Developing device, process cartridge, and image forming apparatus

Abstract

To reduce leakage of a developer preset in the time of transport without providing a sealing member.SOLUTION: A development device includes a first communication port 13f which is opened to a partition part 13e so as to make a first conveyance path B1 communicate to a second conveyance path B2 on one end side in the width direction, and a second communication port 13g which is opened to the partition part 13e so as to make the first conveyance path B1 communicate to the second conveyance path B2 on the other end side in the width direction and is formed in an opening area smaller than an opening area of the first communication port 13f. The development device is configured to be able to execute a reverse rotation mode of rotating a first conveyance screw 13b1 and a second conveyance screw 13b2 in reverse directions. The second conveyance screw 13b2 is configured such that conveyance force conveying the developer G to the other end side in the width direction from the one end side in the width direction in the time of the reverse rotation mode is smaller than the conveyance force conveying the developer G to the one end side in the width direction from the other end side in the width direction in the time of rotation in a positive direction.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a developing device that accommodates a developer such as a two-component developer, and a process cartridge and an image forming apparatus that include the same. [Background technology]

[0002] Conventionally, there have been known developing devices that are detachably installed in image forming devices such as copiers, printers, facsimiles, or combination devices thereof, in which a developer is pre-stored inside the device before shipping from the factory (see, for example, Patent Document 1). In order to prevent the preset developer from leaking from the device during transportation after shipping from the factory, gaps in the device are sealed with a sheet-like sealing member at the factory, and developer is filled into the device through the toner supply port while the device is running, and the toner supply port is also sealed after filling.The sealing member is then removed from the device by the user when the developing device is delivered.

[0003] On the other hand, Patent Document 2 discloses a technology for efficiently discharging the developer contained in the developing device to the outside of the device by rotating a conveying screw installed in the device in reverse at a low speed to guide the developer to an outlet. Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional developing devices are equipped with sealing members that can prevent leakage of preset developer during transportation, but on the other hand, it takes time to install the sealing members when the device is shipped from the factory and to remove the sealing members when the device arrives.

[0005] The present invention has been made to solve the above-mentioned problems, and aims to provide a developing device, a process cartridge, and an image forming apparatus that can reduce leakage of preset developer during transportation without providing a sealing member. [Means for solving the problem]

[0006] a first transport member disposed in a first transport path opposite the first transport member and rotating in a forward direction during a developing process to transport the developer from one widthwise end side to the other widthwise end side while supplying the developer to the developer carrier; a second transport member disposed in a second transport path opposite the first transport member across a partition portion and rotating in the forward direction during a developing process to transport the developer from the other widthwise end side to the first widthwise end side; a first communication port opening in the partition portion at the one widthwise end side to connect the first transport path and the second transport path; and a second communication port opening in the partition portion at the other widthwise end side to connect the first transport path and the second transport path, the second communication port having an opening area smaller than the opening area of ​​the first communication port. the second transport path includes an extension portion that extends toward the other end in the width direction relative to the second communication port and that has a supply port formed therein for supplying toner during a developing process; A reverse rotation mode is configured to be executable in which the first conveying member and the second conveying member are rotated in opposite directions, and the second conveying member is The screw portion is wound around a shaft portion extending in the width direction, a conveying force for conveying the developer from one end side in the width direction to the other end side in the width direction in the reverse rotation mode is smaller than a conveying force for conveying the developer from the other end side in the width direction to the one end side in the width direction in the forward rotation mode; In the extension portion of the screw portion, a first conveying surface inclined at a first inclination angle with respect to a virtual orthogonal plane orthogonal to the axial direction is formed as an opposing surface facing one end side in the width direction, and a second conveying surface inclined at a second inclination angle larger than the first inclination angle with respect to the virtual orthogonal plane is formed as an opposing surface facing the other end side in the width direction. It is something. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a developing device, a process cartridge, and an image forming apparatus that can reduce leakage of preset developer during transportation without providing a sealing member. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is an overall configuration diagram showing an image forming apparatus according to an embodiment of the present invention; [Figure 2] FIG. 2 is a diagram illustrating the configuration of an image forming unit. [Figure 3]FIG. 2 is a schematic cross-sectional view of the developing device as viewed in the longitudinal direction. [Figure 4] 1A is a top view showing a first communication port, and FIG. 1B is a top view showing a second communication port. [Figure 5] 1A is a diagram showing the state of the developer in the developing device during forward rotation, and FIG. 1B is a diagram showing the state of the developer in the developing device during reverse rotation. [Figure 6] 1A is a diagram showing a second conveying screw, and FIG. 1B is an enlarged view showing the screw portion thereof. [Figure 7] 1A is a diagram showing a first conveying screw, and FIG. 1B is an enlarged view showing the screw portion thereof. [Figure 8] 1A is a diagram showing a developing device at the time of shipment from the factory, and FIG. 1B is a diagram showing a developing device at the time of shipment as a comparative example. [Figure 9] 10A is an enlarged view showing a screw portion on the other end side in the width direction of a second conveying screw serving as a modified example 1, and FIG. 10B is an enlarged view showing a screw portion on one end side in the width direction of the second conveying screw serving as a modified example 1. [Figure 10] FIG. 10 is a diagram showing a developing device according to a second modified example. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are designated by the same reference numerals, and redundant explanations will be appropriately simplified or omitted.

[0010] First, the overall configuration and operation of an image forming apparatus 1 will be described with reference to FIG. In FIG. 1, 1 denotes a tandem color copier as an image forming apparatus, 3 denotes a document transport device that transports a document to a document reading section, 4 denotes a document reading section that reads image information of the document, 5 denotes a paper output tray on which output images are stacked, and 7 denotes a paper feed device that stores sheets P such as paper. Further, reference numeral 9 denotes a registration roller that adjusts the timing of conveying the sheet P, and 11Y, 11M, 11C, and 11BK denote photosensitive drums as image carriers on which toner images of each color (yellow, magenta, cyan, and black) are formed. Also, 13 denotes a developing device that develops the electrostatic latent image formed on the surface of each photosensitive drum 11Y, 11M, 11C, and 11BK, and 14 denotes a primary transfer bias roller that transfers the toner image formed on each photosensitive drum 11Y, 11M, 11C, and 11BK onto a sheet P in a superimposed manner. Also, 17 denotes an intermediate transfer belt onto which multiple color toner images are transferred in layers, 18 denotes a secondary transfer bias roller for transferring the color toner image on the intermediate transfer belt 17 onto the sheet P, 20 denotes a fixing device for fixing an unfixed image on the sheet P, and 28 denotes a toner container for each color (yellow, cyan, magenta, black) that supplies toner (toner particles) of each color to the developing device 13. Reference numeral 100 denotes an operation display panel for displaying information relating to the printing operation (image forming operation) and for performing operations.

[0011] Hereinafter, the operation of the image forming apparatus during normal color image formation will be described. For the image forming process performed on the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK, see also FIG. First, the document is transported from the document table by the transport rollers of the document transport device 3 and placed on the contact glass of the document reading device 4. Then, the document reading device 4 optically reads the image information of the document placed on the contact glass.

[0012] More specifically, the document reader 4 scans the image of the document on the contact glass while irradiating it with light emitted from an illumination lamp. The light reflected from the document is then imaged on a color sensor via a group of mirrors and a lens. The color image information of the document is read by the color sensor in units of RGB (red, green, and blue) color separation light, and then converted into electrical image signals. Furthermore, based on the RGB color separation image signals, an image processing unit performs color conversion processing, color correction processing, spatial frequency correction processing, and other processing to obtain color image information of yellow, magenta, cyan, and black.

[0013] The image information for each color (yellow, magenta, cyan, and black) is then sent to a writing device, which then emits laser light L (see FIG. 2) based on the image information for each color toward the surfaces of the corresponding photosensitive drums 11Y, 11M, 11C, and 11BK.

[0014] Meanwhile, the four photoconductor drums 11Y, 11M, 11C, and 11BK each rotate clockwise in FIG. 1. First, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK are uniformly charged at the portions facing the charging device 12 (see FIG. 2) (charging process). In this way, a charging potential is formed on the photoconductor drums 11Y, 11M, 11C, and 11BK. Thereafter, the charged surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK reach the irradiation positions of the respective laser beams L. In the writing device, four light sources emit laser beams corresponding to the image signals, one for each color. Each laser beam passes through a separate optical path for each color component: yellow, magenta, cyan, and black (this is the exposure process).

[0015] The laser light corresponding to the yellow component is irradiated onto the surface of the first photoconductor drum 11Y from the left side of the drawing. At this time, the laser light of the yellow component is scanned in the direction of the rotation axis of the photoconductor drum 11Y (main scanning direction) by a polygon mirror rotating at high speed. In this way, an electrostatic latent image corresponding to the yellow component is formed on the photoconductor drum 11Y after it has been charged by the charging device 12.

[0016] Similarly, the laser light corresponding to the magenta component is irradiated onto the surface of the photosensitive drum 11M, which is the second from the left on the paper, and an electrostatic latent image corresponding to the magenta component is formed. The laser light corresponding to the cyan component is irradiated onto the surface of the photosensitive drum 11C, which is the third from the left on the paper, and an electrostatic latent image corresponding to the cyan component is formed. The laser light corresponding to the black component is irradiated onto the surface of the photosensitive drum 11BK, which is the fourth from the left on the paper, and an electrostatic latent image corresponding to the black component is formed.

[0017] Thereafter, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK on which the electrostatic latent images of each color have been formed reach positions facing the developing devices 13. Then, toner of each color is supplied from each developing device 13 onto the photosensitive drums 11Y, 11M, 11C, and 11BK, and the latent images on the photosensitive drums 11Y, 11M, 11C, and 11BK are developed (this is the developing process). Thereafter, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK after the development process each reach a portion facing the intermediate transfer belt 17. Here, a primary transfer bias roller 14 is installed at each facing portion so as to abut against the inner circumferential surface of the intermediate transfer belt 17. Then, at the position of the primary transfer bias roller 14, the toner images of each color formed on the photosensitive drums 11Y, 11M, 11C, and 11BK are transferred onto the intermediate transfer belt 17 in order, superimposed on top of each other (this is the primary transfer process).

[0018] After the transfer process, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK each reach a position facing the cleaning device 15. The cleaning device 15 then collects untransferred toner remaining on the photosensitive drums 11Y, 11M, 11C, and 11BK (this is the cleaning process). Thereafter, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK pass through a charge eliminating device, and a series of image forming processes on the photosensitive drums 11Y, 11M, 11C, and 11BK is completed.

[0019] Meanwhile, intermediate transfer belt 17, onto which the toner of each color on photosensitive drums 11Y, 11M, 11C, and 11BK has been transferred (carried) in an overlapping manner, travels counterclockwise in FIG. 1 and reaches a position facing secondary transfer bias roller 18. Then, at the position facing secondary transfer bias roller 18, the color toner images carried on intermediate transfer belt 17 are transferred onto sheet P (secondary transfer process). Thereafter, the surface of the intermediate transfer belt 17 reaches the position of the intermediate transfer belt cleaning device, and the untransferred toner adhering to the intermediate transfer belt 17 is collected by the intermediate transfer belt cleaning device, completing the series of transfer processes on the intermediate transfer belt 17.

[0020] Here, the sheet P conveyed between the intermediate transfer belt 17 and the secondary transfer bias roller 18 (secondary transfer nip) is conveyed from the paper feeder 7 via the registration rollers 9 and the like. Specifically, the sheet P is fed by a paper feed roller 8 from a paper feed device 7 that stores the sheet P, passes through a conveyance guide, and is then guided to a registration roller 9. The sheet P that has reached the registration roller 9 is conveyed in time toward the secondary transfer nip.

[0021] Then, the sheet P onto which the full-color image has been transferred is then guided to the fixing device 20. In the fixing device 20, the color image is fixed onto the sheet P at the nip between a fixing roller and a pressure roller. After the fixing process, the sheet P is discharged as an output image to the outside of the apparatus main body 1 by a discharge roller, and is stacked on the discharge tray 5, completing a series of image forming processes.

[0022] Next, the image forming unit in the image forming apparatus of FIG. 1 will be described in detail with reference to FIGS. Fig. 2 is a structural diagram showing the imaging unit, and is a cross-sectional view perpendicular to the rotation axis of the photosensitive drum 11. Fig. 3 is a schematic cross-sectional view (vertical cross-sectional view) of the developing device 13 as seen in the longitudinal direction, and is a schematic diagram showing the positional relationship between the developing device 13 and the photosensitive drum 11 in the longitudinal direction. Since each image forming unit has almost the same structure, the image forming units and developing devices are shown in FIGS. 2 and 3 without the alphabetical symbols (Y, C, M, BK).

[0023] As shown in FIG. 2, the image forming unit is made up of a photosensitive drum 11 as an image carrier, a charging device 12, a developing device 13, a cleaning device 15, and the like. The photosensitive drum 11 serving as an image carrier is a negatively charged organic photosensitive member, and is rotated clockwise by a rotation drive mechanism.

[0024] The charging device 12 is an elastic charging roller in which a medium-resistance foamed urethane layer, which is made by compounding urethane resin, carbon black as conductive particles, a sulfide agent, a foaming agent, etc., is formed on a core metal. The medium-resistance layer of the charging device 12 can be made of rubber materials such as urethane, ethylene-propylene-diene polyethylene (EPDM), butadiene acrylonitrile rubber (NBR), silicone rubber, or isoprene rubber with conductive materials such as carbon black or metal oxide dispersed therein to adjust the resistance, or foamed versions of these materials can also be used. The cleaning device 15 is provided with a cleaning blade that slides against the photosensitive drum 11 and mechanically removes and collects untransferred toner on the photosensitive drum 11 .

[0025] The developing device 13 is arranged such that a developing roller 13a serving as a developer carrier faces the photosensitive drum 11 with a small gap therebetween via an opening A (formed in the developing case 13j). A developing area is formed where the photosensitive drum 11 and a magnetic brush (developer G in a standing state) come into contact with each other at the opposing portion of the developing roller 13a and the photosensitive drum 11. The developing device 13 contains developer G (two-component developer) consisting of toner T and carrier C. The developing device 13 develops the electrostatic latent image formed on the surface of the photosensitive drum 11 (to form a toner image). The configuration and operation of the developing device 13 will be described in detail later.

[0026] 1, toner container 28 stores therein toner T to be supplied into developing device 13. Specifically, based on information on the toner concentration (the ratio of toner in developer G) detected by a magnetic sensor (not shown) installed in developing device 13, toner T is supplied appropriately from toner container 28 to the inside of developing device 13 through a toner transport pipe and a supply port 13d (see FIG. 3).

[0027] The developing device 13 in the image forming apparatus will be described in detail below. 2 and 3, the developing device 13 is composed of a developing roller 13a as a developer carrier, a first transport screw 13b1 as a first transport member, a second transport screw 13b2 as a second transport member, a round doctor rod 13c as a developer regulating member, a partition 13e as a wall, a filter 13k that covers an exhaust port 13j1 of the developing case 13j, etc. These members 13a, 13b1, 13b2, 13c, 13e, and 13k are contained in the developing case 13j (housing).

[0028] The developing roller 13a, which serves as a developer carrier, is configured so that the sleeve 13a2, which is made of a cylindrical non-magnetic material such as aluminum, brass, stainless steel, or conductive resin, is rotated in the direction of the arrow shown in Figure 2 together with the first conveying screw 13b1 and the second conveying screw 13b2 by a drive mechanism (drive motor 91). Referring to FIG. 3, a magnet 13a1 is fixed inside a sleeve 13a2 of the developing roller 13a, and forms a plurality of magnetic poles (S1 pole, N1 pole, S2 pole, N2 pole, N3 pole) on the circumferential surface of the sleeve 13a2. The developer G carried on the developing roller 13a is transported as the developing roller 13a rotates in a predetermined direction (counterclockwise in FIG. 2) and reaches the position of the doctor rod 13c (developer regulating member). The developer G on the developing roller 13a is then regulated to an appropriate amount at this position, and then transported to a position facing the photosensitive drum 11 (the developing area). The toner is then attracted to the latent image formed on the photosensitive drum 11 by the electric field (developing electric field) formed in the developing area.

[0029] Referring to Figure 2 (and Figure 3), the multiple magnetic poles formed around the developing roller 13a (sleeve 13a2) by the magnet 13a1 are composed of an N1 pole (main magnetic pole) formed at a position opposite the photosensitive drum 11, an S2 pole (transport magnetic pole) formed downstream of the N1 pole (downstream in the direction of rotation of the developing roller 13a) at a position overlapping the upper part of the developing case 13j, an N2 pole (pre-agent release magnetic pole) formed downstream of the S2 pole and diagonally above the developing roller 13a, an agent release magnetic pole (N pole) formed above the first transport path B1 at a position sandwiched between the N2 pole and the N3 pole, an N3 pole (post-agent release magnetic pole) formed downstream of the agent release magnetic pole and above the first transport path B1, an S1 pole (pumping magnetic pole) formed from the position opposite the first transport screw 13b1 to the vicinity of the position opposite the round doctor rod 13c, etc. First, the S1 pole (pumping magnetic pole) acts on the carrier as a magnetic body, and the developer G contained in the first transport path B1 is pumped onto the developing roller 13a. A portion of the developer G carried on the developing roller 13a is scraped off at the position of the doctor rod 13c, which serves as a developer regulating member, and returned to the first transport path B1. Meanwhile, at the position of the doctor rod 13c where the magnetic force of the S1 pole acts, the developer G carried on the developing roller 13a passes through the doctor gap between the doctor rod 13c and the developing roller 13a. The developer G then stands up at the position of the N1 pole (main magnetic pole) and forms a magnetic brush in the development area, sliding against the photosensitive drum 11. Thus, the toner T in the developer G carried on the developing roller 13a adheres to the latent image on the photosensitive drum 11. After passing the position of the N1 pole, the developer G is transported to the position of the developer release magnetic pole (N pole) by the S2 and N2 poles. Then, at the position of the developer releasing magnetic pole, a repulsive magnetic field (a magnetic field that acts in a direction away from the developing roller 13a) acts on the carrier, causing the developer G carried on the developing roller 13a after the development process to separate from the developing roller 13a. The released developer G falls into the first transport path B1, is collected by the first transport screw 13b1, and is transported downstream of the first transport path B1.

[0030] The six magnetic poles described above are formed by five poles (S1 pole, N1 pole, S2 pole, N2 pole, and N3 pole) magnetized on the magnet 13a1 of the developing roller 13a. Of the six magnetic poles, only the agent release magnetic pole (N pole) is not formed directly by a pole magnetized on the magnet 13a1, but is formed by being sandwiched between two magnetic poles (N2 pole and N3 pole) of the same polarity (N pole in this embodiment). The five poles described above can also be formed with the south poles and north poles reversed.

[0031] 2, the doctor rod 13c as a developer regulating member is a magnetic cylindrical member disposed below the developing roller 13a. The developing roller 13a rotates counterclockwise in FIG. 2, and the photosensitive drum 11 rotates clockwise in FIG. 2. With this configuration, the photosensitive drum 11 is disposed below the intermediate transfer belt 17 in order to shorten the transport path of the sheet P and reduce the horizontal size of the image forming apparatus main body 1. The rotation direction of the developing roller 13a in the development gap is set to the forward direction relative to the photosensitive drum 11. By setting the rotation direction to the forward direction in this way, it is possible to ensure sufficient development time in the development gap and improve development performance, compared to when the doctor rod 13c is disposed above the developing roller 13a and the rotation direction of the developing roller 13a is reversed relative to the photosensitive drum 11.

[0032] As shown in FIG. 3, two transport members (a first transport screw 13b1 and a second transport screw 13b2) agitate and mix the developer G contained in the developing device 13 while circulating it in the width direction (the direction perpendicular to the plane of the paper in FIG. 2, which is the left-right direction in FIG. 3). The first transport screw 13b1 as a first transport member is disposed below the developing roller 13a in a position facing the developing roller 13a, transports the developer G horizontally in the width direction (axial direction) (from right to left as indicated by the dashed arrow in FIG. 3), supplies the developer G onto the developing roller 13a at the position of the pick-up magnetic pole (S1 pole), and transports the developer G that has fallen off the developing roller 13a and fallen toward the downstream side in the width direction (the other end side in the width direction) at the position of the developer releasing magnetic pole (N pole). The first transport screw 13b1 rotates in the counterclockwise direction in FIG. 2 as its forward direction.

[0033] The second transport screw 13b2, which serves as a second transport member, is disposed below the first transport screw 13b1 and faces the developing roller 13a via the first transport screw 13b1. The second transport screw 13b2 transports the developer G horizontally in the longitudinal direction along the second transport path B2 (from left to right as indicated by the dashed arrow in FIG. 3). In this embodiment, the second transport screw 13b2 is set so that its rotation direction (the forward rotation direction) is opposite to the rotation direction of the first transport screw 13b1 (clockwise in FIG. 2).

[0034] Here, gears are provided on one end (the end on the right side in FIG. 3) of the shafts of the developing roller 13a (sleeve 13a2), first transport screw 13b1, and second transport screw 13b2, respectively, and these form a gear train. The driving force of the drive motor 91 is transmitted to the gear train, causing the developing roller 13a, first transport screw 13b1, and second transport screw 13b2 to rotate in the above-mentioned rotation directions. In this embodiment, the drive motor 91 is a bidirectional motor that can rotate the developing roller 13a, the first transport screw 13b1, and the second transport screw 13b2 in both the above-mentioned rotation direction (the forward rotation direction) and the reverse direction, as will be explained in more detail later.

[0035] The second transport screw 13b2 circulates the developer G from the downstream side in the axial direction of the first transport path B1 defined by the first transport screw 13b1 through a second communication port 13g (second relay portion) that is not partitioned by the partition portion 13e. The second transport screw 13b2 then transports the developer G to the upstream side in the axial direction of the first transport path B1 defined by the first transport screw 13b1 through a first communication port 13f (first relay portion) that is not partitioned by the partition portion 13e (transportation indicated by the dashed arrow in FIG. 3). The first transport screw 13b1 and the second transport screw 13b2 are both disposed so that their rotation axes are substantially horizontal, similar to the developing roller 13a and the photosensitive drum 11. The first transport screw 13b1 and the second transport screw 13b2 each have a screw portion (formed with a predetermined screw pitch and number of threads) spirally wound around the shaft. The screw portion may have one or more threads.

[0036] The first conveying path B1 of the first conveying screw 13b1 and the second conveying path B2 of the second conveying screw 13b2 are separated from each other by a partition 13e (wall) except at both ends. 3, the upstream side of the first transport path B1 formed by the first transport screw 13b1 and the downstream side of the second transport path B2 formed by the second transport screw 13b2 are in communication with each other via a first communication opening 13f. In other words, the first communication opening 13f is formed at one end in the width direction so that the developer on the upstream side of the first transport screw 13b1 (first transport member) and the developer on the downstream side of the second transport screw 13b2 (second transport member) can flow together. The developer G that reaches the downstream side of the second transport path formed by the second transport screw 13b2 remains near the first communication opening 13f and rises up, and is transported (supplied) to the upstream side of the first transport path B1 formed by the first transport screw 13b1 via the first communication opening 13f. 3, the downstream side of the first transport path B1 formed by the first transport screw 13b1 and the upstream side of the second transport path B2 formed by the second transport screw 13b2 are connected via a second communication port 13g. In other words, the second communication port 13g is formed on the other widthwise end side so that the developer downstream of the first transport screw 13b1 (first transport member) and the developer upstream of the second transport screw 13b2 (second transport member) can circulate. Developer G that reaches the downstream side of the first transport path B1 formed by the first transport screw 13b1 (developer G that was not supplied onto the developing roller 13a in the first transport path B1 or developer G that has separated from and fallen from the developing roller 13a at the position of the developer separation magnetic pole (N pole) in the developing roller 13a) falls under its own weight through the second communication port 13g and reaches the upstream side of the second transport path B2.

[0037] With this configuration, the two transport members (first transport screw 13b1 and second transport screw 13b2) form a circulation path that circulates the developer G in the width direction (longitudinal direction) in the developing device 13. That is, when the developing device 13 is operated, the developer G contained in the device flows in the direction of the dashed arrow in FIG. In this way, by forming the circulation paths (first transport path B1 and second transport path B2) of developer G relative to developing roller 13a in the vertical direction instead of the horizontal direction, it is possible to reduce the horizontal size of developing device 13 (make it longer). In particular, in a tandem-type color image forming apparatus 1 in which multiple developing devices 13 (imaging units) are arranged side by side in the horizontal direction, it is possible to effectively reduce the overall horizontal size by reducing the horizontal size of the multiple developing devices 13 (imaging units).

[0038] A magnetic sensor (not shown) that detects the toner concentration of the developer G circulating inside the device is installed in the transport path of the second transport screw 13b2. Based on the information on the toner concentration detected by the magnetic sensor, new toner T is supplied from the toner container 28 (see FIG. 1) into the developing device 13 through the supply port 13d that is disposed on the other end side in the width direction (on the left side in FIG. 3) of the second communication port 13g.

[0039] Also, referring to Figure 3, the supply port 13d (toner supply port) is arranged above the upstream side of the second transport path B2 by the second transport screw 13b2, at a position away from the development area (outside the widthwise range of the development roller 13a). In other words, the second transport path B2 is provided with an extension portion B2a that extends toward the other widthwise end side (the left side in Figure 3) of the second communication port 13g and has a supply port 13d formed therein for supplying toner T during the development process. Then, new toner T discharged from the toner container 28 is appropriately replenished from the replenishing port 13d toward the inside of the developing device 13 (supply in the direction of the white arrow in FIG. 3). By locating the replenishing port 13d in the vicinity of the second communicating port 13g in this way, it is possible to sufficiently disperse and mix the replenished toner over a relatively long period of time with the developer G that is supplied downstream on the second transport path B2 by falling from the second communicating port 13g under its own weight.

[0040] The toner T used in this embodiment (the toner in the developer G and the toner in the toner container 28) may be a polymerized toner having a small particle size with a volume average particle size of about 5.0 to 6.0 μm. Furthermore, as the carrier C in the developer G, a small-diameter carrier formed so as to have a weight average particle diameter of 20 to 60 μm can also be used.

[0041] The characteristic configuration and operation of developing device 13 in this embodiment will be described below. As previously explained using Figures 2, 3, etc., the developing device 13 in this embodiment is equipped with a developing roller 13a as a developer carrier, a first transport screw 13b1 as a first transport member, a second transport screw 13b2 as a second transport member, and the like. The developing roller 13a as a developer carrier develops a latent image formed on the surface of the photosensitive drum 11 as an image carrier. In this embodiment, the developing roller 13a has an outer diameter of about 16 mm.

[0042] The first transport screw 13b1 as a first transport member is installed on the first transport path B1 so as to face the developing roller 13a (developer carrier). Furthermore, the first transport screw 13b1 rotates in the forward direction (the direction of the arrow in FIGS. 2, 3, and 5A) during the development process (normally) to transport the developer G from one end side in the width direction (the right side in FIGS. 3 and 5A) to the other end side in the width direction (the left side in FIGS. 3 and 5A) and supply the developer G to the developing roller 13a. The first conveying screw 13b1 has a shaft 13b11 extending in the width direction (the direction perpendicular to the plane of FIG. 2, and the left-right direction in FIGS. 3 and 5(A)) and a screw portion 13b12 spirally wound around it (see FIG. 7). In this embodiment, the first conveying screw 13b1 has an outer diameter of the shaft 13b11 set to about 8 mm and an outer diameter of the screw portion 13b12 set to about 12 mm.

[0043] The second transport screw 13b2 as a second transport member is installed on the second transport path B2 so as to face the first transport screw 13b1 (first transport member) via the partition 13e. Furthermore, the second transport screw 13b2 rotates in the forward direction (the direction of the arrow in FIGS. 2, 3, and 5A) during the development process (normally) to agitate the developer G while transporting it from the other end side in the width direction (the left side in FIGS. 3 and 5A) to one end side in the width direction (the right side in FIGS. 3 and 5A). The second conveying screw 13b2 has a shaft 13b21 extending in the width direction (the direction perpendicular to the plane of FIG. 2, and the left-right direction in FIGS. 3 and 5(A)) and a screw portion 13b22 spirally wound around it (see FIG. 6). In this embodiment, the second conveying screw 13b2 has a shaft 13b21 with an outer diameter of about 5 mm and a screw portion 13b22 with an outer diameter of about 13 mm. In this embodiment, the second transport path B2 is disposed below the first transport path B1, as shown in FIG. 3, the second transport path B2 is provided with an extension 13b2a extending toward the other end in the width direction (the left side in FIG. 3) of the second communication port 13g. A supply port 13d for supplying toner during the developing process is formed above the extension 13b2a. Note that the supply port 13d is also used as a filling port for filling the developing device 13 with preset developer G at the time of shipping from the factory.

[0044] Here, as previously described using Figure 3 etc., the developing device 13 in this embodiment is provided with a first communication port 13f and a second communication port 13g to form a circulation path between the first transport path B1 and the second transport path B2. The first communication opening 13f opens in the partition portion 13e at one end side in the width direction (the right side in FIG. 3) so as to connect the first transport path B1 and the second transport path B2. On the other hand, the second communication port 13g opens in the partition portion 13e at the other end side in the width direction (the left side in FIG. 3) so as to communicate the first transport path B1 and the second transport path B2.

[0045] In this embodiment, the second communication port 13g is formed with an opening area (N2×M) smaller than the opening area (N1×M) of the first communication port 13f (N1×M>N2×M). Specifically, referring to Figure 4 (and Figure 3), in this embodiment, the widthwise length N1 of the first communication opening 13f is set to approximately 20 mm, the widthwise length N2 of the second communication opening 13g is set to approximately 7 mm, and the lengths M of the first and second communication openings 13f, 13g in the direction perpendicular to the widthwise direction are set to be equal.

[0046] On the other hand, referring to Figure 5 (B), the developing device 13 in this embodiment is configured to be able to execute a "reverse rotation mode" in which the first transport screw 13b1 (first transport member) and the second transport screw 13b2 (second transport member) rotate in opposite directions. Specifically, the drive motor 91 that drives the developing device 13 (developing roller 13a, first and second conveying screws 13b1, 13b2) is a bidirectional motor that can be controlled by the control unit 90, and can switch the direction of rotation by rotating the developing device 13 forward as shown in Figures 2, 3, and 5(A) during the development process or when filling developer, or by rotating the developing device 13 backward as shown in Figure 5(B).

[0047] Here, as shown in Figure 5(B), the "reverse rotation mode" in which the developing device 13 (developing roller 13a, first and second transport screws 13b1, 13b2) is rotated in reverse is mainly executed when the developing device 13 is shipped from the manufacturing factory. Specifically, when the developing device 13 is shipped from the factory, it is shipped with developer G already stored (preset) inside, as shown in FIG. 8A. Specifically, while the empty developing device 13 is rotating forward as shown in FIG. 5A, a predetermined amount of developer G is filled through the supply port 13d. After the developer G is filled, the inside of the developing device 13 is in a state where the developer G has sufficiently spread throughout both the first and second transport paths B1 and B2, as shown in FIG. 5A. However, if the developing device 13 is shipped with a large amount of developer G stored (preset) in the first transport path B1, the preset developer G is likely to leak out of the device from the opening A (see FIG. 2) of the developing device 13 due to vibrations of the transportation means, such as a truck, train, or airplane, during transportation after leaving the factory. 8(B) as a comparative example of the developing device 130, a sheet-like sealing member 13z may be installed to prevent the preset developer G from leaking out of the device from the developing device 130 (opening A). However, this requires the time and effort of installing the sealing member 13z at the time of shipping from the factory, and removing the sealing member 13z at the time of delivery.

[0048] Therefore, in this embodiment, the sealing member 13z is not installed, and the developing device 13 is shipped in a state where almost no developer G is stored (preset) in the first transport path B1. Therefore, the "reverse rotation mode" is executed to move the developer G in the first transport path B1 into the second transport path B2, and the developing device 13 is shipped in a state where almost all of the developer G is stored (preset) in the second transport path B2 (the state shown in Figure 8(A)). By executing the "reverse rotation mode," the transport direction of developer G is reversed not only on the first transport path B1 but also on the second transport path B2. That is, as shown in FIG. 5B, developer G moves from left to right on the first transport path B1, and when it reaches the first communication opening 13f, it falls by gravity onto the second transport path B2, and then moves from right to left on the second transport path B2. However, if the transport force of the second transport screw 13b2 on the second transport path B2 (the force (transport amount) that transports developer G from right to left in FIG. 5B)) is large, developer G is more likely to be transferred from the second transport path B2 to the first transport path B1 via the second communication opening 13g, which would defeat the purpose of reducing the amount of developer in the first transport path B1.

[0049] For this reason, in this embodiment, the second transport screw 13b2 (second transport member) is configured so that the transport force that transports the developer G from one end side in the width direction (right side in Figure 5(B)) to the other end side in the width direction (left side in Figure 5(B)) during reverse rotation mode is smaller than the transport force that transports the developer G from the other end side in the width direction (left side in Figure 5(A)) to one end side in the width direction (right side in Figure 5(A)) during forward rotation mode. That is, in the reverse rotation mode, the conveying force of the second conveying screw 13b2 is reduced compared to normal times. As a result, in the reverse rotation mode, developer G is less likely to move from the second transport path B2 to the first transport path B1 through the second communication port 13g, and as shown in FIG. 8A, almost all of the pre-setting developer G can be stored in the second transport path B2. Therefore, even if a sealing member 13z (see FIG. 8B) is not installed at the time of shipment from the factory, the problem of preset developer G leaking out of the device from the opening A (see FIG. 2) of the developing device 13 during transportation after shipment from the factory is less likely to occur. Furthermore, not installing the sealing member 13z in this way eliminates the need to install the sealing member 13z at the time of shipment from the factory and the need to remove the sealing member 13z when the device arrives.

[0050] In particular, in this embodiment, as described above, the opening area of ​​the second communication port 13g is set smaller than the opening area of ​​the first communication port 13f, so that in the reverse rotation mode, it becomes even more difficult for the developer G to move from the second transport path B2 to the first transport path B1 through the second communication port 13g, making it easier to achieve the above-mentioned effect. During normal forward rotation, developer G moves from the first transport path B1 to the second transport path B2 through the second communication port 13g, which has a small opening area (N2 x M), but since this movement is due to gravity, the movement does not become unsmooth.

[0051] The work of filling the developing device 13 with the preset developer G in the factory will be described below. First, in a factory, an operator (factory worker) places an empty, assembled developing device 13 on a jig (a device that can drive the developing device 13 forward and reverse), and while rotating the developing device 13 forward as shown in FIG. 5A, fills a predetermined amount of developer G through the supply port 13d. After filling with developer G is complete, the operator seals the supply port 13d with a cap-shaped seal member 13x (see FIG. 8A), and rotates the developing device 13 in reverse for about 20 seconds as shown in FIG. 5B (executing the reverse rotation mode). As a result, the developing device 13 is shipped with the preset developer G stored in the second transport path B2 as shown in FIG. 8A.

[0052] In this embodiment, the image forming apparatus is configured so that the "reverse rotation mode" can be executed by operating an operation display panel 100 as an operation unit installed on the image forming apparatus main body 1. More specifically, with the developing device 13 attached to the image forming apparatus 1, the operator operates the operation display panel 100 to display a screen showing an execute button for the reverse rotation mode, and then presses the execute button. This causes the reverse rotation mode of the developing device 13 to be executed in the image forming apparatus 1. The reverse rotation mode of the developing device 13 in such an image forming apparatus 1 can be implemented when the image forming apparatus 1 is shipped with the developing device (containing preset developer G) attached. Furthermore, when a replacement developing device 13 that has been used in the image forming apparatus 1 is collected in the market (at the user's site), the reverse rotation mode of the developing device 13 can be executed in the image forming apparatus 1. In this case, the collected developing device 13 will have most of the used developer G contained in the second transport path B2, so that even when the developing device 13 is transported, leakage of the developer G outside the apparatus can be reduced.

[0053] As explained above, in this embodiment, the conveying force of the second transport screw 13b2 is reduced in the reverse rotation mode, and almost all of the developer G is moved into the second transport path B2 so that the developer G in the first transport path B does not return to the first transport path B1 via the second transport path B2. To ensure such movement of the developer G into the second transport path B2, it is preferable that the conveying force of the first transport screw 13b1 does not decrease even if the conveying force of the second transport screw 13b2 decreases in the reverse rotation mode. However, in order to perform the reverse rotation mode in this way, it is not possible to achieve this by simply slowing down the rotation speed of the drive motor 91 in the reverse rotation mode compared to that in the forward rotation (normal) mode. Therefore, in this embodiment, as described below, the shape of the screw portion 13b22 of the second conveying screw 13b2 is made distinctive so that the conveying force of the second conveying screw 13b2 changes between the reverse rotation mode and the forward rotation mode.

[0054] Fig. 6(A) is a diagram showing the second transport screw 13b2 in the axial direction, and during forward rotation (normal operation), it rotates in the forward direction indicated by the solid line to transport developer G in the direction of the solid line arrow, and during reverse rotation mode (reverse rotation), it rotates in the reverse direction indicated by the dashed line to transport developer G in the direction of the dashed line arrow. Fig. 6(B) is an enlarged view showing one blade of the screw portion 13b2. As shown in Figure 6, the screw portion 13b22 of the second conveying screw 13b2 is formed such that, throughout the entire axial direction (along the axial direction), a first conveying surface 13b22a is inclined at a first inclination angle θ1 (set to 5 degrees or less in this embodiment) with respect to a virtual perpendicular plane S perpendicular to the axial direction, and serves as an opposing surface facing one end side in the width direction (the right side in Figure 6), and a second conveying surface 13b22b is inclined at a second inclination angle θ2 (set to 60 degrees or less in this embodiment) larger than the first inclination angle θ1 with respect to the above-mentioned virtual perpendicular plane S, and serves as an opposing surface facing the other end side in the width direction (the left side in Figure 6). That is, compared to the first transport surface 13b22a, which serves as the transport surface for transporting developer G during forward rotation, the second transport surface 13b22b, which serves as the transport surface for transporting developer G during reverse rotation mode, is inclined more significantly with respect to the virtual perpendicular plane S (it is inclined less significantly with respect to the axial direction). Specifically, in this embodiment, as shown in Fig. 6(B), the first inclination angle θ1 is set to 2 degrees, and the first transport surface 13b22a has a shape with almost no inclination. Therefore, during forward rotation, the developer G receives a relatively large force F1 (transport force) from the first transport surface 13b22a and is transported to the right in Fig. 6. In contrast, the second inclination angle θ2 is set to 30 degrees, and the second transport surface 13b22b has a large inclination. Therefore, in the reverse rotation mode, the developer G receives a relatively small force F2x (transport force) from the second transport surface 13b22b and is transported to the left in Figure 6. Note that this force F2x is a force (F2x = F2 × cos θ2) that is reduced in the axial direction by the inclination of the second transport surface 13b22b. Due to the shape of the screw portion 13b22 of the second transport screw 13b2, the transport force of the second transport screw 13b2 changes between the reverse rotation mode and the forward rotation mode. In particular, by setting the first inclination angle θ1 to 5 degrees or less and the second inclination angle θ2 (>θ1) to 60 degrees or less, the purpose of the reverse rotation mode can be achieved without causing poor transport of the developer G.

[0055] Here, in this embodiment, the screw portion 13b22 of the second conveying screw 13b2 is also formed in the extension portion B2a (see Figure 3) of the second conveying path B2 such that a first conveying surface 13b22a inclined at a first inclination angle θ1 with respect to the virtual perpendicular plane S is formed as an opposing surface facing one end side in the width direction (right side in Figures 3 and 6), and a second conveying surface 13b22b inclined at a second inclination angle θ2 larger than the first inclination angle θ1 with respect to the above-mentioned virtual perpendicular plane S is formed as an opposing surface facing the other end side in the width direction (left side in Figures 3 and 6). That is, even in the extension portion B2a where the supply port 13d is formed, the conveying force of the second conveying screw 13b2 in the reverse rotation mode is made smaller than that in the forward rotation mode. By configuring it in this manner, during the development process (or when developer is being filled), the developer G supplied (or filled) from the supply port 13d flows smoothly downstream, and in the reverse rotation mode, the problem of developer G collected in the second transport path B2 accumulating in large quantities near the supply port 13d is less likely to occur.

[0056] Here, in this embodiment, the first transport screw 13b1 (first transport member) is configured so that the transport force that transports the developer G from the other widthwise end side (left side in Figure 3, right side in Figure 7) to one widthwise end side (right side in Figure 3, left side in Figure 7) during reverse rotation mode is equivalent to the transport force that transports the developer G from one widthwise end side to the other widthwise end side during forward rotation. That is, the conveying force of the first conveying screw 13b1 does not change whether in the forward rotation mode or the reverse rotation mode. In detail, as shown in FIG. 7, the screw portion 13b12 of the first conveying screw 13b1 has a first conveying surface 13b12a formed as an opposing surface facing one end in the width direction, the first conveying surface 13b12a being inclined at a first inclination angle θ1 with respect to the virtual perpendicular plane S along the axial direction, and a second conveying surface 13b12b being inclined at a second inclination angle θ2 equivalent to the first inclination angle θ1 with respect to the virtual perpendicular plane S as an opposing surface facing the other end in the width direction. Specifically, in this embodiment, as shown in Fig. 7(B), the first and second inclination angles θ1 and θ2 are both set to 2 degrees, and the first and second transport surfaces 13b12a and 13b12b are barely inclined. Therefore, during forward rotation, the developer G receives a relatively large force F1 (transport force) from the first transport surface 13b12a and is transported to the right in Fig. 7. Also, during reverse rotation, the developer G receives a relatively large force F2 (transport force) from the second transport surface 13b12b and is transported to the left in Fig. 7. With this configuration, even if the conveying force of the second conveying screw 13b2 decreases in the reverse rotation mode, the conveying force of the first conveying screw 13b1 does not decrease. Therefore, the reverse rotation mode can quickly move the developer G in the first conveying path B to the second conveying path B2, and the problem of the developer G having moved to the second conveying path B2 returning to the first conveying path B1 is less likely to occur.

[0057] In this embodiment, when the reverse rotation mode is being executed and the drive torque of the developing device 13 (drive motor 91) exceeds a predetermined value, the reverse rotation mode is interrupted. 2, the image forming apparatus main body 1 (or the developing device 13) is provided with a torque detection unit 92 (torque detection means) that detects the drive torque of the developing device 13. As the torque detection unit 92, for example, one that detects a change in drive torque from a change in current in the drive motor 91 can be used. By configuring in this manner, it is possible to prevent problems such as developer G clogging the second transport path B2 and causing an increase in drive torque, which could result in damage to the drive system, when the reverse rotation mode is being executed.

[0058] In this embodiment, the conveying force of the second conveying screw 13b2 in the reverse rotation mode is set smaller than the conveying force of the second conveying screw 13b2 in the forward rotation mode across the entire width. In contrast to this, it is also possible to make the conveying force of the second conveying screw 13b2 in the reverse rotation mode smaller than the conveying force of the second conveying screw 13b2 in the forward rotation mode only in the vicinity of the second communication port 13g, rather than over the entire width direction. That is, referring to Figure 3, in the range from the second communication port 13g to a position a predetermined distance X away from one end in the width direction, the conveying force of the second conveying screw 13b2 (second conveying member) to convey the developer G from one end in the width direction to the other end in the width direction during the reverse rotation mode is smaller than the conveying force to convey the developer G from the other end in the width direction to one end in the width direction during rotation in the forward direction. Specifically, in part of the axial direction (within a range of a predetermined length X in FIG. 3), the screw portion 13b22 of the second conveying screw 13b2 has a first conveying surface 13b22a inclined at a first inclination angle θ1 with respect to the imaginary orthogonal plane S as an opposing surface facing one end in the width direction, and a second conveying surface 13b22b inclined at a second inclination angle θ2 larger than the first inclination angle θ1 with respect to the imaginary orthogonal plane S as an opposing surface facing the other end in the width direction. Furthermore, outside the range X described above, both the first conveying surface 13b22a and the second conveying surface 13b22b are formed to be inclined at the same first inclination angle θ1. Even with this configuration, in the reverse rotation mode, the transport force on the developer G is weakened near the second communication port 13g of the second transport path B2, making it less likely that the developer G collected in the second transport path B2 will move to the first transport path B1 through the second communication port 13g. Therefore, it is possible to reduce leakage of the preset developer G during transportation without providing a sealing member 13z.

[0059] <Variation 1> Referring to Figure 9, in the developing device 13 in variant example 1, the screw portion 13b22 of the second transport screw 13b2 (second transport member) is configured so that the second inclination angle θ2' (see Figure 9(B)) of the second transport surface 13b22b located at one end side in the width direction (the upstream side in reverse rotation mode) is smaller than the second inclination angle θ2 (see Figure 9(A)) of the second transport surface 13b22b located at the other end side in the width direction (the downstream side in reverse rotation mode) (θ2'<θ2). When configured in this manner, the second inclination angle θ2 of the second conveying surface 13b22b may be configured to increase continuously (gradually increase) from one end side in the width direction to the other end side in the width direction, or may be configured to increase stepwise from one end side in the width direction to the other end side in the width direction. Even with this configuration, in the reverse rotation mode, the transport force on the developer G is weakened near the second communication port 13g of the second transport path B2, making it less likely that the developer G collected in the second transport path B2 will move to the first transport path B1 via the second communication port 13g. Furthermore, in the first modification, the opening area of ​​the second communication port 13g is set smaller than the opening area of ​​the first communication port 13f. Therefore, leakage of the preset developer G during transportation can be reduced without providing a sealing member 13z.

[0060] <Variation 2> Referring to Figure 10, in the developing device 13 of variant example 2, the number of threads of the screw portion 13b12 of the first transport screw 13b1 is set to 3 and the lead length is set to 45 mm, and the number of threads of the screw portion 13b22 of the second transport screw 13b2 is set to 2 and the lead length is set to 30 mm. Also in the second modification, in the reverse rotation mode, the transport force on the developer G is weakened at least near the second communication port 13g on the second transport path B2. Furthermore, also in the second modification, the opening area of ​​the second communication port 13g is set smaller than the opening area of ​​the first communication port 13f. This makes it possible to reduce leakage of the preset developer G during transportation without providing a sealing member 13z.

[0061] As described above, the developing device in this embodiment is a developing device that contains developer G and includes a developing roller 13a (developer carrier) that develops a latent image formed on the surface of the photosensitive drum 11 (image carrier). Also, a first transport screw 13b1 (first transport member) is provided on the first transport path B1 so as to face the developing roller 13a, and rotates in the forward direction during the developing process to transport the developer G from one widthwise end to the other widthwise end while supplying the developer G to the developing roller 13a. Also, a second transport screw 13b2 (second transport member) is provided on the second transport path B2 so as to face the first transport screw 13b1 across the partition 13e, and rotates in the forward direction during the developing process to transport the developer G from the other widthwise end to the one widthwise end. The first and second transport screws 13b1 and 13b2 are also provided with a first communication opening 13f, which opens through the partition 13e at one widthwise end to connect the first transport path B1 and the second transport path B2, and a second communication opening 13g, which opens through the partition 13e at the other widthwise end to connect the first transport path B1 and the second transport path B2, and has an opening area smaller than that of the first communication opening 13f. The first transport screw 13b1 and the second transport screw 13b2 are configured to be operable in a reverse rotation mode in which they rotate in opposite directions. The second transport screw 13b2 is configured so that the conveying force for conveying the developer G from one widthwise end to the other widthwise end in the reverse rotation mode is smaller than the conveying force for conveying the developer G from the other widthwise end to the first widthwise end in the forward rotation mode. This makes it possible to reduce leakage of preset developer G during transportation without providing a sealing member.

[0062] In this embodiment, the present invention is applied to an image forming apparatus in which the developing device 13 is configured as a unit that is detachably attached to the image forming apparatus main body. However, the application of the present invention is not limited to this, and the present invention can also be applied to an image forming apparatus in which part or all of the image forming unit is configured as a process cartridge. In this case, the ease of maintenance of the image forming unit is improved. Here, in this application, a "process cartridge" is defined as a unit in which an image carrier and at least one of a charging device that charges the image carrier, a developing device that develops a latent image formed on the image carrier, and a cleaning device that cleans the image carrier are integrated, and which is detachably installed in the image forming apparatus main body.

[0063] In this embodiment, the present invention is applied to a developing device 13 in which the first transport path B1 is disposed above the second transport path B2 and the second transport path B2 faces the developing roller 13a via the first transport path B1. However, the developing device to which the present invention is applied is not limited to this, and the present invention can also be applied to a developing device in which, for example, the first transport path is disposed to the side of the second transport path and the second transport path faces the developing roller via the first transport path. In this embodiment, the present invention is applied to a developing device 13 that uses a two-component developer consisting of toner and carrier. However, the present invention can also be applied to a developing device that uses a one-component developer consisting only of toner (including external additives, etc.). In this case, the developing device can be configured so that the developing roller comes into contact with the photosensitive drum (image carrier). In such cases, the same effect as that of this embodiment can be obtained.

[0064] It is clear that the present invention is not limited to the present embodiment, and that within the scope of the technical concept of the present invention, the present embodiment may be modified as appropriate in addition to the modifications suggested in the present embodiment. Furthermore, the number, position, shape, etc. of the above-mentioned components are not limited to the present embodiment, and the number, position, shape, etc. of the components may be any number, position, shape, etc. that is suitable for implementing the present invention. [Explanation of symbols]

[0065] 1 Image forming apparatus (image forming apparatus main body), 11, 11Y, 11C, 11M, 11BK Photosensitive drum (image carrier), 13 developing device, 13a developing roller (developer carrier), 13b1 first conveying screw (first conveying member), 13b2 second conveying screw (second conveying member), 13b11, 13b21 shaft part, 13b12, 13b22 screw part, 13b12a, 13b22a first conveying surface, 13b12b, 13b22b second conveying surface; 13c Round doctor rod (developer regulating member), 13d supply port, 13e Partition (wall), 13f 1st communication port, 13g Second communication port, 90 torque detection unit (torque detection means), 100 Operation display panel (operation unit), B1 First transport route, B2 second conveyance path, B2a extension part, θ1 1st inclination angle, θ2 2nd inclination angle, S virtual orthogonal plane, G Developer (two-component developer), T Toner, C Carrier. [Prior art documents] [Patent documents]

[0066] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-1254 [Patent Document 2] Japanese Patent Application Publication No. 2019-128442

Claims

1. A developing device containing a developer therein, a developer carrier that develops a latent image formed on the surface of the image carrier; a first transport member that is disposed in a first transport path so as to face the developer carrier and that rotates in a forward direction during a developing step to transport the developer from one end side in the width direction to the other end side in the width direction while supplying the developer to the developer carrier; a second transport member that is installed in a second transport path so as to face the first transport member across a partition, and that rotates in a forward direction during a developing step to transport the developer from the other end side in the width direction to the one end side in the width direction; a first communication port that opens into the partition portion at one end side in the width direction so as to communicate the first transport path with the second transport path; a second communication opening that opens into the partition portion at the other end in the width direction so as to connect the first transport path and the second transport path, and that is formed with an opening area smaller than an opening area of ​​the first communication opening; Equipped with the second transport path includes an extension portion that extends toward the other end in the width direction relative to the second communication port and that has a supply port formed therein for supplying toner during a developing process; a reverse rotation mode in which the first conveying member and the second conveying member are rotated in opposite directions, the second conveying member has a shaft portion extending in the width direction and a screw portion wound around it, and a conveying force for conveying the developer from one end side in the width direction to the other end side in the width direction during the reverse rotation mode is smaller than a conveying force for conveying the developer from the other end side in the width direction to the one end side in the width direction during rotation in the forward direction, The screw portion is characterized in that, in the extension portion, a first conveying surface inclined at a first inclination angle with respect to a virtual orthogonal plane perpendicular to the axial direction is formed as an opposing surface facing one end side in the width direction, and a second conveying surface inclined at a second inclination angle larger than the first inclination angle with respect to the virtual orthogonal plane is formed as an opposing surface facing the other end side in the width direction.

2. A developing device containing a developer therein, a developer carrier that develops a latent image formed on the surface of the image carrier; a first transport member that is disposed in a first transport path so as to face the developer carrier and that rotates in a forward direction during a developing step to transport the developer from one end side in the width direction to the other end side in the width direction while supplying the developer to the developer carrier; a second transport member that is installed in a second transport path so as to face the first transport member across a partition, and that rotates in a forward direction during a developing step to transport the developer from the other end side in the width direction to the one end side in the width direction; a first communication port that opens into the partition portion at one end side in the width direction so as to communicate the first transport path with the second transport path; a second communication opening that opens into the partition portion at the other end in the width direction so as to connect the first transport path and the second transport path, and that is formed with an opening area smaller than an opening area of ​​the first communication opening; Equipped with the second transport path includes an extension portion that extends toward the other end in the width direction relative to the second communication port and that has a supply port formed therein for supplying toner during a developing process; a reverse rotation mode in which the first conveying member and the second conveying member are rotated in opposite directions, the second conveying member has a shaft portion extending in the width direction and a screw portion wound around it, and at least in a range from the second communication port to a position spaced a predetermined distance from the one end side in the width direction, a conveying force for conveying the developer from the one end side in the width direction to the other end side in the width direction during the reverse rotation mode is smaller than a conveying force for conveying the developer from the other end side in the width direction to the one end side in the width direction during rotation in the forward direction, The screw portion is characterized in that, in the extension portion, a first conveying surface inclined at a first inclination angle with respect to a virtual orthogonal plane perpendicular to the axial direction is formed as an opposing surface facing one end side in the width direction, and a second conveying surface inclined at a second inclination angle larger than the first inclination angle with respect to the virtual orthogonal plane is formed as an opposing surface facing the other end side in the width direction.

3. A developing device containing a developer therein, a developer carrier that develops a latent image formed on the surface of the image carrier; a first transport member that is disposed in a first transport path so as to face the developer carrier and that rotates in a forward direction during a developing step to transport the developer from one end side in the width direction to the other end side in the width direction while supplying the developer to the developer carrier; a second transport member that is installed in a second transport path so as to face the first transport member across a partition, and that rotates in a forward direction during a developing step to transport the developer from the other end side in the width direction to the one end side in the width direction; a first communication port that opens into the partition portion at one end side in the width direction so as to communicate the first transport path with the second transport path; a second communication opening that opens into the partition portion at the other end in the width direction so as to connect the first transport path and the second transport path, and that is formed with an opening area smaller than an opening area of ​​the first communication opening; Equipped with a reverse rotation mode in which the first conveying member and the second conveying member are rotated in opposite directions, the second conveying member has a shaft portion extending in the width direction and a screw portion wound around it, and a conveying force for conveying the developer from one end side in the width direction to the other end side in the width direction during the reverse rotation mode is smaller than a conveying force for conveying the developer from the other end side in the width direction to the one end side in the width direction during rotation in the forward direction, In the screw portion, in the whole or part of the axial direction, a first conveying surface inclined at a first inclination angle with respect to a virtual orthogonal plane orthogonal to the axial direction is formed as an opposing surface facing one end side in the width direction, and a second conveying surface inclined at a second inclination angle larger than the first inclination angle with respect to the virtual orthogonal plane is formed as an opposing surface facing the other end side in the width direction, A developing device, wherein the first tilt angle is set to 5 degrees or less, and the second tilt angle is set to 60 degrees or less.

4. A developing device containing a developer therein, a developer carrier that develops a latent image formed on the surface of the image carrier; a first transport member that is disposed in a first transport path so as to face the developer carrier and that rotates in a forward direction during a developing step to transport the developer from one end side in the width direction to the other end side in the width direction while supplying the developer to the developer carrier; a second transport member that is installed in a second transport path so as to face the first transport member across a partition, and that rotates in a forward direction during a developing step to transport the developer from the other end side in the width direction to the one end side in the width direction; a first communication port that opens into the partition portion at one end side in the width direction so as to communicate the first transport path with the second transport path; a second communication opening that opens into the partition portion at the other end in the width direction so as to connect the first transport path and the second transport path, and that is formed with an opening area smaller than an opening area of ​​the first communication opening; Equipped with a reverse rotation mode in which the first conveying member and the second conveying member are rotated in opposite directions, the second conveying member has a screw portion wound around a shaft portion extending in the width direction, and at least in a range from the second communication port to a position spaced a predetermined distance from the one end side in the width direction, a conveying force for conveying the developer from the one end side in the width direction to the other end side in the width direction during the reverse rotation mode is smaller than a conveying force for conveying the developer from the other end side in the width direction to the one end side in the width direction during rotation in the forward direction, In the screw portion, in the whole or part of the axial direction, a first conveying surface inclined at a first inclination angle with respect to a virtual orthogonal plane orthogonal to the axial direction is formed as an opposing surface facing one end side in the width direction, and a second conveying surface inclined at a second inclination angle larger than the first inclination angle with respect to the virtual orthogonal plane is formed as an opposing surface facing the other end side in the width direction, A developing device, wherein the first tilt angle is set to 5 degrees or less, and the second tilt angle is set to 60 degrees or less.

5. A developing device as described in claim 3 or claim 4, characterized in that the screw portion of the second conveying member has a second inclination angle of the second conveying surface located at one end side in the width direction that is smaller than the second inclination angle of the second conveying surface located at the other end side in the width direction.

6. A developing device containing a developer therein, a developer carrier that develops a latent image formed on the surface of the image carrier; a first transport member that is disposed in a first transport path so as to face the developer carrier and that rotates in a forward direction during a developing step to transport the developer from one end side in the width direction to the other end side in the width direction while supplying the developer to the developer carrier; a second transport member that is installed in a second transport path so as to face the first transport member across a partition, and that rotates in a forward direction during a developing step to transport the developer from the other end side in the width direction to the one end side in the width direction; a first communication port that opens into the partition portion at one end side in the width direction so as to communicate the first transport path with the second transport path; a second communication opening that opens into the partition portion at the other end in the width direction so as to connect the first transport path and the second transport path, and that is formed with an opening area smaller than an opening area of ​​the first communication opening; Equipped with a reverse rotation mode in which the first conveying member and the second conveying member are rotated in opposite directions, a conveying force of the second conveying member, which conveys the developer from the one end side in the width direction to the other end side in the width direction during the reverse rotation mode, is smaller than a conveying force of the second conveying member, which conveys the developer from the other end side in the width direction to the one end side in the width direction during rotation in the forward direction; The developing device, wherein, when the reverse rotation mode is being executed and a driving torque of the developing device exceeds a predetermined value, the reverse rotation mode is interrupted.

7. A developing device containing a developer therein, a developer carrier that develops a latent image formed on the surface of the image carrier; a first transport member that is disposed in a first transport path so as to face the developer carrier and that rotates in a forward direction during a developing step to transport the developer from one end side in the width direction to the other end side in the width direction while supplying the developer to the developer carrier; a second transport member that is installed in a second transport path so as to face the first transport member across a partition, and that rotates in a forward direction during a developing step to transport the developer from the other end side in the width direction to the one end side in the width direction; a first communication port that opens into the partition portion at one end side in the width direction so as to communicate the first transport path with the second transport path; a second communication opening that opens into the partition portion at the other end in the width direction so as to connect the first transport path and the second transport path, and that is formed with an opening area smaller than an opening area of ​​the first communication opening; Equipped with a reverse rotation mode in which the first conveying member and the second conveying member are rotated in opposite directions, the second conveying member, at least in a range from the second communication port to a position spaced a predetermined distance from the one end in the width direction toward the one end in the width direction, has a smaller conveying force for conveying the developer from the one end in the width direction toward the other end in the width direction during the reverse rotation mode than a conveying force for conveying the developer from the other end in the width direction toward the one end in the width direction during rotation in the forward direction; The developing device, wherein, when the reverse rotation mode is being executed and a driving torque of the developing device exceeds a predetermined value, the reverse rotation mode is interrupted.

8. A developing device as described in any one of claims 1 to 7, characterized in that the conveying force of the first conveying member to convey the developer from the other width end side to the one width end side during the reverse rotation mode is equal to the conveying force to convey the developer from the one width end side to the other width end side during forward rotation.

9. 9. The developing device according to claim 1, wherein the reverse rotation mode is executed by operating an operating section provided on a main body of the image forming apparatus.

10. 10. The developing device according to claim 1, wherein the second transport path is disposed below the first transport path.

11. A process cartridge that is detachably installed in an image forming apparatus main body, 11. A process cartridge comprising the developing device according to claim 1 and the image carrier, the process cartridge being integrally provided with the developing device.

12. An image forming apparatus comprising the developing device according to any one of claims 1 to 10.

Images