Image forming device

Abstract

To provide an ink jet image formation apparatus which can reduce dropping of ink that rises to a side surface of a recording head in the time of wiping.SOLUTION: An image formation apparatus comprises: a recording head 31 provided with a nozzle region N in which a plurality of ink discharge ports open downward; and a wiper 67 which wipes the ink discharge ports by being in contact with the nozzle region N and moving in a prescribed wiping direction. A head attachment part 41 along the wiping direction is provided so as to protrude to the outside at a position higher than the nozzle region N on a side surface 31a of the recording head 31 along the wiping direction. The head attachment part 41 includes: an outside part 43 whose surface has higher water repellent property than the side surface 31a; and an inside part 45 which is provided inside the outside part 43 and whose surface has lower water repellent property than the outside part 43.SELECTED DRAWING: Figure 4B

Description

[Technical Field]

[0001] The present invention relates to an inkjet image forming apparatus equipped with a wiper for wiping ink ejection ports of a recording head. [Background technology]

[0002] Inkjet image forming apparatuses are equipped with wipers that wipe the ink ejection ports of the nozzles in the recording head. The wiper wipes the ink ejection ports by moving in one direction from a wiping start position to a wiping end position while contacting the nozzle area where the ink ejection ports open.

[0003] During this wiping operation, the wiped ink may spill over from the wiper and wrap around the side of the recording head, rising up along the side and adhering to it, resulting in a buildup. Repeated wiping increases the amount of ink that accumulates, causing the accumulated ink to fall onto the sheet, resulting in image defects and contamination inside the machine.

[0004] Therefore, Patent Document 1 discloses an inkjet image forming apparatus equipped with a head cover that covers the side portions of the recording head. The side portions and surface of the head cover are treated with a water-repellent coating. As a result, even if ink gets onto the side portions of the recording head, the ink is repelled by the head cover, reducing the adhesion of ink to the side portions of the recording head. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-310476 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the inkjet recording apparatus described in Patent Document 1, a considerable gap is formed between the head cover and the recording head, and the wiped ink can get into this gap. If a large amount of ink gets in, the ink may fall, causing the above-mentioned image defects and contamination inside the apparatus.

[0007] SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to provide an ink jet type image forming apparatus that can reduce the amount of ink that rises up onto the side surface of the recording head and falls down during wiping. [Means for solving the problem]

[0008] In order to solve the above problem, the image forming apparatus of the present invention comprises a recording head having a nozzle area in which a plurality of ink ejection ports open downward, and a wiper that wipes the ink ejection ports by contacting the nozzle area and moving in a predetermined wiping direction, and is characterized in that a head mounting portion that extends along the wiping direction is provided on a side of the recording head that is along the wiping direction, at a position higher than the nozzle area, so as to protrude outward, and the head mounting portion has an outer portion whose surface has higher water repellency than the side, and an inner portion that is provided inside the outer portion and has a surface that has lower water repellency than the outer portion.

[0009] In the image forming apparatus of the present invention, a lower end surface of the head mounting portion may be substantially parallel to the nozzle region.

[0010] In the image forming apparatus of the present invention, the side surface of the lower end surface of the head mounting portion may be the inner portion.

[0011] In the image forming apparatus of the present invention, the surface of the inner portion may have lower water repellency than the side surface.

[0012] In the image forming apparatus of the present invention, the head mounting portions may be provided on both sides of the recording head. [Effects of the Invention]

[0013] According to the present invention, ink that rises up onto the side of the recording head during wiping is easily retained in the corner between the lower surface of the inner part of the head mounting part and the side of the recording head, preventing the retained ink from falling and preventing image defects and contamination inside the machine. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a front view schematically illustrating an internal structure of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view showing a line head in the image forming apparatus according to the embodiment of the present invention. [Figure 3] FIG. 2 is a plan view showing a cleaning unit in the image forming apparatus according to one embodiment of the present invention. [Figure 4A] 1 is a side view showing a recording head in an image forming apparatus according to an embodiment of the present invention. [Figure 4B] 1 is a front view showing a recording head in an image forming apparatus according to an embodiment of the present invention; [Figure 5] FIG. 10 is a front view showing a modified example of the recording head in the image forming apparatus according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] An image forming apparatus according to an embodiment of the present invention will now be described with reference to the accompanying drawings.

[0016] The image forming apparatus 1 will be described with reference to Fig. 1. Fig. 1 is a front view showing a schematic internal configuration of the image forming apparatus 1 (during image formation). Fr, Rr, L, and R shown in each drawing indicate the front, rear, left, and right directions of the image forming apparatus 1.

[0017] The image forming apparatus 1 includes a paper feed unit 3, an inkjet image forming unit 5, and a transport path 7 along which sheets S fed by the paper feed unit 3 are transported through the image forming unit 5 to an outlet (not shown). The paper feed unit 3 includes a paper feed cassette 9 that stores sheets S, and a paper feed device 11 that feeds sheets S from the paper feed cassette 9 to the transport path 7. The image forming unit 7 includes a head unit 13, a transport unit 15, and a maintenance unit 17.

[0018] First, we will explain the head unit 13. The head unit 13 has four line heads 21 corresponding to four colors of ink (yellow, magenta, cyan, and black). The four line heads 21 are arranged in parallel along the conveying direction (leftward) of the sheet S along the conveying path 7.

[0019] Next, each line head 21 will be described with reference to Fig. 2. Fig. 2 is a perspective view showing the line head 21.

[0020] Each line head 21 has three recording heads 31 and a head base 33 on which the three recording heads 31 are supported.

[0021] Each recording head 31 has a rectangular parallelepiped shape that is long in the front-rear direction, and is equipped with a large number of nozzles arranged in the front-rear and left-right directions. The ejection openings of each nozzle open on the bottom surface of the recording head 31. Each nozzle ejects ink downward from the ejection openings by an ink ejection method such as a piezoelectric or thermal method. The area where the ejection openings open on the bottom surface of the recording head 31 is referred to as the nozzle area N.

[0022] The head base 33 is a flat member that is long in the front-rear direction. The three recording heads 31 are supported by the head base 33 and arranged in a staggered pattern along the front-rear direction. Each recording head 31 is supported so that its nozzle region N protrudes downward from the bottom surface of the head base 33. The recording head 31 is made of a metal such as SUS. The configuration of the recording head 31 will be described later.

[0023] Referring again to Figure 1, the head unit 13 is supported so that it can be raised and lowered between a printing position (see solid line in Figure 1) where image formation is performed and a retracted position (see dashed double-dashed line in Figure 1) where it is retracted above the printing position to perform maintenance and protection of the head unit 13.

[0024] Next, the transport unit 15 will be described with reference to Fig. 1. The transport unit 15 includes a transport belt 51 that is wound around rollers that are spaced apart in the left-right direction and travels in a circulating manner counterclockwise in Fig. 1. The upper running surface of the transport belt 51 forms part of the transport path 7 that passes through the image forming unit 5. When the head unit 13 descends to the printing position, the nozzle area N of each recording head 31 of the four line heads 21 approaches the upper running surface of the transport belt 51.

[0025] During image formation, the head unit 13 descends to the printing position. Furthermore, the sheet S fed by the paper feed unit 3 is transported to the image forming unit 5 along the transport path 7. In the image forming unit 5, ink is ejected from the recording heads 31 of each line head 21 based on image data onto the sheet S transported by the transport belt 51, and an image is formed on the sheet S.

[0026] Next, the maintenance unit 17 will be described with reference to Fig. 1. The maintenance unit 17 includes a cap unit 61 and a wipe unit 63.

[0027] The cap unit 61 has caps corresponding to each recording head 31 of each line head 21 of the head unit 13. The cap unit 61 is supported so as to be movable in the left-right direction between a retracted position on the left side of the head unit 13 and a capping position below the head unit 13 that has risen to the retracted position. After the cap unit 61 has been moved to the capping position, the head unit 13 is lowered, whereby each cap is pressed against the head base 33 and covers the nozzle forming surface N of each recording head 31.

[0028] The wiping unit 63 will be described with reference to FIGS. 1 and 3. FIG. 3 is a plan view showing the wiping unit 63. The wiping unit 63 includes four wiper carriages 65 corresponding to the four line heads 21 of the head unit 13. The wiper carriages 65 are supported so as to be movable in the front-rear direction. The wiper carriage 65 includes three wipers 67 corresponding to the three recording heads 31 of the line head 21, and a tray 69 for collecting ink wiped by each wiper 67. The wipers 67 may be, for example, blades made of an elastic material, or blades or rollers made of an elastic material with cloth attached around them. The wiping unit 63 is supported so as to be movable in the left-right direction between a retracted position on the left side of the head unit 13 and a wiping position below the head unit 13 when raised to the retracted position.

[0029] After the wiping unit 63 is moved to the wiping position, the head unit 13 is lowered to bring the wiper 67 into contact with the nozzle region N, and each wiper carriage 65 is moved from a front wiping start position (see solid line in FIG. 3) to a rear wiping end position (see two-dot chain line in FIG. 3), thereby causing the nozzle region N of each recording head 31 (see FIG. 2) of each line head 21 to be wiped by the wiper 67 of the wiper carriage 65. The ink wiped off by the wiper 67 falls into a tray 69 and is collected through a collection port (not shown). The direction in which the wiper carriage 65 moves is referred to as the wiping direction X. In this embodiment, the wiping direction X is from front to rear.

[0030] Next, the recording head 31 will be described with reference to Figures 4A and 4B. Figure 4A is a view of the recording head 31 as seen from the left side, and Figure 4B is a view of the recording head 31 as seen from the front side.

[0031] A head mounting portion 41 is formed on the side surface 31a of the nozzle region N of the recording head 31 along the front-rear direction, i.e., the wiping direction X. The head mounting portion 41 may be provided on only one side surface 31a, but it is preferable to provide it on both side surfaces 31a. The head mounting portion 41 has a vertically elongated rectangular parallelepiped cross section when viewed from the front-rear direction, and is formed at a position higher than the nozzle region N. The fact that the head mounting portion 41 is formed at a position higher than the nozzle region N means that the side surface 31a is present between the head mounting portion 41 and the nozzle region N. The distance between the head mounting portion 41 and the nozzle region N is preferably 0.03 to 2 mm, more preferably 0.05 to 1 mm, and particularly preferably 0.1 to 0.5 mm.

[0032] As shown in FIG. 4B, the head mounting portion 41 has an outer portion 43 and an inner portion 45 provided between the outer portion 43 and the side surface 31a of the recording head 31. The outer portion 43 is formed of a material (e.g., silicone resin or fluorine-based resin) that has higher water repellency than the recording head 31. In other words, the contact angle of ink with respect to the surface of the outer portion 43 is larger than the contact angle of ink with respect to the side surface 31a of the recording head 31. Alternatively, only the surface of the outer portion 43 may be coated with a material that has high water repellency. As an example, the thickness of the outer portion 43 is 0.2 to 0.3 mm.

[0033] The inner portion 45 is formed of a material (e.g., PET or acrylic double-sided tape) that has lower water repellency than the outer portion 43. In other words, the contact angle of ink with respect to the surface of the outer portion 43 is larger than the contact angle of ink with respect to the surface of the inner portion 45. Preferably, the inner portion 45 is formed of a material that has lower water repellency than the recording head 31. In other words, the contact angle of ink with respect to the surface of the inner portion 45 is smaller than the contact angle of ink with respect to the side surface 31a of the recording head 31. Furthermore, it is preferable that the inner portion 45 is formed of a material that has a smaller contact angle with ink. As an example, the thickness of the inner portion 45 is 0.1 mm.

[0034] The inner portion 45 is fixed to the side surface 31a of the recording head 31 without any gaps by, for example, double-sided tape, adhesive, heat fusion, etc., and the outer portion 43 is fixed to the side surface of the inner portion 45 without any gaps by, for example, double-sided tape, adhesive, heat fusion, etc.

[0035] Wiping in the image forming apparatus 1 having the above configuration will be described with reference to FIGS. 4A and 4B. Wiping is performed, for example, after purging ink from the nozzles of the recording head 31. During wiping, as described above, the wiper carriage 65 (see FIG. 3) of the wiping unit 63 moves in the wiping direction X, and the wiper 67 wipes the nozzle region N. The wiper 67 is pressed against the nozzle region N with a predetermined pressure, and therefore curves downstream in the wiping direction X, as shown in FIG. 4A. Furthermore, because the width of the wiper 67 is slightly wider than the width of the nozzle region N, when pressed against the nozzle region N, both ends of the wiper 67 protrude above the nozzle region N, as shown in FIG. 4B.

[0036] The ink L wiped off by the wiper 67 is pushed up (rising up) from both ends of the wiper 67 onto the side surface 31a of the recording head 31. The rising ink L eventually reaches the head mounting portion 41. Because the inner portion 45 of the head mounting portion 41 has lower water repellency than the side surface 31a of the recording head 31, the ink L fits into the inner portion 45 and is held in the corner between the side surface 31a of the recording head 31 and the inner portion 45. On the other hand, the outer portion 43 has higher water repellency than the side surface 31a of the recording head 31 and the inner portion 45 of the recording head 31, so it easily repels the ink L. As a result, the ink L is held in the corner between the side surface 31a of the recording head 31 and the lower surface of the inner portion 45 by intermolecular forces between both surfaces.

[0037] As is clear from the above description, according to the present invention, the ink L that rises to the side surface 31a of the recording head 31 during wiping is retained at the corner between the lower surface of the head mounting portion 41 and the side surface 31a of the recording head 31. In particular, the inner portion 45 of the head mounting portion 41 has lower water repellency than the side surface 31a of the recording head 31, and therefore is more compatible with the ink L. That is, it is easier to retain the ink L. On the other hand, the outer portion 43 has higher water repellency than the side surface 31a of the recording head 31 and the inner portion 45, and therefore is more likely to repel the ink L. Therefore, even if the amount of retained ink L increases and reaches below the outer portion 43, the outer portion 43 has difficulty retaining the ink L, so the amount of retained ink L does not increase beyond a certain level. In this way, a constant amount of ink L that rises during wiping can always be retained. Note that, with each wiping cycle, ink L is included in the rising and retained ink L, but the retained amount is limited to a certain amount, so the rising ink L and the retained ink L are constantly circulated to replace each other.

[0038] Furthermore, as described above, the ink is held by the intermolecular force between the side surface 31a of the recording head 31 and the underside of the inner portion 45, so the held ink L is unlikely to fall under its own weight. Therefore, even if vibrations are applied to the recording head 31 during image formation, the held ink L is prevented from falling, preventing image defects and contamination inside the machine.

[0039] A thinner inner portion 45 is preferable because it reduces the amount of ink L that is retained. On the other hand, a thicker outer portion 43 provides a stronger ink L repelling force, more reliably preventing an increase in the amount of ink L retained. In this embodiment, by setting the thickness of the inner portion 45 to 0.03 to 0.5 mm, or even 0.05 to 0.2 mm, it is possible to reduce the amount of ink L retained while ensuring the ink L retaining force. Furthermore, by setting the thickness of the outer portion 43 to 0.2 to 0.3 mm, it is possible to reduce the amount of ink L retained while ensuring the ink L retaining force.

[0040] Furthermore, the lower end surface of the head attachment portion 41 is approximately parallel to the nozzle region N. It is preferable that the lower end surface be within ±10 degrees, or even substantially parallel, to the nozzle region N in the wiping direction X. It is also preferable that the lower end surface be within ±30 degrees, or even within ±15 degrees, or especially substantially parallel to the nozzle region N in a direction perpendicular to the wiping direction X. By doing so, it is possible to reduce the amount of ink L held while ensuring the force that holds the ink L.

[0041] The side surface 31a of the bottom surface of the head mounting portion 41 forms an inner portion 45. That is, the water repellency differs at the apex of the corner formed by the side surface 31a of the recording head 31 and the bottom surface of the head mounting portion 41. By doing so, the amount of ink L held can be reduced while ensuring the force to hold the ink L.

[0042] The head mounting portion 41 may also be a separate member that can be separated from the recording head 31. In this case, the angle between the side surface 31a of the recording head 31 and the bottom surface of the head mounting portion 41 becomes sharp, making it easier to hold a small amount of ink L.

[0043] Next, a modified example of the present invention will be described with reference to Fig. 5. Fig. 5 is a view of the recording head 31 as seen from the front side. The outer part 43 of the head mounting part 41 may be formed by coating the outer surface of the inner part 45 with a water-repellent material (for example, fluorine-based resin). Even in this modified example, a certain amount of ink L that rises up during wiping can be held in the corner between the side surface 31a of the recording head 31 and the inner part 45.

[0044] Although the present invention has been described with reference to specific embodiments, the present invention is not limited to the above embodiments, and those skilled in the art may modify the above embodiments without departing from the scope and spirit of the present invention. [Explanation of symbols]

[0045] 1. Image forming device 31 Recording head 41 Head mounting part 43 Outer part 45 inner part 67 Wiper

Claims

1. a recording head provided with a nozzle area in which a plurality of ink ejection ports are open downward; a wiper that comes into contact with the nozzle area and moves in a predetermined wiping direction to wipe the ink ejection openings, a head mounting portion extending in the wiping direction is provided on a side surface of the recording head in a position higher than the nozzle region, the head mounting portion extending in the wiping direction so as to protrude outward; The head mounting portion has an outer portion whose surface has higher water repellency than the side surface, and an inner portion that is provided between the side surface and the outer portion, is fixed to the side surface without any gaps, and has a surface that has lower water repellency than the outer portion.

2. 2. The image forming apparatus according to claim 1, wherein a lower end surface of the head mounting portion is substantially parallel to the nozzle area.

3. 3. The image forming apparatus according to claim 1, wherein the side surface of the lower end surface of the head mounting portion is the inner portion.

4. 4. The image forming apparatus according to claim 1, wherein the surface of the inner portion has lower water repellency than the side surface.

5. 5. The image forming apparatus according to claim 1, wherein the head mounting portion is provided on both sides of the recording head.

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