Patent Grant
9983511
The present invention relates to an image forming apparatus which uses an electrophotographic method, or the like.
Conventionally, in an image forming apparatus such as a copying machine, an electrostatic latent image is formed on the peripheral surface of its photosensitive drum as an image bearing member, and the electrostatic latent image is developed by its developing device into a visible image.
A developing device is such a device that develops a latent image into a visible image, or a toner image (image formed of toner), by supplying a photosensitive drum with toner. One of the widely used developing devices uses two-component developer, which is a mixture of nonmagnetic toner and magnetic carrier. A development process which uses two-component developer is excellent in stability in terms of the amount of toner charge. Thus, it can form color images which are excellent in tone. Therefore, a developing device which uses two-component developer is preferably used as a developing device for a color image forming apparatus.
It has been well known that a developing method which uses two-component developer is such a method that forms an image by charging toner by the friction between carrier and toner, and causing the charged toner to electrostatically adhere to a latent image. In the case of a developing method such as the above-described one which uses two-component developer, it is important to keep the device stable in the amount by which toner is given a triboelectric charge, in order to provide satisfactory images, more specifically, images which are highly durable and stable. Therefore, it is necessary that the carrier in a developing device remains stable in performance in terms of its ability to charge toner.
In reality, however, while the toner in a developing device is gradually consumed by a development operation, the carrier in a developing device is hardly consumed, and therefore, remains in the developing device. Further, as a developing device is used for development, the carrier in the developing device is stirred along with the toner in the developing device. Therefore, if a developing device increases in the length of its cumulative usage (is used for a long time), toner particles, and particles of external additives to the toner, adhere to the surface of a carrier particle. That is, the carrier is contaminated. As the carrier is contaminated, it reduces in performance in terms of its ability to give a toner triboelectrical charge. In other words, the carrier fails to provide the toner with a sufficient amount of triboelectrical charge, resulting in the formation of defective images, such as a foggy image, the fogginess of which is attributable to scattering of toner.
In the past, in order to deal with the above-described problem, the developer in a developing device, was periodically replaced with a fresh supply of developer by a service person or the like, in order to replace the deteriorated developer in the developing device, that is, the developer which has been used beyond its expected life span. This meant that developer life span determined the length of maintenance service interval.
From the standpoint of what is required of maintenance service personnel, maintenance cost, downtime of an image forming apparatus, the longer the maintenance service interval, the better. Thus, efforts have been made to develop developers which are substantially longer in lift life span, and/or a process that does not make the carrier deteriorate. Currently, however, as images are formed on 30,000 to 50,000 sheets of recording medium, one for one, the developer in a developing device reaches the end of its life span.
Therefore, there have been proposed developing devices enabled to prevent the carrier in two-component developer in the devices from deteriorating in its charging performance. Some of them are provided with an internal device which replenishes them with developer or carrier. They are structured so that as they are replenished with a fresh supply of developer or carrier, the developer therein is allowed to overflow through the developer discharge opening, with which one of their walls is provided, and is recovered. The method employed by these types of developing device is sometimes referred to as “trickle replenishment method” (Japanese Laid-open Patent Application No. S59-100471, for example).
A developing device such as those described above is structured so that as it is continuously replenished with a preset amount of fresh supply of developer or carrier, the developer (deteriorated developer) in the device is gradually replaced with the fresh supply of developer or carrier. Thus, the developer in the developing device remains stable in its properties in terms of developing performance, that is, its ability to charge toner. Therefore, it can prevent an image forming apparatus from reducing in the level of quality at which the apparatus outputs images. Thus, various attempts have been made to increase the interval with which the developer in a developing device has to be replaced, or even, to make it unnecessary for the developer in a developing device to be replaced.
There have been proposed, in Japanese Laid-open Patent Applications No. 2006-201528, and No. 2011-242639, such a technology that keeps an initial supply of developer sealed in a replaceable developing device, or a process cartridge, for an image forming apparatus, in order to prevent the initial supply of developer from coming into contact with ambient air. The reason why the initial supply of developer is kept sealed in the developing device or process cartridge is as follows. That is, if developer is left in contact with such ambient air that is high in temperature and humidity, the developer deteriorates by absorbing moisture. Thus, by the time when a replaceable developing device or process cartridge is started up, it becomes impossible for the initial supply of developer in the device or cartridge to perform as expected.
Another reason why the initial supply of developer in a replaceable developing device or process cartridge is kept sealed is to prevent the problem that the developer in a developing device or process cartridge sometimes leaks while the developing device or process cartridge is transported after being shipped out of manufacturing facilities. In the case of the technology disclosed in Japanese Laid-open Patent Application No. 2006-201528, the developing device or process cartridge is structured so that a sealing member used to keep the initial supply of developer sealed therein is to be removed by a user or a service person in order to unseal the developing device or process cartridge. In the case of the technology disclosed in Japanese Laid-open Patent Application No. 2011-242639, the image forming apparatus, and the developing device or process cartridge therefor, are structured so that as the developing device or process cartridge is installed into the main assembly of the image forming apparatus, and begins to be driven, the seal is removed by being rolled up in order to unseal the developing device or process cartridge.
However, when a developing device or process cartridge such as the one disclosed in Japanese Laid-open Patent Application S59-100471, which is provided with an opening through which developer is to be discharged, is structured so that the initial supply of developer is kept sealed in the developing device or process cartridge as disclosed in Japanese Laid-open Patent Applications No. 2006-201528 or No. 2011-242639, the following problems occurred.
In some cases, by the time when the sealing member by which the initial supply of developer was kept sealed in the developing device or process cartridge was removed, the initial supply of developer had shifted to one side of the stirring chamber of the developing device or process cartridge. Consequently, the highest point of the body of developer in the developing device or process cartridge had become excessively high. Thus, as the developing device began to be driven to circularly move the developer therein, the initial supply of developer was discharged by a substantial amount through the afore-mentioned developer discharge opening. Consequently, the developing device was reduced in the amount of the initial supply of developer before it began to be used for development. This problem is likely to occur in a case where the initial supply of developer is stored in the stirring chamber of the developing device, which is provided with the developer discharge opening.
Thus, the primary object of the present invention is to provide an image forming apparatus which is capable of preventing the problem that as the sealing member for keeping the initial supply of developer sealed in a developing device is removed, the initial supply of developer is discharged through the developer discharge opening of the developing device by an excessive amount.
According to an aspect of the present invention, there is provided a developing apparatus for developing an electrostatic latent image formed on an image bearing member, said apparatus comprising a developer carrying member configured to carry a developer; a first accommodation chamber configured to accommodate the developer at a position opposing said developer carrying member; a second accommodation chamber provided opposed to said developer carrying member at a position below said first accommodating chamber and configured to accommodate the developer; a feeding screw provided in said first accommodating chamber and configured to feed the developer during an image forming operation; a first communicating portion configured to move the developer from said first accommodating chamber to said second accommodating chamber during the image forming operation; a second communicating portion configured to move the developer from said second accommodating chamber to said first accommodating chamber during the image forming operation; a supply opening configured to supply the developer into said first accommodating chamber; a discharge opening provided adjacent to said second communicating portion and configured to permit discharge of the developer from said first accommodating chamber; a developer accommodating portion provided in said first accommodating chamber and configured to accommodate the developer to be supplied into said first accommodating chamber during an initial operation; a sealing member configured to unsealably seal said developer accommodating portion; and a controller configured to execute, after the developer is supplied from said developer accommodating portion by movement of said sealing member, an operation in a mode in which said feeding screw is rotated for a predetermined time period in a direction opposite to a normal direction in which said feeding screw is rotated during the image forming operation and then is rotated in the normal direction.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Parts (a)-(c) of
Part (a) and (b) of
Hereinafter, a few embodiments of the present invention are concretely described.
To begin with, referring to
<Image Forming Apparatus>
Referring to
Each of yellow (Y), magenta (M), cyan (C) and black (K) toner images, is formed on the peripheral surface of the corresponding photosensitive drum 28. Then, the four toner images are transferred one by one (primary transfer) onto the outward surface of an intermediary transfer belt 24 so that they are layered on the intermediary transfer belt 24. Then, the four toner images are transferred together from the intermediary transfer belt 24 onto a sheet 27 of recording medium, which is conveyed by an unshown conveying means. Then, the sheet 27 and the toner images thereon are heated and pressed by a fixing device 25 as a fixing means. Consequently, a full-color image is formed on the sheet 27.
Next, referring to
To the electrostatic latent image on the peripheral surface of the photosensitive drum 28, developer 10 is supplied by the developing device 1. Thus, the electrostatic latent image is developed into a visible image, that is, an image formed of toner, which hereafter will be referred to as a toner image. Each of the four toner images, different in color, formed on the peripheral surface of the corresponding photosensitive drum 28, is transferred onto the outward surface of the intermediary transfer belt 24 by a primary transfer roller 23, so that the four toner images, different in color, are layered on the intermediary transfer belt 24.
The intermediary transfer belt 24 is suspended and kept tensioned by belt suspending rollers 24a, 24b and 24c in such a manner that it can be circularly moved in the clockwise direction. Further, there are provided four primary transfer rollers 23 on the inward side of the loop which the intermediary transfer belt 24 forms, in such a manner that they oppose the four photosensitive drums 28, one for one.
The toner which is remaining on the peripheral surface of the photosensitive drum 28 after the transfer of a toner image from the photosensitive drum 28 onto the intermediary transfer belt 24 is removed (scraped away) by a cleaner 26 as a cleaning means.
After being transferred onto the intermediary transfer belt 24 (primary transfer), the four toner images are transferred together (secondary transfer) by a secondary transfer roller 23z, which is a secondary transferring means, onto the sheet 27 of recording medium such as paper. Then, the sheet 27 is conveyed to the fixing device 25 by a conveyer belt 8. Then, the sheet 27 is conveyed through the fixing device 25 while remaining pinched between the heat roller and pressure roller of the fixing device 25, being thereby subjected to the heat and pressure from the heat roller and pressure roller. Consequently, the toner images on the sheet 27 are thermally fixed to the sheet 27.
The toner which is remaining on the outward surface of the intermediary transfer belt 24 after the secondary transfer of the toner images onto the sheet 27 of recording medium is removed (scraped away) by a belt cleaner 26z as a cleaning means.
<Developing Device>
Next, referring to
The developing device 1 in this embodiment has a developer container 2 which has a pair of developer holding chambers, more specifically, a development chamber 11 (first developer holding chamber) and a stirring chamber 12 (second developer holding chamber).
The development chamber 11 has a development sleeve 3. It holds the developer 10 in such a manner that the development sleeve 3 is supplied with developer 10.
The developing device 1 is structured so that the stirring chamber 12 is positioned under the development chamber 11, and the primary opening of the stirring chamber 12 faces the development sleeve 3. The stirring chamber 12 recovers the developer from the development sleeve 3.
The developer container 2 contains the developer 10 which is two-component developer made up of toner and carrier.
The developer container 2 contains the development sleeve 3 which bears and conveys the developer 10 in the developing device 2 and supplies the peripheral surface of the photosensitive drum 28 with the developer 10. Further, the developer container 2 is provided with a regulation blade 5, which functions as a member for regulating in height a “magnetic brush” which the body of developer 10 borne on the peripheral surface of the development sleeve 3 forms.
In this embodiment, there is a partition wall 15 in the developer container 2. The partition wall 15 extends in the direction parallel to the lengthwise direction (left-right direction in
Referring to
In this embodiment, the first and second conveyance screws 13 and 14 are provided with spiral blades 13b and 14b, respectively, which are 20 mm in external diameter D and 20 mm in pitch, and which are attached to the peripheral surface of the rotational shaft 13a of the first conveyance screw 13, and the peripheral surface of the rotational shaft 14a of the second conveyance screw 14, respectively.
The first conveyance screw 13 is disposed in the bottom portion of the development chamber 11. It extends roughly in parallel to the axial line of the development sleeve 3 (left-right direction in
The reason why the normal direction in which the first conveyance screw 13 is to be rotated is made to be the direction indicated by the arrow mark d in
The second conveyance screw 14 is disposed in the bottom portion of the stirring chamber 12. It extends roughly in parallel to the shaft of the first conveyance screw 13 (left-right direction in
As described above, the developer 10 in the development chamber 11 and the developer 10 in the stirring chamber 12 are conveyed in the counterclockwise direction of
The developer container 2 is provided with an opening 2a, which faces the photosensitive drum 28 and corresponds in position to the development area. The development sleeve 3 is rotatably supported by the developer container 2 so that it is partially exposed from the developer container 2 toward the photosensitive drum 28, through the opening 2a.
In this embodiment, the development sleeve 3 and photosensitive drum 28 are 20 mm and 80 mm, respectively, in external diameter. They are positioned so that the smallest distance between the two is roughly 300 μm. Thus, the electrostatic latent image on the peripheral surface of the photosensitive drum 28 is developed by the developer 10 as the developer is borne on the peripheral surface of the development sleeve 3 and conveyed through the development area by the rotation of the development sleeve 3, with the developer 10 on the development sleeve 3 being in contact with the peripheral surface of the photosensitive drum 28.
By the way, the development sleeve 3 in this embodiment is formed of a nonmagnetic substance. There is disposed a stationary magnetic roller 4, as a magnetic field forming means, in the hollow of the development sleeve 3. The magnetic roller 4 has a magnetic pole S2. It is disposed in such an attitude that it is in the development area that the magnetic pole S2 opposes the photosensitive drum 28. Further, the magnetic roller 4 has a magnetic pole N1 which functions as the means for regulating in height the aforementioned “magnetic brush” which the developer 10 on the peripheral surface of the photosensitive drum 28 forms. The magnetic roller 4 is disposed in such an attitude that the magnetic pole N1 opposes the regulation blade 5 as the member for regulating in height the aforementioned “magnetic brush” which the developer 10 on the peripheral surface of the development sleeve 3 forms. Further, the magnetic roller 4 is provided with magnetic poles S1, N2 and N3, which are between the above-described magnetic poles N1 and S2. The magnetic roller 4 is disposed in such an attitude that the magnetic pole N3 opposes the stirring chamber 12.
While the development sleeve 3 is used for development, it rotates in the counterclockwise direction in
While the peripheral surface of the photosensitive drum 28 is supplied with the developer 10 on the development sleeve 3, development voltage, which is a combination of DC voltage and AC voltage, is applied to the development sleeve 3 from a development bias power source, in order to increase the developing device 1 in development efficiency (amount by which toner is adhered to electrostatic latent image). In this embodiment, the development bias (voltage) is a combination of DC voltage which is −500 V in magnitude, and AC voltage which is 1800 V in peak-to-peak voltage Vpp, and 12 kHz in frequency f. However, the DC voltage and the waveform of the AC voltage do not need to be the same in value as those in this embodiment.
The regulation blade 5, which is a member for trimming the “magnetic brush”, is a long and narrow rectangular member formed of a nonmagnetic substance such as aluminum or the like. That is, it is a long and narrow rectangular piece of aluminum plate or the like. It is disposed so that its lengthwise edges are parallel to the lengthwise direction of the development sleeve 3. Referring to
By the way, as the amount of the gap between the regulating edge of the regulation blade 5 and the peripheral surface of the development sleeve 3 is adjusted, the amount by which the magnetic brush, which the developer 10 borne on the peripheral surface of the development sleeve 3 forms, is regulated in height is determined, whereby the amount by which the developer 10 is conveyed to the development area in which the developer 10 on the development sleeve 3 opposes the photosensitive drum 28. In this embodiment, the amount by which the developer 10 coated on the peripheral surface of the development sleeve 3 is allowed to remain on the peripheral surface of the development sleeve 3 per unit area by the regulation blade 5 was set to 30 mg/cm2.
As for the amount of the gap between the regulating edge of the regulation blade 5 and the peripheral surface of the development sleeve 3, it is desired to be set to 200 μm-1000 μm, preferably, 300 μm-700 μm. In this embodiment, it was set to 500 μm.
The development sleeve 3, which is rotatably supported in the developing device 1, is rotated in the aforementioned normal direction, in the development area in which the development sleeve 3 opposes the photosensitive drum 28, its peripheral surface moves in the same direction (indicated by arrow mark h in
Also regarding the ratio in peripheral velocity between the development sleeve 3 and photosensitive drum 28, all that is necessary is that the peripheral surface of the photosensitive drum 3 is 1.0-3.0, preferably, 1.0-2.5, times the peripheral surface of the photosensitive drum 28. Further, the greater the ratio in peripheral velocity between the development sleeve 3 and photosensitive drum 28, the higher the development efficiency. However, if the ratio is excessively large, such problems as scattering of toner and developer deterioration occur. Thus, it is desired that the ratio in peripheral velocity between the development sleeve 3 and photosensitive drum 28 is set to a value within the above-described range.
<Two-Component Developer>
Next, the developer 10 used in this embodiment is described. It is two-component developer, and its primary components are toner and carrier. The toner is a mixture of colored resinous particles made up of bonding resin, coloring agent, and additives added as necessary, and colored particles of external additives such as microscopic particles of colloidal silica. The toner is made up of polyester resin which is negatively chargeable. It is desired to be no less than 4 μm and no more than 10 μm, preferably, no more than 7 μm, in volume average particle diameter.
As the carrier, particles of iron, the surface of which has been oxidized, or particles of iron, nickel, cobalt, manganese, chrome, rare-earth metal, or the like, alloys of preceding substance, ferrite oxide, or the like can be preferably used. There is no requirement regarding the method for manufacturing these magnetic particles.
The carrier is desired to be 20 μm-60 μm, preferably, 30 μm-50 μm, in weight average particle diameter. It is desired to be no less than 1×107 Ω·cm, preferably, no less than 1×108 Ω·cm, in resistivity. In this embodiment, the carrier which was 1×108 Ω·cm in resistivity was used.
In this embodiment, a mixture of toner and carrier, which was 8% in T/D ratio (toner ratio of developer 10), that is, 8:92 in mass ratio between toner and carrier, was used as initial developer 10i (initial supply of developer 10). By the way, “T/D ratio” means the ratio in weight of nonmagnetic toner (T) relative to the developer (D) which is a mixture of magnetic carrier and nonmagnetic toner.
<Method for Replenishing Developing Device with Developer>
Next, referring to
Referring again to
As the toner in the developing device 1 is consumed by an image forming operation which uses the developer 10 in the developing device 1, the replenishment two-component developer 10r in the hopper 31 is delivered by the amount equivalent to the amount by which the toner was consumed, into the development chamber 11 of the developer container 2 by the rotation of the replenishment screw 32 and the weight of the replenishment two-component developer 10r itself, through the replenishment opening 18 of the hopper 31. This is how the replenishment two-component developer 10r is delivered from the hopper 31 into the developing device 1.
In this embodiment, such developer that is 90% in T/D ratio, that is, ratio, in mass, of the toner relative to the developer (mixture of toner and carrier) was used as the replenishment two-component developer 10r.
The amount by which the replenishment two-component developer 10r is delivered to the developing device 1 is determined by the approximate number of revolutions of the replenishment screw 32 as a conveying member. The number of revolutions of the replenishment screw 32 is determined by an unshown controlling portion which determines the amount by which toner is to be delivered. As for the method for controlling the amount by which toner is delivered, various methods are available. For example, the developer 10 in the developer container 2, which is a mixture of toner and carrier, may be optically or magnetically measured in toner density, or a toner image obtained by developing a latent image formed on the peripheral surface of the photosensitive drum 28, may be measured in toner density. That is, the method for controlling the amount by which toner is delivered into the developer container 2 is optional. By the way, the method used in this embodiment is one of examples of supplying the developing device 1 with carrier by mixing carrier into the replenishment developer. However, an image forming apparatus (developing device) may be structured so that carrier is independently supplied from the toner.
<Method for Discharging Developer>
Next, referring to
As the developer 10 in the developer container 2 is used for image formation, it gradually deteriorates. Thus, the developing device 1 is structured so that during an image forming operation, the developer 10 in the developer container 2 is continuously discharged by a certain amount from the discharge opening 40 into the recovery chamber 9, as shown in
By the way, in this embodiment, in terms of the normal direction in which the developer 10 is conveyed in the development chamber 11, the discharge opening 40 is positioned at the downstream end portion (left end portion in
In terms of the vertical direction, the discharge opening 40 is positioned to prevent the problem that the developer 10 in the development chamber 11 is discharged by an amount large enough to make the amount of the developer 10 in the developer container 2 less than the amount necessary to reliably keep the peripheral surface of the development sleeve 3 properly coated for satisfactory development.
Therefore, the developer 10 in the developing device 1 overflows from the development chamber 11 only when the amount of the developer 10 in the developing device 1 is made to exceed the proper amount for satisfactory development, by the replenishment of the developing device 1 with the replenishment two-component developer 10r. Further, as the surface 10s (ridge) of the developer 10 in the development chamber 11 falls below the discharge opening 40, the developer 10 naturally stops being discharged through the discharge opening 40. Thus, it is possible for the peripheral surface of the development sleeve 3 to be reliably coated with a proper amount of developer 10.
Referring to
<Method for Keeping Initial Supply of Developer in Development Chamber>
Next, referring to
The sealing sheet 51 keeps the initial developer 10i sealed in the developing device 1 to prevent the initial developer 10i from leaking out of the developing device 1 prior to the initialization of the developing device 1.
<Initialization Operation>
In the normal initialization operation, the sealing sheet 51 is removed to release the initial developer 10i into the development chamber 11, and then, the developing device 1 is idly rotated. Then, an operation for initializing an unshown inductance detecting portion for detecting the toner density of the developer 10 (initial supply of developer 10i) in the development chamber 11 is carried out (value is set for referential control voltage). Thereafter, a patch (toner image), as a referential image for detecting the toner density, is formed on the peripheral surface of the photosensitive drum 28. Then, the amount by which toner adhered to the peripheral surface of the photosensitive drum 28 to form the patch (toner image) is detected (initial amount by which toner adhered to photosensitive drum 28 is detected).
In a case where the sealing sheet 51 is to be manually removed by a service person or a user, the following operation is carried out. That is, the sealing sheet 51 is removed from a brand-new developing device 1. Then, the brand-new developing device 1 is set in the main assembly of the image forming apparatus 6. Next, an unshown initialization button is pressed by the service person or user.
What occurs as the initialization button (inputting portion) is pressed is as follows, no matter whether the developing device 1 in the image forming apparatus 6 has already been initialized, or it is brand-new. That is, as the initialization button is pressed, signals for causing the developing device 1 to carry out a preprogrammed initialization operation by driving the first and second conveyance screws 13 and 14 is inputted into a CPU 60 as a controlling means.
Thus, the CPU 60 receives the initialization signals, which are the signals to be inputted as the initialization button (inputting portion) is pressed. Consequently, the first and second conveyance screws 13 and 14 are rotated in the opposite direction from the normal direction in which they are rotated in the normal development operation. Thereafter, the developing device 1 is operated in the mode in which the first and second conveyance screws 13 and 14 are rotated in their normal direction while being controlled in rotation.
On the other hand, in a case where the sealing sheet 51 is automatically removed by an unshown means for taking up the sealing sheet 51, that is, in a case where the sealing sheet 51 is automatically removed, the following operation is carried out. As a service person or a user presses the unshown initialization button, the sealing sheet 51 is automatically taken up by an unshown means for taking up the sealing sheet 51 to unseal the storage chamber 19. At the same time, the CPU 60, as a controlling means, receives the initialization signals. Thus, the CPU 60 causes the first and second conveyance screws 13 and 14 to rotate in the opposite direction from the normal direction for development, in response to these initialization signals. Thereafter, the two conveyance screws 13 and 14 are rotated in their normal rotational direction for development.
In a case where the developing device 1 is provided with a sensor 64 for detecting whether or not the installed developing device 1 is brand-new, and it is detected by the sensor 64 that the developing device 1 set in the main assembly of the image forming apparatus 6 is brand-new, the following operation is carried out. The initialization operation is automatically started so that the sealing sheet 51 is automatically taken up by the unshown means for taking up the sealing sheet 51 to unseal the storage chamber 19. At the same time, the CPU 60, as a controlling means, receives the initialization signal. Thus, the first and second conveyance screws 13 and 14, as conveying members, are rotated in the opposite direction from the normal direction in which the two screws 13 and 14 are rotated for development. Thereafter, the image forming apparatus 6 is operated in the mode in which the first and second conveyance screws 13 and 14 are rotated in the normal direction for development, before the initialization operation is started in response to the initialization signals.
As described above, the operational sequence in which the sealing sheet 51 is removed; the first and second conveyance screws 13 and 14 are rotated in the opposite direction from the normal direction in which they are rotated for development; and then, the first and second conveyance screws 13 and 14 are rotated in the normal direction for development, is carried out as a preliminary initialization operation before the above-described normal initialization operation is started.
By the way, in the initialization operation for the developing device 1 in this embodiment, it is detected by the developing device status sensor 64 whether or not the developing device 1 set in the main assembly of the image forming apparatus 6 is brand-new. In this case, the initialization operation is such an operation that the sealing sheet 51 is removed, and the first and second conveyance screws 13 and 14 are rotated in the opposite direction from their normal direction for development.
Referring to
Referring to
The second conveyance screw 14 disposed in the stirring chamber 12 is required to push the developer 10 up into the development chamber 11 which is on top of the stirring chamber 12. Thus, the second conveyance screw 14 is likely to be subjected to a larger amount of load than the first conveyance screw 13; it needs to be provided with a larger amount of torque. Therefore, if the initial developer 10i in the stirring chamber 12 shifts to one side of the stirring chamber 12, the second conveyance screw 14 is subjected to much greater amount of load, making it possible for the second conveyance screw 14 to unexpectedly lock up. In this embodiment, therefore, the initial developer 10i is kept sealed in the top portion of the development chamber 11 provided with the discharge opening 40, as shown in
In this embodiment, the initial developer 10i is kept sealed in the storage chamber 19, with which the top portion of the development chamber 11 of the developer container 2 of the developing device 1 is provided, until the developing device 1 is initialized. Further, the storage chamber 19, in which the initial developer 10i is kept sealed, is above the first conveyance screw 13 which is rotatably disposed in the development chamber 11.
Referring to
Referring to
When the developing device 1 is shipped out from its factory, the initial developer 10i remains sealed in the storage chamber 19, which is the top portion of the development chamber 11, by the sealing sheet 51. Thus, neither carrier or toner of which the developer 10 is made up is present in neither the stirring chamber 12, nor the portion of the development chamber 11, which is on the bottom side of the sealing sheet 51.
Referring to
Referring to
The sealing sheet 51 in this embodiment is to be removed by a user or a service person. That is, a user or a service person is to grip the tab 53, and pull the folded-back portion 51b in the direction indicated by an arrow mark a in
Thus, the top and bottom portions of the development chamber 11, which has remained partitioned from each other by the sealing sheet 51, are united. Regarding the removal of the sealing sheet 51, the image forming apparatus 6 (developing device 1) may be structured so that the sealing sheet 51 is automatically removed by an automatic sheet winding device, that is, without need for the manual intervention from a user or the like.
By the way, regarding the location of the storage chamber 19 which is the top portion of the development chamber 11, and in which the initial developer 10i is kept sealed, in terms of the normal developer conveyance direction for development, the storage chamber 19 is positioned on the upstream side (right side in
Next, referring to
Referring to
Further, the CPU 60 is in connection to various sensors with which each of the developing devices 1 which are different in the color of the toner they use, is provided. Further, the CPU 60 is in connection to an I/O (Input/Output) device 63 for causing each of the development motors 66 or the like, as a driving force source for driving the developing device 1, to operate. Further, the CPU 60 is in connection to the sensor 64, as a detecting means, which detects whether a developing device 1 is brand-new or used one as the developing device 1 is installed into the main assembly of the image forming apparatus 6.
Ordinarily, as the developing device 1 and/or a drum unit such as the photosensitive drum 28, which are in the image forming apparatus 6, is replaced with a brand-new one, an operation for initializing the developing device 1 is carried out. Referring to
Then, in Step S3, the CPU 60 determines whether the developing device 1 in the main assembly of the image forming apparatus 6 is brand-new or used one, based on the detection signals from the status sensor 64.
There are various methods for detecting whether or not the developing device 1 in the main assembly of the image forming apparatus 6 is brand-new or a used one. However, it does not matter which method is used. The developing device 1 in this embodiment is provided with a fuse. Thus, as one of the terminals of the substrate of the fuse comes into contact with the contact point of the main assembly of the image forming apparatus 6, whether the developing device 1 in the main assembly of the image forming apparatus 6 is a brand-new one or used one is detected by the status sensor 64.
If the developing device 1 in the main assembly of the image forming apparatus 6 is a brand-new one, a preset amount of electrical current flows to the fuse, with which the developing device 1 is provided. Consequently, the fuse is blown. Thus, it can be determined by the status sensor 64 that the developing device 1 in the main assembly of the image forming apparatus 6 is a brand-new one.
If the developing device 1 in the main assembly of the image forming apparatus 6 is a used one, its fuse will have been blown, and therefore, electrical current does not flow. Thus, it is possible for the status sensor 64 to determine that the developing device 1 is a used one.
If it is determined in Step S3 that the developing device 1 in the main assembly of the image forming apparatus 6 is a brand-new one, the CPU 60 proceeds to Step S4. In the case of the developing device 1 in this embodiment, the sealing sheet 51 is to be manually removed by a user or a service person. Thus, a message or sign which prompts a user or a service person to remove the sealing sheet 51 is displayed on a display panel 65, as a displaying means, with which the main assembly of the image forming apparatus 6 is provided.
Thereafter, the sealing sheet 51 is removed by a user or a service person. Even if the image forming apparatus 6 (developing device 1) is structured so that the sealing sheet 51 is automatically removed, the timing with which the sealing sheet 51 is removed is the same as the above-described one.
After the removal of the sealing sheet 51 (unsealing of storage chamber 19), driving of the development motor 66 is started in Step S5. At first, the development motor 66 is driven (reversely driven) in the opposite direction from the normal direction for development, for a short length of time. In this embodiment, the development motor 66 is driven in the opposite direction from the normal direction (forward direction) for development, for three seconds.
As the sealing sheet 51 is removed, the initial developer 10i falls from the storage chamber 19 into the bottom portion of the development chamber 11 due to its own weight, as shown in part (b) of
As a part of the initial developer 10i is moved into the stirring chamber 12, it is fed in the direction indicated by the arrow mark c in part (c) of
Thereafter, the development motor 66 is idled in the normal direction for development (forward direction), for a preset length of time, in Step S6. In this embodiment, the length of time the development motor 66 is to be idled in the normal direction for development (forward direction) was set to 120 seconds.
While the development motor 66 is idled for the preset length of time, the initial developer 10i, which has just fallen into the development chamber 11, is circulated through the entirety of the developer container 2. Thus, the toner in the initial developer 10i is increased in the amount of electrical charge, by the rotation of the spiral blades 13b and 14b of the first and second conveyance screws 13 and 14, respectively, while the initial developer 10i in the development chamber 11 is gradually leveled (body of initial developer 10i in the development chamber 11 is reduced in the height of its ridge).
In this embodiment, the sealing sheet 51 is removed at the beginning of the initialization of the developing device 1, whereby the initial developer 10i which was kept sealed in the storage chamber 19 by the sealing sheet 51 is allowed to fall into the upstream side (right side in part (b) of
Thereafter, the first and second conveyance screws 13 and 14 are rotated in the opposite direction (reversely rotated) from the normal direction (forward direction indicated by arrow marks d and e, respectively, in
After the development motor 66 is idly rotated in the forward direction, that is, in the normal direction for development, image formation conditions are set in Step S7. Here, “image formation conditions” include the condition regarding the electrical charge to be given to the peripheral surface of the photosensitive drum 28 by the charge roller 21 as charge bias voltage is applied to the charge roller 21 from an unshown charge bias power source. Further, they include the condition regarding the development bias voltage to be applied to the development sleeve 3 by an unshown development bias power source. Further, they include the condition regarding the primary transfer voltage to be applied to the primary transfer roller 23 by an unshown primary transfer bias power source. Further, they include various other conditions provided by a tone adjustment tables for each color component, and the like tables.
Then, multiple toner test patterns are formed on the peripheral surface of the photosensitive drum 28 under the preset image formation conditions, with the amount of exposure set at various levels (low density and intermediate density). Then, conditions for various sensors are set in Step S8. Then, output values are estimated based on the density information detected by a density sensor 29 disposed adjacent to the intermediary transfer belt 24. Here, “output values” include the optimal value for the charge voltage, optimal value for the development bias voltage, optimal value for the primary transfer voltage, and values in the toner adjustment table.
After the setting of the conditions for these sensors, the driving of the development motor 66 is ended in Step S9, and the initialization operation is ended (Step S10).
<Developer Level During Initialization Operation>
Next, referring to
A user or service person is to grasp the tab attached to the outward end of the folded-back portion 51b of the sealing sheet 51 in a manner to outwardly protrude from the developing device 1, and pull the sealing sheet 51 in the direction indicated by an arrow mark a in part (a) of
Referring to part (b) of
Referring to part (b) of
In this embodiment, therefore, before the initialization operation is started after the installation of the developing device 1 into the main assembly of the image forming apparatus 6, the development motor 66 is rotated in the opposite direction from the normal direction (forward) for development to reversely rotate the first and second conveyance screws 13 and 14.
Referring to part (c) of
In this embodiment, the developing device 1 is structured so that the initial developer 10i (initial supply of developer 10) is kept sealed (stored) on the upstream side (right side in part (b) of
Referring to part (c) of
Thus, the amount of the initial developer 10i in the development chamber 11 reduces to as small as roughly half the initial amount as shown in part (a) of
Thereafter, the development motor 66 is switched in rotational direction so that it rotates in the normal direction for developer to idly rotate the first and second conveyance screws 13 and 14 in their normal direction for development, as shown in part (a) of
Therefore, the body of initial developer 10i in the development chamber 11 is relatively low in height in the adjacencies of the discharge opening 40. Therefore, it is possible to prevent the problem that as the first conveyance screw 13 begins to be rotated in the normal direction for development, a part of the initial developer 10i in the development chamber 11 is wastefully discharged through the discharge opening 40 before it is used for development.
Referring to part (b) of
In this embodiment, 300 g of developer 10 was kept sealed as the initial developer 10i (initial supply of developer 10) in the storage chamber 19. During the initialization operation, 5 g of unused initial developer 10i was discharged through the discharge opening 40.
In comparison, in a case where the first conveyance screw 13 is not rotated in reverse at the beginning of the initialization operation, unlike in this embodiment, 30 g of unused initial developer 10i was discharged through the discharge opening 40 when the amount by which the initial developer 10i was kept sealed in the storage chamber 19 was 300 g.
Thus, it was proved that this embodiment can reduce the amount by which unused initial developer 10i is wastefully discharged through the discharge opening 40 during the initialization operation.
In this embodiment, the length of time the first and second conveyance screws 13 and 14 are to be reversely rotated during the initialization operation was set to 3 seconds. However, the length of time the first and second conveyance screws 13 and 14 are to be reversely rotated during the initialization operation is optional.
Referring to part (b) of
In this embodiment, the pitch P of each of the spiral blade 13b of the first conveyance screw 13 and the spiral blade 14b of the second conveyance screw 14 was set to 20 mm. Further, the number R of revolution (rotational speed) of each of the first and second conveyance screws 13 and 14 was set to 400 rpm (rotation per minute).
If it is assumed that the conveyance efficiency α of the first and second conveyance screws 13 and 14 is 100%, the initial developer 10i is made to advance by 133 mm (=20 [mm]×400 [rotation/min]/60 [sec]) per second by the first and second conveyance screws 13 and 14.
<Conveyance Efficiency>
Here, “R” stands for the number of rotations of the first and second conveyance screws 13 and 14, and “α” stands for the efficiency with which the first and second conveyance screws 13 and 14 can convey the initial developer 10i. Further, “P” stands for the pitch of each of the spiral blade 13b of the first conveyance screw 13 and the spiral blade 14b of the second conveyance screw 14. Thus, the amount by which the initial developer 10i is conveyed in the clockwise direction (indicated by arrow marks b and c in part (c) of
A=R×α×P [1]
Therefore, the amount A by which the initial developer 10i is conveyed by the rotation of the first and second conveyance screws 13 and 14 is measured. As the values for the number R of rotations of the first and second conveyance screws 13 and 14, and the value for the pitch P (20 mm) of the spiral blade 13b of the first conveyance screw 13 and the value for the pitch P of the spiral blade 14b of the second conveyance screw 14, preset values are used.
Thus, the efficiency α with which the initial developer 10i is conveyed by the first and second conveyance screws 13 and 14 can be obtained. By the way, the conveyance efficiency α is affected by the properties of the initial developer 10i, material for the first and second conveyance screws 13 and 14, and the like factors.
That is, under the most idealistic condition, that is, when the efficiency α with which the initial developer 10i is conveyed by the first and second conveyance screws 13 and 14 is 100%, the initial developer 10i is made to advance 133 mm per second, by the rotation of the first and second conveyance screws 13 and 14.
In this embodiment, the length (distance between two developer passages 16 and 17, with which the lengthwise end portions of the development chamber 11 were provided, one for one) of the first conveyance screw 13 in the development chamber 11 was 350 mm in terms of the direction (left-to-right direction in part (a) of
Thus, as the first conveyance screw 13 was reversely rotated, roughly half the initial developer 10i in the development chamber 11, which is equivalent to roughly half (175 mm=350 [mm]/2]) the length of the first conveyance screw 13, was conveyed in the direction indicated by the arrow mark b, by the first conveyance screw 13. The length of time it took for roughly half the initial developer 10i to reach the developer passage 16 was roughly 1.3 seconds (=175 mm/133 [mm/sec]).
Therefore, it takes at least 1.3 seconds for roughly half the initial developer 10i in the development chamber 11 to be moved into the stirring chamber 12 by the reverse rotation of the first and second conveyance screws 13 and 14. When the length of time necessary for half the initial developer 10i in the development chamber 11 to move into the stirring chamber 12 was calculated with the use of the mathematical equation given above, the efficiency α with which the initial developer 10i is conveyed by the first and second conveyance screws 13 and 14 was assumed to be 100%.
In reality, however, the conveyance efficiency α is less than 100% in most cases. In this embodiment, therefore, the length of time the first and second conveyance screws 13 and 14 have to be reversely rotated to move half the initial developer 10i in the development chamber 11 into the stirring chamber 12 through the developer passage 16 was set to 3 seconds.
By the way, if the reverse rotation of the first and second conveyance screws 13 and 14 is continued longer than a certain length of time, a part of the initial developer 10i is returned to the development chamber 11 from the stirring chamber 12 through the developer passage 17 after it is moved into the stirring chamber 12 through the developer passage 16 and conveyed through the stirring chamber 12 in the counterclockwise direction indicated in part (b) of
Referring to part (b) of
Therefore, the shorter the length of time the first and second conveyance screws 13 and 14 are reversely rotated, the better. For example, the total distance the initial developer 10i is made to circulate once in the developer container 2 through the development chamber 11 and stirring chamber 12 of the developer container 2 is 700 mm. Further, the distance between the developer passages 16 and 17 provided in the lengthwise end portions (left and right end portions), one for one, of the developer container 2 in terms of the lengthwise direction of the developer container 2 is 350 mm (length of one-way trip). Further, the length of two-way trip is 700 mm (=350 mm×2).
The length of time necessary for conveying the initial developer 10i by 700 mm which is equal to the distance which the initial developer 10i is required to travel to circulate once in the developer container 2 through the development chamber 11 and stirring chamber 12 has only to be set to no more than 5.2 seconds (=700 mm/133 [mm/sec]).
In this embodiment, the first and second conveyance screws 13 and 14 are provided with the spiral blades 13b and 14b, and spiral return blades 13c and 14c, respectively, which are at the downstream end in terms of the direction in which the developer 10 is conveyed as the first and second conveyance screws 13 and 14 are rotated in the normal direction for development. The spiral return blades 13c and 14c are wound in the opposite direction from the spiral blades 13b and 14b, respectively. “Downstream end in terms of the direction in which the developer 10 is conveyed as the first and second conveyance screws 13 and 14 are rotated in the normal direction” means the left end of the first conveyance screw 13 shown in part (a) of
In terms of the normal direction in which the developer 10 is conveyed by the first and second conveyance screws 13 and 14, the downstream end portion of the first conveyance screw 13 and the downstream end portion of the second conveyance screw 14 are provided with the return blades 13c and 14c, respectively. Thus, as the first and second conveyance screws 13 and 14 are rotated in the normal direction for development, the developer 10 is conveyed downstream by the spiral blades 13b and 14b. Then, as the developer 10 reaches the downstream end portion, it is repelled upstream, that is, in the direction to be moved away from the downstream end portion, by the return blade 13c and 14c.
Therefore, the developer 10 (initial developer 10i) is prevented from entering the adjacencies of the downstream end portion of the first conveyance screw 13 and the adjacencies of the downstream end portion of the second conveyance screw 14. Therefore, it does not occur that the initial developer 10i enters the adjacencies of the downstream end portion of the first conveyance screw 13 and those of the second conveyance screw 14, and is packed into a solid mass.
Referring to part (c) of
In this embodiment, however, the development chamber 11 is on top of the stirring chamber 12. Therefore, as the first and second conveyance screws 13 and 14 are reversely rotated, the following occurs. Referring to part (c) of
Further, referring to part (c) of
Therefore, it does not occur that as the second conveyance screw 14 is reversely rotated, the initial developer 10i is conveyed to the right side of the developer passage 16, shown in part (c) of
Referring to part (c) of
Therefore, in a case where the development chamber 11 is located on top of the stirring chamber 12 as in this embodiment, all that needs to be taken into consideration is that it is only the adjacencies of the left end portion (part (c) of
By the way, it is not mandatory that the developing device 1 is structured so that the development chamber 11 is located straight above the stirring chamber 12. That is, all that is necessary is that the developing device 1 is structured so that as the initial developer 10i is conveyed toward the lengthwise end of the development chamber 11, it falls into the stirring chamber 12 before it reaches the lengthwise end of the development chamber 11. In such a case, as long as the angle of the surface (bottom surface of the development chamber 11) along which the initial developer 10i is conveyed, relative to the horizontal direction, is greater than the angle of repose of the initial developer 10i in the development chamber 11, the initial developer 10i in the development chamber 11 will slide down into the stirring chamber 12.
<Angle of Repose>
Next, referring to
Then, the measurement plate 30 on which the developer 10 is borne is slowly tilted relative to the horizontal direction until the body of developer 10 begins to slide down. Then, the angle between the measurement plate 30 and the horizontal direction is measured when the developer particles in the piles (mountain) of the developer 10 on the measurement plate 30 begin to slide down along the surface of the pile (mountain). The angle of the measurement plate 30 obtained with the use of the above-described method is equal to the angle θ of repose of the developer 10, shown in
The angle θ of repose of the developer 10 is not affected by the amount by which the developer 10 is allowed to free-fall onto the measurement plate 30. However, in order to make it easier to catch the exact moment when the developer particles in the pile (mountain) of developer 10 on the measurement plate 30 begins to slide downward along the surface of the pile (mountain) of the developer 10 as the measurement plate 30 is slowly tilted, 10 g of the developer 10 was placed on the measurement plate 30.
By the way, as the angle θ of repose of the developer 10 is measured for the first time, the top surface of the measurement plate 30 is covered with a thin layer of developer 10. Therefore, the value of the angle θ of repose of the developer 10 obtained by the second try, is substantially different from that obtained by the first try. In this embodiment, therefore, the value of the angle θ of repose of the developer 10 obtained by the second try or thereafter was used as the angle θ of repose of the developer 10.
The initial developer 10i used in this embodiment was such developer 10 that had been kept sealed in the storage chamber 19 of the developing device 1 in an ambience which was 10 g/m3 in absolute amount of moisture, and in which the angle θ of repose of the initial developer 10i was 22°. By the way, “absolute amount of moisture” means the amount (g) of water vapor in 1 m3 of air space saturated with water vapor.
It is only the first and second conveyance screws 13 and 14 that have to be idly rotated at the beginning of the initialization operation. If the development sleeve 3 shown in
In this embodiment, the developing device 1 is structured so that the development motor 66 was used as the driving force source for rotationally driving the development sleeve 3, first conveyance screw 13 and second conveyance screw 14.
Therefore, a one-way clutch 67 (
On the other hand, during the initialization of the developing device 1, the development motor 66 is reversely rotates. However, the rotational driving force from the development motor 66 is not transmitted to the development sleeve 3, because there is the one-way clutch 67 between the unshown driving force transmission gear attached to one of the lengthwise ends of the rotational axle of the development sleeve 3, and the development motor 66. Therefore, the development sleeve 3 is not rotated during the initialization of the developing device 1.
Further, the driving force transmission gear attached to one of the lengthwise ends of the rotational axle of the first conveyance screw 13, and the driving force transmission gear attached to one of the lengthwise ends of the rotational axle of the second conveyance screw 14, are directly engaged with the development motor 66, that is, without the placement of the one-way clutch 67 between the rotational axle and driving force transmission gear. Thus, when the development motor 66 is rotated in the same direction as the normal direction for development, the development sleeve 3 rotates with the first and second conveyance screws 13 and 14. On the other hand, when the development motor 66 is reversely driven during the initialization of the developing device 1, only the first and second conveyance screws 13 and 14 rotate, whereas the development sleeve 3 does not rotate.
In this embodiment, the driving force source for the development sleeve 3, and the driving force source for the first and second conveyance screws 13 and 14, are the same one, which is the development motor 66. Further, there is provided the one-way clutch 67 in the power train between the development sleeve 3 and development motor 66.
During the initialization of the developing device 1, the first and second conveyance screws 13 and 14 are rotated in the opposite direction from the direction in which they are rotated for actual development. However, the development sleeve 3 does not rotate in the opposite direction from the direction in which it rotates for actual development, because of the presence of the one-way clutch 67 in the power train between the development motor 66 and development sleeve 3.
In a case where the developing device 1 is structured so that the driving force source (motor) for the development sleeve 3 is different from the driving force (motor) for the first and second conveyance screws 13 and 14, the developing device 1 is driven in the following manner. During the initialization of the developing device 1, the first and second conveyance screws 13 and 14 are rotated in the opposite direction (reversely rotated) from the normal direction for development by the unshown first driving force source (first motor).
Meanwhile, the development sleeve 3 is not rotated by the unshown second driving force source (second motor) in the opposite direction (reversely rotated) from the normal direction for development.
That is, the developing device 1 may be structured so that while the first and second conveyance screws 13 and 14 are reversely rotated for the initialization of the developing device 1, the second motor, which is for the development sleeve 3, is kept turned off, and only the first motor, which is for the first and second conveyance screws 13 and 14, is reversely driven.
In this embodiment, the developing device 1 is structured so that when the development motor 66 reversely rotates during the initialization of the developing device 1, the development sleeve 3 is not rotationally driven. In a case where the storage chamber 19 in which the initial developer 10i, or the initial supply of developer 10, is kept sealed, is located is the top portion of the development chamber 11 as in this embodiment, there is no developer 10 in the stirring chamber 12 when the first conveyance screw 13 begins to be reversely rotated.
Therefore, it does not occur that as soon as the first conveyance screw 13 begins to be reversely rotated, the developer 10 is supplied to the peripheral surface of the development sleeve 3. Therefore, even if the development sleeve 3 is reversely rotated, there is no harmful effect, unless the first conveyance screw 13 is reversely rotated for a substantial length of time.
The length of time the first and second conveyance screws 13 and 14 are reversely rotated during the initialization of the developing device 1 is as follows. As long as it is kept shorter than the length of time (5.2 seconds according to forgoing calculation) necessary for the developer 10 to circulate once in the clockwise direction in part (c) of
However, it is possible that there will be a small amount of ill effect. Thus, whether to drive the development sleeve 3 or not when the first and second conveyance screws 13 and 14 are reversely rotated may be determined according to the cost, life expectancy, specifications, etc., of the developing device 1.
According to this embodiment, the initial developer 10i (initial supply of developer 10) is kept sealed in the storage chamber 19, which is the top portion of the development chamber 11 of the developing device 1, with the use of the sealing sheet 51, which is to be removed to unseal the storage chamber 19 at the beginning of the initialization of the developing device 1. Thus, it is possible that as the sealing sheet 51 is removed and the initial developer 10i falls into the development chamber 11, certain portions of the surface 10s (ridge) of the initial developer 10i will become higher than the discharge opening 40.
In this embodiment, however, the ordinary (conventional) initialization operation is carried out after the first and second conveyance screws 13 and 14 are reversely rotated. Therefore, it is possible to prevent the initial developer 10i from being excessively discharged through the discharge opening 40.
Next, referring to
Referring to
Further, in the first embodiment, the developing device 1 is provided with the storage chamber 19, which is the top portion of the development chamber 11 in which the developer 10 is supplied to the development sleeve 3, as shown in
Referring to
In terms of the positioning of the storage chamber 19 in which the initial developer 10i is kept sealed, relative to the discharge opening 40, this embodiment is the same as the first embodiment.
Also in this embodiment, the developer container 2 is provided with an unshown replenishment opening through which the developer container 2 is replenished with replenishment two-component developer 10r from the hopper 31 as a replenishing means for replenishing the developer container 2 with the replenishment two-component developer. The developing device 1 is structured so that the discharge opening 40 is located on the upstream side (right side in
Also in this embodiment, the sealing sheet 51 which kept the initial developer 10i in the storage chamber 19, which is the top portion of the stirring chamber 12, and in which the initial developer 10i is stored, is peeled away from the storage chamber 19 to unseal the storage chamber 19, during the initialization operation which is carried out immediately after the installation of the developing device 1 into the main assembly of the image forming apparatus 6. As the sealing sheet 51 is removed, the initial developer 10i which remained sealed in the storage chamber 19 falls into the stirring chamber 12, on the upstream side of the discharge opening 40 in terms of the normal developer conveyance direction (rightward in
Thereafter, the second conveyance screw 14 (conveying member) disposed in the stirring chamber 12, and the first conveyance screw 13 (conveying member) disposed in the development chamber 11, are rotated (reversely rotated) in the opposite direction from the normal direction for development. Then, they are rotated in the normal direction for development (directions indicated by arrow marks e and e, respectively in
As described above, also in this embodiment, as the developing device 1 is installed into the main assembly of the image forming apparatus 6, the first and second conveyance screws 13 and 14 are reversely rotated at the beginning of the initialization of the developing device 1. Thus, it is possible to obtain the same effects as those obtained in the first embodiment.
Referring to
Therefore, initial developer 10i reaches the lengthwise end of the rotational axle 14a of the second conveyance screw 14 shown in
In this embodiment, therefore, the reverse rotation of the first and second conveyance screws 13 and 14 in the initialization operation of the developing device 1 is controlled as follows. That is, the number R (rotational speed) of times the first and second conveyance screws 13 and 14 are rotated per unit length of time during the initialization of the developing device 1 is made smaller in absolute value than the number of time they are rotated in the normal direction for development.
That is, in this embodiment, the speed (first speed) at which the first and second conveyance screws 13 and 14 are rotated in the opposite direction from the normal direction (indicated by arrow marks e and d, respectively) at the beginning of the initialization of the developing device 1 is controlled so that it becomes less than the speed (second speed) at which the first and second conveyance screws 13 and 14 are rotated in the normal direction (indicated by arrow marks e and d, respectively, in
Therefore, the initial developer 10i is prevented from entering into the adjacencies of the lengthwise end portion of the rotational axle 14a of the second conveyance screw 14, shown in
More concretely, the number R of times (second rotational speed) the first and second conveyance screws 13 and 14 are rotated per unit length of time in the normal direction for development is 400 rpm. In comparison, the number R (first rotational speed) of times the first and second conveyance screws 13 and 14 are reversely rotated per unit length of time during the operation for initializing the developing device 1 was set to 100 rpm.
Therefore, it was possible to prevent the initial developer 10i from entering the adjacencies of the lengthwise end of the rotational axle 14a of the second conveyance screw 14, shown in
By the way, in this embodiment, the driving force source for the development sleeve 3, and the driving force source for the first and second conveyance screws 13 and 14, were the same one. Further, the one-way clutch was not provided. Thus, as the first and second conveyance screws 13 and 14 is reversely driven at the beginning of the operation for initializing the developing device 1, not only do the first and second conveyance screws 13 and 14 reversely rotate, but also, the development sleeve 3 reversely rotates.
Referring to
Therefore, it is difficult for the developer 10 to be picked up by the development sleeve 3 when the development sleeve 3 is reversely rotated during the initialization of the developing device 1. Therefore, even though the development sleeve 3 reversely rotates when the first and second conveyance screws 13 and 14 are reversely rotated, the developer 10 is hardly conveyed by the development sleeve 3. Thus, it was unnecessary to provide the developing device 1 with a driving force source dedicated to the development sleeve 3, or the aforementioned one-way clutch. Therefore, it was possible to reduce the image forming apparatus 6 in cost.
According to this embodiment, the sealing sheet 51 for keeping the initial developer 10i in the storage chamber 19, which occupies the top portion of the stirring chamber 12 of the developer container 2 of the developing device 1 is peeled away to unseal the storage chamber 19 during the initialization of the developing device 1. As the sealing sheet 51 is peeled away, the initial developer 10i falls into the development chamber 11, and piles up in the development chamber 11, sometimes high enough for the developer surface 10s to reach higher than the discharge opening 40. However, before the first and second conveyance screws 13 and 14 begin to be rotated in the normal direction for development, they are reversely rotated. Therefore, it is possible to prevent the initial developer 10i from being excessively discharged through the discharge opening 40 during the initialization of the developing device 1. Otherwise, the image forming apparatus (developing device) in this embodiment is the same in structure as that in the first embodiment, and can provide the same effects as those provided by the image forming apparatus 6 in the first embodiment.
According to the present invention, it is possible to prevent the problem that as a sealing member for keeping the initial supply of developer sealed in a developing device is removed, the initial supply of developer is excessively discharged through the discharge opening of the developer container of the developing device, even if the initial supply of developer piles up relatively high in the development chamber and/or stirring chamber of the developing device.
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 Japanese Patent Application No. 2015-210299 filed on Oct. 27, 2015, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-210299 | Oct 2015 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 8131187 | Uno | Mar 2012 | B2 |
| 8355655 | Sakamaki | Jan 2013 | B2 |
| 8855525 | Muto et al. | Oct 2014 | B2 |
| 20150037071 | Yamamoto | Feb 2015 | A1 |
| 20150220018 | Nanno | Aug 2015 | A1 |
| Number | Date | Country |
|---|---|---|
| S59-100471 | Jun 1984 | JP |
| H11-038740 | Feb 1999 | JP |
| 2003-186369 | Jul 2003 | JP |
| 2004-126089 | Apr 2004 | JP |
| 2006-201528 | Aug 2006 | JP |
| 2009-265217 | Nov 2009 | JP |
| 2010-044183 | Feb 2010 | JP |
| 2011-242639 | Dec 2011 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20170115606 A1 | Apr 2017 | US |
