Liquid ejection head and liquid ejection device

Abstract

To provide a liquid ejection head comprising a novel sealing mechanism that achieves both of high sealing characteristics and low driving resistance.SOLUTION: A liquid ejection head according to the present invention comprises: ejection ports for ejecting liquid; needle-shaped valve bodies that each open and close the ejection port by moving along an axial direction; drive means that each drive the valve body to open and close; and sealing members each arranged between the valve body and a housing inner wall surrounding the valve body so as to partition between the liquid chamber through which the valve body passes and the drive unit. The sealing member has a contact point with the valve body and a contact point with the housing inner wall that are at different positions in an axial direction of the valve body; and the contact point with the housing inner wall is slidable along the housing inner wall with other portions being in a substantially non-contact state.SELECTED DRAWING: Figure 10

Description

[Technical Field]

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

[0002] Inkjet heads for painting, which are used for painting large vehicles such as cars, trucks, and airplanes, writing letters on gas cylinders, marking white lines on roads, and writing other text, are required to eject highly viscous liquids such as paint. As a liquid ejection head for ejecting such a highly viscous liquid, a liquid ejection head is known that seals the ejection port with a needle when closed and retracts the needle to open the ejection port when opened (see, for example, Patent Documents 1 to 5, etc.). Furthermore, in order to paint or draw on a large area with high efficiency, there is a constant demand for smaller and finer-pitch ejection ports, as well as higher frequencies for higher speeds and improved productivity. In order to eject high-viscosity ink at high speed, it is necessary to increase the pressure of the ink in the liquid chamber 5 and push out the ink material by overcoming the ejection resistance at the nozzle portion. In order to seal the liquid chamber 5 without succumbing to the increased ink pressure inside the liquid chamber 5, it is necessary to improve the sealing valve that turns on and off. Furthermore, this sealing valve also needs to be arranged at a high pitch to match the nozzles that are arranged at a high pitch.

[0003] A conventional method for sealing involves crushing an elastic O-ring placed around the needle (see, for example, Patent Document 1). However, with this method using a conventional O-ring, the resistance of the O-ring itself caused by the sliding of the needle becomes an obstacle, particularly when the needle is repeatedly turned on and off at high speed, preventing it from being able to operate at high speeds. On the other hand, methods that do not use an O-ring include those that use a membrane-like sealing member (see, for example, Patent Documents 4 and 5), but this has the problem that when the liquid chamber 5 becomes high pressure, the sealing position fluctuates due to the pressure difference between the inside and outside of the membrane.

[0004] Furthermore, even if the pressure difference is minimized, unless high positioning accuracy is ensured when attaching both ends of the membrane, the sealing position will ultimately vary for each individual needle. Such fluctuations in the sealing position manifest themselves as differences in the amount of needle movement when the nozzle is turned on and off, and when multiple needles are arranged at high density, this can cause variations in the amount of ejection from each ejection port. Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, there was a need to develop a new sealing member that could both suppress the resistance that occurs between the needle and the sealing member and solve the problem caused by the pressure difference. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a liquid ejection head having a new sealing mechanism that achieves both high sealing characteristics and low driving resistance. [Means for solving the problem]

[0006] The liquid ejection head of the present invention is a liquid ejection head comprising: an ejection port for ejecting liquid; a needle-shaped valve body that opens and closes the ejection port by moving along the axial direction; a drive means for driving the valve body to open and close; and a sealing member arranged between the valve body and an inner wall of a housing that surrounds the valve body so as to separate a liquid chamber through which the valve body passes and a drive unit, wherein the sealing member is characterized in that the contact point with the valve body and the contact point with the inner wall of the housing are at different positions in the axial direction of the valve body, the other parts are in a substantially non-contact state, and the contact point with the inner wall of the housing is slidable along the inner wall of the housing. [Effects of the Invention]

[0007] According to the present invention, it is possible to achieve both high sealing characteristics and low driving resistance. [Brief explanation of the drawings]

[0008] [Figure 1]1 is a schematic diagram of a liquid ejection device to which an embodiment of the present invention can be applied. [Figure 2] FIG. 2 is a schematic diagram illustrating an example of using the liquid ejection device shown in FIG. [Figure 3] 3 is a diagram showing another example of use of the liquid ejection device shown in FIG. 2. FIG. [Figure 4] 1 is a diagram illustrating an example of a configuration of a liquid ejection head according to an embodiment of the present invention. [Figure 5] FIG. 2 is a diagram illustrating an example of the internal configuration of a liquid ejection head. [Figure 6] FIG. 6 is a diagram showing an example of the configuration of the nozzle plate shown in FIG. 5. [Figure 7] 10A and 10B are diagrams illustrating an example of a method for attaching a nozzle plate and a flow path member. [Figure 8] 3A and 3B are diagrams illustrating an example of the arrangement of liquid ejection modules in a liquid ejection head. [Figure 9] FIG. 2 is a diagram illustrating an example of a configuration of an arm member. [Figure 10] 1A and 1B are diagrams illustrating an example of the configuration of a needle valve body according to the present invention. [Figure 11] FIG. 11 is a diagram showing the tip of FIG. [Figure 12] FIG. 9 is a diagram showing an example of a CC cross section in FIG. 8. [Figure 13] FIG. 9 is a diagram showing an example of a cross section DD of FIG. 8. [Figure 14] FIG. 1 is a diagram showing an example of a conventional sealing method. [Figure 15] FIG. 10 is a diagram showing another example of a conventional sealing method. [Figure 16] 15 is a diagram showing the reaction force of an elastic member in the sealing method shown in FIG. 14. FIG. [Figure 17] FIG. 10 is a diagram showing a comparison of reaction forces between the present invention and a conventional example. [Figure 18] 3A and 3B are diagrams showing an example of the configuration of a sealing member according to the present invention. [Figure 19] 10A and 10B are diagrams showing an example of the operation during sealing when the seal member of the present invention is used. [Figure 20]10A and 10B are diagrams showing an example of an initial state during positioning when the seal member of the present invention is used; [Figure 21] 10A and 10B are diagrams illustrating an example of an operation during positioning when the sealing member of the present invention is used. [Figure 22] FIG. 4 is a diagram showing an example of the configuration of a seal member according to a second embodiment of the present invention. [Figure 23] 10A and 10B are diagrams showing an example of the configuration of a seal member according to a third embodiment of the present invention. [Figure 24] FIG. 10 is a diagram showing an example of the configuration of a seal member according to a fourth embodiment of the present invention. [Figure 25] 10A and 10B are diagrams showing an example of the configuration of a seal member according to a fifth embodiment of the present invention. [Figure 26] FIG. 10 is a diagram showing an example of the configuration of a seal member according to a sixth embodiment of the present invention. [Figure 27] FIG. 10 is a diagram showing an example of the configuration of a seal member according to a seventh embodiment of the present invention. [Figure 28] FIG. 10 is a diagram showing another example of the configuration of the seal member according to the seventh embodiment of the present invention. [Figure 29] FIG. 10 is a diagram showing an example of the configuration of a seal member according to an eighth embodiment of the present invention. [Figure 30] FIG. 13 is a diagram showing an example of the configuration of a sealing member according to a ninth embodiment of the present invention. [Figure 31] FIG. 20 is a diagram showing an example of the configuration of a seal member according to a tenth embodiment of the present invention. [Figure 32] 32 is a diagram showing a schematic example of air pressure and liquid pressure acting on a seal member in the configuration shown in FIG. 31. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] FIG. 1 shows a vehicle body painting apparatus 200 to which an embodiment of the present invention can be applied. In the same figure, the vehicle body painting apparatus 200 has at least one liquid ejection head 100, a camera 832 arranged near the liquid ejection head 100, an XY table 831 that moves the liquid ejection head 100 and the camera 832 in the X and Y directions, image editing software S that edits images captured by the camera 832, a monitor 901a that displays the images to be edited, and a control unit 900. The control unit 900 operates the XY table 831 based on a predetermined control program, and also causes the liquid ejection head 100 to eject a liquid L such as paint or ink.

[0010] As shown in FIG. 2, the vehicle body coating apparatus 200 can apply paint ejected from a liquid ejection head 100 to an object U to be coated, such as a vehicle body.

[0011] XY table 831 has an X axis 833 formed with a linear movement mechanism, and a Y axis 834 that moves X axis 833 in the Y direction while holding X axis 833 with two arms. A shaft 835 is provided on Y axis 834. By holding this shaft 835 with a robot arm 836, liquid ejection head 100 and camera 832 can be freely positioned with respect to object U to be coated. The control unit 900 is a control means that controls the operation of the robot arm 836 based on a predetermined program, and also functions as a control means that controls the amount of liquid L ejected from the liquid ejection head 100 by controlling the opening and closing of the nozzle 14a of the liquid ejection head 100, as described below.

[0012] 1, the object U is an automobile body, and the vehicle body coating device 200 is provided above the object U, but it may be disposed in a horizontal position as shown in Fig. 3. In the case shown in Fig. 3, the liquid ejection head 100 moves freely in the YZ plane in Fig. 1.

[0013] Fig. 4 shows an external perspective view of the liquid ejection head 100, and Fig. 5 shows an example of an AA cross section of the liquid ejection head 100 shown in Fig. 4. In the following explanation, the arrangement shown in Fig. 2 is used as an example, and the nozzle arrangement direction (longitudinal direction of the liquid ejection head) is defined as the X direction, the liquid ejection direction from the nozzles (height direction of the liquid ejection head) is defined as the Z direction, and the direction perpendicular to both the X direction and the Z direction (widthwise direction of the liquid ejection head) is defined as the Y direction, but the present invention is not limited to this configuration.

[0014] The liquid ejection head 100 has a nozzle plate 14 provided on the surface facing the object U to be coated, a flow path member 15 provided so that the liquid L, which is the paint, can flow inside, and a cover 11 which is a containing member. A supply port 12 through which the liquid L is supplied is provided at one end in the X direction of the flow path member 15, and a discharge port 13 through which the liquid L is discharged is provided at the other end in the X direction of the flow path member 15. In other words, the flow path member 15 is a member that connects the supply port 12 and the discharge port 13 to define a flow path for the liquid L. Further, at the top of the cover 11, a harness passage hole 16 is provided through which a harness including a communication cable for communicating with the actuator 2 housed inside the cover 11 is passed.

[0015] The nozzle plate 14 is fixed to the flow path member 15 in a mechanically detachable manner, and the cover 11 is fixed to the flow path member 15 in a mechanically detachable manner. The nozzle plate 14, the flow path member 15 and the cover 11 are all made of metal, resin or ceramic. As shown in FIG.

[0016] The nozzle plate 14 has a plurality of nozzles 14a formed therein as openings for discharging the liquid L. FIG. 6 is a diagram illustrating an example of the arrangement of nozzles in the nozzle plate 14. As shown in FIG. 6(a), one nozzle row can be provided in the center of the nozzle plate in the Y direction (short direction of the head), or as shown in FIG. 6(b), the nozzles 14a can be arranged in a staggered pattern to provide multiple nozzle rows in the Y direction. Note that the nozzle arrangement shown in FIG. 6 is just one example, and for example, two sets of two nozzle rows in the Y direction arranged in a staggered pattern may be provided, for a total of four nozzle rows, or multiple nozzle rows may be provided in which the nozzles are positioned at the same position in the X direction (longitudinal direction of the head). The liquid ejection head 100 of the embodiment described below will be described as having two nozzle rows in the Y direction, with the nozzles 14a arranged in a staggered pattern as shown in FIG. 6(b).

[0017] 7A and 7B are diagrams illustrating the mechanical fixation between the nozzle plate 14 and the flow path member 15. Fig. 7A is a schematic diagram of the nozzle plate 14, and Fig. 7B is a schematic diagram of the connection portion of the flow path member 15 as viewed from below. Five through holes 14b, through which screws pass, are provided at equal intervals in the X direction at each end of the nozzle plate 14 in the Y direction. Furthermore, positioning holes 14c are provided at each end of the nozzle plate 14 in the X direction for positioning the nozzle plate 14 to the flow path member 15. The positioning hole 14c at one end in the X direction serves as a primary positioning reference and is a round hole with approximately the same diameter as the diameter of the positioning pin, while the positioning hole 14c at the other end in the X direction serves as a secondary positioning reference and is an oblong hole that is long in the X direction. In this way, the nozzle plate 14 and the flow path member 15 are positioned by the positioning holes 14c and are fixed by screws.

[0018] As already shown in Fig. 5, the flow path member 15 forms a flow path 5 (liquid chamber 5) through which the liquid L flows. Therefore, a seal member 15a made of an elastic material such as rubber is provided on the lower surface of the flow path member 15 so as to surround the flow path. Furthermore, five female screw portions 15b having thread grooves on the inner peripheral surface are provided at equal intervals in the X direction on both ends of the lower surface of the flow path member 15 in the Y direction. Furthermore, pin fitting holes 15c into which positioning pins are fitted are provided on both ends in the X direction. Note that positioning pins may be formed directly on the flow path member 15.

[0019] When mechanically fixing the nozzle plate 14 and the flow path member 15, first, the positioning pins fitted in the pin fitting holes 15c of the flow path member 15 are inserted into the positioning holes 14c of the nozzle plate 14, and the nozzle plate 14 is positioned with respect to the flow path member 15. Then, screws are inserted into the through holes 14b of the nozzle plate 14, and the screws are screwed into the female thread portions 15b of the flow path member 15, whereby the nozzle plate 14 is mechanically (removably) fixed to the flow path member 15. Furthermore, when the screws are fastened, the seal member 15a provided on the flow path member 15 is crushed by the nozzle plate 14, so that the seal member 15a comes into close contact with the nozzle plate 14, thereby sealing the gap between the nozzle plate 14 and the flow path member 15.

[0020] In this embodiment, the nozzle plate 14 is fixed to the flow path member 15 by screws, so that the nozzle plate 14 can be easily removed by unscrewing the screws, and the nozzle plate can be easily replaced. This makes it possible to replace the nozzle plate with one having a nozzle diameter that provides optimal discharge characteristics for the object U onto which the liquid L is to be discharged.

[0021] As already mentioned, inside the cover 11, a plurality of liquid ejection modules 1 are accommodated, each disposed at a position corresponding to each nozzle 14a, in a staggered arrangement of two rows as shown in FIG. The liquid ejection module 1 includes a needle valve 8, which is a needle-shaped valve body that opens and closes the nozzle 14a, a compression spring 7, which is an elastic member that presses the needle valve 8 downward, an arm member 3 that rotates to press the needle valve 8, and an actuator 2, which is a drive unit that rotates the arm member 3 by pressing one end of it, thereby operating the needle valve 8.

[0022] The liquid discharging modules 1 are arranged alternately in the X direction in two rows with the needle valves 8 facing each other inside the cover 11. As shown in FIG. 4, the liquid discharging modules 1 are arranged so that the arm members 3 partially overlap when viewed from the X direction. Here, we have explained the case where the nozzles 14a are arranged in two staggered rows on the nozzle plate 14 as shown in Figure 6(b), but even if the nozzles 14a are arranged in a single row on the nozzle plate 14 as shown in Figure 6(a), the multiple liquid ejection modules 1 will be arranged so that part of the arm members 3 overlap when viewed from the X direction.

[0023] Here, staggered arrangement of the liquid ejection modules 1 can also be expressed as a state in which a liquid ejection module 1a in which the actuator 2 is located on one side of the nozzle array and a liquid ejection module 1b in which the actuator 2 is located on the other side of the nozzle array are arranged facing each other, and are arranged along the nozzle array direction so that portions of the arm members 3 overlap each other when viewed from the nozzle array direction.

[0024] The actuator 2 comprises a piezoelectric element 2a and a holder 2b that applies a preload to compress the piezoelectric element 2a and fixes it in place, and the holder 2b is fixed to the inner wall surface perpendicular to the Y direction of the cover 11. More specifically, the holder 2b fixes the end of the piezoelectric element 2a in the Z direction, which is the direction in which the piezoelectric element 2a expands and contracts, to the inner wall surface of the cover 11. Fixing is performed mechanically using screws or the like, or chemically, such as by bonding with an adhesive or by thermal diffusion.

[0025] The arm member 3 has a support shaft 4, which is rotatably supported on the cover 11 main body via a bearing. One end of the arm member 3 has a connection part that is connected to the actuator 2, and the other end has a contact part 3a that contacts an arm receiving part 8c fixed to the needle valve 8. The contact part 3a that contacts the arm receiving part 8c at the other end of the arm member 3 has a hemispherical shape that protrudes toward the arm receiving part 8c, or a crescent shape when viewed from the X direction, so that it smoothly contacts the arm receiving part 8c when the arm member 3 rotates.

[0026] Furthermore, a through hole 3b is formed on the other end of the arm member 3 as a penetration portion through which the needle valve 8 passes. The inner diameter of the through hole 3b is larger than the outer diameter of the needle valve 8 so that when the arm member 3 rotates, the inner peripheral surface of the through hole 3b, which is the side surface of the arm, does not come into contact with the outer peripheral surface of the needle valve 8. Figure 9 shows a schematic configuration of these arm members 3.

[0027] The bottom surface of the cover 11 is provided with a plurality of valve through-holes 11b (an example of a housing inner wall) through which needle valves 8 corresponding to the nozzles 14a pass. A seal member 30 is provided at the end of the valve through-hole 11b on the flow path member 15 side. A valve receiving portion 20, which serves as a restricting member, is provided on the side opposite the end of the valve through-hole 11b on the flow path member 15 side to slidably support the needle valve 8 and restrict movement of the needle valve 8 in a direction perpendicular to the opening / closing direction. The end of the needle valve 8 opposite the nozzle plate 14 side passes through a spring receiving plate 18. The needle valve 8 is held in a position parallel to the Z direction by the seal member 30, the valve receiving portion 20, and the spring receiving plate 18.

[0028] A compression spring 7 as a biasing member is provided between the arm receiving portion 8c fixed to the needle valve 8 and the spring receiving plate 18, and biases the needle valve 8 toward the nozzle plate 14 via the arm receiving portion 8c.

[0029] The compression spring 7 biases the needle valve 8 toward the nozzle plate 14, thereby stabilizing the movement of the needle valve 8 between an open position where the nozzle 14a of the needle valve 8 is opened and a closed position where the nozzle 14a is closed. The spring support plate 18 is attached to a fixing member 17 fixed to the cover 11.

[0030] 8, the actuator 2 of each liquid ejection module 1 is connected via a harness to a drive control device 50. The drive control device 50 has a waveform generating circuit 51 and an amplifier circuit 52, which are drive pulse generating units.

[0031] The waveform generating circuit 51 generates a drive pulse waveform, and the amplifier circuit 52 amplifies the voltage value to a required value. The amplified voltage signal is then applied to the actuator 2. By applying this voltage, the drive control device 50 controls the displacement of the piezoelectric element 2a, and the needle valve 8 moves up and down, thereby controlling the opening and closing of the nozzle 14a. This up and down movement of the needle valve 8 controls the ejection of the liquid L from the liquid ejection head 100. However, if the waveform generating circuit 51 can apply a sufficient voltage, the amplifier circuit 52 may be omitted.

[0032] In this embodiment, the actuator 2 has a normally closed configuration, and when no signal is supplied from the drive control device 50 to the actuator 2, the needle valve 8 closes the nozzle 14a due to the biasing force of the compression spring 7. Here, when no signal is supplied to the actuator 2, this may mean either a state where no voltage is always applied or a state where a constant static voltage is applied.

[0033] The waveform generating circuit 51 generates a drive pulse, which is a waveform that varies over time with the voltage applied to the actuator 2. The waveform generating circuit 51 receives print data, for example, from an external PC or a microcomputer inside the device, and generates a drive pulse based on this input data. The waveform generating circuit 51 can change the voltage applied to the actuator 2 and can generate multiple drive pulses. As described above, when the waveform generating circuit 51 generates a drive pulse, the piezoelectric element 2a of the actuator 2 expands and contracts in accordance with the drive pulse.

[0034] The operation of the actuator 2 when such a drive pulse is input will be described below. When a predetermined voltage is applied to the piezoelectric element 2a, the piezoelectric element 2a expands. Because the arm member 3 is supported by the cover 11 via the support shaft 4, when the piezoelectric element 2a expands, the other end of the arm member 3 rotates in a direction that lifts the arm receiving portion 8c. As a result, the arm receiving portion 8c rises (moves toward the spring receiving plate 18) against the biasing force of the compression spring 7, and the needle valve 8 rises together with the arm receiving portion 8c. This opens the nozzle 14a, and the pressure applied to the liquid L in the flow path 5 causes the liquid L to be ejected as droplets from the nozzle 14a.

[0035] Next, the voltage applied to the piezoelectric element 2a is reduced, causing the piezoelectric element 2a to contract. As the piezoelectric element 2a contracts, the arm member 3 rotates so that the other end of the arm member 3 moves downward (toward the nozzle plate 14). Then, the biasing force of the compression spring 7 causes the arm receiving portion 8c to move downward so as to follow the movement of the other end of the arm member 3, and the nozzle 14a is blocked by the needle valve 8, thereby stopping the ejection of droplets from the nozzle 14a.

[0036] In this way, the actuator 2 is connected to the needle valve 8 via the arm member 3, and is connected so that the needle valve 8 moves up and down as the arm member 3 rotates, and the support shaft 4, which is the fulcrum for the rotation of the arm member 3, is located closer to the actuator 2, so that the expansion and contraction displacement of the piezoelectric element 2a is amplified and transmitted to the needle valve 8. In this way, the actuator 2 functions as a drive unit that drives the needle valve 8 using the piezoelectric element 2a, which is the internal drive source. At this time, the arm member 3 functions as a displacement magnifying mechanism that magnifies the displacement of the actuator 2 using the principle of a lever and transmits it to the needle valve 8 .

[0037] In this embodiment, a piezoelectric element 2a is used as the actuator 2, but the actuator 2 may also be driven by other means using electricity, such as a pneumatically driven piston equipped with a solenoid or electromagnetic valve. In this embodiment, a compression spring 7 is used, but a tension spring that pulls the needle valve 8 toward the nozzle plate may also be used. In this case, for example, one end of the tension spring may be fixed to the bottom surface of the cover 11, and the other end may be fixed in a stretched state to the needle valve 8 or the arm receiving portion 8c.

[0038] FIG. 11 is an enlarged view of the area surrounded by the dashed line J in FIG. As shown in FIG. 11, the tip of the needle valve 8 is provided with a needle-shaped sealing member 8a having a tapered cross section. Further, the nozzle 14a has a channel opening / closing section 14d on the channel 5 side, the channel opening / closing section 14d having a cone shape with a tapered cross section. The sealing member 8a is made of any of elastomer, hard rubber, metal, and ceramics, and in the OFF state where the applied voltage is 0, the sealing member 8a abuts against the flow path opening / closing portion 14d, thereby preventing the discharge of the liquid L. Furthermore, the flow path opening / closing portion 14d, where the sealing member 8a and the nozzle plate 14 come into contact when closed, may be coated with a sliding functional film such as ceramic or diamond-like carbon to improve sliding properties and durability. Alternatively, the needle valve 8 and the sealing member 8a may be formed as an integral part.

[0039] In this embodiment, the tip of the sealing member 8a has a needle shape with a tapered cross section, and the flow path opening / closing portion 14d of the nozzle plate 14 also has a cone shape with a tapered cross section, but this configuration is not limited to this. This is just an example, and the tip of the sealing member 8a may have a smoothly convex curved surface such as a spherical shape, and the flow path opening / closing portion 14d of the nozzle plate 14 may have a smoothly concave curved surface that closely contacts the smoothly convex curved surface at the tip of the sealing member 8a. Alternatively, the tip of the sealing member 8a may have a flat surface and be abutted against the periphery of the inlet of the nozzle 14a to block the nozzle 14a. In any case, any combination of shapes may be used as long as the surface of the nozzle 14a facing the flow path 5 is sealed by the needle valve 8.

[0040] The nozzle plate 14 may also be made up of multiple layers, including a layer having the nozzles 14a and a layer having the flow path opening / closing portions 14d. In this case, it is desirable that each layer of the nozzle plate 14 has a structure that defines its position, and that the layers are firmly fixed together by chemical fixation such as bonding by adhesive or joining by thermal diffusion, and that the liquid L does not leak between the layers.

[0041] By providing a sealing member 8a at the tip of the needle valve 8, when the sealing member 8a is pressed against the flow path opening / closing portion 14d by the biasing force of the compression spring 7, the sealing member 8a adheres tightly to the flow path opening / closing portion 14d, thereby reliably closing the nozzle 14a.

[0042] FIG. 12 is a schematic view showing a part of the CC cross section of FIG. As shown in FIG. 12, the fixing member 17, to whose lower end a spring support plate 18 is attached, extends in the X direction (head longitudinal direction) of the cover 11 and is fixed so as to span a pair of inner wall surfaces of the cover 11 perpendicular to the X direction.

[0043] When viewed from the arrangement direction of the nozzles 14a in FIG. 8 (X direction), the spring support plate 18 is provided between the actuator 2 located on one side in the Y direction (upper side in the figure) of the arrangement of the nozzles 14a and the actuator 2 located on the other side in the Y direction (lower side in the figure). In this embodiment, the actuator 2 and the needle valve 8 are connected by the arm member 3, and are therefore arranged so as not to overlap each other when viewed from the movement direction of the needle valve 8 (Z direction). Therefore, in this embodiment, the spring support plate 18 can be arranged in the space above the needle valve 8 (above the Z axis in FIG. 8) and near the needle valve 8. With this configuration, the dimensions of the liquid ejection head 100 in the Y direction and the Z direction can be reduced.

[0044] In this embodiment, the arm member 3 allows the actuator 2, which is the largest component among the components constituting the liquid ejection module 1, to be positioned at the end of the cover 11 in the Y direction. This allows the fixing member 17 to be positioned at the center of the cover 11 in the Y direction, as shown in FIGS. 8 and 12 , and the spring receiving plate 18 can be fixed with a single fixing member 17. For example, if the arm member 3 is not present and the actuator 2 is positioned at the center in the Y direction, both ends of the spring receiving plate 18 in the Y direction or both ends in the X direction must be held by fixing members 17. Thus, if the actuator 2 is positioned at the center in the Y direction, two fixing members 17 must be provided, which may increase the size of the liquid ejection head 100 in the X or Y direction. Furthermore, the spring receiving plate 18 must be extended to a position where it does not face the actuator 2, which increases the size of the spring receiving plate 18.

[0045] In contrast to this, in this embodiment, by arranging one fixing member 17 in the center of the Y direction inside the cover 11, it is possible to hold the spring receiving plate 18, and the liquid ejection head 100 can be made smaller. Also, there is no longer a need to extend the spring receiving plate 18 to a position where it does not face the actuator 2, which also allows for a reduction in the size of the spring receiving plate 18. Furthermore, by providing the arm member 3 and arranging the actuator 2 on the Y-direction end side within the cover 11, the distance between the nozzle rows (distance in the Y direction) can be shortened, as shown in Fig. 13. This allows for a further reduction in the length of the spring receiving plate 18 in the Y direction, which in turn allows for a reduction in material costs and a reduction in the cost of the liquid ejection head 100.

[0046] The liquid ejection head 100 of this embodiment ejects liquid L using a so-called valve jet method, enabling high-viscosity liquid to be projected over greater distances. On the other hand, the droplet size is larger than with methods that do not have valves for each nozzle. Therefore, it is suitable for printing on large substrates U, such as the bodies of large vehicles and airplanes, the walls of buildings, and road surfaces. When printing on such large substrates, the print image is also large, and the small droplet size ejected from the nozzles, as with methods that do not have valves for each nozzle, significantly extends the printing time. Therefore, the valve jet method is preferred. Furthermore, the head cannot be placed close to the bodies of vehicles and airplanes, the walls of buildings, and road surfaces. Furthermore, when applying liquid to inclined surfaces or surfaces perpendicular to the horizontal, high-viscosity liquids are often used to prevent the applied liquid from dripping. Therefore, the valve jet type liquid ejection head 100, which is capable of ejecting highly viscous liquid L and ejects droplets by applying relatively high pressure, is suitable for printing on large objects such as the bodies of large vehicles, the bodies of airplanes, the walls of buildings, and road surfaces.

[0047] As already mentioned, in such a liquid ejection head 100, the liquid L is subjected to a relatively high pressure within the flow path 5, and the liquid pressure within the flow path 5 is set to about 4 to 5 atmospheres in this embodiment. In this embodiment, the flow path 5 is sealed by a sealing member 30 to prevent the liquid L from flowing back toward the actuator 2. However, in such a high-pressure environment, it is preferable that the axial projection area of ​​the sealing member 30 is as small as possible, as this also serves the purpose of preventing backflow. Furthermore, as shown in Figure 13, if nozzles 14a are arranged at high density, the needle valves 8 corresponding to the nozzles 14a will also be arranged at high density, which creates the problem that the cross-sectional area of ​​the sealing member 30 per needle valve 8 must be kept small.

[0048] To solve this problem, in the prior art, an O-ring 19 is arranged around the needle valve 8 as such a sealing member, as shown in FIG. 14 as a comparative example. However, in a method using a conventional O-ring 19, if one wants to maintain sealing performance even in a high-pressure environment, the compression rate of the O-ring 19 must be increased, that is, the surface pressure applied to crush the O-ring 19 must be increased to improve sealing performance. As already mentioned, the needle valve 8 opens and closes the nozzle 14a by moving up and down in accordance with the operation of the actuator 2. Therefore, if the surface pressure is increased in this way, it is known that the O-ring 19 itself acts as a sliding resistance to the up and down movement of the needle valve 8. Such an increase in sliding resistance is undesirable because it leads to a difference in the responsiveness of the needle valve 8 when it is turned on and off. Furthermore, it has been found that if the sliding resistance of the O-ring 19 differs between individual liquid discharging modules 1, such a difference in responsiveness will cause unevenness in the amount of liquid L discharged from the nozzle 14a between channels.

[0049] In order to improve such sliding resistance, as shown in FIG. 15, another reference example has been considered in which an O-ring 19 and a film-like member 19b are combined. In the configuration employing the membrane member 19b, the membrane member 19b is fixed to the needle valve 8, and the membrane member 19b itself extends in the X and Y directions perpendicular to the movement direction of the needle valve 8. Therefore, the elastic deformation of the membrane member 19b when bending absorbs the up and down movement, and therefore no sliding resistance is generated by the movement of the needle valve 8. On the other hand, when the pressure on the liquid side is high and the pressure difference between the top and bottom of the membrane member 19b is large, as in this embodiment, the membrane is pushed by the liquid pressure, generating a force in the axial direction of the needle valve 8, and as a result, resistance is generated in a direction that hinders (or promotes) the movement of the needle valve 8. Furthermore, even when the pressure difference is small, in order to set the state in which the membrane member 19b is stretched in the XY directions as the reference state, the position of the O-ring 19 and the attachment position of the membrane member 19b of the needle valve 8 must match, and the higher the thickness and softness of the material used to make the membrane member 19b more susceptible to elastic deformation, the higher the required assembly precision becomes, which is also an issue.

[0050] Furthermore, when an arm member 3 or the like is used as a displacement magnification mechanism as in this embodiment, the apparent rigidity of the needle valve 8 decreases because the original rigidity of the piezoelectric element 2a is reduced in inverse proportion to the displacement magnification rate due to the displacement magnification function of the arm member 3. That is, if the needle valve 8 side is pushed, there is a concern that the distance traveled by the needle valve 8 side will be greater than expected from the rigidity of the piezoelectric element 2a. Therefore, when a displacement magnifying mechanism is used as in this embodiment, higher accuracy than usual is required for position adjustment when fixing the position of the needle valve 8.

[0051] Now, particularly when an O-ring 19 is used, it is known that there are two phases depending on the amount of movement (advancement) of the needle valve 8: an elastic deformation phase in which the reaction force of the elastic deformation of the O-ring 19 acts as a reaction force against the sealing action, and a sliding resistance phase in which the reaction force generated by the sliding resistance of the sliding movement when the O-ring 19 itself moves acts as a reaction force against the sealing action. This is because, when the movement of the needle valve 8 is small, the press-fitted O-ring 19 absorbs the displacement by elastic deformation of the O-ring 19, as shown in Figure 16, whereas when the movement is large, the O-ring 19 itself slides, changing its contact position with the valve through-hole 11b. According to experiments conducted by the inventors, as shown in FIG. 17, the reaction force of the O-ring 19 first increases linearly up to 2.7 N, and then becomes greater than the frictional resistance at the contact point between the valve through-hole 11b and the O-ring 19, causing the O-ring 19 to start sliding, and from that point on the reaction force stabilizes at a substantially constant value regardless of the amount of movement.

[0052] In the embodiment of the present invention, a sealing member 30 is used, which is a sealing member having a shape different from the O-ring 19 and the membrane member 19b having such characteristics. As shown in FIG. 18 , the sealing member 30 has a fixed portion 31 fixed to the side of the needle valve 8, a conical portion 32 extending from the fixed portion 31 in a truncated cone shape, a cylindrical portion 33 extending from the conical portion 32 in the +Z direction, and a bulging portion 34 attached to the opposite side of the cylindrical portion 33 from the conical portion 32 and having a semicircular cross section that expands like a "brim" from the cylindrical portion 33. Note that although only one side is indicated by a reference numeral in FIG. 18 , the sealing member 30 is a substantially cylindrical member and is therefore configured symmetrically. In other words, the sealing member 30 is a substantially cylindrical member having a through hole 300 through which the needle valve 8 passes. The through hole 300 is a hole that penetrates the center of the sealing member 30 in the Z-axis direction, which is the movement direction of the needle valve 8.

[0053] The fixed portion 31 is a contact surface including a contact point P with the needle valve 8, and in this embodiment, is adhered and fixed to the needle valve 8. Although the contact point P will be referred to hereinafter, the contact point P may be enlarged as shown in Figure 19 and may extend into a plane, and in this embodiment, the contact surface on the circumference of the outer wall of the needle valve 8 is referred to as the contact point P. The conical portion 32 has a truncated cone shape with its tip on the -Z direction side including the fixing portion 31, and when installed, the needle valve 8 and the sealing member 30 are installed in such a manner that the needle valve 8 is inserted into the internal through hole. The cylindrical portion 33 is a cylindrical portion extending in the Z direction from the conical portion 32, and is made thinner than the other portions or is made of a material with a relatively low Shore hardness, thereby providing flexibility. The cylindrical portion 33 functions as a displacement absorbing portion that absorbs the amount of movement of the needle valve 8 by expanding and contracting when a load is applied in the Z direction. The fixed portion 31, conical portion 32, and cylindrical portion 33 function as the tip portion of the seal member 30. The material of the sealing member 30 may be fluorine-based rubber, fluorine-based elastomer, fluorine-based resin, etc., which are resistant to the liquid L that is the discharged liquid, and among these, tetrafluoroethylene-propylene rubber (FEPM), perfluoroelastomer (FFKM), etc., which are resistant to automotive paint and its diluted solution, are particularly preferred. In this way, the fixed portion 31, the conical portion 32, and the cylindrical portion 33 include a contact point P with the needle valve 8, and are tip portions having the shape of at least one of the cylindrical portion 33 or the conical portion 32, which is stretchable in the Z direction.

[0054] 18 and 19, the bulging portion 34 is supported in a manner that does not abut against the needle valve 8 when viewed in cross section, and a contact point Q, which is the abutment position of the bulging portion 34 with the valve through hole 11b, is formed at a different position in the Z direction from the contact point P. In other words, the contact point P between the needle valve 8 and the seal member 30 and the contact point Q between the valve through hole 11b and the seal member 30 are formed apart from each other by a gap R in the Z direction. Furthermore, the bulging portion 34 expands into a flange shape with a diameter at least larger than that of the conical portion 32, and is slightly larger in diameter than the inner diameter of the valve through-hole 11b. Therefore, when the sealing member 30 fixed to the needle valve 8 is inserted into and attached to the valve through-hole 11b, it is pressed into the valve through-hole 11b. The bulging portion 34 seals the liquid L at contact point Q. Like contact point P, contact point Q is also a contact surface formed by surrounding the outer periphery of the bulging portion 34, but is referred to as a contact point here. As described above, unlike sealing using an O-ring 19, the seal member 30 in this embodiment has contact point Q that abuts against the valve through hole 11b and contact point P that is fixed to the needle valve 8 and seals the gap between the needle valve 8 and the seal member 30, located in structurally and shaped different parts.

[0055] The effect of providing the portion that seals the liquid L and the portion that comes into contact with the valve through-hole 11b with different structures will now be described. As shown in FIG. 19(a), in the seal member 30 shaped according to this embodiment, the liquid pressure of the liquid L applies an oblique pressure to the conical portion 32 in a direction perpendicular to the inclination. At this time, the projected area D of the deformation region is smaller than when the film-like member 19b given as the reference example is used, and therefore the reaction force generated by the liquid pressure from the liquid L is smaller. Furthermore, the applied pressure tends to cause the cylindrical portion 33 to shrink in the Z-axis direction, which further deforms the conical portion 32 and changes its shape as shown in Figure 19(b), so that a force acts on the tip portion in a direction that compresses it further in the Z-axis direction.

[0056] Now, when considering the case where the needle valve 8 is operated in the +Z direction, when the needle valve 8 moves upward, the cylindrical portion 33 of the sealing member 30 receives a force in a direction that causes it to contract because the contact point P is fixed to the needle valve 8. At this time, as shown in Figure 19(b), the fluid pressure acts in the +Z direction, which is the direction in which the needle valve 8 returns, and the reaction force of the compression of the cylindrical portion 33 acts in the opposite -Z direction, so the resultant force can be made equal to or less than that of the reference example in which the O-ring 19 and film-like member 19b are simply used. Furthermore, the projected area D of the conical portion 32, which is the deformation region of the sealing member 30, can be made smaller than in the reference example, so the force in the +Z direction generated by the liquid L can be made smaller. Therefore, even if the pressure of the liquid L supplied to the liquid chamber 5 fluctuates, the fluctuation in the +Z direction due to the pressure of the liquid L can be made smaller. As a result, the movement speed of the needle valve 8 in the +Z direction is less affected by fluctuations in the pressure of the liquid L. In other words, the movement speed of the needle valve 8 in the +Z direction is stabilized. That is, when the needle valve 8 is moved upward, it can be operated with a smaller reaction force than in the reference example. The size of the flow path 5 is sufficiently large relative to the valve through hole 11b, and the stroke width of the needle valve 8 is sufficiently small, so that the change in fluid pressure caused by the up and down movement of the needle valve 8 is small.

[0057] Conversely, when the needle valve 8 is moved downward, if the cylindrical portion 33 is extended beyond the balanced position, a reaction force is generated in the +Z direction, and the hydraulic pressure also acts in the +Z direction. However, this can be improved by taking the following measures during installation. In the present invention, as shown in Figure 20, when inserting the needle valve 8, the bulge portion 34 of the sealing member 30 is pushed in the -Z direction by the step portion 9 located above (on the +Z direction side) the contact point P of the needle valve 8. At this time, whether the needle valve 8 has reached a position where it properly seals the nozzle 14a can be determined by using the position where the amount of liquid L discharged from the nozzle 14a becomes zero after the needle valve 8 is inserted as a reference position. When such positioning is performed, for example, as shown in FIG. 21, the initial insertion position, that is, the contact point Q0, is changed to the final reference position, that is, the contact point Q1. If the positions of all needle valves 8 are determined based on the discharge volume from such nozzle 14a and the position where the discharge volume is 0 is used as the reference position, the contact points Q1 between different channels, i.e., different liquid discharge modules 1, will not necessarily be at the same position on the Z axis. However, with this configuration, the reference position is determined for each nozzle 14a by the amount of liquid L discharged from the nozzle 14a when opening and closing, regardless of individual differences in the seal member 30. This state can also be considered as a state in which the displacement of the needle valve 8 caused by the pressure of the liquid L and the displacement of the needle valve 8 caused by the reaction force from the seal member 30 press-fitted into the valve through-hole 11b are exactly balanced.

[0058] Now, with the needle valve 8 positioned in this manner, as already described using Figure 19, when it moves in the +Z direction it moves from the reference position in the compression direction. Therefore, due to the combined force with the pressure of the liquid L, the resistance generated when moving the needle valve 8 can be made equal to or less than that of the reference example, and fluctuations in the resistance due to pressure fluctuations of the liquid L can be reduced. On the other hand, when the needle valve 8 moves downward, the elastic seal member 30 is moved in the direction returning to its natural length, so the cylindrical portion 33 is not extended beyond the balanced position. Therefore, because an elastic force is generated downward, even when the needle valve 8 is pushed in the -Z direction, the resistance generated when moving the needle valve 8 can be kept relatively small. Furthermore, even if the hydraulic pressure L fluctuates, the fluctuation in the resistance acting on the needle valve 8 can be reduced.

[0059] According to experiments by the inventors, the longitudinal elastic modulus of the sealing member 30 in the Z direction is preferably in the range of 1 to 5 MPa from the viewpoint of sealing performance and low resistance during elastic deformation, and it is even more preferable that it be in the range of 1 to 2 MPa in terms of the resistance reduction effect of the needle valve 8. Furthermore, the distance L1 of the inclined surface of the conical portion 32, where the hydraulic pressure acts as a reaction force to the sealing force of the needle valve 8, is preferably set to be half or less of the total length L2 of the seal member 30 in the Z direction. However, even if only the conical portion 32 is provided without the cylindrical portion 33, the gap R between the contact points P and Q allows the portion between the contact points P and Q to function as an elastic body, so it is known that the cylindrical portion 33 itself is not an essential requirement for the effect of the present invention.

[0060] FIG. 17 shows an example of a graph showing the displacement of the needle valve 8 and the reaction force to the sealing action when the seal member 30 of the present invention is used. As is clear from Figure 17, compared to when a conventional O-ring 19 is used, the sealing member 30 of this embodiment was able to reduce the reaction force from the conventional 1.5 N to 0.2 N when opening and closing the needle valve 8 over a stroke of 0.08 mm (80 μm) required for opening and closing. Furthermore, it was revealed that within a stroke range of 0.3 mm, which is the stroke width for adjustment when the liquid discharging module 1 is inserted, there is an elastic region in which the reaction force increases linearly over the entire range. In this way, by providing the cylindrical portion 33 as an elastic portion that is easily deformed in the sealing member 30, the reaction force can be kept low compared to the O-ring 19, and positioning adjustment can be made more easily compared to the membrane-like member 19b. According to this configuration, by reducing the reaction force that occurs when the needle valve 8 operates, it is possible to reduce variations in the amount of liquid L discharged between the channels of the multiple nozzles 14a. Furthermore, the reduction in reaction force also has the effect of improving the responsiveness of the drive of the needle valve 8, making it possible to achieve stable discharge even when the nozzle 14a is opened and closed at high speed.

[0061] Next, various modifications of the seal member 30 will be described in order. As a second embodiment, FIG. 22 shows a modified example in which the cylindrical portion 33 is further thinned to form a cylindrical portion 33b, which is shaped to be easily elastically deformed. In this configuration, the thickness d1 of the seal member 30 constituting the cylindrical portion 33b is set to be smaller than the thickness d2 of the seal member 30 constituting the other portion, for example, the conical portion 32. With this configuration, the rigidity of the cylindrical portion 33 is further reduced, so that the cylindrical portion 33b is crushed first when compressed in the Z direction, thereby improving the effect of absorbing the reaction force of the hydraulic pressure and the operation of the needle valve 8.

[0062] FIG. 23 shows, as a third embodiment, the configuration of a bellows portion 33c in which part of the cylindrical portion 33 is shaped like a bellows. In this configuration, the bellows portion 33c collapses in the Z direction in the same manner as the cylindrical portion 33, so that the effect of absorbing the reaction force of the fluid pressure and the operation of the needle valve 8 is improved.

[0063] FIG. 24 shows a fourth embodiment in which a hard ring-shaped member 37 is disposed inside the bulging portion 34 and the cylindrical portion 33. As shown in FIG. In the liquid ejection head 100, if the viscosity of the liquid L to be ejected is high, it may be difficult to eject the liquid L from the nozzle 14a without applying high pressure. In the configurations described in the first to third embodiments, if the liquid pressure is very high, the conical portion 32 is subjected to a liquid pressure that narrows it toward the center of the Z axis, and as a result, the bulging portion 34 is also subjected to a force that narrows it inward. Although the liquid L is originally sealed by applying pressure to the bulging portion 34 so that it expands toward the valve through-hole 11b, there is a concern that the sealing force may be reduced. Furthermore, there is a gap between the bulge 34 and the needle valve 8, and if this gap is filled and the inner wall of the bulge 34 comes into contact with the needle valve 8, a press-fit configuration similar to that of the O-ring 19 will result, and the contact resistance between the bulge 34 and the needle valve 8 will act as a reaction force, reducing the effect of the present invention.

[0064] Such a ring-shaped member 37 may be, for example, a ring made of a highly rigid metal or an elastic material with a high Shore hardness and high elastic modulus, and is provided between the inner wall surface 34a of the bulge portion 34 and the outer peripheral wall of the needle valve 8, and functions like a sleeve. With such a ring-shaped member 37, even if the bulging portion 34 tries to deform inward and narrow, the ring-shaped member 37 functions as a core to prevent this, so that even if the liquid pressure of the liquid L is even higher than in the first embodiment, the bulging portion 34 can be sealed without losing its airtightness. At this time, it is preferable that the ring-shaped member 37 and the needle valve 8 are not in contact with each other, or that one of the members is coated to maintain low sliding resistance.

[0065] Similarly, even when the seal member 30 falls toward the needle valve 8 under high hydraulic pressure, if the frictional resistance at the contact position is sufficiently small, the reaction force of the needle valve 8 movement caused by the contact resistance as described above can be kept small. Therefore, Fig. 25 shows a fifth embodiment in which a sliding functional film 34b made of a diamond-like carbon (DLC) film or Teflon (registered trademark) coating is applied to the inner wall surface 34a of the bulging portion 34 of the seal member 30. With this sliding function membrane 34b, even if the bulging portion 34 is temporarily pressed against the needle valve 8 by the hydraulic pressure, the sliding resistance is kept low by the sliding function membrane 34b, and the reaction force of the operation of the needle valve 8 is kept small, so that the high sealing characteristics and low driving resistance are not impaired. In this embodiment, the sliding membrane 34b is provided on the inner wall surface 34a of the bulging portion 34, but conversely, a similar sliding membrane may be provided in an area of ​​the needle valve 8 that can come into contact with the bulging portion 34, or both may be coated with the sliding membrane.

[0066] As a sixth embodiment, FIG. 26 shows a configuration in which a fixing portion 31 at the tip of a seal member 30 is fixed to a needle valve 8 by vulcanization adhesion. According to this method, the seal member 30 can be fixed to the needle valve 8 inside the molding machine during molding, so that it can be handled as an integrated part in the subsequent assembly, making assembly easier. Furthermore, by performing vulcanization bonding at the contact point P between the needle valve 8 and the fixed portion 31 of the seal member 30, the sealing performance at the contact point P is improved.

[0067] Moreover, as a seventh embodiment, FIG. 27 shows a configuration in which the fixing portion 31 is provided on the +Z direction side and the bulging portion 34 is provided on the −Z direction side. According to this configuration, as in the first embodiment, the projected area of ​​the conical portion 32, which is the tip portion that deforms, is reduced, thereby making it possible to reduce the influence of the liquid pressure. Furthermore, since the fixed portion 31 is on the +Z direction side, the fixed portion 31 can be seen above the valve through-hole 11b. With this configuration, the fixed portion 31 can be fixed after the needle valve 8 and the nozzle 14a are positioned to the reference positions as described above, so that the discharge amounts from the nozzle 14a can be matched between channels with higher accuracy.

[0068] Furthermore, by fixing the fixing part 31 using a retaining ring 38, which is a ring-shaped fixing member, rather than adhesive, it is possible to readjust the fixing part 31 between the needle valve 8 and the sealing member 30 after positioning the reference positions of the needle valve 8 and the nozzle 14a. In this way, the position of the fixing part 31 can be changed even after it has been positioned, so that the residual axial force of the remaining sealing member 30 can be reduced to approximately zero, thereby further reducing the reaction force when the needle valve 8 operates. These fixing portions 31 may be fixed by adhesive as shown in the first embodiment, or by a fastening means such as a retaining ring 38, or by screws. In any case, in the seventh embodiment, the fixing portion 31 is located on the +Z direction side of the bulging portion 34, and this portion is fixed by adhesive or fastening means.

[0069] Furthermore, in the seventh embodiment, the effects differ depending on the shape, which will be further explained. As already described in the first embodiment and the like, in the seal member 30, the liquid pressure acting on the conical portion 32 acts to narrow the cone toward the center of the Z axis. On the other hand, in the seventh embodiment, the position where the inclined surface of the conical portion 32 and the liquid L come into contact is reversed, so that the pressure difference acts as a force in the outward expanding direction, as shown in FIG. As a result, when the hydraulic pressure side becomes high pressure and the pressure difference becomes large, a force is applied in the direction of expanding the bulging portion 34, thereby improving the sealing performance. Therefore, simply by reversing the Z direction of the seal member 30 in this way, it is possible to provide a seal member 30 that does not experience a decrease in sealing performance even when the liquid pressure is high.

[0070] In addition, in the seventh embodiment, in addition to the assembly method of inserting the needle valve 8 from the +Z direction side, a configuration is also possible in which the needle valve 8 with the sealing member 30 fixed by a retaining ring 38 is inserted from the liquid chamber 5 side, as shown in Figure 28. With this configuration, the conical portion 32 of the seal member 30 is also subjected to a force in the outward expanding direction by the liquid pressure, so that the sealing performance is not reduced even when the liquid pressure is large. Furthermore, with this configuration, the bulging portion 34 of the seal member 30 is pressed against the inner wall 11c of the upper surface of the liquid chamber 5 by the pressure of the liquid L, thereby achieving a stronger seal. Furthermore, even when a soft elastic member is used for the seal member 30, it can be reliably brought into contact with the inner wall 11c of the liquid chamber 5, so that even a seal member 30 with low elasticity and low resistance can reliably prevent the liquid L from leaking toward the valve through-hole 11b. Furthermore, the bulging portion 34 may be configured so that its position in the XY plane is restricted by a position restricting member 380 fixed to the inner wall 11c of the liquid chamber 5 (part of the inner wall of the housing). This prevents the liquid L in the liquid chamber 5 from leaking into the valve through-hole 11b due to misalignment of the bulging portion 34. The bulging portion 34 may be slidable along the inner wall 11c of the liquid chamber 5. That is, when the fixed portion P with the seal member 30 moves in the +Z direction as the needle valve 8 moves, the bulging portion 34 is pulled in the +Z direction by the cylindrical portion 33 and deforms so as to bend. As a result, the reaction force generated when the needle valve 8 is moved in the +Z direction can be reduced. Although the example in which the bulging portion 34 is provided so as to be slidable relative to the inner wall 11c has been described above, the bulging portion 34 may be fixed to the inner wall 11c by a known method such as adhesive. When the bulging portion 34 is fixed to the inner wall 11c, the position restriction member 380 can be omitted, and the gap between the liquid chamber 5 and the valve through-hole 11b can be sealed by the seal member 30 even when the pressure of the liquid L is reduced.

[0071] As another embodiment in which the direction in which the liquid pressure is applied is controlled in this way, an eighth embodiment is shown in FIG. In FIG. 29, the conical portion 32 at the tip has a solid structure and is more rigid than the conical portions 32 in the first to seventh embodiments. As a result, when the sealing member 30 is subjected to a force in the compression direction, deformation occurs mainly due to the compression force in the Z direction of the cylindrical portion 33. The deformation of the conical portion 32 is easily affected by hydraulic pressure, and since the position of the needle valve 8 and the deformation resistance force of the sealing member 30 are not linear, the conical portion 32 at the tip end is less likely to collapse, and therefore deformation due to hydraulic pressure is dominated by deformation of the cylindrical portion 33, and therefore deterioration of sealing performance can be suppressed even when the hydraulic pressure is high.

[0072] In the eighth embodiment, the bulging portion 34 has an inclined portion 34c that is inclined relative to the inner wall surface of the valve through-hole 11b. The inclined portion 34c is a plane that is inclined in both the XY plane and the Z direction, and has a notched structure resembling a so-called "rat bar" when viewed in cross section from the cylindrical portion 33 side. Furthermore, the inclined portion 34c causes the liquid pressure of the liquid L that has entered between the cylindrical portion 33 and the valve through-hole 11b to act as a pushing force in a direction perpendicular to the inclined portion 34c. That is, in the eighth embodiment as well, the liquid pressure acts as a force that presses the bulging portion 34 outward, so that the bulging portion 34 receives a force in a direction that expands the outer diameter thereof, and comes into strong contact with the valve through-hole 11b. This configuration, together with the fact that the conical portion 32 has a solid structure, makes it possible to suppress a decrease in sealing performance even when the liquid pressure is high, thereby achieving both high sealing characteristics and low driving resistance.

[0073] Furthermore, by using the sealing member 30 of the present invention, it is possible to mount the nozzles 14a at a high density. This point will be explained in detail. According to estimates, when using an O-ring 19 made of fluorine-based rubber, in order to achieve sealing performance at an internal pressure of 0.5 MPa, an elastic contact width of 0.4 mm or more is required, and the wire diameter of the donut part of the O-ring 19 (the diameter of the material wire of the O-ring 19) must be 0.8 mm or more. On the other hand, even if the outer diameter of the fitting portion of the O-ring 19 of the needle valve 8 is Φ0.5, if an O-ring 19 with a wire diameter of 0.8 mm or more is fitted, the outer diameter will exceed 2 mm. As already described in Figures 12 and 13, the size of the outer diameter including the sealing portion affects the size and spacing of the nozzles 14a that can actually be formed in the nozzle plate 14. On the other hand, according to the seal member 30 of the eighth embodiment, the bulge portion 34 does not necessarily have to be ring-shaped, and the width of the elastic contact portion can be adjusted arbitrarily independent of the outer diameter of the seal member 30. Therefore, sealing performance can be ensured with a smaller outer diameter, and the nozzles 14a can be mounted at a higher density.

[0074] As a ninth embodiment, FIG. 30 shows a configuration in which a sliding function film 39 having a thickness of 2 μm or less is formed at least in the region inside the valve through-hole 11b that comes into contact with the seal member 30. An example of such a sliding functional film 39 may be a diamond-like carbon (DLC) film or a Teflon (registered trademark) coating. With this configuration, the contact point Q between the bulging portion 34 of the seal member 30 and the valve through-hole 11b can be moved with low resistance while maintaining the sealed state. Therefore, as explained with reference to Figure 21, even when the seal member 30 is press-fitted during assembly, the frictional resistance between the bulging portion 34 and the inner wall surface of the valve through-hole 11b is reduced, making it possible to position the needle valve 8 without applying unnecessary tension (tensile stress) to the seal member 30. Furthermore, since no unnecessary stress is applied to the seal member 30 during assembly, the needle valve 8 can be operated more smoothly and at higher speeds to turn on and off.

[0075] As a tenth embodiment, FIG. 31 shows a configuration in which the area inside the cover 11 on the side of the valve receiving portion 20, which is a bearing, is also made airtight, so that air pressure can be applied to the inside of the cover 11. The air pressure inside the cover 11 is normally in the range of 0.1 to 0.6 MPa, but may be higher depending on the liquid pressure.

[0076] As already mentioned, when a highly viscous ink is used as the liquid L, a high internal ink pressure is required. As already mentioned, in the first embodiment, when the hydraulic pressure is high, the seal member 30 of this embodiment is subjected to hydraulic pressure such that it compresses the seal member 30 toward the central axis of the needle valve 8. Due to these phenomena, if the rigidity of the seal member 30 itself is not sufficiently ensured, there is a concern that the seal member 30 may be deformed in a direction that reduces the outer diameter. In such a case, the contact point Q between the valve through-hole 11b and the bulging portion 34 may be separated, which may cause leakage of the liquid L. In such a case, the inner wall surface 34a of the bulging portion 34 comes into contact with the wall surface of the needle valve 8, causing a large contact resistance to the vertical movement of the needle valve 8.

[0077] Ultimately, this phenomenon is more likely to occur the greater the pressure difference between the hydraulic pressure and the air pressure in the bearing-side region. Therefore, as in the tenth embodiment, by making the cover 11 a sealed structure and providing a compressor 40 (an example of a pressurizing means) as an air pressure application means and a flow control valve 41 in the space on the bearing side as well, and thereby controlling the air pressure inside the cover 11, it is possible to reduce the pressure difference between the liquid pressure and the air pressure as shown schematically in Figure 32, so that even if the liquid pressure increases, leakage is less likely to occur and the sealability is less likely to deteriorate. Furthermore, during assembly, the needle valve 8 is generally inserted from the bearing side, and friction between the seal member 30 and the inner wall of the valve through-hole 11b tends to leave tensile internal stress in the seal member 30 after assembly is complete. This residual stress can also be expected to be reduced by correcting it by pressing the contact point Q between the inner wall of the valve through-hole 11b and the bulge 34 toward the -Z side, i.e., the nozzle 14a side, due to the air pressure behind it. Furthermore, the air pressure applied to the gap between the bearing and the needle valve 8 can be adjusted by the flow rate adjusting valve 41, which also has the effect of reducing friction between the bearing and the needle valve 8.

[0078] The aspects of the present invention are as follows, for example. [1] The liquid ejection head 100 of the present invention is a liquid ejection head 100 comprising: a nozzle 14a that ejects liquid L; a needle-type needle valve 8 that opens and closes the nozzle 14a by moving along the Z-axis direction; a drive means that drives the needle valve 8 to open and close; and a sealing member 30 that is arranged between the needle valve 8 and the inner wall of the valve through-hole 11b that surrounds the needle valve 8 so as to separate the liquid chamber through which the needle valve 8 passes from the drive unit. The sealing member 30 is characterized in that the contact point P with the needle valve 8 and the contact point Q with the inner wall of the valve through hole 11b are at different positions in the axial direction of the needle valve 8, the other parts of the contact point P and the contact point Q are in a substantially non-contact state, and the contact point Q with the inner wall of the valve through hole 11b is slidable along the inner wall of the valve through hole 11b. According to this configuration, it is possible to achieve both high sealing characteristics and low driving resistance.

[0079] [2] In addition to the configuration described in [1], the sealing member 30 is formed of an elastic body, includes a contact point P with the needle valve 8, has a tip portion having at least one shape of a cylindrical portion 33 or a conical portion 32 that is axially stretchable, and has a bulge portion 34 that is a flange portion at least larger in diameter than the tip portion, and has a contact point Q with the inner wall of the valve through hole 11b at some position of the bulge portion 34. According to this configuration, when the needle valve 8 moves up and down, the cylindrical portion 33 or the conical portion 32 elastically contracts to absorb the displacement, so that it is possible to achieve both high sealing characteristics and low driving resistance.

[0080] [3] In addition to the configuration described in [1] or [2], the sealing member 30 has a cylindrical portion 33 between a bulging portion 34 at the end and a conical portion 32 on the opposite side in the axial direction from the bulging portion 34, The cylindrical portion 33 is characterized by having a cylindrical portion 33b having a low elastic structure that expands and contracts in the axial direction compared to the bulging portion 34 and the conical portion 32, or a bellows portion 33c having a bellows structure. With this configuration, elastic contraction of the cylindrical portion 33 is more likely to occur, and displacement is absorbed by elastic contraction within the stroke width of the up and down movement of the needle valve 8, thereby achieving both high sealing characteristics and low driving resistance.

[0081] [4] In addition to the configuration described in any one of [1] to [3], the sealing member 30 is characterized in that it has a through hole in the center into which the needle valve 8 is inserted, and contains a ring-shaped member 37, which is a thin-walled ring part made of a material that is harder and has a higher elastic modulus than the material that forms the sealing member 30, between the through hole and the needle valve 8. With such a ring-shaped member 37, even if the bulging portion 34 tries to deform inward and narrow, the ring-shaped member 37 functions as a core to prevent this, so that even if the liquid pressure of the liquid L is even higher than in the first embodiment, the bulging portion 34 can be sealed without losing its airtightness.

[0082] [5] In addition to the configuration described in any one of [1] to [4], the sealing member 30 has a through hole in the center into which the needle valve 8 is inserted, and a sliding functional membrane 39 is formed between the through hole and the needle valve 8. According to this configuration, the sliding functional film 39 reduces the reaction force, including the contact resistance to the seal member 30, caused by the up and down movement of the needle valve 8, thereby achieving both high sealing characteristics and low driving resistance.

[0083] [6] In addition to the configuration described in any one of [1] to [5], the seal member 30 is characterized in that the contact point P with the needle valve 8 is fixed by a vulcanization adhesive structure. According to this configuration, it is possible to achieve both high sealing characteristics and low driving resistance.

[0084] [7] In addition to the configuration described in any one of [1] to [6], the sealing member 30 has a bulging portion 34 formed on the tip side of the needle valve 8 and abutting against the inner wall of the valve through hole 11b, and a conical portion 32 arranged to protrude from the bulging portion 34 toward the opposite side of the liquid chamber 5, and is characterized in that the contact point P with the needle valve 8 at the end of the conical portion 32 is fixed by adhesive or fastening means. According to this configuration, the needle valve 8 and the fixing portion 31 are bonded by vulcanization at the contact point P, and thus the sealing performance at the contact point P is improved.

[0085] [8] In addition to the configuration described in any one of [1] to [7], the liquid ejection head 100 is characterized in that a sliding functional film 39 is formed on at least the area of ​​the inner wall of the valve through-hole 11b that comes into contact with the sealing member 30. According to this configuration, the contact resistance occurring between the bulging portion 34 and the inner wall of the valve through-hole 11b can be reduced.

[0086] [9] In addition to the configuration described in any one of [1] to [8], the liquid ejection head 100 is characterized by having a compressor 40 in the space on the opposite side of the sealing member 30 from the liquid chamber 5, so that the internal pressure of the space becomes higher than atmospheric pressure. With this configuration, the pressure difference between the hydraulic pressure and the air pressure can be reduced, so that even if the hydraulic pressure increases, leakage is less likely to occur and the sealing performance is less likely to decrease.

[0087] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to such specific embodiments, and unless otherwise specifically limited in the above description, various modifications and changes are possible within the scope of the spirit of the present invention as described in the claims. The effects described in the embodiments of the present invention are merely examples of the most preferable effects resulting from the present invention, and the effects of the present invention are not limited to those described in the embodiments of the present invention. [Explanation of symbols]

[0088] 2. Drive unit (actuator) 5 Liquid chamber (flow path) 8 Needle Valve 11b Housing inner wall (valve through hole) 14a Discharge port (nozzle) 30 Sealing member (sealing member) 31 Fixed part (part of tip) 32 Cone part (part of tip) 32b Cylindrical section 32c bellows structure 33 Cylindrical part (part of tip) 34b Sliding function membrane 37 Ring parts (ring-shaped parts) 39 Sliding function membrane 40 Pressurizing means (compressor) 100 Liquid ejection head 300 through holes P, Q contact point Z axis direction [Prior art documents] [Patent documents]

[0089] [Patent Document 1] Patent No. 7271956 [Patent Document 2] Patent No. 6804204 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-536261 [Patent Document 4] Patent No. 4123897 [Patent Document 5] Patent No. 7071494

Claims

1. a discharge port for discharging a liquid; a needle-type valve element that opens and closes the discharge port by moving along an axial direction; and a drive means that drives the valve element to open and close; a sealing member disposed between the valve body and an inner wall of a housing surrounding the periphery of the valve body so as to separate a liquid chamber through which the valve body passes and a drive unit, A liquid ejection head characterized in that the sealing member has a contact point with the valve body and a contact point with the housing inner wall at different positions in the axial direction of the valve body, other parts are in a substantially non-contact state, and the contact point with the housing inner wall is capable of sliding along the housing inner wall.

2. 2. The liquid ejection head according to claim 1, The sealing member is formed of an elastic material, A liquid ejection head characterized by having a tip portion having the shape of at least one of a cylindrical portion or a cone portion that includes a contact point with the valve body and is axially stretchable, and a flange portion that is at least larger in diameter than the tip portion, and wherein a contact point with the inner wall of the housing is located at some position on the flange portion.

3. 2. The liquid ejection head according to claim 1, the sealing member has a cylindrical portion between a flange portion at an end and a substantially conical portion on the opposite side in the axial direction from the flange portion, The liquid ejection head is characterized in that the cylindrical portion has a low elasticity structure or a bellows structure that expands and contracts in the axial direction compared to the flange portion and the substantially conical portion.

4. 2. The liquid ejection head according to claim 1, the sealing member has a through hole at its center into which the valve body is inserted; A liquid ejection head characterized in that a thin-walled ring component made of a material harder and with a higher modulus of elasticity than the material forming the sealing member is contained between the through hole and the valve body.

5. 2. The liquid ejection head according to claim 1, the sealing member has a through hole at its center into which the valve body is inserted; A liquid ejection head characterized in that a sliding functional film is formed between the through hole and the valve body.

6. 2. The liquid ejection head according to claim 1, The liquid ejection head is characterized in that the sealing member is fixed to the valve body at a contact point with the valve body by a vulcanization adhesive structure.

7. 2. The liquid ejection head according to claim 1, the sealing member has a flange portion formed on a tip side of the valve body and in contact with the inner wall of the housing, and a substantially conical portion provided so as to protrude from the flange portion toward an opposite side to the liquid chamber, A liquid ejection head characterized in that the contact point between the end of the substantially conical portion and the valve body is fixed by adhesive or fastening means.

8. 2. The liquid ejection head according to claim 1, A liquid ejection head characterized in that a sliding functional film is formed on at least an area of ​​the inner wall of the housing that comes into contact with the sealing member.

9. 2. The liquid ejection head according to claim 1, A liquid ejection head comprising a pressurizing means, disposed in a space on the opposite side of the sealing member from the liquid chamber, for making the internal pressure of the space higher than atmospheric pressure.

10. A liquid ejection head according to any one of claims 1 to 9, A liquid ejection device that applies coating to an object by ejecting liquid from the liquid ejection head.

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