Liquid ejection head and liquid ejection device

Abstract

To satisfactorily maintain a ground state of a liquid discharge head.SOLUTION: A liquid discharge head 202 includes: nozzle formation members formed with nozzles for discharging a liquid; opening / closing members for opening / closing the nozzles; piezoelectric bodies 9 expanding and contracting in an axial direction by a driving voltage, and actuating the opening / closing members so as to open / close the nozzles; a cylindrical first storage member 1 storing the piezoelectric bodies 9; and a grounding member 10 coming in contact with the inside of the first storage member 1.SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] 2. Description of the Related Art As an example of a device that ejects liquid, an inkjet image forming device that ejects ink onto paper or the like to form an image is known.

[0003] In such image forming devices, if charges such as static electricity accumulate in the liquid ejection head that ejects ink, this may have a negative impact on print quality, so some image forming devices are provided with a grounding member on the liquid ejection head to remove the accumulated charges.

[0004] For example, Patent Document 1 (Japanese Patent Laid-Open No. 2013-151094) describes a configuration in which a ground member is brought into contact with the outside of a liquid ejection head. Summary of the Invention [Problem to be solved by the invention]

[0005] However, in a configuration in which a grounding member is in contact with the outside of the liquid ejection head, as described in Patent Document 1, if the liquid ejection head is subjected to external impact or vibration, there is a risk that the grounding member may be damaged or may fall off from the liquid ejection head, and it may not be possible to maintain a good grounding state of the liquid ejection head. [Means for solving the problem]

[0006] In order to solve the above problems, the liquid ejection head according to the present invention comprises a nozzle forming member in which a nozzle for ejecting liquid is formed, an opening / closing member for opening and closing the nozzle, a piezoelectric element that operates the opening / closing member so as to open and close the nozzle by expanding and contracting in an axial direction in response to a driving voltage, a cylindrical first housing member that houses the piezoelectric element, and a contact member that comes into contact with the inside of the first housing member. and connected to a ground wire that electrically connects to an external ground point. A grounding member; a second housing member that houses a support member that supports the ground wire and is inserted into the first housing member; Equipped with The grounding member is supported by the second housing member. It is characterized by: [Effects of the Invention]

[0007] According to the present invention, it is possible to maintain the liquid ejection head in a good grounded state. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing the configuration of an embodiment of a liquid ejection device to which a liquid ejection head according to the present invention is applied; [Figure 2] FIG. 1 is a diagram showing an example of the arrangement of painting devices relative to a car to be printed. [Figure 3] FIG. 10 is a diagram showing another example of the arrangement of a painting device relative to an automobile. [Figure 4] 1 is a cross-sectional view showing the overall configuration of a print head according to an embodiment of the present invention. [Figure 5] FIG. 5 is an enlarged cross-sectional view of a portion of the print head shown in FIG. 4. [Figure 6] 1 is a diagram showing the configuration of an embodiment of a head unit including a liquid ejection head according to the present invention; [Figure 7] 10 is a diagram showing an example of another coating device to which the liquid ejection head according to the present invention is applied. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be described below with reference to the accompanying drawings. In each drawing for explaining the present invention, components such as members and components having the same function or shape are designated by the same reference numerals as far as they can be distinguished, and descriptions thereof will be omitted once they have been described.

[0010] First, the configuration of a coating apparatus 201, which is one embodiment of an apparatus for ejecting a liquid to which a liquid ejection head according to the present invention is applied, will be described with reference to Figures 1 to 3. Figure 1 is a diagram showing the configuration of the coating apparatus 201 according to this embodiment. Figure 2 is a diagram showing an example of the arrangement of the coating apparatus 201 relative to an automobile M to be printed. Figure 3 is a diagram showing another example of the arrangement of the coating apparatus 201 relative to an automobile M to be printed.

[0011] As shown in FIG. 1, a coating device 201 according to this embodiment includes a print head 202, an XY table 203, a camera 204, a control unit 209, a drive unit 211, and the like.

[0012] The print head 202 is a liquid ejection head that ejects paint (liquid) toward the surface of the workpiece M. The print head 202 is equipped with multiple valve-type nozzles, and paint is ejected from each valve-type nozzle in a direction perpendicular to the ejection surface of the print head 202. In other words, the paint ejection surface of the print head 202 is parallel to the XY plane formed by the movement of the XY table 203, and the paint dots ejected from each valve-type nozzle are ejected in a direction perpendicular to the XY plane. Furthermore, the paint ejected from each valve-type nozzle is ejected in a parallel direction. Each valve-type nozzle is connected to a paint tank of a respective predetermined color. Furthermore, because the paint tank is pressurized by a pressure device, paint dots can be ejected from each valve-type nozzle onto the print surface without any problems as long as the distance between each valve-type nozzle and the print surface of the workpiece M is approximately 50 mm.

[0013] The XY table 203 is equipped with mechanisms for moving the print head 202 and camera 204 in the X and Y directions, which are perpendicular to each other. Specifically, the XY table 203 is equipped with an X-axis movement mechanism 205 that moves a slider holding the print head 202 and the camera 204 (described later) in the X direction, and a Y-axis movement mechanism 206 that holds the X-axis movement mechanism 205 with two arms and moves it in the Y direction. The Y-axis movement mechanism 206 is also equipped with a shaft 207, which is held and driven by a robot arm 208, allowing the print head 202 to be freely positioned at a predetermined position on the workpiece M where printing is to be performed. For example, if the workpiece M is an automobile, the robot arm 208 can position the print head 202 above the automobile as shown in FIG. 2 or to the side of the automobile as shown in FIG. 3. The operation of the robot arm 208 is controlled based on a program previously stored in a control unit 209.

[0014] The camera 204 is an imaging means such as a digital camera that captures an image of the printing surface of the workpiece M. The camera 204 captures images of a predetermined range of the printing surface of the workpiece M at constant, minute intervals while moving in the X and Y directions using an X-axis movement mechanism 205 and a Y-axis movement mechanism 206. The specifications of the camera 204, such as the lens and resolution, are appropriately selected so that multiple sub-divided images of the predetermined range of the printing surface can be captured. The camera 204 captures the multiple sub-divided images of the printing surface continuously and automatically by a control unit 209, which will be described later.

[0015] The control unit 209 operates the XY table 203 based on image editing software S, which edits images captured by the camera 204, and a preset control program to control the printing operation (paint discharging operation) of the print head 202. The control unit 209 is configured with a so-called microcomputer and includes a storage device that records and saves various programs, data on captured images, and data on images to be printed, a central processing unit that executes various processes in accordance with the programs, input devices such as a keyboard and a mouse, and, if necessary, a DVD player. The control unit 209 also includes a monitor 210. The monitor 210 displays information input to the control unit 209, processing results by the control unit 209, and the like.

[0016] The control unit 209 processes the multiple sub-divided image data captured by the camera 204 using image processing software, generating a composite print surface in which the non-planar print target surface of the workpiece M is projected onto a plane. The control unit 209 also overlays a drawing target image A, which is to be printed so as to be continuous with the image already printed on the print target surface, on the composite print surface, and edits the drawing target image A so that it is continuous with the edge of the already printed image, generating an edited drawing target image B. Then, paint is ejected from the print head 202 onto the print target surface based on the generated edited drawing target image B, so that the new image is printed without any gaps between it and the already printed image. The capturing of the multiple sub-divided images by the camera 204 and the printing operation of ejecting paint from each nozzle of the print head 202 are performed by a drive unit 211 whose operation is controlled by the control unit 209.

[0017] Next, the configuration of the print head according to this embodiment will be described with reference to Figures 4 and 5. Figure 4 is a cross-sectional view showing the overall configuration of the print head according to this embodiment, and Figure 5 is an enlarged cross-sectional view showing a portion of the print head shown in Figure 4.

[0018] As shown in FIG. 4, the print head 202 according to this embodiment is a valve-type liquid ejection head, and includes a nozzle plate 22 as a nozzle forming member in which nozzles 22a (ejection ports) for ejecting paint (liquid) are formed, a liquid chamber housing 23, a needle 21 as an opening / closing member for opening and closing the nozzles 22a, a piezo element 9 as a piezoelectric body, a piezo element frame 8, an outer housing 1 as a first housing member, and an inner housing 2 as a second housing member.

[0019] The outer housing 1 is a cylindrical member that houses therein the needle 21, piezo element 9, piezo element frame 8, and inner housing 2. A nozzle plate 22 is provided at the left end of the outer housing 1 in FIG. 4 via a liquid chamber housing 23. A liquid flow path 27 is provided in the liquid chamber housing 23, and paint is supplied into the liquid chamber housing 23 from the outside via the liquid flow path 27.

[0020] The piezo frame 8 holds both longitudinal ends of the piezo element 9 by sandwiching them from the outside, and the right end of the piezo element frame 8 in FIG. 4 is positioned and fixed to the inner housing 2. A needle 21 is supported at the left end of the piezo element frame 8 in FIG. 4. A bellows-shaped deformation portion 8a that can expand and contract in the axial direction of the outer housing 1 (left and right direction in FIG. 4) is provided near the left end of the piezo element frame 8 in FIG. 4. When the piezo element 9 expands and contracts in the axial direction due to application of a drive voltage, the deformation portion 8a also expands and contracts in the axial direction. This causes the needle 21 supported by the piezo element frame 8 to move in the axial direction, opening and closing a nozzle 22a. As shown in FIG. 4, when the needle 21 retracts to the right in the figure and the nozzle 22a is open, paint in the liquid chamber housing 23 is ejected from the nozzle 22a.

[0021] 5, the inner housing 2 is formed in a cylindrical shape, and lead wires 4 are inserted into the inner housing 2 as supply lines for supplying a drive voltage to the piezo element 9. The piezo element 9 is electrically connected to an external power supply via the lead wires 4, and a drive voltage is applied to the piezo element 9 from the power supply via the lead wires 4.

[0022] The inner housing 2 also has, inside (on its inner wall), a frame positioning portion 2b that positions the piezo frame 8. The right end of the piezo frame 8 in FIG. 5 is inserted into the inner housing 2 and abuts against the frame positioning portion 2b, thereby positioning the piezo frame 8 in the axial direction relative to the inner housing 2.

[0023] A ground wire (earth wire) 3 electrically connected to an external ground point is inserted into the inner housing 2. The ground wire 3 is held together with the lead wire 4 by a heat-shrinkable tube 6 for bundling, which serves as a holding member housed within the inner housing 2. The ground wire 3 and the lead wire 4 are supported by a wiring support disk 11, which serves as a support member housed within the inner housing 2. The wiring support disk 11 has a hole 11a in its center through which the ground wire 3 is inserted, and a hole 11b, located radially outward of the hole 11a, through which the lead wire 4 is inserted. The portion of the internal space of the inner housing 2 to the right of the wiring support disk 11 in FIG. 5 , i.e., the portion including the heat-shrinkable tube 6 for bundling, is filled with resin 5.

[0024] The ground wire 3 is composed of a conductor and an insulating portion that covers the conductor, and the left end of the ground wire 3 in FIG. 5 is a bare ground wire portion 7 where the conductor is exposed. The bare ground wire portion 7 is electrically connected to a leaf spring 10 that serves as a grounding member. The leaf spring 10 has a ground wire connection portion 10a that is arranged inside the inner housing 2, and the bare ground wire portion 7 is electrically connected to this ground wire connection portion 10a.

[0025] The leaf spring 10 is attached to and supported by the inner housing 2. As shown in Fig. 5, when the leaf spring 10 is attached to the inner housing 2, the contact portion 10b of the leaf spring 10 is disposed in a groove 2a provided in the outer peripheral surface of the inner housing 2. The contact portion 10b of the leaf spring 10 is interposed between the inner housing 2 and the outer housing 1 in an elastically deformed state, and the elastic bias of the contact portion 10b causes the leaf spring 10 (contact portion 10b) to elastically contact the outer peripheral surface (groove 2a) of the inner housing 2 and the inner peripheral surface of the outer housing 1.

[0026] In this way, in the print head according to this embodiment, the leaf spring 10 serving as a grounding member resiliently contacts both the outer housing 1 and the inner housing 2, so that the outer housing 1 and the inner housing 2 are electrically connected (grounded) to an external ground point via the leaf spring 10 and the ground wire 3. As a result, even if electric charge accumulates in the outer housing 1 and the inner housing 2, the accumulated electric charge can be removed via the leaf spring 10 and the ground wire 3.

[0027] Moreover, in the print head according to this embodiment, the leaf spring 10 serving as the grounding member is housed within the outer housing 1, so even if the print head is subjected to external shock or vibration, the leaf spring 10 is prevented from being damaged or falling off the print head, thereby maintaining a good grounding state of the print head.

[0028] Furthermore, because the leaf spring 10 is attached to the inner housing 2, the leaf spring 10 can be attached to or detached from the outer housing 1 together with the inner housing 2. In this way, in the print head according to this embodiment, the leaf spring 10 can be attached to or detached from the outer housing 1 together with the inner housing 2, making it easy to replace the housed components, including the leaf spring 10.

[0029] Furthermore, the inner housing 2 to which the leaf spring 10 is attached also serves as a member for positioning the piezo element 9 and the piezo element frame 8, and therefore, when the inner housing 2 is attached to the outer housing 1, both the grounding of the outer housing 1 and the inner housing 2 and the positioning of the piezo element 9 and the piezo element frame 8 can be achieved. In this embodiment, the piezo element 9 and the piezo element frame 8 are first inserted into the outer housing 1, and then the inner housing 2 to which the leaf spring 10 is attached is inserted into the outer housing 1 from right to left in FIG. 5. This allows the outer housing 1 and the inner housing 2 to be grounded via the leaf spring 10, and the positioning of the piezo element 9 and the piezo element frame 8 to be achieved. In this way, the configuration according to this embodiment simplifies the grounding and assembly work of the print head.

[0030] In the print head according to this embodiment, the ground wire 3 and the lead wire 4 are supported by the wiring support disk 11, which prevents the ground wire 3 and the lead wire 4 from being displaced within the inner housing 2 or from coming into contact with surrounding components such as the inner housing 2. Furthermore, the ground wire 3 and the lead wire 4 are supported by the wiring support disk 11 at different positions (out of contact) when viewed from the insertion direction of the inner housing 2 into the outer housing 1 (viewed from the right side in FIG. 5), which reliably prevents the ground wire 3 and the lead wire 4 from coming into contact with each other.

[0031] In this way, in the print head according to this embodiment, the ground wire 3 and the lead wire 4 are supported so that they do not come into contact with each other or with surrounding components, which prevents the ground wire 3 (exposed ground wire portion 7) from falling off the ground wire connecting portion 10a of the leaf spring 10 and causing a grounding failure, or prevents a connection failure of the lead wire 4 to the piezo element 9. Therefore, in the print head according to this embodiment, the grounding state of the outer housing 1 and the inner housing 2 and the electrical continuity of the piezo element 9 to the power source can be satisfactorily ensured.

[0032] Next, an embodiment of a head unit including a liquid ejection head (print head) according to the present invention will be described with reference to Fig. 6. Fig. 6 is a cross-sectional view showing the configuration of the head unit according to this embodiment.

[0033] As shown in Figure 6, the head unit 20 of this embodiment has multiple liquid ejection heads 30 (eight in the example shown in Figure 6), a liquid supply path 32 that supplies paint (liquid) to the liquid ejection heads 30, a liquid supply port 33 that supplies paint to the liquid supply path 32, and a liquid discharge port 34 that discharges the paint from the liquid supply path 32.

[0034] The basic configuration of the plurality of liquid ejection heads 30 is the same as that described with reference to FIGS. 4 and 5, and the same reference numerals are used in FIG. 6 for corresponding elements.

[0035] In the head unit 20 shown in Fig. 6, eight liquid ejection heads 30 are provided so that their nozzles 22a (ejection ports) are arranged at approximately equal intervals in one direction (the left-right direction in Fig. 6). Each liquid ejection head 30 is provided extending in the vertical direction so that paint is ejected downward from the nozzle 22a at the bottom in the figure. Each liquid ejection head 30 shown in Fig. 6 is rotated approximately 90° counterclockwise around the nozzle 22a side from the state shown in Fig. 4.

[0036] A liquid supply path 32 is provided to penetrate the liquid chamber housing 23 of each liquid ejection head 30 so that paint flows from one side (the left side in FIG. 6) to the other side (the right side in FIG. 6) in the arrangement direction of the eight liquid ejection heads 30. That is, the liquid supply path 32 of each liquid ejection head 30 is provided with a fluid flow path 27 into which paint is injected, as well as a discharge port 28 on the opposite side of the fluid flow path 27 from which paint is discharged.

[0037] In the head unit 20 shown in FIG. 6, the liquid outlet 34 is normally closed by a valve or the like. Therefore, under normal circumstances, paint is supplied from the liquid supply port 33, and as shown in FIG. 6, the liquid supply path 32 is filled with paint. In this state, the needle 21 of each liquid ejection head 30 opens the nozzle 22a, causing paint to be ejected from the nozzle 22a of each liquid ejection head 30. On the other hand, during cleaning, the liquid outlet 34 is opened, making it easier to clean the inside of the head unit. In the head unit 20 shown in FIG. 6, the inner housing 2 of any one of the eight liquid ejection heads 30 may be provided with a leaf spring 10 as a grounding member, or the inner housings 2 of all eight liquid ejection heads 30 may be provided with leaf springs 10.

[0038] The present invention can also be applied to a coating apparatus 8000 for coating an automobile body, as shown in FIG. 7, instead of the coating apparatus 201 shown in FIG. 1. The coating apparatus 8000, which serves as a liquid discharging device, includes a robot arm 810 that can move freely like a human arm using multiple joints, and a head unit 820 at the tip of the robot arm 810, which includes eight liquid discharge heads 30 that discharge liquid. The robot arm 810 also includes a 3D sensor 830 near the liquid discharge unit 820. The coating apparatus 8000 can be an articulated robot with an appropriate number of axes, such as five, six, or seven. The coating apparatus 8000 uses the 3D sensor 830 to detect the position of the head unit 820 relative to an object (an automobile in this embodiment) M, and then moves the robot arm 810 based on the detection results to discharge paint from the eight liquid discharge heads 30 included in the head unit 820 onto the object 100, thereby coating the object M.

[0039] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various design modifications can be made without departing from the scope of the invention.

[0040] In the present invention, a "liquid ejecting device" is a device that includes a liquid ejection head or a head unit having this liquid ejection head, and ejects liquid by driving the liquid ejection head. Liquid ejecting 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.

[0041] Furthermore, the term "liquid ejecting 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.

[0042] For example, examples of "liquid ejecting devices" include image forming devices that eject ink to form images on paper, and three-dimensional modeling devices (three-dimensional modeling devices) that eject modeling liquid onto a powder layer formed from layers of powder in order to create a three-dimensional object (a three-dimensional model).

[0043] Furthermore, the term "liquid ejection device" is not limited to devices that use ejected liquid to visualize meaningful images such as letters and figures. For example, it also includes devices that form patterns that have no meaning in themselves, and devices that create three-dimensional images.

[0044] The above-mentioned "object onto which a liquid can adhere" means an object onto which a liquid can adhere at least temporarily, an object onto which the liquid can adhere and stick, an object onto which the liquid can penetrate, etc. Specific examples include media such as paper, recording paper, film, and cloth, electronic circuit boards, electronic components such as piezoelectric elements, powder layers, organ models, and test cells, and unless otherwise specified, includes all objects onto which a liquid can adhere.

[0045] Furthermore, the material of "something to which a liquid can adhere" may be anything to which a liquid can adhere, even temporarily, such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, or ceramics.

[0046] The "liquid" may be any liquid having a viscosity and surface tension that allows it to be ejected from a head, but is not particularly limited thereto. Preferably, the viscosity of the liquid is 30 mPa·s or less at room temperature and pressure, or upon heating or cooling. More specifically, the liquid may be a solution, suspension, emulsion, or the like containing a solvent such as water or an organic solvent, a colorant such as a dye or pigment, a polymerizable compound, a resin, or a surfactant, a biocompatible material such as DNA, amino acids, proteins, or calcium, or an edible material such as a natural dye. These liquids can be used, for example, as inkjet inks, surface treatment liquids, components of electronic devices or light-emitting devices, liquids for forming electronic circuit resist patterns, and liquid materials for 3D modeling.

[0047] Furthermore, the "liquid ejection device" may be a device in which a liquid ejection head and an object onto which liquid can adhere move relatively, but is not limited to this. Specific examples include a serial type device equipped with an element that moves the liquid ejection head (liquid ejection head moving mechanism), a line type device in which the liquid ejection head does not move, and the like.

[0048] Other examples of "liquid ejecting devices" include a treatment liquid application device that ejects a 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 an injection granulation device that ejects a composition liquid in which raw materials are dispersed through a nozzle to granulate fine particles of the raw materials.

[0049] In the present invention, a "head unit" is a device having at least one liquid ejection head, a liquid supply channel that supplies liquid to the liquid ejection head, and a liquid supply port that supplies liquid to the liquid supply channel. [Explanation of symbols]

[0050] 1 outer housing (first housing member) 2 Inner housing (second housing member) 3 Ground wire 4 Lead wire (supply wire) 9 Piezo (piezoelectric material) 10 Leaf spring (grounding member) 11 Wiring support disk (support member) 20 Head Unit 21 Needle (opening and closing member) 22 Nozzle plate (nozzle forming member) 22a nozzle 201 Painting equipment (liquid discharging equipment) 202 Print head (liquid ejection head) 211 Drive unit [Prior art documents] [Patent documents]

[0051] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-151094

Claims

1. a nozzle forming member in which a nozzle for ejecting a liquid is formed; an opening / closing member that opens and closes the nozzle; a piezoelectric element that operates the opening / closing member by expanding and contracting in an axial direction in response to a driving voltage to open and close the nozzle; a cylindrical first housing member that houses the piezoelectric body; a grounding member that contacts the inside of the first housing member and is connected to a grounding wire that is electrically connected to an external grounding point; a second housing member that houses a support member that supports the ground wire and is inserted into the first housing member; Equipped with The liquid ejection head is characterized in that the ground member is supported by the second containing member.

2. A liquid ejection head as described in claim 1, wherein the second accommodating member accommodates a positioning portion that positions the piezoelectric element.

3. 3. The liquid ejection head according to claim 1, wherein the second container member and the grounding member are detachable from the first container member as a single unit.

4. The ground wire; a supply line for supplying a drive voltage to the piezoelectric element; Equipped with 4. The liquid ejection head according to claim 1, wherein the support member supports the ground wire and the supply wire at different positions when viewed from the insertion direction of the second accommodating member into the first accommodating member.

5. the grounding member is elastically deformable, 5. The liquid ejection head according to claim 1, wherein the grounding member is in contact with the inside of the first accommodating member in a state where the grounding member is elastically deformed.

6. The liquid ejection head according to any one of claims 1 to 5, a driving unit that drives the liquid ejection head; A liquid ejection device comprising:

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