Image forming apparatus

Abstract

The present invention provides an image forming apparatus that can appropriately adjust the amount of developer supplied to the pre-storage space in the intermediate hopper according to the condition of the developer. [Solution] An image forming apparatus comprising a cartridge, a developing device, a storage unit capable of transporting and storing developer from the cartridge to the developing device, a replenishment unit 8 for supplying developer from the cartridge to the storage unit, an image forming unit 20 for forming a toner image on an image carrier to be transferred to a sheet, and a control unit 9 for controlling the replenishment unit 8, wherein the storage unit is provided with an inlet, a main storage space, an outlet, a preliminary storage space communicating with the inlet and the main storage space and capable of storing developer internally, and a developer detection unit 74 for detecting the developer stored in the preliminary storage space, and the control unit 9 has a cumulative print rate calculation unit 93 for calculating the cumulative print rate, and changes the conditions for the replenishment operation to the storage unit by the replenishment unit 8 based on the cumulative print rate and the detection result by the developer detection unit 74.

Description

[Technical Field]

[0001] This disclosure relates to image forming apparatus such as photocopiers, multifunction devices, printers, and facsimile machines. [Background technology]

[0002] Conventionally, image forming apparatuses equipped with an intermediate hopper capable of transporting toner supplied from a toner container (cartridge) to a developing device are known (see, for example, Patent Document 1). The image forming apparatus disclosed in Patent Document 1 is equipped with a toner sensor that detects toner emptiness upstream of the transport member of the intermediate hopper in the toner transport direction, and is configured to supply toner from the toner container to the intermediate hopper based on the detection result by the toner sensor. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-16783 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, depending on the state of the toner in the intermediate hopper, there is a risk of false detection by the toner sensor. For example, when printing many documents with high print density, the toner consumption in the developing unit is high, so toner is immediately replenished (discharged) from the intermediate toner hopper, and new toner is supplied to the intermediate toner hopper from the toner container. Therefore, the toner in the intermediate toner hopper is frequently transported and agitated by the transport element of the intermediate hopper, maintaining an appropriate bulk density, so its fluidity does not deteriorate and no particular problems occur. On the other hand, when printing many documents with low print density, the amount of toner supplied (discharged) from the intermediate hopper to the developing unit decreases. In other words, the toner in the intermediate hopper is transported and agitated less frequently by the transport element, so over time it may aggregate and its fluidity may deteriorate (it becomes bulk dense). In such a state, the toner around the toner sensor also becomes difficult to move, and in some cases, it may solidify around the toner sensor, making correct detection impossible. In other words, if the cumulative printing rate by the image forming unit is low, the toner that aggregates in the intermediate hopper may hinder detection by the toner sensor, potentially leading to false detections by the toner sensor.

[0005] Based on the above, if the toner supply operation from the toner container to the intermediate hopper is controlled solely based on the detection results from the toner sensor, as in the conventional technology described above, there is a risk that the amount of toner supplied to the intermediate hopper cannot be appropriately adjusted.

[0006] This disclosure has been made in consideration of the above, and aims to provide an image forming apparatus that can appropriately adjust the amount of developer supplied to the pre-storage space in the intermediate hopper (storage section) according to the condition of the developer. [Means for solving the problem]

[0007] To achieve the above objective, the image forming apparatus according to the present disclosure comprises a cartridge containing a developer including toner, a developing device that supplies toner to an image carrier, a storage unit capable of transporting and storing the developer from the cartridge to the developing device, a supply unit that replenishes the developer from the cartridge to the storage unit, an image forming unit that forms a toner image on the image carrier to be transferred to a sheet, and a control unit that controls the supply unit, wherein the storage unit has a receiving port for receiving the developer supplied from the cartridge and a main storage unit with a transport member disposed inside for transporting the developer received from the receiving port in a predetermined transport direction. The control unit includes a space, a developer discharge port to the developing device located downstream of the main storage space in the direction of transport of the developer by the transport member, a preliminary storage space communicating with the receiving port and the main storage space and capable of storing the developer inside, and a developer detection unit for detecting the developer stored in the preliminary storage space. The control unit has a cumulative print rate calculation unit that calculates a cumulative print rate by accumulating and averaging the print rate, which is the ratio of the toner image formed on the image carrier to the area of ​​the sheet, over the most recent predetermined number of sheets, and changes the conditions for the replenishment operation to the storage unit by the replenishment unit based on the cumulative print rate and the detection result by the developer detection unit. [Effects of the Invention]

[0008] According to this disclosure, the amount of developer supplied to the reserve storage space in the storage section can be appropriately adjusted according to the condition of the developer. [Brief explanation of the drawing]

[0009] [Figure 1] This is a longitudinal cross-sectional view showing a schematic configuration of an image forming apparatus in one embodiment of the present disclosure. [Figure 2] Figure 1 is a schematic diagram showing the developing apparatus and its surrounding parts in the image forming apparatus. [Figure 3] This is a schematic perspective view showing a developing apparatus, cartridge, and intermediate hopper in one embodiment of the present disclosure. [Figure 4]It is a schematic perspective view showing the internal structure of the developing device and the intermediate hopper of FIG. 3 [Figure 5] It is a block diagram showing a control unit and the like in one embodiment of the present disclosure. [Figure 6] It is a cross-sectional view showing the internal structure of the cartridge and the intermediate hopper of FIG. 3. [Figure 7] It is a schematic top view showing a part of the intermediate hopper of FIG. 3. [Figure 8] It is a schematic side view showing a part of the intermediate hopper of FIG. 3. [Figure 9] It is a schematic view showing an example of the developer stored in the reserve storage space. [Figure 10] It is a flowchart showing an example of the procedure of the process by the control unit. [Figure 11] It is a view showing an example of a determination table. [Figure 12] It is a timing chart showing an example of the timing when the processing unit turns on the replenishment operation of the replenishment unit. [Figure 13] It is a timing chart showing an example of the timing when the processing unit turns off the replenishment operation of the replenishment unit.

Mode for Carrying Out the Invention

[0010] Hereinafter, embodiments for implementing the present disclosure will be described with reference to the drawings. (Embodiment 1) <Overall Configuration of Image Forming Apparatus> FIG. 1 is a cross-sectional view showing a schematic configuration of an image forming apparatus 1 according to an embodiment of the present disclosure. For convenience, the direction along the axial direction of the rotation axis of the photosensitive drum 23 is shown as the front-rear direction (axial direction) X, and the direction orthogonal to the front-rear direction X, and as shown in FIG. 1, when the front-rear direction X is viewed as the paper surface direction, the width direction of the image forming apparatus 1 is shown as the left-right direction Y, and the direction orthogonal to the left-right direction Y, and the height direction of the image forming apparatus 1 is shown as the up-down direction Z.

[0011] As shown in FIG. 1, the image forming apparatus 1 is an electrophotographic image forming apparatus and an intermediate transfer type color multifunction peripheral capable of printing full-color images. The image forming apparatus 1 includes an image reading unit 10 and an image forming apparatus main body 11. In the present embodiment, for printing by the image forming apparatus 1, toners of each color of yellow (Y), magenta (M), cyan (C), and black (K) are used.

[0012] The image reading unit 10 is configured to be able to read an image from a document and is provided above the image forming apparatus main body 11. The image reading unit 10 has a document reading device 12, a document placement table 13, and an automatic document feeder 14.

[0013] The document reading device 12 is configured to irradiate light on a document and read an image from the document based on the reflected light thereof. The document reading device 12 incorporates, for example, a light source that irradiates light on the document, a lens and an image sensor, and a mirror that guides the reflected light of the document to the lens. The reflected light of the document incident on the image sensor through the lens is photoelectrically converted by the image sensor, thereby generating image data corresponding to the image of the document. Note that the image data may be generated by the image reading unit 10 or supplied from an external device.

[0014] The document placement table 13 is a portion on which a document is placed by the user and is provided above the document reading device 12. The document placement table 13 is formed of transparent glass. The automatic document feeder 14 is configured to automatically and continuously convey a document inserted by the user to the document reading device 12 and is provided above the document placement table 13. The image of the document is read by the document reading device 12 in a state where the document is placed on the document placement table 13 or in a state where the document is conveyed to the document reading device 12 by the automatic document feeder 14.

[0015] The image forming apparatus body 11 comprises an image forming unit 20, an intermediate transfer unit 3, a secondary transfer unit 40, a fixing device 42, a sheet storage unit 43, a sheet roller group 5, and a sheet discharge unit 44. The image forming apparatus 1 is provided with a sheet transport path S through which sheets are transported.

[0016] The image forming unit 20 is configured to form toner images of each color based on image data. The image forming unit 20 includes an exposure device 21, a developing device 22, a photoreceptor drum 23 (image carrier), a charger 24, and a cleaning device 25. The developing device 22, photoreceptor drum 23, charger 24, and cleaning device 25 are provided according to each color (four of each in this embodiment). The photoreceptor drum 23 has a photosensitive layer on its surface on which an electrostatic latent image is formed, and is rotated in a predetermined direction by a main motor (not shown). The photosensitive layer exhibits insulating properties in the dark and changes to conductive properties in areas irradiated with light. The charger 24 is configured to uniformly charge the surface of the photoreceptor drum 23 to a predetermined potential (for example, about -600V). For example, a contact-type charger (for example, a roller-type or brush-type) or a charger-type charger can be used as the charger 24.

[0017] The exposure apparatus 21 is configured to form electrostatic latent images corresponding to each color on the photoreceptor drum 23 by exposing the surface of the photoreceptor drum 23, which is charged to a predetermined potential, based on image data. The exposure apparatus 21 incorporates a light source that emits a laser beam, a polygon mirror that scans and reflects the laser beam, and optical elements (e.g., lenses and mirrors) for guiding the reflected laser light of the laser beam to the photoreceptor drum 23.

[0018] The developing device 22 is configured to visualize the electrostatic latent images formed on the surface of each photoreceptor drum 23 by using toners of each color (Y, M, C, K) supplied from the cartridge 6 to create a toner image. The cartridge 6 contains a developer containing toner. The configuration of the developing device 22 and the cartridge 6 will be described in detail later.

[0019] The cleaning device 25 is configured to remove and recover any residue (e.g., residual toner) remaining on the surface of the photoreceptor drum 23 after the toner formed on the photoreceptor drum 23 has been first transferred to the intermediate transfer unit 3, which will be described later. Through a series of operations by each component of the image forming unit 20 described above, toner images of each color are continuously formed on the surface of each photoreceptor drum 23.

[0020] The intermediate transfer unit 3 is located above the photoreceptor drums 23 and is used for so-called primary transfer, which involves temporarily transferring the toner images formed on each photoreceptor drum 23 sequentially and then transferring the temporarily transferred toner images onto a sheet all at once. Here, "primary transfer" refers to the transfer of the toner images of each color formed on the photoreceptor drums 23 onto the intermediate transfer belt 30. The intermediate transfer unit 3 includes the intermediate transfer belt 30, a drive roller 31, a driven roller 32, and primary transfer rollers 33. There are four primary transfer rollers 33, corresponding to each color.

[0021] The intermediate transfer belt 30 is an endless belt that rotates in a predetermined direction and is suspended by a drive roller 31 and a driven roller 32. The toner images of each color, which are visualized on the photoreceptor drum 23, are sequentially transferred onto the intermediate transfer belt 30 and transported to the secondary transfer section 40 by the rotation of the intermediate transfer belt 30. The intermediate transfer belt 30 is formed from, for example, a film with a thickness of about 100 μm to 150 μm. The drive roller 31 is a roller that is driven to rotate in a predetermined direction by a belt motor (not shown) and is provided on one end of the intermediate transfer section 3. The rotational drive of the drive roller 31 rotates the intermediate transfer belt 30. The driven roller 32 is a roller that is rotatably mounted along the intermediate transfer belt 30. The driven roller 32 rotates in accordance with the rotation of the intermediate transfer belt 30. The primary transfer rollers 33 are arranged in a row corresponding to the photoreceptor drum 23 via the intermediate transfer belt 30. By applying a transfer bias to the primary transfer roller 33, the toner image from the photoreceptor drum 23 is transferred to the intermediate transfer belt 30.

[0022] The secondary transfer unit 40 is used for secondary transfer and is located on the sheet transport path S. Here, "secondary transfer" refers to the transfer of the toner images of each color transferred onto the intermediate transfer belt 30 to the sheet. The secondary transfer unit 40 has a secondary transfer roller 41 provided at the transfer area where the sheet and the intermediate transfer belt 30 face each other. A voltage is applied to the secondary transfer roller 41 to transfer the toner images of each color on the intermediate transfer belt 30 to the sheet.

[0023] The fixing device 42 is configured to fix the toner image onto the sheet by heating and melting the toner image that has been secondarily transferred onto the sheet and fixing it onto the sheet, and is located downstream of the secondary transfer unit 40 in the sheet transport path S.

[0024] The sheet storage section 43 is configured to accommodate sheets used for image formation and is located at the bottom of the image forming apparatus body 11.

[0025] The sheet roller group 5 includes a pickup roller 5a, transport rollers 5b and 5c, and a registration roller 5d. The pickup roller 5a is configured to pull out the top layer of sheets from the sheet storage section 43 and transport them to the sheet transport path S. The transport rollers 5b and 5c transport the sheets along the sheet transport path S. The registration roller 5d temporarily stops the sheets being transported from the sheet storage section 43 and aligns the leading edges of the sheets. Each of these sheet rollers 5 is rotated by a motor (not shown).

[0026] The sheet ejection unit 44 is located at the top of the image forming apparatus body 11 and is configured to allow printed sheets to be loaded and pulled face down.

[0027] The image forming apparatus 1 described above performs printing on the sheet as follows: First, the image forming unit 20 forms a toner image on the photoreceptor drum 23 based on image data generated by the image reading unit 10 or supplied from an external device. The primary transfer roller 33 transfers this toner image to the intermediate transfer belt 30 of the intermediate transfer unit 3. During this time, the pickup roller 5a pulls the sheet out of the sheet storage unit 43, the transport roller 5b transports the sheet to the register roller 5d, and the register roller 5d transports the sheet to the secondary transfer unit 40. Subsequently, the secondary transfer unit 40 transfers the toner image that was primarily transferred onto the intermediate transfer belt 30 to the sheet. The fixing device 42 fixes the toner image that was secondarily transferred onto the sheet. After that, the sheet is discharged onto the sheet discharge unit 44, completing the printing on the sheet.

[0028] Figure 2 is a schematic diagram showing the developing device 22 and its surrounding area in the image forming apparatus 1 of Figure 1. Figure 3 is a schematic perspective view showing the developing device 22, cartridge 6, and intermediate hopper 7 in one embodiment of the present disclosure. Figure 4 is a schematic perspective view showing the internal structure of the developing device 22 and intermediate hopper 7. Figure 5 is a block diagram showing the control unit 9, etc., in one embodiment of the present disclosure. In addition to the configuration described above, as shown in Figures 2 to 4, the image forming unit 20 has an intermediate hopper 7 (storage unit) and a replenishment unit 8. Also, as shown in Figure 5, the image forming apparatus 1 includes a control unit 9 that controls the replenishment unit 8, and the control unit 9 includes a cumulative print rate calculation unit 93 that calculates the cumulative print rate of the toner image formed by the image forming unit 20 (for example, the average ratio of the number of printed pixels to the total number of image pixels on each page for the most recent 200 pages). Hereinafter, each of these components will be described in detail together with the configuration of the developing device 22 and cartridge 6.

[0029] <Developing equipment> As shown in Figures 2 and 4, the developing apparatus 22 includes a developing tank 220, a first transport screw 221, a second transport screw 222, and a developing roller 223 (developer carrier).

[0030] The developing tank 220 is configured to accommodate the developer inside. As shown in Figure 4, the developing tank 220 is provided with a partition wall 224 that divides the internal space into a first transport chamber 220a and a second transport chamber 220b, communication openings 225 and 226 that connect the first transport chamber 220a and the second transport chamber 220b on both sides of the partition wall 224, and a receiving inlet 227 for receiving the developer into the developing tank 220. In this embodiment, the partition wall 224 extends in the front-rear direction. The communication openings 225 and 226 allow the developer to circulate around the partition wall 224 in a predetermined circulation direction. The receiving inlet 227 is located on the rear side of the first transport chamber 220a. In addition to the above, the developing tank 220 is equipped with a concentration sensor (not shown) for measuring the concentration of toner in the developer. The concentration sensor is composed of, for example, a permeability sensor capable of measuring the ratio of magnetic carriers in the developer as permeability.

[0031] The first transport screw 221 is configured to transport the developer in the circulation direction F1 within the first transport chamber 220a, and the second transport screw 222 is configured to transport the developer in the circulation direction F2 within the second transport chamber 220b (see Figure 4). The first transport screw 221 and the second transport screw 222 each include a rotating shaft 228 that rotates by receiving rotational driving force from a drive unit (not shown), and a helical blade 229 provided on the outer surface of the rotating shaft 228. The first transport screw 221 and the second transport screw 222 are configured so that the rotating shaft 228 is rotationally driven by the drive unit (not shown), causing the helical blade 229 to push the developer in the circulation direction and circulate it.

[0032] The developing roller 223 is configured to carry developer on its surface and supply the developer from the second transport chamber 220b to the photoreceptor drum 23. It is formed by housing a cylindrical magnet roll (not shown) inside a cylindrical non-magnetic sleeve 223a. The sleeve 223a receives rotational driving force from a drive unit (not shown) and rotates in the rotational direction R.

[0033] As shown in Figure 2, the developing roller 223 is positioned parallel to the photoreceptor drum 23, facing it, and forms a nip N, which is a region adjacent to it. The developing roller 223 is supplied with a predetermined voltage, a developing bias (for example, about -450V), from a bias power supply (not shown). As a result, a potential difference is created between the developing roller 223 and the photoreceptor drum 23 at the nip N due to the developing bias. This causes toner to be supplied from the developer supported on the surface of the developing roller 223 to the electrostatic latent image on the surface of the photoreceptor drum 23, and a toner image is formed on the photoreceptor drum 23.

[0034] <Cartridge> Figure 6 is a cross-sectional view showing the internal structure of the cartridge 6 and the intermediate hopper 7. The cartridge 6 is configured to be detachable from the image forming apparatus body 11 (see Figure 1) and includes a housing section 60 and a replenishment blade section 61, as shown in Figure 6.

[0035] The storage section 60 is configured to accommodate the developer inside. The storage section 60 is formed in a cylindrical shape with the front-to-back direction as the axis of the cylinder, and a supply port 62 that communicates with the intermediate hopper 7 is provided at one end in the direction of the axis of the cylinder.

[0036] As shown in Figure 6, the replenishment vane section 61 is located at the end position where the replenishment port 62 is provided and includes a rotating shaft 611 that rotates by receiving rotational driving force from the cartridge replenishment motor 610, and vanes 612 provided on the outer circumferential surface of the rotating shaft 611. The rotating shaft 611 rotates integrally with the peripheral wall of the housing section 60. Here, as shown in Figure 3, a spiral projection 600 is formed on the peripheral wall of the housing section 60 that protrudes into the interior of the housing section 60. Therefore, when the rotating shaft 611 rotates by receiving rotational force from the cartridge replenishment motor 610, the peripheral wall of the housing section 60 also rotates, and the spiral projection 600 provided on the peripheral wall rotates, causing the developer stored inside to move towards the replenishment port 62. The developer that reaches the end on the replenishment port 62 side is then sent to the replenishment port 62 by the vanes 612. The replenishment port 62 is connected to the receiving port 70 of the intermediate hopper 7, which will be described later. Thus, the cartridge replenishment motor 610 functions as a replenishment unit 8 that performs a replenishment operation to supply developer from the cartridge 6 to the intermediate hopper 7 by rotating the rotation shaft 611 of the cartridge 6.

[0037] <Intermediate hopper> The intermediate hopper 7 is configured to transport and store developer supplied from the cartridge 6 to the developing unit 22. By providing the intermediate hopper 7, even if the cartridge 6 becomes empty, printing by the image forming unit 20 can continue using the developer stored in the intermediate hopper 7. Therefore, image formation can continue even while replacing the cartridge 6 with a new one, preventing a decrease in printing efficiency. Furthermore, even if a new cartridge 6 is procured after the cartridge 6 has become empty, image formation can continue for a while. For this reason, it is desirable that the intermediate hopper 7 be configured to store as much developer as possible.

[0038] Figure 7 is a schematic top view showing a part of the intermediate hopper 7. Figure 8 is a schematic side view showing a part of the intermediate hopper 7. As shown in Figures 4, 6 to 8, the intermediate hopper 7 is provided with an inlet 70 for receiving developer supplied from the cartridge 6, an outlet 71 (not shown in Figures 6 and 8) for discharging the developer to the developing device 22, and a main storage space 72 and a reserve storage space 73 (not shown in Figures 4 and 7) that can store the developer inside.

[0039] As shown in Figure 4, the main storage space 72 is provided with a partition wall 720 that divides the internal space into a third transport chamber 72a and a fourth transport chamber 72b, similar to the developing tank 220 of the developing apparatus 22 described above, and a communication opening 721 on one side of the partition wall 720 that connects the third transport chamber 72a and the fourth transport chamber 72b, allowing the developer to be transported in the transport direction T around the partition wall 720. Inside the third transport chamber 72a and the fourth transport chamber 72b, a third transport screw 750 and a fourth transport screw 751 are arranged as transport members 75 that transport the developer in the transport direction T, similar to the first transport screw 221 and the second transport screw 222 of the developing apparatus 22 described above. As shown in Figures 4 and 7, the third conveying screw 750 and the fourth conveying screw 751 each include a rotating shaft 752 that rotates by receiving rotational driving force from a drive unit 76 (intermediate hopper drive motor), and a helical blade 753 provided on the outer surface of the rotating shaft 752. The conveying member 75 is configured such that the rotating shaft 752 is rotationally driven by a drive unit (not shown), and the helical blade 753 pushes the developer in the conveying direction T and conveys it to the discharge port 71.

[0040] As shown in Figures 6 and 8, the preliminary storage space 73 is in communication with the receiving port 70 and the main storage space 72. As shown in Figure 8, in this embodiment, the preliminary storage space 73 is provided below the receiving port 70 and upstream of the transport direction T of the transport member 75. This makes it possible to effectively utilize the space below the receiving port 70 and upstream of the transport direction T of the transport member 75 relative to the receiving port 70, and therefore more developer can be stored. In particular, in an image forming apparatus 1 having an intermediate transfer section 3, the gap between the intermediate transfer section 3 and the cartridge 6 is narrow, so even in such an image forming apparatus 1, providing a preliminary storage space 73 makes it possible to increase the amount of developer that can be stored in the intermediate hopper 7 (making it possible to achieve both a thinner design and increased storage capacity).

[0041] As shown in Figures 6 and 8, a developer detection unit 74 is provided inside the pre-storage space 73 to detect the developer stored in the pre-storage space 73. In this embodiment, the developer detection unit 74 is a sensor that outputs a first value (hereinafter referred to as "LOW") when no developer is detected, and a second value (hereinafter referred to as "HIGH") different from the first value when a developer is detected, and is composed of, for example, a piezoelectric sensor.

[0042] As described above, the intermediate hopper 7 is provided with an inlet 70 for receiving developer supplied from the cartridge 6, a main storage space 72 in which a third transport screw 750 and a fourth transport screw 751 are arranged to transport the developer received from the inlet 70 in a predetermined transport direction T, a discharge port 71 for the developer to the developing device 2 provided downstream of the third transport screw 750 in the transport direction T of the third transport screw 750 in the main storage space 72, a reserve storage space 73 that communicates with the inlet 70 and the main storage space 72 and can store developer inside, and a developer detection unit 74 that detects the developer stored in the reserve storage space 73.

[0043] Figure 9 is a schematic diagram showing an example of developer stored in the pre-storage space 73. In this embodiment, the developer detection unit 74 is positioned in the pre-storage space 73 upstream of the receiving port 70 in the transport direction T of the transport member 75. This is in consideration of the fact that when the pre-storage space 73 extends from below the receiving port 70 to the upstream side of the transport direction T of the transport member 75, as shown in Figure 9, the developer falling from the receiving port 70 will naturally pile up in a mound shape upstream of the transport direction T. Here, the dashed line L1 in Figure 9 indicates the surface position of the developer when the amount of developer in the pre-storage space 73 is small, and the dashed line L2 in Figure 9 indicates the surface position of the developer when the amount of developer in the pre-storage space 73 is large. In other words, by positioning the developer detection unit 74 upstream of the transport member 75 in the transport direction T within the pre-storage space 73, when the amount of developer is small, the amount of developer in the pre-storage space 73 located upstream of the receiving port 70 in the transport direction T can be detected more accurately, as shown by the dashed line L1. Furthermore, by delaying the time between the developer detection unit 74 detecting the developer and the drive unit 76 stopping, the surface position of the developer can be raised to the position shown by the dashed line L2. This means that more developer can be stored in the pre-storage space 73.

[0044] As described above, the developer contained in cartridge 6 is sequentially stored in the main storage space and the reserve storage space 73 in the intermediate hopper 7 by the replenishment operation of the replenishment unit 8. The developer stored in the intermediate hopper 7 is then discharged from the intermediate hopper 7 to the developing device 22 by a transport member 75 provided in the intermediate hopper 7. The amount of developer discharged from the intermediate hopper 7 to the developing device 22 is adjusted based, for example, on the cumulative printing rate by the image forming unit 20 or the detection result by a density sensor provided in the developing device 22. The control for adjusting the amount of developer discharged from the intermediate hopper 7 to the developing device 22 is performed independently of the control for adjusting the amount of developer replenished from cartridge 6 to the intermediate hopper 7.

[0045] Here, in adjusting the amount of developer supplied from cartridge 6 to intermediate hopper 7, that is, the amount of developer initially supplied to the reserve storage space 73, it is conceivable to control the supply operation of the supply unit 8 based solely on the detection result by the developer detection unit 74 provided in the intermediate hopper 7. However, as mentioned above, depending on the state of the developer in the intermediate hopper 7, there is a risk that the developer detection unit 74 may misdetect due to the aggregation of the developer in the intermediate hopper 7. For example, when printing a large number of documents with a low print density, resulting in a relatively low cumulative print density by the image forming unit 20, the amount of developer discharged from the intermediate hopper 7 to the developing device 22 decreases, and the same developer remains in the intermediate hopper 7 for a long time, which may cause the developer to aggregate and the developer detection unit 74 to misdetect. To explain in more detail, if the developer near the developer detection unit 74 happens to aggregate and adhere to the developer detection unit 74, the surrounding developer that has not aggregated may not be detected even if it is transported away by the transport member 75, and there is a risk of false detection that sufficient developer is present. In particular, when the amount of developer in the reserve storage space 73 is at the position of the dashed line L2 in Figure 9, and image formation is performed continuously at a low printing rate, such aggregation tends to occur (the bulk density increases due to the weight of the accumulated developer).

[0046] In light of the above, in order to appropriately adjust the amount of developer supplied to the reserve storage space 73, the control unit 9 that controls the replenishment unit 8 is configured to switch the replenishment operation of the replenishment unit 8 on or off based not only on the detection result by the developer detection unit 74, but also on both the cumulative printing rate by the image forming unit 20 and the detection result by the developer detection unit 74. In other words, the control unit 9 changes the conditions for the replenishment operation of the replenishment unit 8 to the intermediate hopper 7 based on the cumulative printing rate and the detection result by the developer detection unit 74. The configuration of the control unit 9 will be described in detail below.

[0047] <Department Head> As shown in Figure 5, the control unit 9 includes a processing unit 90 and a storage unit 94. The control unit 9 realizes the various functions of the processing unit 90 by reading and executing various programs stored in the storage unit 94 (e.g., storage, ROM (Read Only Memory), etc.). The processing unit 90 includes an image forming processing unit 91 that, when a program is read and executed, controls the image forming unit 20 to form a toner image on the sheet, and when the toner in the developing unit 22 is consumed after the toner image is formed, controls the intermediate hopper drive motor 76 to replenish the toner in the developing unit 22; a cartridge replenishment control unit 92 that controls the cartridge replenishment motor 610 (replenishment unit 8) to replenish the developer in the cartridge when the toner in the intermediate hopper 7 is consumed after the toner image is formed in the image forming processing unit 91; and a cumulative print rate calculation unit 93. The cumulative print rate calculation unit 93 will be described later. Such a control unit 9 may be composed of one or more control devices / arithmetic units (CPU (Central Processing Unit), SoC (System on a Chip)). The control unit 9 may also be composed of one or more control circuits. The control unit 9 is electrically connected to the image forming unit 20, the cartridge replenishment motor 610 (replenishment unit 8), the intermediate hopper drive motor 76, and the developer detection unit 74. The storage unit 94 stores the judgment table 95 used in the judgment by the processing unit 90, as well as various threshold values, etc. The configuration of the judgment table 95 will be described later in conjunction with the processing procedure by the control unit 9.

[0048] The cumulative print rate calculation unit 93 calculates the cumulative print rate (%) by accumulating the print rate (%), which is the ratio of the toner image area to the sheet area of ​​the image formed by the image forming unit 20, for each image formation. This cumulative print rate is the average value obtained by averaging the print rates of a predetermined number of images, for example, 200 sheets (A4 equivalent), and is calculated as a moving average value in which the latest print rate is added when a new sheet is printed and the print rate of the oldest sheet is excluded. In other words, the cumulative print rate calculation unit 93 calculates the cumulative print rate by accumulating and averaging the print rate, which is the ratio of the toner image formed on the photoreceptor drum 23 to the sheet area, over the most recent predetermined number of sheets.

[0049] <Procedure for processing by the control unit> Figure 10 is a flowchart showing an example of the processing procedure by the control unit 9. Next, the processing procedure by the control unit 9 in this embodiment will be described with reference to the flowchart in Figure 10. The processing shown in Figure 10 is executed, for example, after the image forming apparatus 1 is turned on, and is repeatedly executed at regular intervals (for example, 10 milliseconds) while the image forming apparatus 1 is in a state where image forming can be performed or transitions to performance, such as when it is ready, during image forming operation, during image quality adjustment processing, or during toner replenishment.

[0050] As shown in Figure 10, in step S1, the processing unit 90 obtains the cumulative print rate of the image formed by the image forming unit 20 from the cumulative print rate calculation unit 93. Next, in step S2, the processing unit 90 obtains the detection result from the developer detection unit 74.

[0051] Next, in step S3, the processing unit 90 determines whether the detection result obtained from the developer detection unit 74 in step S2 is "LOW" or "HIGH". If the detection result is "LOW", it executes steps S4 to S7. On the other hand, if the detection result is "HIGH", it proceeds to step S9 and executes steps S9 to S12.

[0052] If the detection result is determined to be "LOW" in step S3, the processing unit 90 resets the HIGH counter in step S4, which counts how many times the developer detection unit 74 has detected "HIGH" consecutively, and in step S5, it increments the LOW counter, which counts how many times the developer detection unit 74 has detected "LOW" consecutively.

[0053] Then, in steps S6 to S7, the processing unit 90 determines whether the developer detection unit 74 continuously outputs "LOW" during a predetermined first determination time J1. Specifically, the processing unit 90 determines whether the LOW counter has reached the first determination time J1, which is the LOW determination threshold. The first determination time J1 in the present embodiment is defined (set) in advance in the determination table 95 so as to vary depending on the cumulative printing rate.

[0054] FIG. 11 is a diagram showing an example of the determination table 95. In step S6 of FIG. 10, the processing unit 90 refers to the determination table 95 in the storage unit 94 and obtains a LOW determination threshold based on the cumulative printing rate acquired from the cumulative printing rate calculation unit 93 in step S1. As shown in FIG. 11, the determination table 95 associates the LOW determination threshold (item "LOW determination threshold") with the cumulative printing rate by the image forming unit 20 (item "cumulative printing rate"). The printing rate thresholds P1 to P3 are, for example, in the relationship of 0 < P3 < P2 < P1 < 10 (the unit is percent).

[0055] The LOW determination threshold is the reference value T L (for example, 20 mS) as a reference, and is set (corrected) so that the lower the cumulative printing rate, the longer it becomes step by step. For example, when the cumulative printing rate by the image forming unit 20 exceeds the printing rate threshold P3 (for example, 2.5%) but is less than or equal to the printing rate threshold P2 (for example, 3.5%), the LOW determination threshold is 1.5 times the reference value T L and when the cumulative printing rate by the image forming unit 20 is less than or equal to the printing rate threshold P3, the LOW determination threshold is 2.0 times the reference value T L .

[0056] By obtaining the LOW determination threshold based on the determination table 95 as described above, when the cumulative printing rate by the image forming unit 20 is lower than a predetermined printing rate threshold (in the above case, the printing rate threshold P2), the first determination time J1 corresponding to the LOW determination threshold is a predetermined first reference time (reference value T LThe processing unit 90 sets the first determination time J1 to be longer than the time corresponding to the value. More specifically, if the cumulative printing rate by the image forming unit 20 is lower than a predetermined printing rate threshold, the processing unit 90 sets the first determination time J1 to be progressively longer as the cumulative printing rate decreases. In step S7 of Figure 10, the processing unit 90 determines whether the LOW counter has reached the LOW determination threshold obtained in step S6.

[0057] In step S7, if it is determined that the LOW counter has reached the LOW determination threshold, in other words, if it is determined that the developer detection unit 74 has been continuously outputting "LOW" for a predetermined first determination time J1, the processing unit 90 turns on the replenishment operation of the replenishment unit 8 in step S8. In this way, the replenishment of the developer contained in the cartridge 6, that is, the storage (replenishment) of the developer in the reserve storage space 73 in the intermediate hopper 7 is started.

[0058] Figure 12 is a timing chart showing an example of the timing at which the processing unit 90 turns on the replenishment operation of the replenishment unit 8. The horizontal axis represents time, the upper part of Figure 12 (item "Detection Unit Output") shows the detection signal of the developer detection unit 74 (vertical axis), and the lower part of Figure 12 (item "Replenishment Operation") shows the on / off signal of the replenishment operation of the replenishment unit 8 (vertical axis). The same applies to Figure 13. For example, as shown in Figure 12, with the replenishment operation of the replenishment unit 8 off, if the developer detection unit 74 starts outputting "LOW" at timing T1 and the "LOW" continues until timing T2 after the first judgment time J1 has elapsed, the processing unit 90 turns on the replenishment operation of the replenishment unit 8.

[0059] If, in step S7, it is determined that the LOW counter has not reached a predetermined LOW judgment threshold, in other words, if it is determined that the developer detection unit 74 has not continuously outputted "LOW" for a predetermined first judgment time J1, the process is terminated and the process returns to step S1.

[0060] On the other hand, if the detection result is determined to be "HIGH" in step S3, the processing unit 90 resets the LOW counter in step S9 and increments the HIGH counter in step S10.

[0061] Then, in steps S11 to S12, the processing unit 90 determines whether the developer detection unit 74 continues to output "HIGH" for a predetermined second determination time J2. Specifically, the processing unit 90 determines whether the HIGH counter has reached the second determination time J2, which is the HIGH determination threshold. In this embodiment, the second determination time J2 is also predetermined (set) in the determination table 95 so that it differs depending on the cumulative print rate (%).

[0062] In step S11, the processing unit 90 refers to the determination table 95 of the storage unit 94 and obtains a HIGH determination threshold based on the cumulative printing rate obtained from the cumulative printing rate calculation unit 93 in step S1. As shown in Figure 11, the determination table 95 also associates the HIGH determination threshold (item "HIGH determination threshold") with the cumulative printing rate by the image forming unit 20 (item "cumulative printing rate"). The HIGH determination threshold is set to the reference value T H (For example, 50 mS) is used as a baseline, and the threshold is set to gradually decrease as the cumulative printing rate decreases. For example, if the cumulative printing rate by the image forming unit 20 exceeds the printing rate threshold P2 but is less than or equal to the printing rate threshold P1, the HIGH judgment threshold is the baseline value T H The result is 0.8 times the value, and if the cumulative printing rate by the image forming unit 20 exceeds the printing rate threshold P3 but is less than or equal to the printing rate threshold P2, the HIGH judgment threshold is the reference value T. H This becomes 0.6 times, and if the cumulative printing rate by the image forming unit 20 is less than or equal to the printing rate threshold P3, the HIGH judgment threshold is the reference value T. H This becomes 0.3 times that amount.

[0063] The processing unit 90 obtains a HIGH judgment threshold based on the judgment table 95 described above, and if the cumulative printing rate by the image forming unit 20 is lower than a predetermined printing rate threshold (printing rate threshold P1 in the above case), it sets a second judgment time J2 corresponding to the HIGH judgment threshold to a predetermined second reference time (reference value TH Set it to a time shorter than the time corresponding to the

[0064] In step S12, when it is determined that the HIGH counter has reached the HIGH determination threshold value, in other words, when it is determined that the developer detection unit 74 has continuously output "HIGH" for a predetermined second determination time J2, the processing unit 90 turns off the replenishment operation of the replenishment unit 8 in step S13. In this way, the storage of the developer in the preliminary storage space 73 in the intermediate hopper 7 is stopped.

[0065] FIG. 13 is a timing chart showing an example of the timing when the processing unit 90 turns off the replenishment operation of the replenishment unit 8. For example, as shown in FIG. 13, in a state where the replenishment operation of the replenishment unit 8 is on, after the developer detection unit 74 starts outputting "HIGH" at timing T3 and continuously outputs "HIGH" until timing T4 when the second determination time J2 has elapsed, the processing unit 90 turns off the replenishment operation of the replenishment unit 8.

[0066] In addition, in step S12, when it is determined that the HIGH counter has not reached the predetermined HIGH determination threshold value, in other words, when it is determined that the developer detection unit 74 has not continuously output "HIGH" for a predetermined second determination time J2, the process ends and returns to step S1.

[0067] As described above, the control unit 9 switches the replenishment operation of the replenishment unit 8 on or off based on the cumulative printing rate by the image forming unit 20 and the detection result by the developer detection unit 74. This allows the control unit 9 to switch the replenishment operation of the replenishment unit 8 on or off based on both the cumulative printing rate by the image forming unit 20 and the detection result by the developer detection unit 74, not just the detection result by the developer detection unit 74. This enables the control unit 9 to control the replenishment operation of the replenishment unit 8 while also taking into account the state of the developer, which depends on the cumulative printing rate, and to appropriately adjust the amount of developer replenished to the reserve storage space 73 in the intermediate hopper 7 according to the state of the developer. In other words, if the cumulative printing rate % is lower than P2, the value of the LOW judgment threshold, which is the timing of replenishment, is set to the reference value T. L This becomes 1.5 times the standard value T, and the value of the HIGH judgment threshold, which is the timing to stop supplying, becomes the standard value T. H This becomes 2 / 3 of that. If the cumulative print rate % is lower than P2 or lower than P3, the value of the LOW judgment threshold, which is the timing for replenishment, is the reference value T. L This becomes twice the value of the HIGH judgment threshold, which is the timing to stop supplying, and the reference value T H This becomes 1 / 3 of the original amount. Therefore, the lower the printing rate, the later the start of replenishment and the earlier the end of replenishment, so the amount of developer stored in the reserve storage space 73 can be reduced as the printing rate decreases. This suppresses the aggregation of the developer in the reserve storage space 73 and, consequently, prevents false detection by the developer detection unit 74.

[0068] Through the control described above, when the cumulative print rate is lower than a predetermined print rate threshold, that is, when the amount of developer discharged from the intermediate hopper 7 to the developing device 22 decreases and the developer is prone to agglomeration, the amount of developer supplied from the cartridge 6 to the intermediate hopper 7, i.e., the amount of developer supplied to the reserve storage space 73, can be appropriately reduced.

[0069] Furthermore, as described above, the control unit 9 starts (turns on) the replenishment operation of the replenishment unit 8 when the developer detection unit 74 continuously outputs a first value for a predetermined first judgment time J1, and stops (turns off) the replenishment operation of the replenishment unit 8 when the developer detection unit 74 continuously outputs a second value for a predetermined second judgment time J2. This makes it possible to turn on the replenishment operation of the replenishment unit 8 at a more appropriate timing based on the first value output by the developer detection unit 74, and to turn off the replenishment operation of the replenishment unit 8 at a more appropriate timing based on the second value output by the developer detection unit 74.

[0070] Furthermore, as described above, when the cumulative printing rate by the image forming unit 20 is lower than a predetermined printing rate threshold (printing rate threshold P2 in the above case), the control unit 9 sets the first determination time J1 to be longer than a predetermined first reference time, and sets the second determination time J2 to be shorter than a predetermined second reference time. This allows the timing of turning on the replenishment operation of the replenishment unit 8 (for example, the timing T2 after the first determination time J1 in Figure 12 has elapsed) to be delayed, and the timing of turning off the replenishment operation of the replenishment unit 8 (for example, the timing T4 after the second determination time J2 in Figure 13 has elapsed) to be advanced, and thus the amount of developer replenished in the reserve storage space 73 can be reduced more appropriately.

[0071] Furthermore, as described above, when the cumulative printing rate by the image forming unit 20 is lower than the printing rate threshold, the control unit 9 sets the first determination time J1 (see Figure 12) to be progressively longer as the cumulative printing rate decreases, and sets the second determination time J2 (see Figure 13) to be progressively shorter as the cumulative printing rate decreases. This allows the timing of turning on the replenishment operation of the replenishment unit 8 (for example, the timing T2 after the first determination time J1 in Figure 12 has elapsed) to be progressively delayed, and the timing of turning off the replenishment operation of the replenishment unit 8 (for example, the timing T4 after the second determination time J2 in Figure 13 has elapsed) to be progressively advanced, and therefore, the amount of developer replenished in the reserve storage space 73 can be reduced more appropriately as the cumulative printing rate decreases.

[0072] In other words, the control unit 9 sets the first determination time J1 (see Figure 12) to gradually shorten as the cumulative printing rate by the image forming unit 20 increases, and sets the second determination time J2 (see Figure 13) to gradually lengthen as the cumulative printing rate increases. As a result, the higher the cumulative printing rate, which indicates good fluidity of the developer in the reserve storage space 73, the more the timing of turning on the replenishment operation of the replenishment unit 8 (for example, the timing T2 after the first determination time J1 in Figure 12 has elapsed) is gradually advanced, and the more the timing of turning off the replenishment operation of the replenishment unit 8 (for example, the timing T4 after the second determination time J2 in Figure 13 has elapsed) is gradually delayed, thereby increasing the amount of developer stored in the reserve storage space 73. In this case, since the fluidity of the developer stored in the reserve storage space 73 is good, developer aggregation does not occur, and as a result, false detections in the developer detection unit 74 do not occur.

[0073] As described above, the control unit 9 in this embodiment can effectively suppress the aggregation of the developer and the occurrence of false detections in the developer detection unit 74 by changing the amount of developer stored in the reserve storage space 73 according to the cumulative printing rate.

[0074] Note that the order of the steps described above—the step of obtaining the cumulative print rate from the cumulative print rate calculation unit 93 by the image forming unit 20 (step S1) and the step of obtaining the detection result from the developer detection unit 74 (step S2)—does not matter. The step of obtaining the LOW judgment threshold (step S6) may be performed before the step of determining whether the detection result obtained from the developer detection unit 74 is "LOW" or "HIGH" (step S3), and the same applies to the step of obtaining the HIGH judgment threshold (step S11).

[0075] Although not shown in the diagram, the control unit 9 may also control the supply unit 8 so that its supply operation does not remain on for a predetermined time (for example, about 20 seconds).

[0076] Furthermore, if the cumulative printing rate by the image forming unit 20 is not lower than a predetermined printing rate threshold, the second determination time J2 may be set to be longer than the first determination time J1. This allows a sufficient amount of developer to be supplied to the reserve storage space 73 by turning on the replenishment operation of the replenishment unit 8 early and ensuring sufficient time before turning off the replenishment operation of the replenishment unit 8 when the cumulative printing rate by the image forming unit 20 is not relatively low, that is, when the developer is not easily aggregated.

[0077] The cumulative print rate calculation unit 93 may be part of the functions of the processing unit 90 of the control unit 9. The developer detection unit 74 may be composed of a weight sensor (for example, a load cell type) that detects the weight of the developer stored in the pre-storage space 73, or it may be a sensor that outputs two or more different values ​​depending on the amount of developer stored in the pre-storage space 73.

[0078] The embodiments described above are illustrative in all respects and are not intended to be restrictive. Therefore, the technical scope of this disclosure is not construed solely by the embodiments and examples described above, but is defined by the claims. Furthermore, any modifications or changes within the equivalent scope of the claims are all within the scope of this disclosure. [Explanation of Symbols]

[0079] 1. Image forming apparatus 20 Image forming unit 22 Developing equipment 6 cartridges 7. Intermediate hopper (storage section) 70 Inlet 72 Main storage space 73 Reserve storage space 74 Developer detection unit 75 Conveying components 8 Supply Department 9. Control Unit J1 First Decision Time J2 2nd Judging Time P1~P3 Print density threshold T Conveying direction

Claims

1. The image forming unit comprises a cartridge containing a developer with toner, a developing device that supplies toner to an image carrier, a storage unit capable of transporting and storing the developer from the cartridge to the developing device, and a supply unit that replenishes the developer from the cartridge to the storage unit, and forms a toner image on the image carrier to be transferred to a sheet. An image forming apparatus comprising a control unit for controlling the supply unit, The storage section includes, A receiving port for receiving the developer supplied from the cartridge, A main storage space is provided, which contains a transport member that transports the developer received from the receiving port in a predetermined transport direction, A discharge port for the developer to the developing device is provided downstream of the main storage space in the direction of transport of the developer by the transport member, A preliminary storage space is provided which is in communication with the receiving port and the main storage space and which is capable of storing the developer inside, A developer detection unit is provided for detecting the developer stored in the aforementioned pre-storage space. The control unit, The system includes a cumulative print rate calculation unit that calculates a cumulative print rate by accumulating and averaging the print rate, which is the ratio of the toner image formed on the image carrier to the area of ​​the sheet, over the most recent predetermined number of sheets. An image forming apparatus that changes the conditions for the replenishment operation by the replenishment unit to the storage unit based on the cumulative printing rate and the detection result by the developer detection unit.

2. In the image forming apparatus according to claim 1, The control unit, An image forming apparatus that modifies the conditions for the replenishment operation by the replenishment unit so that when the cumulative print rate is lower than a predetermined print rate threshold, less developer is supplied from the cartridge to the storage unit.

3. In the image forming apparatus according to claim 1, The developer detection unit is a sensor that outputs a first value when the developer is not detected, and outputs a second value different from the first value when the developer is detected. The control unit, If the developer detection unit continues to output the first value for a predetermined first determination time, the replenishment unit starts the replenishment operation. An image forming apparatus that stops the replenishment operation by the replenishment unit when the developer detection unit continues to output the second value for a predetermined second determination time.

4. In the image forming apparatus according to claim 3, The control unit, An image forming apparatus that, when the cumulative print rate is lower than a predetermined print rate threshold, sets the first determination time to be longer than a predetermined first reference time and sets the second determination time to be shorter than a predetermined second reference time.

5. In the image forming apparatus according to claim 4, The control unit, An image forming apparatus that, when the cumulative printing rate is lower than the printing rate threshold, sets the first determination time so that the first determination time becomes progressively longer as the cumulative printing rate decreases, and sets the second determination time so that the second determination time becomes progressively shorter as the cumulative printing rate decreases.

6. In the image forming apparatus according to claim 1, The aforementioned pre-storage space is provided below the receiving port and on the upstream side of the conveying direction of the conveying member in an image forming apparatus.

7. In the image forming apparatus according to claim 6, The developer detection unit is located in the pre-storage space, upstream of the receiving port in the transport direction of the transport member, in an image forming apparatus.

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