JP7650765B2 - Liquid circulating device and liquid ejecting device - Google Patents

Description

Embodiments of the present invention are liquid circulation devices and liquid ejection devices.

A liquid ejection device is known that includes a liquid ejection head (inkjet head) that ejects liquid (ink) and a liquid circulation device that circulates the liquid in a circulation path that includes the liquid ejection head.

The liquid circulation device is equipped with a liquid detection sensor at a specific location in the flow path to detect the state of liquid filling the liquid ejection head. For example, the liquid detection sensor is a capacitance type or a float type sensor.

However, capacitance-type liquid detection sensors are large in size, limiting the locations where they can be installed. Furthermore, float-type liquid detection sensors have low reliability because the moving parts can become stuck due to liquid.

JP 2019-137021 A JP 2010-105169 A

To solve the above problems, we provide a liquid circulation device and a liquid ejection device that can effectively detect when liquid has been filled into the liquid ejection head.

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

FIG. 1 is an explanatory diagram of an example of the configuration of an inkjet recording apparatus according to an embodiment. FIG. 2 is an explanatory diagram of an example of the configuration of a liquid ejection device according to an embodiment. FIG. 3 is an explanatory diagram of an example of the configuration of a liquid ejection head according to an embodiment. FIG. 4 is an explanatory diagram of an example of the configuration of a piezoelectric pump according to an embodiment. FIG. 5 is an explanatory diagram of an example of the configuration of a module control unit according to the embodiment. FIG. 6 is a graph showing the pressure inside the buffer tank according to the embodiment. FIG. 7 is a flowchart for explaining an example of the operation of the circulation device according to the embodiment. FIG. 8 is a flowchart for explaining an example of the operation of the circulation device according to the embodiment. FIG. 9 is a flowchart for explaining an example of the operation of the circulation device according to the embodiment. FIG. 10 is a flowchart for explaining an example of the operation of the circulation device according to the embodiment.

A liquid circulation device and a liquid ejection device according to an embodiment will be described below with reference to the drawings.
A liquid ejection device 10 according to an embodiment and an inkjet recording device 1 including the liquid ejection device 10 will be described below with reference to Figs. 1 to 7. In each drawing, the configuration is enlarged, reduced, or omitted as appropriate for the purpose of explanation. Fig. 1 is a side view showing the configuration of the inkjet recording device 1. Fig. 2 is an explanatory diagram showing the configuration of the liquid ejection device 10. Fig. 3 is an explanatory diagram showing the configuration of the liquid ejection head 20. Fig. 4 is an explanatory diagram showing the configurations of a first circulating pump 33 and a second circulating pump 36.

The inkjet recording device 1 shown in FIG. 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 the recording medium S, and a host control device 13.

As shown in FIG. 1, multiple 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 comprises a liquid ejection head 20 and a circulation device 30. The liquid ejection device 10 ejects liquid, such as ink, from the liquid ejection head 20 to form a desired image on a recording medium S disposed opposite the liquid ejection device 10.

The multiple liquid ejection devices 10 each eject multiple colors, such as cyan ink, magenta ink, yellow ink, black ink, and white ink, but the color or characteristics of the ink used are not limited. For example, instead of white ink, it is possible to eject transparent glossy ink, or special ink that changes color when exposed to infrared or ultraviolet light. The multiple liquid ejection devices 10 have the same configuration, although they each use different inks.

First, the liquid ejection head 20 will be described.
The liquid ejection head 20 shown in Figure 3 is an inkjet head, and is equipped with a supply port 20a through which ink flows in, a recovery 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 bonded opposite 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 between the substrate 22 and the nozzle plate 21. The substrate 22 has partition walls arranged between the ink pressure chambers 25 in the same row. An actuator 24 having electrodes 24a and 24b is provided on the portion of the substrate 22 facing each ink pressure chamber 25.

The actuator 24 is disposed opposite the nozzle hole 21a, and an ink pressure chamber 25 is formed between the actuator 24 and the nozzle hole 21a. The actuator 24 is connected to a drive circuit. The liquid ejection head 20 ejects liquid from the nozzle hole 21a disposed opposite to it by the actuator 24 deforming in response to voltage under the control of the module control unit 38.

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

The circulation device 30 also includes a cartridge 51 that serves as an ink supply tank (liquid supply tank) that is provided outside the circulation path 31.

The cartridge 51 is configured to hold ink, and the internal air chamber 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 supply tank, to the first circulation pump 33. The second flow path 31b connects the first circulation pump 33 to the supply port 20a of the liquid ejection head 20. The third flow path 31c connects the recovery port 20b of the liquid ejection head 20 to the second circulation pump 36. The fourth flow path 31d connects the second circulation pump 36 to the cartridge 51. The first flow path 31a and the fourth flow path 31d 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 31a and the fourth flow path 31d are, for example, PTFE tubes.

The ink circulating through the circulation path 31 passes 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 ejection head 20, and then reaches the inside of the liquid ejection head 20. Also, the ink circulating through the circulation path 31 passes from the liquid ejection head 20 through the recovery port 20b of the liquid ejection head 20, the third flow path 31c, the second circulation pump 36, and the fourth flow path 31d, and then reaches the cartridge 51.

Next, the first circulating pump 33 and the second circulating 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 31a to the second flow path 31b. 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 the operation of an actuator, and supplies the ink to the liquid ejection head 20.

The second circulation pump 36 is a pump that pumps liquid. The second circulation pump 36 pumps liquid from the third flow path 31c toward the fourth flow path 31d. In other words, the second circulation pump 36 is a pressure reduction pump that recovers ink from the liquid ejection head 20 by the operation of the actuator and supplies the ink to the cartridge 51.

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 due to voltage, and check valves 61 and 62 arranged at the inlet and outlet of the pump chamber 58. The piezoelectric actuator 59 is configured to be capable of vibrating 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 a drive circuit by wiring and are configured to be controllable by the module control unit 38.

For example, as the voltage applied to the piezoelectric actuator 59 changes, the piezoelectric actuator 59 deforms in a direction that contracts the pump chamber 58 or in a direction that expands the pump chamber 58, as shown at the top and bottom of FIG. 4. This changes the volume of the pump chamber 58. For example, when the piezoelectric actuator 59 deforms in a direction that expands 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. Also, for example, when the piezoelectric actuator 59 deforms in a direction that contracts the pump chamber 58, the check valve 62 at the outlet of the pump chamber 58 opens, and ink in the pump chamber 58 is sent 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 send ink out from the other side.

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. 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 voltage applied to the piezoelectric actuator 59 to control the liquid delivery capacity of the piezoelectric pump 60.

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 31b and the third flow path 31c. The bypass flow path 34 short-circuits the supply port 20a, which is the primary side of the liquid ejection head 20 in the circulation path 31, and the recovery port 20b, which is the secondary side of the liquid ejection head 20, without passing through the liquid ejection 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 that connects a predetermined location on the lower part of a pair of side walls of the buffer tank 35 to the second flow path 31b, and a second bypass flow path 34b that connects a predetermined location on the lower part of a pair of side walls of the buffer tank 35 to 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 are both configured to be smaller than the circulation path 31. For example, the diameter of the circulation path 31 is set to about two to five 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 the distance between the connection position of the second flow path 31b and the first bypass flow path 34a and the supply port 20a of the liquid ejection head 20 is equal to the distance between the connection position of the third flow path 31c and the second bypass flow path 34b and the recovery port 20b of the liquid ejection head 20.

The buffer tank 35 is connected in parallel to the liquid ejection head 20 between the first circulation pump 33 and the second circulation pump 36. The buffer tank 35 has a flow passage cross-sectional area larger than the flow passage cross-sectional area of the bypass flow passage 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 to be a rectangular box shape forming a storage chamber 35a that stores liquid inside. The connection position between the first bypass flow passage 34a and the buffer tank 35 and the connection position between the second bypass flow passage 34b and the buffer tank 35 are set at the same height. Ink flowing through the bypass flow passage 34 is disposed 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. In addition, the buffer tank 35 is provided with an opening/closing valve 37 and a pressure sensor 39 that are configured to be able to open the air chamber in the buffer tank 35 to the atmosphere.

The opening/closing valve 37 is a normally closed solenoid opening/closing valve that opens, for example, when the power is turned on and closes when the power is turned off. The opening/closing 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.

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 opening/closing 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 will be equal to the atmospheric pressure. The pressure sensor 39 detects the pressure in the air chamber of the buffer tank 35 when the opening/closing valve 37 is closed and the air chamber of the buffer tank 35 is not open to the atmosphere.

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

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. As shown in FIG.
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 opening and closing valve 37. The module control unit 38 includes a processor 71, a memory 72, a communication interface 73, a circulation pump drive circuit 74, a valve drive circuit 76, and a liquid ejection head drive circuit 77.

The processor 71 is a computing element (e.g., a CPU (Central Processing Unit)) that executes calculation processing. The processor 71 performs various processes based on data such as programs stored in the memory 72. The processor 71 functions as a control circuit capable of executing various controls by executing the programs stored in the memory 72.

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

The ROM 72a is a read-only non-volatile memory. The ROM 72a stores programs and data used in the programs. For example, the ROM 72a stores various setting values such as a formula for calculating the ink pressure of the nozzle hole 21a, a target pressure range, and maximum adjustment values for each pump as control data used for pressure control.

RAM 72b is a volatile memory that functions as a working memory. RAM 72b temporarily stores data being processed by processor 71. RAM 72b also temporarily stores programs being executed by processor 71.

The communication interface 73 is an interface for communicating with other devices. For example, the communication interface 73 relays communication with the host control device 13, which transmits print data to the liquid ejection 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, and drives the piezoelectric pump 60. As a result, the circulation pump drive circuit 74 circulates ink in the circulation 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.

The valve drive circuit 76 drives the opening/closing valve 37 under the control of the processor 71, opening the air chamber of the buffer tank 35 to the atmosphere.

Based on the control of the processor 71, the liquid ejection head drive circuit 77 applies a voltage to the actuator 24 of the liquid ejection head 20 to drive the liquid ejection head 20 and eject ink from the nozzle holes 21a of the liquid ejection head 20.

In the above configuration, the processor 71 receives various information such as operating conditions by communicating with the host control device 13 via the communication interface 73. In addition, the various information acquired by the processor 71 is sent to the host control device 13 of the inkjet recording device 1 via the communication interface 73.

The processor 71 also acquires detection results 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 results. For example, the processor 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 results of the pressure sensor 39. In this way, the processor 71 adjusts the ink pressure of the nozzle hole 21a.

The processor 71 also controls the valve drive circuit 76 to open and close the on-off valve 37. This allows the processor 71 to adjust the liquid level in the buffer tank 35.

The processor 71 also acquires the detection result from the pressure sensor 39, and controls the liquid ejection head driving circuit 77 based on the acquired detection result to eject ink droplets from the nozzle hole 21a of the liquid ejection head 20 onto the recording medium. Specifically, the processor 71 inputs an image signal corresponding to the image data to the liquid ejection head driving circuit 77. The liquid ejection head driving circuit 77 drives the actuator 24 of the liquid ejection head 20 according to the image signal. When the liquid ejection head driving circuit 77 drives the actuator 24 of the liquid ejection head 20, the actuator 24 deforms, and the ink pressure (nozzle surface pressure) of the nozzle hole 21a facing the actuator 24 changes. 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 hole 21a. When the nozzle surface pressure exceeds a predetermined value determined by the shape of the nozzle hole 21a and the characteristics of the ink, ink is ejected from the nozzle hole 21a. In this way, the processor 71 forms an image corresponding to the image data on the recording medium.

Next, the pressure inside the buffer tank 35 will be described.
Here, a change in pressure within the buffer tank 35 from when the ink pressure chamber 25 is empty to when it is filled with ink will be described.

Figure 6 is a graph to explain the change in pressure inside the buffer tank 35 from when the ink pressure chamber 25 is empty until it is filled with ink. That is, Figure 6 shows the change in pressure detected by the pressure sensor 39. In Figure 6, the horizontal axis represents time, and the vertical axis represents the pressure inside the buffer tank 35.

In the example shown in FIG. 6, at time T1, the liquid ejection head 20 and the circulation path 31 are not filled with ink. The opening and closing valve 37 is closed. The pressure in the buffer tank 35 at time T1 is 0 kPa.

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

When the supply of ink from the cartridge 51 begins, the pressure in the buffer tank 35 decreases. The pressure in the buffer tank 35 continues to decrease until ink flows into the first flow path 31a and the second flow path 31b, and into the ink pressure chamber 25 of the liquid ejection head 20, the first bypass flow path 34a, and the buffer tank 35. Here, it is assumed that at time T2, the multiple nozzle holes 21a are blocked with ink, and ink begins to flow into the buffer tank 35. In other words, the pressure in the buffer tank 35 is at a minimum at time T2.

When the nozzle holes 21a are clogged with ink and 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 the ink reaches the second circulation pump 36 at time T3. That is, the pressure in the buffer tank 35 peaks at time T3.

When the ink reaches the second circulation pump 36, the pressure in the buffer tank 35 drops again. Thereafter, air bubbles in the ink pressure chamber 25 and the circulation path 31 are discharged, and the liquid level in the buffer tank 35 stabilizes. When the liquid level in the buffer tank 35 stabilizes, the pressure in the buffer tank 35 also stabilizes. Here, it is assumed that the pressure in the buffer tank 35 stabilizes at time T4. That is, in the vicinity of time T4, the change in pressure in the buffer tank 35 becomes small.
Also, it is assumed that the ink pressure chamber 25 is filled with ink at time T4.

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

The processor 71 has the 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 reaches the lower limit (lower limit pressure) (corresponding to time T2), then reaches the upper limit (upper limit pressure) (corresponding to time T3), and then stabilizes (corresponding to time T4).

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 to start circulating ink from the host control device 13 via the communication interface 73. Upon receiving the control signal, the processor 71 starts circulating ink from the cartridge 51 using the first circulation pump 33 and the second circulation pump 36.

When the ink circulation starts, the processor 71 causes the pressure sensor 39 to detect the pressure inside the buffer tank 35. Note that, in this case, the opening and closing valve 37 is assumed to be closed.

The processor 71 continues to acquire pressure data indicating the pressure value from the pressure sensor 39. The processor 71 also sets a variable (P_min_temp) that stores the minimum pressure value. Here, the processor 71 assigns an initial value (for example, 500 Pa) to P_min_temp.

If the pressure (P) detected by the pressure sensor 39 is smaller than P_min_temp, the processor 71 assigns P to P_min_temp. If P_min_temp is not updated for a predetermined period (e.g., 2 s) (i.e., P is greater than P_min_temp), the processor 71 determines that the pressure in the buffer tank 35 has reached the lower limit (lower limit pressure).

When the processor 71 determines that the pressure in the buffer tank 35 has reached the lower limit (lower limit pressure), it assigns P_min_temp to a variable (P_min) that stores the lower limit pressure. When the processor 71 assigns P_min_temp to P_min, it 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.

When the flag indicating that the lower limit pressure has been detected is set, the processor 71 sets a variable (P_max_temp) that stores the maximum pressure value. Here, the processor 71 assigns P_min to P_max_temp as the initial value.

If the pressure (P) detected by the pressure sensor 39 is greater than P_max_temp, the processor 71 assigns P to P_max_temp. If P_max_temp is not updated for a predetermined period (e.g., 2 s) (i.e., P is equal to or less than P_max_temp), the processor 71 calculates the difference between P_max_temp and P_min.

After calculating the difference, the processor 71 determines whether the calculated difference is greater than a predetermined threshold (e.g., 2 kPa). If it determines 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).

When the processor 71 determines that the pressure in the buffer tank 35 has reached the upper limit (upper limit pressure), it assigns P_max_temp to a variable (P_max) that stores the upper limit pressure. When the processor 71 assigns P_max_temp to P_max, it sets a flag indicating that the pressure in the buffer tank 35 has reached the upper limit pressure.

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

Next, the processor 71 detects that the pressure in the buffer tank 35 has stabilized.

When a flag indicating that the upper limit pressure has been detected is set, the processor 71 sets a counter (count_stb) that counts the number of times that the pressure variance falls below a predetermined threshold (e.g., 40).

After setting the counter, the processor 71 calculates the pressure variance (σm). Here, the processor 71 acquires the pressure every 50 ms for the past 2.5 s and calculates the variance of the acquired pressure.

After calculating σm, the processor 71 determines whether σm is smaller than a predetermined threshold (e.g., 40). If it determines that σm is smaller than the predetermined threshold, the processor 71 increments count_stb (adds 1 to count_stb).

The processor 71 repeats the above operation for a predetermined period (e.g., 10 s). After the predetermined period has elapsed, the processor 71 determines whether the count_stb has exceeded a predetermined threshold (e.g., 180). If it is determined that the count_stb has exceeded the predetermined threshold, the processor 71 determines that the pressure has stabilized, and sets a flag indicating that the pressure in the buffer tank 35 has stabilized.

When it is determined that count_stb is equal to or less than the predetermined threshold, the processor 71 returns to the operation of calculating the pressure variance again.

When the processor 71 sets a flag indicating that the pressure in the buffer tank 35 has stabilized, the processor 71 determines that the ink pressure chamber 25 has been filled with ink. For example, when the processor 71 determines that the ink pressure chamber 25 has been filled with ink, the processor 71 transmits a control signal to the host control device 13 via the communication interface 73, indicating that the ink pressure chamber 25 has been filled with ink.

Next, an example of the operation of the processor 71 will be described.
FIG. 7 is a flowchart for explaining an example of the operation of the processor 71.

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

When the processor 71 detects that the pressure in the buffer tank 35 has reached the lower limit pressure, the processor 71 detects that the pressure in the buffer tank 35 has reached the upper limit pressure (ACT 13). When the processor 71 detects that the pressure in the buffer tank 35 has reached the upper limit pressure, the processor 71 detects that the pressure in the buffer tank 35 has stabilized (ACT 14).

When the processor 71 detects that the pressure in the buffer tank 35 has stabilized, it determines that the ink pressure chamber 25 has been filled with ink (ACT 15). When it determines that the ink pressure chamber 25 has been filled with ink, the processor 71 ends the operation.

When the processor 71 determines that the ink pressure chamber 25 is filled with ink, it may eject ink from the ink pressure chamber 25 under the control of the host control device 13.

Next, an operation example (ACT 12) in which the processor 71 detects that the pressure in the buffer tank 35 has reached the lower limit pressure will be described.
FIG. 8 is a flowchart for explaining an operation example (ACT 12) in which the processor 71 detects that the pressure in the buffer tank 35 has reached the lower limit pressure.

First, the processor 71 assigns 500 Pa to P_min_temp (ACT 21). After assigning 500 Pa to P_min_temp, the processor 71 starts the timer t_min (ACT 22).

When the timer t_min is started, the processor 71 determines whether the timer t_min>2s (whether 2 seconds have elapsed) (ACT 23). If it is determined that the timer t_min>2s is not true (ACT 23, NO), the processor 71 determines whether the pressure (P) detected by the pressure sensor 39 is <P_min_temp (ACT 24).

When it is determined that P<P_min_temp (ACT 24, YES), the processor 71 assigns P to P_min_temp (ACT 25). After assigning P to 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<P_min_temp is not satisfied (ACT 24, NO), or if the timer t_min is reset (ACT 26), the processor 71 returns to ACT 23.

When it is determined that the timer t_min>2s (ACT 23, YES), the processor 71 assigns P_min_temp to P_min that stores the lower limit pressure (ACT 27). After assigning P_min_temp to 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).
When the processor 71 sets a flag indicating that the pressure in the buffer tank 35 has reached the lower limit pressure, the processor 71 ends the operation.

Next, an operation example (ACT 13) in which the processor 71 detects that the pressure in the buffer tank 35 has reached the upper limit pressure will be described.
FIG. 9 is a flowchart for explaining an operation example (ACT 13) in which the processor 71 detects that the pressure in the buffer tank 35 has reached the upper limit pressure.

First, the processor 71 assigns P_min to P_max_temp (ACT 31). After assigning P_min to P_max_temp, the processor 71 starts the timer t_max (ACT 32).

When the timer t_max is started, the processor 71 determines whether the timer t_max>2s (whether 2 seconds have elapsed) (ACT 33). If it is determined that the timer t_max>2s is not true (ACT 33, NO), the processor 71 determines whether the pressure (P) detected by the pressure sensor 39>P_max_temp (ACT 34).

When it is determined that P>P_max_temp (ACT 34, YES), the processor 71 assigns P to P_max_temp (ACT 35). After assigning P to 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>P_max_temp is not satisfied (ACT 34, NO), 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>2s (ACT 33, YES), the processor 71 determines whether P_max_temp-P_min>2kPa (ACT 37). If it is determined that P_max_temp-P_min>2kPa is not true (ACT 37, NO), the processor 71 returns to ACT 36.

If it is determined that P_max_temp-P_min>2 kPa (ACT 37, YES), the processor 71 assigns P_max_temp to P_max, which stores the upper limit pressure (ACT 38). After assigning P_max_temp to 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).
When the processor 71 sets a flag indicating that the pressure in the buffer tank 35 has reached the upper limit pressure, the processor 71 ends the operation.

Next, an operation example (ACT 14) in which the processor 71 detects that the pressure in the buffer tank 35 has stabilized will be described.
FIG. 10 is a flowchart for explaining an operation example (ACT 14) in which the processor 71 detects that the pressure in the buffer tank 35 has stabilized.

First, the processor 71 starts the timer t_σ (ACT 41). After starting the timer t_σ, the processor 71 calculates the pressure variance σm (ACT 42). After calculating σm, the processor 71 determines whether σm<40 (ACT 43).

If it is determined that σm<40 (ACT 43, YES), the processor 71 increments count_stb (ACT 44).
When it is determined that σm<40 is not satisfied (ACT 43, NO), or when count_stb is incremented (ACT 44), the processor 71 determines whether the timer t_σ>10s (whether 10 seconds have elapsed) (ACT 45).

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

When it is determined that the timer t_σ>10s (ACT 45, YES), the processor 71 determines whether count_stb>180 (ACT 47). When it is determined that the count_stb>180 is not satisfied (ACT 47, NO), the processor 71 resets the timer t_σ (sets the timer t_σ to 0) (ACT 48).
After resetting the timer t_σ, the processor 71 returns to ACT42.

If it is determined that count_stb>180 (ACT 47, YES), the processor 71 sets a flag indicating that the pressure in the buffer tank 35 has stabilized (ACT 49).
The processor 71 ends the operation when it sets the flag indicating that the pressure in the buffer tank 35 has stabilized. The processor 71 determines that the pressure in the buffer tank 35 has stabilized based on the pressure variance σm.

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.

In addition to the above, the liquid ejection head 20 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.

In the embodiment, the liquid ejection head is used in an inkjet recording device, but the invention is not limited to this and can also be used in, for example, 3D printers, industrial manufacturing machines, and medical applications.

The circulation device configured as described above detects that the ink pressure chamber has been filled with ink based on the pressure in the buffer tank. As a result, the circulation device can detect that the ink pressure chamber has been filled with ink without having to provide a liquid detection sensor in the flow path, etc. Therefore, the circulation device can effectively detect that the ink pressure chamber has been filled with liquid.

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 gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims.

1... inkjet recording device, 10... liquid ejection device, 11... head support mechanism, 12... medium support mechanism, 13... host control device, 20... liquid ejection head, 20a... supply port, 20b... recovery port, 21... nozzle plate, 21a... nozzle hole, 22... substrate, 23... manifold, 24... actuator, 24a... electrode, 24b... electrode, 25... ink pressure chamber, 28... ink flow path, 30... circulation device, 31... circulation path, 31a... first flow path, 31b... second flow path, 31c... second 3 flow path, 31d...fourth flow path, 33...first circulation pump, 34...bypass flow path, 34a...first bypass flow path, 34b...second bypass flow path, 35...buffer tank, 35a...storage chamber, 36...second circulation pump, 37...opening and closing valve, 38...module control unit, 39...pressure sensor, 51...cartridge, 58...pump chamber, 59...piezoelectric actuator, 60...piezoelectric pump, 61...check valve, 62...check valve, 71...processor, 72...memory, 72a...ROM, 72b. RAM, 73...communication interface, 74...circulation pump drive circuit, 76...valve drive circuit, 77...liquid ejection head drive circuit.

Claims (5)

a pressure pump for supplying liquid from a tank to a liquid ejection head;
a pressure reducing pump that recovers the liquid from the liquid ejection head;
a buffer tank connected in parallel to the liquid ejection head between the pressure pump and the pressure reducing pump, the buffer tank storing the liquid;
A sensor for detecting the pressure of the buffer tank;
a processor that determines whether the liquid has been filled into a pressure chamber provided in the liquid ejection head based on the detected pressure;
A liquid circulation device comprising: the processor acquires the pressure from the sensor in time series, and determines whether the pressure chamber is filled with the liquid based on the pressure acquired in time series.
2. The liquid circulation system of claim 1. When the processor detects that the pressure has reached a lower limit pressure, the pressure has reached an upper limit pressure, and the pressure has stabilized, the processor determines that the pressure chamber is filled with the liquid.
3. The liquid circulation system of claim 2. The processor,
determining that the pressure has reached a lower limit when the minimum pressure value has not been updated for a predetermined period of time;
determining that the pressure has reached an upper limit when the maximum pressure value has not been updated for a predetermined period of time;
determining that the pressure has stabilized based on the variance of the pressure;
4. The liquid circulation system of claim 3. a liquid ejection head including a pressure chamber;
a pressure pump for supplying liquid from a tank to the liquid ejection head;
a pressure reducing pump that recovers the liquid from the liquid ejection head;
a buffer tank connected in parallel to the liquid ejection head between the pressure pump and the pressure reducing pump, the buffer tank storing the liquid;
A sensor for detecting the pressure of the buffer tank;
a processor that determines whether the pressure chamber is filled with the liquid based on the detected pressure;
A liquid ejection device comprising: