Liquid discharge apparatus

Abstract

To provide a liquid discharge device capable of strengthening ultrasonic waves transmitted to a cleaning liquid.SOLUTION: The liquid discharging apparatus 1 includes the head 10 having the at least one nozzle 11 that discharges the discharge liquid, the cap 20 that covers the nozzle 11 and holds the cleaning liquid 23 therein, and the ultrasonic device 25 that transmits the ultrasonic wave 24 to the cleaning liquid 23, the cleaning liquid 23 is in contact with the at least one nozzle 11, and the ultrasonic device 25 is disposed so as to be in contact with the cleaning liquid 23 in the cap 20.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Conventionally, a liquid ejection device is known in which an ultrasonic vibrator is placed on the outer surface of a cap that contacts the ejection head, and ultrasonic waves emitted from the ultrasonic vibrator are transmitted to the cap to excite the liquid inside the cap, thereby cleaning the ejection nozzle of the ejection head (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-347000 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the liquid ejection device configured as described above, the ultrasonic waves are propagated through the cap, and therefore there is a problem in that the ultrasonic waves are reflected due to the difference in acoustic impedance between the cap and the liquid, resulting in a decrease in the transmitted strength of the ultrasonic waves. [Means for solving the problem]

[0005] A liquid ejection device according to a first aspect of the present disclosure comprises a head having at least one nozzle for ejecting an ejection liquid, a cap for covering the nozzle and holding a cleaning liquid therein, and an ultrasonic device for transmitting ultrasonic waves to the cleaning liquid, wherein the cleaning liquid abuts against at least one of the nozzles and the ultrasonic device is positioned so as to be in contact with the cleaning liquid in the cap. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a cross-sectional view schematically illustrating a liquid ejection device according to an embodiment of the present disclosure. [Figure 2] FIG. 10 is a cross-sectional view schematically illustrating a liquid ejection device according to another embodiment of the present disclosure. [Figure 3] FIG. 10 is a cross-sectional view showing a cross section of the liquid ejection device of the other embodiment taken in a cross-sectional direction. DETAILED DESCRIPTION OF THE INVENTION

[0007] A liquid ejection device according to an embodiment of the present disclosure will be described below. In FIG. 1, a liquid ejection device 1 includes a head 10 having a plurality of nozzles 11 for ejecting ejection liquid. The head 10 has a nozzle plate 12, and a plurality of nozzles 11 are formed in a row on the nozzle plate 12. A plurality of discharge units 13 corresponding to each of the nozzles 11 are arranged on the back side of the nozzle plate 12. The plurality of discharge units 13 are connected to a discharge control unit 14 installed outside the head 10, and under the control of the discharge control unit 14, the discharge liquid is pressure-fed to the corresponding nozzle 11 and discharged from the nozzle 11. As the discharge liquid, ink for printing, a modeling material for an additive manufacturing device, or the like is used. The discharge control unit 14 has a detection unit 15. The detection unit 15 monitors the discharge state of the discharge liquid from each of the multiple discharge units 13, and can identify a discharge unit 13 where a discharge defect has occurred and the corresponding nozzle 11. For example, the detection unit 15 can detect a narrowing or clogging of the flow path of the nozzle 11 by detecting the discharge resistance from the pressure fluctuation or flow velocity during discharge for each nozzle 11. This allows the detection unit 15 to detect a nozzle 11 with a discharge defect as an abnormal nozzle.

[0008] The liquid ejection device 1 has a cap 20 that collectively covers the multiple nozzles 11. The cap 20 covers the nozzles 11 when the head 10 is not in use or during a cleaning operation, and can be separated from the front of the head 10 when the head 10 is in use to eject liquid from the nozzles 11.

[0009] The cap 20 has a cap body 21 that covers the surface of the nozzle plate 12 . The cap body 21 has a concave shape on the side facing the nozzle plate 12, and an annular rubber packing 22 is installed around the upright periphery. The rubber packing 22 is arranged so as to surround all of the nozzles 11, and is able to seal in the liquid by adhering closely to the surface of the nozzle plate 12 around the entire periphery. This rubber packing 22 forms a flexible member at the position of the cap 20 that abuts against the head 10. As the flexible member, natural or synthetic rubber materials as well as other resin materials can be used, and it is desirable to appropriately select a material that can ensure sealing between the nozzle plate 12 and the cap body 21.

[0010] The inside of the cap body 21 is a closed space sealed by a rubber packing 22, and a cleaning liquid 23 is held in this space. The cleaning liquid 23 is a liquid suitable for cleaning the nozzles 11, and may be a solvent for the ejection liquid such as printing ink, or pure water or the ejection liquid itself may be used as the cleaning liquid 23. A sufficient amount of cleaning liquid 23 is filled inside the cap body 21, and the plurality of nozzles 11 are immersed in the cleaning liquid 23.

[0011] An ultrasonic device 25 that transmits ultrasonic waves 24 to the cleaning liquid 23 is installed on the bottom surface of the recess of the cap body 21. The ultrasonic device 25 is arranged so as to come into contact with the cleaning liquid 23 inside the cap body 21. The ultrasonic device 25 is configured in an array of a plurality of ultrasonic elements 26, such as piezoelectric elements, arranged vertically and horizontally. An example of such an ultrasonic device 25 is a configuration in which a substrate having a two-dimensional array of openings, a vibration plate that closes the openings of the substrate, and piezoelectric elements are arranged at positions corresponding to each opening of the vibration plate. In this case, the region that closes one opening of the vibration plate is used as a vibration section, and one vibration section and the piezoelectric element arranged in the vibration section form one ultrasonic element 26 (thin-film ultrasonic element). The ultrasonic device 25 may be fixed to the bottom surface of the recess of the cap body 21 by mechanical means such as fitting, or by adhesive or other means.

[0012] A drive control unit 27 is connected to the ultrasonic device 25 . The drive control unit 27 individually drives the ultrasonic elements 26 to transmit ultrasonic waves 24 to the cleaning liquid 23 . The multiple ultrasonic elements 26 may be installed in a one-to-one correspondence with the multiple nozzles 11, or multiple ultrasonic elements 26 may correspond to one nozzle 11, or one ultrasonic element 26 may correspond to multiple nozzles 11. For example, by delay control of the ultrasonic waves 24 for the multiple ultrasonic elements 26, the ultrasonic waves 24 from each can be focused on one nozzle 11. This ensures the intensity of the ultrasonic waves 24 acting on one nozzle 11, and also makes it possible to selectively transmit the ultrasonic waves 24 to a specific nozzle 11. By changing the delay control settings, the nozzle 11 on which the ultrasonic waves 24 are focused can be changed to another nozzle 11. The drive control unit 27 can clean all of the nozzles 11 by transmitting ultrasonic waves 24 from the plurality of ultrasonic elements 26.

[0013] Here, the drive control unit 27 can drive the ultrasonic element 26 so as to satisfy the formula f>6 / D, where f [MHz] is the drive frequency of the ultrasonic device 25 and D [μm] is the diameter of the nozzle 11. Generally, when using ultrasonic waves to clean nozzles, depending on the ultrasonic frequency, cavitation occurs throughout the cleaning liquid, particularly when the frequency is low, making selective nozzle cleaning impossible and resulting in uneven cleaning.In response to this, by satisfying the formula f>6 / D, the size of the bubbles generated by cavitation becomes smaller, allowing for efficient ultrasonic cleaning of the nozzle surface.

[0014] The above-mentioned formula f>6 / D is derived as follows. The bubbles generated by cavitation have a resonance frequency fo and a bubble radius ro that satisfy the following relationship: fo=(1 / 2πro)×√(3γPo / ρ) Po: static pressure, γ: specific heat ratio of gas that becomes bubbles ρ: density of the liquid Here, Po=1atm and the liquid is water (ρ=1g / cm^3), fo×ro~3 ("~" indicates approximation, same below), Furthermore, if we substitute the diameter Ro = 2ro, fo×Ro~6, In order for a bubble with a diameter Ro to be able to penetrate into a nozzle with a nozzle diameter D, D>Ro must be satisfied. If the resonance frequency of the ultrasonic element is f=fo, then: f×D>fo×Ro~6, therefore f×D>6, which leads to f>6 / D. From the above, if the ultrasonic frequency is f>6 / D, small-diameter bubbles can be made to enter the nozzle, which prevents cavitation throughout the cleaning liquid and allows selective nozzle cleaning using small-bubble cavitation, thereby eliminating uneven cleaning of the nozzle.

[0015] The drive control unit 27 can clean all the nozzles 11 by transmitting the ultrasonic waves 24 from the ultrasonic elements 26. Furthermore, the drive control unit 27 can refer to the detection result of the detection unit 15 to select the nozzle 11 to be cleaned. If the detection unit 15 detects that one of the plurality of nozzles 11 has a discharge defect and is an abnormal nozzle, the drive control unit 27 selects the ultrasonic element 26 corresponding to the nozzle 11 that the detection unit 15 has detected as the abnormal nozzle, and drives the ultrasonic element 26 so that the ultrasonic waves 24 are focused toward the nozzle 11 that has been detected as the abnormal nozzle. This allows the ultrasonic waves 24 to be focused on the nozzle 11 with the discharge defect, thereby enabling localized nozzle cleaning.

[0016] [Effects of this embodiment] The liquid ejection device 1 of this embodiment comprises a head 10 having a plurality of nozzles 11 that eject the ejected liquid, a cap 20 that covers the plurality of nozzles 11 and holds a cleaning liquid 23 inside, and an ultrasonic device 25 that transmits ultrasonic waves 24 to the cleaning liquid 23, wherein the cleaning liquid 23 abuts against the plurality of nozzles 11 and the ultrasonic device 25 is positioned so as to be in contact with the cleaning liquid 23 in the cap 20. As a result, all of the nozzles 11 are covered with the caps 20, and the cleaning liquid 23 held in the caps 20 comes into contact with the nozzles 11. The ultrasonic device 25 is disposed so as to come into contact with the cleaning liquid 23 in the caps 20, and the ultrasonic waves 24 transmitted from the ultrasonic device 25 are transmitted directly from the ultrasonic device 25 to the cleaning liquid 23, improving the transmittance of the ultrasonic waves 24 reaching the cleaning liquid 23. As a result, the ultrasonic waves 24 transmitted to the cleaning liquid 23 are strengthened, sufficient bubbly cavitation is generated in the cleaning liquid 23, and the cleaning effect on the nozzles 11 can be improved.

[0017] In the liquid discharger 1 of this embodiment, when the drive frequency of the ultrasonic device 25 by the drive control unit 27 is f [MHz] and the diameter of the nozzle is D [μm], the formula f>6 / D is satisfied. This reduces the size of the bubbles caused by cavitation in the cleaning liquid 23 by the ultrasonic waves 24 from the ultrasonic device 25, allowing small-diameter bubbles to enter the nozzle 11, thereby enabling efficient ultrasonic cleaning even on the inner surface of the nozzle 11.

[0018] In the liquid ejection device 1 of this embodiment, the ultrasonic device 25 includes a plurality of ultrasonic elements . This allows the transmission of the ultrasonic waves 24 from each of the plurality of ultrasonic elements 26 to be individually controlled, thereby making it possible to transmit the ultrasonic waves 24 partially and locally rather than from the entire ultrasonic device 25.

[0019] The liquid ejection device 1 of this embodiment is provided with a drive control unit 27 that controls the driving of multiple ultrasonic elements 26, and the drive control unit 27 selectively drives each of the multiple ultrasonic elements 26 so as to focus the ultrasonic waves 24 at the position of the nozzle 11. As a result, the ultrasonic waves 24 focused on the nozzle 11 generate bubble-like cavitation locally around the nozzle 11, resulting in an efficient cleaning effect.

[0020] The liquid ejection device 1 of this embodiment is equipped with a detection unit 15 that detects a nozzle 11 with poor ejection performance as an abnormal nozzle, and a drive control unit 27 drives multiple ultrasonic elements 26 so that ultrasonic waves 24 are focused toward the nozzle 11 that the detection unit 15 has detected as an abnormal nozzle. This allows the ultrasonic waves 24 to be focused on the nozzle 11 with the ejection failure, further increasing the effectiveness of local nozzle cleaning.

[0021] In the liquid ejection device 1 of this embodiment, the flexible rubber packing 22 is disposed at the position of the cap 20 where it comes into contact with the head 10. As a result, the cap 20 and the head 10 are in contact with each other via the flexible rubber packing 22, and the sealing performance for the cleaning liquid 23 can be improved, while the protection performance for the nozzle surface of the head 10 can be improved.

[0022] [Other embodiments] 2 and 3 show another embodiment of the present invention. A liquid ejection device 1A of this embodiment basically has the same configuration as the liquid ejection device 1 described above in Fig. 1. Therefore, a description of the common configuration will be omitted, and different configurations will be described below. 1, the surface of the ultrasonic device 25 was directly immersed in the cleaning liquid 23. In contrast, in the liquid discharger 1A of this embodiment shown in Fig. 2, an acoustic lens 28 is provided in the cap 20A on the surface of the ultrasonic device 25, i.e., the transmission surface of the ultrasonic waves 24. The acoustic lens 28 can be made of a material similar to that of a general ultrasonic probe, such as silicone, which has an acoustic impedance close to that of water.

[0023] In FIG. 3, the acoustic lens 28 has a D-shaped cross section in the direction intersecting the arrangement direction of the plurality of nozzles 11, that is, the arrangement direction of the ultrasonic elements 26. In FIG. 2, the acoustic lens 28 has the above-described cross-sectional shape that continues along the arrangement direction of the plurality of nozzles 11, and has a length that spans the entire length of the ultrasonic device 25 in the same direction. In the ultrasonic device 25 in which such an acoustic lens 28 is installed, ultrasonic waves 24 from the ultrasonic elements 26 are transmitted to the corresponding nozzles 11 under the control of the drive control unit 27. Meanwhile, in a direction intersecting the arrangement of the multiple nozzles 11, the ultrasonic waves 24 from the ultrasonic elements 26 extending in the width direction of the ultrasonic device 25 are deflected by the acoustic lens 28 and focused on the corresponding nozzles 11.

[0024] As described above, in this embodiment, the ultrasonic device 25 has the acoustic lens 28 disposed on the transmission surface from which the ultrasonic waves 24 are transmitted. This allows the ultrasonic waves 24 transmitted from the ultrasonic device 25 to be deflected by the acoustic lens 28, thereby improving the function of focusing the ultrasonic waves 24 onto the nozzle 11. In other words, in the liquid ejection device 1A of this embodiment, ultrasonic waves 24 that cannot be introduced into the nozzle 11 without the acoustic lens 28 can be introduced into the nozzle 11 where they are focused by the acoustic lens 28, thereby improving the cleaning efficiency of the nozzle 11.

[0025] [Variations] The present invention is not limited to the above-described embodiment, and the present invention includes configurations obtained by modifications and improvements within the scope that can achieve the object of the present invention. In the above embodiment, an array of a plurality of ultrasonic elements 26 (thin film ultrasonic elements) arranged vertically and horizontally was used as the ultrasonic device 25, but so-called bulk ultrasonic elements that vibrate themselves when a drive voltage is applied to transmit ultrasonic waves may also be used as the ultrasonic elements 26. When such bulk ultrasonic elements are used as the ultrasonic elements 26, they may be arranged in one or two rows along the arrangement of the nozzles 11. In this case, two or more ultrasonic elements 26 corresponding to the same nozzle 11 may be operated simultaneously in parallel, or may be operated individually. An acoustic lens 28 can be used to focus the ultrasonic waves 24 from two or more rows of ultrasonic elements 26 onto one row of nozzles 11. When there are multiple rows of nozzles 11, one row of ultrasonic elements 26 may correspond to the multiple rows.

[0026] Summary of this disclosure A liquid ejection device according to a first aspect of the present disclosure comprises a head having at least one nozzle for ejecting an ejection liquid, a cap for covering the nozzle and holding a cleaning liquid therein, and an ultrasonic device for transmitting ultrasonic waves to the cleaning liquid, wherein the cleaning liquid abuts against at least one of the nozzles and the ultrasonic device is positioned so as to be in contact with the cleaning liquid in the cap.

[0027] As a result, the nozzle is covered with the cap and the cleaning liquid held in the cap comes into contact with the nozzle. The ultrasonic device is placed so as to come into contact with the cleaning liquid in the cap, and ultrasonic waves transmitted from the ultrasonic device are transmitted directly from the ultrasonic device to the cleaning liquid, improving the transmittance of the ultrasonic waves to the cleaning liquid. This strengthens the ultrasonic waves transmitted to the cleaning liquid, generating sufficient bubbly cavitation in the cleaning liquid and improving the cleaning effect on the nozzle.

[0028] In the liquid discharge device of this aspect, when the drive frequency of the ultrasonic device is f [MHz] and the diameter of the nozzle is D [μm], the formula f>6 / D is satisfied. When using ultrasonic waves to clean nozzles, depending on the frequency of the ultrasonic waves, especially at low frequencies, cavitation can occur throughout the cleaning liquid, making selective nozzle cleaning impossible and resulting in uneven cleaning.In response to this, by satisfying the formula f>6 / D, the size of the bubbles generated by cavitation becomes smaller, allowing for efficient ultrasonic cleaning of the nozzle surface.

[0029] The above-mentioned formula f>6 / D is derived as follows. The bubbles generated by cavitation have a resonance frequency fo and a bubble radius ro that satisfy the following relationship: fo=(1 / 2πro)×√(3γPo / ρ) Po: static pressure, γ: specific heat ratio of gas that becomes bubbles ρ: density of the liquid Here, Po=1atm and the liquid is water (ρ=1g / cm^3), fo×ro~3 ("~" indicates approximation, same below), Furthermore, if we substitute the diameter Ro = 2ro, fo×Ro~6, In order for a bubble with a diameter Ro to be able to penetrate into a nozzle with a nozzle diameter D, D>Ro must be satisfied. If the resonance frequency of the ultrasonic element is f=fo, then: f×D>fo×Ro~6, therefore f×D>6, which leads to f>6 / D. From the above, if the ultrasonic frequency is f>6 / D, small-diameter bubbles can be made to enter the nozzle, which prevents cavitation throughout the cleaning liquid and allows selective nozzle cleaning using small-bubble cavitation, thereby eliminating uneven cleaning of the nozzle.

[0030] In the liquid ejection apparatus of this aspect, the ultrasonic device includes a plurality of ultrasonic elements. This allows for individual control of the transmission of ultrasonic waves from each of the multiple ultrasonic elements, thereby enabling partial and local transmission of ultrasonic waves rather than from the entire ultrasonic device.

[0031] In the liquid ejection device of this aspect, a drive control unit is provided that controls the driving of the multiple ultrasonic elements, and the drive control unit selectively drives each of the multiple ultrasonic elements so as to focus the ultrasonic waves at the position of the nozzle. This allows the ultrasonic waves focused on the nozzle to locally generate bubble-like cavitation around the nozzle, resulting in an efficient cleaning effect.

[0032] In the liquid ejection device of this aspect, a detection unit is provided that detects abnormal nozzles, which are nozzles that are experiencing ejection problems, and the drive control unit drives the multiple ultrasonic elements so that the ultrasonic waves are focused toward the abnormal nozzle detected by the detection unit. This allows ultrasonic waves to be focused on the nozzles with ejection problems, further increasing the effectiveness of localized nozzle cleaning.

[0033] In the liquid ejection apparatus of this aspect, the ultrasonic device has an acoustic lens disposed on a transmission surface from which the ultrasonic waves are transmitted. This allows the ultrasonic waves transmitted from the ultrasonic device to be deflected by the acoustic lens, improving the function of focusing the ultrasonic waves onto the nozzle.

[0034] In the liquid ejection device of this aspect, a flexible member is disposed at a position of the cap where the cap abuts against the head. This allows the cap and the head to abut against each other via a flexible member, such as a rubber packing, improving the sealing performance for the cleaning liquid and improving the protection of the nozzle surface of the head. [Explanation of symbols]

[0035] 1,1A...liquid ejection device, 10...head, 11...nozzle, 12...nozzle plate, 13...ejection section, 14...ejection control section, 15...detection section, 20,20A...cap, 21...cap body, 22...rubber gasket, 23...cleaning liquid, 24...ultrasonic wave, 25...ultrasonic device, 26...ultrasonic element, 27...drive control section, 28...acoustic lens

Claims

1. a head having at least one nozzle for ejecting a liquid; a cap that covers the nozzle and holds a cleaning liquid therein; an ultrasonic device that transmits ultrasonic waves to the cleaning liquid; The cleaning liquid contacts at least one of the nozzles, The ultrasonic device is a liquid ejection apparatus arranged so as to come into contact with the cleaning liquid in the cap.

2. 2. The liquid ejection device according to claim 1, wherein the formula f>6 / D is satisfied, where f [MHz] is the drive frequency of the ultrasonic device and D [μm] is the diameter of the nozzle.

3. The liquid ejection apparatus of claim 1 , wherein the ultrasonic device comprises a plurality of ultrasonic elements.

4. a drive control unit that controls the drive of the plurality of ultrasonic elements; The liquid ejection device according to claim 3 , wherein the drive control unit selectively drives each of the plurality of ultrasonic elements so as to focus the ultrasonic waves at the position of the nozzle.

5. the liquid ejection device includes a detection unit that detects abnormal nozzles that are nozzles with ejection defects, The liquid ejection device according to claim 4 , wherein the drive control unit drives the plurality of ultrasonic elements so that the ultrasonic waves are focused toward the abnormal nozzle detected by the detection unit.

6. The liquid ejection apparatus according to claim 1 , wherein the ultrasonic device has an acoustic lens disposed on a transmission surface from which the ultrasonic waves are transmitted.

7. The liquid ejection device according to claim 1 , wherein a flexible member is disposed on the cap at a position where the cap abuts against the head.

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