Pressing roller and image formation device

Abstract

To make such the failure of a foreign matter adhering to an outer peripheral surface of a pressing roller be less likely to occur.SOLUTION: Disclosed is a pressing roller 8 for bringing a sheet P into close contact with a transportation drum 2 by coming into pressure-contact with the transportation drum 2 via the sheet P, where at least an outer peripheral surface is formed of a conductive material.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a pressing roller for bringing a sheet into close contact with a conveyance drum, and an image forming apparatus including the same.

Background Art

[0002] Conventionally, in an image forming apparatus such as an inkjet printer, there is known one in which a pressing roller for bringing a sheet into close contact with a conveyance drum is installed (see, for example, Patent Document 1).

[0003] Specifically, in the image forming apparatus in Patent Document 1, the pressing roller presses against the conveyance drum via the sheet to bring the sheet into close contact with the conveyance drum. Then, the sheet carried while being in close contact with the conveyance drum by the pressing roller is conveyed to a position facing the head (ink head) by the conveyance drum rotating in a predetermined direction, and ink is sprayed from the head to form a desired image on the sheet surface.

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the conventional technology, there has been a problem that foreign matter such as ink adheres to the outer peripheral surface of the pressing roller. When such a problem occurs, the sheet carried and conveyed by the conveyance drum is soiled with foreign matter.

[0005] The present invention has been made to solve the above-described problems, and an object thereof is to provide a pressing roller and an image forming apparatus in which foreign matter hardly adheres to the outer peripheral surface of the pressing roller.

Means for Solving the Problems

[0006] The pressing roller in the present invention is a pressing roller that presses against a conveyance drum via a sheet to bring the sheet into close contact with the conveyance drum, and at least the outer peripheral surface thereof is formed of a conductive material.

Advantages of the Invention

[0007] According to the present invention, it is possible to provide a pressing roller and an image forming apparatus in which it is difficult for foreign matter to adhere to the outer peripheral surface of the pressing roller.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

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Figure 7

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In each figure, the same or corresponding parts are denoted by the same reference numerals, and the redundant description thereof will be simplified or omitted as appropriate.

[0010] First, with reference to FIG. 1, the overall configuration and operation of the image forming system 100 will be described. In FIG. 1, reference numeral 1 denotes an inkjet printer as an image forming apparatus, 50 denotes an application device that applies a coating liquid as pre-treatment to a sheet P conveyed to the image forming apparatus 1, 80 denotes a sheet feeding device that feeds a sheet P such as paper, 85 denotes a drying device that dries the ink on the sheet P after image formation, and 90 denotes a paper discharging device where the sheet P discharged from the drying device 85 is stacked. As shown in FIG. 1, an image forming system 100 in the present embodiment is connected with, from the upstream side, a sheet feeding device 80, an application device 50, an image forming apparatus 1, a drying device 85, and a paper discharging device 90.

[0011] With reference to FIG. 1, the operation of the image forming system 100 will be briefly described. First, when a print command together with image information is input from a personal computer or the like to the control unit of the image forming system 100, the sheet P is fed from the sheet feeding cassette 81 by the sheet feeding roller 82. The sheet P fed from the sheet feeding cassette 81 is conveyed by the conveying roller via the first conveying path K1 toward the application device 50. In the present embodiment, the sheet feeding device 80 is configured to feed cut paper stored in the sheet feeding cassette 81, but the sheet feeding device 80 can also be configured to feed roll paper.

[0012] Thereafter, the sheet P conveyed to the application device 50 is conveyed to the main body 51 of the application device via the second conveying path K2. Then, in the main body 51 of the application device, a coating liquid (pre-treatment liquid) for suppressing bleeding, back printing, etc. is applied to the lower surface of the sheet P (the sheet surface that becomes the front surface during image formation) (this is the coating step). Thereafter, the sheet P to which the coating liquid has been applied is conveyed to the inversion path K4 (the fourth conveying path), and the conveying direction is reversed and inverted (the state where the sheet surface to which the coating liquid has been applied becomes the front surface (upper surface)), and is conveyed to the image forming apparatus 1 via the third conveying path. Here, when the mode of forming images on both sides of the sheet P (double-sided printing mode) is selected in the image forming apparatus 1, it is necessary to apply the coating liquid to both sides of the sheet P. Therefore, after the coating liquid is applied to one side, the sheet P is conveyed to the reverse path K4, and after the conveyance direction is reversed and the sheet is reversed, it is conveyed to the double-sided path K5 (the fifth conveyance path), and then conveyed to the main part 51 of the coating apparatus again. Then, the sheet P with the coating liquid applied to the other side as well by the main part 51 of the coating apparatus is conveyed to the image forming apparatus 1 as it is via the third conveyance path K3.

[0013] Thereafter, the sheet P conveyed to the image forming apparatus 1 is conveyed to the conveyance drum 2 via the sixth conveyance path K6, and a desired image is formed on the front surface (upper surface) thereof while being conveyed. At this time, since the coating liquid is applied to the front surface of the sheet P as a pretreatment, bleeding and back printing of the image can be suppressed. Then, the sheet P with the image formed thereon is conveyed to the drying apparatus 85 via the seventh conveyance path K7. Note that the configuration and operation of the image forming apparatus 1 will be described in detail later with reference to FIGS. 2 to 4 and the like.

[0014] Thereafter, the sheet P conveyed to the drying apparatus 85 is conveyed to the dryer unit 86 via the eighth conveyance path K8, and the image on the sheet P is dried. Then, the sheet P with the dried image is conveyed to the paper discharge apparatus 90 via the ninth conveyance path K9. Here, when the above-described double-sided printing mode is selected, since it is necessary to form images on both sides of the sheet P, the sheet P after the image on one side is dried is conveyed to the reverse path K10 (the tenth conveyance path), and after the conveyance direction is reversed and inverted, it is conveyed to the double-sided paths K11, K12 (the eleventh and twelfth conveyance paths), and then conveyed again to the conveyance drum 2 of the image forming apparatus 1. Then, on the conveyance drum 2, the sheet P on which the desired image is also formed on the other side is conveyed to the drying device 85 again via the seventh conveyance path K7. Then, in the dryer unit 86, the sheet P on which the image on the other side is dried is conveyed directly to the paper discharge device 90 via the ninth conveyance path K9.

[0015] After that, the sheet P conveyed to the paper discharge device 90 is stacked on the paper discharge tray 91 after passing through the thirteenth conveyance path K13. Thus, a series of operations in the image forming system 100 are completed.

[0016] Hereinafter, the image forming apparatus 1 (inkjet printer) will be described in detail with reference to FIG. 2. In FIG. 2, reference numeral 2 denotes a conveyance drum for conveying the sheet P, 5 denotes a gripper for gripping the sheet P on the conveyance drum 2, 6 denotes a receiving cylinder for receiving the sheet P conveyed to the image forming apparatus 1 and conveying it toward the conveyance drum 2, 7 denotes a delivery cylinder for separating the sheet P from the conveyance drum 2, and 8 denotes a pressing roller that presses against the conveyance drum 2. Reference numerals 10Y, 10M, 10C, 10K, 10S1, and 10S2 denote heads (printing modules) in which image forming units for printing and imaging by an inkjet method are unitized, and 30 denotes a base frame for holding the beam member 35 and the like.

[0017] Here, the image forming apparatus 1 in the present embodiment is for forming a color image. As shown in FIG. 2, a black head 10K, three color (yellow, magenta, cyan) heads 10Y, 10M, 10C for color, and two heads 10S1, 10S2 for coating (special colors) are installed. These six heads 10Y, 10M, 10C, 10K, 10S1, 10S2 face the conveyance drum 2 with a minute gap therebetween, and are arranged radially side by side along the rotation direction of the conveyance drum 2. Note that the six heads 10Y, 10M, 10C, 10K, 10S1, 10S2 have substantially the same structure except that the colors (types) of the ink used for printing are different. The heads 10Y, 10M, 10C, 10K, 10S1, 10S2 are substantially rectangular parallelepiped units, the main part of which is constituted by a piezoelectric actuator, and are provided with nozzles for discharging ink as a liquid (droplets), ink tanks filled with ink, control boards (control units), and the like. Then, the heads 10Y, 10M, 10C, 10K, 10S1, 10S2 form an image by spraying ink onto the sheet P carried on the conveyance drum 2.

[0018] Here, as shown in FIGS. 2 and 3, the conveyance drum 2 rotates in a predetermined direction (the direction of the arrows in FIGS. 2 and 3, which is the counterclockwise direction in FIG. 2) while carrying the sheet P by being driven by a drive mechanism (not shown). The conveyance drum 2 is formed on its surface with a plurality of suction holes 2a for sucking the sheet P and a waste ink receiving portion 9 as a recess for storing waste ink.

[0019] Specifically, referring to FIG. 3, inside the conveyance drum 2 (hollow portion), suction means such as a suction fan capable of sucking air from outside the drum into the drum through the suction holes 2a formed on the drum surface is provided. As a result, the sheet P is sucked through the suction holes 2a and adsorbed (adhered) to the drum surface of the conveyance drum 2. Therefore, image formation on the sheet P on the drum surface by the heads 10Y, 10M, 10C, 10K, 10S1, and 10S2 can be performed well. Note that the air sucked into the conveyance drum 2 by the suction fan is discharged outside the drum from the openings formed at the widthwise end portions of the conveyance drum 2.

[0020] Also, referring to FIGS. 2, 4, etc., the waste ink receiving portion 9 (recessed portion) is a portion recessed from the drum surface in the vicinity (downstream side in the rotation direction) of the gripper 5. And the waste ink receiving portion 9 collects and stores, as waste ink T, the ink remaining on the drum surface without being sprayed onto the sheet P among the ink discharged from the heads 10Y, 10M, 10C, 10K, 10S1, and 10S2 (see FIG. 4). By providing the waste ink receiving portion 9 in the conveyance drum 2 in this way, it is possible to reduce the problem that the back surface of the sheet P carried on the conveyance drum 2 is soiled with ink.

[0021] Referring to FIG. 2, the operation of the image forming apparatus 1 will be briefly described. First, when the sheet P is carried into the image forming apparatus 1, the sheet P is conveyed by the conveyance roller 4 toward the receiving cylinder 6. Then, the receiving cylinder 6 receives the conveyed sheet P while gripping it with the gripper 6a, and rotates in the clockwise direction in FIG. 2 to cause the conveyance drum 2 to receive the sheet P. On the other hand, in the heads 10Y, 10M, 10C, 10K, 10S1, and 10S2 of each color, they are converted into writing information of each color based on the input image information. Then, the sheet P delivered from the receiving cylinder 6 to the conveyance drum 2 is positioned on the conveyance drum 2 while being gripped by the gripper 5, and is conveyed along the counterclockwise rotation of the conveyance drum 2. At this time, the pressing roller 8 presses against the conveyance drum 2 through the sheet P, so that the sheet P is adhered to the conveyance drum 2. Further, the sheet P is adhered to the conveyance drum 2 by suction from the plurality of suction holes 2a formed on the drum surface of the conveyance drum 2. Then, based on the writing information, ink as a liquid is sequentially sprayed from the heads 10Y, 10M, 10C, 10K, 10S1, and 10S2 of each color onto the sheet P conveyed in the direction of the arrow in FIG. 2 by the rotation of the conveyance drum 2, and a desired image is formed on the sheet P. After that, the sheet P on which the desired image has been formed is separated from the conveyance drum 2 by the delivery cylinder 7. Then, the sheet P separated from the conveyance drum 2 is conveyed toward the drying device 85 by the conveyance roller 11.

[0022] Hereinafter, the characteristic pressing roller 8 in the image forming apparatus 1 (image forming system 100) according to the present embodiment will be described in detail. Referring to FIGS. 2 to 4 and the like, the image forming apparatus 1 (image forming system 100) according to the present embodiment is provided with a pressing roller 8 that is in pressure contact with the conveyance drum 2 via the sheet P and brings the sheet P into close contact (contact) with the conveyance drum 2. This pressing roller 8 is formed such that an elastic layer 8b is formed as a roller portion on a shaft 8a (core metal) made of a metal material or the like. The pressing roller 8 is disposed on the downstream side in the rotation direction of the conveyance drum 2 with respect to the receiving cylinder 6 and on the upstream side in the rotation direction of the conveyance drum 2 with respect to the heads 10Y, 10M, 10C, 10K, 10S1, and 10S2 so as to contact the conveyance drum 2. The axial direction (width direction) length of the elastic layer 8b (roller portion) of the pressing roller 8 is formed to be substantially equal to the axial direction length of the conveyance drum 2. Further, both axial ends (both width direction ends) of the shaft 8a of the pressing roller 8 are rotatably installed in the housing of the image forming apparatus 1 via bearings 8c, respectively. Then, the pressing roller 8 rotates in the direction of the arrow in FIGS. 2 to 4 along with the rotation of the conveyance drum 2 or is rotationally driven in the direction of the arrow in FIGS. 2 to 4 by the drive of a drive mechanism, and presses the sheet P against the drum surface of the conveyance drum 2. In the present embodiment, a biasing member such as a compression spring that positively biases the pressing roller 8 toward the conveyance drum 2 can also be connected to the bearing 8c.

[0023] Here, in the pressure roller 8 in this embodiment, at least the outer circumferential surface (the outer circumferential surface of the roller portion that contacts the transport drum 2) is made of a conductive material. Specifically, the pressure roller 8 has an elastic layer 8b (roller portion) formed of a conductive material such as a conductive rubber material. In particular, the elastic layer 8b is made of a rubber material to which a conductive material such as carbon is added, and the electrical resistance value of the outer circumferential surface is 10 4 It is set to be Ω·m or less.

[0024] As described above, in this embodiment, the pressure roller 8 is used, at least the outer peripheral surface of which is made of a conductive material, and therefore the problem of ink or other foreign matter adhering to the outer peripheral surface is less likely to occur compared to the case where the pressure roller 180 (whose elastic layer 180b is made of a rubber material that is not conductive) shown as a comparative example in Fig. 5 is used. Therefore, the problem of the front surface of the sheet P supported and transported by the transport drum 2 being soiled with ink or other foreign matter is also reduced.

[0025] More specifically, when a non-conductive (or weakly conductive) pressure roller 180 shown as a comparative example in FIG. 5 is used, static electricity is generated when the pressure roller 180 (elastic layer 180b) rubs against the sheet P sandwiched between the pressure roller 180 and the transport drum 2. Since the pressure roller 180 is non-conductive (or weakly conductive), once static electricity is generated, the charge on the outer circumferential surface of the pressure roller 180 cannot escape and remains charged. As a result, the waste ink T (including other foreign matter adhering to the surface of the transport drum 2) accumulated in the waste ink receiving section 9 is electrically attracted to the outer circumferential surface of the pressure roller 180, causing ink stains on the surface of the pressure roller 180. 4, even if static electricity is generated by rubbing the pressure roller 8 against the sheet P sandwiched between the pressure roller 8 and the transport drum 2, the charge escapes through the conductive elastic layer 8b, making it difficult for the outer circumferential surface of the pressure roller 8 to become charged. Therefore, the waste ink T (including other foreign matter adhering to the surface of the transport drum 2) accumulated in the waste ink receiving portion 9 is not electrically attracted to the outer circumferential surface of the pressure roller 8, making it difficult for ink stains to form on the surface of the pressure roller 8.

[0026] FIG. 6 is a graph showing the results of an experiment conducted by the inventor of the present invention, in which the amount of charge on the outer circumferential surface of the pressure roller was measured over time. In Fig. 6, the horizontal axis represents printing time, and the vertical axis represents the charge amount of the pressure roller. Also, in Fig. 6, graph S1 shows the change in the charge amount when pressure roller 8 (conductive) of this embodiment is used, and graph S0 shows the change in the charge amount when pressure roller 180 (non-conductive, as shown in Fig. 5) is used as a comparative example. 6, it can be seen that when the non-conductive pressure roller 180 is used, the amount of charge increases as printing time passes, whereas when the conductive pressure roller 8 is used, the amount of charge hardly changes even as printing time passes. From these experimental results, the above-mentioned effects of the present invention can be understood.

[0027] <Modification> As shown in FIG. 7, the pressure roller 8 in this modification has a surface layer 8d made of a conductive material formed on the outer circumferential surface thereof. In more detail, the pressure roller 8 has a roller portion made of an elastic layer 8b formed on a shaft 8a, but the elastic layer 8b does not necessarily have to be made of a conductive material, and in the example of Fig. 7, the elastic layer 8b is made of an elastic material such as a non-conductive rubber material. However, in the pressure roller 8 of the modified example, a conductive surface layer 8d is laminated on the outer peripheral surface side of the elastic layer 8b (roller portion). Such a surface layer 8d can be a tube made of a conductive material that covers the peripheral surface of the roller, or a portion where the peripheral surface of the roller is coated with a conductive material. In either case, the pressure roller 8 has at least an outer peripheral surface that is made of a conductive material, and the electrical resistance of the outer peripheral surface is 10 4 It is set to be Ω·m or less. Therefore, even in the modified example, the problem of foreign matter adhering to the outer peripheral surface of the pressure roller 8 can be prevented.

[0028] As described above, the pressure roller 8 in this embodiment is a pressure roller 8 that presses against the conveying drum 2 via the sheet P to bring the sheet P into close contact with the conveying drum 2, and at least its outer surface is formed of a conductive material. This makes it possible to prevent the problem of foreign matter adhering to the outer peripheral surface of the pressure roller.

[0029] In this embodiment, the present invention is applied to a pressure roller 8 installed in an image forming apparatus 1 as part of an image forming system 100, but the present invention can also be applied to a pressure roller installed in a standalone image forming apparatus rather than as part of an image forming system 100. Furthermore, the image forming system 100 in this embodiment is not limited to the one shown in FIG. 1, and may not include the coating device 50, for example. Furthermore, in this embodiment, the present invention is applied to a pressure roller 8 installed in an image forming apparatus 1 having six heads 10Y, 10M, 10C, 10K, 10S1, and 10S2, but the number of heads is not limited to this, and the present invention can naturally be applied to a pressure roller installed in an image forming apparatus having 1 to 5, or 7 or more heads. Even in these cases, the same effects as those of this embodiment can be obtained.

[0030] It is to be noted that the present invention is not limited to the present embodiment, and it is clear that the present embodiment can be appropriately modified within the scope of the technical concept of the present invention in addition to the modifications suggested in the present embodiment. Furthermore, the number, position, shape, etc. of the components are not limited to the present embodiment, and the number, position, shape, etc. of the components can be any number, position, shape, etc. that is suitable for implementing the present invention.

[0031] 1. Image forming device (inkjet printer), 2 conveying drums, 2a Suction hole, 8 pressure roller, 8a Shaft, 8b elastic layer (roller part), 8d surface layer, 9 Waste ink receiving section (recess), 100 Image forming system, P sheet (recording medium).

[0032] The present invention can also be embodied in a combination of Supplementary Notes 1 to 8, as follows. (Appendix 1) a pressure roller that presses the sheet against the conveying drum to bring the sheet into close contact with the conveying drum, A pressure roller, at least the outer circumferential surface of which is formed from a conductive material. (Appendix 2) 2. The pressure roller according to claim 1, wherein an elastic layer made of a conductive material is formed on a shaft. (Appendix 3) 3. The pressure roller according to claim 1 or 2, wherein a surface layer made of a conductive material is formed on the outer peripheral surface. (Appendix 4) 4. The pressure roller according to claim 3, wherein the surface layer is a tube made of a conductive material that covers the peripheral surface of the roller portion. (Appendix 5) 4. The pressure roller according to claim 3, wherein the surface layer is a portion in which the peripheral surface of the roller portion is coated with a conductive material. (Appendix 6) The electrical resistance of the outer peripheral surface is 104 6. The pressure roller according to any one of claims 1 to 5, wherein the resistance is Ω·m or less. (Appendix 7) A pressure roller according to any one of Supplementary Notes 1 to 6; the conveying drum rotating while carrying a sheet; a head that sprays ink onto the sheet carried on the transport drum to form an image; An image forming apparatus comprising: (Appendix 8) The image forming apparatus according to claim 7, wherein the conveying drum has a plurality of suction holes for sucking the sheet and a recess for storing waste ink formed on the drum surface. [Prior art documents] [Patent documents]

[0033] [Patent Document 1] Japanese Patent Application Publication No. 2017-222078

Claims

1. A pressing roller that presses against a conveyance drum via a sheet to bring the sheet into close contact with the conveyance drum, characterized in that at least the outer peripheral surface is formed of a conductive material.

2. The pressing roller according to claim 1, characterized in that an elastic layer made of a conductive material is formed on the shaft.

3. The pressing roller according to claim 1, characterized in that a surface layer made of a conductive material is formed on the outer peripheral surface.

4. The pressing roller according to claim 3, characterized in that the surface layer is a tube made of a conductive material that covers the circumferential surface of the roller portion.

5. The pressing roller according to claim 3, characterized in that the surface layer is a portion obtained by coating a conductive material on the circumferential surface of the roller portion.

6. The electrical resistance value of the outer peripheral surface is 10 4 Ω·m or less, and the pressing roller according to claim 1, characterized in that.

7. The pressing roller according to claim 1 or claim 2, the conveyance drum that rotates while carrying a sheet, a head that sprays ink onto the sheet carried on the conveyance drum to form an image, and an image forming apparatus characterized by comprising these.

8. The image forming apparatus according to claim 7, characterized in that a plurality of suction holes for sucking the sheet and a recess for storing waste ink are formed on the drum surface of the conveyance drum.

Images