Patent Grant
6892035
The present invention relates to a developing device, a process cartridge and an image forming apparatus, wherein an electrostatic latent image is formed through an electrophotographic process, and then is developed into a visual image with a developer contained in a developing device.
Here, the electrophotographic image forming apparatus is an apparatus which forms an image on a recording material through an electrophotographic process. The electrophotographic image forming apparatus may be an electrophotographic copying machine, an electrophotographic printer (a LED printer, a laser beam printer or the like), an electrophotographic printer type facsimile machine, an electrophotographic printer type word processor or the like.
The process cartridge is a cartridge containing as a unit an electrophotographic photosensitive drum and a charge member, a developing member or a cleaning member, the unit being detachably mountable to the main assembly of the image forming apparatus. The process cartridge is a cartridge containing as a unit an electrophotographic photosensitive drum and at least one of a charge member, a developing member and a cleaning member, the unit being detachably mountable to the main assembly of the image forming apparatus. The process cartridge may contain as a unit an electrophotographic photosensitive drum and at least a developing member, the unit being detachably mountable to a main assembly of the electrophotographic image forming apparatus.
In an electrophotographic image forming apparatus using the electrophotographic image forming process, use has been made of the process cartridge type in which the process cartridge comprises as a unit the electrophotographic photosensitive member and process means actable on the electrophotographic photosensitive member, the unit being detachably mountable to the main assembly of the electrophotographic image forming apparatus. With the use of the process cartridge type apparatus, the maintenance operation can be carried out in effect by the users without the necessity of relying on serviceman, and therefore, the operability is improved. Therefore, the process cartridge type apparatus is widely used in the field of electrophotographic image forming apparatus.
With the electrophotographic image forming apparatus of such a process cartridge type, the user exchanges the cartridge by himself or herself. Therefore, there is provided a developer amount detecting means by which the user is notified of the shortage of the developer in the process cartridge.
As a conventional example of the developer amount detecting means, there is a type in which two electrode rods are provided in the developer container of the developing means, and a change in the part between the two electrode rods to detect the presence or absence of the developer is detected. This is called a “yes-or- no type” device. Various systems of this type have been put into practice.
Recently, it is desired that the remaining amount of the developer is detected continuously or substantially in real-time (real-time or continuous type) and such detection has been provided. With this type of apparatus, the user can be notified of the remaining amount of the developer substantially in real-time to facilitate exchanging of the process cartridge.
Accordingly, it is a principal object of the present invention to provide a developing device, a process cartridge and an electrophotographic image forming apparatus wherein the remaining amount of the developer can be detected in substantially real-time.
It is another object of the present invention to provide a developing device, a process cartridge and an electrophotographic image forming apparatus wherein the remaining amount of the developer can be detected with precision.
According to an aspect of the present invention, there is provided an electrophotographic image forming apparatus, a process cartridge and a developing device for developing an electrostatic latent image formed on an electrophotographic photosensitive member, the developing device being usable with a main assembly of an electrophotographic image forming apparatus, the developing device comprising: a developing member for supplying a developer to the electrophotographic photosensitive member for developing the electrostatic latent image formed on the electrophotographic photosensitive member, a first electrode provided opposed to the developing member; and a second electrode disposed such that at least a lower end thereof takes a position lower than the first electrode when the developing device is mounted to the main assembly of the electrophotographic image forming apparatus. An electrical signal is generated in accordance with an electrostatic capacity between the first electrode and second electrode when the first electrode or second electrode is supplied with a voltage from the main assembly of the electrophotographic image forming apparatus, and is measured by the main assembly of the electrophotographic image forming apparatus to detect a remaining amount of the developer.
These and other objects, features, and advantages of the present invention will become more apparent upon consideration of the following description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings.
Hereinafter, a developing apparatus, a process cartridge, and an electrophotographic image forming apparatus, which are in accordance with the present invention, will be described with reference to the appended drawings.
First, referring to
The laser beam printer A has an electrophotographic photosensitive member in the form of a drum, that is, a photosensitive drum 7. The photosensitive drum 7 is charged by a charge roller 8 as a charging means, and the charged photosensitive drum 7 is exposed to the laser beam projected in accordance with image formation data, from an optical means 1, as an electrostatic latent image forming means, which has a semiconductor laser 1a as a light source, a rotational polygonal mirror 1c rotated by a scanner motor 1b, and a reflection mirror 1d. As a result, a latent image in accordance with the image formation data is formed on the photosensitive drum 7. This latent image is developed into a visible image, or a toner image, by a developing means 9.
More specifically, the developing means 9 has a development chamber 9A equipped with a development roller 9a as a developing member, and a developer container 11, as a developer holding portion. The developer container 11 is located next to the development chamber 9A, and contains a developer stirring-conveying member 9b (developer stirring means). As the developer stirring member 9b is rotated, developer T is sent to the developer roller 9a in the development chamber 9A. In the development chamber 9, a developer stirring member 9e is positioned adjacent to the development roller 9a, and circulates the developer through the development chamber 9A. The developer T used in this embodiment is magnetic developer.
The development roller 9a contains a stationary magnet 9c. As the development roller 9a is rotated, the developer is borne on the development roller 9a and is carried in the rotational direction of the development roller 9a. As the development roller 9a is further rotated, the developer on the development roller 9a is given triboelectrical charge by the development blade 9d while being formed into a developer layer with a predetermined thickness, and then is supplied to the development region of the photosensitive drum 7. As the developer is supplied to the development region, it is transferred onto the latent image on the photosensitive drum 7, forming a toner image. The development roller 9a is electrically connected to a development bias circuit, which applies development bias voltage to the development roller 9a. Normally, the development bias voltage is compound voltage, composed of AC voltage and DC voltage, applied to the development roller 9a.
Meanwhile, a recording medium 2, for example, a piece of ordinary paper, having been placed in a sheet feeder cassette 3a, is conveyed to a transfer station by a pickup roller 3b, conveyer roller pairs 3c and 3d, and a registration roller pair 3e, in synchronism with the formation of the toner image. In the transfer station, a transfer roller 4 as a transferring means is positioned. As voltage is applied to the transfer roller 4, the toner image on the photosensitive drum 7 is transferred onto the recording medium 2.
After the transfer of the toner image onto the recording medium 2, the recording medium 2 is conveyed to a fixing means 5 by a conveyance guide 3f. The fixing means 5 has a driver roller 5c and a fixing roller 5b. The fixing roller 5b contains a heater 5a. As the recording medium 2 is passed through the fixing means 5, the fixing means 5 fixes the unfixed toner image on the recording medium 2 to the recording medium 2 by the application of heat and pressure.
Thereafter, the recording medium is conveyed further, and is discharged into a delivery tray 6, through a reversing path 3j, by discharge roller pairs 3g, 3y, and 3i. The delivery tray 6 is located on top the main assembly 14 of the laser beam printer A, that is, an electrophotographic image forming apparatus. The pointing direction of a pivotal flapper 3k may be switched to discharge the recording medium 2 by a discharge roller pair 8m without passing the recording medium 2 through the reversing path 3j. In this embodiment, the aforementioned pickup roller 3b, the conveyer roller pairs 3c and 3d, the registration roller pair 3c, the conveyance guide 3f, the discharger roller pairs 3g, 3h, and 3i, and the discharge roller pair 3m, constitute a conveying means.
Referring to
The process cartridge B is removably mounted by a user into a cartridge mounting means provided in the main assembly 14 of the electrophotographic image forming apparatus, in the direction indicated by an arrow mark X. In this embodiment, the cartridge mounting means comprises a pair of guiding means 13R and 13L (unillustrated), and a pair of guiding portions 16R and 16L (unillustrated). The guiding means 13R are located, one for one, on the external surfaces of the end walls located at the longitudinal ends of the process cartridge B, as shown in
According to the present invention, the process cartridge B is provided with a developer amount detecting apparatus capable of continuously (substantially in real-time) detecting the amount of the developer remaining in the developer container 11, as the developer is consumed.
Referring to
The developer amount is detected by applying AC voltage to either the first or second electrodes 81 and 82 and measuring the electrical signals generated in accordance with the electrostatic capacity between the electrodes 81 and 82.
Next, the movement of the developer, and the manner in which the amount of the developer decreases, will be described, starting from a point in time prior to the shipment of the process cartridge, through the period in which the developer in a process cartridge is consumed after the mounting of the process cartridge into the main assembly 14 of the electrophotographic image forming apparatus.
Referring to
When a user uses a brand-new process cartridge, the user is to mount the process cartridge into the electrophotographic image forming apparatus main assembly 14 after removing the seal 30. Some of the recent electrophotographic image forming apparatuses, however, are structured so that the seal 30 is automatically removed after the mounting of a process cartridge into the electrophotographic image forming apparatus main assembly 14.
As described previously, the developer stirring-conveying member 9b is provided in the developer container 11. The developer stirring-conveying member 9b comprises a stirring shaft 9b1, and an elastic sheet 9bs (Mylar) attached to the stirring shaft 9b1. The developer within the developer container 11 is conveyed into the development chamber 9A by the rotation of the developer stirring-conveying member 9b. In this embodiment, the developer stirring-conveying member 9b rotates once in every four seconds.
Due to the function of the developer stirring-conveying member 9b, the developer is instantly sent into the development chamber 9A, smoothly readying the image forming apparatus for an image forming operation, even when the process cartridge B is used for the first time, that is, even immediately after the seal 30 is removed. Almost at the same time as the developer is sent into the development chamber 9A, it is also sent into the space between the first and second electrodes 81 and 82, changing the electrostatic capacity between the two electrodes.
There are the following four forces which affect the distribution of the developer in the adjacencies of the first and second electrodes 81 and 82:
When there is a sufficient amount of developer within the developer container 11 and development chamber 9A, the force (1) is extremely large, and the force (3) works as the lid for the recess 80, keeping the developer in the recess 80 confined in the recess 80; in other words, a state in which developer remains packed between the first and second electrodes 81 and 82 is maintained, and therefore, a high electrostatic capacity value is continuously shown.
As the usage of the process cartridge B continues, the amount of the developer in the adjacencies of the development roller 9a decreases due to the developer consumption for development. However, the adjacencies of the development roller 9a are continuously replenished with the developer from the developer container 11 by the function of the developer stirring-conveying member 9b. Thus, with the continuous usage of the process cartridge B, the amount of the developer within the developer container 11 decreases, and the top surface of the developer mass within the developer container 11 descends.
Referring to
Describing further
The manner in which the electrostatic capacity value between the two electrodes 81 and 82 changes in response to the surface of the developer mass position (amount of developer remainder) within the developer container 11 is affected by the fluidity of the developer in use and the conveying performance of the developer stirring conveying member 9b.
For example, when the developer has such fluidity as that of water, the position of the top surface of the developer mass in the developer container 11 perfectly coincides with the position of the top surface of the developer mass between the first and second electrodes 81 and 82. However, the actual fluidity of the developer is far lower than the fluidity of water, and therefore, even after a certain amount of the developer was conveyed into the development chamber 9A by the developer stirring-conveying member 9b, the top surface of the developer mass remains as it was prior to the conveyance of the developer into the development chamber 9A. Therefore, the position of the top surface of the developer mass between the first and second electrodes 81 and 82 also tends to change slightly behind the change in the position of the top surface of the developer mass in the developer container 11 as shown by FIGS. 7(a)-7(d).
The manner in which developer enters between the first and second electrodes 81 and 82 is affected by the performance of the developer stirring-conveying member 9b. In other words, if the conveying performance of the developer stirring-conveying member 9b is either excessively strong or excessively weak, the relationship between the change in the amount of the developer in the developer container 11 and the change in the value of the electrostatic capacity between the two electrodes 81 and 82 deviates
Therefore, the positions and shapes of the first and second electrodes 81 and 82 must be optimized according to the fluidity of the developer and the developer conveyance performance of the developer stirring-conveying member 9b.
As described above, the electrostatic capacity between the first and second electrodes 81 and 82 changes in response to the developer distribution in the regions which affect the sensitivities of the first and second electrodes, that is, the toner distribution in the recess 80 and the adjacencies thereof. However, the developer within the recess 80 remains under the above described various forces (1)-(4), and therefore, there is a tendency that the value of the electrostatic capacity does not stabilize until the aforementioned four forces reach virtual equilibrium. In other words, the value of this electrostatic capacity between the two electrodes 81 and 82 shows some deviations if the developer temporarily enters the aforementioned regions by an excessive amount, or if the entrance of the developer into the aforementioned regions lags.
The graph in
When an excessive amount of developer entered the aforementioned particular regions, the electrostatic capacity value suddenly increased as represented by a point indicated by a referential code p in FIG. 8(b), whereas when the developer entrance into the regions lagged, it took a certain length of time for the electrostatic capacity value to reach its equilibrium level as represented by a range indicated by a referential code q in FIG. 8(c).
One of the means for solving this problem is to reduce the dimension of the recess 80 in terms of the direction in which developer is conveyed; more specifically, the dimension of the recess 80 in terms of the developer conveyance direction should be reduced by shortening the first electrode 81, that is, the electrode having a greater distance from the development roller 9a, in such a manner that the position of the bottom end of the first electrode 81 moves upward. However, if the first electrode 81 is shortened by more than a certain length, the surface area of the condenser made up of the first and second electrodes 81 and 82 becomes too small to provide the condenser with a satisfactory amount of sensitivity. Therefore, the electrode 81 requires a proper length.
On the other hand, if the second electrode 82, that is, the electrode having a shorter distance from the development roller 9a, is extended so that its top end reaches the level of the top end of the recess 80, the distance between the first and second electrodes 81 and 82 within the recess 80 becomes too small, that is, small enough to raise the sensitivity of the aforementioned condenser to a level at which the condenser is capable of detecting the aforementioned fluctuation of the electrostatic capacity value, which occurs while the state of developer mass becomes stabilized. Therefore, the developer amount may not be accurately detected. Thus, it is not desirable to extend the second electrode 82 in the manner described above.
Referring to
In addition to the detecting method employing the above described structural arrangement, there are other detecting methods; for example, if a process cartridge is provided with a recording means, it is possible to record the print count, the duration of the process cartridge, and the like, so that the detection can be started for the first time after the elapse of a certain length of time which is thought to be needed for the aforementioned equilibrium to be realized.
It is desired to improve the accuracy with which the developer remainder amount is continuously detected to increase the amount of the change in the electrostatic capacity. More specifically, this objective can be accomplished by increasing the surface areas of the first and second electrodes 81 and 82, by reducing the distance between the first and second electrodes 81 and 82, and/or by the like methods. In order to increase the surface areas of the electrodes, the electrodes may be corrugated as shown in
Incidentally, if restrictions in cartridge design make it impossible to secure a space large enough for such electrodes as those described above, or if it is necessary to reduce process cartridge cost, one of the first and second electrodes 81 and 82 may be formed of a piece of round rod as shown in
Next, referring to
Referring to
As image formation continues, developer consumption progresses. Eventually, the developer between the longitudinal edge of the development blade 9d for regulating the developer amount on the peripheral surface of the development roller 9a, and the second electrode 82, that is, the developer between the development roller 9a and second electrode 82, is consumed, and thereafter, images with abnormal white spots are produced, signaling the developer depletion, or “no developer condition”.
The accuracy with which the developer level below which an image with abnormal white spots is produced is detected, can be drastically improved by electrically connecting the development roller 9a in such a manner as to create another condenser in which the development roller 9a functions as one of the electrodes (counterpart is the second electrode 82) and which is connected in parallel to the aforementioned condenser constituted of the first and second electrodes 81 and 82, as shown in FIG. 16.
The reason for the occurrence of a larger change in the electrostatic capacity relative to the change (consumption) in the toner amount in terms of the toner unit, immediately before the beginning of the period in which images with abnormal white spots occur, is that the abnormal white spots begin to be created as the amount of the toner on the peripheral surface of the development roller 9a begins to decrease. Therefore, measuring the amount of the developer on the peripheral surface of the development roller 9a as accurately as possible is one of the essential requirements for improving the detection accuracy.
It becomes possible to raise the “detection sensitivity” in the adjacencies of the development roller 9a by making the above described structural arrangement, in which the development roller 9a is made to double as one of the pair of electrodes in the aforementioned second condenser, while placing the second electrode 82, which functions as the counterpart to the development roller 9a, in the adjacencies of the development roller 9a. The difference in detection accuracy between FIGS. 17(a) and 17fb) was created by such a structural arrangement.
Further, in order to improve the accuracy with which the threshold developer level below which images with abnormal white spots are produced, it is necessary to improve “detection sensitivity” in the adjacencies of the peripheral surface of the development roller 9a.
Even when there is almost no developer on the peripheral surface of the development roller 9a, development is possible as long as developer is present in the adjacencies of the development blade 9d as is represented by the developer T in FIG. 18. Therefore, the accuracy, with which the threshold developer level below which images with abnormal white spots is detected, can be improved by improving the sensitivity with which the developer T in the above described region is detected.
Thus, in this embodiment, a third electrode 83 was provided, which was placed close to the longitudinal edge of the development blade 9d and extended in parallel to the development roller 9a as shown in FIG. 19. More specifically, the third electrode 83 was added as an extension of the second electrode 82, being bent toward the development blade 9d. As a result, the accuracy with which the threshold developer level was detected was further improved.
The above described third electrode 83 does not need to be a part of the second electrode 82. In other words, even if the third electrode 83 is independent from the second electrode 82, it does not matter as far as the threshold developer level detection accuracy is concerned. In such a case, the third electrode 83 may be constituted of a piece of a round rod instead of a piece of a metallic plate.
Further, when the third electrode 83 (portion angled relative to electrode 82) is formed as an electrode independent from the second electrode 82, there is a possibility that not only is the third electrode 83 used as a part of the means for continuously detecting developer remainder amount, but also can be used as a part of a means for highly accurately detecting the presence (absence) of developer.
As described above, the developer amount in the development chamber 9A is estimated by measuring the developer amount between the first and second electrodes 81 and 82, and the developer amount between the first and second electrode 61 and 82 can be measured by continuously detecting the electrostatic capacity between the first and second electrodes 81 and 82.
Further, the accuracy with which the threshold developer level below which images with abnormal white spots are formed is detected can be improved by providing the third electrode 83 as an integral part of the second electrode 82 and using the development roller 9a as the counterpart to the third electrode 83 which makes up the additional condenser with the development roller 9a.
In order to detect the developer remainder amount from the early stage of process cartridge usage, it is necessary to place a detecting means on the developer container side. On the other hand, in order to accurately detect the threshold developer level below which images with abnormal white spots are produced, it is necessary to place a detecting means in the adjacencies of the development roller 9a. Being able to satisfy these two mutually contradicting requirements with the provision of only a single detecting means characterizes this embodiment of the present invention. In other words, according to this embodiment, a detecting means is placed in the adjacencies of the development roller in such a manner that the detecting means is enabled to sense the change in the height of the developer mass. In other words, one of the essential characteristics of the process cartridge structure in this embodiment is that the developer amount within the developer container can be determined on the basis of the information regarding the developer sent by the developer stirring-conveying member 9b from the developer container 11.
The provision of the above described structure made it possible to continuously detect the developer remainder amount while maintaining a high degree of accuracy in detecting the threshold developer level below which images with abnormal white spots are produced. Further, the above described two mutually contradicting requirements were satisfied with the provision of only a single detecting means, and therefore, cost was reduced.
As for the electrode material, as long as the electrodes 81, 82, and 83 are formed of an electrically conductive substance, their functions remain similar to those described above. However, in this embodiment, a nonmagnetic metallic substance, for example, nonmagnetic SUS, was used as the electrode material to prevent the electrodes from interfering with developer circulation.
Further, if the electrodes 81, 82, and 83 are directly attached to the frame portion 12, which constitutes the wall of the development chamber 9A, by deposition or printing, for example, or if they are built into the frame portion 12 with the use of two color molding along with electrically conductive resin, the number of problems resulting from the electrode attachment errors and electrode specification errors will be much smaller; in other words, they will be attached to the frame portion 12 with a higher degree of accuracy.
In the above, this embodiment was described with reference to the structure of the process cartridge in which the amount of magnetic developer was continuously detected. However, this embodiment is also applicable to the structure of a developer container for containing on magnetic developer.
Next, referring to
The first electrode 81 and development roller 9a are connected to a development bias circuit 101 as a development bias applying means through a first contact point 92 (contact point 17 on the apparatus main assembly side) and a second contact point 91 (contact point 19 on the apparatus main assembly side), respectively. Among the electrodes on the measuring side, the second electrode 82 or the output electrode is connected to a control circuit 102 through a third contact point 93 (contact point 18 on the main assembly side). The third electrode 83 is provided as an integral part of the second electrode 82 as described above, although it is not illustrated in the drawing.
The development bias circuit 101 is connected to a reference capacity member 88 of the control circuit 102. A reference voltage V1 for detecting the developer remainder amount is set using an AC current I1 supplied from the development bias circuit 101.
The control circuit 102 sets the reference voltage V1 by adding a voltage drop V2 caused by the combination of an AC current I11 created by shunting the AC current I1 supplied to the reference capacity member 88, that is, an impedance element, at a volume VR1, and a resistor R2, to a voltage V3 set by resistors R3 and R4.
Therefore, an AC current 12 supplied to the first and second electrodes 81 and 82, or the electrodes on the measuring side, is inputted to an amplification circuit 103, from which it is outputted as a voltage V4 (V1−12×R5), the value of which represents the developer remainder amount. In other words, the value of this output voltage is used as a value which represents the developer remainder amount.
According to the electrophotographic image forming apparatus in this embodiment, the developer amount between the first and second electrodes is continuously detected as described above, and the amount of the developer consumption is displayed on the basis of the detected information, so that a user can be prompted to prepare a brand-new process cartridge or a developer replenishment cartridge. Further, the developer amount between the third electrode and developing member is detected, and the highly precise time at which developer depletion occurs is displayed on the basis of the detected information, so that a user can be prompted to replenish the process cartridge with developer. Incidentally, in this embodiment, the side from which voltage was applied comprised the development roller and first electrode, and the side from which signals were detected comprised the second and third electrodes. However, the same effects as those described above can be obtained even if the side from which voltage is applied comprises the development roller and second electrode, and the side from which signals are detected comprises the first and third electrodes.
It is difficult to design a process cartridge in which a pair of electrically conductive members are positioned inside the developer container, because such a design affords only a small amount of latitude in terms of the location, the shape, and the size of the conductive members. However, such a design makes it possible to reduce the distance between the pair of electrodes to a level which the conventional structural arrangement cannot match. Further, such a design makes it possible to place the pair of electrically conductive members in the adjacencies of the developing member, and therefore, it can improve the accuracy with which the threshold developer level below which images with abnormal white spots are formed is detected.
To describe the method for displaying the developer remainder amount, for example, there are a method in which the information detected by the above described developer amount detecting apparatus is directly displayed in the form of numerical value (for example, “10%”) on the screen 45 of a monitor of a personal computer 44 of a user as shown in
Next, the second embodiment of the present invention will be described with reference to
The structure and functions of the electrophotographic image forming apparatus in this embodiment are the same as those of the electrophotographic image forming apparatus in the first embodiment, and the components in this embodiment similar to those in the first embodiment are given the same referential codes as those given in the first embodiment. Further, the component arrangement in terms of the longitudinal direction, and the structure in the adjacencies of the electrodes, in this embodiment, which are the duplicates of those in the first embodiment, will not be described here.
Referring to
In this embodiment, the development roller 9a is electrically connected to the development bias circuit 101 as shown in
The magnetic developer in the adjacencies of the bottom surface of the development chamber 9A is always under the influence of the magnetic force generated in the direction to attract the magnetic developer to the development roller 9a, by the magnet 9c in the development roller 9a. Therefore, there is a tendency that as the amount of the developer supplied to the development roller 9a decreases due to the reduction in the amount of the developer in the developer container 11, the developer in the adjacencies of the bottom surface of the development chamber 9A is consumed before the developer in the other parts of the development chamber 9A.
More specifically, referring to
Since the developer in the process cartridge B is consumed as described above, the structural arrangement in this embodiment makes it possible to continuously detect the developer amount in the adjacencies of the bottom surface of the development chamber 9A.
The graph in
Thus, when it is necessary to increase the detection sensitivity to the threshold developer level, it is possible to employ an additional element such as the third electrode 83 in the first embodiment. However, in order to increase the sensitivity of the developer amount detecting apparatus, in the bottom portion of the development chamber 9A, a rod electrode 87 as an intermediary electrode, which extends across the entire longitudinal range of the development roller 9a, in parallel to the development roller 9a and developer path electrode 84, as shown in
Next, the third embodiment of the present invention will be described.
Also in this embodiment, an image forming apparatus which is similar in structure and function to the image forming apparatus in the first or second embodiments was employed. The components in this embodiment similar to those in the first and second embodiments will be given the same referential codes. Further, the component arrangement in terms of the longitudinal direction of the process cartridge, the structures in the adjacencies of the electrodes, and the like, which are identical to those in the first and second embodiments, will not be described.
According to the arrangement in this embodiment, the developer remainder amount can be detected much more accurately than in the first and second embodiments.
As one of the methods for improving detection accuracy, it is possible to increase detection sensitivity. However, it is difficult to substantially increase the sensitivity by simply making a few changes to the shapes and positioning of the electrodes, based on the structures in the first and second embodiments.
Thus, in this embodiment, the structural arrangement in the first embodiment, in other words, the structure having the first, second, and third electrodes 31, 32, and 83 as illustrated in
With regard to the threshold developer level detection, a sufficient level of detection accuracy was achieved by the condenser portion constituted of a combination of the third electrode 83 and development roller 9a in the first embodiment, and therefore, the intermediary electrode 87 was not employed in this embodiment. However, employing the intermediary electrode 87 depending on circumstances does not cause any problem, and will provide the same effects as those provided by this embodiment.
With the provision of the above described structural arrangement, the detection sensitivity increases by a large margin, and therefore, the developer remainder amount can be continuously detected with greater accuracy. Further, the area in which the developer remainder amount can be detected extends across the entire range of the development chamber 9A in terms of its longitudinal direction, and therefore, even if the state of the developer mass in the developer container 11 temporarily changes due to circumstances, for example, because a process cartridge is taken out of the image forming apparatus main assembly and is shaken, the developer remainder amount detected after such a temporary change rarely deviates from the developer remainder amount detected prior to such a change.
In this embodiment, the development roller 9a and first electrode 81 are equalized in electrical potential, and are connected to the development bias circuit 101, whereas the second electrode 82 and developer path electrode 84 are equalized in electrical potential level and are connected to the control circuit 102 of the developer amount detection circuit 100.
How these electrodes or their equivalents are connected in terms of circuit design does not need to be exactly as described above; it does not matter as long as their connection realizes a high level of detection sensitivity, in particular, in the adjacencies of the bottom surface of the development chamber, and also in the adjacencies of the first and second electrodes 81 and 82.
Also regarding the connection of the a electrodes, cost increase can be avoided by equalizing, in electrical potential level, the electrodes which are to be equalized in electrical potential level, by connecting them to each other, because such an arrangement does not increase the number of contact points between these electrodes and the power source on the main assembly side.
FIGS. 30(a) and 30(b) show the relationships between the changes in the developer amount, and the changes in the electrostatic capacity which occurred in response to the changes in the developer amount, in the first and second embodiments, respectively. FIG. 30(c) shows a typical relationship between the changes in the developer amount, and the changes in the electrostatic capacity which occurred in response to the change in the developer amount, when the structure in this embodiment was employed.
It is evident from these graphs that the developer remainder amount can be also accurately detected with the use of the structure in this embodiment.
Also in this embodiment, a flat piece of electrically conductive material was employed as the developer path electrode 84, and was fixed to the internal surface of the container wall. However, the configuration of the developer path electrode 84 does not need to be limited to the one employed in this embodiment. For example, the developer electrode 84 may be fixed to the external surface of the container wall, or it may be fixed in a manner to hold a certain distance from the container wall. Further, it may comprise a plurality of electrically conductive rods placed in parallel. In other words, as long as it is placed across the path through which developer is conveyed to the developing member by the developer stirring-conveying member, it is possible to obtain the same effects as those obtained with the use of the structural arrangement in this embodiment.
Incidentally, in the above described embodiments, the developer remainder amount can be continuously detected while the developer remainder amount is in a range from approximately 30% down to 0%, assuming that the developer container is 100% full prior to its initial usage of a process cartridge. However, the present invention is not limited by this arrangement. In other words, the range in which the developer remainder amount in the container can be continuously detected may be set to a range from 50% down to 0% or a range from 40% down to 0%, for example. Here, an indication that the developer remainder amount is 0% does not means that the developer has been completely depleted. It also includes such a condition that the developer amount in the container has decreased to a level below which an image with a predetermined level of quality can not be obtained.
As is evident from the above description of the embodiments of the present invention, according to the present invention, the developer amount can be continuously detected with a high level of accuracy, and therefore, usability can be improved.
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2000105505 | Apr 2000 | JP | national |
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| Number | Date | Country | |
|---|---|---|---|
| 20020021908 A1 | Feb 2002 | US |
