Developing apparatus and image forming apparatus equipped therewith
The developing apparatus optimizes the reverse rotation angle of the developing roller to address toner aggregation and leakage issues, ensuring effective toner removal and improved image quality.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- KYOCERA DOCUMENT SOLUTIONS INC
- Filing Date
- 2022-02-04
- Publication Date
- 2026-05-11
AI Technical Summary
Existing developing methods using magnetic one-component developers face issues with toner soft-aggregation around the regulating blade, leading to image defects like shading and white streaks, and the challenge of varying required reverse rotation angles for developing roller removal results in either ineffective toner removal or toner leakage.
A developing apparatus with defined reverse rotation angles for the developing roller during developer removal operations, setting the upper limit to prevent toner leakage and the lower limit to ensure effective mixing of aggregated toner with agitation members, thereby resetting it within the container.
Effectively removes aggregated toner while preventing leakage, thereby reducing image defects such as shading and white streaks, by optimizing the reverse rotation angle of the developing roller.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to a developing device used in an image forming apparatus such as a copying machine, a facsimile machine, a printer, etc., and particularly relates to a method for suppressing the clogging of a developer in the gap between a developing roller and a regulating blade.
Background Art
[0002] Conventionally, as a developing method in an image forming apparatus using an electrophotographic process, mainly a powder developer is used, and an electrostatic latent image formed on an image carrier such as a photoreceptor drum is visualized (developed) by the developer, and after the visible image (toner image) is transferred onto a recording medium, a fixing process is generally performed.
[0003] As a developing method using a developer, a magnetic one-component developing method using a one-component developer composed only of magnetized toner is known. In the magnetic one-component developing method, a fixed magnet having a plurality of magnetic poles is arranged inside a developing roller (developer carrier), and the toner in the developing container is carried onto the developing roller by utilizing the magnetic carrying force, and then a toner thin layer is formed by performing layer thickness regulation using a regulating blade (regulating member), and the toner is made to fly onto the photoreceptor drum at the developing position.
[0004] In the magnetic one-component developing method, in order to ensure the stability of the toner layer on the developing roller and improve the charging performance of the toner, sufficient magnetic force is required at the tip of the regulating blade. However, when the developing operation is continuously performed, toner is likely to soft-aggregate around the regulating blade in the developing device. Since the soft-aggregated toner has a different magnetic binding force from other parts, disturbance of the toner layer on the developing roller occurs. As a result, image defects such as shading and white streaks are likely to occur when a halftone image is output.
[0005] Therefore, Patent Document 1 discloses an image forming apparatus that rotates the developer carrier in the opposite direction to the developing direction with the image carrier stopped, so that the toner deposited on the developer regulating member is not developed in the image.
Prior Art Documents
[0006] [Patent Document 1] Japanese Patent Publication No. 2009-258276 [Overview of the Initiative] [Problems that the invention aims to solve]
[0007] When removing softly agglomerated toner around the regulating blade by reversing the developing roller, the required reverse rotation angle (amount of reverse rotation) of the developing roller to remove the agglomerated toner varies depending on the layout of the regulating blade, developing roller, agitation and conveying components, etc. For example, if the reverse rotation angle of the developing roller is too small (the amount of reverse rotation is too small), the removal effect of agglomerated toner will be poor, and if the reverse rotation angle is too large (the amount of reverse rotation is too large), toner may overflow from the jaw of the opening of the developing device where the developing roller is exposed.
[0008] In view of the above problems, the present invention aims to provide a developing apparatus and an image forming apparatus equipped therewith that can remove developer aggregated around a regulating member while suppressing the leakage of developer from the opening of the developing apparatus, regardless of the layout of the components inside the developing apparatus. [Means for solving the problem]
[0009] To achieve the above objective, the first configuration of the present invention is a developing apparatus comprising a developing container, a developer carrier, one or more agitation and transporting members, and a regulating member, for developing an electrostatic latent image formed on an image carrier. The developing container contains a magnetic one-component developer consisting only of magnetic toner. The developer carrier is rotatably supported in the developing container, carries the developer on its outer surface, and is exposed from the opening of the developing container, facing the image carrier. One or more agitation and transporting members are rotatably supported in the developing container and transport the developer in the developing container while agitating it. The regulating member is positioned at a predetermined distance from the developer carrier and forms a regulating portion that regulates the thickness of the developer layer carried on the developer carrier. The developing apparatus is capable of performing a developer removal operation when not forming an image by rotating the developer carrier in the opposite direction to the rotation direction during image formation, thereby removing the developer accumulated between the regulating member and the developer carrier. The developer carrier is positioned adjacent to one of the agitation and conveying members, and above the adjacent agitation and conveying member, so that the developer is transferred from the agitation and conveying member. The upper limit of the reverse rotation angle of the developer carrier during the developer removal operation is the angle at which the first opposing position of the developer carrier, which faces the downstream end in the reverse rotation direction of the area where the developer exists in the developing container, moves to the edge of the opening at the start of reverse rotation, and the lower limit of the reverse rotation angle is the angle at which the second opposing position of the developer carrier, which faces the regulating member, moves to the height of the outer edge of the agitation and conveying member adjacent to the developer carrier at the start of reverse rotation. [Effects of the Invention]
[0010] According to the first configuration of the present invention, by setting the upper limit of the reverse rotation angle of the developer carrier in the developer removal operation to the angle at which the first opposing position of the developer carrier, which faces the downstream end in the reverse rotation direction of the area where the developer exists in the developing container, moves to the edge of the opening of the developing container at the start of reverse rotation, it is possible to prevent the developer from leaking out of the opening of the developing container. Furthermore, by setting the lower limit of the reverse rotation angle to the angle at which the second opposing position of the developer carrier, which faces the regulating member, moves to the height of the outer edge of the adjacent stirring and conveying member at the start of reverse rotation, the developer aggregated near the regulating part comes into contact with and mixes with the developer around the stirring and conveying member, ensuring that it is reliably reset (replaced). [Brief explanation of the drawing]
[0011] [Figure 1] Schematic cross-sectional view of an image forming apparatus 100 equipped with the developing device 4 of the present invention [Figure 2] Side cross-sectional view of a developing apparatus 4 according to one embodiment of the present invention [Figure 3] Side cross-sectional view of the toner container 5 mounted on the image forming apparatus 100. [Figure 4] Block diagram showing an example of a control path used in the image forming apparatus 100. [Figure 5] A side view showing the reverse rotation angle of the developing roller 25 when the developer removal operation is performed in the developing apparatus 4 of the first embodiment of the present invention. [Figure 6] Enlarged view of the area around the developing roller 25 and the second agitation and transport screw 24 in Figure 5. [Figure 7] A side view showing the reverse rotation angle of the developing roller 25 when the developer removal operation is performed in the developing apparatus 4 of the second embodiment of the present invention. [Figure 8] Enlarged view of the area around the developing roller 25 and the second agitation and transport screw 24 in Figure 7. [Modes for carrying out the invention]
[0012] Embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a schematic cross-sectional view of an image forming apparatus 100 equipped with a developing device 4 of the present invention. In the image forming apparatus (e.g., a monochrome printer) 100, when printing is performed, an electrostatic latent image is formed in the image forming unit 9 inside the main body of the image forming apparatus 100 based on original image data transmitted from a personal computer (not shown, hereinafter abbreviated as PC), and toner is attached to the electrostatic latent image by the developing device 4 to form a toner image. Toner is supplied to the developing device 4 from a toner container 5. In the image forming apparatus 100, the image forming process on the photoreceptor drum 1 is performed while the photoreceptor drum 1 is rotated clockwise in Figure 1.
[0013] The image forming unit 9 is equipped with a charging unit 2, an exposure unit 3, a developing device 4, a transfer roller 7, a cleaning device 8, and a static elimination device (not shown) along the rotation direction (clockwise) of the photoreceptor drum 1. The photoreceptor drum 1 is, for example, an aluminum drum with a photosensitive layer laminated on top. The photosensitive layer is not particularly limited, but is preferably made of amorphous silicon (a-Si), which has excellent durability, or an organic photosensitive layer (OPC), which generates less ozone when charged and can produce high-resolution images.
[0014] The charging unit 2 uniformly charges the photosensitive layer on the surface of the photosensitive drum 1. For example, the charging unit 2 may be a corona discharge device that discharges electricity by applying a high voltage using a thin wire or the like as an electrode. Alternatively, a contact-type charging device may be used, in which a voltage is applied while a charging member, such as a charging roller, is in contact with the surface of the photosensitive drum 1. The exposure unit 3 irradiates the surface of the photosensitive drum 1, which has been charged by the charging unit 2, with a light beam (e.g., a laser beam) based on the image data, and forms an electrostatic latent image on the surface of the photosensitive drum 1 with reduced charge.
[0015] The developing device 4 forms a toner image by attaching toner to the electrostatic latent image formed on the surface of the photoreceptor drum 1. In this device, a one-component developer (hereinafter simply referred to as toner) consisting only of magnetic toner components is contained in the developing device 4. Further details of the developing device 4 will be described later. The transfer roller 7 transfers the toner image formed on the surface of the photoreceptor drum 1 to the paper being transported along the paper transport path 11. The cleaning device 8 is equipped with cleaning rollers and blades that make linear contact with the photoreceptor drum 1 in the longitudinal direction, and removes residual toner from the surface of the photoreceptor drum 1 after the toner image has been transferred to the paper.
[0016] When performing image formation, first, the charging unit 2 uniformly charges the surface of the photosensitive drum 1. Then, based on the previously input image data, the exposure unit 3 irradiates the photosensitive drum 1 with a laser beam (light ray), thereby forming an electrostatic latent image based on the image data on the surface of the photosensitive drum 1. After that, the developing device 4 attaches toner to the electrostatic latent image to form a toner image.
[0017] Towards the image forming unit 9 where the toner image is formed as described above, paper is conveyed from the paper storage unit 10 via the paper conveyance path 11 and the registration roller pair 13 at a predetermined timing, and in the image forming unit 9, the toner image on the surface of the photosensitive drum 1 is transferred to the paper by the transfer roller 7. Then, the paper with the transferred toner image is separated from the photosensitive drum 1 and conveyed to the fixing unit 12, where it is heated and pressurized so that the toner image is fixed on the paper. The paper that has passed through the fixing unit 12 passes through the discharge roller pair 14 and is discharged to the paper discharge unit 15.
[0018] FIG. 2 is a side cross-sectional view of the developing device 4 according to an embodiment of the present invention. FIG. 2 shows the state of the developing device 4 as viewed from the back side of FIG. 1, and the arrangement of the constituent members inside the developing device 4 is symmetric with FIG. 1 about the left and right. As shown in FIG. 2, inside the developing container 20, a first conveyance chamber 21 and a second conveyance chamber 22 are formed by a partition wall 20a integrally formed with the developing container 20. A first agitation conveyance screw 23 is disposed in the first conveyance chamber 21, and a second agitation conveyance screw 24 is disposed in the second conveyance chamber 22. A toner supply port 20b is provided at the upper part of the developing container 20, and toner stored in the toner container 5 (see FIG. 1) is supplied according to the detection result of a toner sensor 26 that detects the amount of toner in the developing container 20.
[0019] The first stirring and conveying screw 23 and the second stirring and conveying screw 24 are each configured to have spiral blades around a support shaft, and are rotatably supported in the developing container 20 in a parallel state to each other. Note that partition walls 20a do not exist at both ends in the longitudinal direction of the developing container 20 (the direction perpendicular to the paper surface of FIG. 2), which is the axial direction of the first stirring and conveying screw 23 and the second stirring and conveying screw 24, and toner can be transferred between the first conveying chamber 21 (the first stirring and conveying screw 23) and the second conveying chamber 22 (the second stirring and conveying screw 24). Thereby, the first stirring and conveying screw 23 conveys the toner in the first conveying chamber 21 in a predetermined direction (the first direction) while stirring and transfers it to the second conveying chamber 22. The second stirring and conveying screw 24 conveys the toner transferred from the first conveying chamber 21 to the second conveying chamber 22 in the opposite direction (the second direction) to the first stirring and conveying screw 23 while stirring and supplies it to the developing roller 25.
[0020] The developing roller 25 is rotatably supported in the developing container 20 in a parallel state to the first stirring and conveying screw 23 and the second stirring and conveying screw 24. Inside the developing roller 25, a fixed magnet 27 composed of a permanent magnet having a plurality of magnetic poles is fixed. Toner is attached (carried) to the surface of the developing roller 25 by the magnetic force of this fixed magnet 27 to form a toner thin layer. A part of the outer peripheral surface of the developing roller 25 is exposed from the opening 20c of the developing container 20, and the exposed portion is arranged to face the photosensitive drum 1 (see FIG. 1).
[0021] Then, as the developing roller 25 on which the toner thin layer is formed rotates in accordance with the rotation of the photosensitive drum 1, toner is supplied to the photosensitive layer of the photosensitive drum 1. The first stirring and conveying screw 23, the second stirring and conveying screw 24, and the developing roller 25 are rotationally driven at a predetermined speed by a developing drive motor 35 (see FIG. 4) and a gear train. Further, magnetic seal members 28 for preventing leakage of toner from the gap between the developing container 20 and the developing roller 25 are disposed at both ends of the developing roller 25.
[0022] The regulating blade 29 is formed so that its longitudinal direction is larger than the maximum development width of the developing roller 25, and by being positioned at a predetermined distance from the developing roller 25, it forms a regulating section 30 that regulates the amount of toner supplied to the photoreceptor drum 1. The gap of the regulating section 30 is set to approximately 0.2 mm to 0.4 mm. The material used for the regulating blade 29 is either a magnetic material or a non-magnetic material such as SUS (stainless steel). In this case, a permanent magnet 31 is attached to the magnetic regulating blade 29 to impart magnetism.
[0023] The fixed magnet 27 has multiple (four in this case) magnetic poles consisting of a main pole N1, a restricting pole S1, a transport pole S2, and a lifting pole N2. Since the restricting pole S1 of the fixed magnet 27 faces the restricting blade 29, magnetic field lines concentrate at the tip of the restricting blade 29, generating a magnetic field that attracts the restricting section 30.
[0024] This magnetic field causes a magnetic brush (toner chain) of toner particles to form between the regulating blade 29 and the developing roller 25. The magnetic brush is layer-regulated as it passes through the regulating section 30, and a thin layer of toner is formed on the developing roller 25. By using a magnetic blade for the regulating blade 29, the regulating force is increased not only by the spacing of the regulating section 30 but also by the magnetic field generated in the regulating section 30, forming a thin layer of toner several tens of micrometers thick on the developing roller 25.
[0025] Meanwhile, toner that was not used to form the toner layer accumulates along the upstream side (lower side in Figure 2) of the regulating blade 29. Subsequently, as the developing roller 25 rotates clockwise in Figure 2 and the magnetic brush moves to a position facing the photoreceptor drum 1, the magnetic brush is subjected to a magnetic field by the main pole N1 of the fixed magnet 27, stands upright, and comes into contact with the surface of the photoreceptor drum 1 to form a toner image.
[0026] As the developing roller 25 rotates clockwise, the transport pole S2 applies a magnetic field along the outer surface of the developing roller 25, and toner that was not used to form the toner image is collected on the developing roller 25 along with the magnetic brush. Furthermore, the magnetic brush detaches from the developing roller 25 in the gap between the transport pole S2 and the pumping pole N2 and falls into the housing 20. After being agitated and transported by the second agitation transport screw 24, the magnetic field of the pumping pole N2 causes the magnetic brush to be formed on the developing roller 25 again.
[0027] Figure 3 is a side cross-sectional view showing the internal structure of the toner container 5 that supplies toner to the developing device 4. The toner container 5 comprises a container 51 for storing toner, a supply spiral 52, and a stirring paddle 53.
[0028] The container 51 is equipped with a toner outlet 51a that faces the toner supply port 20b (see Figure 2) of the developing device 4.
[0029] The replenishment spiral 52 is rotatably mounted at the bottom of the container 51, with one end facing the toner outlet 51a. The replenishment spiral 52 consists of a rotating shaft 52a and conveying blades 52b formed spirally at a constant pitch on the outer surface of the rotating shaft 52a. When the replenishment spiral 52 rotates in a predetermined direction (counterclockwise in Figure 3), toner is conveyed toward the toner outlet 51a.
[0030] The stirring paddle 53 consists of a rotating shaft 53a and a paddle-shaped stirring blade 53b that extends radially from the rotating shaft 53a and unfolds axially. When the stirring paddle 53 rotates in a predetermined direction (counterclockwise in Figure 3), the toner in the container 51 is stirred. The replenishment spiral 52 and the stirring paddle 53 are rotationally driven by the container drive motor 37 (see Figure 4).
[0031] Figure 4 is a block diagram showing an example of a control path used in the image forming apparatus 100. Since various controls are performed on different parts of the apparatus during operation, the overall control path of the image forming apparatus 100 is complex. Therefore, this section will focus on explaining the parts of the control path that are necessary for implementing the present invention.
[0032] The image input unit 40 receives image data transmitted to the image forming apparatus 100 from a personal computer or the like. The image signal input from the image input unit 40 is converted into a digital signal and then sent to the temporary storage unit 94.
[0033] The control unit 70 is equipped with a liquid crystal display unit 71 and LEDs 72 that indicate various statuses, showing the status of the image forming apparatus 100, the image forming status, and the number of copies to be printed. Various settings for the image forming apparatus 100 are made using the printer driver on a personal computer.
[0034] In addition, the control unit 70 is equipped with a start button for the user to instruct the start of image formation, a stop / clear button for canceling image formation, and a reset button for returning the various settings of the image forming apparatus 100 to their default state.
[0035] The transmitting / receiving unit 80 communicates with the outside world using telephone lines or internet lines. More specifically, the transmitting / receiving unit 80 receives print commands, including image data, transmitted from a host device such as a personal computer. The received image data is stored in the temporary storage unit 94.
[0036] The control unit 90 includes at least a CPU (Central Processing Unit) 91 as a central processing unit, a ROM (Read Only Memory) 92 as a read-only memory, a RAM (Random Access Memory) 93 as a read-write memory, a temporary memory unit 94 for temporarily storing image data, etc., a counter 95, multiple (in this case, two) I / F (interfaces) 96 for transmitting control signals to each device in the image forming apparatus 100 and receiving input signals from the operation unit 50, and an arithmetic unit 97. Furthermore, the control unit 90 can be placed anywhere within the image forming apparatus 100.
[0037] ROM 92 stores control programs for the image forming apparatus 100, necessary control values, and other data that should not be changed during use of the image forming apparatus 100. RAM 93 stores necessary data generated during the control of the image forming apparatus 100, as well as data temporarily required for the control of the image forming apparatus 100. RAM 93 (or ROM 92) also stores the cumulative number of printed pages since the replacement of the toner container 5, which is used to predict the remaining toner level in the toner container 5, and the cumulative operating time of the container drive motor 37. The temporary storage unit 94 temporarily stores the image signal input from the image input unit 40 and converted into a digital signal. The counter 95 accumulates and counts the number of printed pages.
[0038] Furthermore, the control unit 90 transmits control signals from the CPU 91 to each part and device of the image forming apparatus 100 via the I / F 96. In addition, signals indicating their status and input signals are transmitted from each part and device to the CPU 91 via the I / F 96. Examples of parts and devices controlled by the control unit 90 include the image forming unit 9, the fixing unit 12, the developing drive motor 35, the container drive motor 37, the image input unit 40, the operation unit 70, and the transmitting / receiving unit 80.
[0039] As mentioned above, when continuous printing is performed using a magnetic single-component developer, toner accumulated in the regulating section 30 of the developing device 4 undergoes soft aggregation, causing clogged print heads. In particular, soft aggregation of toner is more likely to occur when a low-melting-point toner is used as the magnetic single-component developer and printing is performed in a high-temperature environment. Therefore, in this embodiment, a developer removal operation is made possible to remove toner (developer) accumulated in the regulating section 30 when not forming an image. The developer removal operation will be described in detail below.
[0040] The developer removal operation involves rotating the developing roller 25 by a predetermined amount (a predetermined angle) in the opposite direction to that during image formation (counterclockwise in Figure 2) when no image is being formed. This applies a force in the direction of rotation of the developing roller 25 to the agglomerated toner adhering to the tip of the regulating blade 29. As a result, the agglomerated toner detaches from the tip of the regulating blade 29. The agglomerated toner detached from the tip of the regulating blade 29 comes into contact with and mixes with the toner in the second transport chamber 22 due to the reverse rotation of the developing roller 25, thereby removing it from the surface of the developing roller 25.
[0041] In this case, if the reverse rotation angle of the developing roller 25 is small (the amount of reverse rotation is small), the removal effect of toner aggregates will be insufficient, and if the reverse rotation angle is large (the amount of reverse rotation is large), there is a risk that toner will leak out from the opening 20c of the developing container 20 where the developing roller 25 is exposed. Therefore, in this invention, the reverse rotation angle (amount of reverse rotation) of the developing roller 25 during the execution of the developer removal operation is defined.
[0042] Specifically, as shown in Figure 6 described later, the upper limit of the reverse rotation angle of the developing roller 25 is set to the angle θ1 at which the position R1 (first opposing position) facing the downstream end in the reverse rotation direction of the toner-containing area in the second transport chamber 22 at the start of reverse rotation moves to the lower edge 20d of the opening 20c of the developing container 20. This prevents toner from leaking out of the opening 20c of the developing container 20. Furthermore, by defining the lower limit of the reverse rotation angle of the developing roller 25 as in the embodiment described later, aggregated toner accumulated on the back surface of the regulating blade 29 can be effectively removed.
[0043] Figure 5 is a side view showing the reverse rotation angle of the developing roller 25 when the developer removal operation is performed in the developing apparatus 4 of the first embodiment of the present invention. Figure 6 is an enlarged view of the area around the developing roller 25 and the second agitation conveying screw 24 in Figure 5. In this embodiment, as shown in Figure 5, the lower limit θ2 of the reverse rotation angle of the developing roller 25 is set to the angle at which the position R2 facing the regulating blade 29 at the start of reverse rotation moves to the height h of the outer edge (upper end) of the second agitation conveying screw 24.
[0044] The amount of toner T in the second transport chamber 22 varies depending on the amount of toner filled in the developing container 20, but it generally extends up to the height h of the outer edge of the second agitation transport screw 24. Furthermore, even if the top surface (agent surface) of the toner T is below the height h of the outer edge of the second agitation transport screw 24, the rotation of the second agitation transport screw 24 causes the toner T to bounce up above the outer edge of the second agitation transport screw 24.
[0045] Therefore, the position R2 (second opposing position) facing the regulating blade 29 at the start of reverse rotation is reversed to the height h of the outer edge of the second stirring conveying screw 24. As a result, as shown in Figure 6, the aggregated toner Tg that was present near the regulating section 30 at the start of reverse rotation of the developing roller 25 comes into contact with and mixes with the toner T around the second stirring conveying screw 24 as the developing roller 25 rotates in reverse and then in the forward direction again after the reverse rotation. As a result, the toner in the regulating section 30 is reliably reset (replaced). Therefore, toner aggregation in the regulating section 30 can be effectively suppressed, and image defects such as shading and white streaks in halftone images can be suppressed.
[0046] In Figure 5, the lower limit θ2 of the reverse rotation angle of the developing roller 25 is set to the angle at which the position R2 facing the regulating blade 29 at the start of reverse rotation moves to the height h of the outer edge of the second stirring and conveying screw 24. However, it is more preferable to set the lower limit θ2 of the reverse rotation angle to the angle at which the position R2 facing the regulating blade 29 at the start of reverse rotation exceeds the height h of the outer edge of the second stirring and conveying screw 24. In this way, the agglomerated toner Tg present in the regulating section 30 can be brought into contact with and mixed with the toner T around the second stirring and conveying screw 24 more reliably.
[0047] Figure 7 is a side view showing the reverse rotation angle of the developing roller 25 when the developer removal operation is performed in the developing apparatus 4 of the second embodiment of the present invention. Figure 8 is an enlarged view of the area around the developing roller 25 and the second agitation conveying screw 24 in Figure 7. In this embodiment, as shown in Figure 7, the lower limit θ3 of the reverse rotation angle of the developing roller 25 is set to the angle at which the position R2 facing the regulating blade 29 at the start of reverse rotation moves to a straight line L passing through the first rotation center O1 of the developing roller 25 and the second rotation center O2 of the second agitation conveying screw 24.
[0048] The amount of toner T in the second transport chamber 22 varies depending on the amount of toner filled in the developing container 20, but it generally extends to the intersection point P (see Figure 8) of the straight line L and the outer surface of the developing roller 25. Furthermore, even if the upper surface (agent surface) of the toner T is below the intersection point P, the rotation of the second agitation transport screw 24 causes the toner T to be bounced up above the intersection point P.
[0049] Therefore, when the developer removal operation is performed, the developing roller 25 is reversed from the position R2 opposite the regulating blade 29 to a straight line L. As a result, as shown in Figure 8, the agglomerated toner Tg present near the regulating section 30 when the developing roller 25 starts to reverse rotation comes into contact with and mixes with the toner T around the second agitation conveying screw 24 as the developing roller 25 reverses and then rotates forward again after the reverse rotation. As a result, the toner in the regulating section 30 is reliably reset (replaced).
[0050] Furthermore, the straight line L passes through the apex of the outer edge of the agitation conveying screw 24 when the second agitation conveying screw 24 is positioned vertically below the developing roller 25. In other words, when the second agitation conveying screw 24 is positioned vertically below the developing roller 25, the lower limit θ3 of the reverse rotation angle of the developing roller 25 is the same angle as the lower limit θ2 in the first embodiment, which reverses the rotation to the height h of the outer edge of the second agitation conveying screw 24 at the opposing position R. That is, when the second agitation conveying screw 24 is positioned diagonally below the developing roller 25 as in this embodiment, the lower limit θ3 of the reverse rotation angle of the developing roller 25 is always greater than the lower limit θ2 of the reverse rotation angle in the first embodiment.
[0051] Therefore, by reversing the rotation of the developing roller 25 from the position R2 opposite the regulating blade 29 to a straight line L, the aggregated toner Tg present near the regulating section 30 can be brought into contact with and mixed with the toner T around the second stirring and conveying screw 24 more reliably than in the first embodiment.
[0052] Furthermore, similar to the first embodiment, by setting the upper limit of the reverse rotation angle of the developing roller 25 to an angle θ1 at which the position R1 opposite the downstream end in the reverse rotation direction of the toner-containing area in the second transport chamber 22 at the start of reverse rotation moves to the lower edge 20d of the opening 20c of the developing container 20, there is no risk of the aggregated toner Tg present in the regulating section 30 being exposed to the outside beyond the lower edge 20d of the opening 20c due to the reverse rotation of the developing roller 25. Therefore, leakage of toner from the developing container 20 can be suppressed.
[0053] In Figure 7, the lower limit θ3 of the reverse rotation angle of the developing roller 25 is set as the angle until the opposing position R2 with respect to the regulating blade 29 moves to the straight line L at the start of reverse rotation. However, it is more preferable to set the lower limit θ2 of the reverse rotation angle of the developing roller 25 as the angle until the opposing position R2 with respect to the regulating blade 29 exceeds the straight line L at the start of reverse rotation. This allows the agglomerated toner Tg present in the regulating section 30 to come into contact with and mix with the toner T around the second stirring and conveying screw 24 more reliably.
[0054] Furthermore, the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. For example, in the embodiments described above, the fixed magnet 27 has a four-pole configuration with two north poles and two south poles, but the present invention is equally applicable to a five-pole or three-pole fixed magnet 27.
[0055] Furthermore, the present invention is not limited to monochrome printers as shown in Figure 1, but can be applied to various image forming devices equipped with a magnetic one-component developing device, such as digital or analog monochrome copiers, color printers, color copiers, and facsimile machines. [Industrial applicability]
[0056] The present invention is applicable to developing apparatuses that use a magnetic single-component developer. By utilizing the present invention, it is possible to provide a developing apparatus and an image forming apparatus equipped therewith that can remove aggregated toner around a regulating member while suppressing toner leakage from the opening of the developing apparatus, regardless of the layout of the components inside the developing apparatus. [Explanation of Symbols]
[0057] 4. Developing device 5 Toner Containers 9 Image forming unit 20 developing containers 20c opening 21. First transport room 22 Second transport room 23. First stirring and conveying screw (first stirring and conveying member) 24. Second stirring and conveying screw (second stirring and conveying member) 25. Developing roller (developer carrier) 27 Fixed Magnets 29. Regulating blade (regulating member) 30 Regulatory Department 100 Image forming apparatus R1 Opposing position (first opposing position) R2 Opposing position (second opposing position) O1 First rotation center O2 Second rotation center
Claims
1. A developing container for containing a magnetic one-component developer consisting only of magnetic toner, A developer carrier is rotatably supported in the developing container, carries the developer on its outer surface, and is exposed from the opening of the developing container and faces the image carrier, One or more stirring and conveying members are rotatably supported in the developing container and convey the developer inside the developing container while stirring it, A restricting member is positioned at a predetermined distance from the developer carrier and forms a restricting portion that restricts the thickness of the developer layer supported on the developer carrier. A developing apparatus comprising the above, for developing an electrostatic latent image formed on the image carrier, When not forming an image, the developer carrier can be rotated in the opposite direction to the rotation direction during image formation to perform a developer removal operation to remove the developer that has accumulated between the regulating member and the developer carrier. The developer carrier is positioned adjacent to one of the agitation and conveying members, and above the adjacent agitation and conveying member, so that the developer is transferred from the agitation and conveying member. The upper limit of the reverse rotation angle of the developer carrier in the developer removal operation is the angle from the start of reverse rotation until the first opposing position of the developer carrier, which is opposite to the downstream end in the reverse rotation direction of the area where the developer is present in the developing container, moves to the edge of the opening. The developing apparatus is characterized in that the lower limit of the reverse rotation angle is the angle at which the second opposing position of the developer carrier facing the regulating member at the start of reverse rotation exceeds the height of the outer edge of the stirring conveying member adjacent to the developer carrier.
2. The developing container has a first transport chamber and a second transport chamber arranged in parallel to each other. The agitation and conveying member comprises a first agitation and conveying member that conveys the developer in the first conveying chamber in a first direction while agitating it, and a second agitation and conveying member that conveys the developer in the second conveying chamber in a second direction opposite to the first direction while agitating it. The developer carrier is positioned adjacent to the second stirring and conveying member and above the second stirring and conveying member so as to receive the developer in the second conveying chamber from the second stirring and conveying member. The developing apparatus according to claim 1, characterized in that the lower limit of the reverse rotation angle is the angle until the second opposing position exceeds the height of the outer edge of the second stirring and conveying member.
3. The developing container has a first transport chamber and a second transport chamber arranged in parallel with each other, The agitation and conveying member comprises a first agitation and conveying member that conveys the developer in the first conveying chamber in a first direction while agitating it, and a second agitation and conveying member that conveys the developer in the second conveying chamber in a second direction opposite to the first direction while agitating it. The developer carrier is positioned adjacent to the second stirring and conveying member and above the second stirring and conveying member so as to receive the developer in the second conveying chamber from the second stirring and conveying member. The developing apparatus according to claim 1 or 2, characterized in that the lower limit of the reverse rotation angle is the angle until the second opposing position exceeds the straight line passing through the first rotation center of the developer carrier and the second rotation center of the second stirring and conveying member.
4. An image forming apparatus comprising a developing apparatus according to any one of Claims 1 to 3.