JP6446231B2 - Inkjet printing device - Google Patents

Description

  The present invention relates to an ink circulation type ink jet printing apparatus.

  2. Description of the Related Art An ink circulation type inkjet printing apparatus that prints by ejecting ink from an inkjet head while circulating ink is known.

  In an ink circulation type ink jet printing apparatus, positive pressure and negative pressure are respectively applied to a pressure tank provided on the upstream side and a negative pressure tank provided on the downstream side with respect to the ink jet head to circulate ink. There is something to do (see, for example, Patent Document 1).

  In such an ink jet printing apparatus, when printing is performed, a positive pressure and a negative pressure are respectively applied to a pressurized tank and a negative pressure tank using an air pump. As a result, ink flows from the pressurized tank toward the inkjet head. Ink that has not been consumed by the inkjet head is collected in a negative pressure tank. Ink is sent from the negative pressure tank to the pressure tank by an ink pump. In this way, ink circulation is performed.

  By the way, in an inkjet printing apparatus, thickened ink etc. may adhere to the nozzle of an inkjet head. Further, the deposit such as the thickened ink may cause ejection failure such as disturbance in the ejection direction of the ink from the nozzle or non-ejection.

  Therefore, in the inkjet printing apparatus, as maintenance, so-called purge is performed in which the inkjet head is pressurized and ink is forcibly discharged from the nozzles. By the purge, thickened ink or the like is pushed out from the nozzle, and the ejection failure is eliminated.

  When purging with the above-described ink circulation type inkjet printing apparatus, pressurized ink is supplied to the inkjet head by pressurizing the pressurized tank, and the ink is forcibly discharged from the nozzle.

JP 2012-153004 A

  However, in the above-described purge in the ink circulation type ink jet printing apparatus, the pressure applied to the pressure tank escapes to the negative pressure tank side, and the ink jet head may not be sufficiently pressurized. For this reason, even if purging is performed, the thickened ink or the like is not discharged from the nozzles, and the ejection failure may not be eliminated.

  The present invention has been made in view of the above, and an object of the present invention is to provide an ink jet printing apparatus capable of improving the performance of eliminating ejection defects.

  In order to achieve the above object, a first feature of an ink jet printing apparatus according to the present invention is that an ink jet head having a nozzle for ejecting ink, a pressurized tank for storing ink to be supplied to the ink jet head, and consumed by the ink jet head. A negative pressure tank that receives ink that has not been formed, a printing unit that circulates ink between the pressure tank, the inkjet head, and the negative pressure tank, and applies positive pressure to the pressure tank. A pressure applying unit that selectively applies a negative pressure and a positive pressure to the negative pressure tank; and controlling the pressure applying unit to apply a positive pressure to the pressurizing tank and the negative pressure tank. And a control unit that executes a purge for discharging ink from the nozzles of the head.

  A second feature of the ink jet printing apparatus according to the present invention is that the ink jet head has a plurality of head modules, and the circulation path is an ink that individually blocks the inflow of ink to the head modules at the time of purging. In the purging, the control unit is configured to block the inflow of ink into the head module that is not purged by the ink blocking unit.

  A third feature of the inkjet printing apparatus according to the present invention is that it includes a plurality of the printing units, and the pressure applying unit is common to all the printing units, and is individually connected to the printing units. The controller has a cutting unit for cutting, and the control unit is configured to cut the connection between the printing unit and the pressure applying unit that are not purged by the cutting unit at the time of purging.

  According to a fourth aspect of the ink jet printing apparatus of the present invention, the ink jet head has a plurality of head modules, and the circulation path is an ink that individually blocks the inflow of ink to the head modules during purging. In the purging, the control unit is configured to block the inflow of ink into the head module outside the purge target in the inkjet head of the printing unit to be purged by the ink blocking unit.

  According to the first feature of the inkjet printing apparatus according to the present invention, the control unit controls the pressure applying unit to apply a positive pressure to the pressurized tank and the negative pressure tank, so that the ink is discharged from the nozzle of the inkjet head. Execute purge to be discharged. Thus, a strong pressure can be applied to the nozzle by applying a positive pressure to the negative pressure tank as well as the pressure tank. For this reason, the thickened ink and the like are easily discharged from the nozzle. Therefore, it is possible to improve the performance for eliminating the discharge failure.

  According to the second feature of the ink jet printing apparatus according to the present invention, the control unit blocks the ink flow into the head module that is not purged by the ink blocking unit during the purge. Thus, if there is a head module that is not purged, the purge can be omitted for each head module. As a result, ink waste can be suppressed.

  According to the third feature of the ink jet printing apparatus according to the present invention, the control unit cuts off the connection between the printing unit that is not purged and the pressure application unit at the time of purging. Accordingly, even if the pressure applying unit is common to all the printing units, the purging can be omitted in the printing unit that does not require purging. As a result, ink waste can be suppressed.

  According to the fourth feature of the ink jet printing apparatus of the present invention, the control unit shuts off the inflow of ink into the head module that is not purged in the ink jet head of the printing unit to be purged by the ink blocking unit during the purge. To do. As a result, even if the printing unit to be purged has a head module that is not purged, the purge can be omitted for each head module. As a result, waste of ink can be further suppressed.

It is a block diagram which shows the structure of the inkjet printing apparatus which concerns on embodiment. It is a block diagram which shows the structure of the control part of the inkjet printing apparatus shown in FIG. It is a schematic block diagram of the printing part and pressure provision part of the inkjet printing apparatus shown in FIG. (A) is explanatory drawing of the negative pressure side pressure reduction setting of the switching valve for negative pressure side pressurization, (b) is explanatory drawing of the negative pressure side pressure reduction setting of the switching valve for negative pressure side pressurization. It is explanatory drawing of liquid level maintenance control. It is a flowchart for demonstrating the operation | movement at the time of purge.

  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.

  FIG. 1 is a block diagram showing a configuration of an ink jet printing apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram illustrating a configuration of a control unit of the ink jet printing apparatus illustrated in FIG. 1. FIG. 3 is a schematic configuration diagram of a printing unit and a pressure applying unit of the inkjet printing apparatus shown in FIG. In the following description, the vertical direction is the vertical direction, and the vertical direction on the paper surface in FIG. 3 is the vertical direction.

  As shown in FIG. 1, the inkjet printing apparatus 1 according to the present embodiment includes four printing units 2, a pressure applying unit 3, a transport unit 4, an operation panel 5, and a control unit 6.

  The printing unit 2 prints an image by ejecting ink onto the paper conveyed by the conveyance unit 4 while circulating the ink. The four printing units 2 eject inks of different colors (for example, black, cyan, magenta, and yellow). The four printing units 2 have the same configuration except that the colors of the ejected ink are different.

  As shown in FIG. 3, the printing unit 2 includes an inkjet head 11, an ink circulation unit 12, and an ink supply unit 13.

  The ink jet head 11 ejects ink supplied by the ink circulation unit 12. The inkjet head 11 has a plurality of head modules 16.

  The head module 16 has an ink chamber (not shown) for storing ink and a plurality of nozzles (not shown) for discharging ink. A piezo element (not shown) is disposed in the ink chamber. By driving the piezo element, ink is ejected from the nozzle.

  The ink circulation unit 12 supplies ink to the inkjet head 11 while circulating the ink. The ink circulation unit 12 includes a pressure tank 21, a negative pressure tank 22, a circulation path 23, an ink pump 24, an ink temperature adjustment unit 25, and an ink temperature sensor 26.

  The pressurized tank 21 stores ink to be supplied to the inkjet head 11. The ink in the pressurized tank 21 is supplied to the inkjet head 11 via an ink circulation pipe 41 and a distributor 44 described later. An air layer 31 is formed in the pressurized tank 21 on the ink surface. The pressurized tank 21 is connected to a later-described pressurized common air chamber 71 via a later-described pressurized-side communication pipe 73. The pressurized tank 21 is disposed at a lower position (downward) than the inkjet head 11.

  The pressurized tank 21 is provided with a pressurized tank liquid level sensor 32 and an ink filter 33.

  The pressurized tank liquid level sensor 32 is for detecting whether or not the liquid level of the ink in the pressurized tank 21 has reached the reference height. The reference height is below the upper end of the pressurized tank 21. The pressurized tank liquid level sensor 32 outputs a signal indicating “ON” when the liquid level in the pressurized tank 21 is equal to or higher than the reference height, and turns “OFF” when the level is lower than the reference height. The signal shown is output.

  The ink filter 33 removes dust and the like in the ink.

  The negative pressure tank 22 receives and stores the ink that has not been consumed by the inkjet head 11 from the collecting unit 45 described later. The negative pressure tank 22 stores ink supplied from an ink cartridge 66 of the ink replenishing unit 13 described later. In the negative pressure tank 22, an air layer 36 is formed on the ink surface. The negative pressure tank 22 is connected to a later-described negative pressure common air chamber 79 via a later-described negative pressure side communication pipe 81. The negative pressure tank 22 is disposed at the same height as the pressurized tank 21.

  The negative pressure tank 22 is provided with a negative pressure tank liquid level sensor 37. The negative pressure tank liquid level sensor 37 is for detecting whether or not the ink level in the negative pressure tank 22 has reached the reference height. The reference height is below the upper end of the negative pressure tank 22. The negative pressure tank liquid level sensor 37 outputs a signal indicating “ON” when the liquid level in the negative pressure tank 22 is equal to or higher than the reference height, and sets “OFF” when lower than the reference height. The signal shown is output.

  The circulation path 23 is a path for circulating ink among the pressurized tank 21, the inkjet head 11, and the negative pressure tank 22. The circulation path 23 includes ink circulation pipes 41 to 43, a distributor 44, and a collection device 45.

  The ink circulation pipe 41 connects the pressurized tank 21 and the distributor 44. A part of the ink circulation pipe 41 is branched into a portion passing through a heater 61 described later and a portion passing through a heat sink 63 described later. During ink circulation, ink flows from the pressurized tank 21 toward the distributor 44 through the ink circulation pipe 41.

  The ink circulation pipe 42 connects the recovery unit 45 and the negative pressure tank 22. During the ink circulation, the ink flows through the ink circulation pipe 42 from the collector 45 toward the negative pressure tank 22.

  The ink circulation pipe 43 connects the negative pressure tank 22 and the pressurization tank 21. During ink circulation, ink flows from the negative pressure tank 22 toward the pressure tank 21 through the ink circulation pipe 43.

  The distributor 44 distributes the ink supplied from the pressurized tank 21 via the ink circulation pipe 41 to each head module 16 of the inkjet head 11. The distributor 44 includes an ink bath 51, a plurality of input pipes 52, and a plurality of input side opening / closing valves 53.

  The ink bath 51 stores ink distributed to each head module 16. During ink circulation, ink flows from the pressurized tank 21 to the ink bus 51 via the ink circulation pipe 41, and ink flows from the ink bus 51 to the head module 16 via the input pipe 52.

  The input tube 52 connects the ink bath 51 and an input port (not shown) of the head module 16. One input tube 52 is provided corresponding to each head module 16. During the ink circulation, the ink flows from the ink bath 51 toward the head module 16 through the input tube 52.

  The input side opening / closing valve 53 opens and closes the ink flow path in the input pipe 52. The input side opening / closing valve 53 and the output side opening / closing valve 58 described later can individually block the inflow of ink into the head module 16 during the purge. The input side opening / closing valve 53 corresponds to a part of the ink blocking portion in the claims.

  The collecting unit 45 collects the ink that has not been consumed by the inkjet head 11 from each head module 16. The collection device 45 includes an ink bath 56, a plurality of output pipes 57, and a plurality of output side on-off valves 58.

  The ink bath 56 stores the ink collected from each head module 16. During ink circulation, ink flows from the head module 16 to the ink bus 56 via the output pipe 57, and ink flows from the ink bus 56 to the negative pressure tank 22 via the ink circulation pipe 42.

  The output tube 57 connects an output port (not shown) of the head module 16 and the ink bus 56. One output tube 57 is provided corresponding to each head module 16. During the ink circulation, the ink flows from the head module 16 to the ink bus 56 through the output tube 57.

  The output side opening / closing valve 58 opens and closes the ink flow path in the output pipe 57. The output side opening / closing valve 58 corresponds to a part of the ink blocking portion in the claims.

  The ink pump 24 sends ink from the negative pressure tank 22 to the pressure tank 21. The ink pump 24 is provided in the middle of the ink circulation pipe 43.

  The ink temperature adjustment unit 25 adjusts the ink temperature in the ink circulation unit 12. The ink temperature adjustment unit 25 is provided in the middle of the ink circulation pipe 41. The ink temperature adjustment unit 25 includes a heater 61, a heater temperature sensor 62, a heat sink 63, and a cooling fan 64.

  The heater 61 heats the ink in the ink circulation pipe 41. The heater temperature sensor 62 detects the temperature of the heater 61. The heat sink 63 cools the ink in the ink circulation pipe 41 by heat radiation. The cooling fan 64 sends cooling air to the heat sink 63.

  The ink temperature sensor 26 detects the temperature of the ink in the ink circulation unit 12. The ink temperature sensor 26 is provided in the middle of the ink circulation pipe 41.

  The ink supply unit 13 supplies ink to the ink circulation unit 12. The ink supply unit 13 includes an ink cartridge 66, an ink supply valve 67, and an ink supply pipe 68.

  The ink cartridge 66 contains ink used for printing by the inkjet head 11. The ink in the ink cartridge 66 is supplied to the negative pressure tank 22 of the ink circulation unit 12 through the ink supply pipe 68.

  The ink supply valve 67 opens and closes the ink flow path in the ink supply pipe 68. When ink is supplied to the negative pressure tank 22, the ink supply valve 67 is opened.

  The ink supply pipe 68 connects the ink cartridge 66 and the negative pressure tank 22. Ink flows from the ink cartridge 66 toward the negative pressure tank 22 through the ink supply pipe 68.

  The pressure applying unit 3 applies a positive pressure to the pressurizing tank 21 and selectively applies a negative pressure and a positive pressure to the negative pressure tank 22. The pressure applying unit 3 is common to all the printing units 2. The pressure application unit 3 includes a pressurization common air chamber 71, four pressurization side communication valves 72, four pressurization side communication pipes 73, a pressurization side atmosphere release valve 74, a pressurization side atmosphere release pipe 75, Pressure side pressure adjustment valve 76, pressure side pressure adjustment pipe 77, pressure side pressure sensor 78, negative pressure common air chamber 79, four negative pressure side communication valves 80, four negative pressure side communication pipes 81, negative Pressure side atmospheric release valve 82, negative pressure side atmospheric release pipe 83, negative pressure side pressure adjustment valve 84, negative pressure side pressure adjustment pipe 85, negative pressure side pressure sensor 86, air pump 87, and negative pressure side pressurization switching valve 88 , An air pump pipe 89, a switching valve atmospheric communication pipe 90, a pressurizing side switching valve connecting pipe 91, a negative pressure side switching valve connecting pipe 92, a junction pipe 93, an air filter 94, and an overflow pan 95. In addition, the pressurization side communication valve 72 and the negative pressure side communication valve 80 correspond to the cutting part of a claim.

  The pressurized common air chamber 71 is an air chamber for equalizing the pressures of the pressurized tanks 21 of the plurality of printing units 2. The pressurized common air chamber 71 is connected to the air layers 31 of the pressurized tanks 21 of the four printing units 2 by the four pressurized communication tubes 73.

  The pressurization side communication valve 72 opens and closes the air flow path in the pressurization side communication pipe 73. The four pressurization side communication valves 72 are provided corresponding to each printing unit 2 one by one. The pressurization side communication valve 72 is arranged in the middle of the pressurization side communication pipe 73. When the pressurization side communication valve 72 is opened, the air layer 31 of the pressurization tank 21 of the printing unit 2 corresponding to the pressurization side communication valve 72 communicates with the pressurization common air chamber 71. Thereby, the pressurization tanks 21 of the respective printing units 2 in which the corresponding pressurization-side communication valves 72 are opened are communicated with each other via the pressurization common air chamber 71 and the pressurization-side communication pipe 73. When the pressurization side communication valve 72 is closed, the connection between the pressurization tank 21 and the pressurization common air chamber 71 of the printing unit 2 corresponding to the pressurization side communication valve 72 is disconnected.

  The pressurization side communication pipe 73 connects the pressurization common air chamber 71 and the air layer 31 of the pressurization tank 21. Four pressurizing side communication pipes 73 are provided corresponding to each printing unit 2 one by one.

  The pressurization side air release valve 74 is configured to switch the pressurization tank 21 between a sealed state (a state shut off from the atmosphere) and an open air state (a state communicated with the atmosphere) via the pressurization common air chamber 71. Open and close the air flow path in the pressurized air release tube 75.

  The pressurization side air release pipe 75 forms an air flow path for opening the pressurization tank 21 to the atmosphere via the pressurization common air chamber 71. One end of the pressurization-side atmosphere release pipe 75 is connected to the pressurization common air chamber 71, and the other end is connected to the junction pipe 93.

  The pressurization side pressure adjustment valve 76 opens and closes the air flow path in the pressurization side pressure adjustment pipe 77 in order to adjust the pressure of the pressurization common air chamber 71 and the pressurization tank 21.

  The pressure side pressure adjustment pipe 77 forms an air flow path for adjusting the pressure of the pressure common air chamber 71 and the pressure tank 21. One end of the pressurization side pressure adjustment pipe 77 is connected to the pressurization common air chamber 71, and the other end is connected to the junction pipe 93.

  The pressure side pressure sensor 78 detects the pressure in the pressure common air chamber 71. The pressure in the pressurization common air chamber 71 is equal to the pressure in the pressurization tank 21 of the printing unit 2 corresponding to the pressurization side communication valve 72 that is opened. This is because the air layer 31 of the pressurization tank 21 of the printing unit 2 corresponding to the open pressurization side communication valve 72 and the pressurization common air chamber 71 communicate with each other.

  The negative pressure common air chamber 79 is an air chamber for equalizing the pressures in the negative pressure tanks 22 of the plurality of printing units 2. The negative pressure common air chamber 79 is connected to the air layers 36 of the negative pressure tanks 22 of the four printing units 2 by four negative pressure side communication pipes 81.

  The negative pressure side communication valve 80 opens and closes the air flow path in the negative pressure side communication pipe 81. Four negative pressure side communication valves 80 are provided corresponding to each printing unit 2 one by one. The negative pressure side communication valve 80 is disposed in the middle of the negative pressure side communication pipe 81. When the negative pressure side communication valve 80 is opened, the air layer 36 of the negative pressure tank 22 of the printing unit 2 corresponding to the negative pressure side communication valve 80 communicates with the negative pressure common air chamber 79. As a result, the negative pressure tanks 22 of the respective printing units 2 in which the corresponding negative pressure side communication valves 80 are open are communicated with each other via the negative pressure common air chamber 79 and the negative pressure side communication pipe 81. When the negative pressure side communication valve 80 is closed, the connection between the negative pressure tank 22 of the printing unit 2 and the negative pressure common air chamber 79 corresponding to the negative pressure side communication valve 80 is disconnected. By closing the pressurization side communication valve 72 and the negative pressure side communication valve 80, the connection with the pressure application unit 3 of the printing unit 2 can be individually disconnected.

  The negative pressure side communication pipe 81 connects the negative pressure common air chamber 79 and the air layer 36 of the negative pressure tank 22. Four negative pressure side communication pipes 81 are provided in correspondence with each printing unit 2.

  The negative pressure side air release valve 82 opens and closes the air flow path in the negative pressure side air release pipe 83 in order to switch the negative pressure tank 22 between a sealed state and an air open state via the negative pressure common air chamber 79. To do.

  The negative pressure side atmosphere release pipe 83 forms an air flow path for releasing the negative pressure tank 22 to the atmosphere via the negative pressure common air chamber 79. The negative pressure side air release pipe 83 has one end connected to the negative pressure common air chamber 79 and the other end connected to the junction pipe 93.

  The negative pressure side pressure adjustment valve 84 opens and closes the air flow path in the negative pressure side pressure adjustment pipe 85 in order to adjust the pressure in the negative pressure common air chamber 79 and the negative pressure tank 22.

  The negative pressure side pressure adjustment pipe 85 forms an air flow path for adjusting the pressure of the negative pressure common air chamber 79 and the negative pressure tank 22. The negative pressure side pressure adjustment pipe 85 has one end connected to the negative pressure common air chamber 79 and the other end connected to the junction pipe 93.

  The negative pressure side pressure sensor 86 detects the pressure in the negative pressure common air chamber 79. The pressure in the negative pressure common air chamber 79 is equal to the pressure in the negative pressure tank 22 of the printing unit 2 corresponding to the open negative pressure side communication valve 80. This is because the air layer 36 of the negative pressure tank 22 of the printing unit 2 corresponding to the open negative pressure side communication valve 80 and the negative pressure common air chamber 79 communicate with each other.

  The air pump 87 sends air from the negative pressure side pressurization switching valve 88 toward the pressurization common air chamber 71. The air pump 87 is provided in the middle of the air pump pipe 89.

  The negative pressure side switching valve 88 switches the pressure applied to the negative pressure common air chamber 79 by driving the air pump 87 between the positive pressure and the negative pressure. The negative pressure side switching valve 88 is a four-way valve. The negative pressure side switching valve 88 has a first port 96a, a second port 96b, a third port 96c, a fourth port 96d, and a fifth port 96e.

  An air pump pipe 89 is connected to the first port 96a. A switching valve atmospheric communication pipe 90 is connected to the second port 96b. The third port 96 c is sealed with a cap 97. A negative pressure side switching valve connection pipe 92 is connected to the fourth port 96d. A pressurization side switching valve connection pipe 91 is connected to the fifth port 96e.

  The negative pressure side switching valve 88 can switch the connection relationship of each port by driving an internal valve body (not shown). Thereby, the setting switch of the negative pressure side pressurization switching valve 88 can be changed between the negative pressure side pressure reduction setting and the negative pressure side pressure setting. FIG. 4A shows the connection relationship of each port in the negative pressure side pressure reduction setting. Moreover, the connection relationship of each port in negative pressure side pressurization setting is shown in FIG.4 (b).

  As shown in FIG. 4A, in the negative pressure side pressure reduction setting, the first port 96a and the fourth port 96d are connected, and the second port 96b and the third port 96c are connected. At this time, the fifth port 96e is closed by a valve body inside the negative pressure side switching valve 88. In this setting, by driving the air pump 87, air is sucked from the negative pressure common air chamber 79 to depressurize the negative pressure common air chamber 79, and air flows into the pressurization common air chamber 71. Chamber 71 is pressurized. That is, a negative pressure is applied to the negative pressure common air chamber 79, and a positive pressure is applied to the pressurized common air chamber 71. Since the third port 96c is sealed by the cap 97, external air does not pass through the third port 96c and the second port 96b and flow into the switching valve atmospheric communication pipe 90.

  As shown in FIG. 4B, in the negative pressure side pressurization setting, the first port 96a and the second port 96b are connected, and the fourth port 96d and the fifth port 96e are connected. At this time, the third port 96c is closed by the valve body inside the negative pressure side switching valve 88. In this setting, when the air pump 87 is driven, air flows from the air pump pipe 89 into the pressurized common air chamber 71 and the pressurized common air chamber 71 is pressurized. Further, air is sent from the pressurization common air chamber 71 to the negative pressure common air chamber 79 through the pressurization side switching valve connection pipe 91, the negative pressure side pressurization switching valve 88, and the negative pressure side switching valve connection pipe 92, and common to the negative pressure. The air chamber 79 is also pressurized. That is, positive pressure is applied to the pressurized common air chamber 71 and the negative pressure common air chamber 79.

  The air pump pipe 89 forms a flow path for air flowing from the negative pressure side pressurizing switching valve 88 to the pressurizing common air chamber 71 by driving the air pump 87. One end of the air pump pipe 89 is connected to the first port 96 a of the negative pressure side switching valve 88, and the other end is connected to the pressurized common air chamber 71.

  The switching valve atmospheric communication pipe 90 connects the second port 96 b of the negative pressure side switching valve 88 and the junction pipe 93. The pressurization side switching valve connection pipe 91 connects the fifth port 96 e of the negative pressure side pressurization switching valve 88 and the pressurization common air chamber 71. The negative pressure side switching valve connecting pipe 92 connects the fourth port 96 d of the negative pressure side pressurizing switching valve 88 and the negative pressure common air chamber 79.

  The merge pipe 93 has one end connected to the overflow pan 95 and the other end (upper end) communicating with the atmosphere via the air filter 94. The end of the merge pipe 93 on the overflow pan 95 side is normally closed by an overflow ball 98 described later. Connected to the junction pipe 93 are a pressurization-side atmosphere release pipe 75, a pressurization-side pressure adjustment pipe 77, a negative pressure-side atmosphere release pipe 83, a negative pressure-side pressure adjustment pipe 85, and a switching valve atmosphere communication pipe 90. As a result, the pressurization side atmosphere release pipe 75, the pressurization side pressure adjustment pipe 77, the negative pressure side atmosphere release pipe 83, the negative pressure side pressure adjustment pipe 85, and the switching valve atmosphere communication pipe 90 are communicated with the atmosphere.

  The air filter 94 prevents entry of dust or the like in the air into the junction pipe 93. The air filter 94 is installed at the upper end of the junction pipe 93.

  The overflow pan 95 is, for example, when ink overflows from the pressurized tank 21 and the negative pressure tank 22 due to an abnormality in the ink supply valve 67 and further overflows from the pressurized common air chamber 71 and the negative pressure common air chamber 79. Then, the ink flowing through the junction tube 93 is received.

  An overflow ball 98 is provided on the overflow pan 95. The overflow ball 98 closes the end of the joining pipe 93 that opens to the bottom surface of the overflow pan 95 when there is no ink in the overflow pan 95 to prevent the inflow of external air into the joining pipe 93. When ink flows from the junction pipe 93 to the overflow pan 95, the overflow ball 98 rises and the ink can flow into the overflow pan 95.

  The overflow pan 95 is provided with an overflow liquid level sensor 99. The overflow liquid level sensor 99 is for detecting whether or not the liquid level of the ink in the overflow pan 95 has reached a predetermined height.

  The overflow pan 95 is connected to a waste liquid tank (not shown). When the liquid level is detected by the overflow liquid level sensor 99, ink is discharged to the waste liquid tank.

  The transport unit 4 takes out the paper from a paper feed table (not shown) and transports the paper along the transport path. The transport unit 4 includes a roller for transporting the paper, a motor for driving the roller (both not shown), and the like.

  The operation panel 5 displays various input screens and accepts input operations by the user. The operation panel 5 includes an input unit having various operation keys, a touch panel, and the like, and a display unit (all not shown) having a liquid crystal display panel and the like.

  The control unit 6 controls the operation of the entire inkjet printing apparatus 1. As shown in FIG. 2, the control unit 6 includes a main controller 101 and a mechanical controller 102.

  The main controller 101 controls the entire inkjet printing apparatus 1. The main controller 101 includes a CPU (Central Processing Unit) 111, a memory 112, an HDD (Hard Disk Drive) 113, an external I / F (interface) 114, a mechanical controller I / F 115, a user I / F 116, A head I / F 117.

  The CPU 111 executes calculation processing. The memory 112 is used as a work area for the CPU 111 during temporary data storage or calculation. The HDD 113 stores various programs and the like.

  The external I / F 114 transmits and receives data to and from an external device via a network. The mechanical controller I / F 115 connects the mechanical controller 102 to the main controller 101. The user I / F 116 connects the operation panel 5 to the main controller 101. The head I / F 117 connects the inkjet head 11 to the main controller 101.

  The mechanical controller 102 controls ink circulation and ink supply in the printing unit 2, pressure control by the pressure applying unit 3, and paper conveyance control by the conveyance unit 4. The mechanical controller 102 includes a CPU 121, a memory 122, a sensor I / F 123, a main controller I / F 124, an actuator I / F 125, and a driver unit 126.

  The CPU 121 executes arithmetic processing. The memory 122 is used as a work area for the CPU 121 during temporary data storage or computation.

  The sensor I / F 123 connects various sensors such as the pressurized tank liquid level sensor 32 to the mechanical controller 102. The main controller I / F 124 connects the mechanical controller 102 to the main controller 101. The actuator I / F 125 transmits a control signal to the driver unit 126.

  The driver unit 126 includes various drivers that drive the ink pump 24, the air pump 87, the motor of the transport unit 4, and the like.

  The control unit 6 performs printing by discharging ink from the inkjet head 11 while performing the ink circulation operation. In the ink circulation operation, the pressure applying unit 3 applies positive pressure and negative pressure to the pressurizing tank 21 and the negative pressure tank 22, respectively, and the ink pump 24 according to the liquid level height of the pressurizing tank 21 and the negative pressure tank 22. In this operation, the ink is circulated along the circulation path 23 by controlling the driving of.

  Further, as a maintenance, the control unit 6 performs a purge for forcibly discharging ink from the nozzles of the head module 16 of the inkjet head 11. Specifically, the control unit 6 controls the pressure applying unit 3 to apply positive pressure to the pressurizing tank 21 and the negative pressure tank 22, thereby forcibly discharging ink from the nozzles.

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

  When a print job is input, the CPU 111 of the main controller 101 divides the print job into image data and job data, and transmits the job data to the mechanical controller 102. The job data includes information indicating the number of printed sheets, paper type, and the like.

  Next, the CPU 121 of the mechanical controller 102 closes the pressurization side air release valve 74 and the negative pressure side air release valve 82. As a result, the pressurization tank 21 of each printing unit 2 is sealed through the pressurization common air chamber 71, and the negative pressure tank 22 is sealed through the negative pressure common air chamber 79.

  In the standby state in which the inkjet printing apparatus 1 does not operate, the pressurization side air release valve 74 and the negative pressure side air release valve 82 are opened. Further, the pressurizing side pressure adjusting valve 76 and the negative pressure side pressure adjusting valve 84 are closed during standby. The input side on / off valve 53, the output side on / off valve 58, the pressurizing side communication valve 72, and the negative pressure side communication valve 80 are all opened from the standby state. The switching valve 88 for negative pressure side pressurization is set to negative pressure side pressure reduction setting.

  Next, the CPU 121 activates the air pump 87. As a result, air is sent from the negative pressure common air chamber 79 to the pressurized common air chamber 71, whereby the negative pressure common air chamber 79 and the negative pressure tank 22 are depressurized, and the pressurized common air chamber 71 and the pressurized tank 21. Is pressurized. As a result, ink flows from the pressurized tank 21 to the negative pressure tank 22 via the inkjet head 11 and ink circulation starts.

  After the air pump 87 is started, the CPU 121 drives the air pump 87 and pressurizes the pressure-side pressure adjustment valve 76 so that the pressures of the pressure tank 21 and the negative pressure tank 22 reach the respective set pressures and are maintained. The opening and closing of the negative pressure side pressure regulating valve 84 is controlled. The set pressures of the pressure tank 21 and the negative pressure tank 22 are preset as pressure values for setting the nozzle pressure of the inkjet head 11 to an appropriate value while circulating the ink.

  After the pressures in the pressurized tank 21 and the negative pressure tank 22 reach the set pressure, the CPU 111 of the main controller 101 and the CPU 121 of the mechanical controller execute a print job. Specifically, the CPU 121 of the mechanical controller causes the transport unit 4 to transport the paper based on the job data. Further, the CPU 111 of the main controller 101 causes ink to be ejected from the inkjet head 11 onto the conveyed paper based on the image data. Thereby, an image is printed on the paper. During execution of the print job, ink is supplied from the pressurized tank 21 to the inkjet head 11, and ink that has not been consumed by the inkjet head 11 flows into the negative pressure tank 22.

  Thus, when performing ink circulation and printing, the CPU 121 performs liquid level maintenance control. The liquid level maintenance control is performed according to the liquid level height of the pressurized tank 21 and the negative pressure tank 22 for circulating ink while maintaining the liquid level height of the pressurized tank 21 and the negative pressure tank 22 at the reference height. Further, the control of the ink pump 24 and the ink supply valve 67 is performed.

  Specifically, as shown in FIG. 5, when both the pressurized tank liquid level sensor 32 and the negative pressure tank liquid level sensor 37 are on, the CPU 121 turns off the ink pump 24 and closes the ink supply valve 67. To do. Similarly, even when the pressurized tank liquid level sensor 32 is on and the negative pressure tank liquid level sensor 37 is off, the CPU 121 turns off the ink pump 24 and closes the ink supply valve 67.

  When the pressurized tank liquid level sensor 32 is off and the negative pressure tank liquid level sensor 37 is on, the CPU 121 turns on the ink pump 24 and closes the ink supply valve 67.

  When both the pressurized tank liquid level sensor 32 and the negative pressure tank liquid level sensor 37 are off, the CPU 121 turns off the ink pump 24 and opens the ink supply valve 67.

  That is, when the pressurized tank liquid level sensor 32 is turned off and the negative pressure tank liquid level sensor 37 is turned on, the ink pump 24 sends ink from the negative pressure tank 22 to the pressurized tank 21 by the liquid level maintenance control. When both the pressurized tank liquid level sensor 32 and the negative pressure tank liquid level sensor 37 are turned off, ink is supplied from the ink cartridge 66 to the negative pressure tank 22 by the liquid level maintenance control. In this manner, ink circulation and printing are performed while maintaining the liquid level height of the pressurized tank 21 and the negative pressure tank 22.

  When the print job ends, the CPU 121 opens the pressurization-side atmosphere release valve 74 and the negative-pressure side atmosphere release valve 82. Here, when the ink pump 24 and the air pump 87 are being driven, the CPU 121 stops it. When the pressure side pressure adjustment valve 76, the negative pressure side pressure adjustment valve 84, and the ink supply valve 67 are opened, the CPU 121 closes them. As a result, the ink circulation operation is completed, and the inkjet printing apparatus 1 enters a standby state.

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

  In the ink jet printing apparatus 1, purging is performed when ejection failure is detected by ejection inspection. For example, the discharge inspection is performed as follows. First, the control unit 6 causes each printing unit 2 to print a predetermined test pattern on a sheet. The control unit 6 acquires image data obtained by reading a print image of the test pattern with a scanner, analyzes the image data, and determines whether or not there is a defective nozzle in each head module 16 of each inkjet head 11. to decide. If it is determined that at least one of the head modules 16 has a defective nozzle, the control unit 6 performs a purge.

  FIG. 6 is a flowchart for explaining the operation at the time of purging. When the purge is started, the inkjet printing apparatus 1 is in a standby state.

  In step S <b> 1 of FIG. 6, the CPU 121 of the mechanical controller closes the pressurization side communication valve 72 and the negative pressure side communication valve 80 corresponding to the printing unit 2 that is not purged. Thereby, the connection between the printing unit 2 and the pressure applying unit 3 that are not purged is disconnected.

  Here, the printing unit 2 to be purged is a printing unit 2 in which the inkjet head 11 has the head module 16 to be purged. The head module 16 to be purged is a head module 16 having nozzles with defective ejection. The printing unit 2 that is not purged is a printing unit 2 other than the printing unit 2 that is purged, and all the head modules 16 are printing units 2 that are head modules 16 that are not purged. The head module 16 that is not purged is a head module 16 other than the purge target head module 16, and is a head module 16 that does not have a defective nozzle.

  Next, in step S <b> 2, the CPU 121 closes the input-side opening / closing valve 53 and the output-side opening / closing valve 58 corresponding to the head module 16 that is not purged in the inkjet head 11 of the purge-target printing unit 2.

  Next, in step S <b> 3, the CPU 121 closes the pressurization side air release valve 74 and the negative pressure side air release valve 82. As a result, the pressurization tank 21 of the printing unit 2 to be purged is sealed through the pressurization common air chamber 71, and the negative pressure tank 22 is sealed through the negative pressure common air chamber 79.

  Next, in step S4, the CPU 121 sets the negative pressure side pressurization switching valve 88 to the negative pressure side pressurization setting.

  Next, in step S5, the CPU 121 activates the air pump 87. As a result, the pressurized common air chamber 71 and the pressurized tank 21 of the printing unit 2 to be purged start to be pressurized, and the negative pressure common air chamber 79 and the negative pressure tank 22 of the purged printing unit 2 are also pressurized. start. The pressure in the pressurized tank 21 and the negative pressure tank 22 of the printing unit 2 to be purged gradually increases. When the pressure reaches a certain level, ink starts to be discharged from the nozzles of the head module 16 to be purged.

  Here, in the standby state of the ink jet printing apparatus 1, the ink circulation pipes 41 and 42, the ink buses 51 and 56, the input pipe 52, the output pipe 57, and the head module 16 are filled with ink. In this state, the pressurization tank 21 and the negative pressure tank 22 are pressurized by driving the air pump 87, so that the ink is discharged so as to be pushed out from the nozzles of the head module 16 to be purged.

  When the negative pressure tank 22 is pressurized, the negative pressure path 22 (the ink circulation pipe 42, the ink bus 56, and the output pipe 57) from the negative pressure tank 22 in the direction opposite to that during ink circulation (printing). An ink flow toward the head module 16 is generated. In the path on the pressure side (the ink circulation pipe 41, the ink bath 51, and the input pipe 52), the ink flows from the pressure tank 21 toward the head module 16 in the same direction as during ink circulation.

  After starting the air pump 87, in step S6, the CPU 121 determines whether or not a purge end condition is satisfied. Specifically, the CPU 121 determines whether or not the pressure in the pressurization tank 21 and the negative pressure tank 22 has reached the specified pressure based on the detection value of at least one of the pressurization side pressure sensor 78 and the negative pressure side pressure sensor 86. Judging. At the time of purging, the pressure tank 21 and the negative pressure tank 22 are pressurized with the negative pressure side pressurization switching valve 88 set as the negative pressure side pressurization setting. Will be equal.

  When determining that the purge end condition is not satisfied (step S6: NO), the CPU 121 repeats step S6.

  If it is determined that the purge end condition is satisfied (step S6: NO), the CPU 121 stops the air pump 87 in step S7. Thereby, the discharge of ink from the nozzles is completed.

  Next, in step S <b> 8, the CPU 121 sets the negative pressure side pressurization switching valve 88 to the negative pressure side pressure reduction setting.

  Next, in step S <b> 9, the CPU 121 opens the pressurization side air release valve 74 and the negative pressure side air release valve 82.

  Next, in step S <b> 10, the CPU 121 opens the input side on / off valve 53 and the output side on / off valve 58 corresponding to the head module 16 that is not purged in the purge target printing unit 2. That is, the CPU 121 opens the input-side on-off valve 53 and the output-side on-off valve 58 that were closed in step S2.

  Next, in step S11, the CPU 121 opens the pressurization side communication valve 72 and the negative pressure side communication valve 80 corresponding to the printing unit 2 that is not purged. That is, the CPU 121 opens the pressurization side communication valve 72 and the negative pressure side communication valve 80 closed in step S2. Thereby, a series of operations are completed.

  After purging, the nozzle surface (lower surface) of the head module 16 is wiped with a wiper (not shown). As a result, the ink discharged from the purge and adhered to the nozzle surface, the thickened ink, and the like are removed from the nozzle surface.

  As described above, in the inkjet printing apparatus 1, the control unit 6 discharges ink from the nozzles of the inkjet head 11 by applying positive pressure to the pressure tank 21 and the negative pressure tank 22 by the pressure applying unit 3. Perform a purge. In this way, by applying positive pressure to the negative pressure tank 22 together with the pressurization tank 21, the inkjet head 11 can be pressurized from both the pressurization side path and the negative pressure side path, and a strong pressure can be applied to the nozzle. it can. For this reason, the thickened ink and the like are easily discharged from the nozzle. Therefore, it is possible to improve the performance for eliminating the discharge failure.

  Further, the control unit 6 closes the pressurization side communication valve 72 and the negative pressure side communication valve 80 corresponding to the printing unit 2 that is not purged, thereby connecting the printing unit 2 that is not purged and the pressure applying unit 3. Disconnect. Thereby, even in the inkjet printing apparatus 1 in which the pressure applying unit 3 is common to all the printing units 2, purging can be omitted in the printing unit 2 that does not require purging. As a result, ink waste can be suppressed.

  Further, the control unit 6 closes the input-side opening / closing valve 53 and the output-side opening / closing valve 58 corresponding to the head module 16 that is not purged in the inkjet head 11 of the printing unit 2 that is purged, thereby removing the head that is not purged. The ink flow into the module 16 is blocked. Thus, even if the printing unit 2 to be purged has a head module 16 that is not purged, the purge can be omitted for each head module 16. As a result, waste of ink can be further suppressed.

  In the above embodiment, the purge end condition is that the pressures of the pressurization tank 21 and the negative pressure tank 22 reach the specified pressure, but the purge end condition is not limited to this.

  For example, the purge end condition may be that the elapsed time from the activation of the air pump 87 has reached a specified time.

  In this case, a specified time may be set according to the number of head modules 16 to be purged in all the printing units 2. Specifically, the specified time can be shortened as the number of head modules 16 to be purged decreases.

  Here, as described above, after the air pump 87 is started, the pressures in the pressure tank 21 and the negative pressure tank 22 of the printing unit 2 to be purged gradually increase. Then, when the discharge of ink from the nozzles of the purge target head module 16 starts, the rate of increase in pressure in the pressurized tank 21 and the negative pressure tank 22 decreases. The smaller the number of head modules 16 to be purged, the smaller the degree of decrease in the rate of increase in pressure in the pressurized tank 21 and the negative pressure tank 22. For this reason, the fewer the head modules 16 to be purged, the shorter the time required to discharge a predetermined amount of ink from each head module 16. Therefore, waste of ink can be suppressed by setting a specified time according to the number of head modules 16 to be purged.

  Further, a liquid level sensor for detecting the liquid level height of the pressurizing tank 21 and the negative pressure tank 22 is provided, and the liquid level height of the pressurizing tank 21 and the negative pressure tank 22 in each printing unit 2 to be purged is set. The purge end condition may be that it has been lowered to a specified height.

  Further, in this case, a specified height corresponding to the number of purge target head modules 16 may be set for each purge target printing unit 2. Specifically, in each printing unit 2 to be purged, the specified height can be increased as the number of purge target head modules 16 decreases.

  In the printing unit 2 to be purged, the smaller the number of head modules 16 to be purged, the smaller the total amount of ink necessary for discharging a predetermined amount of ink from each head module 16. Therefore, waste of ink can be suppressed by setting a specified height corresponding to the number of head modules 16 to be purged.

  In the above-described embodiment, the configuration in which the circulation path 23 includes the input-side on-off valve 53 and the output-side on-off valve 58 and the pressure applying unit 3 includes the pressurization-side communication valve 72 and the negative-pressure side communication valve 80 has been described. The side open / close valve 53, the output side open / close valve 58, the pressurization side communication valve 72, and the negative pressure side communication valve 80 may be omitted. In this case, in the operation at the time of purging, steps S1, S2, S10, and S11 in the flowchart of FIG. 6 are omitted, and purging is performed in all the head modules 16 of all the printing units 2.

  Further, the input side on / off valve 53 and the output side on / off valve 58 may be provided, and the pressurization side communication valve 72 and the negative pressure side communication valve 80 may be omitted. In this case, in the printing unit 2 that does not have the purge-target head module 16 (the printing unit 2 that is not purged), the input-side opening / closing valves 53 and the output-side opening / closing valves 58 corresponding to all the head modules 16 may be closed.

  The pressurization side communication valve 72 and the negative pressure side communication valve 80 may be provided, and the input side on / off valve 53 and the output side on / off valve 58 may be omitted. In this case, in the printing unit 2 to be purged, purging is performed in all the head modules 16. Even in this case, purging of the printing unit 2 that does not require purging can be omitted, and waste of ink can be suppressed.

  Although the case where the inkjet head 11 includes a plurality of head modules 16 has been described in the above embodiment, the inkjet head may include a single member that covers the print width in the main scanning direction.

  In the above embodiment, the inkjet printing apparatus 1 having the four printing units 2 has been described, but the number of printing units 2 is not limited to this.

  The present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiments. For example, some components may be deleted from all the components shown in the embodiment.

DESCRIPTION OF SYMBOLS 1 Inkjet printing apparatus 2 Printing part 3 Pressure application part 4 Conveyance part 5 Operation panel 6 Control part 11 Inkjet head 12 Ink circulation part 13 Ink supply part 21 Pressurization tank 22 Negative pressure tank 23 Circulation path 24 Ink pump 41-43 Ink circulation Pipe 44 Distributor 45 Collector 51, 56 Ink bath 52 Input pipe 53 Input side on / off valve 57 Output pipe 58 Output side on / off valve 71 Pressurization common air chamber 72 Pressurization side communication valve 73 Pressurization side communication pipe 74 Pressurization side air release valve 75 Pressurization side atmosphere release pipe 76 Pressurization side pressure adjustment valve 77 Pressurization side pressure adjustment pipe 78 Pressurization side pressure sensor 79 Negative pressure common air chamber 80 Negative pressure side communication valve 81 Negative pressure side communication pipe 82 Negative pressure side atmosphere release valve 83 Negative pressure side atmosphere release Pipe 84 Negative pressure side pressure adjustment valve 85 Negative pressure side pressure adjustment pipe 86 Negative pressure side pressure sensor 87 Air pump 88 Negative Side pressurizing switching valve 89 pump pipe 90 switching valve atmosphere communicating pipe 91 pressure side switching valve connection pipe 92 the suction side switching valve connection pipe 93 junction pipe 101 main controller 102 mechanical controller

Claims (5)

An inkjet head having a nozzle for ejecting ink; a pressurized tank for storing ink to be supplied to the inkjet head; a negative pressure tank for receiving ink not consumed by the inkjet head; and the pressurized tank, the inkjet head, and the A printing unit having a circulation path for circulating ink between the negative pressure tank and
A pressure applying unit that applies positive pressure to the pressure tank, and selectively applies negative pressure and positive pressure to the negative pressure tank;
Purging is performed by discharging the ink from the nozzles of the inkjet head by controlling the pressure applying unit to apply a positive pressure to the pressure tank and the negative pressure tank. A control unit that terminates the purge when the termination condition is satisfied,
The inkjet head has a plurality of head modules,
The purge end condition is that the liquid level height of the pressurized tank and the negative pressure tank has dropped to a specified height,
The ink jet printing apparatus, wherein the control unit sets the specified height according to the number of the head modules to be purged at the time of purging. A plurality of the printing unit,
The purge end condition is that the liquid level heights of the pressurization tank and the negative pressure tank in the respective printing units to be purged are lowered to the specified height,
2. The inkjet printing apparatus according to claim 1, wherein the control unit sets the specified height in accordance with the number of the head modules to be purged for each of the printing units to be purged during the purge. An inkjet head having a nozzle for ejecting ink; a pressurized tank for storing ink to be supplied to the inkjet head; a negative pressure tank for receiving ink not consumed by the inkjet head; and the pressurized tank, the inkjet head, and the A plurality of printing units each having a circulation path for circulating ink between the negative pressure tanks;
A pressure applying unit that applies positive pressure to the pressure tank, and selectively applies negative pressure and positive pressure to the negative pressure tank;
Purging is performed by discharging the ink from the nozzles of the inkjet head by controlling the pressure applying unit to apply a positive pressure to the pressure tank and the negative pressure tank. A control unit that terminates the purge when the termination condition is satisfied,
The inkjet head has a plurality of head modules,
The purge end condition is that an elapsed time from the start of the pressure applying unit for applying a positive pressure to the pressurized tank and the negative pressure tank has reached a specified time,
Wherein, at the time of purging, all of the printing unit, wherein the to Louis inkjet printing apparatus that sets the predetermined time in accordance with the number of the head module be purged in. The pressure applying unit is common to all the printing units, and has a cutting unit that individually cuts the connection with each printing unit,
Wherein, at the time of purging, ink jet printing device according the connection between the printing portion of the outer be purged and the pressure-applying portion to claim 2 or 3, characterized in that cut by the cutting unit. The circulation path has an ink blocking unit that individually blocks the inflow of ink to the head modules during purging,
5. The ink jet printing apparatus according to claim 1, wherein the control unit blocks the inflow of ink into the head module that is not purged by the ink blocking unit during the purge. .