Patent Publication Number: US-2023134527-A1

Title: Image forming apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of International Patent Application No. PCT/JP2020/011083, filed Mar. 13, 2020, which claims the benefit of Japanese Patent Application No. 2019-049217, filed Mar. 15, 2019, and Japanese Patent Application No. 2020-042020, filed Mar. 11, 2020, 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. 
     Description of the Related Art 
     Typically, an image forming apparatus of an electrophotographic system forms an image by transferring a toner image formed on the surface of a photosensitive drum onto a transfer material serving as a transfer medium. In addition, as a replenishment system of developer, for example, a process cartridge system and a toner replenishment system are known. The process cartridge system is a system in which a photosensitive drum and a developer container are integrated as a process cartridge and the process cartridge is replaced by a new one when the developer is run out. 
     In contrast, the toner replenishment system is a system in which the developer container is replenished with new toner when the toner is run out. According to Japanese Patent Application Laid-Open No. H08-30084, a one-component developing apparatus of a toner replenishment system in which a toner supply box capable of replenishing toner is connected to a toner conveyance path in which toner is conveyed is proposed. Toner reserved in the toner supply box is conveyed to the toner conveyance path by a conveyance screw. 
     In recent years, for an image forming apparatus, users have desired various systems such as the process cartridge system and the toner replenishment system described above. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention, an image forming apparatus to and from which a replenishment container accommodating developer is attachable and detachable and which is configured to form a developer image on a recording material, the image forming apparatus includes an image bearing member configured to rotate while bearing the developer image, a developer bearing member configured to bear the developer and supply the developer to the image bearing member, a developer container to and from which the replenishment container is attachable and detachable, the developer container being configured to rotatably support the developer bearing member and including an accommodating portion configured to accommodate the developer to be borne on the developer bearing member, a transfer portion configured to transfer the developer image on the image bearing member onto a recording material, and a supporting portion configured to support the recording material onto which the developer image has been transferred and which has been discharged to an outside of the image forming apparatus, wherein the developer container includes a projection portion provided at one end portion thereof in a rotation axis direction of the image bearing member, the projection portion projecting toward the supporting portion more than a center portion of the developer container in a crossing direction crossing the rotation axis direction, wherein the projection portion communicates with the accommodating portion and includes, at a distal end portion thereof, an attachment portion which is configured such that the replenishment container is attachable thereto, the attachment portion being provided with a replenishment port for replenishing the accommodating portion with the developer from the replenishment container, wherein the image forming apparatus comprises an opening/closing member movable between a closed position where the opening/closing member is closed to cover the attachment portion and an open position where the opening/closing member is open to open the attachment portion and where attachment of the attachment portion to the replenishment container is allowed, and wherein the opening/closing member is configured such that a movement thereof from the open position to the closed position is hindered by the replenishment container attached to the attachment portion. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1 A  is a section view of an image forming apparatus according to a first embodiment. 
         FIG.  1 B  is a perspective view of the image forming apparatus. 
         FIG.  2 A  is a section view of the image forming apparatus. 
         FIG.  2 B  is a perspective view of the image forming apparatus in a state in which a top cover is open. 
         FIG.  3    is a section view of the image forming apparatus in a state in which a process cartridge is detached. 
         FIG.  4 A  is a perspective view of the image forming apparatus in a state in which a pressure plate of a reading apparatus is closed. 
         FIG.  4 B  is a perspective view of the image forming apparatus in a state in which the pressure plate is open. 
         FIG.  4 C  is a perspective view of the image forming apparatus in a state in which the reading apparatus is open. 
         FIG.  5 A  is a perspective view of a developer container and a toner pack. 
         FIG.  5 B  is a front view of the developer container and the toner pack. 
         FIG.  6 A  is a section view taken along  6 A- 6 A of  FIG.  5 B . 
         FIG.  6 B  is a section view taken along  6 B- 6 B of  FIG.  5 B . 
         FIG.  7    is a perspective view of the toner pack. 
         FIG.  8 A  is a front view of the toner pack. 
         FIG.  8 B  is a front view of a first modification example of the toner pack. 
         FIG.  8 C  is a front view of a second modification example of the toner pack. 
         FIG.  9    is a section view of a first and second toner remainder amount sensors. 
         FIG.  10    is a circuit diagram of the first and second toner remainder amount sensors. 
         FIG.  11 A  is a section view of the developer container in a state in which the toner remainder amount is small. 
         FIG.  11 B  is a section view of the developer container in a state in which the toner remainder amount is large. 
         FIG.  12    is a block diagram illustrating a control system of the image forming apparatus. 
         FIG.  13    is a flowchart illustrating a toner replenishment process. 
         FIG.  14    is a flowchart illustrating a toner remainder amount detection process. 
         FIG.  15    is a perspective view of an operation portion. 
         FIG.  16 A  is a section view illustrating a state in which the toner pack is attached to a replenishment port. 
         FIG.  16 B  is a section view illustrating a state in which toner has started dropping from the toner pack. 
         FIG.  16 C  is a section view illustrating a state in which the developer container has been replenished with all toner in the toner pack. 
         FIG.  17 A  is a perspective view of a toner remainder amount panel in a state in which the toner remainder amount is at a Low level. 
         FIG.  17 B  is a perspective view of the toner remainder amount panel in a state in which the toner remainder amount is at a Mid level. 
         FIG.  17 C  is a perspective view of the toner remainder amount panel in a state in which the toner remainder amount is at a Full level. 
         FIG.  18 A  is a graph illustrating a relationship between the capacity of the developer container and the toner remainder amount level. 
         FIG.  18 B  is a graph illustrating a toner remainder amount when toner is replenished from a toner pack of a small capacity. 
         FIG.  18 C  is a graph illustrating a toner remainder amount when toner is replenished from a toner pack of a large capacity. 
         FIG.  19 A  is a perspective view of a first modification example of the image forming apparatus. 
         FIG.  19 B  is a perspective view of a second modification example of the image forming apparatus. 
         FIG.  19 C  is a perspective view of a third modification example of the image forming apparatus. 
         FIG.  20 A  is a perspective view of a fourth modification example of the image forming apparatus. 
         FIG.  20 B  is a perspective view of a fifth modification example of the image forming apparatus. 
         FIG.  21 A  is a perspective view of an image forming apparatus according to a second embodiment. 
         FIG.  21 B  is a section view of the image forming apparatus. 
         FIG.  22 A  is a perspective view of a modification example of the image forming apparatus according to the second embodiment. 
         FIG.  22 B  is a section view of the modification example of the image forming apparatus according to the second embodiment. 
         FIG.  23 A  is a section view of an image forming apparatus according to a third embodiment. 
         FIG.  23 B  is a section view of the image forming apparatus in a state in which a process cartridge is drawn out. 
         FIG.  24    is a section view illustrating a state in which a toner pack is attached to a process cartridge that has been drawn out. 
         FIG.  25 A  is a perspective view of the image forming apparatus in a state in which the process cartridge is drawn out. 
         FIG.  25 B  is a perspective view illustrating a state in which a toner pack is attached to a process cartridge that has been drawn out. 
         FIG.  26    is a perspective view of a developer container according to a modification example of the first embodiment. 
         FIG.  27    is a perspective view of an agitation member according to the first embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Exemplary embodiments of the present invention will be described below with reference to drawings. 
     First Embodiment 
       FIG.  1 A  is a schematic diagram illustrating a configuration of an image forming apparatus  1  according to a first embodiment. The image forming apparatus  1  is a monochromatic printer that forms an image on a recording material on the basis of image information input from an external device. Examples of the recording material include various sheet materials of different materials like paper sheets such as plain paper sheets and cardboards, plastic films such as sheets for overhead projectors, sheets of irregular shapes such as envelops and index paper sheets, and cloths. 
     Overall Configuration 
     As illustrated in  FIGS.  1 A and  1 B , the image forming apparatus  1  includes a printer body  100  serving as an apparatus body, a reading apparatus  200  openably and closably supported by the printer body  100 , and an operation portion  300  attached to an exterior surface of the printer body  100 . The printer 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 , a process cartridge  20  of an electrophotographic system, and a transfer roller  12  that transfers a toner image serving as a developer image formed on a photosensitive drum  21  of the process cartridge  20  onto the recording material. As illustrated in  FIGS.  6 A and  6 B , the process cartridge  20  includes the photosensitive drum  21 , a charging roller  22  disposed in the vicinity of the photosensitive drum  21 , and a developing apparatus  30  including a pre-exposing apparatus  23  and a developing roller  31 . 
     The photosensitive drum  21  is a photoconductor formed in a cylindrical shape. The photosensitive drum  21  of the present embodiment includes a drum-shaped base body formed from aluminum, and a photosensitive layer formed from a negatively-chargeable organic photoconductor thereon. In addition, the photosensitive drum  21  serving as an image bearing member is rotationally driven by a motor in a predetermined direction (clockwise direction in the figure) at a predetermined process speed. 
     The charging roller  22  comes into contact with the photosensitive drum  21  at a predetermined pressure contact force to form a charging portion. In addition, a desired charging voltage is applied thereto by a charging high-voltage power source, and thus the surface of the photosensitive drum  21  is uniformly charged to a predetermined potential. In the present embodiment, the photosensitive drum  21  is charged to a negative polarity by the charging roller  22 . The pre-exposing apparatus  23  de-electrify the surface potential of the photosensitive drum  21  before entering the charging portion so as to cause stable electrical discharge in the charging portion. 
     The scanner unit  11  serving as an exposing portion exposes the surface of the photosensitive drum  21  in a scanning manner by radiating laser light corresponding to the image information input from the external device or the reading apparatus  200  onto the photosensitive drum  21  by using a polygon mirror. As a result of this exposure, an electrostatic latent image corresponding to the image information is formed on the surface of the photosensitive drum  21 . To be noted, the scanner unit  11  is not limited to a laser scanner apparatus, and for example, an LED exposing apparatus including an LED array in which a plurality of LEDs are arranged in the longitudinal direction of the photosensitive drum  21  may be employed. 
     The developing apparatus  30  includes a developing roller  31  serving as a developer bearing member that bears developer, a developer container  32  serving as a frame member of the developing apparatus  30 , and a supply roller  33  that supplies developer to the developing roller  31 . The developing roller  31  and the supply roller  33  are rotatably supported by the developer container  32 . In addition, the developing roller  31  is disposed at an opening portion of the developer container  32  so as to oppose the photosensitive drum  21 . The supply roller  33  is rotatably in contact with the developing roller  31 , and toner serving as developer accommodated in the developer container  32  is applied on the surface of the developing roller  31  by the supply roller  33 . To be noted, the supply roller  33  is not necessary if a configuration in which enough toner can be supplied to the developing roller  31  is employed. 
     For the developing apparatus  30  of the present embodiment, a contact developing system is used as the development system. That is, a toner layer borne on the developing roller  31  comes into contact with the photosensitive drum  21  in a developing portion (developing region) where the photosensitive drum  21  and the developing roller  31  oppose each other. A developing voltage is applied to the developing roller  31  by a developing high-voltage power source. Under the developing voltage, toner borne on the developing roller  31  transfers from the developing roller  31  onto the drum surface in accordance with the potential distribution of the surface of the photosensitive drum  21 , and thus the electrostatic latent image is developed as a toner image. To be noted, in the present embodiment, a reverse development system is employed. That is, toner attaches to a surface region of the photosensitive drum  21 . which is charged in a charging step, exposed in an exposing step, and thus has a reduced charge amount, and thus a toner image is formed. 
     In addition, in the present embodiment, toner having a particle diameter of 6 μm and a normal charging polarity of a negative polarity is used. For example, as the toner of the present embodiment, polymer toner produced by a polymerization method is employed. In addition, the toner of the present embodiment is so-called nonmagnetic one-component developer that does not contain a magnetic component, and is borne on the developing roller  31  mainly by intermolecular force or electrostatic force (image force). However, one-component developer containing a magnetic component may be used. In addition, in some cases, the one-component developer contains additives (for example, wax and silica fine particles) for adjusting the fluidity and charging performance of toner in addition to toner particles. In addition, two-component developer constituted by nonmagnetic toner and magnetic carrier may be used as the developer. In the case of using magnetic developer, for example, a cylindrical developing sleeve on the inner circumferential surface of which a magnet is disposed is used as the developer bearing member. 
     An agitation member  34  serving as an agitation portion is provided inside the developer container  32 . The agitation member  34  is driven to pivot by a motor M1 (see  FIG.  12   ), thus agitates the toner in the developer container  32 , and delivers (conveys) the toner to the developing roller  31  and the supply roller  33 . In addition, the agitation member  34  has a function of circulating toner not used for development and peeled off from the developing roller  31  in the developer container to uniformize toner in the developer container. To be noted, the agitation member  34  is not limited to a pivoting type. For example, an agitation member of a swinging type may be employed. In addition, another agitation member may be further provided in addition to the agitation member  34 . 
     In addition, a developing blade  35  that regulates the amount of toner borne on the developing roller  31  is disposed at the opening portion of the developer container  32  where the developing roller  31  is disposed. The toner supplied to the surface of the developing roller  31  passes through the opposing portion between the developing roller  31  and the developing blade  35  in accordance with the rotation of the developing roller  31 , thus forms a uniform thin layer, and is negatively charged by frictional electrification. 
     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 body  100 , a tray portion  62 , an inner plate  63 , a tray spring  64 , and a pickup roller  65 . The tray portion  62  constitutes a bottom surface of a recording material accommodation space that is exposed by opening the front door  61 , and the inner plate  63  is supported by the tray portion  62  so as to be capable of ascending and descending. The tray spring  64  urges the inner plate  63  upward, and presses a recording material P supported by the inner plate  63  against the pickup roller  65 . To be noted, the front door  61  closes the recording material accommodation space in the state of being closed with respect to the printer body  100 , and supports the recording material P together with the tray portion  62  and the inner plate  63  in the state of being open with respect to the printer body  100 . 
     The fixing portion  70  is of a thermal fixation system that performs an image fixing process by heating and melting 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 pressurizing roller  72  that is in pressure contact with the fixing film  71 . 
     Next, an image forming operation of the image forming apparatus  1  will be described. When a command of image formation is input to the image forming apparatus  1 , an image forming process by the image forming portion  10  is started on the basis of image information input from an external computer connected to the image forming apparatus  1  or from the reading apparatus  200 . The scanner unit  11  radiates laser light toward the photosensitive drum  21  on the basis of the input image information. At this time, the photosensitive drum  21  has been already charged by the charging roller  22 , and an electrostatic latent image is formed on the photosensitive drum  21  as a result of the laser light irradiation. Then, this electrostatic latent image is developed by the developing roller  31 , and thus a toner image is formed on the photosensitive drum  21 . 
     In parallel with the image forming process described above, the pickup roller  65  of the feeding portion  60  delivers out the recording material P supported by the front door  61 , the tray portion  62 , and the inner plate  63 . The recording material P is fed to a registration roller pair  15  by the pickup roller  65 , and the skew thereof is corrected by abutting a nip of the registration roller pair  15 . Then, the registration roller pair  15  is driven to match 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  serving as a transfer portion from a transfer high-voltage power source, and the toner image borne on the photosensitive drum  21  is transferred onto the recording material P conveyed by the registration roller pair  15 . The recording material P onto which the toner image has been transferred is conveyed to the fixing portion  70 , and the toner image is heated and pressurized when passing through a nip portion between the fixing film  71  and the pressurizing roller  72  of the fixing portion  70 . As a result of this, toner particles melt and then adhere, and thus 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  (outside of the apparatus) by the discharge roller pair  80  serving as a discharge portion, and is supported on a discharge tray  81  serving as a supporting portion formed in an upper portion of the printer body  100 . 
     The discharge tray  81  is inclined upward toward the downstream side in a discharge direction of the recording material, the recording material discharged onto the discharge tray  81  slides down the discharge tray  81 , and thus the trailing end thereof is aligned by a regulating surface  84 . 
     As illustrated in  FIGS.  4 A and  4 B , the reading apparatus  200  includes a reading unit  201  including an unillustrated reading portion therein, and a pressure plate  202  openably and closably supported by the reading unit  201 . A platen glass  203  which transmits light emitted from the reading portion and on which a document is to be placed is provided on the upper surface of the reading unit  201 . 
     In the case where an image of a document is to be read by the reading apparatus  200 , a user places the document on the platen glass  203  in a state in which the pressure plate  202  is open. Then, the pressure plate  202  is closed to prevent displacement of the document on the platen glass  203 , and for example, the operation portion  300  is operated to output a reading command to the image forming apparatus  1 . When a reading operation is started, the reading portion in the reading unit  201  reciprocates in a sub-scanning direction, that is, a left-right direction as viewed from the front of the operation portion  300  of the image forming apparatus  1 . The reading portion receives light reflected on the document by a light receiving portion while emitting light to the document from a light emitting portion, and performs photoelectric conversion to read the image of the document. To be noted, a front-rear direction, a left-right direction, and an up-down direction are defined on the basis of a state as viewed from the front of the operation portion  300 . 
     As illustrated in  FIGS.  2 B and  3   , a first opening portion  101  opening upward is defined in an upper portion of the printer body  100 , and the first opening portion  101  is covered by a top cover  82 . The top cover  82  serving as a supporting tray is supported so as to be openable and closable about a pivot shaft  82   c  extending in the left-right direction with respect to the printer body  100 , and the discharge tray  81  serving as a supporting surface is formed on the upper surface thereof. The top cover  82  is opened from the front side to the rear side in a state in which the reading apparatus  200  is open with respect to the printer body  100 . To be noted, the reading apparatus  200  and the top cover  82  may be configured to be held in an open state and a closed state by a holding mechanism such as a hinge mechanism. 
     For example, in the case where a jam of the recording material occurs due to paper jam or the like in a conveyance path CP which the recording material fed by the pickup roller  65  passes through, the user opens the top cover  82  together with the reading apparatus  200 . Then, the user accesses the process cartridge  20  through the first opening portion  101  exposed by opening the top cover  82 , and draws out the process cartridge  20  along cartridge guides  102 . The cartridge guides  102  slide on and guide projection portions  21   a  (see  FIG.  5 A ) provided at end portions of the photosensitive drum  21  of the process cartridge  20  in the axial direction. 
     Then, as a result of drawing out the process cartridge  20  to the outside through the first opening portion  101 , a space through which a hand can access the conveyance path CP is generated. The user can put their hand in the printer body  100  through the first opening portion  101 , and thus can access the recording material jamming the conveyance path CP to remove the jammed recording material. 
     In addition, in the present embodiment, as illustrated in  FIGS.  1 B and  4 C , an opening/closing member  83  is openably and closably provided on the top cover  82 . A second opening portion  82   a  serving as an opening portion opening upward is defined in the discharge tray  81  of the top cover  82 . The opening/closing member  83  is configured to be movable between a closed position where the opening/closing member  83  covers the replenishment port  32   a  such that the toner pack  40  cannot be attached to the developer container  32 , and an open position where the opening/closing member  83  exposes the replenishment port  32   a  such that the toner pack  40  can be attached to the developer container  32 . The opening/closing member  83  functions as a part of the discharge tray  81  in the closed position. The opening/closing member  83  and the second opening portion  82   a  are formed on the left side of the discharge tray  81 . In addition, the opening/closing member  83  is supported by the top cover  82  so as to be openable and closable about a pivot shaft  83   a  extending in the front-rear direction, and is opened to the left by hooking a finger thereon through a groove portion  82   b  provided on the top cover  82 . The opening/closing member  83  is formed in an approximate L shape in accordance with the shape of the top cover  82 . The opening/closing member  83  is configured such that a movement thereof from the open position to the closed position is hindered by the toner pack  40  attached to an attachment portion  57  described later. 
     The second opening portion  82   a  of the discharge tray  81  is open such that the replenishment port  32   a  for toner replenishment defined in an upper portion of the developer container  32  is exposed, and the user can access the replenishment port  32   a  by opening the opening/closing member  83  without opening the top cover  82 . To be noted, in the present embodiment, a system (direct replenishment system) in which the user replenishes the developing apparatus  30  with toner from the toner pack  40  (see  FIGS.  1 A and  1 B ) filled with toner for replenishment in a state in which the developing apparatus  30  is still attached to the image forming apparatus  1  is employed. Therefore, in the case where the toner remainder amount of the process cartridge  20  is small, an operation of taking out the process cartridge  20  from the printer body  100  and replacing the process cartridge  20  with a brand-new process cartridge is no longer necessary, and thus the usability can be improved. In addition, the developer container  32  can be replenished with toner at lower cost than replacing the whole process cartridge  20 . To be noted, the direct replenishment system can reduce the cost also as compared with the case where only the developing apparatus  30  of the process cartridge  20  is replaced because there is no need to replace various rollers and gears. To be noted, the image forming apparatus  1  and the toner pack  40  constitute an image forming system. 
     Collection of Transfer Residual Toner 
     In the present embodiment, a cleanerless configuration in which transfer residual toner remaining on the photosensitive drum  21  without being transferred onto the recording material P is collected into the developing apparatus  30  and reused is employed. The transfer residual toner is removed by the following process. The transfer residual toner includes, in mixture, toner charged to a positive polarity and toner that is charged to a negative polarity but does not have enough charges. The photosensitive drum  21  after transfer is de-electrified by the pre-exposing apparatus  23 , the charging roller  22  is caused to generate uniform electrical discharge, and thus the transfer residual toner is charged to a negative polarity again. The transfer residual toner charged to a negative polarity again in the charging portion reaches the developing portion in accordance with the rotation of the photosensitive drum  21 . Then, the surface region of the photosensitive drum  21  having passed the charging portion is exposed by the scanner unit  11  in a state in which the transfer residual toner is still attached to the surface thereof, and thus an electrostatic latent image is drawn thereon. 
     Here, the behavior of the transfer residual toner having reached the developing portion will be described separately for an exposed portion and a non-exposed portion of the photosensitive drum  21 . In the developing portion, the transfer residual toner attached to the non-exposed portion of the photosensitive drum  21  is transferred onto the developing roller  31  due to a potential difference between the potential (dark potential) of the non-exposed portion of the photosensitive drum  21  and the developing voltage, and is collected into the developer container  32 . This is because the developing voltage applied to the developing roller  31  is relatively positively polarized with respect to the potential of the non-exposed portion on the premise that the normal charging polarity of the toner is a negative polarity. To be noted, the toner collected into the developer container  32  is dispersed by being agitated by the agitation member  34  with toner in the developer container, and is borne on the developing roller  31  to be used in a developing process again. 
     In contrast, transfer residual toner attached to the exposed portion of the photosensitive drum  21  remains on the drum surface without being transferred from the photosensitive drum  21  to the developing roller  31  in the developing portion. This is because the potential of the developing voltage applied to the developing roller  31  is further on the negative polarity side than the potential (light potential) of the exposed portion on the premise that the normal charging polarity of toner is a negative polarity. The transfer residual toner remaining on the drum surface moves to the transfer portion while being borne on the photosensitive drum  21  together with other toner to be transferred from the developing roller  31  to the exposed portion, and is transferred onto the recording material P in the transfer portion. 
     Although a cleanerless configuration in which transfer residual toner is collected into the developing apparatus  30  and reused is employed in the present embodiment as described above, a conventionally known configuration in which transfer residual toner is collected by a cleaning blade that abuts the photosensitive drum  21  may be employed. In this case, the transfer residual toner collected by the cleaning blade is collected into a collection container provided separately from the developing apparatus  30 . However, employing the cleanerless configuration eliminates the necessity to install a collection container for collecting transfer residual toner and the like and thus enables further miniaturization of the image forming apparatus  1 , and reuse of transfer residual toner can reduce the printing cost. 
     Configuration of Developer Container and Toner Pack 
     Next, the configuration of the developer container  32  and the toner pack  40  will be described.  FIG.  5 A  is a perspective view of the developer container  32  and the toner pack  40 , and  FIG.  5 B  is a front view of the developer container  32  and the toner pack  40 .  FIG.  6 A  is a section view taken along  6 A- 6 A of  FIG.  5 B , and  FIG.  6 B  is a section view taken along  6 B- 6 B of  FIG.  5 B . 
     As illustrated in  FIGS.  5 A to  6 B , the developer container  32  includes a conveyance chamber  36  that accommodates the agitation member  34 , and the conveyance chamber  36  serving as an accommodation chamber that accommodates toner extends over the entirety of the developer container  32  in the longitudinal direction (left-right direction). In addition, the conveyance chamber  36  is integrally formed with a frame member rotatably supporting the developing roller  31  and the supply roller  33 , and accommodates developer to be borne on the developing roller  31 . In addition, the developer container  32  includes a first projection portion  37  serving as a projection portion that projects upward from one end portion of the conveyance chamber  36  in the longitudinal direction and communicates with the conveyance chamber  36 , and a second projection portion  38  that projects upward from the other end portion of the conveyance chamber  36  in the longitudinal direction. That is, the first projection portion  37  is provided at one end portion of the developer container  32  in the rotation axis direction of the developing roller  31 , and projects toward the discharge tray  81  in a crossing direction crossing the rotation axis direction described above more than the center portion of the developer container  32 . The second projection portion  38  is provided at the other end portion of the developer container  32  in the rotation axis direction of the developing roller  31 , and projects toward the discharge tray  81  in the crossing direction more than the center portion of the developer container  32 . In the present embodiment, the first projection portion  37  is formed on the left side of the developer container  32 , and the second projection portion  38  is formed on the right side of the developer container  32 . An attachment portion  57  to which the toner pack  40  can be attached is provided at an upper end portion (distal end portion) of the first projection portion  37 , and a replenishment port  32   a  for replenishing the conveyance chamber  36  with toner from the toner pack  40  is defined in the attachment portion  57 . The toner pack  40  can be attached to the attachment portion  57  in the state of being exposed to the outside of the apparatus. 
     The developer container  32  is configured such that toner supplied through the replenishment port  32   a  reaches the agitation member  34  by only its own weight. Here, “its own weight” means that it is configured that the toner reaches the agitation member  34  by its own weight even though an agitation member (conveyance member) that rotates or swings for conveying toner is not provided between the replenishment port  32   a  of the developer container  32  and the agitation member  34 . In addition, in the developer container  32 , the agitation member  34  serving as a conveyance member is disposed such that the agitation member  34  is the rotary member closest to the replenishment port  32   a  and the rotation thereof causes the toner in the conveyance chamber  36  to reach the developing roller  31  or the supply roller  33 . 
     The first projection portion  37  and the second projection portion  38  extend obliquely upward from the conveyance chamber  36  from the front side of the apparatus. That is, the first projection portion  37  and the second projection portion  38  project downstream and upward in the discharge direction of the discharge roller pair  80 . Therefore, the replenishment port  32   a  formed in the first projection portion  37  is disposed on the front side of the image forming apparatus  1 , and thus toner replenishment operation for the developer container  32  can be performed easily. 
     Particularly, in the present embodiment, since the reading apparatus  200  openable and closable about the rear side of the apparatus is disposed above the opening/closing member  83 , the space between the replenishment port  32   a  and the reading apparatus  200  can be used more efficiently by disposing the replenishment port  32   a  on the front side of the apparatus. Therefore, the operability for replenishing toner from the replenishment port  32   a  can be improved. 
     The upper portion of the first projection portion  37  and the upper portion of the second projection portion  38  are connected to each other by a grip portion  39  serving as a connection portion. A laser passage space SP, serving as a space, through which laser light L (see  FIG.  1 A ) emitted from the scanner unit  11  (see  FIG.  1 A ) toward the photosensitive drum  21  passes is defined between the grip portion  39  and the conveyance chamber  36 . The laser passage space SP is adjacent to the first projection portion  37  in the rotation axis direction of the developing roller  31 . 
     The grip portion  39  includes a pinching portion  39   a  that the user can grip by hooking a finger thereon, and the pinching portion  39   a  is formed to project upward from the top plate of the grip portion  39 . The first projection portion  37  is formed to has a hollow shape, and the replenishment port  32   a  is defined in the upper surface thereof. The replenishment port  32   a  is configured to be connectable to the toner pack  40 . 
     By providing the first projection portion  37 , on a distal end portion of which the replenishment port  32   a  is defined, on one side of the developer container  32  in the longitudinal direction, the laser passage space SP that the laser light L emitted from the scanner unit  11  can pass through can be secured, and the image forming apparatus  1  can be miniaturized. In addition, since the second projection portion  38  is provided on the other side of the developer container  32  in the longitudinal direction, and the grip portion  39  that connects the first projection portion  37  and the second projection portion  38  to each other is formed, the usability for taking out the process cartridge  20  from the printer body  100  can be improved. To be noted, the second projection portion  38  may be formed in a hollow shape similarly to the first projection portion  37 , or may be formed in a solid shape. 
       FIG.  26    is a perspective view of a developer container  320  according to a modification example of the first embodiment. The developer container  320  includes a projection portion  370  disposed at an end portion in the longitudinal direction, and the projection portion  370  projects higher than a center portion of the developer container  320  in the longitudinal direction. An attachment portion  570  for attaching the toner pack  40  is provided on the projection portion  370 , and a replenishment port  320   a  is provided in the attachment portion  570 . 
     The projection portion  370  is different from the first projection portion  37  illustrated in  FIG.  5 B  in that a recess portion  370   a  is provided thereon. The recess portion  370   a  is provided on a side surface of the projection portion  370 , and is recessed in a direction from the center portion to an end portion of the developer container  320  in the longitudinal direction. Further, the recess amount of the recess portion  370   a  is larger at a position closer to the photosensitive drum  21 . Here, it can be considered that in the case where the distance between the scanner unit  11  and the developer container  320  is increased, the irradiation region of the laser light L overlaps with the attachment portion  570  (replenishment port  320   a ) as viewed in the attachment direction of the toner pack  40 . By providing the attachment portion  570  above the laser light L in the vertical direction such that the laser light L passes through the recess portion  370   a , interference between the laser light L and the developer container  320  can be avoided. As a result of this, it is not necessary to move the projection portion  370  further toward the end portion in the longitudinal direction to avoid the interference with the laser light L, and thus the miniaturization of the apparatus can be realized. 
     As illustrated in  FIGS.  5 A to  6 B , the toner pack  40  is configured to be attachable to and detachable from the attachment portion  57  of the first projection portion  37 . In addition, the toner pack  40  includes a shutter member  41  provided at an opening portion and openable and closable, and a plurality of (in the present embodiment, three) protrusions  42  formed in correspondence with a plurality of (in the present embodiment, three) groove portions  32   b  defined in the attachment portion  57 . In the case where the user replenishes the developer container  32  with toner, the user positions the toner pack  40  such that the protrusions  42  pass through the groove portions  32   b  of the attachment portion  57 , and thus connects the toner pack  40  to the attachment portion  57 . Further, when the toner pack  40  is rotated by 180° in this state, the shutter member  41  of the toner pack  40  abuts an unillustrated abutting portion of the attachment portion  57  to rotate with respect to the body of the toner pack  40 , and thus the shutter member  41  is opened. As a result of this, toner accommodated in the toner pack  40  drops from the toner pack  40 , and the dropped toner enters the first projection portion  37  having a hollow shape through the replenishment port  32   a . To be noted, the shutter member  41  may be provided on the replenishment port  32   a.    
     The first projection portion  37  includes an inclined surface  37   a  at a position opposing to the opening of the replenishment port  32   a , and the inclined surface  37   a  is inclined downward toward the conveyance chamber  36 . Therefore, the toner supplied through the replenishment port  32   a  is guided to the conveyance chamber  36  by the inclined surface  37   a .  FIG.  27    is a perspective view of the agitation member  34 . As illustrated in  FIGS.  6  and  27   , the agitation member  34  includes an agitation shaft  34   a  serving as a support portion extending in the longitudinal direction, and a blade portion  34   b  fixed to the agitation shaft  34   a  and extends radially outward from the agitation shaft  34   a . The blade portion  34   b  as a flexible sheet is a sheet having flexibility. The agitation member  34  rotates about a shaft portion  34   c  of the agitation shaft  34   a.    
     The toner replenished through the replenishment port  32   a  disposed upstream of the agitation member  34  in the conveyance direction is delivered to the developing roller  31  and the supply roller  33  in accordance with the rotation of the agitation member  34 . The conveyance direction of the agitation member  34  is parallel to the longitudinal direction of the developer container  32 . Although the replenishment port  32   a  and the first projection portion  37  are disposed at one end portion of the developer container  32  in the longitudinal direction, the toner spreads to the whole developer container  32  by repetitive rotation of the agitation member  34 . To be noted, although the agitation member  34  is constituted by the agitation shaft  34   a  and the blade portion  34   b  in the present embodiment, an agitation shaft of a spiral shape may be used as an element for spreading the toner to the whole developer container  32 . 
     Although the toner pack  40  is constituted by an easily deformable plastic bag as illustrated in  FIGS.  7  and  8 A  in the present embodiment, this is not limiting. For example, the toner pack may be constituted by a bottle container  40   b  having an approximately cone shape as illustrated in  FIG.  8 B , or may be formed from a paper container  40 C formed from paper as illustrated in  FIG.  8 C . In either case, the material and shape of the toner pack may be of any kind. In addition, as a method for discharging toner from the toner pack, it is preferable that the user squeeze the toner pack in the case of the toner pack  40  or the paper container  40 C, and it is preferable that the user causes the toner to drop while vibrating the container by hitting the container or the like in the case of the bottle container  40 B. In addition, 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 engage with the printer body  100  and receive a driving force from the printer body  100 . 
     In addition, the shutter member  41  may be omitted from any of the toner packs, and a shutter member of a sliding type may be used instead of the shutter member  41  of a rotary type. In addition, the shutter member  41  may be configured to be broken when attaching the toner pack to the replenishment port  32   a  or rotating the toner pack in the attached state, or may be a detachable lid structure such as a sticker. 
     Detection Method for Toner Remainder Amount 
     Next, a method for detecting the toner remainder amount of the developer container  32  will be described with reference to  FIGS.  9  to  11 B . A first toner remainder amount sensor  51  and a second toner remainder amount sensor  52  that detect a state corresponding to the toner remainder amount in the developer container  32  are provided in the developing apparatus  30  of the present embodiment. 
     The first toner remainder amount sensor  51  includes a light emitting portion  51   a  and a light receiving portion  51   b , and the second toner remainder amount sensor  52  includes a light emitting portion  52   a  and a light receiving portion  52   b .  FIG.  10    is a circuit diagram illustrating an example of a circuit configuration of the toner remainder amount sensors  51  and  52 . To be noted, the circuit configuration of the first toner remainder amount sensor  51  will be described below, and description of the circuit configuration of the second toner remainder amount sensor  52  will be omitted. 
     Although an LED is used as the light emitting portion  51   a , and a phototransistor that is switched to an ON state by light from the LED is used as the light receiving portion  51   b  in  FIG.  10   , this is not limiting. For example, a halogen lamp or fluorescent light may be used as the light emitting portion  51   a , and a photodiode or an avalanche photodiode may be used as the light receiving portion  51   b . To be noted, an unillustrated switch is provided between the light emitting portion  51   a  and a power source voltage Vcc, and by switching the switch on, the voltage from the power source voltage Vcc is applied to the light emitting portion  51   a , and the light emitting portion  51   a  takes a power-supplied state. Meanwhile, an unillustrated switch is also provided between the light receiving portion  51   b  and the power source voltage Vcc, and by switching the switch on, the light receiving portion  51   b  takes a power-supplied state in accordance with a current corresponding to the amount of detected light. 
     The light emitting portion  51   a  is connected to the power source voltage Vcc and a current-limiting resistor R1, and the light emitting portion  51   a  emits light in accordance with a current determined by the current-limiting resistor R1. As illustrated in  FIG.  9   , the light emitted from the light emitting portion  51   a  passes through an optical path Q1, and is received by the light receiving portion  51   b . A collector terminal of the light receiving portion  51   b  is connected to the power source voltage Vcc, and an emitter terminal thereof is connected to a detection resistor R2. The light receiving portion  51   b  that is a phototransistor receives light emitted from the light emitting portion  51   a , and outputs a signal (current) corresponding to the amount of received light. This signal is converted into a voltage V1 by the detection resistor R2, and is input to an A/D conversion portion  95  of a control portion  90  (see  FIG.  12   ). To be noted, the light receiving portion  52   b  of the second toner remainder amount sensor  52  receives light emitted from the light emitting portion  52   a  and having passed through an optical path Q2, and a voltage V2 corresponding to the amount of received light is output and input to the A/D conversion portion  95  of the control portion  90 . 
     The control portion  90  (CPU  91 ) determines, on the basis of the input voltage level, whether or not the light receiving portions  51   b  and  52   b  have received light from the light emitting portions  51   a  and  51   b . The control portion  90  (CPU  91 ) calculates the toner amount in the developer container  32  on the basis of the length of time in which each light is detected by the light receiving portion  51   b  and  52   b  and the light intensity of the received light when the toner in the developer container  32  is agitated for a certain time by the agitation member  34 . That is, the ROM  93  stores in advance a table that can output a toner remainder amount in accordance with the light reception time and the light intensity of the time when the toner is conveyed by the agitation member  34 , and the control portion  90  estimates/calculates the toner remainder amount on the basis of the input to the A/D conversion portion  95  and the table. 
     More specifically, the optical path Q1 of the first toner remainder amount sensor  51  is set to cross a rotation trajectory T of the agitation member  34 . In addition, time in which light in the optical path Q1 is blocked by toner hit up by the agitation member  34 , that is, time in which the light receiving portion  51   b  does not detect the light from the light emitting portion  51   a  in each rotation of the agitation member  34  changes depending on the toner remainder amount. In addition, the received light intensity of the light receiving portion  51   b  also changes depending on the toner remainder amount. 
     That is, when the toner remainder amount is large, the optical path Q1 is more likely to be blocked by toner, thus the time in which the light receiving portion  51   b  receives light becomes shorter, and the received light intensity of the light received by the light receiving portion  51   b  becomes lower. In contrast, conversely in the case where the toner remainder amount is small, the time in which the light receiving portion  51   b  receives light becomes longer, and the received light intensity of the light received by the light receiving portion  51   b  becomes higher. Therefore, the control portion  90  can determine whether the toner remainder amount is at the Low level or the Mid level on the basis of the light receiving time and the received light intensity of the light receiving portion  51   b  as will be described later. For example, as illustrated in  FIG.  11 A , in the case where the amount of toner in the conveyance chamber  36  of the developer container  32  is small, it is determined that the toner remainder amount is at the Low level. To be noted, although the second toner remainder amount sensor  52  is disposed not to cross the rotation trajectory T of the agitation member  34  in the description above, the second toner remainder amount sensor  52  may be disposed to cross the rotation trajectory T of the agitation member  34  similarly to the first toner remainder amount sensor  51  described above. 
     In addition, the optical path Q2 of the second toner remainder amount sensor  52  is set to be above the rotation trajectory T so as not to cross the rotation trajectory T of the agitation member  34 . Further, the light receiving portion  52   b  of the second toner remainder amount sensor  52  does not detect the light from the light emitting portion  52   a  in the case where light in the optical path Q2 is blocked by toner, and detects the light from the light emitting portion  52   a  in the case where light in the optical path Q2 is not blocked by toner. Therefore, regardless of the rotation operation of the agitation member  34 , the control portion  90  determines whether or not the toner remainder amount is at a Full level on the basis of whether or not the light receiving portion  52   b  has received light as will be described later. For example, as illustrated in  FIG.  11 B , in the case where the amount of toner in the conveyance chamber  36  of the developer container  32  is large, it is determined that the toner remainder amount is at the Full level. To be noted, although the second toner remainder amount sensor  52  is disposed not to cross the rotation trajectory T of the agitation member  34  in the description above, the second toner remainder amount sensor  52  may be disposed to cross the rotation trajectory T of the agitation member  34  similarly to the first toner remainder amount sensor  51  described above. 
     To be noted, the detection/estimation method for the toner remainder amount is not limited to the method of optical toner remainder amount detection described with reference to  FIG.  9   , and various known types of detection/estimation methods for toner remainder amount can be employed. For example, the toner remainder amount may be detected/estimated by disposing two or more metal plates or conductive resin sheets extending in the longitudinal direction of the developing roller on the inner wall of the developer container  32  serving as a frame member and measuring the electrostatic capacity between two metal plates or conductive resin sheets. Alternatively, a load cell supporting the developing apparatus  30  from below may be provided and the CPU  91  may calculate the toner remainder amount by subtracting the weight of the developing apparatus  30  of the case where there is no toner therein from the weight measured by the load cell. In addition, the first toner remainder amount sensor  51  may be omitted, and the control portion  90  (CPU  91 ) may calculate the toner remainder amount from the detection result of the second toner remainder amount sensor  52  and the emission status of the laser light. 
     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  of the image forming apparatus  1  includes a CPU  91  serving as a calculation device, a RAM  92  used as a work area of the CPU  91 , and a ROM  93  storing various programs. In addition, the control portion  90  includes an I/O interface  94  serving 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. 
     The first toner remainder amount sensor  51 , the second toner remainder amount sensor  52 , an attachment sensor  53 , and an opening/closing sensor  54  are connected to the input side of the control portion  90 , and the attachment sensor  53  detects attachment of the toner pack  40  to the replenishment port  32   a  of the developer container  32 . For example, the attachment sensor  53  is constituted by a pressure sensor that is provided at the replenishment port  32   a  and outputs a detection signal by being pressed by the protrusions  42  of the toner pack  40 . In addition, the opening/closing sensor  54  detects whether or not the opening/closing member  83  has been opened with respect to the top cover  82 . The opening/closing sensor  54  is constituted by, for example, a pressure sensor or a magnetic sensor. 
     In addition, the control portion  90  is connected to the operation portion  300 , the image forming portion  10 , and a toner remainder amount panel  400  serving as a notification portion capable of notifying information about the toner remainder amount. The operation portion  300  includes a display portion  301  capable of displaying various setting screens, physical keys, and so forth. The display portion  301  is constituted by, for example, a liquid crystal panel. The image forming portion  10  includes a motor M1 serving as a drive source that drives the photosensitive drum  21 , the developing roller  31 , the supply roller  33 , the agitation member  34 , and so forth. To be noted, the photosensitive drum  21 , the developing roller  31 , the supply roller  33 , and the agitation member  34  may be configured to be each driven by a different motor. 
     The toner remainder amount panel  400  is provided on the right side of the front surface of the casing of the printer body  100 , that is, on the opposite side to the operation portion  300  disposed on the left side as illustrated in  FIGS.  1 B and  17   , and displays information about the toner remainder amount in the developer container  32 . In the present embodiment, the toner remainder amount panel  400  is a panel member constituted by a plurality of (in the present embodiment, three) indicators arranged in the up-down direction, and the indicators respectively correspond to the Low level, the Mid level, and the Full level. 
     That is, as illustrated in  FIG.  17 A , in the case where only the bottom indicator is on, it is indicated that the toner remainder amount of the developer container  32  is at the Low level serving as a third state. As illustrated in  FIG.  17 B , in the case where the bottom and middle indicators are on and the top indicator is off, it is indicated that the toner remainder amount of the developer container  32  is at the Mid level serving as a second state. In the case where all the three indicators are on as illustrated in  FIG.  17 C , it is indicated that the toner remainder amount of the developer container  32  is at the Full level serving as a first state. To be noted, the toner remainder amount panel  400  is not limited to a liquid crystal panel and may be constituted by a light source such as an LED or an incandescent lamp and a diffusing lens. To be noted, although description has been given as a notification portion indicating the toner remainder amount in the example illustrated in  FIG.  17   , this is not limiting. For example, the indication of  FIG.  17 A  may indicate that toner replenishment is needed, the indication of  FIG.  17 B  may indicate that toner replenishment is not needed, and the indication of  FIG.  17 C  may indicate that toner has been sufficiently replenished. 
     Toner Replenishment Process 
     Next, a toner replenishment process of replenishing the developer container  32  with toner in the toner pack  40  will be described. As illustrated in  FIG.  13   , when the toner replenishment process is started, the control portion  90  determines whether or not a replenishment operation starting command has been issued (step S 1 ). In the present embodiment, the replenishment operation starting command is a user operation through the operation portion  300  as illustrated in  FIG.  15   . Specifically, the replenishment operation starting command is output by the user operating the operation portion  300  and thus pushing a button  1  in a state in which the display portion  301  is displaying a message prompting operation of the button  1 . 
     To be noted, at this time, since the toner pack  40  is attached to the replenishment port  32   a  of the developer container  32 , the opening/closing member  83  is open. Since the operation portion  300  and the replenishment port  32   a  are both disposed on the left side of the apparatus, the toner replenishment operation using the toner pack  40  can be easily performed while operating the operation portion  300 . In addition, when the opening/closing sensor  54  detects that the opening/closing member  83  has been opened, the control portion  90  prohibits and stops the image forming operation by the image forming apparatus  1 . Therefore, in the state in which the opening/closing member  83  is open, the conveyance rollers, the photosensitive drum  21 , the scanner unit  11 , and so forth of the image forming apparatus  1  are stopped. 
     To be noted, the replenishment operation starting command is not limited to the pushing operation on the button  1 , and the replenishment operation starting command may be a touch operation on the display portion  301 , or the operation starting command may be output in response to detection of the attachment of the toner pack  40  to the replenishment port  32   a  by the attachment sensor  53 . In addition, a sensor that detects that the shutter member  41  of the toner pack  40  has been opened may be provided, and the replenishment operation starting command may be output on the basis of the detection result of this sensor. In addition, the replenishment operation starting command may be output on the basis of detection of an opening operation on the opening/closing member  83  by the opening/closing sensor  54 . In addition, a configuration in which when the opening/closing member  83  is opened, the high-voltage power source applied to the process cartridge  20  is switched off such that only the motor M1 that drives the agitation member  34  can be driven may be employed. 
     In the case where it has been determined that the replenishment operation starting command has been issued (step S 1 : Yes), the control portion  90  initializes parameters of timers T1 and T2 that will be described later to initial values (for example, zero), and starts the timers T1 and T2 (step S 2 ). Then, the control portion  90  drives the motor M1 (step S 3 ), and the agitation member  34  rotates. 
     Next, the control portion  90  performs the toner remainder amount detection process (step S 4 ). When the toner remainder amount detection process is performed, as illustrated in  FIG.  14   , the control portion  90  causes the light emitting portions  51   a  and  52   a  of the first toner remainder amount sensor  51  and the second toner remainder amount sensor  52  to emit light (step S 41 ). Then, the control portion  90  converts voltages V1 and V2 respectively output from the light receiving portions  51   b  and  52   b  of the first toner remainder amount sensor  51  and the second toner remainder amount sensor  52  into digital signals (hereinafter referred to as A/D converted values) by the A/D conversion portion  95  (step S 42 ). 
     Next, the control portion  90  determines whether or not the A/D converted value of the voltage V2 indicates that light in the optical path Q2 is blocked (step S 43 ). In the case where it is indicated that light in the optical path Q2 is blocked (step S 43 : Yes), the control portion  90  causes the toner remainder amount panel  400  to indicate that the toner remainder amount is at the Full level (step S 44 ). That is, as illustrated in  FIG.  17 C , all the three indicators of the toner remainder amount panel  400  become on. 
     In the case where the A/D converted value of the voltage V2 does not indicate that light in the optical path Q2 is blocked (step S 43 : No), the control portion  90  calculates the toner remainder amount information in the developer container  32  on the basis of the A/D converted value of the voltage V1 (step S 45 ). Then, the control portion  90  causes the toner remainder amount panel  400  to indicate that the toner remainder amount is at the Low level or the Mid level on the basis of the calculated toner remainder amount information (step S 46 ). When step S 44  or step S 46  is completed, the toner remainder amount detection process is finished. That is, the first toner remainder amount sensor  51  and the second toner remainder amount sensor  52  serving as detection portions output remainder amount information corresponding to the amount of developer accommodated in the developer container  32  while the agitation member  34  is operating. 
     Next, the control portion  90  determines whether or not the timer T2 is at a threshold value β or more as illustrated in  FIG.  13    (step S 5 ). The threshold value β is a value that is set in advance, and corresponds to an interval at which the toner remainder amount detection process is repeatedly performed. To be noted, α&gt;β holds. In the case where the timer T2 is at the threshold value β or more, (step S 5 : Yes), the control portion  90  initializes and restarts the timer T2 (step S 6 ), and returns to step S 4 . That is, each time the timer T2 reaches the threshold value β, the toner remainder amount detection process (step S 4 ) is repeatedly performed. For example, in the case where the threshold value β is set to 1 second, the toner remainder amount detection process is repeatedly performed every 1 second in steps S 4 , S 5 , and S 6 . 
     In addition, in the case where the timer T2 is less than the threshold value β (step S 5 : No), the control portion  90  determines whether or not the timer T1 is at a threshold value α or more (step S 7 ). The threshold value a is a value that is set in advance, and corresponds to the driving time of the motor M1 and the agitation member  34  in the toner replenishment process. In the case where the timer T1 is less than the threshold value α (step S 7 : No), the process returns to step S 5 . In the case where the timer T1 is at the threshold value α or more (step S 7 : Yes), the control portion  90  stops the driving of the motor M1 (step S 8 ), and finishes the toner replenishment process. For example, in the case where the threshold value α is set to 10 seconds, the time from when the motor M1 starts driving in step S 3  to when the motor M1 is stopped in step S 8  is 10 seconds. 
     In the case where toner drops from the toner pack  40  into the developer container  32  in the toner replenishment process described above as illustrated in  FIG.  16 A , the toner enters the conveyance chamber  36  through the first projection portion  37 . Since the replenishment port  32   a  and the first projection portion  37  are disposed at one end portion of the developer container  32  in the longitudinal direction, toner is collectively supplied to the one end portion side of the conveyance chamber  36 . 
     Here, a case where the agitation member  34  is not rotating when toner is supplied to the conveyance chamber  36  will be considered. In the case where toner is caused to drop from the toner pack  40  into the developer container  32 , if the agitation member  34  is not rotated in the conveyance chamber  36  accommodating toner, it takes time for the dropped toner to spread to the entirety of the photosensitive drum  21  in the longitudinal direction. If this time is long, it takes time for the user performing the toner replenishment operation to confirm that the conveyance chamber  36  has been replenished with toner, which degrades the usability. 
     Therefore, in the present embodiment, the agitation member  34  is driven for a predetermined time (threshold value α) since the start of replenishment in the toner replenishment process. As a result of this, as illustrated in  FIGS.  16 B and  16 C , toner supplied from the toner pack  40  to one end portion of the developer container  32  is quickly flattened by the agitation member  34  in the entirety of the conveyance chamber  36  of the developer container  32  in the longitudinal direction. Therefore, the time the user takes to confirm that toner replenishment has been performed can be shortened, and the usability can be improved. In addition, since toner accommodated in the developer container  32  is flattened, the precision of the toner remainder amount information from the first toner remainder amount sensor  51  and the second toner remainder amount sensor  52  can be improved. 
     Then, during the toner replenishment process, the toner remainder amount information in the developer container  32  is detected by the first toner remainder amount sensor  51  and the second toner remainder amount sensor  52  every predetermined time (threshold value β). For example, as illustrated in  FIG.  17 A , the user replenishes the developer container  32  with toner from the toner pack  40  in a state in which the toner remainder amount panel  400  indicates that the toner remainder amount is at the Low level. 
     Then, after the toner remainder amount panel  400  indicates that the toner remainder amount is at the Mid level as illustrated in  FIG.  17 B , the toner remainder amount panel  400  indicates that the toner remainder amount is at the Full level as illustrated in  FIG.  17 C . As a result of this, the user can reliably recognize that the developer container  32  has been replenished with toner from the toner pack  40 , and the usability can be improved. 
     Here, section views of  FIGS.  16 A to  16 C  indicates  16 A- 16 A section of  FIG.  6   .  FIGS.  16 A and  16 B  illustrate that the light emitting portion  52   a  is disposed at the right end of the photosensitive drum  21  in the longitudinal direction. In addition, the light emitting portion  51   a  and the light receiving portions  51   b  and  52   b  are disposed at the same/approximately the same position in the longitudinal direction of the photosensitive drum  21 . Due to sensor arrangement restriction in the apparatus body, the sensors might be arranged as illustrated in  FIGS.  16 A and  16 B  in some cases. Also in such cases, the usability can be improved as described above by the rotation of the agitation member  34  in the toner replenishment. 
     In addition, in some cases, a sensor might be disposed approximately right under the replenishment port  32   a . In such a case, as illustrated in  FIG.  16 B , more of the replenished toner might be distributed on the left side and it might take more time to flatten the toner surface in the entirety of the photosensitive drum  21  in the longitudinal direction. To detect the toner replenishment state accurately, the toner surface needs to be flattened in the entire region in the longitudinal direction of the photosensitive drum  21 . However, even in such a case, in the present embodiment, the rotation of the agitation member  34  in toner replenishment flattens the toner surface in the entire region in the longitudinal direction of the photosensitive drum  21 , and the usability can be improved. 
     Relationship Between Amount of Toner Charged into Toner Pack and Capacity of Developer Container 
     Next, the relationship between the amount of toner charged into the toner pack  40  and the capacity of the developer container  32  will be described. The developer container  32  is capable of accommodating toner of Z [g] as illustrated in  FIG.  18 A . To be noted, although illustration is given in terms of grams (g) in  FIGS.  18 A to  18 C , the unit may be converted into a unit indicating capacity such as milliliters (ml). 
     In the case where the developer container  32  accommodates toner of 0 [g] to X [g], the toner remainder amount panel  400  indicates the Low level on the basis of the detection results of the first toner remainder amount sensor  51  and the second toner remainder amount sensor  52 . X [g] corresponds to a second amount, and the toner amount of 0 [g] to X [g] corresponds to a toner amount smaller than the second amount. 
     In the case where the developer container  32  accommodates toner of X [g] to Y [g], the toner remainder amount panel  400  indicates the Mid level on the basis of the detection result of the first toner remainder amount sensor  51  and the second toner remainder amount sensor  52 . Y [g] corresponds to a first amount, and a toner amount of X [g] to Y [g] corresponds to a toner amount smaller than the first amount. 
     In the case where the developer container  32  accommodates toner of Y [g] or more, the toner remainder amount panel  400  indicates the Full level on the basis of the detection result of the first toner remainder amount sensor  51  and the second toner remainder amount sensor  52 . The toner amount of Y [g] or more corresponds to a toner amount of first amount or more. 
       FIG.  18 B  is a graph indicating the toner amount in the case where the developer container  32  is replenished with toner by using the toner pack  40  filled with toner of A [g].  FIG.  18 C  is a graph indicating the toner amount in the case where the developer container  32  is replenished with toner by using the toner pack  40  filled with toner of B [g] (&gt;A). To be noted, the product lineup of the toner pack  40  may include either one or both of a toner pack of a small capacity filled with toner of only A [g] and a toner pack of a large capacity filled with toner of B [g]. In addition, the product lineup of the toner pack  40  is not limited to 2, and 3 or more kinds may be prepared. 
     In the present embodiment, the amount of toner (A,B) charged into the toner pack  40  serving as a replenishment container satisfies the following formulae (1) and (2). 
         Y≤A&lt;Z−Y   (1)
 
         Y≤B&lt;Z−Y   (2)
 
     As illustrated in  FIG.  18 B , if the developer container  32  is replenished with toner of just A [g] by the toner pack  40  in the case where toner remaining in the developer container  32  is R [g] in the range of 0 [g] to X [g], the developer container  32  accommodates toner of (R+A) [g]. Since Y&lt;(R+A) is satisfied according to the formula (1) described above, the toner remainder amount panel  400  after the toner replenishment indicates the Full level. That is, the threshold value Y [g] of the Full level is smaller than the replenishment amount A [g] supplied from the toner pack  40 . 
     In addition, as illustrated in  FIG.  18 C , if the developer container  32  is replenished with toner of B [g] by the toner pack  40  in the case where toner remaining in the developer container  32  is R [g], the developer container  32  accommodates toner of (R+B) [g]. Since Y&lt;(R+B) is satisfied according to the formula (2) described above, the toner remainder amount panel  400  after the toner replenishment indicates the Full level. 
     As described above, the capacity of the developer container  32  is set such that the toner remainder amount panel  400  always indicates the Full level in the case where toner replenishment is performed when the toner remainder amount panel  400  indicates the Mid level or the Low level. To be noted, the capacity of the developer container  32  does not have to be set such that the single toner pack  40  achieves the Full level, and for example, the Full level may be achieved by replenishment using a plurality of toner packs  40  each accommodating a small amount of toner. 
     In addition, the capacity of the developer container  32  is, according to the formulae (1) and (2) described above, set such that all toner charged into the toner pack  40  can move to the developer container  32  when the toner remainder amount panel  400  indicates the Mid level or the Low level. That is, the maximum amount Z [g] of the developer that can be accommodated in the developer container  32  is larger than a value obtained by adding the amount (A [g] or B [g]) of developer accommodated in the toner pack  40  to Y [g], which is the boundary between the Full level and the Mid level. In other words, the amount of toner charged into the toner pack  40  is smaller than the difference between the maximum amount of toner (Z [g]) that can be accommodated in the developer container  32  and the toner remainder amount (Y [g]) that is the boundary between the Mid level and the Full level. 
     As a result of this, the developer container  32  does not become full of toner while replenishing the developer container  32  with toner by using the toner pack  40 , and leakage of toner from the replenishment port  32   a  during toner replenishment can be suppressed. 
     As described above, in the present embodiment, the second opening portion  82   a  is defined in the discharge tray  81  of the top cover  82 , and the opening/closing member  83  openably and closably provided on the top cover  82 . The opening/closing member  83  covers the second opening portion  82   a  in a closed state, and exposes the replenishment port  32   a  of the developer container  32  in an open state. Therefore, the user can access the replenishment port  32   a  by just opening the opening/closing member  83 . 
     In the present embodiment, since the system (direct replenishment system) in which the developer container  32  is replenished with toner directly from the toner pack  40  through the replenishment port  32   a  is employed, the process cartridge  20  does not have to be taken out when replenishing the developer container  32  with toner. In addition, the replenishment port  32   a  of the developer container  32  is defined in the upper surface of the first projection portion  37  projecting upward from one end portion of the conveyance chamber  36  in the longitudinal direction, and is thus disposed in the vicinity of the second opening portion  82   a . Therefore, the user can easily perform the toner replenishment operation on the developer container  32  through the replenishment port  32   a . In addition, parts such as the developing roller  31  and the supply roller  33  are not replaced when replenishing the developer container  32  with toner, and thus the cost can be reduced. 
     In addition, since the laser passage space SP is formed to be surrounded by the first projection portion  37 , the second projection portion  38 , the grip portion  39 , and the conveyance chamber  36 , the developer container  32  and the scanner unit  11  can be disposed in the vicinity of each other, and thus the image forming apparatus  1  can be miniaturized. 
     Further, when attaching the toner pack  40  to the replenishment port  32   a  and performing the toner replenishment operation, since the agitation member  34  is driven, the packing phenomenon can be suppressed even if the replenishment port  32   a  is disposed on the one end side of the developer container  32  in the longitudinal direction. As a result of this, image defects can be reduced, and the detection precision of the toner remainder amount information can be improved. 
     In addition, the maximum amount Z [g] of the developer that can be accommodated by the developer container  32  is set to be larger than a value obtained by adding the amount (A [g] or B [g]) of developer accommodated by the toner pack  40  to Y [g], which is the boundary between the Full level and the Mid level. Therefore, the developer container  32  does not become full of toner while replenishing the developer container  32  with toner by using the toner pack  40 , and leakage of toner from the replenishment port  32   a  during toner replenishment can be suppressed. By configuring the image forming apparatus  1  in this manner, a mode of an image forming apparatus that can satisfy the needs of the user can be provided. 
     To be noted, although the agitation member  34  is driven for a predetermined time (threshold value α) on the basis of operation of the button  1  of the operation portion  300  by the user in the toner replenishment process in the present embodiment, this is not limiting. For example, the driving of the agitation member  34  may be started by pushing the button  1  once, and the driving of the agitation member  34  may be stopped by pushing the button  1  again. Alternatively, the agitation member  34  may be driven only while the button  1  is pushed. 
     In addition, the display portion  301  may display a replenishment notification for prompting toner replenishment when the toner remainder amount of the developer container  32  reaches the Low level. In addition, a replenishment notification for prompting toner replenishment may be displayed on the display portion  301  when the toner is run out. 
     In addition, although the toner remainder amount of the developer container  32  is notified to the user by the toner remainder amount panel  400 , the three-indicator configuration like the present embodiment does not have to be employed. For example, the toner remainder amount panel  400  may be constituted by one indicator, two indicators, four indicators, or more indicators. In addition, a configuration in which the toner remainder amount is continuously indicated by percentage presentation or gauge presentation. In addition, the notification of the toner remainder amount to the user may be performed by sound by using a loudspeaker. 
     First Modification Example 
       FIG.  19 A  illustrates a first modification example of the first embodiment. As illustrated in  FIG.  19 A , in an image forming apparatus  1 B, a replenishment port  132   a  of a developer container is disposed on the right side of the apparatus, and an opening/closing member  83 B is disposed on the right side of the apparatus. The opening/closing member  83 B exposes the replenishment port  132   a  in an open state, and covers the replenishment port  132   a  in a closed state. By disposing the replenishment port  132   a  on the right side of the apparatus as described above, the replenishment port  132   a  is positioned in the vicinity of the toner remainder amount panel  400 . Therefore, the toner remainder amount panel  400  can be easily checked when replenishing the developer container with toner using the toner pack  40 . 
     Second Modification Example 
     In addition, the configuration is not limited to the embodiment illustrated in  FIG.  19 A , and as illustrated in  FIG.  19 B , the present invention may be applied to an image forming apparatus  1 C configured such that an opening/closing member  83 C is opened to the front. 
     Third Modification Example 
     In addition, as illustrated in  FIG.  19 C , the present invention may be applied to an image forming apparatus  1 D configured such that an opening/closing member  83 D is opened to the rear side. 
     Fourth Modification Example 
     In addition, as illustrated in  FIG.  20 A , an operation portion  300 E may be disposed in the reading apparatus  200  instead of in the printer body  100 , or may be disposed on the right side of the apparatus together with the toner remainder amount panel  400 . To be noted, as a matter of course, the operation portion  300 E and the toner remainder amount panel  400  may be both disposed on the right side of the apparatus. 
     Fifth Modification Example 
     In addition, as illustrated in  FIG.  20 B , a toner remainder amount panel  400 F may be disposed on the left side of the apparatus, and an operation portion  300 F may be disposed on the right side of the apparatus. 
     Second Embodiment 
     Next, a second embodiment of the present invention will be described. In the second embodiment, the configuration of the replenishment port  32   a  is changed from the first embodiment. Therefore, elements substantially the same as in the first embodiment will be denoted by the same reference signs in the drawings, or the illustration thereof will be omitted. 
     As illustrated in  FIG.  21 A , in an image forming apparatus  1 G, an opening/closing member  83 G is openably and closably supported by the top cover  82 , and the opening/closing member  83 G is configured to be opened to the rear side of the apparatus. By opening the opening/closing member  83 G, a replenishment port  232   a  of a developer container  32 G is exposed. Further, the replenishment port  232   a  opens downstream and upward in the discharge direction of the discharge roller pair  80  so as to be inclined with respect to the vertical direction. In other words, the replenishment port  232   a  opens obliquely toward the upper front side. 
     By configuring the replenishment port  232   a  in this manner, the toner pack  40  becomes inclined toward the front side in the state of being attached to the replenishment port  232   a . Therefore, the space between the replenishment port  232   a  and the reading apparatus  200  can be utilized efficiently, and also a toner pack of a large capacity can be attached to the replenishment port  232   a.    
     To be noted, as illustrated in  FIGS.  22 A and  22 B , an opening/closing member  83 H and the reading apparatus  200  may be configured to be held at a less steep angle than in  FIGS.  21 A and  21 B . By employing such a configuration, the installation space for the image forming apparatus  1  can be reduced. 
     Third Embodiment 
     Next, a third embodiment of the present invention will be described. In the third embodiment, the configuration of the cartridge guides  102  is changed from the first embodiment. Therefore, elements substantially the same as in the first embodiment will be denoted by the same reference signs in the drawings, or the illustration thereof will be omitted. 
     As illustrated in  FIGS.  23 A and  23 B , an image forming apparatus  1 J includes a printer body  100 J and a reading apparatus  200 , and the printer body  100 J includes cartridge guides  102 J. The cartridge guides  102 J slide on projection portions  21   a  (see  FIG.  5 A ) provided at end portions of the photosensitive drum  21  in the axial direction, and thus guide the process cartridge  20  when drawing out the process cartridge  20 . 
     Draw-out stoppers  102 Ja are formed at the downstream ends of the cartridge guides  102 J in the draw-out direction. Therefore, when the user draws out the process cartridge  20  as illustrated in  FIG.  23 B , the projection portions  21   a  of the process cartridge  20  abut the draw-out stoppers  102 Ja, and thus the process cartridge  20  is not detached from the printer body  100 J. To be noted, unillustrated rotation stoppers are provided in the vicinity of the draw-out stoppers  102 Ja, and the process cartridge  20  is held by the rotation stoppers so as not to rotate in the state of abutting the draw-out stoppers  102 Ja. 
     As described above, in a state in which the process cartridge  20  is drawn out along the cartridge guides  102 J, the replenishment port  32   a  is positioned on the front side of the image forming apparatus  1 J as illustrated in  FIGS.  24 ,  25 A, and  25 B . Therefore, the toner replenishment operation of replenishing the developer container  32  with toner through the replenishment port  32   a  by using the toner pack  40  can be easily performed. In addition, since a large space is provided right above the replenishment port  32   a , a toner pack of a large capacity can be attached to the replenishment port  32   a . To be noted, all the embodiments and modification examples described above may be combined appropriately. 
     To be noted, although the reading apparatus  200  is provided above the printer body in all the embodiments described above, this is not limiting. That is, the image forming apparatus may be a printer that does not include a reading apparatus. In addition, the reading apparatus may be a reading apparatus that includes an auto document feeder (ADF) that feeds a document. 
     Other Embodiment 
     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.