JP2011062934A - Ink filling method for inkjet printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink filling method for an inkjet printer in which the incorporation of foreign matter is eliminated without using a means for sealing a nozzle and initial filling into an ink path is easy. <P>SOLUTION: The inkjet printer includes an ink circulation path including: a recording head; an ink supply path including an upstream tank storing ink supplied to the recording head and an ink path connected between the upstream tank and the recording head; an ink return path including a downstream tank storing the ink discharged from the recording head and an ink path connected between the downstream tank and the recording head; an ink path connected between the ink supply path and the ink return path; and a negative pressure setting means for setting negative pressure in the ink return path. The ink is supplied to the recording head from the ink supply path by gravity and the negative pressure is set in the ink return path by the negative pressure setting means, to fill the recording head with the ink. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for filling ink into an ink jet printer having an ink circulation path.

  In general, an ink jet printer that performs image recording by ejecting ink droplets onto a recording medium by a recording head having a plurality of nozzles is known. As an example of such an ink jet printer, an image recording apparatus equipped with an ink circulation path is disclosed in Patent Document 1, for example.

  In the image recording apparatus of Patent Document 1, as an ink circulation path, an ink supply path for supplying ink to the recording head, and ink feedback for returning ink discharged without being used (discharged) by the recording head to the ink tank. And a path (or an ink discharge path).

  When bubbles enter the ink circulation path and reach the nozzles of the recording head, there is a problem in that the ejection of the ink is hindered to cause the ejection failure or the prescribed amount of ink droplets is not ejected. To eliminate air bubbles from the ink path in order to prevent such problems, the nozzle sealing cap is brought into close contact with the nozzle surface of the recording head, and the ink discharge path side is set to a negative pressure so that the ink supply path is removed. Bubbles in the head are put on the ink newly flowing into the recording head, and discharged to the ink discharge path. This recovery operation can be performed in the same manner as in the case of air bubble removal when the ink is first filled into the recording head and the ink path connected to the recording head (hereinafter referred to as initial filling).

JP 2007-313817 A

  In the conventional method, it is possible to create negative pressure only after the nozzle surface of the recording head is sealed. By this negative pressure, ink is guided from the ink supply path to the recording head, and bubbles adhering to the nozzle holes are separated and discharged. As a means for sealing the nozzle, for example, a rubber cap or the like is used as in the nozzle sealing cap in the cited document 1.

  The cap is effective in terms of preventing the ink from volatilizing from the nozzles, but there are cases where a kind of ink that does not need to be prevented from volatilizing is used. For example, in oil-based inks and UV inks containing a large amount of high-boiling solvents, the volatilization of the ink is very small, and therefore a cap for the purpose of preventing volatilization is not always necessary during normal use. Therefore, providing the cap and its driving mechanism for the initial filling and after repair results in wasted space and cost around the recording head, which is not practical.

  In addition, in the case of an ink path for circulating ink, a filter is provided on the ink path for the purpose of removing foreign matter, a lump of ink, and the like from the ink discharged without being ejected from the recording head. If the purpose is to remove foreign matter, the filter is preferably arranged immediately before the ink supply port of the recording head. However, since ink flows in the ink supply path to the recording head due to the weight of the ink, it is necessary to reduce pressure loss in the ink path. For this reason, it is difficult to provide a fine filter in the ink path near the recording head.

  On the other hand, by eliminating the filter, the ink flow is improved and the initial filling is facilitated. However, dust may be mixed in the ink path when the print head is assembled or during the operation of attaching the print head to the ink path. For this reason, when ink is initially filled into the ink path, dust is removed by a filter provided in the path by circulation.

  SUMMARY OF THE INVENTION In view of the above-described problems, an object of the present invention is to provide an ink filling method for an ink jet printer that can eliminate foreign matter contamination and can easily perform initial filling into an ink path without using a means for sealing a nozzle. And

  According to an embodiment of the present invention, a recording head that discharges ink, an upstream tank that stores ink to be supplied to the recording head, a first tank that communicates between the upstream tank and the recording head, and distributes the ink. An ink supply path disposed above the recording head in a gravitational direction, a downstream tank containing ink discharged from the recording head, and communication between the downstream tank and the recording head. An ink return path having a second ink path through which ink flows, an ink communication path between the ink supply path and the ink return path, and a third ink path through which ink flows; and an ink return path In an ink jet printer having an ink circulation path having a negative pressure setting means for making a negative pressure inside, the ink is supplied from the ink supply path by its own weight. It supplies the click to the recording head, by setting the ink return path to a negative pressure by the negative pressure setting means, an ink filling method for causing filling the ink into the recording head.

  The embodiment according to the present invention also includes a recording head that ejects ink, an upstream tank that stores ink to be supplied to the recording head, and a communication between the upstream tank and the recording head. An ink supply path having a first ink path, a downstream tank that stores ink discharged from the recording head, and a second tank that communicates between the downstream tank and the recording head and circulates the ink. An ink return path having an ink path, a third ink path communicating with the ink supply path and the ink return path, and supplying ink in the ink supply path to the recording head. An ink jet printer having an ink circulation path having an ink supply means for supplying the ink and a negative pressure setting means for setting a negative pressure in the ink return path. The ink supply means supplies ink from the ink supply path toward the recording head, and the negative pressure setting means sets the ink feedback path to a negative pressure so that the recording head is filled with ink. Ink filling method.

  ADVANTAGE OF THE INVENTION According to this invention, the ink filling method of the inkjet printer which can eliminate the mixing of a foreign material and can perform initial filling to an ink path | route easily without using the means to seal a nozzle can be provided.

FIG. 1 is an overall view of an ink path of the ink jet printer according to the first embodiment. FIG. 2 is a cross-sectional view of the recording head. FIG. 3 is a perspective view of the recording head. FIG. 4 is a schematic diagram of the ink path of the first embodiment. FIG. 5 is a schematic diagram of an ink path according to the second embodiment. FIG. 6 is a flowchart for explaining the initial filling operation in the first embodiment. FIG. 7 is a flowchart for explaining the initial filling operation in the second embodiment. FIG. 8 is a flowchart for explaining a circulation operation common to the first and second embodiments. FIG. 9 is a diagram illustrating a state in which air is sucked from the nozzle hole while the nozzle hole is filled with ink. FIG. 10 is a time chart for explaining the initial filling operation in the first embodiment. FIG. 11 is a time chart for explaining the initial filling operation in the second embodiment. FIG. 12 is a time chart for explaining a circulation operation common to the first and second embodiments. FIG. 13 is a diagram illustrating a path sensor that detects ink in Modification 1 of the first embodiment. FIG. 14 is a time chart for explaining the initial filling operation in the first modification of the first embodiment. FIG. 13 is a diagram illustrating a path sensor that detects ink in Modification 2 of the first embodiment. FIG. 15 is a time chart for explaining the initial filling operation in the second modification of the first embodiment.

  Hereinafter, an ink filling method of an ink jet printer (image recording apparatus) according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is an overall view of an ink path of the inkjet printer 1 according to the first embodiment. In the following description, in the horizontal direction in the drawing, the recording medium conveyance direction is defined as the X direction, the direction orthogonal to the recording medium conveyance direction is defined as the Y direction, and the height direction orthogonal to the X direction and the Y direction is defined as the Z direction. .

  The inkjet printer 1 includes a recording head 2 that ejects ink onto a recording medium, an ink bottle 3, a downstream tank 4 that stores ink supplied from the ink bottle 3 and ink discharged from the recording head 2, and a downstream tank 4. A pump 5 for pumping ink, a heat exchanger 6 for transferring heat of the circulating ink, an upstream tank 7 for storing ink to be supplied to the recording head 2, and ink overflowing from the downstream tank 4 and the upstream tank 7 The waste liquid bottle 8 to be stored and the air filter 9 provided in the atmosphere opening path connected to the ink bottle 3 are configured.

  Although the configuration of the ink path related to the gist of the invention is described here, the printer 1 has a configuration provided in a normal printer such as a recording medium supply mechanism, a transport mechanism, a discharge mechanism, and a control unit (not shown). Have.

  Further, the printer 1 communicates from the downstream tank 4 to the upstream tank 7 and communicates with the pump 5 and the heat exchanger 6 on the way, and communicates with the ink path 10 through which ink flows and the upstream tank 7 to the recording head 2. The ink supply path 11 circulates the ink, and the ink discharge path 12 communicates from the recording head 2 to the downstream tank 4 and circulates (discharges) the ink from the recording head 2. The ink path 10, the ink supply path 11, and the ink discharge path 12 constitute an ink circulation path.

  Further, in order to release air to each tank 4, 7 by releasing air, an atmosphere release path 14 connected to the upper part of the downstream tank 4 via the atmosphere release valve 13 and an upstream via the atmosphere release valve 15. The open end 16 is connected to the upper part of the tank 7, and the respective open ends are inserted into the overflow path 17. The air release valve 13 is a solenoid valve, and is normally open so that the path communicates when power is shut off. The atmosphere release valve 15 is an electromagnetic valve and is normally closed when the power is shut off.

  The overflow path 17 has a larger cross-sectional area than the other paths, and is provided, for example, inclined at about 5 degrees in the Z direction as shown in FIG. A lower surface on the lowest side of the overflow path 17 is connected to the waste liquid bottle 8 via a waste liquid path 18, and one end of an air release path 19 (described later) is connected to an upper surface on the highest side. The waste liquid bottle 8 is disposed below the printer 1 and opened to the outside by an air release path 20.

  With this configuration, if any abnormality occurs in the printer 1 with the power turned on (the valve 15 is open), the upstream tank passes through the atmosphere release path 16, the overflow path 17, and the waste liquid path 18. The ink overflowing from 7 can be guided to the waste liquid bottle 8. Further, when any abnormality occurs in the printer 1 with the power off (the valve 13 is open), it overflows from the downstream tank 4 via the atmosphere release path 14, the overflow path 17 and the waste liquid path 18. The ink can be guided to the waste liquid bottle 8.

  Further, the printer 1 passes through the atmosphere release path 19 connected to the air filter 9 from the overflow path 17, the atmosphere release path 21 connected from the air filter 9 to the ink bottle 3, and the ink bottle 3 via the ink supply valve 22. And an ink supply path 23 connected to the downstream tank 4.

  The ink bottle 3 is arranged at a position higher in the Z direction than the upstream tank 7. There is an air layer in the upper part of the ink bottle 3, and this air layer communicates with the atmosphere via an atmosphere opening path 21 for introducing air into the ink bottle 3. The air filter 9 to which the atmosphere release path 21 is connected has a mesh size of about 5 μm, for example, and prevents dust contained in external air from entering the ink path.

  Actuators 24 and 25 for detecting the liquid level in each tank are attached to the downstream tank 4 and the upstream tank 7 so as to be swingable with one end as a fulcrum. The other end side of the swing fulcrum has a float shape holding air, and a magnet is provided in the float shape portion. Outside the tanks 4 and 7, liquid level sensors 26 and 27 including reed switches are provided at positions facing the magnets, respectively. The liquid level sensors 26 and 27 can detect the liquid level in each tank by the actuators 24 and 25 that swing according to the liquid level.

  The liquid level in the downstream tank 4 is designed to be, for example, a height H1 that is about 50 mm lower than the nozzle surface 101a (shown in FIG. 2) of the recording head 2. Further, the liquid level in the upstream tank 7 is designed to have a height H2 that is about 100 mm higher than the nozzle surface 101a of the recording head 2, for example. These design values vary depending on the specifications of the apparatus, and are based on the ink ejection state and the meniscus state of the recording head.

  The pump 5 is a diaphragm pump driven by a pulse motor, and varies the flow rate by controlling the rotational speed of a pulse motor mounted on a drive board (not shown). The heat exchanger 6 is made of a material having good thermal conductivity such as aluminum, copper, and stainless steel. The heat exchanger 6 is in close contact with the heat exchange channel 28 through which ink flows and transfers heat. And a fan 30 for radiating waste heat of the Peltier element 29 to the outside.

  The suction port of the ink path 10 extends to the vicinity of the bottom surface in the downstream tank 4 and is immersed in the ink. The ink in the downstream tank 4 is pumped up by driving the pump 5, and the temperature of the ink is adjusted by the heat exchanger 6 in the middle of the heat exchange 6, and is carried to the upstream tank 7. A pressure sensor 31 for measuring the pressure of the air layer in the downstream tank 4 is provided inside the downstream tank 4. By driving the pump 5 with the valve 13 of the air release path 14 connected to the downstream tank 4 closed, the internal pressure of the downstream tank 4 becomes negative. The pump 5 is controlled by the rotational speed of the pulse motor so that the negative pressure becomes a predetermined value. That is, the pump 5 is controlled to rotate at a relatively high speed when it is desired to increase the negative pressure and to be rotated at a relatively low speed when it is desired to decrease the negative pressure.

  Inside the upstream tank 7 is provided a filter 32 for removing foreign matters (dust or lump of ink) mixed in the ink. The ink transported from the downstream tank 4 to the upstream tank 7 by the pump 5 passes through the filter 32 to remove foreign matters.

  In the above description, only the ink circulation path for one color is shown. However, the inkjet printer 1 that records a color image has, for example, four colors of ink of cyan, black, magenta, and yellow, and each ink color. Have independent ink circulation paths.

Next, the internal structure of the recording head 2 will be described with reference to FIGS.
On one side of the base 103 of the recording head 2, a frame 102 having a peripheral portion and having a hollow at the center is bonded, and the piezoelectric element 104 is bonded in a pair to the one surface of the base 103. ing. The frame 102 and the piezoelectric element 104 are provided at the same height in the Z direction so as to close the cavity. Further, the nozzle plate 101 is laminated and adhered to the frame 102 and the piezoelectric element 104 in the Z direction.

  In the piezoelectric element 104, a plurality of channels 104a are dug in the X direction. These channels 104a are dug so as to be parallel to the Y direction. The channel pitch is, for example, about 170 μm, and the channel shape is, for example, a width of 85 μm and a depth of 300 μm. The two piezoelectric elements 104 forming a pair are arranged with a half pitch shift in the Y direction.

  The nozzle surface 101a of the nozzle plate 101 is provided with a nozzle hole 101b for discharging ink in the Z direction at the center of each channel 104a.

  As shown in FIG. 3, the base 103 has a plurality of holes 103 a arranged in the Y direction at the center of a pair of piezoelectric elements 104. These holes 103a are, for example, through-holes having a diameter of about 1 mm and arranged at intervals of 3 mm. Similarly, a plurality of holes 103b are arranged at positions of gaps on both sides of the frame 102 and the piezoelectric element 104 with the hole 103a in the center in the X direction.

  On the other surface side of the base 103, flow path members 105 and 106 are laminated in the Z direction and bonded. The flow path member 105 is provided with a path that is three parallel grooves in the Y direction. Of the three paths, one path at a position facing the plurality of holes 103a of the base 103 is the forward path 105a, and two paths at a position facing the plurality of holes 103b of the base 103 Is the return path 105b. The flow path member 106 is bonded onto the flow path member 105 so as to cover these paths 105a and 105b.

  The pipe member 106 is provided with two pipe-like ink ports 107 and 108. The hole of the ink port 107 is connected to the forward path 105a, and the hole of the ink port 108 is connected to the connection flow path 106b that connects the two return path paths 105b inside the convex portion 106a of the flow path member 106. Yes. The ink supply path 11 from the upstream tank 7 is connected to the ink port 107, and the ink discharge path 12 to the downstream tank 4 is connected to the ink port 108. Thus, ink that has passed through the ink supply path 11 from the upstream tank 7 flows into the recording head 2 via the ink port 107.

  The ink that has entered the inside of the recording head 2 passes through the forward path 105a and reaches the entire width in the Y direction of the recording head 2, and the width of the recording head 2 passes from the plurality of holes 103a to the center of the pair of piezoelectric elements 104. Supplied throughout. The supplied ink is divided in the direction of each piezoelectric element 104 and reaches the gap between the frame 102 and the piezoelectric element 104 through each channel 104a. Thereafter, the plurality of holes 103 b pass through the two return paths 105 b, merge at the connection flow path 106 b, and go out of the recording head 2 from the ink port 108. The ink discharged from the ink port 108 flows to the downstream tank 4 via the ink discharge path 12. In this way, ink enters the recording head 2 from the upstream tank 7 through the ink supply path 11, and reaches the downstream tank 4 through the ink discharge path 12.

  The electrode wiring of the channel 104a of the recording head 2 is connected to the FPC on which the drive IC 110 is mounted on the electrode connection surface 103c of the base 103, and is driven by applying a voltage waveform to each channel. The base 103 of the recording head 2 is preferably a metal having a sufficiently good thermal conductivity as compared with the piezoelectric element. The ink ports 107 and 108 are provided with temperature sensors 114 and 115 which are thermistors, respectively.

  The ink ports 107 and 108 pass through holes 111c and 111d (111d not shown) provided in the fixing member 111, and are bonded to the fixing member 111 so as to be integrated with the fixing member 111. The fixing member 111 is integrated with the recording head cover 113 by screws at two positions on both ends. The recording head covers 112 and 113 are combined to form a box shape so as to cover the ink ports 107 and 108 inside the recording head 2, the drive IC 110, and the like.

  As shown in FIG. 2, the drive IC 110 is pressed against and closely contacts the inner surfaces of the recording head covers 112 and 113 by an elastic member such as a spring (not shown). In order to enhance the adhesion, grease having a good thermal conductivity is applied to the adhesion part.

  Since the ink ports 107 and 108 are made of a material having good thermal conductivity, the outputs of the temperature sensors 114 and 115 show substantially the same value as the temperature of the ink flowing through these ports. Since the viscosity of the ink changes depending on the temperature of the ink, it is necessary to control the voltage applied to the piezoelectric element to a voltage suitable for the viscosity of the ink at that time in order to always eject ink droplets of the same volume. Since it is difficult to directly detect the ink temperature of the piezoelectric element portion, the ink temperature of the piezoelectric element portion is estimated and controlled to be approximately equal to the average value of the temperatures detected by the temperature sensors 114 and 115.

  When the piezoelectric element 104 is driven and ink is ejected from the nozzle hole 101b, the piezoelectric element 104 generates heat. Part of this heat generation is radiated to the outside together with the ejected ink. A part of the heat generation is transferred to the base 103 and radiated to the air outside the recording head 2. Most of the remaining heat is stored in the base 103 and the flow path members 105 and 106. In order to prevent the temperature of the recording head 2 from rising, the recording head 2 is designed so that ink other than the ejected ink takes away excess heat by putting ink from the ink port 107 and taking it out of the ink port 108. ing. Further, when the piezoelectric element 104 is driven, the drive IC 110 generates heat. The heat is conducted to the recording head covers 112 and 113.

  The recording head covers 112 and 113 are provided with a plurality of heat radiation fins 112a and 113a on the outer surface. The heat radiation fins 112a and 113a are for increasing the surface area in contact with the air around the recording head 2 and increasing the heat radiation effect.

  The fixing member 111 is fixed to the recording head holder 35 by screwing holes opened at both ends. The recording head holder 35 has a cooling fan 36 and a heater 37 in the vicinity of the recording head 2. The cooling fan 36 air-cools the recording head holder 35 and the recording head 2. The heater 37 heats the recording head holder 35.

Next, the ink circulation operation of the ink circulation path will be described.
In the stop state of the apparatus, the valve 13 of the atmosphere release path 14 is open. Therefore, the inside of the downstream tank 4 is opened to the atmosphere by communicating with the overflow path 17, the atmosphere release path 19, and the air filter 9. The upstream tank 7 is sealed because the valve 15 is closed. In this state, since the liquid level in the downstream tank 4 is about 50 mm lower than the nozzle surface 101a of the recording head 2, a meniscus due to negative pressure is formed in the nozzle hole 101b so that ink does not drip from the nozzle hole 101b. It has become.

As preparation for recording an image on the recording medium 33, first, the valve 15 is opened, the valve 13 is closed, and the pump 5 is driven. As a result, the internal air of the downstream tank 4 becomes negative pressure. Further, since the liquid level of the upstream tank 7 is at a position higher by about 100 mm than the nozzle surface 101a by opening the valve 15, positive pressure is applied to the nozzle surface 101a. Driven to control the internal pressure of the downstream tank 4 to a predetermined pressure to quickly give a predetermined negative pressure. Assuming that the specific gravity of the ink is 1 g / cm ³ and the pressure is based on the nozzle surface 101a, a positive pressure of 1 kPa is applied depending on the liquid surface height in the upstream tank 7, and the liquid surface height in the downstream tank 4 Negative pressure of -0.5 kPa is applied. When the negative pressure of the air in the downstream tank 4 created by the pump 5 is −3.5 kPa, the pressure difference between the upstream tank 7 and the downstream tank 4 is 5 kPa in total. When the upstream side flow resistance and the downstream side resistance of the nozzle hole 101b are equal, the pressure in the nozzle hole 101b is calculated to be a negative pressure of -1.5 kPa. The ink meniscus in the nozzle hole 101b is not broken up to a certain negative pressure due to the surface tension of the ink and the hole diameter of the nozzle. Therefore, by controlling the pump 5 so as to keep this negative pressure, the ink does not enter the nozzle hole 101b or the ink leaks out, so that the ink passes from the upstream tank 7 through the recording head 2 to the downstream tank. It flows to 4.

  The pump 5 returns ink from the downstream tank 4 to the upstream tank 7 through the ink path 10 and thus circulates in the ink circulation path. In this state, the recording medium 33 is conveyed by the belt conveyance unit 34, and ink droplets are ejected from the nozzle holes 101b to the recording medium 33 that passes under the recording head 2.

  When ink is consumed by ejection, the liquid level in the upstream tank 7 falls, and the liquid level sensor 27 detects a drop in the ink liquid level. When a drop in the liquid level is detected, the ink supply valve 22 is opened to supply ink from the ink bottle 3 to the downstream tank 4. This replenishment is replenished by its own weight due to the liquid level difference between the ink bottle 3 and the downstream tank 4.

  The pressure sensor 31 in the downstream tank 4 detects a decrease in the internal negative pressure in the downstream tank 4. When a decrease in internal negative pressure is detected, the rotational speed of the pump 5 is controlled and the negative pressure in the downstream tank 4 is kept constant. The ink replenished in the downstream tank 4 is conveyed to the upstream tank 7 and filtered by the filter 32. When the ink level in the upstream tank 7 rises and the liquid level sensor 27 detects the rise in the level, the ink supply valve 22 is closed and the ink supply from the ink bottle 3 is stopped.

Next, an initial filling operation of ink into the ink path according to the first embodiment will be described.
FIG. 4 is a schematic diagram of the ink path of the first embodiment. FIG. 6 is a flowchart of the initial ink filling operation of the first embodiment, and FIG. 10 is a time chart during the initial ink filling operation of the first embodiment.

  When the ink circulation path is filled with ink for the first time, first, an operation of filling the downstream tank 4 with ink is performed. First, the atmosphere release valves 13 and 15 are opened (step S1). Thereby, the inside of the downstream tank 4 and the upstream tank 7 will be in the state open | released by air | atmosphere. Subsequently, the liquid level sensor 26 in the downstream tank detects the presence / absence of ink in the downstream tank 4 (step S2). If the detection result is no ink (Yes), the ink supply valve 22 is opened (step S3), and ink is supplied from the ink bottle 3 to the downstream tank 4 through the ink supply path 23. This replenishment is continued until the liquid level sensor 26 detects the presence of ink. If the detection result is that ink is present (No), the ink supply valve 22 is closed (step S4).

  Next, an operation of filling the upstream tank 7 with ink is performed. First, the liquid level sensor 27 in the upstream tank detects the presence / absence of ink in the upstream tank 7 (step S5). If the detection result is no ink (Yes), the pump 5 is driven (step S6), and the ink in the downstream tank 4 is pumped up to the upstream tank 7 through the ink path 10. During this time, since the ink level in the downstream tank 4 is lowered, the process returns to step S2 as appropriate, and if the liquid level sensor 26 detects the absence of ink while the pump 5 is being driven (Yes), the ink supply valve 22 is turned on again. Open (step S3) and replenish ink from the ink bottle 3. In this way, ink is supplied until the downstream tank 4, the ink path 10, and the upstream tank 7 are filled with ink. In step S5, when the liquid level sensor 27 detects the presence of ink (No), the pump 5 is stopped (step S7).

  Subsequently, the ink is pushed out from the upstream tank 7 to the ink supply path 11. First, the valve 15 is closed (step S8), and the upstream tank 7 is shut off from the atmosphere. After the valve 15 is closed, the pump 5 starts to be driven 1 second later, and is driven for a predetermined time T1 in the time chart shown in FIG. 10 (step S9). By this driving, ink is supplied from the downstream tank 4 to the upstream tank 7 that is sealed, the internal pressure of the upstream tank 7 becomes positive, and the ink is pushed out from the upstream tank 7 to the ink supply path 11. The pushed out ink rises higher than the liquid level in the upstream tank 7, and then fills the ink supply path 11 while descending to the recording head 2 below the upstream tank 7.

  Further, the inside of the downstream tank 4 is set to a negative pressure, and the operation of guiding the ink that has reached the recording head 2 from the ink supply path 11 to the downstream tank 4 is performed. First, when the time T1 has elapsed, the valve 15 is opened and the valve 13 is closed (step S10). As the valve 15 is opened, the air pressure inside the upstream tank 7 becomes atmospheric pressure. The time T1 is at least longer than the time until the ink pushed out into the ink supply path 11 comes below the liquid level in the upstream tank 7, and the pushed ink reaches the recording head 2 and reaches the nozzle hole 101b. It is set shorter than the time until it leaks out. By setting the time T1 in this way, even if the valve 15 is opened, ink continues to be discharged from the upstream tank 7 to the ink supply path 11 by the principle of siphon, and the ink supply path 11 is satisfied. In this state, the pump 5 is driven for a predetermined time T3 shown in the time chart of FIG. 10 following the time T1 (step S11). Since the pump 5 is driven in a state where the valve 13 is closed, the pressure in the downstream tank 4 is slightly negative. Since the nozzle hole 101 b is not yet filled with ink, outside air enters from the nozzle hole 101 b and flows to the downstream tank 4 through the ink discharge path 12. As a result, the liquid level in the downstream tank 4 is lowered, and the liquid level in the upstream tank 7 is raised by the ink pumped up by the pump 5. In the meantime, the ink that fills the ink supply path 11 and descends from the upstream tank 7 permeates into the channel 104a like a capillary phenomenon due to its own weight due to the water head difference from the liquid level in the upstream tank 7. . This state is shown in FIG.

  The ink that has entered the recording head 2 from the ink supply path 11 penetrates the channel 104a through the forward path 105a in the recording head and flows to the return path 105b. The ink does not reach all the channels 104a at a time, but first reaches, for example, the area A shown in FIG. Since ink is not contained in areas other than the area A, outside air continues to be sucked from the nozzle holes in this area. The area A is enlarged in a short time, and the ink permeates all the nozzle holes 101b of the recording head immediately. In the meantime, due to the water head difference between the upstream tank 7 and the nozzle surface 101a of the recording head 2, the portion of the area A that is partially filled with ink has a slight positive pressure. However, since this is a slight positive pressure, ink does not instantaneously exit from the nozzle to the outside.

  After ink has permeated all the nozzle holes 101b, a meniscus is formed in the nozzle holes 101b due to the negative pressure in the ink discharge path 12. The breaking strength of the meniscus is determined by the surface tension of the ink and the circumference of the nozzle hole. For example, when the surface tension of the ink is N and the nozzle hole diameter is D, the meniscus pressure resistance P1 is a pressure represented by P1 = N / (πD). If the negative pressure P generated by driving the pump 5 is set so as not to exceed the pressure resistance P1 of the meniscus at the nozzle hole 101b, the meniscus once formed is not broken. That is, if the pressure corresponding to the water head difference from the nozzle to the liquid level in the downstream tank 4 is δ1, if P> − (P1−δ1), the meniscus formed in the nozzle will not be broken by the negative pressure. .

  In this way, when meniscuses are formed in all the nozzle holes 101b, outside air does not enter the recording head, and ink in the ink supply path 11 flows downstream via the recording head 2 and the ink discharge path 12. Guided to tank 4. The air that was inside the ink discharge path 12 is carried to the downstream tank 4. Since the outlet of the ink discharge path 12 is set at a position inside the liquid level in the downstream tank 4, the air between the outlet and the liquid level has a negative pressure against buoyancy inside the downstream tank 4. Must be drawn into. The predetermined time T3 is set to a time sufficient for the ink inside the ink supply path 11 to fill the recording head 2 and further fill the inside of the ink discharge path 12.

  In a state where the nozzle hole 101b is blocked with ink, the pressure sensor 31 detects a clear negative pressure. For example, when the ink reaches only a part of the nozzle hole 101b and air enters from the nozzle hole 101b, the internal pressure of the downstream tank 4 is a negative pressure of about -0.05 kPa. A negative pressure of about -3.5 kPa is detected from the moment when it is blocked. In this state, after the time T1, the pump 5 is continuously driven for the time T3. However, there is a delay of time T2 after the valve 13 is closed until the pressure sensor 31 detects a clear negative pressure. This time relationship is shown in the time chart of FIG. Whether or not the ink covers all the nozzles 101b depends on whether the negative pressure detected by the pressure sensor 31 changes from a slight negative pressure (-0.05 kPa in the above) to a clear negative pressure (-3.5 kPa in the above). Ink flow can be detected. The time T3 for operating the pump 5 is set to be sufficiently longer than until a clear negative pressure is detected.

  By the operation so far, the entire circulation path is filled with ink. In the operation so far, there is no ink that exits from the inside of the ink path through the nozzles of the recording head.

  On the other hand, the ink liquid level in the downstream tank 4 is lowered due to the suction of air from the nozzle hole 101b and the movement of the air inside the ink discharge path 12 to the downstream tank 4.

Accordingly, an operation for adjusting the liquid level of the downstream tank 4 is further performed. First, the valve 15 is closed and the valve 13 is opened (step S12). Thus, the release of the atmosphere inside the upstream tank 7 is blocked, and the operation of the ink flowing downward is stopped. Then, the liquid level sensor 26 again detects the presence / absence of ink in the downstream tank 4 (step S13). If the detection result is no ink (Yes), the ink supply valve 22 is opened (step S14) to supply ink. This replenishment is continued until the liquid level sensor 26 detects the presence of ink. If the detection result is that ink is present (No), the ink supply valve 22 is closed (step S15).
Thus, the initial filling operation is completed, and then the operation moves to the circulation operation.

  In order to realize the above-described series of initial filling operations, the volume of ink in the upstream tank 7 is designed to be sufficiently larger than the amount of ink necessary to fill the ink supply path 11, the recording head 2, and the ink discharge path 12. ing. Accordingly, when the series of operations shown in FIG. 6 is completed, the ink remains in the upstream tank 7 and the liquid level in the downstream tank 4 is sufficiently high that the liquid level sensor 26 detects that there is ink. It has become.

The height H2 from the nozzle hole 101b to the liquid level of the upstream tank 7 is, for example, 100 mm as described above, and the positive pressure applied to the nozzle in the state shown in FIG. 9 when the specific gravity of the ink is 1 g / cm ³ . Is 1 kPa. With such a pressure, the ink will not drip from the nozzle for 10 seconds or more.
On the other hand, when the nozzle hole diameter is 25 μm and the ink surface tension is 30 dyn / cm, the meniscus is calculated to withstand negative pressures up to −3.8 kPa. If the negative pressure in the downstream tank 4 is detected by the pressure sensor 31 and the number of revolutions of the pump 5 is controlled to set the negative pressure to, for example, -3.5 kPa, ink as shown in FIG. 9 is recorded. Even in a transitional state filled with the head, the meniscus once formed is not destroyed. Of course, in a state where all the ink is filled, the pressure of the nozzle hole 101b of the recording head 2 under the conditions of the positive pressure and the water head difference of the upstream tank 7 and the negative pressure and the water head difference of the downstream tank 4 is -1. The negative pressure is 5 kPa and the meniscus is not broken.

  After the above-described series of initial filling operations, the circulation operation given in the flowchart shown in FIG. 8 is performed. FIG. 12 is a time chart during the circulation operation.

  First, the operation of aligning the liquid level position to a predetermined position is performed. First, in order to adjust the liquid level in the downstream tank 4 to a predetermined height, the liquid level sensor 26 in the downstream tank detects the presence / absence of ink in the downstream tank 4 (step S41). If the detection result is that there is ink (Yes), the valve 15 is opened and the pump 5 is driven (step S42), the ink is lifted to the upstream tank 7, and the liquid level sensor 26 has ink in the downstream tank 4. / None is detected (step S43). While the detection result is ink (No), the pump is continuously driven. When the liquid level sensor 26 detects the absence of ink (Yes), the pump 5 is stopped and the valve 15 is closed (step S44). In step S41, when the detection result is no ink (No), the valve 15 is opened (step S45), and the ink in the upstream tank 7 is lowered to the downstream tank 4 via the recording head 2 due to the water head difference. . As appropriate, the sensor 26 detects the presence / absence of ink in the downstream tank 4 (step S46), and the ink is continuously lowered until the presence of ink is detected. If the detection result indicates that ink is present (Yes), the valve 15 is closed (step S47).

  Thus, ink circulation can be started (step S48). When the ink circulation is started (Yes), the valve 15 is opened and the valve 13 is closed (step S49). Since the hysteresis of the liquid level sensor 26 is only about 2 mm in terms of the liquid level, the liquid level in the downstream tank 4 is brought to a substantially predetermined position (between P1 and P2 in FIG. 12) by the above operation. Can be controlled. That is, the shortage of the negative pressure of the pressure sensor 31 is detected (step S50). When the pressure sensor 31 detects P1 (No), the driving of the pump 5 is stopped (step S52), and when P2 is detected (Yes). By driving the pump 5 again (step S51), the pressure is maintained within a predetermined range. If the internal pressure of the downstream tank 4 is maintained at a predetermined negative pressure, ink is supplied from the upstream tank 7 to the ink supply path 11 and the recording head 2 in relation to the liquid level height (positive pressure) in the upstream tank 7. Then, the ink flows through the ink discharge path 12 to the downstream tank 4. By controlling the pressure to a predetermined value by the pressure sensor 31, the liquid level in the downstream tank 4 is always controlled to be constant. At the same time, by controlling this pressure, for example, to a negative pressure of -3.5 kPa, the pressure of the nozzle hole 101b of the recording head 2 is controlled to a negative pressure of -1.5 kPa.

  In this state, when the recording head 2 is driven and ink in the ink path is ejected from the nozzle holes 101b of the recording head 2, the ink level in the upstream tank 7 is lowered. The liquid level sensor 27 in the upstream tank detects presence / absence of ink (step S53). If the detection result is no ink (Yes), the ink supply valve 22 is opened at the timing when the pump 5 is driven (step S54) to supply ink. If the detection result is that ink is present (No), the ink supply valve 22 is closed (step S55). This circulation continues until a stop command is input from the CPU of the apparatus.

  In step S48, when a circulation stop command is input (No), the ink supply valve 22 is closed (step S56), the pump 5 is stopped (step S57), the valve 15 is closed, and the valve 13 is opened (step S58). ) To stop the circulation. In this state, the pressure sensor 31 detects atmospheric pressure again.

  In the present embodiment, the valve 13 is closed simultaneously with the opening of the valve 15 after the pump is driven for the time T1. However, the timing for closing the valve 13 may be during the time T1. If the valve 13 is closed before the ink leaks from the nozzle hole 101b of the recording head 2 through the ink supply path 11 and the pump 5 is driven, the ink does not leak out from the nozzle hole 101b.

  After the liquid level sensor 27 in the upstream tank detects the presence of ink, the ink supply operation is stopped because the amount of ink in the path cannot be grasped. In this relation, it is desirable that the valve 15 is closed and the pump 5 is driven when the liquid level sensor 27 detects the presence of ink and immediately after the valve 15 is closed, the ink is pushed out to the ink supply path 11. That is, the ink liquid level in the downstream tank 4 may be lowered too much, and the ink liquid level in the upstream tank 7 may be raised too much and overflow.

  In the present embodiment, the pump is driven for a time T3 following the time T1. However, in order to prevent the ink level in the downstream tank 4 from being lowered more than necessary, the pump 5 is driven at the very timing when the ink pushed out from the upstream tank 7 reaches the nozzle hole 101b of the recording head 2. It is desirable to start. Alternatively, it is desirable to re-drive the pump 5 at a timing immediately before reaching the nozzle hole 101b and leaking.

  Modification 1 of this embodiment is demonstrated based on FIG. 13, FIG. FIG. 13 is a diagram for explaining the configuration around the recording head 2, and FIG. 14 is a time chart at the time of initial filling of this modification.

  In the above-described embodiment, the opening operation of the atmosphere release valve 15 and the closing operation of the atmosphere release valve 13 are controlled by time (T1). However, in this modification, a path for directly detecting the arrival of ink immediately before the recording head 2. It is intended to control using the sensor 116.

  A path sensor 116 that detects the presence or absence of ink is disposed immediately before the recording head 2 in the ink supply path 11 (preferably disposed immediately before the nozzle hole 101b). The path sensor 116 is configured by a photo interrupter in which a light emitting element and a light receiving element are integrated, and is arranged so that the ink supply path 11 that is a transparent tube is sandwiched between the light emitting element and the light receiving element. The path sensor 116 can detect the presence or absence of ink by changing the amount of light received by the light receiving element depending on whether or not ink is present in the tube between the light emitting element and the light receiving element. In other words, when the ink descends from the upstream tank 7 toward the recording head 2 and reaches the path sensor 116, the path sensor 116 can detect the arrival of the ink because the amount of light received by the light receiving element changes.

  Next, the initial ink filling operation in Modification 1 will be described with reference to FIG. In addition, since it is the same operation | movement until step S8 in 1st Example, the description of the part is omitted.

  After the valve 15 is closed, the driving of the pump 5 is started after 1 second. By this driving, ink is supplied from the downstream tank 4 to the upstream tank 7 that is sealed, the internal pressure of the upstream tank 7 becomes positive, and the ink is pushed out from the upstream tank 7 to the ink supply path 11. The pushed out ink rises higher than the liquid level in the upstream tank 7, and then fills the ink supply path 11 while descending to the recording head 2 below the upstream tank 7. When the ink flowing down toward the recording head 2 reaches the path sensor 116, the path sensor 116 detects the ink. If the path sensor 116 detects the arrival of ink, the valve 15 is opened and the valve 13 is closed while continuing to drive the pump as shown in FIG. Since the subsequent operations are the same as those after step S11 in the first embodiment, the description thereof is omitted.

  As described above, according to the first modification, since the path sensor 116 directly detects the ink that has reached the recording head and closes the valve 13 in conjunction with the detected timing, the amount of air sucked from the nozzle is reduced. The ink level of the downstream tank 4 does not need to be greatly reduced.

Next, a second modification of the present embodiment will be described based on FIGS. 15 and 16. FIG. 15 is a diagram for explaining the configuration around the recording head 2, and FIG. 16 is a time chart at the time of initial filling in the second modification.
In the first modification, the path sensor 116 is disposed immediately before the recording head 2 in the ink supply path 11, whereas in the second modification, the path sensor 116 is disposed immediately after the recording head 2 in the ink discharge path 12. Is different.

  Hereinafter, the initial ink filling operation in Modification 1 will be described with reference to FIG. In addition, since it is the same operation | movement until step S9 in 1st Example, the description of the part is omitted.

  When the time T1 has elapsed after starting to drive the pump 5, the valve 15 is opened and the driving of the pump is stopped. As the valve 15 is opened, the air pressure inside the upstream tank 7 becomes atmospheric pressure. The time T1 is at least longer than the time until the ink pushed out into the ink supply path 11 comes below the liquid level in the upstream tank 7, and the pushed ink reaches the recording head 2 and reaches the nozzle hole 101b. It is set shorter than the time until it leaks out. By setting the time T1 in this way, even if the valve 15 is opened and the pump 5 is stopped, ink continues to be discharged from the upstream tank 7 to the ink supply path 11 by the siphon principle, and the ink supply path 11 is satisfied. The ink flowing from the ink supply path 11 to the recording head 2 permeates all the nozzle holes 101b of the recording head due to a water head difference from the liquid level in the upstream tank 7. Due to the water head difference between the upstream tank 7 and the nozzle surface 101a of the recording head 2, a slight positive pressure is applied to the nozzle hole 101b. There is no instantaneous exit from the nozzle.

  When ink is filled in the recording head 2, the ink in the recording head 2 flows toward the downstream tank 4 through the ink discharge path 2, but the ink is disposed immediately after the recording head 2. Detected by the path sensor 116.

  If the path sensor 116 detects ink, the atmosphere release valve 13 is closed and the pump 5 is driven again. The pump 5 is driven for a predetermined time T3. Since the pump 5 is driven in a state in which the valve 13 is closed, the pressure in the downstream tank 4 becomes negative, and the ink in the ink discharge path 12 is drawn toward the downstream tank 4, and the ink in the ink discharge path is drawn. Can be filled with.

  As described above, according to the second modification, since the downstream tank 4 is set to a negative pressure after all the nozzle holes 101b are filled, air is not sucked from the nozzle holes 101b.

Next, an initial ink filling operation to the ink circulation path according to the second embodiment will be described.
FIG. 5 is a schematic diagram of an ink circulation path according to the second embodiment. FIG. 7 is a flowchart of the initial ink filling operation of the second embodiment, and FIG. 11 is a time chart during the initial ink filling operation of the second embodiment.

  The difference in configuration between FIG. 4 and FIG. 5 is that an ink supply path 11 for supplying ink from the upstream tank 7 to the recording head 2 protrudes from the bottom surface of the upstream tank 7.

  The second embodiment is the same as the first embodiment until the operation of filling the downstream tank 4 with ink, and steps S1 to S4 correspond to steps S21 to S24, respectively.

  After this operation, the upstream tank 7 is filled with ink and the ink is guided to the downstream tank 4. First, the valve 13 is closed (step S25), and the pump 5 is driven for a predetermined time T6 (step S26). At this time, it is desirable to set the rotational speed of the pump 5 to a rotational speed at which a slightly larger amount than the amount of ink supplied to the downstream tank 4 is pumped up to the upstream tank 7. This setting method can be realized by previously setting an amount larger than the replenishment amount to the number of revolutions pumped to the upstream tank 7. Alternatively, it can be realized by referring to the value of the pressure sensor 31 and setting the number of revolutions to be slightly negative with respect to the pressure when the valve 13 is closed.

  Subsequently, the liquid level sensor 27 detects the presence / absence of ink in the upstream tank 7 (step S27). If the detection result is no ink (Yes), the ink supply valve 22 is opened (step S28), and the process returns to step S22. The ink supplied to the downstream tank 4 by opening the ink supply valve 22 is pumped up to the upstream tank 7 through the ink path 10. Since the ink larger than the replenishment amount is pumped up to the upstream tank 7, the closed air chamber of the downstream tank 4 has a negative pressure. As a result, air is sucked from the nozzles of the recording head that is not yet filled with ink, and the air intermittently enters the downstream tank 4 via the ink discharge path 12. For this reason, a slight negative pressure is detected by the pressure sensor 31.

  In the second embodiment, since the ink supply path 11 is provided below the upstream tank 7, the pumped ink sequentially flows into the ink supply path 11. Since the valve 15 is open, the ink descends the ink supply path 11 by the water head pressure and flows into the recording head 2. When the ink flows into the recording head 2, the valve 13 is already closed, so the same thing as described with reference to FIG. 9 occurs, and the ink sequentially forms a meniscus in the nozzle hole 101b. When all the nozzle holes 101b are closed, the inside of the downstream tank 4 is blocked from the outside air. This pressure change is detected by the pressure sensor 31, and the pressure sensor 31 detects a negative pressure larger than that before the nozzle is blocked.

  The time taken for the ink pumped from the downstream tank 4 to fill the nozzle holes 101b of the recording head 2 via the ink supply path 11 from the upstream tank 7 is shown as time T7 in FIG. . During this time, since air is sucked from the nozzle, only a slight negative pressure is detected. Thereafter, at the timing when the nozzle hole 101b is blocked with ink, the rotational speed of the pump 5 is controlled so that the negative pressure of the pressure sensor 31 becomes −3.5 kPa. When ink flows into the downstream tank 4 through the ink discharge path 12, the entire circulation path is filled with ink.

  In step S27, if the liquid level sensor 27 in the upstream tank detects the presence of ink (No), the pump 5 is stopped, the valve 13 is opened, the ink supply valve 22 is closed (step S29), and the supply is stopped. . Since air has entered the downstream tank 4 from the nozzle hole 101b at this time, it is assumed that the circulation path is not filled with sufficient ink. Further, when both the liquid level sensor 26 in the downstream tank and the liquid level sensor 27 in the upstream tank detect the presence of ink, the amount of ink in the path may be excessive.

  Therefore, the liquid level sensor 27 is temporarily stopped in a state where ink is detected. Subsequently, an operation for adjusting the liquid level in the upstream tank 7 is performed. First, in a state where the valve 15 is opened (the valve 13 is also opened), the liquid level sensor 27 detects the presence / absence of ink (step S30). If the detection result is that ink is present (No), ink flows from the upstream tank 7 to the downstream tank 4 via the recording head 2 due to a water head difference. When the liquid level sensor 27 detects the absence of ink (Yes), the valve 15 is closed (step S31). This time is indicated by time T8 in the time chart of FIG.

  Next, the operation of adjusting the liquid level in the downstream tank 4 is performed. At this time, since the liquid level sensor 26 in the downstream tank detects the absence of ink, the liquid level sensor 26 detects the presence / absence of ink in the downstream tank 4 (step S32). If the detection result is that there is no ink (Yes), the ink supply valve 22 is opened (step S33) to supply ink. This replenishment time is indicated by time T9 in the time chart of FIG. If the detection result is that ink is present (No), the ink supply valve 22 is closed (step S34).

  In a state where the above-described series of operations has been completed, the circulation path is filled with ink, and one of the liquid level sensors 26 and 27 detects the absence of ink, and an appropriate amount of ink enters the path. Even if the ink path 10 is not filled with ink because the liquid level in the downstream tank 4 is too low, the upstream tank 7, the ink supply path 11, the recording head 2, the ink discharge path 12, and the downstream tank 4. If the ink is full, the next circulation operation can be started normally, and there is no problem.

  Also in the second embodiment, as in the first embodiment, ink does not leak out from the nozzles in the process of filling the recording head with ink.

  Also in the second embodiment, the circulation operation given by the flowchart shown in FIG. 8 is performed after a series of initial filling operations.

According to the present invention, the following effects can be obtained.
1. By supplying the ink to the recording head by its own weight from the supply path, the downstream tank side is set to a negative pressure, so that the ink flows from the supply path to the return path without the nozzle being sealed, It is possible to fill the entire path with ink.

2. By making negative pressure on the downstream tank side immediately after ink is supplied from the supply path to the print head, the pressure in the print head can be made negative before the ink in the print head comes out of the nozzle. At the same time, when the means for setting the negative pressure on the downstream tank side is a means for sealing the downstream tank side and feeding the ink in the downstream tank to the upstream tank side, the time for making the negative pressure is minimized. By doing so, it is possible to avoid that the ink on the downstream tank side moves to the upstream tank side and the downstream tank side becomes empty and refilling is necessary.
Further, since the downstream tank side is emptied, it is possible to prevent air from entering the ink return path and bubbles from entering the path.

3. By setting negative pressure on the downstream tank side when ink is supplied from the upstream tank side to the supply path and does not reach the print head, negative pressure is generated in the print head before the ink in the print head comes out of the nozzle. At the same time, if the means for setting the negative pressure on the downstream tank side is a means for sealing the downstream tank side and feeding the ink in the downstream tank to the upstream tank side, the time for making the negative pressure By minimizing this, it can be avoided that the ink on the downstream tank side moves to the upstream tank side and the downstream tank side becomes empty and refilling is necessary.
Further, since the downstream tank side is emptied, it is possible to prevent air from entering the ink return path and bubbles from entering the path.

4). The negative pressure setting on the downstream tank side is set to a negative pressure smaller than (P1−δ1) in consideration of the meniscus resistance pressure P1 determined by the ink physical properties and the nozzle hole circumference and the water head difference δ1 from the nozzle to the downstream tank side. Thus, after the ink reaches the nozzle and forms a meniscus, the meniscus is not broken by negative pressure. Thus, bubbles do not flow from the nozzle to the downstream tank side, bubble formation is suppressed, and ink can be filled in a short time.

  DESCRIPTION OF SYMBOLS 1 ... Inkjet printer, 2 ... Recording head, 3 ... Ink bottle, 4 ... Downstream tank, 5 ... Pump, 6 ... Heat exchanger, 7 ... Upstream tank, 8 ... Waste liquid bottle, 9 ... Air filter, 10 ... Ink path, DESCRIPTION OF SYMBOLS 11 ... Ink supply path, 12 ... Ink discharge path, 13 ... Atmospheric release valve, 14 ... Atmospheric release path, 15 ... Atmospheric release valve, 16 ... Atmospheric release path, 17 ... Overflow path, 18 ... Waste liquid path, 19, 20, DESCRIPTION OF SYMBOLS 21 ... Air release path | route, 22 ... Ink supply valve, 23 ... Ink supply path, 24, 25 ... Actuator, 26, 27 ... Liquid level sensor, 28 ... Heat exchange flow path, 29 ... Peltier element, 30 ... Fan, 31 ... Pressure sensor, 32 ... filter, 33 ... recording medium, 34 ... belt transport unit, 35 ... recording head holder, 36 ... cooling fan, 37 ... heater, 101 ... nozzle plate DESCRIPTION OF SYMBOLS 101a ... Nozzle surface, 101b ... Nozzle hole, 102 ... Frame, 103 ... Base, 103a ... Hole, 103b ... Hole, 103c ... Electrode connection surface, 104 ... Piezoelectric element, 104a ... Channel, 105 ... Channel member, 105a ... Outward path Route, 105b ... Return path, 106 ... Flow path member, 106a ... Projection, 106b ... Connection flow path, 107, 108 ... Ink port, 109 ... FPC, 110 ... IC drive, 111 ... Fixing member, 111c, 111d ... Hole , 112, 113... Print head cover, 112a, 113a ... heat radiation protrusion, 114, 115 ... temperature sensor, 116 ... ink sensor.

Claims (5)

A recording head for ejecting ink;
An upstream tank that stores ink to be supplied to the recording head, and a first ink path that communicates between the upstream tank and the recording head and circulates the ink. An ink supply path disposed above in the direction;
An ink return path having a downstream tank that stores ink discharged from the recording head, and a second ink path that communicates between the downstream tank and the recording head and circulates the ink;
A third ink path that communicates between the ink supply path and the ink return path and distributes the ink;
Negative pressure setting means for making negative pressure in the ink feedback path;
In an ink jet printer having an ink circulation path having
The ink is supplied to the recording head from the ink supply path by its own weight, and the recording head is filled with ink by setting the ink feedback path to a negative pressure by the negative pressure setting means. Ink filling method.   2. The ink filling method according to claim 1, wherein the negative pressure setting means sets the ink feedback path to a negative pressure after the ink supplied from the ink supply path reaches the inside of the recording head.   The negative pressure setting means sets the ink return path to a negative pressure after the ink supplied from the upstream tank reaches the recording head after reaching the ink supply path. Item 2. The ink filling method according to Item 1. A recording head for ejecting ink;
An ink supply path having an upstream tank that stores ink to be supplied to the recording head, and a first ink path that communicates between the upstream tank and the recording head and distributes the ink;
An ink return path having a downstream tank that stores ink discharged from the recording head, and a second ink path that communicates between the downstream tank and the recording head and distributes the ink;
A third ink path that communicates between the ink supply path and the ink return path and distributes the ink;
Ink supply means for supplying ink in the ink supply path to the recording head;
Negative pressure setting means for making negative pressure in the ink feedback path;
In an ink jet printer having an ink circulation path having
The ink is supplied from the ink supply path toward the recording head by the ink supply means, and the ink is filled in the recording head by setting the ink feedback path to a negative pressure by the negative pressure setting means. Ink filling method.   The surface tension N of the ink, the peripheral length L of the nozzle, the water head pressure δ1 from the nozzle after filling to the liquid level of the downstream tank, and the negative pressure P of the downstream tank by the negative pressure setting means is P> − (N / The ink filling method according to claim 1, wherein the ink filling method is set to L−δ1).

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