JP7251293B2 - image forming device - Google Patents

Description

The present invention relates to an image forming apparatus.

There is a demand for an image forming apparatus that can print images on paper with an uneven surface such as embossed paper (hereinafter referred to as "uneven paper") according to user requirements such as image quality, productivity, and texture. It is In image formation, transferability when transferring a toner image from an image carrier to paper is an important property that affects image quality. The transferability of a toner image onto a sheet of paper may vary depending on the degree of unevenness of the surface of the sheet of paper, the state of the developer, the environment, and the like. Therefore, when printing on textured paper, there is a possibility that variations in image quality will increase due to differences in transfer properties.

In general, optimizing transfer performance requires repeated test printing while fine-tuning the process status settings of the image forming apparatus to find the process conditions that provide optimal transfer performance, which is a very time-consuming task. can be Furthermore, since the state of the developer may change in the course of repeated use of the image forming apparatus, it may be necessary to set the process state again.

In relation to this, Japanese Patent Application Laid-Open No. 2002-200001 discloses a technique for reducing the charge amount of toner in a developing device in order to suppress defective transfer of a toner image onto uneven paper.

JP 2016-114718 A

In the technique disclosed in Japanese Patent Application Laid-Open No. 2002-200000, the charge amount of the toner in the developing device is reduced by replacing part of the toner in the developing device or increasing the toner density. However, by forming a solid image over the entire image area, high-density image formation is achieved and the amount of charge on the toner is reduced. There is a possibility that a large amount of waste such as an increase in toner consumption may occur.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of maintaining an appropriate image quality while suppressing an increase in toner consumption.

The above objects of the present invention are achieved by the following means.

(1) An image carrier, a developing section that develops an electrostatic latent image formed on the image carrier with toner, and a toner image on the image carrier developed by the developing section that is transferred to a sheet of paper. An image forming apparatus comprising: a transfer unit, a setting unit for setting a target process state; a control unit for controlling the process state of the image forming apparatus; wherein the process state of the image forming apparatus includes a deterioration state of toner in the developing section, and the control section determines whether the process state of the image forming apparatus is a deterioration state of toner in the developing section. In this case, the deterioration state is controlled to achieve a target process state , and the toner in the developing section is consumed and the consumed amount of toner is replenished to shorten the average residence time, thereby shortening the development. recovery processing for recovering deterioration of toner in the developing unit, or deterioration processing for promoting deterioration of the toner in the developing unit by increasing the average residence time by agitating the toner without replenishing the toner; The deterioration state of the toner in the developing unit is controlled so that the deterioration state of the toner in the developing unit becomes the toner average residence time corresponding to the target deterioration state of the toner, and the deterioration state of the toner in the developing unit is adjusted to the target. an image forming apparatus that executes the recovery process when the target deterioration state of the toner exceeds the upper limit threshold, and executes the deterioration process when the target deterioration state of the toner falls below the lower limit threshold.

(2) The process state of the image forming apparatus includes the charge amount of the toner in the developing section, the deterioration state of the toner in the developing section, the transfer bias in the transfer section, and the durability state of each process member of the image forming apparatus. The image forming apparatus according to (1) above, including at least one of

( 3 ) an image carrier, a developing section that develops the electrostatic latent image formed on the image carrier with toner, and a toner image on the image carrier developed by the developing section that is transferred to paper. an image forming apparatus comprising a transfer unit, a setting unit for setting a target deterioration state of toner, a calculation unit for calculating an average retention time of toner in the developing unit, and a toner in the developing unit being consumed; A recovery process for recovering the deterioration of the toner in the developing section by replenishing the consumed amount of toner to shorten the average residence time, or by agitating the toner without replenishing the toner to lengthen the average residence time. a control unit for executing deterioration processing for promoting deterioration of toner in the developing unit, wherein the control unit controls the state of deterioration of the toner in the developing unit to be a toner average according to the target deterioration state of the toner. The deterioration state of the toner in the developing unit is controlled so as to satisfy the residence time, and the recovery process is performed when the deterioration state of the toner in the developing unit exceeds the target upper limit threshold value of the toner deterioration state. and executing the deterioration process when the target deterioration state of the toner falls below the lower limit threshold .

( 4 ) further comprising an operation panel for receiving user input, wherein the setting unit acquires from the storage unit the toner deterioration state corresponding to the target image on the operation panel selected by the user input; The image forming apparatus according to any one of (1) to ( 3 ) above, wherein the deterioration state is set to the target deterioration state of the toner.

( 5 ) When performing continuous printing, the setting unit sets the toner deterioration state in the developing unit at the start of printing to the target toner deterioration state in (1) to ( 3 ) The image forming apparatus according to any one of 3).

( 6 ) The image forming apparatus according to any one of (1) to ( 5 ) above, wherein the control section controls the deterioration state of toner in the developing section at a timing according to a user's instruction.

( 7 ) The image forming apparatus according to ( 6 ), wherein the setting unit sets the deterioration state of toner in the developing unit at the timing to the target deterioration state of toner.

( 8 ) The image forming apparatus according to any one of (1) to ( 7 ) above, wherein the setting unit sets the target deterioration state of toner based on information about paper to be used for printing. .

( 9 ) When the paper used for printing is embossed paper, the setting unit sets, as the information about the paper, the target toner deterioration state compared to when the paper is plain paper or glossy paper. The image forming apparatus according to ( 8 ) above, wherein the range of is narrowed.

( 10 ) any one of (1) to ( 9 ) above, wherein the control unit controls the state of deterioration of toner in the developing unit in a non-image area between image areas on the image carrier; The described image forming apparatus.

According to the present invention, by controlling the deterioration state of the toner in the developing device, the deterioration state of the toner corresponding to the transferability desired by the user can be obtained. The image quality of the toner image can be made appropriate.

1 is a schematic cross-sectional view illustrating the configuration of an image forming apparatus according to a first embodiment; FIG. 2 is a schematic block diagram illustrating the configuration of the image forming apparatus shown in FIG. 1; FIG. 4 is a flowchart illustrating a processing procedure of a method for controlling the image forming apparatus according to the first embodiment; FIG. 5 is a schematic diagram illustrating the transferability of a toner image onto embossed paper when the deterioration state of toner is different; FIG. 4 is a schematic diagram conceptually illustrating a table for a user to select transcription properties; 6 is a schematic diagram illustrating ranges of deterioration states of toner corresponding to the table shown in FIG. 5; FIG. 5 is a graph conceptually exemplifying control of the deterioration state of toner; 5 is a graph showing changes in average toner residence time for each print coverage; FIG. 10 is a schematic diagram conceptually illustrating a table for the user to select transfer properties in the second embodiment. 10 is a schematic diagram illustrating ranges of toner deterioration states corresponding to the table shown in FIG. 9; FIG. FIG. 11 is a schematic diagram for explaining setting of a target deterioration state of toner in the third embodiment; FIG. 14 is a schematic diagram illustrating a case where recovery processing is executed according to a user's instruction in the fourth embodiment; 7 is a graph illustrating the results of toner state control; As a comparative example, it is a graph illustrating conventional refresh mode processing for refreshing toner in a developing device.

Hereinafter, embodiments of the present invention will be described with reference to the attached drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and overlapping descriptions are omitted.

(First embodiment)
FIG. 1 is a schematic cross-sectional view illustrating the configuration of the image forming apparatus according to the first embodiment, and FIG. 2 is a schematic block diagram illustrating the configuration of the image forming apparatus shown in FIG.

An image forming apparatus 100 shown in FIG. 1 is an image forming apparatus using an electrophotographic process, and is a so-called tandem type image forming apparatus that forms a color image by arranging a plurality of photosensitive drums facing an intermediate transfer belt. It is a color image forming apparatus.

The image forming apparatus 100 is used to form (print) an image on paper, which is a recording medium, using scanned document image data. Image forming apparatus 100 can be, for example, an MFP (MuLti-Function Peripheral) having a copy function, a printer function, and a scan function.

<Configuration of Image Forming Apparatus 100>
Image forming apparatus 100 has image reading section 110 , image forming section 120 , transfer section 130 , paper feeding section 150 , paper conveying section 160 , fixing section 170 , operation display section 180 and control section 190 .

The image reading unit 110 applies light from a light source to a document set at a predetermined reading position on a platen or to a document transported to a predetermined reading position by an ADF (Auto Document Feeder), and detects the reflection of the light. An electric signal is generated by photoelectrically converting light with a light receiving element such as a CCD image sensor or a CMOS image sensor. The generated electrical signal is subjected to A/D conversion, shading correction, filter processing, image compression processing, and the like, and is input to image forming section 120 .

The image forming unit 120 is used to form an image on the paper 10, which is a recording medium, using an electrophotographic process. The image forming section 120 includes an image forming unit 12A that forms a yellow (Y) image, an image forming unit 12B that forms a magenta (M) image, and an image forming unit 12C that forms a cyan (C) image. , and an image forming unit 12D for forming a black (K) color image.

Each unit of the image forming section 120 has a developing device 121, a photosensitive drum 122, a charging section 123, and an optical writing section 124, respectively.

The developing device 121 functions as a developing unit, and forms a toner image by making the electrostatic latent image visible with the toner by attaching toner to the surface of the photosensitive drum 122 . That is, monochrome toner images corresponding to yellow, magenta, cyan, and black are formed on the photosensitive drums 122 of the image forming units 12A, 12B, 12C, and 12D, respectively.

Each developing device 121 of the image forming units 12A to 12D contains a two-component developer composed of small-particle-size toners of different colors of yellow, magenta, cyan and black and a carrier. The two-component developer is composed of a carrier having a core of ferrite and an insulating resin coated around it, and polyester as the main material, with colorants such as carbon black, charge control agents, and external additives such as silica and titanium oxide added. Consists of toner. The carrier has a particle size of 15 to 100 μm and a saturation magnetization of 10 to 80 emu/g. The toner has a particle size of 3 to 15 μm. As the two-component developer, a mixture of these carriers and toner is used so that the toner concentration is 4 to 10 mass %. In this embodiment, the toner is negatively charged.

The toner supply unit 125 conveys toner from a tank (not shown) that stores toner corresponding to each color, and supplies the toner to the developing device 121 .

The photoreceptor drum 122 is an image carrier having a photoreceptor layer made of a resin such as polycarbonate containing an organic photoconductor (OPC), and is configured to rotate at a predetermined speed.

The charging unit 123 is composed of a corona discharge electrode arranged around the photoreceptor drum 122 and charges the surface of the photoreceptor drum 122 with generated ions.

The optical writing unit 124 incorporates a scanning optical device, and exposes the charged photosensitive drum 122 based on the image data input from the image reading unit 110, thereby changing the potential of the exposed portion. to form a charge pattern (electrostatic latent image) corresponding to the image data.

The transfer unit 130 transfers the toner image on the photosensitive drum 122 developed by the developing device 121 onto the paper 10 . The transfer section 130 has an intermediate transfer belt 131, a primary transfer section 132, a secondary transfer section 140, and the like.

The intermediate transfer belt 131 is endless, is arranged on the side of the image forming units 12A to 12D, and is positioned so as to contact the photosensitive drum 122. As shown in FIG. The intermediate transfer belt 131 is made of, for example, a polyimide film.

Monochrome toner images of respective colors formed in the image forming units 12A to 12D are sequentially transferred onto the intermediate transfer belt 131 to form a color toner image in which layers of yellow, magenta, cyan, and black are superimposed. be done. The secondary transfer unit 140 is used to transfer the color toner image formed on the intermediate transfer belt 131 onto the paper 10 being conveyed.

The paper feed unit 150 includes a plurality of paper feed trays 151 and 152 that accommodate the paper 10 . Paper such as plain paper, coated paper, and embossed paper are accommodated in the paper feed trays 151 and 152 by paper type or paper size. The paper 10 is fed to the paper conveying section 160 one by one.

Embossed paper is, for example, art paper or coated paper whose surface is subjected to embossing to give minute irregularities such as satin, texture, and silk texture. There are many uses that make use of the texture, such as unevenness that reproduces the texture of leather like "Leathac 66" and unevenness of small flowers like "Edo Kozome Hana". Embossed paper can be mainly used for book covers and covers, tickets, packages, wallpapers, and the like.

The paper conveying unit 160 conveys the paper 10 within the image forming apparatus 100 . The paper transport section 160 has a paper transport path 161 and a plurality of transport rollers 162 for transporting the paper 10 .

The paper 10 fed from the paper feeding unit 150 is conveyed along the paper conveying path 161 by rotating the plurality of conveying rollers 162 by a drive unit (motor not shown). The paper 10 is conveyed to the secondary transfer section 140 via the registration roller 16R, and after the toner image is transferred in the secondary transfer section 140, is conveyed to the fixing section 170. FIG.

The fixing section 170 is used to fix the toner image transferred to the paper 10 and has a heating roller 171 and a pressure roller 172 . When paper 10 passes between heating roller 171 and pressure roller 172, pressure and heat are applied to melt the toner, thereby fixing the toner image. The paper 10 on which the image is fixed is discharged from the paper discharge unit to the outside of the image forming apparatus 100 .

The operation display unit 180 receives instructions from the user and displays messages to the user on the screen. Operation display unit 180 has a keyboard and an operation panel. A user inputs instructions to the image forming apparatus 100 by operating a keyboard or an operation panel. The screen also displays input information, various setting information, warning messages, and the like.

Control unit 190 integrally controls image reading unit 110, image forming unit 120, transfer unit 130, paper feeding unit 150, paper conveying unit 160, fixing unit 170, and operation display unit 180 to form an image. It implements the functions of the device 100 .

The control unit 190 has a CPU (Central Processing Unit) 191, an auxiliary storage unit 192, a RAM (Random Access Memory) 193, and a ROM 194 (Read Only Memory), and these components are interconnected by an internal bus. there is

The auxiliary storage unit 192 stores an operating system, various application programs, a control program for controlling each unit of the image forming apparatus 100, and the like.

The RAM 193 temporarily stores print image data and the like as a result of arithmetic processing by the CPU 191 . Also, in this embodiment, the RAM 193 functions as a storage unit and is used to store the user's target process state. Details of the process state will be described later.

The ROM 194 stores various parameters and the like used by the CPU 191 in arithmetic processing and the like.

The control unit 190 also has an interface (not shown) for communicating with devices such as client terminals connected to the network, receives print jobs from the client terminals, and transmits the print jobs to the image forming unit 120 .

CPU 191 realizes various functions of image forming apparatus 100 by executing control programs. For example, in order to replace the toner remaining in the developing device 121, the image forming apparatus 100 discharges (discards) part of the toner (developer) outside the developing device 121 and replenishes new toner. has a function of refreshing the toner in the developing device 121 (called a “refresh mode”). This is because, for example, when images with low print coverage (printing ratio) are printed continuously, the amount of toner consumed in the developing device 121 decreases, so the average retention time of toner in the developing device 121 increases. Toner with a long residence time deteriorates due to friction between developers due to agitation and friction with members of the developing device 121 . Specifically, when the toner's external additives peel off from the toner or become embedded in the surface of the toner, the toner deteriorates and its charge amount and adhesive force (releasing property) change, resulting in a toner image on the paper. It affects transferability (hereinafter also simply referred to as “transferability”). The refresh mode is for coping with this and the like, and corresponds to recovery processing to be described later. In the refresh mode, the toner supply unit 125 replenishes the developing device 121 with toner corresponding to the consumed amount so as to maintain the toner density of the developer in the developing device 121 at a predetermined value. The replenished toner is mixed and stirred with the carrier by the stirring screw inside the developing device 121, so that a predetermined charge amount is imparted to the toner.

However, simply executing the refresh mode described above may not be able to achieve or maintain the image quality (transferability) desired by the user when the printing paper is uneven paper. Therefore, the image forming apparatus 100 of this embodiment is configured to be able to control the deterioration state of the toner in the developing device 121 from the viewpoint of realizing or maintaining the transferability desired by the user.

More specifically, the control unit 190 controls the process state of the image forming apparatus 100, and controls the deterioration state of the toner in the developing device 121 when the process state is the deterioration state of the toner in the developing device 121. By doing so, the target deterioration state of the toner is obtained. The process state includes, for example, the toner charge amount in the developing device 121, the transfer bias in the transfer unit 130, the durability state of each process member, and the like, in addition to the deterioration state of the toner in the developing device 121. FIG.

The controller 190 can calculate the toner charge amount based on, for example, the development current and the toner adhesion amount. The development current is the current that flows between the development roller (not shown) and the photosensitive drum 122 during development. The development current is proportional to the total amount of charge per unit time of the transferred toner. The control unit 190 calculates the total charge amount of the developed toner from the development current measured by the ammeter, and based on the density value detected by the density sensor (not shown) arranged on the intermediate transfer belt 131, Calculate the toner adhesion amount. The controller 190 calculates the toner charge amount based on the total toner charge amount and the toner adhesion amount.

In controlling the toner deterioration state, recovery processing or deterioration processing can be executed according to the result of comparison between the target process state and the current process state of the image forming apparatus 100 . The recovery process is a process of discharging part of the toner from the developing device 121 and replenishing toner from the toner supply unit 125 to the developing device 121 to recover the deterioration of the toner in the developing device 121 . Further, the deterioration process is a process of accelerating the deterioration of the toner in the developing device 121 by agitating the toner in the developing device 121 without discharging or replenishing the toner.

Note that the recovery process and the deterioration process may be executed by the user instructing through the operation display unit 180, or as described later, it is automatically determined that the paper to be printed is uneven paper such as embossed paper. It may be detected and executed when the paper is textured paper such as embossed paper.

<Control method>
Hereinafter, the processing procedure of the control method of the image forming apparatus 100 will be described with reference to FIGS. 3 to 8. FIG. FIG. 3 is a flowchart illustrating the processing procedure of the control method of the image forming apparatus 100 according to this embodiment. The processing of the flowchart of FIG. 3 is realized by the CPU 191 of the control unit 190 executing the control program. FIG. 4 is a schematic diagram illustrating the transferability of a toner image onto embossed paper when the deterioration state of toner is different. FIG. 5 is a schematic diagram conceptually illustrating a table for the user to select transferability, and FIG. 6 is a schematic diagram illustrating ranges of toner deterioration states corresponding to the table shown in FIG. . FIG. 7 is a graph conceptually exemplifying control of the deterioration state of toner. In FIG. 7, the vertical axis of the graph represents the deterioration state of toner, and the horizontal axis represents the number of printed sheets. Furthermore, FIG. 8 is a graph showing the transition of the average residence time of toner for each print coverage.

As shown in FIG. 3, first, a target process state is set (step S101). The process state is, for example, the charge amount of the toner in the developing device 121, the deterioration state of the toner in the developing device 121, the transfer bias in the transfer unit 130, the durability state of each process member, or the like, and may be individually or in combination. can be set with The control unit 190 functions as a setting unit and stores the target process state in the RAM 193 .

In the present embodiment, as the process state of the image forming apparatus 100, the toner state in the developing device 121 is particularly focused on, and the toner deterioration state is controlled based on the target toner deterioration state and the current toner deterioration state. will be explained. The deterioration state of the toner is represented by, for example, the average residence time [sec] (described later) of the toner that is agitated without being consumed in the developing device 121 .

Deterioration of toner in the developing device 121 can affect transferability. Usually, when the deterioration of the toner is small, the transferability is high, and when the deterioration of the toner is large, the transferability is low. In this embodiment, the control unit 190 determines an appropriate state of deterioration of the toner in the developing device 121 according to the transferability desired by the user.

The transferability can vary depending on, for example, the type of paper, particularly the degree of unevenness (surface roughness) on the surface of the paper. For example, when printing on glossy paper with almost smooth surface roughness such as OK Topcoat and embossed paper with unevenness of about 100 [μm] such as Leathac 66, the deterioration of toner is about the same. However, there may be a large difference in transferability between the two. Further, even when the toner is in a degraded state that causes no problems on glossy paper, the transfer performance may be poor (non-uniform) on embossed paper.

For example, even if the deterioration state of the toner is within a range that does not cause a difference in transferability to glossy paper, it may cause a difference in transferability to embossed paper, as shown in FIG. can be State 1, which is an example of a halftone image, represents the transferability when toner deterioration is the greatest. In state 1, there are many concave portions W (white portions) where no toner adheres. State 2 represents the transferability when the deterioration state of the toner is moderate. In state 2, there are portions G (gray portions) with little toner adherence and concave portions W (white portions) with no toner adherence. Furthermore, State 3 represents the transferability when the deterioration state of the toner is the smallest. In state 3, there are many portions G (gray portions) where toner is not adhered, but there are few concave portions W (white portions) where toner is not adhered. Thus, transferability is lowest in state 1, moderate in state 2, and highest in state 3. The states 1 to 3 of the solid image are the same as those of the halftone image.

Generally, paper with a smooth surface, such as glossy paper, is required to have a uniform transfer quality (e.g., equal to or higher than state 3 in the case of embossed paper in FIG. 4). However, in the case of special paper such as embossed paper, it is not always necessary to have uniform transfer quality. In some cases, the quality is required in a state where it is not used.

In this embodiment, the user selects the image quality (transferability) from the operation panel, and the target toner deterioration state corresponding to the selected image quality is set. For example, as shown in FIG. 5, the operation display unit 180 displays a plurality of patch images (target images) for selecting transfer properties on the operation panel, and the user selects a number from 1 to 4 corresponding to the patch images. is selected by operating the operation panel. FIG. 5 exemplifies a table in which the transfer property can be selected from four options 1 to 4, and patch images of halftone images and solid images are exemplified for each of the four transfer properties.

Option No. 1 has a strong implication of "emphasizing texture" and has low transferability. That is, the toner image is not evenly transferred. No. 1 can be used, for example, when it is desired to print on embossed paper (for example, Lethac 66) while leaving the texture of leather. On the other hand, option No. 4 has a strong meaning of "emphasizing uniformity", and the toner image is uniformly transferred. No. 4 is used, for example, when it is desired to improve the image quality by causing the toner to adhere to the concave portions. Choices 2 and 3 have an intermediate meaning between choices 1 and 4, and have moderate transferability.

As shown in FIG. 6, the transfer properties selected in FIG. 5 are associated with the range of deterioration of the toner. For convenience of explanation, a curve 201 representing the deterioration state of the toner in the developing device 121 with respect to the number of printed sheets is shown when printing is continued without executing the refresh mode in normal printing. The example shown in FIG. 6 shows a case where printing of N1 sheets has already been performed before the start of printing this time, and the deterioration state of the toner at the start of printing is L1. As the number of printed sheets increases, the deterioration of toner progresses. This is because the external additive adhering to the toner surface is detached or buried, or the amount of charge is reduced. Its progress gradually slows down and approaches Ls.

In the present embodiment, the toner deterioration states L1 to Ls are divided into four ranges (L1 to L2, L2 to L3, L3 to L4, L4 to Ls) that have the same width and do not overlap each other, They are associated with the respective transfer properties 4 to 1 shown in FIG. For example, when the user selects transferability No. 2 in FIG. 5 (displayed in gray), as shown in FIG. handle.

In the above example, the user selects the patch image to select the transferability and determines the target deterioration state of the toner corresponding to the transferability. not. For example, the user may operate the operation panel to directly input the target deterioration state of the toner.

For each transfer property, the range of deterioration of toner can be adjusted in consideration of the type of paper used for printing. More specifically, the control unit 190 acquires information such as the type of paper to be printed from the information on the type of paper selected by the user when setting the tray information, and determines the range of toner deterioration based on this information. can be adjusted.

For example, when the set paper type is glossy paper or the like, the degree of irregularities on the surface is small, so the range of variation in transferability is small. Therefore, the range of deterioration of the toner can be wider than that of the uneven paper. On the other hand, when the set paper type is embossed paper, the width of the range of the target toner deterioration state is narrowed compared to when the paper type is glossy paper.

In addition, the target toner deterioration state is recorded in a paper profile in which the paper settings frequently used by the user are registered in advance. may be updated.

In addition, even if the paper type information is acquired, there are many cases where the roughness cannot be determined. The range of deterioration state of toner may be adjusted. As an automatic discrimination method, the surface roughness can be measured by installing a reflective measuring device that detects the surface condition of the paper in the tray, or by installing a contact-type surface roughness measuring device in the paper path. can be determined.

The range of toner deterioration state set for each transfer property is stored in the RAM 193 .

Returning to FIG. 3 again, the target process state and the current process state are compared (step S102). The control unit 190 functions as a setting unit and acquires a target deterioration state of toner as a target process state from the RAM 193 . Further, the control unit 190 acquires, for example, the deterioration state of the toner in the developing device 121 as the current process state. The state of deterioration of the toner in the developing device 121 is represented, for example, by using the toner average residence time (also called "toner average age" or "deterioration index") below.

Toner average residence time [sec] = (pre-process average residence time [sec] + driving time of developing device [sec]) x (toner amount in developing device [g] x coefficient - toner consumption [g]) / (development Amount of toner in the device [g] x factor). Here, the pre-process average residence time is the toner average residence time [sec] before the start of the printing operation. The controller 190 functions as a calculator and calculates the toner average residence time.

The control unit 190 determines whether the state of deterioration of the toner in the developing device 121 is within the range of the target state of deterioration of the toner. For example, when the user selects transferability No. 2 in FIG. 5, it is determined whether or not the target toner deterioration state range is in the range of L3 to L4.

Next, the deterioration state of toner in the developing device 121 is controlled (step S103). Based on the determination result of step S102, the control unit 190 controls the toner deterioration in the developing device 121 so that the current toner deterioration state falls within the target toner deterioration state range. More specifically, the control unit 190 controls the deterioration state of the toner in the developing device 121 so that the deterioration state of the toner in the developing device 121 becomes the toner average residence time corresponding to the target deterioration state of the toner. to control.

For example, as shown in FIG. 7, a curve 202 represents the toner deterioration state with respect to the number of printed sheets when printing is continued until the number of printed sheets reaches N with a predetermined print coverage. As the number of printed sheets increases, the toner in the developing device 121 deteriorates until the number of printed sheets reaches N sheets. In addition, the transferability deteriorates as the deterioration of the toner in the developing device 121 progresses.

In this embodiment, for example, after the number of printed sheets reaches a predetermined number M, the control unit 190 alternately performs the recovery process and the deterioration process so that the deterioration state of the toner in the developing device 121 is reduced to the target toner level. Control to stay within the deterioration state range. More specifically, the control unit 190 executes the recovery process when the current deterioration state of the toner exceeds the range of the target deterioration state of the toner, and executes the deterioration process when it falls below the range. . In the recovery process, the toner in the developing device 121 is consumed and the toner in the consumed amount is replenished to shorten the average residence time, thereby recovering the deterioration of the toner in the developing device 121 . Further, in the deterioration process, deterioration of the toner in the developing device 121 is accelerated by increasing the average residence time by agitating the toner without replenishing the toner.

Also, the upper threshold value 301 and the lower threshold value 302 correspond to the toner deterioration states L4 and L3, respectively. The control unit 190 executes recovery processing when the deterioration of the toner in the developing device 121 exceeds the upper threshold value 301 (L4), and executes deterioration processing when it falls below the lower threshold value 302 (L3).

Reference numerals 203 and 204 represent changes in the deterioration state of the toner with respect to the number of printed sheets during recovery processing and deterioration processing, respectively. In the example shown in FIG. 7, the recovery process is performed on the non-image areas between the image areas on the photoreceptor drum 122 . The control unit 190 calculates the amount of toner replacement required to maintain the control for keeping the current state of deterioration of toner within the range of the target state of deterioration of toner. Subsequently, the control unit 190 calculates the toner shortage from the print coverage amount during printing and the toner replacement amount.

Based on the calculation result of the toner shortage, the control unit 190 controls to discharge the toner in the developing device 121 and replenish the developing device 121 for each paper interval, for example. Alternatively, the controller 190 may accumulate the amount of toner shortage, temporarily stop printing when a predetermined threshold value is exceeded, and perform control to discharge and replenish the toner all at once.

In FIG. 8, for example, if it is desired to maintain quality at the level of dashed line 303, image quality is satisfied by ejecting and feeding at 3% print coverage at all times.

On the other hand, in the example shown in FIG. 7, the deterioration process is executed in the image area on the photoreceptor drum 122 . In other words, in this case, the deterioration process is carried out as the deterioration of the toner progresses in normal image formation.

Also, the deterioration process may be performed on the non-image area between the image areas on the photosensitive drum 122 . In this case, image formation is not performed by the developing device 121, and the toner in the developing device 121 is agitated without being discharged or supplied.

In this way, the control unit 190 compares the target toner deterioration state with the current toner deterioration state, and controls the toner deterioration state in the developing device 121 according to the comparison result. Desired transferability can be realized continuously.

Note that FIG. 6 illustrates a case where the range of deterioration state of each toner has a uniform width, but the width of the range may be varied depending on the transferability. For example, if both transferability Nos. 2 and 3 are permissible, the upper threshold value and lower threshold value are set within a range that includes the ranges of the toner deterioration states corresponding to the transferability Nos. 2 and 3. good too. As a result, the range that the user can tolerate is widened, so the frequency with which the recovery process is executed is reduced, and a decrease in productivity can be suppressed.

Returning to FIG. 3 again, it is determined whether printing is completed (step S104). The processes of steps S102 and S103 are repeated until printing is completed, such as when the number of printed sheets reaches a predetermined number. If printing is completed (step S104: YES), the process is terminated (end). On the other hand, if the printing process has not been completed (step S104: NO), the process returns to step S102.

The image forming apparatus 100 of the first embodiment described above has the following effects.

By controlling the state of deterioration of the toner in the developing device 121, the state of deterioration of the toner corresponding to the transferability desired by the user can be obtained, so that the transferability can be optimized while suppressing an increase in toner consumption.

(Second embodiment)
In the first embodiment, the case where transferability is selected from the viewpoint of texture and uniformity has been described. In the second embodiment, a case where transferability is selected from the viewpoint of quality stability and productivity will be described. In order to avoid duplication of description, detailed description of the same configuration as in the first embodiment will be omitted.

FIG. 9 is a schematic diagram conceptually illustrating a table for the user to select the transferability in the second embodiment, and FIG. 10 illustrates the range of toner deterioration state corresponding to the table shown in FIG. It is a schematic diagram to do.

FIG. 9 exemplifies a table in which transferability can be selected from four options A to D from the viewpoint of quality stability and productivity. As shown in FIG. 10, the transfer properties selected in FIG. 9 are associated with the range of deterioration of the toner. In the present embodiment, the toner deterioration states L1 to L8 are divided into four ranges (L4 to L5, L3 to L6, L2 to L7, and L1 to L8) overlapping each other and having different widths, as shown in FIG. Each of the transfer properties A to D are associated with each other.

Option A has a strong implication of "prioritizing quality stability" and has the smallest fluctuation in transferability. Therefore, while A can maintain stable transferability, it is necessary to frequently perform recovery processing. On the other hand, option D has a strong implication of "prioritizing productivity", and has the largest fluctuation in transferability. As a result, although the transferability fluctuates, the number of times the recovery process is executed can be reduced. Options B and C have meanings intermediate between A and D, and the range of variation in transferability is moderate.

For example, when the user selects the transferability of B (indicated in gray) in FIG. 9, the range of the target deterioration state of the toner corresponds to the range of B (L3 to L6) as shown in FIG. . The control unit 190 performs control so that the current deterioration state of toner falls within the B range.

In this way, the user can select the range of the deterioration state of the toner using quality stability and productivity as indexes.

The image forming apparatus 100 of the second embodiment described above has the following effects in addition to the effects of the first embodiment.

Since transferability can be selected from the viewpoints of "quality stability is prioritized" and "productivity is prioritized", the user can have a wider range of transferability options.

In the first embodiment, it is explained that transferability is selected from the viewpoints of "emphasis on texture" and "emphasis on uniformity." Although it has been explained that the transferability is selected from the viewpoint of "priority", the transferability may be selected in consideration of two viewpoints, or the transferability may be selected based on either one of the viewpoints.

For example, a user whose quality requirements often change for each print job selects the transferability from the viewpoint of "emphasis on texture" and "emphasis on uniformity" for each print job, and maintains the selected transferability. considered suitable. In addition, when the user has a fixed demand for image quality to some extent, it may be possible to assign a level of stability and productivity to the demanded image quality. According to the image quality requested by the user, it is possible to select the optimum selection method for the transferability.

(Third embodiment)
In the first and second embodiments, the case where the user selects the transferability and sets the target deterioration state of the toner based on the selected transferability has been described. In the third embodiment, a case will be described in which the deterioration state of toner at the start of printing is set as the target deterioration state of toner. In order to avoid duplication of description, detailed description of the same configuration as in the first embodiment will be omitted.

FIG. 11 is a schematic diagram for explaining setting of a target deterioration state of toner in the third embodiment.

Normally, the toner in the developing device 121 and each process member of the image forming apparatus 100 deteriorate as the printing is repeatedly executed. Therefore, the state of deterioration of the toner in the developing device 121 is in the most desirable state at the time the print job is started, and the quality of the image formed in that state of deterioration of the toner is considered to be acceptable to the user. be done. Therefore, it is desirable that the deteriorated state of the toner in the developing device 121 is maintained at the state at the start of printing when performing continuous printing. Also, it is preferable that all prints in a print job maintain the same level of quality.

Therefore, as shown in FIG. 11, in the present embodiment, the control unit 190 stores the toner deterioration state at the start of printing in the RAM 193 as a target toner deterioration state (quality standard 304). is brought close to the target deterioration state of the toner, and is controlled to maintain that state.

The image forming apparatus 100 of the third embodiment described above has the following effects in addition to the effects of the first and second embodiments.

Even if the target toner deterioration state is not set by user input, it is possible to continuously provide the image quality desired by the user.

(Fourth embodiment)
In the first to third embodiments, when the current deterioration state of toner is out of the range of the target deterioration state of toner, the control unit 190 determines to start execution of recovery processing or deterioration processing. explained the case. In the fourth embodiment, a case will be described in which execution of recovery processing or deterioration processing is started according to a user's instruction. In order to avoid duplication of description, detailed description of the same configuration as in the first embodiment will be omitted.

FIG. 12 is a schematic diagram illustrating a case where recovery processing is executed according to a user's instruction in the fourth embodiment.

For example, even if the deterioration state of the toner in the developing device 121 at the start of printing is set as the target deterioration state of the toner, the user cannot understand the deterioration state of the toner due to the use of the image forming apparatus 100 and the condition of each process member. Degradation is difficult to predict. Therefore, while the user uses the image forming apparatus 100, the quality of the printed image may be unexpected.

Therefore, as shown in FIG. 12, in the present embodiment, if the user looks at the image printed on the paper and determines that the quality is not acceptable during the printing of one print job, the printing is interrupted. Then, the recovery process can be executed at the timing Tr1 specified by the user.

In this case, at the timing Tr1, the target deterioration state range of the toner can be updated. For example, as the new target range of deterioration state of toner, the target range of deterioration state of toner described in the above-described first and second embodiments can be applied. The set target toner deterioration range is stored in the RAM 193 .

Also, the quality standard described in the third embodiment may be set instead of the range of deterioration state of toner. Also, instead of setting a new range, a predetermined refresh amount may be used.

Further, in addition to the recovery process, the user may set the timing of the deterioration process to accelerate the deterioration of the toner at any timing.

The timing of the recovery process and the timing of the deterioration process may each be set multiple times as needed. Also, the timing of recovery processing and deterioration processing can be determined by user input through the operation display unit 180 .

Furthermore, it is assumed that a quality standard 305 and an upper limit threshold 306 are set, and the deterioration state of toner at the start of printing is set in the quality standard 305 . For example, if the user determines that the image quality is unacceptable during printing and executes recovery processing at timing Tr1, the control unit 190 determines that the transferability is not sufficient, and from the upper threshold value 306, The upper limit threshold value 307 is changed to a value closer to the quality standard 305 to improve transferability. As a result, subsequent printing can be made closer to the image quality desired by the user.

Although not shown, a quality standard and a lower threshold are set, and when the user instructs deterioration processing, it is determined that the transferability is too high. Change to get closer.

The image forming apparatus 100 of the fourth embodiment described above has the following effects in addition to the effects of the first to third embodiments.

Since execution of the recovery process or deterioration process can be started at any timing Tr1 specified by the user, the transferability desired by the user can be approached early. Therefore, the quality of the image printed on the paper 10 can be quickly brought close to the quality desired by the user.

<Example>
FIG. 13 is a graph exemplifying the results of implementing toner deterioration state control. In this example, after printing 11,000 sheets (11 Kp) of OK top coat paper, printing was performed by switching to embossed paper. Print coverage was 1%. The basis weight of the OK top-coated paper was 128 [gsm], and the basis weight of the embossed paper (LETHAC 66) was 151 [gsm]. Although not shown in FIG. 13, the OK top-coated paper maintained the highest rank (R5) in terms of transferability regardless of the average toner residence time. The level of transferability is represented by ranks (R1 to R5 (R1 to R3.5 are not described)). R1 is the lowest and R5 is the highest.

On the other hand, the transferability of embossed paper decreased to R4 when the number of printed sheets was 11 Kp. Therefore, in this embodiment, the current deterioration state of the toner (average toner retention time of about 5500 [sec]) to the target deterioration state of the toner (for example, toner average residence time range of 1000 to 3000 [sec]). More specifically, the control unit 190 controls the developing device 121 so as to eject the refresh amount of toner and replenish the same amount as the recovery process. bottom. The refresh amount (that is, the amount of toner supplied to the developing device 121) is defined by the following formula.

Refresh amount [g]=(average toner retention time [sec]−threshold value [sec])×developing device toner amount [g]×coefficient/average toner retention time [sec]. Here, the threshold may be either an upper threshold or a lower threshold. It is also possible to use the average value of the upper and lower thresholds. For example, if the target toner deterioration state is in the range of 1000 to 3000 [sec] of toner average residence time, the value of the upper threshold value 309 is 3000, the value of the lower threshold value 308 is 1000, and the average value of the upper and lower threshold values (3000+1000). Either ÷2=2000 can be used. In this way, the refresh amount is calculated based on the target range (threshold value) of the state of deterioration of the toner.

Subsequently, after the toner average residence time recovered to 1000 [sec], the printing was continued by switching to embossed paper (LETHAC 66) while maintaining the print coverage at 1%. This accelerated the deterioration of the toner, and the toner average residence time reached the upper limit threshold value 309 after that when the number of printed sheets was approximately 15 kp. Then, when the upper limit threshold value 309 was exceeded, recovery processing to the target process state was performed.

Further, after that, the user instructed recovery processing at timing Tr2 when the number of printed sheets was about 20 kp, so recovery processing was executed.

In this way, by alternately repeating the recovery treatment and the deterioration treatment, the transferability could always be maintained within the range of the predetermined width a. As a result, the image quality could always be maintained within a predetermined range.

In the above example, the case where the toner average residence time reaches the upper limit threshold value 309 during deterioration processing has been described. Interrupting the threshold 308 may occur.

In that case, it is also possible to adjust in the direction of adding the average toner residence time by calculating the developer drive time using a formula for calculating the average toner residence time.

<Comparative example>
FIG. 14 is a graph illustrating conventional refresh mode processing for refreshing toner in the developing device 121 as a comparative example.

A curve 201 represents the deterioration state of toner with respect to the number of printed sheets when printing is continued with a predetermined print coverage. In the conventional refresh mode, a target value 310 is set with respect to the deterioration state of toner so that sufficient transferability can be obtained for any type of paper. The target value 310 is, for example, a value of the state of deterioration of the toner that aims to transfer the toner onto uneven paper in a state in which the toner uniformly covers all the unevenness of the surface. When the current deterioration state of the toner reaches the target value 310, the control unit 190 discharges (discards) some of the toner outside the developing device 121 and replenishes new toner. As a result, deterioration of the toner in the developing device 121 is recovered.

However, in the case of rugged paper, depending on the user, it may not be necessary to evenly transfer toner to all of the ruggedness in order to retain the texture of the paper. A dashed line indicates the transferability 311 desired by the user. For this reason, a deviation occurs between the target value 310 and the transferability 311 desired by the user. As a result, the quality of the image printed on the textured paper may be unsatisfactory to the user. In addition, repeated test printing takes an extra adjustment time, and there is a risk that the amount of toner used, waste paper, replacement of consumables, and the like will increase.

As described above, the image forming apparatus 100 has been described in the embodiments. However, it goes without saying that those skilled in the art can appropriately add, modify, and omit the present invention within the scope of its technical ideas.

100 image forming apparatus,
110 image reading unit;
120 image forming unit;
121 developing device,
122 photoreceptor drum,
123 charging unit,
124 optical writing unit,
125 toner supply unit;
130 transfer unit,
131 intermediate transfer belt,
132 primary transfer unit;
140 secondary transfer unit;
150 paper feeding unit,
160 paper transport unit,
161 paper transport path,
162 transport rollers,
170 fixing unit,
180 operation display unit,
190 control unit,
191 CPUs,
192 auxiliary storage unit,
193 RAM,
194 ROMs.

Claims (10)

an image carrier;
a developing unit that develops the electrostatic latent image formed on the image carrier with toner;
an image forming apparatus comprising a transfer section for transferring the toner image on the image carrier developed by the developing section onto a sheet of paper,
a setting unit for setting a target process state;
a control unit that controls a process state of the image forming apparatus;
a calculating unit that calculates an average residence time of toner in the developing unit ;
The process state of the image forming apparatus includes a state of deterioration of toner in the developing unit,
The control unit
when the process state of the image forming apparatus is the deterioration state of the toner in the developing unit, the deterioration state is controlled to obtain a target process state ;
Recovery processing for recovering the deterioration of the toner in the developing section by consuming the toner in the developing section and replenishing the consumed amount of toner to shorten the average retention time, or agitating the toner without replenishing the toner. executing deterioration processing for promoting deterioration of the toner in the developing unit by increasing the average residence time;
controlling the deterioration state of the toner in the developing unit so that the deterioration state of the toner in the developing unit becomes a toner average residence time corresponding to the target deterioration state of the toner;
The recovery process is executed when the state of deterioration of the toner in the developing unit exceeds the upper limit threshold of the target state of deterioration of the toner, and the recovery process is executed when the state of deterioration of the toner in the developing unit is less than the lower limit threshold of the target state of deterioration of the toner. An image forming apparatus that performs deterioration processing . The process state of the image forming apparatus is
2. The image forming apparatus according to claim 1, comprising at least one of a charge amount of toner in said developing section, a deterioration state of toner in said developing section, a transfer bias in said transfer section, and an endurance state of each process member of said image forming apparatus. image forming device. an image carrier;
a developing unit that develops the electrostatic latent image formed on the image carrier with toner;
an image forming apparatus comprising a transfer section for transferring the toner image on the image carrier developed by the developing section onto a sheet of paper,
a setting unit for setting a target deterioration state of toner;
a calculating unit that calculates an average residence time of toner in the developing unit;
Recovery processing for recovering the deterioration of the toner in the developing section by consuming the toner in the developing section and replenishing the consumed amount of toner to shorten the average retention time, or agitating the toner without replenishing the toner. a control unit that executes a deterioration process that promotes deterioration of the toner in the developing unit by increasing an average residence time;
The control unit
controlling the deterioration state of the toner in the developing unit so that the deterioration state of the toner in the developing unit becomes a toner average residence time corresponding to the target deterioration state of the toner ;
The recovery process is executed when the state of deterioration of the toner in the developing unit exceeds the upper limit threshold of the target state of deterioration of the toner, and the recovery process is executed when the state of deterioration of the toner in the developing unit is less than the lower limit threshold of the target state of deterioration of the toner. An image forming apparatus that performs deterioration processing . further comprising an operation panel for accepting user input;
The setting unit
2. A toner deterioration state corresponding to a target image on the operation panel selected by a user input is acquired from a storage unit, and the deterioration state is set as the target toner deterioration state. 4. The image forming apparatus according to any one of 3 . The setting unit
4. The image according to any one of claims 1 to 3 , wherein when continuous printing is performed, the state of toner deterioration in the developing unit at the start of printing is set to the target state of deterioration of toner. forming device. The control unit
6. The image forming apparatus according to any one of claims 1 to 5 , wherein the deterioration state of toner in the developing section is controlled at timing according to a user's instruction. The setting unit
7. The image forming apparatus according to claim 6 , wherein the state of deterioration of toner in said developing unit at said timing is set to said target state of deterioration of toner. The setting unit
8. The image forming apparatus according to any one of claims 1 to 7 , wherein the target deterioration state of toner is set based on information about paper to be used for printing. The setting unit, as the information about the paper,
When the paper used for printing is embossed paper, compared to when the paper is plain paper or glossy paper,
9. The image forming apparatus according to claim 8 , wherein the range of the target deterioration state of toner is narrowed. The control unit
10. The image forming apparatus according to any one of claims 1 to 9 , wherein control of the state of deterioration of toner in said developing section is executed in a non-image area between image areas on said image carrier.

Images