Image forming apparatus

Abstract

The present invention provides an image forming apparatus capable of improving the print quality of single-sided or double-sided printing. [Solution] The image forming apparatus 100 includes a first heating unit 41 that heats the first surface P1 of the recording medium P, and a second heating unit 42 that heats the second surface P2 of the recording medium P. The image forming apparatus 100 also includes a printing cylinder 7 that transports the recording medium P with the first surface P1 and the second surface P2 heated, and an image forming unit 10 that forms an ink image on the first surface P1 of the recording medium P transported by the printing cylinder 7. Furthermore, the image forming apparatus 100 includes a fixing unit 20 that fixes the ink image formed in the image forming unit 10, and a cooling unit 50 that cools the recording medium P with the ink image fixed in the fixing unit 20.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus. Background Art

[0002] Conventionally, there has been known an image forming apparatus that reverses paper serving as a recording medium and performs printing on both sides thereof (see Patent Document 1). Prior Art Documents Patent Documents

[0003] Patent Document 1 Japanese Unexamined Patent Application Publication No. 2024-133906 Summary of the Invention Problem to be Solved by the Invention

[0004] It is generally known that when the temperature of a recording medium is high and the printed surface comes into contact with the paper discharge cylinder or reversing cylinder of an image forming apparatus, gloss unevenness occurs in the print on the surface due to the unevenness and shape of these paper discharge cylinders and reversing cylinders. In particular, in an image forming apparatus that performs printing on both sides of a recording medium, wax may precipitate due to the thermal history caused by the print pattern of the first side, causing gloss unevenness or differences in ink spreading on the second side. In such cases, there has been a problem that favorable print quality cannot be obtained due to density and chromaticity unevenness. Therefore, further improvement is required in order to improve print quality.

[0005] The present invention has been made in view of such a background, and an object of the present invention is to provide an image forming apparatus capable of improving the print quality on one side or both sides. Means for Solving the Problem

[0006] The above object of the present invention is solved by the following configuration. That is, (1) The image forming apparatus comprises a first heating unit for heating the first surface of a recording medium, a second heating unit for heating the second surface of the recording medium, and a printing cylinder for transporting the recording medium with the first and second surfaces heated. The image forming apparatus also comprises an image forming unit for forming an ink image on the first surface of the recording medium transported by the printing cylinder, a fixing unit for fixing the ink image formed in the image forming unit, and a cooling unit for cooling the recording medium with the ink image fixed in the fixing unit.

[0007] (2) Furthermore, the image forming apparatus described in (1) includes an inversion unit for inverting the recording medium cooled by the cooling unit. The second heating unit heats the second surface of the recording medium inverted by the inversion unit, and the image forming unit forms an ink image on the second surface heated by the second heating unit. The fixing unit fixes the ink image formed in the image forming unit. The cooling unit cools the recording medium on which the ink image fixed in the fixing unit has been formed.

[0008] (3) The image forming apparatus described in (1) also includes a transport unit that transports the recording medium from the paper feeding unit. The first heating unit heats the first surface of the recording medium transported from the transport unit.

[0009] (4) The image forming apparatus according to (3), wherein the second heating unit heats the second surface of the recording medium that has been heated by the first heating unit.

[0010] (5) The image forming apparatus according to (1), wherein the cooling unit cools the recording medium on which the ink image has been fixed in the fixing unit so that the temperature of the recording medium is in the range of 10 degrees Celsius or more and 30 degrees Celsius or less.

[0011] (6) The image forming apparatus according to (5), wherein the cooling unit has a fan that blows air by rotation, and the direction of the air blown from the fan is directed onto the recording medium on which the ink image has been fixed in the fixing unit, thereby adjusting the temperature of the recording medium to be in the range of 10 degrees Celsius or more and 30 degrees Celsius or less.

[0012] (7) The cooling unit has a fan that blows air onto the recording medium on which the ink image has been fixed in the fixing unit. The direction of the air blown from the fan is adjusted according to the airflow, as described in (1).

[0013] (8) The cooling unit has a fan that blows air onto the recording medium on which the ink image has been fixed in the fixing unit. The image forming apparatus according to (1) further comprises a windbreak plate that is positioned adjacent to the cooling unit upstream or downstream in the transport direction of the recording medium to prevent air from the fan from entering between the printing cylinder and the recording medium.

[0014] (9) The image forming apparatus according to (1), wherein the cooling unit adjusts the cooling capacity according to the transport speed of the recording medium.

[0015] (10) The cooling unit has a cold air generating unit that generates cold air at a temperature lower than the temperature inside the housing in which the image forming unit is provided. The cooling unit has a cold air blowing unit that blows the cold air generated by the cold air generating unit onto the recording medium on which the ink image is formed, as described in (1).

[0016] (11) The image forming apparatus according to (10), wherein the cooling unit has a storage unit that temporarily stores the cold air blown by the cold air blowing unit adjacent to the recording medium on which the ink image is formed, and the storage unit has an opening formed on the surface facing the recording medium.

[0017] (12) The image forming apparatus according to (11), wherein the cooling section has an intermediate air blowing section in the middle of the path to the storage section.

[0018] (13) The image forming apparatus according to (11), wherein the cooling section has an opening air supply section in part of the storage section.

[0019] (14) The image forming apparatus according to (13), wherein the opening blower has a nozzle opening having a flat nozzle shape that blows out compressed air toward the surface of the recording medium, and the nozzle opening forms a gap along the width direction of the recording medium.

[0020] (15) The image forming apparatus according to (14), wherein the compressed air is sent to the storage portion via a compressed air path that is a separate system from a cold air path for cold air generated by the cold air generating portion.

[0021] (16) The image forming apparatus according to (10), wherein the cooling portion is provided between the fixing portion and a discharge portion that discharges the recording medium having the ink image fixed thereon.

[0022] (17) The image forming apparatus according to (2), wherein the cooling portion is provided between the fixing portion and the reversing portion.

[0023] (18) The image forming apparatus according to (10), wherein the cold air generating portion is installed outside a housing provided with the image forming portion.

[0024] (19) The image forming apparatus according to (10), wherein the cold air generating portion changes the temperature of the generated cold air in accordance with the temperature of the recording medium.

[0025] (20) The image forming apparatus according to (10), wherein the cold air generating portion changes the temperature of the generated cold air in accordance with an ink amount of the ink image adhering to the recording medium.

[0026] (21) The image forming apparatus according to (13), wherein the opening blower changes the intensity of the blown air generated thereby in accordance with the temperature of the recording medium.

[0027] (22) The image forming apparatus according to (13), wherein the opening blower changes the intensity of the blown air generated thereby in accordance with an ink amount of the ink image adhering to the recording medium. Effects of the Invention

[0028] According to the present invention, an image forming apparatus is provided that can improve the print quality on one side or both sides. [Brief explanation of the drawing]

[0029] [Figure 1] This is a side view showing the overall configuration of an image forming apparatus according to the first embodiment of the present invention. [Figure 2] This is a side view illustrating the configuration of the printing unit that prints onto the recording medium. [Figure 3] This is a front view of the cooling unit. [Figure 4] This is a cross-sectional view taken along the line IV-IV in Figure 3, illustrating the configuration of the cooling unit. [Figure 5] This is a cross-sectional view illustrating the configuration of the cooling section of an image forming apparatus according to the second embodiment. [Figure 6] This graph shows the relationship between the temperature of the recording medium and the image gloss, based on the properties of the ink. [Figure 7] This graph shows the relationship between temperature and ink viscosity, based on the properties of the ink. [Figure 8] This table shows the relationship between the temperature of the recording medium and image quality. [Figure 9] This is a plan view showing the first surface of an example of a recording medium from which good printing was obtained. [Figure 10] This is a plan view showing the first surface of another example of a recording medium in which good printing was obtained. [Figure 11] This is an example of a recording medium printed on a portion of its first surface, and is a plan view showing the first surface. [Figure 12] This is a plan view showing the second side of a recording medium printed on the first side. [Modes for carrying out the invention]

[0030] Preferred embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. In this specification and drawings, components having substantially the same function are denoted by the same reference numerals to avoid redundant explanation. Also, for explanatory purposes, the direction along the horizontal plane perpendicular to the paper transport direction F is referred to as the width direction W. Furthermore, in Figures 1 and 2, the recording medium P being printed is not shown, and only the direction of the transport path is indicated by arrows.

[0031] The embodiments for carrying out the present invention are described in detail below with reference to the figures. Figure 1 shows an image forming apparatus 100 according to this embodiment. The image forming apparatus 100 includes a paper feeding unit 2 having a paper feeding tray 4 that supplies a recording medium (also called media) P, such as paper, from the upstream side along the transport direction F of the printed material. The image forming apparatus 100 also includes a transport unit 5 that transports the recording medium P from the paper feeding tray 4 of the paper feeding unit 2 to a printing unit 1 provided inside the housing. Furthermore, a paper discharge unit 3, which has a paper discharge tray 6 for placing printed materials, is connected downstream along the transport direction F of the printing unit 1.

[0032] The image forming apparatus 100 can print an ink image using ink on at least one of either the first surface P1, which is one side of the recording medium P, or the second surface P2, which is the back side of the first surface P1.

[0033] In other words, the printing unit 1 comprises a temperature-controlled supply cylinder 33 located downstream of the transport unit 5, and an image forming unit 10. Of these, the temperature-controlled supply cylinder 33 is equipped with a first heating unit 41 of the heating unit 40, which will be described later. The first heating unit 41 directs a heater towards the first surface P1 or the second surface P2 of the recording medium P that has been transported to the printing unit 1 to heat and adjust the temperature. The recording medium P, which has been heated to a temperature suitable for printing, is transported from the temperature-controlled supply cylinder 33 to the printing cylinder 7. In the first embodiment, the printing cylinder 7 transports the recording medium P, whose first surface P1 and second surface P2 have been heated by rotation. As shown in the graph in Figure 6, when the temperature of the recording medium P is high, the change in image gloss is large. In other words, when the temperature of the recording medium P is high, the sensitivity to image gloss is high. For this reason, controlling the temperature of the recording medium P in the first heating unit 41 is important to ensure image quality. Furthermore, the image forming unit 10 uses an inkjet method to perform inkjet printing on the surface of the recording medium P that has been transported from the transport unit 5 to the printing cylinder 7, thereby forming an ink image.

[0034] As shown in Figure 2, the image forming unit 10 has multiple heads that eject ultraviolet (UV) curable inks of various colors, such as Y (yellow), M (magenta), C (cyan), and K (black). As shown in the graph in Figure 7, the ink is ejected from the head in a gel-like state with high temperature and low viscosity. When it adheres to the surface of the recording medium P, the ink temperature rapidly decreases and its viscosity increases, temporarily fixing it in place. This allows the ink image formed by the ink to be maintained in high quality until the next UV irradiation process.

[0035] Furthermore, the printing unit 1 of the embodiment includes a fixing unit 20, a reversing unit 30, a heating unit 40, and a cooling unit 50. The fixing unit 20 has a UV irradiation unit 21. A scanner 22 is also provided downstream of the fixing unit 20. Specifically, the UV irradiation unit 21 is positioned perpendicular to the recording medium P of the printing cylinder 7 over a predetermined width.

[0036] Furthermore, the scanner 22 is located near the downstream side of the UV irradiation unit 21. The scanner 22 has the function of inspecting the image quality of the ink image formed in the image forming unit 10 immediately after UV irradiation when it has hardened or dried. In addition, a temperature sensor for measuring the temperature of the recording medium P may be provided adjacent to the scanner 22. The temperature sensor can be connected to the control unit and configured to use the detected temperature data to control the cooling capacity of the cooling unit 50.

[0037] The fixing unit 20, configured in this way, irradiates the recording medium P supported on the printing cylinder 7 with UV light from the UV irradiation unit 21 according to the characteristics of the ink. The ink image printed with the ink on the surface of the recording medium P is hardened or dried by the irradiation with UV light. In this way, the fixing unit 20 can fix the ink image formed in the image forming unit 10 to the surface of the recording medium P.

[0038] As shown in Figure 2, downstream of the UV irradiation unit 21, a first cooling device 60 and a second cooling device 70 are provided as cold air generating units that constitute the cooling unit 50. The first cooling device 60 is located immediately downstream of the UV irradiation unit 21 and between it and the paper discharge unit 3, which serves as the discharge unit. The second cooling device 70 is located between the paper discharge unit 3 and the reversing unit 30.

[0039] Of these, the first cooling device 60 is provided with a cylindrical air passage connected to a first air conditioner (not shown). At the end of the air passage is a first air outlet 61 that opens toward the printing cylinder 7. The first air outlet 61 blows air onto the recording medium P supported on the printing cylinder 7, cooling the ink image fixed to the surface of the recording medium P to a desired temperature. The air conditioner may be provided outside the housing. The first cooling device 60 cools the recording medium P, on which the ink image has been formed by fixing the ink in the fixing unit 20, so that its temperature is within the range of 10 degrees Celsius or more and 30 degrees Celsius or less. The control unit can also control the cooling capacity of the first air conditioner based on the temperature data detected by the temperature sensor. This allows the first cooling device 60 to more efficiently and easily adjust the temperature of the recording medium P to be within the range of 10 degrees Celsius or more and 30 degrees Celsius or less.

[0040] For example, as shown in Figure 8, in the relationship between the ink used in the first embodiment and the recording medium P, when the temperature of the recording medium P falls below 9 degrees Celsius, a decrease in image quality occurs due to insufficient temperature rise. Furthermore, when the temperature of the recording medium P is in the range of 10 degrees Celsius to 30 degrees Celsius (room temperature), the image quality is very good and is ranked as A. Moreover, when the temperature of the recording medium P is 31 degrees Celsius or higher, the image quality deteriorates and is ranked as B.

[0041] The first cooling device 60, configured in this way, blows air from the first air outlet 61 onto the recording medium P on which the ink image has been fixed in the fixing unit 20, thereby cooling the recording medium P on which the ink image has been formed. As a result, the ink image is cooled to a temperature at which no uneven gloss occurs. In this case, the control unit may adjust the cooling capacity by increasing or decreasing the amount of air blown from the cooling unit 50 according to the temperature of the recording medium P detected using a temperature sensor or the like. Furthermore, the cooling unit 50 may be configured to adjust its cooling capacity according to the transport speed of the recording medium P.

[0042] Furthermore, in the first embodiment, the first cooling device 60 has a first windbreak plate 67 positioned between the first air outlet 61 and the image forming unit 10. The first windbreak plate 67 prevents the air blown out from the first air outlet 61 from flowing towards the image forming unit 10. This prevents air from entering between the recording medium P and the surface of the printing cylinder 7. As a result, the recording medium P supported by the printing cylinder 7 will not be lifted or curled up by the airflow. Consequently, the focus of the scanner 22 will not be misaligned. As shown in Figure 2, the first windbreak plate 67 in the first embodiment is located adjacent to the upstream of the first cooling device 60. The second windbreak plate 77 in the first embodiment is located adjacent to the upstream of the second cooling device 70. However, the location of the windbreak plates is not limited to these. For example, they may be located adjacent to the downstream of the first cooling device 60, and they may be installed at any location as long as they can prevent the airflow from entering between the printing cylinder 7 and the recording medium P.

[0043] Here, recording media P on which only the first side P1 is printed, or recording media P on which both sides of the first side P1 and the second side P2 have already been printed, are sent from the printing unit 1 to the downstream paper output unit 3, where necessary binding and other processes are performed, and then they are discharged into the paper output tray 6.

[0044] Figure 9 shows the first surface P1 of a conventional recording medium P as the printing result of the discharged printed material. In this type of system, the recording medium P makes uneven contact with any of the discharge cylinders located in the path of the paper discharge unit 3, resulting in differences in the amount of cooling in different areas. This caused problems such as the occurrence of linear gloss unevenness 91 in the ink image of the first surface P1.

[0045] In the first embodiment of the image forming apparatus 100, the first cooling device 60 of the cooling unit 50 is located immediately downstream of the UV irradiation unit 21 and adjusts the temperature of the recording medium P to be the same as room temperature, in the range of 10 degrees Celsius or more and 30 degrees Celsius or less. Therefore, uneven gloss does not occur in the ink image on the first side, improving print quality.

[0046] Meanwhile, the recording medium P, on which printing has been done on the first side P1, is transported to the reversal unit 30 for printing on the second side P2 on the reverse side. The inversion unit 30 inverts the recording medium P, which has been cooled by the first cooling device 60. As shown in Figure 2, the reversing unit 30 has a plurality of first reversing cylinders 31 and second reversing cylinders 32. The first reversing cylinder 31 is provided with a first claw portion 34 that engages with the printing cylinder 7. Furthermore, a second claw portion 35 is provided between the second reversing cylinder 32 and the temperature control supply cylinder 44.

[0047] Furthermore, the first reversing cylinder 31, which faces the second claw portion 35 to avoid the claws, is provided with a comb-like relief. The space between the claws can be opened and closed, and when closed, it is possible to grip and hold one end of the recording medium P from both sides. When the recording medium P is supplied from the temperature-controlled supply cylinder 33 to the printing cylinder 7, the claw portion of the temperature-controlled supply cylinder 33 is open. Then, when the recording medium P is transferred from the second reversing cylinder 32 to the temperature-controlled supply cylinder 33, the claw portion of the temperature-controlled supply cylinder 33, which was open, is closed to receive the recording medium P from the second reversing cylinder 32.

[0048] Furthermore, depending on the circumference ratio resulting from the difference in diameter dimensions of each cylinder, for example, when the printing cylinder 7 rotates 120° counterclockwise in the direction shown in Figure 1, the second reversing cylinder 32 rotates 1 full turn in the same direction, and the temperature control supply cylinder 33 rotates 180° clockwise. The claws of each cylinder open and close at opposing positions, allowing the recording medium P to be transferred in conjunction with each other.

[0049] The second reversing cylinder 32 of the reversing unit 30 is equipped with a reversing swing mechanism, a switchback mechanism, and the like (not shown). The reversing swing mechanism is provided at an equidistant distance from the outer surface of the first reversing cylinder 31 and the outer surface of the temperature control supply cylinder 33, respectively, and can reverse the front and back sides of the recording medium P. In the reversing swing mechanism, the recording medium P, guided from the first reversing cylinder 31 to the outer surface of the second reversing cylinder 32, has its rear end gripped by the claw portion of the second reversing cylinder 32 in the transport direction. The second reversing cylinder 32 then changes its rotation direction in the opposite direction.

[0050] As a result, the recording medium P is inverted and switched back, and the rear end portion of the recording medium P in the transport direction during the first image formation operation of the first surface P1 becomes the leading end portion in the transport direction during the second image formation operation of the second surface P2. The configuration of the reversal unit 30 is not limited to the switchback and reversal swing mechanism of this embodiment. Any configuration is acceptable in terms of the shape, quantity, and material of the components, as long as it can reverse the front and back sides of the recording medium P cooled by the cooling unit 50.

[0051] Furthermore, the image forming apparatus 100 is provided with a second heating unit 42 that heats the second surface P2 of the recording medium P that has been inverted by the inversion unit 30. The recording medium P, heated in the second heating unit 42, is returned to the printing cylinder 7 via the temperature control supply cylinder 33.

[0052] Furthermore, the image forming apparatus 100 of this embodiment includes a third heating unit 43 between the temperature control supply cylinder 33 of the printing cylinder 7 and the image forming unit 10. This allows the image forming apparatus 100 to reheat the recording medium P that has been cooled by the cooling unit 50. When the temperature of the recording medium P is raised to a predetermined temperature in the second heating section 42 or the third heating section 43, the image forming section 10 can perform inkjet printing on the second surface P2 of the recording medium P that has been transported to the printing cylinder 7 to form an ink image with good print quality.

[0053] The first cooling device 60 blows air from the first air outlet 61 onto the recording medium P, which has had the ink image fixed in the fixing unit 20. The recording medium P, which has ink printed on both sides, the first side P1 and the second side P2, in the image forming unit 10, is cooled to a temperature at which the ink image does not become uneven in gloss. The recording medium P is then sent from the printing unit 1 to the downstream paper discharge unit 3, and after necessary binding and other processes are performed, it is discharged into the paper discharge tray 6.

[0054] In the first embodiment of the image forming apparatus 100, a second cooling device 70 constituting a cooling unit 50 is provided between the part of the printing cylinder 7 of the printing unit 1 to which the paper discharge unit 3 is connected and the reversing unit 30. As shown in Figure 2, the second cooling device 70 has a storage section 72 consisting of a hollow chamber, and a second air outlet 71 which is connected to an air conditioner and serves as a cold air blowing section that blows cold air into the storage section 72. Of these, the storage section 72 has an opening 73 formed on the surface facing the printing cylinder 7 that blows cooling air towards the recording medium P supported on the printing cylinder 7.

[0055] Furthermore, the storage unit 72 is adjacent to the recording medium P on which the ink image is formed and temporarily stores cold air. An intermediate air blower, such as a blower fan, may be included in the path to the storage unit 72.

[0056] Furthermore, as shown in Figure 3, a horizontally elongated duct 75 is arranged in the internal space of the storage section 72. The horizontally elongated duct 75 is provided in a cylindrical shape along the width direction W of the recording medium P. The end of the compressed air duct 74, which serves as a compressed air path connected to the compressor, is inserted into the horizontally elongated duct 75. As a result, the compressed air from the compressor is sent to the storage unit 72 via a separate compressed air duct 74, which is separate from the cold air path for the cold air generated by the air conditioner.

[0057] Furthermore, the horizontally elongated duct 75 has a nozzle opening 76 along its longitudinal direction. The nozzle opening 76 has a flat nozzle shape that blows compressed air in layers toward the surface of the recording medium P. The nozzle opening 76 forms an air knife-like gap along the vertical direction of the paper surface of the recording medium P, that is, along the width direction of the recording medium P.

[0058] As shown in Figure 4, the nozzle opening 76 of the horizontally elongated duct 75 is provided facing the surface of the recording medium P through the opening 73 of the storage section 72.

[0059] Furthermore, the compressed air is configured to be sent to the horizontally elongated duct 75 in the storage unit 72 via a compressed air duct 74, which is a separate compressed air path from the cold air path of the cold air generated by the second air conditioner.

[0060] In the second cooling device 70 configured in this way, cold air blown from the air conditioner through the second air outlet 71 is stored in the internal space of the storage section 72. Furthermore, compressed air from the compressor is sent to a horizontal duct 75 inside the storage section 72 via a compressed air duct 74, which is a separate system from the second air outlet 71.

[0061] Compressed air is blown in layers toward the surface of the recording medium P from the nozzle opening 76 formed in the horizontally elongated duct 75. The nozzle opening 76 has a flat nozzle shape. As a result, the flow velocity of the compressed air is further increased and blown out from the opening 73. At this time, the cool air from the air conditioner that has been stored in the internal space of the storage unit 72 is accelerated by the Coanda effect and blown out together with the compressed air blown out from the nozzle opening 76.

[0062] Therefore, while supported on the printing cylinder 7, the second cooling device 70 can remove heat that cannot be removed by the first cooling device 60 by blowing cool air onto the recording medium P. Thus, the ink image fixed to the surface of the recording medium P can be cooled to a desired temperature.

[0063] Furthermore, the strength of the airflow generated by the nozzle opening 76 may be varied according to the temperature of the recording medium P. Also, the strength of the airflow generated by the nozzle opening 76 may be varied according to the amount of ink in the ink image attached to the recording medium P. This further improves the cooling efficiency of the recording medium P.

[0064] Furthermore, as shown in Figure 2, a second windbreak plate 77 is positioned between the part of the printing cylinder 7 to which the paper discharge section 3 is connected and the opening 73 of the second cooling device 70, serving as one of the windbreak plates. The second windbreak plate 77 covers the area so that the air blown out from the opening 73 does not flow between the recording medium P and the surface of the printing cylinder 7. This prevents air from entering the space between the recording medium P and the surface of the printing cylinder 7. Therefore, the recording medium P supported by the printing cylinder 7 does not lift and curl up due to the airflow. As a result, the print quality by the image forming unit 10 can be improved.

[0065] In this way, the second cooling device 70 can blow cold air towards the recording medium P as needed, such as when the temperature of the recording medium P has not decreased to the desired temperature by the first cooling device 60. This ensures that the temperature of the recording medium P, on which the ink image has been fixed by the fixing unit 20, is cooled to a range of 10 degrees Celsius or more and 30 degrees Celsius or less.

[0066] In conventional designs, as shown in Figure 10, the claw sections that transfer paper from the printing cylinder 7 to the paper discharge section 3 or to the reversing section 30 have a problem where uneven gloss occurs between the part of the first surface P1 that is in contact with the first reversing cylinder 31 and the part that is not in contact (comb-shaped). This is due to the temperature difference caused by the claw relief gap.

[0067] In the first embodiment of the image forming apparatus 100, in addition to the first cooling device 60 of the cooling unit 50, a second cooling device 70 can direct a faster-speed cold air onto the recording medium P compared to the first cooling device 60. Therefore, if the temperature of the recording medium P has not yet dropped to the desired temperature, or if the temperature of the recording medium P is rising again due to the residual heat of the printing cylinder 7, cold air can be blown towards the recording medium P as needed. This ensures that the recording medium P is reliably cooled to a desired temperature range of 10 degrees Celsius or more and 30 degrees Celsius or less. Therefore, gloss unevenness does not occur in the ink image on the first side P1, and print quality can be improved.

[0068] Furthermore, as shown in Figure 11, when an ink image 95 is printed on the first surface P1, conventionally, if the recording medium P is inverted in the inversion unit 30 without cooling and printing is performed again on the second surface P2 as shown in Figure 12, problems such as uneven gloss, density, and chromaticity 96 occur in the ink image 95 area.

[0069] In the first embodiment of the image forming apparatus 100, the nozzle opening 76 of the second cooling device 70 allows cold air to be blown onto the recording medium P along the width direction of the recording medium P through the gap. As a result, the temperature of the entire surface of the recording medium P can be lowered, and the portion of the second surface P2 corresponding to the ink image 95 can be reliably cooled. Therefore, the ink image on the second side P2 will not exhibit unevenness in gloss, density, or chromaticity, thereby improving print quality.

[0070] Figure 5 shows an image forming apparatus according to the second embodiment. In the second embodiment, a third cooling device 80 is used as one of the cooling units, instead of the second cooling device 70 of the first embodiment. Note that the description of parts that are the same as or equivalent to the second cooling device 70 will be omitted, and the description will focus on the differences.

[0071] The third cooling device 80 has a fan 85 as an open air blower that blows air by rotation. In the second embodiment, the fan 85 is provided in an opening 83 formed in a part of the storage section 82.

[0072] In the image forming apparatus of the second embodiment configured in this way, the rotation of the fan 85 allows cool air to be blown onto the recording medium P stored in the storage section 82, thereby removing heat. As a result, the ink image fixed to the surface of the recording medium P can be cooled to a desired temperature.

[0073] Other configurations and effects are in accordance with the image forming apparatus 100 of the first embodiment described above.

[0074] Although embodiments and modifications thereof of the present invention have been described above, these embodiments and modifications are merely illustrative and do not limit the technical scope of the present invention. The present invention can take various other embodiments, and furthermore, various modifications such as omissions and substitutions can be made without departing from the spirit of the present invention. These embodiments and their variations are included in the scope and spirit of the invention as described herein, and are included in the scope of the invention and its equivalents as described in the claims.

[0075] For example, in the image forming apparatus 100 of the first embodiment, the first cooling device 60 is located immediately downstream of the UV irradiation unit 21 and between the UV irradiation unit and the paper discharge unit 3. However, the apparatus is not limited to this configuration, and a second cooling device 70 may be placed in the position of the first cooling device 60. In other words, the cooling device of the cooling unit 50 can be of any shape, quantity, arrangement position, or combination, as long as it cools the recording medium P on which the ink image has been fixed in the fixing unit 20. [Explanation of symbols]

[0076] 100 Image forming apparatus 1 Printing section 2 Paper feed section 3. Paper output section 5. Conveying section 7 Printing Cylinder 10 Image forming unit 20 Fixing section 21 UV irradiation section 30 Reversal section 40 Heating section 41 First heating section 42 Second heating section 50 Cooling section 60 First cooling device 61 First ventilation port 67 First windbreak plate 70 Second cooling device 71 Second ventilation port 72 Storage section 73 Opening

Claims

1. A first heating unit that heats the first surface of the recording medium, A second heating unit that heats the second surface of the recording medium, A printing cylinder that transports the recording medium with the first and second surfaces heated, An image forming unit that forms an ink image on the first surface of the recording medium conveyed by the printing cylinder, A fixing unit for fixing the ink image formed in the image forming unit, An image forming apparatus comprising a cooling unit for cooling the recording medium on which the ink image has been fixed in the fixing unit.

2. The system includes a reversing unit that inverts the recording medium cooled by the aforementioned cooling unit, The second heating unit heats the second surface of the recording medium that has been inverted by the inversion unit. The image forming unit forms an ink image on the second surface heated by the second heating unit. The image forming apparatus according to claim 1, wherein the fixing unit fixes the ink image formed in the image forming unit, and the cooling unit cools the recording medium on which the ink image fixed in the fixing unit is formed.

3. It includes a transport unit that transports the recording medium from the paper feeding unit, The first heating unit receives the recording medium that was transported from the transport unit. The image forming apparatus according to claim 1, wherein the first surface is heated.

4. The image forming apparatus according to claim 3, wherein the second heating unit heats the second surface of the recording medium that has been heated by the first heating unit.

5. The image forming apparatus according to claim 1, wherein the cooling unit cools the recording medium on which the ink image has been fixed in the fixing unit so that the temperature of the recording medium is in the range of 10 degrees Celsius or more and 30 degrees Celsius or less.

6. The cooling unit has a fan that blows air by rotation, The image forming apparatus according to claim 5, wherein the air blown from the fan is directed onto the recording medium on which the ink image has been fixed in the fixing unit, and the temperature of the recording medium is adjusted to be in the range of 10 degrees Celsius or more and 30 degrees Celsius or less.

7. The cooling unit has a fan that blows air onto the recording medium on which the ink image has been fixed in the fixing unit. The image forming apparatus according to claim 1, wherein the direction of airflow from the fan is adjusted according to the airflow volume.

8. The cooling unit has a fan that blows air onto the recording medium on which the ink image has been fixed in the fixing unit. The image forming apparatus according to claim 1, further comprising a windbreak plate positioned adjacent to the upstream or downstream of the cooling unit in the transport direction of the recording medium, which prevents air from the fan from entering between the printing cylinder and the recording medium.

9. The image forming apparatus according to claim 1, wherein the cooling unit adjusts its cooling capacity according to the transport speed of the recording medium.

10. The image forming apparatus according to claim 1, wherein the cooling unit comprises a cold air generating unit that generates cold air at a temperature lower than the temperature inside the housing in which the image forming unit is provided, and a cold air blowing unit that blows the cold air generated by the cold air generating unit onto the recording medium on which the ink image is formed.

11. The image forming apparatus according to claim 10, wherein the cooling unit has a storage unit that temporarily stores the cold air blown by the cold air blowing unit adjacent to the recording medium on which the ink image is formed, and the storage unit has an opening formed on the surface facing the recording medium.

12. The image forming apparatus according to claim 11, wherein the cooling section has an intermediate air blowing section in the middle of the path to the storage section.

13. The image forming apparatus according to claim 11, wherein the cooling section has an open air blowing section in a part of the storage section.

14. The image forming apparatus according to claim 13, wherein the opening air blower has a nozzle opening with a flat nozzle shape that blows compressed air in layers toward the surface of the recording medium, and the nozzle opening has a gap in the vertical direction.

15. The image forming apparatus according to claim 14, wherein the compressed air is sent to the storage unit via a compressed air path separate from the cold air path of the cold air generated in the cold air generation unit.

16. The image forming apparatus according to claim 1, wherein the cooling unit is provided between the fixing unit and the discharge unit for discharging the recording medium on which the ink image has been fixed.

17. The image forming apparatus according to claim 2, wherein the cooling unit is provided between the fixing unit and the inversion unit.

18. The image forming apparatus according to claim 10, wherein the cold air generating unit is installed outside the housing on which the image forming unit is provided.

19. The image forming apparatus according to claim 10, wherein the cold air generation unit varies the temperature of the cold air it generates according to the temperature of the recording medium.

20. The image forming apparatus according to claim 10, wherein the cold air generating unit varies the temperature of the cold air it generates according to the amount of ink in the ink image attached to the recording medium.

21. The image forming apparatus according to claim 13, wherein the opening air blower varies the strength of the generated airflow according to the temperature of the recording medium.

22. The image forming apparatus according to claim 13, wherein the opening air blower varies the strength of the generated airflow according to the amount of ink in the ink image attached to the recording medium.

Images