JP2017065088A - Ink jet printing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet printing device in which damage to a nozzle surface of an ink jet head can be reduced.SOLUTION: An ink jet printing device 1 comprises: ink jet heads 4A, 4B which have nozzles for ejecting ink; an air pump which causes ink to be forcibly discharged from the nozzles of the ink jet heads 4A, 4B; a wiper for wiping the nozzle surface in which the nozzles of the ink jet heads 4A, 4B are opened; and a control unit 9 which performs the cleaning operation for causing the air pump to discharge the ink from the nozzles and wiping the nozzle surface by the wiper. The control unit 9 adjusts an ink amount to be discharged from the nozzles by the air pump on the basis of the sheet type used in the printing operation performed during the cleaning operation.SELECTED DRAWING: Figure 1

Description

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

  In the ink jet printing apparatus, paper dust generated from paper may adhere to the nozzle surface of the ink jet head. When paper dust accumulates on the nozzle surface, ejection failure such as disturbance in the ejection direction of ink from the nozzle and non-ejection may occur. In order to reduce such discharge defects, the inkjet printing apparatus performs cleaning of the inkjet head.

  As one of the cleaning operations for the inkjet head, a series of operations for forcibly discharging ink from the nozzles of the inkjet head, that is, purging, and then wiping the nozzle surface with a wiper are known (for example, patents). Reference 1). As a result, paper dust or the like on the nozzle surface is removed by the wiper together with the ink discharged from the nozzle and adhered to the nozzle surface.

JP 2011-68092 A

  After the above-described cleaning operation, paper dust removed from the nozzle surface may remain in the wiper. If the next cleaning operation is performed in this state, the nozzle surface may be damaged by paper dust adhering to the wiper.

  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 reducing damage to the nozzle surface of an ink jet head.

  In order to achieve the above object, an ink jet printing apparatus according to the present invention is characterized by an ink jet head having a nozzle for ejecting ink, a purge means for forcibly discharging ink from the nozzle of the ink jet head, and the ink jet head. A wiper for wiping the nozzle surface where the nozzle is open, and a control for discharging the ink from the nozzle by the purge means to attach the ink to the nozzle surface and wiping the nozzle surface with the wiper And the control means is to adjust the amount of ink discharged from the nozzle by the purge means based on the type of printing medium used in the printing operation performed during the cleaning operation.

  According to the characteristics of the ink jet printing apparatus according to the present invention, the control unit adjusts the amount of ink discharged from the nozzle by the purge unit based on the type of the printing medium used in the printing operation performed between the cleaning operations. Thereby, paper dust remaining on the wiper after the cleaning operation can be reduced. As a result, it is possible to reduce damage to the nozzle surface due to paper dust remaining in the wiper during the cleaning operation.

It is a block diagram which shows the structure of the inkjet printing apparatus which concerns on embodiment. FIG. 2 is a schematic configuration diagram of a paper feeding unit, a belt platen unit, and an ink jet head of the ink jet printing apparatus shown in FIG. 1. It is a top view of the inkjet head and belt platen part of the inkjet printing apparatus shown in FIG. It is a schematic block diagram of the head module of the inkjet head of the inkjet printing apparatus shown in FIG. It is a schematic block diagram of the ink circulation part of the inkjet printing apparatus shown in FIG. 1, an ink replenishment part, and a pressure generation part. It is a top view of the maintenance part of the inkjet printing apparatus shown in FIG. FIG. 7 is a partially enlarged perspective view of the maintenance unit shown in FIG. 6. It is sectional drawing along the AA line of FIG. 2 is a flowchart for explaining the operation of the inkjet printing apparatus shown in FIG. 1. It is a figure which shows the state which has a belt platen part and a maintenance part in a standby position. It is a figure which shows the state which has a belt platen part in a standby position, and a maintenance part exists in a retracted position. It is a figure which shows the state which a belt platen part exists in a printing position, and a maintenance part exists in a retracted position. It is explanatory drawing of liquid level maintenance control. It is explanatory drawing of pressure control. It is a flowchart for demonstrating cleaning operation | movement. It is a figure which shows the state which has a belt platen part and a maintenance part in a cleaning position. It is a figure which shows the state which the ink adhered to the nozzle surface by purge. It is explanatory drawing of a wipe operation.

  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 schematic configuration diagram of a paper feeding unit, a belt platen unit, and an inkjet head of the inkjet printing apparatus shown in FIG. FIG. 3 is a plan view of the ink jet head and the belt platen. FIG. 4 is a schematic configuration diagram of a head module of the inkjet head. FIG. 5 is a schematic configuration diagram of an ink circulation unit, an ink supply unit, and a pressure generation unit of the inkjet printing apparatus shown in FIG. 6 is a plan view of a maintenance unit of the inkjet printing apparatus shown in FIG. FIG. 7 is a partially enlarged perspective view of the maintenance unit. FIG. 8 is a cross-sectional view taken along the line AA in FIG.

  In the following description, the direction orthogonal to the paper surface of FIG. 2 is the front-rear direction, and the front surface direction is the front. In addition, the top, bottom, left, and right of the paper surface in FIG. Further, a path indicated by a thick line in FIG. In the following description, upstream and downstream mean upstream and downstream in the transport path R, respectively.

  As shown in FIG. 1, an ink jet printing apparatus 1 according to the present embodiment includes a paper feeding unit 2, a belt platen unit 3, ink jet heads 4A and 4B, ink circulation units 5A to 5D, and an ink supply unit 6A. To 6D, a pressure generation unit 7, a maintenance unit 8, and a control unit (corresponding to control means in claims) 9. In addition, the alphabetic suffixes in the reference numerals of the inkjet heads 4A and 4B, the ink circulation units 5A to 5D, and the ink supply units 6A to 6D may be omitted and may be collectively described.

  The paper feeding unit 2 feeds the paper P to the belt platen unit 3. The paper feed unit 2 includes an external paper feed stand 11, an external paper feed roller 12, a plurality of internal paper feed stands 13, a plurality of pairs of internal paper feed rollers 14, a plurality of pairs of internal paper feed transport rollers 15, A registration roller 16.

  The external paper feed tray 11 is for loading paper P used for printing. The external paper feed tray 11 is partly exposed outside the casing (not shown) of the inkjet printing apparatus 1.

  The external paper feed roller 12 takes out the paper P one by one from the external paper feed tray 11 and conveys it toward the registration rollers 16 along the conveyance path R. The external paper feed roller 12 is rotationally driven by a motor (not shown).

  The internal paper feed tray 13 is for loading paper P used for printing. The internal paper feed tray 13 is disposed inside a housing (not shown) of the inkjet printing apparatus 1.

  The internal paper feed roller 14 takes out the paper P one by one from the internal paper feed tray 13 and sends it out to the transport path R. The internal paper feed roller 14 is rotationally driven by a motor (not shown).

  The internal paper feed conveyance roller 15 conveys the paper P taken out from the internal paper feed tray 13 toward the registration roller 16. The internal paper feeding / conveying roller 15 is disposed along a conveyance path R between the internal paper feeding roller 14 and the registration roller 16. The internal paper feed roller 15 is rotationally driven by a motor (not shown).

  The registration roller 16 temporarily stops the sheet P conveyed from the external sheet feeding roller 12 or the internal sheet feeding conveyance roller 15 and then conveys the sheet P toward the belt platen unit 3. The registration roller 16 is disposed on the downstream side of the external paper feed roller 12 and the internal paper feed conveyance roller 15. The registration roller 16 is rotationally driven by a motor (not shown).

  The belt platen unit 3 conveys the sheet P fed from the sheet feeding unit 2 while holding the sheet P on the belt. The belt platen unit 3 is disposed on the downstream side of the registration roller 16. The belt platen unit 3 is driven by a drive motor (not shown). Further, the belt platen unit 3 is configured to be movable up and down by a lifting motor (not shown). As a result, the belt platen unit 3 can be disposed at a printing position, which is the position of the belt platen unit 3 shown in FIG. 2, a standby position described later (see FIG. 10), and a cleaning position described later (see FIG. 16). ing.

  The inkjet heads 4 </ b> A and 4 </ b> B print images by ejecting ink onto the paper P conveyed by the belt platen unit 3. The inkjet heads 4 </ b> A and 4 </ b> B are disposed above the belt platen unit 3. The ink jet heads 4A and 4B each have six head modules 17 as shown in FIG.

  In the inkjet head 4, the head modules 17 are arranged in a staggered manner along the main scanning direction (front-rear direction) orthogonal to the transport direction (left-right direction) of the paper P. That is, in the inkjet head 4, six head modules 17 arranged along the front-rear direction are alternately shifted in the left-right direction.

  The head module 17 discharges two colors of ink. As shown in FIG. 4, the head module 17 includes two ink chambers 18U and 18D and two nozzle rows 19U and 19D. Here, FIG. 4 is a view of the head module 17 as viewed from below. In addition, the alphabetic suffixes in the reference numerals of the ink chambers 18U and 18D and the nozzle rows 19U and 19D may be omitted and collectively described.

  The ink chamber 18 stores ink. The ink chambers 18U and 18D are arranged in parallel in the conveyance direction (left-right direction) of the paper P. Ink is supplied to the ink chamber 18 by the ink circulation unit 5. Ink of different colors is supplied to the ink chambers 18U and 18D. A piezo element (not shown) is disposed in the ink chamber 18. By driving the piezo element, ink is ejected from a nozzle 20 described later.

  The nozzle row 19 includes a plurality of nozzles 20 that eject ink. The nozzle 20 opens in the nozzle surface 17 a that is the lower surface of the head module 17. The nozzles 20 in the upstream nozzle row 19U discharge ink in the upstream ink chamber 18U, and the nozzles 20 in the downstream nozzle row 19D discharge ink in the downstream ink chamber 18D. In each nozzle row 19U, 19D, the plurality of nozzles 20 are arranged at equal intervals at a predetermined pitch along the front-rear direction. The nozzle rows 19U and 19D are arranged in parallel in the conveyance direction (left-right direction) of the paper P. Further, the nozzles 20 in the nozzle row 19U and the nozzles 20 in the nozzle row 19D are arranged so as to be shifted by a half pitch in the front-rear direction.

  The ink circulation units 5A to 5D supply ink to the inkjet heads 4A and 4B while circulating the ink. The ink circulation units 5A and 5B supply ink to the ink chambers 18U and 18D of the inkjet head 4A, respectively. The ink circulation units 5C and 5D supply ink to the ink chambers 18U and 18D of the inkjet head 4B, respectively. As shown in FIG. 5, the ink circulation unit 5 includes a pressurized tank 21, a distributor 22, an aggregator 23, a negative pressure tank 24, an ink pump 25, an ink temperature adjustment unit 26, and an ink temperature sensor. 27 and ink circulation pipes 28 to 30.

  The pressurized tank 21 stores ink to be supplied to the inkjet head 4. The ink in the pressurized tank 21 is supplied to the inkjet head 4 through the ink circulation pipe 28 and the distributor 22. An air layer 31 is formed in the pressurized tank 21 on the ink surface. The pressurized tank 21 is communicated with a later-described pressurized common air chamber 51 via a later-described pressurized-side communication pipe 52. The pressurized tank 21 is disposed at a lower position (downward) than the inkjet head 4.

  The pressurized tank 21 is provided with a float member 32, a pressurized tank liquid level sensor 33, and an ink filter 34.

  The float member 32 has a support shaft (not shown) in the pressurized tank 21 so as to rotate according to the liquid level until the liquid level of the ink in the pressurized tank 21 reaches the reference height. ) Is pivotally supported at one end. A magnet (not shown) is provided at the other end of the float member 32.

  The pressurized tank liquid level sensor 33 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 33 is a magnetic sensor, and detects the magnet of the float member 32 when the liquid level has reached the reference height. The pressurized tank liquid level sensor 33 outputs a signal indicating “ON” when the magnet of the float member 32 is detected, that is, when the liquid level in the pressurized tank 21 is equal to or higher than the reference height. To do. The pressurized tank liquid level sensor 33 outputs a signal indicating “OFF” when the magnet of the float member 32 is not detected, that is, when the liquid level in the pressurized tank 21 is less than the reference height. To do.

  The ink filter 34 removes dust and the like in the ink.

  The distributor 22 distributes the ink supplied from the pressurized tank 21 via the ink circulation pipe 28 to each head module 17 of the inkjet head 4.

  The aggregator 23 collects ink not consumed by the inkjet head 4 from each head module 17. The ink collected by the collector 23 flows to the negative pressure tank 24 through the ink circulation pipe 29.

  The negative pressure tank 24 receives the ink that has not been consumed by the inkjet head 4 from the collector 23 and stores the ink. Further, the negative pressure tank 24 stores ink replenished from an ink cartridge 46 of the ink replenishing unit 6 described later. In the negative pressure tank 24, an air layer 36 is formed on the liquid surface of the ink. The negative pressure tank 24 communicates with a negative pressure common air chamber 58 described later via a negative pressure side communication pipe 59 described later. The negative pressure tank 24 is disposed at the same height as the pressurized tank 21.

  The negative pressure tank 24 is provided with a float member 37 and a negative pressure tank liquid level sensor 38.

  The float member 37 and the negative pressure tank liquid level sensor 38 are the same as the float member 32 and the pressurized tank liquid level sensor 33 of the pressurized tank 21, respectively. The negative pressure tank liquid level sensor 38 outputs a signal indicating “ON” when the magnet of the float member 37 is detected, that is, when the liquid level in the negative pressure tank 24 is equal to or higher than the reference height. To do. The negative pressure tank liquid level sensor 38 outputs a signal indicating “OFF” when the magnet of the float member 37 is not detected, that is, when the liquid level in the negative pressure tank 24 is less than the reference height. To do. The reference height is below the upper end of the negative pressure tank 24.

  The ink pump 25 sends ink from the negative pressure tank 24 to the pressure tank 21. The ink pump 25 is provided in the middle of the ink circulation pipe 30.

  The ink temperature adjustment unit 26 adjusts the ink temperature in the ink circulation unit 5. The ink temperature adjustment unit 26 is provided in the middle of the ink circulation pipe 28. The ink temperature adjustment unit 26 includes a heater 41, a heater temperature sensor 42, a heat sink 43, and a cooling fan 44.

  The heater 41 heats the ink in the ink circulation pipe 28. The heater temperature sensor 42 detects the temperature of the heater 41. The heat sink 43 cools the ink in the ink circulation pipe 28 by heat radiation. The cooling fan 44 sends cooling air to the heat sink 43.

  The ink temperature sensor 27 detects the temperature of the ink in the ink circulation unit 5. The ink temperature sensor 27 is provided in the middle of the ink circulation pipe 28.

  The ink circulation pipe 28 connects the pressurized tank 21 and the distributor 22. A part of the ink circulation pipe 28 is branched into a part passing through the heater 41 and a part passing through the heat sink 43. Ink flows from the pressurized tank 21 toward the distributor 22 through the ink circulation pipe 28. The ink circulation pipe 29 connects the collector 23 and the negative pressure tank 24. Ink flows through the ink circulation pipe 29 from the collector 23 toward the negative pressure tank 24. The ink circulation pipe 30 connects the negative pressure tank 24 and the pressurization tank 21. Ink flows through the ink circulation pipe 30 from the negative pressure tank 24 toward the pressure tank 21. The ink circulation pipes 28 to 30, the distributor 22 and the aggregator 23 constitute a circulation path for circulating ink among the pressurized tank 21, the inkjet head 4, and the negative pressure tank 24.

  The ink supply units 6A to 6D supply ink to the ink circulation units 5A to 5D, respectively. The ink supply unit 6 includes an ink cartridge 46, an ink supply valve 47, and an ink supply pipe 48.

  The ink cartridge 46 contains ink used for printing by the inkjet head 4. The ink in the ink cartridge 46 is supplied to the negative pressure tank 24 of the ink circulation unit 5 through the ink supply pipe 48.

  The ink supply valve 47 opens and closes the ink flow path in the ink supply pipe 48. When ink is supplied to the negative pressure tank 24, the ink supply valve 47 is opened.

  The ink supply pipe 48 connects the ink cartridge 46 and the negative pressure tank 24. Ink flows from the ink cartridge 46 toward the negative pressure tank 24 through the ink supply pipe 48.

  The pressure generation unit 7 generates pressure for ink circulation in the pressurized tank 21 and the negative pressure tank 24 of each ink circulation unit 5. The pressure generation unit 7 includes a pressurization common air chamber 51, four pressurization side communication pipes 52, a pressurization side atmosphere release valve 53, a pressurization side atmosphere release pipe 54, a pressurization side pressure adjustment valve 55, and a pressurization side Pressure adjustment pipe 56, pressure side pressure sensor 57, negative pressure common air chamber 58, four negative pressure side communication pipes 59, negative pressure side atmosphere release valve 60, negative pressure side atmosphere release pipe 61, and negative pressure side pressure Adjusting valve 62, negative pressure side pressure adjusting pipe 63, negative pressure side pressure sensor 64, air pump (corresponding to the purging means in claims) 65, air pump pipe 66, junction pipe 67, air filter 68, overflow A pan 69.

  The pressurized common air chamber 51 is an air chamber for equalizing the pressure of the pressure tank 21 of each ink circulation unit 5. The pressurized common air chamber 51 is communicated with the air layer 31 of the pressurized tank 21 of the ink circulating units 5A to 5D via the four pressurized communication tubes 52. As a result, the pressurized tanks 21 of the ink circulation units 5 </ b> A to 5 </ b> D are communicated with each other via the pressurized common air chamber 51 and the pressurized side communication pipe 52.

  The pressurization side communication pipe 52 communicates the pressurization common air chamber 51 and the air layer 31 of the pressurization tank 21. The four pressure side communication pipes 52 are provided corresponding to the ink circulation portions 5A to 5D one by one. One end of the pressurization side communication pipe 52 is connected to the pressurization common air chamber 51, and the other end is connected to the air layer 31 of the pressurization tank 21.

  In order to switch the pressurizing 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 pressurizing common air chamber 51, The flow path of the air in the pressurization side air release pipe 54 is opened and closed. The pressurization side air release valve 53 is provided in the middle of the pressurization side air release pipe 54.

  The pressurization side air release pipe 54 forms an air flow path for opening the pressurization tank 21 to the atmosphere via the pressurization common air chamber 51. One end of the pressurization-side air release pipe 54 is connected to the pressurization common air chamber 51, and the other end is connected to the junction pipe 67.

  The pressurization side pressure adjustment valve 55 opens and closes the air flow path in the pressurization side pressure adjustment pipe 56 in order to adjust the pressure of the pressurization common air chamber 51 and the pressurization tank 21. The pressure side pressure adjustment valve 55 is provided in the middle of the pressure side pressure adjustment pipe 56.

  The pressure side pressure adjustment pipe 56 forms an air flow path for adjusting the pressure of the pressure common air chamber 51 and the pressure tank 21. The pressurization side pressure adjustment pipe 56 is a pipe having a larger flow resistance than the pressurization side atmosphere release pipe 54, the negative pressure side atmosphere release pipe 61, and the junction pipe 67. Specifically, the pressurization side pressure adjustment pipe 56 is formed of a pipe that is thinner than the pressurization side atmosphere release pipe 54, the negative pressure side atmosphere release pipe 61, and the merge pipe 67. One end of the pressurizing side pressure adjusting pipe 56 is connected to the pressurizing common air chamber 51, and the other end is connected to the junction pipe 67.

  The pressure side pressure sensor 57 detects the pressure in the pressure common air chamber 51. The pressure in the pressurized common air chamber 51 is equal to the pressure in the pressurized tank 21 of the ink circulation units 5A to 5D. This is because the pressurized common air chamber 51 and the air layer 31 of the pressurized tank 21 of the ink circulation units 5A to 5D communicate with each other.

  The negative pressure common air chamber 58 is an air chamber for equalizing the pressure in the negative pressure tank 24 of each ink circulation unit 5. The negative pressure common air chamber 58 is communicated with the air layer 36 of the negative pressure tank 24 of the ink circulation units 5A to 5D via four negative pressure side communication pipes 59. As a result, the negative pressure tanks 24 of the ink circulation units 5 </ b> A to 5 </ b> D communicate with each other via the negative pressure common air chamber 58 and the negative pressure side communication pipe 59.

  The negative pressure side communication pipe 59 communicates the negative pressure common air chamber 58 and the air layer 36 of the negative pressure tank 24. The four negative pressure side communication pipes 59 are provided corresponding to the ink circulation portions 5A to 5D one by one. The negative pressure side communication pipe 59 has one end connected to the negative pressure common air chamber 58 and the other end connected to the air layer 36 of the negative pressure tank 24.

  The negative pressure side air release valve 60 opens and closes the air flow path in the negative pressure side air release pipe 61 in order to switch the negative pressure tank 24 between a sealed state and an air open state via the negative pressure common air chamber 58. To do. The negative pressure side atmosphere release valve 60 is provided in the middle of the negative pressure side atmosphere release pipe 61.

  The negative pressure side air release pipe 61 forms an air flow path for opening the negative pressure tank 24 to the atmosphere via the negative pressure common air chamber 58. The negative pressure side atmospheric open pipe 61 has one end connected to the negative pressure common air chamber 58 and the other end connected to the junction pipe 67.

  The negative pressure side pressure adjustment valve 62 opens and closes the air flow path in the negative pressure side pressure adjustment pipe 63 in order to adjust the pressure in the negative pressure common air chamber 58 and the negative pressure tank 24. The negative pressure side pressure adjustment valve 62 is provided in the middle of the negative pressure side pressure adjustment pipe 63.

  The negative pressure side pressure adjustment pipe 63 forms an air flow path for adjusting the pressure of the negative pressure common air chamber 58 and the negative pressure tank 24. The negative pressure side pressure adjustment pipe 63 is a pipe having a larger flow resistance than the pressurization side atmosphere release pipe 54, the negative pressure side atmosphere release pipe 61, and the junction pipe 67. Specifically, the negative pressure side pressure adjustment pipe 63 is formed of a pipe that is thinner than the pressurization side atmosphere release pipe 54, the negative pressure side atmosphere release pipe 61, and the junction pipe 67. The negative pressure side pressure adjustment pipe 63 has one end connected to the negative pressure common air chamber 58 and the other end connected to the junction pipe 67.

  The negative pressure side pressure sensor 64 detects the pressure in the negative pressure common air chamber 58. The pressure in the negative pressure common air chamber 58 is equal to the pressure in the negative pressure tank 24 of the ink circulation units 5A to 5D. This is because the negative pressure common air chamber 58 and the air layer 36 of the negative pressure tank 24 of the ink circulation units 5A to 5D communicate with each other.

  The air pump 65 sucks air from the negative pressure tanks 24 of the ink circulation units 5A to 5D through the negative pressure common air chamber 58, and pressurizes the ink circulation units 5A to 5D through the pressurized common air chamber 51. Send air to 21. The air pump 65 is provided in the middle of the air pump pipe 66.

  The air pump pipe 66 forms a flow path for air sent from the negative pressure common air chamber 58 to the pressurized common air chamber 51 by the air pump 65. One end of the air pump pipe 66 is connected to the pressurized common air chamber 51, and the other end is connected to the negative pressure common air chamber 58.

  The merge pipe 67 has one end connected to the overflow pan 69 and the other end (upper end) communicating with the atmosphere via the air filter 68. The end of the merge pipe 67 on the overflow pan 69 side is normally closed by an overflow ball 71 described later. Connected to the junction pipe 67 are a pressurization-side air release pipe 54, a pressurization-side pressure adjustment pipe 56, a negative pressure-side air release pipe 61, and a negative pressure-side pressure adjustment pipe 63. Thereby, the pressurization side air release pipe 54, the pressurization side pressure adjustment pipe 56, the negative pressure side air release pipe 61, and the negative pressure side pressure adjustment pipe 63 are communicated with the atmosphere.

  The air filter 68 prevents entry of dust or the like in the air into the junction pipe 67. The air filter 68 is installed at the upper end of the junction pipe 67.

  The overflow pan 69 overflows ink from the pressurized tank 21 and the negative pressure tank 24 due to, for example, an abnormality in the ink supply valve 47, and further overflows from the pressurized common air chamber 51 and the negative pressure common air chamber 58. Then, the ink flowing through the junction pipe 67 is received.

  The overflow pan 69 is provided with an overflow ball 71. The overflow ball 71 closes the end of the merging pipe 67 that opens to the bottom surface of the overflow pan 69 when there is no ink in the overflow pan 69, and prevents inflow of external air into the merging pipe 67. When ink flows from the junction pipe 67 to the overflow pan 69, the overflow ball 71 rises and ink can flow into the overflow pan 69.

  The overflow pan 69 is provided with a float member 72 and an overflow liquid level sensor 73. The float member 72 and the overflow liquid level sensor 73 are the same as the float member 32 and the pressurized tank liquid level sensor 33 of the pressurized tank 21, respectively.

  The overflow pan 69 is connected to a waste liquid tank (not shown). When the overflow liquid level sensor 73 is turned on, ink is discharged to the waste liquid tank.

  The maintenance unit 8 cleans the inkjet head 4. The maintenance unit 8 is configured to be movable between a retracted position, which is the position of the maintenance unit 8 shown in FIG. 2, and a standby position described later (see FIG. 10) by a motor (not shown). The maintenance unit 8 is disposed at a cleaning position (see FIG. 16) described later during cleaning.

  As shown in FIGS. 6 to 8, the maintenance unit 8 includes an ink receiving member 76, a wiper unit 77, and a wiper driving unit 78. 6 to 8 are diagrams in a state where the maintenance unit 8 is disposed at the cleaning position.

  The ink receiving member 76 receives ink that is removed from the nozzle surface 17a of the head module 17 by the cleaning and falls. The ink receiving member 76 is formed in a rectangular parallelepiped shape. A concave portion 76 a for receiving ink or the like is formed in the central portion of the ink receiving member 76. The recess 76a is formed so as to be larger than a region where the head modules 17 of the inkjet heads 4A and 4B are disposed in a plan view. The upper side of the ink receiving member 76 is opened.

  The wiper unit 77 wipes the nozzle surface 17a of the head module 17 and removes ink and the like on the nozzle surface 17a. The wiper unit 77 includes a mounting base 79 and four wipers 80.

  The mounting base 79 is to which the wiper 80 is attached. The mounting base 79 is formed in a rectangular parallelepiped shape. The mounting base 79 is formed with a pair of screw holes 79a and 79b. The screw gears 84a and 84b, which will be described later, are respectively passed through and screwed into the screw holes 79a and 79b. Due to the rotation of the screw gears 84a and 84b, the mounting base 79 moves in the front-rear direction.

  The wiper 80 is a member that wipes the nozzle surface 17 a of the head module 17. The wiper 80 is made of a material such as elastically deformable rubber and is formed in a rectangular plate shape. The lower end portion of the wiper 80 is fixed to the front surface of the mounting base 79 by a fixture (not shown). As shown in FIG. 6, the four wipers 80 are arranged so as to be positioned on the extended lines of the respective rows along the front-rear direction of the head module 17 in the staggered arrangement in a state where the maintenance unit 8 is arranged at the cleaning position. Has been.

  In a state where the maintenance unit 8 is disposed at the cleaning position, the upper end of the wiper 80 is at a position higher than the nozzle surface 17 a of the head module 17. When the wiper 80 is moved in the front-rear direction and comes into contact with the head module 17, the wiper 80 is elastically deformed and the upper end portion slides (wipes) the nozzle surface 17 a.

  The wiper drive unit 78 moves the wiper unit 77 in the front-rear direction. The wiper drive unit 78 includes a wiper motor 81, a drive belt 82, a pair of drive pulleys 83a and 83b, and a pair of screw gears 84a and 84b.

  The wiper motor 81 generates a rotational driving force for moving the wiper unit 77. The wiper motor 81 is disposed outside the rear wall of the ink receiving member 76. The wiper motor 81 has an output gear 81a. The output gear 81 a transmits the rotational driving force of the wiper motor 81 to the driving belt 82. The output gear 81 a is disposed at the center of the drive belt 82.

  The driving belt 82 transmits the rotational driving force transmitted from the wiper motor 81 to the driving pulleys 83a and 83b. The drive belt 82 is stretched over the drive pulley 83a and the drive pulley 83b.

  The pair of drive pulleys 83a and 83b transmit the rotational driving force transmitted from the drive belt 82 to the screw gears 84a and 84b. The drive pulley 83a and the drive pulley 83b are disposed at the same height with a predetermined interval in the left-right direction. The drive pulleys 83 a and 83 b are rotatably supported on the rear wall of the ink receiving member 76.

  The screw gears 84a and 84b move the wiper unit 77 in the front-rear direction by the rotational driving force transmitted from the drive pulleys 83a and 83b. The screw gears 84a and 84b extend over substantially the entire length of the recess 76a in the front-rear direction. The rear ends of the screw gears 84a and 84b are fixed to drive pulleys 83a and 83b, respectively. The front ends of the screw gears 84 a and 84 b are rotatably supported on the front wall of the ink receiving member 76. Thereby, the screw gears 84a and 84b rotate together with the drive pulleys 83a and 83b, respectively.

  The control unit 9 controls the operation of each unit of the inkjet printing apparatus 1. The control unit 9 includes a CPU, a RAM, a ROM, a hard disk, and the like.

  The control unit 9 executes a cleaning operation for cleaning the nozzle surface 17a of the head module 17 of the inkjet head 4 for each specified number of printed sheets. The control unit 9 adjusts the purge ink amount that is the amount of ink discharged from the nozzles 20 of the head module 17 in the purge during the cleaning operation, based on the paper type used in the printing operation performed during the cleaning operation.

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

  FIG. 9 is a flowchart for explaining the operation of the inkjet printing apparatus 1. The process of the flowchart of FIG. 9 is started when a print job is input to the inkjet printing apparatus 1.

  In step S1 of FIG. 9, the control unit 9 moves the maintenance unit 8 to the retracted position and moves the belt platen unit 3 to the printing position.

  Here, in the standby state before starting the printing operation, the belt platen unit 3 and the maintenance unit 8 are respectively arranged at the standby positions shown in FIG. The standby position of the belt platen unit 3 is below the inkjet heads 4A and 4B and above the printing position that is the position of the belt platen unit 3 shown in FIG. The standby position of the maintenance unit 8 is a position on the belt platen unit 3 at the standby position.

  From the state shown in FIG. 10, first, the control unit 9 moves the maintenance unit 8 to the retracted position as shown in FIG. Next, as shown in FIG. 12, the control unit 9 raises the belt platen unit 3 and moves it to the printing position. As a result, the maintenance unit 8 is retracted to the retracted position, and the belt platen unit 3 is disposed at the printing position.

  Returning to FIG. 9, following step S <b> 1, in step S <b> 2, the control unit 9 starts the liquid level maintenance control. In the liquid level maintenance control, the ink pump 25 and the ink corresponding to the liquid level height of the pressurized tank 21 and the negative pressure tank 24 for maintaining the liquid level of the pressurized tank 21 and the negative pressure tank 24 at the reference height. This is control of the supply valve 47.

  Specifically, as shown in FIG. 13, when both the pressurized tank liquid level sensor 33 and the negative pressure tank liquid level sensor 38 are on, the control unit 9 turns off the ink pump 25 and the ink supply valve 47. Close. Similarly, when the pressurized tank liquid level sensor 33 is on and the negative pressure tank liquid level sensor 38 is off, the control unit 9 turns off the ink pump 25 and closes the ink supply valve 47.

  When the pressurized tank liquid level sensor 33 is off and the negative pressure tank liquid level sensor 38 is on, the control unit 9 turns on the ink pump 25 and closes the ink supply valve 47.

  When both the pressurized tank liquid level sensor 33 and the negative pressure tank liquid level sensor 38 are off, the control unit 9 turns off the ink pump 25 and opens the ink supply valve 47.

  Returning to FIG. 9, following Step S <b> 2, in Step S <b> 3, the control unit 9 closes the pressurization-side atmosphere release valve 53 and the negative-pressure side atmosphere release valve 60. As a result, the pressurized tank 21 is sealed through the pressurized common air chamber 51, and the negative pressure tank 24 is sealed through the negative pressure common air chamber 58.

  Here, while the inkjet printing apparatus 1 is on standby, the pressurization side air release valve 53 and the negative pressure side air release valve 60 are opened, and the pressurization side pressure adjustment valve 55 and the negative pressure side pressure adjustment valve 62 are closed. The liquid level maintenance control may be started after the pressurization side air release valve 53 and the negative pressure side air release valve 60 are closed in step S3.

  Next, in step S4, the control unit 9 starts pressure control. The pressure control generates the set pressures Pks and Pfs in the pressurization tank 21 and the negative pressure tank 24 for ink circulation, and maintains the air pump 65, the pressurization side pressure adjustment valve 55, and the negative pressure side. This is control of the pressure regulating valve 62. Here, the set pressures Pks and Pfs are set in advance as pressure values for setting the nozzle pressure of the inkjet head 4 to an appropriate value while circulating ink at a predetermined flow rate. The set pressure Pks of the pressurizing tank 21 is a positive pressure, and the set pressure Pfs of the negative pressure tank 24 is a negative pressure.

  The control of the air pump 65, the pressure side pressure adjustment valve 55, and the negative pressure side pressure adjustment valve 62 in the pressure control is performed according to the detection value Pk of the pressure side pressure sensor 57 and the detection value Pf of the negative pressure side pressure sensor 64.

  Specifically, as shown in FIG. 14, in the case of Pk <Pks and | Pf | <| Pfs |, the control unit 9 closes the pressurization side pressure adjustment valve 55 and the negative pressure side pressure adjustment valve 62, and the air pump 65 Turn on. As a result, air is sent from the sealed negative pressure tank 24 to the pressurized tank 21 by the air pump 65, whereby the pressure of the negative pressure tank 24 decreases and the pressure of the pressurized tank 21 increases.

  In the case of Pk ≧ Pks and | Pf | <| Pfs |, the control unit 9 opens the pressurization side pressure adjustment valve 55 and closes the negative pressure side pressure adjustment valve 62. Further, the control unit 9 turns on the air pump 65. As a result, the air flows out of the pressurized tank 21 via the pressurized side pressure adjusting pipe 56, so that the pressure of the pressurized tank 21 decreases. Further, the air is sucked from the sealed negative pressure tank 24 by the air pump 65, so that the pressure of the negative pressure tank 24 is lowered.

  When Pk <Pks and | Pf | ≧ | Pfs |, the control unit 9 closes the pressurization side pressure adjustment valve 55 and opens the negative pressure side pressure adjustment valve 62. Further, the control unit 9 turns on the air pump 65. Thereby, the pressure of the pressurization tank 21 rises by sending air by air pump 65 to the pressurization tank 21 of a sealed state. Further, the air flows into the negative pressure tank 24 through the negative pressure side pressure adjustment pipe 63, so that the pressure in the negative pressure tank 24 increases.

  In the case of Pk ≧ Pks and | Pf | ≧ | Pfs |, the control unit 9 opens the pressurization side pressure adjustment valve 55 and the negative pressure side pressure adjustment valve 62 and turns off the air pump 65. As a result, the air flows out of the pressurized tank 21 via the pressurized side pressure adjusting pipe 56, so that the pressure of the pressurized tank 21 decreases. Further, the air flows into the negative pressure tank 24 through the negative pressure side pressure adjustment pipe 63, so that the pressure in the negative pressure tank 24 increases.

  Here, at the start of pressure control, the pressure in the pressurized tank 21 and the negative pressure tank 24 is atmospheric pressure. For this reason, Pk <Pks and | Pf | <| Pfs |. Therefore, the control part 9 will start the drive of the air pump 65, if pressure control is started. By driving the air pump 65, air is sent from the negative pressure common air chamber 58 to the pressurized common air chamber 51. As a result, the negative pressure common air chamber 58 and the negative pressure tank 24 are depressurized, and the pressurized common air chamber 51 and the pressurized tank 21 are pressurized, so that ink flows from the pressurized tank 21 toward the inkjet head 4. Start flowing.

  After the start of the pressure control, in step S5 of FIG. 9, the control unit 9 applies the pressure tank 21 and the negative pressure tank 24 based on the detection value Pk of the pressure side pressure sensor 57 and the detection value Pf of the negative pressure side pressure sensor 64. It is determined whether or not the set pressures Pks and Pfs are generated. When it is determined that the set pressure Pks, Pfs is not generated in at least one of the pressurized tank 21 and the negative pressure tank 24 (step S5: NO), the control unit 9 repeats step S5.

  When it is determined that the set pressures Pks and Pfs are generated in the pressurization tank 21 and the negative pressure tank 24 (step S5: YES), in step S6, the control unit 9 starts executing the print job. Specifically, the control unit 9 sequentially feeds paper P for the number of prints in the print job from the paper feeding unit 2 and ejects ink from the inkjet head 4 while transporting the paper P by the belt platen unit 3. Control to print an image on the paper P. Here, the control unit 9 controls the paper feed unit 2 to feed the paper P of the paper type set in the print job from either the external paper feed tray 11 or the plurality of internal paper feed trays 13.

  During execution of the print job, ink is supplied from the pressurized tank 21 to the inkjet head 4, and ink that has not been consumed by the inkjet head 4 is collected in the negative pressure tank 24. When the pressurized tank liquid level sensor 33 is turned off and the negative pressure tank liquid level sensor 38 is turned on, the ink pump 25 sends ink from the negative pressure tank 24 to the pressurized tank 21 by the liquid level maintenance control. In this way, printing is performed while the ink is circulated.

  Further, the control unit 9 adjusts the ink temperature by controlling the ink temperature adjusting unit 26 so that the temperature detected by the ink temperature sensor 27 is maintained within the appropriate temperature range.

  After starting the execution of the print job, in step S7, the control unit 9 determines whether or not the cumulative number of printed sheets after the previous cleaning operation has reached the specified number of printed sheets. The specified number of printed sheets is preset as the number of printed sheets during the cleaning operation.

  When it is determined that the cumulative number of printed sheets after the previous cleaning operation has reached the specified number of printed sheets (step S7: YES), in step S8, the control unit 9 determines a new sheet P by the sheet feeding unit 2 and the belt platen unit 3. Stop feeding and transporting.

  Next, in step S9, the control unit 9 ends the pressure control. Here, when the air pump 65 is being driven, the control unit 9 stops it. Further, when at least one of the pressurizing side pressure adjusting valve 55 and the negative pressure side pressure adjusting valve 62 is opened, the control unit 9 closes the opened one.

  Next, in step S <b> 10, the control unit 9 opens the pressurization side atmosphere release valve 53 and the negative pressure side atmosphere release valve 60. As a result, the pressurized tank 21 is opened to the atmosphere via the pressurized common air chamber 51, and the negative pressure tank 24 is opened to the atmosphere via the negative pressure common air chamber 58.

  Next, in step S11, the control unit 9 ends the liquid level maintenance control.

  Next, in step S12, the controller 9 performs a cleaning operation. The details of the cleaning operation will be described later.

  Next, in step S13, the control unit 9 determines whether or not the print job is finished. Here, the control unit 9 determines that the print job is finished when printing for the number of printed sheets in the print job is completed when the cumulative number of printed sheets after the previous cleaning operation reaches the specified number of printed sheets.

  If it is determined that the print job has not ended (step S13: NO), the control unit 9 returns to step S2 and restarts the print job. If it is determined that the print job has ended (step S13: YES), the control unit 9 ends the series of operations.

  If it is determined in step S7 that the cumulative number of printed sheets after the previous cleaning operation has not reached the specified number of printed sheets (step S7: NO), in step S14, the control unit 9 determines whether or not the print job has ended. to decide. If it is determined that the print job has not ended (step S14: NO), the control unit 9 returns to step S7.

  When it is determined that the print job has been completed (step S14: YES), in step S15, the control unit 9 stops the paper feeding unit 2 and the belt platen unit 3 to finish the paper feeding and conveyance of the paper P. Thereafter, the control unit 9 proceeds to step S16. The process of steps S16 to S18 is the same as the process of steps S9 to S11 described above.

  Subsequent to step S18, in step S19, the control unit 9 moves the belt platen unit 3 and the maintenance unit 8 to the standby position. Specifically, the control unit 9 first lowers the belt platen unit 3 and moves it from the printing position to the standby position. Next, the control unit 9 moves the maintenance unit 8 from the retracted position to the standby position. Thereby, a series of operation | movement is complete | finished and the inkjet printing apparatus 1 will be in a standby state.

  Next, the cleaning operation performed in step S12 of FIG. 9 described above will be described.

  The cleaning operation is an operation in which ink is forcibly discharged from the nozzles 20 of the inkjet head 4 by purging to adhere the ink to the nozzle surface 17a, and then the wiper 80 wipes the nozzle surface 17a. In the inkjet printing apparatus 1, normal cleaning and strong cleaning can be selectively performed. Strong cleaning is cleaning performed with a larger amount of purge ink than normal cleaning.

  FIG. 15 is a flowchart for explaining the cleaning operation.

  First, in step S21 of FIG. 15, the control unit 9 moves the belt platen unit 3 and the maintenance unit 8 to the cleaning position.

  Here, in the state before starting the cleaning operation, as shown in FIG. 12, the belt platen unit 3 is arranged at the printing position, and the maintenance unit 8 is arranged at the retracted position. From this state, as shown in FIG. 11, the control unit 9 lowers the belt platen unit 3 and moves it to the standby position. Next, as shown in FIG. 10, the control unit 9 moves the maintenance unit 8 to the standby position. And the control part 9 raises the belt platen part 3, and moves the belt platen part 3 and the maintenance part 8 to the cleaning position shown in FIG. The cleaning position of the belt platen unit 3 is above the standby position and below the printing position. The cleaning position of the maintenance unit 8 is a position on the belt platen unit 3 at the cleaning position.

  Returning to FIG. 15, following step S <b> 21, in step S <b> 22, the control unit 9 closes the pressurization-side atmospheric release valve 53. As a result, the pressurized tank 21 is sealed through the pressurized common air chamber 51. Here, the negative pressure side air release valve 60 is opened. The pressurizing side pressure adjusting valve 55 and the negative pressure side pressure adjusting valve 62 are closed.

  Next, in step S23, the control unit 9 activates the air pump 65. Thereby, the pressurized tank 21 starts to be pressurized.

  Next, in step S24, the control unit 9 determines whether or not strong cleaning is to be executed among normal cleaning and strong cleaning.

  Here, when the paper type used in the printing operation after the previous cleaning operation includes the paper type to be subjected to the strong cleaning, the control unit 9 performs the strong cleaning. to decide. The paper type to be subjected to the strong cleaning is designated in advance as a paper type that easily generates paper dust. For example, the paper type to be subjected to strong cleaning is thick paper, rough paper, or the like.

  If it is determined that strong cleaning is to be performed (step S24: YES), in step S25, the control unit 9 determines that the pressure in the pressurized tank 21 is strong cleaning based on the detected value Pk of the pressure side pressure sensor 57. It is determined whether or not the required pressure Ps has been reached.

  When it is determined that the pressure in the pressurized tank 21 has not reached the pressure Ps for strong cleaning (step S25: NO), the control unit 9 repeats step S25. When it is determined that the pressure in the pressurized tank 21 has reached the strong cleaning pressure Ps (step S25: YES), the controller 9 proceeds to step S27.

  When it is determined that normal cleaning is to be executed (step S24: NO), in step S26, the control unit 9 determines that the pressure in the pressurized tank 21 is normal cleaning based on the detection value Pf of the negative pressure side pressure sensor 64. It is determined whether or not the required pressure Pn has been reached. Here, the pressure Pn for normal cleaning is smaller than the pressure Ps for strong cleaning.

  When it is determined that the pressure in the pressurized tank 21 has not reached the pressure Pn for normal cleaning (step S26: NO), the control unit 9 repeats step S26. When it is determined that the pressure in the pressurized tank 21 has reached the pressure Pn for normal cleaning (step S26: YES), the control unit 9 proceeds to step S27.

  In step S27, the control unit 9 stops the air pump 65. Thereby, the pressure rise in the pressurized tank 21 stops.

  Next, in step S28, the control unit 9 determines whether or not a predetermined time has elapsed since the air pump 65 was stopped. When it is determined that the predetermined time has not elapsed since the air pump 65 was stopped (step S28: NO), the control unit 9 repeats step S28.

  When it is determined that a predetermined time has elapsed since the air pump 65 was stopped (step S28: YES), the control unit 9 opens the pressurization-side atmosphere release valve 53 in step S29. As a result, the pressurized tank 21 is opened to the atmosphere.

  By the processing in steps S22 to S29 described above, the pressure tank 21 is pressurized by the air pump 65 in a sealed state, whereby ink is pushed out from the nozzles 20 of the inkjet head 4. That is, purge is performed. Since the strong cleaning pressure Ps is larger than the normal cleaning pressure Pn, the amount of purge ink in the strong cleaning is larger than that in the normal cleaning.

  By purging, as shown in FIG. 17, the ink 91 pushed out from the nozzle 20 is attached to the nozzle surface 17 a. In strong cleaning, the amount of purge ink is larger than in normal cleaning, so the amount of ink adhering to the nozzle surface 17a increases.

  Returning to FIG. 15, following step S <b> 29, in step S <b> 30, the control unit 9 performs a wipe operation by the wiper 80. Specifically, the control unit 9 drives the wiper motor 81 to start moving the wiper unit 77 forward. Here, when the maintenance unit 8 moves to the cleaning position, the wiper unit 77 is in the initial position behind the rearmost head module 17.

  When the wiper unit 77 moves forward and the wiper 80 contacts the head module 17, the wiper 80 is pressed by the head module 17 and elastically deformed. When the wiper unit 77 further moves forward in this state, as shown in FIG. 18, the upper end portion of the wiper 80 slides (wipes) the nozzle surface 17a. As a result, paper dust and the like on the nozzle surface 17a are removed together with the ink 91 adhering to the nozzle surface 17a. When the wiper 80 moves further forward than the frontmost head module 17, the control unit 9 stops the wiper motor 81. As a result, the wiper unit 77 stops. Thereby, the wiping operation is completed.

  Here, since the amount of ink adhering to the nozzle surface 17a is larger in the strong cleaning than in the normal cleaning, the paper dust or the like adhering to the wiper 80 during the wiping operation easily flows down with the ink.

  Returning to FIG. 15, following step S <b> 30, in step S <b> 31, the control unit 9 causes the inkjet heads 4 </ b> A and 4 </ b> B to perform a flushing operation. Specifically, the control unit 9 drives the piezo element of each head module 17 to eject ink from each nozzle 20. Thus, even when color mixing occurs due to the entry of other color inks corresponding to the nozzles 20 of the adjacent nozzle row 19 into the nozzle 20 during the wiping operation, the color mixing can be eliminated.

  Next, in step S32, the control unit 9 determines whether or not to resume the print job after the cleaning operation.

  If it is determined that the print job is to be resumed (step S32: YES), in step S33, the control unit 9 moves the maintenance unit 8 to the retracted position and moves the belt platen unit 3 to the printing position. Specifically, the control unit 9 first lowers the belt platen unit 3 and moves the belt platen unit 3 and the maintenance unit 8 from the cleaning position to the standby position. Further, the control unit 9 drives the wiper motor 81 to move the wiper unit 77 to the initial position. Next, the control unit 9 moves the maintenance unit 8 from the standby position to the retracted position. Then, the control unit 9 raises the belt platen unit 3 and moves it from the standby position to the printing position. As a result, the cleaning operation ends.

  When it is determined that the print job is not resumed (step S32: NO), in step S34, the control unit 9 lowers the belt platen unit 3 and moves the belt platen unit 3 and the maintenance unit 8 from the cleaning position to the standby position. Move. Further, the control unit 9 drives the wiper motor 81 to move the wiper unit 77 to the initial position. As a result, the cleaning operation ends.

  As described above, in the inkjet printing apparatus 1, the control unit 9 adjusts the purge ink amount during the cleaning operation based on the paper type used in the printing operation performed between the cleaning operations. Specifically, the control unit 9 includes a paper type designated in advance as a paper type that is likely to generate paper dust among the used paper types in the printing operation after the previous cleaning operation. If yes, perform strong cleaning. In other cases, the control unit 9 performs normal cleaning.

  In strong cleaning, the amount of purge ink is larger than that in normal cleaning, and the amount of ink adhering to the nozzle surface 17a is larger. Therefore, paper dust and the like adhering to the wiper 80 during the wiping operation easily flows off together with the ink. For this reason, it is possible to reduce the paper dust remaining on the wiper 80 after the cleaning operation when a large amount of paper dust adheres to the nozzle surface 17a by a printing operation using a paper type that is likely to generate paper dust. Thereby, damage to the nozzle surface 17a due to paper dust remaining on the wiper 80 during the cleaning operation can be reduced.

  In the above-described embodiment, the purge ink amount is adjusted in two steps. However, the purge ink amount may be adjusted in three or more steps according to the paper type used in the printing operation.

  Further, the purge ink amount may be adjusted based on the number of printed sheets for each paper type used in the printing operation.

  In the embodiment described above, paper is used as the print medium, but the print medium is not limited to paper. Since the degree of dust generation varies depending on the type of printing medium other than paper, the amount of purge ink during the cleaning operation may be adjusted based on the type of printing medium used in the printing operation between the cleaning operations.

  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 Paper feed part 3 Belt platen part 4,4A, 4B Inkjet head 5,5A-5D Ink circulation part 6,6A-6D Ink replenishment part 7 Pressure generation part 8 Maintenance part 9 Control part 17 Head module 17a Nozzle Surface 20 Nozzle 21 Pressure tank 22 Distributor 23 Aggregator 24 Negative pressure tank 25 Ink pump 28-30 Ink circulation pipe 46 Ink cartridge 47 Ink supply valve 48 Ink supply pipe 51 Pressure common air chamber 52 Pressure side communication pipe 53 Addition Pressure side atmosphere release valve 54 Pressure side atmosphere release pipe 55 Pressure side pressure adjustment valve 56 Pressure side pressure adjustment pipe 57 Pressure side pressure sensor 58 Negative pressure common air chamber 59 Negative pressure side communication pipe 60 Negative pressure side atmosphere release valve 61 Negative pressure side atmosphere release pipe 61 62 Negative pressure side pressure regulating valve 63 Negative pressure side pressure regulating pipe 64 Negative pressure side pressure sensor 65 Air pump 66 Air pump pipe 67 Merge pipe 76 Ink receiving member 77 Wiper unit 78 Wiper drive unit 80 Wiper

Claims (1)

An inkjet head having a nozzle for ejecting ink;
Purge means for forcibly discharging ink from the nozzles of the inkjet head;
A wiper for wiping a nozzle surface where the nozzle of the inkjet head opens;
Control means for discharging the ink from the nozzle by the purge means to attach the ink to the nozzle surface and executing a cleaning operation for wiping the nozzle surface with the wiper;
The ink jet printing apparatus, wherein the control unit adjusts the amount of ink discharged from the nozzle by the purge unit based on a type of a printing medium used in a printing operation performed between cleaning operations.