Patent Publication Number: US-10768551-B2

Title: Conveying screw, toner container and image forming apparatus

Description:
INCORPORATION BY REFERENCE 
     This application is based on and claims the benefit of priority from Japanese patent application No. 2018-162073 filed on Aug. 30, 2018, which is incorporated by reference in its entirety. 
     BACKGROUND 
     The present disclosure relates to a conveying screw configured to convey a toner (a developer), a toner container and an image forming apparatus. 
     An electrophotographic type image forming apparatus includes a conveying screw configured to convey a toner (a developer). 
     For example, there is a dispense auger rotating in a toner supply path communicating a toner storage chamber with a development chamber. The dispense auger includes a spiral blade part formed around a rotational shaft, and the spiral blade is configured such that a pitch of the spiral blade is gradually narrowed from an upstream side to a downstream side in a conveyance direction of the toner. This makes a compressive force of the toner gradually high toward the downstream side in the conveyance direction to decrease an occurrence of a void at the downstream side in the conveyance direction. As a result, it becomes possible to make a supply amount of the toner stable regardless of an amount of the toner in the toner storage chamber. 
     SUMMARY 
     In accordance with an aspect of the present disclosure, a conveying screw configured to convey a toner in an axial direction includes a conveying shaft part and a conveying blade. The conveying shaft part is configured to be rotated around an axis. The conveying blade is spirally formed around an outer circumferential face of the conveying shaft part and configured to convey a toner in a replenishment path. At least one spiral of the conveying blade is formed by two semicircular blade plates which are coupled to in postures inclined in opposite directions to each other. A through hole through which the toner is passed in the axial direction is formed in an area surrounded by the conveying shaft part and the two blade plates. 
     In accordance with an aspect of the present disclosure, a toner container includes a container main body and a conveying screw. The container main body is configured to store a toner and to include a replenishment path communicated with a destination. The conveying screw is configured to convey the toner stored in the container main body in an axial direction. The conveying screw includes a conveying shaft part and a conveying blade. The conveying shaft part is configured to be rotated around an axis. The conveying blade is spirally formed around an outer circumferential face of the conveying shaft part and configured to convey the toner in the replenishment path. At least one spiral of the conveying blade is formed by two semicircular blade plates which are coupled to in postures inclined in opposite directions to each other. A through hole through which the toner is passed in the axial direction is formed in an area surrounded by the conveying shaft part and the two blade plates. 
     In accordance with an aspect of the present disclosure, an image forming apparatus includes the above described toner container. 
     The above and other objects, features, and advantages of the present disclosure will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present disclosure is shown by way of illustrative example. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing a color printer according to one embodiment of the present disclosure. 
         FIG. 2  is a view (a side view) schematically showing an inner structure of the color printer according to the embodiment of the present disclosure. 
         FIG. 3  is a perspective view showing a lid body side portion of a toner container according to a first embodiment of the present disclosure. 
         FIG. 4  is a perspective view showing a case side portion of the toner container according to the first embodiment of the present disclosure. 
         FIG. 5  is a side view showing an inside of the toner container according to the first embodiment of the first present disclosure. 
         FIG. 6  is a sectional view showing the toner container according to the first embodiment of the first present disclosure. 
         FIG. 7  is a perspective view showing a conveying screw according to the first embodiment of the present disclosure. 
         FIG. 8  is a front view showing the conveying screw according to a second embodiment of the present disclosure. 
         FIG. 9  is a sectional view showing the toner container including the conveying screw according to the second embodiment of the present disclosure. 
         FIG. 10  is a front view showing the conveying screw according to a first modified example of the second embodiment of the present disclosure. 
         FIG. 11  is a front view showing the conveying screw according to a second modified example of the second embodiment of the present disclosure. 
         FIG. 12  is a front view showing the conveying screw according to a third modified example of the second embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, with reference to the attached drawings, an embodiment of the present disclosure will be described. Fr, Rr, L, R, U and D marked in each figure respectively indicate a front side, a rear side, a left side, a right side, an upper side and a lower side. 
     [A first embodiment: an outline of a color printer] With reference to  FIG. 1  and  FIG. 2 , an entire structure of a color printer  1  as an example of an image forming apparatus  1  will be described.  FIG. 1  is a perspective view showing the color printer  1 .  FIG. 2  is a view (a side view) schematically showing an inner structure of the color printer  1 . 
     As shown in  FIG. 1  and  FIG. 2 , the color printer includes an apparatus main body  2  formed in an approximately parallelepiped shape. In a lower portion of the apparatus main body  2 , a sheet feeding cassette  3  configured to store a paper sheet S (refer to  FIG. 2 ) is detachably attached. On an upper face of the apparatus main body  2 , a discharge tray  4  is provided. The sheet S is not limited to the paper sheet; may be a resin sheet or the others. 
     As shown in  FIG. 2 , the color printer  1  includes a sheet feeding device  5 , an image forming device  6 , a fixing device  7  and a toner replenishment device  20  (refer to  FIG. 1 ) which are stored inside the apparatus main body  2 . The sheet feeding device  5  is provided at an upstream end portion of a conveyance path  8  extending from the sheet feeding cassette  3  to the discharge tray  4 . The fixing device  7  is provided at a downstream side of the conveyance path  8 , and the image forming device  6  is provided on the conveyance path  8  between the sheet feeding device  5  and the fixing device  7 . 
     As shown in  FIG. 1 , the toner replenishment device  20  is provided in a right side portion of the apparatus main body  2 . The toner replenishment device  20  includes four toner containers  22  configured to store toners (developers) of four colors (yellow, magenta, cyan and black). The toner is a two-component developer; however, the toner is not limited thereto and may be a one-component developer containing a magnetic toner. 
     As shown in  FIG. 2 , the image forming device  6  includes an intermediate transferring belt  11 , four drum units  12  and an optical scanning device  13 . The intermediate transferring belt  11  is rotated in a direction indicated by an arrow in  FIG. 2 . Each drum unit  12  includes a photosensitive drum  14 , a charging device  15 , a development device  16 , a primary transfer roller  17  and a cleaning device  18 . Each primary transfer roller  17  is provided such that the intermediate transferring belt  11  is put between the photosensitive drum  14  and the primary transfer roller  17 . With a rear portion of the intermediate transferring belt  11 , a secondary transfer roller  19  comes into contact to form a transfer nip. 
     A controller (not shown) of the color printer  1  controls each device suitably to carry out an image forming operation as follows. The charging device  15  charges a surface of the photosensitive drum  14 . The photosensitive drum  14  receives a scanning light emitted from the optical scanning device  13  to carry an electrostatic latent image. The development device  16  uses the toner supplied from the toner container  22  and develops the electrostatic latent image on the photosensitive drum  14  into a toner image. The primary transfer roller  17  primarily transfers the toner image on the photosensitive drum  14  to the rotating intermediate transferring belt  11 . The intermediate transferring belt  11  carries a full color toner image formed by superimposing the four color toner images while rotating. The sheet S is fed by the sheet feeding device  5  from the sheet feeding cassette  3  to the conveyance path  8 . The secondary transfer roller  19  secondarily transfers the toner image on the intermediate transferring belt  11  to the sheet S passing through the transfer nip. The fixing device  7  thermally fixes the toner image on the sheet S. After that, the sheet S is discharged on the discharge tray  4 . The cleaning device  18  removes the toner remaining on the photosensitive drum  14 . 
     [The toner replenishment device] Next, with reference to  FIG. 1 ,  FIG. 3  to  FIG. 7 , the toner replenishment device  20  will be described.  FIG. 3  is a perspective view showing a lid body  32  side portion of the toner container  22 .  FIG. 4  is a perspective view showing a cases  30  and  31  side portion of the toner container  22 .  FIG. 5  is a side view showing an inside of the toner container  22 .  FIG. 6  is a sectional view showing the toner container  22 .  FIG. 7  is a perspective view showing a conveying screw  25 . In the following description, “a conveyance direction” shows a conveyance direction of the toner. 
     As shown in  FIG. 1 , the toner replenishment device  20  includes a container attachment part  21  and the four toner containers  22 . 
     [The container attachment part] The container attachment part  21  is provided in the right side portion of the apparatus main body  2 . In the container attachment part  21 , four attachment rooms (not shown) are formed side by side in the front-and-rear direction. To the four attachment rooms, the four toner containers  22  are detachably attached. The apparatus main body  2  is provided with a cover  21 A configured to open and close the container attachment part  21 . 
     [The toner container] As shown in  FIG. 3  to  FIG. 5 , the four toner containers  22  each includes a container main body  23 , an agitating member  24 , a conveying screw  25  and a collecting screw  26 . The container main body  23  stores the toner. The agitating member  24  has a function to agitate the toner stored in the container main body  23 . The conveying screw  25  has a function to convey the toner stored in the container main body  23  in an axial direction. The collecting screw  26  has a function to convey the toner to an inside of the container main body  23  in an axial direction. 
     As shown in  FIG. 1 , the toner container  22  storing the black color toner has a size larger than the toner containers  22  storing the toners other than the black color toner, and is attached to the rearmost attachment room. The four toner containers  22  have almost the same structure other than the size; the toner container  22  storing the toner other than the black color toner will be described hereinafter. In the following description, a state where the toner container  22  is attached to the container attachment part  21  (the attachment room) is set to be a reference state. 
     &lt;The container main body&gt; As shown in  FIG. 3  to  FIG. 5 , the container main body  23  is formed in a box shape extending in the upper-and-lower direction (the longitudinal direction) and having a size shorter in the left-and-right direction (a depth direction perpendicular to the longitudinal direction) than in the upper-and-lower direction. A width of the container main body  23  in the front-and-rear direction is set to be shorter than a length (a height) in the upper-and-lower direction and longer than a length in the left-and-right direction (a depth of each of cases  30  and  31  described later). 
     The container main body  23  includes an upper part case  30  (a case) formed at an upper side, a lower part case  31  formed at a lower side, a lid body  32 , a conveyance guide part  33  and a collection guide part  34 . 
     (The upper part case, the lower part case) The upper part case  30  and the lower part case  31  are made of synthetic resin material and formed integrally, for example. The upper part case  30  and the lower part case  31  are formed in a box shape respectively having openings  30 A and  31 A at their right side faces (refer to  FIG. 5 ). Around outer circumferential edges of the openings  30 A and  31 A of the cases  30  and  31 , a flange part  23 A is formed. Between the upper part case  30  and the lower part case  31 , a recess part  23 B recessing in an approximately rectangular shape from the front side to the rear side is formed. 
     As shown in  FIG. 5  and  FIG. 6 , inside the upper part case  30 , a storage chamber R 1  configured to store a fresh toner is formed. Inside the lower part case  31 , a collection chamber R 2  configured to store a waste toner is formed. The storage chamber R 1  and the collection chamber R 2  have approximately parallelepiped spaces. A bottom face of the storage chamber R 1  is formed in an approximately arc shape. 
     (The lid body) As shown in  FIG. 3 , the lid body  32  is made of synthetic resin and formed in an approximately flat plate shape, for example. The lid body  32  is formed in a shape corresponding to an outer circumferential shape of the flange part  23 A. The lid body  32  is fixed to the flange part  23 A to close the upper and lower openings  30 A and  31 A (refer to  FIG. 6 ). 
     (The conveyance guide part) As shown in  FIG. 4  to  FIG. 6 , the conveyance guide part  33  is formed in a cylindrical shape extending from the upper part case  30  in the left direction (the downstream side in the conveyance direction). In detail, the conveyance guide part  33  is formed integrally with a left side wall of the upper part case  30  near a front lower corner of the upper part case  30 . A length (a depth) of the conveyance guide part  33  in the left-and-right direction is set to be shorter than a height of an entire portion of the container main body  23 . A depth of both the conveyance guide part  33  and the upper part case  30  is set to be shorter than the height of the entire portion of the container main body  23  and to be longer than a width of the entire portion of the container main body  23  in the front-and-rear direction. Inside the conveyance guide part  33 , a replenishment path  35  configured to communicate the storage chamber R 1  with the development device  16  (an example of a destination of the toner) is formed (refer to  FIG. 6 ). A cross sectional area of the conveyance guide part  33  (the replenishment path  35 ) is set to be sufficiently smaller than an area of the storage chamber R 1  when the storage chamber R 1  is viewed from the lateral side (refer to  FIG. 5 ). 
     As shown in  FIG. 6 , on a tip side lower face of the conveyance guide part  33 , a discharge port  35 A through which the toner is discharged to the development device  16  is formed. On the tip side lower face of the conveyance guide part  33 , a discharge shutter  35 B which opens and closes the discharge port  35 A is formed in a slidable manner. The discharge shutter  35 B is moved from a position where the discharge shutter  35 B closes the discharge port  35 A to a position where the discharge shutter  35 B opens the discharge port  35 A during a process where the toner container  22  is attached to the container attachment part  21 .  FIG. 6  shows the discharge shutter  35 B moved to the position where the discharge shutter  35 B opens the discharge port  35 A. 
     (The collection guide part) As shown in  FIG. 3  to  FIG. 5 , the collection guide part  34  is formed in a cylindrical shape extending from the lower part case  31  in the left direction. In detail, the collection guide part  34  is formed integrally with a left side wall of the lower part case  31  near a rear upper corner of the lower part case  31 . The collection guide part  34  is disposed below the conveyance guide part  33  and has almost the same length as the conveyance guide part  33 . Inside the collection guide part  34 , a collection path  36  configured to communicate the collection chamber R 2  with the cleaning device  18  is formed (refer to  FIG. 5 ). 
     As shown in  FIG. 4 , on a tip side upper face of the collection guide part  34 , an introduction port  36 A through which the toner is introduced in the collection path  36  is formed. On the tip side upper face of the collection guide part  34 , an introduction shutter  36 B which opens and closes the introduction port  36 A is provided in a slidable manner. The introduction shutter  36 B is moved from a position where the introduction shutter  36 B closes the introduction port  36 A to a position where the introduction shutter  36 B opens the introduction port  36 A during the process where the toner container  22  is attached to the container attachment part  21 . 
     &lt;The agitating member&gt; As shown in  FIG. 5  and  FIG. 6 , the agitating member  24  is disposed inside the storage chamber R 1  in a posture extending in the left-and-right direction. The agitating member  24  includes an agitating shaft part  24 A and a paddle part  24 B. 
     The agitating shaft part  24 A is made of synthetic resin and formed in a rod shape extending in the left-and-right direction, for example. One axial end portion of the agitating shaft part  24 A is supported by the left side wall of the upper part case  30  in a rotatable manner and the other axial end portion of the agitating shaft part  24 A is supported by the lid body  32  in a rotatable manner. The paddle part  24 B is formed by elastically deformable film material made of synthetic resin. The paddle part  24 B is provided in a state extending outwardly in a radial direction from the agitating shaft part  24 A. The paddle part  24 B is formed so as to have a length enough that a tip end portion of the paddle part  24 B comes into contact with the bottom face of the storage chamber R 1 . 
     &lt;The conveying screw&gt; As shown in  FIG. 5  and  FIG. 6 , the conveying screw  25  is disposed over the storage chamber R 1  and the replenishment path  35  in a posture extending in the left-and-right direction. The conveying screw  25  is provided in a posture where its axial direction extends in the left-and-right direction (the depth direction of the container main body  23 ). Specifically, the conveying screw  25  has an axial length corresponding to a length of both the storage chamber R 1  and the replenishment path  35  in the left-and-right direction and shorter than the height of the entire portion of the container main body  23 . The conveying screw  25  is disposed on almost the same axis as the replenishment path  35  when viewed form the lateral side. 
     As shown in  FIG. 5  to  FIG. 7 , the conveying screw  25  includes a conveying shaft part  25 A and a conveying blade  25 B. The conveying shaft part  25 A and the conveying blade  25 B are made of synthetic resin and formed integrally, for example. 
     As shown in  FIG. 6 , the conveying shaft part  25 A is formed in a rod shape extending in the left-and-right direction. A left end portion of the conveying shaft part  25 A in an axial direction is supported by a left end portion of the conveyance guide part  33 . A right end portion of the conveying shaft part  25 A in the axial direction is fixed to a turnable supporting shaft  32 A provided in the lid body  32  in a turnable manner. 
     As shown in  FIG. 6  and  FIG. 7 , the conveying blade  25 B is spirally formed around an outer circumferential face of the conveying shaft part  25 A. The conveying blade  25 B is formed around the outer circumferential face of the conveying shaft part  25 A for five to five and half spirals while being shifted in the axial direction. The conveying blade  25 B has an outer diameter in such a degree that the conveying blade  25 B does not come into contact with an inner circumferential face of the conveyance guide part  33 . The conveying blade  25 B will be described later. 
     &lt;The collecting screw&gt; As shown in  FIG. 5 , the collecting screw  26  is disposed in the collection path  36  in a posture extending in the left-and-right direction. The collecting screw  26  includes a collecting shaft part  26 A and a collecting blade  26 B formed spirally around an outer circumferential face of the collecting shaft part  26 A. The collecting shaft part  26 A and the collecting blade  26 B are made of synthetic resin and formed integrally, for example. An outer shape of the collecting screw  26  has almost the same shape as the conveying screw  25  and the collecting blade  26 B has a conventional spiral shape formed by a continuous curve, and the description of the collecting screw  26  is omitted. 
     [A conveying operation for the toner in the toner container] For example, when a user attaches the toner container  22  to the container attachment part  21 , the discharge shutter  35 B is opened to communicate the discharge port  35 A with a toner introduction part (not shown) of the development device  16 . At the same time, the introduction shutter  36 B is opened to communicate the introduction port  36 A with a toner discharge port (not shown) of the cleaning device  18 . Furthermore, at the same time, the agitating shaft part  24 A, the conveying shaft part  25 A and the collecting shaft part  26 A are connected to a motor (not shown) via a joint member and a gear train. 
     When the above described image forming operation is started, the motor rotates the agitating member  24 , the conveying screw  25  and the collecting screw  26  around their axes. The paddle part  24 B of the agitating member  24  rotates while coming into contact with the bottom face and the others of the storage chamber R 1  to agitate the toner stored in the storage chamber R 1 . The conveying blade  25 B of the conveying screw  25  conveys the toner stored in the storage chamber R 1  to the downstream side in the replenishment path  35 . The toner is conveyed along the replenishment path  35  and replenished through the discharge port  35 A to the development device  16 . The development device  16  uses the replenished toner and develops the electrostatic latent image on the photosensitive drum  14  into the toner image. 
     The toner remaining on the photosensitive drum  14  after the toner is transferred is removed by the cleaning device  18 . The removed toner is taken into the collection path  36  from the toner discharge part of the cleaning device  18  through the introduction port  36 A. The collecting blade  26 B of the collecting screw  26  conveys the toner taken into the collection path  36  toward the collection chamber R 2 . The toner is conveyed along the collection path  36  and then stored in the collection chamber R 2 . 
     An amount of the toner replenished in the development device  16  is detected by a sensor (not shown), and the controller recognizes a residual amount of the toner in the storage chamber R 1  from a detection result of the sensor. When it is recognized that the residual amount of the toner is less than a predetermined amount (or equal to zero), the controller may display an information to prompt a replacement of the toner container  22  on a liquid crystal display (not shown) of the color printer  1  or order a new toner container  22  through an Internet. 
     By the way, when the residual amount of the toner is large, a sufficient amount of the toner exists around the conveying screw  25  and a sufficient amount of the toner agitated by the agitating member  24  is supplied around the conveying screw  25 . Thereby, the conveying screw  25  can convey an approximately constant amount of the toner so that it becomes possible to make a replenish amount (a supply amount) of the toner to the development device  16  stable. On the other hand, when the residual amount of the toner is small, because an amount of the toner agitated by the agitating member  24  is decreased, it becomes impossible to supply a sufficient amount of the toner around the conveying screw  25 . In this case, a ratio of the toner to the void between the axially adjacent portions of the conveying blade  25 B may be increased or decreased and may become unstable. Thereby, an amount of the toner conveyed by the conveying screw  25  (the replenish amount of the toner to the development device  16 ) becomes unstable. Then, even if the toner remains in the storage chamber R 1 , the controller may misrecognize that an amount of the residual toner is less than the predetermined amount. As a result, the toner container  22  which does not require to be replaced may be replaced. 
     Then, in the conveying screw  25  according to the first embodiment, the conveying blade  25 B is formed so as to convey the toner while compressing the toner in the replenishment path  35 . Specifically, as shown in  FIG. 6 , the toner in the storage chamber R 1  is applied with a conveying force by the rotating conveying blade  25 B and conveyed to the downstream side in the conveyance direction while a part of the toner is released outwardly in the radial direction. When the toner enters the replenishment path  35  from the storage chamber R 1 , the toner is blocked by the conveyance guide part  33  and is eliminated from being released outward in the radial direction so that a compressing force applied on the toner from the conveying blade  25 B is suddenly increased. 
     As described above, the toner container  22  according to the first embodiment is configured such that the compressing force applied on the toner from the conveying blade  25 B is increased as the toner enters the replenishment path  35  from the storage chamber R 1 . According to the configuration, because the toner is conveyed through the replenishment path  35  while being compressed, even if the residual amount of the toner in the storage chamber R 1  is small, it becomes possible to prevent the occurrence of the void in the replenishment path  35 . As a result, regardless of the residual amount of the toner in the storage chamber R 1 , it becomes possible to make the replenishment amount of the toner to the development device  16  stable. 
     When the conveying blade  25 B conveys the toner while compressing the toner in the replenishment path  35  as described above, the toner may be excessively compressed and be solidified. The solidification of the toner becomes apparent when a capsule toner susceptible to be compressed and a toner having a low melting point are used. Then, the conveying screw  25  according to the first embodiment includes the conveying blade  25 B configured to suppress the excessive compressing of the toner. 
     [A structure of the conveying blade] Next, with reference to  FIG. 6  and  FIG. 7 , a structure of the conveying blade  25 B will be described. 
     The conveying blade  25 B is formed by a plurality of blade plates  37 , and the blade plates  37  are spirally coupled across the conveying shaft part  25 A alternately. The blade plates  37  are arranged at approximately equal intervals in the axial direction. That is, the spirals of the conveying blade  25 B are shifted with a uniform pitch in the axial direction. One spiral of the conveying blade  25 B is formed by the two blade plates  37 . The blade plate  37  is formed in an approximately semicircular plate shape. The two blade plates  37  are coupled in postures inclined in the opposite directions to each other. In detail, the two blade plate  37  are coupled in the postures inclined in the opposite directions to each other such that a portion near a center of a chord circumferential portion between circumferential ends of the semicircular circumferential portion of the blade plate  37  is fixed to the conveying shaft part  25 A and one end portions of the chord circumferential portions of the two blade plates  37  are coupled together. Note that the semicircular shape of the blade plate  37  does not require a complete semicircular shape and a small difference is allowable. That is, the blade plate  37  may be an arc shape other than the semicircular shape. For example, the blade plate  37  may be formed by coupling an arc shaped blade plate  37  having a central angle of 180° or larger and an arc shaped blade plate  37  having a central angle of less than 180° (not shown). 
     As shown in  FIG. 6 , the conveying blade  25 B disposed in the replenishment path  35  has through holes  38  through which the toner is passed in the axial direction. As shown in  FIG. 7 , the though hole  38  is formed in an area surrounded by the conveying shaft part  25 A and the two blade plates  37 . The through hole  38  is a triangular hole with a ridge line of the conveying shaft part  25 A as a bottom line and the chord circumferential portions of the two blade plates  37  as inclined lines. The conveying blade  25 B disposed other than the replenishment path  35  (the conveying blade  25 B disposed in the storage chamber R 1 ) does not have the through hole  38  and the portions corresponding to the through holes  38  are filled up (refer to  FIG. 7 ). 
     According to the conveying screw  25  according to the first embodiment as described above, in the replenishment path  35  where the toner may be excessively compressed, the conveying blade  25 B is formed by the blade plates  37  which form the through hole  38  with the conveying shaft part  25 A. According to the configuration, because the toner conveyed along replenishment path  35  while being compressed can be released through the through holes  38  to the upstream side in the conveyance direction, it becomes possible to suppress the toner conveyed along the replenishment path  35  from being excessively compressed. This makes it possible to suppress the solidification of the toner owing to the excessive compressing. 
     According to the conveying screw  25  (the toner container  22 ) of the first embodiment, it becomes possible to obtain both counter effects where one effect is to supply the toner stably by conveying the toner while compressing and the other effect is to prevent the excessive compressing of the toner. 
     In the toner container  22  according to the first embodiment, the conveying screw  25  is formed to have the short axial length to correspond to the depth of the container main body  23  (the conveyance guide part  33 ). In this case, the compressing force of the toner is suddenly changed in a narrow space in the axial direction. However, because the conveying screw  25  makes it possible to release the toner through the through hole  38  to the upstream side in the conveyance direction, even if the conveying screw  25  has the short axial length, it becomes possible to prevent the excessive compressing of the toner. 
     In the conveying screw  25  of the first embodiment, an entire portion of the conveying blade  25 B disposed in the replenishment path  35  is formed by the blade plates  37  which form the through hole  38  with the conveying shaft part  25 A; however, the present disclosure is not limited thereto. A part of the conveying blade  25 B disposed in the replenishment path  35  may be formed by the blade plates  37  which form the through hole  38  with the conveying shaft part  25 A. Alternatively, the entire portion of the conveying blade  25 B disposed in the replenishment path  35  and a part of the conveying blade  25 B disposed in the storage chamber R 1  may be formed by the blade plates  37  which form the through hole  38  with the conveying shaft part  25 A. Additionally, the entire portion of the conveying blade  25 B may be formed by the blade plates  37  which form the through hole  38  with the conveying shaft part  25 A. 
     [A second embodiment] Next, with reference to  FIG. 8  and  FIG. 9 , the conveying screw  27  according to a second embodiment will be described.  FIG. 8  is a front view showing the conveying screw  27 .  FIG. 9  is a sectional view showing the toner container  22  including the conveying screw  27 . In the following description, the same structures as the toner container  22 , the conveying screw  25  and the others in the first embodiment are shown by the same reference numbers as the first embodiment, and their detail descriptions are omitted. 
     In the conveying screw  25  according to the first embodiment, the pitch of the conveying blade  25 B (the blade plate  37 ) is formed at approximately uniform intervals. However, when the residual amount of the toner is small, a change in ratio of the toner to the void between the axially adjacent portions of the conveying blade  25 B becomes large toward the downstream side in the conveyance direction. Thereby, in order to make an amount of the toner conveyed by the conveying screw  25  stable, it may be said that it is effective to increase the compressing force of the toner at the downstream side in the conveyance direction. Then, in the conveying screw  27  according to the second embodiment, the conveying blade  27 B has a configuration which delays the toner conveyance at the downstream side in the conveyance direction. 
     As shown in  FIG. 8 , the conveying screw  27  is formed such that the pitch of the conveying blade  25 B is gradually narrowed from the upstream side to the downstream side in the conveyance direction. In other words, the conveying blade  27 B is formed such that a volume V between the axially adjacent portions of the conveying blade  27 B is gradually decreased from the upstream side to the downstream side in the conveyance direction. For example, as shown in  FIG. 8  and  FIG. 9 , the conveying screw  27  is formed such that, of the conveying blade  27 B disposed in the replenishment path  35 , a gap between the blade plates  37  forming the two to two and half spirals at the downstream side is made to be narrower than a gap between the blade plates  37  forming the other spirals. This makes it possible to increase the compressing force of the toner at the downstream side in the conveyance direction and it becomes possible to make the amount of the toner conveyed by the conveying screw  27  stable regardless of the residual amount of the toner. 
     As shown in  FIG. 8  and  FIG. 9 , the blade plates  37  of which the gap is made to be narrow form the through hole  38  with the conveying shaft part  25 A while the other blade plates  37  do not form the through hole  38  with the conveying shaft part  25 A. According to the configuration, because the conveying blade  27 B has the through hole  38  in an area where the compressing force of the toner becomes high, it becomes possible to release the toner to the upstream side in the conveyance direction. Then, even if the conveying screw  27  has a short axial length, it becomes possible to suppress the excessive compressing of the toner. 
     The through hole  38  may be formed by a part of the blade plates  37  other than the blade plates  37  of which the gap is made to be narrow, or may be formed by all of the blade plates  37 . That is, the conveying blade  27 B may be formed by the blade plates  37  which form the through hole  38  with the conveying shaft part  25 A at the downstream side in the conveyance direction from a position where the volume V between the axially adjacent portions of the conveying blade  27 B is smaller than a set value. The set value of the volume V may be set such that the solidification of the toner does not occur in view of the type and the melting point of the toner. 
     In the conveying screw  27  according to the second embodiment, the conveying blade  27 B (the blade plate  37 ) is formed to have the two different pitches and the pitch is changed for one step (one time). However, the present disclosure is not limited thereto. For example, the conveying blade  27 B (the blade plate  37 ) may be formed to have three or more different pitches and the pitch may be changed for two or more steps (two or more times) (not shown). In a case where the conveying blade  27 B (the blade plate  37 ) is formed to have three or more different pitches, the through hole  38  may be formed only by the blade plate  37  of the most narrow gap (pitch) or may be formed by the blade plate  37  other than the blade plate  37  of the most wide pitch (not shown). 
     In the conveying screw  27  according to the second embodiment, the pitch of the conveying blade  27 B is formed to be gradually narrowed from the upstream side to the downstream side in the conveyance direction. However, the present disclosure is not limited thereto. As the conveying screw  27  of a first modified example, as shown in  FIG. 10 , the pitch of the conveying blade  27 B may be formed to be continuously narrowed from the upstream side to the downstream side in the conveyance direction. In other words, the conveying blade  27 B may be formed such that the volume V between the axially adjacent portions of the conveying blade  27 B is continuously decreased from the upstream side to the downstream side in the conveyance direction. 
     In the conveying screw  27  according to the second embodiment (including the first modified example), by changing the pitch of the conveying blade  27 B, the volume V between the axially adjacent portions of the conveying blade  27 B is changed. However, the present disclosure is not limited thereto. In the conveying screw  27  as a second modified example, as shown in  FIG. 11 , the pitch of the conveying blade  27 B is uniform (equal intervals) while a thickness of the conveying blade  27 B (the blade plate  37 ) in the axial direction is gradually increased from the upstream side to the downstream side in the conveyance direction to decrease the volume V gradually. In this case, it is preferable to form the through hole  38  by the blade plate  37  formed to have a thicker thickness. The thickness of the conveying blade  27 B (the blade plate  37 ) in the axial direction may be continuously increased (not shown). 
     In the conveying screw  27  according to a third modified example, as shown in  FIG. 12 , the pitch of the conveying blade  27 B is uniform (equal intervals) while an outer diameter (a diameter) of the conveying shaft part  27 A is gradually increased from the upstream side to the downstream side in the conveyance direction to decrease the volume V gradually or continuously. Alternatively, the outer diameter (the diameter) of the conveying shaft part  27 A may be gradually increased from the upstream side to the downstream side in the conveyance direction (not shown). 
     Alternatively, to the conveying screw  27  changed in the pitch of the conveying blade  27 B, the conveying blade  27 B (the blade plate  37 ) changed in the thickness and the conveying shaft part  27 A changed in the diameter may be applied (not shown). 
     In the conveying screws  25  and  27  according to the first and second embodiments, the entire portions of the conveying blades  25 B and  27 B are formed by the blade plate  37 . However, the present disclosure is not limited thereto. At least one spiral of the conveying blades  25 B and  27 B may be formed by two semicircular blade plates coupled in the posture inclined in the opposite directions to each other. For example, of the conveying blades  25 B and  27 B, a portion in a range where the through hole  38  is not required is not formed by the blade plate  37 ; may be a conventional spiral blade having no through hole  38  as the same as the collecting blade  26 B of the collecting screw  26 . 
     In the toner container  22  according to the first and second embodiments, the conveyance guide part  33  (the replenishment path  35 ) is formed to have almost the same cross area from the upstream side to the downstream side. The present disclosure is not limited thereto. For example, the conveyance guide part  33  (the replenishment path  35 ) may be formed to have a cross area gradually or continuously decreased from the upstream side to the downstream side (not shown). 
     In the toner container  22  according to the first and second embodiments, the collecting screw  26  includes the conventional spiral collecting blade  26 B having no through hole  38 . The present disclosure is not limited thereto. The collecting blade  26 B may have the same feature as the conveying blades  25 B and  27 B of the conveying screws  25  and  27 . 
     In the toner container  22  according to the first and second embodiments, the container main body  23  includes the upper part case  30  and the lower part case  31  which are separated, and the lower part case  31  has the collection chamber R 2  configured to store the waste toner. The present disclosure is not limited thereto. The container main body  23  may not include the lower part case  31  (the collection chamber R 2 ) (not shown). 
     The conveying screws  25  and  27  according to the first and second embodiments are equipped in the toner container  22 . However, the present disclosure is not limited thereto. They may be equipped in the development device  16  and the cleaning device  18 . 
     In the description of the present embodiment, a case where the present disclosure is applied to the color printer  1  is shown as an example. However, the present disclosure is not limited thereto; may be applied to a monochrome printer, a copying machine, a facsimile and a multifunctional peripheral. 
     The description of the above embodiments shows one aspect in the conveying screw, the toner container and the image forming apparatus according to the present disclosure, and the technical scope of the present disclosure is not limited the above described embodiments. 
     While the present disclosure has been described with reference to the particular illustrative embodiments, it is not to be restricted by the embodiments. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present disclosure.