JP5554759B2 - Liquid ejection device - Google Patents

Description

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

  In an ink jet head that ejects ink droplets from an ejection port, air and foreign matter staying in the ink flow path in the ink jet head are discharged to the outside, so that the ink is forcibly supplied to the ink flow path using a pump. A technique for forcibly discharging air and foreign matter together with ink from an ejection port is known (for example, see Patent Document 1). In Patent Document 1, after closing the three-way valve and closing the discharge path, the supply pump is operated to pressurize the ink for a predetermined time, and the ink is ejected from the nozzle to clean the nozzle.

JP 2009-29111 A

  In order to reliably discharge air and foreign matter from the ejection port, it is necessary to increase the ink pressure in the ink flow path by increasing the amount of ink per unit time supplied to the ink flow path. However, since it takes time until the ink pressure in the ink flow path reaches a desired pressure after the driving of the pump is started, the ink is wasted from the ejection port during that time.

  An object of the present invention is to provide a liquid ejection apparatus capable of suppressing wasteful consumption of liquid while efficiently discharging air and foreign matter together with liquid from an ejection port.

The liquid discharge device of the present invention includes a tank for storing liquid, an inflow channel having an inflow opening that opens to the outside, and a flow path that communicates with the inflow channel and extends from the communication portion to the outflow port that opens to the outside. A supply flow path that connects the tank and the inflow port with a liquid return head that has a plurality of individual liquid flow paths that branch from the return flow path and reach the discharge port. A return flow path that communicates the tank and the outlet, supply means for forcibly supplying the liquid in the tank to the inflow flow path, and an adjustment valve that adjusts the flow rate of the liquid in the return flow path And by driving the supply means with the regulating valve open, the liquid in the tank passes through the supply flow path, the inflow flow path, the reflux flow path, and the return flow path in order. liquid reflux to return to the tank Done so, and a discharge control means for discharging liquid from said discharge port by adjusting to close the adjustment valve in the liquid reflux. In addition, at least a part of the inner wall surface of the inflow channel is formed of a flexible member, and the liquid discharge head is configured such that the flexible member faces the outside of the inner wall surface. It further has a restricting member that restricts deformation beyond a predetermined amount, and the flexible member and the restricting member have the flexibility when the liquid reflux is performed by the discharge control means. The member is configured to be in close contact with the regulating member .

According to the present invention, the internal pressure of the reflux channel is increased by performing liquid reflux. In this state, when the adjustment valve is throttled, the liquid in the reflux channel flows into the individual liquid channel, and the liquid is discharged from the discharge port. At this time, since the liquid is discharged from the discharge port at a high pressure from the start of discharge, the thickened liquid, air and foreign matter in the discharge port can be discharged efficiently and the liquid is wasted. Can be suppressed. In addition, since at least a part of the inner wall surface of the inflow channel is formed by a flexible member, the deformation of the flexible member causes the inflow channel and the reflux channel to The fluctuation of the internal pressure is suppressed, and the liquid can be supplied to the individual liquid channel at a stable pressure every time the droplet is discharged from the discharge port. Even in this case, when the liquid is discharged from the discharge port, since the member having flexibility is stabilized by the liquid reflux, the liquid, air, and foreign matters in the discharge port are efficiently removed. Can be discharged. The flexible member may further include a restricting member that restricts deformation of the flexible member toward the outside of the inner wall surface by a predetermined amount or more when the liquid reflux is performed by the discharge control means. It is comprised so that the member which has this may contact | adhere to the said limitation member . This restricts the flexible member from being further deformed by the pressure increase generated in the internal flow path when the control valve is throttled, so that the pressure is reduced when the liquid is discharged from the discharge port. It can suppress that it falls.

  Furthermore, in the present invention, it is preferable that the discharge control means stops the discharge of the liquid from the discharge port by opening the adjustment valve. According to this, since the liquid can be quickly stopped from being discharged from the discharge port, it is possible to further suppress the wasteful consumption of the liquid.

At this time, the discharge control means may repeat closing and opening of the regulating valve a plurality of times while continuing to drive the supply means. According to this, since the liquid in the reflux channel and the individual liquid channel can be vibrated efficiently by quickly discharging the liquid from the discharge port and stopping the discharge, the thickened liquid in the discharge port, Air and foreign matter can be discharged more efficiently.

  In the present invention, it is preferable that the discharge control means closes the adjustment valve after the adjustment valve is opened and the drive of the supply means is stopped. According to this, it is possible to prevent the liquid discharged from the discharge port from being sucked into the discharge port due to a water head difference between the liquid discharge head and the tank.

In addition, in the present invention, it is preferable that the supply flow path further includes a backflow prevention means for preventing liquid from flowing from the supply flow path to the tank. According to this, liquid reflux can be performed efficiently.

  In the present invention, it is preferable that the apparatus further includes a wiping unit for wiping the discharge surface on which the discharge port is formed within a period in which the adjustment valve is closed after driving of the supply unit is stopped. . According to this, it is possible to remove ink and foreign matter adhering to the ejection surface, and to adjust the meniscus of the ejection port.

  In the present invention, it is preferable that the flow rate of the liquid per unit time supplied by the supply unit during the liquid recirculation is a flow rate at which the liquid is not discharged from the discharge port when the adjustment valve is opened. According to this, since the liquid is not discharged at the time of liquid reflux, it is possible to reliably suppress the wasteful consumption of the liquid.

  In the present invention, the supply means is more preferably a positive displacement pump. According to this, even when the internal pressure of each flow path is high, a desired volume of liquid can be reliably supplied.

In addition, the present invention further includes an ambient temperature detection unit that detects an ambient temperature of the liquid discharge head, and the discharge control unit detects that the ambient temperature detected by the ambient temperature detection unit increases. Te, Rukoto to increase the amount of liquid to be discharged from the discharge port is preferred.

Further, the present invention further includes a non-ejection time detection means for detecting a time during which no liquid is ejected from the ejection port, and the discharge control means has a longer time detected by the non-ejection time detection means. Accordingly, it is preferable to increase the amount of liquid discharged from the discharge port . According to these, the thickened liquid, air and foreign matter in the discharge port can be discharged more efficiently.

According to the present invention, the internal pressure of the reflux channel is increased by performing liquid reflux. In this state, when the adjustment valve is throttled, the liquid in the reflux channel flows into the individual liquid channel, and the liquid is discharged from the discharge port. At this time, since the liquid is discharged from the discharge port at a high pressure from the start of discharge, the thickened liquid, air and foreign matter in the discharge port can be discharged efficiently and the liquid is wasted. Can be suppressed.

1 is a schematic plan view of an ink jet printer according to an embodiment of the present invention. It is sectional drawing of the inkjet head and ink supply unit which are shown in FIG. 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 graph which shows the operating characteristic of the purge pump shown in FIG. It is a functional block diagram of the control apparatus shown in FIG. (A) It is a wave form diagram of the ejection drive signal which a head control part shown in Drawing 6 generates. (B) It is a wave form diagram of the meniscus vibration signal which a head control part shown in Drawing 6 generates. It is a figure which shows the flow of an ink when the purge control part shown in FIG. 6 performs ink circulation. It is a figure which shows the operation | movement sequence of the maintenance operation | movement by the purge control part shown in FIG. It is a graph which shows the change of the ink flow rate in the purge operation | movement by the purge control part shown in FIG. It is a figure for demonstrating the 1st modification of this invention. It is a figure for demonstrating the 2nd modification of this invention.

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

  As shown in FIG. 1, the ink jet printer 101 includes a transport unit 20 that transports the paper P from the upper side to the lower side of FIG. 1, and magenta, cyan, yellow, and black ink on the paper P transported by the transport unit 20. Four inkjet heads 1 that respectively eject droplets, four ink supply units 10 that supply ink to the inkjet head 1, a maintenance unit 31 that performs maintenance of the inkjet head 1, and a control device 16 that controls the entire inkjet printer 101 And have. In the present embodiment, the sub-scanning direction is a direction parallel to the transport direction when the paper P is transported by the transport unit 20, and the main scanning direction is a direction orthogonal to the sub-scanning direction and along the horizontal plane. Direction.

  The transport unit 20 includes two belt rollers 6 and 7 and an endless transport belt 8 wound around the rollers 6 and 7. The belt roller 7 is a driving roller, and rotates when a driving force is applied from a conveyance motor (not shown). The belt roller 6 is a driven roller and rotates as the conveyor belt 8 travels due to the rotation of the belt roller 7. The paper P placed on the outer peripheral surface of the transport belt 8 is transported downward in FIG.

  The four inkjet heads 1 each extend along the main scanning direction and are arranged in parallel to each other in the sub-scanning direction. That is, the ink jet printer 101 is a line type color ink jet printer in which a plurality of ejection openings 108 for ejecting ink droplets in the main scanning direction are arranged. The lower surface of each inkjet head 1 is an ejection surface 2a in which a plurality of ejection ports 108 are arranged (see FIG. 2).

  The outer peripheral surface of the upper loop of the conveyor belt 8 and the discharge surface 2a are parallel to each other while facing each other. When the paper P transported by the transport belt 8 passes immediately below the four ink jet heads 1, ink droplets of each color are sequentially ejected from the respective ink jet heads 1 toward the upper surface of the paper P, and are then onto the paper P. A desired color image is formed.

  The ink supply unit 10 is connected to the vicinity of the left end of FIG. 1 on the lower surface of the inkjet head 1 and supplies ink to the connected inkjet head 1.

  The maintenance unit 31 has four wiper members 32. The four wiper members 32 are elastic members that wipe the ejection surface 2a of the inkjet head 1 in a wipe operation related to a maintenance operation described later, and can be reciprocated along the main scanning direction by an actuator (not shown). (See arrow in FIG. 1).

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

  The reservoir unit 71 is a flow path forming member that is fixed to the upper surface of the head body 2 and supplies ink to the head body 2. In addition, the reservoir unit 71 has an ink inflow channel 72, ten ink outflow channels 75, a first exhaust channel 73, and a second exhaust channel 74 formed therein. In FIG. 2, only one ink outflow channel 75 appears.

  The ink inflow channel 72 is a channel through which ink from the ink supply unit 10 flows through an inflow port 72 a that opens to the lower surface of the reservoir unit 71. The ink inflow channel 72 has a function as an ink reservoir for temporarily storing the inflowed ink. A hole 72 b that penetrates to the outer wall surface of the reservoir unit 71 is formed in the inner wall surface of the ink inflow channel 72. The hole 72b is sealed from the outer wall surface side of the reservoir unit 71 by a resin film 76 having flexibility. The resin film 78 forms a part of the inner wall surface of the ink inflow channel 72. Since the resin film 76 is displaced in accordance with the change in the ink pressure in the ink inflow channel 72, the resin film 76 has a damper function for suppressing the change in the ink pressure. By using the resin film 76, the damper function can be realized with an inexpensive configuration. During normal printing, the resin film 76 is slightly convex toward the ink inflow channel 72. A plate-shaped restricting member 77 is fixed to the outer wall surface of the reservoir unit 71 so as to cover the resin film 76, and restricts the resin film 76 from protruding toward the outside of the reservoir unit 71. 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. An air communication hole 77 a is formed in the restriction member 77, and the atmospheric pressure is always between the restriction member 77 and the resin film 76. Thereby, the resin film 76 becomes easy to displace.

  The ink outflow channel 75 communicates with the ink inflow channel 72 through the filter 75a and also communicates with the ink supply port 105b formed on the upper surface of the channel unit 9 of the head body 2 (FIG. 3). reference). The filter 75 a extends along the direction of ink flow in the ink inflow channel 72. During normal printing, the ink from the ink supply unit 10 flows into the ink inflow channel 72, passes through the ink outflow channel 75, and is supplied from the ink supply port 105 b to the channel unit 9.

  The first exhaust passage 73 communicates with the ink inflow passage 72 on the upstream side of the filter 75 a and is connected to the ink supply unit 10 via a first outlet 73 a formed on the lower surface of the reservoir unit 71. ing. A hole 73 b that penetrates to the outer wall surface of the reservoir unit 71 is formed in the lower inner wall surface of the first exhaust passage 73. The hole 73b is sealed from the outer wall surface below the reservoir unit 71 by a resin film 78 having flexibility. The resin film 78 forms a part of the inner wall surface of the first exhaust flow path 73. Since the resin film 78 is displaced as the ink pressure in the first exhaust passage 73 varies, the resin film 78 has a damper function that suppresses variation in the ink pressure. By using the resin film 78, the damper function can be realized with an inexpensive configuration. During normal printing, the resin film 78 is slightly convex toward the inside of the first exhaust flow path 73. A plate-shaped regulating member 79 is fixed to the lower outer wall surface of the reservoir unit 71 so as to cover the resin film 78, and regulates the resin film 78 from protruding toward the outside of the reservoir unit 71. Yes. This prevents the resin film 78 from being excessively displaced and damaged when the ink pressure in the first exhaust flow path 73 becomes abnormally high. An air communication hole 79 a is formed in the regulating member 79, and the atmospheric pressure is always between the regulating member 79 and the resin film 78. Thereby, the resin film 78 becomes easy to displace. During the first ink circulation (liquid reflux) described later, the ink from the ink supply unit 10 flows into the ink inflow channel 72 through the inflow port 72a, passes through the first exhaust channel 73, and flows. It returns to the ink supply unit 10 through the outlet 73a (see FIG. 8A).

  The second exhaust channel 74 communicates with the channel unit 9 and is connected to the ink supply unit 10 via a second outlet 74 a formed on the lower surface of the reservoir unit 71. During the second ink circulation (liquid reflux), which will be described later, ink from the ink supply unit 10 flows into the ink inflow channel 72 via the inflow port 72 a, and the ink outflow channel 75 and the manifold of the channel unit 9. It passes through the flow path 105 (described later) and the second exhaust flow path 74 in order, and returns to the ink supply unit 10 through the outlet 74a (see FIG. 8B).

  Further, the head body 2 will be described with reference to FIGS. 3 and 4. 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.

  As shown in FIGS. 3 and 4, the head body 2 is a laminated body in which four actuator units 21 are fixed to the upper surface of the flow path unit 9. The flow path unit 9 has an ink flow path including a pressure chamber 110 and the like formed therein. The actuator unit 21 includes a plurality of unimorph actuators corresponding to the pressure chambers 110 and has a function of selectively applying ejection energy to the ink in the pressure chambers 110.

  The flow path unit 9 is a laminated body in which a plurality of metal plates made of stainless steel are aligned with each other. The top surface of the flow path unit 9 communicates with a total of ten ink supply ports 105 b communicating with the ink outflow flow path 75 (see FIG. 2) of the reservoir unit 71 and the second exhaust flow path 74 of the reservoir unit 71. A discharge port (not shown) is open. As shown in FIG. 3, each of the plurality of sub-manifold channels 105 a included in the manifold channel 105 and the manifold channel 105 communicating with the ink supply port 105 b and the discharge port (not shown) is provided inside the channel unit 9. A large number of individual ink flow paths branching from are formed. A large number 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 and 4, during normal printing, the ink supplied from the ink outflow channel 75 of the reservoir unit 71 to the ink supply port 105 b is distributed to the sub-manifold channel 105 a of the manifold channel 105. The The ink in the sub-manifold channel 105 a flows into each individual ink channel and reaches the ejection port 108 via the pressure chamber 110. Further, in the second ink circulation described later, the ink supplied from the ink outflow passage 75 of the reservoir unit 71 to the ink supply port 105b passes through the manifold passage 105 and passes through the manifold passage 105 to the first outlet of the reservoir unit 71. 2 Flows into the exhaust passage 74 (see FIG. 8B).

  The ink supply unit 10 will be described in detail. As shown in FIG. 2, the ink supply unit 10 includes a sub tank 80, an ink supply pipe 81 connected to the sub tank 80, an ink supply pipe 82, a first ink return pipe 83, a second ink return pipe 84, and an ink supply. A purge pump 86 provided in the pipe 82, a first valve 87 provided in the first ink return pipe 83, and a second valve 88 provided in the second ink return pipe 84 are provided.

  The sub tank 80 stores ink supplied to the inkjet head 1, and the ink stored in the ink tank 90 is supplied through the ink supply pipe 81. An air communication hole 80 a is formed in the outer wall of the sub tank 80. As a result, the atmospheric pressure in the sub tank 80 is always the atmospheric pressure regardless of the amount of stored ink, enabling stable ink supply.

  One end of the ink supply pipe 82 is connected to the sub tank 80, and the other end is connected to the inlet 72a of the reservoir unit 71 via the 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 via the ink supply pipe 82. The purge pump 86 functions as supply means for forcibly supplying the ink in the sub tank 80 to the ink inflow passage 72 via the ink supply pipe 82 by being driven, and also from the joint 82a to the sub tank in the ink supply pipe 82. It functions as a check valve that prevents ink from flowing toward 80. The purge pump 86 is a three-phase diaphragm pump that is a positive displacement pump. As shown in FIG. 5, the three diaphragms are driven at different phases to suppress pressure fluctuations during ink delivery. Yes.

  As shown in FIG. 2, one end of the first ink return pipe 83 is connected to the sub tank 80, and the other end is connected to the first outlet 73a of the reservoir unit 71 via a joint 83a. The first valve 87 is an adjustment valve that adjusts the ink flow rate in the first ink return pipe 83.

  One end of the second ink return pipe 84 is connected to the sub tank 80, and the other end is connected to the first outlet 74a of the reservoir unit 71 via the joint 84a. The second valve 88 is an adjustment valve that adjusts the ink flow rate in the second ink return pipe 84.

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 an EEPROM (Electrically Erasable and Programmable Read Only Memory) that stores data used for these programs in a rewritable manner. RA to memorize temporarily
M (Random Access Memory). Each functional unit constituting the control device 16 is constructed by cooperation of these hardware and software in the EEPROM. The control device 16 controls the entire inkjet printer 101, and includes a conveyance control unit 41, an image data storage unit 42, a head control unit 43, a non-ejection time detection unit 46, and a circulation / purge control unit 44. And a maintenance control unit 45.

  The transport control unit 41 controls the transport motor of the transport unit 20 so that the paper P is transported along the transport direction.

  The image data storage unit 42 stores image data relating to an image to be printed on the paper P.

The head controller 43 supplies the generated ejection drive signal to the actuator unit 21 based on the image data during printing. As shown in FIG. 7A, the ejection drive signal is a signal including a pulse that changes from the potential V1 to the ground potential V0 for a predetermined time in one printing cycle. This pulse width is equal to the time during which the pressure wave propagates the distance AL (Acoustic Length) from the outlet of the sub manifold channel 105a to the discharge port 108. The waveform shown in FIG. 7A is a waveform when a small ink droplet is ejected, and has one pulse. The waveform when ejecting a medium ink droplet has two pulses, and the waveform when ejecting a large ink droplet has three pulses.

  Further, the head controller 43 supplies the actuator unit 21 with a meniscus vibration signal that vibrates the ink meniscus formed in all the ejection openings 108 in first and second circulation operations described later. Thereby, the meniscus of the ink formed at each ejection port 108 vibrates, and the meniscus pressure resistance at each ejection port 108 is improved. As shown in FIG. 7B, the meniscus vibration signal is a signal in which a pulse from the potential V1 to the ground potential V0 for a predetermined time is repeated at a predetermined cycle. This pulse width is preferably １ ／ or less of the time for the pressure wave to propagate through the AL length.

  The non-ejection time detection unit 46 detects the time during which no ink droplet is ejected from any ejection port 108 for each inkjet head 1 from the past ejection history.

  The circulation / purge control unit 44 controls the operations of the purge pump 86, the first valve 87, and the second valve 88 of each ink supply unit 10 in a maintenance operation described later. Specific operation contents will be described later.

  The maintenance control unit 45 controls the operation of the maintenance unit 31 in the maintenance operation.

  The maintenance operation will be described with reference to FIGS. The maintenance operation is an operation for performing maintenance of the inkjet head 1 and is started when the inkjet printer 101 is activated, when a standby time exceeds a certain time, and when an instruction is given from the user. During standby and normal printing, the purge pump 86 is stopped and the first valve 87 and the second valve 88 are closed (see FIG. 2). When the maintenance operation is started, the first circulation operation, the second circulation operation, the purge operation, and the wipe operation are sequentially executed. 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.

  When the first circulation operation is started, the head controller 43 supplies the actuator unit 21 with a meniscus vibration signal that vibrates the ink meniscus formed in all the ejection ports 108. Thereby, the meniscus of each discharge port 108 vibrates, and the meniscus pressure resistance increases. Then, as shown in FIGS. 8A and 9, the circulation / purge control unit 44 drives the purge pump 86 after opening the first valve 87 and closing the second valve 88. As a result, the ink in the sub tank 80 is forcibly supplied to the ink inflow channel 72 via the ink supply pipe 82. At this time, since the first valve 87 is open, the flow path resistance in the path from the ink inflow path 72 through the first exhaust path 73 and the first ink return pipe 83 to the sub tank 80 is reduced. It becomes smaller than the flow path resistance of the path from the path 72 to each discharge port 108 via the ink outflow path 75 and the manifold path 105. For this reason, the ink supplied to the ink inflow channel 72 passes through the first exhaust channel 73 and the first ink return pipe 83 in order without returning to the ink outflow channel 75 and returns to the sub tank 80. Ink circulation is performed. By performing the first ink circulation, the air and foreign matter staying in the ink inflow passage 72, particularly the air and foreign matter staying on the filter 75a, together with the ink, the first exhaust passage 73 and the first foreign matter. The ink passes through the ink return pipe 83 in order and is trapped in the sub tank 80.

  Note that when the first ink circulation is performed, the ink pressure in the ink inflow channel 72 and the first exhaust channel 73 is higher than that during printing. The resin film 78 of the first exhaust flow path 73 is in close contact with the restriction member 79 while being in close contact with the restriction member 77. The circulation / purge control unit 44 stops the purge pump 86 when the first ink circulation is performed for a predetermined time, and then closes the first valve 87. At this time, the circulation / purge control unit 44 increases the temperature detected by the temperature sensor 35 that detects the ambient temperature of the inkjet head 1 or the time detected by the non-ejection time detection unit 46 increases. Accordingly, the predetermined time for performing the first ink circulation is lengthened. Thereafter, the head controller 43 stops supplying the meniscus vibration signal to the actuator unit 21. Thus, the first circulation operation is completed.

  Subsequently, when the second circulation operation is started, the head controller 43 supplies the actuator unit 21 with a meniscus vibration signal that vibrates the ink meniscus formed in all the ejection ports 108. Then, as shown in FIGS. 8B and 9, the circulation / purge control unit 44 drives the purge pump 86 after closing the first valve 87 and opening the second valve 88. As a result, the ink in the sub tank 80 is forcibly supplied to the manifold channel 105 via the ink supply pipe 82, the ink inflow channel 72, and the ink outflow channel 75. At this time, since the second valve 88 is open, the flow path resistance in the path from the manifold flow path 105 to the sub tank 80 via the second exhaust flow path 74 and the second ink return pipe 84 is reduced. From the flow path resistance of the path from each through the individual ink flow path to the ejection port 108. Therefore, the ink supplied to the manifold channel 105 passes through the second exhaust channel 74 and the second ink return pipe 84 in order and returns to the sub tank 80 without flowing into the individual ink channels. Circulation takes place. By performing the second ink circulation, the air and foreign matter staying in the ink outflow passage 75 and the manifold passage 105 sequentially pass through the second exhaust passage 74 and the second ink return pipe 84 together with the ink. And trapped in the sub tank 80.

  When the second ink circulation is performed, the ink pressure in the ink inflow channel 72 is increased, and the resin film 76 in the ink inflow channel 72 is in close contact with the regulating member 77. The circulation / purge control unit 44 stops the purge pump 86 and then closes the second valve 88 when the second ink circulation is performed for a predetermined time. At this time, the circulation / purge control unit 44 causes the second ink circulation to occur as the temperature detected by the temperature sensor 35 increases or as the time detected by the non-ejection time detection unit 46 increases. The predetermined time for performing is increased. Thereafter, the head controller 43 stops supplying the meniscus vibration signal to the actuator unit 21. Thus, the second circulation operation is completed.

  In the first and second circulation operations, in order to efficiently move air and foreign matter to the sub tank 80, the ink flow rate per unit time in the purge pump 86 is changed by breaking the ink meniscus formed at the ejection port 108 (meniscus). (Break) It is necessary to increase the flow rate within the range below the flow rate (meniscus break flow rate) at which ink leaks from the ejection port 108 (see FIG. 10). The meniscus break flow rate is a value calculated from the flow path structure of the inkjet head 1, the height relationship between the inkjet head 1 and the sub tank 80 in the inkjet printer 101, the viscosity of the ink, or the value obtained by actual measurement. And is stored in advance. As described above, in the first and second circulation operations, the meniscus at each discharge port 108 is vibrated to increase the meniscus pressure resistance at each discharge port 108. For this reason, the ink flow rate per unit time in the purge pump 86 can be further increased.

  Subsequently, when the purge operation is started, the head control unit 43 supplies the actuator unit 21 with a meniscus vibration signal that vibrates the ink meniscus formed in all the ejection ports 108. As shown in FIGS. 9 and 10, the circulation / purge control unit 44 opens the first valve 87 and closes the second valve 88, and then drives the purge pump 86 to perform the first ink circulation. As a result, the ink pressure in the ink inflow channel 72 increases. Note that the ink flow rate per unit time in the purge pump 86 is less than the meniscus break flow rate, and when the ink is purged from the ejection port 108 later, air and foreign matter staying in the individual ink flow path together with the ink. The flow rate is higher than the flow rate that can be discharged from the discharge port 108 (recoverable flow rate). The recoverable flow rate is a value obtained by actual measurement and is stored in advance.

  Then, the circulation / purge control unit 44 closes the first valve 87 in a state where the ink flow rate per unit time in the purge pump 86 is stable above the recoverable flow rate. As a result, the ink supplied to the ink inflow channel 72 flows into the ink outflow channel 75 without flowing into the first exhaust channel 73, and sequentially passes through the manifold channel 105 and the individual ink channels to be discharged. Purge from outlet 108. The purged ink is received by a waste liquid tray (not shown).

  In this way, since the purge from the ejection port 108 is started in a state where the ink flow rate per unit time in the purge pump 86 is stable above the recoverable flow rate, the ink inflow path 72 starts immediately after the purge starts. The ink pressure becomes high, and the thickened ink in the ejection port 108, the staying air and foreign matter can be efficiently purged from the ejection port 108. In this regard, when such an impact purge is not performed, for example, when driving of the purge pump 86 is started with the first valve 87 and the second valve 88 closed, the purge pump 86 per unit time is started. Until the ink flow rate reaches the recoverable flow rate, ink is purged from the ejection port 108 wastefully.

  When a predetermined amount of ink is purged from the ejection port 108 by closing the first valve 87 for a predetermined period, the circulation / purge control unit 44 opens the first valve 87 to resume the first ink circulation, and the ejection port The purge from 108 is stopped. At this time, the amount of ink purged from the ejection port 108 is calculated based on the ink flow rate per unit time in the purge pump 86 and the period during which the first valve 87 is closed.

  The circulation / purge control unit 44 keeps the first valve 87 in a predetermined cycle so that a predetermined amount of ink is continuously purged three times from the discharge port 108 in a predetermined cycle while the purge pump 86 is driven. Open and close 3 times. The circulation / purge control unit 44 performs the first ink circulation as the temperature detected by the temperature sensor 35 increases or as the time detected by the non-ejection time detection unit 46 increases. The predetermined time of the ink to be purged from the ejection port 108 is increased while extending the time to be performed. Thereafter, the circulation / purge control unit 44 stops the purge pump 86. This completes the purge operation.

  As described above, by performing the first circulation operation, the second circulation operation, and the purge operation in order, the ink inflow passage 72, the manifold passage 105, and the individual ink passages stay in that order. Air and foreign matter can be discharged directly without flowing into the downstream flow path.

  Next, when the wiping operation is started, first, the circulation / purge control unit 44 closes the first valve 87 and the second valve 88. As a result, it is possible to prevent excess ink adhering to the ejection surface 2a due to the purge operation from being sucked into the ejection port 108 again. Then, after the maintenance control unit 45 moves the four inkjet heads 1 upward by a moving mechanism (not shown), the wiper members 32 are discharged while the tips of the four wiper members 32 are in contact with the opposing discharge surfaces 2a. It is moved in the main scanning direction along the surface 2a. As a result, excess ink adhering to the ejection surface 2a by the purge operation is removed, and the meniscus formed at the ejection port 108 is adjusted. After each discharge surface 2a is wiped, the maintenance control unit 45 returns the four wiper members 32 and each inkjet head 1 to their normal positions, and the circulation / purge control unit 44 turns the first valve 87 and the second valve 88 on. open. Thus, the wiping operation is completed.

  As described above, according to the ink jet printer 101 of the present embodiment, in the purge operation, the purge from the discharge port 108 is started in a state where the ink flow rate per unit time in the purge pump 86 is stable above the recoverable flow rate. Therefore, immediately after the start of purging, the ink pressure in the ink inflow channel 72 becomes high, and the thickened ink, the staying air and foreign matter in the ejection port 108 are efficiently purged from the ejection port 108. Can do. Thereby, it is possible to suppress the wasteful consumption of ink while restoring the ink ejection characteristics.

  Further, since only the first ink circulation is performed prior to the purge in the purge operation, no ink flow occurs in the manifold channel 105 until immediately before the purge starts, and pressure fluctuations in the manifold channel 105 can be suppressed. it can. This makes it possible to apply an equal pressure to each individual ink channel at the start of the purge.

  Further, in the purge operation, the purge from the ejection port 108 is stopped by opening the first valve 87, so that the purging of ink from the ejection port 108 can be quickly stopped. Thereby, it is possible to further suppress wasteful consumption of ink.

  In addition, in the purge operation, while the purge pump 86 is driven, the first valve 87 is set to 3 at a predetermined cycle so that a predetermined amount of ink is continuously purged three times from the discharge port 108 at a predetermined cycle. Open and close each time. Accordingly, the ink in the ink inflow channel 72, the manifold channel 105, and each individual ink channel can be efficiently vibrated at a predetermined cycle. It is possible to efficiently purge air and foreign matters staying in the discharge port 108 from the discharge port 108.

  In addition, after the purge operation is completed, the first valve 87 and the second valve 88 are closed in the wipe operation, so that the ink purged from the ejection port 108 is discharged due to a water head difference between the inkjet head 1 and the sub tank 80. Inhalation into the outlet 108 can be prevented.

  Furthermore, since the purge pump 86 functions as a check valve, the first and second ink circulation can be performed efficiently.

  In addition, since the wiping operation is included in the maintenance operation, it is possible to remove ink and foreign matter adhering to the ejection surface 2a, and to adjust the meniscus of the ejection port 108.

  In addition, since the resin film 76 is a part of the inner wall surface of the ink inflow channel 72 and the resin film 78 is a part of the inner wall surface of the first exhaust channel 73, the ink inflow channel. 72 and the first exhaust flow path 73 can be efficiently suppressed. Thereby, the ink can be supplied to each individual ink flow path with a stable pressure.

  At this time, since the restricting members 77 and 79 restrict the resin films 76 and 78 from projecting toward the outside of the reservoir unit 71, the ink pressure in the ink inflow passage 72 and the first exhaust passage 73 is reduced. Can be prevented from excessively displacing and damaging the resin films 76 and 78. Further, in the first ink circulation of the purge operation, the regulating members 77 and 79 regulate the displacement of the resin films 76 and 77. Therefore, the ink pressure in the ink inflow channel 72 is closed by closing the first valve 87 in this state. Even if the temperature rises, the resin films 76 and 78 are not further displaced. Therefore, the increased ink pressure is propagated without loss, and the ink in the ink inflow channel 72 quickly flows into the individual ink channel, so that the ink can be efficiently purged from the ejection port 108.

  Further, since the ink flow rate per unit time of the purge pump 86 in the first ink circulation related to the purge operation is less than the meniscus break flow rate, the ink does not leak from the ejection port 108 in the first ink circulation. It is possible to suppress wasteful consumption of ink.

  Further, since the purge pump 86 is a positive displacement pump, even when the ink pressure is high, the ink can be reliably supplied to the ink inflow channel 72 without causing the ink to flow backward.

  In addition, in the first and second circulation operations and the purge operation, the head control unit 43 vibrates the ink meniscus formed at the ejection port 108, so that the meniscus withstand voltage is increased and the purge pump 86 per unit time is increased. The ink flow rate can be further increased.

  Further, in the purge operation, the circulation / purge control unit 44 detects that the ambient temperature of the inkjet head 1 detected by the temperature sensor 35 is increased or from the ejection port 108 detected by the non-ejection time detection unit 46. As the time during which ink droplets are not ejected becomes longer, the time for performing the first ink circulation is lengthened and the amount of ink purged from the ejection port 108 is increased. As described above, in order to adjust the time for performing the first ink circulation and the amount of ink to be purged in accordance with the degree of thickening of the ink and the predicted amount of air and foreign matter in the inkjet head 1, The thickened ink, air and foreign matter can be discharged efficiently.

  Further, since the filter 75a extends along the direction of ink flow in the ink inflow channel 72, the resistance when flowing from the ink inflow channel 72 through the filter 75a into the ink outflow channel 75 is large. It has become. For this reason, in the first ink circulation, it becomes difficult for the ink to flow into the ink outflow channel 75, and it is possible to prevent the ink from leaking from the ejection port 108.

<First Modification>
A first modification according to the present invention will be described. In the above-described embodiment, in the purge operation, the circulation / purge control unit 44 continuously purges a predetermined amount of ink from the discharge port 108 at a predetermined cycle three times with the purge pump 86 being driven. In addition, the first valve 87 is opened and closed three times at a predetermined cycle. As shown in FIG. 11, every time a predetermined amount of ink is purged from the ejection port 108 while the purge pump 86 is driven. In addition, the operation of stopping the purge pump 86 may be repeated three times at a predetermined cycle.

<Second Modification>
A second modification according to the present invention will be described. In the above-described embodiment, the ink jet head 1 has the head main body 2 including the unimorph actuator, but the ink jet head may have another type of head main body. For example, you may have the thermal head main body 209 as shown in FIG. In the head main body 209, a plurality of individual ink channels are branched from the common ink chamber 205, and an electric heat exchange element is disposed so as to face the ejection port 108 of each individual ink channel. Ink droplets are ejected from the ejection port 108 by thermal energy generated from the electric heat exchange element. According to this configuration, since the configuration of the common ink chamber 205 and the individual ink flow path is simplified, ink can be purged from the ejection port 108 more efficiently in the purge operation described above.

  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. In the above-described embodiment, in the maintenance operation, the first circulation operation, the second circulation operation, the purge operation, and the wipe operation are sequentially performed. However, at least one of the first circulation operation, the second circulation operation, and the wipe operation is performed. The structure which does not perform may be sufficient.

  In the above-described embodiment, in the purge operation, the first ink circulation is performed prior to the ink purge from the ejection port 108, but the second ink circulation may be performed instead of the first ink circulation. . According to this, since air and foreign matter staying in the manifold flow path 105 by the second circulation are trapped in the sub tank 80 immediately before purging the ink from the ejection port 108, they stay in the manifold flow path 105 at the time of purging. Air and foreign matter can be prevented from flowing into the individual ink flow paths.

  Further, in the above-described embodiment, in the purge operation, the purge from the discharge port 108 is stopped by opening the first valve 87 while the purge pump 86 is driven, but the first valve 87 is closed. In this state, the purge from the discharge port 108 may be stopped by stopping the purge pump 86.

  In addition, in the above-described embodiment, in the purge operation, a predetermined amount of ink is purged three times from the ejection port 108 at a predetermined cycle. However, the number of times of purging may be one. It may be twice or four or more times. Further, the ink may be continuously purged from the ejection port 108 at an arbitrary timing. Further, when purging a plurality of times in succession, the valve closing periods may be varied so that the amounts of ink purged each time are different from each other.

  Further, in the above-described embodiment, the purge pump 86 functions as a check valve, but the purge pump 86 may not function as a check valve. At this time, it is preferable to provide a check valve separately.

  In addition, in the above-described embodiment, the resin film 76 is a part of the inner wall surface of the ink inflow channel 72, and the resin film 78 is a part of the inner wall surface of the first exhaust channel 73. However, the reservoir unit may not have at least one of the resin films 76 and 78.

  In the above-described embodiment, the restricting members 77 and 79 are configured to restrict the resin films 76 and 78 from protruding toward the outside of the reservoir unit 71. The configuration may be such that at least one of 79 is not fixed.

  Further, in the above-described embodiment, the ink flow rate per unit time of the purge pump 86 in the first ink circulation related to the purge operation is less than the meniscus break flow rate. If the amount of ink leaking from the outlet 108 is small, the ink flow rate may be equal to or higher than the meniscus break flow rate.

  In addition, in the above-described embodiment, the purge pump 86 is a three-phase diaphragm pump that is a positive displacement pump, but may be another positive displacement pump such as a tube pump, or an impeller pump. A pump other than the positive displacement type may be used.

  In the above-described embodiment, the meniscus of the discharge port 108 is vibrated in the first and second circulation operations and the purge operation. However, in at least one of the cases, the meniscus of the discharge port 108 is not vibrated. There may be. At this time, since the meniscus break flow rate decreases, it is preferable that the ink flow rate per unit time of the purge pump 86 is less than the reduced meniscus break flow rate.

  Further, in the above-described embodiment, the circulation / purge control unit 44 detects the discharge detected by the non-ejection time detection unit 46 as the ambient temperature of the inkjet head 1 detected by the temperature sensor 35 increases. As the time during which no ink droplet is ejected from the outlet 108 becomes longer, the time for performing the first ink circulation is lengthened and the amount of ink purged from the ejection port 108 is increased. A configuration in which at least one of the time for performing the first ink circulation and the amount of ink purged from the ejection port 108 is determined based on only one of the ambient temperature and the time during which no ink droplet is ejected from the ejection port 108. The time for performing the first ink circulation and the amount of ink purged from the ejection port 108 may be determined in advance. It may be.

  In addition, in the above-described embodiment, the ink jet head 1 and the ink supply unit 10 have a flow path configuration that allows the first and second ink circulation, but only one of the first and second ink circulations. It is possible to have a flow path configuration capable of.

  The present invention is also applicable to a recording apparatus that ejects liquid other than ink. Further, the present invention is not limited to a printer, and can be applied to a facsimile, a copier, and the like.

DESCRIPTION OF SYMBOLS 1 Inkjet head 2 Head main body 10 Ink supply unit 16 Control apparatus 31 Maintenance unit 32 Wiper member 35 Temperature sensor 41 Conveyance control part 42 Image data storage part 43 Head control part 44 Circulation / purge control part 45 Maintenance control part 46 Non-ejection time detection Part 71 Reservoir unit 72 Ink inflow path 72a Inlet 73 First exhaust path 73a Outlet 74 Second exhaust path 74a Outlet 75 Ink outflow paths 76, 78 Resin film 77, 79 Restriction member 80 Sub tank 81 Ink supply Pipe 82 Ink supply pipe 83 First ink return pipe 84 Second ink return pipe 86 Purge pump 87 First valve 88 Second valve 101 Inkjet printer 105 Manifold channel 108 Discharge port

Claims (10)

A tank for storing liquid,
An inflow channel having an inflow opening that opens to the outside, a reflux channel that communicates with the inflow channel and extends from the communication portion to an outflow port that opens to the outside, and a branch from the reflux channel A liquid discharge head having a plurality of individual liquid flow paths from the branch point to the discharge port;
A supply flow path communicating the tank and the inlet;
A return flow path communicating the tank and the outlet;
Supply means for forcibly supplying the liquid in the tank to the inflow channel;
An adjustment valve for adjusting the flow rate of the liquid in the return flow path;
By driving the supply means with the regulating valve open, the liquid in the tank is transferred to the tank via the supply flow path, the inflow flow path, the return flow path, and the return flow path in order. A discharge control means for discharging the liquid from the discharge port by performing a liquid reflux to return, and adjusting the valve to close the adjustment valve during the liquid reflux,
At least a part of the inner wall surface of the inflow channel is formed of a flexible member,
The liquid discharge head further includes a regulating member that regulates deformation of the flexible member by a predetermined amount or more toward the outside of the inner wall surface,
The flexible member and the regulating member are configured such that the flexible member is in close contact with the regulating member when the liquid reflux is performed by the discharge control means. A liquid ejection device.   The liquid discharge apparatus according to claim 1, wherein the discharge control unit stops discharge of the liquid from the discharge port by opening the adjustment valve.   The liquid discharge apparatus according to claim 2, wherein the discharge control unit repeats closing and opening of the regulating valve a plurality of times while continuing to drive the supply unit.   4. The liquid ejection apparatus according to claim 2, wherein the discharge control unit closes the adjustment valve after the adjustment valve is opened and the driving of the supply unit is stopped. 5.   5. The liquid ejection apparatus according to claim 4, further comprising backflow prevention means for preventing liquid from flowing from the supply flow path to the tank in the supply flow path. The wiping means for wiping the discharge surface on which the discharge port is formed is further provided within a period in which the adjustment valve is closed after driving of the supply means is stopped. The liquid discharge apparatus according to 1.   The liquid flow rate per unit time supplied by the supply means during the liquid reflux is a flow rate at which liquid is not discharged from the discharge port when the regulating valve is opened. The liquid discharge apparatus according to any one of the above.   The liquid ejecting apparatus according to claim 1, wherein the supply unit is a positive displacement pump. It further comprises ambient temperature detection means for detecting the ambient temperature of the liquid ejection head,
The discharge control unit increases the amount of liquid discharged from the discharge port as the ambient temperature detected by the ambient temperature detection unit increases. The liquid ejection device according to item. A non-ejection time detection means for detecting a time during which no liquid is ejected from the ejection port;
The discharge control means increases the amount of liquid discharged from the discharge port as the time detected by the non-discharge time detection means becomes longer. The liquid discharge apparatus according to 1.

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