Printer and ink meniscus generation method

Abstract

To start a vacuum pump for adjusting a meniscus shape of ink discharged through a nozzle with a simple sequence.SOLUTION: Pressure P1 applied to a gas-liquid interface L1 is adjusted by evacuating, by an exhaust pump 932, a pressure tank 931 connected to a space 911G above the gas-liquid interface L1 of a supply tank 911 to communicate with the space 911G. In this case, discharge piping 933 is used for connecting the pressure tank 931 and the exhaust pump 932. This discharge piping 933 connects the pressure tank 931 and the exhaust pump 932 without an electromagnetic valve between, and communicates the exhaust pump 932 with the pressure tank 931. In other words, there is no electromagnetic valve between the pressure tank 931 and the exhaust pump 932. Thus, a sequence of opening the electromagnetic valve before starting the exhaust pump 932 is made unnecessary.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a technique for adjusting the meniscus shape of ink ejected by an inkjet method. [Background technology]

[0002] Patent Document 1 describes a printing device that performs printing by ejecting ink from nozzles using an inkjet method. In such a printing device, the meniscus shape of the ink in the nozzle is important for proper ink ejection. Therefore, Patent Document 1 describes a method in which an air chamber connected to an inkjet unit that ejects ink is evacuated using a vacuum pump, thereby generating a desired pressure in the air chamber and optimizing the ink meniscus shape. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5777581 Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, a solenoid valve is provided between the vacuum pump and the air chamber. In this configuration, if the vacuum pump is started with the solenoid valve closed, the vacuum pump may malfunction. Therefore, it is necessary to open the solenoid valve before starting the vacuum pump, which makes the sequence for starting the vacuum pump complicated.

[0005] The present invention has been made in view of the above-mentioned problems, and has as its object to enable a vacuum pump for adjusting the meniscus shape of ink ejected from a nozzle to be started in a simple sequence. [Means for solving the problem]

[0006] The printing device according to the present invention comprises a main tank for storing ink, a reservoir tank for storing ink supplied from the main tank, a recording head having an ink storage chamber connected to the ink storage section which is the part of the reservoir tank below the ink liquid level and communicating with the ink storage section, and which ejects the ink stored in the ink storage chamber from a nozzle, an air tank connected to the space above the ink liquid level in the reservoir tank and communicating with the space, a vacuum pump, and a connection section which connects the vacuum pump and the air tank without an electromagnetic valve to communicate between the vacuum pump and the air tank, and the vacuum pump adjusts the pressure applied to the liquid level in the reservoir tank by evacuating the air tank through the connection section.

[0007] The ink meniscus generating method according to the present invention includes the steps of: storing ink supplied from a main tank that stores ink in a reservoir tank; a recording head having an ink storage chamber that is connected to an ink storage section that is a portion of the reservoir tank below the ink liquid level and that communicates with the ink storage section, ejecting the ink stored in the ink storage chamber from a nozzle; and a step of connecting an air tank that is connected to a space in the reservoir tank above the ink liquid level and that communicates with the space to a vacuum pump without using an electromagnetic valve, and adjusting the pressure applied to the liquid level in the reservoir tank by evacuating the air tank through a connection that communicates between the vacuum pump and the air tank.

[0008] In the present invention (printing apparatus and ink meniscus generating method) configured as described above, ink supplied from a main tank is stored in a reservoir tank. The print head also has an ink storage chamber connected to an ink storage section in the reservoir tank below the ink liquid level (gas-liquid interface) and communicating with the ink storage section, and ink stored in the ink storage chamber is ejected from the nozzle. The pressure applied to the gas-liquid interface is adjusted to optimize the ink meniscus shape in the nozzle. Specifically, the pressure applied to the gas-liquid interface is adjusted by evacuating an air tank connected to a space in the reservoir tank above the gas-liquid interface and communicating with that space using a vacuum pump. In this case, a connection is used to connect the air tank to the vacuum pump. This connection connects the air tank to the vacuum pump without an electromagnetic valve, thereby communicating the vacuum pump with the air tank. In other words, no electromagnetic valve is interposed between the air tank and the vacuum pump. This eliminates the need for a sequence such as opening an electromagnetic valve before starting the vacuum pump. As a result, it is possible to start the vacuum pump, which adjusts the meniscus shape of the ink ejected from the nozzle, in a simple sequence.

[0009] The printing device may also be configured so that the vacuum pump is a diaphragm pump. The diaphragm pump has a built-in check valve. Therefore, when the diaphragm pump stops, the check valve prevents air from passing through the diaphragm pump toward the air tank. This allows the negative pressure generated in the air tank to be maintained.

[0010] The printing device may be configured so that the connector is a resin pipe. In this configuration, the connector can be easily realized by the resin pipe.

[0011] The printing device may also be configured to further include a check valve connected to the exhaust port of the vacuum pump and communicating with the exhaust port, the check valve allowing air to pass from the exhaust port toward the check valve and prohibiting air from passing from the check valve toward the exhaust port. In this configuration, when the vacuum pump stops, the check valve prevents air from passing through the vacuum pump toward the air tank. This allows the negative pressure generated in the air tank to be maintained.

[0012] The printing device may further include an atmosphere release pipe connected at one end to the air tank and open at the other end to the atmosphere, an atmosphere release solenoid valve disposed midway along the atmosphere release pipe, and an air filter disposed on the atmosphere release pipe between the atmosphere release solenoid valve and the air tank and communicating with the air tank, so that when the atmosphere release solenoid valve is closed, the air tank is isolated from the atmosphere, and when the atmosphere release solenoid valve is opened, the air tank is opened to the atmosphere via the air filter. With this configuration, the air filter can prevent foreign matter from entering the air tank when the air tank is opened to the atmosphere. [Effects of the Invention]

[0013] As described above, according to the present invention, it is possible to start the vacuum pump for adjusting the meniscus shape of ink ejected from the nozzles in a simple sequence. [Brief explanation of the drawings]

[0014] [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. 10 is a diagram schematically illustrating a modified example of the ink circulation mechanism. DETAILED DESCRIPTION OF THE INVENTION

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] Fig. 2 is a diagram that schematically shows the bottom surface of the ejection head H provided in the head units 321 and 331, and Fig. 3 is a diagram that schematically shows the ejection head H and an ink circulation mechanism that circulates and supplies ink to the ejection head H. 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.

[0027] 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.

[0028] 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. Furthermore, 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. In recent years, higher printing resolution has been required of ejection heads, and accordingly the inner diameter of the nozzles of ejection heads has become smaller.

[0029] 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.

[0030] 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.

[0031] 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 92b 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 level), and air is present in a space 921G above the gas-liquid interface L2.

[0032] The ink return mechanism 9c has a return pipe 951 that connects the recovery tank 921 and the supply tank 911, and a circulation pump 952 that is interposed midway along the return pipe 951. The return pipe 951 connects and communicates the ink storage section 921L of the recovery tank 921 with the ink storage section 911L of the supply tank 911. Therefore, when the circulation pump 952 drives the ink in the return pipe 951 from the recovery tank 921 toward the supply tank 911, the ink is sent 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 send ink along the first path Ca that leads from the recovery tank 921 to the supply tank 911.

[0033] 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 in air from an intake port Gi and discharges it from an exhaust port Go. This exhausts air 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.

[0034] That is, the pressure generating unit 93 has a resin exhaust pipe 933 that connects the pressure tank 931 and the intake port Gi of the exhaust pump 932, and the pressure tank 931 and the intake port Gi are communicated by the exhaust pipe 933. Therefore, when the exhaust pump 932 exhausts air in the exhaust direction Dg, air flows out from the pressure tank 931 into the exhaust pipe 933 and is exhausted to the atmosphere. This generates pressure P1 in the pressure tank 931. 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 pressure P1 in the pressure tank 931 is maintained.

[0035] 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 this pressure transmission pipe 934 communicates the pressure tank 931 and the space 911G of the supply tank 911. 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.

[0036] 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 on the atmosphere release pipe 935 so as to be located between the atmosphere release solenoid valve 936 and the pressure tank 931. One end of the atmosphere release pipe 935 is connected to the pressure tank 931, and the other end of the atmosphere release pipe 935 is open to the atmosphere. 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, an air filter 937 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. There are no moving parts such as valves in the portion of the atmosphere release pipe 935 between the pressure tank 931 and the air filter 937. There are also no moving parts such as valves in the pressure transmission pipe 934.

[0037] Here, the air filter 937 is located closer to the pressure tank 931 than the atmosphere release solenoid valve 936. Therefore, even if dust is generated when the atmosphere release solenoid valve 936 operates, the dust is removed by the air filter 937 and does not flow into the pressure tank 931. Because the gas in the pressure tank 931 is in communication with the ink in the supply tank 911, if the gas in the pressure tank 931 is contaminated with dust or the like, there is a risk that the ink in the supply tank 911 will be contaminated. This dust can clog the nozzles Hn or otherwise cause malfunctions of the ejection head H. On the other hand, according to this embodiment, the air filter 937 can remove even minute dust particles that are generated by the atmosphere release solenoid valve 936, making it possible to further reduce the risk of malfunctions of the ejection head H.

[0038] 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 exhausts air 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.

[0039] That is, the pressure generating unit 94 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 in communication with each other via the exhaust pipe 943. Therefore, when the exhaust pump 942 exhausts air in the exhaust direction Dg, air flows out from the pressure tank 941 into the exhaust pipe 943 and is exhausted to the atmosphere. This generates pressure P2 in the pressure tank 941. 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 pressure P2 in the pressure tank 941 is maintained.

[0040] 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 this pressure transmission pipe 944 communicates the pressure tank 941 and the space 921G of the recovery tank 921. 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.

[0041] 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 along the atmosphere release pipe 945, and an air filter 947 provided on the atmosphere release pipe 945 so as to be located between the atmosphere release solenoid valve 946 and the pressure tank 941. One end of the atmosphere release pipe 945 is connected to the pressure tank 941, and the other end of the atmosphere release pipe 945 is open to the atmosphere. 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 opened, 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, an air filter 947 between the pressure tank 941 and the atmospheric release solenoid valve 946 removes foreign matter from the air before it flows into the pressure tank 941 .

[0042] There are no particular moving parts in the part of the atmospheric release pipe 945 between the pressure tank 941 and the air filter 947. Furthermore, there are no moving parts such as valves in the pressure transmission pipe 944 either.

[0043] Here, the air filter 947 is located closer to the pressure tank 941 than the atmosphere release solenoid valve 946. Therefore, even if dust is generated when the atmosphere release solenoid valve 946 operates, the dust is removed by the air filter 947 and does not flow into the pressure tank 941. Because the gas in the pressure tank 941 is in communication with the ink in the recovery tank 921, if the gas in the pressure tank 941 is contaminated with dust or the like, there is a risk that the ink in the recovery tank 921 will be contaminated. This dust can clog the nozzles Hn or otherwise cause malfunctions of the ejection head H. On the other hand, according to this embodiment, the air filter 947 can remove even minute dust particles that are generated by the atmosphere release solenoid valve 946, making it possible to further reduce the risk of malfunctions of the ejection head H.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] In the ink circulation mechanism 9 configured in this manner, by operating the recovery pump 963 and the supply pump 964, ink flows along the third path Cc that runs from the supply tank 911 to the recovery tank 921 via the main tank 96. Furthermore, the ink that has flowed 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 recovery tank 921 via the main tank 96, and then returns to the supply tank 911.

[0048] In the embodiment described above, ink supplied from the main tank 96 is stored in a supply tank 911 (reservoir tank). The ejection head H (recording head) has an ink supply chamber Hc (ink storage chamber) connected to an ink storage section 911L below the gas-liquid interface L1 in the supply tank 911 and communicating with the ink storage section 911L. The ink stored in the ink supply chamber Hc is ejected from the nozzle Hn. To optimize the meniscus shape of the ink in the nozzle Hn, a pressure P1 applied to the gas-liquid interface L1 is adjusted. Specifically, the pressure P1 applied to the gas-liquid interface L1 is adjusted by evacuating a pressure tank 931 (air tank) connected to a space 911G above the gas-liquid interface L1 in the supply tank 911 and communicating with the space 911G, using an exhaust pump 932 (vacuum pump). An exhaust pipe 933 (connector) is used to connect the pressure tank 931 and the exhaust pump 932. This exhaust pipe 933 connects the pressure tank 931 and the exhaust pump 932 without an electromagnetic valve, and communicates between the exhaust pump 932 and the pressure tank 931. In other words, no electromagnetic valve is interposed between the pressure tank 931 and the exhaust pump 932. Therefore, there is no need for a sequence such as opening the electromagnetic valve before starting the exhaust pump 932. As a result, it is possible to start the exhaust pump 932, which adjusts the meniscus shape of the ink ejected from the nozzle Hn, with a simple sequence.

[0049] Ink supplied from the main tank 96 is stored in a recovery tank 921 (reservoir tank). The ejection head H has an ink supply chamber Hc connected to an ink storage section 921L below the ink gas-liquid interface L2 of the recovery tank 921 and communicating with the ink storage section 921L, and the ink stored in the ink supply chamber Hc is ejected from the nozzle Hn. In order to optimize the meniscus shape of the ink in the nozzle Hn, a pressure P2 applied to the gas-liquid interface L2 is adjusted. Specifically, the pressure P2 applied to the gas-liquid interface L2 is adjusted by evacuating a pressure tank 941 (air tank) connected to a space 921G above the gas-liquid interface L2 of the recovery tank 921 and communicating with the space 921G using an exhaust pump 942 (vacuum pump). At this time, an exhaust pipe 943 (connection section) is used to connect the pressure tank 941 and the exhaust pump 942. This exhaust pipe 943 connects the pressure tank 941 and the exhaust pump 942 without an electromagnetic valve, and communicates the exhaust pump 942 with the pressure tank 941. In other words, no electromagnetic valve is interposed between the pressure tank 941 and the exhaust pump 942. Therefore, there is no need for a sequence such as opening the electromagnetic valve before starting the exhaust pump 942. As a result, it is possible to start the exhaust pump 942, which adjusts the meniscus shape of the ink ejected from the nozzle Hn, with a simple sequence.

[0050] Furthermore, the exhaust pump 932 is a diaphragm pump. The diaphragm pump has a built-in check valve. Therefore, when the diaphragm pump stops, the check valve blocks the flow of air passing through the diaphragm pump toward the supply tank 911. This makes it possible to maintain the pressure P1 (negative pressure) generated in the supply tank 911. In other words, simply stopping the exhaust pump 932 can prevent outside air from flowing from the exhaust port Go of the exhaust pump 932 toward the exhaust pipe 933. In this way, outside air can be prevented from flowing from the exhaust pipe 933 into the pressure tank 931 without providing a valve such as a solenoid valve in the exhaust pipe 933, thereby reducing the number of parts and the cost of the device.

[0051] Furthermore, the exhaust pump 942 is a diaphragm pump. The diaphragm pump has a built-in check valve. Therefore, when the diaphragm pump stops, the check valve blocks the flow of air passing through the diaphragm pump toward the pressure tank 941. This makes it possible to maintain the pressure P2 generated in the pressure tank 941. In other words, simply stopping the exhaust pump 942 can prevent outside air from flowing from the exhaust port Go of the exhaust pump 942 toward the exhaust pipe 943. In this way, outside air can be prevented from flowing from the exhaust pipe 943 into the pressure tank 941 without providing a valve such as a solenoid valve in the exhaust pipe 943, thereby reducing the number of parts and the cost of the device.

[0052] Moreover, the pressure transmission pipe 934 is made of resin. With this configuration, the exhaust pump 932 and the pressure tank 931 can be easily connected by the resin pipe without using a solenoid valve.

[0053] Moreover, the pressure transmission pipe 944 is made of resin. With this configuration, the exhaust pump 942 and the pressure tank 941 can be easily connected by the resin pipe without using a solenoid valve.

[0054] Also provided are an air filter 937 connected to and communicating with the pressure tank 931, and an atmosphere release solenoid valve 936 connected to and communicating with the air filter 937. When the atmosphere release solenoid valve 936 is closed, the pressure tank 931 is isolated from the atmosphere, and when the atmosphere release solenoid valve 936 is opened, the pressure tank 931 is opened to the atmosphere via the air filter 937. With this configuration, when the pressure tank 931 is opened to the atmosphere, the air filter 937 can prevent foreign matter from entering the pressure tank 931.

[0055] Also provided are an air filter 947 connected to and communicating with the pressure tank 941, and an atmosphere release solenoid valve 946 connected to and communicating with the air filter 947. When the atmosphere release solenoid valve 946 is closed, the pressure tank 941 is isolated from the atmosphere, and when the atmosphere release solenoid valve 946 is opened, the pressure tank 941 is opened to the atmosphere via the air filter 947. With this configuration, when the pressure tank 941 is opened to the atmosphere, the air filter 947 can prevent foreign matter from entering the pressure tank 941.

[0056] In the embodiment described above, the main tank 96 corresponds to an example of the "main tank" of the present invention, the supply tank 911 and the recovery tank 921 correspond to an example of the "reservoir tank" of the present invention, the ink storage section 911L and the ink storage section 921L correspond to an example of the "ink storage section" of the present invention, the ink supply chamber Hc corresponds to an example of the "ink storage chamber" of the present invention, the nozzle Hn corresponds to an example of the "nozzle" of the present invention, the ejection head H corresponds to an example of the "recording head" of the present invention, and the space 911G and the space 921G correspond to an example of the "space" of the present invention. pressure tank 931 and pressure tank 941 correspond to an example of an "air tank" of the present invention; exhaust pump 932 and exhaust pump 942 correspond to an example of a "vacuum pump" of the present invention; exhaust pipe 933 and exhaust pipe 943 correspond to an example of a "connection part" of the present invention; printing device 3 corresponds to an example of a "printing device" of the present invention; air filter 937 and air filter 947 correspond to an example of an "air filter" of the present invention; and atmosphere release solenoid valve 936 and atmosphere release solenoid valve 946 correspond to an example of an "atmospheric release solenoid valve" of the present invention.

[0057] The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. Figure 4 is a diagram showing a schematic diagram of a modified ink circulation mechanism. The difference from the example in Figure 3 is that check valves 938 and 948 are provided.

[0058] In the ink supply mechanism 9a, the check valve 938 is provided in the exhaust pipe 933 so as to be interposed between the exhaust port Go of the exhaust pump 932 and the atmosphere. This check valve 938 allows airflow from the exhaust port Go of the exhaust pump 932 toward the atmosphere, while blocking airflow from the atmosphere toward the exhaust port Go of the exhaust pump 932.

[0059] In the ink recovery mechanism 9b, the check valve 948 is provided in the exhaust pipe 943 so as to be interposed between the exhaust port Go of the exhaust pump 942 and the atmosphere. This check valve 948 allows airflow from the exhaust port Go of the exhaust pump 942 toward the atmosphere, while blocking airflow from the atmosphere toward the exhaust port Go of the exhaust pump 942.

[0060] In this modification, a check valve 938 is provided that is connected to the exhaust port Go of the exhaust pump 932 and communicates with the exhaust port Go. The check valve 938 allows air to pass from the exhaust port Go toward the check valve 938, and prohibits air from passing from the check valve 938 toward the exhaust port Go. With this configuration, when the exhaust pump 932 stops, the check valve 938 blocks the flow of air passing through the exhaust pump 932 toward the pressure tank 931. Therefore, the pressure P1 (negative pressure) generated in the pressure tank 931 can be maintained.

[0061] Also provided is a check valve 948 that is connected to and communicates with an exhaust port Go of the exhaust pump 942. The check valve 948 allows air to pass from the exhaust port Go toward the check valve 948, and prohibits air from passing from the check valve 948 toward the exhaust port Go. With this configuration, when the exhaust pump 942 stops, the check valve 948 blocks the flow of air passing through the exhaust pump 942 toward the pressure tank 941. Therefore, the pressure P2 (negative pressure) generated in the pressure tank 941 can be maintained.

[0062] Furthermore, the specific type of exhaust pump 932 and exhaust pump 942 is not limited to a diaphragm pump. [Industrial Applicability]

[0063] The present invention is applicable to all techniques for adjusting the meniscus shape of ink ejected by an inkjet method. [Explanation of symbols]

[0064] 3...Printing device 911…supply tank 911G…Space 911L...Ink reservoir 921...Recovery tank 921G…Space 921L...Ink reservoir 931...Pressure tank 932…Exhaust pump 933...Exhaust piping 936...Atmospheric release solenoid valve 937...Air filter 941...Pressure tank 942…Exhaust pump 943...Exhaust piping 946...Atmospheric release solenoid valve 947...Air filter 96...Main tank H...Discharge head Hc...Ink supply chamber Hn...Nozzle

Claims

1. A main tank that stores ink; a reservoir tank for storing ink supplied from the main tank; a recording head having an ink storage chamber connected to an ink storage section that is a portion of the reservoir tank below the ink liquid surface and communicating with the ink storage section, the recording head discharging ink stored in the ink storage chamber from nozzles; an air tank connected to a space above the ink level in the reservoir tank and communicating with the space; A vacuum pump and a connection portion that connects the vacuum pump and the air tank without an electromagnetic valve, thereby communicating the vacuum pump and the air tank; Equipped with The vacuum pump adjusts the pressure applied to the liquid surface of the reservoir tank by evacuating the air tank through the connection portion.

2. 2. The printing apparatus according to claim 1, wherein the vacuum pump is a diaphragm pump.

3. The printing device according to claim 1 , wherein the connection portion is a resin pipe.

4. a check valve connected to an exhaust port of the vacuum pump and communicating with the exhaust port; 2. The printing device according to claim 1, wherein the check valve allows air to pass from the exhaust port toward the check valve and prohibits air from passing from the check valve toward the exhaust port.

5. an air release pipe having one end connected to the air tank and the other end open to the atmosphere; an atmosphere release solenoid valve interposed in the middle of the atmosphere release pipe; an air filter provided in the atmosphere release pipe so as to be interposed between the atmosphere release electromagnetic valve and the air tank and communicating with the air tank; Furthermore, When the atmospheric release solenoid valve is closed, the air tank is isolated from the atmosphere.

5. The printing apparatus according to claim 1, wherein when the atmosphere release electromagnetic valve is opened, the air tank is opened to the atmosphere via the air filter.

6. A step of storing ink supplied from a main tank that stores ink in a reservoir tank; a step in which a recording head having an ink storage chamber connected to an ink storage section that is a portion of the reservoir tank below the ink liquid surface and communicating with the ink storage section ejects ink stored in the ink storage chamber from a nozzle; a step of connecting an air tank connected to a space above the ink surface in the reservoir tank and communicating with the space to a vacuum pump without using an electromagnetic valve, and adjusting the pressure applied to the liquid surface in the reservoir tank by evacuating the air tank through a connection part that communicates between the vacuum pump and the air tank; An ink meniscus generating method comprising:

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