Image forming device, image forming device control method, and toner cartridge

Abstract

Provided are an image forming device that appropriately detects toner exhaustion, a control method for an image forming device, and a toner cartridge. An image forming device according to one embodiment includes a photosensitive drum, an exposure device, a developer, a toner concentration sensor, a toner supply motor, and a processor. The exposure device exposes the photosensitive drum based on image data. The developer forms a toner image on the photosensitive drum using toner supplied from a toner cartridge. The toner concentration sensor detects the toner concentration in the developer. The toner supply motor supplies toner from the toner cartridge to the developer based on the toner concentration. The processor detects toner exhaustion based on a toner supply rate calculated based on a pixel count value, which is an integrated value of pixel values based on image data, and a toner supply motor count value, which is an integrated value of the driving time of the toner supply motor, the printing rate of image data, and a toner characteristic, which is a characteristic of toner supplied from the toner cartridge to the developer.

Description

Technical Field

[0001] Embodiments of the present invention relate to an image forming apparatus, a method for controlling an image forming apparatus, and a toner cartridge. Background Art

[0002] The image forming apparatus receives toner from a toner cartridge and forms a toner image on a photosensitive drum. The image forming apparatus then transfers the toner image on the photosensitive drum to a printing medium.

[0003] The image forming apparatus estimates the remaining toner amount in the toner cartridge based on the drive amount (toner supply motor count value) of a motor (toner supply motor) for driving a screw (delivery mechanism) that delivers toner from the toner cartridge to the image forming apparatus. The image forming apparatus detects near-end status, indicating that the remaining toner in the toner cartridge is low, when the toner supply motor count value exceeds a near-end threshold.

[0004] The image forming apparatus also includes a toner concentration sensor that detects the toner concentration in a developer that receives toner from a toner cartridge. Upon detecting a decrease in toner concentration, the image forming apparatus replenishes toner via a toner replenishment motor. If the toner concentration does not recover despite operating the toner replenishment motor, the image forming apparatus detects toner end status, indicating that the toner cartridge is empty.

[0005] However, when the print rate of image data used for printing is low, toner end detection based on toner concentration takes time from the detection of toner near end to the detection of toner end. Furthermore, depending on the fluidity of the toner within the toner cartridge, the toner near end detection may differ from the actual remaining toner amount. This creates a problem of discrepancy between toner near end detection and toner end detection. Summary of the Invention

[0006] Technical problem to be solved by the invention

[0007] The technical problem to be solved by the present invention is to provide an image forming apparatus and a control method of the image forming apparatus that can appropriately detect toner exhaustion.

[0008] Solutions for solving technical problems

[0009] An image forming device according to one embodiment includes a photosensitive drum, an exposure device, a developer, a toner concentration sensor, a toner supply motor, and a processor. The exposure device exposes the photosensitive drum based on image data. The developer forms a toner image on the photosensitive drum using toner supplied from a toner cartridge. The toner concentration sensor detects the toner concentration in the developer. The toner supply motor supplies toner from the toner cartridge to the developer based on the toner concentration. The processor detects toner exhaustion based on a toner supply rate, a printing rate of the image data, and toner characteristics. The toner supply rate is calculated based on a pixel count value and a toner supply motor count value. The pixel count value is the cumulative value of the pixel values of the image data. The toner supply motor count value is the cumulative value of the driving time of the toner supply motor. The toner characteristics are the characteristics of the toner supplied from the toner cartridge to the developer.

[0010] A control method for an image forming device according to one embodiment, wherein the image forming device comprises: a photosensitive drum; an exposing device for exposing the photosensitive drum based on image data; a developing device for forming a toner image on the photosensitive drum using toner supplied from a toner cartridge; a toner concentration sensor for detecting the toner concentration in the developing device; a toner supply motor for supplying toner from the toner cartridge to the developing device based on the toner concentration; and a processor for detecting toner exhaustion based on a toner supply rate, a printing rate of the image data, and toner characteristics of the toner cartridge, wherein the toner supply rate is calculated based on a pixel count value and a toner supply motor count value, wherein the pixel count value is an accumulated value of pixel values of the image data, and the toner supply motor count value is an accumulated value of a driving time of the toner supply motor.

[0011] A toner cartridge according to one embodiment is applied to an image forming apparatus, wherein the image forming apparatus comprises: a photosensitive drum; an exposing device for exposing the photosensitive drum based on image data; a developing device for forming a toner image on the photosensitive drum using toner supplied from the toner cartridge; a toner concentration sensor for detecting a toner concentration in the developing device; a toner supply motor for supplying toner from the toner cartridge to the developing device based on the toner concentration; and a processor, wherein the toner cartridge comprises: a toner storage container for storing toner; a toner delivery mechanism for delivering the toner in the toner storage container; and a memory for storing a control table indicating a correlation between a toner supply rate threshold and a printing rate of the image data, the toner supply rate threshold being a threshold for comparison with a toner supply rate calculated in the processor based on a pixel count value which is an integrated value of pixel values of the image data and a toner supply motor count value which is an integrated value of a driving time of the toner supply motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a diagram for explaining a configuration example of an image forming apparatus according to an embodiment.

[0013] Figure 2 This is a diagram for explaining a configuration example of a portion of an image forming unit according to an embodiment.

[0014] Figure 3 This is an explanatory diagram for explaining an example of the operation of the image forming apparatus according to one embodiment.

[0015] Figure 4 This is an explanatory diagram for explaining an example of the operation of the image forming apparatus according to one embodiment.

[0016] Figure 5 This is an explanatory diagram for explaining an example of the operation of the image forming apparatus according to one embodiment.

[0017] Figure 6 This is an explanatory diagram for explaining an example of the operation of the image forming apparatus according to one embodiment.

[0018] Description of Reference Numerals

[0019] 1: Image forming device; 2: Toner cartridge; 11: Housing; 12: Communication interface; 13: System controller; 14: Display unit; 15: Operation interface; 16: Paper tray; 17: Paper discharge tray; 18: Conveyor unit; 19: Image forming unit; 20: Fuser; 21: Processor; 22: Memory; 31: Paper feed path; 32: Paper discharge path; 33: Pickup roller; 41: Loading unit; 42: Processing unit; 43: Exposure unit; 44: Transfer unit Structure; 51: Toner accommodating container; 52: Toner delivery mechanism; 53: Memory; 61: Toner supply motor; 71: Photosensitive drum; 72: Cleaner; 73: Charger; 74: Developer; 81: Developer container; 82: Stirring mechanism; 83: Developing roller; 84: Scraper; 85: ATC sensor; 91: Primary transfer belt; 92: Secondary transfer opposing roller; 93: Primary transfer roller; 94: Secondary transfer roller; 95: Heating roller; 96: Pressurizing roller. DETAILED DESCRIPTION

[0020] Hereinafter, an image forming apparatus and a method for controlling the image forming apparatus according to an embodiment will be described with reference to the drawings.

[0021] Figure 1 It is an explanatory diagram for explaining a configuration example of the image forming apparatus 1 according to one embodiment.

[0022] The image forming apparatus 1 is, for example, a multifunction printer (MFP) that performs various processes such as image formation while conveying a recording medium such as a print medium. The image forming apparatus 1 is, for example, a solid-state scanning printer (e.g., an LED printer) that uses a scanning LED array to convey a recording medium such as a print medium while conveying various processes such as image formation.

[0023] For example, the image forming apparatus 1 receives toner from the toner cartridge 2 and forms an image on a print medium using the received toner. The toner may be a monochrome toner or a color toner such as cyan, magenta, yellow, or black.

[0024] like Figure 1 As shown, the image forming apparatus 1 includes a housing 11 , a communication interface 12 , a system controller 13 , a display unit 14 , an operation interface 15 , a plurality of paper trays 16 , a paper discharge tray 17 , a conveying unit 18 , an image forming unit 19 , and a fixing unit 20 .

[0025] The housing 11 is a main body of the image forming apparatus 1 and houses a communication interface 12 , a system controller 13 , a display unit 14 , an operation interface 15 , a plurality of paper trays 16 , a paper discharge tray 17 , a conveying unit 18 , an image forming unit 19 , and a fixing unit 20 .

[0026] The communication interface 12 is an interface for communicating with other devices. For example, the communication interface 12 is used to communicate with a host device (external device). For example, the communication interface 12 is configured as a LAN connector. Alternatively, the communication interface 12 can wirelessly communicate with other devices using standards such as Bluetooth (registered trademark) or Wi-Fi (registered trademark).

[0027] The system controller 13 controls the image forming apparatus 1. The system controller 13 includes, for example, a processor 21 and a memory 22.

[0028] The processor 21 is a computing element that performs arithmetic processing. The processor 21 is, for example, a CPU. The processor 21 performs various processes based on data such as programs stored in the memory 22. By executing the programs stored in the memory 22, the processor 21 functions as a control unit capable of performing various operations.

[0029] The memory 22 is a storage medium that stores programs and data used in the programs. In addition, the memory 22 also functions as a working memory. That is, the memory 22 temporarily stores data being processed by the processor 21 and programs executed by the processor 21.

[0030] The processor 21 performs various information processing by executing programs stored in the memory 22. For example, the processor 21 generates a print job based on an image acquired from an external device via the communication interface 12. The processor 21 stores the generated print job in the memory 22.

[0031] A print job includes image data representing an image to be formed on a print medium P. The image data may be data for forming an image on a single print medium P or data for forming images on multiple print media P. Furthermore, a print job includes information indicating whether color printing or monochrome printing is to be performed.

[0032] Furthermore, the processor 21 functions as a controller (engine controller) that controls the operations of the transport unit 18, the image forming unit 19, and the fuser 20 by executing programs stored in the memory 22. Specifically, the processor 21 controls the transport of the print medium P by the transport unit 18, controls the formation of an image on the print medium P by the image forming unit 19, and controls the fixing of the image on the print medium P by the fuser 20.

[0033] Alternatively, the image forming apparatus 1 may include an engine controller independently of the system controller 13. In this case, the engine controller controls the conveyance of the print medium P by the conveyance unit 18, the formation of an image on the print medium P by the image forming unit 19, and the fixing of the image on the print medium P by the fuser 20. In this case, the system controller 13 supplies information required for control by the engine controller to the engine controller.

[0034] The display unit 14 includes a monitor that displays images based on image signals input from a display control unit such as the system controller 13 or a graphic controller (not shown). For example, the display unit 14 displays various settings for the image forming apparatus 1 and information such as the remaining toner level.

[0035] The operation interface 15 is connected to an operating member (not shown). The operation interface 15 supplies an operation signal corresponding to the operation of the operating member to the system controller 13. The operating member may be, for example, a touch sensor, a numeric keypad, a power key, a paper feed key, various function keys, or a keyboard. The touch sensor acquires information indicating a designated position within a certain area. The touch sensor is integrally formed with the display unit 14 as a touch panel, thereby inputting a signal indicating the touched position on the screen displayed by the display unit 14 to the system controller 13.

[0036] The plurality of paper trays 16 are cassettes that respectively accommodate printing media P. The paper trays 16 are configured to be able to supply the printing media P from the outside of the housing 11 . For example, the paper trays 16 are configured to be able to be pulled out from the housing 11 .

[0037] The paper discharge tray 17 is a tray that supports the print medium P discharged from the image forming apparatus 1 .

[0038] Next, a configuration for conveying the printing medium P of the image forming apparatus 1 will be described.

[0039] The transport unit 18 is a mechanism for transporting the printing medium P within the image forming apparatus 1. Figure 1 As shown, the transport unit 18 includes a plurality of transport paths. For example, the transport unit 18 includes a paper feed transport path 31 and a paper discharge transport path 32.

[0040] The paper feed path 31 and paper discharge path 32 are each composed of multiple motors, multiple rollers, and multiple guides (not shown). The multiple motors rotate shafts under the control of the system controller 13, thereby rotating the rollers in conjunction with the shaft rotation. The rotation of the multiple rollers moves the print medium P. The multiple guides control the conveyance direction of the print medium P.

[0041] The paper feed conveyance path 31 receives print media P from the paper tray 16 and supplies the received print media P to the image forming unit 19. The paper feed conveyance path 31 includes pickup rollers 33 corresponding to each paper tray. Each pickup roller 33 receives the print media P from the paper tray 16 into the paper feed conveyance path 31.

[0042] The paper discharge transport path 32 is a transport path for discharging the print medium P on which an image is formed from the housing 11 . The print medium P discharged from the paper discharge transport path 32 is supported by the paper discharge tray 17 .

[0043] Next, the image forming section 19 will be described.

[0044] The image forming unit 19 is a configuration for forming an image on the print medium P. Specifically, the image forming unit 19 forms an image on the print medium P based on a print job generated by the processor 21 .

[0045] The image forming unit 19 includes a plurality of loading units 41, a plurality of processing units 42, a plurality of exposure devices 43, and a transfer mechanism 44. The image forming unit 19 includes a loading unit 41 and an exposure device 43 for each processing unit 42. Since the plurality of processing units 42, the plurality of loading units 41, and the plurality of exposure devices 43 have the same structure, the following description will be based on an example of one processing unit 42, one loading unit 41, and one exposure device 43.

[0046] Figure 2 It is an explanatory diagram for explaining an example of a configuration of a part of the image forming unit 19 .

[0047] First, the toner cartridge 2 mounted in the loading portion 41 will be described.

[0048] like Figure 2 As shown, the toner cartridge 2 includes a toner storage container 51 , a toner delivery mechanism 52 , and a memory 53 .

[0049] The toner storage container 51 is a container that stores toner.

[0050] The toner delivery mechanism 52 is a mechanism that delivers the toner in the toner storage container 51. The toner delivery mechanism 52 is, for example, a screw that is provided in the toner storage container 51 and delivers the toner by rotating.

[0051] The memory 53 stores various control data in advance. The memory 53 is, for example, assembled in an IC chip (not shown) and mounted on the toner cartridge 2. The control data stored in the memory 53 include, for example, an "identification code," a "toner supply motor count value," and a "near-end threshold value." The "identification code" indicates the type and model of the toner cartridge 2. The "toner supply motor count value" is the cumulative value of the drive time of the toner cartridge 2 driven by the toner supply motor described later. The "near-end threshold value" is a threshold value used to allow the image forming apparatus 1 to determine whether the remaining toner in the toner cartridge 2 is low. In addition, the control data stored in the memory 53 includes a "control table." The structure of the "control table" will be described later.

[0052] Next, the loading portion 41 in which the toner cartridge 2 is loaded will be described.

[0053] like Figure 2 As shown, the loading section 41 is a module into which each toner cartridge 2 filled with toner is mounted. Each of the multiple loading sections 41 includes a space for mounting the toner cartridge 2 and a toner supply motor 61. Furthermore, each of the multiple loading sections 41 includes a communication interface (not shown) that connects the memory 53 of the toner cartridge 2 to the system controller 13.

[0054] The toner supply motor 61 drives the toner delivery mechanism 52 of the toner cartridge 2 under the control of the processor 21. When the toner cartridge 2 is loaded into the loading portion 41, the toner supply motor 61 is connected to the toner delivery mechanism 52 of the toner cartridge 2. When energized, the toner supply motor 61 rotates its shaft under the control of the processor 21, thereby driving the toner delivery mechanism 52 of the toner cartridge 2. By driving the toner delivery mechanism 52, the toner supply motor 61 supplies toner within the toner container 51 to a developing device (described later).

[0055] Next, the processing unit 42 will be described.

[0056] The processing unit 42 is a structure that forms a toner image. For example, multiple processing units 42 are provided for each color toner. For example, multiple processing units 42 correspond to color toners such as cyan, magenta, yellow, and black. Specifically, a toner cartridge 2 containing a different color toner is connected to each processing unit 42.

[0057] like Figure 2 As shown, the process unit 42 includes a photosensitive drum 71 , a cleaner 72 , a charger 73 , and a developer 74 .

[0058] The photosensitive drum 71 is a photosensitive body including a cylindrical drum and a photosensitive layer formed on the outer peripheral surface of the drum. The photosensitive drum 71 is rotated at a constant speed by a driving mechanism (not shown).

[0059] The cleaner 72 removes toner remaining on the surface of the photoconductor drum 71 .

[0060] The charger 73 uniformly charges the surface of the photosensitive drum 71. For example, the charger 73 applies a voltage to the photosensitive drum 71 using a charging roller, thereby charging the photosensitive drum 71 to a uniform negative potential. The charging roller rotates as the photosensitive drum 71 rotates while applying a predetermined pressure to the photosensitive drum 71.

[0061] The developing device 74 is a device that causes toner to adhere to the photosensitive drum 71. The developing device 74 includes a developer container 81, a stirring mechanism 82, a developing roller 83, a doctor blade 84, an automatic toner control (ATC) sensor 85, and the like.

[0062] The developer container 81 is a container for storing developer including toner and carrier. The developer container 81 receives toner fed from the toner cartridge 2 by the toner feeding mechanism 52. The carrier is stored in the developer container 81 when the developing device 74 is manufactured.

[0063] The stirring mechanism 82 is driven by a motor (not shown) and stirs the toner and the carrier in the developer container 81 .

[0064] The developing roller 83 rotates in the developer container 81 , thereby causing the developer to adhere to the surface.

[0065] The scraper 84 is disposed at a predetermined distance from the surface of the developing roller 83. The scraper 84 removes a portion of the developer adhering to the surface of the rotating developing roller 83. As a result, a layer of developer having a thickness corresponding to the distance between the scraper 84 and the surface of the developing roller 83 is formed on the surface of the developing roller 83.

[0066] The ATC sensor 85 is, for example, a magnetic flux sensor having a coil and detecting a voltage generated in the coil. The detection voltage of the ATC sensor 85 varies depending on the density of the magnetic flux from the toner in the developer container 81. Specifically, the ATC sensor 85 detects a voltage corresponding to the concentration ratio of the toner to the carrier in the developer container 81 (referred to as the toner concentration). The system controller 13 can determine the toner concentration in the developer container 81 based on the detection voltage of the ATC sensor 85.

[0067] Next, the exposure device 43 will be described.

[0068] The exposure device 43 includes multiple light-emitting elements. The exposure device 43 irradiates light from the light-emitting elements onto the charged photosensitive drum 71, thereby forming a latent image on the photosensitive drum 71. The light-emitting elements are, for example, light-emitting diodes (LEDs) or laser diodes (LDs). Each light-emitting element is configured to irradiate light onto a single point on the photosensitive drum 71. The multiple light-emitting elements are arranged in a direction parallel to the rotation axis of the photosensitive drum 71, i.e., in the main scanning direction.

[0069] The exposure device 43 irradiates light onto the photosensitive drum 71 using a plurality of light emitting elements arranged in the main scanning direction, thereby forming a latent image corresponding to one line on the photosensitive drum 71. Furthermore, the exposure device 43 forms a latent image corresponding to multiple lines by continuously irradiating light onto the rotating photosensitive drum 71.

[0070] In the above-described structure, when light is irradiated from the exposure device 43 onto the surface of the photosensitive drum 71, which has been charged by the charger 73, an electrostatic latent image is formed. When the layer of developer formed on the surface of the developing roller 83 approaches the surface of the photosensitive drum 71, the toner contained in the developer adheres to the latent image formed on the surface of the photosensitive drum 71. As a result, a toner image is formed on the surface of the photosensitive drum 71.

[0071] Next, the transfer mechanism 44 will be described.

[0072] The transfer mechanism 44 is a structure that transfers the toner image formed on the surface of the photoconductive drum 71 to the printing medium P.

[0073] like Figure 1 as well as Figure 2 As shown, the transfer mechanism 44 includes, for example, a primary transfer belt 91 , a secondary transfer opposing roller 92 , a plurality of primary transfer rollers 93 , and a secondary transfer roller 94 .

[0074] The primary transfer belt 91 is an endless belt wound around a secondary transfer counter roller 92 and a plurality of winding rollers. The inner surface (inner circumference) of the primary transfer belt 91 contacts the secondary transfer counter roller 92 and the plurality of winding rollers, while the outer surface (outer circumference) faces the photosensitive drum 71 of the process unit 42.

[0075] The secondary transfer opposing roller 92 is rotated by a motor (not shown). The rotation of the secondary transfer opposing roller 92 transports the primary transfer belt 91 in a predetermined transport direction. The plurality of winding rollers are configured to be freely rotatable. The plurality of winding rollers rotate as the primary transfer belt 91 is moved by the secondary transfer opposing roller 92.

[0076] The plurality of primary transfer rollers 93 are configured to bring the primary transfer belt 91 into contact with the photosensitive drums 71 of the process units 42. The primary transfer rollers 93 are positioned to correspond to the photosensitive drums 71 of the process units 42. Specifically, the primary transfer rollers 93 are positioned to face the photosensitive drums 71 of the corresponding process units 42, with the primary transfer belt 91 interposed therebetween. The primary transfer rollers 93 contact the inner circumference of the primary transfer belt 91, displacing the primary transfer belt 91 toward the photosensitive drums 71. This causes the primary transfer rollers 93 to bring the outer circumference of the primary transfer belt 91 into contact with the photosensitive drums 71.

[0077] The secondary transfer roller 94 is positioned opposite the primary transfer belt 91. The secondary transfer roller 94 contacts the outer circumference of the primary transfer belt 91 and applies pressure. This forms a transfer nip where the secondary transfer roller 94 and the outer circumference of the primary transfer belt 91 are in close contact. When the print medium P passes through the transfer nip, the secondary transfer roller 94 presses the print medium P passing through the transfer nip against the outer circumference of the primary transfer belt 91.

[0078] The secondary transfer roller 94 and the secondary transfer opposing roller 92 rotate to sandwich and convey the print medium P supplied from the paper feed conveyance path 31. As a result, the print medium P passes through the transfer nip.

[0079] In the above-described structure, when the outer peripheral surface of the primary transfer belt 91 contacts the photosensitive drum 71, the toner image formed on the surface of the photosensitive drum is transferred to the outer peripheral surface of the primary transfer belt 91. Figure 1 As shown, when the image forming unit 19 includes a plurality of process units 42, the primary transfer belt 91 receives toner images from the photosensitive drums 71 of the plurality of process units 42. The toner images transferred to the outer peripheral surface of the primary transfer belt 91 are conveyed by the primary transfer belt 91 to a transfer nip where a secondary transfer roller 94 is in close contact with the outer peripheral surface of the primary transfer belt 91. When a print medium P is present in the transfer nip, the toner images transferred to the outer peripheral surface of the primary transfer belt 91 are transferred to the print medium P in the transfer nip.

[0080] Next, the configuration related to fixing of the image forming apparatus 1 will be described.

[0081] The fuser 20 melts the toner transferred to the print medium P, thereby fixing the toner image. The fuser 20 operates under the control of the system controller 13. The fuser 20 includes a heating member for applying heat to the print medium P and a pressure member for applying pressure to the print medium P. For example, the heating member is a heating roller 95. Furthermore, for example, the pressure member is a pressure roller 96.

[0082] The heating roller 95 is a fixing rotating body rotated by a motor (not shown). The heating roller 95 comprises a hollow metal core and an elastic layer formed on the outer circumference of the core. The heating roller 95 is heated to a high temperature by a heater located inside the hollow core. The heater is, for example, a halogen heater. Alternatively, the heater may be an induction heating (IH) heater that heats the core through electromagnetic induction.

[0083] The pressure roller 96 is arranged at a position opposite to the heating roller 95. The pressure roller 96 has a core rod formed of metal with a predetermined outer diameter and an elastic layer formed on the outer periphery of the core rod. The pressure roller 96 applies pressure to the heating roller 95 by applying stress from a tension member (not shown). By applying pressure from the pressure roller 96 to the heating roller 95, a nip portion (fixing nip portion) is formed in which the pressure roller 96 and the heating roller 95 are in close contact. The pressure roller 96 is rotated by a motor (not shown). The pressure roller 96 moves the printing medium P that has entered the fixing nip portion by rotating, and presses the printing medium P against the heating roller 95.

[0084] According to the above configuration, the heating roller 95 and the pressure roller 96 apply heat and pressure to the print medium P passing through the fixing nip. This fixes the toner image to the print medium P that has passed through the fixing nip. The print medium P that has passed through the fixing nip is guided into the paper discharge transport path 32 and discharged outside the housing 11. The fixing unit 20 is not limited to the above configuration. The fixing unit 20 may also be configured in a manner as needed to apply heat to the print medium P to which the toner image has been transferred via a film-like member, thereby melting the toner and fixing it.

[0085] Next, control of the image forming apparatus 1 by the system controller 13 will be described.

[0086] Figure 3 This is a flowchart for explaining the process related to toner replenishment performed by the system controller 13 .

[0087] The processor 21 determines whether the toner cartridge 2 has been replaced (ACT 11). For example, the processor 21 determines that the toner cartridge 2 has been replaced when the cover of the loading unit 41 is opened. Alternatively, if a unique ID is stored in the toner cartridge 2, the processor 21 may determine that the toner cartridge 2 has been replaced when the ID of the toner cartridge 2 has changed. Alternatively, the processor 21 may detect replacement of the toner cartridge 2 using any other method.

[0088] When the processor 21 determines that the toner cartridge 2 has not been replaced (No in ACT 11 ), the process proceeds to ACT 13 to be described later.

[0089] Furthermore, when the processor 21 determines that the toner cartridge 2 has been replaced ("YES" in ACT 11), it reads data from the memory 53 of the toner cartridge 2 (ACT 12). For example, the processor 21 reads the "identification code," "toner supply motor count value," "near-end threshold," and "control table" from the memory 53 of the toner cartridge 2 and stores them in the memory 22 of the system controller 13. Furthermore, the processor 21 reads the control table from the memory 53 of the toner cartridge 2 and stores it in the memory 22 of the system controller 13.

[0090] For example, assume that the memory 53 of the toner cartridge 2 stores an "identification code" at address "B001," a "toner supply motor count value" at address "B002," a "near-end threshold" at address "B003," and a "control table" at address "B004." In this case, the processor 21 stores the "identification code" at address "A001" of the memory 22, the "toner supply motor count value" at address "A002," the "near-end threshold" at address "A003," and the "control table" at address "A004."

[0091] When the image forming apparatus 1 is powered on, the processor 21 executes a preparatory operation. During the preparatory operation, the processor 21 may read the "identification code," "toner supply motor count value," "near-end threshold," and "control table" from the memory 53 of the toner cartridge 2 and store them in the memory 22.

[0092] The processor 21 checks the toner concentration in the developer container 81 based on the detection voltage of the ATC sensor 85 (ACT 13 ).

[0093] The processor 21 determines whether to replenish toner (ACT 14). The processor 21 determines whether to replenish toner based on the toner concentration in the developer container 81 confirmed in ACT 13 and a preset reference concentration. For example, if the toner concentration is lower than the reference concentration by a predetermined value or more, the processor 21 determines to cause the toner replenishment motor 61 to perform a toner replenishment operation.

[0094] When the processor 21 determines that toner replenishment is not to be performed (No in ACT 14 ), the process proceeds to ACT 18 to be described later.

[0095] If the processor 21 determines that toner replenishment is to be performed (YES in ACT 14 ), it determines a toner replenishment mode (ACT 15 ). For example, the processor 21 determines one of a plurality of toner replenishment modes in which the drive time of the toner replenishment motor 61 is different based on the difference between the toner concentration and the reference concentration.

[0096] Specifically, the processor 21 determines that toner replenishment is not to be performed when the toner concentration [%] - the reference concentration [%] > -0.3 [%].

[0097] Furthermore, when -0.3 ≥ toner concentration [%] - reference concentration [%] > -0.6 [%], the processor 21 determines toner replenishment to be performed in the first replenishment mode. The first replenishment mode is a toner replenishment mode in which the toner replenishment motor 61 is driven for a predetermined time.

[0098] Furthermore, when -0.6 ≥ toner concentration [%] - reference concentration [%] > -0.9 [%], the processor 21 determines to perform toner replenishment in the second replenishment mode. The second replenishment mode is a toner replenishment mode in which the toner replenishment motor 61 is driven for a longer time than the first replenishment mode.

[0099] Furthermore, when -0.9 ≥ toner concentration [%] - reference concentration [%] > -1.2 [%], the processor 21 determines toner replenishment to be performed in the third replenishment mode. The third replenishment mode is a toner replenishment mode in which the toner replenishment motor 61 is driven for a longer time than in the second replenishment mode.

[0100] Furthermore, when -1.2 ≥ toner concentration [%] - reference concentration [%] > -1.5 [%], the processor 21 determines toner replenishment in the fourth replenishment mode in which the toner replenishment motor 61 is driven for a longer time than in the third replenishment mode.

[0101] Furthermore, when -1.5 ≥ toner concentration [%] - reference concentration [%], the processor 21 determines to perform toner replenishment in the fifth replenishment mode. The fifth replenishment mode is a toner replenishment mode in which the toner replenishment motor 61 is driven for a longer period than in the fourth replenishment mode. Furthermore, the fifth replenishment mode is a toner replenishment mode in which the toner replenishment motor 61 is driven for a longer period due to a significantly low toner concentration within the developer container 81. For example, the fifth replenishment mode may be a mode in which toner replenishment continues until the toner concentration [%] - reference concentration [%] reaches -1.5% or higher.

[0102] The processor 21 executes a toner replenishing operation using the determined toner replenishing mode (ACT 16 ). That is, the processor 21 controls the toner replenishing motor 61 to drive the toner delivery mechanism 52 of the toner cartridge 2 according to the determined toner replenishing mode.

[0103] The processor 21 counts the amount of time the toner supply motor 61 is driven (the driving time) and accumulates this information as a toner supply motor count value (ACT 17). As described above, the toner supply motor count value is information stored in address "A002" of the memory 22 of the system controller 13. Each time the toner supply motor 61 is driven, the processor 21 counts the driving time and adds the value counted in address "A002" of the memory 22. Thus, the toner supply motor count value in the memory 22 of the system controller 13 sequentially accumulates the driving time of the toner supply motor 61.

[0104] The processor 21 determines whether to terminate the process (ACT 18 ). For example, when an operation to terminate the operation of the image forming apparatus 1 is performed, the processor 21 determines to terminate the process.

[0105] When the processor 21 determines that the processing is not to be terminated ("No" in ACT 18), the process proceeds to the process of ACT 11. Thus, the processor 21 repeatedly executes the processes of ACT 11 to ACT 18.

[0106] When the processor 21 determines that the process is to be terminated ("YES" in ACT 18), the processor 21 writes the value of the address "A002" of the memory 22 of the system controller 13 to the address "B002" of the memory 53 of the toner cartridge 2, and terminates the process. Figure 3 Thus, the latest toner supply motor count is stored in the memory 53 of the toner cartridge 2.

[0107] Figure 4 1 is a flowchart for explaining the accumulation of pixel count values by the system controller 13 .

[0108] The processor 21 of the system controller 13 executes the Figure 4 For example, the processor 21 can be executed each time one sheet is printed. Figure 4 The processing structure can also be executed each time a printing task is completed. Figure 4 The structure of the processing can also be executed each time multiple printing is executed. Figure 4 In this example, the processor 21 executes the following processing each time printing is executed: Figure 4 processing.

[0109] The processor 21 determines whether to execute printing (ACT 21 ).

[0110] When the processor 21 determines that printing is not to be executed (No in ACT 21 ), the process proceeds to ACT 24 to be described later.

[0111] When the processor 21 determines that printing is to be executed (YES in ACT 21 ), it executes printing based on the image data for printing ( ACT 22 ). That is, the processor 21 controls the transport unit 18 , the image forming unit 19 , and the fixing unit 20 to form an image on the printing medium P.

[0112] The processor 21 counts and accumulates the pixel values of the image data used for printing, and calculates the pixel count value (ACT 23). The pixel value of the image data corresponds to the number of dots printed for each color. More specifically, the pixel value of the image data corresponds to the number of pixels drawn on the photosensitive drum 71 by the exposer 43. That is, the processor 21 accumulates the number of printed dots as the pixel count value for each color corresponding to the toner cartridge 2. For example, the processor 21 stores the pixel count value in a specified area of the memory 22. The processor 21 executes printing, and each time the pixel value is counted, the pixel value obtained by counting the pixel count value of the specified area of the memory 22 is added. Thus, the pixel count value of the memory 22 of the system controller 13 is accumulated sequentially according to each color of the toner according to printing. In addition, the pixel value counted and accumulated by the processor 21 is not limited to the number of dots printed as described above, and can be any value as long as it at least reflects the amount of toner used based on the image data.

[0113] The processor 21 determines whether to terminate the process (ACT 24 ). For example, when an operation to terminate the operation of the image forming apparatus 1 is performed, the processor 21 determines to terminate the process.

[0114] When the processor 21 determines that the processing is not to be terminated ("No" in ACT 24), the process proceeds to the process of ACT 21. Thus, the processor 21 repeatedly executes the processes of ACT 21 to ACT 24.

[0115] In addition, when the processor 21 determines that the process is to be terminated ("Yes" in ACT24), the processor 21 terminates the process. Figure 4 processing.

[0116] Next, the processing related to toner exhaustion determination in the image forming apparatus 1 will be described. The image forming apparatus 1 detects toner exhaustion based on a pixel count value (the cumulative value of pixel values in the image data), a toner supply motor count value (the cumulative value of the drive time of the toner supply motor 61), a print rate of the image data, and toner characteristics of the toner supplied from the toner cartridge 2 to the developer container 81 of the developer 74.

[0117] Figure 5 This is a flowchart for explaining the determination of toner exhaustion by the system controller 13 .

[0118] The processor 21 of the system controller 13 executes the Figure 5 The processing interval is a processing unit determined by the number of printed sheets, pixel count value, or toner supply motor count value.

[0119] For example, the processing interval is determined based on the number of printed sheets set in advance. Specifically, the processor 21 is configured to execute the processing interval every time 50 sheets are printed. Figure 5 processing.

[0120] In addition, the processing interval may also be an interval until the pixel count value increases by a preset value. In this case, the processor 21 executes each time the pixel count value increases by a preset value. Figure 5 processing.

[0121] In addition, for example, the processing interval may be an interval until the toner supply motor count increases by a preset value. In this case, the processor 21 executes the operation of Figure 5 processing.

[0122] The processor 21 determines whether the preset processing interval has ended (ACT 31). In this example, the processing interval is described as an interval determined based on the number of printed sheets. In this case, the processor 21 determines whether the preset number of printed sheets (e.g., 50 sheets) has been printed.

[0123] When the processor 21 determines that the preset processing period has not ended (No in ACT 31 ), the process proceeds to ACT 40 to be described later.

[0124] When the processor 21 determines that the preset processing interval has ended ("YES" in ACT 31), it determines whether the toner replenishment motor count value is equal to or greater than the near-end threshold (ACT 32). Specifically, the processor 21 determines whether the toner replenishment motor count value at address "A002" of the memory 22 is equal to or greater than the near-end threshold previously acquired from the memory 53 of the toner cartridge 2.

[0125] When the toner replenishment motor count value exceeds the near-end threshold, the processor 21 detects that the toner is near end. In this case, the processor 21 displays a message on the display unit 14 indicating that the toner remaining in the toner cartridge 2 is low. This allows the processor 21 to notify the user that the toner remaining in the toner cartridge 2 is low.

[0126] When the processor 21 determines that the toner replenishment motor count value is smaller than the near-end threshold value (No in ACT 32 ), the process proceeds to ACT 40 described later.

[0127] Furthermore, if the processor 21 determines that the toner replenishment motor count value is equal to or greater than the near-end threshold value ("YES" in ACT 32), it calculates the amount of pixel count increase during the processing interval (ACT 33). Specifically, the processor 21 calculates the amount of pixel count increase during printing of a predetermined number of prints (e.g., 50 sheets).

[0128] The processor 21 also calculates the amount of increase in the toner supply motor count value during the processing period (ACT 34 ). Specifically, the processor 21 calculates the amount of increase in the toner supply motor count value during printing of a preset number of prints (eg, 50 sheets).

[0129] The processor 21 calculates the toner replenishment rate based on the increase in the pixel count value and the increase in the toner replenishment motor count value (ACT 35 ). That is, the processor 21 calculates the toner replenishment rate at the end of each processing interval.

[0130] The toner replenishment rate is the ratio of the toner usage during the processing interval to the toner replenishment amount. The toner usage can be estimated based on the pixel count value. The toner replenishment amount can be estimated based on the drive time of the toner replenishment motor 61. The processor 21 calculates the toner replenishment rate based on the increase in the pixel count value and the increase in the toner replenishment motor count value during the processing interval. Specifically, the processor 21 calculates the toner replenishment rate as the value obtained by dividing the increase in the pixel count value by the increase in the toner replenishment motor count value. In other words, the toner replenishment rate is the ratio of the toner replenishment motor count value to the pixel count value.

[0131] Processor 21 calculates an average printing rate of the image data (ACT 36). The printing rate is the ratio of the number of dots printed based on the image data to the number of dots that can be printed by image forming apparatus 1 per unit area of the image. The unit area of the image in the printing rate is, for example, the area corresponding to the print medium P. For example, processor 21 calculates the printing rates of each of the plurality of image data used for printing in the processing interval and calculates the average of the printing rates. Alternatively, processor 21 may calculate a median value of the printing rate instead of the average.

[0132] The processor 21 determines a toner replenishment rate threshold value, which is a threshold value for comparison with the toner replenishment rate, based on the calculated average value of the print rate of the image data and the toner characteristics of the toner in the toner cartridge 2 (ACT 37). The processor 21 determines the toner replenishment rate threshold value for comparison based on the average value of the print rate and the "control table" acquired from the toner cartridge 2.

[0133] The control table is information indicating the relationship between the print rate and the toner replenishment rate threshold. For example, the control table may be configured as a table in which the toner replenishment rate threshold is associated with each print rate. In other words, the control table sets the toner replenishment rate threshold based on the print rate. Alternatively, the control table may be configured as a table in which the toner replenishment rate threshold is associated with each of multiple ranges defined by the upper and lower limits of the print rate. Furthermore, the control table may be configured as a function indicating the proportional relationship between the print rate of image data and the toner replenishment rate threshold.

[0134] The toner replenishment rate threshold is a toner replenishment rate threshold that increases as the printing rate of image data in a processing section increases. Figure 6 This is an explanatory diagram for explaining an example of a toner replenishment rate threshold value. Figure 6 The horizontal axis represents the printing rate. Figure 6 The vertical axis represents the toner replenishment rate. Figure 6 The first graph 97 is a graph showing the relationship between the toner replenishment rate threshold value and the printing rate according to the first toner characteristic. Figure 6 The second graph 98 is a graph showing the relationship between the toner replenishment rate threshold value and the printing rate according to the second toner characteristic. Figure 6 The third graph 99 is a graph showing the relationship between the toner replenishment rate threshold and the printing rate according to the third toner characteristic. Figure 6 As shown in FIG, the toner supply rate threshold is a value that increases or decreases according to the increase or decrease in the printing rate of the image data in the processing interval. For example, the toner supply rate threshold is a value proportional to the printing rate. Figure 6 As shown, the correlation between the toner replenishment rate threshold and the printing rate varies depending on the toner characteristics.

[0135] The toner contained in the toner container 51 of the toner cartridge 2 may vary in particle size, circularity, and surface condition (e.g., BET specific surface area) depending on the toner's manufacturing batch or specifications. Consequently, toner properties such as the fluidity and bulk density of the toner in the toner cartridge 2 may vary depending on the toner cartridge 2. In this example, the toner properties are described using the fluidity of the toner as an example.

[0136] For example, Figure 6 The first graph 97 shows the correlation between the printing rate and the toner replenishment rate threshold value when the toner cartridge 2 contains the toner with the highest fluidity (the first toner).

[0137] In addition, for example, Figure 6 The second graph 98 shows the correlation between the printing rate and the toner replenishment rate threshold value when the toner cartridge 2 contains a toner (second toner) having lower fluidity than the first toner.

[0138] In addition, for example, Figure 6 A third curve 99 shows the correlation between the printing rate and the toner replenishment rate threshold value when a toner (third toner) having lower fluidity than the second toner, that is, the lowest fluidity, is accommodated in the toner cartridge 2 .

[0139] A control table corresponding to the toner characteristics (fluidity) of the toner contained in the toner container 51 is stored in the memory 53 of the toner cartridge 2 at an arbitrary timing such as at the time of manufacturing or shipment.

[0140] For example, when the toner cartridge 2 contains the first toner, a control table corresponding to the first chart 97 is stored in the memory 53. Furthermore, for example, when the toner cartridge 2 contains the second toner, a control table corresponding to the second chart 98 is stored in the memory 53. Furthermore, for example, when the toner cartridge 2 contains the third toner, a control table corresponding to the third chart 99 is stored in the memory 53.

[0141] Furthermore, when toner fluidity is high (better), the amount the toner replenishment motor 61 is driven increases compared to when toner fluidity is low (poorer). Consequently, the denominator of the toner replenishment rate calculation formula increases, and the toner replenishment rate decreases. Consequently, the value of the first graph 97 is set to the lowest, the value of the second graph 98 is set to a higher value than the first graph 97, and the value of the third graph 99 is set to a higher value than the second graph 98. In other words, for the same print rate, the toner replenishment rate thresholds are set to increase in the order of the third toner, the second toner, and the first toner.

[0142] For example, Figure 3 At the timing of ACT 12 or other timings, the processor 21 reads the control table from the memory 53 of the toner cartridge 2 and stores it in the memory 22. Thus, the processor 2 can determine a toner replenishment rate threshold value to be compared with the toner replenishment rate calculated in ACT 35 based on the toner characteristics of the toner in the toner cartridge 2 and the print rate (average value) of the image data in the processing interval.

[0143] The processor 21 compares the determined toner supply rate threshold with the toner supply rate calculated in ACT 35 , and determines whether the toner supply rate is equal to or greater than the toner supply rate threshold ( ACT 38 ).

[0144] As described above, when the toner concentration in the developer container 81 is lower than the reference concentration by a specified value or more, the processor 21 drives the toner supply motor 61 in a supply mode corresponding to the difference, thereby supplying toner from the toner cartridge 2. When the difference between the toner concentration and the reference concentration is the same (within the same range), since the supply mode is roughly the same, the increase in the toner supply motor count value does not produce a difference. However, the pixel count value counted from the image data changes according to the printing rate of the image data. For example, even when the toner concentration is lower than the reference concentration by a specified value or more in a state where the printing rate is low, the drive amount of the toner supply motor 61 does not change. Therefore, the toner supply motor count value is excessively accumulated. That is, in a state where the printing rate is low, the toner supply rate also decreases. Therefore, the toner supply rate threshold is set to decrease when the printing rate is low and increase when the printing rate is high.

[0145] When the processor 21 determines that the toner replenishment rate is equal to or greater than the toner replenishment rate threshold value (YES in ACT 38 ), the process proceeds to ACT 40 to be described later.

[0146] When the processor 21 determines that the toner replenishment rate is less than the toner replenishment rate threshold (No in ACT 38 ), it determines that the toner is exhausted (ACT 39 ).

[0147] When the toner remaining in the toner cartridge 2 becomes low, the toner replenishment rate gradually decreases. This is because the toner supply amount per unit driving amount of the toner delivery mechanism 52 of the toner cartridge 2 decreases as the toner in the toner cartridge 2 decreases, and the driving time of the toner replenishment motor 61 for supplying the same amount of toner becomes longer.

[0148] When the toner replenishment motor count value increases sufficiently (approaches the end threshold or exceeds it), and the toner replenishment rate is less than the toner replenishment rate threshold, the processor 21 determines that no toner remains in the toner cartridge 2. For example, the processor 21 displays a message indicating toner end on the display of the display unit 14. Thus, the processor 21 can notify the user that no toner remains in the toner cartridge 2.

[0149] Furthermore, the processor 21 independently performs a toner end determination based on the detection results of the ATC sensor 85 in ACT 38 and ACT 39. For example, the processor 21 determines toner end if the difference between the toner concentration and the reference concentration is greater than a predetermined value (e.g., a difference <-1.5%) and the toner concentration does not recover even after forced replenishment. Alternatively, the processor 21 may determine toner end based on either or both the toner end determination based on the detection results of the ATC sensor 85 and the toner end determination in ACT 40.

[0150] The processor 21 determines whether to terminate the process (ACT 40 ). For example, when an operation to terminate the operation of the image forming apparatus 1 is performed, the processor 21 determines to terminate the process.

[0151] When the processor 21 determines that the processing is not to be terminated ("No" in ACT 40), the process proceeds to the process of ACT 31. Thus, the processor 21 repeatedly executes the processes of ACT 31 to ACT 40.

[0152] In addition, when the processor 21 determines that the process is to be terminated ("Yes" in ACT40), the process ends. Figure 5 processing.

[0153] As described above, the processor 21 of the system controller 13 of the image forming apparatus 1 calculates the toner replenishment rate based on the pixel count value, which is the cumulative value of pixel values in the image data, and the toner replenishment motor count value, which is the cumulative value of the drive time of the toner replenishment motor 61. Furthermore, the processor 21 calculates the print rate (or the average value of the print rate) of the image data during the processing interval used to calculate the toner replenishment rate. The processor 21 determines the toner replenishment rate threshold value based on the print rate and a control table that indicates the relationship between the print rate and the toner replenishment rate threshold value, which is pre-set based on the toner characteristics of the toner in the toner cartridge 2. The processor 21 detects toner exhaustion based on the calculated toner replenishment rate and the determined toner replenishment rate threshold value.

[0154] With this configuration, the image forming apparatus 1 can detect toner end based on the toner replenishment rate, taking into account the print rate and the toner characteristics of the toner in the toner cartridge 2. Furthermore, when detecting toner end based on the comparison between the toner replenishment rate and the toner replenishment rate threshold, the toner replenishment rate threshold corresponding to the toner characteristics can be used to mitigate the effects of the toner characteristics on the toner replenishment rate. Consequently, the image forming apparatus 1 can stabilize the timing of toner end detection.

[0155] In addition, in the above embodiment, the toner characteristic is described as toner fluidity, but the present invention is not limited to this structure. The volume specific gravity of the toner can also be used as the toner characteristic to set the correlation between the print rate and the toner replenishment rate threshold (control table). In this case, a state with a higher volume specific gravity of the toner corresponds to a state with higher toner fluidity, and a state with a lower volume specific gravity of the toner corresponds to a state with lower toner fluidity. In other words, in the above embodiment, the level of toner fluidity can be replaced by the level of toner volume specific gravity. In addition, both toner fluidity and toner volume specific gravity can be used as toner characteristics.

[0156] In addition, in the above-mentioned embodiment, a structure in which a control table is pre-stored in the memory 53 of the toner cartridge 2 is described, but the present invention is not limited to this structure. Control tables corresponding to a plurality of toner characteristics may also be pre-stored in the memory 22 of the system controller 13 of the image forming apparatus 1. In this case, information representing the toner characteristics of the toner contained in the toner container 51 is stored in the memory 53 of the toner cartridge 2. The processor 21 obtains the information representing the toner characteristics from the memory 53 of the toner cartridge 2 and determines the toner replenishment rate threshold using the control table corresponding to the toner characteristics. With such a structure, the same effect as in the above-mentioned embodiment can be obtained. In addition, the processor 21 may also be a structure in which the information representing the toner characteristics is obtained based on the input of the operation interface 15. In addition, the processor 21 may also be a structure in which the information representing the toner characteristics is obtained from the device via the communication interface 12.

[0157] Furthermore, the functions described in the above embodiments are not limited to being configured using hardware, but may be implemented using software by having a computer read a program describing each function. Furthermore, each function may be configured using either software or hardware as appropriate.

[0158] While several embodiments of the present invention have been described, these embodiments are provided as examples and are not intended to limit the scope of the invention. These novel embodiments may be implemented in various other ways, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. These embodiments and their variations are intended to be within the scope and spirit of the invention and are encompassed by the invention set forth in the claims and their equivalents.

Claims

1. An image forming apparatus comprising: Photosensitive drum; an exposure device for exposing the photosensitive drum based on image data; a developer for forming a toner image on the photosensitive drum using toner supplied from a toner cartridge; a toner concentration sensor for detecting a toner concentration in the developer; a toner supply motor for supplying toner from the toner cartridge to the developer based on the toner concentration; as well as The processor detects toner exhaustion based on a toner replenishment rate, a print rate of the image data, and toner characteristics, wherein the toner replenishment rate is a ratio of a toner usage amount to a toner replenishment amount in a processing interval, the toner replenishment rate being calculated based on a pixel count value, which is a cumulative value of pixel values of the image data, and a toner replenishment motor count value, which is a cumulative value of a drive time of the toner replenishment motor; the print rate is a ratio of the number of dots printed based on the image data to the number of dots printable per unit area of the image by the image forming apparatus; and the toner characteristics are characteristics of the toner supplied from the toner cartridge to the developer. The processor calculates a toner replenishment rate based on an increase in a pixel count value and an increase in a toner replenishment motor count value during a processing interval; the processor calculates a value obtained by dividing the increase in the pixel count value by the increase in the toner replenishment motor count value as the toner replenishment rate, The processor calculates the toner replenishment rate based on the increase in the pixel count value and the increase in the toner replenishment motor count value in a specified processing interval, and determines a toner replenishment rate threshold based on the printing rate of the image data in the processing interval and the toner characteristics. When the toner replenishment rate is less than the toner replenishment rate threshold, the processor detects that the toner is exhausted.

2. The image forming apparatus according to claim 1, wherein The processor detects toner end based on the toner replenishment rate, the printing rate, and the toner characteristics when detecting that toner is near end based on the toner replenishment motor count value and a preset near-end threshold.

3. The image forming apparatus according to claim 1, wherein The processor acquires, from the toner cartridge, a control table indicating a correlation between the printing rate and the toner replenishment rate threshold value according to the toner characteristics.

4. A method for controlling an image forming apparatus, wherein: The image forming device includes: a photosensitive drum; an exposure device that exposes the photosensitive drum based on image data; a developer that forms a toner image on the photosensitive drum using toner supplied from a toner cartridge; a toner concentration sensor that detects the toner concentration in the developer; a toner supply motor that supplies toner from the toner cartridge to the developer based on the toner concentration; and a processor. The processor detects toner exhaustion based on a toner replenishment rate, a printing rate of the image data, and toner characteristics of the toner cartridge, wherein the toner replenishment rate is a ratio of a toner usage amount to a toner replenishment amount in a processing interval, the toner replenishment rate being calculated based on a pixel count value, which is a cumulative value of pixel values of the image data, and a toner replenishment motor count value, which is a cumulative value of a driving time of the toner replenishment motor, and the printing rate is a ratio of a number of dots printed by the image data to a number of dots printable per unit area of the image by the image forming apparatus. The processor calculates a toner replenishment rate based on an increase in a pixel count value and an increase in a toner replenishment motor count value during a processing interval; the processor calculates a value obtained by dividing the increase in the pixel count value by the increase in the toner replenishment motor count value as the toner replenishment rate, The processor calculates the toner replenishment rate based on the increase in the pixel count value and the increase in the toner replenishment motor count value in a specified processing interval, and determines a toner replenishment rate threshold based on the printing rate of the image data in the processing interval and the toner characteristics. When the toner replenishment rate is less than the toner replenishment rate threshold, the processor detects that the toner is exhausted.

5. A toner cartridge, used in an image forming device, The image forming device includes: a photosensitive drum; an exposure device that exposes the photosensitive drum based on image data; a developer that forms a toner image on the photosensitive drum using toner supplied from a toner cartridge; a toner concentration sensor that detects the toner concentration in the developer; a toner supply motor that supplies toner from the toner cartridge to the developer based on the toner concentration; and a processor. The toner cartridge includes: a toner containing container for containing toner; a toner delivery mechanism that delivers the toner in the toner storage container; and a memory storing a control table indicating a correlation between a toner replenishment rate threshold and a print rate of the image data, the toner replenishment rate threshold being a threshold for comparison with a toner replenishment rate calculated by the processor based on a pixel count value and a toner replenishment motor count value, the toner replenishment rate being a ratio of a toner usage amount to a toner replenishment amount in a processing interval, the pixel count value being a cumulative value of pixel values of the image data, the toner replenishment motor count value being a cumulative value of a drive time of the toner replenishment motor, and the print rate being a ratio of a number of dots printed based on the image data to a number of dots printable per unit area of the image by the image forming apparatus, The processor calculates a toner replenishment rate based on an increase in pixel count value and an increase in toner replenishment motor count value in a processing section; and calculates a value obtained by dividing the increase in pixel count value by the increase in toner replenishment motor count value as the toner replenishment rate.

Images