Liquid ejection head, head unit, liquid ejection device

Abstract

To provide a liquid discharge head, a head unit and a liquid discharge device which can cope with high-frequency drive.SOLUTION: A liquid discharge head 10 includes a nozzle 14 from which ink is discharged, an ink chamber 12 which supplies ink to the nozzle 14, a needle valve 17 which opens and closes the nozzle 14 and a piezoelectric element 18 which causes the needle valve 17 to perform opening and closing movement. The ink chamber 12 has a plurality of ink supply paths 16A, 16B which respectively supply ink from different directions, ink is supplied to the ink chamber 12 through the plurality of ink supply paths 16A, 16B, and ink is discharged from the nozzle 14 according to an operation of causing the needle valve 17 to come close to the nozzle 14.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection head, a head unit, and a liquid ejection apparatus. [Background technology]

[0002] 2. Description of the Related Art There are liquid ejection heads that eject liquid by opening and closing an on-off valve relative to a nozzle.

[0003] For example, Patent Document 1 (US Patent US2012 / 0105522A1) describes a configuration in which a plunger is moved up and down by a solenoid coil to eject ink from an opening of a nozzle.

[0004] In such a liquid ejection head, the challenge is to increase the ejection speed of the liquid from the nozzles to accommodate high frequency driving. Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to realize a liquid ejection head that is compatible with high frequency driving. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention provides a liquid ejection head including a nozzle for ejecting liquid, a liquid chamber for supplying liquid to the nozzle, an on-off valve for opening and closing the nozzle, and a piezoelectric element for opening and closing the on-off valve, After the on-off valve is retracted from the nozzle, a reciprocating operation is performed in which the on-off valve is brought close to the nozzle to a position where the nozzle is not sealed, and after the on-off valve is retracted from the nozzle again, a discharge operation is performed in which the on-off valve is moved to a position where the nozzle is sealed, thereby discharging the liquid from the nozzle. It is characterized by: [Effects of the Invention]

[0007] According to the present invention, high frequency driving can be supported. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view of a liquid ejection device. [Figure 2]FIG. 2 is a cross-sectional view showing a liquid ejection head. [Figure 3] FIG. 4 is a cross-sectional view showing the head unit with the needle valve closed. [Figure 4] FIG. 4 is a cross-sectional view showing the head unit with the needle valve open. [Figure 5] FIG. 10 is a cross-sectional view of the head unit showing a state in which ink is ejected with the needle valve closed. [Figure 6] FIG. 10 is a cross-sectional view showing the head unit in a state where the needle valve is brought close to the nozzle. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. In the following description, a liquid ejection head that ejects ink as a liquid will be described as a liquid ejection head according to an embodiment of the present invention.

[0010] 1, liquid ejection device 100 is installed facing drawing target object 200, which is an example of an object. Liquid ejection device 100 includes an X-axis rail 101, a Y-axis rail 102 that intersects with X-axis rail 101, and a Z-axis rail 103 that intersects with X-axis rail 101 and Y-axis rail 102.

[0011] The Y-axis rail 102 holds the X-axis rail 101 so that the X-axis rail 101 can move in the Y direction. The X-axis rail 101 also holds the Z-axis rail 103 so that the Z-axis rail 103 can move in the X direction. The Z-axis rail 103 then holds the carriage 1 so that the carriage 1 can move in the Z direction. The carriage 1 is equipped with a liquid ejection head 10. The carriage 1 is an example of a head unit equipped with a liquid ejection head.

[0012] The liquid ejection device 100 includes a first Z-direction drive unit 92 that moves the carriage 1 in the Z direction along the Z-axis rail 103, and an X-direction drive unit 72 that moves the Z-axis rail 103 in the X direction along the X-axis rail 101. The liquid ejection device 100 also includes a Y-direction drive unit 82 that moves the X-axis rail 101 in the Y direction along the Y-axis rail 102. The liquid ejection device 100 also includes a second Z-direction drive unit 93 that moves the head holder 70 in the Z direction relative to the carriage 1.

[0013] The carriage 1 is equipped with a head holder 70. The head holder 70 is an example of a holder. The carriage 1 is movable in the Z direction along a Z-axis rail 103 by power from a first Z-direction drive unit 92 shown in FIG. 1. The head holder 70 is movable in the Z direction relative to the carriage 1 by power from a second Z-direction drive unit 93 shown in FIG. 1.

[0014] The liquid ejection device 100 configured as described above ejects ink, an example of a liquid, from the liquid ejection head 10 while moving the carriage 1 in the X-axis, Y-axis, and Z-axis directions, to perform drawing on the drawing target 200. Here, the movement of the carriage 1 and head holder 70 in the Z direction does not need to be parallel to the Z direction, and may be oblique movement as long as it includes at least a component in the Z direction.

[0015] In Figure 1, the surface shape of the drawing object 200 is shown as a flat surface, but the surface shape of the drawing object 200 may also be a nearly vertical surface, such as the body of a car or truck, or the body of an airplane, or a surface with a large radius of curvature.

[0016] 2A and 2B are explanatory diagrams of the liquid ejection head alone, in which Fig. 2A is an overall cross-sectional view of the liquid ejection head, and Fig. 2B is an enlarged view of part B in Fig. 2A.

[0017] The liquid ejection head 10 includes a housing 11. The housing 11 is made of metal or resin.

[0018] The liquid ejection head 10 has a nozzle plate 15. The nozzle plate 15 is joined to the housing 11. The nozzle plate 15 has nozzles 14 that eject ink.

[0019] Inside the housing 11, there are provided a needle valve 17 that opens and closes the nozzle 14, and a piezoelectric element 18 that drives the needle valve 17. A bearing 21 is provided between the needle valve 17 and the housing 11. A seal member 22 such as an O-ring is provided between the bearing 21 and the needle valve 17.

[0020] A piezoelectric element 18 is housed in a space 13 inside the housing 11. A holding member 23 holds the piezoelectric element 18 in a central space 23a. The piezoelectric element 18 and the needle valve 17 are coaxially connected via a tip 23b of the holding member 23. The tip 23b side of the holding member 23 is connected to the needle valve 17, and the rear end 23c side is fixed by a regulating member 19 attached to the housing 11.

[0021] The needle valve 17 has an elastic member 17a at its tip. When the tip of the needle valve 17 is pressed against the nozzle plate 15, the elastic member 17a is compressed, so that the needle valve 17 closes the nozzle 14 reliably.

[0022] Of the space inside the housing 11, the space on the side where the elastic member 17a of the needle valve 17 is provided and which is defined by the seal member 22 is the ink chamber 12 as a liquid chamber.

[0023] The housing 11 is provided with a supply passage 16. The supply passage 16 is a path through which ink is supplied to the ink chamber 12 from an ink supply bottle, which will be described later.

[0024] The housing 11 is provided with a regulating member 19 at a position facing the upper end of the piezoelectric element 18. The regulating member 19 abuts against the upper end of the piezoelectric element 18 and serves as a fixing point for the piezoelectric element 18.

[0025] Here, the nozzle plate 15 is an example of a discharge port forming member, the needle valve 17 is an example of an on-off valve, and the piezoelectric element 18 is an example of a piezoelectric body.

[0026] Next, the head unit 2 of this embodiment, which is equipped with the liquid ejection head 10, will be described, and the process of ejecting ink from the liquid ejection head 10 will be described.

[0027] As shown in FIG. 3, the head unit 2 has a liquid ejection head 10, and a first ink supply bottle 31A and a second ink supply bottle 31B as liquid supply units.

[0028] A first supply path 16A and a second supply path 16B serving as liquid supply paths are connected to the ink chamber 12 from two different directions. A first ink supply bottle 31A and a second ink supply bottle 31B are connected to the supply paths 16A and 16B, respectively. The first ink supply bottle 31A and the second ink supply bottle 31B supply ink to the ink chamber 12. This causes the ink chamber 12 to be filled with ink. However, ink may be supplied to the ink chamber 12 from three or more different directions.

[0029] In FIG. 3, the needle valve 17 abuts against the nozzle plate 15, sealing the open end 14a of the nozzle 14 on the needle valve 17 side.

[0030] In this embodiment, the ink in the ink chamber 12 is not pressurized even during the ink ejection operation described below. However, during the ink ejection operation, the ink in the ink chamber 12 may be pressurized by a pressurizing mechanism to an extent that does not affect the ejection operation.

[0031] When ejecting ink, first, a voltage is applied to the piezoelectric element 18 to cause it to contract. This causes the needle valve 17 to retract from the nozzle 14, opening the opening end 14a of the nozzle 14, as shown in Figure 4. This reduces the pressure near the opening end 14a, allowing ink to be supplied to the nozzle 14 and to the gap region 40 between the nozzle 14 and the needle valve 17.

[0032] From this state, the needle valve 17 is again moved closer to the nozzle 14, and as shown in Figure 5, the needle valve 17 is moved to a position where it seals the nozzle 14. This causes the ink in the gap region 40 and the nozzle 14 to be pushed by the needle valve 17, and ink 90 is ejected from the nozzle 14.

[0033] In the above-described ejection operation, in this embodiment, by supplying ink toward the liquid chamber 12 from multiple directions, it is possible to increase the ink supply speed to the liquid chamber 12 and improve the ink ejection speed of the liquid ejection head 10. Therefore, even in the ejection operation in which ink is ejected by opening and closing the needle valve 17 without pressurizing the ink in the liquid chamber 12, it is possible to support high-frequency driving.

[0034] Furthermore, since the piezoelectric element 18 can respond quickly to the application of voltage, the ink ejection speed from the liquid ejection head 10 can be improved.

[0035] Next, a second embodiment of the present invention, which is different from the above embodiment, will be described, and which is a liquid ejection head that performs a different ejection operation.

[0036] In this embodiment, first, as in the previous embodiment, the needle valve 17 is moved from a state in which the nozzle 14 is sealed to a direction in which the needle valve 17 is retracted from the nozzle 14, as shown in Figures 3 and 4. As a result, ink is supplied to the gap region 40 between the nozzle 14 and the needle valve 17.

[0037] Thereafter, the needle valve 17 is again brought closer to the nozzle 14, and is moved to a position where the needle valve 17 does not seal the nozzle 14, as shown in Fig. 6. The needle valve 17 is then again moved in a direction away from the nozzle 14, for example, to the same position as in Fig. 4. The needle valve 17 is then again brought closer to the nozzle 14, and the nozzle 14 is sealed by the needle valve 17, as shown in Fig. 5. This causes ink to be ejected from the nozzle 14, as in the above-described embodiment.

[0038] As described above, in this embodiment, the needle valve 17 reciprocates twice in its opening and closing direction, as shown in Figures 3, 4, 6, 4, and 5. By first moving the needle valve 17 from the retracted position shown in Figure 4 to a position shown in Figure 6 that does not block the nozzle 14, air bubbles within or near the nozzle 14 can be pushed outward. The needle valve 17 is then opened and closed again to eject ink from the nozzle 14. This increases the volume of the ejected ink droplets. However, the opening positions of the needle valve 17 do not necessarily need to be the same in the two reciprocating movements. For convenience, the explanation is given using Figures 3 to 5, which are the same as those of the previous embodiment, but the mechanisms and operations of the two embodiments are not necessarily the same. For example, the movement distance of the needle valve 17 does not necessarily need to be the same, and the amount of ink 90 ejected in Figure 5 is not necessarily the same in the two embodiments.

[0039] Furthermore, the number of reciprocating motions of the needle valve 17 may be three or more, and this number can be changed in this embodiment. Increasing the number of reciprocating motions makes it possible to increase the volume of ink ejected from the nozzle 14. In other words, by changing the number of reciprocating motions of the needle valve 17, it is possible to eject a desired volume of ink from the nozzle 14.

[0040] In the second embodiment described above, the liquid chamber 12 may be configured to have only one liquid supply path for supplying ink.

[0041] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the spirit of the present invention.

[0042] "Liquid" includes not only ink but also paint.

[0043] In this application, a "liquid ejection device" is a device that includes a liquid ejection head or a head unit and ejects liquid by driving the liquid ejection head. Liquid ejection devices include not only devices that can eject liquid onto objects to which the liquid can adhere, but also devices that eject liquid into air or liquid.

[0044] This "liquid ejection device" can also include means for feeding, transporting, and discharging items onto which liquid can be attached, as well as pre-processing devices and post-processing devices.

[0045] For example, examples of "liquid ejection devices" include image forming devices, which are devices that eject ink to form images on paper, and three-dimensional modeling devices (three-dimensional modeling devices), which eject modeling liquid onto a powder layer formed from layers of powder in order to create a three-dimensional object (a three-dimensional model).

[0046] Furthermore, the term "liquid ejection device" is not limited to devices that visualize meaningful images such as letters and figures using ejected liquid. For example, it also includes devices that form patterns that have no meaning in themselves, and devices that create three-dimensional images.

[0047] The above-mentioned "object onto which a liquid can adhere" refers to the aforementioned object to be drawn, and means an object onto which a liquid can adhere at least temporarily, and onto which the liquid adheres and sticks, or onto which the liquid adheres and penetrates, etc. Specific examples include media such as paper, recording paper, film, and cloth, electronic circuit boards, electronic components such as piezoelectric elements, powder layers, organ models, and test cells, and unless otherwise specified, includes all objects onto which a liquid can adhere.

[0048] The material of the "substance to which a liquid can adhere" may be any material to which a liquid can adhere, even temporarily, such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, or ceramics.

[0049] Furthermore, the term "liquid ejection device" includes, but is not limited to, a device in which a liquid ejection head and an object onto which liquid can be attached move relatively. Specific examples include a serial type device in which the liquid ejection head moves, and a line type device in which the liquid ejection head does not move.

[0050] Other examples of "liquid ejection devices" include treatment liquid application devices that eject treatment liquid onto paper to apply the treatment liquid to the surface of the paper for purposes such as modifying the surface of the paper, and spray granulation devices that spray a composition liquid in which raw materials are dispersed through a nozzle to granulate fine particles of the raw materials.

[0051] In the present application, the terms image formation, recording, printing, copying, printing, modeling, etc. are all synonymous. [Explanation of symbols]

[0052] 2 head units 10 Liquid ejection head 12 Ink chamber (liquid chamber) 14 nozzles 15 Nozzle plate (discharge port forming member) 16A 1st supply path (liquid supply path) 16B 2nd supply path (liquid supply path) 17 Needle valve (on-off valve) 18 Piezoelectric element (piezoelectric body) 31A First ink supply bottle (liquid supply unit) 31B Second ink supply bottle (liquid supply unit) 40 Interstitial Region 100 Liquid dispensing device [Prior art documents] [Patent documents]

[0053] [Patent Document 1] US Patent US2012 / 0105522A1

Claims

1. a nozzle for discharging a liquid; a liquid chamber for supplying liquid to the nozzle; an on-off valve that opens and closes the nozzle; a piezoelectric element that causes the on-off valve to perform an opening and closing operation, a reciprocating motion of moving the on-off valve back from the nozzle and then approaching the nozzle to a position where the on-off valve does not seal the nozzle; and after the on-off valve is retracted from the nozzle again, the on-off valve is moved to a position where the nozzle is sealed, thereby performing a discharge operation in which the liquid is discharged from the nozzle.

2. 2. The liquid ejection head according to claim 1, wherein the number of times that said on-off valve moves back and forth from said nozzle in the direction toward and away from said nozzle when said liquid is ejected from said nozzle can be changed as desired.

3. A head unit comprising the liquid ejection head according to claim 1 or 2.

4. A liquid ejection device comprising the head unit according to claim 3.

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