JP2008000962A - Inkjet recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording apparatus equipped with an ink feeding system which circulates ink by a simple flow path mechanism, excludes air bubbles generated in the ink, feeds stably the ink to a recording head to stabilize delivery of the ink, and prevents the ink from leaking from the recording head. <P>SOLUTION: The inkjet recording apparatus is equipped with an ink feeding system. The system is equipped with: a recording head 17 delivering the ink 21; a second tank 4 provided below the recording head 17 and temporarily storing the ink 21; and a first tank 12 provided above the recording head 17, temporarily stores the ink 21 flowed into from the second tank 4 and feeds the ink 21 into the recording head 17, supplies the ink 21 from which air bubbles are removed to the recording head 17, and prevents the ink 21 from leaking from the recording head 17. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus including an ink supply system that circulates ink from which bubbles have been removed and stably supplies the ink to a recording head with water head pressure.

  In recent inkjet recording apparatuses (inkjet printers), ink is ejected from nozzles provided in a recording head and landed on a recording medium such as recording paper or OHP paper, and images such as characters and figures are recorded.

  In such an ink ejection method, ink is ejected as fine droplets from a nozzle. As a result, an image is recorded on the recording medium at high speed (high quality) and at high speed. However, when an image is recorded, bubbles may be generated in the ink in the tank, the recording head, and the piping connecting these as the ink supply system. Such bubbles obstruct ink flow and cause insufficient supply of ink to the recording head. As a result, ink ejection becomes unstable (ink non-ejection occurs).

Therefore, the ink jet recording apparatus is required to have stable ink ejection. Therefore, Patent Documents 1 to 3 disclose a method of removing bubbles in order to stabilize ink ejection.
In an ink jet printing apparatus disclosed in Patent Document 1, a tank (first tank) is disposed at a position higher than a nozzle (orifice surface) of an ink chamber (recording head), and a nozzle ( A tank (second tank) is disposed at a position lower than the orifice surface. The first tank and the print head are connected via an ink inflow path (first ink outflow path), and ink is discharged from the first tank by a water head difference between the first tank and the orifice surface of the print head. It is flowing to the recording head. The second tank and the recording head are connected via an ink outflow path (second ink outflow path), and ink is supplied from the recording head to the second by a water head difference between the second tank and the orifice surface of the recording head. Flowing into the tank. The second tank and the first tank are connected via a third ink outflow path, and the ink in the second tank is returned to the first tank by a pump or the like.

  In such an ink jet printing apparatus, the ink flowing from the first tank passes through the first ink outflow path, the recording head, the second ink outflow path, the second tank, and the third ink outflow path. It is circulated back to the 1 tank. Bubbles generated in the ink during the circulation flow to the second tank via the first ink outflow path and the second ink outflow path, so that the ink is not affected by the air bubbles and stably from the recording head. It is being discharged.

  Further, in the ink jet apparatus disclosed in Patent Document 2, the ink fed by the liquid feed pump is circulated so as to return to the ink supply system after passing through the ink jet head. As the ink flows out from the inside of the ink jet head, bubbles also flow out of the ink jet head and are excluded from the inside of the ink jet head.

In the ink jet apparatus disclosed in Patent Document 3, a sub tank connected to a negative pressure air pump is disposed above the recording head. The ink in the sub tank flows into the recording head by its own weight (natural fall). At that time, the negative pressure air pump adjusts the pressure of the sub tank. As a result, the inside of the sub tank is maintained at a suitable pressure (negative pressure) so as to prevent ink from leaking from the recording head.
JP-A-61-100461 JP 2005-144554 A JP 2003-182104 A

  However, in the ink jet printing apparatus disclosed in Patent Document 1 described above, the heights of the recording head, the first ink tank, and the second ink tank are not specified in detail. For this reason, it is not easy to prevent ink from leaking from the nozzles of the recording head.

  In addition, in the ink jet apparatus disclosed in Patent Document 2, in order to prevent ink from leaking from the ink jet head, the ink in the nozzle is negatively affected by the water head difference between the liquid surface of the ink reservoir opened to the atmosphere and the nozzle of the recording head. Pressure is acting. However, in order for the ink to circulate, it is necessary to close the valve of the ink reservoir and drive the liquid feed pump.

  That is, while the ink is being circulated, the ink jet recording apparatus cannot apply a negative pressure to the ink in the nozzle due to the liquid head difference between the liquid surface of the ink storage portion and the nozzle of the recording head. The ink jet recording apparatus controls the driving of the liquid feed pump so that ink does not leak from the recording head during ink circulation. However, since the positive pressure is generated while the liquid feed pump is driven, the ink jet recording apparatus can control the ink not to leak from the recording head, but it is difficult to stably discharge the ink. .

  In the ink jet apparatus disclosed in Patent Document 3, it is not easy to control ink leakage due to negative pressure.

  Therefore, the present invention circulates ink by a simple flow path mechanism, eliminates bubbles generated in the ink, stably supplies ink to the recording head, stabilizes ink discharge, and the ink from the recording head. An object of the present invention is to provide an ink jet recording apparatus including an ink supply system that prevents leakage of ink.

In order to attain the object, the present invention communicates with at least one recording head for recording an image by ejecting ink from a plurality of nozzles onto a recording medium, and the recording head via a first pipe, and supplies the recording head to the recording head. A first tank that temporarily stores ink to be retained, and an ink liquid level of the ink in the first tank that is maintained at a predetermined height above the nozzle surface of the nozzle. A first detection unit,
The first tank is provided in the first tank, communicates with the first tank via the second valve and the first valve, and temporarily stores ink to be supplied to the first tank. A second tank, a second detection unit provided in the second tank so that the ink level of the ink in the second tank is maintained at a predetermined height below the nozzle surface of the nozzle, and recording A third pipe communicating the head and the second tank;
The second tank, the second pipe, the first tank, the first pipe, the recording head, and the third pipe form a circulation ink path mechanism that circulates ink, and the ink circulation in the circulation ink path mechanism. Provides an ink jet recording apparatus controlled by an opening / closing operation of a first valve.

  The present invention circulates ink by a simple flow path mechanism, eliminates bubbles generated in the ink, stably supplies the ink to the recording head, stabilizes the ink discharge, and the ink is discharged from the recording head. An ink jet recording apparatus including an ink supply system that prevents leakage can be provided.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In the following description, in the drawing, the conveyance direction of the recording medium is the X-axis direction or the sub-scanning direction, and the direction orthogonal to the conveyance direction is the Y-axis direction, the main scanning direction, or the width direction of the recording medium. A direction orthogonal to the X-axis and Y-axis directions is taken as a Z-axis direction or a vertical direction.

  The first embodiment will be described with reference to FIGS. FIG. 1 is a diagram illustrating a schematic configuration of an ink supply system and a circulation ink path provided in the ink supply system in the ink jet recording apparatus according to the present embodiment, and a control unit that controls these. FIG. 2A is a schematic view when the second tank shown in FIG. 1 is viewed from the direction of arrow a. FIG. 2B is a schematic top view when the second tank shown in FIG. 1 is viewed from above. FIG. 3A is a schematic diagram when the first tank shown in FIG. 1 is viewed from the direction of the arrow b. FIG. 3B is a schematic top view when the first tank shown in FIG. 1 is viewed from above.

  Although not shown in the drawings, the ink jet recording apparatus according to the present embodiment stores a plurality of recording media, and is disposed downstream of the recording medium feeding mechanism, a recording medium feeding mechanism that conveys (feeds) the recording medium downstream, A recording medium conveying mechanism that conveys the recording medium, a recording medium accommodating mechanism that is disposed downstream of the recording medium conveying mechanism and accommodates a recorded recording medium, a maintenance mechanism that maintains the recording head, and the like are provided. .

  An ink supply system in the ink jet recording apparatus includes an ink tank 1, a second tank 4, a first tank 12, a long recording head 17, various pipes connecting them, and various sensors. Has been.

  In the present embodiment, the ink supply system is arranged in the order of the first tank 12, the recording head 17, and the second tank 4 from the upper side (high position) in the Z-axis direction. The liquid level B in the first tank 12 is set above the nozzle surface formed by the plurality of nozzles 18 of the recording head 17, and the liquid level A in the second tank 4 is higher than the nozzle surface of the recording head 17. Is also set downward.

  The ink tank 1 is disposed above the second tank 4 and is held in the ink jet recording apparatus by a holding unit (not shown). The ink tank 1 stores ink 21 to be supplied to the recording head 17. The ink tank 1 is connected to the second tank 4 by a fourth pipe (hereinafter referred to as a pipe) 3. The pipe 3 is provided with a solenoid valve 2 as a second valve. The electromagnetic valve 2 is controlled to be opened and closed by the control unit 22 and controls the flow rate of the ink 21 flowing from the ink tank 1 to the second tank 4 through the pipe 3 by opening and closing.

  The pipe 3 may be a flexible resin tube having a low gas barrier property.

  The second tank 4 temporarily stores the ink 21 flowing from the ink tank 1 and the ink 21 flowing from the recording head 17. The second tank 4 has a wide bottom area in order to suppress fluctuations in the liquid level with respect to changes in the volume of the ink 21 that flows in. The second tank 4 is held in the ink jet recording apparatus by a holding unit (not shown).

  The second tank 4 is provided with an electromagnetic valve 7 and second detection units (liquid level sensors 5 and 6). The opening and closing of the electromagnetic valve 7 is controlled by the control unit 22 and the pressure in the second tank 4 is adjusted by opening and closing. Moreover, the 2nd tank 4 becomes atmospheric pressure because the solenoid valve 7 is open | released. The electromagnetic valve 7 is kept open during normal operation. However, since the second tank 4 is disposed at the lowest point of the ink supply system, the ink 21 overflows from the open electromagnetic valve 7 when, for example, a failure occurs in the liquid level sensors 5 and 6 described later. There is a fear. Therefore, the electromagnetic valve 7 is closed by the control unit 22 to prevent the ink 21 from overflowing to the outside.

  The liquid level sensor 5 detects the lower limit of the ink liquid level in the second tank 4 in order to prevent the ink 21 from being insufficient in the second tank 4 (the liquid level is excessively lowered). The liquid level sensor 6 is disposed above the liquid level sensor 5. The liquid level sensor 6 detects the upper limit of the ink level in the second tank 4 in order to prevent the ink 21 flowing in from the ink tank 1 and the recording head 17 from overflowing from the second tank 4.

  If the liquid level sensor 5 does not detect the ink 21, the control unit 22 opens the electromagnetic valve 2. As a result, the ink 21 is supplied from the ink tank 1 to the second tank 4. When the liquid level sensor 5 detects the ink 21, the control unit 22 closes the electromagnetic valve 2 and stops the supply of the ink 21 to the second tank 4. The solenoid valve 2 is also closed when the liquid level sensor 6 detects the ink 21. Thereby, it is possible to prevent the ink 21 from overflowing from the second tank 4.

  In this way, in the second tank 4, the control unit 22 controls the opening / closing of the electromagnetic valve 2 based on the liquid level detection information by the liquid level sensors 5 and 6. Thereby, the supply amount of the ink 21 is controlled, and the liquid level of the ink 21 is always located between the liquid level sensor 5 and the liquid level sensor 6. In this embodiment, the liquid level A is a state where the liquid level of the ink 21 is located between the liquid level sensor 5 and the liquid level sensor 6. The liquid level sensor 5 and the liquid level sensor 6 may use a float switch, for example.

  The second tank 4 is connected to the first tank 12 by a second pipe (hereinafter, pipe) 11, and the ink 21 is transferred from the second tank 4 to the first tank 12 via the pipe 11. Inflow.

  The pipe 11 may be a flexible resin tube having a low gas barrier property. The pipe 11 is provided with a solenoid valve 8 that is a third valve, a liquid feed pump 9 that is a supply unit, and a cooler 10 that cools the ink 21. As described above, when the ink 21 flows from the second tank 4 to the first tank 12, the ink 21 is flowed by the liquid feed pump 9.

  The first tank 12 temporarily stores the ink 21 that flows from the second tank 4 through the pipe 11. The first tank 12 has a wide bottom area in order to suppress fluctuations in the liquid level with respect to changes in the volume of the ink 21 that flows in, as in the second tank 4. The first tank 12 is held in the ink jet recording apparatus by a holding unit (not shown).

  The first tank 12 is provided with an electromagnetic valve 15 as a first valve and a first detection unit (liquid level sensors 13 and 14).

  The first tank 12 is connected to the recording head 17 by a first pipe (hereinafter, pipe) 16. The first tank 12 is disposed immediately before the recording head 17. The pipe 16 is made of a hard resin tube having a high gas barrier property or a metal pipe.

  The electromagnetic valve 15 is controlled to be opened and closed by the control unit 22 to adjust the pressure in the first tank 12. Further, by opening the electromagnetic valve 15, the first tank 12 becomes atmospheric pressure. The ink 21 is supplied from the first tank 12 to the recording head 17 via the pipe 16 and is discharged from the nozzle 18. As a result, an image is recorded on the recording medium 19.

  The liquid level sensor 13 is the same as the liquid level sensor 5, and the ink level in the first tank 12 is prevented in order to prevent the inflowing ink 21 from being insufficient in the first tank 12 (the liquid level is excessively lowered). Detect the lower limit of.

  The liquid level sensor 14 is disposed above the liquid level sensor 13. Similarly to the liquid level sensor 6, the liquid level sensor 14 detects the upper limit of the ink level in the first tank 12 in order to prevent the inflowing ink 21 from overflowing in the first tank 12.

  If the liquid level sensor 13 does not detect the ink 21, the control unit 22 opens the electromagnetic valve 8 and drives the liquid feed pump 9. As a result, the ink 21 is supplied from the second tank 4 to the first tank 12. When the liquid level sensor 13 detects the ink 21, the control unit 22 stops driving the liquid feed pump 9, closes the electromagnetic valve 8, and supplies the ink 21 from the second tank 4 to the first tank 12. Stop. Even when the liquid level sensor 14 detects the ink 21, the driving of the liquid feed pump 9 is stopped and the electromagnetic valve 8 is closed. Thereby, it is possible to prevent the ink 21 from overflowing from the first tank 12. In this way, in the first tank 12, the control unit 22 controls the opening / closing of the electromagnetic valve 8 and the driving of the liquid feed pump 9 based on the liquid level detection information by the liquid level sensors 13 and 14. Thus, the supply amount of the ink 21 is adjusted, and the liquid level of the ink 21 is always located between the liquid level sensor 13 and the liquid level sensor 14. Note that a state in which the liquid level of the ink 21 is positioned between the liquid level sensor 13 and the liquid level sensor 14 is a liquid level B in the present embodiment.

  The recording head 17 is a single long line head fixed to the ink jet recording apparatus. In the recording head 17, a plurality of nozzles 18 are formed along the Y-axis direction on the surface facing the recording medium 19. These nozzles 18 are formed over a length greater than the width of the recording medium 19. In the recording head 17, the ink 21 flows through an ink flow path provided in the vicinity of the nozzle 18. A recording medium transport mechanism (not shown) that transports the recording medium 19 is provided below the recording head 17.

  When the image is recorded, the control unit 22 opens the electromagnetic valve 15. By opening the solenoid valve 15, the ink 21 flows from the first tank 12 into the recording head 17 via the pipe 16. When the recording medium 19 conveyed by the recording medium conveying mechanism faces the recording head 17, the control unit 22 drives the recording head 17 to eject ink 21 from the nozzles 18. As a result, an image is recorded on the recording medium 19.

  The recording head 17 is connected to the second tank 4 by a third pipe (hereinafter referred to as a pipe) 20. The pipe 20 may be a hard resin tube having a low gas barrier property. The ink 21 that has flowed out of the recording head 17 flows into the second tank 4 via the pipe 20.

  When the recording head 17 is driven, the ink 21 is heated by driving. Therefore, when the ink 21 flows into the second tank 4, the temperature of the ink 21 becomes higher than the optimum temperature for ejection. Therefore, the ink 21 is cooled by the cooler 10 when the ink 21 is supplied from the second tank 4 to the first tank 12.

  In the ink supply system described above, the ink 21 is supplied from the ink tank 1 to the recording head 17 via the pipe 3, the second tank 4, the pipe 11, the first tank 12 and the pipe 16. The ink 21 that has flowed out of the recording head 17 returns to the second tank 4 via the pipe 20 and is stored again. As described above, the second tank 4, the pipe 11, the first tank 12, the pipe 16, the recording head 17, and the pipe 20 form a circulating ink path mechanism.

Here, assuming that the capacity of the second tank 4 is V2, the capacity of the first tank 12 is V1, the total capacity of the pipe 16, the recording head 17, and the pipe 20 is V3.
The relationship between V1 and V2 in this embodiment is
V2> V1
It is.
If the capacity of the second tank 4 is set such that V1> V2, for example, when all of the ink 21 in the first tank 12 flows into the second tank 4, the ink 21 from the second tank 4 Overflows. In order to prevent overflow, the capacity of the second tank 4 is set as described above.

Further, considering that the pipe 16, the recording head 17, and the pipe 20 are filled with the ink 21, the relationship between V1, V2, and V3 is as follows.
V2> V1 + V3
It is desirable that

More preferably,
V2> Ink tank 1 capacity + V1 + V3
It is.

  By setting in this way, even if the ink 21 having the capacity of the ink tank 1 and the total capacity of V1 and V3 flows into the second tank 4, it does not overflow.

If the ink capacity up to the liquid level A of the second tank 4 is Va and the ink capacity up to the liquid level B of the first tank 12 is Vb,
In this embodiment, the relationship between Va and Vb is
Va> Vb
It is.

Next, the arrangement of the liquid level sensor and the piping in the second tank will be described in detail with reference to FIGS. 2 (a) and 2 (b).
As shown in FIG. 2A, both the pipe 20 and the pipe 11 need to be arranged to extend downward from the liquid level A in the second tank 4. For this reason, the pipe 20 and the pipe 11 are arranged extending downward from the liquid level sensor 5. As a result, the ink 21 is supplied from the second tank 4 to the first tank 12 without any air bubbles and without further unevenness. Further, since the pipe 20 extends below the liquid level A, the ink 21 is continuously present from the nozzle 18 of the recording head 17 to the liquid level A. The water head difference can be used. Furthermore, with such an arrangement, the liquid level sensors 5 and 6 can prevent the liquid level A from being erroneously detected by the ink 21 flowing into the second tank 4 from the pipe 20. It is preferable that the pipe 20 and the pipe 11 are extended and arranged so as to be close to the bottom surface of the second tank 4. The pipe 3 is not necessarily arranged below the liquid level A.

  However, the piping 3 is not arranged directly above the liquid level sensors 5 and 6 as shown in FIG. With this arrangement, the liquid level sensors 5 and 6 can prevent the liquid level A from being erroneously detected by the ink 21 flowing into the second tank 4 from the pipe 3.

Next, the arrangement of sensors and pipes in the first tank will be described in detail with reference to FIGS. 3 (a) and 3 (b).
As shown in FIG. 3A, the pipe 16 needs to be disposed below the liquid level B of the first tank 12. Therefore, the pipe 16 is disposed below the liquid level sensor 13. For this reason, the ink 21 is continuously present from the pipe 16 disposed below the liquid surface B to the nozzle 18 of the recording head 17. Therefore, the water head difference between the liquid level B and the nozzle 18 can be used. It is preferable that the pipe 16 is disposed close to the bottom surface of the first tank 12. The pipe 11 does not necessarily have to be arranged below the liquid level B.

  However, the piping 11 is not arranged directly above the liquid level sensors 13 and 14 as shown in FIG. With this arrangement, the liquid level sensors 13 and 14 can prevent the liquid level B from being erroneously detected by the ink 21 flowing into the first tank 12 from the pipe 11.

  In the present embodiment, the liquid level B of the ink 21 in the first tank 12 and the height of the nozzle 18 provided in the recording head 17 are set to a water head difference h2, and the nozzle 18 provided in the recording head 17 and the second The height of the liquid surface A of the ink 21 in the tank 4 is defined as a water head difference h1.

  The ink 21 flows from the first tank 12 into the recording head 17 via the pipe 16 according to its own weight due to the water head difference h2.

  Further, the ink 21 flows from the recording head 17 into the second tank 4 via the pipe 20 according to its own weight due to the water head difference h1.

At this time, the pressure of the difference between the water head difference h2 and the water head difference h1 is applied to the nozzle 18.
That is, if h2−h1> 0, positive pressure is applied to the nozzle 18.
If h2−h1 <0, a negative pressure is applied to the nozzle 18.
For example, in order to prevent ink 21 from leaking from the nozzle 18 when the apparatus is turned off and to stably eject the ink 21 from the nozzle 18 at the time of image recording, for example, the nozzle 18 has a certain range. It needs to be controlled to negative pressure. Therefore, in this embodiment,
h2-h1 <0
Relationship is maintained,
A relationship of −100 (mm) ≦ h2−h1 ≦ −80 (mm) is preferable.

  Thus, the height difference from the liquid level B in the first tank 12 to the liquid level A in the second tank 4 is kept constant during image recording.

  Next, the ink supply and image recording operations will be described with reference to the flowcharts with reference to FIGS.

  FIG. 4 is a flowchart for explaining ink supply and image recording operations. FIG. 5 is a flowchart for explaining a subroutine in the liquid level A adjustment step. FIG. 6 is a flowchart for explaining a subroutine in the adjustment step of the liquid level B and the liquid level A.

In the ink jet recording apparatus, in the initial state, the electromagnetic valves 2, 8, and 15 are closed, and the electromagnetic valve 7 is opened.
First, after the apparatus is turned on, the controller 22 checks and adjusts the liquid level A of the ink 21 (Step 1). Here, the confirmation and adjustment of the liquid level A will be described with reference to the subroutine shown in FIG.
First, the control unit 22 determines whether or not the liquid level sensor 5 has confirmed (detected) the liquid level A of the ink 21 (Step 21). Thereby, it is confirmed that the ink 21 is not excessively lowered in the second tank 4. If the liquid level sensor 5 detects the liquid level A of the ink 21 at Step 21 (Step 21: Yes), the control unit 22 ends the adjustment of the liquid level A, returns to the flowchart shown in FIG. 4, and returns to Step 2. move on.

  If the liquid level sensor 5 does not detect the ink level A at Step 21 (Step 21: No), the control unit 22 opens the electromagnetic valve 2 to adjust the ink 21 (Step 22). By this opening, the ink 21 is supplied from the ink tank 1 to the second tank 4. This supply raises the liquid level A of the ink 21.

  Next, the control unit 22 determines whether or not the liquid level sensor 5 has detected the liquid level A of the ink 21 (Step 23).

  If the liquid level sensor 5 does not detect the liquid level of the ink 21 at Step 23 (Step 23: No), the control unit 22 maintains the open state of the electromagnetic valve 2 until the liquid level sensor 5 detects the ink 21. Further, the ink 21 is supplied from the ink tank 1 to the second tank 4. If the liquid level sensor 5 detects the liquid level A of the ink 21 at Step 23 (Step 23: Yes), the control unit 22 closes the electromagnetic valve 2 (Step 24).

  As a result, the supply of the ink 21 from the ink tank 1 to the second tank 4 is stopped. At this time, the liquid level A of the ink 21 is located between the liquid level sensor 5 and the liquid level sensor 6.

  Thereby, the control part 22 complete | finishes adjustment of the liquid level A, returns to the flowchart shown in FIG. 4, and progresses to Step2.

Returning to the flowchart shown in FIG.
If adjustment of the liquid level A is complete | finished, the control part 22 will confirm and adjust the liquid level A and the liquid level B (Step2).
Here, the confirmation and adjustment of the liquid level A and the liquid level B will be described with reference to the subroutine shown in FIG. First, the control unit 22 determines whether the liquid level sensor 13 has detected the liquid level B of the ink 21 (Step 31). Thereby, it is confirmed that the ink 21 is not excessively lowered in the first tank 12.

  If the liquid level sensor 13 detects the liquid level B of the ink 21 at Step 31 (Step 31: Yes), the control unit 22 ends the adjustment of the liquid level A and the liquid level B, and returns to the flowchart shown in FIG. And it progresses to Step3.

  If the liquid level sensor 13 does not detect the liquid level B of the ink 21 at Step 31 (Step 31: No), the control unit 22 determines whether or not the electromagnetic valve 15 is opened (Step 32).

  If the solenoid valve 15 is not opened (Step 32: No), the controller 22 opens the solenoid valve 15 (Step 33), then opens the solenoid valve 8 and drives the liquid feed pump 9 (Step 34).

  If the solenoid valve 15 is open (Step 32: Yes), the process proceeds to Step 34. By opening the electromagnetic valve 15, the ink 21 is supplied from the second tank 4 to the first tank 12 by the liquid feed pump 9. At that time, bubbles contained in the ink 21 (for example, bubbles generated by the liquid feed pump 9) naturally float in the first tank 12 and are released into the atmosphere through the opened electromagnetic valve 15. Further, since the first tank 12 is disposed immediately before the recording head 17, no bubbles are generated during supply to the recording head 17. Accordingly, the ink 21 from which bubbles have been removed in the first tank 12 is supplied to the recording head 17. Since the first tank 12 is disposed above the recording head 17, the ink 21 passes from the first tank 12 to the recording head 17 via the pipe 16 by its own weight when the electromagnetic valve 15 is opened. Inflow. Further, the ink 21 flows from the recording head 17 to the second tank 4 via the pipe 20. As a result, the ink 21 starts to circulate in the circulation ink path mechanism.

Next, the control unit 22 determines whether or not the liquid level sensor 5 has detected the liquid level A of the ink 21 (Step 35). Thereby, it is confirmed that the liquid level A is not excessively lowered in the second tank 4.
If the liquid level sensor 5 detects the liquid level A of the ink 21 at Step 35 (Step 35: Yes), the control unit 22 determines whether the liquid level sensor 13 has detected the liquid level B of the ink 21 (Step 36). ).

  If the liquid level sensor 5 does not detect the liquid level A of the ink 21 at Step 35 (Step 35: No), the control unit 22 opens the electromagnetic valve 2 (Step 37). By this opening, the ink 21 is supplied from the ink tank 1 to the second tank 4 and the liquid level A of the ink 21 rises.

  Next, the controller 22 determines whether or not the liquid level sensor 5 has detected the liquid level A of the ink 21 (Step 38).

  If the liquid level sensor 5 does not detect the liquid level A of the ink 21 at Step 38 (Step 38: No), the control unit 22 maintains the open state of the electromagnetic valve 2 and further supplies the ink 21 from the ink tank 1 to the first level. 2 is supplied to the tank 4.

  If the liquid level sensor 5 detects the liquid level A of the ink 21 at Step 38 (Step 38: Yes), the control unit 22 closes the electromagnetic valve 2 (Step 39). As a result, the supply of the ink 21 from the ink tank 1 to the second tank 4 is stopped. At this time, the liquid level A of the ink 21 is located between the liquid level sensor 5 and the liquid level sensor 6.

  Next, if the liquid level sensor 13 does not detect the liquid level B of the ink 21 (Step 36: No), the process returns to Step 35.

  If the liquid level sensor 13 detects the liquid level B of the ink 21 at Step 36 (Step 36: Yes), the control unit 22 stops the driving of the liquid feed pump 9 and closes the electromagnetic valve 8 (Step 40). As a result, the supply of the ink 21 from the second tank 4 to the first tank 12 is stopped.

  At this time, the liquid level B of the ink 21 is located between the liquid level sensor 13 and the liquid level sensor 14. As described above, the control unit 22 confirms and adjusts the liquid level A and the liquid level B, so that the ink 21 from which bubbles have been removed can be supplied to the recording head 17, and the relationship of h2-h1 <0 is always maintained. In this case, a negative pressure is applied to prevent the ink 21 from leaking from the nozzle.

  The control unit 22 ends the adjustment of the liquid level A and the liquid level B, returns to the flowchart shown in FIG. 4, and proceeds to Step 3.

Next, returning to the flowchart shown in FIG.
The controller 22 determines whether or not the electromagnetic valve 15 is open (Step 3). If the electromagnetic valve 15 is not opened by this determination (Step 3: No), the control unit 22 opens the electromagnetic valve 15 (Step 4), and proceeds to Step 5. If the solenoid valve 15 is open (Step 3: Yes), the process proceeds to Step 5.

  When the electromagnetic valve 15 is opened, the ink 21 is supplied from the first tank 12 to the recording head 17 via the pipe 16. The first tank 12 is disposed above the recording head 17. Therefore, the ink 21 flows from the first tank 12 to the recording head 17 by its own weight. The air bubbles contained in the ink 21 are naturally lifted in the first tank 12 as described above, and are thus discharged from the ink 21 into the atmosphere through the electromagnetic valve 15. Further, the ink 21 flows from the recording head 17 to the second tank 4 via the pipe 20. As a result, the ink 21 circulates in the circulation ink path mechanism.

  Next, the control unit 22 determines whether or not to record an image (Step 5). If the image is to be recorded (Step 5: Yes), the image is recorded on the transported recording medium 19 (Step 6).

  Thereafter, the control unit 22 determines whether or not to continue recording an image (Step 7). If the image is to be continuously recorded (Step 7: Yes), the process returns to Step 6. Here, the confirmation and adjustment (Step 8) of the liquid level A and the liquid level B are performed by determining whether or not to record an image (Step 5), recording an image (Step 6), and determining whether or not to continue recording an image (Step 7). It is always performed in parallel during the process.

  The confirmation and adjustment of the liquid surface A and the liquid surface B in Step 8 are the same as the confirmation and adjustment of the liquid surface A and the liquid surface B in Step 2 described above (subroutine shown in FIG. 6), and the description thereof is omitted. As described above, since the positions of the liquid levels A and B are adjusted at the time of image recording, the ink 21 from which bubbles are removed is supplied to the recording head 17 while maintaining the relationship of h2−h1 <0. Images can be recorded.

  When an image is not recorded at Step 5 (Step 5: No), or when an image is not continuously recorded (Step 7: No), the control unit 22 ends the recording process (Step 9). After the end, the control unit 22 adjusts the liquid level A and the liquid level B (Step 10). The adjustment of the liquid surface A and the liquid surface B in Step 10 is the same as the adjustment of the liquid surface A and the liquid surface B in Step 2 (subroutine shown in FIG. 6), and the description thereof is omitted here.

  Next, the control unit 22 closes the electromagnetic valve 15 (Step 11). As a result, the supply of the ink 21 from the first tank 12 to the recording head 17 via the pipe 16 is stopped. Further, the inflow of the ink 21 from the recording head 17 to the second tank 4 via the pipe 20 is stopped. As a result, the circulation of the ink 21 in the circulation ink path mechanism is stopped.

  Next, the control part 22 confirms and adjusts the liquid level A (Step 12). The confirmation and adjustment of the liquid level A in Step 12 are the same as the confirmation and adjustment of the liquid level A in Step 1 described above (subroutine shown in FIG. 5), and the description thereof is omitted here.

  Finally, the image recording apparatus is turned off, and the ink supply and image recording operations are completed. At this time, since the liquid levels A and B are always controlled at Step 10 and Step 12, the above-described relationship of h2-h1 <0 is always maintained. Negative pressure is acting. Therefore, ink leakage from the nozzle 18 can be prevented.

  As described above, in the present embodiment, the first tank 12 is disposed immediately before the recording head 17, so that bubbles generated in the ink 21 along the path from the second tank 4 to the first tank 12 (for example, liquid feeding). The bubbles generated by driving the pump 9 are naturally lifted in the first tank 12. Bubbles are released into the atmosphere through the open solenoid valve 15. Further, the ink 21 is supplied from the first tank 12 to the recording head 17 by its own weight, and since the first tank 12 is disposed immediately before the recording head 17, bubbles are newly generated in the ink during supply. There is no. The controller 22 controls the circulation of the ink 21 in the circulation ink path mechanism by controlling the opening / closing operation of the electromagnetic valve 15.

  From the above, in the present embodiment, the ink 21 from which bubbles are removed in the first tank 12 can be stably supplied to the recording head 17. In the present embodiment, the ink 21 from which bubbles are removed can be stably supplied to the recording head 17. Thereby, stable image recording is possible, and high-quality images can be recorded. In the present embodiment, the ink 21 can be used repeatedly. Furthermore, in this embodiment, since the circulation of the ink 21 in the circulation ink path mechanism can be controlled only by the opening / closing operation of the electromagnetic valve 15, the ink 21 can be circulated with a simple configuration and control.

  The second tank 4 is disposed below the recording head 17, and the first tank 12 is disposed above the recording head 17. Specifically, at least the liquid level B of the first tank 12 is located above the nozzles 18 of the recording head 17, and the liquid level A of the second tank 4 is below the nozzles 18 of the recording head 17. Is located. The ink 21 flows from the first tank 12 to the recording head 17 and from the recording head 17 to the second tank 4 according to its own weight. At that time, the control unit 22 adjusts the liquid level A in the second tank 4 and the liquid level B in the first tank 12. Thereby, the relationship between the water head difference h2 and the water head difference h1 is always maintained as h2−h1 <0. Therefore, since negative pressure is applied to the nozzles 18 provided in the recording head 17, the ink 21 does not leak from the nozzles 18 when the apparatus is stopped, for example. Accordingly, it is possible to prevent the ink 21 from leaking from the nozzles and contaminating the recording medium 19.

Next, a second embodiment according to the present invention will be described in detail with reference to FIGS.
FIG. 7 is a diagram illustrating a schematic configuration of an ink supply system and a circulation ink path provided in the ink supply system in the ink jet recording apparatus according to the present embodiment, and a control unit that controls these. FIG. 8 is a schematic view when the second tank and the third tank shown in FIG. 7 are viewed from the direction of the arrow c. FIG. 9 is a schematic view when the recording head, the first tank, and the buffer tank shown in FIG. 7 are viewed from the direction of the arrow d. FIG. 10 is a schematic view of the second tank shown in FIG. 7 when viewed from the direction of the arrow d.

  The ink jet recording apparatus according to the present embodiment is provided with a recording medium feeding mechanism, a recording medium transport mechanism, a recording medium storage mechanism, a maintenance mechanism, and the like, which are not illustrated, as in the first embodiment. It has been.

  The same parts as those in the first embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted. In this embodiment, a state where the liquid level of the ink 21 is located between the liquid level sensor 5 and the liquid level sensor 6 is referred to as a liquid level C. A state in which the liquid level of the ink 21 is located between the liquid level sensor 13 and the liquid level sensor 14 is referred to as a liquid level D.

  Hereinafter, components different from those of the first embodiment will be described.

  The present embodiment is different from the first embodiment described above in that the third tank 30, a plurality of short recording heads 31, and a fourth tank (hereinafter referred to as a buffer tank) provided above the recording head 31. 32 is different. Moreover, the point which provides the 2nd detection unit in the 3rd tank 30, and uses the pressurization pump 36 as a pressurization part differs.

  The second tank 4 temporarily stores the ink 21 flowing from the ink tank 1 and the ink 21 flowing from the buffer tank 32.

  The second tank 4 is connected to the third tank 30 via a ninth pipe (hereinafter referred to as a pipe) 33 and to the buffer tank 32 via an eighth pipe (hereinafter referred to as a pipe) 34.

  The pipe 33 is provided with a solenoid valve 35 that is a fourth valve. When the electromagnetic valve 35 is opened by the control unit 22, the ink 21 is supplied from the second tank 4 to the third tank 30 via the pipe 33 when the electromagnetic valve 7 is open. When the electromagnetic valve 35 is open, the liquid levels of the second tank 4 and the third tank 30 are maintained at the same height.

  Similarly to the second tank 4 and the first tank 12, the third tank 30 has a wide bottom area to suppress fluctuations in the liquid level with respect to changes in the capacity of the ink 21. The third tank 30 is provided with liquid level sensors 5 and 6 and a pressure pump 36. The liquid level sensors 5 and 6 in the present embodiment operate in the same manner as the liquid level sensors 5 and 6 provided in the second tank 4 in the first embodiment described above. The liquid level sensors 13 and 14 in the present embodiment operate in the same manner as the liquid level sensors 13 and 14 provided in the first tank 12 in the first embodiment described above. The third tank 30 is connected to the first tank 12 via a fifth pipe (hereinafter, pipe) 37. If the liquid level sensor 13 does not detect the liquid level D, the control unit 22 closes the electromagnetic valve 35 and drives the pressure pump 36 to pressurize the inside of the third tank 30 so that the ink 21 is supplied to the third tank. 30 is supplied to the first tank 12 through the pipe 37.

  The first tank 12 is connected to the recording heads 31 (31 a to 31 f) via a sixth pipe (hereinafter, pipe) 38. The ink 21 flows from the first tank 12 to each recording head 31 via the pipe 38 according to its own weight. The recording head 31 has a line head configuration that is alternately arranged in the Y-axis direction so as to be larger than the width of the recording medium 19, and is arranged so that no gap of the ink 21 occurs on the recording surface of the recording medium 19 during image recording. ing. In each recording head 31, the ink 21 flows in the vicinity of the nozzle 39. At this time, when the control unit 22 drives each recording head 31, the ink 21 is ejected from the nozzle 39 and landed on the recording medium 19 to record an image.

  Each recording head 31 is connected to the buffer tank 32 via a seventh pipe (hereinafter referred to as a pipe) 40. The ink 21 flows from each recording head 31 to the buffer tank 32 via the pipe 40, and the ink 21 that flows to the buffer tank 32 returns to the second tank 4 via the pipe 34 according to its own weight.

  Next, the arrangement of piping in the second tank and the third tank will be described in detail with reference to FIG.

  As shown in FIG. 8, the pipe 37 needs to be disposed below the liquid level C in the third tank 30. For this reason, the pipe 37 is arranged to extend downward from the liquid level sensor 5. As a result, the ink 21 is supplied from the third tank 30 via the pipe 37 to the first tank 12 without any bubbles, and more uniformly. Note that the pipe 37 is preferably extended until it is close to the bottom surface of the second tank 4. Furthermore, the pipe 34 needs to be disposed below the liquid level C in the second tank 4. For this reason, the pipe 34 is arranged to extend downward from the liquid level sensor 5. Since the pipe 34 is below the liquid level, the ink 21 is continuously present from the nozzle 39 of the recording head 31 to the liquid level C. Therefore, the water head difference between the liquid level C and the nozzle 39 can be used.

  Further, the pipe 33 needs to be arranged below the liquid level sensor 5. Through this pipe 33, the ink 21 is supplied from the second tank 4 to the third tank 30 without unevenness. The pipe 33 is preferably arranged in the vicinity of the bottom surfaces of the second tank 4 and the third tank 30.

  Next, the arrangement of sensors and pipes in the first tank and the buffer tank will be described in detail with reference to FIGS.

  As shown in FIGS. 7, 9, and 10, the pipe 38 connects the first tank 12 and each recording head 31. The pipe 40 connects each recording head 31 and the buffer tank 32. The pipes 38 and 40 are arranged in the same number as the recording head. That is, in this embodiment, since six recording heads 31 are arranged, six pipes 38 and 40 are also arranged respectively.

  The pipe 38 is disposed below the liquid level sensor 13. As a result, the ink 21 smoothly flows from the first tank 12 into each recording head 31 by its own weight.

  The buffer tank 32 is provided in order to simplify the flow path mechanism when the ink 21 is poured from the recording heads into the second tank 4. When the buffer tank 32 is not arranged, the pipes 40 are connected to the second tank 4 respectively, and the flow path mechanism becomes complicated. Therefore, the buffer tank 32 is arranged in order to eliminate the complexity of the flow path mechanism and form a simple flow path mechanism. Thus, the ink 21 is collected by the buffer tank 32 and supplied to the second tank 4.

  In the present embodiment, the capacity of the second tank 4 is V2, the capacity of the first tank 12 is V1, the capacity of the third tank 30 is V4, the pipe 38, the six recording heads 31, and the six pipes. The total capacity of 40, the buffer tank 32, and the pipe 34 is V5.

The relationship between V1 and V2 and V1 and V4 in this embodiment is
V2> V1
V4 ≧ V1
It becomes.
Considering the ink 21 filled in the pipe 38, the six recording heads 31, the six pipes 40, the buffer tank 32, and the pipe 34, the relationship among V1, V2, and V5 is
V2> V1 + V5
It becomes.

More preferably,
V2> V1 + V5 + capacity of ink tank 1
It is.

The ink capacity in the second tank 4 when the ink 21 is stored up to the same height as the liquid level C of the third tank 30 is Vc, the ink capacity up to the liquid level D of the first tank 12 is Vd, When the ink capacity up to the liquid level C of the third tank 30 is Ve,
The relationship between Vc, Vd, and Ve in this embodiment is
Vc> Vd
Ve ≧ Vd
It becomes.

By setting Vc and Ve as described above, a sufficient amount of ink 21 can be supplied to the first tank 12 even when the first tank 12 is nearly empty.
In the present embodiment, the height of the liquid level D of the ink 21 in the first tank 12 and the nozzle 39 provided in the recording head 31 is the water head difference h2, and the nozzle 39 provided in the recording head 31 and the third The height of the ink 21 in the tank 30 from the liquid level C is defined as a water head difference h1.

  At this time, a differential pressure between the water head difference h2 and the water head difference h1 is applied to the nozzle 39.

If h2−h1> 0, positive pressure is applied to the nozzle 39.
If h2−h1 <0, a negative pressure is applied to the nozzle 39.

For example, when the power of the apparatus is turned off, the ink 21 does not leak from the nozzle 39 and, for example, in order to stably discharge the ink 21 from the nozzle 39 during ink discharge, the nozzle 39 has a certain range of negative pressure. Need to be managed. Therefore, in this embodiment,
h2-h1 <0
Relationship is maintained,
A relationship of −100 (mm) ≦ h2−h1 ≦ −80 (mm) is preferable.

Next, the ink supply and image recording operations will be described with reference to flowcharts with reference to FIGS.
In the ink jet recording apparatus, in the initial state, the solenoid valves 2 and 15 are closed and the solenoid valves 7 and 35 are open.

  First, after the apparatus is turned on, the controller 22 checks and adjusts the liquid level C (Step 51). Here, the confirmation and adjustment of the liquid level C will be described with reference to the subroutine shown in FIG.

  First, the controller 22 determines whether or not the liquid level sensor 5 has detected the liquid level C of the ink 21 (Step 71). Thereby, it is confirmed that the liquid level C is not excessively lowered in the third tank 30. If the liquid level sensor 5 detects the liquid level C of the ink 21 at Step 71 (Step 71: Yes), the control unit 22 ends the adjustment of the liquid level C, returns to the flowchart shown in FIG. 11, and returns to Step 52. move on.

  If the liquid level sensor 5 does not detect the liquid level C of the ink 21 at Step 71 (Step 71: No), the control unit 22 opens the electromagnetic valve 2 to adjust the ink amount (Step 72). With this opening, the ink 21 is supplied from the ink tank 1 to the third tank 30 via the pipe 3, the second tank 4, and the pipe 33. As a result, the liquid level C of the ink 21 rises.

  Next, the controller 22 determines whether or not the liquid level sensor 5 has detected the liquid level C of the ink 21 (Step 73).

  If the liquid level sensor 5 does not detect the liquid level of the ink 21 at Step 73 (Step 73: No), the control unit 22 maintains the open state of the electromagnetic valve 2 until the liquid level sensor 5 detects the ink 21. The ink 21 is supplied from the ink tank 1 to the second tank 4, and the ink 21 is supplied from the second tank 4 to the third tank 30 via the pipe 33. This returns to Step 73. If the liquid level sensor 5 detects the liquid level C of the ink 21 at Step 73 (Step 73: Yes), the control unit 22 closes the electromagnetic valve 2 (Step 74). At this time, the liquid level heights of the second tank 4 and the third tank 30 are the same.

  As a result, the supply of the ink 21 from the ink tank 1 to the second tank 4 and the third tank 30 is stopped. At this time, the liquid level C of the ink 21 is located between the liquid level sensor 5 and the liquid level sensor 6. Thereby, the control part 22 complete | finishes confirmation and adjustment of the liquid level C, returns to the flowchart shown in FIG. 11, and progresses to Step52.

  Next, returning to the flowchart shown in FIG.

  If the check and adjustment of the liquid level C are completed, the control unit 22 checks and adjusts the liquid level C and the liquid level D (Step 52).

  Here, the confirmation and adjustment of the liquid level C and the liquid level D will be described with reference to the subroutine shown in FIG. First, the control unit 22 determines whether or not the liquid level sensor 13 has detected the liquid level D of the ink 21 (Step 81). Thereby, it is confirmed that the liquid level D is not excessively lowered in the first tank 12.

  If the liquid level sensor 13 detects the liquid level D of the ink 21 at Step 81 (Step 81: Yes), the control unit 22 ends the confirmation and adjustment of the liquid levels C and D, and returns to the flowchart shown in FIG. And it progresses to Step53. If the liquid level sensor 13 does not detect the liquid level D of the ink 21 in Step 81 (Step 81: No), the control unit 22 determines whether or not the electromagnetic valve 15 is open (Step 82).

  If the solenoid valve 15 is not opened (Step 82: No), the controller 22 opens the solenoid valve 15 (Step 83), closes the solenoid valve 35, and drives the pressurizing pump 36 (Step 84). If the solenoid valve 15 is opened (Step 82: Yes), the process proceeds to Step 84.

  When the pressure pump 36 pressurizes the inside of the third tank 30, the ink 21 is supplied from the third tank 30 to the first tank 12 via the pipe 37. At that time, bubbles contained in the ink 21 naturally float in the first tank 12, are removed from the ink 21, and are released into the atmosphere through the opened electromagnetic valve 15. The ink 21 is supplied from the first tank 12 to the recording head 31 via the pipe 38 by its own weight. In addition, since the first tank 12 is disposed immediately before the recording head 31, no bubbles are generated in the ink 21 supplied to the recording head 31. Therefore, the ink 21 from which bubbles are removed in the first tank 12 is supplied to the recording head 31.

  Next, the controller 22 determines whether or not the liquid level sensor 5 has detected the liquid level C of the ink 21 (Step 85). Thereby, it is confirmed that the liquid level C is not excessively lowered in the third tank 30.

  If the liquid level sensor 5 detects the liquid level C of the ink 21 at Step 85 (Step 85: Yes), the control unit 22 determines whether the liquid level sensor 13 has detected the liquid level D of the ink 21 (Step 86). ). Accordingly, it is confirmed whether the ink 21 has satisfied the liquid level D in the first tank 12 by supplying the ink.

  If the liquid level sensor 5 does not detect the liquid level C of the ink 21 at Step 85 (Step 85: No), the control unit 22 stops driving the pressurizing pump 36 and opens the electromagnetic valve 35 (Step 87). By this opening, the ink 21 is supplied from the second tank 4 to the third tank 30. As a result, the ink 21 is replenished from the second tank 4 to the third tank 30, and the liquid level C of the ink 21 rises.

  Next, the controller 22 determines whether or not the liquid level sensor 5 has detected the liquid level C of the ink 21 (Step 88).

  If the liquid level sensor 5 does not detect the liquid level C of the ink 21 at Step 88 (Step 88: No), the controller 22 opens the electromagnetic valve 2 (Step 89). As a result, the ink 21 is supplied from the ink tank 1 to the second tank 4 and the third tank 30.

  Next, the controller 22 determines whether or not the liquid level sensor 5 has detected the liquid level C of the ink 21 (Step 90). Thereby, it is confirmed whether or not the ink 21 can satisfy the liquid level C in the third tank 30 by supplying the ink. If the liquid level sensor 5 does not detect the liquid level of the ink 21 at Step 90 (Step 90: No), the control unit 22 keeps the electromagnetic valve 2 open, and the ink 21 is further transferred from the ink tank 1 to the second tank. 4 and supplied to the third tank 30. This returns to Step90. If the liquid level sensor 5 detects the liquid level of the ink 21 at Step 90 (Step 90: Yes), the control unit 22 closes the electromagnetic valve 2 (Step 91). As a result, the supply of the ink 21 from the ink tank 1 to the second tank 4 and the third tank 30 is stopped.

  If the liquid level sensor 5 detects the liquid level C of the ink 21 at Step 88 (Step 88: Yes), or if the control unit 22 closes the electromagnetic valve 2 at Step 91, the control unit 22 Is closed, the pressurizing pump 36 is driven (Step 92), and the process proceeds to Step 86. At this time, the liquid level C of the ink 21 is located between the liquid level sensor 5 and the liquid level sensor 6.

  Next, when the liquid level sensor 13 does not detect the liquid level D of the ink 21 at Step 86 (Step 86: No), the process returns to Step 85. If the liquid level sensor 13 detects the liquid level D of the ink 21 at Step 86 (Step 86: Yes), the control unit 22 stops driving the pressurizing pump 36 and opens the electromagnetic valve 35 (Step 93).

  As a result, the supply of the ink 21 from the third tank 30 to the first tank 12 is stopped.

  At this time, the liquid level D of the ink 21 is located between the liquid level sensor 13 and the liquid level sensor 14.

  As described above, the control unit 22 confirms and adjusts the liquid level C and the liquid level D. In this embodiment, the ink 21 from which bubbles are removed can be supplied to the recording head 31, and h2−h1 <0 is always satisfied. The relationship can be maintained, and negative pressure acts on the nozzle 39 to prevent the ink 21 from leaking from the nozzle.

  The control unit 22 ends the confirmation and adjustment of the liquid levels C and D, returns to the flowchart shown in FIG. 11, and proceeds to Step 53. The controller 22 determines whether or not the electromagnetic valve 15 is open (Step 53).

  If the solenoid valve 15 is not open (Step 53: No), the control unit 22 opens the solenoid valve 15 (Step 54), and proceeds to Step 55. If the solenoid valve 15 is open (Step 53: Yes), the process proceeds to Step 55.

  When the electromagnetic valve 15 is opened, the ink 21 is supplied from the first tank 12 to each recording head 31 via the pipe 38. The first tank 12 is disposed above the recording head 31. Therefore, the ink 21 flows from the first tank 12 into the recording head 31 via the pipe 38 according to its own weight. Note that the bubbles contained in the ink 21 are naturally lifted in the first tank 12 as described above, and thus are removed from the ink 21 and released into the atmosphere through the electromagnetic valve 15. The ink 21 circulates back from each recording head 31 to the third tank 30 via the pipe 40, the buffer tank 32, the pipe 34, the second tank 4, and the pipe 33. As a result, the ink 21 circulates in the circulation ink path mechanism.

  Next, the control unit 22 determines whether or not to record an image (Step 55).

  When the image is recorded (Step 55: Yes), the image is recorded (Step 56).

  Next, the control unit 22 determines whether or not to continue recording an image (Step 57).

  When the image is continuously recorded (Step 57: Yes), the process returns to Step 56. Here, the confirmation and adjustment of the liquid level C and the liquid level D (Step 58) are performed by determining whether or not to record an image (Step 55), recording an image (Step 56), and determining whether or not to continue recording an image (Step 57). Always in parallel during the process.

  The confirmation and adjustment of the liquid level C and the liquid level D in Step 58 are the same as the confirmation and adjustment of the liquid level C and the liquid level D in Step 52 (subroutine shown in FIG. 13). Therefore, it is omitted here. As described above, since the liquid levels C and D are always confirmed and adjusted during image recording, the present embodiment records the ink 21 from which bubbles have been removed while maintaining the relationship of h2-h1 <0. It can be supplied to the head 31.

  When the image is not recorded (Step 55: No) or when the image is not continuously recorded (Step 57: No), the image recording is finished (Step 59), and the control unit 22 checks and adjusts the liquid level C and the liquid level D. (Step 60). The confirmation and adjustment of the liquid level C and the liquid level D in Step 60 are the same as the confirmation and adjustment of the liquid level C and the liquid level D in Step 52 (subroutine shown in FIG. 13), and description thereof is omitted here.

  Next, the control unit 22 closes the electromagnetic valve 15 (Step 61). As a result, the supply of the ink 21 from the first tank 12 to the recording head 31 via the pipe 38 is stopped. Further, the ink 21 that has flowed from the recording head 31 to the buffer tank 32 via the pipe 40 stops flowing into the second tank 4 via the pipe 34 according to its own weight.

  As a result, the circulation of the ink 21 in the circulation ink path mechanism is stopped.

  Next, the control part 22 performs confirmation and adjustment of the liquid level C (Step 62). The confirmation and adjustment of the liquid level C in Step 62 are the same as the confirmation and adjustment of the liquid level C in Step 51 (subroutine shown in FIG. 12), and the description thereof is omitted here.

  After confirming and adjusting the liquid level C, the controller 22 turns off the power of the apparatus, and the ink supply and image recording operations are completed. At this time, since the liquid levels C and D are always confirmed and adjusted by Step 60 and Step 62, the above-described relationship of h2-h1 <0 is maintained. The negative pressure is acting. Therefore, ink leakage from the nozzle 39 is prevented.

  As described above, the present embodiment can obtain the same effects as those of the first embodiment described above even when the short recording head 31 is disposed instead of the long recording head. Even if a plurality of short recording heads 31 are provided by arranging the buffer tank 32, a simple flow path mechanism can be configured.

  In the present embodiment, the second tank 4 and the first tank 12 are directly connected by the pipe 37 without providing the third tank 30, the pipe 33 and the electromagnetic valve 35, and similarly to the first embodiment. The piping 37 may be provided with the electromagnetic valve 8 and the liquid feed pump 9. With this configuration, when the liquid level sensor 13 detects the liquid level D, the control unit 22 opens the control unit 22 electromagnetic valve 8 and then drives the liquid feeding pump 9 to remove the liquid tank D from the second tank 4. Ink 21 is supplied to the first tank 12. By this supply, the liquid level D is maintained between the liquid level sensor 13 and the liquid level sensor 14. In the present embodiment, the second tank 4 is divided into two rooms (sub tank chamber a and sub tank chamber b) and two rooms without providing the third tank 30, the pipe 33, and the electromagnetic valve 35. And you may provide a solenoid valve in the partition part of the sub tank chamber a and the sub tank chamber b.

  As described above, the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment.

FIG. 2 is a diagram illustrating a schematic configuration of an ink supply system and a circulation ink path provided in the ink supply system in the ink jet recording apparatus according to the first embodiment of the present invention, and a control unit that controls these. FIG. 2A is a schematic view when the second tank shown in FIG. 1 is viewed from the direction of arrow a. FIG. 2B is a schematic top view when the second tank shown in FIG. 1 is viewed from above. FIG. 3A is a schematic diagram when the first tank shown in FIG. 1 is viewed from the direction of the arrow b. FIG. 3B is a schematic top view when the first tank shown in FIG. 1 is viewed from above. 6 is a flowchart for explaining operations of ink supply and image recording. It is a flowchart for demonstrating the subroutine in the confirmation and adjustment step of the liquid level. It is a flowchart for demonstrating the subroutine in the confirmation and adjustment step of the liquid level A and the liquid level B. FIG. It is a figure which shows the schematic structure of the ink supply system in the inkjet recording device of 2nd Embodiment which concerns on this invention, the circulation ink path | route provided in an ink supply system, and the control part which controls these. It is the schematic when the 2nd tank and 3rd tank shown in FIG. 7 are seen from the arrow c direction. FIG. 8 is a schematic view when the recording head, the first tank, and the buffer tank shown in FIG. 7 are viewed from the direction of the arrow d. It is the schematic when the 1st tank shown in FIG. 7 is seen from the arrow d direction. 6 is a flowchart for explaining operations of ink supply and image recording. It is a flowchart for demonstrating the subroutine in the confirmation and adjustment step of the liquid level. It is a flowchart for demonstrating the subroutine in the confirmation and adjustment step of the liquid level C and the liquid level D. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Ink tank, 2 ... Solenoid valve, 3 ... Piping, 4 ... 1st tank, 5 ... Liquid level sensor, 6 ... Liquid level sensor, 7 ... Solenoid valve, 8 ... Solenoid valve, 9 ... Liquid feed pump, 10 DESCRIPTION OF SYMBOLS ... Cooler, 11 ... Pipe, 12 ... Second tank, 13 ... Liquid level sensor, 14 ... Liquid level sensor, 15 ... Solenoid valve, 16 ... Pipe, 17 ... Recording head, 18 ... Nozzle, 19 ... Recording medium, DESCRIPTION OF SYMBOLS 20 ... Piping, 21 ... Ink, 22 ... Control part, 30 ... 3rd tank, 31 ... Recording head, 32 ... Buffer tank, 33 ... Piping, 34 ... Piping, 35 ... Solenoid valve, 36 ... Pressure pump, 37 ... Piping, 38 ... Piping, 39 ... Nozzle, 40 ... Piping.

Claims (8)

At least one recording head for recording an image by ejecting ink from a plurality of nozzles onto a recording medium;
A first tank that communicates with the recording head via a first pipe and temporarily stores the ink to be supplied to the recording head;
A first detection unit provided in the first tank such that an ink liquid level of the ink in the first tank is maintained at a predetermined height above the nozzle surface of the nozzle;
A first valve provided in the first tank and in communication with the atmosphere;
A second tank that communicates with the first tank via a second pipe and temporarily stores the ink to be supplied to the first tank;
A second detection unit provided in the second tank such that an ink liquid level of the ink in the second tank is maintained at a predetermined height below the nozzle surface of the nozzle;
A third pipe communicating the recording head and the second tank;
Comprising
The second tank, the second pipe, the first tank, the first pipe, the recording head, and the third pipe form a circulating ink path mechanism that circulates the ink. An ink jet recording apparatus, wherein the circulation of the ink in an ink path mechanism is controlled by an opening / closing operation of the first valve.   2. The ink jet recording apparatus according to claim 1, wherein the ink circulates through the circulating ink path mechanism simultaneously with the opening of the first valve.   3. The ink jet recording apparatus according to claim 1, wherein the first valve is opened when the second detection unit detects the ink level in the second tank. 4. . An ink tank for supplying the ink stored in the second tank in communication with the second tank via a fourth pipe;
Based on the detection information detected by the first detection unit, the supply amount of the ink supplied from the ink tank to the second tank is controlled based on detection information detected by the second detection unit. A control unit for controlling a supply amount of the ink supplied from the second tank to the first tank;
The inkjet recording apparatus according to claim 1, further comprising: A second valve provided in the fourth pipe for adjusting the amount of ink supplied from the ink tank to the second tank;
A supply unit provided in the second pipe for supplying the ink from the second tank to the first tank;
A third valve that is provided in the second pipe and adjusts the supply amount of the ink supplied from the second tank to the first tank;
Further comprising
The control unit controls the ink level in the second tank by the second valve and then controls the ink level in the first tank by the third valve and the supply unit. The inkjet recording apparatus according to claim 4, wherein: A third tank for temporarily storing the ink supplied from the second tank;
A fourth tank for temporarily storing the ink that has flowed out of the recording head out of the ink supplied to the recording head from the third tank via the first tank;
The inkjet recording apparatus according to claim 1, further comprising: The third tank communicates with the first tank via a fifth pipe;
The first tank communicates with the recording head via a sixth pipe;
The recording head communicates with the fourth tank via a seventh pipe;
The fourth tank communicates with the second tank via an eighth pipe;
The second tank communicates with the third tank via a ninth pipe;
The second tank, the ninth pipe, the third tank, the fifth pipe, the first tank, the sixth pipe, the recording head, the seventh pipe, the fourth pipe The ink jet recording apparatus according to claim 6, wherein a circulation ink path mechanism for circulating the ink is formed by the tank and the eighth pipe. A pressurization unit provided in the third tank for pressurizing the inside of the third tank;
A fourth valve for controlling a supply amount of the ink supplied from the second tank to the third tank;
The inkjet recording apparatus according to claim 6, comprising:

Images