Image forming apparatus

Abstract

To provide an image forming apparatus that can form good images for a long period by more appropriately controlling voltage to be applied to a supply member according to the degree of deterioration of the supply member.SOLUTION: An image forming apparatus 100 has: an acquisition unit 82 that acquires information on the printing rate of an image formed in image formation; and a control unit 220 that acquires information on the degree of deterioration of a supply member 43 on the basis of information on supply voltage applied to the supply member 43, information on the time when the supply voltage is applied to the supply member 43, and the information on the printing rate. The control unit 220 performs control, on the basis of the information on the degree of deterioration, to change the potential difference between the supply voltage to be applied to the supply member 43 when a developer image is formed on an image carrier 1 in the image formation, and developing voltage to be applied to a developing member 42.SELECTED DRAWING: Figure 9

Description

[Technical field]

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

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

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

[0004] In such a developing device, a predetermined potential difference is generally provided between the developing roller and the supply roller in order to stably supply toner to the developing roller.

[0005] Patent Document 1 discloses a technique for changing the potential difference between a developing roller and a supply roller in accordance with the amount of toner remaining in a developing device in order to suppress a decrease in image density over time. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 07-005765 Summary of the Invention [Problem to be solved by the invention]

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

[0008] The inventors have found that, in the above-mentioned supply roller, when the toner contained inside (inside the cells) of the foamed elastic layer moves to the developing roller, the conductive agent added to the material of the foamed elastic layer tends to be carried away. This tendency is particularly noticeable when images with a high printing ratio are continuously formed. This is due to the following reasons. That is, when an image with a high printing ratio is formed, the amount of toner consumed from the developing roller to the photoconductor increases. In this case, when focusing on the toner contained inside the foamed elastic layer of the supply roller, the amount of toner supplied from the supply roller to the developing roller increases when the printing ratio is high compared to when the printing ratio is low. Therefore, when an image with a high printing ratio is formed and the toner inside the foamed elastic layer of the supply roller is replaced, the conductive agent added to the material of the foamed elastic layer of the supply roller is carried away together with the toner, and the amount of conductive agent remaining on the supply roller is easily reduced. And, this phenomenon does not increase significantly as the printing ratio increases. Therefore, the degree of deterioration of the supply roller varies depending on the usage conditions of the image forming apparatus by the user. Conventionally, no effort has been made to focus on this point and obtain information regarding the degree of deterioration of the supply roller.

[0009] As the supply roller deteriorates, image defects such as poor solid-color tracking can occur. Poor solid-color tracking is an image defect in which, when forming a solid image, the image density at the trailing edge of a page is lower than that at the leading edge, resulting in uneven density. This occurs because, while a sufficient amount of toner is supplied to the developing roller at the leading edge of a page, as the supply roller deteriorates (increasing electrical resistance), the amount of toner supplied to the developing roller at the trailing edge of a page gradually falls short.

[0010] Such image defects can be suppressed by increasing the absolute value of the voltage applied to the supply roller (i.e., increasing the potential difference between the development roller and the supply roller) and thereby increasing the amount of toner supplied to the development roller. However, unless information regarding the deterioration degree of the supply roller is accurately acquired and an appropriate voltage is applied to the supply roller in accordance with the deterioration degree of the supply roller, this will actually accelerate the deterioration of the supply roller, making it difficult to use the supply roller for a long period of time. Conventionally, the degree of deterioration of the supply roller due to the aforementioned decrease in conductive agent has not been taken into consideration, so it can be difficult to apply an appropriate voltage to the supply roller in accordance with the deterioration degree of the supply roller.

[0011] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to make it possible to form good images for a long period of time by more appropriately controlling the voltage applied to the supply member in accordance with the degree of deterioration of the supply member. [Means for solving the problem]

[0012] The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention relates to an image forming apparatus for forming an image on a recording material by transferring a developer image onto the recording material, the image forming apparatus comprising: a rotatable image carrier for carrying a developer image; a developing device for supplying a developer to 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 for supplying the developer to the surface of the image carrier, and a rotatable supply member having an elastic layer containing an ion conductive agent and contacting the developing member to supply the developer to the developing member; a first application unit for applying a development voltage to the developing member; a second application unit for applying a supply voltage to the supply member; and a printing unit for printing the image formed in the image formation. an acquisition unit that acquires information regarding a deterioration degree of the supply member based on information regarding the supply voltage applied to the supply member, information regarding the time for which the supply voltage was applied to the supply member, and information regarding the printing rate; a control unit that acquires information regarding the deterioration degree of the supply member based on information regarding the supply voltage applied to the supply member, information regarding the time for which the supply voltage was applied to the supply member, and information regarding the printing rate; and a memory unit that stores the information regarding the deterioration degree acquired by the control unit, wherein the control unit controls to change the potential difference between the supply voltage applied to the supply member and the developing voltage applied to the developing member when a developer image is formed on the image carrier in the image formation, based on the information regarding the deterioration degree.

[0013] According to another aspect of the present invention, in an image forming apparatus for forming an image on a recording material by transferring a developer image onto the recording material, the image forming apparatus includes a rotatable image carrier for carrying a developer image, and a developing device for supplying a developer to a surface of the image carrier to form a developer image on the surface of the image carrier, the developing device having a rotatable developing member for supplying the developer to the surface of the image carrier, and a rotatable supply member having an elastic layer containing an ion conductive agent and contacting the developing member to supply the developer to the developing member, a first application unit for applying a development voltage to the developing member, a second application unit for applying a supply voltage to the supply member, an acquisition unit for acquiring information regarding a printing rate of an image formed in the image formation, information regarding the supply voltage applied to the supply member, and a voltage applied to the supply member in front of the supply member. An image forming apparatus is provided, comprising: a control unit that acquires information regarding the degree of deterioration of the supply member based on information regarding the time when the supply voltage is applied and information regarding the printing rate; and a memory unit that stores the information regarding the degree of deterioration acquired by the control unit, 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 controlling to perform a recovery operation during the non-image forming operation in which the polarity of the potential difference of the supply voltage applied to the supply member relative to the developing voltage applied to the developing member is opposite to that during the image forming operation, and the control unit controls to perform the recovery operation based on the information regarding the degree of deterioration. Effect of the Invention

[0014] According to the present invention, by more appropriately controlling the voltage applied to the supplying member in accordance with the degree of deterioration of the supplying member, it becomes possible to form good images for a long period of time. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic cross-sectional view of an image forming apparatus. [Diagram 2] FIG. 2 is a schematic cross-sectional view of an image forming unit. [Diagram 3]FIG. 2 is a schematic block diagram of a control configuration of the image forming apparatus. [Figure 4] 4 is a functional block diagram of a control unit related to detection of the life of a developing device. FIG. [Diagram 5] FIG. 11 is a flowchart showing an outline of a procedure for detecting the end of life of a developing device. [Figure 6] FIG. 11 is a flowchart showing a procedure for calculating the remaining amount of toner. [Figure 7] FIG. 11 is a flowchart showing a procedure for calculating the life of a developing roller. [Figure 8] FIG. 11 is a graph showing verification results of characteristics of the supply roller. [Figure 9] FIG. 4 is a flowchart showing an outline of a procedure of a print operation in the first embodiment. [Figure 10] 4 is a schematic diagram showing the application timing of a supply bias in the first embodiment. FIG. [Figure 11] FIG. 11 is a flowchart showing an outline of a procedure of a print operation in the second embodiment. [Figure 12] FIG. 11 is a flowchart showing an outline of a procedure of a print operation in the third embodiment. [Figure 13] FIG. 13 is a flowchart showing an outline of the procedure of a print operation in the fourth embodiment. [Figure 14] FIG. 11 is a graph showing verification results of characteristics of the supply roller. [Figure 15(a)] FIG. 13 is a flowchart showing an outline of the procedure of a print operation in the fifth embodiment. [Figure 15(b)] FIG. 13 is a flowchart showing an outline of the procedure of a print operation in the fifth embodiment. [Figure 16] FIG. 13 is a schematic diagram showing the supply bias application timing in the fifth embodiment. [Figure 17] 13 is a graph showing a schematic diagram of the change in deterioration degree of the supply roller in Example 5. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, the image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

[0017] [Example 1] <Overall Configuration and Operation of Image Forming Apparatus> 1 is a schematic cross-sectional view of an image forming apparatus 100 according to this embodiment. The image forming apparatus 100 according to this embodiment is a tandem-type full-color laser beam printer employing an intermediate transfer method, capable of forming a full-color image on a sheet-shaped recording material P by electrophotography.

[0018] The image forming apparatus 100 has a plurality of image forming units (image forming stations) SY, SM, SC, and SK that form toner images of the respective colors of yellow (Y), magenta (M), cyan (C), and black (K). The configurations of the image forming units SY, SM, SC, and SK are substantially the same except that the colors of toners 90Y, 90M, 90C, and 90K contained in the developing device 4 described later are different. Elements having the same or corresponding functions or configurations provided for each color may be generally described by omitting the Y, M, C, and K at the end of the reference numerals indicating that the elements are provided for any one of the colors. FIG. 2 is a schematic cross-sectional view showing one representative image forming unit S. The image forming unit S is configured to include a photosensitive drum 1, a charging roller 2, an exposure device 3, a developing device 4, a primary transfer roller 51, and a drum cleaning device 5, which will be described later. In this embodiment, the exposure device 3 is configured as one unit common to each image forming unit S, but may be provided for each image forming unit S.

[0019] The photosensitive drum 1, which is a rotatable drum-type (cylindrical) electrophotographic photosensitive member (photosensitive member) serving as an image carrier, is rotated around its rotation axis in the direction of arrow R1 in the figure (counterclockwise direction) by a drive motor (not shown) provided in a drive unit 110 (FIG. 3(a)). In this embodiment, the photosensitive drum 1 is rotated at a peripheral speed (rotation speed, process speed) of, for example, 140 mm / sec.

[0020] The surface (outer circumferential surface) of the rotating photosensitive drum 1 is uniformly charged to a predetermined potential of a predetermined polarity (negative polarity in this embodiment) by the charging roller 2, which is a roller-type charging member (charging device) serving as a charging means. In this embodiment, the charging roller 2 is a conductive roller having a conductive rubber layer provided on a core metal. The charging roller 2 is disposed in contact with the surface of the photosensitive drum 1. The rotation axis direction of the photosensitive drum 1 and the rotation axis direction of the charging roller 2 are approximately parallel. The charging roller 2 is pressed against the photosensitive drum 2 with a predetermined pressure, and rotates in accordance with the rotation of the photosensitive drum 1. During charging, a predetermined charging bias (charging voltage) of the same polarity as the charging polarity (negative polarity in this embodiment) of the photosensitive drum 1 is applied to the charging roller 2 by a charging power source 121 (FIG. 3(b)) serving as a charging bias application unit. In this embodiment, for example, when a DC voltage of −1150 V is applied to the charging roller 2 during image formation (charging process), the surface potential of the photosensitive drum 1 becomes −500 V.

[0021] The surface of the charged photosensitive drum 1 is scanned and exposed by an exposure device 3 as an exposure means in response to an image signal (image information), and an electrostatic latent image (electrostatic image) in response to the image signal is formed on the photosensitive drum 1. The exposure device 3 irradiates the surface of the photosensitive drum 1 for each color with a laser beam in response to the image signal of each color component. As a result, an electrostatic latent image in response to the image signal of each color component is formed on the surface of the photosensitive drum 1 for each color. The image signal is input to the image forming apparatus 100 in response to a request from a user (operator), for example, from an external device (host device) 300 (FIG. 3(a)), such as an image reading device (not shown) or a personal computer connected to the image forming apparatus 100 so as to be able to communicate with the image forming apparatus 100.

[0022] The electrostatic latent image formed on the photosensitive drum 1 is developed (visualized) by supplying toner 90, which is a developer, by the developing device 4 as a developing means, and a toner image (toner image, developer image) is formed on the photosensitive drum 1. In this embodiment, the developing device 4 uses toner 90, which is a non-magnetic one-component developer, as the developer. As shown in FIG. 2, the developing device 4 has a developer container 41, a developing roller 42, a supply roller 43, and a regulating blade 44. The developing roller 42 contacts the surface of the photosensitive drum 1 during image formation (development) to form a developing section, and supplies toner 90 to the photosensitive drum 1 in the developing section. In this embodiment, the image forming apparatus 100 has a contact / separation mechanism that contacts and separates the developing roller 42 from the photosensitive drum 1. In this embodiment, when the image forming apparatus 100 stops operating, the contact / separation mechanism separates the developing roller 42 from the photosensitive drum 1 and stops the developing roller 42. Then, at least during image formation (development), the developing roller 42 is brought into contact with the photosensitive drum 1 by this contact / separation mechanism. For example, when the rotational drive of the photosensitive drum 1 is started in response to the start of an image formation operation or the like, the rotational drive of the developing roller 42 is started in a state in which the developing roller 42 is separated from the photosensitive drum 1. After that, at a predetermined timing, the contact / separation mechanism operates so that the developing roller 42 contacts the photosensitive drum 1 at a predetermined contact width by a biasing means (not shown). In this embodiment, the toner 90 charged to the same polarity (negative polarity in this embodiment) as the charging polarity of the photosensitive drum 1 is attached to the exposed portion (image portion, print portion) on the photosensitive drum 1, the absolute value of the potential of which has been reduced by being exposed after being uniformly charged (reverse development method). In this embodiment, the normal charging polarity of the toner 90, which is the main charging polarity of the toner 90 during development (charging polarity for developing an electrostatic latent image), is negative polarity. The developing device 4 will be described in further detail later.

[0023] An intermediate transfer belt 53, which is an endless belt serving as an intermediate transfer body, is disposed so as to face the four photosensitive drums 1. The intermediate transfer belt 53 is stretched around a drive roller 52a, a tension roller 52b, and a secondary transfer opposing roller 52c serving as a plurality of tension rollers (support rollers), and is stretched with a predetermined tension. The intermediate transfer belt 53 rotates (moves around) in the direction of arrow R2 (clockwise direction) in the figure as the drive roller 52a is driven to rotate by a drive motor (not shown) provided in the drive unit 110 (FIG. 3(a)). On the inner peripheral surface side of the intermediate transfer belt 53, primary transfer rollers 51Y, 51M, 51C, and 51K, which are roller-type primary transfer members (primary transfer devices) serving as primary transfer means, are disposed corresponding to the respective photosensitive drums 1Y, 1M, 1C, and 1K. The primary transfer roller 51 presses the intermediate transfer belt 53 toward the photosensitive drum 1 to form a primary transfer portion (primary transfer nip) N1, which is a contact portion between the photosensitive drum 1 and the intermediate transfer belt 53. The toner image formed on the photosensitive drum 1 is electrostatically transferred (primary transfer) onto the rotating intermediate transfer belt 53 as a transfer target by the action of the primary transfer roller 51 at the primary transfer portion N1. During the primary transfer, a predetermined primary transfer bias (primary transfer voltage), which is a DC voltage of the opposite polarity (positive polarity in this embodiment) to the normal charging polarity of the toner 90, is applied to the primary transfer roller 51 by a primary transfer power source 125 (FIG. 3(b)) as a primary transfer bias application portion. For example, when a full-color image is formed, the toner images of each color of yellow, magenta, cyan, and black formed on each photosensitive drum 1 are transferred to the intermediate transfer belt 53 in a superimposed manner in sequence.

[0024] A secondary transfer roller 6, which is a roller-type secondary transfer member (secondary transfer device) serving as a secondary transfer means, is disposed at a position facing the secondary transfer opposing roller 52c on the outer peripheral surface side of the intermediate transfer belt 53. The secondary transfer roller 6 comes into contact with the secondary transfer opposing roller 52c via the intermediate transfer belt 53 and is pressed toward the secondary transfer opposing roller 52c to form a secondary transfer portion (secondary transfer nip) N2, which is a contact portion between the intermediate transfer belt 53 and the secondary transfer roller 6. The toner image formed on the intermediate transfer belt 53 is transferred (secondarily transferred) by the action of the secondary transfer roller 6 at the secondary transfer portion N2 onto a recording material P, which is a transfer target material being conveyed while being sandwiched between the intermediate transfer belt 53 and the secondary transfer roller 6, by the action of the secondary transfer roller 6. During the secondary transfer, a predetermined secondary transfer bias (secondary transfer voltage), which is a DC voltage of the polarity opposite to the normal charging polarity of the toner 90 (positive polarity in this embodiment), is applied to the secondary transfer roller 6 by a secondary transfer power source 126 (FIG. 3(b)) as a secondary transfer bias application unit. The secondary transfer opposing roller 52c as a secondary transfer opposing member (opposing electrode) is electrically grounded. Note that an inner roller corresponding to the secondary transfer opposing roller 52c in this embodiment may be used as the secondary transfer member, and an outer roller corresponding to the secondary transfer roller 6 in this embodiment may be used as the secondary opposing member. In this case, a secondary transfer bias of the same polarity as the normal charging polarity of the toner 90 is applied to the inner roller, and the outer roller is electrically grounded. Recording materials (transfer materials, recording media, sheets) P ​​such as recording paper and plastic sheets are sent out one by one from a cassette 8 as a recording material storage unit by a feed roller 9 as a feed member, and are transported to a pair of registration rollers 10 as a transport member. This recording material P is conveyed by a pair of registration rollers 10 to a secondary transfer portion N2 in synchronization with the toner image on the intermediate transfer belt 53.

[0025] The recording material P onto which the toner image has been transferred is conveyed to a fixing device 7 serving as a fixing means. The fixing device 7 applies pressure and heat to the recording material P carrying the unfixed toner image, thereby fixing (melting and bonding) the toner image onto the recording material P. A heater (not shown) provided in the fixing device 7 is supplied with power from a fixing power source 127 (FIG. 3(b)). The recording material P onto which the toner image has been fixed is discharged (output) as an image-formed product onto a tray 102 serving as a discharge unit provided outside an apparatus main body 101 of the image forming apparatus 100.

[0026] On the other hand, the toner remaining on the photosensitive drum 1 after the primary transfer (primary transfer residual toner) is removed from the photosensitive drum 1 and collected by a drum cleaning device 5 as a photosensitive body cleaning means. In this embodiment, the drum cleaning device 5 has a cleaning blade as a cleaning member arranged in contact with the surface of the photosensitive drum 1, and a cleaning container. The drum cleaning device 5 scrapes and removes the primary transfer residual toner from the surface of the rotating photosensitive drum 1 by the cleaning blade, and stores it in the cleaning container. The image forming apparatus 100 can also adopt a cleanerless system that does not have a dedicated cleaning member for cleaning the photosensitive drum 1. In that case, the primary transfer residual toner can be collected by, for example, the developing device 4. In addition, a belt cleaning device 54 as an intermediate transfer body cleaning means is provided on the outer circumferential surface side of the intermediate transfer belt 53. The belt cleaning device 54 is arranged downstream of the secondary transfer portion N2 and upstream of the primary transfer portion N1 (the most upstream primary transfer portion N1Y) in the rotation direction (movement direction of the surface) of the intermediate transfer belt 53. The toner remaining on the intermediate transfer belt 53 after the secondary transfer (secondary transfer residual toner) and adhering materials such as paper powder are removed from the intermediate transfer belt 53 and collected by the belt cleaning device 54. In this embodiment, the belt cleaning device 54 has a cleaning blade as a cleaning member arranged in contact with the surface of the intermediate transfer belt 53, and a cleaning container. The belt cleaning device 54 uses the cleaning blade to scrape off and remove adhering materials such as secondary transfer residual toner from the surface of the rotating intermediate transfer belt 53, and collects them in the cleaning container.

[0027] In this embodiment, the photosensitive drum 1, the charging roller 2 as a process means acting on the photosensitive drum 1, the developing device 4, and the drum cleaning device 5 are integrated into a process cartridge 8. The process cartridge 8 is configured to be detachable from an apparatus main body 101 of the image forming apparatus 100. The apparatus main body 101 is a portion of the image forming apparatus 100 excluding detachable units such as the process cartridge 8. The image forming apparatus 100 may be configured such that, for example, the developing device 4 is detachable from the apparatus main body 101 alone.

[0028] Here, the image forming apparatus 100 executes a job (printing operation, printing operation) which is a series of operations for forming and outputting an image on one or more recording materials P, which is started by one start instruction. A job generally includes an image forming process, a pre-rotation process, a paper-interval process in the case of forming images on multiple recording materials P, and a post-rotation process. The image forming process (image forming operation) is a period during which electrostatic image formation, toner image formation, primary transfer of the toner image, secondary transfer, and fixing of the image to be actually formed on the recording material P are performed, and the image forming time refers to the period during these operations. More specifically, the timing of the image forming time differs depending on the position where each of the processes of electrostatic image formation, toner image formation, primary transfer of the toner image, secondary transfer, and fixing is performed. The pre-rotation process (pre-rotation operation) is a period during which a preparatory operation is performed before the image forming process, from when a start instruction is input until the image actually starts to be formed. The sheet interval process (sheet interval operation) is the period corresponding to the interval between recording materials P when image formation is continuously performed on multiple recording materials P (continuous image formation, continuous printing). The post-rotation process (post-rotation operation) is the period during which an arrangement operation (preparatory operation) is performed after the image formation process. The non-image formation time is the period other than the image formation time, and includes the periods of operations (non-image formation operations) such as the pre-rotation process, the sheet interval process, the post-rotation process, and further the pre-multiple rotation process which is a preparatory operation when the image forming apparatus 100 is turned on or when it returns from a sleep state.

[0029] <Developing device> Next, the developing device 4 in this embodiment will be further described.

[0030] As shown in FIG. 2, the developing device 4 has a developing container (developing frame) 41 that contains toner 90, a rotatable developing roller 42 as a developing member (developer carrier), a rotatable supply roller 43 as a supply member, and a regulating blade 44 as a regulating member. The developing roller 42 is located at the opening of the developing container 41 and is rotatably supported by the developing container 41. During image formation (development), the developing roller 42 rotates in contact with the surface of the photosensitive drum 1. The supply roller 43 is rotatably supported by the developing container 41 so as to rotate in contact with the developing roller 42. The regulating blade 44 is supported by the developing container 41 so as to abut against the developing roller 42. The rotation axis direction of the photosensitive drum 1, the rotation axis direction of the developing roller 42, and the rotation axis direction of the supply roller 43 are approximately parallel to each other. The developing roller 42 is rotationally driven in the direction of the arrow R3 in the figure (clockwise direction) by a drive motor (not shown) provided in the drive unit 110 (FIG. 3(a)). That is, the developing roller 42 is rotationally driven in a direction in which the surface of the photosensitive drum 1 and the surface of the developing roller 42 move forward at the contact portion (development portion) between the photosensitive drum 1 and the developing roller 42. In addition, the supply roller 43 is rotationally driven in the direction of the arrow R4 in the figure (clockwise direction) by a drive motor (not shown) provided in the drive unit 110 (FIG. 3(a)). That is, the supply roller 43 is rotationally driven in a direction in which the surface of the developing roller 42 and the surface of the supply roller 43 move in the opposite directions at the contact portion between the developing roller 42 and the supply roller 43. The rotation direction of the supply roller 43 may be a direction in which the surface of the developing roller 42 and the surface of the supply roller 43 move forward at the contact portion between the developing roller 42 and the supply roller 43.

[0031] In the developing device 4, the toner 90 is supplied to the surface of the developing roller 42 by the supply roller 43. The toner 90 held on the developing roller 42 is thinned by regulating the thickness of the layer (hereinafter also referred to as "layer thickness") by the regulating blade 44. The regulating blade 44 has a function of regulating the layer thickness of the toner 90 on the developing roller 42 and also has a function of imparting a predetermined charge to the toner 90 on the developing roller 42. The toner 90 thinned on the developing roller 42 is transported to the contact portion (developing portion) between the photosensitive drum 1 and the developing roller 42 as the developing roller 42 rotates, and adheres to the electrostatic latent image formed on the surface of the photosensitive drum 1 to develop the electrostatic latent image. The toner 90 that is not used for development and remains on the developing roller 42 is removed from the developing roller 42 at the contact portion between the developing roller 42 and the supply roller 43. The toner 90 removed from the developing roller 42 is stirred together with the toner 90 in the developing container 41 and mixed with the toner 90 in the developing container 41 .

[0032] In this embodiment, the developing roller 42 is an elastic roller in which a conductive elastic rubber layer 42b having a predetermined volume resistance is provided on the outer periphery of a metal core 42a. The developing roller 42 is configured so that its surface has a predetermined surface roughness. The developing roller 42 can be a single-layered or multi-layered roller. For example, a single-layered roller can be one in which an elastic layer is formed on a core using a rubber material such as silicone rubber, urethane rubber, or hydrin rubber. For example, a multi-layered roller can be one in which a surface layer is formed by coating a silicone resin, urethane resin, polyamide resin, or fluororesin on the surface of the elastic layer. In this embodiment, in order to obtain an appropriate image density, the developing roller 42 is rotated at a rotational speed (circumferential speed) at which the moving speed (circumferential speed) of the surface of the developing roller 42 is, for example, 125% of the moving speed (circumferential speed) of the surface of the photosensitive drum 1.

[0033] In this embodiment, the supply roller 43 is an elastic sponge roller in which an elastic layer (foamed elastic layer) 43b made of a conductive foam is formed on the outer periphery of a metal core 43a. The supply roller 43 is arranged so as to abut against the developing roller 42 with a predetermined intrusion amount. The intrusion amount of the supply roller 43 into the developing roller 42 can be expressed by the amount by which the supply roller 43 is deformed (depressed) by the developing roller 42. In this embodiment, the supply roller 43 has a urethane foam layer (foamed elastic layer made of a urethane rubber foam) as the foamed elastic layer 43b. In this embodiment, the material of the foamed elastic layer (urethane foam layer) of the supply roller 43 contains an ionic conductive agent (a conductive agent having ionic conductivity) as a conductive agent. As an example, in this embodiment, the supply roller 43 is configured such that an ionic conductive agent made of a salt of a cation and an anion having a reactive functional group that reacts with an isocyanate group is chemically bonded to the material of the urethane foam layer via the reactive functional group. For example, a supply roller 43 having such a configuration can be manufactured by foaming and curing a urethane composition containing an ion conductive agent. Other available ion conductive agents, such as metal complexes, may also be used. In addition, by making the urethane (urethane foam) on the surface layer of the supply roller 43 an open-cell foam, the toner 90 can be contained inside the foamed elastic layer (urethane foam layer) of the supply roller 43, and the toner 90 can be supplied to the development roller 42 more stably.

[0034] In this embodiment, the electrical resistance of a new (unused) supply roller 43 is 1×10 7 The electrical resistance of the supply roller 43 is measured in Ω. Here, a method for measuring the electrical resistance of the supply roller 43 will be described. The supply roller 43 is brought into contact with an aluminum sleeve (a cylindrical aluminum member) having a diameter of 30 mm so that the penetration depth is 1.5 mm. By rotating the aluminum sleeve, the supply roller 43 is rotated relative to the aluminum sleeve at a rotation speed of 30 rpm. In this state, a DC voltage of -50 V is applied to the aluminum sleeve. At this time, a resistor of 10 kΩ is provided on the earth side to which the supply roller 43 is connected, and the current is calculated by measuring the voltage across the resistor, and the electrical resistance of the supply roller 43 is calculated.

[0035] In this embodiment, the cell diameter on the surface of the supply roller 43 is set to 50 μm to 1000 μm. Here, the cell diameter refers to the average diameter of the foam cells in an arbitrary cross section, and the value is obtained as follows. First, the area of ​​the largest foam cell is measured from an enlarged image of the arbitrary cross section, and the maximum cell diameter is obtained by converting the area into a diameter equivalent to a perfect circle. Then, foam cells that are 1 / 2 or less of the maximum cell diameter are removed as noise, and the cell diameters of the remaining individual foam cells are obtained from the cell areas of the remaining individual foam cells by the same conversion as above. The cell diameter on the surface of the supply roller 43 refers to the average value of the converted individual cell diameters. In this embodiment, when checking the cell diameter of the supply roller 43, the measurement was performed using a VK-X200 (manufactured by KEYENCE Corporation).

[0036] In this embodiment, the regulating blade 44 is configured with a plate-shaped elastic member having electrical conductivity and flexibility. The plate-shaped elastic member constituting the regulating blade 44 has a predetermined length and a predetermined thickness in a longitudinal direction disposed substantially parallel to the rotation axis direction of the developing roller 42 and in a lateral direction substantially perpendicular to the longitudinal direction. The elastic member constituting the regulating blade 44 has one end in the lateral direction fixed to the developing container 41 and supported by a cantilever, and the other end in the lateral direction is a free end. The regulating blade 44 is disposed so that the surface near the tip of the free end faces the upstream side of the rotation direction (movement direction of the surface) of the developing roller 42 (counter direction) and the surface of the developing roller 42 near the tip abuts against the surface (outer peripheral surface) of the developing roller 42. The regulating blade 44 is disposed in a state of contact with the surface of the developing roller 42 at a position downstream of the contact portion between the supply roller 43 and the developing roller 42 and upstream of the contact portion between the photosensitive drum 1 and the developing roller 42 in the rotation direction of the developing roller 42. In this embodiment, a SUS material (stainless steel plate material) is used as the elastic member constituting the regulating blade 44.

[0037] During image formation (development), a predetermined developing bias (developing voltage) which is a DC voltage is applied to the developing roller 42 by a developing power source 122 (FIG. 3(b)) which serves as a developing bias application unit. During image formation (development), a predetermined supply bias (supply voltage) which is a DC voltage is applied to the supply roller 43 by a supply power source 123 (FIG. 3(b)) which serves as a supply bias application unit. During image formation (development), a predetermined regulating bias (regulating voltage) which is a DC voltage is applied to the regulating blade 44 by a regulating power source 124 (FIG. 3(b)) which serves as a regulating bias application unit. In this embodiment, for example, during image formation (development), a DC voltage of −350 V is applied to the developing roller 42, a DC voltage of −450 V is applied to the supply roller 43, and a DC voltage of −450 V is applied to the regulating blade 44. In this embodiment, the values ​​of the developing bias, the supply bias, and the regulating bias according to the usage environment of the image forming apparatus 100 are preset and stored in the main body memory 221 (FIG. 4) as table data or the like.

[0038] 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 side to the development roller 42 side. In this embodiment, the normal charging polarity of the toner 90 is negative. Therefore, during image formation (development), a potential difference is provided between the supply roller 43 and the development roller 42 such that the potential of the supply roller 43 is more negative than the potential of the development roller 42.

[0039] Furthermore, during image formation (development), the potential difference between the regulating blade 44 and the developing roller 42 is set to a polarity that urges (moves) the toner 90 from the regulating blade 44 side to the developing roller 42 side. In this embodiment, as described above, the normal charging polarity of the toner 90 is negative. Therefore, during image formation (development), a potential difference is provided between the regulating blade 44 and the developing roller 42 such that the potential of the regulating blade 44 is more negative than the potential of the developing roller 42. This stabilizes the intake of the toner 90 into the contact portion between the regulating blade 44 and the developing roller 42, and stabilizes the application of the electric charge to the toner 90 by the regulating blade 44.

[0040] As will be described in more detail later, in this embodiment, the settings of the developing bias, supply bias, and regulating bias in a job (printing operation) are the same in the pre-rotation process, the inter-sheet process, and the post-rotation process as in the image forming process.

[0041] <Toner> In this embodiment, a non-magnetic toner having a negative charge produced by a suspension polymerization method was used as the toner 90 (90Y, 90M, 90C, 90K). However, the present invention is not limited to this, and toners produced by other polymerization methods such as a pulverization method or an emulsion polymerization method may be used. The volume average particle diameter of the toner 90 is preferably 5.0 μm or more and 8.0 μm or less. Here, the volume average particle diameter of the toner was measured by a precision particle size distribution measuring device Multisizer3 manufactured by Beckman Coulter, Inc. In this embodiment, the volume average particle diameter of the toner 90 is about 7.0 μm.

[0042] In this embodiment, the toner 90 (90Y, 90M, 90C, 90K) is a toner particle containing a toner base particle containing a release agent and an organosilicon polymer on the surface of the toner base particle. The organosilicon polymer is R-Si(O 1 / 2)3. The R represents an alkyl group or a phenyl group having 1 to 6 carbon atoms, and the organosilicon polymer forms a convex portion on the surface of the toner base particle. This creates a spacer effect between the surface of the toner base particle and a member such as the developing roller 42, reducing the adhesive force between the toner base particle and the member. The convex portion is in surface contact with the surface of the toner base particle. By having the convex portion in surface contact with the surface of the toner base particle in this way, an effect of suppressing the movement, detachment, and embedding of the convex portion is obtained. Therefore, for example, even in a configuration in which the developing roller 42 is driven in a state separated from the photosensitive drum 1, the toner 90 can be used for a relatively long period of time. In this embodiment, toner particles containing an organosilicon polymer on the surface of the toner base particle are used as the toner 90, but this is not limited thereto, and for example, toner particles not containing an organosilicon polymer on the surface of the toner base particle may be used.

[0043] 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.

[0044] Examples of the external additive include inorganic oxide particles such as silica particles, alumina particles, and titanium oxide particles; inorganic stearic acid compound particles such as aluminum stearate particles and zinc stearate particles; and inorganic titanic acid compound particles such as strontium titanate and zinc titanate. These may be used alone or in combination of two or more. These inorganic particles are preferably gloss-treated with a silane coupling agent, a titanium coupling agent, a higher fatty acid, a silicone oil, or the like to improve heat-resistant storage properties and environmental stability. The BET specific surface area of ​​the external additive is preferably 10 m 2 / g or more 450m 2 / g or less. Here, the BET specific surface area can be determined by a low-temperature gas adsorption method using a dynamic constant pressure method in accordance with the BET method (preferably the BET multipoint method). For example, a specific surface area measuring device (product name: Gemini 2375 Ver. 5.0, manufactured by Shimadzu Corporation) is used to adsorb nitrogen gas onto the surface of a sample, and the BET multipoint method is used to measure the BET specific surface area (m 2 / g) can be calculated.

[0045] The total amount of these various external additives added is preferably 0.05 parts by mass or more and 5 parts by mass or less, and more preferably 0.1 parts by mass or more and 3 parts by mass or less, relative to 100 parts by mass of the toner base particles. Also, various external additives may be used in combination.

[0046] <Control configuration> Next, a description will be given of the control configuration of the image forming apparatus 100 in this embodiment. Fig. 3(a) is a schematic block diagram showing the control configuration of the image forming apparatus 100 in this embodiment.

[0047] The image forming apparatus 100 includes a video controller 201 and an engine controller 202. The video controller 201 processes an image signal input from an external device 300 such as a personal computer, and sends the image signal to the engine controller 202. The engine controller 202 controls the operation of the image forming apparatus 100, such as an image forming operation based on the image signal input from the video controller 201, in response to an instruction input from the external device 300.

[0048] The engine controller 202 includes a control unit 220, a main memory 221, an input / output unit (I / F) 222, and the like. The control unit 220 is composed of a CPU (Central Processing Unit) and the like as a control means that is a central element for performing arithmetic processing. The main memory 221, which is a storage unit as a storage means, is composed of storage media such as a ROM and a RAM as a storage means. The input / output unit 222 inputs and outputs signals (information) to and from devices outside the engine controller 202. The ROM stores (contains, saves) in advance control programs such as a program for executing an image forming operation, and a program for calculating the remaining amount of toner, the remaining life of a developing roller, the remaining life of a supply roller, and the like, which will be described later. The RAM stores information input to the engine controller 202, detected information, calculation results, and the like. The control unit 220 is a control means for controlling the overall operation of the image forming apparatus 100, and each control target in the image forming apparatus 100 is connected to the control unit 202 via the input / output unit 222. The control unit 220 controls the transmission and reception of various electrical information signals, drive timing, and the like, and executes processes according to the flowcharts described below, for example.

[0049] The control unit 220 is connected to, for example, the drive unit 110, the high-voltage power supply device 120, the temperature and humidity sensor 130, the memory communication unit 140, and the like, which are provided in the main body 101 of the apparatus. In addition, a non-volatile memory (hereinafter, also simply referred to as "memory") 150, which is a storage unit as a storage means provided in the process cartridge 8, is connected to the control unit 220 via the memory communication unit 140. The non-volatile memory 150 is adapted to be attached and detached to the main body 101 of the apparatus integrally with the process cartridge 8, and when the process cartridge 8 is attached to the main body 101 of the apparatus, it is connected to the control unit 220 via the memory communication unit 140. Note that, when the developing device 4 is independently detachable from the main body 101 of the apparatus, the non-volatile memory 150 can be detachable from the main body 101 of the apparatus integrally with the developing device 4. In addition, an operation unit 160 provided in the main body 101 of the apparatus is connected to the control unit 220. Furthermore, an external device 300 such as a personal computer is connected to the control unit 220.

[0050] The driving unit 110 is configured to have various motors as driving sources (power sources) and functions as a driving means for rotating and driving the polygon scanner, the photosensitive drum 1, the developing roller 42, the supply roller 43, and the like provided inside the exposure device 3. The driving unit 110 operates based on a control signal from the control unit 220. At least some of the motors that drive the photosensitive drum 1, the developing roller 42, and the supply roller 43 may be shared. At least some of the motors that drive the members for the colors yellow, magenta, cyan, and black may be shared.

[0051] As shown in FIG. 3B, the high-voltage power supply device 120 includes high-voltage power supplies (high-voltage power supply units) such as a charging power supply 121, a developing power supply 122, a supply power supply 123, a regulating power supply 124, a primary transfer power supply 125, a secondary transfer power supply 126, and a fixing power supply 127. The charging power supply 121 applies a charging bias to the charging roller 2. The developing power supply 122 applies a developing bias to the developing roller 42. The supply power supply 123 applies a supply bias to the supply roller 43. The regulating power supply 124 applies a regulating bias to the regulating blade 44. The primary transfer power supply 125 applies a primary transfer bias to the primary transfer roller 51. The secondary transfer power supply 126 applies a secondary transfer bias to the secondary transfer roller 6. The fixing power supply 127 supplies power to the heater of the fixing device 7. The high-voltage power supply device 120 operates based on a control signal from the control unit 220. At least a part of the power source for applying a bias to the members for each color, yellow, magenta, cyan, and black, may be shared.

[0052] The temperature and humidity sensor 130 is a sensor (environmental sensor) for detecting the temperature and humidity (temperature and humidity) of the environment in which the image forming apparatus 100 is used. The temperature and humidity sensor 130 is an example of an environment detection unit as an environment detection means for detecting the usage environment of the image forming apparatus 100, which is at least one of the temperature and humidity inside or outside the image forming apparatus 100. In this embodiment, the temperature and humidity sensor 130 detects the temperature and humidity of the ambient environment outside the image forming apparatus 100 as the usage environment of the image forming apparatus 100, and inputs a signal (information) indicating the detected temperature and humidity to the control unit 220. The information on the temperature and humidity detected by the temperature and humidity sensor 130 is used by the control unit 220 for control according to the usage environment of the image forming apparatus 100.

[0053] The nonvolatile memory 150 serving as storage means provided in each process cartridge 8 is connected to the control unit 220 via a memory communication unit 140 provided in the apparatus main body 101, and information can be read and written by the control unit 220. Note that, although a non-contact non-volatile memory is adopted as the storage means provided in each process cartridge 8 in this embodiment, any appropriate storage means can be used, such as a contact non-volatile memory, a non-contact non-volatile memory, or a volatile memory having a power source.

[0054] Moreover, the operation unit 160 has keys or the like as an input unit that can input information to the control unit 220 by operation by the user. Moreover, the operation unit 160 has a display screen (display panel) using a liquid crystal panel or the like as a display unit that can display information to the user under the control of the control unit 220. The operation unit 160 may be configured to have a touch panel (operation display unit) that has the function of an input unit and the function of a display unit.

[0055] The non-volatile memory 150 of the process cartridge 8 can store, as information on the usage status of the developing device 4, for example, the cumulative travel distance of the developing roller 42, the image dot cumulative value, and the deterioration degree of the supply roller 43 described later, while updating as needed. The non-volatile memory 150 of the process cartridge 8 can also store, as information on the usage status of the developing device 4, for example, the cumulative travel distance of the developing roller 42, the image dot cumulative value, and the deterioration degree of the supply roller 43, while updating as needed. The non-volatile memory 150 of the process cartridge 8 can also store, as threshold information for detecting various life spans, for example, a threshold value for the image dot cumulative value, a threshold value for the number of recording materials P on which an image is recorded (number of prints), a threshold value for the cumulative travel distance of the developing roller 42, a threshold value for the remaining amount of toner, and a threshold value for the deterioration degree of the supply roller 43. The non-volatile memory 150 of each process cartridge 8 stores information on the components of the respective process cartridges 8. In addition, the non-volatile memory 150 of the process cartridge 8 may store system programs for controlling the image forming apparatus 100, various adjustment values, the serial number of the process cartridge 8, system data indicating the date of manufacture, etc., as information unique to each process cartridge 8.

[0056] In this embodiment, all or part of the information to be stored in the nonvolatile memory 150 of each process cartridge 8 may be stored in a storage unit (such as the main body memory 221) provided in the apparatus main body 101.

[0057] <Detection of the life of the developing device> - Overview of detecting the life of a developing device - Next, detection of the life of the developing device 4 (process cartridge 8) in this embodiment will be described. In this embodiment, the "life" is the timing at which image quality cannot be guaranteed when forming an image on a recording material P in an image forming operation. Generally, when the "life" is reached, a notification is issued to prompt the user to replace the developing device 4 and the process cartridge 8. In this embodiment, the developing device 4 is replaceable as a part of the process cartridge 8, so the life of the developing device 4 means the life of the process cartridge 8. Here, it is also simply referred to as "life of the developing device 4" and "replacement of the developing device 4", but in this embodiment, it is equivalent to "life of the process cartridge 8" and "replacement of the process cartridge 8", respectively. In this embodiment, the process related to detection of the life of the developing device 4 is performed independently for each image forming unit S, but here, one image forming unit S will be focused on and described.

[0058] Fig. 4 is a schematic functional block diagram of the control unit 220 related to detection of the life of the developing device 4 in this embodiment. In this embodiment, each functional block shown in Fig. 4 is realized by the control unit 220 executing a program stored in the main body memory 221. Fig. 5 is a flowchart showing an outline of the procedure for detecting the life of the developing device 4 in this embodiment.

[0059] In this embodiment, the control unit 220 has a toner remaining amount detection unit 70, a developing roller life detection unit 60, and a supply roller life detection unit 80 as functional blocks for detecting the life of the developing device 4. The toner remaining amount detection unit 70 is configured to have a first video count measurement unit 71 and a toner remaining amount calculation unit 72. The developing roller life detection unit 60 is configured to have a developing roller travel distance calculation unit 61. The supply roller life detection unit 80 is configured to have a supply bias application time calculation unit 81, a supply bias measurement unit 82, a second video count measurement unit 83, and a supply roller deterioration degree calculation unit 84. The toner remaining amount detection unit 70, the developing roller life detection unit 60, and the supply roller life detection unit 80 will be described in detail later.

[0060] Here, an outline of a procedure for detecting the life of the developing device 4 will be described with reference to FIG. 5. When a print signal (job information) is input (S101), the control unit 220 starts a print operation (job) (S102). Then, the control unit 220 judges whether the developing device 4 has reached the end of its life at a predetermined timing (e.g., during the post-rotation process) during the print operation (during execution of the job) (S103 to S105). Specifically, in this embodiment, the control unit 220 judges whether the toner remaining amount TJ (%) in the developing device 4 has reached a predetermined threshold value (e.g., 0%) (S103), whether the developing roller remaining life GJ (%) has reached a predetermined threshold value (e.g., 0%) (S104), and whether the supply roller remaining life ηJ (%) has reached a predetermined threshold value (e.g., 0%) (S105). The toner remaining amount TJ is obtained by the toner remaining amount detection unit 70. The developing roller remaining life GJ is obtained by the developing roller life detection unit 60. The remaining supply roller life ηJ is determined by a supply roller life detection unit 80. The specific method for this will be described later.

[0061] When the control unit 220 determines that none of the remaining toner amount TJ, the remaining life of the developing roller GJ, and the remaining life of the supply roller ηJ has reached the predetermined threshold, the control unit 220 ends the print operation (S106). This is because it can be determined that the developing device 4 has not reached the end of its life. On the other hand, when the control unit 220 determines that any one of the remaining toner amount TJ, the remaining life of the developing roller GJ, and the remaining life of the supply roller ηJ has reached the predetermined threshold, the control unit 220 executes a process of notifying the user of information regarding the life (replacement) of the developing device 4 (S107). This is because it can be determined that the developing device 4 has reached the end of its life and needs to be replaced. Specifically, in this embodiment, the control unit 220 controls the operation unit 160 of the image forming apparatus 100 and the display unit of the external device 300 to display information regarding the life (replacement) of the developing device 4. This display may simply indicate that the developing device 4 has reached its life, or may be a display that prompts the user to replace the developing device 4. Then, the control unit 220 ends the print operation (S106).

[0062] In addition, in Figure 5, detection of the life of the developing device 4 based on the remaining toner amount TJ, remaining life of the developing roller GJ, and remaining life of the supply roller ηJ is shown to be performed in this order, but these may be performed in parallel or in an order different from that shown in Figure 5.

[0063] Furthermore, the fact that the remaining toner amount TJ, the remaining life of the developing roller GJ, and the remaining life of the supply roller ηJ have reached a predetermined threshold value (no toner, the life of the developing roller 42, or the life of the supply roller 43) may be notified independently. In this case, it may be possible to simply notify that there is no toner remaining or that the developing roller 42 or the supply roller 43 has reached the end of its life, or to notify that the developing device 4 needs to be replaced due to each of these causes (prompting the user to replace the developing device 4).

[0064] In this embodiment, it is assumed that the remaining toner amount TJ, the remaining life of the developing roller GJ, and the remaining life of the supply roller ηJ reach predetermined thresholds. The remaining toner amount TJ is the amount of toner used, the remaining life of the developing roller GJ is the amount of used of the developing roller, and the remaining life of the supply roller ηJ is the amount of used of the supply roller, and the values ​​may be added as the life approaches the predetermined threshold value, for example, 100%.

[0065] Also, for example, assuming the reuse of components of the developing device 4, information regarding the deterioration levels of the developing roller 42 and the supply roller 43 is acquired and stored in the memory 150, but it is also possible not to detect or notify the end of the life of the developing device 4 based on this information. This information can be read from the memory 150 during the regeneration and reuse process of the developing device 4, and used to determine whether or not the developing roller 42 and the supply roller 43 can be reused.

[0066] -Detection of remaining toner- Next, detection of the remaining toner amount in the developing device 4 in this embodiment will be described. Fig. 6 is a flow chart showing an outline of the procedure of the print operation focusing on detection of the remaining toner amount in this embodiment. The process according to the flow chart in Fig. 6 is executed by the control unit 220 (mainly the remaining toner amount detection unit 70).

[0067] In this embodiment, the control unit 220 detects (calculates) the remaining toner amount in the toner remaining amount detection unit 70 in order to prompt the user to replace the developing device 4 when the remaining toner amount is low. In this embodiment, the toner remaining amount detection unit 70 employs a video counting method (or a pixel counting method) as a developer remaining amount detection method. The video counting method (or the pixel counting method) is a method of counting the ON signal of the laser exposure (a signal that emits a laser, a pixel signal) generated based on image data to obtain information regarding the number of pixels in the printing portion of the image.

[0068] When a print signal (job information) is input (S201), the control unit 220 starts a print operation (job) (S202). At a predetermined timing during the print operation (for example, during the post-rotation process), the first video count measurement unit 71 receives pixel information of an image (hereinafter also referred to as an "output image") to be formed on the recording material P and output (S203), and measures a video count value VCn, which is the number of pixel signals (S204). In this embodiment, the first video count measurement unit 71 obtains pixel information of all images of the print operation (job) contained in the print signal, and measures a video count value VCn of all images. This video count value VCn correlates with the amount of toner 90 used to form images in the print operation (job).

[0069] Next, the remaining toner amount calculation unit 72 calculates a total video count value VCt, which is an accumulated value of the video count value from the start of use of the developing device 4 (process cartridge 8) (S205). That is, the remaining toner amount calculation unit 72 adds (integrates) the video count value VCn measured by the first video count measurement unit 71 to the accumulated video count value VCr from the start of use of the developing device 4 (process cartridge 8) stored in the memory 150, as shown in the following formula (1). In this way, the total video count value VCt is calculated. VCt = Vcr + VCn (1)

[0070] Next, the toner remaining amount calculation unit 72 calculates the remaining toner amount TJ in the developing device 4 from the video count threshold value VCth that is preset and stored in the memory 150 and the calculated total video count value VCt by the following formula (2) (S206). TJ[%]=(1-VCt / VCth)×100 (2)

[0071] Further, the remaining toner amount calculation unit 72 updates and stores the calculated total video count value VCt as a new cumulative video count value VCr in the memory 150 (S207). The remaining toner amount calculation unit 72 may update and store the calculated remaining toner amount TJ in the memory 150.

[0072] Here, when the toner remaining amount TJ=100%, the toner 90 in the developing device 4 is full, and the developing device 4 is brand new. When the toner remaining amount TJ≦0%, the toner 90 in the developing device 4 is almost depleted, and it is time to replace the developing device 4. In other words, when the toner remaining amount TJ≦0%, the total video count value VCt has reached the video count threshold value VCth, and the developing device 4 has reached the end of its life.

[0073] Therefore, the control unit 220 judges whether the remaining toner amount TJ calculated by the remaining toner amount calculation unit 72 is 0% or less (S208). If the control unit 220 judges in S208 that the remaining toner amount TJ is not 0% or less, it ends the printing operation (S209). On the other hand, if the control unit 220 judges in S208 that the remaining toner amount TJ is 0% or less, it controls to execute a process of notifying the user of information related to the life of the developing device 4 (S210). Then, the control unit 220 ends the printing operation (S209).

[0074] In this embodiment, the first video count measurement unit 71 measures the video count value VCn for each printing operation (job), but it may also be configured to measure, for example, the number of pixel signals of an image on one sheet of recording material P as one video count value VCn.

[0075] -Detection of the life of the developing roller- Next, detection of the life of the developing roller 42 in this embodiment will be described. Fig. 7 is a flowchart showing an outline of the procedure of the print operation focusing on detection of the life of the developing roller 42 in this embodiment. The process according to the flowchart in Fig. 7 is executed by the control unit 220 (mainly the developing roller life detection unit 60).

[0076] In this embodiment, the remaining life of the developing roller 42 is detected (calculated) by the developing roller life detection unit 60 in order to prompt the user to replace the developing device 4 when the developing roller 42 deteriorates. In this embodiment, the remaining life of the developing roller 42 is detected (calculated) based on the travel distance (rotation distance, surface movement distance) of the developing roller 42. It is known that the developing roller 42 deteriorates due to an increase in electrical resistance and contamination by deposits as the travel distance increases, and therefore has a lifespan that corresponds to the travel distance.

[0077] When a print signal (job information) is input (S301), the control unit 220 starts a print operation (job) (S302). During the print operation, the developing roller travel distance calculation unit 61 calculates a total developing roller travel distance Ht for each predetermined developing roller travel distance Hu (S303). That is, as shown in the following formula (3), the developing roller travel distance calculation unit 61 adds (integrates) the predetermined developing roller travel distance Hu to the cumulative developing roller travel distance Hr stored in the memory 150 for each predetermined developing roller travel distance Hu. In this way, the total developing roller travel distance Ht is calculated. Ht = Hr + Hu (3)

[0078] Next, the developing roller travel distance calculation unit 61 calculates the developing roller remaining life GJ from the developing roller travel distance threshold Hth that is set in advance and stored in the memory 150 and the calculated total developing roller travel distance Ht using the following formula (4) (S304). GJ[%]=(1-Ht / Hth)×100 ···(4)

[0079] Furthermore, the developing roller travel distance calculation unit 61 updates and stores the calculated total developing roller travel distance Ht as a new accumulated developing roller travel distance Hr in the memory 150 (S305). The developing roller travel distance calculation unit 61 may also update and store the calculated developing roller remaining life GJ in the memory 150.

[0080] Here, when the developing roller remaining life GJ=100%, it indicates that the developing device 4 is brand new. Also, when the developing roller remaining life GJ≦0%, it indicates that it is time to replace the developing device 4. In other words, when the developing roller remaining life GJ≦0%, the total developing roller travel distance Ht has reached the developing roller travel distance threshold Hth, and the developing device 4 has reached the end of its life.

[0081] Therefore, the control unit 220 judges whether the developing roller remaining life GJ calculated by the developing roller travel distance calculation unit 61 is 0% or less (S306). If the control unit 220 judges in S306 that the developing roller remaining life GJ is not 0% or less, it ends the print operation (S307). On the other hand, if the control unit 220 judges in S306 that the developing roller remaining life GJ is 0% or less, it controls to execute a process of notifying the user of information regarding the life of the developing device 4 (S308). Then, the control unit 220 ends the print operation (S307).

[0082] -Detection of the life of the supply roller (calculation of the deterioration level of the supply roller)- 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 and to set an appropriate supply bias as described later. The detection of the life of the supply roller 43 (calculation of the deterioration degree of the supply roller 43) in this embodiment will be described in detail after the explanation of the deterioration mechanism of the supply roller 43.

[0083] <Deterioration of supply roller> - Supply roller deterioration mechanism - Next, the deterioration of the supply roller 43 will be described. In this embodiment, the material of the urethane foam layer 43b of the elastic sponge roller constituting the supply roller 43 contains an ion conductive agent. The supply roller 43 having such a configuration is preferably used from the viewpoints of production stability and cost. According to the study by the present inventors, the deterioration of the supply roller 43 having such a configuration is roughly classified into two types.

[0084] The first type of deterioration of the supply roller 43 is deterioration caused by the supply roller 43 being energized. This mechanism of deterioration of the supply roller 43 is conventionally known. As described above, the supply roller 43 is given electrical conductivity by adding an ion conductive agent during manufacture. In general, when a bias of the same polarity is continuously applied to a member having ion conductivity, the ion conductive agent is unevenly distributed, and the number of ions dispersed in the member to carry electrons decreases compared to the initial state, resulting in an increase in electrical resistance. In this embodiment, a potential difference is provided between the supply roller 43 and the developing roller 42 such that the potential of the supply roller 43 is higher on the negative polarity side than the potential of the developing roller 42. That is, in this embodiment, a bias of the negative polarity side is applied to the supply roller 43 with respect to the developing roller 42. In addition, when such a bias is continuously applied to the supply roller 43 of this embodiment, the ion conductive agent tends to move to the inside (core metal side) of the supply roller 43 and become unevenly distributed. Such uneven distribution of the ion conductive agent progresses in correlation with the applied bias value and application time. Therefore, it is possible to predict the degree of deterioration of the supply roller 43 due to energization from the bias value and application time of the bias to the supply roller 43 .

[0085] The second type of deterioration of the supply roller 43 is deterioration due to a decrease in the ion conductive agent of the supply roller 43. Conventionally, no effort has been made to obtain information on the degree of deterioration of the supply roller 43 by focusing on the mechanism of deterioration of the supply roller 43. The toner contained in the urethane foam layer 43b of the supply roller 43 is successively replaced during the rotation of the supply roller 43. The inventors have confirmed through their studies that the ion conductive agent in the urethane foam layer 43b electrically adheres to the charged toner and is taken out of the urethane foam layer 43b as the toner moves from the supply roller 43 to the development roller 42. This phenomenon is particularly noticeable when the printing rate of the output image is high and the amount of toner moving from the supply roller 43 to the development roller 42 increases. Due to this phenomenon, the amount of the ion conductive agent in the urethane foam layer 43b of the supply roller 43 decreases compared to the initial state. As a result, the electrical resistance value of the supply roller 43 increases, and the ability to supply toner to the development roller 42 decreases as the sensitivity to the applied bias value decreases.

[0086] As the deterioration of the supply roller 43 progresses, image defects such as poor solid image tracking may occur, as will be described in more detail later.

[0087] -Verification 1: Effect of electrical deterioration- A test performed to examine the effect of deterioration of the supply roller 43 due to energization will be described. The following print endurance test was performed under the conditions of a supply bias Vrs of -450V and -650V. The development bias Vdc was set to -350V in both cases. At that time, the electrical resistance of the supply roller 43 was measured at a predetermined timing. Here, as a substitute value for the electrical resistance value of the supply roller 43, the current flowing through the supply roller 43 when a predetermined voltage was applied to the supply roller 43 was measured. By performing continuous operation without consuming toner, the effect of reduction in the conductive agent described later can be eliminated. As a print endurance test, continuous printing of images with a print rate of 0% was performed in the usage environment (ambient environment) of the image forming apparatus 100 with a temperature of 15°C and a humidity (relative humidity) of 10%. By setting the print rate to 0%, the effect of reduction in electrical resistance due to the carry-out of the conductive agent by the toner described later can be eliminated.

[0088] The results are shown in FIG. 8(a). The vertical axis indicates the ratio (decrease rate) of the current value to the initial current value when the initial current value (substitute value for electrical resistance value) is set to 100%, and the horizontal axis indicates the rotation drive time of the supply roller 43 (=supply bias application time). As shown in FIG. 8(a), it can be seen that the decrease in the current value (increase in the electrical resistance value) tends to be greater under the condition of a supply bias Vrs of -650V than under the condition of a supply bias Vrs of -450V. This is due to the ionic conductive agent contained in the supply roller 43 moving and being unevenly distributed due to continuous energization. In this way, it can be seen that there is a characteristic that the increase in the electrical resistance value of the supply roller 43 is greater when the supply bias Vrs (i.e., the potential difference between the supply bias Vrs and the development bias Vdc) is larger, since the amount of movement of the ionic conductive agent is greater. In this embodiment, it is known that when the ratio (decrease rate) of the current value to the initial current value is 30% or less, image defects such as poor solid tracking performance may occur.

[0089] -Verification 2: Differences in the amount of toner contained in the supply roller depending on the printing rate- A test was performed to examine the difference in the amount of toner contained in the supply roller 43 depending on the printing rate. The following print durability test was performed under the conditions of a printing rate of 0% and a printing rate of 100%. At that time, the amount of toner contained in the supply roller 43 was measured at a predetermined timing. The amount of toner contained in the supply roller 43 was calculated from the difference between the weight of the supply roller 43 that did not contain toner (unused) and the weight of the supply roller 43 at each timing. As the print durability test, one-sheet intermittent printing was performed in the usage environment (ambient environment) of the image forming apparatus 100 at a temperature of 23° C. and a humidity of 50%. The supply bias Vrs was set to −450 V, and the development bias Vdc was set to −350 V. Note that N-sheet intermittent printing is a printing method in which a printing operation for continuously forming images on N sheets of recording material P is performed, and then the operation of the development device 4 (image forming apparatus 100) is temporarily stopped, and then a printing operation for continuously forming images on N sheets of recording material P is performed again, and the above operation is repeated.

[0090] The results are shown in FIG. 8(b). The vertical axis indicates the amount of toner contained in the supply roller 43, and the horizontal axis indicates the number of prints. As shown in FIG. 8(b), it can be seen that throughout the print durability test, there is a difference in the amount of toner held on the supply roller 43 between the condition of a print rate of 0% and the condition of a print rate of 100% (the amount of toner held on the supply roller 43 is less under the condition of a print rate of 100% than under the condition of a print rate of 0%). This is because when the print rate of the output image is high, the amount of toner moving from the development roller 42 to the photosensitive drum 1 increases, and therefore the amount of toner supplied from the supply roller 43 to the development roller 42 increases. The reason why the amount of toner contained in the supply roller 43 decreases overall with an increase in the number of prints is that the amount of toner supplied to the supply roller 43 decreases with a decrease in the amount of toner in the development device 4.

[0091] -Verification 3: Impact of reduction in conductive agent- A test performed to examine the difference in the amount of conductive agent reduction depending on the printing rate will be described. The following print durability test was performed under the condition of a printing rate of 1% and the condition of a printing rate of 100%. At that time, a measurement was performed to evaluate the amount of conductive agent components contained in the supply roller 43 at a predetermined timing. Here, the amount of conductive agent components was evaluated by measuring the current flowing through the supply roller 43 when a predetermined voltage was applied to the supply roller 43. When the current value decreases, it can be confirmed that the amount of conductive agent components has decreased by confirming that the current value does not increase (recover) by the amount of the decrease even if a voltage of the opposite polarity to the above-mentioned predetermined voltage is applied. As a print durability test, one sheet was intermittently printed in the usage environment (ambient environment) of the image forming apparatus 100 at a temperature of 23° C. and a humidity of 50%. The supply bias Vrs was set to −450 V, and the development bias Vdc was set to −350 V.

[0092] The results are shown in FIG. 8(c). The vertical axis indicates the ratio (decrease rate) of the current value to the initial current value when the initial current value (substitute value for the amount of conductive agent component) is set to 100%, and the horizontal axis indicates the rotation drive time of the supply roller 43 (=supply bias application time). It can be seen that the decrease in the current value (decrease in the conductive agent) tends to be greater under the condition of a high printing rate (100%) than under the condition of a low printing rate (1%). This is because when the printing rate is high and the amount of toner replacement in the supply roller 43 per unit time is large, the amount of conductive agent discharged out of the developing device 4 together with the toner accompanying printing is greater than when the printing rate is low. In this way, it can be seen that the decrease in the conductive agent is greater when the printing rate is high than when the printing rate is low. In the present invention, the deterioration degree of the supply roller 43 is calculated taking into account the characteristics of the supply roller 43 discovered by the present inventors.

[0093] In other words, the phenomenon in which the conductive agent added to the material of the foamed elastic layer of the supply roller 43 decreases is more noticeable when an image with a high printing rate is formed and toner consumption is large, compared to when an image with a low printing rate is formed and toner consumption is small. Therefore, the degree of deterioration of the supply roller 43 varies depending on the usage conditions of the image forming apparatus 100 by the user. Therefore, it is desired to obtain information on the degree of deterioration of the supply roller 43 more accurately depending on the usage conditions of the image forming apparatus 100.

[0094] Furthermore, in recent years, from the viewpoint of usability, a toner supplying method may be adopted in which only the toner container can be separated from the developing device 4 (process cartridge 8) and replaced. In such a configuration, higher durability is required for the supply roller 43, and the supply roller 43 often has a longer life. Therefore, in such a configuration, there is a possibility that the difference in the progress of deterioration of the supply roller 43 depending on the usage conditions of the image forming apparatus 100 by the user will become large. Therefore, in such a configuration, it can be said that there is an even greater demand for more accurate acquisition of information regarding the deterioration degree of the supply roller 43 depending on the usage conditions of the user.

[0095] <Mechanism of poor solid print conformance> Next, the mechanism by which poor solid image followability occurs will be described.

[0096] The solid image tracking failure occurs when an image with a high printing ratio is repeatedly printed, because the toner on the developing roller 42 becomes insufficient and the desired amount of toner 90 is not supplied to the electrostatic latent image formed on the photosensitive drum 1. In particular, when the image forming apparatus 100 is used for a long period of time, the amount of toner 90 supplied to the developing roller 42 decreases due to deterioration of the supply roller 43 (increase in electrical resistance), and the solid image tracking failure occurs more significantly.

[0097] The amount of toner 90 carried by the developing roller 42 during image formation (development) changes according to the potential difference between the supply roller 43 (supply bias Vrs) and the developing roller 42 (developing bias Vdc). Therefore, the more the supply roller 43 deteriorates (the shorter the remaining life of the supply roller 43 becomes), the supply bias Vrs is set to have a larger potential difference on the negative polarity side with respect to the developing bias Vdc. This makes it possible to actively supply negative toner 90 from the supply roller 43 to the developing roller 42.

[0098] In this embodiment, the potential difference between the supply roller 43 and the development roller 42 is variably controlled according to the degree of deterioration (remaining life) of the supply roller. 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.

[0099] <Calculation of Supply Roller Deterioration Level and Determination of Supply Bias> Next, the calculation of the deterioration degree of the supply roller 43 and the determination of the supply bias Vrs in this embodiment will be described. FIG. 9 is a flow chart showing an outline of the procedure of the print operation focusing on the calculation of the deterioration degree of the supply roller 43 in this embodiment. The process according to the flow chart in FIG. 9 is executed by the control unit 220 (mainly the supply roller life detection unit 80). FIG. 10 is a timing chart showing the transition of the supply bias Vrs applied to the supply roller 43 during the print operation in this embodiment. In this embodiment, the calculation of the deterioration degree of the supply roller 43 and the determination of the supply bias Vrs are performed independently for each image forming unit S, but the process will be described focusing on one image forming unit S here.

[0100] 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 and to set an appropriate supply bias Vrs. In this embodiment, the deterioration degree of the supply roller 43 is calculated for each print operation (job) taking into consideration the print rate of the output image in addition to the voltage value of the supply bias Vrs (or the potential difference between the supply bias Vrs and the developing bias Vdc) and the application time of the supply bias Vrs. Then, the deterioration degree of the supply roller 43 is added for each print operation (job), and when it reaches a predetermined deterioration degree set in advance, information on the life of the developing device 4 is notified to the user. That is, in this embodiment, the supply roller life detection unit 80 detects (calculates) the remaining life of the supply roller 43 based on the voltage value of the supply bias Vrs (or the potential difference between the supply bias Vrs and the developing bias Vdc), the application time of the supply bias Vrs, and the print rate of the output image. In this embodiment, the supply bias Vrs to be applied to the supply roller 43 is determined according to the calculated deterioration level (remaining life) of the supply roller.

[0101] When a print signal (job information) is input (S401), the control unit 220 starts a print operation (job) (S402). In addition, the control unit 220 checks information stored in the memory 150 with the start of the print operation (S403), and reads the supply roller remaining life ηJ stored in the memory 150 (S404). In addition, the control unit 220 determines the supply bias Vrs based on the supply roller remaining life ηJ (S405). Then, the supply power source 123 applies the determined supply bias Vrs to the supply roller 43. The supply bias Vrs applied to the supply roller 43 by the supply power source 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 supply roller remaining life ηJ from table data shown in Table 1, which is preset and stored in the main body memory 221. At the same timing as the application of the supply bias Vrs, the developing power supply 122 applies the developing bias Vdc to the developing roller 42. In this embodiment, the developing bias Vdc is set to -350V and is constant.

[0102] The table data shown in Table 1 is an example of information showing the relationship between the supply roller remaining life ηJ and the supply bias Vrs. As shown in Table 1, the smaller the supply roller remaining life ηJ, the larger the absolute value of the negative polarity supply bias Vrs (same polarity as the normal charging polarity of the toner 90). In other words, the smaller the supply roller remaining life ηJ, the larger the potential difference (Vrs-Vdc) between the supply bias Vrs and the development bias Vdc is toward the negative polarity side (the same polarity as the normal charging polarity of the toner 90).

[0103] [Table 1]

[0104] Next, during the printing operation, the supply bias application time calculation unit 81 measures the time during which the supply bias Vrs is applied to the supply roller 43 (S406), and calculates the supply bias application time tnow in the printing operation (S407). If the supply bias application start timing in the printing operation is tS and the supply bias application end timing in the printing operation is tE, the supply bias application time tnow in the printing operation can be expressed by the following formula (5). tnow=tE-tS (5)

[0105] Also, at a predetermined timing during the printing operation (for example, during the post-rotation process), the second video count measurement unit 83 receives pixel information of the output image and calculates the section printing rate γnow, which is the printing rate in the printing operation, based on the video count value VCn measured (S408). In this embodiment, the second video count measurement unit 83 obtains pixel information of all images of the printing operation (job) contained in the print signal and measures the video count value VCn of the all images. Then, the second video count measurement unit 83 calculates the section printing rate γnow in the all images. Note that the printing rate (image printing rate, image ratio) indicates the area ratio (proportion) of the printing area when the case where all pixels of the image forming area (area where a toner image can be formed) are the printing area is set to 100%. The printing rate in all images of the printing operation can be expressed as the area ratio (proportion) of the printing area in all images when the total number of pixels of all images is set to the total number of pixels. Then, the supply roller deterioration degree calculation unit 84 determines the deterioration correction coefficient ε based on the section printing rate γnow acquired by the second video count measurement unit 83 (S409). In this embodiment, the supply roller deterioration degree calculation unit 84 reads out and determines the deterioration correction coefficient ε corresponding to the section printing rate γnow from the table data shown in Table 2, which is preset and stored in the memory 150. The table data in Table 2 is an example of information indicating the relationship between the printing rate and the deterioration correction coefficient ε. As shown in Table 2, the higher the printing rate, the larger the deterioration correction coefficient ε is made.

[0106] [Table 2]

[0107] Next, the supply roller deterioration level calculation unit 84 calculates the section supply roller deterioration level ηnow, which is an index showing the degree of deterioration of the supply roller 43 in the print operation, by the following formula (6) (S410). ηnow=tnow×|Vrs-Vdc|×ε ···(6)

[0108] When the developing bias Vdc is constant, the deterioration degree ηnow of the section supply roller may be calculated by the following formula: ηnow=tnow×|Vrs|×ε.

[0109] Next, the supply roller deterioration degree calculation unit 84 calculates a total supply roller deterioration degree ηt which is an index showing the degree of deterioration of the supply roller 43 from the start of use of the developing device 4 (supply roller 43) (S411). That is, as shown in the following formula (7), the supply roller deterioration degree calculation unit 84 adds (integrates) the calculated section supply roller deterioration degree ηnow to the cumulative supply roller deterioration degree ηr from the start of use of the developing device 4 (supply roller 43) stored in the memory 150. In this way, the total supply roller deterioration degree ηt is calculated. Then, the supply roller deterioration degree calculation unit 84 updates and stores the calculated total supply roller deterioration degree ηt in the memory 150 as a new cumulative supply roller deterioration degree ηr. ηt = ηnow + ηr (7)

[0110] Next, the supply roller deterioration degree calculation unit 84 calculates the supply roller remaining life ηJ from the supply roller deterioration degree threshold ηth previously set and stored in the memory 150 and the calculated total supply roller deterioration degree ηt by the following formula (8) (S412). The supply roller deterioration degree threshold ηth is determined and set in advance by an experiment or the like so that image defects such as poor solid followability do not occur even when the toner remaining amount is 0%. The supply roller deterioration degree threshold ηth may vary depending on, for example, the elastic material constituting the foamed elastic layer of the supply roller 43, the type and amount of conductive agent contained in the material of the foamed elastic layer, the type of toner 90, and the like. The supply roller deterioration degree calculation unit 84 may update and store the calculated supply roller remaining life ηJ in the memory 150. ηJ[%]=(1-ηt / ηth)×100 ···(8)

[0111] Here, when the supply roller remaining life ηJ=100%, it indicates that the developing device 4 is brand new. Also, when the supply roller remaining life ηJ≦0%, it indicates that it is time to replace the developing device 4. When the supply roller remaining life ηJ≦0%, the total supply roller deterioration degree ηt has reached the supply roller deterioration degree threshold value ηth, and the developing device 4 has reached the end of its life.

[0112] Therefore, the control unit 220 judges whether the supply roller remaining life ηJ calculated by the supply roller deterioration degree calculation unit 84 is 0% or less (S413). If the control unit 220 judges in S413 that the supply roller remaining life ηJ is not 0% or less, it ends the print operation (S415). On the other hand, if the control unit 220 judges in S413 that the supply roller remaining life ηJ is 0% or less, it controls to execute a process of notifying the user of information regarding the life of the developing device 4 (S414). Then, the control unit 220 ends the print operation (S415).

[0113] In FIG. 9, the calculation of the supply bias application time tnow and the calculation of the section printing rate γnow (and the determination of the deterioration correction coefficient ε) are shown to be performed in parallel, but they may be performed in any order. In this embodiment, the section printing rate γnow (and the deterioration correction coefficient ε), the section supply roller deterioration degree ηnow, and the total supply roller deterioration degree ηt are obtained for each print operation (job) at a predetermined timing (for example, during the post-rotation process) during the print operation (during the execution of the job). However, the present invention is not limited to this, and these may be obtained sequentially at a predetermined timing during the print operation. For example, the supply bias application time tnow, the section printing rate γnow (and the deterioration correction coefficient ε), the section supply roller deterioration degree ηnow, and the total supply roller deterioration degree ηt may be obtained every time an image is formed. Also, for example, each time the section supply roller deterioration degree ηnow increases by a predetermined value, the ηnow may be added (integrated) to the cumulative supply roller deterioration degree ηr stored in the memory 150 to calculate the total supply roller deterioration degree ηt. If the supply roller remaining life ηJ becomes 0% or less during the printing operation (job), a process may be executed to notify the user of information regarding the life of the developing device 4, and the printing operation may be terminated (interrupted). This also applies to the remaining toner amount TJ and the remaining developing roller life GJ described above. This also applies to other embodiments described later.

[0114] <Variation 1> In this embodiment, as shown in Table 1, the supply bias Vrs is changed in four steps according to the remaining life ηJ of the supply roller, but this is not limited to this. The increment width of the remaining life ηJ of the supply roller may be made finer or larger. In other words, the supply bias Vrs may be changed in fewer steps (three steps or less) or more steps (five steps or more) according to the remaining life ηJ of the supply roller. The appropriate supply bias Vrs 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.

[0115] The information indicating the relationship between the remaining life η of the supply roller and the supply bias Vrs is not limited to being set as table data, but may be set as a calculation formula. This also applies to the information indicating other relationships described as being set as table data.

[0116] <Variation 2> In this embodiment, the image forming apparatus 100 holds the value of the supply bias Vrs as table data as shown in Table 1, but is not limited to this. The image forming apparatus 100 can also hold the potential difference (Vrs-Vdc) between the supply bias Vrs and the developing bias Vdc as table data, for example, as shown in Table 3. In this embodiment, since the developing bias Vdc is -350V, for example, when the remaining life ηJ of the supply roller is 50% or more, the supply bias Vrs=-350+(-100)=-450V according to Table 3.

[0117] [Table 3]

[0118] <Modification 3> In this embodiment, as shown in Table 2, the deterioration correction coefficient ε is changed into six stages based on the printing rate of the output image, but this is not limited to this. The printing rate increments may be made finer or larger. In other words, the deterioration correction coefficient ε may be changed into fewer stages (five stages or less) or into more stages (seven stages or more). The deterioration correction coefficient ε varies depending on the characteristics of the supply roller 43 and the characteristics of the toner 90, and can be determined based on experimental values, etc.

[0119] <Comparative verification 1> Next, a comparative verification carried out between this embodiment and the following Comparative Example 1 in order to verify the effect of this embodiment will be described.

[0120] -Evaluation method- A print endurance test was performed from the start of use of the developing device 4 (process cartridge 8) (supply roller remaining life ηJ = 100%) until a solid followability defect occurred, which is a guideline for determining that the supply roller remaining life ηJ = 0%. The solid followability defect was evaluated visually, and if it was significantly observed at a level that could be a practical problem, it was deemed that a solid followability defect had occurred. Specifically, a print endurance test was performed under the following conditions using A4 size recording paper. Environment: Temperature 23℃, humidity 50% Print mode: 2 sheets intermittent Print durability Image printing rate: 4% Evaluation image output: Every 500 sheets

[0121] The number of prints until a solid image follow-up failure occurred was compared between this embodiment and Comparative Example 1.

[0122] -Comparative Example 1- In Comparative Example 1, the supply bias Vrs was constant at −500 V. Other points in Comparative Example 1 were substantially the same as those in this embodiment.

[0123] -Evaluation results- The evaluation results are shown in Table 4. Note that, although the evaluation results for solid black images are shown here in particular, in this embodiment, the configuration of the developing device 4 (process cartridge 8) for each color is substantially the same, and similar evaluation results were obtained.

[0124] [Table 4]

[0125] In Comparative Example 1, a supply bias Vrs sufficient to urge (move) the toner 90 from the supply roller 43 side to the developing roller 42 side was applied, but this accelerated deterioration of the supply roller 43, resulting in poor solid tracking performance.

[0126] On the other hand, in this embodiment, control was performed so that an appropriate supply bias Vrs was applied in accordance with the degree of deterioration of the supply roller 43. Therefore, in this embodiment, the number of prints until solid tracking failure occurred could be increased (i.e., the life of the supply roller 43 could be extended) compared to Comparative Example 1.

[0127] <Effects> In this embodiment, an image forming apparatus 100 that performs image formation by transferring a developer image onto a recording material P to form an image on the recording material P includes a rotatable image carrier (photosensitive drum) 1 that carries a developer image, a developing device 4 that supplies a developer to the surface of the image carrier 1 to form a developer image on the surface of the image carrier 1, the developing device 4 having a rotatable developing member 42 that supplies the developer to the surface of the image carrier 1, and a rotatable supply member 43 that has an elastic layer 43b containing an ion conductive agent and comes into contact with the developing member 42 to supply the developer to the developing member 42, a first application unit (development power source) 122 that applies a development voltage to the developing member 42, a second application unit (supply power source) 123 that applies a supply voltage to the supply member 43, and a printing unit 124 that prints the image formed in the image formation. The image forming apparatus includes an acquisition unit (second video count measurement unit) 82 that acquires information about the coverage rate, a control unit 220 (more specifically, a supply roller deterioration degree calculation unit 84) that acquires information about the deterioration degree of the supply member 43 based on information about the supply voltage applied to the supply member 43, information about the time when the supply voltage was applied to the supply member 43, and information about the coverage rate, and a storage unit (non-volatile memory) 150 that stores the information about the deterioration degree acquired by the control unit 220, and the control unit 220 controls to change the potential difference between the supply voltage applied to the supply member 43 and the development voltage applied to the development member 42 when forming a developer image on the image carrier 1 in the image formation based on the information about the deterioration degree. At this time, the control unit 220 can change the potential difference by controlling at least one of the first application unit 122 and the second application unit 123. In this embodiment, the potential difference is a potential difference in which the supply voltage applied to the supply member 43 has the same polarity as the normal charging polarity of the developer with respect to the development voltage applied to the development member 42, and the control unit 220 controls the absolute value of the potential difference to be larger when the deterioration degree indicated by the information on the deterioration degree is a second deterioration degree greater than the first deterioration degree than when the deterioration degree is the first deterioration degree. Also, in this embodiment, the storage unit 150 is detachable from the device body 101 of the image forming apparatus 100 together with the development device 4.In this embodiment, the control unit 220 acquires information on the deterioration degree by correcting a value correlated with a product of voltage and time based on information on the supply voltage applied to the supply member 43 and information on the time during which the supply voltage was applied to the supply member 43, using a correction coefficient (deterioration correction coefficient ε) corresponding to the information on the printing rate. In this embodiment, the acquisition unit 83 acquires information on the printing rate based on image information of an image formed in the image formation. In this embodiment, the developing member 42 contacts the image carrier 1 to form a developing portion, and supplies developer to the image carrier 1 in the developing portion. In this embodiment, the developer is a non-magnetic one-component developer.

[0128] As described above, in this embodiment, information on the deterioration degree of the supply roller 43 is obtained more accurately in consideration of the printing rate of the output image, and the supply bias Vrs is determined according to the deterioration degree. This makes it possible to more appropriately control the supply bias Vrs according to the deterioration degree of the supply roller 43, and to suppress image defects such as poor solid followability that occur due to deterioration (increase in electrical resistance) of the supply roller 43 over a long period of time.

[0129] [Example 2] Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the image forming apparatus of embodiment 1. Therefore, in the image forming apparatus of this embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus of embodiment 1 are given the same reference numerals as those of embodiment 1, and detailed explanations are omitted.

[0130] <Outline of this Example> The supply roller 43 containing an ion conductive agent has a tendency for its electrical resistance to change depending on the environment (particularly temperature). For example, the lower the environmental temperature, the slower the reaction speed of the ions in the ion conductive agent to the electric field becomes, and as a result, the electrical resistance of the supply roller 43 increases.

[0131] Therefore, in this embodiment, the potential difference between the supply roller 43 and the developing roller 42 is variably controlled according to the degree of deterioration (remaining life) of the supply roller 43 and the temperature of the environment in which the image forming apparatus 100 is used.

[0132] <Calculation of Supply Roller Deterioration Level and Determination of Supply Bias> Next, the calculation of the deterioration degree of the supply roller 43 and the determination of the supply bias Vrs in this embodiment will be described. Fig. 11 is a flow chart showing an outline of the procedure of the print operation focusing on the calculation of the deterioration degree of the supply roller 43 in this embodiment. The process according to the flow chart in Fig. 11 is executed by the control unit 220 (mainly the supply roller life detection unit 80). Note that in the procedure in this embodiment shown in Fig. 11, the description of the same process as the procedure in embodiment 1 shown in Fig. 9 will be omitted as appropriate.

[0133] When a print signal (job information) is input (S501), the control unit 220 starts a print operation (job) (S502). In addition, the control unit 220 checks the detection result of the temperature and humidity sensor 130 (S503) with the start of the print operation, and reads the temperature and humidity data (particularly, temperature data in this embodiment) (S504). In addition, the control unit 220 checks the information stored in the memory 150 (S505), and reads the supply roller remaining life ηJ stored in the memory 150 (S506). In addition, the control unit 220 determines the supply bias Vrs based on the temperature and the supply roller remaining life ηJ (S507). Then, the supply power source 123 applies the determined supply bias Vrs to the supply roller 43. In this embodiment, the control unit 220 reads and determines the supply bias Vrs corresponding to the temperature and the supply roller remaining life ηJ from table data shown in Table 5, which is preset and stored in the main body memory 221. At the same timing as the application of the supply bias Vrs, the developing power supply 122 applies the developing bias Vdc to the developing roller 42. In this embodiment, the developing bias Vdc is set to -350V and is constant.

[0134] Table data shown in Table 5 is an example of information showing the relationship between temperature, supply roller remaining life ηJ, and supply bias Vrs. As shown in Table 5, if the supply roller remaining life ηJ is the same, the lower the temperature, the larger the absolute value of the supply bias Vrs of the negative polarity (the same polarity as the normal charging polarity of the toner 90). In other words, if the supply roller remaining life ηJ is the same, the lower the temperature, the larger the potential difference (Vrs-Vdc) between the supply bias Vrs and the development bias Vdc is on the negative polarity side (the same polarity as the normal charging polarity of the toner 90). Also, as shown in Table 5, if the temperature is the same, the smaller the supply roller remaining life ηJ, the larger the absolute value of the supply bias Vrs of the negative polarity (the same polarity as the normal charging polarity of the toner 90). In other words, if the temperature is the same, the smaller the supply roller remaining life ηJ, the larger the potential difference (Vrs-Vdc) between the supply bias Vrs and the development bias Vdc is on the negative polarity side (the same polarity as the normal charging polarity of the toner 90).

[0135] [Table 5]

[0136] The processes in S508 to S517 in FIG. 11 are similar to the processes in S406 to S415 in FIG.

[0137] <Modification 4> In the image forming apparatus 100 of this embodiment, the appropriate supply bias Vrs changes due to factors such as changes in the fluidity of the toner 90 depending on the environment and changes in the electrical resistance of the supply roller 43. Therefore, in this embodiment, the image forming apparatus 100 is capable of changing the supply bias Vrs depending on its operating environment. In this embodiment, as shown in Table 5, the supply bias Vrs is changed in three stages based on temperature information. However, this is not limited to this, and the supply bias Vrs may be changed based on temperature information and humidity information. Table 6 shows an example of table data in the case where the temperature and humidity detected by the temperature and humidity sensor 130 are converted into absolute moisture content to change the supply bias Vrs. In this case, the control unit 220 can calculate the absolute moisture content based on the temperature and humidity detected by the temperature and humidity sensor 130, and read out and determine the corresponding supply bias Vrs from the table data of Table 6 depending on the calculated absolute moisture content. In addition, the supply bias Vrs is not limited to being changed in three stages depending on the environment as shown in Tables 5 and 6. The supply bias Vrs may be changed in fewer steps (two steps) or more steps (four steps or more) depending on the temperature or absolute moisture content. In addition, the supply bias Vrs corresponding to the temperature or absolute moisture content for which data is not available in Table 5 or Table 6 may be determined by interpolation (for example, linear interpolation).

[0138] [Table 6]

[0139] <Variation 5> In this embodiment, the image forming apparatus 100 holds the value of the supply bias Vrs as table data as shown in Table 5, but is not limited to this. The image forming apparatus 100 can also hold offset values ​​for other environments as table data, for example, as shown in Table 7, based on the supply bias Vrs for a specific environment (for example, 15° C. or higher and lower than 25° C.).

[0140] [Table 7]

[0141] <Variation 6> In this embodiment, the image forming apparatus 100 holds the value of the supply bias Vrs as table data as shown in Table 5, but is not limited to this. The image forming apparatus 100 can also hold the potential difference (Vrs-Vdc) between the supply bias Vrs and the development bias Vdc as table data as shown in Table 8. In this embodiment, the development bias Vdc is -350V. Therefore, for example, when the remaining life ηJ of the supply roller is 50% or more and the environment is less than 15°C, the supply bias Vrs=-350+(-150)=-500V according to Table 8.

[0142] [Table 8]

[0143] <Comparative verification 2> Next, a comparative verification carried out between this embodiment and the following Comparative Example 2 in order to verify the effect of this embodiment will be described.

[0144] -Evaluation method- A print endurance test was performed from the start of use of the developing device 4 (process cartridge 8) (supply roller remaining life ηJ = 100%) until a solid followability defect occurred, which is a guideline for determining that the supply roller remaining life ηJ = 0%. The solid followability defect was evaluated visually, and if it was significantly observed at a level that could be a practical problem, it was deemed that a solid followability defect had occurred. Specifically, a print endurance test was performed under the following conditions using A4 size recording paper. Environment: Temperature 14℃, humidity 10% Print mode: 2 sheets intermittent Print durability Image printing rate: 4% Evaluation image output: Every 500 sheets

[0145] The number of prints until solid image follow-up failure occurred was compared between this embodiment and Comparative Example 2.

[0146] -Comparative Example 2- In Comparative Example 2, the supply bias Vrs was constant at −600 V. Other points in Comparative Example 2 were substantially the same as those in this embodiment.

[0147] -Evaluation results- The evaluation results are shown in Table 9. Note that, although the evaluation results for solid black images are shown here in particular, in this embodiment, the configuration of the developing device 4 (process cartridge 8) for each color is substantially the same, and similar evaluation results were obtained.

[0148] [Table 9]

[0149] In comparison example 2, a supply bias Vrs sufficient to urge (move) the toner 90 from the supply roller 43 side to the development roller 42 side was applied, but this accelerated deterioration of the supply roller 43, resulting in poor solid tracking performance.

[0150] On the other hand, in this embodiment, control was performed so that an appropriate supply bias Vrs was applied in accordance with the temperature of the usage environment of the image forming apparatus 100 and the degree of deterioration of the supply roller 43. Therefore, in this embodiment, the number of prints until solid tracking failure occurred could be increased (i.e., the life of the supply roller 43 could be extended) compared to Comparative Example 2.

[0151] <Effects> In this embodiment, the image forming apparatus 100 has an environment detection unit (temperature and humidity sensor) 130 that detects at least one of temperature and humidity, and the control unit 220 controls to change the potential difference between the supply voltage applied to the supply member 43 and the development voltage applied to the development member 42 when forming a developer image on the image carrier 1 in image formation based on the detection result of the environment detection unit 130 and information on the deterioration degree of the supply member 43. Also, in this embodiment, the potential difference is a potential difference in which the supply voltage applied to the supply member 43 is on the same polarity side as the normal charging polarity of the developer with respect to the development voltage applied to the development member 42, and the control unit 220 controls so that the absolute value of the potential difference is larger when the temperature indicated by the detection result of the environment detection unit 130 is a second temperature lower than the first temperature than when the temperature indicated by the first temperature is a first temperature, when the deterioration degree indicated by the information on the deterioration degree is the same.

[0152] As described above, in this embodiment, the supply bias Vrs is determined according to the deterioration degree (remaining life) of the supply roller 43 as well as the temperature of the environment in which the image forming apparatus 100 is used. This provides the same effects as in the first embodiment, and also makes it possible to more appropriately control the supply bias Vrs and suppress image defects such as poor solid-color tracking caused by deterioration (increase in electrical resistance) of the supply roller 43 over a long period of time.

[0153] [Example 3] Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the image forming apparatus of embodiment 1. Therefore, in the image forming apparatus of this embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus of embodiment 1 are given the same reference numerals as those of embodiment 1, and detailed explanations are omitted.

[0154] <Outline of this Example> The amount of toner 90 carried on the developing roller 42 may be affected by the amount of toner 90 in the developing device 4. For example, the smaller the amount of toner 90 in the developing device 4, the lower the amount of toner supplied to the developing roller 42 by the supply roller 43, and the smaller the amount of toner 90 carried on the developing roller 42 may be.

[0155] Therefore, in this embodiment, the potential difference between the supply roller 43 and the developing roller 42 is variably controlled according to the degree of deterioration (remaining life) of the supply roller 43 and the amount of toner remaining in the developing device 4.

[0156] <Calculation of Supply Roller Deterioration Level and Determination of Supply Bias> Next, the calculation of the deterioration degree of the supply roller 43 and the determination of the supply bias Vrs in this embodiment will be described. Fig. 12 is a flow chart showing an outline of the procedure of the print operation focusing on the calculation of the deterioration degree of the supply roller 43 in this embodiment. The process according to the flow chart in Fig. 12 is executed by the control unit 220 (mainly the supply roller life detection unit 80). Note that, in the procedure in this embodiment shown in Fig. 12, the description of the same process as the procedure in embodiment 1 shown in Fig. 9 will be omitted as appropriate.

[0157] When a print signal (job information) is input (S601), the control unit 220 starts a print operation (job) (S602). In addition, with the start of the print operation, the control unit 220 checks the detection result of the toner remaining amount detection unit 70 (information stored in the memory 150 in this embodiment) (S603) and reads the toner remaining amount TJ (S604). In addition, the control unit 220 checks the information stored in the memory 150 (S605) and reads the supply roller remaining life ηJ stored in the memory 150 (S606). In addition, the control unit 220 determines the supply bias Vrs based on the toner remaining amount TJ and the supply roller remaining life ηJ (S607). Then, the supply power source 123 applies the determined supply bias Vrs to the supply roller 43. In this embodiment, the control unit 220 reads and determines the supply bias Vrs corresponding to the remaining toner amount TJ and the remaining life ηJ of the supply roller from table data shown in Table 10, which is preset and stored in the main body memory 221. Note that at the same timing as the application of the supply bias Vrs, the development power source 122 also applies the development bias Vdc to the development roller 42. In this embodiment, the development bias Vdc is set to a constant value of -350V.

[0158] The table data shown in Table 10 is an example of information showing the relationship between the toner remaining amount TJ, the supply roller remaining life ηJ, and the supply bias Vrs. As shown in Table 10, if the supply roller remaining life ηJ is the same, the absolute value of the negative polarity supply bias Vrs (same polarity as the normal charging polarity of the toner 90) is increased as the toner remaining amount TJ decreases. In other words, if the supply roller remaining life ηJ is the same, the potential difference (Vrs-Vdc) between the supply bias Vrs and the development bias Vdc is increased toward the negative polarity side (the same polarity as the normal charging polarity of the toner 90) as the toner remaining amount TJ decreases. Also, as shown in Table 10, if the toner remaining amount TJ is the same, the absolute value of the negative polarity supply bias Vrs (same polarity as the normal charging polarity of the toner 90) is increased as the supply roller remaining life ηJ decreases. That is, if the remaining toner amount TJ is the same, the smaller the supply roller remaining life ηJ, the greater the potential difference (Vrs-Vdc) between the supply bias Vrs and the developing bias Vdc is made to the negative polarity side (the same polarity as the normal charging polarity of the toner 90).

[0159] [Table 10]

[0160] The processes in S608 to S617 in FIG. 12 are similar to the processes in S406 to S415 in FIG.

[0161] <Variation 7> In this embodiment, as shown in Table 10, the supply bias Vrs is changed in four steps according to the remaining toner amount TJ, but this is not limited to this. The increments of the remaining toner amount TJ may be smaller or larger. In other words, the supply bias Vrs may be changed in fewer steps (three steps or less) or more steps (five steps or more) according to the remaining toner amount TJ. The appropriate supply bias Vrs 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.

[0162] <Variation 8> In this embodiment, the image forming apparatus 100 holds the value of the supply bias Vrs as table data as shown in Table 10, but is not limited to this. The image forming apparatus 100 can also hold the potential difference (Vrs-Vdc) between the supply bias Vrs and the developing bias Vdc as table data, for example, as shown in Table 11.

[0163] [Table 11]

[0164] <Comparative Verification 3> Next, a comparative verification carried out between this embodiment and the following Comparative Example 3 in order to verify the effect of this embodiment will be described.

[0165] -Evaluation method- A print endurance test was performed from the start of use of the developing device 4 (process cartridge 8) (supply roller remaining life ηJ = 100%) until a solid followability defect occurred, which is a guideline for determining that the supply roller remaining life ηJ = 0%. The solid followability defect was evaluated visually, and if it was significantly observed at a level that could be a practical problem, it was deemed that a solid followability defect had occurred. Specifically, a print endurance test was performed under the following conditions using A4 size recording paper. Environment: Temperature 23℃, humidity 50% Print mode: 2 sheets intermittent Print durability Image printing rate: 4% Evaluation image output: Every 500 sheets

[0166] The number of prints until poor solid image tracking ability occurred was compared between this embodiment and Comparative Example 3.

[0167] --Comparative Example 3-- In Comparative Example 3, the supply bias Vrs was constant at −500 V. Other points in Comparative Example 3 were substantially the same as those in this embodiment.

[0168] -Evaluation results- The evaluation results are shown in Table 12. Note that, although the evaluation results are shown here particularly for solid black images, in this embodiment, the configuration of the developing device 4 (process cartridge 8) for each color is substantially the same, and similar evaluation results were obtained.

[0169] [Table 12]

[0170] In Comparative Example 3, a supply bias Vrs sufficient to urge (move) the toner 90 from the supply roller 43 side to the developing roller 42 side was applied, but this accelerated deterioration of the supply roller 43, resulting in poor solid tracking performance.

[0171] On the other hand, in this embodiment, control was performed so that an appropriate supply bias Vrs was applied in accordance with the amount of toner 90 in the developing device 4 and the degree of deterioration of the supply roller 43. Therefore, in this embodiment, the number of prints until solid tracking failure occurred could be increased (i.e., the life of the supply roller 43 could be extended) compared to Comparative Example 3.

[0172] <Effects> In this embodiment, the image forming apparatus 100 has a developer amount acquisition unit (toner remaining amount detection unit) 70 that acquires information about the amount of developer in the developing device, and the control unit 220 controls to change the potential difference between the supply voltage applied to the supply member 43 and the development voltage applied to the development member 42 when forming a developer image on the image carrier 1 in image formation, based on information about the amount of developer in the developing device 4 and information about the deterioration degree of the supply member 43. Also, in this embodiment, the potential difference is a potential difference in which the supply voltage applied to the supply member 43 is the same polarity as the normal charging polarity of the developer with respect to the development voltage applied to the development member 42, and the control unit 220 controls so that the absolute value of the potential difference is larger when the amount indicated by the information about the amount of developer in the developing device 4 is a second amount less than the first amount than when the amount indicated by the information about the deterioration degree is a first amount, when the deterioration degree indicated by the information about the deterioration degree is the same.

[0173] As described above, in this embodiment, the supply bias Vrs is determined according to the amount of toner 90 in the developing device 4 in addition to the deterioration degree (remaining life) of the supply roller 43. This provides the same effects as in the first embodiment, and also makes it possible to more appropriately control the supply bias Vrs and suppress image defects such as poor solid-color tracking caused by deterioration (increase in electrical resistance) of the supply roller 43 over a long period of time.

[0174] [Example 4] Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the image forming apparatus of embodiment 1. Therefore, in the image forming apparatus of this embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus of embodiment 1 are given the same reference numerals as those of embodiment 1, and detailed explanations are omitted.

[0175] <Outline of this Example> In this embodiment, the supply bias Vrs is controlled taking into consideration the degree of deterioration (remaining life) of the supply roller 43, as well as the influence of the environment described in the second embodiment and the influence of the amount of toner 90 in the developing device 4 described in the third embodiment.

[0176] In other words, in this embodiment, the potential difference between the supply roller 43 and the developing roller 42 is variably controlled depending on the degree of deterioration (remaining life) of the supply roller 43, the temperature of the operating environment of the image forming apparatus 100, and the amount of toner remaining in the developing device 4.

[0177] <Calculation of Supply Roller Deterioration Level and Determination of Supply Bias> Next, the calculation of the deterioration degree of the supply roller 43 and the determination of the supply bias Vrs in this embodiment will be described. Fig. 13 is a flow chart showing an outline of the procedure of the print operation focusing on the calculation of the deterioration degree of the supply roller 43 in this embodiment. The process according to the flow chart in Fig. 13 is executed by the control unit 220 (mainly the supply roller life detection unit 80). Note that in the procedure in this embodiment shown in Fig. 13, the description of the same process as the procedure in embodiment 1 shown in Fig. 9 will be omitted as appropriate.

[0178] When a print signal (job information) is input (S701), the control unit 220 starts a print operation (job) (S702). In addition, the control unit 220 checks the detection result of the temperature and humidity sensor 130 (S703) with the start of the print operation, and reads the temperature and humidity data (particularly, temperature data in this embodiment) (S704). In addition, the control unit 220 checks the detection result of the toner remaining amount detection unit 70 (information stored in the memory 150 in this embodiment) (S705), and reads the toner remaining amount TJ (S706). In addition, the control unit 220 checks the information stored in the memory 150 (S707), and reads the supply roller remaining life ηJ stored in the memory 150 (S708). In addition, the control unit 220 determines the supply bias Vrs based on the temperature, the toner remaining amount TJ, and the supply roller remaining life ηJ (S709). Then, the supply power source 123 applies the determined supply bias Vrs to the supply roller 43. In this embodiment, the control unit 220 reads and determines the supply bias Vrs corresponding to the temperature, the remaining toner amount TJ, and the remaining life ηJ of the supply roller from table data shown in Tables 13, 14, and 15, which are preset and stored in the main body memory 221. Note that at the same timing as the application of the supply bias Vrs, the development power supply 122 also applies the development bias Vdc to the development roller 42. In this embodiment, the development bias Vdc is set to a constant value of -350V.

[0179] [Table 13]

[0180] [Table 14]

[0181] [Table 15]

[0182] The processes of S710 to S719 in FIG. 13 are similar to the processes of S406 to S415 in FIG.

[0183] It should be noted that the table data in this embodiment, such as those shown in Tables 13, 14, and 15, can also be modified in the same manner as in the modified examples described in the above embodiments.

[0184] <Comparative Verification 4> Next, a comparative verification carried out between this embodiment and the following Comparative Example 4 in order to verify the effect of this embodiment will be described.

[0185] -Evaluation method- A print endurance test was performed from the start of use of the developing device 4 (process cartridge 8) (supply roller remaining life ηJ = 100%) until a solid followability defect occurred, which is a guideline for determining that the supply roller remaining life ηJ = 0%. The solid followability defect was evaluated visually, and if it was significantly observed at a level that could be a practical problem, it was deemed that a solid followability defect had occurred. Specifically, a print endurance test was performed under the following conditions using A4 size recording paper. Environment: Temperature 14℃, humidity 10% Print mode: 2 sheets intermittent Print durability Image printing rate: 4% Evaluation image output: Every 500 sheets

[0186] The number of prints until poor solid image tracking ability occurred was compared between this embodiment and Comparative Example 4.

[0187] --Comparative Example 4-- In Comparative Example 4, the supply bias Vrs was constant at −600 V. Other points in Comparative Example 4 are substantially the same as those in this embodiment.

[0188] -Evaluation results- The evaluation results are shown in Table 16. Note that, although the evaluation results are shown here particularly for solid black images, in this embodiment, the configuration of the developing device 4 (process cartridge 8) for each color is substantially the same, and similar evaluation results were obtained.

[0189] [Table 16]

[0190] In Comparative Example 4, a supply bias Vrs sufficient to urge (move) the toner 90 from the supply roller 43 side to the development roller 42 side was applied, but this accelerated deterioration of the supply roller 43, resulting in poor solid tracking performance.

[0191] On the other hand, in this embodiment, control was performed so that an appropriate supply bias Vrs was applied in accordance with the temperature of the usage environment of the image forming apparatus 100, the amount of toner 90 in the developing device 4, and the degree of deterioration of the supply roller 43. Therefore, in this embodiment, the number of prints until solid tracking failure occurs can be increased (i.e., the life of the supply roller 43 can be extended) compared to Comparative Example 4.

[0192] <Effects> In this embodiment, the image forming apparatus 100 has an environment detection unit (temperature and humidity sensor) 130 that detects at least one of temperature and humidity, and a developer amount acquisition unit (toner remaining amount detection unit) 70 that acquires information regarding the amount of developer in the developing device 4, and the control unit 220 controls to change the potential difference between the supply voltage applied to the supply member 43 and the development voltage applied to the developing member 42 when forming a developer image on the image carrier 1 during image formation, based on the detection result of the environment detection unit 130, the information regarding the amount of developer in the developing device 4, and the information regarding the deterioration degree of the supply member 43.

[0193] As described above, in this embodiment, the supply bias Vrs is determined according to the deterioration degree (remaining life) of the supply roller 43, as well as the temperature of the environment in which the image forming apparatus 100 is used and the amount of toner 90 in the developing device 4. This provides the same effects as in the first embodiment, and also makes it possible to more appropriately control the supply bias Vrs and suppress image defects, such as poor solid-color tracking, that occur due to deterioration (increase in electrical resistance) of the supply roller 43 over a long period of time.

[0194] [Example 5] Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the image forming apparatus of embodiment 1. Therefore, in the image forming apparatus of this embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus of embodiment 1 are given the same reference numerals as those of embodiment 1, and detailed explanations are omitted.

[0195] <Outline of this Example> In this embodiment, based on the acquired information on the deterioration degree of the supply roller 43, control is performed so that a recovery operation for recovering the deterioration of the supply roller 43 (reducing the increased electrical resistance) is performed at an appropriate timing.

[0196] <Recovery Action> First, the recovery operation will be described. The recovery operation is an operation to reduce (return) the raised electrical resistance of the supply roller by eliminating (leveling) the uneven distribution of the ion conductive agent in the supply roller 43. The recovery operation can be performed during non-image formation by rotating the supply roller 43 with the potential difference (Vrs-Vdc) of the supply bias Vrs with respect to the developing bias Vdc set to the opposite polarity to that during image formation.

[0197] In this embodiment, during image formation (development), a supply bias Vrs having a large potential difference (Vrs-Vdc) on the negative polarity side (the same polarity side as the normal charging polarity of the toner 90) with respect to the developing bias Vdc is applied to the supply roller 43. Therefore, during the recovery operation, a supply bias Vrs having a large potential difference (Vrs-Vdc) on the positive polarity side (the opposite polarity side to the normal charging polarity of the toner 90) with respect to the developing bias Vdc is applied to the supply roller 43. Specifically, in this embodiment, the developing bias Vdc is kept at -350 V, the same as during image formation (development), and the supply bias Vdc is set to -250 V. As a result, the potential difference (Vrs-Vdc) between the supply roller 43 (supply bias Vrs) and the developing roller 42 (development bias Vdc) is set to +100 V (=-250 V-(-350 V)), and the supply roller 43 is rotated. The supply bias Vrs during the recovery operation may be a bias having a polarity opposite to that of the supply bias Vrs during image formation (opposite to the normal charging polarity of the toner 90). The supply bias Vrs during the recovery operation may be 0 V.

[0198] <Verification 4: Effect of recovery action on reduction of conductive agent> A test performed to examine the difference in the amount of conductive agent reduced depending on whether or not a recovery operation is performed will be described. The following print endurance test was performed under conditions in which a recovery operation is performed at a predetermined timing and conditions in which a recovery operation is not performed. During image formation, the development bias Vdc was set to -350V, and the supply bias Vrs was set to -450V. Under the condition in which a recovery operation is performed, the development bias Vdc was set to -350V, the same as during image formation, and the supply bias Vrs was changed to -250V, and idle rotation was performed for 10 seconds in each post-rotation process after image formation in the print operation. Therefore, the potential difference (Vrs-Vdc) between the supply roller 43 (supply bias Vrs) and the development roller 42 (development bias Vdc) during the recovery operation is +100V (=-250V-(-350V)). The idle rotation means that the rotating members of the image forming unit S, including the supply roller 43, are rotated without forming an image. Also, during the print endurance test, a measurement was performed at a predetermined timing to evaluate the amount of conductive agent contained in the supply roller 43. Here, 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, it was confirmed that the current value did not increase (recover) by the amount of the decrease even when a voltage of the opposite polarity to the above-mentioned predetermined voltage was applied, thereby confirming that the amount of conductive agent component had decreased. As a print endurance test, one intermittent print of an image with a print rate of 10% was performed in the usage environment (ambient environment) of the image forming apparatus 100, which was a temperature of 23 degrees and a humidity of 50%.

[0199] The results are shown in FIG. 14. The vertical axis indicates the ratio (decrease rate) of the current value to the initial current value when the initial current value (substitute value for the amount of conductive agent component) is set to 100%, and the horizontal axis indicates the rotation drive time of the supply roller 43 (=supply bias application time). It can be seen that the amount of decrease in the current value (amount of conductive agent) tends to be smaller under the condition where the recovery operation is performed than under the condition where the recovery operation is not performed. This is considered to be because, in a state where the ion conductive agent is unevenly distributed, the ion conductive agent is easily taken out of the supply roller 43 due to repulsion between the unevenly distributed ion conductive agents. In other words, it is considered to be because the uneven distribution of the ion conductive agent is eliminated by the recovery operation, and the discharge of the ion conductive agent to the outside of the supply roller 43 is suppressed, thereby suppressing the decrease in the ion conductive agent. From this, it can be seen that the decrease in the conductive agent in the supply roller 43 can be suppressed by performing the recovery operation. On the other hand, if the recovery operation is performed more frequently than necessary, the deterioration of the toner 90 is accelerated, which may cause image defects. Therefore, it is desirable to execute the recovery operation at an appropriate timing according to the degree of deterioration of the supply roller 43.

[0200] As shown in FIG. 14, the conductive agent will decrease as the supply roller 43 continues to be used. The only deterioration of the supply roller 43 that can be restored by the recovery operation is that caused by uneven distribution of the ion conductive agent. When the absolute amount of the conductive agent that causes uneven distribution has decreased due to the decrease in the conductive agent, the electrical resistance value that can be restored (reduced) becomes smaller. In other words, the deterioration degree (including the recovery degree) of the supply roller 43 after the recovery operation changes depending on the deterioration degree of the supply roller 43 at the timing of performing the recovery operation. Therefore, in order to perform the subsequent recovery operation at an appropriate timing and to set an appropriate supply bias Vrs as described above, it is also important to accurately obtain information regarding the deterioration degree (including the recovery degree) of the supply roller 43 after the recovery operation.

[0201] <Calculation of Supply Roller Deterioration Level and Control of Recovery Operation> Next, the calculation of the deterioration degree of the supply roller 43 and the control of the recovery operation in this embodiment will be described. FIG. 15 (divided into FIG. 15(a) and FIG. 15(b) for convenience) is a flow chart showing an outline of the procedure of the print operation focusing on the calculation of the deterioration degree of the supply roller 43 in this embodiment. The process according to the flow chart in FIG. 15 is executed by the control unit 220 (mainly the supply roller life detection unit 80). In the procedure in this embodiment shown in FIG. 15, the same process as the procedure in the first embodiment shown in FIG. 9 will not be described as appropriate. Also, FIG. 16 is a timing chart showing the transition of the bias applied to the supply roller 43 during the print operation when the recovery operation in this embodiment is executed.

[0202] In this embodiment, the remaining life of the supply roller 43 is detected (calculated) in the supply roller life detection unit 80, as in the first embodiment. In this embodiment, the deterioration degree of the supply roller 43 is calculated for each print operation (job), as in the first embodiment. Then, the deterioration degree of the supply roller 43 is added up for each print operation (job), and when it reaches a predetermined deterioration degree set in advance, a recovery operation is performed in a post-rotation process after the end of image formation in the print operation. When the recovery operation is performed, the deterioration degree of the supply roller 43 is subtracted in consideration of the voltage value (or the potential difference between the recovery bias Vrs_p and the development bias Vdc) of the supply bias (herein, also referred to as "recovery bias Vrs_p") during the recovery operation, the application time of the recovery bias Vrs_p, and the total print amount (described later) up to the recovery operation.

[0203] The processes of S801 to S814 in FIG. 15 are similar to the processes of S401 to S414 in FIG. 9, respectively (however, as will be described below, the processes of S808 and S813 in FIG. 15 are slightly different from the processes of S408 and S413 in FIG. 9).

[0204] When the control unit 220 determines in S813 that the remaining life η of the supply 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 (S814), similar to the first embodiment. Then, the control unit 220 ends the print operation (S823).

[0205] Furthermore, if the control unit 220 determines in S813 that the supply roller remaining life ηJ is not 0% or less, it determines (S815) whether the total supply roller deterioration degree ηt stored in the memory 150 is equal to or greater than the recovery operation initiation threshold value Xth that is preset and stored in the memory 150. If the control unit 220 determines in S815 that the total supply roller deterioration degree ηt is not equal to or greater than the recovery operation initiation threshold value Xth, it ends the print operation (S823).

[0206] Then, when the control unit 220 determines in S815 that the total supply roller deterioration degree ηt is equal to or greater than the recovery operation initiation threshold value Xth, it executes the recovery operation in the post-rotation process of the print operation (job) (S816). The control unit 220 controls the supply power source 123 to apply the recovery bias Vrs_p to the supply roller 43 with the start of the recovery operation (post-rotation process). The control unit 220 also controls the development power source 122 to apply the development bias Vdc to the development roller 42 at the same timing as the application of the recovery bias Vrs_p. In this embodiment, the recovery bias Vrs_p=-250V and the development bias Vdc=-350V during the recovery operation. That is, in this embodiment, the potential difference Δ between the supply roller 43 (recovery bias Vrs_p) and the development roller 42 (development bias Vdc) during the recovery operation is Δ=Vrs_p-Vdc=-250V-(-350V)=+100V. The recovery operation initiation threshold Xth is set to a value smaller than the supply roller deterioration degree threshold ηth (a value corresponding to a state in which the degree of deterioration is smaller). The recovery operation initiation threshold Xth is determined and set in advance by an experiment or the like so that, for example, the recovery operation can be executed before the conductive agent in the supply roller 43 decreases to such an extent that the deterioration (increase in electrical resistance) of the supply roller 43 cannot be sufficiently restored. The recovery operation initiation threshold Xth can vary depending on, for example, the elastic material constituting the foamed elastic layer of the supply roller 43, the type and amount of the conductive agent contained in the material of the foamed elastic layer, the type of toner 90, and the like.

[0207] Next, during the recovery operation, the supply bias application time calculation unit 81 measures the time during which the recovery bias Vrs_p is applied to the supply roller 43 (S817). After the recovery operation, the supply bias application time calculation unit 81 calculates the recovery bias application time t'now in the recovery operation (S818). If the recovery bias application start timing in the recovery operation is tE, which is the same as the supply bias application end timing described above, and the recovery bias application end timing is t'E, the recovery bias application time t'now in the recovery operation can be expressed by the following formula (9). It is desirable to set the recovery operation time so that the effect of recovering the deterioration (increase in electrical resistance) of the supply roller 43 can be sufficiently obtained. Also, if the recovery operation time is too long, there is a possibility that image defects will occur due to the accelerated deterioration of the toner 90. The recovery operation time can be appropriately set taking these factors into consideration. The recovery operation time may be a time covering substantially the entire period of the post-rotation process, or a time corresponding to a part of the period of the post-rotation process. However, in order to obtain the effect of the recovery operation over the entire circumference of the supply roller 43, the time is preferably at least the time it takes for the supply roller 43 to make one revolution. Although not limited thereto, the time for the recovery operation is about 1 to 30 seconds, preferably about 5 to 15 seconds. In this embodiment, the time for the recovery operation is about 10 seconds, which is the time that covers almost the entire period of the post-rotation process. t'now=tE-t'E ···(9)

[0208] After the recovery operation, the control unit 220 reads out the total print amount (total print rate) γsum, which is the cumulative value of the print rate of the output image from the start of use of the developing device 4 (supply roller 43) stored in the memory 150 (S819). Here, in this embodiment, the section print rate γnow is calculated in S808, and the total print amount γsum is calculated as follows. That is, as shown in the following formula (10), the second video count measurement unit 83 adds (accumulates) the section print rate γnow acquired during the print operation to the cumulative print rate γpre up to the previous print operation (job) stored in the memory 150. In this way, the total print amount γsum is calculated. Then, the second video count measurement unit 83 updates and stores the calculated total print amount γsum in the memory 150 as a new cumulative print rate γpre. γsum = γpre + γnow (10)

[0209] Next, the supply roller deterioration degree calculation unit 84 determines the recovery amount correction coefficient σ based on the acquired total print amount γsum (S820). In this embodiment, the supply roller deterioration degree calculation unit 84 reads out and determines the recovery amount correction coefficient σ corresponding to the total print amount γsum from table data shown in Table 17, which is preset and stored in the memory 150.

[0210] Here, the "cumulative printing rate within life" in Table 17 is the ratio (printing rate) of the total printing amount γsum when the assumed cumulative printing rate at the end of life calculated from the integration of a predetermined printing rate and the nominal life number of the developing device 4 is taken as 100%. In this embodiment, the "ISO printing rate" according to the following standard was used as the above-mentioned predetermined printing rate. Standard number: JIS X6932 (ISO / IEC 19798) Name of standard: Method for measuring the number of pages that can be printed with a toner cartridge for color electrophotographic printers and multifunction printers Printing rate (%): Y / M / C / K 5.3 / 4.2 / 4.8 / 4.2 All colors average: 4.63

[0211] The table data in Table 17 is an example of information showing the relationship between the within-life cumulative print rate and the recovery amount correction coefficient σ. As shown in Table 17, the greater the within-life cumulative print rate, the smaller the recovery amount correction coefficient σ is set.

[0212] [Table 17]

[0213] Next, the supply roller deterioration level calculation unit 84 calculates the section supply roller recovery level η'now, which is an index showing the degree of recovery of the supply roller 43 from deterioration in the recovery operation, by the following formula (11) (S821). η'now=t'now×|Vrs_p-Vdc|×σ ···(11)

[0214] When the developing bias Vdc is constant, the section supply roller recovery degree η'now may be calculated by the following formula: η'now=t'now×|Vrs_p|×σ.

[0215] Next, the supply roller deterioration degree calculation unit 84 uses the calculated section supply roller recovery degree η'now to correct the cumulative supply roller deterioration degree ηr stored in the memory 150 to calculate the corrected total supply roller deterioration degree ηt (S822). That is, as shown in the following formula (12), the supply roller deterioration degree calculation unit 84 subtracts the calculated section supply roller recovery degree η'now from the cumulative supply roller deterioration degree ηr from the start of use of the development device 4 (supply roller 43) stored in the memory 150. In this way, the corrected total supply roller deterioration degree ηt is calculated. Then, the supply roller deterioration degree calculation unit 84 updates and stores the calculated corrected total supply roller deterioration degree ηt in the memory 150 as a new cumulative supply roller deterioration degree ηr. ηt=ηr-η'now (12)

[0216] Thereafter, the control unit 220 ends the printing operation (S823).

[0217] <Variation 9> In this embodiment, the case where the control of the first embodiment and the recovery operation are combined has been described, but any of the controls of the second to fourth embodiments may be combined with the recovery operation.

[0218] <Comparative Verification 5> Next, a comparative verification carried out for this embodiment and the following Comparative Examples 5-1 to 5-3 in order to verify the effects of this embodiment will be described.

[0219] -Evaluation method- A print endurance test of 3000 sheets was conducted from the start of use of the developing device 4 (process cartridge 8). Specifically, the print endurance test was conducted under the following conditions using A4 size recording paper. After the completion of the 3000 prints, images were output under the respective prescribed conditions to evaluate the occurrence of poor solid-color tracking and fogging. Note that fogging is a type of image defect, and is a phenomenon in which the toner 90, which is subjected to mechanical stress accompanying the rotation of the developing roller 42 and the supply roller 43, becomes difficult to maintain its charged state and adheres to the white background. Environment: Temperature 23℃, humidity 50% Print mode: 2 sheets intermittent Print durability Image printing rate: 25%

[0220] Then, the occurrence of the solid image tracking failure and the fog after printing 3000 sheets was confirmed, and this embodiment was compared with Comparative Examples 5-1 to 5-3. The occurrence of the solid image tracking failure was confirmed by visual inspection, and the case where the solid image tracking failure did not occur was evaluated as ◯ (good), and the case where the solid image tracking failure occurred to a level that was problematic in practical use was evaluated as × (bad). The occurrence of the fog was also confirmed by visual inspection, and the case where the fog was not visible on the image was evaluated as ◯ (good), and the case where the fog occurred to an unacceptable degree was evaluated as × (bad).

[0221] -Comparative Examples 5-1 to 5-3- In Comparative Example 5-1, the recovery operation was not performed. In Comparative Example 5-2, the recovery operation was performed every time a post-rotation operation was performed during the print durability test. In Comparative Example 5-3, the recovery operation was performed during a post-rotation operation every 200 prints. Other points of Examples 5-1 to 5-3 are substantially the same as this embodiment. In this embodiment, the recovery operation was performed based on the above-mentioned control.

[0222] -Evaluation results- The evaluation results are shown in Table 18. Note that, although the evaluation results for black images are shown here in particular, the configurations of the developing devices 4 (process cartridges 8) for each color in this embodiment were substantially the same, and similar evaluation results were obtained.

[0223] [Table 18]

[0224] In Comparative Example 5-1, no fogging occurred, but poor solid-color conformity occurred. In Comparative Example 5-1, since the recovery operation was not performed, the uneven distribution of the ion conductive agent could not be eliminated, and the amount of toner supplied from the supply roller 43 to the development roller 42 by application of the supply bias Vrs decreased, which is thought to be the reason for the poor solid-color conformity.

[0225] In Comparative Example 5-2, no solid followability failure occurred, but fogging occurred. In Comparative Example 5-2, since the recovery operation was performed, the uneven distribution of the ion conductive agent could be eliminated, and it is believed that no solid followability failure occurred. On the other hand, in Comparative Example 5-2, in addition to the image forming operation, the toner 90 is subjected to mechanical stress accompanying the rotation of the developing roller 42 and the supply roller 43 for the recovery operation in each post-rotation operation. This increases the influence of the toner 90, which is now difficult to maintain the charged state, and it is believed that fogging occurs.

[0226] In Comparative Example 5-3, fog did not occur, but poor solid followability occurred. In Comparative Example 5-3, the frequency of recovery operations was reduced compared to Comparative Example 5-2, so the effect of the toner 90 subjected to mechanical stress accompanying the rotation of the developing roller 42 and the supply roller 43 was reduced, and it is believed that fog did not occur. On the other hand, in Comparative Example 5-3, recovery operations were not performed in consideration of the deterioration level of the supply roller 43, and recovery operations were performed every predetermined number of prints. As a result, it is believed that poor solid followability occurred because recovery operations could not be performed in accordance with the deterioration state of the supply roller 43, which progresses due to a combination of the decrease in the ion conductive agent and the uneven distribution of the ion conductive agent.

[0227] In contrast, in this embodiment, neither poor solid tracking nor fogging occurred. FIG. 17 is a graph diagram showing the transition of the deterioration degree of the supply roller 43 in this embodiment. In this embodiment, the recovery operation was performed at an appropriate timing in consideration of the deterioration degree of the supply roller 43, so it is considered that the poor solid tracking did not occur. In other words, in this embodiment, the deterioration state of the supply roller 43, which progresses due to a combination of the decrease in the ion conductive agent and the uneven distribution of the ion conductive agent, was more accurately grasped, and the recovery operation was performed at an appropriate timing, so it is considered that the poor solid tracking did not occur. In addition, in this embodiment, the frequency of performing the recovery operation was reduced compared to Comparative Example 5-2, so that the mechanical stress on the toner 90 caused by the rotation of the development roller 42 and the supply roller 43 was also suppressed, and fogging did not occur.

[0228] <Effects> In this embodiment, in the image formation, an image forming operation in which a developer image is formed on the image carrier 1 and a non-image forming operation in which a developer image is not formed on the image carrier 1 are performed, and the control unit 220 can control the control unit 220 to execute a recovery operation in which the polarity of the potential difference between the development voltage applied to the development member 42 and the supply voltage applied to the supply member 43 is reversed to that in the image forming operation during the non-image forming operation. At this time, the control unit 220 can reverse the polarity of the potential difference to that in the image forming operation by controlling at least one of the first application unit (development power source) 122 or the second application unit (supply power source) 123. In this embodiment, the control unit 220 controls the control unit 220 to execute the recovery operation based on information on the deterioration degree of the supply member 43. In this embodiment, the control unit 220 controls the control unit 220 to execute the recovery operation when the deterioration degree indicated by the information on the deterioration degree reaches a preset threshold value. In other words, in this embodiment, the control unit 220 controls so that the number of recording materials P on which images are formed between the first recovery operation and the next recovery operation when image formation for forming an image with a second printing rate higher than the first printing rate is repeated is smaller than the number of recording materials P on which images are formed between the first recovery operation and the next recovery operation when image formation for forming an image with a first printing rate is repeated. Also, in this embodiment, the control unit 220 changes the information on the deterioration degree stored in the storage unit 150 so that the deterioration degree indicated by the information on the deterioration degree is reduced when the recovery operation is performed. Also, in this embodiment, the storage unit 150 is capable of storing information on the total printing amount in image formation performed using the supply member 43, and the control unit 220 changes the amount by which the deterioration degree indicated by the information on the deterioration degree is reduced based on the information on the total printing amount stored in the storage unit 150 when performing the recovery operation. In this embodiment, the control unit 220 controls the amount by which the deterioration degree indicated by the information on the deterioration degree is reduced to a smaller extent when the printing amount indicated by the information on the total printing amount stored in the memory unit 150 when performing the recovery operation is a second printing amount greater than the first printing amount than when the information on the deterioration degree is a first printing amount.

[0229] As described above, in this embodiment, information on the deterioration degree (including the recovery degree) of the supply roller 43 is acquired more accurately in consideration of the printing rate of the output image, and a recovery operation for recovering the deterioration of the supply roller 43 (reducing the increased electrical resistance) can be performed at an appropriate timing based on the information on the deterioration degree (including the recovery degree). This makes it possible to suppress image defects such as poor solid tracking caused by deterioration (increase in electrical resistance) of the supply roller 43 over a long period of time.

[0230] [others] Although the present invention has been described above with reference to specific embodiments, the present invention is not limited to the above-mentioned embodiments.

[0231] In the above embodiment, the image forming apparatus is a tandem type (in-line type) full-color image forming apparatus, but the present invention is not limited to this. The present invention can also be applied to a monochrome image forming apparatus.

[0232] In the above embodiment, the image forming apparatus is configured such that the process cartridge is detachable from the apparatus main body, but the present invention is not limited to this. For example, the image forming apparatus may be configured such that the developing unit (developing device) and the drum unit (having, for example, a photoconductor, a charging device, and a cleaning device) are each independently detachable from the apparatus main body. The image forming apparatus may also be a toner supply type image forming apparatus in which a toner supply container (toner cartridge, toner bottle, toner pack, etc.) containing toner to be supplied to the developing device is detachably attached to the process cartridge (or developing device). In this case, the image forming apparatus may be configured to perform image formation with the toner supply container connected to the process cartridge (or developing device), or may be configured to perform image formation with the toner supply container removed after toner is supplied to the developing device.

[0233] Furthermore, in order to detect the life of the process cartridge, the life of the photosensitive member may be set separately.

[0234] Furthermore, the notification of information to the user is not limited to being by displaying a message or the like, but may be by emitting light (such as a lit or blinking warning light) or sound (such as a warning sound or voice).

[0235] Furthermore, the information on the printing rate is not limited to the printing rate itself. For example, the printing rate can be calculated based on the number of pixels and the video count value, or the number of prints and the amount of toner consumed. Such information on the basis of which the printing rate can be calculated can also be considered as information on the printing rate.

[0236] In addition, the information on the deterioration level of the supply roller may be used as an index value showing the degree of deterioration of the supply roller due to use, and is not limited to the value calculated by the method of the above embodiment. For example, information calculated based on the deterioration level, such as the remaining life, can also be considered as information on the deterioration level.

[0237] In the above embodiment, the calculation of the deterioration level of the supply roller is used for setting the supply bias, determining whether or not to perform a recovery operation, and also for detecting the life of the developing device, but the present invention is not limited to this. The calculation of the deterioration level of the supply roller is performed for the purpose of at least one of setting the supply bias or determining whether or not to perform a recovery operation, and does not have to be used for detecting the life of the developing device.

[0238] In the above embodiment, the developing bias is assumed to be constant. However, the developing bias may be changed depending on, for example, the environment in which the image forming apparatus is used.

[0239] In the above embodiment, the toner remaining amount is detected by a video counting method, but the present invention is not limited to this. As a developer remaining amount detection method, for example, in addition to the video counting method, any available method such as a capacitance method or a light transmission method can be used. The capacitance method is a method of acquiring information on the developer amount using an electrode whose detected capacitance changes according to a change in the amount of developer inside the developing device. The light transmission method is a method of acquiring the developer amount based on a change in the light receiving state (presence or absence of light reception, amount of light reception, time of light reception, etc.) of the light receiving portion using a light source that irradiates light into the inside of the developing device and a light receiving portion that receives the light that has passed through the inside of the developing device. In addition, a weight detection method that acquires information on the developer amount based on a change in the weight of the developing device can be used. As these other developer remaining amount detection methods, for example, known methods can be used as appropriate. [Explanation of symbols]

[0240] 1 Photosensitive drum 4. Developing device 8 Process cartridge 42 Developing roller 43 Supply roller 90 Toner 100 Image forming device 150 Non-volatile memory 201 Video Controller 202 Engine Controller 220 Control section 221 Main Memory

Claims

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

2. The image forming apparatus according to claim 1, characterized in that the potential difference is a potential difference such that the supply voltage applied to the supply member is on the same polarity as the normal charging polarity of the developer relative to the development voltage applied to the development member, and the control unit controls the absolute value of the potential difference to be larger when the degree of deterioration indicated by the information on the degree of deterioration is a second degree of deterioration greater than the first degree of deterioration than when the degree of deterioration is a first degree of deterioration.

3. An environment detection unit that detects at least one of temperature and humidity, The image forming apparatus according to claim 1, characterized in that the control unit controls to change the potential difference between the supply voltage applied to the supply member and the development voltage applied to the development member when forming a developer image on the image carrier during image formation, based on the detection result of the environment detection unit and information regarding the degree of deterioration.

4. The image forming apparatus according to claim 3, characterized in that the potential difference is a potential difference such that the supply voltage applied to the supply member is on the same polarity side as the normal charging polarity of the developer relative to the developing voltage applied to the developing member, and the control unit controls the potential difference so that, when the degree of deterioration indicated by the information on the degree of deterioration is the same, the absolute value of the potential difference is larger when the temperature indicated by the detection result of the environmental detection unit is a second temperature lower than the first temperature than when the temperature indicated by the detection result of the environmental detection unit is a first temperature.

5. a developer amount acquisition unit that acquires information regarding an amount of developer in the developing device; The image forming apparatus according to claim 1, characterized in that the control unit controls to change the potential difference between the supply voltage applied to the supply member when forming a developer image on the image carrier during image formation and the development voltage applied to the development member based on information regarding the amount of developer in the development device and information regarding the degree of deterioration.

6. The image forming apparatus according to claim 5, characterized in that the potential difference is a potential difference such that the supply voltage applied to the supply member is on the same polarity as the normal charging polarity of the developer relative to the developing voltage applied to the developing member, and the control unit controls the potential difference so that, when the degree of deterioration indicated by the information on the deterioration degree is the same, the absolute value of the potential difference is larger when the amount indicated by the information on the amount of developer in the developing device is a second amount smaller than the first amount than when the amount indicated by the information on the amount of developer in the developing device is a first amount.

7. an environment detection unit that detects at least one of temperature and humidity; a developer amount acquiring unit that acquires information regarding an amount of developer in the developing device; having The image forming apparatus according to claim 1, characterized in that the control unit controls to change the potential difference between the supply voltage applied to the supply member when forming a developer image on the image carrier during image formation and the development voltage applied to the development member based on the detection results of the environmental detection unit, information regarding the amount of developer in the development device, and information regarding the degree of deterioration.

8. In an image forming apparatus for forming an image on a recording material by transferring a developer image onto the recording material, a rotatable image carrier that carries a developer image; a developing device for supplying a developer to a surface of the image carrier to form a developer image on the surface of the image carrier, the developing device including: a rotatable developing member for supplying the developer to the surface of the image carrier; and a rotatable supply member having an elastic layer containing an ion conductive agent, the rotatable supply member being in contact with the developing member to supply the developer to the developing member; a first application unit that applies a development voltage to the developing member; a second applying unit that applies a supply voltage to the supply member; an acquisition unit that acquires information regarding a printing rate of an image formed in the image formation; a control unit that acquires information regarding a deterioration level of the supply member based on information regarding the supply voltage applied to the supply member, information regarding a time during which the supply voltage is applied to the supply member, and information regarding the printing rate; a storage unit that stores information regarding the deterioration degree acquired by the control unit; having In the image formation, an image forming operation for forming a developer image on the image carrier and a non-image forming operation for not forming a developer image on the image carrier are performed, the control unit is capable of performing control to execute a recovery operation in which a polarity of a potential difference between the supply voltage applied to the supply member and the developing voltage applied to the developing member is reversed to a polarity of a potential difference between the supply voltage applied to the supply member and the developing voltage applied to the developing member during the non-image forming operation, The image forming apparatus, wherein the control unit controls the recovery operation to be executed based on information related to the deterioration level.

9. 9. The image forming apparatus according to claim 8, wherein the control unit controls the recovery operation to be executed when the degree of deterioration indicated by the information on the degree of deterioration reaches a preset threshold value.

10. The image forming apparatus according to claim 8, characterized in that the control unit controls the number of recording materials on which images are formed between the previous recovery operation and the next recovery operation when the image formation is repeated to form an image with a first printing rate, so that the number of recording materials on which images are formed between the previous recovery operation and the next recovery operation when the image formation is repeated to form an image with a second printing rate higher than the first printing rate, is smaller than the number of recording materials on which images are formed between the previous recovery operation and the next recovery operation when the image formation is repeated to form an image with a first printing rate.

11. The image forming apparatus according to claim 8, characterized in that, when the recovery operation is performed, the control unit changes the information regarding the deterioration level stored in the memory unit so that the deterioration level indicated by the information regarding the deterioration level becomes smaller.

12. the storage unit is capable of storing information regarding a total amount of printing in the image formation performed using the supply member, The image forming apparatus according to claim 11, characterized in that the control unit changes the amount by which the deterioration degree indicated by the information on the deterioration degree is reduced based on information regarding the total printing amount stored in the memory unit when performing the recovery operation.

13. The image forming apparatus according to claim 12, characterized in that the control unit controls the amount by which the deterioration degree indicated by the information on the deterioration degree is reduced less when the printing amount indicated by the information on the total printing amount stored in the memory unit when performing the recovery operation is a second printing amount greater than the first printing amount than when the information on the deterioration degree is a first printing amount.

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

15. The image forming apparatus according to any one of claims 1 to 13, characterized in that the control unit obtains information regarding the deterioration degree by correcting a value correlated with a product of voltage and time based on information regarding the supply voltage applied to the supply member and information regarding the time for which the supply voltage was applied to the supply member, using a correction coefficient corresponding to information regarding the printing rate.

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

17. 14. The image forming apparatus according to claim 1, wherein the developing member forms a developing portion by contacting the image carrier, and supplies a developer to the image carrier in the developing portion.

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

Images