Powder conveying device and image forming apparatus

Abstract

To reduce the likelihood of the occurrence of a failure in conveying powder.SOLUTION: A toner supply device 90 (powder conveying device) has, arranged inside first and second conveyance paths 91, 92 (conveyance paths), first and second conveying screws 71, 72 (conveying members) that, when a "supply mode" for supplying toner (powder) from a toner storage container 32Y (supply source) to a developing device 5Y (supply destination) is executed, rotate in a normal direction to convey the toner. Before the "supply mode" is executed, a "reverse rotation mode" for rotating the first and second conveying screws 71, 72 (conveying members) in the reverse direction is executed.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, powder conveying devices for conveying powder such as toner have been known that have a conveying member such as a conveying screw installed in the conveying path (see, for example, Patent Document 1).

[0003] On the other hand, Patent Document 2 discloses a technology in which a screw in a screw pump connected to a tube is reversed after the toner supply operation, with the aim of preventing toner clogging in the tube used to supply toner to a developing device. 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 a problem could not be sufficiently solved even if the technology of Patent Document 2 was applied and the conveying member was rotated in the reverse direction after the powder was supplied to the supply destination.

[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 powder transport failure is unlikely to occur. [Means for solving the problem]

[0006] The powder conveying device of the present invention includes a conveying member that is installed in the conveying path and that rotates in a forward direction to convey the powder when a supply mode for supplying powder from a supply source to a supply destination is executed. a first conveying path in which a first conveying member that conveys the powder in a substantially horizontal direction is installed; a drop path in which the powder that flows out from an outlet of the first conveying path falls; and a second conveying path in which a second conveying member that conveys the powder in a substantially horizontal direction is installed and into which the powder that has fallen on the drop path flows in from an inlet. Equipped with the conveying members are the first conveying member and the second conveying member, the conveying path is the first conveying path and the second conveying path, and an amount of powder conveyed by the first conveying member per unit time in the supply mode on the first conveying path is smaller than an amount of powder conveyed by the second conveying member per unit time on the second conveying path in the supply mode, Before the supply mode is performed, a reverse rotation mode is performed in which the conveying member is rotated in the reverse direction. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a powder transport device and an image forming apparatus in which powder transport failure is unlikely to occur. [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] 10 is a flowchart showing an example of control performed in the toner supply device. [Figure 9] 10 is a flowchart showing control performed in the toner supply device according to a first modified example. [Figure 10] FIG. 10 is a schematic diagram showing a toner supply device as a second modified example. [Figure 11] FIG. 11 is a top view showing a second transport path as a third 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 charge eliminating device (not shown), where the residual potential on the photosensitive drum 1Y is eliminated. 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, as shown in FIGS. 3 and 7, the second transport path 92 is arranged so as to be substantially perpendicular to the first transport path 91.

[0039] 6, 7, etc., a toner supply device 90 serving 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 conveying path), 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 91-93, 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.

[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).

[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 (in the direction of the dashed arrow) by the first conveying screw 71 rotating in the forward direction (in the direction of the solid 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 (in the direction of the dashed arrow) by the second conveying screw 72 rotating in the forward direction (in the direction of the solid 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. Hereinafter, the control mode (or operation) for supplying powder toner from the toner container 32Y, which is the supply source, to the developing device 5Y, which is the supply destination, will be referred to as the "supply mode" where appropriate.

[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] Here, the toner supply device 90 (powder transport device) in this embodiment is set so that the amount of powder (toner amount) transported per unit time by the first transport screw 71 (first transport member) in supply mode on 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 supply mode on the second transport path 92. Note that the above-mentioned "amount of powder (toner amount) per unit time" is substantially synonymous with "toner transport speed on the transport path." However, if the amount of powder transported per unit time by the second transport screw 72 increases due to factors such as the temperature and humidity environment and the state of the toner, and the toner transport speed in the downstream transport path 92 becomes too fast compared to the toner transport speed in the upstream transport path 91, the toner may become insufficient in the downstream transport path 92, which may result in poor toner supply from the supply source to the supply destination. For this reason, in this embodiment, the toner transport speed in the downstream transport path 92 is set to be faster than the toner transport speed in the upstream transport path 91 to an extent that does not result in poor toner supply (a speed difference is provided). Specifically, a difference is created in the toner transport speeds of both the downstream and upstream transport paths 92 by varying at least one of the rotation speed of the transport screw, the screw diameter or screw pitch of the screw portion, etc. On the other hand, since the amount of powder transported per unit time by the second transport screw 72 increases, toner clogging is more likely to occur, and therefore in this embodiment, a "reverse rotation mode" is performed as described below.

[0047] As described above, the transport paths (first transport path 91 and second transport path 92) of the toner supply device 90 (powder transport device) in this embodiment are provided with transport members (first transport screw 71 as the first transport member and second transport screw 72 as the second transport member) that rotate in the forward direction to transport toner when the "supply mode" is executed to supply toner (powder) from the toner storage container 32Y as the supply source to the developing device 5Y as the supply destination.

[0048] In the toner supply device 90 (powder conveying device) in this embodiment, before the "supply mode" is executed, a "reverse rotation mode" is executed in which the conveying screws 71 and 72 as conveying members are rotated in the reverse direction (the direction of the dashed arrow in Figure 6). Specifically, the "reverse rotation mode" is a control mode in which the plurality of conveying screws 71, 72 (conveying members) installed in the plurality of conveying paths 91, 92, respectively, are rotated in the reverse direction (the direction of the dashed arrow in FIG. 6). In this embodiment, the "reverse rotation mode" is executed at the timing when the printing operation in the image forming device 100 starts (the timing after the control unit of the image forming device 100 receives a printing command), and is executed immediately before the toner supply operation (supply mode) to the developing device 5Y is performed by the toner supply device 90.

[0049] This makes it less likely that the toner will clog the transport path in the toner supply device 90 (transport failure). Specifically, the toner remaining in the transport paths 91 and 92 without being transported to the developing device 5Y (supply destination) becomes stuck by being left as it is or by being piled up with toner transported from upstream. If the supply mode is resumed when the toner in the transport paths 91 and 92 is stuck in this state, the stuck toner will be transported suddenly, making the transport paths 91 and 92 more likely to become clogged with toner. In particular, in this embodiment, as explained above, the toner transport speed in the downstream transport path 92 is set to be faster than the toner transport speed in the upstream transport path 91, to the extent that toner supply defects do not occur. Therefore, while problems such as toner shortages in the downstream transport path 92 are unlikely to occur, toner clogging is more likely to occur in the transport path (especially near the joints of multiple transport paths). In contrast to this, in this embodiment, before the supply mode is executed, the reverse rotation mode is executed to transport the toner in the transport paths 91 and 92 in the direction opposite to the normal transport direction, thereby reducing the toner clogging in the transport paths 91 and 92. Therefore, even if the supply mode is resumed, toner clogging (transport failure) in the transport paths 91 and 92 is less likely to occur. Therefore, the toner supply device 90 in this embodiment is less likely to have toner transport problems overall, and can stably supply toner from the toner container 32Y (supply source) to the developing device 5Y (supply destination) without excess or deficiency.

[0050] Now, referring to Figure 7, the toner supply device 90 (powder conveying device) in this embodiment is provided with a drive mechanism 110 as a driving means for driving the first conveying screw 71 (first conveying member) and the second conveying screw 72 (second conveying member). That is, in this embodiment, a common drive means is used for both the first conveying screw 71 and the second conveying screw 72, rather than providing separate, independent drive means. Furthermore, in this embodiment, the toner storage container 32Y (container body 33) is also driven by the drive means that respectively drive the first conveying screw 71 and the second conveying screw 72. Therefore, compared to a case where a plurality of driving means are provided separately and independently, the cost and size of the device can be reduced.

[0051] Specifically, referring to FIG. 7, a drive mechanism 110 serving as a drive means is made up of a drive motor 111, a plurality of gear trains 112 to 118, and the like. The driving force of the driving motor 111 is transmitted from a driving gear 112 mounted on the motor shaft to the gear portion 37 of the toner storage container 32Y via idler gears 114 and 115, thereby driving and rotating the toner storage container 32Y (container body 33). In addition, the driving force of the drive motor 111 is transmitted from the drive gear 112 installed on the motor shaft to the driven gear 118 of the first conveying screw 71 in the first conveying path 91 via the spur gear 113a of the two-stage gear 113 and the idler gear 117, thereby driving the first conveying screw 71 to rotate. In addition, the driving force of the drive motor 111 is transmitted from a drive gear 112 mounted on the motor shaft to a two-stage gear 113 (a spur gear 113a and a bevel gear 113b arranged in stages) and then to a bevel gear 116 of the second conveying screw 72 in the second conveying path 92, thereby driving the second conveying screw 72 to rotate. In the drive mechanism 110 configured as above, when the drive motor 111 is driven under the control of the control unit, the toner storage container 32Y (container body 33) and the first and second conveying screws 71 and 72 are each driven to rotate. In the "supply mode," the concentration detection sensor 56 (see FIG. 2) detects the toner concentration in the developer G in the developing device 5Y, and the drive motor 111 is appropriately driven (rotated forward) so that the detection result falls within a predetermined range. Specifically, every time the toner concentration detected by the concentration detection sensor 56 falls below a predetermined value, the drive motor 111 is driven (rotated forward) for a predetermined period of time. The drive motor 111 is a bidirectional motor that rotates forward in the supply mode and rotates backward in the reverse rotation mode under the control of the control unit.

[0052] Here, in this embodiment, the time T1 during which the first and second conveying screws 71, 72 (conveying members) rotate in the reverse direction when the reverse rotation mode is executed once is set to be equal to or less than the time T0 during which the first and second conveying screws 71, 72 (conveying members) rotate in the forward direction when the supply mode is executed once (T1≦T0). Specifically, the time T1 during which the drive motor 111 rotates in the reverse direction in the reverse rotation mode is set to be equal to or less than the time T0 during which the drive motor 111 rotates in the forward direction in the supply mode. By configuring in this manner, it is possible to reduce the problem that when reverse rotation mode is executed, a large amount of toner in the transport paths 91, 92 is transported in the reverse direction, causing the toner transported in the reverse direction to clog the upstream side of the transport paths 91, 92 (the upstream side during forward rotation).

[0053] An example of control relating to the reverse rotation mode in this embodiment will be described below with reference to FIG. 8, first, when a print command is received by the control unit of the image forming apparatus 100, the reverse rotation mode is executed (step S1). That is, the drive motor 111 rotates the first and second conveying screws 71 and 72 in the reverse direction for a predetermined time T1 (which is a time shorter than the execution time T0 of the supply mode). Thereafter, it is determined whether toner replenishment is necessary (step S2). Specifically, it is determined whether the toner concentration detected by the concentration detection sensor 56 (see FIG. 2) of the developing device 5Y is below a predetermined value. As a result, if it is determined that toner replenishment is necessary, the "supply mode" is executed (step S3) and then this flow is terminated, and if it is determined that toner replenishment is not necessary, this flow is terminated.

[0054] In this embodiment, the "reverse rotation mode" is executed at the timing when the printing operation starts (the timing after the printing command is received). In contrast, (1) Timing before or at the start of a printing operation in an image forming apparatus 100 in which a toner supply device 90 (powder transport device) is installed (2) Timing after the main power of the image forming apparatus 100 is turned on (3) Timing of start of driving of developing device 5Y as a supply destination (4) Before the printing operation is started, the timing for adjusting (process control) the image forming conditions of the image forming unit in the image forming apparatus 100 (such as the developing bias applied to the developing roller 51, the charging bias applied to the charging device 4Y, and the exposure amount of the exposure device 7). (5) The timing of starting the driving of the photosensitive drum 1Y (photosensitive body) or the intermediate transfer belt 8 (intermediate transfer body) in the image forming apparatus. (6) When the supply mode has not been performed for a predetermined period of time after the start of printing (for example, when a monochrome mode (printing in black only) is being performed and a color toner supply device is not in the supply mode during that time). It is also possible to set the "reverse rotation mode" to be executed at at least one of the timings. Even in the above-described timings (1) to (6), by executing the reverse rotation mode before executing the supply mode, toner transport failure in the toner supply device 90 is less likely to occur.

[0055] <Variation 1> As shown in FIG. 9, the reverse rotation mode in Modification 1 is a control mode in which the first and second conveying screws 71, 72 (conveying members) are rotated in the reverse direction and then rotated in the forward direction. That is, in the first modification, before the supply mode is executed, the first and second conveying screws 71, 72 are rotated in the reverse direction, and immediately thereafter, the first and second conveying screws 71, 72 are rotated in the forward direction. By controlling in this way, the toner transported in the reverse direction when the reverse rotation mode is started is transported in the forward direction again and returned to (or moved closer to) its original position, thereby reducing the problem of an initial shortage of toner supplied to the developing device 5Y when the supply mode is subsequently resumed. In order to ensure this effect, in the reverse rotation mode, it is preferable that the time T2 during which the first and second conveying screws 71, 72 rotate in the forward direction be set equal to (or slightly shorter than) the time T1 during which the first and second conveying screws 71, 72 rotate in the reverse direction. 9, when a print command is received by the control unit of the image forming apparatus 100, the reverse rotation mode is executed (step S11). That is, the drive motor 111 rotates the first and second transport screws 71 and 72 in the reverse direction for a predetermined time T1, and then rotates the first and second transport screws 71 and 72 in the forward direction for a predetermined time T2. Thereafter, it is determined whether toner replenishment is necessary (step S2). As a result, if it is determined that toner replenishment is necessary, the "supply mode" is executed (step S3) and then this flow is terminated, and if it is determined that toner replenishment is not necessary, this flow is terminated. Furthermore, in the toner supply device 90 of variant example 1, before the "supply mode" is executed, a "reverse rotation mode" is executed in which the first and second transport screws 71, 72 are rotated in the opposite direction, thereby making it less likely that toner transport problems will occur.

[0056] <Variation 2> As shown in FIG. 10, in a toner supply device 90 in the second modification, a drive means for driving a first transport screw 71 and a drive means for driving a second transport screw 72 are provided separately and independently. More specifically, there is provided a first drive motor 121 that rotates the first conveying screw 71, and a second drive motor 122 that rotates the second conveying screw 72. Both of these first and second drive motors 121 and 122 are bidirectional motors that rotate forward and backward. The first and second drive motors 121 and 122 are controlled by the control unit to rotate forward in the supply mode and reverse in the reverse rotation mode, so that the first and second conveying screws 71 and 72 rotate forward as indicated by the solid arrows in the supply mode and reverse as indicated by the dashed arrows in the reverse rotation mode. Furthermore, in the toner supply device 90 of variant example 2, before the "supply mode" is executed, a "reverse rotation mode" is executed in which the first and second transport screws 71, 72 are rotated in the opposite direction, thereby making it less likely that toner transport problems will occur.

[0057] <Variation 3> As shown in FIG. 11, in a toner supply device 90 (powder transport device) in the third modification, a transport path that curves in the second transport path 92 (curved transport path 92c) is formed. The second conveying screw 72 (second conveying member) is made of an elastic material such as rubber, and has elasticity so as to conform to the shape of the second conveying path 92 (curved conveying path 92c). In this way, by providing the curved transport path 92c capable of transporting toner in the second transport path 92, the degree of freedom in the layout of the toner container 32Y (supply source) and the developing device 5Y (supply destination) can be further increased. Furthermore, in the toner supply device 90 of variant example 3, before the "supply mode" is executed, a "reverse rotation mode" is executed in which the first and second transport screws 71, 72 are rotated in the opposite direction, thereby making it less likely that toner transport problems will occur.

[0058] As described above, in the toner supply device 90 (powder transport device) of this embodiment, when a "supply mode" is executed in which toner (powder) is supplied from the toner storage container 32Y (supply source) to the developing device 5Y (supply destination), the first and second transport screws 71, 72 (transport members) that rotate in the forward direction to transport the toner are disposed in the first and second transport paths 91, 92 (transport paths). Then, before the "supply mode" is executed, a "reverse rotation mode" is executed in which the first and second transport screws 71, 72 (transport members) are rotated in the reverse direction. This makes it less likely that toner transport problems will occur.

[0059] 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. In addition, in this embodiment, the present invention is applied to a powder conveying device (toner supply device 90) in which conveying members 71 and 72 are installed on two conveying paths 91 and 92, respectively, but the present invention can also be applied to a powder conveying device in which one conveying member is installed on one conveying path, or to a powder conveying device in which a conveying member is installed on each of three or more conveying paths. Even in such cases, substantially the same effects as those of this embodiment can be obtained.

[0060] 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]

[0061] 5Y developing device (supply destination), 32Y, 32M, 32C, 32K toner container (supplier), 71 first conveying screw (first conveying member, conveying member), 72 second conveying screw (second conveying member, conveying member), 90 Toner supply device (powder transport device), 91 First conveying path (conveying path), 92 second transport path (transport path), 93 Falling path, 100 Image forming apparatus (image forming apparatus main body), 110 Drive mechanism (drive means). [Prior art documents] [Patent documents]

[0062] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-103314 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-172076

Claims

1. a conveying member disposed in the conveying path, rotating in a forward direction to convey the powder when a supply mode for supplying the powder from a supply source to a supply destination is executed; a first conveying path having a first conveying member disposed therein for conveying the powder in a substantially horizontal direction; a fall path along which the powder flowing out from the outlet of the first conveying path falls; a second conveying path having a second conveying member disposed therein, into which the powder that has fallen along the falling path flows through an inlet and which conveys the powder in a substantially horizontal direction; Equipped with The conveying members include the first conveying member and the second conveying member, The transport path includes the first transport path and the second transport path, an amount of powder transported by the first transport member per unit time in the first transport path in the supply mode is smaller than an amount of powder transported by the second transport member per unit time in the second transport path in the supply mode; A powder conveying device, characterized in that a reverse rotation mode is executed in which the conveying member is rotated in a reverse direction before the supply mode is executed.

2. The powder conveying device described in claim 1, characterized in that the reverse rotation mode is executed at at least one of the following times: before or at the start of a printing operation in an image forming device in which the powder conveying device is installed; after the main power of the image forming device is turned on; when the developing device as the supply destination starts to be driven; before the printing operation starts and when the image forming conditions of the image forming unit in the image forming device are adjusted; when the photosensitive body or intermediate transfer body in the image forming device starts to be driven; and after the printing operation starts and when the supply mode has not been performed for a predetermined period of time.

3. 3. The powder conveying device according to claim 1, wherein the reverse rotation mode is a control mode in which the conveying member is rotated in the forward direction after being rotated in the reverse direction.

4. A powder conveying device as described in any one of claims 1 to 3, characterized in that the time during which the conveying member rotates in the reverse direction when the reverse rotation mode is executed once is equal to or less than the time during which the conveying member rotates in the forward direction when the supply mode is executed once.

5. a plurality of the conveying members respectively provided in the plurality of conveying paths; 5. The powder transport device according to claim 1, wherein the reverse rotation mode is a control mode in which each of the plurality of transport members is rotated in a reverse direction.

6. An image forming apparatus characterized by being equipped with a powder conveying device described in any one of claims 1 to 5.

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