Image formation device

Abstract

To lower a surface potential of a print belt, and reduce the possibility that a defect occurs due to influence of an electric field formed between the print belt and a recording head.SOLUTION: An image formation device 1 includes: a belt 25 for carrying a sheet S on a conveyance surface 25a and conveying the sheet S; a plurality of rollers which stretch the belt 25, and have an upstream roller 24 and a downstream roller 21 forming the conveyance surface 25a; a platen unit 300; a suction device 400 for sucking air through the platen unit 300 and sucking the belt 25 and the sheet S; a recording head 100 for discharging liquid for recording to the sheet S conveyed by the belt 25; and a static elimination member 200 which is composed using a conductive material, is arranged on the downstream side of a position E at which the belt 25 is separated from the upstream roller 24 so as to be brought into contact with the surface of the belt 25 on the upstream side of a position C facing the recording head 100, in a rotation direction of the belt 25, and removes at least a part of electric charges of the belt 25 by being electrically grounded.SELECTED DRAWING: Figure 2

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] In recent years, even in the fields of commercial and industrial printing, where analog printing such as offset printing is mainstream, there has been a growing demand for inkjet printing as a digital printing method that can print a wide variety of designs in small quantities without the need for plates. Inkjet image forming devices (inkjet recording devices) eject ink droplets onto a recording medium such as recording paper or a resin sheet to record images such as characters and images. In particular, line-head inkjet recording devices record color images on a recording medium by ejecting different colored droplets from multiple recording heads in conjunction with the transport of the recording medium, without the recording heads moving relative to the main body of the image forming device. Known line-head inkjet recording devices use an endless print belt to transport the recording medium relative to the recording heads. 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 upstream and downstream tension rollers of the multiple recording heads in the direction of rotation of the print belt.

[0003] In such image forming devices, the distance between the recording medium and the recording head (more specifically, the fine nozzles of the recording head that eject ink) is important for achieving high-quality output. Therefore, recording media, such as cut plain paper, are conveyed while being pressed against a flat surface (printing plane) with minimal unevenness, i.e., a highly flat surface. One method for achieving this is to convey the recording medium while suctioning it onto the conveying surface of a print belt (see Patent Document 1). Specifically, the print belt is provided with fine holes, and the print belt is slidably supported by a platen member configured with openings. Air is then sucked from the inner circumferential surface of the print belt, causing the print belt to adhere to the platen member, and the recording medium is conveyed by the print belt while adsorbed to the print belt.

[0004] The technology described in Patent Document 2 relates to an inkjet recording device having a configuration in which a recording medium is electrostatically attracted to a print belt, which is different from the configuration using suction and adsorption described above. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-140997 [Patent Document 2] Japanese Patent Publication No. 2022-125062 Summary of the Invention [Problem to be solved by the invention]

[0006] In the suction-adsorption configuration described above, the print belt rotates while sliding against the platen member, causing both to become charged due to friction. If the surface potential of the print belt exceeds, for example, approximately 2 kV, discharge can occur from the print belt toward the print head nozzle face. This can damage the print head face, potentially hindering accurate ink ejection from the print head. However, by constructing the platen member from a conductive material, the surface potential of the print belt can be reduced to less than 2 kV.

[0007] However, even if the surface potential of the print belt is less than 2 kV, if the surface potential of the print belt is, for example, 500 V or higher, an electric field is generated from the print belt toward the print head face. As a result, when a recording medium such as cut plain paper passes through the print head, paper dust adhering to the recording medium is affected by the electric field and may adhere to the print head face. This can cause problems such as ink not being properly ejected from the print head.

[0008] SUMMARY OF THE INVENTION An object of the present invention is to reduce the surface potential of the print belt, thereby reducing the possibility of problems occurring due to the influence of the electric field formed between the print belt and the recording head. [Means for solving the problem]

[0009] The above object can be achieved by an image forming apparatus according to the present invention. In summary, the present invention is an image forming apparatus comprising: a rotatable endless belt that carries and transports a sheet on a transport surface, the belt being made of a resin material and having a plurality of holes; a plurality of rollers that stretch the belt, the plurality of rollers including upstream and downstream rollers that form the transport surface, the upstream roller being disposed upstream of the upstream and downstream rollers in a direction of movement of the transport surface; a platen member that slidably supports the belt, and a platen unit that includes a holder that holds the platen member; a suction device that urges the belt toward the platen member and the sheet toward the belt by sucking air through the platen unit; a recording head that is disposed opposite the platen unit across the belt and that ejects a recording liquid onto the sheet transported by the belt; and a de-electrifying member that is made of a conductive material and is disposed so as to be in contact with the surface of the belt downstream of a position where the belt separates from the upstream roller and upstream of a position where the belt faces the recording head in a rotation direction of the belt, the de-electrifying member being electrically grounded to remove at least a portion of the charge on the belt. [Effects of the Invention]

[0010] According to the present invention, the surface potential of the print belt can be reduced, thereby reducing the possibility of problems occurring due to the influence of the electric field formed between the print belt and the recording head. [Brief explanation of the drawings]

[0011] [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 schematic perspective view of a part of the configuration of a print belt unit. [Figure 4] FIG. 2 is a perspective view of a recording head. [Figure 5] FIG. 2 is a front view showing a support structure for a recording head. [Figure 6] FIG. 2 is a front view showing a support structure for a recording head. [Figure 7] FIG. 2 is a perspective view showing a support structure for a recording head. [Figure 8] FIG. 2 is a perspective view showing a platen unit frame and a platen support member. [Figure 9] FIG. 2 is a perspective view of a platen support member. [Figure 10] FIG. 2 is a perspective view of a platen unit. [Figure 11] FIG. [Figure 12] 10A and 10B are schematic diagrams for explaining the penetration amount of the charge removing member. [Figure 13] FIG. 2 is a perspective view showing the vicinity of an end of the static eliminator. [Figure 14] FIG. 4 is a perspective view illustrating a mounting portion of the static eliminator. [Figure 15] FIG. 10 is a schematic cross-sectional view of another example of a print module. [Figure 16] FIG. 10 is a schematic cross-sectional view of another example of a print module. DETAILED DESCRIPTION OF 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] <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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] <Print Module> Next, the schematic configuration of the print module 2000 in the inkjet recording apparatus 1 of this embodiment will be described.

[0025] 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.

[0026] 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.

[0027] <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.

[0028] 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.

[0029] 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).

[0030] The first tension roller 21 is rotated by a driving force transmitted from a motor, which is a drive source provided by 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 response to 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. In this embodiment, the first, third, and fourth tension rollers 21, 23, and 24 are elastic rollers having a core metal and an elastic layer formed of an insulating elastic material (such as urethane rubber) provided around the core metal. In this embodiment, the second tension roller 22 is a metal roller formed of a conductive metal material. The number of rollers over which the print belt 25 is stretched is not limited to four, but may be two, three, or four or more.

[0031] Of the surfaces of the print belt 25 formed by the first to fourth tension rollers 21 to 24, a 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. Of the first and fourth tension rollers 21 and 24 that form the transport surface 25a, the fourth tension roller 24 is an upstream roller located upstream in the movement direction of the transport surface 25a, and the first tension roller 21 is a downstream roller located downstream in the movement direction. In other words, 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 surface of the print belt 25 as a belt support unit 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, described later) is positioned so as to be able to contact the print belt 25 over a range 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, travel direction) of the transport surface 25a of the print belt 25. Furthermore, in this embodiment, the platen unit 300 is positioned so as to be able to 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. Details of the platen unit 300 and the suction device 400 will be described later.

[0032] Next, a description will be given of the control of the running position in the width direction of the print belt 25 in the inkjet recording apparatus 1 of this embodiment.

[0033] In this embodiment, the first tension roller 21 is a drive roller as described above, and is supported so as to be movable in the direction of its rotation axis. The first tension roller 21 is moved in the direction of its rotation axis by a driving force from a driving source (motor) provided in the first movement mechanism 40a serving as a moving means. The second tension roller 22 is a tension roller as described above. The third tension roller 23 is a steering roller as described above. The third tension roller 23 is tilted by a driving force from a driving source provided in the tilting mechanism 50 serving as a tilting means. The fourth tension roller 24 is supported so as to be movable in the direction of its rotation axis. The fourth tension roller 24 is moved in the direction of its rotation axis by a driving force from a drive provided in the second movement mechanism 40b serving as a moving means.

[0034] First and second belt position sensors 30a and 30b are disposed near the first and fourth tension rollers 21 and 24, respectively, which are movable in the rotation axis direction, as belt position detection means for reading markers 35 provided at the rear end of the print belt 25 in the width direction. That is, the first belt position sensor 30a is disposed closer to the fourth tension roller 24 than the center of the conveying surface 25a in the direction of movement of the conveying surface 25a. The second belt position sensor 30b is disposed closer to the first tension roller 21 than the center of the conveying surface 25a in the direction of movement of the conveying surface 25a. The sheet S is attracted to the conveying surface 25a of the print belt 25 and conveyed integrally with the print belt 25. Therefore, by accurately determining the position of the conveying surface 25a of the print belt 25, image accuracy can be improved. For this purpose, the tension rollers that can move along their rotational axes to adjust the position of the print belt 25 are preferably the first and fourth tension rollers 21 and 24, which are the two tension rollers that form the conveying surface 25a. Furthermore, first and second belt position sensors 30a and 30b for detecting the position of the print belt 25 are preferably provided near the first and fourth tension rollers 21 and 24, respectively. The first tension roller 21 is moved along its rotational axis to adjust the running position of the print belt 25 in the width direction based on the position detection result of the print belt 25 by the second belt position sensor 30b. The fourth tension roller 24 is moved along its rotational axis to adjust the running position of the print belt 25 in the width direction based on the position detection result of the print belt 25 by the first belt position sensor 30a. By adjusting the running position of the print belt 25 in the width direction by each roller that forms the conveying surface 25a of the print belt 25, the entire conveying surface 25a can be positioned accurately.

[0035] Detection of the position of the print belt 25 by the first and second belt position sensors 30a and 30b will now be described. In this embodiment, circular holes with a diameter of approximately 1 mm in plan view are provided as markers 35 at the rear end of the print belt 25 in the width direction. The holes serving as markers 35 are provided around the entire circumference of the print belt 25 at approximately equal intervals with a center-to-center distance of approximately 6 mm in the rotation direction of the print belt 25. The holes serving as markers 35 are an example of a belt position detection shape serving as a belt position indicating means. The first and second belt position sensors 30a and 30b use a CIS (Contact Image Sensor) sensor to read the holes serving as markers 35, calculate the center positions of the holes, and use the calculation result as the detection result of the running position of the print belt 25 in the width direction. This detection result is input to a control unit (control circuit) (not shown) that controls the operation of the print module 2000 or the inkjet recording apparatus 1 and is used by the control unit to control the operation of the first and second movement mechanisms 40a and 40b. For example, by controlling the print belt 25 so that the widthwise positions detected by the first and second belt position sensors 30a, 30b are the same, it is possible to move (change) the widthwise running position of the print belt 25. Also, by controlling the print belt 25 so that the widthwise positions detected by the first and second belt position sensors 30a, 30b are shifted, it is possible to shift (incline) the transport direction of the print belt 25 with respect to the left and right direction.

[0036] <Recording head> Next, the recording head 100 in the inkjet recording apparatus 1 of this embodiment will be further described.

[0037] As shown in FIG. 4, the recording head 100 has a plurality of nozzle plates 103, each equipped with nozzles for ejecting ink, aligned in the longitudinal direction (front-rear direction) of the recording head 100. Positioning portions 101 are provided at both longitudinal ends of the recording head 100. Specifically, a first contact portion 101a is provided at the front end of the recording head 100, which is a recess with a conical slope that tapers upward. A second contact portion 101b is provided at the rear end of the recording head 100, which is a groove with two V-shaped flat surfaces whose width in the left-right direction tapers upward, and a third contact portion 101c is provided as a substantially horizontal flat surface. The second contact portion 101b is provided at a position opposite the first contact portion 101a in the front-rear direction, and the third contact portion 101c is provided to the left of the second contact portion 101b.

[0038] A first pin 107a extending in the longitudinal direction of the recording head 100 is provided at the rear end of the recording head 100. A second pin 107b and a third pin 107c extending in the longitudinal direction of the recording head 100 are provided at the front end of the recording head 100. The second pin 107b and the third pin 107c are aligned in the vertical direction.

[0039] The first abutment portion 101a and the second abutment portion 101b are precisely positioned so that the line connecting the centers of the first abutment portion 101a and the second abutment portion 101b in the left-right direction is parallel to the arrangement direction of the multiple nozzle plates 103 of the recording head 100.

[0040] <Support structure of the recording head, etc.> Next, a support structure for the recording head 100 in the inkjet recording apparatus 1 of this embodiment, an example of the operation of the recording head 100 to the print position, and a method of positioning the recording head 100 will be described.

[0041] Fig. 5 is a front view illustrating the support structure for the recording head 100. Fig. 5(a) shows the support structure for the recording head 100 when the recording head 100 is not arranged, and Fig. 5(b) shows the support structure for the recording head 100 when the recording head 100 is arranged.

[0042] As shown in FIG. 5A, a recording head support portion (support structure) 81 in a belt unit frame constituting the print belt unit 2200 is provided with positioning members 811 for positioning the multiple recording heads 100. The recording heads 100 are positioned by contacting the positioning members 811. In this embodiment, the positioning members 811 are spherical members (positioning balls). In this embodiment, three positioning members, namely, first, second, and third positioning members 811a, 811b, and 811c, are provided for each recording head 100 (FIGS. 6A and 6B). The front first positioning ball 811a is provided on the front recording head support portion 81a of the belt unit frame. The rear second and third positioning balls 811b and 811c are provided on the rear recording head support portion 81b of the belt unit frame. In this embodiment, the front recording head support portion 81a is located forward of the front end of the print belt 25 in the front-to-rear direction, and the rear recording head support portion 81b is located rearward of the rear end of the print belt 25 in the front-to-rear direction. Retaining holes (not shown) for retaining the positioning members 811a, 811b, and 811c are provided on the upper surface of each recording head support portion 81a and 81b. The positioning members 811a, 811b, and 811c are positioned in the front-to-rear and left-to-right directions by fitting into the retaining holes provided at predetermined positions. As shown in FIG. 5B, the recording head 100, which has been retracted upward relative to the positioning member 811, descends and abuts against the positioning member 811, thereby positioning the recording head 100. The positioning member 811 may be provided separately from the recording head support portion 81 and held by a positioning member holder with the retaining holes attached to the recording head support portion 81.

[0043] FIG. 6 is a front view illustrating an example of the operation of the recording head 100 to the print position and a method for positioning the recording head 100 (showing the recording head 100 in the print position). FIG. 6(a) shows the state as seen from the rear, and FIG. 6(b) shows the state as seen from the front. FIG. 7 is a perspective view illustrating an example of the operation of the recording head 100 to the print position and a method for positioning the recording head 100 (showing the state as seen from the downstream side in the transport direction of the transport surface 25a of the print belt 25). Note that the support and positioning configurations for multiple recording heads 100 are substantially the same, so the following description focuses on one recording head 100.

[0044] As the head holder 106 holding the recording head 100 descends, the recording head 100 descends from the retracted position toward the printing position shown in FIGS. 6A and 6B. Then, as shown in FIGS. 6A and 6B, the first contact portion 101a and the first positioning member 811a come into contact. The second contact portion 101b and the second positioning member 811b come into contact. The third contact portion 101c and the third positioning member 811c come into contact. At this time, the first pin 107a, the second pin 107b, and the third pin 107c of the recording head 100 remain supported by the first groove portion 161a, the second groove portion 162a, and the third groove portion 163a of the head holder 106, respectively. When descending from the retracted position toward the printing position, the recording heads 100 must be moved to a predetermined height. For this reason, a head position sensor (not shown) serving as a head position detection means is provided at a detection position where the recording head 100 descends from the retracted position to the print position. This head position sensor detects the positions of the multiple recording heads 100. Then, each of the multiple recording heads 100 is lowered by a predetermined intrusion amount from the point (detection position) where the position of the recording head 100 is detected by the head position sensor. In this embodiment, the print module 2000 can control the drive amount of a motor serving as a drive source provided in an elevation mechanism (not shown) serving as an elevation means for raising and lowering the recording head 100. This makes it possible to move the multiple recording heads 100 to a predetermined height at the print position and obtain the predetermined intrusion amount.

[0045] <Platen unit> Next, the platen unit 300 in the inkjet recording apparatus 1 of this embodiment will be further described. Fig. 8 is a perspective view showing the configuration of a portion of the platen unit 300 in this embodiment. Fig. 9 is a perspective view showing a platen support member 302, which will be described later and which constitutes the platen unit 300 in this embodiment. Fig. 10 is a perspective view of the platen unit 300 in this embodiment.

[0046] 8, 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, a right wall portion 313 and a left wall portion 314 extending in the front-rear direction, and a bottom wall portion 315 (the bottom wall portion 315 is indicated by a dashed line). 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.

[0047] 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 enhancing 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 and 100h (more specifically, their nozzles) in the movement direction of the transport surface 25a. As shown in FIG. 9 , the platen support member 302 is configured as 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).

[0048] 10, the platen unit 300 is provided with a plurality of platen members 303 that slidably support the print belt 25 and form the side surfaces of the upper portion of the platen unit frame 301. The platen members 303 are arranged at intervals (approximately equal intervals in this embodiment) between each other so as to extend substantially parallel to the left-right direction (the moving direction of the transport surface 25a) across substantially the entire area between the right wall portion 313 and the left wall portion 314. The platen members 303 may be arranged along the moving direction of the transport surface 25a of the print belt 25, or may be arranged at an angle (inclined) of, for example, approximately ±30° with respect to the moving direction of the transport surface 25a of the print belt 25. In this embodiment, the platen members 303 are made of a conductive metal material (such as stainless steel) and are formed of a wire (metal wire) with a circular cross section that is substantially perpendicular to the axial direction (longitudinal direction). The gaps between adjacent platen members 303 form multiple upper openings (air intake openings) 304 of the platen unit 300. In this embodiment, both left and right end portions of the platen members 303 are bent downward, and the front-rear and left-right positions of each platen member 303 are determined by positioning portions (not shown) provided on the right wall portion 313 and the left wall portion 314. The platen members 303 are placed on an upper end surface 321 (FIG. 9) of the platen support member 302, and when the print belt 25 is sucked by the suction device 400, they are supported by the platen support member 302, and their vertical position is determined.

[0049] 8, a bottom wall portion 315 of the platen unit frame 301 is provided with a lower opening (exhaust opening) 316. In this embodiment, a plurality of lower openings 316 are provided in the bottom wall portion 315. Note that substantially the entire lower portion (bottom) of the platen unit 300 may be formed as a lower opening.

[0050] 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.

[0051] In this embodiment, the platen unit 300 is supported by a belt unit frame that constitutes the print belt unit 2200.

[0052] 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.

[0053] In this embodiment, the upper end surface 321 of the platen support member (metal support plate) 302 is formed with a straightness (JIS B 0621) accuracy of 0.03 mm or more and 0.06 mm or less. 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 attached to the platen unit frame 301 by an operator while adjusting their height relative to the platen unit frame 301 (adjustment residual of approximately 0.05 mm). 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.

[0054] While the height is adjusted in this manner, the platen member (metal wire rod) 303 is placed on the upper end surfaces 321 of the nine platen support members 302 attached to the platen unit frame 301. Then, by sucking the print belt 25 with a suction device 400 located below the platen unit frame 301, the platen member 303 deforms to conform to the flatness of the upper end surfaces 321 of the platen support members 302. This allows the straightness of the platen member 303 itself to be ignored as a factor affecting the flatness of the transport surface 25a of the print belt 25, and only the wire diameter tolerance of the platen member 303 (0.02 mm in this embodiment) needs to be considered. To sufficiently increase the flatness of the transport surface 25a of the print belt 25, it is preferable that the wire diameter tolerance of the wire rod constituting the platen member 303 be 0.03 mm or less (or 0 mm).

[0055] In this embodiment, the wire diameter of the 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 multiple platen members 303 is approximately 6.0 mm. 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 print belt 25's transport surface 25a is approximately 700 mm. The wire diameter and pitch can be appropriately set in consideration of factors such as providing a sufficient upper opening 304 and ensuring sufficient flatness of the transport surface 25a of the print belt 25 when the print belt 25 is sucked by the suction device 400. While not limited thereto, the wire diameter of the wire constituting the platen member 303 is preferably approximately 2.0 mm or more and 5.0 mm or less. Although not limited thereto, the pitch of the multiple platen members 303 is preferably approximately 3.0 mm or more and 10 mm or less. The number of platen members 303 may be appropriately set so that they can come into contact with 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. The platen members 303 may have a coating made of a resin material on a base material made of wire.

[0056] With the above-described configuration of the platen unit 200, it is possible to efficiently achieve a wide range of flatness with high precision at low cost.

[0057] <Static electricity removal unit> Next, the generation of charge on the print belt unit 2200 and the configuration for eliminating charge on the print belt 25 in the inkjet recording apparatus 1 of this embodiment will be described.

[0058] As shown in FIG. 2, during the recording process (while the print belt 25 is rotating), the print belt 25 is attracted in the attraction direction B and rotates while sliding against the platen member 303 of the platen unit 300. Therefore, frictional charging occurs between the print belt 25 and the platen unit 300. The print belt 25 is also charged by contact (particularly peeling discharge) with the first, third, and fourth tension rollers 21, 23, and 24, which have insulating elastic layers. Meanwhile, the platen member 303, which is in contact with the print belt 25, is made of a conductive metal material. The second tension roller 22, which is also made of a conductive metal material, is also in contact with the print belt 25. The platen member 303 of the platen unit 300 is electrically grounded (connected to ground potential) via the platen unit frame 301. The second tension roller 22 is also electrically grounded. Therefore, along with the generation of frictional charging, charge leakage also occurs. That is, the surface potential of the print belt 25 appears as a residual charge due to the balance between frictional electrification and charge leakage. The value of this residual charge is approximately 500V or more and 2kV or less.

[0059] Although corona discharge often does not occur between the print belt 25 carrying such a charge and the recording head 100, a small electric field is generated. Therefore, when the sheet S passes through the recording head 100, paper dust adhering to the sheet S is affected by the electric field and may adhere to the face surface (surface of the nozzle plate 103) of the recording head 100. This may cause problems such as non-discharge, where ink is not properly ejected from the recording head 100.

[0060] Therefore, in this embodiment, the inkjet recording apparatus 1 has a charge eliminating means for eliminating (removing at least a part of) the charge from the print belt 25 as it approaches a position facing the recording head 100. This reduces the surface potential of the transport surface 25a of the print belt 25 during recording processing, preferably to 500 V or less. This will be explained in more detail below.

[0061] 2, the print module 2000 is provided with a charge-removing member 200 that contacts the print belt 25 to remove charge from the print belt 25. The charge-removing member 200 is provided to contact the outer circumferential surface (surface) of the print belt 25 at a charge-removing portion (charge-removal position) D in the rotational direction of the print belt 25 so as to remove charge from the print belt 25 as it enters position C opposite the recording head 100. The charge-removing portion D is located downstream of position E in the rotational direction of the print belt 25 where the print belt 25 separates from the fourth tension roller 24, and upstream of position C where the print belt 25 faces the recording head 100 (more specifically, the nozzles of the most upstream recording head 100a). The fourth tension roller 24 is the tension roller that forms the transport surface 25a of the print belt 25 and is located upstream in the direction of movement of the transport surface 25a. That is, in the movement direction of the transport surface 25a of the print belt 25, the static eliminator D is located downstream of a position E where the print belt 25 separates from the fourth tension roller 24 and upstream of a position C where the print belt 25 faces the recording head 100 (more specifically, the nozzles of the most upstream recording head 100a). In particular, in this embodiment, the static eliminator D is located within an area where the print belt 25 is supported by the platen unit 2200 in the movement direction of the transport surface 25a of the print belt 25. That is, in this embodiment, the static eliminator 200 is located at a position facing the platen unit 300 (more specifically, the platen member 303) with the print belt 25 sandwiched therebetween.

[0062] 11 is a perspective view showing the charge removing member 200 in this embodiment. The charge removing member 200 is arranged in a direction intersecting the moving direction of the transport surface 25a of the print belt 25. In particular, in this embodiment, the charge removing member 200 is arranged substantially parallel to a direction substantially perpendicular to the moving direction of the transport surface 25a of the print belt 25, i.e., substantially parallel to the width direction of the print belt 25 (substantially parallel to the front-to-rear direction). However, the charge removing member 200 only needs to be arranged in a direction intersecting the moving direction of the transport surface 25a of the print belt 25, and may be arranged at an angle (inclined) with respect to the direction substantially perpendicular to the moving direction of the transport surface 25a of the print belt 25.

[0063] The static eliminator 200 includes a brush portion 201 and a base portion (holder) 202 that holds the brush portion 201. The brush portion 201 is composed of a plurality of brush bristles arranged in a direction intersecting (substantially perpendicular in this embodiment) the moving direction of the conveying surface 25a of the print belt 25 so as to contact the outer peripheral surface (surface) of the print belt 25. The brush portion 201 is arranged so that its axis is aligned with the vertical direction. The base portion 202 is composed of a plate-like member whose longitudinal direction is aligned in a direction intersecting (substantially perpendicular in this embodiment) the moving direction of the conveying surface 25a of the print belt 25 and whose lateral direction is aligned with (substantially parallel in this embodiment) the vertical direction. Thus, in this embodiment, the static eliminator 200 is configured as a so-called static eliminator brush (static eliminator needle). The charge removal member 200 is fixed to a charge removal support member 501 by any fixing means such as fastening with screws, and this charge removal support member 501 is positioned relative to the print belt 25 and attached to a member constituting the print belt unit 2200. An example of the configuration of the attachment portion of the charge removal member 200 will be described later.

[0064] The brush bristles constituting the brush portion 201 of the static eliminator 200 are made of a conductive material. In this embodiment, the brush bristles are made of SUS, which is a conductive metal material. The base portion 202 of the static eliminator 200 and the static eliminator support member 501 are also made of a conductive metal material (such as SUS or aluminum). The static eliminator 200 is electrically grounded via its mounting portion.

[0065] The length of the bristles constituting the brush portion 201 of the static eliminator 200 (free length L1 from the end of the base portion 202 on the bristles side to the tip of the undeformed bristles; see FIG. 12 ) is not limited to, but is preferably, for example, 10 mm or more and 50 mm or less. The bristles' diameter is also not limited to, but is preferably, for example, 10 μm or more and 100 μm or less. The brush portion 201 of the static eliminator 200 is configured such that the bristles are densely arranged along the longitudinal direction of the base portion 202 and attached to the base portion 202. The spacing between the bristles (which may be an average value) may be as small as the bristles' diameter, or may be relatively large, such as 1 mm or more and 5 mm or less. In particular, in a configuration in which the platen member 303 made of wire is used as in this embodiment and the print belt 25 is sandwiched between the static eliminator 200 and the platen member 303, it is preferable that the spacing between the brush bristles (which may be an average value) is smaller than the pitch (spacing) between the plurality of platen members 303. This allows the print belt 25 to be more securely sandwiched between the brush bristles of the static eliminator 200 and the platen member 303, both of which are made of conductive materials, and the effect of neutralizing the print belt 25 can be more stable.

[0066] It is desirable for the charge-removing member 200 to be in reliable contact with the print belt 25. This is because the surface potential of the print belt 25 during recording without the charge-removing member 200 is relatively small, between 500 V and 2 kV. If this surface potential were relatively high, such as 5 kV, discharge would occur even without the charge-removing member 200 contacting the print belt 25, thereby lowering the surface potential of the print belt 25. In this embodiment, this is not the case, so the charge-removing member 200 is brought into contact with the print belt 25 to allow charge leakage. This allows the surface potential of the print belt 25 to be neutralized to a low value, preferably below 500 V, more preferably below 300 V. To ensure reliable contact between the charge-removing member 200 and the print belt 25, the penetration depth I of the brush portion 201 of the charge-removing member 200 into the print belt 25 is preferably between 0.5 mm and 3 mm. As shown in FIG. 12 , the penetration depth I is represented by the free length L1 of the brush bristles constituting the brush section 201 minus the distance L2 from the end of the base 202 on the brush bristles side to the outer circumferential surface of the print belt 25. The penetration depth I is represented by the value when the print belt 25 is sucked by the suction device 400 and attached to the platen unit 300. If the penetration depth I is too small, it may be difficult to ensure that the charge removal member 200 contacts the print belt 25. If the penetration depth I is too large, frictional charging due to sliding between the charge removal member 200 and the print belt 25 increases, making effective charge removal difficult. In this embodiment, the charge removal member 200 is attached while being adjusted to achieve the penetration depth I during assembly of the print module 2000 (more specifically, the print belt unit 2200).

[0067] In the width direction of the print belt 25, the width W1 of the region where the brush portion 201 of the static eliminator 200 is provided is preferably equal to or greater than the width of the region of the print belt 25 that can support the sheet S. In other words, in the width direction of the print belt 25, the region where the brush portion 201 of the static eliminator 200 is provided preferably includes at least the entire region of the print belt 25 that can support the sheet S.

[0068] In this embodiment, the width W1 of the region where the brush portion 201 of the charge removing member 200 is provided is shorter than the width W2 of the print belt 25. In this embodiment, the front end of the region where the brush portion 201 of the charge removing member 200 is provided is located at the same position as or further forward than the front end of the print belt 25 in the width direction of the print belt 25. Meanwhile, in this embodiment, the rear end of the region where the brush portion 201 of the charge removing brush 200 is provided is located further forward than the rear end of the print belt 25 (closer to the center in the width direction of the print belt 25) in the width direction of the print belt 25. This is for the following reason. FIG. 13 is a perspective view showing the vicinity of the rear end of the charge removing member 200 in this embodiment. As described above, a marker 35 is provided at the rear end of the print belt 25 in the width direction, and first and second belt position sensors 30a and 30b for reading this marker are provided facing the marker 35. Of the first and second belt position sensors 30a and 30b, the first belt position sensor 30a is disposed near the fourth tension roller 24, as described above. Therefore, from the perspective of miniaturizing the print belt unit 2200, the positions of the charge removal member 200 and the first belt position sensor 30a are close to or overlap with each other in the direction of movement of the conveyance surface 25a of the print belt 25. In this case, if the rear end of the area where the brush portion 201 of the charge removal member 200 is provided reaches the rear end of the print belt 25 in the width direction of the print belt 25, the brush portion 201 may enter the detection section of the first belt position sensor 30a. This may cause erroneous detection by the first belt position sensor 30a. Therefore, in this embodiment, the brush portion 201 is disposed as described above so that the area where the brush portion 201 of the charge removal brush 200 is provided does not overlap with the first belt position sensor 30a in the width direction of the print belt 25.

[0069] Next, an example of the configuration of the mounting portion of the static eliminator 200 will be described. Fig. 13 shows the mounting portion at the rear end of the static eliminator 200 in this embodiment. Fig. 14(a) is an enlarged perspective view of a portion of Fig. 13, and Fig. 14(b) is a view similar to Fig. 14(a) showing a state in which a mounting member 503, which will be described later, has been removed. Here, the configuration of the rear end will be described, but the configuration of the front end can also be similar.

[0070] In this embodiment, the static eliminator 200 is fixed to a static eliminator support member 501, which is attached to a recording head support portion 81b of a belt unit frame that constitutes the print belt unit 2200. The recording head support portions 81 (81a, 81b) are formed with high precision to position the recording head 100. Therefore, attaching the static eliminator 200 to the recording head support portion 81 makes it easy to control the penetration amount I with high precision. A columnar support receiving portion 502 is provided at one end of the static eliminator support member 501. The support receiving portion 502 is inserted into a support hole 503a serving as a static eliminator support provided in a mounting member 503, whereby the static eliminator support member 501 is supported by the mounting member 503. The mounting member 503 is fixed to the recording head support portion 81b with a screw 504 serving as a fastener. As described above, in this embodiment, the static eliminator 200 can be attached while adjusting the penetration amount I of the brush portion 201 of the static eliminator 200 relative to the print belt 25 so that it is within a predetermined range. In this embodiment, as shown in FIGS. 14(a) and 14(b), the static eliminator 200 is attached while adjusting the penetration amount I by appropriately interposing shims 505, which are adjustment members, between the attachment member 503 and the print head support portion 81b. The penetration amount I can be adjusted by using shims 505 of different thicknesses or by changing the number of shims 505 of the same or different thicknesses. The shims 505 are an example of an adjustment unit that adjusts the position of the attachment member 503 to change the distance between the static eliminator 200 (static eliminator support member 501) and the outer circumferential surface of the print belt 25. In this embodiment, the shims 505 are formed of a conductive metal material (such as stainless steel or iron).

[0071] In this embodiment, SUS is used as the material for the brush bristles that make up the brush portion 201 of the static eliminator 200, but the material is not limited to this. For example, amorphous metal fibers, organic conductive fibers (such as acrylic fibers made conductive with a conductive material), or fibers made by coating organic fibers (such as nylon fibers) with a conductive material (such as conductive carbon) may also be used.

[0072] In addition, in this embodiment, the print belt 25 is made of resin (e.g., PET), but the print belt 25 may also be made of conductive resin, which can further reduce the surface charge.

[0073] In this embodiment, the platen member 303 is made of a wire material, but is not limited to this. For example, the platen member 303 may be made of a plate-like member (platen plate) made of a conductive metal material (such as SUS). In this case, the plate-like platen member may be provided with a plurality of openings for the suction device 400 to suck the print belt 25.

[0074] Furthermore, the platen member 303 made of wire is preferably arranged along the movement direction of the transport surface 25a of the print belt 25, as this makes it easier to improve the flatness of the transport surface 25a of the print belt 25. However, without being limited to this, the platen member 303 made of wire may be arranged along a direction intersecting the movement direction of the transport surface 25a of the print belt 25. In this case, the platen support member 302 may be arranged along the movement direction of the transport surface 25a of the print belt 25.

[0075] In this embodiment, the charge eliminating member 200 is disposed opposite the platen unit 300 across the print belt 25, but this is not limiting. FIG. 15 is a schematic cross-sectional view showing a partial configuration of another example of a print module 2000 in which the charge eliminating member 200 is disposed differently from the above-described embodiment. In the configuration shown in FIG. 15 , as in the above-described embodiment, the charge eliminating unit D is located downstream of position E where the print belt 25 separates from the fourth tension roller 24 in the movement direction of the transport surface 25a of the print belt 25 and upstream of position C where the charge eliminating unit D faces the print head 100 (more specifically, the nozzles of the most upstream print head 100a). However, in the configuration shown in FIG. 15 , the platen unit 300 is not located opposite the charge eliminating member 200 across the print belt 25. Considering the space required for disposing the charge eliminating member 200, even when the charge eliminating member 200 is disposed in the position shown in FIG. 15 , the same effect as in the above-described embodiment can be obtained.

[0076] Furthermore, although attaching the static eliminator 200 to the recording head support part 81 has the above-mentioned advantages, the location where the static eliminator 200 is attached is not limited to the recording head support part 81. For example, the static eliminator 200 may be fixed to the housing of a sensor unit that is disposed opposite the conveyance surface 25a of the print belt 25 and that detects floating of the sheet S, etc.

[0077] Furthermore, the static elimination member is not limited to being constituted by a static elimination brush (static elimination needle), but may be constituted by, for example, a film-like member, etc. In this case, too, it is preferable to insert the static elimination member into the print belt 25, as described above.

[0078] The adjusting unit for adjusting the penetration amount I is not limited to the shim 505. For example, the adjusting unit may be provided with an adjusting mechanism that moves the mounting member 503 so as to change the distance between the static eliminator 200 (static eliminator support member 501) and the outer circumferential surface of the print belt 25.

[0079] Here, an insulator (insulating material) typically has a volume resistivity of 10 10 Ω cm or more, 1018 A conductor (conductive material) is a substance with a volume resistivity of 10 -4 However, if sufficient effect can be obtained from the viewpoint of suppressing the charging of the print belt 25 or from the viewpoint of eliminating the charge on the print belt 25, a material with a higher volume resistivity (for example, 10 10 Even if the resistance is less than Ω·cm, it can be considered to be conductive.

[0080] 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 a sheet S on a conveying surface 25a, the belt (print belt) 25 being made of a resin material and having a plurality of holes (suction holes) 25b; a plurality of rollers that tension the belt 25, the belt 25 being an upstream roller (fourth tension roller) 24 and a downstream roller (first tension roller) 21 that form the conveying surface 25a, the upstream roller 24 being one of the upstream rollers 24 and the downstream roller 21 being arranged upstream in the moving direction of the conveying surface 25a; a platen member 303 that slidably supports the belt 25; and a holder (platen unit frame) 301 that holds the platen member 303. the platen unit 300, a suction device 400 that urges the belt 25 toward the platen member 303 and urges the sheet S toward the belt 25 by sucking air through the platen unit 300; a recording head 100 that is disposed opposite the platen unit 300 across the belt 25 and that ejects a recording liquid onto the sheet S transported by the belt 25; and a discharging member 200 that is made of a conductive material and is disposed so as to come into contact with the surface of the belt 25 downstream of a position E where the belt 25 separates from the upstream roller 24 in the rotation direction of the belt 25 and upstream of a position C where the belt 25 faces the recording head 100, and that is electrically grounded to remove at least a portion of the charge on the belt 25. In this embodiment, the image forming apparatus 1 has a plurality of recording heads 100a to 100h arranged along the movement direction of the conveying surface 25a, and the de-ionizing member 200 is arranged in the rotation direction of the belt 25 so as to contact the surface of the belt 25 downstream of the position E where the belt 25 separates from the upstream roller 24 and upstream of the position opposite the recording head 100a that is arranged most upstream among the plurality of recording heads 100a to 100h.

[0081] In this embodiment, the static eliminator 200 has a brush portion 201 made of a plurality of brush bristles made of a conductive material, arranged along a direction intersecting the movement direction of the conveying surface 25a, and configured to contact the surface of the belt 25. In this embodiment, the image forming apparatus 1 has a mounting member 503 that mounts the static eliminator 200 to a member (recording head support portion) 81 that determines the position of the recording head 100. In this embodiment, the image forming apparatus 1 also has an adjustment unit (shim) 505 that adjusts the position of the mounting member 503 to change the distance between the static eliminator 200 and the surface of the belt 25. In this embodiment, the static eliminator 200 is positioned opposite the platen unit 300 across the belt 25. The static eliminator 200 is preferably positioned so as to penetrate the belt 25 by 0.5 mm or more and 3 mm or less.

[0082] In this embodiment, the platen unit 300 includes a plurality of platen members 303 made of a conductive material, extending along the movement direction of the conveying surface 25a, and arranged at intervals in a direction intersecting the movement direction of the conveying surface 25a, and a plurality of platen support members 302 held by a holder 301, each supporting the platen members 303, and arranged at intervals along the movement direction of the conveying surface 25a. In this case, when the static eliminator 200 has the brush portion 201 and is positioned opposite the platen unit 300 across the belt 25, it is preferable that the spacing between the brush bristles be smaller than the spacing between the platen members 303. It is also preferable that the platen member 303 be made of a wire material with a wire diameter of 2 mm or more and 5 mm or less, that the wire diameter tolerance of the platen member 303 be 0.03 mm or less, and that the straightness of a surface 321 of the platen support member 302 that abuts against the platen member 303 be 0.06 mm or less. It is also preferable that at least one platen support member 302 is provided at a position facing the recording head 100a arranged at the most upstream position in the moving direction of the transport surface 25a and the recording head 100h arranged at the most downstream position.

[0083] Furthermore, when the de-ionizing member 200 has the brush portion 201, the belt 25 has markers at its widthwise ends for detecting the widthwise position of the belt 25, and the image forming apparatus 1 has a sensor (belt position sensor) 30a for reading the markers 35, which is arranged opposite the widthwise end of the belt 25 downstream of the position E where the belt 25 separates from the upstream roller 24 in the rotation direction of the belt 25 and upstream of the position C where the belt 25 faces the recording head 100, it is preferable that the de-ionizing member 200 does not have the brush portion 201 at a position that overlaps with the sensor 30a in the widthwise direction of the belt 25. In addition, when the image forming device 1 has multiple recording heads 100a to 100h arranged along the movement direction of the conveying surface 25a, the sensor 30a is arranged opposite the end of the belt 25 in the width direction, downstream of the position E where the belt 25 separates from the upstream roller 24 in the rotation direction of the belt 25, and upstream of the position opposite the recording head 100a arranged most upstream among the multiple recording heads 100a to 100h.

[0084] As described above, according to this embodiment, the surface potential of the print belt 25 can be reduced, thereby reducing the possibility of problems occurring due to the influence of the electric field formed between the print belt 25 and the recording head 100.

[0085] [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.

[0086] FIG. 16 is a schematic cross-sectional view showing a partial configuration of a print module 2000 in an inkjet recording apparatus 1 of this embodiment. In the first embodiment, the inkjet recording apparatus 1 had a static eliminator 200, which was configured as a static eliminator brush (static eliminator needle). In contrast, in this embodiment, the inkjet recording apparatus 1 has an ionizer 600 as the static eliminator. The ionizer (static eliminator, static eliminator) 600 can be any ion generating device. Ionizer 600 ion generating methods include, for example, a "corona discharge" type that irradiates ions generated by causing a corona discharge in a discharge needle, a "soft X-ray" type that irradiates weak X-rays, a "radiation" type that irradiates alpha rays or beta rays, and an "ultraviolet" type that irradiates ultraviolet rays. In this embodiment, a corona discharger using a corona discharge method was used as the ionizer 600 because of its relatively low cost. The position of the static eliminator D is the same as in the first embodiment.

[0087] When the static eliminator 200 is brought into contact with the print belt 25 as in the first embodiment, the static eliminator 200 (brush portion 201) may be worn down due to an increase in cumulative usage. Therefore, the static eliminator 200 may need to be replaced periodically. In contrast, the ionizer 600 can be used without the need for replacement. However, the ionizer 600 may need to be cleaned periodically to remove dirt such as paper dust. Furthermore, the ionizer 600 is often larger than the static eliminator 200. In view of these factors, the ionizer 600 can be used as an alternative to the static eliminator 200. [Explanation of symbols]

[0088] 25 Printed Belt 100 recording head 200 Antistatic material 300 Platen Unit 301 Platen unit frame 302 Platen support member 303 Platen member 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, the belt being made of a resin material and having a plurality of holes; a plurality of rollers over which the belt is stretched, the plurality of rollers including upstream and downstream rollers that form the conveying surface, the upstream roller being disposed upstream of the upstream and downstream rollers in a moving direction of the conveying surface; a platen unit including a platen member that slidably supports the belt and a holder that holds the platen member; a suction device that suctions air through the platen unit to urge the belt toward the platen member and urge the sheet toward the belt; 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; a charge removing member made of a conductive material, arranged in contact with the surface of the belt downstream of a position where the belt separates from the upstream roller and upstream of a position where the belt faces the recording head in the rotation direction of the belt, and electrically grounded to remove at least a portion of the charge on the belt; An image forming apparatus comprising:

2. a plurality of the recording heads arranged along the moving direction of the transport surface; 2. The image forming apparatus according to claim 1, wherein the de-electrification member is arranged so as to contact the surface of the belt downstream of the position where the belt separates from the upstream roller in the direction of rotation of the belt and upstream of the position where the belt faces the most upstream of the multiple recording heads.

3. 3. The image forming apparatus according to claim 1, wherein the de-ionizing member has a brush portion consisting of a plurality of brush bristles made of a conductive material, arranged along a direction intersecting the direction of movement of the conveying surface, and contacting the surface of the belt.

4. 3. The image forming apparatus according to claim 1, further comprising a mounting member for mounting the charge removing member to a member for determining the position of the recording head.

5. 5. The image forming apparatus according to claim 4, further comprising an adjustment unit that adjusts the position of the attachment member so as to change the distance of the charge removing member from the surface of the belt.

6. 3. The image forming apparatus according to claim 1, wherein the charge removing member is disposed at a position facing the platen unit across the belt.

7. 3. The image forming apparatus according to claim 1, wherein the charge removing member is disposed so as to have an intrusion amount of 0.5 mm or more and 3 mm or less relative to the belt.

8. The platen unit includes: a plurality of the platen members, each made of a conductive material, extending along the direction of movement of the conveying surface and arranged at intervals in a direction intersecting the direction of movement of the conveying surface; a plurality of platen support members held by the holder and arranged at intervals along the moving direction of the conveying surface, each of the platen support members supporting the platen member; 3. The image forming apparatus according to claim 1, further comprising:

9. the static eliminator has a brush portion including a plurality of brush bristles made of a conductive material, arranged along a direction intersecting the moving direction of the conveying surface, and contacting the surface of the belt; the static eliminator is disposed at a position facing the platen unit across the belt, 9. The image forming apparatus according to claim 8, wherein the intervals between the brush bristles are smaller than the intervals between the platen members.

10. The platen member is made of a wire having a diameter of 2 mm or more and 5 mm or less, The wire diameter tolerance of the platen member is 0.03 mm or less, 9. The image forming apparatus according to claim 8, wherein the straightness of the surface of said platen support member that abuts against said platen member is 0.06 mm or less.

11. a plurality of the recording heads arranged along the moving direction of the transport surface; 9. The image forming apparatus according to claim 8, wherein at least one platen support member is provided at a position facing the recording head arranged at the most upstream position in the movement direction of the transport surface and the recording head arranged at the most downstream position.

12. the static eliminator has a brush portion including a plurality of brush bristles made of a conductive material, arranged along a direction intersecting the moving direction of the conveying surface, and contacting the surface of the belt; the belt has a marker at an end in the width direction for detecting the position of the belt in the width direction, the image forming apparatus has a sensor for reading the marker, the sensor being disposed facing an end of the belt in a width direction downstream of a position where the belt separates from the upstream roller and upstream of a position where the belt faces the recording head in a rotation direction of the belt; 2. The image forming apparatus according to claim 1, wherein the charge removing member does not have the brush portion at a position overlapping the sensor in the width direction of the belt.

13. a plurality of the recording heads arranged along the moving direction of the transport surface; The image forming apparatus according to claim 12, characterized in that the sensor is arranged opposite the end of the belt in the width direction, downstream of the position where the belt separates from the upstream roller in the rotation direction of the belt, and upstream of the position where the belt faces the most upstream of the multiple recording heads.

Images