Ink jet head

Abstract

To provide an ink jet head capable of jetting ink of high viscosity at high speed.SOLUTION: An ink jet head includes an ink liquid chamber in a funnel shape, an impactor, and an actuator vibrating the impactor. A liquid contact surface of the impactor configures a whole upper surface in the funnel shape. The upper surface configured by the impactor moves in parallel horizontally, and discharges ink from an ink discharge port provided for a foot part in the funnel shape. A feed passage feeding the ink liquid chamber with ink is connected to a side surface of the funnel shape and normally communicates with the ink liquid chamber, so that it can continuously feed ink and has high productivity.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an inkjet head, and more particularly to an inkjet head that can be used for electrostatic coating or the like.

Background Art

[0002] For electrostatic coating of vehicle bodies, a rotary atomization method using a bell cup at the paint outlet is frequently used.

[0003] The rotary atomization method is a method in which a bell cup is rotated at high speed, the paint is ejected from its tip by centrifugal force, and the paint is atomized by air and adhered to the body. Since paint dust scatters due to the air rebounded by the body, the coating efficiency is about 80%, and an improvement in coating efficiency is desired.

[0004] Although inkjet coating is expected as a coating technology with a coating efficiency of 100%, since the paint does not spread like the above-mentioned rotary atomization method in inkjet coating, the productivity (coating area per unit time) is low, and it is difficult to adopt it in the coating process of vehicle bodies.

[0005] Although it is not used for coating vehicle bodies, Patent Document 1 describes that according to an inkjet printer that slides a piston rod inserted into a nozzle hole and extrudes the ink supplied into the nozzle hole, high-speed recording is possible.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, in the inkjet printer described in Patent Document 1, since the piston rod retracts to the ink supply port connected to the rear part of the nozzle hole to supply ink to the nozzle hole, the stroke of the piston rod becomes long, the nozzle becomes large, and high-speed driving becomes difficult.

[0008] Furthermore, when ink is ejected, since the piston rod advances to block the ink supply port, ink cannot be continuously supplied to the nozzle hole, and the productivity is low for use in painting the vehicle body.

[0009] The present invention has been made in view of the problems of such conventional technologies, and an object thereof is to provide an inkjet head capable of ejecting high-viscosity ink (paint) at high speed.

Means for Solving the Problems

[0010] As a result of intensive studies to achieve the above object, the present inventor has found that by moving the entire upper surface of the ink liquid chamber having a funnel shape in parallel, even if the ink supply path is always in communication with the ink liquid chamber, the ink is suppressed from flowing back to the ink supply path side, and the ink can be ejected while continuously supplying the ink, and has found that the above object can be achieved, and has completed the present invention.

[0011] That is, the inkjet head of the present invention comprises a funnel-shaped ink liquid chamber, an impactor, and an actuator for vibrating the impactor, the contact surface of the impactor constitutes the entire upper surface of the funnel shape, and the upper surface constituted by the impactor moves up and down in parallel to eject ink from the ink ejection port provided at the foot of the funnel shape, and a supply path for supplying ink to the ink liquid chamber is connected to the side surface of the funnel shape and is always in communication with the ink liquid chamber.

Effects of the Invention

[0012] According to the present invention, since the entire upper surface of the ink liquid chamber having a funnel shape is translated, backflow of the ink can be suppressed, the ink supply path and the ink liquid chamber can be constantly communicated to continuously supply the ink, and an inkjet head with high productivity can be provided.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0014] The inkjet head of the present invention will be described in detail. As shown in FIG. 1, the inkjet head of the present invention includes an ink liquid chamber, an impactor, and an actuator that vibrates the impactor, and a supply path for supplying ink to the ink liquid chamber is constantly communicated with the ink liquid chamber.

[0015] In the inkjet head of the present invention, the impactor presses the ink, and even when it reaches the lowermost end, the ink supply path is not blocked, and the supply path and the ink liquid chamber are constantly communicated, so ink can be continuously supplied to the ink liquid chamber. Therefore, the coating area per unit time is wide and the productivity can be improved.

[0016] In an inkjet head in which the supply path and the ink liquid chamber are constantly communicated in this way, even when the ink liquid chamber is pressed, the pressing force escapes to the supply path and the ink flows back into the supply path, so it is difficult to efficiently transmit the pressing force to the ink and eject it.

[0017] The inkjet head of the present invention has an ink liquid chamber in a funnel shape, the entire upper surface of the funnel shape is formed by the contact surface of the impactor, and the ink ejection port is provided at the foot of the funnel shape, and the contact surface of the impactor and the ejection port face each other.

[0018] The contact surface of the impactor that constitutes the entire upper surface of the ink liquid chamber is a planar shape, and it vibrates in parallel to press the ink liquid chamber. Therefore, the ink in the ink liquid chamber is all pushed downward in the direction of the ejection port, and the flow becomes a flow toward the foot at the lower part of the funnel shape, and the pressing force concentrates on the ejection port.

[0019] And, since the ink supply path is connected to the side surface of the funnel shape and faces a direction substantially orthogonal to the flow direction of the ink by the impactor, the pressure loss on the ink supply path side increases, and the backflow of the ink into the ink supply path can be suppressed. Therefore, the ejection efficiency of the ink from the ejection port can be improved.

[0020] That is, as shown in FIG. 2, when a part of the upper surface of the ink liquid chamber is locally pressed and the upper surface is deformed into a cross-sectional arch shape, that is, the upper surface is deformed into a bowl shape and pressed, the pressing force is radially dispersed, and the ink flow also turns sideward. Therefore, the ink flows in the direction of the ink supply path connected to the side surface of the ink liquid chamber, and backflow is likely to occur.

[0021] As described above, the inkjet head of the present invention vibrates the entire planar upper surface in parallel, so it is difficult for the ink to flow in the direction of the ink supply path connected to the side of the ink liquid chamber, and backflow into the ink supply path can be suppressed.

[0022] In the present invention, the "upper surface of the ink liquid chamber" means the upper surface of the funnel shape having an inverted conical main body portion and a foot portion, and it does not mean that the inkjet head never faces sideways and always ejects ink downward.

[0023] As described above, even when the supply path and the ink liquid chamber are always in communication, the inkjet head of the present invention can efficiently eject ink from the ejection port. Therefore, the diameter of the supply path can be made larger than the diameter of the ejection port, and a large amount of ink can be continuously supplied to the ink liquid chamber, so that productivity can be improved.

[0024] In addition, the ink liquid chamber has a funnel shape, and since the contact surface of the impactor is larger than the diameter of the ejection port, the stroke of the impactor can be shortened, the inkjet head can be miniaturized, and the impactor can be vibrated at high speed, so that the ink ejection amount per unit time can be increased.

[0025] The stroke of the impactor only needs to be able to eject ink droplets, and although it also depends on the size of the upper surface of the ink liquid chamber, that is, the area of the contact surface of the impactor, it is preferably 30 μm or less.

[0026] Thereby, ink droplets can be ejected at a high speed of 1 kHz or more, and productivity is improved. Furthermore, if the volume of one ink droplet is 100 - 200 pl, further improvement in productivity is possible.

[0027] The lower limit of the stroke of the impactor is not particularly limited, but when the stroke becomes shorter, the width of the ink liquid chamber becomes larger, making it difficult to form multiple nozzles. Therefore, it is preferably substantially 800 nm or more.

[0028] The actuator for vibrating the impactor preferably can generate a high pressing force, and an actuator with a driving voltage of 10 V or more can preferably be used because it can eject a high-viscosity ink (paint) containing a large amount of metallic metal powder or resin components.

[0029] As the high-viscosity ink, for example, an ink having a viscosity of 50 - 1000 cP at 25°C can be used.

[0030] Since the above ink has a high viscosity, the ink is discharged only when it is pressed, and even if the supply path is constantly in communication with the ink liquid chamber, unwanted ink leakage from the ink discharge port can be suppressed.

[0031] Also, thixotropic ink can be preferably used because its viscosity decreases and it becomes liquid only when pressed by an impactor, exhibiting fluidity, thus further suppressing ink leakage.

[0032] The above high-viscosity ink can be supplied to the ink liquid chamber by being pumped. By applying pressure to the ink with a pump or the like and forcing it to flow, a large amount of ink can be supplied to the ink liquid chamber, improving productivity.

[0033] The above inkjet head preferably has a structure that can be divided at the boundary between the ink liquid chamber and the impactor.

[0034] By being dividable into a liquid chamber unit having an ink liquid chamber in which an ink discharge port is formed and a drive unit that houses an impactor and an actuator, they can be manufactured separately and assembled, so the inkjet head can be easily manufactured.

[0035] And the inkjet head of the present invention has the contact surface of the impactor being flat as described above. As shown in FIG. 3, by making the contact surface of the impactor and the lower surface of the housing of the drive unit flush, when assembling the drive unit, the liquid chamber unit, and the drive unit, the alignment of the impactor is easy and it can be assembled accurately, so that the ink can be stably discharged.

[0036] The above drive unit preferably has a seal member at the joint portion of the impactor with the actuator. Thereby, ink leakage to the actuator side can be prevented, failure of the actuator can be suppressed, and stable ink discharge becomes possible.

Description of Reference Numerals

[0037] 1 Inkjet head 2 Liquid chamber unit 21 Ink liquid chamber 211 Main body part 212 Foot part 22 Ink ejection port 23 Ink supply path 3 Driving unit 31 Impactor 311 Contact liquid surface 32 Actuator 33 Seal member 4 Ink

Claims

1. A funnel-shaped ink liquid chamber, an impactor, and an actuator for vibrating the impactor, wherein the contact liquid surface of the impactor constitutes the entire upper surface of the funnel shape, the upper surface formed by the impactor moves vertically in parallel and discharges ink from an ink discharge port provided in the leg portion of the funnel shape, an ink supply path for supplying ink to the ink liquid chamber is connected to the side surface of the funnel shape and is always in communication with the ink liquid chamber. An inkjet head characterized by this.

2. The inkjet head according to claim 1, wherein the contact liquid surface of the impactor is flat.

3. The inkjet head according to claim 1, wherein the diameter of the supply path is larger than the diameter of the discharge port.

4. The inkjet head according to claim 1, wherein the stroke of the impactor is 30 µm or less.

5. The inkjet head according to claim 3, characterized in that ink droplets of 100 to 200 pl are discharged.

6. The inkjet head according to claim 5, wherein the driving voltage of the actuator is 10 V or more.

7. The inkjet head according to claim 1, characterized in that a paint having thixotropy and a viscosity of 50 to 1000 cP (25°C) is discharged.

8. The inkjet head according to claim 1, characterized in that ink is pumped into the ink liquid chamber.

9. A liquid chamber unit having the funnel-shaped ink liquid chamber, The inkjet head according to claim 1, characterized in that it has a structure that can be divided into a drive unit having the impactor and the actuator.

10. The inkjet head according to claim 9, wherein the drive unit has a seal member at a joint portion of the impactor with the actuator.

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