JP2016004198A - Development device and image formation device including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a development device and an image formation device including the development device that prevent disappearance of a surface layer of a toner carrier accompanied by sliding friction with a seal member.SOLUTION: A development device 122 comprises: a development housing; a development roller 83; a roller gear 83G; and a pair of toner seals 89. The roller gear 83G is fixed on one end side in an axial direction of the development roller 83, and transmits rotation drive force to the development roller 83, which comprises: a sleeve; and a coat layer 83C. The sleeve is immersed in a prescribed immersion tank along a vertical direction, and thereby the coat layer 83C is formed. The pair of toner seals 89 abut on both ends in an axial direction of the coat layer 83C. The development roller 83 is mounted to the development housing so that a lower end side when immersion of the development roller 83 is immersed becomes another end side opposite to the roller gear 83G in the axial direction.

Description

  The present invention relates to a developing device and an image forming apparatus including the developing device.

  In an image forming apparatus such as a copying machine, a printer, or a facsimile using an electrophotographic system, a developing device supplies toner to an electrostatic latent image formed on a photosensitive drum to develop the electrostatic latent image. Thus, a toner image is formed on the photosensitive drum. The developing device includes a developing roller (toner carrier) that is rotatably supported by a housing. The developing roller is disposed on the photosensitive drum with a predetermined gap, and carries a developer containing at least toner on the peripheral surface. Patent Document 1 discloses a technique in which a resin layer (surface layer) is provided on the surface of a developing roller. A dipping method (a dipping method or a dipping method) is disclosed in which a developing roller is manufactured by dipping a base tube of a developing roller in a resin solution in which a resin material is previously dissolved. Further, Patent Document 2 discloses a seal member that prevents the developer from leaking from the developing device by contacting the end of the developing roller.

JP 2009-300677 A JP 2008-310253 A

  In the technique as described above, there is a problem that the seal member strongly rubs against the resin layer of the developing roller as the developing roller rotates, and wear of the resin layer is promoted.

  The present invention has been made to solve the above-described problems, and includes a developing device that prevents the surface layer of the toner carrier from disappearing due to sliding friction with the seal member, and the developing device. An object is to provide an image forming apparatus.

  A developing device according to one aspect of the present invention is disposed at a distance from a housing that stores a developer containing toner therein and an image carrier on which an electrostatic latent image is formed. A toner carrier that is rotatably supported about an axis and carries toner on a peripheral surface thereof; a drive transmission unit that is fixed to one end side in the axial direction of the toner carrier and that transmits a rotational driving force to the toner carrier; A pair of seal members disposed on the housing so as to contact both axial ends of the peripheral surface of the toner carrier, and preventing the developer from leaking from the housing, The toner carrier includes a cylindrical base material and a surface layer formed on the base material, and the base material is immersed in a predetermined immersion tank so that the axial direction is along the vertical direction. The surface layer is formed by the method The toner carrier is mounted on the housing such that a lower end side of the toner carrier when immersed is the other end side opposite to the drive transmission portion in the axial direction. .

  According to this configuration, the surface layer of the toner carrier is formed by a dipping method. For this reason, the film thickness of the surface layer of the lower end side at the time of immersion tends to become partially thick. Of the toner carrier that is rotatably supported by the housing, the rotation position is difficult to stabilize on the side opposite to the drive transmission unit. In particular, when the eccentricity of the toner carrier increases with the rotation of the toner carrier, the surface layer and the seal member rub against each other strongly. Even in such a case, the toner carrier is mounted on the housing so that the lower end side when the toner carrier is immersed is the other end side opposite to the drive transmission portion in the axial direction. For this reason, on the other end side of the toner carrier, a region where the surface layer is thick comes into contact with the seal member. As a result, the surface layer is prevented from disappearing with the rotation of the toner carrier.

  In the above configuration, the drive transmission unit is a first inclined gear having gear teeth inclined at a predetermined angle with respect to the axial direction, and is capable of rotating in the forward and reverse directions to rotate the toner carrier. A drive unit that generates a rotational drive force; and a drive unit that is connected to the drive unit and rotatably supported by the housing so as to mesh with the first oblique gear, and the rotational drive force is applied to the first oblique gear. A second inclined gear that transmits the electrostatic latent image on the image carrier, and the drive unit is rotated in the forward direction so that the toner carrier is first. By rotating in the rotation direction, the toner is supplied from the toner carrier to the image carrier, and when the toner carrier is rotated in the first rotation direction, the first inclined gear and the first gear The image carrier is engaged by meshing with the two inclined gears. When a pressing force in a direction toward the body is applied to the toner carrier, the driving unit is rotated in the opposite direction, and the toner carrier is rotated in a second rotation direction opposite to the first rotation direction, A pressing force in a direction toward the seal member may be applied to the toner carrier by meshing between the first inclined gear and the second inclined gear.

  According to this configuration, during the developing operation, a pressing force toward the image carrier is applied to the toner carrier by the meshing of the first oblique gear and the second oblique gear. For this reason, the interval between the image carrier and the toner carrier is more stably maintained. On the other hand, when the toner carrier is rotated in the second rotational direction opposite to the first rotational direction, the pressing force toward the seal member is caused by the meshing of the first oblique gear and the second oblique gear. Given to the body. In this case, on the opposite side of the toner carrier from the drive transmission unit, the surface layer is rubbed more strongly with the seal member. Even in such a case, the other end side of the surface layer is prevented from disappearing because the region where the film thickness of the surface layer is thick contacts the seal member on the other end side of the toner carrier.

  In the above configuration, the developer carrying that is rotatably supported by the housing facing the toner carrying member, carries the toner and the carrier on the peripheral surface, and supplies the toner to the toner carrying member. A layer thickness regulating member that is disposed to face the peripheral surface of the developer carrying member along a substantially horizontal direction and regulates the layer thickness of the developer on the developer carrying member, and the developer An input gear fixed to the one end side in the axial direction of the carrier, connected to the drive unit and the second inclined gear, and transmitting the rotational driving force to the developer carrier; The two inclined gears are connected to the driving unit via the input gear, and when a rotational driving force is input from the driving unit to the input gear, the toner carrier and the developer carrier are synchronized with each other. Rotated and during the developing operation, When the moving part is rotated in the forward direction, the developer carrying member rotates in a region facing the layer thickness regulating member from below to above, and when the driving part is rotated in the reverse direction, the developing member is rotated. The agent carrier may rotate in a region facing the layer thickness regulating member from above to below.

  According to this configuration, during the developing operation, the developer carrier rotates in the region facing the layer thickness regulating member from below to above. At this time, toner may accumulate on the upper surface portion of the layer thickness regulating member. On the other hand, when the drive unit is rotated in the reverse direction, the developer carrying member rotates from above to below in the region facing the layer thickness regulating member. At this time, the toner deposited on the layer thickness regulating member is collected by the developer carrier. Thus, even when the toner carrier and the developer carrier are reversely rotated to collect the accumulated toner, there is a region where the surface layer is thick on the other end side of the toner carrier. The contact with the seal member prevents the other end side of the surface layer from disappearing.

  In the above configuration, the base material is made of aluminum, the toner carrier further includes an oxide layer formed on the surface of the base material, and the surface layer is formed on the surface of the oxide layer. Is desirable.

  According to this configuration, the adhesion of the surface layer to the base material is increased by forming the oxide layer on the base material made of aluminum. As a result, peeling of the surface layer is suppressed.

  An image forming apparatus according to another aspect of the present invention includes the developing device according to any one of the above, and the image carrier on which an electrostatic latent image is formed on a surface and the toner is supplied from the toner carrier. And.

  According to this configuration, on the other end side of the toner carrier opposite to the drive transmission unit, the region where the surface layer is thick comes into contact with the seal member. As a result, the surface layer is prevented from disappearing with the rotation of the toner carrier.

  According to the present invention, there is provided a developing device and an image forming apparatus provided with the same, which prevent the surface layer of the toner carrier from disappearing due to the rubbing with the seal member.

1 is a cross-sectional view illustrating an internal structure of an image forming apparatus according to an embodiment of the present invention. 1 is a cross-sectional view of a developing device according to an embodiment of the present invention. Schematic diagram (A) showing the relationship between the axial lengths of the photosensitive drum and the developing roller according to the embodiment of the present invention, and a schematic cross-sectional view showing the state of the film thickness at the end of the developing roller (B) ). It is a graph (A) and (B) which show distribution of the film thickness of the direction of an axis of the development roller concerning an embodiment of the present invention. In the developing device according to the embodiment of the present invention, a schematic rear view (A) showing a state in which the toner carrier is rotated forward, and a schematic rear view showing a state in which the toner carrier is reversely rotated. It is a figure (B). FIG. 6 is a schematic side view showing a state where the toner carrier is rotated forward in the developing device according to the embodiment of the present invention. FIG. 4 is a schematic cross-sectional view illustrating an arrangement of a seal member of the developing device according to the embodiment of the present invention. It is a typical top view which shows arrangement | positioning of the sealing member of the developing device which concerns on embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention can be applied to an image forming apparatus employing an electrophotographic system, such as a copier, a printer, a facsimile machine, and a multifunction machine having these functions.

  FIG. 1 is a front sectional view showing the structure of an image forming apparatus 1 according to an embodiment of the present invention. The image forming apparatus 1 includes an apparatus main body 11 including an image forming unit 12, a fixing device 13, a paper feeding unit 14, a paper discharging unit 15, a document reading unit 16, and the like.

  The apparatus main body 11 includes a lower main body 111, an upper main body 112 disposed opposite to the lower main body 111, and a connecting portion 113 interposed between the upper main body 112 and the lower main body 111. . The connecting portion 113 is a structure for connecting the sheet discharge portion 15 between the lower main body 111 and the upper main body 112 and is erected from the left and rear portions of the lower main body 111. It has an L shape in plan view. The upper body 112 is supported on the upper end portion of the connecting portion 113.

  The lower main body 111 includes the image forming unit 12, the fixing device 13, and the paper feeding unit 14, and the upper main body 112 is mounted with the document reading unit 16.

  The image forming unit 12 executes an image forming operation for forming a toner image on the paper P fed from the paper feeding unit 14. The image forming unit 12 uses a yellow unit 12Y using a yellow toner, a magenta unit 12M using a magenta toner, and a cyan toner, which are sequentially arranged horizontally from the upstream side to the downstream side. A cyan unit 12C, a black unit 12Bk using black toner, an intermediate transfer belt 125 stretched between a plurality of rollers such as a driving roller 125A so as to be able to run endlessly in the sub-scanning direction in image formation, and an intermediate transfer A secondary transfer roller 196 that contacts the outer peripheral surface of the belt 125 and a belt cleaning device 198 are provided.

  Each color unit of the image forming unit 12 includes a photosensitive drum 121 (image carrier), a developing device 122 that supplies toner (developer) to the photosensitive drum 121, and a toner cartridge (not shown) that contains toner. The charging device 123 and the drum cleaning device 127 are integrally provided. An exposure device 124 for exposing each photosensitive drum 121 is horizontally disposed below the adjacent developing device 122.

  The photosensitive drum 121 has a cylindrical shape and is rotated around an axis. The photosensitive drum 121 carries a toner image in which an electrostatic latent image is formed on its peripheral surface and the electrostatic latent image is made visible by toner. In this embodiment, the photoreceptor drum 121 is a known organic (OPC) photoreceptor, and a charge generation layer, a charge transport layer, and the like are formed on the surface by the same dipping method as the developing roller 83 described later.

  The developing device 122 supplies toner to the electrostatic latent image on the peripheral surface of the photoconductive drum 121 rotating in the direction of the arrow and stacks the toner, and the toner corresponding to the image data is formed on the peripheral surface of the photoconductive drum 121. Form an image. Each developing device 122 is appropriately supplied with toner from the toner cartridge.

  The charging device 123 is provided at a position directly below each photosensitive drum 121. The charging device 123 uniformly charges the peripheral surface of each photosensitive drum 121.

  The exposure device 124 is provided below each charging device 123. The exposure device 124 irradiates the peripheral surface of the charged photosensitive drum 121 with laser light corresponding to each color based on image data input from a computer or the like or image data acquired by the document reading unit 16, and each photosensitive member. An electrostatic latent image is formed on the peripheral surface of the drum 121. The exposure device 124 irradiates the laser beam in accordance with a preset exposure light quantity in order to form a predetermined latent image potential on the photosensitive drum 121. The drum cleaning device 127 is provided at the left position of each photoconductive drum 121 and removes residual toner on the peripheral surface of the photoconductive drum 121 for cleaning.

  The intermediate transfer belt 125 is an endless belt, and is a conductive soft belt having a laminated structure including a base layer, an elastic layer, and a coat layer. The intermediate transfer belt 125 is wound around a plurality of stretching rollers arranged in a substantially horizontal direction above the image forming unit 12. The tension roller is disposed in the vicinity of the fixing device 13 and drives the intermediate transfer belt 125 to rotate, and the driven roller 125E rotates at a predetermined interval in the horizontal direction with respect to the drive roller 125A. ,including. The intermediate transfer belt 125 is driven to rotate clockwise in FIG. 1 by applying a rotational driving force to the driving roller 125A.

  A secondary transfer bias application unit (not shown) is electrically connected to the secondary transfer roller 196. The toner image formed on the intermediate transfer belt 125 is transferred to the paper P conveyed from the lower conveying roller pair 192 by a transfer bias applied between the secondary transfer roller 196 and the driving roller 125A. The belt cleaning device 198 is disposed to face the driven roller 125E via the intermediate transfer belt 125.

  The fixing device 13 includes a heating roller 132 provided with an energization heating element such as a halogen lamp as a heating source, and a pressure roller 134 disposed to face the heating roller 132. The fixing device 13 heats the toner image on the paper P transferred by the image forming unit 12 from the heating roller 132 while the paper P passes through the fixing nip portion between the heating roller 132 and the pressure roller 134. To give a fixing process. The color-printed paper P that has been subjected to the fixing process is discharged toward a paper discharge tray 151 provided at the top of the apparatus main body 11 through a paper discharge conveyance path 194 extending from the top of the fixing device 13. .

  The sheet feeding unit 14 is provided with a manual feed tray 141 that can be freely opened and closed on the right side wall of the apparatus main body 11 in FIG. And. The paper feed cassette 142 accommodates a sheet bundle P1 formed by stacking a plurality of sheets P. A pick-up roller 143 is provided above the paper feed cassette 142, and the pick-up roller 143 feeds the uppermost paper P in the paper bundle P 1 accommodated in the paper feed cassette 142 toward the paper transport path 190. The manual feed tray 141 is a tray that is provided at a lower position on the right surface of the lower main body 111 and feeds paper P one by one toward the image forming unit 12 by manual feed operation.

  A paper conveyance path 190 extending in the vertical direction is formed at the left position of the image forming unit 12. The paper conveyance path 190 is provided with a conveyance roller pair 192 at an appropriate position. The conveyance roller pair 192 directs the paper P fed from the paper supply unit 14 to the secondary transfer nip portion having the secondary transfer roller 196. Transport.

  The paper discharge unit 15 is formed between the lower main body 111 and the upper main body 112. The paper discharge unit 15 includes a paper discharge tray 151 formed on the upper surface of the lower main body 111. The paper discharge tray 151 is a tray from which the paper P on which the toner image is formed by the image forming unit 12 is discharged after the fixing device 13 performs the fixing process.

  The document reading unit 16 includes a contact glass 161 mounted on the upper surface opening of the upper main body 112 for placing a document, an openable / closable document pressing cover 162 for pressing the document placed on the contact glass 161, And a scanning mechanism 163 that scans and reads an image of the document placed on the contact glass 161. The scanning mechanism 163 optically reads an image of an original using an image sensor such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS), and generates image data. In addition, the apparatus main body 11 has an image processing unit (not shown) that generates an image formation image from the image data.

<Configuration of developing device>
Next, the developing device 122 will be described in detail. FIG. 2 is a cross-sectional view in the vertical and horizontal directions schematically showing the internal structure of the developing device 122. FIG. 3 is a schematic diagram (A) showing the relationship between the axial lengths of the photosensitive drum 121 and the developing roller 83 according to the present embodiment, and a schematic diagram showing the state of the film thickness at the end of the developing roller 83. It is various sectional drawing (B). FIG. 4 is graphs (A) and (B) showing the distribution of the film thickness in the axial direction of the developing roller 83. The developing device 122 according to the present embodiment employs a touch-down developing method including a developing roller 83 and a magnetic roller 82. The developing device 122 includes a developing housing 80 (housing) that defines an internal space of the developing device 122. The developing housing 80 is provided with a developer storing portion 81 for storing a developer including a non-magnetic toner and a magnetic carrier charged to a predetermined polarity. Further, inside the developing housing 80, a magnetic roller 82 (developer carrying member) disposed above the developer reservoir 81, and a developing roller disposed opposite to the magnetic roller 82 at a position obliquely above the magnetic roller 82. 83 (toner carrier) and a developer regulating blade 84 (layer thickness regulating member) disposed opposite to the magnetic roller 82 are disposed. Further, the developing device 122 includes a driving unit 962 and a developing bias applying unit 88 (FIG. 2).

  Referring to FIG. 2, developer storage unit 81 includes two adjacent first developer storage chamber 81 a and second developer storage chamber 81 b extending in the longitudinal direction of developing device 122. The second developer storage chamber 81 b is disposed to face the magnetic roller 82. The first developer storage chamber 81a and the second developer storage chamber 81b are separated from each other by a partition plate 801 that is integrally formed with the development housing 80 and extends in the longitudinal direction, but at both ends in the longitudinal direction (axial direction). A pair of communicating portions (not shown) communicate with each other. The first developer storage chamber 81a and the second developer storage chamber 81b accommodate a first screw feeder 85 and a second screw feeder 86, respectively, that agitate and convey the developer by rotating around the axis. Although the 1st screw feeder 85 and the 2nd screw feeder 86 are rotationally driven by the drive part 962, the rotation direction is set to the mutually reverse direction. Accordingly, the developer is circulated and conveyed between the first developer storage chamber 81a and the second developer storage chamber 81b while being stirred. By this stirring, the toner and the carrier are mixed, and the toner is charged positively, for example.

  The magnetic roller 82 is rotatably supported by the developing housing 80 so as to face the developing roller 83 along the longitudinal direction of the developing device 122. The magnetic roller 82 is driven to rotate clockwise in FIG. Inside the magnetic roller 82, a fixed so-called magnet roll (fixed magnet, not shown) is arranged. The magnet roll has a plurality of magnetic poles. In this embodiment, the magnet roll has a drawing pole 821, a regulation pole 822, and a main pole 823. The scooping pole 821 faces the developer storage section 81, the regulation pole 822 faces the developer regulation blade 84, and the main pole 823 faces the developing roller 83.

  The magnetic roller 82 magnetically pumps (receives) the developer from the developer reservoir 81 onto its peripheral surface 82A by the magnetic force of the pumping pole 821. The magnetic roller 82 magnetically supports the developer drawn up as a developer layer (magnetic brush layer) on the peripheral surface 82A. The magnetic roller 82 supplies toner to the developing roller 83. As the magnetic roller 82 rotates, the developer is conveyed toward the developer regulating blade 84.

  The developer regulating blade 84 is disposed to face the circumferential surface 82A of the magnetic roller 82 on the upstream side of the developing roller 83 when viewed from the rotation direction of the magnetic roller 82. In the present embodiment, the developer regulating blade 84 extends slightly along the substantially horizontal direction so as to rise slightly toward the magnetic roller 82. The developer regulating blade 84 regulates the layer thickness of the developer magnetically attached to the peripheral surface 82A of the magnetic roller 82. The developer regulating blade 84 forms a regulating gap G having a predetermined size with the peripheral surface 82 </ b> A of the magnetic roller 82. Thereby, a uniform developer layer having a predetermined thickness is formed on the peripheral surface 82A.

  The developing roller 83 is disposed so as to extend along the longitudinal direction of the developing device 122 and in parallel with the magnetic roller 82, and is driven to rotate clockwise in FIG. The developing roller 83 is disposed to face the photosensitive drum 121. The developing roller 83 has a cylindrical shape and is supported by the developing housing 80 so as to be rotatable about an axis. The developing roller 83 has a peripheral surface 83A that receives toner from the developer layer and carries the toner layer while rotating in contact with the developer layer held on the peripheral surface 82A of the magnetic roller 82. At the time of development in which the development operation is performed, the development roller 83 supplies the toner of the toner layer to the peripheral surface of the photosensitive drum 121. In the present embodiment, the developing roller 83 is a roller including a cylindrical sleeve 830 (base material) and a resin coat (surface layer) formed on the surface of the sleeve 830 (FIG. 3B). A gap S (FIG. 2) having a predetermined size is formed between the peripheral surface 83A of the developing roller 83 and the peripheral surface 82A of the magnetic roller 82. The gap S is set to 0.3 mm, for example. The developing roller 83 is disposed so as to face the photosensitive drum 121 through an opening formed in the developing housing 80, and a gap having a predetermined dimension is also formed between the peripheral surface 83A and the peripheral surface of the photosensitive drum 121. Yes. In the present embodiment, the gap is set to 0.12 mm.

  The developing bias applying unit 88 applies a developing bias in which an AC voltage is superimposed on a DC voltage to the magnetic roller 82 and the developing roller 83 during a developing operation. A high AC voltage is applied between the photosensitive drum 121 and the developing roller 83 and between the developing roller 83 and the magnetic roller 82. In particular, toner is supplied from the magnetic roller 82 to the developing roller 83, and further, toner is supplied from the developing roller 83 to the photosensitive drum 121. Therefore, the movement of the toner is compared with known one-component and two-component developing devices. Therefore, a high alternating voltage is applied to the developing roller 83.

  With reference to FIG. 3A, in the present embodiment, the length of the photosensitive drum 121 in the axial direction is set larger than the length of the developing roller 83 in the axial direction. Therefore, both end portions in the axial direction of the developing roller 83 face the photoconductive drum 121 in the region L inside the both end portions in the axial direction of the photoconductive drum 121. A tracking roller (not shown) is fixed to both ends of the developing roller 83 in the axial direction. The tracking roller regulates the gap between the developing roller 83 and the photosensitive drum 121 by contacting both ends of the photosensitive drum 121. Further, the developing housing 80 is biased toward the photosensitive drum 121 by a biasing spring (not shown). As a result, the gap between the developing roller 83 and the photosensitive drum 121 is more stably maintained.

  Referring to FIG. 3B, the sleeve 830 of the developing roller 83 is made of aluminum. The coat layer 83C of the developing roller 83 is formed by the following immersion method. First, the outer peripheral surface of the sleeve 830 is anodized to form an alumite layer (oxidized layer) having a thickness of 10 μm. By forming the oxide layer on the sleeve 830 made of aluminum, the adhesion of the coat layer 83C to the base material is increased. As a result, peeling of the coat layer 83C is suppressed. Thereafter, the surface of the sleeve 830, that is, the surface of the alumite layer is heat-treated at 120 ° C. for 10 minutes or more. This heat treatment is performed in order to intentionally generate a crack in the sleeve 830 in advance in order to suppress the occurrence of a crack in the drying process of the coat layer 83C. The time for the heat treatment is determined in advance, for example, more than the time required for the drying step. The heat treatment is always performed at a constant temperature for a certain time. As a result, almost constant cracks are generated in all the sleeves 830 subjected to the heat treatment. After the heat treatment, a process of forming a coat layer 83C on the alumite layer is performed. Specifically, an alcohol-soluble nylon resin as a binder resin, titanium oxide as a conductive agent, and methanol 800 (parts by weight) as a dispersion medium are mixed with a zirconia bead having a diameter of 1.0 mm in a ball mill for about 48 hours. A mixture is prepared. An alumite-treated sleeve 830 is immersed in the mixed solution for a predetermined time, and then pulled up and dried in a high temperature environment of 130 ° C. for 10 minutes. The sleeve 830 is immersed in the mixed liquid and pulled up so that the cylindrical axial direction is along the vertical direction. As a result, a sleeve 830 coated with a coat layer 83C having a thickness of 2 μm to 11 μm is manufactured. Thus, before the coating layer 83C is coated, cracks are generated in the alumite layer by heat treatment in advance. For this reason, the conductive agent contained in the coat layer 83C is prevented from being unevenly distributed due to the influence of convection generated in the coat layer 83C when the coat layer 83C is dried. As a result, it is possible to form the coat layer 83C in which the conductive material is uniformly dispersed.

  On the other hand, when the coating layer 83 </ b> C is formed by the dipping method as described above, the mixed liquid adhering to the surface of the sleeve 830 is likely to sag downward due to the influence of gravity when pulled up. For this reason, a coat layer 83C that is partially thicker than the central portion in the axial direction is formed on the surface of the sleeve 830 that is positioned on the lower end side during immersion. In particular, the reservoir 83C1 in which the thickness of the coat layer 83C is partially increased is easily formed at the lower end of the sleeve 830. Further, a thin layer portion 83C2 (see FIG. 8), which is a coat layer 83C that is partially thinner than the central portion in the axial direction, is formed on the surface of the sleeve 830 positioned on the upper end side when immersed.

  FIG. 4A shows the distribution of the film thickness on the lower end side when the coat layer 83C formed on the sleeve 830 is immersed. On the other hand, FIG. 4B shows the distribution of the film thickness on the upper end side when the coat layer 83C formed on the sleeve 830 is immersed. In either case, the horizontal axis indicates the distance from the end of the sleeve 830, and the vertical axis indicates the film thickness corresponding to each position in the axial direction as a difference with respect to the average film thickness of the coat layer 83C. As shown in FIGS. 4A and 4B, the length of the thin portion at the upper end of the coat layer 83C is longer than the length of the thick portion at the lower end. Further, the maximum film thickness decrease (3 μm) at the upper end of the coat layer 83C is a value approximated to the maximum film thickness increase (3.5 μm) at the lower end.

  FIG. 5 is a schematic rear view (A) showing how the developing roller 83 is normally rotated in the developing device 122 according to the present embodiment, and a schematic diagram showing how the developing roller 83 is rotated in the reverse direction. It is a typical rear view (B). FIG. 6 is a schematic side view showing a state where the developing roller 83 is normally rotated in the developing device 122.

  The developing roller 83, the magnetic roller 82, the first screw feeder 85, and the second screw feeder 86 are rotationally driven in synchronization by the drive unit 962. As shown in FIGS. 5 and 6, a roller gear 83 </ b> G (drive transmission unit, first inclined gear) is fixed to the rear end portion of the developing roller 83. The roller gear 83G transmits a rotational driving force to the developing roller 83. In the present embodiment, the roller gear 83G is an oblique gear having gear teeth inclined at a predetermined angle with respect to the axial direction.

  An input gear 82G is fixed to the rear end portion of the magnetic roller 82. The input gear 82G transmits the rotational driving force to the magnetic roller 82. Further, an idle gear 80G (second inclined gear) is connected between the input gear 82G and the roller gear 83G. The idle gear 80G is rotatably supported by the developing housing 80 so as to mesh with the roller gear 83G, and transmits a rotational driving force to the roller gear 83G.

  The driving unit 962 is a motor that generates a rotational driving force, and generates a rotational driving force that rotates each roller of the developing device 122. The drive unit 962 can be rotated forward and backward by a control unit (not shown). In the present embodiment, the input gear 82G is arranged on the most upstream side in the drive transmission path. That is, when the developing device 122 is attached to the image forming apparatus 1, the input gear 82 </ b> G is connected to the drive unit 962. The input gear 82G is connected to a screw gear (not shown). When the input gear 82G is rotated, the second screw feeder 86 and the first screw feeder 85 are rotated via the screw gear. The idle gear 80G is connected to the drive unit 962 via the input gear 82G.

  Referring to FIG. 5A, during the developing operation in which the electrostatic latent image on photosensitive drum 121 is developed by developing roller 83, drive unit 962 is rotated in the forward direction by a control unit (not shown). At this time, the input gear 82G is rotated counterclockwise as indicated by an arrow in FIG. At the same time, the magnetic roller 82 is also rotated counterclockwise. At this time, in FIG. 2, the magnetic roller 82 rotates from below to above in the region facing the developer regulating blade 84. Returning to FIG. 5A, when the idle gear 80G rotates clockwise (arrow D61 in FIG. 6) as the input gear 82G rotates, the roller gear is engaged by the meshing of the idle gear 80G and the roller gear 83G. 83G is rotated counterclockwise in FIG. 5A (arrow D62 in FIG. 6). As a result, the developing roller 83 is rotated counterclockwise (first rotation direction) as indicated by an arrow (arrow D63 in FIG. 6). Then, the toner is supplied from the developing roller 83 to the photosensitive drum 121 by the developing bias applied by the developing bias applying unit 88 (FIG. 2). In the present embodiment, when the developing roller 83 is rotated in the first rotation direction shown in FIG. 5A, the pressing force toward the photosensitive drum 121 is developed by the meshing of the roller gear 83G and the idle gear 80G. It is applied to the roller 83 (arrow DA in FIG. 5A). Further, by the meshing of the roller gear 83G and the idle gear 80G, a thrust force as shown by an arrow D64 in FIG. 6 is applied to the developing roller 83. At this time, the thrust force is applied from the rear end side of the developing roller 83 to which the roller gear 83G is fixed toward the front end side opposite to the roller gear 83G.

  On the other hand, a control unit (not shown) rotates the driving unit 962 in reverse when it is different from the developing operation. In this embodiment, as shown in FIG. 2, toner may accumulate on the upper surface portion of the developer regulating blade 84 during the developing operation (toner pool TP). Since the charge of the accumulated toner is unstable, when these toners are supplied to the developing roller 83 by mistake, an image defect such as a color point may occur. For this reason, the control unit executes the reverse rotation operation of the developing device 122 when the image forming operation is completed.

  Specifically, referring to FIG. 5B, when the developing device 122 is rotated in the reverse direction, the driving unit 962 is rotated in the reverse direction by a control unit (not shown). At this time, the input gear 82G is rotated clockwise as indicated by an arrow in FIG. At the same time, the magnetic roller 82 is also rotated clockwise. At this time, in FIG. 2, the magnetic roller 82 rotates from above to below in a region facing the developer regulating blade 84. Therefore, the toner deposited on the developer regulating blade 84 is collected by the magnetic brush on the magnetic roller 82, and image quality defects such as color points are prevented. Returning to FIG. 5B, when the idle gear 80G rotates counterclockwise as the input gear 82G rotates, the roller gear 83G rotates clockwise due to the meshing of the idle gear 80G and the roller gear 83G. The As a result, the developing roller 83 is rotated clockwise (second rotation direction opposite to the first rotation direction) as indicated by an arrow. In the present embodiment, when the developing roller 83 is rotated in the second rotation direction shown in FIG. 5B, the roller gear 83G and the idle gear 80G are engaged with each other in the opposite direction to the photosensitive drum 121. A pressing force is applied to the developing roller 83 (arrow DB in FIG. 5B).

  The developing device 122 further includes a toner seal 89 (seal member). FIG. 7 is a schematic cross-sectional view showing the arrangement of the toner seal 89 of the developing device 122 according to this embodiment. FIG. 8 is a schematic top view showing the arrangement of the toner seal 89 of the developing device 122. A pair of toner seals 89 is a sponge material disposed at both ends of the developing housing 80 in the front-rear direction. The toner seal 89 includes a front seal 89F and a rear seal 89R (FIG. 8). The pair of toner seals 89 are disposed so as to contact both end portions in the axial direction of the peripheral surface (coat layer 83 </ b> C) of the developing roller 83, and prevent the developer from leaking from the developing housing 80. As shown in FIG. 7, the toner seal 89 has an arc shape that contacts the developing roller 83 on the side opposite to the photosensitive drum 121. More specifically, the developing housing 80 includes a support portion 80U (FIGS. 7 and 8). The support portion 80U is a pair of arc-shaped wall portions formed in the developing housing 80 so as to face both end portions of the developing roller 83. The toner seal 89 is adhesively fixed to the support portion 80U so as to be interposed between the support portion 80U and the developing roller 83.

  In FIG. 8, the distribution of the coat layer 83C on the developing roller 83 is exaggerated. As described above, in the present embodiment, the coat layer 83C is formed by a dipping method in which the sleeve 830 is dipped in a predetermined dipping bath so that the axial direction of the developing roller 83 is along the vertical direction. The developing roller 83 is mounted on the developing housing 80 so that the lower end side (the pool portion 83C1) when the developing roller 83 is immersed is the front end side opposite to the roller gear 83G.

  On the rear end side of the developing roller 83, when the rotational driving force is transmitted from the input gear 82G to the roller gear 83G, the developing roller 83 is pressed toward the photosensitive drum 121 by the meshing of both gear teeth. . For this reason, the gap between the rear end portion of the developing roller 83 and the photosensitive drum 121 is stably maintained by the tracking roller. On the other hand, on the front end side of the developing roller 83, since the pressing force due to the meshing between the input gear 82G and the roller gear 83G is not applied strongly, the position of the developing roller 83 is difficult to stabilize. In particular, since the developing roller 83 has an outer periphery touch and eccentricity within a predetermined tolerance range, the coating layer 83C of the developing roller 83 is strongly rubbed against the toner seal 89F and easily wears due to these influences.

  In the present embodiment, as described above, the lower end side (reservoir portion 83C1) when the developing roller 83 is immersed is disposed on the front end side of the developing device 122. For this reason, the coating layer 83C is prevented from disappearing even when the reservoir 83C1 of the coating layer 83C strongly rubs against the front seal 89F as the developing roller 83 rotates. As a result, the sleeve 830 (FIG. 3B) is exposed and leakage between the developing roller 83 and the photosensitive drum 121 is prevented.

  Further, as described above, during the reverse rotation operation of the developing device 122, the pressing force in the direction opposite to the photosensitive drum 121, that is, in the direction toward the toner seal 89 is applied to the developing roller 83 (FIG. 5B). Arrow DB). At this time, on the front end side of the developing roller 83, the coat layer 83C is rubbed more strongly with the front seal 89F. Even in such a case, in the present embodiment, as described above, the reservoir 83C1 of the developing roller 83 is disposed so as to face the toner seal 89F. For this reason, even when the developing operation and the reverse rotating operation of the developing device 122 are repeated, the front end side of the coat layer 83C is prevented from disappearing.

  Further, as indicated by an arrow D64 in FIG. 6, the developing roller 83 is given a thrust force in the forward direction by meshing between the idle gear 80G and the roller gear 83G. In this case, the reservoir 83C1 of the coat layer 83C is in contact with the front seal 89F. Therefore, the developer is prevented from spilling out ahead of the front seal 89F as the developing roller 83 moves in the thrust direction.

  The developing device 122 and the image forming apparatus 1 according to the embodiment of the present invention have been described above. However, the present invention is not limited to this, and for example, the following modified embodiment can be adopted.

  (1) Although the above embodiment has been described using a full-color machine as the image forming apparatus 1, the present invention is not limited to this. The image forming apparatus 1 may be a monochrome machine that prints monochrome images.

  (2) In the above-described embodiment, the embodiment has been described in which the reverse rotation operation is executed in addition to the developing operation in the developing device 122, but the present invention is not limited to this. Even when only the developing operation is executed in the developing device 122, the wear and disappearance of the coat layer 83C accompanying the eccentric rotation of the developing roller 83 is prevented.

Next, a preferable aspect of the developing roller 83 in the developing device 122 will be described based on examples. In addition, each subsequent Example was performed on the following experimental conditions.
<Experimental conditions>
Print speed: 30 sheets / min Photoconductor drum 121: OPC drum Peripheral speed of photoconductor drum 121: 180 mm / sec
Developing roller 83: 20 mm diameter sleeve 830 with anodized surface treatment + nylon resin coat (average thickness 5 μm)
A peripheral speed of the developing roller 83: A peripheral speed ratio of 1.5 (with rotation) with respect to the photosensitive drum 121
-Peripheral speed of magnetic roller 82: Peripheral speed ratio 1.1 (counter rotation) with respect to developing roller 83
-Gap between the photosensitive drum 121 and the developing roller 83: 0.12 mm
・ Gap between magnetic roller 82 and developing roller 83: 0.3 mm
-Surface potential of the photosensitive drum 31: + 430V (background portion), + 100V (image portion)
Developing bias applied to developing roller 83: AC voltage frequency 3.7 kHz, Duty 27%, Vpp 1500 V, DC voltage 190 V
Development bias applied to the magnetic roller 82: AC voltage frequency 3.7 kHz, Duty 73%, Vpp 650 V, DC voltage 490 V
-Average toner particle size: 6.8 μm (positive charge)
Toner seal 89: Sponge seal with an axial width of 10 mm, a circumferential length of 20 mm, and a thickness of 1 mm. Toner seal 89 compression amount: when the developing roller 83 rotates forward, the compression amount by the reservoir 83C1 is 0.4 mm. The amount of compression by the reservoir 83C1 during the reverse rotation of the roller 83 is 0.7 mm.
-Reverse rotation operation condition of developing device 122: Performed once per 100 printed sheets. Each roller is counter-rotated for 1 second at a half rotation speed during the developing operation.

  In Table 1, as an example, the results are shown in which the lower end side when the developing roller 83 is immersed is arranged on the front end side (the side opposite to the roller gear 83G) of the developing device 122 as in the above embodiment. . Table 2 shows a result of disposing the lower end side of the developing roller 83 at the rear end side (roller gear 83G side) of the developing device 122 as a comparative example. In Table 1 and Table 2, transition of the film thickness of the coating layer of each developing roller is shown.

  As shown in Table 1, in the example, when the lower end side (initial film thickness 10 μm) of the developing roller 83 is immersed on the counter driving side opposite to the roller gear 83G, the printing end point of 500K sheets is reached. Thus, the film thickness of the coat layer 83C is not less than 2 μm. As a result, a stable image was maintained. On the other hand, as shown in Table 2, in the comparative example, the upper end side (initial film thickness: 5 μm) when the developing roller 83 is immersed is arranged on the counter driving side opposite to the roller gear 83G. As a result, the coating layer disappeared at 300K sheets. In the subsequent printing, an image defect due to leak occurred.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 11 Apparatus main body 12 Image forming part 121 Photosensitive drum (Image carrier)
122 Developing device 80 Developing housing (housing)
80G idle gear (second inclined gear)
81 Developer storage part 82 Magnetic roller (Developer carrier)
82G Input gear 83 Developing roller (toner carrier)
83G roller gear (drive transmission unit, first inclined gear)
830 Sleeve (base material)
83C Coat layer (surface layer)
83C1 reservoir 83C2 thin layer 84 developer regulating blade (layer thickness regulating member)
89 Toner seal (seal member)
962 Drive unit

Claims (5)

A housing for storing a developer containing toner therein;
A toner carrier that is disposed at an interval with respect to an image carrier on which an electrostatic latent image is formed on the surface, is rotatably supported around the axis by the housing, and carries toner on a peripheral surface;
A drive transmission unit fixed to one end side in the axial direction of the toner carrier, and transmitting a rotational driving force to the toner carrier;
A pair of seal members disposed in the housing so as to contact both axial ends of the peripheral surface of the toner carrier, and preventing the developer from leaking from the housing;
Have
The toner carrier comprises a cylindrical base material and a surface layer formed on the base material,
The surface layer is formed by an immersion method in which the base material is immersed in a predetermined immersion tank so that the axial direction is along the vertical direction,
The toner carrier is mounted on the housing such that a lower end side of the toner carrier when immersed is the other end side opposite to the drive transmission portion in the axial direction. Development device. The drive transmission unit is a first inclined gear having gear teeth inclined at a predetermined angle with respect to the axial direction,
A driving unit that is capable of rotating in the forward and reverse directions and that generates a rotational driving force for rotating the toner carrier;
A second inclined gear connected to the drive unit and rotatably supported by the housing so as to mesh with the first inclined gear, and transmitting the rotational driving force to the first inclined gear;
Further comprising
During the developing operation in which the electrostatic latent image on the image carrier is developed, the drive unit is rotated in the forward direction, and the toner carrier is rotated in the first rotation direction. The toner is supplied to the image carrier,
When the toner carrier is rotated in the first rotation direction, the pressing force in the direction toward the image carrier is applied to the toner carrier by the meshing of the first oblique gear and the second oblique gear. Granted,
When the drive unit is rotated in the opposite direction and the toner carrier is rotated in the second rotation direction opposite to the first rotation direction, the first inclined gear and the second inclined gear are engaged. The developing device according to claim 1, wherein a pressing force in a direction toward the seal member is applied to the toner carrier. A developer carrier that is rotatably supported by the housing opposite the toner carrier, carries a developer comprising the toner and a carrier on a peripheral surface, and supplies the toner to the toner carrier;
A layer thickness regulating member that is disposed to face the peripheral surface of the developer carrier along a substantially horizontal direction and regulates the layer thickness of the developer on the developer carrier;
An input gear fixed to the one end side in the axial direction of the developer carrier, connected to the drive unit and the second inclined gear, and transmitting the rotational driving force to the developer carrier;
Have
The second inclined gear is connected to the drive unit via the input gear,
When a rotational driving force is input from the driving unit to the input gear, the toner carrier and the developer carrier are rotated in synchronization with each other,
When the driving unit is rotated in the forward direction during the developing operation, the developer carrier rotates in an area facing the layer thickness regulating member from below to above, and the driving unit rotates in the reverse direction. 3. The developing device according to claim 2, wherein the developer carrying member rotates a region facing the layer thickness regulating member from above to below. The substrate is made of aluminum,
The toner carrier further comprises an oxide layer formed on the surface of the substrate,
The developing device according to claim 1, wherein the surface layer is formed on a surface of the oxide layer. A developing device according to any one of claims 1 to 4,
An electrostatic latent image formed on the surface, the image carrier to which the toner is supplied from the toner carrier;
An image forming apparatus comprising:

Images