JP6960790B2 - Liquid circulation device, liquid injection recording device, liquid supply device - Google Patents

Description

Embodiments of the present invention relate to a liquid circulation device, a liquid injection recording device, and a liquid supply device.

In an inkjet printer, there is a technique of connecting an ink circulation device to an inkjet head in order to avoid sticking of ink. With this technique, the ink supplied to the inkjet head can be maintained in an optimum state. Therefore, stable ink ejection can be realized even when the ink itself dries easily or when the inkjet head is placed in a high-temperature drying environment.

The ink circulation device often uses a piezoelectric diaphragm pump as the liquid feed pump. Since the piezoelectric diaphragm pump can be easily miniaturized, it can be arranged close to the inkjet head.
However, since the piezoelectric diaphragm pump has a large pulsation during liquid feeding, the back pressure (also referred to as nozzle pressure) of the inkjet head becomes unstable. Therefore, the meniscus of the ink in the head nozzle is disturbed, the amount of ink ejected fluctuates, and the accuracy of ink landing is lowered. Ink may not be ejected or ink may leak out.
Further, since the piezoelectric diaphragm pump has a small suction pressure and discharge pressure, it takes a long time to fill the inkjet head with ink, and purging for removing air bubbles or the like from the inkjet head becomes insufficient.

Japanese Unexamined Patent Publication No. 2014-195932

An object to be solved by the present invention is to provide a liquid circulation device, a liquid injection recording device, and a liquid supply device capable of suppressing pulsation during liquid feeding of a piezoelectric diaphragm pump.

The liquid circulation device of the embodiment includes a supply pump that supplies a liquid from the liquid storage container to the liquid injection device, a recovery pump that collects the liquid from the liquid injection device and returns it to the liquid storage container, and the supply pump. A pump control unit that controls the recovery pump, and one or both of the supply pump and the recovery pump are composed of a plurality of piezoelectric diaphragm pumps connected in series, and the pump control unit is the liquid. When the liquid is circulated between the injection device and the liquid storage container, the voltage or frequency of the drive wave applied to the piezoelectric diaphragm pump adjacent to the liquid injection device among the plurality of piezoelectric diaphragm pumps connected in series is changed. characterized in that to further absorb the pressure of the liquid to be.

The liquid injection recording device of the embodiment is characterized by including a liquid storage container, a liquid injection device, a liquid circulation device of the embodiment, and a medium transfer unit that conveys a recording medium toward the liquid injection device. do.

The liquid supply device of the embodiment includes a supply pump that supplies liquid from the liquid storage container to the liquid injection device, and a pump control unit that controls the supply pump, and the supply pumps are connected in series. The pump control unit is composed of a plurality of piezoelectric diaphragm pumps, and when the liquid is supplied to the liquid injection device, the pump control unit applies the liquid to the piezoelectric diaphragm pump close to the liquid injection device among the plurality of piezoelectric diaphragm pumps connected in series. characterized in that to further absorb the pressure of the liquid to change the voltage or frequency of the driving waves.

It is a schematic diagram which shows the structural example of the inkjet printer 100 of one Embodiment. It is a perspective view which shows the ink circulation apparatus 7 of one Embodiment. It is a figure which shows the piezoelectric diaphragm pump 50, is (a) front view, (b) AA sectional view. It is a figure which shows the operation of the check valve 54, 55, and is (a) at the time of ink inhalation, (b) at the time of ink discharge. It is a system block diagram which shows the structural example of a pump control part 30. The flowchart which shows the operation example of the ink circulation apparatus 7 of embodiment.

Hereinafter, the ink circulation device 7 and the inkjet printer 100 of the embodiment will be described with reference to the drawings. In each figure, the same reference numerals are given to the same configurations.

FIG. 1 is a schematic view showing a configuration example of the inkjet printer 100 of one embodiment.
The inkjet printer (liquid injection recording device) 100 ejects ink K according to the print data and records an image on the recording sheets 103 and 108.

In the following description, the main scanning direction of the inkjet head 1 is referred to as the Z direction. The sub-scanning direction is called the X direction. The vertical (vertical) direction is called the Y direction.

The recording papers (recording media) 103 and 108 are plain recording paper, art paper, coated paper and the like.
Ink (liquid) K is a liquid in which a dye or pigment as a colorant is dissolved or dispersed in a solvent. Examples of the ink solvent include water-based, oil-based, and solvent. Ink K also contains a clear liquid. The transparent liquid is used for forming a base layer or a protective layer for image formation. The base layer is formed on the recording papers 103 and 108 before the ink K containing the colorant is attached to improve the color development property of the attached ink K. The protective layer is formed on the ink layers after the ink K containing the colorant is adhered to the recording sheets 103 and 108.

The inkjet printer 100 includes a box-shaped housing 101.
Inside the housing 101, a paper feed cassette 102, 107, an upstream transport path 106, a transport belt 110, a printing unit 130, a downstream transport path 120, and a paper discharge tray 123 are arranged from the lower part to the upper part. Further, a main control unit 140, a display unit 145, and the like are arranged inside the housing 101.

The paper feed cassette 102 accommodates a plurality of A4 size recording paper 103 sheets. The paper feed cassette 107 accommodates a plurality of A3 size recording paper 108 sheets.
The inkjet printer 100 draws with ink K on two types of recording papers, the paper cassettes 102 and 107. The paper cassettes 102 and 107 are provided in the lower part of the housing 101.

The paper feed roller 104 feeds the recording paper 103 one by one from the paper cassette 102 to the upstream transport path 106. The upstream transport path 106 is composed of feed roller pairs 105a, 105b, 105c and recording paper guide plates 106a, 106b that regulate the transport direction of the recording papers 103, 108. The recording paper 103 is conveyed by the rotation of the feed roller pairs 105a and 105b, and after passing through the feed roller pair 105a, is fed to the upper surface (outer peripheral surface) of the transfer belt 110 by the recording paper guide plate 106a.

The paper feed roller 109 feeds the recording paper 108 one by one from the paper cassette 107 to the upstream transport path 106. The recording paper 108 is conveyed by the rotation of the feed roller pairs 105c, 105a, 105b, and after passing through the feed roller pair 105c, is fed to the upper surface (outer peripheral surface) of the transfer belt 110 by the recording paper guide plates 106a, 106b.

The transport belt (medium transport section) 110 is an endless belt in which fine holes are formed. The transport belt 110 has a width (length in the Z direction) larger than the width of the paper to be transported. In this embodiment, the transport belt 110 has a width of 330 mm in order to transport A3 recording paper.
The transport belt 110 is rotatably supported by three rollers, a drive roller 112a and a driven roller 112b, 112c, without slack. The drive roller 112a is rotated by the motor 111 to rotate the transport belt 110 at a predetermined peripheral speed.
A negative pressure container 113 is provided inside the transport belt 110. A large number of micropores 114 are formed on the upper surface of the negative pressure container 113, and come into contact with the back surface (inner peripheral surface) of the transport belt 110.
The negative pressure container 113 communicates with a fan 115 that depressurizes the inside of the container. An air flow is generated by the rotation of the fan 115, and the inside of the negative pressure container 113 is depressurized. By this depressurization, the recording sheets 103 and 108 are attracted to the upper surface of the transport belt 110 through the fine holes formed in the transport belt 110.
The recording sheets 103 and 108 are conveyed in the X direction through directly under the printing unit 130 by the rotation of the transfer belt 110 in a state of being attracted to the transfer belt 110. After that, the recording sheets 103 and 108 are transported to the downstream transport path 120.

The printing unit 130 includes four inkjet heads (liquid injection devices) 1. The printing unit 130 ejects cyan, magenta, yellow, and black inks K from the four inkjet heads 1 toward the recording sheets 103 and 108, and records an image according to the print data.
The four inkjet heads 1 have the same structure except for the color of the ink to be ejected.

The ink ejection surface of the inkjet head 1 is fixed at a position separated by a distance H from the upper surface of the transport belt 110. In this embodiment, H is 1 mm.
Each inkjet head 1 is long in the Z direction and short in the X direction. Further, the inkjet heads 1 are arranged at intervals in the X direction. Each inkjet head 1 is formed to have a length in the Z direction of 297 mm. In this embodiment, the inkjet head 1 is configured by staggering small heads having a length of 30 mm.

The printing unit 130 includes a maintenance unit 132, an ink tank 5, and an ink circulation device 7 for each inkjet head 1.
The maintenance unit 132 includes a cap 133 that protects the surface of the nozzle of the inkjet head 1, and a blade 134 that removes deposits remaining on the surface of the nozzle.

The ink tank (liquid storage container) 5 is an ink container for storing ink K.
The ink tank 5 is arranged above the inkjet head 1. The ink tank 5 and the inkjet head 1 are connected to each other via an ink supply tube 11 and an ink recovery tube 15. The ink supply tube 11 and the ink recovery tube 15 are resin tubes.
The inkjet head 1 has an ink supply port 2 and an ink recovery port 3, and an ink supply tube 11 is connected to the ink supply port 2 and an ink recovery tube 15 is connected to the ink recovery port 3, respectively.
Ink K is supplied to the inkjet head 1 through the ink supply tube 11, and ink K is collected in the ink tank 5 through the ink recovery tube 15.

The ink circulation device (liquid circulation device, liquid supply device) 7 circulates (flows) the ink K so that the ink K does not stick during non-printing (standby) or printing of the inkjet head 1.
The ink circulation device 7 is arranged between the ink tank 5 and the inkjet head 1. The ink circulation device 7 is connected (attached) to the ink supply pipe 11 and the ink recovery pipe 15.

After the images are formed, the recording sheets 103 and 108 are separated from the transport belt 110 and fed to the feed roller pair 120a. The downstream transport path 120 is composed of feed roller pairs 120a, 120b, 120c, 120d and recording paper guide plates 121a, 121b that regulate the transport direction of the recording papers 103, 108.
The recording sheets 103 and 108 are ejected from the output port 122 to the output tray 123 by the feed roller pairs 120a, 120b, 120c and 120d.

A computer 150 is connected to the inkjet printer 100. The computer 150 generates print data for drawing on the recording sheets 103 and 108. The print data is input to the inkjet printer 100 through the cable 143 and the connectors 141 and 142.

Next, the detailed configuration of the ink circulation device 7 will be described.
FIG. 2 is a perspective view showing the ink circulation device 7 of the embodiment.
The ink circulation device 7 circulates the ink K during non-printing (standby) or printing of the inkjet head 1. At this time, the ink circulation device 7 maintains the ink K inside the inkjet head 1 at a negative pressure with respect to the atmospheric pressure. The internal pressure (negative pressure) of the inkjet head 1 is set to -1 kPa.
Further, the ink circulation device 7 fills the ink jet head 1 with the ink K and purges the ink K from the inkjet head 1.

The ink circulation device 7 is arranged directly above the inkjet head 1.
The ink circulation device 7 includes an ink supply pipe 11, a supply pump 12, an ink recovery pipe 15, a recovery pump 16, a filter 21, a pressure sensor 25, a temperature sensor 26 (see FIG. 5), a pump control unit 30, and the like.

The supply pump 12 includes two piezoelectric diaphragm pumps 50 (main pump 50A and sub pump 50B). The main pump 50A and the sub pump 50B are connected in series in the + Y direction in the path of the ink supply pipe 11. The supply pump 12 supplies ink K from the ink tank 5 to the inkjet head 1 via the ink supply pipe 11 by the operation of the two piezoelectric diaphragm pumps 50 (main pump 50A and sub pump 50B).
The recovery pump 16 includes two piezoelectric diaphragm pumps 50 (sub pump 50C, main pump 50D). The sub pump 50C and the main pump 50D are connected in series in the −Y direction in the path of the ink recovery tube 15. The recovery pump 16 collects ink K from the inkjet head 1 via the ink recovery tube 15 and returns it to the ink tank 5 by the operation of the two piezoelectric diaphragm pumps 50 (sub pump 50C and main pump 50D). That is, the excess ink that has not been ejected from the inkjet head 1 is returned to the ink tank 5.

The filter 21 traps dust and air bubbles contained in the ink K sent from the supply pump 12. The dust and air bubbles trapped by the filter 21 are collected in the ink tank 5 together with a small amount of ink K through the bypass 22 and the ink recovery tube 15.
The bypass 22 is adjusted for pipeline resistance and regulates the flow rate of ink K. Therefore, most of the ink K sent by the supply pump 12 passes through the filter 21 and is sent to the inkjet head 1.

The pressure sensor 25 measures the pressure of ink K at the ink supply port 2 and the ink recovery port 3.
The temperature sensor 26 measures the temperature of the ink K inside the inkjet head 1.
The pump control unit 30 includes a CPU 31, various memories 32, and a drive circuit 33. The pump control unit 30 operates the supply pump 12, the recovery pump 16, the pressure sensor 25, and the temperature sensor 26 without depending on the main control unit 140 of the inkjet printer 100.

FIG. 3 is a view showing the piezoelectric diaphragm pump 50, which is (a) a front view and (b) a cross-sectional view taken along the line AA.
FIG. 4 is a diagram showing the operation of the check valves 54 and 55, which are (a) when ink is sucked and (b) when ink is discharged.
The piezoelectric diaphragm pumps 50 (main pumps 50A, 50D, sub pumps 50B, 50C) are pumps having the same structure and the same capacity. Each piezoelectric diaphragm pump 50 operates the diaphragm by compressing / expanding the piezoelectric element to send the ink K in one direction.

The piezoelectric diaphragm pump 50 includes an ink case 51, an actuator unit 52, a diaphragm 53, and check valves 54 and 55.
The ink case 51 has a ring shape, and an actuator unit 52 and a diaphragm 53 are stretched in the opening of the ink case 51. Further, the ink case 51 has an insole, and check valves 54 and 55 are arranged on the insole.
A pressure chamber 56 and ink chambers 54 and 55 are formed inside the piezoelectric diaphragm pump 50. A check valve 54 is provided between the pressure chamber 56 and the ink chamber 57 to suck the ink K into the pressure chamber 56. A check valve 55 is provided between the pressure chamber 56 and the ink chamber 58 to discharge the ink K from the pressure chamber 56.

The actuator unit 52 is formed by adhering a protective sheet, a piezoelectric ceramic, a metal plate, and a wetted diaphragm in this order, and is fixed in a stretched state in the opening of the ink case 51.
The protective sheet is, for example, a film of polytetrafluoroethylene. The piezoelectric ceramic is made of, for example, PZT (lead zirconate titanate). Piezoelectric ceramics have Ni / Au plated electrodes on both sides and have piezoelectricity due to polarization treatment. The metal plate is made of, for example, brass or SUS. The wetted diaphragm is made of, for example, a polyimide resin or the like. Power cables are connected to the piezoelectric ceramic and the metal plate, respectively.

The diaphragm 53 is a circular resin sheet made of, for example, a polyimide resin, and is fixed in a stretched state in the opening of the ink case 51. The diaphragm 53 vibrates following the operation of the actuator unit 52, and functions as a damper that reduces the pressure generated by the volume fluctuation of the pressure chamber 56. Since the pulsation of the ink K is reduced by the vibration of the diaphragm 53, the basic performances such as the flow rate, suction pressure, and discharge pressure of the piezoelectric diaphragm pump 50 are improved.
The check valves 54 and 55 have the same structure. The check valves 54 and 55 are disk-shaped resin sheets having a center hole, and are made of, for example, a polyimide resin or the like. The check valves 54 and 55 are fixed to the insole of the ink case 51 by inserting a fastening pin into the center hole.

Each piezoelectric diaphragm pump 50 (supply pump 12, recovery pump 16) is driven and controlled by the pump control unit 30. A pulse wave (drive wave) of an AC voltage generated by the drive circuit 33 of the pump control unit 30 is applied to the actuator unit 52, and the actuator unit 52 vibrates. The voltage of the pulse wave is 10 to 400 V, and the frequency is 10 to 500 Hz. In this embodiment, the voltage of the pulse wave is 200 V and the frequency is 100 Hz.
The amplitude of the vibration of the actuator unit 52 increases in proportion to the voltage of the pulse wave. Further, the amplitude of the vibration of the actuator unit 52 becomes maximum when the frequency of the pulse wave is 100 Hz, and the amplitude decreases as the distance from 100 Hz increases.

As shown in FIG. 4A, when the actuator unit 52 vibrates and the volume of the pressure chamber 56 expands, the check valve 54 opens, the check valve 55 closes, and ink enters the pressure chamber 56 from the ink chamber 57. K flows in. That is, the ink K is sucked into the piezoelectric diaphragm pump 50 from the outside.
On the other hand, as shown in FIG. 4B, when the volume of the pressure chamber 56 contracts, the check valve 54 closes, the check valve 55 opens, and ink K flows out from the pressure chamber 56 to the ink chamber 58. That is, the ink K is discharged to the outside from the piezoelectric diaphragm pump 50.

The volume of the pressure chamber 121 changes periodically due to the vibration of the actuator unit 52, and the check valves 54 and 55 open and close accordingly, so that the ink K is sent in one direction.
Each piezoelectric diaphragm pump 50 (supply pump 12, recovery pump 16) repeats such an operation to send the ink K.

FIG. 5 is a system block diagram showing a configuration example of the pump control unit 30.
The pump control unit 30 includes a CPU 31, various memories 32, and a drive circuit 33. A supply pump 12 (main pump 50A, sub pump 50B) and a recovery pump 16 (sub pump 50C, main pump 50D) are connected to the drive circuit 33. A drive circuit 33, a pressure sensor 25, and a temperature sensor 26 are connected to the CPU 31. Further, a power supply 34 is connected to the CPU 31.

The pump control unit 30 operates a supply pump 12 (main pump 50A, sub pump 50B), a recovery pump 16 (sub pump 50C, main pump 50D), a pressure sensor 25, and a temperature sensor 26.
Instructions such as ink circulation start / stop, ink filling start / stop, and purge start / stop are transmitted from the main control unit 140 to the CPU 31 via the communication interface 35. On the other hand, the ink pressure, the ink temperature, and the operation information of each piezoelectric diaphragm pump 50 acquired by the CPU 31 are transmitted to the main control unit 140 via the communication interface 35.

Next, an operation example of the ink circulation device 7 will be described.
FIG. 6 is a flowchart showing an operation example of the ink circulation device 7 of the embodiment.
The pump control unit 30 starts ink circulation when an instruction to start ink circulation is transmitted from the main control unit 140.

(Step S1)
First, the pump control unit 30 sets the drive voltage of the piezoelectric diaphragm pump 50 close to the inkjet head 1 to 0V. That is, the liquid feeding capacity of the sub pumps 50B and 50C is suppressed.

(Step S2)
Next, the pump control unit 30 applies a drive voltage only to the main pumps 50A and 50D to send the ink K. That is, with the sub-pumps 50B and 50C stopped, the ink K is sent (circulated) only by the main pumps 50A and 50D.

(Step S3)
When the ink circulation is started, the pressure sensor 25 measures the pressure of the ink K in the ink supply port 2 and the ink recovery port 3 and outputs the pressure to the CPU 31.
The CPU 31 obtains the differential pressure between the ink supply port 2 and the ink recovery port 3, and further obtains the ink pressure of the inkjet head 1 in consideration of the water head pressure of the inkjet head 1. That is, the pressure (back pressure) of the ink K in the nozzle of the inkjet head 1 is obtained.

(Step S4)
The CPU 31 compares the obtained nozzle pressure with the target pressure (-1 kPa) to adjust the drive voltage of the supply pump 12 (main pump 50A) or the recovery pump 16 (main pump 50D).

(Step S5)
The pump control unit 30 repeats nozzle pressure calculation (step S3) and drive voltage adjustment (step S4) until an instruction to stop ink circulation is transmitted from the main control unit 140. That is, the ink feeding (ink circulation) by the supply pump 12 and the recovery pump 16 is continued.

(Step S6)
The pump control unit 30 stops the operations of the supply pump 12 and the recovery pump 16 when the instruction to stop the ink circulation is transmitted from the main control unit 140. That is, the frequency of the pulse wave applied to the main pumps 50A and 50D is set to 0 Hz.

(Steps S7 and S8)
Next, the pump control unit 30 returns the drive voltage of the main pumps 50A and 50D to the initial value, and further returns the drive voltage of the sub pumps 50B and 50C to the initial value.
As a result, the liquid feeding (circulation) of the ink K by the ink circulation device 7 is completed.

As described above, the ink circulation device 7 includes a plurality of piezoelectric diaphragm pumps 50 in which the supply pump 12 and the recovery pump 16 are connected in series. The ink circulation device 7 individually controls a plurality of piezoelectric diaphragm pumps 50 during ink circulation. Specifically, only the main pumps 50A and 50D are driven and controlled. On the other hand, the drive voltage of the sub pumps 50B and 50C close to the inkjet head 1 is set (changed) to 0V. That is, the liquid feeding capacity of the sub pumps 50B and 50C is suppressed.

The sub pumps 50B and 50C each include a thin actuator unit 52 and a flexible diaphragm 53. Since the actuator unit 52 and the diaphragm 53 have stopped the liquid feeding operation, they function as pulsation damping dampers. That is, the sub pumps 50B and 50C absorb the pressure of the ink K by the actuator unit 52 and the diaphragm 53.
In other words, the sub-pumps 50B and 50C are accumulators (surge tanks) that reduce the pulsation of ink K generated by the supply pump 12 (main pump 50A) and the recovery pump 16 (main pump 50D).

The ink circulation device 7 measures the pressure of ink K in the inkjet head 1 by the pressure sensor 25. Then, the pump control unit 30 controls the supply pump 12 (main pump 50A) and the recovery pump 16 (main pump 50D) based on the measurement result of the pressure sensor 25. As a result, the ink circulation device 7 can maintain the nozzle pressure (back pressure) of the inkjet head 1 at a negative pressure (-1 kPa) with respect to the atmospheric pressure. Therefore, the meniscus of the ink K in the nozzle of the inkjet head 1 is well maintained.
Therefore, the ink circulation device 7 can prevent the ejection amount of the ink K from fluctuating and the landing accuracy of the ink K from being lowered. Further, the ink circulation device 7 can prevent the ink K from being discharged or the ink K from leaking out.
In particular, since the sub pumps 50B and 50C are close to the inkjet head 1, even if the pulsation of the ink K remains, it is difficult to transmit it to the inkjet head 1. Therefore, the meniscus of the ink K in the nozzle of the inkjet head 1 is well maintained.

The ink circulation device 7 drives four piezoelectric diaphragm pumps 50 in operations other than ink circulation. Since the supply pump 12 and the recovery pump 16 have two piezoelectric diaphragm pumps 50 connected in series, the inkjet head 1 can be satisfactorily filled with ink and purged. That is, it is easy to fill the ink jet head 1 with the ink K from the ink tank 5, and it is easy to forcibly discharge the ink K from the inkjet head 1.

The ink circulation device 7 is not limited to the case where the drive voltage of the sub pumps 50B and 50C is adjusted to 0V during ink circulation. A small voltage may be applied to the sub pumps 50B and 50C as long as the ink pressure (back pressure) in the inkjet head 1 is within a stable range. That is, the actuator unit 52 of the sub pumps 50B and 50C is vibrated slightly to suppress the liquid feeding capacity of the sub pumps 50B and 50C. For example, the voltage of the pulse wave applied to the sub pumps 50B and 50C may be halved. For example, pulse waves having a phase that cancels the pulsation of the supply pump 12 (main pump 50A) and the recovery pump 16 (main pump 50D) may be applied to the sub pumps 50B and 50C. Even in such a case, the sub pumps 50B and 50C can absorb the pressure of the ink K by the actuator unit 52 and the diaphragm 53.

The ink circulation device 7 is not limited to the case where the voltage of the drive wave (pulse wave) of the sub pumps 50B and 50C is changed during ink circulation. The frequency of the drive wave may be changed. The frequency of the pulse wave applied to the sub pumps 50B and 50C may be changed to, for example, 10 Hz or 200 Hz. Even in such a case, since the amplitude of the actuator unit 52 of the sub pumps 50B and 50C is reduced, the pressure of the ink K can be absorbed.

Both the supply pump 12 and the recovery pump 16 are not limited to the case where two piezoelectric diaphragm pumps 50 are provided. Either one of the supply pump 12 and the recovery pump 16 may be provided with a plurality of piezoelectric diaphragm pumps 50. For example, the supply pump 12 may include two or more piezoelectric diaphragm pumps 50, and the recovery pump 16 may include only one piezoelectric diaphragm pump 50. Further, the supply pump 12 may be provided with only one piezoelectric diaphragm pump 50, and the recovery pump 16 may be provided with two or more piezoelectric diaphragm pumps 50. Further, the supply pump 12 and the recovery pump 16 may each include three or more piezoelectric diaphragm pumps 50.

The ink circulation device 7 is not limited to the case where the supply pump 12 and the recovery pump 16 are provided. The ink circulation device (liquid supply device) 7 may include only the supply pump 12 (main pump 50A, sub pump 50B). When the ink K is supplied to the inkjet head 1, the pump control unit 30 can stop the sub-pump 50B and drive only the main pump 50A. As a result, the meniscus of the ink K in the nozzle of the inkjet head 1 is well maintained.

The liquid to be flown by the inkjet head 1 may be a liquid other than ink. It also includes reagents and pharmaceuticals used in drug discovery and biotechnology, and liquid resins used in 3D printers.

The recording medium may be other than paper. For example, cloth, vinyl chloride resin film, plastic film, ceramics and the like.

The embodiments of the present invention are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

1 Inkjet head (liquid injection device)
5 Ink tank (liquid storage container)
7 Ink circulation device (liquid circulation device, liquid supply device)
11 Ink supply pipe
12 Supply pump
15 Ink recovery tube
16 Recovery pump
25 pressure sensor
30 Pump control unit
50 Piezoelectric diaphragm pump
50A, 50D main pump
50B, 50C sub pump
100 Inkjet printer (liquid injection recording device)
103, 108 Recording paper (recording medium)
110 Conveyance belt (medium transport section)
K ink (liquid)

Claims (5)

A supply pump that supplies liquid from the liquid storage container to the liquid injection device,
A recovery pump that collects liquid from the liquid injection device and returns it to the liquid storage container.
A pump control unit that controls the supply pump and the recovery pump,
With
One or both of the supply pump and the recovery pump consist of a plurality of piezoelectric diaphragm pumps connected in series.
When the pump control unit circulates the liquid between the liquid injection device and the liquid storage container, the voltage of the drive wave applied to the piezoelectric diaphragm pump close to the liquid injection device among the plurality of piezoelectric diaphragm pumps. or liquid circulation system to further absorb the pressure of the liquid to change the frequency. A pressure sensor for measuring the pressure of the liquid in the liquid injection device is provided.
The liquid circulation device according to claim 1, wherein the pump control unit controls the supply pump and the recovery pump based on the measurement result of the pressure sensor. Liquid storage container and
Liquid injection device and
The liquid circulation device according to claim 1 or 2,
A medium transport unit that transports the recording medium toward the liquid injection device, and
A liquid injection recording device comprising. A supply pump that supplies liquid from the liquid storage container to the liquid injection device,
A pump control unit that controls the supply pump and
With
The supply pump consists of a plurality of piezoelectric diaphragm pumps connected in series.
When supplying a liquid to the liquid injection device, the pump control unit changes the voltage or frequency of the drive wave applied to the piezoelectric diaphragm pump close to the liquid injection device among the plurality of piezoelectric diaphragm pumps. A liquid supply device that absorbs more liquid pressure. A supply pump that supplies liquid from the liquid storage container to the liquid injection device,
A recovery pump that collects liquid from the liquid injection device and returns it to the liquid storage container.
A pump control unit that controls the supply pump and the recovery pump is provided.
One or both of the supply pump and the recovery pump consist of a plurality of piezoelectric diaphragm pumps connected in series.
In the liquid circulation device
The pump control unit
When the liquid is circulated between the liquid injection device and the liquid storage container, the voltage or frequency of the drive wave applied to the piezoelectric diaphragm pump close to the liquid injection device among the plurality of piezoelectric diaphragm pumps is changed. A liquid circulation method characterized in that the pressure of the liquid is controlled to be absorbed by the liquid.

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