Patent Publication Number: US-10317819-B2

Title: Developer supplying device and image forming apparatus

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention is related to a developer supplying device capable of supplying developer to, for example, a developing unit, and is related to an image forming apparatus including the developer supplying device, examples of the image forming apparatus including a copier, a printer, a facsimile machine, and a multifunctional machine having functions of these machines. 
     Description of the Related Art 
     A configuration including a toner cartridge and a hopper as a developer supplying device that supplies developer to a developing unit is known. The hopper temporarily accommodates developer supplied from the toner cartridge and then supplies the developer to the developing unit. In this configuration, a sensor that detects developer in the hopper is provided, and the developer is supplied from the toner cartridge to the hopper on the basis of a result of detection by the sensor. 
     In such a configuration, developer is sometimes not detected by the sensor due to an influence of the fluidity of the developer supplied from the toner cartridge even in the case where the developer has been supplied from the toner cartridge into the hopper. In this case, even if developer remains in the toner cartridge, a control portion of the device will determine that the toner cartridge needs to be replaced. Therefore, Japanese Patent No. 4916039 proposes a configuration in which an agitating member that agitates the developer in the hopper is driven, before performing the determination concerning replacement of the toner cartridge, to level the developer in the hopper and make it easier for the sensor to detect the developer. 
     However, it sometimes takes time to cause the sensor to detect the developer even in the case where an agitating member is driven before performing the determination concerning replacement of the toner cartridge as in the configuration disclosed in Japanese Patent No. 4916039. That is, when developer is supplied from the toner cartridge into the hopper, a heap of developer is formed in the hopper in accordance with the fluidity of the developer. The developer can be detected by the sensor by leveling the heap, and the state of the heap varies depending on the fluidity of the developer at the time of leveling. In particular, a supply property, or a discharge property, of the toner cartridge to supply developer from the toner cartridge to the hopper varies depending on the amount of remaining developer in the toner cartridge. Therefore, a large heap is sometimes formed in the hopper depending on the supply property of the toner cartridge or the fluidity of the developer at the time of supply. In the case where a large heap of developer is formed, the agitating member is driven for a long period to level the heap and cause the sensor to detect the developer. 
     In the case where the agitating member is driven for a long period to cause the sensor to detect the developer, deterioration of the developer is accelerated. It can be also considered to drive the agitating member the whole time, that is, also in other time than before performing the determination concerning replacement of the toner cartridge. However, deterioration of the developer is also accelerated in this case. 
     SUMMARY OF THE INVENTION 
     According to a first aspect to the invention, a developer supplying device includes a developer supplying container configured to accommodate developer and attachable to and detachable from an image forming apparatus, a developer accommodating portion including a discharge port and configured to accommodate the developer supplied from the developer supplying container, the discharge port being configured such that the developer in the developer accommodating portion is discharged through the discharge port, a supply driving portion configured to perform a supply operation of supplying the developer from the developer supplying container to the developer accommodating portion, a developer detection portion configured to detect the developer in the developer accommodating portion, an agitating conveyance portion configured to agitate the developer in the developer accommodating portion and convey the developer in the developer accommodating portion to the discharge port, an agitating driving portion configured to drive the agitating conveyance portion, and, a control portion including a processor and configured to control the supply driving portion and the agitating driving portion such that the supply operation is performed in a case where the developer is not detected by the developer detection portion and such that, each time the agitating conveyance portion is driven by a first driving amount, the supply driving portion is driven by a second driving amount in the supply operation. The control portion is configured to set a different value of the first driving amount on a basis of an amount of remaining developer in the developer supplying container. 
     According to a second aspect to the invention, a developer supplying device includes a developer supplying container configured to accommodate developer and attachable to and detachable from an image forming apparatus, a developer accommodating portion including a discharge port and configured to accommodate the developer supplied from the developer supplying container, the discharge port being configured such that the developer in the developer accommodating portion is discharged through the discharge port, a supply driving portion configured to perform a supply operation of supplying the developer from the developer supplying container to the developer accommodating portion, a developer detection portion configured to detect the developer in the developer accommodating portion, an agitating conveyance portion configured to agitate the developer in the developer accommodating portion and convey the developer in the developer accommodating portion to the discharge port, an agitating driving portion configured to drive the agitating conveyance portion, and, a control portion including a processor and configured to control the supply driving portion and the agitating driving portion such that the supply operation is performed in a case where the developer is not detected by the developer detection portion and such that, each time the agitating conveyance portion is driven by a first driving amount, the supply driving portion is driven by a second driving amount in the supply operation. The control portion is configured to set a different value of the first driving amount on a basis of an amount of developer supplied from the developer supplying container to the developer accommodating portion per unit time. 
     According to a third aspect to the invention, a developer supplying device includes a developer supplying container configured to accommodate developer and attachable to and detachable from an image forming apparatus, a developer accommodating portion including a discharge port and configured to accommodate the developer supplied from the developer supplying container, the discharge port being configured such that the developer in the developer accommodating portion is discharged through the discharge port, a supply driving portion configured to perform a supply operation of supplying the developer from the developer supplying container to the developer accommodating portion, a developer detection portion configured to detect the developer in the developer accommodating portion, an agitating conveyance portion configured to agitate the developer in the developer accommodating portion and convey the developer in the developer accommodating portion to the discharge port, an agitating driving portion configured to drive the agitating conveyance portion, and a control portion including a processor and configured to control the supply driving portion and the agitating driving portion such that the supply operation is performed in a case where the developer is not detected by the developer detection portion and such that, each time the agitating conveyance portion is driven by a first driving amount, the supply driving portion is driven by a second driving amount in the supply operation. The control portion is configured to set a different value of the first driving amount in accordance with a supplying property in a case where the developer is supplied from the developer supplying container to the developer accommodating portion. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic configuration diagram of an image forming apparatus according to a first exemplary embodiment. 
         FIG. 2  is a section view of a developer supplying device according to the first exemplary embodiment. 
         FIG. 3  is a perspective view of a toner cartridge and a cap according to the first exemplary embodiment. 
         FIG. 4  is a perspective view of a hopper for description of a driving mechanism of the toner cartridge according to the first exemplary embodiment. 
         FIG. 5  is a perspective view of a supply port opening/closing mechanism according to the first exemplary embodiment. 
         FIG. 6  is a perspective view of the toner cartridge according to the first exemplary embodiment illustrating how toner is discharged therefrom. 
         FIG. 7  is a perspective view of the toner cartridge according to the first exemplary embodiment attached to an apparatus body. 
         FIG. 8  is an enlarged perspective view of a configuration in which the toner cartridge according to the first exemplary embodiment is rotatably supported. 
         FIG. 9  is a section view of the hopper in a state in which toner is detected by a toner detection sensor. 
         FIG. 10  is a section view of the hopper in a state in which toner is not detected by the toner detection sensor. 
         FIG. 11  illustrates the hopper according to the first exemplary embodiment viewed from above in a state in which a part of the hopper is cut off. 
         FIG. 12A  illustrates the hopper according to the first exemplary embodiment viewed from the side in a state in which a part of the hopper is cut off. 
         FIG. 12B  is an enlarged section view of a part of a second screw. 
         FIG. 13  is a perspective view of the hopper for description of a driving mechanism related to toner supply according to the first exemplary embodiment. 
         FIG. 14  is a control block diagram of the developer supplying device according to the first exemplary embodiment. 
         FIG. 15  is a section view of the hopper illustrating a state in which developer in the hopper reaches a supply port of the toner cartridge. 
         FIG. 16  illustrates a relationship between amounts of toner remaining in and amounts of toner discharged from the toner cartridge according to the first exemplary embodiment. 
         FIG. 17  is a flowchart illustrating a flow of control of the developer supplying device according to the first exemplary embodiment. 
         FIG. 18  illustrates a relationship between accumulated numbers of rotations of and amounts of toner remaining in a toner cartridge according to a second exemplary embodiment. 
         FIG. 19  is a flowchart illustrating a flow of control of a developer supplying device according to a third exemplary embodiment. 
         FIG. 20A  is a section view of the hopper illustrating a state of a powder surface of toner in the hopper when the toner detection sensor is in an off state in the third exemplary embodiment. 
         FIG. 20B  is a section view of the hopper illustrating a state of the powder surface of toner in the hopper after a supply operation to a developing unit is performed twenty times in the third exemplary embodiment. 
         FIG. 20C  is a section view of the hopper illustrating a state of the powder surface of toner in the hopper when the toner detection sensor is in an on state after supplying toner to the hopper in the third exemplary embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     First Exemplary Embodiment 
     A first exemplary embodiment will be described with reference to  FIGS. 1 to 17 . First, a schematic configuration of an image forming apparatus according to the present exemplary embodiment will be described with reference to  FIG. 1 . 
     Image Forming Apparatus 
     An image forming apparatus  60  is a color image forming apparatus employing an electrophotographic system, and is an image forming apparatus of a so-called intermediate transfer tandem type in which image forming portions PY, PM, PC, and PBk of four colors are arranged above an intermediate transfer belt  605 . In the image forming apparatus  60  having such a configuration, toner images formed by respective image forming portions are transferred onto a recording material to form a full-color toner image on the recording material. Examples of the recording material include sheet materials such as paper sheets, plastic films, and cloth. 
     Conveyance Process of Recording Material 
     First, a conveyance process of the recording material will be described. A recording material P is accommodated in a cassette  61  and is supported on a lift-up device  62  in the cassette  61 . The recording material P in the cassette  61  is conveyed to a conveyance path  64  by a feed roller  63   a  at a timing matching a timing of image formation. There is a case where a recording material P is conveyed into the conveyance path  64  from a manual feed tray  61 A provided on a side surface of an apparatus body  60 A of the image forming apparatus  60 . In addition, in the case where plural recording materials P are accommodated in the cassette  61 , one recording material P is separated from the other recording materials P by a frictional force of a separation roller  63   b  and conveyed by the feed roller  63   a.    
     The recording material P sent out by the feed roller  63   a  passes through the conveyance path  64 , and is conveyed to registration rollers  65 . The registration rollers  65  are devices for matching relative positions of the recording material P and a toner image on an intermediate transfer belt  605 , and convey the recording material P to a secondary transfer portion T 2  after performing skew correction and timing correction of the recording material P. The secondary transfer portion T 2  is a transfer nip portion formed by two opposing rollers of a secondary transfer inner roller  608  and a secondary transfer outer roller  66 , and a toner image on the intermediate transfer belt  605  is transferred onto the recording material P at the secondary transfer portion T 2  by being subjected to a predetermined pressurizing force and a predetermined electrostatic load bias. 
     Image Formation Process 
     Next, an image formation process of a toner image conveyed to the secondary transfer portion T 2  at a timing matching the conveyance process of the recording material P to the secondary transfer portion T 2  described above will be described. The image forming portions PY, PM, PC, and PBk respectively form toner images of yellow, magenta, cyan, and black. Hereinafter, correspondence with these colors will be also respectively indicated by reference letters Y, M, C, and Bk. The image forming portions PY, PM, PC, and PBk all have substantially the same configurations except that colors used for development are different. Therefore, the image forming portion PY will be described as a representative, and description of components of the other image forming portions will be omitted by just adding reference letters M, C, and Bk indicating the correspondence of the components with the image forming portions. 
     The image forming portion PY is mainly constituted by a photosensitive drum  611 Y, a charging unit  612 Y, an exposing unit  609 Y, a developing unit  613 Y, a primary transfer roller  618 Y, a drum cleaner  614 Y, and so forth. The photosensitive drum  611 Y is a photoconductor serving as an image bearing member. The surface of the photosensitive drum  611 Y is uniformly charged by the charging unit  612 Y in advance, and the photosensitive drum  611 Y rotates in an arrow D direction in  FIG. 1 . The exposing unit  609 Y is driven, on the basis of a signal of image information transmitted thereto, to expose, through a diffraction portion  610 Y as appropriate, the rotating photosensitive drum  611 Y to form an electrostatic latent image. The electrostatic latent image formed on the photosensitive drum  611 Y is developed by the developing unit  613 Y with toner serving as developer, and is visualized as a toner image on the photosensitive drum  611 Y. 
     Then, a predetermined pressurizing force and a predetermined electrostatic load bias are applied by the primary transfer roller  618 Y, and the toner image on the photosensitive drum  611 Y is transferred onto the intermediate transfer belt  605  through primary transfer. Transfer residual toner remaining on the photosensitive drum  611 Y by a small amount after the primary transfer is collected by the drum cleaner  614 Y for preparation for the next image formation. 
     Next, the intermediate transfer belt  605  will be described. The intermediate transfer belt  605  is stretched by rollers such as a driving roller  606 , a tension roller  607 , and the secondary transfer inner roller  608 , and is driven in an arrow direction in  FIG. 1 . Image formation processes of respective colors are performed in parallel by the image forming portions PY, PM, PC, and PBk at such timings that each downstream toner image is superimposed on each upstream toner image transferred onto the intermediate transfer belt  605  through primary transfer. As a result, a full-color toner image is finally formed on the intermediate transfer belt  605 , and is conveyed to the secondary transfer portion T 2 . 
     Process of Secondary Transfer and Subsequent Processes 
     According to the conveyance process of the recording material P and the image formation process described above, a full-color toner image is transferred onto the recording material P through secondary transfer at the secondary transfer portion T 2 . Transfer residual toner remaining on the intermediate transfer belt  605  by a small amount after the secondary transfer is collected by a belt cleaner  619 . Then, the recording material P is conveyed to a fixing unit  68  by a pre-fixing conveyance portion  67 . The fixing unit  68  applies a predetermined pressurizing force by opposing rollers, belts, or the like and heat by a heat source such as a heater to melt and fix the toner image on the recording material P. The recording material P bearing a fixed image obtained in this way is discharged onto a discharge tray  600 . In the case of forming images on both surfaces of the recording material P, the recording material P is again conveyed to the secondary transfer portion T 2  by an inversion conveyance device  650  through a duplex conveyance path  651 . 
     Supply of Developer to Developing Unit 
     In the case where image formation is performed as described above, toner in developing units  613 Y,  613 M,  613 C, and  613 Bk is consumed. Therefore, toners of respective colors are replenished by developer supplying devices  200 Y,  200 M,  200 C, and  200 Bk to the developing units  613 Y,  613 M,  613 C, and  613 Bk. In the present exemplary embodiment, two-component developer including nonmagnetic toner and magnetic carrier is used as the developer. 
     Therefore, a toner density is detected by an inductance sensor  620  serving as a density detection portion and provided in each of the developing units  613 Y,  613 M,  613 C, and  613 Bk corresponding to respective colors. In addition, developer is supplied from the developer supplying devices  200 Y,  200 M,  200 C, and  200 Bk to the developing units  613 Y,  613 M,  613 C, and  613 Bk on the basis of a result of detection by the inductance sensor  620 . The developer that is supplied may be only toner or include toner and carrier. A case where the developer that is supplied is toner will be described below. 
     Developer may be supplied in accordance with an amount of toner consumed in image formation instead of with the result of detection by the inductance sensor  620 . For example, developer may be supplied on the basis of a video count value obtained by integrating a level of each pixel in image information corresponding to one image. For example, the level is in a range of 0 to 255 levels. In addition, developer may be supplied by forming an image for control, for example, a patch image, on a photosensitive drum or the intermediate transfer belt  605  and detecting the density of the patch image. 
     Developer Supplying Device 
     Next, configurations of the developer supplying devices  200 Y,  200 M,  200 C, and  200 Bk described above will be described. A developer supplying portion A including the developer supplying devices  200 Y,  200 M,  200 C, and  200 Bk is attached to an upper portion of a back surface of the apparatus body  60 A as illustrated in  FIG. 1 . The developer supplying devices  200 Y,  200 M,  200 C, and  200 Bk have substantially the same configurations except that the colors of toner are different. Therefore, the developer supplying device  200 Y will be described as a representative, and description of the other developer supplying devices will be omitted. 
     The developer supplying device  200 Y includes a toner cartridge  14  and a hopper  201  as illustrated in  FIG. 2 . The toner cartridge  14  serves as a developer supplying container configured to accommodate toner serving as developer. The hopper  201  includes a container  202  serving as a developer accommodating portion and including a discharge port  206  illustrated in  FIG. 12 , and developer is supplied to the container  202  from the toner cartridge  14 . In addition, the hopper  201  is capable of supplying the developer to the developing unit  613 Y. That is, functions of the developer supplying device  200 Y include supply of toner to the developing unit  613 Y and supply of toner to the hopper  201  from the toner cartridge  14 . The developer supplying device  200 Y is disposed above the developing unit  613 Y to facilitate supply of toner to the developing unit  613 Y. 
     In the developer supplying device  200 Y, a tip end portion of the toner cartridge  14  is set at a receiving port  201 A of the hopper  201  as illustrated in  FIG. 2 . The developer supplying device  200 Y is configured such that a toner storage portion  18  of the container  202  stores the toner supplied from the toner cartridge  14 , and an agitating conveyance portion  203  in the hopper  201  agitates and conveys the stored toner to the developing unit  613 Y. That is, the agitating conveyance portion  203  agitates the developer in the container  202  and conveys the developer in the container  202  to the discharge port  206 . Therefore, the agitating conveyance portion  203  includes agitating screws  11 , a first screw  12 , and a second screw  13 . The configuration and operation of the agitating conveyance portion  203  will be described later in detail. 
     In addition, the hopper  201  includes a supply port opening/closing mechanism B. The supply port opening/closing mechanism B includes a motor  21 , a drive transmission portion  19 , a cam gear  19 A, and an engagement member  16 . The motor  21  serves as a drive source. When toner is supplied from the toner cartridge  14 , the engagement member  16  of the supply port opening/closing mechanism B is engaged with the cap  15  provided at the tip end of the toner cartridge  14  in a manner that will be described below. As a result of this, the cap  15  is openable and closable, and the toner cartridge  14  is rotatable. As will be described later in detail, in the present exemplary embodiment, toner can be supplied from the toner cartridge  14  to the hopper  201  by rotating the toner cartridge  14 . Details of each component will be sequentially described below. 
     First, a function of supplying toner from the toner cartridge  14  to the hopper  201  will be described. The cap  15  is provided at the tip end of the toner cartridge  14  so as to be movable parallel to a rotational axis direction serving as an axial direction of the toner cartridge  14 . A supply port  14 A illustrated in  FIG. 6  provided at the tip end of the toner cartridge  14  can be opened and closed by the movement of the cap  15  in the axial direction. The supply port  14 A of the toner cartridge  14  is normally closed by the cap  15 , and cannot be easily opened by a user. 
     The user sets the toner cartridge  14  at a predetermined position in the apparatus body  60 A while inserting the tip end of the toner cartridge  14  in the receiving port  201 A of the hopper  201 . At this time, the cap  15  provided at the tip end of the toner cartridge  14  is not engaged with the engagement member  16  of the supply port opening/closing mechanism B as illustrated in  FIG. 3 , and thus toner cannot be supplied from the toner cartridge  14  to the hopper  201 . Next, in the case where the user having securely set the toner cartridge  14  is detected by an unillustrated sensor, a control portion  100  illustrated in  FIG. 14  drives the supply port opening/closing mechanism B to open the cap  15  provided at the tip end of the toner cartridge  14 . The control portion  100  is provided in the apparatus body  60 A, and controls each component of the image forming apparatus  60 . 
     As illustrated in  FIG. 4 , in the case where the motor  21  of the supply port opening/closing mechanism B is rotated in a normal rotation direction, a driving force is transmitted to the cam gear  19 A via the drive transmission portion  19  constituted by a gear train or the like as indicated by an arrow α 1 . The cam gear  19 A includes a gear on an outer peripheral surface and a cam surface on an inner peripheral surface as illustrated in  FIG. 5 , and a cylinder member  28  is disposed inside the cam gear  19 A so as to be movable in the axial direction. The cam surface includes a groove, and the cylinder member  28  engages with the cam surface. In the case where the cam gear  19 A is rotated in an arrow β direction illustrated in  FIG. 5  by the rotation of the motor  21  in the normal rotation direction, the cylinder member  28  moves forward in the axial direction due to the engagement with the cam surface of the cam gear  19 A. That is, the cylinder member  28  moves toward the toner cartridge  14  along the axial direction. 
     At this time, the engagement member  16  moves in the axial direction together with the cylinder member  28 , and thus the engagement member  16  engages with the cap  15  at the tip end of the toner cartridge  14 . In the case where the cam gear  19 A is further rotated in the arrow β direction, the cylinder member  28  moves backward due to the engagement with the cam surface. That is, the cylinder member  28  moves away from the toner cartridge  14  along the axial direction. At this time, the engagement member  16  engaged with the cap  15  moves together with the cylinder member  28 , and thus the cap  15  is pulled out and the supply port  14 A of the toner cartridge  14  is opened as illustrated in  FIG. 6 . 
     Here, in the case where the motor  21  illustrated in  FIG. 4  is rotated in a reverse rotation direction, the driving force is branched off by a one-way gear  20 , and is transmitted to a cartridge driving shaft  27  as indicated by an arrow α 2 . The cartridge driving shaft  27  is connected to the engagement member  16  in an integrated manner, and thus the engagement member  16  is rotated by the rotation of the cartridge driving shaft  27  and the cap  15  engaged with the engagement member  16  is also rotated. The cap  15  is movable in the axial direction with respect to the toner cartridge  14 , and is capable of rotating together with the toner cartridge  14 . Accordingly, the toner cartridge  14  is also rotated by the rotation of the cap  15 . 
     The toner cartridge  14  has a bottle shape in which a spiral groove  14 C is defined in a cartridge body  14 B as illustrated in  FIG. 7 . In addition, as illustrated in  FIG. 2 , a scooping member  14 D is provided in the cartridge body  14 B at a position in the vicinity of an exit port of the cartridge body  14 B. Further, as illustrated in  FIGS. 7 and 8 , the toner cartridge  14  is disposed on a tray  26  so as to be rotatable with rollers  25  interposed therebetween. The tray  26  is provided at a predetermined position in the apparatus body  60 A. Therefore, the rotation of the toner cartridge  14  is smoothened by the rollers  25 . 
     In the case where the toner cartridge  14  rotates as indicated by arrows in  FIG. 6 , toner accommodated in the toner cartridge  14  is conveyed along the groove  14 C to a portion in the vicinity of the exit port of the cartridge body  14 B, and is scooped by the scooping member  14 D to be conveyed to the supply port  14 A. Then, toner is discharged through the supply port  14 A. Since the supply port  14 A has gotten in the hopper  201 , toner discharged through the supply port  14 A drops into the container  202 , and is stored in the toner storage portion  18 . In this way, in the case where the toner cartridge  14  rotates, toner is conveyed as an effect of the spiral groove  14 C, and is supplied from the toner cartridge  14  to the container  202  of the hopper  201 . In the present exemplary embodiment, the toner cartridge  14  corresponds to a developer supplying container, and the motor  21  corresponds to a supply driving portion. 
     As illustrated in  FIGS. 9 and 10 , a toner sensor  17  serving as a developer detection portion configured to detect developer in the container  202  is provided at a predetermined height in the toner storage portion  18 . The toner sensor  17  is a pressure sensor and detects the pressure of toner t in the case where the toner t is present on the surface of the toner sensor  17  as illustrated in  FIG. 9 . Thus, the control portion  100  recognizes that toner is present in the container  202 . 
     In contrast, in the case where the toner in the toner storage portion  18  is consumed by supplying toner from the hopper  201  to the developing unit  613 Y, the toner t becomes no longer present on the surface of the toner sensor  17  as illustrated in  FIG. 10 . In this case, the control portion  100  recognizes that toner is not present in the container  202 , and toner is supplied from the toner cartridge  14  to the hopper  201  as will be described later. That is, the control portion  100  performs a supply operation of toner by rotating the toner cartridge  14  in the case where toner is not detected by the toner sensor  17 . 
     The toner sensor  17  may be configured as a sensor that is not a pressure sensor as long as the toner sensor  17  is capable of detecting the presence of toner. For example, the toner sensor  17  may be an optical sensor that includes a light emitting portion and a light receiving portion configured to receive light emitted by the light emitting portion and detects the presence of toner between the light emitting portion and the light receiving portion. 
     Next, a configuration of supplying toner from the hopper  201  to the developing unit  613 Y will be described. The hopper  201  includes the container  202 , the agitating conveyance portion  203 , a motor  22 , and the drive transmission portion  23 . The motor  22  serves as a drive source and an agitating driving portion. The agitating conveyance portion  203  includes the agitating screws  11 , the first screw  12 , and the second screw  13  each disposed in the container  202  as described above. The agitating screws  11  serve as agitating members, and the second screw  13  serves as a conveyance member. 
     As illustrated in  FIG. 11 , two agitating screws  11  are arranged parallel so as to be capable of agitating toner in the toner storage portion  18 . The agitating screws  11  are each constituted by a rotation shaft  11   a  and an agitating portion  11   b  provided around the rotation shaft  11   a . The agitating portion  11   b  has a substantially elliptical shape that is hollow inside. According to this, toner smoothly flows in arrow  301  directions while being agitated by the rotation of the agitating screws  11 . As described above, the agitating screws  11  are configured to be mainly capable of agitating toner such that clogging with toner does not occur from excess conveyance of toner by the agitating screws  11 . 
     Meanwhile, the first screw  12  is disposed parallel to the two agitating screws  11  between the agitating screws  11  as illustrated in  FIGS. 11 and 12A . The first screw  12  is constituted by a rotation shaft  12   a  and blades  12   b  and  12   c  provided in a spiral shape around the rotation shaft  12   a . The blades  12   b  and  12   c  are formed in opposite directions to each other around the rotation shaft  12   a , and each convey toner in a direction to approach the other of the blades  12   b  and  12   c  as a result of the rotation shaft  12   a  rotating in a predetermined direction. The toner conveyed by the agitating screws  11  in the arrow  301  directions illustrated in  FIG. 11  is conveyed in an arrow  302  direction by the first screw  12  between the two agitating screws  11 . 
     A communication port  204  is defined below a substantially center portion of the first screw  12  as illustrated in  FIGS. 2 and 12A . The toner conveyed in the arrow  302  direction by the first screw  12  drops downward through the communication port  204 . At this time, the toner conveyed in the arrow  302  direction by the blade  12   b  is pushed back by the blade  12   c , and thus drops in the communication port  204  efficiently. 
     A discharge path  205 , which is a part of the container  202 , is formed below the communication port  204 . The discharge path  205  is formed in a direction substantially perpendicular to the agitating screws  11  and the first screw  12 . In addition, the second screw  13  is disposed in the discharge path  205  along the discharge path  205 . 
     As illustrated in  FIGS. 11 and 12A , the second screw  13  is constituted by a rotation shaft  13   a  and a blade  13   b  provided in a spiral shape around the rotation shaft  13   a , and conveys tonner having dropped into the discharge path  205  in an arrow  303  direction. The discharge port  206  that is an opening facing downward is provided at a downstream end portion of the discharge path  205  in the conveyance direction of toner. Accordingly, the second screw  13  conveys the toner in the container  202  to the discharge port  206 . The discharge port  206  communicates with the developing unit  613 Y, and the toner discharged through the discharge port  206  is supplied to the developing unit  613 Y. 
     The agitating screws  11 , the first screw  12 , and the second screw  13  having these configurations are rotated by the motor  22  via the drive transmission portion  23  as illustrated in  FIG. 13 . Specifically, in the case where the control portion  100  receives a signal indicating shortage of toner from the inductance sensor  620  in the developing unit  613 Y, the motor  22  is driven such that an appropriate amount of toner is supplied to the developing unit  613 Y. 
     The driving force of the motor  22  is transmitted to each of the rotation shafts of the agitating screws  11 , the first screw  12 , and the second screw  13  via the drive transmission portion  23 , which is constituted by a gear train or the like, as indicated by arrows γ in  FIG. 13 . According to this, each screw rotates as described above, and toner is supplied from the hopper  201  to the developing unit  613 Y. In the present exemplary embodiment, each screw is driven by rotating a single motor  22  in a predetermined direction as described above, and thus the costs for the developer supplying device  200 Y can be cut. 
     In addition, as illustrated in  FIG. 12A , a sensor flag  29   a  is provided at an end portion of the rotation shaft  13   a  of the second screw  13 . The rotational phase of the second screw  13  can be detected by detecting the sensor flag  29   a  by a rotation sensor  29   b . In the present exemplary embodiment, the control portion  100  detects the rotation of the second screw  13  on the basis of a detection signal of the rotation sensor  29   b . An appropriate amount of toner can be supplied from the hopper  201  to the developing unit  613 Y by rotating the second screw  13  a set number of times. 
     Specifically, the second screw  13  is controlled to rotate once in one supply operation. The weight Q of toner conveyed, that is, the amount of toner supplied to the developing unit  613 Y, by one rotation of the second screw  13  can be obtained as follows. That is, in the case where P represents a screw pitch, D represents an outer diameter of the screw, and d represents a shaft diameter of the screw as illustrated in  FIG. 12B , and μ represents a filling efficiency and γ represents a bulk density of toner in the discharge path  205 , the amount Q of toner supply can be obtained by the following equation. In this case, the outer diameter of the screw corresponds to the outer diameter of the blade  13   b , and the shaft diameter of the screw corresponds to the diameter of the rotation shaft  13   a . 
             Q   =       π   4     ⁢     (       D   2     -     d   2       )     *   μ   ⁢           ⁢   P   *   γ           
Control Portion
 
     Here, relationships between the control portion  100  that performs control as described above and the motors and sensors will be described with reference to  FIG. 14 . The control portion  100  includes a central processing unit: CPU  101 , a read-only memory: and ROM  102 , a random access memory: RAM  103 . The ROM  102  stores programs corresponding to control procedures and so forth. The CPU  101  is configured to read out the programs and control each component. In addition, RAM  102  stores data for work and input data. The CPU  101  is configured to perform control by referring to the data stored in the RAM  102  on the basis of the programs and so forth described above. 
     The operations of the motors  21  and  22  and output of the respective sensors  620 ,  17 , and  29   b  described above are controlled by the CPU  101  of the control portion  100 . That is, the CPU  101  controls the operations of the motors  21  and  22  as described above on the basis of output signals from the respective sensors  620 ,  17 , and  29   b  while referring to the ROM  102  and the RAM  103 . 
     Detection of Toner in Hopper 
     As described above, the toner sensor  17  detects the presence of toner in the hopper  201 . However, it is known that properties of toner change in accordance with the environment and that particularly the fluidity thereof decreases in a high-temperature and high-humidity environment. In addition, the fluidity also decreases due to the deterioration of the toner. The effect of decrease in the fluidity will be described with reference to  FIG. 15 . In the case where the fluidity decreases, a powder surface of the toner in the container  202  of the hopper  201  does not spread in the horizontal direction, and the heap of toner becomes higher in the vertical direction. Here, an angle indicated by θ in  FIG. 15  will be referred to as an angle of repose of toner. 
     In the case where the angle of repose of toner increases, toner does not come into contact with the toner sensor  17  even though a sufficient amount of toner is in the container  202 . The toner cartridge  14  is driven in accordance with the detection of toner by the toner sensor  17  to supply toner to the hopper  201  as described above. Therefore, in the case where the toner cartridge  14  is driven in a state in which the toner is in a shape of a heap, the toner eventually reaches the supply port  14 A of the toner cartridge  14 . In the case where an inclined surface of the heap of toner is not in contact with the toner sensor  17  and the output of the toner sensor  17  does not indicate the presence of toner even in this state, the toner cartridge  14  is kept driven. However, in the state where the supply port  14 A is clogged, toner is not likely to be further discharged no matter how long the toner cartridge  14  is driven. 
     Here, in the case where the toner sensor  17  does not detect toner even after driving the toner cartridge  14  for a predetermined period of time, the CPU  101  of the control portion  100  determines that toner is not present in the toner cartridge  14 . Then, for example, a screen indicating that the toner cartridge  14  needs to be replaced is displayed on a display portion provided for the image forming apparatus  60 . 
     Accordingly, in the case where the toner in the container  202  of the hopper  201  is in a shape of a heap as described above, toner is sometimes not detected by the toner sensor  17  even after driving the toner cartridge  14  for the predetermined period of time. Moreover, there is a possibility that the control portion  100  erroneously determines that toner is not present in the toner cartridge  14  even in the case where toner is present in the toner cartridge  14 . In addition, in the case where the toner cartridge  14  is kept rotating until determination of replacement in a state in which toner is in contact with the toner cartridge  14  in the vicinity of the supply port  14   a , the toner deteriorates due to friction. Therefore, in the present exemplary embodiment, the following toner supply sequence is performed. 
     Toner Supply Sequence 
     A toner supply sequence performed at the time of supplying toner from the toner cartridge  14  into the hopper  201  will be described. In the case where the CPU  101  determines that toner is not present on the basis of a detection signal from the toner sensor  17  provided in the container  202  of the hopper  201 , the CPU  101  outputs a command to drive the toner cartridge  14  in accordance with a flowchart of  FIG. 17  that will be described later. 
     In the present exemplary embodiment, the toner supply sequence is set in three stages 1 to 3 in accordance with the amount of remaining toner in the toner cartridge  14 . The stage 1 is performed at a time immediately after replacement of the toner cartridge  14  at which plenty of new toner is in the toner cartridge  14 . The stage 2 is performed when the amount of remaining toner in the toner cartridge  14  is about 20% to 80% of a filled-up state. The stage 3 is performed when the amount of remaining toner in the toner cartridge  14  is less than 20% of the filled-up state. 
     The reason why the respective stages are set in accordance with the amount of remaining toner in the toner cartridge  14  as described above is because the amount of toner discharged from the toner cartridge  14 , that is, a supply property of the toner cartridge  14 , is not always constant.  FIG. 16  illustrates a relationship between amounts of remaining toner in the toner cartridge  14  and amounts of discharge from the toner cartridge  14  per unit time. To be noted, the driving speed of the toner cartridge  14  is the same in all the stages. In addition, the weight of toner in the case where the toner cartridge  14  is filled up with toner is set as 100%. 
     First, the amount of discharged toner per unit time when the amount of remaining toner is 80% to 100%, that is, 80% or larger and 100% or smaller, is equal to or smaller than 1 g/s. In addition, although the amount of discharge overall has a tendency to increase as the discharge of toner progresses, that is, as the amount of remaining toner in the toner cartridge  14  decreases, the amount of discharged toner also slightly decreases in a part of the whole process. This is because the density of toner becomes uneven in the toner cartridge  14  due to the inclination of the toner cartridge  14  at which the toner cartridge  14  is stored and vibrations applied to the toner cartridge  14  during transportation. However, this unevenness of toner density is temporary, and is cancelled after the toner cartridge  14  is driven and rotated. 
     Next, when the amount of remaining toner is 50% to 80%, that is, 50% or larger and smaller than 80%, the unevenness of toner in the toner cartridge  14  is cancelled, and the amount of discharged toner stably increases. In addition, when the amount of remaining toner is 20% to 50%, that is, 20% or larger and smaller than 50%, the amount of discharged toner gradually decreases along with decrease of the amount of toner in the toner cartridge  14 . 
     Further, when the amount of remaining toner is 0% to 20%, that is, 0% or larger and smaller than 20%, the amount of discharged toner steeply decreases because it becomes difficult for the scooping member  14 D illustrated in  FIG. 2  to scoop toner due to further decrease of the amount of toner in the toner cartridge  14 . 
     In consideration of such a toner discharge property, the stage corresponding to the amount of remaining toner in the toner cartridge  14  of 80% to 100% is set as the stage 1, the stage corresponding to the amount of remaining toner of 20% to 80% is set as the stage 2, and the stage corresponding to the amount of remaining toner 0% to 20% is set as the stage 3. In addition, the range of amount of remaining toner from 20% to 80%, that is, 20% or larger and smaller than 80%, corresponding to the stage 2 is set as a first range, the range of amount of remaining toner from 0% to 20%, that is, 0% or larger and smaller than 20%, corresponding to the stage 3, which corresponds to a smaller amount of remaining toner than the first range, is set as a second range. Meanwhile, the range of amount of remaining toner from 80% to 100%, that is, 80% or larger and 100% or smaller, corresponding to the stage 1, which corresponds to a larger amount of remaining toner than the first range, is set as a third range. 
     Detection of Amount of Remaining Toner in Toner Cartridge 
     Next, a configuration of detecting the amount of remaining toner in the toner cartridge  14  will be described. The control portion  100  calculates the amount of remaining developer in the toner cartridge  14  from the driving amount of the agitating conveyance portion  203 . That is, the control portion  100  detects the amount of remaining developer in the toner cartridge  14  by calculation. Detailed description will be given below. 
     In the case where the CPU  101  of the control portion  100  receives a signal indicating shortage of toner from the inductance sensor  620  of the developing unit  613 Y, the CPU  101  drives the motor  22  to rotate the second screw  13  of the agitating conveyance portion  203 . At this time, the CPU  101  counts the number of rotations of the second screw  13  on the basis of a signal from the rotation sensor  29   b . That is, the CPU  101  can detect the number of rotations serving as a driving amount of the second screw  13  as a result of the rotation sensor  29   b  detecting the sensor flag  29   a  provided on the rotation shaft  13   a  of the second screw  13 . An integrated value of the number of rotations of the second screw  13  is stored in a memory such as the RAM  103 . 
     Here, toner in the toner cartridge  14  is temporarily supplied to the hopper  201 , and is then conveyed to the developing unit  613 Y by the first screw  12  and the second screw  13 . As described above, the amount of conveyance by one supply operation, that is, one rotation, of the second screw  13  is determined in advance. In addition, in the case where the amount of toner in the hopper  201  decreases and the toner sensor  17  indicates absence of toner, the control portion  100  drives the motor  21  to rotate the toner cartridge  14 , and thus toner is supplied from the toner cartridge  14  to the hopper  201 . 
     Therefore, the amount of consumption of the toner in the toner cartridge  14  that has been consumed can be obtained by counting the number of times the supply operation to the developing unit  613 Y has been performed, that is, the number of times the second screw  13  has been rotated, after the toner cartridge  14  has been replaced by a new toner cartridge. Specifically, the amount of consumption of the toner in the toner cartridge  14  can be calculated by multiplying the number of supply operations by the amount of conveyed toner for one supply operation represented by the weight Q of toner. In the present exemplary embodiment, the amount of toner with which the toner cartridge  14  is filled is 1000 g, and the amount of conveyed toner per rotation of the second screw  13  is 0.3 g. Accordingly, each time one supply operation to the developing unit  613 Y is performed, the amount of remaining toner in the toner cartridge  14  decreases by 0.3/1000 =0.03%. 
     As described above, in the present exemplary embodiment, the CPU  101  counts the number of times the supply operation to the developing unit  613  has been performed, and calculates the amount of remaining toner in the toner cartridge  14  from the value of the count, that is, the driving amount of the agitating conveyance portion  203 . Then, to which of the stages 1 to 3 the amount of remaining toner in the toner cartridge  14  corresponds is determined, and the following control is performed. 
     Supply Control of Toner 
     In the present exemplary embodiment, the control portion  100  performs the supply operation of toner by the toner cartridge  14  in the case where toner is not detected by the toner sensor  17  in the hopper  201 , that is, in a sensor off state. As described above, the supply operation of toner is performed by conveying the toner in the toner cartridge  14  by the spiral groove  14 C defined in the toner cartridge  14  by driving the motor  21  to rotate the toner cartridge  14 . Therefore, the driving amount or the number of times of driving of the toner cartridge  14  that will be used in the description below corresponds to the driving amount or the number of times of driving of the motor  21  serving as a supply driving portion. In addition, the control portion  100  controls the motors  21  and  22  such that, in the supply operation, each time the second screw  13  of the agitating conveyance portion  203  is driven by a first driving amount, the toner cartridge  14  is driven by a second driving amount. Further, the control portion  100  sets the first driving amount to a different value on the basis of the amount of remaining toner in the toner cartridge  14  calculated by the CPU  101  as described above and serving as a detection result. In the present exemplary embodiment, different values of the first driving amount are set for the stages 1 to 3 described above, and the second driving amount is set to “1” regardless of the stage. 
     A flow of toner supply control by the developer supplying device  200 Y of the present exemplary embodiment having such a configuration common to the stages 1 to 3 will be described with reference to  FIG. 17 . First, in step S 1 , counts T and N of the number of times of driving of the toner cartridge  14  is set to 0 for preparation for driving of the toner cartridge  14 . 
     Here the count T represents the number of times of driving of the toner cartridge  14  in the supply operation from the toner cartridge  14  to the hopper  201  and corresponds to the second driving amount described above, which is 1 in the present exemplary embodiment. In addition, the count N is a threshold value used for emptiness determination in which it is determined that the toner cartridge  14  is empty, and is set to  50  in the present exemplary embodiment. This count of times of driving of the toner cartridge  14  is performed by the control portion  100 . 
     Next, after a state in which toner has been supplied from the hopper  201  to the developing unit  613 Y and the toner is not detected by the toner sensor  17 , that is, an off state, is taken in step S 2 , the control portion  100  outputs a command to drive the motor  21 , and the toner cartridge  14  starts to be driven. At this time, the toner cartridge  14  keeps on being driven for four seconds in step S 3 , and then stops for one second in step S 4 . The driving and stopping of the toner cartridge  14  in steps S 3  and S 4  will be defined as one cycle. 
     After one cycle of the driving and stopping of the toner cartridge  14  finishes, the counts T and N of times of driving of the toner cartridge  14  are increased by one, that is, T=T+1 and N=N+1 are performed in step S 5 . Next, the state of the toner sensor  17  is checked in step S 6 , and, in the case where the toner sensor  17  is in a state of detecting toner, that is, an on state, information indicating the state is transmitted to the control portion  100 , the process returns to step S 1 , and the counts T and N of times of driving of the toner cartridge  14  are reset to 0. Then, the developer supplying device  200 Y takes a stand-by state until the toner sensor  17  is in the off state again as a result of the supply operation from the hopper  201  to the developing unit  613 Y. 
     In contrast, in the case where the toner sensor  17  is still in the off state in step S 6 , it is determined in step S 7  whether the count T of times of driving of the toner cartridge  14  has reached the threshold value serving as the second driving amount. Since the threshold value is 1, the process proceeds to step S 8  in this case. To be noted, the threshold value can be set as appropriate. For example, in the case where the threshold value is set to 2, the process returns to step S 3 , and the driving and stopping of the toner cartridge  14  is performed for one more cycle. In the case where the count T has reached the threshold value, it is determined in step S 8  whether the count N has reached 50. This determination will be described later. 
     In the case where the count N is equal to or smaller than 50 in step S 8 , whether the supply operation from the hopper  201  to the developing unit  613 Y has been performed a predetermined number of times M corresponding to the first driving amount is checked in step S 9 . That is, the CPU  101  determines whether the second screw  13  of the hopper  201  is driven M times while the toner cartridge  14  is driven for one cycle. The count of the supply operation to the developing unit  613 Y is performed starting from step S 3 . 
     Here, the supply operation from the hopper  201  to the developing unit  613 Y is performed on the basis of the result of detection by the inductance sensor  620 . In the case where the CPU  101  determines, on the basis of the detection result, not to perform the supply operation, the number of times of the supply operation is of course not counted. In the case where the supply operation has not been performed M times, the process returns to step S 6 , and the developer supplying device  200 Y takes a stand-by state for the supply operation of toner. In contrast, in the case where the supply operation has been performed M times, the process returns to step S 3 , and the toner cartridge  14  is driven. 
     This point will be described in further detail. The information from the inductance sensor  620  disposed in the developing unit  613 Y is always transmitted to the control portion  100 . The CPU  101  of the control portion  100  determines the state of the inductance sensor  620 , and determines whether the supply operation is needed from the result of the determination. Then, in the case where it is determined that the supply operation is needed, a command to perform the supply operation is output, for the first time, to the motor  22  that drives the agitating conveyance portion  203 . Therefore, by checking whether the command has been output, the control portion  100  counts the number of times of the supply operation from the hopper  201  to the developing unit  613 Y and further checks whether the supply operation has been performed the predetermined number of times M. 
     In the case where the supply operation to the developing unit  613 Y has been performed M or more times in step S 3  or step S 4  since the most recent start of driving of the toner cartridge  14 , the process transitions to step S 3 , and the flow of the flowchart is sequentially performed in the same manner as the sequence of the first stage. In contrast, in the case where the number of times of the supply operation to the developing unit  613 Y has not reached M, the process returns to step S 6 , and the toner cartridge  14  remains stopped. Accordingly, unless a detection state of the inductance sensor  620  does not indicate that the supply operation is needed, the command to perform the supply operation to the developing unit  613 Y is not output, and the driving of the toner cartridge  14  remains stopped. 
     As described above, in the present exemplary embodiment, the process cannot transition to step S 3  to start the second cycle of driving and stopping of the toner cartridge  14  until the toner sensor  17  takes the off state, the toner cartridge  14  starts the first driving and stopping cycle, and the supply operation to the developing unit  613 Y is performed M times. That is, the toner cartridge  14  is driven once, which corresponds to the second driving amount, each time the supply operation to the developing unit  613 Y is performed M times, in other words, each time the second screw  13  is rotated a number of times corresponding to the first driving amount. 
     In the case where the supply operation to the developing unit  613 Y is performed, the second screw  13  and the agitating screws  11  rotate along with the supply operation. In this case, the heap of toner formed in the container  202  of the hopper  201  is leveled to some extent, and the amount of toner in the container  202  decreases by an amount corresponding to the toner supplied to the developing unit  613 Y. Therefore, even in the case where the heap of toner is so high as to reach the supply port  14   a  of the toner cartridge  14 , the height of the heap is reduced. 
     Here, as described above with reference to  FIG. 16 , the amount of discharged toner per unit time varies depending on the amount of remaining toner in the toner cartridge  14 . That is, the supplying property in a case where the toner is supplied from the toner cartridge  14  to the container  202  of the hopper  201  according to the driving of the toner cartridge  14  varies. Therefore, in the case where the first driving amount described above is set to a uniform value regardless of the amount of remaining toner in the toner cartridge  14 , there is a possibility that the heap of toner in the container  202  cannot be sufficiently leveled or the height of the heap cannot be sufficiently reduced. 
     For example, in the case where the amount of discharged toner per unit time is large and the supply operation is performed once each time the toner cartridge  14  is driven for one cycle, next supply from the toner cartridge  14  is performed before the heap of toner is sufficiently leveled or the height of the heap is sufficiently reduced. In the case where the heap of toner is not sufficiently leveled, the toner is not detected by the toner sensor  17  as illustrated in  FIG. 15 , and toner is further supplied from the toner cartridge  14 . In addition, in the case where toner is supplied again from the toner cartridge  14  without the height of the heap of toner being sufficiently reduced, the heap of toner comes into contact with the toner cartridge  14  in the vicinity of the supply port  14   a , and the toner deteriorates due to the friction. 
     In contrast, in the case where the amount of discharged toner per unit time is small and the supply operation is performed, for example, five times each time the toner cartridge  14  is driven for one cycle, there is a possibility that the supply of toner from the toner cartridge  14  to the hopper  201  does not keep up with the supply of toner from the hopper  201  to the developing unit  613 Y. In addition, in the case where the supply operation is performed more times, the period of time in which the toner is agitated by the rotation of the agitating screws  11  also becomes longer, and thus the deterioration of toner is accelerated. Therefore, in the present exemplary embodiment, different values of the first driving amount are set for the stages 1 to 3 described above. That is, different values of the first driving amount are set in accordance with the supplying property, or, the discharge property, of the toner from the toner cartridge  14 , and, in the present exemplary embodiment, the supplying property is defined by the amount of remaining toner in the toner cartridge  14 . 
     Stage 2 
     First, in the stage 2, the amount of remaining toner is in the range of 20% to 80%, that is, 20% or larger and smaller than 80%, serving as the first range. In this case, the predetermined number of times M serving as the first driving amount is set to 5 serving as a first amount. That is, in the stage 2, the toner cartridge  14  is driven once, that is, for one cycle, each time the supply operation to the developing unit  613 Y is performed five times, that is, each time the second screw  13  is rotated five times. 
     As illustrated in  FIG. 16 , the amount of discharged toner per unit time is large in the stage 2. Therefore, a large amount of toner is supplied to the container  202  of the hopper  201  by driving the toner cartridge  14  for one cycle, and thus the height of the heap of toner in the container  202  is likely to be large. Thus, in the present exemplary embodiment, the supply operation from the hopper  201  to the developing unit  613 Y is performed five times each time the toner cartridge  14  is driven for one cycle. Further, the agitating screws  11  are used for sufficiently leveling the heap of toner, and the height of the heap is reduced by supplying toner to the developing unit  613 Y. 
     As described above, by agitating the toner in the container  202  along with the supply operation to the developing unit  613 Y, the heap of toner in the container  202  can be efficiently leveled. As a way of leveling the heap of toner, also agitating the toner in the hopper  201  in a period in which the supply operation is not performed can be considered. However, the deterioration of toner is accelerated in this case. 
     In contrast, in the present exemplary embodiment, the toner in the container  202  is agitated only during the supply operation, and thus the acceleration of deterioration of toner can be suppressed. In addition, since the threshold value is reset in the case where it is determined by the toner sensor  17  that toner is present, it becomes possible to keep on efficiently discharging toner from the toner cartridge  14 . 
     Stage 3 
     Next, in the stage 3, the amount of remaining toner is in the range of 0% to 20%, that is, 0% or larger and smaller than 20%, serving as the second range, which corresponds to a smaller amount than the first range. In this case, the predetermined number of times M serving as the first driving amount is set to 1 serving as a second amount, which is smaller than 5 serving as the first amount. That is, in the stage 3, the toner cartridge  14  is driven once, that is, for one cycle, each time the supply operation to the developing unit  613 Y is performed once, that is, each time the second screw  13  is rotated once. 
     As illustrated in  FIG. 16 , the amount of discharged toner per unit time steeply decreases in the stage 3. Accordingly, the amount of toner supplied to the container  202  of the hopper  201  by driving the toner cartridge  14  for one cycle is small. Meanwhile, the state of the toner sensor  17  in the container  202  does not change from the off state to the on state unless the amount of toner supplied from the toner cartridge  14  to the hopper  201  surpasses the amount of toner supplied from the hopper  201  to the developing unit  613 Y. Therefore, in the present exemplary embodiment, the supply operation from the hopper  201  to the developing unit  613 Y is performed once each time the toner cartridge  14  is driven for one cycle. Further, the amount of toner supplied from the toner cartridge  14  to the hopper  201  is set so as to surpass the amount of toner supplied from the hopper  201  to the developing unit  613 Y. 
     Stage 1 
     Next, in the stage 1, the amount of remaining toner is in the range of 80% to 100%, that is, 80% or larger and 100% or smaller, serving as the third range, which corresponds to a larger amount than the first range. In this case, the predetermined number of times M serving as the first driving amount is set to 0. That is, in the stage 1, the toner cartridge  14  is driven until the toner sensor  17  takes the on state regardless of the supply operation to the developing unit  613 Y. 
     As illustrated in  FIG. 16 , the toner discharge property of the toner cartridge  14  is not stable in the stage 1. In addition, the image forming apparatus  60  is not operating and toner is not present in the developing unit  613 Y immediately after replacement of the toner cartridge  14 . Therefore, the supply operation from the hopper  201  to the developing unit  613 Y is not performed until the toner sensor  17  in the container  202  of the hopper  201  takes the on state. Thus, in the present exemplary embodiment, the predetermined number of times M is set to 0, and the toner cartridge  14  is driven without waiting for the supply operation to the developing unit  613 Y. 
     The determination of emptiness of the toner cartridge  14  performed in step S 8  will be described herein. In the case where the toner sensor  17  is in the off state in step S 6  and the process proceeds to step S 8 , it is determined whether the count N of times of driving of the toner cartridge  14  exceeds 50. In the case where the count N exceeds 50, the control portion  100  determines that supply of toner to the hopper  201  is not expected even if the toner cartridge  14  is driven further, and determines that the toner cartridge  14  is empty in step S 10 . 
     Here, it is determined that the toner cartridge  14  is empty in the stage 3 in which the amount of remaining toner in the toner cartridge  14  is small. Thus, in the case where the count N is equal to or smaller than 50 in step S 8 , the process proceeds to step S 9 , and it is determined whether the supply operation from the hopper  201  to the developing unit  613 Y has been performed the predetermined number of times M, which is 1 in this case. In the case where such operations are performed and the count N exceeds 50 in step S 8 , it is determined that toner is not present in the toner cartridge  14 . Therefore, in the present exemplary embodiment, it is determined that toner is not present after the agitation and supply operation are performed at least fifty times in the stage 3. Accordingly, there is a chance to cancel the state of the heap of toner in this process. 
     As described above, the predetermined number of times M serving as the first driving amount by which the agitating conveyance portion  203  is driven each time the toner cartridge  14  is driven for one cycle in the supply operation of toner in the developer supplying device  200 Y is set to be variable between each stage. That is, the control portion  100  respectively sets the predetermined number of times M for the stages 1, 2, and 3 to 0, 5, and 1 in accordance with the amount of remaining toner in the toner cartridge  14 . 
     Thus, in accordance with the change of the discharge property according to the amount of remaining toner in the toner cartridge  14 , the formation of the heap of toner in the container  202  of the hopper  201  can be suppressed, or the heap of toner can be appropriately leveled before the heap increases in size. As a result of this, erroneous detection by the toner sensor  17  can be suppressed. In addition, the heap of toner coming into contact with the rotating toner cartridge  14  in the vicinity of the supply port  14   a  of the toner cartridge  14  can be suppressed without agitating the toner in the hopper  201  the whole time, and thus the deterioration of toner can be suppressed. In this way, in the present exemplary embodiment, the detection of toner can be appropriately performed by the toner sensor  17  while suppressing the deterioration of toner. 
     To be noted, the first driving amount and the counts of times of supply to the developing unit  613 Y for transition between the stages 1 to 3 can be changed as appropriate in accordance with the properties of the toner. Here, the first driving amount corresponds to the predetermined number of times used in step S 9 , and the counts of times of supply corresponds to the amount of remaining toner in the toner cartridge  14 . In addition, the amount of remaining toner in the toner cartridge  14  used for the transition between the stages 1 to 3 can be changed as appropriate in accordance with the shape of the toner cartridge  14 , the shape of the hopper  201 , and the placement of the toner sensor  17 . Further, although the amount of remaining toner has been divided into three stages in the description above, the first driving amount may be appropriately set by dividing the amount of remaining toner into plural stages different from the three stages. 
     Second Exemplary Embodiment 
     A second exemplary embodiment will be described with reference to  FIG. 18  and also to  FIGS. 1 to 17 . In the present exemplary embodiment, the detection of the amount of remaining toner in the toner cartridge  14  for the transition between the stages 1 to 3 is performed by using an accumulated number of rotations of the toner cartridge  14 . That is, the control portion  100  calculates the amount of remaining toner in the toner cartridge  14  from the accumulated number of rotations of the toner cartridge  14  serving as a driving amount. 
     The accumulated number of rotations of the toner cartridge  14  serving as a driving amount and the amount of remaining toner in the toner cartridge  14  have a relationship illustrated in  FIG. 18 . Thus, the amount of remaining toner in the toner cartridge  14  is calculated from the driving time of the toner cartridge  14  by setting this relationship as a table. That is, this table is stored in, for example, a memory such as the RAM  103 . Meanwhile, the CPU  101  counts the accumulated number of rotations of the toner cartridge  14 . Then, the CPU  101  refers to the table to obtain the amount of remaining toner in the toner cartridge  14  from the accumulated number of rotations of the toner cartridge  14  that has been counted. For example, in the case where the accumulated number of rotations of the toner cartridge  14  that has been counted since replacement by a new toner cartridge is  100 , the amount of remaining toner can be calculated as 55% from the table illustrated in  FIG. 18 . 
     The control portion  100  determines in which of the stages 1 to 3 the developer supplying device  200 Y is from the amount of remaining toner in the toner cartridge  14  calculated in this way in a similar manner to the first exemplary embodiment, and sets the first driving amount in accordance with the determined stage. The other points of the configuration and the effect are similar to the first exemplary embodiment. 
     To be noted, the amount of remaining toner may be detected by counting the driving time in which the toner cartridge  14  is driven instead of the accumulated number of rotations of the toner cartridge  14 . In addition, the detection of the amount of remaining toner may be performed by measuring the weight of the toner cartridge  14 . For example, the amount of remaining toner in the toner cartridge  14  may be directly measured by attaching a weight detection sensor such as a load cell to the tray  26  or the rollers  25  illustrated in  FIGS. 7 and 8 . 
     Third Exemplary Embodiment 
     A third exemplary embodiment will be described with reference to  FIGS. 19 and 20A to 20C  and also to  FIGS. 1 to 15 and 17 . In the first and second exemplary embodiments described above, the first driving amount is set by using the relationship between the amount of remaining toner in the toner cartridge  14  and the supplying property, or, the discharge property, of the toner cartridge  14 . In contrast, in the present exemplary embodiment, the first driving amount is set by detecting the amount of toner supplied from the toner cartridge  14  to the container  202  of the hopper  201  per unit time. 
     Thus, the control portion  100  can execute a supplied amount detecting mode. In the supplied amount detecting mode, the agitating conveyance portion  203  is driven by a predetermined amount without driving the toner cartridge  14  in the case where the state of the toner sensor  17  has changed from a state of detecting toner to a state of not detecting toner, that is, from the on state to the off state. Along with this operation, after the agitating conveyance portion  203  has been driven by the predetermined amount, the toner cartridge  14  is driven until the toner sensor  17  detects toner without driving the agitating conveyance portion  203 . Then, the control portion  100  calculates the amount of developer supplied per unit time from a relationship between a predetermined amount and the driving amount by which the toner cartridge  14  has been driven in the supplied amount detecting mode. 
     That is, in the supplied amount detecting mode, a certain amount of toner is discharged from the hopper  201  to the developing unit  613 Y by driving the agitating conveyance portion  203  by a predetermined amount from a time point at which the state of the toner sensor  17  has changed to the off state. At this time, the amount of toner in the container  202  of the hopper  201  is reduced by the certain amount from the time point at which the state of the toner sensor  17  has changed to the off state. Then, the toner cartridge  14  is started being driven in this state, and toner is supplied from the toner cartridge  14  to the container  202  until the state of the toner sensor  17  changes to the on state. At this time, the agitating conveyance portion  203  is not driven, and thus toner is not discharged from the container  202 . Thus, the number of rotations or the rotating time which serves as a driving amount and by which or for which the toner cartridge  14  has been driven to supply toner of the certain amount described above from the toner cartridge  14  can be obtained. As a result of this, the amount of toner supplied from the toner cartridge  14  per unit time in the case where the supplied amount detecting mode is executed can be calculated. 
     The control portion  100  sets different values of the first driving amount on the basis of the amount of toner supplied per unit time that has been calculated in this way. That is, the control portion  100  sets the first driving amount to a first amount in the case where the amount of toner supplied per unit time is equal to or larger than a threshold value, and sets the first driving amount to a second amount smaller than the first amount in the case where the amount of toner supplied per unit time is smaller than the threshold value. For example, the case where the amount of toner supplied per unit time is equal to or larger than the threshold value is set as the stage 2, and the case where the amount of toner supplied per unit time is smaller than the threshold value is set as the stage 3. 
     In addition, the control portion  100  integrates the driving amount of the toner cartridge  14 . That is, an accumulated number of rotations or driving time of the toner cartridge  14  is counted. Then, in the case where the integrated driving amount of the toner cartridge  14  is smaller than a predetermined driving amount, the control portion  100  sets the first driving amount to 0 without performing detection of the amount of toner supplied from the toner cartridge  14  per unit time. That is, in the stage 1, for example, immediately after replacement, in which the amount of remaining toner in the toner cartridge  14  is large, the control portion  100  sets the first driving amount to 0 without executing the supplied amount detecting mode. 
     As described above, transition between the stages 1 to 3 is performed on the basis of the amount of toner supplied per unit time and the driving amount of the toner cartridge  14 , and the flow illustrated in  FIG. 17  is performed. The supplied amount detection mode will be described in detail with reference to  FIGS. 19 and 20A to 20C . 
     First, as preparation for driving of the toner cartridge  14 , a count S of times of driving of the toner cartridge  14  is set to 0 in step S 11 . Next, in the case where toner is supplied from the hopper  201  to the developing unit  613 Y and the state of the toner sensor  17  is changed to a state in which toner is not detected, that is, the off state, in step S 12 , the control portion  100  outputs a command to drive the motor  22 , and the agitating conveyance portion  203  starts driving. In step S 12 , the powder surface of the toner t in the container  202  of the hopper  201  takes a state illustrated in  FIG. 20A . 
     Next, the supply operation of toner from the hopper  201  to the developing unit  613 Y is performed twenty times in step S 13 . That is, the second screw  13  of the agitating conveyance portion  203  rotates twenty times. The twenty times serves as a predetermined amount. At this time, the toner cartridge  14  is not driven until the supply operation of toner is performed twenty times in total. In addition, in the case where the amount of toner supplied by one rotation of the second screw  13  is represented by Q, the amount of toner supplied from the hopper  201  to the developing unit  613 Y by performing the supply operation of toner twenty times is  20 Q. In the case where a result of determination of whether the supply operation has been performed twenty times in step S 13  is YES, the powder surface of the toner t in the container  202  of the hopper  201  takes a state illustrated in  FIG. 20B . That is, the amount of toner in the container  202  of the hopper  201  is reduced by  20 Q serving as the certain amount from the time point at which the state of the toner sensor  17  has changed to the off state. 
     After the supply operation of toner has been performed twenty times, the control portion  100  outputs a command to drive the motor  21 , and the toner cartridge  14  starts driving. At this time, the toner cartridge  14  keeps on driving for four seconds in step S 14 , and then stops for one second in step S 15 . The driving and stopping of the toner cartridge  14  of steps S 14  and S 15  will be defined as one cycle. 
     After the toner cartridge  14  has been driven for one cycle, the count S of times of driving of the toner cartridge  14  is increased by one, that is, S=S+1 is performed in step S 16 . Next, the state of the toner sensor  17  is checked in step S 17 . In the case where the toner sensor  17  is in the state of detecting toner, that is, the on state, information indicating the state is transmitted to the control portion  100 , the process returns to step S 11 , and the count S of times of driving of the toner cartridge  14  is reset to 0. Then, the developer supplying device  200 Y takes a stand-by state until the state of the toner sensor  17  changes to the off state again in accordance with the supply operation from the hopper  201  to the developing unit  613 Y. 
     In contrast, in the case where the toner sensor  17  is still in the off state in step S 17 , the process returns to step S 14 , one cycle of the driving and stopping of the toner cartridge  14  is performed in steps S 14  and S 15 , and the count S is further increased by 1 in step S 16 . Then, the state of the toner sensor  17  is checked again in step S 17 . In the case where the toner sensor  17  is still in the off state, the cycle from step S 14  to step S 17  is repeated until the state of the toner sensor  17  changes to the on state, and the count S is increased each time the cycle is repeated. In the case where a result of determination of whether the state of the toner sensor  17  has changed to the on state in step S 17  is YES, the powder surface of the toner t in the container  202  of the hopper  201  is in a state illustrated in  FIG. 20C . That is, toner of an amount approximately equal to  20 Q has been supplied from the toner cartridge  14  to the container  202  of the hopper  201  by driving the toner cartridge  14  S times corresponding to the count S. 
     Here, since the toner cartridge  14  is driven for four seconds each time in step S 14 , an accumulated driving time of the toner cartridge  14  from the state illustrated in  FIG. 20A  to the state illustrated in  FIG. 20C  is 4S seconds. Accordingly, in the supplied amount detecting mode, the amount E g/s of toner supplied, or, discharged, from the toner cartridge  14  per unit time can be obtained by the following equation. 
     
       
         
           
             E 
             = 
             
               
                 
                   20 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   Q 
                 
                 
                   4 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   S 
                 
               
               ⁢ 
               
                   
               
               ⁢ 
               
                 ( 
                 
                   g 
                   ⁢ 
                   
                     / 
                   
                   ⁢ 
                   s 
                 
                 ) 
               
             
           
         
       
     
     In the case where E obtained by this equation is equal to or larger than a threshold value that is 5 g/s in this case, the sequence for the stage 2 of the first exemplary embodiment is performed. That is, the predetermined number of times M serving as the first driving amount is set to 5 serving as the first amount, and the flow illustrated in  FIG. 17  is performed. In addition, in the case where E is smaller than the threshold value, the sequence for the stage 3 of the first exemplary embodiment is performed. That is, the predetermined number of times M serving as the first driving amount is set to 1 serving as the second amount, and the flow illustrated in  FIG. 17  is performed. 
     In the case where the accumulated number of rotations after replacement of the toner cartridge  14  is smaller than 100 serving as a predetermined driving amount, the sequence for the stage 1 of the first exemplary embodiment is performed without executing the supplied amount detecting mode. That is, the predetermined number of times M serving as the first driving amount is set to 0, and the flow illustrated in  FIG. 17  is performed. In other words, the sequence of the stage 1 is performed until the first execution of the supplied amount detecting mode, that is, while the number of times of driving of the toner cartridge  14  is smaller than 100. 
     According to this, supply control of toner can be appropriately performed even in the case where the supplying property cartridge  14  is different from an expected property due to the time or environment for or in which the toner cartridge  14  has been stored, the environment in which the image forming apparatus  60  is used, or the like. As a result of this, formation of the heap of toner in the container  202  of the hopper  201  can be suppressed, and detection of toner can be appropriately performed by the toner sensor  17  while suppressing deterioration of toner. The other elements and effects are similar to the first exemplary embodiment. 
     Other Embodiments 
     Although, cases where two-component developer including toner and carrier is used as developer has been described in the exemplary embodiments described above, the developer may be one-component developer including toner. 
     It has been described above that toner is supplied to a developer accommodating portion by a spiral groove defined in a toner cartridge configured to supply toner by rotating. However, the configuration of supplying toner to the developer accommodating portion may be, for example, a configuration in which a conveyance member such as a screw configured to convey toner is provided in the toner cartridge serving as a developer supplying container. In addition, in the case where the toner cartridge is not configured to rotate, a configuration in which a sensor such as a pressure sensor capable of detecting toner is provided at a predetermined height in the toner cartridge and the amount of remaining toner in the toner cartridge is directly detected may be employed. 
     In addition, although a case where the agitating conveyance portion  203  is constituted by the agitating screws  11  and the first and second screws  12  and  13  has been described, the agitating conveyance portion  203  may be constituted by an agitating conveyance member such as one screw. For example, a discharge screw that discharges toner from a hopper to a developing unit may be configured to include a spiral blade provided around a rotation shaft and ribs for agitation provided at gaps in the spiral blade. According to this, agitation and conveyance of developer in the hopper are performed by one screw. 
     Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No.2016-138698, filed Jul. 13, 2016, which is hereby incorporated by reference wherein in its entirety.