limited to a straight line. As can be seen by comparing the curve γ with the straight line T, if gradation correction is not performed in the illustrated example, in the range where the image data value is low, the image is printed so that the image density is low relative to the image data value, and in the range where the image data value is high, the image is printed so that the image density is high relative to the image data value. In other words, the print is different from the color desired by the user.

[0053] Curve D represents the gradation correction table calculated by the control of this embodiment. The controller 72 calculates the gradation correction table D by determining a symmetric point of the pre-correction gradation characteristic γ with respect to the target gradation characteristic T. The calculated gradation correction table D is stored in the RAM 75.

[0054] When forming a print image, the controller 72 can obtain target gradation characteristics by correcting the image data value with reference to the gradation correction table D. For example, in a range where the image data value is low, the image data value is corrected to be high by using the gradation correction table D. By determining the control value of the image forming apparatus 100 using this corrected image data value, the density of the printed image can be increased and the gradation characteristics can be raised to the straight line T. In addition, the method of controlling the image density performed here may be a known method for controlling the image forming conditions. Examples of the image forming conditions include developing conditions such as a developing bias, charging conditions such as a charging bias, etc. The controller 72 forms a plurality of patches of a predetermined pattern (such as a halftone pattern) on the intermediate transfer belt 31, in which these image forming conditions are changed in a plurality of stages, detects the density of the patch pattern, and calculates the image forming conditions that can obtain the desired density.

[0055] Next, the transition of the curve γ during printing will be described with reference to FIG. Immediately after performing image density control according to the above flow, the relationship between image data value and image density becomes the line of straight line T by correcting with the tone correction table D described above. However, by increasing the number of prints from there, the deviation of density tone becomes larger, and the curve γ changes from γ1 to γ2 to γ3. Here, it is assumed that the deviation of density tone is within the allowable range up to the curve γ2, but exceeds the predetermined allowable range when it changes to the curve γ3. If the curve γ2 is within the allowable range, the image density control is performed at the timing when the deviation becomes the curve γ2, and the curve γ2 is returned to T, making it possible to maintain color reproducibility. This concludes the explanation of image density control (image tone correction) in this embodiment.

[0056] [Image density control execution frequency] In this embodiment, process cartridges 7 with different life spans include a process cartridge with a nominal life span of 10,000 sheets (hereinafter referred to as Type 1, also referred to as the first process cartridge 7a. The first process cartridge 7a is set to a first life span) and a process cartridge with a nominal life span of 50,000 sheets (hereinafter referred to as Type 2, also referred to as the second process cartridge 7b. The second process cartridge 7b is set to a second life span that is longer than the first life span).

[0057] In this embodiment, Type 1 and Type 2 are different in the amount of toner 15 filled. Specifically, the amount of toner 15 filled in the Type 2 cartridge is greater than that in the Type 1 cartridge. First, when a Type 1 cartridge, which has a relatively short lifespan, is used, the transition of the curve γ after image density control is performed at a certain timing is as shown in Table 1. [Table 1]

[0058] That is, in the case of a Type 1 process cartridge, γ immediately after image density control becomes the target curve T, and when 1000 sheets have been printed, the curve γ becomes γ2, so color reproducibility can be maintained by executing image density control at most every 1000 sheets printed (i.e., every 1000 sheets). Here, the timing for executing image density control must be immediately before the curve γ falls out of the allowable range at the latest, which is when 1000 sheets have been printed in the case of Type 1 in this embodiment.

[0059] Next, when Type 2, which has a relatively long life, is used, the transition of the curve γ after image density control is executed at a certain timing is as shown in Table 2. [Table 2]

[0060] That is, in the case of the Type 2 cartridge, γ immediately after image density control becomes the target curve T, and when 2000 sheets are printed, the curve γ becomes γ2. By performing image density control for each print (i.e., every 2000 sheets), it becomes possible to maintain color reproducibility. For example, Type 1 can be considered as the first cartridge, and the frequency at which image density control is performed (1000 sheets) can be called the first frequency. Also, Type 2 can be considered as the second cartridge, and the frequency at which image density control is performed (2000 sheets) can be called the second frequency.

[0061] This is because Type 2 has a large toner loading amount, and therefore the change in toner particle size, toner deterioration, and level of D roller filming differ from those of Type 1, resulting in a smaller change in the curve γ.

[0062] Therefore, in the case where Type1 and Type2 are mixed, i.e., where cartridges with different life settings are in the same image forming apparatus, as in this embodiment, image density control is executed at both timings, that is, every 1000 sheets for Type1 and every 2000 sheets for Type2. If it is assumed that monochrome image density control is executed only for Type1 and only for Type2 at each timing of Type1 and Type2, the transition will be as shown in the following Figure 11. As a result, in the case where Type1 and Type2 are mixed, the total frequency of image density control combining Type1 and Type2 can be increased compared to the case where only one Type is selected, and it becomes possible to reproduce more accurate colors.

[0063] An example of the control of this embodiment will be described with reference to FIG. 11. In the figure, the numbers enclosed in boxes for Type1 and Type2 respectively indicate the number of printed sheets after the previous calibration (or after installation), and are reset to 0 every 1000 sheets for Type1 and every 2000 sheets for Type2. After starting, a new Type2 is installed at timing P1 when 400 sheets have been printed. In this case, at timing P2 after 600 sheets have been printed from the installation of Type2, the number of printed sheets of Type1 becomes 1000 sheets, and the first image density control is performed. Then, at timing P3 after 1000 sheets have been printed from timing P2, the number of printed sheets after the reset of Type1 becomes 1000 sheets, and the second image density control is performed. Then, at timing P3 after 400 sheets have been printed from timing P3, the number of printed sheets of Type2 becomes 2000 sheets, and the third image density control is performed. In this way, the control of this embodiment makes it possible to increase the number of calibrations.

[0064] In this embodiment, since the specified number of sheets for Type 2 (2000 sheets) is twice the specified number of sheets for Type 1 (1000 sheets), the periods may overlap and image density control may be performed at the same timing (every 1000 sheets) as a result. However, even in this case, image density control is still performed at the necessary timing for both Type 1 and Type 2 cartridges.

[0065] An example of control in this case will be described with reference to FIG. 12. In this example, the start is the time when Type1 and Type2 are attached at the same time. After the start, at timing P21 when 1000 sheets have been printed, the number of printed sheets of Type1 becomes 1000 sheets, and the first image density control is performed. Then, at timing P22 after 1000 sheets have been printed from timing P21, the number of printed sheets of Type1 after reset becomes 1000 sheets, and the number of printed sheets of Type2 becomes 2000 sheets, and the second image density control is performed. In this way, when the cycles of Type1 and Type2 overlap, the number of calibrations is every 1000 sheets, which is normally performed for Type1. However, even in this case, calibration can be performed at both the timing required for Type1 and the timing required for Type2.

[0066] In this embodiment, image density control is performed periodically, but it may be performed irregularly depending on the timing when γ2 is reached. Image density control may also be performed when a user instruction is received. The execution timing may be determined using tag information in memory m of the process cartridge 7. In this embodiment, calibration is performed only for the process cartridge of the corresponding color, but both Type 1 and Type 2 calibrations may be performed by triggering either Type 1 or Type 2.

[0067] In the present invention, a calibration request is issued at the timing when γ2 is reached, that is, when the deviation in density gradation is within the allowable range, for both Type 1 and Type 2. However, the control of the present invention is not limited to the above timing, and may be executed during the transition of the curve γ from T to γ2, that is, while the deviation in density gradation is within the allowable range.

[0068] In addition, the timing based on the state of γ may be changed between Type1 and Type2. Note that it is preferable to request calibration between when the curve γ becomes γ1 and when it reaches γ2. For example, consider a case where Type1 deteriorates faster than Type2 and the deviation width of γ in Type1 is larger, resulting in a noticeable density change. In this case, Type1 may perform image density control at the timing when the curve γ becomes γ1, and Type2 may perform calibration at the timing when the curve γ becomes γ2, so that Type1 may perform calibration at the timing when the curve γ becomes γ1 and Type2 may perform calibration at the timing when the curve γ becomes γ2. Note that, in a case where Type2 deteriorates faster than Type2, it may be possible to control Type2 to perform calibration at the timing when the curve γ changes less than Type1. Note that the timing of image density control may be changed depending on the printing conditions and environmental changes such as temperature and humidity. The timing of executing image density control may be appropriately set depending on the life of the process cartridge, that is, the degree of deterioration of the toner.

[0069] In the present invention, the next image density control is controlled based on the number of prints of Type 1 and Type 2 after the image density control is performed. However, the timing of performing the image density control is not limited to this, and may be based on parameter information related to the toner. For example, parameters related to toner deterioration such as the rotation time, rotation number, and surface movement distance of the developing roller may be used. In addition, although the control is performed at a predetermined number of prints, the execution may be controlled by a ratio. For example, the control may be performed such that the first image density control is performed at 99% of the nominal life (100% is new, 0% is end of life) and the second image density control is performed at 95%. Parameters may be appropriately set so that the calibration frequency is changed as the end of life approaches. Furthermore, calibration may be unconditionally performed on all cartridges when they are replaced with new cartridges.

[0070] [Example 2] Next, a second embodiment of the present invention will be described. Note that the description of the same parts as in the first embodiment will be omitted. In this embodiment, there are process cartridges with different life spans, a process cartridge with a nominal life span of 10,000 sheets (hereinafter referred to as Type 1, as in the first embodiment) and a process cartridge with a nominal life span of 50,000 sheets (hereinafter referred to as Type 3). Therefore, the nominal life span of Type 3 is the same as that of the first embodiment. In addition to the difference in toner loading amount, Type 1 and Type 3 have different charging rollers 2. Type 3 employs a charging roller 2 that is compatible with a long life span, and Type 3 has a higher roughness than Type 1.

[0071] As in the first embodiment, the transition of the curve γ after the image density control is executed for the Type 1 process cartridge is as shown in Table 1. Next, in the Type 3 process cartridge, the transition of the curve γ after the image density control is executed at a certain timing is as shown in Table 3. [Table 3]

[0072] That is, in the case of Type 3, γ immediately after image density control becomes the target curve T, and curve γ becomes γ2 when 2400 sheets are printed, so color reproducibility can be maintained by executing image density control every 2400 sheets. This is because, in the case of Type 3, in addition to the large toner loading amount, the roughness of the charging roller 2 is high, so the effect of dirt on the charging roller 2 is reduced and the drop in the drum potential after charging is slower than in Type 1.

[0073] Therefore, in the present embodiment, in a case where Type 1 and Type 3 are mixed, image density control is executed at both timings: every 1000 sheets for Type 1 and every 2400 sheets for Type 3. As a result, in a case where Type 1 and Type 3 are mixed, the frequency of image density control can be increased compared to a case where only one of the Types is selected, making it possible to reproduce colors more accurately.

[0074] An example of the control of this embodiment will be described with reference to FIG. 13. In the figure, the numbers enclosed in boxes for Type1 and Type3 indicate the number of printed sheets after the previous calibration (or installation), and are reset to 0 every 1000 sheets for Type1 and every 2400 sheets for Type3. After starting, a new Type3 is installed at timing P31 when 400 sheets have been printed. In this case, the number of printed sheets of Type1 becomes 1000 sheets at timing P32 after 600 sheets have been printed from the installation of Type3, and the first image density control is performed. Then, the number of printed sheets after resetting Type1 becomes 1000 sheets at timing P33 after 1000 sheets have been printed from timing P32, and the second image density control is performed. Then, the number of printed sheets of Type3 becomes 2400 sheets at timing P34 after 800 sheets have been printed from timing P33, and the third image density control is performed. In this way, the number of calibrations can be increased by the control of this embodiment.

[0075] In this embodiment, the image density control is performed periodically, but the present invention is not limited to this and may be performed irregularly depending on the timing at which γ2 is reached. Also, the execution timing may be determined using tag information in the memory m of the process cartridge 7.

[0076] (Variation 1) Next, a first modified example of the second embodiment will be described. In the first modified example, a Type 1 cartridge and a Type 3 cartridge with a nominal life of 50,000 sheets are used, as in the second embodiment. As for the transition of the curve γ, as in Table 3, image density control is performed every 2,400 sheets in Type 3.

[0077] In this modified example, the cartridges of Type 1 and Type 3 differ not only in the amount of toner filled, but also in the layer structure of the charging roller 2. That is, the charging roller 2 of Type 1 has a single-layer structure (only a base layer without a surface layer), while the charging roller of Type 3 has a two-layer structure (surface layer + base layer) that supports a long life. Controller 2 is installed.

[0078] In addition to the large toner loading amount, the Type 3 cartridge of this modification has a coated surface for the charging roller 2, which suppresses contamination of the charging roller compared to the single-layer structure charging roller 2 of Type 1. Due to this effect, the drop in drum potential after charging is slower than that of Type 1, and the change in curve γ is also slower. Therefore, when Types 1 and 3 are mixed, image density control can be performed at both timings, every 1000 sheets for Type 1 and every 2400 sheets for Type 3, to increase the frequency of image density control, which makes it possible to reproduce more accurate colors.

[0079] In addition, in this embodiment, the image density control is performed periodically, but the present invention is not limited to this and may be performed irregularly depending on the timing at which γ2 is reached. The execution timing may be determined using tag information in the process cartridge.

[0080] (Variation 2) In the second modification, a cartridge of Type 1 and a cartridge of Type 3 with a nominal life of 50,000 sheets are used. As for the transition of the curve γ, in the same manner as in Table 3, the image density control is performed every 2400 sheets in Type 3. In this modification, in addition to the difference in the toner filling amount, Type 1 and Type 3 are different in the surface layer material of the photosensitive drum 1. That is, the photosensitive drum 1 with a material that easily wears on the surface layer is attached to Type 1, and the photosensitive drum 1 with a material that does not easily wear on the surface layer is attached to Type 3. In such a cartridge of Type 3, in addition to the large amount of toner filling, the photosensitive drum 1 is not easily worn, so that the drop in the drum potential after charging is slower than that of Type 1, and the change in the curve γ is also slower. Therefore, when Type 1 and Type 3 are mixed, the image density control can be performed at both timings, every 1000 sheets for Type 1 and every 2400 sheets for Type 3, to increase the frequency of the image density control, and it becomes possible to reproduce more accurate colors.

[0081] The difference in the photosensitive drum 1 may be not only the difference in the material of the surface layer, but also the difference in the film thickness of the surface layer or the difference in the susceptibility to photodegradation. In any case, as long as there is a difference in the rate of change of the curve γ, this embodiment can be applied. Also, in this embodiment, the image density control is performed periodically, but this is not limiting and may be performed irregularly depending on the timing at which γ2 is reached. Also, the execution timing may be determined using tag information in the process cartridge.

[0082] (Variation 3) In the second modification, a Type 1 cartridge and a Type 3 cartridge with a nominal life of 50,000 sheets are also used. As with Table 3, the image density control is performed every 2,400 sheets for Type 3 in terms of the progression of the curve γ. In this modification, in addition to the difference in the toner loading amount, Types 1 and 3 each have a different developing roller 17. That is, the developing roller 17 of Type 6 has a lower hardness than the developing roller 17 of Type 1. In such a Type 6 cartridge, the toner loading amount is large and the hardness of the developing roller 17 is low, so that the deterioration of developing roller filming is suppressed, and therefore the change in the curve γ is slower than that of Type 1.

[0083] Therefore, in this embodiment, when Type 1 and Type 3 are mixed, image density control is performed at either every 1,000 sheets for Type 1 or every 2,400 sheets for Type 3. This increases the frequency of image density control, making it possible to reproduce colors more accurately.

[0084] In this embodiment, the image density control is periodically performed. However, the present invention is not limited to this. It may be performed irregularly depending on the timing. Also, the execution timing may be determined using tag information on the process cartridge. As shown in the above modified examples, the nominal life of a cartridge is determined by factors such as the material and structure of each component in addition to the toner filling amount. In any case, however, by performing image density control at a timing appropriate for each cartridge with a different life, it becomes possible to accurately reproduce colors.

[0085] [Example 3] In the third embodiment, a case will be described in which only the image density control timing of a cartridge having the shortest nominal life among a plurality of process cartridges is used as a trigger for performing image density control.

[0086] An example of control in this embodiment will be described with reference to FIG. 14. The same symbols as in FIG. 11 are used. In the figure, the numbers enclosed in boxes for Type 1 and Type 2 indicate the number of printed sheets after the previous calibration (or installation), and are reset to 0 every 1000 sheets for Type 1 and every 2000 sheets for Type 2. After starting, a new Type 2 is installed at timing P1 when 400 sheets have been printed. In this case, at timing P2 after 600 sheets have been printed since the installation of Type 2, the number of printed sheets for Type 1 reaches 1000 sheets, and the first image density control is performed. In this embodiment, the number of printed sheets for Type 2 is also reset.

[0087] Then, at timing P3 after 1000 sheets have been printed since timing P2, the number of printed sheets after resetting Type 1 becomes 1000 sheets, and a second image density control is performed. In this embodiment, the number of printed sheets is also reset for Type 2. Then, at timing P4 after 1000 sheets have been printed since timing P3, a third image density control is performed.

[0088] In this embodiment, only the image density control timing for Type 1, which has the fewest number of printed sheets before reset among the process cartridges mounted in the image forming apparatus 100, is a trigger. That is, in this embodiment, the sheet count for Type 2 never reaches 2000 sheets. With this type of control, calibration is performed according to the shortest cycle, so a sufficient number of calibrations can be obtained. Furthermore, in this embodiment, the number of calibrations is never excessive.

[0089] [Example 4] Next, a sixth embodiment of the present invention will be described. Note that a description of parts that overlap with the above-mentioned embodiments will be omitted. In this embodiment, the image density control method is different from the above-mentioned embodiments.

[0090] In the above embodiment, a toner patch is formed on the intermediate transfer belt, and the image density and gradation are adjusted using the results of measuring the toner patch by the density sensor 41. In contrast, the controller 72 in this embodiment obtains calculation parameters for image density control stored in advance in the ROM 74 of the image forming apparatus 100, and adjusts the image density and gradation using these calculation parameters. These calculation parameters are obtained, for example, at the product development stage by performing machine learning using temperature and humidity information, the number of prints, cartridge life information, toner amount and member information in the cartridge (type of charging roller and developing roller), etc.

[0091] By using these calculation parameters to execute image density control, there is no need for a series of operation times such as patch formation on the intermediate transfer belt and measurement by a density sensor, and image density control can be completed in just the calculation processing time.

[0092] With this method, when process cartridges with different life spans are mixed within the same image forming device, it is possible to maintain high color reproducibility without increasing downtime for users, even if the frequency of image density control increases.

[0093] As described above, according to the method of each embodiment, even when process cartridges with different life settings are mounted in the same image forming apparatus, an image forming apparatus capable of correct color adjustment can be provided. That is, when cartridges with different lifespans are mounted in the same image forming apparatus, the calibration frequency can be increased by performing image density control according to each lifespan, so that color reproducibility can be maintained. Although the embodiment has been described with respect to a case where there are two types of lifespan settings, the number of lifespan settings is not limited to this. Even when cartridges with three or more lifespan settings are mixed, it is possible to maintain color reproducibility by performing calibration according to each lifespan. Although the configurations that cause the cartridge lifespans to differ in each embodiment are different, these configurations can be arbitrarily combined in an actual cartridge.

[0094] [Configuration 1] an image carrier on whose surface an electrostatic latent image is formed by exposure based on image data; and a developer carrier on which the electrostatic latent image is developed with a developer to form a developer image; an image forming apparatus capable of simultaneously mounting a plurality of cartridges each having a developer storage chamber, wherein each of the plurality of cartridges has a usable life set; an intermediate transfer body onto which the developer images formed by the plurality of cartridges are transferred; a detection means for irradiating the developer image transferred to the intermediate transfer body with light, detecting reflected light, and outputting information regarding the reflected light; A control unit; Equipped with The control unit is an image density control is performed to control an image density when the developer image is formed based on a value of the image data and information about the reflected light; When a first cartridge having a first lifespan set and a second cartridge having a second lifespan set different from the first lifespan are simultaneously mounted in the image forming device, the image density control is performed more frequently than when only the second cartridge is mounted. 1. An image forming apparatus comprising: [Configuration 2] The image forming apparatus of claim 1, characterized in that, when the first cartridge and the second cartridge are simultaneously installed in the image forming device, the control unit performs the image density control at both a first frequency determined for performing the image density control for the first cartridge and a second frequency determined for performing the image density control for the second cartridge. [Configuration 3] a first frequency determined as a frequency for performing the image density control is set for the first cartridge; a second frequency determined as a frequency for performing the image density control is set for the second cartridge; When the first frequency has a shorter cycle than the second frequency, the control unit performs the image density control at the first frequency when the first cartridge and the second cartridge are simultaneously mounted in the image forming apparatus. 3. The image forming apparatus according to claim 1, wherein the first and second ink cartridges are arranged on a first surface side. [Configuration 4] The frequency of performing the image density control is determined based on the number of prints of the recording material in the image forming apparatus. 4. The image forming apparatus according to claim 2, wherein the first and second electrodes are arranged in a first direction. [Configuration 5] The control unit performs the image density control when a change in gradation characteristics when forming the developer image according to an increase in the number of prints of the recording material in the image forming apparatus exceeds a predetermined allowable range. 3. The image forming apparatus according to claim 2, The first frequency is determined based on the first lifespan of the first cartridge, and the second frequency is determined based on the second lifespan of the second cartridge. 4. The image forming apparatus according to claim 2, wherein the first and second electrodes are arranged in a first direction. [Configuration 6] An image forming apparatus capable of detachably mounting a plurality of cartridges, each of which has an image carrier on whose surface an electrostatic latent image is formed by exposure based on image data, a developer carrier which develops the electrostatic latent image with a developer to form a developer image, and a storage chamber which stores the developer, wherein each of the plurality of cartridges has a set usable life; an intermediate transfer body onto which the developer images formed by the plurality of cartridges are transferred; a detection means for irradiating the developer image transferred to the intermediate transfer body with light, detecting reflected light, and outputting information regarding the reflected light; A control unit; Equipped with The control unit is an image density control is performed to control an image density when the developer image is formed based on the value of the image data and information about the reflected light; When a first cartridge having a first lifespan set and a second cartridge having a second lifespan set different from the first lifespan are simultaneously mounted in the image forming device, the image density control is performed at both a first frequency determined for performing the image density control on the first cartridge and a second frequency determined for performing the image density control on the second cartridge. 1. An image forming apparatus comprising: [Configuration 7] The first cartridge and the second cartridge have different life spans based on the difference in the amount of developer contained in the container. 7. The image forming apparatus according to claim 1, wherein the image forming apparatus is a multi-layered image forming apparatus. [Configuration 8] The cartridge has a charging means for charging the image carrier, and different life spans are set for the first cartridge and the second cartridge based on the difference in at least one of roughness and hardness of the charging means. 7. The image forming apparatus according to claim 1, wherein the image forming apparatus is a multi-layered image forming apparatus. [Configuration 9] The cartridge has a charging means for charging the image carrier, and the first cartridge and the second cartridge have different life spans based on the difference in layer structure of the charging means. 7. The image forming apparatus according to claim 1, wherein the image forming apparatus is a multi-layered image forming apparatus. [Configuration 10] The first cartridge and the second cartridge have different life spans based on at least one of the material of the surface layer of the image carrier, the film thickness of the surface layer, and the susceptibility of the surface layer to photodegradation. 7. The image forming apparatus according to claim 1, wherein the image forming apparatus is a multi-layered image forming apparatus. [Configuration 11] The first cartridge and the second cartridge have different life spans based on the difference in at least one of roughness and hardness of the developer carrying body. 7. The image forming apparatus according to claim 1, wherein the image forming apparatus is a multi-layered image forming apparatus. [Configuration 12] The life of the cartridge is the number of printed pages. 7. The image forming apparatus according to claim 1, wherein the image forming apparatus is a multi-layered image forming apparatus. [Configuration 13] 7. The image forming apparatus according to claim 1, wherein the life of the cartridge is expressed in units based on the time the cartridge is used. [Configuration 14] The cartridge is provided with a memory for storing information related to determining the frequency of performing the image density control. 7. The image forming apparatus according to claim 1, wherein the image forming apparatus is a multi-layered image forming apparatus. [Configuration 15] The control unit obtains an image density of the developer image based on intensity information of the reflected light, obtains gradation characteristics when forming the developer image based on a value of the image data and the image density, and performs the image density control so that the gradation characteristics become target gradation characteristics. 7. The image forming apparatus according to claim 1, wherein the image forming apparatus is a multi-layered image forming apparatus. [Explanation of symbols]

[0095] 1: photosensitive drum, 4: developing roller, 7: process cartridge, 10: toner, 41: density sensor, 72: controller, 100: image forming apparatus

Claims

1. An image carrier on which an electrostatic latent image is formed on its surface by exposure based on image data, A developer carrier, which develops the electrostatic latent image with a developer to form a developer image, A storage chamber for containing the developer, An image forming apparatus capable of simultaneously mounting multiple cartridges, each having the following: Each of the aforementioned cartridges has a set usable lifespan. An intermediate transfer body onto which the developer image formed by the plurality of cartridges is transferred, A detection means that irradiates light onto the developer image transferred to the intermediate transfer medium, detects the reflected light, and outputs information regarding the reflected light, Control unit and Equipped with, The control unit performs image density control, which controls the image density when forming the developer image, based on the image data values ​​and the information regarding reflected light. The image forming apparatus is characterized in that, when a first cartridge with a set first lifespan and a second cartridge with a second lifespan different from the first lifespan are simultaneously installed in the image forming apparatus, the frequency of image density control is increased compared to when the first cartridge is not installed and only the cartridge with the second lifespan is installed.

2. The image forming apparatus according to claim 1, characterized in that, when the first cartridge and the second cartridge are installed in the image forming apparatus at the same time, the control unit performs the image density control at both a first frequency determined to be performed for the first cartridge and a second frequency determined to be performed for the second cartridge.

3. The first cartridge is set to a first frequency determined to perform the image density control, The second cartridge is configured with a second frequency determined to perform the image density control. If the period corresponding to the first frequency is shorter than the period corresponding to the second frequency, the control unit shall, when the first cartridge and the second cartridge are installed in the image forming apparatus at the same time, perform the image density control at the first frequency. The image forming apparatus according to claim 1, characterized by...

4. The image forming apparatus according to claim 2 or 3, characterized in that the frequency of performing the image density control is determined based on the number of prints of the recording material in the image forming apparatus.

5. The image forming apparatus according to claim 2, characterized in that the control unit performs image density control before the change in the gradation characteristics when forming the developer image, in accordance with the increase in the number of prints of the recording material in the image forming apparatus, exceeds a predetermined allowable range.

6. The image forming apparatus according to claim 2 or 3, characterized in that the first frequency is determined based on the first lifespan of the first cartridge, and the second frequency is determined based on the second lifespan of the second cartridge.

7. An image carrier on which an electrostatic latent image is formed on its surface by exposure based on image data, A developer carrier, which develops the electrostatic latent image with a developer to form a developer image, A storage chamber for containing the developer, An image forming apparatus having multiple cartridges, each having a certain feature, which can be attached and detached, Each of the aforementioned cartridges has a set usable lifespan. An intermediate transfer body onto which the developer image formed by the plurality of cartridges is transferred, A detection means that irradiates light onto the developer image transferred to the intermediate transfer medium, detects the reflected light, and outputs information regarding the reflected light, Control unit and Equipped with, The control unit performs image density control, which controls the image density when forming the developer image, based on the values ​​of the image data and the information regarding the reflected light. The image forming apparatus is characterized in that, when a first cartridge having a set first lifespan and a second cartridge having a set second lifespan different from the first lifespan are installed in the image forming apparatus at the same time, the image density control is performed at both a first frequency determined for the first cartridge and a second frequency determined for the second cartridge.

8. The image forming apparatus according to claim 1 or 7, characterized in that the first cartridge and the second cartridge have different lifespans based on the different amounts of developer contained in the storage chamber.

9. The cartridge has a charging means for charging the image carrier, The image forming apparatus according to claim 1 or 7, characterized in that different lifespans are set for the first cartridge and the second cartridge based on the difference in at least one of the roughness and hardness of the charging means.

10. The cartridge has a charging means for charging the image carrier, The image forming apparatus according to claim 1 or 7, characterized in that different lifespans are set for the first cartridge and the second cartridge based on the different layer structures of the charging means.

11. The image forming apparatus according to claim 1 or 7, characterized in that the first cartridge and the second cartridge have different lifespans based on differences in at least one of the following: the material of the surface layer of the image carrier, the thickness of the surface layer, and the susceptibility of the surface layer to photodegradation.

12. The first cartridge and the second cartridge have the coarseness and hardness of the developer carrier. The image forming apparatus according to claim 1 or 7, characterized in that different lifespans are set based on at least one of the following differences.

13. The image forming apparatus according to claim 1 or 7, characterized in that the lifespan of the cartridge is the number of printed pages.

14. The image forming apparatus according to claim 1 or 7, characterized in that the lifespan of the cartridge is expressed in units based on the time the cartridge has been used.

15. The image forming apparatus according to claim 1 or 7, characterized in that the cartridge is provided with a memory for storing information related to determining the frequency of performing the image density control.

16. The control unit acquires the image density of the developer image based on the intensity information of the reflected light, Based on the image data values ​​and the image density, the tonal characteristics when forming the developer image are obtained. The image forming apparatus according to claim 1 or 7, characterized in that the image density control is performed so that the aforementioned gradation characteristics become the target gradation characteristics.

Images