Image formation apparatus

Abstract

An image formation apparatus 100 is configured to comprise: a development device 4 that has an image carrier 1 and a supply member 43 provided with a development member 42 and an elastic layer (urethane foam layer) 43b containing an ion conductive agent; a first application unit 122 that applies a development voltage to the development member 42; a second application unit 123 that applies a supply voltage to the supply member 43; an acquisition unit 83 that acquires information relating to a printing rate of an image formed in image formation; a control unit 220 that acquires information relating to the deterioration degree of the supply member 43 on the basis of information relating to the supply voltage applied to the supply member 43, information relating to a time when the supply voltage is applied to the supply member 43, and the information relating to the printing rate; and a storage unit 150 that stores the information relating to the deterioration degree acquired by the control unit 220.

Description

Image forming device

[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.

[0002] In the image forming process, an image forming apparatus, such as a printer using an electrophotographic system (electrophotographic process), forms an electrostatic image on a photosensitive member as an image carrier, and develops the electrostatic image using a developer to form a toner image on the photosensitive member. The developing device that performs the developing process may be configured as an independent unit or as part of a process cartridge that is detachably attached to the main body of the image forming apparatus (hereinafter simply referred to as the "main body"). Note that a process cartridge is a unit that is detachably attached to the main body of the image forming apparatus, and includes a photosensitive member and at least one of a charging means, a developing means, and a cleaning means that act on the photosensitive member.

[0003] A developing device generally includes a developing container that contains developer, a developing member (developer carrier) that is rotatably disposed 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 includes 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 depending on the configuration of the developing device and the characteristics of the toner in order to move the toner from the supply roller to the developing roller.

[0005] Japanese Patent Application Laid-Open No. 2009-237549 discloses the following technique: when forming an image longer than one rotation 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, thereby suppressing a decrease in image density.

[0006] Furthermore, Japanese Patent Application Laid-Open No. 2010-160236 discloses the following technology. That is, during the first rotation of the developing roller, the potential difference between the developing roller and the supply roller is increased so as to strip toner from the developing roller. Then, from the second rotation of the developing roller onward, the potential difference between the developing roller and the supply roller is gradually increased so as to supply toner to the developing roller. This is intended to prevent uneven image density.

[0007] A widely used supply roller has a foamed elastic layer made conductive by adding an ionic conductive agent, and the foamed elastic layer is made of, for example, a urethane rubber foam (urethane sponge) containing the ionic conductive agent.

[0008] Through research by the present inventors, it has been found that when the toner contained inside the foamed elastic layer (inside the cells) of the supply roller described above 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 rate are formed continuously. The reason for this is as follows.

[0009] In other words, when an image with a high print ratio is formed, the amount of toner consumed from the developing roller to the photoreceptor increases. Focusing on the toner contained within the foamed elastic layer of the supply roller, the amount of toner supplied from the supply roller to the developing roller increases as the print ratio increases. Therefore, when an image with a high print ratio is formed and the toner within the foamed elastic layer of the supply roller is replaced, the conductive agent added to the material of the foamed elastic layer of the supply roller is carried away along with the toner, and the amount of conductive agent remaining on the supply roller is likely to decrease. This phenomenon of the conductive agent added to the material of the foamed elastic layer of the supply roller decreasing is more pronounced when an image with a high print ratio is formed and toner consumption is high compared to when an image with a low print ratio is formed and toner consumption is low. Therefore, the degree of supply roller deterioration varies depending on the user's usage of the image forming device. Until now, no effort has been made to acquire information regarding the degree of supply roller deterioration while focusing on this point.

[0010] As the supply roller deteriorates, image defects such as poor solid image tracking may occur. Poor solid image tracking refers to 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 (increased electrical resistance), the amount of toner supplied to the developing roller at the trailing edge of the page gradually falls short.

[0011] SUMMARY OF THE INVENTION It is therefore an object of the present invention to make it possible to acquire information on the degree of deterioration of a supply member with higher accuracy in accordance with the usage status of an image forming apparatus.

[0012] The above object can be achieved by an image forming apparatus according to the present invention. In summary, the present invention provides an image forming apparatus that forms an image on a recording material by transferring a developer image onto the recording material, the image forming apparatus comprising: a rotatable image carrier that carries the developer image; a developing device that supplies developer to a surface of the image carrier to form the developer image on the surface of the image carrier, the developing device having a rotatable developing member that supplies developer to the surface of the image carrier, and a rotatable supply member that has an elastic layer containing an ion conductive agent and is in contact with the developing member to supply developer to the developing member; a first application unit that applies a development voltage to the developing member; a second application unit that applies a supply voltage to the supply member; an acquisition unit that acquires information about a printing rate of an image formed in the image formation; a control unit that acquires information about a deterioration level of the supply member based on information about the supply voltage applied to the supply member, information about a time during which the supply voltage was applied to the supply member, and information about the printing rate; and a storage unit that stores the information about the deterioration level acquired by the control unit.

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

[0014] FIG. 1 is a schematic cross-sectional view of an image forming apparatus.

[0015] FIG. 2 is a schematic cross-sectional view of the image forming unit.

[0016] FIG. 3 is a schematic block diagram of the control configuration of the image forming apparatus.

[0017] FIG. 4 is a functional block diagram of a control unit related to detection of the life of a developing device.

[0018] FIG. 5 is a flow chart showing an outline of the procedure for detecting the end of life of a developing device.

[0019] FIG. 6 is a flowchart showing the procedure for calculating the remaining amount of toner.

[0020] FIG. 7 is a flow chart showing the procedure for calculating the life of the developing roller.

[0021] FIG. 8 is a graph showing the results of verification of the characteristics of the supply roller.

[0022] FIG. 9 is a flowchart showing a procedure for calculating the deterioration level of the supply roller in the first embodiment.

[0023] FIG. 10 is a schematic diagram showing the application timing of the supply bias in the first embodiment.

[0024] FIG. 11 is a schematic diagram showing the timing of supply roller bias application in the second embodiment.

[0025] FIG. 12 is a flowchart showing a procedure for calculating the deterioration level of the supply roller in the second embodiment.

[0026] FIG. 13 is a flowchart showing a procedure for calculating the deterioration level of the supply roller in the third embodiment.

[0027] FIG. 14 is a schematic diagram showing the relationship between the printing unit and the supply roller when the letter "A" is formed.

[0028] FIG. 15 is a schematic diagram showing the relationship between the print area and the supply roller for an image having the same print rate as that of FIG. 14 but a different pattern.

[0029] FIG. 16 is a schematic diagram showing the relationship between the print area and the supply roller for an image having the same print rate as that of FIG. 14 but a different pattern.

[0030] FIG. 17 is a graph showing the relationship between deterioration of the supply roller and image density.

[0031] FIG. 18 is a schematic diagram showing an example of an image in which the printing ratio differs between regions divided in the main scanning direction.

[0032] FIG. 19 is a schematic diagram for explaining density unevenness in a halftone image after the image of FIG. 18 is continuously formed.

[0033] FIG. 20 is a flowchart showing a procedure for calculating the deterioration level of the supply roller in the fourth embodiment.

[0034] FIG. 21 is a graph showing the relationship between deterioration of the supply roller and the amount of remaining toner at which poor solid image tracking occurs.

[0035] FIG. 22 is a graph for explaining the setting of the life in the first embodiment.

[0036] FIG. 23 is a flow chart showing the procedure for detecting the life of the developing device in the fifth embodiment.

[0037] FIG. 24 is a graph showing the relationship between the remaining life of the supply roller and the video count threshold value in the fifth embodiment.

[0038] FIG. 25 is a graph showing the timing at which poor solid image followability occurs in Example 5.

[0039] FIG. 26 is a graph showing the corrected video count threshold value in Example 5.

[0040] FIG. 27 is a graph showing the corrected video count threshold value in the modified example of the fifth embodiment.

[0041] FIG. 28 is a graph showing the video count thresholds of Examples 1 and 2 for explaining the effect of Example 5.

[0042] FIG. 29 is a flow chart showing the procedure for detecting the life of the developing device in the sixth embodiment.

[0043] FIG. 30 is a graph showing the supply roller deterioration level threshold value after correction in the sixth embodiment.

[0044] The image forming apparatus according to the present invention will be described in more detail below with reference to the drawings.

[0045] 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 full-color laser beam printer employing an intermediate transfer system, capable of forming a full-color image on a sheet-shaped recording material P using an electrophotographic system.

[0046] The image forming apparatus 100 includes multiple image forming units (image forming stations) SY, SM, SC, and SK, which form toner images of yellow (Y), magenta (M), cyan (C), and black (K), respectively. The configurations of the image forming units SY, SM, SC, and SK are essentially the same, except for the colors of toner 90Y, 90M, 90C, and 90K contained in the developing device 4 (described later). Elements having the same or corresponding functions or configurations for each color may be generally described by omitting the Y, M, C, or K suffixes to designate elements for a specific color. Figure 2 is a schematic cross-sectional view of a representative image forming unit S. The image forming unit S includes a photosensitive drum 1, a charging roller 2, an exposure device 3, a developing device 4, a primary transfer roller 51, a drum cleaning device 5, and other components (described later). In this embodiment, the exposure device 3 is configured as a single unit common to all image forming units S, but may also be provided for each image forming unit S.

[0047] The photosensitive drum 1, which is a rotatable drum-type (cylindrical) electrophotographic photosensitive member (photosensitive member) serving as an image carrier, is driven to rotate around its rotation axis in the direction of arrow R1 in the drawing (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 driven to rotate at a peripheral speed (rotational speed, process speed) of, for example, 140 mm / sec.

[0048] The surface (outer periphery) of the rotating photosensitive drum 1 is uniformly charged to a predetermined potential of a predetermined polarity (negative in this embodiment) by a charging roller 2, which is a roller-type charging member (charging device) serving as charging means. In this embodiment, the charging roller 2 is a conductive roller having a conductive rubber layer provided on a metal core. The charging roller 2 is disposed in contact with the surface of the photosensitive drum 1. The rotational axis of the photosensitive drum 1 and the rotational axis of the charging roller 2 are substantially 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 of the photosensitive drum 1 (negative in this embodiment) is applied to the charging roller 2 by a charging power source 121 ( FIG. 3B ) 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.

[0049] The surface of the charged photosensitive drum 1 is scanned and exposed by an exposure device 3 serving as an exposure means in accordance with an image signal (image information), and an electrostatic latent image (electrostatic image) in accordance with 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 laser light in accordance with the image signal for each color component. As a result, an electrostatic latent image in accordance with the image signal for each color component is formed on the surface of the photosensitive drum 1 for each color. In response to a request from a user (operator), the image signal is input to the image forming apparatus 100 from an external device (host device) 300 ( FIG. 3A ), such as an image reading device (not shown) or a personal computer, communicably connected to the image forming apparatus 100.

[0050] The electrostatic latent image formed on the photosensitive drum 1 is developed (visualized) by the developing device 4, which serves as a developing means, by supplying toner 90 as a developer, thereby forming a toner image (toner image, developer image) on the photosensitive drum 1. In this embodiment, the developing device 4 uses toner 90, which is a non-magnetic single-component developer. As shown in FIG. 2 , the developing device 4 includes a developer container 41, a developing roller 42, a supply roller 43, and a regulating blade 44. During image formation (development), the developing roller 42 contacts the surface of the photosensitive drum 1 to form a development zone, and supplies toner 90 to the photosensitive drum 1 in the development zone. Note that in this embodiment, the image forming apparatus 100 includes 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 is stopped, the contact / separation mechanism separates the developing roller 42 from the photosensitive drum 1 and keeps it stationary. At least during image formation (development), the contact / separation mechanism causes the developing roller 42 to contact the photosensitive drum 1. 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. Thereafter, at a predetermined timing, the contact / separation mechanism operates by a biasing means (not shown) so that the developing roller 42 contacts the photosensitive drum 1 with a predetermined contact width.

[0051] In this embodiment, toner 90 charged with the same polarity (negative in this embodiment) as the charge polarity of the photosensitive drum 1 adheres to the exposed area (image area, print area) on the photosensitive drum 1, which has been uniformly charged and then exposed to light to reduce the absolute value of its potential (reverse development method). In this embodiment, the normal charge polarity of the toner 90, which is the main charge polarity of the toner 90 during development (the charge polarity for developing an electrostatic latent image), is negative. The developing device 4 will be described in further detail below.

[0052] An intermediate transfer belt 53, which is an endless belt serving as an intermediate transfer body, is disposed facing the four photosensitive drums 1. The intermediate transfer belt 53 is stretched over a plurality of support rollers (driving roller 52a, tension roller 52b, and secondary transfer opposing roller 52c) and tensioned with a predetermined tension. The intermediate transfer belt 53 rotates (circulates) in the direction of arrow R2 (clockwise) in the figure when the driving roller 52a is driven to rotate by a driving motor (not shown) provided in the driving unit 110 ( FIG. 3A ). 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 on the inner circumferential surface of the intermediate transfer belt 53, corresponding to the photosensitive drums 1Y, 1M, 1C, and 1K, respectively. The primary transfer roller 51 presses the intermediate transfer belt 53 against the photosensitive drum 1, forming a primary transfer portion (primary transfer nip) N1, which is the contact portion between the photosensitive drum 1 and the intermediate transfer belt 53. At the primary transfer portion N1, the toner image formed on the photosensitive drum 1 is electrostatically transferred (primary transfer) onto the rotating intermediate transfer belt 53, which serves as a transfer receiving member, by the action of the primary transfer roller 51. 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 supply 125 ( FIG. 3B ) serving as a primary transfer bias application portion. For example, when a full-color image is formed, the toner images of yellow, magenta, cyan, and black formed on each photosensitive drum 1 are transferred sequentially onto the intermediate transfer belt 53, superimposed on top of each other.

[0053] A secondary transfer roller 6, which is a roller-type secondary transfer member (secondary transfer device) serving as secondary transfer means, is disposed on the outer peripheral surface of the intermediate transfer belt 53 at a position facing the secondary transfer opposing roller 52c. The secondary transfer roller 6 contacts the secondary transfer opposing roller 52c via the intermediate transfer belt 53 and is pressed against the secondary transfer opposing roller 52c, thereby forming 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. At the secondary transfer portion N2, the toner image formed on the intermediate transfer belt 53 is transferred (secondarily transferred) by the action of the secondary transfer roller 6 onto a recording material P, serving as a transfer target, which is being conveyed while being sandwiched between the intermediate transfer belt 53 and the secondary transfer roller 6. During secondary transfer, a predetermined secondary transfer bias (secondary transfer voltage), which is a DC voltage of opposite polarity (positive polarity in this embodiment) to the normal charging polarity of the toner 90, is applied to the secondary transfer roller 6 by a secondary transfer bias application unit, a secondary transfer power supply 126 (FIG. 3B). The secondary transfer opposing roller 52c, which serves as a secondary transfer opposing member (opposing electrode), is electrically grounded. Alternatively, 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 or plastic sheets, are fed one sheet at a time from a cassette 8, which serves as a recording material storage unit, by a feed roller 9 or the like, and transported to a pair of registration rollers 10, which serve as transport members. This recording material P is conveyed by a pair of registration rollers 10 to the secondary transfer portion N2 in synchronization with the toner image on the intermediate transfer belt 53.

[0054] 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 bearing the unfixed toner image, thereby fixing (melting and solidifying) 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. 3B ). 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 the apparatus main body 101 of the image forming apparatus 100.

[0055] Meanwhile, toner remaining on the photosensitive drum 1 after the primary transfer (primary transfer residual toner) is removed and collected from the photosensitive drum 1 by a drum cleaning device 5 serving as a photosensitive body cleaning means. In this embodiment, the drum cleaning device 5 includes a cleaning blade as a cleaning member disposed in contact with the surface of the photosensitive drum 1 and a cleaning container. The drum cleaning device 5 uses the cleaning blade to scrape and remove the primary transfer residual toner from the surface of the rotating photosensitive drum 1 and collect it in the cleaning container. Note that the image forming apparatus 100 may also employ a cleanerless system that does not have a dedicated cleaning member for cleaning the photosensitive drum 1. In this case, the primary transfer residual toner can be collected by, for example, the developing device 4. A belt cleaning device 54 serving as an intermediate transfer body cleaning means is provided on the outer peripheral surface of the intermediate transfer belt 53. The belt cleaning device 54 is disposed 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 (surface movement direction) of the intermediate transfer belt 53. Toner remaining on the intermediate transfer belt 53 after the secondary transfer (secondary transfer residual toner) and adhering matter such as paper dust 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 and remove adhering matter such as secondary transfer residual toner from the surface of the rotating intermediate transfer belt 53, and collects the adhering matter in the cleaning container.

[0056] 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 the apparatus main body 101 of the image forming apparatus 100. The apparatus main body 101 is the 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.

[0057] Here, the image forming apparatus 100 executes a job (printing operation) that is a series of operations that starts with a single start command and forms and outputs an image on one or more recording materials P. A job generally includes an image forming process, a pre-rotation process, a sheet spacing process when 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 that will actually be formed and output on the recording materials P are performed, and the image formation time refers to the period during which these operations are performed. More specifically, the timing of the image formation time varies depending on the position where each of the electrostatic image formation, toner image formation, primary transfer of the toner image, secondary transfer, and fixing processes is performed. The pre-rotation process (pre-rotation operation) is a period during which preparatory operations are performed before the image forming process, from when the start command is input until the actual image formation begins. The sheet interval process (sheet interval operation) is the period corresponding to the interval between recording materials P when image formation is performed continuously on multiple recording materials P (continuous image formation, continuous printing). The post-rotation process (post-rotation operation) is the period during which an arranging 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, sheet interval process, 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. <Developing device>

[0058] Next, the developing device 4 in this embodiment will be further described.

[0059] As shown in FIG. 2 , the developing device 4 includes a developing container (developing frame) 41 that contains toner 90, a rotatable developing roller 42 serving as a developing member (developer carrier), a rotatable supply roller 43 serving as a supply member, and a regulating blade 44 serving 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 rotational axis of the photosensitive drum 1, the rotational axis of the developing roller 42, and the rotational axis of the supply roller 43 are substantially parallel to one another. The developing roller 42 is driven to rotate in the direction of arrow R3 (clockwise) in the figure by a drive motor (not shown) provided in the drive unit 110 ( FIG. 3A ). That is, the developing roller 42 is driven to rotate 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. The supply roller 43 is driven to rotate in the direction of arrow R4 (clockwise) in the figure by a drive motor (not shown) provided in the drive unit 110 ( FIG. 3A ). That is, the supply roller 43 is driven to rotate in a direction in which the surface of the developing roller 42 and the surface of the supply roller 43 move in 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 also 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.

[0060] In the developing device 4, toner 90 is supplied to the surface of the developing roller 42 by a supply roller 43. The toner 90 held on the developing roller 42 is then thinned by a regulating blade 44, which regulates the thickness of the toner layer (hereinafter also referred to as "layer thickness"). The regulating blade 44 not only regulates the thickness of the toner 90 layer on the developing roller 42, but also imparts a predetermined charge to the toner 90 on the developing roller 42. The thin layer of toner 90 on the developing roller 42 is transported to the contact area (developing section) 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, thereby developing the electrostatic latent image. Furthermore, any toner 90 remaining on the developing roller 42 without being used for development is removed from the developing roller 42 at the contact area between the developing roller 42 and a 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 .

[0061] In this embodiment, the developing roller 42 is an elastic roller having a metal core 42a and a conductive elastic rubber layer 42b with a predetermined volume resistivity provided on the outer periphery thereof. The developing roller 42 is configured to have a predetermined surface roughness. The developing roller 42 may have a single-layer or multiple-layer structure. A single-layer roller may have, for example, a core metal on which an elastic layer made of a rubber material such as silicone rubber, urethane rubber, or hydrin rubber is formed. A multiple-layer roller may have, for example, a similar elastic layer coated with a surface layer made of silicone resin, urethane resin, polyamide resin, or fluororesin. In this embodiment, in order to obtain an appropriate image density, the developing roller 42 is rotated at a rotational speed (circumferential speed) such that 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.

[0062] In this embodiment, the supply roller 43 is an elastic sponge roller having a metal core 43a and an elastic layer (foamed elastic layer) 43b made of conductive foam formed on the outer periphery thereof. The supply roller 43 is positioned so as to abut against the developing roller 42 with a predetermined penetration depth. The penetration depth of the supply roller 43 into the developing roller 42 can be expressed as the amount of deformation (depression) of the supply roller 43 by the developing roller 42. In this embodiment, the supply roller 43 has a urethane foam layer (a foamed elastic layer made of 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 composed 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.

[0063] 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. Furthermore, by forming the urethane (urethane foam) on the surface layer of the supply roller 43 into an open-cell foam, the toner 90 can be contained within the foamed elastic layer (urethane foam layer) of the supply roller 43, thereby enabling the toner 90 to be more stably supplied to the developing roller 42.

[0064] In this embodiment, the electrical resistance of a new (unused) supply roller 43 is 1×10 ７The electrical resistance of the supply roller 43 is (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 member made of aluminum) having a diameter of 30 mm, with a penetration depth of 1.5 mm. By rotating this aluminum sleeve, the supply roller 43 is rotated relative to the aluminum sleeve at a rotational speed of 30 rpm. In this state, a DC voltage of −50 V is applied to the aluminum sleeve. At this time, a 10 kΩ resistor 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.

[0065] In this embodiment, the cell diameter on the surface of the supply roller 43 was set to 50 μm to 1000 μm. Here, the cell diameter refers to the average diameter of foam cells in an arbitrary cross section, and its value can be determined as follows. First, the area of ​​the largest foam cell is measured from an enlarged image of the arbitrary cross section, and this area is converted into a diameter equivalent to a perfect circle to obtain the maximum cell diameter. Foam cells with a diameter equal to or smaller than half of this maximum cell diameter are then eliminated as noise, and the cell diameters of the remaining individual foam cells are obtained from their cell areas using the same conversion method as above. The cell diameter on the surface of the supply roller 43 refers to the average value of these converted individual cell diameters. In this embodiment, the cell diameter of the supply roller 43 was measured using a VK-X200 (manufactured by KEYENCE Corporation).

[0066] In this embodiment, the regulating blade 44 is configured with a plate-shaped elastic member that is conductive and flexible. The plate-shaped elastic member that constitutes the regulating blade 44 has a predetermined length and a predetermined thickness in both a longitudinal direction, which is approximately parallel to the rotational axis of the developing roller 42, and a lateral direction, which is approximately perpendicular to the longitudinal direction. The elastic member that constitutes the regulating blade 44 has one end in the lateral direction fixed to the developer container 41 and supported as a cantilever, and the other end in the lateral direction is a free end. The regulating blade 44 is positioned so that the tip of the free end faces upstream in the rotation direction (the direction of movement of the surface) of the developing roller 42 (counter direction), and the surface near the tip abuts against the surface (outer peripheral surface) of the developing roller 42. The regulating blade 44 is positioned in contact with the surface of the developing roller 42 downstream of the contact point between the supply roller 43 and the developing roller 42 and upstream of the contact point between the photosensitive drum 1 and the developing roller 42 in the rotation direction of the developing roller 42. In this embodiment, the elastic member constituting the regulating blade 44 is made of SUS material (stainless steel plate material).

[0067] 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. 3B) 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. 3B) 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. 3B) 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 to the supply roller 43, and a DC voltage of −450 V 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.

[0068] During image formation (development), the potential difference between the supply roller 43 and the development roller 42 is set to a polarity that urges (moves) the toner 90 from the supply roller 43 toward the development roller 42. In this embodiment, the normal charge polarity of the toner 90 is negative. Therefore, during image formation (development), a potential difference is established 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 depending on the operating environment of the image forming apparatus 100. This control stabilizes the supply of 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.

[0069] 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 toward the developing roller 42 side. In this embodiment, as described above, the normal charged 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 area between the regulating blade 44 and the developing roller 42, and also stabilizes the application of an electric charge to the toner 90 by the regulating blade 44.

[0070] As will be explained in more detail later, in this embodiment, the settings of the development bias, supply bias, and regulation bias in a job (print operation) are the same in the pre-rotation process, the inter-sheet process, and the post-rotation process as in the image forming process.

[0071] In this example, toner 90 (90Y, 90M, 90C, 90K) was a negatively charged non-magnetic toner manufactured by suspension polymerization. However, this is not limited to this, and toner manufactured by other polymerization methods, such as pulverization or emulsion polymerization, may also be used. Furthermore, the volume average particle diameter of 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 using a precision particle size distribution measuring device, Multisizer 3, manufactured by Beckman Coulter, Inc. In this example, the volume average particle diameter of toner 90 was approximately 7.0 μm.

[0072] 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 ) ３The toner 90 has a T3 unit structure represented by the formula: where R represents an alkyl group or phenyl group having from 1 to 6 carbon atoms, and the organosilicon polymer forms convex portions on the surface of the toner base particles. This creates a spacer effect between the surface of the toner base particles and components such as the developing roller 42, thereby reducing the adhesive force between the toner base particles and the component. Furthermore, the convex portions are in surface contact with the surface of the toner base particles. This surface contact of the convex portions with the surface of the toner base particles inhibits the migration, detachment, and embedding of the convex portions. Therefore, for example, the toner 90 can be used for a relatively long period of time even in a configuration in which the developing roller 42 is driven while spaced apart from the photosensitive drum 1. While this embodiment uses toner particles containing an organosilicon polymer on the surface of the toner base particles, the toner 90 is not limited to this, and toner particles not containing an organosilicon polymer on the surface of the toner base particles may also be used.

[0073] 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.

[0074] Examples of external additives 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 can 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 stability and environmental stability. The BET specific surface area of ​​the external additive is 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 (trade name: Gemini 2375 Ver. 5.0, manufactured by Shimadzu Corporation) is used to adsorb nitrogen gas onto the surface of a sample, and measurement is performed using the BET multipoint method, thereby determining the BET specific surface area (m ２ / g) can be calculated.

[0075] 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. Furthermore, various external additives may be used in combination. <Control Configuration>

[0076] Next, a description will be given of the control configuration of the image forming apparatus 100 in this embodiment. Fig. 3A is a schematic block diagram showing the control configuration of the image forming apparatus 100 in this embodiment.

[0077] The image forming apparatus 100 has 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 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.

[0078] The engine controller 202 includes a control unit 220, a main memory 221, an input / output (I / F) unit 222, and the like. The control unit 220 is composed of a CPU (Central Processing Unit) and other components serving as control means, which is a central element for performing arithmetic processing. The main memory 221, which serves as a storage unit, is composed of storage media such as ROM and RAM. The input / output unit 222 inputs and outputs signals (information) to and from devices external to the engine controller 202. The ROM pre-stores (contains, saves) control programs such as a program for executing image forming operations and a program for calculating the remaining toner amount, remaining life of the developing roller, remaining life of the supply roller, and the like (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 unit that comprehensively controls the 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 sending and receiving of various electrical information signals, drive timing, etc., and executes processes according to the flowcharts described below, for example.

[0079] The control unit 220 is connected to, for example, the drive unit 110, the high-voltage power supply 120, the temperature and humidity sensor 130, the memory communication unit 140, and other components provided in the apparatus main body 101. The control unit 220 is also connected to a nonvolatile memory (hereinafter also simply referred to as "memory") 150, which is a storage unit provided in the process cartridge 8 as storage means, via the memory communication unit 140. The nonvolatile memory 150 is detachably attached to the apparatus main body 101 together with the process cartridge 8, and is connected to the control unit 220 via the memory communication unit 140 when the process cartridge 8 is attached to the apparatus main body 101. Note that, if the developing device 4 is detachably attached to the apparatus main body 101 independently, the nonvolatile memory 150 can also be detachably attached to the apparatus main body 101 together with the developing device 4. The control unit 220 is also connected to an operation unit 160 provided in the apparatus main body 101. An external device 300, such as a personal computer, is also connected to the control unit 220.

[0080] The drive unit 110 is configured with various motors as drive sources (power sources) and functions as a drive means for rotating and driving the polygon scanner, photosensitive drum 1, developing roller 42, supply roller 43, etc. provided inside the exposure device 3. The drive unit 110 operates based on control signals from the control unit 220. Note that at least some of the motors that drive the photosensitive drum 1, developing roller 42, and supply roller 43 may be shared. Also, at least some of the motors that drive the members for each color, yellow, magenta, cyan, and black, may be shared.

[0081] As shown in FIG. 3B , the high-voltage power supply device 120 is configured to include 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 control signals from the control unit 220. At least a part of the power supplies for applying bias to the members for the colors yellow, magenta, cyan, and black may be common.

[0082] 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 serving 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 signals (information) indicating the detected temperature and humidity to the control unit 220. The temperature and humidity information detected by the temperature and humidity sensor 130 is used by the control unit 220 to control the image forming apparatus 100 in accordance with the usage environment.

[0083] The nonvolatile memory 150 provided as storage means 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. In this embodiment, a non-contact non-volatile memory is used as storage means provided in each process cartridge 8, but any appropriate storage means can be used, such as a contact non-volatile memory, a non-contact non-volatile memory, or a volatile memory with a power source.

[0084] The operation unit 160 also has keys or the like as an input unit that can be operated by the user to input information to the control unit 220. The operation unit 160 also 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 functions of both an input unit and a display unit.

[0085] The nonvolatile memory 150 of the process cartridge 8 can store, as information regarding the usage status of the developing device 4, information such as the cumulative travel distance of the developing roller 42, the image dot cumulative value, and the degree of deterioration of the supply roller 43 (described later), which can be updated as needed. The nonvolatile memory 150 of the process cartridge 8 can also store, as information regarding the usage status of the developing device 4, information such as the amount of toner used, the remaining life of the photosensitive drum 1, and the number of sheets of recording material P on which an image has been recorded (number of prints), which can be updated as needed. The nonvolatile memory 150 of the process cartridge 8 can also store, as threshold information for detecting various life spans, information such as the threshold value for the image dot cumulative value, the threshold value for the number of sheets of recording material P on which an image has been recorded (number of prints), the cumulative travel distance of the developing roller 42, the threshold value for the remaining toner, and the threshold value for the degree of deterioration of the supply roller 43. The nonvolatile memory 150 of each process cartridge 8 stores information regarding the components of the respective process cartridge 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.

[0086] In this embodiment, all or part of the information 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. <Detection of Life of Developing Device> - Overview of Detection of Life of Developing Device -

[0087] Next, detection of the lifespan of the developing device 4 (process cartridge 8) in this embodiment will be described. In this embodiment, "lifespan" refers to the point at which image quality can no longer be guaranteed when forming an image on a recording material P during an image formation operation. Generally, when the "lifespan" is reached, a notification is issued to prompt the user to replace the developing device 4 and process cartridge 8. Note that in this embodiment, the developing device 4 is replaceable as part of the process cartridge 8, so the lifespan of the developing device 4 refers to the lifespan of the process cartridge 8. Here, although terms such as "lifespan of the developing device 4" and "replacement of the developing device 4" are simply used, in this embodiment they are equivalent to "lifespan of the process cartridge 8" and "replacement of the process cartridge 8," respectively. In this embodiment, the process for detecting the lifespan of the developing device 4 is performed independently for each image forming station S, but the following description focuses on one image forming station S.

[0088] Fig. 4 is a schematic functional block diagram of the control unit 220 relating to detection of the end of 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 end of life of the developing device 4 in this embodiment.

[0089] 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 include 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 include a developing roller travel distance calculation unit 61. The supply roller life detection unit 80 is configured to include 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 level calculation unit 84. Details of 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 later.

[0090] Here, the procedure for detecting the end of life of the developing device 4 will be outlined with reference to FIG.

[0091] When a print signal (job information) is input (S101), the control unit 220 starts a print operation (job) (S102). Then, at a predetermined timing during the print operation (job execution) (e.g., during the post-rotation process), the control unit 220 determines whether the developing device 4 has reached the end of its life (S103-S105). Specifically, in this embodiment, the control unit 220 determines whether the remaining toner amount TJ (%) in the developing device 4 has reached a predetermined threshold value (e.g., 0%) (S103), whether the remaining developing roller life GJ (%) has reached a predetermined threshold value (e.g., 0%) (S104), and whether the remaining supply roller life ηJ (%) has reached a predetermined threshold value (e.g., 0%) (S105). The remaining toner amount TJ is determined by the toner remaining amount detection unit 70. The remaining developing roller life GJ is determined by the developing roller life detection unit 60. The remaining supply roller life ηJ is determined by the supply roller life detection unit 80. Specific methods for these determinations will be described later.

[0092] If 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 have reached their respective predetermined thresholds, the control unit 220 terminates the print operation (S106). In this case, it can be determined that the developing device 4 has not reached the end of its life. On the other hand, if 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 its respective predetermined threshold, the control unit 220 executes a process to notify the user of information regarding the life (replacement) of the developing device 4 (S107). In this case, 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 the end of its life, or it may be a display that prompts the user to replace the developing device 4. The control unit 220 then terminates the print operation (S106).

[0093] In Figure 5, the detection of the life of the developing device 4 based on the remaining toner amount TJ, the remaining life of the developing roller GJ, and the 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.

[0094] Furthermore, the fact that the remaining toner amount TJ, the remaining life GJ of the developing roller, and the remaining life ηJ of the supply roller 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 reported independently. In this case, the fact that the remaining toner amount has run out or that the developing roller 42 or the supply roller 43 has reached the end of its life may simply be reported, or the fact that the developing device 4 needs to be replaced due to each of these causes (prompting the user to replace the developing device 4) may be reported.

[0095] 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 developing roller, and the remaining life of the supply roller ηJ is the amount of used supply roller, and a method may be used in which values ​​are added as the lives approach the predetermined thresholds, for example, to 100%.

[0096] Furthermore, assuming the reuse of components of the developing device 4, for example, information regarding the degree of deterioration 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. -Detection of remaining toner amount-

[0097] Next, detection of the remaining amount of toner in the developing device 4 in this embodiment will be described. Fig. 6 is a flowchart outlining the procedure for detecting the end of life of the developing device 4, focusing on detection of the remaining amount of toner. The process according to the flowchart in Fig. 6 is executed by the control unit 220 (mainly the remaining toner detection unit 70).

[0098] 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 a pixel counting method) is a method of obtaining information about the number of pixels in the printed portion of an image by counting laser exposure ON signals (signals that cause the laser to emit light, pixel signals) generated based on image data.

[0099] 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 (e.g., during the post-rotation process), the first video count measurement unit 71 receives pixel information of an image to be formed on the recording material P and output (hereinafter also referred to as an "output image") (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 acquires pixel information of all images in the print operation (job) contained in the print signal and measures the video count value VCn of all images. This video count value VCn correlates with the amount of toner 90 used to form the images in the print operation (job).

[0100] Next, the remaining toner amount calculation unit 72 calculates a total video count value VCt, which is the cumulative value of the video count value since 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 cumulative video count value VCr since the start of use of the developing device 4 (process cartridge 8) stored in the memory 150, as shown in the following equation (1). In this way, the total video count value VCt is calculated: VCt=VCr+VCn (1)

[0101] Next, the remaining toner amount calculation unit 72 calculates the remaining toner amount TJ in the developing device 4 using the video count threshold value VCth, which is preset and stored in the memory 150, and the calculated total video count value VCt, according to the following formula (2) (S206): TJ [%] = (1 - VCt / VCth) x 100 (2)

[0102] Furthermore, the remaining toner amount calculation unit 72 updates the calculated total video count value VCt as a new cumulative video count value VCr and stores it in the memory 150 (S207). The remaining toner amount calculation unit 72 may also update the calculated remaining toner amount TJ and store it in the memory 150.

[0103] 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 gone, 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.

[0104] Therefore, the control unit 220 determines 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 determines 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 determines in S208 that the remaining toner amount TJ is 0% or less, it controls the execution of a process to notify the user of information regarding the life of the developing device 4 (S210). Then, the control unit 220 ends the printing operation (S209).

[0105] In this embodiment, the first video count measurement unit 71 measures the video count value VCn for each print 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.

[0106] Next, detection of the lifespan of the developing roller 42 in this embodiment will be described. Fig. 7 is a flowchart outlining the procedure for detecting the lifespan of the developing device 4, focusing on detection of the lifespan of the developing roller 42. The process in accordance with the flowchart in Fig. 7 is executed by the control unit 220 (mainly the developing roller lifespan detection unit 60).

[0107] In this embodiment, the developing roller life detection unit 60 detects (calculates) the remaining life of the developing roller 42 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 running distance (rotation distance, surface movement distance) of the developing roller 42. It is known that the developing roller 42 deteriorates as the running distance increases due to an increase in electrical resistance and contamination by deposits, and therefore has a lifespan that corresponds to the running distance.

[0108] 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 the total developing roller travel distance Ht for each predetermined developing roller travel distance Hu (S303). That is, as shown in the following equation (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)

[0109] Next, the developing roller travel distance calculation unit 61 calculates the remaining life GJ of the developing roller from the developing roller travel distance threshold Hth, which 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) x 100 (4)

[0110] Furthermore, the developing roller travel distance calculation unit 61 updates the calculated total developing roller travel distance Ht as a new cumulative developing roller travel distance Hr and stores it in the memory 150 (S305). The developing roller travel distance calculation unit 61 may also update the calculated developing roller remaining life GJ and store it in the memory 150.

[0111] Here, when the developing roller remaining life GJ=100%, it indicates that the developing device 4 is brand new. 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.

[0112] Therefore, the control unit 220 determines whether the remaining life GJ of the developing roller calculated by the developing roller travel distance calculation unit 61 is 0% or less (S306). If the control unit 220 determines in S306 that the remaining life GJ of the developing roller is not 0% or less, it ends the print operation (S307). On the other hand, if the control unit 220 determines in S306 that the remaining life GJ of the developing roller is 0% or less, it controls to execute a process to notify the user of information regarding the life of the developing device 4 (S308). Then, the control unit 220 ends the print operation (S307). -Detection of the Life of the Supply Roller-

[0113] 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. The detection of the life of the supply roller 43 in this embodiment will be explained in detail after explaining the mechanism of deterioration of the supply roller 43. <Deterioration of the Supply Roller> -Mechanism of Deterioration of the Supply Roller-

[0114] Next, 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 that constitutes the supply roller 43 contains an ion conductive agent. A supply roller 43 having such a configuration is preferably used from the viewpoints of production stability and cost. Furthermore, according to the inventors' investigation, deterioration of a supply roller 43 having such a configuration can be broadly divided into two types.

[0115] The first type of deterioration of the supply roller 43 is deterioration due to the passage of current through the supply roller 43. This mechanism of deterioration of the supply roller 43 is conventionally known. As described above, the supply roller 43 is imparted with conductivity by adding an ionic conductive agent during manufacturing. Generally, when a bias of the same polarity is continuously applied to a material having ionic conductivity, the ionic conductive agent becomes unevenly distributed, reducing the number of ions dispersed within the material capable of transporting electrons compared to the initial state, resulting in an increase in electrical resistance. In this embodiment, a potential difference is established between the supply roller 43 and the developing roller 42 such that the potential of the supply roller 43 is more negative than the potential of the developing roller 42. In other words, in this embodiment, a bias of negative polarity is applied to the supply roller 43 relative to the developing roller 42. When such a bias is continuously applied to the supply roller 43 of this embodiment, the ionic conductive agent tends to migrate and become unevenly distributed inside the supply roller 43 (toward the core metal). This uneven distribution of the ionic 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 applied to the supply roller 43 .

[0116] The second type of deterioration of the supply roller 43 is deterioration due to a decrease in the ionic conductive agent in the supply roller 43. Conventionally, no efforts have been made to acquire information on the degree of deterioration of the supply roller 43 while focusing on this second mechanism of deterioration. The toner contained in the urethane foam layer 43b of the supply roller 43 is replaced successively during rotation of the supply roller 43. The inventors' research has confirmed that the ionic conductive agent in the urethane foam layer 43b electrically adheres to charged toner and is removed from the urethane foam layer 43b as the toner moves from the supply roller 43 to the developing roller 42. This phenomenon is particularly pronounced when the print rate of the output image is high and the amount of toner moving from the supply roller 43 to the developing roller 42 increases. This phenomenon reduces the amount of ionic conductive agent in the urethane foam layer 43b of the supply roller 43 compared to the initial state. As a result, the electrical resistance of the supply roller 43 increases, and its sensitivity to the applied bias decreases, reducing its ability to supply toner to the developing roller 42.

[0117] As the deterioration of the supply roller 43 progresses, image defects such as poor solid image tracking may occur, as described above.

[0118] Tests conducted to examine the effects of degradation due to energization of the supply roller 43 are described below. The following print endurance tests were conducted under conditions of a supply bias Vrs of −450 V and −650 V. The development bias Vdc was set to −350 V in both cases. The electrical resistance of the supply roller 43 was measured at predetermined timings. Here, the current flowing through the supply roller 43 when a predetermined voltage was applied to the supply roller 43 was measured as a proxy for the electrical resistance of the supply roller 43. Continuous operation without toner consumption can eliminate the effects of conductive agent reduction, described below. For the print endurance test, continuous printing of images with a print rate of 0% was performed in the operating environment (ambient environment) of the image forming apparatus 100, which was a temperature of 15°C and a humidity (relative humidity) of 10%. Setting the print rate to 0% can eliminate the effects of reduced electrical resistance due to the conductive agent carried away by the toner, described below.

[0119] The results are shown in Figure 8(a). The vertical axis represents the ratio (decrease rate) of the current value to the initial current value (a proxy for electrical resistance) when the initial current value (a proxy for electrical resistance) is set to 100%, and the horizontal axis represents the rotational drive time of the supply roller 43 (= supply bias application time). As shown in Figure 8(a), the decrease in the current value (increase in the electrical resistance value) tends to be greater when the supply bias Vrs is -650V than when the supply bias Vrs is -450V. This is due to the ionic conductive agent contained in the supply roller 43 moving and becoming unevenly distributed due to continuous current application. As such, it can be seen that a larger supply bias Vrs (i.e., the potential difference between the supply bias Vrs and the development bias Vdc) leads to a greater amount of movement of the ionic conductive agent, resulting in a greater increase in the electrical resistance value of the supply roller 43. Note that in this example, it was found 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-color tracking may occur. - Verification 2: Difference in the amount of toner contained in the supply roller depending on the printing rate -

[0120] A test was conducted 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 conducted under two conditions: a printing rate of 0% and a printing rate of 100%. The amount of toner contained in the supply roller 43 was measured at predetermined intervals. The amount of toner contained in the supply roller 43 was calculated from the difference between the weight of a supply roller 43 without toner (unused) and the weight of the supply roller 43 at each interval. For the print durability test, intermittent printing of one sheet was performed in the operating environment (ambient environment) of the image forming apparatus 100, which was a temperature of 23°C and a humidity of 50%. The supply bias Vrs was −450 V, and the development bias Vdc was −350 V. Note that N-sheet intermittent printing refers to a printing method in which a printing operation in which images are continuously formed on N sheets of recording material P is performed, followed by temporarily stopping the operation of the developing device 4 (image forming apparatus 100), and then performing a printing operation in which images are continuously formed on N sheets of recording material P again. This operation is repeated.

[0121] 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 0% print rate and the condition of a 100% print rate (less toner held on the supply roller 43 under the condition of a 100% print rate than under the condition of a 0% print rate). 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 overall decrease in the amount of toner contained in the supply roller 43 as the number of prints increases is due to, for example, the decrease in the amount of toner supplied to the supply roller 43 as the amount of toner in the development device 4 decreases. -Verification 3: Effect of decrease in conductive agent-

[0122] A test was conducted to examine the difference in the amount of conductive agent reduction depending on the printing rate. The following print durability test was conducted under two conditions: a printing rate of 1% and a printing rate of 100%. Measurements were then conducted at predetermined timings to evaluate the amount of conductive agent component contained in the supply roller 43. The amount of conductive agent component 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 decreased, applying a voltage of opposite polarity to the predetermined voltage confirmed that the current value did not increase (recover) by the amount of the decrease, thereby confirming that the amount of conductive agent component had been reduced. For the print durability test, intermittent printing of one sheet was conducted in the operating environment (ambient environment) of the image forming apparatus 100, which was a temperature of 23°C and humidity of 50%. The supply bias Vrs was set to −450 V, and the development bias Vdc was set to −350 V.

[0123] The results are shown in Figure 8(c). The vertical axis represents the ratio (decrease rate) of the current value to the initial current value (a proxy value for the amount of conductive agent component) when the initial current value (a proxy value for the amount of conductive agent component) is set to 100%, and the horizontal axis represents the rotational 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 amount of conductive agent) tends to be greater under conditions of a high printing rate (100%) than under conditions of a low printing rate (1%). This is because when the printing rate is high and the amount of toner replacement within the supply roller 43 per unit time is large, a larger amount of conductive agent is discharged out of the developing device 4 along with the toner during printing than when the printing rate is low. As such, it can be seen that the decrease in the amount of conductive agent is greater when the printing rate is high than when the printing rate is low. In this invention, the deterioration level of the supply roller 43 is calculated taking into account the characteristics of the supply roller 43 discovered by the inventors.

[0124] In other words, the phenomenon of the conductive agent added to the material of the foam elastic layer of the supply roller 43 decreasing is more pronounced when a high-print-ratio image is formed and toner consumption is high, compared to when a low-print-ratio image is formed and toner consumption is low. Therefore, the degree of deterioration of the supply roller 43 varies depending on the user's usage of the image forming apparatus 100. Therefore, it is desirable to obtain information regarding the degree of deterioration of the supply roller 43 more accurately depending on the usage of the image forming apparatus 100.

[0125] Furthermore, in recent years, from the viewpoint of usability, a toner supply system has been 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 lifespan. Therefore, in such a configuration, the timing at which the supply roller 43 reaches the end of its lifespan may vary greatly depending on the degree of deterioration of the supply roller 43 depending on the user's usage of the image forming apparatus 100. Therefore, in such a configuration, it is even more necessary to obtain more accurate information regarding the deterioration level of the supply roller 43 according to the user's usage conditions so that the developing device 4 can be replaced at the appropriate time. <Calculation of Supply Roller Deterioration Level (Detection of Supply Roller Lifespan)>

[0126] Next, detection of the lifespan of the supply roller 43 (calculation of the deterioration level of the supply roller 43) in this embodiment will be described. Fig. 9 is a flowchart outlining the procedure for detecting the lifespan of the developing device 4, focusing on detection of the lifespan of the supply roller 43. The process according to the flowchart in Fig. 9 is executed by the control unit 220 (mainly the supply roller lifespan 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.

[0127] 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 degree of deterioration of the supply roller 43 is calculated for each print operation (job) taking into account 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. The deterioration degree of the supply roller 43 is then added up for each print operation (job), and when a predetermined deterioration level is reached, information regarding 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.

[0128] Upon receiving a print signal (job information) (S401), the control unit 220 starts a print operation (job) (S402). The control unit 220 also acquires the detection results of the temperature and humidity sensor 130 (S403) upon starting the print operation and determines the supply bias Vrs based on the detection results (particularly, temperature in this embodiment) of the temperature and humidity sensor 130 (S404). The supply bias Vrs applied to the supply roller 43 by the 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 greater the absolute value of the negative polarity supply bias Vrs (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 set constant at -350V.

[0129] Subsequently, during the printing operation, the supply bias application time calculation unit 81 measures the time for which the supply bias Vrs is applied to the supply roller 43 (S405), and calculates the supply bias application time tnow for the printing operation (S406). If the supply bias application start timing for the printing operation is tS and the supply bias application end timing for the printing operation is tE, the supply bias application time tnow for the printing operation can be expressed by the following equation (5): tnow=tE-tS (5)

[0130] Furthermore, at a predetermined timing during the printing operation (e.g., during the post-rotation process), the second video count measurement unit 83 receives pixel information for the output image and calculates the section printing rate γnow, which is the printing rate for the printing operation, based on the measured video count value VCn (S407). In this embodiment, the second video count measurement unit 83 acquires pixel information for all images in the printing operation (job) contained in the print signal and measures the video count value VCn for all images. The second video count measurement unit 83 then calculates the section printing rate γnow for all images. Note that the printing rate (image printing rate, image ratio) indicates the area ratio (proportion) of the printed area, where 100% is the area where all pixels in the image formation area (area where a toner image can be formed) are printed. The printing rate for all images in a printing operation can be expressed as the area ratio (proportion) of the printed area for all images, where the total number of pixels in all images is the total pixel count. Then, the supply roller deterioration level 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 level 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 showing 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.

[0131] 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, using the following formula (6) (S409): ηnow=tnow×|Vrs|×ε (6)

[0132] In this embodiment, the deterioration degree ηnow of the section supply roller is calculated by the above formula (6) because the development bias Vdc is constant. However, for example, when the development 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.

[0133] Next, the supply roller deterioration level calculation unit 84 calculates a total supply roller deterioration level ηt, which is an index showing the degree of deterioration of the supply roller 43 since 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 level calculation unit 84 adds (integrates) the calculated section supply roller deterioration level ηnow to the cumulative supply roller deterioration level ηr since the start of use of the developing device 4 (supply roller 43), which is stored in the memory 150. In this way, the total supply roller deterioration level ηt is calculated. Then, the supply roller deterioration level calculation unit 84 updates the calculated total supply roller deterioration level ηt with the calculated total supply roller deterioration level ηt and stores it in the memory 150 as a new cumulative supply roller deterioration level ηr. ηt = ηnow + ηr (7)

[0134] Next, the supply roller deterioration level calculation unit 84 calculates the supply roller remaining life ηJ from the supply roller deterioration level threshold ηth, which is preset and stored in the memory 150, and the calculated total supply roller deterioration level ηt, using the following formula (8) (S411). The supply roller deterioration level threshold ηth is determined in advance through experiments or the like so that image defects such as poor solid image tracking do not occur even when the toner remaining amount is 0%. The supply roller deterioration level 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 level calculation unit 84 may update and store the calculated supply roller remaining life ηJ in the memory 150. ηJ [%] = (1 - ηt / ηth) × 100 ... (8)

[0135] Here, when the supply roller remaining life ηJ=100%, it indicates that the developing device 4 is brand new. 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%, it means that the total supply roller deterioration level ηt has reached the supply roller deterioration level threshold value ηth, and the developing device 4 has reached the end of its life.

[0136] Therefore, the control unit 220 determines whether the supply roller remaining life ηJ calculated by the supply roller deterioration level calculation unit 84 is 0% or less (S412). If the control unit 220 determines in S412 that the supply roller remaining life ηJ is not 0% or less, it terminates the printing operation (S413). On the other hand, if the control unit 220 determines in S412 that the supply roller remaining life ηJ is 0% or less, it controls the execution of a process to notify the user of information regarding the life of the developing device 4 (S414). Then, the control unit 220 terminates the printing operation (S413).

[0137] While FIG. 9 shows 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) performed in parallel, these calculations may be performed sequentially, and the order in which they are performed is arbitrary. 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 calculated for each printing operation (job) at a predetermined timing (e.g., during the post-rotation process) during the printing operation (during job execution). However, the present invention is not limited to this, and these may be calculated sequentially at predetermined timings during the printing operation. For example, the supply bias application time tnow, the section printing rate ynow (and the deterioration correction coefficient ε), the section supply roller deterioration degree ηnow, and the total supply roller deterioration degree ηt may be calculated each 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 memory 150 to calculate the total supply roller deterioration degree ηt. If the supply roller remaining life ηJ becomes 0% or less during a print operation (job), a process may be executed to notify the user of information regarding the life of the developing device 4, and the print operation may be terminated (interrupted). This also applies to the remaining toner amount TJ and the remaining development roller life GJ described above. This also applies to other embodiments described later. <Calculation Example>

[0138] An example of calculating the deterioration level of the supply roller 43 in this embodiment will be described. This example illustrates a case where two-sheet intermittent printing is performed, in which a printing operation is repeated to form an image with an average printing rate of 3.5% on two sheets of A4-sized recording material P in the operating environment (ambient environment) of the image forming apparatus 100 at 23°C. When performing a printing operation to form an image on two sheets of A4-sized recording material P 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 printing operation is 7.26 seconds. In other words, tnow = 7.26 (seconds). Furthermore, when the image forming apparatus 100 is in a room temperature environment of 23°C, from Table 1, the supply bias Vrs = -450 (V). Furthermore, when the section printing rate γnow is calculated to be 3.5%, from Table 2, the deterioration correction coefficient ε = 1.5. Therefore, the section supply roller deterioration level ηnow for one printing operation under the above conditions is calculated as follows: ηnow=7.26×|-450|×1.5=4900.5

[0139] The value of this section supply roller deterioration level ηnow is stored in memory 150 as the cumulative supply roller deterioration level ηr, and the section supply roller deterioration level ηnow is recalculated in the subsequent printing operation. The recalculated section supply roller deterioration level ηnow is added to the cumulative supply roller deterioration level ηr to calculate the total supply roller deterioration level ηt. Then, as described above, when the remaining supply roller life ηJ becomes 0% or less, that is, when the total supply roller deterioration level ηt reaches the supply roller deterioration level threshold value ηth, it is determined that the supply roller 43 has reached the end of its life. <Variation 1>

[0140] In the image forming apparatus 100 of this embodiment, the appropriate supply bias Vrs for supplying toner 90 to the developing roller 42 changes due to factors such as changes in the fluidity of the toner 90 and changes in the electrical resistance of the supply roller 43 depending on the environment. 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, the supply bias Vrs is changed in three stages based on temperature information, as shown in Table 1. However, this is not limited to this, and the supply bias Vrs may also be changed based on temperature information and humidity information. Table 3 shows an example of table data for changing the supply bias Vrs by converting the temperature and humidity detected by the temperature and humidity sensor 130 into absolute moisture content. In this case, the control unit 220 calculates the absolute moisture content based on the temperature and humidity detected by the temperature and humidity sensor 130, and then reads and determines the corresponding supply bias Vrs from the table data in Table 3 according to the calculated absolute moisture content. 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).

[0141] 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, and the same applies to other information indicating relationships that have been described as being set as table data. <Modification 2>

[0142] In this embodiment, the image forming apparatus 100 stores the values ​​of the supply bias Vrs as table data as shown in Table 1, but is not limited to this. For example, as shown in Table 4, the image forming apparatus 100 can store offset values ​​for other environments as table data, using the supply bias Vrs for a predetermined environment (for example, 15° C. or higher and lower than 25° C.) as a reference. <Modification 3>

[0143] In this embodiment, image forming apparatus 100 stores the value of supply bias Vrs as table data as shown in Table 1, but is not limited to this. For example, when development bias Vdc is variably controlled, image forming apparatus 100 can also store the difference (Vrs - Vdc) between development bias Vdc and supply bias Vrs as table data, as shown in Table 5. In this embodiment, development bias Vdc is -350 V, so that, for example, in an environment below 15°C, supply bias Vrs = -350 + (-200) = -550 V according to Table 5. <Modification 4>

[0144] In this embodiment, as shown in Table 2, the deterioration correction coefficient ε is changed in six steps based on the print rate of the output image, but this is not limited to this. The print rate intervals may be smaller or larger. In other words, the deterioration correction coefficient ε may be changed in fewer steps (five steps or less) or in more steps (seven steps 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. <Comparative Verification 1>

[0145] Next, a comparative test performed on this example and Comparative Example 1 below to verify the effects of this example will be described. - Evaluation Method -

[0146] In the image forming apparatus 100 configured in this embodiment, a print durability 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 durability test was conducted in a full-color image formation mode in an operating environment (ambient environment) of the image forming apparatus 100, with a temperature of 23°C and humidity of 50%, with the following cycles (1) to (3) being one cycle: (1) A horizontal line image (a plurality of straight lines extending in a direction substantially perpendicular to the conveyance direction of the recording material P) with a 2% coverage was formed on 100 sheets of A4-size recording paper by intermittent printing on two sheets; (2) A horizontal line image (a 20% coverage) was formed on 100 sheets of A4-size recording paper by intermittent printing on two sheets; and (3) A horizontal line image (a 100% coverage) was formed on 100 sheets of A4-size recording paper by intermittent printing on two sheets.

[0147] Then, as image defects, solid image followability defects (whiteout images) in solid images were visually evaluated according to the following criteria. Note that here, evaluation results for solid black images in particular are shown, but in this example, the configurations of the developing devices 4 (process cartridges 8) for each color were essentially the same, and similar evaluation results were obtained. ○: No solid image followability defects occurred (no practical problems) ×: Significant solid image followability defects occurred (problems in practical use) - Comparative Example 1 -

[0148] 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 of the developing roller 42 and the amount of remaining toner. Other points of Comparative Example 1 were substantially the same as those of this example. - Evaluation Results -

[0149] Table 6 shows the evaluation results.

[0150] In this embodiment, when the remaining life of the developing roller GJ was 35% and the remaining amount of toner TJ was 7%, the remaining life of the supply roller 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.

[0151] On the other hand, in Comparative Example 1, the remaining life of the developing roller GJ was 32% and the remaining amount of toner TJ was 6%, and even though this was before the end of the life of the developing device 4 was notified, poor solid image tracking occurred.

[0152] In this embodiment, an image forming apparatus 100 that forms an image on a recording material P by transferring a developer image (toner image) onto the recording material P includes a rotatable image carrier (photosensitive drum) 1 that carries the developer image, a developing device 4 that supplies developer (toner) to the surface of the image carrier 1 to form the 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 that comes into contact with the developing member 42 to supply the developer to the developing member 42, and a developing voltage that is applied to the developing member 42. The image forming apparatus includes a first applying unit (developing power source) 122, a second applying unit (supply power source) 123 that applies a supply voltage to the supply member 43, an acquiring unit (second video count measurement unit) 83 that acquires information regarding the print rate of the image formed in the image formation, a control unit 220 (more specifically, a supply roller deterioration level calculation unit 84) that acquires information regarding the deterioration level of the supply member 43 based on information regarding the supply voltage applied to the supply member 43, information regarding the time during which the supply voltage is applied to the supply member 43, and information regarding the print rate, and a storage unit (non-volatile memory) 150 that stores the information regarding the deterioration level acquired by the control unit 220. In this embodiment, 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 deterioration level. The control unit 220 can obtain information regarding the degree of deterioration by correcting a value correlated with the product of voltage and time based on information regarding the supply voltage applied to the supply member 43 and information regarding the time the supply voltage was applied to the supply member 43 using a correction coefficient (deterioration correction coefficient ε) corresponding to information regarding the printing rate.

[0153] The control unit 220 may acquire the information regarding the deterioration level based on information regarding the potential difference between the supply voltage applied to the supply member 43 and the development voltage applied to the developing member 42, information regarding the time during which the supply voltage was applied to the supply member 43, and information regarding the printing rate. In this embodiment, the image forming apparatus 100 includes 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 results of the environment detection unit 130. In this embodiment, the control unit 220 can execute a process to notify the 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 main body 101 of the image forming apparatus 100 along with the developing device 4. In this embodiment, the acquisition unit 83 acquires the information regarding the printing rate based on image information of the image formed during the image formation. In this embodiment, the developing member 42 forms a developing portion in contact with the image carrier 1, and supplies developer to the image carrier 1 in the developing portion. In this embodiment, the developer is a non-magnetic one-component developer.

[0154] As described above, in this embodiment, the deterioration level 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 development bias Vdc), the application time of the supply bias Vrs, and the print rate of the output image. This makes it possible to obtain information about the deterioration level of the supply roller 43 with greater accuracy. This also makes it possible to notify the user of information about the lifespan of the development device 4 before an image defect such as a solid image tracking defect occurs. [Embodiment 2]

[0155] 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 assigned the same reference numerals as those of embodiment 1, and detailed description thereof will be omitted. <Method of applying supply bias>

[0156] 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, image forming process, inter-sheet process, and post-rotation process. As an example, Table 7 shows the settings of the supply bias Vrs and the development bias Vdc in the usage environment of the image forming apparatus 100 at 23°C.

[0157] In the pre-rotation process, the development bias Vdc is −350 V, while the supply bias Vr (particularly also referred to as “supply bias VD”) is −250 V. In this case, when considering the potential of supply roller 43 based on the potential of development roller 42, the potential difference (Vrs−Vdc) is +100 V. Similarly, in the image formation process, the supply bias Vr (particularly also referred to as “supply bias VE”) is −450 V, and the potential difference (Vrs−Vdc) is −100 V.

[0158] In the sheet interval process, the supply bias Vrs (particularly also referred to as "supply bias VF") is -350 V, and the potential difference (Vrs-Vdc) is 0 V. In the post-rotation process, the supply bias Vrs (particularly also referred to as "supply bias VG") is -300 V, and the potential difference (Vrs-Vdc) is +50 V.

[0159] By controlling the supply bias Vrs in this manner, it is possible to supply the toner 90 necessary for image formation to the development roller 42 while suppressing deterioration of the supply roller 43. That is, a conventional method for preventing deterioration of the supply roller 43 is to apply a bias ("reverse bias") of opposite polarity to that used during image formation (development) to the supply roller 43, thereby restoring the uneven distribution of the ionic conductive agent on the supply roller 43 to an equilibrium state. In this embodiment, by changing the supply bias Vrs during the pre-rotation process, the inter-sheet process, and the post-rotation process as described above, the apparent potential difference of the supply bias Vrs relative to the development bias Vdc can be switched between positive (positive polarity) and negative (negative polarity). This makes it possible to suppress deterioration of the ionic conductive agent on the supply roller 43 due to uneven distribution. The supply bias Vrs during the pre-rotation process, the inter-sheet process, and the post-rotation process may be a bias of opposite polarity to that used during image formation (opposite polarity to the normal charging polarity of the toner 90), or may be 0 V.

[0160] As described above, the degree of deterioration of the supply roller 43 varies depending on the potential difference between the developing roller 42 (developing bias Vdc) and the supply roller 43 (supply bias Vrs). Therefore, in this embodiment, the degree of deterioration of the supply roller 43 is calculated in more detail using a potential deterioration correction coefficient ε2 that corresponds to the potential difference between the developing roller 42 (developing bias Vdc) and the supply roller 43 (supply bias Vrs).

[0161] The potential deterioration correction coefficient ε2 is set as shown in Table 9, which will be 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 more positive with respect to the potential of the developing roller 42), the potential deterioration correction coefficient ε2 acts to alleviate the bias of the ionic conductive agent, resulting in a low value. In this case, the larger the absolute value of the potential difference, the lower the value of the potential deterioration correction coefficient ε2. 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 more negative with respect to the potential of the developing roller 42), the larger the absolute value of the potential difference, the higher the value of the potential deterioration correction coefficient ε2. This reflects the result, such as that in Test 1 ( FIG. 8A ) described in Example 1, that the larger the negative potential difference (Vrs-Vdc) between the developing roller 42 and the supply roller 43, the more pronounced the bias of the ionic conductive agent becomes.

[0162] 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, etc. Furthermore, 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). Furthermore, 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 as the potential difference (Vrs-Vdc) changes from the positive side to the negative side. <Calculation of Supply Roller Deterioration Level (Detection of Supply Roller Life)>

[0163] Next, detection of the lifespan of the supply roller 43 (calculation of the deterioration level of the supply roller 43) in this embodiment will be described. Fig. 12 is a flowchart outlining the procedure for detecting the lifespan of the developing device 4, focusing on detection of the lifespan 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 lifespan detection unit 80).

[0164] 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). Based on the detection result (particularly temperature in this embodiment) of the temperature and humidity sensor 130, the control unit 220 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 sheet-to-sheet interval process, and the supply bias VG during the post-rotation process (collectively referred to as "supply bias Vrs2" in this embodiment) (S504). In this embodiment, the control unit 220 reads and determines the supply bias Vrs2 corresponding to the temperature, i.e., the supply bias VD during the pre-rotation process, the supply bias VE during the image forming process, the supply bias VF during the sheet-to-sheet 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 showing the relationship between the environment and the supply biases VD, VE, VF, and VG. In this embodiment, the development bias Vdc is set to a constant value of -350V.

[0165] The supply roller deterioration level 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) relative to the development bias Vdc, respectively, and determines a potential deterioration correction coefficient ε2 corresponding to each potential difference (S505). That is, the supply roller deterioration level calculation unit 84 determines a potential deterioration correction coefficient ε2D for the pre-rotation process, a potential deterioration correction coefficient ε2E for the image formation process, a potential deterioration correction coefficient ε2F for the inter-sheet 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 level calculation unit 84 reads 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 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 development bias Vdc) and the potential deterioration correction coefficient ε2.

[0166] 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 for the printing operation (S507). If the supply bias application start timing for the printing operation is tS and the supply bias application end timing for the printing operation is tE, the supply bias application time tnow2 for the printing operation can be expressed by the following formula (9). In the following formula (9), tA is the time for the pre-rotation process, tB is the total time for the image forming process, tC is the total time for the inter-sheet process, and tD is the time for the post-rotation process. tnow2=tE-tS=tA+tB+tC+tD (9)

[0167] 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 and calculates the section printing rate γnow, which is the printing rate for the printing operation, based on the measured video count value VCn (S508). The supply roller deterioration level calculation unit 84 then determines a 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 level calculation unit 84 reads and determines the deterioration correction coefficient ε corresponding to the section printing rate γnow from table data shown in Table 10, which is preset and stored in 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.

[0168] 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, using the following formula (10) (S510): ηnow2=tA×ε2D+tB×ε×ε2E+tC×ε2F+tD×ε2G (10)

[0169] Next, the supply roller deterioration level calculation unit 84 calculates a total supply roller deterioration level ηt, which is an index showing the degree of deterioration of the supply roller 43 since 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 level calculation unit 84 adds (integrates) the calculated section supply roller deterioration level ηnow2 to the cumulative supply roller deterioration level ηr since the start of use of the developing device 4 (supply roller 43), which is stored in the memory 150. In this way, the total supply roller deterioration level ηt is calculated. Then, the supply roller deterioration level calculation unit 84 updates the calculated total supply roller deterioration level ηt with the calculated total supply roller deterioration level ηt and stores it in the memory 150 as a new cumulative supply roller deterioration level ηr. ηt = ηnow2 + ηr ... (11)

[0170] Next, the supply roller deterioration level calculation unit 84 calculates the supply roller remaining life ηJ from the supply roller deterioration level threshold ηth, which is preset and stored in the memory 150, and the calculated total supply roller deterioration level ηt, using the following formula (12) (S512). Note that the supply roller deterioration level threshold ηth in this embodiment is preset in accordance with the method for calculating the total supply roller deterioration level ηt in this embodiment described above. The supply roller deterioration level calculation unit 84 may update and store the calculated supply roller remaining life ηJ in the memory 150. ηJ [%] = (1 - ηt / ηth) × 100 ... (12)

[0171] Next, the control unit 220 determines whether the supply roller remaining life ηJ calculated by the supply roller deterioration level calculation unit 84 is 0% or less (S513). If the control unit 220 determines 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 determines in S513 that the supply roller remaining life ηJ is 0% or less, it controls the execution of a process to notify the user of information regarding the life of the developing device 4 (S515). Then, the control unit 220 ends the print operation (S514). <Calculation Example>

[0172] An example of calculating the deterioration level of the supply roller 43 in this embodiment will be described. This example describes a case where two-sheet intermittent printing is performed, in which a printing operation is repeated to form an image with an average printing rate of 3.5% on two sheets of A4-sized recording material P in the usage environment (ambient environment) of the image forming apparatus 100 at 23° C. When performing a printing operation to form an image on two sheets of A4-sized recording material P in the image forming apparatus 100 of this embodiment, the time for which the supply bias Vrs2 is applied to the supply roller 43 during the printing operation is approximately expressed by the following equation: tnow2 = tA + tB + tC + tD = 0.5 (seconds) + 2.8 (seconds) × 2 + 0.25 (seconds) × 2 + 0.5 (seconds). Furthermore, when the image forming apparatus 100 is in a room temperature environment of 23° C., the supply bias Vrs2 is VD = −250 (V), VE = −450 (V), VF = −350 (V), and VG = −300 (V) from Table 8. At this time, since the development bias Vdc is -350 (V), the potential differences between the supply roller 43 and the development 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. Furthermore, when the section printing rate γnow is calculated to be 3.5%, from Table 10, the deterioration correction coefficient ε is 1.5. Therefore, the section supply roller deterioration degree ηnow2 for 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

[0173] The value of this section supply roller deterioration level ηnow2 is stored in memory 150 as the cumulative supply roller deterioration level ηr, and the section supply roller deterioration level ηnow2 is recalculated in the subsequent printing operation. The recalculated section supply roller deterioration level ηnow2 is added to the cumulative supply roller deterioration level ηr to calculate the total supply roller deterioration level ηt. Then, as described above, when the total supply roller deterioration level ηt reaches the supply roller deterioration level threshold ηth, it is determined that the supply roller 43 has reached the end of its life. <Variation 5>

[0174] In this embodiment, the image forming apparatus 100 stores the potential deterioration correction coefficient ε2 as table data that corresponds to the potential difference between the supply roller 43 (supply bias Vrs) and the development roller 42 (development bias Vdc), but this is not limited to this. The image forming apparatus 100 may store the potential deterioration correction coefficient ε2 as table data that corresponds to the supply bias Vrs, for example. <Modification 6>

[0175] In this embodiment, the image forming apparatus 100 stores the potential deterioration correction coefficient ε2 as table data that corresponds to the potential difference between the supply roller 43 (supply bias Vrs) and the development roller 42 (development bias Vdc), but this is not limited to this. The image forming apparatus 100 may calculate the potential deterioration correction coefficient ε2 using a correction formula such as the following formula (13), for example: ε2=1−0.005VΔ (13) <Modification 7>

[0176] In this embodiment, the supply bias Vrs (the potential difference between the supply bias Vrs and the development bias Vdc) is set differently in the pre-rotation process, the inter-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 development bias Vdc in at least one of the pre-rotation process, the inter-sheet process, and the post-rotation process to be more positive than that in the image forming 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 development bias Vdc to a positive value (a polarity opposite to the normal charging polarity of the toner 90) in at least one of the pre-rotation process, the inter-sheet process, and the post-rotation process. <Variation 8>

[0177] In this embodiment, the deterioration level of the supply roller 43 was estimated for each of the pre-rotation process, image forming process, inter-sheet process, and post-rotation process, and then the estimated deterioration level was calculated by combining the estimated deterioration levels. This is because, in this embodiment, when the supply bias Vrs (the potential difference between the supply bias Vrs and the development bias Vdc) is different in the pre-rotation process, inter-sheet process, and post-rotation process from that in the image formation process, information regarding the deterioration level of the supply roller 43 can be obtained more accurately. However, even when the supply bias Vrs (the potential difference between the supply bias Vrs and the development bias Vdc) is not changed during printing, as in Example 1, the deterioration level of the supply roller 43 may be estimated for each of the pre-rotation process, image forming process, inter-sheet process, and post-rotation process, and then the estimated deterioration level may be calculated by combining the estimated deterioration levels. In this case, the accuracy of the information regarding the deterioration level of the supply roller 43 obtained can be improved by applying a deterioration correction coefficient ε corresponding to the print rate of the output image only to the image formation process in which a toner image is formed. <Comparative Verification 2>

[0178] Next, a comparative test performed on this example and Comparative Example 2 below to verify the effects of this example will be described. - Evaluation Method -

[0179] In the image forming apparatus 100 configured in this embodiment, a print durability 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 durability test was conducted in a full-color image formation mode in an operating environment (ambient environment) of the image forming apparatus 100, with a temperature of 23°C and humidity of 50%, with the following cycles (1) to (3) being one cycle: (1) A horizontal line image with a 2% coverage was formed on 100 sheets of A4-size recording paper, with four-sheet intermittent printing; (2) A horizontal line image with a 20% coverage was formed on 100 sheets of A4-size recording paper, with four-sheet intermittent printing; and (3) A horizontal line image with a 100% coverage was formed on 100 sheets of A4-size recording paper, with four-sheet intermittent printing.

[0180] Then, as image defects, solid image followability defects (whiteout images) in solid images were visually evaluated according to the following criteria. Note that here, evaluation results for solid black images in particular are shown, but in this example, the configurations of the developing devices 4 (process cartridges 8) for each color were essentially the same, and similar evaluation results were obtained. ○: No solid image followability defects occurred (no practical problems) ×: Significant solid image followability defects occurred (problems in practical use) - Comparative Example 2 -

[0181] 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 of the developing roller 42 and the amount of remaining toner. Other points of Comparative Example 2 were substantially the same as those of this Example. -Evaluation Results-

[0182] Table 11 shows the evaluation results.

[0183] In this embodiment, when the remaining life of the developing roller GJ was 45% and the remaining amount of toner TJ was 9%, the remaining life of the supply roller 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.

[0184] On the other hand, in Comparative Example 2, the remaining life of the developing roller GJ was 41% and the remaining amount of toner TJ was 7%, and even though this was before the end of the life of the developing device 4 was notified, poor solid image tracking occurred.

[0185] In this embodiment, image formation by the image forming apparatus 100 involves an image forming operation (image forming step) in which a developer image is formed on the image carrier 1, and non-image forming operations (pre-rotation step, paper interval step, post-rotation step) in which a developer image is not formed on the image carrier 1. The control unit 220 is capable of changing the supply voltage applied to the supply member 43 during the image forming operation and at least a portion of the non-image forming operation, and acquires information about the degree of deterioration of the supply roller 43 based on information about the respective supply voltages applied to the supply member 43, information about the time during which each supply voltage was applied to the supply member 43, and information about the printing rate acquired by the acquisition unit (second video count measurement unit) 83. In this embodiment, the control unit 220 is also capable of changing the supply voltage applied to the supply member 43 so that the polarity of the potential difference between the supply voltage and the developing voltage is opposite during the image forming operation and at least a portion of the non-image forming operation.

[0186] As described above, according to this embodiment, the same effects as those of the first embodiment can be obtained, and by switching the potential difference (Vrs-Vdc) between the supply bias Vrs and the development bias Vdc between positive and negative during printing, it is possible to suppress deterioration of the supply roller 43. Furthermore, by calculating the deterioration level of the supply roller 43 using the potential deterioration correction coefficient ε2 corresponding to the potential difference (Vrs-Vdc) between the supply bias Vrs and the development bias Vdc, it is possible to accurately obtain information regarding the deterioration level of the supply roller 43. [Embodiment 3]

[0187] 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 assigned the same reference numerals as those of embodiment 1, and detailed descriptions thereof will be omitted. <Outline of this embodiment>

[0188] In this embodiment, the image formation area is divided into multiple areas in the laser main scanning direction of the exposure device 3, and the printing rate is obtained for each area, and the deterioration level of the supply roller 43 in each area is calculated based on the printing rate of each area. Note that this main scanning direction is approximately parallel to the rotational axis direction of the supply roller 43, and the rotational axis direction of the supply roller 43 corresponding to this main scanning direction is also called the "longitudinal direction."

[0189] This improves the accuracy of the acquired information regarding the degree of deterioration of the supply roller 43. That is, in this embodiment, it is possible to accurately detect localized deterioration in the longitudinal direction of the supply roller 43. This makes it possible to prevent localized deterioration in the longitudinal direction of the supply roller 43 and the occurrence of image defects such as poor solid tracking in a portion of the longitudinal direction when the print rate of the output image is high in a portion of the longitudinal direction.

[0190] In this embodiment, the magnitude of the contribution of the deterioration level at each position in the longitudinal direction of the supply roller 43 to the deterioration level of the supply roller 43 (deterioration correction coefficient ε) is estimated by integrating the print ratio of the image formed at that position along the sub-scanning direction. The sub-scanning direction is approximately perpendicular to the main scanning direction and approximately parallel to the direction of movement of the surface of the supply roller 43. Specifically, the print ratio (print information) along the sub-scanning direction is obtained using a pixel counting method (or a video counting method). The pixel counting method (or a video counting method) is a method of obtaining information about the number of pixels in the printed portion of an image by counting laser exposure ON signals (signals that cause the laser to emit light, pixel signals) generated based on image data. Since the laser-exposed area of ​​the photosensitive drum 1 is printed (to which toner transferred from the developing roller 42 adheres), the count value of the laser ON signal corresponds to the count value of the dots in the printed portion of the image.

[0191] 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 supply roller 43, thereby indicating the positional relationship of the 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 using Fig. 14.

[0192] When image formation begins, the control unit 220 integrates laser ON signals along the sub-scanning direction in each region in the main scanning direction. Dividing this integrated value by the total number of dots in the sub-scanning direction yields the printing rate γ(n) (%) for 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 formation region is divided into 12 parts in the main scanning direction (longitudinal direction). The regions in the main scanning direction of the image formation region are designated n = 1, 2, 3, 4, ... (1 ≤ n ≤ 12) from left to right in the figure. In addition, the image formation region is divided into, for example, 15 parts in the sub-scanning direction. In this case, the image formation region is divided into a total of 12 x 15 = 180 sections (dots, pixels). The blacked-out sections (dots) in Figure 14 are sections (printing areas, image areas) where printing is performed and where deterioration of the supply roller 43 accelerates. On the other hand, the white sections in Figure 14 are sections (non-printed areas, non-image areas) where no printing is performed and where deterioration of the supply roller 43 is gradual. In an area where n = 2 in the main scanning direction, when forming an image of "A," 3 dots out of 15 dots in the sub-scanning direction are printed. Therefore, the printing rate γ(2) for 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.

[0193] In this embodiment, the longitudinal direction is divided into 12 sections, but this is not limiting and any number of longitudinal divisions can be selected. For example, the longitudinal direction can be divided more roughly into three sections (1≦n≦3)—the left end, the center, and the right end. It is also possible to divide the longitudinal direction up to the maximum number of pixel counts. For example, to form a 300 dpi image, 300 dots are arranged per inch. In this case, approximately 1≦n≦25,000, meaning that the image formation area can be divided into approximately 25,000 sections in the longitudinal direction. However, the maximum available memory capacity may be a constraint. Furthermore, density unevenness in the longitudinal direction due to localized deterioration of the supply roller 43 in the longitudinal direction tends to be noticeable when the localized deterioration occurs over a certain width in the longitudinal direction.

[0194] For these reasons, it is preferable to divide the sheet in the longitudinal direction so that the width of each region in the longitudinal direction is approximately 5 mm to 50 mm, typically 10 mm to 30 mm. From this perspective, for example, when the maximum size for image formation is LTR size (or A4 size (portrait feed)), it is preferable to divide the sheet in the longitudinal direction into approximately 8 to 20 divisions (12 divisions in this embodiment), as in this embodiment. <Calculation of Deterioration Level of Supply Roller (Detection of Supply Roller Life)>

[0195] Next, detection of the lifespan of the supply roller 43 (calculation of the deterioration level of the supply roller 43) in this embodiment will be described. Fig. 13 is a flowchart showing an outline of the procedure for detecting the lifespan of the developing device 4, focusing on detection of the lifespan of the supply roller 43. The process according to the flowchart in Fig. 13 is executed by the control unit 220 (mainly the supply roller lifespan detection unit 80). Note that in the procedure in this embodiment shown in Fig. 13, the same processes as those in the procedure in embodiment 1 shown in Fig. 9 will not be described as appropriate.

[0196] The processes of S601 to S606 in FIG. 13 are the same as the processes of S401 to S406 in FIG. 9, respectively.

[0197] In this embodiment, 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 and calculates the section printing rate γnow(n) for each region in the main scanning direction during the printing operation based on the video count values ​​for each region in the main scanning direction measured (S607).Then, the supply roller deterioration level calculation unit 84 determines the deterioration correction coefficient ε(n) for each region in the main scanning direction based on the section printing rate γnow(n) for each region in the main scanning direction acquired by the second video count measurement unit 83 (S608).In this embodiment, the supply roller deterioration level calculation unit 84 reads and determines the deterioration correction coefficient ε(n) corresponding to the section printing rate γnow(n) for each region in the main scanning direction from table data shown in Table 2 (see Example 1), which is preset and stored in memory 150.

[0198] Next, the supply roller deterioration level calculation unit 84 calculates the section supply roller deterioration level 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, using the following formula (14) (S609): ηnow(n)=tnow×|Vrs|×ε(n) (14)

[0199] In this embodiment, the development bias Vdc is constant, so the section supply roller deterioration degree ηnow(n) is calculated by the above formula (14). However, for example, when the development bias Vdc is variably controlled, the section supply roller deterioration degree ηnow(n) may be calculated by the following formula: ηnow(n)=tnow×|Vrs−Vdc|×ε(n).

[0200] Next, the supply roller deterioration level calculation unit 84 calculates a total supply roller deterioration level ηt(n), which is an index indicating the degree of deterioration of the supply roller 43 in each longitudinal region since the start of use of the developing device 4 (supply roller 43) (S610). That is, as shown in the following equation (15), the supply roller deterioration level calculation unit 84 adds (integrates) the calculated section supply roller deterioration level ηnow(n) of each longitudinal region to the cumulative supply roller deterioration level ηr(n) of each longitudinal region since the start of use of the developing device 4 (supply roller 43), which is stored in the memory 150. In this way, the total supply roller deterioration level ηt(n) of each longitudinal region is calculated. Then, the supply roller deterioration level calculation unit 84 updates and stores the calculated total supply roller deterioration level ηt(n) of each longitudinal region as a new cumulative supply roller deterioration level ηr(n) of each longitudinal region in the memory 150. ηt(n) = ηnow(n) + ηr(n) (15)

[0201] Next, the supply roller deterioration level calculation unit 84 calculates the remaining supply roller life ηJ(n) of each longitudinal region from the supply roller deterioration level threshold ηth, which is set in advance and stored in the memory 150, and the calculated total supply roller deterioration level ηt(n) of each longitudinal region, using the following formula (16) (S611). The supply roller deterioration level calculation unit 84 may update and store the calculated remaining supply roller life ηJ(n) of each longitudinal region in the memory 150. ηJ(n) [%] = (1 - ηt(n) / ηth) × 100 ... (16)

[0202] Next, the supply roller deterioration level calculation unit 84 selects the smallest value among the supply roller remaining life ηJ(n) of each longitudinal region (S612). In other words, the supply roller deterioration level 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).

[0203] Next, the control unit 220 determines whether the minimum supply roller remaining life ηJ(n) selected by the supply roller deterioration level calculation unit 84 is 0% or less (S613). If the control unit 220 determines in S613 that the minimum supply roller remaining life ηJ(n) is not 0% or less, it terminates the printing operation (S614). On the other hand, if the control unit 220 determines in S613 that the minimum supply roller remaining life ηJ(n) is 0% or less, it controls the execution of a process to notify the user of information regarding the life of the developing device 4 (S615). Then, the control unit 220 terminates the printing operation (S614).

[0204] In this way, in this embodiment, the degree of deterioration of the supply roller 43 is calculated for each region 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 region with the most advanced deterioration.

[0205] An example of calculating the deterioration level of the supply roller 43 in this embodiment will be described. A case will be described in which two-sheet intermittent printing is performed, in which a printing 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. When a printing 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 Example 1. Furthermore, when the image forming apparatus 100 is in an environment at room temperature of 23° C., Vrs = -450 (V) according to Table 1 (see Example 1).

[0206] For the image shown in Fig. 14, the deterioration correction coefficient ε(n) corresponding to the section printing rate γnow(n) can be determined from Table 2 (see Example 1) as follows: n = 1: section printing rate γ(1) = 0%, deterioration correction coefficient ε(1) = 1.0 n = 2: section printing rate γ(2) = 20%, deterioration correction coefficient ε(2) = 2.0 n = 3: section printing rate γ(3) = 27%, deterioration correction coefficient ε(3) = 2.0 n = 4: section printing rate γ(4) = 33%, deterioration correction coefficient ε(4) = 2.5

[0207] Although the example has been given for the region where n=1 to 4, the deterioration correction coefficient ε(n) is determined in the same manner for the region where n=5 to 12.

[0208] 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

[0209] Although the example has been given for the region where n=1 to 4, the section supply roller deterioration degree ηnow(n) is calculated in the same manner for the region where n=5 to 12.

[0210] This value of the 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 printing operation. The recalculated section supply roller deterioration degree ηnow(n) is then added to the cumulative supply roller deterioration degree ηr(n) to calculate the total supply roller deterioration degree ηt(n). In other words, the section supply roller deterioration degree ηnow(n) calculated in the first printing operation is set as the cumulative supply roller deterioration degree ηr(n). When the section supply roller deterioration degree ηnow(n) calculated in the second printing 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 calculated 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

[0211] Although the example has been given for the region where n=1 to 4, the total supply roller deterioration degree ηt(n) is calculated in the same manner for the region where n=5 to 12.

[0212] As mentioned above, when the minimum value of the remaining supply roller life ηJ(n) becomes 0% or less, that is, when the maximum value of the total supply roller deterioration level ηt(n) reaches the supply roller deterioration level threshold value ηth, it is determined that the supply roller 43 has reached the end of its life.

[0213] The supply roller deterioration level threshold value ηth is experimentally determined in advance so as not to cause poor solid image tracking performance. In this embodiment, the supply roller deterioration level threshold value ηth=3.9×10 ７ However, the supply roller deterioration level threshold 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. <Comparative Verification 3>

[0214] Next, a comparative test conducted to verify the effects of this embodiment will be described.

[0215] In the image forming apparatus 100 having the configuration of this embodiment, a print durability test was conducted from the start of use of the developing device 4 (process cartridge 8) until the supply roller 43 reached the end of its life.

[0216] Specifically, a print durability test was conducted in an operating environment (ambient environment) of the image forming apparatus 100, where a temperature of 23°C and humidity of 50% were used. The following image pattern was formed on A4-size recording paper in full-color image formation mode, with two sheets printed intermittently. The three image patterns used were those shown in Figures 14, 15, and 16, which had the same average print rate of 25.5% but different print rates in each longitudinal region. The image pattern in Figure 16 has the same average print rate as the image patterns in Figures 14 and 15, but the printed area is unevenly distributed in the longitudinal direction. The image pattern in Figure 15 has the same average print rate as the image patterns in Figures 14 and 16, but the printed area is evenly distributed across 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 Example was used to calculate the deterioration level of the supply roller 43. The occurrence of solid image tracking failure (whiteout images) was evaluated visually according to the following criteria. Here, the evaluation results for solid black images are shown in particular, but in this example, the configuration of the developing device 4 (process cartridge 8) for each color is substantially the same, and similar evaluation results were obtained. ○: No solid image tracking defects ○△: Slight solid image tracking defects (within practically acceptable range) - Evaluation Results -

[0217] The evaluation results for the method of Example 1 are shown in Table 12.

[0218] In the method of Example 1, the printing rate is calculated to be 25.5% for all of the image patterns shown in Figures 14, 15, and 16. Therefore, regardless of the image pattern, the deterioration correction coefficient ε = 2.0 corresponding to a printing rate of 25.5% is used to calculate the deterioration level of the supply roller 43, and the supply roller 43 reaches the end of its life at the same timing. As a result, when the image patterns shown in Figures 14 and 16 were continuously printed, slight solid image tracking defects were confirmed when the supply roller 43 reached the end of its life. This is due to the supply roller 43's localized deterioration in the longitudinal direction, as a result of a large amount of toner 90 being continuously consumed in a portion of its longitudinal direction.

[0219] Next, the evaluation results for the method of this example are shown in Table 13.

[0220] In the method of this embodiment, in the image pattern of Figure 14, the area in the longitudinal direction where the printing rate is locally 33% is the maximum printing rate, so 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 Figure 16, the area in the longitudinal direction where the printing rate is locally 100% is the maximum printing rate, so 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 larger deterioration correction coefficient ε is selected than in the method of Example 1 to calculate the deterioration level of the supply roller 43. Therefore, in the method of this embodiment, solid tracking failure did not occur when the supply roller 43 reached the end of its life. <Effects>

[0221] In this embodiment, the acquisition unit (second video count measurement unit) 83 acquires information about the printing rate for each region obtained by dividing the image forming area on the image carrier 1 in the main scanning direction substantially perpendicular to the direction of movement of the surface of the image carrier 1, and the control unit 220 acquires information about the deterioration level of the supply member 43 for each region based on the information about the printing rate for each region. Also, 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 about the deterioration level for each region. Also, in this embodiment, the control unit 220 can determine whether the developing device 4 has reached the end of its life based on information that indicates the greatest degree of deterioration among the information about the deterioration level for each region.

[0222] As described above, in this embodiment, the deterioration level of the supply roller 43 is calculated based on the printing rate for each region divided in the main scanning direction (longitudinal direction). This makes it possible to obtain more accurate information on the deterioration level of the supply roller 43 in accordance with local deterioration in the longitudinal direction of the supply roller 43, even when an image is formed with uneven printing in the main scanning direction. This also makes it possible to more accurately notify the user of information on the lifespan of the developing device 4 before image defects such as poor solid image tracking occur. [Embodiment 4]

[0223] 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 assigned the same reference numerals as those of embodiment 1, and detailed descriptions thereof will be omitted. <Outline of this embodiment>

[0224] In this embodiment, as in the third embodiment, the image formation area is divided into a plurality of areas in the main scanning direction, and the printing rate is obtained for each of these areas. Then, in this embodiment, information regarding the deterioration level of the supply roller 43 is obtained based on the printing rate between adjacent areas in the main scanning direction. In particular, in this embodiment, information regarding the deterioration level of the supply roller 43 is obtained based on the difference in printing rate between adjacent areas in the main scanning direction. This improves the accuracy of the information regarding the deterioration level of the supply roller 43 that is obtained. In other words, when an image is formed with a large difference in printing rate between adjacent areas in the main scanning direction, and the difference in the deterioration level of the supply roller 43 between the adjacent areas is large, it is possible to prevent image defects such as uneven density from becoming more noticeable.

[0225] Generally, as the supply roller 43 deteriorates, its ability to supply toner to the developing roller 42 deteriorates. This tends to result in a decrease in the amount of toner coated on the developing roller 42 or the accumulation of toner with excessive charge 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 consecutively forming images with a large difference in print rate between adjacent regions in the main scanning direction, the image density may vary in the main scanning direction. This is because when the difference in print rate between adjacent regions in the main scanning direction is large, localized deterioration progresses in the longitudinal direction of the supply roller 43, and the difference in toner supply performance to the developing roller 42 in the boundary region becomes apparent as density unevenness in the image. In this embodiment, to address this phenomenon, information regarding the degree of deterioration of the supply roller 43 is acquired, taking into account 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 density unevenness described above. <Verification 4>

[0226] A print durability test was conducted to confirm changes in image density in response to deterioration of the supply roller 43. In the operating environment (ambient environment) of the image forming apparatus 100, a temperature of 23°C and humidity of 50% were used. A print operation was performed intermittently, forming 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 reached four levels of deterioration, and the supply roller 43 was temporarily removed from the developing device 4. The supply roller 43 was then reassembled into the same developing device 4, and a print operation was performed. By keeping the condition of the components other than the supply roller 43 consistent, factors other than changes in the condition of the supply roller 43 could be eliminated. The print operation was performed on a solid image (100% print rate) and a halftone image (23% print rate).

[0227] The results are shown in Figure 17. The vertical axis represents image density (reflection density), and the horizontal axis represents the rotational drive time of the supply roller 43 (= supply bias application time). The reflection density was measured using an eXact (X-rite Corporation). It can be seen that the image density gradually decreased as the print durability test progressed (the rotational drive time of the supply roller 43 increased). It can also be seen that the image density decreased more significantly in halftone images than in solid images, indicating that the change in image density is more pronounced in halftone images than in solid images. Therefore, for example, if an image with different printing rates in the longitudinal direction as shown in Figure 18 is continuously formed, a halftone image with low image density will be output in areas with high printing rates, as shown in Figure 19.

[0228] Taking this into consideration, this embodiment makes it possible to obtain information regarding the deterioration level 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. <Calculation of the Deterioration Level of the Supply Roller (Detection of the Life of the Supply Roller)>

[0229] Next, detection of the lifespan of the supply roller 43 (calculation of the deterioration level of the supply roller 43) in this embodiment will be described. Fig. 20 is a flowchart showing an outline of the procedure for detecting the lifespan of the developing device 4, focusing on detection of the lifespan of the supply roller 43. The process according to the flowchart in Fig. 20 is executed by the control unit 220 (mainly the supply roller lifespan detection unit 80). Note that in the procedure in this embodiment shown in Fig. 20, the same processes as those in the procedure in embodiment 3 shown in Fig. 13 will not be described as appropriate.

[0230] The processes of S701 to S712 in FIG. 20 are the same as the processes of S601 to S612 in FIG. 13, respectively.

[0231] In this embodiment, the supply roller deterioration level calculation unit 84 calculates the deterioration level difference Δηt(n), which is the difference between the total supply roller deterioration levels ηt(n) of adjacent regions, from the calculated total supply roller deterioration level 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)

[0232] Next, the supply roller deterioration level calculation unit 84 selects the maximum value among the absolute values ​​(i.e., differences) of the calculated deterioration level differences Δηt(n) - the deterioration level difference absolute values ​​|Δηt(n)| (S714).

[0233] Then, the supply roller deterioration level calculation unit 84 updates and stores in the memory 150 the calculated total supply roller deterioration level ηt(n) for each longitudinal region as a new cumulative supply roller deterioration level ηr(n) for each longitudinal region (S715). The supply roller deterioration level calculation unit 84 may also update and store in the memory 150 the calculated remaining supply roller life ηJ(n) for each longitudinal region.

[0234] Next, the control unit 220 determines whether the supply roller 43 has reached the end of its life (S715). First, as in the third embodiment, the control unit 220 determines whether the minimum supply roller remaining life ηJ(n) selected by the supply roller deterioration level calculation unit 84 is equal to or less than 0%. In this embodiment, the control unit 220 also determines whether the maximum deterioration level difference absolute value |Δηt(n)| selected by the supply roller deterioration level calculation unit 84 is equal to or greater than a deterioration level difference threshold Δηth that is preset and stored in the memory 150. The deterioration level difference threshold Δηth is experimentally determined in advance by visually checking density unevenness in, for example, a solid image (an image printed entirely at 100%) or a halftone image (an image with the same halftone density throughout the entire image) so that the density unevenness falls within a range that is perceptually acceptable. If the control unit 220 determines in S715 that the minimum supply roller remaining life ηJ(n) is not less than 0% and that the maximum absolute value of the deterioration level difference |Δηt(n)| is not greater than the deterioration level difference threshold value Δηth, the control unit 220 terminates 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 less than 0% or that the maximum absolute value of the deterioration level difference |Δηt(n)| is greater than the deterioration level difference threshold value Δηth, the control unit 220 controls the execution of a process to notify the user of information regarding the life of the developing device 4 (S717). Then, the control unit 220 terminates the print operation (S716). <Calculation Example>

[0235] An example of calculating the deterioration level of the supply roller 43 in this embodiment will be described. A case will be described in which two-sheet intermittent printing is performed, in which a printing 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. When a printing 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 Example 1. Furthermore, when the image forming apparatus 100 is in an environment at room temperature of 23° C., Vrs = -450 (V) according to Table 1 (see Example 1).

[0236] For the image shown in Fig. 18, the deterioration correction coefficient ε(n) corresponding to the section printing rate γnow(n) can be determined from Table 2 (see Example 1) as follows: n = 1: section printing rate γ(1) = 0%, deterioration correction coefficient ε(1) = 1.0 n = 2: section printing rate γ(2) = 40%, deterioration correction coefficient ε(2) = 2.5 n = 3: section printing rate γ(3) = 40%, deterioration correction coefficient ε(3) = 2.5 n = 4: section printing rate γ(4) = 0%, deterioration correction coefficient ε(4) = 1.0

[0237] Although the example has been given for the region where n=1 to 4, the deterioration correction coefficient ε(n) is determined in the same manner for the region where n=5 to 12.

[0238] 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

[0239] Although the example has been given for the region where n=1 to 4, the section supply roller deterioration degree ηnow(n) is calculated in the same manner for the region where n=5 to 12.

[0240] Further, the deterioration 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

[0241] 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

[0242] Similarly, at the end of the second print operation under the above conditions, the deterioration 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

[0243] 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.

[0244] As mentioned 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., when the maximum value of the total supply roller deterioration level ηt(n) reaches the supply roller deterioration level threshold value ηth), or when the maximum value of the deterioration level difference absolute value |Δηt(n)| becomes equal to or greater than the deterioration level difference threshold value Δηth.

[0245] The deterioration level difference threshold 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 level difference threshold Δηth=1.7×10 ７ The setting is as follows. <Modification 9>

[0246] The method of acquiring information about the deterioration level of the supply roller 43 based on the printing rate of each longitudinal region is not limited to the method of the third embodiment and this embodiment. In the third embodiment, the life of the supply roller 43 was determined based on the deterioration level of the region where the remaining supply roller life ηJ was the smallest (the total supply roller deterioration level ηt(n) was the largest). Alternatively, the supply roller 43 may be determined to have reached the end of its life when, for example, the number of regions where the remaining supply roller life ηJ(n) is 0% or less (i.e., where the total supply roller deterioration level ηt(n) has reached the supply roller deterioration level threshold ηth) is equal to or greater than a predetermined value. Furthermore, in this embodiment, the life of the supply roller 43 was determined based on the maximum absolute value of the deterioration level difference |Δηt(n)| between adjacent longitudinal regions. Alternatively, the supply roller 43 may be determined to have reached the end of its life when the number of regions where the absolute value of the deterioration level difference |Δηt(n)| is equal to or greater than the deterioration level difference threshold Δηth is equal to or greater than a predetermined value. Furthermore, the relationship between the printing rates of adjacent regions in the longitudinal direction is not limited to determining the difference in printing rate between the regions, but may instead be determined as the ratio (proportion) of the printing rates between the regions and used for control according to this embodiment. Furthermore, the relationship between the printing rates of regions divided in the longitudinal direction is not limited to the relationship between the printing rates of adjacent regions, but may also be, for example, the relationship between the printing rates of the end and center in the longitudinal direction, or between both ends. <Comparative Verification 4>

[0247] Next, a comparative test conducted to verify the effects of this embodiment will be described.

[0248] In the image forming apparatus 100 having the configuration of this embodiment, a print durability test was conducted from the start of use of the developing device 4 (process cartridge 8) until the supply roller 43 reached the end of its life.

[0249] Specifically, a print durability test was conducted in the operating environment (ambient environment) of the image forming apparatus 100, where a temperature of 23°C and humidity of 50% were used. The print operation involved forming the following image pattern on an A4-size recording material P in full-color image formation mode, with two sheets printed intermittently. The image pattern used was the image pattern shown in Figure 18. Then, the occurrence of image defects was compared between the case where the method of Example 3 was used to calculate the deterioration level of the supply roller 43 and the case where the method of this example was used. As for image defects, the occurrence of density unevenness in halftone images (HT: printing rate 23%) was evaluated visually according to the following criteria. In addition, solid image tracking defects were also evaluated in the same manner as in Comparative Verification 3 described in Example 3. Note that while the evaluation results for solid black images are shown here, the configuration of the developing devices 4 (process cartridges 8) for each color was essentially the same in this example, and similar evaluation results were obtained. ○: No HT density unevenness occurred. ○△: Slight HT density unevenness occurred (within practically acceptable range). —Evaluation Results—

[0250] The evaluation results are shown in Table 14.

[0251] In the method of Example 3, the maximum printing rate is found in the region where the printing rate is 40% locally in the longitudinal direction, and therefore a deterioration correction coefficient ε = 2.5 is used to calculate the deterioration level of the supply roller 43. Therefore, in the method of Example 3, when the supply roller 43 reached the end of its life, the occurrence of poor solid print tracking performance was suppressed, but slight HT density unevenness occurred. This is because the difference in printing rate is large in the boundary region between adjacent regions in the longitudinal direction, and local deterioration of the supply roller 43 causes changes in the toner coating amount and the charged charge amount on the development roller 42.

[0252] In contrast, with the method of this embodiment, the difference in deterioration level between adjacent regions in the longitudinal direction of the supply roller 43 can be calculated using the absolute value of the deterioration level difference |Δηt(n)|. Therefore, with the method of this embodiment, HT density unevenness did not occur when the supply roller 43 reached the end of its life. <Effects>

[0253] In this embodiment, as in the fourth embodiment, the acquisition unit (second video count measurement unit) 83 acquires information about the printing rate for each region obtained by dividing the image forming area on the image carrier 1 in the main scanning direction, which is substantially perpendicular to the direction of movement of the surface of the image carrier 1. The control unit 220 acquires information about the deterioration level of the supply member 43 for each region based on the information about the printing rate for each region. Furthermore, 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 about the deterioration level for each region. Furthermore, in this embodiment, the control unit 220 can acquire information about the difference in the deterioration levels between at least two of the regions based on the information about the deterioration level for each region, and determine whether the developing device 4 has reached the end of its life based on the information about the difference. Furthermore, in this embodiment, the control unit 220 can determine whether the developing device 4 has reached the end of its life based on information about the largest difference among the differences between multiple adjacent regions as the information about the difference.

[0254] As described above, in this embodiment, the same effects as those of the third embodiment can be obtained, and information regarding local deterioration in the longitudinal direction of the supply roller 43 can be acquired 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 acquire information regarding the degree of deterioration of the supply roller 43 with greater accuracy, and to prevent image defects such as uneven density from becoming more noticeable. [Embodiment 5]

[0255] 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 assigned the same reference numerals as those of embodiment 1, and detailed descriptions thereof will be omitted. <Outline of this embodiment>

[0256] FIG. 21 is a graph showing the relationship between the degree of deterioration of the supply roller 43 and the amount of remaining toner in the developing device 4 at the timing when solid-image-coverage defects occur in the image forming apparatus 100 of this embodiment. The horizontal axis represents the degree of deterioration of the supply roller 43, and the vertical axis represents the amount of remaining toner in the developing device 4. The solid line in FIG. 21 indicates the timing when solid-image-coverage defects occur. From FIG. 21, it can be seen that as the degree of deterioration of the supply roller 43 increases, the amount of remaining toner at which solid-image-coverage defects occur 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) just before solid-image-coverage defects occur, it is desirable to determine the end of life of the developing device 4 from both the degree of deterioration of the supply roller 43 and the amount of remaining toner.

[0257] In the first embodiment, threshold values ​​were set separately for the deterioration level of the supply roller 43 and the remaining toner amount, respectively, to determine the end of life of the developing device 4 based on the deterioration level of the supply roller 43 and the remaining toner amount. To issue a lifespan warning to the user before solid print tracking failure occurs using this method, the threshold values ​​must be set as follows. First, the supply roller deterioration threshold ηth must be set so that a lifespan warning can be issued at a timing when solid print tracking failure will not occur until the toner remaining amount reaches 0%. In addition, the toner remaining amount threshold (video count threshold VCth) must be set so that a lifespan warning can be issued at a timing when solid print tracking failure will not occur even when the remaining life of the supply roller is 0%. FIG. 22 illustrates the above threshold settings in a graph similar to FIG. 21 . With such threshold values, a lifespan warning for the developing device 4 is issued, assuming that the supply roller 43 has reached the end of its life, even when solid print tracking failure has not yet occurred due to the remaining toner amount. Furthermore, if such a threshold value 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-color tracking, a warning will be issued for the end of the life of the developing device 4, indicating that the remaining toner has reached 0%.

[0258] The present embodiment aims 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 tracking failure occurs.

[0259] Next, detection of the lifespan of the developing device 4 in this embodiment will be described. Fig. 23 is a flowchart showing an outline of the procedure for detecting the lifespan of the developing device 4 in this embodiment, focusing on calculating the deterioration level of the supply roller 43 and calculating the remaining amount of toner. The process according to the flowchart in Fig. 23 is executed by the control unit 220 (mainly the remaining toner amount detection unit 70 and the supply roller lifespan detection unit 80). Note that the image forming apparatus 100 may also be configured to detect the lifespan of the developing device 4 based on the detection result of the remaining lifespan GJ of the developing roller, as in the above-described embodiment. - Calculation of the Deterioration Level of the Supply Roller (Detection of the Lifespan of the Supply Roller) -

[0260] First, detection of the life of the supply roller 43 (calculation of the deterioration level of the supply roller 43) will be described.

[0261] When a print signal (job information) is input (S801), the control unit 220 starts the print operation (job) (S802). Furthermore, upon start of the print operation, the control unit 220 determines the supply bias Vrs based on the detection results (particularly temperature in this embodiment) 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 −350 V.

[0262] Subsequently, 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 for the printing operation (S804). If the timing at which the supply bias application for the printing operation starts is tS and the timing at which the supply bias application ends is tE, the supply bias application time tnow for the printing operation can be expressed by the following equation (18): tnow=tE-tS (18)

[0263] 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 calculates a section printing rate γnow, which is the printing rate for the printing operation, based on the video count value VCn, and the supply roller deterioration level calculation unit 84 determines a deterioration correction coefficient ε based on the section printing rate γnow (S807). In this embodiment, the supply roller deterioration level calculation unit 84 reads and determines the deterioration correction coefficient ε corresponding to the section printing rate γnow from table data shown in Table 2 (see Example 1), which is preset and stored in memory 150.

[0264] 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, using the following formula (19) (S808): ηnow=tnow×|Vrs|×ε (19)

[0265] In this embodiment, the deterioration degree ηnow of the section supply roller is calculated by the above formula (19) because the development bias Vdc is constant. However, for example, when the development 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.

[0266] Next, the supply roller deterioration level calculation unit 84 calculates a total supply roller deterioration level ηt, which is an index showing the degree of deterioration of the supply roller 43 since the start of use of the developing device 4 (supply roller 43) (S809). That is, the supply roller deterioration level calculation unit 84 adds (integrates) the calculated section supply roller deterioration level ηnow to the cumulative supply roller deterioration level ηr since the start of use of the developing device 4 (supply roller 43), which is stored in the memory 150, as shown in the following formula (20).

[0267] In this way, the total supply roller deterioration degree ηt is calculated. Then, the supply roller deterioration degree calculation unit 84 updates the calculated total supply roller deterioration degree ηt as a new cumulative supply roller deterioration degree ηr and stores it in the memory 150. ηt=ηnow+ηr (20)

[0268] Next, the supply roller deterioration level calculation unit 84 calculates the supply roller remaining life ηJ from the supply roller deterioration level threshold ηth, which is determined in advance and stored in the memory 150, and the calculated total supply roller deterioration level ηt, using the following formula (21) (S810). The supply roller deterioration level calculation unit 84 may update and store the calculated supply roller remaining life ηJ in the memory 150. ηJ [%] = (1 - ηt / ηth) × 100 ... (21)

[0269] In this embodiment, the supply roller degradation threshold value ηth is set to a value at which solid image tracking failure may occur even when the remaining toner amount is 100%. Therefore, when the remaining supply roller life ηJ reaches 0%, solid image tracking failure may occur even if the toner in the developing device 4 has not been consumed.

[0270] Next, the control unit 220 determines whether the supply roller remaining life ηJ calculated by the supply roller deterioration level calculation unit 84 is 0% or less (S811). If the control unit 220 determines 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 determines in S811 that the supply roller remaining life ηJ is 0% or less, it controls the execution of a process to notify the user of information regarding the life of the developing device 4 (S813). In this case, it can be determined that the supply roller 43 has reached the end of its life. Then, the control unit 220 ends the print operation (S812). -Detection of remaining toner amount-

[0271] Next, the detection (calculation) of the remaining amount of toner will be described.

[0272] 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 acquired in S805 or S806 by either the first video count unit 71 or the second video count unit 83 may be used in common to calculate the deterioration level of the supply roller 43 and the remaining toner amount.

[0273] Next, the remaining toner amount calculation unit 72 calculates a total video count value VCt, which is the cumulative value of the video count value since the start of use of the developing device 4 (process cartridge 8) (S814). 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 cumulative video count value VCr since the start of use of the developing device 4 (process cartridge 8), as shown in the following equation (22). In this way, the total video count value VCt is calculated. Then, the remaining toner amount calculation unit 72 updates the calculated total video count value VCt and stores it in the memory 150 as a new cumulative video count value VCr. VCt=VCr+VCn (22)

[0274] Next, the remaining toner 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 remaining toner amount calculation unit 72 reads 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 memory 150. The table data in Table 15 is an example of information showing the relationship between the supply roller remaining life ηJ and the video count threshold correction coefficient ζ. As shown in Table 15, the video count threshold correction coefficient ζ is made smaller as the supply roller remaining life ηJ is shorter.

[0275] Next, the remaining toner amount calculation unit 72 calculates the remaining toner amount TJ in the developing device 4 using 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, using the following equation (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)

[0276] 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 the execution of a process to notify the user of information regarding the life of the developing device 4 (S818). 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). - Transition of the video count threshold after correction -

[0277] 24 is a graph showing the change in the corrected video count threshold (VCth×ζ) with a decrease in the remaining supply roller life ηJ in detecting the life of the developing device 4 in this embodiment. In FIG. 24, the horizontal axis represents the remaining supply roller life ηJ, and the vertical axis represents the video count threshold correction coefficient ζ. Multiplying the value on the vertical axis in FIG. 24 by the corrected video count threshold VCth gives the corrected video count threshold VCth×ζ.

[0278] In this embodiment, unlike the first embodiment, the corrected video count threshold value (VCth x ζ) is set to become 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 until the remaining amount of toner reaches 0%, and information regarding the life of the developing device 4 is notified to the user. <Calculation Example>

[0279] 25 is a graph showing the relationship between the total supply roller deterioration level ηt and the total video count value VCt at the timing when solid image tracking failure occurs in the image forming apparatus 100 of this embodiment. The horizontal axis represents the total supply roller deterioration level ηt, and the vertical axis represents the total video count value VCt. The solid line in FIG. 25 shows the timing when solid image tracking failure occurs, which was determined by experiment.

[0280] 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). Specifically, when the total supply roller deterioration degree ηt is 2.5×10 ７ In the following cases, the total video count value VCt at which poor solid tracking occurs is 1.0×10 ７ On the other hand, the total supply roller deterioration degree ηt is 2.5×10 ７ When the total video count value VCt exceeds 1.0×10, poor solid tracking occurs. ７ and becomes smaller as the total supply roller deterioration degree ηt increases. ７ If it exceeds this value, poor solid image tracking will occur even when the total video count value VCt is 0 (i.e., the remaining toner amount is 100%).

[0281] In this embodiment, the supply roller deterioration level threshold value ηth is set to 5.0×10 ７ and the video count threshold VCth is set 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 ６Furthermore, when the remaining life ηJ of the supply roller 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 x ζ) calculated in this manner is overlaid on the graph of FIG. 25, the graph shown in FIG. 26 results. The corrected video count threshold (VCth x 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 end of the life of the developing device 4 when the remaining toner amount drops below 0% (also referred to as "toner out" here) before poor solid tracking performance occurs. <Modification 10>

[0282] In this embodiment, the video count threshold correction coefficient ζ is set as shown in Table 15. However, as shown in Table 16, the remaining life ηJ of the supply roller may be divided into smaller categories, and a corresponding video count threshold correction coefficient ζ may be set for each category.

[0283] 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 shown in Table 16 is used, it is possible to notify the user of information regarding the lifespan of the developing device 4 due to toner out closer to the point at which poor solid tracking occurs than when the video count threshold correction coefficient ζ shown in Table 15 shown in FIG. 26 is used. The finer the increment width of the supply roller remaining life ηJ, the more accurate the notification of information regarding the lifespan of the developing device 4 due to toner out will be, but this will require a larger capacity for the memory 150. Therefore, the increment width of the supply roller remaining life ηJ may be set appropriately depending on, for example, the capacity of the memory 150.

[0284] Furthermore, 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).

[0285] In this case, it is possible to suppress a sudden change in the video count threshold correction coefficient ζ, and to more accurately notify information about the life of the developing device 4. <Modification 11>

[0286] In this embodiment, the remaining toner amount is detected using a video counting method, but this is not limiting. The remaining developer amount detection method can be, for example, a video counting method, a capacitance method, a light transmission method, or any other available method. The capacitance method acquires developer amount information using electrodes whose detected capacitance changes in response to changes in the amount of developer inside the developing device 4. The light transmission method acquires developer amount information based on changes in the light reception state of the light reception unit (e.g., whether or not light is received, the amount of light received, and the time for light reception). Other methods, such as a weight detection method, can be used to acquire developer amount information based on changes in the weight of the developing device 4. These other remaining developer amount detection methods, for example, known methods, can be used as appropriate. <Variation 12>

[0287] In this embodiment, the method of the first embodiment is used as the method for calculating the deterioration level of the supply roller 43, but the methods of the second to fourth embodiments may also be used.

[0288] 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.

[0289] 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 total video count value VCt does not exceed 2.5×10, information about the life of the developing device 4 due to toner out will not be notified. The maximum supply roller deterioration level threshold value ηth for preventing solid followability failure from occurring at any time point of the total video count value VCt before toner out is 2.5×10 ７In the area surrounded by dots in Figure 28(a), the developing device 4 can be used without causing poor solid image tracking. 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 just before the area surrounded by dots.

[0290] Next, Example 2 will be described with reference to FIG. 28B. FIG. 28B 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 level threshold value ηth for preventing solid image follow-up failure from occurring at any total video count value VCt before 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 poor solid image tracking. Nevertheless, if 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.

[0291] In contrast, 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 image tracking occurs, so the developing device 4 can be used without poor solid image tracking. 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 end of the life of the supply roller 43 or toner out can be delayed compared to Examples 1 and 2 shown in Figs. 28(a) and 28(b). Therefore, this embodiment allows for more effective use of the supply roller 43 and toner.

[0292] 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 able to determine 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 other acquisition unit 70 and a preset threshold value (video count threshold value VCt), and is also able to correct the threshold value based on information regarding the degree of deterioration of the supply member 43, and the control unit 220 makes 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.

[0293] As described above, according to this embodiment, it is possible to notify the user of information regarding the lifespan of the developing device 4 before a solid image tracking failure occurs. At the same time, this embodiment can prevent the user from being notified of information regarding the lifespan of the developing device 4 due to toner being out even when there is sufficient toner. [Embodiment 6]

[0294] 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 assigned the same reference numerals as those of embodiment 1, and detailed descriptions thereof will be omitted. <Outline of this embodiment>

[0295] Similar to the fifth embodiment, the present embodiment aims to provide a user with a warning about the end of life of the developing device 4 at a more appropriate timing before a solid image tracking failure 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. <Detection of the End of Life of the Developing Device>

[0296] Next, detection of the lifespan of the developing device 4 in this embodiment will be described. Fig. 29 is a flowchart showing an outline of the procedure for detecting the lifespan of the developing device 4 in this embodiment, focusing on calculating the deterioration level of the supply roller 43 and calculating the remaining amount of toner. The process according to the flowchart in Fig. 29 is executed by the control unit 220 (mainly the remaining toner amount detection unit 70 and the supply roller lifespan detection unit 80). Note that the image forming apparatus 100 may also be configured to detect the lifespan of the developing device 4 based on the detection result of the remaining lifespan GJ of the developing roller, as in the above-described embodiment. -Detection of remaining amount of toner-

[0297] First, the detection (calculation) of the remaining amount of toner will be described.

[0298] 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 step), 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).

[0299] Next, the remaining toner amount calculation unit 72 calculates a total video count value VCt, which is the cumulative value of the video count value since the start of use of the developing device 4 (process cartridge 8) (S905). 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 cumulative video count value VCr since the start of use of the developing device 4 (process cartridge 8), as shown in the following equation (24). In this way, the total video count value VCt is calculated. Then, the remaining toner amount calculation unit 72 updates the calculated total video count value VCt and stores it in the memory 150 as a new cumulative video count value VCr. VCt=VCr+VCn (24)

[0300] 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, using 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)

[0301] 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 regarding the life of the developing device 4 (S909). 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). - Calculation of the Deterioration Level of the Supply Roller (Detection of the Life of the Supply Roller) -

[0302] Next, detection of the life of the supply roller 43 (calculation of the deterioration level of the supply roller 43) will be described.

[0303] When a print signal (job information) is input (S901), the control unit 220 starts the print operation (job) (S902). Furthermore, upon start of the print operation, the control unit 220 determines the supply bias Vrs based on the detection results (particularly temperature in this embodiment) 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 −350 V.

[0304] Subsequently, 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 for the printing operation (S911). If the supply bias application start timing for the printing operation is tS and the supply bias application end timing for the printing operation is tE, the supply bias application time tnow for the printing operation can be expressed by the following equation (26): tnow=tE-tS (26)

[0305] 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 (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 the printing rate for the printing operation, based on the video count value VCn. The supply roller deterioration level calculation unit 84 determines a deterioration correction coefficient ε based on the section printing rate γnow (S912). In this embodiment, the supply roller deterioration level calculation unit 84 reads and determines the deterioration correction coefficient ε corresponding to the section printing rate γnow from table data shown in Table 2 (see Example 1), which is preset and stored in memory 150. The video count value VCn acquired 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 level of the supply roller 43 and the remaining toner amount.

[0306] 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, using the following formula (27) (S913): ηnow=tnow×|Vrs|×ε (27)

[0307] In this embodiment, the development bias Vdc is constant, so the deterioration degree ηnow of the section supply roller is calculated by the above formula (27). However, for example, when the development 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.

[0308] Next, the supply roller deterioration level calculation unit 84 calculates a total supply roller deterioration level ηt, which is an index showing the degree of deterioration of the supply roller 43 since the start of use of the developing device 4 (supply roller 43) (S914). That is, the supply roller deterioration level calculation unit 84 adds (integrates) the calculated section supply roller deterioration level ηnow to the cumulative supply roller deterioration level ηr since the start of use of the developing device 4 (supply roller 43), which is stored in the memory 150, as shown in the following formula (28).

[0309] In this way, the total supply roller deterioration degree ηt is calculated. Then, the supply roller deterioration degree calculation unit 84 updates the calculated total supply roller deterioration degree ηt as a new cumulative supply roller deterioration degree ηr and stores it in the memory 150. ηt=ηnow+ηr (28)

[0310] Next, the supply roller deterioration level calculation unit 84 determines a supply roller deterioration level 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 level calculation unit 84 reads and determines the supply roller deterioration level threshold correction coefficient μ corresponding to the remaining toner amount TJ from table data shown in Table 18, which is preset and stored in 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 level 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.

[0311] Next, the supply roller deterioration level calculation unit 84 calculates the supply roller remaining life ηJ from the supply roller deterioration level threshold ηth that is preset and stored in the memory 150, the determined supply roller deterioration level threshold correction coefficient μ, and the calculated total supply roller deterioration level ηt, using the following formula (29) (S916). The supply roller deterioration level 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)

[0312] Next, the control unit 220 determines whether the supply roller remaining life ηJ calculated by the supply roller deterioration level calculation unit 84 is 0% or less (S917). If the control unit 220 determines 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 determines in S917 that the supply roller remaining life ηJ is 0% or less, it controls the execution of a process to notify the user of information regarding the life of the developing device 4 (S918). This is because in this case, it can be determined that the supply roller 43 has reached the end of its life. Then, the control unit 220 ends the print operation (S908). <Calculation Example>

[0313] The relationship between the total supply roller deterioration level 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 the same as that of the third embodiment shown in the graph of FIG. 25. In this embodiment, as in the third embodiment, the supply roller deterioration level threshold value ηth is set to 5.0×10 ７ and the video count threshold VCth is set 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 ７Furthermore, when the remaining toner amount TJ is between 42% and 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 ７ When the thus calculated corrected supply roller deterioration level threshold (ηth×μ) is overlaid on the graph of FIG. 25, the graph of FIG. 30 results. The corrected supply roller deterioration level threshold (ηth×μ) shown in FIG. 30 does not exceed the point at which poor solid tracking performance occurs. Therefore, it is possible to notify the user of information regarding the lifespan of the developing device 4 due to toner out before poor solid tracking performance occurs.

[0314] Note that the present embodiment can also be modified in the same manner as the modified example described in the fifth embodiment.

[0315] 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 able to determine whether the developing device 4 has reached the end of its life based on information regarding the degree of deterioration of the supply member 43 and a preset threshold value (supply roller deterioration degree threshold value ηth), and is able to correct the threshold value based on the information regarding the amount of developer, and the control unit 220 makes the correction so that the degree of deterioration 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.

[0316] As described above, in the third embodiment, the toner remaining amount threshold (video count threshold VCth) is corrected in accordance with the deterioration level of the supply roller 43, whereas in this embodiment, the supply roller deterioration level threshold ηth is corrected in accordance with the remaining toner amount. The configuration of this embodiment also provides the same effects as in the third embodiment. [Others]

[0317] Although the present invention has been described above with reference to specific embodiments, the present invention is not limited to the above-described embodiments.

[0318] In the above-described embodiment, the image forming apparatus is a tandem (in-line) 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.

[0319] In the above-described embodiment, the image forming apparatus has a configuration in which the process cartridge is detachably attached to the apparatus main body. However, the present invention is not limited to this. For example, the image forming apparatus may have a configuration in which the development unit (developing device) and the drum unit (e.g., including a photosensitive member, a charging device, and a cleaning device) are each detachably attached to the apparatus main body. Furthermore, the image forming apparatus may have a toner supply type in which a toner supply container (such as a toner cartridge, toner bottle, or toner pack) containing toner to be replenished 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 form images with the toner supply container connected to the process cartridge (or developing device), or may be configured to form images with the toner supply container removed after toner is replenished to the developing device.

[0320] Furthermore, the life of the photosensitive member may be separately set in order to detect the life of the process cartridge.

[0321] Furthermore, the notification of information to the user is not limited to being by displaying a message or the like, but may also be by emitting light (such as a warning light turning on or flashing) or sound (such as a warning sound or voice).

[0322] Furthermore, information about 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 that can be used to calculate the printing rate can also be considered information about the printing rate.

[0323] Furthermore, the information regarding the deterioration level of the supply roller is not limited to the value calculated by the method of the above embodiment, as long as it can be used as an index value indicating the degree of deterioration of the supply roller due to use. For example, information calculated based on the degree of deterioration, such as the remaining life, can also be considered as information regarding the deterioration level.

[0324] Furthermore, in the above embodiment, the developing bias is assumed to be constant, but the developing bias may be changed depending on, for example, the environment in which the image forming apparatus is used.

[0325] According to the present invention, there is provided an image forming apparatus that acquires information regarding the degree of deterioration of a supply member.

[0326] The present invention is not limited to the above-described embodiments, and various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the following claims are appended to apprise the public of the scope of the present invention.

[0327] This application claims priority based on Japanese Patent Application No. 2023-122072, filed on July 26, 2023, the entire contents of which are incorporated herein by reference.

Claims

1. An image forming apparatus which performs image formation by transferring a developer image onto a recording material to form an image on the recording material, comprising: a rotatable image carrier which carries a developer image; a developing device which supplies developer to a 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 which supplies developer to the surface of the image carrier, and a rotatable supply member which has an elastic layer containing an ion conductive agent and comes into contact with the developing member to supply developer to the developing member; a first application unit which applies a development voltage to the developing member; a second application unit which applies a supply voltage to the supply member; an acquisition unit which acquires information regarding a printing rate of an image formed in the image formation; a control unit which acquires information regarding a deterioration degree 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 was applied to the supply member, and information regarding the printing rate; and a memory unit which stores the information regarding the deterioration degree acquired by the control unit.

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 relating to the degree of deterioration.

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

4. An image forming apparatus as described in claim 1, wherein 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 image forming apparatus as described in claim 1, further comprising an environmental detection unit that detects at least one of temperature and humidity, and the control unit is capable of changing the supply voltage applied to the supply member based on the detection result of the environmental detection unit.

6. The image forming apparatus of claim 1, wherein the image formation includes an image forming operation in which a developer image is formed on the image carrier and a non-image forming operation in which a developer image is not formed on the image carrier, and 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 is applied to the supply member, and information regarding the printing rate.

7. An image forming apparatus as described in 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 between the supply voltage and the developing voltage is opposite during the image forming operation and during at least a portion of the non-image forming operation.

8. The image forming apparatus of claim 1, wherein the acquisition unit acquires information regarding the printing rate for each region obtained by dividing the image forming area on the image carrier in a main scanning direction approximately perpendicular to the direction of movement of the surface of the image carrier, and the control unit acquires information regarding the degree of deterioration of the supply member for each region based on the information regarding the printing rate for each region.

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 information relating to the degree of deterioration for each of the areas.

10. An image forming apparatus as described in claim 9, wherein 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. The image forming apparatus according to 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 or not the developing device has reached the end of its life based on the information regarding the difference.

12. The image forming apparatus of 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 that is the largest difference among the differences between multiple adjacent areas.

13. An image forming apparatus as described in claim 1, further comprising a separate acquisition unit that acquires information regarding the amount of developer in the developing device, wherein the control unit is capable of determining whether the developing device has reached the end of its life based on the information regarding the amount of developer in the developing device acquired by the separate acquisition unit and a preset threshold value, and is capable of correcting the threshold value based on information regarding the degree of deterioration, wherein 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 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. An image forming apparatus as described in claim 1, further comprising a separate acquisition unit which acquires information regarding the amount of developer in the developing device, wherein the control unit is capable of determining whether the developing device has reached the end of its life based on the information regarding the degree of deterioration and a preset threshold value, and is capable of correcting the threshold value based on the information regarding the amount of developer, and wherein 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 regarding the amount of developer is a second amount less than the first amount than when the amount of developer indicated by the information regarding the amount of developer is a first amount.

15. An image forming apparatus as described in any one of claims 2, 9, 13, and 14, 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. The image forming apparatus according to any one of claims 1 to 14, wherein the memory unit is detachable from the main body of the image forming apparatus together with the developing device.

17. An image forming apparatus according to any one of claims 1 to 14, wherein the acquisition unit acquires information regarding the printing rate based on image information of an image formed during the image formation.

18. An image forming apparatus according to any one of claims 1 to 14, wherein the developing member contacts the image carrier to form a developing section, and supplies developer to the image carrier in the developing section.

19. An image forming apparatus according to any one of claims 1 to 14, wherein the developer is a non-magnetic one-component developer.

Images