Image forming apparatus

Abstract

This system accurately detects the toner end state of a toner container using a simple configuration. [Solution] A control unit 80 (determination means) is provided to determine whether or not a fluctuation exceeding a threshold has occurred in the bulk density of the developer G contained in the developing device 5Y. When the difference between the detection result detected by the toner density detection sensor 56 (toner density detection means) and a predetermined target value exceeds a predetermined value A, if the control unit 80 determines that the bulk density has not exceeded the threshold, it determines that the remaining amount of toner contained in the toner container 32Y is zero or less than a predetermined amount, resulting in a toner end state. If the control unit 80 determines that the bulk density has exceeded the threshold, it performs a predetermined control mode and then determines whether or not it is in a toner end state.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine in which a toner container is detachably installed.

Background Art

[0002] Conventionally, in image forming apparatuses such as copying machines and printers, many are used in which a toner container is detachably (replaceably) installed with respect to the image forming apparatus main body (see, for example, Patent Documents 1 and 2). And in such an image forming apparatus, when the toner accommodated inside the toner container becomes empty, a toner end state is detected to prompt the user to replace the toner container.

[0003] On the other hand, Patent Document 1 discloses an image forming apparatus that directly supplies toner discharged from a toner container to a developing device by rotationally driving a bottle-shaped toner container, and grasps the remaining amount of toner in the toner container by detecting the driving torque of the toner container. Further, Patent Document 2 discloses a technique for detecting the toner concentration (mixing ratio of toner and carrier) in the developer accommodated in the developing device, and replenishing toner from the toner container to the developing device based on the detection result. Also, when performing such toner replenishment, a technique for estimating the time when the toner charge amount becomes constant from the operation time and the standby time of the developing device, and changing the toner replenishment control from the estimated time is disclosed.

Summary of the Invention

Problems to be Solved by the Invention

[0004] In conventional image forming apparatuses, the method for detecting the toner end state of the toner container has been complicated or the detection accuracy has not been high. Therefore, there has been a possibility of problems such as an increase in the cost and size of the apparatus, or an inability to replace the toner container at the right timing.

[0005] This invention was made to solve the above-mentioned problems and aims to provide an image forming apparatus that can accurately detect the toner end state of a toner container with a simple configuration. [Means for solving the problem]

[0006] The image forming apparatus in this invention comprises a toner container detachably installed on the main body of the image forming apparatus, a developing device containing a developer consisting of toner and a carrier for developing a latent image formed on the surface of an image carrier, a toner concentration detection means for directly or indirectly detecting the mixing ratio of toner and carrier in the developer contained in the developing device, a toner supply device for supplying toner contained in the toner container to the developing device based on the detection result of the toner concentration detection means, and a determination means for determining whether or not a fluctuation exceeding a threshold has occurred in the bulk density of the developer contained in the developing device. When the difference between the detection result detected by the toner concentration detection means and a predetermined target value exceeds a predetermined value, if the determination means determines that the bulk density does not exceed the threshold, it is determined that the remaining amount of toner contained in the toner container is zero or less than a predetermined amount, and if the determination means determines that the bulk density exceeds the threshold, it is determined that the toner is in a toner-end state. [Effects of the Invention]

[0007] According to the present invention, an image forming apparatus can be provided that can accurately detect the toner end state of a toner container with a simple configuration. [Brief explanation of the drawing]

[0008] [Figure 1] This is an overall configuration diagram showing an image forming apparatus according to an embodiment of the present invention. [Figure 2] This is a cross-sectional view showing the image-forming section. [Figure 3]This is a schematic diagram showing the toner container, toner replenishment device, and developing device. [Figure 4] This flowchart shows the control system for detecting the toner end state of a toner container. [Figure 5] This graph shows the fluctuations in toner concentration. [Figure 6] This flowchart shows a control mechanism for detecting the toner end state of a toner container, as an example of modification 1. [Figure 7] This flowchart shows a control mechanism for detecting the toner end state of a toner container, as an example of modification 2. [Modes for carrying out the invention]

[0009] Hereinafter, embodiments for carrying out this invention will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and redundant explanations will be simplified or omitted as appropriate.

[0010] First, the overall configuration and operation of the image forming apparatus 100 will be explained using Figures 1 to 3. In this embodiment, the image forming apparatus 100 functions as a printer. As shown in Figure 1, four roughly cylindrical toner containers 32Y, 32M, 32C, and 32K, corresponding to each color (yellow, magenta, cyan, and black), are detachably (replaceable) mounted on the mounting section 31 (toner container holder) located above the main body 100 of the image forming apparatus. Below each toner container 32Y, 32M, 32C, and 32K, toner supply hoppers 81Y, 81M, 81C, and 81K are respectively provided. Furthermore, an intermediate transfer unit 15 is positioned below the installation section 31. Opposite the intermediate transfer belt 8 of the intermediate transfer unit 15, image units 6Y, 6M, 6C, and 6K corresponding to each color (yellow, magenta, cyan, and black) are arranged side by side. Furthermore, a thermometer / hygrometer 75 (temperature / humidity sensor) capable of detecting the absolute humidity (or relative humidity, temperature) around the image-forming units 6Y, 6M, 6C, and 6K (developing devices) is installed near the image-forming units 6Y, 6M, 6C, and 6K.

[0011] Referring to Figure 2, the image-forming unit 6Y corresponding to yellow consists of a photoreceptor drum 1Y (image carrier) and a charging device 4Y, a developing device 5Y, a cleaning device 2Y, a static elimination device, etc., arranged around the photoreceptor drum 1Y. The image-forming process (charging process, exposure process, developing process, transfer process, cleaning process, static elimination process) is then performed on the photoreceptor drum 1Y, and a yellow image is formed on the surface of the photoreceptor drum 1Y.

[0012] Furthermore, the other three image units, 6M, 6C, and 6K, have almost the same configuration as the yellow-compatible image unit 6Y, except for the color of the toner used, and each forms an image corresponding to its respective toner color. Below, we will omit explanations of the other three image units, 6M, 6C, and 6K, and only explain the yellow-compatible image unit 6Y.

[0013] Referring to Figure 2, the photoreceptor drum 1Y is driven to rotate clockwise by a motor as shown in Figure 2. Then, at the position of the charging device 4Y, the surface of the photoreceptor drum 1Y is uniformly charged (this is the charging process). Subsequently, the surface of the photoreceptor drum 1Y reaches the irradiation position of the laser beam L emitted from the exposure device 7 (writing unit), and an electrostatic latent image corresponding to yellow is formed by exposure scanning at this position (this is the exposure process).

[0014] Subsequently, the surface of the photoreceptor drum 1Y reaches a position opposite the developing device 5Y, where the electrostatic latent image is developed and a yellow toner image is formed (this is the developing process). Thereafter, the surface of the photoreceptor drum 1Y reaches the position facing the intermediate transfer belt 8 and the primary transfer roller 9Y, and at this position, the toner image on the photoreceptor drum 1Y is transferred onto the intermediate transfer belt 8 (this is the primary transfer process). At this time, a small amount of untransferred toner remains on the photoreceptor drum 1Y.

[0015] Thereafter, the surface of the photoreceptor drum 1Y reaches the position facing the cleaning device 2Y, and at this position, the untransferred toner remaining on the photoreceptor drum 1Y is recovered (this is the cleaning process). Finally, the surface of the photoreceptor drum 1Y reaches the position facing the charge elimination device (not shown), and at this position, the residual potential on the photoreceptor drum 1 is removed. Thus, a series of image forming processes performed on the photoreceptor drum 1Y is completed.

[0016] Note that the above-described image forming process is also performed in the same manner as in the yellow image forming unit 6Y in the other image forming units 6M, 6C, and 6K. That is, the laser beam L based on the image information is irradiated onto the photoreceptor drums of the respective image forming units 6M, 6C, and 6K from the exposure device 7 disposed below the image forming unit. Specifically, the exposure device 7 emits the laser beam L from a light source, scans the laser beam L with a polygon mirror driven to rotate, and irradiates it onto the photoreceptor drum through a plurality of optical elements. Thereafter, the toner images of each color formed on each photoreceptor drum after the development process are transferred and overlapped onto the intermediate transfer belt 8. Thus, a color image is formed on the intermediate transfer belt 8.

[0017] Here, the intermediate transfer unit 15 is composed of an intermediate transfer belt 8, four primary transfer rollers 9Y, 9M, 9C, 9K, a secondary transfer opposing roller 12, a cleaning backup roller 13, a tension roller 14, an intermediate transfer cleaning device 10, etc. The intermediate transfer belt 8 is stretched and supported by three rollers 12 to 14, and is endlessly moved in the direction of the arrow in FIG. 1 by the rotational drive of one roller 12.

[0018] The four primary transfer rollers 9Y, 9M, 9C, and 9K sandwich the intermediate transfer belt 8 between the photosensitive drums 1Y, 1M, 1C, and 1K, respectively, to form primary transfer nips. Then, a transfer bias opposite to the polarity of the toner is applied to the primary transfer rollers 9Y, 9M, 9C, and 9K. Then, the intermediate transfer belt 8 travels in the direction of the arrow and sequentially passes through the primary transfer nips of the respective primary transfer rollers 9Y, 9M, 9C, and 9K. In this way, the toner images of each color on the photosensitive drums 1Y, 1M, 1C, and 1K are primarily transferred and superimposed on the intermediate transfer belt 8.

[0019] After that, the intermediate transfer belt 8 on which the toner images of each color are superimposed and transferred reaches the position opposite to the secondary transfer roller 19. At this position, the secondary transfer opposing roller 12 sandwiches the intermediate transfer belt 8 between it and the secondary transfer roller 19 to form a secondary transfer nip. Then, the four-color toner image formed on the intermediate transfer belt 8 is transferred onto a sheet P such as paper conveyed to the position of this secondary transfer nip. At this time, untransferred toner that has not been transferred to the sheet P remains on the intermediate transfer belt 8.

[0020] After that, the intermediate transfer belt 8 reaches the position of the intermediate transfer cleaning device 10. And at this position, the untransferred toner on the intermediate transfer belt 8 is recovered. In this way, a series of transfer processes performed on the intermediate transfer belt 8 are completed.

[0021] Here, the sheet P conveyed to the position of the secondary transfer nip is conveyed from the paper feeding device 26 disposed below the apparatus main body 100 via the paper feeding roller 27, the registration roller pair 28, and the like. Specifically, a plurality of sheets P such as paper are stored in the paper feeding device 26 in a stacked manner. When the paper feeding roller 27 is rotationally driven counterclockwise in FIG. 1, the uppermost sheet P is fed toward the space between the rollers of the registration roller pair 28.

[0022] The sheet P, transported to the position of the register roller pair 28 (timing roller pair), temporarily stops at the roller nip of the register roller pair 28, where the rotational drive has been stopped. Then, in time with the color image on the intermediate transfer belt 8, the register roller pair 28 is driven to rotate, and the sheet P is transported toward the secondary transfer nip. In this way, the desired color image is transferred onto the sheet P.

[0023] Subsequently, the sheet P, on which the color image has been transferred at the secondary transfer nip, is transported to the fixing device 20. At this location, the color image transferred to the surface is fixed onto the sheet P by heat and pressure from the fixing roller and pressure roller. Subsequently, the sheet P is discharged outside the device via the rollers of the paper discharge roller pair 29. The sheet P discharged outside the device by the paper discharge roller pair 29 is sequentially stacked on the stacking unit 30 as an output image. Thus, the series of image formation processes in the image forming apparatus are completed.

[0024] Next, Figure 2 will provide a more detailed explanation of the configuration and operation of the developing device 5Y in the image-making section. The developing device 5Y consists of a developing roller 51 facing the photoreceptor drum 1Y, a doctor blade 52 facing the developing roller 51, two transport screws 55 arranged in the developer storage sections 53 and 54, and a toner concentration detection sensor 56 as a toner concentration detection means for detecting the toner concentration of the developer G (which is the mixing ratio of toner and carrier in the developer G). The developing roller 51 consists of a magnet fixed inside and a sleeve that rotates around the magnet. The developer storage sections 53 and 54 contain a two-component developer G consisting of a carrier and toner.

[0025] The developing apparatus 5Y, configured in this way, operates as follows: The sleeve of the developing roller 51 rotates in the direction of the arrow in Figure 2. The developer, which is supported on the developing roller 51 by the magnetic field formed by the magnet, moves along the developing roller 51 as the sleeve rotates. Here, the developer G in the developing device 5Y is adjusted so that the proportion of toner in the developer G (toner concentration) is within a predetermined range. Specifically, in accordance with the toner consumption in the developing device 5Y, the toner contained in the toner container 32Y is replenished into the developer container 54 via the toner replenishment device 90 (see Figure 3). In other words, the toner replenishment device 90 replenishes the toner contained in the toner container 32Y to the developing device 5Y based on the detection result of the toner concentration detection sensor 56 (toner concentration detection means). In this embodiment, a known magnetic sensor that directly and magnetically detects the mixing ratio (toner concentration) of toner and carrier in the developer G is used as the toner concentration detection sensor 56 (toner concentration detection means). Furthermore, in this embodiment, the developing device 5Y is driven by a developing motor 77 that can independently drive only the developing device 5Y. Specifically, the developing motor 77, controlled by the control unit 80, rotates the developing roller 51 and the two transport screws 55 in predetermined directions.

[0026] Subsequently, the toner supplied to the developer container 54 is mixed and agitated with the developer G by two transport screws 55, and circulates through the two developer containers 53 and 54 (movement in the longitudinal direction perpendicular to the paper surface in Figure 2). The toner in the developer G is then attracted to the carrier by triboelectric charging and, together with the carrier, is supported on the developing roller 51 by the magnetic force formed on the developing roller 51. The developer G supported on the developing roller 51 is transported in the direction of the arrow in Figure 3 to the position of the doctor blade 52. At this position, the amount of developer G on the developing roller 51 is adjusted to the appropriate level, and then it is transported to the position opposite the photoreceptor drum 1Y (the developing area). Then, the toner is attracted to the latent image formed on the photoreceptor drum 1Y by the electric field formed in the developing area. After that, the developer G remaining on the developing roller 51 reaches above the developer storage section 53 as the sleeve rotates, and at this position it is detached from the developing roller 51.

[0027] Referring to Figure 2, in this embodiment, a known toner adhesion amount detection sensor 78 (toner adhesion amount detection means) capable of optically detecting the amount of toner adhesion (image density) of the toner image (image) formed on the surface of the intermediate transfer belt 8 by the developing device 5Y is provided at a position downstream of the developing roller 51 (developing device 5Y) in the direction of travel of the intermediate transfer belt 8. In this embodiment, the target value of the mixing ratio (toner density) of the developer G in the developing device 5Y is appropriately determined based on the toner image detected by the toner adhesion amount detection sensor 78 (for example, a solid black or a gradation patch pattern formed during the warm-up or between the sheets of paper after the development process). Specifically, if the detection result of the toner adhesion amount detection sensor 78 is low, the target value of the mixing ratio (toner density) of the developer G in the developing device 5Y is set higher than when the result is high. By performing this control, a good image (toner image) with stable image density is formed on the photoreceptor drum 1Y.

[0028] Next, Figure 3 will briefly explain the configuration and operation of the toner supply device 90. As explained earlier using Figure 2, the toner supply device 90 is a device for supplying toner contained in the toner container 32Y to the developing device 5Y based on the detection result of the toner density detection sensor 56 (toner density detection means) installed in the developing device 5Y. As shown in Figure 3, the toner supply device 90 in this embodiment does not use a sub-hopper or the like as an intermediary, but directly supplies the toner discharged from the toner container 32Y to the developing device 5Y via the transport pipe 96 (toner transport pipe). More specifically, the toner supply device 90 rotates the container body 33 of the toner container 32Y installed in the installation section 31 in a predetermined direction (the direction of the arrow in Figure 3), thereby discharging the toner stored inside the toner container 32Y to the outside of the container and guiding it to the developing device 5Y via the transport pipe 96. Note that Figure 3 shows the toner container 32Y, toner replenishment device 90, and developing device 5Y arranged in different directions for easier understanding. In reality, in Figure 3, the toner container 32Y and a portion of the toner replenishment device 90 are arranged so that their longitudinal directions are perpendicular to the plane of the paper (see Figure 1). Also, the orientation and arrangement of the transport pipe 96 are simplified in the illustration.

[0029] The toner in each toner container 32Y, 32M, 32C, and 32K installed in the mounting section 31 of the image forming apparatus main body 100 is replenished into each developing unit as needed, via toner replenishment devices provided for each toner color, according to the toner consumption in each developing unit. The four toner replenishment devices have almost identical structures except for the different toner colors used in the image formation process. For details, please refer to Figure 3. When the toner container 32Y is set in the installation section 31 of the image forming apparatus body 100, the shutter member 36 of the toner container 32Y is pushed by the toner transport nozzle 91 of the image forming apparatus body 100, and the toner transport nozzle 91 is inserted into the inside of the toner container 32Y (container body 33) through the through hole. This enables the discharge of the toner contained inside the toner container 32Y (discharge via the toner transport nozzle 91). Furthermore, a gripping portion 33d is formed at the bottom of the toner container 32Y (the left side in Figure 3) to facilitate the operation of attaching the toner container 32Y to the installation portion 31. The user will hold the gripping portion 33d while setting the toner container 32Y into the installation portion 31 or removing the toner container 32Y from the installation portion 31.

[0030] Referring to Figure 3, the toner container 32Y is provided with a container body 33 having a spiral groove 33a formed in the longitudinal direction (the left-right direction in Figure 3, which is the rotation axis direction of the container body 33). Specifically, this spiral groove 33a is formed from the outer circumferential surface to the inner circumferential surface of the container body 33 and is for rotating the container body 33 to transport the toner inside the container body 33 from left to right in Figure 3. The toner transported from left to right in Figure 3 inside the container body 33 is discharged to the outside of the container via the toner transport nozzle 91. Furthermore, a gear 33b is formed on the outer circumferential surface of the top side (right side in Figure 3) of the container body 33, which meshes with the drive gear 110 of the image forming apparatus body 100. When the toner container 32Y is mounted on the installation section 31, the gear 33b of the container body 33 meshes with the drive gear 110 of the image forming apparatus body 100. Then, when the toner supply motor 115 (drive motor) is driven, the drive (rotational drive) is transmitted from the drive gear 110 installed on the motor shaft to the gear 33b, causing the container body 33 to rotate. In other words, the toner supply motor 115 and the drive gear 110 function as a drive mechanism that rotates the container body 33.

[0031] On the other hand, referring to Figure 3, a transport screw 92 is installed inside the toner transport nozzle 91. The transport screw 92 is rotated by the motor 93, and the toner that flows into the toner transport nozzle 91 from the opening 91a (inlet, see Figure 6) inside the toner container 32Y is transported by the transport screw 92 from left to right in Figure 3. The toner is then discharged from the outlet of the toner transport nozzle 91 toward the transport pipe 96. The toner discharged toward the transport pipe 96 is then supplied to the developing device 5Y. Based on the detection results of the toner density detection sensor 56 installed inside the developing device 5Y, the driving timing and driving time of the toner supply motor 115 that rotates the toner container 32Y (container body 33) and the motor 93 (transport screw drive motor) that rotates the transport screw 92 are controlled. Specifically, if the toner density detection sensor 56 determines that the toner density (mixing ratio) has not reached the target value, the toner supply motor 115 and motor 93 are driven for a predetermined time, and if the toner density detection sensor 56 determines that the toner density (mixing ratio) has reached the target value, the driving of the toner supply motor 115 and motor 93 is stopped. In this embodiment, the control for determining whether the toner contained inside the toner container 32Y is empty (or nearly empty) (toner end state) is unique and will be explained next.

[0032] The characteristic configuration and operation of the image forming apparatus 100 in this embodiment will be described below. In this embodiment, the image forming apparatus 100 is provided with a control unit 80, which serves as a determination means for determining whether or not a fluctuation exceeding a threshold has occurred in the bulk density of the developer G contained in the developing apparatus 5Y. Specifically, the control unit 80, acting as a determination means, determines whether the time the developing device 5Y is left idle exceeds a predetermined time B, thereby determining whether a fluctuation exceeding a threshold has occurred in the bulk density of the developer G inside the developing device 5Y. There is a close correlation between the standing time of developer G and its bulk density, which also affects the amount of charge on the toner in developer G, and the bulk density tends to increase as the standing time increases. Therefore, if the time between the end of the previous printing operation and the start of the current printing operation (standing time) exceeds a predetermined time B, it is determined that the bulk density of developer G has exceeded the threshold, and if it exceeds the predetermined time B, it is determined that the bulk density of developer G has not exceeded the threshold. The idle time is measured moment by moment by the timer 76 and stored in the memory unit of the control unit 80. Based on this time, the calculation unit of the control unit 80 calculates the idle time.

[0033] Then, if the difference between the detection result detected by the toner concentration detection sensor 56 (toner concentration detection means) and a predetermined target value exceeds a predetermined value A, the control unit 80 (determination means) makes the following determination based on the determination result of the control unit 80 described above, regarding whether or not the toner container 32Y is in a toner end state (a state in which the remaining amount of toner contained in the toner container 32Y is zero (or less than a predetermined amount)).

[0034] First, if the difference in toner density described above exceeds a predetermined value A, and the control unit 80 (determination means) determines that the bulk density of the developer G does not exceed a threshold, it is determined that the toner container 32Y is in a toner-end state (empty or nearly empty). In other words, if the control unit 80 determines that the development device 5Y has been left unattended for longer than the predetermined time B, it determines that the toner container 32Y is in the toner end state. When such a determination is made, a display panel (not shown) installed on the exterior of the image forming apparatus 100 prompts the replacement of the toner container 32Y. Furthermore, it is possible to control the system so that subsequent printing cannot be performed when the toner end state is detected.

[0035] In contrast, if the difference in toner density described above exceeds a predetermined value A, and the control unit 80 (determination means) determines that the bulk density of the developer G exceeds a threshold (when it is determined that the development device 5Y has been left standing for a predetermined time B), a predetermined control mode is executed, and then a determination is made as to whether or not the toner container 32Y is in a toner-end state. In this embodiment, the "control mode" described above is an agitation mode in which the developing device 5Y is idle-driven (driven by the developing motor 77 without printing) for a predetermined time. When the developer G in the developing device 5Y is agitated by the transport screw 55, its bulk density returns to what it was before the change, and the judgment made based on the bulk density of the developer G that changed after standing will now be made based on the bulk density before the change, thus making it less likely for errors to occur in determining the toner end state. Then, when it is determined that the bulk density of the developer G exceeds a threshold, after performing the stirring mode (idle operation of the developing device 5Y), if the difference between the detection result detected by the toner density detection sensor 56 (toner density detection means) and the target value described above exceeds a predetermined value A, it is determined that the toner is in a toner end state. If the difference does not exceed the predetermined value A, it is determined that the toner is not in a toner end state.

[0036] The reason for performing this control is that, as explained earlier, if the developer G (developing device 5Y) is left for a long time, the bulk density of the developer G fluctuates, causing the toner concentration (mixing ratio of toner to carrier) detected by the toner concentration detection sensor 56 to fluctuate, which may lead to a misjudgment (false detection) of whether or not the toner end state is determined based on the detection result of the toner concentration detection sensor 56. Therefore, in this embodiment, even if the toner end state is determined once based on the detection result of the toner concentration detection sensor 56, if the standing time exceeds a predetermined time B, the determination of whether or not the toner end state is determined again based on the detection result of the toner concentration detection sensor 56 is performed once more.

[0037] If the re-evaluation determines that the toner is running out, a display panel (not shown) installed on the exterior of the image forming apparatus 100 will prompt the user to replace the toner container 32Y. Conversely, if the re-evaluation determines that the toner is not running out, no prompting for replacement of the toner container 32Y will be displayed, and the system will remain in a state where normal printing is possible.

[0038] In this embodiment, when performing the control to detect the toner end state described above, the detection of toner concentration (mixing ratio) by the toner concentration detection sensor 56 (toner concentration detection means) is performed each time a series of prints (jobs) is completed. Specifically, after the previous print (job) is completed and before the next (current) print is started, the toner concentration is detected by the toner concentration detection sensor 56, and control is performed to detect the toner end state of the toner container 32Y. Furthermore, during continuous printing or while a series of print jobs are in progress (printing), the toner supply motor 115 and motor 93 are controlled to appropriately supply toner from the toner container 32Y to the developer 5Y, based on the toner concentration detection result from the toner concentration detection sensor 56, so that the toner concentration of the developer G in the developer 5Y reaches the target value.

[0039] Furthermore, in this embodiment, as explained earlier using Figure 2, the amount of toner deposited (image density) in the toner image (image) formed on the surface of the intermediate transfer belt 8 by the developing device 5Y is optically detected by the toner deposit amount detection sensor 78, and a target value for the mixing ratio (toner density) of the developer G in the developing device 5Y is appropriately determined based on the detection result. Therefore, the toner deposit amount detection sensor 78, together with the control unit 80, also functions as a determination means for determining whether or not the toner container 32Y is in a toner end state.

[0040] Thus, the method for detecting the toner end state of the toner container 32Y in this embodiment uses a toner concentration detection sensor 56 used in toner replenishment control, without detecting the driving torque of the toner container 32Y, thereby reducing the complexity, cost, and size of the device. Furthermore, in this embodiment, when the bulk density of the developer G in the developing device 5Y changes significantly and the detection result of the toner density detection sensor 56 is likely to be greatly inaccurate, a stirring mode (control mode) is executed to restore the change in bulk density to its original state, and after execution, the presence or absence of a toner end state is re-determined. As a result, the toner end state of the toner container 32Y can be determined (detected) with high accuracy, and problems such as not being able to replace the toner container 32Y at the right time are less likely to occur.

[0041] Figure 5 is a graph showing an example of the time-dependent fluctuation of the toner concentration of the developer G in the developing device 5Y. In Figure 5, line M shows the change in the target value of the toner concentration, which is appropriately optimized based on the detection results of the toner adhesion amount detection sensor 78, and line N shows the toner concentration (detection result) actually detected by the toner concentration detection sensor 56. As shown in Figure 5, if the standing time is long, the detection result of the toner concentration deviates greatly from the target value, and the accuracy of determining whether or not the toner is running out decreases (toner level misdetection occurs). In contrast, in this embodiment, since the control described above is performed, such problems are less likely to occur.

[0042] Below, an example of the toner end determination control described above will be explained using the flowchart in Figure 4. First, when a series of print jobs are started and finished (steps S1, S2), the toner concentration (mixing ratio) of the developer G in the developing device 5Y is detected by the toner concentration detection sensor 56 (step S3). Then, it is determined whether the difference between the toner concentration detected by the toner concentration detection sensor 56 (detection result) and the predetermined target value of the toner concentration is greater than or equal to a predetermined value A (step S4). If the difference is not greater than or equal to the predetermined value A, it is determined that there is a sufficient amount of toner remaining in the toner container 32Y, and this flow is terminated. In contrast, if the difference in step S4 is greater than or equal to a predetermined value A, it is further determined whether the time elapsed between the previous print and the start of the current print is greater than or equal to a predetermined time B (step S5). If the time elapsed is not greater than or equal to the predetermined time B, it is determined that there is little change in bulk density due to the time elapsed, and the toner is in a toner-end state (step S9). In contrast, if the standing time in step S5 is longer than the predetermined time B, the stirring mode is executed (step S6) to restore the bulk density fluctuation, and then the toner concentration (mixing ratio) of the developer G in the developing device 5Y is detected again by the toner concentration detection sensor 56 (step S7). Then, it is determined whether the difference between the toner concentration detected by the toner concentration detection sensor 56 (detection result) and the predetermined target value of the toner concentration is greater than or equal to the predetermined value A (step S8). If the difference is not greater than or equal to the predetermined value A, this flow is terminated, as it is assumed that there is a sufficient amount of toner remaining in the toner container 32Y. In contrast, if the difference is greater than or equal to the predetermined value A, it is determined that the toner is at its end (step S9).

[0043] <Example 1> Using the flowchart in Figure 6, we will explain the control for detecting the toner end state of the toner container 32Y in Modified Example 1. In the modified example 1, the control unit 80, which functions as a determination means, determines whether a fluctuation in any of the absolute humidity, relative humidity, or temperature around the developing device 5Y (a fluctuation relative to the one at the time the previous printing was completed) exceeds a predetermined difference, thereby determining whether a fluctuation exceeding a threshold has occurred in the bulk density of the developer G inside the developing device 5Y. The reason for performing this control is, as shown in Figure 5, that if the absolute humidity (or relative humidity or temperature) around the developing device 5Y fluctuates significantly, the bulk density of the developer G will fluctuate, causing the toner concentration (mixing ratio of toner to carrier) detected by the toner concentration detection sensor 56 to fluctuate, which may lead to a misjudgment (false detection) of whether or not the toner end state is present, based on the detection result of the toner concentration detection sensor 56. Therefore, in Modification 1, even if the toner end state is determined once based on the detection result of the toner concentration detection sensor 56, if the fluctuation in the absolute humidity (or relative humidity or temperature) around the developing device 5Y exceeds a predetermined difference C, the determination of whether or not the toner end state is present is performed again based on the detection result of the toner concentration detection sensor 56. The absolute humidity (or relative humidity or temperature) around the developing device 5Y is detected inside the image forming apparatus 100 by a thermometer / hygrometer 75 installed near the developing device 5Y. Based on the data measured moment by moment by the thermometer / hygrometer 75 and stored in the memory unit of the control unit 80, the calculation unit of the control unit 80 calculates the difference C before and after printing. Specifically, in the control shown in Figure 6, step S10 is executed instead of step S5 in Figure 4. That is, if the difference in step S4 is greater than or equal to a predetermined value A, it is further determined whether the change in absolute humidity since the last print is greater than or equal to a predetermined difference C (step S10). As a result, if the change in absolute humidity is not greater than or equal to the predetermined difference C, it is determined that there is almost no change in bulk density due to the standing time, and the toner is in the end state (step S9). In response to this, if the absolute humidity fluctuation in step S10 is greater than or equal to a predetermined difference C, the stirring mode is executed (step S6) to restore the bulk density fluctuation, and then the toner concentration (mixing ratio) of the developer G in the developing device 5Y is detected again by the toner concentration detection sensor 56 (step S7). Then, it is determined whether the difference between the toner concentration detected by the toner concentration detection sensor 56 (detection result) and the predetermined target value of the toner concentration is greater than or equal to a predetermined value A (step S8). If the difference is not greater than or equal to the predetermined value A, this flow is terminated, assuming that there is a sufficient amount of toner remaining in the toner container 32Y. In contrast, if the difference is greater than or equal to the predetermined value A, it is determined that the toner is at its end (step S9). In this embodiment, when detecting and controlling the toner end state as described above, the fluctuation in absolute humidity (or relative humidity or temperature) around the developing device 5Y was used as the fluctuation relative to the value at the end of the previous print run. However, it is also possible to use the fluctuation relative to the average value at the end of multiple print runs prior to the previous print run. Furthermore, even when control is performed as in Modification 1, the toner end state of the toner container 32Y can be detected accurately with a simple configuration.

[0044] <Modification 2> Using the flowchart in Figure 7, we will explain the control for detecting the toner end state of the toner container 32Y in Modified Example 2. In Modification 2, instead of the agitation mode, a correction mode is used as the control mode performed during re-determination. This correction mode adjusts the detection result detected by the toner concentration detection sensor 56 (toner concentration detection means) according to the extent to which the bulk density of the developer G in the developing device 5Y exceeds a threshold. Specifically, if the bulk density of the developer G exceeds the threshold significantly, the toner concentration detection result is corrected to reduce the difference, assuming that there were no factors causing fluctuations in bulk density, compared to the case where the threshold is only slightly exceeded. Then, when it is determined that the bulk density of the developer G exceeds the threshold, a correction mode (correction of the toner density detection result) is executed. If the difference between the detection result of the toner density detection sensor 56 corrected by the correction mode and the target value described earlier exceeds a predetermined value A, it is determined that the toner is in a toner end state. If the difference does not exceed the predetermined value A, it is determined that the toner is not in a toner end state. Specifically, in the control shown in Figure 7, steps S11 and S12 are executed instead of steps S6 to S8 in Figure 6. That is, if the fluctuation in absolute humidity in step S10 is greater than or equal to a predetermined difference C, a correction mode is executed (step S11), and it is determined whether the difference between the corrected toner concentration detection result (toner concentration) of the toner concentration detection sensor 56 and the predetermined target value of toner concentration is greater than or equal to a predetermined value A (step S12). If the difference is not greater than or equal to the predetermined value A, this flow is terminated, assuming that there is a sufficient amount of toner remaining in the toner container 32Y. On the other hand, if the difference is greater than or equal to the predetermined value A, it is determined that the toner is out (step S9). Furthermore, even when control is performed as in the modified example 2, the toner end state of the toner container 32Y can be detected accurately with a simple configuration. In the modified example 2, the magnitude of the fluctuation in the bulk density of the developer G inside the developing device 5Y was determined by the magnitude of the fluctuation in the absolute humidity (or relative humidity and temperature) around the developing device 5Y. Alternatively, the magnitude of the fluctuation in the bulk density of the developer G inside the developing device 5Y can also be determined by the length of time the developing device 5Y is left standing. That is, instead of step S10 in Figure 7, step S5 in Figure 4 can be performed. Furthermore, the magnitude of fluctuations in the bulk density of the developer G inside the developing device 5Y can be determined by the magnitude of fluctuations in the absolute humidity (or relative humidity, temperature) around the developing device 5Y and the length of time the developing device 5Y is left standing.

[0045] As described above, the image forming apparatus 100 in this embodiment includes a toner container 32Y that is detachably installed on the main body of the image forming apparatus, and a developing device 5Y that contains a developer G consisting of toner and a carrier and develops the latent image formed on the surface of the photoreceptor drum 1Y (image carrier). The developing device 5Y also includes a toner concentration detection sensor 56 (toner concentration detection means) that directly or indirectly detects the mixing ratio of toner and carrier in the developer G contained in the developer G, and a toner supply device 90 that replenishes the toner contained in the toner container 32 to the developing device 5Y based on the detection result of the toner concentration detection sensor 56. Furthermore, the developing device 5Y is provided with a control unit 80 (determination means) that determines whether or not a fluctuation exceeding a threshold has occurred in the bulk density of the developer G contained in the developing device 5Y. Then, if the difference between the detection result detected by the toner density detection sensor 56 and a predetermined target value exceeds a predetermined value A, the control unit 80 determines that the bulk density does not exceed the threshold, and determines that the remaining amount of toner in the toner container 32Y is zero or less than a predetermined amount, and if the control unit 80 determines that the bulk density exceeds the threshold, it performs a predetermined control mode and then determines whether or not it is in a toner end state. This allows for accurate detection of the toner end state of the toner container 32Y with a simple configuration.

[0046] In this embodiment, the present invention was applied to an image forming apparatus 100 in which a bottle-shaped toner container 32Y, whose body is rotatably driven, is detachably installed. However, the toner container is not limited to this, and the present invention can also be applied to an image forming apparatus in which, for example, a box-shaped toner container is detachably installed. Furthermore, in this embodiment, a magnetic sensor that directly detects the mixing ratio (toner concentration) of toner and carrier in the developer G contained in the developing device 5Y is used as the toner concentration detection means. However, the toner concentration detection means is not limited to this, and a means that indirectly detects the mixing ratio (toner concentration) of toner and carrier in the developer G contained in the developing device 5Y (for example, a sensor that optically detects the density of the image formed on the photoreceptor drum) can also be used. Furthermore, in this embodiment, at least one of the factors that cause fluctuations in the bulk density of the developer G in the developing device 5Y is set, and the necessity of re-determining the toner end state is determined based on the detection result. However, if there are other factors that cause fluctuations in bulk density, the necessity of re-determining the toner end state can be determined based on the detection result of those fluctuation factors. Furthermore, the toner supply device 90 and the developing device 5Y are not limited to those of this embodiment, and various forms can be used within the scope of the technical concept of the present invention. Furthermore, even in such cases, it is possible to obtain effects that are almost the same as those of this embodiment.

[0047] It should be noted that the present invention is not limited to this embodiment, and within the scope of the technical concept of the present invention, this embodiment can be modified as appropriate in ways other than those suggested here. Furthermore, the number, position, shape, etc. of the above-mentioned components are not limited to this embodiment, and can be set to a number, position, shape, etc. that is suitable for carrying out the present invention. [Explanation of symbols]

[0048] 5Y developing machine, 32Y, 32M, 32C, 32K toner containers, 56 Toner density detection sensor (toner density detection means), 75. Temperature and humidity meter (temperature and humidity sensor), 76 timers, 77 Developing motor, 78. Toner adhesion amount detection sensor, 80 Control unit (decision-making means), 90 Toner replenishment device, 93 Motor, 100 Image forming apparatus (image forming apparatus main unit), 115. Toner replenishment motor.

[0049] Furthermore, the embodiments of the present invention can also be, for example, combinations of appendices 1 to 8 as follows. (Note 1) A toner container that is detachably installed on the main body of the image forming apparatus, A developing device containing a developer consisting of toner and carrier, which develops a latent image formed on the surface of an image carrier, A toner concentration detection means for directly or indirectly detecting the mixing ratio of toner and carrier in the developer contained in the developing device, A toner supply device that supplies toner contained in the toner container to the developing device based on the detection result of the toner concentration detection means, A determination means for determining whether or not a fluctuation exceeding a threshold has occurred in the bulk density of the developer contained in the developing device, Equipped with, If the difference between the detection result detected by the toner concentration detection means and a predetermined target value exceeds a predetermined value, When the determination means determines that the bulk density does not exceed the threshold, it is determined that the remaining amount of toner contained in the toner container is zero or less than a predetermined amount, and the toner is in a toner-end state. The image forming apparatus is characterized in that, when the determination means determines that the bulk density exceeds the threshold, it performs a predetermined control mode and then determines whether or not the toner is in the end state. (Note 2) The image forming apparatus according to Appendix 1, characterized in that the detection of the mixing ratio by the toner concentration detection means is performed each time a series of prints is completed. (Note 3) The image forming apparatus according to Appendix 1 or Appendix 2, characterized in that the determination means determines whether the time during which the developing device is not driven exceeds a predetermined time, thereby determining whether a fluctuation exceeding the threshold has occurred in the bulk density. (Note 4) The image forming apparatus according to any one of the appendices 1 to 3, characterized in that the determination means determines whether a fluctuation in any of the absolute humidity, relative humidity, or temperature around the developing apparatus exceeds a predetermined difference, thereby determining whether a fluctuation exceeding the threshold has occurred in the bulk density. (Note 5) The image forming apparatus according to Appendix 4, characterized in that the aforementioned variation is a variation relative to the one at the time the previous printing was completed. (Note 6) The image forming apparatus according to Appendix 4, characterized in that the aforementioned variation is a variation of the average value when multiple printings prior to the previous printing have been completed. (Note 7) The control mode is an agitation mode in which the developing device is idle-driven for a predetermined time, The image forming apparatus according to any one of the appendices 1 to 6, characterized in that, after performing the stirring mode, if the difference between the detection result detected by the toner concentration detection means and the target value exceeds the predetermined value, it is determined that the toner is in an end state, and if the difference does not exceed the predetermined value, it is determined that the toner is not in an end state. (Note 8) The control mode is a correction mode that corrects the detection result detected by the toner concentration detection means according to the extent to which the bulk density exceeds the threshold, The image forming apparatus according to any one of the appendices 1 to 6, characterized in that, after executing the correction mode, if the difference between the detection result corrected by the correction mode and the target value exceeds the predetermined value, it is determined that the toner end state is in effect, and if the difference does not exceed the predetermined value, it is determined that the toner end state is not in effect. [Prior art documents] [Patent Documents]

[0050] [Patent Document 1] Japanese Patent Publication No. 2017-122887 [Patent Document 2] Japanese Patent Publication No. 2014-16604

Claims

1. A toner container that is detachably installed on the main body of the image forming apparatus, A developing device containing a developer consisting of toner and carrier, which develops a latent image formed on the surface of an image carrier, A toner concentration detection means for directly or indirectly detecting the mixing ratio of toner and carrier in the developer contained in the developing device, A toner supply device that supplies toner contained in the toner container to the developing device based on the detection result of the toner concentration detection means, A determination means for determining whether or not a fluctuation exceeding a threshold has occurred in the bulk density of the developer contained in the developing device, Equipped with, If the difference between the detection result detected by the toner concentration detection means and a predetermined target value exceeds a predetermined value, When the determination means determines that the bulk density does not exceed the threshold, it is determined that the remaining amount of toner contained in the toner container is zero or less than a predetermined amount, and the toner is in a toner-end state. The image forming apparatus is characterized in that, when the determination means determines that the bulk density exceeds the threshold, it performs a predetermined control mode and then determines whether or not the toner is in the end state.

2. The image forming apparatus according to claim 1, characterized in that the detection of the mixing ratio by the toner concentration detection means is performed each time a series of prints is completed.

3. The image forming apparatus according to claim 1 or 2, characterized in that the determination means determines whether the time during which the developing device is not driven exceeds a predetermined time, thereby determining whether a fluctuation exceeding the threshold has occurred in the bulk density.

4. The image forming apparatus according to claim 1 or 2, characterized in that the determination means determines whether a fluctuation in any of the absolute humidity, relative humidity, or temperature around the developing apparatus exceeds a predetermined difference, thereby determining whether a fluctuation exceeding the threshold has occurred in the bulk density.

5. The image forming apparatus according to claim 4, characterized in that the aforementioned variation is a variation relative to the one at the time the previous printing was completed.

6. The image forming apparatus according to claim 4, characterized in that the aforementioned variation is a variation of the average value when multiple prints prior to the previous print have been completed.

7. The control mode is an agitation mode in which the developing device is idle-driven for a predetermined time, The image forming apparatus according to claim 1 or 2, characterized in that, after performing the stirring mode, if the difference between the detection result detected by the toner concentration detection means and the target value exceeds the predetermined value, it is determined that the toner is in a toner-end state, and if the difference does not exceed the predetermined value, it is determined that the toner is not in a toner-end state.

8. The control mode is a correction mode that corrects the detection result detected by the toner concentration detection means according to the extent to which the bulk density exceeds the threshold, The image forming apparatus according to claim 1 or 2, characterized in that, after executing the correction mode, if the difference between the detection result corrected by the correction mode and the target value exceeds the predetermined value, it is determined that the toner end state is in effect, and if the difference does not exceed the predetermined value, it is determined that the toner end state is not in effect.

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