Image forming apparatus

Abstract

To provide an image forming apparatus that can more accurately acquire information on the degree of deterioration of a supply member according to the state of usage of the image forming apparatus.SOLUTION: An image forming apparatus 100 has: an image carrier 1; a developing device 4 that has a developing member 42, and a supply member 43 including an elastic layer (urethane foam layer) 43b containing an ion conductive agent; a first application unit 122 that applies developing voltage to the developing member 42; a second application unit 123 that applies supply voltage to the supply member 43; an acquisition unit 83 that acquires information on the printing rate of an image formed in image formation; a control unit 220 that acquires information on the degree of deterioration of the supply member 43 on the basis of information on the supply voltage applied to the supply member 43, information on the time when the supply voltage is applied to the supply member 43, and the information on the printing rate; and a storage unit 150 that stores the information on the degree of deterioration acquired by the control unit 220.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus, such as a printer, a copying machine, or a facsimile machine, that uses an electrophotographic or electrostatic recording method. [Background technology]

[0002] Conventionally, an image forming apparatus such as a printer using an electrophotographic method (electrophotographic process) forms an electrostatic image on a photoconductor as an image carrier in an image forming process, and develops the electrostatic image using a developer to form a toner image on the photoconductor. The developing device that performs the developing process may be configured as an independent unit or as a part of a process cartridge so as to be detachable from the main body of the image forming apparatus (hereinafter, also simply referred to as the "main body"). Note that a process cartridge is a device in which a photoconductor and at least one of a charging means, a developing means, and a cleaning means as process means acting on the photoconductor are integrally configured so as to be detachable from the main body of the apparatus.

[0003] A developing device generally has a developing container that contains a developer, a developing member (developer carrier) that is rotatably arranged at the opening of the developing container and carries and transports the developer, and a regulating member that regulates the amount of developer carried and transported by the developing member. For example, a developing device that uses a non-magnetic one-component developer as the developer further has a supplying member that supplies toner, which is the developer, to the developing member. A developing roller is often used as the developing member, and a supplying roller is often used as the supplying member.

[0004] In such a developing device, a potential difference is generally provided between the developing roller and the supply roller in order to move the toner from the supply roller to the developing roller, depending on the configuration of the developing device and the characteristics of the toner.

[0005] Patent Document 1 discloses the following technology. In other words, when forming an image longer than one revolution of the developing roller, the potential difference between the developing roller and the supply roller is increased on the side that supplies toner to the developing roller. This is intended to suppress a decrease in image density.

[0006] Furthermore, Patent Document 2 discloses the following technology. That is, in the first rotation of the developing roller, the potential difference between the developing roller and the supply roller is increased so that toner is stripped from the developing roller. Then, from the second rotation of the developing roller onwards, the potential difference between the developing roller and the supply roller is gradually increased so that toner is supplied to the developing roller. This is intended to prevent uneven image density. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2009-237549 A [Patent Document 2] JP 2010-160236 A Summary of the Invention [Problem to be solved by the invention]

[0008] A widely used supply roller has a foamed elastic layer that is made conductive by adding an ionic conductive agent. The foamed elastic layer is made of, for example, a urethane rubber foam (urethane sponge) containing the ionic conductive agent.

[0009] The inventors have found that, in the above-mentioned supply roller, when the toner contained inside (inside the cells) of the foamed elastic layer moves to the developing roller, the conductive agent added to the material of the foamed elastic layer tends to be carried away. This tendency is particularly noticeable when images with a high printing ratio are continuously formed. This is due to the following reasons. That is, when an image with a high printing ratio is formed, the amount of toner consumed from the developing roller to the photoreceptor increases. In this case, when focusing on the toner contained inside the foamed elastic layer of the supply roller, the amount of toner supplied from the supply roller to the developing roller increases as the printing ratio increases. Therefore, when an image with a high printing ratio is formed and the toner inside the foamed elastic layer of the supply roller is replaced, it has been found that the conductive agent added to the material of the foamed elastic layer of the supply roller is carried away together with the toner, and the amount of conductive agent remaining on the supply roller is likely to decrease. In this way, the phenomenon of the conductive agent added to the material of the foamed elastic layer of the supply roller decreasing is more noticeable when an image with a high printing ratio is formed and the amount of toner consumed is large, compared to when an image with a low printing ratio is formed and the amount of toner consumed is small. Therefore, the degree of deterioration of the supply roller varies depending on how the user uses the image forming apparatus. Conventionally, no effort has been made to obtain information regarding the deterioration degree of the supply roller while paying attention to this point.

[0010] As the supply roller deteriorates, image defects such as poor solid-color tracking can occur. Poor solid-color tracking is an image defect in which, when forming a solid image, the image density at the trailing edge of a page is lower than that at the leading edge, resulting in uneven density. This occurs because, while a sufficient amount of toner is supplied to the developing roller at the leading edge of a page, as the supply roller deteriorates (increasing electrical resistance), the amount of toner supplied to the developing roller at the trailing edge of a page gradually falls short.

[0011] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to make it possible to obtain information regarding the degree of deterioration of a supply member with higher accuracy in accordance with the usage status of an image forming apparatus. [Means for solving the problem]

[0012] The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention is an image forming apparatus for forming an image on a recording material by transferring a developer image to the recording material, the image forming apparatus comprising: a rotatable image carrier for carrying a developer image; a developing device for supplying a developer to the surface of the image carrier to form a developer image on the surface of the image carrier, the developing device having a rotatable developing member for supplying the developer to the surface of the image carrier, and a rotatable supply member having an elastic layer containing an ion conductive agent and contacting the developing member to supply the developer to the developing member; a first application unit for applying a development voltage to the developing member; a second application unit for applying a supply voltage to the supply member; an acquisition unit for acquiring information on the printing rate of an image formed in the image formation; a control unit for acquiring information on the deterioration degree of the supply member based on information on the supply voltage applied to the supply member, information on the time when the supply voltage was applied to the supply member, and information on the printing rate; and a storage unit for storing information on the deterioration degree acquired by the control unit. Effect of the Invention

[0013] According to the present invention, it is possible to obtain information on the degree of deterioration of the supply members with higher accuracy in accordance with the usage status of the image forming apparatus. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic cross-sectional view of an image forming apparatus. [Diagram 2] FIG. 2 is a schematic cross-sectional view of an image forming unit. [Diagram 3] FIG. 2 is a schematic block diagram of a control configuration of the image forming apparatus. [Figure 4] 4 is a functional block diagram of a control unit related to detection of the life of a developing device. FIG. [Diagram 5] FIG. 11 is a flowchart showing an outline of a procedure for detecting the life of a developing device. [Figure 6]FIG. 11 is a flowchart showing a procedure for calculating the remaining amount of toner. [Figure 7] FIG. 11 is a flowchart showing a procedure for calculating the life of a developing roller. [Figure 8] FIG. 11 is a graph showing verification results of characteristics of the supply roller. [Figure 9] FIG. 11 is a flowchart showing a procedure for calculating a deterioration level of the supply roller in the first embodiment. [Figure 10] 4 is a schematic diagram showing the application timing of a supply bias in the first embodiment. FIG. [Figure 11] 10 is a schematic diagram showing the application timing of a supply roller bias in the second embodiment. FIG. [Figure 12] FIG. 11 is a flowchart showing a procedure for calculating a deterioration level of a supply roller in the second embodiment. [Figure 13] FIG. 11 is a flowchart showing a procedure for calculating the deterioration degree of the supply roller in the third embodiment. [Figure 14] 4 is a schematic diagram showing the relationship between the printing unit and the supply roller when the letter "A" is formed. FIG. [Figure 15] 15 is a schematic diagram showing the relationship between the printing portion and the supply roller of an image having a different pattern but with the same printing rate as in FIG. 14. [Figure 16] 15 is a schematic diagram showing the relationship between the printing portion and the supply roller of an image having a different pattern but with the same printing rate as in FIG. 14. [Figure 17] 11 is a graph showing the relationship between deterioration of the supply roller and image density. [Figure 18] 11A and 11B are schematic diagrams showing an example of an image in which the printing rates differ between areas divided in the main scanning direction. [Figure 19] 19 is a schematic diagram for explaining density unevenness in a halftone image obtained after continuing to form the image of FIG. 18. [Figure 20] FIG. 13 is a flowchart showing a procedure for calculating the deterioration degree of the supply roller in the fourth embodiment. [Figure 21] 11 is a graph showing the relationship between deterioration of the supply roller and the remaining amount of toner at which poor solid image tracking occurs; [Figure 22]FIG. 4 is a graph for explaining setting of a life span in the first embodiment. [Figure 23] FIG. 13 is a flowchart showing a procedure for detecting the life of a developing device in the fifth embodiment. [Figure 24] FIG. 13 is a graph showing the relationship between the remaining life of the supply roller and the video count threshold value in the fifth embodiment. [Diagram 25] FIG. 13 is a graph showing the timing at which poor solid image follow-up occurs in Example 5. [Figure 26] FIG. 13 is a graph showing a corrected video count threshold value in Example 5. [Figure 27] FIG. 13 is a graph showing a corrected video count threshold value in a modified example of the fifth embodiment. [Figure 28] FIG. 13 is a graph showing video count thresholds in Examples 1 and 2 for explaining the effect of the fifth embodiment. [Figure 29] FIG. 23 is a flowchart showing a procedure for detecting the life of a developing device in the sixth embodiment. [Diagram 30] FIG. 23 is a graph showing a supply roller deterioration level threshold value after correction in the sixth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, the image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

[0016] [Example 1] <Overall Configuration and Operation of Image Forming Apparatus> 1 is a schematic cross-sectional view of an image forming apparatus 100 according to this embodiment. The image forming apparatus 100 according to this embodiment is a tandem-type full-color laser beam printer employing an intermediate transfer method, capable of forming a full-color image on a sheet-shaped recording material P by electrophotography.

[0017] The image forming apparatus 100 has a plurality of image forming units (image forming stations) SY, SM, SC, and SK that form toner images of the respective colors of yellow (Y), magenta (M), cyan (C), and black (K). The configurations of the image forming units SY, SM, SC, and SK are substantially the same except that the colors of toners 90Y, 90M, 90C, and 90K contained in the developing device 4 described later are different. Elements having the same or corresponding functions or configurations provided for each color may be generally described by omitting the Y, M, C, and K at the end of the reference numerals indicating that the elements are provided for any one of the colors. FIG. 2 is a schematic cross-sectional view showing one representative image forming unit S. The image forming unit S is configured to include a photosensitive drum 1, a charging roller 2, an exposure device 3, a developing device 4, a primary transfer roller 51, and a drum cleaning device 5, which will be described later. In this embodiment, the exposure device 3 is configured as one unit common to each image forming unit S, but may be provided for each image forming unit S.

[0018] The photosensitive drum 1, which is a rotatable drum-type (cylindrical) electrophotographic photosensitive member (photosensitive member) serving as an image carrier, is rotated around its rotation axis in the direction of arrow R1 in the figure (counterclockwise direction) by a drive motor (not shown) provided in a drive unit 110 (FIG. 3(a)). In this embodiment, the photosensitive drum 1 is rotated at a peripheral speed (rotation speed, process speed) of, for example, 140 mm / sec.

[0019] The surface (outer circumferential surface) of the rotating photosensitive drum 1 is uniformly charged to a predetermined potential of a predetermined polarity (negative polarity in this embodiment) by the charging roller 2, which is a roller-type charging member (charging device) serving as a charging means. In this embodiment, the charging roller 2 is a conductive roller having a conductive rubber layer provided on a core metal. The charging roller 2 is disposed in contact with the surface of the photosensitive drum 1. The rotation axis direction of the photosensitive drum 1 and the rotation axis direction of the charging roller 2 are approximately parallel. The charging roller 2 is pressed against the photosensitive drum 2 with a predetermined pressure, and rotates in accordance with the rotation of the photosensitive drum 1. During charging, a predetermined charging bias (charging voltage) of the same polarity as the charging polarity (negative polarity in this embodiment) of the photosensitive drum 1 is applied to the charging roller 2 by a charging power source 121 (FIG. 3(b)) serving as a charging bias application unit. In this embodiment, for example, when a DC voltage of −1150 V is applied to the charging roller 2 during image formation (charging process), the surface potential of the photosensitive drum 1 becomes −500 V.

[0020] The surface of the charged photosensitive drum 1 is scanned and exposed by an exposure device 3 as an exposure means in response to an image signal (image information), and an electrostatic latent image (electrostatic image) in response to the image signal is formed on the photosensitive drum 1. The exposure device 3 irradiates the surface of the photosensitive drum 1 for each color with a laser beam in response to the image signal of each color component. As a result, an electrostatic latent image in response to the image signal of each color component is formed on the surface of the photosensitive drum 1 for each color. The image signal is input to the image forming apparatus 100 in response to a request from a user (operator), for example, from an external device (host device) 300 (FIG. 3(a)), such as an image reading device (not shown) or a personal computer connected to the image forming apparatus 100 so as to be able to communicate with the image forming apparatus 100.

[0021] The electrostatic latent image formed on the photosensitive drum 1 is developed (visualized) by supplying toner 90, which is a developer, by the developing device 4 as a developing means, and a toner image (toner image, developer image) is formed on the photosensitive drum 1. In this embodiment, the developing device 4 uses toner 90, which is a non-magnetic one-component developer, as the developer. As shown in FIG. 2, the developing device 4 has a developer container 41, a developing roller 42, a supply roller 43, and a regulating blade 44. The developing roller 42 contacts the surface of the photosensitive drum 1 during image formation (development) to form a developing section, and supplies toner 90 to the photosensitive drum 1 in the developing section. In this embodiment, the image forming apparatus 100 has a contact / separation mechanism that contacts and separates the developing roller 42 from the photosensitive drum 1. In this embodiment, when the image forming apparatus 100 stops operating, the contact / separation mechanism separates the developing roller 42 from the photosensitive drum 1 and stops the developing roller 42. Then, at least during image formation (development), the developing roller 42 is brought into contact with the photosensitive drum 1 by this contact / separation mechanism. For example, when the rotational drive of the photosensitive drum 1 is started in response to the start of an image formation operation or the like, the rotational drive of the developing roller 42 is started in a state in which the developing roller 42 is separated from the photosensitive drum 1. After that, at a predetermined timing, the contact / separation mechanism operates so that the developing roller 42 contacts the photosensitive drum 1 at a predetermined contact width by a biasing means (not shown). In this embodiment, the toner 90 charged to the same polarity (negative polarity in this embodiment) as the charging polarity of the photosensitive drum 1 is attached to the exposed portion (image portion, print portion) on the photosensitive drum 1, the absolute value of the potential of which has been reduced by being exposed after being uniformly charged (reverse development method). In this embodiment, the normal charging polarity of the toner 90, which is the main charging polarity of the toner 90 during development (charging polarity for developing an electrostatic latent image), is negative polarity. The developing device 4 will be described in further detail later.

[0022] An intermediate transfer belt 53, which is an endless belt serving as an intermediate transfer body, is disposed so as to face the four photosensitive drums 1. The intermediate transfer belt 53 is stretched around a drive roller 52a, a tension roller 52b, and a secondary transfer opposing roller 52c serving as a plurality of tension rollers (support rollers), and is stretched with a predetermined tension. The intermediate transfer belt 53 rotates (moves around) in the direction of arrow R2 (clockwise direction) in the figure as the drive roller 52a is driven to rotate by a drive motor (not shown) provided in the drive unit 110 (FIG. 3(a)). On the inner peripheral surface side of the intermediate transfer belt 53, primary transfer rollers 51Y, 51M, 51C, and 51K, which are roller-type primary transfer members (primary transfer devices) serving as primary transfer means, are disposed corresponding to the respective photosensitive drums 1Y, 1M, 1C, and 1K. The primary transfer roller 51 presses the intermediate transfer belt 53 toward the photosensitive drum 1 to form a primary transfer portion (primary transfer nip) N1, which is a contact portion between the photosensitive drum 1 and the intermediate transfer belt 53. The toner image formed on the photosensitive drum 1 is electrostatically transferred (primary transfer) onto the rotating intermediate transfer belt 53 as a transfer target by the action of the primary transfer roller 51 at the primary transfer portion N1. During the primary transfer, a predetermined primary transfer bias (primary transfer voltage), which is a DC voltage of the opposite polarity (positive polarity in this embodiment) to the normal charging polarity of the toner 90, is applied to the primary transfer roller 51 by a primary transfer power source 125 (FIG. 3(b)) as a primary transfer bias application portion. For example, when a full-color image is formed, the toner images of each color of yellow, magenta, cyan, and black formed on each photosensitive drum 1 are transferred to the intermediate transfer belt 53 in a superimposed manner in sequence.

[0023] A secondary transfer roller 6, which is a roller-type secondary transfer member (secondary transfer device) serving as a secondary transfer means, is disposed at a position facing the secondary transfer opposing roller 52c on the outer peripheral surface side of the intermediate transfer belt 53. The secondary transfer roller 6 comes into contact with the secondary transfer opposing roller 52c via the intermediate transfer belt 53 and is pressed toward the secondary transfer opposing roller 52c to form a secondary transfer portion (secondary transfer nip) N2, which is a contact portion between the intermediate transfer belt 53 and the secondary transfer roller 6. The toner image formed on the intermediate transfer belt 53 is transferred (secondarily transferred) by the action of the secondary transfer roller 6 at the secondary transfer portion N2 onto a recording material P, which is a transfer target material being conveyed while being sandwiched between the intermediate transfer belt 53 and the secondary transfer roller 6, by the action of the secondary transfer roller 6. During the secondary transfer, a predetermined secondary transfer bias (secondary transfer voltage), which is a DC voltage of the polarity opposite to the normal charging polarity of the toner 90 (positive polarity in this embodiment), is applied to the secondary transfer roller 6 by a secondary transfer power source 126 (FIG. 3(b)) as a secondary transfer bias application unit. The secondary transfer opposing roller 52c as a secondary transfer opposing member (opposing electrode) is electrically grounded. Note that an inner roller corresponding to the secondary transfer opposing roller 52c in this embodiment may be used as the secondary transfer member, and an outer roller corresponding to the secondary transfer roller 6 in this embodiment may be used as the secondary opposing member. In this case, a secondary transfer bias of the same polarity as the normal charging polarity of the toner 90 is applied to the inner roller, and the outer roller is electrically grounded. Recording materials (transfer materials, recording media, sheets) P ​​such as recording paper and plastic sheets are sent out one by one from a cassette 8 as a recording material storage unit by a feed roller 9 as a feed member, and are transported to a pair of registration rollers 10 as a transport member. This recording material P is conveyed by a pair of registration rollers 10 to a secondary transfer portion N2 in synchronization with the toner image on the intermediate transfer belt 53.

[0024] The recording material P onto which the toner image has been transferred is conveyed to a fixing device 7 serving as a fixing means. The fixing device 7 applies pressure and heat to the recording material P carrying the unfixed toner image, thereby fixing (melting and bonding) the toner image onto the recording material P. A heater (not shown) provided in the fixing device 7 is supplied with power from a fixing power source 127 (FIG. 3(b)). The recording material P onto which the toner image has been fixed is discharged (output) as an image-formed product onto a tray 102 serving as a discharge unit provided outside an apparatus main body 101 of the image forming apparatus 100.

[0025] On the other hand, the toner remaining on the photosensitive drum 1 after the primary transfer (primary transfer residual toner) is removed from the photosensitive drum 1 and collected by a drum cleaning device 5 as a photosensitive body cleaning means. In this embodiment, the drum cleaning device 5 has a cleaning blade as a cleaning member arranged in contact with the surface of the photosensitive drum 1, and a cleaning container. The drum cleaning device 5 scrapes and removes the primary transfer residual toner from the surface of the rotating photosensitive drum 1 by the cleaning blade, and stores it in the cleaning container. The image forming apparatus 100 can also adopt a cleanerless system that does not have a dedicated cleaning member for cleaning the photosensitive drum 1. In that case, the primary transfer residual toner can be collected by, for example, the developing device 4. In addition, a belt cleaning device 54 as an intermediate transfer body cleaning means is provided on the outer circumferential surface side of the intermediate transfer belt 53. The belt cleaning device 54 is arranged downstream of the secondary transfer portion N2 and upstream of the primary transfer portion N1 (the most upstream primary transfer portion N1Y) in the rotation direction (movement direction of the surface) of the intermediate transfer belt 53. The toner remaining on the intermediate transfer belt 53 after the secondary transfer (secondary transfer residual toner) and adhering materials such as paper powder are removed from the intermediate transfer belt 53 and collected by the belt cleaning device 54. In this embodiment, the belt cleaning device 54 has a cleaning blade as a cleaning member arranged in contact with the surface of the intermediate transfer belt 53, and a cleaning container. The belt cleaning device 54 uses the cleaning blade to scrape off and remove adhering materials such as secondary transfer residual toner from the surface of the rotating intermediate transfer belt 53, and collects them in the cleaning container.

[0026] In this embodiment, the photosensitive drum 1, the charging roller 2 as a process means acting on the photosensitive drum 1, the developing device 4, and the drum cleaning device 5 are integrated into a process cartridge 8. The process cartridge 8 is configured to be detachable from an apparatus main body 101 of the image forming apparatus 100. The apparatus main body 101 is a portion of the image forming apparatus 100 excluding detachable units such as the process cartridge 8. The image forming apparatus 100 may be configured such that, for example, the developing device 4 is detachable from the apparatus main body 101 alone.

[0027] Here, the image forming apparatus 100 executes a job (printing operation, printing operation) which is a series of operations for forming and outputting an image on one or more recording materials P, which is started by one start instruction. A job generally includes an image forming process, a pre-rotation process, a paper-interval process in the case of forming images on multiple recording materials P, and a post-rotation process. The image forming process (image forming operation) is a period during which electrostatic image formation, toner image formation, primary transfer of the toner image, secondary transfer, and fixing of the image to be actually formed on the recording material P are performed, and the image forming time refers to the period during these operations. More specifically, the timing of the image forming time differs depending on the position where each of the processes of electrostatic image formation, toner image formation, primary transfer of the toner image, secondary transfer, and fixing is performed. The pre-rotation process (pre-rotation operation) is a period during which a preparatory operation is performed before the image forming process, from when a start instruction is input until the image actually starts to be formed. The sheet interval process (sheet interval operation) is the period corresponding to the interval between recording materials P when image formation is continuously performed on multiple recording materials P (continuous image formation, continuous printing). The post-rotation process (post-rotation operation) is the period during which an arrangement operation (preparatory operation) is performed after the image formation process. The non-image formation time is the period other than the image formation time, and includes the periods of operations (non-image formation operations) such as the pre-rotation process, the sheet interval process, the post-rotation process, and further the pre-multiple rotation process which is a preparatory operation when the image forming apparatus 100 is turned on or when it returns from a sleep state.

[0028] <Developing device> Next, the developing device 4 in this embodiment will be further described.

[0029] As shown in FIG. 2, the developing device 4 has a developing container (developing frame) 41 that contains toner 90, a rotatable developing roller 42 as a developing member (developer carrier), a rotatable supply roller 43 as a supply member, and a regulating blade 44 as a regulating member. The developing roller 42 is located at the opening of the developing container 41 and is rotatably supported by the developing container 41. During image formation (development), the developing roller 42 rotates in contact with the surface of the photosensitive drum 1. The supply roller 43 is rotatably supported by the developing container 41 so as to rotate in contact with the developing roller 42. The regulating blade 44 is supported by the developing container 41 so as to abut against the developing roller 42. The rotation axis direction of the photosensitive drum 1, the rotation axis direction of the developing roller 42, and the rotation axis direction of the supply roller 43 are approximately parallel to each other. The developing roller 42 is rotationally driven in the direction of the arrow R3 in the figure (clockwise direction) by a drive motor (not shown) provided in the drive unit 110 (FIG. 3(a)). That is, the developing roller 42 is rotationally driven in a direction in which the surface of the photosensitive drum 1 and the surface of the developing roller 42 move forward at the contact portion (development portion) between the photosensitive drum 1 and the developing roller 42. In addition, the supply roller 43 is rotationally driven in the direction of the arrow R4 in the figure (clockwise direction) by a drive motor (not shown) provided in the drive unit 110 (FIG. 3(a)). That is, the supply roller 43 is rotationally driven in a direction in which the surface of the developing roller 42 and the surface of the supply roller 43 move in the opposite directions at the contact portion between the developing roller 42 and the supply roller 43. The rotation direction of the supply roller 43 may be a direction in which the surface of the developing roller 42 and the surface of the supply roller 43 move forward at the contact portion between the developing roller 42 and the supply roller 43.

[0030] In the developing device 4, the toner 90 is supplied to the surface of the developing roller 42 by the supply roller 43. The toner 90 held on the developing roller 42 is thinned by regulating the thickness of the layer (hereinafter also referred to as "layer thickness") by the regulating blade 44. The regulating blade 44 has a function of regulating the layer thickness of the toner 90 on the developing roller 42 and also has a function of imparting a predetermined charge to the toner 90 on the developing roller 42. The toner 90 thinned on the developing roller 42 is transported to the contact portion (developing portion) between the photosensitive drum 1 and the developing roller 42 as the developing roller 42 rotates, and adheres to the electrostatic latent image formed on the surface of the photosensitive drum 1 to develop the electrostatic latent image. The toner 90 that is not used for development and remains on the developing roller 42 is removed from the developing roller 42 at the contact portion between the developing roller 42 and the supply roller 43. The toner 90 removed from the developing roller 42 is stirred together with the toner 90 in the developing container 41 and mixed with the toner 90 in the developing container 41 .

[0031] In this embodiment, the developing roller 42 is an elastic roller in which a conductive elastic rubber layer 42b having a predetermined volume resistance is provided on the outer periphery of a metal core 42a. The developing roller 42 is configured so that its surface has a predetermined surface roughness. The developing roller 42 can be a single-layered or multi-layered roller. For example, a single-layered roller can be one in which an elastic layer is formed on a core using a rubber material such as silicone rubber, urethane rubber, or hydrin rubber. For example, a multi-layered roller can be one in which a surface layer is formed by coating a silicone resin, urethane resin, polyamide resin, or fluororesin on the surface of the elastic layer. In this embodiment, in order to obtain an appropriate image density, the developing roller 42 is rotated at a rotational speed (circumferential speed) at which the moving speed (circumferential speed) of the surface of the developing roller 42 is, for example, 130% of the moving speed (circumferential speed) of the surface of the photosensitive drum 1.

[0032] In this embodiment, the supply roller 43 is an elastic sponge roller in which an elastic layer (foamed elastic layer) 43b made of a conductive foam is formed on the outer periphery of a metal core 43a. The supply roller 43 is arranged so as to abut against the developing roller 42 with a predetermined intrusion amount. The intrusion amount of the supply roller 43 into the developing roller 42 can be expressed by the amount by which the supply roller 43 is deformed (depressed) by the developing roller 42. In this embodiment, the supply roller 43 has a urethane foam layer (foamed elastic layer made of a urethane rubber foam) as the foamed elastic layer 43b. In this embodiment, the material of the foamed elastic layer (urethane foam layer) of the supply roller 43 contains an ionic conductive agent (a conductive agent having ionic conductivity) as a conductive agent. As an example, in this embodiment, the supply roller 43 is configured such that an ionic conductive agent made of a salt of a cation and an anion having a reactive functional group that reacts with an isocyanate group is chemically bonded to the material of the urethane foam layer via the reactive functional group. For example, a supply roller 43 having such a configuration can be manufactured by foaming and curing a urethane composition containing an ion conductive agent. Other available ion conductive agents, such as metal complexes, may also be used. In addition, by making the urethane (urethane foam) on the surface layer of the supply roller 43 an open-cell foam, the toner 90 can be contained inside the foamed elastic layer (urethane foam layer) of the supply roller 43, and the toner 90 can be supplied to the development roller 42 more stably.

[0033] In this embodiment, the electrical resistance of a new (unused) supply roller 43 is 1×10 7 The electrical resistance of the supply roller 43 is measured in Ω. Here, a method for measuring the electrical resistance of the supply roller 43 will be described. The supply roller 43 is brought into contact with an aluminum sleeve (a cylindrical aluminum member) having a diameter of 30 mm so that the penetration depth is 1.5 mm. By rotating the aluminum sleeve, the supply roller 43 is rotated relative to the aluminum sleeve at a rotation speed of 30 rpm. In this state, a DC voltage of -50 V is applied to the aluminum sleeve. At this time, a resistor of 10 kΩ is provided on the earth side to which the supply roller 43 is connected, and the current is calculated by measuring the voltage across the resistor, and the electrical resistance of the supply roller 43 is calculated.

[0034] In this embodiment, the cell diameter on the surface of the supply roller 43 is set to 50 μm to 1000 μm. Here, the cell diameter refers to the average diameter of the foam cells in an arbitrary cross section, and the value is obtained as follows. First, the area of ​​the largest foam cell is measured from an enlarged image of the arbitrary cross section, and the maximum cell diameter is obtained by converting the area into a diameter equivalent to a perfect circle. Then, foam cells that are 1 / 2 or less of the maximum cell diameter are removed as noise, and the cell diameters of the remaining individual foam cells are obtained from the cell areas of the remaining individual foam cells by the same conversion as above. The cell diameter on the surface of the supply roller 43 refers to the average value of the converted individual cell diameters. In this embodiment, when checking the cell diameter of the supply roller 43, the measurement was performed using a VK-X200 (manufactured by KEYENCE Corporation).

[0035] In this embodiment, the regulating blade 44 is configured with a plate-shaped elastic member having electrical conductivity and flexibility. The plate-shaped elastic member constituting the regulating blade 44 has a predetermined length and a predetermined thickness in a longitudinal direction disposed substantially parallel to the rotation axis direction of the developing roller 42 and in a lateral direction substantially perpendicular to the longitudinal direction. The elastic member constituting the regulating blade 44 has one end in the lateral direction fixed to the developing container 41 and supported by a cantilever, and the other end in the lateral direction is a free end. The regulating blade 44 is disposed so that the surface near the tip of the free end faces the upstream side of the rotation direction (movement direction of the surface) of the developing roller 42 (counter direction) and the surface of the developing roller 42 near the tip abuts against the surface (outer peripheral surface) of the developing roller 42. The regulating blade 44 is disposed in a state of contact with the surface of the developing roller 42 at a position downstream of the contact portion between the supply roller 43 and the developing roller 42 and upstream of the contact portion between the photosensitive drum 1 and the developing roller 42 in the rotation direction of the developing roller 42. In this embodiment, a SUS material (stainless steel plate material) is used as the elastic member constituting the regulating blade 44.

[0036] During image formation (development), a predetermined developing bias (developing voltage) which is a DC voltage is applied to the developing roller 42 by a developing power source 122 (FIG. 3(b)) which serves as a developing bias application unit. During image formation (development), a predetermined supply bias (supply voltage) which is a DC voltage is applied to the supply roller 43 by a supply power source 123 (FIG. 3(b)) which serves as a supply bias application unit. During image formation (development), a predetermined regulating bias (regulating voltage) which is a DC voltage is applied to the regulating blade 44 by a regulating power source 124 (FIG. 3(b)) which serves as a regulating bias application unit. In this embodiment, voltages according to the usage environment of the image forming apparatus 100 (particularly, the temperature in this embodiment) are applied as the developing bias, the supply bias, and the regulating bias. For example, in an environment with a temperature of 23° C., during image formation (development), a DC voltage of −350 V is applied to the developing roller 42, a DC voltage of −450 V is applied to the supply roller 43, and a DC voltage of −450 V is applied to the regulating blade 44. In this embodiment, the values ​​of the developing bias, supply bias, and regulating bias according to the usage environment of the image forming apparatus 100 are each set in advance and stored in the main body memory 221 (FIG. 4) as table data or the like.

[0037] During image formation (development), the potential difference between the supply roller 43 and the development roller 42 is set to a polarity that biases (moves) the toner 90 from the supply roller 43 side to the development roller 42 side. In this embodiment, the normal charging polarity of the toner 90 is negative. Therefore, during image formation (development), a potential difference is provided between the supply roller 43 and the development roller 42 such that the potential of the supply roller 43 is more negative than the potential of the development roller 42. In this embodiment, as will be described in detail later, the potential difference between the supply roller 43 and the development roller 42 is variably controlled according to the usage environment of the image forming apparatus 100. This control stabilizes the supply of the toner 90 from the supply roller 43 to the development roller 42. The potential difference between the supply roller 43 and the development roller 42 can be variably controlled by changing at least one of the supply bias and the development bias.

[0038] Furthermore, during image formation (development), the potential difference between the regulating blade 44 and the developing roller 42 is set to a polarity that urges (moves) the toner 90 from the regulating blade 44 side to the developing roller 42 side. In this embodiment, as described above, the normal charging polarity of the toner 90 is negative. Therefore, during image formation (development), a potential difference is provided between the regulating blade 44 and the developing roller 42 such that the potential of the regulating blade 44 is more negative than the potential of the developing roller 42. This stabilizes the intake of the toner 90 into the contact portion between the regulating blade 44 and the developing roller 42, and stabilizes the application of the electric charge to the toner 90 by the regulating blade 44.

[0039] As will be described in more detail later, in this embodiment, the settings of the developing bias, supply bias, and regulating bias in a job (printing operation) are the same in the pre-rotation process, the inter-sheet process, and the post-rotation process as in the image forming process.

[0040] <Toner> In this embodiment, a non-magnetic toner having a negative charge produced by a suspension polymerization method was used as the toner 90 (90Y, 90M, 90C, 90K). However, the present invention is not limited to this, and toners produced by other polymerization methods such as a pulverization method or an emulsion polymerization method may be used. The volume average particle diameter of the toner 90 is preferably 5.0 μm or more and 8.0 μm or less. Here, the volume average particle diameter of the toner was measured by a precision particle size distribution measuring device Multisizer3 manufactured by Beckman Coulter, Inc. In this embodiment, the volume average particle diameter of the toner 90 is about 7.0 μm.

[0041] In this embodiment, the toner 90 (90Y, 90M, 90C, 90K) is a toner particle containing a toner base particle containing a release agent and an organosilicon polymer on the surface of the toner base particle. The organosilicon polymer is R-Si(O 1 / 2)3. The R represents an alkyl group or a phenyl group having 1 to 6 carbon atoms, and the organosilicon polymer forms a convex portion on the surface of the toner base particle. This creates a spacer effect between the surface of the toner base particle and a member such as the developing roller 42, reducing the adhesive force between the toner base particle and the member. The convex portion is in surface contact with the surface of the toner base particle. By having the convex portion in surface contact with the surface of the toner base particle in this way, an effect of suppressing the movement, detachment, and embedding of the convex portion is obtained. Therefore, for example, even in a configuration in which the developing roller 42 is driven in a state separated from the photosensitive drum 1, the toner 90 can be used for a relatively long period of time. In this embodiment, toner particles containing an organosilicon polymer on the surface of the toner base particle are used as the toner 90, but this is not limited thereto, and for example, toner particles not containing an organosilicon polymer on the surface of the toner base particle may be used.

[0042] In addition, additives (hereinafter also referred to as "external additives") such as a fluidizing agent and a cleaning aid may be added to the toner 90 (90Y, 90M, 90C, 90K) in order to improve the fluidity, chargeability, cleaning properties, etc.

[0043] Examples of the external additive include inorganic oxide particles such as silica particles, alumina particles, and titanium oxide particles; inorganic stearic acid compound particles such as aluminum stearate particles and zinc stearate particles; and inorganic titanic acid compound particles such as strontium titanate and zinc titanate. These may be used alone or in combination of two or more. These inorganic particles are preferably gloss-treated with a silane coupling agent, a titanium coupling agent, a higher fatty acid, a silicone oil, or the like to improve heat-resistant storage properties and environmental stability. The BET specific surface area of ​​the external additive is preferably 10 m 2 / g or more 450m 2 / g or less. Here, the BET specific surface area can be determined by a low-temperature gas adsorption method using a dynamic constant pressure method in accordance with the BET method (preferably the BET multipoint method). For example, a specific surface area measuring device (product name: Gemini 2375 Ver. 5.0, manufactured by Shimadzu Corporation) is used to adsorb nitrogen gas onto the surface of a sample, and the BET multipoint method is used to measure the BET specific surface area (m 2 / g) can be calculated.

[0044] The total amount of these various external additives added is preferably 0.05 parts by mass or more and 5 parts by mass or less, and more preferably 0.1 parts by mass or more and 3 parts by mass or less, relative to 100 parts by mass of the toner base particles. Also, various external additives may be used in combination.

[0045] <Control configuration> Next, a description will be given of the control configuration of the image forming apparatus 100 in this embodiment. Fig. 3(a) is a schematic block diagram showing the control configuration of the image forming apparatus 100 in this embodiment.

[0046] The image forming apparatus 100 includes a video controller 201 and an engine controller 202. The video controller 201 processes an image signal input from an external device 300 such as a personal computer, and sends the image signal to the engine controller 202. The engine controller 202 controls the operation of the image forming apparatus 100, such as an image forming operation based on the image signal input from the video controller 201, in response to an instruction input from the external device 300.

[0047] The engine controller 202 includes a control unit 220, a main memory 221, an input / output unit (I / F) 222, and the like. The control unit 220 is composed of a CPU (Central Processing Unit) and the like as a control means that is a central element for performing arithmetic processing. The main memory 221, which is a storage unit as a storage means, is composed of storage media such as a ROM and a RAM as a storage means. The input / output unit 222 inputs and outputs signals (information) to and from devices outside the engine controller 202. The ROM stores (contains, saves) in advance control programs such as a program for executing an image forming operation, and a program for calculating the remaining amount of toner, the remaining life of a developing roller, the remaining life of a supply roller, and the like, which will be described later. The RAM stores information input to the engine controller 202, detected information, calculation results, and the like. The control unit 220 is a control means for controlling the overall operation of the image forming apparatus 100, and each control target in the image forming apparatus 100 is connected to the control unit 202 via the input / output unit 222. The control unit 220 controls the transmission and reception of various electrical information signals, drive timing, and the like, and executes processes according to the flowcharts described below, for example.

[0048] The control unit 220 is connected to, for example, the drive unit 110, the high-voltage power supply device 120, the temperature and humidity sensor 130, the memory communication unit 140, and the like, which are provided in the main body 101 of the apparatus. In addition, a non-volatile memory (hereinafter, also simply referred to as "memory") 150, which is a storage unit as a storage means provided in the process cartridge 8, is connected to the control unit 220 via the memory communication unit 140. The non-volatile memory 150 is adapted to be attached and detached to the main body 101 of the apparatus integrally with the process cartridge 8, and when the process cartridge 8 is attached to the main body 101 of the apparatus, it is connected to the control unit 220 via the memory communication unit 140. Note that, when the developing device 4 is independently detachable from the main body 101 of the apparatus, the non-volatile memory 150 can be detachable from the main body 101 of the apparatus integrally with the developing device 4. In addition, an operation unit 160 provided in the main body 101 of the apparatus is connected to the control unit 220. Furthermore, an external device 300 such as a personal computer is connected to the control unit 220.

[0049] The driving unit 110 is configured to have various motors as driving sources (power sources) and functions as a driving means for rotating and driving the polygon scanner, the photosensitive drum 1, the developing roller 42, the supply roller 43, and the like provided inside the exposure device 3. The driving unit 110 operates based on a control signal from the control unit 220. At least some of the motors that drive the photosensitive drum 1, the developing roller 42, and the supply roller 43 may be shared. At least some of the motors that drive the members for the colors yellow, magenta, cyan, and black may be shared.

[0050] As shown in FIG. 3B, the high-voltage power supply device 120 includes high-voltage power supplies (high-voltage power supply units) such as a charging power supply 121, a developing power supply 122, a supply power supply 123, a regulating power supply 124, a primary transfer power supply 125, a secondary transfer power supply 126, and a fixing power supply 127. The charging power supply 121 applies a charging bias to the charging roller 2. The developing power supply 122 applies a developing bias to the developing roller 42. The supply power supply 123 applies a supply bias to the supply roller 43. The regulating power supply 124 applies a regulating bias to the regulating blade 44. The primary transfer power supply 125 applies a primary transfer bias to the primary transfer roller 51. The secondary transfer power supply 126 applies a secondary transfer bias to the secondary transfer roller 6. The fixing power supply 127 supplies power to the heater of the fixing device 7. The high-voltage power supply device 120 operates based on a control signal from the control unit 220. At least a part of the power source for applying a bias to the members for each color, yellow, magenta, cyan, and black, may be shared.

[0051] The temperature and humidity sensor 130 is a sensor (environmental sensor) for detecting the temperature and humidity (temperature and humidity) of the environment in which the image forming apparatus 100 is used. The temperature and humidity sensor 130 is an example of an environment detection unit as an environment detection means for detecting the usage environment of the image forming apparatus 100, which is at least one of the temperature and humidity inside or outside the image forming apparatus 100. In this embodiment, the temperature and humidity sensor 130 detects the temperature and humidity of the ambient environment outside the image forming apparatus 100 as the usage environment of the image forming apparatus 100, and inputs a signal (information) indicating the detected temperature and humidity to the control unit 220. The information on the temperature and humidity detected by the temperature and humidity sensor 130 is used by the control unit 220 for control according to the usage environment of the image forming apparatus 100.

[0052] The nonvolatile memory 150 serving as storage means provided in each process cartridge 8 is connected to the control unit 220 via a memory communication unit 140 provided in the apparatus main body 101, and information can be read and written by the control unit 220. Note that, although a non-contact non-volatile memory is adopted as the storage means provided in each process cartridge 8 in this embodiment, any appropriate storage means can be used, such as a contact non-volatile memory, a non-contact non-volatile memory, or a volatile memory having a power source.

[0053] Moreover, the operation unit 160 has keys or the like as an input unit that can input information to the control unit 220 by operation by the user. Moreover, the operation unit 160 has a display screen (display panel) using a liquid crystal panel or the like as a display unit that can display information to the user under the control of the control unit 220. The operation unit 160 may be configured to have a touch panel (operation display unit) that has the function of an input unit and the function of a display unit.

[0054] The non-volatile memory 150 of the process cartridge 8 can store, as information on the usage status of the developing device 4, for example, the cumulative travel distance of the developing roller 42, the image dot cumulative value, and the deterioration degree of the supply roller 43 described later, while updating as needed. The non-volatile memory 150 of the process cartridge 8 can also store, as information on the usage status of the developing device 4, for example, the cumulative travel distance of the developing roller 42, the image dot cumulative value, and the deterioration degree of the supply roller 43, while updating as needed. The non-volatile memory 150 of the process cartridge 8 can also store, as threshold information for detecting various life spans, for example, a threshold value for the image dot cumulative value, a threshold value for the number of recording materials P on which an image is recorded (number of prints), a threshold value for the cumulative travel distance of the developing roller 42, a threshold value for the remaining amount of toner, and a threshold value for the deterioration degree of the supply roller 43. The non-volatile memory 150 of each process cartridge 8 stores information on the components of the respective process cartridges 8. In addition, the non-volatile memory 150 of the process cartridge 8 may store system programs for controlling the image forming apparatus 100, various adjustment values, the serial number of the process cartridge 8, system data indicating the date of manufacture, etc., as information unique to each process cartridge 8.

[0055] In this embodiment, all or part of the information to be stored in the nonvolatile memory 150 of each process cartridge 8 may be stored in a storage unit (such as the main body memory 221) provided in the apparatus main body 101.

[0056] <Detection of the life of the developing device> - Overview of detecting the life of a developing device - Next, detection of the life of the developing device 4 (process cartridge 8) in this embodiment will be described. In this embodiment, the "life" is the timing at which image quality cannot be guaranteed when forming an image on a recording material P in an image forming operation. Generally, when the "life" is reached, a notification is issued to prompt the user to replace the developing device 4 and the process cartridge 8. In this embodiment, the developing device 4 is replaceable as a part of the process cartridge 8, so the life of the developing device 4 means the life of the process cartridge 8. Here, it is also simply referred to as "life of the developing device 4" and "replacement of the developing device 4", but in this embodiment, it is equivalent to "life of the process cartridge 8" and "replacement of the process cartridge 8", respectively. In this embodiment, the process related to detection of the life of the developing device 4 is performed independently for each image forming unit S, but here, one image forming unit S will be focused on and described.

[0057] Fig. 4 is a schematic functional block diagram of the control unit 220 related to detection of the life of the developing device 4 in this embodiment. In this embodiment, each functional block shown in Fig. 4 is realized by the control unit 220 executing a program stored in the main body memory 221. Fig. 5 is a flowchart showing an outline of the procedure for detecting the life of the developing device 4 in this embodiment.

[0058] In this embodiment, the control unit 220 has a toner remaining amount detection unit 70, a developing roller life detection unit 60, and a supply roller life detection unit 80 as functional blocks for detecting the life of the developing device 4. The toner remaining amount detection unit 70 is configured to have a first video count measurement unit 71 and a toner remaining amount calculation unit 72. The developing roller life detection unit 60 is configured to have a developing roller travel distance calculation unit 61. The supply roller life detection unit 80 is configured to have a supply bias application time calculation unit 81, a supply bias measurement unit 82, a second video count measurement unit 83, and a supply roller deterioration degree calculation unit 84. The toner remaining amount detection unit 70, the developing roller life detection unit 60, and the supply roller life detection unit 80 will be described in detail later.

[0059] Here, an outline of a procedure for detecting the life of the developing device 4 will be described with reference to FIG. 5. When a print signal (job information) is input (S101), the control unit 220 starts a print operation (job) (S102). Then, the control unit 220 judges whether the developing device 4 has reached the end of its life at a predetermined timing (e.g., during the post-rotation process) during the print operation (during execution of the job) (S103 to S105). Specifically, in this embodiment, the control unit 220 judges whether the toner remaining amount TJ (%) in the developing device 4 has reached a predetermined threshold value (e.g., 0%) (S103), whether the developing roller remaining life GJ (%) has reached a predetermined threshold value (e.g., 0%) (S104), and whether the supply roller remaining life ηJ (%) has reached a predetermined threshold value (e.g., 0%) (S105). The toner remaining amount TJ is obtained by the toner remaining amount detection unit 70. The developing roller remaining life GJ is obtained by the developing roller life detection unit 60. The remaining supply roller life ηJ is determined by a supply roller life detection unit 80. The specific method for this will be described later.

[0060] When the control unit 220 determines that none of the remaining toner amount TJ, the remaining life of the developing roller GJ, and the remaining life of the supply roller ηJ has reached the predetermined threshold, the control unit 220 ends the print operation (S106). This is because it can be determined that the developing device 4 has not reached the end of its life. On the other hand, when the control unit 220 determines that any one of the remaining toner amount TJ, the remaining life of the developing roller GJ, and the remaining life of the supply roller ηJ has reached the predetermined threshold, the control unit 220 executes a process of notifying the user of information regarding the life (replacement) of the developing device 4 (S107). This is because it can be determined that the developing device 4 has reached the end of its life and needs to be replaced. Specifically, in this embodiment, the control unit 220 controls the operation unit 160 of the image forming apparatus 100 and the display unit of the external device 300 to display information regarding the life (replacement) of the developing device 4. This display may simply indicate that the developing device 4 has reached its life, or may be a display that prompts the user to replace the developing device 4. Then, the control unit 220 ends the print operation (S106).

[0061] In addition, in Figure 5, detection of the life of the developing device 4 based on the remaining toner amount TJ, remaining life of the developing roller GJ, and remaining life of the supply roller ηJ is shown to be performed in this order, but these may be performed in parallel or in an order different from that shown in Figure 5.

[0062] Furthermore, the fact that the remaining toner amount TJ, the remaining life of the developing roller GJ, and the remaining life of the supply roller ηJ have reached a predetermined threshold value (no toner, the life of the developing roller 42, or the life of the supply roller 43) may be notified independently. In this case, it may be possible to simply notify that there is no toner remaining or that the developing roller 42 or the supply roller 43 has reached the end of its life, or to notify that the developing device 4 needs to be replaced due to each of these causes (prompting the user to replace the developing device 4).

[0063] In this embodiment, it is assumed that the remaining toner amount TJ, the remaining life of the developing roller GJ, and the remaining life of the supply roller ηJ reach predetermined thresholds. The remaining toner amount TJ is the amount of toner used, the remaining life of the developing roller GJ is the amount of used of the developing roller, and the remaining life of the supply roller ηJ is the amount of used of the supply roller, and the values ​​may be added as the life approaches the predetermined threshold value, for example, 100%.

[0064] Also, for example, assuming the reuse of components of the developing device 4, information regarding the deterioration levels of the developing roller 42 and the supply roller 43 is acquired and stored in the memory 150, but it is also possible not to detect or notify the end of the life of the developing device 4 based on this information. This information can be read from the memory 150 during the regeneration and reuse process of the developing device 4, and used to determine whether or not the developing roller 42 and the supply roller 43 can be reused.

[0065] -Detection of remaining toner- Next, detection of the remaining amount of toner in the developing device 4 in this embodiment will be described. Fig. 6 is a flow chart showing an outline of the procedure for detecting the life of the developing device 4 with a focus on detecting the remaining amount of toner. The process according to the flow chart in Fig. 6 is executed by the control unit 220 (mainly the remaining toner detection unit 70).

[0066] In this embodiment, the control unit 220 detects (calculates) the remaining toner amount in the toner remaining amount detection unit 70 in order to prompt the user to replace the developing device 4 when the remaining toner amount is low. In this embodiment, the toner remaining amount detection unit 70 employs a video counting method (or a pixel counting method) as a developer remaining amount detection method. The video counting method (or the pixel counting method) is a method of counting the ON signal of the laser exposure (a signal that emits a laser, a pixel signal) generated based on image data to obtain information regarding the number of pixels in the printing portion of the image.

[0067] When a print signal (job information) is input (S201), the control unit 220 starts a print operation (job) (S202). At a predetermined timing during the print operation (for example, during the post-rotation process), the first video count measurement unit 71 receives pixel information of an image (hereinafter also referred to as an "output image") to be formed on the recording material P and output (S203), and measures a video count value VCn, which is the number of pixel signals (S204). In this embodiment, the first video count measurement unit 71 obtains pixel information of all images of the print operation (job) contained in the print signal, and measures a video count value VCn of all images. This video count value VCn correlates with the amount of toner 90 used to form images in the print operation (job).

[0068] Next, the remaining toner amount calculation unit 72 calculates a total video count value VCt, which is an accumulated value of the video count value from the start of use of the developing device 4 (process cartridge 8) (S205). That is, the remaining toner amount calculation unit 72 adds (integrates) the video count value VCn measured by the first video count measurement unit 71 to the accumulated video count value VCr from the start of use of the developing device 4 (process cartridge 8) stored in the memory 150, as shown in the following formula (1). In this way, the total video count value VCt is calculated. VCt = Vcr + VCn (1)

[0069] Next, the toner remaining amount calculation unit 72 calculates the remaining toner amount TJ in the developing device 4 from the video count threshold value VCth that is preset and stored in the memory 150 and the calculated total video count value VCt by the following formula (2) (S206). TJ[%]=(1-VCt / VCth)×100 (2)

[0070] Further, the remaining toner amount calculation unit 72 updates and stores the calculated total video count value VCt as a new cumulative video count value VCr in the memory 150 (S207). The remaining toner amount calculation unit 72 may update and store the calculated remaining toner amount TJ in the memory 150.

[0071] Here, when the toner remaining amount TJ=100%, the toner 90 in the developing device 4 is full, and the developing device 4 is brand new. When the toner remaining amount TJ≦0%, the toner 90 in the developing device 4 is almost depleted, and it is time to replace the developing device 4. In other words, when the toner remaining amount TJ≦0%, the total video count value VCt has reached the video count threshold value VCth, and the developing device 4 has reached the end of its life.

[0072] Therefore, the control unit 220 judges whether the remaining toner amount TJ calculated by the remaining toner amount calculation unit 72 is 0% or less (S208). If the control unit 220 judges in S208 that the remaining toner amount TJ is not 0% or less, it ends the printing operation (S209). On the other hand, if the control unit 220 judges in S208 that the remaining toner amount TJ is 0% or less, it controls to execute a process of notifying the user of information related to the life of the developing device 4 (S210). Then, the control unit 220 ends the printing operation (S209).

[0073] In this embodiment, the first video count measurement unit 71 measures the video count value VCn for each printing operation (job), but it may also be configured to measure, for example, the number of pixel signals of an image on one sheet of recording material P as one video count value VCn.

[0074] -Detection of the life of the developing roller- Next, detection of the life of the developing roller 42 in this embodiment will be described. Fig. 7 is a flowchart showing an outline of the procedure for detecting the life of the developing device 4, focusing on detection of the life of the developing roller 42. The process according to the flowchart in Fig. 7 is executed by the control unit 220 (mainly the developing roller life detection unit 60).

[0075] In this embodiment, the remaining life of the developing roller 42 is detected (calculated) by the developing roller life detection unit 60 in order to prompt the user to replace the developing device 4 when the developing roller 42 deteriorates. In this embodiment, the remaining life of the developing roller 42 is detected (calculated) based on the travel distance (rotation distance, surface movement distance) of the developing roller 42. It is known that the developing roller 42 deteriorates due to an increase in electrical resistance and contamination by deposits as the travel distance increases, and therefore has a lifespan that corresponds to the travel distance.

[0076] When a print signal (job information) is input (S301), the control unit 220 starts a print operation (job) (S302). During the print operation, the developing roller travel distance calculation unit 61 calculates a total developing roller travel distance Ht for each predetermined developing roller travel distance Hu (S303). That is, as shown in the following formula (3), the developing roller travel distance calculation unit 61 adds (integrates) the predetermined developing roller travel distance Hu to the cumulative developing roller travel distance Hr stored in the memory 150 for each predetermined developing roller travel distance Hu. In this way, the total developing roller travel distance Ht is calculated. Ht = Hr + Hu (3)

[0077] Next, the developing roller travel distance calculation unit 61 calculates the developing roller remaining life GJ from the developing roller travel distance threshold Hth that is set in advance and stored in the memory 150 and the calculated total developing roller travel distance Ht using the following formula (4) (S304). GJ[%]=(1-Ht / Hth)×100 ···(4)

[0078] Furthermore, the developing roller travel distance calculation unit 61 updates and stores the calculated total developing roller travel distance Ht as a new accumulated developing roller travel distance Hr in the memory 150 (S305). The developing roller travel distance calculation unit 61 may also update and store the calculated developing roller remaining life GJ in the memory 150.

[0079] Here, when the developing roller remaining life GJ=100%, it indicates that the developing device 4 is brand new. Also, when the developing roller remaining life GJ≦0%, it indicates that it is time to replace the developing device 4. In other words, when the developing roller remaining life GJ≦0%, the total developing roller travel distance Ht has reached the developing roller travel distance threshold Hth, and the developing device 4 has reached the end of its life.

[0080] Therefore, the control unit 220 judges whether the developing roller remaining life GJ calculated by the developing roller travel distance calculation unit 61 is 0% or less (S306). If the control unit 220 judges in S306 that the developing roller remaining life GJ is not 0% or less, it ends the print operation (S307). On the other hand, if the control unit 220 judges in S306 that the developing roller remaining life GJ is 0% or less, it controls to execute a process of notifying the user of information regarding the life of the developing device 4 (S308). Then, the control unit 220 ends the print operation (S307).

[0081] -Detection of supply roller life- In this embodiment, in order to prompt the user to replace the developing device 4 when the supply roller 43 deteriorates, the supply roller life detection unit 80 detects (calculates) the remaining life of the supply roller 43. The detection of the life of the supply roller 43 in this embodiment will be described in detail after the mechanism of deterioration of the supply roller 43 is described.

[0082] <Deterioration of supply roller> - Supply roller deterioration mechanism - Next, the deterioration of the supply roller 43 will be described. In this embodiment, the material of the urethane foam layer 43b of the elastic sponge roller constituting the supply roller 43 contains an ion conductive agent. The supply roller 43 having such a configuration is preferably used from the viewpoints of production stability and cost. According to the study by the present inventors, the deterioration of the supply roller 43 having such a configuration is roughly classified into two types.

[0083] The first type of deterioration of the supply roller 43 is deterioration caused by the supply roller 43 being energized. This mechanism of deterioration of the supply roller 43 is conventionally known. As described above, the supply roller 43 is given electrical conductivity by adding an ion conductive agent during manufacture. In general, when a bias of the same polarity is continuously applied to a member having ion conductivity, the ion conductive agent is unevenly distributed, and the number of ions dispersed in the member to carry electrons decreases compared to the initial state, resulting in an increase in electrical resistance. In this embodiment, a potential difference is provided between the supply roller 43 and the developing roller 42 such that the potential of the supply roller 43 is higher on the negative polarity side than the potential of the developing roller 42. That is, in this embodiment, a bias of the negative polarity side is applied to the supply roller 43 with respect to the developing roller 42. In addition, when such a bias is continuously applied to the supply roller 43 of this embodiment, the ion conductive agent tends to move to the inside (core metal side) of the supply roller 43 and become unevenly distributed. Such uneven distribution of the ion conductive agent progresses in correlation with the applied bias value and application time. Therefore, it is possible to predict the degree of deterioration of the supply roller 43 due to energization from the bias value and application time of the bias to the supply roller 43 .

[0084] The second type of deterioration of the supply roller 43 is deterioration due to a decrease in the ion conductive agent of the supply roller 43. Conventionally, no effort has been made to obtain information on the degree of deterioration of the supply roller 43 by focusing on the mechanism of deterioration of the supply roller 43. The toner contained in the urethane foam layer 43b of the supply roller 43 is successively replaced during the rotation of the supply roller 43. The inventors have confirmed through their studies that the ion conductive agent in the urethane foam layer 43b electrically adheres to the charged toner and is taken out of the urethane foam layer 43b as the toner moves from the supply roller 43 to the development roller 42. This phenomenon is particularly noticeable when the printing rate of the output image is high and the amount of toner moving from the supply roller 43 to the development roller 42 increases. Due to this phenomenon, the amount of the ion conductive agent in the urethane foam layer 43b of the supply roller 43 decreases compared to the initial state. As a result, the electrical resistance value of the supply roller 43 increases, and the ability to supply toner to the development roller 42 decreases as the sensitivity to the applied bias value decreases.

[0085] When the supply roller 43 deteriorates, image defects such as poor solid image tracking may occur, as described above.

[0086] -Verification 1: Effect of electrical deterioration- A test performed to examine the effect of deterioration of the supply roller 43 due to energization will be described. The following print endurance test was performed under the conditions of a supply bias Vrs of -450V and -650V. The development bias Vdc was set to -350V in both cases. At that time, the electrical resistance of the supply roller 43 was measured at a predetermined timing. Here, as a substitute value for the electrical resistance value of the supply roller 43, the current flowing through the supply roller 43 when a predetermined voltage was applied to the supply roller 43 was measured. By performing continuous operation without consuming toner, the effect of reduction in the conductive agent described later can be eliminated. As a print endurance test, continuous printing of images with a print rate of 0% was performed in the usage environment (ambient environment) of the image forming apparatus 100 with a temperature of 15°C and a humidity (relative humidity) of 10%. By setting the print rate to 0%, the effect of reduction in electrical resistance due to the carry-out of the conductive agent by the toner described later can be eliminated.

[0087] The results are shown in FIG. 8(a). The vertical axis indicates the ratio (decrease rate) of the current value to the initial current value when the initial current value (substitute value for electrical resistance value) is set to 100%, and the horizontal axis indicates the rotation drive time of the supply roller 43 (=supply bias application time). As shown in FIG. 8(a), it can be seen that the decrease in the current value (increase in the electrical resistance value) tends to be greater under the condition of a supply bias Vrs of -650V than under the condition of a supply bias Vrs of -450V. This is due to the ionic conductive agent contained in the supply roller 43 moving and being unevenly distributed due to continuous energization. In this way, it can be seen that there is a characteristic that the increase in the electrical resistance value of the supply roller 43 is greater when the supply bias Vrs (i.e., the potential difference between the supply bias Vrs and the development bias Vdc) is larger, since the amount of movement of the ionic conductive agent is greater. In this embodiment, it is known that when the ratio (decrease rate) of the current value to the initial current value is 30% or less, image defects such as poor solid followability may occur.

[0088] -Verification 2: Differences in the amount of toner contained in the supply roller depending on the printing rate- A test was performed to examine the difference in the amount of toner contained in the supply roller 43 depending on the printing rate. The following print durability test was performed under the conditions of a printing rate of 0% and a printing rate of 100%. At that time, the amount of toner contained in the supply roller 43 was measured at a predetermined timing. The amount of toner contained in the supply roller 43 was calculated from the difference between the weight of the supply roller 43 that did not contain toner (unused) and the weight of the supply roller 43 at each timing. As the print durability test, one-sheet intermittent printing was performed in the usage environment (ambient environment) of the image forming apparatus 100 at a temperature of 23° C. and a humidity of 50%. The supply bias Vrs was set to −450 V, and the development bias Vdc was set to −350 V. Note that N-sheet intermittent printing is a printing method in which a printing operation for continuously forming images on N sheets of recording material P is performed, and then the operation of the development device 4 (image forming apparatus 100) is temporarily stopped, and then a printing operation for continuously forming images on N sheets of recording material P is performed again, and the above operation is repeated.

[0089] The results are shown in FIG. 8(b). The vertical axis indicates the amount of toner contained in the supply roller 43, and the horizontal axis indicates the number of prints. As shown in FIG. 8(b), it can be seen that throughout the print durability test, there is a difference in the amount of toner held on the supply roller 43 between the condition of a print rate of 0% and the condition of a print rate of 100% (the amount of toner held on the supply roller 43 is less under the condition of a print rate of 100% than under the condition of a print rate of 0%). This is because when the print rate of the output image is high, the amount of toner moving from the development roller 42 to the photosensitive drum 1 increases, and therefore the amount of toner supplied from the supply roller 43 to the development roller 42 increases. The reason why the amount of toner contained in the supply roller 43 decreases overall with an increase in the number of prints is that the amount of toner supplied to the supply roller 43 decreases with a decrease in the amount of toner in the development device 4.

[0090] -Verification 3: Impact of reduction in conductive agent- A test performed to examine the difference in the amount of conductive agent reduction depending on the printing rate will be described. The following print durability test was performed under the condition of a printing rate of 1% and the condition of a printing rate of 100%. At that time, a measurement was performed to evaluate the amount of conductive agent components contained in the supply roller 43 at a predetermined timing. Here, the amount of conductive agent components was evaluated by measuring the current flowing through the supply roller 43 when a predetermined voltage was applied to the supply roller 43. When the current value decreases, it can be confirmed that the amount of conductive agent components has decreased by confirming that the current value does not increase (recover) by the amount of the decrease even if a voltage of the opposite polarity to the above-mentioned predetermined voltage is applied. As a print durability test, one sheet was intermittently printed in the usage environment (ambient environment) of the image forming apparatus 100 at a temperature of 23° C. and a humidity of 50%. The supply bias Vrs was set to −450 V, and the development bias Vdc was set to −350 V.

[0091] The results are shown in FIG. 8(c). The vertical axis indicates the ratio (decrease rate) of the current value to the initial current value when the initial current value (substitute value for the amount of conductive agent component) is set to 100%, and the horizontal axis indicates the rotation drive time of the supply roller 43 (=supply bias application time). It can be seen that the decrease in the current value (decrease in the conductive agent) tends to be greater under the condition of a high printing rate (100%) than under the condition of a low printing rate (1%). This is because when the printing rate is high and the amount of toner replacement in the supply roller 43 per unit time is large, the amount of conductive agent discharged out of the developing device 4 together with the toner accompanying printing is greater than when the printing rate is low. In this way, it can be seen that the decrease in the conductive agent is greater when the printing rate is high than when the printing rate is low. In the present invention, the deterioration degree of the supply roller 43 is calculated taking into account the characteristics of the supply roller 43 discovered by the present inventors.

[0092] In other words, the phenomenon in which the conductive agent added to the material of the foamed elastic layer of the supply roller 43 decreases is more noticeable when an image with a high printing rate is formed and toner consumption is large, compared to when an image with a low printing rate is formed and toner consumption is small. Therefore, the degree of deterioration of the supply roller 43 varies depending on the usage conditions of the image forming apparatus 100 by the user. Therefore, it is desired to obtain information on the degree of deterioration of the supply roller 43 more accurately depending on the usage conditions of the image forming apparatus 100.

[0093] In recent years, from the viewpoint of usability, a toner supplying method may be adopted in which only the toner container can be separated from the developing device 4 (process cartridge 8) and replaced. In such a configuration, the supply roller 43 is required to have higher durability, and the supply roller 43 often has a longer life. Therefore, in such a configuration, the difference in the degree of deterioration of the supply roller 43 depending on the usage conditions of the image forming apparatus 100 by the user may cause a large difference in the timing at which the supply roller 43 reaches the end of its life. Therefore, in such a configuration, it can be said that it is even more necessary to obtain information on the deterioration degree of the supply roller 43 more accurately depending on the usage conditions of the user so that the developing device 4 can be replaced at an appropriate time.

[0094] <Calculating the deterioration level of the supply roller (detecting the life of the supply roller)> Next, detection of the life of the supply roller 43 (calculation of the deterioration degree of the supply roller 43) in this embodiment will be described. Fig. 9 is a flow chart showing an outline of the procedure for detecting the life of the developing device 4 with a focus on detection of the life of the supply roller 43. The process according to the flow chart in Fig. 9 is executed by the control unit 220 (mainly the supply roller life detection unit 80). Fig. 10 is a timing chart showing the transition of the supply bias Vrs applied to the supply roller 43 during a printing operation in this embodiment.

[0095] In this embodiment, the supply roller life detection unit 80 detects (calculates) the remaining life of the supply roller 43 in order to prompt the user to replace the developing device 4 when the supply roller 43 deteriorates. In this embodiment, the deterioration degree of the supply roller 43 is calculated for each print operation (job) taking into consideration the print rate of the output image in addition to the voltage value of the supply bias Vrs (or the potential difference between the supply bias Vrs and the developing bias Vdc) and the application time of the supply bias Vrs. Then, the deterioration degree of the supply roller 43 is added for each print operation (job), and when it reaches a predetermined deterioration degree set in advance, information on the life of the developing device 4 is notified to the user. That is, in this embodiment, the supply roller life detection unit 80 detects (calculates) the remaining life of the supply roller 43 based on the voltage value of the supply bias Vrs (or the potential difference between the supply bias Vrs and the developing bias Vdc), the application time of the supply bias Vrs, and the print rate of the output image.

[0096] When a print signal (job information) is input (S401), the control unit 220 starts a print operation (job) (S402). In addition, the control unit 220 acquires the detection result of the temperature and humidity sensor 130 with the start of the print operation (S403), and determines the supply bias Vrs based on the detection result of the temperature and humidity sensor 130 (particularly, temperature in this embodiment) (S404). The supply bias Vrs applied to the supply roller 43 by the supply power supply 123 is measured and controlled by the supply bias measurement unit 82. In this embodiment, the control unit 220 reads and determines the supply bias Vrs corresponding to the temperature from table data shown in Table 1, which is preset and stored in the main body memory 221. The table data in Table 1 is an example of information indicating the relationship between the environment and the supply bias Vrs. As shown in Table 1, the lower the temperature, the larger the absolute value of the supply bias Vrs of the negative polarity (the same polarity as the normal charging polarity of the toner 90). That is, the lower the temperature, the larger the potential difference (Vrs-Vdc) between the supply bias Vrs and the developing bias Vdc is made to be on the negative polarity side (the same polarity as the normal charging polarity of the toner 90). In this embodiment, the developing bias Vdc is constant at -350V.

[0097] [Table 1]

[0098] Next, during the printing operation, the supply bias application time calculation unit 81 measures the time during which the supply bias Vrs is applied to the supply roller 43 (S405), and calculates the supply bias application time tnow in the printing operation (S406). If the supply bias application start timing in the printing operation is tS and the supply bias application end timing in the printing operation is tE, the supply bias application time tnow in the printing operation can be expressed by the following formula (5). tnow=tE-tS (5)

[0099] Also, at a predetermined timing during the printing operation (for example, during the post-rotation process), the second video count measurement unit 83 receives pixel information of the output image and calculates the section printing rate γnow, which is the printing rate in the printing operation, based on the video count value VCn measured (S407). In this embodiment, the second video count measurement unit 83 obtains pixel information of all images of the printing operation (job) contained in the print signal and measures the video count value VCn of the all images. Then, the second video count measurement unit 83 calculates the section printing rate γnow in the all images. Note that the printing rate (image printing rate, image ratio) indicates the area ratio (proportion) of the printing area when the case where all pixels of the image forming area (area where a toner image can be formed) are the printing area is set to 100%. The printing rate in all images of the printing operation can be expressed as the area ratio (proportion) of the printing area in all images when the total number of pixels of all images is set to the total number of pixels. Then, the supply roller deterioration degree calculation unit 84 determines the deterioration correction coefficient ε based on the section printing rate γnow acquired by the second video count measurement unit 83 (S408). In this embodiment, the supply roller deterioration degree calculation unit 84 reads out and determines the deterioration correction coefficient ε corresponding to the section printing rate γnow from the table data shown in Table 2, which is preset and stored in the memory 150. The table data in Table 2 is an example of information indicating the relationship between the printing rate and the deterioration correction coefficient ε. As shown in Table 2, the higher the printing rate, the larger the deterioration correction coefficient ε is made.

[0100] [Table 2]

[0101] Next, the supply roller deterioration level calculation unit 84 calculates the section supply roller deterioration level ηnow, which is an index showing the degree of deterioration of the supply roller 43 in the print operation, by the following formula (6) (S409). ηnow=tnow×|Vrs|×ε ···(6)

[0102] In this embodiment, the deterioration degree ηnow of the section supply roller is calculated by the above formula (6) because the developing bias Vdc is constant. However, for example, when the developing bias Vdc is variably controlled, the deterioration degree ηnow of the section supply roller may be calculated by the following formula, ηnow=tnow×|Vrs-Vdc|×ε.

[0103] Next, the supply roller deterioration degree calculation unit 84 calculates a total supply roller deterioration degree ηt which is an index showing the degree of deterioration of the supply roller 43 from the start of use of the developing device 4 (supply roller 43) (S410). That is, as shown in the following formula (7), the supply roller deterioration degree calculation unit 84 adds (integrates) the calculated section supply roller deterioration degree ηnow to the cumulative supply roller deterioration degree ηr from the start of use of the developing device 4 (supply roller 43) stored in the memory 150. In this way, the total supply roller deterioration degree ηt is calculated. Then, the supply roller deterioration degree calculation unit 84 updates and stores the calculated total supply roller deterioration degree ηt in the memory 150 as a new cumulative supply roller deterioration degree ηr. ηt=ηnow+ηr (7)

[0104] Next, the supply roller deterioration degree calculation unit 84 calculates the supply roller remaining life ηJ from the supply roller deterioration degree threshold ηth previously set and stored in the memory 150 and the calculated total supply roller deterioration degree ηt by the following formula (8) (S411). The supply roller deterioration degree threshold ηth is determined and set in advance by an experiment or the like so that image defects such as poor solid followability do not occur even when the toner remaining amount is 0%. The supply roller deterioration degree threshold ηth may vary depending on, for example, the elastic material constituting the foamed elastic layer of the supply roller 43, the type and amount of conductive agent contained in the material of the foamed elastic layer, the type of toner 90, and the like. The supply roller deterioration degree calculation unit 84 may update and store the calculated supply roller remaining life ηJ in the memory 150. ηJ[%]=(1-ηt / ηth)×100 ···(8)

[0105] Here, when the supply roller remaining life ηJ=100%, it indicates that the developing device 4 is brand new. Also, when the supply roller remaining life ηJ≦0%, it indicates that it is time to replace the developing device 4. When the supply roller remaining life ηJ≦0%, the total supply roller deterioration degree ηt has reached the supply roller deterioration degree threshold value ηth, and the developing device 4 has reached the end of its life.

[0106] Therefore, the control unit 220 judges whether the supply roller remaining life ηJ calculated by the supply roller deterioration degree calculation unit 84 is 0% or less (S412). If the control unit 220 judges in S412 that the supply roller remaining life ηJ is not 0% or less, it ends the print operation (S413). On the other hand, if the control unit 220 judges in S412 that the supply roller remaining life ηJ is 0% or less, it controls to execute a process of notifying the user of information regarding the life of the developing device 4 (S414). Then, the control unit 220 ends the print operation (S413).

[0107] In FIG. 9, the calculation of the supply bias application time tnow and the calculation of the section printing rate γnow (and the determination of the deterioration correction coefficient ε) are shown to be performed in parallel, but they may be performed in any order. In this embodiment, the section printing rate γnow (and the deterioration correction coefficient ε), the section supply roller deterioration degree ηnow, and the total supply roller deterioration degree ηt are obtained for each print operation (job) at a predetermined timing (for example, during the post-rotation process) during the print operation (during the execution of the job). However, the present invention is not limited to this, and these may be obtained sequentially at a predetermined timing during the print operation. For example, the supply bias application time tnow, the section printing rate γnow (and the deterioration correction coefficient ε), the section supply roller deterioration degree ηnow, and the total supply roller deterioration degree ηt may be obtained every time an image is formed. Also, for example, each time the section supply roller deterioration degree ηnow increases by a predetermined value, the ηnow may be added (integrated) to the cumulative supply roller deterioration degree ηr stored in the memory 150 to calculate the total supply roller deterioration degree ηt. If the supply roller remaining life ηJ becomes 0% or less during the printing operation (job), a process may be executed to notify the user of information regarding the life of the developing device 4, and the printing operation may be terminated (interrupted). This also applies to the remaining toner amount TJ and the remaining developing roller life GJ described above. This also applies to other embodiments described later.

[0108] <Calculation example> A calculation example of the deterioration degree of the supply roller 43 in this embodiment will be described. A case will be described in which a print operation of forming an image with an average print rate of 3.5% on two sheets of A4 size recording material P is repeated in a usage environment (ambient environment) of the image forming apparatus 100 at 23°C, and two-sheet intermittent printing is performed. When a print operation of forming an image on two sheets of A4 size recording material P is performed in the image forming apparatus 100 of this embodiment, the time (tE-tS) during which the supply bias Vrs is applied to the supply roller 43 during the print operation is 7.26 seconds. That is, tnow=7.26 (seconds). Also, when the image forming apparatus 100 is in an environment of room temperature of 23°C, from Table 1, the supply bias Vrs=-450 (V). Also, when the section print rate γnow is calculated to be 3.5%, from Table 2, the deterioration correction coefficient ε=1.5. Therefore, the section supply roller deterioration degree ηnow in one print operation under the above conditions is calculated as follows. ηnow=7.26×|-450|×1.5=4900.5

[0109] The value of this section supply roller deterioration degree ηnow is stored in memory 150 as the cumulative supply roller deterioration degree ηr, and the section supply roller deterioration degree ηnow is recalculated in the subsequent print operation. The recalculated section supply roller deterioration degree ηnow is added to the cumulative supply roller deterioration degree ηr to calculate the total supply roller deterioration degree ηt. Then, as described above, when the supply roller remaining life ηJ becomes 0% or less, that is, when the total supply roller deterioration degree ηt reaches the supply roller deterioration degree threshold value ηth, it is determined that the supply roller 43 has reached the end of its life.

[0110] <Variation 1> In the image forming apparatus 100 of this embodiment, the appropriate supply bias Vrs for supplying the toner 90 to the developing roller 42 changes due to factors such as changes in the fluidity of the toner 90 depending on the environment and changes in the electrical resistance of the supply roller 43. Therefore, in this embodiment, the image forming apparatus 100 is capable of changing the supply bias Vrs depending on its operating environment. In this embodiment, as shown in Table 1, the supply bias Vrs is changed in three stages based on the temperature information. However, this is not limited to this, and the supply bias Vrs may be changed based on the temperature information and the humidity information. Table 3 shows an example of table data in the case where the temperature and humidity detected by the temperature and humidity sensor 130 are converted into the absolute moisture amount to change the supply bias Vrs. In this case, the control unit 220 can calculate the absolute moisture amount based on the temperature and humidity detected by the temperature and humidity sensor 130, and read out and determine the corresponding supply bias Vrs from the table data of Table 3 according to the calculated absolute moisture amount. Furthermore, the supply bias Vrs is not limited to being changed in three steps as shown in Tables 1 and 3, but may be changed in fewer steps (two steps) or more steps (four steps or more) depending on the temperature or absolute moisture content. Furthermore, the supply bias Vrs corresponding to a temperature or absolute moisture content for which data is not available in Tables 1 and 3 may be determined by interpolation (for example, linear interpolation).

[0111] The information indicating the relationship between the environment and the supply bias Vrs is not limited to being set as table data, but may be set as a calculation formula. This also applies to other information indicating relationships described as being set as table data.

[0112] [Table 3]

[0113] <Variation 2> In this embodiment, the image forming apparatus 100 holds the value of the supply bias Vrs as table data as shown in Table 1, but is not limited to this. The image forming apparatus 100 can also hold offset values ​​for other environments as table data, for example, as shown in Table 4, with the supply bias Vrs for a specific environment (for example, 15° C. or higher and lower than 25° C.) as a reference.

[0114] [Table 4]

[0115] <Variation 3> In this embodiment, the image forming apparatus 100 holds the value of the supply bias Vrs as table data as shown in Table 1, but is not limited to this. For example, when the development bias Vdc is variably controlled, the image forming apparatus 100 can hold the difference (Vrs-Vdc) between the development bias Vdc and the supply bias Vrs as table data as shown in Table 5. In this embodiment, the development bias Vdc is -350V, so that, for example, in an environment below 15°C, the supply bias Vrs=-350+(-200)=-550V according to Table 5.

[0116] [Table 5]

[0117] <Modification 4> In this embodiment, as shown in Table 2, the deterioration correction coefficient ε is changed into six stages based on the printing rate of the output image, but this is not limited to this. The printing rate increments may be made finer or larger. In other words, the deterioration correction coefficient ε may be changed into fewer stages (five stages or less) or into more stages (seven stages or more). The deterioration correction coefficient ε varies depending on the characteristics of the supply roller 43 and the characteristics of the toner 90, and can be determined based on experimental values, etc.

[0118] <Comparative verification 1> Next, a comparative verification carried out between this embodiment and the following Comparative Example 1 in order to verify the effect of this embodiment will be described.

[0119] -Evaluation method- In the image forming apparatus 100 having the configuration of this embodiment, a print endurance test was conducted from the start of use of the developing device 4 (process cartridge 8) until it reached the end of its life. Specifically, the print endurance test was conducted in a full-color image formation mode in a usage environment (ambient environment) of the image forming apparatus 100 with a temperature of 23°C and a humidity of 50%, in which a print operation was performed with the following (1) to (3) as one cycle. (1) A horizontal line image (a plurality of straight lines extending in a direction substantially perpendicular to the conveying direction of the recording material P) with a printing rate of 2% is formed on 100 sheets of A4 size recording paper by intermittent printing on two sheets. (2) A horizontal line image with a print rate of 20% is printed on 100 sheets of A4 size recording paper by intermittent printing on two sheets. (3) A horizontal line image with a printing rate of 100% is formed on 100 sheets of A4 size recording paper by intermittent printing on two sheets.

[0120] As image defects, solid image tracking defects (whiteout images) in solid images were visually evaluated according to the following criteria. Note that, although the evaluation results for solid black images are shown here in particular, in this embodiment, the configurations of the developing devices 4 (process cartridges 8) for each color were substantially the same, and similar evaluation results were obtained. ○: No solid tracking problems (no practical problems) ×: Significantly poor solid-color conformability (problems in practical use)

[0121] -Comparative Example 1- In Comparative Example 1, the life of the developing device 4 was not detected based on the deterioration degree of the supply roller 43, but was detected based on the life and remaining amount of toner of the developing roller 42. Other points of Comparative Example 1 are substantially the same as those of this embodiment.

[0122] -Evaluation results- The evaluation results are shown in Table 6.

[0123] [Table 6]

[0124] In this embodiment, when the developing roller remaining life GJ was 35% and the toner remaining amount TJ was 7%, the supply roller remaining life ηJ became 0%, and it was notified that the developing device 4 had reached the end of its life. In this way, in this embodiment, it was possible to notify the user of information regarding the life (replacement) of the developing device 4 before a solid tracking defect occurred.

[0125] On the other hand, in comparison example 1, the remaining life of the developing roller GJ was 32% and the remaining toner amount TJ was 6%, and even though this was before it was notified that the developing device 4 had reached the end of its life, poor solid tracking occurred.

[0126] <Effects> In this embodiment, an image forming apparatus 100 that forms an image on a recording material P by transferring a developer image (toner image) to the recording material P includes a rotatable image carrier (photosensitive drum) 1 that carries a developer image, and a developing device 4 that supplies a developer (toner) to the surface of the image carrier 1 to form a developer image on the surface of the image carrier 1, the developing device 4 having a rotatable developing member (developing roller) 42 that supplies the developer to the surface of the image carrier 1, and a rotatable supply member (supply roller) 43 that is provided with an elastic layer (urethane foam layer) 43b containing an ion conductive agent and comes into contact with the developing member 42 to supply the developer to the developing member 42, and a developing voltage is applied to the developing member 42. The image forming apparatus includes a first application unit (development power source) 122, a second application unit (supply power source) 123 that applies a supply voltage to the supply member 43, an acquisition unit (second video count measurement unit) 83 that acquires information about the printing rate of an image formed in the image formation, a control unit 220 (more specifically, a supply roller deterioration degree calculation unit 84) that acquires information about the deterioration degree of the supply member 43 based on information about the supply voltage applied to the supply member 43, information about the time when the supply voltage was applied to the supply member 43, and information about the printing rate, and a storage unit (non-volatile memory) 150 that stores information about the deterioration degree acquired by the control unit 220. In this embodiment, the control unit 220 is capable of determining whether the development device 4 has reached the end of its life based on the information about the deterioration degree. The control unit 220 can acquire the information regarding the deterioration degree by correcting a value correlated with a product of voltage and time based on information regarding the supply voltage applied to the supply member 43 and information regarding the time during which the supply voltage was applied to the supply member 43, using a correction coefficient (deterioration correction coefficient ε) corresponding to the information regarding the printing rate. The control unit 220 may acquire the information regarding the deterioration degree based on information regarding the potential difference between the supply voltage applied to the supply member 43 and the developing voltage applied to the developing member 42, information regarding the time during which the supply voltage was applied to the supply member 43, and the information regarding the printing rate.In this embodiment, the image forming apparatus 100 has an environment detection unit (temperature and humidity sensor) 130 that detects at least one of temperature and humidity, and the control unit 220 can change the supply voltage applied to the supply member 43 based on the detection result of the environment detection unit 130. In this embodiment, the control unit 220 can execute a process for notifying a user of information regarding replacement of the developing device 4 when the developing device 4 reaches the end of its life. In this embodiment, the storage unit 150 is detachable from the device body 101 of the image forming apparatus 100 together with the developing device 4. In this embodiment, the acquisition unit 83 acquires information regarding the printing rate based on image information of an image formed in the image formation. In this embodiment, the developing member 42 abuts against the image carrier 1 to form a developing unit, and the developing unit supplies developer to the image carrier 1. In this embodiment, the developer is a non-magnetic one-component developer.

[0127] As described above, in this embodiment, the deterioration degree of the supply roller 43 is calculated based on the voltage value of the supply bias Vrs (or the potential difference between the supply bias Vrs and the developing bias Vdc), the application time of the supply bias Vrs, and the printing rate of the output image. This makes it possible to obtain information on the deterioration degree of the supply roller 43 with higher accuracy. This also makes it possible to notify the user of information on the life of the developing device 4 before an image defect such as a solid tracking defect occurs.

[0128] [Example 2] Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the image forming apparatus of embodiment 1. Therefore, in the image forming apparatus of this embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus of embodiment 1 are given the same reference numerals as those of embodiment 1, and detailed explanations are omitted.

[0129] <How to apply supply bias> 11 is a timing chart showing the transition of the supply bias Vrs applied to the supply roller 43 during the printing operation in this embodiment. In this embodiment, the supply bias Vrs applied to the supply roller 43 is changed in the pre-rotation process, the image forming process, the sheet interval process, and the post-rotation process. As an example, the settings of the supply bias Vrs and the developing bias Vdc in the usage environment of the image forming apparatus 100 at 23° C. are shown in Table 7.

[0130] [Table 7]

[0131] In the pre-rotation process, the development bias Vdc is −350V, whereas the supply bias Vr (particularly also referred to as “supply bias VD”) is −250V. In this case, when considering the potential of the supply roller 43 based on the potential of the development roller 42, the potential difference (Vrs−Vdc) is +100V. Similarly, in the image forming process, the supply bias Vr (particularly also referred to as “supply bias VE”) is −450V, and the potential difference (Vrs−Vdc) is −100V. In the paper interval process, the supply bias Vrs (particularly also referred to as “supply bias VF”) is −350V, and the potential difference (Vrs−Vdc) is 0V. In the post-rotation process, the supply bias Vrs (particularly also referred to as “supply bias VG”) is −300V, and the potential difference (Vrs−Vdc) is +50V.

[0132] By controlling the supply bias Vrs in this way, it is possible to supply the toner 90 required for image formation to the development roller 42 while suppressing deterioration of the supply roller 43. That is, a method of applying a bias ("reverse bias") of a polarity opposite to that during image formation (development) to the supply roller 43 to return the uneven distribution of the ion conductive agent in the supply roller 43 to an equilibrium state has been known as a measure against deterioration of the supply roller 43. In this embodiment, by changing the supply bias Vrs in the pre-rotation process, the inter-paper process, and the post-rotation process as described above, the apparent potential difference of the supply bias Vrs with respect to the development bias Vdc can be switched between plus (positive polarity) and minus (negative polarity). Therefore, it is possible to suppress deterioration due to uneven distribution of the ion conductive agent in the supply roller 43. Note that the supply bias Vrs in the pre-rotation process, the inter-paper process, and the post-rotation process may be a bias of a polarity opposite to that of the supply bias Vrs during image formation (opposite polarity to the normal charging polarity of the toner 90), or may be 0V.

[0133] As described above, the deterioration degree of the supply roller 43 differs depending on the potential difference between the development roller 42 (development bias Vdc) and the supply roller 43 (supply bias Vrs). Therefore, in this embodiment, the deterioration degree of the supply roller 43 is calculated in more detail using a potential deterioration correction coefficient ε2 according to the potential difference between the development roller 42 (development bias Vdc) and the supply roller 43 (supply bias Vrs).

[0134] The potential deterioration correction coefficient ε2 is set as shown in Table 9 described later. That is, when the potential difference (Vrs-Vdc) between the developing roller 42 and the supply roller 43 is on the positive side (the potential of the supply roller 43 is on the positive side with respect to the potential of the developing roller 42), the bias of the ion conductive agent is alleviated, and the potential deterioration correction coefficient ε2 is a low value. In this case, the potential deterioration correction coefficient ε2 is low as the absolute value of the potential difference increases. On the other hand, when the potential difference (Vrs-Vdc) between the developing roller 42 and the supply roller 43 is on the negative side (the potential of the supply roller 43 is on the negative side with respect to the potential of the developing roller 42), the potential deterioration correction coefficient ε2 is high as the absolute value of the potential difference increases. This reflects the result in the verification 1 (FIG. 8(a)) described in the first embodiment that the bias of the ion conductive agent becomes more noticeable as the negative side potential difference (Vrs-Vdc) between the developing roller 42 and the supply roller 43 increases.

[0135] The potential deterioration correction coefficient ε2 varies depending on the characteristics of the supply roller 43 and the characteristics of the toner 90, and can be determined based on experimental values. The potential deterioration correction coefficient ε2 is not limited to being changed linearly (linearly) with respect to the supply bias Vrs (or the potential difference Vrs-Vdc) as in this embodiment. The potential deterioration correction coefficient ε2 may be changed quadratically (curvilinearly) with respect to the supply bias Vrs (or the potential difference Vrs-Vdc). Depending on the configuration of the image forming apparatus 100 (developing device 4), the potential deterioration correction coefficient ε2 may be changed so as to decrease with the change in the potential difference (Vrs-Vdc) from the positive side to the negative side.

[0136] <Calculating the deterioration level of the supply roller (detecting the life of the supply roller)> Next, detection of the life of the supply roller 43 (calculation of the deterioration degree of the supply roller 43) in this embodiment will be described. Fig. 12 is a flowchart showing an outline of the procedure for detecting the life of the developing device 4 with a focus on detection of the life of the supply roller 43. The process according to the flowchart in Fig. 12 is executed by the control unit 220 (mainly the supply roller life detection unit 80).

[0137] When a print signal (job information) is input (S501), the control unit 220 starts a print operation (job) (S502). With the start of the print operation, the control unit 220 acquires the detection result of the temperature and humidity sensor 130 (S503), and determines the supply bias VD during the pre-rotation process, the supply bias VE during the image forming process, the supply bias VF during the paper-to-paper interval process, and the supply bias VG during the post-rotation process (these are also collectively referred to as "supply bias Vrs2" in this embodiment) based on the detection result of the temperature and humidity sensor 130 (particularly, temperature in this embodiment) (S504). In this embodiment, the control unit 220 reads and determines the supply bias Vrs2 corresponding to the temperature, that is, the supply bias VD during the pre-rotation process, the supply bias VE during the image forming process, the supply bias VF during the paper-to-paper interval process, and the supply bias VG during the post-rotation process, from table data shown in Table 8, which is preset and stored in the main body memory 221. The table data in Table 8 is an example of information indicating the relationship between the environment and the supply biases VD, VE, VF, and VG. In this embodiment, the developing bias Vdc is set to a constant value of -350V.

[0138] [Table 8]

[0139] Further, the supply roller deterioration degree calculation unit 84 converts the determined supply biases VD, VE, VF, and VG into potential differences (VD-Vdc, VE-Vdc, VF-Vdc, and VG-Vdc) between the supply biases VD, VE, VF, and VG, respectively, and determines a potential deterioration correction coefficient ε2 corresponding to each potential difference (S505). That is, the supply roller deterioration degree calculation unit 84 determines a potential deterioration correction coefficient ε2D for the pre-rotation process, a potential deterioration correction coefficient ε2E for the image forming process, a potential deterioration correction coefficient ε2F for the paper interval process, and a potential deterioration correction coefficient ε2G for the post-rotation process (these are also collectively referred to as "potential deterioration correction coefficient ε2" in this embodiment). In this embodiment, the supply roller deterioration degree calculation unit 84 reads out and determines the potential deterioration correction coefficients ε2D, ε2F, ε2F, and ε2G corresponding to each of the potential differences from table data shown in Table 9, which is preset and stored in the memory 150. The table data of Table 9 is an example of information indicating the relationship between the supply bias Vrs (or the potential difference between the supply bias Vrs and the developing bias Vdc) and the potential deterioration correction coefficient ε2.

[0140] [Table 9]

[0141] Next, during the printing operation, the supply bias application time calculation unit 81 measures the time during which the supply bias Vrs2 is applied to the supply roller 43 (S506), and calculates the supply bias application time tnow2 in the printing operation (S507). If the supply bias application start timing in the printing operation is tS and the supply bias application end timing in the printing operation is tE, the supply bias application time tnow2 in the printing operation can be expressed by the following formula (9). In the following formula (9), tA is the time of the pre-rotation process, tB is the total time of the image formation process, tC is the total time of the paper interval process, and tD is the time of the post-rotation process. tnow2=tE-tS =tA+tB+tC+tD (9)

[0142] Furthermore, at a predetermined timing during the printing operation (e.g., during the post-rotation step), the second video count measurement unit 83 calculates the section printing rate γnow, which is the printing rate in the printing operation, based on the video count value VCn measured by receiving pixel information of the output image (S508). Then, the supply roller deterioration degree calculation unit 84 determines the deterioration correction coefficient ε based on the section printing rate γnow acquired by the second video count measurement unit 83 (S509). In this embodiment, the supply roller deterioration degree calculation unit 84 reads out and determines the deterioration correction coefficient ε corresponding to the section printing rate γnow from the table data shown in Table 10, which is preset and stored in the memory 150. The table data in Table 10 is an example of information indicating the relationship between the section printing rate γnow and the deterioration correction coefficient ε.

[0143] [Table 10]

[0144] Next, the supply roller deterioration level calculation unit 84 calculates the section supply roller deterioration level ηnow2, which is an index showing the degree of deterioration of the supply roller 43 in the print operation, by the following formula (10) (S510). ηnow2=tA×ε2D+tB×ε×ε2E+tC×ε2F+tD×ε2G (10)

[0145] Next, the supply roller deterioration degree calculation unit 84 calculates a total supply roller deterioration degree ηt which is an index showing the degree of deterioration of the supply roller 43 from the start of use of the developing device 4 (supply roller 43) (S511). That is, as shown in the following formula (11), the supply roller deterioration degree calculation unit 84 adds (integrates) the calculated section supply roller deterioration degree ηnow2 to the cumulative supply roller deterioration degree ηr from the start of use of the developing device 4 (supply roller 43) stored in the memory 150. In this way, the total supply roller deterioration degree ηt is calculated. Then, the supply roller deterioration degree calculation unit 84 updates and stores the calculated total supply roller deterioration degree ηt in the memory 150 as a new cumulative supply roller deterioration degree ηr. ηt = ηnow2 + ηr (11)

[0146] Next, the supply roller deterioration degree calculation unit 84 calculates the supply roller remaining life ηJ from the supply roller deterioration degree threshold value ηth preset and stored in the memory 150 and the calculated total supply roller deterioration degree ηt by the following formula (12) (S512). Note that the supply roller deterioration degree threshold value ηth in this embodiment is preset in accordance with the above-mentioned method of calculating the total supply roller deterioration degree ηt in this embodiment. The supply roller deterioration degree calculation unit 84 may update and store the calculated supply roller remaining life ηJ in the memory 150. ηJ[%]=(1-ηt / ηth)×100 ···(12)

[0147] Next, the control unit 220 judges whether the supply roller remaining life ηJ calculated by the supply roller deterioration degree calculation unit 84 is 0% or less (S513). If the control unit 220 judges in S513 that the supply roller remaining life ηJ is not 0% or less, it ends the print operation (S514). On the other hand, if the control unit 220 judges in S513 that the supply roller remaining life ηJ is 0% or less, it controls to execute a process of notifying the user of information regarding the life of the developing device 4 (S515). Then, the control unit 220 ends the print operation (S514).

[0148] <Calculation example> A calculation example of the deterioration degree of the supply roller 43 in this embodiment will be described. A case where two-sheet intermittent printing is performed in which a print operation of forming an image with an average print rate of 3.5% on two sheets of A4-sized recording material P is repeated in a usage environment (ambient environment) of the image forming apparatus 100 at 23°C will be described. In the image forming apparatus 100 of this embodiment, when a print operation of forming an image on two sheets of A4-sized recording material P is performed, the time during which the supply bias Vrs2 is applied to the supply roller 43 during the print operation is approximately expressed by the following formula. That is, tnow2=tA+tB+tC+tD=0.5 (seconds)+2.8 (seconds)×2+0.25 (seconds)×2+0.5 (seconds). In addition, when the image forming apparatus 100 is in an environment of room temperature of 23°C, from Table 8, the supply bias Vrs2 is VD=-250 (V), VE=-450 (V), VF=-350 (V), and VG=-300 (V). At this time, since the developing bias Vdc=-350 (V), the potential differences between the supply roller 43 and the developing roller 42 are VD-Vdc=+100 (V), VE-Vdc=-100 (V), VF-Vdc=0 (V), and VG-Vdc=+50 (V). Therefore, from Table 9, the potential deterioration correction coefficient ε2 is ε2D=0.5, ε2E=1.50, ε2F=1.00, and ε2G=0.75. In addition, when the section printing rate γnow is calculated to be 3.5%, from Table 10, the deterioration correction coefficient ε=1.5. Therefore, the section supply roller deterioration degree ηnow2 in one printing operation under the above conditions is calculated as follows. ηnow2=tA×ε2D+tB×ε×ε2E+tC×ε2F+tD×ε2G =0.5×0.5+2.8×2×1.5×1.50+0.25×2×1.00+0.5×0.75 =0.25+12.6+0.5+0.375 =13.725

[0149] The value of this section supply roller deterioration degree ηnow2 is stored in memory 150 as the cumulative supply roller deterioration degree ηr, and the section supply roller deterioration degree ηnow2 is recalculated in the subsequent print operation. The recalculated section supply roller deterioration degree ηnow2 is added to the cumulative supply roller deterioration degree ηr to calculate the total supply roller deterioration degree ηt. Then, as described above, when the total supply roller deterioration degree ηt reaches the supply roller deterioration degree threshold value ηth, it is determined that the supply roller 43 has reached the end of its life.

[0150] <Variation 5> In this embodiment, the image forming apparatus 100 holds the potential deterioration correction coefficient ε2 as table data associated with the potential difference between the supply roller 43 (supply bias Vrs) and the development roller 42 (development bias Vdc), but is not limited to this. The image forming apparatus 100 may hold the potential deterioration correction coefficient ε2 as table data associated with the supply bias Vrs, for example.

[0151] <Variation 6> In this embodiment, the image forming apparatus 100 holds the potential deterioration correction coefficient ε2 as table data corresponding to the potential difference between the supply roller 43 (supply bias Vrs) and the development roller 42 (development bias Vdc), but is not limited to this. The image forming apparatus 100 may calculate the potential deterioration correction coefficient ε2 from a correction formula such as the following formula (13). ε2=1―0.005VΔ (13)

[0152] <Variation 7> In this embodiment, the supply bias Vrs (the potential difference between the supply bias Vrs and the developing bias Vdc) is different in the pre-rotation process, the sheet-to-sheet process, and the post-rotation process from that in the image forming process, but this is not limited to this. By changing the potential difference (Vrs-Vdc) between the supply bias Vrs and the developing bias Vdc to a more positive side than that in the image forming process in at least one of the pre-rotation process, the sheet-to-sheet process, and the post-rotation process, a corresponding effect of suppressing deterioration of the supply roller 43 can be obtained. However, it is preferable to change the potential difference (Vrs-Vdc) between the supply bias Vrs and the developing bias Vdc to a positive polarity (opposite polarity to the normal charging polarity of the toner 90) in at least one of the pre-rotation process, the sheet-to-sheet process, and the post-rotation process.

[0153] <Variation 8> In this embodiment, the deterioration degree of the supply roller 43 is estimated by dividing it into the pre-rotation process, the image forming process, the sheet interval process, and the post-rotation process, and the deterioration degree of the supply roller 43 is finally calculated by combining them. This is to obtain information on the deterioration degree of the supply roller 43 more accurately when the supply bias Vrs (the potential difference between the supply bias Vrs and the development bias Vdc) is made different from that of the image forming process in the pre-rotation process, the sheet interval process, and the post-rotation process in this embodiment. However, even when the supply bias Vrs (the potential difference between the supply bias Vrs and the development bias Vdc) is not changed during the printing operation as in the first embodiment, the deterioration degree of the supply roller 43 may be estimated by dividing it into the pre-rotation process, the image forming process, the sheet interval process, and the post-rotation process, and the deterioration degree of the supply roller 43 may finally be calculated by combining them. In this case, the accuracy of the information on the deterioration degree of the supply roller 43 obtained can be improved by applying the deterioration correction coefficient ε according to the printing rate of the output image only to the image forming process in which the toner image is formed.

[0154] <Comparative verification 2> Next, a comparative verification carried out between this embodiment and the following Comparative Example 2 in order to verify the effect of this embodiment will be described.

[0155] -Evaluation method- In the image forming apparatus 100 having the configuration of this embodiment, a print endurance test was conducted from the start of use of the developing device 4 (process cartridge 8) until it reached the end of its life. Specifically, the print endurance test was conducted in a full-color image formation mode in a usage environment (ambient environment) of the image forming apparatus 100 with a temperature of 23°C and a humidity of 50%, in which a print operation was performed with the following (1) to (3) as one cycle. (1) A horizontal line image with a print rate of 2% is printed on 100 sheets of A4 size recording paper by intermittent printing on four sheets. (2) A horizontal line image with a print rate of 20% is printed on 100 sheets of A4 size recording paper by intermittent printing on four sheets. (3) A horizontal line image with a printing rate of 100% is formed on 100 sheets of A4 size recording paper by intermittent printing on four sheets.

[0156] As image defects, solid image tracking defects (whiteout images) in solid images were visually evaluated according to the following criteria. Note that, although the evaluation results for solid black images are shown here in particular, in this embodiment, the configurations of the developing devices 4 (process cartridges 8) for each color were substantially the same, and similar evaluation results were obtained. ○: No solid tracking problems (no practical problems) ×: Significantly poor solid-color conformability (problems in practical use)

[0157] -Comparative Example 2- In Comparative Example 2, the life of the developing device 4 was not detected based on the deterioration degree of the supply roller 43, but was detected based on the life and remaining amount of toner of the developing roller 42. Other points of Comparative Example 2 are substantially the same as those of this embodiment.

[0158] -Evaluation results- The evaluation results are shown in Table 11.

[0159] [Table 11]

[0160] In this embodiment, when the developing roller remaining life GJ was 45% and the toner remaining amount TJ was 9%, the supply roller remaining life ηJ became 0%, and it was notified that the developing device 4 had reached the end of its life. In this way, in this embodiment, it was possible to notify the user of information regarding the life (replacement) of the developing device 4 before a solid tracking defect occurred.

[0161] On the other hand, in comparison example 2, the remaining life of the developing roller GJ was 41% and the remaining toner amount TJ was 7%, and even though this was before it was notified that the developing device 4 had reached the end of its life, poor solid tracking occurred.

[0162] <Effects> In this embodiment, in the image formation by the image forming apparatus 100, an image forming operation (image forming process) in which a developer image is formed on the image carrier 1 and non-image forming operations (pre-rotation process, paper interval process, post-rotation process) in which a developer image is not formed on the image carrier 1 are performed, and the control unit 220 can change the supply voltage applied to the supply member 43 during the image forming operation and at least a part of the non-image forming operation, and acquires information on the deterioration degree of the supply roller 43 based on information on each supply voltage applied to the supply member 43, information on the time when each supply voltage was applied to the supply member 43, and information on the printing rate acquired by the acquisition unit (second video count measurement unit) 83. Also, in this embodiment, the control unit 220 can change the supply voltage applied to the supply member 43 so that the polarity of the potential difference of the supply voltage with respect to the development voltage is reversed during at least a part of the image forming operation and non-image forming operation.

[0163] As described above, according to this embodiment, the same effects as those of the first embodiment can be obtained, and the potential difference (Vrs-Vdc) between the supply bias Vrs and the developing bias Vdc can be switched between positive and negative during a printing operation, thereby making it possible to suppress deterioration of the supply roller 43. In addition, at that time, by calculating the deterioration degree of the supply roller 43 using the potential deterioration correction coefficient ε2 according to the potential difference (Vrs-Vdc) between the supply bias Vrs and the developing bias Vdc, information on the deterioration degree of the supply roller 43 can be obtained with high accuracy.

[0164] [Example 3] Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the image forming apparatus of embodiment 1. Therefore, in the image forming apparatus of this embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus of embodiment 1 are given the same reference numerals as those of embodiment 1, and detailed explanations are omitted.

[0165] <Outline of this Example> In this embodiment, the printing rate is obtained for each region obtained by dividing the image forming region into a plurality of regions in the laser main scanning direction of the exposure device 3, and the deterioration degree of the supply roller 43 in each region is calculated based on the printing rate of each region. Note that this main scanning direction is approximately parallel to the rotation axis direction of the supply roller 43, and the rotation axis direction of the supply roller 43 corresponding to this main scanning direction is also called the "longitudinal direction". This improves the accuracy of the information regarding the deterioration degree of the supply roller 43 obtained. That is, in this embodiment, it is possible to accurately detect the case where the supply roller 43 is locally deteriorated in the longitudinal direction. This makes it possible to suppress the occurrence of image defects such as solid tracking defects in a part of the longitudinal direction due to the local deterioration of the supply roller 43 in the longitudinal direction when the printing rate of the output image is high in a part of the longitudinal direction.

[0166] In this embodiment, the degree of contribution of the deterioration degree at each position in the longitudinal direction of the supply roller 43 to the deterioration degree of the supply roller 43 (deterioration correction coefficient ε) is estimated by accumulating the printing rate of the image formed at that position along the sub-scanning direction. The sub-scanning direction is a direction that is approximately perpendicular to the main scanning direction and is approximately parallel to the moving direction of the surface of the supply roller 43. Specifically, the printing rate (printing information) along the sub-scanning direction is obtained using a pixel counting method (or a video counting method). The pixel counting method (or the video counting method) is a method of acquiring information on the number of pixels in the printing part of the image by counting the ON signal of the laser exposure (a signal that emits a laser, a pixel signal) generated based on image data. In the photosensitive drum 1, the area exposed to the laser is printed (toner moved from the developing roller 42 adheres to it), so the count value of the laser ON signal corresponds to the count value of the dots in the printing part of the image.

[0167] Fig. 14 is a schematic diagram showing each dot of an image formed on one sheet of recording material P, and shows, as an example, a case where an image of the letter "A" is formed on recording material P. Fig. 14 also shows the positional relationship of supply roller 43 with respect to the image. A method of calculating the printing rate in each region in the main scanning direction will be described with reference to Fig. 14.

[0168] When image formation is started, the control unit 220 accumulates the laser ON signal along the sub-scanning direction in each region in the main scanning direction. The accumulated value is divided by the total number of dots in the sub-scanning direction to obtain the printing rate γ(n) (%) in each region in the main scanning direction. The subscript n corresponds to each region in the main scanning direction. In this embodiment, the image data in the image forming region is divided into 12 in the main scanning direction (longitudinal direction). Each region in the main scanning direction of the image forming region is n=1, 2, 3, 4... (1≦n≦12) from the left in the figure. In addition, in the sub-scanning direction, the image forming region is divided into, for example, 15. In this case, it is divided into a total of 12×15=180 sections (dots, pixels). The sections (dots) filled in black in FIG. 14 are sections (printing section, image section) where printing is performed and deterioration of the supply roller 43 is accelerated. On the other hand, the white sections in FIG. 14 are sections (non-printed areas, non-image areas) where no printing is performed and where the supply roller 43 is deteriorating slowly. In an area where n=2 in the main scanning direction, 3 dots out of 15 dots in the sub-scanning direction are printed when forming an image of "A". Therefore, the printing rate γ(2) of the area where n=2 is 20%. Similarly, in an area where n=6, 5 ​​dots out of 15 dots in the sub-scanning direction are printed, so the printing rate γ(6) is approximately 33.3%. Using this method, the printing rate for each area in the main scanning direction of the output image can be calculated.

[0169] In this embodiment, the longitudinal direction is divided into 12 parts, but the number of divisions in the longitudinal direction is not limited to this, and can be selected arbitrarily. For example, it is possible to divide the longitudinal direction into three parts more roughly, that is, into three regions (1≦n≦3) on the left end side, the center, and the right end side. It is also possible to divide the longitudinal direction up to the maximum number of pixel counts. For example, if an image of 300 dpi is formed, 300 dots are arranged per inch. In this case, approximately 1≦n≦25000, and the image formation region can be divided into approximately 25,000 parts in the longitudinal direction. However, the maximum memory capacity that can be used may be a constraint. In addition, the uneven density in the longitudinal direction due to local deterioration in the longitudinal direction of the supply roller 43 tends to be noticeable when the local deterioration occurs over a certain width in the longitudinal direction. For these reasons, it is preferable to divide the longitudinal direction so that the width of each region in the longitudinal direction is about 5 mm to 50 mm, typically about 10 mm to 30 mm. From this viewpoint, for example, when the maximum size of image formation is LTR size portrait feed (or A4 size portrait feed), it is preferable to have a longitudinal division number of about 8 to 20 divisions (12 divisions in this embodiment) as in this embodiment.

[0170] <Calculating the Deterioration Level of the Supply Roller (Detecting the Life of the Supply Roller)> Next, detection of the life of the supply roller 43 (calculation of the deterioration degree of the supply roller 43) in this embodiment will be described. Fig. 13 is a flow chart showing an outline of the procedure for detecting the life of the developing device 4 with a focus on detection of the life of the supply roller 43. The process according to the flow chart in Fig. 13 is executed by the control unit 220 (mainly the supply roller life detection unit 80). Note that, in the procedure in this embodiment shown in Fig. 13, the description of the same process as the procedure in embodiment 1 shown in Fig. 9 will be omitted as appropriate.

[0171] The processes in S601 to S606 in FIG. 13 are similar to the processes in S401 to S406 in FIG.

[0172] In this embodiment, at a predetermined timing during the printing operation (for example, during the post-rotation process), the second video count measurement unit 83 receives pixel information (pixel information) of the output image and calculates the section printing rate γnow(n) of each area in the main scanning direction in the printing operation based on the video count value in each area in the main scanning direction measured (S607). Then, the supply roller deterioration degree calculation unit 84 determines the deterioration correction coefficient ε(n) of each area in the main scanning direction based on the section printing rate γnow(n) of each area in the main scanning direction acquired by the second video count measurement unit 83 (S608). In this embodiment, the supply roller deterioration degree calculation unit 84 reads out and determines the deterioration correction coefficient ε(n) corresponding to the section printing rate γnow(n) of each area in the main scanning direction from the table data shown in Table 2 (see Example 1) that is preset and stored in the memory 150.

[0173] Next, the supply roller deterioration degree calculation unit 84 calculates the section supply roller deterioration degree ηnow(n), which is an index showing the degree of deterioration of the supply roller 43 in each region in the longitudinal direction during the printing operation, by the following formula (14) (S609). ηnow(n)=tnow×|Vrs|×ε(n) ···(14)

[0174] In this embodiment, the deterioration degree ηnow(n) of the section supply roller is calculated by the above formula (14) because the developing bias Vdc is constant. However, for example, when the developing bias Vdc is variably controlled, the deterioration degree ηnow(n) of the section supply roller may be calculated by the following formula, ηnow(n)=tnow×|Vrs-Vdc|×ε(n).

[0175] Next, the supply roller deterioration degree calculation unit 84 calculates a total supply roller deterioration degree ηt(n) which is an index indicating the deterioration degree of the supply roller 43 in each region in the longitudinal direction from the start of use of the developing device 4 (supply roller 43) (S610). That is, as shown in the following formula (15), the supply roller deterioration degree calculation unit 84 adds (integrates) the calculated section supply roller deterioration degree ηnow(n) of each region in the longitudinal direction to the accumulated supply roller deterioration degree ηr(n) of each region in the longitudinal direction from the start of use of the developing device 4 (supply roller 43) stored in the memory 150. In this way, the total supply roller deterioration degree ηt(n) of each region in the longitudinal direction is calculated. Then, the supply roller deterioration degree calculation unit 84 updates and stores the calculated total supply roller deterioration degree ηt(n) of each region in the longitudinal direction as a new accumulated supply roller deterioration degree ηr(n) of each region in the longitudinal direction in the memory 150. ηt(n)=ηnow(n)+ηr(n) ···(15)

[0176] Next, the supply roller deterioration degree calculation unit 84 calculates the supply roller remaining life ηJ(n) of each longitudinal region from the supply roller deterioration degree threshold value ηth set in advance and stored in the memory 150 and the calculated total supply roller deterioration degree ηt(n) of each longitudinal region by the following formula (16) (S611). The supply roller deterioration degree calculation unit 84 may update and store the calculated supply roller remaining life ηJ(n) of each longitudinal region in the memory 150. ηJ(n)[%]=(1-ηt(n) / ηth)×100 ···(16)

[0177] Next, the supply roller deterioration degree calculation unit 84 selects the minimum value of the supply roller remaining life ηJ(n) of each region in the longitudinal direction (S612). In other words, the supply roller deterioration degree calculation unit 84 selects the supply roller remaining life ηJ(n) of the longitudinal region that is most deteriorated (has the greatest degree of deterioration).

[0178] Next, the control unit 220 judges whether the minimum supply roller remaining life ηJ(n) selected by the supply roller deterioration degree calculation unit 84 is 0% or less (S613). If the control unit 220 judges in S613 that the minimum supply roller remaining life ηJ(n) is not 0% or less, it ends the print operation (S614). On the other hand, if the control unit 220 judges in S613 that the minimum supply roller remaining life ηJ(n) is 0% or less, it controls to execute a process of notifying the user of information regarding the life of the developing device 4 (S615). Then, the control unit 220 ends the print operation (S614).

[0179] In this manner, in this embodiment, the degree of deterioration of the supply roller 43 is calculated for each area divided in the main scanning direction (longitudinal direction), and the life of the supply roller 43 can be determined based on the degree of deterioration of the area with the most deterioration.

[0180] <Calculation example> A calculation example of the deterioration degree of the supply roller 43 in this embodiment will be described. A case where two-sheet intermittent printing is performed in which a print operation of forming an image as shown in FIG. 14 on two sheets of A4-sized recording material P is repeated in a usage environment (ambient environment) of the image forming apparatus 100 at 23° C. is described. When a print operation of forming an image on two sheets of A4-sized recording material P is performed in the image forming apparatus 100 of this embodiment, tnow=7.26 (seconds), as in the calculation example described in the first embodiment. Furthermore, when the image forming apparatus 100 is in an environment at room temperature of 23° C., Vrs=−450 (V) from Table 1 (see the first embodiment).

[0181] For the image shown in FIG. 14, when the deterioration correction coefficient ε(n) corresponding to the section printing rate γnow(n) is determined from Table 2 (see Example 1), the result is as follows. n=1: Section print rate γ(1)=0%, deterioration correction coefficient ε(1)=1.0 n=2: Section print rate γ(2)=20%, deterioration correction coefficient ε(2)=2.0 n=3: Section print rate γ(3)=27%, deterioration correction coefficient ε(3)=2.0 n=4: Section print rate γ(4)=33%, deterioration correction coefficient ε(4)=2.5

[0182] Although the range of n=1 to 4 has been exemplified, the deterioration correction coefficient ε(n) is determined in the same manner for the range of n=5 to 12.

[0183] Therefore, the section supply roller deterioration degree ηnow(n) in the first printing operation under the above conditions is calculated as follows. n=1:ηnow(1)=7.26×|-450|×1.0=3267 n=2:ηnow(2)=7.26×|-450|×2.0=6534 n=3:ηnow(3)=7.26×|-450|×2.0=6534 n=4:ηnow(4)=7.26×|-450|×2.5=8167.5

[0184] Although the region where n=1 to 4 has been exemplified, the sectional supply roller deterioration degree ηnow(n) is calculated in the same manner for the region where n=5 to 12.

[0185] The value of this section supply roller deterioration degree ηnow(n) is stored in memory 150 as the cumulative supply roller deterioration degree ηr(n), and the section supply roller deterioration degree ηnow(n) is recalculated in the subsequent print operation. Then, the recalculated section supply roller deterioration degree ηnow(n) is added to the cumulative supply roller deterioration degree ηr(n) to calculate the total supply roller deterioration degree ηt(n). That is, the section supply roller deterioration degree ηnow(n) calculated in the first print operation is set as the cumulative supply roller deterioration degree ηr(n). Then, when the section supply roller deterioration degree ηnow(n) calculated in the second print operation under the above conditions is added to this cumulative supply roller deterioration degree ηr(n), the total supply roller deterioration degree ηt(n) is as follows: ηt(1)=ηr(1)+ηnow(1)=3267+3267=6534 ηt(2)=ηr(2)+ηnow(2)=6534+6534=13068 ηt(3)=ηr(3)+ηnow(3)=6534+6534=13068 ηt(4)=ηr(4)+ηnow(4)=8167.5+8167.5=16335

[0186] Although the range of n=1 to 4 has been exemplified, the total supply roller deterioration degree ηt(n) is calculated in the same manner for the range of n=5 to 12.

[0187] Then, as described above, when the minimum value of the supply roller remaining life ηJ(n) becomes 0% or less, that is, when the maximum value of the total supply roller deterioration degree ηt(n) reaches the supply roller deterioration degree threshold value ηth, it is determined that the supply roller 43 has reached the end of its life.

[0188] The supply roller deterioration threshold value ηth is experimentally determined in advance so as not to cause a solid image followability defect. In this embodiment, the supply roller deterioration threshold value ηth=3.9×10 7 However, the supply roller deterioration level threshold value ηth may vary depending on the elastic material constituting the foamed elastic layer of the supply roller 43, the type and amount of conductive agent contained in the material of the foamed elastic layer, the type of toner 90, etc.

[0189] <Comparative Verification 3> Next, a comparative test carried out to verify the effect of this embodiment will be described.

[0190] -Evaluation method- In the image forming apparatus 100 having the configuration of this embodiment, a print endurance test was performed from the start of use of the developing device 4 (process cartridge 8) until the supply roller 43 reached the end of its life. Specifically, a print endurance test was performed in which a print operation was performed in which the following image pattern was formed on an A4-sized recording paper in a full-color image formation mode with two-sheet intermittent printing in a usage environment (ambient environment) of the image forming apparatus 100 at a temperature of 23° C. and a humidity of 50%. As the image patterns, three image patterns were used, as shown in FIG. 14, FIG. 15, and FIG. 16, which have the same average print rate of 25.5% but different print rates in each area in the longitudinal direction. The image pattern in FIG. 16 has the same average print rate as the image patterns in FIG. 14 and FIG. 15, but the printed portion is biased in the longitudinal direction. The image pattern in FIG. 15 has the same average print rate as the image patterns in FIG. 14 and FIG. 16, but the printed portion is present evenly over the entire longitudinal direction. The occurrence of image defects was compared between the case where the method of Example 1 was used and the case where the method of this embodiment was used as a method for calculating the deterioration degree of the supply roller 43. As for the image defects, the occurrence of solid image tracking defects (whiteout images) was visually evaluated according to the following criteria. Note that, although the evaluation results are shown here in particular for solid black images, in this embodiment, the configurations of the developing devices 4 (process cartridges 8) for each color are substantially the same, and similar evaluation results were obtained. ○: No solid tracking failure ○△: Slight solid-color conformity problems (within practical acceptable range)

[0191] -Evaluation results- The evaluation results for the method of Example 1 are shown in Table 12.

[0192] [Table 12]

[0193] In the method of the first embodiment, the printing rate is calculated to be 25.5% for all the image patterns of Figs. 14, 15, and 16. Therefore, the deterioration correction coefficient ε=2.0 corresponding to the printing rate=25.5% is used to calculate the deterioration degree of the supply roller 43 regardless of the image pattern, and the supply roller 43 reaches the end of its life at the same timing. As a result, when the image patterns of Figs. 14 and 16 are continuously printed, it was confirmed that a slight solid followability defect occurs at the time when the supply roller 43 reaches the end of its life. This is due to the fact that the toner 90 continues to be consumed in large amounts in a part of the longitudinal direction, causing the supply roller 43 to deteriorate locally in the longitudinal direction.

[0194] Next, the evaluation results for the method of this example are shown in Table 13.

[0195] [Table 13]

[0196] In the method of this embodiment, since the image pattern of FIG. 14 has a region in the longitudinal direction where the printing rate is locally 33% and thus the maximum printing rate, a deterioration correction coefficient ε=2.0 is used to calculate the deterioration level of the supply roller 43. Similarly, in the image pattern of FIG. 16, since the image pattern of FIG. 16 has a region in the longitudinal direction where the printing rate is locally 100% and thus the maximum printing rate, a deterioration correction coefficient ε=4.0 is used to calculate the deterioration level of the supply roller 43. In this way, in the method of this embodiment, a deterioration correction coefficient ε having a larger value than that of the method of embodiment 1 is selected to calculate the deterioration level of the supply roller 43. Therefore, in the method of this embodiment, no solid tracking failure occurred when the supply roller 43 reached the end of its life.

[0197] <Effects> In this embodiment, the acquisition unit (second video count measurement unit) 83 acquires information on the printing rate for each region obtained by dividing the image forming region on the image carrier in the main scanning direction substantially perpendicular to the moving direction of the surface of the image carrier 1, and the control unit 220 acquires information on the deterioration level of the supply member 43 for each region based on the information on the printing rate for each region. Also, in this embodiment, the control unit 220 can determine whether or not the developing device 4 has reached the end of its life based on the information on the deterioration level for each region. Also, in this embodiment, the control unit 220 can determine whether or not the developing device 4 has reached the end of its life based on information indicating the greatest degree of deterioration among the information on the deterioration level for each region.

[0198] As described above, in this embodiment, the deterioration degree of the supply roller 43 is calculated based on the printing rate for each area divided in the main scanning direction (longitudinal direction). As a result, even when an image with uneven printing in the main scanning direction is formed, information on the deterioration degree of the supply roller 43 can be obtained more accurately according to local deterioration in the longitudinal direction of the supply roller 43. This also makes it possible to notify the user of information on the life of the developing device 4 more accurately before image defects such as solid followability problems occur.

[0199] [Example 4] Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the image forming apparatus of embodiment 1. Therefore, in the image forming apparatus of this embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus of embodiment 1 are given the same reference numerals as those of embodiment 1, and detailed explanations are omitted.

[0200] <Outline of this Example> In this embodiment, as in the third embodiment, the printing rate is obtained for each of the regions obtained by dividing the image forming region into a plurality of regions in the main scanning direction. In this embodiment, information on the deterioration degree of the supply roller 43 is obtained based on the printing rate between adjacent regions in the main scanning direction. In particular, in this embodiment, information on the deterioration degree of the supply roller 43 is obtained based on the difference in printing rate between adjacent regions in the main scanning direction. This can improve the accuracy of the information on the deterioration degree of the supply roller 43 obtained. In other words, when an image is formed with a large difference in printing rate between adjacent regions in the main scanning direction and the difference in the deterioration degree of the supply roller 43 between the adjacent regions is large, it is possible to suppress image defects such as uneven density from becoming more noticeable.

[0201] In general, the supply roller 43 deteriorates in its ability to supply toner to the developing roller 42. This tends to reduce the amount of toner coat on the developing roller 42, or toner with an excessively high charge tends to accumulate on the developing roller 42. Therefore, when a solid image (100% print image) or a halftone image (halftone image) with a uniform print rate in the main scanning direction is output after images with a large difference in print rate between adjacent regions in the main scanning direction are continuously formed, the image density may change in the main scanning direction. This is because when the difference in print rate between adjacent regions in the main scanning direction is large, local deterioration progresses in the longitudinal direction of the supply roller 43, and the difference in the performance of supplying toner to the developing roller 42 in the boundary area becomes apparent as uneven density of the image. In this embodiment, in order to deal with such a phenomenon, information on the degree of deterioration of the supply roller 43 is acquired in consideration of the difference in print rate between adjacent regions in the main scanning direction (longitudinal direction). This makes it possible to suppress image defects such as the above-mentioned uneven density.

[0202] <Verification 4> A print durability test was carried out to confirm the change in image density according to the deterioration of the supply roller 43. In the usage environment (ambient environment) of the image forming apparatus 100 at a temperature of 23°C and a humidity of 50%, a print operation was carried out by intermittent printing of one sheet to form an image with a uniform print rate of 25.5% in the main scanning direction (longitudinal direction). The print operation was completed so that the supply roller 43 had four levels of deterioration, and the supply roller 43 was once removed from the developing device 4, and the supply roller 43 was reassembled in the developing device 4 in the same state, and a print operation was carried out. By making the conditions of the parts other than the supply roller 43 uniform, factors other than the change in the condition of the supply roller 43 can be eliminated. The print operation was carried out for a solid image (print rate of 100%) and a halftone image (print rate of 23%).

[0203] The results are shown in FIG. 17. The vertical axis indicates image density (reflection density), and the horizontal axis indicates the rotation drive time of the supply roller 43 (= supply bias application time). The reflection density was measured using eXact (X-rite). It can be seen that the image density gradually decreases as the print endurance test progresses (the rotation drive time of the supply roller 43 increases). It can also be seen that the image density decreases more significantly in the halftone image than in the solid image, and the change in image density is more noticeable in the halftone image than in the solid image. Therefore, for example, if an image with different printing rates in the longitudinal direction as shown in FIG. 18 continues to be formed, a halftone image with low image density will be output in the area with high printing rate as shown in FIG. 19.

[0204] In this embodiment, this is taken into consideration, and it is possible to obtain information regarding the degree of deterioration of the supply roller 43 based on the difference in printing rate between adjacent regions in the longitudinal direction. This makes it possible to suppress uneven density between adjacent regions in the longitudinal direction.

[0205] <Calculating the deterioration level of the supply roller (detecting the life of the supply roller)> Next, detection of the life of the supply roller 43 (calculation of the deterioration degree of the supply roller 43) in this embodiment will be described. Fig. 20 is a flow chart showing an outline of the procedure for detecting the life of the developing device 4 with a focus on detecting the life of the supply roller 43. The process according to the flow chart in Fig. 20 is executed by the control unit 220 (mainly the supply roller life detection unit 80). Note that, in the procedure in this embodiment shown in Fig. 20, the description of the same process as the procedure in embodiment 3 shown in Fig. 13 will be omitted as appropriate.

[0206] The processes in S701 to S712 in FIG. 20 are similar to the processes in S601 to S612 in FIG. 13, respectively.

[0207] In this embodiment, the supply roller deterioration degree calculation unit 84 calculates the deterioration degree difference Δηt(n), which is the difference in the total supply roller deterioration degree ηt(n) of adjacent regions, from the calculated total supply roller deterioration degree ηt(n) of each region in the longitudinal direction, as shown in the following equation (17) (S713). Δηt(n)=ηt(n)-ηt(n+1) ···(17)

[0208] Next, the supply roller deterioration level calculation unit 84 selects the maximum value among the deterioration level difference absolute values ​​|Δηt(n)|, which are absolute values ​​(ie, differences) of the calculated deterioration level differences Δηt(n) (S714).

[0209] Then, the supply roller deterioration degree calculation unit 84 updates and stores in the memory 150 the calculated total supply roller deterioration degree ηt(n) of each longitudinal region as a new accumulated supply roller deterioration degree ηr(n) of each longitudinal region (S715). The supply roller deterioration degree calculation unit 84 may update and store in the memory 150 the calculated remaining supply roller life ηJ(n) of each longitudinal region.

[0210] Next, the control unit 220 judges whether the supply roller 43 has reached the end of its life (S715). First, the control unit 220 judges whether the minimum supply roller remaining life ηJ(n) selected by the supply roller deterioration degree calculation unit 84 is 0% or less, as in the third embodiment. In addition, in this embodiment, the control unit 220 judges whether the maximum deterioration degree difference absolute value |Δηt(n)| selected by the supply roller deterioration degree calculation unit 84 is equal to or greater than the deterioration degree difference threshold value Δηth previously set and stored in the memory 150. The deterioration degree difference threshold value Δηth is experimentally obtained in advance, for example, by actually visually checking the density unevenness in a solid image (a 100% printed image over the entire surface) or a halftone image (an image with the same halftone density over the entire surface) so that the density unevenness falls within a range that is permissible in terms of sensitivity. If the control unit 220 determines in S715 that the minimum supply roller remaining life ηJ(n) is not 0% or less and that the maximum deterioration degree difference absolute value |Δηt(n)| is not equal to or greater than the deterioration degree difference threshold value Δηth, the control unit 220 ends the print operation (S716). On the other hand, if the control unit 220 determines in S715 that the minimum supply roller remaining life ηJ(n) is 0% or less or that the maximum deterioration degree difference absolute value |Δηt(n)| is equal to or greater than the deterioration degree difference threshold value Δηth, the control unit 220 controls to execute a process of notifying the user of information regarding the life of the developing device 4 (S717). Then, the control unit 220 ends the print operation (S716).

[0211] <Calculation example> A calculation example of the deterioration degree of the supply roller 43 in this embodiment will be described. A case where two-sheet intermittent printing is performed in which a print operation of forming an image as shown in FIG. 18 on two sheets of A4-sized recording material P is repeated in a usage environment (ambient environment) of the image forming apparatus 100 at 23° C. is described. When a print operation of forming an image on two sheets of A4-sized recording material P is performed in the image forming apparatus 100 of this embodiment, tnow=7.26 (seconds), as in the calculation example described in the first embodiment. Furthermore, when the image forming apparatus 100 is in an environment at room temperature of 23° C., Vrs=−450 (V) from Table 1 (see the first embodiment).

[0212] For the image shown in FIG. 18, when the deterioration correction coefficient ε(n) corresponding to the section printing rate γnow(n) is determined from Table 2 (see Example 1), the result is as follows. n=1: Section print rate γ(1)=0%, deterioration correction coefficient ε(1)=1.0 n=2: Section print rate γ(2)=40%, deterioration correction coefficient ε(2)=2.5 n=3: Section print rate γ(3)=40%, deterioration correction coefficient ε(3)=2.5 n=4: Section print rate γ(4)=0%, deterioration correction coefficient ε(4)=1.0

[0213] Although the range of n=1 to 4 has been exemplified, the deterioration correction coefficient ε(n) is determined in the same manner for the range of n=5 to 12.

[0214] Therefore, the section supply roller deterioration degree ηnow(n) in the first printing operation under the above conditions is calculated as follows. n=1:ηnow(1)=7.26×|-450|×1.0=3267 n=2:ηnow(2)=7.26×|-450|×2.5=8167.5 n=3:ηnow(3)=7.26×|-450|×2.5=8167.5 n=4:ηnow(4)=7.26×|-450|×1.0=3267

[0215] Although the region where n=1 to 4 has been exemplified, the sectional supply roller deterioration degree ηnow(n) is calculated in the same manner for the region where n=5 to 12.

[0216] Moreover, the deterioration degree difference Δηt(n) in one print operation under the above conditions is calculated as follows. Δηt(1)=ηt(1)-ηt(2)=3267-8167.5=-4900.5 Δηt(2)=ηt(2)-ηt(3)=8167.5-8167.5=0 Δηt(3)=ηt(3)-ηt(4)=8167.5-3267=4900.5

[0217] Then, at the end of the second printing operation under the above conditions, the total supply roller deterioration degree ηt(n) is as follows: ηt(1)=ηr(1)+ηnow(1)=3267+3267=6534 ηt(2)=ηr(2)+ηnow(2)=8167.5+8167.5=16335 ηt(3)=ηr(3)+ηnow(3)=8167.5+8167.5=16335 ηt(4)=ηr(4)+ηnow(4)=3267+3267=6534

[0218] Similarly, at the end of the second print operation under the above conditions, the deterioration degree difference Δηt(n) is as follows: Δηt(1)=ηt(1)-ηt(2)=6534-16335=-9801 Δηt(2)=ηt(2)-ηt(3)=16335-16335=0 Δηt(3)=ηt(3)-ηt(4)=16335-6534=9801

[0219] In this way, the total supply roller deterioration degree ηt(n) and the partial deterioration degree difference absolute value |Δηt(n)| increase with each repetition of the printing operation.

[0220] As described above, the supply roller 43 is determined to have reached the end of its life when the minimum value of the supply roller remaining life ηJ(n) becomes 0% or less (i.e., the maximum value of the total supply roller deterioration degree ηt(n) reaches the supply roller deterioration degree threshold value ηth), or when the maximum value of the deterioration degree difference absolute value |Δηt(n)| becomes equal to or greater than the deterioration degree difference threshold value Δηth.

[0221] The deterioration degree difference threshold value Δηth is experimentally determined in advance so that the density unevenness does not reach a level at which it can be visually recognized. In this embodiment, the deterioration degree difference threshold value Δηth=1.7×10 7 It is set as follows.

[0222] <Variation 9> The method of acquiring information on the deterioration degree of the supply roller 43 based on the printing rate of each region in the longitudinal direction is not limited to the method of the third embodiment and the present embodiment. In the third embodiment, the life of the supply roller 43 is judged based on the deterioration degree of the region in which the supply roller remaining life ηJ is the smallest (the total supply roller deterioration degree ηt(n) is the largest). In contrast, for example, when the number of regions in which the supply roller remaining life ηJ(n) is 0% or less (i.e., the total supply roller deterioration degree ηt(n) has reached the supply roller deterioration degree threshold value ηth) is equal to or greater than a predetermined value, it may be judged that the supply roller 43 has reached the end of its life. Also, in this embodiment, the life of the supply roller 43 is judged based on the maximum value of the deterioration degree difference absolute value |Δηt(n)| between adjacent regions in the longitudinal direction. In contrast, when the number of regions in which the deterioration degree difference absolute value |Δηt(n)| is equal to or greater than the deterioration degree difference threshold value Δηth is equal to or greater than a predetermined value, it may be judged that the supply roller 43 has reached the end of its life. Furthermore, the relationship of the printing rates between adjacent regions in the longitudinal direction is not limited to obtaining the difference in printing rates between the regions, and for example, the ratio (proportion) of the printing rates between the regions may be obtained and used for control corresponding to this embodiment. Furthermore, the relationship of the printing rates between regions divided in the longitudinal direction is not limited to the relationship of the printing rates between adjacent regions, and for example, the relationship of the printing rates between the end and center in the longitudinal direction, or between both ends, may be used.

[0223] <Comparative Verification 4> Next, a comparative test carried out to verify the effect of this embodiment will be described.

[0224] -Evaluation method- In the image forming apparatus 100 having the configuration of this embodiment, a print endurance test was performed from the start of use of the developing device 4 (process cartridge 8) until the supply roller 43 reached the end of its life. Specifically, a print endurance test was performed in which a print operation was performed in which the following image pattern was formed on an A4-sized recording material P in a full-color image formation mode in a usage environment (ambient environment) of the image forming apparatus 100 at a temperature of 23° C. and a humidity of 50%, with two sheets of intermittent printing. The image pattern used was the image pattern shown in FIG. 18. Then, as a method for calculating the deterioration degree of the supply roller 43, the occurrence of image defects was compared between the case where the method of embodiment 3 was used and the case where the method of this embodiment was used. As the image defect, the occurrence of density unevenness in a halftone image (HT: printing rate 23%) was visually evaluated according to the following criteria. In addition, an evaluation of solid followability defects was also performed in the same manner as in the comparative verification 3 described in embodiment 3. Here, the evaluation results are shown particularly for solid black images, but in this embodiment, the configurations of the developing devices 4 (process cartridges 8) for each color are substantially the same, and similar evaluation results were obtained. 〇: No unevenness in HT density ○△: Slight unevenness in HT density (within acceptable range for practical use)

[0225] -Evaluation results- The evaluation results are shown in Table 14.

[0226] [Table 14]

[0227] In the method of Example 3, the area in the longitudinal direction where the printing rate is locally 40% is the maximum printing rate, so the deterioration correction coefficient ε=2.5 is used to calculate the deterioration degree of the supply roller 43. Therefore, in the method of Example 3, when the supply roller 43 reaches the end of its life, the occurrence of poor solid print tracking performance is suppressed, but slight HT density unevenness occurs. This is because the difference in printing rate is large in the boundary area between adjacent areas in the longitudinal direction, and the local deterioration of the supply roller 43 causes changes in the coat amount of toner and the amount of charge on the development roller 42.

[0228] In contrast, in the method of this embodiment, the difference in deterioration level between adjacent regions in the longitudinal direction of the supply roller 43 can be obtained by the absolute deterioration level difference |Δηt(n)|. Therefore, in the method of this embodiment, no HT density unevenness occurs when the supply roller 43 reaches the end of its life.

[0229] <Effects> In this embodiment, similarly to the fourth embodiment, the acquisition unit (second video count measurement unit) 83 acquires information on the printing rate for each region obtained by dividing the image forming region on the image carrier in the main scanning direction substantially perpendicular to the moving direction of the surface of the image carrier 1, and the control unit 220 acquires information on the deterioration degree of the supply member 43 for each region based on the information on the printing rate for each region. In addition, in this embodiment, the control unit 220 can determine whether the developing device 4 has reached the end of its life based on the information on the deterioration degree for each region. In addition, in this embodiment, the control unit 220 can acquire information on the difference in the deterioration degree between at least two of the regions based on the information on the deterioration degree for each region, and determine whether the developing device 4 has reached the end of its life based on the information on the difference. In addition, in this embodiment, the control unit 220 can determine whether the developing device 4 has reached the end of its life based on the information on the difference, which is the largest difference among the differences between the multiple adjacent regions, as the information on the difference.

[0230] As described above, in this embodiment, the same effects as those of the third embodiment can be obtained, and information on local deterioration in the longitudinal direction of the supply roller 43 can be obtained when an image is formed in which the difference in printing rate between adjacent regions in the main scanning direction is large. This makes it possible to obtain information on the deterioration degree of the supply roller 43 with higher accuracy, and to prevent image defects such as uneven density from becoming more noticeable.

[0231] [Example 5] Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the image forming apparatus of embodiment 1. Therefore, in the image forming apparatus of this embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus of embodiment 1 are given the same reference numerals as those of embodiment 1, and detailed explanations are omitted.

[0232] <Outline of this Example> FIG. 21 is a graph showing the relationship between the deterioration degree of the supply roller 43 and the amount of toner remaining in the developing device 4 at the timing when the solid tracking defect occurs in the image forming apparatus 100 of this embodiment. The horizontal axis shows the deterioration degree of the supply roller 43, and the vertical axis shows the amount of toner remaining in the developing device 4. The solid line in FIG. 21 shows the timing when the solid tracking defect occurs. It can be seen from FIG. 21 that as the deterioration degree of the supply roller 43 increases, the amount of toner remaining at which the solid tracking defect occurs increases. Therefore, in order to notify the user that the developing device 4 has reached the end of its life (to issue a life warning) at a timing immediately before the solid tracking defect occurs, it is desirable to judge the life of the developing device 4 from both the deterioration degree of the supply roller 43 and the amount of toner remaining.

[0233] In the first embodiment, the life of the developing device 4 is determined based on the deterioration degree of the supply roller 43 and the remaining amount of toner, using thresholds set individually for the deterioration degree of the supply roller 43 and the remaining amount of toner. In order to issue a life warning to the user before a solid followability defect occurs using this method, it is necessary to set the thresholds as follows. First, it is necessary to set the supply roller deterioration degree threshold ηth so that a life warning can be issued at a timing when a solid followability defect does not occur until the toner remaining amount reaches 0%. In addition, it is necessary to set the toner remaining amount threshold (video count threshold VCth) so that a life warning can be issued at a timing when a solid followability defect does not occur even when the remaining life of the supply roller is 0%. FIG. 22 shows the above threshold setting in a graph similar to FIG. 21. When the thresholds are set in this way, even if a solid followability defect does not yet occur depending on the remaining amount of toner, a life warning for the developing device 4 is issued as the supply roller 43 has reached its life. Furthermore, when such a threshold is set, depending on the degree of deterioration of the supply roller 43, even if an image can still be formed with the remaining toner without causing poor solid tracking performance, a warning for the end of life of the developing device 4 will be issued, indicating that the remaining toner has reached 0%.

[0234] The present embodiment is intended to provide a warning to the user about the end of life of the developing device 4 at a more appropriate timing before a solid image follow-up defect occurs.

[0235] <Detection of the life of the developing device> Next, detection of the life of the developing device 4 in this embodiment will be described. Fig. 23 is a flow chart showing an outline of the procedure for detecting the life of the developing device 4 in this embodiment, focusing on calculation of the deterioration degree of the supply roller 43 and calculation of the remaining amount of toner. The process according to the flow chart of Fig. 23 is executed by the control unit 220 (mainly the remaining toner amount detection unit 70 and the supply roller life detection unit 80). Note that the image forming apparatus 100 may be further configured to detect the life of the developing device 4 based on the detection result of the remaining life GJ of the developing roller, as in the above-mentioned embodiment.

[0236] - Calculation of the deterioration level of the supply roller (detection of the life of the supply roller) - First, detection of the life of the supply roller 43 (calculation of the deterioration degree of the supply roller 43) will be described.

[0237] When a print signal (job information) is input (S801), the control unit 220 starts a print operation (job) (S802). In addition, with the start of the print operation, the control unit 220 determines the supply bias Vrs based on the detection result (particularly, in this embodiment, temperature) of the temperature and humidity sensor 130 (S803). In this embodiment, the control unit 220 reads and determines the supply bias Vrs corresponding to the temperature from table data shown in Table 1 (see Example 1) that is preset and stored in the main body memory 221. In this embodiment, the development bias Vdc is assumed to be constant at -350V.

[0238] Next, during the printing operation, the supply bias application time calculation unit 81 measures the time during which the supply bias Vrs is applied to the supply roller 43, and calculates the supply bias application time tnow in the printing operation (S804). If the supply bias application start timing in the printing operation is tS and the supply bias application end timing in the printing operation is tE, the supply bias application time tnow in the printing operation can be expressed by the following formula (18). tnow=tE-tS (18)

[0239] Furthermore, at a predetermined timing during the printing operation (e.g., during the post-rotation step), the second video count measurement unit 83 receives pixel information of the output image (S805) and measures a video count value VCn, which is the number of pixel signals (S806). The second video count measurement unit 83 also calculates a section printing rate γnow, which is the printing rate in the printing operation, based on this video count value VCn, and the supply roller deterioration degree calculation unit 84 determines a deterioration correction coefficient ε based on this section printing rate γnow (S807). In this embodiment, the supply roller deterioration degree calculation unit 84 reads out and determines the deterioration correction coefficient ε corresponding to the section printing rate γnow from table data shown in Table 2 (see embodiment 1) that is preset and stored in the memory 150.

[0240] Next, the supply roller deterioration level calculation unit 84 calculates the section supply roller deterioration level ηnow, which is an index showing the degree of deterioration of the supply roller 43 in the print operation, by the following formula (19) (S808). ηnow=tnow×|Vrs|×ε ···(19)

[0241] In this embodiment, the deterioration degree ηnow of the section supply roller is calculated by the above formula (19) because the developing bias Vdc is constant. However, for example, when the developing bias Vdc is variably controlled, the deterioration degree ηnow of the section supply roller may be calculated by the following formula, ηnow=tnow×|Vrs-Vdc|×ε.

[0242] Next, the supply roller deterioration degree calculation unit 84 calculates a total supply roller deterioration degree ηt which is an index showing the degree of deterioration of the supply roller 43 from the start of use of the developing device 4 (supply roller 43) (S809). That is, as shown in the following formula (20), the supply roller deterioration degree calculation unit 84 adds (integrates) the calculated section supply roller deterioration degree ηnow to the cumulative supply roller deterioration degree ηr from the start of use of the developing device 4 (supply roller 43) stored in the memory 150. In this way, the total supply roller deterioration degree ηt is calculated. Then, the supply roller deterioration degree calculation unit 84 updates and stores the calculated total supply roller deterioration degree ηt in the memory 150 as a new cumulative supply roller deterioration degree ηr. ηt = ηnow + ηr (20)

[0243] Next, the supply roller deterioration degree calculation unit 84 calculates the supply roller remaining life ηJ from the supply roller deterioration degree threshold value ηth previously obtained and stored in the memory 150 and the calculated total supply roller deterioration degree ηt by the following formula (21) (S810). The supply roller deterioration degree calculation unit 84 may update and store the calculated supply roller remaining life ηJ in the memory 150. ηJ[%]=(1-ηt / ηth)×100 ···(21)

[0244] In this embodiment, the supply roller deterioration threshold value ηth is set to a value at which a solid followability defect may occur even when the remaining toner amount is 100%. Therefore, when the remaining life ηJ of the supply roller becomes 0%, a solid followability defect may occur even if the toner in the developing device 4 is not consumed.

[0245] Next, the control unit 220 judges whether the supply roller remaining life ηJ calculated by the supply roller deterioration degree calculation unit 84 is 0% or less (S811). If the control unit 220 judges in S811 that the supply roller remaining life ηJ is not 0% or less, it ends the print operation (S812). On the other hand, if the control unit 220 judges in S811 that the supply roller remaining life ηJ is 0% or less, it controls to execute a process of notifying the user of information related to the life of the developing device 4 (S813). This is because in this case, it can be judged that the supply roller 43 has reached the end of its life. Then, the control unit 220 ends the print operation (S812).

[0246] -Detection of remaining toner- Next, the detection (calculation) of the remaining toner amount will be described.

[0247] When a print signal (job information) is input (S801), the control unit 220 starts a print operation (job) (S802). At a predetermined timing during the print operation (e.g., during the post-rotation process), the first video count measurement unit 71 receives pixel information of the output image (S805) and measures a video count value VCn, which is the number of pixel signals (S806). Note that the video count value VCn obtained in S805 or S806 by either the first video count unit 71 or the second video count unit 83 may be used in common for calculating the deterioration degree of the supply roller 43 and the remaining toner amount.

[0248] Next, the remaining toner amount calculation unit 72 calculates a total video count value VCt, which is the accumulated video count value from the start of use of the developing device 4 (process cartridge 8) (S814). That is, as shown in the following formula (22), the remaining toner amount calculation unit 72 adds (integrates) the video count value VCn measured by the first video count measurement unit 71 to the accumulated video count value VCr from the start of use of the developing device 4 (process cartridge 8) stored in the memory 150. In this way, the total video count value VCt is calculated. Then, the remaining toner amount calculation unit 72 updates and stores the calculated total video count value VCt in the memory 150 as a new accumulated video count value VCr. VCt = Vcr + VCn (22)

[0249] Next, the toner remaining amount calculation unit 72 determines the video count threshold correction coefficient ζ based on the supply roller remaining life ηJ calculated in S810 as described above (S815). In this embodiment, the toner remaining amount calculation unit 72 reads out and determines the video count threshold correction coefficient ζ corresponding to the supply roller remaining life ηJ from the table data shown in Table 15, which is preset and stored in the memory 150. The table data in Table 15 is an example of information indicating the relationship between the supply roller remaining life ηJ and the video count threshold correction coefficient ζ. As shown in Table 15, the smaller the supply roller remaining life ηJ, the smaller the video count threshold correction coefficient ζ is made.

[0250] [Table 15]

[0251] Next, the remaining toner amount calculation unit 72 calculates the remaining toner amount TJ in the developing device 4 from the video count threshold value VCth that is set in advance and stored in the memory 150, the determined video count threshold correction coefficient ζ, and the calculated total video count value VCt by the following formula (23) (S816). The remaining toner amount calculation unit 72 may update and store the calculated remaining toner amount TJ in the memory 150. TJ[%]=(1-VCt / (VCth×ζ))×100 ···(23)

[0252] Next, the control unit 220 determines whether the remaining toner amount TJ calculated by the remaining toner amount calculation unit 72 is 0% or less (S817). If the control unit 220 determines in S817 that the remaining toner amount TJ is not 0% or less, it ends the print operation (S812). On the other hand, if the control unit 220 determines in S817 that the remaining toner amount TJ is 0% or less, it controls to execute a process to notify the user of information related to the life of the developing device 4 (S818). This is because in this case, it can be determined that the toner in the developing device 4 has run out. Then, the control unit 220 ends the print operation (S812).

[0253] -Changes in video count threshold after correction- Fig. 24 is a graph showing the change in the corrected video count threshold (VCth x ζ) with the decrease in the supply roller remaining life ηJ in detecting the life of the developing device 4 in this embodiment. In Fig. 24, the horizontal axis shows the supply roller remaining life ηJ, and the vertical axis shows the video count threshold correction coefficient ζ. By multiplying the value on the vertical axis in Fig. 24 by the corrected video count threshold VCth, the corrected video count threshold VCth x ζ is obtained.

[0254] In this embodiment, unlike the first embodiment, the corrected video count threshold value (VCth×ζ) is set to be smaller as the remaining life ηJ of the supply roller decreases as shown in Fig. 24. In other words, in this embodiment, as the remaining life ηJ of the supply roller decreases, the total video count value VCt becomes smaller when the remaining amount of toner reaches 0%, and information regarding the life of the developing device 4 is notified to the user.

[0255] <Calculation example> Fig. 25 is a graph showing the relationship between the total supply roller deterioration degree ηt and the total video count value VCt at the timing when the solid tracking failure occurs in the image forming apparatus 100 of this embodiment. The horizontal axis shows the total supply roller deterioration degree ηt, and the vertical axis shows the total video count value VCt. The solid line in Fig. 25 shows the timing when the solid tracking failure occurs, which was found by experiment.

[0256] 25, it can be seen that the greater the total supply roller deterioration degree ηt, the smaller the total video count value VCt at which solid image tracking failure occurs (i.e., the greater the amount of toner remaining in the developing device 4 at which solid image tracking failure occurs). 7 In the following cases, the total video count value VCt at which solid tracking failure occurs is 1.0×10 7 In contrast, the total supply roller deterioration degree ηt is 2.5×10 7 When the total video count value VCt exceeds 1.0×10, the solid tracking failure occurs. 7 As the total supply roller deterioration degree ηt increases, the deterioration degree ηt decreases. 7 If it exceeds this value, poor solid image tracking will occur even if the total video count value VCt is 0 (that is, the remaining toner amount is 100%).

[0257] In this embodiment, the supply roller deterioration degree threshold value ηth is set to 5.0×10 7 and set the video count threshold VCth to 1.0×10 7 In this embodiment, the video count threshold correction coefficient ζ is set to the value shown in Table 15 according to the remaining life ηJ of the supply roller. Therefore, in this embodiment, the corrected video count threshold (VCth×ζ) changes according to the remaining life ηJ of the supply roller. For example, when the remaining life ηJ of the supply roller is 49% to 40%, the video count threshold correction coefficient ζ is 0.95, and the corrected video count threshold (VCth×ζ) is 9.5×10 6In addition, when the remaining life of the supply roller ηJ is 29% to 20%, the video count threshold correction coefficient ζ is 0.57, so the corrected video count threshold (VCth×ζ) is 5.7×10 6 When the corrected video count threshold (VCth×ζ) calculated in this way is overlaid on the graph of FIG. 25, it becomes as shown in the graph of FIG. 26. The corrected video count threshold (VCth×ζ) shown in FIG. 26 does not exceed the point at which poor solid tracking performance occurs. Therefore, it is possible to notify the user of information regarding the life of the developing device 4 when the remaining toner amount falls to 0% or less (also referred to as "toner out" here) before poor solid tracking performance occurs.

[0258] <Modification 10> In this embodiment, the video count threshold correction coefficient ζ is set as shown in Table 15. However, as shown in Table 16, the supply roller remaining life ηJ may be divided into smaller sections and the video count threshold correction coefficient ζ may be set corresponding to each section.

[0259] [Table 16]

[0260] FIG. 27 shows a graph similar to FIG. 26 when the video count threshold correction coefficient ζ shown in Table 16 is used. As shown in FIG. 27, when the video count threshold correction coefficient ζ in Table 16 is used, it is possible to notify the user of information about the life of the developing device 4 due to toner-out at a point closer to the occurrence point of poor solid tracking performance than when the video count threshold correction coefficient ζ in Table 15 shown in FIG. 26 is used. The finer the interval of the supply roller remaining life ηJ is set, the higher the accuracy of notifying the user of information about the life of the developing device 4 due to toner-out is, but the larger the capacity of the memory 150 becomes. Therefore, the interval of the supply roller remaining life ηJ may be set appropriately according to, for example, the capacity of the memory 150.

[0261] In addition, as shown in Table 17, a relationship between the value of a certain supply roller remaining life ηJ and the value of the video count threshold correction coefficient ζ may be set, and the value of the video count threshold correction coefficient ζ for the section between the supply roller remaining life ηJ may be determined by interpolation (e.g., linear interpolation).

[0262] [Table 17]

[0263] In this case, it is possible to suppress a sudden change in the video count threshold correction coefficient ζ, and to notify information regarding the life of the developing device 4 with higher accuracy.

[0264] <Modification 11> In this embodiment, the toner remaining amount is detected by a video counting method, but the present invention is not limited to this. As a developer remaining amount detection method, for example, in addition to the video counting method, any available method such as a capacitance method or a light transmission method can be used. The capacitance method is a method of acquiring information on the developer amount using an electrode whose detected capacitance changes according to a change in the amount of developer inside the developing device 4. The light transmission method is a method of acquiring the developer amount based on a change in the light receiving state (presence or absence of light reception, amount of light reception, time of light reception, etc.) of the light receiving portion using a light source that irradiates light into the inside of the developing device 4 and a light receiving portion that receives the light that has passed through the inside of the developing device 4. In addition, a weight detection method that acquires information on the developer amount based on a change in the weight of the developing device 4, etc., can be used. As these other developer remaining amount detection methods, for example, known methods can be used as appropriate.

[0265] <Modification 12> In this embodiment, the method of calculating the deterioration degree of the supply roller 43 is the method of embodiment 1, but the methods of embodiments 2 to 4 may also be used.

[0266] <Effects> An example in which the video count threshold value VCth is constant regardless of the remaining life ηJ of the supply roller as in this embodiment will be described.

[0267] First, Example 1 will be described with reference to FIG. 28(a). FIG. 28(a) shows the threshold setting in Example 1 in a graph similar to FIG. 25. In Example 1, the video count threshold VCth is set to 1.0×10 7 In this case, the total video count value VCt is 1.0×10 7 If the threshold value ηth does not exceed 2.5×10, information about the life of the developing device 4 due to toner out is not notified. The maximum supply roller deterioration threshold value ηth for preventing a solid followability defect from occurring at any time point of the total video count value VCt before the toner out occurs is 2.5×10 7 In the area surrounded by dots in Fig. 28(a), the developing device 4 can be used without causing poor solid tracking performance. Nevertheless, if the threshold value is set as in this example, the user will be notified of information regarding the life of the developing device 4 due to the life of the supply roller 43 or toner out before the area surrounded by dots.

[0268] Next, Example 2 will be described with reference to FIG. 28(b). FIG. 28(b) shows the threshold setting in Example 2 in a graph similar to FIG. 25. In Example 2, the video count threshold VCth is set to 8.0×10 6 In this case, the maximum supply roller deterioration threshold value ηth for preventing the occurrence of a solid image follow-up defect at any total video count value VCt before the toner out is 3.5×10 7 In this case, the supply roller deterioration level threshold ηth is larger than in Example 1, but the video count threshold VCth is smaller. In the area surrounded by dots in FIG. 28(b), the developing device 4 can be used without causing a solid tracking failure. Nevertheless, when the thresholds are set as in this example, the user will be notified of information regarding the life of the supply roller 43 or the life of the developing device 4 due to toner out just before the area surrounded by dots.

[0269] In contrast to this, in this embodiment, in the shaded area in Fig. 26, the corrected video count threshold (VCth x ζ) does not exceed the point at which poor solid tracking performance occurs, so the developing device 4 can be used without causing poor solid tracking performance. In other words, in this embodiment, as shown in Fig. 26, the timing at which information regarding the life of the developing device 4 is notified to the user due to the life of the supply roller 43 or toner out can be delayed more than in Examples 1 and 2 shown in Figs. 28(a) and (b). Therefore, according to this embodiment, the supply roller 43 and toner can be used more effectively.

[0270] Thus, in this embodiment, the image forming apparatus 100 has another acquisition unit (toner remaining amount detection unit) 70 that acquires information regarding the amount of developer in the developing device, and the control unit 220 is capable of determining whether the developing device 4 has reached the end of its life based on the information regarding the amount of developer in the developing device 4 acquired by the another acquisition unit 70 and a preset threshold value (video count threshold value VCt), and is also capable of correcting the threshold value based on information regarding the deterioration degree of the supply member 43, and the control unit 220 performs the correction so that the amount of developer indicated by the threshold value is less when the deterioration degree indicated by the information regarding the deterioration degree is a second deterioration degree that is greater than the first deterioration degree than when the deterioration degree indicated by the information regarding the deterioration degree is a first deterioration degree.

[0271] As described above, according to this embodiment, it is possible to inform the user of information regarding the life of the developing device 4 before a solid tracking failure occurs. At the same time, this embodiment makes it possible to prevent the user from being notified of information regarding the life of the developing device 4 due to toner out even when there is sufficient toner.

[0272] [Example 6] Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the image forming apparatus of embodiment 1. Therefore, in the image forming apparatus of this embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus of embodiment 1 are given the same reference numerals as those of embodiment 1, and detailed explanations are omitted.

[0273] <Outline of this Example> Similar to the fifth embodiment, the present embodiment aims to provide a user with a more appropriate warning of the end of life of the developing device 4 before a solid tracking defect occurs. Unlike the fifth embodiment, the present embodiment corrects the supply roller deterioration level threshold value ηth according to the remaining toner amount TJ, so that the corrected supply roller deterioration level threshold value ηth becomes smaller as the remaining toner amount TJ decreases.

[0274] <Detection of the life of the developing device> Next, detection of the life of the developing device 4 in this embodiment will be described. Fig. 29 is a flow chart showing an outline of the procedure for detecting the life of the developing device 4 in this embodiment, focusing on calculation of the deterioration degree of the supply roller 43 and calculation of the remaining amount of toner. The process according to the flow chart in Fig. 29 is executed by the control unit 220 (mainly the remaining toner amount detection unit 70 and the supply roller life detection unit 80). Note that the image forming apparatus 100 may be further configured to detect the life of the developing device 4 based on the detection result of the remaining life GJ of the developing roller, as in the above-mentioned embodiment.

[0275] -Detection of remaining toner- First, the detection (calculation) of the remaining toner amount will be described.

[0276] When a print signal (job information) is input (S901), the control unit 220 starts a print operation (job) (S902). At a predetermined timing during the print operation (e.g., during the post-rotation process), the first video count measurement unit 71 receives pixel information of the output image (S903) and measures a video count value VCn, which is the number of pixel signals (S904).

[0277] Next, the remaining toner amount calculation unit 72 calculates a total video count value VCt, which is the cumulative video count value from the start of use of the developing device 4 (process cartridge 8) (S905). That is, as shown in the following formula (24), the remaining toner amount calculation unit 72 adds (integrates) the video count value VCn measured by the first video count measurement unit 71 to the cumulative video count value VCr from the start of use of the developing device 4 (process cartridge 8) stored in the memory 150. In this way, the total video count value VCt is calculated. Then, the remaining toner amount calculation unit 72 updates and stores the calculated total video count value VCt in the memory 150 as a new cumulative video count value VCr. VCt = Vcr + VCn (24)

[0278] Next, the remaining toner amount calculation unit 72 calculates the remaining toner amount TJ in the developing device 4 from the video count threshold value VCth, which is set in advance and stored in the memory 150, and the calculated total video count value VCt, by the following formula (25) (S906). The remaining toner amount calculation unit 72 may update and store the calculated remaining toner amount TJ in the memory 150. TJ[%]=(1-VCt / VCth)×100 (25)

[0279] Next, the control unit 220 determines whether the remaining toner amount TJ calculated by the remaining toner amount calculation unit 72 is 0% or less (S907). If the control unit 220 determines in S907 that the remaining toner amount TJ is not 0% or less, it ends the print operation (S908). On the other hand, if the control unit 220 determines in S907 that the remaining toner amount TJ is 0% or less, it controls to execute a process to notify the user of information related to the life of the developing device 4 (S909). This is because in this case, it can be determined that the toner in the developing device 4 has run out. Then, the control unit 220 ends the print operation (S908).

[0280] - Calculation of the deterioration level of the supply roller (detection of the life of the supply roller) - Next, detection of the life of the supply roller 43 (calculation of the deterioration degree of the supply roller 43) will be described.

[0281] When a print signal (job information) is input (S901), the control unit 220 starts a print operation (job) (S902). In addition, with the start of the print operation, the control unit 220 determines the supply bias Vrs based on the detection result (particularly, in this embodiment, temperature) of the temperature and humidity sensor 130 (S910). In this embodiment, the control unit 220 reads and determines the supply bias Vrs corresponding to the temperature from table data shown in Table 1 (see Example 1) that is preset and stored in the main body memory 221. In this embodiment, the development bias Vdc is assumed to be constant at -350V.

[0282] Next, during the printing operation, the supply bias application time calculation unit 81 measures the time during which the supply bias Vrs is applied to the supply roller 43, and calculates the supply bias application time tnow in the printing operation (S911). If the supply bias application start timing in the printing operation is tS and the supply bias application end timing in the printing operation is tE, the supply bias application time tnow in the printing operation can be expressed by the following formula (26). tnow=tE-tS (26)

[0283] Also, at a predetermined timing during the printing operation (for example, during the post-rotation process), the second video count measurement unit 83 receives pixel information of the output image (S903) and measures a video count value VCn, which is the number of pixel signals (S904). The second video count measurement unit 83 calculates a section printing rate γnow, which is a printing rate in the printing operation, based on this video count value VCn, and the supply roller deterioration degree calculation unit 84 determines a deterioration correction coefficient ε based on this section printing rate γnow (S912). In this embodiment, the supply roller deterioration degree calculation unit 84 reads out and determines a deterioration correction coefficient ε corresponding to the section printing rate γnow from table data shown in Table 2 (see embodiment 1) that is preset and stored in the memory 150. Note that the video count value VCn obtained in S903 and S904 by either the first video count unit 71 or the second video count unit 83 may be used in common for calculating the deterioration degree of the supply roller 43 and calculating the remaining toner amount.

[0284] Next, the supply roller deterioration level calculation unit 84 calculates the section supply roller deterioration level ηnow, which is an index showing the degree of deterioration of the supply roller 43 in the print operation, by the following formula (27) (S913). ηnow=tnow×|Vrs|×ε ···(27)

[0285] In this embodiment, the deterioration degree ηnow of the section supply roller is calculated by the above formula (27) because the developing bias Vdc is constant. However, for example, when the developing bias Vdc is variably controlled, the deterioration degree ηnow of the section supply roller may be calculated by the following formula, ηnow=tnow×|Vrs-Vdc|×ε.

[0286] Next, the supply roller deterioration degree calculation unit 84 calculates a total supply roller deterioration degree ηt which is an index showing the degree of deterioration of the supply roller 43 from the start of use of the developing device 4 (supply roller 43) (S914). That is, as shown in the following formula (28), the supply roller deterioration degree calculation unit 84 adds (integrates) the calculated section supply roller deterioration degree ηnow to the cumulative supply roller deterioration degree ηr from the start of use of the developing device 4 (supply roller 43) stored in the memory 150. In this way, the total supply roller deterioration degree ηt is calculated. Then, the supply roller deterioration degree calculation unit 84 updates and stores the calculated total supply roller deterioration degree ηt in the memory 150 as a new cumulative supply roller deterioration degree ηr. ηt = ηnow + ηr (28)

[0287] Next, the supply roller deterioration degree calculation unit 84 determines the supply roller deterioration degree threshold correction coefficient μ based on the remaining toner amount TJ calculated in S906 as described above (S915). In this embodiment, the supply roller deterioration degree calculation unit 84 reads out and determines the supply roller deterioration degree threshold correction coefficient μ corresponding to the remaining toner amount TJ from table data shown in Table 18, which is preset and stored in the memory 150. The table data in Table 18 is an example of information showing the relationship between the remaining toner amount TJ and the supply roller deterioration degree threshold correction coefficient μ. As shown in Table 18, the smaller the remaining toner amount TJ, the smaller the video count threshold correction coefficient ζ is made.

[0288] [Table 18]

[0289] Next, the supply roller deterioration degree calculation unit 84 calculates the supply roller remaining life ηJ from the supply roller deterioration degree threshold value ηth previously set and stored in the memory 150, the determined supply roller deterioration degree threshold correction coefficient μ, and the calculated total supply roller deterioration degree ηt by the following formula (29) (S916). The supply roller deterioration degree calculation unit 84 may update and store the calculated supply roller remaining life ηJ in the memory 150. ηJ[%]=(1-ηt / (ηth×μ))×100 ···(29)

[0290] Next, the control unit 220 judges whether the supply roller remaining life ηJ calculated by the supply roller deterioration degree calculation unit 84 is 0% or less (S917). If the control unit 220 judges in S917 that the supply roller remaining life ηJ is not 0% or less, it ends the print operation (S908). On the other hand, if the control unit 220 judges in S917 that the supply roller remaining life ηJ is 0% or less, it controls to execute a process of notifying the user of information regarding the life of the developing device 4 (S918). This is because in this case, it can be judged that the supply roller 43 has reached the end of its life. Then, the control unit 220 ends the print operation (S908).

[0291] <Calculation example> The relationship between the total supply roller deterioration degree ηt and the total video count value VCt at the timing when the solid followability failure occurs in the image forming apparatus 100 of this embodiment is similar to that of the third embodiment shown in the graph of Fig. 25. In this embodiment, as in the third embodiment, the supply roller deterioration degree threshold value ηth is set to 5.0 x 10 7 and set the video count threshold VCth to 1.0×10 7 In this embodiment, the supply roller deterioration level threshold correction coefficient μ is set to the value shown in Table 18 according to the toner life TJ. Therefore, in this embodiment, the supply roller deterioration level threshold (ηth×μ) after correction changes according to the toner life TJ. For example, when the toner life TJ is 99% to 70%, the supply roller deterioration level threshold correction coefficient μ is 0.9, so the supply roller deterioration level threshold (ηth×μ) after correction is 4.5×10 7 In addition, when the remaining toner amount TJ is 42% to 20%, the supply roller deterioration level threshold correction coefficient μ is 0.7, so the supply roller deterioration level threshold value (ηth×μ) after correction is 3.5×10 7When the thus calculated corrected supply roller deterioration level threshold value (ηth×μ) is overlaid on the graph of FIG. 25, it becomes as shown in the graph of FIG. 30. The corrected supply roller deterioration level threshold value (ηth×μ) shown in FIG. 30 does not exceed the point at which poor solid tracking performance occurs. Therefore, it becomes possible to inform the user of information regarding the life of the developing device 4 due to toner out before poor solid tracking performance occurs.

[0292] In addition, the present embodiment can also be modified in the same manner as the modified example described in the fifth embodiment.

[0293] <Effects> In this embodiment, the image forming device 100 has another acquisition unit (toner remaining amount detection unit) 70 that acquires information regarding the amount of developer in the developing device, and the control unit 220 is capable of determining whether the developing device 4 has reached the end of its life based on information regarding the deterioration degree of the supply member 43 and a preset threshold value (supply roller deterioration degree threshold value ηth), and is also capable of correcting the threshold value based on the information regarding the amount of developer, and the control unit 220 performs the correction so that the deterioration degree indicated by the threshold value is smaller when the amount of developer indicated by the information regarding the amount of developer is a second amount that is smaller than the first amount than when the amount of developer indicated by the information regarding the amount of developer is a first amount.

[0294] As described above, in the third embodiment, the toner remaining amount threshold (video count threshold VCth) is corrected according to the deterioration degree of the supply roller 43, whereas in the present embodiment, the supply roller deterioration degree threshold ηth is corrected according to the remaining toner amount. The configuration of the present embodiment also provides the same effects as those of the third embodiment.

[0295] [others] Although the present invention has been described above with reference to specific embodiments, the present invention is not limited to the above-mentioned embodiments.

[0296] In the above embodiment, the image forming apparatus is a tandem type (in-line type) full-color image forming apparatus, but the present invention is not limited to this. The present invention can also be applied to a monochrome image forming apparatus.

[0297] In the above embodiment, the image forming apparatus is configured such that the process cartridge is detachable from the apparatus main body, but the present invention is not limited to this. For example, the image forming apparatus may be configured such that the developing unit (developing device) and the drum unit (having, for example, a photoconductor, a charging device, and a cleaning device) are each independently detachable from the apparatus main body. The image forming apparatus may also be a toner supply type image forming apparatus in which a toner supply container (toner cartridge, toner bottle, toner pack, etc.) containing toner to be supplied to the developing device is detachably attached to the process cartridge (or developing device). In this case, the image forming apparatus may be configured to perform image formation with the toner supply container connected to the process cartridge (or developing device), or may be configured to perform image formation with the toner supply container removed after toner is supplied to the developing device.

[0298] Furthermore, in order to detect the life of the process cartridge, the life of the photosensitive member may be set separately.

[0299] Furthermore, the notification of information to the user is not limited to being by displaying a message or the like, but may be by emitting light (such as a lit or blinking warning light) or sound (such as a warning sound or voice).

[0300] Furthermore, the information on the printing rate is not limited to the printing rate itself. For example, the printing rate can be calculated based on the number of pixels and the video count value, or the number of prints and the amount of toner consumed. Such information on the basis of which the printing rate can be calculated can also be considered as information on the printing rate.

[0301] In addition, the information on the deterioration level of the supply roller may be used as an index value showing the degree of deterioration of the supply roller due to use, and is not limited to the value calculated by the method of the above embodiment. For example, information calculated based on the deterioration level, such as the remaining life, can also be considered as information on the deterioration level.

[0302] In the above embodiment, the developing bias is assumed to be constant. However, the developing bias may be changed depending on, for example, the environment in which the image forming apparatus is used. [Explanation of symbols]

[0303] 1 Photosensitive drum 4. Developing device 8 Process cartridge 42 Developing roller 43 Supply roller 90 Toner 100 Image forming device 150 Non-volatile memory 201 Video Controller 202 Engine Controller 220 Control section 221 Main Memory

Claims

1. In an image forming apparatus for forming an image on a recording material by transferring a developer image onto the recording material, a rotatable image carrier that carries a developer image; a developing device for supplying a developer to a surface of the image carrier to form a developer image on the surface of the image carrier, the developing device including: a rotatable developing member for supplying the developer to the surface of the image carrier; and a rotatable supply member having an elastic layer containing an ion conductive agent, the rotatable supply member being in contact with the developing member to supply the developer to the developing member; a first application unit that applies a development voltage to the developing member; a second applying unit that applies a supply voltage to the supply member; an acquisition unit that acquires information regarding a printing rate of an image formed in the image formation; a control unit that acquires information regarding a deterioration level of the supply member based on information regarding the supply voltage applied to the supply member, information regarding a time during which the supply voltage is applied to the supply member, and information regarding the printing rate; a storage unit that stores information regarding the deterioration degree acquired by the control unit; An image forming apparatus comprising:

2. 2. The image forming apparatus according to claim 1, wherein the control unit is capable of determining whether or not the developing device has reached the end of its life based on the information regarding the degree of deterioration.

3. The image forming apparatus according to claim 1, characterized in that the control unit obtains information regarding the degree of deterioration by correcting a value correlated with a product of voltage and time based on information regarding the supply voltage applied to the supply member and information regarding the time for which the supply voltage was applied to the supply member, using a correction coefficient corresponding to information regarding the printing rate.

4. The image forming apparatus according to claim 1, characterized in that the control unit obtains information regarding the degree of deterioration based on information regarding the potential difference between the supply voltage applied to the supply member and the developing voltage applied to the developing member, information regarding the time during which the supply voltage is applied to the supply member, and information regarding the printing rate.

5. An environment detection unit that detects at least one of temperature and humidity, 2. The image forming apparatus according to claim 1, wherein the control unit is capable of changing the supply voltage applied to the supply member based on a detection result of the environment detection unit.

6. In the image formation, an image forming operation for forming a developer image on the image carrier and a non-image forming operation for not forming a developer image on the image carrier are performed, The image forming apparatus according to claim 1, characterized in that the control unit is capable of changing the supply voltage applied to the supply member during the image forming operation and at least a portion of the non-image forming operation, and obtains information regarding the degree of deterioration based on information regarding each of the supply voltages applied to the supply member, information regarding the time each of the supply voltages was applied to the supply member, and information regarding the printing rate.

7. 7. The image forming apparatus according to claim 6, wherein the control unit is capable of changing the supply voltage applied to the supply member so that the polarity of the potential difference of the supply voltage with respect to the developing voltage is opposite during the image forming operation and during at least a portion of the non-image forming operation.

8. the acquiring unit acquires information regarding a printing rate for each area obtained by dividing an image forming area on the image carrier in a main scanning direction substantially perpendicular to a moving direction of a surface of the image carrier, The image forming apparatus according to claim 1 , wherein the control unit acquires information regarding a deterioration level of the supply member for each of the regions based on information regarding a printing rate for each of the regions.

9. 9. The image forming apparatus according to claim 8, wherein the control unit is capable of determining whether or not the developing device has reached the end of its life based on the information on the degree of deterioration for each of the areas.

10. The image forming apparatus according to claim 9, characterized in that the control unit is capable of determining whether the developing device has reached the end of its life based on information indicating the greatest degree of deterioration among the information regarding the degree of deterioration for each of the areas.

11. 10. The image forming apparatus of claim 9, wherein the control unit is capable of obtaining information regarding the difference in the degree of deterioration between at least two of the areas based on information regarding the degree of deterioration for each of the areas, and determining whether the developing device has reached the end of its life based on the information regarding the difference.

12. The image forming apparatus according to claim 11, wherein the control unit is capable of determining whether the developing device has reached the end of its life based on information regarding the difference, which is information regarding the largest difference among the differences between multiple adjacent areas.

13. a separate acquisition unit for acquiring information regarding an amount of developer in the developing device; the control unit is capable of determining whether the developing device has reached the end of its life based on information regarding an amount of developer in the developing device acquired by the other acquisition unit and a preset threshold value, and is also capable of correcting the threshold value based on information regarding the deterioration degree, The image forming apparatus according to claim 1, characterized in that the control unit performs the correction so that the amount of developer indicated by the threshold value is less when the degree of deterioration indicated by the information regarding the degree of deterioration is a second degree of deterioration that is greater than the first degree of deterioration than when the degree of deterioration indicated by the information regarding the degree of deterioration is a first degree of deterioration.

14. a separate acquisition unit for acquiring information regarding an amount of developer in the developing device; the control unit is capable of determining whether the developing device has reached the end of its life based on information about the deterioration level and a preset threshold value, and is capable of correcting the threshold value based on information about the amount of developer, The image forming apparatus according to claim 1, characterized in that the control unit performs the correction so that the degree of deterioration indicated by the threshold value is smaller when the amount of developer indicated by the information on the amount of developer is a second amount that is smaller than the first amount than when the amount of developer indicated by the information on the amount of developer is a first amount.

15. 15. The image forming apparatus according to claim 2, wherein the control unit is capable of executing a process for notifying a user of information regarding replacement of the developing device when the developing device reaches the end of its life.

16. 15. The image forming apparatus according to claim 1, wherein the storage unit is detachable from the main body of the image forming apparatus together with the developing device.

17. 15. The image forming apparatus according to claim 1, wherein the acquisition unit acquires the information regarding the printing rate based on image information of an image formed in the image formation.

18. 15. The image forming apparatus according to claim 1, wherein the developing member contacts the image carrier to form a developing portion, and supplies a developer to the image carrier in the developing portion.

19. 15. The image forming apparatus according to claim 1, wherein the developer is a non-magnetic one-component developer.

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