JP6928036B2 - Liquid circulation device and liquid discharge recording device - Google Patents

Description

Embodiment, the liquid circulating apparatus for circulating the liquid to be supplied to the liquid discharge portion, and relates to a liquid discharge recording equipment.

There is a liquid circulation type liquid discharge device that can circulate a liquid between a liquid tank and a liquid discharge head to remove air bubbles generated in the nozzle of the inkjet head and foreign matter mixed in the nozzle from the vicinity of the nozzle. In the conventional liquid ejection device, when the ink in the liquid tank is detected to be low, the printing operation is stopped, the ink is replenished from the replenishing liquid tank, and the printing operation is restarted when the ink replenishment to the liquid tank is completed. .. Therefore, in the conventional liquid ejection device, printing cannot be performed at the time of ink replenishment, and the productivity of the liquid ejection device may decrease. In particular, when the volume of the liquid tank is small, the refilling operation of ink from the refilling liquid tank to the liquid tank frequently occurs, which may further reduce the production efficiency of the liquid discharge device.

Japanese Unexamined Patent Publication No. 2005-125670

The problem to be solved by the present invention is to prevent the liquid discharge operation from stopping due to new liquid replenishment to the liquid tank that circulates the liquid with the liquid discharge portion, and to improve the productivity by the liquid discharge. liquid circulation device for improved, and to provide a liquid discharge recording equipment.

In order to achieve the above object, the liquid circulation device of the embodiment includes a liquid recovery chamber capable of circulating the liquid between the liquid discharge unit for discharging the liquid and collecting the liquid from the liquid discharge unit. A liquid casing having a liquid supply chamber for supplying the liquid to the liquid discharge portion and being sealed to the outside air, an ink supply pump for replenishing the liquid casing with a new liquid, and the like. A gas pressure adjusting pump different from the ink supply pump, which replenishes the liquid casing with outside air when the pressure in the liquid casing is lower than a predetermined lower limit value at which bubbles are not sucked from the liquid discharge portion, and the liquid casing. The liquid level sensor for detecting the liquid level is provided, and the liquid casing is replenished with the new liquid by the ink supply pump, and when the liquid level of the liquid casing is higher than a predetermined height, the gas pressure adjusting pump is provided. By replenishing the liquid casing with the outside air, the pressure inside the liquid casing is pressurized and adjusted.

The schematic front view which shows the inkjet recording apparatus of embodiment. The schematic plan view which shows the inkjet recording apparatus of embodiment. The schematic block diagram which shows the inkjet head of an embodiment. The schematic explanatory view which shows the state which ink stays in a nozzle in the inkjet head of embodiment. The schematic explanatory view which shows the ejection of the ink drop from the nozzle of embodiment. The schematic block diagram which shows the ink circulation apparatus of embodiment. The schematic explanatory view which shows the circulation and pressure adjustment of the ink of an embodiment. The schematic block diagram which shows the control system which controls the inkjet recording apparatus of embodiment. A timing chart showing the adjustment of the pressure applied to the nozzle of the embodiment. The flowchart which shows the control of the adjustment of the pressure applied to the nozzle of an embodiment.

The inkjet recording device 1 which is the liquid discharge recording device of the embodiment will be described with reference to FIGS. 1 to 10. 1 and 2 show an example of the inkjet recording apparatus 1. The inkjet recording device 1 includes an image forming unit 6, a recording medium moving unit 7 which is a conveying unit, and a maintenance unit 310. The image forming unit 6 includes an inkjet recording unit 4, a carriage 100 that supports the inkjet recording unit 4, a carriage belt 101 that reciprocates the carriage 100 in the direction of arrow A, and a carriage motor 102 that drives the carriage belt 101.

The inkjet recording unit 4 includes an inkjet head 2 which is a liquid ejection unit and an ink ejection unit, and an ink circulation device 3 which is a circulation unit. The ink circulation device 3 is above the inkjet head 2 and is integrally formed with the inkjet head 2. The inkjet recording unit 4 ejects ink to the recording medium S to form a desired image.

The inkjet recording unit 4 includes, for example, inkjet recording units 4a, 4b, 4c, 4d, and 4e that eject cyan ink, magenta ink, yellow ink, black ink, and white ink, respectively. The colors or characteristics of the inks used by the inkjet recording units 4a, 4b, 4c, 4d, and 4e are not limited. For example, the inkjet recording unit 4e can eject transparent glossy ink, special ink that develops color when irradiated with infrared rays or ultraviolet rays, or the like instead of white ink. The inkjet recording units 4a, 4b, 4c, 4d, and 4e have the same configuration although the inks used are different. Therefore, it will be described using a common reference numeral.

The width of the inkjet recording unit 4 can be narrowed by loading the ink circulation device 3 above the inkjet head 2. Therefore, the width of the carriage 100 that supports the plurality of inkjet recording units 4a to 4e in parallel can be narrowed. By narrowing the width of the carriage 100, the image forming unit 6 can reduce the transport distance of the carriage 100, obtain a miniaturization of the inkjet recording device 1, and increase the printing speed.

The image forming unit 6 includes an ink cartridge 81 for replenishing the ink circulation device 3 with new ink. 81a, 81b, 81c, 81d, and 81e of the ink cartridge 81 hold cyan ink, magenta ink, yellow ink, black ink, and white ink, respectively. The ink cartridges 81a, 81b, 81c, 81d, and 81e have the same configuration, although they have different inks. Therefore, it will be described using a common reference numeral. The ink cartridge 81 communicates with the ink circulation device 3 of the inkjet recording unit 4 via the tube 82. The ink cartridge 81 is arranged relatively below the ink circulation device 3 in the direction of gravity.

The recording medium moving unit 7 includes a table 103 for sucking and fixing the recording medium S. The table 103 is mounted on the slide rail device 105 and reciprocates in the direction of arrow B. The inside of the table 103 is negatively pressed by the pump 104 to attract and fix the recording medium S from the small-diameter hole 110 on the upper surface. While the inkjet recording unit 4 reciprocates along the transport belt 101 in the direction of arrow A, the distance h between the nozzle plate 52 of the inkjet head 2 and the recording medium S is maintained constant. The inkjet head 2 includes nozzles 51, which are 300 liquid ejection portions, in the longitudinal direction of the nozzle plate 52. The longitudinal direction of the nozzle plate 52 is the same as the transport direction of the recording medium S.

The image forming unit 6 forms an image on the recording medium S while reciprocating the inkjet head 2 in a direction orthogonal to the conveying direction of the recording medium S. The inkjet head 2 ejects ink I from a nozzle 51 provided on the nozzle plate 52 in accordance with an image forming signal to form an image on the recording medium S. The inkjet recording unit 4 forms an image on the recording medium S with a width of, for example, 300 nozzles.

The maintenance unit 310 is arranged at a position outside the moving range of the table 103, which is the scanning range of the inkjet recording unit 4 in the arrow A direction. The inkjet head 2 faces the maintenance unit 310 at the standby position Q. The maintenance unit 310 is a case in which the upper part is open, and is provided so as to be movable up and down (in the directions of arrows C and D in FIG. 1).

When the carriage 100 is moving in the direction of arrow A to print an image, the maintenance unit 310 moves downward (in the direction of arrow C) and separates from the nozzle plate 52. When the printing operation is completed, the maintenance unit 310 moves upward (in the direction of arrow D). When the printing operation is completed and the inkjet head 2 returns to the standby position Q, the maintenance unit 310 moves upward to cover the nozzle plate 52 of the inkjet head 2. The maintenance unit 310 prevents the ink from evaporating from the nozzle plate 52 and prevents dust and paper dust from adhering to the nozzle plate 52. The maintenance unit 310 has a cap function of the nozzle plate 52.

The maintenance unit 310 includes a rubber blade 120 and a waste ink receiving portion 130. The rubber blade 120 removes ink, dust, paper dust, and the like adhering to the nozzle plate 52 of the inkjet head 2. The waste ink receiving unit 130 receives waste ink, dust, paper dust, etc. generated during the maintenance operation. The maintenance unit 310 includes a mechanism for moving the blade 120 in the direction of arrow B, and the blade 120 wipes the surface of the nozzle plate 52.

The inkjet head 2 performs maintenance (spit function) for forcibly ejecting ink from the nozzle 51 in order to remove the deteriorated ink in the vicinity of the nozzle. The inkjet head 2 performs maintenance (purge function) in which ink is slightly discharged from the nozzle 51, paper dust and dust adhering to the surface of the inkjet head 2 are taken into the discharged ink film, and wiped off by the blade 120. The waste ink receiving unit 130 collects the waste ink generated by the spit function or the purge function.

The inkjet recording device 1 ejects ink from the nozzle 51 while reciprocating the inkjet head 2 in a direction orthogonal to the transport direction of the recording medium S by the recording medium moving unit 7, and outputs an image to the recording medium S. Form.

The structure of the inkjet recording device 1 is not limited. For example, instead of using the table 103 for moving the recording medium, a device may be used that moves the roll-shaped recording medium by winding it in a direction orthogonal to the moving direction of the inkjet recording unit 4. Alternatively, the device may be a device that moves the sheet-shaped recording medium by a platen roller in a direction orthogonal to the moving direction of the inkjet recording unit 4.

The inkjet recording unit 4 will be described in detail. As shown in FIG. 3, for example, the inkjet head 2 of the inkjet recording unit 4 includes a nozzle plate 52 including a nozzle 51, a substrate 60 including an actuator 54, and a manifold 61 connected to the substrate 60. The substrate 60 includes an ink flow path 180 through which ink flows between the nozzle 51 and the actuator 54. The actuator 54 faces the ink flow path 180 and is provided corresponding to each nozzle 51.

The substrate 60 is provided with a boundary wall 190 between adjacent nozzles 51 so that the pressure generated in the ink in the ink flow path 180 by the actuator 54 is concentrated on the nozzles 51. The ink flow path 180 surrounded by the nozzle plate 52, the actuator 54, and the boundary wall 190 serves as the ink pressure chamber 150. A plurality of ink pressure chambers 150 are provided corresponding to the respective nozzles 51a in the first nozzle row 57a and the respective nozzles 51b in the second nozzle row 57b. The first nozzle row 57a and the second nozzle row 57b include 300 nozzles 51a and 51b, respectively.

The substrate 60 has a common ink supply chamber 58 that supplies ink to the ink flow paths 180 of the plurality of ink pressure chambers 150, and a common ink chamber 59 that collects ink from the plurality of ink flow paths 180 on the first nozzle row 57a side and the first. Two nozzle rows are provided on the 57b side, respectively.

The manifold 61 includes an ink supply port 160 for inflowing ink in the direction of arrow F, and an ink discharge port 170 for discharging ink in the direction of arrow G. The ink supply port 160 supplies ink I from the ink circulation device 3, and the ink discharge port 170 returns the ink to the ink circulation device 3. The manifold 61 has an ink distribution passage 62 that communicates from the ink supply port 160 to the common ink supply chamber 58. The manifold 61 has an ink recirculation passage 63 that communicates from the common ink chamber 59 to the ink discharge port 170.

The ink I flowing in the direction of the arrow F flows through the ink distribution passage 62 from the common ink supply chamber 58 into the plurality of ink pressure chambers 150. The ink I that has not been ejected from the nozzle 51 in the ink pressure chamber 150 flows into the common ink chamber 59 and returns to the ink recirculation passage 63.

The actuator 54 of the inkjet head 2 is composed of, for example, a unimorph type piezoelectric diaphragm in which a piezoelectric element 55 and a diaphragm 56 are laminated. The piezoelectric element 55 is made of a piezoelectric ceramic material such as PZT (lead zirconate titanate). The diaphragm 56 is made of, for example, SiN (silicon nitride) or the like.

As shown in FIGS. 4 and 5, the piezoelectric element 55 includes electrodes 55a and 55b at the top and bottom. When no voltage is applied to the electrodes 55a and 55b, the piezoelectric element 55 is not deformed as shown in FIG. 4, so that the actuator 54 is not deformed. When the actuator 54 is not deformed, the surface tension of the ink causes the meniscus 290, which is the interface between the ink I and the air, to be formed in the nozzle 51. Ink I in the ink pressure chamber 150 stays in the nozzle 51 due to the meniscus 290.

When a voltage (V) is applied to the electrodes 55a and 55b, the piezoelectric element 55 is deformed, and the actuator 54 is deformed as shown in FIG. Due to the deformation of the actuator 54, the pressure applied to the meniscus 290 becomes higher than the air pressure (positive pressure), and the ink I breaks the meniscus 290 to become an ink droplet ID and is discharged from the nozzle 51.

The structure of the inkjet head 2 is not limited as long as it causes pressure fluctuations in the ink in the ink pressure chamber. The inkjet head may have, for example, a structure in which the diaphragm is deformed by static electricity to eject ink droplets, or a structure in which ink droplets are ejected from a nozzle by utilizing thermal energy of a heater or the like. Further, since the viscosity of the ink changes depending on the temperature and the ejection characteristics from the nozzles change, the inkjet head may be provided with a temperature sensor in order to control the ink ejection satisfactorily.

As shown in FIGS. 6 and 7, for example, the ink circulation device 3 of the inkjet recording unit 4 includes an ink casing 70 which is a liquid chamber and an ink chamber, an ink circulation unit 76, and a pressure adjusting unit 90 which is a gas replenishment unit. Be prepared. The ink circulation device 3 circulates and supplies ink to the inkjet head 2 and adjusts the pressure in the ink pressure chamber 150 of the inkjet head 2. The ink circulation device 3 adjusts the pressure of the ink pressure chamber 150 to adjust the pressure of the meniscus 290 of the nozzle 51. The ink circulation device 3 circulates and supplies ink to the inkjet head 2 to absorb air bubbles contained in the ink I or remove foreign substances.

In the inkjet head 2, if the pressure applied to the meniscus 290 of the nozzle 51 is higher than the air pressure (positive pressure), the ink I leaks from the nozzle 51. If the pressure applied to the meniscus 290 is lower than the air pressure (negative pressure), the ink I maintains the meniscus 290 and stays in the nozzle 51. For example, when the pressure in the ink pressure chamber 150 is adjusted to −0.5 to −4.0 kPa, the inkjet head 2 maintains the meniscus 290 and does not eject ink from the nozzle 51.

For example, if the nozzle 51 is arranged so that the ink I is ejected in the direction of gravity (downward), the pressure in the ink pressure chamber 150 is slightly greater than -0.5 to -4.0 kPa (positive pressure side). Ink I leaks from the nozzle 51 due to excessive vibration or the like. Further, when the pressure in the ink pressure chamber 150 is smaller than −0.5 to −4.0 kPa (negative pressure side), air bubbles are sucked from the nozzle 51, causing poor ink ejection. The ink circulation device 3 maintains the pressure of the meniscus 290 in the range of −0.5 to −4.0 kPa to prevent unnecessary ink leakage or suction of air bubbles.

The ink casing 70 includes an ink recovery chamber 71 that collects ink I from the inkjet head 2, and an ink supply chamber 72 that supplies ink I to the inkjet head 2. The ink recovery chamber 71 and the ink supply chamber 72 are adjacent to each other via a common wall 73. The ink casing 70 is sealed with respect to the outside air. The ink recovery chamber 71 and the ink supply chamber 72 hold the ink I downward via the first liquid level α1 or the second liquid level α2, respectively. The ink recovery chamber 71 and the ink supply chamber 72 form a first air chamber β1 or a second air chamber β2 upward via the first α1 or the second liquid level α2, respectively.

The ink recovery chamber 71 includes an ink return tube 71a that communicates with the ink discharge port 170 of the inkjet head 2 and returns the ink I from the inkjet head 2 to the ink recovery chamber 71. The ink recovery chamber 71 includes an ink supply pump 71b for replenishing new ink from the ink cartridge 81 via the tube 82. The ink supply pump 71b is a liquid replenishment unit and constitutes an ink replenishment unit. The ink recovery chamber 71 includes a liquid feeding hole 71c for feeding ink to the ink circulation unit 76. The ink recovery chamber 71 includes a first communication hole 71d that communicates with the first pressure adjustment unit 91 of the pressure adjustment unit 90.

The ink supply chamber 72 includes an ink supply pipe 72a that communicates with the ink supply port 160 of the inkjet head 2 and inflows ink I into the inkjet head 2. The ink supply chamber 72 includes a discharge hole 72b from which the ink I sent from the ink circulation unit 76 is discharged. The ink supply chamber 72 includes a second communication hole 72c that communicates with the second pressure adjustment unit 92 of the pressure adjustment unit 90.

The structure of the ink recovery chamber or the ink supply chamber is not limited as long as the ink can be circulated well with the inkjet head. For example, a heater for heating the ink may be provided so as to keep the temperature of the ink within a predetermined range.

By arranging the ink cartridge 81 relatively below the ink circulation device 3 in the direction of gravity, the water head pressure of the ink in the ink cartridge 81 is kept lower than the set pressure of the ink recovery chamber 71. By arranging the ink cartridge 81 below the ink circulation device 3, the ink cartridge 81 supplies new ink to the ink recovery chamber 71 only when the ink supply pump 71b is driven.

The ink supply pump 71b is, for example, a piezoelectric pump. The ink supply pump 71b periodically changes the volume inside the pump (volume of the pump chamber) by bending the piezoelectric vibrating plate in which the piezoelectric element and the metal plate are bonded together. The ink supply pump 71b is the volume of the pump chamber. Due to the change, ink is conveyed from the ink cartridge 81 to the pump chamber. The ink supply pump 71b uses a check valve to unidirectionally convey ink from the ink cartridge 81 to the ink recovery chamber 71. When the pump chamber of the ink supply pump 71b expands due to the deflection of the piezoelectric diaphragm, ink flows into the pump chamber. In the ink supply pump 71b, when the pump chamber contracts due to the deflection of the piezoelectric diaphragm, ink flows out from the pump chamber. The ink supply pump 71b repeatedly expands and contracts the pump chamber to send ink from the ink cartridge 81 to the ink recovery chamber 71.

The arrangement position of the ink cartridge 81 is not limited. For example, when the ink cartridge 81 is arranged at a position higher than the ink circulation device 3, the head pressure of the ink in the ink cartridge 81 becomes higher than the set pressure of the ink recovery chamber 71. When the ink cartridge 81 is arranged at a position higher than the ink circulation device 3, ink can be supplied from the ink cartridge 81 to the ink recovery chamber 71 by opening and closing the solenoid valve using the head difference.

As shown in FIG. 7, the ink circulation unit 76 of the ink circulation device 3 includes a circulation path 76a that reaches from the liquid feed hole 71c of the ink collection chamber 71 to the discharge hole 72b of the ink supply chamber 72. The ink circulation unit 76 includes a circulation pump 77 and a filter 78 on the circulation path 76a. The circulation pump 77 is provided so as to straddle the adjacent ink recovery chamber 71 and the ink supply chamber 72. As shown by the arrow J, the circulation pump 77 circulates the ink I from the ink recovery chamber 71 to the ink recovery chamber 71 via the ink supply chamber 72 and the inkjet head 2. The ink circulation unit 76 sucks ink from the liquid feeding hole 71c and sends the ink I to the ink supply chamber 72 through the discharge hole 72b. As the circulation pump 77, for example, a tube pump, a diaphragm pump, a piston pump, or the like is used.

The filter 78 is located downstream of the circulation pump 77 in the circulation path 76a, for example, in the circulation direction, and removes foreign matter mixed in the ink I. As the filter 78, for example, a mesh filter such as polypropylene, nylon, polyphenylene sulfide, or stainless steel is used.

While the ink is circulated from the ink recovery chamber 71 to the ink supply chamber 72 by the ink circulation unit 76, the bubbles in the ink I rise in the direction opposite to the direction of gravity (upward) due to buoyancy. The bubbles raised by the buoyancy reach the first liquid level α1 of the ink recovery chamber 71 or the air chambers β1 and β2 above the second liquid level α2 of the ink supply chamber 72 and are removed.

As shown in FIG. 7, the ink circulation device 3 has a first ink amount sensor (liquid level sensor) 88a for measuring the amount of ink in the ink collection chamber 71 and a second ink for measuring the amount of ink in the ink supply chamber 72. A volume sensor (liquid level sensor) 88b is provided. The first ink amount sensor (liquid level sensor) 88a or the second ink amount sensor (liquid level sensor) 88b vibrates, for example, a piezoelectric vibrating plate with an AC voltage to move the ink recovery chamber 71 or the ink supply chamber 72. The amount of ink is measured by detecting the transmitted vibration of the ink. The structure of the ink amount sensor is not limited, and may be a structure for measuring the height of the first liquid level α1 or the second liquid level α2.

As shown in FIG. 7, the ink circulation device 3 communicates with the first pressure sensor 91b communicating with the first communication hole 71d of the ink recovery chamber 71 and the second communication hole 72c communicating with the second communication hole 72c of the ink supply chamber 72. The pressure sensor 92b is provided. The first pressure sensor 91b detects the pressure in the first air chamber β1 of the ink recovery chamber 71. The second pressure sensor 92b detects the pressure in the second air chamber β2 of the ink supply chamber 72. The structures of the pressure sensors 91b and 92b are not limited. The pressure sensors 91b and 92b output the air pressure of the first air chamber β1 or the second air chamber β2 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 the surface of the diaphragm, and electricity due to the piezoresistive effect generated in the strain gauge due to deformation of the diaphragm due to external pressure. The pressure is detected by converting the change in resistance into an electric signal.

The first pressure adjusting unit 91 of the ink circulation device 3 includes a first pressure adjusting pump 91a, and the second pressure adjusting unit 92 includes a second pressure adjusting pump 92a. The pressure adjusting pumps 91a and 92a send air to the ink recovery chamber 71 or the ink supply chamber 72, respectively, to increase the pressure in the circulation path 76a. The first or second pressure adjusting pumps 91a and 92a release the air from the ink recovery chamber 71 or the ink supply chamber 72 to the outside to reduce the pressure in the circulation path 76a, respectively. As the pressure adjusting pumps 91a and 92a, for example, a tube pump or a bellows pump can be used.

The control system 200 that controls the operation of the inkjet recording apparatus 1 will be described with reference to the block diagram shown in FIG. The control board 500 of the control system 200 is a control unit and is a microcomputer (microcomputer) 510 that controls the entire inkjet recording device 1, a recording unit drive circuit 540 that drives the inkjet recording device 1, an amplifier circuit 541, and a recording medium moving unit 7. A moving unit drive circuit 542 for driving the device is provided. The microcomputer 510 includes a memory 520 for storing programs, various data, and the like, and an AD conversion unit 530 for capturing the output voltage from the inkjet recording unit 4.

The control board 500 is connected to a power supply 550, a display device 560 that displays the status of the inkjet recording device 1, and a keyboard 570 as an input device. The control board 500 is connected to the drive unit and the detection unit of the inkjet recording unit 4. The control board 500 is connected to the pump 104 of the recording medium moving unit 7, the slide rail device 105, the driving unit of the maintenance unit 310, and the carriage motor 102 of the transport belt 101.

When the inkjet recording device 1 is first operated for printing, the ink cartridge 81 fills the inkjet recording unit 4 with ink I. In order to fill the ink I, the microcomputer 510 returns the inkjet recording unit 4 to the standby position, raises the maintenance unit 310 in the direction of arrow D, and covers the nozzle plate 52. The microcomputer 510 drives the ink supply pump 71b to send ink from the ink cartridge 81 to the ink recovery chamber 71. When the ink I reaches the liquid feeding hole 71c in the ink recovery chamber 71, the microcomputer 510 adjusts the pressure of the ink casing 70 by the pressure adjusting unit 90 and drives the circulation pump 77. When the ink I reaches the liquid feed hole 71c of the ink recovery chamber 71 and the discharge hole 72b of the ink supply chamber 72, the microcomputer 510 completes the initial filling of the ink I.

In the inkjet recording device 1, the cyan ink, magenta ink, yellow ink, black ink, and white ink of the respective ink cartridges 81a, 81b, 81c, 81d, and 81e are initially set in the inkjet recording units 4a, 4b, 4c, 4d, and 4e, respectively. Fill.

When the initial filling of the ink I is completed, the pressure in the ink casing 70 is maintained at a negative pressure such that the ink I does not leak from the nozzle 51 of the inkjet head 2 and bubbles are not sucked from the nozzle 51. Due to the negative pressure of the ink casing 70, the nozzle 51 maintains the negative pressure meniscus 290. Negative pressure is the pressure when the atmospheric pressure is zero. Even when the power supply 550 of the inkjet recording apparatus 1 is turned off after the initial filling of ink I is completed, the ink casing 70 is in a sealed state, and the meniscus 290 in the nozzle 51 is maintained at a negative pressure to prevent ink leakage. ..

When printing is started, the microcomputer 510 controls the recording medium moving unit 7, sucks and fixes the recording medium S to the table 103, and moves the table 103 back and forth in the direction of arrow B. The microcomputer 510 moves the maintenance unit 310 in the direction of arrow C, controls the carriage motor 102 to convey the carriage 100 in the direction of the recording medium S, and reciprocates in the direction of arrow A.

The microcomputer 510 selectively drives the actuator 54 of the inkjet head 2 by, for example, an image signal corresponding to the image data stored in the memory 520, and ejects the ink droplet ID from the nozzle 51 to the recording medium S. The microcomputer 510 drives the circulation pump 77 to circulate the ink I recirculated from the inkjet head 2 to the inkjet head 2 via the ink recovery chamber 71, the filter 78, and the ink supply chamber 72. By circulating the ink I, the inkjet recording unit 4 removes air bubbles and foreign substances mixed in the ink I, maintains good ink ejection performance, and improves the print image quality of the inkjet recording unit 4.

The pressure of the ink casing 70 fluctuates due to the ejection of the ink droplet ID from the nozzle 51, the driving of the circulation pump 77, or the like. The microcomputer 510 adjusts the pressure of the ink casing 70 in order to maintain the pressure of the ink casing 70 in a stable range in which ink does not leak from the nozzle 51 or bubbles are not sucked from the nozzle 51. The microcomputer 510 switches the drive of the pressure adjusting unit 90 and the ink supply pump 71b to adjust the pressure of the ink casing 70.

For example, when the ink droplet ID is ejected from the nozzle 51 during printing, the amount of ink in the ink casing 70 is instantaneously reduced, and the pressure in the ink recovery chamber 71 is reduced. When the first pressure sensor 91b detects a decrease in the pressure of the ink recovery chamber 71, the microcomputer 510 includes the first pressure sensor 91b, the second pressure sensor 92b, the first ink amount sensor (liquid level sensor) 88a, and the like. From the detection result of the second ink amount sensor (liquid level sensor) 88b, the pressure adjusting unit 90 or the ink supply pump 71b is driven. When the pressure applied to the nozzle 51 is not in the stable range, the microcomputer 510 takes in outside air into the ink casing 70 or takes in outside air according to the height of the first liquid level α1 or the second liquid level α2, or the ink recovery chamber. The pressure applied to the nozzle 51 is adjusted by switching whether to replenish the 71 with new ink.

The adjustment control of the pressure applied to the nozzle 51 will be described with reference to FIGS. 9 and 10. In the inkjet recording unit 4, the lower limit of the stable region of the pressure value P of the nozzle 51, which does not leak ink from the nozzle 51 or suck air bubbles from the nozzle 51, is set to, for example, Pt1, and the upper limit is set to, for example, Pt2. After turning on the power supply 550 at time t1, when the pressure value P of the nozzle 51 is lower than the lower limit value Pt1 as shown in FIG. 9, the microcomputer 510 pressurizes and adjusts the inside of the ink casing 70.

The pressurization adjustment is performed by switching between taking in outside air into the ink casing 70 and replenishing the ink recovery chamber 71 with new ink from the ink cartridge 81. When the pressure value P of the nozzle 51 reaches the range of the lower limit value Pt1 to the upper limit value Pt2 at the time t2, the microcomputer 510 stops the pressurization adjustment. The ink casing 70 is refilled with new ink to adjust the pressure of the nozzle 51. That is, the inkjet recording unit 4 replenishes the ink recovery chamber 71 with new ink when the pressure of the nozzle 51 is adjusted while the ink I is ejected from the nozzle 51 and printing is performed.

When the pressure value P of the nozzle 51 becomes higher than the upper limit value Pt2 at the time t3 of FIG. 9, the microcomputer 510 discharges the air in the ink casing 70 to the outside to adjust the pressure reduction of the nozzle 51. When the pressure value P of the nozzle 51 reaches the range of the lower limit value Pt1 to the upper limit value Pt2 at the time t4, the microcomputer 510 stops the decompression adjustment.

When the power supply 550 of the inkjet recording device 1 is turned on, the microcomputer 510 starts the pressure adjustment of the nozzle 51 according to the flowchart of FIG. From the detection results of the first pressure sensor 91b and the second pressure sensor 92b, the microcomputer 510 determines whether the pressure value P of the nozzle 51 is in the range of Pt1 ≦ P ≦ Pt2 (ACT100). The range of the pressure value P of the nozzle 51 may be determined from the detection result of either the first pressure sensor 91b or the second pressure sensor 92b.

When the pressure value P of the nozzle 51 is not in the range of Pt1 ≦ P ≦ Pt2 (No. in ACT100), the microcomputer 510 determines whether the pressure value P of the nozzle 51 is larger than the upper limit value Pt2 (ACT101). When the pressure value P of the nozzle 51 is less than the upper limit value Pt2 (No. in ACT101), the microcomputer 510 determines whether the first liquid level α1 and the second liquid level α2 are higher than the height f (ACT103). .. The height f is arbitrary, and may be higher than the liquid feeding holes 71c and the discharging holes 72b of the ink casing 70. Further, the height f of the ACT 103 is arbitrarily determined by the height of either the first liquid level α1 or the second liquid level α2.

When the first liquid level α1 and the second liquid level α2 are higher than the height f (Yes. In ACT103), the microcomputer 510 proceeds to (ACT104). In the ACT 104, the microcomputer 510 pressurizes and adjusts the pressure of the nozzle 51 by driving the first pressure adjusting pump 91a and the second pressure adjusting pump 92a to take in the outside air into the ink casing 70. When the pressure value P of the nozzle 51 reaches the range of Pt1 ≦ P ≦ Pt2 in the ACT 104, the microcomputer 510 ends the pressure adjustment of the nozzle 51. When adjusting the pressure of the ACT 104, the pressure of the nozzle 51 may be adjusted by taking in outside air from either the first pressure adjusting pump 91a or the second pressure adjusting pump 92a.

When the first liquid level α1 and the second liquid level α2 have a height f or less (No. in ACT103), the microcomputer 510 proceeds to (ACT105). In the ACT 105, the microcomputer 510 pressurizes and adjusts the pressure of the nozzle 51 by driving the ink supply pump 71b to replenish the ink recovery chamber 71 with new ink I from the ink cartridge 81. When the pressure value P of the nozzle 51 reaches the range of Pt1 ≦ P ≦ Pt2 in the ACT 105, the microcomputer 510 ends the pressure adjustment of the nozzle 51.

That is, when the pressure value P of the nozzle 51 is less than the lower limit value Pt1 (No. in ACT101), the microcomputer 510 adjusts the first pressure adjusting pump 91a and the second pressure according to the amount of ink in the ink casing 70. The drive of the pump 92a and the drive of the ink supply pump 71b are switched to pressurize and adjust the pressure value P of the nozzle 51. If the amount of ink in the ink casing 70 is reduced during the pressure adjustment, the microcomputer 510 replenishes the ink casing 70 with new ink I from the ink cartridge 81. The pressure value P of the nozzle 51 is pressure-adjusted by increasing the volume of the ink I in the ink casing 70. The ink I in the ink casing 70 maintains a height f. The inkjet recording unit 4 can replenish the ink recovery chamber 71 with new ink by adjusting the pressure of the nozzle 51 without stopping the printing operation.

In ACT101, when the pressure value P of the nozzle 51 is equal to or higher than the upper limit value Pt2 (Yes. In ACT101), the microcomputer 510 proceeds to ACT102. In the ACT 102, the microcomputer 510 drives the first pressure adjusting pump 91a and the second pressure adjusting pump 92a to discharge the air in the ink casing 70 to reduce the pressure of the nozzle 51. When the pressure value P of the nozzle 51 reaches the range of Pt1 ≦ P ≦ Pt2, the microcomputer 510 ends the pressure adjustment of the nozzle 51.

The inkjet recording unit 4 maintains the pressure value P of the nozzle 51 in the range of Pt1 ≦ P ≦ Pt2, maintains good ink ejection characteristics of the nozzle 51, and obtains image quality improvement. The inkjet recording unit 4 maintains the pressure value P of the nozzle 51 in the range of Pt1 ≦ P ≦ Pt2 to prevent unnecessary ink leakage or suction of air bubbles from the nozzle 51.

The pressure adjustment of the nozzle 51 shown in FIG. 10 is always performed at an arbitrary timing specified by the microcomputer 510.

According to the embodiment, the inkjet recording unit 4 circulates the ink I by the ink circulation device 3 to remove air bubbles or foreign substances contained in the ink I. The ink ejection performance of the inkjet head 2 is well maintained, and the print image quality of the inkjet recording unit 4 is improved.

According to the embodiment, the inkjet recording unit 4 drives the first pressure adjusting pump 91a and the second pressure adjusting pump 92a and the ink supply pump 71b in order to pressurize and adjust the pressure value P of the nozzle 51. Switch between driving. The drive of the first pressure adjusting pump 91a and the second pressure adjusting pump 92a and the driving of the ink supply pump 71b are switched according to the height of the ink I in the ink casing 70. When the pressure value P of the nozzle 51 is less than the lower limit value Pt1, and the height of the ink I in the ink casing 70 is higher than f, the first pressure adjusting pump 91a and the second pressure adjusting pump 92a are driven. If the height of the ink I in the ink casing 70 is higher than f, the outside air is taken into the ink casing 70 to pressurize and adjust the pressure value P of the nozzle 51.

When the pressure value P of the nozzle 51 is less than the lower limit value Pt1 and the height of the ink I in the ink casing 70 is f or less, the ink supply pump 71b is driven. If the height of the ink I in the ink casing 70 is f or less, the ink recovery chamber 71 is replenished with new ink, and the pressure value P of the nozzle 51 is pressure-adjusted. The inkjet recording unit 4 can replenish the ink casing 70 with new ink I from the ink cartridge 81 even during the pressure adjustment during the printing operation. The inkjet recording unit 4 can replenish the ink I in the ink casing 70 while adjusting the pressure value P of the nozzle 51 without stopping the printing operation, and prevents the print production efficiency of the inkjet recording device 1 from being lowered. can.

The configuration of the liquid circulation device of the embodiment described above is not limited. For example, the liquid chamber and the liquid discharge portion do not have to be integrally formed as long as the liquid can be circulated while replenishing the liquid chamber. The liquid circulation device can also discharge a liquid other than ink. The liquid ejection device for ejecting other than ink may be, for example, a device for ejecting a liquid containing conductive particles for forming a wiring pattern of a printed wiring board.

Although embodiments of the present invention have been described, the embodiments are presented as examples and are not intended to limit the scope of the invention. This novel embodiment can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. This embodiment and its modifications 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 recording device 2 ... Inkjet head 3 ... Inkjet recording device 4 ... Inkjet recording unit 70 ... Ink casing 71 ... Ink recovery chamber 71b ... Ink supply pump 72 ... Ink supply chamber 77 ... Circulation pump 81 ... Ink cartridge 90 ... Pressure adjustment Part 510 ... Microcomputer

Claims (4)

A liquid recovery chamber that can circulate the liquid between the liquid discharge unit and collects the liquid from the liquid discharge unit, and a liquid supply chamber that supplies the liquid to the liquid discharge unit. A liquid casing that constitutes a liquid chamber and is sealed to the outside air,
An ink supply pump that replenishes the liquid casing with new liquid,
A gas pressure adjusting pump different from the ink supply pump, which replenishes the liquid casing with outside air when the pressure in the liquid casing is lower than a predetermined lower limit value at which air bubbles are not sucked from the liquid ejection portion .
A liquid level sensor for detecting the liquid level of the liquid casing is provided.
Replenishing the liquid casing with the new liquid with the ink supply pump,
When the liquid level of the liquid casing is higher than a predetermined height, the gas pressure adjusting pump is used to replenish the liquid casing with the outside air.
A liquid circulation device that pressurizes and adjusts the pressure in the liquid casing. The liquid circulation device according to claim 1, wherein the gas pressure adjusting pump is directly connected to the liquid casing. A liquid recovery chamber that can circulate the liquid between the liquid discharge unit and collects the liquid from the liquid discharge unit, and a liquid supply chamber that supplies the liquid to the liquid discharge unit. A liquid casing that constitutes a liquid chamber and is sealed to the outside air,
An ink supply pump that replenishes the liquid casing with new liquid,
A liquid level sensor that detects the liquid level of the liquid casing and
The liquid casing is provided with a gas pressure adjusting pump different from the ink supply pump for replenishing the outside air.
Replenishing the liquid casing with the new liquid with the ink supply pump,
A liquid circulation device that pressurizes and adjusts the pressure in the liquid casing by replenishing the outside air with the gas pressure adjusting pump when the liquid level of the liquid casing is higher than a predetermined height. The liquid circulation device according to any one of claims 1 to 3.
A liquid discharge recording device including a transport unit that transports a recording medium to a position where the liquid is discharged from the liquid discharge unit.

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