Patent Grant
9217953
This patent application is based on and claims priority pursuant to 35 U.S.C. §119(a) to Japanese Patent Application No. 2013-133814, filed on Jun. 26, 2013, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein.
1. Technical Field
Embodiments of the present invention generally relate to a developing device; and a process unit and an image forming apparatus, such as a copier, a printer, a facsimile machine, or a multifunction machine including at least two of these functions, that include a developing device.
2. Description of the Related Art
In general, electrophotographic image forming apparatuses such as copiers, printers, facsimile machines, or multifunction machines including at least two of these functions include a developing device to develop latent images formed on an image bearer with developer, and a toner container (i.e., a toner cartridge) for containing developer such as toner. As the toner in the development device is consumed in image development, fresh toner is supplied from the toner container to the developing device. If mixing of the toner supplied from the toner container and the toner existing in the developing device is insufficient, the ratio of supplied toner becomes uneven between a portion adjacent to a toner supply inlet formed in the developing device and other portions inside the developing device. In such a state, it is possible that image density becomes uneven or toner scatters on the backgrounds of output images.
Therefore, toner is circulated inside the developing device to equalize the state of toner (the ratio of the supplied toner) inside the developing device. For example, an interior of the development housing (or a casing) is divided with a partition into first and second compartments that communicate with each other in both axial end portions, and conveyance members such as conveyance screws are provided in the first compartment and the second compartment, respectively, to transport the toner therein. Toner is supplied from the toner cartridge to the first compartment, and a developing roller is provided in the second compartment. The conveyance screws transport the toner in the respective compartments in the opposite directions, and the toner transported to an end portion in one compartment is transported through a communication opening at the end of the partition to the other compartment. Then, toner is transported by the conveyance screw to the opposite end portion, after which the toner moves through the communication opening again to the other compartment. Toner can be circulated between the first compartment and the second compartment by repeating this operation. Accordingly, the supplied toner can be mixed with the toner existing in the developing device, and the ratio of supplied toner can become uniform.
Even in developing devices in which developer is thus circulated, it is possible that the amount of toner therein decreases to a degree that image density becomes insufficient if toner is not timely supplied to the developing device.
For example, JP-2012-155141-A proposes, for controlling the timing of toner supply, providing an optical sensor, as a developer amount detector, to the first compartment to which toner is supplied and detecting the amount of toner remaining therein according to changes in the amount of light in a detection area thereof.
In view of the foregoing, an embodiment of the present invention provides a developing device that includes a developer container to contain developer; a developer bearer to bear developer on a surface thereof; a partition to divide an interior of the developer container into a first compartment to which developer is supplied and a second compartment in which the developer bearer is disposed; developer conveyance members provided in the first compartment and the second compartment to circulate developer between the first compartment and the second compartment; and a developer amount detector to detect an amount of developer in a detection area positioned in the first compartment. Main communication openings are provided at both ends of the partition so that the first compartment and the second compartment communicate with each other through the main communication openings. Further, a sub-communication opening is provided in an intermediate portion of the partition so that the first compartment and the second compartment communicate with each other through the sub-communication opening, and the detection area in the first compartment is adjacent to the sub-communication opening.
In another embodiment, a process unit removably installable in an image forming apparatus includes an image bearer on which an image is formed; and the above-described developing device.
In yet another embodiment, an image forming apparatus includes the above-described process unit.
A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
In describing preferred embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this patent specification is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner and achieve a similar result.
In developing devices in which toner is transported by rotating a conveyance screw inside a housing of the developing device, the force of the conveyance screw to transport toner is hardly exerted outside an orbit of rotation of the conveying screw (in gaps between the outer circumference of a screw blade of the conveyance screw and an inner wall of the housing) although toner moves slightly following the movement of toner inside the orbit of rotation of the conveyance screw. Thus, toner is likely to aggregate (so-called state of bridges) and accumulate. In an arrangement in which the detection area of a developer amount detector, such as an optical sensor, is outside the orbit of rotation of the conveyance screw, the amount of toner in the detection area is less likely to change. In this case, it is possible that the developer amount detector erroneously detects that the amount of toner is sufficient although the amount of toner in the housing as a whole is below a predetermined amount.
Inside the orbit of rotation of the conveyance screw to transport toner inside the developing device, the force to transport toner is exerted, and toner can be loosened. To use this effect, the detection area of the developer amount detector may be disposed inside the orbit of rotation of the conveyance screw.
The inventor of the present invention, however, recognizes that there still be the possibility of erroneous detection of the amount of toner remaining in the developing device in this arrangement.
For example, to secure the detection area of the developer amount detector inside the orbit of rotation of the conveyance screw, the screw blade is absent in a partial range in an axial direction of the conveyance screw. In the partial range where the screw blade is absent, however, the force to transport toner is weaker, and there is a risk of aggregation and retention of toner outside the orbit of rotation in that range. Accordingly, in the arrangement in which the detection area of the developer amount detector is inside the orbit of rotation of the conveyance screw, it is possible that the amount of toner flowing from outside the orbit of rotation into the detection area is extremely small, and the developer amount detector erroneously detects that the amount of toner is sufficient although the amount of toner in the housing as a whole is below a predetermined amount.
Additionally, the housing of the developing device is reduced in size due to a current trend of compact image forming apparatuses. It makes difficult to reliably circulate toner inside the housing. Consequently, it is possible that the amount of toner can defer between the first compartment and the second compartment, and the amount of toner in the second compartment is not known correctly based on the detection area in the first compartment, resulting in erroneous detection of the amount of toner.
Although a conceivable approach is to dispose the detection area in the second compartment, such an arrangement is not desirable since components of the detector disposed in the second compartment may hinder the flow of toner close to the developing roller and thus adversely affect image quality.
If toner is supplied according to the erroneous detection, the amount of toner inside the developing device can become extremely large or small. If the amount of toner therein is extremely large, the pressure of toner (i.e., powder pressure), increases, and the possibility of leak of toner from the developing device increases. If the amount of toner therein is extremely small, output images tend to fade. In either case, there are risks of image quality degradation and damage to the device.
It is to be noted that, the inconveniences described above can arise in configurations employing two-component developer including toner and carrier as well as configurations employing one-component developer consisting essentially of toner.
According to the embodiment described below, even when developer aggregates and remains adjacent to the detection area in the first compartment, the remaining developer is moved by developer flowing from the second compartment through a sub-communication opening to the detection area in the first compartment. The sub-communication opening to cause such flow of developer is disposed in an intermediate portion of the partition.
Accordingly, with the effects of developer flowing through the sub-communication opening, the amount of developer in the detection area in the first compartment can be kept to a desirable level reflecting the amount of developer adjacent to the developer bearer and inside the second compartment. Accordingly, erroneous detection of the amount of developer can be reduced, and accuracy of the detection can improve.
Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views thereof, and particularly to
Referring to
The image forming apparatus 200 shown in
Additionally, a toner cartridge 7 serving as a developer container is removably attached to the process unit 1. In the present embodiment, the toner cartridge 7 includes a toner chamber 8 to contain toner supplied to the developing device 4 and a waste-toner chamber 9 in which toner removed by the cleaning blade 5 is collected. The toner chamber 8 and the waste-toner chamber 9 are united together in a container body 22 of the toner cartridge 7.
The image forming apparatus 200 further includes a sheet feeder 11, a transfer device 10 to transfer images onto sheets of recording media fed by the sheet feeder 11, a fixing device 12 to fix images on the sheets, and a discharge device 13 to discharge the sheets outside the image forming apparatus 200.
The transfer device 10 includes a transfer roller 14 serving as a transfer member. The transfer roller 14 is in contact with the photoreceptor 2 in a state in which the process unit 1 is installed in the apparatus body 100, and the contact portion therebetween is called a transfer nip. Additionally, the transfer roller 14 is electrically connected to a power source and receives a predetermined amount of voltage that is either direct-current (DC) voltage, alternating current (AC) voltage, or superimposed voltage including both.
The sheet feeder 11 includes a sheet tray 15 to contain sheets P and a feed roller 16 to transport the sheets P. Downstream from the feed roller 16 in a direction in which the sheet P is transported, a pair of registration rollers 17 is provided as timing rollers to transport the sheet P timely to the transfer nip. It is to be noted that “recording media” used there include, in addition to standard copy paper, heavy paper, post cards, thin paper such as tracing paper, coated paper, art paper, and special purpose sheets. Additionally, overhead projector (OHP) sheets or films may be used as the recording media.
The fixing device 12 includes a fixing roller 18 serving as a fixing member and a pressure roller 19 serving as a pressure member. The fixing roller 18 is heated by a heat source such as a heater. The pressure roller 19 is pressed against the fixing roller 18, and the contact portion therebetween serves as a fixing nip.
The discharge device 13 includes a pair of discharge rollers 20. An upper face of the apparatus body 100 is partly recessed into a discharge tray 21, and the sheet P discharged by the discharge rollers 20 is stacked on the discharge tray 21.
Referring to
When image formation is started, the photoreceptor 2 is rotated, and the charging roller 3 uniformly charges the surface of the photoreceptor 2 to a predetermined polarity. Then, the LED head array 6 directs a laser beam onto the charged surface of the photoreceptor 2 according to, for example, image data captured by a reading unit or transmitted from computers. Thus, an electrostatic latent image is formed on the photoreceptor 2. The electrostatic latent image on the photoreceptor 2 is developed into a toner image with toner supplied by the developing device 4.
Additionally, when image formation is started, the feed roller 16 rotates, thereby transporting the sheet P from the sheet tray 15. Then, the registration rollers 17 stop the sheet P temporarily and resume rotation at a predetermined timing to transport the sheet P to the transfer nip, timed to coincide with the arrival of the toner image on the photoreceptor 2.
At that time, a transfer bias voltage whose polarity is opposite a toner charge polarity of the toner image on the photoreceptor 2 is applied to the transfer roller 14, and thus a transfer electrical field is generated in the transfer nip. The transfer electrical field transfers the toner image from the photoreceptor 2 onto the sheet P (i.e., a transfer process). After the transfer process, the cleaning blade 5 removes toner remaining on the photoreceptor 2, and the removed toner is collected in the waste-toner chamber 9 of the toner cartridge 7.
The sheet P carrying the toner image is transported to the fixing device 12, and the toner image is fixed thereon with heat and pressure while the sheet P passes through the fixing nip between the fixing roller 18 and the pressure roller 19. Then, the pair of discharge rollers 20 discharges the sheet P onto the discharge tray 21.
Referring to
In the configuration shown in
As shown in
The developing roller 41 rotates counterclockwise in
Additionally, the supply roller 42 is in contact with the developing roller 41 and supplies toner in the development housing 40 to an outer layer of the developing roller 41 by rotating in a direction (counterclockwise in
An end of the doctor blade 43 is in contact with the surface of the developing roller 41. When toner passes through a nip between the doctor blade 43 and the developing roller 41 (i.e., a regulation nip), the amount (layer thickness) of toner supplied by the supply roller 42 onto the developing roller 41 is adjusted, and the toner is frictionally charged simultaneously.
Additionally, the toner cartridge 7 serving as a developer container is provided above the development housing 40 and removably attached thereto. The developing device 4 and the toner cartridge 7 may be integrated into a single unit.
A toner inlet 40a (i.e., a supply inlet) is formed in an upper portion of the development housing 40 to supply toner from the toner cartridge 7 to the development housing 40.
Toner is supplied to the development housing 40 according to detection results by a developer amount detector 50 to be described later, configured to detect the amount of toner remaining in the development housing 40. More specifically, when the developer amount detector 50 detects that the amount of toner inside the development housing 40 is blow a predetermined amount, the toner cartridge 7 is driven a predetermined period of time, thereby supplying a predetermined amount of toner to the development housing 40.
Additionally, a partition 46 extending substantially parallel to an axial direction of the developing roller 41 divides, but not completely, the development housing 40 into a first compartment A in which the toner inlet 40a is positioned and a second compartment B in which the developing roller 41, the doctor blade 43, and the like are provided. In the present embodiment, the partition 46 stands vertically or substantially vertically, and the first and second compartments A and B are arranged horizontally or substantially horizontally. The first and second developer conveyance members 44 and 45 are positioned in the first and second compartments A and B, respectively.
As shown in
The developer amount detector 50 is provided in the first compartment A to detect an area (i.e., a detection area) adjacent to the sub-communication opening 46b in the partition 46.
The developer amount detector 50 includes a light-emitting element 51, a light-receiving element 52, and first and second light guides 53 and 54. The light-emitting element 51 and the light-receiving element 52 together constitute an optical element. The first and second light guides 53 and 54 are provided to the development housing 40. For example, the light-emitting element 51 and the light-receiving element 52 are disposed outside the development housing 40 and attached to the apparatus body 100. For example, the first and second light guides 53 and 54 can be constructed of a material, such as an acrylic material and polycarbonate, that excels in light permeability or optical fiber.
In the present embodiment, each of the first and second light guides 53 and 54 is introduced into the first compartment A from above. A first end of the first light guide 53 is exposed outside the development housing 40 and is positioned to face the light-emitting element 51. By contrast, a second end of the first light guide 53 is positioned in the first compartment A inside the development housing 40. Additionally, a first end of the second light guide 54 is positioned in the first compartment A and at a predetermined distance from the second end of the first light guide 53 in a longitudinal direction of the partition 46. By contrast, a second end of the second light guide 54 is exposed from the development housing 40 and is positioned to face the light-receiving element 52.
The light emitted from the light-emitting element 51 enters the first end of the first light guide 53 and exits from the second end of the first light guide 53. The light exiting the first light guide 53 enters the second light guide 54 from the first end thereof and exits from the second end of the second light guide 54. Then, the light reaches the light-receiving element 52. Thus, the second end of the first light guide 53 and the first end of the second light guide 54 facing each other defines a light transmission path L (i.e., a gap) therebetween.
When the amount of toner in the development housing 40 is sufficient, light is blocked by the toner present in the gap between the second end of the first light guide 53 and the first end of the second light guide 54 facing each other. Thus, the light-receiving element 52 does not receive the light. However, as toner is consumed in printing, the level of toner in the development housing 40 descends below the first and second light guides 53 and 54, that is, no toner is present between the second end of the first light guide 53 and the first end of the second light guide 54. Accordingly, the light reaches the light-receiving element 52. Thus, the amount of toner inside the development housing 40 can be detected according to changes in the output value of the light-receiving element 52. Specifically, for example, when the amount of toner is recognizable, a reference waveform obtained with the light-receiving element 52 is stored in a memory of a controller of the apparatus, and a measured waveform in the detection is compared with the reference waveform, thereby determining the amount of toner. In the present embodiment, the light transmission path L (indicated with hatching in
The first and second developer conveyance members 44 and 45 rotate to transport toner in opposite directions as indicated by arrows X shown in the drawings. The toner transported by the first and second developer conveyance members 44 and 45 to axial ends of the first and second compartments A and B is not transported further in the axial direction but is transported through the main communication openings 46a to the other compartment (from the first compartment A to the second compartment B, or from the second compartment B to the first compartment A). Then, toner is transported by the first and second developer conveyance members 44 and 45 in the first and second compartments A and B to the opposite ends, respectively, after which toner is transported again through the main communication openings 46a to the other compartment. Toner can be circulated between the first compartment A and the second compartment B by repeating this operation. The first and second compartments A and B together constitute a toner conveyance route.
To mix the supplied toner with the toner inside the development housing 40 sufficiently, it is preferable that the distance from the toner inlet 40a to the second compartment B, which corresponds to the development range, be relatively long so that the supplied toner is mixed in for a longer time. Accordingly, as the location of the toner inlet 40a, the first compartment A is more preferable than the second compartment B. More preferably, the toner inlet 40a is positioned on the upstream side in the first compartment A in a developer conveyance direction as shown in
Additionally, while toner is circulated as described above, toner flows from the second compartment B through the sub-communication opening 46b into the light transmission path L (shown in
Accordingly, when toner flows from the sub-communication opening 46b thereto, the toner in the light transmission path L of the first compartment A can be kept to a level reflecting the amount of toner inside the second compartment B and adjacent to the developing roller 41. This configuration can reduce erroneous detection of the amount of toner in the light transmission path L, and accuracy of toner amount detection can improve. This configuration is advantageous particularly in compact developing devices. Toner is more likely to aggregate when the developing device 4 becomes compact and accordingly the toner conveyance route inside the development housing 40 is reduced in size. With the sub-communication opening 46b, however, a desirable flow of toner can be maintained around the light transmission path L.
Additionally, as shown in
Consequently, in the first compartment A, the first and second light guides 53 and 54 hinder toner from flowing into the light transmission path L from above on the upstream side in the developer conveyance direction. Accordingly, the flow of toner through the sub-communication opening 46b into the light transmission path L is particularly effective. In other words, with the sub-communication opening 46b, both of compactness of the developing device 4 and higher accuracy in toner amount detection can be secured.
Additionally, as shown in
In the axial direction of the developing roller 41, a length W1 (i.e., a width) of the sub-communication opening 46b is greater than a length W2 of the light transmission path L. With this configuration, since toner flows in a greater range than a range of the light transmission path L, the inflow of toner into the light transmission path L can be secured.
A lower end 46b1 of the sub-communication opening 46b is positioned higher than a lower end 46a1 the main communication opening 46a. With this arrangement, toner can flow in the sub-communication opening 46b only when the amount of toner exceeds a predetermined amount. Accordingly, when the amount of toner is smaller than the predetermined amount, toner circulates through only the main communication openings 46a without flowing in the sub-communication opening 46b. It is to be noted that the amount of toner at which toner starts flowing in the sub-communication opening 46b can be adjusted with the height of the lower end 46b1 of the sub-communication opening 46b.
As shown in
A cleaner 60 is provided to the rotary shaft 44a of the first developer conveyance member 44 to clean the ends (in particular, end faces 531 and 541 shown in
Additionally, in the axial direction, the first developer conveyance member 44 includes a partial range Q where the conveyance blade 44b is not present, and the ends of the first and second light guides 53 and 54 facing each other are disposed within the partial range Q. This arrangement can prevent the first and second light guides 53 and 54 from interfering with the conveyance blade 44b, and the light transmission path L (shown in
It is to be noted that, although the entire light transmission path L is within the orbit of rotation in the present embodiment, alternatively, the light transmission path L may be positioned, partly or entirely, outside the orbit of rotation of the conveyance blade 44b. Additionally, the light transmission path L between the first and second light guides 53 and 54 substantially parallels the direction in which the first developer conveyance member 44 transports developer, that is, the axis of the first developer conveyance member 44. It is to be noted that, alternatively, the light transmission path L may be in a direction crossing (for example, perpendicular to) the axial direction of the first developer conveyance member 44.
As shown in
Additionally, as in the configuration shown in
By contrast, although the second developer conveyance member 45 is a screw including a rotary shaft 45a and a spiral blade spirally provided to the outer circumference of the rotary shaft 45a, the spiral blade is discontinuous in the axial direction and constructed of multiple conveyance blades 45b. As shown in
Specifically, as shown in
It is to be noted that, in the present embodiment, when the second developer conveyance member 45 is viewed in the axial direction, the two ranges R of the conveyance blades 45b axially adjacent overlap partly in the circumferential direction, thus eliminating circumferential ranges where only the ranges without the conveyance blades 45b overlap each other. It is preferable that the ranges R where the conveyance blades 45b are provided be identical or similar in size and shifted by an identical or similar amount in the circumferential direction.
The above-described configuration of the second developer conveyance member 45 is advantageous as follows. Due to the demand for more compact image forming apparatuses, gears to give rotational driving force to the developer conveyance members continue to shrink. In this case, it is possible that the velocity of rotation of the developer conveyance member increases and the toner conveyance speed is accelerated extremely. Accordingly, it is preferred to adjust the toner conveyance speed using a configuration different from a drive transmission system such as the gears for reliable toner conveyance. In view of the foregoing, the conveyance blades 45b are configured as described above in the present embodiment. Thus, the toner conveyance speed can be adjusted without modifying the drive transmission system. It is to be noted that this configuration may be used also in the first developer conveyance member 44 provided in the first compartment A not limited to the second developer conveyance member 45 provided in the second compartment B.
As described above, according to the embodiment described above, with the effects of toner flowing through the sub-communication opening 46b in the partition 46, the amount of toner in the first compartment A (the light transmission path L in particular) can be kept to a desirable level reflecting the amount of toner adjacent to the developing roller 41 and inside the second compartment B. Accordingly, erroneous detection of the amount of toner can be reduced, and accuracy of toner amount detection can improve.
Numerous additional modifications to the above-described embodiment and variations are possible. It is therefore to be understood that, within the scope of the appended claims, the disclosure of this patent specification may be practiced otherwise than as specifically described herein.
For example, although the description above concerns the configuration in which the first and second compartments A and B are horizontally adjacent via the partition 46, alternatively, the first and second compartments A and B may be vertically adjacent to each other via the partition 46. In this case, the first compartment A is above the second compartment B.
Additionally, although a sensor to detect transmitted light is used as the developer amount detector 50 in the above-described embodiment, alternatively, a sensor to detect reflected light, a magnetic permeability sensor, or the like may be used instead. Additionally, although one-component developer consisting essentially toner is used in the above-described embodiment, two-component developer including toner and carrier may be used instead.
Additionally, although the toner cartridge 7 is removably installed in the amount of the process unit 1 in the above-described embodiment, alternatively, the toner cartridge 7 may be removably installed in a mount of the apparatus body 100 directly.
Additionally, although the monochrome image forming apparatus 200 is described above, various aspects of this specification can adapt to image forming apparatuses of other types, such as a multicolor image forming apparatus employing an intermediate-transfer method shown in
The image forming apparatus shown in
It is to be noted that elements of the image forming apparatuses shown in
Yet additionally, various aspects of this specification are applicable to printers, copiers, facsimile machines, and multifunction machines or multifunction peripherals (MFPs) having these capabilities.
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|---|---|---|---|
| 2013-133814 | Jun 2013 | JP | national |
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| Number | Date | Country | |
|---|---|---|---|
| 20150003848 A1 | Jan 2015 | US |
