JP5428321B2 - Fluid discharge method and droplet discharge device - Google Patents

Description

  The present invention relates to a fluid discharge method and a droplet discharge device.

In an ink jet apparatus, when an ink pack or carriage is replaced, reconnection of an ink flow path for supplying ink occurs, so that bubbles may enter the ink flow path. This bubble may reduce the ejection characteristics of the droplet discharge head. For this reason, a method is adopted in which ink is sucked from the discharge nozzles to discharge bubbles in the ink flow path together with the ink (for example, Patent Document 1).
JP 2004-284291 A

  In the suction method as described above, ink is sucked by driving a suction pump (pressure changing means) connected to a cap that seals the nozzle plate for a predetermined time under a constant output. If the ink is sucked at high speed, relatively large bubbles in the flow path are discharged together with the ink, but the minute amount attached to the inner wall of the ink flow path due to the difference in flow velocity between the central part of the ink flow path and the surrounding area. Often, bubbles are not easily discharged and remain in the flow path. In order to discharge such residual bubbles (micro bubbles), it is necessary to lower the output of the suction pump and suck the ink at a low speed. However, since the suction amount is small, the processing time becomes long. Met.

  The present invention has been made in view of the above-described problems of the prior art, and aims to provide a fluid discharge method and a droplet discharge device capable of improving the bubble discharge performance in the droplet discharge head. Yes.

  In order to solve the above problems, a fluid discharge method of the present invention is a fluid discharge method for discharging a fluid from a nozzle of a droplet discharge head by bringing a cap into contact with a nozzle forming surface of the droplet discharge head. During the operation of discharging the fluid from the nozzle, the discharge flow rate of the fluid is continuously changed from the first flow rate to the second flow rate.

  According to the present invention, the fluid discharge flow rate is changed from the first flow rate to the second flow rate during the operation of discharging the fluid from the nozzles of the droplet discharge head while the cap is in contact with the nozzle formation surface of the droplet discharge head. Therefore, it is possible to improve the discharge performance of bubbles mixed in the droplet discharge head. That is, by discharging the fluid while changing the flow rate, it is possible to discharge even fine bubbles that are likely to remain in the droplet discharge head. As in the present invention, it is possible to improve the bubble discharge performance by continuously changing the ink discharge flow rate in a single discharge operation. For this reason, the processing time can be shortened, the efficiency of the discharging process can be improved, and good discharge characteristics of the droplet discharge head can be secured.

  Further, a fluid suction means for reducing the pressure in the cap is connected to the cap, and the suction pressure of the fluid suction means is continuously changed from the first suction pressure to the second suction pressure during the operation of discharging the fluid from the nozzle. It has a period to change to.

  According to the present invention, during the operation of discharging the fluid from the nozzle of the droplet discharge head while the cap is in contact with the nozzle formation surface of the droplet discharge head, the suction pressure of the fluid suction operation for reducing the pressure in the cap is set. Since there is a period during which the first suction force is continuously changed to the second suction force, it is possible to improve the discharge performance of bubbles mixed in the droplet discharge head. That is, by sucking the fluid while changing the suction flow rate, it is possible to discharge even microbubbles that are likely to remain in the droplet discharge head.

  In addition, a fluid pumping means for supplying fluid to a flow path communicating with the nozzle is connected to the droplet discharge head, and during the operation of discharging the fluid from the nozzle, the transport pressure of the fluid pumping means is set to the first transport pressure. To a second conveying pressure continuously.

  According to the present invention, during the operation of discharging the fluid from the nozzle of the droplet discharge head while the cap is in contact with the nozzle formation surface of the droplet discharge head, the transfer pressure of the fluid supply means is the first transfer pressure. In this case, it is possible to improve the discharge performance of the bubbles mixed in the droplet discharge head. That is, by discharging the fluid while changing the transport flow rate, it is possible to discharge even microbubbles that tend to remain in the droplet discharge head.

Moreover, it is preferable to have a period in which the discharge flow rate is continuously changed from the second flow rate to the third flow rate.
According to the present invention, in addition to the period in which the first flow rate is continuously changed to the second flow rate, and the period in which the second flow rate is continuously changed to the third flow rate, the fluid is pulsated. Therefore, the bubble discharge efficiency is further improved.

Further, it is preferable to change the discharge flow rate at a constant speed.
By changing the fluid discharge flow rate at a constant speed as in the present invention, the fluid suction means or the fluid pressure feeding means can be easily controlled.

Moreover, it is preferable to change the discharge flow rate intermittently.
According to the present invention, by intermittently changing the fluid discharge flow rate, fine pulsations can be imparted to the fluid, and the bubble discharge performance can be improved.

Moreover, it is preferable to change the said discharge flow rate according to the kind or viscosity of a fluid.
According to the present invention, it is possible to efficiently discharge the bubbles in the droplet discharge head by changing the discharge flow rate according to the type and viscosity of the fluid.

Moreover, it is preferable to change the said discharge flow rate based on the signal from the pressure detection sensor which detects the pressure in a cap.
According to the present invention, by changing the discharge flow rate based on the signal from the pressure detection sensor, efficient suction processing can be performed with an appropriate suction sequence.

Moreover, it is preferable that the fluid is an ink containing a surfactant.
According to the present invention, if the ink contains a surfactant, bubbles are easily discharged together with the ink, and bubbles remaining in the droplet discharge head can be reduced.

Moreover, it is preferable to continuously change the rotation speed of the pump used as the fluid suction means or the fluid pressure feeding means.
According to the present invention, fluid can be discharged at a desired discharge flow rate. In addition, the pump can be easily controlled.

  The droplet discharge device of the present invention has a droplet discharge head having a nozzle for discharging droplets, a cap provided so as to be able to contact the nozzle formation surface of the droplet discharge head, and the nozzle formation surface. And a control device for controlling the operation of discharging the fluid into the cap. The control device continuously changes the fluid discharge flow rate from the first flow rate to the second flow rate during the operation of discharging the fluid from the nozzle. Execute the action to be changed.

  According to the present invention, the fluid discharge flow rate is changed from the first flow rate to the second flow rate during the operation of discharging the fluid from the nozzles of the droplet discharge head while the cap is in contact with the nozzle formation surface of the droplet discharge head. Therefore, it is possible to improve the discharge performance of bubbles mixed in the droplet discharge head. That is, by discharging the fluid while changing the flow rate, it is possible to discharge even fine bubbles that are likely to remain in the droplet discharge head. As in the present invention, it is possible to improve the bubble discharge performance by continuously changing the ink discharge flow rate in a single discharge operation. For this reason, the processing time can be shortened, the efficiency of the discharging process can be improved, and good discharge characteristics of the droplet discharge head can be secured.

In addition, the controller includes a fluid suction unit that is connected to the cap and depressurizes the inside of the cap, and the control device continues the suction pressure of the fluid suction unit from the first suction force to the second suction force during the operation of discharging the fluid. It is preferable to carry out an operation that changes automatically.
According to the present invention, it is possible to improve the discharge performance of bubbles mixed in the droplet discharge head. That is, by sucking the fluid while changing the suction flow rate, it is possible to discharge even microbubbles that are likely to remain in the droplet discharge head.

The cap is preferably provided with a pressure detection sensor for detecting the pressure in the cap, and the control device preferably controls the fluid suction means or the fluid pressure feeding means based on the output of the pressure detection sensor.
According to the present invention, since the drive of the fluid suction means or the fluid pressure feeding means can be controlled according to the detection result of the pressure in the cap by the pressure detection sensor, efficient suction processing can be performed with an appropriate suction sequence.

  Embodiments of the present invention will be described below with reference to the drawings. In each drawing used for the following description, the scale of each member is appropriately changed to make each member a recognizable size.

[Droplet discharge device]
FIG. 1 is a perspective view showing a schematic configuration of a droplet discharge device according to an embodiment of the present invention. In the following description, if necessary, an XYZ orthogonal coordinate system is set in the drawing, and the positional relationship of each member will be described with reference to this XYZ orthogonal coordinate system. In the XYZ orthogonal coordinate system, the XY plane is set to a plane parallel to the horizontal plane, and the Z axis is set to the vertically upward direction. In this embodiment, the moving direction of the droplet discharge head 20 is set in the X direction, and the moving direction of the stage ST is set in the Y direction.

  As shown in FIG. 1, the droplet discharge device IJ of the present embodiment is supported on a base 10, a stage ST that supports a substrate P such as a glass substrate on the base 10, and above the stage ST (+ Z direction). And a droplet discharge head 20 capable of discharging predetermined droplets onto the substrate P. Between the base 10 and the stage ST, a first moving device 12 that supports the stage ST so as to be movable in the Y direction is provided. Further, a second moving device 14 that supports the droplet discharge head 20 so as to be movable in the X direction is provided above the stage ST.

  The droplet discharge head 20 is connected to an ink tank 16 for storing a solvent (liquid material) of droplets discharged from the droplet discharge head 20 via the flow path 18.

  A capping unit 22 and a cleaning unit 24 are disposed on the base 10. The maintenance device 19 is configured by the capping unit 22 and the cleaning unit 24 and the suction pump (fluid suction means) 21 installed on the side of the stage ST. A waste ink tank 17 is disposed downstream of the suction pump 15.

  The control device 26 controls each part (for example, the first moving device 12, the second moving device 14, and the maintenance device 19) of the droplet discharge device IJ to control the entire operation of the droplet discharge device IJ.

  The first moving device 12 is installed on the base 10 and is positioned along the Y-axis direction. The first moving device 12 includes, for example, a linear motor, and includes guide rails 12a and 12a, and a slider 12b provided to be movable along the guide rail 12a. The slider 12b of the linear motor type first moving device 12 can be positioned by moving in the Y-axis direction along the guide rail 12a.

  The slider 12b includes a motor 12c for rotating around the Z axis (θZ). The motor 12c is, for example, a direct drive motor, and the rotor of the motor 12c is fixed to the stage ST. Thus, by energizing the motor 12c, the rotor and the stage ST can rotate along the θZ direction to index (rotate index) the stage ST. That is, the first moving device 12 can move the stage ST in the Y-axis direction and the θZ direction. The stage ST holds the substrate P and positions it at a predetermined position.

  The stage ST has a suction holding device (not shown). When this suction holding device is operated, the substrate P is sucked and held on the stage ST through a suction hole (not shown) provided in the stage ST. .

  The second moving device 14 is mounted upright with respect to the base 10 using the support columns 28 a and 28 a, and is mounted at the rear portion 10 a of the base 10. The second moving device 14 is constituted by a linear motor and is supported by a column 28b fixed to the columns 28a and 28a. The second moving device 14 includes a guide rail 14a supported by the column 28b, and a slider 14b supported so as to be movable in the X-axis direction along the guide rail 14a. The slider 14b can be positioned by moving in the X-axis direction along the guide rail 14a. The droplet discharge head 20 is attached to the slider 14b.

  The droplet discharge head 20 has motors 30, 32, 34, and 36 as swing positioning devices. When the motor 30 is driven, the droplet discharge head 20 can be moved up and down along the Z direction, and the droplet discharge head 20 can be positioned at an arbitrary position in the Z direction. When the motor 32 is driven, the droplet discharge head 20 can be swung along the β direction around the Y axis, and the angle of the droplet discharge head 20 can be adjusted. When the motor 34 is driven, the droplet discharge head 20 can be swung along the γ direction around the X axis, and the angle of the droplet discharge head 20 can be adjusted. When the motor 36 is driven, the droplet discharge head 20 can be swung along the α direction around the Z axis, and the angle of the droplet discharge head 20 can be adjusted.

  As described above, the droplet discharge head 20 shown in FIG. 1 can move linearly in the Z direction, and can swing and adjust the angle along the α, β, and γ directions. It is supported by the slider 14b. The position and posture of the droplet discharge head 20 are accurately controlled by the control device 26 so that the position or posture of the nozzle forming surface 20a with respect to the substrate P on the stage ST side becomes a predetermined position or a predetermined posture. A plurality of ejection nozzles NZ (FIG. 2A) for ejecting droplets are provided on the nozzle forming surface 20a of the droplet ejection head 20.

  Droplets discharged from the droplet discharge head 20 include organic EL such as ink containing a coloring material, a dispersion containing a material such as metal fine particles, a hole injection material such as PEDOT: PSS, and a light emitting material. Droplets containing various materials such as solutions containing substances, high-viscosity functional liquids such as liquid crystal materials, functional liquids containing microlens materials, biopolymer solutions containing proteins, nucleic acids, etc. Adopted.

  FIG. 2 is a schematic diagram of a droplet discharge head provided in the droplet discharge apparatus of the present embodiment. 2A is a schematic cross-sectional view, FIG. 2B is an explanatory view showing the configuration of a surface (lower surface) for discharging droplets, and FIG. 2C is a configuration including a plurality of droplet discharge heads. FIG.

  A droplet discharge head 20 shown in FIG. 2A is a multi-nozzle type droplet discharge head including a plurality of discharge nozzles NZ. The plurality of discharge nozzles NZ are provided on the lower surface of the droplet discharge head 20 in one direction at regular intervals. The amount of one droplet discharged from the discharge nozzle NZ of the droplet discharge head 20 is about 1 to 300 nanograms.

  In the present embodiment, a droplet discharge head 20 that employs an electromechanical conversion type discharge technique is used. In this method, the piezoelectric element PZ is installed adjacent to the liquid chamber 161 that stores the liquid material. The liquid material is supplied to the liquid chamber 161 via a liquid material supply system 163 including a material tank that stores the liquid material. The piezoelectric element PZ is connected to the drive circuit 164. By applying a voltage to the piezoelectric element PZ via the drive circuit 164 and deforming the piezoelectric element PZ, the liquid chamber 161 is deformed to increase the internal pressure, and the discharge is performed. Liquid droplets are ejected from the nozzle NZ. In this case, the amount of distortion of the piezoelectric element PZ is controlled by changing the value of the applied voltage, and the discharge amount of the liquid material is controlled.

  As shown in FIG. 2B, the droplet discharge head 20 is provided with a nozzle row 170 composed of, for example, 180 discharge nozzles NZ (NZ1 to NZ180) in which discharge nozzles NZ are arranged on the lower surface thereof. Here, the discharge nozzles NZ are arranged in parallel with the major axis direction of the lower surface of the droplet discharge head 20 having a substantially rectangular shape in plan view. In the figure, the discharge nozzles NZ are arranged in one row, but for example, two rows may be arranged in a staggered manner, or three or more rows may be arranged. Further, the number of discharge nozzles NZ constituting the nozzle row 170 is not particularly limited.

  The carriage is configured by mounting a plurality of droplet discharge heads 20. In FIG. 2C, the number of droplet discharge heads 20 mounted on the carriage 21 is three, but the present invention is not limited to this. Here, the three droplet discharge heads 20 are continuously arranged in one row in the major axis direction in which the discharge nozzles NZ are arranged, but the plurality of droplet discharge heads 20 are arranged in two rows in a staggered manner, for example. It may be arranged, or may be arranged in three or more rows.

FIG. 3 is a cross-sectional view showing a schematic configuration of the maintenance device 19.
As shown in FIG. 3, the cap 23 which is a component of the capping unit 22 includes a cap holder 23a and a cap member 23b. The cap holder 23 a is formed in a box shape having an upper opening, and is disposed so that the opening surface faces the nozzle forming surface 20 a of the droplet discharge head 20. The cap member 23b is made of a flexible material such as an elastomer and is supported by the inner wall surface of the cap holder 23a. The upper end edge of the cap member 23b protrudes above the upper end edge of the cap holder 23a.

Two cap-shaped ink absorbing materials (fluid absorbing materials) S made of a sponge material or the like are accommodated in the cap member 23b. The ink absorber S receives and absorbs ink ejected from the droplet ejection head 20.
Further, a pressure detection sensor 29 is further connected to the cap member 23b, and the internal pressure of the cap 23 that seals the nozzle forming surface 20a of the droplet discharge head 20 can be detected.

  An ink discharge port 25 is formed through the bottom surface of the cap holder 23a, and a discharge tube 27 is connected to the bottom surface of the cap holder 23a. The ink discharge port 25 and the flow path in the discharge tube 27 are arranged to communicate with each other. The ink discharged into the cap 23 flows into the flow path in the discharge tube 27 through the ink discharge port 25.

  The suction pump 15 is connected to the other end side (the side opposite to the cap 23) of the discharge tube 27. The suction pump 15 is for discharging ink or the like in the discharge nozzle NZ into the cap 23. The maintenance process is performed when an execution command is sent out by the printer control device 26, such as when the printer resumes printing after pausing printing for a long period of time. At that time, the carriage 21 is moved to the home position, and the droplet discharge head 20 is disposed above the cap 23.

  In addition, an air communication port (not shown) is formed through the bottom surface of the cap 23, and an air release valve 42 is provided at the air communication port via an air communication tube 41. When the atmosphere release valve 42 is opened, a space formed between the nozzle forming surface 20 a and the cap 23 (hereinafter referred to as a sealed space K) is opened to the atmosphere via the atmosphere communication tube 41.

  Such a capping unit 22 is used in a suction operation or a flushing operation for recovering or maintaining the ink ejection characteristics of the droplet discharge head 20. Further, the capping unit 22 dries the discharge nozzle NZ by volatilizing the ink solvent absorbed in the sealed space K between the nozzle formation surface 20a and the cap 23 when the cap 23 seals the nozzle formation surface 20a. Can also be prevented.

  By the way, when the ink tank 16 or the carriage 21 is replaced, reconnection of the flow path 18 occurs, so that bubbles may enter the flow path 18. These bubbles need to be discharged before printing because they may cause a discharge failure of the droplet discharge head 20. Conventionally, bubbles are discharged by sucking ink at a high speed (the suction flow rate per unit time is constant). However, due to a difference in flow velocity generated between the center of the flow path (hereinafter simply referred to as the ink flow path) in which the ink flows in the flow path 18 connected to the ink tank 16 and the droplet discharge head 20 and the periphery thereof. The minute bubbles attached to the flow path 18 and the inner wall of the droplet discharge head 20 remained difficult to be discharged.

  In order to solve such a problem, in the present embodiment, bubbles are discharged by sucking the ink in the droplet discharge head 20 from the discharge nozzle NZ at the time of refilling the ink. Examples of the ink suction method (fluid discharge method) according to the present invention will be described below.

[Example 1]
FIG. 4 is a diagram illustrating a suction sequence in the ink suction method according to the first embodiment. The vertical axis represents the suction pressure P (KPa) by the suction pump 15 and the horizontal axis represents the elapsed time (sec).

  In this embodiment, first, the carriage 21 is lowered, and the droplet discharge head 20 is brought into contact with the cap 23 to seal the nozzle forming surface 20a.

  In a state where the nozzle forming surface 20 a of the droplet discharge head 20 is sealed with the cap 23, the suction pump 15 is driven with the first output so that a predetermined space is formed in the sealed space K formed between the nozzle forming surface 20 a and the cap 23. The suction pressure P1 (first suction pressure) is applied, and the ink is discharged from the discharge nozzle NZ into the cap 23 at a high speed (first flow rate) (S1: first discharge step). By this step, bubbles mixed in the flow path 18 and the droplet discharge head 20 are discharged to some extent together with the ink.

  Next, by gradually decreasing the output of the suction pump 15 from the first output to the second output, the suction pressure P1 applied to the sealed space K is changed to the suction pressure P2 (second suction force), The ink suction speed (flow rate) is changed from high speed (first flow rate) to low speed (second flow rate) (S2: flow rate changing step). In the present embodiment, the output of the suction pump 15 is changed from the first output to the second output over a time approximately equal to the processing time in the first discharge process. In this way, the difference in flow velocity that occurs between the center of the flow path (ink flow path) through which the ink flows and the periphery thereof is gradually eliminated. That is, by changing the flow of ink, the microbubbles remaining in the ink flow path are moved, and the concentrated growth of the microbubbles is promoted.

  Next, the output of the suction pump 15 is changed to the second output and is maintained in that state, and the suction pressure P2 lower than the suction pressure P1 is applied to the sealed space K for a predetermined time, whereby ink is discharged from the discharge nozzle NZ. Discharge at a low speed (second flow rate) (S3: second discharge step). By performing the low speed ink suction for a predetermined time, the microbubbles are further concentrated and grown and discharged together with the ink. If the microbubbles grow together with other bubbles to a certain size, they are easily discharged together with the ink. In the same process, for example, an action of spontaneously eliminating extremely small bubbles is also included.

Further, by sucking ink at a low speed, a meniscus for preparation for ejection is formed in the discharge nozzle NZ while preventing foaming of the ink.
Thereafter, the drive of the suction pump 15 is stopped and the air release valve 42 is opened to release the sealed space K to the atmosphere, and the series of processes is terminated (S4).

  In this embodiment, in each step, the output of the suction pump 15 is appropriately controlled according to the type and viscosity of ink, the pressure detection result in the cap 23 by the pressure detection sensor 29, and the like.

  In the ink discharge method of the present embodiment, the output of the suction pump 15 during processing, that is, the rotation speed thereof, is continuously changed so that a negative pressure is continuously applied to the sealed space K. The discharge flow rate of the discharged ink is continuously changed. By continuously changing the ink discharge flow rate during the operation of discharging ink from the droplet discharge head 20, it is possible to improve the discharge performance of bubbles mixed in the droplet discharge head 20. In other words, by continuously changing the ink suction flow rate, it is possible to discharge even microbubbles that tend to remain in the flow path 18 and the droplet discharge head 20. Rather than sucking ink at a constant flow rate as in the prior art, microbubbles are concentrated and grown by continuously changing the ink suction flow rate by a single suction process, and are easily discharged together with ink.

  Therefore, in the present embodiment, since there is a flow rate changing step (S2) in which the ink discharge flow rate is continuously changed during the operation of discharging the ink from the droplet discharge head 20, Air bubbles can be efficiently discharged, and as a result, the ink discharge characteristics of the droplet discharge head 20 can be maintained well.

  Conventionally, there is a method in which ink is discharged intermittently at a constant flow rate by dividing the ink discharge operation into a plurality of times. For example, the ink is discharged and the bubbles are removed by intermittently performing the ink high-speed suction step and the low-speed suction step at a constant pressure for a predetermined time. Specifically, in this method, since the sealing of the nozzle forming surface by the cap was once released between the high-speed suction process and the low-speed suction process, the pressure in the sealed space is stable during the movement of the cap and re-suction. There has been a problem such as a long waiting time until it is turned on.

  On the other hand, in this embodiment, a series of suction operations are performed while the nozzle forming surface 20a is sealed with the cap 23, and the cap 23 is not moved during the processing as in the prior art. For this reason, the moving time of the cap 23 and the waiting time until the pressure in the sealed space K is stabilized can be reduced and the processing time can be shortened, so that the efficiency of the suction processing can be improved.

  Note that the suction sequence is not limited to that in FIG. 4, and it is possible to control the driving of the suction pump 15 according to the type and viscosity of the ink and the detection result of the pressure in the cap 23 by the pressure detection sensor 29. Efficient suction processing can be performed by the suction sequence. Here, for example, a table corresponding to the type and viscosity of the ink may be prepared in advance. Thereby, the bubbles in the droplet discharge head 20 can be efficiently discharged. Further, if ink containing a surfactant is used, bubbles are easily discharged together with the ink, and bubbles remaining in the droplet discharge head 20 can be reduced.

[Example 2]
FIG. 5 is a diagram illustrating a suction sequence in the ink suction method according to the second embodiment. The vertical axis represents the suction pressure P (KPa) by the suction pump 15 and the horizontal axis represents the elapsed time (sec). Note that the description of the same steps as in the previous embodiment will be simplified.

  After sealing the nozzle forming surface 20a of the droplet discharge head 20 with the cap 23 as shown in FIG. 3, the suction pump 15 is first driven with the second output, and the suction pressure P2 is applied to the sealed space K for a predetermined time. Apply (S11). First, the ink in the flow path 18 or the droplet discharge head 20 is caused to flow by sucking the ink at a low speed (first flow rate) for a predetermined time. For example, the inner wall of the ink flow path in the flow path 18 or the droplet discharge head 20 The bubbles adhering to the ink and the bubbles caught in the pressure chamber are caused to flow together with the ink.

  Next, the output of the suction pump 15 is gradually increased (S12: flow rate changing step), and the pressure applied to the sealed space K is changed from the suction pressure P2 to a higher suction pressure P1. The suction pump 15 is maintained at the first output for a predetermined time (S13), and the flowing ink is sucked at a high speed (second flow rate).

  Thereafter, the output of the suction pump 15 is gradually reduced to the second output, and the pressure applied to the sealed space K is changed from the suction pressure P1 to the suction pressure P2 (S14: flow rate changing step). Thereafter, the suction pump 15 is driven with the second output for a predetermined time to suck the ink again at a low speed (third flow rate) (S15), and the suction pressure P2 is applied to the sealed space K for a predetermined time.

  Thus, by continuously changing the ink suction speed in the order of low speed, high speed, and low speed, it is possible to pulsate the flow of ink, and it is possible to discharge bubbles more efficiently. It is possible to further promote the collective growth of the microbubbles in the ink flow path by causing the ink in the ink flow path to flow at a low speed in advance and then gradually increasing the flow velocity.

Therefore, in this embodiment, since the ink discharge flow rate is changed continuously (S12, S14) during the operation of discharging the ink from the droplet discharge head 20, the droplet discharge head 20 is provided. The bubbles inside can be efficiently discharged, and as a result, the ink discharge characteristics of the droplet discharge head 20 can be maintained well.
The suction sequence is not limited to that shown in FIG. 5 and can be changed as appropriate.

  The preferred embodiments according to the present invention have been described above with reference to the accompanying drawings. However, it goes without saying that the present invention is not limited to such examples, and the above embodiments may be combined. It is obvious for those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea described in the claims. It is understood that it belongs to.

  For example, in the previous embodiment, the ink discharge flow rate is changed at a constant speed in each flow rate changing step (S2, S12, S14), but the ink discharge flow rate changes continuously in a plurality of stages. Thus, fine pulsation may be imparted to the ink by controlling the output of the suction pump 15 as described above. As a result, the ink can be vibrated and the remaining bubbles can be discharged more effectively.

  Further, an ejector may be used in place of the suction pump 15, and in that case, the ink suction flow rate is changed by continuously changing the set value of the ejector through each process by the control device 26.

  In the bubble removal process in the previous embodiment, it is also possible to provide an action for eliminating clogging of the discharge nozzle NZ.

  Further, a pressure pump (fluid pressure feeding means) may be disposed on the flow path 18 connecting the ink tank 16 and the droplet discharge head 20. In the previous embodiment, the ink is sucked from the droplet discharge head 20 by the action of the suction pump 15 of the maintenance device 19, but the droplet discharge is performed by transporting the ink in the flow path 18 by the action of the pressure pump. Ink may be forcibly discharged from the head 20. As the sequence for discharging the ink by the pressurizing pump at this time, the sequence by the suction pump 15 in the first and second embodiments can be applied. For example, the ink transport pressure of the pressure pump in the flow rate changing process is continuously from the first transport pressure (for example, corresponding to the suction pressure P1 in FIG. 4) to the second transport pressure (corresponding to the suction pressure P2 in FIG. 4). In this way, the ink discharge flow rate is continuously changed.

  In addition, ink (bubbles) in the droplet discharge head 20 can be efficiently discharged by appropriately changing the ink transport pressure and suction time by the pressure pump in each process according to the type and viscosity of the ink. It is.

1 is a schematic diagram illustrating the entirety of a droplet discharge device according to an embodiment. FIG. 3 is a schematic diagram of a droplet discharge head according to the present embodiment. Schematic of the maintenance apparatus which concerns on this embodiment. 6 is a suction sequence of the ink discharging method in Embodiment 1. 9 is a suction sequence of the ink discharging method in Embodiment 2.

Explanation of symbols

IJ: droplet discharge device, 20: droplet discharge head, NZ: discharge nozzle, 20a ... nozzle forming surface, 23 ... cap, 15 ... suction pump (fluid suction means), 29 ... pressure detection sensor, 26 ... control device, P1 ... suction pressure (first suction pressure), P2 ... suction pressure (second suction pressure)

Claims (12)

A fluid discharge method for discharging a fluid from a nozzle of the droplet discharge head by bringing a cap into contact with a nozzle forming surface of the droplet discharge head,
During the operation of discharging the fluid from the nozzle, the fluid discharging method has a period of continuously changing the fluid discharge flow rate from the first flow rate to the second flow rate at a constant speed . Fluid suction means for reducing the pressure in the cap is connected to the cap,
2. The method according to claim 1, further comprising a period during which the suction pressure of the fluid suction means is continuously changed from the first suction pressure to the second suction pressure during the operation of discharging the fluid from the nozzle. Fluid discharge method. A fluid pumping means for supplying the fluid to a flow path communicating with the nozzle is connected to the droplet discharge head,
2. The method according to claim 1, further comprising a period of continuously changing the transport pressure of the fluid pumping unit from the first transport pressure to the second transport pressure during the operation of discharging the fluid from the nozzle. Fluid discharge method.   The fluid discharge method according to claim 1, further comprising a period in which the discharge flow rate is continuously changed from the second flow rate to the third flow rate. The fluid discharge method according to any one of claims 1 to 4 , wherein the discharge flow rate is changed in accordance with the type or viscosity of the fluid. The fluid discharge method according to any one of claims 1 to 5 , wherein the discharge flow rate is changed based on a signal from a pressure detection sensor that detects a pressure in the cap. The fluid discharging method according to any one of claims 1 to 6 , wherein the fluid is an ink containing a surfactant. 4. The fluid discharging method according to claim 2, wherein the number of revolutions of a pump used as the fluid suction means or the fluid pressure feeding means is continuously changed. A droplet discharge head having a nozzle for discharging droplets;
A cap provided so as to be able to contact the nozzle forming surface of the droplet discharge head;
A control device for controlling the operation of discharging the fluid into the cap in contact with the nozzle forming surface;
The controller performs an operation of continuously changing the discharge flow rate of the fluid from the first flow rate to the second flow rate at a constant speed during the operation of discharging the fluid from the nozzle. Droplet discharge device. A fluid suction means connected to the cap and depressurizing the inside of the cap;
The control device performs an operation of continuously changing the suction pressure of the fluid suction means from a first suction force to a second suction force during the operation of discharging the fluid. 9. A droplet discharge device according to item 9 . Fluid pressure feeding means connected to the droplet discharge means and supplying the fluid to a flow path communicating with the nozzle;
The said control apparatus performs the operation | movement which changes continuously the conveyance pressure of the said fluid pumping means from a 1st conveyance pressure to a 2nd conveyance pressure during the operation | movement which discharges | emits the said fluid. 9. A droplet discharge device according to item 9 . The cap is provided with a pressure detection sensor for detecting the pressure in the cap, and the control device controls the fluid suction means or the fluid pressure feeding means based on an output of the pressure detection sensor. The droplet discharge device according to any one of claims 9 to 11 .

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