JP6204302B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that forms an image.

  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 (developer 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 developing roller disposed to face a photosensitive drum. The developing roller is rotated in a predetermined rotation direction by rotating the gear disposed on the shaft portion of the developing roller. Further, a technique in which a resin layer is provided on the surface of the developing roller is disclosed. 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.

JP 2009-300677 A

  In the above technique, when the toner scattered from the developing roller adheres to the gear, an image defect corresponding to the gear tooth pitch or a rotation failure of the developing roller may occur.

  The present invention has been made to solve the above-described problems, and provides an image forming apparatus that suppresses developer contamination of a developer carrying body and a gear that transmits a rotational driving force to the image carrying body. With the goal.

  An image forming apparatus according to an aspect of the present invention includes an image carrier that includes a first shaft portion, is rotated about the first shaft portion, and forms an electrostatic latent image on a surface thereof, and the first shaft portion. A first rotating gear that is disposed on one end side in the axial direction and transmits a rotational driving force to the image carrier, and a developing device that is disposed to face the image carrier, the developing device comprising: A peripheral surface including a housing having an opening and a second shaft disposed in parallel with the first shaft, and supported by the housing so as to be rotatable around the second shaft, and exposed from the opening Is disposed at a distance from the image carrier, and is disposed on the one end side in the axial direction of the second shaft portion, a developer carrier that carries the developer on the peripheral surface, A second rotation gear that transmits a rotational driving force to the developer carrier, and the image carrier has a cylindrical first base material, A first surface layer formed on the first substrate, and the developer carrying member includes a cylindrical second substrate and a second surface layer formed on the second substrate. The first surface layer by an immersion method in which the first substrate and the second substrate are immersed in a predetermined immersion tank so that the axial direction of the developer carrier and the image carrier is along the vertical direction. And the second surface layer are formed, and the image bearing member and the developing member are formed such that lower end sides of the developer bearing member and the image bearing member at the time of immersion are opposed to each other on the one end side in the axial direction. An agent carrier is arranged.

  According to this configuration, the developer carrying member of the developing device is disposed at a distance from the image carrying member and is supported by the housing so as to be rotatable around the second shaft portion. A developer is carried on the peripheral surface of the developer carrying member. When the image carrier and the developer carrier rotate, a laminar flow is formed between them. Such a laminar flow diffuses the developer scattered from the peripheral surface of the developer carrier around the developing device. If the developer continues to adhere to the first rotating gear and the second rotating gear, the torque of these rotating gears and rotation failure are likely to occur. In addition, lateral stripes (jitter) corresponding to the pitch of the gear teeth of the rotating gear may occur on the image. According to the above configuration, the image carrier and the developer carrier are arranged so that the lower ends when the developer carrier and the image carrier are immersed are opposed to each other at one end in the axial direction. On the lower end side during immersion, the first surface layer and the second surface layer are partially thickened. For this reason, the gap between the developer carrying member and the image carrying member adjacent to the first rotating gear and the second rotating gear is partially narrowed. As a result, the laminar flow is blocked, and the air flow including the developer is prevented from flowing toward the first rotating gear and the second rotating gear. Accordingly, developer contamination of the first rotating gear and the second rotating gear is reduced, and the occurrence of gear rotation failure and image defect is prevented.

  In the above configuration, it is preferable that the image carrier and the developer carrier are rotated in the same direction in regions facing each other.

  According to this configuration, a laminar flow is easily formed toward the downstream side in the rotation direction of the image carrier and the developer carrier. As a result, the air flow containing the developer is further prevented from flowing toward the first rotating gear and the second rotating gear.

  In the above configuration, an air path communicating with the other end side opposite to the one end side in the axial direction in an area where the image carrier and the developer carrier face each other, and connected to the air path It is preferable that the air flow generation unit sucks air from a region where the image carrier and the developer carrier face each other through the air path.

  According to this configuration, the first surface layer and the second surface layer are partially thinned on the upper end side during immersion. Therefore, in the region where the image carrier and the developer carrier are opposed to each other, the distance between the developer carrier and the image carrier is partially widened on the other end side in the axial direction. According to said structure, air is inhaled through the area | region where the said space | interval is wide. Therefore, the air flow containing the developer can be quickly sucked from the area where the developer carrier and the image carrier face each other. As a result, the developer contamination of the first rotating gear and the second rotating gear is further reduced.

  In the above configuration, the first base is made of aluminum, the image carrier further includes a first oxide layer formed on a surface of the first base, and the first surface layer is the first It is desirable that it be formed on the surface of the oxide layer.

  According to this configuration, the first oxide layer is formed on the first base material made of aluminum, whereby the adhesion force of the first surface layer to the first base material is increased. As a result, peeling of the first surface layer is further suppressed. Therefore, the developer contamination of the first rotating gear and the second rotating gear is reduced over a long period of time.

  In the above configuration, the second base material is made of aluminum, the developer carrier further includes a second oxide layer formed on a surface of the second base material, and the second surface layer is the first surface layer. It is desirable that it be formed on the surface of the two oxide layer.

  According to this configuration, the adhesion of the second surface layer to the second substrate is increased by forming the second oxide layer on the second substrate made of aluminum. As a result, peeling of the second surface layer is suppressed. Therefore, the developer contamination of the first rotating gear and the second rotating gear is further reduced over a long period of time.

  According to the present invention, there is provided an image forming apparatus that suppresses developer contamination of a gear that transmits a rotational driving force to a developer carrier and an image carrier.

1 is a cross-sectional view illustrating an internal structure of an image forming apparatus according to an embodiment of the present invention. FIG. 1 is a schematic plan view (A) showing the periphery of an image carrier and a developer carrier according to an embodiment of the present invention, and a schematic diagram showing the state of film thickness at the ends of the image carrier and the developer carrier. It is various sectional drawing (B). 5 is graphs (A) and (B) showing the distribution of the film thickness in the axial direction of the developer bearing member according to the embodiment of the present invention. FIG. 6 is a schematic cross-sectional view of an image carrier and a developer carrier according to a modified embodiment of the present invention, showing an air flow generation unit and an air path.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram schematically showing an internal structure of a printer 100 (image forming apparatus) according to an embodiment of the present invention. The printer 100 shown in FIG. 1 is a so-called monochrome printer, but in other embodiments, the image forming apparatus is a color printer, a facsimile machine, a multifunction machine having these functions, or a toner image to form a sheet on a sheet. Other devices may be used. Note that the terms used in the following description, such as “up”, “down”, “front”, “rear”, “left” and “right”, are merely for the purpose of clarifying the description. There is no limitation on the principle of the image forming apparatus.

  The printer 100 includes a housing 200 that houses various apparatuses for forming an image on the sheet S. The housing 200 includes an upper wall 210 that defines the upper surface of the housing 200, a bottom wall 220 that defines the bottom surface of the housing 200, a rear wall 230 that stands upright between the upper wall 210 and the bottom wall 220, and a rear surface. And a manual feed tray 240 attached to the opposite side of the wall 230. The manual feed tray 240 can be turned up and down with the lower end as a fulcrum (arrow D1 in FIG. 1). As shown in FIG. 1, when the manual feed tray 240 is rotated downward, the main body opening 290 formed in the housing 200 is opened. The main body opening 290 communicates with the internal space 260 of the housing 200. Therefore, the user can access various devices accommodated in the internal space 260 of the housing 200 through the main body opening 290. When the manual feed tray 240 is rotated upward, the main body opening 290 is closed. As a result, unnecessary access to the internal space 260 by the user is prevented.

  The printer 100 includes a cassette 110, a pickup roller 112, a first paper feed roller 113, a second paper feed roller 114, a transport roller 115, a registration roller pair 116, and an image forming unit 12.

  The cassette 110 accommodates the sheet S inside. The cassette 110 includes a lift plate 111 that supports the sheet S. The lift plate 111 is inclined so as to push up the leading edge of the sheet S.

  The pickup roller 112 is disposed on the leading edge of the sheet S pushed up by the lift plate 111. When the pickup roller 112 rotates, the sheet S is pulled out from the cassette 110.

  The first paper feed roller 113 is disposed downstream of the pickup roller 112. The first paper feed roller 113 sends the sheet S further downstream. The second paper feed roller 114 is disposed near the fulcrum of the manual feed tray 240. The second paper feed roller 114 pulls the sheet S on the manual feed tray 240 into the housing 200. The user can selectively use the sheet S accommodated in the cassette 110 or the sheet S placed on the manual feed tray 240.

  The transport roller 115 is disposed downstream of the first paper feed roller 113 and the second paper feed roller 114. The transport roller 115 transports the sheet S sent out by the first paper feed roller 113 and the second paper feed roller 114 further downstream.

  The registration roller pair 116 defines the position of the sheet in a direction orthogonal to the conveyance direction. Thereby, the position of the image formed on the sheet S is adjusted. The registration roller pair 116 supplies the sheet S to the image forming unit 12 in accordance with the timing of image formation by the image forming unit 12.

  The image forming unit 12 includes a photosensitive drum 121 (image carrier), a charger 124, an exposure device 123, a developing device 122, a toner container 125, a transfer roller 126, and a cleaning device 127.

  The photosensitive drum 121 has a substantially cylindrical shape. The photosensitive drum 121 has an electrostatic latent image formed on the surface and carries a toner image corresponding to the electrostatic latent image. The photosensitive drum 121 is rotatably supported by a drum unit (not shown). The drum unit is detachable from the housing 200.

  The charger 124 is applied with a predetermined voltage and charges the peripheral surface of the photosensitive drum 121 substantially uniformly. The exposure device 123 irradiates the peripheral surface of the photosensitive drum 121 charged by the charger 124 with laser light. The laser light is emitted in accordance with image data output from an external device (not shown) such as a personal computer that is communicably connected to the printer 100. As a result, an electrostatic latent image corresponding to the image data is formed on the peripheral surface of the photosensitive drum 121.

  The developing device 122 is disposed to face the photosensitive drum 121 and supplies toner to the peripheral surface of the photosensitive drum 121 on which the electrostatic latent image is formed. The toner container 125 supplies toner to the developing device 122. When the developing device 122 supplies toner to the photosensitive drum 121, the electrostatic latent image formed on the peripheral surface of the photosensitive drum 121 is developed (visualized). As a result, a toner image is formed on the peripheral surface of the photosensitive drum 121.

  The transfer roller 126 is rotatably disposed so as to contact the peripheral surface of the photosensitive drum 121. When the sheet S conveyed from the registration roller pair 116 passes between the photosensitive drum 121 and the transfer roller 126, the toner image formed on the peripheral surface of the photosensitive drum 121 is transferred to the sheet S. .

  The cleaning device 127 removes the toner remaining on the peripheral surface of the photosensitive drum 121 after the toner image is transferred to the sheet S. The peripheral surface of the photosensitive drum 121 cleaned by the cleaning device 127 passes again below the charger 124 and is uniformly charged. Thereafter, the above-described toner image is newly formed.

  The printer 100 further includes a fixing device 130 that fixes the toner image on the sheet S downstream of the image forming unit 12 in the conveyance direction. The fixing device 130 includes a heating roller 131 that melts the toner on the sheet S and a pressure roller 132 that causes the sheet S to adhere to the heating roller 131. When the sheet S passes between the heating roller 131 and the pressure roller 132, the toner image is fixed on the sheet S.

  The printer 100 further includes a plurality of transport roller pairs 133 disposed downstream of the fixing device 130 and a discharge roller pair 134 disposed downstream of the transport roller pair 133. The sheet S is conveyed upward by the conveyance roller pair 133 and is finally discharged from the housing 200 by the discharge roller pair 134. Sheets S discharged from the housing 200 are stacked on the upper wall 210.

  Next, the photosensitive drum 121 and the developing device 122 according to the present embodiment will be described in detail. FIG. 2 is a schematic plan view (A) showing the periphery of the developing roller 83 of the photosensitive drum 121 and the developing device 122 according to the present embodiment, and the film thickness of the end portions of the photosensitive drum 121 and the developing device 122. It is typical sectional drawing (B) which shows the mode.

  The photosensitive drum 121 includes a drum shaft 121J (first shaft portion). The drum shaft 121J serves as a rotation axis in the rotation of the photosensitive drum 121. The drum shaft 121J is pivotally supported by a bearing provided in the aforementioned drum unit. The photosensitive drum 121 is rotated around the drum shaft 121J. Further, the printer 100 includes a drum gear 121G (first rotation gear) (FIG. 2A), a first motor M1, and a second motor M2. The drum gear 121G is a gear that is disposed on one end side (right end side) of the drum shaft 121J in the axial direction and transmits a rotational driving force to the photosensitive drum 121. The first motor M1 generates a rotational driving force that rotates the photosensitive drum 121. As shown in FIG. 2A, the first motor M1 is coupled to the drum gear 121G. The second motor M2 generates a rotational driving force that rotates the developing roller 83 of the developing device 122.

  The developing device 122 includes a developing housing 80 (FIG. 1) (housing) and a developing roller 83 (developer carrier). The developing housing 80 is a housing portion of the developing device 122 and stores toner therein. The developing housing 80 includes an opening 122H (FIG. 1) in a region facing the photosensitive drum 121. The developing roller 83 has a cylindrical shape. The developing roller 83 includes a roller shaft 83J (second shaft portion). The roller shaft 83J serves as a rotation axis in the rotation of the developing roller 83. The developing roller 83 is supported by the developing housing 80 so as to be rotatable around the roller shaft 83J. As shown in FIG. 2A, the roller shaft 83J is arranged in parallel with the drum shaft 121J of the photosensitive drum 121. As shown in FIG. 1, a part of the peripheral surface of the developing roller 83 exposed from the opening 122 </ b> H of the developing housing 80 is disposed at a distance from the photosensitive drum 121. The developing roller 83 carries toner (developer) on the peripheral surface. Since the toner carried on the peripheral surface is supplied to the photosensitive drum 121, a developing bias in which an AC voltage is superimposed on a DC voltage is applied to the developing roller 83.

  Further, the developing device 122 includes a roller gear 83G (FIG. 2A) (second rotating gear). The roller gear 83G is disposed on one end side (right end side) of the roller shaft 83J in the axial direction, and transmits a rotational driving force to the developing roller 83. As shown in FIG. 2A, the aforementioned second motor M2 is connected to a roller gear 83G. As described above, in the present embodiment, the roller gear 83G and the drum gear 121G are disposed on the same side in the axial direction with respect to the developing roller 83 and the photosensitive drum 121.

  With reference to FIG. 2A, in the present embodiment, the length of the photosensitive drum 121 in the axial direction is set to be substantially the same as the length of the developing roller 83 in the axial direction. The developing roller 83 includes a pair of tracking rollers (not shown). The tracking roller is a cylindrical member that is pivotally supported by the roller shaft 83J of the developing roller 83. The tracking roller is a thin plate member having a slight thickness in the axial direction of the developing roller 83. When the circumferential surface of the tracking roller is in contact with both end portions of the surface of the photosensitive drum 121 or the above-described drum unit, the interval (gap) between the developing roller 83 and the photosensitive drum 121 is regulated.

  Referring to FIG. 2B, the developing roller 83 includes a cylindrical sleeve 830 (second base material) and a coat layer 83C (second surface layer) formed on the sleeve 830. The sleeve 830 having a diameter of 12 to 20 mm is mainly used according to the specifications of the developing device 122. The photosensitive drum 121 includes a cylindrical drum base tube 120 (first base material) and a functional layer 120C (first surface layer) formed on the drum base tube 120.

  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 (second oxide layer) having a thickness of 10 μm. By forming the oxide layer on the sleeve 830 made of aluminum, the adhesion force of the coat layer 83C to the sleeve 830 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 (100 parts by weight) as a binder resin, titanium oxide (50 to 125 parts by weight) as a pigment, and methanol (800 parts by weight) as a dispersion medium have a diameter of 1.0 mm. A mixed solution is prepared by mixing for about 48 hours with a zirconia bead in a ball mill. 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. At this time, the excess liquid mixture is peeled off by a polytetrafluoroethylene blade. 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.

  The functional layer 120C of the photosensitive drum 121 is also formed by the dipping method in the same manner as the coat layer 83C. The functional layer 120 </ b> C includes a known charge generation layer and charge transport layer having a function for forming an electrostatic latent image on the surface of the photosensitive drum 121. Note that an alumite layer (first oxide layer) is formed in advance on the surface of the drum base tube 120 made of aluminum, and then a functional layer 120C is formed on the alumite layer. For this reason, the adhesion force of the functional layer 120C to the drum base tube 120 is increased. As a result, peeling of the functional layer 120C is suppressed.

  On the other hand, when the coat layer 83C and the functional layer 120C are formed by the dipping method as described above, the mixed liquid adhering to the surfaces of the sleeve 830 and the drum base tube 120 is likely to sag downward due to the influence of gravity during pulling. For this reason, a roller thick layer portion 83C1, which is 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 positioned on the lower end side during immersion (FIG. 2B). ). In addition, a roller thin layer portion 83C2, 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 that is positioned on the upper end side when immersed. Similarly, a drum thick layer portion 120C1, which is a functional layer 120C that is partially thicker than the central portion in the axial direction, is formed on the surface of the drum base tube 120 located on the lower end side during immersion. In addition, a drum thin layer portion 120C2, which is a functional layer 120C that is partially thinner than the central portion in the axial direction, is formed on the surface of the drum base tube 120 that is positioned on the upper end side during immersion.

  FIG. 3A shows the distribution of the film thickness on the lower end side of the coat layer 83 </ b> C formed on the sleeve 830 of the developing roller 83. On the other hand, FIG. 3B shows the film thickness distribution on the upper end side of the coat layer 83 </ b> C formed on the sleeve 830. 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. 3A and 3B, the length of the thin portion of the upper end portion of the coat layer 83C is longer than the length of the thick portion of the lower end portion. 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. Thus, the axial length of the roller thin layer portion 83C2 tends to be longer than the axial length of the roller thick layer portion 83C1 due to the influence of gravity during pulling. Similarly, the axial length of the drum thin layer portion 120C2 tends to be longer than the axial length of the drum thick layer portion 120C1.

  2A and 2B, in the present embodiment, the lower end side when the developing roller 83 and the photosensitive drum 121 are immersed is one end side (right end side) of the drum shaft 121J and the roller shaft 83J in the axial direction. ), The photosensitive drum 121 and the developing roller 83 are arranged so as to face each other. That is, as shown in FIG. 2B, the roller thick layer portion 83C1 is disposed to face the drum thick layer portion 120C1, and the drum thin layer portion 120C2 is disposed to face the roller thin layer portion 83C2. At this time, the roller thick layer portion 83C1 and the drum thick layer portion 120C1 are arranged at positions close to the drum gear 121G and the roller gear 83G, and the drum thin layer portion 120C2 and the roller thin layer portion 83C2 are far from the drum gear 121G and the roller gear 83G. Placed in position.

  As indicated by the arrows in FIG. 2A, when the photosensitive drum 121 and the developing roller 83 rotate, a laminar flow is formed between them. In addition to the laminar flow, a part of the toner is scattered from the peripheral surface of the developing roller 83 exposed through the opening 122H (FIG. 1) by the centrifugal force of the developing roller 83. If the scattered toner continues to adhere to the drum gear 121G and the roller gear 83G, the torque of these rotating gears and rotation failure tend to occur. In addition, horizontal stripes (jitter) corresponding to the pitch of the gear teeth of the drum gear 121G and the roller gear 83G may occur on the image.

  On the other hand, in the present embodiment, as described above, the lower end side when the photosensitive drum 121 and the developing roller 83 are immersed is opposed to each other on one end side (right end side) in the axial direction of the drum shaft 121J and the roller shaft 83J. A photosensitive drum 121 and a developing roller 83 are disposed. For this reason, as shown in FIGS. 2A and 2B, at the right end portion of the photosensitive drum 121 and the developing roller 83 adjacent to the drum gear 121G and the roller gear 83G, the distance between them is partially narrowed. As a result, as indicated by the arrow DS in FIG. 2B, even if a part of the air flow (laminar flow) advances in the axial direction, the drum thick layer portion 120C1 and the roller thick layer portion 83C1 Is blocked. As a result, the air flow containing toner is prevented from flowing toward the drum gear 121G and the roller gear 83G. Therefore, toner contamination of the drum gear 121G and the roller gear 83G is reduced, and the occurrence of gear rotation failure and image defect is prevented. Further, even when an air flow is introduced between the photosensitive drum 121 and the developing roller 83 in order to cool the periphery of the photosensitive drum 121 and the developing device 122, the drum gear 121G and the roller gear 83G are prevented from being contaminated. be able to. This reduces the need to frequently stop the printing operation of the printer 100 and provide a cooling time, particularly in a high temperature environment. Therefore, the productivity of the printer 100 is maintained high.

  Further, as described above, in the region adjacent to the drum gear 121G and the roller gear 83G, when the interval between the photosensitive drum 121 and the developing roller 83 is partially narrow, the developing electric field in the region is partially increased. For this reason, even a toner with a low charge amount contained in the air flow is easily controlled by the developing electric field. Therefore, before such toner reaches the drum gear 121G and the roller gear 83G, the toner can be developed on the surface of the photosensitive drum 121 or collected on the peripheral surface of the developing roller 83.

  Further, in the present embodiment, as indicated by the arrows in FIG. 2A, the photosensitive drum 121 and the developing roller 83 are in the same direction in the regions facing each other (see FIG. 1 from top to bottom). It is rotated. Therefore, a laminar flow tends to be formed toward the downstream side (downward) in the rotation direction of the photosensitive drum 121 and the developing roller 83. As a result, the air flow containing the toner is further prevented from flowing in the axial direction toward the drum gear 121G and the roller gear 83G.

  Furthermore, in this embodiment, as described above, in the photosensitive drum 121, an oxide layer is formed on the drum base tube 120, and a functional layer 120C is formed on the oxide layer. In the developing roller 83, an oxide layer is formed on the sleeve 830, and a coat layer 83C is formed on the oxide layer. For this reason, peeling of the functional layer 120C and the coat layer 83C is suppressed. Therefore, the drum thick layer portion 120C1 and the roller thick layer portion 83C1 are maintained over a long period of time, and toner contamination of the drum gear 121G and the roller gear 83G is reduced.

  The image forming apparatus 1 according to each embodiment of the present invention has been described above, but 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 monochrome machine as the image forming apparatus 1, the present invention is not limited to this. The image forming apparatus 1 may be a full-color machine that prints a color image.

  (2) FIG. 4 is a schematic cross-sectional view of the photosensitive drum 121 (image carrier) and the developing roller 83 (developer carrier) in the printer 100A (image forming apparatus) according to a modified embodiment of the present invention. FIG. 6 is a view showing a fan 85 and a duct 86.

  The printer 100 </ b> A includes a fan 85 (air flow generation unit) and a duct 86 (air passage). The duct 86 extends in the printer 100A. The duct 86 is the other end opposite to one end side (right end side) in the axial direction of the drum shaft 121J and the roller shaft 83J (FIG. 2A) in the region where the photosensitive drum 121 and the developing roller 83 face each other. Communicates with the left side (left end side). The fan 85 sucks air from a region where the photosensitive drum 121 and the developing roller 83 face each other through the duct 86. When the fan 85 is rotated by a control unit (not shown), an air flow is generated as indicated by an arrow DF in FIG.

  As described above, the functional layer 120C of the photosensitive drum 121 and the coat layer 83C of the developing roller 83 are partially thinned on the upper end side during immersion (drum thin layer portion 120C2 and roller thin layer portion 83C2). Therefore, in the region where the photosensitive drum 121 and the developing roller 83 are opposed to each other, the gap between the photosensitive drum 121 and the developing roller 83 is partially widened on the other end side (left end side) in the axial direction. According to the present modified embodiment, air is sucked by the fan 85 through the region where the interval is wide. Therefore, an air flow containing toner can be quickly sucked from a region where the photosensitive drum 121 and the developing roller 83 face each other. In particular, since the atmospheric pressure is partially increased around the drum thick layer portion 120C1 and the roller thick layer portion 83C1 on the right end side, the air flow is more likely to flow toward the left end side at a relatively low pressure. As a result, toner contamination of the drum gear 121G and the roller gear 83G is further reduced.

Next, preferable modes of the photosensitive drum 121 and the developing roller 83 in the printer 100 will be described based on examples. In addition, each subsequent Example was performed on the following experimental conditions.
<Experimental conditions>
Printing speed: 45 sheets / min Photoconductor drum 121: OPC drum Peripheral speed of photoconductor drum 121: 210 mm / sec
Developing roller 83: Anodized surface treatment + nylon resin coating Peripheral speed of developing roller 83: peripheral speed ratio 1.6 (with rotation) with respect to the photosensitive drum 121
-Gap between the photosensitive drum 121 and the developing roller 83: 0.3 mm
-Surface potential of the photosensitive drum 31: +400 V (background portion), +50 V (image portion)
Developing bias applied to developing roller 83: AC voltage frequency 2.7 kHz, Duty 45%, Vpp 1600 V, DC voltage 290 V
-Average toner particle diameter: 7.8 μm (positive chargeability)

  Table 1 shows the arrangement conditions of the photosensitive drum 121 and the developing roller 83 and the evaluation results in Examples and Comparative Examples.

  In Example 1, as in the above-described embodiment, the lower end portion (drum) of the photosensitive drum 121 and the developing roller 83 is immersed on the right end side (drive side) where the drum gear 121G and the roller gear 83G are arranged in the axial direction. A thick layer portion 120C1 and a roller thick layer portion 83C1) are disposed. In Comparative Example 1, the upper end portions (drum thin layer portion 120C2 and roller thin layer portion 83C2) when the photosensitive drum 121 and the developing roller 83 are immersed are arranged on the driving side in the axial direction. On the other hand, in Comparative Example 2, the lower end portion (drum thick layer portion 120C1) when the photosensitive drum 121 is immersed and the upper end portion (roller thin layer portion 83C2) when the developing roller 83 is immersed are disposed on the driving side in the axial direction. Is done. Further, in Comparative Example 3, the upper end portion (drum thin layer portion 120C2) when the photosensitive drum 121 is immersed and the lower end portion (roller thick layer portion 83C1) when the developing roller 83 is immersed are disposed on the axial drive side. Is done.

  In each experiment, 100,000 sheets of A4 vertical size images were printed in a room temperature environment, and toner contamination (gear contamination) of the drum gear 121G and the roller gear 83G was evaluated. Furthermore, Table 1 shows a large value among the torque increases of the drum gear 121G and the roller gear 83G before and after printing (torque change amount).

  As shown in Table 1, the lower end side when the photosensitive drum 121 and the developing roller 83 are immersed is arranged at a position close to the drum gear 121G and the roller gear 83G, so that the gap between the photosensitive drum 121 and the developing roller 83 is set. The sealing effect is increased. As a result, toner contamination of the drum gear 121G and the roller gear 83G is reduced, and an increase in rotational torque of these gears is suppressed. On the other hand, in Comparative Examples 1 to 3, the air flow containing toner tends to flow toward the drum gear 121G and the roller gear 83G. As a result, the occurrence of gear contamination and the increase in rotational torque are increased.

100, 100A printer (image forming apparatus)
120 drum base pipe (first base material)
120C functional layer (first surface layer)
120C1 Drum thick layer portion 120C2 Drum thin layer portion 121 Photosensitive drum (image carrier)
121G drum gear (first rotating gear)
121J Drum shaft (first shaft)
122 Developing Device 80 Developing Housing (Housing)
83 Development roller (developer carrier)
830 Sleeve (second base material)
83C Coat layer (second surface layer)
83C1 Roller thick layer part 83C2 Roller thin layer part 83G Roller gear (second rotating gear)
83J Roller shaft (second shaft part)
85 fans (air flow generator)
86 Duct (wind passage)
M1 1st motor M2 2nd motor

Claims (4)

An image carrier including a first shaft portion, rotated about the first shaft portion, and having an electrostatic latent image formed on a surface thereof;
A first rotation gear disposed on one end side in the axial direction of the first shaft portion and transmitting a rotational driving force to the image carrier;
A developing device disposed opposite to the image carrier,
The developing device includes:
A housing with an opening;
A second shaft portion disposed in parallel with the first shaft portion, supported by the housing so as to be rotatable around the second shaft portion, and a part of a peripheral surface exposed from the opening portion being the image bearing member; A developer carrying body disposed at a distance from the body and carrying a developer on the peripheral surface;
A second rotating gear disposed on the one end side in the axial direction of the second shaft portion and transmitting a rotational driving force to the developer carrier;
With
The image carrier comprises a cylindrical first substrate and a first surface layer formed on the first substrate,
The developer carrier includes a cylindrical second base material, and a second surface layer formed on the second base material,
By the immersion method in which the first base material and the second base material are immersed in a predetermined immersion tank so that the axial direction of the developer carrier and the image carrier is along the vertical direction, the first surface layer and the image carrier A second surface layer is formed, and the film thickness of the first surface layer on the lower end side when the image carrier is immersed is thicker than the central portion in the axial direction, and the upper end side when the image carrier is immersed The film thickness of the first surface layer is thinner than the central portion in the axial direction, and the film thickness of the second surface layer on the lower end side during the immersion of the developer carrier is thicker than the central portion in the axial direction. The film thickness of the second surface layer on the upper end side during the immersion of the developer carrier is thinner than the central portion in the axial direction,
The image carrier and the developer carrier are arranged so that the lower ends of the developer carrier and the image carrier when immersed are opposed to each other on the one end side in the axial direction ,
An air path communicating with the other end side opposite to the one end side in the axial direction in a region where the image carrier and the developer carrier face each other;
An air flow generating unit that is connected to the air path and sucks air from a region where the image carrier and the developer carrier face through the air path;
An image forming apparatus further comprising:   The image forming apparatus according to claim 1, wherein the image carrier and the developer carrier are rotated in the same direction in regions facing each other. The first substrate is made of aluminum,
The image carrier further comprises a first oxide layer formed on the surface of the first substrate,
Wherein the first surface layer is an image forming apparatus according to claim 1 or 2, characterized in that it is formed on a surface of the first oxide layer. The second substrate is made of aluminum,
The developer carrier further comprises a second oxide layer formed on the surface of the second substrate,
Wherein the second surface layer image forming apparatus according to any one of claims 1 to 3, characterized in that it is formed on a surface of the second oxide layer.

Images