JP2019098737A - Ink jet recording device - Google Patents

Abstract

To provide an ink jet recording device which is capable of stabilizing discharge operation of ink droplets from a nozzle part of an ink jet head, even when ink can be circulated in the ink jet head according to a comparatively simple constitution.SOLUTION: In an ink jet recording device 1, a pump 7 for feeding ink from a main tank 6 to a sub-tank 5 is connected to an ink supply port 2a of an ink jet head 2, in a first ink chamber 5a inside the sub-tank 5, whereas a pump 8 for feeding ink from the sub-tank 5 to the main tank 6 is connected to an ink discharge port 2b of the ink jet head 2, in a second ink chamber 5b inside the sub-tank 5. A control unit 9 of the pumps 7 and 8 drives and controls at least the pump 7 so that an ink liquid level on a first ink chamber 5a side inside the sub-tank 5 has the same height as an ink liquid level on a second ink chamber 5b side, when ink droplets are discharged by a nozzle part 2c of at least the ink jet head 2.SELECTED DRAWING: Figure 1

Description

  BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an inkjet recording apparatus for printing on a print target.

  2. Description of the Related Art Conventionally, there is known an inkjet recording apparatus which ejects ink droplets to print on a paper medium (see, for example, Patent Document 1). The ink jet recording apparatus described in Patent Document 1 includes an ink jet head (recording head) in which a plurality of nozzles are formed, a sub tank that supplies ink to the ink jet head, and a main tank connected to the sub tank via a diaphragm pump or the like. Is equipped.

  In addition, as a conventional inkjet head (liquid ejection head) for ejecting a liquid, a circulation type inkjet head for circulating the liquid in the inkjet head is known (see, for example, Patent Document 2). The ink jet head described in Patent Document 2 includes a plurality of nozzles for discharging liquid, a plurality of individual liquid chambers communicating with the nozzles, a common liquid chamber for supplying the liquid to the plurality of individual liquid chambers, and a plurality of individual liquid chambers A circulation common liquid chamber in which the liquid returns is provided. In this inkjet head, by circulating the liquid in the inkjet head, it is possible to prevent the drying of the nozzles, the sedimentation of the ink particles, and the like and stabilize the discharge performance of the liquid.

JP 2003-182104 A JP, 2017-159561, A

  The inventor of the present application has studied the circulation of the ink in the inkjet head as in the inkjet head described in Patent Document 2 in the inkjet recording apparatus provided with the sub tank as in the inkjet recording device described in Patent Document 1. There is. That is, the inventor of the present invention has studied that the ink is circulated in the inkjet head by circulating the ink between the inkjet head and the sub tank.

  Specifically, in the ink jet recording apparatus provided with the sub tank, the inventor of the present invention forms two ink chambers, a first ink chamber and a second ink chamber, in which ink is stored, inside the sub tank. Forming a partition wall that defines an ink chamber and a second ink chamber, an ink supply port for supplying ink from a sub tank to an ink jet head, an ink discharge port for discharging ink toward the sub tank, and ink Forming a nozzle portion for discharging droplets; connecting an ink supply port to the first ink chamber through a pipe; connecting an ink discharge port to the second ink chamber through the pipe; By making the height of the ink surface of the chamber higher than the height of the ink surface of the second ink chamber, the height of the ink surface of the first ink chamber and the height of the second ink chamber By utilizing the difference between the height of the liquid surface of the ink (water head difference) by circulating the ink between the ink jet head and the sub tank, it is considering circulating the ink in the ink jet head.

  According to the study of the inventor of the present invention, when the ink is thus circulated in the inkjet head, the ink can be circulated in the inkjet head with a relatively simple configuration. However, when the ink is circulated in the ink jet head in this manner, the pressure on the ink supply port side and the pressure on the ink discharge port side are generated inside the ink jet head due to the influence of the water head difference. The inventors of the present application have made it clear that the operation of ejecting ink droplets from the unit becomes unstable. Moreover, since the discharge operation of the ink droplet from the nozzle portion becomes unstable, for example, when printing is performed on the print target by the inkjet recording apparatus, there is a possibility that the print quality may be degraded. It became clear by examination.

  Therefore, it is an object of the present invention to provide an ink jet apparatus capable of stabilizing the discharge operation of ink droplets from the nozzle portion of the ink jet head even though it is possible to circulate the ink in the ink jet head with a relatively simple configuration. It is in providing a recording device.

  In order to solve the above-described problems, the inkjet recording apparatus according to the present invention includes an inkjet head for ejecting ink droplets, a sub tank in which the ink supplied to the inkjet head is stored, and a main in which the ink supplied to the sub tank is stored. The inkjet head includes: a tank; a first pump that sends ink from the main tank to the sub tank; a second pump that sends ink from the sub tank to the main tank; and a control unit that drives and controls the first pump and the second pump A circulation type inkjet head including an ink supply port to which ink from a sub tank is supplied, an ink discharge port from which ink is discharged toward the sub tank, and a nozzle unit that discharges ink droplets, and the inside of the sub tank is , And a first ink chamber and a second ink chamber for containing ink are formed. In addition, a partition wall which defines the first ink chamber and the second ink chamber is formed, the partition wall rises from the bottom surface of the sub tank, and the first ink chamber and the second ink chamber are connected above the partition wall The first pump is connected to the first ink chamber via a pipe and the ink supply port is connected via a pipe, and the second pump is connected to the second ink chamber via a pipe. The ink discharge port is connected through a pipe, and the control unit makes the liquid level of the ink in the sub tank at least the height of the upper end of the partition wall when the nozzle unit discharges the ink droplet, and the first ink chamber side At least the first pump is driven and controlled so that the liquid surface of the ink and the liquid surface of the ink on the second ink chamber side are at the same height.

  In the ink jet recording apparatus of the present invention, the first ink chamber and the second ink chamber are formed inside the sub tank. In the present invention, a first pump for sending ink from the main tank to the sub tank is connected to the first ink chamber to which the ink supply port of the ink jet head is connected, and a second ink to which the ink discharge port of the ink jet head is connected Connected to the chamber is a second pump that sends ink discharged from the sub tank to the main tank. Therefore, in the present invention, the drive control of the first pump and the second pump is performed so that the height of the ink surface of the first ink chamber is higher than the height of the ink surface of the second ink chamber. The water head can be used to circulate the ink between the inkjet head and the sub tank, and as a result, the ink can be circulated in the inkjet head. That is, in the present invention, it is possible to circulate the ink in the ink jet head with a relatively simple configuration utilizing the water head difference.

  Further, in the present invention, when the nozzle portion ejects the ink droplet, at least the liquid surface of the ink in the sub tank becomes higher than the upper end of the partition wall in the control portion, and the liquid surface of the ink on the first ink chamber side At least the first pump is drive-controlled so that the ink level on the second ink chamber side and the ink level on the second ink chamber side become the same. Therefore, in the present invention, when the nozzle portion ejects ink droplets, the influence of the water head difference is eliminated to suppress the difference between the pressure on the ink supply port side and the pressure on the ink discharge port side inside the ink jet head. Becomes possible. Therefore, in the present invention, it is possible to stabilize the discharge operation of the ink droplet from the nozzle portion of the ink jet head.

  Further, in the present invention, the first ink chamber and the second ink chamber are connected above the partition wall, and a first pump for sending the ink from the main tank to the sub tank is connected to the first ink chamber. Connected to the chamber is a second pump for transferring ink from the sub tank to the main tank. Therefore, in the present invention, even if the first pump supplies excess ink to the sub-tank with the amount of ink consumed by the inkjet head, the excess ink supplied to the sub-tank is returned to the main tank by the second pump. Becomes possible. Therefore, in the present invention, it is possible to circulate the ink between the sub tank and the main tank regardless of the amount of ink consumed by the ink jet head. As a result, according to the present invention, it is possible to suppress the settling of the ink particles in the piping path between the sub tank and the main tank and the sub tank, and the gas in the ink in the piping path between the sub tank and the main tank By arranging the degassing module to remove the gas, it is possible to effectively remove the gas in the ink.

  In the present invention, the inkjet recording apparatus includes a supply side pipe connecting the first ink chamber and the ink supply port, and a discharge side pipe connecting the second ink chamber and the ink discharge port. For example, in the supply side pipe, The ink can always flow between the first ink chamber and the ink supply port, and the ink can always flow between the second ink chamber and the ink discharge port in the discharge side pipe. In this case, as compared with the case where a pump or a valve is disposed in the piping path between the first ink chamber and the ink supply port or in the piping path between the second ink chamber and the ink discharge port. The configuration of the inkjet recording apparatus can be simplified.

  In the present invention, for example, the ink jet recording apparatus includes a carriage on which the ink jet head and the sub tank are mounted, and an apparatus main body for holding the carriage so that movement in the main scanning direction is possible. When the stopped state continues for a predetermined time, the height of the ink level in the first ink chamber becomes higher than the height of the ink level in the second ink chamber, and the ink level from the first ink chamber through the inkjet head At least a second pump is driven and controlled so that the ink flows into the second ink chamber. In this case, the ink is circulated in the ink jet head using the water head difference until the predetermined operation of the ink jet recording apparatus is started after the state in which the carriage is stopped continues for a predetermined time. Becomes possible.

  In the present invention, for example, the ink jet recording apparatus includes a carriage on which the ink jet head and the sub tank are mounted, an apparatus main body which holds the carriage so as to be movable in the main scanning direction, a first pump and a first ink chamber And a second pipe for connecting the second pump and the second ink chamber, wherein the main tank, the first pump and the second pump are attached to the apparatus main body, The pipe and the second pipe are formed of a flexible tube, and are bent at at least one place, and follow the carriage while changing the bending portion as the carriage moves in the main scanning direction.

  In this case, when the carriage moves in the main scanning direction, the inertial force acting on the ink in the first pipe and the ink in the second pipe causes the carriage to move in the main scanning direction. As a result, the pressure in the ink jet head fluctuates. Therefore, when the nozzle portion ejects an ink droplet, if there is an influence of the water head difference, a large difference easily occurs between the maximum pressure on the ink supply port side and the minimum pressure on the ink discharge port side inside the ink jet head. However, according to the present invention, since the influence of the water head difference when the nozzle portion ejects the ink droplet can be eliminated, even if the pressure in the ink jet head fluctuates with the movement of the carriage in the main scanning direction, the nozzle It becomes possible to suppress the difference between the maximum pressure on the ink supply port side and the minimum pressure on the ink discharge port side inside the ink jet head when the unit ejects ink droplets, and as a result, the nozzle portion of the ink jet head It becomes possible to stabilize the discharge operation of the ink droplet from

  In the present invention, the ink jet recording apparatus includes a first liquid level detection mechanism for detecting that the liquid level of ink in the sub tank is at a predetermined position above the upper end of the partition wall, and in the second ink chamber. It is preferable to provide a second liquid level detection mechanism for detecting that the liquid level of the ink is at a predetermined position lower than the upper end of the partition wall. With this configuration, when the liquid surface of the ink on the first ink chamber side and the liquid surface of the ink on the second ink chamber side have the same height, the control unit detects the detection result of the first liquid surface detection mechanism. It is possible to drive and control the first pump and the second pump based on the above. Further, when the height of the ink surface of the first ink chamber is made higher than the height of the ink surface of the second ink chamber, the control unit determines based on the detection result of the second liquid surface detection mechanism. It becomes possible to drive and control the first pump and the second pump. Therefore, control of the first pump and the second pump is relatively easy.

  In the present invention, the inkjet recording apparatus is connected to the degassing module disposed in the ink supply path from the main tank to the subtank or the discharge path of the ink from the subtank to the main tank and removing the gas in the ink And a pressure sensor for detecting the suction pressure of the suction pump, the suction pump and the pressure sensor are electrically connected to the control unit, and the control unit detects the pressure sensor It is preferable to drive and control the suction pump based on the result.

  With this configuration, it is possible to properly control the degassing pressure in the degassing module based on the detection result of the pressure sensor. Therefore, it becomes possible to extend the life of the degassing membrane such as the hollow fiber membrane constituting the degassing module. Also, with this configuration, the atmospheric pressure changes due to the change in altitude of the place where the ink jet recording apparatus is used (for example, when the ink jet recording apparatus is used in high altitude or low altitude) Even if it does, it becomes possible to control the degassing pressure in a degassing module appropriately. Furthermore, this configuration makes it possible to properly control the degassing pressure in the degassing module even if the type of ink changes or the ink flow rate fluctuates. In addition, this configuration makes it possible to detect that the degassing module or the suction pump has a defect based on the detection result of the pressure sensor when the degassing module or the suction pump has a defect .

  As described above, in the ink jet recording apparatus according to the present invention, even if it is possible to circulate the ink in the ink jet head with a relatively simple configuration, the discharge operation of ink droplets from the nozzle portion of the ink jet head is stabilized. It becomes possible.

FIG. 1 is a schematic view for explaining the configuration of an ink jet recording apparatus according to an embodiment of the present invention. It is the schematic which shows the state when the ink is circulating through the inside of the inkjet head shown in FIG. It is the schematic which shows the motion of 1st piping and 2nd piping when the carriage shown in FIG. 1 operate | moves. It is a figure for demonstrating the pressure fluctuation in the inkjet head accompanying the movement of the carriage shown in FIG. It is a figure for demonstrating the effect of the inkjet recording device shown in FIG.

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

(Configuration of inkjet recording apparatus)
FIG. 1 is a schematic view for explaining the configuration of an inkjet recording apparatus 1 according to an embodiment of the present invention. FIG. 2 is a schematic view showing a state in which the ink circulates in the ink jet head 2 shown in FIG. FIG. 3 is a schematic view showing the movement of the pipes 12 and 13 when the carriage 3 shown in FIG. 1 operates. FIG. 4 is a diagram for explaining pressure fluctuations in the ink jet head 2 accompanying the movement of the carriage 3 shown in FIG.

  The inkjet recording device 1 of the present embodiment is, for example, a device for printing on a print target such as a printing sheet. The inkjet recording apparatus 1 includes an inkjet head 2 (hereinafter, referred to as “head 2”) that discharges ink droplets, and a carriage 3 on which the head 2 is mounted. The inkjet recording apparatus 1 further includes an apparatus main body 4 for holding the carriage 3 so as to be movable in the main scanning direction, and a carriage drive mechanism (not shown) for moving the carriage 3 in the main scanning direction. There is. When printing on an object to be printed by the inkjet recording apparatus 1, the head 2 discharges ink droplets while the carriage 3 reciprocates in the main scanning direction.

  The ink jet recording apparatus 1 also includes a sub tank 5 in which the ink supplied to the head 2 is stored, a main tank 6 in which the ink supplied to the sub tank 5 is stored, and a pump for sending the ink from the main tank 6 to the sub tank 5 7, a pump 8 for feeding ink from the sub tank 5 to the main tank 6, and a control unit 9 for driving and controlling the pumps 7 and 8. The pumps 7 and 8 are electrically connected to the control unit 9. The pump 7 of this embodiment is a first pump, and the pump 8 is a second pump. The inkjet recording apparatus 1 according to this embodiment includes a plurality of heads 2, a plurality of subtanks 5, a plurality of main tanks 6 corresponding to the number of subtanks 5, and a plurality of subtanks 5 and the number of main tanks 6. The pumps 7 and 8 are provided.

  The head 2 is a circulation type inkjet including an ink supply port 2a to which ink from the sub tank 5 is supplied, an ink discharge port 2b from which the ink is discharged toward the sub tank 5, and a nozzle unit 2c which discharges ink droplets. It is a head. The inkjet recording apparatus 1 includes a positive pressure pump (not shown) for making the pressure in the sub tank 5 a positive pressure, and a negative pressure pump (not shown) for making the pressure in the sub tank 5 a negative pressure. And have. During normal use of the ink jet recording apparatus 1, a negative pressure pump maintains negative pressure in the sub tank 5. Further, when cleaning or the like in the head 2 is performed, the positive pressure pump is activated, the pressure in the sub tank 5 becomes positive pressure, and the ink is ejected from the nozzle portion 2 c of the head 2.

  Inside the sub tank 5, two ink chambers of a first ink chamber 5a and a second ink chamber 5b in which the ink is stored are formed. Further, inside the sub tank 5, a partition wall 5c is formed which defines a first ink chamber 5a and a second ink chamber 5b. That is, inside the sub tank 5, the first ink chamber 5a and the second ink chamber 5b are defined by the partition wall 5c disposed between the first ink chamber 5a and the second ink chamber 5b. The partition wall 5 c rises from the bottom of the sub tank 5. The first ink chamber 5a and the second ink chamber 5b are connected above the partition wall 5c. That is, the upper end portion of the sub tank 5 is not partitioned by the partition wall 5 c.

  The pump 7 is connected to the first ink chamber 5 a via the pipe 12, and the pump 8 is connected to the second ink chamber 5 b via the pipe 13. That is, the inkjet recording apparatus 1 includes a pipe 12 for connecting the pump 7 and the first ink chamber 5a, and a pipe 13 for connecting the pump 8 and the second ink chamber 5b. In the present embodiment, the pump 7 is connected to the first ink chamber 5a via the pipe 12 and the degassing module 16 for removing the gas in the ink. That is, the degassing module 16 is disposed in the piping path between the piping 12 and the pump 7. The pipe 12 of the present embodiment is a first pipe, and the pipe 13 is a second pipe. Note that the degassing module 16 may be disposed in a piping path between the piping 13 and the pump 8.

  Further, the ink supply port 2a is connected to the first ink chamber 5a via the pipe 14, and the ink discharge port 2b is connected to the second ink chamber 5b via the pipe 15. That is, the inkjet recording apparatus 1 includes a pipe 14 connecting the first ink chamber 5a and the ink supply port 2a, and a pipe 15 connecting the second ink chamber 5b and the ink discharge port 2b. In the pipe 14, the ink can always flow between the first ink chamber 5a and the ink supply port 2a. Similarly, in the piping 15, ink can always flow between the second ink chamber 5b and the ink discharge port 2b. That is, in the piping path between the first ink chamber 5a and the ink supply port 2a and in the piping path between the second ink chamber 5b and the ink discharge port 2b, the flow of ink such as a pump or a valve is obstructed. There is no equipment. The pipe 14 of this embodiment is a supply side pipe, and the pipe 15 is a discharge side pipe.

  The ink jet recording apparatus 1 also has a liquid level detection mechanism 20 for detecting that the liquid level of ink in the sub tank 5 is at a predetermined position above the upper end of the partition wall 5c, and in the second ink chamber 5b. And a liquid level detection mechanism 21 for detecting that the liquid level of the ink is at a predetermined position lower than the upper end of the partition wall 5c. The liquid level detection mechanism 20 of this embodiment is a first liquid level detection mechanism, and the liquid level detection mechanism 21 is a second liquid level detection mechanism.

  The liquid level detection mechanism 20 includes a float 22 disposed on the side of the first ink chamber 5 a in the sub tank 5 and a sensor 23 for detecting the float 22. The liquid level detection mechanism 21 includes a float 24 disposed on the side of the second ink chamber 5 b in the sub tank 5 and a sensor 25 for detecting the float 24. The floats 22 and 24 float in the ink in the subtank 5. The sensors 23 and 25 are electrically connected to the control unit 9. The sensor 23 is fixed to the outer surface of the sub tank 5 on the first ink chamber 5 a side, and the sensor 25 is fixed to the outer surface of the sub tank 5 on the second ink chamber 5 b side.

  In the liquid level detection mechanism 20, when the sensor 23 detects the float 22, it is detected that the liquid level of the ink in the sub tank 5 is at a predetermined position above the upper end of the partition wall 5c (see FIG. 1). . Similarly, in the liquid level detection mechanism 21, when the sensor 25 detects the float 24, it is detected that the liquid level of the ink in the second ink chamber 5b is at a predetermined position lower than the upper end of the partition wall 5c. (See Figure 2).

  The sub tank 5 is mounted on the carriage 3. Further, the sub tank 5 is disposed above the head 2. The main tank 6, the pumps 7, 8 and the degassing module 16 are attached to the apparatus body 4. The pipes 12 to 15 are formed of flexible tubes. Specifically, the pipes 12 to 15 are formed of a flexible resin tube. Most parts of the pipes 12 and 13 are accommodated in a cable bea (registered trademark) 27. One end of the CableBeer (registered trademark) 27 is fixed to the apparatus body 4, and the other end of the CableBeard (registered trademark) 27 is fixed to the carriage 3.

  As shown in FIG. 3, the pipes 12 and 13 are bent at one place. Specifically, the pipes 12 and 13 are folded back at 180 ° at one place. The pipes 12 and 13 follow the carriage 3 while changing the bending position as the carriage 3 moves in the main scanning direction. When the carriage 3 moves in the main scanning direction, the pressure in the head 2 fluctuates with the movement of the carriage 3 in the main scanning direction due to the influence of the inertial force acting on the ink in the pipes 12 and 13. For example, when the carriage 3 continuously reciprocates in the main scanning direction, the pressure in the head 2 fluctuates as shown in FIG.

  Specifically, when the carriage 3 moving toward one side in the main scanning direction (arrow V1 side in FIG. 3A) accelerates, the carriages 12 and 13 in the carriages than the bent portions 12a and 13a. The ink in the three side portions 12b and 13b moves in a direction away from the sub tank 5 (in the direction of the arrow V2 in FIG. 3A) by the inertial force, so the negative pressure in the sub tank 5 due to the influence of the inertial force of the ink. As a result, negative pressure is applied to the head 2. Further, when the carriage 3 moving toward one side in the main scanning direction (arrow V3 side in FIG. 3B) is decelerating, the pipes 12, 13 on the carriage 3 side of the bending portions 12a, 13a. Since the ink in the portions 12b and 13b moves in the direction approaching the sub tank 5 (in the direction of the arrow V3 in FIG. 3B) by inertia force, positive pressure is applied to the sub tank 5 under the influence of the inertia force of the ink, As a result, positive pressure is applied to the head 2.

  Further, when the carriage 3 moving toward the other side in the main scanning direction (arrow V4 side in FIG. 3B) is accelerating, the pipes 12, 13 are closer to the carriage 3 than the bending portions 12a, 13a. Since the ink in the portions 12b and 13b moves in the direction approaching the sub tank 5 (in the direction of the arrow V3 in FIG. 3B) by inertia force, positive pressure is applied to the sub tank 5 under the influence of the inertia force of the ink, As a result, positive pressure is applied to the head 2. Further, when the carriage 3 moving toward the other side in the main scanning direction (arrow V2 side in FIG. 3A) is decelerating, the pipes 12 and 13 are closer to the carriage 3 than the bending portions 12a and 13a. Since the ink in the portions 12b and 13b moves in the direction away from the subtank 5 (in the direction of the arrow V2 in FIG. 3A) by the inertial force, negative pressure is applied to the subtank 5 under the influence of the inertial force of the ink. As a result, negative pressure is applied to the head 2.

  Therefore, when the carriage 3 continuously reciprocates in the main scanning direction, the head 2 moves along with the reciprocation of the carriage 3 in the main scanning direction due to the influence of the inertial force acting on the ink in the pipes 12 and 13. The pressure inside fluctuates, for example, as shown in FIG.

  As described above, the degassing module 16 is disposed in the piping path between the piping 12 and the pump 7. That is, the inkjet recording apparatus 1 includes the degassing module 16 disposed in the ink supply path from the main tank 6 to the sub tank 5. The inkjet recording apparatus 1 also includes a suction pump (vacuum pump) 30 for degassing connected to the degassing module 16 and a pressure sensor 31 for detecting the suction pressure of the suction pump 30. In addition, the degassing module 16 may be arrange | positioned in the piping path | route between the piping 13 and the pump 8 as mentioned above. That is, the degassing module 16 may be disposed in the ink discharge path from the sub tank 5 to the main tank 6.

  Inside the degassing module 16 is disposed a degassing film made of a functional material that allows gas to pass without passing ink. The degassing membrane is, for example, a hollow fiber membrane. Further, the degassing film is formed, for example, in a tubular shape, and inside the degassing module 16, a plurality of degassing films are gathered in a bundle. In the degassing module 16, the ink passes, for example, the inner peripheral side of the degassing film formed in a tubular shape. In this case, the suction pump 30 depressurizes the outer peripheral side of the tube-like degassing membrane. Alternatively, in the degassing module 16, the ink passes through the outer peripheral side of the tubular degassing film. In this case, the suction pump 30 depressurizes the inner peripheral side of the tube-like degassing membrane.

  The suction pump 30 and the pressure sensor 31 are attached to the apparatus main body 4. The suction pump 30 and the pressure sensor 31 are electrically connected to the control unit 9. The controller 9 drives and controls the suction pump 30 based on the detection result of the pressure sensor 31. In the present embodiment, when the ink jet recording apparatus 1 is powered on, the pressure sensor 31 always measures the suction pressure of the suction pump 30, regardless of whether the ink jet recording apparatus 1 is printing on the print target. The controller 9 controls the drive of the suction pump 30 based on the detection result of the pressure sensor 31. For example, the control unit 9 controls the drive of the suction pump 30 so that the suction pressure of the suction pump 30 becomes -80 to -85 (kPa).

(Operation of inkjet recording apparatus)
In the inkjet recording apparatus 1, when the carriage 3 is stopped for a predetermined time or more without printing on the print target, as shown in FIG. 2, the level of the ink surface of the first ink chamber 5a is high. The height is higher than the height of the ink surface of the second ink chamber 5b. At this time, the ink is circulated between the head 2 and the sub tank 5 due to the difference (head difference) between the height of the ink surface of the first ink chamber 5a and the height of the ink surface of the second ink chamber 5b. The ink is circulating in the head 2. When the ink discharged from the ink discharge port 2b flows into the second ink chamber 5b and the level of the ink in the second ink chamber 5b becomes high, the control unit 9 causes the liquid level detection mechanism 21 to Based on the detection result, the pump 8 is driven and controlled to discharge the ink from the second ink chamber 5b to the main tank 6 until the level of the ink surface in the second ink chamber 5b becomes a predetermined height. Do.

  Further, in the present embodiment, the ink is circulated between the sub tank 5 and the main tank 6 when the carriage 3 is stopped for a predetermined time or more without printing on the print target. That is, when printing on the print target is not performed and the carriage 3 is stopped for a predetermined time or more, the control unit 9 drives and controls the pump 7 so that the main tank 6 to the first ink chamber 5a. The ink supplied to the first ink chamber 5a passes through the partition wall 5c and flows into the second ink chamber 5b. In addition, when printing on the print target is not performed and the carriage 3 is stopped for a predetermined time or more, the control unit 9 drives the pump 8 based on the detection result of the liquid level detection mechanism 21. By control, the excess ink flowing into the second ink chamber 5 b is returned to the main tank 6.

  As described above, in the present embodiment, the control unit 9 controls the pumps 7 and 8 based on the detection result of the liquid level detection mechanism 21 so that the height of the liquid level of the ink in the first ink chamber 5a is A state of being higher than the level of the ink surface of the two-ink chamber 5b is maintained. In the present embodiment, when the height of the ink surface of the first ink chamber 5a is higher than the height of the ink surface of the second ink chamber 5b, the ink surface of the first ink chamber 5a Is the same height as the upper end of the partition wall 5c.

  If printing of a print target is input to the control unit 9 in a state where the carriage 3 is stopped for a predetermined time or more without printing on the print target, the control unit 9 at least When 2c ejects ink droplets, the liquid surface of the ink in the sub tank 5 becomes higher than the upper end of the partition wall 5c, and the liquid surface of the ink on the side of the first ink chamber 5a and the ink on the side of the second ink chamber 5b At least the pump 7 is controlled so as to have the same level as the liquid level (see FIG. 1). That is, when the print command of the print object is input to the control unit 9, the control unit 9 causes the ink surface of the first ink chamber 5a and the second ink to discharge at least when the nozzle unit 2c discharges the ink droplet. The pump 7 is drive-controlled or the pump 7 and the pump 8 are drive-controlled so that the level of the ink on the chamber 5 b side becomes the same level.

  Specifically, when a command to print a print target is input to the control unit 9, the control unit 9 sets the first ink chamber 5a side by a predetermined timing before the nozzle unit 2c performs an ink droplet discharge operation. To supply the ink from the main tank 6 to the first ink chamber 5a by driving control of the pump 7 so that the ink level of the ink and the ink level on the second ink chamber 5b side become the same height. Alternatively, the pump 7 and the pump 8 are drive-controlled to supply the ink from the main tank 6 to the first ink chamber 5a, and the ink is returned from the second ink chamber 5b to the main tank 6. Further, in the control unit 9, the liquid surface of the ink on the side of the first ink chamber 5 a and the liquid surface of the ink on the side of the second ink chamber 5 b have the same height based on the detection result by the liquid level detection mechanism 20. In this way, drive control of the pump 7 or drive control of the pump 7 and the pump 8 is performed.

  Further, in the present embodiment, the first ink is continued until the state in which the carriage 3 is stopped continues for a predetermined time after the printing on the printing object is finished (that is, the ink droplet discharge operation of the nozzle portion 2c is finished). The state in which the liquid surface of the ink on the chamber 5a side and the liquid surface of the ink on the second ink chamber 5b side are at the same height is maintained. At this time, ink does not circulate between the head 2 and the sub tank 5 because there is no water head difference. That is, the ink does not circulate in the head 2.

  In this embodiment, even when the liquid surface of the ink on the side of the first ink chamber 5 a and the liquid surface of the ink on the side of the second ink chamber 5 b are at the same height, the space between the sub tank 5 and the main tank 6 is I am circulating ink. That is, the control unit 9 drives and controls the pump 7 to supply the ink from the main tank 6 to the sub tank 5, and drives and controls the pump 8 to return the ink supplied to the sub tank 5 to the main tank 6. As described above, in the present embodiment, the control unit 9 controls the driving of the pumps 7 and 8 based on the detection result of the liquid level detection mechanism 20, whereby the liquid level of the ink on the side of the first ink chamber 5a and the second ink A state in which the liquid level of the ink on the chamber 5b side is the same height is maintained.

  In addition, when the ink droplet discharge operation of the nozzle unit 2c is finished and the state in which the carriage 3 is stopped continues for a predetermined time, the control unit 9 determines that the ink level of the first ink chamber 5a is second. At least the pump 8 is drive-controlled so that the ink flows from the first ink chamber 5a to the second ink chamber 5b via the head 2 higher than the level of the ink surface of the ink chamber 5b. That is, when the operation of discharging ink droplets from the nozzle unit 2c is finished and the carriage 3 is stopped for a predetermined time, the control unit 9 sets the ink level of the first ink chamber 5a to the second level. The pump 8 is driven to control the second ink chamber 5b so that the ink flows from the first ink chamber 5a to the second ink chamber 5b via the head 2 higher than the level of the ink surface of the ink chamber 5b. The ink is returned from the main tank 6 to the main tank 6, or the pumps 7 and 8 are driven and controlled to supply the ink from the main tank 6 to the first ink chamber 5a while returning the ink from the second ink chamber 5b to the main tank 6 . Further, based on the detection result of the liquid level detection mechanism 21, the control section 9 makes the height of the ink level of the first ink chamber 5a higher than the height of the ink level of the second ink chamber 5b. In this way, drive control of the pump 8 or drive control of the pump 7 and the pump 8 is performed.

(Main effects of this form)
As described above, in the present embodiment, the first ink chamber 5 a and the second ink chamber 5 b are formed inside the sub tank 5. Further, in the present embodiment, the pump 7 for sending ink from the main tank 6 to the sub tank 5 is connected to the first ink chamber 5a to which the ink supply port 2a of the head 2 is connected, and the ink discharge port 2b of the head 2 is connected. A pump 8 for sending ink from the sub tank 5 to the main tank 6 is connected to the second ink chamber 5 b. Furthermore, in the present embodiment, when the ink droplet discharge operation of the nozzle unit 2c ends and the carriage 3 is stopped for a predetermined time, the control unit 9 determines that the ink level of the first ink chamber 5a is high. At least the pump 8 is drive-controlled so that the ink flow from the first ink chamber 5a to the second ink chamber 5b via the head 2 higher than the height of the ink surface of the second ink chamber 5b. There is. Therefore, in the present embodiment, as described above, it is possible to circulate the ink in the head 2 by circulating the ink between the head 2 and the sub tank 5 using the water head difference. That is, in the present embodiment, it is possible to circulate the ink in the head 2 by a relatively simple configuration using the water head difference.

  In the present embodiment, the control unit 9 causes the liquid surface of the ink in the sub tank 5 to be at least as high as the upper end of the partition wall 5c when the nozzle unit 2c discharges the ink droplet, at least the ink on the first ink chamber 5a side At least the pump 7 is driven and controlled so that the liquid surface of the ink and the liquid surface of the ink on the side of the second ink chamber 5 b have the same height. Therefore, in the present embodiment, when the nozzle portion 2c ejects the ink droplet, the influence of the water head difference is eliminated, and the difference between the pressure on the ink supply port 2a side and the pressure on the ink discharge port 2b side inside the head 2 is calculated. It is possible to eliminate it. Therefore, in the present embodiment, it is possible to stabilize the discharge operation of the ink droplet from the nozzle portion 2c.

  In particular, in the present embodiment, when the carriage 3 moves in the main scanning direction, the head 2 is moved along with the reciprocating movement of the carriage 3 in the main scanning direction under the influence of the inertial force acting on the ink in the pipes 12 and 13. Because the internal pressure fluctuates (see FIG. 4), when the nozzle unit 2c ejects ink droplets, the pressure on the ink supply port 2a side and the ink discharge port 2b side in the head 2 due to the influence of the water head difference. When a difference occurs in the pressure, as shown in FIG. 5, a large difference ΔP occurs between the maximum pressure on the ink supply port 2a side and the minimum pressure on the ink discharge port 2b inside the head 2, and from the nozzle portion 2c The ink droplet ejection operation is likely to be unstable. However, in the present embodiment, when the nozzle portion 2c ejects ink droplets, the influence of the water head difference is eliminated, and the difference between the pressure on the ink supply port 2a side and the pressure on the ink discharge port 2b side inside the head 2 is calculated. Since it becomes possible to eliminate, even if the pressure in the head 2 fluctuates with the movement of the carriage 3 in the main scanning direction, it becomes easy to stabilize the discharge operation of the ink droplet from the nozzle portion 2c.

  In the present embodiment, the first ink chamber 5a and the second ink chamber 5b are connected above the partition wall 5c. Further, in the present embodiment, the pump 7 for sending the ink from the main tank 6 to the sub tank 5 is connected to the first ink chamber 5a, and the pump 8 for sending the ink from the sub tank 5 to the main tank 6 is connected to the second ink chamber 5b. It is done. Therefore, in the present embodiment, as described above, the height of the liquid surface of the ink in the first ink chamber 5a is higher than the height of the liquid surface of the ink in the second ink chamber 5b, and In any case where the liquid surface of the ink on the chamber 5a side and the liquid surface of the ink on the second ink chamber 5b side have the same height, the relationship is related to the amount of ink consumed by the head 2 Instead, the ink can be circulated between the sub tank 5 and the main tank 6. Therefore, in the present embodiment, it is possible to suppress the sedimentation of the ink particles in the piping path between the sub tank 5 and the main tank 6 and the sub tank 5, and the degassing module 16 effectively prevents the gas in the ink. It can be removed.

  In the present embodiment, the controller 9 controls the liquid level of the ink on the side of the first ink chamber 5a and the liquid level of the ink on the side of the second ink chamber 5b based on the detection result of one liquid level detection mechanism 20. At least the pump 7 is controlled so as to have the same height. Further, in the present embodiment, the control unit 9 determines that the liquid level of the ink in the first ink chamber 5a is the ink liquid in the second ink chamber 5b based on the detection result of one liquid level detection mechanism 21. At least the pump 8 is controlled to be higher than the height of the surface. Therefore, in the present embodiment, control of the pumps 7 and 8 is relatively easy.

  In the present embodiment, the control unit 9 controls the suction pump 30 for degassing connected to the degassing module 16 based on the detection result of the pressure sensor 31. Therefore, in the present embodiment, the degassing pressure in the degassing module 16 can be properly controlled. Therefore, in the present embodiment, it is possible to extend the life of the degassing membrane such as the hollow fiber membrane constituting the degassing module 16. Further, in this embodiment, even if the atmospheric pressure changes due to a change in the altitude of the place where the ink jet recording apparatus 1 is used, the degassing pressure in the degassing module 16 can be appropriately controlled. Furthermore, in the present embodiment, even if the type of ink used or the flow rate of the ink fluctuates, the degassing pressure in the degassing module 16 can be appropriately controlled. Further, in the present embodiment, when a defect occurs in the degassing module 16 or the suction pump 30, it is detected that the defect occurred in the degassing module 16 or the suction pump 30 based on the detection result of the pressure sensor 31. It will be possible.

  In addition, the inkjet recording device by which the degassing apparatus was arrange | positioned to the supply path of the ink conventionally is known (for example, refer Unexamined-Japanese-Patent No. 11-42795). This conventional ink jet recording apparatus includes a polaro-type dissolved oxygen meter connected to the degassing apparatus, and a vacuum pump connected to the degassing apparatus. The dissolved oxygen meter is composed of an oxygen electrode, a low voltage power supply, and a direct current ammeter. The oxygen electrode comprises an electrode body and a diaphragm covering an opening at one end of the electrode body. The electrode body comprises a silver anode and a platinum cathode. The vacuum pump is controlled based on the detection result of the dissolved oxygen meter. That is, the degassing pressure in the degassing device is controlled based on the detection result of the dissolved oxygen meter.

  In this conventional ink jet recording apparatus, since the dissolved oxygen meter measures the oxygen concentration in the ink by a chemical method, it takes time to measure the oxygen concentration. For example, in this inkjet recording apparatus, it takes about 30 seconds to 5 minutes to measure the oxygen concentration. Therefore, in this inkjet recording device, it is difficult to control the degassing pressure in the degassing device at an appropriate timing based on the detection result of the dissolved oxygen meter. In addition, in the ink jet recording apparatus, there are problems of the life of the electrode body of the dissolved oxygen meter and the clogging of the diaphragm of the dissolved oxygen meter.

  On the other hand, in the inkjet recording apparatus 1 of the present embodiment, since the suction pump 30 for degassing connected to the degassing module 16 is controlled based on the detection result of the pressure sensor 31, the degassing module 16 is It becomes possible to control the degassing pressure at the appropriate timing. Further, in the ink jet recording apparatus 1 of the present embodiment, the problem of the life of the electrode body of the dissolved oxygen meter and the problem of clogging of the diaphragm of the dissolved oxygen meter do not occur.

(Other embodiments)
In the embodiment described above, when the ink droplet discharge operation of the nozzle unit 2c ends and the carriage 3 is stopped for a predetermined time, the control unit 9 determines the height of the ink surface of the first ink chamber 5a. At least the pump 8 is driven and controlled so that the height of the ink surface of the second ink chamber 5b becomes higher than that of the second ink chamber 5b. The control unit 9 may drive and control at least the pump 8 so that the height of the ink surface of the first ink chamber 5a is higher than the height of the ink surface of the second ink chamber 5b.

  In the embodiment described above, the sensor 23 may be fixed to the outer surface of the sub tank 5 on the side of the second ink chamber 5 b. In this case, the liquid surface of the ink in the sub tank 5 is at a predetermined position above the upper end of the partition wall 5c using the common float 24 and the ink in the second ink chamber 5b. It may be detected that the liquid level is at a predetermined position lower than the upper end of the partition wall 5c. Further, in the embodiment described above, the pipes 12 and 13 may be bent at two or more places.

  In the embodiment described above, the degassing module 16 may be mounted on the carriage 3. Further, in the embodiment described above, the suction pump 30 and the pressure sensor 31 may be mounted on the carriage 3. Further, in the embodiment described above, the main tank 6 and the pumps 7 and 8 may be mounted on the carriage 3. In this case, the pressure fluctuation in the head 2 accompanying the movement of the carriage 3 in the main scanning direction is eliminated. Further, in the embodiment described above, the inkjet recording apparatus 1 is an apparatus for printing an object to be printed, but the inkjet recording apparatus 1 may be used for applications other than printing.

1 Ink jet recording apparatus 2 head (ink jet head)
2a Ink supply port 2b Ink discharge port 2c Nozzle part 3 Carriage 4 Device body 5 Sub tank 5a First ink chamber 5b Second ink chamber 5c Partition wall 6 Main tank 7 Pump (First pump)
8 pump (second pump)
9 control unit 12 piping (first piping)
13 Piping (second piping)
14 Piping (supply side piping)
15 Piping (discharge side piping)
16 Degassing Module 20 Liquid Level Detection Mechanism (First Liquid Level Detection Mechanism)
21 Liquid Level Detection Mechanism (Second Liquid Level Detection Mechanism)
30 suction pump 31 pressure sensor

Claims (6)

An ink jet head for discharging ink droplets, a sub tank containing ink supplied to the ink jet head, a main tank containing ink supplied to the sub tank, and sending ink from the main tank to the sub tank 1 pump, a second pump for sending ink from the sub tank to the main tank, and a control unit for driving and controlling the first pump and the second pump,
The inkjet head is a circulating inkjet head including an ink supply port to which ink from the sub tank is supplied, an ink discharge port from which ink is discharged toward the sub tank, and a nozzle unit that discharges ink droplets. Yes,
Inside the sub-tank, a first ink chamber and a second ink chamber for containing ink are formed, and a partition wall which defines the first ink chamber and the second ink chamber is formed.
The partition wall rises from the bottom of the sub tank,
The first ink chamber and the second ink chamber are connected above the partition wall, and
The first pump is connected to the first ink chamber via a pipe and the ink supply port is connected via the pipe.
The second pump is connected to the second ink chamber via a pipe and the ink discharge port is connected via the pipe.
The control unit causes the liquid surface of the ink in the sub tank to be at a height higher than the upper end of the partition wall at least when the nozzle unit ejects the ink droplet, and the liquid surface of the ink on the first ink chamber side An ink jet printing apparatus characterized in that at least the first pump is driven and controlled so that the ink level on the second ink chamber side becomes the same level. A supply-side pipe connecting the first ink chamber and the ink supply port; and a discharge-side pipe connecting the second ink chamber and the ink discharge port.
In the supply side piping, the ink can always flow between the first ink chamber and the ink supply port,
2. The ink jet recording apparatus according to claim 1, wherein, in the discharge side pipe, the ink can be always circulated between the second ink chamber and the ink discharge port. A carriage on which the inkjet head and the sub tank are mounted, and an apparatus main body holding the carriage so as to be movable in a main scanning direction,
When the state where the carriage is stopped continues for a predetermined time, the control unit causes the ink level of the first ink chamber to be higher than the ink level of the second ink chamber. 3. The ink jet recording apparatus according to claim 1, wherein at least the second pump is driven and controlled so that the ink flows from the first ink chamber to the second ink chamber via the ink jet head. A carriage for connecting the first pump and the first ink chamber, wherein the inkjet head and a carriage on which the sub tank is mounted, an apparatus main body for holding the carriage so that movement in the main scanning direction is possible, and 1 piping, and a second piping for connecting the second pump and the second ink chamber,
The main tank, the first pump and the second pump are attached to the device body,
The first pipe and the second pipe are formed of a flexible tube, and are bent at at least one place, and the carriage is changed while changing the bending portion along with the movement of the carriage in the main scanning direction. The ink jet recording apparatus according to any one of claims 1 to 3, wherein the ink jet recording apparatus follows.   A first liquid level detection mechanism for detecting that the liquid level of ink in the sub tank is at a predetermined position above the upper end of the partition wall, and the liquid level of ink in the second ink chamber The ink jet recording apparatus according to any one of claims 1 to 4, further comprising: a second liquid level detection mechanism for detecting that the predetermined position is lower than the upper end of the partition wall. A degassing module disposed in an ink supply path from the main tank to the sub tank or an ink discharge path from the sub tank to the main tank for removing a gas in the ink, and a degassing module connected to the degassing module And a pressure sensor for detecting the suction pressure of the suction pump,
The suction pump and the pressure sensor are electrically connected to the control unit,
The inkjet recording apparatus according to any one of claims 1 to 5, wherein the control unit drives and controls the suction pump based on a detection result of the pressure sensor.

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