Patent Publication Number: US-2022221809-A1

Title: Powder transport device, developing device, and image forming apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2021-002814 filed Jan. 12, 2021. 
     BACKGROUND 
     (i) Technical Field 
     The present disclosure relates to a powder transport device, a developing device, and an image forming apparatus. 
     (ii) Related Art 
     Developing devices that develop electrostatic latent images with toner may experience lowering of toner transport force due to aggregation of toner. 
     Japanese Unexamined Patent Application Publication No. 2009-276631 discloses a structure in which a flattening member for flattening toner is provided near a toner entry port to prevent clogging of the toner. 
     Japanese Unexamined Patent Application Publication No. 2015-184310 discloses a structure in which a helical coil and a helical screw that is coaxial with the helical coil and has a larger pitch than the helical coil are disposed in a downward-sloping transport hose in which toner fall by gravity. With this structure, the helical screw inhibits the toner from moving through the helical coil, thus preventing solidification of the toner. 
     SUMMARY 
     Aspects of non-limiting embodiments of the present disclosure relate to reducing adhesion of powder to a transport member or a storage part for powder, such as toner, compared with a case where a swing member is not disposed in the storage part. 
     Aspects of certain non-limiting embodiments of the present disclosure address the above advantages and/or other advantages not described above. However, aspects of the non-limiting embodiments are not required to address the advantages described above, and aspects of the non-limiting embodiments of the present disclosure may not address advantages described above. 
     According to an aspect of the present disclosure, there is provided a powder transport device including: a storage part that stores powder; a transport member disposed in the storage part, the transport member extending in an axial direction and rotating to transport the powder in the storage part in the axial direction; and a swing member supported by the transport member so as to be rotated by the rotation of the transport member, the swing member swinging in a direction different from the axial direction while rotating. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present disclosure will be described in detail based on the following figures, wherein: 
         FIG. 1  schematically shows the structure of an image forming apparatus according to an exemplary embodiment of the present disclosure; 
         FIG. 2  is a plan view of a developing device; 
         FIG. 3  is a sectional view taken along line III-III in  FIG. 2 ; 
         FIG. 4  shows the internal structure of the developing device; 
         FIG. 5  is an enlarged perspective vertical-sectional view of a portion near a toner supply port in a second chamber, indicated by circle V, VI in  FIG. 4 ; and 
         FIG. 6  is an enlarged perspective vertical-sectional view of the same portion as in  FIG. 5 , at a point in time during swinging of a swing member. 
     
    
    
     DETAILED DESCRIPTION 
     An exemplary embodiment of the present disclosure will be described below. 
       FIG. 1  schematically shows the structure of an image forming apparatus  1 , serving as an exemplary embodiment of the present disclosure. The image forming apparatus  1  includes a developing device and a powder transport device, serving as exemplary embodiments of the present disclosure. 
     The image forming apparatus  1  shown in  FIG. 1  is a tandem color printer in which image forming units  10 Y,  10 M,  10 C, and  10 K, corresponding to yellow (Y), magenta (M), cyan (C), and black (K), are arranged in parallel. The image forming apparatus  1  can print not only monochrome images, but also full-color images that are formed of toner images of four colors. 
     The image forming apparatus  1  includes: an exposure device  20  that irradiates each of the image forming units  10 Y,  10 M,  10 C, and  10 K with exposure light; an intermediate transfer belt  30  to which toner images are transferred from the image forming units  10 Y,  10 M,  10 C, and  10 K corresponding to the respective colors; a second transfer device  50  that transfers the toner images from the intermediate transfer belt  30  to a sheet; a fixing device  60  that fixes the toner images to the sheet; a belt cleaner  70  that recovers the toner from the intermediate transfer belt  30 ; a sheet transport part  80  that transports the sheet; and a sheet container C that stores sheets P. The image forming apparatus  1  also includes: toner containers  18 Y,  18 M,  18 C, and  18 K that store toners of the respective colors Y, M, C, and K; and toner supply devices  19 Y,  19 M,  19 C, and  19 K that supply the toners in the toner containers  18 Y,  18 M,  18 C, and  18 K to the image forming units  10 Y,  10 M,  10 C, and  10 K, respectively. 
     Herein, the toner containers  18 Y,  18 M,  18 C, and  18 K are replaceable cartridge-type containers. When any of the toner containers  18 Y,  18 M,  18 C, and  18 K becomes empty, that container is replaced with a new container. Hence, before the toner containers become empty, new toner containers for replacement are prepared and stored until those in use become empty. At this time, if the toner containers are stored in a high-temperature environment, the surface of the toner in the containers could become half-melted. 
     The four image forming units  10 Y,  10 M,  10 C, and  10 K have substantially the same structure. Hence, the image forming unit  10 Y corresponding to yellow will be described as a representative example. The image forming unit  10 Y includes an image carrier  11 Y, a charger  12 Y, a developing device  14 Y, a first transfer device  15 Y, and an image-carrier cleaner  16 Y. The image carrier  11 Y has a cylindrical surface and is rotated in the direction of arrow a, which is the axial direction of the cylinder, with an image formed on the surface thereof. 
     The charger  12 Y includes a charging roller  121 Y, which rotates while being in contact with the image carrier  11 Y, and charges the surface of the image carrier  11 Y. 
     The developing device  14 Y stores developer containing toner and magnetic carrier. The developing device  14 Y includes a developing roller  146 Y. The developing roller  146 Y transports the developer to a position facing the image carrier  11 Y. Then, the toner in the developer is adhered to the image carrier  11 Y, forming a toner image on the image carrier  11 Y. When the amount of toner in the developing device  14 Y has decreased, the toner in the toner container  18 Y is supplied to the developing device  14 Y by the toner supply device  19 Y. The toner supply device  19 Y accommodates a toner transport mechanism (not shown) that is driven under the control of a controller  1 A. 
     The first transfer device  15 Y transfers the toner image formed on the image carrier  11 Y to the intermediate transfer belt  30 . The image-carrier cleaner  16 Y cleans the surface of the image carrier  11 Y after the transfer. 
     The exposure device  20  emits exposure light based on an externally supplied image signal to expose the image carriers  11 Y,  11 M,  11 C, and  11 K. 
     The intermediate transfer belt  30  is an endless belt-like member that is supported by belt support rollers  31 ,  32 ,  33 , and  34  and runs in the direction of arrow b while passing through the image forming units  10 Y,  10 M,  10 C, and  10 K and the second transfer device  50 . The intermediate transfer belt  30  carries color toner images formed by the image forming units  10 Y,  10 M,  10 C, and  10 K. 
     The second transfer device  50  includes a roller opposed to the backup roller  34 , which is one of the belt support rollers  31  to  34 , and rotating with the intermediate transfer belt  30  and a sheet therebetween. A voltage for generating a toner-transferring electric field is supplied between the second transfer device  50  and the backup roller  34 , and the toner images on the intermediate transfer belt  30  are transferred to the sheet. 
     The belt cleaner  70  removes the toner remaining on the intermediate transfer belt  30  with a blade  71  that is in contact with the intermediate transfer belt  30 . 
     The fixing device  60  includes a heating roller  61  and a pressure roller  62 . By allowing a sheet with an unfixed toner images to pass between the heating roller  61  and the pressure roller  62 , the fixing device  60  fixes the toner images to the sheet. 
     The sheet transport part  80  picks a sheet P from the sheet container C and transports the sheet P along a sheet transport path r extending through the second transfer device  50  and the fixing device  60 . The sheet transport part  80  includes a pickup roller  81  that picks a sheet P stored in the sheet container C, separation rollers  82  that separate the sheet P from the remaining sheets, transport rollers  83  that transport the sheet P, registration rollers  84  that transport the sheet P to the second transfer device  50 , discharging rollers  86  that discharge the sheet P to the outside, and reversing transport rollers  88  and  89  that transport the sheet P in duplex printing. 
     The basic operation of the image forming apparatus  1  shown in  FIG. 1  will be described. In the image forming unit  10 Y corresponding to yellow, the image carrier  11 Y is rotated in the direction of arrow a, and the charger  12 Y charges the surface of the image carrier  11 Y. This structure is common to the image forming units  10 M,  10 C, and  10 K corresponding to the other colors. The exposure device  20  irradiates the image carrier  11 Y,  11 M,  11 C, and  11 K with exposure light based on data corresponding to the respective colors in an image signal. Formation of a yellow (Y) image will be described as an example. The exposure device  20  irradiates the surface of the image carrier  11 Y with exposure light based on an image signal corresponding to yellow in an externally supplied image signal to form an electrostatic latent image on the surface of the image carrier  11 Y. The developing device  14 Y develops the electrostatic latent image with the yellow toner to form a toner image. The toner supply device  19 Y supplies the toner to the developing device  14 Y from the toner container  18 Y. The image carrier  11 Y rotates with a yellow toner image formed on the surface thereof. The toner image formed on the surface of the image carrier  11 Y is transferred to the intermediate transfer belt  30  by the first transfer device  15 Y, which applies a transfer electric potential between the surface of the image carrier  11 Y and the intermediate transfer belt  30 . The toner remaining on the image carrier  11 Y after the transfer is removed and recovered by the image-carrier cleaner  16 Y. 
     The intermediate transfer belt  30  is supported by the support rollers  31  to  34  and runs in the direction of arrow b. The image forming units  10 M,  10 C, and  10 K corresponding to the other colors form magenta, cyan, and black toner images, respectively, in the same way as the image forming unit  10 Y and transfer the toner images to the intermediate transfer belt  30  so as to be superimposed on the toner image transferred by the image forming unit  10 Y. Meanwhile, a sheet P in the sheet container C is picked by the pickup roller  81  and is transported in the direction of arrow c, toward the second transfer device  50 , along the sheet transport path r by the separation rollers  82 , the transport rollers  83 , and the registration rollers  84 . The sheet P is fed to the second transfer device  50  by the registration rollers  84  in accordance with the timing when the toner images are transferred to the intermediate transfer belt  30 . The second transfer device  50  transfers the toner images on the intermediate transfer belt  30  to the sheet P by applying a transfer bias electric potential between the intermediate transfer belt  30  and the sheet P. The sheet P, to which the toner images have been transferred by the second transfer device  50 , is transported to the fixing device  60 , where the toner images transferred to the sheet P are fixed to the sheet P. In this way, an image is formed on the sheet P. The sheet P with an image formed thereon is discharged from the discharge port  87  to the upper part of the image forming apparatus  1  by the discharging rollers  86 . The toner remaining on the intermediate transfer belt  30  after the transfer by the second transfer device  50  is removed by the belt cleaner  70 . 
     In duplex printing, in which an image is formed also on the back of the side with an image, the discharging rollers  86  discharge the sheet P from the discharge port  87  halfway and then transport the sheet P in the reverse direction. The sheet P transported in the reverse direction is transported along a reversing transport path r′ by the reversing transport rollers  88  and  89 . The sheet P passes through the registration rollers  84  and is fed to the second transfer device  50  in a reversed state, where an image is formed on the back. 
       FIG. 2  is a plan view of the developing device  14 . 
     The image forming apparatus  1  shown in  FIG. 1  includes four developing devices,  14 Y,  14 M,  14 C, and  14 K having substantially the same structure. Hence, in the description below and the drawings after  FIG. 2 , the reference signs Y, M, C, and K representing the colors of toner are omitted, and the developing devices  14 Y,  14 M,  14 C, and  14 K will be simply called the developing devices  14 . Components of the developing devices  14  are also mentioned without the reference signs Y, M, C, or K. Similarly, components of devices other than the developing devices  14  in  FIG. 1  are also described without the reference signs Y, M, C, or K. 
       FIG. 2  shows the top surface of the developing device  14 . A housing  140  of the developing device  14  has a toner supply port  147  in the upper part thereof. The housing  140  of the developing device  14  also has a developer discharge port  148  in the lower part thereof. The position of the developer discharge port  148  is indicated by a dashed-line rectangle. 
       FIG. 3  is a sectional view taken along line III-III in  FIG. 2 . 
       FIG. 4  shows the internal structure of the developing device  14 . 
     The developing device  14  has two developer storage chambers, namely, a first chamber  141  and a second chamber  142 , in the housing  140 . The two storage chambers (the first chamber  141  and the second chamber  142 ) are divided by a partition wall  143 . The first chamber  141  accommodates a supply auger  144 , and the second chamber  142  accommodates an admix auger  145 . The supply auger  144  and the admix auger  145  are rod-like members, and rotation shafts  144   a  and  145   a  thereof are arranged substantially horizontally and substantially parallel to each other. The supply auger  144  has the rotation shaft  144   a  with a circular section and a helical blade  144   b  wound therearound in a helical manner so as to extend along the rotation shaft  144   a.  Similarly to the supply auger  144 , the admix auger  145  has the rotation shaft  145   a  with a circular section and a helical blade  145   b  wound therearound in a helical manner so as to extend along the rotation shaft  145   a.  The admix auger  145  has a portion  145   x  where the helical blade  145   b  is not formed. The developing device  14  has, at a position corresponding to the portion  145   x  where the helical blade  145   b  is not formed, a sensor (not shown) that detects the toner density (the ratio of toner to carrier) in the developer in the developing device  14 . By providing the portion  145   x,  where the helical blade  145   b  is not formed, in the admix auger  145 , interference between the sensor and the helical blade  145   b  is avoided. 
     The supply auger  144  and the admix auger  145  rotate in the same direction, as shown by arrows e and f in  FIG. 3 . The helical blade  144   b  of the supply auger  144  and the helical blade  145   b  of the admix auger  145  rotate in the opposite directions. When the supply auger  144  and the admix auger  145  rotate in the same direction (the directions shown by arrows e and f), the developer in the first chamber  141  and the second chamber  142  is transported in the opposite directions while being stirred. Specifically, the developer in the first chamber  141 , which accommodates the supply auger  144 , is transported in the direction of arrow g, and the developer in the second chamber  142 , which accommodates the admix auger  145 , is transported in the direction of arrow h. 
     The partition wall  143  between the first chamber  141  and the second chamber  142  has a first window  143   a  and a second window  143   b  at the ends thereof, via which the first chamber  141  and the second chamber  142  communicate with each other. Hence, the developer transported in the direction of arrow g in the first chamber  141  enters the second chamber  142  through the first window  143   a,  and the developer transported in the direction of arrow h in the second chamber  142  enters the first chamber  142  through the second window  143   b.  In this manner, the developer in the developing device  14  circulates between the first chamber  141  and the second chamber  142  while being stirred. Of the supply auger  144  and the admix auger  145 , the admix auger  145  is an example of a transport member in the present disclosure. The second chamber  142  accommodating the admix auger  145  is an example of a storage part in the present disclosure. 
     The developing device  14  also has a developing roller  146  near the first chamber  141  accommodating the supply auger  144 . A portion of the developing roller  146  is exposed from the housing  140 . The developing device  14  is set in the image forming apparatus  1  (see  FIG. 1 ) such that the exposed portion of the developing roller  146  is near the image carrier  11 . 
     The developing roller  146  rotates in the direction of arrow d while magnetically attracting the developer in the first chamber  141  to the surface thereof to transport the developer to the position facing the image carrier  11 . As a result, an electrostatic latent image formed on the surface of the image carrier  11  is developed with the toner in the developer, and thus, a toner image is formed on the surface of the image carrier  11 . After developing the image with the toner, the developer on the surface of the developing roller  146  returns to the inside of the housing  140  as the developing roller  146  rotates, is separated from the developing roller  146 , and is circulated with the remaining developer in the first chamber  141  while being stirred. 
     As the development with the toner is repeated, the amount of toner in the developer stored in the developing device  14  decreases. Hence, the developing device  14  has the toner supply port  147 , through which the toner in the toner container  18 , as shown in  FIG. 1 , is supplied to the developing device  14  by the toner supply device  19 . As shown in  FIG. 4 , the toner supply port  147  is provided upstream (i.e., on the side opposite to the direction indicated by arrow h) of the first window  143   a  in the second chamber  142  accommodating the admix auger  145 . The admix auger  145  extends to the position of the toner supply port  147 . The shape of the portion of the helical blade  145   b  extending to the position of the toner supply port  147  is different from the shape of the portion of the helical blade  145   b  extending beside the supply auger  144 . The toner supplied from the toner supply port  147  is transported downstream (i.e., in the direction of arrow h) through the second chamber  142  by the admix auger  145 , is merged with the developer entering through the first window  143   a,  and is transported further downstream (i.e., in the direction of arrow h) through the second chamber  142 . 
     The developing device  14  has, in the bottom surface thereof, a developer discharge port  148  through which the developer in the developing device  14  is gradually discharged. The developer in the developing device  14  is gradually discharged from the developer discharge port  148  to prevent excessive progress of deterioration of the developer in the developing device  14  due to stirring and transporting. Not only the toner, but also the carrier is discharged from the developer discharge port  148 . Hence, the toner in the toner container  18  (see  FIG. 1 ) to be supplied through the toner supply port  147  contains a small amount of carrier to compensate for the decrease of the carrier. 
     The developer discharged from the developing device  14  through the developer discharge port  148  is stored in a waste toner tank (not shown) through a waste-toner discharge path (not shown). 
       FIG. 5  is an enlarged perspective vertical-sectional view of a portion near the toner supply port  147  in the second chamber  142 , shown by circle V, VI in  FIG. 4 . 
       FIG. 6  is an enlarged perspective vertical-sectional view of the same portion as in  FIG. 5 , at a point in time during swinging of a swing member. 
       FIG. 5  shows an end of the admix auger  145  near the toner supply port  147 . 
     The admix auger  145  is supported by a housing  141  of the developing device  14  in a manner capable of rotation. 
     Furthermore, a swing member  240  is disposed in the second chamber  142 , at a portion near the toner supply port  147 . The toner supply port  147  is an example of an inlet according to the present disclosure. 
     When the amount of toner in the developing device  14  becomes smaller than a certain level, the toner in the toner container  18  is transported by the toner supply device  19  and is supplied to the developing device  14  through the toner supply port  147 . The toner supplied to the developing device  14  is transported in the direction of arrow h by the rotation of the admix auger  145 . The toner supplied through the toner supply port  147  contains only a small amount of carrier. If toner with half-melted surface is supplied, the toner particles may aggregate together, adhere to and deposited on an inner wall  142   a  of the second chamber  142  and the admix auger  145 , and consequently be fixed. 
     Herein, “adhere” means a state in which toner is in contact with a member, “deposit” means a state in which toner further adheres to the toner that has already adhered to the member, and “fix” means a state in which the bulk density of the deposited toner has increased, and the toner has become solid. 
     When the toner is fixed to the inner wall  142   a  of the second chamber  142  or the admix auger  145 , a gap between the admix auger  145  and the inner wall  142   a  of the second chamber  142 , through which the toner is transported, becomes narrow, which lowers the transport capacity. This may further increase the bulk density of the toner and cause deposition and fixing of the toner, inhibiting proper transport. 
     To avoid this problem, the developing device  14  has the swing member  240 , which flattens the toner that has started to solidify, to prevent deposition of the toner. 
     The swing member  240  is disposed at a position at least partially facing the toner supply port  147 . Because the swing member  240  is disposed at such a position, adhesion of the toner near the toner supply port  147  is reduced, compared with a case where the swing member  240  is disposed at a position not facing the toner supply port  147 . 
     The length of the swing member  240  in the direction parallel to the rotation shaft  145   a  of the admix auger  145  is smaller than the admix auger  145 . Hence, aggregation of toner near the toner supply port  147 , where the carrier density is low, and thus, aggregation of toner is likely to occur, is efficiently prevented. 
     The swing member  240  is supported by the admix auger  145  so as to be rotated by the rotation of the admix auger  145  and swings in a direction different from the direction in which the rotation shaft  145   a  of the admix auger  145  extends. More specifically, the swing member  240  according to this exemplary embodiment is a coil-like member having the same helical pitch as the helical blade  145   b  of the admix auger  145 . A wire of the coil is wound around the rotation shaft  45   a  in a helical manner so as to be located between adjoining turns of the helical blade  145   b  when the rotation shaft  145   a  is viewed in the axial direction. In this exemplary embodiment, the coil-like swing member  240  has substantially the same diameter as the helical blade  145   a  of the admix auger  145 . 
     Because the swing member  240  according to this exemplary embodiment is a coil-like member, the swing member  240  contributes to transportation of the toner, compared with a case where the swing member  240  is, for example, a plate-like member. Furthermore, because the swing member  240  is wound around the rotation shaft  45   a  in a helical manner such that the wire of the coil is located between adjoining turns of the helical blade  145   b,  both aggregation of toner on the rotation shaft  145   a  of the admix auger  145  and aggregation of toner on the inner wall  142   a  of the second chamber  142  are prevented. 
     More specifically, the wire of the coil of the swing member  240  is disposed at a position between adjoining turns of the helical blade  145   b  in the axial direction and away from both of the adjoining turns of the helical blade  145   b;  that is, substantially in the middle between the adjoining turns of the helical blade  145   b.  Hence, compared with a case where the swing member  240  is located near one of the adjoining turns of the helical blade  145   b,  a transport performance close to that obtained when the admix auger  145  has a double helical blade is obtained. 
     One end  241  of the swing member  240  is supported by the admix auger  145 , and the other end  242  of the swing member  240  is a free end that can swing freely. Hence, the other end  242  (free end) swings in the directions of arrows U and D, as shown in  FIG. 6 , which are different from the direction in which the rotation shaft  145   a  of the admix auger  145  extends. Because the other end  242  of the swing member  240  is a free end that can swing freely, the swing member  240  can swing by a large degree, compared with a case where both ends of the swing member  240  are supported by the admix auger  145 . This structure prevents both fixing of toner to the rotation shaft  145   a  of the admix auger  145  and fixing of toner to the inner wall  142   a  of the second chamber  142 . 
     More specifically, the one end  241  of the swing member  240  according to this exemplary embodiment is supported by the admix auger  145  with a certain allowance so as to allow swinging of the other end  242 . When the one end  241  is supported with a certain allowance, the other end  242  can swing more freely, compared with a case where the one end  241  is fixed to the admix auger  145 . 
       FIG. 6  shows the swing member  240  in a state in which the other end  242  (free end) has swung in the direction of arrow D and is in contact with the inner wall  142   a  of the second chamber  142 . 
     In this exemplary embodiment, because the swing member  240  is provided, aggregation of toner near the toner supply port  147  is prevented, and consequently, a decrease in the toner transport force is prevented. 
     Although the swing member  240  is disposed at a position at least partially facing the toner inlet  147  in this exemplary embodiment, the swing member  240  may be disposed at any position where aggregation of toner could occur. 
     Furthermore, although an example case has been described in which the present disclosure is applied to the developing device  14  used in the image forming apparatus  1 , which is a so-called tandem image forming apparatus, as shown in  FIG. 1 , the present disclosure may be applied to various types of image forming apparatuses, such as monochrome printers, besides the image forming apparatus of the type shown in  FIG. 1 . 
     Furthermore, although an example case in which the swing member  240  is provided in the developing device  14  has been described, the swing member  240  may be provided in a device other than the developing device  14 , such as a waste-toner recovery device (not shown) that transports the developer discharged through the developer discharge port  148  toward a waste toner tank (not shown). 
     Furthermore, the present disclosure may be applied to a powder transport device that transports a powder other than toner. 
     The foregoing description of the exemplary embodiments of the present disclosure has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the disclosure and its practical applications, thereby enabling others skilled in the art to understand the disclosure for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the disclosure be defined by the following claims and their equivalents.