Droplet ejection device

Abstract

This prevents mist-like droplets from being drawn into the intake of the air curtain's blower. [Solution] The droplet ejection device 100 of the present invention has a droplet ejection head 10 on a nozzle surface 11 facing a recording medium M, on which a plurality of nozzles 12 are formed. The droplet ejection head 10 has a cross-flow fan 30 as a blower that forms an air curtain C toward the recording medium M on the front side of the nozzle surface 11 in the scanning direction while droplets are ejected from the plurality of nozzles 12 toward the recording medium M. The cross-flow fan 30 has a cylindrical rotating blade 31 whose axis is in a direction perpendicular to the scanning direction and parallel to the recording medium M, and a duct 32 that covers the periphery of the rotating blade 31 and is arranged from the rotating blade 31 to the nozzle surface 11 to guide the airflow. The duct 32 has an intake port 32a and an outlet port 32b, and the intake port 32a opens toward the front side of the rotating blade 31 in the scanning direction.

Description

Technical Field

[0001] The present invention relates to a droplet ejection device, and particularly to a droplet ejection device that forms an air curtain toward a recording medium on the front side of a nozzle surface facing the recording medium.

Background Art

[0002] In recent years, an inkjet printer, which is one type of droplet ejection device, improves the landing accuracy of droplets by making the gap between the inkjet head and the recording medium as narrow as possible, and improves productivity by transporting the inkjet head or the recording medium at high speed. However, in order to be compatible with a variety of media, it is necessary to widen the gap between the inkjet head and the recording medium to some extent. When the inkjet head and the recording medium are transported at high speed with such a gap, the flight trajectory of the droplets is likely to deviate due to the influence of the air flow.

[0003] Then, the landing accuracy of the droplets decreases, or the flying droplets are split, resulting in a decrease in print quality. Therefore, for example, the droplet ejection device of Patent Document 1 (Japanese Patent No. 5702950) prevents the influence of the air flow on the droplet flight trajectory by means of air curtains formed around the nozzle surface.

Disclosure of the Invention

Problems to be Solved by the Invention

[0004] However, it has been found that mist-like droplets of the liquid remain around the inkjet head, and this mist-like droplets are sucked into the suction port of the blower device that forms the air curtain and adhere to the recording medium, thereby deteriorating the print quality. The present invention has been made in view of the above circumstances, and an object thereof is to prevent mist-like droplets from being sucked into the suction port of the blower device of the air curtain.

Means for Solving the Problems

[0005] A droplet ejection device of the present invention for achieving the above objective is a droplet ejection device equipped with a droplet ejection head that is held so as to be movable in the scanning direction and has a plurality of nozzles formed on a nozzle surface facing a recording medium, wherein the droplet ejection head has a cross-flow fan as a blower that forms an air curtain toward the recording medium on the front side of the nozzle surface in the scanning direction while droplets are ejected from the plurality of nozzles toward the recording medium, wherein the cross-flow fan has a cylindrical rotating blade having an axis in a direction perpendicular to the scanning direction and parallel to the recording medium, and a duct that covers the periphery of the rotating blade and is disposed from the rotating blade to the nozzle surface to guide the flow of air, wherein the duct has an intake port for drawing air into the rotating blade and an outlet port for blowing out the air curtain, and the intake port is characterized in that it opens toward the front side of the rotating blade in the scanning direction. [Effects of the Invention]

[0006] According to the present invention, it is possible to prevent mist-like droplets from being sucked into the intake port of the blower. [Brief explanation of the drawing]

[0007] [Figure 1A] This is a side view of a droplet dispensing device according to an embodiment of the present invention. [Figure 1B] This is a side view of a droplet dispensing device according to a modified embodiment 1 of the present invention. [Figure 1C] This is a side view of a droplet dispensing device according to a modified embodiment 2 of the present invention. [Figure 1D] This is a side view of a droplet dispensing device according to a modified embodiment 3 of the present invention. [Figure 2] This is a perspective view of a cross-flow fan. [Figure 3] This diagram illustrates the shift in the point of impact due to the effects of airflow. [Figure 4] (a) Plan view of a single-head and (b) multi-head droplet dispensing device. [Figure 5]This is a plan view of an image forming apparatus in which the recording medium is transported in a direction perpendicular to the scanning direction of the droplet ejection head. [Figure 6] (a) A plan view of a droplet dispensing device according to modified embodiment 4 of the present invention and (b) A plan view of a droplet dispensing device according to modified embodiment 5. [Modes for carrying out the invention]

[0008] A droplet dispensing device according to an embodiment of the present invention will be described below with reference to the drawings. The droplet dispensing device shown in the drawings is illustrative and not limited thereto. Furthermore, components such as members and parts having the same function and shape will be denoted by the same reference numerals, and their description will be omitted as appropriate after their initial explanation.

[0009] As shown in Figure 1A, the droplet dispensing device 100 according to an embodiment of the present invention has a droplet dispensing head 10 and a cross-flow fan 30 as a blower. The droplet dispensing head 10 has a nozzle surface 11 at its lower part, on which a plurality of nozzles are formed.

[0010] The nozzle surface 11 is positioned parallel to the surface of the recording medium M with a gap between them. Droplets are ejected from multiple nozzles onto the recording medium M, and an image is formed on the surface of the recording medium M by these droplets.

[0011] Various methods can be used to eject droplets from the nozzle of the droplet ejection head 10, including piezoelectric, thermal, and electrostatic methods. In the piezoelectric method, a piezoelectric element is used to deform a diaphragm that forms the wall of the liquid channel, thereby changing the volume of the liquid channel and ejecting droplets.

[0012] The thermal method uses a heating resistor to heat the liquid in the liquid channel, causing droplets to be ejected by the pressure from the bubbles that are generated. The electrostatic method uses an electrostatic force generated between the diaphragm and the electrode to deform the diaphragm, changing the volume of the liquid channel and ejecting droplets.

[0013] The cross-flow fan 30 has a cylindrical rotating blade 31 and a duct 32 that guides the airflow. As shown in Figure 2, the rotating blade 31 has a plurality of blades 31a that extend in the longitudinal direction (axial direction) of the rotating blade 31, and the rotation axis 31b at the center of each blade 31a is connected to a motor Mo. The opposite end of the rotation axis 31b is rotatably supported on the inner wall of the duct 32.

[0014] The rotating blades 31 are surrounded by a duct 32. The duct 32 can be integrally molded from, for example, resin, and extends vertically downward from the rotating blades 31. An intake port 32a is formed on the side of the upper end of the duct 32 (left side in Figure 1A).

[0015] The suction port 32a is directed upstream in the transport direction of the recording medium M (in front of the droplet ejection head 10). There is little space above the droplet ejection head 10 due to liquid (ink) piping and harnesses, so it is difficult to direct the suction port 32a downstream in the transport direction of the recording medium M due to space limitations.

[0016] A safety louver 33 is provided at the intake port 32a. By making the louver 33, for example, mesh-like, it is possible to prevent dust and dirt from being sucked into the intake port 32a.

[0017] A slit-shaped outlet 32b is formed at the lower end of the duct 32, which extends vertically toward the recording medium M. This outlet 32b is positioned on the forward extension line of the nozzle surface 11. Therefore, the outlet 32b does not get in the way when wiping the nozzle surface 11 with a wiper blade.

[0018] When wiping the nozzle surface 11, a voltage waveform of a driving voltage is applied to the piezoelectric element of the droplet discharge head 10 such that droplets are not discharged from the nozzle and the nozzle surface 11 is sufficiently wetted by the liquid (ink). By moving the wiper blade along the nozzle surface 11 in a state where the nozzle surface 11 is sufficiently wetted with the liquid (ink), it is possible to remove (wipe) the deposits on the nozzle surface 11 without damaging the nozzle surface 11.

[0019] While the recording medium M is being conveyed in the direction of the arrow in FIG. 1A (Y direction), by discharging the droplets L from the nozzle surface 11, an image can be formed on the surface of the recording medium M. Here, Z is the height direction of the droplet discharge device 100, and X in FIGS. 2, 4, and 6 is the width direction of the droplet discharge device 100.

[0020] An air current F1 is generated as the recording medium M is conveyed in the Y direction. When the recording medium M is stationary, as shown in FIG. 3(a), the droplets L discharged from the nozzle surface 11 land exactly vertically at the target ideal position on the surface of the recording medium M.

[0021] However, as shown in FIG. 3(b), when the recording medium M is conveyed in the Y direction, an air current F1 is generated along the surface of the recording medium M due to this conveyance. Due to the influence of this air current F1, the flight trajectory of the droplet L is shifted to the right as shown in the figure. Also, since another air current F2 is generated along the flight trajectory of the droplet L, the flight trajectory of the droplet L is also shifted to the right as shown in the figure due to the influence of this air current F2.

[0022] In the present embodiment, as shown in FIG. 1A, an air curtain C is formed by the air blown out from the blowout port 32b at the lower end of the duct 32. This air curtain C is formed vertically in front of the nozzle surface 11.

[0023] Therefore, the airflow F1 generated along the surface of the recording medium M can be blocked by the air curtain C. As a result, the flight trajectory of the droplet L is not affected by the airflow F1, and the droplet L discharged from the nozzle surface 11 can be precisely and vertically landed at the target ideal position on the surface of the recording medium M. In addition, by using the cross-flow fan 30, a uniform airflow volume and velocity can be obtained in the direction of the nozzle row, effectively preventing the influence of airflows F1 and F2 on the droplet flight trajectory, and effectively preventing droplet breakage during flight.

[0024] Figure 1B shows a modified embodiment 1 in which the direction of the outlet 32b of the duct 32 is tilted towards the rear in the transport direction of the recording medium M (behind the nozzle surface 11). The air curtain C can cancel the effect of the airflow F2 so that the droplet flight path itself does not shift as shown in Figure 3(c) due to the airflow F2 generated along the flight path of the droplet L.

[0025] As shown in Figure 1B, only the orientation of the outlet 32b at the lower end of the duct 32 needs to be tilted, so this can be addressed by changing only the shape of the lower end of the duct 32. In other words, the orientation of the intake port 32a of the duct 32 does not need to be changed at all, so it is possible to prevent mist-like droplets accompanying the rear side of the droplet discharge head 10 (right side in Figure 1B) from being sucked into the intake port 32a. In addition, since the posture of the duct 32 does not need to be changed, the space efficiency of piping, harnesses, etc. above the droplet discharge head 10 can be improved.

[0026] Figure 1C shows a modified embodiment 2 in which the duct 32 is tilted forward at an angle α. This allows the direction of the outlet 32b to be tilted towards the rear in the direction of transport of the recording media M (behind the nozzle surface 11).

[0027] Since it only requires tilting the duct 32 forward overall, there is no need to change the shape of the duct 32 itself, and the implementation can be done at low cost. In addition, by tilting the intake port 32a of the duct 32 forward and downward, the effect is obtained that mist-like droplets that diffuse and accompany the droplet discharge head 10 to the rear and above are less likely to be sucked in by the intake port 32a. Furthermore, by making the cross-flow fan 30 rotatable around the outlet port 32b of the duct 32 (angle α is adjustable), it is possible to accommodate various transport speeds, droplet speeds, airflow volumes, and wind speeds of the recording media M.

[0028] Figure 1D shows a modified embodiment 3 of the droplet ejection device 100, in which droplet ejection heads 10 and 20 are arranged in two stages (tandem) along the transport direction of the recording medium M. By making the droplet ejection device 100 a multi-head system in this way, productivity can be improved.

[0029] In the multi-head droplet dispensing device 100, cross-flow fans 30 and 40 can be provided for each droplet dispensing head 10 and 20. The rear cross-flow fan 40 has almost the same structure as the front cross-flow fan 30, except that the vertical length of the duct 42 is longer than that of the front cross-flow fan 30's duct 32.

[0030] The intake port 42a of the duct 42 is located above the intake port 32a of the front cross-flow fan 30. This prevents the airflow entering the intake port 42a of the rear duct 42 from being obstructed by the front cross-flow fan 30.

[0031] The outlet 42b of the rear cross-flow fan 40 is also positioned on the forward extension of the nozzle surface 21. Therefore, the outlet 42b does not get in the way when wiping the nozzle surface 21 with a wiper blade.

[0032] Furthermore, the rotating blades 41, the multiple blades 41a, and the rotating shaft 41b have the same structure as the front cross-flow fan 30. Note that in Figure 1D, the outlets 32b and 42b can also be tilted as shown in Figures 1B and 1C.

[0033] Figure 4 is a plan view of the single-head and multi-head droplet dispensing devices 100 as seen from the nozzle surfaces 11 and 21 side (bottom side). Figure 4(a) shows the single-head device, and Figure 4(b) shows the multi-head device. As can be seen from Figure 4, the outlet 32b is located in front of the nozzle surfaces 11 and 21.

[0034] The width of the outlet 32b in the X direction is formed to exceed the row length of the nozzles 12 and 22 on each nozzle surface 11 and 21. This effectively prevents the airflow from affecting the droplet flight path through the air curtain.

[0035] In the case of the multi-head system shown in Figure 4(b), by branching the duct 32 of one cross-flow fan 30, air can be blown out from four outlets 32b, forming an air curtain in front of each nozzle surface 11, 21. Branching the duct 32 can reduce the cost of the multi-head droplet dispensing device 100.

[0036] There are two types of image forming apparatuses: so-called line-type image forming apparatuses and serial-type image forming apparatuses. The aforementioned droplet ejection device 100 is applicable to line-type image forming apparatuses in which the recording medium M is transported in the Y direction.

[0037] Line-type image forming apparatuses use a head (line head) in which the length between the nozzles at one end and the nozzle at the other end (recording width) is greater than or equal to the width of the paper.

[0038] Figure 5 shows a serial-type image forming apparatus in which the recording medium M is transported in a direction perpendicular to the scanning direction of the droplet ejection head 10. A serial-type image forming apparatus uses a head (serial head) whose recording width is shorter than the recording width of the line head.

[0039] A pair of guide rails 50 are arranged perpendicular to the transport direction of the recording medium M. A carriage 60 is movably mounted on the pair of guide rails 50. A droplet ejection head 10 is mounted on this carriage 60. When droplets are ejected, the transport of the recording medium M is temporarily stopped.

[0040] In this case, the intake port 32a of the cross-flow fan 30 is formed on the front side of the droplet discharge head 10 in the scanning direction indicated by the arrow. This prevents mist-like droplets accompanying the rear side of the droplet discharge head 10 (the lower side in Figure 5) from being sucked into the intake port 32a.

[0041] If the droplet discharge head 10 discharges droplets during its reciprocating movement, a cross-flow fan 30 and duct 32 can also be provided on the opposite side of the droplet discharge head 10 in Figure 5. Alternatively, only one cross-flow fan 30 can be used, and the duct 32 can be branched to the opposite side, splitting the airflow from the cross-flow fan 30 into two branch ducts. Furthermore, a valve installed in the branch duct can be opened and closed according to the direction of movement of the droplet discharge head 10, allowing air to be supplied only from the outlet 32b in the direction where an air curtain is needed.

[0042] Figures 6(a) and 6(b) show modified embodiments of the present invention. Specifically, in modified embodiment 4 of Figure 6(a), a plurality of ribs 32c are formed on the inner surface of the duct 32 in the direction of airflow. The plurality of ribs 32c are formed at equal intervals in the lateral width direction of the duct 32.

[0043] Multiple ribs 32c are formed along the longitudinal direction of the duct 32, preferably extending to the outlet 32b. These ribs 32c provide a rectifying effect on the airflow within the duct 32, thereby ensuring uniformity of the air velocity in the width direction of the air curtain C.

[0044] Therefore, the deviation of the droplet L's flight path due to the airflows F1 and F2 shown in Figures 3(b) and 3(c) can be effectively prevented. In addition, the rigid strength of the duct 32 can be improved by the multiple ribs 32c.

[0045] In the modified embodiment 5 shown in Figure 6(b), the outlet 32b of the duct 32 is formed to surround the front and both sides of the nozzle surface 11 in a U-shape. Therefore, in Figure 6(b), an air curtain can be formed in a U-shape, and the U-shaped air curtain makes it more difficult for the droplet flight path to deviate.

[0046] Although the present invention has been specifically described above based on embodiments, it goes without saying that the present invention is not limited to the above embodiments and can be modified in various ways within the scope of the technical idea described in the claims. For example, in the multi-head droplet ejection device 100 of Figure 4, a switching valve can be installed in the branched duct 32 of the cross-flow fan 30. By opening and closing this switching valve, the air supply to the outlet 32b of the idle head can be stopped, and the air from the cross-flow fan 30 can be used effectively. In addition, it is possible to prevent the ink of the idle head from drying out due to the air curtain. Furthermore, it is also possible to install a dedicated cross-flow fan 30 for each head of the multi-head droplet ejection device 100 of Figure 4.

[0047] <Note> Preferred embodiments of the present invention are described below. <First aspect> A droplet ejection device equipped with a droplet ejection head that is held so as to be movable in the scanning direction and has a plurality of nozzles formed on the nozzle surface facing the recording medium, The droplet ejection head has a cross-flow fan, which acts as a blower, that forms an air curtain toward the recording medium on the scanning front side of the nozzle surface while ejecting droplets from the plurality of nozzles toward the recording medium. The cross-flow fan has a cylindrical rotating blade having an axis in a direction perpendicular to the scanning direction and parallel to the recording medium, and a duct that covers the periphery of the rotating blade and is arranged from the rotating blade to the nozzle surface to guide the airflow. The duct has an intake port for drawing air into the rotating blades and an outlet port for blowing out the air curtain. A droplet dispensing device characterized in that the suction port opens to the front side in the scanning direction of the rotating blade. <Second aspect> A droplet dispensing device according to the first embodiment, characterized in that the outlet is arranged on the extension of the nozzle surface. <Third aspect> A droplet dispensing device according to the first or second embodiment, characterized in that the outlet is inclined toward the nozzle surface of the droplet dispensing head. <Fourth aspect> A droplet dispensing device according to the first or second embodiment, characterized in that the entire duct is inclined forward in the scanning direction, so that the outlet is inclined toward the nozzle surface of the droplet dispensing head. <Fifth aspect> A droplet dispensing device according to any one of the first to fourth embodiments, characterized in that a plurality of droplet dispensing heads are arranged, and air from one of the cross-flow fans is distributed to each droplet dispensing head through a branch duct of the duct. <Sixth aspect> A droplet dispensing device according to any one of the first to fifth embodiments, characterized in that a plurality of ribs are formed on the inner surface of the duct in the direction of airflow. <Seventh aspect> A sixth embodiment of a droplet dispensing device, characterized in that the plurality of ribs are formed up to the outlet. <Eighth aspect> A droplet dispensing device according to any one of the first to seventh embodiments, characterized in that the nozzle surface has outlets formed on the front side in the scanning direction and on both the left and right sides. <Ninth aspect> A line-type image forming apparatus characterized by having a droplet dispensing device according to any one of the first to eighth embodiments. <Tenth aspect> A serial image forming apparatus characterized by having a droplet ejection device according to any one of the first to eighth embodiments. [Explanation of Symbols]

[0048] 10, 20: Droplet dispensing head 11, 21: Nozzle surface 12, 22: Nozzle 30, 40: Cross-flow fan 31, 41: Rotating blades 31a, 41a: Blade 31b, 41b: Rotation axis 32, 42: Duct 32a, 42a: Inlet 32b, 42b: Air outlet 32c: Rib 33: Luba 50: Guide rail 60: Carriage 100:Droplet discharge device C: Air Curtain F1, F2: Airflow L: droplet M: Recording media Mo: motor [Prior art documents] [Patent Documents]

[0049] [Patent Document 1] Patent No. 5702950

Claims

1. A droplet ejection device equipped with a droplet ejection head that is held so as to be movable in the scanning direction and has a plurality of nozzles formed on the nozzle surface facing the recording medium, The droplet ejection head has a cross-flow fan, which acts as a blower, that forms an air curtain toward the recording medium on the scanning front side of the nozzle surface while ejecting droplets from the plurality of nozzles toward the recording medium. The cross-flow fan has a cylindrical rotating blade having an axis in a direction perpendicular to the scanning direction and parallel to the recording medium, and a duct that covers the periphery of the rotating blade and is arranged from the rotating blade to the nozzle surface to guide the airflow. The duct has an intake port for drawing air into the rotating blades and an outlet port for blowing out the air curtain. A droplet dispensing device characterized in that the suction port opens to the front side in the scanning direction of the rotating blade.

2. The droplet dispensing device according to claim 1, characterized in that the outlet is arranged on the extension of the nozzle surface.

3. The droplet dispensing device according to claim 1, characterized in that the outlet is inclined toward the nozzle surface of the droplet dispensing head.

4. The droplet dispensing device according to claim 3, characterized in that the entire duct is inclined forward in the scanning direction, so that the outlet is inclined toward the nozzle surface of the droplet dispensing head.

5. The droplet dispensing device according to claim 1, characterized in that a plurality of droplet dispensing heads are arranged, and air from one of the cross-flow fans is distributed to each droplet dispensing head through a branch duct of the duct.

6. The droplet dispensing device according to claim 1, characterized in that a plurality of ribs are formed on the inner surface of the duct in the direction of airflow.

7. The droplet dispensing device according to claim 6, characterized in that the plurality of ribs are formed up to the outlet.

8. The droplet dispensing device according to claim 1, characterized in that the outlets are formed on the front side and on both the left and right sides in the scanning direction of the nozzle surface.

9. A line-type image forming apparatus characterized by having a droplet dispensing device according to claims 1 to 8.

10. A serial image forming apparatus characterized by having a droplet ejection device according to claims 1 to 8.

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