Powder conveying device and image forming apparatus

Abstract

To reduce the occurrence of clogging with powder.SOLUTION: A powder conveying device is provided with: a first conveyance path 91 that is provided therein with a first conveying screw 71 (first conveying member) conveying toner (powder); a fall path 93 through which the toner flowing out from an outflow port 91b of the first conveyance path 91 falls; a second conveyance path 92 into which the toner falling through the fall path 93 flows from an inflow port 92a, and is provided therein with a second conveying screw 72 (second conveying member) conveying toner; and a bypass path 99 for returning a part of the toner remaining in the first conveyance path 91 (or the fall path 93) to an upstream side in a conveyance direction.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a powder transport device for transporting powder such as toner, and an image forming apparatus including the same. [Background technology]

[0002] Conventionally, in image forming devices such as copiers, printers, facsimiles, or combination machines thereof, a powder conveying device for conveying powder such as toner has been known that causes powder flowing out from a first conveying path to fall down a fall path and then flow into a second conveying path (see, for example, Patent Document 1).

[0003] On the other hand, Patent Document 1 discloses a technology for predicting toner clogging by detecting the movement of a movable member that is pushed by toner, with the aim of preventing clogging of the transport path with toner (powder). Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional powder conveying devices sometimes experience powder clogging (conveyance failure), which can lead to problems such as a powder shortage (supply failure) at the supply destination where the powder is delivered by the powder conveying device. Such problems could not be fully resolved even with the application of the technology of Patent Document 1. In particular, when a large amount of toner is transported in the transport path all at once, there is a possibility that powder clogging will occur before any warning signs are detected.

[0005] The present invention has been made to solve the above-mentioned problems, and has an object to provide a powder transport device and an image forming apparatus in which clogging with powder is unlikely to occur. [Means for solving the problem]

[0006] The powder conveying device of the present invention comprises: a first conveying path in which a first conveying member for conveying powder is installed; a fall path along which powder flowing out from an outlet of the first conveying path falls; a second conveying path into which the powder that has fallen along the fall path flows in from an inlet and in which a second conveying member for conveying the powder is installed; and a bypass path for returning a portion of the powder remaining on the first conveying path or the fall path to the upstream side in the conveying direction. The bypass path is provided above the first transport path and communicates with a portion above the outlet and a portion upstream of the outlet in the transport direction. It is something. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a powder transport device and an image forming apparatus that are less likely to become clogged with powder. [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. [Figure 3] FIG. 2 is an overall configuration diagram showing a toner supply device (powder transport device) and its vicinity. [Figure 4] FIG. 2 is a cross-sectional view showing a main part of the toner storage container. [Figure 5] 10A and 10B are schematic diagrams illustrating an operation of attaching the first transport path to the toner container. [Figure 6] FIG. 2 is a schematic diagram showing a toner supply device (powder transport device). [Figure 7] FIG. 3 is a diagram showing a driving unit of the toner supply device. [Figure 8] FIG. 2 is a cross-sectional perspective view showing a part of the inside of the toner supply device. [Figure 9] FIG. 10 is a diagram showing a state in which toner accumulates in a conveying path of the toner supply device. [Figure 10] FIG. 10 is a diagram showing a toner supply device as a first modified example. [Figure 11] FIG. 10 is a cross-sectional perspective view showing a part of the inside of a toner supply device as 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 image forming apparatus 100 will be described with reference to FIGS. FIG. 1 is a structural diagram showing a printer as an image forming apparatus, FIG. 2 is an enlarged view showing an image forming unit, and FIG. 3 is a structural diagram showing a toner supply device as a powder transport device and its vicinity. As shown in FIG. 1, four approximately cylindrical toner storage containers 32Y, 32M, 32C, and 32K corresponding to each color (yellow, magenta, cyan, and black) are detachably (replaceably) placed on an installation section 31 (toner container receiving stand) located above the image forming apparatus main body 100. An intermediate transfer unit 15 is disposed below the installation section 31. Opposite to the intermediate transfer belt 8 of the intermediate transfer unit 15, image forming sections 6Y, 6M, 6C, and 6K corresponding to each color (yellow, magenta, cyan, and black) are arranged side by side.

[0011] 2, the image forming unit 6Y corresponding to yellow is made up of a photosensitive drum 1Y (image carrier), a charging device 4Y, a developing device 5Y, a cleaning device 2Y, a static eliminator (not shown), etc., which are arranged around the photosensitive drum 1Y. Then, an image forming process (charging process, exposure process, developing process, transfer process, cleaning process, static eliminator process) is performed on the photosensitive drum 1Y, and a yellow image is formed on the surface of the photosensitive drum 1Y.

[0012] The other three image forming units 6M, 6C, and 6K are configured in a manner similar to that of the image forming unit 6Y corresponding to yellow, except that they use different toner colors, and form images corresponding to their respective toner colors. Below, we will omit the explanation of the other three image forming units 6M, 6C, and 6K as appropriate, and will only explain the image forming unit 6Y corresponding to yellow.

[0013] 2, the photosensitive drum 1Y as a photosensitive member is rotated by a motor in the clockwise direction in Fig. 2. Then, at the position of the charging device 4Y, the surface of the photosensitive drum 1Y is uniformly charged (charging step). Thereafter, the surface of the photosensitive drum 1Y reaches the irradiation position of the laser light L emitted from the exposure device 7 (writing unit), and an electrostatic latent image corresponding to yellow is formed by exposure scanning at this position (exposure process).

[0014] Thereafter, the surface of the photosensitive drum 1Y reaches a position facing the developing device 5Y, where the electrostatic latent image is developed to form a yellow toner image (developing step). Thereafter, the surface of the photosensitive drum 1Y reaches a position facing the intermediate transfer belt 8 and the primary transfer roller 9Y, where the toner image on the photosensitive drum 1Y is transferred onto the intermediate transfer belt 8 (the primary transfer step). At this time, a small amount of untransferred toner remains on the photosensitive drum 1Y.

[0015] Thereafter, the surface of the photosensitive drum 1Y reaches a position facing the cleaning device 2Y, where untransferred toner remaining on the photosensitive drum 1Y is collected (cleaning process). Finally, the surface of the photosensitive drum 1Y reaches a position facing a static eliminator (not shown), where the residual potential on the photosensitive drum 1Y is removed. Thus, a series of image forming processes performed on the photosensitive drum 1Y is completed.

[0016] The above-described image forming process is also performed in the other image forming units 6M, 6C, and 6K in the same manner as in the yellow image forming unit 6Y. That is, laser light L based on image information is irradiated onto the photosensitive drum of each image forming unit 6M, 6C, and 6K from an exposure device 7 disposed below the image forming units. More specifically, the exposure device 7 emits laser light L from a light source, and irradiates the laser light L onto the photosensitive drum via multiple optical elements while scanning with a rotationally driven polygon mirror. Thereafter, the toner images of each color formed on each photosensitive drum through the development process are transferred onto the intermediate transfer belt 8 in a superimposed manner, thereby forming a color image on the intermediate transfer belt 8.

[0017] Here, the intermediate transfer unit 15 is composed of an intermediate transfer belt 8 as an intermediate transfer body, four primary transfer rollers 9Y, 9M, 9C, and 9K, a secondary transfer opposing roller 12, a cleaning backup roller 13, a tension roller 14, and an intermediate transfer cleaning device 10. The intermediate transfer belt 8 is stretched and supported by three rollers 12 to 14, and is moved endlessly in the direction of the arrow in FIG. 1 by the rotational drive of one roller 12.

[0018] The four primary transfer rollers 9Y, 9M, 9C, and 9K sandwich the intermediate transfer belt 8 between themselves and the photosensitive drums 1Y, 1M, 1C, and 1K, respectively, to form primary transfer nips. A transfer bias opposite to the polarity of the toner is applied to the primary transfer rollers 9Y, 9M, 9C, and 9K. The intermediate transfer belt 8 then travels in the direction of the arrow and passes through the primary transfer nips of the primary transfer rollers 9Y, 9M, 9C, and 9K in sequence. In this way, the toner images of each color on the photosensitive drums 1Y, 1M, 1C, and 1K are primarily transferred onto the intermediate transfer belt 8 in a superimposed manner.

[0019] Thereafter, the intermediate transfer belt 8, onto which the toner images of each color have been transferred and superimposed, reaches a position facing a secondary transfer roller 19. At this position, a secondary transfer nip is formed between the secondary transfer opposing roller 12 and the secondary transfer roller 19, sandwiching the intermediate transfer belt 8. The four-color toner images formed on the intermediate transfer belt 8 are then transferred onto a sheet P, such as paper, that has been transported to the position of this secondary transfer nip. At this time, untransferred toner that has not been transferred to the sheet P remains on the intermediate transfer belt 8.

[0020] Thereafter, the intermediate transfer belt 8 reaches the position of the intermediate transfer cleaning device 10. At this position, untransferred toner on the intermediate transfer belt 8 is collected. Thus, the series of transfer processes performed on the intermediate transfer belt 8 is completed.

[0021] Here, the sheet P transported to the position of the secondary transfer nip is transported from a paper feed device 26 arranged below the device main body 100 via a paper feed roller 27, a pair of registration rollers 28, etc. More specifically, a plurality of sheets P such as paper are stacked and stored in the paper feed device 26. When the paper feed roller 27 is rotated counterclockwise in FIG. 1, the topmost sheet P is fed toward between the pair of registration rollers 28.

[0022] The sheet P conveyed to the position of the registration roller pair 28 (timing roller pair) is temporarily stopped at the roller nip position of the registration roller pair 28, which has stopped rotating. Then, the registration roller pair 28 is rotated in synchronization with the color image on the intermediate transfer belt 8, and the sheet P is conveyed toward the secondary transfer nip. In this way, the desired color image is transferred onto the sheet P.

[0023] Thereafter, the sheet P onto which the color image has been transferred at the secondary transfer nip position is transported to the position of the fixing device 20. Then, at this position, the color image transferred onto the surface is fixed onto the sheet P by heat and pressure from the fixing roller and pressure roller. Thereafter, the sheet P is discharged to the outside of the apparatus through the rollers of the discharge roller pair 29. The sheets P discharged to the outside of the apparatus by the discharge roller pair 29 are sequentially stacked on a stack unit 30 as output images. In this way, a series of image forming processes (printing operations) in the image forming apparatus is completed.

[0024] Next, the configuration and operation of the developing device (supply destination) in the image forming unit will be described in more detail with reference to FIG. The developing device 5Y is composed of a developing roller 51 facing the photosensitive drum 1Y, a doctor blade 52 facing the developing roller 51, two conveying screws 55 disposed in developer containers 53 and 54, and a concentration detection sensor 56 that detects the toner concentration in the developer. The developing roller 51 is composed of a magnet fixed inside and a sleeve that rotates around the magnet. The developer containers 53 and 54 contain a two-component developer consisting of a carrier and toner.

[0025] The developing device 5Y configured in this manner operates as follows. The sleeve of the developing roller 51 rotates in the direction of the arrow in Figure 2. The developer carried on the developing roller 51 by the magnetic field generated by the magnet moves on the developing roller 51 as the sleeve rotates. Here, the developer G in the developing device 5Y is adjusted so that the ratio of toner (toner concentration) in the developer G falls within a predetermined range. Specifically, in accordance with the toner consumption in the developing device 5Y, the toner contained in the toner storage container 32Y is replenished into the developer storage unit 54 via a toner supply device 90 serving as a powder conveying device.

[0026] Thereafter, the powder toner supplied to the developer storage section 54 is circulated between the two developer storage sections 53 and 54 while being mixed and stirred together with the developer G by the two conveying screws 55 (moving in the longitudinal direction perpendicular to the plane of the paper in FIG. 2). The toner in the developer G is then attracted to the carrier due to frictional charging with the carrier, and is carried on the developing roller 51 together with the carrier by the magnetic force formed on the developing roller 51. The developer carried on the developing roller 51 is transported in the direction of the arrow in FIG. 3 and reaches the position of the doctor blade 52. The developer on the developing roller 51 is adjusted to an appropriate amount at this position, and then transported to a position facing the photosensitive drum 1Y (the developing area). The toner is then attracted to the latent image formed on the photosensitive drum 1Y by an electric field formed in the developing area. Thereafter, the developer remaining on the developing roller 51 reaches above the developer container 53 as the sleeve rotates, and is released from the developing roller 51 at this position.

[0027] Next, the configuration and operation of the toner supply device 90 as a powder transport device will be briefly described with reference to FIG. The toner supply device 90 (powder conveying device) rotates the container body 33 of the toner storage container 32Y installed in the installation section 31 in a predetermined direction (the direction of the arrow in Figure 3) to discharge the toner as powder stored inside the toner storage container 32Y out of the container and guide it to the developing device 5Y via the first conveying path 91, the fall path 93 (first fall path), the second conveying path 92, and the conveying pipe 96 (second conveying path), thereby forming a toner supply path (toner conveying path).

[0028] The toner in each of the toner containers 32Y, 32M, 32C, and 32K installed in the installation section 31 of the image forming apparatus main body 100 is supplied to each developing device as needed via a toner supply device provided for each toner color, depending on the toner consumption in the developing device of each color. The four toner supply devices have almost the same structure, except for the color of toner used in the image forming process. 3 (and 5), when the toner storage container 32Y is set in the installation portion 31 of the apparatus main body 100, the shutter member 35 of the toner storage container 32Y is pushed by the first transport path 91 (nozzle portion) of the apparatus main body 100, and the first transport path 91 is inserted into the toner storage container 32Y (container main body 33) via the through-hole portion 34a1. This allows the toner stored in the toner storage container 32Y to be discharged (via the first transport path 91). A grip portion 33d is formed on the bottom (on the left side in FIG. 3) of the toner storage container 32Y to facilitate the operation of attaching the toner storage container 32Y to the installation portion 31. The user sets the toner storage container 32Y in the installation portion 31 or removes the toner storage container 32Y from the installation portion 31 while holding the grip portion 33d.

[0029] 3, the toner storage container 32Y is provided with a container body 33 having a spiral groove 33a formed in the longitudinal direction (the left-right direction in FIG. 3, which is the direction of the rotation axis of the container body 33). Specifically, this spiral groove 33a is formed from the outer peripheral surface to the inner peripheral surface of the container body 33, and is intended to transport the toner in the container body 33 from left to right in FIG. 3 by driving the container body 33 to rotate. The toner transported inside the container body 33 from left to right in FIG. 3 is discharged to the outside of the container via a first transport path 91. Furthermore, a gear portion 37 that meshes with a gear 115 of a drive mechanism 110 (see FIG. 7) of the image forming apparatus main body 100 (toner supply device 90) is formed on the outer peripheral surface of the head side (right side in FIG. 3) of the container main body 33. When the toner storage container 32Y is attached to the installation portion 31, the gear portion 37 of the container main body 33 meshes with the gear 115 (see FIG. 7) of the image forming apparatus main body 100. When the drive motor 111 (see FIG. 7) is driven, the drive is transmitted to the gear portion 37 via a gear train, and the container main body 33 is rotated. The configuration and operation of the toner supply device 90 will be described in more detail later with reference to FIGS. 6 to 8.

[0030] The toner container 32Y (32M, 32C, 32K) will be described in more detail below with reference to FIGS. 4 and 5 are side cross-sectional views of the toner storage container 32Y, but are shown from the opposite direction to the direction of the toner storage container 32Y shown in FIG. 3 (the views are reversed).

[0031] As previously described with reference to FIGS. 1 to 3, the toner storage container 32Y stores toner therein and is detachably installed in the image forming apparatus main body 100 (toner supply device 90). 4, 5, etc., the toner storage container 32Y is made up of a container main body 33 and shutter units 34 to 36, 38. The shutter unit is made up of a holding member 34, a shutter member 35, a rod member 36, a compression spring 38, etc. The holding member 34 is formed with an upright portion 34a that functions as a cap portion. The container main body 33 is fixed to the upright portion 34a (holding member 34), and is a bottle-shaped member with a spiral groove 33a (see FIG. 3) formed on its inner circumferential surface (inner circumferential portion). Then, when the toner storage container 32Y is attached to the image forming apparatus main body 100 (installation portion 31), the holding member 34 (and the shutter member 35, rod member 36, and compression spring 38) on which the standing portion 34a is formed and the container main body 33 are rotated by the drive motor 111 (drive mechanism 110) installed in the image forming apparatus main body 100, and the toner stored inside the toner storage container 32Y is discharged via the first conveying path 91.

[0032] 4, 5, etc., the shutter member 35 opens and closes the through-hole 34a1, through which the first transport path 91 (installed in the toner supply device 90) is inserted, in conjunction with the installation operation of the toner storage container 32Y into the image forming apparatus main body 100. The shutter member 35 is made of a resin material and is integrally molded together with a rod member 36 (described later). The shutter member 35 is configured to fit into and lock onto the through-hole 34a1 from the inside of the container and not to be removed from the container. When the shutter member 35 closes the through-hole 34a1, toner is prevented from being discharged from the toner storage container 32Y to the outside, and when the shutter member 35 opens the through-hole 34a1, toner can be discharged from the toner storage container 32Y to the outside. The through-hole portion 34a1 is a substantially cylindrical hole portion centered on the rotation center of the container body 33. The shutter member 35 is a plug-like member formed to fit into the through-hole portion 34a1 having such a shape.

[0033] The toner container 32Y is provided with a seal member 40 that seals the gap between the shutter member 35 and the through-hole portion 34a1 when the shutter member 35 closes the through-hole portion 34a1. The rod member 36 is provided integrally with the shutter member 35. The rod member 36 is formed to extend in the opening and closing direction of the shutter member 35 inside the toner storage container 32Y (the left-right direction in FIGS. 4 and 5). 4, the rod member 36 is disposed so that its axial center substantially coincides with the rotation center of the container body 33. This makes it less likely that problems such as the shutter member 35 becoming misaligned when the container body 33 is rotationally driven.

[0034] Referring to Figures 4 and 5, the holding member 34 is composed of an upright portion 34a (cap portion), an extension portion 34b, etc., and is a member fixed to the container body 33, and rotates around the first conveying path 91 together with the container body 33 upon receiving a rotational driving force from the device body 100. The upright portion 34a (cap portion) of the holding member 34 has a through-hole portion 34a1 formed therein and stands in the direction in which the first conveying path 91 is inserted (the insertion direction, which is the left-right direction in Figures 4 and 5). The upright portion 34a has an opening 34a2 (hollow portion) that opens to the front side in the direction in which the first transport path 91 is inserted (the upstream side in the insertion direction, which is to the left in FIGS. 4 and 5). The opening 34a2 is a substantially cylindrical recess that is centered on the rotation center of the container body 33.

[0035] The extending portion 34b of the holding member 34 is formed inside the toner storage container 32Y on the opposite side (the right side in FIGS. 4 and 5) from the side where the shutter member 35 is installed so as to hold the rod member 36 movably in the opening and closing direction. The extending portion 34b is formed in a substantially U-shape so as to extend in the left-right direction in FIGS. 4 and 5 inside the toner storage container 32Y (container body 33). A compression spring 38 serving as a biasing means is wound around the rod member 36 between the shutter member 35 and the wall of the extension portion 34b. The compression spring 38 biases the shutter member 35 in a direction (to the left in FIGS. 4 and 5) in which the through-hole portion 34a1 is closed.

[0036] With this configuration, the shutter member 35 is pushed into the first transport path 91 in conjunction with the mounting operation on the image forming apparatus main body 100 (installation section 31), and moves into the toner storage container 32Y together with the rod member 36 against the biasing force of the compression spring 38 (biasing means), thereby opening the through-hole 34a1. Specifically, the shutter member 35 (and the rod member 36) operates in the order of Figures 5(A) and (B) when opening. On the other hand, in conjunction with the removal operation from the image forming apparatus main body 100 (installation section 31), the pressing of the shutter member 35 on the first transport path 91 is released, and the urging force of the compression spring 38 causes the shutter member 35 to move toward the through-hole portion 34a1 together with the rod member 36, thereby closing the through-hole portion 34a1. Specifically, the shutter member 35 (and the rod member 36) operates in the order of Figures 5(B) and (A) when closed. 5(B), when the toner storage container 32Y has been completely set in the apparatus main body 100, the shutter member 35 abuts against the wall of the extension portion 34b, and the compression spring 38 is housed in the recess of the shutter member 35. This prevents the toner inside the container from adhering to the compression spring 38 when the toner storage container 32Y is set in the apparatus main body 100.

[0037] Furthermore, referring to FIG. 5, in this embodiment, first transport path 91 is provided with fitting portion 94 that fits into opening 34a2 in conjunction with the insertion operation into through-hole 34a1. Specifically, the fitting portion 94 has an outer diameter larger than the outer diameter of the main portion of the first transport path 91 and is formed in a generally cylindrical shape so as to fit into the opening 34a2 of the standing portion 34a. The fitting portion 94 is slidably mounted in the mounting direction relative to the main portion of the first transport path 91. A compression spring 97 is mounted in the first transport path 91 to bias the fitting portion 94 downstream in the insertion direction (to the right in FIG. 5). The fitting portion 94 also functions as a cover member that covers the first inlet 91a of the first transport path 91. When the toner container 32Y is not set, it covers the first inlet 91a as shown in FIG. 5A. When the toner container 32Y is set, the fitting portion 94 slides and the main portion of the first transport path 91 is inserted into the container body 33 as shown in FIG. 5B. FIG. 5(A') shows a state in which the fitting portion 94 has been slid to expose the first inlet 91a. With this configuration, when the first transport path 91 is inserted into the toner storage container 32Y in conjunction with the mounting operation of the toner storage container 32Y, the fitting portion 94 is biased by the compression spring 97 and fits into the opening 34a2. On the other hand, when the first transport path 91 is pulled out from the toner storage container 32Y in conjunction with the removal operation of the toner storage container 32Y, the fitting portion 94 is pulled out from the opening 34a2.

[0038] Hereinafter, the characteristic configuration and operation of the toner supply device 90 as the powder conveying device in this embodiment will be described with reference to FIGS. 6 to 8. FIG. 6, for ease of understanding, the arrangement direction of the second transport path 92 is changed relative to the first transport path 91. In reality, the second transport path 92 is arranged so as to be substantially perpendicular to the first transport path 91, as shown in FIGS. 3, 7, and 8.

[0039] 6 to 8, a toner supply device 90 as a powder conveying device is provided with a first conveying path 91, a falling path 93 (first falling path), a second conveying path 92, a conveying pipe 96 (second falling path), a bypass path 99, etc. Toner as powder discharged from a toner storage container 32Y (supply source) is conveyed to a developing device 5Y (supply destination) via these conveying paths 91 to 96.

[0040] Here, the first transport path 91 is provided with a first transport screw 71 as a first transport member that transports the toner (powder) in a substantially horizontal direction. The first conveying screw 71 has a screw portion 71b wound spirally around a shaft portion 71a, and is made of a metal material (or a resin material). The first transport path 91 is a transport pipe having a circular cross section and is made of a metal material (or a resin material). The first transport path 91 has a first inlet 91a on the upstream side that communicates with the toner container 32Y, and a first outlet 91b (outlet) on the downstream side that communicates with the drop path 93. In this embodiment, a bypass path 99 is provided above the first transport path 91, which will be described in detail later.

[0041] The fall path 93 is a path along which the toner flowing out from the outlet (first outlet 91b) of the first transport path 91 falls (by its own weight), and is formed to extend in a substantially vertical direction. The fall path 93 may be a transport pipe having a circular cross section or a transport pipe having a polygonal cross section. It is also possible to use a fall path 93 that is inclined relative to the vertical direction. In this case, the state in which the toner slides down the inclined surface of the inclined fall path is also defined as the state in which "toner (powder) falls." In addition, in this embodiment, the fall path 93 is a path that connects the first conveying path 91 and the second conveying path 92, which are spaced apart by a certain distance in the approximately vertical direction. However, even if the first conveying path 91 and the second conveying path 92 are arranged side by side so as to be in close contact with each other in the approximately vertical direction, the fall path is defined as being formed at the relay portion.

[0042] The second transport path 92 receives the toner that has fallen on the fall path 93 from an inlet (second inlet 92a), and includes a second transport screw 72 disposed therein as a second transport member that transports the toner in a substantially horizontal direction. The second conveying screw 72 has a screw portion 72b wound spirally around a shaft portion 72a, and is made of a rubber material such as elastomer (or a metal material or a resin material). The second transport path 92 is a transport pipe having a circular cross section and is made of a metal material (or a resin material). The second transport path 92 has a second inlet 92a on the upstream side that communicates with the drop path 93, and a second outlet 92b on the downstream side that communicates with the transport pipe 96 (second drop path). In this embodiment, the first transport path 91 and the second transport path 91 are each formed to extend in a substantially horizontal direction. However, at least one of the first transport path 91 and the second transport path 91 may be formed to be inclined with respect to the horizontal direction.

[0043] The transport pipe 96 (second drop path) is a path through which the toner flowing out from the second outlet 92b of the second transport path 92 falls under its own weight, and is formed to extend in a substantially vertical direction. The toner that falls under its own weight through the transport pipe 96 is supplied into the developing device 5Y. In this embodiment, the toner is transported from the second transport path 92 to the developing device 5Y via the transport pipe 96, but it is also possible to transport the toner directly from the second transport path 92 to the developing device 5Y.

[0044] In the toner supply device 90 (powder conveying device) configured as described above, as shown in FIG. 6, toner flowing from the toner container 32Y into the first conveying path 91 in the direction of the white arrow is conveyed from left to right in a substantially horizontal direction (the direction of the dashed arrow) by the first conveying screw 71 rotating in a predetermined direction (the direction of the arrow in FIG. 6), and then falls under its own weight along a falling path 93 in the direction of the dashed arrow (from top to bottom). The toner then flows from the falling path 93 into the second conveying path 92, where it is conveyed from right to left in a substantially horizontal direction (the direction of the dashed arrow) by the second conveying screw 72 rotating in a predetermined direction (the direction of the arrow in FIG. 6). The toner then flows from the second conveying path 92 into the conveying pipe 96, falls under its own weight along the conveying pipe 96, and then flows into the developing device 5Y. In this way, the toner in powder form is supplied from the toner container 32Y, which is the supply source, to the developing device 5Y, which is the supply destination.

[0045] By providing the toner supply device 90 with multiple transport paths 91-93, 96, toner can be supplied even if the toner storage container 32Y, which is the supply source, and the developing device 5Y, which is the supply destination, are separated from each other or facing in different directions. In other words, the degree of freedom in the layout of the toner storage container 32Y and the developing device 5Y can be increased. 7, in this embodiment, the direction in which the toner (powder) is transported in the first transport path 91 intersects with the direction in which the toner is transported in the second transport path 92 (in this embodiment, they are substantially perpendicular to each other), which further increases the degree of freedom in the layout of the toner storage container 32Y and the developing device 5Y.

[0046] In the present embodiment, the toner supply device 90 (powder transport device) is set so that the amount of powder (toner amount) transported per unit time by the first transport screw 71 (first transport member) in the first transport path 91 is smaller than the amount of powder (toner amount) transported per unit time by the second transport screw 72 (second transport member) in the second transport path 92. The above-mentioned "amount of powder (toner amount) per unit time" is substantially synonymous with "toner transport speed in the transport path."

[0047] Now, referring to Figures 6, 8, 9(A), etc., the toner supply device 90 (powder conveying device) in this embodiment is provided with a bypass path 99 for returning a portion of the toner T (powder) accumulating in the first conveying path 91 (near the junction with the fall path 93) to the upstream side in the conveying direction (on the left side in Figures 6 and 9(A)). In detail, the bypass path 99 is provided above the first conveying path 91 and is connected to the portion above the outlet 91b (where the first opening 99a is formed) and the portion upstream in the conveying direction from the outlet 91b (where the second opening 99b is formed).

[0048] More specifically, as shown in Figures 6, 8, and 9(A), the bypass path 99 is an approximately C-shaped (or approximately U-shaped) path separated by a partition wall 99c, which serves as a wall portion formed approximately perpendicular to the conveying direction in the first conveying path 91. In other words, the bypass path 99 is partitioned by the partition wall 99c (wall portion) into a downstream side in the conveying direction (the side of the first opening 99a) and an upstream side in the conveying direction (the side of the second opening 99b). A space connecting the downstream side in the conveying direction (the side of the first opening 99a) and the upstream side in the conveying direction (the side of the second opening 99b) separated by the partition wall 99c (wall portion) is formed above the partition wall 99c.

[0049] By providing the bypass path 99 in this way, clogging of the toner T in the transport path (transport failure) is less likely to occur. Specifically, when the bypass path 99 is not provided, as in the toner supply device 190 shown as a comparative example in FIG. 9B , toner T tends to accumulate in the transport path (particularly, the area surrounded by the dashed line near the confluence (outlet 91b) of the first transport path 91 and the drop path 93). In particular, referring to FIG. 9B , when a large amount of toner is stored in the toner storage container 32Y, which serves as the supply source (such as when a new toner storage container 32Y has just been used), a large amount of toner T unintentionally flows in through the inlet 91a even when the container body 33 is not rotated. This increases the amount of toner in the transport paths 91-93 of the toner supply device 90, making it more likely for toner T to accumulate. If toner accumulation progresses in this way, the toner clogs the accumulated portion, resulting in a shortage of toner T (poor supply) in the developing device 5Y, which serves as the supply destination. In contrast, the toner supply device 90 in this embodiment is provided with a bypass path 99 as shown in Figure 9(A), so that some of the toner T that has accumulated near the confluence (outlet 91b) of the first conveying path 91 and the fall path 93 flows (escapes) to the upstream side of the first conveying path 91 via the bypass path 99, making it less likely that the toner T will clog. Specifically, when the amount of toner T accumulated near the outlet 91b increases to a certain level, it flows into the bypass path 99 from the first opening 99a and gradually increases in volume upward. Then, when the volume exceeds the height of the partition wall 99c, the toner T exceeds the partition wall 99c and is returned to the first conveying path 91 via the second opening 99b (flow in the direction of the arrow in FIG. 9A). This prevents the toner T accumulated near the outlet 91b from becoming too tightly packed. In this way, the bypass path 99 functions as an escape route for the accumulated toner T. By optimizing (adjusting) the height of the partition wall 99c (wall portion), it is possible to set the amount of toner T that escapes to the bypass path 99 to a target value.

[0050] <Variation 1> 10, in the toner supply device 90 of the first modification, similar to that shown in Fig. 6, a bypass path 99 is provided above the first transport path 91. The bypass path 99 of the first modification is also a substantially U-shaped path partitioned by a partition wall 99c (wall portion) formed so as to be substantially perpendicular to the transport direction of the first transport path 91. Here, the bypass path 99 in the first modification communicates with a portion (where the first opening 99a is formed) on the upstream side in the conveying direction relative to the outlet 91b of the first conveying path 91 and a portion (where the second opening 99b is formed) on the upstream side in the conveying direction relative to that portion. In other words, the bypass path 99 in the first modification is shifted upstream in the conveying direction from the outlet 91b. Therefore, it is possible to prevent the toner T that has flowed into the bypass path 99 from the first opening 99a from directly flowing (falling) into the fall path 93 via the outflow port 91b. Even when the bypass path 99 is configured as in the first modification, clogging of the toner T can be reduced.

[0051] <Variation 2> As shown in FIG. 11, in a toner supply device 90 (powder transport device) in the second modification, a bypass path 99 is provided on the side of a drop path 93. The bypass path 99 in the second modification is configured to communicate with a portion of the first transport path 91 downstream in the transport direction from the outlet 91b (where the first opening 99a is formed) and a portion on a side of the first transport path 91 (where the second opening 99b is formed). In other words, the bypass path 99 is configured to communicate with the upper and lower parts of the drop path 93. The bypass path 99 in variant example 2 is an approximately U-shaped path separated by a partition wall 99c, which serves as a wall portion formed along the conveying direction (falling direction) of the fall path 93. The bypass path 99 configured in this manner is intended to return some of the toner remaining in the fall path 93 to the upstream side in the transport direction. That is, some of the toner remaining in the fall path 93 flows into the bypass path 99 from the first opening 99a and gradually increases in volume upward. Although the volume does not exceed the volume of the toner remaining in the fall path 93, when the combined volumes exceed the height of the partition wall 99c, the toner T exceeds the partition wall 99c and is returned to the first transport path 91 (fall path 93) through the second opening 99b. This prevents the toner T remaining in the fall path 93 from becoming too tightly packed. Even when the bypass path 99 is configured as in the second modification, clogging of the toner T can be reduced. In particular, in variant example 2, when toner accumulates (piles up) in the fall path 93 up to the height of the first opening 99a, it becomes possible to release some of the accumulated toner into the bypass path 99, making it easier to prevent toner clogging in the fall path 93.

[0052] As described above, the toner supply device 90 (powder conveying device) in this embodiment is provided with a first conveying path 91 having a first conveying screw 71 (first conveying member) therein for conveying toner (powder), a fall path 93 along which toner flowing out from the outlet 91b of the first conveying path 91 falls, a second conveying path 92 having a second conveying screw 72 (second conveying member) therein for conveying the toner by allowing the toner that has fallen along the fall path 93 to flow in from the inlet 92a, and a bypass path 99 for returning a portion of the toner remaining on the first conveying path 91 (or the fall path 93) to the upstream side in the conveying direction. This makes it less likely that toner will clog.

[0053] In this embodiment, the present invention is applied to a toner supply device 90 (powder conveying device) that conveys toner as a powder, but the powder conveying device to which the present invention is applied is not limited to this, and the present invention can also be applied to a powder conveying device that conveys, for example, waste toner, recycled toner, or two-component developer (a developer consisting of toner and carrier) as powder. In addition, in this embodiment, the present invention is applied to a toner supply device 90 (powder conveying device) that conveys toner (powder) from a toner storage container 32Y as a supply source to a developing device 5Y as a supply destination, but the supply sources and supply destinations of the powder conveying device to which the present invention is applied are not limited to these, and various supply sources and supply destinations can be set. In addition, in this embodiment, a bottle-shaped toner storage container 32Y serving as a supply source is used, which discharges toner by rotating the container body 33. However, the toner storage container serving as a supply source is not limited to this, and for example, a container having a conveying member installed inside the container that conveys toner toward an outlet, or a box-shaped container may also be used. Furthermore, in this embodiment, the first and second transport paths 91, 92 are both formed in a substantially straight line, but at least one of the first and second transport paths 91, 92 may be formed in a curved line. Even in such cases, substantially the same effects as those of this embodiment can be obtained.

[0054] 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.

[0055] In this specification, the "conveying direction" of powder in a powder conveying device is defined as the direction in which the powder is conveyed by the first and second conveying members in the first and second conveying paths, and as the direction in which the powder falls in the falling path. [Explanation of symbols]

[0056] 5Y developing device (supply destination), 32Y, 32M, 32C, 32K toner container (supplier), 71 first conveying screw (first conveying member), 72 second conveying screw (second conveying member), 90 Toner supply device (powder transport device), 91 First transport route, 92 Second transport route, 93 Falling path, 99 Bypass route (powder return route), 99a 1st opening, 99b second opening, 99c Partition wall (wall section), 100 Image forming apparatus (image forming apparatus main body). [Prior art documents] [Patent documents]

[0057] [Patent Document 1] Japanese Patent Application Publication No. 2019-159129

Claims

1. a first conveying path having a first conveying member disposed therein for conveying powder; a fall path along which the powder flowing out from the outlet of the first conveying path falls; a second conveying path into which the powder that has fallen on the falling path flows through an inlet and into which a second conveying member that conveys the powder is disposed; a bypass path for returning a portion of the powder remaining in the first conveying path or the falling path to an upstream side in the conveying direction; Equipped with The powder conveying device according to claim 1, wherein the bypass path is provided above the first conveying path and is in communication with a portion above the outlet and a portion upstream of the outlet in the conveying direction.

2. A first conveying path having a first conveying member for conveying powder disposed therein; a fall path along which the powder flowing out from the outlet of the first conveying path falls; a second conveying path into which the powder that has fallen on the falling path flows through an inlet and into which a second conveying member that conveys the powder is disposed; a bypass path for returning a portion of the powder remaining in the first conveying path or the falling path to an upstream side in the conveying direction; Equipped with The bypass path is provided above the first conveying path and is connected to a portion upstream of the outlet in the conveying direction and a portion upstream of the outlet in the conveying direction.

3. A powder conveying device as described in claim 1 or claim 2, characterized in that the bypass path is an approximately C-shaped or U-shaped path separated by a wall portion formed approximately perpendicular to the conveying direction in the first conveying path.

4. A first conveying path having a first conveying member for conveying powder disposed therein; a fall path along which the powder flowing out from the outlet of the first conveying path falls; a second conveying path into which the powder that has fallen on the falling path flows through an inlet and into which a second conveying member that conveys the powder is disposed; a bypass path for returning a portion of the powder remaining in the first conveying path or the falling path to an upstream side in the conveying direction; Equipped with The bypass path is provided to the side of the drop path and is connected to a portion downstream of the outlet in the conveying direction and a portion to the side of the first conveying path.

5. A powder conveying device as described in Claim 4, characterized in that the bypass path is an approximately C-shaped or U-shaped path separated by a wall portion formed along the conveying direction in the fall path.

6. A powder conveying device as described in any one of claims 1 to 5, characterized in that the first conveying path and the second conveying path are each formed to extend in an approximately horizontal direction.

7. An image forming apparatus comprising a powder conveying device according to any one of claims 1 to 6.

Images