Image forming apparatus

Abstract

The invention relates to an image forming apparatus. There is provided an image forming apparatus having a process cartridge, the process cartridge including: an image bearing member; a developer bearing member that develops an electrostatic latent image with a developer; an accommodating chamber that accommodates the developer; and a memory. The image forming apparatus includes: a detector configured to emit light to a color block of a developer image and detect reflected light; and a controller for performing image density control when controlling an image density to form the developer image based on a value of image data and information on the reflected light. The memory stores information corresponding to an amount of developer in the accommodating chamber, and the controller changes a color patch pattern between a case where the information in the memory is information related to a first amount and a second amount.

Description

Technical Field

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

[0002] As an image forming apparatus such as a laser beam printer, an in-line color type image forming apparatus is known, which includes a plurality of photosensitive drums, i.e., image bearing members, linearly arranged in the rotational direction of an intermediate transfer member. In such an image forming apparatus, a process cartridge type is generally used, in which a process cartridge integrating an image bearing member, a developing unit, and a toner accommodating unit is removably mounted in a main unit of the image forming apparatus. In addition, such an image forming apparatus can be provided with a plurality of process cartridges having a plurality of service life settings. A user selects and purchases any process cartridge having a set service life considering price and the like, and installs these cartridges in the image forming apparatus. In some cases, process cartridges having different service lives depending on color can be installed.

[0003] By performing density control (calibration) according to the degree of use of the process cartridge in such an image forming apparatus, colors can be adjusted. Japanese Patent Application Laid-Open No. 2003-270901 discloses a process cartridge type image forming apparatus capable of printing in color, in which image density control is performed based on the result of detecting the density of a test image (patch) in order to suppress changes in image density generated as the number of prints increases.

[0004] In addition, Japanese Patent Application Laid-Open No. 2022-064626 proposes a correction method for correcting image forming conditions (such as the correction amounts of gradation and color deviation) according to conditions of a combination between unit identification information stored in a replaceable image forming unit (including a process cartridge) and installation part identification information of an installation part. Summary of the Invention

[0005] Among process cartridges having different service lives as mentioned above, the types of functional components (e.g., rollers) used in each process of charging and developing and the toner filling amount are different. Therefore, the trend of the image gradation characteristics before image density control and the degree of its change tend to be different from each other. However, in the case of an image forming apparatus having the above-mentioned conventional configuration, the image density of each test image (patch) for image density control and the number of test images (the number of patches) are basically determined for each color. Therefore, even if the type (e.g., service life) of each process cartridge is different, the above-mentioned problems have not been considered.

[0006] In view of the foregoing, an object of the present invention is to improve the accuracy of adjustment operations of image density control performed in an image forming apparatus in which a plurality of types of process cartridges are installed.

[0007] The present invention provides an image forming apparatus to which a processing cartridge can be attached,

[0008] wherein the processing cartridge is configured to include: an image bearing member whose surface is exposed based on image data to form an electrostatic latent image on the surface; a developer bearing member that develops the electrostatic latent image with a developer to form a developer image; a storage chamber that stores the developer; and a memory,

[0009] wherein the image forming apparatus includes:

[0010] a detection unit configured to emit light to a color patch of the developer image, detect the reflected light, and output information about the reflected light, and

[0011] a control unit configured to perform image density control on the processing cartridge based on the value of the image data and the information related to the reflected light to control the image density when forming the developer image,

[0012] wherein the memory stores information corresponding to the amount of developer stored in the storage chamber, and

[0013] wherein the control unit controls to change the pattern of the color patch to be used for the image density control between a case where the information in the memory is first information and a case where the information is second information, the case where the information in the memory is first information corresponds to a case where the amount of developer is a first amount, the case where the information is second information corresponds to a case where the amount of developer is a second amount, and the second amount is different from the first amount.

[0014] According to the present invention, it is possible to improve the accuracy of adjustment operations of image density control performed in an image forming apparatus in which a plurality of types of processing cartridges are installed.

[0015] Further features of the present invention will become clear from the following description of exemplary embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic cross-sectional view depicting the configuration of an image forming apparatus according to Embodiment 1;

[0017] Figure 2 is a schematic cross-sectional view depicting the configuration of a developing device and a processing cartridge according to Embodiment 1;

[0018] Figure 3 is a control block diagram of the image forming apparatus according to Embodiment 1;

[0019] Figure 4 is a diagram depicting the configuration of a concentration sensor;

[0020] Figure 5 is a diagram for describing the characteristics of a concentration sensor;

[0021] Figure 6 is a diagram for describing the normalization correction of the output of a concentration sensor;

[0022] Figure 7 is a flowchart of an image concentration control method;

[0023] Figure 8 is a diagram for describing the color patch pattern on an intermediate transfer belt;

[0024] Figure 9 is a diagram for describing another example of the color patch pattern on an intermediate transfer belt;

[0025] Figure 10 is a diagram for describing image gradient control;

[0026] Figure 11 is a diagram for describing the transition of curve γ;

[0027] Figure 12A and Figure 12B is a diagram indicating each transition of the concentration gradient of a process cartridge having different service lives; and

[0028] Figure 13 is a diagram indicating an example of the transition of the concentration gradient according to Embodiment 2. Detailed Description of the Invention

[0029] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The dimensions, materials, shapes, and relative positions of the constituent elements to be described in the embodiments are not intended to limit the scope of the invention only to these descriptions, unless otherwise specified. In the following description, the materials, shapes, etc. of the components described once are the same as those initially described, unless otherwise specified. For configurations and steps that are not particularly described or explained, known techniques or conventional techniques in the technical field can be applied. Repeated descriptions may be omitted.

[0030] Embodiment 1

[0031] First, reference will be made to Figure 1 and Figure 2 for the schematic cross-sectional views therein and Figure 3The control block diagram in [description] shows the overall configuration of the electrophotographic type image forming apparatus 100. The image forming apparatus 100 of Embodiment 1 is an in-line type and intermediate transfer type full-color laser printer. 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 unit 110 from a personal computer ( Figure 3 PC 120 in [description]) connected to be communicable with the image forming apparatus main unit 110, or a host device (e.g., an image reader) connected to the image forming apparatus main unit 110.

[0032] The plurality of image forming units of the image forming apparatus 100 include first, second, third, and fourth image forming units SY, SM, SC, and SK that respectively form images of each of yellow (Y), magenta (M), cyan (C), and black (K). In Embodiment 1, the first to fourth image forming units SY, SM, SC, and SK are linearly arranged along the intermediate transfer belt 31. The image forming unit S includes a primary transfer roller 32 and a process cartridge 7.

[0033] In Embodiment 1, except for the color of the image to be formed, the configurations and operations of the first to fourth image forming units are substantially the same. Therefore, unless distinction is required, the subscripts Y, M, C, and K attached to the reference signs to indicate the colors for which the elements are used will be omitted, and the [configurations and operations] will be generally described.

[0034] In Embodiment 1, as a plurality of image bearing members, the image forming apparatus 100 includes four photosensitive drums 1 arranged along the intermediate transfer belt 31. Figure 2 is a schematic cross-sectional view of the process cartridge 7 in the longitudinal direction (rotation axis direction) of the photosensitive drum 1. The four photosensitive drums 1 have the same configuration. Figure 3 is a block diagram indicating the control block of the image forming apparatus 100.

[0035] The photosensitive drum 1 is rotated in the direction of arrow A by a drive source 140 (drive unit) ( Figure 1 and Figure 2Rotation drive in the counterclockwise direction (in the figure). A charging roller 2 (charging member) is deployed around the photosensitive drum 1. The charging roller 2 (charging member) is a charging unit that uniformly charges the surface of the photosensitive drum 1 while rotating in the direction of arrow J. The charging roller 2 can be rotated by the rotation of the photosensitive drum 1 or can be rotationally driven by a drive source 140. A developing roller 17 and a cleaning blade 6 are deployed around the photosensitive drum 1. The developing roller 17 is a developing unit for developing an electrostatic latent image into a toner image and constitutes the developing unit 4 (developing device). The cleaning blade 6 is a cleaning unit for removing toner (untransferred toner) remaining on the surface of the photosensitive drum 1 after transfer. The cleaning blade 6 is in contact with the surface of the photosensitive drum 1, and this part [in contact with the surface of the photosensitive drum 1] is called the "contact part". The processing cartridge 7 will be described in detail later. The recording material 12 is loaded in the recording material holding unit 44, conveyed on the conveyance path R by a pickup roller, and reaches the section between the secondary transfer roller 33 and the secondary transfer opposing roller 38.

[0036] In Embodiment 1, the photosensitive drum 1, the charging roller 2 (processing unit acting on the photosensitive drum 1), the developing unit 4, and the cleaning blade 6 are integrated into a cartridge, and this cartridge becomes the processing cartridge 7. The processing cartridge 7 is removable from the image forming apparatus 100. In Embodiment 1, the processing cartridges 7 for each color are identical in main constituent elements. The processing cartridges 7 for each color differ in that they respectively accommodate toner (developer) of each color (yellow (Y), magenta (M), cyan (C), or black (K)).

[0037] Processing cartridge

[0038] The overall configuration of the processing cartridge 7 that can be installed in the image forming apparatus 100 of Embodiment 1 will be continued to be described. In Embodiment 1, except for the type (color) of the accommodated developer, the basic configuration and operation of the processing cartridges 7 for each color are exactly the same. The processing cartridge 7 includes: a photosensitive unit 13 including the photosensitive drum 1 etc., and a developing unit 4 including the developing roller 17 etc.

[0039] The photosensitive unit 13 includes a cleaning frame 14, and the cleaning frame 14 is a frame that supports various elements in the photosensitive unit 13. On the cleaning frame 14, the photosensitive drum 1 is rotatably mounted via a bearing (not shown). When the driving force of a driving motor (drive source 140) is transmitted to the photosensitive unit 13, the photosensitive drum 1 is rotationally driven in the direction of arrow A (clockwise direction) according to the image forming operation. In Embodiment 1, the photosensitive drum 1, which is the center of the image forming process, is an organic photosensitive member, in which functional films (undercoat layer, charge generation layer, charge transport layer) are sequentially coated on the outer peripheral surface of an aluminum cylinder.

[0040] In addition, a cleaning blade 6 and a charging roller 2 are disposed on the photosensitive unit 13 so as to contact the outer peripheral surface of the photosensitive drum 1. The untransferred toner removed from the surface of the photosensitive drum 1 by the cleaning blade 6 falls due to gravity and is stored in the cleaning frame 14.

[0041] The roller portion of the charging roller 2 (charging unit) made of conductive rubber is crimped to the photosensitive drum 1, and the charging roller 2 rotates as the photosensitive drum 1 rotates. In the charging step, a predetermined DC voltage is applied from the charging power source 142d to the core metal of the charging roller 2, whereby a uniform dark area potential (Vd) is formed on the surface of the photosensitive drum 1. The spot pattern of the laser beam emitted from the scanner unit 30 according to the image data exposes the photosensitive drum 1, and in the exposed portion, the charge on the surface is dissipated by the carriers from the carrier generation layer, and the potential drops. As a result, an electrostatic latent image is formed on the photosensitive drum 1, where the exposed portion has a predetermined bright area potential (Vl) and the unexposed portion has a dark area potential (Vd).

[0042] On the other hand, the developing unit 4 includes a developing roller 17 (developer carrier member), a developing blade 19, a toner supply roller 18 (supply unit), and a toner storage chamber 16. The toner storage chamber 16 is a chamber for storing the toner 15. The toner 15 used in the first embodiment is a non-magnetic single-component spherical toner, which is usually charged to have a negative polarity and has a particle diameter of 7 μm. On the surface of the toner 15, silica particles having a particle diameter of 20 nm are added as external additives (external addition particles) of the toner.

[0043] The developing blade 19 faces and contacts the developing roller 17, controls the coating amount of the toner supplied by the toner supply roller 18, and provides a change to the developing roller 17. The developing blade 19 is a thin plate member, and the contact pressure is generated using the spring elasticity of the thin plate, whereby the surface of the developing blade 19 contacts the toner 15 and the developing roller 17. When the toner 15 is charged by triboelectrification generated between the developing blade 19 and the developing roller 17, the layer thickness of the toner 15 is controlled at the same time. In the first embodiment, a predetermined voltage is applied from the blade voltage power source to the developing blade 19 to stabilize the toner coating.

[0044] The developing roller 17 and the photosensitive drum 1 rotate such that the respective surfaces move in the same direction at the relative portion N1 (contact portion) (the photosensitive drum 1 moves in the direction of arrow A, and the developing roller 17 moves in the direction of arrow G). In the first embodiment, the toner 15 charged to a negative polarity by triboelectrification for the predetermined DC voltage applied to the developing roller 17 from the developing power source 142f is transferred only to the bright area potential portion due to the potential difference at the relative portion N1 where the photosensitive drum 1 is contacted, whereby the electrostatic latent image is developed.

[0045] The toner supply roller 18 is deployed to form a predetermined clamping portion N2 on the circumferential surface of the developing roller 17. The toner supply roller 18 rotates in the direction of arrow E ( Figure 2 counterclockwise in the figure). The toner supply roller 18 of Embodiment 1 is an elastic sponge roller, in which a foam body is deployed 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 intrusion amount, and rotate in opposite directions at the clamping portion N2 to move. Due to this rotation operation, toner is supplied to the developing roller 17 through the toner supply roller 18, and the residual toner remaining on the developing roller 17 after development is scraped off.

[0046] A toner stirring member 20 is deployed in the toner storage chamber 16. The toner stirring member 20 includes a sheet-shaped member that rotates in the direction of arrow H to stir the toner 15 accommodated in the toner storage chamber 16 and transfer the toner 15 to the upper part of the toner supply roller 18. In Embodiment 1, the outer diameters of both the developing roller 17 and the toner supply roller 18 are φ20, and the intrusion amount of the toner supply roller 18 into the developing roller 17 is set to 1.5 mm. In Embodiment 1, a predetermined DC voltage applied to the developing roller 17 is applied from the developing power source 142f to the toner supply roller 18, and due to this potential difference, the toner is transferred only to the bright area potential portion at the developing unit in contact with the photosensitive drum 1, whereby the electrostatic latent image is developed.

[0047] A memory m composed of a non-volatile memory or the like is deployed in the process cartridge 7. The memory m stores information regarding the gradation and quantity of toner color patches for performing image density control. This information is related to the amount of developer used by the controller 72 to perform the adjustment operation for image density control. Here, the information regarding the gradation and quantity of toner color patches for performing image density control is, for example: at least one of the nominal service life, the toner filling amount, and the roughness and hardness of the charging roller 2; at least one of the information regarding the layer structure of the charging roller 2 and the roughness and hardness of the developing roller 17; at least one of the material, film thickness, and susceptibility to photographic deterioration of the surface layer of the photosensitive drum 1; and so on. The predetermined gradation and quantity of toner color patches for calibration set for this cartridge can be stored.

[0048] The memory m is configured to be communicable with the controller 72 (control unit) of the image forming apparatus 100 shown in Figure 1 either non-contactingly or via electrical contacts. In other words, the controller 72 can read information from the memory m and write information into the memory m. In Figure 2In this case, the memory m is installed in the photosensitive unit 13, but it may be installed in the developing unit 4. Additionally, the memory m may be installed in both the photosensitive unit 13 and the developing unit 4. In such a case, information regarding the photosensitive drum 1 and the charging roller 2 is stored in the memory m on the photosensitive unit 13 side, and information regarding the developing roller 17 and the toner 15 is stored in the memory m on the developing unit 4 side.

[0049] In Embodiment 1, for each process cartridge 7 of each color, there are multiple types of cartridges with different set service lives. Here, the service life of the process cartridge 7 refers to the value indicating the period during which the cartridge can be used, and is typically set according to the toner capacity. In the case where the service life is set based on the number of printed sheets, the number of printable sheets fed when printing a typical image using the toner accommodated in the process cartridge 7 can be regarded as the service life, or a value with a margin can be set as the service life. Additionally, the service life is typically expressed by the number of printable sheets of the recording material, but it can be expressed by another unit based on the time the process cartridge 7 is used (such as the number of days or hours the process cartridge 7 is used).

[0050] For the process cartridge 7, the manufacturer has set a nominal service life. Here, it is assumed that there are 2 types: a process cartridge 7 with a relatively short service life (10,000 sheets); and a process cartridge 7 with a relatively long service life (50,000 sheets).

[0051] Additionally, as Figure 1 shown, the image forming apparatus 100 includes a scanner unit 30, which is an exposure unit (exposure device) for emitting a laser beam onto the photosensitive drum 1 based on image information and thereby forming an electrostatic latent image. Further, the image forming apparatus 100 includes an intermediate transfer belt 31 (intermediate transfer unit) facing four photosensitive drums 1 for transferring the toner image on the photosensitive drum 1 to the recording material 12.

[0052] As Figure 1 shown, the intermediate transfer belt 31 formed of an endless belt contacts all the photosensitive drums 1 and rotates (moves) in the direction of arrow B ( Figure 1 counterclockwise in this case). The intermediate transfer belt 31 bypasses a plurality of support members, namely, a tension roller 37, a secondary transfer opposing roller 38 (which also functions as a driving roller), and a driven roller (not shown). As a primary transfer unit (transfer member), four primary transfer rollers 32 are arranged on the inner peripheral surface side of the intermediate transfer belt 31 so as to face each photosensitive drum 1. Then, a voltage having a polarity opposite to the normal charging polarity of the toner is applied from the primary transfer voltage power source 142a to the primary transfer rollers 32. Thereby, the toner image on the photosensitive drum 1 is transferred onto the intermediate transfer belt 31.

[0053] In addition, as the secondary transfer unit, the secondary transfer roller 33 is disposed on the outer peripheral surface side of the intermediate transfer belt 31 so as to face the secondary transfer counter roller 38. Then, a voltage having a polarity opposite to the normal charging polarity of the toner is applied from the secondary transfer voltage power source 142b to the secondary transfer roller 33. Thereby, the toner image on the intermediate transfer belt 31 is transferred onto the recording material 12.

[0054] As Figure 3 indicated in, the image forming apparatus 100 includes a power source 142. According to an instruction from the controller 72, the power source 142 serves as the above-mentioned primary transfer voltage power source 142a and secondary transfer voltage power source 142b, as well as a blade voltage power source 142c which will be described later. In Figure 3 the example in, one power source 142 serves as the primary transfer voltage power source 142a, secondary transfer voltage power source 142b, blade voltage power source 142c, a charging power source 142d for applying a voltage to the charging roller 2, a supply power source 142e for applying a voltage to the toner supply roller 18, and a developing power source 142f for applying a voltage to the developing roller 17. However, the power source configuration is not limited thereto, and different power sources may be deployed for each component. Additionally, a common power supply device may be used for multiple power sources according to required functions, performances, etc. For example, a common power supply device may be used for the primary transfer voltage power source 142a and the secondary transfer voltage power source 142b.

[0055] When forming an image, the surface of the photosensitive drum 1 is uniformly charged by the charging roller 2. Then, an electrostatic latent image according to the image information is formed on the photosensitive drum 1 by a laser beam emitted from the scanner unit 30 according to the image information. Then, the developing unit 4 supplies a developer to the electrostatic latent image, whereby a toner image (developer image) is developed on the photosensitive drum. The developed toner image is then transferred onto the intermediate transfer belt 31 (primary transfer) by the function of the primary transfer roller 32.

[0056] For example, in the case of forming a full-color image, the above-mentioned processes are sequentially performed in the first to fourth image forming units SY, SM, SC, and SK such that toner images of each color are superimposed on the intermediate transfer belt 31, thereby forming a four-color toner image. The four-color toner image on the intermediate transfer belt 31 is then collectively transferred onto the recording material 12 (secondary transfer). The toner image is then fixed to the recording material 12 by applying heat and pressure to the recording material 12 by the fixing device 34.

[0057] The primary transfer residual toner remaining on the photosensitive drum 1 after the primary transfer step is removed and collected by the cleaning blade 6. The secondary transfer residual toner remaining on the intermediate transfer belt 31 after the secondary transfer step is cleaned by the intermediate transfer belt cleaning device 39.

[0058] AsFigure 3 As indicated, the image forming apparatus 100 includes a controller 72. The controller 72 is an information processing device including computing resources such as a CPU 73, a ROM 74, and a RAM 75, and serves as a control unit that operates according to a program or instructions via a touch panel of the PC 120 or the image forming apparatus main unit 110. The controller 72 controls, for example, each constituent element in the image forming apparatus, such as a drive source 140 (e.g., a motor), a power supply 142, a scanner unit 30, and a density sensor 41.

[0059] The image forming apparatus 100 of Example 1 includes a density sensor 41 (detection unit). The density sensor 41 is an optical sensor that detects the amount of toner and is used to control the image density for calibration. The density sensor 41 is disposed to face the intermediate transfer belt 31, as Figure 1 shown. The density sensor 41 measures the intensity information of reflected light corresponding to the density of the toner color patch formed on the surface of the intermediate transfer belt 31.

[0060] Figure 4 An example of the configuration of the density sensor 41 is indicated. The density sensor 41 includes a light emitting element 51, light receiving elements 52 (a first light receiving element 52a and a second light receiving element 52b), and a processing circuit (not shown) such as an IC that processes the received light data, and these constituent elements are housed in a holder. The density sensor 41 is configured such that information can be sent to / received from the controller 72. For the light emitting element 51, for example, an infrared light emitting element such as an LED can be used. On the other hand, for the light receiving elements 52, a photodiode, a CdS element, etc. can be used.

[0061] The light emitting element 51 emits light toward the intermediate transfer belt 31. The first light receiving element 52a detects the intensity of the directly reflected light from the toner color patch 64, and the second light receiving element 52b detects the intensity of the diffusely reflected light from the toner color patch 64. By detecting both the directly reflected light intensity and the diffusely reflected light intensity, the density of the toner color patch 64 can be detected from high density to low density. To couple the light emitting element 51 and the light receiving elements 52, optical elements (not shown) such as lenses can be used.

[0062] In Example 1, the intermediate transfer belt 31 is a single-layer resin belt formed of polyimide, and its circumference is 880 mm. To adjust the resistance of the belt, an appropriate amount of carbon particles have been dispersed in the resin, and the surface color of the belt is black. In addition, the surface of the intermediate transfer belt 31 is very smooth and shiny, and the glossiness is approximately 100% (measured by a gloss meter IG-320 manufactured by Horiba Ltd.).

[0063] In a state where the surface of the intermediate transfer belt 31 is exposed (toner amount is zero), mainly the first light receiving element 52a of the density sensor 41 detects the reflected light. This is because the surface of the intermediate transfer belt 31 has gloss. On the other hand, when a toner image is formed on the intermediate transfer belt 31, as the density (toner amount) of the toner image increases, the positive reflection output gradually decreases. This is because, since the toner covers the surface of the belt, the positive reflected light from the surface of the belt decreases.

[0064] Figure 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 positive reflection output is indicated. In Figure 5 the vertical axis indicates the output value voltage of the density sensor 41, and the horizontal axis indicates the image density (corresponding to the toner amount). The maximum output value voltage of the density sensor 41 used in Example 1 is 5V.

[0065] The image forming apparatus 100 of Example 1 uses the output value (background output value) of the intermediate transfer belt 31 in a state where no toner is present to correct the output of the density sensor 41. Specifically, the output value of the toner patch is normalized (toner patch output / background output) by the background output value of the intermediate transfer member ( Figure 5 the output value when the image density is zero in ). Figure 6 indicates the sensor output characteristics after normalization. By performing normalization, even when the gloss of the intermediate transfer belt 31 decreases due to contamination, scratches, etc., the same correction can be performed.

[0066] The method described above for correcting the output of the density sensor 41 by normalizing the toner patch output using the background output is a known method and has been used in many color image forming apparatuses. For the density sensor 41, any conventional configuration for detecting density can be used. The wavelength of the light is not limited to infrared light.

[0067] Image density control common to each embodiment

[0068] Next, the image density control using the toner patch in each embodiment will be described with reference to the flowchart in Figure 7 The image density control in the image forming apparatus 100 in the present invention is an image gradation control for adjusting the density gradation characteristics of the image. Each step of the process is executed by the controller 72 referring to the information stored in the memory m of each process cartridge 7, the output value of the density sensor 41, etc.

[0069] Image density control

[0070] Image density control can be performed at any timing, and can be performed periodically, or when a change in the expected image density is anticipated. In Embodiment 1, even for a plurality of different types of process cartridges 7, the formation of toner patches for this image density control is appropriately controlled.

[0071] First, in step S101, the controller 72 reads the information stored in the memory m of each process cartridge 7. Then, in step S102, background measurement of the intermediate transfer belt 31 is performed (i.e., density measurement in a state where no toner is placed). Here, the controller 72 rotates and moves the intermediate transfer belt 31 using the drive source 140 so that a predetermined measurement position on the intermediate transfer belt 31 to be the target of density measurement sequentially enters the measurement range of the density sensor 41. The measurement position and the number of points are set to be the same as those of the toner patches for image density control.

[0072] Then, in step S103, the controller 72 controls the image forming unit and forms toner patches. A reference Figure 8 will describe an example of the 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 deployed at 2 mm intervals at positions corresponding to the position of the density sensor 41.

[0073] In Embodiment 1, based on the information read in step S101 and stored in the memory m of each process cartridge, the gradation and the number of patches at the time of performing image control are changed. Figure 8 The patch pattern in is an example of a case where the maximum number of toner patches is formed in one execution of the image density control in Embodiment 1. The patches 88 include a yellow patch 88Y, a magenta patch 88M, a cyan patch 88C, and a black patch 88K. Each of the patches 88Y to 88K of each color includes 8 patches, and the image print ratio (density gradation) thereof is changed in 8 steps (hereinafter 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.

[0074] Each patch 88 and its print ratio are set as follows.

[0075] Y1, M1, C1, K1 = 12.5%

[0076] Y2, M2, C2, K2 = 25%

[0077] Y3, M3, C3, K3 = 37.5%

[0078] Y4, M4, C4, K4 = 50%

[0079] Y5, M5, C5, K5 = 62.5%

[0080] Y6, M6, C6, K6 = 75%

[0081] Y7, M7, C7, K7 = 87.5%

[0082] Y8, M8, C8, K8 = 100%

[0083] The background measurement of the intermediate transfer belt 31 is performed before forming the color patches 88 at the positions where the above-mentioned 32 color patches 88 are formed. For example, the background measurement can be performed one cycle before forming the color patches 88. Additionally, each color patch 88 can be printed using only a single color in order to perform single-color image density control, as described later.

[0084] Figure 9 is another example of the color patch pattern. In this example, 4 color patches 88 are formed for each color. As Figure 9 shown, toner color patches having the same color can be continuously deployed without intervals. For example, changing the number of image density values of the toner color patches in Figure 9 from 4 to 3 is included in the case of changing the number of toner color patches in the present invention.

[0085] The controller 72 rotates the intermediate transfer belt 31 using the drive source 140 of the image forming apparatus 100 so as to sequentially move each color patch forming position to a position facing the image forming unit. Then, controlling the image forming unit, the controller 72 forms toner color patches 88 on the intermediate transfer belt 31 as Figure 8 shown.

[0086] Then, in step S104, the controller 72 controls the positions of the color patches formed on the intermediate transfer belt 31 to sequentially enter the measurement range of the density sensor 41 so that the density sensor 41 detects the amount of reflected light from the toner color patches 88. Then, in step S105, the controller 72 calculates the density of each toner color patch 88. Here, the output value of the toner density of each toner color patch 88 is first normalized by the background output value of the intermediate transfer belt 31 (toner output / background output). This normalization of the color patch output is performed for all color patches 88 using the background output value obtained at the position corresponding to each color patch. Then, the controller 72 converts the normalized value into a density value using a density conversion table. The density conversion table has been previously stored in the ROM 74.

[0087] Then, in step S106, the controller 72 performs image gradation control (gradation correction). The reference Figure 10 will describe this image gradation control. Here, only the gradation correction for cyan will be described, but the same method is also used to correct the gradation for magenta, yellow, and black.

[0088] In Figure 10 it, the horizontal axis indicates image data (e.g., pixel value %), and the vertical axis indicates the concentration detection value of the concentration sensor 41 (the value of the output voltage after normalization correction). Figure 10 The white circle symbols (circles without internal painting) in it indicate the detected concentration values of the concentration sensor 41 for each color patch of C1, C2, C3, C4, C5, C6, C7, and C8. The curve γ passing through each point from C1 to C8 indicates the concentration gradient characteristic in a state where concentration control (gradient correction control) has not been performed. For the image concentration under the gradient when no color patch is formed, the controller 72 calculates the value of the image data by performing spline interpolation so that the line passes through the origin and each point C1 to C8.

[0089] The straight line T indicates the target concentration gradient characteristic of the image concentration control. In the first embodiment, the target gradient characteristic T is determined such that the image data and the concentration are proportional to each other. The gradient characteristic is not limited to a straight line. As indicated by the comparison between the curve γ and the straight line T, in this example, without performing gradient correction, the image is printed such that the image concentration with respect to the image data value becomes lower in the range where the image data value is low, and the image concentration with respect to the image data value becomes higher in the range where the image data value is high. In other words, the image is printed in a color that the user does not expect.

[0090] The curve D indicates the gradient correction table calculated under the control of the first embodiment. The controller 72 calculates the gradient correction table D by determining the symmetric point of the gradient characteristic γ before correction with respect to the target gradient characteristic T. The calculated gradient correction table D is stored in the RAM 75.

[0091] When forming a printed image, the controller 72 corrects the value of the image data with reference to the gradient correction table D, whereby the target gradient characteristic can be obtained. For example, in the range where the image data value is low, the image data value is corrected to be higher using the gradient correction table D. By determining the control value of the image forming apparatus 100 using these corrected image data values, the concentration of the image to be printed can be increased, and the gradient characteristic can be improved to the straight line T.

[0092] The method of image concentration control used here can be any known method for controlling image forming conditions. The image forming conditions are, for example, the spot pattern conditions of the laser beam emitted from the scanner unit according to the image data, the developing conditions (e.g., developing voltage), and the charging conditions (e.g., charging voltage). The controller 72 forms color patches having a plurality of predetermined patterns (e.g., halftone patterns) on the intermediate transfer belt 31, where these image forming conditions are changed in multiple steps, detects the concentration of the color patch pattern, and calculates the image forming conditions to obtain the desired concentration.

[0093] Now, reference will be made to Figure 11 Describe the transition of the change in curve γ when printing an image. Immediately after performing image density control according to the above-mentioned process, the relationship between the image data value and the image density forms a straight line T through correction using the above-mentioned gradient correction table D. However, thereafter, as the number of printed sheets increases, the deviation of the density gradient increases. When the tolerance of the image density is between curve Li_u and curve Li_b, image density control is performed at the timing when the gradient on curve γ extends outside the tolerance, and curve γ is returned to T. Thus, the color reproducibility can be maintained. The above is the description of the image density control (image gradient correction) according to Embodiment 1.

[0094] Example of adjustment operation of image density control

[0095] In Embodiment 1, there are process cartridges 7 with different service lives: a process cartridge with a nominal service life of 10,000 sheets (hereinafter referred to as Type 1, or the first process cartridge 7a. The first service life is set for the first process cartridge 7a); and a process cartridge with a nominal service life of 50,000 sheets (hereinafter referred to as Type 2, or the second process cartridge 7b. The second service life longer than the first service life is set for the second process cartridge 7b). In Embodiment 1, the filling amounts of the toner 15 in Type 1 and Type 2 are different. Specifically, the filling amount of the toner 15 is more in the Type 2 cartridge than in the Type 1 cartridge.

[0096] In a predetermined temperature / humidity environment, the image forming apparatus of Embodiment 1 performs image density control every 1000 sheets in order to maintain color reproducibility. FIGS. 12 and Table 1 indicate the results of the Type 1 and Type 2 process cartridges with different service lives when observing the density states of the toner color patches C1 to C8 for image density control with respect to curves Li_u and Li_b (tolerance) at the timing just exceeding the predetermined number of sheets (1000 sheets). Figure 12A Indicates the results of the Type 1 process cartridge, and Figure 12B Indicates the results of the Type 2 process cartridge, and the toner color patches exceeding the tolerance are indicated by black dots (black-painted circles).

[0097] [Table 1]

[0098]

[0099] As indicated in FIGS. 12 and Table 1, in the type 1 process cartridge with a short service life, a wide range of toner color patches exceed the tolerance, but in the type 2 process cartridge with a long service life, only C2, C3, and C4 with intermediate tones (where the concentration gradient is easily changed) exceed the tolerance. These results are likely because the mixing ratio of the old toner and the new toner in the developing unit is high in the process cartridge with a short service life, but is limited in the process cartridge with a long service life (where the toner is supplied entirely from the developer container).

[0100] Based on these results, in the image forming apparatus of Example 1, as indicated in Table 2, the gradient and the number of toner color patches for image density control preset for each of the type 1 and type 2 process cartridges are stored in the memory m of the process cartridge. In this case, information corresponding to the amount of the developer housed in the housing chamber is stored in the memory m. For example, if the amount of the developer housed in the type 1 cartridge is the first amount, and the amount of the developer housed in the type 2 cartridge is the second amount, then the first information indicating that the amount of the developer is the first amount is stored in the memory of the type 1 cartridge. In the same manner, the second information indicating that the amount of the developer is the second amount is stored in the memory of the type 2 cartridge. Here, only two types of information are used to simplify the description, but various information can be used according to the amount of the developer that can be housed.

[0101] [Table 2]

[0102] Memory m Type 1 Type 2 Gradient of toner color patches ALL C2, C3, C4 Number of toner color patches 8 3

[0103] In the example of Table 2, all the toner color patches are formed in the type 1 process cartridge to simplify the description, but C5 and C8 can be removed therefrom. In the above example, the gradient and the number of the toner color patches are stored in the memory m, but the present invention is not limited thereto. For example, variables for each type of process cartridge can be stored in the memory m, and information such as that in Table 2 can be obtained by performing calculations by referring to the mathematical expressions and coefficients held by the reference controller 72. Additionally, referring to the filling amount and the service life stored in the memory m, the controller 72 can perform control to simply reduce the number of toner color patches in the case where the filling amount is high (the service life is long).

[0104] As described above, in Example 1, the characteristics of the gradient change generated by the predetermined specifications of the process cartridges with different service lives (different toner filling amounts) are used to optimize the adjustment operation of the image density control. In other words, by using the nominal service life (i.e., the toner filling amount) as the information related to the gradient and the number of the toner color patches, compared with the type 1 process cartridge, fewer toner color patches can be used to adjust the image density control in the type 2 process cartridge with a longer service life.

[0105] In the present invention, it is sufficient that the amount of toner for image density control can be changed by controlling the calibration pattern according to the toner filling amount and the service life, and thus the operation can be optimized. As long as such calibration pattern control can be performed, methods other than controlling the number of toner patches can be used. For example, if the filling amount is high, the amount of toner can be adjusted by reducing the surface area of each toner patch. For example, if the toner patch is rectangular, the width of the toner patch can be reduced, or its length can be reduced (the interval between toner patches can be increased) to reduce the surface area of the toner patch. If the toner patch is a shape other than rectangular, the size of the toner patch can be reduced according to the shape.

[0106] In addition, in the case where it is determined that the process cartridge is a high-capacity cartridge, the accuracy of image density control can be improved while maintaining the number of toner patches without reducing the number. For example, in the case of using 8 toner patches for a high-capacity (type 2) process cartridge as indicated in Table 2, the blocks of C2, C3, and C4 are divided into 8 to create 8 toner patches, and thus image density control is performed. In this example, the blocks of C2 to C4 can be divided by a number less than 8 (for example, 5) to create a smaller number of toner patches. Then, in the blocks where image density control is required, the accuracy is improved, but the number of toner patches can be reduced.

[0107] For type 1 and type 2, the gradient of the toner patches can be set to ALL, but the division number can be changed while maintaining the same gradient, such as 8 divisions for type 1 and 7 divisions for type 2.

[0108] The image forming apparatus of Example 1 is not limited to the above. For example, during manufacturing, the tip position of the developing blade in each process cartridge, the sensitivity of the drum included in each process cartridge, etc. can be written in the memory m, so that the conditions of the toner patches are changed according to the change in the gradient characteristics generated by these values. In addition, the conditions of the toner patches can be changed based on the information about the parameters related to the toner. For example, generally, as the intrusion amount of the tip position of the blade increases, the amount of toner taken in by the developing roller increases, and the toner charge amount decreases. Therefore, even a small amount of electrostatic latent image can be developed more easily, and the gradient generally becomes darker. This can be recognized to adjust the image density control. Another example is that even when the light amount is the same during exposure, as the drum sensitivity becomes higher, the amount of change in the surface potential increases, so the gradient generally becomes darker. In addition to the service life, there are various other factors that affect the change in the gradient. Considering these factors, the gradient and number of toner patches can be determined.

[0109] In Embodiment 1, a method of optimizing an adjustment operation for image density control based on information in a memory included in each process cartridge that stores information related to a developing dose for an adjustment operation for image density control is described. As a result, it is possible to suppress the amount of toner consumed for one execution of density control while maintaining quality. As a result, even when the toner filling amount in the process cartridge is the same, the number of printable sheets can be increased, or a lightweight and easy-to-manipulate process cartridge can be provided.

[0110] Embodiment 2

[0111] Embodiment 2 will be described next. A description of parts overlapping with Embodiment 1 will be omitted. In Embodiment 2, even when the image forming apparatus is used in a wider range than in Embodiment 1, it is possible to suppress the amount of toner consumed in one execution of image density control while maintaining quality.

[0112] In Embodiment 1, the characteristics of the gradual change of process cartridges having different service lives (different toner filling amounts) are used, and the adjustment operation for image density control is optimized based on predetermined specifications or information determined during manufacturing. On the other hand, in Embodiment 2, information regarding the operation history of the image forming apparatus is also used to optimize the adjustment operation for image density control, which is different from Embodiment 1. In Embodiment 2, as in Embodiment 1, type 1 and type 2 process cartridges having different service lives will also be used for description.

[0113] Figure 13 The results of the type 2 process cartridge when observing the density states of toner color patches C1 to C8 for image density control with respect to curves Li_u and Li_b (tolerances) at a timing just exceeding a predetermined number (1000 sheets) of sheets are indicated in the same manner as in Embodiment 1. The paper feeding condition of Embodiment 2 different from Embodiment 1 here is that the toner consumption when feeding 1000 sheets is higher. In other words, in Embodiment 2, the printing ratio when feeding sheets is higher than in Embodiment 1. The printing ratio here refers to the ratio of the area where the developer image is formed to the area where an image can be formed on the recording material 12. For example, a solid black image has a printing ratio of 100%, and a white image has a printing ratio of 0%.

[0114] Compared with Figure 12A and Figure 12B compared to Figure 13 Similar to the results of the type 1 process cartridge having a short service life Figure 12A This is because, even when using a process cartridge having a long service life, if the toner consumption during printing is high, the mixing ratio of the old toner and the new toner at the developing unit also becomes high (equivalent to the case of a process cartridge having a short service life), and thus the density gradient changes in a wider gradient range.

[0115] Thus, in Embodiment 2, the gradual change characteristics including the toner consumption amount are detected in advance and stored in the memory m. Then, additionally, the adjustment operation of the image density control is optimized using the information related to the developer consumption amount (e.g., the print ratio, its history) written in the memory m each time printing is executed.

[0116] The controller 72 of Embodiment 2 calculates the print ratio based on the image data for each sheet feed, and changes the gradation and the number of toner patches according to the average print ratio at the timing of the image density control (e.g., when 1000 sheets are fed). For example, if the average print ratio is a predetermined threshold or more, then even when using the type 2 process cartridge with a long service life, the number of toner patches is set to 8 as in the Figure 12A case (the case of type 1). The number of types of the patch patterns is not limited to 2, and the number of toner patches can be gradually changed according to the print ratio.

[0117] In addition, in Embodiment 2, the control can be performed using the integrated value of the consumed toner amount instead of the print ratio. In this case, the controller 72 calculates the consumed toner amount based on the image data and integrates this value each time a sheet is fed. Then, at the timing of the image density control (e.g., when 1000 sheets are fed), the patch pattern is selected such that the number of toner patches increases as the integrated value of the consumed toner amount becomes higher.

[0118] The image forming apparatus of Embodiment 2 is not limited to the above examples, and parameters related to the deterioration of the toner, such as the rotation time, rotation frequency, and surface movement distance of the developing roller 17, can be used. The controller 72 can determine the number and gradation of the toner patches for the image density control based on these parameters according to a predetermined program. The patch pattern is selected such that the number of toner patches increases as the rotation time of the developing roller 17 becomes longer, its rotation frequency becomes higher, or the surface movement distance becomes longer.

[0119] As the service life of the process cartridge approaches expiration, parameters can be set to change the gradation and quantity of toner color patches to be used. Specifically, even in the case of the type 2 process cartridge with a long service life, all toner color patches C1 to C8 are formed at the start of use (until the remaining service life reaches a predetermined value), and after the remaining service life becomes a predetermined % or less (20% or less in Embodiment 2), only toner color patches C2 to C4 are used to perform image density control, as indicated in Table 3. This is because the toner circulation in the developing chamber is not in a sufficient state for a period of time after the new product starts to be used (until the remaining service life becomes a predetermined %), where toner with a small diameter and high charge tendency to be selectively developed and transferred, and the gradation characteristics may be unstable.

[0120] [Table 3]

[0121]

[0122] In addition, image density control can be performed using all toner color patches C1 to C8 once every predetermined number of times of image density control (which is performed at a predetermined page interval).

[0123] Embodiment 3

[0124] Next, Embodiment 3 of the present invention will be described. Descriptions of parts overlapping with Embodiments 1 and 2 will be omitted. In Embodiment 3, the image density control method is different from that of Embodiments 1 and 2.

[0125] In Embodiments 1 and 2, toner color patches are formed on the intermediate transfer belt 31, and the image density and gradation are adjusted based on the result of measuring the toner color patches using the density sensor 41. On the other hand, the controller 72 of Embodiment 3 obtains the calculation parameters for image density control pre-stored in the ROM 74 of the image forming apparatus 100, the parameters stored in the memory m of each process cartridge, and uses these calculation parameters without using the detection result of the toner color patches to adjust the image density and gradation by calculation as predictive control.

[0126] Specifically, the controller 72 refers to the information pre-stored in the memory m of each process cartridge to determine whether image density control (predictive control) can be performed by calculation of parameters. If the controller 72 determines that the image density control based on calculation is effective, the subsequent image density control is switched to the image density control by calculation. The controller 72 calculates the image density at each point using the parameters regarding the process cartridge recorded in the memory m related to the member information (types of the charging roller and the developing roller, drum sensitivity) and the service life of the cartridge, and the temperature / humidity information, the number of printed sheets, the amount of toner in the cartridge, etc. obtained by the controller 72 from the image forming apparatus.

[0127] The density calculation program stored in the ROM 74 is determined in advance by performing machine learning using the above-mentioned parameters. By performing image density control using these calculation parameters, the image density control can be completed only within the calculation processing time, without a series of operation times required for forming color patches on the intermediate transfer belt, measurement by the density sensor, etc. Therefore, the control frequency can be increased, and thereby the color reproducibility can be improved to a level equal to or even exceeding that of the image density control based on toner patch detection.

[0128] As described above, regardless of the type of the processing cartridge, the image density control has been performed by the same method, and thus, in some cases, more toner patches than necessary are formed. However, according to the present invention, the adjustment operation of the image density control can be optimized based on the information related to the developing dose of the adjustment operation for the image density control, which is stored in the memory m of each processing cartridge. Therefore, the amount of toner consumed for each density control process can be suppressed while maintaining the quality, without updating the device control software of the image forming apparatus. As a result, even when the toner filling amount in the processing cartridge is the same, the number of printable sheets can be increased, and a lightweight and easy-to-manipulate processing cartridge can be provided. In each of the above embodiments, 4 processing cartridges are used, but the number of processing cartridges is not limited thereto, and may be 1 or other numbers other than 4.

[0129] Although the present invention has been described with reference to the exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the appended claims is to be accorded the broadest interpretation so as to cover all such modifications as well as equivalent structures and functions.

Claims

1. An image forming device to which a process cartridge can be attached, The process box is configured to include: an image bearing member, a surface of which is exposed based on image data to form an electrostatic latent image on the surface; a developer carrying member that develops the electrostatic latent image with a developer to form a developer image; a containing chamber, wherein the containing chamber contains a developer; and memory, The image forming device comprises: a detection unit configured to emit light to a color patch of the developer image, detect reflected light, and output information about the reflected light, and a control unit configured to perform image density control on the process cartridge based on a value of the image data and information related to the reflected light to control an image density when the developer image is formed, wherein the memory stores information corresponding to the amount of developer contained in the containing chamber, and The control unit controls to change the pattern of the color block to be used for the image density control between a case where the information in the memory is first information and a case where the information is second information, wherein the case where the information in the memory is the first information corresponds to a case where the developer amount is a first amount, and the case where the information is the second information corresponds to a case where the developer amount is a second amount, and the second amount is different from the first amount.

2. The image forming apparatus according to claim 1, wherein The control unit controls to refer to the memory and changes the pattern of the patches so that as the amount of developer accommodated in the accommodation chamber is higher, the amount of developer to be used to form the patches in the image density control is lower.

3. The image forming apparatus according to claim 2, wherein The control unit controls to change the pattern of the color patches so that the number of color patches is lower as the amount of the developer accommodated in the accommodation chamber is higher.

4. The image forming apparatus according to claim 2, wherein The control unit controls to change the pattern of the color patches so that the size of the color patches is smaller as the amount of the developer accommodated in the accommodation chamber is higher.

5. The image forming apparatus according to claim 1, wherein The memory stores, as the information corresponding to the developer amount, an amount of the developer accommodated in the accommodation chamber, the amount of the developer accommodated in the accommodation chamber having been determined as a specification of the process cartridge or having been determined when the process cartridge is manufactured.

6. The image forming apparatus according to claim 1, wherein The memory stores the service life of the process cartridge as the information corresponding to the developer amount.

7. The image forming apparatus according to claim 6, wherein The service life of the process cartridge refers to the number of sheets of recording material on which images can be formed by using the process cartridge.

8. The image forming apparatus according to any one of claims 1 to 7, wherein The control unit performs control to change the pattern of the patches in the image density control based on information on a history of image formation on a recording material by the image forming apparatus.

9. The image forming apparatus according to claim 8, wherein The control unit controls to change the pattern of the color patches so that the amount of developer to be used to form the color patches in the image density control is higher as the average print ratio of a predetermined number of recording materials for forming images by the image forming device is higher.

10. The image forming apparatus according to claim 8, wherein The control unit controls to change the pattern of the color patches so that the amount of developer to be used to form the color patches in the image density control is higher as the amount of developer consumed when the image forming apparatus forms images on a predetermined number of recording materials is higher.

11. The image forming apparatus according to any one of claims 1 to 7, wherein The memory stores information on whether the adjustment operation of the image density control is changed to prediction control as the information corresponding to the developer amount used for the adjustment operation of the image density control.

12. The image forming apparatus according to any one of claims 1 to 7, wherein The control unit controls to obtain a gradation characteristic for forming the developer image based on a value of the image data and an image density acquired by an adjustment operation of the image density control, and performs the image density control so that the gradation characteristic becomes a target gradation characteristic.

13. The image forming apparatus according to any one of claims 1 to 7, wherein In the image forming apparatus, a plurality of process cartridges can be attached simultaneously, and The control unit performs control to change the content of the adjustment operation of the image density control for each of the plurality of process cartridges.

14. The image forming apparatus according to any one of claims 1 to 7, further comprising an intermediate transfer member onto which the developer image formed by the process cartridge is transferred, wherein The pattern of the color patches is formed on the intermediate transfer member.

Images