Patent Application
20250208553
The present invention relates to an image forming apparatus.
An inline color type image forming apparatus, which includes a plurality of photosensitive drums, i.e., image bearing members, arranged linearly in the rotating direction of an intermediate transfer member, has been known as an image forming apparatus, such as a laser beam printer. In such an image forming apparatus, a process cartridge type has been commonly used, where a process cartridge, integrating an image bearing member, developing means and a toner accommodating unit, is removably installed in the image forming apparatus main unit. Furthermore, such an image forming apparatus may be provided with a plurality of process cartridges having a plurality of service life settings. The user selects and purchases any process cartridges of which service lives are set, considering the price or the like, and installs these cartridges in the image forming apparatus. In some cases, process cartridges, of which service lives are different depending on the color, may be installed.
By performing density control (calibration) in such an image forming apparatus in accordance with the degree of use of the process cartridge, tinge can be adjusted. Japanese Patent Application Publication No. 2003-270901 discloses a process cartridge type image forming apparatus that can print colors, in which image density control is performed based on a result of detecting the density of a test image (patch), so as to suppress image density change that is generated as a number of prints increases.
Furthermore, Japanese Patent Application Publication No. 2022-064626 proposes a correction method of correcting image forming conditions, such as correction amounts of density gradation and color deviation, in accordance with the conditions of combination between unit identification information stored in a replaceable image forming unit, including a process cartridge, and installation portion identification information of a unit installation portion.
Between the process cartridges in which mutually different service lives are set, as mentioned above, the types of functional components, e.g., roller, and the toner filling amount used in each process of charging and development are different. Therefore, the tendency of image gradation characteristics and degree of change thereof before the image density control tend to be different from each other. However, in the case of the image forming apparatus having the conventional configuration mentioned above, the image density of each test image (patch) used for the image density control and the number of the test images (the number of patches) are basically determined for each color. Hence even if the type (e.g. service life) of each process cartridge is different, the abovementioned problem has not been considered.
With the foregoing in view, it is an object of the present invention to improve the accuracy of the adjustment operation for the image density control, which is performed in the image forming apparatus in which a plurality of types of process cartridges are installed.
The present invention provides an image forming apparatus to which a process cartridge is attachable,
According to the present invention, the accuracy of the adjustment operation for the image density control, which is performed in the image forming apparatus in which a plurality of types of process cartridges are installed, can be improved.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Preferred embodiments of the present invention will now be described in detail with reference to the drawings. Dimensions, materials, and shapes of composing elements, and relative positions thereof, which will 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, a material, a shape and the like of a member described once are the same as first described unless otherwise specified. For configurations and steps that are not especially illustrated or described, a known technique or conventional technique in this technical field may be applied. Redundant description may be omitted.
A general configuration of an electrophotographic type image forming apparatus 100 will be described first with reference to the schematic cross-sectional views in
A plurality of image forming units of the image forming apparatus 100 includes: a first, second, third and fourth image forming units SY, SM, SC and SK for forming an image of each color of yellow (Y), magenta (M), cyan (C) and black (K) respectively. In Embodiment 1, the first to fourth image forming units SY, SM, SC and SK are disposed linearly along an intermediate transfer belt 31. The image forming unit S includes a primary transfer roller 32 and a process cartridge 7.
In Embodiment 1, the configuration and operation of the first to fourth image forming units are virtually the same, except for the color of the image to be formed. Hence unless a distinction is necessary, the subscripts Y, M C and K attached to the reference sign, to indicate the color which the element is used for, will be omitted, and [the configuration and operation] will be described in general.
In Embodiment 1, as a plurality of image bearing members, the image forming apparatus 100 includes 4 photosensitive drums 1 which are disposed along an intermediate transfer belt 31.
The photosensitive drum 1 is rotary-driven by a driving source 140 (driving unit) in the arrow A direction (counterclockwise in
In Embodiment 1, the photosensitive drum 1, a charging roller 2 (process unit that acts on the photosensitive drum 1), the developing unit 4 and the cleaning blade 6 are integrated into a cartridge, which becomes the process cartridge 7. The process cartridge 7 is removable from the image forming apparatus 100. In Embodiment 1, the process cartridge 7 for each color is identical in major composing elements. The process cartridge 7 for each color differs in that it contains toner (developer) for each color: yellow (Y), magenta (M), cyan (C) or black (K) respectively.
A general configuration of the process cartridge 7, that can be installed in the image forming apparatus 100 of Embodiment 1, will continue to be described. In Embodiment 1, the basic configuration and operation of the process cartridge 7 for each color are identical, except for the type (color) of the contained developer. The process cartridge 7 includes: a photosensitive unit 13 which includes the photosensitive drum 1 and the like, and the developing unit 4 which includes the developing roller 17 and the like.
The photosensitive unit 13 includes a cleaning frame 14, which is a frame to support various elements in the photosensitive unit 13. On the cleaning frame 14, the photosensitive drum 1 is rotatably installed via a bearing (not illustrated). When the driving force of the driving motor (driving source 140) is transferred to the photosensitive unit 13, the photosensitive drum 1 is rotary driven in the arrow A direction (clockwise direction) in accordance with 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, where functional films (undercoat layer, carrier generation layer, carrier transfer layer) are sequentially coated on the outer peripheral surface of an aluminum cylinder.
Further, on the photosensitive unit 13, the cleaning blade 6 and the charging roller 2 are disposed, so as to contact the peripheral surface of the photosensitive drum 1. The untransferred toner removed from the surface of the photosensitive drum 1 by the cleaning blade 6 drops due to gravity, and is stored in the cleaning frame 14.
A roller portion, made of conductive rubber, of the charging roller 2 (charging unit) press-contacts the photosensitive drum 1, and the charging roller 2 is rotated by the rotation of the photosensitive drum 1. In the charging step, predetermined DC voltage is applied to the core metal of the charging roller 2 from a charging power supply 142d, whereby a uniform dark area potential (Vd) is formed on the surface of the photosensitive drum 1. A spot pattern of a laser beam, which is emitted from the scanner unit 30 in accordance with the image data, exposes the photosensitive drum 1, and in the exposed portion, charges on the surface are dissipated by carriers from the carrier generation layer, and the potential drops. As a result, an electrostatic latent image, where an exposed portion has a predetermined light-area potential (Vl) and an unexposed portion has a dark-area potential (Vd), is formed on the photosensitive drum 1.
The developing unit 4, on the other hand, includes the developing roller 17 (developer bearing member), a developing blade 19, a toner supply roller 18 (supplying unit), and a toner accommodating chamber 16. The toner accommodating chamber 16 is a accommodating chamber where toner 15 is contained. The toner 15, used in Embodiment 1, is non-magnetic one component spherical toner, which is normally charged to have negative polarity, and has a 7 μm particle diameter. On the surface of the toner 15, silica particles, having a 20 nm particle diameter, have been added as external additive for toner (external additive particles).
The developing blade 19 faces and contacts the developing roller 17, controls the coat amount of the toner supplied by the toner supply roller 18, and provides changes to the developing roller 17. The developing blade 19 is a thin plate member, and generates contact pressure using the spring elasticity of the thin plate, whereby the surface of the developing blade 19 contacts with the toner 15 and the developing roller 17. When the toner 15 is charged by the tribo-electric charging 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 Embodiment 1, predetermined voltage is applied from a blade voltage power supply to the developing blade 19, so as to stabilize the toner coating.
The developing roller 17 and the photosensitive drum 1 rotate such that the respective surfaces move in the same direction at an opposing portion N1 (contact portions) (the photosensitive drum 1 moves in arrow A direction, and the developing roller 17 moves in arrow G direction). In Embodiment 1, the toner 15, which is charged to be minus polarity by the tribo-electric charging with respect to the predetermined DC voltage applied from a developing power supply 142f to the developing roller 17, is transferred only to the light-area potential portion, because of the potential difference, at the opposing portion N1 contacting the photosensitive drum 1, whereby the electrostatic latent image is developed.
The toner supply roller 18 is disposed so as to form a predetermined nip portion N2 on the peripheral surface of the developing roller 17. The toner supply roller 18 rotates in the arrow E direction (counterclockwise in
A toner stirring member 20 is disposed in the toner accommodating chamber 16. The toner stirring member 20 includes a sheet type member which rotates in the arrow H direction, to stir the toner 15 contained in the toner accommodating chamber 16, and conveys the toner 15 to the upper portion of the toner supply roller 18. In Embodiment 1, the outer diameters of the developing roller 17 and the toner supply roller 18 are both $20, and the intrusion amount of the toner supply roller 18 to 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 to the toner supply roller 18 from the developing power supply 142f, and toner is transferred only to the light-area potential portion at the developing unit contacting the photosensitive drum 1, due to this potential difference, whereby the electrostatic latent image is developed.
A memory m, constituted of a non-volatile memory and the like, is disposed in the process cartridge 7. The memory m stores information on gradation and a number of toner patches to perform image density control. This information related to the amount of developer which a controller 72 uses to perform adjustment operation for the image density control. The information on the gradation and a number of toner patches to perform image density control here is, for example: at least one of nominal service life, toner filling amount, and roughness and hardness of the charging roller 2; at least one of information on the layer structure of the charging roller 2, and roughness and hardness of the developing roller 17; at least one of the material of the surface layer of the photosensitive drum 1, film thickness, and susceptibility to photograph deterioration; or the like. The predetermined gradation and a number of toner patches for calibration that are set for this cartridge may be stored.
The memory m is configured to be communicable with the controller 72 (control unit) of the image forming apparatus 100 illustrated in
In Embodiment 1, for each process cartridge 7 of each color, there are a plurality of types of cartridges of which service life settings are different. The service life of the process cartridge 7 here refers to a value indicating a period in which the cartridge can be used, and is normally set in accordance with the capacity of the toner. In the case of setting the service life using a number of print sheets, a number of printable sheets, that are fed in the case of printing a typical image using the toner contained in the process cartridge 7, may be regarded as the service life, or a numeric value providing a margin may be set as the service life. Further, the service life is typically expressed by a printable number of sheets of the recording material, but may be expressed by another unit based on the time the process cartridge 7 was used, such as the number of days or number of hours that the process cartridge 7 was used.
For the process cartridge 7, a nominal service life has been set by the manufacturer. Here it is assumed that there are 2 types: the process cartridge 7 of which service life is relatively short (10,000 sheets); and the process cartridge 7 of which service life is relative long (50,000 sheets).
Further, as illustrated in
As illustrated in
Further, as 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 opposing roller 38. Then voltage, of which polarity is the opposite of the normal charging polarity of the toner, is applied from a secondary transfer voltage power supply 142b to the secondary transfer roller 33. Thereby the toner image on the intermediate transfer belt 31 is transferred onto the recording material 12.
As indicated in
When an image is formed, the surface of the photosensitive drum 1 is uniformly charged by the charging roller 2. Then an electrostatic latent image, in accordance with the image information, is formed on the photosensitive drum 1 by a laser beam emitted from a scanner unit 30 in accordance with the image information. Then the developing unit 4 supplies 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 to the intermediate transfer belt 31 (primary transfer) by the function of the primary transfer roller 32.
In the case of forming a full color image, for example, the abovementioned processing is sequentially performed in the first to fourth image forming units SY, SM, SC and SK, so that the toner images having each color are superimposed on the intermediate transfer belt 31, whereby the four-color toner image is formed. 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 the fixing apparatus 34 applying heat and pressure to the recording material 12.
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 second transfer step is cleaned by an intermediate transfer belt cleaning device 39.
As indicated in
The image forming apparatus 100 of Embodiment 1 includes the density sensor 41 (detecting unit). The density sensor 41 is an optical sensor to detect the toner amount, and is used to control the image density for calibration. The density sensor 41 is disposed facing the intermediate transfer belt 31, as illustrated in
The light-emitting element 51 emits light toward the intermediate transfer belt 31. The first light-receiving element 52a detects the intensity of regular reflection light from the toner patch 64, and the second light-receiving element 52b detects the intensity of diffused reflection light from the toner patch 64. By detecting both the regular reflection light intensity and the diffused reflection light intensity, the density of the toner patch 64 can be detected from the high density to the low density. To couple the light-emitting element 51 and the light-receiving elements 52, an optical element (not illustrated), such as a lens, may be used.
In Embodiment 1, the intermediate transfer belt 31 is a single layer resin belt formed of polyimide, of which perimeter 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. Further, the surface of the intermediate transfer belt 31 is very smooth and glossy, and the gloss is about a 100% (measured by Gloss Meter IG-320, manufactured by Horiba Ltd.).
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 reflection light. This is because the surface of the intermediate transfer belt 31 has glossiness. In a case where a toner image is formed on the intermediate transfer belt 31, on the other hand, the regular reflection output gradually decreases as the density (toner amount) of the toner image increases. This is because the regular reflection light decreases from the surface of the belt due to the toner covering the surface of the intermediate transfer belt 31.
The image forming apparatus 100 of Embodiment 1 corrects the output of the density sensor 41 using the output value of the intermediate transfer belt 31 in a state where toner does not exist (background output value). Specifically, the output value of the toner patch is normalized by the background output value of the intermediate transfer member (output value when image density is zero in
The abovementioned method for correcting the output of the density sensor 41 by normalizing the toner patch output by the background output is a known method, and has been used for 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.
Image density control using a toner patch in each embodiment will be described next with reference to the flow chart in
The image density control can be executed at an arbitrary timing, and may be performed periodically, or performed when changes of the image density is expected. In Embodiment 1, the forming of the toner patch for this image density control is controlled appropriately, even for a plurality of different types of process cartridges 7.
First, in step S101, the controller 72 reads information stored in the memory m of each process cartridge 7. Then in step S102, the background measurement of the intermediate transfer belt 31 (that is, density measurement in the state where toner is not laid on) is executed. Here the controller 72 rotates and moves the intermediate transfer belt 31 using the driving source 140, so that a predetermined measurement position, to be the target of the density measurement on the intermediate transfer belt 31, sequentially comes within the measurement range of the density sensor 41. The measurement position and a number of points are set to be the same as the toner patch used for the image density control.
Then in step S103, the controller 72 controls the image forming unit and forms a toner patch. An example of a patch pattern formed on the intermediate transfer belt 31 will be described with reference to
In Embodiment 1, a gradation and a number of patches when the image control is performed are changed based on the information stored in the memory m of each process cartridge read in step S101. The patch pattern in
Each patch 88 and print ratio thereof are set as follows.
The background measurement of the intermediate transfer belt 31 is performed before forming the patches 88 at locations where the abovementioned 32 patches 88 are formed. For example, the background measurement may be performed one cycle before forming the patches 88. Further, each patch 88 may be printed with a single color alone, so as to execute the image density control of the single color, as described later.
The controller 72 rotates the intermediate transfer belt 31 using the driving source 140 of the image forming apparatus 100, so as to sequentially move each patch forming position to a position facing the image forming unit. Then controlling the image forming unit, the controller 72 forms the toner patches 88, as described in
Then in step S104, the controller 72 controls the positions of the patches formed on the intermediate transfer belt 31 sequentially to come to within the measurement range of the density sensor 41, so that the density sensor 41 detects the reflection light quantity from the toner patches 88. Then in step S105, the controller 72 calculates the density of each toner patch 88. Here the output value of the toner density of each toner patch 88 is first normalized by the background output value of the intermediate transfer belt 31 (toner output/background output). This normalization of the patch output is performed for all the patches 88 using the background output value acquired at a position corresponding to each patch. Then the controller 72 converts the normalized value to a density value using a density conversion table. The density conversion table has been stored in the ROM 74 in advance.
Then in step S106, the controller 72 performs image gradation control (gradation correction). This image gradation control will be described with reference to
In
A straight line T indicates a target density gradation characteristic of the image density control. In Embodiment 1, the target gradation characteristic T is determined such that the image data and the density are in proportion to each other. The gradation characteristic is not limited to a straight line. As the comparison of the curved line y and the straight line T indicates, in a case where the gradation correction is not performed in this example, the image is printed such that the image density, with respect to the image data value, becomes low in a range where the image data value is low, and the image density, with respect to the image data value, becomes high in a range where the image data value is high. In other words, an image is printed at a tinge not desired by the user.
A curved line D indicates a gradation correction table calculated in the control of Embodiment 1. The controller 72 calculates the gradation correction table D by determining the symmetric points of the pre-correction gradation characteristic y with respect to the target gradation characteristic T. The calculated gradation correction table D is stored in the RAM 75.
When a print image is formed, the controller 72 corrects the values of the image data with reference to the gradation correction table D, whereby the target gradation characteristic can be acquired. For example, in a range where the image data values are low, the image data values are correct to be higher using the gradation correction table D. By determining a control value of the image forming apparatus 100 using these post-correction image data values, the density of the image to be printed can be increased, and the gradation characteristic can be lifted to a straight line T.
The method of the image density control used here may be any known method for controlling the image forming conditions. The image forming conditions are, for example, the spot pattern conditions of a laser beam which is emitted from the scanner unit in accordance with the image data, developing conditions (e.g. developing voltage), and charging conditions (e.g. charging voltage). The controller 72 forms patches having a plurality of predetermined patterns (e.g. half tone patterns) on the intermediate transfer belt 31, where these image forming conditions are changed in a plurality of steps, detects the densities of the patch patterns, and calculates the image forming conditions to obtain the desired density.
Now the transition of the change of the curved line y when images are printed will be described with reference to
In Embodiment 1, there are process cartridges 7 of which service lives are different: a process cartridge of which nominal service life is 10,000 sheets (hereafter called Type 1, or first process cartridge 7a. A first service life is set for the first process cartridge 7a); and a process cartridge of which nominal service life is 50,000 sheets (hereafter called Type 2, or second process cartridge 7b. A second service life, which is longer than the first service life, is set for the second process cartridge 7b). In Embodiment 1, the filling amount of the toner 15 of Type 1 and that of Type 2 are different. Specifically, the filling amount of the toner 15 is more in the cartridge of Type 2 than the cartridge of Type 1.
In a predetermined temperature/humidity environment, the image forming apparatus of Embodiment 1 executes the image density control every 1,000 sheets, so as to maintain the tinge reproducibility.
As
Based on these results, in the image forming apparatus of Embodiment 1, as indicated in Table 2 the gradation and a number of toner patches for the image density control, which are set in advance for each Type 1 and Type 2 process cartridges, are saved in the memory m of the process cartridge respectively. In this case, information corresponding to the amount of developer contained in the accommodating chamber is stored in the memory m. For example, if the amount of developer contained in the Type 1 cartridge is a first amount, and the amount of developer contained in the Type 2 cartridge is a second amount, first information, that the amount of the developer is the first amount, is stored in the memory of the Type 1 cartridge. In the same manner, second information, that the amount of developer is the second amount, is stored in the memory of the Type 2 cartridge. Here only 2 types of information are used to simplify description, but various information can be used in accordance with the amount of developer that can be contained.
In the example of Table 2, all the toner patches are formed in the Type 1 process cartridge to simplify description, but C5 and C8 may be removed therefrom. In the above example, the gradation and a number of toner patches are stored in the memory m, but the present invention is not limited to this. For example, a variable for each type of process cartridge may be stored in the memory m, and such information as Table 2 may be obtained by performing calculations referring to mathematical expressions and coefficient held by the controller 72. Further, referring to the filling amount and the service life stored in the memory m, the controller 72 may perform control to simply decrease a number of toner patches in a case where the filling amount is high (service life is long).
As described above, in Embodiment 1, the adjustment operation of the image density control is optimized using the characteristics of the gradation change generated by predetermined specifications of the process cartridges, which service lives are different (toner filling amounts are different). In other words, by using a nominal service life (that is, the toner filling amount) as the information related to the gradation and a number of toner patches, the image density control can be adjusted with less toner patches in the Type 2 process cartridge having a longer service life, compared with the Type 1 process cartridge.
In the present invention, it is sufficient if the toner amount used for the image density control can be changed by controlling the calibration pattern in accordance with the toner filling amount and the service life, whereby the operation can be optimized. As long as such calibration pattern control is possible, a method other than controlling a number of toner patches may be used. For example, the toner amount may be adjusted by decreasing the surface area of each toner patch if the filling amount is high. For example, if the toner patch is rectangular, the width of the toner patch may be decreased, or the length thereof may be decreased (intervals of the toner patches may be increased) to decrease the surface area of the toner patch. If the toner patch is a shape other than a rectangle, the size of the toner patch may be reduced in accordance with the shape.
Further, in a case where it is determined that the process cartridge is a large capacity cartridge, the accuracy of the image density control may be improved while maintaining a number of toner patches, without decrease the number. For example, in the case of using 8 toner patches, as indicated in Table 2, for the large capacity (Type 2) process cartridge, the block of C2, C3 and C4 is divided into 8 so as to create 8 toner patches, and the image density control is performed thereby. In this example, the block of C2 to C4 may be divided by a number less than 8 (e.g. 5) to create less number of toner patches. Then in the block where the image density control is required, accuracy improves but a number of toner patches can be reduced.
For both Type 1 and Type 2, the gradation of the toner patch may be set to ALL, but the division numbers may be changed while maintaining the same gradation, such as 8 division for Type 1 and 7 division for Type 2.
The image forming apparatus of Embodiment 1 is not limited to the content described above. For example, the tip position of the developing blade in each process cartridge, the sensitivity of the drum included in each process cartridge, and the like may be written in the memory m during manufacture, so that the conditions of the toner patches are changed in accordance with the change of gradation characteristics generated by these values. Further, the conditions of the toner patches may be changed based on the information on the parameters related to toner. For example, generally as the intruding amount of the tip position of the blade is higher, the amount of toner taken in by the developing roller increases, and the toner charging amount decreases. Therefore even a small amount of electrostatic latent images can be more easily developed, and gradation generally becomes darker. The image density control may be adjusted recognizing this. Another example is that the amount of change of surface potential increases as the drum sensitivity becomes higher, hence gradation generally becomes darker even if the quantity of light is the same during exposure. There are various other factors, besides service life, that influence the characteristics of the gradation change. Considering these factors, the gradation and a number of tone patches may be determined.
In Embodiment 1, the method of optimizing the adjustment operation for the image density control, based on the information in the memory which saves information related to the developer amount used for an adjustment operation for the image density control, included in each process cartridge, was described. Thereby the toner amount to be consumed for one execution of density control can be suppressed while maintaining quality. As a result, a number of printable sheets can be increased even if the toner filling amount in the process cartridge is the same, or a process cartridge that is light and easy to handle can be provided.
Embodiment 2 will be described next. Description on portions overlapping with Embodiment 1 will be omitted. In Embodiment 2, even if the image forming apparatus is used in a wider range than Embodiment 1, the toner amount consumed in one execution of the image density control can be suppressed while maintaining quality.
In Embodiment 1, the adjustment operation for the image density control is optimized based on the predetermined specifications or information determined during manufacturing, using the characteristics of gradation changes of the process cartridges of which service lives are different (toner filling amounts are different). In Embodiment 2, on the other hand, the adjustment operation for the image density control is optimized also using the information on the operation history of the image forming apparatus, which is different from Embodiment 1. In Embodiment 2 as well, Type 1 and Type 2 process cartridges having different service lives will be used for description, just like Embodiment 1.
Compared with
Hence in Embodiment 2, the gradation change characteristics, including the toner consumption amount, are detected and saved in the memory m in advance. Then the adjustment operation for the image density control is optimized, additionally using the information related to the consumption amount of the developer (e.g. print ratio, history thereof), which is written in the memory m each time printing is performed.
The controller 72 of Embodiment 2 calculates the print ratio based on the image data for each paper feed, and changes the gradation and a number of toner patches in accordance with the average print ratio at a timing of the image density control (e.g. when 1,000 sheets are fed). For example, if the average print ratio is a predetermined threshold or more, a number of toner patches is set to 8, just like the case of
Further, in Embodiment 2, the control may be performed using an integrated value of 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 the value each time a sheet is fed. Then at a timing of the image density control (e.g. when 1,000 sheets are fed), the patch pattern is selected so that a number of toner patches increases as the integrated value of the consumed toner amount is higher.
The image forming apparatus of Embodiment 2 is not limited to the above example, and parameters related to deterioration of toner, such as rotation time, rotation frequency and surface moving distance of the developing roller 17, may be used. The controller 72 can determine a number and gradation of the toner patches used for the image density control based on the predetermined program in accordance with these parameters. The patch pattern is selected such that a number of toner patches increases as the rotation time of the developing roller 17 is longer, the rotation frequency thereof is higher, or the surface moving distance thereof is longer.
As the service life of the process cartridge approaches expiration, the parameters may be set to change the gradation and a number of toner patches to be used. Specifically, even in a case of the Type 2 process cartridge having a long service life, all the toner patches C1 to C8 are formed in the beginning of use (until the remaining service life reaches a predetermined value), and only toner patches C2 to C4 are used to perform the image density control after the remaining service life becomes a predetermined % or less (20% or less in Embodiment 2), as indicated in Table 3. This is because the toner circulation in the developer chamber is not in a sufficient state for a while after a new product starts to be used (until the remaining service life becomes a predetermined %), where small diameter and highly charged toner tends to be selectively developed and transferred, and the gradation characteristics may not be stable.
Further, the image density control may be performed using all the toner patches C1 to C8 once every predetermined number of times of image density control, which is performed at predetermined page intervals.
Embodiment 3 of the present invention will be described next. Description of portions overlapping with Embodiments 1 and 2 will be omitted. In Embodiment 3, the image density control method is different from Embodiments 1 and 2.
In Embodiments 1 and 2, toner 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 patches using the density sensor 41. The controller 72 of Embodiment 3, on the other hand, obtains calculation parameters for the image density control, which are stored in the ROM 74 of the image forming apparatus 100 in advance, the parameters stored in the memory m of each process cartridge, and adjusts the image density and gradation by calculation as prediction control, using these calculation parameters, without using the detection result of the toner patches.
Specifically, the controller 72 refers to information to determine whether the image density control (prediction control) can be performed by the calculation of parameters stored in the memory m of each process cartridge in advance. If the controller 72 determines that the image density control based on the calculation is effective, 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 on the process cartridges related to the member information (types of charging roller and developing roller, drum sensitivity) and service life of the cartridge recorded in the memory m, and the temperature/humidity information, a number of print sheets, toner amount in the cartridge, and the like, which the controller 72 obtains from the image forming apparatus.
The density calculation program, which is stored in the ROM 74, has been determined in advance by performing machine learning using the abovementioned parameters. By executing the 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 patches on the intermediate transfer belt, measurement by the density sensor, and the like. Hence control frequency can be increased, whereby tinge reproducibility can be improved to a level equivalent to or even exceeding the image density control based on the toner patch detection.
As described above, the image density control has been performed by a same method regardless the type of process cartridge, hence in some cases, more toner patches are formed than necessary. According to the present invention, however, the adjustment operation for the image density control can be optimized based on the information related to the developer amount used for the adjustment operation for the image density control, which is stored in the memory m of each process cartridge. Therefore the toner amount to be consumed for each density control process can be suppressed while maintaining quality, without updating the apparatus control software of the image forming apparatus. As a result, a number of printable sheets can be increased even if the toner filling amount in the process cartridge is the same, and a process cartridge that is light and easy to handle can be provided. In each of the above embodiments, 4 process cartridges are used, but a number of process cartridges is not limited to this, and may be 1 or a number other than 4.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2023-214787, filed on Dec. 20, 2023, which is hereby incorporated by reference wherein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-214787 | Dec 2023 | JP | national |
