Electrophotographic image forming apparatus, process cartridge, developing device, developer supply container and measuring part therefor

Abstract: An electrophotographic image forming apparatus for forming an image on a recording material includes a first electrostatic capacity generating portion disposed at such a position that first electrostatic capacity generating portion is contacted to the developer accommodated in said developer accommodating portion when a predetermined amount of the developer is accommodated in said developer accommodating portion, said first electrostatic capacity generating portion generating an electrostatic capacity corresponding to an amount the developer when said first electrostatic capacity generating portion is supplied with a voltage, and a second electrostatic capacity generating portion disposed at such a position that second electrostatic capacity generating portion is not contacted to the developer accommodated in said developer accommodating portion, said second electrostatic capacity generating portion generating a reference electrostatic capacity when said second electrostatic capacity generating portion is supplied with a voltage; developer amount detecting means for detecting an amount of the developer accommodated in said developer accommodating portion on the basis of the electrostatic capacity generated by said first electrostatic capacity generating portion and the reference electrostatic capacity generated by said second electrostatic capacity generating portion; electrostatic latent image forming means for forming an electrostatic latent image on said electrophotographic photosensitive member.

Description: FIELD OF THE INVENTION AND RELATED ART: The present invention relates to an electrophotographic image forming apparatus, a process cartridge therefor, a developing device therefor, a developer supply container therefor and a measuring part. Here, the electrophotographic image forming apparatus includes an electrophotographic copying machine, an electrophotographic printer, for example, a, LED printer or laser beam printer, an electrophotographic printer type facsimile, an electrophotographic printer type word or the like. The process cartridge is a cartridge containing as a unit an electrophotographic photosensitive member and at least one process means which is a charging means, a developing means or cleaning means, or a cartridge containing as an unit an electrophotographic photosensitive member and at least developing means as process means, said process cartridge being detachably mountable to a main assembly of an electrophotographic image forming apparatus. Heretofore, a process cartridge including is used in an image forming apparatus using an electrophotographic image forming process, widely used is a process cartridge which contains as a unit an electrophotographic photosensitive member and process means actable on the electrophotographic photosensitive member, which cartridge is detachably mountable to the main assembly of the electrophotographic image forming apparatus. Such process cartridge is advantageous in that maintenance operation can be carried out in effect by the users. Therefore, the process cartridge type is widely used in electrophotographic image forming apparatus. With such an electrophotographic image forming apparatus of a process cartridge type, the user is supposed to exchange the process cartridge, and therefore, it is desirable that there is provided means by which the user is notified of the consumption of the developer. Heretofore, it is known that two electrode rods are provided in the developer container of the developing means, and the change of the electrostatic capacity between the electrode rods is detected to provide the amount of the developer. Japanese Laid-open Patent Application No. HEI- 5-100571 discloses a developer detection electrode member comprising two parallel electrodes disposed on the same surface with a predetermined gap, in place of the two electrode rods, wherein the developer detection electrode member is placed on the lower surface of the developer container. It detects the developer remainder by detecting the change of the electrostatic capacity between the parallel electrodes disposed on a surface. US-A-4,133,453 describes a capacitive developer amount detection system having detecting electrodes contacting the developer and compensating electrodes not in contact with the developer material. JP-A-05188782 describes a capacitive toner level sensor arrangement with a compensating capacitor positioned outside the toner container and compensating for ambient conditions. EP-A-0757303 describes an arrangement for electrical contacts to a toner detecting capacitor of a process cartridge. US-A-4,296,630 discloses a capacitive liquid level sensing probe having a compensating capacitor positioned in a liquid exit duct of a liquid container vessel. The probe itself comprises a flexible substrate on which measurement and reference capacitors are arranged. SUMMARY OF THE INVENTION: Accordingly, it is a principal object of the present invention to provide an electrophotographic image forming apparatus, a process cartridge, a developing device, a developer supply container and a measuring part which is capable of detecting the remaining amount of the developer substantially real-time. It is another object of the present invention to provide an electrophotographic image forming apparatus, a process cartridge, a developing device and a developer supply container which is capable of detecting a remaining amount of the developer in the developer accommodating portion substantially real-time in accordance with the consumption of the developer. It is a further object of the present invention to provide an electrophotographic image forming apparatus, a process cartridge, a developing device, a developer supply container which is capable of detecting a remaining amount of the developer using a change in the electrostatic capacity between electrodes, wherein measurement errors attributable to changes of the ambient conditions, thus minimizing the detection error. It is a further object of the present invention to provide a measuring part for detecting an amount of the developer substantially real-time in accordance with the consumption of the developer in the developer accommodating portion. It is a further object of the present invention to provide a measuring part capable of detecting a developer remainder using a change of the electrostatic capacity between electrodes, wherein the measurement error attributable to the changes of the ambient conditions to accomplish detection of the amount of the developer with small detection error. According to the present invention, there is provided an electrophotographic image forming apparatus, a process cartridge, and a developing device as defined in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS: Figure 1 shows a general arrangement of an electrophotographic image forming apparatus according to an embodiment of the present invention. Figure 2 is the perspective view of an outer appearance of an electrophotographic image forming apparatus according to an embodiment of the present invention. Figure 3 is a longitudinal sectional view of a process cartridge according to an embodiment of the present invention. Figure 4 is a perspective view of an outer appearance of a process cartridge according to an embodiment of the present invention, as seen from the bottom. Figure 5 is the perspective view of an outer appearance illustrating a mounting portion of a main assembly of an apparatus for mounting a process cartridge. Figure 6 is a perspective view of a developer container provided with a detecting device for detecting an amount of a developer. Figure 7 is a perspective view of a developer container provided with a detecting device for amount of the developer. Figure 8 is a perspective view of a developer container provided with a detecting device for an amount of the developer. Figure 9 is a perspective view of a developer container provided with a detecting device for an amount of the developer according to an embodiment of the present invention. Figure 10 is a front view of a measuring electrode member and a reference electrode member according to an embodiment of the present invention. Figure 11 is a front view of a measuring electrode member and a reference electrode member according to another embodiment of the present invention. Figure 12 is an illustration of accommodation of a developer in a developer container. Figure 13 is a perspective view of a developing means provided with a detecting device for an amount of a developer. Figure 14 is an illustration of accommodation of a developer in the developer container. Figure 15 is a graph explaining a detection principle for the amount of the developer according to an embodiment of the present invention. Figure 16 is a graph explaining a detection principle for an amount of the developer according to an embodiment of the present invention. Figure 17 shows a detecting circuit for an amount of the developer for detecting device for the amount of the developer according to an embodiment of the present invention. Figure 18 shows alternative arrangements of a measuring electrode member and a reference electrode member. Figure 19 shows a schematic arrangement of a measuring electrode member and a reference electrode member according to one embodiment of the present invention. Figure 20 is an illustration of display of an amount of the developer. Figure 21 shows another example of display of an amount of the developer. Figure 22 shows a further example of display of an amount of the developer. Figure 23 is a schematic illustration of an electrophotographic image forming apparatus according to another embodiment of the present invention. Figure 24 is a perspective view of a developing device provided with a detecting device for an amount of a developer. Figure 25 is a perspective view of a developing device provided with a detecting device for an amount of a developer. Figure 26 is a perspective view of a developing device provided with a detecting device for an amount of the developer. Figure 27 is a perspective view of a developing device provided with a detecting device for an amount of a developer. Figure 28 is an illustration of accommodation of the developer in developer accommodating portion. Figure 29 is a perspective view of a developing device provided with a detecting device for an amount of a developer. Figure 30 is an illustration of accommodation of the developer in a developer accommodating portion. Figure 31 is an illustration of arrangements of a measuring electrode member and a reference electrode member. Figure 32 is an schematic illustration of arrangements of a measuring electrode member and a reference electrode member. Figure 33 is a schematic illustration of an electrophotographic image forming apparatus. DESCRIPTION OF THE PREFERRED EMBODIMENTS: Referring to the accompanying drawings, the description will be made as to an electrophotographic image forming apparatus, a process cartridge, a developing device, a developer supply container and a measuring part. (Embodiment 1) Referring to Figure 1, the description will be made as to an electrophotographic image forming apparatus to which a process cartridge is a detachably mountable, according to one embodiment of the present invention. In this embodiment, the electrophotographic image forming apparatus is in the form of a laser beam printer A of an electrophotographic type in which images are formed on a recording material such as recording paper, an OHP sheet or textile through an electrophotographic image forming process. The laser beam printer A comprises an electrophotographic photosensitive member, that is, a photosensitive drum 7. The photosensitive drum 7 is electrically charged by a charging roller 8 (charging means), and is exposed to a laser beam modulated in accordance with image information coming from optical means 1 including a laser diode 1a, a polygonal mirror 1b, a lens 1c and a reflection mirror 1d, so that latent image is formed on the photosensitive drum in accordance with the image information. The latent image is developed by developing means 9 into a visualized image, that is, toner image. The developing means 9 includes a developer chamber 9A provided with a developing roller 9a (developer carrying member), wherein the developer in developer container 11A (developer accommodating portion) disposed adjacent to the developer chamber 9A is fed out to a developing roller 9a in the developer chamber 9A by rotation of a developer feeding member 9b. The developer chamber 9A is provided with a developer stirring member 9e adjacent to the developing roller 9a to circulate the developer in the developer chamber. The developing roller 9a contains therein a fixed magnet 9c so that developer is fed by rotation of the developing roller 9a, and the developer is electrically charged by triboelectric charge by the friction with a developing blade 9d, and is formed into a developer layer having a predetermined thickness, which layer is supplied to a developing zone of the photosensitive drum 7. The developer the supplied to the developing zone is transferred onto the latent image on the photosensitive drum 7 so that toner image is formed. The developing roller 9a is electrically connected with a developing bias circuit which is normally supplied with a developing bias voltage in the form of an AC voltage biased with a DC voltage. On the other hand, a recording material 2 in a sheet feeding cassette 3a is fed out and supplied to an image transfer position by a pick-up roller 3b, a pair of feeding rollers 3c, 3d, a pair of registration rollers, in timed relation with the formation of the toner image. In the transfer position, there is provided a transfer roller 4 (transferring means), which functions to transfer the toner image onto the recording material 2 from the photosensitive drum 7 by being supplied with a voltage. The recording material 2 now having the toner image transferred there onto is fed to fixing means 5 along a feeding guide 3f. The fixing means 5 includes driving roller 5c and a fixing roller 5b containing therein a heater 5a to apply pressure and heat to the recording material 2 passing therethrough to fix the toner image on the recording material 2. The recording material is then fed by pairs of discharging rollers 3g, 3h, 3i and is discharged to a discharging tray 6 along a reverse path 3j. The discharging tray 6 is disposed on the top surface of the main assembly 14 of the electrophotographic image forming apparatus in the form of a laser beam printer A. A deflectable flapper 3K is usable to discharge the recording material 2 by a pair of discharging rollers without using the reversing passage 3j. In this embodiment, the 3g, 3h, 3i, the pair of feeding rollers 3c, 3d, the pair of registration rollers, the feeding guide 3f, the pair of discharging rollers and the pair of discharging rollers 3m, constitute sheet feeding means. The photosensitive drum 7 after the transfer roller 4 transfers the toner image onto the recording material 2, is cleaned by cleaning means 10 so that developer remaining on the photosensitive drum 7 is removed so as to be prepared for the next image forming process operation. The cleaning means 10 scrapes the remaining developer off the photosensitive drum 7 by an elastic cleaning blade provided contacted to the photosensitive drum 7, and collect it to a residual developer container 10b. In this embodiment, a process cartridge B includes a developing unit comprising a developer frame 11 including the developer container developer 11A accommodating the developer and the developer feeding member 9b, and a developing device frame 12 supporting the developing means 9 such as the developing roller 9a and the developing blade 9d, and the process cartridge B further includes a cleaning frame 13 supporting the photosensitive drum 7, the cleaning means 10 such as the cleaning blade 10a and the charging roller 8. The process cartridge B is detachably mounted to the cartridge mounting means in the main assembly 14 of the electrophotographic image forming apparatus. In this embodiment, the cartridge mounting means comprises guide means 13R (13L) on the outer surface of the process cartridge B and guide portions 16R (16L) of the main assembly 14 of the apparatus for guiding the guide means 13R (13L), as shown in Figures 4 and 5. According to one example, the process cartridge B is provided with a developer amount detecting device for detecting substantially real-time the remaining amount of the developer when the developer in the developer container 11A is consumed. In the example shown in Figure 6, and included for illustrative purposes only the developer amount detecting device comprises a measuring electrode member 20A which is a first electrostatic capacity generating portion for detecting the amount of the developer, and a reference electrode member 20B which is a second electrostatic capacity generating portion for generating a reference signal on the basis of detection of the temperature and humidity of the ambiance. The measuring electrode member 20A is provided on an inside surface of the developer container 11A of the developing means 9 as shown in Figure 6, or on such a portion in the developer container 11A that it is contacted to the developer and that contact area thereof with the developer changes with reduction of the developer such as a bottom portion, as in the example shown in Figure 7 included for illustrative purposes only. As shown in Figure 6, the reference electrode member 20B may be provided at any position of the main assembly 14 of the apparatus if it is not contacted to the developer, but the reference electrode member 20B may be disposed in the developer container 11A at such position as is opposite from the measuring electrode member 20A and is separated by a partition wall 21 so as not to be in contact with the developer. As shown in Figure 9, the detecting device according to the invention has a measuring electrode member 20A and a reference electrode member 20B integrally manufactured so as to have a symmetric structure, and in this case, the reference electrode member 20B may be bent outwardly to the opposite side of the partition wall 21 (the side not contacted to the developer) at the same side as the measuring electrode member 20A. In the example shown in Figure 10, the measuring electrode member 20A comprises a pair of electroconductive portions (electrodes 23, 24) which are extended in parallel with each other with a predetermined gap on the substrate 22. Each of the electrodes 23, 24 may have a base portion and a plurality of branch portions extended from the base portion, and the branch portions may be in parallel with a predetermined gap between adjacent ones alternately, that is, in an interlaced fashion. In this embodiment, the electrodes 23, 24 have at least one pair of electrode portions 23a-23f, 24a-24f juxtaposed in parallel with a predetermined gap G, and the electrode portions 23a-23f, 24a-24f are connected to the connecting electrode portions 23g, 24g, respectively. Thus, the two electrodes 23 and 24 have a comb-like configuration with the branch portions interlaced with each other. However, the electrode pattern of the measuring electrode member 20 is not limited to those examples, and in a further example shown in Figure 11, the electrodes 23, 24 may be extended in the volute pattern with constant gap. The measuring electrode member 20A detects the remaining amount of the developer (the developer remainder) in the developer container 11A by detecting the electrostatic capacity between the parallel electrodes 23, 24. Since the developer has a dielectric constant which is larger than that of the air, the contact of the developer on the surface of the measuring electrode member 20A increases the electrostatic capacity between the electrodes 23, 24. The measuring electrode member 20A can detect the developer in the developer container 11A on the basis of the area of the developer contacted to the surface of the measuring electrode member 20A, using a predetermined calibration curve, irrespective of the cross-sectional configuration of the developer container 11A or the configuration of the measuring electrode member 20A. The electrode patterns 23, 24 of the measuring electrode member 20A can be provided by, by way or a comparative example forming electroconductive metal patterns 23, 24of copper or the like through etching or printing on a hard print board 22 such as paper phenol, glass epoxy resin or the like having a thickness of 0.4-1.6mm or , as in an embodiment of the present invention, on a flexible printed board 22 of polyester, polyimide or the like resin material having a thickness of 0.1 mm. That is, they can be manufactured through the same in manufacturing method as with ordinary printed boards and wiring patterns. Therefore, the complicated electrode pattern as shown in Figures 10 and 11 can be easily manufactured at the same cost as with simple patterns. When a complicated pattern shown in Figure 10 or 11 is used, the length along which the electrodes 23, 24are opposed to each other can be increased, and in addition, by using a pattern forming method such as etching, the gap between the electrodes 23, 24 can be reduced to several tens µm approx., so that large electrostatic capacity can be provided. The detection can be enhanced by increasing the amount of change of the electrostatic capacity. More particularly, the electrodes 23, 24have a width of 0.1-0.5mm, and a thickness of 17.5-70µm with the gap G therebetween of 0.1-0.5mm. The surface on which the metal pattern is formed can be laminated with thin resin film having a thickness of 12.5-125µm for example. As described in the foregoing, according to the detecting device for the amount of the developer according to the present invention, the measuring electrode member 20A is disposed on the inner surface of the developer container 11A or on such an inner bottom surface that contact area with a developer reduces with consumption of the developer, and the total amount of the developer in the developer container can be detected by the change of the electrostatic capacity of the measuring electrode member 20A, which change is indicative of the change of the contact area with the developer. Since the dielectric constant of the developer is larger than that of the air, the electrostatic capacity is larger at the portion where the developer is contacted to the measuring electrode member 20A (where the developer exists) than at the portion where no developer is contacted thereto (where the developer does not exist). Therefore, the amount of the developer in the developer container 11A can be detected by detecting the change of the electrostatic capacity. As shown in Figure 6, by disposing the measuring electrode member 20A on one inner side of the developer container 11A, the percentage of the area contacted to the developer to the cross-sectional area of the developer container in the YZ flat surface in Figure 12, can be deduced or estimated from the detected electrostatic capacity. As shown in Figure 14, the developer may exist unevenly along the longitudinal direction due to the event that process cartridge is demounted and mounted for jam clearance, for example, due to inclination of the process cartridge or due to uneven printing pattern, as shown in Figure 14. By providing the measuring electrode member 20A at each inner longitudinal end of the developer container, the uneven distribution of the developer can be detected on the basis of the outputs of the two electrode members 20A, 20A, so that correct detection of the developer remainder is accomplished. As shown in Figure 7, when the measuring electrode member 20A is disposed on the inner bottom surface of the developer container 11A, the percentage of the contact area occupying the bottom area can be estimated so that influence of the uneven distribution of the developer in the longitudinal direction is minimized. Since the bottom area is larger than the end area in the developer container 11A, the area of the developer amount detecting member 20A can be made larger than when the developer amount detecting member 20A is disposed at the end of the developer container 11A, so that amount of the change of the electrostatic capacity can be made larger, that is, the output of the detector can be made larger, and therefore, the measurement error can be minimized. When the electrode members are provided on the inner bottom surface and the inner end surface or surfaces of the developer container 11A, the amount of the developer in the developer container 11A can be estimated in three dimensions, so that amount of the developer can be more correctly detected. The detecting device for the remaining amount of the developer comprises a reference electrode member 20B which functions as a second electrostatic capacity generating portion as shown in Figure 9. The reference electrode member 20B has the similar structure as the measurement electrode member 20A, and as shown in Figure 10, it comprises a pair of electroconductive portions, namely, electrodes 23(23a-23f), 24 (24a-24f) which are disposed in parallel with a predetermined gap on a substrate 22. The branch portions of the electrodes 23and 24 are interlaced, or the volute patterns shown in Figure 11 are also usable. The reference electrode member 20B can be manufactured through the same manufacturing process as with the printed boards and the wiring patterns. According to this embodiment, the electrostatic capacity of the reference electrode member 20B changes in accordance with the ambient condition such as the temperature and the humidity as described hereinbefore, so that it functions as a calibration member (reference electrode or member) for the measuring electrode member 20A. Thus, according to the detecting device for the amount of the developer of this embodiment, the output of the measuring electrode member 20A is compared with the output of the reference electrode member 20B which is indicative of the change of the ambient conditions. For example, the electrostatic capacity of the reference electrode member 20B in a predetermined state is set to be the same as the electrostatic capacity of the measuring electrode member 20A when no developer exists, and then, the difference of the outputs of the reference electrode member 20B and the measuring electrode member 20A is indicative of the change of the electrostatic capacity caused by the presence of the developer, so that accuracy of the detection of the remaining amount of the developer can be enhanced. The description will be made in more detail as to the detection principle of the amount of the developer. The measuring electrode member 20A detects the electrostatic capacity of the contact portion of the surface of the pattern to estimate the amount of the developer in the developer container 11A, and therefore, the output is influenced by the change of the ambiance (humidity, temperature or the like). For example, when the humidity is high, which means that content of the moisture in the air is high, with the result that dielectric constant of the atmospheric air contacted to the detecting member 20A is high. Therefore, even when the amount of the developer is the same, the output of the measuring electrode member 20A changes if the ambient condition changes. Additionally, if the material of the substrate 22 constituting the pattern absorbs moisture, the dielectric constant changes with the result, in effect, of the ambient conditions change. By the use of the reference electrode member 20B, as the calibration element, which exhibits the same change as the measuring electrode member 20A in accordance with the ambient condition change, that is by the use of the reference electrode member 20B having the same structure as the measuring electrode member 20A but not contacted to the developer, the reference electrode member 20B being placed under the same condition as the measuring electrode member 20A, the developer remainder can be detected without the influence of the ambient condition variation when the difference of the outputs of the measuring electrode member 20A and the reference electrode member 20B used for the detection. As shown in the bar graph of Figure 15, at the leftmost part, the electrostatic capacity determined by the measuring electrode member 20A for detecting the amount of the developer, indicative of the variation of the developer contacted to the surface of the detecting member plus the variation of the ambient condition. If the same situation is placed to under the high temperature and high humidity ambience, the electrostatic capacity increases despite the fact that amount of the developer is the same, since the electrostatic capacity increases corresponding to the ambient condition change, as indicated at the leftmost part in Figure 16. As shown in the middle parts of Figures 15 and 16, the reference electrode member (calibration electrode) 20B exhibiting the same response to the ambient condition variation as the measuring electrode member (detecting member) 20A, is used, and the difference therebetween (right side of the graph) is taken, by which the electrostatic capacity indicative of the amount of the developer only, can be provided. Referring to Figure 17, the detecting device for the amount of the developer embodying the above described principle will be described. Figure 17 shows an example of a circuit for developer detection, more particularly, the connection between the measuring electrode member 20A and the reference electrode member 20B in the image forming apparatus. The measuring electrode member 20A, as the detecting member having an electrostatic capacity Ca which changes in accordance with the amount of the developer, and the reference electrode member 20B, as a calibration the electrode having the electrostatic capacity Cb which changes in accordance with the ambient condition, are connected as indicated; more particularly, one of the electrodes 23is connected to the developing bias circuit 101 (developing bias applying means), and the other is connected to the control circuit 102 of developer amount detecting circuit 100. The reference electrode member 20B uses an AC (alternating) current I 1 supplied through a developing bias circuit 101, and a reference voltage V1 for detecting the developer remainder is set. The control circuit 102, as shown in Figure 17, adds, to the voltage V3 set by the resistances R3, R4, the voltage drop V2 determined by the resistance R2 and the AC current I 1 ' which is the current branched by a volume VR1 from the AC current I 1 supplied to the reference electrode member 20B, that is, an impedance element. The AC (alternating) current I 2 applied to the measuring electrode member 20A is inputted to the amplifier, and is outputted as the detected value V4 (V1-I 2 xR5) indicative of the developer remainder. The voltage output is the detected value indicative of the developer remainder. As described in the foregoing, according to the developer amount detecting device of this embodiment, the use is made with the reference electrode member 20B (calibration element) exhibiting the same capacity change in accordance with the ambient condition change as the measuring electrode member 20A, so that detection error due to the variation of the ambient condition can be canceled or compensated so that high accuracy of the detection for the developer remainder can be accomplished. In examples of a detecting device included for illustrative purposes only, the reference electrode member 20B as the calibration member may have another structure and can be disposed at another place. For example, as shown in Figures 6 and 18, the reference electrode member 20B having the same structure as the measuring electrode member 20A may be placed in the main assembly of the image forming apparatus. With this structure, the electrostatic capacity of the reference electrode member 20B changes in the same manner as the measuring electrode member 20A in accordance with the change of the ambiance, so that output of the changes attributable to the ambience variation can be canceled from the output of the measuring electrode member 20A. As shown in Figure 9, the measuring electrode member 20A and the reference electrode member 20B having the same structure as the measuring electrode member can be placed in the developer container 11A of the developing means 4. In this case, since measuring electrode member 20A and the reference electrode member 20B for calibration are provided in the developer container, the variation due to the ambience change can be canceled, and since the measurement electrode member (detecting member) 20A and the reference electrode member (calibration member) 20B are placed in the same ambient conditions, the detection accuracy can be enhanced. In the description of the foregoing embodiment, the electrode patterns 23, 24of the reference electrode member 20B have substantially the same electrostatic capacities, and substantially the same pattern widths, lengths, clearances and opposing areas. In such a case, the pattern design is easy, and the variations resulting from the differences in the electrostatic capacity among the products and the differences in the ambient conditions, can be minimized. In addition, it is possible that area of the electrode patterns 23, 24of the reference electrode member 20B for calibration is different from the area of the electrode patterns 23, 24of the measuring electrode member 20A. In this case, the output of the reference electrode member 20B is multiplied by a predetermined coefficient, and the multiplied output is compared with the output of the measuring electrode member 20A. Using such a structure, the size of the reference electrode member 20B can be reduced so that space occupied by the detecting member can be reduced. The members 20A and 20B may be placed on the same wall of the developer container 11A at the same side, and the reference electrode member 20B is prohibited from contacting to the developer, and in this case, it is possible to increase the percentage of the pattern area of the detecting member 20A in the limited the area, therefore, the amount of the change of the electrostatic capacity and the detection accuracy can be enhanced. In the foregoing, the same configurations or same dimensions do not mean exactly identical configuration or dimensions, and do not exclude those having a difference due to manufacturing errors or the like as long as the intended detection can be made with practical accuracy. As described in the foregoing, according to this embodiment, the developer container 11A is provided with the measuring electrode member 20A and the reference electrode member 20B for substantially real-time detection of the developer remainder, further preferably, the developer chamber 9A of the developing means 9 is provided with an antenna rod, that is, an electrode rod 9h Figure 3 is extended by a predetermined length in the longitudinal direction of the developing roller 9a with a predetermined clearance from the developing roller 9a. With this structure, the emptiness of the developer in the developer container can be detected by detecting the change of the electrostatic capacity between the developing roller 9a and the electrode rod 9h. According to the image forming apparatus of this embodiment, the amount of the developer in the developer container 11A can be detected substantially real-time, and on the basis of the detection, the consumption amount of the developer may be displayed so as to promote the user to prepare the replenishing cartridge and further to supply the developer upon the display of the emptiness. The description will be made as to the manner of display of the amount of the developer. The detected information provided by the developer amount detecting device is displayed on the screen of the terminal equipment such as a personal computer of the user in the manner, shown in Figures 20and 21. In Figures 20and 21, an indicator 41 moves in accordance with the amount of the developer so that user is aware of the amount of the developer. Figure 22 shows an alternative, wherein the main assembly of the electrophotographic image forming apparatus is provided with a display portion of, LED (43) or the like, which is lit on or off, in accordance with the amount of the developer. (Example 2) Figure 23 is a schematic view of another exemplary electrophotographic image forming apparatus. The general arrangement of the electrophotographic image forming apparatus will first be described. The electrophotographic image forming apparatus comprises an electrophotographic photosensitive drum 51 as an image bearing member, which rotates in the direction indicated by the arrow. The photosensitive drum 51 is uniformly charged by a charging device 52, and then, is subjected to image exposure of an original O through a projection optical system 53, so that electrostatic latent image is formed on the photosensitive drum 51. The electrostatic latent image on the photosensitive drum 51 is developed by a developing device 50 into a visualized image (toner image). The developing device 50 includes a developing zone 56 having a developing sleeve 55 (developer carrying member) and a developer accommodating portion 57 (developer accommodating container) for accommodating the developer. The developer in the developer accommodating portion 57 is supplied to a developing zone 56 and is carried on the developing sleeve 55 to a developing zone where the developing sleeve 55 is opposed to the photosensitive drum 51, so that electrostatic latent image on the photosensitive drum 51 is developed. The developing sleeve 55 is electrically connected to the developing bias circuit and is supplied with a developing bias voltage which is in the form of an AC voltage biased with DC voltage. The visualized image on the photosensitive drum 51, that is, the toner image is transferred by a transfer charging device 60 onto a transfer sheet P (recording material) fed from a transfer sheet accommodating portion 64 by feeding means 63. The toner image transferred onto the transfer sheet P is fixed on the transfer sheet P by a fixing device 61, and then the transfer sheet P is discharged to the outside of the apparatus. On their hand, the developer or remaining on the photosensitive drum 51 is removed by a cleaning device 62 so that photosensitive drum 51 is prepared for the next image forming operation. According to this example, the electrophotographic image forming apparatus is provided with a developer amount detecting device for detecting substantially real-time the remaining amount in response to the consumption of the developer in the developer accommodating portion 57 (developer accommodating container) of the developing device 50. The developer amount detecting device has the same structure and that described with Embodiment 1. As shown in Figure 24, it comprises a measuring electrode member 20A as a first electrostatic capacity generating portion for detecting an amount of the developer, and a reference electrode member 20B as a second electrostatic capacity generating portion (calibration electrode) for outputting a reference signal, which is generated on the basis of the detected ambience, that is, the temperature and the humidity of the ambience. The measuring electrode member 20A is disposed at such a position that it contacts the developer and that contact area thereof with the developer changes with the reduction of the developer, for example, on the inside surface of the developer accommodating portion 57 as shown in Figure 24 or on an inner bottom surface of the developer accommodating portion 57 as shown in Figure 25. The reference electrode member 20B may be disposed at any place in the main assembly of the apparatus if it is not contacted to the developer as shown in Figure 24, or it may be disposed on the outside or outer surface of the developer accommodating portion as shown in Figure 26, or at such a position within the developer accommodating portion 57 that it is separated from the developer accommodating portion by a partition wall 21 so as not to be contacted to the developer, as shown in Figure 27. The measuring electrode member 20A has the same structure as that described in conjunction with Figures 10 and 11. More particularly, as shown in Figure 10, it comprises a pair of electrodes 23, 24which are arranged in parallel with each other with a predetermined gap therebetween on the substrate 22. In this embodiment, the electrodes 23, 24have at least one pair of electrode portions 23a-23f, 24a-24f juxtaposed in parallel with a predetermined gap G, and the electrode portion 23a-23f, 24a-24f are connected to the connecting electrode portions 23g, 24g, respectively. Thus, the two electrodes 23and 24 have a comb-like configuration with the branch portions interlaced with each other. However, the electrode pattern of the measuring electrode member 20 is not limited to those examples, and for example, as shown in Figure 11, the electrodes 23, 24may be extended in the volute pattern with constant gap. The measuring electrode member 20A detects the developer remainder in the developer accommodating portion 57 by detecting the electrostatic capacity between the parallel electrodes 23, 24. Since the developer has a dielectric constant which is larger than that of the air, and therefore, the contact of the developer on the surface of the measuring electrode member 20A increases the electrostatic capacity between the electrodes 23, 24. Therefore, the measuring electrode member 20A can detect the developer in the developer container 11A on the basis of the area of the developer contacted to the surface of the measuring electrode member 20A, using a predetermined calibration curve, irrespective of the cross-sectional configuration of the developer container 11A or the configuration of the measuring electrode member 20A. The measuring electrode member 20A of these examples included for illustrative purposes only can be manufactured in the same manner as described above. Therefore, the detailed description will be omitted for simplicity. As described in the foregoing, according to the detecting device for the amount of the developer of this illustrative example, the measuring electrode member 20A is disposed on the inner surface of the developer accommodating portion 57 or on such an inner bottom surface that contact area with a developer reduces with consumption of the developer, and the total amount of the developer in the developer container can be detected by the change of the electrostatic capacity of the measuring electrode member 20A, which change is indicative of the change of the contact area with the developer. Since the dielectric constant of the developer is larger than that of the air, the electrostatic capacity is larger at the portion where the developer is contacted to the measuring electrode member 20A (where the developer exists) than at the portion where no developer is contacted thereto (where the developer does not exist). Thus, the amount of the developer in the developer accommodating portion 57 can be deduced from the electrostatic capacity. As shown in Figure 24, by disposing the measuring electrode member 20A on one inner side of the developer accommodating portion 57, the percentage of the area contacted to the developer to the cross-sectional area of the developer container in the YZ flat surface in Figure 28 12, can be deduced or estimated from the detected electrostatic capacity. As shown in Figure 29, the developer may exist unevenly along the longitudinal direction due to the event that process cartridge is demounted and mounted for jam clearance or the like, due to inclination of the process cartridge or due to uneven printing pattern, as shown in Figure 30. By providing the measuring electrode member 20A at each inner longitudinal end of the developer container, the uneven distribution of the developer can be detected on the basis of the output of the two electrode members 20A, 20A, so that correct detection of the developer remainder is accomplished. As shown in Figure 25, when the measuring electrode member 20A is disposed on the inner bottom surface of the developer container 11A, the percentage of the contact area occupying the bottom area can be estimated so that influence of the uneven distribution of the developer in the longitudinal direction can be minimized. Since the bottom area is larger than the end area in the developer accommodating portion 57, the area of the developer amount detecting member 20A can be made larger than when the developer amount detecting member 20A is disposed at the end of the developer accommodating portion 57, so that amount of the change of the electrostatic capacity can be made larger, that is, the output of the detector can be made larger, and therefore, the measurement error can be minimized. When the electrode members are provided on the inner bottom surface and the inner end surface or surfaces of the developer accommodating portion 57, the amount of the developer in the developer accommodating portion 57 can be estimated in three dimensions, so that amount of the developer can be more correctly detected. According to this example, the developer remaining amount detecting device comprises a reference electrode member 20B having the same structure as the measuring electrode member 20A, as shown in Figure 24. As has been described, the reference electrode member 20B has the same structure as the measurement electrode member 20A. More particularly, as shown in Figure 10, it comprises a pair of electrodes 23(23a-23f) and 24 (24a-24f) formed parallel with a gap G on the substrate 22, and the two electrodes 23, 24 may be interlaced, or it may be in the form of a volute, as shown in Figure 11. The reference electrode member 20B can be manufactured through the same manufacturing process as with the printed boards and the wiring patterns. The electrostatic capacity of the reference electrode member 20B changes in accordance with the ambient condition such as the temperature and the humidity as described hereinbefore, so that it functions as a calibration member (reference electrode or member) for the measuring electrode member 20A. Thus, the output of the measuring electrode member 20A is compared with the output of the reference electrode member 20B which is influenced by the change of the ambient conditions. For example, the electrostatic capacity of the reference electrode member 20B in a predetermined state is set to be the same as the electrostatic capacity of the measuring electrode member 20A when no developer exists, and then, the difference of the outputs of the reference electrode member 20B and the measuring electrode member 20A is indicative of the change of the electrostatic capacity caused by the presence of the developer, so that accuracy of the detection of the remaining amount of the developer can be enhanced. The detection principle on the developer amount and the detecting device for the amount of the developer are the same as those described in conjunction with Figure 17, therefore, the description thereof is omitted for simplicity. As described in the foregoing, use is made with the reference electrode member 20B (calibration element) exhibiting the same capacity change in accordance with the ambient condition change as the measuring electrode member 20A, so that detection error due to the variation of the ambient condition can be canceled or compensated so that high accuracy of the detection for the developer remainder can be accomplished. In further examples included for illustrative purposes only, the reference electrode member 20B as the calibration member may have another structure and can be disposed at another place. For example, as shown in Figures 24 and 31, the reference electrode member 20B having the same structure as the measuring electrode member 20A may be placed in the main assembly of the image forming apparatus. With this structure, the electrostatic capacity of the reference electrode member 20B changes in the same manner as the measuring electrode member 20A in accordance with the change of the ambiance, so that output of the changes attributable to the ambience variation can be canceled from the output of the measuring electrode member 20A. As shown in the examples of Figures 26 and 27 included for illustrative purposes only, the measuring electrode member 20A and the reference electrode member 20B having the same structure as the measuring electrode member can be placed in the developer accommodating portion 57 of the developing device 50. In this case, since the measuring electrode member 20A and the reference electrode member 20B for calibration are provided in the developer accommodating portion 57, the variation due to the ambience change can be canceled, and since the measurement electrode member (detecting member) 20A and the reference electrode member (calibration member) 20B are placed in the same ambient conditions, the detection accuracy can be enhanced. In the description of the foregoing , the electrode patterns 23, 24of the reference electrode member 20B have substantially the same electrostatic capacities, and substantially the same pattern widths, lengths, gaps and opposing areas. In such a case, the pattern design is easy, and the variations resulting from the differences in the electrostatic capacity among the products and the differences in the ambient conditions, can be minimized. In addition, it is possible that area of the electrode patterns 23, 24of the reference electrode member 20B for calibration is different from the area of the electrode patterns 23, 24of the measuring electrode member 20A. In this case, the output of the reference electrode member 20B is multiplied by a predetermined coefficient, and the multiplied output is compared with the output of the measuring electrode member 20A. Using such a structure, the size of the reference electrode member 20B can be reduced so that space occupied by the detecting member can be reduced. Both of the members 20A and 20B are disposed at the same side of the developer accommodating portion, and in this case, the percentage of the pattern of the detecting member 20A in the limited area can be increased so that degree of the change of the electrostatic capacity can be increased, and the accuracy can be enhanced. In the foregoing, the same configurations or same dimensions do not mean exactly identical configuration or dimensions, and do not exclude those having a difference due to manufacturing errors or the like as long as the intended detection can be made with practical accuracy. As described in the foregoing, the developer accommodating portion 57 is provided with the measuring electrode member 20A and the reference electrode member 20B. Further preferably, the developing zone 56 of the developing device is provided with an antenna rod, that is, electrode rod 54 (Figure 23) which is extended through a predetermined length in the longitudinal direction of the developing sleeve 55 with a predetermined gap from the developing sleeve 55. By doing so, the change of the electrostatic capacity between the developing sleeve 55 and the electrode rod 25 can be detected, so that emptiness of the developer can be detected. The amount of the developer in the developer accommodating portion 57 can be detected substantially real-time, and on the basis of the detection, the consumption amount of the developer may be displayed so as to promote the user to prepare the replenishing cartridge and further to supply the developer upon the display of the emptiness. The detected information provided by the developer amount detecting device is displayed on the screen of the terminal equipment such as a personal computer of the user in the manner, shown in Figures 20and 21, or as shown in Figure 22, the main assembly of the electrophotographic image forming apparatus may be provided with a display portion of, LED or the like, and the LED is flickered in accordance with the amount of the developer. Example 3 Figure 33 shows a further exemplary electrophotographic image forming apparatus. The electrophotographic image forming apparatus of this embodiment is generally the same as the image forming apparatus of example 2 except for the developing device 50. Therefore, the same reference numerals are assigned to the element having the corresponding functions, and the detailed description thereof is omitted for simplicity. In this example, the developing device 50 comprises a developing zone 56 including a developing sleeve 55 (developer carrying member), a developer hopper 58 for accommodating the developer and supplying the developer to the developing zone 56, and a developer supply container 59 for supplying the developer to the developer hopper 58. In such a developing device 50, similarly to the developer accommodating portion 57 according to example 2, the developer hopper 58 and the developer supply container 59 constitute a developer supply container, and therefore, the developer amount detecting device according to the present invention is provided in the developer hopper 58 and the developer supply container 59. More particularly, in the case that developer amount detecting member 20A is provided in the developer hopper 58, the developer remainder in the developer hopper 58 is detected, and in the case that developer amount detecting member is provided in the developer supply container 59, the developer remainder in the developer supply container 59 can be detected. In this example, even in the case that developer amount detecting members 20A are provided in the developer hopper 58 and the developer supply container 59, respectively, in order to detect the developer remainders in the developer hopper 58 and the developer supply container 59, the reference electrode member 20B may be provided in the developer hopper 58, the developer supply container 59, or the main assembly of the electrophotographic image forming apparatus, for all the developer amount detecting members. In the foregoing examples, the range of substantially real-time detection of the remaining amount of the developer is not limited to the full range, that is, the range of 100% (Full) -0% (Empty). The substantially real-time detection range may be properly determined by one skilled in the art, for example, the range of, 100%-25%, or, 30%-0%, or the like. The remaining amount of 0% does not necessarily mean that there exists no developer at all. The remaining amount of 0% may be indicative of the event that developer has decreased to such an extent that predetermined image quality is not provided. 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 scope of the following claims.

Claims: A developing device for an electrophotographic image forming apparatus, said developing device comprising: (a) a developer accommodation portion (50) for accommodating a developer and including a partition wall (21) having one face exposed to developer contained in the developer accommodation portion (50) and a second face not contacted by developer contained in the developer accommodation portion (50); (b) developing means (55, 56) for developing an electrostatic latent image formed on an electrophotographic photosensitive member (51) using the developer accommodated in said developer accommodation portion (50); characterized by (c) an integral measuring part for measuring an amount of a developer contained in the developer accommodation portion (50), said measuring part comprising: a flexible insulating substrate (22); a first electrostatic capacity generation portion (20A) and a second electrostatic capacity generation portion (20B) symmetrically provided on said flexible insulating substrate; and electrical contacts (23, 24) for transmitting to the electrophotographic image forming apparatus a first electrical signal corresponding to an electrical capacity generated by said first electrostatic capacity generation portion (20A) when a voltage is applied thereto from the electrophotographic image forming apparatus and a second electrical signal corresponding to an electrical capacity generated by said second electrostatic capacity generation portion (20B) when a voltage is applied thereto from the electrophotographic image forming apparatus; wherein the insulating substrate (22) is folded so that the first electrostatic capacity generation portion (20A) is disposed in a position in contact with the said one face of the partition wall (21) and is operable to generate an electrostatic capacity corresponding to an amount of the developer when said first electrostatic capacity generation portion (20A) is supplied with a voltage; and said second electrostatic capacity generation portion (20B) is disposed in a position in contact with said second face of said partition wall (21) and is operable to generate a reference electrostatic capacity, which is a developer-free electrostatic capacity, when said second electrostatic capacity generation portion (20B) is supplied with a voltage. A developing device according to claim 1, wherein said first electrostatic capacity generation portion (20A) includes a first electroconductive portion (23) and a second electroconductive portion (24), and said second electrostatic capacity generation portion (20B) includes a third electroconductive portion (23), and a fourth electroconductive portion (24), wherein said first electroconductive portion and said second electroconductive portion are juxtaposed with each other, and said third electroconductive portion and said fourth electroconductive portion are juxtaposed with each other. A developing device according to claim 2, wherein each of said first electroconductive portion (23) and said second electroconductive portion (24) includes portions which are arranged at regular intervals, and each of said third electroconductive portion (23) and said fourth electroconductive portion (24) includes portions which are arranged at regular intervals. A developing device according to claim 3, wherein the regular interval portions of said first electroconductive portion (23) and said second electroconductive portion (24) are parallel with each other, and the regular interval portions of said third electroconductive portion (23) and said fourth electroconductive portion (24) are parallel with each other. A developing device according to any of claims 1 to 3, wherein said first electroconductive portion and said second electroconductive portion include alternatingly arranged portions, and said third electroconductive portion and said fourth electroconductive portion include alternatingly arranged portions. A developing device according to any one of claims 2 to 4, wherein said first electroconductive portion (23) includes a base portion and a plurality of branched portions (23a-f) extended from the base portion, and said second electroconductive portion (24) includes a base portion and a plurality of branched portions (24a-f) extended from the base portion of said second electroconductive portion, wherein said branched portions (23a-f) of said first electroconductive portion and the branched portions (24a-f) of said second electroconductive portion are alternatingly arranged in parallel with each other at regular intervals. A developing device according to claim 6, wherein said first electroconductive portion and said second electroconductive portion include portions which are opposed to each other, wherein the branched portions (23a-f) of said first electroconductive portion (23) extend toward said second electroconductive portion (24), and the branched portions (23a-f) of said second electroconductive portion (24) extend toward said first electroconductive portion (23). A developing device according to any one of claims 2 to 5, wherein said third electroconductive portion (23) includes a base portion and a plurality of branched portions (23a-f) extended from the base portion, and said fourth electroconductive portion (24) includes a base portion and a plurality of branched portions (24a-f) extended from the base portion of said fourth electroconductive portion, wherein said branched portions (23a-f) of said third electroconductive portion and the branched portions (24a-f) of said fourth electroconductive portion are alternatingly arranged in parallel with each other at regular intervals. A developing device according to claim 8, wherein said third electroconductive portion and said fourth electroconductive portion include portions which are opposed to each other, wherein the branched portions (23a-f) of said third electroconductive portion extend toward said fourth electroconductive portion (24), and the branched portions (24a-f) of said fourth electroconductive portion extend toward said third electroconductive portion (23). A developing device according to any one of claims 1 to 9, wherein said first electrostatic capacity generation portion (20A) and said second electrostatic capacity generation portion (20B) have respective electroconductive portions (23, 24) of the same configuration. A developing device according to any one of claims 1 to 10, wherein said first electrostatic capacity generation portion (20A) and said second electrostatic capacity generation portion (20B) generate the same electrostatic capacities when voltages are applied thereto, when said first electrostatic capacity generating portion and said second electrostatic capacity generating portion are not contacted to the developer. A developing device according to claim 11, wherein, said first and third electroconductive portions are electrically connected with each other, and are electrically connected to a common electric input contact (23). A developing device according to any of claims 1 to 12, wherein said developing device is detachably mountable to said electrophotographic image forming apparatus. A developing device according to claim 13, wherein said electrical contacts (23, 24) are provided exposed from a cartridge frame at two portions which are spaced from each other. A developing device according to claim 14, wherein said electrical contacts (23, 24) include a first electrical contact element for transmitting the first electrical signal to the electrophotographic image forming apparatus and a second electrical contact element for transmitting the second electrical signal to the electrophotographic image forming apparatus. A developing device according to any one of claims 1 to 12, wherein said developing device is fixed to said electrophotographic image forming apparatus A process cartridge (B) detachably mountable to a main assembly of an electrophotographic image forming apparatus (A), said process cartridge comprising: (a) an electrophotographic photosensitive member (7); (b) a developing device (9) according to any of claims 1 to 12, for developing a latent image formed on said electrophotographic photosensitive member (7). A process cartridge according to claim 17, wherein said electrical contacts (23, 24) are provided exposed from a cartridge frame at two portions which are spaced from each other. An electrophotographic image forming apparatus (A) for forming an image on a recording material, including a detachably mountable process cartridge (B) according to claim 17 or claim 18, said apparatus comprising: (a) mounting means (16) for detachably mounting said process cartridge (B) (b) electrostatic latent image forming means (1) for forming an electrostatic latent image on said electrophotographic photosensitive member of said process cartridge; (c) electrical contacts (24) for receiving a first electrical signal corresponding to an electrostatic capacity generated by said first electrostatic capacity generation portion (20A) and a second electrical signal corresponding to a reference electrostatic capacity generated by said second electrostatic capacity generation portion (20B) of said process cartridge mounted to the main assembly of said electrophotographic image forming apparatus; developer amount detecting means (100, 101, 102, 103) for detecting an amount of the developer accommodated in the developer accommodating portion of said process cartridge on the basis of the first electrical signal and the second electrical signal. An image-forming apparatus according to claim 19, wherein the means (100, 101, 102, 103) for detecting the amount of the developer accommodated in said developer accommodation portion (11A) is operable to detect the amount of developer in substantially real-time, and wherein the apparatus further comprises display means (41, 42) for displaying a result of the detection. An image-forming apparatus according to claim 20, wherein the display means (41, 42) is operable to display the result of the detection stepwisely.

Inventors: KARAKAMA TOSHIYUKI, MATSUMOTO HIDEKI, SAKATA SHIROU, YOKOI AKIYOSHI, KARAKAMA, TOSHIYUKI, MATSUMOTO, HIDEKI, SAKATA, SHIROU, YOKOI, AKIYOSHI
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1999
Main classification: G03G15
IPC codes: G03G21, G03G15