Patent Publication Number: US-8971768-B2

Title: Developer container including an elastically deformable transporting member and image forming apparatus including the developer container

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims priority from Japanese Patent Application Nos. 2011-151771 and 2012-137523, filed on Jul. 8, 2011, and Jun. 19, 2012, respectively, the disclosures of which are incorporated herein by reference in their entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image forming apparatus in which an electrophotography is adopted, and a developer container which is equipped in the image forming apparatus. 
     2. Description of the Related Art 
     As an electrophotographic color printer, an intermediate-transfer type color printer which includes a plurality of developing units, a plurality of photosensitive drums which are disposed in parallel above the developing units corresponding to the respective developing units, an endless belt which makes a contact with each photosensitive drum from an upper side thereof, and a secondary transfer roller which makes a contact with one end of the endless belt has hitherto been known. 
     As a developing unit which is equipped in such intermediate-transfer type color printer, for instance, a developing unit which includes a developing chamber in which a supply roller, a developing roller and a stirring member are provided, and a developer accommodating chamber disposed below the developing chamber, which accommodates a developer such as toner, and in which a transporting member configured to transport the developer to the developing chamber is provided, has been proposed. 
     Moreover, in such developing unit, the developer accommodated in the developer accommodating chamber is charged in the developing chamber from a direction of rotation of the transporting member, by the transporting member which is rotatably provided, and is supplied to the supply roller while being stirred by the stirring member in the developing chamber. 
     SUMMARY OF THE INVENTION 
     However, in the developing unit in which the developing chamber is disposed above the developer accommodating chamber, the developer is supplied from the developer accommodating chamber to the developing chamber against the gravitational force. Therefore, there is a fear that the developer is not supplied evenly to the developing chamber, which may give rise to an uneven level of developer. Moreover, due to such uneven level of developer, the developer may not be supplied uniformly to the supply roller, and furthermore, the developer may not be carried uniformly on the developing roller, which may lead to a defective image formation. 
     Therefore, in the above described developing unit, the uneven level of the developer is suppressed by providing the stirring member and stirring the developer. 
     However, when the stirring member is provided in the developing chamber, the structure of the developing unit becomes complicated, and facilitating small-sizing and cost-reduction of the developing unit becomes difficult. 
     Therefore, an object of the present invention is to provide a developer container which is capable of preventing the defective image formation caused due to the uneven level of developer while having a simple structure, and an image forming apparatus equipped with the developer container. 
     According to a first aspect of the present invention, there is provided a developer container including: 
     a developer accommodating chamber configured to accommodate the developer; and 
     a transporting member configured to elastically deform and to rotate in the developer accommodating chamber, and further configured to transport the developer accommodated in the developer accommodating chamber, 
     wherein the developer accommodating chamber includes: 
     a dividing wall having a sliding portion configured to deform the transporting member by making a sliding contact with the transporting member, the dividing wall defining a part of the developer accommodating chamber to divide the developer accommodating chamber and an upper space thereof; 
     a communicating portion arranged at a downstream side in a direction of rotation of the transporting member with respect to the sliding portion, the communicating portion communicating an inner side and an outer side of the developer accommodating chamber, the communicating portion being configured to allow the transporting member, which has been elastically deformed by the sliding portion, to restore; and 
     a contacting portion arranged at the downstream side in the direction of rotation of the transporting member with respect to the communicating portion, the transporting member restored by the communicating portion being configured to contact with the contacting portion. 
     When such an arrangement is made, the transporting member makes a sliding contact with the sliding portion by rotating, and is elastically deformed along the shape of the sliding portion. Moreover, when the transporting member rotates further and moves from the sliding portion to the communicating portion, the sliding contact between the sliding portion and the transporting member terminates, and the transporting member which has been deformed is restored toward the downstream side of the direction of rotation, or in other words, toward the contacting portion. Therefore, a part of the developer transported by the transporting member is dispersed by being discharged to the communicating portion with the restoration of the transporting member. Moreover, the developer which has not been discharged to the communicating portion is transported toward the contacting portion, and collides with the contacting portion together with transporting member. 
     As the developer hits the contacting portion, the developer which has been transported to the contacting portion upon being discharged is supplied from the contacting portion to an outside of the developer accommodating chamber with an air flow generated by the collision of the transporting member with the contacting portion. Moreover, by the air flow, the developer discharged to the communicating portion is also supplied to the outside of the developer accommodating chamber. In other words, the developer dispersed is supplied to the outside of the developer accommodating chamber from a direction opposite to the direction of rotation of the transporting member. Therefore, it is possible to suppress the uneven level of developer supplied to the outside of the developer accommodating chamber as compared to a case in which, the developer is charged by the transporting member from the direction of rotation of the transporting member to the outside of the developer accommodating chamber. 
     Consequently, it is possible to suppress the uneven level of developer supplied to the developer accommodating chamber, and to prevent defective image formation due to the uneven level of developer, while facilitating small-sizing and cost-reduction. 
     According to a second aspect of the present invention, there is provided an image forming apparatus configured to form an image on a medium, including: 
     a plurality of developer containers according to the first aspect of the present invention; 
     a plurality of photosensitive drums arranged above the developer containers, corresponding to the plurality of developer containers; 
     an endless belt arranged above the photosensitive drums; 
     a plurality of primary transfer rollers arranged to face the photosensitive drums, sandwiching the endless belt between the primary transfer rollers and the photosensitive drums; and 
     a secondary transfer roller arranged at one end side of the endless belt. 
     According to such an arrangement, since the developer is supplied to the supply roller uniformly, and is held on the developing roller uniformly, it is possible to prevent defective image formation. 
     Consequently, in the image forming apparatus according to the present invention, it is possible to suppress the uneven level of developer in the developing chamber, and to prevent defective image formation which may be caused due to the uneven level of developer, while enabling to facilitate small-sizing and cost reduction. 
     In the developer container and the image forming apparatus according to the present invention, it is possible to suppress the uneven level of developer to be supplied to the outside of the developer accommodating chamber, to prevent defective image formation which may be caused due to the uneven level of developer, while enabling to facilitate small-sizing and cost reduction. 
     According to a third aspect of the present invention, there is provided a developer container including: 
     a housing defining a developer accommodating chamber for accommodating developer, the housing having an opening which communicates an inner side and an outer side of the developer accommodating chamber; and 
     an elastically deformable transporting member configured to rotate in a first direction for transporting the developer accommodated in the developer accommodating chamber, the transporting member being located below the opening of the housing, 
     wherein the housing includes: 
     a sliding portion located at an upstream side in the first direction with respect to the opening, the sliding portion being configured to elastically deform the transporting member, the opening being configured to allow the transporting member, which has been elastically deformed by the sliding portion, to restore; 
     a contacting portion located at a downstream side in the first direction with respect to the opening, and configured to contact with the restored transporting member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side cross-sectional view of a color printer as an embodiment of an image forming apparatus; 
         FIG. 2  is a side-sectional view showing an embodiment of a developing unit shown in  FIG. 1 ; 
         FIG. 3  is a front view of a contacting portion of the developing unit shown in  FIG. 1 ; 
         FIG. 4  is an enlarged view of a developing chamber of the developing unit shown in  FIG. 1 ; and 
         FIG. 5  is a side-sectional view showing another embodiment of a developing unit. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     &lt;A. Overall Structure of Color Printer&gt; 
     As shown in  FIG. 1 , a color printer  1  as an example of an image forming apparatus is an intermediate transfer type color printer of a horizontally-mounted type. 
     Moreover, the color printer  1  includes a main-body casing  2 , and a paper feeding section  3  for feeding a paper P, and an image forming section  4  for forming an image on the supplied paper P. The paper feeding section  3  and the image forming section  4  are accommodated in the casing  2 . 
     &lt;1. Main-body Casing&gt; 
     The main-body casing  2  is formed to be box-shaped in a substantially rectangular form in a side view, and is configured to accommodate the paper feeding section  3  and the image forming section  4 . A front cover  5  is swingably or pivotably provided on one side wall of the main-body casing  2 . A lower-end portion of the front cover  5  is fixed on the one side wall as a supporting point of a pivot. 
     In the following description, a side at which the front cover  5  is provided is defined as a front side, and an opposite side thereof is defined as a rear side. In other words, a left side and a right side in  FIG. 1  are defined as a front side and a rear side respectively. Moreover, a view of the color printer  1  from a front side is let to be a basis for left and right. 
     &lt;2. Paper Feeding Section&gt; 
     The paper feeding section  3  includes a paper feeding tray  6  which is configured to accommodate papers P. The paper feeding tray  6  is detachably installed on a bottom portion inside the main-body casing  2 . 
     Moreover, the paper feeding section  3  is provided with a pickup roller  9  which is arranged at an upper side of a rear-end portion of the paper feeding tray  6 , a paper feeding roller  10  which is arranged at a rear side of the pickup roller  9 , a paper feeding pad  11  which is arranged to face a lower side of the paper feeding roller  10 , a pair of transporting rollers  12  which are arranged at a rear upper side of the paper feeding roller  10 , and a pair of register rollers  13  which are arranged at a front upper side of the transporting roller  12 , and which are facing mutually. 
     Papers P (refer to a solid line in  FIG. 1 ) accommodated in the paper feeding tray  6  are sent between the paper feeding roller  10  and the paper feeding pad  11  by the rotation of the pickup roller  9 , and are separated one by one by the rotation of the paper feeding roller  10 . Thereafter, the paper P which has been separated is fed upwardly toward a gap between the register rollers  13 , and is supplied to the image forming section  4  (between an intermediate transfer belt  30  and a secondary transfer roller  27  which will be described later) by the rotation of the register rollers  13  at a predetermined timing. 
     &lt;3. Image Forming Section&gt; 
     The image forming section  4  is arranged above the paper feeding section  3 , and includes a processing unit  15 , a transfer unit  17 , and a fixing unit  18 . 
     &lt;3-1. Processing Unit&gt; 
     The processing unit  15  is provided on an upper side of the paper feeding tray  6 , and is configured to be movable along a front-rear direction, between an installing position at which the processing unit  15  is to be installed in the main-body casing  2  and a drawing position at which the processing unit  15  is to be drawn from the main-body casing  2 . 
     The processing unit  15  includes a processing frame  20  and a developing unit  25  as an example of a developer container which is detachably held by the processing frame  20 . 
     The processing frame  20  is formed to be box-shaped in a substantially rectangular form, and is elongated in the front-rear direction in a side view. Further, the processing frame  20  is configured to be slidable in the front-rear direction. 
     Moreover, the processing frame  20  includes four photosensitive drums  22  as an example of a photosensitive body, four scorotron chargers  23 , four drum cleaning rollers  24 , four LED units  44 , and a belt cleaning unit  43 . 
     Each photosensitive drum  22  is formed to be substantially circular cylinder shaped with a longitudinal direction in the left-right direction, and the four photosensitive drums  22  are arranged in parallel at an interval in the front-rear direction such that an upper portions of the photosensitive drums  22  are exposed from an upper-end edge of the processing frame  20 . Moreover, each photosensitive drum  22  is rotatably supported by two side walls which are not shown in the diagram, of the processing frame  20 . 
     Each scorotron charger  23  is arranged to face the corresponding photosensitive drum  22  leaving an interval, on a rear lower side of the corresponding photosensitive drum  22 , and is extended in the left-right direction, and is supported by two side walls which are not shown in the diagram, of the processing frame  20 . 
     Each drum cleaning roller  24  is arranged face the photosensitive drum  22  at an upper side of the scorotron charger  23  and at a rear side of the corresponding photosensitive drum  22  such that the drum cleaning roller  24  makes a contact with the photosensitive drum  22 . Each drum cleaning roller  24  is extended in the left-right direction and is rotatably supported by two side walls which are not shown in the diagram, of the processing frame  20 . 
     Each LED unit  44  is supported by the processing frame  20  to face the corresponding photosensitive drum  22  from the lower side. The LED unit  44  exposes a surface of the corresponding photosensitive drum  22  based on predetermined image data. 
     The belt cleaning unit  43  is arranged inside the processing frame  20  at a front side thereof, and includes a waste-developer accommodating portion  45  which is formed to be rectangular box shaped in a side view, a cleaning roller  46  which is provided at an upper end inside the waste developer accommodating portion  45 , a scraping roller  47 , and a scraping blade  48 . A developer on a surface of the intermediate transfer belt  30  (which will be described later) is cleaned by the cleaning roller  46 , and after being held on the scraping roller  47  once, the developer is scraped by the scraping blade  48 , thereby accommodating in the waste developer accommodating portion  45 . 
     Four developing units  25  corresponding to respective colors are provided. The developing units  25  are arranged at a front lower side of the corresponding photosensitive drums  22 , in a state of being held by the processing frame  20 , and are arranged in parallel at an interval in the front-rear direction. 
     Moreover, the developing unit  25 , as it will described later in detail, includes a developing frame  32  which includes a developing chamber  67  and a developer accommodating chamber  68 . 
     The developing chamber  67  is provided with a developing roller  33 , a supply roller  34 , and a layer-thickness regulating blade  35 . 
     The developer accommodating chamber  68  is provided with a transporting member  37  and accommodates a developer of the corresponding color. 
     &lt;3-2. Transfer Unit&gt; 
     The transfer unit  17  is arranged above the processing unit  15 , and includes a belt unit  26  and the secondary transfer roller  27 . 
     The belt unit  26  is arranged along the front-rear direction, to face each photosensitive drum  22  from an upper side. 
     The belt unit  26  includes a drive roller  28 , a driven roller  29 , an intermediate transfer belt  30  as an example of an endless belt, and four primary transfer rollers  31 . 
     The drive roller  28  is arranged to face the driven roller  29  at an interval in the front-rear direction. 
     The intermediate transfer belt  30  is arranged above each photosensitive drum  22  such that a lower portion of the intermediate transfer belt  30  makes a contact with each photosensitive drum  22 , and is put around the drive roller  28  and the driven roller  29 . Moreover, the intermediate transfer belt  30  is turned by driving the drive roller  28  and by being driven by the driven roller  29  such that, a lower portion of the intermediate transfer belt  30  which is in contact with each photosensitive drum  22  moves from a front side toward the rear side. 
     Each primary transfer roller  31  is provided to face each photosensitive drum  22 , sandwiching a lower portion of the intermediate transfer belt  30 . 
     The secondary transfer roller  27  is provided at a rear side of the belt unit  26  (one-end side of the intermediate transfer belt  30 ) to face the drive roller  28 , sandwiching the intermediate transfer belt  30 . 
     &lt;3-3. Fixing Unit&gt; 
     The fixing unit  18  is arranged above the secondary transfer roller  27 , and includes a heating roller  38  and a pressurizing roller  39  which makes a pressed contact with the heating roller  38  from an upper side thereof 
     &lt;3-4. Image Forming Operation&gt; 
     &lt;3-4-1. Developing Operation&gt; 
     The developer in the developing unit  25  is supplied to the supply roller  34 , and furthermore, is supplied to the developing roller  33 . 
     A thickness of the developer supplied to the developing roller  33  is regulated by the layer-thickness regulating blade  35 , with the rotation of the developing roller  33 , and is carried on a surface of the developing roller  33  as a thin layer of a constant thickness. 
     On the other hand, after a surface of the photosensitive drum  22  is charged uniformly to a positive electric charge by the scorotron charger  23 , the surface of the photosensitive drum  22  is exposed by the LED unit  44 . Accordingly, an electrostatic latent image corresponding to an image which is to be formed on the paper P is formed on the surface of the photosensitive drum  22 . 
     As the photosensitive drum  22  rotates further, the developer carried on a surface of the developing roller  33  is supplied to the electrostatic latent image formed on the surface of the photosensitive drum  22 . Accordingly, the electrostatic latent image on the photosensitive drum  22  becomes a visible image, and a developer image by inverse developing is formed on the surface of the photosensitive drum  22 . 
     &lt;3-4-2. Transferring—Fixing Operation&gt; 
     The developer image carried on the surface of the photosensitive drum  22  is subjected to a primary transfer sequentially at a lower portion of the intermediate transfer belt  30  which moves from the front side to the rear side. Accordingly, a color image is formed on the intermediate transfer belt  30 . 
     The color image formed on the intermediate transfer belt  30  is subjected to a secondary transfer on the paper P which is supplied from the paper feeding section  3  while the intermediate transfer belt  30  passes a position facing the secondary transfer roller  27 . 
     Next, the color image which has been transferred to the paper P is subjected to thermal fixing on the paper P in the fixing unit  18  by being heated and pressurized while the paper P passes between the heating roller  38  and the pressurizing roller  39 . 
     &lt;4. Paper Discharge&gt; 
     The paper P having the developer image fixed thereon in the fixing unit  18  is discharged on to a paper discharge tray  51  which is formed on an upper surface of the main-body casing  2 , by a paper discharge roller  50 . 
     &lt;B. Details of Developing Unit&gt; 
     &lt;1. Developing Frame&gt; 
     The developing frame  32  (an example of a housing) is formed to have a hollow shape extended in the left-right direction as shown in  FIG. 2 , and two end portions thereof on left side and right side respectively are closed by two side walls which are not shown in the diagram. 
     Moreover, the developing frame  32  includes a lower frame  54  and an upper frame  55  which is arranged adjacent to an upper side of the lower frame  54 . 
     The lower frame  54  includes a circular-arc wall  56  and a contacting wall  57 . 
     The circular-arc wall  56  is formed to be substantially circular arc shaped in a side view, which opens toward a rear upper side. 
     The contacting wall  57  is formed to be substantially flat-plate shaped, and is formed to be projected or protruded obliquely frontward and upward, from a rear-end portion of the circular-arc wall  56 . 
     Moreover, an inner-side surface (a front surface) of the contacting wall  57  is demarcated as a contacting portion  58 . 
     A plurality of projections  62  extended along the vertical direction is provided to the contacting portion  58 . 
     As shown in  FIG. 3 , a cross-sectional surface of each projection  62  is formed to have a substantially triangular shape which is projecting frontward. The projections  62  are arranged in parallel at an interval in the left-right direction (horizontal direction). Moreover, a recess  66  as an example of the recess is formed between the adjacent projections  62 . 
     A damming portion  88  which defines an end of each recess  66  is provided between the two adjacent projections  62  of the recess  66 . 
     As shown in  FIG. 2 , the damming portion  88  is formed to be substantially rectangular shaped in a side view, and arranged at a position which is substantially ⅓ of a length of the recess  66  from an upper-end portion of each recess  66 , in the vertical direction. 
     Moreover, a blade supporting portion  63  is provided to an outer-side surface (rear surface) of the contacting wall  57 . 
     The blade supporting portion  63  includes a base  64  and a supporting plate  65 . 
     The base  64  is formed to be substantially rectangular shaped in a side view, which is projected rearward, and is formed on an outer side surface of the contacting wall  57  at an upper end portion thereof. 
     The supporting plate  65  is formed to be L-shaped in a side view, to bend frontward, and is fixed to a rear surface of the base  64 . Moreover, the base  64  and the supporting plate  65  are arranged such that a portion of the supporting plate  65  which is bent frontward and an upper surface of the base  64  are arranged to face with an interval in the vertical direction. 
     A lower portion  83  of the upper frame  55  is formed to be substantially circular arc shaped along an outer peripheral surface of the supply roller  34 , and an upper portion  84  of the upper frame  55  is formed to be extended upward from an upper end portion of the lower portion  83 , and to bend frontward. 
     The lower frame  54  and the upper frame  55  are joined, wherein a lower end portion of the lower portion  83  of the upper frame  55  and an upper end portion of the circular-arc wall  56  of the lower frame  54  are joined. 
     A dividing wall  59  is provided in an internal space of the developing frame  32 . 
     The dividing wall  59  is formed to be a plate shaped and is projected from a joining portion of the circular arc wall  56  and the lower portion  83 , along a direction of rotation X of the transporting member  37  (which will be described later), to be extending obliquely upward toward the contacting portion  58 . An upper end portion of the dividing wall  59  is cut at a slant to be projected rearward so that an upper side of the dividing wall  59  is more protruded rearward than a lower side thereof. 
     The upper end portion of the dividing wall  59  is arranged to be positioned at a lower front side with respect to an upper end portion of the contacting wall  57 . In other words, an upper end portion of the dividing wall  59  and an upper end portion of the contacting wall  57  are arranged to face with a distance therebetween. Moreover, the upper end portion of the dividing wall  59  is arranged to face a front end portion of the projection  62 , with a distance in the frontward-rearward direction. 
     It is possible to set a supplementary angle θ 2  of an angle θ 1  in a range between 90 degrees and 160 degrees, wherein the angle θ 1  is formed by a straight line L 1  along a direction of projection of the dividing wall  59  and a straight line L 2  along a direction of projection of the contacting wall  57 . In the embodiment, the supplementary angle θ 2  may be set to be 126 degrees. Alternatively, the supplementary angle θ 2  may be set to be 145 degrees. 
     A communicating portion  60  is formed by the upper end portion of the dividing wall  59  and the upper end portion of the contacting wall  57 . 
     Accordingly, the internal space of the developing frame  32  is divided into a space at an upper side of the dividing wall  59  and a space at a lower side of the dividing wall  59 , and the two spaces communicate via the communicating portion  60 . 
     More elaborately, the space at the upper side of the dividing wall  59  is divided as the developing chamber  67  by an inner side surface of the upper frame  55  and an upper surface of the dividing wall  59 . Moreover, the space at the lower side of the dividing wall  59  is divided as the developer accommodating chamber  68  by an inner side surface of the lower frame  54  (an inner side surface of the circular-arc wall  56  and the contacting portion  58 ), and a lower surface of the dividing wall  59  (a sliding portion  80  (which will be described later)). 
     In other words, the dividing wall  59  divides the internal space of the developing frame  32  into the developing chamber  67  which is arranged at the upper side, and the developer accommodating chamber  68  which is arranged at the lower side. Moreover, the developing chamber  67  and the developer accommodating chamber  68  communicate via the communicating portion  60 . 
     A lower surface of the dividing wall  59  forms the sliding portion  80 . 
     The sliding portion  80  is arranged between the transporting member  37  and the supply roller  34 , in an area facing the transporting member  37  and the supply roller  34 . 
     &lt;2. Developer Accommodating Chamber&gt; 
     A developer is accommodated in the developer accommodating chamber  68 . 
     An example of a developer is a toner. Concretely, a positively charged non-magnetic single-component toner is an example. A polymer toner can be cited as an example of such toner. A polymer toner has a spherical shape and has an extremely favorable fluidity, and is capable of forming a high quality image. 
     Moreover, the developer accommodating chamber  68  is provided with a transporting member  37 , e.g. an agitator, for stirring the developer accommodated in the developer accommodating chamber  68 , and transporting the developer to the developing chamber  67 . 
     The transporting member  37  includes a rotating shaft  70  and a transporting blade  71 . 
     The rotating shaft  70  is positioned at a substantially central portion in a side-sectional view, of the developer accommodating chamber  68 , and is extended in the left-right direction. The rotating shaft  70  is rotatably supported by the both side walls (not shown in the diagram) of the developing frame  32 . 
     Moreover, a fixing portion  72  which fixes the transporting blade  71  is formed integrally on the rotating shaft  70 . 
     The fixing portion  72  is formed to be substantially L-shaped in a side view, and one end portion thereof is joined to a peripheral surface of the rotating shaft  70 . In the embodiment, although there is only one fixing portion  72 , two fixing portions  72  may be provided to face with each other in a radial direction of the rotating shaft  70  (refer to  FIG. 5 ). 
     The transporting blade  71  is formed of a flexible film and has a substantially flat-plate shape which is elastically deformable. The transporting blade  71  is fixed to a free end portion of the fixing portion  72  (end portion of the fixing portion  72  on opposite side of the rotating shaft  70 ), to be extended toward an outer side of the direction of rotation of the transporting member  37 . 
     When the transporting member  37  is driven to be rotated, the free end portion (end portion on the opposite side of the fixing portion  72 ) of the transporting blade  71  makes a sliding contact with an inner side surface of the circular arc wall  56 , and the sliding portion  80 , and the contacting portion  58  (e.g. front end portion of the projection  62 ). 
     Moreover, a driving force from a drive source which is not shown in the diagram, such as a motor which is to be provided to the main-body casing  2  is input to the transporting member  37 . As the driving force is input to the rotating shaft  70 , the rotating shaft  70  is driven to be rotated, and accordingly, the transporting blade  71  rotates in the direction of rotation X (a clockwise direction as viewed from a right-side thereof) shown by an arrow in  FIG. 2 . 
     In other words, a base-end portion side of the dividing wall  59  is an upstream side of the direction of rotation X of the transporting member  37 , and a free-end portion side is a downstream side of the direction of rotation X of the transporting member  37 . 
     Moreover, the sliding portion  80 , the communicating portion  60 , and the contacting portion  58  are arranged serially (one after the other) from the upstream side to the downstream side of the direction of rotation X of the transporting member  37 . 
     &lt;3. Developing Chamber&gt; 
     The developing chamber  67  is provided with the supply roller  34 , the developing roller  33 , and the layer-thickness regulating blade  35  as an example of the layer-thickness regulating member. 
     The supply roller  34  is arranged at an inner side of the lower portion  83  of the upper frame  55 , and at an upper side of the base end portion of the dividing wall  59 , so that a center of rotation coincides with a center of a circular arc of the lower portion  83  of the upper frame  55 . 
     Moreover, the supply roller  34  is extended in the left-right direction, and is rotatably supported by two side walls which are not shown in the diagram, of the developing frame  32 . 
     When viewed from the left-right direction, the center of rotation of the supply roller  34  is positioned at a lower side of a lower end edge of the communicating portion  60 , or in other words, at a lower side of the upper end portion of the dividing wall  59 . 
     Moreover, the supply roller  34  is arranged to satisfy the following expression (1). Here, as shown in  FIG. 4 , a point of intersection of a straight line L 3  extended in a vertical direction including the upper end portion of the dividing wall  59  and a straight line L 4  extended in a horizontal direction including the center of rotation of the supply roller  34  is defined as a point of intersection Q. A distance in the horizontal direction between the point of intersection Q and a surface (Q 1 ) of the supply roller  34  is defined as a distance A. A distance in the vertical direction between the upper end portion of the dividing wall  59  and the point of intersection Q is defined as a distance h, and a collapse angle of the developer is defined as θ.
 
h&gt;A tan θ  Expression (1)
 
     Moreover, the collapse angle of the developer is an angle of an inclined surface when an apex of developer which has been deposited in a conical shape is made to collapse by an impact of the developer which is supplied to the developing chamber  67 , and is calculated with the developer stored in the developer accommodating chamber  68  as a basis when developing of the maximum number of prints of the developing unit  25  is completed. 
     Concretely, the collapse angle θ of the developer is in a range of 14 degrees to 20 degrees. 
     At the time of developing, a driving force from a drive source such as a motor which is not shown in the diagram, provided to the main-body casing  2  is transmitted to the supply roller  34 . Moreover, at the time of developing, a supply bias is applied to the supply roller  34  from a power supply which is not shown in the diagram. As the driving force from the drive source is transmitted to the supply roller  34 , the supply roller  34 , as shown in  FIG. 2 , rotates in a direction opposite to the direction of rotation of the developing roller  33 , at a portion (which will be described later) which makes face-to-face contact with the developing roller  33 . In other words, the supply roller  34  is driven to rotate in a direction of rotation Y (counterclockwise direction in a right-side view) shown by an arrow in  FIG. 2 . In other words, the direction of rotation Y of the supply roller  34  is a direction opposite to the direction of rotation X of the transporting member  37 . 
     The developing roller  33  is arranged to face the supply roller  34  at an upper side of the center of rotation of the supply roller  34  such that, an outer peripheral surface on a lower-front side of the developing roller  33  makes a pressed contact with an outer peripheral surface of an upper-rear side of the supply roller  34 . Moreover, the developing roller  33  is arranged at an upper side inside the developing chamber  67  such that, a surface of an upper side and of a rear side of the developing roller  33  are exposed from the developing frame  32 . 
     The developing roller  33  is extended in the left-right direction, and is rotatably supported by the two side walls which are not shown in the diagram, of the developing frame  32 . 
     At the time of developing, a driving force from a drive source such as a motor which is not shown in the diagram, provided to the main-body casing  2  is transmitted to the developing roller  33 . Moreover, at the time of developing, a developing bias is applied to the developing roller  33  from a power supply which is not shown in the diagram. As the driving force from the drive source is transmitted to the developing roller  33 , the developing roller  33  is driven to rotate in the direction of an arrow shown in  FIG. 2  (counterclockwise direction in a right-side view) such that the developing roller  33  rotates in an opposite direction of the supply roller  34 , at a portion in contact with, and face-to-face with the supply roller  34 . 
     The layer-thickness regulating blade  35  is formed to be substantially flat-plate shaped, and is provided throughout the left-right direction of the developing frame  32 . 
     Moreover, one end portion of the layer-thickness regulating blade  35  is fixed to a free end portion of the supporting plate  65  to make a contact elastically with an outer peripheral surface on a lower side of the developing roller  33 . The layer-thickness regulating blade  35  is arranged to be extended from a side of the contacting portion  58  toward the developing roller  33 , at an upper side of the communicating portion  60 . 
     A portion of contact between the layer-thickness regulating blade  35  and the developing roller  33  is positioned at a downstream direction in the direction of rotation of the developing roller  33 , than a portion of contact between the developing roller  33  and the supply roller  34 , at a lower-half portion of the developing roller  33 . 
     The portion of contact between the layer-thickness regulating blade  35  and the developing roller  33  is positioned frontward of the communicating portion  60  when viewed from the vertical direction. 
     &lt;4. Details of Developing Operation&gt; 
     Next, details of a developing operation in the developing unit  25  will be described below. 
     As a driving force is input to the rotating shaft  70  at the time of developing operation, the transporting member  37  rotates in the direction of rotation X. 
     At this time, the free end portion of the transporting blade  71  is deformed, resisting an elastic force along a shape of the inner peripheral surface of the circular-arc wall  56 . Concretely, the transporting blade  71  bends to be warped in a direction opposite to the direction of rotation X. 
     Moreover, the developer which is accommodated in the developer accommodating chamber  68  is transported toward the sliding portion  80  while being trapped between the inner peripheral surface of the circular-arc wall  56  and the transporting blade  71 , with the rotation of the transporting member  37 . 
     Next, as the free end portion of the transporting blade  71  reaches the sliding portion  80 , the free end portion of the transporting blade  71  and the sliding portion  80  make a sliding contact. Further, the transporting blade  71 , with the developer retained thereon, is maintained in an elastically deformed state along the shape of the sliding portion  80 . 
     As the transporting member  37  rotates further, the free end portion of the transporting blade  71  moves along the inclined dividing wall  59  while making a sliding contact with the sliding portion  80 . 
     As the free end portion of the transporting blade  71  reaches a free end portion of the dividing wall  59 , the free end portion of the transporting blade  71  reaches the communicating portion  60  after being moved further rearward, along an inclined surface of the free end portion of the dividing wall  59 . 
     At this time, the sliding contact between the free end portion of the transporting blade  71  and the sliding portion  80  terminates. Therefore, the transporting blade  71  restores substantially flat-plate shape from the elastically deformed state (state of being bent to be warped in the direction opposite to the direction of rotation x). In other words, the free end portion of the transporting blade  71  moves toward the downstream side in the direction of rotation X of the transporting member  37 . 
     Accordingly, with the restoration of the transporting blade  71 , some of the developer transported by the transporting blade  71  is transported to the downstream side in the direction of rotation X of the transporting member  37 , or in other words, is transported toward the contacting portion  58  and is dispersed upon colliding with the contacting portion  58 . 
     Further, the developer which has dispersed is supplied to the developer chamber  67  via the communicating portion  60  in a direction of supply Z which is opposite to the direction of rotation X of the transporting member  37 , by an air flow which is generated by the collision of the transporting member  37  with the contacting portion  58 . The direction of supply Z is indicated by an arrow in a counterclockwise direction in  FIG. 2 . 
     The developer flows into a space secured in the recess  66  provided to the contacting portion  58 , and collides with a bottom portion of the recess  66  (a front surface of the recess  66 ). As the developer collides with the bottom portion of the recess  66 , the developer is dispersed by being reflexed at the bottom portion of the recess  66 . 
     Moreover, a downward flow of the developer dispersed is intercepted by the damming portion  88  provided between the recesses  66 . Moreover, the recess  66  being open at an upper side, the developer dispersed is jetted from the upper side of the recess  66 , and upon being spread in the space, is supplied in the direction of supply Z which is opposite to the direction of rotation X of the transporting member  37 , to the developing chamber  67 . 
     At this time, since the layer-thickness regulating blade  35  is provided at an upper side of the communicating portion  60 , the developer spread in the space is restricted from moving above the layer-thickness regulating blade  35  by a lower surface of the layer-thickness regulating blade  35 . 
     Next, the developer supplied to the developing chamber  67  falls due to the gravitation force, and is deposited uniformly on an upper surface of the dividing wall  59 , and is accumulated in the developing chamber  67 . 
     Since the dividing wall  59  is inclined, the developer moves toward a base-end portion along the slope of the dividing wall  59 , or in other words, toward an area near the supply roller  34 . 
     At this time, the developer supplied newly is accumulated at the downstream side in the direction of rotation of the supply roller  34  at the communicating portion  60  side (rear half portion) of the supply roller  34 , than the developer which has been accumulated in the developing chamber  67 . Therefore, the developer which is supplied newly is supplied to the developing roller  33  by the supply roller  34  with a higher priority over the developer which has been accumulated. 
     The developer supplied to the developing roller  33  is held on the surface of the developing roller  33  upon the thickness being regulated by the layer-thickness regulating blade  35  as mentioned above. 
     Further, the developer which is held on the developing roller  33  is supplied to an electrostatic latent image which is formed on the surface of the photosensitive drum  22 . Accordingly, a developer image is formed on the surface of the photosensitive drum  22  by inverse developing. 
     Meanwhile, the transporting blade  71  which has passed the communicating portion  60  collides with the front end portion of each projection  62  and undergoes elastic deformation once again with the rotation of the transporting member  37 . 
     &lt;C. Technical Effect&gt; 
     According to the developing unit, as shown in  FIG. 2 , as the free end portion of the transporting blade  71  of the transporting member  37  reaches the communicating portion  60 , the sliding contact with the sliding portion  80  terminates, and due to the elastic force, the transporting blade  71  restores the substantially flat-plate shape from the state of being deformed to be bent. 
     Therefore, some of the developer which is transported to the transporting blade  71  is dispersed when the developer is discharged to the communicating portion  60 , with the restoring of the transporting blade  71 . Further, the developer which has not been discharged to the communicating portion  60  is transported toward the contacting portion  58  and is dispersed upon colliding with the contacting portion  58  together with the transporting member  37 . 
     Accordingly, the developer which has dispersed is supplied from the communicating portion  60  to the developing chamber  67  by the air flow generated by the transporting member  37  which has collided with the contacting portion  58 . In other words, the developer which has dispersed favorably is supplied to the developing chamber  67  from the direction of supply Z which is opposite to the direction of rotation X of the transporting member  37 . 
     Therefore, it is possible to suppress uneven level of developer in the developing chamber  67 . 
     As a result, since the developer is supplied to the supply roller  34  uniformly, and carried on the developing roller  33  uniformly, it is possible to prevent defective image formation. 
     Consequently, in the developing unit  25 , it is possible to suppress the uneven level of developer in the developing chamber  67 , and to prevent the defective image formation caused by the uneven level of developer, while making it possible to facilitate small-sizing and low cost. Moreover, the direction of rotation Y of the supply roller  34  is opposite to the direction of rotation x of the transporting member  37 . 
     Therefore, at a side where the supply roller  34  transports the developer to the developing roller  33 , it is possible to supply the developer to the supply roller  34 . In other words, since it is possible to supply the developer to the supply roller  34 , at a rear side of the supply roller  34  in  FIG. 2 , it is possible to prevent the developer from being packed between the supply roller  34  and the upper surface of the dividing wall  59 , and to supply the developer sufficiently to the developing roller  33 . Moreover, in the developing chamber  67 , it is possible to suppress the aggregate of the developer which is generated by being accumulated, from being supplied to the developing roller  33 . 
     Consequently, it is possible to prevent the developer from being packed between the supply roller  34  and the upper surface of the dividing wall  59 , and the defective image formation which is caused by the aggregate of the developer being supplied to the developing roller  33 . The contacting portion  58  includes the plurality of projections  62  extended along the vertical direction, which are arranged at an interval in the horizontal direction to allow the inflow of the developer therebetween. The space between the adjacent projections  62  is demarcated as the recess  66 . 
     Therefore, when the transporting blade  71  has collided with the front-end portion of the projection  62 , the developer transported by the transporting blade  71  flows into the space secured by each recess  66 . 
     As a result, it is possible to prevent that the developer is trapped between the transporting blade  71  and the contacting portion  58 , and is compressed to be aggregated by a rotative force of the transporting member  37 . 
     Moreover, since the upper side of each recess  66  is open, the developer which has flowed into each recess  66  is jetted upward from each recess  66 . 
     Therefore, it is possible to facilitate an increase in an amount of supply of the developer while suppressing the generation of the aggregate of the developer. Moreover, the damming portion  88  which blocks each recess  66  is provided to each recess  66  at an area between the adjacent projections  62 . 
     Therefore, a downward flow of the developer which has flowed into each recess  66  is regulated. 
     As a result, it is possible to facilitate the increase in the amount of developer which is jetted upward from each recess  66 , and to facilitate an increase in the amount of supply of the developer to the developing chamber  67 . Moreover, the dividing wall  59  is formed to be inclined upward toward rear side, from a joining portion of the lower frame  54  and the upper frame  55 . In other words, the dividing wall  59  is formed to be extending obliquely upward, from an inner-side surface of the front side (first inner-side surface) of the developing frame  32  toward an inner-side surface of the rear side (second inner-side surface). 
     Therefore, the developer supplied to the developing chamber  67  moves along the slope of the dividing wall  59 , and is accumulated at a front side of the developing chamber  67 , or in other words, in an area near the supply roller  34 . 
     Therefore, it is possible to supply the developer to the supply roller  34  stably, and to suppress an occurrence of defective image formation which is caused due to an insufficient supply of the developer to the developing roller  33 . Moreover, the upper end portion of the dividing wall  59  is positioned at an upper side of the center of rotation of the supply roller  34 . Here, as shown in  FIG. 4 , the point of intersection of the straight line L 3  extended in the vertical direction including the upper end portion of the dividing wall  59  and the straight line L 4  extended in the horizontal direction including the center of rotation of the supply roller  34  is defined as the point of intersection Q. At this time, an arrangement is made such that the distance A in a horizontal direction between the point of intersection Q, and the surface (Q 1 ) of the supply roller  34 , the distance h in the vertical direction between the upper end portion of the dividing wall  59  and the point of intersection Q, and the collapse angle θ of the developer satisfy an expression of h&gt;A tan θ. 
     Therefore, even when the collapse angle θ of the developer becomes large with the developing operation of the developing unit  25 , it is possible to supply the developer above the center of rotation of the supply roller  34 . 
     Concretely, it is possible to supply the developer above the point of intersection Q 1  of the straight line L 4  and the surface of the supply roller  34 . 
     As a result, it is possible to supply the developer sufficiently from the supply roller  34  to the developing roller  33 . Moreover, the contacting wall  57  is formed to be projected to be inclined toward the communicating portion  60  (toward the front side), in the upward direction. 
     Accordingly, the contacting portion  58  is arranged near the communicating portion  60 . 
     Therefore, it is possible to facilitate the increase in the amount of developer which is to be supplied to the developing chamber  67  along the direction of supply Z, from the communicating portion  60 , upon being hit and reflexed at the contacting portion  58 . Moreover, an upper end of the contacting wall  57  is positioned above an upper end of the dividing wall  59 . 
     Therefore, it is possible to provide the contacting portion  58  further above, or in other words, toward the developing chamber  67 . Consequently, it is possible to facilitate the increase in the amount of supply of developer. The communicating portion  60  is positioned above the center of rotation of the supply roller  34 , when projected in the left-right direction. In other words, a lower-end edge of the communicating portion  60 , or in other words, the free end portion (upper end portion) of the dividing wall  59  is positioned above the center of rotation of the supply roller  34 . 
     Therefore, it is possible to accumulate the developer in the developing chamber  67  till a level of the developer reaches above the center of rotation of the supply roller  34 . 
     As a result, it is possible to supply the developer to the supply roller  34  steadily, and to suppress further the occurrence of defective image formation which is caused due to the insufficient supply of developer to the developing roller  33 . Moreover, the developing unit  25  includes the layer-thickness regulating blade  35 . 
     The layer-thickness regulating blade  35  is arranged to be extended from the contacting portion  58  toward the developing roller  33 , above the communicating portion  60 . 
     Therefore, the developer which has been supplied to the developing chamber  67 , particularly, the developer filled in the space, is restricted from moving above the layer-thickness regulating blade  35  by the lower surface of the layer-thickness regulating blade  35 . 
     Therefore, it is possible to prevent the developer from being supplied to (adhered to) the developing roller  33  without being supplied by the supply roller  34 . 
     As a result, it is possible to prevent defective image formation which is caused due to an unintended supply (deposition, adhesion) of developer to the developing roller  33 . Moreover, a supplementary angle of an angle formed by a straight line along the direction of projection of the dividing wall  59  and a straight line along the direction of projection of the contacting wall  57  is in the range of 90 degrees to 160 degrees. (For example, the supplementary angle is 126 degrees.) 
     Therefore, it is possible to facilitate the increase in the amount of developer supplied to the developing chamber  67 . Moreover, the color printer  1  includes the developing unit  25 . 
     Therefore, the color printer  1  is capable of suppressing the uneven level of developer in the developing chamber  67  and to prevent the defective image formation caused due to the uneven level of developer, while facilitating small-sizing and low cost. 
     D. Modified Embodiment 
     It is also possible to include a fan  86  as an example of an air flow generator in the abovementioned developing unit  25 . 
     In this case, the fan  86  is provided at an upper end portion of the contacting wall  57  as shown by virtual lines in  FIG. 2 . More elaborately, the fan  86  is provided to an upper surface of the base  64  to generate an air flow from a side (rear side) of the contacting portion  58  toward the communicating portion  60  (front side), above (at the upper side of) the communicating portion  60 . 
     In this modified embodiment, since the air flow is generated from the side (rear side) of the contacting portion  58  toward the communicating portion  60  (front side), due to the air flow, the developer which is spread in the space by being reflexed upon hitting the contacting portion  58  is supplied to the developing chamber  67  favorably. Therefore, it is possible to facilitate the increase in the amount of supply of developer. 
     Moreover, it is also possible to include further an elastic portion  87  in the developing unit  25 . 
     In this case, the elastic portion  87  is formed to be substantially sheet-shaped by an elastically deformable member (such as rubber), and is stuck to the sliding portion  80  as shown by virtual lines in  FIG. 2 . 
     In the present modified embodiment, when the transporting blade  71  makes a sliding contact with the sliding portion  80 , the transporting blade  71  makes a contact with the elastic portion  87 . Therefore, the transporting blade  71  vibrates and enables to prevent the aggregation of the developer which is transported by the transporting blade  71 . 
     Moreover, in the developing unit  25 , the transporting member  37  includes one transporting blade  71  and one fixing portion  72  which fixes the transporting blade  71 . However, the present teaching is not restricted to such arrangement, and the transporting member  37  may include arbitrary number of transporting blades  71  and fixing portions  72 . For instance, the transporting member  37  may include two transporting blades  71  and two fixing portions  72 . 
     In this case, two fixing portions  72  are provided to face with each other in a radial direction of the rotating shaft  70 . 
     In the present modified embodiment, it is possible to transport the developer accommodated in the developer accommodating chamber  68  to the developing chamber  67  efficiently. 
     In the embodiment, the developing unit  25  is exemplified as the developer container. However, the present teaching is not restricted to such an arrangement, and is applicable to an arbitrary developer container. For instance, the developer container may be a toner cartridge. 
     It is possible to combine the abovementioned modified embodiments appropriately.