Inkjet recording apparatus

Abstract

To provide a technique that can further shorten the time of initial printing.SOLUTION: An inkjet recording apparatus 1 comprises: a degassing device 30 that degasses ink I flowing through a second flow path 92; a circulation pump 62 that applies pressure to a circulation path of the ink I constituted by a sub tank 52, the second flow path 92, the degassing device 30, a third flow path 93, a head 11, and a fourth flow path 94 to generate an ink flow of the ink I within the circulation path; and a damper 13 that is provided in the fourth flow path 94 to suppress fluctuations of pressure applied to the head 11. The degassing device 30 has an ink inflow port 12A and an ink outflow port 12B, and, in the direction in which the ink I is discharged from a nozzle row 16, the ink inflow port 12A is disposed at a position closer to the head 11 than the ink outflow port 12B.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present application relates to an inkjet recording apparatus that records (prints) by ejecting ink from a head and spraying it onto a recording medium. [Background technology]

[0002] Patent document 1 describes an ink supply device that includes a main tank in which ink is stored, a first flow path that transports ink from the main tank, a sub-tank that temporarily holds ink from the first flow path and adjusts the pressure of the ink, a second flow path that transports ink from the sub-tank, a head unit that ejects ink from the second flow path, and a degassing device provided in part of the path from the main tank to the head unit, and that is characterized in that it also has a return flow path that returns ink downstream of the sub-tank to the sub-tank. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-59476 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the ink supply device described in Patent Document 1, the positional relationship between the head unit and the degassing device is not clearly defined, and depending on the environment in which the device is used, there is a risk that the ink path may be cut off inside the degassing device when the ink is being filled, causing problems with the ink supply. Also, because a sub-tank is located downstream of the degassing device on the path to the head unit, it takes time for the ink degassed by the degassing device to reach the head unit, and it can take a long time for initial printing to change from a non-printing state to a printing state.

[0005] An object of the present application is to provide a technique that can further reduce the time required for initial printing. [Means for solving the problem]

[0006] In order to achieve the above object, the inkjet recording apparatus of the present application comprises: a head having a nozzle row that ejects ink; a main tank that stores ink; a first flow path that transports ink from the main tank; a sub-tank connected to the first flow path and temporarily storing ink flowing through the first flow path; a second flow path that transports ink from the sub-tank; a degassing device connected to the second flow path and degassing the ink flowing through the second flow path; a third flow path that transports the ink degassed by the degassing device to the head; a fourth flow path that connects the head and the sub-tank and returns the ink from the head to the sub-tank; a circulation pump that applies pressure to an ink circulation path consisting of the sub-tank, the second flow path, the degassing device, the third flow path, the head, and the fourth flow path, to generate an ink flow in the circulation path; and a damper provided in the fourth flow path for suppressing fluctuations in the pressure applied to the head, wherein the degassing device has an ink inlet and an ink outlet, and the ink inlet is positioned closer to the head than the ink outlet in the direction in which ink is ejected from the nozzle row. [Effects of the Invention]

[0007] According to the present application, the degassing device is located downstream of the subtank and closer to the head, thereby reducing the amount of ink in the flow path connecting the degassing device and the head. This reduces the time it takes for ink degassed by the degassing device to reach the head, further shortening the initial printing time from a non-printing state to a printing state. Furthermore, the degassing device is located such that its ink inlet is closer to the head than the ink outlet in the direction in which ink is ejected from the nozzle array, preventing the ink path from being disrupted inside the degassing device during ink refilling, thereby reducing ink supply problems. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a diagram illustrating a control configuration of an inkjet printing apparatus according to an embodiment of the present application. [Figure 2] FIG. 2 is a perspective view showing the appearance of a head unit included in the inkjet recording apparatus of FIG. [Figure 3] 3 is a perspective view showing a state in which a cover is removed from the head unit of FIG. 2. FIG. [Figure 4] FIG. 4 is a right side view of the head unit of FIG. 3. [Figure 5] FIG. 4 is a bottom view of the head unit of FIG. 3. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present application will be described in detail with reference to the drawings. In the drawings used in the following description, some basic components may be omitted, and the dimensional ratios of the depicted components may not be accurate. In Figures 2 to 5, the front-rear direction D1, the up-down direction D2, and the left-right direction D3 are as shown in each figure.

[0010] Fig. 1 shows the control configuration of an inkjet recording apparatus 1 according to an embodiment of the present application. As shown in Fig. 1, the inkjet recording apparatus 1 is mainly composed of a head unit 10 and an ink supply unit 50. The head unit 10 and the ink supply unit 50 are connected via a cable 90.

[0011] The head unit 10 includes a box-shaped head unit housing 100 (see Figure 2 for its specific shape) that houses a head 11 that ejects ink, a degassing module 12 that degasses dissolved gas contained in the ink supplied to the head 11, a damper 13 that suppresses fluctuations in pressure applied to the head 11, and a check valve 14.

[0012] The head 11 includes a nozzle row 16 in which a plurality of nozzles 15 that eject ink are arranged vertically, and an ink storage section 17 connected to the nozzle row 16 and that stores the ink ejected from each nozzle 15. In this embodiment, the nozzle row 16 includes, for example, two rows, and therefore one ink storage section 17 is provided for each nozzle row 16. An ink inlet 11A is provided at the bottom of each ink storage section 17, and an ink outlet 11B is provided at the top of each ink storage section 17. The number of nozzle rows 16 is not limited to two, and may be one row, three rows, or more. The number of ink storage sections 17 may be determined according to the number of nozzle rows 16, but even if there are multiple rows, one ink storage section 17 may be used to cover all of them. The number of ink inlet 11A and ink outlet 11B may also be determined according to the number of ink storage sections 17.

[0013] A nozzle protection cap 21 is detachably attached to the head 11 to protect the nozzle array 16 from external impacts, dust, and the like. In this embodiment, the ink ejected from the head 11 is, for example, UV ink, which is an ultraviolet-curable ink. Therefore, to prevent the UV ink from being exposed to external light, including ultraviolet rays, through the nozzle array 16, the nozzle protection cap 21 is attached to cover the periphery of the nozzle array 16 when printing is not being performed. Furthermore, UV ink has the property that oxygen and other substances in the air dissolve in the ink when left in contact with air for a long period of time. The more dissolved gases in the ink, the more deterioration in print quality occurs, and the longer it takes to degas the dissolved gases. Therefore, the nozzle protection cap 21 also serves the function of preventing the ink in the nozzle array 16 from coming into contact with air as much as possible when printing is not being performed.

[0014] The degassing module 12 has, for example, a plurality of hollow fibers, and removes dissolved gas from the ink by passing ink through each hollow fiber and reducing the pressure outside each hollow fiber. Of course, the method of removing dissolved gas from the ink is not limited to this, and other methods may be used, such as passing ink outside each hollow fiber and reducing the pressure inside each hollow fiber to remove dissolved gas from the ink. In short, any type of degassing module 12 may be used as long as it can remove dissolved gas from the ink, but it is necessary to use a module that is small enough to fit inside the head unit 10.

[0015] The ink supply unit 50 is provided with a box-shaped ink supply unit housing 110 (the specific shape of which is not shown) that contains a main tank 51 that stores ink I, a sub-tank 52 that temporarily stores ink I transported from the main tank 51, four pumps 60-63, two pressure gauges 64, 65, two valves 66, 67, three check valves 71-73, and a pump control unit 80 that controls the operation of each pump 61-64.

[0016] The pump control unit 80 is composed of, for example, a CPU, a ROM, a RAM, etc. The CPU executes a pump control program stored in the ROM to control the pumps 60 to 63 and the valves 66, 67. The RAM stores data when the pump control program is executed and stores calculation results.

[0017] The main tank 51 is, for example, a pouch-packaged container (hereinafter referred to as a "pouch"), and when the ink I in the pouch runs out, it can be replaced with a new pouch. The main tank 51 and the sub-tank 52 are connected via a first flow path 91 for transporting the ink I in the main tank 51 to the sub-tank 52. The first flow path 91 is provided with a transport pump 60 that transports the ink I from the main tank 51 to the sub-tank 52, and a first check valve 71 that prevents backflow, which is a flow in a direction opposite to the flow of the ink I in the transport direction. The first flow path 91 is formed, for example, by a flexible pipe. Similar to the first flow path 91, second to fourth flow paths 92 to 94, which will be described later, are also formed, for example, by flexible pipes.

[0018] As described above, the subtank 52 is a tank that temporarily stores the ink I transported from the main tank 51, and has a storage amount detection sensor 53 for detecting the storage amount of ink I in the subtank 52. The storage amount detection sensor 53 is, for example, a float sensor, and outputs an ON signal when the liquid level of the ink I in the subtank 52 reaches a predetermined upper limit position, and outputs an OFF signal when the liquid level reaches a predetermined lower limit position. Once the storage amount detection sensor 53 outputs an ON signal, it continues to output the ON signal until it outputs an OFF signal, and once it outputs an OFF signal, it continues to output the OFF signal until it outputs an ON signal.

[0019] Therefore, the pump control unit 80 can determine that the liquid level of the ink I in the subtank 52 has reached the upper limit position when the detection signal output from the storage amount detection sensor 53 switches from an off signal to an on signal, and can determine that the liquid level of the ink I in the subtank 52 has reached the lower limit position when the detection signal output from the storage amount detection sensor 53 switches from an on signal to an off signal. Therefore, the pump control unit 80 can control the storage amount of ink I in the subtank 52 within a range from a predetermined upper limit amount to a predetermined lower limit amount by starting to drive the conveying pump 60 when it determines that the liquid level of the ink I has reached the lower limit position and stopping to drive the conveying pump 60 when it determines that the liquid level of the ink I has reached the upper limit position.

[0020] The subtank 52 and the degassing module 12 in the head unit 10 are connected via a second flow path 92 for transporting the ink I in the subtank 52. In addition, one end of a positive pressure path 97 for applying positive pressure to the subtank 52 is connected to the subtank 52, and the other end of the positive pressure path 97 is connected to an electromagnetic valve 66 for the subtank 52. Hereinafter, this electromagnetic valve 66 will be referred to as the subtank valve 66.

[0021] The subtank valve 66 switches between a closed state and an open state in response to an on / off signal from the pump control unit 80. A subtank valve 66 that is normally open, for example, is used, and the subtank valve 66 switches to the closed state when an on signal is output from the pump control unit 80, and switches to the open state when an off signal is output from the pump control unit 80.

[0022] An air pump 61 and a pressure gauge 64 are connected to the positive pressure path 97. When the inkjet recording apparatus 1 receives a maintenance command such as an initial introduction of ink or a purging operation, the air pump 61 pressurizes the subtank 52 via the positive pressure path 97 and transports the ink I in the subtank 52 to the head 11 through the second flow path 92, the degassing module 12, and the third path 93. The pressure gauge 64 detects the pressure in the subtank 52 via the positive pressure path 97 and outputs the detected pressure to the pump control unit 80. During the initial introduction of ink, the pump control unit 80 outputs an ON signal to the subtank valve 66 to close the subtank valve 66 and then drives the air pump 61 and the circulation pump 62. The pump control unit 80 then controls the operation of the air pump 61 so that the pressure value in the subtank 52 detected by the pressure gauge 64 becomes a predetermined pressurized value. As a result, the ink I is transported from the subtank 52 to the head 11 via the degassing module 12 at a predetermined flow rate. The air pump 61 and circulation pump 62 are driven until the ink I flows from the head 11 through the damper 13 and the fourth flow path 94 and reaches the subtank 52, after which they are turned off along with the subtank valve 66. During the purging operation, the pump control unit 80 outputs an ON signal to the subtank valve 66 while keeping the circulating pump 62 stopped, closing the subtank valve 66, and controls the driving of the air pump 61 so that the pressure value inside the subtank 52 detected by the pressure gauge 64 becomes a predetermined pressurized value. As a result, the ink I is pressurized from the subtank 52 toward the head 11 and is forcibly ejected from the nozzle array 16. After the purging operation, the air pump 61 and subtank valve 66 are turned off.

[0023] The degassing module 12 and the ink inlet 11A of the head 11 are connected via a third flow path 93 for transporting the ink I degassed by the degassing module 12. Since the inside of the degassing module 12 needs to be depressurized as described above, a negative pressure pump 63 is connected to the degassing module 12 via a negative pressure path 98. A pressure gauge 65, an electromagnetic valve 67, and a third check valve 73 are connected to the negative pressure path 98. The degassing module 12, the negative pressure pump 63, etc. constitute a degassing device 30.

[0024] The electromagnetic valve 67 switches between an open state and a closed state in response to an on / off signal from the pump control unit 80. For example, a normally closed electromagnetic valve is used as the electromagnetic valve 67, and when an on signal is output from the pump control unit 80, the electromagnetic valve 67 switches the valve to an open state, and when an off signal is output from the pump control unit 80, the electromagnetic valve 67 switches the valve to a closed state.

[0025] The pressure gauge 65 detects the pressure value applied to the degassing module 12 via the negative pressure path 98 and outputs the detected pressure to the pump control unit 80. The pump control unit 80 controls the operation of the negative pressure pump 63 so that the pressure value detected by the pressure gauge 65 becomes a predetermined negative pressure value. Since the electromagnetic valve 67 is normally closed as described above, the electromagnetic valve 67 remains closed unless the pump control unit 80 outputs an ON signal to the electromagnetic valve 67. When the pressure value detected by the pressure gauge 65 reaches a predetermined negative pressure value, the pump control unit 80 stops the operation of the negative pressure pump 63. The third check valve 73 operates to maintain the negative pressure value in the negative pressure path 98, thereby stopping the operation of the negative pressure pump 63. When the negative pressure value in the negative pressure path 98 becomes equal to or lower than a predetermined threshold value, the pump control unit 80 resumes the operation of the negative pressure pump 63. In this way, the negative pressure in the negative pressure path 98 is controlled to a constant value while the degassing module 12 is degassing the ink I.

[0026] The ink outlet 11B of the head 11 and the subtank 52 in the ink supply unit 50 are connected via a fourth flow path 94 for returning the ink I flowing out from the head 11 to the subtank 52. The fourth flow path 94 is provided with a damper 13, a check valve 14, a circulation pump 62, and a second check valve 72, in this order, in the direction in which the ink I returns to the subtank 52. The subtank 52, the second flow path 92, the degassing module 12, the third flow path 93, the head 11, and the fourth flow path 94 form a circulation path for the ink I. The second flow path 92, the fourth flow path 94, and the negative pressure path 98 pass through the cable 90 and connect the head unit housing 100 and the ink supply unit housing 110. When the ink I remaining in the circulation path contains a large amount of dissolved gas, such as when a predetermined period of time has passed since the head 11 did not eject the ink I, the pump control unit 80 can drive the circulation pump 62 to return the ink I remaining in the circulation path to the subtank 52. At this time, by circulating the ink with the degassing device 30 driven, the ink in the head 11 is replaced with ink that has been properly degassed and passed through the degassing module 12. Since the ink I containing a large amount of dissolved gas that has returned to the subtank 52 is also degassed through the degassing module 12, the appropriate ink is used when the ink I is ejected from the head 11 for printing. This prevents deterioration of print quality and reduces waste of the ink I remaining in the circulation path. The head unit housing 100 is an example of a “first housing,” and the ink supply unit housing 110 is an example of a “second housing.”

[0027] The control processes executed by the inkjet recording device 1 configured as described above, particularly the pump control unit 80, will be described below as being divided into a printing process and a circulation process. For simplicity's sake, the following description will be based on the premise that the initial introduction of ink I into the inkjet recording device 1 has already been completed. Here, the printing process refers to the process of printing by ejecting ink I from the head 11 onto a recording medium, and the circulation process refers to the process of circulating the ink I in the circulation path and returning it to the subtank 52. The printing process may be initiated, for example, when a user issues a command to start printing. The circulation process may be initiated, for example, at a predetermined timing before the printing process begins. Examples of predetermined timing include when the inkjet recording device 1 is powered on, when a user issues a command to start the circulation process, or when a predetermined condition is satisfied. As described above, the predetermined condition may be when a predetermined period of time has elapsed during which ink I is not ejected from the head 11. Therefore, even if the user instructs the start of printing, if the timing falls within the above-mentioned specified timing, the pump control unit 80 will not immediately start the printing process, but will start the printing process after completing the circulation process.

[0028] When printing processing begins, the pump control unit 80 first starts driving the negative pressure pump 63. At this time, the electromagnetic valve 67 needs to be closed, but because the electromagnetic valve 67 is normally closed, the pump control unit 80 does not need to output a signal to the electromagnetic valve 67. However, when an ON signal is output to the electromagnetic valve 67 and the electromagnetic valve 67 is open, the pump control unit 80 needs to output an OFF signal to the electromagnetic valve 67. The pump control unit 80 then continues driving the negative pressure pump 63 until the pressure gauge 65 detects a predetermined negative pressure value, and stops driving the negative pressure pump 63 when the pressure gauge 65 detects the predetermined negative pressure value.

[0029] Next, if ink I is not stored in the subtank 52, the pump control unit 80 starts driving the conveying pump 60. Then, when the pump control unit 80 detects that the storage amount detection sensor 53 has switched from outputting an OFF signal to outputting an ON signal, it stops driving the conveying pump 60. On the other hand, if ink I is stored in the subtank 52, the pump control unit 80 controls the storage amount of ink I in the subtank 52 to be within a range from a predetermined upper limit amount to a predetermined lower limit amount, as described above.

[0030] When the head 11 is driven in response to a print command signal, ink I is ejected from each nozzle 15 constituting the nozzle row 16, and printing is performed. At this time, the damper 13 suppresses fluctuations in the pressure applied to the head 11. Note that, during execution of the printing process, the pump control unit 80 controls the operation of the circulation pump 62 to a stopped state. Note that, ink consumed by driving the head 11 is replenished from the subtank 52 via the second flow path 92 and the degassing module 12 by the negative pressure generated by the ink consumption. Therefore, during the printing operation, an appropriate amount of ink is supplied via the degassing module 12, thereby achieving good quality print results.

[0031] On the other hand, when the circulation process is started, just as when the printing process is started, the pump control unit 80 first starts driving the negative pressure pump 63. The pump control unit 80 then continues driving the negative pressure pump 63 until the pressure gauge 65 detects a predetermined negative pressure value, and stops driving the negative pressure pump 63 when the pressure gauge 65 detects the predetermined negative pressure value. At this time, the solenoid valve 67 is in the closed state as described above, and the third check valve 73 operates to maintain the negative pressure value in the negative pressure path 98 as described above, so the predetermined negative pressure value is maintained inside the negative pressure path 98.

[0032] Next, the pump control unit 80 starts driving the circulation pump 62. At this time, assuming that ink I is stored in the subtank 52, driving the circulation pump 62 returns the ink I in the circulation path to the subtank 52. The ink I containing dissolved gas is in the third flow path 93 and the ink storage unit 17 of the circulation path. This is because, during the printing process, the circulation pump 62 is controlled to be in a stopped state as described above, and therefore ink I is not transported to the fourth flow path 94. Therefore, if the amount of ink I in the third flow path 93 and the ink storage unit 17 is returned to the subtank 52, the third flow path 93 and the ink storage unit 17 will be filled with ink I degassed by the degassing module 12. However, to allow for some leeway, it is also possible to return up to 1.2 times the amount of ink I in the third flow path 93 and the ink storage unit 17.

[0033] In this manner, when 1 to 1.2 times the amount of ink I in the third flow path 93 and the ink storage unit 17 has returned to the subtank 52, the pump control unit 80 stops driving the circulation pump 62. Here, the pump control unit 80 may determine whether 1 to 1.2 times the amount of ink I in the third flow path 93 and the ink storage unit 17 has returned to the subtank 52, for example, based on the driving time and / or rotation speed of the circulation pump 62. The pump control unit 80 also controls the circulation pump 62, for example, to flow the ink I through the circulation path at a flow rate greater than 2 ml / min and less than 8 ml / min. The reason for flowing the ink I through the circulation path at such a flow rate is to ensure that the meniscus of the nozzle row 16 of the head 11 is not broken by pressure fluctuations caused by the pump 62, and to shorten the time it takes for the third flow path 93 and the ink storage unit 17 to be filled with ink I that has been sufficiently degassed by the degassing module 12.

[0034] Fig. 2 shows the external appearance of the head unit 10. As shown in Fig. 2, the head unit 10 includes a head unit housing 100 that is substantially rectangular parallelepiped. The top, left side, and right side of the head unit housing 100 are covered by cover parts 100A. The head 11 is provided on the front side of the head unit housing 100, and a nozzle protection cap 21 is attached to the head 11 when not in printing operation.

[0035] Figures 3 to 5 show the head unit 10 of Figure 2 with the cover part 100A removed. Figure 3 is a perspective view, Figure 4 is a right side view, and Figure 5 is a bottom view. Hereinafter, with reference to Figures 3 to 5, we will explain how the components included in the head unit 10 are arranged inside the head unit housing 100.

[0036] The degassing module 12 and damper 13 are arranged inside the head unit housing 100 so as to avoid the head 11 in the direction in which the nozzle row 16 extends, that is, in the up-down direction. In other words, the degassing module 12 and damper 13 do not overlap with the head 11 when viewed from the front-to-back direction or the left-to-right direction. Furthermore, the degassing module 12 and damper 13 are arranged horizontally in the front-to-back direction at the top of the head unit housing 100. The reason for this arrangement is that a substrate 40 is provided upright at the bottom of the head unit housing 100, and the degassing module 12 and damper 13 need to be arranged so as to avoid the substrate 40.

[0037] Furthermore, because the connection terminals on the substrate 40 and the head 11 are connected by a flexible cable (not shown) that transmits drive signals, the placement of the connectors avoids interfering with the routing of the cable. This layout facilitates assembly and maintenance of the head unit 10 and also reduces the risk of contamination of the electrical system in the event of ink leakage from the ink flow path. Furthermore, since the degassing unit 12 is longer than the head 11, if it were placed upright within the head unit 10, the height of the head unit housing 100 that houses the degassing unit 12 would be excessively large compared to the length of the nozzle array 16. This is undesirable because it would restrict the environment in which the head unit 10 can be installed relative to the printing target. Furthermore, in this embodiment, to reduce the size of the head unit housing 100, thin dampers 13 extending in the front-to-rear direction are placed adjacent to and above the degassing module 12. This reduces the left-to-right size of the head unit housing 100, thereby enabling the head unit 10 to be made more compact.

[0038] The degassing module 12 is provided with an ink inlet 12A, an ink outlet 12B, and a negative pressure supply port 12C. The ink inlet 12A is located at the bottom of the degassing module 12, closer to the front than the center in the front-to-rear direction. The ink outlet 12B is located at the rear of the degassing module 12. The head unit 10 is intended to print in either a first printing mode in which printing is performed from the side on a recording medium positioned in the vertical direction, or a second printing mode in which printing is performed from above on a recording medium positioned in the horizontal direction.

[0039] When printing in the first printing mode, the head unit 10 is installed as shown in FIG. 2 , i.e., the head unit 10 is installed so that its bottom surface is horizontal, and printing is performed on a recording medium facing the head 11. The ink inlet 12A is provided at the bottom of the degassing module 12, and the ink outlet 12B is provided at the rear of the degassing module 12 to prevent deterioration of print quality when printing in the first printing mode. That is, when the ink inlet 12A is provided at the bottom of the degassing module 12, the ink flowing into the degassing module 12 fills the degassing module 12 from the bottom, reaches the top, and when the degassing module 12 is full, it flows out from the ink outlet 12B. In this way, when the ink flows out of the degassing module 12, the degassing module 12 is filled with ink, and no gaps are created, so the ink path is not interrupted. Therefore, sufficiently degassed ink is supplied from the degassing module 12 to the head 11. As a result, sufficiently degassed ink is ejected from the head 11, thereby suppressing deterioration of print quality.

[0040] On the other hand, when printing in the second printing mode, the head unit 10 is installed with its front surface horizontal and facing downward, and printing is performed on a recording medium facing the head 11. The ink inlet 12A is located closer to the front than the center in the front-to-back direction of the degassing module 12, and the ink outlet 12B is located at the rear of the degassing module 12, to prevent degradation of print quality when printing in the second printing mode. In other words, when the ink inlet 12A is located closer to the front than the center in the front-to-back direction, the ink flowing into the degassing module 12 fills the degassing module 12 from the front, reaches the rear, and flows out from the ink outlet 12B when the degassing module 12 is full. In this way, when the ink flows out of the degassing module 12, the degassing module 12 is filled with ink, and no space is created, so the ink path is not interrupted, and sufficiently degassed ink is supplied from the degassing module 12 to the head 11. As a result, ink that has been sufficiently degassed is ejected from the head 11, making it possible to suppress deterioration in print quality.

[0041] In this way, the ink inlet 12A is located at the bottom of the degassing module 12, closer to the front than the center in the front-to-back direction, and the ink outlet 12B is located at the rear of the degassing module 12, so that deterioration of print quality can be suppressed regardless of whether printing is performed in the first printing mode or the second printing mode.

[0042] A second flow path 92 is connected to the ink inlet 12A, a third flow path 93 is connected to the ink outlet 12B, and a negative pressure path 98 is connected to the negative pressure supply port 12C. The third flow path 93 is routed along the rear and bottom surfaces of the head unit housing 100 and branches into two flow paths 93A and 93B. One flow path 93A is connected to the ink inlet 11A of one of the two nozzle rows 16, and the other flow path 93B is connected to the ink inlet 11A of the other of the two nozzle rows 16. The length of the third flow path 93 is preferably as short as possible, and its flow path diameter is preferably as small as possible, provided that it does not interfere with the supply of ink for printing. This is because, as described above, the amount of ink I containing dissolved gases returned to the subtank 52 during the circulation process is reduced. In other words, the smaller the amount of ink I containing dissolved gases returned to the subtank 52 during the circulation process, the shorter the time from the start of the circulation process to the start of the printing process. For this reason, it is preferable to adopt a path length of 500 mm or less and a path diameter of 2 mm to 4 mm, for example, as the third flow path 93. However, because the path length must be the entire length of the degassing module 12 in terms of the layout of the wiring, in this embodiment, for example, a path length of 150 mm or more is ensured.

[0043] As described above, the inkjet recording apparatus 1 of this embodiment includes the head 11 having the nozzle row 16 that ejects the ink I, the main tank 51 that stores the ink I, the first flow path 91 that transports the ink I from the main tank 51, the sub-tank 52 that is connected to the first flow path 91 and temporarily stores the ink I that flows through the first flow path 91, the second flow path 92 that transports the ink I from the sub-tank 52, the degassing device 30 that is connected to the second flow path 92 and degas ... The ink supply system includes a third flow path 93 that transports the ink I collected in the ink supply passage to the head 11, a fourth flow path 94 that connects the head 11 and the sub-tank 52 and returns the ink I from the head 11 to the sub-tank 52, a circulation pump 62 that applies pressure to the circulation path of the ink I consisting of the sub-tank 52, the second flow path 92, the degassing device 30, the third flow path 93, the head 11, and the fourth flow path 94, thereby generating an ink flow of the ink I in the circulation path, and a damper 13 that is provided in the fourth flow path 94 and that suppresses fluctuations in the pressure applied to the head 11.

[0044] The degassing device 30 has an ink inlet 12A and an ink outlet 12B, and is characterized in that the ink inlet 12A is positioned closer to the head 11 than the ink outlet 12B in the direction in which the ink I is ejected from the nozzle row 16.

[0045] As described above, in the inkjet recording apparatus 1 of this embodiment, the degassing device 30 is disposed downstream of the subtank, so the amount of ink in the flow path connecting the degassing device 30 and the head 11 is reduced. This reduces the time it takes for the ink I degassed by the degassing device 30 to reach the head 11, making it possible to further reduce the initial printing time required to transition from a non-printing state to a printing state. Furthermore, the degassing device 30 has its ink inlet 12A disposed closer to the head 11 than the ink outlet 12B in the direction in which ink is ejected from the nozzle row 16. This prevents the ink path from being broken inside the degassing module 12 during ink filling, reducing ink supply problems.

[0046] The inkjet recording device 1 also comprises a head unit housing 100 and an ink supply unit housing 110, the degassing device 30 comprises a degassing module 12 having a flow path through which the ink to be degassed flows, and a negative pressure pump 63 that applies negative pressure to the degassing module 12, the head unit housing 100 houses the head 11, the degassing module 12, and the damper 13, the ink supply unit housing 110 houses the main tank 51, the sub-tank 52, the circulation pump 62, and the negative pressure pump 63, and the head unit housing 100 and the ink supply unit housing 110 are connected via a cable 90 through which a second flow path 92 and a fourth flow path 94 pass.

[0047] As described above, in the inkjet recording apparatus 1 of this embodiment, the head 11, degassing module 12, and damper 13 are housed in the head unit housing 100, and the main tank 51, sub-tank 52, circulation pump 62, and negative pressure pump 63 are housed in the ink supply unit housing 110. In other words, the ejection of ink I and the supply of ink I are performed by the head unit housing 100 and the ink supply unit housing 110, respectively, and the head 11 and the degassing module 12 are arranged close to each other within the head unit housing 100. This reduces the time it takes for the ink I degassed by the degassing module 12 to reach the head 11, making it possible to further reduce the initial printing time required to change from a non-printing state to a printing state.

[0048] Another feature is that the degassing module 12 and the damper 13 are arranged within the head unit housing 100 to avoid the head 11 in the direction in which the nozzle row 16 extends, which in this embodiment is the vertical direction. As a result, the layout is such that they do not interfere with the flexible cable that connects the signal lines that drive the substrate 40 and the head 11, which not only leads to easier assembly and maintenance of the head unit 10, but also makes it less likely that the electrical system will be soiled or damaged if ink leaks from the ink flow paths, etc.

[0049] Another feature is that the degassing module 12 and the damper 13 are arranged adjacent to each other in the direction in which the nozzle row 16 extends, which in this embodiment is the vertical direction, inside the head unit housing 100. This allows the degassing module 12 and the damper 13 to be arranged space-efficiently inside the head unit housing 100 while avoiding the substrate 40. As a result, the size of the head unit housing 100 in the left-right direction can be reduced, and the head unit 10 can be made smaller.

[0050] The third flow path 93 has a length of 500 mm or less and a diameter of 2 mm to 4 mm. By specifying the length and diameter of the third flow path 93 in this way, it is possible to limit the amount of ink I containing a large amount of dissolved gas that remains in the third flow path 93, and therefore it is possible to reduce the amount of ink I returned from the head 11 to the subtank 52.

[0051] The inkjet recording device 1 further includes a pump control unit 80 that controls the operation of the circulation pump 62 and the negative pressure pump 63. When the inkjet recording device 1 is turned on or before a recording operation is performed by the head 11, the pump control unit 80 drives the negative pressure pump 63, and after the negative pressure pump 63 has applied negative pressure to the degassing module 12, drives the circulation pump 62 to cause a predetermined amount of ink I to flow into the circulation path. During a recording operation by the head 11, the pump control unit 80 controls the circulation pump 62 to be stopped while the negative pressure pump 63 is applying negative pressure to the degassing module 12.

[0052] In this way, when the inkjet recording device 1 is turned on or before recording operation by the head 11, only a predetermined amount of ink I is flowed into the circulation path, and when recording operation by the head 11 is performed, ink I is not flowed into the circulation path, so that ink I can be flowed into the circulation path only when it is necessary to return ink I from the head 11 to the subtank 52.

[0053] The predetermined amount is characterized in that it is 1.0 to 1.2 times the ink volume of the third flow path 93 and the head 11. This allows the minimum necessary amount of ink I to flow in the circulation path even when it is necessary to return the ink I from the head 11 to the subtank 52.

[0054] The inkjet recording apparatus 1 is also characterized by including a negative pressure path 98 that connects the negative pressure pump 63 and the degassing module 12, and a check valve provided in the negative pressure path 98, and the pump control unit 80 controls the negative pressure pump 63 to a stopped state when the negative pressure applied to the negative pressure path 98 by the negative pressure pump 63 reaches a target pressure. As a result, there is a period during which the negative pressure pump 63 is controlled to a stopped state, and power consumption can be reduced.

[0055] The pump control unit 80 is also characterized in that it drives the circulation pump 62 while negative pressure is applied to the degassing module 12, and controls the ink I to flow through the circulation path at a flow rate greater than 2 ml / min and less than 8 ml / min. This makes it possible to quickly supply sufficiently degassed ink to the head 11 without causing problems such as collapse of the nozzle meniscus in the head 11, allowing the user to start printing without having to wait.

[0056] The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention.

[0057] (1) In the above embodiment, the pump control unit 80 is provided inside the ink supply unit 50, but this is not limiting and the pump control unit 80 may be provided outside the ink supply unit 50. In this case, the pump control unit 80 may be configured by a general-purpose device such as a PC.

[0058] (2) In the above embodiment, the degassing module 12 and the damper 13 are arranged lying in the front-to-back direction at the top of the head unit housing 100, but in cases where the substrate 40 is erected at the top of the head unit housing 100, they may also be arranged lying in the front-to-back direction at the bottom of the head unit housing 100.

[0059] (3) In the above embodiment, the pump control unit 80 starts driving the negative pressure pump 63 in conjunction with the start of printing processing or circulation processing. However, this is not limited to this. The pump control unit 80 may start driving the negative pressure pump 63 when the inkjet recording device 1 is turned on, and may appropriately control the driving of the negative pressure pump 63 so as to maintain the negative pressure value in the negative pressure path 98 until the inkjet recording device 1 is turned off. [Explanation of symbols]

[0060] 1...inkjet recording device, 11...head, 15...nozzle, 16...nozzle row, 17...ink storage section, 12...degassing module, 12A...ink inlet, 12B...ink outlet, 13...damper, 14...check valve, 30...degassing device, 50...ink supply unit, 51...main tank, 52...sub-tank, 53...storage amount detection sensor, 61...air pump, 62...circulation pump, 63...negative pressure pump, 64, 65...pressure gauge, 66...subtank valve, 67...electromagnetic valve, 71...first check valve, 72...second check valve, 73...third check valve, 80...pump control unit, 90...cable, 91...first flow path, 92...second flow path, 93...third flow path, 94...fourth flow path, 97...positive pressure path, 98...negative pressure path, 100...head unit housing (first housing), 110...ink supply unit housing (second housing), I...ink.

Claims

1. a head having a nozzle array that ejects ink; a main tank for storing the ink; a first flow path that transports the ink from the main tank; a sub-tank connected to the first flow path and configured to temporarily store the ink flowing through the first flow path; a second flow path that transports the ink from the subtank; a degassing device connected to the second flow path and configured to degas the ink flowing in the second flow path; a third flow path that transports the ink degassed by the degassing device to the head; a fourth flow path that connects the head and the sub-tank and returns the ink from the head to the sub-tank; a circulation pump that applies pressure to the ink circulation path, which is made up of the sub-tank, the second flow path, the degassing device, the third flow path, the head, and the fourth flow path, to generate an ink flow in the circulation path; a damper provided in the fourth flow path for suppressing fluctuations in pressure applied to the head; Equipped with the degassing device has an ink inlet and an ink outlet; the ink inlet is disposed at a position closer to the head than the ink outlet in a direction in which the ink is ejected from the nozzle row; An inkjet recording apparatus characterized by:

2. The inkjet recording apparatus includes a first housing and a second housing, the degassing device includes a degassing module having a flow path through which ink to be degassed flows, and a negative pressure pump that applies negative pressure to the degassing module; the first housing accommodates the head, the degassing module, and the damper; the second housing accommodates the main tank, the sub-tank, the circulation pump, and the negative pressure pump; The first housing and the second housing are connected via a cable through which the second flow path and the fourth flow path pass.

2. The inkjet recording apparatus according to claim 1, wherein the inkjet recording apparatus is a recording medium.

3. the degassing module and the damper are disposed in the first housing so as to avoid the head in the direction in which the nozzle row extends.

3. The inkjet recording apparatus according to claim 2, wherein the inkjet recording apparatus is a recording medium.

4. the degassing module and the damper are disposed adjacent to each other in the direction in which the nozzle row extends within the first housing.

4. The inkjet recording apparatus according to claim 3,

5. The flow path length of the third flow path is 500 mm or less, The flow path diameter of the third flow path is 2 mm or more and 4 mm or less.

2. The inkjet recording apparatus according to claim 1, wherein the inkjet recording apparatus is a recording medium.

6. The inkjet recording apparatus further comprises: a pump control unit that controls the driving of the circulation pump and the negative pressure pump, The pump control unit When the power supply of the inkjet recording device is turned on or before a recording operation is performed by the head, the negative pressure pump is driven, and after a state in which a negative pressure is applied to the degassing module by the negative pressure pump, the circulation pump is driven to control so as to cause a predetermined amount of the ink to flow into the circulation path, During a recording operation by the head, the circulation pump is controlled to be stopped while the negative pressure pump applies negative pressure to the degassing module.

5. The inkjet recording apparatus according to claim 2, wherein the inkjet recording apparatus is a recording medium.

7. the predetermined amount is an amount of ink that is 1.0 to 1.2 times the internal volume of the third flow path and the head; 7. The inkjet recording apparatus according to claim 6,

8. The inkjet recording apparatus includes: a negative pressure path connecting the negative pressure pump and the degassing module; a check valve provided in the negative pressure path; Equipped with The pump control unit When the negative pressure applied to the negative pressure path by the negative pressure pump reaches a target pressure, the negative pressure pump is controlled to a stopped state.

7. The inkjet recording apparatus according to claim 6,

9. the pump control unit drives the circulation pump while negative pressure is applied to the degassing module, and controls the ink to flow through the circulation path at a flow rate greater than 2 ml / min and less than 8 ml / min.

7. The inkjet recording apparatus according to claim 6,

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