Image formation device

Abstract

To enable continuous use of a platen member, in a case in which the platen member wears, and reduce running cost of an image formation device.SOLUTION: An image formation device 1 has a belt 25, a platen unit 300 having a platen member 303 and a holding body 301, and a recording head 100. The holding body 301 includes regulation parts 351 and 352 capable of regulating rotation of the platen member 303 in an axial direction of the platen member 303. The platen member 303 includes regulated parts 331 and 332 capable of regulating the position in the axial direction of the platen member 303 to a first position and a second position different from the first position, by being set to the regulation part 351, and an image can be recorded on a sheet S, in a first state in which the platen member 303 is set at the first position, and a second state in which the platen member 303 is set at the second position.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus, such as a printing machine, a copying machine, or a printer, which forms an image using an inkjet method. [Background technology]

[0002] Conventionally, there are inkjet image forming devices (inkjet recording devices) that eject ink droplets onto a recording medium such as recording paper or a resin sheet to record images such as characters or pictures. One such image forming device is a line-head inkjet recording device that records an image on a recording medium by ejecting ink droplets from the recording head in conjunction with the transport of the recording medium, without the recording head moving relative to the image forming device body. Another known line-head inkjet recording device uses an endless print belt to transport the recording medium relative to the recording head. This print belt is stretched over multiple tension rollers, and the recording medium is attracted to and transported on a transport surface formed between the tension rollers upstream and downstream of the multiple recording heads in the rotational direction of the print belt.

[0003] In such image forming devices, in order to print high-quality images on a recording medium with high precision, it is necessary to control the distance between the recording head (more specifically, the tiny nozzles that eject ink from the recording head) and the recording medium with high precision.

[0004] To achieve this, as described in Patent Document 1, a belt support member called a platen member is used, which contacts the inner peripheral surface of the print belt and slidably supports the print belt. Also, as described in Patent Document 1, there is a method of suction-adhering the recording medium to the transport surface of the print belt. That is, the print belt is provided with minute holes, and the print belt is slidably supported by a platen member configured with openings. Then, by suctioning air from the inner peripheral surface of the print belt, the print belt is adsorbed to the platen member, and the recording medium is transported by the print belt while being adsorbed to the print belt. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6380135 Summary of the Invention [Problem to be solved by the invention]

[0006] By using a platen member that contacts the inner surface of the print belt and supports the print belt in a slidable manner, the accuracy of the distance between the recording head and the transport surface of the print belt can be improved, and the accuracy of the distance between the recording head and the sheet can be improved.

[0007] However, the inner circumferential surface of the print belt rubs against the platen member, increasing the drive torque of the print belt. In particular, in the case of a configuration using suction and adsorption as described above, ink mist generated when ink is ejected from the print head is sucked in and adheres to the platen member, which can become contaminated with ink. This contamination can increase the drive torque of the print belt.

[0008] Therefore, it is desirable to use a material that provides low friction to the print belt or a material with low surface energy that makes it difficult for ink to adhere to the platen member. In either case, a resin-coated member made of resin or metal is suitable. While such members have good sliding properties and are less susceptible to ink adhesion, they are subject to wear due to friction with the print belt. For example, in the case of a platen member with a coating, this wear can cause problems such as increased print belt drive torque due to loss of the coating. Therefore, it is desirable to replace the platen member, for example, periodically. However, because the platen member is a high-precision component, this can increase running costs.

[0009] Even if the platen member does not have a coating, its condition may change due to wear caused by friction with the print belt, which may affect, for example, the flatness of the conveying surface. It may also cause image defects due to a shift in the distance between the recording head and the print belt. Therefore, even in this case, it may be desirable to replace the platen member, for example, periodically.

[0010] Therefore, an object of the present invention is to enable the platen member to continue to be used even when it has worn out, thereby reducing the running costs of the image forming apparatus. [Means for solving the problem]

[0011] The above-mentioned object can be achieved by an image forming apparatus according to the present invention. In summary, the present invention provides an image forming apparatus comprising: a rotatable endless belt that carries a sheet on a conveying surface and conveys the sheet; a platen member formed of wire extending in an axial direction and slidably supporting the belt; and a holder that holds the platen member; and a recording head that is disposed opposite the platen unit across the belt and ejects recording liquid onto the sheet conveyed by the belt, the holder having a restricting portion that restricts rotation of the platen member about the axis of the platen member, and the platen member having a regulated portion that, when set in the restricting portion, can regulate the position of the platen member about the axis between a first position and a second position different from the first position, and the image forming apparatus is capable of recording an image on the sheet in a first state in which the platen member is set at the first position and a second state in which the platen member is set at the second position. [Effects of the Invention]

[0012] According to the present invention, even if the platen member becomes worn, it is possible to continue using the platen member, thereby reducing the running costs of the image forming apparatus. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic cross-sectional view of an image forming apparatus. [Figure 2] FIG. 2 is a schematic cross-sectional view of a print module. [Figure 3] FIG. 2 is a perspective view of a platen unit. [Figure 4] 10A and 10B are a schematic perspective view and a schematic front view of the end of the platen member for explaining a contact position regulation configuration of the platen member; [Figure 5] 10A and 10B are a schematic perspective view and a schematic front view of the end of the platen member for explaining a contact position regulation configuration of the platen member; [Figure 6] 10 is a schematic front view of an end portion of the platen member for explaining a contact position regulation configuration of the platen member. FIG. [Figure 7] 10A and 10B are schematic front views of an end portion of the platen member for explaining another example of the contact position regulation configuration of the platen member. [Figure 8] FIG. 10 is a perspective view of another example of the platen unit; [Figure 9] 10A and 10B are schematic side views of the platen member and the platen support member for explaining another example of the contact position regulation configuration of the platen member. DETAILED DESCRIPTION OF THE INVENTION

[0014] The image forming apparatus according to the present invention will be described in more detail below with reference to the drawings.

[0015] <Image forming device> 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 uses an inkjet system. FIG. 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 liquid 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 product.

[0016] In the following description, the inkjet recording apparatus 1 is assumed to be installed on a horizontal surface. With respect to the inkjet recording apparatus 1 and its elements, the front side of the paper in FIG. 1 is the "front" side, the back side of the paper in FIG. 1 is the "rear" side, the right side in FIG. 1 is the "right" side, the left side in FIG. 1 is the "left" side, the top side in FIG. 1 is the "up" side, and the bottom side in FIG. 1 is the "down" side. The front-to-back direction is perpendicular to the left-to-right direction and the up-to-down direction. When the inkjet recording apparatus 1 is installed on a horizontal surface, the up-to-down direction is parallel to the direction of gravity (vertical direction). However, with respect to the inkjet recording apparatus 1 and its elements, up-to-down does not mean just above or just below, but also includes above and below with respect to a horizontal plane passing through the element or position of interest.

[0017] In the following description, the sheet S may be referred to as paper, but the sheet S may also be formed from materials other than paper or materials containing materials other than paper (such as synthetic paper or film formed using synthetic resin, or metal-deposited paper having a metal layer). For convenience, the recording liquid such as a reaction liquid or ink may be simply referred to as "ink," but it may be any liquid such as a reaction liquid used to record an image.

[0018] The inkjet recording apparatus 1 has modules (sheet processing sections) including a paper feed module 1000, a print module 2000, a drying module 3000, a fixing module 4000, a cooling module 5000, an inverting module 6000, and a paper discharge stacking module 7000. A cut sheet S supplied from the paper feed module 1000 is transported along a transport path, processed in each module, and guided to the paper discharge stacking module 7000.

[0019] The paper feed module 1000 includes three storage cabinets 1100a, 1100b, and 1100c that store sheets S, and a housing 1200 that houses these. Each of the storage cabinets 1100a, 1100b, and 1100c is configured to be able to be pulled out toward the front of the housing 1200. The sheets S are fed one by one from each of the storage cabinets 1100a, 1100b, and 1100c by a separation belt and a transport roller, and are transported to the print module 2000. The number of storage cabinets 1100a, 1100b, and 1100c is not limited to three, and may be one, two, four, or more.

[0020] The print module 2000 includes a registration correction unit (pre-imaging registration correction unit) 2400, a print belt unit 2200 as a belt conveying device, a recording unit 2300, and a housing 2500 that houses these components. The sheet S conveyed from the paper feed module 1000 to the print module 2000 has its tilt and position corrected by the registration correction unit 2400 and is then conveyed to the print belt unit 2200. The recording unit 2300 is positioned opposite the print belt unit 2200 across the conveyance path of the sheet S. The recording unit 2300 performs recording processing (image formation, printing, and character printing) on ​​the sheet S conveyed by the print belt unit 2200 from above using the recording head 100 to form an image on the sheet S. The sheet S is attracted and conveyed by the print belt 25 of the print belt unit 2200, ensuring clearance between the sheet S and the recording head 100. The print belt unit 2200 transports the sheet S from right to left. The recording unit 2300 has multiple line-type recording heads 100 arranged along the transport direction of the sheet S. In this embodiment, the recording unit 2300 has eight line-type recording heads 100 (100a-100h) corresponding to four colors (Y (yellow), M (magenta), C (cyan), and Bk (black)), as well as three special colors (white and neon colors) and reactive liquids (FIG. 2). The number of colors and the number of recording heads 100 are not limited to eight. The inkjet method for the recording heads 100 can be a method using heat elements, a method using piezoelectric elements, a method using electrostatic elements, or a method using MEMS elements. Each color of ink is supplied to the corresponding recording head 100 from an ink tank provided in the print module 2000 via an ink tube. The sheet S on which the recording process has been performed by the recording unit 2300 is transported by the print belt unit 2200 and passes through an in-line scanner (not shown) arranged downstream of the recording unit 2300 in the transport direction of the sheet S. The inkjet recording apparatus 1 can correct the print image based on the misalignment and color density of the image formed on the sheet S detected by the in-line scanner.

[0021] The drying module 3000 includes a decoupling unit 3200, a drying belt unit 3300, a hot air blowing unit 3400, and a housing 3500 that houses these components. The drying module 3000 reduces the liquid content of the ink applied to the sheet S by the recording unit 2300, improving the fixation of the ink to the sheet S. After the sheet S has been recorded by the recording unit 2300 of the print module 2000, it is transported to the decoupling unit 3200 located within the drying module 3000. The decoupling unit 3200 transports the sheet S by using air pressure from above and friction with the belt 3200a of the decoupling unit 3200. The decoupling unit 3200 loosely holds the sheet S on the belt 3200a while transporting it, thereby preventing the sheet S from shifting as the ink image forms on the print belt 25 of the print belt unit 2200. The sheet S transported from the decoupling section 3200 to the drying belt unit 3300 is attracted and transported by the belt 3300a of the drying belt unit 3300. At the same time, hot air is blown from a hot air blowing section 3400 arranged above the belt 3300a of the drying belt unit 3300, drying the ink-coated surface of the sheet S. In addition to the method of blowing hot air, other drying methods can be used, such as irradiating the surface of the sheet S with electromagnetic waves (ultraviolet rays, infrared rays, etc.) or conducting heat transfer by contact with a heating element. These methods may be used in any combination.

[0022] The fixing module 4000 includes a fixing belt unit 4100 and a housing 4300 that houses the fixing belt unit 4100. The fixing module 4000 fixes ink to the sheet S by passing the sheet S, which has been transported from the drying module 3000, between a heated upper belt unit 4100a and a heated lower belt unit 4100b.

[0023] The cooling module 5000 includes multiple 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 fixing module 4000 to the cooling module 5000. The cooling unit 5100 is configured to cool the sheet S by drawing in outside air into a cooling box with a fan to increase the pressure inside the cooling box and blowing air from nozzles formed in a transport guide onto the sheet S. The cooling units 5100 are arranged on both sides of the transport path of the sheet S, allowing the sheet S to be cooled from both sides. The cooling module 5000 also includes 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 to be transported to the inversion module 6000 or to a duplex transport path used for duplex printing. During double-sided printing, the sheet S is transported to a double-sided transport path provided below the cooling module 5000, and further transported along double-sided transport paths provided in the fixing module 4000, drying module 3000, print module 2000, and paper feed module 1000. As a result, the sheet S is transported again to the registration correction unit 2400, print belt unit 2200, and recording unit 2300 of the print module 2000, where it is subjected to recording processing by the recording unit 2300. Note that the double-sided transport path of the fixing module 4000 is provided with a first reversing unit 4200 that reverses the sheet S, so that during double-sided printing, the sheet S can be reversed and then transported again to the recording unit 2300.

[0024] The reversing module 6000 has a second reversing unit 6400 and a housing 6500 that houses the second reversing unit 6400. The reversing module 6000 can reverse the front and back of the sheet S transported from the cooling module 5000 to the reversing module 6000, and can freely change the front and back and the orientation of the leading and trailing ends in the transport direction of the sheet S discharged from the reversing module 6000.

[0025] The discharge stacking module 7000 has a top tray 7200, a stacking section 7500, and a housing 7600 in which these are provided. The discharge stacking module 7000 aligns the sheets S transported from the reversing module 6000 to the discharge stacking module 700, and can discharge and stack the sheets onto the top tray 7200, or can stack the sheets onto the stacking section 7500 and store them.

[0026] <Print Module> Next, the schematic configuration of the print module 2000 in the inkjet recording apparatus 1 of this embodiment will be described.

[0027] 2 is a schematic cross-sectional view of the print module 2000. The print module 2000 is an image forming unit that performs a recording process from above on a sheet S transported by a print belt unit 2200 using the recording head 100 of a recording unit 2300 to form an image (ink image) on the sheet S. The print module 2000 is provided with the print belt unit 2200 that transports the sheet S by suction and adsorption so that the transport behavior of the sheet S directly below the recording head 100 is stable. The print belt unit 2200 has a plurality of tension rollers 21 to 24, a print belt 25, a platen unit 300, and a suction device 400.

[0028] The print module 2000 performs a recording process on a sheet S that is carried and transported on a transport surface (image forming surface, printing surface) 25a of the print belt 25 that faces the recording head 100 directly below the recording head 100. A platen unit 300 is provided on the inner peripheral surface of the print belt 25 as a belt support unit that slidably supports the print belt 25 while applying suction. The recording head 100 performs a recording process on the sheet S that is transported while being sucked and adsorbed to the transport surface 25a of the print belt 25. The sheet S that is transported while being sucked and adsorbed to the transport surface 25a of the print belt 25 is transported with a clearance from the recording head 100 ensured.

[0029] In this embodiment, the recording head 100 is supported and positioned by a recording head support portion (support structure portion) in a belt unit frame (not shown) that constitutes the print belt unit 2200.

[0030] <Print belt unit> Next, a description will be given of the schematic configuration of the print belt unit 2200 in the inkjet recording apparatus 1 of this embodiment. As described above, the print belt unit 2200 has a plurality of tension rollers 21 to 24, the print belt 25, the platen unit 300, and the suction device 400.

[0031] In this embodiment, the print belt (transport belt) 25, which is an endless belt, is stretched over four tension rollers, namely, first, second, third, and fourth tension rollers 21, 22, 23, and 24, and is stretched under a predetermined tension. In this embodiment, the print belt 25 is made of PET (polyethylene terephthalate), which is a resin material. In this embodiment, the surface resistivity of the print belt 25 is 1×10 10 The resistance is about Ω / □. In this embodiment, the print belt 25 has a size in the width direction (a direction substantially perpendicular to the moving direction of the surface) set so that a B3 size (364 mm x 515 mm) sheet S can be fed laterally (conveyed in a direction in which the short side is along the conveying direction). The resin material constituting the print belt 25 is not limited to PET, and other resin materials such as polyimide and polycarbonate may also be used.

[0032] In this embodiment, the first tension roller 21 is a drive roller that rotates (circulates) the print belt 25 in the direction indicated by arrow R1 (counterclockwise) in the figure. The second tension roller 22 is a tension roller that is biased from the inner circumferential surface of the print belt 25 toward the outer circumferential surface of the print belt 25 by a biasing mechanism (not shown) serving as a biasing means, and applies a force to the print belt 25 to tension the print belt 25. The third tension roller 23 is a steering roller that is movable at one end in the direction of its rotation axis and can tilt so that its rotation axis is inclined relative to the rotation axes of the other tension rollers. The print belt unit 2200 is configured so that tilting the steering roller 23 can correct the running position of the print belt 25 in the width direction (a direction substantially perpendicular to the surface movement direction) (suppressing meandering).

[0033] The first tension roller 21 is rotated by a driving force transmitted from a motor, which is a drive source provided in a belt drive unit (not shown) serving as a driving means provided in the print belt unit 2200. The second, third, and fourth tension rollers 22, 23, and 24 are rotated in accordance with the rotation of the print belt 25. The first, second, third, and fourth tension rollers 21, 22, 23, and 24 are rotatably supported at both ends of their respective rotational axes by support side plates (not shown) that constitute the print belt unit 2200. These support side plates are attached to a belt unit frame (not shown), which is a support structure that constitutes the print belt unit 2200. The number of tension rollers for the print belt 25 is not limited to four, and may be two, three, or more than four.

[0034] Of the surfaces of the print belt 25 formed by the first to fourth tension rollers 21 to 24, the sheet S is carried and transported on a transport surface 25a, which is the outer surface of the print belt 25 stretched between the first tension roller 21 and the fourth tension roller 24. That is, the print belt 25 carries and transports the sheet S on the transport surface 25a directly below and facing the recording head 100. A platen unit 300 is provided on the inner peripheral surface of the print belt 25 as a belt support section that slidably supports the print belt 25 while applying suction. The platen unit 300 slidably supports the inner peripheral surface of the print belt 25 between the fourth tension roller 24 and the first tension roller 21 in the rotation direction (travel direction) of the print belt 25, i.e., the inner peripheral surface of the print belt 25 corresponding to the transport surface 25a. In particular, in this embodiment, the platen unit 300 (more specifically, a platen member 303, which will be described later) is disposed so as to be able to come into contact with the print belt 25 over an area that includes at least the entire area from a position facing the most upstream print head 100a (more specifically, its nozzles) to a position facing the most downstream print head 100h (more specifically, its nozzles) in the movement direction (left-right direction, running direction) of the transport surface 25a of the print belt 25. Also, in this embodiment, the platen unit 300 is disposed so as to be able to come into contact with the print belt 25 over an area that includes at least substantially the entire area in the width direction (front-rear direction) of the print belt 25 that can support the sheet S. The platen unit 300 and the suction device 400 will be described in detail later.

[0035] <Platen unit> Next, the platen unit 300 in the inkjet recording apparatus 1 of this embodiment will be further described. Figure 3 is a perspective view showing the platen unit 300 in this embodiment. Note that in Figure 3, in order to show the internal structure of the platen unit 300, part of a platen member 303, which will be described later, is not shown.

[0036] The platen unit 300 has a predetermined length in the longitudinal direction along the left-right direction and in the width direction along the front-rear direction, and has a predetermined height in the up-down direction, and is formed in a box shape as a whole. That is, the platen unit 300 has a front wall portion 311 and a rear wall portion 312 extending in the left-right direction, and a right wall portion 313 and a left wall portion 314 extending in the front-rear direction, and a bottom wall portion 315. The front wall portion 311, the rear wall portion 312, the right wall portion 313, the left wall portion 314, and the bottom wall portion 315 are connected to one another to form a platen unit frame (suction box) 301 as a holder.

[0037] The platen unit 300 also has a plurality of platen support members 302 extending in the front-rear direction, spaced apart from one another between the right wall 313 and the left wall 314, connecting the front wall 311 and the rear wall 312. In this embodiment, the platen unit 300 has nine platen support members 302 arranged at approximately equal intervals in the left-right direction. From the viewpoint of sufficiently increasing the flatness of the transport surface 25a of the print belt 25 facing the recording heads 100, the platen support members 302 are preferably arranged as follows: That is, it is preferable that at least one platen support member 302 is provided at each of positions facing the most upstream and most downstream recording heads 100a, 100h (more specifically, their nozzles) in the movement direction of the transport surface 25a. The platen support member 302 is composed of a plate-shaped member (platen support plate) whose longitudinal direction is arranged approximately parallel to the front-rear direction and whose lateral direction is arranged approximately parallel to the up-down direction. The platen support member 302 may be disposed along a direction intersecting the movement direction of the transport surface 25a of the print belt 25, or may be disposed at an angle (inclined) relative to a direction substantially perpendicular to the movement direction of the transport surface 25a of the print belt 25. In this embodiment, the front wall 311, rear wall 312, right wall 313, left wall 314, bottom wall 315, and each platen support member 302 are formed of plate-like members (sheet metal) made of a conductive metal material (such as stainless steel (SUS)). Furthermore, the connecting portions of the front wall 311, rear wall 312, right wall 313, left wall 314, bottom wall 315, and each platen support member 302 are fixed by any fixing means such as fastening or welding (a combination of multiple means is also possible).

[0038] The platen unit 300 is also provided with a plurality of platen members 303 that slidably support the print belt 25 and form the side surfaces of the upper part of the platen unit frame 301. The plurality of platen members 303 are arranged side by side at intervals (approximately equal intervals in this embodiment) so as to extend substantially parallel to the left-right direction (the direction of movement of the transport surface 25a) over substantially the entire area between the right wall portion 313 and the left wall portion 314. Note that the platen members 303 only need to be arranged along the direction of movement of the transport surface 25a of the print belt 25, and may be arranged at an angle (inclined) of, for example, approximately ±30° with respect to the direction of movement of the transport surface 25a of the print belt 25.

[0039] In this embodiment, the platen member 303 is composed of a wire (rod-shaped member) extending in the axial direction. In this embodiment, at least the cross section of the platen member 303, which is approximately perpendicular to the axial direction (longitudinal direction), in the region that can contact the print belt 25 in the axial direction (longitudinal direction) is circular. In particular, in this embodiment, the platen member 303 has a base material made of a conductive metal material (such as SUS) and composed of a wire (metal wire) having a circular cross section approximately perpendicular to the axial direction (longitudinal direction). Furthermore, in this embodiment, the platen member 303 has a coating of a resin material on the base material made of the metal wire. That is, in this embodiment, the platen member 303 is composed of a rod-shaped member (wire) in which the surface of a base material made of a metal wire is coated with a resin. Suitable materials for the resin coating include fluororesins such as PTFE (polytetrafluoroethylene) and PFA (perfluoroalkoxyalkane). The gaps between adjacent platen members 303 form a plurality of upper openings (air intake openings) 304 (see FIG. 4A) of the platen unit 300. In this embodiment, the positions of both left and right ends of the platen member 303 in the front-rear and left-right directions are determined by platen positioning members 305 provided on the right wall portion 313 and the left wall portion 314. The platen member 303 is placed on an upper end surface 321 of the platen support member 302, and when the print belt 25 is sucked by the suction device 400, it is supported by the platen support member 302 and its position in the up-down direction is determined.

[0040] Furthermore, a bottom wall portion 315 of the platen unit frame 301 is provided with a lower opening portion (exhaust opening portion) 316. In this embodiment, the bottom wall portion 315 is provided with a plurality of lower opening portions 316. Note that substantially the entire lower portion (bottom portion) of the platen unit 300 may be formed as a lower opening portion.

[0041] A suction device 400 is connected to a lower opening 316 of the platen unit 300. As shown in FIG. 2, in this embodiment, the suction device 400 is disposed below the lower opening 316 of the platen unit 300 on the inner circumferential surface side of the print belt 25. The suction device 400 includes a suction fan that operates to suck air from the inside of the box-shaped platen unit 300 through the lower opening 316. During the recording process (image formation), the suction device 400 sucks air out through the lower opening 263, thereby creating a negative pressure inside the platen unit 300. As a result, the print belt 25 on the multiple platen members 303 of the platen unit 300 is attracted to the platen members 303 (the sliding surface formed by the multiple platen members 303) by being sucked at the upper opening 304 (the gaps between the platen members 303). Furthermore, the print belt 25 has a large number of suction holes 25b (see the schematic enlarged plan view in FIG. 2) with a diameter of, for example, about 0.3 mm bored all around. As a result, the sheet S transported by the print belt 25 is sucked into the suction holes 25b and adhered to the transport surface 25a of the print belt 25. The suction device 400 is configured to exhaust air to the outside of the print belt unit 2200 via a duct (not shown), and further to the outside of the housing 2500 of the print module 2000. Note that the source of the suction force of the suction device 400 is not limited to a fan and may be, for example, a vacuum pump.

[0042] In this embodiment, the platen unit 300 is supported by a belt unit frame that constitutes the print belt unit 2200.

[0043] As shown in FIG. 2, the sheet S is conveyed by the print belt 25 of the print belt unit 2200 in the conveying direction indicated by arrow A (from right to left). The suction device 400 suctions (pushes) the print belt 25 in the suction direction indicated by arrow B (from top to bottom). Therefore, during the printing process, the print belt 25, which has fine pores along its entire circumference, is suctioned in the suction direction B. The print belt 25 contacts the platen member 303 of the platen unit 300 and rotates while rubbing against the platen member 303. This allows the conveying surface 25a of the print belt 25 to conform to the sliding surface formed by the multiple platen members 303 of the platen unit 300, thereby achieving high flatness of the conveying surface 25a. Enhancing the flatness of the sliding surface formed by the multiple platen members 303 of the platen unit 300 contributes to maintaining the accuracy of the distance (print gap) between the print head 100 and the sheet S. The sheet S is also sucked (urged) by the suction device 400 in the suction direction B. Therefore, even if the sheet S floats or curls, it is sucked onto the conveyance surface 25a of the print belt 25, and conforms to the flatness of the conveyance surface 25a, i.e., the flatness of the sliding surface formed by the plurality of platen members 303. As a result, the recording head 100 can perform recording on the sheet S, which is kept flat with high precision, and it becomes possible to form a high-precision, high-quality image.

[0044] As described above, the platen unit frame 301 is provided with a platen support member 302 that supports the platen member 303 and determines its vertical position. The platen support member 302 is positioned with high precision to accurately support the print belt 25 from its inner peripheral surface. By arranging the rod-shaped platen member 303 relative to the platen support member 302, the accuracy of the portion of the platen member 303 that comes into contact with the print belt 25 can be maintained.

[0045] In this embodiment, the upper end surface 321 of the platen support member (metal support plate) 302 is formed with sufficiently high accuracy of straightness. In this embodiment, this accuracy is achieved by polishing only the upper end surface 321 of the platen support member 302. Then, for example, nine platen support members 302 are assembled by an operator by attaching them to the platen unit frame 301 while adjusting the height of each platen support member 302 relative to the platen unit frame 301. This not only achieves high accuracy for each platen support member 302, but also high surface accuracy for the end surfaces 321 of the nine platen support members 302. In this way, in this embodiment, the platen unit frame 301 (front wall portion 311, rear wall portion 312) and the platen support member 302 are configured so that the vertical position of the platen support member 302 relative to the platen unit frame 301 is adjustable. While the height is adjusted in this manner, the platen member (metal wire rod) 303 is placed on the upper end faces 321 of the nine platen support members 302 attached to the platen unit frame 301. Then, by sucking the print belt 25 with the suction device 400 located below the platen unit frame 301, the platen member 303 deforms to conform to the flatness of the upper end faces 321 of the platen support members 302.

[0046] As described above, the platen unit frame 301 is provided with platen positioning members 305 that determine the position of the platen member 303 in the front-to-rear direction (width direction of the print belt 25). The platen positioning members 305 are provided at the upper end of each of the right wall portion 313 and the left wall portion 314. By using the platen positioning members 305 to evenly position the platen member 303 in the front-to-rear direction, local deformation of the print belt 25 is suppressed when the print belt 25 is sucked by the suction device 400, and the conveying surface 25a is configured to be a stable plane.

[0047] In this embodiment, the diameter of the metal wire constituting the platen member 303 is approximately 3.2 mm, and the pitch (the distance between the centers of adjacent platen members 303 in the front-to-rear direction) of the platen members 303 is approximately 6.0 mm. The thickness of the resin coating on the platen member 303 is approximately several μm to several tens of μm (e.g., 3 μm to 50 μm). In this embodiment, the length of the portion of the platen member 303 that can contact the print belt 25 in the direction of movement of the conveying surface 25a of the print belt 25 is approximately 700 mm. The outer diameter and pitch of the platen member 303 can be appropriately set in consideration of providing a sufficient upper opening 304 and ensuring sufficient flatness of the conveying surface 25a of the print belt 25 when the print belt 25 is sucked by the suction device 400. While not limited thereto, the outer diameter of the platen member 303 is preferably approximately 2.0 mm to 5.0 mm. Although not limited thereto, the pitch of the plurality of platen members 303 is preferably about 3.0 mm or more and 10 mm or less. The number of platen members 303 may be appropriately set so that they can contact the print belt 25 over a range that includes at least substantially the entire area in the width direction (front-rear direction) of the print belt 25 that can support the sheet S.

[0048] Use of the platen unit 300 described above can improve the accuracy of the distance between the recording head 100 and the transport surface 25a of the print belt 25. Furthermore, the platen member 303 described above has good sliding properties and is resistant to ink adhesion, which can prevent an increase in the drive torque of the print belt 25. However, the platen member 303 wears out due to friction with the print belt 25. Therefore, it is desirable to replace the platen member periodically, for example. However, because the platen member is a highly accurate part, this can increase running costs.

[0049] Therefore, in this embodiment, when the platen member 303 becomes worn, the inkjet recording apparatus 1 can continue to use the platen member 303 by changing the contact portion of the platen member 303 that comes into contact with the print belt 25. This will be explained in more detail below.

[0050] <Configuration for restricting contact position of platen member> FIG. 4 is a schematic perspective view (FIG. 4(a)) of the vicinity of an end portion in the axial direction of the platen member 303 and a schematic front view (FIG. 4(b)) of the end portion in the axial direction of the platen member 303, for explaining an example of a contact position restricting configuration of the platen member 303 in this embodiment. FIG. 5 is a schematic perspective view (FIG. 5(a)) of the vicinity of an end portion in the axial direction of the platen member 303 and a schematic front view (FIG. 5(b)) of the end portion in the axial direction of the platen member 303, for explaining another example of a contact position restricting configuration of the platen member 303 in this embodiment. In this embodiment, the contact position restricting configuration is substantially the same at both end portions in the axial direction of the platen member 303, so the description will focus on one end portion (here, the right end portion).

[0051] The platen member 303 is positioned on the platen support member 302, thereby determining its vertical position. The platen member 303 is also positioned in the front-rear direction by the platen positioning member 305. In this embodiment, the platen positioning member 305 determines the front-rear position of the platen member 303 and also regulates the contact position of the platen member 303 with the print belt 25. In other words, it determines the position (phase) of the platen member 303 in the rotational direction around its axis.

[0052] In the example shown in FIG. 4 , a rod-shaped platen member 303 has a circular cross section substantially perpendicular to the axial direction. A notched shape is formed at the axial end of the platen member 303 so that the outer surface becomes a flat surface along the axial direction of the platen member 303 (substantially parallel in this embodiment). In this example, two substantially parallel flat surfaces are formed facing each other across the axial center of the platen member 303. That is, a notched shape is formed at the axial end of the platen member 303 so that the cross section substantially perpendicular to the axial direction becomes a substantially elliptical (oval) shape. This shape can be formed by any processing means such as cutting or polishing. As a result, a first regulated surface 331 and a second regulated surface 332 are formed as regulated portions (regulated receiving portions) at the axial end of the platen member 303.

[0053] The platen positioning member 305 is also provided with grooves 353 that are substantially rectangular (U-shaped with a bottom) and have an opening at the top when viewed in the left-right direction, corresponding to each platen member 303. In this embodiment, the distance between the substantially parallel inner surfaces of the grooves 353 facing each other in the front-rear direction is set to be larger than the distance between the first regulated surface 331 and the second regulated surface 332 of the platen member 303. The platen positioning member 305 is also provided with regulating members 354 that are arranged to narrow the width of the opening at the top of the grooves 353, corresponding to each platen member 303. The regulating members 354 can be fixed to the platen positioning member 305 by any fixing means such as fastening or welding (or a combination of multiple means is also possible). As a result, one of the substantially parallel inner surfaces of the grooves 353 facing each other in the front-rear direction (for example, the rear inner surface) constitutes the first regulating surface 351 as a regulating portion. Further, the side surface of the regulating member 354 opposite to the first regulating surface 351 and adjacent to the platen member 303 constitutes a second regulating surface 352 as a regulating portion.

[0054] 4, the axial end of the platen member 303 is disposed on the platen positioning member 305, so that the first and second regulating surfaces 351 and 352 are respectively substantially engaged with the first and second regulated surfaces 331 and 332. This restricts the platen member 303 from rotating about its axis. By restricting the rotation of the platen member 303 about its axis in this manner, the contact position of the platen member 303 with the inner circumferential surface of the print belt 25 can be restricted to the first contact portion 335a or the second contact portion 335b. For example, in the state shown in FIG. 4(b), the contact position of the platen member 303 is restricted so that the first contact portion 335a contacts the inner circumferential surface of the print belt 25 (first state). From this state, the platen member 303 is rotated 180 degrees (1 / 2 revolution) around the axis and placed on the platen positioning member 303, whereby the contact position of the platen member 303 is regulated so that the second contact portion 335b contacts the inner surface of the print belt 25 (second state).

[0055] 5, a cutout is formed at the end of the axial direction of the rod-shaped platen member 303, which has a circular cross section approximately perpendicular to the axial direction, so that the cross section approximately perpendicular to the axial direction has a quadrangular shape (approximately a square in this example). This shape can also be formed by any processing means such as cutting or polishing, as described above. As a result, first to fourth regulated surfaces 331 to 334 are formed as regulated portions at the end of the axial direction of the platen member 303.

[0056] 4. The platen positioning member 305 is provided with first and second regulating surfaces 351 and 352 similar to those in the example shown in FIG.

[0057] 5, the axial end of the platen member 303 is disposed on the platen positioning member 305, so that the first and second regulating surfaces 351 and 352 each approximately engage with one of the first to fourth regulated surfaces 331 to 334. More specifically, the first and second regulating surfaces 351 and 352 each approximately engage with one of the first and third regulated surfaces 331 and 333, or approximately engage with one of the second and fourth regulated surfaces 332 and 334. This restricts rotation of the platen member 303 around its axis. By restricting rotation of the platen member 303 around its axis in this manner, the contact position of the platen member 303 with the inner circumferential surface of the print belt 25 can be restricted to one of the first to fourth contact portions 335a to 335d. 5B, for example, the contact position of the first contact portion 335a of the platen member 303 is restricted so that it contacts the inner circumferential surface of the print belt 25 (first state). From this state, by rotating the platen member 303 90 degrees (1 / 4 revolution) about its axis, for example counterclockwise, and positioning it on the platen positioning member 303, the contact position of the second contact portion 335b of the platen member 303 is restricted so that it contacts the inner circumferential surface of the print belt 25 (second state). Similarly, each time the platen member 303 is rotated 90 degrees (1 / 4 revolution) about its axis, the contact positions of the third contact portion 335c and the fourth contact portion 335d are restricted so that they contact the inner circumferential surface of the print belt 25 (third and fourth states, respectively).

[0058] The regulation of the regulated portion by the regulating portion may have backlash (play) within an allowable range, allowing for sufficient variation in the contact position of the platen member 303 with the print belt 25 and sufficient flatness of the conveyance surface 25a of the print belt 25. In other words, when the regulated portion is set (engageably arranged) in the regulating portion, the platen member 303 may be able to rotate around the axis with the above-mentioned amount of backlash. Restricting the contact position of the platen member 303 with the print belt 25, setting the regulated portion in the regulating portion, or setting the position of the platen member 303 includes a state with the above-mentioned backlash.

[0059] 6(a) and 6(b) are plan views showing an axial end surface 336 of a platen member 303 having a shape similar to that of the examples shown in FIGS. 4 and 5, respectively. To facilitate identification of which contact portions of the platen member 303 are used (or unused), a mark 337 serving as a contact portion indicator can be provided, for example, on the axial end surface 336 of the platen member 303. In the illustrated example, the mark 337 is provided at a position closer to one of the contact portions on the end surface 336 than to the other contact portions. The mark 337 can be provided, for example, by drawing an arbitrary mark with a pen, forming an arbitrary shape such as a recess by any means such as cutting or engraving, or attaching a sticker. Furthermore, by providing the mark 337 in advance in association with one of the contact portions, it can be used to identify a used (or unused) contact portion based on the position of the mark 337. Alternatively, the marks 337 can be associated with each contact before and after use and used to identify used (or unused) contacts based on the position and number of the marks 337.

[0060] For example, if the platen member 303 has been used for a predetermined period of time with any of its contact portions in contact with the print belt 25, the platen member 303 can be rotated about its axis and repositioned on the platen positioning member 305. This predetermined period can be set in advance based on, for example, the period until the coating on the platen member 303 wears away and is no longer visible. This predetermined period can also be set based on any indicator, such as time or the amount of drive of the device (the number of sheets S on which images are formed, the number of rotations and rotation time of the print belt 25, etc.). In the example shown in FIG. 4, by rotating the platen member 303 to switch between the first state and the second state, the period until replacement of the platen member 303 can be approximately doubled compared to when this embodiment is not applied. In the example shown in FIG. 5, by rotating the platen member 303 to selectively switch between the first to fourth states, the period until replacement of the platen member 303 can be approximately quadrupled compared to when this embodiment is not applied. This reduces the cost of replacing parts during maintenance.

[0061] In this embodiment, substantially the same contact position restricting structure is provided on both axial ends of the platen member 303, but it may be provided on only one end.

[0062] Furthermore, in this embodiment, a regulating member 354 is provided on the platen positioning member 305, and a second regulating surface 352 is provided on this regulating member 354. This makes it possible to adjust, for example, the attachment position of the regulating member 354, thereby adjusting the distance between the first regulating surface 351 and the second regulating surface 352, and thereby adjust the position of the platen member 303 in the front-rear direction, the degree of phase regulation, and the like. However, this is not limited to such a configuration, and, for example, inner surfaces of the groove portion 305 facing each other in the front-rear direction may form the first and second regulating surfaces 351 and 352, respectively.

[0063] Furthermore, if a change in the print gap due to a contact portion whose coating has peeled off due to wear being supported by the platen support member 302 is not acceptable, for example, in the example of FIG. 5, the contact portion opposite the used contact portion can be made unused. Even in this case, as in the example shown in FIG. 4, the period during which the platen member 303 can be used can be extended by switching between the two contact portions. However, depending on the initial (unused) coating thickness, the effect on images of a change in the print gap due to coating wear can be negligible. Even in this case, it may be desirable to change the contact portion from the perspective of, for example, the effect on the flatness of the transport surface 25a of the print belt 25 due to uneven wear of the coating, or the effect on the drive torque of the print belt 25 due to coating wear.

[0064] As mentioned above, even for platen members that do not have a coating, it may be desirable to replace them periodically, for example, and this embodiment is also effective in such cases.

[0065] The shape of the regulated portion may be different at both ends of the platen member 303 in the axial direction. As a modification of the example shown in FIG. 4, the end of the platen member 303 may be provided with only one flat surface along the axial direction of the platen member 303, and this flat surface may serve as the regulated surface. In this case, too, the contact position of the platen member 303 with the print belt 25 can be regulated by regulating this regulated surface with either the first or second regulating surface 351, 352. The cross section of the end of the platen member 303 is not limited to a substantially elliptical or rectangular shape. If the cross section is polygonal, it is preferable that the polygonal cross section has opposing sides, but is not limited to this.

[0066] Furthermore, wire rods with circular cross sections are suitable for use in the platen member 303 because wire rods with sufficiently small wire diameter tolerances are readily available. However, as long as each surface is sufficiently straight, a rod-shaped member with a polygonal (e.g., rectangular) cross section may also be used. In this case, each surface of the end portion can constitute a regulated surface without forming a special shape at the end portion of the platen member 303 in the axial direction.

[0067] Furthermore, the rod-shaped platen member 303 is preferably arranged along the moving direction of the transport surface 25a of the print belt 25, as this facilitates increasing the flatness of the transport surface 25a of the print belt 25. However, without being limited to this, the rod-shaped platen member 303 may be arranged along a direction intersecting the moving direction of the transport surface 25a of the print belt 25. In this case, the platen support member 302 may be arranged along the moving direction of the transport surface 25a of the print belt 25. The same can be said for the extending direction of the platen unit 502 described in the third embodiment.

[0068] As described above, in this embodiment, the image forming apparatus (inkjet recording apparatus) 1 includes a rotatable endless belt (print belt) 25 that carries and conveys the sheet S on a conveying surface 25a, a platen member 303 that is made of a wire extending in the axial direction and slidably supports the belt 25, a platen unit 300 that includes a holder (platen unit frame) 301 that holds the platen member 303, and a recording head 100 that is disposed opposite the platen unit 300 across the belt 25 and ejects recording liquid onto the sheet S conveyed by the belt 25, and the holder 301 includes a restricting portion that can restrict the platen member 303 from rotating in a direction around the axis of the platen member 303. The platen member 303 has regulated portions (e.g., first and second regulating surfaces) 331, 332 that, when set on the regulating portions 351, 352, can regulate the position of the platen member 303 around the axis to a first position (e.g., a position where the first contact portion 335a contacts the belt 25) and a second position different from the first position (e.g., a position where the second contact portion 335b different from the first contact portion 335a contacts the belt 25), and an image can be recorded on the sheet S in a first state where the platen member 303 is set to the first position, and a second state where the platen member 303 is set to the second position. That is, the image forming apparatus 1 is placed in a first state by setting the regulated portions 331 and 332 in the regulating portions 351 and 352 so that the platen member 303 is set to a first position. The image forming apparatus 1 is placed in a second state by setting the regulated portions 331 and 332 in the regulating portions 351 and 352 so that the platen member 303 is set to a second position. In this embodiment, the regulated portions 331 and 332 are formed as flat surfaces along the axial direction. The platen member 303 is a member having a circular cross section, approximately perpendicular to the axial direction, of a region of the platen member 303 that can come into contact with the belt 25 in the axial direction. In this embodiment, the platen member 303 has a base material (metal wire) made of a metal material and a coating (resin coating) made of a resin material formed on the base material.

[0069] As described above, according to this embodiment, when the platen member 303 becomes worn, the platen member 303 can be used continuously by changing the contact portion of the platen member 303 that comes into contact with the print belt 25. This makes it possible to reduce the running costs of the inkjet recording apparatus 1.

[0070] [Example 2] Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the image forming apparatus of embodiment 1. Therefore, in the image forming apparatus of this embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus of embodiment 1 are given the same reference numerals as those of the image forming apparatus of embodiment 1, and detailed explanations thereof will be omitted.

[0071] In this embodiment, the contact position restricting configuration (positioning configuration) differs between one end and the other end in the axial direction of the platen member 303.

[0072] Fig. 7(a) is a schematic front view of the end of the platen member 303 in this embodiment. In Fig. 7(a), the right and left views respectively show the right end (upstream side in the movement direction of the conveying surface 25a) and the left end (downstream side in the movement direction of the conveying surface 25a) when the platen member 303 is disposed at a certain rotational position (phase). Fig. 7(b) is a schematic front view of the vicinity of the axial end of the platen member 303 in this embodiment. In Fig. 7(b), the right and left views respectively show the right and left end.

[0073] In this embodiment, the regulated portions provided at the ends of the platen member 303 are provided at different phases between one end (first end) and the other end (second end) of the platen member 303. For example, as shown in the right diagram of FIG. 7(a), the first end of the platen member 303 is formed with a shape similar to that described with reference to FIG. 5, such that the cross section substantially perpendicular to the axial direction is a square. That is, the first end of the platen member 303 is formed with first to fourth regulated surfaces 331 to 334 similar to that described with reference to FIG. 5. In this case, as shown in the left diagram of FIG. 7(b), the second end of the platen member 303 is formed with a shape similar to that formed at the first end, but with a phase shift from that of the shape formed at the first end. In this embodiment, this phase shift is 45 degrees. Note that this phase shift is not limited to 45 degrees, and is preferably 10 degrees or more from the viewpoint of sufficiently changing the contact position of the platen member 303 with the print belt 25, and may be any angle at which both ends of the platen member 303 do not have the same shape (less than the angle at which they have the same shape) (for example, 80 degrees or less in this embodiment). This phase shift may be, for example, 30 degrees. In other words, fifth to eighth regulated portions 361 to 364 are formed at the second end of the platen member 303, and are shifted in phase by 45 degrees from the first to fourth regulated surfaces 331 to 334 formed at the first end.

[0074] In this embodiment, as shown in the right diagram of FIG. 7(b), the right-side platen positioning member 305 is provided with first and second restricting portions 351 and 352 similar to those described with reference to FIGS. 4 and 5. On the other hand, as shown in the left diagram of FIG. 7(b), the left-side platen positioning member 305 does not have the restricting member 354 described with reference to FIGS. 4 and 5. Therefore, in the left-side platen positioning member 305, the end of the platen member 303 is disposed with a gap g between, for example, the inner surfaces of the groove 353 formed in the platen positioning member 305, which are substantially parallel and face each other in the front-rear direction. Note that the gap may be formed only on one of the inner surfaces. It is sufficient that the platen member 303 is free to rotate around its axis without being restricted. This prevents, for example, the platen member 303 from being restricted to different phases at both ends in the axial direction, which could affect the position of contact between the platen member 303 and the print belt 25.

[0075] In this embodiment, the contact portion of the platen member 303 that contacts the inner circumferential surface of the print belt 25 can be changed as follows. For example, first, as shown in the right diagram of FIG. 7A, the first end of the platen member 303 is positioned on the right side. In this state, the first and second regulating surfaces 351 and 352 and the first to fourth regulated surfaces 331 to 334 are used to restrict rotation of the platen member 303 around its axis, as described with reference to FIG. 5. This allows any one of the first to fourth contact portions 335a to 335d to contact the print belt 25 (first to fourth states). After using the first to fourth contact portions 335a to 335d in this manner, the orientations of the first and second end portions of the platen member 303 are reversed, and the second end of the platen member 303 is positioned on the right side, as shown in the left diagram of FIG. 7A. In this state, the first and second regulating surfaces 351, 352 and the fifth to eighth regulated surfaces 361-364 are used to regulate the rotation of the platen member 303 about its axis, in the same manner as described with reference to Figure 5. This allows one of the fifth to eighth contact portions 335e-335h to come into contact with the print belt 25 (fifth to eighth states). In this manner, the fifth to eighth contact portions 335e-335h can be used. Note that the above-described modification of the contact portions is merely an example, and the order in which the contact portions are used is arbitrary.

[0076] In this embodiment, by rotating the platen member 303 and changing its left / right orientation so as to selectively switch between the first to eighth states, the period until replacement of the platen member 303 can be extended by approximately eight times compared to the first embodiment and a case in which this embodiment is not applied. Therefore, according to this embodiment, the cost of replacing parts during maintenance can be further reduced compared to the first embodiment.

[0077] FIG. 7(c) is a schematic front view of an end of the platen member 303 in a modified example of this embodiment. In FIG. 7(c), the right and left views respectively show the right and left ends of the platen member 303 when the platen member 303 is positioned at a certain rotational position (phase). In the example shown in FIG. 7(c), the first and second ends of the platen member 303 have rectangular cross sections, including the first to fourth regulated portions 331 to 334 and the fifth to eighth regulated portions 361 to 364, respectively, which are formed inside the circular cross section of the wire material constituting the platen member 303. This reduces the possibility that the corners of the rectangular shape of the end of the platen member 303 positioned on the left platen positioning member 305 (left view of FIG. 7(b)) will come into contact with the inner circumferential surface of the print belt 25, thereby reducing the possibility of damage to the print belt 25.

[0078] In the configuration of this embodiment, the marks described in the first embodiment can also be used.

[0079] Thus, in this embodiment, the platen member 303 is provided with first regulated portions (e.g., first and second regulated surfaces) 331, 332 at one end in its axial direction, which are set on regulating portions (e.g., first and second regulating surfaces) 351, 352, thereby enabling the position of the platen member 303 around its axis to be regulated to a first position (e.g., a position where the first contact portion 335a contacts the belt 25) and a second position different from the first position (e.g., a position where the second contact portion 335b different from the first contact portion 335a contacts the belt 25), and the image forming apparatus 1 is capable of recording an image on the sheet S in a first state in which the platen member 303 is set to the first position, and in a second state in which the platen member 303 is set to the second position. In addition, in this embodiment, the platen member 303 is provided with second regulated portions (e.g., fifth and sixth regulated surfaces) 361 and 362 at the other end in the axial direction, which are set on regulating portions (e.g., first and second regulating surfaces) 351 and 352, thereby enabling the position of the platen member 303 around the axial direction to be regulated to a third position different from the first and second positions (e.g., a position where the fifth contact portion 335e contacts the belt 25), and a fourth position different from the first, second, and third positions (e.g., a position where the sixth contact portion 335f contacts the belt 25), and the image forming apparatus 1 is capable of recording an image on the sheet S in a third state in which the platen member 303 is set to the third position, and in a fourth state in which the platen member 303 is set to the fourth position. That is, the image forming apparatus 1 is placed in the third state when the second regulated portions 361, 362 are set in the regulating portions 351, 352 so that the platen member 303 is set in the third position. The image forming apparatus 1 is placed in the fourth state when the second regulated portions 361, 362 are set in the regulating portions 351, 352 so that the platen member 303 is set in the fourth position.In this embodiment, the holder 301 is provided with restricting portions 351, 352 only on one end side of both ends of the platen member 303 in the axial direction when the holder 301 holds the platen member 303, and the axial direction is reversed when the first regulated portions 331, 332 are set in the restricting portions 351, 352 and when the second regulated portions 361, 362 are set in the restricting portions 351, 352 and the platen member 303 is held by the holder 301. In this embodiment, the platen member 303 is a member having a circular cross section, approximately perpendicular to the axial direction, of a region that can come into contact with the belt 25 in the axial direction. In this embodiment, the first regulated portions 331, 332 and the second regulated portions 361, 362 are each formed of a flat surface along the axial direction. In this embodiment, the first restricted portions 331, 332 and the second restricted portions 361, 362 are located at different positions in the direction around the axis.

[0080] As described above, according to this embodiment, it is possible to continuously use the platen member 303 for an even longer period of time than in Example 1. This makes it possible to further reduce the running costs of the inkjet recording apparatus 1.

[0081] [Example 3] Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the image forming apparatus of embodiment 1. Therefore, in the image forming apparatus of this embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus of embodiment 1 are given the same reference numerals as those of the image forming apparatus of embodiment 1, and detailed explanations thereof will be omitted.

[0082] This embodiment differs from the first embodiment mainly in the configuration of the platen member, the support configuration of the platen member, and the contact position regulation configuration of the platen member.

[0083] <Platen unit> Fig. 8 is a perspective view of the vicinity of one end of the platen unit 300 in this embodiment. Note that in Fig. 8, in order to show the internal structure of the platen unit 300, a portion of a platen member 500, which will be described later, is not shown.

[0084] In this embodiment, the platen unit 300 has a plurality of platen support members 302 extending in the left-right direction and arranged at intervals between the front wall portion 311 and the rear wall portion 312 so as to connect the right wall portion 313 and the left wall portion 312.

[0085] In this embodiment, the platen unit 300 is provided with a plate-shaped platen member 500 that slidably supports the print belt 25 and forms the side surface of the upper part of the platen unit frame 301. The platen member 500 has a flat, plate-shaped base 501 and multiple platen portions 502 that protrude from one side surface and the other side surface of the base 501 in directions that intersect (approximately perpendicular in this embodiment) with the plane of the base 501. The platen portions 502 protrude (height) from the base 501 by approximately the same amount on one side surface and the other side surface of the platen member 502. The multiple platen portions 502 are arranged side by side at intervals (approximately equal intervals in this embodiment) so as to extend approximately parallel to the left-right direction (the direction of movement of the transport surface 25a). The platen member 500 is also provided with a plurality of suction holes 503 (see the schematic enlarged plan view in FIG. 8) that enable the suction device 400 to suck in air. In this embodiment, the suction holes 503 are provided in the base portion 501 located between adjacent platen portions 502. The suction holes 503 form a plurality of upper openings (suction openings) of the platen unit 300.

[0086] The platen member 500 can be made of a resin material. Alternatively, the platen member 500 can be formed by coating the surface of a metal material (such as SUS) with a resin. As the resin, a fluororesin similar to that described above can be suitably used. In this embodiment, the platen member 500 is integrally formed of a resin material.

[0087] In this embodiment, a plurality of platen members 500 (eight in this embodiment) configured as described above are arranged on the platen support member 302 so as to form a side surface over substantially the entire upper area of ​​the platen unit frame 301. The platen member 500 is supported by the platen support member 302 at the base portion 501 between the downward-facing platen portions 502. The tip surfaces of the upward-facing platen portions 502 of the platen member 500 contact the inner circumferential surface of the print belt 25, slidably supporting the print belt 25. In this way, by arranging the platen member 500 divided into multiple pieces in a tiled pattern on the platen support member 302, it becomes easier to improve the flatness of the conveying surface 25a of the print belt 25. This is because dividing the platen member 500 into multiple pieces in a tiled pattern makes it easier to improve the straightness of the portions of the platen portions 502 supported by the platen support member 302 and the portions in contact with the print belt 25.

[0088] <Configuration for restricting contact position of platen member> FIG. 9 is a side view showing the platen member 500 and the platen support member 302 for explaining the contact position regulation structure of the platen member 303 in this embodiment.

[0089] In this embodiment, because the platen member 500 is plate-shaped, there is no need for a member for restricting the rotation of the platen member 303 as in the first embodiment. In this embodiment, the portion (end surface) of the platen support member 302 that determines the vertical position of the platen member 500 and supports the platen member 500 constitutes a restricting surface 322 as a restricting portion that restricts the contact position of the platen member 500 with the print belt 25. Also, in this embodiment, the portions of one side and the other side of the platen member 500 that are supported by the platen support member 302 of the base 501 (bottoms of the recesses between the platen portions 502) constitute first and second regulated surfaces 511 and 512 as first and second regulated portions, respectively. For example, in the state shown in FIG. 9 , the platen member 500 is positioned so that the first regulated portion 511 of the platen member 500 abuts against the restricting surface 322 of the platen support member 302. In this state, the platen member 500 is regulated so that the first contact portion 521, which is formed by the tip surface of the platen portion 502 protruding upward from the base portion 501, contacts the inner circumferential surface of the print belt 25 (first state). From this state, the platen member 500 is turned over to position the platen member 500 so that the second regulated portion 511 of the platen member 500 abuts against the regulating surface 322 of the platen support member 302. In this state, the platen member 500 is regulated so that the second contact portion 522, which is formed by the tip surface of the platen portion 502 protruding upward from the base portion 501, contacts the inner circumferential surface of the print belt 25 (second state).

[0090] For example, if the platen member 500 has been used for a predetermined period with either contact portion in contact with the print belt 25, the platen member 500 can be turned over and repositioned on the platen support member 302. This predetermined period can be set in advance based on, for example, the period until the change in the print gap due to wear of the platen member 502 becomes unacceptable. In this embodiment, even if one contact portion wears out, the platen member 500 is supported by the platen support member 302 at the base portion 501, so the protrusion (height) of the other contact portion from the base portion 501 maintains a predetermined value, and the print gap is not affected.

[0091] In the configuration of this embodiment, it is also possible to use marks such as those described in embodiment 1. In the configuration of this embodiment, for example, marks may be provided on the base 501 or the like.

[0092] As described above, in this embodiment, the platen member 500 is a plate-like member having, on each side thereof, a plurality of platen portions 502 that are capable of contacting the belt 25 and extend in a predetermined direction, and the holder 301 has support members 302 that support the platen member 500 in recesses between the platen portions 502 on both side surfaces of the platen member 500, the portions of the platen member 500 that are supported by the support members 302 on both side surfaces constitute regulated portions 511 and 512, the portion of the support member 302 that contacts the platen member 500 constitutes the regulating portion 322, the portion of the platen portion 502 on one side surface of the platen member 500 that is capable of contacting the belt 25 constitutes the first contact portion 521, and the portion of the platen portion 502 on the other side surface of the platen member 500 that is capable of contacting the belt 25 constitutes the second contact portion 522. Also, in this embodiment, the platen member 500 is formed of a resin material.

[0093] As described above, even with the configuration of this embodiment, if the platen member 500 becomes worn, it is possible to continue using the platen member 500 by changing the contact portion of the platen member 500 that comes into contact with the print belt 25. This makes it possible to reduce the running costs of the inkjet recording apparatus 1. [Explanation of symbols]

[0094] 25 Printed Belt 100 recording head 300 Platen Unit 301 Platen unit frame 302 Platen support member 303 Platen member 331~334 Regulated surface 335a~335d Contact part 351, 352 Regulatory aspects 400 Suction device 2000 Print Module 2200 Print Belt Unit 2300 Recording Department S seat

Claims

1. a rotatable endless belt that carries and transports a sheet on a transport surface; a platen unit including a platen member formed of a wire rod extending in an axial direction and slidably supporting the belt, and a holder for holding the platen member; a recording head that is disposed opposite the platen unit across the belt and that ejects a recording liquid onto a sheet that is conveyed by the belt; and the holder includes a restricting portion that restricts the platen member from rotating in a direction around the axis of the platen member, the platen member includes a regulated portion that, when set in the regulating portion, enables the position of the platen member around the axis to be regulated to a first position and a second position different from the first position, An image forming apparatus characterized in that it is possible to record an image on a sheet in a first state in which the platen member is set to the first position and in a second state in which the platen member is set to the second position.

2. 2. The image forming apparatus according to claim 1, wherein the regulated portion is formed of a flat surface along the axial direction.

3. 2. The image forming apparatus according to claim 1, wherein the platen member is a member having a circular cross section, which is substantially perpendicular to the axial direction, of a region of the platen member that can come into contact with the belt in the axial direction.

4. the regulated portion is a first regulated portion provided at one end of the platen member in the axial direction, the platen member includes a second regulated portion at the other end in the axial direction, the second regulated portion being set in the regulating portion to regulate the position of the platen member in the direction around the axis to a third position different from the first and second positions and a fourth position different from the first, second, and third positions; 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is capable of recording an image on a sheet in a third state in which the platen member is set to the third position and in a fourth state in which the platen member is set to the fourth position.

5. the holder includes the restricting portion only on one end side of both ends of the platen member in the axial direction when the platen member is held by the holder, 5. The image forming apparatus according to claim 4, wherein the platen member is held by the holder with the axial direction oriented in the opposite direction when the first regulated portion is set in the regulating portion and when the second regulated portion is set in the regulating portion.

6. 5. The image forming apparatus according to claim 4, wherein the platen member is a member having a circular cross section, substantially perpendicular to the axial direction, of a region of the platen member that can come into contact with the belt in the axial direction.

7. 5. The image forming apparatus according to claim 4, wherein the first and second regulated portions are each formed of a flat surface extending along the axial direction.

8. 5. The image forming apparatus according to claim 4, wherein the first regulated portion and the second regulated portion are located at different positions in the direction around the axis.

9. 9. The image forming apparatus according to claim 1, wherein the platen member has a base material made of a metal material and a coating made of a resin material on the base material.

Images