inkjet printer

Abstract

To suppress frequent open and close of a valve provided in an ink flow path.SOLUTION: An inkjet printer includes: an ink container 61; an ink head 50; an ink flow path 62; a liquid transmission pump 63 provided in the ink flow path 62; a valve 64 provided in the ink flow path 62; an intermediate container 65 provided with a storage chamber 65a in which an ink is temporarily stored; and a pressure sensor 66 that measures a pressure of the ink in the storage chamber 65a. The inkjet printer acquires the pressure of the ink in the storage chamber 65a from the pressure sensor 66. When the acquired pressure falls below a first threshold, the inkjet printer drives the liquid transmission pump 63, and, when the acquired pressure reaches a second threshold larger than the first threshold, the inkjet printer stops the liquid transmission pump 63. In a state where the valve 64 is opened, the inkjet printer keeps opening the valve 64 until the acquired pressure reaches a third threshold larger than the second threshold, and, when the acquired pressure exceeds the third threshold, the inkjet printer closes the valve 64.SELECTED DRAWING: Figure 3

Description

TECHNICAL FIELD

[0001] The present invention relates to an inkjet printer.

BACKGROUND ART

[0002] Inkjet printers that perform printing by ejecting ink from an ink head have been conventionally known. For example, Patent Document 1 discloses an inkjet printer including: an ink cartridge that stores ink; an ink head that ejects ink; an ink path that communicates the ink cartridge and the ink head; a valve capable of opening or closing the ink path; a damper that is provided in the ink path and has a storage chamber in which ink is temporarily stored; and a supply pump that is provided in the ink path and feeds ink to the ink head. In the inkjet printer described in Patent Document 1, a detection device that detects whether the pressure of ink in the storage chamber is equal to or lower than a predetermined pressure is provided in the damper. When it is detected that the pressure of ink in the storage chamber is equal to or lower than the predetermined pressure, the inkjet printer described in Patent Document 1 drives the supply pump to supply ink to the damper.

[0003] Patent Document 1 describes that leakage may occur in the supply pump due to deterioration or the like. According to Patent Document 1, if the leakage of the supply pump continues, there is a risk that ink may unintentionally leak from the ink head.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0004]

PATENT DOCUMENT 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0005] Some inkjet printers have a mechanism to prevent ink leaks from the ink pump, which could cause ink to leak from the print head. This mechanism closes a valve when the ink pump is stopped and opens it when the pump is running. Closing the valve when the pump is stopped reduces the risk of ink leaking from the print head. However, because the ink pump is driven intermittently, the valve is opened and closed frequently. This can shorten the valve's lifespan.

[0006] The present invention has been made in view of the above, and its purpose is to provide an inkjet printer that can reduce the risk of ink leakage from the ink head and suppress the frequent opening and closing of valves provided in the ink flow path. [Means for solving the problem]

[0007] The inkjet printer disclosed herein comprises an ink container containing ink, an ink head for ejecting ink, an ink channel connecting the ink container and the ink head, a liquid delivery pump provided in the ink channel and, when driven, delivers ink from the ink container toward the ink head, a valve provided in the ink channel for opening or closing the ink channel, an intermediate container provided in the ink channel downstream of the liquid delivery pump and the valve in the ink delivery direction, having a storage chamber where ink is temporarily stored, a pressure sensor for measuring the pressure of the ink in the storage chamber, and a control device connected to the ink head, the liquid delivery pump, the valve, and the pressure sensor. The control device comprises a pressure acquisition unit, a liquid delivery control unit, and a valve control unit. The pressure acquisition unit acquires the pressure of the ink in the storage chamber from the pressure sensor. The liquid delivery control unit drives the liquid delivery pump when the pressure acquired by the pressure acquisition unit falls below a predetermined first threshold, and stops the liquid delivery pump when it reaches a second threshold greater than the first threshold. The valve control unit keeps the valve open while the valve is open, until the pressure acquired by the pressure acquisition unit reaches a third threshold greater than the second threshold, and closes the valve when the pressure exceeds the third threshold.

[0008] According to the inkjet printer described above, the third threshold is set higher than the second threshold, which is the pressure at which the liquid delivery pump stops. When there is no leakage in the liquid delivery pump, the pressure in the storage chamber does not significantly exceed the second threshold and does not reach the third threshold. Furthermore, the valve provided in the ink path will not close from its open state unless the pressure in the storage chamber exceeds the third threshold. Therefore, this control can suppress frequent opening and closing of the valve. Also, if a leak occurs in the liquid delivery pump or the ink pressure in the storage chamber exceeds the third threshold, the valve will close. This stops the supply of ink to the storage chamber. Therefore, according to the inkjet printer described above, the risk of ink leakage from the ink head can also be reduced. [Brief explanation of the drawing]

[0009] [Figure 1] This is a front view of a printer according to one embodiment. [Figure 2] This is a schematic plan view showing the configuration of the underside of the carriage. [Figure 3] This is a schematic diagram showing the configuration of the ink supply system. [Figure 4] This is a block diagram of a printer. [Figure 5] This flowchart shows the operation of the liquid transfer pump in pump control mode. [Figure 6] This is a flowchart showing the operation of the valve. [Figure 7] This is a flowchart showing the operation of the liquid transfer pump in a conventional inkjet printer. [Figure 8] This is a flowchart showing the operation of a valve in a conventional inkjet printer. [Modes for carrying out the invention]

[0010] [Inkjet printer configuration] The following describes an inkjet printer according to one embodiment, with reference to the drawings. It should be noted that the embodiment described herein is not intended to limit the present invention. Furthermore, the same reference numerals are used for components and parts that perform the same function, and redundant explanations are omitted or simplified as appropriate. In the following description, when viewing the inkjet printer from the front, the direction away from the inkjet printer is considered the front, and the direction towards the inkjet printer is considered the rear. Also, the reference numerals F, Rr, L, R, U, and D in the drawings represent front, rear, left, right, up, and down, respectively. However, these are merely directions for the convenience of explanation and do not limit the installation configuration of the inkjet printer.

[0011] Figure 1 is a front view of a large-format inkjet printer (hereinafter referred to as "printer") 10 according to one embodiment. The printer 10 prints an image on the recording medium 5 by moving the roll-shaped recording medium 5 in the front-to-back direction and ejecting ink from an ink head 50 mounted on a carriage 20 that moves in the left-to-right direction.

[0012] The recording medium 5 is the object on which the image is printed. The recording medium 5 is not particularly limited. For example, the recording medium 5 may be paper such as plain paper or inkjet printing paper, or it may be a transparent sheet made of resin or glass. The recording medium 5 may also be a sheet made of metal or rubber, or it may be a fabric.

[0013] As shown in Figure 1, the printer 10 includes a carriage 20, a carriage moving device 30, a transport device 40, an ink head 50, an ink supply system 60, a capping device 70, and a control device 100.

[0014] The carriage moving device 30 comprises a guide rail 31, a belt 32, left and right pulleys 33a and 33b, and a carriage motor 34. The carriage 20 is slidably engaged with the guide rail 31. The guide rail 31 extends in the left-right direction. The guide rail 31 guides the left-right movement of the carriage 20. The belt 32 is fixed to the carriage 20. The belt 32 is an endless belt. The belt 32 is wrapped around a pulley 33a located on the right side of the guide rail 31 and a pulley 33b located on the left side. The carriage motor 34 is attached to the right pulley 33a. The carriage motor 34 is electrically connected to the control device 100. The carriage motor 34 is controlled by the control device 100. When the carriage motor 34 is driven, the pulley 33a rotates and the belt 32 travels. As a result, the carriage 20 moves left and right along the guide rail 31.

[0015] Below the carriage 20, a platen 12 is positioned. The platen 12 extends in the left-right direction. A recording medium 5 is placed on the platen 12. The recording medium 5 on the platen 12 is moved in the front-rear direction by a conveying device 40. The conveying device 40 includes a pinch roller 41, a grid roller 42, and a feed motor 43. The pinch roller 41 is positioned above the platen 12 and presses down on the recording medium 5 from above. The pinch roller 41 is positioned behind the carriage 20. The platen 12 is provided with a grid roller 42. The grid roller 42 is positioned below the pinch roller 41. The grid roller 42 is positioned opposite the pinch roller 41. The grid roller 42 is connected to the feed motor 43. The grid roller 42 is rotatable by the driving force of the feed motor 43. The feed motor 43 is electrically connected to the control device 100. The feed motor 43 is controlled by the control device 100. When the grid roller 42 rotates with the recording medium 5 sandwiched between the pinch roller 41 and the grid roller 42, the recording medium 5 is transported in the forward and backward directions.

[0016] Figure 2 is a plan view schematically showing the configuration of the lower surface of the carriage 20. As shown in Figure 2, a plurality of ink heads 50 are provided on the lower surface of the carriage 20. The ink heads 50 are configured to eject ink. The plurality of ink heads 50 are arranged side by side in the left-right direction on the carriage 20. A plurality of nozzles 51 are respectively formed on the lower surfaces of the plurality of ink heads 50. The nozzles 51 are fine holes through which ink is ejected. The lower surface of each ink head 50 constitutes a nozzle surface 50a on which the plurality of nozzles 51 are formed. On the nozzle surface 50a, the plurality of nozzles 51 are aligned in the front-rear direction to form a nozzle array. Here, two nozzle arrays are formed for each one ink head 50. However, the arrangement of the ink heads 50 and the nozzles 51 is not limited to the above-described arrangement. The ink heads 50 here are piezoelectric drive type inkjet heads. However, the system by which the ink heads 50 eject ink is not limited to the piezoelectric drive type, and may be, for example, a thermal type or the like.

[0017] As shown in Figure 1, ink is supplied to the ink heads 50 by the ink supply system 60. Figure 3 is a schematic diagram showing the configuration of the ink supply system 60. In the present embodiment, the ink supply system 60 is provided for each nozzle array. As shown in Figure 3, each ink supply system 60 includes an ink cartridge 61, an ink flow path 62, a liquid feeding pump 63, a valve 64, and a damper 65.

[0018] The ink cartridge 61 is an example of an ink container that stores ink. One ink cartridge 61 stores, for example, one ink selected from process color inks and special color inks. The material of the ink is not particularly limited, and various materials conventionally used as ink materials for inkjet printers can be used. The above ink may be, for example, a solvent-based pigment ink or an aqueous pigment ink. Alternatively, it may be an aqueous dye ink, an ultraviolet curable pigment ink that cures upon receiving ultraviolet rays, or the like.

[0019] The ink flow path 62 connects the ink cartridge 61 and the ink head 50. Ink is supplied from the ink cartridge 61 to the ink head 50 through the ink flow path 62. The configuration of the ink flow path 62 is not limited, and for example, it is constituted by a flexible tube.

[0020] The liquid feed pump 63 is provided in the ink flow path 62. The liquid feed pump 63 is configured to feed ink in the direction from the ink cartridge 61 toward the ink head 50 during operation. In the present embodiment, the liquid feed pump 63 is a tube pump. However, the type of the liquid feed pump 63 is not limited, and may be, for example, a diaphragm pump or the like. Although not illustrated, the liquid feed pump 63 here includes an internal flow path constituted by a flexible tube, a roller that squeezes the internal flow path, and a motor that moves the roller along the internal flow path. The liquid feed pump 63 drives the motor to move the roller along the internal flow path, thereby squeezing the internal flow path and delivering the ink in the internal flow path. The liquid feed pump 63 is electrically connected to the control device 100 and controlled by the control device 100.

[0021] The valve 64 is provided in the ink flow path 62, specifically, in a portion of the ink flow path 62 between the ink cartridge 61 and the liquid feed pump 63. The valve 64 is provided upstream of the liquid feed pump 63 in the ink feeding direction. However, the valve 64 may be provided downstream of the liquid feed pump 63 in the ink feeding direction. The valve 64 opens or closes the ink flow path 62. The valve 64 is, for example, a solenoid valve. However, the type of the valve 64 is not limited, and may be, for example, an air-driven valve. The valve 64 is electrically connected to the control device 100 and controlled by the control device 100.

[0022] The damper 65 is located downstream of the liquid delivery pump 63 and valve 64 in the ink flow path 62. Here, the damper 65 is located between the liquid delivery pump 63 and the ink head 50. The damper 65 is an example of an intermediate container equipped with a storage chamber 65a where ink is temporarily stored. The damper 65 mitigates ink pressure fluctuations by temporarily storing ink in the storage chamber 65a.

[0023] The damper 65 is provided with a pressure sensor 66 for measuring the pressure of the ink in the storage chamber 65a. The pressure sensor 66 is a sensor that continuously measures the pressure of the ink. The pressure sensor 66 is, for example, a pressure sensor that utilizes the piezoelectric effect of a piezo element. The pressure sensor 66 may be configured to output a current or voltage corresponding to the measured pressure of the ink. Alternatively, the pressure sensor 66 may be configured to output a signal when the measured pressure is above a set pressure or below a set pressure. In this embodiment, the pressure sensor 66 outputs a signal in a manner that can distinguish whether the pressure of the ink exceeds a first threshold T1 (see Figure 5), whether it exceeds a second threshold T2 (see Figure 5), or whether it exceeds a third threshold T3 (see Figure 6). Details of the first threshold T1, the second threshold T2, and the third threshold T3 will be described later.

[0024] For example, if the pressure sensor 66 is configured to output a signal when the measured pressure exceeds a set pressure, the control device 100 will determine whether the ink pressure exceeds a first threshold T1, a second threshold T2, or a third threshold T3 based on the presence or absence of the signal. For example, if the pressure sensor 66 is configured to output a voltage or current corresponding to the measured pressure, the control device 100 will determine whether the ink pressure exceeds a first threshold T1, a second threshold T2, or a third threshold T3 based on the voltage or current value.

[0025] As shown in Figure 1, a home position P1 is set at the rightmost end of the carriage 20's range of motion. Home position P1 is the position where the carriage 20 is positioned when waiting to print. Below the carriage 20 in home position P1, a capping device 70 is located. As shown in Figure 1, the capping device 70 comprises a cap 71, a cap moving device 72, and a suction pump 73. The capping device 70 is an example of a suction device that is attached to the ink head 50 and sucks ink from the ink head 50.

[0026] The cap 71 is configured to be attachable to the ink head 50. The same number of caps 71 are provided as there are ink heads 50. One cap 71 is attached to each ink head 50. However, one cap 71 may be configured to be attached to multiple ink heads 50. The cap 71 has a container-like shape with an open top. The cap 71 is made of rubber or the like. When attached to the ink head 50, the upper edge of the cap 71 is in close contact with the nozzle surface 50a of the ink head 50.

[0027] Multiple caps 71 are supported by a single cap moving device 72. The cap moving device 72 attaches or separates the multiple caps 71 from the nozzle surface 50a of the ink head 50. The cap moving device 72 supports the caps 71 from below and moves them in the vertical direction. As a result, the caps 71 are attached to and separated from the ink head 50. The cap moving device 72 includes, for example, a drive motor (not shown). The cap moving device 72 is electrically connected to and controlled by a control device 100. In this embodiment, the cap moving device 72 moves the caps 71 in the vertical direction to attach them to the ink head 50, but it may also be configured to attach them by sliding them diagonally, for example.

[0028] As shown in Figure 1, the suction pump 73 is connected to multiple caps 71. The suction pump 73 reduces the pressure inside the caps 71 while they are attached to the ink head 50. This causes the suction pump 73 to draw ink from the ink head 50. The suction pump 73 is, for example, a pressure reducing pump. The suction pump 73 is electrically connected to and controlled by the control device 100.

[0029] Figure 4 is a block diagram of the printer 10 according to this embodiment. As shown in Figure 4, the control device 100 is electrically connected to the carriage motor 34, the feed motor 43, the ink head 50, the liquid supply pump 63, the valve 64, the cap moving device 72, and the suction pump 73, and is configured to control them. The control device 100 is also electrically connected to the pressure sensor 66 and receives signals from the pressure sensor 66.

[0030] The configuration of the control device 100 is not particularly limited. The control device 100 is, for example, a microcomputer. The hardware configuration of the microcomputer is not particularly limited, but for example, it includes an interface (I / F) for receiving print data etc. from an external device such as a host computer, a central processing unit (CPU) that executes instructions for the control program, a ROM (read-only memory) that stores the program executed by the CPU, a RAM (random access memory) used as a working area for expanding the program, and a storage device such as memory that stores the above program and various data. Note that the control device 100 does not necessarily have to be installed inside the printer 10, and may be, for example, a computer installed outside the printer 10 and connected to the printer 10 via wired or wireless means so as to be able to communicate with the printer 10.

[0031] As shown in Figure 4, the control device 100 includes a printing control unit 101, a capping control unit 102, a suction control unit 103, a flushing control unit 104, a pressure acquisition unit 105, a liquid delivery control unit 106, a valve control unit 107, and a mode registration unit 108. The control device 100 may also include other processing units, but these are not shown or described here.

[0032] The print control unit 101 controls the printing operation of the printer 10. The print control unit 101 drives the carriage motor 34 to move the carriage 20 in the left-right direction and ejects ink from the ink head 50, thereby printing an image on a portion of the recording medium 5. The print control unit 101 further drives the feed motor 43 to move the recording medium 5 in the front-back direction, thereby moving the printing position on the recording medium 5. Through these operations, an image is printed on the recording medium 5. Hereinafter, the mode in which ink is ejected from the ink head 50 and an image is formed in the printer 10 will also be referred to as the "print mode".

[0033] The capping control unit 102 controls the cap moving device 72 to attach the cap 71 to the ink head 50. When the carriage 20 is positioned at the home position P1 during non-printing, the capping control unit 102 is basically set to attach the cap 71 to the ink head 50.

[0034] The suction control unit 103 controls the suction pump 73 to reduce the pressure inside the cap 71 while the cap 71 is attached to the ink head 50. As a result, the capping device 70, acting as a suction device, sucks ink from the ink head 50. This ink suction is performed periodically or as needed. Hereinafter, the mode in which the printer 10 sucks ink from the ink head 50 by the capping device 70 will also be referred to as "suction mode".

[0035] The flushing control unit 104 controls the ink head 50 to eject ink toward the cap 71 and performs flushing to discard the ink in the nozzle 51. However, the ink ejection during flushing is not limited to the cap 71. The ink ejection during flushing may also be directed to, for example, a dedicated flushing stage. Flushing is performed periodically or as needed. Hereinafter, the mode in which ink is ejected from the ink head 50 and the ink in the nozzle 51 is also referred to as the "flushing mode".

[0036] The pressure acquisition unit 105 acquires the pressure of the ink in the storage chamber 65a of the damper 65 from the pressure sensor 66. The pressure acquisition unit 105 acquires at least the following data from the pressure sensor 66: whether the ink pressure exceeds a first threshold T1, whether it exceeds a second threshold T2, and whether it exceeds a third threshold T3.

[0037] The liquid supply control unit 106 is configured to drive the liquid supply pump when the pressure acquired by the pressure acquisition unit 105 falls below a first threshold T1, and to stop the liquid supply pump 63 when it reaches a second threshold T2. The first threshold T1 is a threshold indicating that the amount of ink in the storage chamber 65a has become low. The second threshold T2 is a threshold indicating that the amount of ink in the storage chamber 65a has become sufficient. The second threshold T2 is set to be higher than the first threshold T1. Through this control, the liquid supply control unit 106 supplies ink to the ink head 50 via the damper 65.

[0038] The valve control unit 107 controls the operation of the valve 64. The valve control unit 107 is configured to keep the valve 64 open when the valve 64 is open, until the pressure acquired by the pressure acquisition unit 105 reaches a third threshold T3 which is greater than the second threshold T2, and then close the valve 64 when it exceeds the third threshold T3. The third threshold T3 is a threshold that indicates that the amount and pressure of ink in the storage chamber 65a have reached their upper limits. The third threshold T3 is set to be lower than the pressure at which ink leaks from the ink head 50 due to the pressure of the ink in the storage chamber 65a. By closing the valve 64 when the pressure of the ink in the storage chamber 65a exceeds the third threshold T3, it is prevented that the pressure of the ink in the storage chamber 65a will not exceed the third threshold T3 by a large margin. This prevents ink from leaking from the ink head 50.

[0039] Furthermore, the valve control unit 107 is configured to open the valve 64 after closing the valve 64 from an open state, if the pressure acquired by the pressure acquisition unit 105 falls below the first threshold T1. When the pressure acquired by the pressure acquisition unit 105 falls below the first threshold T1, the liquid delivery pump 63 is driven under the control of the liquid delivery control unit 106. The valve control unit 107 opens the valve 64 in conjunction with the start of operation of the liquid delivery pump 63.

[0040] The mode registration unit 108 has registered a pump control mode in which the liquid delivery pump 63 is driven or stopped according to the pressure acquired by the pressure acquisition unit 105, and a pump stop mode in which the liquid delivery pump 63 remains stopped. Here, "modes are registered" broadly means that each mode is processed in a way that makes it recognizable as an "ink consumption mode," including forms other than registering one or more modes as a list. For example, each mode may be processed individually without going through a list. In this embodiment, the mode registration unit 108 has registered a print mode, a suction mode, and a flushing mode as pump control modes. In print mode, ink is consumed when ink is ejected from the ink head 50 for printing an image, and the liquid delivery pump 63 is driven accordingly. In suction mode, ink is consumed when ink is sucked from the ink head 50 and discarded, and the liquid delivery pump 63 is driven accordingly. In flushing mode, ink is consumed when ink is ejected from the ink head 50 and discarded, and the liquid delivery pump 63 is driven accordingly.

[0041] The registered pump control modes may include modes other than the printing mode, suction mode, and flushing mode. Another example of a pump control mode is a recovery operation that drives the liquid transfer pump 63 to raise the pressure in the storage chamber 65a that has decreased due to prolonged non-use. The pump control modes may consist of more granular conditions than, for example, the printing mode. Alternatively, the pump control modes may not include some of the printing mode, suction mode, and flushing mode.

[0042] The mode registration unit 108 also registers a pump stop mode in which the liquid transfer pump 63 remains stopped. Here, the pump stop mode may simply be a state in which a particular mode is not registered as a pump control mode. The pump stop mode only needs to be processed in a way that distinguishes it from the pump control modes. Here, the pump stop mode is all modes other than the printing mode, suction mode, and flushing mode that constitute the pump control modes.

[0043] The valve control unit 107 closes the valve 64 in pump stop mode. This prevents ink from moving in pump stop mode, but this does not cause any problems as there is no need to move ink in pump stop mode. Closing the valve 64 suppresses ink leakage from the ink head 50 in pump stop mode.

[0044] The printer 10 may be configured to allow selection of a pressurized cleaning mode, which cleans the ink supply system 60 by applying pressure to the ink exceeding a third threshold T3 to cause it to leak from the ink head 50. The ink pressure in pressurized cleaning mode may be set to a pressure (e.g., -0.6 to +1 kPa) that does not destroy the ink meniscus in the nozzle 51 and does not cause ink to leak from the ink head 50. If the ink pressure in pressurized cleaning mode is set to a pressure that does not destroy the meniscus, the ink will not leak from the ink head 50, but it may swell. If a pressurized cleaning mode is available, the printer 10 may include other valve control units that open the valve 64 during pressurized cleaning mode. Alternatively, the valve control unit 107 may be configured to control the valve 64 as described above in pump control mode and pump stop mode, and to open the valve 64 in pressurized cleaning mode.

[0045] [Ink supply system operation] The following describes the operation of the ink supply system 60 of the printer 10 according to this embodiment. Figure 5 is a flowchart showing the operation of the liquid supply pump 63 in pump control mode. Figure 6 is a flowchart showing the operation of the valve 64. In this embodiment, the liquid supply pump 63 and the valve 64 are controlled independently. For comparison purposes, Figure 7 shows a flowchart showing an example of the operation of the liquid supply pump in a conventional inkjet printer, and Figure 8 shows a flowchart showing an example of the operation of the valve in a conventional inkjet printer. The conventional inkjet printer described here is assumed to be an inkjet printer equipped with a sensor similar to the detection device in Patent Document 1. Although Figures 7 and 8 are separate, in a conventional inkjet printer, the control of the liquid supply pump 63 and the control of the valve 64 are related.

[0046] As shown in Figure 5, in step S01 of the control of the liquid transfer pump 63 in pump control mode, the acquired ink pressure in the storage chamber 65a (hereinafter referred to as "ink pressure," etc., as appropriate) is compared with a first threshold T1. If the ink pressure is greater than or equal to the first threshold T1 in step S01 (the result of step S01 is NO), step S01 is repeated. For example, if the ink pressure falls below the first threshold T1 due to ink consumption (the result of step S01 is YES), the liquid transfer pump 63 is driven in step S02.

[0047] In step S03 of the control of the liquid delivery pump 63, the ink pressure is compared with a second threshold T2. If the ink pressure is below the second threshold T2 in step S03 (the result of step S03 is NO), the liquid delivery pump 63 continues to operate and step S03 is repeated. When the ink pressure becomes equal to or above the second threshold T2 due to the supply of ink (the result of step S03 is YES), the liquid delivery pump 63 is stopped in step S04. As long as the pump control mode is active, steps S01 to S04 are repeated. As a result, the operation and stopping of the liquid delivery pump 63 are repeated.

[0048] As shown in Figure 7, the control of the ink delivery pump in a conventional inkjet printer is generally the same as the control shown in Figure 5. However, with a sensor like the one described in Patent Document 1, it is only possible to detect whether the ink pressure is below a predetermined pressure or above a predetermined pressure, so the first threshold and the second threshold coincide except for the deviation due to the detection direction. Hereinafter, in a conventional inkjet printer, the state in which the ink pressure is below a predetermined pressure will be referred to as a hit state, and the state in which the pressure is above a predetermined pressure will be referred to as an unhit state.

[0049] As shown in Figure 7, in step S21 of the conventional liquid transfer pump control, it is determined whether the sensor is in a hit state. If the sensor is not in a hit state in step S21 (the result of step S21 is NO), step S21 is repeated. If the sensor becomes in a hit state due to ink consumption (the result of step S21 is YES), the liquid transfer pump is driven in step S22.

[0050] In step S23, it is determined whether the sensor is in an unhit state. If the sensor is in a hit state in step S23 (the result of step S23 is NO), the liquid delivery pump continues to run and step S23 is repeated. When the sensor becomes unhit due to ink supply (the result of step S23 is YES), the liquid delivery pump is stopped in step S24. As long as the pump control mode is active, steps S21 to S24 are repeated. As a result, the liquid delivery pump is repeatedly driven and stopped.

[0051] Next, the control of valve 64 will be described. As shown in Figure 6, in step S11 of the control of valve 64, it is checked whether the pump is in control mode. If the pump is in stop mode in step S11 (the result of step S11 is NO), then valve 64 is closed in step S15. Alternatively, valve 64 is kept closed. After step S15, step S11 is repeated.

[0052] In step S11, if the pump control mode is active (if the result of step S11 is YES), in step S12, the pressure of the ink in the storage chamber 65a is compared with the third threshold T3. In step S12, if the ink pressure exceeds the third threshold T3 (if the result of step S12 is NO), the valve 64 is closed in step S16. The third threshold T3 is the threshold for determining whether there is a risk of ink leakage from the ink head 50. As can be seen from Figure 5, if the ink pressure exceeds the third threshold T3, which is greater than the second threshold T2, it indicates that there is a possibility of leakage from the liquid delivery pump 63. When the control in Figure 5 is functioning normally, the ink pressure will not significantly exceed the second threshold T2. Therefore, if left unchecked, there is a risk of ink leakage from the ink head 50. To prevent this, the valve 64 is closed. After step S16, step S11 is repeated.

[0053] If, in step S12, the ink pressure is less than or equal to the third threshold T3 (if the result of step S12 is YES), then in step S13, the ink pressure in the storage chamber 65a is compared with the first threshold T1. If the ink pressure falls below the first threshold T1 (if the result of step S13 is YES), then in step S14, the valve 64 is opened. As shown in Figure 5, when the ink pressure in the storage chamber 65a falls below the first threshold T1, the liquid transfer pump 63 is driven. In step S14, the valve 64 is opened in conjunction with the driving of the liquid transfer pump 63. This allows the ink to move. If the ink pressure is greater than or equal to the first threshold T1 (if the result of step S13 is NO), then step S11 is repeated. Step S11 is also repeated after step S14.

[0054] If there is no leak in the liquid delivery pump 63 and the mode is pump control mode, the valve 64 is controlled in a loop that goes through steps S11, S12, S13, and S14 and returns to step S11. If there is no leak in the liquid delivery pump 63, the result of step S12 is basically not "NO". In this loop, the valve 64 is opened once and then remains open. That is, in this embodiment, the printer 10 keeps the valve 64 open until the pressure acquired by the pressure acquisition unit 105 reaches the third threshold T3 when the valve 64 is open. Therefore, frequent opening and closing of the valve 64 is suppressed.

[0055] In conventional inkjet printers, valve control is synchronized with the control of the ink delivery pump, as shown in Figure 8. If we replace "ink delivery pump drive" with "valve open" and "ink delivery pump stop" with "valve closed" in Figure 7, we get Figure 8. As shown in Figure 8, in step S31 of the conventional valve control, it is determined whether the sensor is in a hit state. If the sensor is not in a hit state in step S31 (the result of step S31 is NO), step S31 is repeated. If the sensor becomes in a hit state due to ink consumption (the result of step S31 is YES), the valve is opened in step S32.

[0056] In step S33, it is determined whether the sensor is in an unhit state. If the sensor is in a hit state in step S33 (the result of step S33 is NO), step S33 is repeated. When the sensor becomes unhit due to ink supply (the result of step S33 is YES), the valve is closed in step S34. As long as the pump control mode is active, steps S31 to S34 are repeated. As a result, the valve is opened and closed repeatedly. In conventional inkjet printers, the valve is opened and closed frequently in this way, and the increased number of openings and closings tends to shorten the valve's lifespan. In contrast, in the printer 10 according to this embodiment, as described above, the frequent opening and closing of the valve 64 is suppressed. Therefore, the lifespan of the valve 64 can be extended.

[0057] [Effects of the Embodiment] The following describes the effects and advantages that can be achieved by the printer 10 according to this embodiment.

[0058] The printer 10 according to this embodiment includes an ink cartridge 61 containing ink, an ink head 50 for ejecting ink, an ink channel 62 connecting the ink cartridge 61 and the ink head 50, a liquid delivery pump 63 provided in the ink channel 62 and, when driven, sends ink from the ink cartridge 61 toward the ink head 50, a valve 64 provided in the ink channel 62 for opening or closing the ink channel 62, a damper 65 provided in the ink channel 62 downstream of the liquid delivery pump 63 and the valve 64 in the ink delivery direction, a storage chamber 65a where ink is temporarily stored, a pressure sensor 66 for measuring the pressure of the ink in the storage chamber 65a, and a control device 100 connected to the ink head 50, the liquid delivery pump 63, the valve 64, and the pressure sensor 66. The control device 100 includes a pressure acquisition unit 105, a liquid delivery control unit 106, and a valve control unit 107. The pressure acquisition unit 105 acquires the pressure of the ink in the storage chamber 65a from the pressure sensor 66. The liquid delivery control unit 106 drives the liquid delivery pump 63 when the pressure acquired by the pressure acquisition unit 105 falls below a predetermined first threshold T1, and stops the liquid delivery pump 63 when it reaches a second threshold T2 which is greater than the first threshold T1. The valve control unit 107 keeps the valve 64 open when the valve 64 is open, until the pressure acquired by the pressure acquisition unit 105 reaches a third threshold T3 which is greater than the second threshold T2, and closes the valve 64 when it exceeds the third threshold T3.

[0059] With this printer 10, as described above, frequent opening and closing of the valve 64 can be suppressed. Furthermore, if the ink pressure exceeds the third threshold T3 due to leakage in the liquid supply pump 63 or the like, the valve 64 can be closed to suppress ink leakage from the ink head 50.

[0060] In this embodiment, the third threshold T3 is set to a pressure lower than the pressure at which ink leaks from the ink head 50 due to the pressure of the ink in the storage chamber 65a. With this printer 10, ink leakage from the ink head 50 can be reliably prevented. Even if the third threshold T3 is set to a pressure at which ink could leak from the ink head 50, the valve 64 is closed, so at least the amount of ink leakage from the ink head 50 can be kept to a minimum.

[0061] In this embodiment, the valve control unit 107 is configured to open the valve 64 after closing the valve 64 from an open state, when the pressure acquired by the pressure acquisition unit 105 falls below a first threshold T1. This control further reduces the frequency of opening and closing the valve 64. For example, it is also possible to configure the valve 64 to open after closing the valve 64 from an open state, when the pressure acquired by the pressure acquisition unit 105 falls below a third threshold T3, but in this case, the frequency of opening and closing the valve 64 may be higher than in this embodiment. When the valve 64 is closed, a leak in the liquid transfer pump 63 is suspected. If the liquid transfer pump 63 is leaking, opening the valve 64 when the ink pressure falls below the third threshold T3 may cause the ink pressure to immediately exceed the third threshold T3. In that case, the frequency of opening and closing the valve 64 will increase. However, since the valve 64 needs to be opened when the liquid transfer pump 63 is driven, the first threshold T1 is preferred as the pressure threshold for opening the valve 64 after it has been closed.

[0062] In this embodiment, the control device 100 includes a mode registration unit 108 that registers a pump control mode in which the liquid delivery pump 63 is driven or stopped according to the pressure acquired by the pressure acquisition unit 105, and a pump stop mode in which the liquid delivery pump 63 remains stopped. The valve control unit 107 is configured to close the valve 64 in the pump stop mode. By closing the valve 64 in the pump stop mode, ink leakage from the ink head 50 in the pump stop mode can be prevented more reliably. Even in the pump stop mode, it is possible to keep the valve 64 open until the ink pressure exceeds the third threshold T3, and even then, ink leakage from the ink head 50 in the event of a leak in the liquid delivery pump 63 can be suppressed. However, in the pump stop mode, there is no need to move the ink, so there is no need to open the valve 64, and closing the valve 64 can more reliably prevent ink leakage.

[0063] [Other embodiments] A preferred embodiment of the present invention has been described above. However, the above embodiment is merely illustrative, and the technology disclosed herein can be implemented in various other forms.

[0064] For example, in the above embodiment, the ink flow path 62 simply connected the ink cartridge 61 and the ink head 50, but it may further include other components such as a circulation flow path to prevent ink component sedimentation, a bubble separator, etc. The configuration of the ink supply system is not limited to those described above.

[0065] In the above embodiment, the pressure sensor 66 was a sensor capable of continuously measuring the pressure of the ink, but it is not limited to that. The pressure sensor may be a sensor equipped with multiple detection devices, each detecting whether the ink pressure exceeds a threshold.

[0066] Furthermore, the configuration of the inkjet printer is not limited unless otherwise specified. For example, the technology disclosed herein can be used with flatbed inkjet printers, etc. It can also be used with devices in which an inkjet printer is incorporated as part of the device, such as inkjet printers with cutting heads. [Explanation of symbols]

[0067] 10 Inkjet Printers 50 Inkheads 60 Ink Supply System 61 Ink cartridge (ink container) 62 Ink channels 63. Liquid transfer pump 64 valves 65 Damper (intermediate container) 65a Storage Chamber 66 Pressure Sensor 100 Control device 105 Pressure acquisition section 106 Fluid delivery control unit 107 Valve Control Unit 108 Mode Registration Section T1 First threshold T2 Second threshold T3 (Third Threshold)

Claims

1. An ink container holding ink, The ink head that ejects ink, An ink channel connecting the ink container and the ink head, A liquid supply pump is provided in the ink flow path and, when driven, sends ink from the ink container toward the ink head, A valve provided in the ink channel for opening or closing the ink channel, The system includes a storage chamber for temporarily storing ink, and an intermediate container located downstream of the liquid delivery pump and the valve in the ink flow path, A pressure sensor for measuring the pressure of the ink in the storage chamber, The system comprises the ink head, the liquid delivery pump, the valve, and a control device connected to the pressure sensor, The control device is A pressure acquisition unit that acquires the pressure of the ink in the storage chamber from the pressure sensor, A liquid transfer control unit drives the liquid transfer pump when the pressure acquired by the pressure acquisition unit falls below a predetermined first threshold, and stops the liquid transfer pump when it reaches a second threshold greater than the first threshold. The system includes a valve control unit that, while the valve is open, keeps the valve open until the pressure acquired by the pressure acquisition unit reaches a third threshold greater than the second threshold, and closes the valve when the pressure exceeds the third threshold. Inkjet printer.

2. The third threshold is set to be less than the pressure at which ink leaks from the ink head due to the pressure of the ink in the storage chamber. The inkjet printer according to claim 1.

3. The valve control unit, after closing the valve from an open state, opens the valve when the pressure acquired by the pressure acquisition unit falls below the first threshold. The inkjet printer according to claim 1.

4. The control device includes a registration unit which registers a control mode in which the liquid transfer pump is driven or stopped according to the pressure acquired by the pressure acquisition unit, and a stop mode in which the liquid transfer pump remains stopped. The valve control unit closes the valve in the stop mode. The inkjet printer according to claim 1.

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