Liquid circulation device and liquid discharge device

Abstract

To provide a liquid circulation device and a liquid discharge device which can determine clogging of a filter.SOLUTION: A liquid circulation device includes a first pump, a second pump, a filter, a buffer tank, a pressure sensor, and a control part. The first pump supplies liquid of a liquid supply tank to a liquid discharge head. The second pump recovers the liquid from the liquid discharge head, and supplies the liquid to the liquid supply tank. The filter is provided on a flow channel between the liquid supply tank and the liquid discharge head. The buffer tank is connected to a flow channel between the filter and the liquid discharge head, and a flow channel between the liquid discharge head and the second pump, and the liquid discharged from the first pump is flowed thereto. The pressure sensor detects a pressure in the buffer tank. The control part determines clogging of the filter on the basis of a drive voltage of the second pump during adjustment circulation of adjusting a nozzle surface pressure of the liquid discharge head on the basis of the pressure of the buffer tank.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Conventionally, liquid circulation devices that circulate liquid using two pumps have been known among liquid ejection devices that eject liquid. Such liquid circulation devices are equipped with a filter, either inside or outside the liquid circulation device, for purposes such as removing foreign matter. This filter can become clogged due to various factors, but this clogging has not been detected. While methods for detecting filter clogging include using a flow sensor or multiple pressure sensors to detect a decrease in the circulation flow rate, these methods pose concerns such as increased costs due to increased parts and spatial constraints, and a larger device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-137021 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a liquid circulation device and a liquid discharge device that can determine whether a filter is clogged. [Means for solving the problem]

[0005] The liquid circulation device includes a first pump, a second pump, a filter, a buffer tank, a pressure sensor, and a control unit. The first pump supplies liquid from a liquid supply tank to a liquid ejection head. The second pump recovers the liquid from the liquid ejection head and supplies it to the liquid supply tank. The filter is provided in a flow path between the liquid supply tank and the liquid ejection head. The buffer tank is connected to the flow path between the filter and the liquid ejection head and to the flow path between the liquid ejection head and the second pump, and receives the liquid ejected from the first pump. The pressure sensor detects the pressure in the buffer tank. The control unit determines whether the filter is clogged based on the drive voltage of the second pump during adjustment circulation, which adjusts the nozzle surface pressure of the liquid ejection head based on the pressure in the buffer tank. The control unit determines that the filter is clogged when a state in which the output of the first pump is equal to or greater than a first threshold and the output of the second pump is equal to or less than a second threshold continues for a predetermined time. The first threshold is an adjusted maximum value of a drive voltage of the first pump. The second threshold is an adjusted minimum value of a drive voltage of the second pump. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is an explanatory diagram illustrating an example of the configuration of a printer according to an embodiment. [Figure 2] FIG. 2 is an explanatory diagram illustrating an example of the configuration of a liquid ejection device according to an embodiment. [Figure 3] FIG. 3 is an explanatory diagram illustrating an example of the configuration of a liquid ejection head according to an embodiment. [Figure 4] FIG. 4 is an explanatory diagram illustrating an example of the configuration of a piezoelectric pump according to an embodiment. [Figure 5] FIG. 5 is an explanatory diagram illustrating an example of the configuration of a module control unit according to an embodiment. [Figure 6] FIG. 6 is a flowchart illustrating control of nozzle surface pressure by a module control unit according to an embodiment. [Figure 7] FIG. 7 is a flowchart illustrating a process for determining whether a filter is clogged according to one embodiment. [Figure 8] FIG. 8 is an explanatory diagram showing an example of the output of the pressure pump and the output of the pressure reduction pump when clogging occurs in the internal filter of the liquid circulation device according to one embodiment. [Figure 9]FIG. 9 is an explanatory diagram showing an example of the output of the pressure pump and the output of the pressure reduction pump when clogging occurs in the external filter of the liquid circulation device according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] A liquid circulation device 30 according to one embodiment, a liquid ejection device 10 including the liquid circulation device 30, and a printer 1 including the liquid ejection device 10 will be described below with reference to FIGS. 1 to 9. For ease of explanation, the configurations in each drawing are enlarged, reduced, or omitted as appropriate. FIG. 1 is a side view schematically illustrating the configuration of the printer 1. FIG. 2 is an explanatory diagram illustrating the configuration of the liquid ejection device 10. FIG. 3 is an explanatory diagram illustrating the configuration of the liquid ejection head 20. FIG. 4 is an explanatory diagram illustrating the configurations of the first circulation pump 33 and the second circulation pump 36.

[0008] 1 includes a plurality of liquid ejection devices 10, a head support mechanism 11 that movably supports the liquid ejection devices 10, a medium support mechanism 12 that movably supports a recording medium S, and a host control device 13. The printer 1 is an inkjet recording device that ejects ink as a liquid.

[0009] A liquid ejection device 10 ejects a liquid, such as ink I, from a liquid ejection head 20 to form a desired image on a recording medium S disposed opposite the liquid ejection head 20. As shown in FIG. 1, a plurality of liquid ejection devices 10 are arranged in parallel in a predetermined direction and supported by a head support mechanism 11. Each liquid ejection device 10 integrally includes a liquid ejection head 20 and a liquid circulation device 30. The liquid ejection device 10 also includes a cartridge 51 serving as an ink supply tank (liquid supply tank), and an external filter 52 provided in a flow path between the cartridge 51 and a first circulation pump 33. The cartridge 51 and the external filter 52 are, for example, replaceable. The cartridge 51 is configured to hold ink, and an internal air chamber is open to the atmosphere. The external filter 52 removes foreign matter from the ink.

[0010] The liquid ejection device 10 may be configured to include a liquid supply tank 51 that can be replenished with liquid, instead of a replaceable cartridge 51. Such a liquid supply tank 51 and external filter 52 may be configured to be provided integrally with the liquid circulation device 30.

[0011] The multiple liquid ejection devices 10 eject ink of multiple colors, for example, cyan ink, magenta ink, yellow ink, black ink, and white ink, but the color or characteristics of the ink I used are not limited. For example, instead of white ink, it is possible to eject transparent glossy ink, special ink that changes color when irradiated with infrared or ultraviolet light, etc. The multiple liquid ejection devices 10 have the same configuration but use different inks.

[0012] First, the liquid ejection head 20 will be described. The liquid ejection head 20 shown in Figure 3 is an inkjet head, and includes a supply port 201 through which ink flows in, a recovery port 202 through which ink flows out, a nozzle plate 21 having a plurality of nozzle holes 211, a substrate 22, and a manifold 23 bonded to the substrate 22.

[0013] The substrate 22 is bonded to face the nozzle plate 21 and is configured in a predetermined shape to form predetermined ink flow paths 28 including a plurality of ink pressure chambers 25 between the substrate 22 and the nozzle plate 21. The substrate 22 has partition walls arranged between the plurality of ink pressure chambers 25 in the same row. An actuator 24 including electrodes 241, 242 is provided on the substrate 22 at a portion facing each ink pressure chamber 25.

[0014] The actuator 24 is disposed opposite the nozzle hole 211, and an ink pressure chamber 25 is formed between the actuator 24 and the nozzle hole 211. The actuator 24 is connected to a drive circuit. The liquid ejection head 20 ejects liquid from the nozzle hole 211 disposed opposite it by the actuator 24 being deformed in response to voltage under the control of the module control unit 38.

[0015] Next, the liquid circulation device 30 will be described. 2, the liquid circulation device 30 is integrally connected to the upper part of the liquid ejection head 20 by a metal connecting part. The liquid circulation device 30 includes a predetermined circulation flow path 31 configured to enable the circulation of liquid passing through the liquid ejection head 20, a first circulation pump 33, a bypass flow path 34, a buffer tank 35 serving as the buffer device 100, a second circulation pump 36, an opening / closing valve 37, and a module control unit 38 that controls the liquid ejection operation.

[0016] First, the circulation flow path 31 will be described. The circulation flow path 31 includes a first flow path 311, a second flow path 312, a third flow path 313, and a fourth flow path 314. The circulation flow path 31 also includes a filter 315. The first flow path 311 connects the cartridge 51, which is an ink supply tank, to the first circulation pump 33. The second flow path 312 connects the first circulation pump 33 to the supply port 201 of the liquid ejection head 20. The third flow path 313 connects the recovery port 202 of the liquid ejection head 20 to the second circulation pump 36. The fourth flow path 314 connects the second circulation pump 36 to the cartridge 51.

[0017] The first flow path 311 and the fourth flow path 314 include pipes made of metal or resin material and tubes covering the outer surfaces of the pipes. The tubes covering the outer surfaces of the pipes of the first flow path 311 and the fourth flow path 314 are, for example, PTFE tubes. The filter 315 is provided in a flow path on the primary side of the liquid ejection head 20 in the ink flow direction, for example, the first flow path 311 or the second flow path 312.

[0018] As a specific example, the filter 315 is provided in the second flow path 312. The filter 315 is provided in the second flow path 312 on the upstream side (the first circulation pump 33 side) of the bypass flow path 34 connected to the second flow path 312. The filter 315 filters the ink. The filter 315 removes foreign matter from the ink. The filter 315 is an internal filter provided in the liquid circulation device 30. For the sake of explanation, the filter 315 will be described below as the internal filter 315.

[0019] The ink circulating through the circulation flow path 31 passes from the cartridge 51 through the first flow path 311, the first circulation pump 33, the second flow path 312, and the supply port 201 of the liquid ejection head 20 to reach the inside of the liquid ejection head 20. In addition, the ink circulating through the circulation flow path 31 passes from the liquid ejection head 20 through the recovery port 202 of the liquid ejection head 20, the third flow path 313, the second circulation pump 36, and the fourth flow path 314 to reach the cartridge 51.

[0020] Next, the first circulation pump (first pump) 33 and the second circulation pump (second pump) 36 will be described. The first circulation pump 33 is a pump that pumps out liquid. The first circulation pump 33 pumps out liquid from the first flow path 311 to the second flow path 312. In other words, the first circulation pump 33 is a pressure pump that sucks up ink from the cartridge 51, which is an ink supply tank, by operation of an actuator, and supplies the ink to the liquid ejection head 20.

[0021] The second circulation pump 36 is a pump that pumps out liquid. The second circulation pump 36 pumps out liquid from the third flow path 313 to the fourth flow path 314. In other words, the second circulation pump 36 is a decompression pump that recovers ink from the liquid ejection head 20 by the operation of an actuator and supplies the ink to the cartridge 51.

[0022] The first circulation pump 33 and the second circulation pump 36 are configured as a piezoelectric pump 60, for example, as shown in Fig. 4. The piezoelectric pump 60 includes a pump chamber 58, a piezoelectric actuator 59 provided in the pump chamber 58 and vibrating in response to voltage, and check valves 61, 62 disposed 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, approximately 50 Hz to 200 Hz. The first circulation pump 33 and the second circulation pump 36 are connected to a drive circuit by wiring and are configured to be controllable by the module control unit 38.

[0023] For example, by changing the voltage applied to the piezoelectric actuator 59, the piezoelectric actuator 59 is deformed in a direction that contracts the pump chamber 58 or in a direction that expands the pump chamber 58, as shown in the lower and upper diagrams of FIG. 4. This changes the volume of the pump chamber 58. For example, when the piezoelectric actuator 59 is deformed in a direction that expands the pump chamber 58, a check valve 61 at the inlet of the pump chamber 58 opens, and ink is drawn into the pump chamber 58. Also, for example, when the piezoelectric actuator 59 is deformed in a direction that contracts the pump chamber 58, a check valve 62 at the outlet of the pump chamber 58 opens, and ink in the pump chamber 58 is pumped out to the other side. By repeating this operation, the first circulation pump 33 and the second circulation pump 36 each draw ink in from one side and pump ink out from the other side.

[0024] The maximum amount of change of the piezoelectric actuator 59 depends on the voltage applied to the piezoelectric actuator 59. As the voltage applied to the piezoelectric actuator 59 increases, the maximum amount of change of the piezoelectric actuator 59 increases. Conversely, as the voltage applied to the piezoelectric actuator 59 decreases, the maximum amount of change of the piezoelectric actuator 59 decreases. The liquid delivery capacity of the piezoelectric pump 60 depends on the maximum amount of change of the piezoelectric actuator 59. That is, the module control unit 38 controls the liquid delivery capacity of the piezoelectric pump 60 by controlling the voltage applied to the piezoelectric actuator 59.

[0025] Next, the bypass flow path 34 and the buffer tank 35 will be described. The bypass flow path 34 is a flow path that connects the second flow path 312 and the third flow path 313. The bypass flow path 34 connects the supply port 201, which is the primary side of the liquid ejection head 20 in the circulation flow path 31, to the recovery port 202, which is the secondary side of the liquid ejection head 20, in a short-circuit manner without passing through the liquid ejection head 20.

[0026] The buffer tank 35 is connected to the bypass flow path 34. Specifically, the bypass flow path 34 includes a first bypass flow path 341 that connects a predetermined location on the lower part of a pair of side walls of the buffer tank 35 with the second flow path 312, and a second bypass flow path 342 that connects a predetermined location on the lower part of the pair of side walls of the buffer tank 35 with the third flow path 313.

[0027] For example, the first bypass flow path 341 and the second bypass flow path 342 have the same length and the same diameter, and are both configured to have a smaller diameter than the circulation flow path 31. For example, the diameter of the circulation flow path 31 is set to about two to five times the diameter of the first bypass flow path 341 and the second bypass flow path 342. The first bypass flow path 341 and the second bypass flow path 342 are provided so that the distance between the connection position of the second flow path 312 and the first bypass flow path 341 and the supply port 201 of the liquid ejection head 20 is equal to the distance between the connection position of the third flow path 313 and the second bypass flow path 342 and the recovery port 202 of the liquid ejection head 20.

[0028] 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 is configured, for example, in the shape of a rectangular box having an upper wall, a lower wall, a rear wall, a front wall, and a pair of left and right side walls, and forming a storage chamber 351 for storing liquid therein. The connection position between the first bypass flow path 341 and the buffer tank 35 and the connection position between the second bypass flow path 342 and the buffer tank 35 are set at the same height. Ink flowing through the bypass flow path 34 is disposed in a lower region of the storage chamber 351 in the buffer tank 35, and an air chamber is formed in an upper region of the storage chamber 351. In other words, the buffer tank 35 is capable of storing a predetermined amount of liquid and air. The buffer tank 35 is also provided with an open / close valve 37 configured to open the air chamber in the buffer tank 35 to the atmosphere, and a pressure sensor 39.

[0029] The on-off valve 37 is, for example, 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 configured to be able to open and close the air chamber of the buffer tank 35 to the atmosphere by being opened and closed under the control of the module control unit 38. In other words, when the on-off valve 37 is opened, the buffer tank 35 is opened to the atmosphere.

[0030] The pressure sensor 39 detects the pressure in the air chamber in the buffer tank 35 and sends pressure data indicating the pressure value 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 is equal to atmospheric pressure. The pressure sensor 39 detects the pressure in 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.

[0031] The pressure sensor 39 uses, for example, a semiconductor piezoresistive pressure sensor to output pressure as an electrical signal. The semiconductor piezoresistive pressure sensor includes a diaphragm that receives external pressure and a semiconductor strain gauge formed on the surface of the diaphragm. The semiconductor piezoresistive pressure sensor detects pressure by converting into an electrical signal a change in electrical resistance caused by the piezoresistive effect that occurs in the strain gauge when the diaphragm is deformed by external pressure.

[0032] Next, the module control unit 38 will be described. FIG. 5 is an explanatory diagram for explaining an example of the configuration of the module control unit 38. The module control unit 38 controls the operations of the liquid ejection head 20, the first circulation pump 33, the second circulation pump 36, and the on-off valve 37. The module control unit 38 includes a CPU (Central Processing Unit) 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.

[0033] The CPU 71 is a computing element (for example, a processor) that executes arithmetic processing. The CPU 71 is a control unit that performs various processes based on data such as programs stored in the memory 72. The CPU 71 is a processing circuit that can execute various controls by executing the programs stored in the memory 72.

[0034] The memory 72 is a storage device that stores various information, and includes, for example, a read only memory (ROM) 721 and a random access memory (RAM) 722.

[0035] The ROM 721 is a read-only nonvolatile memory. The ROM 721 stores programs, data used in the programs, etc. For example, the ROM 721 stores, as control data used for pressure control, a calculation formula for calculating the ink pressure of the nozzle holes 211, a set pressure range, a first threshold value, a second threshold value, a third threshold value, and a fourth threshold value, etc.

[0036] The first threshold value is, for example, the maximum adjustment value of the first circulation pump 33, which is a pressure-boosting pump. The second threshold value is, for example, the maximum adjustment value of the second circulation pump 36, which is a pressure-reducing pump. The third threshold value is a threshold value for determining that either the external filter 52 or the internal filter 315 is clogged. The third threshold value is, for example, the output value of the first circulation pump 33 and / or the second circulation pump 36 when the external filter 52 or the internal filter 315 is clogged. For example, the third threshold value is the minimum value (minimum adjustment value) of the drive voltage at which the piezoelectric actuator 59 of the second circulation pump 36 can operate.

[0037] The fourth threshold value is the time required to determine whether the external filter 52 and the internal filter 315 are clogged. The fourth threshold value is, for example, the time required to determine whether the external filter 52 and the internal filter 315 are clogged, as a result of the output of the second circulation pump 36 being maintained, from when the output of the second circulation pump 36 reaches the third threshold value. In this embodiment, the fourth threshold value is, for example, 10 seconds.

[0038] The RAM 722 is a volatile memory that functions as a working memory. The RAM 722 temporarily stores data being processed by the CPU 71. The RAM 722 also temporarily stores programs that the CPU 71 executes.

[0039] The communication interface 73 is an interface for communicating with other devices, and relays communication with the host control device 13 that transmits print data to the liquid ejection device 10, for example.

[0040] The circulation pump drive circuit 74 applies a drive voltage to the piezoelectric actuator 59 of the piezoelectric pump 60 under the control of the CPU 71, thereby driving the piezoelectric pump 60. In this way, the circulation pump drive circuit 74 circulates ink through the circulation flow path 31. A circulation pump drive circuit 74 is provided for each circulation pump. The circulation pump drive circuit 74 connected to the first circulation pump 33 applies a drive voltage to the piezoelectric actuator 59 of the first circulation pump 33. The circulation pump drive circuit 74 connected to the second circulation pump 36 applies a drive voltage to the piezoelectric actuator 59 of the second circulation pump 36.

[0041] The valve drive circuit 76 drives the on-off valve 37 under the control of the CPU 71, and opens the air chamber of the buffer tank 35 to the atmosphere.

[0042] The liquid ejection head driving circuit 77 applies a voltage to the actuator 24 of the liquid ejection head 20 under the control of the CPU 71 to drive the liquid ejection head 20 and eject ink from the nozzle holes 211 of the liquid ejection head 20 .

[0043] In the above configuration, the CPU 71 receives various information such as operating conditions by communicating with the host control device 13, which is an external terminal, via the communication interface 73. In addition, the various information acquired by the CPU 71 is sent to the host control device 13 of the printer 1 via the communication interface 73.

[0044] Furthermore, the CPU 71 acquires the detection result from the pressure sensor 39, and controls the operation of the circulation pump drive circuit 74 and the valve drive circuit 76 based on the acquired detection result. For example, the CPU 71 controls the liquid delivery capacity of the first circulation pump 33 and the second circulation pump 36 by controlling the circulation pump drive circuit 74 based on the detection result of the pressure sensor 39. In this way, the CPU 71 adjusts the ink pressure of the nozzle holes 211.

[0045] Furthermore, the CPU 71 controls the valve drive circuit 76 to open and close the on-off valve 37. In this way, the CPU 71 adjusts the liquid level in the buffer tank 35.

[0046] The CPU 71 also acquires detection results from the pressure sensor 39 and controls the liquid ejection head drive circuit 77 based on the acquired detection results to eject ink droplets from the nozzle holes 211 of the liquid ejection head 20 onto a recording medium. Specifically, the CPU 71 inputs an image signal corresponding to image data to the liquid ejection head drive circuit 77. The liquid ejection head drive circuit 77 drives the actuator 24 of the liquid ejection head 20 in accordance with the image signal. When the liquid ejection head drive circuit 77 drives the actuator 24 of the liquid ejection head 20, the actuator 24 deforms, changing the ink pressure (nozzle surface pressure) of the nozzle holes 211 facing the actuator 24. The nozzle surface pressure is the pressure that the ink in the ink pressure chamber 25 applies to the meniscus Me formed by the ink in the nozzle holes 211. When the nozzle surface pressure exceeds a predetermined value determined by the shape of the nozzle holes 211, the characteristics of the ink, and the like, ink is ejected from the nozzle holes 211. In this way, the CPU 71 forms an image corresponding to the image data on a recording medium.

[0047] Furthermore, the CPU 71 executes an ink shortage determination process based on the detection result of the pressure sensor 39 to determine whether or not there is a possibility that the ink in the cartridge 51, which is an ink supply tank, is insufficient.

[0048] Next, the control of the nozzle surface pressure by the CPU 71 of the module control unit 38 will be described. When not printing, the CPU 71 maintains a negative pressure on the nozzle surface of the nozzle holes 211 of the liquid ejection head 20 to prevent ink droplets from dripping from the nozzle holes 211 of the liquid ejection head 20. Furthermore, during printing, the CPU 71 maintains a nozzle surface pressure sufficient to eject ink droplets from the nozzle holes 211 of the liquid ejection head 20 (a pressure suitable for maintaining a meniscus Me). The CPU 71 controls the liquid delivery capacities of the first circulation pump 33 and the second circulation pump 36 to control the nozzle surface pressure of the nozzle holes 211 of the liquid ejection head 20.

[0049] The nozzle surface pressure is increased or decreased depending on the relative liquid delivery capacity of the first circulation pump 33 and the liquid delivery capacity of the second circulation pump 36. Specifically, when the liquid delivery capacity of the first circulation pump 33 is greater than that of the second circulation pump 36, the nozzle surface pressure is increased. On the other hand, when the liquid delivery capacity of the first circulation pump 33 is weaker than that of the second circulation pump 36, the nozzle surface pressure is decreased.

[0050] FIG. 6 is a flowchart for explaining the control of the nozzle surface pressure by the CPU 71 of the module control unit 38.

[0051] In ACT1, the CPU 71 waits for an instruction to start circulation. For example, when the CPU 71 detects an instruction to start circulation from a command from the host control device 13 (ACT1, YES), the CPU 71 proceeds to the processing of ACT2. As a printing operation, the host control device 13 performs an ink ejection operation while reciprocating the liquid ejection device 10 in a direction perpendicular to the transport direction of the recording medium S, thereby forming an image on the recording medium S. Specifically, the CPU 71 transports the carriage 111 provided on the head support mechanism 11 toward the recording medium S, and moves it back and forth in the direction of arrow A. The CPU 71 also supplies an image signal corresponding to the image data to the liquid ejection head drive circuit 77, thereby driving the actuator 24 of the liquid ejection head 20 corresponding to the image signal and causing ink droplets to be ejected from the nozzle holes 211 onto the recording medium S.

[0052] In ACT2, the CPU 71 drives the first circulation pump 33 and the second circulation pump 36 to start the ink circulation operation. The ink circulating through the circulation flow path 31 passes from the cartridge 51 through the first flow path 311, the first circulation pump 33, the second flow path 312, and the supply port 201 of the liquid ejection head 20 to reach the inside of the liquid ejection head 20. In addition, the ink circulating through the circulation flow path 31 passes from the liquid ejection head 20 through the recovery port 202 of the liquid ejection head 20, the third flow path 313, the second circulation pump 36, and the fourth flow path 314 to reach the cartridge 51.

[0053] In ACT 3, the CPU 71 detects the pressure data of the buffer tank 35 transmitted from the pressure sensor 39.

[0054] In ACT4, the CPU 71 detects from the pressure data the ink pressure of the nozzle orifice 211. Specifically, based on the pressure data of the buffer tank 35 sent from the pressure sensor 39, the CPU 71 calculates the ink pressure of the nozzle orifice 211 using a predetermined arithmetic expression.

[0055] First, if the density of ink is ρ, the acceleration of gravity is g, and the heightwise distance between the ink surface in the buffer tank 35 and the nozzle surface is h, the pressure generated by the head difference between the ink surface in the buffer tank 35 and the nozzle surface is ρgh. For example, the CPU 71 calculates the nozzle ink pressure (nozzle surface pressure) Pn by adding the pressure ρgh to the pressure data of the buffer tank 35 sent from the pressure sensor 39.

[0056] The CPU 71 performs various comparisons based on the calculated nozzle surface pressure Pn, and thereby controls the drive voltage applied to the piezoelectric actuator 59 of the first circulation pump 33 and the drive voltage applied to the piezoelectric actuator 59 of the second circulation pump 36, thereby controlling the liquid delivery capacities of the first circulation pump 33 and the second circulation pump 36. In this way, the CPU 71 controls the nozzle surface pressure Pn to an appropriate value.

[0057] The CPU 71 acquires a set pressure range, which is a target pressure for the set nozzle surface pressure Pn, from the ROM 721. The set pressure range may be a single value, or may have an upper limit and a lower limit. The CPU 71 may also be configured to successively acquire the set pressure range from the host control device 13 via the communication interface 73. In this example, the description will be given assuming that the set pressure range is a single value (set pressure).

[0058] First, in ACT5, the CPU 71 determines whether the nozzle surface pressure Pn is smaller than the set pressure.

[0059] If the CPU 71 determines that the nozzle surface pressure Pn is lower than the set pressure (ACT 5, YES), it determines in ACT 6 whether the output of the first circulation pump 33, which is a pressure pump, is equal to or greater than the adjusted maximum value (first threshold value). That is, the CPU 71 determines whether the drive voltage applied to the piezoelectric actuator 59 constituting the first circulation pump 33, which is a pressure pump, is the maximum value (adjusted maximum value) of the drive voltage at which the piezoelectric actuator 59 can operate in controlling the nozzle surface pressure.

[0060] When the CPU 71 determines that the first circulation pump 33, which is a pressure-reducing pump, is at the maximum adjustment value (ACT6, YES), in ACT7, the CPU 71 reduces the drive voltage of the second circulation pump 36, which is a pressure-reducing pump. That is, the CPU 71 reduces the liquid delivery capacity of the second circulation pump 36. As a result, the nozzle surface pressure Pn is increased.

[0061] If the CPU 71 determines that the first circulation pump 33 is not at its maximum adjustment value (ACT6, NO), in ACT8, the CPU 71 increases the drive voltage of the first circulation pump 33. That is, the CPU 71 increases the liquid delivery capacity of the first circulation pump 33. As a result, the nozzle surface pressure Pn is increased.

[0062] Furthermore, when the CPU 71 determines that the nozzle surface pressure Pn is equal to or greater than the set pressure (ACT5, NO), it determines in ACT9 whether the nozzle surface pressure Pn is greater than the set pressure.

[0063] If the CPU 71 determines that the nozzle surface pressure Pn is greater than the set pressure (ACT 9, YES), it determines in ACT 10 whether the output of the second circulation pump 36, which is a pressure-reducing pump, is equal to or greater than the adjusted maximum value (second threshold value). That is, the CPU 71 determines whether the drive voltage applied to the piezoelectric actuator 59 that constitutes the second circulation pump 36, which is a pressure-reducing pump, is the maximum value at which the piezoelectric actuator 59 can operate in controlling the nozzle surface pressure.

[0064] When the CPU 71 determines that the pressure of the decompression pump is at the maximum adjustment value (ACT10, YES), in ACT11, the CPU 71 reduces the drive voltage of the first circulation pump 33. That is, the CPU 71 reduces the liquid delivery capacity of the first circulation pump 33. As a result, the nozzle surface pressure Pn is reduced.

[0065] When the CPU 71 determines that the pressure reduction pump is not at its maximum adjustment value (ACT10, NO), in ACT12, the CPU 71 increases the drive voltage of the second circulation pump 36. That is, the CPU 71 increases the liquid delivery capacity of the second circulation pump 36. As a result, the nozzle surface pressure Pn is reduced.

[0066] The CPU 71 performs a filter clogging determination process in ACT 13 when the drive voltage of the second circulation pump 36 is lowered in ACT 7, when the drive voltage of the first circulation pump 33 is increased in ACT 8, when the drive voltage of the first circulation pump 33 is lowered in ACT 11, and when the drive voltage of the second circulation pump 36 is increased in ACT 12. Here, the filter clogging determination process performed in ACT 13 is a function in which the CPU 71 determines whether either the external filter 52 or the internal filter 315 is clogged.

[0067] When the CPU 71 performs the filter clogging determination process, in ACT14, it determines whether or not a circulation end command has been output to the filter clogging determination process and whether or not a circulation end command has been received from the host control device 13. Furthermore, if the CPU 71 determines that the nozzle surface pressure Pn is not greater than the set pressure (ACT9, NO), it proceeds to the process of ACT14.

[0068] If the CPU 71 has not received a circulation end command from the host control device 13 (ACT14, NO), the CPU 71 proceeds to the processing of ACT3. That is, the CPU 71 repeatedly executes the processing of ACT3 to ACT13 until it receives a circulation end command. As a result, the CPU 71 sequentially controls the nozzle surface pressure Pn to be the set pressure.

[0069] When the CPU 71 receives a circulation end command from the host control device 13 (ACT 14, YES), it ends the circulation of ink in ACT 15. That is, the CPU 71 stops the operation of the circulation pump drive circuit 74, thereby stopping the operation of the first circulation pump 33 and the second circulation pump 36. As a result, the circulation of ink between the cartridge 51 and the circulation flow path 31 ends.

[0070] Next, the filter clogging determination process in ACT13 of Fig. 6 will be described with reference to Figs. 7 to 9. Fig. 7 is a flowchart showing an example of the filter clogging determination process. Fig. 8 is an explanatory diagram showing an example of the drive voltage of the first circulation pump 33 and the drive voltage of the second circulation pump 36 when the internal filter 315 is clogged. Fig. 9 is an explanatory diagram showing an example of the drive voltage of the first circulation pump 33 and the drive voltage of the second circulation pump 36 when the external filter 52 is clogged.

[0071] When ink is repeatedly circulated and foreign matter is removed from the ink by the external filter 52 and the internal filter 315, there is a possibility that the foreign matter will clog the external filter 52 and the internal filter 315. If the external filter 52 and the internal filter 315 become clogged in this way, ink will not be supplied to the liquid ejection head 20, or the ink supply will be insufficient, causing a decrease in the nozzle surface pressure Pn.

[0072] When the nozzle surface pressure Pn decreases due to the control of the nozzle surface pressure by the CPU 71 of the module control unit 38 described above, the CPU 71 increases the output of the first circulation pump 33, which is a pressurizing pump, and decreases the output of the second circulation pump 36, which is a decompression pump, to increase the nozzle surface pressure Pn. If the external filter 52 and the internal filter 315 are not clogged, the nozzle surface pressure Pn becomes the set pressure through the output control of the first circulation pump 33 and the second circulation pump 36 by the CPU 71. Thereafter, the outputs of the first circulation pump 33 and the second circulation pump 36 are changed by any of ACT7, ACT8, ACT11, and ACT12. However, if the external filter 52 or the internal filter 315 is clogged, the nozzle surface pressure Pn does not increase even if the output of the first circulation pump 33, which is a pressurizing pump, is increased and the output of the second circulation pump 36, which is a decompression pump, is decreased. Therefore, as shown in FIGS. 8 and 9 , the output of the first circulation pump 33 becomes the adjusted maximum value, and the output of the second circulation pump 36 becomes the adjusted minimum value.

[0073] Therefore, the CPU 71 determines whether the external filter 52 and the internal filter 315 are clogged based on the output of the first circulation pump 33 and / or the output of the second circulation pump .

[0074] According to the process of FIG. 6, when the nozzle surface pressure Pn decreases and is lower than the set pressure, the CPU 71 controls the first circulation pump 33 to increase the drive voltage to increase the nozzle surface pressure Pn (ACT8). Next, when the drive voltage of the first circulation pump 33 reaches the adjusted maximum value (ACT6, Yes), the CPU 71 controls the second circulation pump 36 to decrease the drive voltage to decrease the nozzle surface pressure Pn (ACT7). When the nozzle surface pressure Pn remains lower than the set pressure even after lowering the drive voltage of the second circulation pump 36, the CPU 71 lowers the drive voltage of the second circulation pump 36 to the minimum drive voltage value (adjusted minimum value) at which the piezoelectric actuator 59 can operate. For example, when the nozzle surface pressure Pn is still lower than the set pressure after a predetermined time has elapsed after lowering the output of the second circulation pump 36 to the adjusted minimum value, the CPU 71 determines that at least one of the external filter 52 and the internal filter 315 is clogged.

[0075] As a specific example, the CPU 71 executes a filter clogging determination process shown in FIG. 7 to determine whether at least one of the external filter 52 and the internal filter 315 is clogged.

[0076] First, in ACT 21, the CPU 71 determines whether the output of the second circulation pump 36, which is a pressure-reducing pump, is at the minimum adjustment value. Specifically, the CPU 71 compares the drive voltage of the second circulation pump 36 with a third threshold value to determine whether the drive voltage of the second circulation pump 36 is within a range of drive voltages set by the third threshold value. Here, the third threshold value has, for example, upper and lower limit values ​​at which the drive voltage of the second circulation pump 36 approximates the minimum adjustment value. The CPU 71 then determines, for example, whether the drive voltage of the second circulation pump 36 is within the range of the third threshold value. This is because, as shown in FIGS. 8 and 9 , the drive voltage of the second circulation pump 36 at the minimum adjustment value does not indicate a constant voltage value but varies within a predetermined range.

[0077] For example, the CPU 71 has a timer function that measures time by executing a processing circuit or a program, and starts measuring time as a clogging detection timer that determines whether the filter is clogged when the drive voltage of the second circulation pump 36 falls within the range of a third threshold value. For example, the CPU 71 uses a predetermined area on the RAM 722 as the timer.

[0078] For example, if the CPU 71 determines that the drive voltage of the second circulation pump 36 is not within the range of the third threshold (ACT21, NO), it resets the clogging detection timer in ACT22. That is, the CPU 71 sets the value of the area in RAM 722 corresponding to the timer to 0. As a specific example, if the CPU 71 determines in ACT22 that the drive voltage of the second circulation pump 36 is not within the range of the third threshold, it resets the clogging detection timer and does not start timing. Then, the CPU 71 proceeds to the processing of ACT14.

[0079] When the CPU 71 determines that the drive voltage of the second circulation pump 36 is within the range of the third threshold (ACT 21, YES), the CPU 71 increments the clogging detection timer in ACT 23. For example, the CPU 71 increments a value in a predetermined area in the RAM 722 by +1. That is, the CPU 71 starts timing when it determines that the drive voltage of the second circulation pump 36 is within the range of the third threshold, and counts the elapsed time since the drive voltage of the second circulation pump 36 entered the range of the third threshold.

[0080] In ACT24, the CPU 71 determines whether the time measured by the clogging detection timer is equal to or greater than the time (fourth threshold) for determining whether the filter is clogged.

[0081] When the CPU 71 determines that the time measured by the clogging detection timer is less than the fourth threshold value (ACT24, NO), the CPU 71 proceeds to the process in ACT14.

[0082] If the CPU 71 determines that the time measured by the clogging detection timer is equal to or greater than the fourth threshold value (ACT 24, YES), it determines that clogging has occurred in at least one of the external filter 52 and the internal filter 315, and sets a filter clogging detection flag in ACT 25. The CPU 71 outputs a circulation end command in ACT 26, and proceeds to the processing in ACT 14.

[0083] The CPU 71 may transmit information indicating that at least one of the external filter 52 and the internal filter 315 is clogged to the host control device 13 via the communication interface 73 based on the filter clogging detection flag. If the printer 1 is equipped with a speaker as a notification means, the CPU 71 may be configured to output a sound from the speaker indicating that at least one of the external filter 52 and the internal filter 315 is clogged. If the printer 1 is equipped with a display, the CPU 71 may be configured to display on the display an indication that at least one of the external filter 52 and the internal filter 315 is clogged. The CPU 71 may also be configured to stop printing by stopping the operation of the liquid ejection head drive circuit 77.

[0084] The liquid circulation device 30 configured as described above removes foreign matter from the ink that is sucked up from the cartridge 51, which is an ink supply tank, and supplied to the liquid ejection head 20, using the external filter 52 and internal filter 315. The CPU 71 of the liquid circulation device 30 controls the drive voltages of the first circulation pump 33 and the second circulation pump 36 based on the nozzle surface pressure of the liquid ejection head 20 calculated based on pressure data detected by the pressure sensor 39. The CPU 71 also determines whether the external filter 52 and the internal filter 315 are clogged, based on the output of the first circulation pump 33 and the output of the second circulation pump 36.

[0085] That is, the CPU 71 determines whether ink is circulating due to clogging of the external filter 52 and the internal filter 315 from the drive voltage of the first circulation pump 33, which is adjusted based on the nozzle surface pressure, and the drive voltage of the second circulation pump 36. For example, when the drive voltage of the second circulation pump 36 is at its adjusted minimum value, the CPU 71 determines that the external filter 52 and the internal filter 315 are clogged. In this way, the liquid circulation device 30 can detect clogging of the external filter 52 and the internal filter 315 without adding any additional components, such as sensors, for detecting clogging of the external filter 52 and the internal filter 315.

[0086] Furthermore, the CPU 71 determines that the external filter 52 and the internal filter 315 are clogged when the time during which the drive voltage of the second circulation pump 36 is at the adjusted minimum value (third threshold) is equal to or longer than a preset time (fourth threshold). This is because even during normal operation when no filter clogs occur, the output of the pressure reducing pump (second circulation pump 36) may momentarily become minimum due to the influence of air bubbles entering the circulation flow path 31. However, the CPU 71 can appropriately determine that the external filter 52 and the internal filter 315 are clogged by determining that the external filter 52 and the internal filter 315 are clogged when the drive voltage of the second circulation pump 36 maintains the adjusted minimum value for a predetermined time (fourth threshold).

[0087] According to the embodiment described above, the liquid circulation device 30, the liquid ejection device 10, and the printer 1 can determine whether the external filter 52 and the internal filter 315 are clogged.

[0088] In the above embodiment, the CPU 71 determines whether the external filter 52 and the internal filter 315 are clogged when the output of the second circulation pump 36 is at the third threshold. This is because, when the output of the second circulation pump 36 is at the third threshold, the output of the first circulation pump 33 is at the first threshold (adjusted maximum value). However, the CPU 71 may be configured to determine whether the output of the second circulation pump 36 is at the third threshold, as well as whether the output of the first circulation pump 33 is at the first threshold, as the filter clog determination process. In the above embodiment, the CPU 71 determines whether the filter is clogged when the output of the second circulation pump 36 remains at the third threshold for a predetermined period of time. However, the CPU 71 may determine whether the filter is clogged when the cumulative time or cumulative number of times the output of the second circulation pump 36 remains at the third threshold for a predetermined period of time is equal to or exceeds a predetermined threshold, in addition to when the output of the second circulation pump 36 remains at the third threshold for a predetermined period of time.

[0089] In the above embodiment, the first threshold value used to control the nozzle surface pressure is set to the maximum adjusted value of the drive voltage of the first circulation pump 33, and the second threshold value is set to the maximum adjusted value of the drive voltage of the second circulation pump 36. However, this is not limiting. For example, the first threshold value and the second threshold value used to control the nozzle surface pressure may be the maximum voltages at which the first circulation pump 33 and the second circulation pump 36 can be driven, or may be voltage values ​​lower than the maximum voltages at which the first circulation pump 33 and the second circulation pump 36 can be driven. Similarly, the third threshold value used in the filter clogging determination process is set to the range of the minimum adjusted value of the second circulation pump 36. However, this is not limiting. For example, the third threshold value may be set to a value greater than the minimum adjusted value of the second circulation pump 36, and the CPU 71 may determine that the filter is clogged when the second circulation pump 36, which is equal to or less than the third threshold, continues to be equal to or greater than a fourth threshold.

[0090] In the above embodiment, the pressure sensor 39 is described as being configured to detect the pressure in the air chamber of the buffer tank 35, but is not limited to this configuration. The pressure sensor 39 may be configured to detect the pressure in the second flow path 312 and the pressure in the third flow path 313, respectively, and supply an average value to the module control unit 38.

[0091] Furthermore, in the above-described embodiment, the liquid circulation device 30 has a filter 315, and the liquid ejection device 10 has an external filter 52 provided outside the liquid circulation device 30, but this is not limited to this.

[0092] Furthermore, the liquid to be ejected is not limited to ink for printing, but may be, for example, a device that ejects liquid containing conductive particles for forming a wiring pattern on a printed wiring board.

[0093] In addition to the above, the liquid ejection head may have a structure in which ink droplets are ejected by deforming a vibration plate using static electricity, or a structure in which ink droplets are ejected from a nozzle using thermal energy from a heater or the like.

[0094] Furthermore, in the above embodiment, the liquid ejection head is used in an inkjet recording device, etc., but this is not limited to this, and it can also be used in, for example, 3D printers, industrial manufacturing machines, and medical applications.

[0095] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. The following is a description equivalent to the invention described in the original claims of the present application. [1] A first pump that supplies liquid from a liquid supply tank to a liquid ejection head; a second pump that recovers the liquid from the liquid ejection head and supplies the liquid to the liquid supply tank; a filter provided in a flow path between the liquid supply tank and the liquid ejection head; a buffer tank connected to a flow path between the filter and the liquid ejection head and a flow path between the liquid ejection head and the second pump, into which the liquid ejected from the first pump flows; a pressure sensor for detecting the pressure in the buffer tank; a control unit that determines whether the filter is clogged based on a drive voltage of the second pump during adjustment circulation that adjusts the nozzle surface pressure of the liquid ejection head based on the pressure of the buffer tank; A liquid circulation device comprising: [2] The liquid circulation device described in [1], wherein the control unit determines that the filter is clogged when the output of the first pump is greater than or equal to a first threshold value and the output of the second pump is less than or equal to a second threshold value. [3] The liquid circulation device described in [2], wherein the control unit determines that the filter is clogged when the output of the second pump remains below the second threshold for a predetermined period of time. [4] The liquid circulation device according to any one of [1] to [3], wherein the filter is provided in a flow path between the first pump and the liquid ejection head. [5] A liquid circulation device according to any one of [1] to [4], the liquid supply tank connected to the first pump; the liquid ejection head; an external filter provided between the liquid circulation device and the liquid supply tank; A liquid ejection device comprising: [Explanation of symbols]

[0096] 1...printer, 10...liquid ejection device, 11...head support mechanism, 11a...carriage, 12...medium support mechanism, 13...host control device, 20...liquid ejection head, 21...nozzle plate, 22...substrate, 23...manifold, 24...actuator, 25...ink pressure chamber, 28...ink flow path, 30...liquid circulation device, 31...circulation flow path, 33...first circulation pump (first pump), 33...first circulation pump, 34...bypass flow path, 35...buffer tank, 36...second circulation pump (second pump), 36...second circulation pump, 37...opening / closing valve, 38...module control unit, 39...pressure sensor, 51...cartridge (liquid supply tank), 52...external filter (filter) filter), 58...pump chamber, 59...piezoelectric actuator, 60...piezoelectric pump, 61...check valve, 62...check valve, 71...CPU (control unit), 72...memory, 73...communication interface, 74...circulation pump drive circuit, 76...valve drive circuit, 77...liquid ejection head drive circuit, 100...buffer device, 111...carriage, 201...supply port, 202...recovery port, 211...nozzle hole, 241...electrode, 242...electrode, 311...first flow path, 312...second flow path, 313...third flow path, 314...fourth flow path, 315...internal filter (filter), 341...first bypass flow path, 342...second bypass flow path, 351...storage chamber, 721...ROM, 722...RAM.

Claims

1. a first pump that supplies liquid from a liquid supply tank to the liquid ejection head; a second pump that recovers the liquid from the liquid ejection head and supplies the liquid to the liquid supply tank; a filter provided in a flow path between the liquid supply tank and the liquid ejection head; a buffer tank connected to a flow path between the filter and the liquid ejection head and a flow path between the liquid ejection head and the second pump, into which the liquid ejected from the first pump flows; a pressure sensor for detecting the pressure in the buffer tank; a control unit that determines whether the filter is clogged based on a drive voltage of the second pump during adjustment circulation that adjusts the nozzle surface pressure of the liquid ejection head based on the pressure of the buffer tank; Equipped with the control unit determines that the filter is clogged when a state in which the output of the first pump is equal to or greater than a first threshold value and the output of the second pump is equal to or less than a second threshold value continues for a predetermined time; the first threshold is an adjusted maximum value of the drive voltage of the first pump; The liquid circulation apparatus, wherein the second threshold value is an adjusted minimum value of a drive voltage of the second pump.

2. The liquid circulation device according to claim 1 , wherein the filter is provided in a flow path between the first pump and the liquid ejection head.

3. The liquid circulation device according to claim 1 or 2; the liquid supply tank connected to the first pump; the liquid ejection head; an external filter provided between the liquid circulation device and the liquid supply tank; A liquid ejection device comprising:

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