WO2021144877A1 - Ink-jet recording device and recording operation driving method - Google Patents

Abstract

Provided is an ink-jet recording device in which a head driving unit for driving a recording operation of an ink-jet head is configured to be able to apply a discharge driving pulse Pa for causing an ink to be discharged from a nozzle, and a non-discharge driving pulse Pb for moving a meniscus formed in the nozzle without causing the ink to be discharged from the nozzle. Furthermore, the head driving unit carries out: during an ink discharge period for forming one dot during the recording operation, discharge driving in which the discharge driving pulse is applied a number of times up to a number n of gradations with respect to one dot to be landed on a recording medium, wherein the dot diameter is changed according to the number of times; and, during an ink non-discharge period during the recording operation, non-discharge driving in which the non-discharge driving pulse is applied m times which is equal to or greater than the number n of gradations for a period equal to the ink discharge period for forming the one dot, to move the meniscus.

Description

Inkjet recording device and recording operation drive method

The present invention relates to an inkjet recording device and a recording operation driving method.

Conventionally, there is known an inkjet device that circulates ink through an inkjet head and ejects ink from a nozzle of the inkjet head.
Generally, an inkjet recording device is equipped with an inkjet head in which a large number of nozzles for ejecting minute ink droplets are arranged.
Since these nozzles eject ink from a ejection port having a minute diameter, the state of the meniscus formed in the nozzles before ejection has a significant influence on the flying state of the droplets, that is, it is related to the image quality of the printed matter. Improving the stability of the droplets ejected from the inkjet head nozzle is an important issue because it affects the image quality of printed matter.

On the other hand, it has been realized that a multi-drive signal including a plurality of drive pulses is generated and a relatively large droplet is ejected.
However, when discharge and non-discharge are repeated, the state and position of the meniscus before discharge also change. Therefore, at the time of ejection after the non-ejection period, there is a high possibility that the ejection becomes unstable due to non-ejection of droplets, flight bending, or the like.

The invention described in Patent Document 1 supplies the inkjet head with a non-ejection drive voltage that moves the meniscus to the outside of the non-ejection nozzle in order to prevent ejection abnormalities caused by foreign matter adhering to the edge of the nozzle. At this time, the relationship between the diameter dn of the non-discharge nozzle and the meniscus diameter dm moved to the outside of the non-discharge nozzle satisfies 1.1 ≦ dm / dn ≦ 1.4.

Japanese Unexamined Patent Publication No. 2013-199021

However, the invention described in Patent Document 1 aims to prevent discharge abnormalities due to foreign matter adhesion, and the meniscus formed by a non-discharge drive voltage is statically indeterminate.
Even by forming a static meniscus at the time of non-ejection as in the invention described in Patent Document 1, it is not possible to eliminate the instability that causes non-ejection of droplets and flight bending at the time of subsequent ejection. ..

The present invention has been made in view of the above problems in the prior art, and an object of the present invention is to stably eject large droplets by an inkjet recording device.

One aspect of the present invention includes an inkjet head having a pressure chamber communicating with a nozzle and ejecting ink in the pressure chamber from the nozzle.
A head drive unit that drives a recording operation by the inkjet head is provided.
The head drive unit
A drive pulse voltage that expands and contracts the pressure chamber, and is a non-ejection to the extent that the discharge drive pulse that ejects ink from the nozzle and the meniscus formed in the nozzle without ejecting ink from the nozzle behave. Drive pulse and can be applied,
During the ink ejection period for forming one dot during the recording operation, the ejection drive pulse is applied as many times as the number of gradations n is applied to one dot landed on the recording medium, and the dots are applied according to the number of times. Execute discharge drive to change the diameter,
During the ink non-ejection period during the recording operation, m non-ejection drive pulses, which are equal to or greater than the number of gradations n, are applied to the period equal to the ink ejection period for forming one dot. , An inkjet recording device that executes a non-ejection drive that causes the meniscus to behave.

Another aspect of the present invention is a recording operation driving method having a pressure chamber communicating with a nozzle and driving a recording operation by an inkjet head that ejects ink in the pressure chamber from the nozzle.
A drive pulse voltage that expands and contracts the pressure chamber, and is a non-ejection to the extent that the discharge drive pulse that ejects ink from the nozzle and the meniscus formed in the nozzle without ejecting ink from the nozzle behave. Using a drive pulse
During the ink ejection period for forming one dot during the recording operation, the ejection drive pulse is applied as many times as the number of gradations n is applied to one dot landed on the recording medium, and the dots are applied according to the number of times. Execute discharge drive to change the diameter,
During the ink non-ejection period during the recording operation, m non-ejection drive pulses, which are equal to or greater than the number of gradations n, are applied to the period equal to the ink ejection period for forming one dot. This is a recording operation driving method for executing a non-ejection driving that causes the meniscus to behave.

According to the present invention, a large droplet can be stably ejected by an inkjet recording device.

It is a block diagram which shows the functional structure of the inkjet recording apparatus which concerns on one Embodiment of this invention. It is a schematic diagram of the pressure chamber and the nozzle seen in the axial direction of the nozzle, and shows the change of the pressure chamber corresponding to the drive pulse voltage. It is a schematic diagram which shows the operation of the ink droplet ejected from a nozzle. It is a drive signal waveform diagram which shows the example of the drive pulse voltage which concerns on one Embodiment of this invention. It is a drive signal waveform diagram which shows the drive pulse voltage which concerns on a comparative example. It is sectional drawing of the nozzle and the meniscus in a statically stable state. It is sectional drawing of the nozzle and the meniscus after continuous discharge.

An embodiment of the present invention will be described below with reference to the drawings. The following is an embodiment of the present invention and does not limit the present invention.

The inkjet recording device 1 includes a transport unit 10, a recording operation unit 20, a cleaning unit 30, a control unit 40, a storage unit 50, a communication unit 70, an operation reception unit 81, a display unit 82, and a power supply unit. 90 and the like are provided.

The transport unit 10 moves the recording medium on which the image is to be recorded so as to face the recording range of the recording operation unit 20. The transport unit 10 includes, for example, a transport motor 14 that pulls out a long recording medium rolled up in a roll shape at a predetermined speed. The recording medium is, for example, cloth, but may be another material such as paper.

The recording operation unit 20 performs an operation of ejecting ink onto a recording medium and recording an image. The recording operation unit 20 is a piezoelectric element that deforms a nozzle 27 in which a large number of inks are arranged in a predetermined pattern to discharge ink and an ink flow path (pressure chamber) that supplies ink to the nozzle 27 to give pressure fluctuation to the ink. It includes an inkjet head 21 having 26, a head drive unit 25 that outputs a drive pulse voltage that deforms each piezoelectric element 26, and the like.
By applying the drive pulse voltage P to the piezoelectric element 26 as shown in FIG. 2, the side wall 29 of the pressure chamber 28 communicating with the nozzle 27 is deformed and formed in the vicinity of the discharge opening of the nozzle 27 as shown in FIG. The meniscus 22 is shaken to separate the ink droplet 23 from the meniscus 22 and eject it.

The cleaning unit 30 includes a wiping member 32 for removing ink and solidified substances thereof adhering to the nozzle surface where the openings of the nozzle 27 are arranged, a drive unit 31 for operating the wiping member 32, and the like. The wiping member 32 is not particularly limited, but is, for example, a non-woven fabric that sucks ink, a resin member on a blade that scrapes solids, and the like.

The control unit 40 is a processor that controls the overall operation of the inkjet recording device 1. The control unit 40 includes, for example, a CPU 41 (Central Processing Unit) and a RAM 42 (Random Access Memory). The CPU 41 performs arithmetic operations and performs various control processes. The RAM 42 provides the CPU 41 with a working memory space and stores temporary data.

The storage unit 50 stores image data to be recorded and its processing data, and stores other setting data, programs, and the like. The image data may be stored in, for example, a DRAM capable of temporarily storing a large amount of data and outputting it at high speed. Further, the setting data, the program, and the like are stored in a non-volatile memory such as a flash memory that can be stored even when the power supply to the inkjet recording device 1 is stopped, and / or in an HDD (Hard Disk Drive) or the like.

The communication unit 70 controls data transmission / reception with an external device according to a predetermined communication standard (for example, TCP / IP). The communication unit 70 may be connected to a LAN (Local Area Network) or the like and can be connected to the external Internet via a router or the like, or may be directly connected to a peripheral device via a USB cable connected to a USB terminal. It may be.
The power supply unit 90 supplies power to the inkjet recording device 1 from the power supply.

Next, the driving of the recording operation will be described.
The head drive unit 25 applies a drive pulse voltage P that expands and contracts the pressure chamber 28 to the piezoelectric element 26. As the drive pulse voltage P, two types (Pa, Pb) shown in FIG. 4 are used. The head drive unit 25 applies a discharge drive pulse Pa that ejects ink from the nozzle 27 and a non-ejection drive pulse Pb that causes the meniscus 22 formed in the nozzle 27 to behave without ejecting ink from the nozzle 27. It is made possible.
The voltage value of the discharge drive pulse Pa is Va, the pulse width (time from the rise of the pulse to the start of the fall) is Pwa, the voltage value of the non-discharge drive pulse Pb is Vb, and the pulse width is Pwb.

The head drive unit 25 ejects the ink ejection period Ta (= period T) for forming one dot during the recording operation as many times as the number of gradations n is the upper limit for one dot landed on the recording medium. A pulse is applied to execute a discharge drive that changes the dot diameter according to the number of times.
In this embodiment, n = 8.
In the example shown in FIG. 4, an ejection drive pulse Pa of 8 pulses is applied in the period T in order to form the largest dot diameter.
By applying the ejection drive pulse Pa for each pulse, ink droplets are ejected as shown in FIG. 3 and land on the recording medium.
By selecting the number of pulses of the discharge drive pulse Pa, the number of droplets to be discharged is selected and the dot diameter changes. The inkjet recording device 1 employs a recording method that expresses gradation by this.

The head drive unit 25 applies m non-ejection drive pulses Pb equal to or greater than the number of gradations n to the ink non-ejection period Tb (= period T) during the recording operation to generate the meniscus 22. Perform non-discharge drive to behave. The non-ejection period Tb is equal to the ink ejection period Ta for forming one dot, and corresponds to the period T. Further, in the present embodiment, n = m = 8.
The voltage value Vb of the non-discharge drive pulse Pb is set lower than the voltage value Va of the discharge drive pulse Pa. Further, the pulse width Pwb of the non-discharge drive pulse Pb is set to be narrower than the pulse width Pwa of the discharge drive pulse Pa. This is to prevent ink from being ejected by applying the non-ejection drive pulse Pb. It is a condition that ink is not ejected by applying the non-ejection drive pulse Pb, but the meniscus 22 is set so that it can behave as large as it is at the time of ejection. Therefore, the pulse width should satisfy the condition of 0.6Pwa <Pwb ≦ Pwa. Further, the voltage value may satisfy the condition of 0.3 <Vb / Va <0.5.
Either one of the voltage value Vb and the pulse width Pwb of the non-ejection drive pulse Pb may be equal to the ejection drive pulse Pa, or may be adjusted so that ink is not ejected by the other.
The ink ejection period Ta and the ink non-ejection period Tb during the recording operation are for individual nozzles. When one nozzle is in the ink ejection period Ta, the other nozzle may be in the ink non-ejection period Tb, so that the ink ejection period Ta or the ink non-ejection period Tb is not determined for the entire device.

FIG. 5 shows a drive pulse of a comparative example.
This comparative example differs in that the pulse voltage is not applied to the ink non-ejection period Tb, and is the same as the drive pulse of the present embodiment shown in FIG.
In the statically stable state before applying the drive pulse, the meniscus 22a is kept concave at the substantially discharge opening position of the nozzle 27 as shown in FIG.
When there is continuous ejection, particularly continuous ejection of large droplets (n = 8), the meniscus gradually recedes to the back of the nozzle 27. When the ink non-ejection period Tb is entered after continuous ejection, the meniscus 22b is located behind the nozzle 27 as shown in FIG. 7, and the shaking is attenuated with the passage of time. Approaching. However, when the pulse voltage is not applied to the ink non-ejection period Tb, the position and the shaking state of the meniscus 22b are unstable and vary at the start of the next ink ejection period Ta of the ink non-ejection period Tb. Further, during continuous discharge, the state of FIG. 6 and the state of FIG. 7 are repeated, and the meniscus becomes unstable. As a result, in the ink ejection period Ta after the ink non-ejection period Tb, there is a high possibility that the ejection becomes unstable due to non-ejection of droplets, flight bending, and the like.

In the demonstration experiment of the comparative example driven by the repeating pattern of FIG. 5 with the period T = 175.4 μs and Pwa = 1.2AL, the occurrence of non-ejection of droplets was confirmed when the droplet velocity reached 7.6 m / s. did it.
On the other hand, in the demonstration experiment of the example of the present invention in which the period was T = 175.4 μs and Pwa = Pwb = 1.2AL and driven by the repeating pattern of FIG. 4, even if the droplet velocity reached 9.1 m / s. It was confirmed that ink could be ejected stably without non-ejection of droplets.
In the example of the present invention, in the ink non-ejection period Tb, a constant fluctuation of the meniscus having a frequency and amplitude close to the ink ejection period Ta occurs, and the behavior is dynamically stable to that of the ink ejection period Ta.
Therefore, the ink ejection period Ta next to the ink non-ejection period Tb is a condition close to the ink ejection period Ta before the ink ejection period Tb, and the ink ejection is as stable as in the case of continuous ejection.
In order to obtain the above effects, it is preferable to set m ≧ n. In particular, it is preferable to set m = n as in the present embodiment. In the ink non-ejection period Tb, the meniscus can be shaken as many times as the ink ejection period Ta, and the ink ejection becomes stable in the next ink ejection period Ta.

In order to effectively obtain the above effects, it is further carried out under the following conditions.
The discharge opening diameter of the nozzle 27 is dn, and the condition of 20 μm <dn <50 μm is satisfied. More preferably, the condition of 30 μm <dn <50 μm is particularly satisfied.
Ink with a specific density greater than 1 is applied.
The condition of 1AL ≦ Pwa ≦ 1.4AL is satisfied. More preferably, 1.2AL ≦ Pwa ≦ 1.4AL is satisfied. AL is half of the natural vibration cycle of the pressure chamber 28.

As described above, according to the present embodiment, a large droplet can be stably ejected by the inkjet recording device.

The present invention can be used for an inkjet recording device.

1 Inkjet recording device 20 Recording operation unit 21 Inkjet head 22 Meniscus 23 Ink droplet 25 Head drive unit 27 Nozzle 28 Pressure chamber 40 Control unit P Drive pulse voltage T cycle

Claims (18)

An inkjet head that has a pressure chamber that communicates with a nozzle and ejects ink in the pressure chamber from the nozzle.
A head drive unit that drives a recording operation by the inkjet head is provided.
The head drive unit
A drive pulse voltage that expands and contracts the pressure chamber, and is a non-ejection to the extent that the discharge drive pulse that ejects ink from the nozzle and the meniscus formed in the nozzle without ejecting ink from the nozzle behave. Drive pulse and can be applied,
During the ink ejection period for forming one dot during the recording operation, the ejection drive pulse is applied as many times as the number of gradations n is applied to one dot landed on the recording medium, and the dots are applied according to the number of times. Execute discharge drive to change the diameter,
During the ink non-ejection period during the recording operation, m non-ejection drive pulses, which are equal to or greater than the number of gradations n, are applied to the period equal to the ink ejection period for forming one dot. , An inkjet recording device that executes a non-ejection drive that causes the meniscus to behave. The inkjet recording apparatus according to claim 1, wherein the pulse width of the discharge drive pulse is Pwa and the pulse width of the non-discharge drive pulse is Pwb, and 0.6 Pwa <Pwb ≦ Pwa is satisfied. The inkjet recording apparatus according to claim 1 or 2, wherein the voltage value of the discharge drive pulse is Va and the voltage value of the non-discharge drive pulse is Vb, and 0.3 <Vb / Va <0.5 is satisfied. The inkjet recording apparatus according to any one of claims 1 to 3, which satisfies m = n. The inkjet recording apparatus according to any one of claims 1 to 4, wherein the discharge opening diameter of the nozzle is dn, and 20 μm <dn <50 μm is satisfied. The inkjet recording apparatus according to any one of claims 1 to 4, wherein the discharge opening diameter of the nozzle is dn, and 30 μm <dn <50 μm is satisfied. The inkjet recording apparatus according to any one of claims 1 to 6, wherein the specific gravity of the ink is greater than 1. The invention according to any one of claims 1 to 7, wherein the pulse width of the discharge drive pulse is Pwa, and half of the natural vibration cycle of the pressure chamber is AL, and 1AL ≤ Pwa ≤ 1.4AL is satisfied. Inkjet recording device. One of claims 1 to 7 satisfying 1.2AL ≤ Pwa ≤ 1.4AL, where Pwa is the pulse width of the discharge drive pulse and half of the natural vibration cycle of the pressure chamber is AL. The inkjet recording device described. A recording operation driving method that has a pressure chamber communicating with a nozzle and drives a recording operation by an inkjet head that ejects ink in the pressure chamber from the nozzle.
A drive pulse voltage that expands and contracts the pressure chamber, and is a non-ejection to the extent that the discharge drive pulse that ejects ink from the nozzle and the meniscus formed in the nozzle without ejecting ink from the nozzle behave. Using a drive pulse
During the ink ejection period for forming one dot during the recording operation, the ejection drive pulse is applied as many times as the number of gradations n is applied to one dot landed on the recording medium, and the dots are applied according to the number of times. Execute discharge drive to change the diameter,
During the ink non-ejection period during the recording operation, m non-ejection drive pulses, which are equal to or greater than the number of gradations n, are applied to the period equal to the ink ejection period for forming one dot. , A recording operation driving method for executing a non-ejection driving that causes the meniscus to behave. The recording operation driving method according to claim 10, wherein the pulse width of the discharge drive pulse is Pwa and the pulse width of the non-discharge drive pulse is Pwb, and 0.6 Pwa <Pwb ≦ Pwa is satisfied. The recording operation driving method according to claim 10 or 11, wherein 0.3 <Vb / Va <0.5 is satisfied, where Va is the voltage value of the discharge drive pulse and Vb is the voltage value of the non-discharge drive pulse. The recording operation driving method according to any one of claims 10 to 12, wherein m = n is satisfied. The recording operation driving method according to any one of claims 10 to 13, wherein the discharge opening diameter of the nozzle is dn, and 20 μm <dn <50 μm is satisfied. The recording operation driving method according to any one of claims 10 to 13, wherein the discharge opening diameter of the nozzle is dn, and 30 μm <dn <50 μm is satisfied. The recording operation driving method according to any one of claims 10 to 15, wherein the specific gravity of the ink is greater than 1. The method according to any one of claims 10 to 16, wherein the pulse width of the discharge drive pulse is Pwa, and half of the natural vibration cycle of the pressure chamber is AL, and 1AL ≦ Pwa ≦ 1.4AL is satisfied. Recording operation drive method. One of claims 10 to 16 satisfying 1.2AL ≤ Pwa ≤ 1.4AL, where Pwa is the pulse width of the discharge drive pulse and half of the natural vibration cycle of the pressure chamber is AL. The described recording operation driving method.

Images