Sheet transport device and image forming apparatus

Abstract

To suppress the occurrence of damage to a conveyed sheet in comparison to a case where a plurality of endless belt pairs arranged along a bent conveyance path of the sheet are not provided.SOLUTION: A sheet conveyance device comprises: a bent conveyance path which conveys a sheet; and a plurality of endless belt pairs which are arranged along the conveyance path and in which conveyance surfaces thereof contact each other.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a sheet conveying apparatus and an image forming apparatus. [Background Art]

[0002] Conventionally, as technologies relating to sheet conveying apparatuses, for example, those disclosed in Patent Document 1 and the like have already been proposed.

[0003] Patent Document 1 includes a first conveying means that conveys a sheet, and a first conveying means disposed on the downstream side of the first conveying means in the sheet conveying direction, which conveys the sheet conveyed by the first conveying means to the first conveying means. and a second conveying means forming a nipping portion for nipping and conveying the sheet in a sheet conveying direction different from the sheet conveying direction of the conveying means, wherein one of the opposing pairs forming the nipping portion is capable of transmitting driving force by rotating. The other of the opposing pairs is a rotary conveyance driving means, and the other of the opposing pairs is disposed in an outer direction of a sheet conveyance path formed between the first conveyance means and the second conveyance means, and is driven by the rotary conveyance driving means toward the nipping portion. It is a belt conveying means provided with a belt for conveying a sheet, and the belt conveying means includes the belt made of an elastic member, at least a pair of belt holding rotating members that hold the belt so that it can travel, and each of the belt holding rotating members. each of the belt holding rotating members is supported by the support member so as to keep a constant center distance between the belt holding rotating members; the belt has a hardness of 40 to 80 degrees, and The belt is configured such that an elongation rate, which is a percentage of the elongation from the circumference of the single belt when the belt is wound between the respective belt holding rotating members, satisfies a condition of 10 to 5%. [Prior Art Document] [Patent Document]

[0004] [Patent Document 1] Japanese Unexamined Patent Publication No. 2013-49579 [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] The objective of this invention is to reduce damage to the conveyed sheets compared to a system without multiple endless belt pairs arranged along the curved conveying path of the sheets. [Means for solving the problem]

[0006] The invention described in claim 1 is a curved transport path for transporting a sheet, A plurality of endless belt pairs arranged along the aforementioned transport path, with their transport surfaces in contact with each other, Equipped with 、 Each of the aforementioned endless belt pairs consists of an elastic belt stretched between a pair of rolls. The plurality of endless belt pairs are configured as a conveyor belt that is positioned and driven on the outer circumference along the curved conveying path, and a conveyor belt that is positioned and driven on the inner circumference along the curved conveying path. This is a sheet conveying device.

[0008] Claim 2 The invention described herein is a sheet conveying device according to claim 1, wherein the endless belt pair arranged downstream along the sheet conveying direction has a change angle of 60 degrees or less in the sheet conveying direction compared to the endless belt pair arranged adjacent to it upstream.

[0009] Claim 3 The invention described herein is a sheet conveying device according to claim 1, wherein the conveying path is a path that conveys the sheet in a semicircular shape.

[0010] Claim 4 The invention described herein is characterized in that the plurality of endless belt pairs are arranged in groups of four or more along the conveying path. Claim 3 This is the sheet conveying device described above.

[0011] Claim 5 The invention described herein is a sheet conveying device according to claim 1, wherein the endless belt pair comprises a conveying belt disposed on the outer circumference side of the conveying path and a conveying belt disposed on the inner circumference side of the conveying path, wherein the conveying belt disposed on the outer circumference side of the conveying path has a longer circumference than the conveying belt disposed on the inner circumference side of the conveying path.

[0012] Claim 6 The invention recited in is an image forming apparatus comprising: an image forming unit configured to form an image on a recording medium; a conveying unit configured to convey the recording medium to the image forming unit; wherein as the conveying unit, Claims 1 to 5 the sheet conveying apparatus according to any one of is used. Effect of the Invention

[0013] According to the invention as recited in claim 1, compared to a case where a plurality of pairs of endless belts disposed along the curved conveying path of the sheet are not provided, occurrence of damage to the conveyed sheet can be suppressed.

[0015] Claim 2 According to the invention as recited in , the pair of endless belts disposed on the downstream side in the sheet conveying direction is, Located adjacent to the upstream side compared with the pair of endless belts, Change angle of the conveying direction of the sheet compared to a case where exceeds 60 degrees, occurrence of buckling or the like of the sheet can be reliably suppressed.

[0016] Claim 3 According to the invention as recited in , compared to a case where the conveying path is not configured from a path for conveying a sheet in a semicircular shape, it becomes possible to employ the same pairs of endless belts.

[0017] Claim 4 According to the invention as recited in , compared to a case where less than four pairs of endless belts are disposed along the conveying path, the sheet can be conveyed smoothly.

[0018] Claim 5 According to the invention as recited in , compared to a case where the conveying belt disposed on the outer peripheral side of the conveying path has a shorter circumference than the conveying belt disposed on the inner peripheral side of the conveying path, the sheet can be conveyed reliably.

[0019] Claim 6 According to the invention as recited in , as the conveying means, Claims 1 to 5Compared to a case where the sheet conveying apparatus described in any one of the above is not used, occurrence of damage to a conveyed sheet can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] [Figure 1] FIG. 1 is an overall configuration diagram showing an image forming apparatus to which the sheet conveying apparatus according to Embodiment 1 of the present invention is applied. [Figure 2] FIG. 2 is a configuration diagram showing an image forming apparatus of the image forming apparatus according to Embodiment 1 of the present invention. [Figure 3] FIG. 3 is a configuration diagram showing a main part of the sheet conveying apparatus according to Embodiment 1 of the present invention. [Figure 4] FIG. 4 is a configuration diagram showing a conveying state of recording paper. [Figure 5] FIG. 5 is an explanatory diagram showing an angle formed by a pair of sheet conveying belts. [Figure 6] FIG. 6 is a configuration diagram showing a mechanism that changes the belt length of the pair of sheet conveying belts. [Figure 7] FIG. 7 is a configuration diagram showing a conveying state of recording paper in the sheet conveying apparatus according to Embodiment 1 of the present invention. [Figure 8] FIG. 8 is a configuration diagram showing a conveying state of recording paper in the sheet conveying apparatus according to Embodiment 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] Embodiments of the present invention will be described below with reference to the drawings.

[0022] [Embodiment 1] FIG. 1 is a configuration diagram showing an overall outline of an image forming apparatus to which the sheet conveying apparatus according to Embodiment 1 of the present invention is applied.

[0023] <Overall Configuration of Image Forming Apparatus> The image forming apparatus 1 according to Embodiment 1 is configured as, for example, a color printer. As shown in Figure 1, this image forming apparatus 1 includes a plurality of image forming devices 10 that form toner images developed with toner constituting the developer, an intermediate transfer device 20 that holds the toner images formed by each image forming device 10 and transports them to a secondary transfer position where they are ultimately transferred to a recording paper 5, which is an example of a recording medium (sheet), a paper feed device 50 that receives and transports the required amount of recording paper 5 to be supplied to the secondary transfer position of the intermediate transfer device 20, and a fixing device 40 that fixes the toner image on the recording paper 5 that has been secondarily transferred by the intermediate transfer device 20. In the figure, 1a represents the main body of the image forming apparatus 1. This main body 1a is composed of support structural members and an outer cover, etc. The dashed line in the figure indicates the main transport path through which the recording paper 5 is transported within the main body 1a. In this Embodiment 1, the plurality of image forming devices 10, the intermediate transfer device 20, and the fixing device 40 constitute the image forming means.

[0024] The imaging device 10 consists of five imaging devices 10Y, 10M, 10C, 10K, and 10T, each dedicated to forming toner images of five colors: yellow (Y), magenta (M), cyan (C), black (K), and transparent (T). These five imaging devices 10 (Y, M, C, K, T) are arranged in a single row along the horizontal direction within the internal space of the device body 1a.

[0025] Each imaging apparatus 10 (Y, M, C, K, T) is equipped with a rotating photoreceptor drum 11 as an example of an image holder, as shown in Figure 2. Surrounding the photoreceptor drum 11 are a charging device 12 that charges the image-forming surface (image-holding surface) of the photoreceptor drum 11 to a required potential, an exposure device 13 that irradiates the charged surface of the photoreceptor drum 11 with light based on image information (signals) to form electrostatic latent images (for each color) with potential differences, a developing device 14 (Y, M, C, K, T) as an example of a developing means that develops the electrostatic latent images with toners of the corresponding colors (Y, M, C, K, T) to form toner images, a primary transfer device 15 (Y, M, C, K, T) that transfers each of these toner images to an intermediate transfer device 20, and a drum cleaning device 16 (Y, M, C, K, T) that removes and cleans any toner or other deposits remaining on the image-holding surface of the photoreceptor drum 11 after primary transfer.

[0026] The photoreceptor drum 11 has an image-holding surface formed on the circumferential surface of a cylindrical or columnar substrate that is grounded, and the photoreceptor drum 11 has a photoconductive layer (photosensitive layer) made of a photosensitive material. The photoreceptor drum 11 is supported so as to rotate in the direction indicated by arrow A by a driving force transmitted from a driving means (not shown).

[0027] The charging device 12 consists of a scorotron that is positioned in a non-contact manner on the photoreceptor drum 11. A charging voltage is supplied to the charging device 12. If the developing device 14 performs reverse development, the charging voltage supplied is a voltage or current with the same polarity as the charging polarity of the toner supplied from the developing device 14. Of course, the charging device 12 may also be a contact-type charging roll that is positioned in contact with the photoreceptor drum 11.

[0028] The exposure apparatus 13 uses a device that deflects and scans laser light, configured according to image information, along the axial direction of the photoreceptor drum 11. Alternatively, the exposure apparatus 13 may consist of an LED print head that uses multiple LEDs (Light Emitting Diodes) arranged along the axial direction of the photoreceptor drum 11 to irradiate the photoreceptor drum 11 with light according to image information to form an electrostatic latent image.

[0029] Each developing device 14 (Y, M, C, K, T) is configured with a housing 140 having an opening facing the photoreceptor drum 11 and a developer storage chamber, and includes a developing roll 141 that holds the developer and transports it to the developing area facing the photoreceptor drum 11, an agitation supply member 142 consisting of a screw auger or the like that supplies the developer while agitating it and passing it through the developing roll 141, an agitation transport member 143 consisting of a screw auger or the like that transports the developer to the agitation supply member 142 while agitating it, and a layer thickness regulating member 144 that regulates the amount (layer thickness) of developer held by the developing roll 141. In this developing device 14, a developing voltage is supplied between the developing roll 141 and the photoreceptor drum 11 from a power supply unit (not shown). As for the four-color developers, for example, a two-component developer containing non-magnetic toner and a magnetic carrier is used.

[0030] The primary transfer device 15 (Y, M, C, K, T) is a contact-type transfer device equipped with a primary transfer roll that rotates in contact with the photoreceptor drum 11 via an intermediate transfer belt 21 and to which a primary transfer voltage is supplied. The primary transfer voltage is a DC voltage with polarity opposite to that of the toner charge polarity, supplied from a power supply device (not shown).

[0031] The drum cleaning device 16 consists of a container-shaped main body 160 with a partial opening, a cleaning plate 161 positioned to contact the circumferential surface of the photoreceptor drum 11 after primary transfer with the required pressure to remove and clean residual toner and other deposits, and a delivery member 162 such as a screw auger that collects the toner and other deposits removed by the cleaning plate 161 and transports them to a collection system (not shown). The cleaning plate 161 is made of a plate-shaped member (for example, a blade) made of a material such as rubber.

[0032] As shown in Figure 1, the intermediate transfer device 20 is positioned above each imaging device 10 (Y, M, C, K, T) in the vertical direction. The intermediate transfer device 20 mainly consists of an intermediate transfer belt 21 that rotates in the direction indicated by arrow B while passing through a primary transfer position between the photoreceptor drum 11 and the primary transfer device 15 (primary transfer roll); a plurality of belt support rolls 22 to 24 that hold the intermediate transfer belt 21 in a desired state from its inner surface and support it so that it can rotate; a secondary transfer device 30 as an example of a secondary transfer means that is positioned on the outer peripheral surface (image holding surface) side of the intermediate transfer belt 21 supported by the belt support rolls 22 and transfers the toner image on the intermediate transfer belt 21 to the recording paper 5; and a belt cleaning device 25 that removes and cleans any toner, paper dust, and other deposits that remain and adhere to the outer peripheral surface of the intermediate transfer belt 21 after it has passed through the secondary transfer device 30.

[0033] The intermediate transfer belt 21 is an endless belt made of a material in which a resistance modifier such as carbon black is dispersed in a synthetic resin such as polyimide resin or polyamide resin. The belt support roll 22 also serves as the opposing roll of the belt cleaning device 25 and is configured as a drive roll that is rotationally driven by a drive device (not shown). The belt support roll 23 is configured as the opposing roll that faces the secondary transfer device 30, and the belt support roll 24 is configured as a surface-setting roll that forms the image-forming surface of the intermediate transfer belt 21.

[0034] As shown in Figure 1, the secondary transfer device 30 is a contact-type transfer device equipped with a secondary transfer roll 31 that rotates in contact with the circumferential surface of the intermediate transfer belt 21, which is supported by the belt support roll 23 of the intermediate transfer device 20, at the secondary transfer position, which is the outer circumferential surface portion of the intermediate transfer belt 21, and to which a secondary transfer voltage is supplied. Furthermore, a DC voltage with the opposite or same polarity as the charge polarity of the toner is supplied to the secondary transfer roll 31 or the belt support roll 23 of the intermediate transfer device 20 as the secondary transfer voltage from a power supply device (not shown).

[0035] The fixing device 40 is constructed by arranging a heating rotating body 41 in the form of a roll or belt, which rotates in the direction indicated by the arrow and is heated by a heating means so that its surface temperature is maintained at a predetermined temperature, and a pressurizing rotating body 42 in the form of a belt or roll, which rotates in contact with the heating rotating body 41 at a predetermined pressure and is driven to rotate, substantially aligned with the axial direction of the heating rotating body 41. In this fixing device 40, the contact area where the heating rotating body 41 and the pressurizing rotating body 42 come into contact becomes the fixing processing area where the required fixing process (heating and pressurizing) is performed.

[0036] The paper feeder 50 is positioned below the imaging device 10 (Y, M, C, K, T) and the intermediate transfer device 20. The paper feeder 50 mainly consists of a plurality (or single) paper storage unit 51 that stores recording paper 5 of a desired size and type, and a feeding device 52 that feeds out the recording paper 5 one sheet at a time from the paper storage unit 51. The paper storage unit 51 is mounted so that it can be pulled out, for example, from the front side (the side that the user faces when operating) of the device body 1a.

[0037] Examples of recording paper 5 include plain paper used in electrophotographic copiers and printers, thin paper such as tracing paper, or OHP sheets. To further improve the smoothness of the image surface after fixing, it is preferable that the surface of the recording paper 5 be as smooth as possible. For example, coated paper, which is plain paper with the surface coated with resin, or so-called thick paper with a relatively large basis weight, such as art paper for printing, can also be suitably used.

[0038] Furthermore, in response to recent evolving needs, the recording paper 5 may include gold or silver paper, which have a metallic surface, or special recording media with a glossy surface, such as OHP sheets or coated paper (hereinafter referred to as "special paper"). This special paper has a metallic surface or a glossy surface, and it has the characteristic that its quality is more easily degraded compared to ordinary paper if even slight scratches or streaks occur on the surface, whether before or after image formation.

[0039] Between the paper feed device 50 and the secondary transfer device 30, there is a paper feed transport path 57 consisting of multiple paper transport roll pairs 53-56 and a transport guide (not shown) that transport the recording paper 5 fed from the paper feed device 50 to the secondary transfer position. In the paper feed transport path 57, the paper transport roll pair 56 positioned immediately before the secondary transfer position is configured, for example, as a roll (resist roll) that adjusts the transport timing of the recording paper 5. Furthermore, between the secondary transfer device 30 and the fuser device 40, there is a paper transport belt 58 for transporting the recording paper 5 after secondary transfer fed from the secondary transfer device 30 to the fuser device 40. In addition, near the paper discharge port formed on the main body 1a of the image forming apparatus 1, there is an discharge transport path 62 equipped with paper discharge roll pairs 59-61 for discharging the fixed recording paper 5 fed from the fuser device 40 to a paper discharge section (not shown) located on the side of the main body 1a.

[0040] Furthermore, the image forming apparatus 1 includes a duplex unit 63 for forming images on both sides of the recording paper 5. The duplex unit 63 does not transport the recording paper 5, on which an image has been formed on one side, to a paper discharge section (not shown) by paper discharge roll pairs 59-61, but rather switches the transport direction of the recording paper 5 downwards by a transport path switching unit 62a located downstream of the paper discharge roll pair 60, and transports it to a reversible transport path 66 equipped with multiple reversible transport roll pairs 64, 65. The reversible transport roll pair 65 is configured to be able to switch its rotation direction between forward and reverse. The reversible transport path 66 of the duplex unit 63 is connected to a duplex transport path 69 equipped with multiple paper transport roll pairs 68 via a duplex transport path 67. The recording paper 5 transported to the reversible transport path 66 of the duplex unit 62 is transported again to the paper feed transport path 57 via the duplex transport path 69.

[0041] In Figure 1, reference numeral 100 indicates a control unit that comprehensively controls the operation of the image forming apparatus 1. The control unit 100 includes a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), a bus connecting the CPU, ROM, etc., and a communication interface (not shown). The receiving unit 101 receives image information sent from an external host device such as a personal computer or an image reading device. The user interface 102 allows the user to input and set various conditions when operating the image forming apparatus 1, and includes a liquid crystal display panel for setting various conditions and displaying messages to the user.

[0042] <Operation of the image forming apparatus> The following describes the basic image forming operation of the image forming apparatus 1.

[0043] This section describes the operation in full-color mode, where a full-color image is formed by combining five toner images of five colors (Y, M, C, K, T) using the five imaging devices 10 (Y, M, C, K, T).

[0044] When the image forming apparatus 1 receives image information and command information requesting a full-color image forming operation (print) from a host device such as a personal computer (not shown) or an image reading device, the control unit 100 starts five image forming devices 10 (Y, M, C, K, T), an intermediate transfer device 20, a secondary transfer device 30, a fixing device 40, etc.

[0045] Then, in each imaging apparatus 10 (Y, M, C, K, T), as shown in Figures 1 and 2, first each photoreceptor drum 11 rotates in the direction indicated by arrow A, and each charging apparatus 12 charges the surface of each photoreceptor drum 11 to the required polarity (negative polarity in Embodiment 1) and potential. Subsequently, the exposure apparatus 13 irradiates the surface of the charged photoreceptor drum 11 with light emitted based on the image signal obtained by converting it into each color component (Y, M, C, K, T), and forms electrostatic latent images of each color component, each composed of the required potential difference, on its surface.

[0046] Next, each imaging device 10 (Y, M, C, K, T) supplies toner of the corresponding color (Y, M, C, K, T), charged with the required polarity (negative polarity), from the developing roll 141 to electrostatically deposit onto the electrostatic latent images of each color component formed on the photoreceptor drum 11, thereby performing development. Through this development, the electrostatic latent images of each color component formed on each photoreceptor drum 11 are revealed as five-color (Y, M, C, K, T) toner images, each developed with the corresponding color toner.

[0047] Next, when the toner images of each color formed on the photoreceptor drum 11 of each imaging device 10 (Y, M, C, K, T) are transported to the primary transfer position, the primary transfer device 15 (Y, M, C, K, T) performs a primary transfer in which the toner images of each color are sequentially superimposed on the intermediate transfer belt 21 of the intermediate transfer device 20, which rotates in the direction indicated by arrow B.

[0048] Furthermore, in each imaging apparatus 10 (Y, M, C, K, T) where the primary transfer has been completed, the drum cleaning device 16 cleans the surface of the photoreceptor drum 11 by scraping off any attached material. This prepares each imaging apparatus 10 (Y, M, C, K, T) for the next imaging operation.

[0049] Next, the intermediate transfer device 20 holds the toner image transferred in the first stage by the rotation of the intermediate transfer belt 21 and transports it to the secondary transfer position. Meanwhile, the paper feed device 50 feeds the required recording paper 5 into the paper feed transport path 57 in accordance with the image formation operation. In the paper feed transport path 57, a pair of paper transport rolls 56 acting as registration rolls feed and supply the recording paper 5 to the secondary transfer position in accordance with the transfer timing.

[0050] At the secondary transfer position, the secondary transfer device 30 transfers the toner image on the intermediate transfer belt 21 onto the recording paper 5 in one go. After the secondary transfer is complete, the belt cleaning device 25 cleans the intermediate transfer belt 21 by removing any toner or other deposits remaining on its surface.

[0051] Next, the recording paper 5 on which the toner image has been secondarily transferred is peeled off the intermediate transfer belt 21 and then transported to the fixing device 40 via the paper transport belt 58. In the fixing device 40, the recording paper 5 after the secondary transfer is introduced and passed through the contact area between the rotating heating body 41 and the pressing body 42, and the necessary fixing process (heating and pressurizing) is performed to fix the unfixed toner image to the recording paper 5. Finally, after fixing is complete, the recording paper 5 is discharged by paper discharge rolls 59-61 to a paper discharge section (not shown) located on the side of the main body 1a of the device.

[0052] Furthermore, when forming an image on both sides of the recording paper 5, the recording paper 5 with the image formed on one side is not discharged directly to a paper discharge section (not shown) via the discharge transport path 62. Instead, the transport path switching unit 62a switches the transport direction of the recording paper 5 downwards, and it is transported to the reversal transport path 66 of the duplex unit 63. The recording paper 5 transported to the reversal transport path 66 of the duplex unit 63 has its transport direction switched by the reversal transport roll pair 65 and is transported again to the paper feed transport path 57 via the duplex transport path 69. Then, on the back side of the recording paper 5, after the toner image is transferred at the secondary transfer position of the intermediate transfer device 20, it is fixed by the fuser device 40 and discharged by the paper discharge roll pairs 59-61 to a paper discharge section (not shown) installed on the side of the main body 1a.

[0053] Through the above operations, a recording sheet 5 is output, on which a full-color image formed by combining five toner images is created.

[0054] <Configuration of the sheet conveying device> Figures 1 and 3 are configuration diagrams showing an image forming apparatus to which a paper transport device, as an example of a sheet transport device according to Embodiment 1 of the present invention, is applied.

[0055] As shown in Figure 4, the conventional paper transport device 70 is configured to include a plurality of paper transport roll pairs 53, 54 for transporting the recording paper 5, and a guide member G for guiding the recording paper 5.

[0056] In the conventional paper transport device 70 configured as described above, if there are variations or fluctuations in the transport speed of the recording paper 5 between the paper transport rolls 53 and 54, the surface and / or back surface of the recording paper 5 may come into contact with or rub against the guide member G of the paper feed transport path 57.

[0057] To explain further, as the leading edge 5a of the recording paper 5 is being fed from the paper transport roll pair 53 to the paper transport roll pair 54, when transporting curled paper or the like, as shown in Figure 4, the front or back surface of the recording paper 5 may come into contact with and rub against the guide members G of the paper feed transport path 57, or the front or back surface of the recording paper 5 may come into contact with an opposing guide member G after coming into contact with a guide member G of the paper feed transport path 57.

[0058] Furthermore, after the leading edge 5a of the recording paper 5 is fed from the paper transport roll pair 53 to the paper transport roll pair 54 and moves to a position where it is transported by the paper transport roll pair 54, as shown in Figure 5, the back surface of the recording paper 5 may come into contact with the guide member G of the paper feed transport path 57, or the front surface of the recording paper 5 may come into contact with the guide member G of the paper feed transport path 57, due to inconsistencies in the transport speeds between the paper transport roll pair 53 and the paper transport roll pair 54. In addition, after the leading edge 5a of the recording paper 5 has passed the paper transport roll pair 53, the front surface of the recording paper 5 may come into contact with the guide member G of the paper feed transport path 57 again.

[0059] Thus, when the front and / or back surfaces of the recording paper 5 come into contact with the guide member G of the paper feed transport path 57, it is not much of a problem if the recording paper 5 is ordinary paper. However, if the recording paper 5 is a metallic or glossy specialty paper, streaky scratches and other damage are likely to occur on the front and back surfaces of the specialty paper, which degrades the quality of the specialty paper and therefore becomes a problem.

[0060] Therefore, the paper transport device 70 according to this embodiment 1 is configured to include a curved transport path for transporting sheets and a plurality of endless belt pairs arranged along the transport path with their transport surfaces in contact with each other.

[0061] In other words, the paper transport device 70 according to this embodiment 1 is configured such that, as shown in Figure 3, in the paper feed transport path 57, a plurality of paper transport belt pairs 71 to 75 are arranged along a curved transport path that transports the recording paper 5 fed from the paper feed device 50 to the secondary transfer position of the intermediate transfer device 20, as an example of an endless belt pair whose transport surfaces are in contact with each other.

[0062] Each of the multiple paper conveyor belt pairs 71-75 consists of drive-side paper conveyor belts 71a-75a and driven-side paper conveyor belts 71b-75b. Each of the multiple paper conveyor belt pairs 71-75 may be configured to be driven by its own drive source, or each of the drive-side paper conveyor belts 71a-75a may be configured to be driven by one or fewer drive sources than the number of paper conveyor belt pairs via drive gears, drive pulleys, etc. The multiple paper conveyor belt pairs 71-75 are arranged adjacent to each other along a curved conveyor path with a predetermined distance (approximately 3 mm) between them.

[0063] Multiple paper transport belt pairs 71-75 are set so that the transport speed of the recording paper 5 is all equal. In other words, multiple paper transport belt pairs 71-75 are configured to transport the recording paper 5 along a curved transport path at a constant speed.

[0064] In the illustrated embodiment 1, of the multiple paper transport belt pairs 71 to 75, the driving paper transport belts 71a to 75a are located on the outer circumference of the transport path, and the driven paper transport belts 71b to 75b are located on the inner circumference of the transport path.

[0065] The reason why the drive-side paper transport belts 71a to 75a are positioned on the outer circumference of the transport path 57 is that the leading edge of the recording paper 5 being transported from the upstream side comes into contact with the paper transport belts 71a to 75a located on the tangential side along the transport direction, that is, on the outer circumference of the transport path. This ensures that the leading edge of the recording paper 5 comes into contact with the drive-side paper transport belts 71a to 75a and is reliably transported to the next paper transport belt pair 71 to 75.

[0066] As shown in Figure 5, the multiple paper transport belt pairs 71a to 75a are arranged such that the transport direction of the recording paper 5 forms a predetermined angle θ with respect to each other. Since the paper transport belt pairs themselves transport the recording paper 5 in a straight line, the recording paper 5 will be curved or bent when passed between adjacent paper transport belt pairs 71 to 75.

[0067] According to the inventors' studies, as shown in Figures 5(b) and 5(c), when the material (basis weight) of the recording paper 5 is varied, changing the angle between adjacent paper transport belt pairs results in buckling or paper jams occurring in the recording paper 5 when the basis weight of the recording paper 5 exceeds 300 gsm, which is undesirable.

[0068] Therefore, in the paper transport device 70 according to this embodiment 1, the angle θ between adjacent paper transport belt pairs 71 to 75 is set to 60 degrees or less. Setting the angle θ between adjacent paper transport belt pairs 71 to 75 to less than 60 degrees is desirable for the transportability of the recording paper 5, but depending on the transport path, the number of paper transport belt pairs 71 to 75 increases, making the configuration more complex. Note that when changing the transport direction of the recording paper 5 by 180 degrees, the number of paper transport belt pairs should be at least four, and preferably five or more.

[0069] In the paper transport device 70 according to this embodiment 1, the angle θ formed by adjacent paper transport belt pairs 71 to 75 is set to 60 degrees, thereby achieving both efficient transport of the recording paper 5 and a simplified structure.

[0070] Furthermore, in the paper transport device 70 according to this embodiment 1, the distances L1, L2 and L3, L4 between pairs of rolls constituting the paper transport belt pairs 71-75 are adjustable. As shown in Figure 6, the pairs of rolls constituting the paper transport belt pairs 71-75 are rotatably mounted on different support bases 200 and 201. The two support bases 200 and 201 are supported by studs 202, elongated holes 203, and fixing screws 204 so that the pair of rolls can move toward or apart from each other. The two support bases 200 and 201 are also rotatably supported by a rotation axis 205 and an arc-shaped moving groove 206, and the angle between the pair of rolls is adjustable via fixing screws 207. The belt is made of an elastic material.

[0071] <Operation of the paper transport device> In the paper transport device according to this embodiment 1, it is possible to suppress damage to the sheet compared to when the sheet being transported along a curved transport path comes into contact with a fixed guide, as described below.

[0072] In other words, as shown in Figure 1, when the control unit 100 starts the image forming operation, the paper transport device 70 according to this embodiment 1 starts feeding recording paper 5 from the paper feed device 50 and transports the recording paper 5 along the paper feed transport path 57 to the secondary transfer position of the intermediate transfer device 20.

[0073] In this case, as shown in Figure 3, in the paper feed transport path 57, multiple pairs of paper transport belts 71 to 75 are arranged along the curved transport path so as to form a predetermined angle θ with respect to each other.

[0074] As shown in Figure 7(a), the recording paper 5 fed from the paper feeder 50 is transferred by a pair of paper transport rolls to the first of the multiple pairs of paper transport belts 71 to 75, namely the first pair of paper transport belts 71. At this time, the leading edge of the recording paper 5 being transported by the pair of paper transport rolls comes into contact with the drive-side paper transport belt 71a, which is located on the outer circumference of the pair of paper transport belts 71. Therefore, the leading edge of the recording paper 5 is reliably introduced by the drive-side paper transport belt 71a into the nip portion between it and the driven-side paper transport belt 71b.

[0075] Subsequently, the recording paper 5 is held between the driving paper conveyor belt 71a and the driven paper conveyor belt 71b that constitute the first pair of paper conveyor belts 71, and is conveyed linearly in the conveying direction of the first pair of paper conveyor belts 71.

[0076] Next, the recording paper 5 is transported while being held by the first pair of paper transport belts 71, and then its leading edge is passed from the first pair of paper transport belts 71 to the second pair of paper transport belts 72. At this time, since the recording paper 5 is passed from the pair of paper transport belts 71 to the same pair of paper transport belts 72, the recording paper 5 does not come into contact with (rub against) any fixed guide members, etc., and there is no risk of damage to the surface and / or back surface of the recording paper 5.

[0077] Similarly, the recording paper 5 is passed sequentially from the second paper transport belt pair 72 to the third paper transport belt pair 73, as shown in Figure 8.

[0078] Finally, the recording paper 5 is transferred from the fifth paper transport belt pair 75 to the paper transport roll pair 55. The paper transport roll pair 55 can be positioned near the exit of the fifth paper transport belt pair 75, thereby avoiding the risk of the recording paper 5 being damaged by contact (rubbing) with other fixed guide members, etc.

[0079] In the above embodiment 1, we described a case in which multiple paper transport roll pairs 71 to 75 are arranged in the curved section of the paper feed transport path 57. However, the invention is not limited to this, and it is of course possible to apply the same method to a curved transport path from the paper feed device 50 to the paper feed transport path 57, as shown in Figure 1. [Explanation of Symbols]

[0080] 1…Image forming apparatus 1a...Main unit of the device 10…Image creation device 70...Paper transport device 71-75... Paper transport belt pair

Claims

1. A curved transport path for transporting the sheets, A plurality of endless belt pairs arranged along the aforementioned transport path, with their transport surfaces in contact with each other, Equipped with, Each of the aforementioned endless belt pairs consists of an elastic belt stretched between a pair of rolls. The plurality of endless belt pairs are configured as a sheet conveying device consisting of a conveying belt that is arranged on the outer circumference along the curved conveying path and driven, and a conveying belt that is arranged on the inner circumference along the curved conveying path and is driven.

2. The sheet conveying device according to claim 1, wherein the endless belt pair arranged downstream along the sheet conveying direction has a change angle of the sheet conveying direction of 60 degrees or less compared to the endless belt pair arranged adjacent to it upstream.

3. The sheet conveying device according to claim 1, wherein the conveying path comprises a path for conveying the sheet in a semicircular shape.

4. The sheet conveying device according to claim 3, wherein four or more pairs of endless belts are arranged along the conveying path.

5. The sheet conveying device according to claim 1, wherein the endless belt pair comprises a conveying belt disposed on the outer circumference side of the conveying path and a conveying belt disposed on the inner circumference side of the conveying path, wherein the conveying belt disposed on the outer circumference side of the conveying path has a longer circumference than the conveying belt disposed on the inner circumference side of the conveying path.

6. Image forming means for forming an image on a recording medium, A transport means for transporting the recording medium to the image forming means, Equipped with, An image forming apparatus using the sheet conveying device described in any one of claims 1 to 5 as the conveying means.

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