Liquid circulation device and liquid ejection device

Abstract

A liquid circulation device and a liquid ejection device, which effectively detect that a liquid ejection head is filled with liquid. According to an embodiment, the circulation device includes a pressure pump, a pressure reducing pump, a buffer tank, a sensor, and a processor. The pressure pump supplies liquid from a tank to the liquid ejection head. The pressure reducing pump recovers the liquid from the liquid ejection head. The buffer tank is connected in parallel with the liquid ejection head between the pressure pump and the pressure reducing pump, and stores the liquid. The sensor detects the pressure of the buffer tank. The processor determines whether the pressure chamber of the liquid ejection head is filled with the liquid based on the detected pressure.

Description

Technical Field

[0001] Embodiments of the present invention relate to a liquid circulation device and a liquid ejection device. Background Art

[0002] There is known a liquid ejection device including: a liquid ejection head (inkjet head) for ejecting liquid (ink); and a liquid circulation device for circulating the liquid in a circulation path including the liquid ejection head.

[0003] The liquid circulation device is provided with a liquid detection sensor at a specific position of the flow path in order to detect the filling state of the liquid in the liquid ejection head. For example, the liquid detection sensor is a capacitance type or a floating type sensor.

[0004] However, the electrostatic capacitance type liquid detection sensor is large in size, so the installation place is limited. In addition, the floating type liquid detection sensor may have a movable part fixed by the liquid, and the reliability is low. Summary of the invention

[0005] In order to solve the above-mentioned problems, a liquid circulation device and a liquid ejection device are provided which can effectively detect that a liquid ejection head is filled with liquid.

[0006] According to an embodiment, a liquid circulation device is characterized in that it comprises: a pressure pump that supplies liquid from a tank to a liquid ejection head; a pressure reduction pump that recovers the liquid from the liquid ejection head; a buffer tank that is connected in parallel with the liquid ejection head between the pressure pump and the pressure reduction pump and stores the liquid; a sensor that detects the pressure of the buffer tank; and a processor that determines whether a pressure chamber of the liquid ejection head is filled with the liquid based on the detected pressure.

[0007] According to an embodiment, a liquid ejection device is characterized in that it comprises: a liquid ejection head having a pressure chamber; a pressure increasing pump that supplies liquid from a tank to the liquid ejection head; a pressure reducing pump that recovers the liquid from the liquid ejection head; a buffer tank that is connected in parallel with the liquid ejection head between the pressure increasing pump and the pressure reducing pump and stores the liquid; a sensor that detects the pressure of the buffer tank; and a processor that determines whether the pressure chamber is filled with the liquid based on the detected pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is an explanatory diagram of a configuration example of an inkjet recording device according to an embodiment.

[0009] Figure 2 It is an explanatory diagram of a configuration example of a liquid ejecting device according to an embodiment.

[0010] Figure 3It is an explanatory diagram of a structural example of a liquid ejection head according to an embodiment.

[0011] Figure 4 It is an explanatory diagram of a configuration example of a piezoelectric pump according to an embodiment.

[0012] Figure 5 It is an explanatory diagram of a configuration example of a module control unit according to an embodiment.

[0013] Figure 6 It is a graph showing the pressure in the buffer tank according to the embodiment.

[0014] Figure 7 This is a flowchart for explaining an operation example of the circulation device according to the embodiment.

[0015] Figure 8 This is a flowchart for explaining an operation example of the circulation device according to the embodiment.

[0016] Fig. 9 This is a flowchart for explaining an operation example of the circulation device according to the embodiment.

[0017] Fig.10 This is a flowchart for explaining an operation example of the circulation device according to the embodiment.

[0018] Description of Reference Numerals

[0019] 1… inkjet recording device; 10… liquid ejection device; 11… head support mechanism; 12… medium support mechanism; 13… host control device; 20… liquid ejection head; 20a… supply port; 20b… recovery port; 21… nozzle plate; 21a… nozzle hole; 22… substrate; 23… manifold; 24… actuator; 24a… electrode; 24b… electrode; 25… ink pressure chamber; 28… ink flow path; 30… circulation device; 31… circulation path; 31a… first flow path; 31b… second flow path; 31c… third flow path; 31d… fourth flow path; 33… first Circulation pump; 34…bypass flow path; 34a…first bypass flow path; 34b…second bypass flow path; 35…buffer tank; 35a…accommodation chamber; 36…second circulation pump; 37…opening and closing valve; 38…module control unit; 39…pressure sensor; 51…ink cartridge; 58…pump chamber; 59…piezoelectric actuator; 60…piezoelectric pump; 61…check valve; 62…check valve; 71…processor; 72…memory; 72a…ROM; 72b…RAM; 73…communication interface; 74…circulation pump drive circuit; 76…valve drive circuit; 77…liquid ejection head drive circuit. DETAILED DESCRIPTION

[0020] Hereinafter, a liquid circulation device and a liquid discharge device according to embodiments will be described with reference to the drawings.

[0021] Below, refer to Figure 1 to Figure 7 The following describes a liquid ejection device 10 according to the embodiment and an inkjet recording device 1 including the liquid ejection device 10. In each drawing, the structure is appropriately enlarged, reduced, or omitted for the purpose of explanation. Figure 1 It is a side view showing the structure of the inkjet recording device 1 . Figure 2 It is an explanatory diagram showing the structure of the liquid ejecting device 10. Figure 3 It is an explanatory diagram showing the structure of the liquid ejecting head 20. Figure 4 It is an explanatory diagram showing the structure of the first circulation pump 33 and the second circulation pump 36 .

[0022] Figure 1 The illustrated inkjet recording apparatus 1 includes: a plurality of liquid ejecting devices 10 ; a head support mechanism 11 that movably supports the liquid ejecting devices 10 ; a medium support mechanism 12 that movably supports a recording medium S; and a host control device 13 .

[0023] like Figure 1 As shown, a plurality of liquid ejection devices 10 are arranged in parallel in a predetermined direction and supported by a head support mechanism 11. The liquid ejection device 10 integrally includes a liquid ejection head 20 and a circulation device 30. The liquid ejection device 10 ejects, for example, ink as a liquid from the liquid ejection head 20 to form a desired image on a recording medium S disposed opposite thereto.

[0024] The plurality of liquid ejection devices 10 eject a plurality of colors, such as cyan ink, magenta ink, yellow ink, black ink, and white ink, respectively, but the color or characteristics of the ink used are not limited. For example, instead of white ink, transparent glossy ink or special ink that develops color when irradiated with infrared or ultraviolet rays can be ejected. The plurality of liquid ejection devices 10 use different inks, but have the same structure.

[0025] First, the liquid ejection head 20 will be described.

[0026] Figure 3 The liquid ejection head 20 shown is an inkjet head and includes: a supply port 20 a for ink to flow in; a recovery port 20 b for ink to flow out; a nozzle plate 21 having a plurality of nozzle holes 21 a; a substrate 22; and a manifold 23 joined to the substrate 22.

[0027] The substrate 22 is bonded to the nozzle plate 21 and is configured to have a predetermined shape so as to form a predetermined ink flow path 28 including a plurality of ink pressure chambers 25 between the substrate 22 and the nozzle plate 21. The substrate 22 includes partition walls disposed between the plurality of ink pressure chambers 25 in the same row. An actuator 24 including an electrode 24a and an electrode 24b is provided at a portion of the substrate 22 facing each ink pressure chamber 25.

[0028] The actuator 24 is disposed opposite to the nozzle hole 21a, and an ink pressure chamber 25 is formed between the actuator 24 and the nozzle hole 21a. The actuator 24 is connected to a driving circuit. The liquid ejection head 20 causes the actuator 24 to deform according to a voltage under the control of the module control unit 38, thereby ejecting liquid from the oppositely disposed nozzle hole 21a.

[0029] Next, the circulation device 30 (liquid circulation device) will be described.

[0030] like Figure 2 As shown, the circulation device 30 is integrally connected to the upper part of the liquid ejection head 20 through a metal connecting member. The circulation device 30 includes a predetermined circulation path 31 that passes through the liquid ejection head 20 and is configured to circulate the liquid, a first circulation pump 33, a bypass flow path 34, a buffer tank 35, a second circulation pump 36, an on-off valve 37, and a module control unit 38 that controls the liquid ejection action.

[0031] Furthermore, the circulation device 30 includes an ink cartridge 51 which is an ink supply tank (liquid supply tank) provided outside the circulation path 31 .

[0032] The ink cartridge 51 is configured to hold ink, and an air chamber inside the ink cartridge 51 is open to the atmosphere.

[0033] First, the circulation path 31 will be described.

[0034] The circulation path 31 includes a first flow path 31a, a second flow path 31b, a third flow path 31c, and a fourth flow path 31d. The first flow path 31a connects the ink cartridge 51, which is an ink supply tank, to the first circulation pump 33. The second flow path 31b connects the first circulation pump 33 to the supply port 20a of the liquid ejection head 20. The third flow path 31c connects the recovery port 20b of the liquid ejection head 20 to the second circulation pump 36. The fourth flow path 31d connects the second circulation pump 36 to the ink cartridge 51. The first flow path 31a and the fourth flow path 31d include a pipe made of a metal or resin material and a tube covering the outer surface of the pipe. The tube covering the outer surface of the pipe of the first flow path 31a and the fourth flow path 31d is, for example, a PTFE tube.

[0035] The ink circulating in the circulation path 31 reaches the liquid ejection head 20 from the ink cartridge 51 through the first flow path 31a, the first circulation pump 33, the second flow path 31b, and the supply port 20a of the liquid ejection head 20. In addition, the ink circulating in the circulation path 31 reaches the ink cartridge 51 from the liquid ejection head 20 through the recovery port 20b of the liquid ejection head 20, the third flow path 31c, the second circulation pump 36, and the fourth flow path 31d.

[0036] Next, the first circulation pump 33 and the second circulation pump 36 will be described.

[0037] The first circulation pump 33 is a pump for delivering liquid. The first circulation pump 33 delivers liquid from the first flow path 31a to the second flow path 31b. That is, the first circulation pump 33 is a pressure pump that sucks up ink from the ink cartridge 51 as an ink supply tank through the action of the actuator and supplies it to the liquid ejection head 20.

[0038] The second circulation pump 36 is a pump that delivers liquid. The second circulation pump 36 delivers liquid from the third flow path 31c toward the fourth flow path 31d. That is, the second circulation pump 36 is a pressure-reducing pump that collects ink from the liquid ejection head 20 and supplies it to the ink cartridge 51 by the operation of the actuator.

[0039] The first circulation pump 33 and the second circulation pump 36 are, for example, Figure 4 The piezoelectric pump 60 is configured as shown in FIG. The piezoelectric pump 60 includes: a pump chamber 58; a piezoelectric actuator 59 provided in the pump chamber 58 and vibrated by a voltage; and check valves 61 and 62 provided at the inlet and outlet of the pump chamber 58. The piezoelectric actuator 59 is configured to be able to vibrate at a frequency of, for example, about 50 Hz to 200 Hz. The first circulation pump 33 and the second circulation pump 36 are connected to the drive circuit by wiring, and are configured to be controllable by the control of the module control unit 38.

[0040] For example, the voltage applied to the piezoelectric actuator 59 changes, thereby Figure 4 As shown above and below, the piezoelectric actuator 59 is deformed in a direction to contract the pump chamber 58 or in a direction to expand the pump chamber 58. As a result, the volume of the pump chamber 58 changes. For example, when the piezoelectric actuator 59 is deformed in a direction to expand the pump chamber 58, the check valve 61 at the inlet of the pump chamber 58 opens, and ink is introduced into the pump chamber 58. In addition, for example, when the piezoelectric actuator 59 is deformed in a direction to contract the pump chamber 58, the check valve 62 at the outlet of the pump chamber 58 opens, and the ink in the pump chamber 58 is sent to the other side. By repeating this action, the first circulating pump 33 and the second circulating pump 36 each introduce ink from one side and send ink from the other side.

[0041] In addition, the maximum change amount of the piezoelectric actuator 59 corresponds to the voltage applied to the piezoelectric actuator 59. If the voltage applied to the piezoelectric actuator 59 increases, the maximum change amount of the piezoelectric actuator 59 increases. In addition, if the voltage applied to the piezoelectric actuator 59 decreases, the maximum change amount of the piezoelectric actuator 59 decreases. In addition, the infusion capacity of the piezoelectric pump 60 corresponds to the maximum change amount of the piezoelectric actuator 59. That is, the module control unit 38 controls the infusion capacity of the piezoelectric pump 60 by controlling the voltage applied to the piezoelectric actuator 59.

[0042] Next, the bypass flow path 34 and the buffer tank 35 will be described.

[0043] The bypass flow path 34 connects the second flow path 31b and the third flow path 31c. The bypass flow path 34 short-circuits the supply port 20a on the primary side of the liquid ejection head 20 and the recovery port 20b on the secondary side of the liquid ejection head 20 in the circulation path 31 without passing through the liquid ejection head 20.

[0044] The buffer tank 35 is connected to the bypass flow path 34. Specifically, the bypass flow path 34 includes: a first bypass flow path 34a connecting a predetermined portion of a pair of side walls of the buffer tank 35 to the second flow path 31b; and a second bypass flow path 34b connecting a predetermined portion of a pair of side walls of the buffer tank 35 to the third flow path 31c.

[0045] For example, the first bypass flow path 34a and the second bypass flow path 34b have the same length and the same diameter, and are both configured to be smaller than the diameter of the circulation path 31. For example, the diameter of the circulation path 31 is set to be about 2 to 5 times the diameter of the first bypass flow path 34a and the second bypass flow path 34b. The first bypass flow path 34a and the second bypass flow path 34b are set so that the distance between the connection position where the second flow path 31b and the first bypass flow path 34a are connected and the supply port 20a of the liquid ejection head 20 is equal to the distance between the connection position where the third flow path 31c and the second bypass flow path 34b are connected and the recovery port 20b of the liquid ejection head 20.

[0046] The buffer tank 35 is connected in parallel with the liquid ejection head 20 between the first circulation pump 33 and the second circulation pump 36. The buffer tank 35 has a flow path cross-sectional area larger than the flow path cross-sectional area of ​​the bypass flow path 34, and is configured to be able to store liquid. The buffer tank 35, for example, has an upper wall, a lower wall, a rear wall, a front wall, and a pair of left and right side walls, and is configured to be a rectangular box-shaped containing chamber 35a for storing liquid inside. The connection position where the first bypass flow path 34a is connected to the buffer tank 35 and the connection position where the second bypass flow path 34b is connected to the buffer tank 35 are set to the same height. The ink flowing in the bypass flow path 34 is arranged in the lower area of ​​the containing chamber 35a in the buffer tank 35, and an air chamber is formed in the upper area of ​​the containing chamber 35a. That is, the buffer tank 35 can store a predetermined amount of liquid and air. In addition, the buffer tank 35 is provided with an on-off valve 37 and a pressure sensor 39 configured to open the air chamber in the buffer tank 35 to the atmosphere.

[0047] The on-off valve 37 is a normally closed solenoid on-off valve that opens when the power is turned on and closes when the power is turned off. The on-off valve 37 is controlled by the module control unit 38 to open and close the air chamber of the buffer tank 35 to the atmosphere.

[0048] The pressure sensor 39 detects the pressure of the air chamber in the buffer tank 35, and transmits pressure data indicating the value of the pressure to the module control unit 38. When the on-off valve 37 is open and the air chamber of the buffer tank 35 is open to the atmosphere, the pressure data detected by the pressure sensor 39 becomes a value equal to the atmospheric pressure. The pressure sensor 39 detects the pressure of the air chamber of the buffer tank 35 when the on-off valve 37 is closed and the air chamber of the buffer tank 35 is not open to the atmosphere.

[0049] The pressure sensor 39 outputs pressure as an electrical signal using, for example, a semiconductor piezoresistive pressure sensor. The semiconductor piezoresistive pressure sensor includes: a diaphragm that receives pressure from the outside; and a semiconductor strain gauge formed on the surface of the diaphragm. The semiconductor piezoresistive pressure sensor detects pressure by converting a change in resistance caused by a piezoresistive effect in the strain gauge due to deformation of the diaphragm caused by the external pressure into an electrical signal.

[0050] Next, the module control unit 38 will be described.

[0051] Figure 5 It is an explanatory diagram for explaining a configuration example of the module control unit 38 .

[0052] The module control unit 38 controls the operation of the liquid ejection head 20, the first circulation pump 33, the second circulation pump 36 and the opening and closing valve 37. The module control unit 38 includes a processor 71, a memory 72, a communication interface 73, a circulation pump drive circuit 74, a valve drive circuit 76 and a liquid ejection head drive circuit 77.

[0053] The processor 71 is a computing element (for example, a CPU (Central Processing Unit)) that performs arithmetic processing. The processor 71 performs various processes based on data such as programs stored in the memory 72. The processor 71 functions as a control circuit capable of performing various controls by executing the programs stored in the memory 72.

[0054] The memory 72 is a storage device that stores various information and includes, for example, a ROM (Read Only Memory) 72a and a RAM (Random Access Memory) 72b.

[0055] ROM72a is a non-volatile memory dedicated to readout. ROM72a stores programs and data used in the programs, etc. For example, ROM72a stores various set values ​​such as a calculation formula for calculating the ink pressure of the nozzle hole 21a, a target pressure range, and the maximum adjustment value of each pump as control data for pressure control.

[0056] The RAM 72 b is a volatile memory that functions as a working memory. The RAM 72 b temporarily stores data being processed by the processor 71 , etc. The RAM 72 b also temporarily stores a program that the processor 71 executes.

[0057] The communication interface 73 is an interface for communicating with other devices. For example, the communication interface 73 relays communication with the host control device 13 that transmits print data to the liquid ejection device 10 .

[0058] The circulation pump driving circuit 74 applies a driving voltage to the piezoelectric actuator 59 of the piezoelectric pump 60 based on the control of the processor 71, and drives the piezoelectric pump 60. Thus, the circulation pump driving circuit 74 circulates the ink in the circulation path 31. The circulation pump driving circuit 74 is provided for each circulation pump. The circulation pump driving circuit 74 connected to the first circulation pump 33 applies a driving voltage to the piezoelectric actuator 59 of the first circulation pump 33. The circulation pump driving circuit 74 connected to the second circulation pump 36 applies a driving voltage to the piezoelectric actuator 59 of the second circulation pump 36.

[0059] The valve driving circuit 76 drives the on-off valve 37 based on the control of the processor 71 to open the air chamber of the buffer tank 35 to the atmosphere.

[0060] The liquid ejection head driving circuit 77 applies a voltage to the actuator 24 of the liquid ejection head 20 based on the control of the processor 71 to drive the liquid ejection head 20 and eject ink from the nozzle holes 21 a of the liquid ejection head 20 .

[0061] In the above configuration, the processor 71 communicates with the host control device 13 using the communication interface 73 to receive various information such as operating conditions. The various information acquired by the processor 71 is transmitted to the host control device 13 of the inkjet recording apparatus 1 through the communication interface 73 .

[0062] In addition, the processor 71 obtains the detection result from the pressure sensor 39, and based on the obtained detection result, controls the operation of the circulation pump drive circuit 74 and the valve drive circuit 76. For example, the processor 71 controls the circulation pump drive circuit 74 based on the detection result of the pressure sensor 39, thereby controlling the liquid delivery capacity of the first circulation pump 33 and the second circulation pump 36. Thus, the processor 71 adjusts the ink pressure of the nozzle hole 21a.

[0063] In addition, the processor 71 opens and closes the on-off valve 37 by controlling the valve drive circuit 76. Thus, the processor 71 adjusts the liquid level of the buffer tank 35.

[0064] In addition, the processor 71 obtains the detection result from the pressure sensor 39, and controls the liquid ejection head driving circuit 77 based on the obtained detection result, thereby ejecting ink drops from the nozzle hole 21a of the liquid ejection head 20 to the recording medium. Specifically, the processor 71 inputs an image signal corresponding to the image data to the liquid ejection head driving circuit 77. The liquid ejection head driving circuit 77 drives the actuator 24 of the liquid ejection head 20 corresponding to the image signal. When the liquid ejection head driving circuit 77 drives the actuator 24 of the liquid ejection head 20, the actuator 24 is deformed, and the ink pressure (nozzle surface pressure) of the nozzle hole 21a at the position opposite to the actuator 24 changes. The nozzle surface pressure is the pressure given by the ink in the ink pressure chamber 25 to the curved liquid surface Me formed by the ink in the nozzle hole 21a. When the nozzle surface pressure exceeds a predetermined value specified according to the shape of the nozzle hole 21a and the characteristics of the ink, ink is ejected from the nozzle hole 21a. Thus, the processor 71 forms an image corresponding to the image data on the recording medium.

[0065] Next, the pressure in the buffer tank 35 will be described.

[0066] Here, a description will be given of a change in the pressure in the buffer tank 35 during a period from when the ink pressure chamber 25 is empty to when it is filled with ink.

[0067] Figure 6: is a graph for explaining the change in pressure in the buffer tank 35 during the period from when the ink pressure chamber 25 is empty to when it is filled with ink. Figure 6 Indicates changes in pressure detected by the pressure sensor 39 . Figure 6 In FIG. 1 , the horizontal axis represents time, and the vertical axis represents the pressure in the buffer tank 35 .

[0068] exist Figure 6 In the example shown, at time T1, the liquid ejection head 20 and the circulation path 31 are not filled with ink. In addition, the on-off valve 37 is closed. In addition, the pressure in the buffer tank 35 at time T1 is "0 kPa".

[0069] At time T1 , the processor 71 starts circulation of ink from the ink cartridge 51 using the first circulation pump 33 and the second circulation pump 36 .

[0070] When the ink starts to be supplied from the ink cartridge 51, the pressure in the buffer tank 35 decreases. The pressure in the buffer tank 35 continues to decrease until the ink flows into the first flow path 31a and the second flow path 31b, and flows into the ink pressure chamber 25 of the liquid ejection head 20, the first bypass flow path 34a, and the buffer tank 35. Here, at time T2, the plurality of nozzle holes 21a are clogged with ink, and ink starts to flow into the buffer tank 35. That is, the pressure in the buffer tank 35 is minimum at time T2.

[0071] When the plurality of nozzle holes 21a are clogged with ink or ink flows into the buffer tank 35, the pressure in the buffer tank 35 increases. The pressure in the buffer tank 35 continues to increase until the ink reaches the second circulation pump 36. Here, at time T3, the ink reaches the second circulation pump 36. That is, the pressure in the buffer tank 35 reaches a peak at time T3.

[0072] When the ink reaches the second circulation pump 36, the pressure in the buffer tank 35 decreases again. Thereafter, the bubbles in the ink pressure chamber 25 and the circulation path 31 are discharged, and the liquid level in the buffer tank 35 stabilizes. When the liquid level in the buffer tank 35 stabilizes, the pressure in the buffer tank 35 also stabilizes. Here, at time T4, the pressure in the buffer tank 35 stabilizes. That is, near time T4, the change in the pressure in the buffer tank 35 becomes small.

[0073] Furthermore, at time T4 , the ink pressure chamber 25 is filled with ink.

[0074] Next, the functions realized by the circulator 30 will be described. The functions realized by the circulator 30 are realized by the processor 71 executing a program stored in the memory 72 or the like.

[0075] The processor 71 has a function of determining whether or not the ink pressure chamber 25 is filled with ink based on the pressure in the buffer tank 35 .

[0076] The processor 71 acquires the pressure in the buffer tank 35 in a time series. The processor 71 determines whether the ink pressure chamber 25 is filled with ink based on the pressure acquired in a time series.

[0077] That is, the processor 71 detects that the pressure in the buffer tank 35 reaches the lower limit (lower limit pressure) (corresponding to time T2), then reaches the upper limit (upper limit pressure) (corresponding to time T3), and then stabilizes (corresponding to time T4).

[0078] First, the processor 71 detects that the pressure in the buffer tank 35 has reached the lower limit pressure.

[0079] For example, the processor 71 receives a control signal for starting the circulation of ink from the host control device 13 via the communication interface 73 . Upon receiving the control signal, the processor 71 starts the circulation of ink from the ink cartridge 51 using the first circulation pump 33 and the second circulation pump 36 .

[0080] When the circulation of the ink starts, the processor 71 causes the pressure sensor 39 to detect the pressure in the buffer tank 35. In addition, here, the on-off valve 37 is closed.

[0081] The processor 71 continues to acquire pressure data indicating the value of pressure from the pressure sensor 39. In addition, the processor 71 sets a variable (P_min_temp) storing the minimum value of pressure. Here, the processor 71 substitutes an initial value (eg, 500 Pa) into P_min_temp.

[0082] When the pressure (P) detected by the pressure sensor 39 is less than P_min_temp, the processor 71 substitutes P into P_min_temp. When P_min_temp is not updated for a predetermined period (e.g., 2 seconds) (i.e., when P is greater than P_min_temp), the processor 71 determines that the pressure in the buffer tank 35 has reached the lower limit (lower limit pressure).

[0083] If it is determined that the pressure in the buffer tank 35 has reached the lower limit (lower limit pressure), the processor 71 substitutes P_min_temp into the variable (P_min) storing the lower limit pressure. If P_min_temp is substituted into P_min, the processor 71 sets a flag indicating that the pressure in the buffer tank 35 has reached the lower limit pressure.

[0084] Next, the processor 71 detects that the pressure in the buffer tank 35 has reached the upper limit pressure.

[0085] When the flag indicating that the lower limit pressure is detected is set, the processor 71 sets a variable (P_max_temp) storing the maximum value of the pressure. Here, the processor 71 substitutes P_min as an initial value in P_max_temp.

[0086] When the pressure (P) detected by the pressure sensor 39 is greater than P_max_temp, the processor 71 substitutes P into P_max_temp. When P_max_temp is not updated for a predetermined period (eg, 2 seconds) (ie, when P is equal to or less than uP_max_temp), the processor 71 calculates the difference between P_max_temp and P_min.

[0087] If the difference is calculated, the processor 71 determines whether the calculated difference is greater than a predetermined threshold value (eg, 2 kPa). If the calculated difference is determined to be greater than the predetermined threshold value, the processor 71 determines that the pressure in the buffer tank 35 has reached the upper limit (upper limit pressure).

[0088] If it is determined that the pressure in the buffer tank 35 has reached the upper limit (upper limit pressure), the processor 71 substitutes P_max_temp into the variable (P_max) storing the upper limit pressure. If P_max_temp is substituted into P_max, the processor 71 sets a flag indicating that the pressure in the buffer tank 35 has reached the upper limit pressure.

[0089] If it is determined that the calculated difference is less than or equal to the predetermined threshold, the processor 71 returns to the operation of determining whether the pressure (P) detected by the pressure sensor 39 is greater than P_max_temp.

[0090] Next, the processor 71 detects whether the pressure in the buffer tank 35 is stable.

[0091] If the flag indicating that the upper limit pressure is detected is set, the processor 71 sets a counter (count_stb) that counts the number of times the dispersion of the pressure is below a predetermined threshold (eg, 40).

[0092] When the counter is set, the processor 71 calculates the dispersion of the pressure (σm). Here, the processor 71 acquires the pressure every 50 ms in the past 2.5 seconds and calculates the dispersion of the acquired pressure.

[0093] When σm is calculated, the processor 71 determines whether σm is smaller than a predetermined threshold value (eg, 40). If it is determined that σm is smaller than the predetermined threshold value, the processor 71 increments count_stb (adds 1 to count_stb).

[0094] The processor 71 repeats the above operation for a predetermined period (e.g., 10 seconds). When the predetermined period has passed, the processor 71 determines whether count_stb exceeds a predetermined threshold value (e.g., 180). If it is determined that count_stb exceeds the predetermined threshold value, the processor 71 determines that the pressure is stable and sets a flag indicating that the pressure in the buffer tank 35 is stable.

[0095] If it is determined that count_stb is less than the predetermined threshold, the processor 71 returns to the operation of calculating the pressure dispersion again.

[0096] If a flag indicating that the pressure in the buffer tank 35 is stable is set, the processor 71 determines that the ink pressure chamber 25 is filled with ink. For example, if it is determined that the ink pressure chamber 25 is filled with ink, the processor 71 sends a control signal indicating that the ink pressure chamber 25 is filled with ink to the host control device 13 through the communication interface 73.

[0097] Next, an operation example of the processor 71 will be described.

[0098] Figure 7 This is a flowchart for explaining an example of the operation of the processor 71 .

[0099] First, the processor 71 starts circulation of ink from the ink cartridge 51 using the first circulation pump 33 and the second circulation pump 36 (ACT 11). When the circulation of ink starts, the processor 71 detects that the pressure in the buffer tank 35 reaches the lower limit pressure (ACT 12).

[0100] If the pressure in the buffer tank 35 reaches the lower limit pressure, the processor 71 detects that the pressure in the buffer tank 35 reaches the upper limit pressure (ACT 13). If the pressure in the buffer tank 35 reaches the upper limit pressure, the processor 71 detects that the pressure in the buffer tank 35 is stable (ACT 14).

[0101] When it is detected that the pressure in the buffer tank 35 is stable, the processor 71 determines that the ink pressure chamber 25 is filled with ink (ACT 15 ). When it is determined that the ink pressure chamber 25 is filled with ink, the processor 71 ends the operation.

[0102] Furthermore, when the processor 71 determines that the ink pressure chamber 25 is filled with ink, the processor 71 may eject the ink from the ink pressure chamber 25 under the control of the host control device 13 .

[0103] Next, an operation example (ACT 12) in which the processor 71 detects that the pressure in the buffer tank 35 has reached the lower limit pressure will be described.

[0104] Figure 8This is a flowchart for explaining an operation example (ACT 12 ) in which the processor 71 detects that the pressure in the buffer tank 35 has reached the lower limit pressure.

[0105] First, the processor 71 substitutes 500 Pa into P_min_temp (ACT 21 ). When 500 Pa is substituted into P_min_temp, the processor 71 starts a timer t_min (ACT 22 ).

[0106] When the timer t_min starts, the processor 71 determines whether the timer t_min>2s (whether 2 seconds have passed) (ACT23). If it is determined that the timer t_min is not>2s (ACT23, No), the processor 71 determines whether the pressure (P) detected by the pressure sensor 39 is less than P_min_temp (ACT24).

[0107] If it is determined that P<P_min_temp (ACT24, YES), the processor 71 substitutes P into P_min_temp (ACT25). If P is substituted into P_min_temp, the processor 71 resets the timer t_min (sets the timer t_min to 0) (ACT26).

[0108] When it is determined that P<P_min_temp is not satisfied (ACT 24 , No), or when the timer t_min is reset (ACT 26 ), the processor 71 returns to ACT 23 .

[0109] If it is determined that the timer t_min>2s (ACT23, YES), the processor 71 substitutes P_min storing the lower limit pressure into P_min_temp (ACT27). If P_min is substituted into P_min_temp, the processor 71 sets a flag indicating that the pressure in the buffer tank 35 has reached the lower limit pressure (ACT28).

[0110] When the flag indicating that the pressure in the buffer tank 35 has reached the lower limit pressure is set, the processor 71 ends the operation.

[0111] Next, an operation example (ACT 13) in which the processor 71 detects that the pressure in the buffer tank 35 has reached the upper limit pressure will be described.

[0112] Fig. 9 This is a flowchart for explaining an operation example (ACT 13 ) in which the processor 71 detects that the pressure in the buffer tank 35 has reached the upper limit pressure.

[0113] First, the processor 71 substitutes P_min into P_max_temp (ACT 31 ). When P_min is substituted into P_max_temp, the processor 71 starts a timer t_max (ACT 32 ).

[0114] When the timer t_max starts, the processor 71 determines whether the timer t_max>2s (whether 2 seconds have passed) (ACT33). If it is determined that the timer t_max is not>2s (ACT33, No), the processor 71 determines whether the pressure (P) detected by the pressure sensor 39>P_max_temp (ACT34).

[0115] If it is determined that P>P_max_temp (ACT34, YES), the processor 71 substitutes P into P_max_temp (ACT35). If P is substituted into P_max_temp, the processor 71 resets the timer t_max (sets the timer t_max to 0) (ACT36).

[0116] When it is determined that P>P_max_temp is not satisfied (ACT 34 , No), or when the timer t_max is reset (ACT 36 ), the processor 71 returns to ACT 33 .

[0117] If it is determined that the timer t_max>2s (ACT33, YES), the processor 71 determines whether P_max_temp-P_min>2kPa (ACT37). If it is determined that P_max_temp-P_min>2kPa (ACT37, NO), the processor 71 returns to ACT36.

[0118] If it is determined that P_max_temp-P_min>2 kPa (ACT37, YES), the processor 71 substitutes P_max_temp for P_max of the storage upper limit pressure (ACT38). If P_max_temp is substituted for P_max, the processor 71 sets a flag indicating that the pressure in the buffer tank 35 has reached the upper limit pressure (ACT39).

[0119] When the flag indicating that the pressure in the buffer tank 35 has reached the upper limit pressure is set, the processor 71 ends the operation.

[0120] Next, an operation example (ACT 14 ) in which the processor 71 detects that the pressure in the buffer tank 35 is stabilized will be described.

[0121] Fig.10 This is a flowchart for explaining an operation example (ACT 14 ) in which the processor 71 detects that the pressure in the buffer tank 35 is stabilized.

[0122] First, the processor 71 starts the timer t_σ (ACT 41). When the timer t_σ starts, the processor 71 calculates the pressure dispersion σm (ACT 42). When σm is calculated, the processor 71 determines whether σm<40 (ACT 43).

[0123] If it is determined that σm<40 (ACT43, YES), the processor 71 increments count_stb (ACT44).

[0124] When it is determined that σm is not less than 40 (ACT 43 , No), or when count_stb is incremented (ACT 44 ), the processor 71 determines whether the timer t_σ>10s (whether 10 seconds have elapsed) (ACT 45 ).

[0125] If it is determined that the timer t_σ is not greater than 10 s (ACT 45, No), the processor 71 waits for 50 ms (S46). If it waits for 50 ms, the processor 71 returns to ACT 42.

[0126] If it is determined that the timer t_σ>10s (ACT45, YES), the processor 71 determines whether count_stb>180 (ACT47). If it is determined that count_stb>180 (ACT47, NO), the processor 71 resets the timer t_σ (sets the timer t_σ to 0) (ACT48).

[0127] When the timer t_σ is reset, the processor 71 returns to ACT 42 .

[0128] If it is determined that count_stb>180 (ACT 47 , YES), the processor 71 sets a flag indicating that the pressure in the buffer tank 35 is stable (ACT 49 ).

[0129] If the flag indicating that the pressure in the buffer tank 35 is stable is set, the processor 71 ends the operation. The processor 71 determines that the pressure in the buffer tank 35 is stable based on the pressure dispersion σm.

[0130] Furthermore, the liquid to be discharged is not limited to the ink for printing, and may be a device that discharges a liquid containing conductive particles for forming a wiring pattern of a printed wiring board, for example.

[0131] In addition to the above, the liquid ejection head 20 may have a structure that ejects ink droplets by deforming a vibration plate using static electricity, or a structure that ejects ink droplets from a nozzle using thermal energy of a heater or the like.

[0132] In the embodiments, an example in which the liquid ejection head is used in an inkjet recording device or the like is shown, but the invention is not limited thereto and can also be applied to, for example, a 3D printer, industrial manufacturing machinery, and medical use.

[0133] The circulation device constructed as described above detects that the ink pressure chamber is filled with ink based on the pressure in the buffer tank. As a result, the circulation device can detect that the ink pressure chamber is filled with ink even if the circulation device does not have a liquid detection sensor in the flow path, etc. Therefore, the circulation device can effectively detect that the ink pressure chamber is filled with liquid.

[0134] Although several embodiments are described, these embodiments are only presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the scope of the purpose of the invention. These embodiments and their variations are included in the scope and purpose of the invention, and are also included in the invention described in the claims and their equivalents.

Claims

1. A liquid circulation device, characterized in that: have: A pressure pump supplies liquid from the tank to the liquid ejection head; a pressure reducing pump for recovering the liquid from the liquid ejection head; A buffer tank is connected in parallel with the liquid ejection head between the pressure pump and the pressure reducing pump, and stores the liquid; A sensor for detecting the pressure of the buffer tank; as well as The processor determines whether the pressure chamber provided in the liquid ejection head is filled with the liquid based on the detected pressure, The processor acquires the pressure from the sensor in time series, and determines whether the pressure chamber is filled with the liquid based on the pressure acquired in time series. The processor determines that the pressure chamber is filled with the liquid when detecting that the pressure reaches a lower limit pressure, then reaches an upper limit pressure, and then stabilizes.

2. The liquid circulation device according to claim 1, characterized in that: When the minimum value of the pressure is not updated within a predetermined period, the processor determines that the pressure has reached a lower limit, When the maximum value of the pressure is not updated within a predetermined period, the processor determines that the pressure has reached an upper limit. The processor determines that the pressure is stable based on the dispersion of the pressure.

3. The liquid circulation device according to claim 1 or 2, characterized in that: The liquid circulation device comprises a circulation path and a bypass flow path. The cycle path includes: a first flow path connecting the tank and the pressure pump; a second flow path connecting the pressure pump and the liquid ejection head; a third flow path connecting the liquid ejection head and the pressure reducing pump; and A fourth flow path connects the pressure reducing pump and the tank, The bypass flow path comprises: a first bypass flow path connecting the second flow path and the buffer tank; and a second bypass flow path connecting the buffer tank and the third flow path, The first bypass flow path and the second bypass flow path have the same length and the same diameter, and are both configured to be smaller than the diameter of the circulation path.

4. A liquid ejection device, characterized in that: have: A liquid ejection head having a pressure chamber; a pressure pump for supplying liquid from a tank to the liquid ejection head; a pressure reducing pump for recovering the liquid from the liquid ejection head; A buffer tank is connected in parallel with the liquid ejection head between the pressure pump and the pressure reducing pump, and stores the liquid; A sensor for detecting the pressure of the buffer tank; as well as a processor, based on the detected pressure, determining whether the pressure chamber is filled with the liquid, The processor acquires the pressure from the sensor in time series, and determines whether the pressure chamber is filled with the liquid based on the pressure acquired in time series. The processor determines that the pressure chamber is filled with the liquid when detecting that the pressure reaches a lower limit pressure, then reaches an upper limit pressure, and then stabilizes.

5. The liquid ejection device according to claim 4, characterized in that: When the minimum value of the pressure is not updated within a predetermined period, the processor determines that the pressure has reached a lower limit, When the maximum value of the pressure is not updated within a predetermined period, the processor determines that the pressure has reached an upper limit. The processor determines that the pressure is stable based on the dispersion of the pressure.

6. The liquid ejection device according to claim 4 or 5, characterized in that: The liquid ejection device comprises a circulation path and a bypass flow path. The cycle path includes: a first flow path connecting the tank and the pressure pump; a second flow path connecting the pressure pump and the liquid ejection head; a third flow path connecting the liquid ejection head and the pressure reducing pump; and A fourth flow path connects the pressure reducing pump and the tank, The bypass flow path comprises: a first bypass flow path connecting the second flow path and the buffer tank; and a second bypass flow path connecting the buffer tank and the third flow path, The first bypass flow path and the second bypass flow path have the same length and the same diameter, and are both configured to be smaller than the diameter of the circulation path.

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