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

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, an 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, the process cartridge being detachably mountable to a main assembly of an electrophotographic image forming apparatus.

Heretofore, a process cartridge widely is used in an image forming apparatus using an electrophotographic image forming process, 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 a maintenance operation can be carried out in effect by the users. Therefore, this 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.

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 that is capable of detecting the remaining amount of the developer substantially in 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 that is capable of detecting a remaining amount of the developer in the developer-accommodating portion substantially in 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, and a developer-supply container that is capable of detecting a remaining amount of the developer using a change in the electrostatic capacity between electrodes, wherein measurement errors are 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 in 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 is attributable to the changes of the ambient conditions, to accomplish detection of the amount of the developer with a small detection error.

According to an aspect of the present invention, there is provided an electrophotographic image forming apparatus, a process cartridge, a developing device, and a developer-supply container wherein there is provided a measuring part comprising an insulative substrate; a first electrostatic-capacity generating portion disposed at such a position that the first electrostatic-capacity generating portion contacts the developer accommodated in the developer-accommodating portion when a predetermined amount of the developer is accommodated in the developer-accommodating portion, the first electrostatic-capacity generating portion generating an electrostatic capacity corresponding to an amount the developer when the 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 does not contact to the developer accommodated in the developer accommodating portion, the second electrostatic-capacity generating portion generating a reference electrostatic capacity when the second electrostatic-capacity generating portion is supplied with a voltage, wherein the first electrostatic capacity generating portion and the second electrostatic capacity generating portion are provided on the substrate.

According to another aspect of the present invention, there is provided an electrophotographic image forming apparatus, a process cartridge, a developing device, and a developer supply container wherein there is provided a measuring part comprising an insulative substrate; a first electrostatic-capacity generating portion including first electroconductive portions and second electroconductive portions alternatingly arranged in parallel with each other at regular intervals and a second electrostatic-capacity generating portion including third electroconductive portions and fourth electroconductive portions alternatingly arranged in parallel with each other at regular intervals, wherein the first electrostatic capacity generating portion and the second electrostatic capacity generating portion are provided on the insulative substrate.

According to a father aspect of the present invention, there is provided a measuring part comprising an insulative substrate; a first electrostatic-capacity generating portion disposed at such a position that the first electrostatic-capacity generating portion contacts the developer accommodated in the developer-accommodating portion when a predetermined amount of the developer is accommodated in the developer-accommodating portion, the first electrostatic-capacity generating portion generating an electrostatic capacity corresponding to the amount of 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 the second electrostatic-capacity generating portion does not contact to the developer accommodated in said developer-accommodating portion, the second electrostatic-capacity generating portion generating a reference electrostatic capacity when the second electrostatic-capacity generating portion is supplied with a voltage, wherein the first electrostatic-capacity generating portion and the second electrostatic-capacity generating portion are provided on the substrate.

According to a further aspect of the present invention, there is provided a measuring part comprising an insulative substrate; a first electrostatic-capacity generating portion including first electroconductive portions and second electroconductive portions alternatingly arranged in parallel with each other at regular intervals and a second electrostatic-capacity generating portion including third electroconductive portions and fourth electroconductive portions alternatingly arranged in parallel with each other at regular intervals, wherein said first electrostatic-capacity generating portion and the second electrostatic-capacity generating portion are provided on the insulative substrate.

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.

FIG. 1 shows a general arrangement of the electrophotographic image forming apparatus according to an embodiment of the present invention.

FIG. 2 is the perspective view of the outer appearance of an electrophotographic image forming apparatus according to an embodiment of the present invention.

FIG. 3 is a longitudinal sectional view of a process cartridge according to an embodiment of the present invention.

FIG. 4 is a perspective view of the outer appearance of a process cartridge according to an embodiment of the present invention, as seen from the bottom.

FIG. 5 is the perspective view of the outer appearance illustrating a mounting portion of a main assembly of an apparatus for mounting a process cartridge.

FIG. 6 is a perspective view of a developer container according to one embodiment of the present invention provided with a detecting device for detecting an amount of a developer.

FIG. 7 is a perspective view of a developer container provided with a detecting device for detecting the amount of the developer according to an embodiment of the present invention.

FIG. 8 is a perspective view of a developer container provided with a detecting device for detecting an amount of the developer according to an embodiment of the present invention.

FIG. 9 is a perspective view of a developer container provided with a detecting device for detecting an amount of the developer according to an embodiment of the present invention.

FIG. 10 is a front view of a measuring electrode member and a reference electrode member according to an embodiment of the present invention.

FIG. 11 is a front view of a measuring electrode member and a reference electrode member according to another embodiment of the present invention.

FIG. 12 is an illustration of the accommodation of a developer in a developer container.

FIG. 13 is a perspective view of a developing means provided with a detecting device for detecting an amount of a developer according to one embodiment of the present invention.

FIG. 14 is an illustration of accommodation of a developer in the developer container.

FIG. 15 is a graph explaining a detection principle for the amount of the developer according to an embodiment of the present invention.

FIG. 16 is a graph explaining a detection principle for an amount of the developer according to an embodiment of the present invention.

FIG. 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.

FIG. 18 shows arrangements of a measuring electrode member and a reference electrode member according to one embodiment of the present invention.

FIG. 19 shows arrangements of a measuring electrode member and a reference electrode member according to one embodiment of the present invention.

FIG. 20 is an illustration of the display of an amount of the developer according to an embodiment of the present dimension.

FIG. 21 shows another example of the display of an amount of the developer according to an embodiment of the present invention.

FIG. 22 shows a further example of the display of an amount of the developer according to an embodiment of the present invention.

FIG. 23 is a schematic illustration of an electrophotographic image forming apparatus according to another embodiment of the present invention.

FIG. 24 is a perspective view of a developing device provided with a detecting device for detecting an amount of a developer according to an embodiment of the present invention.

FIG. 25 is a perspective view of a developing device provided with a detecting device for detecting an amount of a developer according to a further embodiment of the present dimension.

FIG. 26 is a perspective view of a developing device provided with a detecting device for detecting an amount of the developer according to a further embodiment of the present invention.

FIG. 27 is a perspective view of a developing device provided with a detecting device for detecting an amount of a developer according to a further embodiment of the present invention.

FIG. 28 is an illustration of accommodation of the developer in developer accommodating portion.

FIG. 29 is a perspective view of a developing device provided with a detecting device for detecting an amount of a developer according to a further embodiment of the present invention.

FIG. 30 is an illustration of accommodation of the developer in a developer accommodating portion.

FIG. 31 is an illustration of arrangements of a measuring electrode member and a reference electrode member according to an embodiment of the present invention.

FIG. 32 is an illustration of arrangements of a measuring electrode member and a reference electrode member according to a further embodiment of the present invention.

FIG. 33 is a schematic illustration of an electrophotographic image forming apparatus according to a further embodiment of the present invention.

Referring to a accompanying drawings, the description will be provided 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 FIG. 1, a description will be provided 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, or 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 1 a, a polygonal mirror 1 b, a lens 1 c, and a reflection mirror 1 d, so that a 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, a toner image.

The developing means 9 includes a developer chamber 9 A provided with a developing roller 9 a (developer carrying member), wherein the developer in developer container 11 A (developer accommodating portion) disposed adjacent to the developer chamber 9 A is fed out to a developing roller 9 a in the developer chamber 9 A by rotation of a developer-feeding member 9 b. The developer chamber 9 A is provided with a developer-stirring member 9 e adjacent to the developing roller 9 a to circulate the developer in the developer chamber. The developing roller 9 a contains therein a fixed magnet 9 c so that developer is fed by rotation of the developing roller 9 a, and the developer is electrically charged by triboelectric charge by friction with a developing blade 9 d, 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 the toner image is formed. The developing roller 9 a 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 3 a is fed out and supplied to an image-transfer position by a pick-up roller 3 b, a pair of feeding rollers 3 c, 3 d, and 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 3 f. The fixing means 5 includes driving roller 5 c and a fixing roller 5 b containing therein a heater 5 a 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 3 g, 3 h, 3 i and is discharged to a discharging tray 6 along a reverse path 3 j. 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 3 k is usable to discharge the recording material 2 by a pair of discharging rollers without using the reversing passage 3 j. In this embodiment, the discharging rollers 3 g, 3 h, 3 i, the pair of feeding rollers 3 c, 3 d , the pair of registration rollers, the feeding guide 3 f, the pair of discharging rollers and the pair of discharging rollers 3 m, 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 contacting the photosensitive drum 7 , and collects it to a residual developer container 10 b.

In this embodiment, a process cartridge B includes a developing unit comprising a developer frame 11 including the developer-container developer 11 A accommodating the developer and the developer-feeding member 9 b, and a developing-device frame 12 supporting the developing means 9 , such as the developing roller 9 a and the developing blade 9 d, 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 10 a, 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 13 R ( 13 L) on the outer surface of the process cartridge B and guide portions 16 R ( 16 L) of the main assembly 14 of the apparatus for guiding the guide means 13 R ( 13 L), as shown in FIGS. 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 in real-time the remaining amount of the developer when the developer in the developer container 11 A is consumed.

As shown in FIG. 6, the developer-amount detecting device comprises a measuring electrode member 20 A, which is a first electrostatic-capacity generating portion for detecting the amount of the developer, and a reference electrode member 20 B, which is a second electrostatic-capacity generating portion for generating a reference signal on the basis of the detection of the ambient temperature and humidity.

The measuring-electrode member 20 A is provided on an inside surface of the developer container 11 A of the developing means 9 as shown in FIG. 6, or on such a portion in the developer container 11 A that it is contacts the developer and that contact area thereof with the developer changes with a reduction of the developer, such as a bottom portion, as shown in FIG. 7 . As shown in FIG. 6, the reference-electrode member 20 B may be provided at any position of the main assembly 14 of the apparatus if it does not contact the developer, but the reference electrode member 20 B may be disposed in the developer container 11 A at such position as is opposite from the measuring-electrode member 20 A and is separated by a partition wall 21 so as not to be in contact with the developer. Alternatively, as shown in FIG. 9, the measuring-electrode member 20 A and the reference-electrode member 20 B may be integrally manufactured so as to have a symmetric structure, and in this case, the reference-electrode member 20 B may be bent outwardly to the opposite side of the partition wall 21 (the side not contacting the developer) at the same side as the measuring-electrode member 20 A.

As shown in FIG. 10, the measuring-electrode member 20 A comprises a pair of electroconductive portions (electrodes 23 , 24 ) that 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 23 a - 23 f, 24 a - 24 f juxtaposed in parallel with a predetermined gap G, and the electrode portions 23 a - 23 f, 24 a - 24 f are connected to the connecting electrode portions 23 g, 24 g, 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 is not limited to those examples, and for example, as shown in FIG. 11, the electrodes 23 , 24 may be extended in a volute pattern with constant gap.

The measuring-electrode member 20 A detects the remaining amount of the developer (the developer remainder) in the developer container 11 A by detecting the electrostatic capacity between the parallel electrodes 23 , 24 . Since the developer has a dielectric constant that is larger than that of the air, the contact of the developer on the surface of the measuring-electrode member 20 A increases the electrostatic capacity between the electrodes 23 , 24 .

Therefore, according to this embodiment, the measuring-electrode member 20 A can detect the developer in the developer container 11 A on the basis of the area of the developer contacting the surface of the measuring electrode member 20 A, using a predetermined calibration curve, irrespective of the cross-sectional configuration of the developer container 11 A or the configuration of the measuring-electrode member 20 A.

The electrode patterns 23 , 24 of the measuring electrode member 20 A can be provided by, for example, forming electroconductive metal patterns 23 , 24 of 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 0.4-1.6 mm 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 manufacturing method as with ordinary printed boards and wiring patterns. Therefore, the complicated electrode pattern as shown in FIGS. 10 and 11 can be easily manufactured at the same cost as with simple patterns.

When a complicated pattern shown in FIG. 10 or 11 is used, the length along which the electrodes 23 , 24 are 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 approximately, so that a 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 , 24 have a width of 0.1-0.5 mm, and a thickness of 17.5-70 μm with the gap G therebetween of 0.1-0.5 mm. The surface on which the metal pattern is formed can be laminated with thin resin film having a thickness of 12.5-125 μm 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 20 A is disposed on the inner surface of the developer container 11 A or on such an inner bottom surface that the 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 20 A, 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 contacts the measuring-electrode member 20 A (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 11 A can be detected by detecting the change of the electrostatic capacity.

As shown in FIG. 6, by disposing the measuring-electrode member 20 A on one inner side of the developer container 11 A, the percentage of the area contacting the developer to the cross-sectional area of the developer container in the YZ flat surface in FIG. 12, can be deduced or estimated from the detected electrostatic capacity.

As shown in FIG. 14, the developer may exist unevenly along the longitudinal direction due to the demounting and mounting of the process cartridge for jam clearance, for example, due to the inclination of the process cartridge or due to an uneven printing pattern, as shown in FIG. 14 . By providing the measuring-electrode member 20 A 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 20 A, 20 A, so that the correct detection of the developer remainder is accomplished.

As shown in FIG. 7, when the measuring electrode member 20 A is disposed on the inner bottom surface of the developer container 11 A, the percentage of the contact area occupying the bottom area can be estimated so that the 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 11 A, the area of the developer-amount detecting member 20 A can be made larger than when the developer-amount detecting member 20 A is disposed at the end of the developer container 11 A, so that the 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 11 A, the amount of the developer in the developer container 11 A can be estimated in three dimensions, so that the amount of the developer can be more correctly detected.

According to this embodiment, the detecting device for the remaining amount of the developer comprises a reference-electrode member 20 B what functions as a second electrostatic-capacity generating portion, as shown in FIG. 6 .

The reference-electrode member 20 B has a similar structure as the measurement electrode member 20 A, and as shown in FIG. 10, it comprises a pair of electroconductive portions, namely, electrodes 23 ( 23 a - 23 f ), 24 ( 24 a - 24 f ) which are disposed in parallel with a predetermined gap on a substrate 22 . The branch portions of the electrodes 23 and 24 are interlaced, or the volute patterns shown in FIG. 11 are also usable. The reference-electrode member 20 B 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 20 B 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 20 A.

Thus, according to the detecting device for the amount of the developer of this embodiment, the output of the measuring-electrode member 20 A is compared with the output of the reference-electrode member 20 B, which is indicative of the change of ambient conditions. For example, the electrostatic capacity of the reference-electrode member 20 B in a predetermined state is set to be the same as the electrostatic capacity of the measuring-electrode member 20 A when no developer exists, and then, the difference of the outputs of the reference-electrode member 20 B and the measuring-electrode member 20 A is indicative of the change of the electrostatic capacity caused by the presence of the developer, so that the accuracy of the detection of the remaining amount of the developer can be enhanced.

A description will be provided in more detail as to the detection principle of the amount of the developer. The measuring-electrode member 20 A 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 11 A, 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 the content of the moisture in the air is high, the dielectric constant of the atmospheric air contacting the detecting member 20 A is high. Therefore, even when the amount of the developer is the same, the output of the measuring-electrode member 20 A 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 20 B, as the calibration element, which exhibits the same change as the measuring-electrode member 20 A in accordance with the ambient condition change, that is by the use of the reference-electrode member 20 B having the same structure as the measuring-electrode member 20 A but not contacting the developer, the reference electrode-member 20 B being placed under the same condition as the measuring-electrode member 20 A, 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 20 A and the reference-electrode member 20 B are used for the detection.

As shown in the bar graph of FIG. 15, at the leftmost part, the electrostatic capacity is determined by the measuring-electrode member 20 A for detecting the amount of the developer, which is indicative of the variation of the developer contacting the surface of the detecting member plus the variation of the ambient condition. If the same situation is placed under a high temperature and high humidity ambience, the electrostatic capacity increases despite the fact that the 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 FIG. 16 .

As shown in the middle parts of FIGS. 15 and 16, the reference-electrode member (calibration electrode) 20 B exhibiting the same response to the ambient condition variation as the measuring-electrode member (detecting member) 20 A, 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 FIG. 17, the detecting device for the amount of the developer embodying the above described principle will be described. FIG. 17 shows an example of a circuit for developer detection, more particularly, the figure shows the connection between the measuring-electrode member 20 A and the reference-electrode member 20 B in the image forming apparatus.

The measuring-electrode member 20 A, as the detecting member having an electrostatic capacity Ca that changes in accordance with the amount of the developer, and the reference-electrode member 20 B, as a calibration electrode having an electrostatic capacity Cb that changes in accordance with the ambient condition, are connected as indicated; more particularly, one of the electrodes 23 is 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 20 B uses an AC (alternating) current I 1 supplied through a developing-bias circuit 101 , and a reference voltage V 1 for detecting the developer remainder is set.

The control circuit 102 , as shown in FIG. 17, adds, to the voltage V 3 set by the resistances R 3 , R 4 , the voltage drop V 2 determined by the resistance R 2 and the AC current I 1 ′, which is the current branched by a volume VR 1 from the AC current I 1 supplied to the reference electrode member 20 B, that is, an impedance element.

The AC (alternating) current I 2 applied to the measuring-electrode member 20 A is inputted to the amplifier, and is outputted as the detected value V 4 (V 1 −I 2 ×R 5 ) 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, use is made of the reference-electrode member 20 B (calibration element) exhibiting the same capacity change in accordance with the ambient-condition change as the measuring-electrode member 20 A, so that detection error, due to a variation of the ambient condition, can be canceled or compensated for so that high accuracy in the detection for the developer remainder can be accomplished.

According to this embodiment, the reference-electrode member 20 B as the calibration member may have another structure and can be disposed at another place.

For example, as shown in FIGS. 6 and 18, he reference-electrode member 20 B having the same structure as the measuring-electrode member 20 A may be placed in the main assembly of the image forming apparatus. With this structure, the electrostatic capacity of the reference-electrode member 20 B changes in the same manner as the measuring-electrode member 20 A in accordance with the change of the ambiance, so that the output of the changes attributable to the ambience variation can be canceled from the output of the measuring-electrode member 20 A.

As shown in FIGS. 8, 9 and 19 , the measuring-electrode member 20 A and the reference-electrode member 20 B having the same structure as the measuring-electrode member can be placed in the developer container 11 A of the developing means 94 . In this case, since the measuring-electrode member 20 A and the reference-electrode member 20 B 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) 20 A and the reference-electrode member (calibration member) 20 B are placed in the same ambient conditions, the detection accuracy can be enhanced.

In the description of the foregoing embodiment, the electrode patterns 23 , 24 of the reference electrode member 20 B 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 , 24 of the reference-electrode member 20 B for calibration is different from the area of the electrode patterns 23 , 24 of the measuring-electrode member 20 A. In this case, the output of the reference-electrode member 20 B is multiplied by a predetermined coefficient, and the multiplied output is compared with the output of the measuring-electrode member 20 A. Using such a structure, the size of the reference-electrode member 20 B can be reduced so that the space occupied by the detecting member can be reduced. The members 20 A and 20 B may be placed on the same wall of the developer container 11 A at the same side, and the reference-electrode member 20 B 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 20 A in the limited the area, and 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 11 A is provided with the measuring-electrode member 20 A and the reference-electrode member 20 B for substantially real-time detection of the developer remainder, further preferably, the developer chamber 9 A of the developing means 9 is provided with an antenna rod, that is, an electrode rod 9 h FIG. 3 is extended by a predetermined length in the longitudinal direction of the developing roller 9 a with a predetermined clearance from the developing roller 9 a. 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 9 a and the electrode rod 9 h.

According to the image forming apparatus of this embodiment, the amount of the developer in the developer container 11 A can be detected substantially in real-time, and on the basis of the detection, the consumption amount of the developer may be displayed so as to influence the user to prepare the replenishing cartridge and further to supply the developer upon the display of the emptiness.

A description will be provided 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 FIGS. 20 and 21. In FIGS. 20 and 21, an indicator 41 moves in accordance with the amount of the developer so that user is aware of the amount of the developer.

FIG. 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.

(Embodiment 2)

FIG. 23 is a schematic view of an electrophotographic image forming apparatus according to another embodiment of the present invention. The general arrangement of the electrophotographic image forming apparatus will first be described. In this embodiment, 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 an 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 the 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 the other 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 embodiment, the electrophotographic image forming apparatus is provided with a developer-amount detecting device for detecting substantially in 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 FIG. 24, it comprises a measuring-electrode member 20 A as a first electrostatic-capacity generating portion for detecting an amount of the developer, and a reference-electrode member 20 B 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 20 A 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 FIG. 24 or on an inner bottom surface of the developer-accommodating portion 57 as shown in FIG. 25 . The reference-electrode member 20 B may be disposed at any place in the main assembly of the apparatus if it does not contact the developer as shown in FIG. 24, or it may be disposed on the outside or outer surface of the developer-accommodating portion as shown in FIG. 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 contact the developer, as shown in FIG. 27 .

The measuring-electrode member 20 A has the same structure as that of Embodiment 1, as has been described in conjunction with FIGS. 10 and 11. More particularly, as shown in FIG. 10, it comprises a pair of electrodes 23 , 24 which are arranged in parallel with each other with a predetermined gap therebetween on the substrate 22 . In this embodiment, the electrodes 23 , 24 have at least one pair of electrode portions 23 a - 23 f, 24 a - 24 f juxtaposed in parallel with a predetermined gap G, and the electrode portion 23 a - 23 f, 24 a - 24 f are connected to the connecting-electrode portions 23 g, 24 g, 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 is not limited to those examples, and for example, as shown in FIG. 11, the electrodes 23 , 24 may be extended in a volute pattern with constant gap.

In this embodiment, too, the measuring-electrode member 20 A 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 20 A increases the electrostatic capacity between the electrodes 23 , 24 .

Therefore, according to this embodiment, the measuring-electrode member 20 A can detect the developer in the developer container 11 A on the basis of the area of the developer contacting the surface of the measuring-electrode member 20 A, using a predetermined calibration curve, irrespective of the cross-sectional configuration of the developer container 11 A or the configuration of the measuring-electrode member 20 A.

The measuring electrode member 20 A can be manufactured in the same manner as with Embodiment 1. Therefore, a 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 embodiment, the measuring-electrode member 20 A is disposed on the inner surface of the developer-accommodating portion 57 or on such an inner bottom surface that the 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 20 A, 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 contacts the measuring-electrode member 20 A (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 FIG. 24, by disposing the measuring-electrode member 20 A on one inner side of the developer-accommodating portion 57 , the percentage of the area contacting the developer to the cross-sectional area of the developer container in the YZ flat surface in FIG. 28, can be deduced or estimated from the detected electrostatic capacity. As shown in FIG. 29, the developer may exist unevenly along the longitudinal direction due to the demounting and mounting of the process cartridge for jam clearance or the like, due to the inclination of the process cartridge or due to an uneven printing pattern, as shown in FIG. 30 . By providing the measuring-electrode member 20 A 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 20 A, 20 A, so that correct detection of the developer remainder is accomplished.

As shown in FIG. 25, when the measuring-electrode member 20 A is disposed on the inner bottom surface of the developer container 11 A, the percentage of the contact area occupying the bottom area can be estimated so that the 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 20 A can be made larger than when the developer-amount detecting member 20 A is disposed at the end of the developer-accommodating portion 57 , so that the 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 the amount of the developer can be more correctly detected.

According to this embodiment, the developer-remaining-amount detecting device comprises a reference-electrode member 20 B having the same structure as the measuring-electrode member 20 A, as shown in FIG. 24 .

As has been described with Embodiment 1, the reference-electrode member 20 B has the same structure as the measurement-electrode member 20 A. More particularly, as shown in FIG. 10, it comprises a pair of electrodes 23 ( 23 a - 23 f ) and 24 ( 24 a - 24 f ) 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 FIG. 11 . The reference-electrode member 20 B 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 20 B 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 20 A.

Thus, according to the detecting device for the amount of the developer of this embodiment, the output of the measuring-electrode member 20 A is compared with the output of the reference-electrode member 20 B which is influenced by the change of the ambient conditions. For example, the electrostatic capacity of the reference-electrode member 20 B in a predetermined state is set to be the same as the electrostatic capacity of the measuring-electrode member 20 A when no developer exists, and then, the difference of the outputs of the reference-electrode member 20 B and the measuring-electrode member 20 A is indicative of the change of the electrostatic capacity caused by the presence of the developer, so that the 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 of the Embodiment 1 has been described in conjunction with FIG. 17, and therefore, the description thereof is omitted for simplicity.

As described in the foregoing, according to the developer-amount detecting device of this embodiment, use is made of the reference electrode member 20 B (calibration element) exhibiting the same capacity change in accordance with the ambient condition change as the measuring-electrode member 20 A, so that the detection error due to the variation of the ambient condition can be canceled or compensated for so that a high accuracy in the detection for the developer remainder can be accomplished.

According to this embodiment, the reference-electrode member 20 B as the calibration member may have another structure and can be disposed at another place.

For example, as shown in FIGS. 24 and 31, the reference-electrode member 20 B having the same structure as the measuring-electrode member 20 A may be placed in the main assembly of the image forming apparatus. With this structure, the electrostatic capacity of the reference-electrode member 20 B changes in the same manner as the measuring-electrode member 20 A 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 20 A.

As shown in FIGS. 26 and 27, the measuring-electrode member 20 A and the reference-electrode member 20 B 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 20 A and the reference-electrode member 20 B 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) 20 A and the reference-electrode member (calibration member) 20 B are placed in the same ambient conditions, the detection accuracy can be enhanced.

In the description of the foregoing embodiment, the electrode patterns 23 , 24 of the reference-electrode member 20 B 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 the area of the electrode patterns 23 , 24 of the reference-electrode member 20 B for calibration is different from the area of the electrode patterns 23 , 24 of the measuring electrode member 20 A. In this case, the output of the reference-electrode member 20 B is multiplied by a predetermined coefficient, and the multiplied output is compared with the output of the measuring-electrode member 20 A. Using such a structure, the size of the reference-electrode member 20 B can be reduced so that the space occupied by the detecting member can be reduced. Both of the members 20 A and 20 B are disposed at the same side of the developer accommodating portion, and in this case, the percentage of the pattern of the detecting member 20 A 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, according to this employment of the present invention, the developer-accommodating portion 57 is provided with the measuring-electrode member 20 A and the reference-electrode member 20 B. Further preferably, the developing zone 56 of the developing device is provided with an antenna rod, that is, electrode rode 54 (FIG. 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.

According to the image forming apparatus of this embodiment, the amount of the developer in the developer-accommodating portion 57 can be detected substantially in real-time, and on the basis of the detection, the consumption amount of the developer may be displayed so as to influence the user to prepare the replenishing cartridge and further to supply the developer upon the display of the emptiness.

In this embodiment, similarly to Embodiment 1, 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 FIGS. 20 and 21, or as shown in FIG. 22, and the main assembly of the electrophotographic image forming apparatus may be provided with a display portion of an LED or the like, and the LED is flickered in accordance with the amount of the developer.

(Embodiment 3)

FIG. 33 shows an electrophotographic image forming apparatus according to a further embodiment of the present invention. The electrophotographic image forming apparatus of this embodiment is generally the same as the image forming apparatus of Embodiment 2 except for the developing device 50 . Therefore, the same reference numerals are assigned to the element having the corresponding functions, and a detailed description thereof is omitted for simplicity.

In this embodiment, 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 Embodiment 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 the developer amount detecting member 20 A 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 embodiment, even in the case that developer-amount detecting members 20 A 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 20 B 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 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 a developer has decreased to such an extent that predetermined image quality is not provided.

According to an aspect of the present invention, the first electrostatic-capacity generating portion includes a first electroconductive portion and a second electroconductive portion, and the second electrostatic-capacity generating portion includes a third electroconductive portion and a fourth electroconductive portion, wherein the first electroconductive portion and the second electroconductive portion are juxtaposed with each other, and the third electroconductive portion and the fourth electroconductive portion are juxtaposed with each other.

According to another aspect of the present invention, each of the first electroconductive portion and the second electroconductive portion includes portions that are arranged at regular intervals, and each of the third electroconductive portion and the fourth electroconductive portion includes portions that are arranged at regular intervals, and the regular interval portions of the first electroconductive portion and the second electroconductive portion are parallel with each other, and the regular interval portions of the third electroconductive portion and the fourth electroconductive portion are parallel with each other.

According to a further aspect of the present invention, the first electroconductive portion and the second electroconductive portion include alternatingly arranged portions, and the third electroconductive portion and the fourth electroconductive portion include alternatingly arranged portions, and the first electroconductive portion includes a base portion and a plurality of branched portions extended from the base portion, and the second electroconductive portion includes a base portion and a plurality of branched portions extended from the base portion of the second electroconductive portion, wherein the branched portions of the first electroconductive portion and the branched portions of the second electroconductive portion are alternatingly arranged in parallel with each other at regular intervals.

According to a further aspect of the present invention, the first electroconductive portion and the second electroconductive portion include portions that are opposed to each other, wherein the branched portions of the first electroconductive portion are expended toward the second electroconductive portion, and the branched portion of the second electroconductive portion are expended toward the first electroconductive portion.

According to a further aspect of the present invention, the third electroconductive portion includes a base portion and a plurality of branched portions extended from the base portion, and the fourth electroconductive portion includes a base portion and a plurality of branched portions extended from the base portion of the fourth electroconductive portion, wherein the branched portions of the third electroconductive portion and the branched portions of the fourth electroconductive portion are alternatingly arranged in parallel with each other at regular intervals.

According to a further aspect of the present invention, the third electroconductive portion and the fourth electroconductive portion include portions which are opposed to each other, wherein the branched portions of the third electroconductive portion are expended toward the fourth electroconductive portion, and the branched portion of the fourth electroconductive portion are expended toward the third electroconductive portion.

According to a further aspect of the present invention, the first electrostatic-capacity generating portion and the second electrostatic-capacity generating portion have the same configuration, and the first electrostatic-capacity generating portion and the second electrostatic-capacity generating portion generate the same electrostatic capacities when voltages are applied thereto, when the first electrostatic-capacity generating portion and the second electrostatic-capacity generating portion do not contact the developer.

According to a further aspect of the present invention, the first electrostatic-capacity generating portion and the second electrostatic-capacity generating portion are disposed inside the developer-accommodating portion, and the first electrostatic-capacity generating portion is disposed inside the developer-accommodating portion, and the second electrostatic-capacity generating portion is disposed outside the developer-accommodating portion.

According to a further aspect of the present invention, the amount of the developer accommodated in the developer-accommodating portion is detected substantially in real-time on the basis of the electrostatic capacities generated by the first electrostatic-capacity generating portion and the second electrostatic-capacity generating portion when they are supplied with voltages, and a result of the detection is continuously or stepwisely displayed.

As described in the foregoing, according to the present invention, the remaining amount of the developer in the developer-accommodating portion can be detected in accordance with the consumption of the developer substantially in real-time. Regarding the detection of the remaining amount of the developer using the change of the electrostatic capacity between electrodes, the measurement errors attributable to the variation of the ambient conditions can be reduced.

While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claims.