Developing apparatus and image forming apparatus equipped therewith

Abstract

To provide a developing device that can prevent leakage of developer from an opening of the developing device, while removing developer aggregated around a regulation member, and an image forming apparatus including the same.SOLUTION: A developing device comprises a developer container that stores magnetic one-component developer, a developer carrier, stirring and conveying members, and a magnet member. The developing device can execute a developer removal operation to reversely rotate the developer carrier during a non-image formation period. The upper limit of the reverse rotation angle of the developer carrier in the developer removal operation is an angle at which a first opposite position of the developer carrier opposite to a downstream end in the reverse rotation direction of an area where the developer is present in the developer container moves to an edge of the opening at the start of reverse rotation, and the lower limit of the reverse rotation angle is an angle at which a second opposite position of the developer carrier opposite to the regulation member moves to a position exceeding the minimum point in a magnetic force distribution between a regulation pole and an adjacent pole arranged adjacent to the downstream side of the regulation pole with respect to the reverse rotation direction of the developer carrier at the start of reverse rotation.SELECTED DRAWING: Figure 5

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 clogging of a developer in a 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 photosensitive drum is visualized (developed) by the developer, and the visible image (toner image) is transferred onto a recording medium, and then a fixing process is performed. This process is common.

[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 using 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 photosensitive 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 restraint force from other parts, disturbance of the toner layer on the developing roller occurs. As a result, image defects such as uneven density 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 a developer carrier in a direction opposite 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 project] [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 suppress toner leakage from the opening of the developing apparatus while removing aggregated toner around a regulating member, 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 for developing an electrostatic latent image formed on an image carrier, comprising a developing container, a developer carrier, one or more stirring and transporting members, a regulating member, and a magnetic member. 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 circumferential surface, and is exposed from the opening of the developing container, facing the image carrier. One or more stirring and transporting members are rotatably supported in the developing container and transport the developer in the developing container while stirring 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 magnetic member is fixed non-rotatably inside the developer carrier and has a plurality of magnetic poles, including a main pole facing the image carrier and a regulating pole facing the regulating member. 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 to remove the developer that has accumulated between the regulating member and the developer carrier. The upper limit of the reverse rotation angle of the developer carrier in the developer removal operation is the angle from when the first opposing position of the developer carrier, which is facing 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 the 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 is facing the regulating member, moves to a position that exceeds the minimum point of the magnetic force distribution between the regulating pole and the adjacent pole, which is positioned adjacent to the downstream side of the regulating pole with respect to the reverse rotation direction of the developer carrier. [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 a position that exceeds the minimum point of the magnetic force distribution between the regulating pole and the adjacent pole, 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 this embodiment. [Figure 6] A schematic diagram showing the relationship between the vertical magnetic force distribution of the fixed magnet 27 and the lower limit value θ2 of the reverse rotation angle of the developing roller 25 in the developing apparatus 4 of this embodiment. [Figure 7] Enlarged view of the area around the developing roller 25 and the second agitation and transport screw 24 in Figure 5. [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 forming an image, the charging unit 2 first uniformly charges the surface of the photoreceptor drum 1. Then, based on pre-input image data, the exposure unit 3 irradiates the photoreceptor drum 1 with a laser beam (light ray) to form an electrostatic latent image on the surface of the photoreceptor drum 1 based on the image data. After that, the developing device 4 deposits toner onto the electrostatic latent image to form a toner image.

[0017] As described above, paper is transported from the paper storage unit 10 to the image forming unit 9, where the toner image has been formed, via the paper transport path 11 and the registration roller pair 13 at a predetermined timing. In the image forming unit 9, the toner image on the surface of the photoreceptor drum 1 is transferred to the paper by the transfer roller 7. The paper with the transferred toner image is then separated from the photoreceptor drum 1 and transported to the fuser unit 12, where it is heated and pressurized to fix the toner image to the paper. The paper that has passed through the fuser 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 in the developing device 4 is symmetrical with FIG. 1 about the left and right. As shown in FIG. 2, in 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 stirring and conveying screw 23 is disposed in the first conveyance chamber 21, and a second stirring and conveying 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 the toner stored in the toner container 5 (see FIG. 1) is supplied according to the detection result of the 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 a spiral blade around a support shaft, and are rotatably supported by the developing container 20 in a state parallel to each other. Note that 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, the partition wall 20a does not exist, and the toner can be transferred between the first conveyance chamber 21 (the first stirring and conveying screw 23) and the second conveyance chamber 22 (the second stirring and conveying screw 24). Thereby, the first stirring and conveying screw 23 conveys the toner in the first conveyance chamber 21 in a predetermined direction (the first direction) while stirring and transfers it to the second conveyance chamber 22. The second stirring and conveying screw 24 conveys the toner transferred from the first conveyance chamber 21 to the second conveyance chamber 22 in the direction opposite to the first stirring and conveying screw 23 (the second direction) 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 state parallel 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 thin layer of toner. 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 with the toner thin layer formed rotates in response to 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 the leakage of the developer 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 such that its longitudinal direction is larger than the maximum developing width of the developing roller 25, and by being disposed at a predetermined interval from the developing roller 25, a regulating portion 30 for regulating the amount of toner supplied to the photosensitive drum 1 is formed. The gap of the regulating portion 30 is set to about 0.2 mm to 0.4 mm. As the material of the regulating blade 29, a magnetic material or a non-magnetic SUS (stainless steel), etc. is used. Here, a permanent magnet 31 is attached to the magnetic regulating blade 29 to impart magnetism.

[0023] The fixed magnet 27 has a plurality (here, four) of magnetic poles including a main pole N1, a regulating pole S1, a conveying pole S2, and a pumping pole N2. Since the regulating pole S1 of the fixed magnet 27 faces the regulating blade 29, magnetic lines of force are concentrated at the tip of the regulating blade 29, and a magnetic field in a direction attracting the regulating portion 30 is generated.

[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 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). 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 is then removed from the surface of the developing roller 25 by contacting and mixing with the toner in the second transport chamber 22 due to the reverse rotation 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 7 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, toner aggregates 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 this embodiment. Figure 6 is a schematic diagram showing the relationship between the vertical magnetic force distribution of the fixed magnet 27 and the lower limit value θ2 of the reverse rotation angle of the developing roller 25 in the developing apparatus 4 of this embodiment. Figure 7 is an enlarged view of the area around the developing roller 25 and the second agitation conveying screw 24 in Figure 5.

[0044] In this embodiment, the lower limit θ2 of the reverse rotation angle of the developing roller 25 during the developer removal operation is determined based on the magnetic force influence of the pumping pole N2, which is positioned adjacent to the downstream side of the regulating pole S1 of the fixed magnet 27 with respect to the reverse rotation direction of the developing roller 25.

[0045] Specifically, as shown in Figure 6, the lower limit of the reverse rotation angle θ2 is defined as the angle until the magnetic force distribution between the magnetic force peak P1 of the regulating pole S1 and the magnetic force peak P2 of the pumping pole N2 exceeds the minimum point Q. At positions closer to the pumping pole N2 than the minimum point Q of the magnetic force distribution, the magnetic force of the pumping pole N2 acts on the toner in the second transport chamber 22. Therefore, there is toner that is attracted by the influence of the magnetic force of the pumping pole N2.

[0046] Therefore, the position R2 (second opposing position) facing the regulating blade 29 at the start of reverse rotation is reversed to a position that exceeds the minimum point Q of the magnetic force distribution between the magnetic force peak P1 of the regulating pole S1 and the magnetic force peak P2 of the pumping pole N2. As a result, as shown in Figure 7, the agglomerated toner Tg that was present near the regulating section 30 before the developing roller 25 was reversed is reliably brought into contact with and mixed with the toner T around the second agitation conveying screw 24 by the magnetic force of the pumping pole N2. Consequently, the toner in the regulating section 30 is reliably reset (replaced).

[0047] If the magnetic force distribution between the regulating pole S1 and the lifting pole N2 is not complex, the lower limit of the reverse rotation angle θ2 can also be calculated. Specifically, using the magnetic force M1 [mT] of the regulating pole S1, the magnetic force M2 [mT] of the lifting pole N2, and the angle α [°] between the regulating pole S1 and the lifting pole N2 as seen from the center of the fixed magnet 27, the angle θm of the magnetic force ratio (angle from the regulating pole S1 to the minimum point Q) is calculated using the following equation (1). θm = α × M1 / ​​(M1 + M2) ... (1)

[0048] For example, if the magnetic force M1 of the regulating pole S1 is 85 [mT], the magnetic force M2 of the developing pole N2 is 60 [mT], and the angle α between the regulating pole S1 and the developing pole N2 is 86°, then θm = 86 × (85 / 85 + 60) = 50.4 [°]. Therefore, the magnetic influence of the adjacent developing pole N2 begins at a position exceeding 50° from the regulating pole S1. In this case, the lower limit of the reverse rotation angle θ2 of the developing roller 25 is set to an angle exceeding 50°.

[0049] Furthermore, since the magnetic force influence of the pumping electrode N2 increases as it approaches the magnetic force peak P2, it is more preferable to set the reverse rotation angle of the developing roller 25 to be greater than 50° and below the magnetic force peak position of the pumping electrode N2. In this way, the aggregated 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 by the magnetic force of the pumping electrode N2.

[0050] In this embodiment, the developing roller 25 is positioned adjacent to the downstream side of the regulating pole S1 with respect to the reverse rotation direction of the developing roller 25. Therefore, the lower limit θ2 of the reverse rotation angle of the developing roller 25 was determined based on the magnetic force influence of the developing pole N2. However, if, for example, one or more magnetic poles (carrier poles) are positioned between the regulating pole S1 and the developing pole N2, the lower limit θ2 of the reverse rotation angle should be set to a position beyond the minimum point of the magnetic force distribution between the magnetic force peak of the regulating pole S1 and the magnetic force peak of the carrier pole. Alternatively, the lower limit θ2 of the reverse rotation angle of the developing roller 25 can also be determined by calculating the angle θm of the magnetic force ratio at which the magnetic force influence of the carrier pole adjacent to the downstream side of the regulating pole S1 begins, using equation (1).

[0051] 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 above embodiments, 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.

[0052] 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]

[0053] 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]

[0054] 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 magnet (magnetic component) 29. Regulating blade (regulating member) 30 Regulatory Department 100 Image forming apparatus R1 Opposing position (first opposing position) R2 Opposing position (second opposing position) S1 Regulatory Pole N1 Main pole S2 Transport Pole N2 Pumping pole (adjacent pole)

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 magnetic member is fixed inside the developer carrier in a manner that prevents rotation, and has multiple magnetic poles, including a main pole facing the image carrier and a restricting pole facing the restricting member. 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 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 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 moves to a position that exceeds the minimum point of the magnetic force distribution between the regulating pole and the adjacent pole positioned adjacent to the regulating pole on the downstream side of the regulating pole with respect to the reverse rotation direction of the developer carrier. A developing apparatus characterized in that, when the magnetic force of the restricting pole is M1 [mT], the magnetic force of the adjacent pole is M2 [mT], and the angle between the restricting pole and the adjacent pole as viewed from the center of the magnetic member is α [°], the angle θm from the restricting pole to the minimum point is calculated by the following equation (1), and the lower limit of the reverse rotation angle is set to an angle greater than the angle θm. θm=α×M1 / (M1+M2)...(1)

2. The developing apparatus according to Claim 1, characterized in that the reverse rotation angle is greater than the angle to a position beyond the minimum point and less than or equal to the magnetic force peak position of the adjacent pole.

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 so as to receive the developer from the second stirring and conveying member into the second conveying chamber. The developing apparatus according to claim 1 or 2, characterized in that the adjacent electrode is a pumping electrode that pumps the developer in the second transport chamber to the developer carrier.

4. An image forming apparatus comprising a developing apparatus according to any one of Claims 1 to 3.

Images