JP2005201924A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of steadily forming satisfactory images. <P>SOLUTION: The image forming apparatus 2 includes an image carrier 6, an endless belt 18 to which a toner image on the image carrier is transferred, and a plurality of supporting rollers 14, 28, 30, and 32 stretching the belt so that it rotates. At least one of the plurality of supporting rollers has a core shaft, and a plurality of resin rollers supported by the core shaft, each resin roller having the shape of a truncated cone that has a large-diameter end face and a small-diameter end face. Each adjacent resin rollers are supported on the core shaft such that the large-diameter end faces or short-diameter end faces are joined to each other. Since the large-diameter end faces or small-diameter end faces of each adjacent resin rollers are disposed next to each other, the external face of the support roller has no large level differences in the joints of the resin rollers and has a smooth shape. This constitution prevents the endless belt from being damaged due to load applied from the support roller and concentrating on the internal face of the belt. Accordingly, satisfactory images can steadily be formed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a printer, a copying machine, and a facsimile.

  As a roller used in an image forming apparatus, an inexpensive and simple metal roller (for example, an aluminum roller) including an outer tube, an inner tube into which a core shaft is inserted, and a rib connecting the outer tube and the inner tube are widely used. (For example, refer to Patent Document 1).

However, in recent years, there has been a demand for using a cheaper resin roller instead of a metal roller. Since it is difficult to produce a resin roller having a sufficient width by resin molding, a resin roller is produced by resin-molding a plurality of rollers having relatively small widths and passing through the core shaft and aligning the end surfaces. In the mold configuration that pulls out in the circumferential direction of the roller, when the resin-molded roller is released from the mold, a joint seam (burr, etc.) is generated on the outer peripheral surface of the roller. It is necessary to prepare.
JP 2002-91158 A

  However, when the mold is pulled out in the axial direction, the outer peripheral surface of the roller has a slight taper. Therefore, when the large-diameter end surface of one roller and the small-diameter end surface of the other roller are combined when the resin rollers are fitted to each other on the core shaft, a steep step appears in the resin roller. As a result, when the resin roller is used as a support roller for stretching a belt or a paper transport roller, the resin roller locally comes into contact with a contacted body such as a belt or paper, and the contacted body is damaged and the image is damaged. Noise may occur.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus capable of obtaining a stable and stable image without damaging a contacted body that contacts a resin roller.

In order to achieve the above object, a first aspect of an image forming apparatus according to the present invention includes:
An endless belt that rotatably supports an endless belt and an image bearing member that carries a toner image and an endless belt on which the toner image on the image bearing member is transferred or transferred onto a sheet that is conveyed on the belt A plurality of support rollers,
At least one of the plurality of support rollers includes a core shaft, and a plurality of resin rollers that are supported by the core shaft and have a truncated cone shape having a large-diameter end surface and a small-diameter end surface,
Adjacent resin rollers are supported by the core shaft in a state where the large-diameter end faces or the small-diameter end faces are combined.

According to a second aspect of the image forming apparatus of the present invention,
A conveyance system that includes a conveyance roller that conveys the sheet by rotating in contact with the sheet, and an image forming unit that forms a toner image on the sheet conveyed by the conveyance system,
The transport roller includes a core shaft, and a plurality of resin rollers that are supported by the core shaft and have a truncated cone shape having a large-diameter end surface and a small-diameter end surface,
Adjacent resin rollers are supported by the core shaft in a state where the large-diameter end faces or the small-diameter end faces are combined.

  According to the first aspect of the present invention, since the adjacent resin rollers constituting the support roller have large diameter end surfaces or small diameter end surfaces adjacent to each other, the outer peripheral surface of the support roller is steep at the joint position of the resin roller. There is no step and it has a smooth shape. Therefore, the unauthorized belt is not damaged because the load from the support roller is not concentrated on the inner surface of the belt, so that a stable and high-quality image can be formed.

  According to the second aspect of the present invention, since the adjacent resin rollers constituting the conveying roller have large diameter end surfaces or small diameter end surfaces adjacent to each other, the outer peripheral surface of the conveying roller is steep at the joint position of the resin roller. There is no step and it has a smooth shape. Therefore, the sheet is not damaged because the load from the conveying roller is not concentrated on the surface of the sheet, so that the sheet can be stably formed with a good quality image.

  Hereinafter, an embodiment of an image forming apparatus according to the present invention will be described with reference to the accompanying drawings. Hereinafter, an example in which the present invention is applied to a full-color laser printer (hereinafter referred to as a printer) will be described.

  In FIG. 1, the printer denoted by reference numeral 2 as a whole is provided with a photosensitive drum 6 that is driven to rotate in the direction of arrow A by a motor (not shown) as an image carrier at substantially the center of the inside. Around the photosensitive drum 6, a charging device (corona charger in the illustrated example) 8 that uniformly charges the surface of the photosensitive drum 6 along the rotation direction A, and a static for each color on the photosensitive drum 6. An exposure unit 10 for sequentially forming an electrostatic latent image, a developing unit 12 that sequentially supplies toner of each color to the photosensitive drum 6, and thereby developing an electrostatic latent image, a primary transfer roller 14, and a cleaner 16 are sequentially arranged.

  The primary transfer roller 14 is for transferring the toner adhering to the photosensitive drum 6 to the endless intermediate transfer belt 18, and a predetermined bias voltage is appropriately applied from a bias power source (not shown).

  The cleaner 16 includes a blade 20 that comes into contact with the surface of the photosensitive drum 6, and scrapes off toner remaining on the photosensitive drum 6 after transfer.

  The exposure unit 10 is for selectively irradiating the photosensitive drum 6 with laser light. Specifically, when an image signal is input from an external device (for example, a personal computer) to the image signal processing unit (not shown) of the printer 2, the image signal is color-converted into yellow, cyan, magenta, and black by the image signal processing unit. A digital image signal is generated and this signal is transmitted to a drive circuit (not shown). The drive circuit controls the exposure unit 10 based on the input digital signal to expose the photosensitive drum 6.

  The developing unit 12 includes four developing units 21 (21Y, 21M, 21C, and 21K) containing yellow (Y), magenta (M), cyan (C), and black (K) toners in a counterclockwise direction in FIG. Are sequentially attached to the developing rack 22 by 90 degrees, and can be rotated counterclockwise about the shaft 24. Each time an electrostatic latent image of each color is formed on the photosensitive drum 6, the developing unit 12 moves the developing roller 26 of the corresponding developing device 21 to a developing position that is close to or in contact with the photosensitive drum 6. Rotate. A predetermined bias voltage is appropriately applied to the developing roller 26 from a bias power source (not shown).

  The intermediate transfer belt 18 is supported by the outer peripheral portions of the primary transfer roller 14 and the other three rollers 28, 30, and 32 and is driven to rotate in the direction of arrow B. The roller 28 is a tension roller that applies tension to the intermediate transfer belt 18. The roller 32 is connected to a drive motor (not shown), and the rollers 14, 28, and 30 are driven to rotate as the roller 32 rotates. In the present embodiment, the primary transfer roller 14 is positioned immediately downstream of the photosensitive drum 6 with respect to the rotation direction B of the intermediate transfer belt 18, thereby pressing the intermediate transfer belt 18 toward the photosensitive drum 6, It is ensured that the transfer belt 18 is conveyed between the photosensitive drum 6 and the primary transfer roller 14 in a state of being in close contact with the photosensitive drum 6.

  In this embodiment, the roller 32 that is a driving roller is, for example, an aluminum metal roller, and the rollers 14, 28, and 30 that are driven rollers are resin rollers. As shown in FIG. 2, the resin roller 34 includes a core shaft 36 made of, for example, stainless steel, and a plurality of (six in the illustrated example) resins rotatably supported on the core shaft 36 so that the end surfaces thereof are aligned with each other. The roller 38 and a pair of E-rings 40 attached to both ends of the core shaft 36 in order to fix the axial positions of the plurality of resin rollers 38 are configured. The core shaft 36 is fixed to the main body of the printer 2. Instead, the resin roller 38 may be fixed to the core shaft 36 and the core shaft 36 may be rotatably supported by a bearing provided in the printer 2 body. Each resin roller 38 is manufactured by pulling out a die in the roller axis direction after resin molding, and has a truncated cone shape having a large-diameter end surface 38L and a small-diameter end surface 38S. Although the taper angle is about 3 ° at the maximum, the taper angle is shown to be larger than the actual one in the drawing (note that the hole into which the core shaft 36 is inserted also has a taper angle, but the illustration is omitted). .) These resin rollers 38 are formed using the same mold, and as a result, the taper angles are substantially the same. Adjacent resin rollers 38 are supported by the core shaft 36 in a state where the large-diameter end surfaces 38L or the small-diameter end surfaces 38S are aligned. Since the primary transfer roller 14 needs to have conductivity, a resin roller is formed by mixing a resin material with a conductive material such as carbon black.

  Returning to FIG. 1, the secondary transfer roller 44 is pressed against the portion of the intermediate transfer belt 18 supported by the roller 32. A predetermined bias voltage is applied to the secondary transfer roller 44 from a bias power source (not shown), and a nip portion between the secondary transfer roller 44 and the intermediate transfer belt 18 is a secondary transfer region 46. .

  A blade 47 for scraping off residual toner on the intermediate transfer belt 18 is pressed against a portion of the intermediate transfer belt 18 supported by the roller 30. The blade 47 and the secondary transfer roller 44 are configured to be able to contact and separate from the intermediate transfer belt 18.

  A paper feed cassette 48 is detachably disposed below the printer 2. The sheets S stacked and stored in the sheet cassette 48 are one sheet at a time from the uppermost one by the rotation of the sheet supply roller 50 disposed at a position facing the vicinity of the front end of the sheet S stacked in the sheet cassette 48. It is sent out to the conveyance path 52.

  The conveyance path 52 includes a nip portion of the conveyance roller pair 54, a nip portion of the timing roller pair 56, a secondary transfer region 46, a nip portion of the fixing roller pair 57, and a nip portion of the discharge roller pair 58 from the paper feed cassette 48. It extends to the paper discharge unit 60 provided on the upper surface of the printer 2.

  In the present embodiment, the photosensitive drum 6, the charging device 8, the exposure unit 10, the developing unit 12, the primary transfer roller 14, the intermediate transfer belt 18, and the secondary transfer roller 44 constitute an image forming unit. Further, the paper feed roller 50, the transport roller 54, the timing roller 56, and the paper discharge roller 58 constitute a transport system.

  Next, the printing operation (image forming operation) of the printer 2 will be described.

  At the start of the printing operation, the secondary transfer roller 44 and the cleaning blade 47 are separated from the intermediate transfer belt 18. When the printing operation is started, the photosensitive drum 6 is rotationally driven in the arrow A direction and the intermediate transfer belt 18 in the arrow B direction at the same peripheral speed, and the surface of the photosensitive drum 6 is uniformly charged by the charging device 8. .

  Subsequently, after the developing unit 12 is rotated and the developing unit 21Y is moved to the developing position, exposure is performed by the exposure device 10, and an electrostatic latent image of a yellow toner image is formed on the photosensitive drum 6. The electrostatic latent image is developed by the developing device 21Y, and the developed yellow toner image is primarily transferred onto the intermediate transfer belt 18 by the action of the primary transfer roller 14. Next, the developing device 21M moves to the developing position, and exposure, development, and primary transfer relating to the magenta toner image are performed. Subsequently, the developing unit 21C moves to the development position, and exposure, development, and primary transfer for the cyan toner image are performed. Thereafter, the developing device 21K moves to the developing position, and exposure, development, and primary transfer relating to the black toner image are performed. In this way, the toner images of the respective colors are primarily transferred in a superimposed manner on the intermediate transfer belt 18 moving in the arrow B direction.

  At the same time as the primary transfer of black is completed, the secondary transfer roller 44 and the cleaning blade 47 are pressed against the intermediate transfer belt 18. Subsequently, the superimposed toner image formed on the intermediate transfer belt 18 reaches the secondary transfer region 46 as the intermediate transfer belt 18 moves. In this secondary transfer region 46, the superimposed toner images are collectively sent onto the sheet S fed from the paper feed cassette 48 to the conveyance path 52 by the action of the secondary transfer roller 44 and then supplied by the timing roller pair 56. Secondary transferred. When the secondary transfer is completed, the secondary transfer roller 44 is separated from the intermediate transfer belt 18. Further, the toner remaining on the intermediate transfer belt 18 after the secondary transfer is removed by the blade 47.

  The sheet S on which the toner image is secondarily transferred is sent to the fixing roller pair 57 through the conveyance path 52, and the toner image is fixed on the sheet S there. Then, the paper S is discharged to the paper discharge unit 60 via the paper discharge roller pair 58.

  By the way, when a resin roller is formed by randomly arranging the truncated cone-shaped resin rollers 38, for example, one large-diameter end surface 38L and the other small-diameter end surface 38S of the adjacent resin rollers 38 like the resin roller 70 in FIG. May be adjacent to each other, and as a result, a steep step 72 appears on the outer peripheral surface of the resin roller. When such a resin roller 70 is used for the rollers 14, 28, and 30 that stretch the intermediate transfer belt 18, a concentrated load acts on the inner surface of the belt. If the intermediate transfer belt 18 continues to rotate in this state, the inner surface of the belt is damaged, and the shape and electric resistance value of the belt are locally altered. As a result, poor cleaning, uneven transfer, etc. occur and image quality deteriorates. Further, the photosensitive drum 6 that contacts the outer peripheral surface of the intermediate transfer belt 18 and the sheet S conveyed to the secondary transfer region 46 may be damaged. Further, for example, when the direction of the taper of the resin roller 38 is aligned as in the resin roller 74 of FIG. 3B, there is a problem that the intermediate transfer belt 18 meanders toward the small diameter end surface.

  On the other hand, in this embodiment, since the adjacent resin rollers 38 have the large-diameter end surfaces 38L or the small-diameter end surfaces 38S adjacent to each other as shown in FIG. There is no steep step at the joint position of the roller 38, and it has a smooth shape. The intermediate transfer belt 18 is not damaged because the load from the resin roller 34 is not concentrated on the inner surface of the intermediate transfer belt 18, so that the intermediate transfer belt 18 can stably form a high-quality image.

  In the above description, the resin rollers 38 are resin-molded with the same mold, but the large diameters of the resin rollers 38 can be easily matched between the large diameter end surfaces 38L or the small diameter end surfaces 38S of the adjacent resin rollers 38. Two types of molds are provided in which a concave portion and / or a convex portion are formed on at least one of the end surface and the small-diameter end surface, so that the large-diameter end surfaces or the small-diameter end surfaces can be matched. It is preferable that it cannot be matched with the small-diameter end face. FIG. 4 shows the conical cone-shaped resin rollers 76 and 78 adjacent to each other. The concave portion 80 is provided only on the large-diameter end surface 76L of one resin roller 76, and the convex portion 82 is formed only on the large-diameter end surface 78L of the other resin roller 78. This is an example. In consideration of the point that the resin roller composed of such a resin roller is used as a driven roller, the concave and convex portions provided in the resin roller are, for example, as cylindrical holes 80 and protrusions 82 as shown in the figure. Preferably, the resin rollers 76 and 78 adjacent to each other in a state where the holes 80 and the projections 82 are fitted can be relatively rotated.

  The above description relates to an embodiment of the present invention, and the present invention is not limited to this and can be variously modified. For example, in the above-described embodiment, the present invention has been described by taking an example of an image forming apparatus that primarily transfers a toner image onto the intermediate transfer belt 18 and secondarily transfers the toner image onto a sheet. However, the present invention is not limited thereto. The present invention can also be applied to a type of apparatus that directly transfers a toner image onto a sheet conveyed on a sheet conveying belt having the same configuration as the intermediate transfer belt.

  In the above embodiment, the resin roller having a plurality of frustoconical resin rollers is applied to the driven rollers 14, 28, and 30 that stretch the intermediate transfer belt 18, but may be applied to the drive roller 32. In this case, an outer peripheral layer made of a material such as a rubber having a high static friction coefficient is provided on the outer periphery of the resin roller as a base, and the resin roller is fixed to the core shaft to produce a resin roller. As in the case of the driven roller, a concave portion and / or a convex portion are formed on at least one of the large diameter end surface and the small diameter end surface of each resin roller so that the large diameter end surfaces or the small diameter end surfaces of the resin rollers can be easily aligned. Such two types of molds are prepared, and thereby it is possible to match the large diameter end surfaces or the small diameter end surfaces, but it is preferable that the large diameter end surface and the small diameter end surface cannot be matched. FIG. 5 relates to the adjacent truncated cone-shaped resin rollers 84, 86. The large diameter end surface 84 </ b> L and the small diameter end surface 84 </ b> S of one resin roller 84 are provided with recesses 88 </ b> L, 88 </ b> S, respectively. In this example, convex portions 90L and 90S are formed on the small-diameter end face 86S, respectively. The resin roller composed of such a resin roller transmits the driving force from the drive motor to the intermediate transfer belt with high efficiency. It is preferable that can be integrally rotated.

  It is also possible to apply a resin roller having a plurality of frustoconical resin rollers to a conveying roller (base body) that conveys a sheet by rotating in a state of contacting the sheet, such as a timing roller. Further, if the transport system uses a transport belt, the present invention can also be applied to a support roller (drive roller, driven roller) that stretches the belt.

  As described above, a conductive roller can be formed by mixing a resin material with a conductive material and molding a resin roller. However, in addition to the primary transfer roller 14, for example, a photosensitive drum is used for such a conductive roller. The present invention can be applied to a charging roller as a charging device that uniformly charges the surface, a cleaning roller as a cleaning means for scraping off residual toner on the intermediate transfer belt 18, and the like.

1 is a configuration diagram showing an embodiment of an image forming apparatus according to the present invention. (A) The side view which shows the resin roller used for the support roller which stretches the intermediate transfer belt of FIG. (B) The perspective view which shows the resin roller which comprises the resin roller of Fig.2 (a). The side view which shows two comparative examples of the resin roller from which arrangement | positioning of the resin roller differs from Fig.2 (a). The perspective view which shows a pair of resin roller which can mutually be rotated in the state fitted. The perspective view which shows a set of resin rollers which can rotate integrally in the state fitted.

Explanation of symbols

2 Printer (image forming device)
18 Intermediate transfer belt (endless belt)
14, 28, 30, 32 Support roller 34 Resin roller (support roller)
38 Tapered resin roller 38L Large diameter end surface 38S Small diameter end surface

Claims (5)

An image carrier for carrying a toner image;
An endless belt in which a toner image on an image carrier is transferred or transferred onto a sheet conveyed on the belt;
A plurality of support rollers that rotatably stretch the endless belt;
With
At least one of the plurality of support rollers includes a core shaft, and a plurality of resin rollers that are supported by the core shaft and have a truncated cone shape having a large-diameter end surface and a small-diameter end surface,
Adjacent resin rollers are supported by the core shaft in a state where the large-diameter end faces or the small-diameter end faces are combined. A transport system having transport rollers for transporting paper by rotating in contact with the paper;
An image forming unit that forms a toner image on a sheet conveyed by a conveyance system;
With
The transport roller includes a core shaft and a plurality of resin rollers that are supported by the core shaft and have a truncated cone shape having a large-diameter end surface and a small-diameter end surface,
Adjacent resin rollers are supported by the core shaft in a state where the large-diameter end faces or the small-diameter end faces are combined.   At least one of the large-diameter end face and the small-diameter end face of each resin roller is provided with a convex part and / or a concave part, so that the concave part and the convex part of adjacent resin rollers can be fitted. The image forming apparatus according to claim 1 or 2.   The image forming apparatus according to claim 3, wherein the convex portion and the concave portion to be fitted are formed such that adjacent resin rollers are relatively rotatable. The image forming apparatus according to claim 3, wherein the convex portion and the concave portion to be fitted are formed so that adjacent resin rollers can be integrally rotated.

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