JP4534245B2 - Inkjet printing device - Google Patents

Description

  The present invention relates to an ink jet printing apparatus, and more particularly to an ink jet printing apparatus having an ink tank mounting type head, an ink supply method of the apparatus, and an ink deaeration method.

  Conventionally, as an ink tank mounting type head, a horizontal jet type head in which nozzles are arranged horizontally is well known. In this horizontal jet type nozzle, ink is bent in the direction of gravity and ink after landing on the paper. Ink jet printers with heads facing downward have been developed due to problems such as dripping.

  When the ink tank is disposed above the head with the head facing down, it is necessary to maintain the ink tank portion at a negative pressure in order to apply an appropriate negative pressure to the nozzles of the inkjet head. For this reason, a method has already been proposed in which the inside of the ink tank is formed into a bag shape and a negative pressure is created by loading a leaf spring or the like into the bag, or a method of creating a negative pressure by filling a continuous pore-shaped sponge inside the ink tank. Has been.

  However, with these methods, it is difficult to always apply an appropriate negative pressure to the nozzles of the inkjet head according to the amount of ink consumed, and it is not suitable for a structure equipped with a large-capacity ink tank for industrial use. is there.

  As a technique related to the present invention described below, Patent Document 1 discloses a technique for replacing an ink tank without stopping printing at the time of ink replacement. Patent Document 2 discloses a technique for forcibly controlling ink supply to a sub-tank whose remaining amount has not reached the upper limit when the remaining amount of ink in the main tank decreases. Patent Document 3 discloses a method of removing dissolved air in ink by reducing the space facing the ink to a pressure equal to or lower than atmospheric pressure through a gas permeable film.

JP 2001-113716 A JP 2002-120374 A Japanese Patent Laid-Open No. 2003-341083

  In view of the above, the present invention stores a large amount of ink on the top of the ink jet head by always forming an appropriate negative pressure on the nozzle of the ink jet head according to the ink consumption and the ink water level in the ink chamber. It is an object of the present invention to provide an ink jet printing apparatus that is equipped with an ink tank that can move and integrally move an ink jet head and a large capacity ink tank.

In order to achieve the above object, the present invention provides an inkjet head having a plurality of nozzles for ejecting ink droplets in the direction of gravity, an ink tank for storing a large volume of ink disposed above the inkjet head, and Provided in an ink supply path between the ink tank and the inkjet head, and connected to a first ink chamber, a second ink chamber, and first and second ink chambers, respectively, for storing small volumes of ink; An ink supply method for an ink jet printing apparatus having an ink chamber negative pressure adjusting means for adjusting a negative pressure applied to a nozzle of an ink jet head, wherein ink is supplied from a first ink chamber to the ink jet head. When the second ink chamber is filled with ink from the large-capacity ink tank, and the ink level in the first ink chamber drops below a predetermined level. There is one feature that has to supply the ink from the second ink chamber to the ink jet head.

Another feature of the present invention is that an inkjet head having a plurality of nozzles that eject ink droplets in the direction of gravity, an ink tank that is disposed above the inkjet head and stores a large volume of ink, and the ink tank, An ink chamber for storing a small amount of ink in the ink tank provided in an ink supply path between the ink jet head and the ink chamber is connected to the ink chamber and applied to the nozzle of the ink jet head. An ink chamber negative pressure adjusting means for adjusting a negative pressure, wherein the ink chamber is moved integrally with the ink jet head and the large-capacity ink tank, and the ink chamber includes a first ink compartment and a second ink compartment. An ink compartment for opening and closing a supply path of ink supplied from the ink tank to the second ink compartment; An electromagnetic valve; an electromagnetic valve for opening and closing a supply path of ink supplied from the first ink compartment to the inkjet head; an ink remaining amount sensor for detecting an ink amount in the first ink compartment; It has an air reservoir in the upper part of the compartment, and is equipped with a vacuum pump communicating with the air reservoir and a pressure regulator for reducing pressure.

Another feature of the present invention is that an inkjet head having a plurality of nozzles that eject ink droplets in the direction of gravity, an ink tank that is disposed above the inkjet head and stores a large volume of ink, and the ink tank, A first ink chamber and a second ink chamber, which are provided in an ink supply path with the ink jet head and store a small amount of ink, respectively, and are connected to the first and second ink chambers. In the ink jet printing apparatus, comprising: an ink chamber negative pressure adjusting means for adjusting a negative pressure applied to the nozzle, wherein the ink jet head and the large capacity ink tank are integrally moved to perform printing. Each of the ink chambers has a first ink compartment and a second ink compartment, and the second ink chambers of the first and second ink chambers from the ink tank. A solenoid valve for opening and closing a supply path of ink supplied to the ink compartment, and an electromagnetic for opening and closing the supply path of ink supplied from the first ink compartment of the first and second ink chambers to the inkjet head. A valve, an ink remaining amount sensor for detecting the amount of ink in the first ink compartments of the first and second ink chambers, and an air reservoir in the upper part of the first ink compartments of the first and second ink chambers And having a vacuum pump communicating with each air reservoir and a pressure regulator for reducing the pressure of the vacuum pump.

Another feature of the present invention is that the pressure of the air reservoir in the upper part of the first ink compartment is P, the specific gravity of the ink is ρ, and the height from the nozzle surface of the inkjet head to the surface level of the ink in the first ink compartment is H. When
P = −ρ · H−X (Pa)
And adjusting the pressure so that X is in the range of 100 to 300.

Another feature of the present invention resides in that when the ink jet head is in a non-printing state, the first and second ink chambers are maintained in a high vacuum state to degas the ink in the ink chambers.

  According to the present invention, the ink chamber is provided between the ink tank and the ink supply path of the ink jet head, and the ink chamber has means for properly maintaining the negative pressure always applied to the nozzle according to the ink water level of the ink chamber. It is possible to provide an ink jet apparatus having a structure in which the nozzles of the head are provided downward and ink droplets are ejected in the direction of gravity, and a large-capacity ink tank is mounted.

  FIG. 1 is a schematic configuration diagram of an ink jet printing apparatus showing a first embodiment of the present invention.

  In FIG. 1, an inkjet head 11 having a plurality of nozzles (not shown) for ejecting ink droplets in the direction of gravity at the lower end of a support guide 13, an ink tank 81 at the top, and an ink chamber 31 at the center. . An ink tank side ink conduit 40 is attached between the ink tank 81 and the ink chamber 31 so that ink can be supplied to the ink chamber 31. An ink path opening / closing solenoid valve 32 is attached in the middle of the ink conduit 40 so that ink supply can be adjusted. In addition, two ink sensors 82 and 83 are attached to the ink tank 81 so that the ink tank 81 can detect the amount of ink 85 in the tank 81.

  A head-side ink conduit 39 is disposed between the ink chamber 31 and the head 11, and a filter unit 12 for removing foreign matter in the ink is provided in front of the head. Further, an ink path opening / closing electromagnetic valve 33 for adjusting ink supply to the head 11 is attached in the middle of the ink conduit 39.

  The ink chamber 31 has two chambers, a first ink compartment 34 and a second ink compartment 35. The first ink compartment 34 and the second ink compartment 35 communicate with each other through a lower opening. The upper portion of the first ink compartment 34 communicates with the ink conduit 40, and the lower portion of the second ink compartment 35 communicates with the head-side ink conduit 39. Even if the head side ink conduit 39 communicates with the first ink compartment 34, there is no functional problem. However, when air bubbles flow backward from the head 11 and enter the first ink compartment 34, the upper side of the first ink compartment 34 is It is anticipated that the air bubbles accumulated in the air will interfere with the ink supply, so it is better to communicate with the second ink compartment 35 side.

  Two ink sensors 36 and 37 are attached to the second ink compartment 35 at height positions ha and hb from the lower surface of the head 11, respectively. Reference numeral 38 denotes an air reservoir in the upper part of the second ink compartment 35. The air reservoir 38 communicates with the air buffer 72 through a tube 75 and further communicates with the vacuum pump 71. The vacuum pump 71 is connected to an air discharge solenoid valve 76. On the other hand, a pressure regulator 74 for branching in the middle of the tube 75 and adjusting the pressure, and an electromagnetic valve 73 for opening and closing a pipe line to the pressure regulator are attached.

  Next, a pressure adjustment method for forming a negative pressure suitable for printing on the nozzle (not shown) of the inkjet head 11 will be described.

  In the case of a structure in which the nozzle of the inkjet head is provided downward and ink droplets are ejected in the direction of gravity, the gravity of the ink prevents the ink from dripping from the nozzle in a static state (when no electrical signal is applied). It is necessary to apply a negative pressure to the nozzle that balances the pressure applied in the direction. The phenomenon in which the ink in the nozzle becomes concave or convex due to surface tension is called meniscus.

  In general, in order to form a meniscus suitable for printing, it is desirable that the ink water level of the ink chamber for supplying ink is 10 to 30 mm below the nozzle surface of the inkjet head. However, in the case of the above-described first embodiment, the ink water level in the ink compartment 35 is disposed above the nozzle surface of the inkjet head 11 by h, so that a vacuum is applied to form an appropriate negative pressure on the nozzle. A pump 71 is provided to adjust the pressure of the air reservoir 38 to an appropriate negative pressure.

  In order to form a negative pressure in the air reservoir 38, first, the upper and lower electromagnetic valves 32 and 33 of the ink chamber 31 are closed, whereby the ink 85 is transferred from the ink tank 81 to the ink chamber 31 and from the ink chamber 31 to the head 11. After not flowing in, the vacuum pump 71 is driven to open the air solenoid valves 73 and 76 connected to the vacuum pump 71. As a result, the air reservoir 38 in the upper part of the second ink compartment 35 in the ink chamber 31 becomes negative pressure. In the present embodiment, the pressure regulator 74 is adjusted in consideration of the suction capability of the vacuum pump 71, and the suction pressure of the air reservoir 38 is set. FIG. 7 shows an example of the pressure-flow rate characteristic of the vacuum pump 71. The pressure adjustment is performed by attaching a manometer to the air buffer 72 and adjusting the opening amount of the pressure regulator 74.

As described above, in order to form an appropriate meniscus for the nozzle, the negative pressure applied to the nozzle may be −10 mm to −30 mmH ₂ O (= −100 Pa to −300 Pa). When the negative pressure is P, the specific gravity of the ink is ρ, and the water level of the ink with respect to the nozzle surface is h,
P = −ρ · h−X (1)
And P may be controlled so that X = 100 to 300 Pa.

  In order to adjust the pressure of the air reservoir 38 in this way, the following expressions (2) and (3) may be established for the heights ha and hb of the sensors 36 and 37.

P = −ρ · ha−100 (2)
P = −ρ. hb-300 (3)
However, this is an example of a pressure adjustment method, and various other control methods are conceivable. Further, if the pressure adjustment is set once by the pressure adjuster 74 at the first time, it is not necessary to automatically adjust the pressure during the printing operation, so the adjustment work is very easy.

  Next, the ink supply operation of the apparatus of this embodiment will be described with reference to FIG.

  In order to supply ink 85 from the ink tank 81 to the ink chamber 31, the electromagnetic valve 32 on the ink tank 81 side is opened, and the electromagnetic valve 33 on the side supplying ink to the head 11 is closed. Since it is better to keep the air reservoir 38 of the second ink compartment 35 at a negative pressure, the electromagnetic valves 73 and 76 are opened and the vacuum pump 71 is turned on. The ink 85 in the ink tank 81 easily flows into the ink chamber 31 due to the water level difference between the upper surface of the ink tank 81 and the second ink compartment 35.

  When the water level of the ink tank decreases and becomes lower than the position of the lower ink sensor 83, it is necessary to supply ink to the ink tank 81. Ink replenishment can be performed easily by pouring the ink tank 81 from the large capacity ink container (not shown).

  Next, the movement operation of the head 11 will be described.

  In the present embodiment, since the head 11 and the ink tank 81 are integrally formed, the support guide 13 is moved in the vertical and horizontal directions and moved above the medium (not shown). As shown in FIG. 8, the upper and lower electromagnetic valves 32 and 33 of the ink chamber 31 are closed while the head 11 is moving so that ink does not flow from the ink tank 81 to the ink chamber 31 and from the ink chamber 31 to the head 11. Then, the vacuum pump 71 is turned on, and the air solenoid valves 73 and 76 connected to the vacuum pump 71 are opened. As a result, the air reservoir 38 above the second ink compartment 35 in the ink chamber 31 becomes negative pressure. In the structure according to the present embodiment, when the head 11 is moved, the electromagnetic valves 32 and 33 are closed even if the ink in the ink tank 81 is shaken, so that the meniscus of the head 11 is not destroyed.

  Next, the printing operation will be described.

  The support guide 13 is moved to the upper part of the media position (not shown), the electromagnetic valve 32 on the ink tank 81 side is closed, and the electromagnetic valve 33 on the side for supplying ink to the head 11 is opened. Further, in order to keep the air reservoir 38 of the second ink compartment 35 at a negative pressure, the electromagnetic valves 73 and 76 are opened and the vacuum pump 71 is turned on. Since the water level h of the air reservoir 38 of the second ink compartment 35 is maintained at ha> h> hb, a stable meniscus is formed without causing ink leakage from the nozzle even when the solenoid valve 33 is suddenly opened. it can.

  When printing is continued and the water level h of the air reservoir 38 of the second ink compartment 35 falls to hb, which is the position of the lower ink sensor 37, an ink supply signal is generated. At this time, the ink supply operation is returned to the above-described ink supply operation, and the ink supply is continued until the water level h of the air reservoir 38 of the second ink compartment 35 becomes h = ha. During ink supply, printing is interrupted because the electromagnetic valve 33 on the head side is closed. However, since the place of ink replenishment is not selected, ink replenishment can be performed on the medium, and printing can be continuously executed when ink replenishment is completed.

  When printing is completed and the next medium is waited for, the state is stopped for a short time in FIG. The state of each solenoid valve 32, 33, 73 remains the same as during printing, and the vacuum pump 71 remains on. The head can be moved to a standby position (for example, a capping position of the head (not shown)).

  Next, the case of long-term stop will be described.

  When the head 11 is left unprinted for a long time (for example, when it is stopped for a short time of 10 minutes or more), the head 11 is moved to the capping position of the head, and the upper and lower electromagnetic valves 32 in the ink chamber 31 are moved. 33 and the three solenoid valves of the solenoid valve 73 in front of the pressure regulator 74 are closed. Then, since the vacuum pump remains on, the degree of vacuum in the second ink compartment 35 increases. As shown in FIG. 7, when the flow rate becomes almost zero, the pump rises to almost the maximum vacuum. In this embodiment, it is increased to near -50 kPa. When the degree of vacuum is substantially increased, if the vacuum pump air discharge solenoid valve 76 is closed and the vacuum pump 76 is turned off immediately, the air reservoir 38 of the second ink compartment 35 is held in a high vacuum state. Ink in the first ink compartment 34 and the second ink compartment 35 can be degassed. Here, the tube 75 is preferably a nylon resin tube having low air permeability and not crushed even under high vacuum, or a tube having high chemical resistance inside and a two-layer tube using nylon as the outer shell.

  In FIG. 1, the air discharge solenoid valve 76 is attached to the right side of the vacuum pump 71. However, the solenoid valve 76 may be omitted as long as the airtightness when the vacuum pump is stopped is sufficiently secured. In addition, when a suction pump is used instead of the vacuum pump and the hermeticity at the time of stopping is extremely poor, the solenoid valve 76 may be installed on the left side of the pump.

  As described above, according to the first embodiment, an ink chamber is provided in the ink supply path of the large-capacity ink tank and the inkjet head, and means for maintaining the pressure of the air reservoir in the ink chamber at an appropriate negative pressure is provided. Therefore, it is possible to always form an appropriate negative pressure on the nozzles regardless of fluctuations in the ink water level in the ink chamber, and it is therefore possible to provide an ink jet printing apparatus equipped with a large capacity tank.

  Next, a second embodiment of the printing apparatus of the present invention will be described with reference to FIGS. 2, 3, 4-1, 4-2, and 4-3.

  The present embodiment has a structure in which a bag-like container is used instead of the ink tank 81 and ink is filled therein. The advantage in this case is that dust and foreign matter do not enter the ink path because it is only necessary to replace the bag-like ink tank when replenishing ink. Moreover, since it can be set as a sealed container, there also exists an advantage that the deaerated ink can be used.

  FIG. 2 is a view showing the bag-shaped ink tank 91 attached, FIG. 3 is a view showing the bag-shaped ink tank 91 and the mounting member 92, and FIG. The same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

  In FIG. 2, the bag-shaped ink tank 91 is inserted into the mounting member 92 from above. A flexible hose 93 connects between the electromagnetic valve 32 on the ink tank 91 side and the ink tank mounting member 92. As a material, a plastic hose with high ink resistance and a bellows-like stainless steel pipe are used. Next, as shown in FIG. 3, the bag-shaped ink tank 91 is tilted sideways. In order to fix the bag-shaped ink tank 91, a fixing arm (not shown) may be extended from the support guide 13 extending in the lateral direction to hold the body of the ink tank 91.

  FIG. 4A shows the structure of the bag-shaped ink tank 91 on the attachment member 92 side. The bag-shaped ink tank 91 has a slide rod 102 inserted into the mouth portion 101, and an O-ring 103 for preventing ink leakage in the tank is attached to the tip of the slide rod 102. The slide rod 102 is pushed downward by a spring (not shown), and the O-ring 103 prevents ink leakage. Further, another O-ring 104 is inserted into the mouth portion 101.

  FIG. 4B shows the structure of the ink tank mounting member 92. A support column 115 is erected on a part of the support guide 13, and the outer frame 116 of the mounting member 92 is rotatably supported by a fulcrum 114. The inner diameter of the frame 113 is slightly larger than the outer diameter of the mouth portion 101 of the ink tank. An insertion pin 111 having an ink inlet 112 on the side surface is attached to the inside of the frame 113, and the ink inlet 112 communicates with a flexible hose 93.

  FIG. 4C shows a state in which the bag-shaped ink tank 91 is attached to the attachment member 92. The side surface of the insertion pin 111 is sealed by an O-ring 104 inserted in the mouth portion 101 of the bag-shaped ink tank, and the slide rod 102 that prevents leakage of ink in the ink tank 91 is inserted into the insertion pin 111. Therefore, the ink flows into the ink inlet 112 and can be supplied to the ink chamber 31 through the hose 93.

  It is difficult to attach the ink sensors 82 and 83 as shown in FIG. 1 to the bag-shaped ink tank 91. Therefore, in this embodiment, when the ink level does not rise to the position of the upper ink sensor 36 of the second ink compartment 35 even after a predetermined time has passed during ink replenishment, the ink tank replacement time is set. When replacing the ink tank 91, the two solenoid valves 32 and 33 are closed, the fixing arm of the ink tank 91 is removed, the ink tank 91 is set up, and the ink tank 91 is further removed from the mounting member 92. Thereafter, a new ink tank 91 is attached in the reverse procedure. After the new ink tank 91 is attached, ink supply can be resumed and printing can be performed again.

  According to the second embodiment, since the ink tank can be mounted as a bag-like degassing ink bag, ink replenishment is facilitated, and ink can be easily discharged because the inside of the ink path can be maintained without air bubbles remaining. It becomes. Further, after the deaeration ink bag is attached in the direction of gravity, the height when the ink tank is attached can be kept as low as possible by tilting it sideways.

  Next, a third embodiment of the printing apparatus of the present invention will be described with reference to FIGS.

  In this embodiment, two ink chambers 31a and 31b are provided between the ink tank 81 and the head 11, and when one of the ink chambers is used for printing, the other ink chamber fills the ink up to a predetermined position and waits. When the ink in one ink chamber runs out, the other ink chamber is opened to continue printing.

  In FIG. 5, an inkjet head 11 having a plurality of nozzles for ejecting ink droplets in the direction of gravity at the lower end of a support guide 13, an ink tank 81 at the top, and two ink chambers at the center, that is, a first ink chamber 31a, A second ink chamber B31b is attached. The ink tank 81 communicates with the first ink chamber 31a and the second ink chamber 31b through the ink tank side ink conduits 40a and 40b, and ink can be supplied to the two ink chambers 31a and 31b. An ink path opening / closing electromagnetic valve 32a for adjusting ink replenishment is attached in the middle of the ink conduit 40a. An ink path opening / closing electromagnetic valve 32b is attached in the middle of the ink conduit 40b.

  A head-side ink conduit 39 a is disposed between the first ink chamber 31 a and the head 11. Similarly, a head-side ink conduit 39 b is disposed between the second ink chamber 31 b and the head 11. Two ink conduits 39a and 39b are integrated into one in front. An ink path opening / closing electromagnetic valve 33a is attached in the middle of the ink conduit 39a so that the supply of ink to the head 11 can be interrupted. Similarly, an ink path opening / closing electromagnetic valve 33b is attached in the middle of the ink pipe path 39b.

  Air reservoirs 38a and 38b are formed above the two ink chambers 31a and 31b. These air reservoirs 38 a and 38 b are connected to one vacuum pump 71 and an air discharge solenoid valve 76 by a tube 75. An air buffer 72 is attached between the vacuum pump 71 and the air reservoir 38. Moreover, a pressure regulator 74 for branching in the middle of the tube 75 and adjusting the pressure, and an electromagnetic valve 73 for opening and closing a pipe line to the pressure regulator are attached.

  Next, the ink supply operation will be described with reference to FIG. The case where ink is supplied to the first ink chamber 31a out of the two ink chambers will be described as an example.

  In order to supply the ink 85 from the ink tank 81 to the first ink chamber 31 a, the electromagnetic valve 32 a on the ink tank side is opened, and the electromagnetic valve 33 a on the side that supplies ink to the head 11 is closed. The two solenoid valves 32b and 33b on the second ink chamber 31b side are closed because ink is not supplied. Further, since it is better to keep the air reservoirs 38a and 38b in the ink chamber with a negative pressure, the electromagnetic valves 73 and 76 are opened, and the vacuum pump 71 is turned on. The ink 85 in the ink tank 81 easily flows into the first ink chamber 31a due to the water level difference between the upper surface of the ink tank and the first ink compartment 35a of the first ink chamber 31a.

  When the water level of the ink tank 81 decreases and becomes lower than the position of the lower ink sensor 83, it is necessary to supply ink to the ink tank 81. Ink replenishment can be performed easily by pouring the ink tank 81 from the large capacity ink container (not shown). At this time, all the solenoid valves 32a, 33a, 32b, and 33b are closed.

  Next, the movement of the head will be described.

  As shown in FIG. 9, the upper and lower electromagnetic valves 32a, 32b, 33a, 33b of the two ink chambers 31a, 31b are closed while the head is moving, and ink is transferred from the ink tank 81 to the ink chambers 31a, 31b, and the ink chambers. The vacuum pump 71 is turned on so as not to flow into the head 11 from 31a and 31b, and the air solenoid valves 73 and 76 connected to the vacuum pump 71 are opened. As a result, the air reservoirs 38a and 38b above the first ink compartments 35a and 35b in the ink chambers 31a and 31b are held at a negative pressure.

  Next, the printing operation will be described. First, a case where printing is performed using the first ink chamber 31a will be described as an example.

  The support guide 13 is moved to the upper part of the media position (not shown), the electromagnetic valve 32a on the ink tank 81 side is closed, and the electromagnetic valve 33a on the side for supplying ink to the head is opened. The two solenoid valves 32b and 33b on the second ink chamber 31b side are closed. Further, in order to hold the air reservoirs 38a and 38b of the first ink compartments 35a and 35b with a negative pressure, the electromagnetic valves 73 and 76 are opened and the vacuum pump 71 is turned on. Since ink is supplied from the first ink chamber 31a to the head, printing can be executed.

  When printing is continued, the water level h of the air reservoir 38a of the first ink compartment 35a of the first ink chamber 31a is lowered to the position hb of the lower ink sensor 37a, and an ink supply signal is generated. At this time, before supplying ink to the first ink chamber 31a, the ink chamber for supplying ink to the head 11 is instantaneously switched from the first ink chamber 31a to the second ink chamber 31b. The switching method is performed by closing the electromagnetic valve 33a and opening the electromagnetic valve 33b.

  Thereafter, returning to the above-described ink supply operation, the ink supply is continued until the water level h of the air reservoir 38a of the first ink compartment 35a of the first ink chamber 31a becomes h = ha. When the ink in the first ink chamber 31a runs out in this way, the ink in the second ink chamber 31b is used, and the ink in the ink tank 81 is continuously filled by filling the ink in the first ink chamber 31a during that time. Can print. Also, printing by switching the ink chamber in the middle of media printing by switching the ink chamber to be used when the end of the media is performed using a sensor (not shown) that detects the start and end of the print media. You can prevent mistakes.

  This embodiment can be used as an industrial printing apparatus that performs printing of several thousand copies at a time by using this ink supply system.

  When printing is completed and the next medium is waited for, the state is stopped for a short time in FIG. The state of each solenoid valve is the same as during printing, and the vacuum pump 71 remains on. The head 11 can be moved to a standby position, for example, a capping position (not shown) of the head.

  Next, the case of long-term stop will be described.

  When the head 11 is left unprinted for a long time (for example, when it is stopped for a short time of 10 minutes or more), the head 11 is moved to the capping position of the head, and the two ink chambers 31a and 31b are moved. The upper and lower solenoid valves 32a, 33a, 32b, 33b and the solenoid valve 73 in front of the pressure regulator 74 are closed. Then, since the vacuum pump 71 remains on, the degree of vacuum in the first ink compartments 38a and 38b increases. As shown in FIG. 7, when the flow rate becomes almost zero, the pump 71 rises to almost the maximum degree of vacuum. In this embodiment, it is increased to near -50 kPa. When the degree of vacuum is almost increased, if the air discharge solenoid valve 76 of the vacuum pump 71 is closed and the vacuum pump 71 is turned off immediately, the air reservoir 38a and the second ink in the first ink compartment 35a of the first ink chamber 31a. The air reservoir 38b of the first ink compartment 35b of the chamber 31b is held in a high vacuum state, and the ink in the first ink chamber 31a and the second ink chamber 31b can be degassed.

  In this embodiment, the case where there are two ink chambers has been described. However, for the convenience of ink supply, when three or more ink chambers are provided, one ink chamber is used for standby and the rest is used for supplying ink to the head. By doing so, it can be configured with almost the same operation. If the ink sensor positions in the ink chamber are the same regardless of the number of ink chambers, the negative pressure condition of the air reservoir is the same, and the negative pressure can be set with one vacuum pump and a pressure regulator. .

  Next, a fourth embodiment of the device of the present invention will be described with reference to FIG.

In this embodiment, ink is filled in a bag-like container 91 instead of the ink tank 81 of the third embodiment. In the figure, the bag-shaped ink tank 91 is attached to the attachment member 92 and then laid down sideways.
The advantage in this case is that dust and foreign matter do not enter the ink path because it is only necessary to replace the bag-shaped ink tank when replenishing ink. Further, since it can be a sealed container, there is an advantage that continuous printing can be performed until the ink tank is almost empty using the deaerated ink.

  According to the third to fourth embodiments, two ink chambers for holding the meniscus of the ink jet head at a negative pressure suitable for printing are provided between the ink tank and the ink supply path of the ink jet head, and each ink chamber is provided. Since it is configured to be connected to the negative pressure holding means, it is possible to continuously print until the ink in the ink tank is used up.

  In addition, while ink is being supplied from one ink chamber to the inkjet head, the other ink chamber is filled with ink and held at a predetermined pressure, and when the ink level in the first ink chamber drops below a predetermined position, Since ink is supplied from the two ink chambers to the inkjet head, it is possible to continuously supply ink to the head.

  Further, according to the first to fourth embodiments, the ink chamber is divided into the first ink compartment and the second ink compartment, and the electromagnetic valve for opening and closing the ink between the ink tank and the second ink compartment, A solenoid valve for opening and closing the ink in the ink compartment and the ink jet head, two remaining ink sensors for detecting the amount of ink in the first ink compartment, and an air reservoir at the top of the first ink compartment The internal pressure of the air reservoir is set to an arbitrary pressure because it includes a vacuum pump communicating with the air reservoir, a pressure regulator for reducing pressure, and an electromagnetic valve that opens and closes the conduit of the pressure regulator. Is possible.

  Further, when the ink jet head is in a non-printing state, the second ink compartment and the first ink compartment of the ink chamber can be kept in a high vacuum state, and the ink in the ink chamber can be deaerated. It is possible to supply the vaporized ink, and it is possible to greatly reduce nozzle non-ejection due to remaining minute air.

1 is a schematic configuration diagram illustrating a first embodiment of an inkjet printing apparatus according to the present invention. The schematic block diagram which shows the 2nd Example of the inkjet printing apparatus which concerns on this invention. Explanatory drawing which shows the state which fell the bag-shaped ink tank of FIG. Explanatory drawing for demonstrating the attachment state of a bag-shaped ink tank and an attachment member. Explanatory drawing for demonstrating the attachment state of a bag-shaped ink tank and an attachment member. Explanatory drawing for demonstrating the attachment state of a bag-shaped ink tank and an attachment member. The schematic block diagram which shows the 3rd Example of the inkjet printing apparatus which concerns on this invention. The schematic block diagram which shows the 4th Example of the inkjet printing apparatus which concerns on this invention. The pressure-flow rate characteristic diagram of a vacuum pump. It is explanatory drawing for demonstrating operation | movement of the inkjet printing apparatus which concerns on this invention. It is explanatory drawing for demonstrating operation | movement of the inkjet printing apparatus which concerns on this invention.

Explanation of symbols

11: inkjet head, 13: head support guide, 31: ink chamber, 32, 33: solenoid valve, 34: first ink chamber, 35: second ink chamber, 36, 37: ink sensor, 38: ink b chamber 71: Vacuum pump, 73: Solenoid valve, 74: Pressure regulator, 75: Tube, 76: Solenoid valve, 81: Ink tank

Claims (5)

An ink jet head having a plurality of nozzles for ejecting ink droplets in the direction of gravity, an ink tank for storing a large volume of ink disposed above the ink jet head, and an ink supply path between the ink tank and the ink jet head The negative pressure applied to the nozzles of the inkjet head is connected to the first ink chamber, the second ink chamber, and the first and second ink chambers, respectively, for storing a small volume of ink. An ink supply method for an ink jet printing apparatus having an ink chamber negative pressure adjusting means for performing ink supply from a large capacity ink tank to a second ink chamber while supplying ink from the first ink chamber to the ink jet head And when the ink level in the first ink chamber falls below a predetermined level, the ink is ejected from the second ink chamber. Ink supply method for supplying ink to the head. An ink jet head having a plurality of nozzles for ejecting ink droplets in the direction of gravity, an ink tank disposed above the ink jet head and storing a large amount of ink, and an ink between the ink tank and the ink jet head An ink chamber provided in the supply path for storing a small amount of ink in the ink tank, and an ink chamber negative connected to the ink chamber and for adjusting a negative pressure applied to the nozzle of the inkjet head. In an ink jet printing apparatus that includes a pressure adjusting means and moves and prints the ink jet head and the large-capacity ink tank integrally, the ink chamber includes a first ink compartment and a second ink compartment. An electromagnetic valve for opening and closing a supply path of ink supplied from the tank to the second ink compartment; An electromagnetic valve for opening and closing a supply path of ink supplied from the compartment to the inkjet head, an ink remaining amount sensor for detecting the amount of ink in the first ink compartment, and an air reservoir above the first ink compartment An inkjet printing apparatus comprising a vacuum pump communicating with the air reservoir and a pressure regulator for reducing pressure. An inkjet head having a plurality of nozzles that eject ink droplets in the direction of gravity, an ink tank that is disposed above the inkjet head and stores a large volume of ink, and an ink supply path between the ink tank and the inkjet head Are connected to the first and second ink chambers, respectively, for storing a small volume of ink, and negative pressure applied to the nozzles of the inkjet head. An ink chamber negative pressure adjusting means for adjusting, wherein the ink jet head and the large-capacity ink tank are integrally moved to perform printing, and in the ink jet printing apparatus, the first and second ink chambers each include a first ink. The ink tank has a compartment and a second ink compartment, and is supplied from the ink tank to the second ink compartment of the first and second ink chambers. A solenoid valve for opening and closing the ink supply path, an electromagnetic valve for opening and closing the ink supply path supplied to the inkjet head from the first ink compartments of the first and second ink chambers, and the first And an ink remaining amount sensor for detecting the amount of ink in the first ink compartment of the second ink chamber, and an air reservoir in the upper portion of the first ink compartment of the first and second ink chambers. An ink jet printing apparatus comprising a vacuum pump communicating with a reservoir and a pressure regulator for reducing the pressure of the vacuum pump. 4. The pressure in the air reservoir in the upper part of the first ink compartment is P, the specific gravity of the ink is ρ, and the height from the nozzle surface of the inkjet head to the surface level of the ink in the first ink compartment is H in claim 2 or 3. When
P = −ρ · H−X (Pa)
The pressure is adjusted so that X is in the range of 100-300. 4. The ink jet printing apparatus according to claim 2, wherein when the ink jet head is in a non-printing state, the first and second ink chambers are held in a high vacuum state to degas the ink in the ink chambers. .

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