Image forming apparatus

Abstract

An image forming apparatus is provided. The image forming apparatus has a recording head and a wiper. The recording head has a nozzle area in which a plurality of ink ejection ports are open toward a lower side. The wiper wipes the ink ejection ports by contacting the nozzle area and moving in a prescribed wiping direction. On a side surface of the recording head along the wiping direction, a recording head mounting portion along the wiping direction is provided in a manner projecting outward at a position higher than the nozzle area. The recording head mounting portion has an outer side portion and an inner side portion, wherein a surface of the outer side portion has a higher water repellency than the side surface, and the inner side portion is provided inside the outer side portion and has a surface with a lower water repellency than the outer side portion. Accordingly, it is possible to reduce the falling of ink that is pushed up to the side surface of the recording head when wiping is performed.

Description

Technical Field

[0001] The present invention relates to an inkjet image forming apparatus having a wiper for wiping the inkjet nozzles of a recording head. Background Technology

[0002] Inkjet imaging apparatuses include a wiper for wiping the inkjet nozzles of the recording head. The wiper moves in one direction from a wiping start position to a wiping end position while contacting the nozzle area of ​​the inkjet nozzle opening.

[0003] During such wiping, ink that is wiped away may sometimes be expelled from the wiper and travel back to the side surface of the recording head, where it may be pushed up and deposited. If wiping is repeated, the amount of deposited ink may increase, causing problems such as ink falling onto the film and resulting in poor image quality or contamination of the equipment's interior.

[0004] Therefore, there exists an inkjet image forming apparatus having a recording head cover that covers the side surface of the recording head. The side and surface surfaces of the recording head cover are waterproofed. Accordingly, even if ink detours to the side surface of the recording head, the ink is repelled by the recording head cover, thus reducing ink adhesion to the side surface of the recording head.

[0005] However, in the inkjet recording device described above, a considerable gap exists between the recording head cover and the recording head. Sometimes, ink that has been wiped away can enter this gap. If the amount of ink that enters increases, the ink may fall out and cause the aforementioned image defects or internal contamination of the device. Summary of the Invention

[0006] Therefore, in view of the above, the object of the present invention is to provide an inkjet image forming apparatus that can reduce the amount of ink that is pushed (gradually raised) to the side surface of the recording head during wiping.

[0007] The image forming apparatus of the present invention includes a recording head and a wiper. The recording head has a nozzle area with multiple inkjet nozzles opening downwards. The wiper wipes the inkjet nozzles by contacting the nozzle area and moving in a predetermined wiping direction. On a side surface of the recording head along the wiping direction, a recording head mounting portion is provided at a position higher than the nozzle area and protruding outwards along the wiping direction. The recording head mounting portion has an outer portion and an inner portion, wherein the surface of the outer portion has higher water resistance than the side surface, and the inner portion is provided inside the outer portion, and its surface has lower water resistance than the outer portion. Attached Figure Description

[0008] Figure 1 This is a front view schematically illustrating the internal structure of an image forming apparatus according to an embodiment of the present invention.

[0009] Figure 2 This is a perspective view showing the line head in an image forming apparatus according to an embodiment of the present invention.

[0010] Figure 3 This is a top view showing the wiping unit in an image forming apparatus according to an embodiment of the present invention.

[0011] Figure 4A This is a side view of the recording head in an image forming apparatus according to an embodiment of the present invention.

[0012] Figure 4B This is a front view of the recording head in an image forming apparatus according to an embodiment of the present invention.

[0013] Figure 5 This is a front view showing a modified example of the recording head in an image forming apparatus according to an embodiment of the present invention. Detailed Implementation

[0014] Below, refer to the appendix. Figure 1 The image forming apparatus according to one embodiment of the present invention will be described below.

[0015] Reference Figure 1 The image forming apparatus 1 will now be described. Figure 1 This is a schematic front view showing the internal structure of the image forming apparatus 1 (during image forming). Fr, Rr, L, and R in each figure represent the front, rear, left, and right sides of the image forming apparatus 1.

[0016] The image forming apparatus 1 includes a paper supply unit 3, an inkjet image forming unit 5, and a transport path 7. The transport path 7 is a path for transporting the sheet S supplied by the paper supply unit 3 through the image forming unit 5 to the discharge port (not shown). The paper supply unit 3 includes a paper tray 9 and a paper supply device 11. The paper tray 9 houses the sheet S, and the paper supply device 11 supplies the sheet S from the paper tray 9 to the transport path 7. The image forming unit 7 includes a recording head unit 13, a transport unit 15, and a maintenance unit 17.

[0017] First, the recording head unit 13 will be described. The recording 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 side by side along the conveying direction (left side) of the sheet S in the conveying path 7.

[0018] Next, refer to Figure 2The header 21 of each line is explained. Figure 2 This is a three-dimensional diagram representing line header 21.

[0019] Each row header 21 has three recording heads 31 and a recording head base 33 supporting the three recording heads 31.

[0020] Each recording head 31 has a long cuboid shape in the front-to-back direction and has multiple nozzles arranged in both the front-to-back and left-to-right directions. The nozzle exit point is open on the lower surface of the recording head 31. Each nozzle ejects ink downwards from its exit point using an ink ejection method such as piezoelectric or thermal ejection. The area where the exit point is open on the lower surface of the recording head 31 is designated as nozzle area N.

[0021] The recording head base 33 is a flat plate-shaped component that is relatively long in the front-to-back direction. Three recording heads 31 are supported on the recording head base 33 in a staggered arrangement in the front-to-back direction. Each recording head 31 is supported such that its nozzle region N protrudes downward from the lower surface of the recording head base 33. The recording heads 31 are formed of metals such as SUS. The structure of the recording heads 31 will be described later.

[0022] Refer again Figure 1 The recording head unit 13 is supported at the printing position in a height-adjustable manner (see reference). Figure 1 (solid line) and retreat position (refer to) Figure 1 (double-dotted line), wherein the printing position is the position where image formation can be performed, and the retreat position is the position where the recording head unit 13 is maintained and protected by retreating to a position above the printing position.

[0023] Next, refer to Figure 1 The conveying unit 15 will be described below. The conveying unit 15 has a conveyor belt 51 wound between rollers arranged separately in the left-right direction, and... Figure 1 The conveyor belt 51 travels in a counter-clockwise direction. The upper travel surface of the conveyor belt 51 forms part of the transport path 7 through the image forming unit 5. When the recording 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 travel surface of the conveyor belt 51.

[0024] During image formation, the recording head unit 13 descends to the printing position. Meanwhile, the sheet S supplied by the paper supply unit 3 is conveyed 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 print head 21 onto the sheet S conveyed by the conveyor belt 51 according to image data, thereby forming an image on the sheet S.

[0025] Next, refer to Figure 1The maintenance unit 17 is described below. The maintenance unit 17 has an end cap unit 61 and a wiping unit 63.

[0026] End cap unit 61 has end caps corresponding to each recording head 31 of each row of heads 21 of recording head unit 13. End cap unit 61 is supported in a manner that allows it to move in the left-right direction between a retracted position and a capping position, wherein the retracted position is a position to the left of recording head unit 13, and the capping position is a position below recording head unit 13 raised to the retracted position. After moving end cap unit 61 to the capping position, each end cap is pushed against recording head base 33 by lowering recording head unit 13, thereby covering the nozzle forming surface N of each recording head 31.

[0027] Reference Figure 1 and Figure 3 The wiping unit 63 will now be described. Figure 3 This is a top view showing the wiping unit 63. The wiping unit 63 has four wiper carriages 65, which correspond to the four line heads 21 of the recording head unit 13. The wiper carriages 65 are supported in a manner that allows them to move in the front-to-back direction. The wiper carriages 65 have: three wipers 67, which correspond to the three recording heads 31 of the line heads 21; and a tray 69, which collects the ink wiped by each wiper 67. The wipers 67 can be, for example, a scraper formed of an elastic member, or a component made by attaching fabric around a scraper formed of an elastic member or a roller. The wiping unit 63 is supported in a manner that allows it to move in the left-to-right direction between a retracted position and a wiping position, wherein the retracted position is a position to the left of the recording head unit 13, and the wiping position is a position below the recording head unit 13 that has risen to the retracted position.

[0028] After moving the wiping unit 63 to the wiping position, the recording head unit 13 is lowered so that the wiper 67 contacts the nozzle area N, and each wiper holder 65 is moved from the front wiping start position (refer to...). Figure 3 Move the solid line to the end of the wiping position behind it (refer to...). Figure 3 (The double-dotted line), thereby wiping each recording head 31 of each row head 21 by the wiper 67 of the wiper holder 65 (see reference). Figure 2 The nozzle area N is the ink wiped off by the wiper 67. The ink falls onto the tray 69 and is collected through the recovery port (not shown). The moving direction of the wiper holder 65 is set as the wiping direction X. In this embodiment, the wiping direction X is from front to back.

[0029] Next, refer to Figure 4A and Figure 4B Let's explain the record header 31. Figure 4A This is a diagram of the record head 31 viewed from the left. Figure 4B This is a diagram of the recording head 31 viewed from the front.

[0030] A recording head mounting portion 41 is formed on the side surface 31a of the nozzle region N of the recording head 31 in the front-back direction, i.e., the wiping direction X. The recording head mounting portion 41 may be provided on only one side surface 31a, but is preferably provided on two side surfaces 31a. The recording head mounting portion 41 is a cuboid with a longitudinally elongated rectangular cross-section when viewed from the front-back direction, and is formed at a position higher than the nozzle region N. The fact that the recording head mounting portion 41 is formed at a position higher than the nozzle region N means that there is a side surface 31a between the recording head mounting portion 41 and the nozzle region N. The distance between the recording 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.

[0031] like Figure 4B As shown, the recording head mounting portion 41 has an outer portion 43 and an inner portion 45, wherein the inner portion 45 is disposed 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 fluoropolymer resin) having higher water resistance than the recording head 31. In other words, the contact angle of the ink with respect to the surface of the outer portion 43 is greater than the contact angle of the ink with respect to the side surface 31a of the recording head 31. Alternatively, the outer portion 43 may only have its surface coated with a material having high water resistance. As an example, the thickness of the outer portion 43 is 0.2 to 0.3 mm.

[0032] The inner portion 45 is formed of a material with lower water resistance than the outer portion 43 (e.g., PET (polyethylene terephthalate) or acrylic double-sided tape). In other words, the contact angle of the ink with respect to the surface of the outer portion 43 is greater than the contact angle of the ink with respect to the surface of the inner portion 45. Preferably, the inner portion 45 is formed of a material with lower water resistance than the recording head 31. In other words, the contact angle of the ink with respect to the surface of the inner portion 45 is smaller than the contact angle of the ink with respect to the side surface 31a of the recording head 31. Moreover, the inner portion 45 is preferably formed of a material with a smaller contact angle with the ink. As an example, the thickness of the inner portion 45 is 0.1 mm.

[0033] The inner part 45 is fixed to the side surface 31a of the recording head 31 in a seamless manner, for example by means of double-sided tape, adhesive, heat fusion or other methods. The outer part 43 is fixed to the side surface of the inner part 45 in a seamless manner, for example by means of double-sided tape, adhesive, heat fusion or other methods.

[0034] Reference Figure 4A and Figure 4BThe wiping process in the image forming apparatus 1 having the above-described structure will be described. For example, wiping is performed after the ink in the nozzle of the recording head 31 is cleared. During wiping, as described above, the wiper holder 65 of the wiping unit 63 (see reference 63) Figure 3 The wiper 67 moves along the wiping direction X, causing it to wipe the nozzle area N. The wiper 67 is pressed against the nozzle area N with a specified pressure, therefore, as... Figure 4A It bends upstream in the wiping direction X as shown. Furthermore, the width of the wiper 67 is slightly wider than the width of the nozzle region N; therefore, when pressed against the nozzle region N, as... Figure 4B As shown, the two ends of the wiper 67 protrude upwards more than the nozzle area N.

[0035] The ink L wiped away by the wiper 67 is pushed (lifted) upwards from both ends of the wiper 67 to the side surface 31a of the recording head 31. The pushed ink L soon reaches the recording head mounting portion 41. Since the water resistance of the inner portion 45 of the recording head mounting portion 41 is lower than that of the side surface 31a of the recording head 31, the ink L is attracted to the inner portion 45 and held at the corner of the side surface 31a and the inner portion 45 of the recording head 31. On the other hand, since the water resistance of the outer portion 43 is higher than that of the side surface 31a and the inner portion 45 of the recording head 31, it easily repels the ink L. As a result, the ink L is held at the corner between the side surface 31a and the lower surface of the inner portion 45 of the recording head 31 by the intermolecular forces between the side surface 31a and the lower surface of the inner portion 45.

[0036] As can be seen from the above description, according to the present invention, the ink L pushed up to the side surface 31a of the recording head 31 during wiping is held at the corner between the lower surface of the recording head mounting portion 41 and the side surface 31a of the recording head 31. In particular, since the inner portion 45 of the recording head mounting portion 41 has lower water resistance than the side surface 31a of the recording head 31, it is easier to attract the ink L. That is, it is easier to retain the ink L. On the other hand, the outer portion 43 has higher water resistance than the side surface 31a and the inner portion 45 of the recording head 31, and therefore it is easier to repel the ink L. Therefore, even if the amount of ink L retained increases and reaches below the outer portion 43, the amount of ink L retained will not increase by more than a certain amount because the outer portion 43 has difficulty retaining the ink L. In this way, it is possible to always maintain a certain amount of ink L pushed up during wiping. Furthermore, with each repeated wiping, ink L is pushed up and contained within the retained ink L, but since the amount retained is limited to a certain amount, the pushed ink L and the retained ink L are constantly alternating.

[0037] Furthermore, as described above, the ink is held in place by the intermolecular forces between the side surface 31a of the recording head 31 and the lower surface of the inner portion 45, thus preventing the held ink L from falling off due to its own weight. Therefore, even when vibration is applied to the recording head 31 during image formation, the held ink L can be prevented from falling off, thereby preventing image defects and internal contamination of the device.

[0038] Furthermore, a thinner inner portion 45 reduces the amount of ink L retained, making this feature preferable. Conversely, a thicker outer portion 43 increases the force repelling the ink L, thus 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 0.03–0.5 mm, and further to 0.05–0.2 mm, the amount of ink L retained is reduced while ensuring the force of ink L retention. Similarly, by setting the thickness of the outer portion 43 to 0.2–0.3 mm, the amount of ink L retained is reduced while ensuring the force of ink L retention.

[0039] Furthermore, the lower end face of the recording head mounting portion 41 is substantially parallel to the nozzle region N. The lower end face is preferably within ±10 degrees relative to the nozzle region N in the wiping direction X, and more preferably substantially parallel. Additionally, the lower end face is preferably within ±30 degrees relative to the nozzle region N in a direction orthogonal to the wiping direction X, more preferably within ±15 degrees, and particularly preferably substantially parallel. Accordingly, while ensuring the force required to retain the ink L, the amount of ink L retained is reduced.

[0040] Furthermore, the side surface 31a of the lower end face of the recording head mounting portion 41 becomes the inner side portion 45. That is, the apex of the corner formed by the side surface 31a of the recording head 31 and the lower end face of the recording head mounting portion 41 becomes a state with different water resistance. Accordingly, while ensuring the force of holding the ink L, the amount of ink L held is reduced.

[0041] Alternatively, the recording head mounting portion 41 can be configured as a separate component that can be detached from the recording head 31. In this way, the angle between the side surface 31a of the recording head 31 and the lower end surface of the recording head mounting portion 41 becomes sharp, making it easier to retain a small amount of ink L.

[0042] Next, refer to Figure 5 Modifications of the present invention will be described. Figure 5 This is a view of the recording head 31 from the front. The outer side 43 of the recording head mounting portion 41 may also be coated with a waterproof material (e.g., fluoropolymer resin) on the outer surface of the inner side 45. In this modified example, it is also possible to maintain a certain amount of ink L pushed up during wiping at the corner of the side surface 31a and the inner side 45 of the recording head 31.

[0043] While specific embodiments have been described in this invention, the invention is not limited to these embodiments. Those skilled in the art can modify the described embodiments without departing from the scope and spirit of the invention.

Claims

1. An image forming apparatus characterized by comprising: a recording head and a wiper, wherein the recording head is provided with a plurality of ink ejection ports opening toward a lower side in a nozzle region; the wiper wipes the ink ejection ports by contacting the nozzle region and moving in a prescribed wiping direction, a recording head mounting portion along the wiping direction is provided in a manner projecting toward an outer side at a position higher than the nozzle region on a side surface of the recording head along the wiping direction, and a corner portion is formed between the side surface of the recording head and a lower surface of the recording head mounting portion, the recording head mounting portion has an outer side portion and an inner side portion, and a surface of the outer side portion has a higher water repellency than the side surface; the inner side portion is provided between the outer side portion and the recording head and has a surface with a lower water repellency than the outer side portion.

2. The image forming apparatus according to claim 1, characterized in that a lower end surface of the recording head mounting portion is parallel to the nozzle region.

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

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

5. The image forming apparatus according to claim 1, characterized in that the recording head mounting portion is provided on both side surfaces of the recording head.

6. The image forming apparatus according to claim 1, characterized in that a lower end surface of the recording head mounting portion is parallel to a direction orthogonal to the wiping direction.

7. The image forming apparatus according to claim 1, characterized in that a thickness of the inner side portion is thinner than a thickness of the outer side portion.

8. The image forming apparatus according to claim 1, characterized in that no gap is formed between the side surface and the inner side portion, and no gap is formed between the inner side portion and the outer side portion.

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