Electrophotographic image forming apparatus, process cartridge, developing device and measuring part

Abstract: A process cartridge detachably mountable to an electrophotographic image forming apparatus, said process cartridge includes (a) an electrophotographic photosensitive member; (b) process means actable on the electrophotographic photosensitive member; (c) a measuring electrode member having input side and output side electrodes having at least one juxtaposed portions, the measuring electrode member being disposed at such a position that it is contacted to a developer; (d) a reference electrode member having input side and output side electrodes having at least one juxtaposed portions, the reference electrode member being disposed at such a position that it is out of contact to the developer; (e) an output contact for the measuring electrode member, connected electrically to the output side electrode of the measuring electrode member; (f) an output contact for the reference electrode member, connected electrically to the output side electrode of the reference electrode member; and (g) a common input contact connected electrically to the input side electrodes of the measuring electrode member and the reference electrode member.

Description: FIELD OF THE INVENTION AND RELATED ART: The present invention relates to an electrophotographic image forming apparatus, a process cartridge, a developing device 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 a 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 has been used in an image forming apparatus using an electrophotographic image forming process, the process cartridges containing as a unit an electrophotographic photosensitive member and process means actable on the electrophotographic photosensitive member, and which cartridge is detachably mountable to the main assembly of the electrophotographic image forming apparatus. Such a 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. JP-A-05188782 discloses a detector for measuring a residual toner amount on the basis of a measurement of capacitance between a conductor and a developing roller, and a comparison of that measured capacitance with a reference capacitor whose capacitance is selected to be the same as the capacitance between the conductor and the developing roller when the residual amount of developer corresponds to that required for a "no toner" indication to the user. US-A-4,296,630 describes a probe for measuring a level of a liquid in a tank, the probe comprising a first capacitor partially immersed in the liquid in dependence on the depth of liquid in the tank, and a second capacitor wholly immersed in the liquid by being placed in an exit tube for liquid from the tank. US-A-4,133,453 describes a toner hopper for an electrophotographic image-forming apparatus wherein a residual amount of toner in the hopper is measured by comparing the capacitance of a number of capacitance plates positioned within the toner in the hopper with the capacitance of a reference capacitor. 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 and a developer in which a remaining amount of the developer can be detected substantially real-time. It is another object of the present invention to provide an electrophotographic image forming apparatus, a process cartridge and a developing device wherein a remaining amount of developer in a developer accommodating portion can be detected substantially real-time with consumption of the developer. It is a further object of the present invention to provide an electrophotographic image forming apparatus, a process cartridge and a developing device wherein a remaining amount of the developer is detected by an electrostatic capacity between electrodes, and a measurement error attributable to a change of the ambience is compensated, so that detection error is minimized. It is a further object of the present invention to provide a process cartridge, a developing device and an electrophotographic image forming apparatus wherein a detection accuracy of an amount of a developer is improved, and the number of parts of contact portions thereof is reduced to suppress the cost. It is a further object of the present invention to provide a process cartridge, a developing device and an electrophotographic image forming apparatus wherein an assembling operativity is improved. According to an aspect of the present invention, there is provided a process cartridge according to claim 1. According to another aspect of the present invention, there is provided a developing device according to claim 7, and image forming, apparatus for use with the process cartridge and the developing device. These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF 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 illustrating a description for a detecting device of an amount. Figure 7 is front views of a measuring electrode member and a reference electrode member according to an embodiment of the present invention. Figure 8 is front views of a measuring electrode member and a reference electrode member according to another embodiment of the present invention. Figure 9 is a graph explaining a detection principle of an amount of a developer. Figure 10 is a graph explaining a detection principle for an amount of the developer according to an embodiment of the present invention. Figure 11 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 12 is an illustration of arrangement of a measuring electrode member and a reference electrode member. Figure 13 is a perspective view of a developer container having a developer amount detecting device according to an embodiment of the present invention. Figure 14 is similar to Figure 13, and is a perspective view of a developer container illustrating a developer container having a reference electrode member therein. Figure 15 is an illustration of connection of contacts of a measuring electrode member and a reference electrode member. Figure 16 is an illustration of 3 contacts provided in a process cartridge. Figure 17 is an illustration of display of an amount of the developer according to an embodiment of the present dimension. Figure 18 shows a further example of display of an amount of the developer according to an embodiment of the present invention. Figure 19 shows a further example of display of an amount of the developer according to an embodiment of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the accompanying drawings, the description will be made as to a process cartridge and an electrophotographic image forming apparatus according to embodiments of the present invention. Referring to Figures 1-3, 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 thereonto 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 provided on a top side of the main assembly 14 of the apparatus, that is, 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 cartridge mounting means of the main assembly 14 of the image forming apparatus by the user. 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 the embodiment of the present invention, 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. As shown in Figure 6, the developer amount detecting device comprises a measuring electrode member 20A for detecting the amount of the developer, and a reference electrode member 20B 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 shown in Figures 13 and 14, the reference electrode member 20B may be disposed at such position in the developer container as is the same side as 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 7, the measuring electrode member 20A comprises a pair of electroconductive portions (input side electrode 23 and an output side electrode 24) which are extended in parallel with each other with a predetermined gap 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 8, 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, 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, according to this embodiment, 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, 24of the measuring electrode member 20A can be provided by, for 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 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 7 and 8 can be easily manufactured at the same cost as with simple patterns. When a complicated pattern shown in Figure 7 or 8 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, 24can 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. According to the present invention, the developer remainder detecting device, as shown in Figure 6, further comprises the reference electrode member 20B having the similar structure as the measuring electrode member 20A. The reference electrode member 20B has the same structure as the measurement electrode member 20A. More particularly, as shown in Figure 7, it comprises a pair of electrodes (input side electrodes 23(23a-23f) and output side electrodes 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 8. 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 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 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 9, 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 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 9 and 10, 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 11, the detecting device for the amount of the developer embodying the above described principle will be described. Figure 11 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, the input side electrodes 23is connected to the developing bias circuit 101 (developing bias applying means) by way of a contact 30C (main assembly side contact 32C), and the output side electrode 24 is connected to the control circuit 102 of developer amount detecting circuit 100 by way of contacts 30A (a main assembly side contact 32A) and 30B (main assembly side contact 32B). 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 11, 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 x R5) 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. According to this embodiment, the reference electrode member 20B as the calibration member and the measuring electrode member 20A have the same structure and disposed in the developer container 11A, as shown in Figures 12-14. With this structure, the developer container is provided both with the measuring electrode member 20A and the reference electrode member 20B, so that variation due to the ambience can be removed or canceled, and since the measuring electrode member 20A and the reference electrode member can be placed under the substantially same ambient conditions, the detection accuracy can be enhanced. Furthermore, according to this embodiment, as shown in Figures 11 and 12, the process cartridge B is provided with three contacts, namely, an input side contact 30C, which is common for the detection and the comparison, detection and comparison output contacts 30A and 30B. With such a structure, the number of contacts can be reduced. Additionally, by using a common contacts for the input, the input pulse can be made identical, so that accuracy is enhanced. According to this embodiment, as will be understood from Figures 13 and 14, the electrodes 23, 24 of the measuring electrode member 20A and the reference electrode member 20B are formed on one side of one bendable substrate 22 such as a flexible printed board, and is folded when it is mounted to the developer container. In this embodiment, the measuring electrode member 20A and the reference electrode member 20B have the same electrode pattern. Therefore, the patterns of the electrodes 23, 24 of the measuring electrode member 20A and the reference electrode member 20B provide substantially the same electrostatic capacities, and the width, the length, the clearance and the opposing areas are substantially the same. The reference electrode member 20B thus manufactured is folded back substantially at the center of the substrate, and it is disposed at such a position in the developer container 11A containing the measuring electrode member that it is partitioned by a partition wall 21 and it is not contacted to the developer. The measuring electrode member 20A and the reference electrode member 20B are manufactured in the similar manner as with the normal manufacturing step of the printed boards, and therefore, there are variations in the electrostatic capacities of the substrates due to the variations in the width, the height of the electrode pattern, resulting from the variation of the moisture absorbed rate and/or the dielectric constant of the equipment or material, and/or the etching conditions. According to this embodiment, the measuring electrode member 20A and the reference electrode member 20B are formed on the same side of the substrate, so that single substrate is both for the detecting member and the calibration member, and therefore, the cost can be saved. Additionally, the electrode pattern are formed on the same material, the variations attributable to the differences of the natures of the base material can be minimized. Moreover, since the patterns are formed on the same side of the base material, the variations during the pattern formation, such as during the etching, can be suppressed. Furthermore, with such a structure, the detection pattern can be provided toward the top of the developer container, so that detection of the developer is possible even if the developer container is full to the top. According to this embodiment, as shown in Figure 13, from the substrate 22 on which the measuring electrode member 20A and the reference electrode member 20B are formed, there are projected the output contact 31A for the measuring electrode connected electrically with the output side electrode 24 of the measuring electrode member 20A, the output contact 31B for the reference electrode connected electrically with the output side electrode 24 of the reference electrode member 20B, and the common input contact 31C connected with the input side electrodes 23 of the measuring electrode member 20A and the reference electrode member 20B. These three contacts 31A, 31B, 31C, are fixed to a front wall portion 11a of the developer frame 11 bridging the weld portion relative to the developing device frame 12 Figure 16) of the developer container 11A as shown in Figure 15; and the three contacts 31A, 31B, 31C are exposed outwardly from the contact port 12c formed in the side member 12b fixed to the side of the developing device frame 12, as shown in Figures 16 and 4 and are connected electrically to the output contact 30A of the measuring electrode and to the output contact 30B of the common input contact 30C mounted to the side member 12b. As shown in Figure 5, the contacts 30A, 30B, 30C of the process cartridge are electrically connected to the contacts 32A, 32B, 32C in the main assembly 14 of the apparatus when the process cartridge B is mounted to the main assembly 14 of the apparatus, and therefore, the measuring electrode member 20A and the reference electrode member 20B provided in the process cartridge B are connected to the developer amount measuring circuit 100 shown in Figure 11. In the foregoing description of the embodiment, the patterns of the electrodes 23, 24 of the reference electrode member 20B and the measuring electrode member 20A have substantially the same electrostatic capacities, pattern widths, lengths, clearances and opposing areas. However, the areas of the electrode patterns 23, 24 of the reference electrode member 20B for calibration may be different from that of the electrode patterns 23, 24 of 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 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. According to the above embodiments, said measuring electrode member is disposed in a developer accommodating portion for accommodating the developer to be used for development of an electrostatic latent image by developing means as said process means, and the position of said measuring electrode member is such that it is contacted to the developer in said developer accommodating portion, and the position of said reference electrode member is such that it is out of contact to the developer in said developer accommodating portion. The measuring electrode member and said reference electrode member are manufactured by forming electrode patterns on the same side of one substrate, and preferably said measuring electrode member and said reference electrode member generate substantially the same electrostatic capacity when a voltage is applied thereto. A length of an opposed portion of said juxtaposed portions and a gap therebetween in said measuring electrode member are substantially the same as those of said reference electrode member, respectively. In a further embodiment said developing means has an electrode rod for detecting substantial absence of the developer. As described in the foregoing, the present invention provides the following advantages: (1) the remaining amount of the developer in the developer accommodating portion can be detected substantially real-time in accordance with consumption of the developer: (2) the detection in (1) can be effected with minimum measurement error which may otherwise results due to the change of the ambient conditions. (3) the number of parts of the contact portions can be reduced, and therefore, the manufacturing cost can be reduced. (4) the assembling operativity of the developing device and/or the process cartridge can be improved. In the foregoing embodiments, 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. As described, the present invention can accomplish the detection of the amount of the developer substantially real-time. Furthermore, the present invention can reduce the number of parts. 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 process cartridge (B) detachably mountable in an operating position to an electrophotographic image forming apparatus (A), said process cartridge comprising: an electrophotographic photosensitive member (7); process means (8, 9, 10) operable on said electrophotographic photosensitive member to develop a latent image thereon by means of a developer material; a developer container (11A) for containing said developer material; a measuring electrode member (20A) having input and output electrodes (23, 24) with at least one juxtaposed portion, said measuring electrode member (20A) being disposed within said developer container (11A) at such a position as to be contactable by developer material within the developer container when the process cartridge (B) is in its operating position; a reference electrode member (20B) having input and output electrodes (23, 24) with at least one juxtaposed portion, said reference electrode member (20B) being disposed at such a position as not to be contactable by developer material within the developer container when the process cartridge (B) is in its operating position; a first output contact (31A) electrically connected to said output electrode (24) of said measuring electrode member (20A); a second output contact (31B) electrically connected to said output electrode (24) of said reference electrode member (20B); and a common input contact (30C) electrically connected to said input electrodes (23) of said measuring electrode member (20A) and said reference electrode member (20B); characterised in that said measuring electrode member (20A) and said reference electrode member (20B) are formed on a common flexible substrate (22). A process cartridge according to claim 1, comprising a partition wall (21) dividing the developer container (11A) into a first region for receiving the developer material and a second region wherein the flexible substrate (22) is folded so as to position the measuring electrode (20A) against a face of the partition wall (21) exposed to said first region and to position the reference electrode (20B) against a face of the partition wall (21) exposed to the second region. A process cartridge according to claim 1, wherein the measuring electrode (20A) and the reference electrode (20B) are positioned on the same side of a wall of the developer container. A process cartridge according to any of claims 1 to 3, wherein the measuring electrode member (20A) and the reference electrode member (20B) have substantially the same electrical capacitance in the absence of developer material. A process cartridge according to any of claims 1 to 4, wherein the area of the reference electrode (20B) is less than that of the measuring electrode (20A). A process cartridge according to claim 4 wherein the reference and measuring electrodes (20B, 20A) have substantially the same pattern widths, lengths, clearances and opposing areas. A developing device for use in an electrophotographic image-forming apparatus the developing device comprising a developing means (9) a developer container (11A) for containing a developer material for developing a latent image on an electrophotographic photosensitive member (7), and a sensor element (20A, 20B) for detecting an amount of developer material present in said developer container, the sensor element comprising: a measuring electrode member (20A) having input and output electrodes (23, 24) with at least one juxtaposed portion, said measuring electrode member (20A) being disposed within said developer container (11A) at such a position as to be contactable by developer material within the developer container; a reference electrode member (20B) having input and output electrodes (23, 24) with at least one juxtaposed portion, said reference electrode member (20B) being disposed at such a position as not to be contactable by developer material within the developer container; a first output contact (31A) electrically connected to said output electrode (24) of said measuring electrode member (20A); a second output contact (31B) electrically connected to said output electrode (24) of said reference electrode member (20B); and a common input contact (30C) electrically connected to said input electrodes (23) of said measuring electrode member (20A) and said reference electrode member (20B); wherein said measuring electrode member (20A) and said reference electrode member (20B) are formed on a common flexible substrate (22). A developing device according to claim 7, comprising a partition wall (21) dividing the developer container (11A) into a first region for receiving the developer material and a second region and wherein the flexible substrate (22) is folded so as to position the measuring electrode (20A) against a face of the partition wall (21) exposed to said first region and to position the reference electrode (20B) against a face of said partition wall exposed to said second region. A developing device according to claim 7, wherein the measuring electrode (20A) and the reference electrode (20B) are positioned on the same side of a wall (21) of the developer container. A developing device according to any of claims 7 to 9, wherein the measuring electrode member (20A) and the reference electrode member (20B) have substantially the same electrical capacitance in the absence of developer material. A developing device according to any of claims 7 to 10, which is a cartridge detachably mountable to an electrophotographic image-forming apparatus An electrophotographic image-forming apparatus in combination with a process cartridge according to any of claims 1 to 6. An electrophotographic image-forming apparatus having a developing device according to any of claims 7 to 11.

Inventors: KARAKAMA TOSHIYUKI, MATSUMOTO HIDEKI, SAKATA SHIROU, YOKOI AKIYOSHI, KARAKAMA, TOSHIYUKI, MATSUMOTO, HIDEKI, SAKATA, SHIROU, YOKOI, AKIYOSHI, Karakama, Toshiyuki, Canon Kabushiki Kaisha, Matsumoto, Hideki, Canon Kabushiki Kaisha, Sakata, Shirou, Canon Kabushiki Kaisha, Yokoi, Akiyoshi, Canon Kabushiki Kaisha
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1999
Main classification: G03G21
IPC codes: G03G15, G03G21