Developing device

Abstract

A configuration is provided that can suppress the occurrence of abnormal images. [Solution] The developer container 2 is disposed in the developing chamber 11 upstream of the second opening 15b in the direction of arrow g, and has a discharge port 20 for discharging the developer transported by the spiral blade 13e of the supply screw 13. Further, a third opening 15c is provided in the partition 15 upstream of the second opening 15b in the direction of arrow g, which allows airflow to communicate between the developing chamber 11 and the stirring chamber 12. With respect to the direction of arrow g, the downstream end of the third opening 15c is located downstream of the downstream end of the discharge port 20.

Description

[Technical Field]

[0001] The present invention relates to a developing device that develops an electrostatic latent image with a developer. [Background technology]

[0002] In image forming apparatuses using electrophotography or the like, an electrostatic latent image formed on an image carrier such as a photosensitive drum is developed into a toner image by a developing device. Specifically, a developer is carried on a developer carrier provided in the developing device, and the developer is supplied to the image carrier at a development position to form a toner image. Conventionally, such developing devices use a two-component developer containing toner and carrier. In developing devices using a two-component developer, a developer container containing the developer includes a first chamber for supplying the developer to the developer carrier, a second chamber separated from the first chamber by a partition wall, and a communication portion provided in the partition wall that allows the developer to communicate between the first and second chambers. A first conveying screw and a second conveying screw are disposed in the first and second chambers, respectively, to convey the developer. The first and second conveying screws are rotated to agitate and circulate the developer between the first and second chambers.

[0003] In addition, in such a developing device, a configuration employing a so-called ACR (Auto Carrier Refresh) method is known in which a developer container is provided with a discharge port for discharging developer, and deteriorated developer in the developer container is gradually discharged from the discharge port. For example, Patent Document 1 discloses a configuration in which a discharge port is provided in a first chamber downstream of a communication portion that allows developer to communicate from the first chamber to the second chamber. Furthermore, Patent Document 2 discloses a configuration in which a discharge port is provided in a first chamber upstream of a communication portion that allows developer to communicate from the second chamber to the first chamber. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-98422 [Patent Document 2] Japanese Patent Application Laid-Open No. 2018-10078 Summary of the Invention [Problem to be solved by the invention]

[0005] Here, the rotation of the developer carrier draws air currents from the outside into the inside of the developing device. Particularly when the developer carrier rotates at high speed, air currents may be generated inside the developing container toward the discharge port, which may then escape to the outside through the discharge port. When such air currents are generated, the developer in the developing container may be mixed with the air current and discharged through the discharge port, potentially reducing the amount of developer in the developing container. In this case, the amount of developer supplied to the developer carrier also decreases, potentially affecting the output image and resulting in abnormal images.

[0006] An object of the present invention is to provide a configuration that can suppress the occurrence of abnormal images. [Means for solving the problem]

[0007] The developing device of the present invention includes a developer carrier that carries and transports developer containing toner and a carrier to a development position; a developer container that contains the developer, the developer container having a first chamber for supplying the developer to the developer carrier, a second chamber that is partitioned from the first chamber by a partition wall, a first communication portion that is provided in the partition wall and allows the developer to communicate from the first chamber to the second chamber, and a second communication portion that is provided in the partition wall and allows the developer to communicate from the second chamber to the first chamber; and a first transport screw provided in the first chamber, the first transport screw having a first portion that transports the developer in a first direction from the second communication portion toward the first communication portion, and a second portion that is located upstream of the first portion in the first direction and transports a portion of the developer that has flowed into the first chamber from the second communication portion in a direction opposite to the first direction. The developer container is provided with a clew, and a second conveying screw provided in the second chamber, the second conveying screw having a third portion that conveys developer in a second direction from the first communicating portion toward the second communicating portion, and a fourth portion that is located downstream in the second direction from the third portion and conveys the developer that has been conveyed downstream in the second direction from the second communicating portion in a direction opposite to the second direction, wherein the developing container has, in the first chamber, an outlet that is located upstream in the first direction from the second communicating portion and that discharges the developer conveyed by the second portion, and a third communicating portion that is provided upstream in the first direction from the second communicating portion of the partition and that allows air flow to communicate between the first chamber and the second chamber, and wherein, with respect to the first direction, the downstream end of the third communicating portion is located downstream of the downstream end of the outlet. [Effects of the Invention]

[0008] According to the present invention, the occurrence of abnormal images can be suppressed. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram illustrating the configuration of an image forming apparatus according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing the schematic configuration of the developing device according to the first embodiment. [Figure 3]FIG. 2 is a vertical cross-sectional view showing the schematic configuration of the developing device according to the first embodiment. [Figure 4] FIG. 3 is a diagram illustrating the flow of air currents in the developing device according to the first embodiment. [Figure 5] FIG. 2 is an enlarged vertical cross-sectional view of a schematic configuration of a discharge port side portion of the developing device according to the first embodiment. [Figure 6] FIG. 4 is a schematic view of the feed screw cut in a direction perpendicular to the rotation axis in the region of the third opening. [Figure 7] FIG. 4 is a schematic diagram of the stirring screw cut in a direction perpendicular to the rotation axis direction in the region of the third opening. [Figure 8] (a) A schematic diagram of the developing device cut at a first opening, (b) A schematic diagram of the developing device cut at a second opening, and (c) A schematic diagram of the developing device cut at a third opening. [Figure 9] 6 is a graph showing the relationship between the amount of developer in the developing device and the amount of developer discharged from the discharge port. [Figure 10] Graphs showing the relationship between the amount of developer and the discharge amount when the rotation speed of the developing sleeve is low and high, respectively, for (a) a comparative example without a third opening, and (b) an example with a third opening. [Figure 11] FIG. 10 is a vertical cross-sectional view showing the schematic configuration of a developing device according to a second embodiment. [Figure 12] FIG. 10 is a diagram illustrating the flow of air currents in a developing device according to a second embodiment. [Figure 13] FIG. 11 is a vertical cross-sectional view showing the schematic configuration of a developing device according to a third embodiment. [Figure 14] 10A and 10B are diagrams illustrating the flow of air currents in a developing device according to a third embodiment. [Figure 15] FIG. 10 is an enlarged vertical cross-sectional view of a schematic configuration of a developing device according to a fourth embodiment, showing a discharge port side portion thereof. [Figure 16] FIG. 10 is a perspective view showing a discharge port side portion of a developing device according to a fourth embodiment, with some parts omitted. [Figure 17] 10A and 10B are diagrams illustrating the relationship between the discharge port and the third opening of the developing device according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] First Embodiment The first embodiment will be described with reference to Figures 1 to 10. First, the schematic configuration of an image forming apparatus according to this embodiment will be described with reference to Figure 1.

[0011] [Image forming equipment] Image forming apparatus 100 is an electrophotographic full-color printer having four image forming units PY, PM, PC, and PK corresponding to the four colors of yellow, magenta, cyan, and black. In this embodiment, the image forming units PY, PM, PC, and PK are arranged in tandem along the rotation direction of an intermediate transfer belt 24 (described later). Image forming apparatus 100 forms a toner image (image) on recording material 27 in response to an image signal from a document reading device (not shown) connected to the image forming apparatus main body or a host device such as a personal computer connected to the image forming apparatus main body so as to be able to communicate with the image forming apparatus main body. Examples of recording materials include sheet materials such as paper, plastic film, and cloth.

[0012] To briefly explain this image formation process, first, each image forming station PY, PM, PC, and PK forms a toner image of each color on a photosensitive drum 28Y, 28M, 28C, or 28K, respectively. The toner image of each color thus formed is transferred onto an intermediate transfer belt 24, and then transferred from the intermediate transfer belt 24 onto a recording material 27. The recording material onto which the toner image has been transferred is transported to a fixing device 25, where the toner image is fixed to the recording material. This process will be explained in detail below. Each image forming station PY, PM, PC, and PK is composed of a drum cartridge having a photosensitive drum 28Y, 28M, 28C, or 28K, which is detachable from the image forming apparatus main body, and a developing device (developing cartridge) 1Y, 1M, 1C, or 1K. These may be integrated into a process cartridge that is detachable from the image forming apparatus main body.

[0013] The four image forming units PY, PM, PC, and PK included in the image forming apparatus 100 have substantially the same configuration except for the different developing colors. Therefore, the following description will focus on the image forming unit PY as a representative, and the configurations of the other image forming units will be shown by replacing the suffix "Y" in the reference numerals attached to the configuration of the image forming unit PY with M, C, and K, respectively, and descriptions thereof will be omitted.

[0014] The image forming station PY is provided with a cylindrical photosensitive member, i.e., a photosensitive drum 28Y, as an image carrier. The photosensitive drum 28Y is driven to rotate in the direction of the arrow in the figure at a predetermined process speed (circumferential speed). A charging roller 21Y (charging device), a developing device 1Y, a primary transfer roller 23Y, and a cleaning device 26Y are arranged around the photosensitive drum 28Y. An exposure device (laser scanner) 22Y is arranged above the photosensitive drum 28Y in the figure.

[0015] The charging roller 21Y is rotated by the photosensitive drum 28Y during image formation. The charging roller 21Y is biased toward the photosensitive drum 28Y by a pressure spring (not shown). A charging bias is applied to the charging roller 21Y from a high-voltage power supply. As a result, the photosensitive drum 28Y is almost uniformly charged by the charging roller 21Y.

[0016] An intermediate transfer belt 24 is disposed facing the photosensitive drums 28Y, 28M, 28C, and 28K. The intermediate transfer belt 24 is tensioned by a plurality of tension rollers including an inner secondary transfer roller 29a, and is rotated in the direction of the arrow in the figure by the drive of a drive roller among the plurality of tension rollers. An outer secondary transfer roller 29b as a secondary transfer member is disposed at a position facing the inner secondary transfer roller 29a across the intermediate transfer belt 24, and constitutes a secondary transfer unit T2 that transfers the toner image on the intermediate transfer belt 24 to a recording material P. A fixing device 25 is disposed downstream of the secondary transfer unit T2 in the recording material conveyance direction.

[0017] The process of forming an image by the image forming apparatus 100 configured as described above will be described. First, when the image forming operation starts, the surface of the rotating photosensitive drum 28Y is uniformly charged by the charging roller 21Y. Next, the photosensitive drum 28Y is exposed to laser light L corresponding to an image signal emitted from the exposure device 22Y. As a result, an electrostatic latent image corresponding to the image signal is formed on the photosensitive drum 28Y. The electrostatic latent image on the photosensitive drum 28Y is visualized by toner contained in the developing device 1Y, becoming a visible image (toner image).

[0018] The toner image formed on the photosensitive drum 28Y is primarily transferred onto the intermediate transfer belt 24 at a primary transfer section T1Y configured between the photosensitive drum 28Y and a primary transfer roller 23Y arranged across the intermediate transfer belt 24. Toner remaining on the surface of the photosensitive drum 28Y after the primary transfer (transfer residual toner) is removed by a cleaning device 26Y.

[0019] This operation is also performed in turn in each of the magenta, cyan, and black image forming units, and the four color toner images are superimposed on the intermediate transfer belt 24. Thereafter, in synchronization with the timing of toner image formation, a recording material 27 stored in a recording material storage cassette (not shown) is conveyed to the secondary transfer unit T2, and the four color toner images on the intermediate transfer belt 24 are secondarily transferred all at once onto the recording material 27. Any toner that was not transferred at the secondary transfer unit T2 and remains on the intermediate transfer belt 24 is removed by an intermediate transfer belt cleaner 24a.

[0020] Next, the recording material 27 is conveyed to the fixing device 25. The fixing device 25 applies heat and pressure to the toner on the recording material 27, melting and mixing the toner, and fixing the toner as a full-color image to the recording material 27. The recording material 27 is then discharged outside the machine. This completes the image forming process. It is also possible to form a desired single-color or multi-color image using only the desired image forming units.

[0021] [Developing device] Next, developing device 1Y will be described with reference to Figures 2 and 3. The same applies to developing devices 1M, 1C, and 1K. Developing device 1Y has a developing container 2 that contains a two-component developer containing non-magnetic toner and magnetic carrier. The developing container 2 has an opening in the development area facing photosensitive drum 28Y, and a developing sleeve 3 serving as a developer carrier, with a magnet roll 4 non-rotatingly disposed inside, is rotatably installed so as to be partially exposed to this opening.

[0022] In this embodiment, the developing sleeve 3 is made of a non-magnetic material and rotates at a predetermined process speed (circumferential speed) during development in the direction of the arrow in Fig. 2. The magnetic roll 4, which serves as a magnetic field generating means, has five magnetic poles, N1, N2, N3, S1, and S2, arranged in the circumferential direction, and the magnetic field generated causes the developer to be carried on the surface of the developing sleeve 3.

[0023] That is, the developing sleeve 3 rotates in the direction of the arrow in the figure, transporting the developer attracted at the N1 pole (attraction pole) of the magnetic roll 4 toward the blade 5, which serves as a regulating member. The developer formed into chains on the developing sleeve 3 by the S1 pole passes through the gap between the developing sleeve 3 and the blade 5 while its amount is regulated by the blade 5, forming a developer layer of a predetermined thickness on the developing sleeve 3. The developer layer is then carried and transported to the development area (development position) facing the photosensitive drum 28, where it develops the electrostatic latent image formed on the surface of the photosensitive drum 28 with the magnetic chains formed by the N2 pole. After being used for development, the developer is transported to the magneticless zone between the N3 pole (separation pole) and the N1 pole, where it is peeled off from the developing sleeve 3 and taken into the developer circulation path.

[0024] In this embodiment, a blade 5 is arranged below the developing sleeve 3 to regulate the developer on the upstream side of the rotation direction of the surface of the developing sleeve 3 in the development area, which is the opposing portion between the photosensitive drum 28Y and the developing sleeve 3.

[0025] The interior of the developing container 2 is partitioned by a vertically extending partition wall (partition member) 15 into a developing chamber 11 as a first chamber and an agitating chamber 12 as a second chamber. As shown in FIG. 3 , a first opening 15a and a second opening 15b are provided at both ends of the partition wall 15 in the longitudinal direction (the direction of the rotation axis of the developing sleeve 3) as a first communication portion and a second communication portion that communicate the developing chamber 11 and the agitating chamber 12, respectively. The first opening 15a allows the developer to communicate from the developing chamber 11 to the agitating chamber 12. The second opening 15b allows the developer to communicate from the agitating chamber 12 to the developing chamber 11. This forms a developer circulation path between the developing chamber 11 and the agitating chamber 12. In this embodiment, a third opening 15c is provided in the partition wall 15 as a third communication portion, which will be described later.

[0026] Further, in the developing container 2, there are arranged a supply screw 13 as a first conveying screw and a stirring screw 14 as a second conveying screw, each of which stirs and conveys the developer.

[0027] The supply screw 13 is disposed in the developing chamber 11, and conveys the developer in the developing chamber 11 (first chamber) while stirring it in a first direction (the direction of arrow g in FIG. 3) from the second opening 15b toward the first opening 15a, and supplies the developer to the developing sleeve 3. The stirring screw 14 is disposed in the stirring chamber 12, and conveys the developer in the stirring chamber 12 (second chamber) while stirring it in a second direction (the direction of arrow h in FIG. 3) from the first opening 15a toward the second opening 15b. The second direction is opposite to the first direction. In this way, the developer is conveyed by the supply screw 13 and the stirring screw 14, and circulates within the developing container 2 via the first opening 15a and the second opening 15b.

[0028] Since the developing device 1 uses a two-component developer, developer is appropriately replenished into the developing device 1 through a supply port 19 (FIG. 3) provided in a part of the developing device 1 in accordance with toner consumption in the developing device 1. Specifically, a supply transport path 19a is connected to the upstream side in the transport direction (upstream side in the second direction) of the agitating screw 14 of the stirring chamber 12. The supply transport path 19a is for supplying replenishment developer to the circulation path, and a supply port 19 is provided in the supply transport path 19a. The supply port 19 is connected to a supply transport section (supply pipe) of a developer replenishment device (not shown). The agitating screw 14 extends from the supply transport path 19a, and the developer replenished through the supply port 19 is transported into the circulation path by the agitating screw 14.

[0029] The supplied developer is stirred and mixed together with the developer in the developing device 1Y while being transported in the circulation path by the stirring screw 14 and the supply screw 13. In this way, a part of the developer stirred and mixed by the stirring screw 14 and the supply screw 13 is supplied to the surface of the developing sleeve 3 and carried on the surface.

[0030] In this embodiment, a two-component development system is used, and the developer is a mixture of negatively charged non-magnetic toner and magnetic carrier. The non-magnetic toner is made by incorporating colorants, wax components, etc. into resins such as polyester or styrene acrylic, which are then pulverized or polymerized to form a powder, to which fine powders such as titanium oxide and silica are added on the surface. The magnetic carrier is made by applying a resin coating to the surface of a core made of resin particles kneaded with ferrite particles or magnetic powder. In this embodiment, the toner concentration in the developer in the initial state (weight ratio of toner contained in the developer) is 10%.

[0031] Generally, in two-component development using toner and carrier, the toner and carrier are charged to a predetermined polarity by frictional contact, which means that the toner is subjected to less stress than in single-component development using a single-component developer.

[0032] Furthermore, because the surface area of ​​the carrier in the developer is larger than that of the toner, the carrier is less likely to become soiled by toner adhering to its surface in the early stages of use. However, with long-term use, the amount of dirt (spent) adhering to the carrier surface increases, gradually reducing the carrier's ability to charge the toner. This results in problems such as fogging and toner scattering. While it is conceivable to increase the life of a two-component development device by increasing the amount of carrier contained in the device, this is undesirable because it would increase the size of the device.

[0033] For this reason, the developing device 1Y of this embodiment employs an ACR (Auto Carrier Refresh) system. As described above, the ACR system gradually replenishes new developer into the developer container 2 and gradually discharges developer with deteriorated charging performance from the developing device, thereby suppressing the increase of deteriorated carrier. This developing device 1Y utilizes fluctuations in the volume of the developer to discharge excess deteriorated developer and maintain a roughly constant volume level of the developer in the developer container 2. With this ACR-type developing device 1Y, deteriorated carrier in the developer container 2 is gradually replaced with new carrier, making it possible to maintain a roughly constant charging performance of the carrier in the developer container 2. The ACR-type developing device 1Y uses a replenishment developer with a high toner ratio. Typically, the weight ratio of carrier to toner is about 5 to 10%. In other words, the replenishment developer has a toner concentration of 90% or more, for example, about 90 to 95% (90% or more and 95% or less).

[0034] 2, the top plate portion 2b covering the upper part of the stirring chamber 12 of the developing container 2 is provided with an exhaust port 16 that can exhaust airflow from the inside of the stirring chamber 12 to the outside. In this embodiment, the top plate portion 2b is arranged so as to cover the upper parts of the developing chamber 11 and the stirring chamber 12, and the exhaust port 16 is formed above the stirring screw 14 arranged in the stirring chamber 12.

[0035] The developing device 1Y will be described in more detail with reference to FIG. 3. The arrows in the figure indicate the flow of developer transported by the rotation of the supply screw 13 and the stirring screw 14, respectively. As described above, the developing device 1Y has two storage chambers for storing developer, consisting of the developing chamber 11 and the stirring chamber 12, provided in the developer container 2. These two storage chambers are separated from each other by a partition wall 15. The developing chamber 11 is provided with the supply screw 13, and the stirring chamber 12 is provided with the stirring screw 14.

[0036] Both the supply screw 13 and the stirring screw 14 extend in a rod-like shape and are disposed horizontally and parallel to each other. The supply screw 13 has a rotation shaft (first rotation shaft) 13a with a circular cross section and a helical blade 13b as a first blade that is spirally provided around the rotation shaft 13a in the direction of the rotation axis. Similarly to the supply screw 13, the stirring screw 14 also has a rotation shaft (second rotation shaft) 14a with a circular cross section and a helical blade 14b that is spirally provided around the rotation shaft 14a in the direction of the rotation axis. Both the supply screw 13 and the stirring screw 14 are provided with helical blades other than the helical blades 13b and 14b, which will be described later.

[0037] The helical blade 13b of the supply screw 13 and the helical blade 14b of the stirring screw 14 are helical blades that revolve in opposite directions, and when the supply screw 13 and the stirring screw 14 rotate, the developer in the developing chamber 11 and the stirring chamber 12 is stirred and transported in opposite directions. That is, the developer in the developing chamber 11, in which the supply screw 13 is located, is transported in the direction of arrow g of the supply screw 13, and the developer in the stirring chamber 12, in which the stirring screw 14 is located, is transported in the direction of arrow h of the stirring screw 14.

[0038] Meanwhile, a first opening 15a and a second opening 15b connecting the developing chamber 11 and the stirring chamber 12 are formed at both ends of the partition wall 15 separating the developing chamber 11 and the stirring chamber 12. Therefore, the developer in the developing chamber 11 transported in the direction of arrow g flows into the stirring chamber 12 through the first opening 15a, and the developer in the stirring chamber 12 transported in the direction of arrow h flows into the developing chamber 11 through the second opening 15b. In this way, the developer in the developing device 1 circulates while being stirred within the developing chamber 11 and the stirring chamber 12. Note that areas d1 and d2 shown in FIG. 3 indicate the opening areas of the first opening 15a and the second opening 15b provided in the partition wall 15 separating the developing chamber 11 and the stirring chamber 12.

[0039] The developing device 1Y also includes a developing sleeve 3 at a position adjacent to the developing chamber 11 in which the supply screw 13 is disposed. A part of the developing sleeve 3 is exposed from the developing container 2. The developing device 1Y is disposed in the image forming apparatus 100 (see FIG. 1) so that the exposed part of the developing sleeve 3 is close to the photosensitive drum 28Y.

[0040] The developing sleeve 3 magnetically adheres the developer in the developing chamber 11 to its surface, and rotates in the direction of the arrow in Figure 2, transporting the developer to a position (developing position) facing the photosensitive drum 28Y. Then, the electrostatic latent image formed on the surface of the photosensitive drum 28Y is developed with the toner in the developer, and a toner image is formed on the surface of the photosensitive drum 28Y. Meanwhile, after development with the toner, the developer adhering to the surface of the developing sleeve 3 returns into the developing container 2 as the developing sleeve 3 rotates, separates from the developing sleeve 3, and is stirred while circulating together with the other developer in the developing chamber 11.

[0041] When development using toner as described above is repeated, the toner in the developer inside the developing container 2 decreases. Therefore, the developing container 2 is provided with a supply port 19 for receiving a supply of developer containing toner. The developer inside the developer container 8 shown in FIG. 1 is supplied into the developing device 1 through the supply port 19 by a developer supply device. As shown in FIG. 3, the supply port 19 is provided further upstream (opposite the direction of arrow h) of the first opening 15a of the stirring chamber 12 in which the stirring screw 14 is disposed. The stirring screw 14 extends to the position where the supply port 19 is provided, and the developer supplied from the supply port 19 is transported downstream (in the direction indicated by arrow h) inside the stirring chamber 12. Then, the developer merges with the developer that has flowed in through the first opening 15a and is transported further downstream (in the direction indicated by arrow h) inside the stirring chamber 12.

[0042] A discharge port 20 that opens downward is provided in the bottom plate portion 2a of the developer container 2 (the lower surface of the developer container 2, see Figure 2) to gradually discharge the developer in the developer container 2. The developer in the developing device 1 is discharged little by little from this discharge port 20, which prevents the developer in the developing device 1 from excessively deteriorating due to stirring and transport. Not only toner but also carrier is discharged from the discharge port 20. For this reason, the developer replenished from the replenishing port 19, i.e., the developer in the developer container 8, contains not only toner but also a small amount of carrier to compensate for the loss of carrier.

[0043] The discharge port 20, which gradually discharges the developer in the developer container 2, is located at the position indicated by the dashed line in FIG. 3 and opens downward. That is, the discharge port 20 is located further upstream than the second opening 15b, into which the developer in the stirring chamber 12 flows, in terms of the transport direction (arrow g direction) of the developer in the developing chamber 11 in which the supply screw 13 is disposed. Most of the developer that flows into the developing chamber 11 through the second opening 15b is transported downstream (arrow g direction), but some of the developer proceeds upstream (opposite to the arrow g direction), i.e., toward the discharge port 20, and is discharged from the developing device 1 through the discharge port 20 to the outside of the developing device 1Y. The developer discharged from the discharge port 20 to the outside of the developing device 1Y passes through a recovered toner discharge path (not shown) and is stored in a recovered toner tank (not shown).

[0044] [Configuration of each screw] Next, the configuration of each screw of the developing device 1Y will be described. First, the stirring screw 14 is a screw that transports the developer in the stirring chamber 12 in the direction of the arrow h. That is, the stirring screw 14 has a spiral blade 14b provided around a rotation shaft 14a, and when the stirring screw 14 rotates, the spiral blade 14b transports the developer in the direction of the arrow h (second direction). The stirring screw 14 extends to the supply port 19, and the developer supplied from the supply port 19 is also transported in the direction of the arrow h.

[0045] Additionally, another helical blade 14c, which rotates in the opposite direction to helical blade 14b, is provided downstream of agitating screw 14 in the direction of arrow h. When the developer pushed by helical blade 14b of agitating screw 14 in the direction of arrow h attempts to proceed further downstream than second opening 15b, it is pushed back by helical blade 14c, which rotates in the opposite direction. Helical blade 14c is spirally provided around rotation shaft 14a so as to transport the developer in the direction opposite to the direction of arrow h. That is, agitating screw 14 has a third portion that transports developer in the direction of arrow h (second direction), and a fourth portion that is located downstream of the third portion in the direction of arrow h (downstream in the second direction) and transports developer that has been transported downstream of second opening 15b in the direction opposite to the direction of arrow h. Helical blade 14b is provided in the third portion, and helical blade 14c is provided in the fourth portion. Therefore, the developer transported to the second opening 15b in the direction of the arrow h passes through the second opening 15b and is delivered to the developing chamber 11. The fourth portion extends in the direction of the arrow h to an area where a third opening 15c, which will be described later, is located.

[0046] Next, the structure of the supply screw 13 will be described. Basically, the supply screw 13 transports the developer that has flowed into the developing chamber 11 through the second opening 15b provided in the region d2, in the direction of arrow g, to the first opening 15a provided in the region d1, using the spiral blade 13b. The screw then serves to transfer the transported developer from the first opening 15a toward the stirring chamber 12.

[0047] The supply screw 13 is provided with a helical blade 13f downstream of the helical blade 13b, which rotates in the opposite direction to the helical blade 13b. The helical blade 13f is spirally provided around the rotation shaft 13a so as to transport the developer in the direction opposite to the direction of arrow g. The boundary between these two helical blades 13b and the helical blade 13f is within the region d1 where the first opening 15a is provided. Therefore, the developer transported in the direction of arrow g is prevented from advancing further by the helical blade 13f, and flows into the stirring chamber 12 through the first opening 15a.

[0048] Further, this supply screw 13 is provided with a short helical blade 13c that is located upstream of helical blade 13b in the developer transport direction (first direction) indicated by the arrow g direction and within region d2 of second opening 15b that receives developer from stirring chamber 12 in which stirring screw 14 is disposed. This helical blade 13c revolves in the opposite direction to helical blade 13b and plays a role in pushing part of the developer that has passed through second opening 15b upstream, in the direction opposite to the arrow g direction.

[0049] Furthermore, another helical blade 13d is provided further upstream (opposite the direction of arrow g) of helical blade 13c, which is provided in region d2 of second opening 15b and rotates in the opposite direction, on supply screw 13. This helical blade 13d rotates in the same direction as helical blade 13b, which is responsible for transporting developer in the direction of arrow g.

[0050] Here, helical blade 13c provided within region d2 of second opening 15b pushes some of the developer that has flowed into developing chamber 11 through second opening 15b upstream (toward helical blade 13d). On the other hand, helical blade 13d provided upstream of helical blade 13c is a helical blade that rotates in the same direction as helical blade 13b, which transports developer in the direction of arrow g, and therefore pushes back the developer that has been pushed upstream by helical blade 13c downstream (in the direction of arrow g). Then, some of the developer in the region between helical blade 13c and helical blade 13d advances further upstream against the barrier created by helical blade 13d that tries to push it back downstream.

[0051] Furthermore, another helical blade 13e is provided further upstream of helical blade 13d of supply screw 13. This helical blade 13e serves to transport the developer that has advanced upstream over the barrier created by helical blade 13d, which tries to push the developer back downstream, further upstream (in the direction opposite to the direction of arrow g) to discharge port 20.

[0052] That is, supply screw 13 has a first portion that transports developer in the direction of arrow g (first direction), and a second portion that is located upstream of the first portion in the direction of arrow g (upstream in the first direction) and transports a portion of the developer that has flowed into developing chamber 11 from second opening 15b in the direction opposite to the direction of arrow g. Helical blade 13b, serving as a first blade, is disposed in the first portion and spirals around rotation shaft 13a to transport developer in the direction of arrow g. Helical blades 13c, 13d, and 13e, serving as second, third, and fourth blades, are disposed in the second portion.

[0053] Helical blade 13c as the second blade is spirally provided around rotating shaft 13a so as to transport developer in the direction opposite to the direction of arrow g. Helical blade 13d as the third blade is located upstream of second portion helical blade 13c in the direction of arrow g and is spirally provided around rotating shaft 13a so as to transport developer in the direction of arrow g. Helical blade 13e as the fourth blade is located upstream of second portion helical blade 13d in the direction of arrow g and is spirally provided around rotating shaft 13a so as to transport developer that has passed over helical blade 13d toward discharge outlet 20 in the direction opposite to the direction of arrow g.

[0054] Furthermore, at the most upstream side in the direction of arrow g of supply screw 13, there is provided helical blade 13g which serves to transport developer downstream in the direction of arrow g (downstream in the first direction) so as to push back toward discharge outlet 20 any developer that has been transported by helical blade 13e and passed through discharge outlet 20 but has not been successfully discharged from discharge outlet 20. That is, helical blade 13g is provided in a spiral shape around rotation shaft 13a so as to transport the developer in the direction of arrow g.

[0055] Here, by adopting the above-described configuration, the amount of developer discharged from the discharge port 20 is discharged little by little when there is a large amount of developer in the developing device 1Y. However, the developer discharged from the discharge port 20 is divided into two types: one that is transported to the discharge port 20 by the rotation of the supply screw 13 and the other that is carried to the discharge port 20 by the air current flowing inside the developing device 1Y.

[0056] The air current flowing inside the developing device 1Y is mainly drawn in from outside the developing device 1Y by the rotation of the developing sleeve 3, the supply screw 13, and the stirring screw 14. The developer stirred up by the rotation of the supply screw 13 and the stirring screw 14, and part of the developer separated from the non-magnetic zone (shown in FIG. 2) of the developing sleeve 3 described above, mix with the air current and flow through the developing device 1Y.

[0057] In particular, in a configuration in which the discharge port 20 is located on the supply screw 13 side, i.e., on the developing chamber 11 side closer to the developing sleeve 3, the airflow drawn in by the rotation of the developing sleeve 3 and supply screw 13 has a large effect on the amount of developer discharged from the discharge port 20. In particular, when the process speed itself of the image forming apparatus 100 is fast, if the rotation speeds of the developing sleeve 3, supply screw 13, and stirring screw 14 are fast, the amount of air drawn in from outside the developing device 1Y also increases, and the amount of developer mixed with the airflow inside the developing device 1Y and flowing away increases.

[0058] [Air flow inside the developing unit] Here, the airflow in the developing device 1Y will be described with reference to FIG. 4. Due to the rotation of the developing sleeve 3 and the supply screw 13, an airflow as indicated by the arrows in FIG. 4 flows from the outside into the vicinity of the supply screw 13 inside the developing device 1Y. As will be described in detail later, this airflow then flows from the supply screw 13 toward the agitator screw 14. In the developing device 1Y, an exhaust port 16 (see FIG. 2) is disposed above the agitator screw 14, and the airflow that has flowed toward the agitator screw 14 escapes to the outside of the developing device 1Y through the exhaust port 16 of the developing device 1Y. As described above, the exhaust port 16 serves to exhaust air from the inside of the developing device 1Y to the outside, and a collecting member such as a filter is disposed in the exhaust port 16 to prevent the developer inside from escaping outside the developing device 1Y. However, the exhaust port 16 does not necessarily need to be provided with a collecting member.

[0059] Next, we will explain the flow of air toward the upstream side of supply screw 13. Because developer is transferred from the agitating screw 14 side to the supply screw 13 side at second opening 15b formed in partition wall 15, the developer surface height in region d2 naturally becomes high. As a result, the space in region d2 is occupied by developer, and because developer is transported from the agitating screw 14 side to the supply screw 13 side, it is difficult for air to flow from the supply screw 13 side to the agitating screw 14 side, and most of the airflow continues to flow further upstream in the transport direction of supply screw 13 (the direction of arrow g in Figure 3).

[0060] [Third opening] For this reason, in this embodiment, a third opening 15c is provided in the partition wall 15 as a third communication portion, and d3 indicates the area where the third opening 15c is located. That is, the third opening 15c is provided upstream of the second opening 15b in the partition wall 15 in the direction of arrow g, and allows airflow to communicate between the developing chamber 11 and the stirring chamber 12. In addition, with respect to the direction of arrow g, the downstream end of the third opening 15c is located downstream of the downstream end of the discharge port 20. In addition, the opening area of ​​the third opening 15c is larger than the opening area of ​​the discharge port 20.

[0061] That is, by arranging the third opening 15c downstream of the supply screw 13 in the direction of arrow g with respect to the discharge port 20, the airflow that did not flow from the supply screw 13 to the agitating screw 14 in region d2 is sent from the supply screw 13 to the agitating screw 14 side in region d3. At this time, the helical blade 14c on the agitating screw 14 side rotates in the direction of transport from region d3 to region d2 as shown in Figures 3 and 4, and the rotation of the helical blade 14c functions to draw the airflow from the supply screw 13 side to the agitating screw 14 side in region d3.

[0062] The airflow drawn from the supply screw 13 side to the stirring screw 14 side will be described in more detail below. Fig. 5 is an enlarged view of the vicinity of region d2 and region d3 in Figs. 3 and 4. Figs. 6 and 7 are cross-sectional views of the supply screw 13 and the stirring screw 14 in Fig. 5 cut in a direction perpendicular to the longitudinal direction at region d3.

[0063] First, for helical blade 13e of supply screw 13 and helical blade 14c of agitator screw 14 in region d3, the areas through which helical blades 13e and 14c pass when supply screw 13 and agitator screw 14 rotate as desired, i.e., the volumes of the spaces through which the blades pass, are compared. Note that helical blade 13e corresponds to the first chamber-side blade spirally arranged around rotation shaft 13a so as to transport developer toward discharge outlet 20 in the area where third opening 15c is located in the direction of arrow g. Furthermore, helical blade 14c corresponds to the second chamber-side blade spirally arranged around rotation shaft 14a so as to transport developer in the area where third opening 15c is located in the direction of arrow h.

[0064] As shown in Figures 5 and 6, for the helical blade 13e, when the pitch per rotation of the helical blade is 13eP, the diameter of the helical blade is 13eL, and the diameter of the rotation shaft 13a of the supply screw 13 is 13aL, the volume 13eV passing through when the helical blade 13e makes one rotation is expressed by the following formula. (1) 13 eV = π × ((13 eL / 2) 2 -(13aL / 2) 2 )×13eP

[0065] Similarly, as shown in Figures 5 and 7, when the pitch of the helical blade 14c per rotation of the helical blade is 14cP, the diameter of the helical blade is 14cL, and the diameter of the rotation shaft 14a of the stirring screw 14 is 14aL, the volume 14cV passing through the helical blade 14c when it makes one rotation is expressed by the following formula. (2) 14cV = π × ((14cL / 2) 2 -(14aL / 2) 2 )×14cP

[0066] As described above, 13eV and 14cV in equations (1) and (2) represent the volume of the space through which helical blade 13e and helical blade 14c pass when supply screw 13 and stirring screw 14 rotate once. This volume corresponds to the amount of airflow drawn in from the area outside the helical blades when helical blades 13e and 14c rotate. In other words, the larger the volume of the space through which the helical blade passes when it rotates once, the larger the airflow drawn in by the helical blade.

[0067] In this embodiment, in the region d3, the relationship between 13 eV and 14 cV in the expressions (1) and (2) is as follows: (3) 14cV≧13e

[0068] Equation (3) indicates that in region d3, the airflow flows from the supply screw 13 side to the stirring screw 14 side. In particular, in this embodiment, it is preferable to make the region through which the spiral blade 14c passes per unit time due to the rotation of the rotary shaft 14a larger than the region through which the spiral blade 13e passes per unit time due to the rotation of the rotary shaft 13a. That is, 14cV>13eV It is preferable to have the following relationship.

[0069] In the above embodiment, the supply screw 13 and the stirring screw 14 are single-thread screws with a single blade, but the supply screw 13 and the stirring screw 14 may also be multi-thread screws with multiple blades. The number of blades of the multi-thread screws is set to 13eM for the helical blade 13e and 14cM for the helical blade 14c, and in addition, taking into consideration the case where the rotation speeds per unit time of the supply screw 13 and the stirring screw 14 are different, the rotation speeds per unit time are set to 13N and 14N, respectively. In this case, it is preferable to satisfy the following formula: (4) [14cV × 14cM × 14N] ≥ [13eV × 13eM × 13N]

[0070] In addition to the relationship between the spiral blades 13e and 14c of the supply screw 13 and the stirring screw 14 as described above, the third opening 15c is positioned downstream of the discharge outlet 20 in the direction of arrow g in the longitudinal direction of the supply screw 13, so that the airflow flowing in from region d2 flows into the stirring screw 14 side from the third opening 15c in region d3 before reaching the discharge outlet 20.

[0071] Here, the term "third opening 15c downstream of discharge outlet 20 in the direction of arrow g" means that, as shown in Fig. 5, tip end (downstream end) 15cW of third opening 15c is located downstream of discharge outlet 20 and tip end (downstream end) 20W in the direction of arrow g. That is, the entire third opening 15c does not have to be located downstream of tip end 20W of discharge outlet 20 in the direction of arrow g. However, the entire third opening 15c may be located downstream of tip end 20W of discharge outlet 20 in the direction of arrow g.

[0072] [About the height of each opening] Next, the height direction of the wall surfaces of first opening 15a, second opening 15b, and third opening 15c will be described. Figures 8(a) to 8(c) show cross-sectional views of first opening 15a, second opening 15b, and third opening 15c. Figure 8(a) is a cross-sectional view of first opening 15a, Figure 8(b) is a cross-sectional view of second opening 15b, and Figure 8(c) is a cross-sectional view of third opening 15c.

[0073] 8(a) to 8(c), the developer surface height toward the discharge port 20 is lower than the developer surface height in regions d1 and d2 of the first opening 15a and the second opening 15b, where the developer is transferred between the stirring screw 14 side (stirring chamber 12) and the supply screw 13 side (developing chamber 11). In this embodiment, the heights of the partition wall 15 are different in regions d1, d2, and d3 of the first opening 15a, the second opening 15b, and the third opening 15c. That is, in the vertical direction, the lower end of the opening of the third opening 15c is positioned higher than the lower ends of the openings of the first opening 15a and the second opening 15b.

[0074] Basically, the developer is transferred through the regions d1 and d2 of the first opening 15a and the second opening 15b, and circulates between the developing chamber 11 and the stirring chamber 12. Therefore, if the height of the partition wall 15 at the first opening 15a and the second opening 15b is too high, the developer transferability will be reduced.

[0075] On the other hand, the purpose of the third opening 15c is to send the airflow flowing toward the discharge port 20 into the stirring chamber 12 in the region d3. In addition, the developer that has advanced upstream over the barrier created by the spiral blade 13d of the supply screw 13, which tries to push it back downstream, is excess developer, so it is basically desirable to transport it to the discharge port 20 without passing it to the stirring chamber 12.

[0076] Therefore, by making the height of the third opening 15c higher than the heights of the first opening 15a and the second opening 15b, generally, only the airflow flowing toward the discharge outlet 20 is sent into the stirring chamber 12 in the area d3 of the third opening 15c, and the developer that should be discharged is transported to the discharge outlet 20 without being handed over to the stirring chamber 12.

[0077] With the above configuration, the developer carried by the airflow moves toward the stirring screw 14 without being discharged from the discharge port 20. The airflow that has flowed toward the stirring screw 14 exits through the exhaust port 16 located vertically above the stirring screw 14 as described above, and the developer mixed in the airflow is separated from the airflow by gravity as the airflow rises to the exhaust port 16, and falls into the stirring chamber 12. The developer is again carried to region d2 by the spiral blade 14c of the stirring screw 14, where it is mixed with the developer that has been carried by the stirring screw 14.

[0078] [Discharge characteristics of the outlet] Next, the discharge characteristics of the developer discharged from the discharge port 20 in the developing device 1Y will be described with reference to Figure 9. Figure 9 shows an outline of the relationship between the amount of developer and the discharge amount, where the horizontal axis represents the amount of developer in the developing device 1Y and the vertical axis represents the discharge amount of developer discharged from the discharge port 20 of the developing device 1Y (ACR discharge amount).

[0079] As described above, when the amount of developer in the developing device 1Y increases due to a replenishment operation or the like, the volume of the developer in the developing container 2 increases, and the amount of developer discharged from the discharge port 20 in the developing device 1Y also increases accordingly, as shown by the dotted line in Figure 9. However, the amount of developer in the developing device 1Y does not increase more than a certain amount, and only the amount of developer replenished into the developing device 1Y is discharged from the discharge port 20. On the other hand, on the side with less developer, the volume of the developer in the developing container 2 is small, so the amount of developer discharged from the discharge port 20 remains zero or approaches zero.

[0080] [Effect of the third opening] Next, the effect of having the third opening 15c in the region d3 as in this embodiment will be described with reference to Figures 10(a) and 10(b). Here, the amount of developer discharged from the discharge port 20 (ACR discharge amount) was measured when the driving speed of the developing device was changed in a comparative example (Figure 10(a)) without the third opening 15c and an example (Figure 10(b)) with the third opening 15c.

[0081] The developing device 1Y used in the comparative example and examples has the following configuration: The developing sleeve 3 used had a diameter of 18 mm. The following supply screw 13 was used: The diameter of the helical blade was 14 mm for helical blades 13b, 13c, 13d, 13e, 13f, and 13g. The diameter (shaft diameter) of the rotating shaft 13a was 8 mm. The pitch per revolution of the screw was 20 mm for helical blade 13b, 10 mm for helical blades 13c and 13e, and 5 mm for 13d, 13g, and 13f.

[0082] The stirring screw 14 used was as follows: The diameter of the spiral blades 14b and 14c was 14 mm. The diameter (shaft diameter) of the rotating shaft 14a was 6 mm, and the pitch per revolution of the screw was 20 mm for both 14b and 14c. The width (length in the direction of the rotation axis) of each of the openings 15a, 15b, and 15c on the partition wall 15 was 15 to 20 mm. Note that the comparative example did not have the third opening 15c. It is desirable that each opening be approximately the same as or larger than the pitch of the supply screw 13 and stirring screw 14.

[0083] 10(a) and 10(b) show the results of measuring the amount of developer discharged from the discharge port 20 under each developer amount when the third opening 15c is "absent" (a state in which the partition 15 is left as is, a comparative example) and when the third opening 15c is "present" (an example) and the rotation speed of the developing sleeve 3 is 600 [mm / s] (high speed) and 200 [mm / s] (low speed). Here, as in FIG. 9, the horizontal axis represents the amount of developer in the developing device 1Y and the vertical axis represents the amount of discharge (ACR discharge) discharged from the discharge port 20 of the developing device 1Y. The discharge amount at high speed is indicated by a solid triangle (FIG. 10(a)) and a circle (FIG. 10(b)), and the discharge amount at low speed is indicated by a hollow triangle (FIG. 10(a)) and a circle (FIG. 10(b)).

[0084] 10(a), in the case where the third opening 15c is "absent" in the region d3 of the comparative example, when the rotation speed of the developing sleeve 3 is high, as the amount of developer in the developing container 2 changes from small to large (from left to right in FIG. 10(a)), the amount of developer increases to a certain extent, and even though this is an amount of developer that should not be discharged, the amount of ACR discharge increases, resulting in excessive discharge. This is because, as described above, the amount of developer that is stirred up by the spiral blades of the supply screw 13 and the stirring screw 14 mixes with the airflow drawn in from outside the developing device 1Y by the rotation of the developing sleeve 3, the supply screw 13, and the stirring screw 14 and flows increases.

[0085] If the amount of developer in the developing container 2 further increases, the amount of ACR discharged increases rapidly regardless of whether the rotation speed of the developing sleeve 3 is high or low. This is an expected normal discharge, and as the amount of developer increases, the amount of developer flowing into the region d2 increases, and the amount of developer transported toward the discharge port 20 by the spiral blade 13d also increases.

[0086] Furthermore, when the configuration of the comparative example was actually installed in an image forming apparatus and images were output with the developing sleeve 3 rotating at a high speed, the amount of developer in the developing container 2 further decreased due to excessive discharge caused by the air flow described above. As a result, the developer was no longer transported to the developing sleeve 3, and white streak images (abnormal images) where toner was not present in some parts were generated in the output images of the image forming apparatus.

[0087] 10(b), when the third opening 15c is "present" in the region d3 of the embodiment, the excessive discharge caused by the airflow is suppressed as described above, and therefore the amount of developer in the developer container 2 is kept constant regardless of whether the rotation speed of the developing sleeve 3 is high or low. The configuration of the embodiment is actually mounted on an image forming apparatus, image formation is performed, and no white streak images are generated when the output image is checked.

[0088] In this manner, in this embodiment, it is possible to prevent the developer from being discharged from the discharge port 20 due to the airflow drawn in by the rotation of the developing sleeve 3, thereby preventing the occurrence of abnormal images. That is, from the above results, the developing device 1Y of this embodiment is able to prevent the developer from being discharged from the discharge port 20 due to the airflow even when the process speed is high, and it is possible to realize an image forming device that can output stable images even over time.

[0089] <Second embodiment> The second embodiment will be described with reference to FIGS. 11 and 12. In the first embodiment described above, the supply port 19 is located upstream of the agitating screw 14 in the developer transport direction, and the discharge port 20 is located upstream of the supply screw 13 in the developer transport direction. In contrast, in the present embodiment, the supply port 19 is located upstream of the agitating screw 14A in the developer transport direction, and the discharge port 20 is located downstream of the supply screw 13A in the developer transport direction, both of which are located on the bottom surface of the developer container 2. That is, the position of the discharge port 20 is different from that of the first embodiment. Furthermore, in accordance with the change in the location of the discharge port 20, the shape and orientation of the spiral blades of the supply screw 13A and the agitating screw 14A, and the longitudinal position of the third opening 15c have been changed. Since the other configurations and functions are the same as those of the first embodiment, the same components are denoted by the same reference numerals, and their description and illustration will be omitted or simplified. The following description will focus on the differences from the first embodiment.

[0090] 11, in the present embodiment, as in the first embodiment, the rotation of supply screw 13A and stirring screw 14A transports developer in the direction of arrow g (first direction) and the direction of arrow h (second direction), respectively, and the developer in developing device 1Y circulates while being stirred within developing chamber 11 and stirring chamber 12. As in the first embodiment, supply port 19 is also provided further upstream in the direction of arrow h than first opening 15a of stirring chamber 12 in which stirring screw 14A is disposed.

[0091] Meanwhile, a discharge port 20, which gradually discharges the developer in the developing device 1Y, is provided at a position indicated by a dashed line in FIG. 11 so as to open downward in the bottom plate portion 2a (see FIG. 2) of the developing container 2. That is, the discharge port 20 is provided at a position further downstream than the first opening 15a, through which the developer flows into the stirring chamber 12, in terms of the direction of developer transport (the direction of arrow g) in the developing chamber 11 in which the supply screw 13A is disposed. Most of the developer transported in the developing chamber 11 is transferred to the stirring chamber 12 at the first opening 15a. Meanwhile, some of the developer advances toward the discharge port 20 and is discharged from the discharge port 20 to the outside of the developing device 1. The developer discharged from the discharge port 20 to the outside of the developing device 1Y passes through a recovered toner discharge path (not shown) and is collected in a recovered toner tank (not shown).

[0092] Agitating screw 14A, which serves as a second conveying screw and conveys the developer in stirring chamber 12 in the direction of arrow h, has spiral blade 14b disposed around rotation shaft 14a, as in the first embodiment. That is, agitating screw 14A has a third conveying section that conveys the developer in the direction of arrow h from first opening 15a toward second opening 15b, and spiral blade 14b is disposed in the third conveying section. This agitating screw 14A extends to supply port 19, and is conveyed in the direction of arrow h together with toner supplied from supply port 19.

[0093] Additionally, another helical blade 14c that rotates in the opposite direction to helical blade 14b is provided downstream of stirring screw 14A in the direction of arrow h. In this embodiment, the arrangement of discharge port 20 is different from that of the first embodiment, and therefore the length and position of another helical blade 14c that rotates in the opposite direction to helical blade 14b of stirring screw 14A are different. A second opening 15b is provided at the boundary between helical blade 14b and helical blade 14c, allowing the developer to be delivered to developing chamber 11.

[0094] Similar to the first embodiment, the supply screw 13A, which serves as a first transport screw and transports the developer in the developing chamber 11 in the direction of arrow g, has a spiral blade 13b mounted around a rotation shaft 13a. The supply screw 13A also has a spiral blade 13d located downstream in the developer transport direction, rotating in the opposite direction to the spiral blade 13b, to push back the developer transported in the direction of arrow g. That is, the supply screw 13A has a first transport section that transports the developer in the direction of arrow g from the second opening 15b toward the first opening 15a, and a second transport section that is located downstream of the first transport section in the direction of arrow g and transports a portion of the developer in the opposite direction to the direction of arrow g. The first transport section has the spiral blade 13b as the first transport blade, and the second transport section has the spiral blade 13d as the second transport blade. The discharge port 20 is located downstream of the first opening 15a in the direction of arrow g in the developing chamber 11, and discharges the developer that has passed over the second transport section.

[0095] By providing first opening 15a at the boundary between helical blade 13b and helical blade 13d, most of the developer is transferred to developing chamber 11. Then, some of the developer in the area between helical blade 13c and helical blade 13d advances further downstream against the barrier created by helical blade 13d that tries to push it back upstream, and the developer that has overcome the barrier and advanced downstream is transported by helical blade 13e to discharge outlet 20. That is, helical blade 13e, which serves as the third transport blade, is positioned downstream of helical blade 13d in the direction of arrow g, and transports the developer that has overcome helical blade 13d toward discharge outlet 20 in the direction of arrow g.

[0096] Furthermore, at the most downstream side of the supply screw 13A in the direction of arrow g, as in the first embodiment, there is provided a spiral blade 13g which serves to transport the developer upstream in the direction of arrow g so as to push back to the side of the discharge outlet 20 any developer which has been transported by the spiral blade 13e and passed through the discharge outlet 20 but has not been successfully discharged from the discharge outlet 20.

[0097] In this embodiment, the third opening 15c is located downstream of the spiral blade 13d of the supply screw 13A in the direction of arrow g and upstream of the discharge port 20 in the direction of arrow g, and d3 indicates the area where the third opening 15c is located. That is, the third opening 15c is located downstream of the first opening 15a of the partition wall 15 in the direction of arrow g, and allows airflow to communicate between the developing chamber 11 and the stirring chamber 12. In addition, with respect to the direction of arrow g, the upstream end of the third opening 15c is located upstream of the upstream end of the discharge port 20. The opening area of ​​the third opening 15c is larger than the opening area of ​​the discharge port 20.

[0098] The third opening 15c is disposed upstream of the supply screw 13A in the direction of arrow g with respect to the discharge port 20, so that the airflow that did not flow from the developing chamber 11 to the stirring chamber 12 in region d1 is sent from the developing chamber 11 to the stirring chamber 12 in region d3. At this time, the spiral blade 14b of the stirring screw 14A on the stirring chamber 12 side rotates in a direction that transports the developer from region d3 toward region d1, and the rotation of the spiral blade 14b functions to draw the airflow from the developing chamber 11 to the stirring chamber 12 side in region d3.

[0099] That is, stirring screw 14A has helical blade 14b as a second chamber side blade spirally provided around rotating shaft 14a so as to transport developer in the area where third opening 15c exists in the direction of arrow h. Furthermore, helical blade 14b arranged in the third transport section extends to the area where third opening 15c exists in the direction of arrow h. On the other hand, supply screw 13A has helical blade 13e as a first chamber side blade spirally provided around rotating shaft 13a so as to transport developer toward discharge outlet 20 in the area where third opening 15c exists in the direction of arrow g.

[0100] Furthermore, when helical blade 14c in formula (2) is replaced with helical blade 14b, formula (3) is satisfied. That is, the volume 13eV through which helical blade 13e passes during one rotation and the volume 14bV through which helical blade 14b passes during one rotation satisfy 14bV ≥ 13eV. In particular, in this embodiment, it is preferable to make the area through which helical blade 14b passes per unit time due to the rotation of rotating shaft 14a larger than the area through which helical blade 13e passes per unit time due to the rotation of rotating shaft 13a.

[0101] 12, in this embodiment, part of the airflow generated by the rotation of the developing sleeve 3 and supply screw 13A in the developing device 1Y flows into the stirring chamber 12 through the first opening 15a, and part of the airflow flows toward the discharge port 20. The airflow that flows toward the discharge port 20 is drawn into the third opening 15c by the rotation of the stirring screw 14A, and the airflow flowing toward the discharge port 20 is reduced.

[0102] As a result, the developer stirred up by the rotation of the supply screw 13A and the stirring screw 14A and some of the developer peeled off from the magnetic-free zone (shown in Figure 2) of the developing sleeve 3 described above mix with the airflow, reducing the amount of developer discharged at the discharge port 20.

[0103] In addition, in the configuration of this embodiment, the effect of the third opening 15c within the region d3 was examined by measuring the amount of developer discharged from the discharge port 20 in each state in an example having the third opening 15c and a comparative example having no third opening 15c, and the results showed that the same effect as in Figures 10(a) and (b) was obtained.

[0104] The developing device 1Y used in the examples and comparative examples of the present embodiment has the following configuration: The developing sleeve 3 used had a diameter of 18 mm. The supply screw 13A used was as follows: The diameter of the helical blade was 14 mm for helical blades 13b, 13d, 13e, and 13g. The diameter (shaft diameter) of the rotating shaft 13a was 8 mm. The pitch per revolution of the screw was 20 mm for helical blade 13b, 10 mm for helical blade 13e, and 5 mm for 13d and 13g.

[0105] The stirring screw 14A used was as follows: The diameter of the helical blades was 14 mm for helical blades 14b and 14c. The diameter (shaft diameter) of the rotating shaft 14a was 6 mm, and the pitch per revolution of the screw was 20 mm for 14b and 5 mm for helical blade 14c. The width (length in the direction of the rotation axis) of each of the openings 15a, 15b, and 15c on the partition wall 15 was 15 to 20 mm. Note that the comparative example did not have the third opening 15c. It is desirable that each opening be approximately the same as or larger than the pitch of the supply screw 13A and stirring screw 14A.

[0106] In this embodiment, too, the occurrence of abnormal images can be suppressed. That is, as a result of the above, the developing device 1Y of this embodiment is configured such that the discharge port 20 is provided downstream of the developer transport in the developing chamber 11, and even if the process speed changes, it is possible to discharge the developer little by little in an amount corresponding to the amount of developer contained in the developing device 1Y. That is, even when the process speed is high, it is possible to suppress the discharge of developer from the discharge port 20 due to airflow, and it is possible to realize an image forming device that can output stable images even over time.

[0107] <Third embodiment> The third embodiment will be described with reference to FIGS. 13 and 14. In the first and second embodiments described above, the discharge port 20 is provided upstream or downstream of the supply screw 13 in the developer transport direction. In contrast, in this embodiment, the supply port 19 is provided upstream of the agitating screw 14B in the developer transport direction, and the discharge port 20 is provided downstream of the agitating screw 14B in the developer transport direction, both of which are located on the bottom surface of the developer container 2. That is, the discharge port 20 is located in the agitating chamber 12. In addition, in accordance with the change in the location of the discharge port 20, the shape and orientation of the spiral blades of the supply screw 13B and the agitating screw 14B, and the longitudinal position of the third opening 15c have been changed. Since the other configurations and functions are the same as those of the first embodiment, the same components are denoted by the same reference numerals, and their description and illustration will be omitted or simplified. The following description will focus on the differences from the first embodiment.

[0108] 13, in the present embodiment, as in the first embodiment, the rotation of supply screw 13B and stirring screw 14B transports developer in the direction of arrow g (first direction) and the direction of arrow h (second direction), respectively, and the developer in developing device 1Y circulates while being stirred within developing chamber 11 and stirring chamber 12. As in the first embodiment, supply port 19 is also provided further upstream in the direction of arrow h than first opening 15a of stirring chamber 12, where stirring screw 14B is disposed.

[0109] Agitating screw 14B, which serves as a second conveying screw and conveys the developer in stirring chamber 12 in the direction of arrow h, has helical blade 14b, which serves as a first screw blade, provided around rotation shaft 14a, as in the first embodiment. That is, agitating screw 14B has a second conveying portion that conveys the developer in the direction of arrow h from first opening 15a toward second opening 15b, and helical blade 14b is disposed in the second conveying portion. This agitating screw 14B extends to supply port 19, and conveys the toner supplied from supply port 19 in the direction of arrow h together with the developer.

[0110] The discharge port 20, which gradually discharges the developer in the developing device 1Y, is located at a position indicated by a dashed line in FIG. 13 and opens downward in the bottom plate portion 2a (see FIG. 2) of the developing container 2. That is, the discharge port 20 is located further downstream than the second opening 15b, through which the developer flows into the developing chamber 11, in the direction of developer transport (the direction of arrow h) in the stirring chamber 12 in which the stirring screw 14B is disposed. Most of the developer transported in the stirring chamber 12 is transferred to the developing chamber 11 through the second opening 15b. Meanwhile, some of the developer proceeds toward the discharge port 20 and is discharged from the discharge port 20 to the outside of the developing device 1Y. The developer discharged from the discharge port 20 to the outside of the developing device 1Y passes through a recovered toner discharge path (not shown) and is collected in a recovered toner tank (not shown).

[0111] Further, on the downstream side of stirring screw 14B in the direction of arrow h, helical blade 14c is provided, which rotates in the opposite direction to helical blade 14b, and pushes back the developer being transported in the direction of arrow h. By providing second opening 15b at the boundary between helical blade 14b and helical blade 14c, most of the developer is transferred to developing chamber 11. Then, some of the developer in the area between helical blade 14b and helical blade 14c advances further downstream against the barrier created by helical blade 14c that tries to push it back upstream, and the developer that has overcome the barrier and advanced downstream is transported to discharge port 20 by helical blade 14d.

[0112] That is, the stirring screw 14B has the second transport portion described above and a third transport portion disposed downstream of the second transport portion in the direction of arrow h. The third transport portion transports the developer transported downstream of the second opening 15b in the direction of arrow h in the opposite direction to the direction of arrow h. The second transport portion is provided with a helical blade 14b as a first screw blade, and the third transport portion is provided with a helical blade 14c as a second screw blade. The third screw blade is provided downstream of the helical blade 14c in the direction of arrow h. Specifically, the helical blade 14b is spirally disposed around the rotation shaft 14a to transport the developer in the direction of arrow h. The helical blade 14c is spirally disposed around the rotation shaft 14a to transport the developer in the direction opposite to the direction of arrow h. The spiral blade 14d is provided spirally around the rotation shaft 14a so as to transport the developer that has passed over the spiral blade 14c toward the discharge port 20 in the direction of the arrow h.

[0113] Furthermore, at the most downstream side in the direction of arrow h of stirring screw 14, there is provided helical blade 14e which serves to transport developer upstream in the direction of arrow h so as to push back toward discharge outlet 20 any developer that has been transported by helical blade 14d and passed through discharge outlet 20 but has not been successfully discharged from discharge outlet 20. That is, helical blade 14e is provided in a spiral shape around rotation shaft 14a so as to transport the developer in the direction opposite to the direction of arrow h.

[0114] As in the first embodiment, supply screw 13B as a first conveying screw conveys developer that has flowed into developing chamber 11 through second opening 15b provided in region d2 in the direction of arrow g using helical blade 13b to first opening 15a provided in region d1, and then transfers the conveyed developer from first opening 15a to stirring chamber 12. That is, supply screw 13B has a first conveying portion that conveys developer in the direction of arrow g from second opening 15b toward first opening 15a. And, helical blade 13b is arranged in the first conveying portion.

[0115] Additionally, downstream of spiral blade 13b in the direction of arrow g, spiral blade 13f is provided, which rotates in the opposite direction to spiral blade 13b. The boundaries between these spiral blades 13b and spiral blade 13f are within area d1 where first opening 15a is provided. Therefore, the developer transported in the direction of arrow g is prevented from advancing any further by spiral blade 13f, and flows into mixing chamber 12 through first opening 15a.

[0116] In this embodiment, the third opening 15c is provided downstream in the direction of arrow h from the spiral blade 14c of the stirring screw 14B and upstream in the direction of arrow h from the discharge port 20, and d3 indicates the area where the third opening 15c is located. That is, the third opening 15c is provided downstream in the direction of arrow h from the second opening 15b of the partition wall 15, and allows airflow to communicate between the developing chamber 11 and the stirring chamber 12. In addition, with respect to the direction of arrow h, the upstream end of the third opening 15c is located upstream from the upstream end of the discharge port 20. In addition, the opening area of ​​the third opening 15c is larger than the opening area of ​​the discharge port 20.

[0117] The third opening 15c is disposed upstream of the stirring screw 14B in the direction of arrow h with respect to the discharge port 20, so that the airflow that did not flow from the stirring chamber 12 to the developing chamber 11 in region d2 is sent from the stirring chamber 12 to the developing chamber 11 in region d3. At this time, the spiral blade 13b of the supply screw 13B on the developing chamber 11 side rotates in a direction that transports the developer from region d3 toward region d2, and the rotation of the spiral blade 13b functions to draw the airflow from the stirring chamber 12 to the developing chamber 11 side in region d3.

[0118] That is, supply screw 13B has helical blade 13b as a first chamber side blade spirally arranged around rotating shaft 13a so as to transport developer in the area where third opening 15c is located in the direction of arrow g. More specifically, helical blade 13b arranged in the first transport portion extends to the area where third opening 15c is located in the direction of arrow g. On the other hand, stirring screw 14B has helical blade 14e as a second chamber side blade spirally arranged around rotating shaft 14a so as to transport developer in the area where third opening 15c is located in the direction of arrow h.

[0119] Then, by replacing helical blade 13e in equation (1) with helical blade 13b, replacing helical blade 14c in equation (2) with helical blade 14e, and further reversing the inequality sign in equation (3), the equation is satisfied. That is, volume 13bV passed through when helical blade 13b makes one rotation and volume 14eV passed through when helical blade 14e makes one rotation satisfy 14eV≦13bV. Particularly in this embodiment, it is preferable to make the area passed through per unit time by helical blade 13b due to the rotation of rotation shaft 13a larger than the area passed through per unit time by helical blade 14e due to the rotation of rotation shaft 14a.

[0120] 13, in this embodiment, part of the airflow generated by the rotation of the developing sleeve 3 and supply screw 13B in the developing device 1Y flows into the stirring chamber 12 through the second opening 15b, and part of the airflow flows toward the discharge port 20. In addition, part of the airflow generated by the rotation of the stirring screw 14 also flows toward the discharge port 20. The airflow that flows toward the discharge port 20 is drawn into the third opening 15c by the rotation of the supply screw 13B, and the airflow flowing toward the discharge port 20 is reduced.

[0121] As a result, the developer stirred up by the rotation of the supply screw 13B and the stirring screw 14B and some of the developer peeled off from the magnetic-free zone (shown in Figure 2) of the developing sleeve 3 described above mix with the airflow, reducing the amount of developer discharged at the discharge port 20.

[0122] In addition, in the configuration of this embodiment, the effect of the third opening 15c within the region d3 was examined by measuring the amount of developer discharged from the discharge port 20 in each state in an example having the third opening 15c and a comparative example having no third opening 15c, and the results showed that the same effect as in Figures 10(a) and (b) was obtained.

[0123] The developing device 1Y used in the examples and comparative examples of the present embodiment has the following configuration: The developing sleeve 3 used had a diameter of Φ18 mm. The following supply screw 13B was used: The diameter of the helical blades 13b and 13f was 14 mm. The diameter (shaft diameter) of the rotating shaft 13a was 8 mm. The pitch per revolution of the screw was 20 mm for helical blade 13b and 5 mm for helical blade 13f.

[0124] The stirring screw 14B used was as follows: The diameter of the helical blades 14b, 14c, 14d, and 14e was 14 mm. The diameter (shaft diameter) of the rotating shaft 14a was 6 mm, and the pitch per revolution of the screw was 20 mm for 14b, 10 mm for helical blades 14c and 14d, and 5 mm for helical blade 14e. The width (length in the direction of the rotation axis) of each opening 15a, 15b, and 15c on the partition wall 15 was 15 to 20 mm. Note that the comparative example did not have the third opening 15c. It is desirable that each opening be approximately the same as or larger than the pitch of the supply screw 13B and stirring screw 14B.

[0125] In this embodiment, too, the occurrence of abnormal images can be suppressed. That is, as a result of the above, the developing device 1Y of this embodiment is configured such that the discharge port 20 is provided downstream of the developer transport in the agitation chamber 12, and even if the process speed changes, it is possible to discharge the developer little by little in an amount corresponding to the amount of developer contained in the developing device 1Y. That is, even when the process speed is high, it is possible to suppress the discharge of developer from the discharge port 20 due to airflow, and it is possible to realize an image forming device that can output stable images even over time.

[0126] <Fourth embodiment> The fourth embodiment will be described with reference to Figures 15 to 17. In the first embodiment described above, the discharge port 20 is provided so as to open downward in the bottom plate portion 2a (see Figure 2) of the developing container 2 at a position upstream in the developer transport direction of the supply screw 13. In contrast, in this embodiment, the discharge port 20A is provided so as to open laterally in the side wall 2c of the developing container 2. Since the other configurations and functions are the same as those of the first embodiment, the same reference numerals are used for the same configurations, and explanations and illustrations will be omitted or simplified. The following description will focus on the points that are different from the first embodiment.

[0127] In this embodiment, as shown in FIGS. 15 and 16, the discharge port 20A is provided in the side wall 2c that faces the partition wall 15 and forms the developing chamber 11 between the partition wall 15. In other words, the discharge port 20A is provided on the wall surface of the developing chamber 11 opposite the partition wall 15. The supply screw 13 and the stirring screw 14 in this embodiment have the same configuration as those in the first embodiment. The positional relationships in the developer transport direction between the spiral blades of the supply screw 13 and the stirring screw 14 and the first opening 15a, the second opening 15b, and the third opening 15c are also the same. The opening area of ​​the third opening 15c is larger than the opening area of ​​the discharge port 20A.

[0128] As shown in Figure 15, between the most upstream spiral blade 13g in the direction of arrow g (first direction) of the supply screw 13 and the downstream spiral blade 13e, developer that has overcome the barrier created by the spiral blade 13d downstream of that in the direction of arrow g and proceeded upstream in the direction of arrow g is discharged from the discharge port 20A.

[0129] As described in the first embodiment, the developer is transferred from the agitating screw 14 side to the supply screw 13 side through the second opening 15b formed in the partition wall 15, so the developer level height in the region d2 naturally becomes high. This makes it difficult for airflow to flow from the supply screw 13 side to the agitating screw 14 side, and most of the airflow flows directly upstream in the conveyance direction of the supply screw 13. For this reason, in this embodiment, as in the first embodiment, the partition wall 15 is provided with a third opening 15c as a third communication portion, and d3 indicates the region where the third opening 15c is located. With this configuration, as in the first embodiment, the airflow flowing toward the discharge port 20A can be sent into the agitating chamber 12 through the third opening 15c in the region d3, thereby reducing the amount of developer discharged from the discharge port 20A by the airflow.

[0130] Here, if the discharge port is located on the bottom plate portion 2a of the developer as in the first embodiment, if the amount of developer suddenly increases for various reasons within the developing device 1Y and a large amount of developer overflows the spiral blade 13d of the supply screw 13, there is a risk that the developer will be discharged directly from the discharge port. Therefore, in this embodiment, the discharge port 20A is provided in the side wall 2c to temporarily store the developer. That is, by providing the discharge port 20A on the wall surface, the developer transported by the spiral blade 13e is pushed back by the spiral blade 13g between the spiral blades 13e and 13g and temporarily accumulates in this area. This prevents excessive developer from being discharged when the amount of developer suddenly changes.

[0131] In particular, the above phenomenon is likely to occur immediately after the developer in the developing device 1Y is replaced, and by adopting the configuration of this embodiment, it is possible to prevent the newly replaced developer from being immediately discharged.

[0132] 17, the lower end of the opening of the discharge port 20A is positioned lower than the lower end of the opening of the third opening 15c. In particular, in this embodiment, the upper end of the opening of the discharge port 20A is positioned lower than the lower end of the opening of the third opening 15c. In this way, by positioning the discharge port 20A lower than the lower limit of the opening of the third opening 15c, developer near the discharge port 20A is prevented from flowing out from the third opening 15c.

[0133] In addition, in the configuration of this embodiment, the effect of the third opening 15c within the region d3 was examined by measuring the amount of developer discharged from the discharge port 20 in each state in an example having the third opening 15c and a comparative example having no third opening 15c, and the results showed that the same effect as in Figures 10(a) and (b) was obtained.

[0134] The developing device 1Y used in the comparative example and examples has the following configuration: The developing sleeve 3 used had a diameter of 18 mm. The following supply screw 13 was used: The diameter of the helical blade was 14 mm for helical blades 13b, 13c, 13d, 13e, 13f, and 13g. The diameter (shaft diameter) of the rotating shaft 13a was 8 mm. The pitch per revolution of the screw was 20 mm for helical blade 13b, 10 mm for helical blades 13c and 13e, and 5 mm for 13d, 13g, and 13f.

[0135] The stirring screw 14 used was as follows: The diameter of the spiral blades 14b and 14c was 14 mm. The diameter (shaft diameter) of the rotating shaft 14a was 6 mm, and the pitch per revolution of the screw was 20 mm for both 14b and 14c. The width (length in the direction of the rotation axis) of each of the openings 15a, 15b, and 15c on the partition wall 15 was 15 to 20 mm. Note that the comparative example did not have the third opening 15c. It is desirable that each opening be approximately the same as or larger than the pitch of the supply screw 13 and stirring screw 14.

[0136] <Other embodiments> In the first to third embodiments described above, the discharge port is provided in the bottom plate of the developer container, and in the fourth embodiment, the discharge port is provided in the side wall of the developer container. However, the configuration in which the discharge port is provided in the side wall of the developer container may also be applied to the second and third embodiments. That is, in the second and third embodiments, the position of the discharge port may be changed from the bottom plate of the developer container to the side wall, as in the fourth embodiment.

[0137] In the above-described embodiments, the image forming apparatus is a printer, but the present invention can also be applied to copiers, facsimiles, multifunction peripherals, etc. Furthermore, the above-described embodiments have been described as examples in which the present invention is applied to a developing device provided in a so-called tandem-type image forming apparatus. However, the present invention is not limited to such image forming apparatuses, and can be applied to various types of image forming apparatuses, such as monochrome printers. [Explanation of symbols]

[0138] 1Y, 1M, 1C, 1K...developing device 2. Developer container 2a...Bottom plate part 2b Top plate 2c...Side wall 3. Developing sleeve (developer carrier) 11...Development chamber (1st chamber) 12... Stirring chamber (2nd chamber) 13, 13A, 13B... Supply screw (first conveying screw) 13a Rotation axis (first rotation axis) 13b... Spiral blade (first blade, first conveying blade) 13c... Spiral blade (second blade) 13d Spiral blade (third blade, second conveying blade) 13e Spiral blades (first chamber side blade, fourth blade, third conveying blade) 14, 14A, 14B...Agitating screw (second conveying screw) 14a Rotation axis (second rotation axis) 14b... Spiral blade (second chamber side blade, first screw blade) 14c... Spiral blade (second chamber side blade, second screw blade) 14d... Spiral blade (third screw blade) 14e Spiral blade (second chamber side blade) 15a...1st opening (1st communication part) 15b...Second opening (second communication part) 15c...Third opening (third communication part) 16···Exhaust port 20, 20A...Discharge port

Claims

1. A developing rotating body that carries and transports a developer containing toner and carrier to a position where an electrostatic latent image formed on an image carrier is developed, A developing container having a first chamber in which the developing rotating body is arranged and the developing agent is supplied to the developing rotating body, and a second chamber separated from the first chamber by a partition wall, and in which the developing agent circulates between the first chamber and the second chamber, A first communication region that allows the developer to be communicated from the first chamber to the second chamber, A second communication region that allows the developer to be communicated from the second chamber to the first chamber, The first conveying screw is arranged in the first chamber, The first axis of rotation and A first vane portion is provided, which is located downstream of the second communication region with respect to the first direction from the second communication region toward the first communication region, and is spirally formed on the outer surface of the first rotating shaft, for transporting the developer in the first direction, A second blade portion is positioned upstream of the second communication region in the first direction and upstream of the first blade portion in the first direction, and is spirally formed on the outer circumferential surface of the first rotating shaft, for transporting the developer in the first direction. A first conveying screw having, A second conveying screw arranged in the second chamber, The second axis of rotation and A third vane portion is provided, which is positioned upstream of the second communication region in a second direction opposite to the first direction, and is spirally formed on the outer surface of the second rotating shaft, for transporting the developer in the second direction, A fourth blade portion is located downstream of the second communication region with respect to the second direction, and is located downstream of the third blade portion with respect to the second direction, and is formed spirally on the outer circumferential surface of the second rotating shaft, and conveys the developer in the second direction. A fifth blade, which is positioned downstream of the third blade in the second direction and upstream of the fourth blade in the second direction, and is spirally formed on the outer surface of the second rotating shaft, conveys the developer in the first direction, A second conveying screw having, A third communication region is located downstream of the second communication region in the second direction, and allows air to be communicated between the first chamber and the second chamber. A developer outlet is provided in the second chamber, positioned downstream of the third communication region in the second direction, for discharging the developer from the developing container, Equipped with, The lower end of the third communication region is located vertically above the lower end of the second communication region. With respect to the first direction, the third communication region overlaps with the second wing portion. A developing apparatus characterized by the following features.

2. The pitch of the fourth blade section per rotation is P, and the diameter of the fourth blade section is L. ｂ The diameter of the second rotation axis is L ｓ year, The pitch of the second blade section per rotation is P', and the diameter of the second blade section is L. ｂ ', the diameter of the first rotation axis is L ｓ If we use ', π×((L) ｂ (2) ２ - (8) ｓ (2) ２ )×P≦π×((L ｂ ( / 2)) ２ - (8) ｓ ( / 2)) ２ )×P´ satisfies The developing apparatus according to feature 1.

3. π×((L) ｂ (2) ２ - (8) ｓ (2) ２ )×0P<π×((L ｂ ( / 2)) ２ - (8) ｓ ( / 2)) ２ )×P´ satisfies The developing apparatus according to feature 2.

4. The pitch of the fourth blade section per rotation is P, and the diameter of the fourth blade section is L. ｂ The diameter of the second rotation axis is L ｓ Let M be the number of threads in the fourth blade section, and let N be the number of rotations per unit time of the second conveying screw. The pitch of the second blade section per rotation is P', and the diameter of the second blade section is L. ｂ ', the diameter of the first rotation axis is L ｓ When the number of threads in the second blade section is M' and the number of rotations per unit time of the first conveying screw is N', π×((L) ｂ (2) ２ - (8) ｓ (2) ２ )×P×M×N<π×((L ｂ ( / 2)) ２ - (8) ｓ ( / 2)) ２ )×0´×M´×N´ satisfies The developing apparatus according to feature 1.

5. The second transport screw is positioned downstream of the fourth blade section with respect to the second direction and further has a sixth blade section formed spirally on the outer circumferential surface of the second rotating shaft, which transports the developer in the first direction. With respect to the first direction, the developer discharge port overlaps with the six-blade section. A developing apparatus according to any one of claims 1 to 4.

6. The developer discharge port is provided on the lower surface of the developing container. The developing apparatus according to any one of claims 1 to 5, characterized by the features described herein.

7. It is further provided with an exhaust port positioned vertically above the second transport screw, which discharges air from inside the developing container to the outside of the developing container. A developing apparatus according to any one of claims 1 to 6.

8. The second chamber is provided with a developer supply port for supplying the developer to the developing container, which is located upstream of the first communication region in the second direction. A developing apparatus according to any one of claims 1 to 7, characterized by the following:

Images