Printer and printing control method

Abstract

To enable an ink or air bubbles overflowing to an air pipe connecting a reservoir tank with pressure generating means to be detected before the ink or air bubbles reach an air filter provided in the air pipe.SOLUTION: A printer includes a sensor Sa which detects an ink or air bubbles in a pressure transmission pipe 934 (a first air pipe) between a supply tank 911 (a first reservoir tank) and an air filter Fa. Thus, it is possible to detect the ink or air bubbles overflowing to the pressure transmission pipe 934 connecting the supply tank 911 with a pressure generation part 93 (pressure generating means) before the ink or air bubbles reach the air filter Fa provided in the pressure transmission pipe 934.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a technique for dealing with the overflow of ink or air bubbles from a reservoir tank that communicates with a print head that ejects ink. [Background technology]

[0002] The inkjet printing devices disclosed in Patent Documents 1 and 2 are provided with a recording head that ejects ink and a reservoir tank that communicates with the recording head, and ink is sent between the recording head and the reservoir tank. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5777581 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-160773 Summary of the Invention [Problem to be solved by the invention]

[0004] In such a printing device, the pressure (negative pressure) applied to the reservoir tank is controlled to optimize the meniscus shape of the ink in the recording head. Specifically, the pressure generating means and the reservoir tank are connected by an air pipe, and the pressure generated by the pressure generating means is applied to the reservoir tank via the air pipe. In addition, an air filter is provided in the air pipe to prevent foreign matter from entering the reservoir tank.

[0005] However, a malfunction of the printing device or other reasons can cause ink to overflow from the reservoir tank into the air piping. Alternatively, as pointed out in Patent Document 2, air can become mixed into the ink. If this air mixing causes the ink to foam in the reservoir tank, air bubbles can overflow from the reservoir tank into the air piping. If the ink or air bubbles that have overflowed into the air piping reach the air filter and wet the air filter, the pressure generated by the pressure generating means will no longer be applied to the reservoir tank. As a result, ink may leak from the recording head, potentially soiling the interior of the printing device or the floor on which the printing device is installed.

[0006] The present invention has been made in consideration of the above-mentioned problems, and aims to make it possible to detect the overflow of ink or air bubbles into the air piping connecting the reservoir tank and the pressure generating means before they reach the air filter provided in the air piping. [Means for solving the problem]

[0007] The printing device of the present invention comprises a first reservoir tank for storing ink, a recording head having an ink storage chamber connected to a first ink storage section that is a portion of the first reservoir tank below the ink level and communicating with the first ink storage section, and ejecting the ink stored in the ink storage chamber from a nozzle, a first pressure generating means for generating a first pressure, a first air pipe that connects a first space in the first reservoir tank above the ink level to the first pressure generating means and applies the first pressure generated by the first pressure generating means to the first space, a first air filter that is provided in the first air pipe between the first reservoir tank and the first pressure generating means and removes foreign matter from the air in the first air pipe, and a sensor that detects ink or air bubbles in the first air pipe between the first reservoir tank and the first air filter.

[0008] The printing control method of the present invention includes the steps of: applying a first pressure generated by a first pressure generating means to a first space via a first air pipe connecting a first space above the ink level in a first reservoir tank that stores ink to a first pressure generating means that generates the first pressure; a recording head connected to a first ink storage section that is a portion of the first reservoir tank below the ink level and having an ink storage chamber that communicates with the first ink storage section, ejecting ink stored in the ink storage chamber from a nozzle; and a first air filter provided in the first air pipe between the first reservoir tank and the first pressure generating means to remove foreign matter from the air in the first air pipe, and a sensor detecting ink or air bubbles in the first air pipe between the first reservoir tank and the first pressure generating means.

[0009] The present invention (printing device and printing control method) configured in this way is equipped with a sensor that detects ink or air bubbles in the first air pipe between the first reservoir tank and the first air filter. Therefore, it is possible to detect ink or air bubbles overflowing into the air pipe connecting the reservoir tank and the pressure generating means before they reach the air filter provided in the air pipe.

[0010] The printing device may also be configured to further include an air buffer attached to the first air pipe between the sensor and the first air filter, thereby slowing the progress of ink and air bubbles that have reached the sensor and preventing them from reaching the air filter.

[0011] The printing device may be configured so that the volume of the air buffer is smaller than the volume of the first reservoir tank. In this configuration, providing an air buffer can prevent the printing device from becoming larger.

[0012] The printing device may also be configured to further include a notification unit that notifies the user when the sensor detects ink or air bubbles, allowing the user to take the necessary action when ink or air bubbles overflow into the air pipe.

[0013] The printing device may further include a second reservoir tank for storing ink, a second pressure generating means for generating a second pressure, a second air pipe connecting a second space in the second reservoir tank above the ink level to the second pressure generating means and applying the second pressure generated by the second pressure generating means to the second space, and a control unit for controlling the first pressure generating means and the second pressure generating means, wherein the ink storage chamber of the print head is connected to a second ink storage section that is a section of the second reservoir tank below the ink level and communicates with the second ink storage section, and the control unit controls the first pressure generating means and the second pressure generating means so that the first pressure and the second pressure become the same emergency pressure when the sensor detects ink or bubbles. With this configuration, when the sensor detects that ink or bubbles have overflowed into the air pipe, the flow of ink between the first reservoir tank and the second reservoir tank is stopped, thereby preventing further overflow of ink or bubbles from the reservoir tank.

[0014] The printing device may also be configured so that the first and second reservoir tanks are located above the print head, and the emergency pressure is a pressure that prevents ink from flowing out of the nozzles against the difference between the ink head pressure caused by the difference in height between the first reservoir tank and the print head and the ink head pressure caused by the difference in height between the second reservoir tank and the print head. With this configuration, ink is prevented from flowing out of the nozzles of the print head, and the interior of the printing device and the floor on which the printing device is installed can be prevented from being soiled with ink.

[0015] The printing device may also be configured to further include a circulation pump that sends ink between the first reservoir tank and the second reservoir tank, and the control unit may be configured to stop the circulation pump when the sensor detects ink or air bubbles. In this configuration, when the sensor detects that ink or air bubbles have overflowed into the air pipe, the flow of ink between the first reservoir tank and the second reservoir tank is stopped, thereby preventing further overflow of ink or air bubbles from the reservoir tank.

[0016] The printing device may also be configured to include a main tank for storing ink, a first pump for transferring ink between the main tank and a first reservoir tank, and a second pump for transferring ink between the main tank and a second reservoir tank, and the control unit stops the first pump and the second pump when a sensor detects ink or air bubbles. In this configuration, when the sensor detects that ink or air bubbles have overflowed into the air pipe, the flow of ink between the main tank and the first and second reservoir tanks is stopped, thereby preventing further overflow of ink or air bubbles from the reservoir tanks. [Effects of the Invention]

[0017] As described above, according to the present invention, it is possible to detect the overflow of ink or air bubbles into the air piping connecting the reservoir tank and the pressure generating means before they reach the air filter provided in the air piping. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a front view schematically showing a printing apparatus according to the present invention. [Figure 2] FIG. 2 is a diagram schematically illustrating the bottom surface of an ejection head provided in the head unit. [Figure 3] FIG. 2 is a diagram schematically illustrating a discharge head and an ink circulation mechanism that circulates ink to the discharge head. [Figure 4] FIG. 4 is a block diagram showing an electrical configuration provided in the printing apparatus for controlling the ink circulation mechanism of FIG. 3. [Figure 5] FIG. 2 is a perspective view partially showing the external configuration of the ejection head and the ink circulation mechanism. [Figure 6] 4A and 4B are diagrams showing several modes that can be performed by the ink circulation mechanism of FIG. 3; [Figure 7A] FIG. 10 is a diagram schematically showing a modified example of the air buffer. [Figure 7B] FIG. 10 is a diagram schematically showing a modified example of the air buffer. DETAILED DESCRIPTION OF THE INVENTION

[0019] Fig. 1 is a front view showing a schematic diagram of a printing device according to the present invention. A horizontal direction X and a vertical direction Z are shown in Fig. 1. Also shown are one side X1 and the other side X2 of the horizontal direction X, which face in opposite directions. The printing device 3 includes a housing 31, a color printing unit 32 disposed within the housing 31, a white printing unit 33 disposed above the color printing unit 32 within the housing 31, and a transport unit 4 that transports a printing medium M using a plurality of rollers disposed within the housing 31.

[0020] The color printing unit 32 has a plurality of (six) head units 321 arranged above the printing medium M transported by the transport unit 4 in the direction of travel of the printing medium M (the direction from the other side X2 to the one side X1). Each of the plurality of head units 321 has nozzles facing from above onto the surface M1 of the printing medium M passing below, and ejects different color inks from the nozzles using an inkjet method. Here, color ink refers to ink other than white, and includes inks such as cyan, magenta, yellow, and black. In this way, the plurality of head units 321 of the color printing unit 32 eject color inks from above onto the surface M1 of the printing medium M passing below, thereby printing a color image on the surface M1 of the printing medium M.

[0021] The white printing section 33 also has a single head unit 331 arranged above the printing medium M transported by the transport section 4. The head unit 331 has nozzles facing from above the surface M1 of the printing medium M passing below it, and ejects white ink from the nozzles using an inkjet method. In this way, the head unit 331 of the white printing section 33 prints a white image on the surface M1 of the printing medium M by ejecting white ink from above onto the surface M1 of the printing medium M passing below it.

[0022] An inlet 311 opens in the side wall on the other side X2 of the housing 31, while an outlet 312 opens in the side wall on the one side X1 of the housing 31. The transport unit 4 transports the printing medium M from the inlet 311 to the outlet 312, passing through the color printing unit 32 and the white printing unit 33.

[0023] The transport unit 4 has an inlet unit 41 provided below the color printing unit 32, an upward transport unit 42 provided on one side X1 of the color printing unit 32, an upward transport unit 43 provided above the color printing unit 32, and a downward transport unit 44 provided on the other side X2 of the color printing unit 32. The inlet unit 41 transports the printing medium M transported from the inlet 311 to the one side X1 using rollers 411, the upward transport unit 42 transports the printing medium M transported by the inlet unit 41 upward using rollers 421, the upward transport unit 43 transports the printing medium M transported by the upward transport unit 42 to the other side X2 using rollers 431, and the downward transport unit 44 transports the printing medium M transported by the upward transport unit 43 downward using rollers 441.

[0024] Furthermore, the transport unit 4 has a color transport unit 45 that supports the printing medium M facing the color printing unit 32 from below, and the printing medium M that has passed through the descending transport unit 44 enters the color transport unit 45. This color transport unit 45 has a plurality of rollers 451 arranged from the other side X2 to one side X1, and each roller 451 contacts the back surface M2 of the printing medium M from below. In this way, the front surface M1 of the printing medium M supported by the color transport unit 45 faces upward, and each head unit 321 of the color printing unit 32 ejects color ink while facing this front surface M1 from above.

[0025] The transport unit 4 also has rollers 461, 462, and 463 arranged between the color transport unit 45 and the downward transport unit 44 in the traveling direction of the printing medium M. The roller 461 is a drive roller that drives the printing medium M. The rollers 462 and 463 are driven rollers that rotate in response to the printing medium M.

[0026] Furthermore, the transport unit 4 has a reverse transport unit 47 that turns upside down twice the printing medium M transported from the color transport unit 45 to one side X1. This reverse transport unit 47 has multiple rollers 471 to 477, including a drive roller 471, and these rollers 471 to 477 turn the printing medium M upside down twice while contacting the back side M2 ​​of the printing medium M. That is, the reverse transport unit 47 transports the printing medium M transported from the color transport unit 45 downward using rollers 471 and 472, and then changes the traveling direction of the printing medium M to the other side X2 using roller 472 and transports it, thereby turning upside down the front side M1 and back side M2 ​​of the printing medium M. Next, the reverse transport unit 47 transports the printing medium M from one side X1 to the other side X2 using multiple rollers 473, and then transports the printing medium M upward using rollers 474 to 476. Furthermore, the reverse conveying section 47 changes the direction of travel of the printing medium M to one side X1 using roller 476, thereby again inverting the front surface M1 and back surface M2 of the printing medium M upside down, and conveys the printing medium M from the other side X2 toward one side X1 using roller 477.

[0027] The transport unit 4 also has a white transport unit 48 that supports the printing medium M facing the white printing unit 33 from below, and the printing medium M that has been turned upside down twice by the reversing transport unit 47 enters the white transport unit 48. This white transport unit 48 has a roller 481 that contacts the back surface M2 of the printing medium M from below. Thus, the front surface M1 of the printing medium M supported by the white transport unit 48 faces upward, and the head unit 331 of the white printing unit 33 ejects white ink while facing this front surface M1 from above.

[0028] The conveying unit 4 also has an output unit 49 located above the upper conveying unit 43. The output unit 49 has a plurality of rollers 491 arranged from the other side X2 to one side X1 in the horizontal direction X. The output unit 49 conveys the printing medium M conveyed by the white conveying unit 48 to the one side X1 using the plurality of rollers 491, thereby conveying the printing medium M from the output opening 312 of the housing 31.

[0029] As described above, the color printing unit 32 and the white printing unit 33 of the printing device 3 have head units 321 and 331. Next, we will explain the ejection heads H that the head units 321 and 331 have and the ink circulation mechanism 9 that circulates ink to the ejection heads H. The basic configurations of the ejection heads H and the ink circulation mechanism 9 are common to both the head unit 321 that ejects white ink and the head unit 331 that ejects color inks. Therefore, here we will explain the configuration related to the head unit 331 that ejects white ink.

[0030] Fig. 2 is a diagram schematically showing the bottom surface of the ejection head H provided in the head units 321 and 323, Fig. 3 is a diagram schematically showing the ejection head H and the ink circulation mechanism 9 that circulates and supplies ink to the ejection head H, and Fig. 4 is a block diagram showing the electrical configuration provided in the printing device 3 for controlling the ink circulation mechanism 9 of Fig. 3. In Fig. 2, in addition to the horizontal direction X and the vertical direction Z, a horizontal direction Y that is perpendicular to the horizontal direction X is also shown.

[0031] 4, the printing device 3 has a control unit 10. The control unit 10 is, for example, a processor such as a CPU (Central Processing Unit). The printing device 3 also has a UI (User Interface) 11. The UI 11 has output devices such as a display and a speaker, and notifies the operator by displaying an image on the display or outputting audio from the speaker.

[0032] 2, in the head unit 331, a plurality of ejection heads H that eject ink of the same color (white ink) are arranged in a row in the horizontal direction Y, and each ejection head H has a rectangular shape when viewed from the bottom. Note that the shape of the ejection head H is not limited to the example in FIG. 2, and may be a parallelogram. Furthermore, the arrangement of the plurality of ejection heads H is not limited to the example in FIG. 2, and the plurality of ejection heads H may be arranged in a staggered pattern.

[0033] As shown in FIG. 3, the ejection head H has a housing Ha, and a plurality of nozzles Hn are opened on the bottom surface of the housing Ha in a staggered arrangement in the horizontal direction Y. Inside the housing Ha, a plurality of cavities Hb are provided, each communicating with the plurality of nozzles Hn, and an ink supply chamber Hc is provided, each communicating with the plurality of cavities Hb. Ink supplied from the ink supply chamber Hc is stored in the cavities Hb. Each cavity Hb is provided with a piezoelectric element D, and the piezoelectric element D is displaced in response to a drive signal (electrical signal), thereby applying a pressure fluctuation to the ink in the cavity Hb. This pressure fluctuation pushes ink out of the cavity Hb, causing the ink to be ejected from the nozzle Hn communicating with the cavity Hb. In addition, an ink inlet Hd and an ink outlet He are opened at the top of the ejection head H, and ink flows from the ink circulation mechanism 9 into the ink supply chamber Hc via the ink inlet Hd, and flows out from the ink supply chamber Hc towards the ink circulation mechanism 9 via the ink outlet He.

[0034] The ink circulation mechanism 9 includes an ink supply mechanism 9a that supplies ink to the ink supply chamber Hc of the ejection head H, an ink recovery mechanism 9b that recovers ink from the ink supply chamber Hc of the ejection head H, and an ink return mechanism 9c that returns ink from the ink recovery mechanism 9b to the ink supply mechanism 9a.

[0035] The ink supply mechanism 9a includes an ink supply unit 91 that supplies ink to the ink supply chamber Hc of the ejection head H, and a pressure generation unit 93 that generates a supply pressure to be applied to the ink supply unit 91. The ink supply unit 91 includes a supply tank 911 that stores ink to be supplied to the ejection head H, and a supply pipe 912 that sends the ink supplied from the supply tank 911 to the ink supply chamber Hc of the ejection head H. The supply tank 911 is disposed above the ejection head H. In the supply tank 911, ink is stored in an ink storage unit 911L below the gas-liquid interface L1 (i.e., the ink liquid level), and air is present in a space 911G above the gas-liquid interface L1.

[0036] The ink recovery mechanism 9b includes an ink recovery unit 92 that recovers ink from the ink supply chamber Hc of the ejection head H, and a pressure generation unit 94 that generates pressure to be applied to the ink recovery unit 92. The ink recovery unit 92 includes a recovery tank 921 that stores the ink recovered from the ejection head H, and a recovery pipe 922 that sends the ink recovered from the ink supply chamber Hc of the ejection head H to the recovery tank 921. The recovery tank 921 is disposed above the ejection head H. In the recovery tank 921, ink is stored in an ink storage unit 921L below the gas-liquid interface L2 (i.e., the ink liquid surface), and air is present in a space 921G above the gas-liquid interface L2.

[0037] The ink return mechanism 9c has a return pipe 951 that connects the recovery tank 921 and the supply tank 911. The return pipe 951 connects and communicates with an ink storage section 921L of the recovery tank 921 and an ink storage section 911L of the supply tank 911. The ink return mechanism 9c also has a circulation pump 952 that is located midway along the return pipe 951. The circulation pump 952 operates under the control of the control unit 10. When the control unit 10 sends a liquid transfer command to the circulation pump 952, the circulation pump 952 drives the ink in the return pipe 951 from the recovery tank 921 to the supply tank 911. This transfers ink from the ink storage section 921L of the recovery tank 921 to the ink storage section 911L of the supply tank 911. In other words, the ink return mechanism 9c can use the circulation pump 952 to transfer ink along a first path Ca that leads from the recovery tank 921 to the supply tank 911. Furthermore, when the control unit 10 sends a stop command to the circulation pump 952, the circulation pump 952 stops, thereby stopping the transfer of ink from the recovery tank 921 to the supply tank 911.

[0038] As described above, the ink supply mechanism 9a has a pressure generating unit 93 that applies pressure P1 (negative pressure) to the supply tank 911. This pressure generating unit 93 has a pressure tank 931 and an exhaust pump 932 that exhausts the pressure tank 931 to generate pressure P1 in the pressure tank 931. The exhaust pump 932 is a diaphragm pump that sucks air through an intake port Gi and discharges it through an exhaust port Go. This causes air to be exhausted in an exhaust direction Dg from the intake port Gi toward the exhaust port Go. The exhaust port Go of the exhaust pump 932 is open to the atmosphere. Meanwhile, the intake port Gi of the exhaust pump 932 is connected to the pressure tank 931. The pressure generating unit 93 also has a resin exhaust pipe 933 that connects the pressure tank 931 and the intake port Gi of the exhaust pump 932, and the exhaust pipe 933 connects the pressure tank 931 and the intake port Gi.

[0039] The exhaust pump 932 operates under the control of the control unit 10. When the control unit 10 outputs an exhaust command to the exhaust pump 932, the exhaust pump 932 exhausts air in the exhaust direction Dg. Therefore, air flows out of the pressure tank 931 into the exhaust pipe 933 and is exhausted to the atmosphere. This generates pressure P1 in the pressure tank 931. Furthermore, when the control unit 10 sends a stop command to the exhaust pump 932, the exhaust pump 932 stops exhausting. Note that the exhaust pump 932 is a diaphragm pump. Therefore, when the exhaust pump 932 stops, a check valve built into the diaphragm pump blocks the flow of air in the direction opposite to the exhaust direction Dg, and the pressure P1 in the pressure tank 931 is maintained.

[0040] The pressure generating unit 93 also has a pressure transmission pipe 934 that connects the pressure tank 931 and the space 911G of the supply tank 911, and a solenoid valve Va that is provided in the pressure transmission pipe 934 between the pressure tank 931 and the supply tank 911. The pressure transmission pipe 934 connects the pressure tank 931 and the space 911G of the supply tank 911. The solenoid valve Va operates under the control of the control unit 10. When the control unit 10 sends an open command to the solenoid valve Va, the solenoid valve Va opens, connecting the pressure tank 931 and the space 911G of the supply tank 911 via the pressure transmission pipe 934. Therefore, the pressure P1 generated in the pressure tank 931 is applied to the space 911G of the supply tank 911 via the pressure transmission pipe 934. As a result, the pressure P1 is applied to the gas-liquid interface L1. When the control unit 10 sends a close command to the solenoid valve Va, the solenoid valve Va closes, and the pressure tank 931 and the supply tank 911 are isolated from each other.

[0041] The pressure generating unit 93 also has an atmosphere release pipe 935 connecting the pressure tank 931 to the atmosphere, an atmosphere release solenoid valve 936 located midway along the atmosphere release pipe 935, and an air filter 937 provided in the atmosphere release pipe 935 so as to be located between the atmosphere release solenoid valve 936 and the pressure tank 931. When the atmosphere release solenoid valve 936 is closed, the pressure tank 931 is isolated from the atmosphere, and pressure P1 in the pressure tank 931 is maintained. On the other hand, when the atmosphere release solenoid valve 936 is open, the pressure tank 931 is connected to the atmosphere via the atmosphere release pipe 935. Therefore, air flows from the atmosphere into the pressure tank 931 via the atmosphere release pipe 935, and pressure P1 in the pressure tank 931 increases. At this time, the air filter 937 located between the pressure tank 931 and the atmosphere release solenoid valve 936 removes foreign matter from the air before it flows into the pressure tank 931.

[0042] As described above, the ink recovery mechanism 9b has a pressure generating unit 94 that applies pressure P2 (negative pressure) to the recovery tank 921. This pressure generating unit 94 has a pressure tank 941 and an exhaust pump 942 that exhausts the pressure tank 941 to generate pressure P2 in the pressure tank 941. The exhaust pump 942 is a diaphragm pump that sucks air through an intake port Gi and discharges it through an exhaust port Go. This causes air to be exhausted in an exhaust direction Dg from the intake port Gi toward the exhaust port Go. The exhaust port Go of the exhaust pump 942 is open to the atmosphere. Meanwhile, the intake port Gi of the exhaust pump 942 is connected to the pressure tank 941. The pressure generating unit 94 also has a resin exhaust pipe 943 that connects the pressure tank 941 and the intake port Gi of the exhaust pump 942, and the pressure tank 941 and the intake port Gi are communicated by the exhaust pipe 943.

[0043] The exhaust pump 942 operates under the control of the control unit 10. When the control unit 10 outputs an exhaust command to the exhaust pump 942, the exhaust pump 942 exhausts air in the exhaust direction Dg. Therefore, air flows out of the pressure tank 941 into the exhaust pipe 943 and is exhausted to the atmosphere. This generates pressure P2 in the pressure tank 941. Furthermore, when the control unit 10 sends a stop command to the exhaust pump 942, the exhaust pump 942 stops exhausting. Note that the exhaust pump 942 is a diaphragm pump. Therefore, when the exhaust pump 942 stops, a check valve built into the diaphragm pump blocks the flow of air in the direction opposite to the exhaust direction Dg, and the pressure P2 in the pressure tank 941 is maintained.

[0044] The pressure generating unit 94 also has a pressure transmission pipe 944 that connects the pressure tank 941 and the space 921G of the recovery tank 921, and a solenoid valve Vb that is provided in the pressure transmission pipe 944 between the pressure tank 941 and the recovery tank 921. The pressure transmission pipe 944 connects the pressure tank 941 and the space 921G of the recovery tank 921. The solenoid valve Vb operates under the control of the control unit 10. When the control unit 10 sends an open command to the solenoid valve Vb, the solenoid valve Vb opens, connecting the pressure tank 941 and the space 921G of the recovery tank 921 via the pressure transmission pipe 944. Therefore, the pressure P2 generated in the pressure tank 941 is applied to the space 921G of the recovery tank 921 via the pressure transmission pipe 944. As a result, the pressure P2 is applied to the gas-liquid interface L2. When the control unit 10 sends a close command to the solenoid valve Vb, the solenoid valve Vb closes, and the pressure tank 941 and the recovery tank 921 are isolated from each other.

[0045] The pressure generating unit 94 also has an atmosphere release pipe 945 connecting the pressure tank 941 to the atmosphere, an atmosphere release solenoid valve 946 located midway through the atmosphere release pipe 945, and an air filter 947 provided in the atmosphere release pipe 945 so as to be located between the atmosphere release solenoid valve 946 and the pressure tank 941. When the atmosphere release solenoid valve 946 is closed, the pressure tank 941 is isolated from the atmosphere, and pressure P2 in the pressure tank 941 is maintained. On the other hand, when the atmosphere release solenoid valve 946 is open, the pressure tank 941 is connected to the atmosphere via the atmosphere release pipe 945. Therefore, air flows from the atmosphere into the pressure tank 941 via the atmosphere release pipe 945, and pressure P2 in the pressure tank 941 increases. At this time, the air filter 947 located between the pressure tank 941 and the atmosphere release solenoid valve 946 removes foreign matter from the air before it flows into the pressure tank 941.

[0046] In this way, the pressure generating unit 93 applies pressure P1 to the gas-liquid interface L1 of the supply tank 911, and the pressure generating unit 94 applies pressure P2 to the gas-liquid interface L2 of the recovery tank 921. At this time, the pressure P2 applied to the recovery tank 921 is lower than the pressure P1 applied to the supply tank 911. The difference between the pressures P2 and P1 causes ink to flow along a second path Cb that leads from the supply tank 911 to the recovery tank 921 via the ink supply chamber Hc of the ejection head H. Furthermore, the ink that has flowed into the recovery tank 921 along the second path Cb is returned to the supply tank 911 by the circulation pump 952 along the first path Ca. In this way, the ink circulates along a circulation path (second path Cb+first path Ca) that leads from the supply tank 911 via the ejection head H to the recovery tank 921 and then back to the supply tank 911.

[0047] The ink circulation mechanism 9 includes a bypass pipe 953 connecting the supply tank 911 and the recovery tank 921, and a solenoid valve Vc attached to the bypass pipe 953 between the supply tank 911 and the recovery tank 921. The bypass pipe 953 connects the space 911G of the supply tank 911 with the space 921G of the recovery tank 921. The solenoid valve Vc operates under the control of the control unit 10. When the control unit 10 sends a close command to the solenoid valve Vc, the solenoid valve Vc closes. This blocks the space 911G of the supply tank 911 from the space 921G of the recovery tank 921. As described above, when different pressures P1 and P2 are generated to send ink along the second path Cb, the control unit 10 closes the solenoid valve Vc. On the other hand, when the control unit 10 sends an open command to the solenoid valve Vc, the solenoid valve Vc opens. As a result, the same pressure P3 is applied to the gas-liquid interface L1 and the gas-liquid interface L2, and the ink transfer along the second path Cb is stopped.

[0048] The ink circulation mechanism 9 also has a main tank 96. This main tank 96 can store a larger amount of ink than the supply tank 911 and the recovery tank 921. The ink circulation mechanism 9 includes a pipe 961 that connects the main tank 96 and the supply tank 911, and a pipe 962 that connects the main tank 96 and the recovery tank 921. In other words, the main tank 96 communicates with the supply tank 911 via the pipe 961, and with the recovery tank 921 via the pipe 962.

[0049] Furthermore, the ink circulation mechanism 9 includes a recovery pump 963 attached to a pipe 961 between the main tank 96 and the supply tank 911, and a supply pump 964 attached to a pipe 962 between the main tank 96 and the recovery tank 921. Therefore, the recovery pump 963 recovers ink from the supply tank 911 to the main tank 96, and the supply pump 964 supplies ink from the main tank 96 to the recovery tank 921.

[0050] The recovery pump 963 and the supply pump 964 each operate under the control of the control unit 10. When the control unit 10 sends a liquid sending command to the recovery pump 963, the recovery pump 963 sends ink from the supply tank 911 to the main tank 96. When the control unit 10 sends a stop command to the recovery pump 963, the recovery pump 963 stops sending ink from the supply tank 911 to the main tank 96. When the control unit 10 sends a liquid sending command to the supply pump 964, the supply pump 964 sends ink from the main tank 96 to the recovery tank 921. When the control unit 10 sends a stop command to the supply pump 964, the supply pump 964 stops sending ink from the main tank 96 to the recovery tank 921.

[0051] In this configuration, the recovery pump 963 and the supply pump 964 pump ink, causing the ink to flow along a third path Cc that runs from the supply tank 911 to the recovery tank 921 via the main tank 96. The ink that flows into the recovery tank 921 along the third path Cc is returned to the supply tank 911 by the circulation pump 952 along the first path Ca. In this way, the ink circulates along a circulation path (third path Cc+first path Ca) that runs from the supply tank 911 to the main tank 96, reaches the recovery tank 921, and then returns to the supply tank 911.

[0052] The ink supply mechanism 9a also has an air filter Fa provided in the pressure transmission pipe 934 between the solenoid valve Va and the supply tank 911. The air filter Fa removes foreign matter from the air flowing through the pressure transmission pipe 934. The ink supply mechanism 9a also has a sensor Sa provided in the pressure transmission pipe 934 between the air filter Fa and the supply tank 911. The sensor Sa detects ink or air bubbles that have overflowed from the supply tank 911 into the pressure transmission pipe 934. The detection result of the sensor Sa is sent to the control unit 10. For example, a capacitance sensor or an optical sensor can be used as the sensor Sa. The ink supply mechanism 9a also has an air buffer 97a provided in the pressure transmission pipe 934 between the sensor Sa and the air filter Fa. The air buffer 97a has a volume smaller than the volume of the supply tank 911 and buffers air flowing from the sensor Sa to the air filter Fa. The air buffer 97a has the function of slowing down the speed at which air travels through the air path from the sensor Sa to the air filter Fa, compared to when the air path is connected only by the pressure transmission pipe 934.

[0053] The ink recovery mechanism 9b has an air filter Fb provided in the pressure transmission pipe 944 between the solenoid valve Vb and the recovery tank 921. The air filter Fb removes foreign matter from the air flowing through the pressure transmission pipe 944. The ink recovery mechanism 9b also has a sensor Sb provided in the pressure transmission pipe 944 between the air filter Fb and the recovery tank 921. The sensor Sb detects ink or air bubbles that have overflowed from the recovery tank 921 into the pressure transmission pipe 944. The detection result of the sensor Sb is sent to the control unit 10. For example, a capacitance sensor or an optical sensor can be used as the sensor Sb. The ink recovery mechanism 9b also has an air buffer 97b provided in the pressure transmission pipe 944 between the sensor Sb and the air filter Fb. The air buffer 97b has a volume smaller than the volume of the recovery tank 921 and buffers air flowing from the sensor Sb to the air filter Fb. The air buffer 97b has the function of slowing down the speed at which air travels through the air path from the sensor Sb to the air filter Fb, compared to when the air path is connected only by the pressure transmission pipe 944.

[0054] Fig. 5 is a perspective view partially illustrating the external configuration of the ejection head and the ink circulation mechanism, showing the (+X) side and (-X) side of the horizontal direction X, which face in opposite directions, and the (+Y) side and (-Y) side of the horizontal direction Y, which face in opposite directions.

[0055] As shown in Fig. 5, the supply tank 911 includes a vertical supply tank 911V and a horizontal supply tank 911H. The vertical supply tank 911V is a rectangular parallelepiped tank that is long in the vertical direction Z. The horizontal supply tank 911H is a cylindrical tank that is long in the horizontal direction Y, and extends parallel to the horizontal direction Y from the (-Y) side surface of the vertical supply tank 911V in the horizontal direction Y. Of the vertical supply tank 911V and the horizontal supply tank 911H, only the vertical supply tank 911V is shown in Fig. 3 described above.

[0056] Similarly, the recovery tank 921 has a vertical recovery tank 921V and a horizontal recovery tank 921H. The vertical recovery tank 921V is a rectangular parallelepiped tank that is long in the vertical direction Z. The horizontal recovery tank 921H is a cylindrical tank that is long in the horizontal direction Y, and extends parallel to the horizontal direction Y from the side wall on the (-Y) side of the vertical recovery tank 921V in the horizontal direction Y. Of the vertical recovery tank 921V and the horizontal recovery tank 921H, only the vertical recovery tank 921V is shown in FIG. 3 above.

[0057] The vertical supply tank 911V and the vertical recovery tank 921V are adjacent to each other with no gap in the horizontal direction X. The horizontal supply tank 911H and the horizontal recovery tank 921H are adjacent to each other with a gap in the horizontal direction X.

[0058] The multiple discharge heads H arranged in the horizontal direction Y are disposed below the horizontal supply tank 911H and the horizontal recovery tank 921H in the vertical direction Z. In particular, each discharge head H faces the horizontal supply tank 911H from below in the vertical direction Z. The horizontal supply tank 911H and the discharge heads H are connected by supply piping 912, and the horizontal recovery tank 921H and the discharge heads H are connected by recovery piping 922. Furthermore, the vertical supply tank 911V is connected to the pressure tank 931 by pressure transmission piping 934, and the vertical recovery tank 921V is connected to the recovery tank 921 by pressure transmission piping 944.

[0059] The pressure transmission pipe 934 connected to the supply tank 911 is provided on the (+Y) side of the vertical supply tank 911V. This pressure transmission pipe 934 includes an attachment pipe 71, a vertical pipe 72, a branch pipe 73, a horizontal pipe 74, a connection pipe 75, and a connection pipe 76. An attachment end 711 of the attachment pipe 71 is attached to the (+Y) side of the vertical supply tank 911V and communicates with a space 911G within the supply tank 911. The attachment pipe 71 protrudes from the attachment end 711 to the (+Y) side and bends downward in the vertical direction Z. An upper end 721 of the vertical pipe 72 is connected to a lower end 712 of the attachment pipe 71. The vertical pipe 72 extends diagonally downward in the vertical direction Z from the lower end of the attachment pipe 71. An upper end 731 of the branch pipe 73 is connected to a lower end 722 of the vertical pipe 72. The branch pipe 73 extends downward in the vertical direction Z, and a discharge pipe 81 and a drainage section 82 (described later) are connected to a lower end 732 of the branch pipe 73. The branch pipe 73 has a branch opening facing the (+X) side between an upper end 731 and a lower end 732, and the (-X) side end of the horizontal pipe 74 is connected to the branch opening of the branch pipe 73. A lower end 971 of the air buffer 97a is connected to an end 742 on the (+X) side of the horizontal pipe 74. A lower end 751 of the connection pipe 75 is connected to the upper end 972 of the air buffer 97a. The connection pipe 75 extends obliquely upward from the lower end 751, and one end of the air filter Fa is connected to the upper end 752 of the connection pipe 75. A lower end 761 of the connection pipe 76 is connected to the other end of the air filter Fa. In other words, the air filter Fa is disposed between the upper end 752 of the connection pipe 75 and the lower end 761 of the connection pipe 76. The connecting pipe 76 extends from its lower end 761 and is connected to the solenoid valve Va.

[0060] That is, the pressure P1 generated in the pressure tank 931 is applied to the space 911G of the supply tank 911 via the connecting pipe 76, air filter Fa, connecting pipe 75, air buffer 97a, horizontal pipe 74, branch pipe 73, vertical pipe 72, and mounting pipe 71, in that order. The pressure transmission pipe 944 has a common configuration with the pressure transmission pipe 934, except that the mounting end 711 is attached to the vertical recovery tank 921V and the connecting pipe 76 is connected to the solenoid valve Vb.

[0061] The printing device 3 also has a discharge pipe 81 extending downward from the lower end 732 of the branch pipe 73, and a drainage section 82 attached to the lower end of the discharge pipe 81. The drainage section 82 has a lower opening and a plug that closes the lower opening (neither of which is shown). Therefore, ink or air bubbles that overflow from the vertical supply tank 911V reach the drainage section 82 via the mounting pipe 71, the vertical pipe 72, the branch pipe 73, and the discharge pipe 81. The drainage section 82 stores the ink or air bubbles that have reached the drainage section 82. When an operator opens the plug of the drainage section 82, the ink or air bubbles are discharged downward from the drainage section 82. The discharge pipe 81 and the drainage section 82 are similarly configured in the vertical recovery tank 921V as well.

[0062] The air buffer 97a includes an air buffer main body 973, an attachment portion 974 attached to one end (lower end) of the air buffer main body 973, and an attachment portion 975 attached to the other end (upper end) of the air buffer main body 973. The air buffer main body 973 is a pipe extending in the vertical direction Z. The inner diameter of the air buffer main body 973 is larger than the inner diameters of the horizontal pipes 74 and the connecting pipes 75. Here, the inner diameters of the pipes 74 and the connecting pipes 75 are equal, but may be different. The attachment portion 974 protrudes downward from the lower end of the air buffer main body 973. The lower end of this attachment portion 974 bends toward the (-X) side, and the end of the attachment portion 974 on the (-X) side corresponds to the lower end 971 of the air buffer 97a described above. The attachment portion 975 protrudes upward from the upper end of the air buffer main body 973, and the upper end of the attachment portion 975 corresponds to the upper end 972 of the air buffer 97a described above.

[0063] Fig. 6 is a diagram showing a number of modes that can be executed by the ink circulation mechanism of Fig. 3. Each mode in Fig. 6 is executed under the control of the control unit 10. Fig. 6 shows a normal mode, a first emergency mode, and a second emergency mode.

[0064] The normal mode is executed when the operation of the printing device 3 is normal. For example, the normal mode is executed when a printing operation is performed in which ink is ejected from the nozzles Hn of the ejection head H onto the printing medium M. In the normal mode, the solenoid valves Va and Vb are opened, and the solenoid valve Vc is closed. The exhaust pump 932 generates a pressure P1 in the pressure tank 931, and this pressure P1 is applied to the ink storage section 911L of the supply tank 911. The exhaust pump 942 generates a pressure P2 in the pressure tank 941, and this pressure P2 is applied to the ink storage section 921L of the recovery tank 921. As a result, ink is sent along the second path Cb due to the pressure difference between the pressures P1 and P2. In addition, the circulation pump 952 is activated (ON), and ink is sent along the first path Ca. In addition, the recovery pump 963 and the piping 962 are activated (ON), and ink is sent along the third path Cc.

[0065] In the first emergency mode, the exhaust pump 932, the exhaust pump 942, the circulation pump 952, the recovery pump 963, and the supply pump 964 are all stopped. The solenoid valve Va is closed to isolate the pressure tank 931 from the supply tank 911, and the solenoid valve Vb is closed to isolate the pressure tank 941 from the recovery tank 921. The solenoid valve Vc is opened to connect the space 911G of the supply tank 911 to the space 921G of the recovery tank 921. As a result, the same pressure P3 is applied to the air-liquid interface L1 and the air-liquid interface L2, and the transfer of ink along the second path Cb is stopped.

[0066] In the second emergency mode, the solenoid valves Va and Vb are opened, and the solenoid valve Vc is closed. The exhaust pump 932 generates a pressure P4 (negative pressure) in the pressure tank 931, and the exhaust pump 942 generates a pressure P4 in the pressure tank 941. Therefore, the same pressure P4 is applied to the gas-liquid interface L1 in the supply tank 911 and the gas-liquid interface L2 in the recovery tank 921, and ink transfer along the second path Cb is stopped. Note that the pressure P4 (emergency pressure) is a pressure that prevents ink from flowing out of the nozzles Hn against the difference between the ink head pressure caused by the difference in height between the supply tank 911 and the ejection head H and the ink head pressure caused by the difference in height between the recovery tank 921 and the ejection head H. In addition, the circulation pump 952, the recovery pump 963, and the supply pump 964 are all stopped. Therefore, ink transfer along the first path Ca is stopped, and ink transfer along the third path Cc is stopped.

[0067] As described above, a sensor Sa is provided for the pressure transmission pipe 934 between the supply tank 911 and the air filter Fa. Also, a sensor Sb is provided for the pressure transmission pipe 944 between the recovery tank 921 and the air filter Fb. In response to this, the control unit 10 switches between the normal mode and the second emergency mode based on the detection results of the sensors Sa and Sb.

[0068] That is, when the normal mode is executed, the control unit 10 monitors the detection results of the sensors Sa and Sb. Then, when at least one of the sensors Sa and Sb detects ink or bubbles, the control unit 10 executes the second emergency mode. Furthermore, the control unit 10 causes the UI 11 to issue a warning.

[0069] In the embodiment described above, a sensor Sa is provided that detects ink or air bubbles in the pressure transmission pipe 934 (first air pipe) between the supply tank 911 (first reservoir tank) and the air filter Fa. Therefore, it is possible to detect ink or air bubbles overflowing into the pressure transmission pipe 934 that connects the supply tank 911 and the pressure generating unit 93 (pressure generating means) before they reach the air filter Fa provided in the pressure transmission pipe 934.

[0070] Similarly, a sensor Sb is provided that detects ink or air bubbles in the pressure transmission pipe 944 (in the first air pipe) between the recovery tank 921 (first reservoir tank) and the air filter Fb (first air filter). Therefore, it is possible to detect ink or air bubbles overflowing into the pressure transmission pipe 944 that connects the recovery tank 921 and the pressure generating unit 94 (pressure generating means) before they reach the air filter Fb provided in the pressure transmission pipe 944.

[0071] In addition, an air buffer 97a is provided between the sensor Sa and the air filter Fa and attached to the pressure transmission pipe 934. This allows the air buffer 97a to slow the progress of ink and air bubbles that have reached the sensor Sa, preventing them from reaching the air filter Fa.

[0072] The volume of this air buffer 97a is smaller than the volume of the supply tank 911. In this configuration, the provision of the air buffer 97a can prevent the printing device 3 from becoming larger.

[0073] In addition, an air buffer 97b is provided between the sensor Sb and the air filter Fb and attached to the pressure transmission pipe 944. This allows the air buffer 97b to slow the progress of ink and air bubbles that have reached the sensor Sb, preventing them from reaching the air filter Fb.

[0074] Furthermore, the volume of the air buffer 97b is smaller than the volume of the collection tank 921. In this configuration, the provision of the air buffer 97b can prevent the printing device 3 from becoming larger.

[0075] Furthermore, when the sensor Sa or the sensor Sb detects ink or air bubbles, the UI 11 notifies the user. With this configuration, the user can take necessary measures when ink or air bubbles overflow into the pressure transmission pipe 934 or the pressure transmission pipe 944. For example, the user can perform the task of removing the ink or air bubbles from the drainage section 82.

[0076] Furthermore, when the sensor Sa or the sensor Sb detects ink or bubbles, the control unit 10 applies the same pressure P4 (emergency pressure) to the gas-liquid interface L1 of the supply tank 911 and the gas-liquid interface L2 of the recovery tank 921. In this configuration, when the sensors Sa and Sb detect that ink or bubbles have overflowed into the pressure transmission pipes 934 and 944, the flow of ink between the recovery tank 921 and the supply tank 911 is stopped, thereby preventing further overflow of ink or bubbles from the recovery tank 921 or the supply tank 911.

[0077] Furthermore, the supply tank 911 and the recovery tank 921 are disposed above the ejection head H (recording head). In contrast, pressure P4 (emergency pressure) is a pressure that prevents ink from flowing out from the nozzles Hn against the difference between the ink head pressure caused by the difference in height between the supply tank 911 and the ejection head H and the ink head pressure caused by the difference in height between the recovery tank 921 and the ejection head H. With this configuration, ink is prevented from flowing out from the nozzles Hn of the ejection head H, and the interior of the printing device 3 and the floor on which the printing device 3 is installed can be prevented from being soiled with ink.

[0078] Also provided is a circulation pump 952 that sends ink between the recovery tank 921 and the supply tank 911. In response to this, when the sensor Sa or the sensor Sb detects ink or air bubbles, the control unit 10 stops the circulation pump 952. With this configuration, when the sensor Sa or the sensor Sb detects that ink or air bubbles have overflowed into the pressure transmission pipe 934 or the pressure transmission pipe 944, the flow of ink between the recovery tank 921 and the supply tank 911 is stopped, thereby making it possible to prevent further overflow of ink or air bubbles from the recovery tank 921 or the supply tank 911.

[0079] The system also includes a main tank 96 that stores ink, a recovery pump 963 that sends ink between the main tank 96 and the supply tank 911, and a supply pump 964 that sends ink between the main tank 96 and the recovery tank 921. In response to this, when the sensor Sa or the sensor Sb detects ink or air bubbles, the control unit 10 stops the recovery pump 963 and the supply pump 964. With this configuration, when the sensor Sa or the sensor Sb detects that ink or air bubbles have overflowed into the pressure transmission pipe 934 or the pressure transmission pipe 944, the flow of ink between the main tank 96 and the supply tank 911 and the flow of ink between the main tank 96 and the recovery tank 921 can be stopped, thereby preventing further overflow of ink or air bubbles from the recovery tank 921 or the supply tank 911.

[0080] In the embodiment described above, the supply tank 911 and the recovery tank 921 correspond to an example of the "first reservoir tank" or the "second reservoir tank" of the present invention, respectively, the ejection head H corresponds to an example of the "recording head" of the present invention, the pressure generating unit 93 and the pressure generating unit 94 correspond to an example of the "first pressure generating means" or the "second pressure generating means" of the present invention, respectively, the pressure transmission pipe 934 and the pressure transmission pipe 944 correspond to an example of the "first air pipe" or the "second air pipe" of the present invention, and the air filter Fa and air filter Fb each correspond to an example of a "first air filter" or a "second air filter" of the present invention, sensors Sa and Sb each correspond to an example of a "sensor" of the present invention, air buffers 97a and 97b each correspond to an example of an "air buffer" of the present invention, UI11 corresponds to an example of an "alarm unit" of the present invention, circulation pump 952 corresponds to an example of a "circulation pump" of the present invention, and recovery pump 963 and supply pump 964 each correspond to an example of a "first pump" or a "second pump" of the present invention.

[0081] The present invention is not limited to the above-described embodiment, and various modifications other than those described above are possible without departing from the spirit of the present invention. For example, the mode executed when the sensor Sa or the sensor Sb detects ink or an air bubble is not limited to the second emergency mode, but may be the first emergency mode.

[0082] Furthermore, the specific configuration of the air buffer main body 973 of the air buffers 97a, 97b does not need to be the piping described above. In other words, any configuration that has the function of slowing the speed at which air travels through the air path from the sensors Sa, Sb to the air filters Fa, Fb, compared to when the air path is connected only by the pressure transmission piping 934, 944, can be used as an air buffer. FIGS. 7A and 7B are schematic diagrams showing modified air buffers. In FIG. 7A, the air buffer main body 973 is a cylindrical tank. The inner diameter of this tank is larger than the inner diameters of the horizontal piping 74 and the connecting piping 75. In addition, in FIG. 7B, the air buffer main body 973 is a spiral piping. In other words, by configuring the piping in a spiral shape, the length of the piping is secured and the volume of the air buffer main body 973 is increased.

[0083] Furthermore, the specific type of exhaust pump 932 and exhaust pump 942 is not limited to a diaphragm pump. [Industrial Applicability]

[0084] The present invention is applicable to all techniques for dealing with the overflow of ink or air bubbles from a reservoir tank that communicates with a print head that ejects ink. [Explanation of symbols]

[0085] 11...UI 911…supply tank 921...Recovery tank 93...Pressure generating section 934...Pressure transmission piping 94...Pressure generating section 944...Pressure transmission piping 952...Circulation pump 963...Recovery pump 964...Supply pump 97a...Air buffer Fa...Air filter Fb...Air filter H...Discharge head Sa…sensor

Claims

1. a first reservoir tank for storing ink; a recording head having an ink storage chamber connected to a first ink storage section that is a portion of the first reservoir tank below the ink liquid surface and communicating with the first ink storage section, the recording head discharging ink stored in the ink storage chamber from nozzles; a first pressure generating means for generating a first pressure; a first air pipe that connects a first space above the ink surface in the first reservoir tank to the first pressure generating means and applies the first pressure generated by the first pressure generating means to the first space; a first air filter provided in the first air piping between the first reservoir tank and the first pressure generating means, for removing foreign matter from the air in the first air piping; a sensor for detecting ink or air bubbles in the first air pipe between the first reservoir tank and the first air filter; A printing device comprising:

2. 2. The printing device of claim 1, further comprising an air buffer attached to the first air line between the sensor and the first air filter.

3. 3. The printing apparatus according to claim 2, wherein the volume of the air buffer is smaller than the volume of the first reservoir tank.

4. 4. The printing apparatus according to claim 1, further comprising a notification unit that notifies a user when the sensor detects ink or air bubbles.

5. a second reservoir tank for storing ink; a second pressure generating means for generating a second pressure; a second air pipe that connects a second space above the ink liquid surface in the second reservoir tank to the second pressure generating means and applies the second pressure generated by the second pressure generating means to the second space; a control unit that controls the first pressure generating means and the second pressure generating means; Furthermore, the ink storage chamber of the recording head is connected to a second ink storage section that is a portion of the second reservoir tank below the ink liquid surface, and communicates with the second ink storage section; 2. The printing device according to claim 1, wherein the control unit controls the first pressure generating means and the second pressure generating means so that the first pressure and the second pressure become the same emergency pressure when the sensor detects ink or an air bubble.

6. the first reservoir tank and the second reservoir tank are disposed above the recording head; 6. A printing device according to claim 5, wherein the emergency pressure is a pressure that prevents ink from flowing out of the nozzles against a difference between an ink head pressure caused by a difference in height between the first reservoir tank and the recording head and an ink head pressure caused by a difference in height between the second reservoir tank and the recording head.

7. further comprising a circulation pump that transfers ink between the first reservoir tank and the second reservoir tank; The printing apparatus according to claim 5 , wherein the control unit stops the circulation pump when the sensor detects ink or air bubbles.

8. A main tank that stores ink; a first pump that transfers ink between the main tank and the first reservoir tank; a second pump that transfers ink between the main tank and the second reservoir tank; Equipped with The printing apparatus according to claim 5 , wherein the control unit stops the first pump and the second pump when the sensor detects ink or air bubbles.

9. applying the first pressure generated by a first pressure generating means to a first space via a first air pipe connecting a first space above the ink liquid level in a first reservoir tank that stores ink to a first pressure generating means that generates a first pressure; a step in which a recording head having an ink storage chamber connected to a first ink storage section that is a portion of the first reservoir tank below the ink liquid surface and communicating with the first ink storage section ejects ink stored in the ink storage chamber from a nozzle; a step of detecting ink or air bubbles in the first air pipe between the first reservoir tank and the first pressure generating means, the step of detecting ink or air bubbles in the first air pipe between the first reservoir tank and the first air filter that removes foreign matter from the air in the first air pipe and the first reservoir tank; A printing control method comprising:

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