JP7037433B2 - Inkjet recording device - Google Patents

Description

The present invention relates to an inkjet recording device for printing on an object to be printed.

Conventionally, an inkjet recording device that ejects ink droplets and prints on a paper medium is known (see, for example, Patent Document 1). The inkjet recording device described in Patent Document 1 includes an inkjet head (recording head) in which a plurality of nozzles are formed, a sub tank that supplies ink to the inkjet head, and a main tank that is connected to the sub tank via a diaphragm pump or the like. It is equipped with.

Further, conventionally, as an inkjet head (liquid ejection head) for ejecting a liquid, a circulation type inkjet head that circulates the liquid in the inkjet head is known (see, for example, Patent Document 2). The inkjet head described in Patent Document 2 is composed of a plurality of nozzles for discharging liquid, a plurality of individual liquid chambers leading to the nozzles, a common liquid chamber for supplying liquid to a plurality of individual liquid chambers, and a plurality of individual liquid chambers. It is equipped with a common liquid chamber for circulation in which the liquid returns. In this inkjet head, by circulating the liquid in the inkjet head, it is possible to prevent the nozzle from drying and the ink particles from settling, and to stabilize the liquid ejection performance.

Japanese Patent Application Laid-Open No. 2003-182104 Japanese Unexamined Patent Publication No. 2017-159561

The inventor of the present application has studied in an inkjet recording apparatus provided with a sub-tank like the inkjet recording apparatus described in Patent Document 1, in which ink is circulated in the inkjet head as in the inkjet head described in Patent Document 2. There is. That is, the inventor of the present application is studying to circulate the ink in the inkjet head by circulating the ink between the inkjet head and the sub tank.

Specifically, the inventor of the present application forms two ink chambers, a first ink chamber and a second ink chamber, in which ink is housed in an inkjet recording apparatus including a sub tank, and first. To form a partition wall that defines the ink chamber and the second ink chamber, the ink supply port for supplying ink from the sub tank to the inkjet head, the ink discharge port for discharging ink toward the sub tank, and the ink. Forming a nozzle for ejecting drops, connecting an ink supply port to the first ink chamber via a pipe, connecting an ink discharge port to the second ink chamber via a pipe, and connecting the first ink. By making the height of the liquid level of the ink in the chamber higher than the height of the liquid level of the ink in the second ink chamber, the height of the liquid level of the ink in the first ink chamber and the liquid level of the ink in the second ink chamber We are considering circulating ink in the inkjet head by circulating ink between the inkjet head and the sub tank using the difference from the height (waterhead difference).

According to the study of the inventor of the present application, when the ink is circulated in the inkjet head in this way, 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 way, the pressure on the ink supply port side and the pressure on the ink discharge port side are different inside the inkjet head due to the influence of the head difference, and the nozzle It has been clarified by the study of the inventor of the present application that the operation of ejecting ink droplets from the portion becomes unstable. Further, since the operation of ejecting ink droplets from the nozzle portion becomes unstable, for example, when printing on an object to be printed with an inkjet recording device, the print quality may deteriorate. It became clear by the examination.

Therefore, the subject of the present invention is an inkjet capable of stabilizing the ejection operation of ink droplets from the nozzle portion of the inkjet head even if the ink can be circulated in the inkjet head by a relatively simple configuration. The purpose is to provide a recording device.

In order to solve the above problems, the inkjet recording apparatus of the present invention has an ink jet head that ejects ink droplets, a sub tank that houses ink supplied to the ink jet head, and a main tank that houses ink supplied to the sub tank. The tank, the first pump that sends ink from the main tank to the sub tank, the second pump that sends ink from the sub tank to the main tank, the control unit that drives and controls the first pump and the second pump, and the ink in the sub tank It is equipped with a first liquid level detection mechanism for detecting the position of the liquid level, and the ink jet head has an ink supply port to which ink is supplied from the sub tank, an ink discharge port to discharge ink toward the sub tank, and an ink discharge port. It is a circulation type ink jet head provided with a nozzle portion for ejecting ink droplets. Inside the sub tank, a first ink chamber and a second ink chamber for accommodating ink are formed, and a first ink chamber and a first ink chamber are formed. A partition wall defining the two ink chambers is formed, the partition wall rises from the bottom surface of the sub tank, the first ink chamber and the second ink chamber are connected above the partition wall, and the first ink chamber is connected to the first ink chamber. The first pump is connected via the pipe, the ink supply port is connected via the pipe, the second pump is connected to the second ink chamber via the pipe, and the ink discharge port is connected via the pipe. Connected, the first liquid level detection mechanism detects that the liquid level of the ink in the sub tank is at a predetermined position above the upper end of the partition wall, and the control unit ejects ink droplets at least by the nozzle unit. Sometimes the liquid level of the ink in the sub tank becomes higher than the upper end of the partition wall so that the liquid level of the ink on the first ink chamber side and the liquid level of the ink on the second ink chamber side are at the same height. In addition, it is characterized in that at least the first pump is driven and controlled.

In the inkjet recording apparatus of the present invention, a first ink chamber and a second ink chamber are formed inside the sub tank. Further, in the present invention, the 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 inkjet head is connected, and the second ink to which the ink discharge port of the inkjet head is connected is connected. A second pump is connected to the chamber to send the ink discharged from the sub tank to the main tank. Therefore, in the present invention, the first pump and the second pump are driven and controlled so that the height of the liquid level of the ink in the first ink chamber is higher than the height of the liquid level of the ink in the second ink chamber. Ink can be circulated between the inkjet head and the sub-tank by utilizing the water head difference, and as a result, the ink can be circulated in the inkjet head. That is, in the present invention, the ink can be circulated in the inkjet head by a relatively simple configuration utilizing the head difference.

Further, in the present invention, in the control unit, at least when the nozzle unit ejects ink droplets, the liquid level of the ink in the sub tank becomes higher than the upper end of the partition wall, and the liquid level of the ink on the first ink chamber side becomes high. At least the first pump is driven and controlled so that the liquid level of the ink on the second ink chamber side and the liquid level of the ink on the second ink chamber side are at the same level. Therefore, in the present invention, when the nozzle portion ejects ink droplets, the influence of the head difference is eliminated and the difference between the pressure on the ink supply port side and the pressure on the ink discharge port side is suppressed inside the inkjet head. Will be possible. Therefore, in the present invention, it is possible to stabilize the operation of ejecting ink droplets from the nozzle portion of the inkjet head. Further, in the present invention, the inkjet recording device is provided with a first liquid level detecting mechanism for detecting that the liquid level of the ink in the sub tank is at a predetermined position above the upper end of the partition wall. When the liquid level of the ink on the 1st ink chamber side and the liquid level of the ink on the 2nd ink chamber side are set to the same height, the control unit performs the first pump based on the detection result of the first liquid level detection mechanism. And the second pump can be driven and controlled. Therefore, the control of the first pump and the second pump becomes relatively easy.

Further, in the present invention, the first ink chamber and the second ink chamber are connected above the partition wall, and the first ink chamber is connected to the first pump that sends ink from the main tank to the sub tank, so that the second ink is used. A second pump that sends ink from the sub tank to the main tank is connected to the chamber. Therefore, in the present invention, even if excess ink that exceeds the amount of ink consumed by the inkjet head is supplied to the sub tank by the first pump, the excess ink supplied to the sub tank is returned to the main tank by the second pump. Will be possible. Therefore, in the present invention, it is possible to circulate ink between the sub tank and the main tank regardless of the amount of ink consumed by the inkjet head. As a result, in the present invention, it is possible to suppress the sedimentation of 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 ink, it is possible to effectively remove the gas in the ink.

In the present invention, the inkjet recording device 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. Ink can always be circulated between the first ink chamber and the ink supply port, and ink can always be circulated between the second ink chamber and the ink discharge port in the discharge side pipe. In this case, compared with the case where the pump or the valve is arranged in the piping path between the first ink chamber and the ink supply port and the piping path between the second ink chamber and the ink discharge port. , It becomes possible to simplify the configuration of the ink jet recording device.

In the present invention, for example, the ink jet recording device includes a carriage on which an inkjet head and a sub tank are mounted, and a device main body that holds the carriage so that the ink jet can be moved in the main scanning direction. When the stopped state continues for a predetermined time, the height of the ink liquid level in the first ink chamber becomes higher than the height of the ink liquid level in the second ink chamber, and the ink jet head is used from the first ink chamber. At least the second pump is driven and controlled so that the ink flows into the second ink chamber. In this case, after the carriage has been stopped for a predetermined time, the ink is circulated in the inkjet head by utilizing the head difference until the predetermined operation of the inkjet recording device is started. Will be possible.

In the present invention, for example, the inkjet recording device includes a carriage on which an inkjet head and a sub tank are mounted, a device body that holds the carriage so that it can be moved in the main scanning direction, a first pump, and a first ink chamber. It is provided with a first pipe for connecting the second pump and a second pipe for connecting the second pump and the second ink chamber, and the main tank, the first pump and the second pump are attached to the main body of the apparatus and the first 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 bent place 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. The pressure inside the inkjet head fluctuates. Therefore, when the nozzle portion ejects ink droplets, if there is an influence of the head difference, a large difference is likely to occur between the maximum pressure on the ink supply port side and the minimum pressure on the ink discharge port side inside the inkjet head. However, in the present invention, since the influence of the water head difference when the nozzle portion ejects ink droplets can be eliminated, even if the pressure in the inkjet head fluctuates due to the movement of the carriage in the main scanning direction, the nozzle When the ink jet ejects ink droplets, it is possible to suppress the difference between the maximum pressure on the ink supply port side and the minimum pressure on the ink ejection port side inside the inkjet head, and as a result, the nozzle portion of the inkjet head. It becomes possible to stabilize the ejection operation of ink droplets from.

In the present invention, the inkjet recording apparatus may include a second liquid level detecting mechanism for detecting that the liquid level of the ink in the second ink chamber is at a predetermined position lower than the upper end of the partition wall. preferable. With this configuration, when the height of the liquid level of the ink in the first ink chamber is higher than the height of the liquid level of the ink in the second ink chamber, the control unit receives the detection result of the second liquid level detection mechanism. It becomes possible to drive and control the first pump and the second pump based on the above. Therefore, the control of the first pump and the second pump becomes relatively easy.

In the present invention, the inkjet recording device is connected to a degassing module arranged in the ink supply path from the main tank to the sub tank or the ink discharge path from the sub tank to the main tank to remove the gas in the ink, and the degassing module. It is equipped with a suction pump for degassing 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 appropriately control the degassing pressure in the degassing module based on the detection result of the pressure sensor. Therefore, it is 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 fluctuates due to changes in the altitude of the place where the ink jet recording device is used (for example, when the ink jet recording device is used in high altitude or low altitude). Even so, it becomes possible to appropriately control the degassing pressure in the degassing module. Further, with such a configuration, it becomes possible to appropriately control the degassing pressure in the degassing module even if the type of ink changes or the flow rate of the ink fluctuates. Further, with this configuration, when a malfunction occurs in the degassing module or the suction pump, it becomes possible to detect that the malfunction has occurred in the degassing module or the suction pump based on the detection result of the pressure sensor. ..

As described above, in the inkjet recording apparatus of the present invention, even if ink can be circulated in the inkjet head by a relatively simple configuration, the operation of ejecting ink droplets from the nozzle portion of the inkjet head is stabilized. Will be possible.

It is a schematic diagram for demonstrating the structure of the inkjet recording apparatus which concerns on embodiment of this invention. It is a schematic diagram which shows the state when the ink circulates in the inkjet head shown in FIG. 1. It is a schematic diagram which shows the movement of the 1st pipe and the 2nd pipe when the carriage shown in FIG. 1 operates. It is a figure for demonstrating the pressure fluctuation in the inkjet head with the movement of the carriage shown in FIG. It is a figure for demonstrating the effect of the inkjet recording apparatus shown in FIG.

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

(Configuration of inkjet recording device)
FIG. 1 is a schematic diagram for explaining the configuration of the inkjet recording apparatus 1 according to the embodiment of the present invention. FIG. 2 is a schematic view showing a state when ink is circulated in the inkjet 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 the pressure fluctuation in the inkjet head 2 due to the movement of the carriage 3 shown in FIG.

The inkjet recording device 1 of the present embodiment is a device for printing on an object to be printed such as printing paper. The inkjet recording device 1 includes an inkjet head 2 (hereinafter referred to as “head 2”) that ejects ink droplets, and a carriage 3 on which the head 2 is mounted. Further, the inkjet recording device 1 includes a device main body 4 that holds the carriage 3 so that the carriage 3 can be moved in the main scanning direction, and a carriage drive mechanism (not shown) that moves the carriage 3 in the main scanning direction. There is. When printing on an object to be printed by the inkjet recording device 1, the head 2 ejects ink droplets while the carriage 3 reciprocates in the main scanning direction.

Further, the inkjet recording device 1 includes a sub tank 5 containing ink supplied to the head 2, a main tank 6 containing ink supplied to the sub tank 5, and a pump that sends ink from the main tank 6 to the sub tank 5. A pump 8 that sends ink from the sub tank 5 to the main tank 6 and a control unit 9 that drives and controls the pumps 7 and 8 are provided. 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 device 1 of the present embodiment has a plurality of heads 2, a plurality of sub tanks 5, a plurality of main tanks 6 according to the number of sub tanks 5, and a plurality of sub tanks 5 and a plurality of main tanks 6. It is equipped with pumps 7 and 8.

The head 2 is a circulation type inkjet including an ink supply port 2a to which ink is supplied from the sub tank 5, an ink discharge port 2b to discharge ink toward the sub tank 5, and a nozzle portion 2c to discharge ink droplets. The head. The inkjet recording device 1 has a positive pressure pump (not shown) for making the pressure in the sub tank 5 positive pressure and a negative pressure pump (not shown) for making the pressure in the sub tank 5 negative pressure. And have. During normal use of the inkjet recording device 1, the inside of the sub tank 5 is maintained at a negative pressure by a negative pressure pump. Further, when cleaning the inside of the head 2, the positive pressure pump is started, the pressure in the sub tank 5 becomes positive pressure, and ink is ejected from the nozzle portion 2c of the head 2.

Inside the sub tank 5, two ink chambers, a first ink chamber 5a and a second ink chamber 5b, in which ink is housed are formed. Further, a partition wall 5c defining the first ink chamber 5a and the second ink chamber 5b is formed inside the sub tank 5. That is, inside the sub tank 5, the first ink chamber 5a and the second ink chamber 5b are defined by a partition wall 5c arranged between the first ink chamber 5a and the second ink chamber 5b. The partition wall 5c rises from the bottom surface of the sub tank 5. The first ink chamber 5a and the second ink chamber 5b are connected to each other on the upper side of the partition wall 5c. That is, the upper end of the sub tank 5 is not partitioned by the partition wall 5c.

The pump 7 is connected to the first ink chamber 5a via the pipe 12, and the pump 8 is connected to the second ink chamber 5b via the pipe 13. That is, the inkjet recording device 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 this embodiment, the pump 7 is connected to the first ink chamber 5a via a pipe 12 and a degassing module 16 for removing gas in the ink. That is, the degassing module 16 is arranged in the piping path between the piping 12 and the pump 7. The pipe 12 of this embodiment is the first pipe, and the pipe 13 is the second pipe. The degassing module 16 may be arranged in the 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 device 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, ink can always be distributed between the first ink chamber 5a and the ink supply port 2a. Similarly, in the pipe 15, ink can always be distributed between the second ink chamber 5b and the ink discharge port 2b. That is, the piping path between the first ink chamber 5a and the ink supply port 2a and the piping path between the second ink chamber 5b and the ink discharge port 2b obstruct the flow of ink such as a pump or a valve. No equipment is placed. The pipe 14 of this embodiment is a supply-side pipe, and the pipe 15 is a discharge-side pipe.

Further, the inkjet recording device 1 has a liquid level detecting mechanism 20 for detecting 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, and the inside of the second ink chamber 5b. It is provided with a liquid level detecting mechanism 21 for detecting that the liquid level of the ink of the above ink is at a predetermined position lower than the upper end of the partition wall 5c. The liquid level detection mechanism 20 of the present 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 arranged on the first ink chamber 5a side inside the sub tank 5 and a sensor 23 for detecting the float 22. The liquid level detection mechanism 21 includes a float 24 arranged on the second ink chamber 5b side inside the sub tank 5 and a sensor 25 for detecting the float 24. The floats 22 and 24 are floating on the ink in the sub tank 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 5a side, and the sensor 25 is fixed to the outer surface of the sub tank 5 on the second ink chamber 5b 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, the sensor 25 detects the float 24 to detect 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 Fig. 2).

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

As shown in FIG. 3, the pipes 12 and 13 are bent at one point. 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 point 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 as the carriage 3 moves 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) is accelerating, the carriage is more than the bent portions 12a and 13a of the pipes 12 and 13. Since the ink in the portions 12b and 13b on the 3 side moves in the direction away from the sub tank 5 due to the inertial force (arrow V2 side in FIG. 3A), the negative pressure in the sub tank 5 due to the influence of the inertial force of the ink. As a result, a 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 carriage 3 side of the pipes 12 and 13 with respect to the bent portions 12a and 13a. Since the ink in the portions 12b and 13b moves in the direction approaching the sub tank 5 due to the inertial force (the arrow V3 side in FIG. 3B), a positive pressure is applied to the sub tank 5 due to the influence of the inertial 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 carriage 3 side of the pipes 12 and 13 with respect to the bent portions 12a and 13a. Since the ink in the portions 12b and 13b moves in the direction approaching the sub tank 5 due to the inertial force (the arrow V3 side in FIG. 3B), a positive pressure is applied to the sub tank 5 due to the influence of the inertial 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 carriage 3 side of the pipes 12 and 13 with respect to the bent portions 12a and 13a. Since the ink in the portions 12b and 13b moves in the direction away from the sub tank 5 due to the inertial force (the arrow V2 side in FIG. 3A), a negative pressure is applied to the sub tank 5 due to the influence of the inertial force of the ink. As a result, a negative pressure is applied to the head 2.

Therefore, when the carriage 3 continuously reciprocates in the main scanning direction, the head 2 moves back and forth 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 varies, for example, as shown in FIG.

As described above, the degassing module 16 is arranged in the piping path between the piping 12 and the pump 7. That is, the inkjet recording device 1 includes a degassing module 16 arranged in an ink supply path from the main tank 6 to the sub tank 5. Further, the inkjet recording device 1 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. As described above, the degassing module 16 may be arranged in the piping path between the piping 13 and the pump 8. That is, the degassing module 16 may be arranged in the ink discharge path from the sub tank 5 to the main tank 6.

Inside the degassing module 16, a degassing film made of a functional material that allows gas to pass through without passing ink is arranged. The degassing membrane is, for example, a hollow fiber membrane. Further, the degassing membrane is formed in a tubular shape, for example, and a plurality of degassing membranes are bundled together inside the degassing module 16. In the degassing module 16, the ink passes through, for example, the inner peripheral side of the degassing film formed in a tubular shape. In this case, the outer peripheral side of the tubular degassing membrane is decompressed by the suction pump 30. Alternatively, in the degassing module 16, the ink passes through the outer peripheral side of the tubular degassing film. In this case, the inner peripheral side of the tubular degassing membrane is decompressed by the suction pump 30.

The suction pump 30 and the pressure sensor 31 are attached to the apparatus main body 4. Further, the suction pump 30 and the pressure sensor 31 are electrically connected to the control unit 9. The control unit 9 drives and controls the suction pump 30 based on the detection result of the pressure sensor 31. In this embodiment, when the power of the ink jet recording device 1 is turned on, the pressure sensor 31 always presses the suction pressure of the suction pump 30 regardless of whether or not the ink jet recording device 1 is printing on the object to be printed. The control unit 9 drives and controls the suction pump 30 based on the detection result of the pressure sensor 31. For example, the control unit 9 drives and controls the suction pump 30 so that the suction pressure of the suction pump 30 is −80 to −85 (kPa).

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

Further, in the present embodiment, ink is circulated between the sub tank 5 and the main tank 6 when the carriage 3 is stopped for a predetermined time or longer without printing on the object to be printed. That is, when the carriage 3 is stopped for a predetermined time or longer without printing on the object to be printed, the control unit 9 drives and controls the pump 7 from 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. Further, when the carriage 3 is stopped for a predetermined time or longer without printing on the object to be printed, the control unit 9 drives the pump 8 based on the detection result by the liquid level detection mechanism 21. By controlling, the excess ink that has flowed into the second ink chamber 5b is returned to the main tank 6.

As described above, in this embodiment, the control unit 9 drives and 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 the second. 2 The state of being higher than the height of the liquid level of the ink in the ink chamber 5b is maintained. Further, in the present embodiment, when the height of the liquid level of the ink in the first ink chamber 5a is higher than the height of the liquid level of the ink in the second ink chamber 5b, the liquid level of the ink in the first ink chamber 5a. The height of the ink is the same as the upper end of the partition wall 5c.

When a print command for a print target is input to the control unit 9 while the carriage 3 is stopped for a predetermined time or longer without printing on the print target, the control unit 9 is at least a nozzle unit. When the 2c ejects ink droplets, the liquid level of the ink in the sub tank 5 becomes higher than the upper end of the partition wall 5c, and the liquid level of the ink on the first ink chamber 5a side and the ink on the second ink chamber 5b side. At least the pump 7 is driven and controlled so that the liquid level of the ink is at the same level as that of the ink (see FIG. 1). That is, when the control unit 9 receives a print command for the object to be printed, the control unit 9 has at least the liquid level of the ink on the first ink chamber 5a side and the second ink when the nozzle unit 2c ejects ink droplets. The pump 7 is driven and controlled, or the pump 7 and the pump 8 are driven and controlled so that the liquid level of the ink on the chamber 5b side is at the same level.

Specifically, when a print command for an object to be printed is input to the control unit 9, the control unit 9 is on the first ink chamber 5a side by a predetermined timing before the nozzle unit 2c performs an ink droplet ejection operation. The pump 7 is driven and controlled so that the liquid level of the ink in the second ink chamber 5b and the liquid level of the ink on the second ink chamber 5b side are at the same level, and the ink is supplied from the main tank 6 to the first ink chamber 5a. Alternatively, the pump 7 and the pump 8 are driven and controlled to supply 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, in the control unit 9, the liquid level of the ink on the first ink chamber 5a side and the liquid level of the ink on the second ink chamber 5b side become the same height based on the detection result by the liquid level detection mechanism 20. As described above, the pump 7 is driven and controlled, or the pump 7 and the pump 8 are driven and controlled.

Further, in the present embodiment, the first ink is used until the carriage 3 is stopped for a predetermined time after printing on the object to be printed is completed (that is, the ink droplet ejection operation of the nozzle portion 2c is completed). The state in which the liquid level of the ink on the chamber 5a side and the liquid level of the ink on the second ink chamber 5b side are maintained at the same level is maintained. At this time, since there is no head difference, the ink does not circulate between the head 2 and the sub tank 5. That is, the ink does not circulate in the head 2.

In this embodiment, even when the liquid level of the ink on the first ink chamber 5a side and the liquid level of the ink on the second ink chamber 5b side are at the same height, between the sub tank 5 and the main tank 6. Ink is circulated. That is, the control unit 9 drives and controls the pump 7 to supply ink from the main tank 6 to the sub tank 5, and also 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 this embodiment, the control unit 9 drives and controls the pumps 7 and 8 based on the detection result of the liquid level detection mechanism 20, so that the liquid level of the ink on the first ink chamber 5a side and the second ink The state where the liquid level of the ink on the chamber 5b side is at the same level is maintained.

Further, when the state in which the ink droplet ejection operation of the nozzle unit 2c is completed and the carriage 3 is stopped continues for a predetermined time, the control unit 9 has a second ink liquid level in the first ink chamber 5a. At least the pump 8 is driven and controlled so that the ink flows from the first ink chamber 5a to the second ink chamber 5b via the head 2 so as to be higher than the height of the liquid level of the ink in the ink chamber 5b. That is, when the state in which the ink droplet ejection operation of the nozzle unit 2c is completed and the carriage 3 is stopped continues for a predetermined time, the control unit 9 raises the height of the ink liquid level in the first ink chamber 5a to the second. The pump 8 is driven and controlled so that the ink flows from the first ink chamber 5a to the second ink chamber 5b via the head 2 so as to be higher than the height of the ink liquid level in the ink chamber 5b and the second ink chamber 5b. 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 ink from the main tank 6 to the first ink chamber 5a while returning ink from the second ink chamber 5b to the main tank 6. .. Further, in the control unit 9, the height of the liquid level of the ink in the first ink chamber 5a becomes higher than the height of the liquid level of the ink in the second ink chamber 5b based on the detection result by the liquid level detection mechanism 21. As described above, the pump 8 is driven and controlled, or the pump 7 and the pump 8 are driven and controlled.

(Main effect of this form)
As described above, in the present embodiment, the first ink chamber 5a and the second ink chamber 5b are formed inside the sub tank 5. Further, in the present embodiment, the pump 7 that sends 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 5b. Further, in the present embodiment, when the ink droplet ejection operation of the nozzle unit 2c is completed and the carriage 3 is stopped for a predetermined time, the control unit 9 raises the ink liquid level of the first ink chamber 5a. At least the pump 8 is driven and controlled so that the ink is higher than the height of the liquid level of the ink in the second ink chamber 5b and the ink flows from the first ink chamber 5a to the second ink chamber 5b via the head 2. There is. Therefore, in the present embodiment, as described above, the ink can be circulated between the head 2 and the sub tank 5 by utilizing the head difference, and the ink can be circulated in the head 2. That is, in this embodiment, the ink can be circulated in the head 2 by a relatively simple configuration utilizing the head difference.

In the present embodiment, in the control unit 9, at least when the nozzle unit 2c ejects ink droplets, the liquid level of the ink in the sub tank 5 becomes higher than the upper end of the partition wall 5c, and the ink on the first ink chamber 5a side. The pump 7 is driven and controlled so that the liquid level of the ink and the liquid level of the ink on the second ink chamber 5b side are at the same level. Therefore, in the present embodiment, when the nozzle portion 2c ejects ink droplets, the influence of the 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 reduced. It will be possible to eliminate it. Therefore, in this embodiment, it is possible to stabilize the operation of ejecting ink droplets from the nozzle portion 2c.

In particular, in this embodiment, when the carriage 3 moves in the main scanning direction, the head 2 moves back and forth in the main scanning direction due to the influence of the inertial force acting on the ink in the pipes 12 and 13. Since the pressure inside fluctuates (see FIG. 4), when the nozzle portion 2c ejects ink droplets, the pressure on the ink supply port 2a side and the ink discharge port 2b side inside the head 2 due to the influence of the water head difference. When there is a difference between the pressure and the pressure, as shown in FIG. 5, a large difference ΔP is generated between the maximum pressure on the ink supply port 2a side and the minimum pressure on the ink discharge port 2b side inside the head 2, and the nozzle portion 2c Ink droplet ejection operation tends to be unstable. However, in this embodiment, when the nozzle portion 2c ejects ink droplets, the influence of the 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 reduced. Since it can be eliminated, 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 ink ejection operation from the nozzle portion 2c.

In this embodiment, the first ink chamber 5a and the second ink chamber 5b are connected on the upper side of the partition wall 5c. Further, in the present embodiment, the pump 7 that sends ink from the main tank 6 to the sub tank 5 is connected to the first ink chamber 5a, and the pump 8 that sends ink from the sub tank 5 to the main tank 6 is connected to the second ink chamber 5b. Has been done. Therefore, in the present embodiment, as described above, when the height of the liquid level of the ink in the first ink chamber 5a is higher than the height of the liquid level of the ink in the second ink chamber 5b, and the first ink. Regardless of whether the ink liquid level on the chamber 5a side and the ink liquid level on the second ink chamber 5b side are at the same height, it is related to the amount of ink consumed by the head 2. Instead, 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 removes the gas in the ink. It will be possible to remove it.

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

In this embodiment, the control unit 9 controls the degassing suction pump 30 connected to the degassing module 16 based on the detection result of the pressure sensor 31. Therefore, in this embodiment, it is possible to appropriately control the degassing pressure in the degassing module 16. Therefore, in this 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 the present embodiment, even if the atmospheric pressure fluctuates due to the change in the altitude of the place where the ink jet recording device 1 is used, the degassing pressure in the degassing module 16 can be appropriately controlled. Further, in the present embodiment, it is possible to appropriately control the degassing pressure in the degassing module 16 even if the type of ink used changes or the flow rate of the ink fluctuates. Further, in the present embodiment, when a malfunction occurs in the degassing module 16 or the suction pump 30, it is possible to detect that the malfunction has 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.

Conventionally, an inkjet recording device in which a degassing device is arranged in an ink supply path is known (see, for example, Japanese Patent Application Laid-Open No. 11-42795). This conventional inkjet recording device includes a polaro-type dissolved oxygen meter connected to the degassing device and a vacuum pump connected to the degassing device. The dissolved oxygen meter consists of an oxygen electrode, a low voltage power supply, and a DC ammeter. The oxygen electrode includes an electrode body and a diaphragm covering an opening at one end of the electrode body. The electrode body includes 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 inkjet recording device, 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 device, 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. Further, this inkjet recording device has a problem of the life of the electrode body of the dissolved oxygen meter and a problem that the diaphragm of the dissolved oxygen meter is clogged.

On the other hand, in the inkjet recording device 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 It becomes possible to control the degassing pressure at an appropriate timing. Further, in the inkjet recording apparatus 1 of the present embodiment, there is no 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.

(Other embodiments)
In the above-described embodiment, when the state in which the ink droplet ejection operation of the nozzle unit 2c is completed and the carriage 3 is stopped continues for a predetermined time, the control unit 9 raises the liquid level of the ink in the first ink chamber 5a. At least the pump 8 is driven and controlled so that is higher than the height of the liquid level of the ink in the second ink chamber 5b, but after a predetermined time has elapsed from the completion of the ink droplet ejection operation of the nozzle portion 2c, The control unit 9 may drive and control at least the pump 8 so that the height of the liquid level of the ink in the first ink chamber 5a is higher than the height of the liquid level of the ink in the second ink chamber 5b.

In the above-described embodiment, the sensor 23 may be fixed to the outer surface of the sub tank 5 on the second ink chamber 5b side. In this case, using the common float 24, 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, and the ink in the second ink chamber 5b is in a predetermined position. 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 above-described form, the pipes 12 and 13 may be bent at two or more points.

In the above-described embodiment, the degassing module 16 may be mounted on the carriage 3. Further, in the above-described embodiment, the suction pump 30 and the pressure sensor 31 may be mounted on the carriage 3. Further, in the above-described embodiment, 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 due to the movement of the carriage 3 in the main scanning direction disappears. Further, in the above-described embodiment, the inkjet recording device 1 is a device for printing on an object to be printed, but the inkjet recording device 1 may be used for purposes other than printing.

1 Inkjet recording device 2 Head (inkjet head)
2a Ink supply port 2b Ink discharge port 2c Nozzle part 3 Carriage 4 Device body 5 Sub tank 5a 1st ink chamber 5b 2nd ink chamber 5c Partition wall 6 Main tank 7 Pump (1st pump)
8 pump (second pump)
9 Control unit 12 Piping (first piping)
13 Piping (second piping)
14 Piping (supply side piping)
15 Piping (Discharging side piping)
16 Degassing module 20 Liquid level detection mechanism (1st liquid level detection mechanism)
21 Liquid level detection mechanism (second liquid level detection mechanism)
30 Suction pump 31 Pressure sensor

Claims (6)

An inkjet head that ejects ink droplets, a sub-tank that houses ink supplied to the inkjet head, a main tank that houses ink that is supplied to the sub-tank, and a first tank that sends ink from the main tank to the sub-tank. 1 pump, a second pump that sends ink from the sub tank to the main tank, a control unit that drives and controls the first pump and the second pump, and detects the position of the ink liquid level in the sub tank. Equipped with a first liquid level detection mechanism for
The inkjet head is a circulation type inkjet head including an ink supply port to which ink is supplied from the sub tank, an ink discharge port to discharge ink toward the sub tank, and a nozzle portion for ejecting ink droplets. can be,
Inside the sub-tank, a first ink chamber and a second ink chamber for accommodating ink are formed, and a partition wall defining the first ink chamber and the second ink chamber is formed.
The partition wall rises from the bottom surface of the sub tank and rises.
The first ink chamber and the second ink chamber are connected above the partition wall, and are connected to each other.
The first pump is connected to the first ink chamber via a pipe, and the ink supply port is connected to the first ink chamber via a pipe.
The second pump is connected to the second ink chamber via a pipe, and the ink discharge port is connected to the second ink chamber via a pipe.
The first liquid level detection mechanism detects that the liquid level of the ink in the sub tank is at a predetermined position above the upper end of the partition wall.
In the control unit, at least when the nozzle unit ejects ink droplets, the liquid level of the ink in the sub tank becomes higher than the upper end of the partition wall and becomes the liquid level of the ink on the first ink chamber side. An inkjet recording apparatus characterized in that at least the first pump is driven and controlled so that the liquid level of the ink on the second ink chamber side is at 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 are provided.
In the supply-side piping, ink can always be distributed between the first ink chamber and the ink supply port.
The inkjet recording apparatus according to claim 1, wherein ink can always be distributed between the second ink chamber and the ink discharge port in the discharge side pipe. A carriage on which the inkjet head and the sub-tank are mounted, and a main body of a device that holds the carriage so as to be able to move in the main scanning direction are provided.
In the control unit, when the carriage is stopped for a predetermined time, the height of the liquid level of the ink in the first ink chamber becomes higher than the height of the liquid level of the ink in the second ink chamber. The inkjet recording apparatus according to claim 1 or 2, wherein at least the second pump is driven and controlled so that ink flows from the first ink chamber to the second ink chamber via the inkjet head. A first for connecting the first pump and the first ink chamber to the carriage on which the inkjet head and the sub tank are mounted, the main body of the device that holds the carriage so as to be able to move in the main scanning direction, and the first pump. It is provided with one pipe and a second pipe for connecting the second pump and the second ink chamber.
The main tank, the first pump and the second pump are attached to the main body of the apparatus.
The first pipe and the second pipe are formed of a flexible tube and are bent at at least one position, and the carriage is bent while changing the bending point as the carriage moves in the main scanning direction. The inkjet recording apparatus according to any one of claims 1 to 3, wherein the inkjet recording apparatus follows. According to claim 1, the second liquid level detecting mechanism for detecting that the liquid level of the ink in the second ink chamber is at a predetermined position lower than the upper end of the partition wall is provided. 4. The inkjet recording apparatus according to any one of 4. A degassing module arranged in the ink supply path from the main tank to the sub tank or the ink discharge path from the sub tank to the main tank to remove gas in the ink, and degassing connected to the degassing module. A suction pump for the purpose and a pressure sensor for detecting the suction pressure of the suction pump are provided.
The suction pump and the pressure sensor are electrically connected to the control unit, and the suction pump and the pressure sensor are electrically connected to the control unit.
The inkjet recording device according to any one of claims 1 to 5, wherein the control unit drives and controls the suction pump based on the detection result of the pressure sensor.

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