Abstract:
A developing apparatus for developing a latent image formed on an image bearing member, the apparatus includes a developer accommodating portion for accommodating the developer; developing means for developing the latent image; a light transmitting portion, provided in the developer accommodating portion, for transmitting light for detecting a remaining amount of the developer; a first developer feeding member, provided in the developer accommodating portion, for feeding the developer toward the developing means by rotation thereof; and a second developer feeding member for feeding the developer onto a light transmission surface of the light transmitting portion after the first developer feeding member rubs the light transmission surface by a free end with respect to a radial direction of the rotation, the second developer feeding member being provided on a rotation shaft which is also a rotation shaft of the first developer feeding member, wherein second developer feeding member does not rub the light transmission surface when the second developer feeding member rotates.

Description:
FIELD OF THE INVENTION AND RELATED ART  
       [0001]     The present invention relates to a developing apparatus, a process cartridge, and an image forming apparatus.  
         [0002]     Here, an image forming apparatus means an apparatus for forming an image on recording medium. For example, it includes an electrophotographic copying machine, an electrophotographic printer (for example, laser beam printer, LED printer, etc.), an electrostatic printer, a magnetic recording printer, a facsimileing apparatus, a wordprocessor, etc.  
         [0003]     A developing apparatus means an apparatus for developing a latent image formed on an image bearing member, with the use of developer.  
         [0004]     A process cartridge means a cartridge in which a minimum of a developing means and an electrophotographic photosensitive member are integrally disposed, and which is removably mountable in the main assembly of an image forming apparatus.  
         [0005]     In the field of an electrophotographic image forming apparatus employing one of the electrophoto-graphic image formation processes, it has been a common practice to employ a process cartridge system, which integrally places an electrophotographic photosensitive member, and a single or plurality of processing means which act on an electrophotographic photosensitive member, in a cartridge removably mountable in the main assembly of an electrophoto-graphic image forming apparatus. The employment of this process cartridge system makes it possible for a user himself to maintain an electrophotographic image forming apparatus, without help from service personnel, drastically improving the apparatus in operational efficiency. Thus, a process cartridge system has been widely used in the field of an electrophotographic image forming apparatus.  
         [0006]     A process cartridge is enabled to inform a user of the information regarding the amount of the developer remaining therein, in order to facilitate smooth process cartridge exchange. There are various methods for detecting the amount of the developer remainder in a process cartridge. Known as one of such methods is of a beam transmission type (which hereinafter may be referred to simply as transmission type).  
         [0007]     At this time, referring to  FIG. 13 , the structure of a transmission type developer remainder amount detecting apparatus in accordance with the prior art will be described. A beam L is emitted from a beam emitting portion  102  attached to the main assembly of an electrophotographic image forming apparatus. Then, the beam L is guided so that it enters the developer storage portion  70  through the transparent portion  61  of the developer storage portion  70 , travels through the developer storage portion  70 , exits from the developer storage portion  70  through the transparent portion  62  of the developer storage portion  70 , and reaches the beam receiving portion  103 , for example, a photo-transistor, attached to the image forming apparatus main assembly. The condition under which the beam L is allowed to travel through the developer storage portion  70  is affected by the amount of the developer remaining in the developer storage portion  70 . To describe more concretely, there is a developer conveying member  74  located in the developer storage portion  70  to convey the developer D toward the development roller while stirring the developer D, and when there is a substantial amount of the developer in the developer storage portion  70 , the beam L is completely blocked by the developer D. However, as the amount of the developer remaining in the developer storage portion  70  reduces, it becomes possible for the beam L to travel through the developer storage portion  70  for a certain length of time. In other words, the smaller the amount of the developer remaining in the developer storage portion  70 , the shorter the length of time the beam L remains blocked by the developer D, that is, the longer the length of time the beam L is allowed to travel through the developer storage portion  70 . Thus, by detecting the length of time the beam L is allowed to travel through the developer storage portion  70 , it is possible to estimate the amount of the developer remainder in the developer storage portion  70  (Japanese Laid-open Patent Applications 3-181973, 2003-131479 ( FIG. 12 , P. 9)).  
         [0008]     At this time, the developer remainder amount detecting method of a transmission type will be described with reference to  FIG. 13 .  
         [0009]     As will be evident from  FIG. 13 , the developer conveying member  82  is in the developer storage portion  70 , and is rotated in contact with the internal surface of the developer storage portion  70 . As the developer conveying member  82  is rotated, it conveys the developer D toward the development roller  22  while wiping the internal surface  62   a  of the transparent portion  62 . As soon as the developer conveying member  82  is moved past the transparent portion  62  while wiping the internal surface  62   a  of the transparent portion  62 , the developer D which was conveyed toward the development roller  22 , but did not adhere to the development roller  22 , returns to the transparent portion  62 , covering the internal surface  62   a  of the transparent portion  62 . The present invention is one of the results of the further development of the prior art regarding a transmission type developer remainder amount detecting method.  
       SUMMARY OF THE INVENTION  
       [0010]     Thus, the primary object of the present invention is to provide a combination of a developing apparatus, a process cartridge, and an image forming apparatus, which makes it possible to precisely detect the amount of the developer remaining in the process cartridge.  
         [0011]     Another object of the present invention is to provide a combination of a developing apparatus, a process cartridge, and an image forming apparatus, which makes it possible to make as linear as possible the correlation between the length of time a beam of light is allowed to travel through the developer storage portion of a process cartridge, and the amount of the developer in the process cartridge.  
         [0012]     Another object of the present invention is to provide a combination of a developing apparatus, a process cartridge, and an image forming apparatus, which is capable of stabilizing the amount of the developer on the internal surfaces of the transparent portions of the developer storage portion of the process cartridge.  
         [0013]     Another object of the present invention is to provide a combination of a developing apparatus, a process cartridge, and an image forming apparatus, in which the developing apparatus comprises: a transparent portion with which the developer storage portion of the process cartridge is provided to detect the amount of the developer in the process cartridge; a first developer conveying member which is placed in the developer storage portion to convey the developer toward the developing means as it is rotated; and a second developer conveying member which is placed in the developer storage portion, being attached to the rotational shaft to which the first developer conveying member is attached, in order to convey the developer to the internal surface, that is, beam exit surface, of the transparent portion after the first developer conveying member wipes the beam exit surface of the transparent portion, by its free edge in terms of the radius direction of the sweeping range of the first developer conveying member, and which does not wipe the beam exit surface of the transparent portion of the developer storage portion while being rotated.  
         [0014]     These and other objects, features, and advantages of the present invention will become more apparent upon consideration of the following description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a sectional view of the process cartridge in one of the preferred embodiments of the present invention.  
         [0016]      FIG. 2  is a perspective view of the process cartridge in the preferred embodiment of the present invention.  
         [0017]      FIG. 3  is a perspective view of the process cartridge in the preferred embodiment of the present invention, the photosensitive drum unit  2   a  and developing apparatus  2   b  of which are separated from each other.  
         [0018]      FIG. 4  is a perspective view of the developer conveying member in the preferred embodiment of the present invention.  
         [0019]      FIG. 5  is a perspective view of the developer remainder amount detecting portion in the preferred embodiment of the present invention, showing the structure thereof.  
         [0020]      FIG. 6  is a sectional view of the process cartridge in the preferred embodiment of the present invention, showing the state thereof, in which the beam for detecting the amount of the developer remainder is not receivable.  
         [0021]      FIG. 7  is a sectional view of the process cartridge in the preferred embodiment of the present invention, showing the state thereof, in which the beam for detecting the amount of the developer remainder is receivable.  
         [0022]      FIG. 8  is a graph showing the relationship between the amount of the developer remainder in the process cartridge and the length of time the beam is allowed to travel through the developer storage portion of the process cartridge, in the preferred embodiment of the present invention.  
         [0023]      FIG. 9  is a flowchart showing the developer remainder amount detection sequence in the preferred embodiment of the present invention.  
         [0024]      FIG. 10  is a sectional view of the developer storage portion in the preferred embodiment of the present invention.  
         [0025]      FIG. 11  is a block diagram of the developer remainder amount detection process in the preferred embodiment of the present invention.  
         [0026]      FIG. 12  is a sectional view an image forming apparatus in the preferred embodiment of the present invention, which is forming an image.  
         [0027]      FIG. 13  is a sectional view of the developer storage portion of a process cartridge in accordance with the prior art.  
         [0028]      FIG. 14  is a graph showing the relationship between the developer remainder amount and pulse width.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     Embodiment  
       [0000]     [General Description of Image Forming Apparatus] 
         [0029]     First, referring to  FIG. 12 , the general structure of a typical color image forming apparatus will be described.  
         [0030]      FIG. 12  is a drawing for describing the overall structure of an electrophotographic color image forming apparatus as an example of an image forming apparatus, in which a plurality of process cartridges  2  are in the process cartridge holding portion  200 .  
         [0031]     As is evident from  FIG. 12 , the image forming apparatus A has a cartridge holding portion  200  in which process cartridges  2 Y,  2 M,  2 C, and  2 Bk are mounted. The process cartridges  2 Y,  2 M,  2 C, and  2 Bk, corresponding to the yellow (Y), magenta (M), cyan (C), and black (Bk) color components of a full-color image, respectively, each have a photosensitive drum  21  as an image bearing member. In the image forming apparatus A, multiple images different in color are developed by the cartridges  2 , one for one, are transferred in layers onto an intermediary transferring member  35 , and are transferred onto a delivered recording medium P. The image forming apparatus A is also provided with a fixing station  50  for fixing the transferred color images, different in color, on the recording medium P to the recording medium P, and multiple pairs of discharge rollers  53 ,  54 , and  55 , which discharge the recording medium P onto the delivery tray  56  on top of the apparatus main assembly.  
         [0032]     Further, the image forming apparatus A is provided with a beam emitting portion  102  for emitting a beam L for detecting the amount of the remaining developer D, and a beam receiving portion for receiving the beam L having traveled through the internal space of the developer storage portion  70 . It is also provided with a CPU (information processing unit)  104  for processing the information regarding the length of time the beam receiving portion  103  received the beam L.  
         [0033]     Incidentally, the aforementioned four cartridge  2  different in the color of the developer therein can be individually and removably mountable in the cartridge holding portion  200  of the apparatus main assembly  100 .  
         [0000]     [Description of Process Cartridge] 
         [0034]     Next, referring to  FIGS. 1, 2 , and  3 , the process cartridge  2  in this preferred embodiment of the present invention will be described in detail.  FIG. 1  is a sectional view of the process cartridge  2 , and  FIG. 2  is a perspective view of the cartridge  2 .  FIG. 3  is a perspective view of the process cartridge in the preferred embodiment, the photosensitive drum unit  2   a  and developing apparatus  2   b  of which are separated from each other. Incidentally, the four cartridges for yellow, magenta, cyan, and black color components, one for one, are the same in structure.  
         [0035]     The cartridge  2  is separable into the photosensitive drum unit  2   a  and development unit  2   b.  The drum unit  2   a  has the electrophotographic photosensitive member  21  (which hereinafter will be referred to as photosensitive drum  21 ), as an image bearing member, in the form of a drum, a charge roller  23 , and a cleaning blade  28 , whereas the development unit  2   b  has the development roller  22  (developing means) for developing an electrostatic latent image formed on the photosensitive drum  21 .  
         [0036]     The drum unit  2   a  has a drum unit frame  24 , to which the photosensitive drum  21  is rotatably attached, with a pair of bearings  27  placed between the photosensitive drum  21  and drum unit frame  24 . The photosensitive drum  21  comprises an aluminum cylinder, and a layer of organic conductor coated on the peripheral surface of the aluminum cylinder. The charge roller  23  as a primary charging means for uniformly charging the peripheral surface of the photosensitive drum  21  is placed in contact with the peripheral surface of the photosensitive drum  21 . Also placed in contact with the peripheral surface of the photosensitive drum  21  is the cleaning blade  28  for removing the developer D (toner) remaining on the peripheral surface of the photosensitive drum  21 . The charge roller  23  is of a type which employs one of the contact charging methods. In this embodiment, the charge roller  23  is an electrically conductive roller, and is placed in contact with the peripheral surface of the photosensitive drum  21 . As voltage is applied to the charge roller  23 , the peripheral surface of the photosensitive drum  21  is uniformly charged. The developer D remaining on the peripheral surface of the photosensitive drum  21  is removed by the blade  28 . The removed developer D is continuously conveyed rearward by the developer conveying mechanism  29 , to a waste toner chamber  30  located in the rear portion of the drum unit frame  24 . The driving force from a motor (unshown) of the apparatus main assembly  100  is transmitted to the photosensitive drum  21 , rotating thereby the photosensitive drum  21  in the counterclockwise direction (direction indicated by arrow mark X) in synchronism with an image forming operation.  
         [0037]     The development unit  2   b  has the development roller  22 , which is rotated (direction indicated by arrow mark Y) in contact with the photosensitive drum  21 , developer storage portion  70  in which the developer D is stored, and a developing means container  71 . The development roller  22  is rotatably supported by the developing means container  71 , with the interposition of a pair of bearings  83  and  84 . Placed in contact with the peripheral surface of the development roller  22  are a developer supply roller  72 , which is rotated (in the direction indicated by arrow mark Z), and the development blade  73 . Further, development unit  2   b  is provided with a first developer conveying member  74 , which is placed in the developer storage portion  70 . The first developer conveying member  74  conveys the developer D in the developer storage portion  70 , to the developer supply roller  72  while stirring the developer D.  
         [0038]     The bearings  83  and  84  attached to the lengthwise ends of the development unit  2   b  are provided with a hole  77 , through which a pin  77   a  is put to enable the development unit  2   b  to rotationally move relative to the drum unit  2   a,  about the axial line of the hole  77  (pin  77   a ). When the cartridge  2  is out of the apparatus main assembly  100 , the development unit  2   b  is kept pressured by the moment generated by a pair of springs (unshown) provided for keeping the development unit  2   b  pressured in the direction to rotate about the axial line of the hole  77 , so that the development roller  22  is kept in contact with the peripheral surface of the photosensitive drum  21 .  
         [0039]     In a development operation, the developer D stored in the developer storage portion  70  is conveyed to the developer supply roller  72  by the first developer conveying member  74 , which is being rotated in contact with the development roller  22 , which also is being rotated. As a result, the peripheral surface of the developer supply roller  72 , which is bearing the developer D, rubs against the peripheral surface of the development roller  22 . Consequently, the developer D on the peripheral surface of the developer supply roller  72  is supplied to the peripheral surface of the development roller  22 ; the developer D is adhered to the peripheral surface of the development roller  22 . As the development roller  22  is rotated, the developer D having adhered to the peripheral surface of the development roller  22  reaches the development blade  73 , which regulates the amount by which the developer D is allowed to remain adhered to the peripheral surface of the development roller  22 , forming thereby the developer D into a thin layer with a predetermined thickness. Then, as the development roller  22  is further rotated, the thin layer of the developer D reaches the development station, which is the contact area between the peripheral surfaces of the photosensitive drum  21  and development roller  22 . To the development roller  22 , development bias (DC voltage) is being applied from a power source (unshown) with which the apparatus main assembly  100  is provided. As a result, the electrostatic latent image on the photosensitive drum  21  is developed by the developer D; the developer D on the peripheral surface of the development roller  22  is adhered to the peripheral surface of the photosensitive drum  21  in the pattern of the latent image. While the developer D is supplied to the peripheral surface of the development roller  22  by the developer supply roller  72 , the developer D remaining on the peripheral surface of the development roller  22  is removed by the development supply roller  72 , and recovered into the developing means container  71 . Then, the recovered developer D is stirred into the main body of the developer D in the developing means container  71 , by the first developer conveying member  74 .  
         [0040]     In the case of a contact developing method, such as the one in this embodiment, in which the development roller  22  is kept in contact with the photosensitive drum  21 , it is desired that the photosensitive drum  21  is rigid, whereas the development roller  22  is elastic. As for an elastic roller usable as the development roller  22 , there are an elastic roller comprising a core, and a solid rubber layer formed around the core, an elastic roller comprising a core, a solid rubber layer formed around the core, and a resin layer coated on the peripheral surface of the solid rubber layer in consideration of the charging of the developer D, and the like.  
         [0000]     (Developer Conveying Member, and Developer Remainder Amount Detection Structure)  
         [0041]     Next, referring to  FIGS. 4-11 , and  14 , the first developer conveying member  74 , second developer conveying member  75 , and developer remainder amount detection structure, in the preferred embodiment of the present invention will be described.  
         [0042]      FIG. 4  is a perspective view of the developer conveying member in the preferred embodiment of the present invention, and  FIG. 5  is a perspective view of the developer remainder amount detecting portion in the preferred embodiment.  FIG. 6  is a sectional view of the process cartridge in the preferred embodiment, showing the state thereof, in which the beam for detecting the amount of the developer remainder is not receivable, and  FIG. 7  is a sectional view of the process cartridge in the preferred embodiment, showing the state thereof, in which the beam for detecting the amount of the developer remainder is receivable.  FIG. 8  is a graph showing the correlation between the amount of the developer remainder in the process cartridge and the length of time the beam is allowed to travel through the developer storage portion of the process cartridge, and  FIG. 9  is a flowchart showing the developer remainder amount detection sequence.  FIG. 10  is a sectional view of the developer storage portion in the preferred embodiment, and  FIG. 11  is a block diagram of the developer remainder amount detection process.  FIG. 14  is a graph showing the relationship between the developer remainder amount and pulse width.  
         [0043]     First, referring to  FIGS. 9 and 11 , the developer remainder amount detection sequence in the preferred embodiment will be described. As a printer start signal is sent to the CPU  104  as an information processing means from the controller  300  (S 1 ), the beam receiving portion  103  (for example, PRT (photo-transistor)) detects the beam L, which was emitted from the beam emitting portion  102  (for example, LED) and traveled through the developer storage portion  70 . The beam receiving portion  103  sends to the CPU  104  the signals representing the amount of the beam detected by the beam receiving portion  103  during a predetermined length of time, or the signals representing the length of time the beam L was allowed to travel through the developer storage portion  70  (S 2 ). Then, the CPU  104  converts these signals into the amount of the developer remainder, based on the relationship between the length of time the beam L is allowed to travel through the developer storage portion  70 , and the amount of the developer remainder in the developer storage portion  70 , such as the one shown in  FIG. 8  (S 3 ). When the amount of the developer remainder has not reached 0% of the full amount, an intended image forming operation is performed (S 5 ). When the amount of the developer remainder has reached 0% of the full amount, the image forming operation is not performed (S 6 ), and the message indicating the necessity of replacing the cartridge  2  is presented on a display  105  as an information displaying means (S 7 ).  
         [0044]     The controller  300 , beam emitting portion  102 , beam receiving portion  103 , CPU  104 , and display  105  are parts of the apparatus main assembly  100 . 0% does not mean that the entirety of the developer D in the developer storage portion  70  has been completely consumed. It includes the state of the cartridge  2 , in which the amount of the developer D in the developer storage portion  70  has been reduced to the level at or below which a satisfactory image cannot be formed. Further, a message warning that the cartridge  2  is about to run out of the developer D may be displayed before the amount of the developer remainder in the developer storage portion  70  reaches 0%.  
         [0045]     As the information displaying means, the monitor of the PC connected to the image forming apparatus  100 , a buzzer, etc., can be used in addition to the display  105  of the apparatus main assembly  100  in this embodiment.  
         [0046]     Next, the developer remainder detecting means in this embodiment will be described regarding its structure.  
         [0047]     Referring to  FIG. 4 , there are the first developer conveying member  74 , second developer conveying member  75 , and rotational shaft  76  in the developer storage portion  70 . The first developer conveying member  74  conveys the developer D in the developer storage portion  70  toward the development roller  22 . The second developer conveying member  75  scoops up the developer D in the developer storage portion  70 , and delivers it to the beam exit surface  61   a  of the transparent beam entrance portion  61 . In other words, the second developer conveying member  75  drops the developer D it scooped up, onto the beam exit surface  61   a  of the transparent beam entrance portion  61 . The first developer conveying member  74  is a piece of flexible sheet formed of resin, and is attached to the rotational shaft  76  by thermal welding, ultrasonic welding, screws, or the like, at the locations E. The rotational shaft  76  is molded of resin. Designated by a referential letter F is a boss used for precisely positioning the first developer conveying member  74  and rotational shaft  76  relative to each other when attaching the former to the latter. The first developer conveying member  74  is provided with multiple holes  74   a.  The free end portion of the first developer conveying member  74  is elastically bent in contact with the internal surface of the developer storage portion  70 . One of the lengthwise ends of the rotational shaft  76  is fitted with a gear (unshown), to which driving force is transmitted from the apparatus main assembly  100  in order to rotate the rotational shaft  76 . As the rotational shaft  76  is rotated, the first developer conveying member  74  is rotated while remaining in contact with the internal surface of the developer storage portion  70  (at least, partially). As a result, the developer D is conveyed toward the development roller  22  by the first developer conveying member  74 . When the amount of the developer D in the developer storage portion  70  is large, the developer D partially slips backward through the aforementioned holes  74   a  while being conveyed toward the development roller  22 . In other words, the presence of the holes  74   a  controls the amount by which the developer D is conveyed toward the development roller  22 , preventing thereby the development roller  22  from being supplied with an excessive amount of the developer D. Further, as the first developer conveying member  74  is rotated, it wipes the beam exit surface  61   a  of the transparent beam entrance portion  61  as the first transparent portion of the developer storage portion  70 , and the beam entrance surface  62   a  of the transparent beam exit portion  62  as the second transparent portion of the developer storage portion  70 . In other words, as the first developer conveying member  74  is rotated, it removes the developer D adhering to the beam exit surface  61   a  (located inward of developer storage portion  70 ) of the transparent beam entrance portion  61  as the first transparent portion of the developer storage portion  70 , and the beam entrance surface  62   a  (located inward of developer storage portion  70 ) of the transparent beam exit portion  62  as the second transparent portion of the developer storage portion  70 .  
         [0048]     Next, referring to  FIG. 5 , the transparent beam entrance portion  61  and transparent beam exit portion  62  are attached to the developer storage portion  70  so that the beam exit surface  61   a  (inward surface) and beam entrance surface  62   a  (inward surface) are positioned a predetermined distance inward of the developer storage portion  70  relative to the internal surface of the developer storage portion  70 . In this embodiment, the transparent beam entrance portion  61  is located on the opposite side of the vertical plane coinciding with the rotational axis of the first developer conveying member  74 , from the development roller  22 . Further, the transparent beam entrance portion  61  is located below the horizontal plane coinciding with the rotational axis of the first developer conveying member  74 . The transparent beam entrance portion  61  guides inward of the developer storage portion  70  the beam L emitted from the beam emitting portion  102  of the apparatus main assembly  100 , whereas the transparent beam exit portion  62  guides the beam L having traveled through the developer storage portion  70 , to the beam receiving portion  103  of the apparatus main assembly  100 . In this embodiment, an LED and a photo-transistor (PTR) are employed as the beam emitting portion  102  and beam receiving portion  103 , respectively.  
         [0049]     Referring to  FIG. 14 , the length of time the beam L is allowed to travel through the developer storage portion  70  is detected as the width t of the pulse in the output of the beam receiving portion  103 , per rotational cycle T of the first developer conveying member  74 . The greater the amount of the beam L, or the length of time the beam L is allowed to travel through the developer storage portion  70 , the wider the pulse width t. In other words, as the amount of the developer remainder in the developer storage portion  70  reduces, the pulse width t becomes greater. Therefore, the CPU  104  calculates the amount of the developer remainder, based on the pulse width t detected by the beam receiving means  103 . Then, the display  105  as an information displaying means informs a user of the calculated value.  
         [0050]     Next, the second developer conveying member  75  will be described.  
         [0051]     The second developer conveying member  75  conveys the developer D to the beam exit surface (inward surface)  61   a  of the transparent beam entrance portion  61 , after the first developer conveying member  74  wipes the beam exit surface  61   a.    
         [0052]     If the second developer conveying member  75  is not present, the beam L is sometimes allowed to continue to travel through the developer storage portion  70  during the period between the wiping of the beam exit surface  61   a  by the first developer conveying member  74  and the conveyance of the developer D to the beam exit surface  61   a  by the rotation of the first developer conveying member  74  following the wiping. In this embodiment, therefore, the second developer conveying member  75 , which is enabled to convey the developer D to the beam exit surface  61   a  during the above described period, is provided to reduce the length of time the beam L is allowed to travel through the developer storage portion  70 .  
         [0053]     In other words, if the second developer conveying member  75  is not present, the correlation between the length of time the beam L is allowed to travel through the developer storage portion  70 , that is, the length of time the receiving portion  104  receives the beam L, and the amount of the developer remainder, sometimes becomes as indicated by the portion (a) in  FIG. 8 . However, with the provision of the second developer conveying member  75 , the developer D is conveyed to the beam exit surface  61   a  even during the aforementioned period by the second developer conveying member  75 . As a result, the correlation between the length of time the beam receiving portion  103  receives the beam L, and the amount of the developer remainder in the developer storage portion  70  is rectified as indicated by the portion (b) in  FIG. 8 , making it possible to accurately detect the amount of the developer remainder.  
         [0054]     In other words, this embodiment makes it possible to keep virtually linear the relationship between the length of time the beam L is allowed to travel through the developer storage portion  70 , and the amount of the developer remainder in the developer storage portion  70 , from the beginning of the first-time usage of a cartridge  2  to when the amount of the developer remainder becomes zero, making it thereby possible to more accurately detect the amount of the developer remainder than the prior art.  
         [0055]     In this embodiment, the dimension of the second developer conveying member  75  is such that its free end does not wipe the beam exit surface  61   a  of the transparent beam entrance portion  61 , being therefore better suited for depositing the developer D on the beam exit surface  61   a.  In other words, the first developer conveying member  74  having the function of removing the developer D on the beam exit surface  61   a,  and the second developer conveying member  75  having the function of depositing the developer D on the beam exit surface  61   a  are separated from each other in function, making it thereby possible to more easily and more accurately detecting the amount of the developer remainder.  
         [0056]     Also in this embodiment, the first developer conveying member  74  is directly attached to the rotational shaft  76 , and the second developer conveying member  75  is pasted to the mount  76   a  of the rotational shaft  76  dedicated to the mounting of the second developer conveying member  75 , with the use of a piece of two-sided adhesive tape. In other words, both the first and second developer conveying members  74  and  75  are attached to the same rotational member, or the rotational shaft  76 . Therefore their rotational axes coincide, making it possible to more accurately detect the amount of the developer remainder, with the addition of only a single component, as described above.  
         [0057]     Also in this embodiment, the first developer conveying member  74  wipes the portion of the internal surface of the developer storage portion  70 , below the horizontal plane coinciding with the rotational axis of the rotational shaft  76  and on the developing means side of the vertical plane coinciding with the rotational axis of the rotational shaft  76 . With the employment of this structural arrangement, the developer D in the developer storage portion  70  can be scooped up by a greater amount, making it easier to more accurately detect the developer remainder amount.  
         [0058]     Also in this embodiment, the second developer conveying member  75  is attached to the mount  76   a  of the rotational shaft  76  dedicated to the mounting of the second developer conveying member  75  as described above, and the dimension of the flexible portion  75   c  of the second developer conveying member  75  in terms of the radius direction of the sweeping range of the second developer conveying member  75  is made less than the dimension of the flexible portion  74   c  of the first developer conveying member  74  in terms of the radius direction of the sweeping range of the first developer conveying member  74 . Therefore, the second developer conveying member  75  is greater in the amount of the pressure generated in the direction to scoop up the developer D than the first developer conveying member  74 , being therefore greater in the capacity to scoop up the developer D. Therefore, it can scoop up the developer D in the developer storage portion  70  by a greater amount, making it easier to more accurately detect the developer remainder amount.  
         [0059]     Incidentally, the dimension of the second developer conveying member  75  in terms of the direction parallel to the axial direction of the rotational shaft  76  may be large enough to match the entire length of the developer storage portion  70 . In other words, it may be the same as the dimension of the first developer conveying member  74  in terms the direction parallel to the axial direction of the rotational shaft  76 . In this embodiment, however, the dimension of the second developer conveying member  75  in terms of the direction of its rotational axis is made shorter than the dimension of the first developer conveying member  74  in terms of the direction of its rotational axis. Further, the second developer conveying member  75  is positioned so that as it is rotated, its free edge moves across the area a predetermined distance away from the beam exit surface  61   a  of the transparent beam entrance portion  61 , preventing thereby the provision of the second developer conveying member  75  from sending the developer D toward the development roller  22  by an excessive amount. Therefore, satisfactory development is assured. Also, the deterioration of the developer D is prevented for the following reason: the reduction of the surface area of the second developer conveying member  75  reduces the amount of the load (pressure) which the second developer conveying member  75  applies to the developer D. Further, this embodiment can reduce the cost of the second developer conveying member  75 , and the torque necessary to rotate the rotational shaft  76 .  
         [0060]     Also in this embodiment, in terms of their rotational phase, the first and second developer conveying members  74  and  75  are positioned relative to each other so that after the first developer conveying member  74  wipes the beam exit surface  61   a  of the transparent beam entrance portion  61 , the developer D is supplied to the beam entrance surface  61   a  by the second developer conveying member  75 . The direction in which the first and second developer conveying members  74  and  75  are rotated is the direction indicated by an arrow mark R in  FIG. 1 . The developer D used in this embodiment begins to slide downward, as the surface on which the developer D is borne tilts no less than 45°. Therefore, the second developer conveying member  75  is structured so that by the time it becomes necessary for the developer D to be slid downward, the angle of the surface of the second developer conveying member  75  will become no less than 45°. Also in this embodiment, the relationship in terms of rotational phase (difference in angle) between the second developer conveying member  75  and first developer conveying member  74  is desired to be in the range of 60°-120°, preferably, 75°-105°, more preferably, roughly 90°. This angle is the angle between the first developer conveying member  74 , and the second developer conveying member  75 , in terms of the rotational direction of the rotational shaft  76 .  
         [0061]     Thus, it is assured that the second developer conveying member  75  is enabled to scoop up the developer D before the first developer conveying member  74  wipes the beam exit surface  61   a  of the transparent beam entrance portion  61 , and also, that the developer D scooped up by the second developer conveying member  75  is slid down onto the beam exit surface  61   a  after the beam exit surface  61   a  is wiped by the first developer conveying member  74 . Further, it is possible to assure that the amount by which the developer D is supplied to the beam exit surface  61   a,  is limited to the amount just enough to prevent the beam L from entering the developer storage portion  70  from the beam exit surface  61   a.    
         [0062]     Next, the developer remainder amount detection process will be described.  
         [0063]     As the cartridge  2  receives the driving force from the apparatus main assembly  100 , the first developer conveying member  74  is rotated, while remaining in contact with the internal surface of the developer storage portion  70 , wiping therefore beam exit surface  61   a,  which is positioned a predetermined distance inward of the developer storage portion  70  relative to the internal surface of the developer storage portion  70 . As a result, the developer D adhering to the beam exit surface  61   a  is removed, allowing thereby the beam L to travel through the developer storage portion  70 . Then, after the first developer conveying member  74  passes the beam exit surface  61   a,  the developer D, which is being conveyed toward the development roller  22  by the first developer conveying member  74 , partially escapes backward through the aforementioned holes  74   a  of the first developer conveying member  74 , returning toward the beam exit surface  61   a.  At the same time, the second developer conveying member  75  scoops up the developer D having escaped backward through the holes  74   a  of the first developer conveying member  74  and returning toward the beam exit surface  61   a,  and drops the scooped developer D, onto the beam exit surface  61   a,  covering thereby the beam exit surface  61   a  with the developer D, and therefore, blocking the beam L. Meanwhile, the beam receiving portion  103  on the apparatus main assembly  100  side measures the length of time the beam L is allowed to travel through the developer storage portion  70 .  
         [0064]     When the amount of the developer remainder is large, the developer D having escaped backward through the aforementioned holes  74  of the first developer conveying member  74  deviates from its straight path and covers the beam exit surface  61   a,  after the first developer conveying member  74  finishes wiping the beam exit surface  61   a.  It should be noted here that the holes  74   a  are located so that they do not directly face the beam exit surface  61   a,  and also, that the holes  74   a  of the first developer conveying member  74  do not overlap with the second developer conveying member  75 , in terms of the axial direction of the rotational shaft  76 . In other words, the portions of the internal space of the developer storage portion  70 , which do not correspond in position to the holes  74   a,  are made greater in the rate at which the developer D is conveyed through them, that is, the level of performance at which the developer D is removed from the beam exit surface  61   a  (level of performance at which the beam exit surface  61   a  is wiped, than the portions of the internal space of the developer storage portion  70 , which correspond in position to the holes  74 . With the employment of the above described structural arrangement, the changes in the length of time the beam L is allowed to travel through the developer storage portion  70  can be increased by removing the developer D on the beam exit surface  61   a,  while preventing the problem that when the amount of the developer remainder is large, the developer D is conveyed toward the development roller  22  by an excessive amount, and also, the problem that when the amount of the developer remainder is large, the developer D is deteriorated as it is conveyed.  
         [0065]     On the other hand, when the amount of the developer remainder is small, the amount by which the developer D escape backward through the holes  74   a  is small, causing thereby the time necessary for the beam exit surface  61   a  to be covered by the developer D, to fluctuate. In a situation such as the above described one, that is, when the amount of the developer remainder is small, the beam exit surface  61   a  is covered mainly by the developer D that was scooped up by the second developer conveying member  75  and is dropped onto the beam exit surface  61   a  ( FIG. 7 ).  
         [0066]     With the employment of the above described structural arrangement, therefore, the correlation between the length of time the beam L is allowed to travel through the developer storage portion  70  and the developer remainder amount in the developer storage portion  70  becomes virtually linear, making it possible to reliably detect the developer remainder amount, across the entire period of cartridge usage (from when developer remainder amount is large to when it will have become small), in which the developer remainder amount is detectable.  
         [0067]     Next, the task the second developer conveying member  75  performs after the developer D scooped up by the second developer conveying member  75  slides down on the second developer conveying member  75  and covers the beam exit surface  61   a,  will be described in detail.  
         [0068]     As the rotational shaft  75  is rotated, the second developer conveying member  75  scoops up the developer D in the developer storage portion  70 . The amount by which the developer D is scooped up by the second developer conveying member  75  is affected by the amount of the developer remainder in the developer storage portion  70 . That is, when the developer remainder amount in the developer storage portion  70  is large, the developer D covers the second developer conveying member  75  from the base  75   a  of the second developer conveying member  75  to the free end portion  75   b  of the second developer conveying member  75 . On the other hand, when the amount of the developer remainder in the developer storage portion  70  is small, the developer D reaches only the free end portion  75   b  of the second developer conveying member  75 . Further, when the amount of the developer remainder is large, the developer D scooped up by the portion of the second developer conveying member  75  next to the base  75   a  begins to slide down on the second developer conveying member  75 , and fall onto the transparent beam entrance portion  61 , covering the beam exit surface  61   a,  relatively earlier. However, as the amount of the developer D in the developer storage portion  70  gradually reduces, the amount by which the developer D is scooped up by the second developer conveying member  75  also gradually reduces. As the amount of the developer D in the developer storage portion  70  reduces to the level at which only the free end portion  75   b  touches the developer D, the length of time from when the developer D begins to slide down on the second developer conveying member  75  to when it reaches the beam exit surface  61   a  becomes substantial, making the length of time necessary for the beam exit surface  61   a  to be covered with the developer D longer than when a large amount of the developer D is on the second developer conveying member  75  (length of time beam L is allowed to travel through developer storage portion  70  becomes longer).  
         [0069]     As described above, the length of time it takes for the developer D scooped up by the second developer conveying member  75  to slide down on the second developer conveying member  75  and cover the beam exit surface  61   a  (length of time beam L is allowed to travel through developer storage portion  70 ) is affected by the amount by which the developer D is scooped up by the second developer conveying member  75 .  
         [0070]     Referring to  FIG. 8 , when the second developer conveying member  75  was not present, as the amount of the developer in developer storage portion  70  became smaller, the correlation between the length of time the beam receiving portion  104  received the beam L, and the amount of the developer remainder, became as represented by the chain line portion (a). In comparison, when the second developer conveying member  75  was provided as in this embodiment, the correlation remained virtually linear as represented by the solid line portion (b), until the amount of the developer remainder became zero, making it possible to reliably detect the developer remainder amount.  
         [0071]     Next, the relationship between the developer storage portion  70  and transparent beam entrance portion  61  will be described. In this embodiment, the internal surface of the developer storage portion  70  is not flat; the internal surface of the developer storage portion  70  has irregularities in terms of the lengthwise direction thereof. That is, the transparent beam entrance portion  61  is attached to the developer storage portion  70  so that the beam exit surface  61   a  is placed a predetermined distance inward of the developer storage portion  70  relative to the internal surface of the developer storage portion  70  ( FIGS. 1 and 10 ). More specifically, the transparent beam entrance portion  61  is attached to the portion  702  of the developer storage portion  70 , and the developer storage portion  70  is structured so that the internal surface  702   a  of the portion  702  is positioned closer to the axial line of the rotational shaft  76  (more upward in  FIGS. 1 and 10 ) than the internal surface  701   a  of the portion  701 , that is, the internal surface of the portion of the developer storage portion  70  other than the portion  702 .  
         [0072]     With the employment of the above described structural arrangement, it is possible to prevent dead spaces, which overlap with the transparent beam entrance portion  61  in terms of the lengthwise direction of the developer storage portion  70 , from being created. Therefore, it is possible to reduce the developer storage portion  70  in the size of the space it occupies. This structural arrangement is particularly effective in the case of such an image forming apparatus as a color laser beam printer that employs multiple cartridges.  
         [0073]     The employment of the above described structural arrangement sometimes makes the apparent amount of the developer remainder appear smaller than the actual amount of the developer remainder. Even in such cases, the provision of the second developer conveying member  75  makes it possible to accurately detect the developer remainder amount. Further, even if the beam exit surface  61   a  of the transparent beam entrance portion  61  is positioned inward of the developer storage portion  70  relative to the internal surface  701   a  of the bottom portion of the developer storage portion  70  by a distance substantially greater than the distance by which the beam exit surface  61   a  is positioned inward of the developer storage portion  70  relative to the internal surface  701   a,  the above described effects can be obtained.  
         [0074]     Next, the above described preferred embodiment will be summarized.  
         [0075]     A developing apparatus (development unit)  2   b  for developing a latent image formed on the photosensitive drum  21  as an image bearing member, further comprises: 
        the developer storage portion  70  for storing the developer D;     the development roller  22  as a developing means for developing the latent image with the use of the developer D;     the transparent beam entrance portion  61 , with which the said developer storage portion  70  is provided to allow the beam for detecting the amount of the remainder of the developer D in the developer storage portion  70 , to travel through the developer storage portion  70 ;     the first developer conveying member  74  placed in said developer storage portion  70  to convey the developer D toward the development roller  22  as a developing means, and wipe the beam exit surface  61   a  of the transparent beam entrance portion  61 ; and     the second developer conveying member  75  placed in the developer storage portion  70  to convey the developer D to the beam exit surface  61   a  after the first developer conveying member  74  wipes the beam exit surface  61   a.          
 
         [0081]     The second developer conveying member  75  does not wipe the beam exit surface  61   a.    
         [0082]     The first and second developer conveying members  74  and  75  are attached to the rotational shaft  76 , being thereby rotatably placed in the developer storage portion  70 , so that the rotational axes of the first and second developer conveying members  74  and  75  coincide with that of the rotational axis of the rotational member  76 .  
         [0083]     The second developer conveying member  75  is flexible, and scoops up the developer D while rubbing the internal surface of the developer storage portion  70 , in the area below the horizontal plane coinciding with the rotational axis of the rotational shaft  76  and on the same side as the side where the development roller  22  as a developing means is placed, with respect to the vertical plane coinciding with the axial line of the rotational shaft  76 .  
         [0084]     The dimension of the second developer conveying member  75  in terms of the direction parallel to the rotational axis of the rotational shaft  76  is smaller than the dimension of the first developer conveying member  74  in terms of the direction parallel to the rotational axis thereof. Further, in terms of the direction parallel to their rotational axes, the second developer conveying member  75  is positioned so that as it is rotated, it moves through the area directly above the beam exit surface  61   a.    
         [0085]     The first developer conveying member  74  is provided with the multiple holes  74   a  through which the developer D is allowed to escape in the direction opposite to the rotational direction of the first developer conveying member  74 , and which are not located so that they correspond in position to the beam exit surface  61   a.    
         [0086]     The transparent beam entrance portion  61  is located on the opposite side of the vertical plane coinciding with the rotational axis of the rotational shaft  76 , from the development roller  22  as a developing means, and below the horizontal plane coinciding with the rotational axis of the rotational shaft  76 .  
         [0087]     The second developer conveying member  75  begins to scoop up the developer D before the first developer conveying member  74  begins to wipe the beam exit surface  61   a.  Further, the second developer conveying member  75  conveys the developer D it scooped up, to the beam exit surface  61   a  after the first developer conveying member  74  wipes the beam exit surface  61   a.    
         [0088]     The beam exit surface  61   a  is positioned inward of the developer storage portion  70 , relative to the internal surface of the developer storage portion  70 .  
         [0089]     Incidentally, in the above described embodiment, the first transparent portion of the developer storage portion  70  is the portion of the developer storage portion  70 , through which the beam L is guided into the developer storage portion  70 , and the second transparent portion of the developer storage portion  70  is the portion of the developer storage portion  70 , through which the beam L is guided out of the developer storage portion  70  after traveling through the developer storage portion  70 . However, the first transparent portion may be used as the portion through which the beam L is guided out of the developer storage portion  70 , and the second transparent portion may be used as the portion through which the beam L is guided into the developer storage portion  70 . Such an arrangement provides the same effects as those described above. Although the preceding embodiment was described with reference to a process cartridge, the present invention is also applicable to a developing apparatus itself. Also in this embodiment, the first and second developer conveying members were described as pieces of flexible sheet. However, they may be pieces of felt. Also in this embodiment, the image bearing member is described as an electrophotographic photosensitive member. However, the image bearing member may be an electrostatically recordable member on which a latent image can be borne. Further, the shape of the image bearing member does not need to be limited to the drum shape; the image bearing member may be in the form of a sheet, a belt, or the like.  
         [0090]     As described above, the present invention makes it possible to provide a combination of a developing apparatus, a process cartridge, and an image forming apparatus, which makes it possible to accurately detect the amount of the developer remainder.  
         [0091]     While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth, and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claims.  
         [0092]     This application claims priority from Japanese Patent Application No. 364728/2003 filed Oct. 24, 2003, which is hereby incorporated by reference.