Image forming apparatus

Abstract

Even if the conveying surface of the print belt moves up and down in conjunction with the raising and lowering of the platen member, it is possible to stably convey the sheet to the conveying surface of the print belt. [Solution] The image forming apparatus 1 includes an endless belt 24, a recording head 100, a platen member 25, a first guide member 35 and a second guide member 36, which are provided so as to be movable in a direction intersecting the conveying surface 24a of the belt 24, with at least a portion of the guide member 35 facing the conveying surface 24a, and a first support portion 34 which is provided connected to the first guide member 35 and contacts the conveying surface 24a to support the first guide member 35 with respect to the conveying surface 24a, and a second support portion 36 which is provided between the first guide member 35 and the second guide member 36 and supports the first guide member 35 with respect to the second guide member 36, wherein the first support portion 34 is provided so as to be movable together with the first guide member 34 as the platen member 25 moves.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus such as a printing machine, a copying machine, and a printer that performs image formation using an inkjet method.

Background Art

[0002] In recent years, in the fields of commercial printing and industrial printing where analog printing such as offset printing is mainstream, the need for inkjet printing as digital printing capable of printing small quantities and a variety of designs has been increasing. The inkjet method has many advantages such as not requiring a plate and being able to obtain high-quality products, so it has become extremely popular. An inkjet method image forming apparatus (inkjet recording apparatus) ejects ink droplets onto a recording medium (sheet) such as recording paper or a resin sheet to record an image such as characters or an image. As an inkjet method image forming apparatus, there is a line head type inkjet recording apparatus. This is a device that records a color image on a recording medium by ejecting droplets of different colors from a plurality of recording heads in conjunction with the conveyance of the recording medium while the recording head does not move relative to the main body of the image forming apparatus. Also, as a line head type inkjet recording apparatus, there is a device that conveys the recording medium with respect to the recording head using a print belt composed of an endless belt. The print belt is stretched by a plurality of stretching rollers, and the recording medium is adsorbed and conveyed on a conveyance surface that is a surface formed between the stretching roller on the upstream side and the stretching roller on the downstream side of the plurality of recording heads in the rotation direction.

[0003] In such image forming apparatuses, the distance between the recording medium and the recording head (more specifically, the fine nozzles that eject ink from the recording head) (also referred to here as the "print gap") is important for obtaining high-quality results. Therefore, a method is known for transporting the cut recording medium along a plane with high flatness (printing plane). One such method involves transporting the recording medium while suctioning it to the transport surface of a print belt (Patent Document 1). In other words, the print belt is provided with fine holes, and the print belt is slidably supported by a platen member configured to have an opening. Then, by suctioning air from the inner circumferential surface of the print belt, the print belt is attracted to the platen member, and the recording medium is attracted to the print belt while the recording medium is transported by the print belt. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2016-140997 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] In inkjet printers, variations in print gap can lead to differences in image quality. For example, if the print gap disappears due to the thickness of the recording medium, meaning the recording medium and the printing head come into contact, it can lead not only to a decrease in the quality of the output but also to damage to the printing head.

[0006] Therefore, it is desirable to prevent the print gap from changing beyond a certain tolerance. One possible method to achieve this is to raise and lower the platen member so that the print gap remains approximately constant according to the thickness of the recording medium.

[0007] However, if the platen member is configured to be raised and lowered, and a guide member for guiding the recording medium is fixed to the transport surface of the print belt, there is a risk that the transport of the recording medium may become unstable, for example, if the distance between the print belt and the guide member becomes narrow.

[0008] Therefore, the objective of the present invention is to enable stable conveyance of sheets to the conveying surface of the print belt even when the conveying surface of the print belt moves up and down in conjunction with the raising and lowering of the platen member. [Means for solving the problem]

[0009] The above objective is achieved by the image forming apparatus according to the present invention. In summary, the present invention comprises a rotatable endless belt for carrying and transporting a sheet, a recording head for discharging a recording liquid onto the sheet transported by the belt, a platen member disposed on the inner circumferential surface side of the belt and slidably supporting the belt to form a transport surface on the belt for transporting the sheet, the platen member being movable in the thickness direction of the belt while supporting the belt, and a first guide member for guiding the sheet being transported toward the transport surface, the first guide member being disposed on the same side as the recording head with respect to the sheet being transported toward the transport surface, with at least a portion facing the transport surface and being movable in a direction intersecting the transport surface. The image forming apparatus comprises a first guide member, a second guide member for guiding a sheet being transported toward the transport surface, the second guide member being positioned on the opposite side of the recording head to the sheet being transported toward the transport surface, a first support portion connected to the first guide member and in contact with the transport surface to support the first guide member toward the transport surface, and a second support portion provided between the first guide member and the second guide member and supporting the first guide member toward the second guide member, wherein the first support portion is provided so as to move together with the first guide member as the platen member moves. [Effects of the Invention]

[0010] According to the present invention, even if the conveying surface of the print belt moves up and down in conjunction with the raising and lowering of the platen member, it is possible to stably convey the sheet to the conveying surface of the print belt. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic cross-sectional view of an image forming apparatus. [Figure 2] This is a schematic cross-sectional view of a printed circuit board. [Figure 3] This is a perspective view of the printed belt unit. [Figure 4] This is a perspective view of the suction box. [Figure 5] This is a perspective view of the print gap adjustment mechanism. [Figure 6] This is a perspective view showing the guide member and the belt-guide gap adjustment mechanism. [Figure 7] This is a schematic cross-sectional view showing the guide member and the belt-guide gap adjustment mechanism. [Figure 8] This is a schematic diagram of the guide member as viewed along the sheet transport direction. [Figure 9] This is a schematic diagram illustrating other movements of the guide member. [Modes for carrying out the invention]

[0012] The image forming apparatus according to the present invention will be described in more detail below with reference to the drawings.

[0013] [Example 1] <Image forming apparatus> First, the overall configuration of the image forming apparatus of this embodiment will be described. The image forming apparatus of this embodiment is a line-head type inkjet recording apparatus that utilizes an inkjet method. Figure 1 is a schematic cross-sectional view showing the overall configuration of the inkjet recording apparatus 1 of this embodiment. This inkjet recording apparatus 1 is a sheet-fed inkjet recording apparatus that uses two liquids, a reaction solution and ink, as recording liquids to form an ink image on a sheet S such as cut plain paper, which is a recording medium (recording material, paper), and outputs a recorded material.

[0014] In the following explanation, the inkjet recording device 1 is assumed to be installed on a horizontal plane. With respect to the inkjet recording device 1 and its elements, the front side of the paper in Figure 1 is referred to as the "front" side, the back side of the paper in Figure 1 as the "back" side, the right side in Figure 1 as the "right" side, the left side in Figure 1 as the "left" side, the top side in Figure 1 as the "top" side, and the bottom side in Figure 1 as the "bottom" side. The front-to-back direction is perpendicular to the left-to-right and up-to-down directions. When the inkjet recording device 1 is installed on a horizontal plane, the up-to-down direction is parallel to the direction of gravity (vertical direction). However, with respect to the inkjet recording device 1 and its elements, up and down does not only mean directly above and directly below, but also includes the upper and lower sides with respect to the horizontal plane through which the element or position of interest passes.

[0015] Furthermore, in the following explanation, sheet S may sometimes be referred to as paper, but sheet S includes materials other than paper, or materials that include materials other than paper (such as synthetic paper or film made using synthetic resin, or metallized paper with a metal layer). Also, for convenience, recording liquids such as reaction solutions or inks may sometimes be simply referred to as "ink," but any liquid such as reaction solutions or inks used for image recording may be used.

[0016] The inkjet recording apparatus 1 has each module (sheet processing unit) of a paper feeding module 1000, a printing module 2000, a drying module 3000, a fixing module 4000, a cooling module 5000, a reversing module 6000, and a paper discharging and stacking module 7000. The cut paper sheet S supplied from the paper feeding module 1000 is conveyed along the conveyance path, processed by each module, and guided to the paper discharging and stacking module 7000.

[0017] The paper feeding module 1000 has three storage bins 1100a, 1100b, and 1100c that accommodate the sheet S, a housing 1200 that houses these inside, and the like. Each of the storage bins 1100a, 1100b, and 1100c is configured to be pullable forward with respect to the housing 1200. The sheet S is fed one by one from each of the storage bins 1100a, 1100b, and 1100c by a separation belt and a conveyance roller, and conveyed to the printing module 2000. Note that the number of the storage bins 1100a, 1100b, and 1100c is not limited to three, and may be one, two, or four or more.

[0018] The print module 2000 includes a register correction unit (pre-image register correction unit) 2400, a print belt unit 2200 as a belt transport device, a recording unit (image forming unit) 2300, and a housing 2500 that houses these internally. The sheet S, transported from the paper feed module 1000 to the print module 2000, has its tilt and position corrected by the register correction unit 2400 and is then transported to the print belt unit 2200. The recording unit 2300 is positioned opposite the print belt unit 2200 across the transport path of the sheet S. The recording unit 2300 performs recording processing (image formation, printing, inscription, print) from above on the sheet S transported by the print belt unit 2200 using a recording head 100 to form an image on the sheet S. The sheet S is transported by the print belt 24 of the print belt unit 2200, ensuring clearance with the recording head 100. The sheet S is transported by the print belt unit 2200 from right to left. The recording unit 2300 has a plurality of recording heads (line-type recording heads) 100 arranged along the transport direction of the sheet S. In this embodiment, the recording unit 2300 has a total of five recording heads 100 (100a to 100e) corresponding to the four colors Y (yellow), M (magenta), C (cyan), and Bk (black), as well as the reaction solution (Figure 2). Note that the number of colors and the number of recording heads 100 are not limited to five. As for the inkjet method of the recording head 100, a method using a heating element, a method using a piezoelectric element, a method using an electrostatic element, a method using a MEMS element, etc., can be adopted. The ink of each color is supplied to the corresponding recording head 100 via an ink tube from an ink tank provided in, for example, the print module 2000. The sheet S, which has been recorded by the recording unit 2300, is transported by the print belt unit 2200 and passes through an inline scanner (not shown) located downstream of the recording unit 2300 in the transport direction of the sheet S. The inkjet recording device 1 can correct the printed image based on the misalignment and color density of the image formed on the sheet S detected by the inline scanner.

[0019] The drying module 3000 includes a decoupling unit 3200, a drying belt unit 3300, a warm air blowing unit 3400, a housing 3500 for accommodating these components, etc. The drying module 3000 reduces the liquid content in the ink applied on the sheet S by the recording unit 2300, and enhances the fixing property between the sheet S and the ink. The sheet S after the recording process by the recording unit 2300 of the printing module 2000 is conveyed to the decoupling unit 3200 disposed within the drying module 3000. The decoupling unit 3200 can convey the sheet S by the frictional force between the wind pressure from above and the belt 3201 of the decoupling unit 3200. In the decoupling unit 3200, by weakly holding and conveying the sheet S on the belt 3201, it is possible to prevent the displacement of the sheet S on which the ink image is formed on the printing belt 24 of the print belt unit 2200. The sheet S conveyed from the decoupling unit 3200 to the drying belt unit 3300 is adsorbed and conveyed by the belt 3301 of the drying belt unit 3300. At the same time, hot air is applied from the warm air blowing unit 3400 disposed above the belt 3301 of the drying belt unit 3300, and the surface of the sheet S to which the ink is applied is dried. In addition to the method of applying hot air, as the drying method, a method of irradiating the surface of the sheet S with electromagnetic waves (such as ultraviolet rays and infrared rays) or a method of conduction heat transfer by contact with a heating element can be used. These methods may be used in any combination.

[0020] The fixing module 4000 includes a fixing belt unit 4100, a housing 4300 for accommodating it, etc. The fixing module 4000 can fix the ink to the sheet S by passing the sheet S conveyed from the drying module 3000 through between the heated upper belt unit 4101 and the lower belt unit 4102.

[0021] The cooling module 5000 includes a plurality of cooling units 5100 and a housing 5200 that houses them. The cooling module 5000 cools the high-temperature sheet S that has been transported from the fuser module 4000 to the cooling module 5000. The cooling units 5100 are configured to cool the sheet S by drawing in outside air into the cooling box with a fan, increasing the pressure inside the cooling box, and blowing air from nozzles formed in the transport guide onto the sheet S. The cooling units 5100 are arranged on both sides of the transport path of the sheet S, so that the sheet S can be cooled from both sides. In addition, the cooling module 5000 is provided with a switching unit that switches the transport path of the sheet S. This switching unit can switch the transport path of the sheet S depending on whether the sheet S is being transported to the inversion module 6000 or to the double-sided transport path used during double-sided printing. During double-sided printing, the sheet S is transported to a double-sided transport path located below the cooling module 5000, and further transported along the double-sided transport paths provided in the fuser module 4000, drying module 3000, print module 2000, and paper feed module 1000. As a result, the sheet S is transported again to the register correction unit 2400, print belt unit 2200, and recording unit 2300 of the print module 2000, where recording processing is performed by the recording unit 2300. The double-sided transport path of the fuser module 4000 is provided with a first reversal unit 4200 that reverses the front and back sides of the sheet S, so that the front and back sides of the sheet S can be reversed during double-sided printing before being transported back to the recording unit 2300.

[0022] The reversal module 6000 includes a second reversal unit 6400 and a housing 6500 that accommodates it. The reversal module 6000 can reverse the front and back sides of the sheet S transported from the cooling module 5000 to the reversal module 6000, and can freely change the orientation of the front and back sides and the leading and trailing ends in the transport direction of the sheet S discharged from the reversal module 6000.

[0023] The paper output and stacking module 7000 includes a top tray 7200, a stacking section 7500, and a housing 7600 on which these are provided. The paper output and stacking module 7000 can align the sheets S transported from the reversing module 6000 to the paper output and stacking module 7000, discharge them onto the top tray 7200 for stacking, or stack them on the stacking section 7500 for storage.

[0024] <Printed Belt Unit> Next, the print belt unit 2200 in this embodiment will be described. Figure 2 is a schematic cross-sectional view of the print module 2000 equipped with the print belt unit 2200 in this embodiment.

[0025] The printed belt unit 2200 includes a plurality of tension rollers 20-23, a printed belt 24, a suction box (vacuum box, platen unit) 26, and a negative pressure generating unit (suction device) 27.

[0026] The rotatable print belt (conveyor belt) 24, which is composed of an endless belt, is stretched over four tension rollers, the first, second, third, and fourth tension rollers 20, 21, 22, and 23, and is taut with a predetermined tension. The print belt 24 is made of, for example, a resin material such as PET (polyethylene terephthalate). The print belt 24 is also sized in the width direction (a direction approximately perpendicular to the direction of surface movement) so that, for example, a B3 size (364 mm x 515 mm) sheet S can be transported horizontally (transported in a direction where the short side is along the transport direction). Note that the resin material that makes up the print belt 24 is not limited to PET, and other resin materials such as polyimide or polycarbonate, or metal materials may be used.

[0027] The sheet S is carried and conveyed on the conveying surface 24a, which is the outer circumferential surface of the printed belt 24 stretched between the first tensioning roller 20 and the second tensioning roller 21, among the surfaces of the printed belt 24 formed by the first to fourth tensioning rollers 20 to 23. The first tensioning roller 20 and the second tensioning roller 21 function as conveying surface forming rollers that form the conveying surface 24a of the printed belt 24. The second tensioning roller 20 also functions as a drive roller that rotates (circumferentially moves) the printed belt 24 in the direction of arrow R1 (counterclockwise direction) in the figure. The third tensioning roller 22 is biased from the inner circumferential surface side to the outer circumferential surface side of the printed belt 24 by a biasing mechanism (not shown) as a biasing means, and functions as a tension roller that applies force to the printed belt 24 to stretch it. Furthermore, the fourth tension roller 23 has one end movable in the direction of its rotation axis and functions as a steering roller that can tilt so that its rotation axis is inclined with respect to the rotation axes of the other tension rollers. The second tension roller 21 is rotationally driven by a driving force transmitted from a motor, which is a drive source of a belt drive unit (not shown) that serves as a driving means provided in the printed belt unit 2200. The first, third, and fourth tension rollers 20, 22, and 23 rotate in association with the rotation of the printed belt 24. The multiple tension rollers 20 to 23 are rotatably supported at both ends in the direction of their respective rotation axes by support side plates (not shown) that constitute the printed belt unit 2200. These support side plates are attached to a belt unit frame (not shown), which is a support structure that constitutes the printed belt unit 2200. Note that the number of tension rollers on the printed belt 24 is not limited to four, and may be two, three, or four or more.

[0028] The print belt unit 2200 transports the sheet S in the direction of arrow A in the figure by the rotation of a print belt 24 stretched by a plurality of tension rollers 20 to 23. The print belt 24 has a plurality of suction holes (through holes) 24b, for example, with a diameter of about 0.3 mm, all around it in order to attract and transport the sheet S. A suction box 26 is provided on the side of the print belt 24 opposite to the recording unit 2300, in a direction perpendicular to the transport direction A of the sheet S. The suction box 26 is composed of a platen member 25 that forms the transport surface 24a of the print belt 24, and a suction box frame 26a that holds the platen member 25 and forms the suction box 26. In this embodiment, the suction box 26 has a predetermined length in the longitudinal direction along the left-right direction and the width direction along the front-back direction, and a predetermined height in the vertical direction, and is formed in a box shape overall. The suction box 26 (more specifically, the platen member 25) is positioned to be in contact with the print belt 24 over a range that includes at least the entire area from the position facing the upstream recording head 100a (more specifically, its nozzle) to the position facing the downstream recording head 100e (more specifically, its nozzle) in the direction of movement (left-right direction, travel direction) of the transport surface 24a of the print belt 24. In this embodiment, the suction box 26 is also positioned to be in contact with the print belt 24 over a range that includes at least substantially the entire area in the width direction (front-back direction) of the print belt 24 that can carry the sheet S. The platen member 25 is provided to form the upper side surface of the suction box 26 and forms a sliding surface that slidably supports the print belt 24. The platen member 25 is provided with a plurality of intake openings (through holes) 25a. In addition, an exhaust opening (through hole) 26b (Figure 4) is provided on the lower side surface (bottom surface) of the suction box frame 26a. A negative pressure generating unit 27, which serves as a negative pressure generating means (suction means) for generating negative pressure inside the suction box 26, is connected to this exhaust opening 26b.

[0029] Figure 3 is a perspective view of the printed belt unit 2200 in this embodiment, showing the suction box 26 and the negative pressure generating unit 27. The negative pressure generating unit 27 is equipped with a fan F. The negative pressure generating unit 27 generates negative pressure inside the suction box 26 by discharging the air inside the suction box 26. Due to the negative pressure generated by the negative pressure generating unit 27, the pressure inside the suction box 26 becomes approximately constant. As a result, the printed belt 24 on the platen member 25 is sucked in at the multiple intake openings 25a of the platen member 25 and is adsorbed onto the platen member 25. In addition, the negative pressure inside the suction box 26 generates a suction force at the multiple suction holes 24b provided in the printed belt 24, causing the sheet S to be adsorbed onto the printed belt 24. Note that the source of the suction force of the negative pressure generating unit 27 is not limited to a fan, but may be, for example, a vacuum pump.

[0030] In this manner, the print belt 24 carries and transports the sheet S on a transport surface 24a facing the recording head 100, directly below the recording head 100. A suction box 26, which serves as a belt support, is provided on the inner circumferential surface side of the print belt 24, supporting the print belt 24 in a slidable manner while being sucked in. The suction box 26 slidably supports the inner circumferential surface of the print belt 24 between the first tension roller 20 and the second tension roller 21 in the rotational direction (traveling direction) of the print belt 24, that is, the inner circumferential surface of the print belt 24 corresponding to the transport surface 24a.

[0031] Furthermore, the print belt unit 2200 is provided with an upper guide 35 and a lower guide 36 as guide members for guiding the sheet S onto the conveying surface 24a of the print belt 24 (Figure 2). The print belt unit 2200 is also provided with a print gap adjustment mechanism 50 for adjusting the print gap (Figures 4 and 5). In addition, the print belt unit 2200 is provided with a belt-guide gap adjustment mechanism 60 for adjusting the distance between the conveying surface 24a of the print belt 24 and the upper guide 35 (also referred to here as the "belt-guide gap") (Figure 7). These guide members (upper guide 35, lower guide 36), the print gap adjustment mechanism 50, and the belt-guide gap adjustment mechanism 60 will be described later.

[0032] <Print gap adjustment mechanism> In inkjet printers, variations in the print gap, which is the clearance between the printing head and the printing sheet, can result in differences in image quality. For example, if the print gap disappears due to factors such as the thickness of the sheet, meaning the sheet and the printing head come into contact, it can lead not only to a decrease in the quality of the output but also to damage to the printing head.

[0033] Therefore, it is desirable to prevent the print gap from changing beyond a certain tolerance. As a means of achieving this, it is effective to raise and lower the platen member to maintain the print gap at a substantially constant distance according to the thickness of the sheet. For example, by rotating a cam to a predetermined phase (position in the rotational direction) by an amount corresponding to the thickness of the sheet using a drive mechanism, the platen member can be raised and lowered by the cam to adjust the print gap.

[0034] In the inkjet recording device 1 of this embodiment, the position of the recording unit 2300, on which the recording head 100 is located, is fixed by a belt unit frame (not shown), which is a non-moving component other than the suction box 26, and the position of the suction box 26 is variable. Furthermore, in the inkjet recording device 1 of this embodiment, when the sheet S on which the image is formed is changed to a sheet S of a different thickness, the print gap is adjusted by moving the suction box 26 and thereby moving the platen member 25. In addition, as will be described in more detail later, in this embodiment, the inkjet recording device 1 has a print gap adjustment mechanism that adjusts the print gap by changing the height of the suction box 26 by rotating a cam.

[0035] Figure 4 is a perspective view of a part of the configuration of the print belt unit 2200 in this embodiment, showing the suction box 26 and the cam 29 that constitutes the print gap adjustment mechanism 50. Figure 5 is a schematic perspective view of the print gap adjustment mechanism 50 in this embodiment.

[0036] As shown in Figure 4, the suction box 26 is in contact with the cam 29 at pressurizing sections 28 located approximately at the four corners. As shown in Figure 5, driving force is transmitted from the stepping motor M, which is the drive source, to the shaft 31 to which the cam 29, which is the working part, is attached, via the drive belt 30, which is the drive transmission member, causing the cam 29 to rotate. If the rotation direction of the stepping motor M changes, the rotation angle and the height of the highest point of the cam 29 may not be uniquely determined due to circumferential play caused by the dimensional tolerances of each component. Therefore, in this embodiment, the stepping motor M is controlled so that the cam 29 rotates in only one direction, as indicated by arrow B in the figure.

[0037] The cam 29 receives a force from the pressurizing section 28 toward the cam 29 due to the weight of the suction box 26 and the tension of the stretched print belt 24. As a result, a force is applied to the cam 29 in the opposite direction to the rotation direction B. Therefore, in this embodiment, the one-way clutch 32 is positioned on the shaft 31 and its rotation in the opposite direction to the rotation direction B is restricted by the frame (not shown) of the print belt unit 2200. This prevents the cam 29 from rotating in the opposite direction to the rotation direction B due to a force in the opposite direction to the rotation direction B during printing, thereby preventing a change in the height of the suction box 26. Furthermore, in this embodiment, since the one-way clutch 32 prevents fluctuations in the height of the suction box 26 due to the cam 29 rotating in the opposite direction to the rotation direction B, power is not supplied to the stepping motor M except when adjusting the print gap. A sensor flag 33 is provided on the shaft 31, making it possible to detect the reference rotation angle of the cam 29 using a phase detection sensor 51. The phase detection sensor 51 is composed of an optical sensor.

[0038] In this embodiment, the print gap adjustment mechanism 50 consists of a cam 29, a stepping motor M, a drive belt 30, a shaft 31, a one-way clutch 32, a sensor flag 33, a phase detection sensor 51, and the like.

[0039] In this embodiment, when assembling the print belt unit 2200, the rotation angle of the cam 29 is determined when the uppermost point of the cam 29 (or the suction box 26 or transport surface 24a) reaches the desired height, once the print gap adjustment mechanism 50 is installed. Information showing the relationship between this height and the rotation angle is then stored in the ROM 72, a memory device provided in the print belt unit 2200. At this time, the rotation angle stored in the ROM 72 corresponds to the number of rotation steps of the stepping motor M from a reference detected by the sensor flag 33. Furthermore, multiple rotation angles can be stored in the ROM 72 depending on the type of desired height. By storing the above information in the ROM 72 during the assembly of the print belt unit 2200, variations in height due to part tolerances can be suppressed. Therefore, even when using multiple adjustment mechanisms 50 (four in this embodiment), precise print gap adjustment with suppressed variations becomes possible.

[0040] <Challenges> As described above, when the platen member 25 is configured to be raised and lowered, if a guide member for guiding the sheet S is fixed to the conveying surface 24a of the print belt 24, the distance between the print belt 24 and the guide member increases or decreases in accordance with the raising and lowering of the platen member 25. The conveying resistance force on the sheet S received from the guide member increases as the distance between the guide member and the print belt 24 decreases. Therefore, for example, if the distance between the print belt 24 and the guide member decreases due to the raising and lowering of the platen member 25, there is a risk that the conveying of the sheet S may become unstable.

[0041] Therefore, in this embodiment, even when the platen member 25 moves up and down, the distance between the print belt 24 and the guide member can be kept at a desired distance and approximately constant, thereby enabling stable transport of the sheet S onto the transport surface 24a of the print belt 24.

[0042] <Belt-guide gap adjustment mechanism> Next, the guide members (upper guide 35, lower guide 36) and the belt-guide gap adjustment mechanism 60 in this embodiment will be described. Figure 6 is a perspective view showing the guide members (upper guide 35, lower guide 36) and the belt-guide gap adjustment mechanism 60 in this embodiment. Figure 7 is a schematic cross-sectional view of a part of the configuration of the printed belt unit 2200, showing the guide members (upper guide 35, lower guide 36) and the belt-guide gap adjustment mechanism 60 in this embodiment. Figure 8 is a schematic view of the guide members (upper guide 35, lower guide 36) in this embodiment as seen along the conveying direction of the sheet S (only one end side in the width direction of the printed belt 24 is shown).

[0043] As shown in Figures 6 and 7, the print belt unit 2200 is provided with an upper guide (first guide member) 35 and a lower guide (second guide member) 36, which serve as guide members for guiding the sheet S onto the transport surface 24a of the print belt 24.

[0044] The upper guide 35 has a flat upper guide portion 35a that has a predetermined width in the left-right direction (the direction in which the sheet S is transported) and extends in the front-rear direction (the width direction of the print belt 24), and holding portions 35b, 35b that extend upward from the upper guide portion 35a at both ends in the front-rear direction. The upper guide portion 35a is positioned on the side (upper side) of the sheet S where recording processing by the recording unit 2300 takes place immediately after passing the guide members (upper guide 35, lower guide 36). In this embodiment, the upper guide portion 35a and the holding portions 35b, 35b are integrally formed from a metal plate-like member (sheet metal). At least a portion of the left end of the upper guide portion 35a in the left-right direction (downstream side in the direction in which the sheet S is transported) faces the transport surface 24a of the print belt 24 formed by the suction box 26 (they overlap in the left-right direction). At least a portion of the right end of the upper guide portion 35a in the left-right direction (upstream side in the direction of conveying the sheet S) faces the lower guide portion 36a of the lower guide 36, which will be described later (they overlap in the left-right direction).

[0045] The upper guide member 35 is provided with support mounting portions 35c, 35c on its holding portions 35b, 35b. A first support portion 34, extending in the front-rear direction, is attached to the support mounting portions 35c, 35c of the upper guide member 35. The first support portion 34 is composed of a plurality of rotating members (rotating bodies) called rollers 34a that act as contact portions, and a support shaft (rotating shaft) 34b that rotatably supports the rollers 34a. Both ends of the support shaft 34b in the front-rear direction are attached to the support mounting portions 35c, 35c of the upper guide 35, respectively. In addition, second support portions 37, 37 are attached near the right end of the upper guide portion 35b in the left-right direction and near both ends in the front-rear direction, respectively. In this embodiment, the second support portions 37, 37 are composed of pins (approximately cylindrical members in this embodiment) that extend toward the lower guide portion 36a of the lower guide 36, which will be described later, along a direction that intersects (approximately perpendicular in this embodiment) with the surface of the upper guide portion 35a.

[0046] The roller 34a of the first support part 34 contacts the print belt 24 located at the top of the suction box 26, that is, the conveying surface 24a of the print belt 24. The first support part 34 pushes down the print belt 24 at the roller 34a due to the weight of the upper guide 35 and the first support part 34. The first support part 34 is integrated with the upper guide 35 by the fact that both ends of the support shaft 34b in the axial direction are attached to the holding parts 35b, 35b of the upper guide 35, respectively. The roller 34a of the first support part 34 rotates in conjunction with the rotation of the print belt 34 while in contact with the print belt 34. The sheet S passes between the roller 34a and the conveying surface 24a of the print belt 24. The roller 34a has the function of pressing the sheet S against the conveying surface 24a of the print belt 24 and suppressing the sheet S from lifting off the conveying surface 24a of the print belt 24. In this embodiment, the upper guide portion 35a of the upper guide 35 is positioned substantially parallel to the conveying surface 24a of the print belt 24. The second support portion 37 abuts against the upper surface (the surface facing the upper guide portion 35a) of the lower guide 36, which will be described later. In this way, the upper guide 35 is supported by the first support portion 34 against the conveying surface 24a of the print belt 24. The upper guide 35 is also supported by the second support portion 37 against the lower guide 36. As a result, the upper guide 35 is installed in the print belt unit 2200 with its upper guide portion 35a spaced a predetermined distance from the conveying surface 24a of the print belt 24 and the lower guide portion 36a of the lower guide 36.

[0047] The lower guide 36 has a flat plate-shaped lower guide portion 36a that has a predetermined width in the left-right direction (the direction in which the sheet S is transported) and extends in the front-rear direction (the width direction of the print belt 24). The lower guide portion 36a is positioned on the side (lower side) of the sheet S opposite to the side where recording processing by the recording unit 2300 takes place immediately after passing the guide members (upper guide 35, lower guide 36). In this embodiment, the lower guide 36 is formed from a metal plate-shaped member (sheet metal). In this embodiment, at least a portion of the left end side of the lower guide portion 36a in the left-right direction (downstream side in the direction in which the sheet S is transported) faces the print belt 24 in the area wrapped around the first tension roller 20 (overlapping in the left-right direction).

[0048] The lower guide 36 is fixed to a stationary block (not shown) at the position where the sheet S is received from the upstream unit of the print belt unit 2200 in the conveying direction of the sheet S. This block is, for example, attached to the belt unit frame (not shown), which is a support structure constituting the print belt unit 2200. The lower guide 36 supports (supports from below) the second support portion 37 attached to the upper guide 35 at its lower guide portion 36a. This makes it possible to keep the distance K between the upper guide portion 35a of the upper guide 35 and the lower guide portion 36a of the lower guide 36 (also referred to here as the "upper and lower guide gap") approximately constant.

[0049] As shown in Figure 8, in this embodiment, in the width direction (front-to-back direction) of the print belt 24, the width W1 of the upper guide portion 35a is wider than the width W3 of the area on which the print belt 24 can support the sheet S (the range of width W3 is contained within the range of width W1). Also in this embodiment, in the width direction of the print belt 24, the width W2 of the lower guide portion 36a is wider than the width W5 of the print belt 24 (the range of width W5 is contained within the range of width W2). Also in this embodiment, in the width direction of the print belt 24, the width (distance) W4 between both second support portions 37, 37 is wider than the width W3 of the area on which the print belt 24 can support the sheet S (the range of width W3 is contained within the range of width W4). Furthermore, the rollers 34a of the first support portion 34 are provided in multiples at approximately equal intervals within the width W1 of the upper guide portion 35a (the distance between both holding portions 35b, 35b), and in particular within the width W3 of the region on which the print belt 24 can support the sheet S.

[0050] In this embodiment, the ends of the upper guide 35 and the lower guide 36 on the upstream side in the conveying direction of the sheet S are provided with inclined sections 35d and 36b, respectively, which are angled to move further apart from each other as they move upstream, in order to create a wide area for receiving the sheet S.

[0051] Both holding portions 35b, 35b of the upper guide 35 are provided with elongated guide holes 35e, 35e that extend vertically (approximately parallel in this embodiment). Guide shafts (approximately cylindrical members in this embodiment) 38, 38 that extend vertically (approximately parallel in this embodiment) are inserted from the outside (opposite the side where the upper guide portion 35a is provided in the front-to-back direction) into the approximate center of these guide holes 35e, 35e in the vertical direction. The guide shafts 38, 38 are fixed to immovable shaft support portions 61, 61. These shaft support portions 61, 61 are attached, for example, to a belt unit frame (not shown), which is a support structure that constitutes the print belt unit 2200. The width of the guide holes 35e and the width of the guide shafts 38 are approximately the same in the left-to-right direction. Thus, the position of the upper guide 35 in the conveying direction of the sheet S is determined by the guide shafts 38 and the guide holes 35e.

[0052] The upper guide 35 is movable so as to rotate around the second support portion 37 (more specifically, the contact portion between the second support portion 37 and the lower guide portion 36a) as the pivot point, in conjunction with the vertical movement of the first support portion 34, within the range in which the guide shaft 38 can move vertically within the guide hole 35e. In other words, the first support portion 34, which is in contact with the transport surface 24a, moves up and down in accordance with the vertical movement of the transport surface 24a of the print belt 24 caused by the raising and lowering of the suction box 26 (movement of the print belt 24 in the thickness direction on the transport surface 24a). At that time, the upper guide 35 moves so as to rotate (oscillate) in the direction of arrow C in Figure 7, with the second support portion 37 as the pivot point. In this embodiment, as the guide shaft 38 moves almost back and forth vertically along the guide hole 35e, the upper guide portion 35a moves almost back and forth vertically (in a direction approximately perpendicular to the transport surface 24a). This makes it possible to keep the belt-guide gap G, which is the distance between the upper guide portion 35a of the upper guide 35 and the conveying surface 24a of the printed belt 24, approximately constant as the suction box 26 moves up and down.

[0053] The guide hole 35e is provided with a space T sufficient to allow the suction box 26 to move up and down. In this embodiment, the space T is provided with a value of ±1.5 mm relative to the vertical movement distance of the suction box 26 (more specifically, the platen member 25), which is ±1 mm. Therefore, the print belt 24 located above the suction box 26 moves in conjunction with the vertical movement of the suction box 26 while maintaining a predetermined distance between it and the upper guide portion 35a (approximately parallel to the transport surface 24a of the print belt 24), which is integrated with the first support portion 34.

[0054] In this embodiment, the belt-guide gap adjustment mechanism 60 is composed of a guide shaft 38, a guide hole 35e, a first support part 34, a second support part 37, a lower guide part 36a, and the like.

[0055] <Printing operation> Next, we will describe examples of the operation of the print gap adjustment mechanism 50 and the belt-guide gap adjustment mechanism 60 during printing.

[0056] The inkjet recording device 1 (e.g., print module 2000) is equipped with a storage device 73 (Figure 5), such as ROM or non-volatile memory, which stores information about the thickness of the sheets S used in the print job. The storage device 73 stores, for example, thickness information for each of several types of sheets S. A control unit 71 (Figure 5), such as a CPU, provided in the inkjet recording device 1 (e.g., print module 2000), can obtain information about the thickness of the sheets S used in the print job from the storage device 73, based on information such as the type of sheet S used in the print job that the user has fed into the inkjet recording device 1.

[0057] The control unit 71 starts the print job if the height of the suction box 26 is set to obtain an appropriate print gap. On the other hand, if the height of the suction box 26 is not set to obtain an appropriate print gap, the control unit 71 rotates the stepping motor M (Figure 5) of the print gap adjustment mechanism 50 by a number of steps pre-stored in the ROM 71 (Figure 5) to the desired height. As described above, after the stepping motor M has been rotated, the cam 29 stops rotating due to the one-way clutch 32 (Figure 5), so the excitation of the stepping motor M can be cut off. When the height of the suction box 26 changes, the tension on the print belt 24 changes, which may cause changes in the rotation speed and orientation of the print belt 24. In that case, the control unit 71 rotates the print belt 24 for the amount of time required for the print belt 24 to settle before starting the print job.

[0058] In this embodiment, the height of the suction box 26 is changed according to the thickness of the sheet S, and even if the height of the conveying surface 24a of the print belt 24 changes accordingly, the belt-guide gap adjustment mechanism 60 keeps the belt-guide gap G approximately constant. This reduces the possibility of unstable conveyance of the sheet S between the print belt 24 and the upper guide 35. Furthermore, in the conveyance direction of the sheet S, only the end of the upper guide 35 on the side of the first support portion 34, which is in contact with the print belt 24 at the top of the suction box 26, moves up and down, while the end on the side of the second support portion 37 does not move up and down. Therefore, even if the position of the lower guide 36 is fixed, the gap K between the upper and lower guides does not change, thus reducing the possibility of unstable conveyance of the sheet S between the upper guide 35 and the lower guide 36.

[0059] <Opening operation> In this embodiment, a guide hole 35e and a guide shaft 38 are provided to guide the vertical movement of the upper guide 35, which is linked to the vertical movement of the suction box 26, with the second support portion 37 as the pivot point.

[0060] As shown in Figure 9, the upper guide 35, configured in this way, can also be rotated in the direction of arrow D in the figure, with the second support portion 37 rotating around the engagement portion between the guide hole 35e and the guide shaft 38 as the pivot point. When the upper guide 35 is rotated in the direction of arrow D in the figure, the roller 34a of the first support portion 34 moves away from the print belt 24 after traveling along the print belt 24. By rotating the upper guide 35 in this way, the upper guide 35 can be separated from the print belt 24 and the lower guide 36 more than in the state during printing operation shown in Figure 7. This makes it easier to perform maintenance and other operations on the area hidden under the upper guide 35 in the state during printing operation shown in Figure 7. Examples of such maintenance include jamming when a jam occurs in the sheet S.

[0061] Thus, in this embodiment, the image forming apparatus (inkjet recording apparatus) 1 includes a rotatable endless belt (print belt) 24 for carrying and transporting a sheet S, a recording head 100 for discharging recording liquid onto the sheet S transported by the belt 24, a platen member 25 positioned on the inner circumferential surface side of the belt 24, which slidably supports the belt 24 and forms a transport surface 24a on the belt 24 for transporting the sheet S, the platen member 25 being movable in the thickness direction of the belt 24 while supporting the belt 24, and a first guide member 35 for guiding the sheet S being transported toward the transport surface 24a, which is positioned on the same side as the recording head 100 with respect to the sheet S being transported toward the transport surface 24a, and at least a portion of it facing the transport surface 24a, and the transport surface The platen member 25 has a first guide member (upper guide) 35 that is movable in a direction intersecting 24a, a second guide member 36 that guides the sheet S being transported toward the transport surface 24a, and a second guide member (lower guide) 36 that is positioned on the opposite side of the sheet S being transported toward the transport surface 24a from the recording head 100, a first support portion 34 that is connected to the first guide member 35 and is in contact with the transport surface 24a to support the first guide member 35 toward the transport surface 24a, and a second support portion 37 that is provided between the first guide member 35 and the second guide member 36 and is in contact with the second guide member 36 to support the first guide member 35 toward the second guide member 36, wherein the first support portion 34 is provided so as to move together with the first guide member 35 as the platen member 25 moves.In this embodiment, the first support portion 34 has a rotatable rotating member (roller) 34a that is in contact with the transport surface 24a. In this embodiment, the first guide member 35 is rotatably mounted on the second support portion 37 as its pivot point. In this embodiment, the image forming apparatus 1 has a restricting portion (guide hole 35e, guide shaft 38) that restricts the direction of movement of the first guide member 35 in conjunction with the movement of the platen member 25. In this embodiment, the restricting portion (guide hole 35e, guide shaft 38) is provided to allow the first guide member 35 to rotate on the restricting portion as its pivot point. In this embodiment, the restricting portion (guide hole 35e, guide shaft 38) is configured to have a hole provided in the first guide member 35 and a shaft that engages with this hole.In this embodiment, the second support portion 37 is connected to the first guide member 35 and abuts against the second guide member 36 to support the first guide member 35 relative to the second guide member 36.

[0062] Furthermore, according to this embodiment, even if the conveying surface 24a of the print belt 24 moves up and down as the platen member 25 moves up and down, the gap between the belt and the guide can be kept substantially constant at a desired distance. Therefore, according to this embodiment, it is possible to stably convey the sheet S to the conveying surface 24a of the print belt 24.

[0063] [others] Although the present invention has been described above with reference to specific embodiments, the present invention is not limited to the embodiments described above.

[0064] In the above-described embodiment, the upper guide portion and the holding portion of the upper guide were formed integrally, but they may be composed of separate members and connected to each other.

[0065] Furthermore, although the second support was attached to the upper guide in the above embodiment, it is not limited to this. The second support only needs to be provided between the first guide and the second guide and be able to support the first guide relative to the second guide, and it may also be attached to the second guide.

[0066] Furthermore, in the above-described embodiment, a guide hole was provided in the upper guide and a guide shaft was provided in another fixed member of the print belt unit. However, the relationship between the member on which the guide hole and the guide shaft are provided may be reversed from the above.

[0067] Furthermore, the restricting portion that controls the direction of movement of the upper guide due to the movement of the platen member is not limited to being composed of a hole and a shaft that engage with each other, but may also be composed of a convex portion (projection) and a concave portion (groove) that engage with each other. [Explanation of symbols]

[0068] 24 Printed Belts 25 Platen component 26 Suction Box 27. Negative pressure generating unit 34 First support 35 Upper Guide 36 Lower Guide 37 Second support 50 Print gap adjustment mechanism 60 Belt-guide gap adjustment mechanism

Claims

1. A rotatable, endless belt for carrying and transporting sheets, A recording head that dispenses recording liquid onto a sheet transported by the aforementioned belt, A platen member is positioned on the inner circumferential surface side of the belt, slidably supports the belt, and forms a conveying surface for conveying a sheet on the belt, wherein the platen member is movable in the thickness direction of the belt while supporting the belt, A first guide member for guiding a sheet being transported toward the transport surface, the first guide member being positioned on the same side as the recording head with respect to the sheet being transported toward the transport surface, with at least a portion facing the transport surface, and movable in a direction intersecting the transport surface, A second guide member for guiding a sheet being transported toward the transport surface, the second guide member being positioned on the opposite side of the sheet being transported toward the transport surface from the recording head, A first support portion is provided connected to the first guide member and in contact with the transport surface to support the first guide member with respect to the transport surface, A second support portion is provided between the first guide member and the second guide member, and supports the first guide member with respect to the second guide member, It has, The image forming apparatus is characterized in that the first support portion is provided so as to be movable together with the first guide member as the platen member moves.

2. The image forming apparatus according to claim 1, characterized in that the first support portion has a rotatable rotating member that contacts the transport surface.

3. The image forming apparatus according to claim 1, characterized in that the first guide member is rotatably provided with respect to the second support portion as the pivot point.

4. The image forming apparatus according to claim 1, characterized in that it has a restricting portion that restricts the direction of movement of the first guide member accompanying the movement of the platen member.

5. The image forming apparatus according to claim 4, characterized in that the restricting portion is provided such that the first guide member can rotate about the restricting portion as a pivot point.

6. The image forming apparatus according to claim 4, characterized in that the regulating portion is configured to have a hole provided in the first guide member and a shaft that engages with the hole.

7. The image forming apparatus according to claim 1, characterized in that the second support portion is connected to the first guide member and abuts against the second guide member to support the first guide member relative to the second guide member.

Images