Patent Publication Number: US-10310407-B2

Title: Development device and image forming apparatus

Description:
INCORPORATION BY REFERENCE 
     This application is based on and claims the benefit of priorities from Japanese patent application No. 2017-156417 filed on Aug. 14, 2017 and Japanese patent Application No. 2018-105983, filed on Jun. 1, 2018 which are incorporated by reference in their entirety. 
     BACKGROUND 
     The present disclosure relates to a development device and an image forming apparatus including the development device. 
     An electrophotographic type image forming apparatus conventionally includes a development device. A casing of the development device stores a developer. A toner in the developer is supplied to a surface of an image carrier (for example, a photosensitive drum) to develop an electrostatic latent image formed on the surface of the image carrier. 
     In the above development device, when the toner in the developer is scattered outside the casing, the scattered toner may contaminate an inner space of the image forming apparatus and exert bad influence on operations of members constituting the image forming apparatus. Then, various methods to inhibit the scattering of the toner from the development device are proposed. 
     For example, in some cases, outside air is introduced toward an inner space of the casing of the development device through a flow gap formed between the casing of the development device and the surface of the photosensitive drum in order to inhibit the toner scattering from the development device. 
     SUMMARY 
     In accordance with an aspect of the present disclosure, a development device includes a developer carrier, a blade and a cover. The developer carrier carries a developer containing a toner. The blade regulates a thickness of the developer carried on the developer carrier. The cover includes a cover main body covering an outer side of the blade and a facing rib protruding from an inner face of the cover main body and facing the developer carrier at an interval. A storage space to store the toner which contacts the facing rib and falls is formed below the facing rib. 
     In accordance with an aspect of the present disclosure, an image forming apparatus includes the development device. 
     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 schematic view schematically showing an image forming apparatus according to an embodiment of the present disclosure. 
         FIG. 2  is a sectional view showing a development device according to the embodiment of the present disclosure. 
         FIG. 3  is a perspective sectional view showing a cover according to the embodiment of the present disclosure. 
         FIG. 4  is a sectional view showing the cover according to the embodiment of the present disclosure. 
         FIG. 5  is a sectional view showing the development device according to another embodiment of the present disclosure. 
         FIG. 6  is a sectional view showing the development device according to still another embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, with reference to the attached drawings, an image forming apparatus  1  according to an embodiment of the present disclosure will be described. Arrows Fr, Rr, L, R, U and Lo suitably 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 of the image forming apparatus  1 . 
     First, an entire structure of the image forming apparatus  1  will be described. The image forming apparatus  1  is a multifunctional peripheral multiply containing a print function, a copying function and a facsimile function, for example. 
     With reference to  FIG. 1 , the image forming apparatus  1  includes a box-shaped apparatus main body  2 . At an upper end portion of the apparatus main body  2 , an image reading device  3  configured to read an image of a document is provided. 
     In an upper portion of the apparatus main body  2 , an ejected sheet tray  4  is provided. In an approximately center portion of the apparatus main body  2 , an intermediate transferring belt  5  and four image forming parts  6  are stored. Each image forming part  6  includes a photosensitive drum  7  (an example of an image carrier) and a development device  8 . In a lower portion of the apparatus main body  2 , an exposure device  10  is stored. In a lower end portion of the apparatus main body  2 , a sheet feeding cassette  11  storing a sheet S (an example of a recording medium) is stored. 
     In a right side portion of the apparatus main body  2 , a conveying path P for the sheet S is provided. At an upstream side end portion of the conveying path P, a sheet feeding part  12  is provided. At a midstream portion of the conveying path P, a secondary transferring part  13  is provided. Ata downstream portion of the conveying path P, a fixing device  14  is provided. 
     In the upper portion of the apparatus main body  2 , four toner containers  15  are stored below the ejected sheet tray  4 . The toner containers  15  respectively store a toner of different colors (for example, black, cyan, magenta and yellow). 
     Next, an example of an operation of the image forming apparatus  1  will be described. 
     First, a laser (refer to a dotted line arrow in  FIG. 1 ) from the exposure device  10  forms an electrostatic latent image on the photosensitive drum  7  of each image forming part  6 . The development device  8  of each image forming part  6  develops the above electrostatic latent image. Thereby, a toner image is carried on the photosensitive drum  7  of each image forming part  6 . The toner image is primarily transferred on the intermediate transferring belt  5  from the photosensitive drum  7  of each image forming part  6 . Thereby, a full color toner image is formed on the intermediate transferring belt  5 . 
     On the other hand, the sheet S fed from the sheet feeding cassette  11  by the sheet feeding part  12  is conveyed to a downstream side along the conveying path P and then enters the secondary transferring part  13 . At the secondary transferring part  13 , the full color toner image formed on the intermediate transferring belt  5  is secondarily transferred on the sheet S. The sheet S on which the toner image is secondarily transferred is further conveyed to the downstream side along the conveying path P and then enters the fixing device  14 . The fixing device  14  fixes the toner image on the sheet S. The sheet S on which the toner image is fixed is ejected on the ejected sheet tray  4 . 
     Next, the development device  8  will be further described. 
     With reference to  FIG. 2 , the development device  8  includes a casing  21 , a pair of left and right agitating screws  22  stored in a lower portion of the casing  21 , a magnetic roller  23  (an example of a developer carrier) provided at a right upper side of the right agitating screw  22 , a blade  24  provided at a right side of the casing  21 , a cover  25  provided from a right side to a lower side of the blade  24 , a seal member  26  fixed to an upper end portion of the cover  25  and an elastic member  27  provided between the blade  24  and the cover  25 . 
     The casing  21  of the development device  8  has a box-like shape elongated in a front-and-rear direction. An inner space P of the casing  21  stores a two-component developer (hereinafter, called as “a developer” simply) containing a non-magnetic toner and a magnetic carrier. That is, the development device  8  employs a two-component development method. 
     On a right face of the casing  21 , an opening part  31  is provided. On the right face of the casing  21 , an attachment face  32  is provided below the opening part  31 . On a left side portion of an upper face of the casing  21 , a replenishment port  33  is provided. Through the replenishment port  33 , the toner is replenished from the corresponding toner container  15  (refer to  FIG. 1 ) to the inner space P of the casing  21 . 
     With reference to  FIG. 2 , the pair of left and right agitating screws  22  each has a shape elongated in the front-and-rear direction. Each agitating screw  22  is stored in the inner space P of the casing  21 . Each agitating screw  22  is rotatably supported by the casing  21 . 
     The magnetic roller  23  of the development device  8  has a shape elongated in the front-and-rear direction. A left side portion of the magnetic roller  23  is stored in the inner space P of the casing  21 . A right side portion of the magnetic roller  23  is exposed to an outside of the casing  21  through the opening part  31  of the casing  21 . 
     The magnetic roller  23  includes a plurality of magnetic poles  35  and a sleeve  36  covering an outer circumference of the plurality of magnetic poles  35 . The plurality of magnetic poles  35  are fixed to the casing  21 . The sleeve  36  rotates along a rotation direction Y around a rotation axis X extending along the front-and-rear direction. That is, in the present embodiment, the front-and-rear direction is a rotation axis direction of the sleeve  36 . An outer circumferential face of the sleeve  36  faces an outer circumferential face of the photosensitive drum  7  at an interval. 
     The blade  24  of the development device  8  has a shape elongated in the front-and-rear direction. The blade  24  has an L-shaped cross section. A tip end portion  24 A (an upper end portion) of the blade  24  faces the outer circumferential face of the sleeve  36  of the magnetic roller  23  at an interval. 
     The blade  24  includes a main body plate  38  extending to a right lower side and a bent plate  39  bent from a lower end portion of the main body plate  38  to a left lower side. The main body plate  38  is attached to the attachment face  32  of the casing  21  via an elastic body  40  made of sponge. An outer face of the main body plate  38  is flat. 
     With reference to  FIG. 2  to  FIG. 4 , the cover  25  of the development device  8  includes a cover main body  43  extending along an upper-and-lower direction, a bent piece  44  bent from a lower end portion of the cover main body  43  to a left lower side, and a facing rib  45  and a reinforcement rib  46  and a plurality of restriction ribs  47  which are protruded from an inner face  43 A of the cover main body  43 . All of the cover main body  43 , the bent piece  44  and the ribs  45  to  47  are integrally formed. 
     The cover main body  43  of the cover  25  covers an outer side of the blade  24 . On an upper portion of the inner face  43 A of the cover main body  43 , a recess  49  is provided. On a center portion in the upper-and-lower direction of the inner face  43 A of the cover main body  43 , a curved face  50  is provided at a lower end side of the recess  49 . On a lower portion of the inner face  43 A of the cover main body  43 , a stepped portion  51  is provided. 
     The bent piece  44  of the cover  25  covers a lower side of the blade  24 . An upper face of the bent piece  44  faces a lower face of the bent plate  39  of the blade  24  at an interval. 
     The facing rib  45  of the cover  25  extends from a front end side to a rear end side of the cover  25  along the front-and-rear direction. The facing rib  45  protrudes from the recess  49  of the cover main body  43  to a left lower side. A protruding length L 1  of the facing rib  45  from the recess  49  is from 0.1 mm to 3.0 mm inclusive. The facing rib  45  inclines to a lower side toward its tip end side. The facing rib  45  does not come into contact with the blade  24 . 
     A tip end portion  45 A of the facing rib  45  of the cover  25  faces the outer circumferential face of the sleeve  36  of the magnetic roller  23  at an interval. The tip end portion  45 A of the facing rib  45  is positioned at a downstream side of the tip end portion  24 A of the blade  24  in the rotation direction Y of the sleeve  36 . The tip end portion  45 A of the facing rib  45  is positioned above the tip end portion  24 A of the blade  24 . 
     With reference to  FIG. 2 , below the facing rib  45  of the cover  25 , a storage space Q to store the developer which contacts the facing rib  45  and then falls is formed. An upper face of the storage space Q is opened. A bottom face of the storage space Q is constituted by an upper face of the elastic member  27  and the curved face  50  of the cover main body  43 . An inner face of the storage space Q is constituted by the outer face of the main body plate  38  of the blade  24 . An outer face of the storage space Q is constituted by the recess  49  of the cover main body  43 . The storage space Q is provided outside the inner space P of the casing  21 . 
     The reinforcement rib  46  of the cover  25  extends from the front end side to the rear end side of the cover  25  along the front-and-rear direction. The reinforcement rib  46  protrudes below the facing rib  45  from the recess  49  of the cover main body  43  to a left lower side. A protruding length L 2  of the reinforcement rib  46  from the recess  49  is shorter than the protruding length L 1  of the facing rib  45  from the recess  49 . The reinforcement rib  46  is provided parallel to the facing rib  45  and is inclined to a lower side toward its tip end side. The reinforcement rib  46  does not comes into contact with the blade  24 . The reinforcement rib  46  is arranged inside the storage space Q. A tip end portion  46 A of the reinforcement rib  46  is positioned below the tip end portion  24 A of the blade  24 . 
     With reference to  FIG. 2  to  FIG. 4 , the plurality of restriction ribs  47  of the cover  25  are provided at intervals in the front-and-rear direction. Each restriction rib  47  extends along the upper-and-lower direction, and couples the facing rib  45  to the reinforcement rib  46 . Each restriction rib  47  protrudes from the recess  49  of the cover main body  43  to a left lower side. A protruding length L 3  of each restriction rib  47  from the recess  49  is longer than the protruding length L 1  of the facing rib  45  from the recess  49  and the protruding length L 2  of the reinforcement rib  46  from the recess  49 . 
     A tip end portion  47 A of each restriction rib  47  is flat, and comes into surface contact with the outer face of the main body plate  38  of the blade  24 . The tip end portion  47 A of each restriction rib  47  is positioned below the tip end portion  24 A of the blade  24 . 
     With reference to  FIG. 2 , the seal member  26  of the development device  8  has a shape elongated in the front-and-rear direction. The seal member  26  is made of sheet-like film, for example. A lower end portion of the seal member  26  is fixed to an upper end portion of an outer face of the cover main body  43  of the cover  25 . An upper end portion of the seal member  26  comes into contact with the outer circumferential face of the photosensitive drum  7 . 
     The elastic member  27  of the development device  8  has a shape elongated in the front-and-rear direction. The elastic member  27  is made of sponge material, for example. The elastic member  27  has a rectangular cross section. An inner face of the elastic member  27  comes into contact with the outer face of the main body plate  38  of the blade  24 . An outer face of the elastic member  27  comes into contact with the inner face  43 A of the cover main body  43  of the cover  25 . That is, the elastic member  27  is arranged between the main body plate  38  of the blade  24  and the cover main body  43  of the cover  25 . A lower face of the elastic member  27  comes into contact with the stepped portion  51  of the cover main body  43  of the cover  25 . 
     When the development device  8  configured as described above develops the electrostatic latent image formed on the photosensitive drum  7 , each agitating screw  22  and the sleeve  36  of the magnetic roller  23  are rotated. When each agitating screw  22  is thus rotated, the developer stored in the inner space P of the casing  21  is agitated by each agitating screw  22  and then charged. 
     The charged developer is brought up by magnetic force of the plurality of magnetic poles  35  of the magnetic roller  23  and then carried by the sleeve  36  of the magnetic roller  23 . The developer carried by the sleeve  36  is conveyed by the sleeve  36  along the rotation direction Y and its thickness is regulated by the tip end portion  24 A of the blade  24 . The developer whose thickness is regulated is further conveyed by the sleeve  36  along the rotation direction Y and introduced to a facing area between the sleeve  36  and the photosensitive drum  7 . Then, depending on a voltage difference between the sleeve  36  and the photosensitive drum  7 , the toner in the developer is adhered on the electrostatic latent image formed on the photosensitive drum  7 . That is, the toner is supplied from the sleeve  36  to the photosensitive drum  7 . Thereby, the electrostatic latent image formed on the photosensitive drum  7  is developed. 
     By the way, as the sleeve  36  is rotated as described above, the developer is passed through a facing area between the tip end portion  24 A of the blade  24  and the outer circumferential face of the sleeve  36 . This generates an air flow containing the toner (refer to an arrow F in  FIG. 2 ). If the air flow is discharged outside the development device  8 , the toner contained in the air flow is scattered outside the development device  8  and an inner space of the image forming apparatus  1  may be contaminated with the toner. 
     Then, the present embodiment is configured that the facing rib  45  of the cover  25  faces the outer circumferential face of the sleeve  36  at an interval. By applying such a configuration, it becomes possible to slow down a flow rate of the air flow containing the toner greatly by hitting the air flow against the facing rib  45  and to make the toner in the air flow fall. Thereby, it becomes possible to inhibit the toner scattering from the development device  8 . 
     Additionally, an interval between the tip end portion  45 A of the facing rib  45  and the outer circumferential face of the sleeve  36  becomes narrow by the developer (refer to a dotted line D in  FIG. 2 ) carried on the outer circumferential face of the sleeve  36 . Thereby, the air flow containing the toner is hardly passed through the above interval so that it becomes possible to hit most of the air flow against the facing rib  45 . 
     Additionally, below the facing rib  45 , the storage space Q to store the toner which contacts the facing rib  45  and then falls is formed. Thereby, it becomes possible to store the toner which contacts the facing rib  45  and then falls, inside the development device  8  surely and to inhibit the toner scattering from the development device  8  more surely. 
     Additionally, the cover  25  includes not only the facing rib  45  but also the reinforcement rib  46 . By applying such a configuration, it becomes possible to improve a strength of the cover  25 . Additionally, the protruding length L 2  of the reinforcement rib  46  from the recess  49  of the cover main body  43  is shorter than the protruding length L 1  of the facing rib  45  from the recess  49  of the cover main body  43 . By applying such a configuration, it becomes possible to prevent the introduction of the toner to the storage space Q from being inhibited by the reinforcement rib  46 . 
     Additionally, the tip end portion  45 A of the facing rib  45  is positioned above the tip end portion  24 A of the blade  24 . By applying such a configuration, it becomes possible to hit the air flow containing the toner against the facing rib  45  surely. The tip end portion  46 A of the reinforcement rib  46  is positioned below the tip end portion  24 A of the blade  24 . By applying such a configuration, compared with a case where both the tip end portion  45 A of the facing rib  45  and the tip end portion  46 A of the reinforcement rib  46  are positioned above the tip end portion  24 A of the blade  24 , it becomes possible to make an interval between the facing rib  45  and the reinforcement rib  46  wide. Then, it becomes possible to further improve the strength of the cover  25 . 
     Additionally, the facing rib  45  and the reinforcement rib  46  extend along the front-and-rear direction (the rotation axis direction of the sleeve  36 ). By applying such a configuration, it becomes possible to further improve the strength of the cover  25 . 
     Additionally, the cover  25  further includes the plurality of restriction ribs  47  protruding from the inner face of the cover main body  43 , and each restriction rib  47  comes into contact with the blade  24 . By applying such a configuration, it becomes possible to inhibit the cover main body  43  from being deflected inward and to inhibit a leakage of the toner from a periphery of the cover  25 . 
     Additionally, the tip end portion  47 A of each restriction rib  47  is flat, and comes into surface contact with the outer face of the main body plate  38  of the blade  24 . By applying such a configuration, the tip end portion  47 A of each restriction rib  47  is allowed to come into contact with the outer face of the main body plate  38  of the blade  24  stably. 
     Additionally, the plurality of restriction ribs  47  are provided in the front-and-rear direction (the rotation axis direction of the sleeve  36 ) at intervals, each restriction rib  47  extends along the upper-and-lower direction (a direction perpendicular to the rotation axis direction of the sleeve  36 ), and is coupled to the facing rib  45 . By applying such a configuration, it becomes possible to further improve the strength of the cover  25 . 
     Additionally, the protruding length L 1  of the facing rib  45  from the recess  49  of the cover main body  43  is from 0.1 mm to 3.0 mm inclusive. By making the protruding length L 1  0.1 mm or longer as described above, it becomes possible to improve a function to slow the air flow rate down by the facing rib  45 . By making the protruding length L 1  3.0 mm or shorter as described above, it becomes possible to inhibit the tip end portion  45 A of the facing rib  45  from coming into contact with the developer (refer to the dotted line D in  FIG. 2 ) carried on the outer circumferential face of the sleeve  36 . 
     Additionally, a part of the bottom face of the storage space Q is constituted by the elastic member  27 . By applying such a configuration, varying a shape and a size of the elastic member  27  makes it possible to vary a volume of the storage space Q freely. 
     Additionally, the image forming apparatus  1  includes the above development device  8 . By applying such a configuration, it becomes possible to provide the image forming apparatus  1  capable of inhibiting the toner scattering from the development device  8 . 
     In the present embodiment, the cover  25  includes the reinforcement rib  46  protruding from the recess  49  of the cover main body  43  below the facing rib  45 . On the other hand, in other embodiments, as shown in  FIG. 5 , the cover  25  may not include another rib protruding from the recess  49  of the cover main body  43  below the facing rib  45 . In other words, the recess  49  of the cover main body  43  may be flat below the facing rib  45 . By applying such a configuration, it becomes possible to make the volume of the storage space Q large. 
     In the present embodiment, the facing rib  45  protrudes from the recess  49  of the inner face  43 A of the cover main body  43 . On the other hand, in other embodiments, the facing rib  45  may protrude from a portion other than the recess  49  of the inner face  43 A of the cover main body  43 . This is similar to the reinforcement rib  46  and each restriction rib  47 . 
     In the present embodiment, the tip end portion  47 A of each restriction rib  47  is flat. On the other hand, in other embodiments, as shown in  FIG. 6 , the tip end portion  47 A of each restriction rib  47  may be curved. 
     In the present embodiment, each restriction rib  47  comes into contact with the blade  24 . On the other hand, in other embodiments, each restriction rib  47  may face the blade  24  at an interval. 
     In the present embodiment, the two-component developer containing the toner and the carrier is employed as the developer. On the other hand, in other embodiments, a one-component developer containing the toner only may be employed as the developer. 
     In the present embodiment, the toner is directly supplied from the magnetic roller  23  to the photosensitive drum  7 . On the other hand, in other embodiments, the toner may be supplied from the magnetic roller  23  to the photosensitive drum  7  via another roller. 
     In the present embodiment, the image forming apparatus  1  is a multifunctional peripheral. On the other hand, in other embodiments, the image forming apparatus  1  may be a printer, a copying machine and a facsimile. 
     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.