Patent Publication Number: US-2023161282-A1

Title: Image forming apparatus and image forming system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of International Patent Application No. PCT/JP2021/028132, filed Jul. 29, 2021, which claims the benefit of Japanese Patent Applications No. 2020-129008, filed Jul. 30, 2020, and No. 2020-129009, filed Jul. 30, 2020, all of which are hereby incorporated by reference herein in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to an image forming apparatus that forms an image on a recording material, and an image forming system. 
     Background Art 
     Generally, an electrophotographic image forming apparatus transfers a toner image formed on a surface of a photosensitive drum to a transfer material as a transfer medium, thereby forming an image. Then, as a method for supplying a developer, for example, a process cartridge method and a toner supply method are known. The process cartridge method is a method for integrating a photosensitive drum and a developing container into a process cartridge and, if a developer runs out, replacing the process cartridge with a new process cartridge. 
     On the other hand, the toner supply method is a method for, if toner runs out, newly supplying toner to a developing container. Japanese Patent Application Laid-Open No. 2015-148768 discusses a configuration of a toner cartridge as a toner supply container that is attached to a process cartridge attachable to and detachable from an image forming apparatus and that supplies toner. 
     In recent years, an image forming apparatus is required to be used in various ways such as the process cartridge method and the toner supply method by a user. 
     CITATION LIST 
     Patent Literature 
     PTL 1: Japanese Patent Application Laid-Open No. 2015-148768 
     SUMMARY OF THE INVENTION 
     According to an aspect of the present invention, an image forming apparatus that performs image formation for forming a toner image on a recording material includes a photosensitive drum, a developing container configured to store toner, the developing container provided with a replenishment opening for toner supply from outside of the image forming apparatus, a developing roller configured to supply the toner stored in the developing container to the photosensitive drum, a detection portion configured to detect an amount of the toner stored in the developing container, a display portion configured to perform display depending on a detection result of the detection portion, and a control portion configured to control the display portion, wherein the control portion controls the detection portion to execute a first detection to reflect a decrease in the amount of the toner in the developing container due to the image formation on a display of the display portion, and a second detection to reflect an increase in the amount of the toner in the developing container due to the toner supply on the display of the display portion, wherein the display portion, in a case where the detection result of the first detection is greater than or equal to a first threshold, displays a first display and, in a case where the detection result of the first detection is less than the first threshold, displays a second display different from the first display, and in a case where the detection result of the second detection is greater than or equal to a second threshold, displays the first display and, in a case where the detection result of the second detection is less than the second threshold, displays the second display, and wherein the second threshold is smaller than the first threshold. 
     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 A  is a cross-sectional view illustrating an image forming apparatus according to a first exemplary embodiment. 
         FIG.  1 B  is a perspective view illustrating the image forming apparatus. 
         FIG.  2 A  is a cross-sectional view illustrating the image forming apparatus. 
         FIG.  2 B  is a perspective view illustrating the image forming apparatus in a state where a top cover is opened. 
         FIG.  3    is a cross-sectional view illustrating the image forming apparatus in a state where a process cartridge is detached. 
         FIG.  4 A  is a perspective view illustrating the image forming apparatus in a state where a pressure plate of a reading device is closed. 
         FIG.  4 B  is a perspective view illustrating the image forming apparatus in a state where the pressure plate is opened. 
         FIG.  4 C  is a perspective view illustrating the image forming apparatus in a state where the reading device is opened. 
         FIG.  5 A  is a perspective view illustrating a developing container and a toner pack. 
         FIG.  5 B  is a front view illustrating the developing container and the toner pack. 
         FIG.  6 A  is a  6 A- 6 A cross-sectional view in  FIG.  5 B . 
         FIG.  6 B  is a  6 B- 6 B cross-sectional view in  FIG.  5 B . 
         FIG.  7    is a perspective view illustrating the toner pack. 
         FIG.  8 A  is a front view illustrating the toner pack. 
         FIG.  8 B  is a front view illustrating a first modification of the toner pack. 
         FIG.  8 C  is a front view illustrating a second modification of the toner pack. 
         FIG.  9 A  is a cross-sectional view illustrating a toner remaining amount sensor. 
         FIG.  9 B  is a C-C cross-sectional view in  FIG.  9 A . 
         FIG.  10    is a circuit diagram illustrating first and second toner remaining amount sensors. 
         FIG.  11 A  is a cross-sectional view illustrating the developing container in a state where a remaining amount of toner is small. 
         FIG.  11 B  is a cross-sectional view illustrating the developing container in a state where the remaining amount of toner is great. 
         FIG.  12    is a block diagram illustrating a control system of the image forming apparatus. 
         FIG.  13 A  is a perspective view illustrating a toner remaining amount panel when the remaining amount of toner is at a near out level. 
         FIG.  13 B  is a perspective view illustrating the toner remaining amount panel when the remaining amount of toner is at a low level. 
         FIG.  13 C  is a perspective view illustrating the toner remaining amount panel when the remaining amount of toner is at a mid level. 
         FIG.  13 D  is a perspective view illustrating the toner remaining amount panel when the remaining amount of toner is at a full level. 
         FIG.  14    is a graph illustrating a relationship between a capacity of the developing container and a level of the remaining amount of toner. 
         FIG.  15    is a graph illustrating the relationship between the capacity of the developing container and the level of the remaining amount of toner when toner is supplied. 
         FIG.  16    is a flowchart illustrating a flow of control according to a second exemplary embodiment. 
         FIG.  17 A  is a schematic diagram illustrating display during replenishment according to a third exemplary embodiment. 
         FIG.  17 B  is a schematic diagram illustrating another pattern of the display during replenishment according to the third exemplary embodiment. 
         FIG.  18    is a flowchart illustrating a flow of control according to the third exemplary embodiment. 
         FIG.  19    is a schematic diagram illustrating a configuration of an image forming apparatus according to a modification. 
         FIG.  20 A  is a perspective view illustrating another exemplary embodiment of the image forming apparatus. 
         FIG.  20 B  is a perspective view illustrating the other exemplary embodiment of the image forming apparatus. 
         FIG.  20 C  is a perspective view illustrating the other exemplary embodiment of the image forming apparatus. 
         FIG.  21    is a graph illustrating a relationship between a capacity of a developing container and a level of the remaining amount of toner according to a fourth exemplary embodiment. 
         FIG.  22    is a flowchart illustrating a flow of control according to a fifth exemplary embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Exemplary embodiments for carrying out the present invention will be described below with reference to the drawings. However, the dimensions, the materials, the shapes, and the relative arrangement of components described in the following exemplary embodiments should be appropriately changed depending on the configuration of an apparatus to which the invention is applied, or various conditions, and are not intended to limit the scope of the invention to the following exemplary embodiments. 
     First Exemplary Embodiment 
       FIG.  1 A  is a schematic diagram illustrating a configuration of an image forming apparatus  1  according to a first exemplary embodiment. The image forming apparatus  1  is a monochrome printer that forms an image on a recording material based on image information input from an external device. The recording material may be a sheet material made of a different material, e.g., paper such as plain paper and thick paper, a plastic film such as an overhead projector sheet, sheets having special shapes such as an envelope and index paper, and cloth. 
     [Overall Configuration] 
     As illustrated in  FIGS.  1 A and  1 B , the image forming apparatus  1  includes a printer main body  100  as an apparatus main body, a reading device  200  openably and closably supported by the printer main body  100 , and an operation portion  300  attached to an exterior surface of the printer main body  100 . The printer main body  100  includes an image forming portion  10  that forms a toner image on a recording material, a feeding portion  60  that feeds the recording material to the image forming portion  10 , a fixing portion  70  that fixes the toner image formed by the image forming portion  10  to the recording material, and a discharge roller pair  80 . 
     The image forming portion  10  includes a scanner unit  11 , an electrophotographic process cartridge  20 , and a transfer roller  12  that transfers a toner image formed on a photosensitive drum  21  of the process cartridge  20  to a recording material. As illustrated in  FIGS.  6 A and  6 B , the process cartridge  20  includes the photosensitive drum  21  and a charging roller  22 , a pre-exposure device  23 , and a developing device  30  including a developing roller  31  that are placed around the photosensitive drum  21 . 
     The photosensitive drum  21  is a photosensitive member formed into a cylindrical shape. The photosensitive drum  21  according to the present exemplary embodiment includes a photosensitive layer formed of a negatively charged organic photosensitive member on a drum-like base formed of aluminum. The photosensitive drum  21  as an image bearing member is rotationally driven at a predetermined process speed in a predetermined direction (a clockwise direction in  FIGS.  6 A and  6 B ) by a motor. 
     The charging roller  22  comes into contact with the photosensitive drum  21  with a predetermined pressure contact force, thereby forming a charging portion. A desired charging voltage is applied to the charging roller  22  by a charging high-voltage power supply, thereby a surface of the photosensitive drum  21  is uniformly charged to a predetermined potential. In the present exemplary embodiment, the photosensitive drum  21  is charged to a negative polarity by the charging roller  22 . To cause the charging portion to perform stable discharge, the pre-exposure device  23  removes charge from the surface potential of the photosensitive drum  21  before the photosensitive drum  21  enters the charging portion. 
     The scanner unit  11  as an exposure means emits laser light corresponding to image information input from the external device or the reading device  200  to the photosensitive drum  21  using a polygon mirror, thereby scanning and exposing the surface of the photosensitive drum  21 . The exposure forms an electrostatic latent image according to the image information on the surface of the photosensitive drum  21 . The scanner unit  11  is not limited to a laser scanner device, and for example, a light-emitting diode (LED) exposure device including an LED array in which a plurality of LEDs is arranged in the longitudinal direction of the photosensitive drum  21  may be employed. 
     The developing device  30  includes the developing roller  31  as a developer bearing member that bears a developer, a developing container  32  as a frame member of the developing device  30 , and a supply roller  33  capable of supplying a developer to the developing roller  31 . The developing roller  31  and the supply roller  33  are rotatably supported by the developing container  32 . The developing roller  31  is placed in an open portion of the developing container  32  to be opposed to the photosensitive drum  21 . The supply roller  33  is in contact with the developing roller  31  in a rotatable manner, and toner as a developer stored in the developing container  32  is applied to a surface of the developing roller  31  by the supply roller  33 . The supply roller  33  is not necessarily required as long as a configuration is employed in which toner can be sufficiently supplied to the developing roller  31 . 
     The developing device  30  according to the present exemplary embodiment uses a contact developing method as a developing method. More specifically, a toner layer borne on the developing roller  31  comes into contact with the photosensitive drum  21  in a developing portion (a developing area) where the photosensitive drum  21  and the developing roller  31  are opposed to each other. A developing voltage is applied to the developing roller  31  by a developing high-voltage power supply. At the developing voltage, toner borne on the developing roller  31  is transferred from the developing roller  31  to the surface of the drum according to the potential distribution of the surface of the photosensitive drum  21 , thereby an electrostatic latent image is developed into a toner image. In the present exemplary embodiment, a reversal developing method is employed. More specifically, toner is attached to the surface area of the photosensitive drum  21  where the amount of charge is attenuated by the surface of the photosensitive drum  21  being charged in a charging step and then exposed in an exposure step, thereby forming a toner image. 
     In the present exemplary embodiment, toner of which the grain size is 6 μm and the normal charge polarity is a negative polarity is used. As the toner according to the present exemplary embodiment, as an example, polymerized toner generated by a polymerization method is employed. The toner according to the present exemplary embodiment is what is called a nonmagnetic one-component developer, which is toner that does not contain a magnetic component and is borne on the developing roller  31  mainly by an intermolecular force or an electrostatic force (an image force). However, a one-component developer containing a magnetic component may be used. There is a case where a one-component developer includes an additive (e.g., wax or silica microparticles) for adjusting the fluidity or the charging performance of toner in addition to toner particles. Alternatively, a two-component developer composed of nonmagnetic toner and a magnetic carrier may be used as a developer. In a case where a magnetic developer is used, for example, a cylindrical developing sleeve in which a magnet is placed is used as the developer bearing member. 
     Within the developing container  32 , an agitation member  34  as an agitation means is provided. The agitation member  34  rotationally moves by being driven by a motor M 1  (see  FIG.  12   ), thereby agitating toner in the developing container  32  and feeding toner to the developing roller  31  and the supply roller  33 . The agitation member  34  has the function of circulating toner that is not used in development and is scraped off from the developing roller  31  in the developing container and uniformizing toner in the developing container. The agitation member  34  is not limited to a form in which the agitation member  34  rotationally moves. For example, an agitation member in a form in which the agitation member swings may be employed. 
     In the open portion of the developing container  32  where the developing roller  31  is placed, a developing blade  35  that regulates an amount of toner borne on the developing roller  31  is placed. Toner supplied to the surface of the developing roller  31  is uniformly formed into a thin layer by passing through a portion opposed to the developing blade  35  with the rotation of the developing roller  31  and is also charged to a negative polarity by frictional charging. 
     As illustrated in  FIGS.  1 A and  1 B , the feeding portion  60  includes a front door  61  openably and closably supported by the printer main body  100 , a tray portion  62 , an intermediate plate  63 , a tray spring  64 , and a pickup roller  65 . The tray portion  62  forms a bottom surface of a recording material storage space that appears when the front door  61  is opened. The intermediate plate  63  is supported by the tray portion  62  so that the intermediate plate  63  can be lifted and lowered. The tray spring  64  urges the intermediate plate  63  upward and presses a recording material P stacked in the intermediate plate  63  against the pickup roller  65 . The front door  61  blocks the recording material storage space in the state where the front door  61  is closed relative to the printer main body  100 . The front door  61  supports the recording material P together with the tray portion  62  and the intermediate plate  63  in the state where the front door  61  is opened relative to the printer main body  100 . 
     The fixing portion  70  uses a heat fixing method for performing the process of fixing an image by heating and fusing toner on a recording material. The fixing portion  70  includes a fixing film  71 , a fixing heater such as a ceramic heater that heats the fixing film  71 , a thermistor that measures the temperature of the fixing heater, and a pressure roller  72  that comes into pressure contact with the fixing film  71 . 
     Next, an image forming operation of the image forming apparatus  1  is described. If an image forming command is input to the image forming apparatus  1 , the image forming portion  10  starts an image forming process based on image information input from an external computer connected to the image forming apparatus  1  or the reading device  200 . The scanner unit  11  emits laser light to the photosensitive drum  21  based on the input image information. At this time, the photosensitive drum  21  is charged in advance by the charging roller  22 . The photosensitive drum  21  is irradiated with the laser light, thereby an electrostatic latent image is formed on the photosensitive drum  21 . Then, the developing roller  31  develops the electrostatic latent image, thereby forming a toner image on the photosensitive drum  21 . 
     In parallel with the above image forming process, the pickup roller  65  of the feeding portion  60  sends out the recording material P supported by the front door  61 , the tray portion  62 , and the intermediate plate  63 . The recording material P is fed by the pickup roller  65  to a registration roller pair  15  and hits a nip of the registration roller pair  15 , thereby the skew of the recording material P is corrected. Then, the registration roller pair  15  is driven in synchronization with a transfer timing of the toner image and conveys the recording material P to a transfer nip formed by the transfer roller  12  and the photosensitive drum  21 . 
     A transfer voltage is applied to the transfer roller  12  as a transfer means by a transfer high-voltage power supply, and the toner image borne on the photosensitive drum  21  is transferred to the recording material P conveyed by the registration roller pair  15 . The recording material P to which the toner image is transferred is conveyed to the fixing portion  70 , and when the recording material P passes through a nip portion between the fixing film  71  and the pressure roller  72  of the fixing portion  70 , the toner image is heated and pressurized. This fuses toner particles, and then, the toner particles are firmly fixed, thereby the toner image is fixed to the recording material P. The recording material P having passed through the fixing portion  70  is discharged to the outside of the image forming apparatus  1  (the outside of the apparatus) by the discharge roller pair  80  as a discharge means and stacked on a discharge tray  81  as a stacking portion formed in an upper portion of the printer main body  100 . 
     The discharge tray  81  slopes upward downstream in the discharge direction of the recording material. The recording material discharged to the discharge tray  81  slides down the discharge tray  81 , thereby the rear end of the recording material is aligned by a regulation surface  84 . 
     As illustrated in  FIGS.  4 A and  4 B , the reading device  200  includes a reading unit  201  having a reading portion (not illustrated) built-in, and a pressure plate  202  openably and closably supported by the reading unit  201 . On an upper surface of the reading unit  201 , a document platen glass  203  is provided which transmits light emitted from the reading portion and on which a document is placed. 
     To cause the reading device  200  to read an image of a document, a user places the document on the document platen glass  203  in a state where the pressure plate  202  is opened. Then, the user prevents a positional shift in the document on the document platen glass  203  by closing the pressure plate  202  and outputs a reading command to the image forming apparatus  1 , for example, by operating the operation portion  300 . If a reading operation is started, the reading portion in the reading unit  201  reciprocates in a sub-scanning direction, i.e., a left-right direction in a state where the user faces the operation portion  300  of the image forming apparatus  1 . The reading portion emits light to the document using a light-emitting portion, receives the light reflected by the document using a light-receiving portion, and photoelectrically converts the light, thereby reading an image of the document. In the following description, a front-back direction, a left-right direction, and an up-down direction are defined based on the state where the user faces the operation portion  300 . 
     As illustrated in  FIGS.  2 B and  3   , in the upper portion of the printer main body  100 , a first open portion  101  open upward is formed. The first open portion  101  is covered by a top cover  82 . The top cover  82  as a stacking tray is supported openably and closably relative to the printer main body  100  about a rotational movement shaft  82   c  extending in the left-right direction. On an upper surface of the top cover  82 , the discharge tray  81  as a stacking surface is formed. The top cover  82  is opened from the near side to the far side in a state where the reading device  200  is opened relative to the printer main body  100 . The reading device  200  and the top cover  82  may be configured to be held in an opened state and a closed state by a holding mechanism such as a hinge mechanism. 
     For example, if the recording material causes a jam such as a paper jam in the conveying path CP through which the recording material fed by the pickup roller  65  passes, the user opens the top cover  82  together with the reading device  200 . Then, the user accesses the process cartridge  20  through the first open portion  101  exposed when the top cover  82  is opened and pulls out the process cartridge  20  along a cartridge guide  102 . The cartridge guide  102  guides the process cartridge  20  by sliding the process cartridge  20  in contact with a protruding portion  21   a  (see  FIG.  5 A ) provided in an end portion in the axial direction of the photosensitive drum  21  of the process cartridge  20 . 
     Then, the process cartridge  20  is pulled out through the first open portion  101  to the outside, thereby a space that enables the user to put his or her hand in the conveying path CP is formed. The user puts his or her hand inside the printer main body  100  through the first open portion  101  and accesses the recording material jamming the conveying path CP and thereby can handle the jamming recording material. 
     In the present exemplary embodiment, as illustrated in  FIGS.  1 B and  4 C , an opening/closing member  83  is openably and closably provided in the top cover  82 . In the discharge tray  81  of the top cover  82 , a second open portion  82   a  as an open portion open upward is formed. The opening/closing member  83  is configured to be movable between a closed position where a replenishment opening  32   a  is covered so that a toner pack  40  cannot be attached to the developing container  32 , and an opened position where the replenishment opening  32   a  is exposed so that the toner pack  40  can be attached to the developing container  32 . The opening/closing member  83  functions as a part of the discharge tray  81  at the closed position. The opening/closing member  83  and the second open portion  82   a  are formed on the left side of the discharge tray  81 . The opening/closing member  83  is openably and closably supported by the top cover  82  about a rotational movement shaft  83   a  extending in the front-back direction and is opened in the left direction by the user hooking his or her finger in a groove portion  82   b  provided in the top cover  82 . The opening/closing member  83  is formed into a substantially L-shape along the shape of the top cover  82 . 
     The second open portion  82   a  of the discharge tray  81  is open so that the replenishment opening  32   a  for supplying toner that is formed in an upper portion of the developing container  32  is exposed. The opening/closing member  83  is opened, whereby the user can access the replenishment opening  32   a  without opening the top cover  82 . In the present exemplary embodiment, a method is employed in which the user supplies toner from the toner pack  40  (see  FIGS.  1 A and  1 B ) filled with replenishment toner to the developing device  30  in a state where the developing device  30  remains attached to the image forming apparatus  1  (a direct supply method). Thus, in a case where a remaining amount of toner in the process cartridge  20  is small, work of taking the process cartridge  20  out of the printer main body  100  and replacing the process cartridge  20  with a new process cartridge is unnecessary. Thus, it is possible to improve usability. Further, the method enables toner to be supplied to the developing container  32  less expensively than by a method where the entire process cartridge  20  is replaced. The direct supply method, as compared to a case where only the developing device  30  of the process cartridge  20  is replaced, can reduce costs because it is not necessary to replace various rollers and gears. The image forming apparatus  1  and the toner pack  40  are included in an image forming system. 
     [Collection of Transfer Residual Toner] 
     In the present exemplary embodiment, a cleanerless configuration is employed in which transfer residual toner that is not transferred to the recording material P and remains on the photosensitive drum  21  is collected in the developing device  30  and reused. The transfer residual toner is removed by the following step. The transfer residual toner includes a mix of toner charged to a positive polarity and toner that is charged to a negative polarity but does not have sufficient charges. The pre-exposure device  23  removes charge from the photosensitive drum  21  after the transfer, and the charging roller  22  uniformly discharges, thereby charging the transfer residual toner to the negative polarity again. The transfer residual toner charged to the negative polarity again by the charging portion reaches the developing portion with the rotation of the photosensitive drum  21 . Then, the surface area of the photosensitive drum  21  having passed through the charging portion is exposed by the scanner unit  11 , and an electrostatic latent image is written to the surface area in the state where the transfer residual toner remains attached to the surface. 
     Behavior of the transfer residual toner reaching the developing portion is described separately for an exposed portion and a non-exposed portion of the photosensitive drum  21 . Transfer residual toner attached to the non-exposed portion of the photosensitive drum  21  is transferred to the developing roller  31  by a potential difference between the potential of the non-exposed portion (a dark portion potential) of the photosensitive drum  21  and the developing voltage in the developing portion and collected in the developing container  32 . This is because, on the assumption that the normal charge polarity of toner is a negative polarity, the developing voltage applied to the developing roller  31  has a positive polarity relative to the potential of the non-exposed portion. The toner collected in the developing container  32  is agitated and dispersed with toner in the developing container by the agitation member  34  and is borne on the developing roller  31 , thereby being used in a developing step again. 
     On the other hand, transfer residual toner attached to the exposed portion of the photosensitive drum  21  is not transferred from the photosensitive drum  21  to the developing roller  31  in the developing portion and remains on the surface of the drum. This is because, on the assumption that the normal charge polarity of toner is a negative polarity, the developing voltage applied to the developing roller  31  has a more negative polarity than the potential of the exposed portion (a light portion potential). The transfer residual toner remaining on the surface of the drum is borne on the photosensitive drum  21  and moved to a transfer portion together with other toner to be transferred from the developing roller  31  to the exposed portion, and is transferred to the recording material P in the transfer portion. 
     As described above, in the present exemplary embodiment, the cleanerless configuration is employed in which transfer residual toner is collected in the developing device  30  and reused. Alternatively, a conventionally known configuration may be employed in which transfer residual toner is collected using a cleaning blade that comes into contact with the photosensitive drum  21 . In this case, the transfer residual toner collected by the cleaning blade is collected in a collection container installed separately from the developing device  30 . With the cleanerless configuration, however, an installation space for the collection container that collects the transfer residual toner is unnecessary, and it is possible to further miniaturize the image forming apparatus  1 . It is also possible to reduce printing costs by reuse of the transfer residual toner. 
     [Configurations of Developing Container and Toner Pack] 
     Now, the configurations of the developing container  32  and the toner pack  40  are described.  FIG.  5 A  is a perspective view illustrating the developing container  32  and the toner pack  40 .  FIG.  5 B  is a front view illustrating the developing container  32  and the toner pack  40 .  FIG.  6 A  is a  6 A- 6 A cross-sectional view in  FIG.  5 B .  FIG.  6 B  is a  6 B- 6 B cross-sectional view in  FIG.  5 B . 
     As illustrated in  FIGS.  5 A to  6 B , the developing container  32  includes a conveying chamber  36  that stores the agitation member  34 . The conveying chamber  36  as a storage portion that stores toner extends over the entire length in the longitudinal direction (the left-right direction) of the developing container  32 . The conveying chamber  36  rotatably supports the developing roller  31  and the supply roller  33  and stores a developer to be borne on the developing roller  31 . The developing container  32  includes a first protruding portion  37  as a protruding portion that protrudes upward from one end portion in the longitudinal direction of the conveying chamber  36  and communicates with the conveying chamber  36 , and a second protruding portion  38  that protrudes upward from the other end portion in the longitudinal direction of the conveying chamber  36 . In other words, the first protruding portion  37  is provided in one end portion of the developing container  32  in the rotational axis direction of the developing roller  31  and protrudes toward the discharge tray  81  more in an intersection direction intersecting the rotational axis direction than at a central portion of the developing container  32 . The second protruding portion  38  is provided in the other end portion of the developing container  32  in the rotational axis direction of the developing roller  31  and protrudes toward the discharge tray  81  more in the intersection direction than at the central portion of the developing container  32 . In the present exemplary embodiment, the first protruding portion  37  is formed on the left side of the developing container  32 , and the second protruding portion  38  is formed on the right side of the developing container  32 . In an upper end portion (a front end portion) of the first protruding portion  37 , an attachment portion  57  to which the toner pack  40  can be attached is provided. In the attachment portion  57 , the replenishment opening  32   a  for supplying a developer from the toner pack  40  to the conveying chamber  36  is formed. The toner pack  40  can be attached to the attachment portion  57  in a state where the toner pack  40  is exposed to the outside of the apparatus. 
     The first protruding portion  37  and the second protruding portion  38  obliquely extend from the conveying chamber  36  toward the near side of the apparatus and upward. In other words, the first protruding portion  37  and the second protruding portion  38  protrude upward and toward downstream in the discharge direction of the discharge roller pair  80 . Thus, the replenishment opening  32   a  formed in the first protruding portion  37  is placed on the near side of the image forming apparatus  1 , and work of replenishing the developing container  32  with toner can be easily performed. 
     Particularly, in the present exemplary embodiment, the reading device  200  openable and closable about the far side of the apparatus is placed above the opening/closing member  83 . Thus, placement of the replenishment opening  32   a  on the near side of the apparatus enables the more effective use of the space between the replenishment opening  32   a  and the reading device  200 . Thus, it is possible to improve workability when toner is supplied through the replenishment opening  32   a.    
     An upper portion of the first protruding portion  37  and an upper portion of the second protruding portion  38  are connected together by a handle portion  39  as a connection portion. Between the handle portion  39  and the conveying chamber  36 , a laser passage space SP is formed as a gap through which laser L (see  FIG.  1 A ) emitted from the scanner unit  11  (see  FIG.  1 A ) to the photosensitive drum  21  can pass. 
     The handle portion  39  includes a knob portion  39   a  that the user can hold by hooking his or her finger on the knob portion  39   a . The knob portion  39   a  is formed to protrude upward from a top surface of the handle portion  39 . The inside of the first protruding portion  37  is formed into a hollow shape, and the replenishment opening  32   a  is formed in an upper surface of the first protruding portion  37 . The replenishment opening  32   a  is configured to be connectable with the toner pack  40 . 
     The first protruding portion  37  in the front end portion of which the replenishment opening  32   a  is formed is provided on one side in the longitudinal direction of the developing container  32 , whereby it is possible to secure the laser passage space SP through which the laser L emitted from the scanner unit  11  can pass. Thus, it is possible to miniaturize the image forming apparatus  1 . Further, the second protruding portion  38  is provided on the other side in the longitudinal direction of the developing container  32 , and the handle portion  39  connecting the first protruding portion  37  and the second protruding portion  38  is also formed. Thus, it is possible to improve usability when the process cartridge  20  is taken out of the printer main body  100 . The second protruding portion  38  may be formed into a hollow shape similar to the first protruding portion  37 , or may be formed into a solid shape. 
     The toner pack  40  is configured to be attachable to and detachable from the attachment portion  57  of the first protruding portion  37 . The toner pack  40  includes a shutter member  41  that is provided in an open portion and openable and closable, and a plurality of (three in the present exemplary embodiment) protrusions  42  formed corresponding to a plurality of (three in the present exemplary embodiment) groove portions  32   b  formed in the attachment portion  57 . The shutter member  41  is configured to be movable between an opened position where the open portion is opened and a closed position where the open portion is closed. To supply toner to the developing container  32 , the user positions the toner pack  40  so that the protrusions  42  of the toner pack  40  pass through the groove portions  32   b  of the attachment portion  57 , and connects the toner pack  40  to the attachment portion  57 . Then, if the toner pack  40  is rotated 180 degrees in this state, the shutter member  41  of the toner pack  40  hits a hitting portion (not illustrated) of the attachment portion  57 , whereby the shutter member  41  rotates relative to a main body of the toner pack  40  and is opened. Consequently, toner stored in the toner pack  40  drops from the toner pack  40 , and the toner having dropped passes through the replenishment opening  32   a  and enters the first protruding portion  37 , which has a hollow shape. The shutter member  41  may be provided on the replenishment opening  32   a  side. 
     The first protruding portion  37  includes a sloping surface  37   a  at a position opposed to the opening of the replenishment opening  32   a , and the sloping surface  37   a  slopes down toward the conveying chamber  36 . Thus, the toner supplied through the replenishment opening  32   a  is guided to the conveying chamber  36  by the sloping surface  37   a . The agitation member  34  includes an agitation shaft  34   a  extending in the longitudinal direction of the agitation member  34 , and a blade portion  34   b  that extends further outward in the radial direction of the agitation member  34  than the agitation shaft  34   a  does. 
     The toner supplied through the replenishment opening  32   a  placed upstream in the conveying direction of the agitation member  34  is fed to the developing roller  31  and the supply roller  33  by the rotation of the agitation member  34 . The conveying direction of the agitation member  34  is a direction parallel to the longitudinal direction of the developing container  32 . Although the replenishment opening  32   a  and the first protruding portion  37  are placed in one end portion in the longitudinal direction of the developing container  32 , the agitation member  34  repeats the rotation, thereby spreading the toner over the entire length of the developing container  32 . Although the agitation member  34  includes the agitation shaft  34   a  and the blade portion  34   b  in the present exemplary embodiment, an agitation shaft having a spiral shape may be used as a component for spreading the toner over the entire length of the developing container  32 . 
     In the present exemplary embodiment, as illustrated in  FIGS.  7  and  8 A , the toner pack  40  is composed of a bag member made of plastic that is easily deformable. The toner pack  40 , however, is not limited thereto. For example, the toner pack may be composed of a bottle container  40 B having a substantially circular cone shape as illustrated in  FIG.  8 B , or may be composed of a paper container  40 C made of paper as illustrated in  FIG.  8 C . In any case, the material and the shape of the toner pack may be any material and shape. As a method for discharging toner from the toner pack, in the case of the toner pack  40  or the paper container  40 C, a method in which the user squeezes the toner pack with his or her fingers is suitable, and in the case of the bottle container  40 B, a method in which the user drops toner while causing the container to vibrate by tapping the container is suitable. A discharge mechanism may be provided in the bottle container  40 B to discharge toner from the bottle container  40 B. Further, the discharge mechanism may be configured to be engaged with the printer main body  100  and receive a driving force from the printer main body  100 . 
     In any of the toner packs, the shutter member  41  may be omitted, or a sliding shutter member may be applied instead of the rotary shutter member  41 . The shutter member  41  may be configured to be torn by the toner pack being attached to the replenishment opening  32   a  or being rotated in the attached state, or may have a removable cover structure such as a seal. 
     [Method for Detecting Remaining Amount of Toner] 
     Now, with reference to  FIGS.  9  to  11   , a method for detecting the remaining amount of toner in the developing container  32  is described. In the developing device  30  according to the present exemplary embodiment, a toner remaining amount sensor  51  (a detection means) that detects remaining amount information according to the remaining amount of toner in the developing container  32  is installed. 
     The toner remaining amount sensor  51  includes a light-emitting portion  51   a  and a light-receiving portion  51   b .  FIG.  9 A  is a cross-sectional view illustrating the toner remaining amount sensor  51 .  FIG.  9 B  is a schematic cross-sectional view of a C-C cross section in  FIG.  9 A  viewed in a direction from the process cartridge  20  side toward the developing container  32 .  FIG.  10    is a circuit diagram illustrating an example of a circuit configuration of the toner remaining amount sensor  51 . 
     In  FIG.  10   , an LED is used as the light-emitting portion  51   a , and a phototransistor that is turned on by light from the LED is used as the light-receiving portion  51   b . The light-emitting portion  51   a  and the light-receiving portion  51   b , however, are not limited thereto. For example, a halogen lamp or a fluorescent light may be applied to the light-emitting portion  51   a , and a photodiode or an avalanche photodiode may be applied to the light-receiving portion  51   b . Between the light-emitting portion  51   a  and a power supply voltage Vcc, a switch (not illustrated) is provided. The switch is turned on, whereby a voltage from the power supply voltage Vcc is applied to the light-emitting portion  51   a , and the light-emitting portion  51   a  becomes conductive. On the other hand, between the light-receiving portion  51   b  and the power supply voltage Vcc, a switch (not illustrated) is also provided. The switch is turned on, whereby the light-receiving portion  51   b  becomes conductive by a current depending on an amount of detected light. 
     To the light-emitting portion  51   a , the power supply voltage Vcc and a current-limiting resistor R 1  are connected. The light-emitting portion  51   a  emits light by a current determined by the current-limiting resistor R 1 . The light emitted from the light-emitting portion  51   a  passes through an optical path Q 1  and is received by the light-receiving portion  51   b  as illustrated in  FIG.  9 B . To a collector terminal of the light-receiving portion  51   b , the power supply voltage Vcc is connected. To an emitter terminal thereof, a detection resistor R 2  is connected. The light-receiving portion  51   b  that is a phototransistor receives the light emitted from the light-emitting portion  51   a  and outputs a signal (a current) depending on an amount of the received light. This signal is converted into a voltage V 1  by the detection resistor R 2 , and the voltage V 1  is input to an analog-to-digital (A/D) conversion portion  95  of a control portion  90  (see  FIG.  12   ). 
     Based on the level of the input voltage, the control portion  90  (a central processing unit (CPU)  91 ) determines whether the light-receiving portion  51   b  has received light from the light-emitting portion  51   a . Based on the length of the time and the light intensity of the received light when the light-receiving portion  51   b  detects each beam of light when toner in the developing container  32  is agitated for a certain period of time by the agitation member  34 , the control portion  90  (the CPU  91 ) calculates the amount of toner (the amount of developer) in the developing container  32 . More specifically, a read-only memory (ROM)  93  stores in advance a table that enables output of the remaining amount of toner based on the light reception time and the light intensity when toner is conveyed by the agitation member  34 . Based on the input to the A/D conversion portion  95  and the table, the control portion  90  estimates and calculates the remaining amount of toner. 
     More specifically, the optical path Q 1  of the toner remaining amount sensor  51  is set to intersect a trajectory T of the rotation of the agitation member  34  when viewed from the rotational axis direction of the agitation member  34  illustrated in  FIG.  9 A . Then, the time the optical path Q 1  is shielded from light by toner conveyed by the agitation member  34 , i.e., the time the light-receiving portion  51   b  does not detect light from the light-emitting portion  51   a , in one revolution of the agitation member  34  changes depending on the remaining amount of toner. The light intensity of the light received by the light-receiving portion  51   b  also changes depending on the remaining amount of toner. 
     In other words, when the remaining amount of toner is great, the optical path Q 1  is likely to be blocked by toner, and therefore, the time the light-receiving portion  51   b  receives light is short, and the light intensity of the light received by the light-receiving portion  51   b  is small. On the other hand, when the remaining amount of toner is small, conversely, the time the light-receiving portion  51   b  receives light is long, and the light intensity of the light received by the light-receiving portion  51   b  is great. Thus, based on the light reception time and the light intensity of the light-receiving portion  51   b  in this manner, the control portion  90  can determine the level of the remaining amount of toner as described below. 
     For example, as illustrated in  FIG.  11 A , if the amount of toner in the conveying chamber  36  of the developing container  32  is a minute amount, the time the light-receiving portion  51   b  receives light is long, and the light intensity of the light received by the light-receiving portion  51   b  is great. Thus, it is determined that the remaining amount of toner is small. On the other hand, as illustrated in  FIG.  11 B , if the amount of toner in the conveying chamber  36  of the developing container  32  is great, the time the light-receiving portion  51   b  receives light is short, and the light intensity of the light received by the light-receiving portion  51   b  is small. Thus, it is determined that the remaining amount of toner is great. 
     The method for detecting or estimating the remaining amount of toner is not limited to the optical toner remaining amount detection system described with reference to  FIG.  9   , and methods for detecting or estimating the remaining amount of toner using various known systems can be employed. For example, two or more metal plates or conductive resin sheets extending in the longitudinal direction of the developing roller may be placed on an inner wall of the developing container  32  that is the frame member, the capacitance between the two metal plates or conductive resin sheets may be measured, and the remaining amount of toner may be detected or estimated. Alternatively, a load cell may be provided to support the developing device  30  from below, and the CPU  91  may subtract the weight of the developing device  30  when there is no toner therein from the weight measured by the load cell, thereby calculating the remaining amount of toner. 
     [Control System of Image Forming Apparatus] 
       FIG.  12    is a block diagram illustrating a control system of the image forming apparatus  1 . The control portion  90  as a control means of the image forming apparatus  1  includes the CPU  91  as a calculation device, a random-access memory (RAM)  92  used as a work area for the CPU  91 , and the ROM  93  that stores various programs. The control portion  90  also includes an input/output (I/O) interface  94  as an input/output port connected to an external device, and the A/D conversion portion  95  that converts an analog signal into a digital signal. 
     To the input side of the control portion  90 , the toner remaining amount sensor  51 , an attachment sensor  53 , and an opening/closing sensor  54  are connected. The attachment sensor  53  detects that the toner pack  40  is attached to the replenishment opening  32   a  of the developing container  32 . For example, the attachment sensor  53  is provided in the replenishment opening  32   a  and includes a pressure-sensitive switch that outputs a detection signal when pressed by the protrusions  42  of the toner pack  40 . The opening/closing sensor  54  detects whether the opening/closing member  83  is opened relative to the top cover  82 . The opening/closing sensor  54  includes, for example, a pressure-sensitive switch or a magnetic sensor. 
     To the control portion  90 , the operation portion  300 , the image forming portion  10 , and a toner remaining amount panel  400  as an informing means capable of providing information regarding the remaining amount of toner are connected. The operation portion  300  includes a display portion  301  capable of displaying various setting screens, a physical key or the like. The display portion  301  includes, for example, a liquid crystal panel. The image forming portion  10  includes the motor M 1  as a driving source that drives the photosensitive drum  21 , the developing roller  31 , the supply roller  33 , the agitation member  34 , and the like. The photosensitive drum  21 , the developing roller  31 , the supply roller  33 , and the agitation member  34  may be configured to be driven by separate motors. 
     As illustrated in  FIGS.  1 B and  13   , the toner remaining amount panel  400  is provided on the right side on a front surface of a housing of the printer main body  100 , i.e., on the opposite side of the operation portion  300  placed on the left side, and displays information regarding the remaining amount of toner in the developing container  32 . In the present exemplary embodiment, the toner remaining amount panel  400  is a panel member including a plurality of (three in the present exemplary embodiment) graduations arranged vertically, and the graduations correspond to a low level, a mid level, and a full level described below. 
     More specifically, as illustrated in  FIG.  13 A , if only the lowest graduation is turned on and blinks, it indicates that the remaining amount of toner in the developing container  32  is at a near out level, which is a fourth state. As illustrated in  FIG.  13 B , if only the lowest graduation is turned on, it indicates that the remaining amount of toner in the developing container  32  is at the low level, which is a third state (third display). As illustrated in  FIG.  13 C , if the lowest gradation and a middle graduation are turned on, and the highest graduation is turned off, it indicates that the remaining amount of toner in the developing container  32  is at the mid level, which is a second state. As illustrated in  FIG.  13 D , if all of the three graduations are turned on, it indicates that the remaining amount of toner in the developing container  32  is at the full level, which is a first state. 
     The toner remaining amount panel  400  is not limited to a liquid crystal panel, and may be composed of a light source such as an LED or an incandescent light and a diffusing lens. Alternatively, a configuration may be employed in which the toner remaining amount panel  400  is not separately provided, and the remaining amount of toner may be displayed using graduations as described in the present exemplary embodiment on a display of the operation portion  300 . While the configuration has been described in which four states are displayed using three graduations in the present exemplary embodiment, the number of graduations is not limited to this, and may be appropriately set according to the configuration of the image forming apparatus. While the informing means indicating the remaining amount of toner has been described in the example illustrated in  FIG.  13   , the toner remaining amount panel  400  is not limited to this. For example, the display in  FIG.  13 B  may be display indicating that toner supply is necessary, the display in  FIG.  13 C  may be display indicating that the toner supply is unnecessary, and the display in  FIG.  13 D  may be display indicating that the toner supply is sufficiently performed. 
     [Toner Supply Process] 
     &lt;Display of Toner Remaining Amount Panel when Toner is Consumed&gt; 
     Now, a description is given of the switching of the display of the toner remaining amount panel  400  when toner is consumed according to the present exemplary embodiment.  FIG.  14    is a schematic diagram illustrating thresholds for switching the display of the toner remaining amount panel  400  depending on the remaining amount of toner in the developing container  32  and the display patterns of the toner remaining amount panel  400  when toner is consumed. 
     As illustrated in  FIG.  14   , if toner in the developing container  32  is consumed by the image forming operation, the display of the toner remaining amount panel  400  is switched based on a detection result of the toner remaining amount sensor  51  described above. In other words, detection (first detection) is made by the toner remaining amount sensor  51  to reflect a decrease in the amount of toner in the developing container  32  by the image forming operation on the display of the toner remaining amount panel  400 . Specifically, if the detection result of the remaining amount of toner in the developing container  32  by the toner remaining amount sensor  51  is greater than or equal to a threshold D (a first threshold), the control portion  90  sets the display of the toner remaining amount panel  400  to the first state (first display) which indicates the full level and where all the three graduations are turned on. If the detection result of the remaining amount of toner in the developing container  32  by the toner remaining amount sensor  51  is less than the threshold D as toner is consumed, the control portion  90  sets the display of the toner remaining amount panel  400  to the second state (second display) which indicates the mid level and where the two graduations are turned on. In the present exemplary embodiment, the value of the threshold D is set to 5.0 K. Various thresholds described below including the threshold D may be appropriately set depending on the volume of toner to be supplied or various configurations of the image forming apparatus. 
     If the detection result of the remaining amount of toner in the developing container  32  by the toner remaining amount sensor  51  is less than a threshold C (2.5 K in the present exemplary embodiment) as toner is consumed, the control portion  90  sets the display of the toner remaining amount panel  400  to the third state (third display) which indicates the low level and where one graduation is turned on. If the detection result of the remaining amount of toner in the developing container  32  by the toner remaining amount sensor  51  is less than a threshold B (0.5 K in the present exemplary embodiment), the control portion  90  sets the display of the toner remaining amount panel  400  to the fourth state (fourth display) which indicates the near out level and where one lowest graduation blinks. Then, if the detection result of the remaining amount of toner in the developing container  32  by the toner remaining amount sensor  51  is less than a threshold A (0 K in the present exemplary embodiment), the control portion  90  determines that toner in the developing container  32  has run out, and then sets the display to the state where all the three graduations are turned off. 
     More specifically, if the detection result of the toner remaining amount sensor  51  is between 2.5 K and 5.0 K, the control portion  90  sets the display of the toner remaining amount panel  400  to the second state. If the detection result of the toner remaining amount sensor  51  is between 0.5 K and 2.5 K, the control portion  90  sets the display of the toner remaining amount panel  400  to the third state. If the detection result of the toner remaining amount sensor  51  is between 0 K and 0.5 K, the control portion  90  sets the display of the toner remaining amount panel  400  to the fourth state. If it is determined that there is no remaining amount of toner, the control portion  90  sets the display to the state where all the graduations are turned off. 
     The interval between the threshold D and the threshold C, i.e., the interval between thresholds related to the switching of the display of the top graduation, according to the present exemplary embodiment is set to an amount of supply corresponding to one toner pack  40 . Similarly, the interval between the threshold C and the threshold A, i.e., the interval between thresholds related to the switching of the display of the middle graduation, according to the present exemplary embodiment is also set to the amount of supply corresponding to one toner pack  40 . The interval between the thresholds related to the switching of the display of the graduation is thus set, whereby the user can easily identify the number of toner packs  40  that can be supplied. Thus, it is possible to improve visibility of the status where toner can be supplied for the user. 
     On the other hand, in a case where the interval between the thresholds related to the switching of the display of a single graduation is set to be smaller than the amount of supply corresponding to one toner pack  40 , the following concern arises depending on a setting range of the interval between the thresholds. For example, if the interval between the thresholds related to the switching of the display of one graduation is set to 1 K on the premise of the capacity of the toner pack  40  and the capacity of the developing container  32  according to the present exemplary embodiment, it is necessary to increase the number of graduations to enable the display of the entire capacity of the developing container  32 . This leads to an increase in cost. If the interval between the thresholds related to the switching of the display of one graduation is set to 1 K without increasing the number of graduations to avoid an increase in cost, a setting range of the volume of toner in the developing container  32  is narrowed. From these viewpoints, in the present exemplary embodiment, the interval between the thresholds related to the switching of the display of one graduation is set corresponding to the amount of supply corresponding to one toner pack  40 . 
     &lt;Display of Toner Remaining Amount Panel when Toner is Supplied&gt; 
     Now, a description is given of the switching of the display of the toner remaining amount panel  400  when toner is supplied according to the present exemplary embodiment.  FIG.  15    is a schematic diagram illustrating the thresholds for switching the display of the toner remaining amount panel  400  depending on the remaining amount of toner in the developing container  32  and the display patterns of the toner remaining amount panel  400  when toner is supplied. 
     As illustrated in  FIG.  15   , if toner is supplied to the developing container  32  by the user supplying toner using the toner pack  40 , the display of the toner remaining amount panel  400  is switched based on the detection result of the toner remaining amount sensor  51  as described above. Detection (second detection) is made by the toner remaining amount sensor  51  to reflect an increase in the amount of toner in the developing container  32  by the supply of toner on the display of the toner remaining amount panel  400 . Specifically, if the detection result of the remaining amount of toner in the developing container  32  by the toner remaining amount sensor  51  is greater than or equal to a threshold D′ (a second threshold), the control portion  90  sets the display of the toner remaining amount panel  400  to the first state which indicates the full level and where all the three graduations are turned on. If the detection result of the remaining amount of toner in the developing container  32  by the toner remaining amount sensor  51  is greater than or equal to a threshold C′ as toner is supplied, the control portion  90  sets the display of the toner remaining amount panel  400  to the second state which indicates the mid level and where the two graduations are turned on. 
     In the present exemplary embodiment, the values of the thresholds for switching the display between the full level and the mid level are set to different values between when toner is supplied and when toner is consumed. More specifically, as illustrated in  FIG.  15   , the threshold D′ (3.5 K in the present exemplary embodiment) for turning on the top graduation by supplying toner from the second state is set to a value smaller than the threshold D (5.0 K) when toner is consumed. Similarly, the threshold C′ (2.0 K in the present exemplary embodiment) for turning on the middle graduation by supplying toner from the third state is set to a value smaller than the threshold C (2.5 K) when toner is consumed. The display of the low level as the third state and the near out level as the fourth state and the thresholds B and A are similar to those when toner is consumed, and therefore are not described. 
     More specifically, in the configuration of the present exemplary embodiment, if the detection result of the toner remaining amount sensor  51  after toner is supplied using the toner pack  40  is greater than or equal to 2.0 K, the control portion  90  sets the display of the toner remaining amount panel  400  to the second state. If the detection result of the toner remaining amount sensor  51  after toner is supplied using the toner pack  40  is greater than or equal to 3.5 K, the control portion  90  sets the display of the toner remaining amount panel  400  to the first state. In other words, on the toner remaining amount panel  400 , the amount of toner in the developing container  32  when the second state switches to the first state when toner is supplied (when the second detection is made) is smaller than the amount of toner in the developing container  32  when the first state switches to the second state when toner is consumed (when the first detection is made). While the value of the threshold D′ is set to 3.5 K and the value of the threshold C′ is set to 2.0 K in the present exemplary embodiment, the thresholds are not limited thereto. The above thresholds may be appropriately set depending on the volume of toner to be supplied or various configurations of the image forming apparatus as long as each threshold is at least set to a value smaller than a threshold when toner is consumed. 
     The reason for varying the thresholds D′ and C′ when toner is supplied from the thresholds D and C when toner is consumed is described in detail below. 
     As described above, the interval between the thresholds corresponding to the switching of the display of one graduation, i.e., each of the interval between the thresholds D and C and the interval between the thresholds C and A, according to the present exemplary embodiment is set to the amount of supply corresponding to one toner pack  40 . This enables the user to easily identify the number of toner packs  40  that can be supplied. Thus, it is possible to improve the visibility of the status where toner can be supplied for the user. 
     In a case where the interval between the thresholds corresponding to the switching of the display of one graduation is set to a value greater than the amount of supply corresponding to one toner pack  40 , and when the user supplies toner using the toner pack  40 , the display of the toner remaining amount panel  400  may not change. In this case, the display of the toner remaining amount panel  400  does not change even though the user supplies an amount corresponding to one toner pack  40 . Thus, it is difficult to identify whether the replenishment is successful. Thus, as in the configuration of the present exemplary embodiment, it is desirable that the interval between the thresholds corresponding to the switching of the display of one graduation be set corresponding to the amount of supply corresponding to one toner pack  40 . 
     If the method for detecting the remaining amount of toner by the toner remaining amount sensor  51  is used, a slight error in detection may occur between the remaining amount of toner in the developing container  32  and the detection result although the error is set within an acceptable range of each apparatus. Further, in the toner supply configuration according to the present exemplary embodiment, since the user supplies toner using the toner pack  40 , an error in replenishment, e.g., an actual amount of supply is smaller than an assumed amount of supply, may occur depending on handling thereof by the user. If the detection is influenced by these errors, the display of the toner remaining amount panel  400  may not switch even though the user has supplied toner, whereby it may be difficult for the user to identify whether the supply of toner is successful. 
     Accordingly, in the present exemplary embodiment, the thresholds D′ and C′ when toner is supplied are set to be smaller than the thresholds D and C when toner is consumed. Consequently, even if the detection is influenced by the error in detection by the toner remaining amount sensor  51  or the error in handling when toner is supplied by the user, it is possible to appropriately switch the display of the toner remaining amount panel  400  when toner is supplied by the user. As a result, it is possible to notify the user that the toner is appropriately supplied. Thus, it is possible to improve the visibility of the toner supply status. 
     Second Exemplary Embodiment 
     Now, with reference to  FIG.  16   , a second exemplary embodiment of the present invention is described. The second exemplary embodiment is different from the first exemplary embodiment in that the timing of the switching of the display of the toner remaining amount panel  400  after the supply of toner is adjusted. Other operations and configurations of the image forming apparatus are substantially the same as those in the first exemplary embodiment. Thus, in the following description, the configurations and operations in common with those in the first exemplary embodiment are designated by the same signs, and are not described. 
     As described in the first exemplary embodiment, if the supply of toner by the user is completed, the display of the toner remaining amount panel  400  switches after the detection by the toner remaining amount sensor  51  is made. At this time, if the toner is supplied to be in a range where the detection result comes out to be close to a threshold for switching the display, a graduation of the toner remaining amount panel  400  may switch immediately after the replenishment under the influence of the error in detection by the toner remaining amount sensor  51 . For example, a description is given of a possible concern after the detection result of the toner remaining amount sensor  51  exceeds the threshold D′ by supply of toner from the second state, and the display of the toner remaining amount panel  400  switches to the first state. In this case, depending on the error in detection by the toner remaining amount sensor  51 , the detection result of the toner remaining amount sensor  51  becomes less than the threshold D shortly after the image forming operation is started, whereby the display of the toner remaining amount panel  400  switches to the second state. 
     Accordingly, in the present exemplary embodiment, based on image forming information in the image forming operation after toner is supplied, the timing of the switching of the display of the toner remaining amount panel  400  is controlled.  FIG.  16    is a flowchart illustrating a flow of control according to the present exemplary embodiment. 
     As illustrated in  FIG.  16   , in S 51 , if the supply of toner by the user is completed, the display of the toner remaining amount panel  400  switches based on the detection result of the toner remaining amount sensor  51 . A case is described where toner is supplied from the mid level, which is the second state. Thus, a threshold X illustrated in S 52  refers to the threshold D′. By a sequence in S 52 , the top graduation is turned on, and the display of the toner remaining amount panel  400  switches from the second state to the first state. Then, when the supply of toner by the user is completed, as illustrated in S 53 , recording of a count value in a storage medium (not illustrated) built into the control portion  90  is started. In the present exemplary embodiment, the presence or absence of an image signal with respect to each pixel at a predetermined frequency that is obtained from an image signal regarding a formed image when image formation is performed is counted and recorded. Then, the count is accumulated every time image formation is performed. 
     Then, if toner in the developing container  32  is consumed in the image forming operation, then as illustrated in S 54 , the control portion  90  determines whether the detection result of the toner remaining amount sensor  51  is less than the threshold D. If the remaining amount of toner is below the threshold D in S 54  (YES), then in S 55 , the control portion  90  determines whether the previously recorded count value is greater than or equal to a predetermined value. If the remaining amount of toner is not below the threshold D in S 54  (NO), the detection of the remaining amount of toner is repeated at a predetermined timing until the remaining amount of toner is below the threshold D in S 54 . 
     If the count value is greater than or equal to the predetermined value in S 55  (YES), then in S 56 , the control portion  90  turns off the graduation corresponding to the threshold D, i.e., switches the display of the toner remaining amount panel  400  from the first state to the second state. On the other hand, if the count value is less than the predetermined value in S 55  (NO), the determination of the count value is repeated until the count value is greater than or equal to the predetermined value in S 55 . In the present exemplary embodiment, the predetermined value used in the determination in S 55  is set to a value corresponding to the number of pixels in a case where a predetermined image is formed on 100 recording materials. However, the predetermined value is not limited thereto. The predetermined value used in the determination of the count value may be appropriately set depending on various configurations or control of the image forming apparatus. 
     Although the control is performed based on the count value of the result of counting the presence or absence of an image signal with respect to each pixel at the predetermined frequency in the present exemplary embodiment, the control is not limited thereto. For example, a configuration may be employed in which the counting of the accumulated number of recording materials on which image formation is performed is started in S 53 , and if the accumulated count value of recording materials is greater than or equal to a predetermined number in S 55 , the graduation corresponding to the threshold X is turned off, thereby the display of the toner remaining amount panel  400  is switched. As the counting of the presence or absence of an image signal with respect to each pixel, a method for counting based on an image signal emitted from an exposure device to the photosensitive drum  21  may be used, or a method for counting based on image information loaded into the control portion  90  in advance may be used. 
     Third Exemplary Embodiment 
     Now, with reference to  FIGS.  17  and  18   , a third exemplary embodiment of the present invention is described. The third exemplary embodiment is different from the first exemplary embodiment in that the display of the toner remaining amount panel  400  when toner is supplied is controlled. Other operations and configurations of the image forming apparatus, however, are substantially the same as those in the first exemplary embodiment. Thus, in the following description, the configurations and operations in common with those in the first exemplary embodiment are designated by the same signs, and are not described. 
       FIGS.  17 A and  17 B  are schematic diagrams illustrating the patterns of the display of the toner remaining amount panel  400  when toner is supplied from the toner pack  40  to the developing container  32  by the user according to the present exemplary embodiment.  FIG.  18    is a flowchart illustrating a flow of control according to the present exemplary embodiment. 
     As described above, in the first exemplary embodiment, after the toner supply by the user, the display of the toner remaining amount panel  400  is switched based on the detection result of the toner remaining amount sensor  51 . In contrast, in the present exemplary embodiment, display during replenishment is performed in which, while the user supplies toner by attaching the toner pack  40  to the attachment portion  57  (the replenishment opening  32   a ), the display of the toner remaining amount panel  400  is switched as illustrated in  FIG.  17 A or  17 B . Then, after the toner supply is completed, the display of the toner remaining amount panel  400  is switched based on the detection result of the toner remaining amount sensor  51 . The display during replenishment is thus performed, whereby, when the user performs a replenishment operation, it is possible to notify the user of the status where toner is currently being supplied. Thus, it is possible to improve visibility of the replenishment status for the user. 
     As the display during replenishment, a pattern where a state where the three graduations are turned on one by one is repeated as illustrated in  FIG.  17 A , and a pattern where a state where all the three graduations are turned off and a state where all the three graduations are turned on are repeated as illustrated in  FIG.  17 B  are possible. However, the display during replenishment is not limited to these two patterns. For example, a pattern where the first to fourth states are randomly switched, such as a pattern where the state where the three graduations are turned off one by one from the state where all the three graduations are turned on is repeated, is also possible. As the display during replenishment, a configuration may be employed in which at least two out of the five states that are the first to fourth states illustrated in  FIGS.  14  and  15    and an all-turned-off state where none of the graduations is turned on are repeatedly displayed. Consequently, it is possible to perform the display during replenishment corresponding to none of the above five states. Thus, it is possible to allow the user to visually recognize that toner is currently being supplied. 
       FIG.  18    is a flowchart illustrating control according to the present exemplary embodiment. In S 61 , if the user attaches the toner pack  40  to the attachment portion  57  to supply toner, then in S 62 , the control portion  90  determines whether a trigger for starting the replenishment is on. In the present exemplary embodiment, a detection portion (not illustrated) detects that the toner pack  40  is connected to the attachment portion  57 , whereby the control portion  90  determines that the trigger is on. Then, if it is determined in S 62  that the trigger is on (YES), then in S 63 , the control portion  90  starts the display during replenishment described above by switching the display of the toner remaining amount panel  400 . On the other hand, if it is determined in S 62  that the trigger is not on (NO), the determination in S 62  is repeated until the trigger is on. While the user supplies toner, the display during replenishment is continued. 
     Then, in S 64 , it is determined whether the toner supply is completed. If it is determined that the toner supply is completed (YES), then in S 65 , the control portion  90  ends the display during replenishment by switching the display of the toner remaining amount panel  400 . In the present exemplary embodiment, if the detection portion (not illustrated) detects release of the connection between the toner pack  40  and the attachment portion  57 , the control portion  90  determines that the toner supply is completed. If it is determined in S 64  that the toner supply is not completed (NO), the determination in S 64  is repeated until the toner supply is completed. Then, in S 66 , the display of the toner remaining amount panel  400  is switched based on the detection result of the toner remaining amount sensor  51 . 
     While the detection of the release of the connection between the toner pack  40  and the attachment portion  57  is used as the determination of whether the toner supply is completed in S 64  in the present exemplary embodiment, the determination is not limited thereto. For example, the timing when the detection result of the toner remaining amount sensor  51  when toner is supplied is obtained may be used as the determination of whether the toner supply is completed. In this case, regardless of whether the user completes the release of the connection between the toner pack  40  and the attachment portion  57 , the display during replenishment is ended at the timing when the detection result of the toner remaining amount sensor  51  is obtained, and then, the display of the toner remaining amount panel  400  is performed based on the detection result. 
     The determination of whether the toner supply is completed in S 64  may be made coincident with the later one of timings when the release of the connection between the toner pack  40  and the attachment portion  57  is detected and when the detection result of the toner remaining amount sensor  51  as toner is supplied is obtained. Alternatively, as the determination of whether the toner supply is completed in S 64 , a timing a predetermined time after the detection of the remaining amount of toner ends may be used. A timing of an operation for closing the opening/closing member  83  or an operation performed by the user on the operation portion  300  may be used. The time for the detection of the remaining amount of toner somewhat depends on the amount of toner in the developing container  32 . Thus, for example, if the detection of the remaining amount of toner ends sooner than the user ends the replenishment operation, the user may forget to perform an operation of detaching the toner pack depending on the situation. Thus, as the timing of ending the display during replenishment, a timing other than that of the detection of the remaining amount of toner described above may be used, whereby it is possible to prevent the user from forgetting to perform the operation of detaching the toner pack and from moving away from the image forming apparatus. 
       FIG.  19    is a schematic diagram illustrating the configuration of an image forming apparatus  1  according to a modification of the present exemplary embodiment. In the first to third exemplary embodiments, the configurations have been described in which the toner pack  40  is attached to the attachment portion  57  and the toner pack  40  is rotated, thereby toner is supplied. The configuration, however, is not limited thereto. As illustrated in  FIG.  19   , a configuration may be employed in which a lever portion  157   a  is provided in an attachment portion  157 , and after the toner pack  40  is attached to the attachment portion  157 , the lever portion  157   a  is rotated, thereby the shutter member  41  is moved from the closed position to the opened position to supply toner. In this case, as the determination of whether the trigger is on in S 62  in  FIG.  18    according to the present exemplary embodiment, the rotation of the lever portion  157   a  may be used. Specifically, a lever sensor (not illustrated) is provided that detects at which of the opened position and the closed position the lever portion  157   a  is. Then, a state where the sensor detects that the lever portion  157   a  moves from the closed position to the opened position may be used in S 62  in  FIG.  18   . As the determination of whether the toner supply is completed in S 64 , an operation of rotating the lever portion  157   a  to return the lever portion  157   a  to the position before the toner pack  40  is attached may be used. Specifically, a state where the lever sensor detects that the lever portion  157   a  moves from the opened position to the closed position may be used in S 64  in  FIG.  18   . Also in the configuration according to the modification, as the determination of whether the toner supply is completed in S 64 , various timings as described above can be used in combination. 
     While the present exemplary embodiment has been described above with reference to the first exemplary embodiment, the invention according to the present exemplary embodiment may not be premised on the first exemplary embodiment. When the user supplies toner, the display during replenishment described in the present exemplary embodiment is performed, whereby it is possible to improve the visibility of the toner supply status for the user. 
     [Others] 
     As illustrated in  FIG.  20 A , an operation portion  300 E may be placed not in the printer main body  100  but in the reading device  200 , or may be placed on the right side of the apparatus together with the toner remaining amount panel  400 . As a matter of course, both the operation portion  300 E and the toner remaining amount panel  400  may be placed on the right side of the apparatus. Alternatively, as illustrated in  FIG.  20 B , a toner remaining amount panel  400 F may be placed on the left side of the apparatus, and an operation portion  300 F may be placed on the right side of the apparatus. Alternatively, as illustrated in  FIG.  20 C , an operation portion  300 G may be provided in the printer main body  100 , and a toner remaining amount panel  400 G and the operation portion  300 G may be placed on the same side of the apparatus. 
     While the reading device  200  is provided above the printer main body  100  in any of the above embodiments, the image forming apparatus is not limited to this. More specifically, the image forming apparatus may be a printer without the reading device. The reading device may be a reading device including an auto document feeder (ADF) that feeds a document. 
     Fourth Exemplary Embodiment 
     [Toner Supply Process] 
     &lt;Display of Toner Remaining Amount Panel&gt; 
     Now, a description is given of the switching of the display of the toner remaining amount panel  400  when toner is consumed and when toner is supplied according to the present exemplary embodiment. The operations and the configurations of the image forming apparatus are substantially the same as those in the first exemplary embodiment. Thus, in the following description, the configurations and operations in common with those in the first exemplary embodiment are designated by the same signs, and are not described. 
       FIG.  21    is a schematic diagram illustrating thresholds for switching the display of the toner remaining amount panel  400  depending on the remaining amount of toner in the developing container  32  and the display patterns of the toner remaining amount panel  400 . 
     As illustrated in  FIG.  21   , if toner in the developing container  32  is consumed by the image forming operation, the display of the toner remaining amount panel  400  is switched based on a detection result of the toner remaining amount sensor  51  described above. Specifically, if the detection result of the remaining amount of toner in the developing container  32  by the toner remaining amount sensor  51  is greater than or equal to a threshold D (a first threshold), the control portion  90  sets the display of the toner remaining amount panel  400  to the first state which indicates the full level and where all the three graduations are turned on. If the detection result of the remaining amount of toner in the developing container  32  by the toner remaining amount sensor  51  is less than the threshold D as toner is consumed, the control portion  90  sets the display of the toner remaining amount panel  400  to the second state which indicates the mid level and where the two graduations are turned on. In the present exemplary embodiment, the value of the threshold D is set to 3.5 K. Various thresholds described below including the threshold D may be appropriately set depending on the volume of toner to be supplied or various configurations of the image forming apparatus. 
     If the detection result of the remaining amount of toner in the developing container  32  by the toner remaining amount sensor  51  is less than a threshold C (a second threshold) as toner is consumed, the control portion  90  sets the display of the toner remaining amount panel  400  to the third state which indicates the low level and where one graduation is turned on. In the present exemplary embodiment, the value of the threshold C is set to 2.0 K. If the detection result of the remaining amount of toner in the developing container  32  by the toner remaining amount sensor  51  is less than a threshold B (0.5 K in the present exemplary embodiment), the control portion  90  sets the display of the toner remaining amount panel  400  to the fourth state which indicates the near out level and where one lowest graduation blinks. Then, if the detection result of the remaining amount of toner in the developing container  32  by the toner remaining amount sensor  51  is less than a threshold A (0 K in the present exemplary embodiment), the control portion  90  determines that toner in the developing container  32  has run out, and then sets the display to the state where all the three graduations are turned off. 
     More specifically, if the detection result of the toner remaining amount sensor  51  is between 2.0 K and 3.5 K, the control portion  90  sets the display of the toner remaining amount panel  400  to the second state. If the detection result of the toner remaining amount sensor  51  is between 0.5 K and 2.0 K, the control portion  90  sets the display of the toner remaining amount panel  400  to the third state. If the detection result of the toner remaining amount sensor  51  is between 0 K and 0.5 K, the control portion  90  sets the display of the toner remaining amount panel  400  to the fourth state. If it is determined that there is no remaining amount of toner, the control portion  90  sets the display to the state where all the graduations are turned off. 
     While the thresholds and the display of the toner remaining amount panel  400  when toner is consumed have been described above, the display of the toner remaining amount panel  400  is switched based on the thresholds described with reference to  FIG.  21    also when toner is supplied. More specifically, the graduations are turned on based on the detection result of the toner remaining amount sensor  51  when toner is supplied. 
     The interval (the difference) between the threshold D (the amount of toner corresponding to the threshold D) and the threshold C (the amount of toner corresponding to the threshold C), i.e., the interval (the difference) between thresholds (the amounts of toner corresponding to the thresholds) related to the switching of the display of the top graduation, according to the present exemplary embodiment is set to be less than the amount of supply corresponding to one toner pack  40 . Similarly, the interval (the difference) between the threshold C (the amount of toner corresponding to the threshold C) and the threshold A (the amount of toner corresponding to the threshold A), i.e., the interval (the difference) between thresholds (the amounts of toner corresponding to the thresholds) related to the switching of the display of the middle graduation, according to the present exemplary embodiment is also set to be less than the amount of supply corresponding to one toner pack  40 . The amount of supply corresponding to one toner pack  40  is the same as the amount of toner stored in the toner pack  40  in an unused state. 
     The reason for this is described in detail below. 
     In a case where the interval between the thresholds corresponding to the switching of the display of one graduation is set to a value greater than the amount of supply corresponding to one toner pack  40 , and when the user supplies toner using the toner pack  40 , the display of the toner remaining amount panel  400  may not change. In this case, the display of the toner remaining amount panel  400  does not change even though the user supplies an amount corresponding to one toner pack  40 . Thus, it is difficult to identify whether the replenishment is successful. 
     If the method for detecting the remaining amount of toner by the toner remaining amount sensor  51  is used, a slight error in detection may occur between the remaining amount of toner in the developing container  32  and the detection result although the error is set within an acceptable range of each apparatus. Further, in the toner supply configuration according to the present exemplary embodiment, since the user supplies toner using the toner pack  40 , an error in replenishment, e.g., an actual amount of supply is smaller than an assumed amount of supply, may occur depending on handling thereof by the user. If the detection is influenced by these errors, the display of the toner remaining amount panel  400  may not switch even though the user has supplied toner, whereby it may be difficult for the user to identify whether the supply of toner is successful. 
     Accordingly, in the present exemplary embodiment, the interval between the thresholds corresponding to the switching of the display of one graduation is set to be less than the amount of supply corresponding to one toner pack  40 . Consequently, even if the detection is influenced by the error in detection by the toner remaining amount sensor  51  or the error in handling when toner is supplied by the user, it is possible to appropriately switch the display of the toner remaining amount panel  400  when toner is supplied by the user. As a result, it is possible to notify the user that the toner is appropriately supplied. Thus, it is possible to improve the visibility of the toner supply status. 
     In a case where the interval (the difference) between the thresholds related to the switching of the display of a single graduation is set to be smaller than the amount of supply corresponding to one toner pack  40 , and if the setting range of the interval between the thresholds is set to be too small, the following concern arises. For example, if thresholds having a range less than or equal to a half of one toner pack  40  are set and when one toner pack  40  is supplied, two graduations in the display of the toner remaining amount panel  400  may be turned on. From a viewpoint of the visibility of the supply status for the user, it is desirable that the replenishment with one toner pack  40  correspond to one graduation. Thus, the interval between the thresholds related to the switching of the display of one graduation is set to be less than the amount of supply corresponding to one toner pack  40  and greater than or equal to a half of the amount of supply corresponding to one toner pack  40 . To obtain the effect of the present exemplary embodiment, however, it is only necessary to at least set the interval between the thresholds related to the switching of the display of one graduation to be less than the amount of supply corresponding to one toner pack  40 , and it is not essential to set the interval between the thresholds to be greater than or equal to a half of the amount of supply corresponding to one toner pack  40 . 
     Fifth Exemplary Embodiment 
     Now, with reference to  FIG.  22   , a fifth exemplary embodiment of the present invention is described. The fifth exemplary embodiment is different from the first exemplary embodiment in that the timing of the switching of the display of the toner remaining amount panel  400  after supply of toner is adjusted. Other operations and configurations of the image forming apparatus, however, are substantially the same as those in the first exemplary embodiment. Thus, in the following description, the configurations and operations in common with those in the first exemplary embodiment are designated by the same signs, and are not described. 
     As described in the first exemplary embodiment, if the supply of toner by the user is completed, the display of the toner remaining amount panel  400  switches after the detection by the toner remaining amount sensor  51  is made. At this time, if the toner is supplied to be in a range where the detection result comes out to be close to a threshold for switching the display, a graduation of the toner remaining amount panel  400  may switch immediately after the replenishment under the influence of the error in detection by the toner remaining amount sensor  51 . For example, a description is given of a possible concern after the detection result of the toner remaining amount sensor  51  exceeds the threshold D′ by supply of toner from the second state, and the display of the toner remaining amount panel  400  switches to the first state. In this case, depending on the error in detection by the toner remaining amount sensor  51 , the detection result of the toner remaining amount sensor  51  becomes less than the threshold D shortly after the image forming operation is started, whereby the display of the toner remaining amount panel  400  switches to the second state. 
     Accordingly, in the present exemplary embodiment, based on image forming information in the image forming operation after toner is supplied, the timing of the switching of the display of the toner remaining amount panel  400  is controlled.  FIG.  22    is a flowchart illustrating a flow of control according to the present exemplary embodiment. 
     As illustrated in  FIG.  22   , in S 51 , if the supply of toner by the user is completed, the display of the toner remaining amount panel  400  switches based on the detection result of the toner remaining amount sensor  51 . A case is described where toner is supplied from the mid level, which is the second state. Thus, a threshold X illustrated in S 52  refers to the threshold D′. By a sequence in S 52 , the top graduation is turned on, and the display of the toner remaining amount panel  400  switches from the second state to the first state. Then, when the supply of toner by the user is completed, as illustrated in S 53 , recording of a count value in a storage medium (not illustrated) built into the control portion  90  is started. In the present exemplary embodiment, the presence or absence of an image signal with respect to each pixel at a predetermined frequency that is obtained from an image signal regarding a formed image when image formation is performed is counted and recorded. Then, the count is accumulated every time image formation is performed. 
     Then, if toner in the developing container  32  is consumed in the image forming operation, then as illustrated in S 54 , the control portion  90  determines whether the detection result of the toner remaining amount sensor  51  is less than the threshold D. If the remaining amount of toner is below the threshold D in S 54  (YES), then in S 55 , the control portion  90  determines whether the previously recorded count value is greater than or equal to a predetermined value. If the remaining amount of toner is not below the threshold D in S 54  (NO), the detection of the remaining amount of toner is repeated at a predetermined timing until the remaining amount of toner is below the threshold D in S 54 . 
     If the count value is greater than or equal to the predetermined value in S 55  (YES), then in S 56 , the control portion  90  turns off the graduation corresponding to the threshold D, i.e., switches the display of the toner remaining amount panel  400  from the first state to the second state. On the other hand, if the count value is less than the predetermined value in S 55  (NO), the determination of the count value is repeated until the count value is greater than or equal to the predetermined value in S 55 . In the present exemplary embodiment, the predetermined value used in the determination in S 55  is set to a value corresponding to the number of pixels in a case where a predetermined image is formed on 100 recording materials. However, the predetermined value is not limited thereto. The predetermined value used in the determination of the count value may be appropriately set depending on various configurations or control of the image forming apparatus. 
     Although the control is performed based on the count value of the result of counting the presence or absence of an image signal with respect to each pixel at the predetermined frequency in the present exemplary embodiment, the control is not limited thereto. For example, a configuration may be employed in which the counting of the accumulated number of recording materials on which image formation is performed is started in S 53 , and if the accumulated count value of recording materials is greater than or equal to a predetermined number in S 55 , the graduation corresponding to the threshold X is turned off, thereby the display of the toner remaining amount panel  400  is switched. As the counting of the presence or absence of an image signal with respect to each pixel, a method for counting based on an image signal emitted from an exposure device to the photosensitive drum  21  may be used, or a method for counting based on image information loaded into the control portion  90  in advance may be used. 
     The present invention is not limited to the above exemplary embodiments, and can be changed and modified in various ways without departing from the spirit and the scope of the present invention. Therefore, the following claims are appended to apprise the public of the scope of the present invention. 
     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.