JP5673201B2 - Liquid ejection device - Google Patents

Description

  The present invention relates to a liquid ejection device that ejects liquid from ejection ports.

  In an inkjet head that ejects ink droplets from a plurality of ejection openings, a predetermined path for circulating the ink is formed between the ink tank and the head flow path in the inkjet head, and the ink in the ink tank is discharged using a pump. A technique is known that removes foreign matters such as bubbles remaining in the head flow path by sending the pressure to the head flow path and circulating the ink in the circulation path (see, for example, Patent Document 1).

JP 2009-29111 A

  However, in the technique described in Patent Document 1, ink is delivered to the head flow path at a predetermined pressure. However, depending on the shape and arrangement of the head flow path, foreign matters such as bubbles staying in the head flow path May not be carried on the ink flow and pushed downstream of the flow path. Increasing the flow rate of ink delivered to the head channel can push away foreign matter in the head channel, but the pressure generated in the head channel increases and exceeds the pressure resistance of the ink meniscus formed at the ejection port. Then, there arises a problem that ink leaks from the ejection port.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid ejection device capable of improving bubble discharge without increasing waste liquid from ejection ports.

The liquid discharge apparatus according to the present invention includes an inflow port through which a liquid flows in, an outflow port through which the liquid flows out, an internal flow path that connects the inflow port and the outflow port, and a plurality of discharge ports for discharging the liquid. A liquid discharge head having a plurality of individual liquid flow paths branched from the internal flow path to reach the plurality of discharge ports, a first tank for storing liquid supplied to the liquid discharge head, and the first A first supply passage communicating with one tank and the inlet, a first discharge passage communicating with the outlet, and a liquid stored in the first tank via the first supply passage. Liquid supply means for supplying to the internal flow path, a sealed state in which the discharge spaces facing the plurality of discharge ports are sealed from the external space, and an unsealed state in which the discharge space is open to the external space Cap means capable of taking a stopped state and supplied to the discharge space A second tank for storing wet air, communicates with said discharge space and the second tank, a second supply passage that to supply humidified air stored in the second tank to the discharge space, the discharge is communicating the spatial second tank, wherein the humidified air supplied to the discharge space and the second discharge passage for discharging into the second tank, the humidified air that has been stored in the second tank, the second Humidified air supply means for supplying the discharge space to the discharge space via a supply flow path, the discharge space to be in the sealed state, and humid air in the second tank to the second supply flow path, the discharge space, and the second The cap means and the humidified air supply means are controlled so as to perform a humidifying operation for transferring in order of the discharge flow path, and the liquid in the first tank is supplied to the first supply flow path, the internal flow path, and the first discharge flow. Purge movement to transfer in order of flow path And a control means for controlling the liquid supply means so as to perform. When the control unit performs the purge operation, the pressure difference between the pressure on the liquid side and the pressure on the gas side sandwiching the liquid meniscus formed at the discharge port does not destroy the liquid meniscus. The humidified air supply means and the liquid supply means are controlled so that they are balanced below the pressure resistance of the liquid meniscus, which is the maximum pressure.

According to the liquid ejection device of the present invention, when performing the purge operation, the liquid meniscus is reduced even if the flow rate of the liquid is increased to increase the flow rate of the liquid in order to effectively remove the bubbles in the internal flow path. Since the pressure difference between the pressure on the sandwiched liquid side and the pressure on the gas side is less than the pressure resistance of the liquid meniscus is generated in the discharge space, it prevents the liquid meniscus from breaking and liquid leaking from the discharge port It becomes possible to do. That is, it is possible to improve the bubble discharge performance by the purge operation without increasing the waste liquid from the discharge port. In the humidification operation, the humidified air in the second tank is circulated to the discharge space, and the air in the discharge space is circulated to the second tank.

1 is a schematic plan view of an ink jet printer according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the head and ink supply unit shown in FIG. 1. FIG. 3 is a plan view of the head main body shown in FIG. 2. It is an enlarged view of the area | region enclosed with the dashed-dotted line shown in FIG. It is a fragmentary sectional view of the inkjet head shown in FIG. It is a graph which shows the operating characteristic of the purge pump shown in FIG. It is the schematic which shows the head holder and humidified air supply mechanism which are included in the printer of FIG. It is a fragmentary sectional view which shows the area | region VIII enclosed with the dashed-dotted line of FIG. 7, and is a figure which shows the condition which has a cap in a separation position. It is a functional block diagram of the control apparatus shown in FIG. It is a flowchart which shows the control content of the purge operation | movement which the control apparatus of a printer performs. It is a flowchart which shows the control content of the thickening prevention operation | movement which the control apparatus of a printer performs. It is sectional drawing which shows the modification of an ink supply unit. It is the schematic which shows the modification of a humidified air supply mechanism.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  The inkjet printer 101 includes a paper feeding unit that stores and supplies paper P, a transport unit that transports the paper P, an image forming unit that forms an image on the paper P, and a paper discharge unit that stores the paper P after image formation. Arranged along the paper transport path. Among these, the transport unit is mainly composed of the transport unit 20. The image forming unit controls the operation of four inkjet heads 1 (hereinafter referred to as head 1), four ink supply units 10, a humidification supply mechanism 50 used for humidification maintenance (see FIG. 7), and the entire inkjet printer 101. A control device 16 is included. When performing image formation, ink is ejected from the head 1 onto the paper P transported by the transport unit 20.

  As shown in FIG. 1, the transport unit 20 includes two belt rollers 6 and 7 and an endless transport belt 8 that is stretched between the rollers 6 and 7. The belt roller 7 is a driving roller, and is rotated by a driving force from a conveyance motor (not shown). When the belt roller 7 rotates, the conveyor belt 8 runs. The belt roller 6 is a driven roller and rotates as the transport belt 8 travels. The paper P placed on the surface 8a of the transport belt 8 is transported from the top to the bottom in FIG. In the present embodiment, the sub-scanning direction is a direction parallel to the conveyance direction of the paper P by the conveyance unit 20, and the main scanning direction is a direction orthogonal to the sub-scanning direction and along the horizontal plane. is there.

  An ink removing member 22 is provided at a position facing the belt roller 7. The ink removing member 22 has a base portion 23 and an ink absorbing member 24 fixed to the base portion 23. The ink absorbing member 24 is made of a porous material such as sponge. The length of the ink absorbing member 24 in the main scanning direction is substantially the same as the width of the transport belt 8. In addition, the ink absorbing member 24 is disposed in contact with the surface 8 a of the conveyance belt 8 so as to face the lower portion of the belt roller 7 with respect to the vertical direction. Thereby, foreign matters such as ink adhering to the surface 8 a are removed by running the transport belt 8.

  The four heads 1 are line-type heads that extend along the main scanning direction, and eject black, magenta, cyan, and yellow ink droplets onto the paper P, respectively. These heads 1 are supported by a carriage 4 via a head holder 3 and are arranged parallel to each other and adjacent to each other in the sub-scanning direction. The head holder 3 is a frame-like member fixed to the head 1, and four head holders 3 are supported on the carriage 4. The lower surface of each head 1 is a discharge surface 2a in which a plurality of discharge ports 108 are opened (see FIG. 5). The carriage 4 holds the head 1 so that a predetermined gap suitable for recording is formed between the ejection surface 2 a of the head 1 and the surface 8 a of the transport belt 8. The head holder 3 is provided with an annular cap 40 in the vicinity of the lower end of the head 1. The cap 40 includes the head 1 in a plan view and surrounds the ejection surface 2a. The configuration, operation, function, and the like of the cap 40 will be described in detail later.

  Each ink supply unit 10 is connected to the vicinity of the left end in FIG. The ink supply unit 10 supplies ink to the connected head 1.

  Next, the control device 16 will be described. The control device 16 controls the operation of each part of the printer 101 and controls the operation of the entire printer 101. For example, the control device 16 controls the image forming operation based on image data supplied from an external device (such as a PC connected to the printer 101). Specifically, the control device 16 controls the transport operation of the paper P, the ink discharge operation synchronized with the transport of the paper P, and the like. The control device 1p also controls a maintenance operation for the head 1.

  The control device 16 controls each operation of the paper feed unit (not shown), the transport unit 20, and the paper discharge unit (not shown) based on the recording command received from the external device. The paper feeding unit sends the paper P from the paper feeding unit to the transport unit 20. The transport unit 20 transports the paper P in the sub-scanning direction (paper P transport direction). When the paper P passes directly below each head 1, ink is sequentially ejected from each ejection surface 2 a under the control of the control device 16, and a color image is formed on the paper P. The ink ejection operation is performed based on a detection signal from the paper sensor 32 that detects the leading edge of the paper P. The paper sensor 32 is provided upstream of the head 1 along the transport direction. Then, the paper P on which the image is formed is discharged to the paper discharge unit by the paper discharge unit.

  The control device 16 makes preparations related to recovery / maintenance of ink ejection characteristics of the head 1 and recording by a maintenance operation. The maintenance operation includes a purge or flushing operation, a cleaning operation of the ejection surface 2a by wiping, an ink thickening prevention operation by capping or humidification, and the like.

  The purge operation includes bubble purge and discharge port purge, and a purge pump 86 (described later) is driven. In the bubble purge, bubbles (foreign matter) are discharged from the internal flow path of the reservoir unit 71 (described later). In the ejection port purge, ink is forcibly discharged from all the ejection ports 108. In the flushing operation, the actuator is driven and ink is ejected from all the ejection ports 108. Ink ejection is performed based on flushing data (data different from image data). In wiping, the discharge surface 2a is wiped by a wiper (plate-like elastic member). The wiping is performed after the ink discharging operation (discharge port purge and flushing), and residual ink and foreign matter on the discharge surface 2a are removed. In the capping, as shown in FIG. 7, the discharge space (the space facing the discharge surface 2a (discharge port 108)) S1 is isolated from the external space S2 by the cap 40. In the humidification operation (humidification maintenance), as shown in FIG. 7, humidified air is supplied to the isolated discharge space S1. In the present embodiment, a humidification operation is performed when bubble purge is performed, and the pressure difference between the ink side and the gas side of the ink meniscus formed at the ejection port 108 is the maximum pressure at which the ink meniscus is not destroyed. It is adjusted to be less than the meniscus pressure resistance.

  In the bubble purge, ink is circulated through the reservoir unit 71, and bubbles in the circulation channel are removed. At this time, ink is not discharged from the ejection port 108. In the present embodiment, the discharge port purge is performed following the bubble purge. Ink discharge operations such as discharge port purging and flushing involve a cleaning operation, and the discharge characteristics of the discharge port 108 are restored, and the discharge surface 108 is cleaned. The capping suppresses drying of the meniscus, and the humidification further suppresses drying. The bubble purge and ink discharge operation is performed, for example, immediately after the printer 101 is turned on, after a paper jam (clogging) in the conveyance path, after image formation that has continued for a predetermined time or after non-ejection. The ink discharge operation (particularly flushing) immediately after the power is turned on is a preparatory operation for recording. The ink thickening prevention operation is performed, for example, when the printer 1 is stopped or stopped.

  Next, the head 1 will be described in detail with reference to FIG. As shown in FIG. 2, the head 1 has a reservoir unit 71 and a head body 2.

  The reservoir unit 71 is a substantially rectangular parallelepiped flow path forming member fixed to the upper surface of the head body 2. The reservoir unit 71 supplies ink to the head body 2. In the reservoir unit 71, an inflow port 72a and an outflow port 73a are arranged on the lower surface, and an internal flow path is formed inside. The internal flow path includes an ink inflow path 72, an exhaust path 73, and ten ink outflow paths 75. The inflow port 72 a is one end of the ink inflow channel 72, and the outflow port 73 a is one end of the exhaust channel 73. Inside, the ink inflow channel 72 is connected to the exhaust channel 73, and the ink outflow channel 75 is branched from the vicinity of the connecting portion on the ink inflow channel 72 side. The ink outflow channel 75 communicates with the head body 2. In FIG. 2, only one ink outflow channel 75 appears.

  Ink from the ink supply unit 10 is supplied to the ink inflow channel 72 via the inflow port 72a. The ink inflow channel 72 functions as an ink reservoir that temporarily stores ink. A hole 72 b is formed in the upper wall of the ink inflow channel 72. The hole 72b is sealed with a flexible resin film 76 for damper. Since the resin film 76 is displaced according to the fluctuation of the ink pressure, the pressure fluctuation in the ink inflow channel 72 is suppressed. During normal printing, the resin film 76 is slightly convex toward the ink inflow channel 72. A plate-shaped regulating member 77 is fixed to the upper outer wall surface of the reservoir unit 71 so as to cover the resin film 76, and the free deformation of the resin film 76 is regulated. Thus, when the ink pressure in the ink inflow channel 72 becomes abnormally high, the resin film 76 is prevented from being excessively displaced and damaged. The restriction member 77 is formed with an air communication hole 77a, and the ease of deformation of the resin film 76 is not impaired.

  The ink outflow channel 75 communicates with the ink inflow channel 72 through the filter 75a at one end and is connected to the ink supply port 105b on the upper surface of the channel unit 9 at the other end (see FIG. 3). During normal printing, the ink from the ink supply unit 10 passes through the ink outflow channel 75 and is supplied to the channel unit 9 from the ink supply port 105b.

  The exhaust passage 73 is connected to the ink inflow passage 72 on the upstream side of the filter 75a, and is connected to the ink supply unit 10 through the outflow port 73a. When ink flows into the exhaust passage 73, the ink flows into the exhaust passage 73 across the upstream surface of the filter 75a.

  A hole 73 b is formed in the lower wall of the exhaust passage 73. The hole 73b is sealed with a flexible resin film 78 for damper. A regulating member 79 is fixed to the lower outer wall surface of the reservoir unit 71. Here, the resin film 78 and the regulating member 79 correspond to the resin film 76 and the regulating member 77 and have the same function and arrangement relationship. In a bubble purge operation related to a maintenance operation described later, ink from the ink supply unit 10 flows into the ink inflow channel 72 through the inflow port 72a and is supplied from the outflow port 73a through the exhaust channel 73a. Reflux to unit 10.

  Further, the head main body 2 will be described with reference to FIGS. In FIG. 4, for convenience of explanation, the pressure chamber 110, the aperture 112, and the discharge port 108 that are to be drawn by broken lines below the actuator unit 21 are drawn by solid lines.

  The head body 2 includes a flow path unit 9 and four actuator units 21 fixed to the upper surface of the flow path unit 9. In the flow path unit 9, an ink flow path including the pressure chamber 110 is formed. The actuator unit 21 includes a plurality of unimorph actuators corresponding to the pressure chambers 110 and selectively applies ejection energy to the ink in the pressure chambers 110.

  The flow path unit 9 is a laminated body in which nine metal plates 122 to 130 made of stainless steel are laminated. A total of ten ink supply ports 105 b communicating with the ink outflow channel 75 (see FIG. 2) of the reservoir unit 71 are opened on the upper surface of the channel unit 9. As shown in FIGS. 4 and 5, a manifold channel 105 having an ink supply port 105 b as one end and a plurality of sub-manifold channels 105 a branched from the manifold channel 105 are formed inside the channel unit 9. Has been. Furthermore, a plurality of individual ink flow paths 132 are formed in the flow path unit 9 from the outlets of the sub-manifold flow paths 105a to the discharge ports 108 of the discharge surface 2a via the pressure chambers 110. A plurality of discharge ports 108 are arranged in a matrix on the discharge surface 2a.

  The ink flow in the flow path unit 9 will be described. As shown in FIGS. 3 to 5, during normal printing, the ink supplied from the ink outflow channel 75 of the reservoir unit 71 to the ink supply port 105 b flows into the manifold channel 105 (sub-manifold channel 105 a). To do. The ink in the sub-manifold channel 105 a is distributed to each individual ink channel 132 and reaches the ejection port 108 via the aperture 112 and the pressure chamber 110.

  Next, the ink supply unit 10 will be described in detail with reference to FIG. The ink supply unit 10 includes a sub tank (first tank) 80, a supply pump 91, a valve 92, an ink supply pipe 81, a purge pump (liquid supply means) 86, an ink supply pipe (first supply flow path) 82, and a valve (liquid). A shutoff valve) 87 and an ink return pipe (first discharge flow path) 83. The ink supply unit 10 is connected to an ink supply pipe 81, an ink supply pipe 82, and an ink return pipe 83 with a sub tank 80 as a center. The ink supply pipe 81 is provided with a supply pump 91 and a valve 92. The ink tank 90 and the sub tank 80 are connected by the ink supply pipe 81. A purge pump 86 is provided in the ink supply pipe 82. The sub tank 80 and the inflow port 72a are connected by the ink supply pipe 82. Further, the ink return pipe 83 is provided with a valve 87. The sub tank 80 and the outlet 73a are connected by the ink return pipe 83. In this configuration, the valve 87 is an open / close valve capable of blocking the ink flow in the ink return pipe 83.

  The sub tank 80 stores ink supplied to the inkjet head 1. When the ink storage amount decreases, the valve 92 is opened and the supply pump 91 is driven, whereby fresh ink is supplied from the ink tank 90. In addition, an air communication hole 88 is formed in the upper wall of the sub tank 80 to communicate the inside of the sub tank 80 and the atmosphere. As a result, the atmospheric pressure in the sub tank 80 is always atmospheric pressure regardless of the amount of ink stored, and stable ink supply is possible.

  Further, as shown in FIG. 2, the sub tank 80 is arranged such that the liquid level of the ink stored inside is below the ejection surface 2 a in the vertical direction. As a result, a water head difference occurs between the ink meniscus formed in the vicinity of the ejection port 108 and the ink liquid level of the sub tank 80, and the ink side of the ink meniscus has a negative pressure compared to the atmospheric pressure. The negative pressure at this time is adjusted to such an extent that the ink meniscus is not destroyed.

  The ink supply pipe 82 is connected to the inlet 72a of the reservoir unit 71 through a joint 82a. As a result, the ink in the sub tank 80 is supplied to the ink inflow channel 72 of the reservoir unit 71. The purge pump 86 forcibly supplies the ink in the sub tank 80 to the ink inflow channel 72. The purge pump 86 is also a check valve that prevents ink from flowing from the joint 82 a toward the sub tank 80. Even when the purge pump 86 is stopped, the ink in the sub tank 80 can be supplied to the reservoir unit 71 through the ink supply pipe 82.

  In the present embodiment, an electric three-phase diaphragm pump that is a positive displacement pump is used as the purge pump 86. As shown in FIG. 6, the three diaphragms are displaced at different phases, so that the pressure fluctuation during ink delivery is suppressed. The purge pump 86 can control the amount of ink delivered per unit time by changing the power supplied. In the present embodiment, the purge pump 86 is driven in two types of modes with different ink delivery amounts. Here, a mode in which the amount of ink delivered is small is referred to as LO mode, and a mode in which the amount of ink delivered is greater than LO mode is referred to as HI mode. In the LO mode, the amount of ink delivered is small, so the pressure generated in the ink inflow channel 72 is also small. However, the purge pump 86 is set so that the pressure difference at the ink meniscus exceeds the ink meniscus pressure resistance in a state where the valve 87 is open (a state where ink circulates). Further, in the HI mode, the pressure generated in the ink inflow channel 72 becomes larger than in the LO mode.

  Next, the configuration of the head holder 3, the cap 40 attached to the head holder 3, and the joint 51 will be described with reference to FIGS.

  The head holder 3 is a frame-shaped frame made of metal or the like, and supports the side surface of the reservoir unit 71 over the entire circumference. A cap 40 and a pair of joints 51 are attached to the head holder 3. As shown in FIG. 7, the pair of joints 51 are disposed close to the end portions of the corresponding head 1 in the main scanning direction. Specifically, as shown in FIG. 7, the pair of joints 51 includes a left joint 51 having a supply port 51a and a right joint 51 having a discharge port 51b, and sandwiches the reservoir unit 71 in the main scanning direction. Has been placed. In the humidification maintenance, humidified air is supplied from the supply port 51a to the discharge space S1, and air is discharged from the discharge port 51b. Further, as shown in FIG. 7, the supply port 51 a and the discharge port 51 b are arranged at positions away from the discharge surface 2 a toward the reservoir unit 71 with respect to the surface 8 a of the transport belt 8.

  As shown in FIG. 8, the joint 51 includes a rectangular base end portion 51x and a columnar tip end portion 51y extending from the base end portion 51x. The proximal end portion 51x has a larger outer size than the distal end portion 51y. A cylindrical hollow space 51z along the vertical direction is formed in the interior from the base end portion 51x to the tip end portion 51y. The hollow space 51z has a constant cross-sectional size along the vertical direction. The base end portion 51x has the sub-scanning direction as the longitudinal direction, and the width (length) in the longitudinal direction is substantially the same as that of the ejection surface 2a.

  The head holder 3 is formed with a circular through-hole 3a in plan view, and the joint 51 is fixed to the head holder 3 with the tip 51y inserted into the through-hole 3a. The tip 51y is slightly smaller than the through hole 3a, but the gap between them is filled with a sealing material or the like and sealed.

  The cap 40 is a rectangular annular member that surrounds the outer periphery of the head 1 in plan view, and is long in the main scanning direction. As shown in FIG. 8, the cap 40 includes an elastic body 41 supported by the head holder 3 and a movable body 42 that can be moved up and down.

  The elastic body 41 is made of an annular elastic material such as rubber and surrounds the head 1 in a plan view. As shown in FIG. 8, the elastic body 41 includes a base portion 41x, a protruding portion 41a protruding downward from the base portion 41x, a fixing portion 41c fixed to the head holder 3, and a connection for connecting the base portion 41x and the fixing portion 41c. Part 41d is included. Among these, the protrusion part 41a protrudes from the lower surface of the base part 41x, and a cross section is a triangle. The cross section of the fixing portion 41c is T-shaped. The upper end portion of the fixing portion 41c is fixed to the head holder 3 with an adhesive or the like. The fixing portion 41 c is also sandwiched between the head holder 3 and the base end portion 51 x of each joint 51. The connecting portion 41d is curved from the lower end of the fixed portion 41c and extends outward (in a direction away from the ejection surface 2a in plan view), and is connected to the lower end of the base portion 41x. The connecting portion 41d can be deformed as the movable body 42 is raised and lowered. A concave portion 41 b is formed on the upper surface of the base portion 41 x and is fitted to the lower end of the movable body 42.

  The movable body 42 is made of an annular rigid material (for example, stainless steel) and surrounds the outer periphery of the head 1 in a plan view. The movable body 42 is movable relative to the head holder 3 in the vertical direction while being supported by the head holder 3 via the elastic body 41. The movable body 42 is connected to a plurality of gears 43. When the lift motor 44 (see FIG. 9) is driven under the control of the control device 16, the gear 43 rotates and moves up and down. At this time, the base 41x also moves up and down together with the movable body 42. Thereby, the relative position of the front-end | tip 41a1 of the protrusion part 41a and the discharge surface 2a changes to a perpendicular direction. In the present embodiment, the driving force is selectively transmitted from one lifting motor 44 to the plurality of gears 43 for each cap 40.

  As the movable body 42 moves up and down, the protruding portion 41a has a contact position (position shown in FIG. 7) where the tip 41a1 comes into contact with the surface 8a of the conveyor belt 8, and a separation position where the tip 41a1 is separated from the surface 8a (see FIG. The position shown in FIG. At the contact position, the discharge space S1 is in a sealed state sandwiched between the discharge surface 2a and the surface 8a and isolated from the external space S2. Further, at the separation position, the discharge space S1 is in an unsealed state opened to the external space S2. Such a cap 40, a transmission mechanism including a plurality of gears 43, the head holder 3, the elevating motor 44, and the transport belt 8 constitute a cap unit.

  Next, the configuration of the humidified air supply mechanism 50 will be described with reference to FIG.

  As shown in FIG. 7, the humidified air supply mechanism 50 includes a pair of joints 51, tubes 55 and 57, a pump 56, a valve 59, a water temperature sensor 46, a heater 58, a tank 54, and the like. The tube (second supply flow path) 55 includes a main portion 55 a common to the four heads 1 and four branch portions 55 b branched from the main portion 55 a and extending to the joint 51. The pump 56 is provided in the main portion 55a. Similarly to the tube 55, the tube (second discharge flow path) 57 includes a main portion 57 a common to the four heads 1 and four branch portions 57 b branched from the main portion 57 a and extending to the joint 51. In FIG. 7, a connection state between one set of branch portions 55 b and 57 b and one head 1 is shown. In practice, four heads 1 are connected in parallel to one main portion 55a, 57a via branch portions 55b, 57b.

  One end of the tube 55 (the tip of the branch portion 55 b) is fitted to the tip portion 51 y of the left joint 51, and the other end is connected to the tank 54. On the other hand, one end of the tube 57 (the tip of the branching portion 57 b) is fitted to the tip 51 y of the right joint 51, and the other end is connected to the tank 54. Thus, the tubes 55 and 57 make the discharge space S1 and the tank 54 communicate with each other.

  The tank 54 stores water in the lower space, and stores humidified air humidified by the water in the lower space in the upper space. In addition, an air communication hole 53 that communicates the inside of the tank 54 and the atmosphere is formed on the upper wall of the tank 54. The tube 57 communicates with the lower space (underwater) of the tank 54. On the other hand, the tube 55 communicates with the upper space of the tank 54. In addition, a check valve (not shown) is attached to the tube 57 so that water in the tank 54 does not flow into the tube 57, and air flows only in the direction of the white arrow in FIG.

  Further, a water temperature sensor 46 for measuring the temperature of water is installed in the tank 54, and a heater 58 for heating water in the tank 54 is installed in the vicinity of the tank 54 (lower space). During humidification, under the control of the control device 16, the heater 58 is controlled based on the temperature detection result by the water temperature sensor 46, and the humidity of the humidified air is adjusted. In the present embodiment, when the printer 1 is turned on, the humidity of the humidified air is automatically adjusted to a desired humidity. When the amount of water stored in the tank 54 is reduced, water is supplied from a supply tank (not shown).

  The valve 59 is an on-off valve that can block air flow in the tube 57. As a modification, the valve may be an air restriction valve capable of restricting the flow of air in the tube 57 in a stepwise manner. In this case, the flow path resistance of the tube 57 can be increased at the closing timing similar to the valve 59. Furthermore, it becomes possible to increase the flow path resistance step by step, and it becomes easier to balance the pressure on both sides of the ink meniscus.

  In this embodiment, the pump 56 is also an electric three-phase diaphragm pump that is a positive displacement pump, and has the same configuration as the purge pump 86. In other words, the three diaphragms are displaced at different phases, thereby suppressing the pressure fluctuation when the humidified air is sent out. The pump 56 can control the amount of humidified air delivered per unit time to the discharge space S1 by changing the power supplied.

  In the present embodiment, the pump 56 is driven in two types of modes with different humidified air delivery amounts. Here, a mode in which the amount of humidified air delivered is small is referred to as LO mode, and a mode in which the amount of humidified air delivered is greater than LO mode is referred to as HI mode. In the LO mode, the amount of humidified air delivered is small, so the pressure generated in the sealed discharge space S1 is also small. At this time, the pump 56 is set so that the pressure generated in the sealed discharge space S1 is equal to or lower than the ink meniscus pressure resistance when the valve 59 is open. On the other hand, in the HI mode, since the amount of humidified air delivered is large, the pressure generated in the sealed discharge space S1 also increases. In this embodiment, when the purge pump 86 is driven in the LO mode and the pump 56 is driven in the HI mode with the valve 59 closed, the pressure generated in the discharge space S1 and the ink meniscus ink The pressure difference from the pressure generated on the side is set to be equal to or less than the pressure resistance of the ink meniscus.

  In this configuration, when the humidification maintenance for the thickening prevention operation is executed, the pump 56 is driven under the control of the control device 16, and the humidified air in the tank 54 flows along the white arrow in FIG. The humid air in the upper space flows from the tank 54 toward the supply port 51a and is supplied to the discharge space S1. At this time, a negative pressure is generated in the tank 54, and the air in the discharge space S1 is sucked from the discharge port 51b and flows toward the tank 54. The valve 59 is kept open. Further, since the tube 57 communicates with the tank 54 in the water, the humidified air in the tank 54 circulates to the discharge space S1 and the air in the discharge space S1 circulates to the tank 54 in humidification maintenance. On the other hand, when the humidifying operation is executed in the purge operation, the pressure generated in the discharge space S1 becomes larger than that in the humidifying maintenance of the thickening preventing operation as described later.

  Next, the control device 16 will be described with reference to FIG. The control device 16 includes a CPU (Central Processing Unit), a program executed by the CPU and a ROM (Read Only Memory) that stores data used in these programs in a rewritable manner, and temporarily stores data when the program is executed. RAM (Random Access Memory). Each functional unit constituting the control device 16 is constructed by cooperation of these hardware and software in the ROM. The control device 16 controls the entire inkjet printer 101, and includes a transport control unit 141, an image data storage unit 142, a head control unit 143, a purge control unit 144, and a maintenance control unit 145. Yes.

  The transport controller 141 controls the transport motor of the transport unit 20 so that the paper P is transported at a predetermined speed along the transport direction. The image data storage unit 142 stores image data related to an image to be printed on the paper P.

  The head controller 143 supplies the generated ejection drive signal to the actuator unit 21 so that a desired volume of ink droplets based on the image data is ejected from the ejection port 108 at a desired timing during normal printing.

  The purge control unit 144 controls the operation of the purge pump 86 and the valve 87 of each ink supply unit 10 in the purge operation. Specific operation contents will be described later. The purge controller 144 also controls the replenishment pump 91 and the replenishment valve 92 for replenishing ink, but is omitted in FIG.

  The maintenance control unit 145 controls the raising / lowering operation of the cap 40 and the operations of the heater 58, the pump 56, the valve 59, and the like of the humidified air supply mechanism 50 in the humidifying operation. Further, the maintenance control unit 145 controls the transport motor of the transport unit 20 in the ink removing operation for removing the ink ejected on the surface 8a in the ink discharging operation. The maintenance control unit 145 also controls a wiping mechanism (not shown) such as a wiper to wipe off foreign matters such as ink attached to the ejection surface 2a.

  Next, the control content of the purge operation (bubble purge and discharge port purge) executed by the control device 16 will be described with reference to FIG.

  As shown in FIG. 10, the control device 16 first determines whether or not a purge command has been received (F1). Prior to receiving the purge command, the cap 40 is in the spaced position. The pump 56 and the purge pump 86 are stopped, and the valve 59 is open and the valve 87 is closed. Further, the supply pump 91 is also stopped, and the supply valve 92 is closed. Further, the transport unit 20 is also stopped.

  When receiving the purge command (F1: YES), the control device 16 first performs a bubble purge operation for circulating the ink. The maintenance control unit 145 drives the elevating motor 44 to bring the tip 41a1 of each cap 40 into contact with the surface 8a of the transport belt 8 (moving from the separation position to the contact position) (Step 2: F2). As a result, the discharge space S1 formed between the discharge surface 2a and the surface 8a is sealed from the external space S2 (see FIG. 7).

  After step 2, the purge control unit 144 controls the valve 87 to open from the closed state. At this time, the maintenance control unit 145 controls the valve 59 so that the valve 59 is opened to closed (step 3: F3). As a result, the air flow is blocked in the tube 57 (that is, the flow path resistance is increased). On the other hand, ink can be circulated in the ink return pipe 83.

  After step 3, the maintenance control unit 145 controls the pump 56 so that the drive origin of the pump 56 is obtained. At this time, the purge control unit 144 also controls the purge pump 86 so as to obtain the drive origin of the purge pump 86 (step 4: F4). After the origins of the pumps 56 and 86 are set in step 4, the purge control unit 144 and the maintenance control unit 145 simultaneously drive the pumps 56 and 86 (step 5: F5). Thereby, the phases of the diaphragms of the pumps 56 and 86 are aligned, and the pulsation at the time of humidified air supply by the pump 56 and ink supply by the purge pump 86 is aligned. For this reason, the pressure difference between the pressure (pressure on the ink side of the ink meniscus) generated in the internal flow path in the bubble purge operation and the pressure (pressure on the gas side of the ink meniscus) generated in the ejection space S1 is stabilized.

  As a modification, the drive of the pump 56 may be started after the start of the drive of the purge pump 86 so that the phases of the diaphragms of both the pumps 56 and 86 are aligned. In this way, during the bubble purge operation, positive pressure is generated in the internal flow paths (ink inflow flow path 72 and exhaust flow path 73) prior to the discharge space S1. For this reason, it becomes possible to prevent the air in the discharge space S1 from entering from the discharge port 108.

  Further, by driving the pumps 56 and 86, the humidified air in the tank 54 is forcibly supplied from the supply port 51a to the discharge space S1 (humidification operation), and the ink in the sub tank 80 is forcibly supplied to the ink inflow channel 72. Is done. Since the valve 59 is closed, the pressure in the discharge space S1 rises above atmospheric pressure. At this time, the pressure difference between the pressure generated in the ejection space S1 (pressure on the gas side of the ink meniscus) and the pressure generated in the ink inflow channel 72 (pressure on the ink side of the ink meniscus) is equal to or lower than the ink meniscus pressure resistance. Thus, the pump 56 is driven in the HI mode. The purge pump 86 is driven in the LO mode, and the valve 87 is open.

  As described above, since the pressure difference in the ink meniscus is equal to or less than the ink meniscus pressure resistance, the ink does not flow into the ink outflow passage 75 but sequentially passes through the exhaust passage 73 and the ink return pipe 83 to the sub tank 80. Return. The pressure generated in the ink inflow channel in this ink circulation is a pressure that destroys the ink meniscus when the gas side of the ink meniscus is at atmospheric pressure. By performing this ink circulation while maintaining such a high pressure, foreign matters such as bubbles staying in the flow path from the purge pump 86 to the sub tank 80 in the circulation path, particularly on the filter 75a. Foreign matter such as bubbles staying in the tank is efficiently trapped in the sub tank 80 in a short time (bubble purge). When ink circulation is performed in the bubble purge operation, the ink pressure in the ink inflow channel 72 and the exhaust channel 73 is higher than that in normal printing, so the resin film 76 is in close contact with the regulating member 77. The resin film 78 is in close contact with the regulating member 79.

  After driving the pumps 56 and 86 for a predetermined time, the maintenance control unit 145 stops the pump 56 (step 6: F6). After step 6, the purge control unit 44 switches the operation of the purge pump 86 from the LO mode to the HI mode, and closes the valve 87 from open. At this time, the maintenance control unit 145 sets the pressure in the discharge space S1 to atmospheric pressure by opening the valve 59 from the closed state (step 7: F7).

  As a result, the amount of ink delivered increases, and the ink flowing in the exhaust flow path 73 is suddenly blocked, so that the ink pressure in the exhaust flow path 73 and the ink inflow flow path 72 rises rapidly. On the other hand, the pressure in the discharge space S1 rapidly decreases. For this reason, the pressure on the ink side of the ink meniscus is much larger than that on the gas side, which greatly exceeds the ink meniscus pressure resistance. Thus, the entire amount of ink supplied to the ink inflow channel 72 flows into the ink outflow channel 75 and is discharged from all the ejection ports 108 (ejection port purge). The discharged ink is received on the surface 8 a of the conveyor belt 8. Further, since the inside of the ejection space S1 is sealed by the cap 40 during the ejection port purge, the ejected ink does not scatter around.

  In this embodiment, in order to shift from the bubble purge operation to the discharge port purge operation, the pressure in the ink inflow channel 72 and the exhaust channel 73 is increased in advance (that is, when the gas side of the ink meniscus is at atmospheric pressure). The discharge port purging operation can be performed in a state where the pressure has been increased to a pressure at which the ink meniscus is destroyed. For this reason, it is possible to instantaneously set the pressure in the ink inflow channel 72 and the exhaust channel 73 to a desired pressure (pressure that greatly exceeds the ink meniscus pressure resistance), and all the ejection ports from the start of the ejection port purge. A high pressure is applied to 108 and ink is discharged. At this time, the filter 75a to the ejection port 108 are promptly replaced with fresh ink, and foreign matters (including bubbles) and thickened ink remaining after the ink outflow passage 75 are discharged in a short time. The During this time, the amount of wasted ink consumed can be reduced.

  In this embodiment, when the bubble purge operation is shifted to the discharge port purge operation, the drive mode of the purge pump 86 and the valve 87 are switched at the same time. However, after the valve 87 is switched first. The drive mode of the pump 86 may be switched. Also in this modified example, as described above, the ink pressure in the exhaust flow path 73 and the ink inflow flow path 72 is rapidly increased, and the ink containing the foreign matter can be discharged from the ejection port 108 in a short time. it can.

  When a predetermined amount of ink is discharged from the ejection port 108 (that is, when the purge pump 86 is driven in the HI mode for a predetermined time), the purge control unit 144 stops driving the purge pump 86 (step 8: F8). . After Step 8, the maintenance control unit 145 controls the lifting motor 44 to separate the tip 41a1 of each cap 40 from the surface 8a (move from the contact position to the separation position) (Step 9: F9). As a result, the discharge space S1 is in an unsealed state opened to the external space S2 (see FIG. 6). The above purging operation may be performed on the heads 1 that require this, and is not always performed on all the heads 1.

  After step 9, the maintenance control unit 145 controls a lifting mechanism (not shown) to move the carriage 4 from a printing position suitable for image formation to a wiping position suitable for a wiping operation with a wiper. Thereby, a space necessary for wiping is formed between the surface 8a of the conveyor belt 8 and the discharge surface 2a. Subsequently, the maintenance control unit 145 controls a wiping mechanism (not shown) to move the wiper in the main scanning direction along the ejection surface 2a while contacting the ejection surface 2a (step 10: F10). Thereby, excess ink adhering to the ejection surface 2a is removed by the ejection port purge operation, and the meniscus formed at the ejection port 108 is adjusted (cleaning operation).

  After step 10, the maintenance control unit 145 controls a lifting mechanism (not shown) to return the carriage 4 from the wiping position to the printing position. Further, the maintenance control unit 145 controls the transport motor of the transport unit 20 to cause the transport belt 8 to travel by several revolutions (step 11: F11). Thereby, the ink adhering to the surface 8a is removed by the ink removing member 22 (ink removing operation). In this way, the purge operation is completed, and a print standby state is entered.

  Next, referring to FIG. 11, the control contents of the ink thickening prevention operation (capping and humidification maintenance) executed by the control device 16 will be described.

  As shown in FIG. 11, the control device 1p first determines whether or not a thickening prevention command has been received (G1). Before receiving the thickening prevention command, the carriage 4 is in the printing position and the cap 40 is in the separation position. The pump 56 is stopped and the valve 59 is open. Further, the transport unit 20 is also stopped.

  When receiving the thickening prevention command (G1: YES), the control device 16 first performs capping. That is, the maintenance control unit 145 drives the elevating motor 44 to bring the tip 41a1 of each cap 40 into contact with the surface 8a (moving from the separation position to the contact position) (step 2: G2). As a result, the discharge space S1 is sealed from the external space S2.

  After step 2, the maintenance control unit 145 drives the pump 56 in the LO mode, supplies humidified air in the tank 54 to the discharge space S1, and performs humidification maintenance for discharging the air in the discharge space S1 for a predetermined time. Perform (Step 3: G3). Thereby, humidified air circulates from the tank 54 to the discharge space S1 and from the discharge space S1 to the tank 54, and the humidity of the air in the discharge space S1 is adjusted to a desired humidity. Thereby, it is possible to suppress the viscosity increase of the ink in the ejection port 108.

  Thus, the capping and humidification maintenance is completed. Thereafter, when a signal such as a recording command is received from the external device, the control device 1p drives the elevating motor 44 to separate the tip 41a1 of the cap 40 from the surface 8a (move from the contact position to the separation position). As a result, the ejection space S1 is opened to the external space S2, and the recording operation is performed under the control of the control device 16 as described above.

  As described above, according to the ink jet printer 101 of this embodiment, when the bubble purge operation is performed, the pressure difference between the ink side pressure and the gas side pressure sandwiching the ink meniscus is equal to or lower than the pressure resistance of the ink meniscus. Therefore, the pressure generated in the internal flow path is increased by increasing the ink flow rate in order to effectively remove the bubbles in the internal flow path (ink inflow flow path 72 and exhaust flow path 73). Even if it rises, it is possible to suppress the ink meniscus from being broken and the ink from leaking out from the ejection port 108. That is, it is possible to improve the bubble discharge performance by the bubble purge operation without increasing the waste liquid from the discharge port 108.

  Further, when performing the bubble purge operation, the pump 56 is driven in the HI mode so that the amount of humidified air delivered is larger than that in humidification maintenance. Thus, the pressure in the discharge space S1 can be easily increased only by changing the driving conditions of the pump 56.

  Further, when the bubble purge operation is performed, the valve 59 is controlled to increase the flow path resistance in the tube 57, so that the pressure balance between both sides of the ink meniscus can be accurately taken. Further, the valve 59 is closed when the bubble purge operation is performed. Thereby, the pressure in the discharge space S1 can be easily increased.

  Further, since the ink return pipe 83 communicates with the sub tank 80, the ink transferred to the ink return pipe 83 is returned to the sub tank 80 (ink circulation) in the bubble purge operation. Therefore, the amount of ink to be discarded can be effectively reduced. As a modification, the ink return pipe 83 may be communicated with a waste tank (not shown), or may be configured to be selectively switchable between the sub tank 80 and the waste tank. For example, in the preceding stage of ink circulation, the ink return pipe 83 is communicated with a waste tank, and ink containing foreign matters is discarded. In the subsequent ink circulation, the ink is returned to the sub tank 80 by communicating with the sub tank 80. At least in the subsequent ink circulation operation, clean ink returns to the sub tank 80. As a result, accumulation of foreign matter or the like in the sub tank 80 can be suppressed.

  Further, since the tube 57 communicates with the tank 54, the humidified air in the bubble purge operation is circulated to the discharge space S <b> 1 and the air in the discharge space S <b> 1 circulates to the tank 54. As a modification, the tube 57 may be opened to the atmosphere, or may be configured to be selectively switchable between the tank 54 and the atmosphere.

  In the above-described embodiment, a positive pressure is generated in the internal flow path of the reservoir unit 71 and a positive pressure is generated in the discharge space S1 in the bubble purge operation. However, a negative pressure is generated in the internal flow path and the discharge space S1. Pressure may be generated. That is, as shown in FIG. 12, the inlet 72 a and the sub tank 80 are directly connected by the ink supply pipe 82, and a purge pump 86 is provided in the ink return pipe 83 instead of the valve 87. As shown in FIG. 13, the pump 56 is provided in the tube 57 without providing the valve 59. In this configuration, when the purge pump 86 is driven, the ink return pipe 83 and the internal flow paths (the ink inflow flow path 72 and the exhaust flow path 73) are negative pressure, and the ink in the sub tank 80 passes through the ink supply pipe 82. Supplied to the internal flow path. On the other hand, when the pump 56 is driven, negative pressure is generated in the tube 57 and the discharge space S1, and the humidified air in the tank 54 is supplied to the discharge space S1 through the tube 55. At this time, both pumps 56 and 86 are driven in the same phase.

  In the bubble purge operation, as in the above-described embodiment, the control device drives these pumps 56 and 86 to cause a negative pressure (pressure on the gas side of the ink meniscus) generated in the ejection space S1 and an ink inflow channel. The pressure difference from the negative pressure generated in the ink 72 (pressure on the ink side of the ink meniscus) is equal to or lower than the ink meniscus pressure resistance. That is, in the purge operation, a negative pressure that is equal to or lower than the pressure resistance of the ink meniscus is generated in the ejection space S1. As a result, ink circulation is performed while maintaining a high pressure (negative pressure), and foreign matters such as bubbles staying in the flow path of the circulation path sequentially pass through the exhaust flow path 73 and the ink return pipe 83 together with the ink. Then, it is trapped in the sub tank 80. In such a modified example, similarly to the above-described embodiment, it is possible to suppress the ink meniscus from being broken and the ink from leaking out from the ejection port 108 in the bubble purge operation, and the waste liquid from the ejection port 108 can be removed. It is possible to improve the bubble discharge performance of the bubble purge operation without increasing it. Note that the same effect can be obtained in a configuration similar to that of the above-described embodiment.

  As a modified example, the purge pump 86 may be driven so that the phases of the diaphragms of both the pumps 56 and 86 are aligned after the pump 56 is started. By so doing, a negative pressure is generated in the ejection space S1 prior to the internal flow path (the ink inflow flow path 72 and the exhaust flow path 73) during the bubble purge operation. For this reason, it becomes possible to prevent the air in the discharge space S1 from entering from the discharge port 108.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made as long as they are described in the claims. For example, in the above-described embodiment, the bubble purge operation is continuously shifted from the discharge port purge operation. However, the bubble purge operation and the discharge port purge operation may be performed separately (discontinuously). That is, only the bubble purge operation or the discharge port purge operation may be performed independently. A flushing operation may be performed following the bubble purge operation.

  Further, as cap means that can take the discharge space S1 in a sealed state and an unsealed state, a cap having a bottom portion facing the discharge surface 2a and an annular portion standing on the periphery of the bottom portion, and a tip of the annular portion May be configured to include a moving mechanism that moves the cap to a position in contact with the discharge surface 2a and a position separated from the discharge surface 2a. In this case, a supply port for supplying humidified air and a discharge port may be provided at the bottom of the cap.

  Further, in the above-described embodiment, the drive mode of the purge pump 86 is changed in the bubble purge operation and the discharge port purge operation, but it may not be changed. In this case, the pressure in the internal flow path (ink inflow flow path 72 and exhaust flow path 73) of the reservoir unit 71 may be changed only by opening and closing the valve 87. Further, if the pressure generated in the internal flow path by the bubble purge is a pressure that destroys the ink meniscus when the gas side of the ink meniscus is at atmospheric pressure, the pressure in the discharge space S1 can be simply reduced to atmospheric pressure. Good.

  Further, the driving mode of the pump 56 may not be changed in the humidifying operation in the bubble purge and the humidifying operation in the thickening preventing operation. In this case, the pressure in the discharge space S1 may be changed only by opening and closing the valve 59. Further, the valves 59 and 87 may not be provided. In this case, the amount of ink delivered by the purge pump 86 may be changed between the bubble purge operation and the discharge port purge operation to change the pressure generated in the internal flow path. What is necessary is just to change the pressure which arises in the discharge space S1 by making the humidification air delivery amount by the pump 56 differ by the humidification operation | movement in bubble purge, and the humidification operation | movement in a thickening prevention operation | movement. At this time, the pressure generated in the ejection space S1 may be balanced with the pressure on the ink side of the ink meniscus. Moreover, both the pumps 56 and 86 may be positive displacement pumps other than the diaphragm pump.

  The present invention can be applied to both a line type and a serial type, and is not limited to a printer, and can also be applied to a facsimile machine, a copier, and the like. Further, recording is performed by discharging a liquid other than ink. The present invention can also be applied to a liquid ejection apparatus that performs the above. The recording medium is not limited to the paper P, and may be various recording media. Furthermore, the present invention can be applied regardless of the ink ejection method. For example, although a piezoelectric element is used in this embodiment, a resistance heating method or a capacitance method may be used.

1 Inkjet head (liquid ejection head)
2a Discharge surface 16 Control device (control means)
54 Tank (2nd tank)
55 Tube (second supply flow path)
56 pump (humidified air supply means: second pump)
57 Tube (second discharge flow path)
59 Valve (Air restriction valve)
72 Ink flow path (part of internal flow path)
72a Inlet 73 Exhaust flow path (part of internal flow path)
73a Outflow port 75 Ink outflow channel (part of internal channel)
80 Sub tank (first tank)
82 Ink supply pipe (first supply flow path)
83 Ink return pipe (first discharge flow path)
86 Purge pump (liquid supply means: first pump)
87 Valve (Liquid shutoff valve)
101 Inkjet printer (liquid ejection device)
105 Manifold channel (part of individual liquid channel)
105a Sub manifold channel (part of individual liquid channel)
108 Discharge port 132 Individual ink flow path (part of individual liquid flow path)
S1 Discharge space S2 External space

Claims (9)

An inflow port through which the liquid flows in, an outflow port through which the liquid flows out, an internal flow path that connects the inflow port and the outflow port, a plurality of discharge ports for discharging the liquid, and a branch from the internal flow path A liquid discharge head having a plurality of individual liquid flow paths leading to the plurality of discharge ports;
A first tank for storing liquid supplied to the liquid discharge head;
A first supply channel communicating the first tank and the inlet;
A first discharge channel communicating with the outlet;
Liquid supply means for supplying the liquid stored in the first tank to the internal flow path via the first supply flow path;
Cap means capable of taking a sealed state in which a discharge space facing the plurality of discharge ports is sealed from an external space and a non-sealed state in which the discharge space is open to the external space;
A second tank for storing humid air supplied to the discharge space;
Communicated with said discharge space and the second tank, a second supply passage that to supply humidified air stored in the second tank to the discharge space,
It is communicating the second tank and the discharge space, and a second discharge passage for discharging the humidified air supplied to the discharge space to the second tank,
Humidified air supply means for supplying humidified air stored in the second tank to the discharge space via the second supply flow path;
The cap means and the cap means so as to perform a humidifying operation in which the discharge space is in the sealed state and humid air in the second tank is transferred in the order of the second supply channel, the discharge space, and the second discharge channel. The humidified air supply means is controlled, and the liquid supply means is controlled to perform a purge operation for transferring the liquid in the first tank in the order of the first supply flow path, the internal flow path, and the first discharge flow path. Control means to
When the control unit performs the purge operation, the pressure difference between the pressure on the liquid side and the pressure on the gas side sandwiching the liquid meniscus formed at the discharge port is the maximum pressure at which the liquid meniscus is not destroyed. A liquid ejection apparatus, wherein the humidified air supply means and the liquid supply means are controlled so as to balance with each other below a pressure resistance of the liquid meniscus. The first tank and the second tank are open to the atmosphere;
The liquid supply means is a first pump for supplying the liquid stored in the first tank to the internal flow path so that a positive pressure is generated in the internal flow path in the purge operation;
The humidified air supply means is a second pump for supplying humidified air stored in the second tank to the discharge space so that a positive pressure is generated in the discharge space in the humidifying operation;
2. The liquid ejection apparatus according to claim 1, wherein when the purge operation is performed, the control unit starts driving the second pump after starting the driving of the first pump. 3.   The control means sets the discharge space in the sealed state, and sends the humidified air to the discharge space when performing the purge operation as compared with the case where the humidification operation is performed without performing the purge operation. The liquid discharge apparatus according to claim 2, wherein the second pump is controlled so as to increase the amount. An air restriction valve capable of restricting the flow of air in the second discharge flow path;
The control means controls the air restriction valve so as to increase the flow resistance of the second discharge flow path by restricting the flow of the air when performing the purge operation. The liquid ejection device according to 2 or 3.   The liquid ejection apparatus according to claim 4, wherein the control unit controls the air restriction valve so as to close the air restriction valve when performing the purge operation. A liquid shut-off valve capable of shutting off the flow of liquid in the first discharge flow path;
The control means closes the liquid shut-off valve and opens the air restriction valve during the purge operation, and performs the discharge port purge operation for forcibly discharging the liquid from the plurality of discharge ports. The liquid discharge apparatus according to claim 5, wherein the valve and the liquid cutoff valve are controlled. The first tank and the second tank are open to the atmosphere;
The liquid supply means is a first pump for supplying the liquid stored in the first tank to the internal flow path so that a negative pressure is generated in the internal flow path in the purge operation;
The humidified air supply means is a second pump for supplying humidified air stored in the second tank to the discharge space so that a negative pressure is generated in the discharge space in the humidifying operation;
2. The liquid ejection apparatus according to claim 1, wherein when the purge operation is performed, the control unit starts driving the first pump after starting the driving of the second pump. 3.   The liquid ejecting apparatus according to claim 2, wherein the control unit aligns the phases of the first pump and the second pump when performing the purge operation.   9. The liquid ejection apparatus according to claim 1, wherein the first discharge channel communicates the first tank with the outlet. 10.

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