Patent Publication Number: US-10310411-B2

Title: Image forming apparatus

Description:
CROSS-NOTING PARAGRAPH 
     This non-provisional application is a continuation application of U.S. application Ser. No. 15/782,314, filed on Oct. 12, 2017, which is a divisional application of co-pending U.S. application Ser. No. 14/802,133, filed on Jul. 17, 2015 and now U.S. Pat. No. 9,851,657, and claims priorities under 35 U.S.C. § 119(a) on Patent Application No. 2014-169163 filed in JAPAN on Aug. 22, 2014 and No. 2014-243778 filed in JAPAN on Dec. 2, 2014, the entire contents of which are hereby incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to an image forming apparatus including a cartridge storage portion that is installed in an image forming apparatus main body and a toner cartridge that is configured so as to be able to be inserted into and removed from the cartridge storage portion. 
     BACKGROUND OF THE INVENTION 
     In an electrophotographic image forming apparatus, a charging device charges a surface of an electrostatic latent image carrier (for example, photoreceptor), an exposure device exposes the charged region according to image information to form an electrostatic latent image, and a developing device develops this electrostatic latent image with toner. 
     This developing device includes a toner cartridge in which toner is stored, and all the stored toner is desired to be used up. For example, Japanese Laid-Open Patent Publication No. 2011-8142, Japanese Laid-Open Patent Publication No. 2010-256557 and Japanese Laid-Open Patent Publication No. 2011-59296 disclose a technology in which a mechanism which locks pulling-out of a toner cartridge so as not to be pulled out by a user easily even when it is detected that there is no toner is provided, in which it is not able to be pulled out unless operation for releasing lock is performed on an operation screen of an image forming apparatus main body. 
     However, since Japanese Laid-Open Patent Publication No. 2011-8142, Japanese Laid-Open Patent Publication No. 2010-256557 and Japanese Laid-Open Patent Publication No. 2011-59296 have a structure in which a cover of the image forming apparatus main body is locked, there is a problem that, supposedly, when lock of the cover of the image forming apparatus main body is able to be released on the operation screen or when the cover of the image forming apparatus main body is able to be opened, the toner cartridge is able to be detached from the image forming apparatus main body and toner is not able to be used up. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an image forming apparatus capable of preventing a toner cartridge from being detached from an image forming apparatus main body without using a mechanism of locking pulling-out of the toner cartridge so that toner is able to be used up. 
     An object of the present invention is to provide an image forming apparatus, comprising: a cartridge storage portion that is installed in an image forming apparatus main body; and a toner cartridge that is configured so as to be able to be inserted into and removed from the cartridge storage portion, wherein the cartridge storage portion has a storage opening that receives the toner cartridge, and has a gap between an end part of the toner cartridge and the storage opening, through which the end part of the toner cartridge is not able to be held, when the toner cartridge is stored in the cartridge storage portion. 
     Another object of the present invention is to provide the image forming apparatus, wherein the image forming apparatus further includes a driving unit that is installed in the image forming apparatus main body and configured so as to be removable from the toner cartridge, and the driving unit has a toner cartridge pushing-out device that allows the end part of the toner cartridge to be held by pushing out the toner cartridge when the toner cartridge is detached from the driving unit. 
     Another object of the present invention is to provide the image forming apparatus, wherein the toner cartridge pushing-out device has an arm member capable of pushing out the toner cartridge, a cam member that rotates based on driving force from the driving unit and pushes the arm member in a direction to be proximate to the toner cartridge, and a spring member that biases the arm member in a direction away from the toner cartridge. 
     Another object of the present invention is to provide the image forming apparatus, wherein the toner cartridge pushing-out device pushes out the toner cartridge when the toner remaining amount in the toner cartridge is detected to be zero. 
     Another object of the present invention is to provide the image forming apparatus, wherein the toner cartridge further includes a toner conveyance member or a stirring member that is driven by the driving unit, and the toner cartridge pushing-out device pushes out the toner cartridge when abnormality of toner conveyance operation by the toner conveyance member or stirring operation by the stirring member is detected. 
     Another object of the present invention is to provide the image forming apparatus, wherein the image forming apparatus further includes an operation portion that receives operation for the image forming apparatus, and the toner cartridge pushing-out device pushes out the toner cartridge when detachment of the toner cartridge is set at the operation portion. 
     Moreover, an object of the present invention is to provide an image forming apparatus capable of preventing a toner cartridge from being detached from a driving unit. 
     An object of the present invention is to provide an image forming apparatus, comprising: a driving unit that is installed in an image forming apparatus main body; and a toner cartridge that is configured so as to be removable from the driving unit, wherein the driving unit has a locking member that is engaged with the toner cartridge to prevent the toner cartridge from being detached from the driving unit. 
     Another object of the present invention is to provide the image forming apparatus, wherein the locking member is engaged with the toner cartridge when a toner remaining amount in the toner cartridge is not detected to be zero, and is released from the engagement with the toner cartridge when the toner remaining amount in the toner cartridge is detected to be zero. 
     Another object of the present invention is to provide the image forming apparatus, wherein the toner cartridge further includes a toner conveyance member or a stirring member that is driven by the driving unit, and the locking member is released from the engagement with the toner cartridge when abnormality of toner conveyance operation by the toner conveyance member or stirring operation by the stirring member is detected. 
     Another object of the present invention is to provide the image forming apparatus, wherein the image forming apparatus further includes an operation portion that receives operation for the image forming apparatus, and the locking member is released from the engagement with the toner cartridge when detachment of the toner cartridge is set at the operation portion. 
     Another object of the present invention is to provide the image forming apparatus, wherein the driving unit has a spring that biases the locking member in a direction to be engaged with the toner cartridge, and a cam that rotates based on driving force from the driving unit and presses the locking member in a direction away from the toner cartridge. 
     Another object of the present invention is to provide the image forming apparatus, wherein the driving unit has a cam that rotates in one direction to cause the locking member to be engaged with the toner cartridge as well as rotates in an opposite direction to cause the locking member to be separated from the toner cartridge, and a motor for a cam that rotates the cam. 
     Another object of the present invention is to provide the image forming apparatus, wherein the driving unit has a solenoid that operates so that the locking member is caused to be engaged with the toner cartridge by turning-on operation and operates so that the locking member is caused to be separated from the toner cartridge by turning-off operation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of an image forming apparatus of the present invention; 
         FIG. 2  is a perspective view showing a state where a toner cartridge and a driving unit are mounted; 
         FIG. 3  is a cross-sectional view of the toner cartridge; 
         FIG. 4  is a perspective view of the driving unit according to a first embodiment; 
         FIG. 5  is a perspective view of a cartridge storage portion; 
         FIG. 6  is a view showing a state where the toner cartridge is attached; 
         FIG. 7  is a view illustrating operation of the driving unit of  FIG. 4 ; 
         FIG. 8  is a view showing a replaceable state of the toner cartridge; 
         FIG. 9  is a view showing a replaceable state of the toner cartridge according to a second embodiment; 
         FIG. 10  is a view showing a replaceable state of the toner cartridge according to a third embodiment; 
         FIG. 11  is a view illustrating operation of the driving unit according to a fourth embodiment; 
         FIG. 12A  and  FIG. 12B  are views illustrating operation of the driving unit of  FIG. 11 ; 
         FIG. 13  is a view illustrating operation of the driving unit of  FIG. 11 ; 
         FIG. 14  is a partial enlargement view of the toner cartridge; 
         FIG. 15  is a perspective view of the driving unit according to a fifth embodiment; 
         FIG. 16A  and  FIG. 16B  are views showing a lock state of the toner cartridge; 
         FIG. 17A  and  FIG. 17B  are views showing a lock released state of the toner cartridge; 
         FIG. 18A  and  FIG. 18B  are illustrative views of the driving unit according to a sixth embodiment; and 
         FIG. 19A  and  FIG. 19B  are illustrative views of the driving unit according to a seventh embodiment. 
     
    
    
     PREFERRED EMBODIMENTS OF THE INVENTION 
     Description will hereinafter be given for embodiments of the present invention specifically with reference to drawings.  FIG. 1  is a schematic view of an image forming apparatus of the present invention. 
     An image forming apparatus  1  is able to apply predetermined image processing to image data transmitted from an external device via a network and output a color image or a monochrome image to a sheet of paper. Note that, though description will be given by taking an example of a printer in  FIG. 1 , the image forming apparatus of the present invention may be a copy machine, a facsimile apparatus, a multi-functional peripheral including functions thereof, or the like capable of applying predetermined image processing to image data read by a scanner or the like and outputting a color image or a monochrome image to a sheet of paper. 
     The image forming apparatus  1  includes a supply portion  10 , an image forming portion  20 , a conveyance portion  30  and a fixing portion  40  inside an image forming apparatus main body  2 , for example, in a box shape. The supply portion  10  supplies a sheet of paper to the image forming portion  20  at a predetermined timing, and the image forming portion  20  forms a toner image on the sheet of paper. 
     Specifically, the supply portion  10  has a paper feed tray  11  and a manual tray  12 , and sheets of paper in the paper feed tray  11  and the manual tray  12  are sent to the image forming portion  20  through a pickup roller  13  and a conveyance roller  14 . 
     The image forming portion  20  has, for example, a tandem system, and has four stations  20 Y,  20 M,  20 C and  20 B for a yellow image, a magenta image, a cyan image and a black image. 
     The station  20 Y for a yellow image is arranged in a vicinity of a belt cleaning device  34 , and the station  20 B for a black image is arranged in a vicinity of a fixing portion  40 , respectively, and the station  20 Y for a yellow image, the station  20 M for a magenta image, the station  20 C for a cyan image and the station  20 B for a black image are arranged in this order when viewed in a direction in which a conveyance belt  33  of the conveyance portion  30  moves. 
     Each of the stations  20 Y,  20 M,  20 C and  20 B has substantially same components. Therefore, reference numerals are assigned to the components of the station  20 Y for a yellow image and reference numerals to components of other stations  20 M,  20 C and  20 B are omitted in  FIG. 1 . Note that, in addition to the aforementioned four colors, for example, a light cyan (LC) or a light magenta (LM) which has same color hue as that of cyan or magenta and has a low density may be added. 
     To give description by taking the station  20 Y for a yellow image as an example, this station  20 Y has a photoreceptor  21 , and around the photoreceptor  21 , when viewed in a rotation direction thereof, a charging device  22 , an exposure device  23 , a developing device  24 , a transfer roller  25 , and a photoreceptor cleaning device  26  are arranged in this order. 
     The photoreceptor  21  is in a cylindrical shape, has a surface formed by, for example, an OPC (organic photo conductor) or the like, and is rotatable in a predetermine direction by a driving device (not shown in the figure). 
     The charging device  22 , for example, has a roller which makes contact with the surface of the photoreceptor  21 , and charges the surface of the photoreceptor  21  to a predetermined polarity (for example, minus) uniformly. Note that, a charging device of a brush system, an ion emission system or the like may be used in addition to one of a contact-type roller system. 
     The exposure device  23  irradiates the surface of the photoreceptor  21  which is charged with laser light based on the aforementioned image data, and an electrostatic latent image according to the image data is formed on the surface of the photoreceptor  21 . Note that, an exposure device such as a writing head in which light emitting elements such as LEDs are arranged in an array may be used in addition to a laser scanning unit (LSU) including a laser irradiation portion and a reflection mirror. 
     The developing device  24  develops the electrostatic latent image formed on the surface of the photoreceptor  21  with toner to form a visible image (also referred to as a toner image). The toner is supplied from a toner cartridge  28  which is coupled to the developing device  24 , and is charged with a same polarity (for example, minus) with a surface potential of the photoreceptor  21 . An intermediate hopper  27  in which toner is accumulated temporarily is provided between the toner cartridge  28  and the developing device  24 . Only the toner may be stored or carrier may be mixed therewith to be stored in the toner cartridge  28 . 
     The transfer roller  25  faces the photoreceptor  21  across the conveyance belt  33 . When a bias voltage with a polarity (for example, plus) opposite to a charging polarity of the toner is applied to the transfer roller  25 , the toner image on the photoreceptor  21  is transferred to a sheet of paper on the conveyance belt  33 . 
     The photoreceptor cleaning device  26  removes the toner remaining on the surface of the photoreceptor  21  after transfer onto the sheet of paper, and the toner removed from the photoreceptor  21  is collected, for example, into an inside of the photoreceptor cleaning device  26 . 
     The conveyance portion  30  includes a driving roller  31 , a driven roller  32  and the conveyance belt  33 . For example, the driving roller  31  is arranged in the vicinity of the fixing portion  40 , and the driven roller  32  is arranged in the vicinity of the belt cleaning device  34 , respectively, and the conveyance belt  33  is hung around between the driving roller  31  and the driven roller  32 . In the case of outputting a color image, when the conveyance belt  33  moves in a direction of an arrow Z, toner images of respective colors from the stations  20 Y,  20 M,  20 C and  20 B are transferred onto the conveyance belt  33  in order, and then transferred onto the sheet of paper from the conveyance belt  33 . 
     The fixing portion  40  includes a heating roller  41  and a pressure roller  42 , and fixes the toner images transferred onto the sheet of paper at a nip portion thereof. Then, in the case of outputting only to a front side of the sheet of paper, the sheet of paper delivered from the fixing portion  40  is discharged to a paper discharge tray  50 . 
       FIG. 2  is a perspective view showing a state where the toner cartridge and a driving unit of the present invention are mounted, and  FIG. 3  is a cross-sectional view of the toner cartridge. 
     As shown in  FIG. 2 , the toner cartridge  28  includes a container main body  60  which is formed thin and long along a lateral direction. The toner cartridge  28  is provided for each color, and in the case of the example described in  FIG. 1 , four toner cartridges  28  in total are arranged in the image forming apparatus main body  2 . 
     In the image forming apparatus main body  2 , four cartridge storage portions  80  in total described below in  FIG. 5  and the like, which respectively correspond to the toner cartridges  28  of the respective colors are installed, and each driving unit  29  is installed in a depth side of each of the cartridge storage portions  80 . 
     A front cover  64  is positioned at a rear end surface with respect in an insertion direction of the toner cartridge  28 , and by causing the toner cartridge  28  to go frontward in the cartridge storage portion  80  along a longitudinal direction thereof with an opposite side to the front cover  64  set in a front, and, as shown in  FIG. 2 , coupling the toner cartridge  28  to the driving unit  29  which is positioned in the depth side of the cartridge storage portion  80 , it is possible to stir or convey the toner in the container main body  60  with driving force of a motor  70  of the driving unit  29 . On the other hand, by causing the toner cartridge  28  to go backward with respect to the driving unit  29  with the front cover  64  set in a front, it is possible to remove the toner cartridge  28  from the cartridge storage portion  80 . Note that, the front cover  64  corresponds to an end part of a toner cartridge of the present invention. 
       FIG. 3  is a cross-sectional view taken along a III-III line of  FIG. 2 , and, for example, a toner conveyance member  61  and a stirring member  62  are arranged in parallel in the container main body  60  of the toner cartridge  28 . 
     The toner conveyance member  61  has a rotation axis  61   b , a screw  61   a  provided around the rotation axis  61   b , and a driving transmission member  61   c  provided at a tip end of the rotation axis  61   b . The toner conveyance member  61  is coupled to the motor  70  of the driving unit  29  via the driving transmission member  61   c  outside the container main body  60 , and is rotatable in a predetermined direction with driving force of the motor  70 . 
     The stirring member  62  has a sheet  62   a  whose material is, for example, PET or the like, a rotation axis  62   b  and a driving transmission member  62   c , and the sheet  62   a  is formed, for example, in a thin plate shape having flexibility so as to be able to make contact with an inner surface of the container main body  60 . In the same manner as the toner conveyance member  61 , the stirring member  62  is coupled to the motor  70  of the driving unit  29  via the driving transmission member  62   c  outside the container main body  60 , and is rotatable in a predetermined direction with driving force of the motor  70 . 
     A partition wall  63  is disposed upright between the toner conveyance member  61  and the stirring member  62 , and toner stirred by the stirring member  62  reaches around the toner conveyance member  61  over the partition wall  63 . The toner collected to a surround of the toner conveyance member  61  is conveyed by the toner conveyance member  61  and is directed to the intermediate hopper  27  described in  FIG. 1 . 
     First Embodiment 
       FIG. 4  is a perspective view of the driving unit according to a first embodiment, which is viewed from obliquely left upward in the same manner as  FIG. 2 . The driving unit  29  has driving transmission members  71 ,  72  and  73  for transmitting driving force of the aforementioned motor  70 , for example. The driving transmission member  71  is formed so as to be able to be coupled to the driving transmission member  61   c  shown in  FIG. 3 , and transmits the driving force of the motor  70  to the toner conveyance member  61 . The driving transmission member  72  is formed so as to be able to be coupled to the driving transmission member  62   c , and transmits the driving force of the motor  70  to the stirring member  62 . 
     Here, the driving unit  29  has a toner cartridge pushing-out device. Specifically, it is composed of an eject cam  75 , an eject arm  77  and an arm position detection sensor  78 , and the arm  77  is formed so as to be able to abut against the toner cartridge  28  described in  FIG. 2  and  FIG. 3 . Note that, the cam  75  corresponds to a cam member of the present invention and the arm  77  corresponds to an arm member of the present invention, respectively. 
     The driving transmission member  73  is coupled to the cam  75 , and this cam  75  is configured so as to be rotatable, for example, with the driving force of the motor  70 . A shaft of the cam  75  is connected to a one-way clutch (not shown in the figure), and the cam  75  runs idle in a predetermined rotation direction. Note that, the cam  75  may be rotatable with power transmitted from the driving transmission member  72  instead of the driving transmission member  73 . 
     The cam  75  shown in  FIG. 4  is, for example, a solid cam, and a convex portion  75   b  and a flat portion  75   c  are provided around a shaft portion  75   a . The convex portion  75   b  rises toward the arm  77  in a range corresponding to, for example, a quarter rotation of the shaft portion  75   a , and is formed at height capable of abutting against the arm  77 . On the other hand, the flat portion  75   c  is provided in a range corresponding to, for example, three-quarters rotation of the shaft portion  75   a , and is formed to be lower than the convex portion  75   b.    
     The arm  77  has a shaft portion  77   a  which extends in a direction orthogonal to an axis line of the cam  75  in a vicinity thereof, and an arm portion  77   b  which is rotatable with respect to the shaft portion  77   a . Moreover, a spring  77   c  (for example, torsion coil spring) is installed in the shaft portion  77   a  to bias the arm portion  77   b  in a direction away from the toner cartridge  28 . Note that, the spring  77   c  corresponds to a spring member of the present invention. 
     The arm position detection sensor  78  having, for example, a light emitting element and a light receiving element is provided in a vicinity of the arm portion  77   b , and when light from the light emitting element is blocked by the arm portion  77   b , pushing-out position (also referred to as eject position) by the arm  77  is able to be detected. Note that, the arm position detection sensor  78  and the shaft portion  77   a  of the arm  77  are fixed to a pedestal  78   a  which extends from a lower end of the driving unit  29 . 
       FIG. 5  is a perspective view of the cartridge storage portion, and  FIG. 6  is a view showing a state where the toner cartridge is attached. As shown in  FIG. 5 , the cartridge storage portion  80  has a storage opening  81  which is formed, for example, in a rectangular shape, and is formed thin and long toward the driving unit  29  described in  FIG. 2  and the like so as to be able to receive the toner cartridge  28 . 
     Specifically, the toner cartridge  28  is caused to go frontward along a longitudinal direction thereof with an opposite side to the front cover  64  described in  FIG. 2  and  FIG. 3  set in a front, and inserted into the cartridge storage portion  80  from the storage opening  81  shown in  FIG. 5 . Then, when the toner cartridge  28  is caused to go frontward until being coupled to the driving unit  29  which is positioned in the depth side of the cartridge storage portion  80  in a state where the front cover  64  is seen from a user, for example, a rear side (the side on an opposite side to the front side seen from the user) of the front cover  64  makes contact with a peripheral part of the storage opening  81 , and, as shown in  FIG. 6 , the cartridge storage portion  80  does not cause a predetermined gap which allows holding the front cover  64 , for example, a gap to an extent where a finger of the user enters therein to be formed between the rear side of the front cover  64  and the storage opening  81 . 
     According to this first embodiment, the front cover  64  is positioned in a front side of the storage opening  81 , but the rear side of the front cover  64  is hidden, so that the user is not able to hold this front cover  64 . Thus, it is possible to prevent the toner cartridge from being detached from the image forming apparatus main body without using a mechanism for locking pulling-out of the cartridge so that tone is able to be used up. 
       FIG. 7  is a view illustrating operation of the driving unit of  FIG. 4 , and  FIG. 8  is a view showing a replaceable state of the toner cartridge. In the present embodiment, for example, based on a detected signal of a toner detection device (not shown in the figures), operation of the driving unit  29  shown in  FIG. 4  is switched. Note that, for example, a piezoelectric sensor is able to be used for detection of a toner remaining amount, and when there is carrier in addition to the toner, for example, a magnetic permeability sensor is able to be used to detect the toner remaining amount. 
     Specifically, when the toner remains in the toner cartridge  28 , the motor  70  of the driving unit  29  normally rotates, for example, until the toner remaining amount is detected to be zero after the toner cartridge  28  is coupled to the driving unit  29 . Thereby, the driving transmission members  71  and  72  shown in  FIG. 4  rotate in a counterclockwise manner when viewed in  FIG. 4  and the toner conveyance member  61  and the stirring member  62  shown in  FIG. 3  rotate to stir the toner while conveying. 
     When this motor  70  normally rotates, the driving transmission member  73  rotates, for example, in a clockwise manner when viewed in  FIG. 4 . A direction of the clockwise rotation by the driving transmission member  73  is restricted by the one-way clutch, so that power of the motor  70  is not transmitted to the cam  75  and the cam  75  continues to run idle at that position. Therefore, as shown in  FIG. 4 , the convex portion  75   b  of the cam  75  remains being separated from the arm  77 , and the arm  77  is kept at a position where the toner cartridge  28  is not pushed out (also referred to as a home position). 
     On the other hand, when the toner remaining amount in the toner cartridge  28  is detected to be zero, the motor  70  of the driving unit  29  reversely rotates, for example, until another toner cartridge is mounted in the driving unit  29  after the toner remaining amount is detected to be zero. Thereby, for example, the driving transmission members  71  and  72  shown in  FIG. 4  rotate in the clockwise manner when viewed in  FIG. 4 , the driving transmission member  73  rotates in the counterclockwise manner when viewed in  FIG. 4 , and the cam  75  also rotates in the counterclockwise manner. 
     In addition, when the cam  75  rotates, for example, by about 90° in the counterclockwise manner from the position of  FIG. 4 , the convex portion  75   b  of the cam  75  starts to push the arm  77 . Subsequently, when the cam  75  rotates, for example, by 180° in the counterclockwise manner from the position of  FIG. 4 , the convex portion  75   b  reaches a position of pushing out the arm  77  to the maximum, so that the arm  77  is at the eject position. 
     Specifically, as shown in  FIG. 7 , when the arm  77  is pushed by the convex portion  75   b  of the cam  75 , the arm portion  77   b  of the arm  77  rotates in the clockwise manner in a plan view of  FIG. 7  against biasing force of the spring  77   c , thus making it possible to push out the toner cartridge  28 . 
     In this manner, when the toner cartridge  28  is detached, only this toner cartridge  28  is pushed out, for example, by about 15 mm toward a user side. Thereby, as shown in  FIG. 8 , for example, a gap to an extent where the finger of the user enters therein is formed between the rear side of the front cover  64  and the storage opening  81 , so that the user is able to hold the front cover  64 . 
     Moreover, according to this first embodiment, since the pushing-out device pushes out the toner cartridge  28  with the driving force from the driving unit  29  which drives the toner conveyance member and the stirring member, it is possible to push out the toner cartridge with the less number of components than a case where a different driving unit from the driving unit is used for operation of the arm  77 . 
     Note that, when the toner remaining amount in the toner cartridge  28  is detected to be zero, an attention-drawing message that please replace the toner cartridge may be displayed, for example, on an operation portion  51  which is provided in a vicinity of the paper discharge tray  50  of  FIG. 1  and receives operation for the image forming apparatus  1 . It is also possible to carry out audio guidance. Pop-up display also may be carried out. 
     Further, a plurality of types of stepwise attention-drawing messages that the toner cartridge is still able to be used may be displayed on the operation portion  51  until toner end indicating that the usable toner completely runs out is detected by the toner detection device in the intermediate hopper  27  described in  FIG. 1 . Specifically, when toner near end indicating that the toner in the toner cartridge  28  runs out completely is detected by the toner detection device in the toner cartridge  28 , an attention-drawing message that the toner cartridge is replaceable is displayed on the operation portion  51 . Then, when toner near near end indicating that usable toner is little left is detected by the toner detection device in the intermediate hopper  27 , an attention-drawing message that the toner cartridge needs to be replaced is displayed on the operation portion  51 , and thereafter, when toner end indicating that the usable toner runs out completely is detected, an attention-drawing message that please replace the toner cartridge is displayed on the display portion  51 . Audio guidance or pop-up display may be carried out. 
     Note that, in the embodiment described above, the cam  75  is rotatable in the counterclockwise manner even after pushing the arm  77  with the convex portion  75   b  thereof. Therefore, when the cam  75  further rotates from the position of  FIG. 7  and pushing-out of the arm  77  by the convex portion  75   b  is finished, the arm  77  shown in  FIG. 7  returns to the home position shown in  FIG. 4  with biasing force of the spring  77   c , and then, is to be at the eject position and the home position repeatedly with rotation of the cam  75 . 
     Thus, for example, when it is determined that shift from the eject position to the home position was able to be detected by the arm position detection sensor  78 , driving of the motor  70  may be stopped, in order to keep the home position which was switched from the eject portion. Alternatively, a time required to move to the home position again through the eject position from the home position may be measured in advance, and when it is determined that the moving time has elapsed after the toner remaining amount is detected to be zero and the motor  70  is driven reversely, the reverse driving of the motor  70  may be stopped. Note that, a driving time of the motor  70  is also able to be managed with a pulse number. 
     Second Embodiment 
       FIG. 9  is a view showing a replaceable state of the toner cartridge according to a second embodiment. In the aforementioned first embodiment, as described in  FIG. 6 , the rear side of the front cover  64  makes contact with the peripheral part of the storage opening  81  and the front cover  64  is positioned in the front side of the storage opening  81 . 
     Meanwhile, this storage opening  81  may be formed with such an area that allows covering all peripheral edges of the front cover  64  and the cartridge storage portion  80  may be formed with such a depth that allows making the front cover  64  (surface seen from the user) and the peripheral part of the storage opening  81  flat as shown in  FIG. 9 . In this case, the user is not able to hold the front cover. 
     Third Embodiment 
       FIG. 10  is a view showing a replaceable state of the toner cartridge according to a third embodiment, and the cartridge storage portion  80  may be formed with such a depth that the front cover  64  enters further deeply compared to the first and second embodiments. In this case as well, in the same manner as the first and second embodiments, a gap formed between the front cover  64  and the storage opening  81  has a size less than a predetermined gap through which the front cover  64  is able to be held, so that the user is not able to hold the front cover. 
     Note that, according to these second and third embodiments, also when the front cover is formed with thickness to an extent of being able to be held by the user, the front cover is not able to be held. 
     Fourth Embodiment 
       FIG. 11  is a view illustrating operation of the driving unit according to another embodiment. Though description has been given by taking the solid cam as an example in the aforementioned first embodiment, a plane cam is also able to be used. Specifically, to describe a difference from  FIG. 4  mainly, a pushing-out device shown in  FIG. 11  is composed of a one-way clutch  74 , the eject cam  75 , an eject lever  76 , the eject arm  77  and the arm position detection sensor  78 . Note that, the cam  75  corresponds to the cam member of the present invention and the arm  77  corresponds to the arm member of the present invention, respectively. 
     Moreover, a shaft of the cam  75  is connected to the one-way clutch  74 , and the cam  75  runs idle in a predetermined rotation direction. The cam  75  shown in  FIG. 11  is, for example, a plane cam, and a convex portion thereof extends in the direction orthogonal to an axis line of the cam  75 . 
     The lever  76  is arranged between the cam  75  and the arm  77 , and has a shaft portion  76   a  which extends in the direction orthogonal to the axis line of the cam  75  and an arm portion  76   c  which extends toward the cam  75  from the shaft portion  76   a . On the other hand, the arm  77  has the shaft portion  77   a  which extends in the direction orthogonal to the axis line of the cam  75  and the arm portion  77   b  which is integrally formed with the shaft portion  77   a.    
     Note that, the lever  76  has, for example, a pin (or long hole), which is not shown in the figure, between the shaft portions  76   a  and  77   a , and the arm  77  has a long hole (or pin) which is engaged with this pin (or long hole). Therefore, when, with rotation of the lever  76 , the pin (or long hole) on the lever  76  side causes the shaft portion  77   a  to rotate with the long hole (or pin) on the arm  77  side, the arm portion  77   b  rotates about the shaft portion  77   a.    
     Moreover, a spring  76   b  (for example, torsion coil spring) is installed in the shaft portion  76   a  of the lever  76  to bias the arm portion  77   b  of the arm  77  in a direction away from the toner cartridge  28 . Note that, the spring  76   b  corresponds to the spring member of the present invention. 
       FIG. 12A ,  FIG. 12B  and  FIG. 13  are views illustrating operation of the driving unit of  FIG. 11 , and, for example, when the toner remains in the toner cartridge  28 , the motor  70  of the driving unit  29  shown in  FIG. 11  normally rotates and the toner conveyance member  61  and the stirring member  62  shown in  FIG. 3  rotate to stir the toner while conveying. In this case, a direction of clockwise rotation by the driving transmission member  73  is restricted by the one-way clutch  74 , so that power of the motor  70  is not transmitted to the cam  75  and the cam  75  continues to run idle at that position. Therefore, as shown in  FIG. 11  and  FIG. 12A , the arm portion  76   c  of the lever  76  remains being proximate to an axial center of the cam  75  and the arm  77  is kept at the home position. 
     On the other hand, when the toner remaining amount in the toner cartridge  28  is detected to be zero, the motor  70  of the driving unit  29  reversely rotates, and, for example, the driving transmission members  71  and  72  shown in  FIG. 11  rotate in the clockwise manner when viewed in  FIG. 11 , the driving transmission member  73  rotates in the counterclockwise manner when viewed in  FIG. 11 , and the cam  75  also rotates in the counterclockwise manner. 
     Then, when the cam  75  rotates, for example, by 332° in the counterclockwise manner from the position of  FIG. 12A , the arm portion  76   c  of the lever  76  reaches a position farthest from the axial center of the cam  75 , so that the arm  77  is at the eject position. 
     Specifically, as shown in  FIG. 12B , when the arm portion  76   c  is pushed by the convex portion of the cam  75 , the lever  76  rotates in the counterclockwise manner in a plan view of  FIG. 13  against biasing force of the spring  76   b , so that the arm portion  77   b  of the arm  77  is able to rotate in the clockwise manner in a plan view to push the toner cartridge  28 . 
     Thereby, only the toner cartridge  28  is pushed out, for example, by about 15 mm toward the user side, and as described in  FIG. 8 , the user is able to hold the front cover  64 . 
     In the meantime, description has been given in each of the aforementioned embodiments by taking an example in which the toner cartridge is pushed out based on the toner remaining amount. However, the present invention may be configured so that when a trouble is caused in the toner cartridge, or when detachment of the toner cartridge is set, for example, at the operation portion  51  shown in  FIG. 1 , the toner cartridge is pushed out. 
     Specifically, for example, when abnormality of toner conveyance operation or stirring operation by the toner conveyance member  61  or the stirring member  62  described in  FIG. 3  is detected, a trouble content thereof and the like may be displayed on the operation portion  51  as well as the toner cartridge may be pushed out toward the user side. Audio guidance or pop-up display may be carried out. In this case, it is possible to make replacement of the toner cartridge difficult until a trouble is caused in the toner cartridge. 
     Further, when detachment of the toner cartridge is set, for example, like when, for example, a “detach the toner cartridge” button is pressed at the operation portion  51 , the toner cartridge may be pushed out toward the user side. In this case, it is possible to make replacement of the toner cartridge difficult until detachment of the toner cartridge is set at the operation portion. 
     Note that, the eject cam described above may be driven with a motor dedicated for the cam, and, though the motor and the cam are used for moving the eject arm, a solenoid may be used. Moreover, also a locking member for positioning the toner cartridge may be provided in the image forming apparatus main body. 
     Further, a dent may be provided on the rear side of the front cover described above. Specifically, this dent has a size to an extent where the finger of the user does not enter therein when the toner cartridge is coupled to the driving unit, but when the toner cartridge is pushed out, it is formed with a size to an extent where the user is able to hold the front cover easily, thus making it possible to make the user recognize a holding position of the front cover. 
     As described above, according to the present invention, when the toner cartridge is attached, the cartridge storage portion prevents the end part of the toner cartridge from being held. Thus, it is possible to prevent the toner cartridge from being detached from the image forming apparatus main body without using a mechanism for locking pulling-out of the cartridge so that toner is able to be used up. 
     Subsequently,  FIG. 14  is a partial enlargement view of the toner cartridge.  FIG. 14  shows the toner cartridge  28  of  FIG. 3  when viewed from bottom, and a to-be-locked portion  64 ′ is provided on a lower surface of the container main body  60 . Specifically, the to-be-locked portion  64 ′ is formed by, for example, a wall surface which extends across a longitudinal direction of the container main body  60  or the like, and is installed to be visible from outside the container main body  60  in a vicinity of the driving transmission member  61   c  or the driving transmission member  62   c  described above. 
     Fifth Embodiment 
       FIG. 15  is a perspective view of the driving unit according to a fifth embodiment, which is viewed from obliquely left upward in the same manner as  FIG. 2 . The driving unit  29  has driving transmission members  71 ,  72  and  73  for transmitting driving force of the aforementioned motor  70 . The driving transmission member  71  is formed so as to be able to be coupled to the driving transmission member  61   c  shown in  FIG. 3  and  FIG. 14 , and transmits the driving force of the motor  70  to the toner conveyance member  61 . The driving transmission member  72  is formed so as to be able to be coupled to the driving transmission member  62   c , and transmits the driving force of the motor  70  to the stirring member  62 . 
     The driving transmission member  73  is coupled to the cam  75 , and the cam  75  is configured so as to be rotatable, for example, with driving force of the motor  70 . Note that, the shaft of the cam  75  is connected to a torque limiter  74 ′, and rotation torque from the motor  70  is blocked in a predetermined rotation direction when a set torque value is exceeded, so that the cam  75  runs idle. 
     Here, the driving unit  29  has a locking member  80 ′. Specifically, the locking member  80 ′ is composed of an shaft portion  80   a ′ (shown in  FIG. 16A ,  FIG. 16B ,  FIG. 17A  and  FIG. 17B  described below), a hook portion  80   b ′ and an abutting portion  80   c ′, the abutting portion  80   c ′ abuts against or is separated from the cam  75 , and the hook portion  80   b ′ is formed so as to be able to be engaged with the to-be-locked portion  64 ′ of the toner cartridge  28 , which has been described in  FIG. 14 . 
     The shaft portion  80   a ′ shown in  FIG. 16A ,  FIG. 16B ,  FIG. 17A  and  FIG. 17B  described below is arranged between the hook portion  80   b ′ and the abutting portion  80   c ′, and extends in the direction orthogonal to the shaft of the cam  75 . Moreover, a spring  76 ′ (for example, torsion coil spring) is installed in the shaft portion  80   a ′, and biases the locking member  80 ′ in a direction to be engaged with the to-be-locked portion  64 ′ of the toner cartridge  28 . Note that, for example, a retreat position detection sensor  77 ′ having a light emitting element and a light receiving element is provided in a vicinity of the hook portion  80   b ′, and when light from the light emitting element is blocked by the hook portion  80   b ′, retreat of the locking member  80 ′ is able to be detected. 
     In this manner, since the driving unit  29  has the locking member  80 ′ which is engaged with the to-be-locked portion  64 ′ of the toner cartridge  28 , even if lock of a cover of the image forming apparatus main body is released or the cover of the image forming apparatus main body is opened, it is possible to prevent the toner cartridge  28  from being detached from the driving unit  29 . 
     Further, since a state of the locking member  80 ′ is attained by the cam  75  and the spring  76 ′, it is possible to seek reduction of manufacturing cost of the image forming apparatus. 
       FIG. 16A  and  FIG. 16B  are views showing a lock state of the toner cartridge, and  FIG. 17A  and  FIG. 17B  are views showing a lock released state of the toner cartridge, all of which show the toner cartridge  28  of  FIG. 3  when viewed from bottom in the same manner as  FIG. 14 . 
     The locking member  80 ′ of the present embodiment is engaged with the toner cartridge  28  or has engagement with the toner cartridge  28  released based on a detection signal of a toner detection sensor (not shown in the figures), for example. 
     Specifically, when the toner remaining amount in the toner cartridge  28  is not detected to be zero, the motor  70  of the driving unit  29  normally rotates, for example, until the toner remaining amount is detected to be zero after the toner cartridge  28  is mounted in the driving unit  29 . Thereby, the driving transmission members  71 ,  72  and  73  shown in  FIG. 15  rotate in the counterclockwise manner when viewed in  FIG. 15  and the toner conveyance member  61  and the stirring member  62  shown in  FIG. 3  rotate to stir toner while conveying as well as the cam  75  also rotates in the counterclockwise manner in the case of the set torque value or less. 
     A direction of this counterclockwise rotation is restricted by the torque limiter  74 ′, and when the convex portion of the cam  75  reaches a position farthest from the abutting portion  80   c ′ of the locking member  80 ′ as shown in  FIG. 16A  and the set torque value is exceeded, the cam  75  continues to run idle at that position. Therefore, as shown in  FIG. 16B , the hook portion  80   b ′ of the locking member  80 ′ moves toward the to-be-locked portion  64 ′ of the toner cartridge  28  with biasing force of the spring  76 ′ and is engaged with the to-be-locked portion  64 ′ (also referred to as a lock state of the locking member). 
     On the other hand, when the toner remaining amount in the toner cartridge  28  is detected to be zero, the motor  70  of the driving unit  29  reversely rotates, for example, until another toner cartridge is mounted in the driving unit  29  after the toner remaining amount is detected to be zero. Thereby, the driving transmission members  71 ,  72  and  73  shown in  FIG. 15  rotate in the clockwise manner when viewed in  FIG. 15 , and the cam  75  also rotates in the clockwise manner. 
     This cam  75  which rotates in the clockwise manner retreats the locking member  80 ′. Specifically, as shown in  FIG. 17A , the abutting portion  80   c ′ of the locking member  80 ′ is pushed by the convex portion of the cam  75 . Therefore, as shown in  FIG. 17B , the hook portion  80   b ′ of the locking member  80 ′ moves in a direction away from the to-be-locked portion  64 ′ of the toner cartridge  28  against biasing force of the spring  76 ′ so that engagement with the to-be-locked portion  64 ′ is released (also referred to as a lock released state of the locking member). 
     In this manner, since the state of the locking member  80 ′ is set based on the toner remaining amount in the toner cartridge  28 , when toner remains in the toner cartridge  28 , it is possible to make replacement of the toner cartridge  28  difficult. 
     Note that, when the toner remaining amount in the toner cartridge  28  is detected to be zero, an attention-drawing message that please replace the toner cartridge may be displayed, for example, on the operation portion  51  which is provided in the vicinity of the paper discharge tray  50  of  FIG. 1  and receives operation for the image forming apparatus  1 . It is also possible to carry out audio guidance. 
     Moreover, when the toner cartridge is removed in the lock state of the locking member, damage of the locking member is caused. Thus, in order to prevent the damage of the locking member, it may be set so that removal of the toner cartridge is not made impossible, but the toner cartridge is able to be removed, in which a load at that time is increased. Further, an attention-drawing message that the toner cartridge is not able to be detached in the lock state of the locking member or that the toner cartridge is still able to be used until the toner remaining amount is detected to be zero may be displayed on the operation portion  51  or audio guidance may be carried out. 
     Note that, in the embodiment described above, the direction of counterclockwise rotation is restricted by the torque limiter  74 ′, but the direction of clockwise rotation is not restricted by the torque limiter  74 ′. Therefore, when the cam  75  still continues to rotate in the clockwise manner, the locking member  80 ′, after being in the aforementioned lock released state, is to repeat postures of the lock state, the lock released state and the lock state. Thus, after being in the lock released state, in order to keep this state, for example, when it is determined that it was possible to detect retreat of the locking member  80 ′ by the retreat position detection sensor  77 ′, driving of the motor  70  may be stopped. Alternatively, a time required for the locking member to move from the lock state to the lock released state may be measured in advance, and when it is determined that the moving time has elapsed after the toner remaining amount is detected to be zero and the motor  70  is driven reversely, the reverse driving of the motor  70  may be stopped. Note that, a driving time of the motor  70  is also able to be managed with a pulse number. Further, the direction of counterclockwise rotation is restricted when the set torque value is exceeded. Thus, a time required for the locking member to move from the lock released state to the lock state may be measured in advance, and when it is determined that the moving time has elapsed after the motor  70  is driven normally, driving force of the motor  70  in a normal rotation direction may be controlled so as to exceed the set torque value. 
     Sixth Embodiment 
       FIG. 18A  and  FIG. 18B  are illustrative views of the driving unit according to a sixth embodiment. Though description has been given by taking an example in which the cam in the aforementioned fifth embodiment is driven by the motor  70  of the driving unit  29 , a motor dedicated for the cam may be provided. 
     Specifically, as shown in  FIG. 18A , the driving unit  29  includes a motor for a cam  81 ′ separately from the motor  70 , and the cam  75  rotates with driving force of the motor for a cam  81 ′, and, for example, when the toner remaining amount in the toner cartridge  28  is not detected to be zero, takes a posture making the locking member into a lock state ( FIG. 18A ), and when the toner remaining amount in the toner cartridge  28  is detected to be zero, takes a posture making the locking member into a lock released state ( FIG. 18B ). 
     In this manner, by using the motor dedicated for the cam, the driving unit  29  for conveying toner while stirring is able to use, for example, a versatile motor capable of only normal rotation. Moreover, since it is driven separately from the motor  70  of the driving unit  29 , the torque limiter is also able to be omitted. 
     Seventh Embodiment 
       FIG. 19A  and  FIG. 19B  are illustrative views of the driving unit according to a seventh embodiment. Though the cam is used for moving the locking member in the aforementioned fifth and sixth embodiments, a solenoid may be used. 
     Specifically, a solenoid  82  having a plunger  82   a  is arranged in a vicinity of the locking member  80 ′ as shown in  FIG. 19A  and  FIG. 19B . The plunger  82   a  is coupled to the abutting portion  80   c ′, and, for example, when the toner remaining amount in the toner cartridge  28  is not detected to be zero, the plunger  82   a  is sucked into the solenoid  82  by turning-on operation of the solenoid  82  ( FIG. 19A ), so that the locking member is made into the lock state. On the other hand, when the toner remaining amount in the toner cartridge  28  is detected to be zero, the plunger  82   a  is protruded outward with turning-off operation of the solenoid  82  ( FIG. 19B ), so that the locking member is made into the lock released state. 
     In this manner, since the lock state and the lock released state of the locking member is performed by the solenoid  82 , the cam and the like are able to be omitted, and it is possible to save a space in the image forming apparatus main body. 
     Meanwhile, description has been given in each of the aforementioned embodiments by taking an example in which the locking member is turned into the lock state or the lock released state based on the toner remaining amount. However, in the present invention, the locking member may be turned into the lock state or the lock released state when a trouble is caused in the toner cartridge, or when detachment of the toner cartridge is set, for example, at the operation portion  51  shown in  FIG. 1 . 
     Specifically, for example, when abnormality of toner conveyance operation or stirring operation by the toner conveyance member  61  or the stirring member  62  described in  FIG. 3  is detected, a trouble content thereof and the like may be displayed on the operation portion  51  as well as engagement of the locking member with the to-be-locked portion of the toner cartridge may be released. Audio guidance also may be carried out. In this case, it is possible to make replacement of the toner cartridge difficult until a trouble is caused in the toner cartridge. 
     Further, when detachment of the toner cartridge is set, for example, like when, for example, a “detach the toner cartridge” button is pressed at the operation portion  51 , engagement of the locking member with the to-be-locked portion of the toner cartridge may be released. In this case, it is possible to make replacement of the toner cartridge difficult until detachment of the toner cartridge is set at the operation portion. 
     As above, according to the present invention, since the driving unit has the locking member which is engaged with the toner cartridge, even if the cover of the image forming apparatus main body is opened, it is possible to prevent the toner cartridge from being detached from the driving unit.