Patent Publication Number: US-7912409-B2

Title: Toner cartridge

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a continuation of application Ser. No. 11/603,836 filed Nov. 24, 2006, which claims priority under 35 USC 119 from Japanese Patent Application No. 2006-126172. The entire disclosures of the prior applications are incorporated by reference herein. 
    
    
     BACKGROUND 
     Technical Field 
     The present invention relates to a toner cartridge, and more particularly, to a toner cartridge of an image forming apparatus using an electrophotography system which develops an electrostatic image with toner. 
     Conventionally, in an image forming apparatus such as a copier and a laser printer employing the electrophotography system, it is required to reduce the number of exchanging times of consumable items to reduce page cost. For example, if a toner capacity in a toner cartridge, which supplies toner to the image forming apparatus, the frequency of exchanging operations of the cartridge, can be reduced. 
     In order to increase the maximum toner charging amount of the toner cartridge, it is possible to increase a surface area of a bottom surface of the toner cartridge, or when the toner cartridge is of a cylindrical shape, it is possible to increase a diameter of a cylindrical portion. 
     However, when the maximum toner charging amount of a toner cartridge which is attached to or detached to an existing image forming apparatus, it is impossible to increase the surface area of the bottom surface of the toner cartridge or to increase the diameter of the cylindrical portion. Even when the image forming apparatus is new one, in the case of a color copier which needs cartridges of four colors (YMCK), if the surface area of the bottom surface of the toner cartridge is increased or the diameter of the cylindrical portion is increased, the apparatus size is increased. 
     In order to increase the maximum toner charging amount, it seems possible to increase the toner capacity by making a portion of the toner cartridge in its longitudinal direction in a projecting form to increase its height. 
     However in the toner cartridge of such a shape, when toner is sent by a toner transfer member from a side of the toner cartridge where a cross-sectional area thereof in the longitudinal direction is large to a side of the toner cartridge where the cross-sectional area is small, toner is blocked, the rotation torque of the toner transfer member is increased, and there are fears that a gear is damaged and a motor burns. 
     SUMMARY 
     One aspect of the invention provides an exchangeable toner cartridge which can be attached to or detached from an apparatus main body. The toner cartridge includes the toner transfer member which is provided along a longitudinal direction of the toner cartridge and which can rotate. At the first range of the toner upstream side in a toner transfer direction the toner transfer member is formed into a substantially spiral shape, and at the second range of the downstream side in the toner transfer direction on a side of a toner supply port the toner transfer member has a shape different from that of the first range. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present invention will be described in detail based on the following figures, wherein: 
         FIG. 1  is a schematic diagram showing an image forming apparatus according to the present invention; 
         FIG. 2  is a perspective view showing the image forming apparatus of the present invention; 
         FIGS. 3A and 3B  are perspective views showing a toner cartridge of the present invention; 
         FIG. 4  is a perspective view showing an inner housing of the toner cartridge of the present invention; 
         FIG. 5  is a sectional view showing an internal structure of the toner cartridge of the present invention; 
         FIG. 6  is a diagram of a toner transfer operation of a conventional toner cartridge; 
         FIG. 7  is a diagram of a toner transfer operation of the toner cartridge of the present invention; 
         FIG. 8  is a diagram showing a toner transfer operation of a toner cartridge according to a second exemplary embodiment of the present invention; 
         FIG. 9  is a diagram showing a toner transfer operation of a toner cartridge according to a modification of the present invention; 
         FIG. 10  is a diagram showing a toner transfer operation of a toner cartridge according to a modification of the second exemplary embodiment of the present invention; and 
         FIG. 11  is a sectional view showing toner movement in the toner cartridge of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     &lt;Basic Structure&gt; 
       FIGS. 1 to 2  show a basic structure of an image forming apparatus of the present invention. 
       FIGS. 1 to 2  show an example of a four color image forming apparatus according to the present invention. 
     As shown in  FIGS. 1 and 2 , an image forming apparatus  10  includes a main body frame  12  in which image carriers (photosensitive bodies)  20  and developing units  16  are detachably accommodated, and a cover body  14  for opening and closing the image carriers  20  and the developing units  16 . A transfer unit  18  having a transfer belt  34  is detachably mounted on the cover body  14 . The transfer belt  34  can suction and transfer a recording sheet P. 
     Each of the developing units  16  includes a charged roller  22  for uniformly charging a surface of the roll-shaped image carrier  20 , an optical box  24  which irradiates the image carrier  20  with image light based on image data and forms a latent image by a difference of electrostatic potentials, a developing roller  26  which selectively transfers toner to the latent image to make it visible, and a cleaning member  28  which comes into slidably contact with the image carrier  20  after the toner image is transferred to clean the toner remaining on the image carrier  20 . 
     The image carrier  20  is provided at its surface (peripheral surface) with a photosensitive body layer. After the surface (peripheral surface) of the image carrier  20  is uniformly charged by the charged roller  22 , the surface (peripheral surface) is exposed to laser light (image light) emitted from the optical box  24 , the potential of the exposed portion is attenuated, thereby forming an electrostatic latent image (image). The charged roller  22  abuts against the image carrier  20 , voltage is applied to therebetween, electricity is discharged in a fine gap near the abutment portion, and the surface of the image carrier  20  is substantially uniformly charged. 
     The optical box  24  allows flashing laser light to scan a surface (peripheral surface) of the image carrier  20 , and forms an electrostatic latent image on the surface (peripheral surface) of the image carrier  20  based on the image data. As the optical box  24 , luminous elements such as LEDs may be arranged and they are allowed to flash based on the image data. 
     The developing roller  26  is disposed close to the image carrier  20  such as to be opposed thereto, and developing bias voltage is applied to between the developing roller  26  and the image carrier  20 . With this, a developing bias electric field is formed between the developing roller  26  and the image carrier  20 , and toner having electric charge is transferred to the exposed portion on the image carrier  20  to form a visible image. 
     The transfer unit  18  includes a transfer belt  34  which is stretched around at least a drive roller  30  and a roller  32  which is rotated by the rotation of the drive roller  30 . A plurality of (four corresponding to later-described colors) transfer rollers  36  are disposed at predetermined distances from one another at predetermined positions between the drive roller  30  and the roller  32  at the inner surface side the transfer belt  34 . 
     When the cover body  14  is closed (when the cover body  14  is turned toward the main body frame  12  to close the image carrier  20  and the like), the transfer roller  36  is opposed to the image carrier  20  with the transfer belt  34  interposed therebetween. A transfer electric field is formed between the image carrier  20  and the cover body  14  so that a toner image (non-fixed image) on the surface of the image carrier  20  is transferred onto the recording sheet P which is suctioned and transferred by the transfer belt  34 . 
     Here, the developing units  16  are disposed in the vertical direction in the order of yellow (Y), magenta (M), cyan (C), black (K) along the transfer direction of the recording sheet P from below so that full color printing can be carried out, and a fixing apparatus  38  is disposed on the downstream side in the transfer direction of the recording sheet P from the developing units  16 Y to  16 K. 
     The developing units  16 Y to  16 K develop electrostatic images on the image carriers  20 Y to  20 K by toner of yellow (Y), magenta (M), cyan (C), black (K), and transfers the formed toner image on the recording sheet P. 
     Since toner T Y  to T K  in the developing units  16 Y to  16 K are consumed by forming toner image, the processing is carried out while the amount of toner of colors in the developing units  16 Y to  16 K is maintained in a state where toner is appropriately supplemented from the toner cartridges  17 Y to  17 K. 
     The fixing apparatus  38  includes a heating roller  40  and a pressing roller  42  whose peripheral surfaces are opposed to each other and which are nipped under predetermined pressure. The heating roller  40  and the pressing roller  42  heat and press a non-fixed toner image transferred onto the recording sheet P, thereby fixing the toner image on the recording sheet P. 
     The recording sheet P which is heated and pressed by the fixing apparatus  38  (heating roller  40  and the pressing roller  42 ) is discharged on an output tray  44 . After the toner image is transferred to the recording sheet P, a surface (peripheral surface) of the image carrier  20  is cleaned by the cleaning member  28  so that preparations for a next image forming processing can be made. 
     The main body frame  12  is provided at its lower portion with a detachable paper feed cassette  46 . The paper feed cassette  46  can be pulled out in a direction opposite to a direction where the recording sheet P is sent out, and a recording sheet P can be appropriately supplied. 
     A pair of paper feed rollers  48  which sends out recording sheets P one-sheet by one-sheet from the paper feed cassette  46  is provided in the vicinity of a tip end of the paper feed cassette  46 . The recording sheet P sent out from the pair of paper feed rollers  48  is sent out to a suction transfer surface of the transfer belt  34  at predetermined timing by a pair of resist rollers  49 , and is transferred to a transfer position of each toner image of the corresponding color. 
     In the image forming apparatus  10  of the above-described structure, the transfer unit  18  detachably mounted on the cover body  14  will be explained in more detail. 
     The transfer unit  18  includes a substantially rectangular frame-shaped casing  50 . The drive roller  30  is rotatably supported on one end (upper end) of the casing  50 , and the roller  32  is rotatably supported on the other end (lower end). The transfer belt  34  capable of suctioning the recording sheet P statically is stretched around the drive roller  30  and the roller  32 . 
     The transfer rollers  36 Y to  36 K are disposed at predetermined distances from one another based on colors between the drive roller  30  and the roller  32  on the inner surface side of the transfer belt  34 . The transfer rollers  36 Y to  36 K are rotatably supported by the casing  50 . When the cover body  14  is closed, the transfer rollers  36 Y to  36 K can sandwich the transfer belt  34  and bring the transfer belt  34  into contact with the image carriers  20 Y to  20 K under predetermined pressure, and the transfer rollers  36 Y to  36 K rotate when the transfer belt  34  runs. 
     &lt;Toner Cartridge&gt; 
       FIGS. 3A to 5  show the toner cartridge of the image forming apparatus according to the present invention. 
     The toner cartridge  17  of the present invention comprises three blocks, i.e., a central portion  74 , and projections  76 A and  76 B as shown in  FIGS. 3A and 3B . An upper portion of the central portion  74  has a substantially square shape. Lower portions of the cylindrical projections  76 A and  76 B and the central portion  74  are continuously integrally formed. 
     The central portion  74  is a space for accommodating toner T therein, the capacity of the central portion  74  is reduced for toner whose consuming amount is small as shown in FIG.  3 A, and the capacity of the central portion  74  is increased for toner whose consuming amount is large as shown in  FIG. 3B  so as to cope with variation in toner capacity. At that time, if only a size of the cover body  78  constituting the upper portion of the central portion  74  is changed, other portions can be common. Therefore, it is possible to reduce cost while the capacity is secured. 
       FIG. 4  shows a structure of an inner housing  72  which is inserted into an outer housing  70  of the toner cartridge  17 . 
     The toner cartridge  17  comprises the outer housing  70  and the substantially cylindrical inner housing  72  fitted into the outer housing  70 . A spiral agitator  80  provided in the inner housing  72  turns the toner T in the central portion  74  by external power through a drive gear  90 , thereby transferring the toner T toward a toner supply opening  84  provided in the outer housing  70 . 
     As shown in  FIG. 5 , the toner cartridge  17  comprises a substantially cylindrical portion  77  (first region) which transfers and supplies toner T into the developing unit  16  of the image forming apparatus  10 , and an extension portion  79  (second region) which is added securing the capacity of the toner cartridge  17  and for increasing toner T. 
     As shown in  FIG. 4 , the inner housing  72  is of substantially cylindrical shape. The inner housing  72  transfers toner T in the central portion  74  of the outer housing  70  from the opening  72 A by the toner transfer direction (agitator  80 , hereinafter), and transfers the toner T out from the toner supply opening  73 . The position between the outer housing  70  and the inner housing  72  is determined by butting convex portions  94  provided on the inner housing  72  against a butting surface of an inner wall of the outer housing  70  at a position corresponding to a boundary wall  75  of the central portion  74  of the outer housing  70 . 
     There are two pairs of convex portions  94 . A ring-shaped V-shaped seal member  82  is formed between each pair of convex portions  94 . The V-shaped seal member  82  has V-shaped cross section, and the V-shaped seal member  82  prevents toner T from leaking outside. The V-shaped seal members  82  have the V-shaped cross sections. Opening sides of the V-shaped cross section are opposed to each other, and this can effectively prevent toner T from leaking out. Since the seal member is of the ring-shaped shape, a nip amount of seal can be secured equally over the entire circumference, and it is possible to reliably prevent toner T from leaking. 
     The agitator  80 , which transfers the toner T, is driven by external power through a gear  90 . The agitator  80  transfers toner T which dropped into the inner housing  72  from the opening  72 A formed in substantially the entire region superposing on the central portion  74  in a direction shown with a white arrow in the figure, and supplies the toner T from the toner supply opening  73  to the apparatus main body through the toner supply opening  84  of the outer housing  70 . 
     &lt;Spiral Shape Changing Point&gt; 
       FIG. 5  shows a longitudinal cross section structure of the inner housing  72  inserted into the outer housing  70  and the outer housing  70 . 
     As shown in  FIG. 5 , the agitator  80  is located in the inner housing  72  and stirs and transfers toner. The agitator  80  is of substantially spiral shape, however the spiral shape is changed at predetermined locations in the toner transfer direction (white arrow direction in the figure). 
     That is, the agitator  80  transfers toner T in the direction of the white arrow at the time of rotating, biasing and pressing the toner in the transfer direction by the spiral shape upstream in the toner transfer direction (left side in the figure), however the spiral shape is changed at a changing point  80 A. With this, a toner transfer amount is reduced downstream in the transfer direction (right side in the figure). 
     More specifically, if the number of windings of the agitator  80  is reduced or the agitator  80  is formed into a straight shape and the number of windings is set to zero, the toner transfer amount per one rotation of the agitator  80  can be reduced. 
     If the spiral shape of the agitator  80  is one direction as shown in  FIG. 6 , toner T is transferred from the central portion  74  side where the cross-sectional area is greater to the projection  76 B side where the cross-sectional area is smaller. At that time, toner is deposited near the boundary wall  75 B where the cross-sectional area becomes smaller, and the blocking of the toner is generated. 
     Whereas, in the exemplary embodiment of the present invention, the spiral shape of the agitator  80  is changed at the predetermined location in the longitudinal direction, the toner transfer amount is reduced so that the amount of toner staying near the boundary wall  75 B is reduced, and toner blocking can be avoided. 
     The spiral changing point  80 A of the agitator  80  which transfers toner is on the upstream side in the transfer direction from the boundary wall  75 B where the cross-sectional area becomes smaller in the toner transfer direction. With this, the toner transfer amount of downstream side from the boundary wall  75 B can be reduced. 
     &lt;Effect Obtained by Position of Spiral Shape Changing Point&gt; 
     As shown in  FIGS. 7 and 8 , the spiral changing point  80 A of the agitator  80  which transfers toner is on the upstream side in the transfer direction from the boundary wall  75 B where the cross-sectional area becomes smaller in the toner transfer direction. If the spiral changing point  80 A is located at the further upstream side from the boundary wall  75 B in the transfer direction, the blocking of toner can be prevented more reliably. 
     That is, if the spiral changing point  80 A is located at the further upstream side (left side in the figure) from the boundary wall  75 B in the transfer direction, the force pressing the toner on the boundary wall  75 B becomes smaller and thus, the blocking of toner around the boundary wall  75 B can be prevented more reliably also when the spiral direction becomes opposite after the changing point  80 A with the straight portion interposed therebetween as shown in  FIG. 7 , or also when only the straight portion is formed after the changing point  80 A without forming the spiral shape thereafter as shown in  FIG. 8 . 
     On the other hand, if the position of the changing point  80 A is located on the downstream side from the boundary wall  75 B in the transfer direction as shown in  FIGS. 9 and 10 , the agitator  80  tries to transfer toner to a location downstream from the boundary wall  75 B in the transfer direction where the cross-sectional area becomes smaller. As a result, toner is collected around the boundary wall  75 B, the blocking of toner is prone to be generated in this area. Therefore, to prevent the blocking of toner, it is preferable that the changing point  80 A is located on the upstream side from the boundary wall  75 B in the transfer direction. 
     However, as the changing point  80 A is located at the further upstream side in the transfer direction, the amount of toner remaining in the toner cartridge  17  is increased when no-toner signal is detected on the side of the image forming apparatus. That is, even when toner still remains in the toner cartridge  17 , since the changing point  80 A is located on the upstream side in the transfer direction, toner is not transferred to the toner supply opening  84  in the area downstream in the transfer direction, and toner is reversely transferred toward the upstream side in the transfer direction. 
     If sufficient toner remains in the toner cartridge  17 , toner on the downstream side is pressed by toner on the upstream side in the transfer direction, and the former toner is pushed out into the toner supply opening  84 , and if the toner is consumed and the remaining amount is reduced, toner on the downstream side is not transferred to the toner supply opening  84 , no-toner signal is detected on the side of the image forming apparatus, and it is determined that no toner remains in the toner cartridge  17 . 
     That is, even when toner still remains in the toner cartridge  17 , no-toner signal is detected on the side of the image forming apparatus. Therefore, if a user exchanges the toner cartridge  17  at this time point, toner remaining in the toner cartridge  17  is not used and the toner cartridge  17  is dumped. Thus, a constant amount of toner is wasted and as a result, cost of the toner cartridge  17  is increased. 
     Whereas, if the spiral changing point  80 A of the agitator  80  is located on the downstream side from the boundary wall  75 B, the blocking of toner is prone to be generated as described above. 
     From this reason, to prevent the blocking of toner and to reduce the amount of remaining toner, it can be found that the most preferable position of the changing point  80 A is near the boundary wall  75 B and upstream therefrom in the transfer direction. 
     At that time, the agitator  80  may be driven from outside through a gear from the upstream side in the transfer direction (left side in the figure). The time when the agitator  80  is driven at the time of start of use of the toner cartridge  17  is time when the amount of toner inside is the greatest naturally, and the greatest torque is required for driving the agitator  80 . 
     As shown in  FIG. 11 , when the toner cartridge  17  is transferred in a state where the downstream side thereof in the transfer direction (projection  76 B) is directed downward, toner is prone to be agglutinated around the downstream projection  76 B due to gravity, and high density toner is clogged. Here, if the agitator  80  is driven from the downstream projection  76 B and the transfer of toner is started by turning motion of the agitator  80 , the driving torque of the agitator  80  is high, and the gear  90  may be damaged. 
     On the contrary, if the gear  90  is provided on the upstream side (on the side of the projection  76 A) and the agitator  80  is driven from the upstream projection  76 A, it is possible to prevent the gear  90  from being damaged. When the toner cartridge  17  is transferred in a state where the downstream (projection  76 B) side thereof in the transfer direction is oriented upward before start of use, toner is prone to be agglutinated around the upstream projection  76 A due to gravity, and high density toner is clogged. In this case, if the transfer of toner is started by tuning the agitator  80 , toner moves in a direction where toner is discharged out from the projection  76 A. Therefore, it is possible to reduce the load (driving torque) applied to the gear  90  as compared with a case where the agitator  80  is driven from downstream (on the side of the projection  76 B). 
     &lt;Another Shape&gt; 
       FIG. 8  shows a toner cartridge according to a second exemplary embodiment of the present invention. 
     If the spiral shape of the agitator  80  which transfers the toner is changed at the changing point  80 A and the spiral direction is reversed from the straight portion as shown in  FIG. 7 , the toner transfer amount downstream from the boundary wall  75 B can be reduced as described above. 
     In the exemplary embodiment of the present invention, as shown in  FIG. 8 , the spiral shape of the agitator  80  is not employed downstream from the changing point  80 A in the transfer direction, and only the straight portion is formed, the reversed spiral shape is not employed on the downstream side, i.e., toner is not transferred in a direction opposite from the transfer direction, and the blocking of toner near the boundary wall  75 B can be prevented. 
     That is, the agitator  80  does not transfer the toner downstream from the changing point  80 A, however since there is only the straight portion, the toner is stirred, toner is transferred to the toner supply opening  84  sequentially by toner pressed by the upstream spiral portion. With this, toner is not concentrated near the boundary wall  75 B, and the blocking of toner can effectively be prevented. 
     At that time, if the straight portion of the agitator  80  is provided at a position where it turns along an inner wall of the inner housing  72 , the straight portion of the agitator  80  scrapes off toner adhering to the inner wall and thus, toner is effectively used and the amount of remaining toner can be reduced. 
     &lt;Others&gt; 
     The present invention is not limited to the exemplary embodiment. 
     For example, although the toner cartridge is for electrophotography in the exemplary embodiment, the present invention is not limited to this, and the present invention can be applied to other type product only if fine powder is transferred out from a storing container.