EP4151418A1

EP4151418A1 - Liquid circulation device and liquid discharge device

Info

Publication number: EP4151418A1
Application number: EP22174762.9A
Authority: EP
Inventors: Satoshi Miura
Original assignee: Toshiba TEC Corp
Current assignee: Riso Technologies Corp
Priority date: 2021-09-17
Filing date: 2022-05-23
Publication date: 2023-03-22
Also published as: JP2023044166A; CN115817021A

Abstract

According to one embodiment, there is provided a circulation device (30) including a pressurizing pump (33), a depressurizing pump (36), a buffer tank (35), a sensor (39), and a processor (71). The pressurizing pump is configured to supply liquid from a tank to a liquid discharge head. The depressurizing pump is configured to collect the liquid from the liquid discharge head. The buffer tank is connected in parallel with the liquid discharge head between the pressurizing pump and the depressurizing pump to store the liquid. The sensor is configured to measure pressure in the buffer tank. The processor is configured to determine whether a pressure chamber included in the liquid discharge head is filled with the liquid based on the measured pressure.

Description

FIELD

Embodiments described herein relate generally to a liquid circulation device and a liquid discharge device.

BACKGROUND

A liquid discharge device including a liquid discharge head (ink jet head) for discharging liquid (ink) and a liquid circulation device for circulating the liquid in a circulation path including the liquid discharge head is known.
The liquid circulation device includes a liquid detection sensor at a specific location in a flow path in order to detect a state of filling the liquid discharge head with the liquid. For example, the liquid detection sensor is an electrostatic capacitance type or float type sensor.
However, an installation place of the electrostatic capacitance type liquid detection sensor is limited because the electrostatic capacitance type liquid detection sensor is large in size. The float type liquid detection sensor has low reliability because a moving part thereof may be stuck by liquid.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory diagram of a configuration example of an ink jet recording apparatus according to an embodiment;
FIG. 2 is an explanatory diagram of a configuration example of a liquid discharge device;
FIG. 3 is an explanatory diagram of a configuration example of a liquid discharge head;
FIG. 4 is an explanatory diagram of a configuration example of a piezoelectric pump;
FIG. 5 is an explanatory diagram of a configuration example of a module control unit;
FIG. 6 is a graph illustrating pressure in a buffer tank;
FIG. 7 is a flowchart illustrating an action example of a circulation device;
FIG. 8 is a flowchart illustrating an action example of the circulation device;
FIG. 9 is a flowchart illustrating an action example of the circulation device; and
FIG. 10 is a flowchart illustrating an action example of the circulation device.

DETAILED DESCRIPTION

Embodiments provide a liquid circulation device and a liquid discharge device for effectively detecting that a liquid discharge head is filled with liquid.
In general, according to one embodiment, there is provided a circulation device configured to be connected to a liquid discharge head, including a pressurizing pump, a depressurizing pump, a buffer tank, a sensor, and a processor. The pressurizing pump is configured to supply liquid from a tank (replenishment tank) to the liquid discharge head. The depressurizing pump is configured to collect the liquid from the liquid discharge head. The buffer tank is connected in parallel with the liquid discharge head between the pressurizing pump and the depressurizing pump, and configured to store the liquid. The sensor is configured to measure pressure in the buffer tank. The processor is configured to determine whether a pressure chamber included in the liquid discharge head is filled with the liquid based on the measured pressure.
Preferably, the processor is configured to acquire the pressure from the sensor in time series, and determine whether the pressure chamber is filled with the liquid based on the pressure acquired in time series.
Preferably, the processor is configured to determine that the pressure chamber is filled with the liquid, when detecting that the pressure reaches lower limit pressure, the pressure reaches upper limit pressure, and the pressure is stable.
Preferably, the processor is configured to determine that the pressure reaches the lower limit if a minimum value of the pressure is not updated for a predetermined period of time, determine that the pressure reaches the upper limit if a maximum value of the pressure is not updated for a predetermined period of time, and determine that the pressure is stable based on variance of the pressure.
Preferably, the processor is configured to acquire a plurality of the pressures from the sensor in a predetermined time period to calculate the variance of the acquired pressures.
Preferably, the processor is configured to count the number of times the variance falls below a predetermined threshold, and determine that the pressure is stable when the counted number exceeds a predetermined threshold.
There is also provided a liquid discharge device which comprises a liquid discharge head comprising a pressure chamber and the liquid circulation device as described above.
There is also provided an ink jet recording apparatus comprising a plurality of the liquid discharge devices as described above.
Hereinafter, a liquid circulation device and a liquid discharge device according to an embodiment will be described with reference to the drawings.
Hereinafter, a liquid discharge device 10 according to the embodiment and an ink jet recording apparatus 1 including the liquid discharge device 10 will be described with reference to FIGS. 1 to 7. For the sake of illustration in each figure, the configuration is appropriately enlarged, reduced, or omitted. FIG. 1 is a side view illustrating a configuration of the ink jet recording apparatus 1. FIG. 2 is an explanatory diagram illustrating a configuration of the liquid discharge device 10. FIG. 3 is an explanatory diagram illustrating a configuration of a liquid discharge head 20. FIG. 4 is an explanatory diagram illustrating a configuration of a first circulation pump 33 and a second circulation pump 36.
The ink jet recording apparatus 1 illustrated in FIG. 1 includes a plurality of liquid discharge devices 10, a head support mechanism 11 that movably supports the liquid discharge devices 10, a medium support mechanism 12 that movably supports a recording medium S, and a host control device 13.
As illustrated in FIG. 1, the plurality of liquid discharge devices 10 are arranged in parallel in a predetermined direction and supported by the head support mechanism 11. The liquid discharge device 10 integratedly includes the liquid discharge head 20 and a circulation device 30. The liquid discharge device 10 forms a desired image on the recording medium S arranged to face the liquid discharge device 10 by discharging, for example, ink as liquid from the liquid discharge head 20.
The plurality of liquid discharge devices 10 discharge a plurality of colors, for example, cyan ink, magenta ink, yellow ink, black ink, and white ink, respectively, but are not limited in the color or characteristics of the ink used. For example, instead of white ink, transparent glossy ink, special ink that develops a color when irradiated with infrared rays or ultraviolet rays, and the like can be discharged. The plurality of liquid discharge devices 10 have the same configuration although the inks respectively used are different from each other.
First, the liquid discharge head 20 will be described.
The liquid discharge head 20 illustrated in FIG. 3 is an ink jet head, and includes a supply port 20a through which ink flows in, a collection port 20b through which ink flows out, a nozzle plate 21 having a plurality of nozzle holes 21a, a substrate 22, and a manifold 23 joined to the substrate 22.
The substrate 22 is joined to face the nozzle plate 21 and is configured in a predetermined shape to form a predetermined ink flow path 28 including a plurality of ink pressure chambers 25 with the nozzle plate 21. The substrate 22 is provided with partition walls arranged between a plurality of ink pressure chambers 25 in the same row. An actuator 24 provided with electrodes 24a and 24b is provided at a portion of the substrate 22 facing each ink pressure chamber 25.
The actuator 24 is disposed to face the nozzle hole 21a, and the ink pressure chamber 25 is formed between the actuator 24 and the nozzle hole 21a. The actuator 24 is connected to a drive circuit. The liquid discharge head 20 discharges liquid from the nozzle hole 21a arranged to face the actuator 24 by deforming the actuator 24 according to a voltage under the control of the module control unit 38.
Next, the circulation device 30 (liquid circulation device) will be described.
As illustrated in FIG. 2, the circulation device 30 is integratedly connected to a top portion of the liquid discharge head 20 by a metal connecting component. The circulation device 30 includes a predetermined circulation path 31 configured to allow liquid to circulate through the liquid discharge head 20, 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 a liquid discharge action.
The circulation device 30 includes a cartridge 51 as an ink replenishment tank (liquid replenishment tank) provided outside the circulation path 31.
The cartridge 51 is configured to be able to hold ink, and an air chamber inside the cartridge 51 is open to the atmosphere.
First, the circulation path 31 will be described.
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 cartridge 51, which is an ink replenishment tank, and the first circulation pump 33. The second flow path 31b connects the first circulation pump 33 and the supply port 20a of the liquid discharge head 20. The third flow path 31c connects the collection port 20b of the liquid discharge head 20 and the second circulation pump 36. The fourth flow path 31d connects the second circulation pump 36 and the 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 an outer surface of the pipe. The tube covering the outer surface of the pipes of the first flow path 31a and the fourth flow path 31d is, for example, a PTFE tube.
The ink circulating in the circulation path 31 reaches the inside of the liquid discharge head 20 from the 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 discharge head 20. The ink circulating in the circulation path 31 reaches the cartridge 51 from the liquid discharge head 20 through the collection port 20b of the liquid discharge head 20, the third flow path 31c, the second circulation pump 36, and the fourth flow path 31d.
Next, the first circulation pump 33 and the second circulation pump 36 will be described.
The first circulation pump 33 is a pump that sends out liquid. The first circulation pump 33 sends out the liquid from the first flow path 31a toward the second flow path 31b. That is, the first circulation pump 33 is a pressurizing pump that sucks up ink from the cartridge 51, which is an ink replenishment tank, and supplies the ink to the liquid discharge head 20 by the action of the actuator.
The second circulation pump 36 is a pump that sends out liquid. The second circulation pump 36 sends out the liquid from the third flow path 31c toward the fourth flow path 31d. That is, the second circulation pump 36 is a depressurizing pump that collects the ink from the liquid discharge head 20 and replenishes the ink to the cartridge 51 by the action of the actuator.
The first circulation pump 33 and the second circulation pump 36 are configured as a piezoelectric pump 60, for example, as illustrated in FIG. 4. The piezoelectric pump 60 includes a pump chamber 58, a piezoelectric actuator 59 that is provided in the pump chamber 58 and vibrates by a voltage, and check valves 61 and 62 arranged at an inlet and outlet of the pump chamber 58. The piezoelectric actuator 59 is configured to be vibratable 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.
For example, by changing the voltage applied to the piezoelectric actuator 59, the piezoelectric actuator 59 deforms in the direction in which the pump chamber 58 is contracted or in the direction in which the pump chamber 58 is expanded, as illustrated in the upper and lower parts of FIG. 4. With this configuration, the volume of the pump chamber 58 changes. For example, if the piezoelectric actuator 59 is deformed in the direction of expanding the pump chamber 58, the check valve 61 at the inlet of the pump chamber 58 opens and ink is drawn into the pump chamber 58. For example, if the piezoelectric actuator 59 is deformed in the direction of contracting 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 out to the other side. By repeating this action, the first circulation pump 33 and the second circulation pump 36 each draw ink from one side and send out ink from the other side.
The maximum change amount 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 change amount of the piezoelectric actuator 59 increases. If the voltage applied to the piezoelectric actuator 59 becomes smaller, the maximum change amount of the piezoelectric actuator 59 becomes smaller. A liquid feeding capacity of the piezoelectric pump 60 depends on the maximum change amount of the piezoelectric actuator 59. That is, the module control unit 38 controls the liquid feeding capacity of the piezoelectric pump 60 by controlling the voltage applied to the piezoelectric actuator 59.
Next, the bypass flow path 34 and the buffer tank 35 will be described.
The bypass flow path 34 is a flow path connecting the second flow path 31b and the third flow path 31c. The bypass flow path 34 connects the supply port 20a which is the primary side of the liquid discharge head 20 and the collection port 20b which is the secondary side of the liquid discharge head 20 in the circulation path 31 in a short-circuit manner without passing through the liquid discharge head 20.
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 location on a lower portion of one side wall of a pair of side walls of the buffer tank 35 and the second flow path 31b, and a second bypass flow path 34b connecting a predetermined location on a lower portion of the other side wall of the pair of side walls of the buffer tank 35 and the third flow path 31c.
For example, the first bypass flow path 34a and the second bypass flow path 34b have the same length and the same diameter, and the first and second bypass flow paths are configured to have a smaller diameter than that 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 provided so that a distance between a connection position between the second flow path 31b and the first bypass flow path 34a and the supply port 20a of the liquid discharge head 20 and a distance between a connection position between the third flow path 31c and the second bypass flow path 34b and the collection port 20b of the liquid discharge head 20 are equal.
The buffer tank 35 is connected in parallel with the liquid discharge 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 has, for example, an upper wall, a lower wall, a rear wall, a front wall, and a pair of left and right side walls, and is configured in a rectangular box shape forming a storage chamber 35a for storing the liquid inside thereof. The connection position between the first bypass flow path 34a and the buffer tank 35 and the connection position between the second bypass flow path 34b and the buffer tank 35 are set to be at the same height. Ink flowing through the bypass flow path 34 is arranged in the lower region of the storage chamber 35a in the buffer tank 35, and an air chamber is formed in the upper region of the storage chamber 35a. That is, the buffer tank 35 can store a predetermined amount of liquid and air. The buffer tank 35 is provided with the on-off valve 37 configured to open the air chamber in the buffer tank 35 to the atmosphere and the pressure sensor 39.
The on-off valve 37 is a normally closed solenoid on-off valve that opens if a power source is turned on and closes if the power source 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 with respect to the atmosphere by being opened and closed under the control of the module control unit 38.
The pressure sensor 39 measures the pressure in the air chamber of the buffer tank 35, and sends pressure data indicating a pressure value to the module control unit 38. If the on-off valve 37 is open and the air chamber of the buffer tank 35 is open to the atmosphere, pressure data measured by the pressure sensor 39 is equal to the atmospheric pressure. The pressure sensor 39 measures the pressure in the air chamber of the buffer tank 35 if the on-off valve 37 is closed and the air chamber of the buffer tank 35 is not open to the atmosphere.
The pressure sensor 39 outputs the pressure as an electric signal by using, for example, a semiconductor piezoresistive pressure sensor. The semiconductor piezoresistive pressure sensor includes a diaphragm that receives external pressure and a semiconductor strain gauge formed on a surface of the diaphragm. The semiconductor piezoresistive pressure sensor measures the pressure by converting a change in electrical resistance due to a piezoresistive effect that occurs in the strain gauge accompanied by the deformation of the diaphragm due to external pressure into an electric signal.
Next, the module control unit 38 will be described.
FIG. 5 is an explanatory diagram illustrating a configuration example of the module control unit 38.
The module control unit 38 controls the action of the liquid discharge 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 processor 71, a memory 72, a communication interface 73, a circulation pump drive circuit 74, a valve drive circuit 76, and a liquid discharge head drive circuit 77.
The processor 71 is a computing element (for example, a central processing unit (CPU)) that executes computation processing. The processor 71 performs various processing based on data such as a program stored in the memory 72. The processor 71 functions as a control circuit capable of executing various controls by executing the program stored in the memory 72.
The memory 72 is a memory device for storing various information. The memory 72 includes, for example, a read only memory (ROM) 72a and a random access memory (RAM) 72b.
The ROM 72a is a read-only non-volatile memory. The ROM 72a stores a program, data used in the program, and the like. For example, the ROM 72a stores various setting values such as a calculation formula for calculating ink pressure of the nozzle hole 21a, a target pressure range, and an adjustment maximum value of each pump as control data used for pressure control.
The RAM 72b is a volatile memory that functions as a working memory. The RAM 72b temporarily stores data and the like in processing by the processor 71. The RAM 72b temporarily stores a program executed by the processor 71.
The communication interface 73 is an interface for communicating with another device. The communication interface 73 relays, for example, communication with the host control device 13 that transmits print data to the liquid discharge device 10.
The circulation pump drive circuit 74 applies a drive voltage to the piezoelectric actuator 59 of the piezoelectric pump 60 based on the control of the processor 71 to drive the piezoelectric pump 60. With this configuration, the circulation pump drive circuit 74 circulates ink in the circulation path 31. The 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.
The valve drive 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.
The liquid discharge head drive circuit 77 applies a voltage to the actuator 24 of the liquid discharge head 20 to drive the liquid discharge head 20 based on the control of the processor 71, and causes ink to be discharged from the nozzle hole 21a of the liquid discharge head 20.
In the configuration described above, the processor 71 receives various information such as action conditions by communicating with the host control device 13 through the communication interface 73. Various information acquired by the processor 71 is sent to the host control device 13 of the ink jet recording apparatus 1 through the communication interface 73.
The processor 71 acquires a measurement result from the pressure sensor 39, and controls the action of the circulation pump drive circuit 74 and the valve drive circuit 76 based on the acquired measurement result. For example, the processor 71 controls the liquid feeding capacity of the first circulation pump 33 and the second circulation pump 36 by controlling the circulation pump drive circuit 74 based on the measurement result of the pressure sensor 39. With this configuration, the processor 71 adjusts the ink pressure of the nozzle hole 21a.
The processor 71 controls the valve drive circuit 76 to cause the on-off valve 37 to be opened and closed. With this configuration, the processor 71 adjusts a liquid level of the buffer tank 35.
The processor 71 acquires a measurement result from the pressure sensor 39, and controls the liquid discharge head drive circuit 77 based on the acquired measurement result to cause ink droplets to be discharged from the nozzle hole 21a of the liquid discharge head 20 to the recording medium. Specifically, the processor 71 inputs an image signal corresponding to image data to the liquid discharge head drive circuit 77. The liquid discharge head drive circuit 77 drives the actuator 24 of the liquid discharge head 20 in response to the image signal. If the liquid discharge head drive circuit 77 drives the actuator 24 of the liquid discharge head 20, the actuator 24 is deformed and ink pressure (nozzle surface pressure) of the nozzle hole 21a at a position facing the actuator 24 changes. The nozzle surface pressure is pressure given by ink in the ink pressure chamber 25 to a meniscus Me formed by ink in the nozzle hole 21a. If the nozzle surface pressure exceeds a predetermined value determined by the shape of the nozzle hole 21a, the characteristics of the ink, and the like, the ink is discharged from the nozzle hole 21a. With this configuration, the processor 71 forms an image corresponding to the image data on the recording medium.
Next, the pressure in the buffer tank 35 will be described.
Here, a change in pressure in the buffer tank 35 between the time when the ink pressure chamber 25 is in an empty state and the time when the ink pressure chamber 25 is filled with ink will be described.
FIG. 6 is a graph illustrating the change in pressure in the buffer tank 35 between the time when the ink pressure chamber 25 is in the empty state and the time when the ink pressure chamber 25 is filled with the ink. That is, FIG. 6 illustrates the change in pressure measured by the pressure sensor 39. In FIG. 6, the horizontal axis represents the time and the vertical axis represents the pressure in the buffer tank 35.
In the example illustrated in FIG. 6, it is assumed that the liquid discharge head 20 and the circulation path 31 are not filled with ink at a time point T1. It is assumed that the on-off valve 37 is closed. It is assumed that the pressure in the buffer tank 35 at the time point T1 is "0 kPa".
At the time point T1, the processor 71 starts circulation of ink from the cartridge 51 using the first circulation pump 33 and the second circulation pump 36.
If the supply of ink from the cartridge 51 starts, the pressure in the buffer tank 35 is reduced. 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 discharge head 20, the first bypass flow path 34a, and the buffer tank 35. Here, it is assumed that at a time point T2, the plurality of nozzle holes 21a are filled with ink, and ink starts to flow into the buffer tank 35. That is, the pressure in the buffer tank 35 becomes the minimum at the time point T2.
If the plurality of nozzle holes 21a are filled with ink and the ink flows into the buffer tank 35, the pressure in the buffer tank 35 rises. The pressure in the buffer tank 35 continues to rise until the ink reaches the second circulation pump 36. Here, it is assumed that at a time point T3, the ink reaches the second circulation pump 36. That is, at the time point T3, the pressure in the buffer tank 35 reaches the peak thereof.
If the ink reaches the second circulation pump 36, the pressure in the buffer tank 35 decreases again. After that, air bubbles in the ink pressure chamber 25 and the circulation path 31 are discharged, and the liquid level of the buffer tank 35 is stabilized. If the liquid level in the buffer tank 35 is stabilized, the pressure in the buffer tank 35 is also stabilized. Here, it is assumed that at a time point T4, the pressure in the buffer tank 35 is stable. That is, in the vicinity of the time point T4, the change in pressure in the buffer tank 35 becomes small.
It is assumed that at the time point T4, the ink pressure chamber 25 is filled with ink.
Next, a function realized by the circulation device 30 will be described. The function realized by the circulation device 30 is realized by the processor 71 executing the program stored in the memory 72 or the like.
The processor 71 has a function of determining whether the ink pressure chamber 25 is filled with ink based on the pressure in the buffer tank 35.
The processor 71 acquires the pressure in the buffer tank 35 in time series. The processor 71 determines whether the ink pressure chamber 25 is filled with ink based on the pressure acquired in time series.
That is, the processor 71 detects that the pressure in the buffer tank 35 has reached (corresponding to time point T2) a lower limit (lower limit pressure), then has reached (corresponding to time point T3) an upper limit (upper limit pressure), and then is stable (corresponding to time point T4).
First, the processor 71 detects that the pressure in the buffer tank 35 has reached the lower limit pressure.
For example, the processor 71 receives a control signal for starting circulation of ink from the host control device 13 through the communication interface 73. If the control signal is received, the processor 71 starts circulation of ink from the cartridge 51 by using the first circulation pump 33 and the second circulation pump 36.
If the circulation of ink is started, the processor 71 causes the pressure sensor 39 to measure the pressure in the buffer tank 35. Here, it is assumed that the on-off valve 37 is closed.
The processor 71 continues to acquire pressure data indicating a value of pressure from the pressure sensor 39. The processor 71 sets a variable P_min_temp for storing a minimum value of pressure. Here, the processor 71 substitutes an initial value (for example, 500 Pa) into P_min_temp.
If pressure P measured by the pressure sensor 39 is smaller than P_min_temp, the processor 71 substitutes the pressure P into P_min_temp. If P_min_temp is not updated (that is, if P is greater than P_min_temp) for a predetermined period of time (for example, 2 s), the processor 71 determines that the pressure in the buffer tank 35 has reached the lower limit (lower limit pressure).
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 a variable P_min for 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.
Next, the processor 71 detects that the pressure in the buffer tank 35 has reached the upper limit pressure.
If the flag indicating that the lower limit pressure has been detected is set, the processor 71 sets a variable P_max_temp for storing a maximum value of the pressure. Here, the processor 71 substitutes P_min as an initial value into the variable P_max_temp.
If the pressure P measured by the pressure sensor 39 is greater than P_max_temp, the processor 71 substitutes the pressure P into P_max_temp. If P_max_temp is not updated (that is, if P is less than or equal to P_max_temp) for a predetermined period of time (for example, 2 s), the processor 71 calculates a difference between P_max_temp and P_min.
If the difference is calculated, the processor 71 determines whether the calculated difference is greater than a predetermined threshold (for example, 2 kPa). If it is determined that the calculated difference is greater than the predetermined threshold, the processor 71 determines that the pressure in the buffer tank 35 has reached the upper limit (upper limit pressure).
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 a variable P_max for 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.
If it is determined that the calculated difference is equal to or less than the predetermined threshold, the processor 71 returns to the action of determining whether the pressure P measured by the pressure sensor 39 is greater than P_max_temp.
Next, the processor 71 detects that the pressure in the buffer tank 35 is stable.
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 variance of pressure falls below a predetermined threshold (for example, 40).
If the counter is set, the processor 71 calculates the variance σm of pressure. Here, the processor 71 acquires the pressure every 50 ms in the past 2.5 s and calculates the variance of the acquired pressure.
If the variance σm of pressure is calculated, the processor 71 determines whether the variance σm of pressure is smaller than the predetermined threshold (for example, 40). If it is determined that the variance σm of pressure is smaller than the predetermined threshold, the processor 71 increments the count stb (adds 1 to count_stb).
The processor 71 repeats the action described above for a predetermined period of time (for example, 10 s). If the predetermined period of time elapses, the processor 71 determines whether the count_stb exceeds a predetermined threshold (for example, 180). If it is determined that the count_stb exceeds the predetermined threshold, the processor 71 determines that the pressure is stable, and sets a flag indicating that the pressure in the buffer tank 35 is stable.
If it is determined that the count_stb is equal to or less than the predetermined threshold, the processor 71 returns to the action of calculating the variance of pressure again.
If the 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 transmits 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.
Next, an action example of the processor 71 will be described.
FIG. 7 is a flowchart illustrating the action example of the processor 71.
First, the processor 71 starts circulation of ink from the cartridge 51 by using the first circulation pump 33 and the second circulation pump 36 (ACT 11). If the circulation of ink is started, the processor 71 determines whether the pressure in the buffer tank 35 has reached a lower limit pressure (ACT 12).
If it is detected that the pressure in the buffer tank 35 has reached the lower limit pressure, the processor 71 determines whether the pressure in the buffer tank 35 has reached an upper limit pressure (ACT 13). If it is detected that the pressure in the buffer tank 35 has reached the upper limit pressure, the processor 71 determines whether the pressure in the buffer tank 35 is stable (ACT 14).
If 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). If it is determined that the ink pressure chamber 25 is filled with ink, the processor 71 ends the action.
If it is determined that the ink pressure chamber 25 is filled with ink, the processor 71 may cause ink to be discharged from the ink pressure chamber 25 according to the control of the host control device 13.
Next, an action 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.
FIG. 8 is a flowchart illustrating the action example (ACT 12) in which the processor 71 detects that the pressure in the buffer tank 35 has reached the lower limit pressure.
First, the processor 71 substitutes 500 Pa into P_min_temp (ACT 21). If 500 Pa is substituted into P_min_temp, the processor 71 starts a timer t_min (ACT 22).
If the timer t_min is started, the processor 71 determines whether the timer t_min is greater than 2 s (whether 2 seconds have elapsed) (ACT 23). If it is determined that the timer t_min is not greater than 2 s (NO in ACT 23), the processor 71 determines whether the pressure P, which is measured by the pressure sensor 39, is less than P_min_temp (ACT 24).
If it is determined that P is less than P_min_temp (YES in ACT 24), the processor 71 substitutes P into P_min_temp (ACT 25). If P is substituted into P_min_temp, the processor 71 resets the timer t_min (sets the timer t_min to 0) (ACT 26).
If it is determined that P is not less than P_min_temp (NO in ACT 24), or if the timer t_min is reset (ACT 26), the processor 71 returns to ACT 23.
If it is determined that the timer t_min is greater than 2 s (YES in ACT 23), the processor 71 substitutes P_min_temp into P_min for storing the lower limit pressure (ACT 27). 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 (ACT 28).
If the flag indicating that the pressure in the buffer tank 35 has reached the lower limit pressure is set, the processor 71 ends the action.
Next, an action 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.
FIG. 9 is a flowchart illustrating the action example (ACT 13) in which the processor 71 detects that the pressure in the buffer tank 35 has reached the upper limit pressure.
First, the processor 71 substitutes P_min into P_max_temp (ACT 31). If P_min is substituted into P_maxtemp, the processor 71 starts the timer t_max (ACT 32).
If the timer t_max is started, the processor 71 determines whether the timer t_max is greater than 2 s (whether 2 seconds have elapsed) (ACT 33). If it is determined that the timer t_max is not greater than 2 s (NO in ACT 33), the processor 71 determines whether the pressure P measured by the pressure sensor 39 is greater than P_max_temp (ACT 34).
If it is determined that P is greater than P_max_temp (YES in ACT 34), the processor 71 substitutes P into P_max_temp (ACT 35). If P is substituted into P_max_temp, the processor 71 resets the timer t_max (sets the timer t_max to 0) (ACT 36).
If it is determined that P is not greater than P_max_temp (NO in ACT 34), or if the timer t_max is reset (ACT 36), the processor 71 returns to ACT 33.
If it is determined that the timer t_max is greater than 2 s (YES in ACT 33), the processor 71 determines whether P_max_temp - P_min is greater than 2 kPa (ACT 37). If it is determined that P_max_temp - P_min is not greater than 2 kPa (NO in ACT 37), the processor 71 returns to ACT 36.
If it is determined that P_max_temp - P_min is greater than 2 kPa (YES in ACT 37), the processor 71 substitutes P_max_temp into P_max for storing the upper limit pressure (ACT 38). 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 (ACT 39).
If the flag indicating that the pressure in the buffer tank 35 has reached the upper limit pressure is set, the processor 71 ends the action.
Next, an action example (ACT 14) in which the processor 71 detects that the pressure in the buffer tank 35 is stable will be described.
FIG. 10 is a flowchart illustrating the action example (ACT 14) in which the processor 71 detects that the pressure in the buffer tank 35 is stable.
First, the processor 71 starts a timer t_σ (ACT 41). If the timer t_σ is started, the processor 71 calculates the variance σm of pressure (ACT 42). If the variance σm of pressure is calculated, the processor 71 determines whether the variance σm of pressure is less than 40 (ACT 43).
If it is determined that the variance σm of pressure is less than 40 (YES in ACT 43), the processor 71 increments count_stb (ACT 44).
If it is determined that the variance σm of pressure is not less than 40 (NO in ACT 43) or if count stb is incremented (ACT 44), the processor 71 determines whether the timer t_σ is greater than 10 s (whether 10 seconds have elapsed) (ACT 45).
If it is determined that the timer t_σ is not greater than 10 s (NO in ACT 45), the processor 71 waits for 50 ms (ACT 46). After waiting for 50 ms, the processor 71 returns to ACT 42.
If it is determined that the timer t_σ is greater than 10 s (YES in ACT 45), the processor 71 determines whether count_stb is greater than 180 (ACT 47). If it is determined that count stb is not greater than 180 (NO in ACT 47), the processor 71 resets the timer t_σ (sets the timer t_σ to 0) (ACT 48).
If the timer t_σ is reset, the processor 71 returns to ACT 42.
If it is determined that count stb is greater than 180 (YES in ACT 47), the processor 71 sets a flag indicating that the pressure in the buffer tank 35 is stable (ACT 49).
If the flag indicating that the pressure in the buffer tank 35 is stable is set, the processor 71 ends the action. The processor 71 determines that the pressure in the buffer tank 35 is stable based on the variance σm of pressure.
The liquid to be discharged is not limited to ink for printing, and application to, for example a device that discharges a liquid containing conductive particles for forming a wiring pattern of a printed wiring board, and the like, may also be contemplated.
In addition to the matters described above, the liquid discharge head 20 may have a structure in which a diaphragm is deformed by static electricity to discharge ink droplets, or a structure in which ink droplets are discharged from a nozzle by using thermal energy of a heater or the like.
In the embodiment, the liquid discharge head is illustrated as an example of being used in the ink jet recording apparatus or the like, but the exemplary embodiment is not limited thereto. The liquid discharge head can be used, for example, in a 3D printer, an industrial manufacturing machine, or a medical application.
The circulation device configured 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 flow path or the like is not provided with a liquid detection sensor. Therefore, the circulation device can effectively detect that the ink pressure chamber is filled with liquid.
While certain embodiments have been described, these embodiments are presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.

Claims

A liquid circulation device configured to be connected to a liquid discharge head, comprising:
a pressurizing pump configured to supply liquid from a tank to the liquid discharge head;

a depressurizing pump configured to collect the liquid from the liquid discharge head;

a buffer tank connected in parallel with the liquid discharge head between the pressurizing pump and the depressurizing pump, and configured to store the liquid;

a sensor configured to measure pressure in the buffer tank; and

a processor configured to determine whether a pressure chamber included in the liquid discharge head is filled with the liquid based on the measured pressure.
The liquid circulation device according to claim 1, wherein
the processor is configured to acquire the pressure from the sensor in time series, and determine whether the pressure chamber is filled with the liquid based on the pressure acquired in time series.
The liquid circulation device according to claim 2, wherein
the processor is configured to determine that the pressure chamber is filled with the liquid, when detecting that the pressure reaches lower limit pressure, the pressure reaches upper limit pressure, and the pressure is stable.
The liquid circulation device according to claim 3, wherein
the processor is configured to:
determine that the pressure reaches the lower limit if a minimum value of the pressure is not updated for a predetermined period of time,

determine that the pressure reaches the upper limit if a maximum value of the pressure is not updated for a predetermined period of time, and

determine that the pressure is stable based on variance of the pressure.
The liquid circulation device according to claim 4, wherein the processor is configured to acquire a plurality of the pressures from the sensor in a predetermined time period to calculate the variance of the acquired pressures.
The liquid circulation device according to claim 4 or 5, wherein the processor is configured to:
count the number of times the variance falls below a predetermined threshold; and

determine that the pressure is stable when the counted number exceeds a predetermined threshold.
A liquid discharge device comprising:
a liquid discharge head comprising a pressure chamber; and

the liquid circulation device according to any one of claims 1 to 6.
An ink jet recording apparatus comprising a plurality of the liquid discharge devices according to claim 7.