Liquid ejection head and liquid ejection device

Abstract

To improve adhesiveness of an elastic member with respect to a core material end part.SOLUTION: A liquid discharge head 10 having a nozzle 14 for discharging ink and an on-off valve 31 provided movably for opening and closing the nozzle 14. The on-off valve 31 includes a core material 310, and the core material 310 includes a core material end part 311 at an end part on a nozzle 14 side. The core material end part 311 includes a recessed part 312 opened to the nozzle 14 side inside it. A seal member 40 is provided over the recessed part 312 and the outside lateral face 311a of the core material end part 311.SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] There are liquid ejection heads that control the ejection of liquid by opening and closing an on-off valve relative to an ejection port. In such liquid ejection heads, an elastic member is provided in the on-off valve to seal the ejection port when the on-off valve is closed.

[0003] For example, in Patent Document 1 (US Patent US2012 / 0105522A1), an elastic member made of perfluoroelastomer is provided in a recess provided on the inner surface of the discharge port side of an on-off valve.

[0004] However, if the elastic member does not adhere tightly to the on-off valve, a gap will form between the elastic member and the on-off valve. In particular, if the on-off valve is repeatedly moved up and down and the elastic member is pressed against the discharge port repeatedly, the elastic member may peel off from the on-off valve, creating a gap between them.

[0005] This gap, when opened, causes variations in the size of the gap formed between the on-off valve and a component such as a nozzle plate having an ejection port, resulting in variations in the amount of liquid ejected from the ejection port. Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to improve the adhesion of the elastic member to the end portion of the core material. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a liquid ejection head including an ejection port for ejecting liquid, and an on-off valve that is movably provided and opens and closes the ejection port, wherein the on-off valve has a core, and a core end is provided at an end of the core on the ejection port side, and the core end has a recess on the inside that opens to the ejection port side, and an elastic member is provided across an outer side surface of the core end and the recess. The core end has a bottom surface which is an end surface on the discharge port side in the movement direction of the on-off valve, and the bottom surface is provided so as to surround the recess when viewed from the discharge port side in the movement direction of the on-off valve. If a corner connecting the bottom surface of the core end and the outer side surface is defined as an outer corner, the elastic member is provided so as to cover the outer side surface, the outer corner, and the bottom surface. The elastic member has a flat portion at a position facing the bottom surface in the movement direction of the on-off valve, and an inclined portion inclined with respect to the flat portion and the outer side surface at a position overlapping the outer corner when viewed from the discharge port side in the movement direction of the on-off valve. It is characterized by: [Effects of the Invention]

[0008] According to the present invention, the adhesiveness of the elastic member to the end portion of the core material can be improved. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view showing the appearance of a liquid ejection head according to an embodiment of the present invention. [Figure 2] 1 is an overall cross-sectional view of a liquid ejection head according to an embodiment of the present invention. [Figure 3] FIG. 3 is a diagram showing the positions of heaters provided in the liquid ejection head. [Figure 4] FIG. 2 is a cross-sectional view of the liquid ejection head. [Figure 5] FIG. 2 is a plan view showing the configuration of the nozzle-side tip of the on-off valve. [Figure 6] 10A and 10B are diagrams illustrating the opening and closing operation of an on-off valve. [Figure 7] FIG. 4 is a diagram illustrating the width of a sealing member. [Figure 8] FIG. 10 is a plan view showing another embodiment of the on-off valve. [Figure 9] 10 is a plan view showing an on-off valve in which an adhesive is provided between the end of the core material and the sealing member. FIG. [Figure 10] FIG. 10 is a plan view showing a configuration of an on-off valve different from that of the present embodiment. [Figure 11] 11 is a diagram showing the relationship between the displacement amount and lift amount of a piezoelectric element in the comparative example of FIG. 10. FIG. [Figure 12] 4 is a diagram showing the relationship between the displacement amount and lift amount of a piezoelectric element in the embodiment of FIG. 3. FIG. [Figure 13] 1 is a schematic diagram illustrating the overall configuration of a liquid ejection device. [Figure 14] FIG. 14 is a schematic diagram illustrating the overall configuration of a liquid ejection device different from that shown in FIG. [Figure 15] 2 is a perspective view showing an example of the arrangement of the liquid ejection device of FIG. 1 in an automobile. FIG. [Figure 16] 1. FIG. 4 is a perspective view showing another example of the arrangement of the liquid ejection device of FIG. 1 in an automobile. [Figure 17] 10A and 10B are explanatory diagrams illustrating a case where liquid is discharged onto a spherical surface by the liquid discharge device. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is an explanatory view of the appearance of a liquid ejection head according to an embodiment of the present invention. Fig. 1(a) is an overall perspective view of the liquid ejection head, and Fig. 1(b) is an overall side view of the same head. The liquid ejection head of this embodiment ejects ink as a liquid.

[0011] The liquid ejection head 10 includes a first housing 11a as a first housing and a second housing 11b as a second housing. The second housing 11b is stacked and joined to the first housing 11a. The first housing 11a is made of a material with high thermal conductivity such as metal, and the second housing 11b is made of a material with low thermal conductivity such as resin. In the following description, the two housings will be referred to collectively as housing 11.

[0012] The first housing 11a is provided with heaters 12 as heating means on its front and back surfaces. The heaters 12 are temperature-controllable and heat the first housing 11a. The second housing 11b is provided with a connector 13 on its top for communicating electrical signals.

[0013] 2 is an overall cross-sectional view of a liquid ejection head 10 according to an embodiment of the present invention, taken along the arrow AA in FIG. 1(a). The first housing 11a holds a nozzle plate 15 as an ejection port forming member. The nozzle plate 15 has nozzles 14 as ejection ports for ejecting liquid. The first housing 11a also has a flow path 17 as a liquid supply section. The flow path 17 sends ink from the supply port 16 side over the nozzle plate 15 to the recovery port 18 side.

[0014] The second housing 11b has a supply port 16 and a recovery port 18. The supply port 16 and the recovery port 18 are connected to one side and the other side of the flow path 17, respectively. A plurality of liquid ejection modules 30 are arranged between the supply port 16 and the recovery port 18. The liquid ejection modules 30 eject ink in the flow path 17 from the nozzles 14. A restriction member 20 is also provided above the liquid ejection modules 30.

[0015] The number of liquid ejection modules 30 corresponds to the number of nozzles 14 provided in the first housing 11a, and in this example, a configuration is shown in which eight liquid ejection modules 30 are provided corresponding to the eight nozzles 14 arranged in a row. Note that the number and arrangement of the nozzles 14 and liquid ejection modules 30 are not limited to those described above. For example, the number of nozzles 14 and liquid ejection modules 30 may be one instead of multiple. Furthermore, the nozzles 14 and liquid ejection modules 30 may be arranged in multiple rows instead of one row.

[0016] 2, reference numeral 19 denotes a housing seal member provided at the joint between the first housing 11a and the second housing 11b. In this example, an O-ring is used as the housing seal member, which prevents ink from leaking from the joint between the first housing 11a and the second housing 11b.

[0017] With the above configuration, supply port 16 takes in pressurized ink from the outside, sends the ink in the direction of arrow a1, and supplies the ink to flow path 17. Flow path 17 sends the ink from supply port 16 in the direction of arrow a2. Then, recovery port 18 recovers ink that was not ejected from nozzles 14 arranged along flow path 17 in the direction of arrow a3.

[0018] The liquid ejection module 30 includes an on-off valve 31 and a piezoelectric element 32 as a driver. The on-off valve 31 opens and closes the nozzle 14. The piezoelectric element 32 drives the on-off valve 31. When a voltage is applied to the piezoelectric element 32, it expands and contracts in the longitudinal direction, which is the vertical direction in FIG. 2.

[0019] In the above configuration, when the piezoelectric element 32 is operated to move the on-off valve 31 upward, the nozzle 14 that was closed by the on-off valve 31 opens, allowing ink to be ejected from the nozzle 14. When the piezoelectric element 32 is operated to move the on-off valve 31 downward, the tip of the on-off valve 31 seals the nozzle 14, causing the nozzle 14 to be closed, and ink will no longer be ejected from the nozzle 14.

[0020] 3 is an explanatory diagram showing the positional relationship with the heating means of the liquid ejection head 10 according to the embodiment of the present invention. The first housing 11a has the heater 12 disposed in the vicinity of the nozzles 14 so as to cross the nozzles 14, as shown by the dashed lines in FIG.

[0021] Next, the details of the liquid ejection module 30 will be described with reference to Fig. 4. Fig. 4(a) is a cross-sectional view of a single liquid ejection module, and Fig. 4(b) is an enlarged view of the main part of Fig. 4(a). Two O-rings 34 are attached, one above the other, to the outer periphery of the shaft of the on-off valve 31 to prevent leakage of high-pressure ink.

[0022] The liquid ejection module 30 mainly includes the aforementioned on-off valve 31, piezoelectric element 32, fixing member 33, holder 35, plug 36, and the like.

[0023] The holder 35 has a driver housing portion 35a therein, and the driver housing portion 35a houses and holds the piezoelectric element 32. The holder 35 is made of a metal that can elastically expand and contract in the longitudinal direction of the piezoelectric element 32. As the elastically expandable metal, stainless steel such as SUS304 or SUS316L can be used. The holder 35 is a frame in which a plurality of elongated members extending in the longitudinal direction are arranged around the piezoelectric element 32 (for example, four members arranged at 90° intervals), and the piezoelectric element 32 can be inserted inside the holder 35 by passing between the elongated members.

[0024] 4(a), which is also the longitudinal direction of the on-off valve 31, the liquid discharge module 30, and the second housing 11b.

[0025] An on-off valve 31 is connected to the tip of the holder 35 on the nozzle 14 side. In addition, a bellows portion 35b is formed on the nozzle 14 side of the holder 35. The bellows portion 35b is used to cause the tip side of the holder 35 to expand and contract in the longitudinal direction in the same manner as the piezoelectric element 32 when the piezoelectric element 32 is expanded and contracted.

[0026] Furthermore, a fixed member 33 is connected to the base end side of the holder 35, which is opposite to the nozzle 14 side. In other words, the fixed member 33 is housed in the upper end part of the second housing 11b.

[0027] The fixing member 33 has a through-hole 33a extending in the radial direction, into which a positioning screw 60 is screwed from outside the second housing 11b.

[0028] The positioning screw 60 is inserted into a longitudinally elongated hole 11b1 formed in the upper end of the second housing 11b, and is movable a predetermined distance in the longitudinal direction of the second housing 11b in Figure 4. With the fixing member 33 positioned in the longitudinal direction, the positioning screw 60 is tightened.

[0029] Meanwhile, a female screw hole 11b2 is formed in the upper end opening of the second housing 11b. A plug 36 that abuts against the restricting member 20 of Fig. 2 is screwed into this female screw hole 11b2. The plug 36 abuts against the upper end of the fixing member 33 that has been positioned in the longitudinal direction by the positioning screw 60, thereby finally fixing the fixing member 33 in position.

[0030] A compression spring 37 is disposed at the bottom end of the second housing 11b. This compression spring 37 biases the piezoelectric element 32, the holder 35 that holds the piezoelectric element 32, and the like upward.

[0031] Next, we will explain the configuration of one longitudinal end of the on-off valve 31, which is the end facing the nozzle 14. This one longitudinal end of the on-off valve 31 is the part of the on-off valve 31 that opens and closes the nozzle 14.

[0032] As shown in FIG. 5, the on-off valve 31 includes a core 310 and a sealing member 40 serving as an elastic member. The core 310 is made of a metal material such as stainless steel. The core 310 has a core end 311 at the end on the nozzle 14 side, which is the lower side in FIG. 5. The core end 311 has a recess 312 inside that opens toward the nozzle. The core end 311 is cylindrical in the longitudinal portion corresponding to the recess 312, and the remaining portion is columnar. However, the cross section does not necessarily have to be circular. The recess 312 can be formed by, for example, cutting or polishing a columnar member. By providing the recess 312, the linear travel distance of ink can be increased.

[0033] The sealing member 40 is provided across the recess 312 and the outer side surface 311a of the core end portion 311, which is the outer peripheral surface of the core end portion 311. The sealing member 40 of this embodiment is made of a perfluoroelastomer. Specifically, it is preferable to use "DAIEL GA-55: registered trademark of Daikin Industries, Ltd.," "AFLAS Premium PM1100: registered trademark of Asahi Glass Co., Ltd.," "Kerlez: registered trademark of DuPont Co., Ltd.", or the like as the sealing member 40.

[0034] The length of the recess 312 and the seal member 40 in the radial direction of the core end 311 is set to be larger than the diameter of the nozzle 14. In other words, when the on-off valve 31 is closed, the seal member 40 can cover and seal the nozzle 14.

[0035] Next, the opening and closing operation of the on-off valve 31 will be described.

[0036] When the piezoelectric element 32 is activated and pushes down the on-off valve 31 in the direction of arrow a4 in Figure 4(a), the bottom surface of the sealing member 40 comes into contact with the nozzle plate 15, covering the nozzle 14, as shown in Figure 6(a). However, in this state, the nozzle 14 is not completely sealed.

[0037] As shown in Fig. 6(b), when the piezoelectric element 32 presses the on-off valve 31 further downward from the state shown in Fig. 6(a), the sealing member 40 is crushed between the core material 310 and the nozzle plate 15. In this state, stress is generated in the direction of arrow b1 from the nozzle plate 15 to the sealing member 40. When this stress becomes higher than the ink supply pressure shown by arrow b2, the nozzle 14 can be sealed by the sealing member 40.

[0038] 6(c), the piezoelectric element 32 is actuated to move the on-off valve 31 upward. This forms a gap g between the nozzle plate 15 and the on-off valve 31. This causes ink to be supplied in the direction of arrow a5. The nozzle 14 is opened. This gap g can be rephrased as the lift amount of the on-off valve 31 from the nozzle plate 15, and hereinafter this gap g will also be referred to as the lift amount g of the on-off valve 31. Then, the on-off valve 31 moves up and down due to the driving of the piezoelectric element 32, causing ink to be ejected from the nozzle 14.

[0039] When molding the core end portion 311 equipped with the sealing member 40 made of the perfluoroelastomer, the core 310 is molded by pressing or injection molding, and the perfluoroelastomer is filled into a heated mold and vulcanized. This results in the core 310 and the sealing member 40 being molded integrally.

[0040] Peroxide vulcanization is preferably used for vulcanizing perfluoroelastomers. In peroxide vulcanization, iodine and bromine incorporated in the raw polymer serve as reaction sites, and a polyfunctional unsaturated compound serves as a crosslinking aid, resulting in a radical reaction generated by peroxide to form a crosslinked structure. Radicals generated by thermal decomposition of the compounded peroxide react with iodine and bromine to form polymer radicals. This polymer radical then loads the polyfunctional unsaturated compound, forming a crosslinked structure. Such iodine and bromine can be introduced by copolymerization as a crosslinking monomer, or by chain transfer reaction at the molecular end. Triallyl isocyanurate (TAIC) or trimethallyl isocyanurate (TMAIC) is preferably used as the polyfunctional unsaturated compound.

[0041] In vulcanizing perfluoroelastomers, it is preferable to perform a primary vulcanization followed by a secondary vulcanization. This allows the vulcanization reaction to be fully completed, stabilizing the mechanical properties of the perfluoroelastomer, such as compression set. The optimal conditions for the vulcanization method can be selected depending on the molding method selected. For example, primary vulcanization using a press is preferably performed at 160 to 180 degrees for several minutes to 20 minutes. Furthermore, secondary vulcanization is preferably performed at 220 to 250 degrees for 2 to 4 hours.

[0042] In this way, by providing the recess 312 in the core end 311, the portion of the seal member 40 provided within the recess 312 functions as a retainer for the seal member 40 from coming out of the core end 311. In particular, in this embodiment, by integrally molding the seal member 40 with the on-off valve 31, the seal member 40 can be provided without gaps within the recess 312, and gaps are less likely to form between the seal member 40 and the recess 312.

[0043] If the seal member 40 does not adhere sufficiently to the core end portion 311 and a gap is formed between the recess 312 and the seal member 40, the amount of ink ejected from the nozzle 14 will vary. In other words, in a configuration where such a gap is likely to occur, the position of the underside of the seal member 40 in FIG. 6 will tend to vary. Furthermore, if a gap is formed between the recess 312 and the seal member 40, when the on-off valve 31 is pressed against the nozzle plate 15 as shown in FIG. 6(b), the error in the amount of compression of the seal member 40 increases. This causes an error in the actual amount of movement of the on-off valve relative to the amount of movement of the piezoelectric element, and also causes variation in the lift amount g of the on-off valve 31 in FIG. 6(c).

[0044] In contrast, in this embodiment, by providing the seal member 40 across the recess 312 and the side surface 311a of the core end 311, the adhesion of the seal member 40 to the core end 311 can be improved. In other words, by holding the seal member 40 by the side surface 311a, it is possible to prevent the seal member 40 provided in the recess 312 from peeling off and forming a gap in the recess 312, or the seal member 40 in the recess 312 from falling off the core end 311, for example, when the on-off valve 31 repeatedly moves up and down. This makes it possible to suppress variation in the position of the bottom surface of the seal member 40, which is the end of the on-off valve 31 on the nozzle 14 side, when the on-off valve 31 is pressed against the nozzle plate and compressed by the opening and closing operation of the on-off valve 31 (described later), and when the on-off valve 31 is released from this compressed state to release the compressed state. This suppresses variation in the lift amount g, and thus variation in the amount of ink ejected from the nozzle 14. In particular, in this embodiment, by providing the seal member 40 around the entire periphery of the side surface 311a of the core end portion 311, the adhesion of the seal member 40 to the core end portion 311 can be further improved.

[0045] Furthermore, by providing the sealing member 40 not only within the recess 312 but also across the bottom surface 311b and the side surface 311a (particularly the portion of the side surface 311a on the bottom surface 311b side), the sealing ability of the nozzle 14 can be improved when the on-off valve 31 is closed.

[0046] As shown in FIG. 5 , the thickness of the portion of the seal member 40 facing the nozzle is defined as thickness T1. The portion of the core end 311 surrounding the recess 312 is defined as a protrusion 319, and the thickness of the portion of the seal member 40 corresponding to the bottom surface 311b of the core end 311, which is the longitudinal end face of the protrusion 319 on the nozzle 14 side, is defined as thickness T2. The protrusion 319 is cylindrical. In this case, the value of T1 / T2 is preferably 1.6 or more and 6 or less. Increasing thickness T1 increases the size of the seal member 40 placed within the recess 312, but this increases the tendency for the recess 312 to deform downward during thermal expansion. Increasing thickness T2 is advantageous for the sealing of the nozzle 14 by the on-off valve 31, but increases the operating amount of the piezoelectric element 32. Taking these factors into consideration, thicknesses T1 and T2 are set within the above ranges. In other words, the thickness T1 is the length in the longitudinal direction from the bottom of the upper end of the recess 312 in FIG. 5 to the end of the seal member 40 on the nozzle 14 side.

[0047] As shown in FIG. 7 , the seal member 40 may have a thin-walled portion 40a at a position corresponding to the edges D1 and D2 of the protrusion 319. Specifically, the thin-walled portion 40a has a shape in which the corners of the seal member 40 corresponding to the edges D1 and D2 (see the dotted lines in FIG. 7 ) are round-chamfered or C-chamfered. However, the chamfering angle is not limited to 45 degrees as in the C-chamfer. In this embodiment, the thin-walled portion 40a is a portion having a smaller thickness than the other portions of the seal member 40. This "portion having a smaller thickness" does not necessarily mean a portion having a smaller absolute value of thickness. It may also mean a portion in which, assuming that the seal member 40 has a shape following the shape of the core material end 311, the offset of the end of the seal member 40 from the core material end 311 is smaller than the other portions of the seal member 40. For example, the thin-walled portion 40a in this embodiment is thinner than the shape shown by the dotted lines in FIG. 7 and is smaller in offset from the core material end 311 than the other portions of the seal member 40. Furthermore, the "portions corresponding to" the edges D1, D2, etc. of the core end 311 of the seal member 40 refer to portions corresponding to the edges D1, D2, etc. of the core end 311 when it is assumed that the seal member 40 has a shape that follows the core end 311. The edges D1, D2 are peripheral edges on the bottom surface 311b of the core end 311 or on the end surface of the protrusion 319 on the nozzle 14 side in the longitudinal direction, with edge D1 being the outer peripheral edge and edge D2 being the inner peripheral edge.

[0048] In other words, the width W1 of the sealing member 40 is set smaller than the width W2. The width W1 is the width of the flat portion 40b provided facing the nozzle plate 15 on the lower side in FIG. 7, which is closer to the nozzle plate 15 (see FIG. 4(b)) than the convex portion 319 of the sealing member 40. The width W2 is the radial width of the convex portion 319. The radial width W2 of the convex portion 319 referred to here does not refer to the outer diameter W0 of the convex portion 319 or the core end portion 311 in FIG. 5, but refers to the radial width of a thick portion provided in the circumferential direction of the convex portion 319.

[0049] 7, when the seal member 40 thermally expands or swells, the portions of the seal member 40 corresponding to the edges D1 and D2 of the core end portion 311 are particularly likely to become larger. Therefore, by previously making the portions of the seal member 40 that are likely to expand small as described above, it is possible to prevent the surface of the seal member 40 that comes into contact with the nozzle plate 15 from becoming sharp at the positions corresponding to the edges D1 and D2 of the seal member 40 due to expansion of the seal member 40, and other such large deformations. This makes it possible to suppress variations in the gap g when the on-off valve 31 is open, and to stabilize the amount of ink ejected by the liquid ejection head.

[0050] 8, a groove 313 may be provided on the side surface 311a of the core end 311. The groove 313 is provided circumferentially on the side surface 311a, and multiple grooves 313 are provided in the longitudinal direction of the core end 311.

[0051] By providing the groove 313, the perfluoroelastomer that is the material that constitutes the seal member 40 enters the groove 313 when the seal member 40 is molded. As a result, the portion of the seal member 40 that has entered the groove 313 after the seal member 40 is molded functions as a retainer for the seal member 40 from the core end 311. This further improves the adhesion of the seal member 40 to the core end 311.

[0052] 9, an adhesive 41 may be applied to the contact area between the core end 311 and the seal member 40. This can further improve the adhesion of the seal member 40 to the core end 311. When molding the seal member 40 and the on-off valve 31, it is preferable to apply the adhesive to the core end 311 beforehand and then perform the primary vulcanization.

[0053] Next, the results of an experiment on the effect of suppressing fluctuations in the amount of ink ejected from the nozzle 14 by the on-off valve and the seal member of the above embodiment will be described.

[0054] The present embodiment uses an on-off valve 31 and a seal member 40 configured as shown in FIG. 5. The perfluoroelastomer used to make the seal member is formulated as follows: 100 parts by weight of "Dai-el GA-55" (registered trademark of Daikin Industries, Ltd.), 20 parts by weight of MT carbon black, 4 parts by polymerization of triallyl isocyanurate, and 1 part by polymerization of peroxide. The core material 310 and the seal member 40 are integrally molded by press processing. The primary vulcanization of the seal member 40 involves press vulcanization at 160°C for 10 minutes, and the secondary vulcanization involves thermal retention oven vulcanization at 250°C for 4 hours. The liquid ejection head having the on-off valve 31 thus formed is referred to as "Example."

[0055] Here, a liquid ejection head having an on-off valve of a different configuration from that of this embodiment will be tested as a "comparative example." The configuration of the on-off valve and sealing member provided in this liquid ejection head of the "comparative example" will be described with reference to FIG. 10 . An on-off valve 400 has a recess 402 on the bottom surface of a tip portion 401 on the nozzle side. A sealing member 440 is provided within the recess 402. The sealing member 440 is fitted into the recess 402 by applying pressure while in the form of a molded part. This liquid ejection head having the on-off valve 400 described above will be referred to as the "comparative example." In this on-off valve 400, the sealing member 440 is merely mechanically fitted into the recess 402 as described above, and therefore the sealing member 440 does not adhere sufficiently within the recess 402, resulting in a gap being formed between the recess 402 and the sealing member 440 as shown in FIG. 10 .

[0056] The on-off valves having the sealing members of the above "Example" and "Comparative Example" were connected to piezoelectric elements, and lead wires were drawn out from the liquid ejection module to fabricate liquid ejection heads.

[0057] Other setting conditions are as follows: The initial sealing position of the on-off valve, 5 μm, is the displacement of the piezoelectric element in the sealed state shown in FIG. 6(b) when the position where the sealing member 40 in FIG. 6(a) contacts the nozzle plate 15 is set as the reference position for the displacement of the piezoelectric element. Initial sealing position of piezoelectric valve: 5 μm Initial setting of lift amount of on-off valve: 20 μm Diameter of the recess on the nozzle side: 500 μm Nozzle hole diameter: 150 μm Ink viscosity: 30 mPa·S Pressure applied to the ink chamber: 0.45 MPa Ink supply time: 30 minutes

[0058] For each of the liquid ejection heads of the above "Example" and "Comparative Example," the ink flow rate was measured after 1 minute, 10 minutes, and 30 minutes. As a result, the ink flow rate for the "Example" remained almost constant until 30 minutes had passed, whereas for the "Comparative Example," the flow rate increased over time, eventually resulting in leakage. When the liquid ejection head of the "Comparative Example" was disassembled after evaluation and the surface position of the sealing member was checked, it was found to have shrunk in the longitudinal direction of the on-off valve. This is thought to be due to a gap between the sealing member and the core material, which caused the sealing member to shift position.

[0059] In this way, the configuration of the on-off valve 31 of this embodiment makes it possible to suppress variations in the ink flow rate due to the liquid ejection head.

[0060] Fig. 11 is a diagram showing variations in the lift amount g in the configuration of the "comparative example." The horizontal axis X in Fig. 11 represents the displacement amount of the piezoelectric element, and the vertical axis in Fig. 11 represents the lift amount g.

[0061] 11, the lift amount g varies between dotted line B1, which plots its upper limit, and dotted line B2, which plots its lower limit. This variation is mainly caused by the gap formed between seal member 440 and recess 402. In other words, because of this gap, the position of the bottom surface of the seal member is prone to variation, and the amount of compression of the seal member when the on-off valve is closed also varies.

[0062] In contrast, Fig. 12 is a diagram showing the variation in lift amount g when the on-off valve 31 of the "Example" is used. As can be seen by comparing Fig. 11 and Fig. 12, in this embodiment, the fluctuation range of the lift amount g, shown as the width between the dotted lines C1 and C2, is smaller than when the on-off valve 400 of Fig. 11 is used. Therefore, it can be seen that the configuration of this embodiment allows a stable amount of ink to be ejected from the nozzle 14. This is because the on-off valve 31 of this embodiment has good adhesion of the seal member 40 to the core material 310.

[0063] Next, a liquid ejection apparatus equipped with the liquid ejection head 10 described above will be described.

[0064] Fig. 13 is a schematic diagram of the overall configuration of a liquid ejection device 100. Fig. 13(a) is a side view of the liquid ejection device, and Fig. 13(b) is a plan view of the same device. The liquid ejection device 100 is installed facing a liquid application target 500, which is an example of a target object. The liquid ejection device 100 includes an X-axis rail 101, a Y-axis rail 102 that intersects with the X-axis rail 101, and a Z-axis rail 103 that intersects with the X-axis rail 101 and the Y-axis rail 102. In particular, in this embodiment, the rails 101, 102, and 103 extend in directions that are perpendicular to each other.

[0065] The Y-axis rail 102 holds the X-axis rail 101 so that the X-axis rail 101 can move in the Y-axis 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-axis direction. The Z-axis rail 103 then holds the carriage 1 so that the carriage 1 can move in the Z-axis direction.

[0066] The liquid ejection device 100 includes a first Z-direction drive unit 92 that moves the carriage 1 in the Z-axis direction along the Z-axis rail 103, and an X-direction drive unit 72 that moves the Z-axis rail 103 in the X-axis 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-axis 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-axis direction relative to the carriage 1.

[0067] The liquid ejection head described above is attached to the head holder 70 so that the nozzles 14 (see FIG. 2) of the liquid ejection head 10 face the liquid-receiving target 500. The liquid ejection device 100 configured in this manner ejects ink, an example of a liquid, from the liquid ejection head attached to the head holder 70 toward the liquid-receiving target 500 while moving the carriage 1 in the X-axis, Y-axis, and Z-axis directions, thereby drawing on the liquid-receiving target 500.

[0068] Next, the configuration of an inkjet printer 201, which is another embodiment of a liquid ejection device, will be described with reference to FIGS. 14 to 17. FIG. 14 is a diagram showing the configuration of an inkjet printer 201 as an example of a liquid ejection device according to an embodiment. FIG. 15 is an explanatory diagram showing an example of the arrangement of the inkjet printer 201 shown in FIG. 14 relative to an automobile M, which is an object to be printed. FIG. 16 is an explanatory diagram showing another example of the arrangement of the inkjet printer 201 shown in FIG. 14 relative to an automobile M, which is an object to which liquid is to be applied. FIG. 17 is an explanatory diagram of an image printed on a spherical surface by an inkjet printer. FIG. 17(a) is an explanatory diagram of an image printed on a spherical surface by the inkjet printer 201, FIG. 17(b) is an explanatory diagram showing the result of printing a rectangle on a spherical surface, and FIG. 17(c) is an explanatory diagram of an image printed on a spherical surface by the inkjet printer 201.

[0069] As shown in FIG. 14, the inkjet printer 201 generally comprises a liquid ejection head 202, a camera 204 as an image capturing unit, an XY table 203, image editing software S, a control unit 209, and a drive unit 211. The camera 204 is disposed near the liquid ejection head 202. The XY table 203 moves the liquid ejection head 202 and the camera 204 in the X and Y directions. The image editing software S edits the images captured by the camera 204. The control unit 209 operates the XY table 203 based on a preset control program to cause the liquid ejection head 202 to eject ink. The drive unit 211 moves the camera 204 to an image capturing position and moves the liquid ejection head 202 to a liquid ejection position under the control of the control unit 209.

[0070] The liquid ejection head 202 is configured with multiple valve-type nozzles. The liquid ejection head 202 ejects ink toward the surface of the workpiece M to which the liquid is to be applied. Note that the term "ink" here also includes "paint."

[0071] Ink is ejected from each valve-type nozzle perpendicular to the liquid ejection head 202. In other words, the ink ejection surface of the liquid ejection head 202 is parallel to the XY plane formed by the movement of the XY table 203, and the ink dots ejected from each valve-type nozzle are ejected in a direction perpendicular to the XY plane. The ejection direction of the ink ejected from each valve-type nozzle is also parallel to the XY plane. Each valve-type nozzle is connected to an ink tank of a specific color. This ink tank is pressurized by a pressure device. If the distance between each valve-type nozzle and the printing surface of the object M to be liquid-applied is about 20 cm, ink dots can be ejected onto the printing surface without any problems.

[0072] The XY table 203 is generally configured with an X-axis 205 and a Y-axis 206. The X-axis 205 has a linear movement mechanism. The Y-axis 206 holds the X-axis 205 with two arms and moves the X-axis 205 in the Y direction. The liquid ejection head 202 and a camera 204 (described later) are attached to a slider of the X-axis 205. A shaft 207 is provided on the Y-axis 206. This shaft 207 is held by a robot arm 208. The robot arm 208 allows the liquid ejection head 202 to be freely positioned at a predetermined position where ink should be ejected onto the liquid application target M. For example, if the liquid application target M is an automobile, the liquid ejection head 202 can be positioned horizontally as shown in FIG. 16 or above as shown in FIG. 15. The operation of the robot arm 208 is controlled based on a program previously stored in a control unit 209.

[0073] The camera 204 is disposed on a slider of the X-axis 205 near the liquid ejection head 202. The camera 204 photographs a predetermined range of the liquid application surface of the liquid application target M at constant, minute intervals while moving in the X and Y directions. The camera 204 is a so-called digital camera. The specifications of the camera 204, such as the lens specifications and resolution, are appropriately selected so that the camera 204 can photograph a plurality of sub-divided images of the predetermined range of the liquid application surface. The camera 204 photographs a plurality of sub-divided images of the liquid application surface continuously and automatically in accordance with a program pre-installed in the control unit 209.

[0074] The control unit 209 is composed of a so-called microcomputer equipped with a storage device, a central processing unit, input devices such as a keyboard and a mouse, a monitor 210, and a DVD player, etc., as necessary. The storage device records and saves various programs, data on captured images, data on images to be printed, etc. The central processing unit executes various processes in accordance with the programs. The monitor 210 displays information input to the control unit 209, processing results by the control unit 209, etc.

[0075] The control unit 209 performs image processing on the multiple pieces of subdivision image data captured by the camera 204 using image processing software. Specifically, the control unit 209 generates a composite print surface by projecting the liquid application surface of the non-planar liquid application target M onto a plane. The control unit 209 also generates an edited image of the drawing target by editing the drawing target image so that it is continuous with the image formed on the liquid application surface. For example, the control unit 209 generates an edited image of the drawing target by editing the print image 252b, which is the drawing target image shown in FIG. 17(c), so that the print image 252b is aligned with the composite print surface so that no non-print area 253 is formed between the print image 252a and the adjacent print image 252a. Then, by actually ejecting ink from the liquid ejection head 202 based on this edited image of the drawing target, it is possible to form the print image 252b without any gaps between it and the print image 252a. The driving unit 211, whose operation is controlled by the control unit 209, captures the multiple subdivision images using the camera 204 and forms an image by ejecting ink from each nozzle of the liquid ejection head 202.

[0076] 17(a) shows the ejection direction of ink ejected from each inkjet nozzle mounted on nozzle head 250 in the case where a two-dimensional rectangle is formed by inkjet nozzles on the spherical surface of spherical object 251 to which liquid is to be applied. In Fig. 17(b), since ink ejected from each inkjet nozzle mounted on nozzle head 250 is ejected in a direction perpendicular to nozzle head 250, it is shown that print image 252a printed on the surface of object 251 to which liquid is to be applied is a rectangle with a distorted periphery.

[0077] 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.

[0078] In this application, a "liquid ejection device" is a device that includes a liquid ejection head 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.

[0079] 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.

[0080] 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).

[0081] 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.

[0082] The above-mentioned "object onto which a liquid can adhere" refers to the aforementioned object to which the liquid can be applied, and means an object onto which the liquid can adhere at least temporarily, an object onto which the liquid adheres and sticks, an object 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 the liquid can adhere.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] In the present application, the terms image formation, recording, printing, copying, printing, modeling, etc. are all synonymous. [Explanation of symbols]

[0087] 10 Liquid ejection head 14 Nozzle (outlet) 15 Nozzle plate (discharge port forming member) 30 Liquid Dispensing Module 31 On-off valve 311 Core material end 311a Outer side of core end 311b Bottom surface of core end 312 recess 313 Groove 319 Convex 32 Piezoelectric element (driver) 40 Sealing member (elastic member) 40b Flat portion of sealing member 41 Adhesive 100 Liquid dispensing device A Longitudinal direction (direction of movement of on-off valve) D1 Outer periphery of the nozzle side end face of the convex part D2 Inner edge of the nozzle side end face of the convex part [Prior art documents] [Patent documents]

[0088] [Patent Document 1] US Patent US2012 / 0105522A1

Claims

1. a discharge port for discharging a liquid; a movable opening / closing valve for opening and closing the ejection port, The on-off valve has a core material, a core end portion is provided at an end portion of the core material on the discharge port side, The core end portion has a recessed portion on the inside thereof that is open to the discharge port side, an elastic member is provided across the outer side surface of the core end portion and the recess; the end of the core has a bottom surface which is an end surface on the discharge port side in the movement direction of the on-off valve, the bottom surface is provided so as to surround the recess when viewed from the discharge port side in the movement direction of the on-off valve, If a corner connecting the bottom surface of the core end and the outer side surface is defined as an outer corner, the elastic member is provided to cover the outer side surface, the outer corner portion, and the bottom surface, the elastic member has a flat portion at a position facing the bottom surface in the movement direction of the on-off valve, A liquid ejection head characterized in that the elastic member has an inclined portion that is inclined with respect to the flat portion and the outer side surface at a position that overlaps the outer corner when viewed from the ejection port side in the movement direction of the opening / closing valve.

2. The core end has an inner side surface that forms the recess, If the portion connecting the bottom surface and the inner side surface is defined as an inner corner, 2. The liquid ejection head according to claim 1, wherein the elastic member has an inclined portion inclined with respect to the bottom surface and the inner side surface at a position overlapping the inner corner when viewed from the ejection port side in the movement direction of the on-off valve.

3. The end of the core material has a cylindrical convex portion on the discharge port side in the movement direction of the on-off valve, the bottom surface is an end surface of the convex portion, the outer side surface is an outer peripheral surface of the convex portion, and the inner side surface is an inner peripheral surface of the convex portion, 3. A liquid ejection head according to claim 2, wherein the width of the flat portion of said elastic member in the radial direction is W1 and the width of said bottom surface in the radial direction is W2, and W1<W2 are set.

4. 4. The liquid ejection head according to claim 1, wherein a groove is formed on an outer side surface of the end of the core material, and the elastic member is provided in the groove.

5. 5. The liquid ejection head according to claim 1, wherein the elastic member is adhered to the end of the core material by an adhesive.

6. The end of the core material has a cylindrical convex portion on the discharge port side in the movement direction of the on-off valve, the bottom surface is an end surface of the convex portion, the outer side surface is an outer peripheral surface of the convex portion, and the inner side surface is an inner peripheral surface of the convex portion, Let T1 be the thickness of the elastic member in the movement direction of the on-off valve, which is the thickness of a portion thereof facing the discharge port, and T2 be the thickness of the elastic member in the movement direction of the on-off valve, which is the thickness of a portion of the elastic member corresponding to the bottom surface of the convex portion in the movement direction of the on-off valve, 6. The liquid ejection head according to claim 1, wherein T1 / T2 is set to 1.6≦T1 / T2≦6.

7. 7. The liquid ejection head according to claim 1, wherein the elastic member is provided over the entire periphery of the outer side surface of the end portion of the core material.

8. A liquid ejection device comprising the liquid ejection head according to claim 1 .

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