Patent Publication Number: US-6704525-B2

Title: Developing device, process cartridge and electrophotographic image forming apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electrophotographic image forming apparatus which forms an electrostatic latent image on an electrophotographic photosensitive member by an electrophotographic method and visualize the electrostatic latent image by developer contained in a developing device, a developing device and a process cartridge. 
     Here, the electrophotographic image forming apparatus includes, for example, an electrophotographic copying machine, an electrophotographic printer (e.g., an LED printer, a laser beam printer), an electrophotographic facsimile machine and an electrophotographic word processor. 
     In addition, the process cartridge is a cartridge in which at least one of charging means, developing means and cleaning means and an electrophotographic photosensitive member are integrally incorporated and which is detachably mountable on an electrophotographic image forming apparatus main body, or a cartridge in which at least developing means and an electrophotographic photosensitive member are integrally incorporated and which is detachably mountable on an electrophotographic image forming apparatus main body. 
     2. Related Background Art 
     Conventionally, in an electrophotographic image forming apparatus using an electrophotographic image forming process, a process-cartridge method is widely employed with which an electrophotographic photosensitive member and processing means acting on the electrophotographic photosensitive member are integrally incorporated in a cartridge, which is made detachably mountable on an electrophotographic image forming apparatus main body. 
     In such a process cartridge method, operability can be remarkably improved because an apparatus can be maintained by a user in person rather than by a repairer. 
     In addition, in an electrophotographic image forming apparatus of such a process cartridge method, a user replaces the cartridge in person. Thus, some apparatuses are provided with toner amount detecting means in order to let a user notice that only a little developer (toner) remains. As the toner amount detecting means, there is a method of detecting a toner amount by detecting a change of capacitance between two electrodes disposed in a process cartridge. 
     As a configuration of such electrodes, a conductive member is disposed a predetermined distance apart from a developer bearing member (for detecting capacitance between the conductive member and a developing roller). 
     The present invention has been devised by further developing the above-mentioned conventional art. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a developing device and a process cartridge which prevent developer from leaking outside, an electrophotographic image forming apparatus using the developing device, and an electrophotographic image forming apparatus on which the process cartridge is detachably mountable. 
     It is another object of the present invention to provide a developing device and a process cartridge which can be easily assembled, an electrophotographic image forming apparatus using the developing device, and an electrophotographic image forming apparatus on which the process cartridge is detachably mountable. 
     It is yet another object of the present invention to provide a developing device and a process cartridge which is capable of securely making electrical connection with an apparatus main body, an electrophotographic image forming apparatus using the developing device, and an electrophotographic image forming apparatus on which the process cartridge is detachably mountable. 
     It is yet another object of the present invention to provide a developing device, a process cartridge and an electrophotographic image forming apparatus which can be easily assembled and are capable of certainly preventing the occurrence of developer leakage and securely making electrical connection with the inside and the outside of a developing container. 
     It is yet another object of the present invention to provide a developing device that comprises a developing container; an electrode to be mounted inside the developing container; a conductive member for securing electric conduction from the inside to the outside of the developing container, wherein the conductive member and the electrode are electrically connected by the conductive member being pressed into a fitting portion provided in the electrode; and an elastic seal member pressed into an interval between the conductive member and the developing container, a process cartridge having the developing device, an electrophotographic image forming apparatus using the developing device and an electrophotographic image forming apparatus on which the process cartridge is detachably mountable. 
    
    
     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 
     FIG. 1 is a schematic view showing a configuration of an embodiment of an electrophotographic image forming apparatus in accordance with the present invention; 
     FIG. 2 is a vertical sectional view of an embodiment of a process cartridge in accordance with the present invention; 
     FIG. 3 is a pictorial perspective view of the process cartridge in accordance with the present invention which is viewed upward from the bottom; 
     FIG. 4 is a pictorial perspective view showing an inserting portion of an apparatus main body in which a process cartridge is inserted; 
     FIG. 5 is a side view of the process cartridge of FIG. 2; 
     FIG. 6 is an exploded perspective view of an embodiment of a developing frame in accordance with the present invention; 
     FIG. 7 is an enlarged view of the developing frame of FIG. 6; 
     FIG. 8 is a partially enlarged view of a detection electrode in accordance with the present invention; 
     FIG. 9 is a vertical sectional view of another embodiment of a developing device in accordance with the present invention; 
     FIG. 10 is an exploded perspective view showing a developing frame in the developing device of FIG. 9; 
     FIG. 11 is an enlarged view showing a main part of the developing frame of FIG. 9; 
     FIG. 12 is an illustration showing an embodiment of a toner amount indication; 
     FIGS. 13A and 13B are illustrations showing other embodiments of a toner amount indication; and 
     FIG. 14 is an illustration showing another embodiment of a toner amount indication. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A developing device, a process cartridge and an electrophotographic image forming apparatus in accordance with the present invention will be hereinafter described in detail with reference to the accompanying drawings. 
     Embodiment 1 
     An embodiment of an electrophotographic image forming apparatus on which a process cartridge is detachably mountable, which is configured in accordance with the present invention, will be described first with reference to FIGS. 1 and 2. 
     An electrophotographic image forming apparatus A has a drum-shaped electrophotographic photosensitive member, that is, a photosensitive drum  7 . The photosensitive drum  7  is charged by a charging roller  8  being charging means and, then, an electrostatic latent image corresponding to image information is formed on the photosensitive drum  7  by irradiation with laser beams corresponding to the image information from optical means  1  as electrostatic latent image forming means having a laser diode, a polygon mirror, a lens and a reflecting mirror. This electrostatic latent image is developed by developing means  10  to be a visible image, that is, a toner image. 
     The developing means  10  forms a developer container  11  in which a developing frame  13  holding a developing roller  12  being a developer bearing member and a toner containing portion  14  containing toner being developer are connected. Further, the developer used in this embodiment is magnetic developer. 
     The developing frame  13  has a developing chamber  13   a , and toner in the toner containing portion  14  adjacent to the developing chamber  13   a  is fed to the developing roller  12  of the developing chamber  13   a  by the rotation of a toner feeding member  15 . The developing frame  13  is provided with a toner agitating member  16  in the vicinity of the developing roller  12 , which circulates the toner in the developing chamber  13   a . In addition, the developing roller  12  incorporates a stationary magnet  17  being magnetic field generating means, and the toner is conveyed by rotating the developing roller  12 . Then, triboelectrification charge is induced by a developing blade  18  to layer the toner in a predetermined thickness and the toner layer is conveyed to a developing region of the photosensitive drum  7 . The toner fed to this developing region is transferred to an electrostatic latent image on the photosensitive drum  7  to form a toner image. The developing roller  12  is connected to a developing bias circuit (not shown), and, developing bias voltage, which is alternating voltage with direct voltage superimposed, is usually impressed on the developing roller  12 . 
     On the other hand, a recording medium  2  set in a feed cassette  3   a  is conveyed to a transferring position by a pickup roller  3   b , a conveying roller pairs  3   c  and  3   d , and a registration roller pair  3   e  in synchronism with forming the toner image. A transferring roller  4  as transferring means is disposed in the transferring position, which transfers the toner image on the photosensitive drum  7  to the recording medium  2  by impressing voltage. 
     The recording medium  2  having received the transfer of the toner image is conveyed to fixing means  5  by a conveying guide  3   f . The fixing means  5  is provided with a driving roller  5   c  and a fixing roller  5   b  incorporating a heater  5   a , and fixes the transferred toner image on the recording medium  2  by impressing heat and pressure on the passing recording medium  2 . 
     The recording medium  2  is conveyed by a discharge roller pairs  3   g  and  3   h , and is discharged to a discharge tray  6  through a surface reverse path  3   j . The discharge tray  6  is provided on an upper surface of the electrophotographic image forming apparatus A. Further, the recording medium  2  can also be discharged without passing through the surface reverse path  3   j  by activating a swingable flapper  3   k . In this embodiment, conveying means is composed of the pickup roller  3   b , the conveying roller pairs  3   c  and  3   d , the registration roller pair  3   e , the conveying guide  3   f , and the discharging roller pairs  3   g  and  3   h.    
     The photosensitive drum  7  after the toner image is transferred to the recording medium  2  by the transferring roller  4  is supplied to the next image forming process after removing residual toner on the photosensitive drum  7  by cleaning means  9 . The cleaning means  9  scrapes off and collects the residual toner on the photosensitive drum  7  to a waste toner reservoir  9   b  by an elastic cleaning blade  9   a  that is in contact with the photosensitive drum  7 . 
     On the other hand, in this embodiment, the developing container  11  is formed by integrally welding the developing frame  13  holding developing means, such as the developing roller  12 , and the developing blade  18  to the toner containing portion  14 , which contains toner and has the toner feeding member  15 , and a cleaning unit  19  to which the photosensitive drum  7 , the cleaning means  9 , such as the cleaning blade  9   a,  and the charging roller  8  are attached is integrally connected to the developing container  11 , thereby forming a process cartridge B as a cartridge as shown in FIG.  2 . 
     This process cartridge B is detachably mounted on cartridge inserting means provided in the image forming apparatus main body by a user. According to this embodiment, the cartridge mounting means is composed of guiding means  19 R ( 19 L), shown in FIG. 3, formed on both sides of the process cartridge B and a guide portion  40 R ( 40 L) (see FIG. 4) formed in the image forming apparatus main body A to which this guiding means  19 R ( 19 L) can be mounted. 
     Referring to FIG. 2 again, the process cartridge B of this embodiment is provided with a first and a second detection electrodes  20  and  21  as the toner amount detecting means that is capable of detecting a residual amount of toner according to the consumption of the toner in the developing container  11 . The first and the second detection electrodes  20  and  21  are arranged in a position where they contact the toner in the developing container  11  and where a contacting area with the toner fluctuates as the toner decreases. According to this embodiment, the first and the second detection electrodes  20  and  21  are arranged opposing the developing roller  12  along its longitudinal direction, and are configured to induce a capacitance between both the electrodes  20  and  21  by impressing voltage on either the first detection electrode  20  or the second detection electrode  21  and detect a toner amount by measuring the output voltage at this point in the electrophotographic image forming apparatus main body A. 
     When the process cartridge B is mounted in the image forming apparatus main body, the first and the second detection electrodes  20  and  21  are required to be electrically connected to the electrophotographic image forming apparatus main body A. Therefore, a first and a second electric contacts  22  and  23  for securing electric conduction with the image forming apparatus main body A are exposed on the side of the process cartridge B as shown in FIG.  5 . 
     A method for connecting from the first detection electrode  20  to the first electric contact  22  will now be described with reference to FIGS. 6 to  8 . 
     The detection electrode  20  is positioned by a positioning pin  13   c  provided on an attaching surface  13   b  of the developing frame  13 , and is stuck to the attaching surface  13   b  by, for example, a pressure sensitive adhesive double coated tape. An arm portion  20   a  extends from one end of the detection electrode  20  in its longitudinal direction, and an incised clinch  20   b  is formed as a fitting portion at the end of the arm portion  20   a . When the detection electrode  20  is attached to the developing frame  13 , the incised clinch  20   b  is inserted in a groove  13   d  formed in the developing frame  13 . 
     On the other hand, a hole  13   e  that penetrates from the inside to the outside of the frame is drilled beside the groove  13   d  of the developing frame  13 , which matches a hole  20   c  of the incised clinch  20   b . In addition, the hole  13   e  of the developing frame  13  is shaped such that an elastic sealing member  24  of the type described in Japanese Patent Application Laid-Open No. 8-314359 is fit, in which the elastic sealing member  24  is press-fit from the outside of the developing frame  13 . Thereafter, an electrode  25  penetrates the elastic sealing member  24  to be inserted in the developing frame  13 , and is press-fit in the incised clinch  20   b  of the detection electrode  20  attached inside the developing frame  13  to be electrically connected. 
     As shown in FIG. 8, the incised clinch  20   b  is provided with a pair of pawls  20   d  opposing in the vertical direction in FIG.  8 . Since the interval between the points of the pawls  20   d  is made smaller than the external diameter of the electrode before the electrode  25  is combined with the detection electrode  20 , when the electrode  25  is press-fit, the points of the pawls  20   d  are embedded in the electrode  25 , and thus electric conduction can be secured. In addition, since a rib  13   h  is provided in the developing frame  13  in order to support the incised clinch  20   b  when the electrode  25  is combined with the detection electrode  20 , the electrode  25  can be easily combined with the detection electrode  20  simply by forcing it in. 
     The interval between the points of the pawls  20   d  may be appropriately determined according to a material or a thickness of an electrode to be used, a diameter of an electrode, or the like. In this embodiment, an SUS material with a thickness of 0.3 mm is used as the detection electrode  20 , and an SUS rod with an external diameter of 2 mm is used as the electrode  25 . In addition, the interval between the points of the pawls  20   d  is set at 1.6 to 1.8 mm. 
     As shown in FIG. 6, a holder  26  for rotatably retaining the developing roller  12  via a bearing is attached to the side of the developing frame  13 , to which the above-mentioned electric contact  22  is attached. A contact portion  22   a  is provided in the electric contact  22  and, when the holder  26  is attached to the developing frame  13 , the electric contact  22  and the detection electrode  20  are electrically connected by the contact portion  22   a  contacting the electrode  25 . 
     A configuration of combining the developing frame  13  and the toner containing portion  14  will now be described. 
     Protrusions  13   f  and  13   g  that fit in grooves (not shown) for connection provided in the toner containing portion  14  are provided on the surface of the developing frame  13  contacting the toner containing portion  14 . Triangle ribs formed for ultrasonic welding are provided on the top surfaces of the protrusions  13   f  and  13   g . In addition, frame seals  27  and  28  are stuck to both the ends of the developing frame  13  for preventing toner from leaking through a gap between the developing frame  13  and the toner containing portion  14 . A sponge-like material is used as the frame seals  27  and  28 . 
     The developing frame  13  after various parts are incorporated and the toner containing portion  14  are pressed in the state in which the grooves of the toner containing portion  14  and the protrusions  13   f  and  13   g  of the developing frame  13  are fit, and ultrasonic vibration is applied to the part between the groove and the protrusion  13   f  and  13   g . Then, the above-mentioned triangle ribs are melted by frictional heat and welded to the bottom of the groove, and the developing frame  13  and the toner containing portion  14  are integrally connected. 
     As described above, in this embodiment, electric conduction can be secured by connecting the detection electrode  20  and the electric contact  22  using the electrode  25 . In addition, since an electrode or the like is not disposed under the frame seal  27 , a preferable sealing characteristic free from toner leakage from the frame seal portion can be attained. In addition, the gap between the electrode  25  and the developing frame  13  is securely sealed by the elastic sealing member  24 . 
     Thus, according to this embodiment. a developing device, a process cartridge and an electrophotographic image forming apparatus that can be easily assembled, prevent the occurrence of toner leakage, and securely connect the inside and the outside of a developing container electrically are provided. 
     Embodiment 2 
     A second embodiment of the present invention will now be described. 
     As shown in FIG. 9, a developing device C of this embodiment is integrally formed as a cartridge by a developing container  31  that is connected with a developing frame  29 , which retains developing means such as a developing roller  12  and a developing blade  18 , by welding a toner containing portion  30  to the developing frame  29 . That is, the developing device C of this embodiment can be considered as a unit version of a developing device forming portion of the process cartridge B described in the first embodiment, and an integrally formed version of the process cartridge B excluding the cleaning unit. 
     The developing device C of this embodiment is provided with a third detection electrode  34  in addition to a first and a second detection electrodes  32  and  33  as toner amount detecting means that are capable of detecting a residual amount of toner in accordance with the consumption of the toner in the developing container  31 . Since the first and the second detection electrodes  32  and  33  have the same configuration as the first embodiment, their description is omitted. 
     The third detection electrode  34  is arranged at the bottom of the developing frame  29 , and forms a capacitor between the second detection electrode  33  and the third detection electrode  34 . That is, two capacitors are formed in the developing container  31 ; one capacitor is between the first detection electrode  32  and the third detection electrode  33  and the other is between the second detection electrode  33  and the third detection electrode  34 . A toner amount is detected by measuring a composited capacitance of these capacitors. Further, the third detection electrode  34  is in the same electric potential as the first detection electrode  32 . 
     Since the overall capacitance can be increased and sensitivity to the change in a toner amount in the developing container  31  can be improved with such a configuration, more accurate detection of a toner amount can be performed. 
     A configuration for attaching the developing frame  29  and the first and the third detection electrodes  32  and  34  of the developing device C in this embodiment will now be described with reference to FIGS. 10 and 11. 
     The first detection electrode  32  has the same configuration as that in the first embodiment, and the method of attaching the electrode to the developing frame  29  and the method of wiring the electrode to the outside of the frame are also the same as those in the first embodiment. 
     Arm portions  34   a  and  34   b  extending upward in FIG. 10 are formed at the both ends of the third detection electrode  34  in the longitudinal direction. The third detection electrode  34  is fixed by mounting it on an attaching portion  29   a  of the developing frame  29  and screwing the arm portions  34   a  and  34   b  onto the developing frame  29 . An incised clinch  34   c  of the same shape as an incised clinch  32   a  of the first detection electrode  32  is formed at the upper end of the arm portion  34   a  in FIG. 11, and, when a third detection electrode  34  is attached to the developing frame  29 , the incised clinch  34   c  of the third detection electrode  34  and the incised clinch  32   a  of the first detection electrode stand side by side or overlap each other. 
     An electrode  25  is inserted in the developing frame  29  assembled in this way and is press-fit in the incised clinches  32   a  and  34   c  of the first detection electrode  32  and the third detection electrode  34 , thus, the first and the third detection electrodes  32  and  34  are securely connected electrically and the wiring from the inside to the outside of the developing container  31  is made. In addition, an elastic sealing member  24  is press-fit into the gap between the electrode  25  and the developing frame  29  as in the first embodiment to prevent toner from leaking. 
     A method of connecting the developing frame  29  and the toner containing portion  30  and a method of sealing toner at the end of the frame by the frame sealing thereafter are the same as those in the first embodiment. 
     With such a configuration, reliability of the electric connection can be improved as in the first embodiment and the effect of toner leakage prevention can be attained. Moreover, connection of the two electrodes and wiring to the outside of the developing container can be realized by easy assembling. 
     According to the toner amount detecting means of each of the above-mentioned embodiments, a residual toner amount can be successively detected with high accuracy. 
     Detection information from the toner amount detecting means is indicated by the toner amount indicating means. Concerning the toner amount indicating means, for example, the detection information is indicated or displayed on a screen  45  of a terminal such as a personal computer  44  of a user as shown in FIG. 12, or as shown in FIGS. 13A and 13B. In FIGS. 13A and 13B, a user is informed of a toner amount as indicated by which part of a gauge  72  a pointer  71  that moves in response to the toner amount points at. 
     In addition, as shown in FIG. 14, an indicating portion such as the one made of LED may be provided directly in the electrophotographic image forming apparatus main body A to turn on and off LED  73  in response to a toner amount. 
     Further, in the above-mentioned embodiment, if it is assumed that an amount of developer contained in a container is initially 100%, a residual amount of the developer can be successively detected over the entire range of approximately 30% to 0%. However, the present invention is not limited to this, but may be configured to successively detect the residual amount of the developer over the range of 50% to 0% or 40% to 0%. Here, the indication that the residual amount of developer is 0% does not mean that the developer has been completely consumed. For example, the indication that the residual amount of developer is 0% also refers to the state in which, even if the developer remains in the container, the residual amount of the developer has decreased to a level at which a predetermined image quality (development quality) cannot be obtained. 
     As is evident from the above descriptions, according to the present invention, a developing device, a process cartridge and an electrophotographic image forming apparatus that can be easily assembled, prevent the occurrence of toner leakage, and securely connect the inside and the outside of a developing container electrically are provided. 
     While the invention has been described with reference to the structure 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 purpose of the improvements or the scope of the following claims.