Image forming apparatus, method for replenishing developer, and program

Abstract

The present invention provides an image forming apparatus capable of efficiently supplying an appropriate amount of toner to a developing device, a method for supplying developer, and a program for doing so. [Solution] The image forming apparatus is an image forming apparatus that forms an image on a recording material using a two-component developer containing toner and a carrier, and comprises an image carrier, a developing apparatus that supplies toner to the image carrier to form a toner image, a developer supply unit that supplies developer to the developing apparatus through a developer supply port with a variable opening area, a toner concentration detection unit that detects the toner concentration in the developing apparatus, and a control unit that controls the operation of supplying developer from the developer supply unit to the developing apparatus, wherein the control unit changes the opening area of ​​the developer supply port based on the toner concentration and the rate of change of toner concentration detected by the toner concentration detection unit.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus, a method for replenishing a developer, and a program.

Background Art

[0002] In an image forming apparatus (such as a printer, a copier, a facsimile machine, etc.) that uses electrophotographic process technology, a laser beam based on image data is irradiated (exposed) onto a uniformly charged photoreceptor, thereby forming an electrostatic latent image on the surface of the photoreceptor. Then, by supplying toner to the photoreceptor, the electrostatic latent image is visualized as a toner image. After the toner image is transferred onto a recording material, it is heated and pressurized in a fixing unit. Through the above steps, an image is formed on the recording material.

[0003] Generally, in an image forming apparatus that uses a two-component developer containing toner and a carrier, in order to stabilize image quality, the developer is replenished in a timely manner so that the toner concentration in the developing device is maintained constant. The toner concentration is the ratio of toner to the developer (toner + carrier). For example, Patent Document 1 discloses adjusting the opening area of a replenishment port according to the toner concentration in the developing device and replenishing an appropriate amount of developer from a developer replenishment unit such as a toner bottle to the developing device.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the replenishment method disclosed in Patent Document 1, the opening area of ​​the replenishment port, i.e., the amount of developer replenished, is adjusted according to the toner concentration. However, since this method increases the amount of developer replenished as the toner concentration decreases, the toner concentration will not recover unless the amount of toner replenished (the amount of toner in the replenished developer) exceeds the amount of toner consumed. In other words, if the coverage is high and the amount of toner consumed exceeds the amount of toner replenished, there is a risk that the toner concentration cannot be recovered quickly.

[0006] On the other hand, if the opening area of ​​the toner supply port is set so that the amount of toner supplied reliably exceeds the amount of toner consumed, the toner density will recover quickly even in the case of high coverage. However, if the coverage is not high, there is a risk of oversupply, causing the toner density to become too high and the image quality to become unstable.

[0007] The object of the present invention is to provide an image forming apparatus, a method for supplying developer, and a program that can efficiently supply an appropriate amount of toner to the developing apparatus. [Means for solving the problem]

[0008] The image forming apparatus according to the present invention is An image forming apparatus that forms an image on a recording material using a two-component developer containing toner and carrier, Image carrier and, A developing apparatus that supplies toner to the image carrier to form a toner image, A developer supply unit that supplies developer to the developing apparatus through a developer supply port with a variable opening area, A toner concentration detection unit for detecting the toner concentration in the developing device, The system includes a control unit that controls the operation of supplying developer from the developer supply unit to the developing device, The control unit changes the opening area of ​​the developer supply port based on the toner concentration detected by the toner concentration detection unit and the rate of change of the toner concentration.

[0009] The method for replenishing the developer according to the present invention is: A method for replenishing developer in an image forming apparatus that forms an image on a recording material using a two-component developer containing toner and carrier, The toner concentration in the developing device is detected, Based on the detected toner concentration and the rate of change of the toner concentration, the opening area of ​​the developer supply port is changed. The developer is supplied to the developing device through the developer supply port.

[0010] The program according to the present invention is A program that causes a computer in an image forming apparatus to perform a predetermined process, which forms an image on a recording material using a two-component developer containing toner and carrier, The aforementioned predetermined process is, A process for detecting the toner concentration in the developing device, A process to change the opening area of ​​the developer supply port based on the detected toner concentration and the rate of change of the toner concentration, The process includes supplying the developer to the developing device through the developer supply port. [Effects of the Invention]

[0011] According to the present invention, an appropriate amount of toner can be efficiently supplied to the developing device. Therefore, the quality of the image formed by the image forming apparatus is stabilized. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a schematic diagram showing the overall configuration of the image forming apparatus. [Figure 2] Figure 2 shows the main components of the control system of an image forming apparatus. [Figure 3] Figures 3A to 3C are schematic diagrams showing an example of the developer supply unit 40. [Figure 4] Figure 4 is a flowchart showing an example of the developer replenishment process. [Figure 5] Figure 5 is a flowchart showing an example of toner blocking avoidance processing.

Best Mode for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

[0014] FIG. 1 is a diagram schematically showing the overall configuration of an image forming apparatus 1 according to an embodiment. FIG. 2 is a diagram showing the main part of the control system of the image forming apparatus 1.

[0015] The image forming apparatus 1 is an intermediate transfer type color image forming apparatus using electrophotographic process technology. The image forming apparatus 1 primarily transfers the Y (yellow), M (magenta), C (cyan), and K (black) toner images formed on the photosensitive drum 213 to the intermediate transfer belt 221. Further, the image forming apparatus 1 forms an image by superposing the four-color toner images on the intermediate transfer belt 221 and then secondarily transferring them to a recording material.

[0016] In the present embodiment, a vertical tandem system is adopted for the image forming apparatus 1. In the vertical tandem system, the photosensitive drums 213 corresponding to the four colors of CMYK are arranged in series along the running direction (vertical direction) of the intermediate transfer belt 221, and the toner images of each color are sequentially transferred to the intermediate transfer belt 221 in one procedure.

[0017] As shown in FIGS. 1 and 2, the image forming apparatus 1 includes a document reading unit 11, an operation display unit 12, an image processing unit 13, a paper feeding unit 14, a paper discharging unit 15, a recording material conveying unit 16, an image forming unit 20, a control unit 30, and the like. The image forming unit 20 includes an image forming section 21, an intermediate transfer section 22, and a fixing section 23.

[0018] The control unit 30 performs overall control of the image forming apparatus 1 by controlling the document reading unit 11, the operation display unit 12, the image processing unit 13, the paper feeding unit 14, the paper discharging unit 15, the recording material conveying unit 16, and the image forming unit 20 according to their respective functions. Further, the control unit 30 controls the operation (developer replenishment operation) of the developer replenishment unit 40 (shutter unit 41) based on the detection results of the shutter position detection unit 44 and the toner density detection unit 45.

[0019] The control unit 30 includes a CPU (Central Processing Unit) 31 as a processing unit (processor), and ROM (Read Only Memory) 32 and RAM (Random Access Memory) 33 as main memory. The ROM 32 stores basic programs and basic setting data. The ROM 32 also stores programs for implementing image forming processes such as developer replenishment. The CPU 31 reads programs from the ROM 32 according to the processing content, loads them into the RAM 33, and executes the loaded programs to control the operation of each functional block of the image forming apparatus 1.

[0020] In this embodiment, the functions of each functional block are realized through the coordinated operation of each hardware component of the functional block and the control unit 30. Alternatively, the control unit 30 may execute a program to realize some or all of the functions of each functional block. Furthermore, some or all of the processing performed by the control unit 30 may be executed by electronic circuits such as a DSP (Digital Signal Processor), ASIC (Application Specific Integrated Circuit), or PLD (Programmable Logic Device), depending on the processing required.

[0021] The document reading unit 11 includes an automatic document feeder 111 called an ADF (Auto Document Feeder), a document image scanning device 112, and the like.

[0022] The automatic document feeder 111 transports documents placed in the document tray using a transport mechanism and sends them to the document image scanner 112. The automatic document feeder 111 makes it possible to continuously scan images (including both sides) of multiple documents placed in the document tray.

[0023] The document image scanning device 112 reads a document transported from the automatic document feeder 111 onto the contact glass or a document placed on the contact glass. Specifically, the document image scanning device 112 optically scans the document, forms an image of the reflected light from the document onto the light-receiving surface of an image sensor (e.g., a CCD (Charge Coupled Device)), and reads the document image. The document reading unit 11 generates input image data based on the reading result by the document image scanning device 112. The input image data is subjected to predetermined image processing in the image processing unit 13.

[0024] The operation display unit 12 is composed of, for example, a flat panel display with a touch panel. A liquid crystal display, an organic EL display, or the like can be used as the flat panel display. The operation display unit 12 has a display unit 121 and an operation unit 122.

[0025] The display unit 121 displays various operation screens, image status, and the operating status of each function in accordance with the display control signals input from the control unit 30.

[0026] The operation unit 122 is equipped with various operation keys such as a numeric keypad and a start key. The operation unit 122 receives various input operations from the user and outputs operation signals to the control unit 30. The user can operate the operation display unit 12 to make settings related to image formation, such as document settings, image quality settings, magnification settings, application settings, output settings, and recording material settings.

[0027] The image processing unit 13 includes circuits and other components that perform digital image processing on the input image data according to initial settings or user settings. For example, the image processing unit 13 performs gradation correction based on gradation correction data under the control of the control unit 30. The image processing unit 13 also applies various correction processes to the input image data, such as color correction, shading correction, and density correction. The image forming unit 20 is controlled based on the image data that has undergone these processes.

[0028] The image-forming unit 21 forms a toner image using colored toners for the Y, M, C, and K components based on the input image data. The intermediate transfer unit 22 transfers the toner image formed by the image-forming unit 21 onto the recording material. The fixing unit 23 fixes the transferred toner image onto the recording material.

[0029] Specifically, the image-forming unit 21 is composed of four image-forming units 21Y, 21M, 21C, and 21K, one for the Y component, one for the M component, one for the C component, and one for the K component. Since the image-forming units 21Y, 21M, 21C, and 21K have similar configurations, for the sake of illustration and explanation, common components are indicated by the same reference numeral, and when distinguishing between them, Y, M, C, and K are added to the reference numerals. Note that in Figure 1, reference numerals are only assigned to the components of the image-forming unit 21Y for the Y component, and the reference numerals for the components of the other image-forming units 21M, 21C, and 21K are omitted.

[0030] The image-forming unit 21 includes an exposure device 211, a developing device 212, a photosensitive drum 213, a charging device 214, and a drum cleaning device 215, etc. Although not shown in the figures, the image-forming unit 21 may also include a static elimination device for removing residual charge remaining on the surface of the photosensitive drum 213 after primary transfer.

[0031] The photosensitive drum 213 is, for example, a negatively charged organic photoconductor (OPC). The photosensitive drum 213 has a structure in which an undercoat layer, a charge generation layer, and a charge transport layer are sequentially laminated on the circumferential surface of a conductive cylindrical body (aluminum tube) made of aluminum.

[0032] The charge generation layer consists of an organic semiconductor in which a charge generation material (e.g., phthalocyanine pigment) is dispersed in a resin binder (e.g., polycarbonate). The charge generation layer generates a pair of positive and negative charges upon exposure by the exposure apparatus 211. The charge transport layer has a structure in which a hole transporting material (electron-donating nitrogen-containing compound) is dispersed in a resin binder (e.g., polycarbonate resin). The charge transport layer transports the positive charges generated in the charge generation layer to the surface of the charge transport layer.

[0033] The charging device 214 consists of a corona discharge generator, such as a scorotron charging device or a corotron charging device. The charging device 214 uniformly charges the surface of the photosensitive drum 213 with negative polarity by corona discharge.

[0034] The exposure apparatus 211 is composed of, for example, an LED print head (LPH). The LPH includes an LED array, an LPH driver unit (driver IC), and a lens array. Multiple light-emitting diodes (LEDs) are arranged linearly in the LED array. The LPH driver unit drives each individual LED. The lens array images the light emitted from the LED array onto the photosensitive drum 213. One LED in the LED array corresponds to one dot of the image.

[0035] The exposure apparatus 211 irradiates the photosensitive drum 213 with light corresponding to the image of each color component. The positive charge generated in the charge generation layer of the photosensitive drum 213 upon irradiation with light is transported to the surface of the charge transport layer, thereby neutralizing the surface charge (negative charge) of the photosensitive drum 213. As a result, an electrostatic latent image of each color component is formed on the surface of the photosensitive drum 213 due to the potential difference with the surroundings.

[0036] The developing device 212 contains developers for each color component (for example, a two-component developer including toner and carrier), and forms a toner image by visualizing the electrostatic latent image by depositing the toner of each color component onto the surface of the photosensitive drum 213. Specifically, a developing bias voltage is applied to the developer carrier (not shown in the symbols, for example, a developing roller), and an electric field is formed between the photosensitive drum 213 and the developer carrier. Due to the potential difference between the photosensitive drum 213 and the developer carrier, the charged toner on the developer carrier moves to the exposed area on the surface of the photosensitive drum 213 and adheres to it. This makes the electrostatic latent image on the photosensitive drum 213 visible.

[0037] The developing device 212 receives developer as needed from the developer supply unit 40. The developer supply unit 40 includes a developer storage unit 41, a developer transport unit 42, and a shutter unit 43, etc. Details of the developer supply unit 40 will be described later.

[0038] The drum cleaning device 215 removes any remaining toner from the surface of the photosensitive drum 213 after the primary transfer.

[0039] The intermediate transfer section 22 includes an intermediate transfer belt 221, a primary transfer roller 222, a plurality of support rollers 223, 224, a belt cleaning device 225, and a secondary transfer roller 226, etc.

[0040] The intermediate transfer belt 221 is an image carrier that holds the toner image and is the transfer target onto which the toner image on the photosensitive drum 213 is transferred. The intermediate transfer belt 221 is made up of an endless belt and is stretched in a loop shape between a plurality of support rollers 223. At least one of the plurality of support rollers 223 is made up of a drive roller, and the others are made up of driven rollers. As the drive roller rotates, the intermediate transfer belt 221 travels at a constant speed.

[0041] The primary transfer roller 222 is positioned on the inner circumferential side of the intermediate transfer belt 221, facing the photosensitive drum 213 for each color component. By pressing the primary transfer roller 222 against the photosensitive drum 213 with the intermediate transfer belt 221 in between, a primary transfer nip is formed for transferring the toner image from the photosensitive drum 213 to the intermediate transfer belt 221.

[0042] The support roller 223 includes an opposing roller 224 positioned opposite the secondary transfer roller 226. The secondary transfer roller 226 is positioned on the outer circumferential side of the intermediate transfer belt 221 and is pressed against the opposing roller 224 with the intermediate transfer belt 221 in between. This forms a secondary transfer nip for transferring the toner image from the intermediate transfer belt 221 to the recording material.

[0043] In the primary transfer nip, the toner image on the photosensitive drum 213 is sequentially transferred onto the intermediate transfer belt 221. Specifically, by applying a primary transfer voltage to the primary transfer roller 222, a charge opposite in polarity to the toner is applied to the inner surface side of the intermediate transfer belt 221 (the side that contacts the primary transfer roller 222). The toner image is electrostatically transferred from the photosensitive drum 213 to the intermediate transfer belt 221.

[0044] Subsequently, as the recording material passes through the secondary transfer nip, the toner image on the intermediate transfer belt 221 is transferred to the recording material. Specifically, by applying a secondary transfer voltage to the secondary transfer roller 226, a charge with the opposite polarity to the toner is applied to the back side of the recording material (the side that contacts the secondary transfer roller 226). The toner image is electrostatically transferred from the intermediate transfer belt 221 to the recording material. The recording material with the transferred toner image is then transported toward the fixing unit 23.

[0045] The belt cleaning device 225 has a belt cleaning blade (reference numeral omitted) that slides against the surface of the intermediate transfer belt 221. The belt cleaning device 225 removes the transfer residue toner remaining on the surface of the intermediate transfer belt 221 after secondary transfer.

[0046] The fixing unit 23 includes an upper fixing unit 231, a lower fixing unit 232, a heating source 233, and a pressure-contact separation unit (not shown), etc. The upper fixing unit 231 has a fixing surface side member that is positioned on the fixing surface side (the surface on which the toner image is formed) of the recording material. The lower fixing unit 232 has a back surface side support member that is positioned on the back surface side (the surface opposite the fixing surface) of the recording material. The heating source 233 heats the fixing surface side member. The pressure-contact separation unit presses the back surface side support member against the fixing surface side member.

[0047] The toner image is transferred to the recording material, and as the material is transported along the paper path, it is heated and pressurized as it passes through the fixing unit 23. This fixes the toner image to the recording material.

[0048] The paper feeding unit 14 has a paper feeding tray 141 and a manual feed unit 142. The paper feeding tray 141 holds sheets of paper (standard paper, special paper) identified based on basis weight, size, etc., according to pre-set paper types. Multiple paper feeding roller units (not shown) are arranged on the paper feeding tray 141 and the manual feed unit 142. A high-capacity external paper feed device (not shown) can be connected to the manual feed unit 142. The external paper feed device may be capable of feeding continuous paper such as roll paper. The paper feeding unit 14 delivers the recording material fed from the paper feeding tray 141 or the manual feed unit 142 to the recording material transport unit 16.

[0049] The paper discharge unit 15 includes a paper discharge transport roller unit 151, etc. The paper discharge unit 15 discharges the recording material sent from the recording material transport unit 16 to the outside of the machine.

[0050] The recording material transport unit 16 includes a main transport unit 161, a switchback transport unit 162, a transport unit for reverse printing 163, and a paper path switching unit (not shown), etc. A part of the recording material transport unit 16 may be incorporated into a single unit together with the fixing unit 23, for example, and detachably mounted on the image forming apparatus 1.

[0051] The main transport unit 161 has a recording material transport element that grips and transports the recording material. The recording material transport element includes, for example, a plurality of transport roller sections (not shown in numerals) including a loop roller section and a resist roller section. The main transport unit 161 transports the recording material fed from the paper feeding unit 14 and passes it through to the image forming unit 20 (intermediate transfer section 22, fixing section 23). The main transport unit 161 also transports the recording material discharged from the image forming unit 20 (fixing section 23) toward the paper discharge section 15 or the switchback transport unit 162.

[0052] The switchback transport unit 162 temporarily stops the recording material sent from the fixing unit 23, reverses the transport direction, and transports it to the paper discharge unit 15 or the back side printing transport unit 163.

[0053] The reverse-side printing transport unit 163 circulates the recording material that has been switched back in the switchback transport unit 162 to the main transport unit 161. The recording material is fed into the main transport unit 161 with the reverse side facing the image-forming surface.

[0054] The paper path switching unit (not shown) is located downstream of the fixing unit 23 in the recording material transport direction. The paper path switching unit switches the paper path depending on whether the recording material sent from the fixing unit 23 is ejected as is, ejected inverted, or transported to the reverse side printing transport unit 163. Specifically, the control unit 30 controls the operation of the paper path switching unit (not shown) based on the processing content of the image forming process (single-sided / double-sided printing, face-up / face-down ejection, etc.).

[0055] The recording material fed from the paper feeding section 14 is transported to the image forming section 20 by the main transport section 161. As the recording material passes through the secondary transfer section, the toner image on the intermediate transfer belt 221 is transferred to the first surface (front) of the recording material in one go, and fixing is performed in the fixing section 23. The recording material with the image formed on it is discharged outside the machine (for example, to a paper discharge unit (not shown)) by the paper discharge section 15. When forming images on both sides of the recording material, the recording material with the image formed on the first surface is sent to the switchback transport section 162. The recording material is then reversed by passing through the back-side printing transport section 163 and returning to the main transport section 161, and an image is formed on the second surface (back side).

[0056] A specific example of the developer replenishment unit 40 will be described below with reference to Figures 3A to 3C. Figures 3A to 3C are schematic diagrams showing an example of the developer replenishment unit 40. As shown in Figures 3A to 3C, the developer replenishment unit 40 includes a developer storage unit 41, a developer transport unit 42, and a shutter unit 43, etc. The developer replenishment unit 40 is positioned directly above the developing device 212 such that the developer replenishment port 422 and the opening 212a of the developing device 212 coincide in the vertical direction.

[0057] Furthermore, the developing device 212 is equipped with a toner concentration detection unit 45 (see Figure 2) for detecting the toner concentration in the developing container. For example, an optical sensor or an electrical sensor can be applied to the toner concentration detection unit 45. By supplying developer as needed from the developer supply unit 40, the toner concentration of the developing device 212 is maintained within an appropriate range.

[0058] The developer storage section 41 has a storage container for storing a two-component developer. The developer storage section 41 may be provided with a stirring screw or the like for stirring the stored developer. The developer stored in the developer storage section 41 is supplied to the developer transport section 42 as needed.

[0059] The developer transport unit 42 has transport elements such as a transport screw 421 and a drive motor (not shown). The developer transport unit 42 horizontally transports the developer supplied from the developer storage unit 41 to the developer replenishment port 422 by driving the transport screw 421. The transported developer free-falls through the developer replenishment port 422 and is supplied to the developing device 212.

[0060] The developer replenishment port 422 has a variable opening area. The opening area of ​​the developer replenishment port 422 changes according to the operation of the shutter unit 43. The operation of the shutter unit 43 is controlled by the control unit 30.

[0061] The shutter unit 43 includes a shutter 431 and a shutter drive unit 432. The shutter unit 43 can adjust the opening area of ​​the developer supply port 422 by opening and closing the shutter 431.

[0062] The shutter 431 is positioned vertically below the developer transport unit 42, for example, when the developer supply unit 40 is mounted on the main body of the image forming apparatus 1. The shutter 431 can close and open the developer supply port 422. The shutter 431 is connected to the shutter drive unit 432 (specifically, the rack 433).

[0063] The shutter drive unit 432 includes, for example, a rack 433, a pinion 434, and a drive motor 435. The shutter 431 is mounted on the rack 433 and moves integrally with the rack 433. The rack 433 is arranged to extend horizontally with the developer supply unit 40 mounted on the main body of the image forming apparatus 1. The pinion 434 is mounted on the motor shaft of the drive motor 435 and meshes with the rack 433. When the drive motor 435 is driven, the power of the drive motor 435 is transmitted to the rack 433 via the pinion 434. The rack 433 moves linearly along the horizontal direction.

[0064] For example, the developer storage unit 41, the developer transport unit 42, the shutter 431, and the rack 433 are integrally provided in a developer supply unit such as a toner bottle. The pinion 434 and the drive motor 435 are provided on the main body side of the image forming apparatus 1. The developer supply unit is detachable from the image forming apparatus 1. When the developer supply unit is attached to the image forming apparatus 1, the rack 433 and the pinion 434 engage.

[0065] The shutter 431 moves horizontally (in the direction of extension of the rack 433) by the power of the shutter drive unit 432, switching the opening state of the developer supply port 422. Specifically, the shutter 431 switches the developer supply port 422 to an open state where developer can be supplied (see Figures 3A and 3B) or a closed state where developer cannot be supplied (see Figure 3C).

[0066] The open state of the shutter 431 includes multiple open states with different opening areas. For example, the open state of the shutter 431 includes a fully open state where the entire developer supply port 422 is open (see Figure 3A) and a half-open state where a part (e.g., half) of the developer supply port 422 is open (see Figure 3B). The opening area of ​​the developer supply port 422 in the half-open state should be smaller than that of the fully open state. Furthermore, the half-open state may be provided in multiple stages with different opening areas.

[0067] When the transport speed by the developer transport unit 42 is the same, the amount of developer supplied per unit time (developer supply rate) is greater in the fully open state compared to the half-open state. The developer supply rate is set, for example, so that the developer is supplied in the fully open and half-open states as follows.

[0068] In other words, in the fully open state, when printing with high coverage, the toner density of the developer unit 212 increases, meaning that the amount of toner supplied exceeds the amount of toner consumed. In the half-open state, when printing with low coverage, the developer is supplied in such a way that the toner density of the developer unit 212 does not become excessively high.

[0069] The fully open, half-open, and closed states of the shutter 431 can be detected by the shutter position detection unit 44. The shutter position detection unit 44 includes, for example, a first light sensor 441, a second light sensor 442, and a light shielding plate 443. The light shielding plate 443 moves horizontally together with the shutter 431. The first light sensor 441 and the second light sensor 442 are reflective light sensors having a light source and a light receiving element.

[0070] The first light sensor 441 is positioned to be shielded by the light shielding plate 443 when the shutter 431 is half-open. The second light sensor 442 is positioned to be shielded by the light shielding plate 443 only when the shutter 431 is fully open. The first light sensor 441 and the second light sensor 442 receive reflected light from the light source using their light-receiving elements and detect the position of the light shielding plate 443, i.e., the fully open and half-open states of the shutter 431, based on the received light intensity. If no reflected light is received by the first light sensor 441 and the second light sensor 442, the shutter 431 is considered to be closed.

[0071] The shutter position detection unit 44 may be capable of detecting the position of the shutter 431 mechanically, electrically, or magnetically.

[0072] Figure 4 is a flowchart showing an example of a developer replenishment process performed by the control unit 30. This process is achieved, for example, when a print job is started in the image forming apparatus 1, by the CPU 31 executing a developer replenishment program stored in the ROM 32.

[0073] In this embodiment, the developer replenishment process is performed only during printing. That is, when the print job is completed, the developer replenishment process is forcibly terminated. If the print job is completed while the developer is being replenished, the shutter 431 remains open.

[0074] The appropriate range for toner density is set to a range of ±1% from the standard density (e.g., 6.5%). Here, the lower limit of the appropriate range for toner density (standard density - 1%) is used as the lower threshold for deciding whether or not to replenish the developer. The upper limit of the appropriate range for toner density (standard density + 1%) is used as the upper threshold for deciding whether or not to stop replenishing the developer. Note that the lower and upper thresholds may be set to values ​​that have a sufficient margin relative to the appropriate range.

[0075] In step S101 of Figure 4, the control unit 30 acquires the toner concentration of the developing device 212 based on the detection signal from the toner concentration detection unit 45. Although not shown in the flowchart of Figure 4, the control unit 30 continues to acquire the toner concentration during the developer replenishment process.

[0076] In step S102, the control unit 30 determines whether the toner density is below the lower threshold (reference density - 1%). If the toner density is below the lower threshold (YES in step S102), the process proceeds to step S104 and toner is replenished. If the toner density is greater than the lower threshold (NO in step S102), the process proceeds to step S103. In this case, toner is not replenished.

[0077] In step S103, the control unit 30 controls the operation of the shutter drive unit 432 so that the shutter 431 is in the closed state. Specifically, if the shutter 431 is in the fully open or half-open state, that is, if the previous print job was completed while the developer was being replenished, the shutter 431 will move to the closed state as a result of the process in step S103. On the other hand, if the shutter 431 is in the closed state, the shutter drive unit 432 will not be driven in the process in step S103, and the closed state of the shutter 431 will be maintained. After step S103, the process proceeds to step S101.

[0078] In step S104, the control unit 30 determines whether the rate of change in toner concentration is greater than or equal to a predetermined value. The rate of change in toner concentration is the amount of change in toner concentration per unit time. The rate of change in toner concentration is calculated, for example, based on the detection result of the toner concentration detection unit 45. Alternatively, for example, the rate of change in toner concentration may be estimated from the coverage of the print job being executed. When the coverage of the print job is high and the toner consumption is large, the rate of change in toner concentration will be greater than or equal to the predetermined value. If the rate of change in toner concentration is less than the predetermined value ("NO" in step S104), the process proceeds to step S105. If the rate of change in toner concentration is greater than or equal to the predetermined value ("YES" in step S104), the process proceeds to step S106.

[0079] In step S105, the control unit 30 controls the operation of the shutter drive unit 432 so that the shutter 431 is in a half-open state. The control unit 30 also controls the operation of the developer transport unit 42 to start replenishing the developer. The developer is replenished through the developer replenishment port 422 in an amount corresponding to the half-open state. By replenishing the developer in the half-open state, when the rate of change in toner concentration is below a predetermined value and the change in toner concentration is gradual, the toner concentration of the developing device 212 can be appropriately restored without oversupply.

[0080] In step S106, the control unit 30 controls the operation of the shutter drive unit 432 so that the shutter 431 is fully open. The control unit 30 also controls the operation of the developer transport unit 42 to start replenishing the developer. The developer is replenished through the developer replenishment port 422 in an amount corresponding to the fully open state. By replenishing the developer in the fully open state, the amount of toner replenished becomes greater than the amount of toner consumed, even in the case of high coverage, and the toner density of the developing device 212 can be appropriately restored.

[0081] In step S107, the control unit 30 determines whether the toner density is increasing. When developer is supplied in the fully open state, a large amount of developer is supplied, so the toner density should increase. In other words, if the toner density does not increase despite the developer being supplied in the fully open state, it can be determined that the developer storage unit 41 is empty. If the toner density is increasing (YES in step S107), the developer supply in the fully open state continues, and the process proceeds to step S108. If the toner density is not increasing (NO in step S107), the process proceeds to step S110.

[0082] In step S108, the control unit 30 determines whether the toner concentration has reached the upper threshold (reference concentration + 1%). If the toner concentration has reached the upper threshold (YES in step S108), the process proceeds to step S109. If the toner concentration has not reached the upper threshold (NO in step S108), the supply continues in a half-open or fully open state, and the process in step S108 is repeated.

[0083] In step S109, the control unit 30 controls the operation of the shutter drive unit 432 so that the shutter 431 is in the closed state. The control unit 30 also controls the operation of the developer transport unit 42 to stop the replenishment of the developer. After step S109, the process proceeds to step S101.

[0084] In step S110, the control unit 30 displays an alert indicating that the developer storage unit 41 is empty. The alert is displayed, for example, by a message on the display unit 121. Alternatively, the alert may include an audible notification. By displaying the alert, the user can be prompted to replace the developer replenishment unit.

[0085] In step S111, the control unit 30 controls the operation of the shutter drive unit 432 so that the shutter 431 is in the closed state. The control unit 30 also controls the operation of the developer transport unit 42 to stop the replenishment of the developer. After step S111, the developer replenishment process is completed.

[0086] Through the above process, the appropriate amount of developer can be efficiently supplied, and the toner concentration of the developing device 212 can be maintained within the appropriate range.

[0087] If the shutter 431 is held open for an extended period, toner blocking is likely to occur around the developer supply port 422. Toner blocking is a phenomenon in which toner powder aggregates and hardens. In particular, if toner blocking occurs in the developer accumulated on the shutter 431 when it is held in a half-open position, there is a risk of malfunction in the operation of the shutter 431. Therefore, it is preferable to perform a toner blocking process to avoid toner blocking.

[0088] Figure 5 is a flowchart showing an example of toner blocking avoidance processing performed by the control unit 30. This processing is achieved, for example, when stabilization processing is started in the image forming apparatus 1, by the CPU 31 executing a toner blocking avoidance program stored in the ROM 32.

[0089] In step S201 of Figure 5, the control unit 30 determines whether the shutter 431 is in a half-open state or not. If the shutter 431 is in a half-open state (YES in step S201), the process proceeds to step S202. If the shutter 431 is not in a half-open state (NO in step S201), that is, if the shutter 431 is in a fully open or closed state, the process proceeds to step S203.

[0090] In step S202, the control unit 30 controls the operation of the shutter drive unit 432 so that the shutter 431 is fully open. The developer that had accumulated on the partially open shutter 431 is scraped off and removed at the periphery of the developer supply port 422.

[0091] In step S203, the control unit 30 controls the operation of the shutter drive unit 432 so that the shutter 431 is closed. If the shutter 431 is already closed, the closed state is maintained. Since the shutter 431 is held in the closed state, the occurrence of toner blocking is suppressed.

[0092] In this embodiment, toner blocking avoidance processing is performed when stabilization processing is started in the image forming apparatus 1, but toner blocking avoidance processing may also be performed at the start or end of a print job.

[0093] Thus, the image forming apparatus 1 according to this embodiment is equipped with the following features individually or in appropriate combinations.

[0094] In other words, the image forming apparatus 1 is an image forming apparatus that forms an image on a recording material using a two-component developer containing toner and a carrier, and comprises a photosensitive drum 213 (image carrier), a developing apparatus 212 that supplies toner to the photosensitive drum 213 to form a toner image, a developer supply unit 40 that supplies developer to the developing apparatus 212 via a developer supply port 422 with a variable aperture area, a toner concentration detection unit 45 that detects the toner concentration in the developing apparatus 212, and a control unit 30 that controls the operation of supplying developer from the developer supply unit 40 to the developing apparatus 212. The control unit 30 changes the aperture area of ​​the developer supply port 422 based on the toner concentration and the rate of change of toner concentration detected by the toner concentration detection unit 45.

[0095] Furthermore, the developer replenishment method according to the embodiment is a method for replenishing developer in an image forming apparatus 1 that forms an image on a recording material using a two-component developer including toner and carrier, wherein the toner concentration in the developing apparatus 212 is detected (step S101 in Figure 4), the opening area of ​​the developer replenishment port 422 is changed based on the detected toner concentration and the rate of change of toner concentration (steps S102, S104~S106), and the developer is replenished to the developing apparatus 212 via the developer replenishment port 422 (steps S105, S106).

[0096] Furthermore, in this embodiment, the image forming apparatus according to the present invention is realized by the control unit 30 of the image forming apparatus 1 executing a developer replenishment program. That is, the developer replenishment program is a program that causes the control unit 30 (computer) of the image forming apparatus 1, which forms an image on a recording material using a two-component developer including toner and carrier, to execute a predetermined process, the predetermined process including a process to detect the toner concentration in the developing apparatus 212 (step S101 in Figure 4), a process to change the opening area of ​​the developer replenishment port 422 based on the detected toner concentration and the rate of change of the toner concentration (steps S102, S104~S106), and a process to replenish the developer to the developing apparatus 212 via the developer replenishment port 422 (steps S105, S106).

[0097] The developer replenishment program can be provided, for example, via a computer-readable portable storage medium (including, for example, optical discs, magneto-optical discs, and memory cards) on which the program is stored. Alternatively, the developer replenishment program can be provided by download from a server that holds the program via a network.

[0098] According to the image forming apparatus 1, developer replenishment method, and program of this embodiment, the appropriate amount of toner can be efficiently supplied to the developer 212 without causing oversupply when printing at low coverage or undersupply when printing at high coverage. Therefore, the quality of the image formed by the image forming apparatus 1 is stable.

[0099] In the image forming apparatus 1, the developer supply unit 40 includes a shutter unit 43 that can open and close a shutter 431 to adjust the opening area of ​​the developer supply port 422, and the control unit 30 controls the opening and closing operation of the shutter unit 43. This makes it possible to easily change the opening area of ​​the developer supply port 422 with a simple configuration.

[0100] In the image forming apparatus 1, the developer supply unit 40 has a developer storage unit 41 and a developer transport unit 42. The developer transport unit 42 horizontally transports the developer and allows it to free-fall from the developer supply port. This allows the amount of developer supplied to be appropriately adjusted simply by changing the opening area of ​​the developer supply port 422.

[0101] In the image forming apparatus 1, the control unit 30 fully opens the shutter 431 to replenish the developer when the rate of change in toner density is greater than or equal to a predetermined value, and replenishes the developer by partially opening the shutter 431 to a lesser amount than the fully open state when the rate of change in toner density is less than the predetermined value (steps S104 to S106 in Figure 4). This makes it possible to replenish an appropriate amount of developer according to the rate of change in toner density.

[0102] In the image forming apparatus 1, the control unit 30 replenishes the developer when the toner concentration is below a predetermined lower threshold (steps S102, S104-S106). This allows the developer to be replenished at an appropriate timing according to the toner concentration.

[0103] In the image forming apparatus 1, if the toner density does not increase even when the developer is replenished in the fully open state, the control unit 30 displays an alert indicating that the developer replenishment unit 40 is empty and closes the shutter 431 (steps S107, S110, S111 in Figure 4). This prompts the user to replace the developer replenishment unit and suppresses the decrease in productivity due to insufficient developer.

[0104] In the image forming apparatus 1, the control unit 30, when the shutter 431 is held in a half-open state, fully opens the shutter 431 and then closes it (steps S201 to S203 in Figure 4). This suppresses malfunctions caused by toner blocking that may occur when the shutter 431 is held in a half-open state, and allows for proper replenishment of the developer.

[0105] In the image forming apparatus 1, the shutter unit 43 includes a rack 433, a pinion 434, and a drive motor 435. The shutter 431 is mounted on the rack 433, and the power of the drive motor 435 is transmitted to the rack 433 via the pinion 434, causing the shutter 431 to move integrally with the rack 433. This allows the opening area of ​​the developer supply port 422 to be changed with a simple structure, and improves the responsiveness when starting or stopping developer supply.

[0106] Furthermore, in the image forming apparatus 1, the developer supply unit 40 has a developer supply unit that can be attached to and detached from the image forming apparatus 1, the shutter 431 and rack 433 are provided on the developer supply unit, and the pinion 434 and drive motor 435 are provided on the image forming apparatus 1, and when the developer supply unit is attached to the image forming apparatus 1, the rack 433 and pinion 434 mesh together. This makes it possible to realize a shutter unit 43 that changes the opening area of ​​the developer supply port 422 with a simple structure, while improving the workability when replacing the developer supply unit.

[0107] Although the present invention has been specifically described above based on embodiments, the present invention is not limited to the above embodiments and can be modified without departing from its spirit.

[0108] For example, although the present invention is applied to an electrophotographic color image forming apparatus, it can also be applied to an inkjet color image forming apparatus. Furthermore, the present invention can also be applied to a monochrome image forming apparatus.

[0109] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]

[0110] 1. Image forming apparatus 30 Control Unit 40 Developer replenishment unit 41 Developer storage section 42 Developer transport section 43 Shutter section 44 Shutter position detection unit 45 Toner concentration detection unit 431 Shutter 432 Shutter drive unit 433 racks 434 pinion 435 Drive motor

Claims

1. An image forming apparatus that forms an image on a recording material using a two-component developer containing toner and carrier, Image carrier and, A developing apparatus that supplies toner to the image carrier to form a toner image, A developer supply unit that supplies developer to the developing apparatus through a developer supply port with a variable opening area, A toner concentration detection unit for detecting the toner concentration in the developing device, The system includes a control unit that controls the operation of supplying developer from the developer supply unit to the developing device, The control unit changes the opening area of ​​the developer supply port based on the toner concentration detected by the toner concentration detection unit and the rate of change of the toner concentration. Image forming apparatus.

2. The developer supply unit includes a shutter that can open and close the shutter to adjust the opening area of ​​the developer supply port. The control unit controls the opening and closing operation of the shutter section. The image forming apparatus according to claim 1.

3. The developer supply unit has a developer storage unit and a developer transport unit, The developer transport unit horizontally transports the developer and allows it to fall freely from the developer supply port. The image forming apparatus according to claim 2.

4. The control unit, when the rate of change of the toner concentration is greater than or equal to a predetermined value, fully opens the shutter to replenish the developer, and when the rate of change of the toner concentration is less than the predetermined value, it partially opens the shutter to a state where the amount of developer supplied is less than that supplied when the shutter is fully open. The image forming apparatus according to claim 2.

5. The control unit replenishes the developer when the toner concentration is below a predetermined lower threshold. The image forming apparatus according to claim 4.

6. If the toner concentration does not increase even after supplying the developer in the fully open state, the control unit will display an alert indicating that the developer supply unit is empty and close the shutter. The image forming apparatus according to claim 4.

7. The control unit, when the shutter is held in the half-open state, moves the shutter to the fully open state and then closes the shutter. The image forming apparatus according to claim 4.

8. The shutter section includes a rack, a pinion, and a drive motor. The shutter is mounted on the rack, and the power of the drive motor is transmitted to the rack via the pinion, so that it moves integrally with the rack. The image forming apparatus according to claim 2.

9. The developer supply unit has a developer supply unit that is detachable from the image forming apparatus. The shutter and the rack are provided in the developer supply unit. The pinion and the drive motor are provided in the image forming apparatus. As the developer supply unit is mounted on the image forming apparatus, the rack and the pinion engage. The image forming apparatus according to claim 8.

10. A method for replenishing developer in an image forming apparatus that forms an image on a recording material using a two-component developer containing toner and carrier, The toner concentration in the developing device is detected, Based on the detected toner concentration and the rate of change of the toner concentration, the opening area of ​​the developer supply port is changed. The developer is supplied to the developing device through the developer supply port. How to replenish the developer.

11. A program that causes a computer in an image forming apparatus to perform a predetermined process, which forms an image on a recording material using a two-component developer containing toner and carrier, The aforementioned predetermined process is, A process for detecting the toner concentration in the developing device, A process to change the opening area of ​​the developer supply port based on the detected toner concentration and the rate of change of the toner concentration, The process includes supplying the developer to the developing device via the developer supply port, program.

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