Patent Application
20240419111
The present invention relates to an image forming apparatus.
A image forming apparatus of an inline color system having a configuration, in which a plurality of photosensitive drums serving as image bearing members are arranged in a rotating direction of an intermediate transfer member, has been known conventionally as an image forming apparatus such as a laser beam printer. The image forming apparatuses generally employ a process cartridge system in which an image bearing member, developing means, and a toner accommodation unit are integrated to serve as a process cartridge so as to be attachable to and detachable from an image forming apparatus body. In addition, in some cases process cartridges having a plurality of lifespan settings are prepared for such an image forming apparatus. A user selects and purchases any of a process cartridge having lifespan setting on the basis of prices or the like, and install the same in the image forming apparatus. At that time, the user may install process cartridges having different lifespan, depending on a color.
In such an image forming apparatus, image density control (calibration) is executed according to use degrees of the process cartridge, thereby enabling execution of tinge adjustment. It is proposed in Japanese Patent Application Laid-open No. 2003-270901 that image density control is executed on the basis of results of density detection to suppress a change in image density accompanied by an increase in the number of printed sheets in an image forming apparatus of a process cartridge system, which is capable of color printing.
However, in the configuration of a conventional example as described above, tinges do not match between cartridges in a case where process cartridges having different lifespan settings are installed in the same image forming apparatus. This is because the timing of image density control for the process cartridges varies depending on the lifespan settings, resulting in a deviation of the timing of the image density control when the process cartridges having different lifespans are simultaneously installed.
The present invention has been made in view of the above problem. The present invention has an object of providing a technology to execute image density control at an appropriate timing in an image forming apparatus in which a plurality of cartridges having different lifespans are capable of being simultaneously installed.
The present invention provides an image forming apparatus comprising:
The present invention also provides an image forming apparatus comprising:
According to the present invention, it is possible to provide a technology to execute image density control at an appropriate timing in an image forming apparatus in which a plurality of cartridges having different lifespans are capable of being simultaneously installed.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Hereinafter, preferred embodiments of the present invention will be exemplarily described in detail with reference to the drawings. However, dimensions, materials, shapes, their relative arrangements, or the like of constituting components mentioned in the embodiments will not intend to limit the scope of the invention unless otherwise particularly mentioned. Further, materials, shapes, or the like once described in preceding descriptions will be the same also in subsequent descriptions unless otherwise particularly mentioned again. Particularly for configurations or processes that will not be shown in figures or described, general or publicly-known technologies in the technical field concerned are applicable. Further, duplicated descriptions will be omitted depending on cases.
First, the entire configuration of an electrophotographic image forming apparatus 100 will be described with reference to the schematic cross-sectional view of
The image forming apparatus 100 has first to fourth image forming units SY, SM, SC, and SK for forming images of respective colors yellow (Y), magenta (M), cyan (C), and black (K) as a plurality of image forming units. In the present embodiment, the first to fourth image forming units SY, SM, SC, and SK are arranged in a line along an intermediate transfer belt 31. Note that each of image forming units SY, SM, SC, and SK is assumed to include a primary transfer roller 32 and a process cartridge 7.
Note that the configurations and operations of the first to fourth image forming units are substantially the same except for the colors to be formed by the image forming units in the present embodiment. Accordingly, subscripts Y, M, C, and K added to symbols to express elements provided corresponding to the respective colors will be omitted and comprehensively described when there is no need to particularly distinguish the elements from each other.
In the present embodiment, the image forming apparatus 100 has four photosensitive drums 1 arranged along the intermediate transfer belt 31 as a plurality of image bearing members.
The photosensitive drum 1 is rotationally driven by a driving source 140 serving as a driving unit in an arrow A direction (clockwise direction in
In the present embodiment, the photosensitive drum 1, the charging roller 2 serving as a process unit that acts on the photosensitive drum 1, the developing unit 4, and the cleaning blade 6 are integrated into a cartridge to form the process cartridge 7. The process cartridge 7 is made attachable to and detachable from the image forming apparatus 100. In the present embodiment, main constituting elements of the process cartridges 7 for the respective colors have the same shapes. The process cartridges 7 for the respective colors differ from each other in that they each accommodate toner of the respective colors yellow (Y), magenta (M), cyan (C), and black (K).
The entire configuration of the process cartridge 7 attachable to the image forming apparatus 100 of the present embodiment will be continuously described. Note that the basic configurations and operations of the process cartridges 7 for the respective colors are the same except for types (colors) of accommodated developer in the present embodiment. The process cartridge 7 has a photosensitive member unit 13 including the photosensitive drum 1 or the like and the developing unit 4 including the developing roller 17 or the like.
The photosensitive member unit 13 has a cleaning frame body 14 as a frame body that supports various elements inside the photosensitive member unit 13. The photosensitive drum 1 is rotatably attached to the cleaning frame body 14 via a bearing not shown. When a driving force of a driving motor serving as the driving source 140 is transmitted to the photosensitive member unit 13, the photosensitive drum 1 is rotationally driven in the arrow A direction (clockwise direction) according to an image forming operation. In the present embodiment, an organic photosensitive member in which an undercoating layer, a carrier generation layer, and a carrier transfer layer serving as function films are sequentially coated on an outer peripheral surface of an aluminum cylinder is used as the photosensitive drum 1 that plays a central role in an image forming process.
Further, the cleaning blade 6 and the charging roller 2 are arranged in the photosensitive member unit 13 so as to be in contact with an outer peripheral surface of the photosensitive drum 1. Untransferred toner removed from the surface of the photosensitive drum 1 by the cleaning blade 6 falls due to gravity and is accommodated in the cleaning frame body 14.
The charging roller 2 serving as a charging unit is driven to rotate by bringing a roller portion of its conductive rubber into pressure contact with the photosensitive drum 1. Here, a prescribed DC voltage is applied from a charging power supply 142d to a cored bar of the charging roller 2 in a charging process, whereby a uniform dark potential (Vd) is formed on the surface of the photosensitive drum 1. A spot pattern of laser light emitted corresponding to image data by the laser light from a scanner unit 30 exposes the photosensitive drum 1. At an exposed area, surface charges disappear due to carriers from the carrier generation layer, and a potential reduces. As a result, an electrostatic latent image is formed on the photosensitive drum 1, where exposed areas have a prescribed bright potential (Vl), while unexposed areas have a prescribed dark potential (Vd).
Meanwhile, the developing unit 4 includes the developing roller 17 (developer bearing member), a developing blade 19, a toner supply roller 18 (supply unit), toner 15, and a toner accommodation chamber 16 serving as an accommodation chamber for the toner 15. As the toner 15 of the present embodiment, nonmagnetic mono-component spherical toner that negatively charges as a regular polarity and has a particle diameter of 7 μm is used. Further, silica particles having a particle diameter of 20 nm are added to a surface of the toner 15 as toner additives (external additive particles).
The developing blade 19 is in counter-contact with the developing roller 17. The developing blade 19 controls a coated amount of toner supplied by the toner supply roller 18, and applies charges to the toner. The developing blade 19 is made of a thin plate-shaped member. The developing blade 19 forms a contact pressure by making use of the spring elasticity of the thin plate, and its surface comes in contact with the toner 15 and the developing roller 17. The toner 15 is charged by friction when the developing blade 19 and the developing roller 17 rub against each other, whereby charges are applied to the toner 15. At the same time, the thickness of a toner layer is controlled. Further, in the present embodiment, a prescribed voltage is applied from a blade bias power supply to the developing blade 19 to stabilize a coated amount of the toner.
The developing roller 17 and the photosensitive drum 1 rotate such that their mutual surfaces move in the same direction (the photosensitive drum 1 rotates in the arrow A direction, and the developing roller 17 rotates in an arrow G direction) at a facing portion N1 (contact portion). In the present embodiment, with respect to a prescribed DC voltage applied from a developing power supply 142f to the developing roller 17, the toner 15 negatively charged by friction transfers only to a bright potential portion to visualize an electrostatic latent image due to a potential difference at the facing portion N1 at which the developing roller 17 comes in contact with the photosensitive drum 1.
The toner supply roller 18 is disposed with a prescribed nip portion N2 formed on a peripheral surface of the developing roller 17. The toner supply roller 18 rotates in an arrow E direction (counterclockwise direction in
Inside the toner accommodation chamber 16, a toner stirring member 20 is provided. The toner stirring member 20 includes a sheet-shaped member that rotates in an arrow H direction, and transports the toner 15 to an upper portion of the toner supply roller 18 while stirring the toner 15 accommodated in the toner accommodation chamber 16. Note that both the developing roller 17 and the toner supply roller 18 have an outer diameter of q 20, and a penetration amount of the toner supply roller 18 into the developing roller 17 is set at 1.5 mm in the present embodiment. In the present embodiment, a prescribed DC bias is applied from the developing power supply 142f to the developing roller 17, and the toner is transferred only to a bright potential portion due to a potential difference at a developing portion at which the developing roller 17 comes in contact with the photosensitive drum 1, thereby visualizing an electrostatic latent image.
The process cartridge 7 has a memory m made up of a non-volatile memory or the like. In the memory m, information related to determination of an execution frequency of image density control by a controller 72 is stored. Here, the information related to the determination of the execution frequency of the image density control includes, for example, a nominal lifespan, a toner filling amount, at least one of the roughness and hardness of the charging roller 2, information related to the layer structure of the charging roller 2, at least one of the coarse and hardness of the developing roller 17, at least one of the material, film thickness, and susceptibility to light degradation of a surface layer of the photosensitive drum 1, or the like. Further, a calibration frequency set in advance for the cartridge may be stored. Note that the memory m is configured to be capable of communicating with the controller 72 serving as a control unit of the image forming apparatus 100 shown in
Here, in the present embodiment, a plurality of cartridges having different lifespan settings are assumed as the process cartridges 7 of the respective colors. Here, the lifespans of the process cartridges 7 refer to numeric values expressing the available periods of the cartridges, and are typically set according to toner capacities. In a case where the lifespans are set on the basis of the number of printed sheets, the number of sheets printable when typical images are printed using the toner accommodated in the process cartridges 7 may be set as the lifespans, or numeric values with some margins may be set as the lifespans. Further, the lifespans are typically expressed by the number of sheets of printable recording materials, but may be expressed by other units based on used hours of the process cartridges 7 such as used days and the number of used hours. The process cartridges 7 have nominal lifespans set by a manufacturer. Here, two types of the process cartridges 7, i.e., relatively short-life process cartridges 7 each having a nominal lifespan of 10,000 sheets and relatively long-life process cartridges 7 each having a nominal lifespan of 50,000 sheets are assumed.
Further, as shown in
As shown in
In addition, the secondary transfer roller 33 serving as a secondary transfer unit is arranged at a position facing the secondary transfer facing roller 38 on the side of an outer peripheral surface of the intermediate transfer belt 31. Further, a bias having a polarity opposite to the regular charging polarity of the toner is applied from a secondary transfer bias power supply to the secondary transfer roller 33. Thus, toner images on the intermediate transfer belt 31 are transferred onto the recording material 12.
Note that the image forming apparatus 100 includes a power supply 142 as shown in
First, the surfaces of the photosensitive drums 1 are uniformly charged by the charging rollers 2 during an image formation. Next, electrostatic latent images corresponding to image information are formed on the photosensitive drums 1 by laser light corresponding to the image information emitted from the scanner unit 30. Then, developer is supplied to the electrostatic latent images by the developing units 4, and the electrostatic latent images are developed on the photosensitive drums as toner images (developer images). Next, the developed toner images are transferred (primarily transferred) onto the intermediate transfer belt 31 by an operation of the primary transfer rollers 32.
For example, when a full-color image is formed, the above processes are successively performed in the first to fourth image forming units SY, SM, SC to SK, and toner images of the respective colors are superimposed one upon another on the intermediate transfer belt 31, whereby toner images of the four colors are formed. Then, the toner images of the four colors on the intermediate transfer belt 31 are collectively and secondarily transferred onto a recording material 12. In addition, the toner images are fixed onto the recording material 12 as a fixing apparatus 34 applies heat and pressure to the recording material 12.
Note that primarily untransferred toner residual on the photosensitive drums 1 after the primary transfer process is removed and collected by cleaning blades 6. Further, secondarily untransferred toner residual on the intermediate transfer belt 31 after the secondary transfer process is cleaned by an intermediate transfer belt cleaning apparatus (not shown).
As illustrated in
The image forming apparatus 100 of the present embodiment includes the density sensor 41 as a detection unit. The density sensor 41 is an optical sensor that detects a toner amount, and is employed in image density control as a calibration process. The density sensor 41 is arranged so as to face the intermediate transfer belt 31 as shown in
The light-emitting element 51 applies light toward the intermediate transfer belt 31. The first light-receiving element 52a detects the intensity of regularly-reflected light from a toner patch 64, and the second light-receiving element 52b detects the intensity of irregularly-reflected light from the toner patch 64. By detecting both the intensity of the regularly-reflected light and the intensity of the irregularly-reflected light, the density sensor 41 is capable of detecting the density of the toner patch 64 from high density to low density. Note that it is also possible to use an optical element such as a lens not shown to couple the light-emitting element 51 and the light-receiving element 52 together.
Further, the intermediate transfer belt 31 is a polyimide single-layer resin belt having a peripheral length of 880 mm in the present embodiment. Further, an appropriate amount of carbon fine particles are dispersed inside a resin to adjust the resistance of the belt, and a surface color of the belt is black. Moreover, the surface of the intermediate transfer belt 31 has high smoothness and glossiness, and the glossiness is about 100% (measured by a glossmeter IG-320 manufactured by HORIBA, Ltd.).
The density sensor 41 detects reflected light mainly with the first light-receiving element 52a in a case where the surface of the intermediate transfer belt 31 is exposed (a toner amount is zero). This is because the surface of the intermediate transfer belt 31 has glossiness as described above. On the other hand, in a case where toner images are formed on the intermediate transfer belt 31, an output of regular reflection gradually reduces with an increase in the density (toner amount) of the toner images. This is because regularly-reflected light from the surface of the belt reduces when the surface of the intermediate transfer belt 31 is covered up by toner.
The above method for correcting a toner patch output to be normalized using a base output is a known method, and has been employed in many color image forming apparatuses put on the market. Note that any existing configuration for density detection is available as the density sensor 41. Further, the wavelength of light is not limited to infrared light.
Next, image density control in respective embodiments will be described using the flowchart of
Note that the image density control in the image forming apparatus 100 of the present invention refers to image gradation control to adjust the density gradation characteristics of an image. In a flow, respective steps are executed by the controller 72 with reference to an output value of the density sensor 41 or the like.
The image density control is executable at any timing. That is, the image density control may be executed periodically, or may be executed when a variation in image density is expected. In the present embodiment, the timing of the image density control is appropriately controlled also at installation of the plurality of process cartridges having different lifespans. First, in step S101, measurement of a base of the intermediate transfer belt 31, that is, measurement of density in a state in which toner is not placed is executed. At this time, the controller 72 rotates and moves the intermediate transfer belt 31 by the driving source 140 to cause prescribed measurement positions that are density measurement targets in the intermediate transfer belt 31 to sequentially fall within a measurement range of the density sensor 41. The measurement positions and the number of points are made to correspond to toner patches used in the image density control.
Here,
The corresponding relationships between the respective patches 88 and the printing ratios (gradation degrees) are set as follows.
The measurement of the base of the intermediate transfer belt 31 is executed with respect to formed positions of the above 32 patches 88 before the patches 88 are formed. For example, the measurement of the base may be executed one cycle before the patches 88 are formed.
Further, as will be described later, the respective patches 88 may be printed in a monochrome color only, and monochrome image density control may be executed.
Referring back to
Next, in step S103, the controller 72 causes the patch formed positions on the intermediate transfer belt 31 to sequentially fall within the measurement range of the density sensor 41, and detects reflected light amounts from the toner patches 88 using the density sensor 41. Then, in step S104, the controller 72 calculates the density of the toner patches 88. At this time, output values of the density of the toner patches 88 are normalized using base output values of the intermediate transfer belt 31 (toner output/base output). The normalization of the patch output is executed for all the patches 88 using the base output values acquired at the positions corresponding to the patches. Next, the controller 72 converts the normalized values into density values according to a density conversion table. The density conversion table is stored in advance in the ROM 74.
Next, in step S105, the controller 72 executes image gradation control (gradation correction). The image gradation control will be described using
In
Next, a straight line T shows target density gradation characteristics of the image density control. In the present embodiment, the target gradation characteristics T are set so as to have the direct proportionality between image data and density. Note that the gradation characteristics are not limited to a straight line. It is clear from the comparison between the curved line γ and the straight line T that, when gradation correction is not executed in the illustrated example, printing is executed such that the image density becomes low with respect to the image data values in a range in which the image data values are low, while printing is executed such that the image density becomes high with respect to the image data values in a range in which the image data values are high. That is, printing is executed by tinge different from one desired by a user.
Further, a curved line D shows a gradation correction table calculated in the control of the present embodiment. The controller 72 calculates the gradation correction table D by finding out symmetrical points of the gradation characteristics γ before correction with respect to the target gradation characteristics T. The calculated gradation correction table D is stored in the RAM 75.
When forming a print image, the controller 72 is enabled to achieve target gradation characteristics by correcting values of image data while referring to the gradation correction table D. For example, in a range in which image data values are low, the image data values are corrected to be high by using the gradation correction table D. By determining control values of the image forming apparatus 100 with the corrected image data values, it is possible to increase printing image density to raise the gradation characteristics up to the straight line T. Further, a method for executing the image density control here may be a known method for controlling image forming conditions. The image forming conditions include, for example, a developing condition for a developing bias or the like and a charging condition for a charging bias or the like. The controller 72 forms a plurality of prescribed pattern (such as halftone pattern) patches on the intermediate transfer belt 31 by changing the image forming conditions in multiple stages, detects the density of the pattern patches, and calculates image forming conditions that achieve desired density.
Next, the transition of the curved line γ at printing will be described using
In the present embodiment, a process cartridge having a nominal lifespan of 10,000 sheets (that will be called a Type 1 or a first process cartridge 7a below. The first process cartridge 7a has a first lifespan) and a process cartridge having a nominal lifespan of 50,000 sheets (that will be called a Type 2 or a second process cartridge 7b. The second process cartridge 7b has a second lifespan longer than the first lifespan) are assumed as the process cartridges 7 having different lifespans.
In the present embodiment, each of the Type 1 and the Type 2 has a different filling amount for the toner 15. Specifically, the cartridge of the Type 2 has a greater filling amount for the toner 15 than the cartridge of the Type 1. First, the cartridge of the Type 1 having a relatively short lifespan is employed. The transition of the curved line γ after execution of the image density control at a certain timing is shown in Table 1.
That is, in the case of the process cartridge of the Type 1, the curved line γ immediately after the image density control becomes the targeted straight line T, and becomes the curved line γ2 when 1,000 sheets have been printed. Therefore, it is possible to maintain tinge reproduction by executing the image density control every time 1,000 sheets have been printed (that is, for every 1,000 sheets) at a maximum. Here, the timing when the image density control is executed has to be immediately before the curved line γ exceeds the allowable range at the latest. In the case of the Type 1 of the present embodiment, the timing corresponds to the time when 1,000 sheets have been printed.
Next, the Type 2 having a relative long lifespan is employed. The transition of the curved line γ after execution of the image density control at a certain timing is shown in Table 2.
That is, in the case of the cartridge of the Type 2, the curved line γ immediately after the image density control becomes the targeted straight line T, and becomes the curved line γ2 when 2,000 sheets have been printed. Therefore, it is possible to maintain tinge reproduction by executing the image density control every time 2,000 sheets have been printed (that is, for every 2,000 sheets) at a maximum. Here, for example, assuming that the Type 1 is defined as a first cartridge, the execution frequency (1,000 sheets) of the image density control may be called a first frequency. Further, assuming that the Type 2 is defined as a second cartridge, the execution frequency (2,000 sheets) of the image density control may be called a second frequency.
This is because the Type 2 has a greater toner filling amount, leading to differences in the transition of a toner particle diameter, toner degradation, and a D roller filming level compared to the Type 1. As a result, a transition amount of the curved line γ becomes smaller.
In a case where the Type 1 and the Type 2 coexist, that is, in a case where cartridges having different lifespan settings are provided in the same image forming apparatus as in the present embodiment, the image density control is executed at both the timing when 1,000 sheets have been printed for the Type 1 and the timing when 2,000 sheets have been printed for the Type 2. When it is assumed that monochrome image density control is executed only for the Type 1 or the Type 2 at each timing of the Type 1 and the Type 2, the image density control transitions as shown in
An example of the control of the present embodiment will be described with reference to
Note that the prescribed number of sheets (2,000 sheets) of the Type 2 is twice the prescribed number of sheets (1,000 sheets) of the Type 1 in the case of the present embodiment. Therefore, there could be a case that the image density control is consequently executed at the same timing (for every 1,000 sheets) due to their overlapping cycles. However, in this case, the image density control is executed for both cartridges of the Type 1 and the Type 2 at necessary timings without exception.
An example of the control of this case will be described with reference to
Note that the image density control is periodically executed in the present embodiment but may be non-periodically executed according to the timing when the curved line transitions to the curved line γ2. Further, the image density control may also be executed at the timing when instructions are received from a user. Further, an execution timing may be determined using tag information stored in the memories m of the process cartridges 7. Further, calibration is executed only for a process cartridge of a corresponding color in the present embodiment, but may be executed for both the Type 1 and the Type 2 using one of the Type 1 and the Type 2 as a trigger.
Further, in the invention of the present application, for both of the Type 1 and Type 2 a calibration execution request is controlled to be executed at the timing when the curved line transitions to the curved line γ2, that is, at the timing when the deviation of the density gradation falls within the allowable range. However, the control of the invention of the present application is not limited to the above timing, and may only be executed before the curved line γ transitions to the curved line γ2 from the straight line T, that is, during a period in which the deviation of the density gradation falls within the allowable range.
Further, a timing based on a state of the curved line γ may be changed between the Type 1 and the Type 2. Note that it is preferable to make a calibration execution request before the curved line γ transitions from γ1 to γ2. For example, a case where toner of the Type 1 degrades faster than toner of the Type 2 and the curved line γ of the Type 1 deviates to a greater extent to cause a remarkable density change will be considered on the basis of the comparison between the Type 1 and the Type 2. In this case, control may be made such that the Type 1 executes the image density control at the timing when the curved line γ becomes the curved line γ1, and such that the Type 2 executes the calibration at the timing when the curved line γ becomes the curved line γ2. Like this, the Type 1 may be controlled to execute the image density control at the timing when the curved line γ less changes compared to the Type 2. Note that in a case where the toner of the Type 2 degrades faster than that of the Type 1 or the like, the Type 2 may be controlled to execute the image density control at the timing when the curved line γ less changes compared to the Type 1 as a matter of course. Further, the timing of the image density control may be changed according to environment changes such as printing conditions, temperature, and humidity. The timing of the image density control may be appropriately set according to the lifespans of the process cartridges, that is, the degradation degree of the toner.
Further, in the invention of the present application, the next image density control is controlled to be executed on the basis of number of printed sheets for each of the Type 1 and the Type 2 after execution of the image density control. However, the execution timing of the image density control is not limited to this, and may only be based on parameter information related to the toner. For example, parameters related to degradation of the toner such as a rotating hour, a rotating number, and a surface movement distance of a developing roller may be used. Further, the image density control is controlled to be executed on the basis of a prescribed number of printed sheets, but may be executed on the basis of a percentage. For example, the image density control may be controlled to be executed for the first time when the lifespan of a cartridge has reached 99% relative to a nominal lifespan (the cartridge is brand new at 100%, and reaches the end of the lifespan at 0%), and may be executed for the second time when the lifespan has reached 95%. Parameters may be appropriately set such that a calibration frequency is changed as a product reaches the end of a lifespan.
Further, calibration may be absolutely executed for all cartridges at the timing when a brand new cartridge has been installed.
Next, a second embodiment of the present invention will be described. Note that descriptions will be omitted for parts overlapping with the first embodiment. In the present embodiment, a process cartridge having a nominal lifespan of 10,000 sheets (that will be called a Type 1 below like the first embodiment) and a process cartridge having a nominal lifespan of 50,000 sheets (that will be called a Type 3 below) are assumed as process cartridges having different lifespans. Accordingly, the nominal lifespan of the Type 3 is the same as that of the Type 2 of the first embodiment. The Type 1 and the Type 3 differ not only in a toner filling amount but also in a charging roller 2. The Type 3 employs a long-life compatible charging roller 2, and has higher roughness than the Type 1.
Like the first embodiment, a curved line γ after execution of image density control of the process cartridge of the Type 1 transitions as shown in Table 1. Next, in the process cartridge of the Type 3 a curved line γ after execution of image density control at a certain timing transitions as shown in Table 3.
That is, in the case of the Type 3, the curved line γ immediately after execution of the image density control becomes a targeted straight line T, and becomes a curved line γ2 when 2,400 sheets have been printed. Therefore, it is possible to maintain tinge reproduction by executing the image density control every time 2,400 sheets have been printed. This is because the Type 3 has a greater toner filling amount and has the charging roller 2 with higher roughness, leading to reduced influence of stains on the charging roller 2 and a slower reduction in a drum potential after charging compared to the Type 1.
In a case where the Type 1 and the Type 3 coexist like the present embodiment, the image density control is executed at both the timing when 1,000 sheets have been printed for the Type 1 and the timing when 2,400 sheets have been printed for the Type 3. Thus, in the case where the Type 1 and the Type 3 coexist, the execution frequency of the image density control is increased to a greater extent compared to a case where one of the Types is selected, thereby making it possible to reproduce more accurate tinges.
An example of the control of the present embodiment will be described with reference to
Note that the image density control is periodically executed in the present embodiment but may be non-periodically executed according to the timing when the curved line transitions to the curved line γ2. Further, an execution timing may be determined using tag information stored in memories m of process cartridges 7.
Next, a first modified example of the second embodiment will be described. In the first modified example as well, the cartridge of the Type 1 and the cartridge of the Type 3 having a nominal lifespan of 50,000 sheets are employed like the second embodiment. As for the transition of the curved line γ as well, the image density control is executed for every 2,400 sheets in the Type 3 like Table 3.
In the present modified example, the Type 1 and the Type 3 differ not only in a toner filling amount but also in the layer structure of a charging roller 2. That is, the Type 1 has a charging roller 2 having a single-layer structure (having only a base layer without a surface layer), and the Type 3 has a long-life compatible charging roller 2 having a two-layered structure (having a surface layer and a base layer).
The cartridge of the Type 3 of the present modified example has a greater toner filling amount, and reduces stains on the charging roller 2 to a greater extent compared to the charging roller 2 having the single-layer structure of the Type 1 since the surface layer of the charging roller 2 is coated. As a result, a reduction in a drum potential after charging becomes slower compared to the Type 1, and therefore the transition of the curved line γ also becomes slower. In a case where the Type 1 and the Type 3 coexist, the image density control is executed at both the timing when 1,000 sheets have been printed for the Type 1 and the timing when 2,400 sheets have been printed for the Type 3. Thus, the execution frequency of the image density control is increased, thereby making it possible to reproduce more accurate tinges.
Further, the image density control is periodically executed in the present embodiment but may be non-periodically executed according to the timing when the curved line transitions to the curved line γ2. Further, an execution timing may be determined using tag information stored in the process cartridges.
In a second modified example as well, the cartridge of the Type 1 and the cartridge of the Type 3 having a nominal lifespan of 50,000 sheets are employed. As for the transition of the curved line γ as well, the image density control is executed for every 2,400 sheets in the Type 3 like Table 3. In the present modified example, the Type 1 and the Type 3 differ not only in a toner filling amount but also in the surface layer material of a photosensitive drum 1. That is, the Type 1 has a photosensitive drum 1 having a surface layer made of a material that easily wears, and the Type 3 has a photosensitive drum 1 having a surface layer made of a material that hardly wears. The cartridge of the Type 3 has a greater toner filling amount, and has the photosensitive drum 1 that hardly wears. Therefore, a reduction in a drum potential after charging becomes slower than the Type 1. As a result, a change in the curved line γ also becomes slower. In a case where the Type 1 and the Type 3 coexist, the image density control is executed at both the timing when 1,000 sheets have been printed for the Type 1 and the timing when 2,400 sheets have been printed for the Type 3. Thus, the execution frequency of the image density control is increased, thereby making it possible to reproduce more accurate tinges.
Note that the difference between the photosensitive drums 1 may not be a difference in the materials of their surface layers but may be a difference in the film thickness of the surface layers or susceptibility to light degradation. In any way, the present embodiment is applicable so long as the transition speed of the curved line γ varies. Further, the image density control is periodically executed in the present embodiment but may be non-periodically executed according to the timing when the curved line transitions to the curved line γ2. Further, an execution timing may be determined using tag information stored in the process cartridges.
In a third modified example as well, the cartridge of the Type 1 and the cartridge of the Type 3 having a nominal lifespan of 50,000 sheets are employed. As for the transition of the curved line γ as well, the image density control is executed for every 2,400 sheets in the Type 3 like Table 3. In the present modified example, the Type 1 and the Type 3 differ not only in a toner filling amount but also in a developing roller 17. That is, a developing roller 17 of the Type 3 has lower hardness than that of the Type 3. The cartridge of the Type 3 has a greater toner filling amount, and has the developing roller 17 having lower hardness. Therefore, degradation of developing roller filming is reduced. As a result, the transition of the curved line γ becomes slower compared to the Type 1.
In a case where the Type 1 and the Type 3 coexist like the present embodiment, the image density control is executed at both the timing when 1,000 sheets have been printed for the Type 1 and the timing when 2,400 sheets have been printed for the Type 3. Thus, the execution frequency of the image density control is increased, thereby making it possible to reproduce more accurate tinges.
Further, the image density control is periodically executed in the present embodiment but may be non-periodically executed according to the timing when the curved line transitions to the curved line γ2. Further, an execution timing may be determined using tag information stored in the process cartridges. As described in the above modified example, the nominal lifespans of the cartridges are also determined by elements such as materials, structures, or the like of respective members other than toner filling amounts. However, in any case, it is possible to accurately reproduce color tinges by executing the image density control at a timing suited to each of the cartridges having different lifespans.
A third embodiment will describe a case where only an image density control timing in a cartridge having the shortest nominal lifespan among a plurality of process cartridges is used as a trigger for executing image density control.
An example of the control of the present embodiment will be described with reference to
Subsequently, as the number of printed sheets after reset of the Type 1 reaches 1,000 sheets at a timing P3 when 1,000 sheets have been printed since the timing P2, the image density control is executed for the second time. In the present embodiment, the number of printed sheets is reset also for the Type 2. Subsequently, at a timing P4 when 1,000 sheets have been printed since the timing P3, the image density control is executed for the third time.
In the present embodiment, only an image density control timing related to the Type 1 that has the smallest number of printed sheets until reset among the process cartridges installed in an image forming apparatus 100 serves as a trigger. That is, in the present embodiment, the number of counted sheets of the Type 2 does not reach 2,000 sheets. In this control, calibration is executed according to the shortest cycle, and therefore a sufficient number of calibration times is achieved. In addition, the number of calibration times does not become excessive in the present embodiment.
Next, a fourth embodiment of the present invention will be described. Note that descriptions will be omitted for parts overlapping with the above embodiments. The present embodiment differs from the above embodiments in an image density control method.
In the above embodiments, the toner patches are formed on the intermediate transfer belt, and then adjustment of image density or gradation is executed using results obtained by measuring the toner patches with the density sensor 41. Conversely, a controller 72 of the present embodiment acquires computation parameters for image density control stored in advance in a ROM 74 of an image forming apparatus 100, and then executes adjustment of image density or gradation using the computation parameters. The computation parameters are calculated by performing machine learning using temperature and humidity information, the number of printed sheets, cartridge lifespan information, toner amounts inside cartridges and member information (types of charging rollers and developing rollers), or the like at the development stage of a product.
By executing image density control using the computation parameters, a series of operation times such as patch formation on an intermediate transfer belt and measurement with a density sensor are eliminated, and the image density control is completed using only a computation processing time.
By this method, it is possible to maintain high tinge reproduction without increasing downtime for a user even if the execution frequency of the image density control becomes high in a case where process cartridges having different lifespans coexist in the same image forming apparatus.
As described above, according to the methods of the respective embodiments, it is possible to provide an image forming apparatus capable of executing accurate tinge adjustment even in a case where process cartridges having different lifespan settings are installed in the same image forming apparatus. That is, when respective cartridges having different lifespans are installed in the same image forming apparatus, executing image density control corresponding to the respective lifespans increases a calibration frequency, thereby enabling the maintenance of tinge reproduction. Note that the respective embodiments describe cases where the lifespans of two types are set. However, the number of lifespans set is not limited to this. Even in a case where cartridges having the lifespans of at least three types coexist, it is possible to maintain tinge reproduction by executing calibration corresponding to the respective lifespans. Note that configurations causing a factor for different cartridge lifespans differ between the respective embodiments, but any combination of these configurations is possible in actual cartridges.
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. 2023-099180, filed on Jun. 16, 2023, which is hereby incorporated by reference wherein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-099180 | Jun 2023 | JP | national |
