JP2018199248A - Ink jet printer - Google Patents

Abstract

To provide an ink jet printer which can carry out an initial filling of ink into an ink tank in a short time.SOLUTION: An ink supply part 4 is connected to an ink tank 12A of an ink tank pair 20A and an ink tank 12B of an ink tank pair 20B. In an initial filling of ink into a printing part 2, the ink supply part 4 supplies the ink to both of the ink tanks 12A, 12B.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an inkjet printing apparatus that prints by ejecting ink from an inkjet head.

  2. Description of the Related Art An ink jet printing apparatus that performs printing by driving an ink jet head while circulating ink between the ink tank on the upstream side of the ink jet head, the ink jet head, and the ink tank on the downstream side is known (for example, patents). Reference 1).

  In such a printing apparatus, printing is performed by supplying ink stored in an upstream ink tank to an inkjet head and ejecting the ink from the inkjet head. Ink that has not been consumed by the inkjet head is collected and stored in the ink tank on the downstream side. The ink in the downstream ink tank is sent to the upstream ink tank, and is supplied to the inkjet head from the upstream ink tank to be used for printing. In this way, ink circulation and printing are performed.

JP 2012-153004 A

  In the ink jet printing apparatus as described above, for example, when the apparatus is not used, the ink tank is empty. In order to make the printing operation possible from such a state, it is necessary to perform initial filling to fill the ink tank with ink.

  In the initial filling of the ink into the ink tank, the ink is supplied up to a specified amount to the empty ink tank, so that it takes a certain amount of time to complete the initial filling. The printing operation cannot be performed until the initial ink filling is completed. For this reason, it is desirable that the time required for the initial ink filling is short.

  The present invention has been made in view of the above, and an object thereof is to provide an ink jet printing apparatus capable of performing initial filling of ink into an ink tank in a short time.

  In order to achieve the above object, an ink jet printing apparatus according to the present invention includes an ink jet head, a plurality of ink tank pairs each of which is a pair of a first ink tank and a second ink tank for storing ink, and the ink jet head through the ink jet head. An ink flow path connecting between the first ink tank and the second ink tank of each ink tank pair, and the ink flow path in one ink tank pair of the plurality of ink tank pairs; Printing is performed by discharging ink from the inkjet head while performing ink feeding between the first ink tank and the second ink tank via the inkjet head, and the first ink tank and the second ink tank While sequentially switching one ink tank pair that performs ink feeding with the second ink tank, Connected to the first ink tank of each of the ink tank pairs and discharging the ink from the ink jet head, and when the ink is initially filled in the printing parts, And an ink supply unit that supplies ink to the first ink tank at the same time.

  According to the ink jet printing apparatus of the present invention, it is possible to perform the initial filling of the ink into the ink tank in a short time.

It is a block diagram which shows the structure of the inkjet printing apparatus which concerns on 1st Embodiment. It is a schematic block diagram of the printing part of the inkjet printing apparatus which concerns on 1st Embodiment, a pressure production | generation part, and an ink replenishment part. It is a flowchart for demonstrating the operation | movement at the time of printing of the inkjet printing apparatus in 1st Embodiment. It is operation | movement explanatory drawing at the time of printing of the inkjet printing apparatus in 1st Embodiment. It is operation | movement explanatory drawing at the time of printing of the inkjet printing apparatus in 1st Embodiment. It is operation | movement explanatory drawing at the time of printing of the inkjet printing apparatus in 1st Embodiment. It is operation | movement explanatory drawing at the time of printing of the inkjet printing apparatus in 1st Embodiment. It is operation | movement explanatory drawing at the time of printing of the inkjet printing apparatus in 1st Embodiment. It is operation | movement explanatory drawing at the time of printing of the inkjet printing apparatus in 1st Embodiment. It is a flowchart of the preparation process including ink replenishment. 6 is a flowchart for explaining an operation at the time of initial filling of ink into a printing unit in the first embodiment. FIG. 6 is an operation explanatory diagram at the time of initial filling of ink into a printing unit according to the first embodiment. FIG. 6 is an operation explanatory diagram at the time of initial filling of ink into a printing unit according to the first embodiment. FIG. 6 is an operation explanatory diagram at the time of initial filling of ink into a printing unit according to the first embodiment. It is explanatory drawing of the pressure detection of the ink tank in the ink supply in 2nd Embodiment. It is explanatory drawing of the pressure detection of the ink tank in the ink supply in 2nd Embodiment. It is a block diagram which shows the structure of the inkjet printing apparatus which concerns on 3rd Embodiment. It is a schematic block diagram of the printing part of the inkjet printing apparatus which concerns on 3rd Embodiment, a pressure production | generation part, and an ink replenishment part. It is a flowchart for demonstrating the operation | movement at the time of printing of the inkjet printing apparatus in 3rd Embodiment. It is explanatory drawing of liquid level maintenance control. It is explanatory drawing of pressure control. 12 is a flowchart for explaining an operation at the time of initial filling of ink into a printing unit in the third embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. Throughout the drawings, the same or equivalent parts and components are denoted by the same or equivalent reference numerals.

  The following embodiments exemplify devices for embodying the technical idea of the present invention, and the technical idea of the present invention is the material, shape, structure, arrangement, etc. of each component. Is not specified as follows. The technical idea of the present invention can be variously modified within the scope of the claims.

[First Embodiment]
FIG. 1 is a block diagram showing the configuration of the ink jet printing apparatus according to the first embodiment of the present invention. FIG. 2 is a schematic configuration diagram of a printing unit, a pressure generation unit, and an ink supply unit of the inkjet printing apparatus shown in FIG.

  As shown in FIG. 1, the inkjet printing apparatus 1 according to the first embodiment includes printing units 2 </ b> A and 2 </ b> B, a pressure generation unit 3, ink supply units 4 </ b> A and 4 </ b> B, and a control unit 5. In some cases, the alphabetic suffixes in the reference numerals of the printing units 2A, 2B, etc. are omitted and collectively described.

  The printing units 2A and 2B print images by ejecting ink onto paper (not shown). The printing units 2A and 2B eject inks of different colors. The printing units 2A and 2B have the same configuration except that the colors of the ejected ink are different. In FIG. 2, illustration of a part of the printing unit 2B is omitted.

  The printing unit 2 includes an inkjet head 11, ink tanks 12A to 12D, liquid level sensors 13A to 13D, an ink outflow path 14, ink outflow valves 15A to 15D, an ink inflow path 16, and ink inflow valves 17A to 17A. 17D.

  The inkjet head 11 has a plurality of nozzles (not shown) and ejects ink from the nozzles.

  The ink tanks 12 </ b> A to 12 </ b> D store ink used for printing by the inkjet head 11. In the ink tanks 12A to 12D, air layers 18A to 18D are formed on the liquid surface of the ink. The ink tanks 12A to 12D constitute two ink tank pairs 20A and 20B for ink feeding. The ink tank pair 20A includes an ink tank 12A (first ink tank) and an ink tank 12C (second ink tank). The ink tank pair 20B includes an ink tank 12B (first ink tank) and an ink tank 12D (second ink tank).

  The ink tank 12 </ b> A and the ink tank 12 </ b> C of the ink tank pair 20 </ b> A are connected via the inkjet head 11 by the ink outflow path 14 and the ink inflow path 16. Similarly, the ink tank 12 </ b> B and the ink tank 12 </ b> D of the ink tank pair 20 </ b> B are connected via the inkjet head 11 by the ink outflow path 14 and the ink inflow path 16. That is, the ink outflow path 14 and the ink inflow path 16 form an ink flow path that connects the two ink tanks 12 of each ink tank pair 20.

  The liquid level sensors 13A to 13D are installed in the ink tanks 12A to 12D, respectively, and detect the height of the ink level in the ink tanks 12A to 12D, respectively.

  The ink outflow path 14 is an ink flow path that flows out from the ink tanks 12 </ b> A to 12 </ b> D toward the inkjet head 11. The ink outflow path 14 includes individual outflow pipes 21A to 21D and common outflow pipes 22A and 22B.

  The individual outflow pipe 21A forms an ink flow path that flows out of the ink tank 12A toward the common outflow pipe 22A. One end of the individual outflow pipe 21A is connected to the ink tank 12A, and the other end of the individual outflow pipe 21A is connected to one end of the common outflow pipe 22A. The individual outflow pipe 21B forms a flow path of ink that flows out of the ink tank 12B toward the common outflow pipe 22B. One end of the individual outflow pipe 21B is connected to the ink tank 12B, and the other end of the individual outflow pipe 21B is connected to one end of the common outflow pipe 22A.

  The individual outflow pipe 21C forms an ink flow path that flows out of the ink tank 12C toward the common outflow pipe 22C. One end of the individual outflow pipe 21C is connected to the ink tank 12C, and the other end of the individual outflow pipe 21C is connected to one end of the common outflow pipe 22B. The individual outflow pipe 21D forms an ink flow path that flows out of the ink tank 12D to the common outflow pipe 22D. One end of the individual outflow pipe 21D is connected to the ink tank 12D, and the other end of the individual outflow pipe 21D is connected to one end of the common outflow pipe 22B.

  The common outflow pipe 22 </ b> A forms an ink flow path between the individual outflow pipes 21 </ b> A and 21 </ b> B and the inkjet head 11. The common outflow pipe 22 </ b> A forms part of the ink flow path between the individual outflow pipes 21 </ b> C and 21 </ b> D and the inkjet head 11. One end of the common outflow pipe 22A is connected to the other ends of the individual outflow pipes 21A and 21B, and the other end of the common outflow pipe 22A is connected to the inkjet head 11.

  The common outflow pipe 22B forms a part of the ink flow path between the individual outflow pipes 21C and 21D and the inkjet head 11. One end of the common outflow pipe 22B is connected to the other end of the individual outflow pipes 21C and 21D, and the other end of the common outflow pipe 22B is connected in the middle of the common outflow pipe 22A.

  The ink outflow valves 15A to 15D permit and block the outflow of ink from the ink tanks 12A to 12D, respectively. The ink outflow valves 15A to 15C are disposed in the individual outflow pipes 21A to 21D, respectively.

  The ink inflow path 16 is a flow path of ink that flows into the ink tanks 12 </ b> A to 12 </ b> D without being consumed by the inkjet head 11. The ink inflow path 16 includes common inflow pipes 26A and 26B and individual inflow pipes 27A to 27D.

  The common inflow pipe 26A forms an ink flow path between the inkjet head 11 and the individual inflow pipes 27A and 27B. The common inflow pipe 26A forms part of the ink flow path between the inkjet head 11 and the individual inflow pipes 27C and 27D. One end of the common inflow pipe 26A is connected to the inkjet head 11, and the other end of the common inflow pipe 26A is connected to one end of the individual inflow pipes 27A and 27B.

  The common inflow pipe 26B forms part of the ink flow path between the inkjet head 11 and the individual inflow pipes 27C and 27D. One end of the common inflow pipe 26B is connected to the common inflow pipe 26A, and the other end of the common inflow pipe 26B is connected to one end of the individual inflow pipes 27C and 27D.

  The individual inflow pipes 27A and 27B form ink flow paths from the common inflow pipe 26A to the ink tanks 12A and 12B, respectively. One ends of the individual inflow pipes 27A and 27B are connected to the other end of the common inflow pipe 26A, and the other ends of the individual inflow pipes 27A and 27B are connected to the ink tanks 12A and 12B, respectively.

  The individual inflow pipes 27C and 27D form ink flow paths from the common inflow pipe 26B to the ink tanks 12C and 12D, respectively. One ends of the individual inflow pipes 27C and 27D are connected to the other end of the common inflow pipe 26B, and the other ends of the individual inflow pipes 27C and 27D are connected to the ink tanks 12C and 12D, respectively.

  The ink inflow valves 17A to 17D allow and block the inflow of ink from the ink jet head 11 to the ink tanks 12A to 12D, respectively. The ink inflow valves 17A to 17D are disposed in the individual inflow pipes 27A to 27D, respectively.

  The pressure generator 3 selectively generates a positive pressure and a negative pressure in each of the ink tanks 12A to 12D. The pressure generating unit 3 is common to the printing units 2A and 2B. The pressure generating unit 3 includes an air pump 31, an air path 32, pressure valves 33A to 33D, pressure adjusting valves 34A and 34B, atmospheric release valves 35A and 35B, and pressure sensors 36A and 36B.

  The air pump 31 moves air between one ink tank 12 and the other ink tank 12 in the ink tank pair 20. The air pump 31 is disposed in a common air pipe 41 of an air path 32 described later.

  The air path 32 connects the air layer 18 of one ink tank 12 and the air layer 18 of the other ink tank 12 of each ink tank pair 20 via the air pump 31. The air path 32 includes a common air pipe 41, individual air pipes 42A to 42D, individual branch air pipes 43A to 43D, pressure adjusting pipes 44A and 44B, and air release pipes 45A and 45B.

  The common air pipe 41 forms part of the air flow path between the ink tanks 12A and 12C of the ink tank pair 20A. The common air pipe 41 forms a part of an air flow path between the ink tanks 12B and 12D of the ink tank pair 20B. One end of the common air pipe 41 is connected to one end of the individual air pipes 42A and 42B, and the other end of the common air pipe 41 is connected to one end of the individual air pipes 42C and 42D.

  The individual air pipes 42A and 42B form air flow paths between the ink tanks 12A and 12B of the printing unit 2A and the common air pipe 41, respectively. One ends of the individual air tubes 42A and 42B are connected to one end of the common air tube 41, and the other ends of the individual air tubes 42A and 42B are connected to the air layers 18A and 18B of the ink tanks 12A and 12B, respectively.

  The individual air pipes 42C and 42D form air flow paths between the ink tanks 12C and 12D of the printing unit 2A and the common air pipe 41, respectively. One end of each of the individual air pipes 42C and 42D is connected to the other end of the common air pipe 41, and the other end of each of the individual air pipes 42C and 42D is connected to the air layers 18C and 18D of the ink tanks 12C and 12D, respectively.

  The individual branch air pipes 43A to 43D communicate the individual air pipes 42A to 42D with the air layers 18A to 18D of the ink tanks 12A to 12D of the printing unit 2B, respectively. One ends of the individual branch air pipes 43A to 43D are connected to the individual air pipes 42A to 42D, respectively, and the other ends of the individual branch air pipes 43A to 43D are connected to the air layers 18A to 18D of the ink tanks 12A to 12D of the printing unit 2B, respectively. Has been.

  The pressure adjusting tube 44A forms an air flow path for adjusting the pressure of the ink tanks 12A and 12B. One end of the pressure adjusting pipe 44A is connected to the common air pipe 41 on the ink tanks 12A and 12B side from the air pump 31, and the other end of the pressure adjusting pipe 44A communicates with the atmosphere.

  The pressure adjusting pipe 44B forms an air flow path for adjusting the pressure of the ink tanks 12C and 12D. One end of the pressure adjustment pipe 44B is connected to the common air pipe 41 on the ink tanks 12C and 12D side from the air pump 31, and the other end of the pressure adjustment pipe 44B communicates with the atmosphere.

  The air release pipe 45A forms an air flow path for opening the ink tanks 12A and 12B to the atmosphere. One end of the atmosphere release pipe 45A is connected to the common air pipe 41 between the point where the pressure adjustment pipe 44A is connected to the common air pipe 41 and the air pump 31, and the other end of the atmosphere release pipe 45A communicates with the atmosphere. .

  The air release pipe 45B forms an air flow path for opening the ink tanks 12C and 12D to the atmosphere. One end of the atmosphere release pipe 45B is connected to the common air pipe 41 between the point where the pressure adjustment pipe 44B is connected to the common air pipe 41 and the air pump 31, and the other end of the atmosphere release pipe 45B communicates with the atmosphere. .

  The pressure valves 33A to 33D allow and block air inflow and outflow through the individual air pipes 42A to 42D in the ink tanks 12A to 12D of the printing unit 2A, respectively. The pressure valves 33A to 33D allow and block air inflow and outflow through the individual air tubes 42A to 42D and the individual branch air tubes 43A to 43D in the ink tanks 12A to 12D of the printing unit 2B, respectively. . The pressure valves 33A to 33D are arranged in the individual air pipes 42A to 42D between one end of the individual air pipes 42A to 42D and the point where the individual branch air pipes 43A to 43D are connected to the individual air pipes 42A to 42D, respectively. Has been.

  The pressure adjustment valve 34A opens and closes the air flow path in the pressure adjustment pipe 44A in order to adjust the pressure of the ink tanks 12A and 12B. The pressure adjustment valve 34B opens and closes the air flow path in the pressure adjustment pipe 44B in order to adjust the pressure of the ink tanks 12C and 12D.

  The air release valve 35A opens and closes the air flow path in the air release pipe 45A in order to switch the ink tanks 12A and 12B between a sealed state where the ink tanks 12A and 12B are shut off from the atmosphere and an atmosphere open state which communicates with the atmosphere. The atmosphere release valve 35B opens and closes the air flow path in the atmosphere release pipe 45B in order to switch the ink tanks 12C and 12D between the sealed state and the atmosphere released state.

  The pressure sensor 36A is for detecting the pressure in the ink tanks 12A and 12B. The pressure sensor 36A is connected to the pressure adjustment pipe 44A between one end of the pressure adjustment pipe 44A and the pressure adjustment valve 34A. The pressure sensor 36B is for detecting the pressure in the ink tanks 12C and 12D. The pressure sensor 36B is connected to the pressure adjustment pipe 44B between one end of the pressure adjustment pipe 44B and the pressure adjustment valve 34B.

  The ink supply units 4A and 4B are connected to the ink tanks 12A and 12B of the printing units 2A and 2B, respectively, and supply ink to the ink tanks 12A and 12B. The ink replenishing portions 4A and 4B have the same configuration except that the colors of ink to be replenished are different.

  The ink supply unit 4 includes an ink cartridge 51, an ink supply path 52, and ink supply valves 53A and 53B.

  The ink cartridge 51 contains ink used for printing by the inkjet head 11. The ink cartridge 51 is disposed at a position higher than the ink tanks 12A to 12D.

  The ink supply path 52 is a path for ink to be supplied from the ink cartridge 51 to the ink tanks 12A and 12B. The ink supply path 52 includes a common supply pipe 56 and branch supply pipes 57A and 57B.

  The common supply pipe 56 forms a common part of a flow path of ink supplied to the ink tanks 12A and 12B. One end of the common supply pipe 56 is connected to the ink cartridge 51, and the other end of the common supply pipe 56 is connected to one end of the branch supply pipes 57A and 57B.

  The branch supply pipes 57A and 57B form individual ink flow paths to be supplied to the ink tanks 12A and 12B, respectively. One end of the branch supply pipes 57A and 57B is connected to the other end of the common supply pipe 56, and the other end of the branch supply pipes 57A and 57B is connected to the ink tanks 12A and 12B, respectively.

  The ink supply valves 53A and 53B allow and block the inflow of ink from the ink cartridge 51 to the ink tanks 12A and 12B, respectively. When the ink supply valves 53A and 53B are opened, ink flows to the ink tanks 12A and 12B, respectively. The ink supply valves 53A and 53B are disposed in the branch supply pipes 57A and 57B, respectively.

  The control unit 5 controls the operation of each unit of the inkjet printing apparatus 1. The control unit 5 includes a CPU, a RAM, a ROM, a hard disk, and the like.

  When performing printing, the control unit 5 controls the pressure generation unit 3 to generate positive pressure and negative pressure for ink feeding in one ink tank 12 and the other ink tank 12 of the ink tank pair 20, respectively. To do. As a result, the control unit 5 feeds ink from one ink tank 12 to the other ink tank 12 via the ink outflow path 14, the inkjet head 11, and the ink inflow path 16. At the same time, the control unit 5 controls to eject ink from the inkjet head 11 and perform printing.

  And the control part 5 switches the ink tank pair 20 which performs an ink feeding alternately in each of printing part 2A, 2B at the time of printing. For this purpose, the control unit 5 performs a preparation process for the other ink tank pair 20 during the ink feeding in the one ink tank pair 20 in each of the printing units 2A and 2B. In the preparatory process, positive pressure and negative pressure for ink feeding were generated in one ink tank 12 and the other ink tank 12 in the ink tank pair 20 opposite to the ink tank pair 20 during ink feeding, respectively. This is a process for setting the preparation state. Then, the control unit 5 switches the ink tank pair 20 that performs ink feeding to the ink tank pair 20 in the ready state. The control unit 5 controls to perform printing by ejecting ink from the inkjet head 11 while repeatedly switching the ink tank pair 20 that performs ink feeding.

  Further, the control unit 5 supplies ink to each ink tank pair 20 during the printing operation, and the ink replenishing unit 4 of the ink tank pair 20 is connected during a period when the ink tank pair 20 is not feeding ink. Control is performed by supplying ink to the ink tank 12 on the side. Specifically, the control unit 5 supplies ink to the ink tank pair 20A during the printing operation by supplying ink from the ink supply unit 4 to the ink tank 12A in the preparation process for the ink tank pair 20A. Further, the control unit 5 supplies ink to the ink tank pair 20B during the printing operation by supplying ink from the ink supply unit 4 to the ink tank 12B in the preparation process for the ink tank pair 20B.

  In addition, when the ink is initially filled in the printing unit 2, the control unit 5 supplies ink from the ink supply unit 4 to both the ink tank 12A of the ink tank pair 20A and the ink tank 12B of the ink tank pair 20B at the same time. Control as follows.

  Next, the operation at the time of printing of the inkjet printing apparatus 1 will be described.

  FIG. 3 is a flowchart for explaining the operation of the inkjet printing apparatus 1 during printing. The process of the flowchart of FIG. 3 starts when a print job is input to the inkjet printing apparatus 1.

  In step S <b> 1 of FIG. 1, the control unit 5 controls the pressure generation unit 3 to generate pressure for ink feeding between the ink tanks 12 in any one of the ink tank pairs 20.

  Specifically, for example, when generating a positive pressure and a negative pressure for ink feeding in the ink tanks 12A and 12C of the ink tank pair 20A, respectively, the control unit 5 first has the atmosphere release valves 35A and 35B, and The pressure valves 33B and 33D are closed.

  Here, in the inkjet printing apparatus 1 in a standby state before a print job is input, the atmosphere release valves 35A and 35B and the pressure valves 33A to 33D are opened, and the ink tanks 12A to 12D are in the atmosphere release state. In addition, the ink outflow valves 15A to 15D, the ink inflow valves 17A to 17D, the pressure adjustment valves 34A and 34B, and the ink supply valves 53A and 53B are closed.

  Next, the control unit 5 starts driving the air pump 31 so as to send air from the ink tank 12C to the ink tank 12A. Accordingly, the ink tank 12C starts to be depressurized and the ink tank 12A starts to be pressurized.

  Thereafter, when the pressure (positive pressure) of the ink tank 12A and the pressure (absolute value of the negative pressure) of the ink tank 12C detected by the pressure sensors 36A and 36B exceed the respective set pressures, the control unit 5 31 is stopped.

  Next, the control unit 5 controls the pressure adjustment valves 34A and 34B to adjust the pressures of the ink tanks 12A and 12C to the respective set pressures. When the pressures of the ink tanks 12A and 12C become the respective set pressures, the control unit 5 closes the pressure valves 33A and 33C and the pressure adjustment valves 34A and 34B. Thereby, the pressure generation for ink feeding is completed.

  Next, in step S2, the control unit 5 starts ink feeding between the ink tanks 12 in the ink tank pair 20 in which the pressure is generated in step S1.

  Specifically, for example, when a positive pressure and a negative pressure for ink feeding are respectively generated in the ink tanks 12A and 12C of the ink tank pair 20A in step S1, the control unit 5 determines that the ink outflow valve 15A and the ink The inflow valve 17C is opened. In this case, as shown in FIG. 4, ink flows from the ink tank 12A to the ink tank 12C via the inkjet head 11.

  Further, in step S2 of FIG. 3, the control unit 5 starts the preparation process in the ink tank pair 20 opposite to the ink tank pair 20 in which the pressure is generated in step S1.

  Specifically, for example, when the pressure is generated in the ink tank pair 20A as described above in step S1, the control unit 5 supplies ink to the ink tanks 12B and 12D of the ink tank pair 20B, respectively. Preparation processing for generating negative pressure and positive pressure is started. In this preparation process, as shown in FIG. 4, air is sent from the ink tank 12B to the ink tank 12D by the air pump 31, and negative pressure and positive pressure for ink feeding are generated in the ink tanks 12B and 12D, respectively. . Details of the preparation process will be described later.

  Next, in step S3 of FIG. 3, the control unit 5 controls the inkjet head 11 to start printing based on the print job. As a result, a part of the ink supplied from the ink tank 12 in the positive pressure state to the inkjet head 11 in the ink tank pair 20 during ink feeding is ejected, and the remaining ink flows to the ink tank 12 in the negative pressure state. For example, when ink is being fed as shown in FIG. 4, a part of the ink supplied from the ink tank 12A to the inkjet head 11 is ejected, and the remaining ink flows to the ink tank 12C.

  Next, in step S4 of FIG. 3, the control unit 5 determines whether or not the preparation process in the ink tank pair 20 opposite to the ink tank pair 20 that is performing ink feeding is completed. Here, when the pressures (positive pressure and negative pressure) of the two ink tanks 12 of the ink tank pair 20 to be subjected to the preparation process become the respective set pressures, the preparation process ends.

  When it is determined that the preparatory process has been completed (step S4: YES), in step S5, the control unit 5 in either of the printing units 2A and 2B, the ink in the positive pressure state in the ink tank pair 20 during ink feeding. It is determined whether or not the height of the ink liquid level in the tank 12 is equal to or lower than a predetermined switching height. Here, the switching height is set in advance as a value of the height of the ink liquid level in the ink tank 12 in the positive pressure state for determining the timing of switching the ink tank pair 20 that performs ink feeding between the ink tanks 12. It has been done. The control unit 5 switches the height of the ink liquid level in the ink tank 12 based on the output signal of the liquid level sensor 13 installed in the ink tank 12 in the positive pressure state of the ink tank pair 20 during ink feeding. Judge whether it is below the height.

  In any one of the printing units 2A and 2B, when it is determined that the height of the ink liquid level in the ink tank 12 in the positive pressure state in the ink tank pair 20 during ink feeding is equal to or lower than the switching height (step S5: YES), in step S6, the controller 5 executes a switching process.

  The switching process is a process of switching the ink tank pair 20 that performs ink feeding between the ink tanks 12. Specifically, the control unit 5 sets the ink outflow valve 15 corresponding to the ink tank 12 in the positive pressure state and the ink inflow valve 17 corresponding to the ink tank 12 in the negative pressure state in the ink tank pair 20 during ink feeding. Close. At the same time, the control unit 5 includes the ink outflow valve 15 corresponding to the ink tank 12 in the positive pressure state and the ink inflow valve 17 corresponding to the ink tank 12 in the negative pressure state in the ink tank pair 20 for which the preparation process has been completed in step S4. Is released. As a result, the ink tank pair 20 that performs ink feeding is switched.

  For example, during the ink feeding in the ink tank pair 20A as shown in FIG. 4, when the ink level in the ink tank 12A of either of the printing units 2A and 2B falls below the switching height, the control unit 5 Then, the ink outflow valve 15A and the ink inflow valve 17C are closed. At the same time, the control unit 5 opens the ink outflow valve 15D of the ink tank 12D and the ink inflow valve 17B of the ink tank 12B of the ready ink tank pair 20B. As a result, as shown in FIG. 5, ink feeding between the ink tanks 12 in the ink tank pair 20B is started.

  In step S6 in FIG. 3, the control unit 5 sets the ink tank pair 20 opposite to the ink tank pair 20 that performs ink feeding after the switching process, that is, the ink tank that performed the ink feeding before the switching process. The preparation process in the pair 20 is started. Here, the control unit 5 generates a positive pressure in the ink tank 12 that was in the negative pressure state during the immediately preceding ink feeding, and a negative pressure in the ink tank 12 that was in the positive pressure state during the immediately preceding ink feeding. Prepare to do so.

  Specifically, for example, when the ink tank pair 20 is switched from the state of FIG. 4 to the state of FIG. 5, the ink tank pair 20A that has performed the ink feeding before the switching process is in a negative pressure state. It was the ink tank 12C. Therefore, in this case, as shown in FIG. 5, the preparatory process after the switching process is performed so as to generate a positive pressure in the ink tank 12C and a negative pressure in the ink tank 12A.

  As a result, in each ink tank pair 20, the positive pressure state and the negative pressure state of each ink tank 12 when ink is supplied between the ink tanks 12 are switched from the previous ink supply time. . That is, the direction of ink flow in the ink feeding is opposite to that in the previous ink feeding. As a result, it is possible to prevent the ink amount from being biased to any one of the ink tanks 12 in the ink tank pair 20.

  In step S6, when the switching process is performed and the preparation process is started, the control unit 5 returns to step S4.

  If it is determined in step S4 that the preparation process has not ended (step S4: NO), in step S7, the control unit 5 determines whether printing based on the print job has ended. If it is determined that printing based on the print job has not ended (step S7: NO), the control unit 5 returns to step S4.

  If it is determined that printing based on the print job has ended (step S7: YES), the control unit 5 stops the preparation process in step S8.

  Next, in step S9, the control unit 5 opens the atmosphere release valves 35A and 35B and the pressure valves 33A to 33D, and sets the ink tanks 12A to 12D to the atmosphere release state. Thereby, the ink feeding in the ink tank pair 20 during the ink feeding is finished, and a series of operations is finished. Here, the control unit 5 sets the ink outflow valves 15A to 15D and the ink inflow valves 17A to 17D to the closed state.

  In step S5, when both the printing units 2A and 2B determine that the height of the ink liquid surface in the ink tank 12 in the positive pressure state in the ink tank pair 20 during ink feeding is higher than the switching height (step S5). (S5: NO) In step S10, the control unit 5 determines whether printing based on the print job is finished. If it is determined that printing based on the print job has not ended (step S10: NO), the control unit 5 returns to step S5.

  When it is determined that printing based on the print job is completed (step S10: YES), the control unit 5 opens the ink tanks 12A to 12D in step S11 as in step S9 described above. Thereby, the ink feeding in the ink tank pair 20 during the ink feeding is finished, and a series of operations is finished. Here, the control unit 5 sets the ink outflow valves 15A to 15D and the ink inflow valves 17A to 17D to the closed state.

  With the operation described with reference to the flowchart of FIG. 3 described above, printing by the inkjet head 11 is performed while the ink tank pairs 20 that perform ink feeding between the ink tanks 12 are alternately switched.

  For example, as described above, during the ink feeding in the ink tank pair 20A as shown in FIG. 4, when the liquid level of the ink in the ink tank 12A of the printing unit 2A or 2B becomes equal to or lower than the switching height. Then, switching to ink feeding in the ink tank pair 20B as shown in FIG.

  When the liquid level of the ink in the ink tank 12C of either of the printing units 2A and 2B is equal to or lower than the switching height during ink feeding in the ink tank pair 20B as shown in FIG. 5, the ink as shown in FIG. It switches to ink feeding in the tank pair 20A.

  Here, in the state of FIG. 5, the ink tank 12B to which the ink supply unit 4 is connected is in a negative pressure state during ink feeding in the ink tank pair 20B. In this case, as described above, in the preparation process after switching to the ink feeding by the ink tank pair 20A, the negative pressure state is generated before the positive pressure is generated in the ink tank 12B and the negative pressure is generated in the ink tank 12D. Ink is supplied to the ink tank 12B. That is, after the ink supply unit 4 supplies ink to the ink tank 12B in the negative pressure state as shown in FIG. 6, positive pressure and negative pressure are generated in the ink tanks 12B and 12D, respectively, as shown in FIG. The

  When the liquid level of the ink in the ink tank 12C of either of the printing units 2A and 2B is equal to or lower than the switching height during ink feeding in the ink tank pair 20A as shown in FIG. 7, the ink as shown in FIG. It switches to ink feeding in the tank pair 20B.

  Here, in the state of FIG. 7, the ink tank 12A to which the ink replenishing unit 4 is connected is in a negative pressure state during the ink feeding in the ink tank pair 20A. In this case, as described above, in the preparation process after switching to the ink feeding by the ink tank pair 20B, the negative pressure state is generated before the positive pressure is generated in the ink tank 12A and the negative pressure is generated in the ink tank 12C. Ink is supplied to the ink tank 12A. That is, after ink is supplied to the ink tank 12A in the negative pressure state by the ink supply unit 4 as shown in FIG. 8, positive pressure and negative pressure are generated in the ink tanks 12A and 12C, respectively, as shown in FIG. The

  When the liquid level of the ink in the ink tank 12B of either of the printing units 2A and 2B is equal to or lower than the switching height during the ink feeding in the ink tank pair 20B as shown in FIG. 9, the ink as shown in FIG. It switches to ink feeding in the tank pair 20A.

  As described above, printing by the ink jet head 11 is performed while the ink tank pair 20 that performs ink feeding is switched as in FIG. 4 → FIG. 5 → FIG. 6, 7 → FIG. 8, 9 → FIG.

  Next, the preparation process will be described.

  As described above, the preparatory processing includes one for generating pressure for ink replenishment and ink feeding, and one for generating pressure for ink feeding without ink replenishment.

  First, a preparation process including ink replenishment (ink replenishment and pressure generation) will be described with reference to the flowchart of FIG.

  The preparatory process including ink replenishment is performed as a preparatory process after the ink tank pair 20B is switched to ink liquid feeding when the ink tank 12A is in a negative pressure state during ink liquid feeding in the ink tank pair 20A. The preparatory process including ink replenishment is also performed as a preparatory process after the ink tank pair 20A is switched to ink liquid supply when the ink tank 12B is in a negative pressure state during ink liquid supply in the ink tank pair 20B. Is called.

  In other words, the preparatory process including ink replenishment is for ink feeding in which the ink tanks 12A and 12C in the ink tank pair 20A are in a positive pressure state and a negative pressure state, respectively, and ink flows from the ink tank 12A to the ink tank 12C. It is performed as a preparation process. In addition, the preparatory process including ink replenishment is a preparation for ink feeding in which the ink tanks 12B and 12D in the ink tank pair 20B are in a positive pressure state and a negative pressure state, respectively, and ink flows from the ink tank 12B to the ink tank 12D. It is done as a process.

  Here, when the ink tank 12B is in a negative pressure state during ink feeding in the ink tank pair 20B, ink replenishment performed for the ink tank pair 20B after switching to the ink feeding by the ink tank pair 20A is performed. An example of the preparatory process will be described. This is a preparation process performed when the state of FIG. 5 is switched to the state of FIG.

  In this case, the process of the flowchart in FIG. 10 is performed when the ink tank 12B is in a negative pressure state during the ink feeding in the ink tank pair 20B and the switching process to the ink feeding by the ink tank pair 20A is performed. Will start.

  In step S21 of FIG. 10, the control unit 5 controls the ink supply units 4A and 4B so as to supply ink to the ink tanks 12B of the printing units 2A and 2B.

  Specifically, the control unit 5 opens the ink supply valve 53B of the ink supply units 4A and 4B. As a result, as shown in FIG. 6, ink starts to be supplied from the ink cartridge 51 to the ink tank 12B in the negative pressure state via the common supply pipe 56 and the branch supply pipe 57B.

  After the ink supply valve 53B is opened, the control unit 5 determines that the ink liquid level in the ink tank 12B has reached a predetermined supply completion height in each of the printing units 2A and 2B. 53B is closed. Thereby, the ink supply to the ink tank 12B is completed. The replenishment completion height is set in advance as a value of the ink liquid level when ink replenishment in the ink tanks 12A and 12B is completed. Based on the output signal from the liquid level sensor 13B, the controller 5 determines whether or not the height of the ink liquid level in the ink tank 12B has reached the replenishment completion height.

  Next, in step S22 of FIG. 10, the control unit 5 opens the pressure valves 33B and 33D corresponding to the ink tanks 12B and 12D of the ink tank pair 20B that is the target of the preparation process.

  Next, in step S23, the control unit 5 starts driving the air pump 31 to send air from the ink tank 12D to the ink tank 12B, as shown in FIG. Thereby, the ink tank 12D starts to be depressurized and the ink tank 12B starts to be pressurized.

  Next, in step S24, the control unit 5 determines that the pressure of the ink tank 12B (positive pressure) and the pressure of the ink tank 12D (absolute value of negative pressure) are the set pressures based on the detection values of the pressure sensors 36A and 36B. It is determined whether or not this is the case. If it is determined that at least one of the pressure in the ink tank 12B and the pressure in the ink tank 12D is less than the set pressure (NO in step S24), the control unit 5 repeats step S24.

  When it is determined that the pressure in the ink tank 12B and the pressure in the ink tank 12D are equal to or higher than the respective set pressures (step S24: YES), the control unit 5 stops the air pump 31 in step S25. Thereby, pressurization of the ink tank 12B and pressure reduction of the ink tank 12D by the air pump 31 are completed.

  Next, in step S26, the control unit 5 controls the pressure adjusting valves 34A and 34B to adjust the pressures of the ink tanks 12B and 12D to the respective set pressures. When the pressures of the ink tanks 12B and 12D become the respective set pressures, the control unit 5 closes the pressure valves 33B and 33D and the pressure adjustment valves 34A and 34B. Thereby, the preparation process including ink replenishment is completed.

  As described above, in the preparatory process including ink supply to the ink tank pair 20B, ink supply from the ink cartridge 51 to the ink tank 12B is performed with the negative pressure of the ink tank 12B left during the previous ink feeding. Is called. Thereby, in addition to the water head difference between the ink cartridge 51 and the ink tank 12B, ink replenishment is performed in a short time by performing ink replenishment using the negative pressure state of the ink tank 12B. For this reason, the time required for ink replenishment is shortened compared to the case of supplying ink to the ink tank 12B while generating positive pressure to the ink tank 12B and generating negative pressure to the ink tank 12D. The time required for the preparation process including replenishment can be shortened.

  In the preparation process including ink supply to the ink tank pair 20A, after ink supply to the ink tank 12A is performed as shown in FIG. 8, positive pressure and negative pressure are respectively applied to the ink tanks 12A and 12C as shown in FIG. Generated. Also in this case, the time required for ink replenishment is shortened compared to the case where ink is replenished to the ink tank 12A while generating positive pressure to the ink tank 12A and negative pressure to the ink tank 12C. The time required for the preparation process including ink supply can be shortened.

  Next, a preparation process that does not include ink supply will be described.

  The preparatory process that does not include ink replenishment is performed in the procedure after step S22 in the flowchart of FIG.

  Here, the case of a preparation process for generating a positive pressure in the ink tank 12C of the ink tank pair 20A and generating a negative pressure in the ink tank 12A will be described. This preparatory process is performed by performing the switching process from the ink feeding by the ink tank pair 20A in which the ink tank 12A is in the positive pressure state and the ink tank 12B in the negative pressure state to the ink feeding by the ink tank pair 20B. It will start. That is, this preparation process is started when the switching process from the state of FIG. 4 to the state of FIG. 5 is performed.

  In this preparation process, first, the controller 5 opens the pressure valves 33A and 33C corresponding to the ink tanks 12A and 12C of the ink tank pair 20A that is the object of the preparation process (step S22).

  Next, as shown in FIG. 5, the control unit 5 starts driving the air pump 31 so as to send air from the ink tank 12A to the ink tank 12C. Accordingly, the ink tank 12A starts to be depressurized and the ink tank 12C starts to be pressurized.

  Next, the control unit 5 determines that the pressure (positive pressure) of the ink tank 12C and the pressure (absolute value of the negative pressure) of the ink tank 12C are equal to or higher than the set pressures based on the detection values of the pressure sensors 36A and 36B. It is determined whether or not there is (step S24).

  If it is determined that the pressure in the ink tank 12A and the pressure in the ink tank 12C are equal to or higher than the respective set pressures (step S24: YES), the control unit 5 stops the air pump 31 (step S25). Thereby, pressurization of the ink tank 12B and pressure reduction of the ink tank 12D by the air pump 31 are completed.

  Then, the control unit 5 controls the pressure adjustment valves 34A and 34B to adjust the pressures of the ink tanks 12A and 12C to the respective set pressures (step S26). When the pressures of the ink tanks 12A and 12C reach the respective set pressures, the control unit 5 closes the pressure valves 33A and 33C and the pressure adjustment valves 34A and 34B. As a result, the preparation process ends.

  Next, the operation at the time of initial filling of ink into the printing unit 2 will be described.

  The initial filling of the ink into the printing unit 2 is performed in order to change the ink tanks 12A to 12D from an empty state where there is no ink to a state where a printing operation can be performed. The tanks 12A and 12B are filled with ink.

  FIG. 11 is a flowchart for explaining an operation at the time of initial filling of ink into the printing unit 2. The process of the flowchart of FIG. 11 is started when a print job is input to the inkjet printing apparatus 1 in a state where the ink is not initially charged into the printing unit 2.

  In step S31 of FIG. 11, the control unit 5 closes the atmosphere release valve 35A and the pressure valves 33C and 33D.

  Here, before the operation of initial filling of the ink into the printing unit 2 is started, the atmosphere release valves 35A and 35B and the pressure valves 33A to 33D are opened, and the ink tanks 12A to 12D are in the atmosphere release state. In addition, the ink outflow valves 15A to 15D, the ink inflow valves 17A to 17D, the pressure adjustment valves 34A and 34B, and the ink supply valves 53A and 53B are closed. Further, the ink tanks 12A to 12D are empty without ink.

  Next, in step S32, the control unit 5 opens the ink supply valves 53A and 53B. At the same time, the control unit 5 starts driving the air pump 31 so as to suck air from the ink tanks 12A and 12B.

  Thereby, as shown in FIG. 12, negative pressure is generated in the ink tanks 12A and 12B, and ink is supplied from the ink supply unit 4 to the ink tanks 12A and 12B.

  Next, in step S33 of FIG. 11, the control unit 5 performs an ink supply end process. Specifically, when the ink level detected by the level sensor 13 corresponding to each of the ink tanks 12A and 12B of the printing units 2A and 2B reaches the replenishment completion height, the control unit 5 Then, the ink supply valve 53 corresponding to each is closed. As a result, the ink tanks 12A and 12B of the printing units 2A and 2B are filled with ink up to the replenishment completion height.

  Next, in step S <b> 34, the control unit 5 stops the air pump 31.

  Next, in step S35, the control unit 5 opens the atmosphere release valve 35A and the pressure valves 33C and 33D. Thereby, the initial filling of the ink into the printing unit 2 is completed.

  When the initial filling of the ink into the printing unit 2 is completed, the control unit 5 controls the pressure generation unit 3 to generate pressure for ink feeding with respect to one of the ink tank pairs 20A and 20B. .

  Here, it is assumed that pressure generation for ink feeding is performed on the ink tank pair 20B. In this case, in order to send ink from the ink tank 12B to the ink tank 12D, a positive pressure is generated in the ink tank 12B and a negative pressure is generated in the ink tank 12D.

  Therefore, first, the control unit 5 opens the pressure valves 33B and 33D. Next, as shown in FIG. 13, the control unit 5 starts driving the air pump 31 so as to send air from the ink tank 12D to the ink tank 12B. Thereby, the ink tank 12D starts to be depressurized and the ink tank 12B starts to be pressurized.

  Based on the detection values of the pressure sensors 36A and 36B, the controller 5 determines that the pressure of the ink tank 12B (positive pressure) and the pressure of the ink tank 12D (absolute value of negative pressure) are equal to or higher than the respective set pressures. If determined, the air pump 31 is stopped. Thereby, pressurization of the ink tank 12B and pressure reduction of the ink tank 12D by the air pump 31 are completed.

  Thereafter, the control unit 5 controls the pressure adjustment valves 34A and 34B to adjust the pressures of the ink tanks 12B and 12D to the respective set pressures. When the pressures of the ink tanks 12B and 12D become the respective set pressures, the control unit 5 closes the pressure valves 33B and 33D and the pressure adjustment valves 34A and 34B. As a result, the generation of pressure for ink feeding to the ink tank pair 20B is completed.

  Next, the control unit 5 starts ink feeding between the ink tanks 12 in the pressure-generated ink tank pair 20B. Specifically, the control unit 5 opens the ink outflow valve 15B and the ink inflow valve 17D. As a result, as shown in FIG. 14, ink flows from the ink tank 12B to the ink tank 12D through the inkjet head 11.

  Further, as shown in FIG. 14, the control unit 5 performs preparatory processing for generating a positive pressure and a negative pressure for ink feeding in the ink tanks 12A and 12C, respectively, with respect to the ink tank pair 20A.

  After starting the ink feeding between the ink tanks 12 in the ink tank pair 20B, the control unit 5 controls the inkjet head 11 to start printing based on the print job.

  The state of FIG. 14 corresponds to the state of FIG. 9 described above. When the ink level in the ink tank 12B of either of the printing units 2A and 2B is equal to or lower than the switching height during ink feeding in the ink tank pair 20B as shown in FIG. 14, the ink as shown in FIG. It switches to ink feeding in the tank pair 20A. Thereafter, printing by the inkjet head 11 is performed while the ink tank pair 20 that performs ink feeding is switched as shown in FIG. 4 → FIG. 5 → FIG. 6, 7 → FIG. 8, 9 → FIG.

  As described above, in the inkjet printing apparatus 1, the control unit 5 controls to supply ink from the ink supply unit 4 to both the ink tanks 12A and 12B at the same time when the printing unit 2 is initially filled with ink. To do.

  Here, as described above, ink replenishment to each ink tank pair 20 during the printing operation is performed during a period in which the ink tank pair 20 is not being fed with ink. That is, ink replenishment to each ink tank pair 20 during the printing operation is performed during the preparation process. As a result, since ink is not supplied to the ink tank pair 20 during ink feeding during the printing operation, fluctuations in the nozzle pressure due to the influence of liquid level fluctuations in the ink tank 12 due to ink supply can be suppressed. As a result, a decrease in print image quality due to variations in the ink discharge amount due to nozzle pressure fluctuations is reduced.

  As described above, ink replenishment to each ink tank pair 20 during the printing operation is performed during a period when the ink tank pair 20 is not in the ink supply state, and therefore ink replenishment to each of the ink tanks 12A and 12B is performed. It is done at different times. For this reason, assuming that the ink replenishment control is performed during the printing operation and the ink is initially filled in the printing unit 2, the ink is initially filled in the ink tanks 12A and 12B at different timings. It will be. In other words, after the initial filling of ink into one of the ink tanks 12A and 12B is performed, the initial filling of ink into the other is performed.

  On the other hand, as described above, when the ink is initially filled in the printing unit 2, the ink is simultaneously supplied to both the ink tanks 12A and 12B. Therefore, the initial filling of the ink into the ink tanks 12A and 12B is shortened. Can be done in time.

  When the ink is initially filled in the printing unit 2, the control unit 5 controls the pressure generation unit 3 to generate negative pressure in the ink tanks 12 </ b> A and 12 </ b> B. Thereby, the time required for the initial filling of the ink into the ink tanks 12A and 12B can be further shortened by using the suction force by the negative pressure.

[Second Embodiment]
Next, a second embodiment in which a part of the first embodiment described above is changed will be described.

  In the second embodiment, the control unit 5 monitors the pressure of the ink tanks 12A and 12B to which ink is supplied when ink is supplied to the ink tanks 12A and 12B during the printing operation. Then, when the pressure of the ink tanks 12A and 12B reaches a predetermined replenishment stop pressure value in a state where the liquid level height of the ink cannot be determined based on the output signals of the liquid level sensors 13A and 13B, the control unit 5 Stop supplying. Here, when the liquid level sensors 13A and 13B have an abnormality due to a failure or the like, it may be impossible to determine the ink liquid level based on the output signals of the liquid level sensors 13A and 13B.

  Specifically, for example, the control unit 5 opens the pressure valve 33A as shown in FIG. 15 during ink supply during preparation processing including ink supply to the ink tank pair 20A. Thereby, the pressure sensor 36A detects the pressure in the ink tank 12A. The controller 5 monitors the detected value of the pressure in the ink tank 12A by the pressure sensor 36A.

  Then, the control unit 5 detects the pressure sensor 36A in a state where it cannot be determined whether or not the liquid level of the ink in the ink tank 12A has reached the replenishment completion height based on the output signal of the liquid level sensor 13A. When the value reaches the supply stop pressure value, the ink supply valve 53A is closed at that time.

  Similarly, the controller 5 opens the pressure valve 33B as shown in FIG. 16 during the ink supply during the preparation process including the ink supply to the ink tank pair 20B. Thereby, the pressure sensor 36B detects the pressure of the ink tank 12B. The control unit 5 monitors the detected value of the pressure in the ink tank 12B by the pressure sensor 36B.

  Then, the control unit 5 detects the pressure sensor 36B in a state where it cannot determine whether or not the liquid level of the ink in the ink tank 12B has reached the replenishment completion height based on the output signal of the liquid level sensor 13B. When the value reaches the supply stop pressure value, the ink supply valve 53B is closed at that time.

  Here, the pressure in the ink tanks 12A and 12B increases as the liquid level of the ink increases due to the ink supply to the ink tank 12A. The above-described supply stop pressure value is set in advance as a pressure value in the ink tanks 12A and 12B when the ink level in the ink tanks 12A and 12B becomes higher than the supply completion height.

  That is, when the liquid level sensors 13A and 13B are operating normally, the liquid level sensor 13A and 13B determines the ink level level before the detected values of the pressure sensors 36A and 36B reach the replenishment stop pressure value. It is detected that the replenishment completion height has been reached. At that time, the ink supply valves 53A and 53B are closed.

  As described above, in the second embodiment, the controller 5 stops the ink supply when the ink tanks 12A and 12B reach the supply stop pressure value during the ink supply to the ink tanks 12A and 12B. Thereby, even when an abnormality occurs in the pressure sensor 36, the ink supply can be stopped. As a result, overflow of the ink tanks 12A and 12B can be reduced.

[Third Embodiment]
FIG. 17 is a block diagram illustrating a configuration of an inkjet printing apparatus according to the third embodiment. FIG. 18 is a schematic configuration diagram of a printing unit, a pressure generation unit, and an ink supply unit of the inkjet printing apparatus shown in FIG.

  As shown in FIG. 17, the inkjet printing apparatus 61 according to the third embodiment includes four printing units 62, a pressure generation unit 63, four ink supply units 64, and a control unit 65.

  The printing unit 62 prints an image by ejecting ink onto a sheet (not shown) while circulating the ink. The four printing units 62 eject inks of different colors (for example, black, cyan, magenta, and yellow). The four printing sections 62 have the same configuration except that the colors of the ejected ink are different. The printing unit 62 includes an inkjet head 71 and an ink circulation unit 72.

  The ink jet head 71 ejects ink supplied by the ink circulation unit 72. The inkjet head 71 has a plurality of head modules 76.

  The head module 76 has a plurality of nozzles (not shown) and ejects ink from the nozzles.

  The ink circulation unit 72 supplies ink to the inkjet head 71 while circulating the ink. The ink circulation unit 72 includes a pressurized tank (first ink tank) 81, a distributor 82, an aggregator 83, a negative pressure tank (second ink tank) 84, an ink pump 85, and an ink temperature adjustment unit 86. And an ink temperature sensor 87 and ink circulation pipes 88 to 90.

  The pressurized tank 81 stores ink to be supplied to the inkjet head 71. The ink in the pressurized tank 81 is supplied to the inkjet head 71 via the ink circulation pipe 88 and the distributor 82. In the pressurized tank 81, an air layer 91 is formed on the ink surface. The pressurized tank 81 is communicated with a later-described pressurized common air chamber 111 via a later-described pressurized-side communication pipe 112. The pressurized tank 81 is disposed at a position (downward) lower than the inkjet head 71.

  The pressurized tank 81 is provided with a pressurized tank liquid level sensor 92 and an ink filter 93.

  The pressurized tank liquid level sensor 92 is for detecting whether or not the height of the ink liquid level in the pressurized tank 81 has reached a predetermined reference height. The pressurized tank liquid level sensor 92 outputs a signal indicating “ON” when the height of the ink level in the pressurized tank 81 is equal to or higher than the reference height. The pressurized tank liquid level sensor 92 outputs a signal indicating “OFF” when the height of the ink liquid level in the pressurized tank 81 is less than the reference height.

  The ink filter 93 removes dust and the like in the ink.

  The distributor 82 distributes the ink supplied from the pressurized tank 81 via the ink circulation pipe 88 to each head module 76 of the inkjet head 71.

  The collector 83 collects ink that has not been consumed by the inkjet head 71 from each head module 76. The ink collected by the collector 83 flows to the negative pressure tank 84 through the ink circulation pipe 89.

  The negative pressure tank 84 receives the ink that has not been consumed by the inkjet head 71 from the collector 83 and stores it. Further, the negative pressure tank 84 stores ink replenished by an ink replenishing unit 64 described later during the printing operation. In the negative pressure tank 84, an air layer 96 is formed on the ink surface. The negative pressure tank 84 communicates with a negative pressure common air chamber 118 described later via a negative pressure side communication pipe 119 described later. The negative pressure tank 84 is disposed at the same height as the pressurized tank 81.

  The negative pressure tank 84 is provided with a negative pressure tank liquid level sensor 97. The negative pressure tank liquid level sensor 97 is for detecting whether or not the height of the ink liquid level in the negative pressure tank 84 has reached a predetermined reference height. The negative pressure tank liquid level sensor 97 outputs a signal indicating “ON” when the height of the ink liquid level in the negative pressure tank 84 is equal to or higher than the reference height. The negative pressure tank liquid level sensor 97 outputs a signal indicating “OFF” when the height of the ink liquid level in the negative pressure tank 84 is less than the reference height.

  The ink pump 85 sends ink from the negative pressure tank 84 to the pressure tank 81. The ink pump 85 is provided in the middle of the ink circulation pipe 90.

  The ink temperature adjustment unit 86 adjusts the ink temperature in the ink circulation unit 72. The ink temperature adjustment unit 86 is provided in the middle of the ink circulation pipe 88. The ink temperature adjustment unit 86 includes a heater 101, a heater temperature sensor 102, a heat sink 103, and a cooling fan 104.

  The heater 101 heats the ink in the ink circulation pipe 88. The heater temperature sensor 102 detects the temperature of the heater 101. The heat sink 103 cools the ink in the ink circulation pipe 88 by radiating heat. The cooling fan 104 sends cooling air to the heat sink 103.

  The ink temperature sensor 87 detects the temperature of the ink in the ink circulation unit 72. The ink temperature sensor 87 is provided in the middle of the ink circulation pipe 88.

  The ink circulation pipe 88 connects the pressurized tank 81 and the distributor 82. A part of the ink circulation pipe 88 branches into a part passing through the heater 101 and a part passing through the heat sink 103. Ink flows from the pressurized tank 81 toward the distributor 82 through the ink circulation pipe 88. The ink circulation pipe 89 connects the collector 83 and the negative pressure tank 84. Ink flows from the collector 83 toward the negative pressure tank 84 through the ink circulation pipe 89. The ink circulation pipe 90 connects the negative pressure tank 84 and the pressurization tank 81. Ink flows from the negative pressure tank 84 toward the pressure tank 81 through the ink circulation pipe 90. The ink circulation pipes 88 to 90, the distributor 82 and the collector 83 constitute a circulation path for circulating the ink among the pressurized tank 81, the inkjet head 71 and the negative pressure tank 84.

  The pressure generation unit 63 generates pressure for ink circulation in the pressurization tank 81 and the negative pressure tank 84 of each printing unit 62. The pressure generator 63 includes a pressurization common air chamber 111, four pressurization side communication pipes 112, a pressurization side air release valve 113, a pressurization side air release pipe 114, a pressurization side pressure adjustment valve 115, and a pressurization side. Pressure adjusting pipe 116, pressure side pressure sensor 117, negative pressure common air chamber 118, four negative pressure side communication pipes 119, negative pressure side atmospheric release valve 120, negative pressure side atmospheric release pipe 121, and negative pressure side pressure The adjustment valve 122, the negative pressure side pressure adjustment pipe 123, the negative pressure side pressure sensor 124, an air pump 125, an air pump pipe 126, a merging pipe 127, an air filter 128, and an overflow pan 129 are provided.

  The pressurized common air chamber 111 is an air chamber for equalizing the pressure of the pressure tank 81 of each printing unit 62. The pressurized common air chamber 111 communicates with the air layers 91 of the pressurized tanks 81 of the four printing units 62 via the four pressurized side communication pipes 112. Thereby, the pressurization tanks 81 of the printing units 62 are communicated with each other via the pressurization common air chamber 111 and the pressurization side communication pipe 112.

  The pressurization side communication pipe 112 allows the pressurization common air chamber 111 and the air layer 91 of the pressurization tank 81 to communicate with each other. Four pressurizing side communication pipes 112 are provided in correspondence with each printing unit 62. One end of the pressurization side communication pipe 112 is connected to the pressurization common air chamber 111, and the other end is connected to the air layer 91 of the pressurization tank 81.

  The pressurization side air release valve 113 opens and closes the air flow path in the pressurization side air release pipe 114 in order to switch the pressurization tank 81 between a sealed state and an air release state via the pressurization common air chamber 111. To do. The pressurization side air release valve 113 is provided in the middle of the pressurization side air release pipe 114.

  The pressurization side air release pipe 114 forms an air flow path for opening the pressurization tank 81 to the atmosphere via the pressurization common air chamber 111. One end of the pressurization-side atmosphere opening pipe 114 is connected to the pressurization common air chamber 111, and the other end is connected to the junction pipe 127.

  The pressurization side pressure adjustment valve 115 opens and closes the air flow path in the pressurization side pressure adjustment pipe 116 in order to adjust the pressure of the pressurization common air chamber 111 and the pressurization tank 81. The pressure side pressure adjustment valve 115 is provided in the middle of the pressure side pressure adjustment pipe 116.

  The pressure side pressure adjustment pipe 116 forms an air flow path for adjusting the pressure of the pressure common air chamber 111 and the pressure tank 81. The pressurization side pressure adjustment pipe 116 is composed of a pressurization side atmosphere release pipe 114, a negative pressure side atmosphere release pipe 121, and a pipe having a larger flow resistance than the junction pipe 127. Specifically, the pressurizing side pressure adjusting pipe 116 is composed of a pipe that is thinner than the pressurizing side atmospheric open pipe 114, the negative pressure side atmospheric open pipe 121, and the merging pipe 127. One end of the pressurizing side pressure adjusting pipe 116 is connected to the pressurizing common air chamber 111, and the other end is connected to the merging pipe 127.

  The pressure side pressure sensor 117 detects the pressure in the pressure common air chamber 111. The pressure in the pressurized common air chamber 111 is equal to the pressure in the pressurized tank 81 of each printing unit 62. This is because the pressurized common air chamber 111 and the air layer 91 of the pressurized tank 81 of each printing unit 62 communicate with each other.

  The negative pressure common air chamber 118 is an air chamber for equalizing the pressure in the negative pressure tank 84 of each printing unit 62. The negative pressure common air chamber 118 is communicated with the air layer 96 of the negative pressure tanks 84 of the four printing units 62 via the four negative pressure side communication pipes 119. Thereby, the negative pressure tanks 84 of the printing units 62 are communicated with each other via the negative pressure common air chamber 118 and the negative pressure side communication pipe 119.

  The negative pressure side communication pipe 119 allows the negative pressure common air chamber 118 and the air layer 96 of the negative pressure tank 84 to communicate with each other. Four negative pressure side communication pipes 119 are provided in correspondence with each printing unit 62. One end of the negative pressure side communication pipe 119 is connected to the negative pressure common air chamber 118, and the other end is connected to the air layer 96 of the negative pressure tank 84.

  The negative pressure side atmospheric release valve 120 opens and closes the air flow path in the negative pressure side atmospheric release pipe 121 in order to switch the negative pressure tank 84 between a sealed state and an atmospheric release state via the negative pressure common air chamber 118. To do. The negative pressure side atmospheric release valve 120 is provided in the middle of the negative pressure side atmospheric release pipe 121.

  The negative pressure side air release pipe 121 forms an air flow path for opening the negative pressure tank 84 to the atmosphere via the negative pressure common air chamber 118. One end of the negative pressure side air release pipe 121 is connected to the negative pressure common air chamber 118, and the other end is connected to the junction pipe 127.

  The negative pressure side pressure adjustment valve 122 opens and closes the air flow path in the negative pressure side pressure adjustment pipe 123 in order to adjust the pressure in the negative pressure common air chamber 118 and the negative pressure tank 84. The negative pressure side pressure adjustment valve 122 is provided in the middle of the negative pressure side pressure adjustment pipe 123.

  The negative pressure side pressure adjusting pipe 123 forms an air flow path for adjusting the pressure of the negative pressure common air chamber 118 and the negative pressure tank 84. The negative pressure side pressure adjustment pipe 123 is formed of a pipe having a larger flow resistance than the pressurization side atmospheric release pipe 114, the negative pressure side atmospheric release pipe 121, and the merging pipe 127. Specifically, the negative pressure side pressure adjustment pipe 123 includes a pipe that is thinner than the pressurization side atmospheric release pipe 114, the negative pressure side atmospheric release pipe 121, and the merging pipe 127. The negative pressure side pressure adjusting pipe 123 has one end connected to the negative pressure common air chamber 118 and the other end connected to the junction pipe 127.

  The negative pressure side pressure sensor 124 detects the pressure in the negative pressure common air chamber 118. The pressure in the negative pressure common air chamber 118 is equal to the pressure in the negative pressure tank 84 of each printing unit 62. This is because the negative pressure common air chamber 118 and the air layer 96 of the negative pressure tank 84 of each printing unit 62 communicate with each other.

  The air pump 125 sucks air from the negative pressure tank 84 of each printing unit 62 through the negative pressure common air chamber 118 and supplies air to the pressure tank 81 of each printing unit 62 through the pressurized common air chamber 111. send. The air pump 125 is provided in the middle of the air pump pipe 126.

  The air pump pipe 126 forms a flow path for air sent from the negative pressure common air chamber 118 to the pressurized common air chamber 111 by the air pump 125. One end of the air pump pipe 126 is connected to the pressurized common air chamber 111, and the other end is connected to the negative pressure common air chamber 118.

  The joining pipe 127 has one end connected to the overflow pan 129 and the other end (upper end) communicating with the atmosphere via the air filter 128. The end of the merge pipe 127 on the overflow pan 129 side is normally closed by an overflow ball 131 described later. Connected to the junction pipe 127 are a pressurization-side atmosphere release pipe 114, a pressurization-side pressure adjustment pipe 116, a negative pressure-side atmosphere release pipe 121, and a negative pressure-side pressure adjustment pipe 123. Thereby, the pressurization side atmosphere release pipe 114, the pressurization side pressure adjustment pipe 116, the negative pressure side atmosphere release pipe 121, and the negative pressure side pressure adjustment pipe 123 are communicated with the atmosphere.

  The air filter 128 prevents entry of dust or the like in the air into the junction pipe 127. The air filter 128 is installed at the upper end of the junction pipe 127.

  The overflow pan 129 overflows ink from the pressure tank 81 and the negative pressure tank 84 due to, for example, an abnormality in the pressure side ink supply valve 138 and the negative pressure side ink supply valve 139 described later, and further, the pressure common air chamber 111 and the negative pressure common. When the ink overflows from the air chamber 118, the ink flowing through the junction tube 127 is received.

  An overflow ball 131 is provided on the overflow pan 129. When there is no ink in the overflow pan 129, the overflow ball 131 closes the end of the joining pipe 127 that opens to the bottom surface of the overflow pan 129, and prevents the outside air from flowing into the joining pipe 127. When ink flows from the junction tube 127 to the overflow pan 129, the overflow ball 131 rises and ink can flow into the overflow pan 129.

  The overflow pan 129 is provided with an overflow liquid level sensor 132. The overflow liquid level sensor 132 is for detecting whether or not the height of the ink liquid level in the overflow pan 129 has reached a predetermined height.

  The overflow pan 129 is connected to a waste liquid tank (not shown), and ink is discharged to the waste liquid tank when the overflow liquid level sensor 132 is turned on.

  The ink supply unit 64 supplies ink to the ink circulation unit 72 of the printing unit 62. The ink supply unit 64 is connected to the pressure tank 81 and the negative pressure tank 84. The ink supply unit 64 includes an ink cartridge 136, an ink supply path 137, a pressure side ink supply valve 138, and a negative pressure side ink supply valve 139.

  The ink cartridge 136 contains ink used for printing by the inkjet head 71. The ink cartridge 136 is disposed at a position (above) higher than the pressure tank 81 and the negative pressure tank 84.

  The ink supply path 137 is a path for ink supplied from the ink cartridge 136 to the pressure tank 81 and the negative pressure tank 84. The ink supply path 137 includes a main supply pipe 141 and a branch supply pipe 142.

  The main supply pipe 141 forms an ink flow path from the ink cartridge 136 to the negative pressure tank 84. The main supply pipe 141 forms part of the ink flow path from the ink cartridge 136 to the pressure tank 81. One end of the main supply pipe 141 is connected to the ink cartridge 136, and the other end of the main supply pipe 141 is connected to the negative pressure tank 84.

  The branch supply pipe 142 forms a part of the ink flow path from the ink cartridge 136 to the pressure tank 81. One end of the branch supply pipe 142 is connected to the main supply pipe 141, and the other end of the branch supply pipe 142 is connected to the pressurized tank 81.

  The pressure-side ink supply valve 138 allows and blocks the inflow of ink from the ink cartridge 136 to the pressure tank 81. The pressure side ink supply valve 138 is disposed in the branch supply pipe 142.

  The negative pressure side ink supply valve 139 allows and blocks the inflow of ink from the ink cartridge 136 to the negative pressure tank 84. The negative pressure side ink supply valve 139 is disposed in the main supply pipe 141 on the negative pressure tank 84 side from the point where the branch supply pipe 142 is connected to the main supply pipe 141.

  The control unit 65 controls the operation of each unit of the inkjet printing apparatus 61. The control unit 65 includes a CPU, RAM, ROM, hard disk, and the like.

  The control unit 65 controls the printing unit 62 and the pressure generation unit 63 so as to eject ink from the inkjet head 71 while circulating the ink in the ink circulation unit 72 during the printing operation.

  In addition, during the printing operation in the printing unit 62, the control unit 65 performs ink supply unit 64 according to the height of the ink level in the pressurized tank 81 and the negative pressure tank 84 by liquid level maintenance control described later. The negative pressure tank 84 is controlled to be refilled with ink.

  The control unit 65 also controls to supply ink from the ink supply unit 64 to the pressure tank 81 and the negative pressure tank 84 at the same time when the printing unit 62 is initially filled with ink.

  Next, the operation at the time of printing of the inkjet printing apparatus 61 will be described.

  FIG. 19 is a flowchart for explaining the operation of the inkjet printing apparatus 61 during printing. The process of the flowchart in FIG. 19 is started when a print job is input to the inkjet printing apparatus 61.

  In step S41 of FIG. 19, the control unit 5 starts the liquid level maintenance control. In the liquid level maintenance control, the ink liquid level in the pressure tank 81 and the negative pressure tank 84 is used to maintain the height of the ink liquid level in the pressure tank 81 and the negative pressure tank 84 near the reference height. The ink pump 85 and the negative pressure side ink supply valve 139 are controlled in accordance with the height of the ink.

  Specifically, as shown in FIG. 20, when the pressurized tank liquid level sensor 92 and the negative pressure tank liquid level sensor 97 are both on, the control unit 65 turns off the ink pump 85 and supplies the negative pressure side ink. The valve 139 is closed. Similarly, even when the pressurized tank liquid level sensor 92 is on and the negative pressure tank liquid level sensor 97 is off, the control unit 65 turns off the ink pump 85 and closes the negative pressure side ink supply valve 139.

  When the pressurized tank liquid level sensor 92 is off and the negative pressure tank liquid level sensor 97 is on, the control unit 65 turns on the ink pump 85 and closes the negative pressure side ink supply valve 139.

  When both the pressurized tank liquid level sensor 92 and the negative pressure tank liquid level sensor 97 are off, the control unit 65 turns off the ink pump 85 and opens the negative pressure side ink supply valve 139.

  Returning to FIG. 19, in step S <b> 42, the control unit 65 closes the pressurization-side atmosphere release valve 113 and the negative-pressure side atmosphere release valve 120. As a result, the pressurized tank 81 is sealed through the pressurized common air chamber 111, and the negative pressure tank 84 is sealed through the negative pressure common air chamber 118.

  Here, during standby before a print job is input to the inkjet printing apparatus 61, the pressurization side air release valve 113 and the negative pressure side air release valve 120 are opened, and the pressurization side pressure adjustment valve 115 and the negative pressure side pressure adjustment valve 122 are opened. Is closed. Further, the pressure side ink supply valve 138 and the negative pressure side ink supply valve 139 are closed. The liquid level maintenance control may be started after the pressurization side air release valve 113 and the negative pressure side air release valve 120 are closed in step S42.

  Next, in step S43, the control unit 65 starts pressure control. The pressure control generates the set pressures Pks and Pfs in the pressurization tank 81 and the negative pressure tank 84 for ink circulation, and maintains the air pump 125, the pressurization side pressure adjustment valve 115, and the negative pressure side. This is control of the pressure regulating valve 122. Here, the set pressures Pks and Pfs are set in advance as pressure values for setting the nozzle pressure of the inkjet head 71 to an appropriate value while circulating the ink at a predetermined flow rate. The set pressure Pks of the pressurizing tank 81 is a positive pressure, and the set pressure Pfs of the negative pressure tank 84 is a negative pressure.

  The control of the air pump 125, the pressure side pressure adjustment valve 115, and the negative pressure side pressure adjustment valve 122 in the pressure control is performed according to the detection value Pk of the pressure side pressure sensor 117 and the detection value Pf of the negative pressure side pressure sensor 124.

  Specifically, as shown in FIG. 21, in the case of Pk <Pks and | Pf | <| Pfs |, the control unit 65 closes the pressurization side pressure adjustment valve 115 and the negative pressure side pressure adjustment valve 122, and the air pump 125 Turn on. As a result, air is sent from the sealed negative pressure tank 84 to the pressurized tank 81 by the air pump 125, whereby the pressure of the negative pressure tank 84 decreases and the pressure of the pressurized tank 81 increases.

  In the case of Pk ≧ Pks and | Pf | <| Pfs |, the control unit 65 opens the pressurization side pressure adjustment valve 115 and closes the negative pressure side pressure adjustment valve 122. Further, the control unit 65 turns on the air pump 125. As a result, the air flows out of the pressurized tank 81 via the pressurized side pressure adjustment pipe 116, thereby reducing the pressure of the pressurized tank 81. Further, the air is sucked by the air pump 125 from the sealed negative pressure tank 84, so that the pressure of the negative pressure tank 84 is reduced.

  When Pk <Pks and | Pf | ≧ | Pfs |, the control unit 65 closes the pressurization side pressure adjustment valve 115 and opens the negative pressure side pressure adjustment valve 122. Further, the control unit 65 turns on the air pump 125. Thereby, the pressure of the pressurization tank 81 rises because air is sent to the pressurization tank 81 of the sealed state by the air pump 125. Further, the air flows into the negative pressure tank 84 via the negative pressure side pressure adjusting pipe 123, whereby the pressure of the negative pressure tank 84 increases.

  In the case of Pk ≧ Pks and | Pf | ≧ | Pfs |, the control unit 65 opens the pressure side pressure adjustment valve 115 and the negative pressure side pressure adjustment valve 122 and turns off the air pump 125. As a result, the air flows out of the pressurized tank 81 via the pressurized side pressure adjustment pipe 116, thereby reducing the pressure of the pressurized tank 81. Further, the air flows into the negative pressure tank 84 via the negative pressure side pressure adjusting pipe 123, whereby the pressure of the negative pressure tank 84 increases.

  Here, at the start of pressure control, the pressure in the pressurized tank 81 and the negative pressure tank 84 is atmospheric pressure. For this reason, Pk <Pks and | Pf | <| Pfs |. Therefore, the control unit 65 starts driving the air pump 125 when the pressure control is started. By driving the air pump 125, air is sent from the negative pressure common air chamber 118 to the pressurized common air chamber 111. As a result, the negative pressure common air chamber 118 and the negative pressure tank 84 are depressurized, and the pressurized common air chamber 111 and the pressure tank 81 are pressurized, so that ink is supplied from the pressure tank 81 toward the inkjet head 71. Start flowing.

  After the start of the pressure control, in step S44 of FIG. It is determined whether or not the set pressures Pks and Pfs are generated. When it is determined that the set pressures Pks and Pfs are not generated in at least one of the pressurized tank 81 and the negative pressure tank 84 (step S44: NO), the control unit 65 repeats step S44.

  When it is determined that the set pressures Pks and Pfs are generated in the pressurization tank 81 and the negative pressure tank 84 (step S44: YES), in step S45, the control unit 65 starts execution of the print job. Specifically, the control unit 65 prints an image by ejecting ink from the inkjet head 71 onto a sheet conveyed by a conveyance unit (not shown) based on a print job.

  During execution of the print job, ink is supplied from the pressurized tank 81 to the inkjet head 71, and ink that has not been consumed by the inkjet head 71 is collected in the negative pressure tank 84. When the pressurized tank liquid level sensor 92 is turned off and the negative pressure tank liquid level sensor 97 is turned on, the ink pump 85 sends ink from the negative pressure tank 84 to the pressurized tank 81 by the liquid level maintenance control. The ink sent from the negative pressure tank 84 to the pressurization tank 81 is supplied to the inkjet head 71 from the pressurization tank 81 and used for printing. In this way, the printing unit 62 performs printing by ejecting ink from the inkjet head 71 while circulating ink along the circulation path.

  If both the pressurized tank liquid level sensor 92 and the negative pressure tank liquid level sensor 97 are turned off during the execution of the print job, the negative pressure side ink supply valve 139 is opened by the liquid level maintenance control, and the negative pressure tank 84 is opened. Ink is replenished.

  Further, during the execution of the print job, the control unit 65 adjusts the ink temperature by controlling the ink temperature adjustment unit 86 so that the temperature detected by the ink temperature sensor 87 is within the appropriate temperature range.

  After starting the execution of the print job, in step S46, the control unit 65 determines whether or not the print job has ended. If it is determined that the print job has not ended (step S46: NO), the control unit 65 repeats step S46.

  When it is determined that the print job has been completed (step S46: YES), in step S47, the control unit 65 ends the pressure control. Here, when the air pump 125 is being driven, the control unit 65 stops it. Further, when at least one of the pressurization side pressure adjustment valve 115 and the negative pressure side pressure adjustment valve 122 is opened, the control unit 65 closes the opened one.

  Next, in step S <b> 48, the control unit 65 opens the pressurization side atmosphere release valve 113 and the negative pressure side atmosphere release valve 120. As a result, the pressurized tank 81 is opened to the atmosphere via the pressurized common air chamber 111, and the negative pressure tank 84 is opened to the atmosphere via the negative pressure common air chamber 118.

  Next, in step S49, the control unit 65 ends the liquid level maintenance control. Thereby, the ink circulation in the ink circulation unit 72 is finished, and a series of operations is finished.

  Next, an operation at the time of initial filling of ink into the printing unit 62 will be described.

  The initial filling of the ink into the printing unit 62 is performed in order to change the pressure tank 81 and the negative pressure tank 84 from an empty state where there is no ink to a state where a printing operation can be performed. The pressure tank 81 and the negative pressure tank 84 are filled with ink by the initial filling.

  FIG. 22 is a flowchart for explaining the operation when the printing unit 62 is initially filled with ink. The process of the flowchart of FIG. 22 starts when a print job is input to the inkjet printing apparatus 61 in a state where the ink is not initially charged into the printing unit 62. The process of the flowchart in FIG. 22 is performed for each printing unit 62.

  In step S51 of FIG. 22, the controller 65 opens the pressure side ink supply valve 138 and the negative pressure side ink supply valve 139. Thereby, ink starts to be supplied from the ink cartridge 136 to the pressure tank 81 and the negative pressure tank 84.

  Here, as described above, the pressure-side ink supply valve 138 and the negative-pressure side ink supply valve 139 are closed during standby before a print job is input to the inkjet printing apparatus 61. Further, the pressurization side air release valve 113 and the negative pressure side air release valve 120 are opened, and the pressurization side pressure adjustment valve 115 and the negative pressure side pressure adjustment valve 122 are closed.

  Next, in step S52, the control unit 65 determines whether the pressurized tank liquid level sensor 92 is on.

  When it is determined that the pressurized tank liquid level sensor 92 is off (step S52: NO), the control unit 65 determines whether or not the negative pressure tank liquid level sensor 97 is on in step S53. When it is determined that the negative pressure tank liquid level sensor 97 is off (step S53: NO), the control unit 65 returns to step S52.

  When it is determined that the negative pressure tank liquid level sensor 97 is on (step S53: YES), the control unit 65 closes the negative pressure side ink supply valve 139 in step S54. As a result, the supply of ink from the ink cartridge 136 to the negative pressure tank 84 is completed while the negative pressure tank 84 is filled with ink to the reference height. Thereafter, the control unit 65 returns to Step S52.

  If it is determined in step S52 that the pressurized tank liquid level sensor 92 is on (step S52: YES), the control unit 65 closes the pressure-side ink supply valve 138 in step S55. Accordingly, the supply of ink from the ink cartridge 136 to the pressure tank 81 is completed in a state where the pressure tank 81 is filled with ink to the reference height.

  Next, in step S56, the control unit 65 determines whether or not the negative pressure side ink supply valve 139 is open. Here, when the negative pressure tank liquid level sensor 97 is turned on before the pressurized tank liquid level sensor 92, the negative pressure is determined by the process of step S54 before the pressure side ink supply valve 138 is closed in step S55. The pressure side ink supply valve 139 is closed.

  When it is determined that the negative pressure side ink supply valve 139 is open (step S56: YES), in step S57, the control unit 65 determines whether or not the negative pressure tank liquid level sensor 97 is on. When it is determined that the negative pressure tank liquid level sensor 97 is off (step S57: NO), the control unit 65 repeats step S57.

  When it is determined that the negative pressure tank liquid level sensor 97 is on (step S57: YES), the control unit 65 closes the negative pressure side ink supply valve 139 in step S58. As a result, the supply of ink from the ink cartridge 136 to the negative pressure tank 84 is completed while the negative pressure tank 84 is filled with ink to the reference height. As a result, the initial filling of the ink into the pressurizing tank 81 and the negative pressure tank 84 is completed, and the operation of the initial filling of the ink into the printing unit 62 is completed.

  In step S56, when the control unit 65 determines that the negative pressure side ink supply valve 139 is closed (step S56: NO), the initial filling of the ink into the pressurized tank 81 and the negative pressure tank 84 is completed. Therefore, the operation of initial filling of the ink into the printing unit 62 is completed.

  When the operation of initial filling of the ink into the printing unit 62 is completed, the printing operation is subsequently performed according to the procedure of the flowchart of FIG.

  As described above, in the ink jet printing apparatus 61, the ink supply unit 64 is connected to the pressure tank 81 and the negative pressure tank 84. The control unit 65 controls to supply ink from the ink supply unit 64 to the pressure tank 81 and the negative pressure tank 84 at the same time when the printing unit 62 is initially filled with ink.

  Here, unlike the present embodiment, when the ink replenishing unit is connected only to the negative pressure tank 84 and not connected to the pressure tank 81, the ink replenishing unit is used when the printing unit 62 is initially filled with ink. Ink is supplied only to the negative pressure tank 84. The initial filling of the ink into the pressurized tank 81 is performed by sending ink from the negative pressure tank 84 to the pressurized tank 81 by the same liquid level maintenance control as that during the printing operation.

  On the other hand, as described above, in the ink jet printing apparatus 61, ink is simultaneously supplied from the ink replenishing unit 64 to the pressure tank 81 and the negative pressure tank 84 at the time of initial filling. The ink can be initially filled in a short time.

[Other Embodiments]
As described above, the present invention has been described according to the first to third embodiments. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  In the first and second embodiments described above, the configuration in which each printing unit 2 includes two ink tank pairs 20 is shown, but the configuration in which each printing unit 2 includes three or more ink tank pairs 20 may be employed.

  In this case, the control unit 5 sets the ink tank pair 20 other than the ink tank pair 20 that is in the ink feeding state in a ready state, and sequentially sets one ink tank pair 20 that performs ink feeding to the ink tank pair 20 in the ready state. Control to switch. In this case, in order to set the ink tank pair 20 other than the ink tank pair 20 during ink feeding to the ready state, when the control unit 5 performs the switching process, the ink feeding is performed immediately before the switching process. Preparation processing is performed on the ink tank pair 20. Then, the control unit 5 causes each ink tank pair 20 in the preparation state to stand by in the preparation state until the next order for performing the ink feeding comes.

  In this case, the ink replenishing unit 4 is connected to one ink tank 12 of each ink tank pair 20 in each printing unit 2. When the ink is initially filled in the printing unit 2, the control unit 5 generates a negative pressure in all the ink tanks 12 to which the ink supply unit 4 is connected by the pressure generation unit 3, and these ink tanks 12. Are controlled to supply ink simultaneously.

  In the first embodiment described above, when the ink is initially filled in the printing unit 2, the ink tanks 12A and 12B may be open to the atmosphere. Even in the configuration in which each printing unit 2 includes three or more ink tank pairs 20, all the ink tanks 12 to which the ink replenishing unit 4 is connected are used when the ink is initially filled in the printing unit 2. It may be open to the atmosphere.

  As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

[Appendix]
The present application discloses the following inventions.

(Appendix 1)
An ink jet head, a plurality of ink tank pairs each of which is a pair of a first ink tank and a second ink tank for storing ink, and the first ink tank and the second ink of each ink tank pair via the ink jet head An ink flow path connecting between the first ink tank and the second ink tank pair via the ink flow path and the inkjet head in one of the plurality of ink tank pairs. Ink printing is performed by ejecting ink from an ink jet head while performing ink feeding with an ink tank, and one ink feeding is performed between the first ink tank and the second ink tank. A printing unit that discharges and prints ink from the inkjet head while sequentially switching the ink tank pairs;
An ink replenishing unit connected to the first ink tank of each of the ink tank pairs and supplying ink to the first ink tanks of all the ink tank pairs at the time of initial filling of the ink into the printing unit; An ink jet printing apparatus comprising:

(Appendix 2)
The inkjet printing apparatus according to claim 1, further comprising a pressure generation unit that generates a negative pressure in the first ink tank of each ink tank pair when the ink is initially filled in the printing unit.

(Appendix 3)
An ink jet head, a first ink tank for storing ink to be supplied to the ink jet head, a second ink tank for receiving and storing ink not consumed by the ink jet head, the first ink tank, the ink jet head, and the second ink tank. A printing unit having a circulation path for circulating ink between the ink tank and performing printing by discharging ink from the inkjet head while circulating the ink along the circulation path;
And an ink replenishing unit connected to the first and second ink tanks and supplying ink to the first and second ink tanks at the time of initial filling of the ink into the printing unit. Printing device.

DESCRIPTION OF SYMBOLS 1 Inkjet printing apparatus 2,2A, 2B Printing part 3 Pressure generation part 4,4A, 4B Ink supply part 5 Control part 11 Inkjet head 12,12A-12D Ink tank 14 Ink outflow path 15,15A-15D Ink outflow valve 16 Ink Inflow path 17, 17A to 17D Ink inflow valve 20, 20A, 20B Ink tank pair 51 Ink cartridge 52 Ink supply path 53A, 53B Ink supply valve 61 Inkjet printing device 62 Printing unit 63 Pressure generating unit 64 Ink supply unit 65 Control unit 71 Inkjet head 72 Ink circulation section 81 Pressure tank 82 Distributor 83 Aggregator 84 Negative pressure tank 85 Ink pump 88 to 90 Ink circulation pipe 136 Ink cartridge 137 Ink supply path 138 Pressure side ink supply valve 139 Negative Side ink supply valve

Claims (3)

An ink jet head, a plurality of ink tank pairs each of which is a pair of a first ink tank and a second ink tank for storing ink, and the first ink tank and the second ink of each ink tank pair via the ink jet head An ink flow path connecting between the first ink tank and the second ink tank pair via the ink flow path and the inkjet head in one of the plurality of ink tank pairs. Ink printing is performed by ejecting ink from an ink jet head while performing ink feeding with an ink tank, and one ink feeding is performed between the first ink tank and the second ink tank. A printing unit that discharges and prints ink from the inkjet head while sequentially switching the ink tank pairs;
An ink replenishing unit connected to the first ink tank of each of the ink tank pairs and supplying ink to the first ink tanks of all the ink tank pairs at the time of initial filling of the ink into the printing unit; An ink jet printing apparatus comprising:   The inkjet printing apparatus according to claim 1, further comprising a pressure generation unit that generates a negative pressure in the first ink tank of each of the ink tank pairs when the ink is initially filled in the printing unit. An ink jet head, a first ink tank for storing ink to be supplied to the ink jet head, a second ink tank for receiving and storing ink not consumed by the ink jet head, the first ink tank, the ink jet head, and the second ink tank. A printing unit having a circulation path for circulating ink between the ink tank and performing printing by discharging ink from the inkjet head while circulating the ink along the circulation path;
And an ink replenishing unit connected to the first and second ink tanks and supplying ink to the first and second ink tanks at the time of initial filling of the ink into the printing unit. Printing device.