Ink supply control system and method

Abstract

The invention discloses an ink supply control system and method, and belongs to the technical field of ink-jet printing. The ink supply control system comprises an ink supply device and an air pressure control device; the ink supply device comprises a nozzle, a first ink bottle and a second ink bottle, the first ink bottle supplies ink to the second ink bottle through a first ink supply pipeline, the second ink bottle supplies ink to the nozzle through a second ink supply pipeline, and a flow sensor is arranged in the second ink supply pipeline; the air pressure control device comprises a positive pressure air path, a negative pressure air path, a piezoelectric proportional valve and a control unit; the piezoelectric proportional valve is linked with the positive-pressure and negative-pressure gas circuit, and real-time detection of the flow sensor is combined, so that the control unit can adjust the gas pressure in the second ink bottle in real time according to the actual flow, the ink flow of the spray head is accurately regulated and controlled, and the stable and accurate ink supply flow of the spray head is kept. According to the ink supply control system, the problem of ink outlet fluctuation caused by external disturbance is solved, high precision and high stability of ink supply of the spray head are achieved, and the requirement of a high-precision printing process is met.

Description

Technical Field

[0001] This invention belongs to the field of inkjet printing technology, specifically relating to an ink supply control system and method. Background Technology

[0002] Inkjet printing is performed on an inkjet printing device. During operation, the ink material used by the inkjet printing device is delivered to the printhead through the ink supply system. Then, the printhead prints the ink material evenly onto the glass substrate to form the film structure required by the process. It can be seen that the ink supply system is an important component of the inkjet printing device, and the rationality of the ink supply system design directly affects the printing quality of the inkjet printing device.

[0003] In existing technologies, ink flow is typically controlled by either pneumatic or mechanical force during printhead ink supply. Mechanical pump-based ink volume control suffers from insufficient precision, making it unsuitable for high-precision printing processes. Pneumatic ink supply, on the other hand, is susceptible to fluctuations in ink output under the same pressure input due to factors such as ink residue in the printhead tubing and ink bottle level oscillations, resulting in inconsistent ink supply accuracy and making it unsuitable for high-precision printing applications. Summary of the Invention

[0004] In view of one or more of the above-mentioned defects or improvement needs of the prior art, the present invention provides an ink supply control system and method, which can adjust the ink flow in the printhead in real time, maintain the stability of ink supply to the printhead, and meet the requirements of high-precision printing process.

[0005] To achieve the above objectives, the present invention provides an ink supply control system, which includes an ink supply device and an air pressure control device; The ink supply device includes a printhead, a first ink bottle, and a second ink bottle; the first ink bottle is connected to the second ink bottle through a first ink supply line, and the second ink bottle is connected to the printhead through a second ink supply line, for supplying ink to the printhead; a first solenoid valve is provided on the first ink supply line; a second solenoid valve and a flow sensor are provided on the second ink supply line, and the flow sensor is used to collect the ink flow rate in the second ink supply line in real time. The pneumatic control device includes a positive pressure air circuit, a negative pressure air circuit, a piezoelectric proportional valve, and a control unit; the piezoelectric proportional valve is connected to the positive pressure air circuit, the negative pressure air circuit, and the second ink bottle, respectively; The control unit is electrically connected to the flow sensor and the piezoelectric proportional valve respectively. The control unit can control the piezoelectric proportional valve to adjust the air pressure in the second ink bottle according to the data collected by the flow sensor, so as to achieve precise control of the printhead flow rate.

[0006] As a further improvement of the present invention, a first pressure sensor is provided in the positive pressure gas path, the first pressure sensor being used to detect the pressure value of the compressed gas in the positive pressure gas path; a second pressure sensor is provided in the negative pressure gas path, the second pressure sensor being used to detect the vacuum value of the negative pressure gas path; The control unit is electrically connected to the first pressure sensor and the second pressure sensor respectively. Based on the detection data of the first pressure sensor and / or the second pressure sensor, it can output a corresponding electrical signal to control the opening and closing degree of the valve core of the piezoelectric proportional valve, so as to accurately control the air pressure state in the second ink bottle.

[0007] As a further improvement of the present invention, a first three-way valve is connected in series in the positive pressure air circuit. The air inlet of the first three-way valve is connected to the positive pressure air circuit, and the two air outlets are respectively connected to the piezoelectric proportional valve and the first ink bottle. A second three-way valve is connected in series in the negative pressure air circuit. The two inlet ends of the second three-way valve are respectively connected to the piezoelectric proportional valve and the second ink bottle, and its outlet end is connected to the negative pressure output end of the negative pressure air circuit.

[0008] As a further improvement of the present invention, a negative pressure container and a negative pressure pump are connected in series in the negative pressure air circuit. The air inlet of the negative pressure container is connected to the air outlet of the second three-way valve, and the air outlet of the negative pressure container is connected to the air suction end of the negative pressure pump. The negative pressure pump is used to evacuate the negative pressure container to form a vacuum environment. The second pressure sensor is mounted on the negative pressure container and is used to detect the vacuum level inside the negative pressure container.

[0009] As a further improvement of the present invention, a pressure reducer and a first shut-off valve are connected in series in the positive pressure gas path, and the first pressure sensor and the first shut-off valve are arranged between the pressure reducer and the inlet end of the first three-way valve along the gas transmission direction of the positive pressure gas path.

[0010] As a further improvement of the present invention, the ink supply device further includes a liquid collection bottle, which is connected to the printhead through an ink return pipeline; The second ink supply line is equipped with a first liquid level sensor, and the ink return line is equipped with a second liquid level sensor; the first liquid level sensor and the second liquid level sensor are respectively electrically connected to the control unit, and are used to collect the ink level information in the corresponding line in real time and feed it back to the control unit.

[0011] On the other hand, the present invention also provides an ink supply control method, which utilizes the above-mentioned ink supply control system and includes the following process: (1) Close the second solenoid valve, open the first solenoid valve, and the control unit controls the piezoelectric proportional valve to connect the negative pressure air path to the second ink bottle, so that a negative pressure environment is formed in the second ink bottle, and the first ink bottle is driven to supply ink to the second ink bottle. (2) Close the first solenoid valve, open the second solenoid valve, and the control unit controls the piezoelectric proportional valve to connect the positive pressure air circuit to the second ink bottle, so that a positive pressure environment is formed in the second ink bottle and ink is supplied to the print head; (3) The flow sensor collects the ink flow in the second ink supply line in real time and feeds it back to the control unit. The control unit dynamically adjusts the opening and closing degree of the piezoelectric proportional valve according to the collected data, thereby adjusting the air pressure in the second ink bottle and realizing precise control of the ink flow of the printhead.

[0012] As a further improvement of the present invention, the control unit controls the piezoelectric proportional valve to connect the positive pressure air path to the second ink bottle, so that a positive pressure environment is formed in the second ink bottle and ink is supplied to the printhead, including the following steps: The control unit calculates the required design pressure value of the second ink bottle based on the set flow rate of the printhead and the preset formula, and controls the piezoelectric proportional valve to adjust the air pressure in the second ink bottle to the design pressure value.

[0013] As a further improvement of the present invention, the control unit regulating the air pressure in the second ink bottle in step (3) includes the following process: S31. Calculate the difference between the actual flow rate and the set flow rate based on the actual flow rate value collected by the process sensor; S32. Determine if the absolute value of the difference exceeds 1 μL / min; if it does not exceed, there is no need to adjust the air pressure in the second ink bottle; if it exceeds, proceed to S33. S33. Determine whether the absolute value of the difference exceeds 2 μL / min. If it does not exceed, control the air pressure in the second ink bottle to increase or decrease by 0.1 kPa. If it exceeds, proceed to S34. S34. Determine whether the absolute value of the difference exceeds 3 μL / min. If it does not exceed, control the air pressure in the second ink bottle to increase or decrease by 0.3 kPa. If it exceeds, proceed to S35. S35. Determine whether the absolute value of the difference exceeds 4 μL / min. If it does not exceed, control the air pressure in the second ink bottle to increase or decrease by 0.4 kPa. If it exceeds, proceed to S36. S36. Determine whether the absolute value of the difference exceeds 5 μL / min. If it does not exceed, control the air pressure in the second ink bottle to increase or decrease by 0.6 kPa. If it exceeds, proceed to S37. S37. Control the air pressure in the second ink bottle to increase or decrease by 0.8 kPa.

[0014] As a further improvement of the present invention, the process of obtaining the preset formula includes the following steps: Let the relationship between the flow rate Q in the second ink supply line and the air pressure P in the second ink bottle be Q=a P 3 +b P 2 +c P+d; The air pressure in the second ink bottle is controlled to be at different air pressure states Pi, and the flow sensor collects the corresponding ink flow rate Qi in the second ink supply line under each air pressure. Multiple groups (P) i Q i Substituting the data into the above equations, an overdetermined system of equations is constructed. The coefficient matrix [a,b,c,d] of the above equations is then solved using the least squares method. T This allows us to obtain the relationship between flow rate Q and air pressure P.

[0015] The aforementioned improved technical features can be combined with each other as long as they do not conflict with each other.

[0016] In summary, the beneficial effects of the above-described technical solutions conceived by this invention compared with the prior art include: (1) The ink supply control system of the present invention includes an ink supply device and an air pressure control device; the ink supply device includes a printhead, a first ink bottle and a second ink bottle, the first ink bottle supplies ink to the second ink bottle through a first ink supply pipeline, and the second ink bottle supplies ink to the printhead through a second ink supply pipeline, wherein a flow sensor is provided in the second ink supply pipeline; the air pressure control device includes a positive pressure air path, a negative pressure air path, a piezoelectric proportional valve and a control unit; by linking the positive and negative pressure air paths through the piezoelectric proportional valve, combined with the real-time detection of the flow sensor, the control unit can adjust the air pressure in the second ink bottle in real time according to the actual flow rate, thereby achieving precise control of the ink flow rate of the printhead and maintaining a stable and precise ink supply flow rate for the printhead. The ink supply control system of the present invention solves the problem of ink output fluctuation caused by external disturbances, achieves high precision and high stability of printhead ink supply, and meets the requirements of high-precision printing processes.

[0017] (2) The ink supply control system of the present invention has a first pressure sensor in the positive pressure air path and a second pressure sensor in the negative pressure air path. The pressure / vacuum of the positive pressure air path and the negative pressure air path are detected in real time and the data is fed back to the control unit. This provides accurate and reliable air pressure data for the control unit to regulate the piezoelectric proportional valve, and ultimately ensures the ink supply accuracy of the printhead.

[0018] (3) The ink supply control system of the present invention has a first three-way valve connected in series on the positive pressure air line and a second three-way valve connected in series on the negative pressure air line to realize the synergistic effect of the positive and negative pressure air lines on the two ink bottles, forming a composite air pressure difference to drive the first ink bottle to supply ink to the second ink bottle, replacing the simple liquid level difference ink supply, which is faster, more uniform in flow, and improves the efficiency of supplying ink from the first ink bottle to the second ink bottle.

[0019] (4) The ink supply control method of the present invention calculates the design pressure value in the second ink bottle according to the set flow rate value, and then calculates and converts the pressure value that needs to be adjusted in the second ink bottle by discrete proportional control based on the difference between the actual flow rate value collected by the flow sensor and the set flow rate value, and outputs the control valve core opening degree of the piezoelectric proportional valve to adjust the ink flow rate in the print head, maintain the stability of ink supply to the print head, and improve the consistency of ink jetting. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the ink supply control system in an embodiment of the present invention; Figure 2 This is a flowchart of the ink supply control method in an embodiment of the present invention; In all the accompanying drawings, the same reference numerals denote the same technical features, specifically: 1. Ink supply device; 101. First ink bottle; 102. Second ink bottle; 103. Printhead; 104. First solenoid valve; 105. Second solenoid valve; 106. Flow sensor; 107. Collection bottle; 108. Third solenoid valve; 2. Air pressure control device; 21. Positive pressure air path; 211. First pressure sensor; 212. First three-way valve; 213. Pressure reducer; 214. First shut-off valve; 215. Dryer; 216. Oil-gas separator; 22. Negative pressure air path; 221. Second pressure sensor; 222. Second three-way valve; 223. Negative pressure container; 224. Negative pressure pump; 23. Piezoelectric proportional valve; 24. Third shut-off valve. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0023] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0024] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0025] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0026] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0027] Example: Please see Figure 1 In a preferred embodiment of the present invention, the ink supply control system includes an ink supply device 1 and an air pressure control device 2.

[0028] The ink supply device 1 includes a printhead 103, a first ink bottle 101, and a second ink bottle 102. The first ink bottle 101 is connected to the second ink bottle 102 via a first ink supply line, and the second ink bottle 102 is connected to the printhead 103 via a second ink supply line, for supplying ink to the printhead 103. A first solenoid valve 104 is provided on the first ink supply line; a second solenoid valve 105 and a flow sensor 106 are provided on the second ink supply line, the flow sensor 106 being used to collect the ink flow rate in the second ink supply line in real time. Preferably, the second ink bottle 102 is provided with limit indicators, including an upper limit and a lower limit. The upper limit indicates that ink supply to the second ink bottle 102 should stop, and the lower limit indicates that ink needs to be supplied to the second ink bottle 102.

[0029] Furthermore, the air pressure control device 2 includes a positive pressure air path 21, a negative pressure air path 22, a piezoelectric proportional valve 23, and a control unit; the piezoelectric proportional valve 23 is connected to the positive pressure air path 21, the negative pressure air path 22, and the second ink bottle 102 respectively; the control unit is electrically connected to the flow sensor 106 and the piezoelectric proportional valve 23 respectively, and the control unit can control the piezoelectric proportional valve 23 to adjust the air pressure in the second ink bottle 102 according to the data collected by the flow sensor 106, so as to achieve precise control of the flow rate of the printhead 103.

[0030] In this embodiment, the positive pressure air path 21 is used to transmit positive pressure gas, and the negative pressure air path 22 is used to transmit vacuum negative pressure. The piezoelectric proportional valve 23 is connected to the positive pressure air path 21, the negative pressure air path 22, and the second ink bottle 102 respectively. By switching or proportionally conducting the positive / negative pressure air path 22, continuous, stepless, and precise positive and negative pressure adjustment of the internal air pressure of the second ink bottle 102 can be achieved. The ink supply process of this system is as follows: First, the first ink bottle 101 supplies ink to the second ink bottle 102. The first solenoid valve 104 is opened, and the second solenoid valve 105 is closed. The piezoelectric proportional valve 23 connects the negative pressure air passage 22 to the second ink bottle 102. By adjusting the valve core opening and closing degree, the airflow rate of the negative pressure air passage 22 to the second ink bottle 102 is precisely controlled, keeping the second ink bottle 102 under negative pressure. Ink from the first ink source is then smoothly drawn in through the first ink path. Due to the continuous negative pressure suction function of the secondary ink bottle, the ink... During water delivery, larger air bubbles are continuously expelled. Next, the second ink bottle 102 supplies ink to the printhead 103. The first solenoid valve 104 and the second solenoid valve 105 are closed. The piezoelectric proportional valve 23 connects the positive pressure air path 21 to the second ink bottle 102 and precisely controls the positive pressure gas flow from the positive pressure air path 21 to the second ink bottle 102 by adjusting the valve core opening degree, ensuring the second ink bottle 102 is under positive pressure. This allows the ink from the second ink source to be stably supplied to the printhead 103 through the second ink supply pipeline. Furthermore, during the ink supply process from the second ink bottle 102 to the printhead 103, the flow sensor 106 collects the ink flow rate in the second ink supply pipeline in real time and feeds it back to the control unit. Based on this collected data, the control unit can dynamically adjust the valve core opening degree of the piezoelectric proportional valve 23, thereby adjusting the air pressure inside the second ink bottle 102 and achieving precise control of the ink flow rate to the printhead 103, ensuring a stable and accurate ink supply flow rate.

[0031] Preferably, a first pressure sensor 211 is provided on the positive pressure air path 21, which is used to detect the pressure value of the compressed gas in the positive pressure air path 21; a second pressure sensor 221 is provided on the negative pressure air path 22, which is used to detect the vacuum value of the negative pressure air path 22; the control unit is electrically connected to the first pressure sensor 211 and the second pressure sensor 221 respectively, and can output a corresponding electrical signal to control the opening degree of the valve core of the piezoelectric proportional valve 23 according to the detection data of the first pressure sensor 211 and / or the second pressure sensor 221, so as to accurately control the air pressure state in the second ink bottle 102.

[0032] In this embodiment, the first pressure sensor 211 and the second pressure sensor 221 respectively detect the pressure / vacuum of the positive pressure air path 21 and the negative pressure air path 22 in real time and feed back the data to the control unit, so as to provide the control unit with accurate and reliable air pressure data for regulating the piezoelectric proportional valve 23, and ultimately ensure the ink supply accuracy of the printhead 103.

[0033] More preferably, a first three-way valve 212 is connected in series on the positive pressure air path 21. The air inlet of the first three-way valve 212 is connected to the positive pressure air path 21, and the two air outlets are connected to the piezoelectric proportional valve 23 and the first ink bottle 101, respectively. A second three-way valve 222 is connected in series on the negative pressure air path 22. The two air inlets of the second three-way valve 222 are connected to the piezoelectric proportional valve 23 and the second ink bottle 102, respectively, and its air outlet is connected to the negative pressure output end of the negative pressure air path 22.

[0034] In this preferred embodiment, the first three-way valve 212 splits the single gas source of the positive pressure gas path 21 into two paths, and the second three-way valve 222 merges the two paths of the negative pressure gas path 22 into a single source, thereby expanding the range of gas pressure application. During the process of ink being transported from the first ink bottle 101 to the second ink bottle 102, there is no need to precisely control the transport flow rate. At this time, when the air outlet of the first three-way valve 212 is connected to the first ink bottle 101 and the air inlet of the second three-way valve 222 is connected to the negative pressure air path 22, the air pressure of the positive pressure air path 21 and the negative pressure air path 22 simultaneously act on the first ink bottle 101 and the second ink bottle 102 respectively, realizing coordinated air pressure control of the two ink bottles, so that a large pressure difference is formed in the two ink bottles, which can quickly transport ink from the first ink bottle 101 to the second ink bottle 102. When supplying ink to the printhead 103, the air outlet of the first three-way valve 212 and the air inlet of the second three-way valve 222 are both connected to the piezoelectric proportional valve 23 respectively. The piezoelectric proportional valve 23 precisely controls the air pressure in the second ink bottle 102, thereby maintaining the stability of ink supply to the printhead 103.

[0035] Preferably, a third shut-off valve 24 is provided in the air passage between the piezoelectric proportional valve 23 and the second ink bottle 102. Before the first ink bottle 101 supplies ink to the second ink bottle 102, the third shut-off valve 24 is closed to prevent the air passage between the piezoelectric proportional valve 23 and the second ink bottle 102 from affecting the air pressure in the second ink bottle 102.

[0036] More specifically, an oil-gas separator 216 and a dryer 215 are preferably connected in series on the positive pressure gas path 21. The oil-gas separator 216, the dryer 215, and the pressure reducer 213 are arranged sequentially along the gas transmission direction of the positive pressure gas path 21. Among them, the oil-gas separator 216 is used to separate oil impurities in the compressed gas, and the dryer 215 is used to remove moisture from the compressed gas, so as to purify the compressed gas transported by the positive pressure gas path 21 and avoid oil and moisture affecting the working accuracy and service life of the pressure reducer 213, the first pressure sensor 211, and the piezoelectric proportional valve 23.

[0037] More preferably, a negative pressure container 223 and a negative pressure pump 224 are connected in series on the negative pressure air path 22. The air inlet of the negative pressure container 223 is connected to the air outlet of the second three-way valve 222, and the air outlet of the negative pressure container 223 is connected to the air intake of the negative pressure pump 224. The negative pressure pump 224 is used to evacuate the negative pressure container 223 to form a vacuum environment. A second pressure sensor 221 is mounted on the negative pressure container 223 to detect the vacuum level inside the negative pressure container 223. In this embodiment, the negative pressure pump 224 provides a vacuum source for the negative pressure air path 22, and the negative pressure container 223 can buffer the evacuation fluctuations of the negative pressure pump 224 to form a stable vacuum environment for the second pressure sensor 221 to detect, and stabilize the overall vacuum level of the negative pressure air path 22, thereby achieving stable operation of the negative pressure air path 22.

[0038] Preferably, a second shut-off valve is provided on the negative pressure air passage 22 of the negative pressure container 223 and the second three-way valve 222. When the vacuum value in the negative pressure container 223 detected by the second pressure sensor 221 exceeds the preset negative pressure threshold, the second shut-off valve closes, cutting off the negative pressure air passage 22 and the negative pressure air passage 22 of the second three-way valve 222, so as to prevent the abnormal vacuum of the negative pressure air passage 22 from causing the air pressure in the second ink bottle 102 to become unstable.

[0039] More specifically, the negative pressure air path 22 preferably also includes a filter connected in series, with the filter positioned between the suction end of the negative pressure pump 224 and the outlet end of the negative pressure container 223. In this embodiment, the filter is used to filter impurities and residual ink particles in the gas, preventing impurities from entering the negative pressure pump 224 and causing wear, while also preventing residual ink particles from contaminating the negative pressure air path 22, ensuring the operational stability of the negative pressure pump 224 and the stability of the vacuum level in the negative pressure air path 22. Preferably, a pressure reducer 213 and a first shut-off valve 214 are connected in series on the positive pressure air path 21, with the first pressure sensor 211 and the first shut-off valve 214 positioned between the pressure reducer 213 and the inlet end of the first three-way valve 212 along the gas transmission direction of the positive pressure air path 21. In this embodiment, the pressure reducer 213 accurately reduces the pressure of the external high-pressure gas source to the working range suitable for this ink supply system, eliminates pressure fluctuations of the external gas source, stabilizes the pressure of the positive pressure gas path 21, and when the pressure data detected by the first pressure sensor 211 exceeds the pressure threshold, the first shut-off valve 214 closes, cutting off the gas supply from the positive pressure gas path 21 to the first three-way valve 212, so as to prevent the high-pressure gas from impacting and damaging the piezoelectric proportional valve 23.

[0040] Preferably, the ink supply device 1 further includes a collection bottle 107, which is connected to the printhead 103 via a return ink pipeline and is used to collect excess ink generated during the operation of the printhead 103. In this embodiment, when the printhead 103 is started, stopped, cleaned, or the ink is switched, the return ink pipeline forms a return channel. Combined with the thrust of the positive pressure air path 21, it can quickly empty the old ink / air bubbles in the flow channel of the printhead 103 and fill it with new ink, eliminating printing defects caused by flow channel residue and ensuring the working condition of the printhead 103.

[0041] More preferably, a first liquid level sensor is provided in the second ink supply pipeline, and a second liquid level sensor is provided in the ink return pipeline; the first liquid level sensor and the second liquid level sensor are electrically connected to the control unit respectively, and are used to collect the ink level information in the corresponding pipeline in real time and feed it back to the control unit.

[0042] In this embodiment, before the printhead 103 operates, the control unit can determine whether the printhead 103's pipeline and internal flow channel are full of ink based on the liquid level information fed back by the first liquid level sensor and the second liquid level sensor. Specifically, when the first liquid level sensor is triggered, it indicates that the second ink supply pipeline is full of ink. Furthermore, when the first liquid level sensor is continuously triggered and the second liquid level sensor is triggered, it indicates that the ink return pipeline is full of ink, that is, it indicates that the printhead 103 is full of ink, thus realizing the printhead 103's de-foaming function.

[0043] Preferably, a third solenoid valve 108 is provided on the ink return pipeline, and the third solenoid valve 108 is electrically connected to the control unit.

[0044] In practical use, the present invention also provides an ink supply control method, which utilizes the aforementioned ink supply control system and includes the following process: (1) Close the second solenoid valve 105, open the first solenoid valve 104, and the control unit controls the piezoelectric proportional valve 23 to connect the negative pressure air passage 22 and the second ink bottle 102, so that a negative pressure environment is formed in the second ink bottle 102, and the first ink bottle 101 is driven to supply ink to the second ink bottle 102. (2) Close the first solenoid valve 104, open the second solenoid valve 105, and the control unit controls the piezoelectric proportional valve 23 to connect the positive pressure air passage 21 and the second ink bottle 102, so that a positive pressure environment is formed in the second ink bottle 102 and ink is supplied to the print head 103. (3) The flow sensor 106 collects the ink flow in the second ink supply pipeline in real time and feeds it back to the control unit. The control unit dynamically adjusts the valve core opening degree of the piezoelectric proportional valve 23 according to the collected data, thereby adjusting the air pressure in the second ink bottle 102 and realizing precise control of the ink flow of the print head 103.

[0045] Furthermore, the control unit controls the piezoelectric proportional valve 23 to connect the positive pressure air path 21 and the second ink bottle 102, creating a positive pressure environment inside the second ink bottle 102 and supplying ink to the printhead 103, including the following steps: The control unit calculates the required design pressure value of the second ink bottle 102 based on the set flow rate of the printhead 103 and the preset formula, and controls the piezoelectric proportional valve 23 to adjust the air pressure in the second ink bottle 102 to the design pressure value.

[0046] More preferably, the process by which the control unit regulates the air pressure inside the second ink bottle 102 in step (3) includes the following steps: S31. Calculate the difference between the actual flow rate and the set flow rate based on the actual flow rate value collected by the process sensor; S32. Determine whether the absolute value of the difference exceeds 1 microliter / minute; if it does not exceed, the control unit does not need to adjust the air pressure in the second ink bottle 102; if it exceeds, proceed to S33. S33. Determine whether the absolute value of the difference exceeds 2 μL / min. If it does not exceed, control the air pressure in the second ink bottle 102 to increase or decrease by 0.1 kPa. If it exceeds, proceed to S34. S34. Determine whether the absolute value of the difference exceeds 3 μL / min. If it does not exceed, control the air pressure in the second ink bottle 102 to increase or decrease by 0.3 kPa. If it exceeds, proceed to S35. S35. Determine whether the absolute value of the difference exceeds 4 microliters / minute. If it does not exceed, control the air pressure in the second ink bottle 102 to increase or decrease by 0.4 kPa. If it exceeds, proceed to S36. S36. Determine whether the absolute value of the difference exceeds 5 microliters / minute. If it does not exceed, control the air pressure in the second ink bottle 102 to increase or decrease by 0.6 kPa. If it exceeds, proceed to S37. S37. Control the air pressure inside the second ink bottle 102 to increase or decrease by 0.8 kPa.

[0047] In this embodiment, in each of the above steps S32 to S37, when the difference between the actual flow rate and the set flow rate is positive, the air pressure in the second ink bottle 102 is controlled to decrease; when the difference between the actual flow rate and the set flow rate is negative, the air pressure in the second ink bottle 102 is controlled to increase.

[0048] More preferably, since the change in flow rate lags behind the change in air pressure, after each adjustment of the air pressure in the second ink bottle 102, a certain time interval is elapsed before comparing the actual flow rate value with the set flow rate value and then proceeding to the next round of adjustment.

[0049] More preferably, the process of obtaining the preset formula includes the following steps: Let the relationship between the flow rate Q in the second ink supply line and the air pressure P in the second ink bottle 102 be Q=a P 3 +b P 2 +c P+d; The air pressure inside the second ink bottle 102 is controlled to be at different pressure states P. i The flow sensor 106 collects the corresponding ink flow rate Q in the second ink supply line under each air pressure. i ; Multiple groups (P) i Q i Substituting the data into the above equations, an overdetermined system of equations is constructed. The coefficient matrix [a,b,c,d] of the above equations is then solved using the least squares method. T This allows us to obtain the relationship between flow rate Q and air pressure P.

[0050] The ink supply control method of this invention involves a control unit that calculates the design pressure value in the second ink bottle 102 based on a set flow rate value. Then, based on the difference between the actual flow rate value collected by the flow sensor 106 and the set flow rate value, a discrete proportional control is used to calculate and convert the pressure value that needs to be adjusted in the second ink bottle 102. The control unit outputs the control valve core opening degree of the piezoelectric proportional valve 23 to adjust the ink flow rate in the printhead 103, maintain the stability of ink supply to the printhead 103, and improve the consistency of ink jetting.

[0051] Those skilled in the art will readily understand that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An ink supply control system, characterized in that, Including ink supply device and air pressure control device; The ink supply device includes a printhead, a first ink bottle, and a second ink bottle; the first ink bottle is connected to the second ink bottle through a first ink supply line, and the second ink bottle is connected to the printhead through a second ink supply line, for supplying ink to the printhead; a first solenoid valve is provided on the first ink supply line; a second solenoid valve and a flow sensor are provided on the second ink supply line, and the flow sensor is used to collect the ink flow rate in the second ink supply line in real time. The pneumatic control device includes a positive pressure air circuit, a negative pressure air circuit, a piezoelectric proportional valve, and a control unit; the piezoelectric proportional valve is connected to the positive pressure air circuit, the negative pressure air circuit, and the second ink bottle, respectively; The control unit is electrically connected to the flow sensor and the piezoelectric proportional valve respectively. The control unit can control the piezoelectric proportional valve to adjust the air pressure in the second ink bottle according to the data collected by the flow sensor, so as to achieve precise control of the printhead flow rate.

2. The ink supply control system according to claim 1, characterized in that, A first pressure sensor is installed on the positive pressure gas path, which is used to detect the pressure value of the compressed gas in the positive pressure gas path; a second pressure sensor is installed on the negative pressure gas path, which is used to detect the vacuum value of the negative pressure gas path. The control unit is electrically connected to the first pressure sensor and the second pressure sensor respectively. Based on the detection data of the first pressure sensor and / or the second pressure sensor, it can output a corresponding electrical signal to control the opening and closing degree of the valve core of the piezoelectric proportional valve, so as to accurately control the air pressure state in the second ink bottle.

3. The ink supply control system according to claim 2, characterized in that, A first three-way valve is connected in series in the positive pressure air circuit. The air inlet of the first three-way valve is connected to the positive pressure air circuit, and the two air outlets are connected to the piezoelectric proportional valve and the first ink bottle, respectively. A second three-way valve is connected in series in the negative pressure air circuit. The two inlet ends of the second three-way valve are respectively connected to the piezoelectric proportional valve and the second ink bottle, and its outlet end is connected to the negative pressure output end of the negative pressure air circuit.

4. The ink supply control system according to claim 3, characterized in that, A negative pressure container and a negative pressure pump are connected in series in the negative pressure air circuit. The air inlet of the negative pressure container is connected to the air outlet of the second three-way valve, and the air outlet of the negative pressure container is connected to the air suction end of the negative pressure pump. The negative pressure pump is used to evacuate the negative pressure container to form a vacuum environment. The second pressure sensor is mounted on the negative pressure container and is used to detect the vacuum level inside the negative pressure container.

5. The ink supply control system according to claim 3, characterized in that, A pressure reducer and a first shut-off valve are connected in series in the positive pressure gas path. The first pressure sensor and the first shut-off valve are arranged between the pressure reducer and the inlet end of the first three-way valve along the gas transmission direction of the positive pressure gas path.

6. The ink supply control system according to claim 1, characterized in that, The ink supply device also includes a liquid collection bottle, which is connected to the printhead via an ink return pipeline; The second ink supply line is equipped with a first liquid level sensor, and the ink return line is equipped with a second liquid level sensor; the first liquid level sensor and the second liquid level sensor are respectively electrically connected to the control unit, and are used to collect the ink level information in the corresponding line in real time and feed it back to the control unit.

7. An ink supply control method, characterized in that, This method is implemented using the ink supply control system described in any one of claims 1 to 6, and includes the following process: (1) Close the second solenoid valve, open the first solenoid valve, and the control unit controls the piezoelectric proportional valve to connect the negative pressure air path to the second ink bottle, so that a negative pressure environment is formed in the second ink bottle, and the first ink bottle is driven to supply ink to the second ink bottle. (2) Close the first solenoid valve, open the second solenoid valve, and the control unit controls the piezoelectric proportional valve to connect the positive pressure air circuit to the second ink bottle, so that a positive pressure environment is formed in the second ink bottle and ink is supplied to the print head; (3) The flow sensor collects the ink flow in the second ink supply line in real time and feeds it back to the control unit. The control unit dynamically adjusts the opening and closing degree of the piezoelectric proportional valve according to the collected data, thereby adjusting the air pressure in the second ink bottle and realizing precise control of the ink flow of the printhead.

8. The ink supply control method according to claim 7, characterized in that, The control unit controls the piezoelectric proportional valve to connect the positive pressure air path to the second ink bottle, creating a positive pressure environment inside the second ink bottle and supplying ink to the printhead, including the following steps: The control unit calculates the required design pressure value of the second ink bottle based on the set flow rate of the printhead and the preset formula, and controls the piezoelectric proportional valve to adjust the air pressure in the second ink bottle to the design pressure value.

9. The ink supply control method according to claim 8, characterized in that, Step (3) involves the control unit regulating the air pressure inside the second ink bottle, which includes the following process: S31. Calculate the difference between the actual flow rate and the set flow rate based on the actual flow rate value collected by the process sensor; S32. Determine if the absolute value of the difference exceeds 1 microliter / minute; if it does not, there is no need to adjust the air pressure in the second ink bottle; If it exceeds, proceed to S33; S33. Determine whether the absolute value of the difference exceeds 2 μL / min. If it does not exceed, control the air pressure in the second ink bottle to increase or decrease by 0.1 kPa. If it exceeds, proceed to S34. S34. Determine whether the absolute value of the difference exceeds 3 μL / min. If it does not exceed, control the air pressure in the second ink bottle to increase or decrease by 0.3 kPa. If it exceeds, proceed to S35. S35. Determine whether the absolute value of the difference exceeds 4 μL / min. If it does not exceed, control the air pressure in the second ink bottle to increase or decrease by 0.4 kPa. If it exceeds, proceed to S36. S36. Determine whether the absolute value of the difference exceeds 5 μL / min. If it does not exceed, control the air pressure in the second ink bottle to increase or decrease by 0.6 kPa. If it exceeds, proceed to S37. S37. Control the air pressure in the second ink bottle to increase or decrease by 0.8 kPa.

10. The ink supply control method according to claim 8 or 9, characterized in that, The process of obtaining the preset formula includes the following steps: Let the relationship between the flow rate Q in the second ink supply line and the air pressure P in the second ink bottle be Q=a P 3 +b P 2 +c P+d; The air pressure in the second ink bottle is controlled to be at different air pressure states Pi, and the flow sensor collects the corresponding ink flow rate Qi in the second ink supply line under each air pressure. Multiple groups (P) i Q i Substituting the data into the above relational expression, an overdetermined system of equations is constructed. The coefficient matrix [a,b,c,d] of the above relational expression is then solved using the least squares method. T This allows us to obtain the relationship between flow rate Q and air pressure P.

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