Patent Application
20140140732
This application is based upon and claims the benefit of priority from the corresponding Japanese Patent Application No. 2012-256073 filed on Nov. 22, 2012, and No. 2012-256074 filed on Nov. 22, 2012, the entire contents of which are incorporated herein by reference.
The present disclosure relates to developing apparatuses that are suitably used for image forming apparatuses such as copy machines and printers, and image forming apparatuses having the developing apparatuses mounted therein.
To date, developing devices for use in image forming apparatuses have been known. The developing device includes: a development housing having a developing roller and an agitating screw; and a toner container that is detachably mounted to the development housing for supplying toner. A toner outlet is formed in a bottom portion of the toner container so as to be openable and closable, and a toner supply inlet is formed in the development housing at a position corresponding to the toner outlet. When the toner container is mounted to the development housing, and the toner outlet and the toner supply inlet are opened, toner in the toner container is supplied into a predetermined circulation-conveying path formed in the development housing.
The circulation-conveying path includes a forward conveying path for the toner supply inlet, and a return conveying path for the developing roller. In each conveying path in the circulation-conveying path, an agitating screw having helical blades provided around a rotation shaft is mounted. Toner is circulated and conveyed, by the agitating screws, in and between the forward conveying path and the return conveying path.
In the developing device having such a structure, a conveying capability reduction portion configured to locally reduce conveying capability is provided, downstream of the toner supply inlet, on the downstream side of the agitating screw disposed in the forward conveying path. Due to the conveying capability reduction portion, an accumulation portion for toner is formed, near the toner supply inlet, upstream of the conveying capability reduction portion. When an amount of toner is increased in the accumulation portion, the toner supply inlet is blocked with toner in the accumulation portion. On the other hand, when an amount of toner is reduced in the accumulation portion, a gap is generated between the toner supply inlet and the accumulation portion for toner, and toner enters the development housing from the toner container. Thus, an amount of toner to be additionally supplied from the toner container into the development housing is adjusted according to an amount of toner accumulated in the accumulation portion.
A developing apparatus according to one aspect of the present disclosure includes a housing, an additional-developer storage portion, a developing roller, a developer conveying path, a divider, a first communication path, a second communication path, a developer reception opening, a conveying member, a downstream-side conveying capability reduction portion, and an upstream-side conveying capability reduction wall. The housing has a pair of wall portions, and a top cover that extends between the pair of wall portions. The additional-developer storage portion is detachably mounted to the housing and stores additional developer to be supplied into the housing. The developing roller is rotatably supported, by the housing, between the pair of wall portions, and carries developer. The developer conveying path includes a first conveying path which is disposed in the housing so as to be spaced from the developing roller, and in which the developer is conveyed in a first direction, and a second conveying path which is disposed between the developing roller and the first conveying path, in which the developer is conveyed in a second direction opposite to the first direction, and by which the developer is supplied to the developing roller, and the developer conveying path has an upper portion defined by the top cover. The divider is disposed in the housing and divides the first conveying path and the second conveying path from each other. The first communication path disposed between one of the paired wall portions and a corresponding one of end portions of the divider, and has a function of delivering the developer from the first conveying path to the second conveying path. The second communication path is disposed between the other of the paired wall portions and the other of the end portions of the divider, and has a function of delivering the developer from the second conveying path to the first conveying path. The developer reception opening is formed in the housing so as to oppose a position on a downstream side, in the first direction, of the first conveying path, and allows the additional developer to be received therethrough and supplied into the developer conveying path. The conveying member is disposed in the first conveying path, is driven to rotate, and conveys the developer in the first direction such that the developer passes by a position where the developer reception opening opposes the first conveying path. The downstream-side conveying capability reduction portion is disposed, in the conveying member or the housing, downstream of the developer reception opening in the first direction, and locally reduces a developer conveying capability, for the developer, of the conveying member, to form a first accumulation portion in which the developer is accumulated at a position opposing the developer reception opening. The upstream-side conveying capability reduction wall is disposed upstream of the developer reception opening in the first direction so as to project from the top cover toward the conveying member, and locally reduces a developer conveying capability, for the developer, of the conveying member, to form a second accumulation portion in which the developer is accumulated upstream of the developer reception opening in the first direction.
A developing apparatus according to another aspect of the present disclosure includes a housing, an additional-developer storage portion, a developing roller, a developer conveying path, a developer reception opening, a conveying member, and a conveying capability reduction wall. The housing has a pair of wall portions, and a top cover that extends between the pair of wall portions. The additional-developer storage portion is detachably mounted to the housing and stores additional developer to be supplied into the housing. The developing roller is rotatably supported, by the housing, between the pair of wall portions, and carries developer. The developer conveying path includes a first conveying path which is disposed in the housing so as to be spaced from the developing roller, and in which the developer is conveyed in a first direction, and a second conveying path which is disposed between the developing roller and the first conveying path, in which the developer is conveyed in a second direction opposite to the first direction, and by which the developer is supplied to the developing roller, and the developer conveying path has an upper portion defined by the top cover, and allows the developer to be circulated and conveyed therein. The developer reception opening is formed in the housing so as to oppose a position on a downstream side, in the first direction, of the first conveying path, and allows the additional developer to be received therethrough and supplied into the developer conveying path. The conveying member is disposed in the first conveying path, is driven to rotate, and conveys the developer in the first direction such that the developer passes by a position where the developer reception opening opposes the first conveying path. The conveying capability reduction wall is disposed downstream of the developer reception opening in the first direction so as to project from the top cover toward the conveying member, and locally reduces a developer conveying capability, for the developer, of the conveying member, to form an accumulation portion in which the developer is accumulated at a position opposing the developer reception opening.
An image forming apparatus according to still another aspect of the present disclosure includes a developing apparatus, an image carrier, and a transfer device. The image carrier has a surface on which an electrostatic latent image is formed, and to which developer is supplied from the developing apparatus. The transfer device transfers an image from the image carrier to a sheet. The developing apparatus includes a housing, an additional-developer storage portion, a developing roller, a developer conveying path, a divider, a first communication path, a second communication path, a developer reception opening, a conveying member, a downstream-side conveying capability reduction portion, and an upstream-side conveying capability reduction wall. The housing has a pair of wall portions, and a top cover that extends between the pair of wall portions. The additional-developer storage portion is detachably mounted to the housing and stores additional developer to be supplied into the housing. The developing roller is rotatably supported, by the housing, between the pair of wall portions, and carries developer. The developer conveying path includes a first conveying path which is disposed in the housing so as to be spaced from the developing roller, and in which the developer is conveyed in a first direction, and a second conveying path which is disposed between the developing roller and the first conveying path, in which the developer is conveyed in a second direction opposite to the first direction, and by which the developer is supplied to the developing roller, and the developer conveying path has an upper portion defined by the top cover. The divider is disposed in the housing and divides the first conveying path and the second conveying path from each other. The first communication path is disposed between one of the paired wall portions and a corresponding one of end portions of the divider and has a function of delivering the developer from the first conveying path to the second conveying path. The second communication path is disposed between the other of the paired wall portions and the other of the end portions of the divider, and has a function of delivering the developer from the second conveying path to the first conveying path. The developer reception opening is formed in the housing so as to oppose a position on a downstream side, in the first direction, of the first conveying path, and allows the additional developer to be received therethrough and supplied into the developer conveying path. The conveying member is disposed in the first conveying path, is driven to rotate, and conveys the developer in the first direction such that the developer passes by a position where the developer reception opening opposes the first conveying path. The downstream-side conveying capability reduction portion is disposed, in the conveying member or the housing, downstream of the developer reception opening in the first direction, and locally reduces a developer conveying capability, for the developer, of the conveying member, to form a first accumulation portion in which the developer is accumulated at a position opposing the developer reception opening. The upstream-side conveying capability reduction wall is disposed upstream of the developer reception opening in the first direction so as to project from the top cover toward the conveying member, and locally reduces a developer conveying capability, for the developer, of the conveying member, to form a second accumulation portion in which the developer is accumulated upstream of the developer reception opening in the first direction.
An image forming apparatus according to still another aspect of the present disclosure includes a developing apparatus, an image carrier, and a transfer device. The image carrier has a surface on which an electrostatic latent image is formed, and to which developer is supplied from the developing apparatus. The transfer device transfers an image from the image carrier to a sheet. The developing apparatus includes a housing, an additional-developer storage portion, a developing roller, a developer conveying path, a developer reception opening, a conveying member, and a conveying capability reduction wall. The housing has a pair of wall portions, and a top cover that extends between the pair of wall portions. The additional-developer storage portion is detachably mounted to the housing and stores additional developer to be supplied into the housing. The developing roller is rotatably supported, by the housing, between the pair of wall portions, and carries developer. The developer conveying path includes a first conveying path which is disposed in the housing so as to be spaced from the developing roller, and in which the developer is conveyed in a first direction, and a second conveying path which is disposed between the developing roller and the first conveying path, in which the developer is conveyed in a second direction opposite to the first direction, and by which the developer is supplied to the developing roller, and the developer conveying path has an upper portion defined by the top cover, and allows the developer to be circulated and conveyed therein. The developer reception opening is formed in the housing so as to oppose a position on a downstream side, in the first direction, of the first conveying path, and allows the additional developer to be received therethrough and supplied into the developer conveying path. The conveying member is disposed in the first conveying path, is driven to rotate, and conveys the developer in the first direction such that the developer passes by a position where the developer reception opening opposes the first conveying path. The conveying capability reduction wall is disposed downstream of the developer reception opening in the first direction so as to project from the top cover toward the conveying member, and locally reduces a developer conveying capability, for the developer, of the conveying member, to form an accumulation portion in which the developer is accumulated at a position opposing the developer reception opening.
This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description with reference where appropriate to the accompanying drawings. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure.
Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.
The image forming apparatus 1 includes a main body housing 10 structured as an almost rectangular parallelepiped housing, and includes, in the main body housing 10, an image forming portion 30, a fixing portion 40, a toner container 50, and a sheet feed portion 90.
A front cover 11 and a rear cover 12 are provided on the front surface side and the rear surface side, respectively, of the main body housing 10. When the front cover 11 is opened, the toner container 50 is exposed on the front surface side. Thus, a user is allowed to take out the toner container 50 from the main body housing 10 on the front surface side when toner is consumed. The rear cover 12 is opened at occurrence of sheet jam, or for maintenance. Units of the image forming portion 30 and the fixing portion 40 can be taken out from the main body housing 10 on the rear surface side when the rear cover 12 is opened.
Further, on the side surfaces of the main body housing 10, a left cover 12L (
The image forming portion 30 performs image forming process in which a toner image is formed on a sheet fed by the sheet feed portion 90. The image forming portion 30 includes a photosensitive drum 31 (image carrier), and includes a charging device 32, an exposure device (which is not shown in
The photosensitive drum 31 includes a rotation shaft and a cylindrical surface that rotates about the rotation shaft. On the cylindrical surface, an electrostatic latent image is formed, and a toner image corresponding to the electrostatic latent image is carried on the cylindrical surface. As the photosensitive drum 31, a photosensitive drum formed by an amorphous-silicon-(a-Si)-based material, may be used.
By the charging device 32, the surface of the photosensitive drum 31 is uniformly charged. The charging device 32 includes a charging roller that abuts the photosensitive drum 31.
The cleaning device 35 includes a not-illustrated cleaning blade, and removes, for cleaning the photosensitive drum 31, toner attached to the circumferential surface of the photosensitive drum 31 from which a toner image has been transferred, and conveys the removed toner to a not-illustrated recovery device.
The exposure device includes a laser light source and optical devices such as a mirror and a lens, and applies, to the circumferential surface of the photosensitive drum 31, light modulated based on image data obtained from an external device such as a personal computer, to form an electrostatic latent image. The developing apparatus 20 supplies toner to the circumferential surface of the photosensitive drum 31 in order to develop the electrostatic latent image on the photosensitive drum 31 and form a toner image. The developing apparatus 20 includes a developing roller 21 that carries toner to be supplied to the photosensitive drum 31, and a first agitating screw 24 and a second agitating screw 23 that circulate and convey, in a development housing 210 (
The transfer roller 34 is a roller that transfers, to a sheet, the toner image formed on the circumferential surface of the photosensitive drum 31. The transfer roller 34 abuts the cylindrical surface of the photosensitive drum 31, thereby forming a transfer nip portion. Transfer bias having a polarity opposite to that of the toner is applied to the transfer roller 34.
The fixing portion 40 performs a fixing process in which the transferred toner image is fixed onto a sheet. The fixing portion 40 includes a fixing roller 41 having a heat source thereinside, and a pressurizing roller 42 that is pressed against the fixing roller 41, to form a fixing nip portion between the pressurizing roller 42 and the fixing roller 41. When the sheet having the toner image transferred thereto passes through the fixing nip portion, the toner image is heated by the fixing roller 41 and pressurized by the pressurizing roller 42, to be fixed onto the sheet.
The toner container 50 (additional-developer storage portion) stores toner to be additionally supplied to the developing apparatus 20. The toner container 50 includes: a container body 51 that is a main storage portion for additional toner to be supplied; a cylindrical portion 52 that projects from a lower portion of one side surface of the container body 51; a lid member 53 that covers the other side surface of the container body 51; and a rotating member 54, accommodated in the container, which conveys toner. The additional toner stored in the toner container 50, is supplied, into the developing apparatus 20, through a toner outlet 521 that is disposed at the bottom surface of the end portion of the cylindrical portion 52, by the rotating member 54 being driven to rotate. Further, a container top cover 50H that covers the upper portion of the toner container 50 is positioned below the sheet discharge portion 13 (see
The sheet feed portion 90 includes a sheet feed cassette 91 that stores sheets on which image forming process is to be performed (
In the main body housing 10, a main conveying path 92F and a reverse conveying path 92B, for conveying a sheet, are formed. The main conveying path 92F extends from the sheet feeding portion 91A of the sheet feed portion 90 through the image forming portion 30 and the fixing portion 40 to a sheet discharge outlet 14 that opposes the sheet discharge portion 13 on the top surface of the main body housing 10. The reverse conveying path 92B is a conveying path through which a sheet on which one-side printing has been performed is returned to the upstream side of the image forming portion 30 in the main conveying path 92F when double-side printing is performed for the sheet.
The main conveying path 92F extends so as to pass through the transfer nit portion formed by the photosensitive drum 31 and the transfer roller 34, from the lower side toward the upper side. Further, a pair of registration rollers 93 is disposed upstream of the transfer nit portion in the main conveying path 92F. The sheet is temporarily stopped at the pair of registration rollers 93, to perform skew correction for the sheet, and is thereafter fed to the transfer nit portion at a predetermined time for image transfer. A plurality of conveying rollers for conveying sheets are disposed at appropriate positions in the main conveying path 92F and the reverse conveying path 92B. For example, a pair of sheet discharge rollers 94 is disposed near the sheet discharge outlet 14.
The reverse conveying path 92B is formed between an outer side surface of a reversing unit 95 and an inner surface of the rear cover 12 of the main body housing 10. In inner side surfaces of the reversing unit 95, the transfer roller 34 and one of the paired registration rollers 93 are disposed. The rear cover 12 and the reversing unit 95 are each pivotable about a shaft of a pivot portion 121 disposed at the lower ends of the rear cover 12 and the reversing unit 95. When sheet jam occurs in the reverse conveying path 92B, the rear cover 12 is opened. When sheet jam occurs in the main conveying path 92F, or when units of the photosensitive drum 31 or the developing apparatus 20 are taken out, the reversing unit 95 in addition to the rear cover 12 is opened.
<Developing Apparatus>
Next, the developing apparatus 20 according to a first embodiment of the present disclosure will be described in detail.
In the internal space 220, the developing roller 21, the first agitating screw 23 (conveying member) and the second agitating screw 24, and a toner supply inlet 25 (developer reception opening) are disposed. In the present embodiment, a one-component development mode in which the internal space 220 is filled with toner, as developer, including a magnetic material, is used. Toner is agitated and conveyed in the internal space 220, and is sequentially supplied from the developing roller 21 to the photosensitive drum 31 in order to develop an electrostatic latent image.
The developing roller 21 is rotatably supported, by the development housing 210, between the first wall portion 210A and the second wall portion 210B that are paired, and the developing roller 21 carries developer on the surface thereof. The developing roller 21 has a cylindrical shape that extends in the longitudinal direction of the development housing 210. The developing roller 21 includes a sleeve 21S that has a cylindrical shape and is driven to rotate, and a magnet 21M that has a circular-column-like shape and is fixedly disposed inside the sleeve 21S along the axial direction. The sleeve 21S is driven, by not-illustrated driving means, to rotate in the direction indicated by an arrow D31 shown in
In
The internal space 220 in the development housing 210 is covered with the top cover 211 (
The toner supply inlet 25 is an opening that is a hole formed in the top cover 211, and is disposed above a region near the left end (the downstream side in the first direction) of the first conveying path 221 (
The first agitating screw 23 is disposed in the first conveying path 221. The first agitating screw 23 includes a first rotation shaft 23a (rotation axis), and first helical blades 23b (screw blades) that are helically disposed so as to project on the circumference of the first rotation shaft 23a. The first agitating screw 23 is driven to rotate about the first rotation shaft 23a (in the direction indicated by an arrow D33 in
The second agitating screw 24 is disposed in the second conveying path 222. The second agitating screw 24 includes a second rotation shaft 24a, and second helical blades 24b that are helically disposed so as to project on the circumference of the second rotation shaft 24a. The second agitating screw 24 is driven to rotate about the second rotation shaft 24a (in the direction indicated by an arrow D32 in
The second agitating screw 24 is disposed in front of and below the developing roller 21. Namely, the second agitating screw 24 is disposed so as to oppose the N2 pole of the magnet 21M. Toner is supplied from the second agitating screw 24 to the sleeve 21S according to rotation of the second agitating screw 24 (in the direction indicated by the arrow D32 in
A second paddle 24c is disposed on the downstream side, in the toner conveying direction (the direction indicated by the arrow D2), of the second agitating screw 24. The second paddle 24c is a plate-like member disposed on the second rotation shaft 24a. The second paddle 24c rotates with the second rotation shaft 24a, and delivers toner from the second conveying path 222 to the first conveying path 221 in the direction indicated by an arrow D4 in
The developing apparatus 20 further includes a layer regulation member 60 and a magnet plate 70.
The layer regulation member 60 is disposed in front of and above the developing roller 21. The layer regulation member 60 is disposed along the axial direction of the developing roller 21 so as to oppose the circumferential surface of the developing roller 21 (the sleeve 21S). Specifically, the layer regulation member 60 is disposed above the developing roller 21 so as to oppose the S1 pole of the magnet 21M. The layer regulation member 60 is a plate-like member formed by a magnetic material. The layer regulation member 60 has a rectangular shape having a long side in the direction toward the developing roller 21, on a cross-section orthogonal to the rotation axis of the developing roller 21. The end portion of the layer regulation member 60 is spaced from the sleeve 21S of the developing roller 21. As a result, a layer regulation gap G is formed between the end portion and the sleeve 21S. The layer regulation member 60 functions to regulate the thickness of a layer of toner scooped from the second agitating screw 24 onto the sleeve 21S.
The magnet plate 70 is disposed along and in front of the layer regulation member 60. In other words, the magnet plate 70 is disposed upstream of the layer regulation member 60 in the rotation direction (the direction indicated by an arrow D31 in
Thus, in the present embodiment, the magnet plate 70 is disposed upstream of the layer regulation member 60 in the rotation direction of the developing roller 21 (the sleeve 21S). In other words, the magnet plate 70 and the layer regulation member 60 are disposed in order, respectively, from the upstream side toward the downstream side in the rotation direction of the developing roller 21, so as to oppose the circumferential surface of the developing roller 21.
The second agitating screw 24 supplies toner toward a first position P1, on the circumferential surface of the sleeve 21S, which faces vertically downward, to supply toner to the sleeve 21S. The layer regulation member 60 regulates a thickness of toner on the sleeve 21S at a second position P2, on the circumferential surface of the sleeve 21S, which is located above the first position P1 and faces vertically upward. At this time, the S1 pole of the magnet 21M and the S pole of the magnet plate 70 have magnetic forces, respectively, of the same polarity, whereby a repelling magnetic field is generated between the sleeve 21S and the magnet plate 70. The repelling magnetic field is divided into a magnetic field toward the upstream side in the rotation direction of the sleeve 215, and a magnetic field toward the downstream side (the layer regulation member 60 side) in the rotation direction of the sleeve 21S. Therefore, to toner conveyed on the sleeve 21S to under the magnet plate 70, a force for moving the toner on the circumferential surface of the sleeve 21S is applied. As a result, in a state where a layer of the toner is thin, toner layer regulation can be performed. Further, toner that has not entered the layer regulation gap G of the layer regulation member 60 is promoted by the repelling magnetic field to move toward the upstream side in the rotation direction of the sleeve 21S.
<Accumulation Portion>
The toner container 50 described above is disposed above the toner supply inlet 25 of the development housing 210. The toner container 50 includes thereinside a toner conveying path 50a in which toner is conveyed, the rotating member 54, and the toner outlet 521. The toner container 50 is mounted to the developing apparatus 20 such that the longitudinal direction (the direction in which the toner conveying path 50a extends) of the toner container 50 is orthogonal to the longitudinal direction (the direction in which developer is conveyed by the first agitating screw 23, the direction indicated by the arrow D1, the first direction) of the developing apparatus 20.
The toner outlet 521 is disposed at the bottom portion of the toner container 50 so as to correspond to the toner supply inlet 25 of the developing apparatus 20. The rotating member 54 has a shaft portion and a blade portion that rotates about the shaft portion (see
Next, a flow of supply of new toner through the toner supply inlet 25 into the developing apparatus 20 according to the present embodiment will be described.
Additional toner T2 supplied through the toner outlet 521 of the toner container 50, falls into the first conveying path 221, is mixed with existing toner T1, and is conveyed in the direction indicated by the arrow D1 by the first agitating screw 23. At this time, the toner T1 and the toner T2 are agitated and electrically charged.
In the first agitating screw 23, the first shaft portion 26A that locally reduces developer conveying performance is provided downstream of the toner supply inlet 25 in the toner conveying direction. The first shaft portion 26A is formed by eliminating the first helical blades 23b of the first agitating screw 23 (see
Further, the developing apparatus 20 includes a downstream-side reduction wall 28A (downstream-side conveying capability reduction portion). The downstream-side reduction wall 28A is a wall portion that is disposed downstream of the toner supply inlet 25 in the first direction (the direction indicated by the arrow D1) so as to project downward from the top cover 211 of the development housing 210. The downstream-side reduction wall 28A is disposed such that the lower end of the downstream-side reduction wall 28A is closer to the first rotation shaft 23a than the outer diameter end of the first helical blades 23b of the first agitating screw 23 is. As described above, the downstream-side reduction wall 28A is disposed so as to oppose the first shaft portion 26A, thereby preventing the first agitating screw 23 and the downstream-side reduction wall 28A from interfering with each other. In this structure, toner accumulation portions can be stably formed upstream and downstream of the toner supply inlet 25 by the downstream-side reduction wall 28A and the upstream-side reduction wall 28B.
In the first conveying path 221, toner conveyed from a region upstream of the downstream-side reduction wall 28A hits against the downstream-side reduction wall 28A, and starts to be accumulated. Toner is accumulated at a position, immediately upstream of the downstream-side reduction wall 28A, at which the toner supply inlet 25 opposes the first conveying path 221, and in a region preceding the position. As a result, a downstream-side accumulation portion 27 (first accumulation portion) for developer is formed near the entrance of the toner supply inlet 25.
When an amount of toner in the internal space 220 is increased due to the additional toner T2 being supplied through the toner supply inlet 25, the toner supply inlet 25 is blocked (sealed) with toner accumulated in the downstream-side accumulation portion 27, to reduce additional supply of toner. Thereafter, when toner in the internal space 220 is consumed by the developing roller 21, and toner accumulated in the downstream-side accumulation portion 27 is reduced, toner with which the toner supply inlet 25 is blocked is reduced, whereby a gap is generated between the downstream-side accumulation portion 27 and the toner supply inlet 25. As a result, the additional toner T2 enters the internal space 220 again through the toner supply inlet 25. Thus, in the present embodiment, a volume-based toner supply mode is used in which a received amount of toner to be additionally supplied, is adjusted according to reduction of toner accumulated in the downstream-side accumulation portion 27.
<Dispersion of Additionally Supplied Toner>
Next, a problem with supply of toner by a developing apparatus 20Z as compared to supply of toner in the present embodiment will be described.
In the developing apparatus 20Z having the volume-based toner supply mode as described above, when toner remaining in the toner container is reduced, an amount of supplied toner is reduced, thereby reducing an amount of toner in a development housing 210Z. In this case, when it is determined, by a not-illustrated density sensor, that an amount of remaining toner is small, exchange of the toner containers is prompted. At this time, since an amount of toner in the development housing 210Z is small, an amount of toner in the downstream-side accumulation portion 27Z located downstream of the toner supply inlet 25Z is also small. Additional toner enters the development housing 210Z from a new toner container mounted, by a user, to the developing apparatus 20Z. The new toner container is filled with a large amount of toner, and therefore the additional toner is likely to rapidly enter the development housing 210Z.
Toner that has entered the development housing 210Z enters the downstream-side accumulation portion 27Z. The toner is conveyed to a second conveying path 222Z (not shown) that communicates with a first conveying path 221Z, according to a first agitating screw 23Z being driven to rotate. At this time, a surface state or an electrically charged state may be different between a large amount of additional toner that has been supplied to the development housing 210Z from the new toner container, and existing toner having been circulated in the development housing 210Z, in many cases. Although the additional toner and the existing toner are circulated in the development housing 210Z, to gradually have approximate characteristics, the toner may be charged so as to be polarized into two poles, due to difference in surface state between the additional toner and the existing toner, immediately after the entering of the additional toner. Namely, one of the additional toner and the existing toner is positively charged, and the other thereof is negatively charged. As a result, developer fogging may occur in an image on the photosensitive drum 31 and on a sheet. In particular, in the developing apparatus 20Z shown in
In addition, additionally supplied toner, which rapidly enters the development housing 210Z, is less likely to sink toward the bottom portion of the development housing 210Z even if a rotational force of the first agitating screw 23Z is applied. In particular, in the conveying capability reduction portion 26Z located downstream of the toner supply inlet 25Z, toner agitating capability is reduced, so that toner dispersion becomes more difficult. In this case, the additional toner that has entered the development housing 210Z, enters the second conveying path 222Z through a first communication path 223Z (not shown) while moving over the surface layer (the upper layer, a draft surface portion) of the toner layer in the first conveying path 221Z. If toner that has entered the second conveying path 222Z without sufficiently dispersing, is supplied as a lump to a developing roller 21Z (not shown) as it is, a problem arises that vertically-striped developer fogging occurs in an image.
Downstream-Side Reduction Wall 28A and Upstream-Side Reduction Wall 28B>
The developing apparatus 20 according to the present embodiment includes the downstream-side reduction wall 28A and the upstream-side reduction wall 28B (upstream-side conveying capability reduction portion) as described above.
As shown in
As shown in
In
In other words, due to the downstream-side reduction wall 28A, toner is densely distributed upstream of the downstream-side reduction wall 28A, and toner is sparsely distributed downstream of the downstream-side reduction wall 28A. Further, due to the upstream-side reduction wall 28B, toner is densely distributed upstream of the upstream-side reduction wall 28B, and toner is sparsely distributed downstream of the upstream-side reduction wall 28B. Therefore, in a region that opposes the toner supply inlet 25, toner can be maintained sparse on the upstream side and toner can be maintained dense on the downstream side. The additional toner moves into a space in which toner is sparsely distributed, and, in the space, the upstream-side reduction wall 28B is provided, and further toner that has been circulated in the development housing 210 is accumulated upstream of the upstream-side reduction wall 28B in a dense state. Thus, even when a pressure in the toner container 50 is high, toner is not pushed into a region upstream of the upstream-side reduction wall 28B, and toner is distributed near the toner supply inlet 25 in the development housing 210 as uniformly as possible.
Further, in the present embodiment, the downstream-side reduction wall 28A is disposed in an upper portion of a region downstream of the toner supply inlet 25. Therefore, additional toner supplied through the toner supply inlet 25 is conveyed so as to sink under the downstream-side reduction wall 28A due to a rotational force of the first agitating screw 23. Thus, the additional toner is appropriately mixed with toner therearound. In other words, additional toner is less likely to be supplied to the second conveying path 222 and the developing roller 21 in an insufficiently dispersed state while moving over the upper layer (draft surface) of the toner layer in a region downstream of the toner supply inlet 25.
Next, a developing apparatus 20A according to a second embodiment of the present disclosure will be described with reference to
The reduction paddle 28C is disposed, in a first agitating screw 23A, downstream of a toner supply inlet 25A in the first direction. The reduction paddle 28C is a rib member that is extended on and between the helical blades adjacent to each other in the first agitating screw 23A. The reduction paddle 28C locally reduces toner conveying capability of the first agitating screw 23A, to form a downstream-side accumulation portion 27A in which toner is accumulated at a position that opposes the toner supply inlet 25A.
In addition, also in the developing apparatus 20A, an upstream-side accumulation portion 29A is formed upstream of the toner supply inlet 25A due to the upstream-side reduction wall 28B disposed upstream of the toner supply inlet 25A. Therefore, toner accumulation portions can be stably formed upstream and downstream of the toner supply inlet 25A without depending on an amount of toner in a development housing 210A1. As a result, a stable amount of additional toner enters the development housing 210A1 (an arrow D81 in
Next, examples for the first embodiment and the second embodiment of the present disclosure will be described. However, the present disclosure is not restricted by examples described below. Examples described below were implemented under the following experimental conditions.
<Experimental Conditions>
Photosensitive drum 31: OPC drum
Circumferential speed of photosensitive drum 31: 146 mm/sec
Layer regulation gap G: 0.3 mm
Developing bias AC component: rectangular wave having amplitude of 1.7 kV and duty ratio of 50%
Developing bias DC component: 270V
Surface potential of photosensitive drum 31 (background portion/image portion): 430V/30V
Diameter of developing roller 21: 16 mm
Diameter of photosensitive drum 31: 24 mm
Average particle diameter of magnetic toner: 6.8 μm (D50)
Minimum distance in axial direction between toner supply inlet 25 and first communication path 223: 10 mm
Minimum distance in axial direction between toner supply inlet 25 and second communication path 224: 140 mm
<Experiment 1>
Firstly, a new toner container 50 was mounted to the image forming apparatus 1, and an image was continuously printed with the coverage rate being 3.8% until toner was consumed and the toner container 50 became empty. In this state, a new toner container 50 the weight of which was previously obtained was further mounted to the image forming apparatus 1. Printing of 100 white paper sheets was performed, and thereafter stripe fogging was evaluated. The stripe fogging represents fogging that occurs when additionally supplied toner slides over a toner layer, and is supplied to the developing roller 21 in a condensed state. Further, an amount of additional toner that entered the development housing 210 from the toner container 50 when the new toner container 50 was mounted, was evaluated based on a difference between a weight of the development housing 210 before exchange of the toner containers and a weight of the development housing 210 after exchange of the toner containers.
Table 1 indicates results of the stripe fogging and measurement of the weights of the toner container 50. The level of the stripe fogging was evaluated in a background portion of a sheet. As the level of the stripe fogging as described below, “excellent” represents a state where stripe fogging did not occur at all, “good” represents a state where stripe fogging occurred in five paper sheets or less among 100 paper sheets, “standard” represents a state where stripe fogging occurred in 15 paper sheets or less among 100 paper sheets, and “poor” represents a state where stripe fogging occurred in 16 paper sheets or more among 100 paper sheets.
In Table 1, Comparative example 1 represents a structure of the conventional developing apparatus 20Z as shown in
<Experiment 2>
Next, evaluation results obtained when the heights, in the downward projecting direction, of the downstream-side reduction wall 28A and the upstream-side reduction wall 28B from the top cover 211 were changed in the structure of the developing apparatus 20, as shown in
The toner in the development housings 210 became weakly charged under the condition of the stress as described above. At this time, when highly charged toner was additionally supplied, occurrence of fogging was significant. In Table 2, edge portion fogging represents fogging that occurs when a rate of additionally supplied toner in the development housing 210 is relatively high although agitating is sufficient. Further, when heights of the downstream-side reduction wall 28A and the upstream-side reduction wall 28B are increased, the weight of toner in the development housing 210 is reduced, and vertical stripes appear in a halftone image. Therefore, this problem was simultaneously examined (vertical stripe in halftone image).
The criterion of evaluation for stripe fogging was the same as in Experiment 1. The evaluations for the vertical stripe in halftone image and the edge portion fogging were made in the following manners.
Vertical strip in halftone image: “Excellent”: not greatly different from that of the conventional developing apparatus 20Z, “standard”: slightly poorer than that of the conventional developing apparatus 20Z, and “poor”: much poorer than that of the conventional developing apparatus 20Z
Edge portion fogging was at Level 1 in the case of F.D≧0.010 being satisfied, at Level 2 in the case of 0.007≦F.D≦0.009 being satisfied, at Level 3 in the case of 0.004≦F.D≦0.006 being satisfied, and at Level 4 in the case of 0≦F.D≦0.003 being satisfied. (A maximum value obtained by measurement of 400 paper sheets was used as the F. D. The F. D value was measured by a reflection densitometer (TC-6DS manufactured by Tokyo Denshoku Co., Ltd.)
Table 2 indicates a result that, particularly in the case of a ratio (H1/H2) of the height H1 of the downstream-side reduction wall 28A to the height H2 of the upstream-side reduction wall 28B ranging from 1.0 to 2.0 (NOS. 3 to 5 in Table 2), toner was stably distributed upstream and downstream of the toner supply inlet 25, and the vertical stripe in the halftone image, the stripe fogging, and the edge portion fogging were reduced. Further, it was confirmed that, in each example, an amount of toner that entered the development housing 210 when the new toner container 50 was mounted, was reduced as compared to in Comparative example 1 described above.
According to the first embodiment and the second embodiment, the downstream-side accumulation portion 27 in which toner is accumulated at a position that opposes the toner supply inlet 25 is formed due to the downstream-side reduction wall 28A or the reduction paddle 28C disposed downstream of the toner supply inlet 25 in the first direction. Further, the upstream-side accumulation portion 29 in which toner is accumulated upstream of the toner supply inlet 25 in the first direction is formed due to the upstream-side reduction wall 28B disposed upstream of the toner supply inlet 25 in the first direction. Therefore, even when an amount of toner in the development housing 210 is changed, a toner accumulation portion is stably formed downstream and upstream of the toner supply inlet 25. Accordingly, even when change of an amount of toner in the toner container 50 causes change of a pressure applied to the toner supply inlet 25 by additionally supplied toner, change of an amount of additional toner that enters the internal space 220 is reduced.
Further, according to the first embodiment and the second embodiment, the additional toner supplied through the toner supply inlet 25 is conveyed in the first direction so as to sink under the downstream-side reduction wall 28A. Therefore, the additionally supplied toner enters the second conveying path 222 in a state where the additionally supplied toner is sufficiently mixed with toner therearound. In other words, the additionally supplied toner is less likely to enter the second conveying path 222 while moving over an upper layer of the toner layer. Therefore, the additional toner is less likely to be supplied as a lump to the developing roller 21. Further, since the downstream-side reduction wall 28A and the upstream-side reduction wall 28B are provided downstream and upstream, respectively, of the toner supply inlet 25, so as to project, a large amount of toner is less likely to enter the development housing 210 from the toner container 50.
Further, according to the first embodiment and the second embodiment, the height of the downstream-side reduction wall 28A is set so as to be greater than or equal to the height of the upstream-side reduction wall 28B, but not greater than twice the height of the upstream-side reduction wall 28B. In this case, the additional toner supplied through the toner supply inlet 25 is conveyed to the lower portion of the toner layer, and the additional toner can be stably dispersed. Further, toner is stably distributed upstream and downstream of the toner supply inlet 25.
Further, in the image forming apparatus 1 including the developing apparatus 20 according to the first embodiment or the developing apparatus 20A according to the second embodiment, occurrence of developer fogging in an image formed on a sheet is advantageously reduced.
Next, a developing apparatus 20B according to a third embodiment of the present disclosure will be described with reference to
The first agitating screw 23 of the developing apparatus 20B according to the third embodiment of the present disclosure is disposed in the first conveying path 221. The first agitating screw 23 includes the first rotation shaft 23a (rotation axis), and the first helical blades 23b (screw blades) that are helically disposed so as to project on the circumference of the first rotation shaft 23a. The first agitating screw 23 is driven to rotate about the first rotation shaft 23a (in the direction indicated by an arrow D33 in
In the first agitating screw 23, the conveying capability reduction shaft portion 26C described above is disposed downstream of the toner supply inlet 25 in the toner conveying direction. The conveying capability reduction shaft portion 26C is formed by eliminating the first helical blades 23b of the first agitating screw 23 (see
Further, the developing apparatus 20B includes the conveying capability reduction wall 28D. The conveying capability reduction wall 28D is a wall portion that is disposed downstream of the toner supply inlet 25 in the first direction (the direction indicated by the arrow D1) so as to project downward from the top cover 211 of the development housing 210. The conveying capability reduction wall 28D locally reduces toner conveying capability of the first agitating screw 23, thereby forming an accumulation portion 27B in which toner is accumulated at a position that opposes the toner supply inlet 25. The conveying capability reduction wall 28D is disposed such that the lower end of the conveying capability reduction wall 28D is closer to the first rotation shaft 23a than the outer diameter end of the first helical blades 23b of the first agitating screw 23 is. As described above, the conveying capability reduction shaft portion 26C is disposed so as to oppose the conveying capability reduction wall 28D, thereby preventing the first agitating screw 23 and the conveying capability reduction wall 28D from interfering with each other.
In the first conveying path 221, toner conveyed from a region upstream of the conveying capability reduction wall 28D hits against the conveying capability reduction wall 28D, and starts to be accumulated. Toner is accumulated at a position, immediately upstream of the conveying capability reduction wall 28D, at which the toner supply inlet 25 opposes the first conveying path 221, and in a region preceding the position. As a result, the accumulation portion 27B for toner is formed near the entrance of the toner supply inlet 25.
When an amount of toner in the internal space 220 is increased due to the additional toner T2 being supplied through the toner supply inlet 25, the toner supply inlet 25 is blocked (sealed) with toner accumulated in the accumulation portion 27B, to reduce additional supply of toner. Thereafter, when toner in the internal space 220 is consumed by the developing roller 21, and toner accumulated in the accumulation portion 27B is reduced, toner with which the toner supply inlet 25 is blocked is reduced, whereby a gap is generated between the accumulation portion 27B and the toner supply inlet 25. As a result, the additional toner T2 enters the internal space 220 again through the toner supply inlet 25. Thus, in the present embodiment, a volume-based toner supply mode is used in which a received amount of toner to be additionally supplied, is adjusted according to reduction of toner accumulated in the accumulation portion 27B.
Next, a problem with supply of toner by a developing apparatus 20Y as compared to supply of toner in the present embodiment will be described.
In the developing apparatus 20Y having the volume-based toner supply mode as described above, when toner remaining in the toner container is reduced, an amount of supplied toner is reduced, thereby reducing an amount of toner in a development housing 210Y. In this case, when it is determined, by a not-illustrated density sensor, that an amount of remaining toner is small, exchange of the toner containers is prompted. At this time, since an amount of toner in the development housing 210Y is small, an amount of toner in the accumulation portion 27Y is also small. Additional toner enters the development housing 210Y from a new toner container mounted, by a user, to the developing apparatus 20Y. The new toner container is filled with a large amount of toner, and therefore the additional toner is likely to rapidly enter the development housing 210Y.
Toner that has entered the development housing 210Y enters the accumulation portion 27Y. The toner is conveyed to a second conveying path 222Y (not shown) that communicates with a first conveying path 221Y, according to a first agitating screw 23Y being driven to rotate. At this time, a surface state or an electrically charged state may be different between a large amount of additional toner that has been supplied to the development housing 210Y from the new toner container, and existing toner having been circulated in the development housing 210Y, in many cases. Although the additional toner and the existing toner are circulated in the development housing 210Y, to gradually have approximate characteristics, the toner may be charged so as to be polarized into two poles, due to difference in surface state between the additional toner and the existing toner, immediately after the entering of the additional toner. Namely, one of the additional toner and the existing toner is positively charged, and the other thereof is negatively charged. As a result, developer fogging may occur in an image on the photosensitive drum 31 and on a sheet.
In addition, additionally supplied toner, which rapidly enters the development housing 210Y, is less likely to sink toward the bottom portion of the development housing 210Y even if a rotational force of the first agitating screw 23Y is applied. In particular, in the conveying capability reduction portion 26Y located downstream of the toner supply inlet 25Y, toner agitating capability is reduced, so that toner dispersion becomes more difficult. In this case, the additional toner that has entered the development housing 210Y, enters the second conveying path 222Y through a first communication path 223Y (not shown) while moving over the surface layer (the upper layer, a draft surface portion) of the toner layer in the first conveying path 221Y (an arrow D152). If toner that has entered the second conveying path 222Y without sufficiently dispersing, is supplied as a lump to a developing roller 21Y (not shown) as it is, a problem arises that vertically-striped developer fogging occurs in an image.
<Conveying Capability Reduction Wall 28D>
The developing apparatus 20B according to the present embodiment includes the conveying capability reduction wall 28D described above. As shown in
In the present embodiment, as indicated by an arrow D52 in
Next, a developing apparatus 20C according to a fourth embodiment of the present disclosure will be described.
Similarly to the conveying capability reduction wall 28D, the conveying capability reduction wall 28E is a plate-like member that extends in a direction orthogonal to the first rotation shaft 23a, and is a wall portion that is disposed downstream of the toner supply inlet 25 in the first direction so as to project downward from the top cover 211 of the development housing 210. The conveying capability reduction wall 28E locally reduces toner conveying capability of the first agitating screw 23, thereby forming an accumulation portion 27B in which toner is accumulated at a position that opposes the toner supply inlet 25 (see
Also in the developing apparatus 20C that includes the conveying capability reduction wall 28E having such a structure, additionally supplied toner is advantageously prevented from sliding over the upper layer of the tone layer. Further, since the end portion 28E2 of the conveying capability reduction wall 28E extends so as to be lower than the center portion 28E1, additionally supplied toner that is moved outward of outer circumferential edges of the first helical blades 23b due to a rotational force of the first agitating screw 23 hits against an end portion 28E2, and can be conveyed downward of the end portion 28E2. Therefore, the additionally supplied toner is less likely to move up to the upper layer of the toner layer in a state where the additionally supplied toner is not sufficiently dispersed.
Next, a developing apparatus 20D according to a fifth embodiment of the present disclosure will be described.
The conveying capability reduction wall 28F and the conveying capability reduction wall 28G are disposed downstream of the toner supply inlet 25 in the first direction (the direction indicated by an arrow D1), so as to be spaced from each other in the first direction. Similarly to the conveying capability reduction wall 28D described above, each of the conveying capability reduction wall 28F and the conveying capability reduction wall 28G is a plate-like member that extends in a direction orthogonal to a first rotation shaft 23B1, and is a wall portion that projects downward from a top cover 211B of the development housing 210. The conveying capability reduction wall 28F and the conveying capability reduction wall 28G locally reduce toner conveying capability of the first agitating screw 23B, thereby forming an accumulation portion 27C in which toner is accumulated at a position that opposes the toner supply inlet 25.
Also in the developing apparatus 20D that includes the conveying capability reduction wall 28F and the conveying capability reduction wall 28G having such a structure, additionally supplied toner is advantageously prevented from sliding over the upper layer of the tone layer. Further, as indicated by an arrow D103 in
In a case where, in the plurality of conveying capability reduction walls, H3 represents a height, in the downward projecting direction, of the conveying capability reduction wall 28F (first reduction wall) disposed on the downstream side in the first direction, from the top cover 211B, and H4 represents a height, in the downward projecting direction, of the conveying capability reduction wall 28G (second reduction wall) disposed on the upstream side in the first direction, from the top cover 211B, a relationship of H3>H4 is preferably satisfied. In this case, turbulent flow of toner is likely to occur, and additionally supplied toner is conveyed so as to gradually sink downward, thereby dispersing additionally supplied toner with an enhanced effectiveness.
Next, a developing apparatus 20E according to a sixth embodiment of the present disclosure will be described with reference to
Similarly to the conveying capability reduction wall 28D described above, the conveying capability reduction wall 28H is a wall portion that is disposed downstream of the toner supply inlet 25 in the first direction (the direction indicated by an arrow D1) so as to project downward from a top cover 211C of a development housing 210C. Further, the conveying capability reduction wall 28H is a plate-like member that extends in a direction orthogonal to a first rotation shaft 23e. The conveying capability reduction wall 28H locally reduces toner conveying capability of a first agitating screw 23C, thereby forming an accumulation portion 27D in which toner is accumulated at a position that opposes the toner supply inlet 25. The conveying capability reduction wall 28H is disposed such that the lower end of the conveying capability reduction wall 28H is closer to the first rotation shaft 23e than the outer circumferential edge of first helical blades 23f of the first agitating screw 23C is.
The reduction paddle 29 projects from the first rotation shaft 23e in the radial direction so as to oppose the conveying capability reduction wall 28H. The reduction paddle 29 passes below the conveying capability reduction wall 28H according to the rotation of the first agitating screw 23C. Additional toner supplied through the toner supply inlet 25 is conveyed downward of the conveying capability reduction wall 28H, and mixed with toner therearound by the reduction paddle 29.
As shown in
Next, examples for the third to the sixth embodiments of the present disclosure will be described. However, the present disclosure is not restricted by examples described below. Examples described below were implemented under the following common experimental conditions.
<Common Experimental Conditions>
Photosensitive drum 31: OPC drum
Circumferential speed of photosensitive drum 31: 146 mm/sec
Layer regulation gap G: 0.3 mm
Developing bias AC component: rectangular wave having amplitude of 1.7 kV, and duty ratio of 50%
Developing bias DC component: 270V
Surface potential of photosensitive drum 31 (background portion/image portion): 430V/30V
Diameter of developing roller 21: 16 mm
Diameter of photosensitive drum 31: 24 mm
Average particle diameter of magnetic toner: 6.8 μm (D50)
Shape of each of first agitating screw 23 and second agitating screw 24: Outer diameter of 14 mm, screw pitch of 20 mm
The number of rotations of each of first agitating screw 23 and second agitating screw 24: :50 rpm
Length X, in axial direction, of conveying capability reduction shaft portion 26C: 12 mm
Opening width B, in axial direction, of first communication path 223: 20 mm
Opening width A, in axial direction, of second communication path 224: 40 mm
Opening shape of toner supply inlet 25: 14×8 mm
Minimum distance Z, in axial direction, between toner supply inlet 25 and first communication path 223: 10 mm
Minimum distance, in axial direction, between toner supply inlet 25 and second communication path 224: 140 mm
<Experiment 3>
Firstly, a new toner container 50 was mounted to the image forming apparatus 1, and an image was continuously printed with the coverage rate being 3.8% until toner was consumed and the toner container 50 became empty. In this state, a new toner container 50 the weight of which was previously obtained was further mounted to the image forming apparatus 1. Printing of 100 white paper sheets was performed, and thereafter supply fogging and stripe fogging were evaluated. The supply fogging represents a phenomenon in which toner fogging occurs over the entirety of a surface of a paper sheet due to electrical charging being not stable between additional toner supplied from the toner container 50 and toner being circulated in the development housing 210. The stripe fogging represents fogging that occurs when additionally supplied toner slides over a toner layer, and is supplied to the developing roller 21 in a condensed state.
As wall types in the following experiments, a wall type A represents the conveying capability reduction wall 28D shown in
Table 3 indicates results for supply fogging and stripe fogging. An overlap represents a portion in which each conveying capability reduction wall and the first helical blade 23b of the first agitating screw 23 are positioned so as to overlap each other in the vertical direction (corresponds to H−S in
<Experiment 4>
Next, in the developing apparatus 20D shown in
As indicated in Table 4, particularly when the wall height of the conveying capability reduction wall 28F was greater than the wall height of the conveying capability reduction wall 28G (Examples 13 to 15), the results for the supply fogging and the stripe fogging were good. In Example 12, since 1 mm was assuredly obtained for the overlap of each conveying capability reduction wall with the first agitating screw 23B from the outer circumferential edge of the first agitating screw 23B, even when the wall height of the conveying capability reduction wall 28F and the wall height of the conveying capability reduction wall 28G were equal to each other, the results for the supply fogging and the stripe fogging were good.
<Experiment 5>
Next, in the developing apparatus 20E shown in
As indicated in Table 5, when S<H was satisfied, i.e., when the conveying capability reduction wall 28H was disposed such that the lower end of the conveying capability reduction wall 28H was closer to the first rotation shaft 23e than the outer end of the first helical blade 23f was, it was confirmed that stripe fogging did not occur at all, and an amount of additionally supplied toner was particularly reduced. The criterion of evaluation for the stripe fogging was the same as that for Experiment 1.
<Experiment 6>
Next, for the developing apparatus 20E shown in
The criterion of evaluation for stripe fogging was the same as that for Experiment 1. The evaluation for edge portion fogging was made in the following manner. Edge portion fogging was at Level 1 in the case of F.D≧0.010 being satisfied, at Level 2 in the case of 0.005≦F.D≦0.009 being satisfied, and at Level 3 in the case of 0≦F.D≦0.004 being satisfied. A maximum value obtained by measurement of 400 paper sheets for an image was used as the F. D value. The F. D value was measured by a reflection densitometer (TC-6DS manufactured by Tokyo Denshoku Co., Ltd.). The result of Experiment 6 is indicated in Table 6.
As indicated in Table 6, when the conveying capability reduction wall 28H and the reduction paddle 29 were used in combination, results for the stripe fogging and the edge portion fogging were particularly good. Further, it was confirmed that an amount of additionally supplied toner was the lowest, and an excessive amount of additional toner was prevented from entering the development housing 210.
<Experiment 7>
Next, for the developing apparatus 20E shown in
As indicated in Table 7, when the minimum distance was excessively long (2.5 mm), an action and effect of the reduction paddle 29 was reduced and stripe fogging slightly occurred. On the other hand, when the minimum distance was excessively short (0.3 mm), toner was condensed between the conveying capability reduction wall 28H and the reduction paddle 29, and ghost occurred in the image. Therefore, the minimum distance between the reduction paddle 29 and the conveying capability reduction wall 28H according to rotation of the first agitating screw 23C is preferably longer than or equal to 0.5 mm, and preferably not longer than 2.0 mm.
The developing apparatuses 20, 20A, 20B, 20C, 20D, and 20E according to the embodiments of the present disclosure and the image forming apparatus 1 that includes the developing apparatus 20, 20A, 20B, 20C, 20D, or 20E are described above. However, the present disclosure is not limited to the embodiments described above, and, for example, modifications as described below may be implemented.
In the embodiments described above, additional supply of toner from the toner container 50 to the developing apparatus 20, 20A, 20B, 20C, 20D, or 20E is adjusted according to the accumulation portion 27, the accumulation portion 27A, the accumulation portion 27B, the accumulation portion 27C, or the accumulation portion 27D. However, the present disclosure is not limited thereto. Toner may be additionally supplied from the toner container 50 into the development housing 210 according to a detection result from a not-illustrated density sensor that detects an image density, or a not-illustrated toner sensor that detects an amount of toner in the development housing 210.
In the embodiments described above, magnetic toner is used as developer. However, the present disclosure is not limited thereto. Non-magnetic toner, or two-component developer may be used as developer.
In the embodiment described above, the conveying capability reduction wall 28H that is used in combination with the reduction paddle 29 is formed as a flat-plate-like member (
It is to be understood that the embodiments herein are illustrative and not restrictive, since the scope of the disclosure is defined by the appended claims rather than by the description preceding them, and all changes that fall within metes and bounds of the claims, or equivalence of such metes and bounds thereof are therefore intended to be embraced by the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-256073 | Nov 2012 | JP | national |
| 2012-256074 | Nov 2012 | JP | national |
