The present invention relates to a developing device in which a two-component developer that is a mixture of a toner and a carrier is used for a latent image formed on an image bearing member, and an excessive portion of the developer is dischargeable while a fresh portion of the developer is supplied.
In a hitherto known electrophotographic image forming apparatus, a latent image formed on an image bearing member is developed with a developer contained in a developing device, whereby the latent image is visualized as a toner image. A two-component developing method employing, as the developer, a two-component developer that is a mixture of a nonmagnetic toner and a magnetic carrier, mainly, is more beneficial in the long-term stability of image quality and so forth than other developing methods that are currently proposed.
As described above, in the developing device 4 that uses the two-component developer, the toner and the carrier of the two-component developer contained in the developing device 4 are stirred and are charged by friction. Subsequently, the charged toner is supplied to the photoconductor drum 1 by the developing sleeve 41. Thus, the latent image on the photoconductor drum 1 is developed. In this process, while the toner is consumed and supplied, the carrier is neither consumed nor supplied but remains in the developing device 4. Therefore, the carrier is stirred in the developing device 4 more frequently than the toner. Such a situation tends to lead to a deterioration in the charging ability due to accumulation of external additives, adhesion of wax, toner spent, and so forth. Consequently, the amount of developer conveyed is reduced, the amount of charge generated by physical friction of particles of the developer becomes insufficient, and the resulting image may have defects such as nonuniformity in density or fog in a white background.
Accordingly, in the related art, such deterioration of the carrier is suppressed by supplying not only the toner but also the carrier, according to need, into the developing device 4 from a developer supply port 49. Meanwhile, an excessive portion of the two-component developer that gradually builds up in the developing device 4 with the supply of the carrier is collected from a developer discharge port. Thus, while the toner whose amount is reduced with the consumption thereof is supplied, the deteriorated portion of the carrier in the developing device 4 is replaced with a fresh refill of the carrier. Such a developing method is proposed by PTL 1.
In the above developing method, the two-component developer containing the carrier is supplied while being discharged. Therefore, the deterioration of the carrier is suppressed, and the development characteristics exhibited by the two-component developer in the developer container are kept constant. Consequently, the deterioration in the image quality due to changes in the development characteristics of the developer can be suppressed over a long time.
Regarding an image forming apparatus or an exchangeable developing device or process cartridge, shipping techniques in which an initial portion of the developer that is to be used initially is sealed in the developing device so as to be isolated from outside air are proposed by PTL 2 and PTL 3. This is because of the following reason. If the developer is left exposed to outside air having a high temperature and a high humidity, the developer absorbs the moisture and is deteriorated. Consequently, the developer becomes unable to exhibit desired performance at the time of initial startup. The above techniques also produce an effect of preventing the developer from leaking from the developing device or the process cartridge during transportation after the shipment. The technique according to PTL 2 includes a proposal in which a sealing member that seals in the developer is released by a user or a serviceman. The technique according to PTL 3 includes a proposal in which, when the developing device is attached to an image-forming-apparatus body and is activated, a sealing member is wound up and is thus released.
PTL 1: Japanese Patent Publication No. 2-21591
PTL 2: Japanese Patent Laid-Open No. 2006-201528
PTL 3: Japanese Patent Laid-Open No. 2011-242639
However, when the configuration proposed by PTL 2 or PTL 3 in which the initial developer was sealed in the developing device was applied to the developing device or the process cartridge disclosed by PTL 1 that had the discharge port for discharging the developer, the following hindrance occurred.
At the time of initialization of the developing device or the process cartridge, a load torque that occurred at the releasing of the sealing member that sealed in the developer caused cracking of gears/chipping of gear teeth or damage to the stirring screw in some cases. This hindrance tended to be pronounced particularly when the initial developer in the developing device or the process cartridge was distributed unevenly in the development container as a result of transportation or the like.
The present invention is based on the above background, an aspect of the present invention is to provide a developing device including a sealing member that seals an initial portion of a developer in a developing device and in which the load torque generated at the releasing of the sealing member is small even if the distribution of the developer in a development container at the releasing of the sealing member is uneven.
The above aspect is achieved by the following developing device according to the present invention. Specifically, a developing device includes: a first chamber that contains developer in an initial state; a second chamber that provides, in combination with the first chamber, a path of circulation of the developer; a partition that separates the first chamber and the second chamber from each other; a first conveying member that conveys the developer in the first chamber; a second conveying member that conveys the developer in the second chamber; a first communication port provided on a downstream side in a direction of conveyance in the first chamber and that delivers the developer from the first chamber to the second chamber; a second communication port provided on an upstream side in the direction of conveyance in the first chamber and that delivers the developer from the second chamber to the first chamber; a first sealing portion bonded to a periphery of the first communication port and that releasably seals the first communication port; a second sealing portion bonded to a periphery of the second communication port and that releasably seals the second communication port; a supply port from which the developer is supplied, the developer being a mixture of a magnetic carrier and a nonmagnetic toner; a discharge port from which an excessive portion of the developer is dischargeable; a third sealing portion bonded to a periphery of the discharge port and that releasably seals the discharge port; and a winding shaft to which the first sealing portion, the second sealing portion, and the third sealing portion are attached and that is capable of winding up the sealing portions when receiving a driving force, wherein a total bonded area of each of the sealing portions in a width direction that is orthogonal to a direction of releasing of the sealing portion varies in the direction of releasing of the sealing portion, wherein positions of the respective sealing portions at each of which the bonded area in the width direction is largest start to be released at different timings, and wherein the first communication port, the discharge port, and the second communication port start to be opened in that order.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
First Embodiment
An image forming apparatus according to a first embodiment of the present invention will now be described in detail with reference to the drawings. The first embodiment concerns an exemplary full-color, two-component-developer image forming apparatus of a so-called tandem type in which photosensitive drums for different colors are arranged side by side. Nevertheless, the present invention only needs to have features of a developing device according to the following embodiment. For example, the present invention may be a structure that transfers an image formed on a photosensitive drum to an intermediate transfer member and further transfers the image transferred to the intermediate transfer member to a recording material (an intermediate transfer method). Alternatively, the present invention may be a structure that directly transfers an image formed on a photosensitive drum to a recording material. Alternatively, the present invention may be an image forming apparatus including one photosensitive drum. Moreover, the present invention can be embodied regardless of whether it is of a full-color or monochrome type.
<Outline of Image Forming Apparatus According to First Embodiment> See
As illustrated in
The exposure devices 3a, 3b, 3c, and 3d each include a light source device and a polygon mirror that are provided in a lower part of the image forming apparatus but are not illustrated. Laser light emitted from the light source device is scanningly moved with the rotation of the polygon mirror. The scanning beam of light is deflected by a plurality of reflecting mirrors. Subsequently, the deflected beam of light is focused, i.e., exposure is performed, on the generating line of a corresponding one of the photosensitive drums 1a, 1b, 1c, and 1d by an fθ lens. Thus, an electrostatic latent image corresponding to an image signal is formed on the corresponding one of the photosensitive drums 1a, 1b, 1c, and 1d.
The developing devices 4a, 4b, 4c, and 4d are each filled with a predetermined amount of two-component developer in which a nonmagnetic toner having a corresponding one of colors of yellow, magenta, cyan, and black and a magnetic carrier are mixed at a predetermined mixing ratio. The developing devices 4a, 4b, 4c, and 4d sequentially form toner images by developing the latent images on the photosensitive drums with the toners having the respective colors. The toner images obtained through the development undergo primary transfer to the intermediate transfer belt 11. Furthermore, a transfer material P stored in a transfer-material cassette 14 is conveyed to a secondary transfer device 12. The toner images on the intermediate transfer belt 11 undergo secondary transfer to the transfer material P. The toner images are then fixed with heat and pressure by a fixing unit 9. Subsequently, the transfer material P having the thus obtained recorded image is discharged to the outside of the apparatus.
An intermediate-transfer-belt-cleaning blade 13 for cleaning fog toner particles, post-secondary-transfer toner particles, and the like off the surface of the intermediate transfer belt 11 is provided constantly in contact with a position of the intermediate transfer belt 11 that is on the downstream side with respect to the position of secondary transfer to the transfer material P in the direction of rotation of the intermediate transfer belt. Meanwhile, post-primary-transfer toner particles and the like remaining on the photosensitive drums 1a, 1b, 1c, and 1d are collected by the respective cleaning devices 6a, 6b, 6c, and 6d.
<Outline of Image Forming Station of Image Forming Apparatus> See
As illustrated in
The developing device 4a includes a development container 40a. The development container 40a contains a two-component developer (a developer) mainly composed of a nonmagnetic toner (a toner) and a magnetic carrier (a carrier). The development container 40a has an opening in a portion thereof that faces the photosensitive drum 1a. A developing sleeve 41a as a developer bearing member is rotatably provided in the opening, with a portion of the developing sleeve 41a exposed to the outside.
The developing sleeve 41a is made of a nonmagnetic material. The surface of the developing sleeve 41a is roughened so as to be able to bear and convey the developer. The developing sleeve 41a includes thereinside a fixed magnet 42a as magnetic-field-generating means. In the developing operation, the developing sleeve 41a rotates in a direction of an arrow X (the counterclockwise direction) illustrated in
A predetermined development bias is applied to the developing sleeve 41a by a high-voltage power supply 102a. In the first embodiment, the development bias voltage is an oscillation voltage in which a direct-current voltage and an alternating-current voltage are superimposed on each other. More specifically, the development bias voltage is an oscillation voltage in which a direct-current voltage of −350 V and an alternating-current voltage in the form of a rectangular wave that is at a frequency of 8.0 kHz and whose peak-to-peak voltage Vpp is 1.8 kV are superimposed on each other. With the development bias and the electric field of the electrostatic latent image formed on the surface of the photosensitive drum 1a, the electrostatic latent image is reversely developed.
A transfer bias voltage under predetermined conditions is applied to the primary transfer device 7a by a high-voltage power supply 103a. In the first embodiment, the primary-transfer bias voltage is a direct-current voltage. More specifically, the primary-transfer bias voltage is a direct-current voltage of +800 V. With the primary-transfer voltage, the toner image formed on the photosensitive drum 1a undergoes primary transfer to the intermediate transfer belt 11.
<Outline of Developer Contained in Developing Device According to First Embodiment>
Now, the two-component developer composed of the toner and the carrier and that is contained in the developing device 4a according to the first embodiment will be described in detail.
The toner is composed of pre-colored resin particles to which binder resin, a colorant, and any other additives, if necessary, are added; and pre-colored particles to which an external additive such as colloidal-silica fine powder is externally added. The toner is a negatively chargeable polyester-based resin and preferably has a volume-mean particle size of 4 μm or larger and 10 μm or smaller, or more preferably 8 μm or smaller. The mean particle size of the nonmagnetic toner according to the first embodiment was set to about 6.0 μm, considering the image quality and the ease of handling. For better fixability, many of recent-year toners have low melting points or low glass-transition points Tg (for example, Tg≦70° C.). Furthermore, for better releasability after fixing, some toners contain wax.
The developer according to the first embodiment is a wax-containing pulverized toner.
Preferable examples of the carrier are metals such as iron, nickel, cobalt, manganese, chromium, and rare earth each containing particles having oxidized or unoxidized surfaces; an alloy of any of the foregoing metals; oxide ferrite; and the like. The method of manufacturing such magnetic particles is not specifically limited. The carrier has a weight-mean particle size of 20 to 60 μm or preferably 30 to 50 μm, and a resistivity of 10^7 Ωcm or higher or preferably 10^8 Ωcm or higher. In the first embodiment, a carrier having a resistivity of 10^8 Ωcm was used.
Regarding the toner used in the first embodiment, the volume-mean particle size was measured by the following instrument and method. The measuring instrument used was a sheath-flow electric-resistance particle-size-distribution-measuring instrument SD-2000 (manufactured by Sysmex Corporation). The measurement method was as follows. Specifically, 0.1 ml of a surface-active agent as a dispersant, preferably, alkylbenzene sulfonate, was added to 100 to 150 ml of 1% NaCl electrolytic aqueous solution prepared by using primary sodium chloride, and 0.5 to 50 mg of a measurement sample was added thereto. The electrolytic aqueous solution in which the sample had been suspended was dispersed for about 1 to 3 minutes by using an ultrasonic dispersion device. Then, the volume-mean distribution was measured by using the above sheath-flow electric-resistance particle-size-distribution-measuring instrument SD-2000. As a condition for the measurement, the particle-size distribution of particles whose size was 2 to 40 μm was measured by using an aperture of 100 μm, whereby the volume-mean distribution was obtained. On the basis of the thus obtained volume-mean distribution, the volume-mean particle size was obtained.
The resistivity of the carrier used in the first embodiment was measured as follows. A sandwich-type cell having a measurement-electrode area of 4 cm and a distance between electrodes of 0.4 cm was used. A voltage E (V/cm) was applied between the two electrodes while a pressure corresponding to a weight of 1 kg was applied to one of the electrodes. On the basis of the current that flowed through the circuit, the resistivity of the carrier was obtained.
In the first embodiment, the development container 40 contains 240 g of two-component developer in which the toner and the carrier described above are mixed at a weight ratio of about 8:92, so that the toner concentration (the proportion (ratio) of the weight of the toner with respect to the total weight of the developer: the TD ratio) becomes 8%. Toner bottles Ta, Tb, Tc, and Td each contain refill developer in which the toner and the carrier are mixed at a weight ratio of about 90:10, so that the toner concentration (the proportion (ratio) of the weight of the toner with respect to the total weight of the developer: the TD ratio) becomes 90%.
<Outline of Developer Circulation in Developing Device According to First Embodiment> See
<Outline of Configuration Around Discharge Port of Developing Device According to First Embodiment> See
Referring to
In the developing device configured as described above, when the image forming operation progresses and the refill developer containing the carrier is supplied to the developing device, the amount of developer in the development container 40 tends to gradually increase because only the toner is consumed in the image forming operation. Accordingly, the surface level of the developer in the development container 40 rises with the increase in the amount of developer. If the surface level of the developer goes over a certain point, the conveying ability of the reverse screw 452 is disabled. In such an event, the developer flows over the reverse screw 452. The developer discharge mechanism is provided on the downstream side of the reverse screw 452 and includes a small-size discharge screw 453 as a third screw portion that is capable of conveying the developer in the direction of conveyance B. The discharge screw 453 includes a helical blade whose direction of the helix is the same as that of the blade forming the fin 451 having the helical blade-like shape. The small-size discharge screw 453 conveys the developer to a developer discharge port 50 and drops the developer into a waste toner container that is not illustrated. Thus, the used carrier particles are replaced with initial carrier particles. The developer discharge port 50 is provided with a discharge port shutter 51 with which the developer discharge port 50 is openable and closable. When the developing device 4 is detached from the image-forming-apparatus body 100, the developer discharge port 50 is closed by the discharge port shutter 51, whereby the developer is prevented from leaking from the developing device 4.
<Outline of Configuration for Sealing Initial Developer in Developing Device According to First Embodiment> See
A configuration that seals in the initial developer according to the first embodiment will now be described with reference to
As illustrated in
<Outline of Configuration for Winding Up Seals that Seal Initial Developer in Developing Device According to First Embodiment> See
The gear train 56 will now be described with reference to
Furthermore, the gear 562 and gears 565, 566, and 567 that are in mesh with one another cause the winding shaft 55 to rotate. The gears 566 and 567 are worm gears that significantly reduce the speed of rotation so that the winding shaft 55 can generate a torque required for releasing the sealing sheets 52, 53, and 54. Hence, according to the first embodiment, the developing sleeve 41, the first stirring screw 44, the second stirring screw 45, and the winding shaft 55 are all rotated together by the driving of one driving motor 58.
Thus, the developing sleeve 41 rotates at a rotation speed of 300 rpm, the first stirring screw 44 rotates at a rotation speed of 400 rpm, the second stirring screw 45 rotates at a rotation speed of 450 rpm, and the winding shaft 55 rotates at a rotation speed of 9.5 rpm. Furthermore, in the developing device 4 according to the first embodiment, the developing sleeve 41 has an outside diameter φ of 20 mm, the first stirring screw 44 and the second stirring screw 45 each have an outside diameter φ of 16 mm, and the winding shaft 55 has an outside diameter φ of 4 mm.
<Controlling Operation at Initialization of Developing Device According to First Embodiment> See
Initialization executed when the developing device 4 is attached to the image forming apparatus 100 will now be described with reference to
The image forming apparatus 100 includes a CPU 60. The CPU 60 is connected to a RAM 61 used as a working memory, and to a ROM 62 that stores programs to be executed by the CPU and various data. The CPU 60 is also connected to an I/O 63 that activates various sensors provided to the developing devices for the respective colors, the development motors 58 for the respective colors that drive the respective developing devices, and so forth; and to new/old detecting means 64 that detects whether or not the individual developing devices 4 attached are new.
Normally, if any of the developing devices 4 or drum units of the image forming apparatus 100 are replaced with new ones, each of those developing devices 4 is initialized. The initialization progresses as follows. When the power of the image forming apparatus 100 is turned on (step S1), the new/old detecting means 64 detects whether the current developing devices 4 are new or old (step S2) and determines whether the developing devices 4 are new or used (step S3). The developing devices 4 according to the first embodiment are each provided with a fuse as the new/old detecting means 64. A substrate-side terminal of the fuse is in contact with a contact point provided on the body of the image forming apparatus 100. Here, if the developing device 4 is new, a predetermined current is supplied to the fuse and the fuse is broken. Thus, it is determined that the developing device 4 is new. If the developing device 4 is not new but used, the current does not flow because the fuse has already been broken. Therefore, it is determined that the developing device 4 is used. If it is determined that the developing device 4 is new in step S3, the development motor 58 starts to be driven (step S4) and is idled for a predetermined period of time (step S5). In the first embodiment, the idling period was set to 120 sec. During the idling period, the developing sleeve 41, the first stirring screw 44, second stirring screw 45, and the winding shaft 55 are rotated, and the sealing sheets 52 and 53 and the discharge port sealing sheet 54 are released. Thus, the two-component developer contained in the stirring chamber is allowed to circulate throughout the developing device. Consequently, while the surface level of the developer is evened out, the amount of charge imparted to the toner is increased by stirring.
After the developing device 4 is idled for the predetermined period of time, conditions for image formation are set (step S6). Under predetermined conditions for image formation (conditions regarding the photoconductor drum 1 such as the charging voltage, the development bias voltage, the transfer voltage, a tone-correction table, and so forth), toner test patterns based on different exposure values (for a low density and an intermediate density) are formed on the photoconductor drum 1. Subsequently, conditions for sensors are set (step S7). Then, output values (the optimum charging voltage, the optimum development bias voltage, the optimum transfer voltage, and the optimum tone-correction table) are estimated by a density sensor provided on the intermediate transfer belt 11. When the above conditions are all set, the driving of the development motor 58 is stopped (step S8). Thus, the initialization ends (step S9).
Now, the most characteristic feature of the present invention will be described.
First, regarding the driving-torque load applied to the developing device during 120 sec of idling performed in the initialization of the developing device, results of experiments conducted without the developer will be described in detail. This is considered to be the base of the driving-torque load applied to the developing device. Subsequently, the order of winding of the seals, which is characteristic of the present invention, will be described.
Then, temporal changes in the driving-torque load in a state where the stirring chamber is filled with the developer will be described.
Lastly, how the torque load applied to the developing device increases with changes in the state of the developer in the stirring chamber will be described. Thus, an effect of suppressing the torque that is generated in the first embodiment of the present invention will be described.
<Driving-Torque Load Applied to Developing Device (without Developer)> See
As illustrated in
First, the torque load generated when the seals 52, 53, and 54 are wound up and thus released will be described.
First, in a period from 0 to 3 sec, as illustrated in
In a subsequent period from 3 to 4.8 sec, as illustrated in
In a subsequent period from 5 to 13 sec, as illustrated in
In a subsequent period from 13 to 14.8 sec, as illustrated in
In the last period from 15 to 120 sec, all of the thermally welded parts between the first opening 461 and the seal 52 have been released, which is the same state as the state 520. The developing device is driven only with the torque (=0.1 kgf·cm) that is required for driving the winding shaft 55, the developing sleeve 41, and the first and second stirring screws 44 and 45 (a state 524).
Thus, the driving-torque load changes with time when initialization is executed without the developer and with only the seal 52 thermally welded. Other experiments that are the same as the above were conducted, in one of which only the seal 53 was thermally welded, and in another of which only the seal 54 was thermally welded. The results are graphed in
Lastly,
<Order of Winding of Seals> See
A configuration according to the first embodiment that defines the order of winding of the seals, which is characteristic of the present invention, will now be described. In the first embodiment, as described above with reference to
Specifically, as graphed in
Furthermore, regarding the positions of the bonded parts of the seal 52 and the seal 53, the seals are each thermally welded in areas each having a width of about 4 mm and that are on the lower side and on the upper side, respectively, of a corresponding one of the first opening 461 and the second opening 462. The first opening 461 and the second opening 462 each have a height of 16 mm. These thermally welded parts are each wound up by the winding shaft 55 of φ4 that is rotated at 9.5 rpm. In this case, it takes about twelve seconds from the start to the completion of the releasing. The seal 54 provided over the developer discharge port having an opening width in the winding direction of 4 mm is thermally welded in areas each having a width of about 4 mm and that are on the upstream side and on the downstream side, respectively, of the developer discharge port in the direction of winding. These thermally welded parts are each wound up by the winding shaft 55 of φ4 that is rotated at 9.5 rpm. In this case, it takes about six seconds from the start to the completion of the releasing.
In the first embodiment, as graphed in
The method of controlling the order of winding of the seals is not limited to providing such play slacks and may be any other method. For example, the diameter of the winding shaft 55 may be varied with the positions to which the seals are pasted. Such a method also produces the advantageous effect of the present invention without hindrance.
While the first embodiment concerns an exemplary case where the first opening 461, the second opening 462, and the developer discharge port 50 each have a substantially rectangular shape, the present invention is not limited to such a case. The timings of rapid increases in the driving torque at the time of releasing only need to be staggered with respect to one another, considering the shapes of the seals.
<Temporal Changes in Driving-Torque Load with Stirring Chamber Filled with Developer>
Now, temporal changes in the driving-torque load according to the first embodiment that are observed during initialization performed in a state where the stirring chamber is filled with the developer will be described in detail.
First, a case where the developer in the stirring chamber is distributed substantially evenly in the longitudinal direction will be discussed.
First, before the seal 52 starts to be released, the developer that is conveyed by the stirring screw cannot be discharged anywhere from the stirring chamber. Therefore, the developer is pushed toward the first opening 461 and toward the developer discharge port 50. Such a movement of the developer increases the driving-torque load, and the driving-torque load becomes largest (peak (1)) when the seal is released. As the first opening 461 is gradually opened, the rate of increase in the torque that is attributed to the developer is reduced a little. However, the torque attributed to the pushing of the developer that is conveyed by the stirring screw continues to increase. When the seal 54 starts to be released (at peak (2)) and the discharge port 50 starts to be opened, the increase in the torque attributed to the pushing of the developer subsides at last. Then, the seal 54 continues to be released, and the discharge port 50 is completely opened (at peak (3)). Substantially at this point of time, the torque load attributed to the developer starts to be reduced. Subsequently, when the seal 52 is released and the first opening 461 is completely opened (at peak (4)), the torque attributed to the developer is further reduced. Then, the torque load attributed to the developer is stabilized at about 0.5 kgf·cm. In this state, the seal 53 starts to be released (at peak (5)) and is then completely released (at peak (6)).
As described above, in the first embodiment of the present invention, the total torque applied to the developing device in the above case can be suppressed to about 1.4 kgf·cm at maximum.
Now, another case will be discussed where the developer in the stirring chamber is distributed more on the side of the first opening 461 in the longitudinal direction. Such a situation is triggered by, for example, transportation or the like.
First, before the seal 52 starts to be released, the developer that is conveyed by the stirring screw cannot be discharged anywhere from the stirring chamber. Therefore, the developer is pushed toward the first opening 461 and toward the discharge port 50. Such a movement of the developer increases the driving-torque load, and a peak of the driving-torque load (peak (7)) appears when the seal is released. The driving-torque load at this point of time was very large, about 3.2 kgf·cm, because the developer was initially distributed more on the side of the first opening 461. Subsequently, as the first opening 461 is gradually opened, the rate of increase in the torque that is attributed to the developer is reduced a little. However, the torque attributed to the pushing of the developer that is conveyed by the stirring screw continues to increase. When the seal 54 starts to be released (at peak (8)) and the discharge port 50 starts to be opened, the increase in the torque attributed to the pushing of the developer subsides at last. Then, the seal 54 continues to be released, and the discharge port 50 is completely opened (at peak (9)). Substantially at the same point of time, the torque load attributed to the developer starts to be reduced. Subsequently, when the seal 52 is released and the first opening 461 is completely opened (at peak (10)), the torque attributed to the developer is further reduced. Then, the torque load attributed to the developer continues to be reduced and is saturated at about 0.5 kgf·cm at the elapse of about thirty-five seconds. During this process, the seal 53 starts to be released (at peak (11)) and is then completely released (at peak (12)).
As described above, if the developer in the stirring chamber is distributed more on the side of the first opening 461 as a result of transportation or the like, the driving-torque load included in the total torque applied to the developing device tends to increase because the load attributed to the developer tends to be large. However, even in such a case, according to the first embodiment of the present invention, the total torque applied to the developing device can be suppressed to about 4.3 kgf·cm at maximum.
Lastly, a comparative embodiment in which the seals start to be released in the order of the seal 52, the seal 53, and the seal 54 will be described. In the comparative embodiment also, the case where the developer in the stirring chamber is distributed more on the side of the first opening 461 in the longitudinal direction will be discussed.
First, before the seal 52 starts to be released, the developer that is conveyed by the stirring screw cannot be discharged anywhere from the stirring chamber. Therefore, the developer is pushed toward the first opening 461 and toward the discharge port 50. Such a movement of the developer increases the driving-torque load, and a peak of the driving-torque load (peak (13)) appears when the seal is released. Subsequently, as the first opening 461 is gradually opened, the rate of increase in the torque that is attributed to the developer is reduced a little. However, the torque attributed to the pushing of the developer that is conveyed by the stirring screw continues to increase significantly. Even after the seal 53 starts to be released (at peak (14)), the driving-torque load continues to increase. Then, when the first opening 461 is about to be completely opened (immediately before peak (15)), the increase in the driving-torque load attributed to the developer subsides at last. Then, the releasing of the seal 53 is completed (at peak (16)), the seal 54 starts to be released (peak (17)), and the discharge port 50 starts to be opened. Hence, the driving-torque load attributed to the developer starts to be reduced at last. Then, the releasing of the seal 54 is completed (peak (18)). Accordingly, the torque attributed to the developer and the total torque applied to the developing device continue to be reduced and are saturated at about 0.5 kgf·cm at the elapse of about forty-five seconds.
As described above, in the developing device that does not have the characteristic feature of the present invention, when the developer in the stirring chamber is distributed more on the side of the first opening 461 as a result of transportation or the like, the total torque applied to the developing device increases significantly, occasionally reaching about 7.0 kgf·cm at maximum. Moreover, when such an experiment was conducted for a plurality of times, the driving-torque load broke the second stirring screw 45 in some cases.
Considering the above results, in the configuration according to the first embodiment of the present invention, the driving-torque load occurring at the time of initialization of the developing device can be reduced effectively. The feature that is most characteristic of the present invention is winding up the seals in the order of the seal 52, the seal 54, and the seal 53 and thus providing a path that allows the developer conveyed in the stirring chamber to be discharged, whereby the increase in the torque attributed to the pushing of the developer that is conveyed is suppressed.
According to the present invention, in the developing device including the sealing member that seals an initial portion of the developer in the developing device, the load torque generated at the releasing of the sealing member can be made small even if the distribution of the developer in the development container at the releasing of the sealing member is uneven.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of International Patent Application No. PCT/JP2015/051629, filed Jan. 22, 2015, which is hereby incorporated by reference herein in its entirety.
Number | Date | Country | Kind |
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PCT/JP2015/051629 | Jan 2015 | WO | international |
Number | Name | Date | Kind |
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20050053393 | Harada | Mar 2005 | A1 |
20110286768 | Muto | Nov 2011 | A1 |
Number | Date | Country |
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H0221591 | Jan 1990 | JP |
2006201528 | Aug 2006 | JP |
2010085970 | Apr 2010 | JP |
2011100064 | May 2011 | JP |
2011242639 | Dec 2011 | JP |
Number | Date | Country | |
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20160216639 A1 | Jul 2016 | US |