Airless tank positive and negative pressure generation system and inkjet printer

Abstract

The embodiment of the present invention relates to the field of inkjet printing technology, and discloses an airless tank positive and negative pressure generating system, including: a control unit and a pressure generating unit; the control unit is used to receive a feedback signal from a printing unit, and send a pressure control signal to the pressure generating unit according to the feedback signal, and protect the printing unit from ink overflow according to a first ink overflow probe signal of the printing unit; the pressure generating unit includes: an air pump for providing positive and negative air pressure to the printing unit; an inlet and outlet solenoid valve for adjusting the working mode of the pressure generating unit to a positive pressure outlet mode or a negative pressure exhaust mode; a sealing solenoid valve for controlling the opening and closing of the air path; the pressure generating unit is connected to the printing unit through an external air port. In the above manner, the embodiment of the present invention realizes the effective reduction of system space occupancy by setting the pressure generating unit and using a probe to detect and protect the ink cartridge of the printing unit from ink overflow.

Description

Technical Field

[0001] The embodiment of the present invention relates to the technical field of inkjet printing, and in particular to an airless tank positive and negative pressure generating system applied to an ink path of an inkjet printer and an inkjet printer. Background Art

[0002] In order to achieve the voltage stabilization effect, the positive and negative voltage stabilization system currently used in the ink circuit of the inkjet printer needs to use a large gas tank as a buffer. However, the inventor of the present application found that the existing voltage stabilization system using a gas tank not only occupies a large system space and has a complex machine design, but also lacks effective ink overflow protection means for the ink cartridge. The ink overflow detection can only be performed from the safety bottle side through the safety bottle signal, and the ink overflow detection is not timely and accurate. In addition, some existing inkjet printers do not have space for installing a safety bottle, so ink overflow detection cannot be performed.

[0003] In order to solve the above problems, an airless tank positive and negative pressure generating system and an inkjet printer applied to the ink path of an inkjet printer are provided on the basis of the prior art. Summary of the invention

[0004] In view of the above problems, an embodiment of the present invention provides an air tank-less positive and negative pressure generating system and an inkjet printer for use in the ink circuit of an inkjet printer, which are used to solve the problems in the prior art that the air tank occupies too much space and there is no direct ink overflow detection and protection for the ink cartridge.

[0005] According to one aspect of an embodiment of the present invention, there is provided an airless tank positive and negative pressure generating system applied to an ink circuit of an inkjet printer, the airless tank positive and negative pressure generating system comprising: a control unit and a pressure generating unit; the control unit and the pressure generating unit are connected to an external printing unit;

[0006] The control unit is used to receive a feedback signal from the printing unit and send a pressure control signal to the pressure generating unit according to the feedback signal;

[0007] The pressure generating unit is used to provide positive pressure or negative pressure to the printing unit according to the pressure control signal; the pressure generating unit includes an air pump, an air inlet and outlet solenoid valve, a sealing solenoid valve and an external air port which are connected in sequence through an air pipe; the air pump is used to provide positive pressure or negative pressure to the printing unit in a positive pressure outlet mode or a negative pressure exhaust mode according to the pressure control signal; the air inlet and outlet solenoid valve is used to adjust the working mode of the pressure generating unit to a positive pressure outlet mode or a negative pressure exhaust mode according to the pressure control signal; the sealing solenoid valve is used to control the opening and closing of the air path between the air inlet and outlet solenoid valve and the external air port according to the pressure control signal; the pressure generating unit is connected to the printing unit through the external air port.

[0008] The control unit is also used to obtain a first ink overflow probe signal of the printing unit, and to protect the printing unit from ink overflow according to the first ink overflow probe signal; the first ink overflow probe signal is a signal generated by performing ink overflow detection on the ink cartridge of the printing unit through a probe.

[0009] In an optional manner, the printing unit also includes a safety bottle connected to the ink cartridge, and the control unit is further used to obtain a safety bottle trigger signal and / or a second ink overflow probe signal of the printing unit, and perform ink overflow protection on the printing unit according to the safety bottle trigger signal and / or the second ink overflow probe signal; the safety bottle trigger signal is a signal generated by performing ink overflow detection on the safety bottle of the printing unit; the second ink overflow probe signal is a signal generated by performing ink overflow detection on the safety bottle of the printing unit through a probe.

[0010] In an optional manner, the air inlet and outlet solenoid valves include an air inlet solenoid valve and an air outlet solenoid valve connected in parallel, and both the air inlet solenoid valve and the air outlet solenoid valve are three-way solenoid valves;

[0011] The first common port of the air intake solenoid valve is connected to the air inlet of the air pump, the first normally closed port of the air intake solenoid valve is connected to the external atmosphere, and the first normally open port of the air intake solenoid valve is connected to the sealing solenoid valve;

[0012] The second common port of the air outlet solenoid valve is connected to the air outlet of the air pump, the second normally closed port of the air outlet solenoid valve is connected to the sealing solenoid valve, and the second normally open port of the air outlet solenoid valve is connected to the external atmosphere;

[0013] The air inlet solenoid valve is used to open the first normally closed port and close the first normally open port according to the pressure control signal, so that the first normally closed port and the first common port are connected; the air outlet solenoid valve is used to open the second normally closed port and close the second normally open port according to the pressure control signal, so that the second common port and the second normally closed port are connected, so as to adjust the working mode of the pressure generating unit to the positive pressure air outlet mode;

[0014] The air intake solenoid valve is also used to connect the first normal opening and the first common port according to the pressure control signal, and the air outlet solenoid valve is also used to connect the second common port and the second normal opening according to the pressure control signal, so as to adjust the working mode of the pressure generating unit to the negative pressure exhaust mode.

[0015] In an optional manner, the pressure generating unit further includes a secondary air pump connected in parallel with the air pump;

[0016] The control unit is also used to detect the working state of the pressure generating unit. If it is detected that the air pump fails, the auxiliary air pump is switched to provide positive pressure or negative pressure to the printing unit.

[0017] In an optional manner, the control unit is further used to calculate the target operating parameters of the printing unit through a PID algorithm based on the feedback signal; generate and send the pressure control signal to the pressure generating unit based on the target operating parameters, so that the pressure generating unit provides positive pressure or negative pressure according to the pressure control signal.

[0018] According to another aspect of an embodiment of the present invention, there is provided an inkjet printer, comprising a printing unit and the above-mentioned airless tank positive and negative pressure generating system, wherein the printing unit comprises an air circuit unit and an ink cartridge; the airless tank positive and negative pressure generating system is connected to the air circuit unit, which is connected to the ink cartridge, and the probe is arranged in the air circuit unit of the printing unit; one end of the probe is electrically connected to the control unit, and the other end of the probe is connected to the ink cartridge.

[0019] In an optional manner, the gas circuit unit includes a three-way solenoid valve and a four-way pipe structure, and the probe includes two probe wires;

[0020] The normally open port of the three-way solenoid valve is connected to the pressure generating unit through an air pipe; the common port of the three-way solenoid valve is connected to the four-way pipe structure through an air pipe;

[0021] The first through tube of the four-way tube structure is connected to the common port of the three-way solenoid valve through an air pipe, the second through tube of the four-way tube structure is connected to the air port of the ink cartridge through an air pipe, the third through tube and the fourth through tube of the four-way tube structure are respectively provided with a probe wire, one end of the two probe wires is electrically connected to the control unit, and the other ends of the two probe wires pass through the second through tube and are connected to the ink cartridge through the air port.

[0022] In an optional manner, the printing unit further comprises a safety bottle connected to the ink cartridge;

[0023] The second through-tube of the four-way tube structure is connected to the first gas port of the safety bottle through an air pipe;

[0024] The second air port of the safety bottle is connected to the air port of the ink cartridge through an air pipe.

[0025] In an optional manner, the printing unit further includes an ink supply system and a nozzle connected to the ink cartridge;

[0026] The ink supply system is used to provide ink to the ink cartridge, and the nozzle is used to spray ink according to the ink in the ink cartridge.

[0027] In an optional manner, the nozzle is an internal circulation nozzle, and the internal circulation nozzle includes an input end, an output end and a printing end; the ink cartridge includes an ink return cartridge and an ink supply cartridge;

[0028] The ink supply cartridge is connected to the input end, and the ink return cartridge is connected to the output end; ink enters the ink supply cartridge through the ink supply system, enters the ink return cartridge via the internal circulation nozzle, and then returns to the ink supply system to form an ink circulation.

[0029] In the embodiment of the present invention, the pressure generating unit replaces the original gas tank to provide positive pressure or negative pressure to the printing unit, which can effectively reduce the space occupied by the system and simplify the machine design.

[0030] Furthermore, the embodiment of the present invention takes into account that sometimes, due to structural design or wiring habits, the signal of the safety bottle is only connected to the ink supply system board, and the positive and negative pressure generating system without an air tank cannot obtain the signal. For this reason, the embodiment of the present invention introduces a probe, and uses the probe to detect ink overflow on the ink cartridge of the printing unit, so as to perform ink overflow protection according to the detected signal. When there is not enough space in the printing unit to set up the safety bottle, or the positive and negative pressure generating system cannot obtain the safety bottle signal, the ink cartridge can be directly protected from ink overflow, thereby effectively reducing the system space occupancy.

[0031] Furthermore, the embodiment of the present invention adjusts the working mode of the pressure generating unit to a positive pressure exhaust mode or a negative pressure suction mode through the air inlet and outlet solenoid valves, and controls the opening and closing of the air path between the air inlet and outlet solenoid valves and the external air port through a sealing solenoid valve, thereby improving the system's delivery accuracy and efficiency of positive and negative air pressure to the printing unit, so as to provide stable positive and negative air pressure.

[0032] The above description is only an overview of the technical solution of the embodiment of the present invention. In order to more clearly understand the technical means of the embodiment of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the embodiment of the present invention more obvious and easy to understand, the specific implementation mode of the present invention is specifically listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings are only used to illustrate the embodiments and are not to be considered as limiting the present invention. In addition, the same reference symbols are used to represent the same components throughout the accompanying drawings. In the accompanying drawings:

[0034] Figure 1 A schematic diagram of the structure of a positive and negative pressure generating system for an airless tank provided by an embodiment of the present invention is shown;

[0035] Figure 2 A schematic diagram showing the structure of a printing unit provided in an embodiment of the present invention is shown;

[0036] Figure 3 A schematic diagram of the structure of a gas circuit unit provided in an embodiment of the present invention is shown;

[0037] Figure 4 A schematic structural diagram of a printing unit provided in another embodiment of the present invention is shown. DETAILED DESCRIPTION

[0038] Exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Example

[0039] Figure 1 The schematic diagram of the structure of the positive and negative pressure generating system of the airless tank provided by the embodiment of the present invention is shown. Figure 1 As shown, the airless tank positive and negative pressure generating system 100 includes: a control unit 120 and a pressure generating unit 110; the control unit 120 and the pressure generating unit 110 are connected to an external printing unit.

[0040] The control unit 120 is used to receive a feedback signal from the printing unit, and send a pressure control signal to the pressure generating unit 110 according to the feedback signal.

[0041] The pressure generating unit 110 is used to provide positive pressure or negative pressure to the printing unit according to the pressure control signal; the pressure generating unit 110 includes an air pump 111, an air inlet and outlet solenoid valve 112, a sealing solenoid valve 113 and an external air port 130 which are connected in sequence through an air pipe; the air pump 111 is used to provide positive pressure or negative pressure to the printing unit in a positive pressure outlet mode or a negative pressure exhaust mode according to the pressure control signal; the air inlet and outlet solenoid valve 112 is used to adjust the working mode of the pressure generating unit to a positive pressure outlet mode or a negative pressure exhaust mode according to the pressure control signal; the sealing solenoid valve 113 is used to control the opening and closing of the air path between the air inlet and outlet solenoid valve 112 and the external air port according to the pressure control signal; the pressure generating unit 110 is connected to the printing unit through the external air port 130.

[0042] The control unit 120 is also used to obtain the first ink overflow probe signal of the printing unit, and to protect the printing unit from ink overflow according to the first ink overflow probe signal; the first ink overflow probe signal is a signal generated by detecting ink overflow on the ink cartridge of the printing unit through a probe. The embodiment of the present invention takes into account that sometimes due to structural design or wiring habits, the signal of the safety bottle is only connected to the ink supply system board, and the airless positive and negative pressure generating system cannot obtain the signal. For this reason, the embodiment of the present invention introduces a probe, and performs ink overflow detection on the ink cartridge of the printing unit through the probe, so as to perform ink overflow protection according to the detected signal. When there is not enough space in the printing unit to set up a safety bottle, or the positive and negative pressure generating system cannot obtain the safety bottle signal, the ink cartridge can be directly protected from ink overflow, effectively reducing the system space occupation.

[0043] The airless tank positive and negative pressure generating system 100 further includes a signal interface 160 electrically connected to the control unit 120 , and the signal interface 160 is electrically connected to the printing unit for information transmission between the printing unit and the control unit 120 .

[0044] Among them, the airless tank positive and negative pressure generating system 100 measures the ink resistivity of the ink cartridge in the printing unit through a probe to obtain the first ink overflow probe signal of the printing unit. Specifically, one end of the probe is electrically connected to the control unit 120 through a signal interface 160, and the other end is connected to the ink cartridge of the printing unit, for measuring the resistivity of the ink in the ink cartridge and generating the first ink overflow probe signal. For example, the probe is arranged in the air path between the airless tank positive and negative pressure generating system 100 and the printing unit, one end of the probe is electrically connected to the control unit 120 through a signal interface 160, and one end of the probe is connected to the air port of the ink cartridge.

[0045] The control unit 120 performs ink overflow protection on the printing unit according to the first ink overflow probe signal. Specifically, when the probe measures that the ink resistivity is less than the preset resistivity, the corresponding first ink overflow probe signal is the first ink overflow alarm signal. The control unit 120 performs ink overflow protection according to the first ink overflow alarm signal, such as timely shutting down the pressure generating unit 110, etc. The present application does not limit the specific measures of ink overflow protection. When the ink in the ink cartridge does not cover the probe, the ink resistivity measured by the probe is the resistivity of air, and the resistivity of air is insulation, that is, much greater than the preset resistivity. When the ink in the ink cartridge covers the probe, the ink resistivity measured by the probe is the resistivity of the ink. Since ink can conduct electricity, and the conductive material generally refers to a resistivity of (1.5 to 10) × Ω*m, in this regard, the present application can take the preset resistivity as 20 megaΩ*m, that is, when the probe measures that the ink resistivity is less than the preset resistivity, it indicates that the ink has already flooded the probe, and the corresponding first ink overflow probe signal is the first ink overflow alarm signal; wherein 1 megaΩ= .

[0046] The control unit 120 includes a main control module 121 , an IO module 122 and a feedback module 123 . Both the IO module 122 and the feedback module 123 are electrically connected to the main control module 121 .

[0047] The main control module 121 transmits and controls signals to the IO module 122 and the feedback module 123 respectively. Specifically, the feedback signal includes a pressure feedback signal and an ink pressure signal. The IO module 122 is used to obtain the ink pressure signal of the printing unit and transmit the signal to the pressure generating unit 110. The ink pressure signal is a user's operation signal on the printing unit. The feedback module 123 is used to obtain the pressure feedback signal of the printing unit. The pressure feedback signal is a signal of the air pressure in the ink cartridge or the safety bottle in the printing unit measured by the air pressure sensor. The main control module 121 obtains the ink pressure signal sent by the IO module 122 and the pressure feedback signal sent by the feedback module 123, generates a pressure control signal according to the ink pressure signal and the pressure feedback signal, and sends the pressure control signal to the pressure generating unit 110 through the IO module, so that the pressure generating unit 110 provides the printing unit with positive pressure or negative pressure according to the pressure control signal.

[0048] Among them, the IO module 122 is electrically connected to the printing unit through the ink pressure port 150. The printing unit is provided with a button electrically connected to the ink pressure port. An ink pressure signal is generated by obtaining the user's triggering operation on the button, and the ink pressure signal is transmitted to the IO module through the ink pressure port.

[0049] Among them, the number of interfaces of the ink pressure port 150 is consistent with the number of air circuits of the airless tank positive and negative pressure generating system 100. For example, when the airless tank positive and negative pressure generating system 100 is provided with two air circuits, the ink pressure port 150 includes a first ink pressure port 151 and a second ink pressure port 152. Correspondingly, the printing unit is provided with buttons having the same number of interfaces as the ink pressure port 150, and the first ink pressure port 151 and the second ink pressure port 152 are each electrically connected to a button.

[0050] Among them, an air pressure sensor is provided in the air path connecting the pressure generating unit 110 and the printing unit, and the air pressure sensor is used to obtain the real-time air pressure in the ink cartridge or safety bottle in the printing unit and generate a pressure feedback signal; the feedback module 123 is used to obtain the pressure feedback signal of the air pressure sensor.

[0051] Among them, the control unit 120 also includes a human-machine module 124, and the human-machine module 124 is used to obtain the user's operation information and obtain the parameter information of the printing unit. Specifically, the airless tank positive and negative pressure generating system 100 also includes an operation panel 170. Optionally, the operation panel is arranged on the device housing, including a display screen and a rotary button. The display screen is used to display the parameter information of the printing unit, and the rotary button is used to obtain the user's operation information; the airless tank positive and negative pressure generating system 100 is also provided with a Modbus (Modbus serial communication protocol, Modbus serial communication protocol) port 140, and the human-machine module 124 is electrically connected to the Modbus port 140, and the actual operating parameters of the printing unit are remotely read through the Modbus port and the parameter information is generated; the human-machine module 124 is also used to set the target operating parameters of the printing unit through the Modbus port according to the user's operation information, and remotely control the printing unit to complete the ink pressing operation.

[0052] The human-machine module 124 is electrically connected to the main control module 121 , and the main control module 121 is further used to generate the pressure control signal according to the operation information and the feedback signal.

[0053] The embodiment of the present invention supports the Modbus protocol and can use the human-machine module 124 through the Modbus port 140 to remotely read the actual operating parameters of the printing unit, set the target operating parameters of the printing unit, and remotely control the printing unit to complete the ink pressing operation, which meets the needs of most industrial communication fields and supports multi-device cascade control.

[0054] Furthermore, when providing multiple channels of positive and negative pressure, the embodiment of the present invention can be centrally controlled by using PLC or computer software through Modbus cascading.

[0055] Among them, the control unit 120 also includes an ink overflow protection module 125 electrically connected to the main control module 121, and the ink overflow protection module 125 is electrically connected to the signal interface 160, obtains the first ink overflow probe signal of the printing unit through the signal interface 160, and sends the first ink overflow probe signal to the main control module 121, so that the main control module 121 performs ink overflow protection according to the first ink overflow probe signal.

[0056] Among them, the signal interface 160 includes a probe signal input port and a probe alarm output port; the probe signal input port is used to obtain the first ink overflow probe signal of the printing unit and send it to the ink overflow protection module 125; the main control module 121 is also used to generate a first ink overflow alarm signal according to the first ink overflow probe signal and feed it back to the ink overflow protection module 125, and the ink overflow protection module 125 sends the first ink overflow alarm signal to the printing unit through the probe alarm output port, so that the printing unit performs ink overflow protection according to the first ink overflow alarm signal, such as stopping the ink pressing operation, recovering waste ink, etc. The present application does not limit the specific measures of ink overflow protection.

[0057] The signal interface 160 further includes a safety bottle signal input port and a safety bottle alarm output port. When the printing unit is provided with a safety bottle connected to the ink cartridge, the safety bottle signal input port is used to obtain a safety bottle trigger signal of the safety bottle in the printing unit and send it to the ink overflow protection module 125; the main control module 121 is also used to generate a safety bottle alarm signal according to the safety bottle trigger signal and feed it back to the ink overflow protection module 125, and the ink overflow protection module 125 sends the safety bottle alarm signal to the printing unit through the probe alarm output port, so that the printing unit performs ink overflow protection according to the safety bottle alarm signal.

[0058] When the printing unit is provided with a safety bottle connected to the ink cartridge, the probe signal input port is used to obtain the second ink overflow probe signal of the printing unit and send it to the ink overflow protection module 125; the second ink overflow probe signal is a signal generated by detecting ink overflow on the safety bottle of the printing unit through a probe; the main control module 121 is also used to generate a second ink overflow alarm signal according to the second ink overflow probe signal and feed it back to the ink overflow protection module 125, and the ink overflow protection module 125 sends the second ink overflow alarm signal to the printing unit through the probe alarm output port, so that the printing unit performs ink overflow protection according to the second ink overflow alarm signal.

[0059] The embodiment of the present invention adopts a multiple ink overflow protection method, which can not only obtain the first ink overflow probe signal of the ink cartridge, but also obtain the second probe ink overflow signal of the safety bottle and / or the safety bottle trigger signal, thereby achieving more accurate and reliable ink overflow protection.

[0060] The pressure generating unit 110 includes at least two gas paths. In a specific embodiment, the pressure generating unit 110 includes two gas paths, namely a first pressure generating unit 101 and a second pressure generating unit 102; the first pressure generating unit 101 and the second pressure generating unit 102 have the same specifications, and each gas path supports positive and negative pressure switching; the external air port 130 includes a first air outlet 131 and a second air outlet 132, the first pressure generating unit 101 is connected to the first air outlet 131 through an air pipe, and the second pressure generating unit 102 is connected to the second air outlet 132 through an air pipe.

[0061] Taking the first pressure generating unit 101 as an example, the first pressure generating unit 101 includes an air pump 111, an air inlet and outlet solenoid valve 112, a sealing solenoid valve 113 and a first air outlet 131 in the external air port 130 which are sequentially connected through an air pipe.

[0062] The air pump 111 is used to provide positive pressure or negative pressure to the printing unit in a positive pressure air outlet mode or a negative pressure air suction mode according to the pressure control signal.

[0063] The control unit 120 is further used to calculate the target operating parameters of the printing unit through the PID algorithm according to the pressure feedback signal and the ink pressure signal; generate and send the pressure control signal to the pressure generating unit 110 according to the target operating parameters, so that the pressure generating unit 110 provides positive pressure or negative pressure according to the pressure control signal. Specifically, taking the first pressure generating unit 101 as an example, the real-time air pressure of the printing unit is determined according to the pressure feedback signal, the first pressure difference is determined according to the real-time air pressure and the set target pressure value, and the target operating parameters of the printing unit are calculated through the PID algorithm according to the first pressure difference and the ink pressure signal, and the pressure control signal is generated and sent to the first pressure generating unit 101 according to the target operating parameters, so that the first pressure generating unit 101 adjusts the efficiency of the air pump 111 to pump or deliver air in real time according to the pressure control signal; the efficiency of the air pump 111 to pump or deliver air is positively correlated with the size of the first pressure difference.

[0064] The embodiment of the present invention adopts the PID algorithm to adjust the vacuum or air delivery efficiency of the pressure generating unit 110 in real time, and outputs a relatively smooth airflow, which can avoid the generation of high instantaneous pressure during the ink pressing process. In this way, the present application can achieve airbag-like manual extrusion, and when positive pressure is applied, it slowly climbs from low pressure to the set target pressure value and maintains within the vicinity of the set value. For the nozzle of the printing unit, the pressure is gentle, which effectively protects the nozzle from high-pressure damage.

[0065] The inlet and outlet solenoid valve 112 is used to adjust the working mode of the first pressure generating unit 101 to a positive pressure outlet mode or a negative pressure exhaust mode according to the pressure control signal.

[0066] The sealing solenoid valve 113 is used to control the opening and closing of the gas path between the inlet and outlet solenoid valve 112 and the first gas outlet 131 according to the pressure control signal.

[0067] Specifically, the air inlet and outlet solenoid valve 112 includes an air inlet solenoid valve 1121 and an air outlet solenoid valve 1122 connected in parallel, and the air inlet solenoid valve 1121 and the air outlet solenoid valve 1122 are both three-way solenoid valves; the first common port of the air inlet solenoid valve 1121 is connected to the air inlet of the air pump 111, the first normally closed port of the air inlet solenoid valve 1121 is connected to the external atmosphere, and the first normally open port of the air inlet solenoid valve 1121 is connected to the sealing solenoid valve 113; the second common port of the air outlet solenoid valve 1122 is connected to the air outlet of the air pump 111, the second normally closed port of the air outlet solenoid valve 1122 is connected to the sealing solenoid valve 113, and the second normally open port of the air outlet solenoid valve 1122 is connected to the external atmosphere.

[0068] The inlet and outlet solenoid valves 112 are used to adjust the working mode of the first pressure generating unit 101 to the positive pressure outlet mode according to the pressure control signal, specifically including: the inlet solenoid valve 1121 opens the first normally closed port and closes the first normally open port according to the pressure control signal, so that the first normally closed port and the first common port are connected; the outlet solenoid valve 1122 opens the second normally closed port and closes the second normally open port according to the pressure control signal, so that the second common port and the second normally closed port are connected, so as to adjust the working mode of the first pressure generating unit 101 to the positive pressure outlet mode; After the first pressure generating unit 101 is adjusted to the positive pressure air outlet mode, that is, after the action of the air inlet solenoid valve 1121 and the air outlet solenoid valve 1122 is completed, the sealing solenoid valve 113 is opened, and the air pump 111 enters the working state, and the external atmosphere is drawn into the air inlet of the air pump 111 from the first normally closed port, and pumped out from the air outlet, and the air pressure is pumped into the sealing solenoid valve 113 through the second normally closed port, and pumped into the printing unit from the first air outlet 131, thereby providing positive pressure air pressure for the printing unit, and when the measured real-time pressure value reaches the set target pressure value, the air pump 111 stops working.

[0069] The inlet and outlet solenoid valves 112 are used to adjust the working mode of the pressure generating unit 101 to the negative pressure exhaust mode according to the pressure control signal, specifically including: the inlet solenoid valve 1121 is also used to connect the first normally open port and the first common port according to the pressure control signal, and the outlet solenoid valve 1121 is also used to connect the second common port and the second normally open port according to the pressure control signal, so as to adjust the working mode of the pressure generating unit to the negative pressure exhaust mode; when the first pressure generating unit 101 is adjusted to the negative pressure exhaust mode mode, that is, after the air inlet solenoid valve 1121 and the air outlet solenoid valve 1122 are actuated, the sealing solenoid valve 113 is opened, and the air pump 111 enters the working state, and the airflow of the printing unit is drawn out through the first air outlet 131, and is drawn into the air inlet of the air pump 111 through the sealing solenoid valve 113 and the first normally open port, and is pumped out from the air outlet, and the airflow is discharged through the second normally open port, thereby providing negative pressure for the printing unit. When the measured real-time pressure value reaches the set target pressure value, the air pump 111 stops working.

[0070] The sealing solenoid valve 113 further comprises an air leakage hole structure, through which pressure is released when the sealing solenoid valve 113 is opened. The sealing solenoid valve 113 is also used to adjust tiny pressure fluctuations through millisecond-level rapid actions after the air pump 111 stops working.

[0071] The embodiment of the present invention replaces the original gas tank with a pressure generating unit 110, and provides positive pressure or negative pressure for the printing unit by drawing the external atmosphere in or exhausting the airflow of the printing unit to the external atmosphere, which can effectively reduce the space occupied by the system and simplify the machine design.

[0072] Furthermore, the embodiment of the present invention can enable the airless tank positive and negative pressure generating system 100 to provide a stable negative pressure or positive pressure for the printing unit by providing a sealed electromagnetic valve 113 including an air leakage hole structure.

[0073] Furthermore, the embodiment of the present invention adjusts the working mode of the pressure generating unit 110 to a positive pressure exhaust mode or a negative pressure exhaust mode through the mutual cooperation of the air inlet solenoid valve 1121 and the air outlet solenoid valve 1122, and controls the opening and closing of the air path between the air inlet and outlet solenoid valves 112 and the first air outlet 131 through the sealing solenoid valve 113, thereby improving the system's delivery accuracy and efficiency of positive and negative air pressure to the printing unit, so as to provide stable positive and negative air pressure.

[0074] In another embodiment of the present invention, the first normally open port of the air intake solenoid valve 1121 is connected to the sealing solenoid valve 113 , and connected to the first air outlet 131 through the sealing solenoid valve 113 ; the second normally closed port of the air outlet solenoid valve 1122 is directly connected to the first air outlet 131 .

[0075] The inlet and outlet solenoid valves 112 are used to adjust the working mode of the first pressure generating unit 101 to the positive pressure outlet mode according to the pressure control signal, specifically including: the inlet solenoid valve 1121 opens the first normally closed port and closes the first normally open port according to the pressure control signal, so that the first normally closed port and the first common port are connected; the outlet solenoid valve 1122 opens the second normally closed port and closes the second normally open port according to the pressure control signal, so that the second common port and the second normally closed port are connected, so as to adjust the working mode of the first pressure generating unit 101 to the positive pressure outlet mode. The working mode of the first pressure generating unit 101 is adjusted to the positive pressure outlet mode; after the first pressure generating unit 101 is adjusted to the positive pressure outlet mode, the air pump 111 enters the working state, draws the external atmosphere into the air inlet of the air pump 111 from the first normally closed port, and pumps it out from the air outlet, pumps the air pressure into the first air outlet 131 through the second normally closed port, and pumps it into the printing unit from the first air outlet 131, thereby providing positive pressure air pressure for the printing unit, and when the measured real-time pressure value reaches the set target pressure value, the air pump 111 stops working.

[0076] The inlet and outlet solenoid valves 112 are used to adjust the working mode of the pressure generating unit 101 to the negative pressure exhaust mode according to the pressure control signal, specifically including: the inlet solenoid valve 1121 is also used to connect the first normally open port and the first common port according to the pressure control signal, and the outlet solenoid valve 1121 is also used to connect the second common port and the second normally open port according to the pressure control signal, so as to adjust the working mode of the pressure generating unit to the negative pressure exhaust mode; when the first pressure generating unit 101 is adjusted to the negative pressure exhaust mode mode, that is, after the air inlet solenoid valve 1121 and the air outlet solenoid valve 1122 are actuated, the sealing solenoid valve 113 is opened, and the air pump 111 enters the working state, and the airflow of the printing unit is drawn out through the first air outlet 131, and is drawn into the air inlet of the air pump 111 through the sealing solenoid valve 113 and the first normally open port, and is pumped out from the air outlet, and the airflow is discharged through the second normally open port, thereby providing negative pressure for the printing unit. When the measured real-time pressure value reaches the set target pressure value, the air pump 111 stops working.

[0077] In this way, the embodiment of the present invention can not call the sealing solenoid valve 113 when the airless tank positive and negative pressure generating system 100 provides positive pressure air pressure, while not affecting the system air pressure transmission efficiency, and effectively improves the service life of the sealing solenoid valve 113.

[0078] Among them, a backup air pump is provided in each air circuit of the airless tank positive and negative pressure generating system 100. For example, the first pressure generating unit 101 also includes an auxiliary air pump 114 connected in parallel with the air pump 111; the control unit 120 is also used to detect the working status of the first pressure generating unit 101. If it is detected that the air pump 111 fails, the auxiliary air pump 114 is switched to provide positive pressure or negative pressure to the printing unit.

[0079] The embodiment of the present invention can effectively reduce the possibility of failure during use by providing a backup air pump in each air path and automatically switching after a failure is detected. Example

[0080] The embodiment of the present invention provides an inkjet printer, comprising the airless tank positive and negative pressure generating system 100 and a printing unit as described in the first embodiment. The inkjet printer can be applied to industrial printers, UV printers, printing machines, etc. Figure 2 , Figure 2 A structural schematic diagram of a printing unit provided in an embodiment of the present invention is shown, wherein the printing unit 200 includes an air circuit unit 220 and an ink cartridge 230; the airless tank positive and negative pressure generating system 100 is connected to the air circuit unit 220, the air circuit unit 220 is connected to the ink cartridge 230, and the probe 211 is arranged in the air circuit unit of the printing unit 200; one end of the probe 211 is electrically connected to the control unit 120, and the other end of the probe 211 is connected to the ink cartridge 230.

[0081] In which, the printing unit 200 is provided with an air circuit unit 220 and an ink cartridge 230 having the same number of air circuits as the airless tank positive and negative pressure generating system 100, and each air circuit is connected to an air circuit unit 220 and an ink cartridge 230; specifically, when the pressure generating unit 110 includes a first pressure generating unit 101 and a second pressure generating unit 102, the printing unit includes a first air circuit unit and a first ink cartridge connected to the first pressure generating unit 101, and a second air circuit unit and a second ink cartridge connected to the second pressure generating unit 101.

[0082] See also Figure 3 , Figure 3A structural schematic diagram of the air circuit unit provided in an embodiment of the present invention is shown, wherein the air circuit unit 220 includes a three-way solenoid valve 221, a four-way pipe structure 222 and a waste ink barrel 223, the probe includes two probe wires, namely a first probe wire 2221 and a second probe wire 2222; the three-way solenoid valve 221 includes a normally open port 2211, a common port 2212 and a normally closed port 2213; the normally open port 2211 of the three-way solenoid valve 221 is connected to the pressure generating unit 110 through an air pipe; the common port 2212 of the three-way solenoid valve 2221 is connected to the four-way pipe structure 222 through an air pipe; the normally closed port 2213 of the three-way solenoid valve 2221 is connected to the waste ink barrel 223 through an air pipe.

[0083] Among them, the first through tube of the four-way tube structure 222 is connected to the common port 2212 of the three-way solenoid valve 221 through an air pipe, the second through tube of the four-way tube structure 222 is connected to the air port of the ink cartridge 230 or through an air pipe, and the third through tube and the fourth through tube of the four-way tube structure 222 are respectively provided with a probe wire, one end of the two probe wires is electrically connected to the control unit 120, and the other end of the two probe wires passes through the second through tube and is connected to the ink cartridge 230 through the air port.

[0084] One end of the two probe wires is electrically connected to the control unit 120 , specifically, is electrically connected to the control unit 120 via a probe signal input interface in the signal interface 160 .

[0085] Among them, the control unit 120 performs ink overflow protection on the printing unit according to the first ink overflow probe signal. Specifically, when the probe 211 measures that the ink resistivity is less than the preset resistivity, the corresponding first ink overflow probe signal is the first ink overflow alarm signal. The control unit 120 performs ink overflow protection according to the first ink overflow alarm signal, such as timely closing the pressure generating unit 110, etc. The present application does not limit the specific measures of ink overflow protection of the airless tank positive and negative pressure generating unit 100; the control unit 120 is also used to send the first ink overflow alarm signal to the printing unit 200 through the signal interface 160, so that the printing unit 200 performs ink overflow protection according to the first ink overflow alarm signal, for example, the printing unit 200 stops the ink pressing operation according to the first ink overflow alarm signal. The present application does not limit the specific measures of ink overflow protection of the printing unit 200.

[0086] When the probe 211 measures that the ink resistivity is less than the preset resistivity, the corresponding first ink overflow probe signal is the first ink overflow alarm signal. The two probe wires are not connected to each other. When the ink in the ink cartridge 230 does not cover the two probe wires, the resistance measured by the two probe wires is the resistance of air, and its resistivity is insulation, that is, much greater than the preset resistivity; when the ink in the ink cartridge 230 covers the two probe wires, the resistivity measured by the two probe wires is the ink resistivity, and the ink resistivity is usually not more than 20 megohm*m. In this regard, the present application can take the preset resistivity of 20 megohm*m. When the two probe wires measure that the ink resistivity is less than the preset resistivity, it means that the ink has covered the two probe wires at this time, and the corresponding first ink overflow probe signal is the first ink overflow alarm signal.

[0087] The embodiment of the present invention measures the ink resistivity of the ink cartridge 230 in the printing unit 200 by setting a probe in the trachea, and can provide ink overflow detection and protection for the ink cartridge 230 when there is not enough space in the printing unit 200 to set a safety bottle, thereby effectively reducing the space occupied by the system.

[0088] In an alternative approach, see Figure 4 , Figure 4 A schematic structural diagram of a printing unit provided in another embodiment of the present invention is shown, wherein the printing unit 200 further comprises a safety bottle 240 connected to an ink cartridge 230; the second through-tube of the four-way tube structure 222 is connected to a first air port of the safety bottle 240 via an air pipe; the second air port of the safety bottle is connected to the air port of the ink cartridge via an air pipe; the control unit 120 is further used to obtain a safety bottle trigger signal and / or a second ink overflow probe signal of the printing unit 200, and to perform ink overflow protection on the printing unit 200 according to the safety bottle trigger signal and / or the second ink overflow probe signal; the safety bottle trigger signal is a signal generated by performing ink overflow detection on the safety bottle 240 of the printing unit 200; the second ink overflow probe signal is a signal generated by performing ink overflow detection on the safety bottle 240 of the printing unit 200 via a probe 211.

[0089] Among them, the safety bottle 240 also includes a safety bottle float 241 arranged in the safety bottle 240, and the safety bottle float 241 is electrically connected to the signal interface 160 of the control unit 120. Specifically, the safety bottle float 241 is connected to the safety bottle signal input port; the safety bottle float 241 rises or falls with the depth of ink in the safety bottle 240. When the safety bottle float 241 floats to a preset liquid level, the safety bottle trigger signal is generated and transmitted to the ink overflow protection module 125 of the control unit 120.

[0090] The control unit 120 is further configured to generate a safety bottle alarm signal, a first ink overflow alarm signal or a second ink overflow alarm signal according to the safety bottle trigger signal, the first ink overflow probe signal and / or the second ink overflow probe signal, and send the signal to the printing unit 200 .

[0091] The three-way solenoid valve 221 is electrically connected to the signal interface 160 of the airless tank positive and negative pressure generating system 100 . Specifically, the three-way solenoid valve 221 is electrically connected via the safety bottle alarm output port and / or the probe alarm output port.

[0092] In which, the printing unit 200 is also used to control the three-way solenoid valve 221 to close the normally open port 2211 and open the normally closed port 2213 according to the safety bottle trigger signal, the first ink overflow probe signal and / or the second ink overflow probe signal, so as to connect the common port 2212 and the normally closed port 2213, and draw the waste ink into the waste ink barrel 223.

[0093] The printing unit 200 is further configured to stop the ink pressing operation according to the safety bottle alarm signal, the first ink overflow alarm signal or the second ink overflow alarm signal.

[0094] The embodiment of the present invention sets a waste ink barrel 223 in the printing unit 200, and guides the overflowed ink into the waste ink barrel 223 according to the alarm signal, so as to prevent the ink from entering the air path in the negative pressure mode, thereby avoiding the backflow of ink to cause pollution or even damage to the equipment. In this way, the present application can automatically protect the equipment when there is no one to watch over it.

[0095] Among them, the printing unit 200 also includes an alarm, which is electrically connected to the airless tank positive and negative pressure generating system 100 through the signal interface 160. Specifically, the alarm is electrically connected to the safety bottle alarm output port and / or the probe alarm output port. The printing unit 200 is also used to give an alarm prompt through the alarm according to the safety bottle alarm signal, the first ink overflow alarm signal or the second ink overflow alarm signal; preferably, the alarm is an audible and visual alarm.

[0096] Among them, the printing unit 200 is also provided with a button, which is electrically connected to the airless tank positive and negative pressure generating system 100 through the ink pressure port 150, and generates an ink pressure signal by obtaining the user's triggering operation on the button, and sends it to the control unit 120 through the ink pressure port, so that the control unit 120 generates a pressure control signal to the pressure generating unit 110 according to the ink pressure signal and the pressure feedback signal, and the pressure generating unit 110 provides positive pressure air pressure or negative pressure air pressure to the printing unit 200 according to the pressure control signal; the number of the buttons is consistent with the number of interfaces of the ink pressure port 150, for example, when the ink pressure port 150 includes a first ink pressure port 151 and a second ink pressure port 152, the first ink pressure port 151 and the second ink pressure port 152 are each electrically connected to a button.

[0097] Among them, the ink cartridge 230 is a secondary ink cartridge, and the printing unit 200 also includes an ink supply system 250 and a nozzle 260 connected to the ink cartridge 230; the ink supply system 250 is used to provide ink to the ink cartridge 230, and the nozzle 260 is used to spray ink according to the ink in the ink cartridge 230.

[0098] The printing unit 200 further includes a filter 270 connecting the ink cartridge 230 and the nozzle 260 .

[0099] The ink cartridge 230 further includes an ink cartridge float 231 disposed inside the ink cartridge, the ink cartridge float 231 is electrically connected to the ink supply system 250, the ink supply system 250 obtains a float signal through the ink cartridge float, and determines the liquid level of the ink in the ink cartridge 230 according to the float signal.

[0100] The ink supply system 250 is also used to supply ink to the ink cartridge 230 when it is detected that the liquid level of the ink in the ink cartridge 230 is lower than a preset liquid level. Specifically, the ink supply system 250 also includes an ink pump, and the ink supply system 250 controls the ink pump to supply ink to the ink cartridge 230 according to the float signal of the ink cartridge float 231. When the airless tank positive and negative pressure generating system 100 detects that the real-time air pressure of the ink cartridge 230 changes, the air pressure in the ink cartridge 230 is adjusted to the set target air pressure in real time to provide a stable negative pressure air pressure.

[0101] The embodiment of the present invention provides a stable negative pressure, which is delivered to the ink cartridge 230 through a series of protective pipes, thereby ensuring that the ink does not drip by itself during the printing process.

[0102] Furthermore, the embodiment of the present invention sets an ink cartridge float to detect the liquid level of the ink in the ink cartridge 230 in real time. When the ink in the ink cartridge 230 decreases, ink is supplied in real time through the ink supply system 250. When the ink supply causes the negative pressure in the ink cartridge 230 to change, the airless tank positive and negative pressure generating system 100 is used to quickly adjust to the set target negative pressure.

[0103] Furthermore, in the embodiment of the present invention, when ink pressing is required, positive pressure is sent into the ink cartridge 230 , and the target positive pressure is set to ensure that ink can be squeezed out of the nozzle 260 .

[0104] In another embodiment of the present invention, the nozzle 260 is an internal circulation nozzle, which includes an input end, an output end and a printing end; the ink cartridge 230 includes an ink return cartridge and an ink supply cartridge; the ink supply cartridge is connected to the input end, and the ink return cartridge is connected to the output end; due to the air pressure difference between the ink return cartridge and the ink supply cartridge, the ink enters the ink supply cartridge through the ink supply system, enters the ink return cartridge via the internal circulation nozzle, and then returns to the ink supply system to form an ink circulation.

[0105] Among them, the ink return cartridge and the ink supply cartridge are each connected to an air circuit. Specifically, the ink supply cartridge is connected to the first pressure generating unit 101 through the first air outlet 131, and the first pressure generating unit 101 is used to provide a stable positive pressure or negative pressure of air pressure for the ink supply cartridge; the ink return cartridge is connected to the second pressure generating unit 102 through the second air outlet 132, and the second pressure generating unit 102 is used to provide a stable positive pressure or negative pressure of air pressure for the ink return cartridge.

[0106] In an optional manner, the printing unit 200 further includes an ink supply safety bottle connected to the ink supply cartridge, and an ink return safety bottle connected to the ink return cartridge.

[0107] Among them, the feedback module 123 is used to obtain the pressure feedback signal of the printing unit 200; specifically, a first air pressure sensor is arranged in the air circuit connecting the first pressure generating unit 101 and the printing unit 200, and the first air pressure sensor is used to obtain the first real-time air pressure in the ink supply cartridge or the ink supply safety bottle, and generate a first pressure feedback signal; a second air pressure sensor is arranged in the air circuit connecting the second pressure generating unit 102 and the printing unit 200, and the second air pressure sensor is used to obtain the second real-time air pressure in the ink return cartridge or the ink return safety bottle, and generate a second pressure feedback signal; the feedback module 123 is used to obtain the first pressure feedback signal and the second pressure feedback signal.

[0108] Among them, the control unit 120 is also used to obtain the first pressure feedback signal and the second pressure feedback signal according to the feedback module 123, determine the real-time air pressure difference between the first real-time air pressure and the second real-time air pressure, and adjust the circulation speed of ink between the ink supply cartridge and the ink return cartridge by adjusting the real-time air pressure difference.

[0109] Among them, the circulation speed of the ink also determines the printing effect of the internal circulation nozzle. The control unit 120 is also used to control the circulation speed of the ink to adjust the printing effect of the internal circulation nozzle. Specifically, the ink circulation is completed by coarse adjustment so that the circulation speed of the ink reaches within the predetermined range of the expected flow rate, and then the circulation speed of the ink reaches the expected flow rate through fine adjustment.

[0110] The control unit 120 is also used to calculate the target operating parameters of the printing unit 200 through the PID algorithm when inkjet is required; generate and send the pressure control signal to the pressure generating unit 110 according to the target operating parameters, so that the pressure generating unit 110 provides positive pressure or negative pressure according to the pressure control signal. Specifically, the control unit 120 determines the first real-time air pressure, the second real-time air pressure and the real-time air pressure difference according to the first pressure feedback signal and the second pressure feedback signal, and calculates the target operating parameters of the printing unit 200 through the PID algorithm according to the ink pressure signal, the set first target pressure value, the second target pressure value, the target pressure difference value, the real-time pressure difference, the first real-time air pressure, the second real-time air pressure and the real-time air pressure difference, and generates and sends the pressure control signal to the pressure generating unit 110 according to the target operating parameters, so that the first pressure generating unit 101 and the second pressure generating unit 102 respectively adjust the efficiency of air extraction or air delivery in real time according to the pressure control signal to provide a stable positive pressure.

[0111] Preferably, the embodiment of the present invention can use two positive pressures with the same pressure to press ink on the internal circulation nozzle at the same time.

[0112] The embodiment of the present invention uses an internal circulation nozzle and an airless tank positive and negative pressure generating system 100 to circulate ink between the ink supply cartridge, the internal circulation nozzle, the ink return cartridge, and the ink supply system. This can effectively reduce the occurrence of ink condensation and adhesion inside the printing unit 200 and nozzle clogging during the printing process, and is not prone to damage the precision nozzle.

[0113] Furthermore, the embodiment of the present invention adopts a PID algorithm to adjust the air extraction or air delivery efficiency of the pressure generating unit 110 in real time, and outputs a relatively smooth airflow, which can avoid the generation of high instantaneous pressure during the ink pressing process. In this way, the present application can achieve airbag-like manual extrusion, and when positive pressure is applied, it slowly climbs from low pressure to the set target pressure value and maintains within the vicinity of the set value. For the nozzle of the printing unit, the pressure is gentle, which effectively protects the nozzle from high-pressure damage.

[0114] The algorithm or display provided herein is not inherently related to any particular computer, virtual system or other equipment. Various general purpose systems can also be used together with the teachings based on this. According to the above description, it is obvious to construct the structure required for this type of system. In addition, the embodiment of the present invention is not directed to any specific programming language yet. It should be understood that various programming languages ​​can be utilized to realize the content of the present invention described herein, and the description made to specific languages ​​above is for disclosing the best mode of the present invention.

[0115] In the description provided herein, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

[0116] Similarly, it should be understood that in order to streamline the present invention and aid in understanding one or more of the various inventive aspects, in the above description of exemplary embodiments of the present invention, various features of the embodiments of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, this method of disclosure should not be interpreted as reflecting an intention that the claimed invention requires more features than those expressly recited in each claim.

[0117] Those skilled in the art will appreciate that the modules in the devices in the embodiments may be adaptively changed and set in one or more devices different from the embodiments. The modules or units or components in the embodiments may be combined into one module or unit or component, and may be divided into multiple submodules or subunits or subcomponents. All features disclosed in this specification (including the accompanying claims, abstracts and drawings) and all processes or units of any method or device disclosed in this manner may be combined in any combination, except that at least some of such features and / or processes or units are mutually exclusive. Unless otherwise expressly stated, each feature disclosed in this specification (including the accompanying claims, abstracts and drawings) may be replaced by an alternative feature that provides the same, equivalent or similar purpose.

[0118] It should be noted that the above embodiments illustrate the present invention rather than limit it, and that those skilled in the art may devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference symbol between brackets shall not be construed as a limitation on the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "one" or "an" preceding an element does not exclude the presence of a plurality of such elements. The present invention may be implemented by means of hardware comprising a number of different elements and by means of a suitably programmed computer. In a unit claim enumerating a number of devices, several of these devices may be embodied by the same hardware item. The use of the words first, second, and third, etc. does not indicate any order. These words may be interpreted as names. The steps in the above embodiments, unless otherwise specified, should not be understood as limitations on the order of execution.

Claims

1. An airless tank positive and negative pressure generating system applied to the ink circuit of an inkjet printer, characterized in that: The airless tank positive and negative pressure generating system comprises: a control unit and a pressure generating unit; the control unit and the pressure generating unit are connected to an external printing unit; The control unit is used to receive a feedback signal from the printing unit and send a pressure control signal to the pressure generating unit according to the feedback signal; The pressure generating unit is used to provide positive pressure or negative pressure to the printing unit according to the pressure control signal; the pressure generating unit comprises an air pump, an air inlet and outlet solenoid valve, a sealing solenoid valve and an external air port which are connected in sequence through an air pipe; the air pump is used to provide positive pressure or negative pressure to the printing unit in a positive pressure outlet mode or a negative pressure exhaust mode according to the pressure control signal; the air inlet and outlet solenoid valve is used to adjust the working mode of the pressure generating unit to a positive pressure outlet mode or a negative pressure exhaust mode according to the pressure control signal; the sealing solenoid valve is used to control the opening and closing of the air path between the air inlet and outlet solenoid valve and the external air port according to the pressure control signal; the pressure generating unit is connected to the printing unit through the external air port; The control unit is further used to obtain a first ink overflow probe signal of the printing unit, and perform ink overflow protection on the printing unit according to the first ink overflow probe signal; the first ink overflow probe signal is a signal generated by performing ink overflow detection on the ink cartridge of the printing unit through a probe; The printing unit further comprises a safety bottle connected to the ink cartridge, the control unit is further used to obtain a safety bottle trigger signal and / or a second ink overflow probe signal of the printing unit, and perform ink overflow protection on the printing unit according to the safety bottle trigger signal and / or the second ink overflow probe signal; the safety bottle trigger signal is a signal generated by performing ink overflow detection on the safety bottle of the printing unit; the second ink overflow probe signal is a signal generated by performing ink overflow detection on the safety bottle of the printing unit through a probe; the printing unit comprises an air circuit unit and an ink cartridge; The air circuit unit includes a three-way solenoid valve, a four-way pipe structure and a waste ink barrel, and the probe includes two probe wires; the normally open port of the three-way solenoid valve is connected to the pressure generating unit through an air pipe; the common port of the three-way solenoid valve is connected to the four-way pipe structure through an air pipe; the first through pipe of the four-way pipe structure is connected to the common port of the three-way solenoid valve through an air pipe, and the second through pipe of the four-way pipe structure is connected to the air port of the ink cartridge through an air pipe; the third through pipe and the fourth through pipe of the four-way pipe structure are respectively provided with one probe wire, one end of the two probe wires is electrically connected to the control unit, and the other ends of the two probe wires pass through the second through pipe and are connected to the ink cartridge through the air port; the normally closed port of the three-way solenoid valve is connected to the waste ink barrel through an air pipe.

2. The airless tank positive and negative pressure generating system according to claim 1, characterized in that: The air inlet and outlet solenoid valves include an air inlet solenoid valve and an air outlet solenoid valve connected in parallel, and both the air inlet solenoid valve and the air outlet solenoid valve are three-way solenoid valves; The first common port of the air intake solenoid valve is connected to the air inlet of the air pump, the first normally closed port of the air intake solenoid valve is connected to the external atmosphere, and the first normally open port of the air intake solenoid valve is connected to the sealing solenoid valve; The second common port of the air outlet solenoid valve is connected to the air outlet of the air pump, the second normally closed port of the air outlet solenoid valve is connected to the sealing solenoid valve, and the second normally open port of the air outlet solenoid valve is connected to the external atmosphere; The air inlet solenoid valve is used to open the first normally closed port and close the first normally open port according to the pressure control signal, so that the first normally closed port and the first common port are connected; the air outlet solenoid valve is used to open the second normally closed port and close the second normally open port according to the pressure control signal, so that the second common port and the second normally closed port are connected, so as to adjust the working mode of the pressure generating unit to the positive pressure air outlet mode; The air intake solenoid valve is also used to connect the first normal opening and the first common port according to the pressure control signal, and the air outlet solenoid valve is also used to connect the second common port and the second normal opening according to the pressure control signal, so as to adjust the working mode of the pressure generating unit to the negative pressure exhaust mode.

3. The airless tank positive and negative pressure generating system according to claim 1, characterized in that: The pressure generating unit further comprises a secondary air pump connected in parallel with the air pump; The control unit is also used to detect the working state of the pressure generating unit. If it is detected that the air pump fails, the auxiliary air pump is switched to provide positive pressure or negative pressure to the printing unit.

4. The airless tank positive and negative pressure generating system according to claim 1, characterized in that: The control unit is further used to calculate the target operating parameters of the printing unit through a PID algorithm according to the feedback signal; The pressure control signal is generated according to the target operating parameter and sent to the pressure generating unit, so that the pressure generating unit provides positive pressure or negative pressure according to the pressure control signal.

5. A printing machine, characterized in that: It comprises a printing unit and an airless tank positive and negative pressure generating system as described in any one of claims 1 to 4, wherein the printing unit comprises an air circuit unit and an ink cartridge; the airless tank positive and negative pressure generating system is connected to the air circuit unit, the air circuit unit is connected to the ink cartridge, and the probe is arranged in the air circuit unit of the printing unit; one end of the probe is electrically connected to the control unit, and the other end of the probe is connected to the ink cartridge.

6. The inkjet printer according to claim 5, characterized in that: The printing unit also includes a safety bottle connected to the ink cartridge; The second through-tube of the four-way tube structure is connected to the first gas port of the safety bottle through an air pipe; The second air port of the safety bottle is connected to the air port of the ink cartridge through an air pipe.

7. The inkjet printer according to claim 5, characterized in that: The printing unit also includes an ink supply system and a nozzle connected to the ink cartridge; The ink supply system is used to provide ink to the ink cartridge, and the nozzle is used to spray ink according to the ink in the ink cartridge.

8. The inkjet printer according to claim 7, characterized in that: The nozzle is an internal circulation nozzle, and the internal circulation nozzle includes an input end, an output end and a printing end; the ink cartridge includes an ink return cartridge and an ink supply cartridge; The ink supply cartridge is connected to the input end, and the ink return cartridge is connected to the output end; The ink enters the ink supply cartridge through the ink supply system, enters the ink return cartridge via the internal circulation nozzle, and then returns to the ink supply system, thus forming an ink circulation.

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