Liquid discharge apparatus and liquid discharge method

Abstract

The invention provides a liquid ejecting apparatus and a liquid ejecting method. Under the condition that a driving signal is not appropriate, the printing quality is likely to be reduced. The liquid ejecting apparatus includes: an inkjet head that ejects a liquid based on a drive signal; an observation unit that observes the liquid discharged from the inkjet head; and a control unit that changes the drive signal in accordance with the ejection state of the liquid observed by the observation unit.

Description

Technical Field

[0001] The present disclosure relates to a liquid ejection device and a liquid ejection method. Background Art

[0002] In recent years, liquid ejection heads such as inkjet heads have been used to decorate the manufacture of electronic devices and the housings of products. The liquid ejected from the liquid ejection head uses a liquid suitable for the purpose. In addition, a drive signal for ejecting the liquid from the liquid ejection head is appropriately set according to the type of the liquid.

[0003] Conventionally, ink ejected from an inkjet head is captured continuously in time, and a drive signal is outputted so that no spray is generated (for example, see Patent Document 1).

[0004] Prior Art Literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2021-133571

[0007] However, when the driving signal is inappropriate, the volume and speed of the ejected liquid become inappropriate, resulting in a deviation in the amount of liquid applied and the position in the printed object, which may lead to a decrease in printing quality. Summary of the invention

[0008] An object of the present disclosure is to provide a liquid ejection device and a liquid ejection method that can appropriately generate a drive signal for a liquid ejection head.

[0009] The liquid ejection device in one embodiment of the present disclosure comprises: an inkjet head that ejects liquid based on a drive signal; an observation unit that observes the liquid ejected from the inkjet head; and a control unit that changes the drive signal according to the ejection state of the liquid observed by the observation unit.

[0010] A liquid ejection method in an embodiment of the present disclosure includes: a step of observing liquid ejected from an inkjet head that ejects liquid based on a drive signal; and a step of changing the drive signal according to an ejection state of the liquid.

[0011] Effects of the Invention

[0012] According to an embodiment of the present disclosure, a driving signal for a liquid ejection head can be appropriately generated. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a cross-sectional view showing the structure of an inkjet head.

[0014] Figure 2 It is a figure which shows an inkjet head and a flying observation device.

[0015] Figure 3 A diagram showing a plurality of images captured by an imaging unit.

[0016] Figure 4 2 is a diagram showing an example of a voltage waveform signal S.

[0017] Figure 5 This is a diagram showing an example of the relationship between the resonance period T1 and the ejection speed.

[0018] Figure 6 2 is a diagram showing an example of the relationship between the vibration reduction timing T4 and the time when the seepage disappears.

[0019] Figure 7 The diagram shows an example of a plurality of images captured by the imaging unit.

[0020] Figure 8 This is a schematic diagram of a cross section of a nozzle that ejects ink.

[0021] Fig. 9 This is a diagram showing the relationship between the ink ejection state and the parameters to be controlled.

[0022] Fig.10 This is a diagram showing the relationship between the vibration reduction depth Vcal and the number of sprays.

[0023] Fig.11 This is a diagram showing the relationship between the vibration reduction timing T4 and the number of sprays.

[0024] Fig.12 This is a diagram showing a state where a ligament bend occurs.

[0025] Fig.13 This is a diagram showing the relationship between the intermediate potential Vmid and the deviation of the flying angle.

[0026] Fig.14 This is a diagram showing the relationship between the preliminary vibration depth V1 and the deviation of the flying angle.

[0027] Fig.15 3 is a diagram showing the relationship between the vibration reduction timing T4 and the deviation of the flying angle.

[0028] Fig.16 This is a diagram showing the relationship between the preliminary vibration depth V1 and the droplet formation speed.

[0029] Fig.17 It is a graph showing the relationship between the vibration reduction depth Vcal, the droplet formation speed, and the seepage time.

[0030] Fig.18 This is a diagram showing the relationship between the slew rate SR and the volume of ink at a discharge speed of 4.8 m / s.

[0031] Fig.19 This is a diagram showing the relationship between the intermediate potential Vmid and the volume of ink at a discharge speed of 5 m / s.

[0032] Fig. 20 : is a flowchart showing the control process of the drive signal performed by the control unit.

[0033] Fig.21 This is another flowchart showing the control process of the drive signal performed by the control unit.

[0034] Description of Reference Numerals

[0035] 1: Inkjet head

[0036] 2: Flying observation device

[0037] 2a: Light source

[0038] 2b: Camera Department

[0039] 2c: Control Unit

[0040] 10: Head body

[0041] 11: Main body part 1

[0042] 12: Second main body

[0043] 13: Nozzle plate

[0044] 20: Vibration plate

[0045] 30: Pressurized components

[0046] 40: Control device

[0047] 51: Common supply flow path

[0048] 52: Supply flow path

[0049] 53: Ink Room

[0050] 54: Discharge flow path

[0051] 55: Common discharge flow path

[0052] 56: Nozzle

[0053] 57: 1st throttling flow path

[0054] 58: Second throttling flow path. DETAILED DESCRIPTION

[0055] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In addition, the embodiments described below are examples, and the present disclosure is not limited to the following embodiments.

[0056] However, sometimes the necessary detailed description is omitted. For example, sometimes the detailed description of the well-known matters and the repeated description of the substantially same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art.

[0057] Hereinafter, regarding the embodiment of the present disclosure, a case where the liquid ejection device is an ink ejection device will be described with reference to the drawings.

[0058] Figure 1 1 is a cross-sectional view showing the structure of the inkjet head 1. Figure 1 As shown by arrows, the height direction of the inkjet head 1 is called the Z-axis direction, the width direction of the inkjet head 1 is called the X-axis direction, and the depth direction of the inkjet head 1 is called the Y-axis direction.

[0059] The inkjet head 1 ejects ink to print on an object. The ink is, for example, printing ink. The ink may also be other liquid materials, such as solder paste, silver paste, stamp paste, fluorescent paste, or cell suspension.

[0060] The inkjet head 1 is configured to circulate ink between the inkjet head 1 and a liquid supply device (not shown). That is, the ink is supplied from the liquid supply device to the inkjet head 1, and the ink that is not ejected from the inkjet head 1 flows back to the liquid supply device. In addition, the inkjet head 1 may not be a circulating type, but a non-circulating type in which the ink supplied to the inkjet head 1 is retained inside the inkjet head 1.

[0061] The inkjet head 1 includes a head body 10 , a vibration plate 20 , a pressurizing member 30 , and a control device 40 .

[0062] The head body 10 is formed in a rectangular parallelepiped shape, for example. The head body 10 is composed of a first body portion 11, a second body portion 12, and a nozzle plate 13. Figure 1 As shown in the figure, the nozzle plate 13, the second main body portion 12, and the first main body portion 11 are stacked in this order to form the head main body 10.

[0063] The first body 11 is formed in a rectangular parallelepiped shape, for example, and constitutes the upper portion of the head body 10. The first body 11 forms a common supply flow path 51 and a common discharge flow path 55 described later. The first body 11 is formed by cutting alloy steel such as stainless steel, for example.

[0064] The second main body 12 is formed in a rectangular parallelepiped shape, for example, and constitutes the lower part of the head main body 10. The second main body 12 forms a supply flow path 52, an ink chamber 53, and a discharge flow path 54 corresponding to each nozzle 56 described later. The second main body 12 is formed by laminating stainless steel plates formed by etching and pressing, for example.

[0065] The nozzle plate 13 is disposed on the bottom surface of the second body portion 12. The nozzle plate 13 is formed by, for example, molding a stainless steel plate by etching and pressing.

[0066] The head body 10 includes a common supply flow path 51, a plurality of supply flow paths 52, a plurality of ink chambers 53, a plurality of discharge flow paths 54, a common discharge flow path 55, and a plurality of nozzles 56. Figure 1 The positive direction of the Y axis is referred to as the arrangement direction. The supply flow path 52, the ink chamber 53, and the discharge flow path 54 are arranged one-to-one with the nozzles 56. That is, in the head body 10, the supply flow path 52, the ink chamber 53, and the discharge flow path 54 are arranged in the same number as the nozzles 56.

[0067] The common supply flow path 51 is formed in the first main body 11 so as to extend in the arrangement direction. Ink is supplied from the liquid supply device to the common supply flow path 51. The common supply flow path 51 is connected to a plurality of supply flow paths 52. The ink flowing through the common supply flow path 51 is divided into the plurality of supply flow paths 52.

[0068] The supply flow path 52 is formed in the second main body portion 12 . The ink supplied to the supply flow path 52 is supplied to the ink chamber 53 via the first throttle flow path 57 .

[0069] The ink chamber 53 is formed in the second main body 12. The upper wall of the ink chamber 53 is formed by the vibration plate 20. Of the ink supplied to the ink chamber 53, the ink not ejected from the nozzle 56 is discharged to the discharge flow path 54 through the second throttle flow path 58.

[0070] The discharge flow path 54 is formed in the second main body portion 12 . The ink discharged to the discharge flow path 54 is discharged to the common discharge flow path 55 .

[0071] The common discharge flow path 55 is formed in the first main body 11 so as to extend in the arrangement direction and is connected to the plurality of discharge flow paths 54. Ink discharged from the plurality of discharge flow paths 54 merges in the common discharge flow path 55 and flows back to the liquid feeding device.

[0072] The nozzle 56 is a hole formed in the nozzle plate 13, and ejects the ink in the ink chamber 53 to the outside. In addition, a liquid-repellent film having liquid-repellent properties for repelling ink may be formed on the bottom surface of the nozzle plate 13.

[0073] The vibration plate 20 is disposed between the first main body 11 and the second main body 12, and serves as the upper wall of the ink chamber 53. The vibration plate 20 is a thin plate-shaped elastic body, and is deformed into a convex shape toward the inside and outside of the ink chamber 53. That is, the vibration plate 20 is deformed to increase or decrease the volume (capacity) of the ink chamber 53.

[0074] The pressure member 30 is attached to the plate surface of the vibration plate 20 on the side opposite to the ink chamber 53. The inkjet head 1 includes a plurality of pressure members 30. The pressure members 30 correspond to the ink chambers 53 one-to-one and are arranged in the same number as the ink chambers 53. The pressure members 30 are, for example, piezoelectric elements.

[0075] The pressure member 30 is extended and contracted by applying a drive signal (voltage waveform signal S) of the inkjet head 1 described later to the pressure member 30, thereby deforming the vibration plate 20. The vibration plate 20 is deformed to reduce the volume of the ink chamber 53, and the ink in the ink chamber 53 is pressurized, thereby ejecting the ink from the nozzle 56.

[0076] The control device 40 controls the ejection of ink. Specifically, the control device 40 vibrates the vibration plate 20 by outputting a voltage waveform signal S, which will be described later, to the pressure member 30 .

[0077] Figure 2 1 is a diagram showing an ink jetting device including an ink jet head 1 and a flying observation device 2. The flying observation device 2 observes the ink ejected from the ink jet head 1 and the vicinity of the nozzle 56 on the bottom surface of the nozzle plate 13. The flying observation device 2 includes a light source unit 2a, an imaging unit 2b, and a control unit 2c.

[0078] The light source unit 2a irradiates light to the periphery of the nozzle 56 and the ink ejected from the nozzle 56. The light source unit 2a includes a light source (eg, a light emitting diode) and an optical system for adjusting the traveling direction of light emitted by the light emitting diode.

[0079] The imaging unit 2b observes the ink ejected from the inkjet head 1. The imaging unit 2b is an imaging device that captures the periphery of the nozzle 56 and the ink ejected from the nozzle 56 and generates an image of the captured periphery of the nozzle 56 and the ink. The imaging unit 2b outputs the generated image to the control unit 2c.

[0080] The control unit 2c controls the light source unit 2a and the camera unit 2b. Specifically, the control unit 2c controls the light source unit 2a to perform stroboscopic light that flickers at relatively short intervals. In addition, the control unit 2c controls the stroboscopic light of the light source unit 2a in synchronization with the drive signal for the inkjet head 1, and controls the camera unit 2b to capture the ink ejected from the inkjet head 1 and the surrounding area of ​​the nozzle 56 at multiple timings.

[0081] The control unit 2c calculates the ejection speed and volume of the ink ejected from the inkjet head 1 based on the multiple images output from the camera unit 2b. Specifically, the control unit 2c calculates the ejection speed of the ink based on the position of the ink in the multiple images. In addition, the control unit 2c calculates the volume of the ink based on the area of ​​the ink in the multiple images. The volume of the ink can also be measured by other means.

[0082] Figure 3 2a and 2b are diagrams showing a plurality of images captured by the imaging unit 2b. For example, the control unit 2c controls the light source unit 2a to flash at intervals of 10 microseconds and captures images using the imaging unit 2b. Figure 3 This is an image showing the ink ejection status every 10 to 90 microseconds after the ink is ejected. The ink ejection speed can be calculated based on the positions of two inks at two different times. For example, the speed can be calculated with an accuracy of 0.2 m / s, the angle can be calculated with an accuracy of 2.5 milliradians, and the volume can be calculated with an accuracy of 0.1 picoliters.

[0083] When ink is ejected from the nozzle 56, a meniscus of ink is exposed from the nozzle 56. After the ink is ejected, the meniscus of ink is pulled into the nozzle 56 due to the decrease in the pressure of the ink in the ink chamber 53. The control unit 2c calculates the time from the ejection of ink to the pulling of the meniscus of ink exposed from the nozzle 56 into the nozzle 56 based on the plurality of images output from the imaging unit 2b.

[0084] The control unit 2c controls the inkjet head 1 so that ink is ejected from the nozzles 56. The control unit 2c generates a voltage waveform signal S and outputs it to the control device 40 of the inkjet head 1. The control unit 2c and the control device 40 may be integrated.

[0085] Next, the voltage waveform signal S output by the control device 40 will be described. Figure 4 2 is a diagram showing an example of a voltage waveform signal S.

[0086] Figure 4 The voltage waveform signal S shown has a pulse waveform W1 ( t10 - t15 ) and a second pulse waveform W2 ( t1 - t4 ).

[0087] The pulse waveform W1 is a waveform that vibrates the vibration plate 20 to eject ink from the nozzle 56. The pulse waveform W1 vibrates the vibration plate 20 so that the volume of the ink chamber 53 decreases after the volume of the ink chamber 53 increases. Specifically, the pulse waveform W1 is formed such that the potential value decreases from the potential when the voltage waveform signal S is in a steady state, that is, the intermediate potential Vmid, and then increases.

[0088] More specifically, the pulse waveform W1 is formed such that the potential value starts to drop from the intermediate potential Vmid (time t10), reaches the first potential Va lower than the intermediate potential Vmid (time t11), and then starts to rise after being maintained at the first potential Va (time t12). Furthermore, the pulse waveform W1 is formed such that the potential value reaches the second potential Vb higher than the intermediate potential Vmid (time t13), and is maintained at the second potential Vb.

[0089] The pulse waveform W1 is formed such that the potential value rises and then falls. Specifically, the pulse waveform W1 is formed such that after the potential value is maintained at the second potential Vb, the potential value starts to fall (time t14) and reaches the intermediate potential Vmid (time t15).

[0090] In the pulse waveform W1, the potential value decreases from the middle potential Vmid to the first potential Va, thereby deforming the vibration plate 20 to increase the volume of the ink chamber 53. Thereafter, the potential value increases to the second potential Vb, thereby deforming the vibration plate 20 to reduce the volume of the ink chamber 53, and the ink in the ink chamber 53 is pressurized and ejected from the nozzle 56.

[0091] The second pulse waveform W2 is a waveform for causing the pressure wave generated in the ink chamber 53 due to the vibration of the vibration plate 20 to resonate.

[0092] The second pulse waveform W2 is located ahead of the pulse waveform W1 in time. The second pulse waveform W2 vibrates the vibration plate 20 so that the volume of the ink chamber 53 changes. Specifically, the second pulse waveform W2 is formed such that the potential value rises after falling. More specifically, the second pulse waveform W2 is formed such that the potential value starts to fall from the middle potential Vmid (time t1), the potential value reaches the third potential Vc between the middle potential Vmid and the first potential Va (time t2), the potential value starts to rise after being maintained at the third potential Vc (time t3), and returns to the middle potential Vmid from the third potential Vc (time t4).

[0093] By decreasing the potential value from the middle potential Vmid to the third potential Vc in the second pulse waveform W2 , the vibration plate 20 is deformed so that the volume of the ink chamber 53 increases, and then, by returning the potential value to the middle potential Vmid, the vibration plate 20 returns to its original shape.

[0094] Here, the time from the time point (time t1) when the potential value starts to change from the middle potential Vmid to the third potential Vc to the time point (time t3) when the potential value starts to change from the third potential Vc to the middle potential Vmid is referred to as the first resonance period T1.

[0095] The time from the time point (time t3) when the potential value starts to change from the third potential Vc to the intermediate potential Vmid to the time point (time t10) when the potential value starts to change from the intermediate potential Vmid to the first potential Va is defined as the second resonance period T2.

[0096] The time from the time point (time t10) when the potential value starts to change from the intermediate potential Vmid to the first potential Va to the time point (time t12) when the potential value starts to change from the first potential Va to the second potential Vb is defined as a third resonance period T3.

[0097] The time from the time point (time t12) when the potential value starts to change from the first potential Va to the second potential Vb to the time point (time t14) when the potential value starts to change from the second potential Vb to the intermediate potential Vmid is defined as the damping timing T4.

[0098] The potential difference between the intermediate potential Vmid and the third potential Vc is defined as the preliminary vibration depth V1.

[0099] The slope of the potential value from the time point (time t12) when the potential value starts to change from the first potential Va to the second potential Vb to the time point (time t13) when the potential value changes from the first potential Va to the second potential Vb is set as the conversion rate SR1, and the slope of the potential value from the time point (time t14) when the potential value starts to change from the second potential Vb to the intermediate potential Vmid to the time point (time t15) when the potential value reaches the intermediate potential Vmid is set as the conversion rate SR2. The slope of other parts (for example, the slope of the potential value from time t1 to time t2, etc.) is also called the conversion rate SR in the same way, but in this manuscript, the slope SR1 of the potential value from time t12 to time t13 is mainly processed.

[0100] The time from the time point (time t1) when the potential value starts to change from the intermediate potential Vmid to the third potential Vc to the time point (time t4) when the potential value returns from the third potential Vc to the intermediate potential Vmid is the preliminary vibration.

[0101] The period from the time point (time t10 ) when the potential value starts to change from the intermediate potential Vmid to the first potential Va to the time point (time t13 ) when the potential value reaches the second potential Vb is the actual oscillation.

[0102] The time from the time point (time t14) when the potential value starts to change from the second potential Vb to the intermediate potential Vmid to the time point (time t15) when the potential value reaches the intermediate potential Vmid is the damping vibration.

[0103] The control device 40 controls the ink ejection based on the ink ejection velocity (Droplet velocity), residual vibration (ink seepage time), the presence or absence of ink spray (Mist), the presence or absence of ink liquid line bending (Angle), the presence or absence of ink satellite points (Satellite), and the ink ejection volume (Volume). Since the longer the ink seepage time, the more ink is ejected, and therefore, the longer the liquid line length (Ligament Length) is.

[0104] The control device 40 controls the ejection of ink by controlling at least one of the parameters of the voltage waveform signal S of the inkjet head, namely, the resonance period (T1, T2, T3), the damping timing (T4), the damping depth (Vcal), the intermediate potential (Vmid), the preliminary vibration depth (V1) and the conversion rate (SR).

[0105] Next, the determination of the ink ejection state based on the camera data is described. The control unit 2c determines the ink ejection state based on the image captured by the camera unit 2b. The so-called ejection state refers to the presence or absence of spray, the presence or absence of liquid line bending, the presence or absence of satellite points, and the ejection volume. The control unit 2c can perform AT (Artificial Intelligence) ejection state determination based on the result of machine learning of the ink ejection state.

[0106] Here, the so-called spray refers to a part of the ink ejected from the nozzle of the inkjet head in the form of small drops or mist, and is a droplet whose position is not reproducible. In other words, the spray is a droplet whose position cannot be controlled. In addition, the spray is a droplet whose timing of generation cannot be controlled. The spray becomes a cause of stains on the workpiece due to adhesion to the workpiece, so it is desired to suppress the generation.

[0107] The so-called liquid line is a thin and long ink extending behind the main drop after the ink drop is ejected. The so-called liquid line bend is a state in which the liquid line bends in the middle.

[0108] Satellite dots are small droplets that separate from the main droplet of ejected ink droplets.

[0109] The ejection volume is the volume of the ejected ink and is calculated by the control unit 2c based on the areas of the ink in the plurality of images.

[0110] Next, the method of discharge control will be described. First, the control unit 2c adjusts the basic waveform.

[0111] For example, the control unit 2 c sets the vibration reduction timing after setting the resonance periods T1 , T2 , and T3 as the adjustment of the basic waveform.

[0112] Figure 5 : is a diagram showing an example of the relationship between T1 and the ejection speed. Figure 5 As shown in the figure, by changing the resonance period T1, the speed of the droplets ejected from the nozzle, that is, the ejection speed, changes. In addition, although not shown in the figure, by changing the resonance periods T2 and T3, the ejection speed also changes. In the setting of the resonance periods T1, T2, and T3, the control unit 2c sets T2 after setting T1 and T3 to the same value. The control unit 2c can, for example, set T1, T2, and T3 to the same value and set T1, T2, and T3 to the value at which the ejection speed becomes the fastest.

[0113] Figure 6 2 is a diagram showing an example of the relationship between T4 and the time until the ink seepage disappears. The so-called time until the ink meniscus exposed from the nozzle 56 is pulled into the nozzle 56.

[0114] like Figure 6 As shown, by controlling the damping timing T4, the time for the seepage to disappear changes. The control unit 2c sets the damping timing T4 to a value at which the time for the seepage to disappear becomes the minimum.

[0115] When the amplitude of the entire waveform is set to 1, the basic waveform adjusted as described above is, for example, as follows: the intermediate potential Vmid is 0.5, the preliminary vibration depth V1 is 0.2, the slew rate SR is 30 V / μs, and the vibration reduction depth Vcal is 0.5.

[0116] Figure 7 FIG. 2 is a diagram showing an example of a plurality of images captured by the imaging unit 2 b. Figure 7 Six images captured in synchronization with stroboscopic light emission are shown in order from the left: 610 indicates the bleeding of the meniscus.

[0117] Figure 8 1 is a schematic diagram of a cross section of a nozzle 56 for ejecting ink. The tip of the nozzle 56 for ejecting ink is a straight tube portion as a cylindrical space, and the meniscus needs to be contained in the straight tube portion of the nozzle 56.

[0118] After adjusting the basic waveform, the control unit 2 c determines the discharge state based on a plurality of images of ink captured by the imaging unit 2 b and changes the basic waveform.

[0119] Here, the discharge state refers to the presence or absence of ink spray, the presence or absence of ink liquid line bending, the presence or absence of ink satellites, and the discharge volume of ink.

[0120] Fig. 9 This is a diagram showing the relationship between the ink ejection state and the parameters to be controlled. Circles indicate parameters that are strongly correlated with the ink ejection state, and double circles indicate parameters that are most strongly correlated with the ink ejection state.

[0121] like Fig. 9 As shown, the ejection speed is most strongly correlated with the resonance periods T1, T2, and T3, and is strongly correlated with the intermediate potential Vmid.

[0122] The residual vibration is most strongly correlated with the vibration reduction timing T4 and is strongly correlated with the vibration reduction depth Vcal.

[0123] The spray is most strongly correlated with the vibration reduction depth Vcal, and is strongly correlated with the vibration reduction timing T4, the intermediate potential Vmid, and the preliminary vibration depth Vcal.

[0124] The liquid line curvature is most strongly correlated with the intermediate potential Vmid, and is strongly correlated with the vibration reduction timing T4 and the preparatory vibration depth Vcal.

[0125] The satellite points are most strongly correlated with the preparatory vibration depth V1 and strongly correlated with the vibration reduction depth Vcal.

[0126] The volume is most strongly correlated with the slew rate SR, and is strongly correlated with the resonance periods T1, T2, T3, the damping depth Vcal, the intermediate potential Vmid, and the preparatory vibration depth V1.

[0127] In addition, the control unit 2c can use AI such as machine learning to determine the ejection state. For example, the control unit 2c can obtain multiple images from the camera unit 2b and perform image analysis on these images to determine the ejection state. The multiple images represent the behavior of the ink ejected according to multiple different drive signals. The drive signal includes a waveform formed by at least 4 parameters (damping depth Vcal, intermediate potential Vmid, preliminary vibration depth V1, and conversion rate SR).

[0128] In addition, the user determines the ejection state from the image of the ink captured by the camera unit 2b. The user inputs the ejection state from an input unit not shown in the figure, and the control unit 2c can determine the ejection state based on the input information (ejection state information). The control unit 2c adjusts (changes) the basic waveform according to the ejection state. The control unit 2c can adjust the basic waveform based on the result of the test printing performed in advance, or can adjust the basic waveform based on the actual printing. The adjustment is performed quasi-statically or dynamically. The control unit 2c changes the parameters little by little to make the ejection state the best state.

[0129] In Control Fig. 9 In the case of each parameter in, the control unit 2c adjusts the parameter most related to the ejection state, and then adjusts the parameter most related to the ejection state. In the case of determining that multiple phenomena such as spray and liquid line bending have occurred, the control unit 2c adjusts the parameters in order from the phenomenon with the largest number of related parameters.

[0130] Next, the adjustment of parameters when spray is generated will be described. When the control unit 2c determines that spray is generated in the ink, first, it changes the damping depth Vcal. Fig.10 This is a graph showing the relationship between the vibration reduction depth Vcal and the number of sprays. Fig.10 As shown, the number of sprays changes by changing the damping depth Vcal. Therefore, the control unit 2c sets the damping depth Vcal so that the number of sprays becomes the minimum.

[0131] For example, the control unit 2c obtains a plurality of images showing the behavior of ink ejected according to a plurality of drive signals having a plurality of different damping depths Vcal. The control unit 2c performs image analysis on the plurality of images to measure the number of sprays in each image. The control unit 2c determines the damping depth Vcal corresponding to the image with the least number of sprays.

[0132] If the damping depth Vcal is changed, the time for ink seepage to disappear (the time for the meniscus to be drawn in) may be prolonged. Therefore, the control unit 2c may change the damping timing T4 related to the time for ink seepage to disappear.

[0133] In this case, the control unit 2c changes the vibration reduction timing T4 after changing the vibration reduction depth Vcal. Fig.11 : is a graph showing the relationship between the vibration reduction timing T4 and the number of sprays. Fig.11 As shown, the number of sprays changes by changing the damping timing T4. Therefore, the control unit 2c sets the damping timing T4 to a value at which the number of sprays becomes the minimum.

[0134] For example, the control unit 2c obtains a plurality of images showing the behavior of ink ejected according to a plurality of drive signals having a plurality of different damping timings T4. In the plurality of drive signals, the damping depth Vcal is a common damping depth Vcal that has been determined. The control unit 2c performs image analysis on the plurality of images to measure the number of sprays in each image. The control unit 2c determines the damping timing T4 corresponding to the image with the least number of sprays.

[0135] Furthermore, the control unit 2c may change the intermediate potential Vmid and the preliminary vibration depth V1 to values ​​at which the number of sprays becomes the minimum.

[0136] like Fig. 9 As shown, the spray is most strongly related to the vibration reduction depth Vcal, and is strongly related to the vibration reduction timing T4, the intermediate potential Vmid, and the preliminary vibration depth V1. The control unit 2c first determines the vibration reduction depth Vcal, and then determines the vibration reduction timing T4, the intermediate potential Vmid, and the preliminary vibration depth V1. By this determination order, the number of sprays can be minimized.

[0137] Next, adjustment of parameters when liquid line bending occurs will be described. Fig.12 11 is a diagram showing a state where a curvature of the liquid line has occurred. In the image captured by the imaging unit 2 b , it can be understood that a curvature of the liquid line has occurred in the region 1110 .

[0138] When the control unit 2c determines that the liquid line is bent in the ink, it first changes the intermediate potential Vmid. The liquid line is bent, and the flying direction of the ink deviates from the vertical downward. That is, if the liquid line is bent, the flying angle deviates from the vertical downward.

[0139] Fig.13 Graph showing the relationship between the intermediate potential Vmid and the deviation (3 times the variance) of the flying angle (miradian). Fig.13 As shown in FIG. 1 , the flying angle of the ink changes by changing the intermediate potential Vmid. The control unit 2 c sets the intermediate potential Vmid so that the variation (variance) of the flying angle of the ink becomes minimum.

[0140] For example, the control unit 2c obtains a plurality of images showing the behavior of the ink ejected according to a plurality of drive signals having a plurality of different intermediate potentials Vmid. The control unit 2c performs image analysis on the plurality of images to measure the deviation of the flying angle of the ink in each image. The control unit 2c determines the intermediate potential Vmid corresponding to the image with the smallest deviation of the flying angle of the ink.

[0141] If the intermediate potential Vmid is changed, spray may be generated, or the droplet formation speed may be slowed down. The droplet formation speed is the fastest speed at which the ink becomes a droplet of ink at a given distance (e.g., 0.4 mm) from the nozzle. Therefore, the control unit 2c can further change the vibration reduction preparatory vibration depth V1 related to the droplet formation speed and the vibration reduction depth Vcal related to the generation of spray.

[0142] In this case, the control unit 2 c changes the preliminary vibration depth V1 and the vibration reduction timing T4 after changing the intermediate potential Vmid. Fig.14 This is a diagram showing the relationship between the preliminary vibration depth V1 and the deviation (three times the variance) of the flying angle (miradian). Fig.15 This is a diagram showing the relationship between the vibration reduction timing T4 and the deviation (3 times the variance) of the flying angle (miradian). The flying angle changes by changing the preliminary vibration depth V1 and the vibration reduction timing T4. The control unit 2c sets the preliminary vibration depth V1 and the vibration reduction timing T4 to the values ​​at which the deviation (variance) of the flying angle of the ink becomes the smallest.

[0143] For example, the control unit 2c obtains a plurality of images showing the behavior of the ink ejected according to a plurality of drive signals having a plurality of different preliminary vibration depths V1 and damping timings T4. In the plurality of drive signals, the intermediate potential Vmid is a common intermediate potential Vmid that has been determined. The control unit 2c performs image analysis on the plurality of images to measure the deviation of the flying angle of the ink in each image. The control unit 2c determines the preliminary vibration depth V1 and the damping timing T4 corresponding to the image with the smallest deviation of the flying angle of the ink.

[0144] like Fig. 9As shown, the curvature of the liquid line is most strongly related to the intermediate potential Vmid, and is strongly related to the damping timing T4 and the preliminary vibration depth V1. The control unit 2c first determines the intermediate potential Vmid, and then determines the damping timing T4 and the preliminary vibration depth V1. By this determination order, the deviation of the flying angle of the ink can be minimized.

[0145] Next, the adjustment of parameters when satellite dots are generated will be described. When the control unit 2c determines that satellite dots are generated in the ink, first, it changes the preliminary vibration depth V1. Fig.16 2c is a graph showing the relationship between the preliminary vibration depth V1 and the droplet formation speed. If the droplet formation speed becomes the fastest, the satellite points are suppressed. In addition, the droplet formation speed changes by changing the preliminary vibration depth V1. Therefore, the control unit 2c sets the preliminary vibration depth V1 so that the droplet formation speed of the nozzle becomes the fastest.

[0146] For example, the control unit 2c obtains a plurality of images showing the behavior of ink ejected according to a plurality of drive signals having a plurality of different preliminary vibration depths V1. The control unit 2c performs image analysis on the plurality of images to measure the droplet formation speed in each image. The control unit 2c determines the preliminary vibration depth V1 corresponding to the image with the fastest droplet formation speed.

[0147] Furthermore, if the preliminary vibration depth V1 is changed, there is a possibility that spray may be generated or that a liquid line may be bent. Therefore, the control unit 2c may further change the vibration reduction depth Vcal related to the generation of spray.

[0148] In this case, the control unit 2c changes the vibration reduction depth Vcal after changing the preliminary vibration depth V1. Fig.17 Graph showing the relationship between the vibration reduction depth Vcal and the droplet velocity and the seepage time. Fig.17 As shown in FIG. 1 , the droplet formation speed changes by changing the vibration reduction depth Vcal. The control unit 2 c sets the vibration reduction depth Vcal to a value at which the droplet formation speed of the nozzle becomes the fastest.

[0149] For example, the control unit 2c obtains a plurality of images showing the behavior of ink ejected according to a plurality of drive signals having a plurality of different vibration reduction depths Vcal. In the plurality of drive signals, the preliminary vibration depth V1 is a common preliminary vibration depth V1 that has been determined. The control unit 2c performs image analysis on the plurality of images to measure the droplet velocity in each image. The control unit 2c determines the vibration reduction depth Vcal corresponding to the image with the fastest droplet velocity.

[0150] like Fig. 9As shown, the satellite point is most strongly correlated with the preliminary vibration depth V1 and is most strongly correlated with the vibration reduction depth Vcal. The control unit 2c first determines the preliminary vibration depth V1 and then determines the vibration reduction depth Vcal. This determination order can maximize the droplet formation speed, so the satellite point is suppressed.

[0151] Next, adjustment of the volume of ink will be described. When changing the volume of ink, the control unit 2c first changes the slew rate SR. Fig.18 : is a graph showing the relationship between the conversion rate SR and the volume of ink when the ejection speed is 4.8 m / s. Fig.18 As shown in FIG. 1 , by changing the conversion rate SR, the volume of the ink changes. The same is true for the ejection speed of 5 m / s. In addition, if the amplitude (damping depth and intermediate potential) changes by changing the conversion rate SR, the ejection speed of the ink also changes. Therefore, the control unit 2c sets the conversion rate SR without changing the ejection speed so that the volume of the ink when flying from the nozzle at, for example, 5 m / s becomes the volume to be set.

[0152] For example, the control unit 2c obtains a plurality of images showing the behavior of ink ejected according to a plurality of drive signals having a plurality of different slew rates SR. The control unit 2c performs image analysis on the plurality of images to measure the volume of ink in each image. The control unit 2c determines the slew rate SR corresponding to the image that is closest to the volume to be set.

[0153] In addition, if the slew rate SR is changed, the resonance period T1 may be deviated. In addition, when the slew rate SR is small, there is a tendency that the resonance period T1 must be reduced. Therefore, the control unit 2c may further change the resonance period T1.

[0154] The control unit 2 c may change the resonance periods T2 and T3 , the damping timing T4 , the damping depth Vcal , the intermediate potential Vmid , and the preliminary vibration depth V1 after changing the slew rate SR and the resonance period T1 .

[0155] In addition, the control unit 2c may change the intermediate potential Vmid instead of or together with the slew rate SR. Fig.19 This is a diagram showing the relationship between the intermediate potential Vmid and the volume of ink when the ejection speed is 5 m / s. By changing the intermediate potential Vmid, the volume of ink and the ejection speed change. For example, the control unit 2c sets the intermediate potential Vmid so that the volume of ink when flying from the nozzle at 5 m / s becomes the volume to be set. If the intermediate potential Vmid is changed, the flying angle may deteriorate, thereby causing the liquid line to bend. Therefore, the control unit 2c can further change the damping timing T4 and the damping depth Vcal related to the generation of the liquid line bend.

[0156] Next, the adjustment of parameters in the case of multiple ejection states among the ejection states in which there are errors in ink spray, liquid line bending, satellite points, and ejection volume is described. When it is determined that there are multiple ejection states, the control unit 2c can adjust the parameters for any one of the ejection states, or can adjust the parameters for improving the ejection state determined to have the greatest impact on the printing quality. Alternatively, the control unit 2c can control the parameters for improving each ejection state in sequence.

[0157] In this case, the control unit 2c may adjust the parameters in order from the ejection state having the largest number of parameters to be adjusted. Fig. 9 , the number of parameters to be adjusted for spray is 4, the number of parameters to be adjusted for liquid line bending is 3, the number of parameters to be adjusted for satellite points is 2, and the number of parameters to be adjusted for ejection volume is 5. Therefore, the control unit 2c adjusts the parameters in the order of the parameters for ejection volume, the parameters for spray, the parameters for liquid line bending, and the parameters for satellite points. In addition, the order of adjusting the parameters is not limited to this, and other orders may be used.

[0158] Next, the control of the driving signal by the control unit 2c will be described. Fig. 20 2 is a flowchart showing a control process of a drive signal performed by the control unit 2c.

[0159] First, the control unit 2c sets the resonance periods T1 and T3 (step S2001), and then sets the resonance period T2 (step S2002). In the present disclosure, T1 and T3 are set to the same value, but they can also be set to different values. The resonance periods T1, T2, and T3 are set to the values ​​that make the ejection speed the fastest.

[0160] Next, the control unit 2c sets the damping timing T4 (step S2003). The damping timing T4 is set to a value at which the time when the ink seepage from the nozzle disappears (the time when the meniscus is drawn in) becomes the fastest. The basic waveform adjustment is completed by the processing of step S2003.

[0161] Thereafter, the control unit 2c determines whether or not there is spray (step S2004). When the control unit 2c determines that there is spray (step S2004, Yes), it sets the vibration reduction depth Vcal to a value that minimizes the number of sprays (step S2005).

[0162] In addition, the control unit 2c may set the vibration reduction timing T4 to a value at which the number of sprays becomes the minimum, following the setting of the vibration reduction depth Vcal.

[0163] When the control unit 2c determines that there is no spray (step S2004, No), it determines whether the liquid line is bent (step S2006).

[0164] When the control unit 2c determines that the liquid line is bent (step S2006, Yes), it sets the intermediate potential Vmid to a value at which the deviation (variance) of the flying angle of the ink is minimized (step S2007).

[0165] Furthermore, the control unit 2 c may set the preliminary vibration depth V1 and the vibration reduction timing T4 to values ​​at which the variation in the flying angle of the ink is minimized, following the setting of the intermediate potential Vmid.

[0166] When the control unit 2c determines that there is no curvature of the liquid line (step S2006, No), it determines whether a satellite point is generated (step S2008).

[0167] When the control unit 2c determines that a satellite point has been generated (step S2008, Yes), it sets the preliminary vibration depth V1 to a value that makes the droplet formation speed the fastest (step S2009).

[0168] Furthermore, the control unit 2c may set the damping depth Vcal to a value at which the droplet formation speed becomes the fastest, following the setting of the intermediate potential Vmid.

[0169] When the control unit 2c determines that no satellite points are generated (step S2008, No), it determines whether to adjust the volume of ink (step S2010).

[0170] When the volume adjustment is performed (step S2010 , Yes), the control unit 2 c sets the slew rate SR to a value at which the volume of the ink when flying at 5 m / s becomes a desired volume (step S2011 ).

[0171] The control unit 2c may set the intermediate potential Vmid following the setting of the slew rate SR. In this case, the control unit 2c sets the intermediate potential Vmid to a value at which the volume of the ink when flying at 5 m / s becomes a desired volume.

[0172] After the control unit 2c sets the vibration reduction depth Vcal in step S2005, sets the intermediate potential Vmid in step S2007, sets the preliminary vibration depth V1 in step S2009, sets the conversion rate SR in step S2011, or terminates the control processing of the drive signal without performing volume adjustment (step S2019, No).

[0173] Fig.21 This is another flowchart showing the control process of the drive signal performed by the control unit 2c. Fig.21The control processing of the drive signal represents the following situation: the control unit 2c determines that there are multiple ejection states among the ejection states in which there are errors in ink spray, liquid line bending, satellite points and ejection volume, and changes the parameters in the order of the ejection states from the largest number of parameters to be adjusted to the smallest number.

[0174] Fig.21 Steps S2101 to S2103 shown in FIG. Fig. 20 Steps S2001 to S2003 shown are the same.

[0175] After the processing of step S2103, the control unit 2c determines whether to adjust the volume of the ink (step S2104). When the volume adjustment is performed (step S2104, yes), the control unit 2c sets the conversion rate SR to a value that makes the volume of the ink when flying at 5 m / s become the desired volume (step S2105).

[0176] When the volume adjustment is not performed (step S2104, No), or when the process of step S2105 is completed, the control unit 2c determines whether there is spray (step S2106). Then, when the control unit 2c determines that there is spray (step S2106, Yes), it sets the vibration reduction depth Vcal to a value that minimizes the number of sprays (step S2107).

[0177] When the control unit 2c determines that there is no spraying (step S2106, No), or when the processing of step S2107 is completed, it determines whether the liquid line is bent (step S2108). When the control unit 2c determines that there is a liquid line bending (step S2108, Yes), the intermediate potential Vmid is set to a value that minimizes the deviation (variance) of the flight angle of the ink (step S2109).

[0178] When the control unit 2c determines that there is no liquid line bending (step S2108, No), or when step S2109 is finished, it determines whether satellite points are generated (step S2110). When the control unit 2c determines that satellite points are generated (step S2110, Yes), it sets the preliminary vibration depth V1 to a value that makes the dropletization speed the fastest (step S2111).

[0179] When the control unit 2c determines that no satellite point is generated (step S2110, No) or when step S2111 is completed, the control process of the drive signal is terminated.

[0180] In the present disclosure, the case where the liquid ejected from the inkjet head is ink is described, but liquid other than ink may also be used.

[0181] The above embodiments are described with reference to the accompanying drawings, but the present disclosure is not limited to the relevant examples. It is obvious that a person skilled in the art can think of various variations or modifications within the scope of the claims. It should be understood that such variations or modifications also belong to the technical scope of the present disclosure. In addition, the constituent elements in the embodiments can be arbitrarily combined within the scope of the subject matter of the present disclosure.

[0182] (1) A liquid ejection device in one embodiment of the present disclosure includes: an inkjet head that ejects liquid based on a drive signal; an observation unit that observes the liquid ejected from the inkjet head; and a control unit that changes the drive signal according to the ejection state of the liquid observed by the observation unit.

[0183] (2) In an embodiment of the present disclosure, in the liquid ejection device of (1), the control unit determines the type of the parameter of the drive signal according to the ejection state.

[0184] (3) The liquid ejection device in one embodiment of the present disclosure is based on the liquid ejection device of (2), wherein the driving signal is a signal having a preliminary vibration part, a formal vibration part and a vibration-damping vibration part, and the control part controls the vibration-damping depth of the vibration-damping vibration part when it is determined that there is spray in the liquid.

[0185] (4) In one embodiment of the present disclosure, the liquid ejection device is based on the liquid ejection device of (3), wherein the control unit controls at least one of the damping timing of the damping vibration unit, the intermediate potential of the drive signal, and the preparatory vibration depth of the preparatory vibration unit after controlling the damping depth.

[0186] (5) The liquid ejection device in one embodiment of the present disclosure is based on the liquid ejection device of (2), wherein the driving signal is a signal having a preliminary vibration part, a formal vibration part and a damping vibration part, and the control part controls the intermediate potential of the driving signal when it is determined that there is a liquid line bend in the liquid.

[0187] (6) In an embodiment of the present disclosure, the liquid ejection device is based on the liquid ejection device of (5), wherein the control unit controls at least one of the damping timing of the damping vibration unit and the preliminary vibration depth of the preliminary vibration unit after controlling the intermediate potential.

[0188] (7) The liquid ejection device in one embodiment of the present disclosure is based on the liquid ejection device of (2), wherein the driving signal is a signal having a preliminary vibration part, a formal vibration part and a damping vibration part, and when the control part determines that there are satellite points in the liquid, the control part controls the preliminary vibration depth of the preliminary vibration part.

[0189] (8) In an embodiment of the present disclosure, in the liquid ejection device of (7), the control unit controls the vibration reduction depth of the vibration reduction vibrator after controlling the preliminary vibration depth.

[0190] (9) The liquid ejection device in one embodiment of the present disclosure is based on the liquid ejection device of (2), wherein the driving signal is a signal having a preparatory vibration part, a formal vibration part and a damping vibration part, and the control part controls the conversion rate of the formal vibration part according to the ejection volume of the liquid.

[0191] (10) The liquid ejection device in one embodiment of the present disclosure is based on the liquid ejection device of (9), and the control unit controls the resonance period of the preparatory vibration unit and the formal vibration unit, the damping depth of the damping vibration unit, the middle potential of the drive signal, and at least one of the preparatory vibration depth of the preparatory vibration unit after controlling the conversion rate.

[0192] (11) The liquid ejection device in one embodiment of the present disclosure is based on the liquid ejection device of (2), and when the control unit observes multiple ejection states including the spray of the liquid, the curvature of the liquid line, the satellite point of the liquid, and the error in the ejection volume of the liquid as the ejection state of the liquid, the control unit sequentially changes the parameters that regulate the drive signal for each ejection state.

[0193] (12) The liquid ejection device in one embodiment of the present disclosure is based on the liquid ejection device of (11), and the control unit changes the parameters regulating the driving signal in the order of the spray of the liquid, the bending of the liquid line of the liquid and the satellite points of the liquid when observing the spray of the liquid, the bending of the liquid line of the liquid and the satellite points of the liquid.

[0194] (13) A liquid ejection method in one embodiment of the present disclosure includes: a step of observing liquid ejected from an inkjet head that ejects liquid based on a drive signal; and a step of changing the drive signal according to the ejection state of the liquid.

Claims

1. A liquid ejection device, comprising: An inkjet head ejects liquid based on a driving signal; an observation section that observes the liquid ejected from the inkjet head; and The control unit changes the driving signal according to the discharge state of the liquid observed by the observation unit.

2. The liquid ejection device according to claim 1, wherein: The control unit determines a type of parameter of the drive signal according to the discharge state.

3. The liquid ejection device according to claim 2, wherein: The driving signal is a signal having a preliminary vibration part, a main vibration part, and a damping vibration part. The control unit controls the vibration reduction depth of the vibration reduction vibrator when it is determined that there is spray in the liquid.

4. The liquid ejection device according to claim 3, wherein: The control section controls at least one of the vibration reduction timing of the vibration reduction vibrator section, the intermediate potential of the drive signal, and the preliminary vibration depth of the preliminary vibration section after controlling the vibration reduction depth.

5. The liquid ejection device according to claim 2, wherein: The driving signal is a signal having a preliminary vibration part, a main vibration part, and a damping vibration part. The control unit controls the intermediate potential of the drive signal when it is determined that the liquid line is bent in the liquid.

6. The liquid ejection device according to claim 5, wherein: The control section controls at least one of the vibration reduction timing of the vibration reduction section and the preliminary vibration depth of the preliminary vibration section after controlling the intermediate potential.

7. The liquid ejection device according to claim 2, wherein: The driving signal is a signal having a preliminary vibration part, a main vibration part, and a damping vibration part. The control unit controls a preliminary vibration depth of the preliminary vibration unit when it is determined that there are satellite spots in the liquid.

8. The liquid ejection device according to claim 7, wherein: The control unit controls the vibration reduction depth of the vibration reduction vibrating unit after controlling the preliminary vibration depth.

9. The liquid ejection device according to claim 2, wherein: The driving signal is a signal having a preliminary vibration part, a main vibration part, and a damping vibration part. The control unit controls a switching rate of the main vibration unit according to a discharge volume of the liquid.

10. The liquid ejection device according to claim 9, wherein: The control unit controls at least one of the resonance periods of the preliminary vibration unit and the main vibration unit, the damping depth of the damping vibration unit, the intermediate potential of the drive signal, and the preliminary vibration depth of the preliminary vibration unit after controlling the slew rate.

11. The liquid ejection device according to claim 2, wherein: When the control unit observes multiple ejection states including the spray of the liquid, the curvature of the liquid line of the liquid, the satellite points of the liquid, and the error in the ejection volume of the liquid as the ejection states of the liquid, the control unit sequentially changes the parameters that regulate the drive signal for each ejection state.

12. The liquid ejection device according to claim 11, wherein: When observing the spray of the liquid, the curvature of the liquid line, and the satellite of the liquid, the control unit changes the parameter defining the drive signal in the order of the spray of the liquid, the curvature of the liquid line, and the satellite of the liquid.

13. A liquid ejection method, comprising: a step of observing liquid ejected from an inkjet head that ejects the liquid based on a driving signal; and The step of changing the driving signal according to the discharge state of the liquid.

Images