JP4433760B2 - Liquid ejection device - Google Patents

Liquid ejection device Download PDF

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Publication number
JP4433760B2
JP4433760B2 JP2003364942A JP2003364942A JP4433760B2 JP 4433760 B2 JP4433760 B2 JP 4433760B2 JP 2003364942 A JP2003364942 A JP 2003364942A JP 2003364942 A JP2003364942 A JP 2003364942A JP 4433760 B2 JP4433760 B2 JP 4433760B2
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liquid
ink
tank
head
print head
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JP2005125670A (en
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積治 中道
真人 安藤
淳 小田
滋義 平島
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ソニー株式会社
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  The present invention relates to a liquid discharge apparatus that discharges a predetermined liquid from a plurality of liquid discharge nozzles formed on a liquid discharge head to an object, and more specifically, a liquid tank is disposed below the liquid discharge nozzle of the liquid discharge head. In this state, the liquid is discharged by generating a negative pressure in the liquid discharge head between the two to circulate the liquid, thereby preventing liquid leakage from the nozzle during liquid circulation and removing bubbles contained in the liquid. It relates to the device.

  A conventional liquid ejecting apparatus, for example, an ink jet printer of an ink jet system, applies energy to ejection driving means such as a heat generating element and a piezoelectric element installed in a liquid chamber in a print head, and ink (predetermined liquid in the liquid chamber). ) Are ejected as ink droplets from ink ejection nozzles and attached to recording paper for printing, and the unit price is low, the running cost is low, the image quality is small, and it is generally widespread. .

  The inkjet printer includes a print head that ejects ink from a plurality of ink ejection nozzles formed on a nozzle surface, an ink tank that stores ink to be supplied to a liquid chamber in the print head, and the ink tank that An ink supply line for supplying ink to the print head, an ink reflux line for returning the ink from the print head to the ink tank, and a liquid feed pump for circulating the ink between the print head and the ink tank. Be prepared.

  In such an ink jet printer, it is necessary to stably discharge, for example, picoliter order ink droplets from the ink discharge nozzles of the print head. However, since the ink discharge nozzles are formed with a fine hole diameter, Due to the cause, ink ejection failure may occur and print quality may deteriorate. One such factor is air bubbles mixed in and near the print head. If air bubbles are mixed in the ink supply pipe or the liquid chamber, not only ink cannot be ejected stably from the ink ejection nozzle, but also ink non-ejection may occur and printing may become impossible.

  The reason why air bubbles are mixed in and in the vicinity of the print head is as follows: when the ink tank that is made detachable from the print head is replaced, the air entering the attachment / detachment opening, the ink due to the change in temperature and pressure, etc. Precipitation of dissolved air in the air, mixing of bubbles from the ink ejection nozzle due to vibration or impact during printing or printing stop, and permeation of air from the pipe member constituting the ink flow path between the ink tank and the print head and so on.

In order to remove the air bubbles mixed in this way, conventionally, the air in the print head has been removed by circulating the ink between the ink tank and the print head. For example, an ink supply path from the ink tank and a circulation pump for circulating the ink in the liquid chamber of the print head are provided on the ink supply path, the ink is circulated between the ink tank and the print head, and the print head There is a type in which a head cap capable of sealing the discharge port surface is brought into contact with the discharge port surface, and the inside of the head cap is decompressed to suck ink (see, for example, Patent Document 1).
JP 10-138515 A (page 4, FIG. 1)

  However, in the conventional liquid ejecting apparatus, ink is circulated while applying a positive pressure to the print head by the circulation pump, and ink leaks from the ink ejection nozzle of the print head during this ink circulation. There was a thing. Therefore, the periphery of the nozzle may be stained with the leaked ink. Further, in a full-line type print head in which the nozzle member is formed long across the width of one side of the recording paper (for example, A4 size), since the number of nozzles is large, the amount of ink pushed out from the ink ejection nozzle during circulation As a result, the ink was wasted and was uneconomical.

  Furthermore, a means for dealing with ink leaking from the nozzles during ink circulation is required. Therefore, in the conventional example, the head cap is brought into contact with the discharge port surface of the print head, and the leaked ink is sucked by the head cap. In order to cope with this, it is conceivable to provide an ink circulation system for reusing the leaked ink. However, the size of the apparatus increases and the cost increases.

  Accordingly, the present invention addresses such a problem and generates a negative pressure in the liquid discharge head between the two in a state where the liquid tank is disposed below the liquid discharge nozzle of the liquid discharge head. An object of the present invention is to provide a liquid ejecting apparatus that prevents liquid leakage from a nozzle during liquid circulation and removes bubbles contained in the liquid.

In order to achieve the above object, a liquid ejection apparatus according to the present invention supplies a liquid ejection head that ejects a predetermined liquid from a plurality of liquid ejection nozzles formed on a nozzle surface and a liquid chamber in the liquid ejection head. A liquid supply line for supplying liquid from the liquid tank storing liquid to the liquid discharge head, a liquid return line for returning liquid from the liquid discharge head to the liquid tank, and the liquid return line disposed on the liquid return line. become provided with a liquid circulation means for circulating liquid between the liquid discharge head and the liquid tank, the liquid tank installed to be disposed below the liquid ejection nozzle of the liquid discharge head Rutotomoni, Foreign matter mixed in the liquid circulating between the liquid discharge head and the liquid tank between the liquid circulating means and the liquid reflux port of the liquid tank on the liquid reflux line. The filter filters is provided, by generating a negative pressure within the liquid discharge head by the drive of the liquid circulation means, in which circulates the liquid between the liquid discharge head and the liquid tank.

  Further, a replenishment liquid tank storing a predetermined liquid may be connected in the middle of the liquid reflux conduit, and the liquid in the replenishment liquid tank may be supplied to the liquid tank by the liquid circulation means.

According to the liquid ejection device of the first aspect, the liquid to be supplied to the liquid chamber in the liquid ejection head that ejects the predetermined liquid from the plurality of liquid ejection nozzles formed on the nozzle surface is stored in the liquid tank. Liquid is supplied from the liquid tank to the liquid discharge head through the liquid supply line, and the liquid is returned from the liquid discharge head to the liquid tank through the liquid return line, and the liquid tank is placed below the liquid discharge nozzle of the liquid discharge head. A liquid is circulated between the liquid discharge head and the liquid tank by generating a negative pressure in the liquid discharge head by driving a liquid circulation means provided on the liquid reflux line. it can. Therefore, without generating a positive pressure in the liquid discharge head and pushing the liquid out of the nozzle, it is possible to prevent liquid leakage from the nozzle during liquid circulation and to remove bubbles contained in the liquid. Thereby, it is possible to prevent the periphery of the nozzle from being contaminated with liquid and improve the liquid discharge performance. Moreover, it is possible to prevent the liquid from being wasted. Furthermore, there is no need for means corresponding to the liquid leaking from the nozzle, and the apparatus can be reduced in size and cost. Furthermore, since it is not necessary to provide a special means for generating a negative pressure in the liquid discharge head on the liquid reflux line, the flow resistance of the liquid circulating between the liquid tank and the liquid discharge head is reduced, and The flow rate of the liquid in the liquid discharge head can be ensured. And a filter for filtering foreign matter mixed in the liquid circulating between the liquid discharge head and the liquid tank between the liquid circulation means and the liquid reflux port of the liquid tank on the liquid reflux line. By providing the liquid, the liquid can be circulated at a negative pressure within a range where the meniscus of the liquid formed in the liquid discharge nozzle is maintained, and foreign matters mixed in the liquid can be filtered. Further, even when the filter is air-locked, the air lock of the filter can be recovered by circulation of the liquid, and air can be prevented from being drawn into the liquid discharge head from each liquid discharge nozzle.

  According to the second aspect of the present invention, the liquid discharge head can be detached from the liquid discharge device by being detachably provided to the liquid discharge device main body. Accordingly, maintenance of the liquid discharge head can be easily performed.

  According to a third aspect of the present invention, a replenishing liquid tank storing a predetermined liquid is connected in the middle of the liquid reflux conduit, and the liquid in the replenishing liquid tank is By supplying to the liquid tank, the replenishment liquid tank can be arranged at an arbitrary position. Therefore, the degree of freedom in design is increased, and the liquid tank for replenishment can have a large capacity.

  Furthermore, according to a fourth aspect of the present invention, since the liquid circulating means is a liquid feed pump, the liquid can be circulated between the liquid discharge head and the liquid tank with a simple configuration.

  According to the fifth aspect of the present invention, the driving of the liquid circulation means generates a negative pressure within a range in which the liquid meniscus formed in each liquid discharge nozzle of the liquid discharge head is maintained. As a result, the meniscus in each liquid discharge nozzle is not destroyed, and bubbles can be prevented from being mixed from the nozzle.

  According to the invention of claim 6, the operation of the liquid discharge head is provided by providing a valve mechanism for preventing the backflow of the liquid from the liquid circulation means side to the liquid discharge head side inside the liquid circulation means. It is possible to prevent liquid from leaking from the liquid discharge nozzle due to a pressure difference during standby or when the liquid tank is removed.

  According to the seventh aspect of the present invention, a valve mechanism for preventing a back flow of liquid from the liquid circulation means side to the liquid discharge head side is provided on the liquid reflux conduit, so that the liquid discharge head It is possible to prevent liquid from leaking from the liquid discharge nozzle due to a pressure difference during operation standby or when the liquid tank is removed.

  Furthermore, according to the eighth aspect of the invention, the liquid discharge head includes a liquid supply port at one end and a liquid discharge port at the other end, thereby simplifying the structure and reducing the number of parts. And the number of assembly steps can be reduced. In addition, the liquid can be circulated stably without impairing the left and right flow rate balance in the length direction of the liquid ejection head during the liquid circulation.

  According to the ninth aspect of the invention, the liquid discharge head includes the liquid supply port at the substantially central portion thereof and the liquid discharge ports at both end portions thereof, so that the center of the liquid discharge head in the length direction of the liquid discharge head is provided. There is almost no dynamic negative pressure loss from the part to both ends, and the liquid can be circulated stably.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a schematic view showing an embodiment of an ink jet printer as an example of a liquid ejection apparatus according to the present invention. This ink jet printer is a device that ejects ink droplets onto recording paper, which is a discharge target, and includes a print head 1, an ink tank 2, an ink supply line 3, an ink reflux line 4, and a liquid feed. A pump 5 and a filter 6 are provided.

  The print head 1 serves as a liquid ejection head for ejecting ink (predetermined liquid) onto a recording paper. The print head 1 includes a common liquid chamber 8 that accommodates ink 7 to be ejected, and forms a nozzle surface. The thin plate-like nozzle member 9 has a large number of ink discharge nozzles 10 formed in a row. Here, as an example, a full-line type print head 1 is shown in which a nozzle member 9 is formed to be long across the width of one side of a recording paper (for example, A4 size), and an ink supply port is provided at one end of the upper surface thereof. 11 and an ink discharge port 12 at the other end. A joint 13 is connected to one ink supply port 11 for connection to an ink supply line 3 described later, and a joint is connected to the other ink discharge port 12 for connection to an ink return line 4 described later. 14 is attached. Thereby, the print head 1 can be attached to and detached from the ink jet printer main body. That is, the print head 1 can be removed from the ink jet printer main body by removing the joint 13 from the ink supply line 3 and detaching the joint 14 from the ink reflux line 4. Therefore, maintenance of the print head 1 can be easily performed. The lower surface of the nozzle member 9 of the print head 1 is closed by the head cap 15 to prevent the ink of each ink discharge nozzle 10 from being dried and clogged.

  An ink tank 2 is disposed below each ink discharge nozzle 10 of the print head 1 so as to be disposed. The ink tank 2 serves as a liquid tank for storing ink 7 to be supplied to the common liquid chamber 8 in the print head 1 and is formed in a box shape having a predetermined volume. An air communication hole 16 is formed on the top plate. It has been drilled. An ink outlet 17 is formed in the vicinity of the bottom plate on the left side wall of the ink tank 2 shown in FIG. 1, and an ink return port 18 is formed in the vicinity of the top plate on the right side wall of the ink tank 2. The ink tank 2 can be attached to and detached from the print head 1 by using the ink outlet 17 and the ink return port 18 as connection ports to the ink supply line 3 or the ink return line 4 described later. Yes. Therefore, since the ink tank 2 is detachable from the print head 1, the ink tank 2 can be replaced according to ink consumption. Therefore, the head cartridge can be used repeatedly.

  An ink supply line 3 is connected between the ink outlet 17 of the ink tank 2 and the joint 13 attached to the ink supply port 11 of the print head 1. The ink supply line 3 is a liquid supply line for supplying ink 7 from the ink tank 2 to the print head 1 and is made of, for example, a flexible resin tube or a metal pipe such as stainless steel.

  An ink return line 4 is connected between the joint 14 attached to the ink discharge port 12 of the print head 1 and the ink return port 18 of the ink tank 2. The ink reflux line 4 is a liquid reflux line for returning the ink 7 from the print head 1 to the ink tank 2 and is made of, for example, a flexible resin tube or a metal pipe such as stainless steel.

  Further, a liquid feed pump 5 is provided in the middle of the ink reflux line 4. The liquid feed pump 5 serves as a liquid circulation means for circulating the ink 7 between the print head 1 and the ink tank 2, and includes, for example, a tube pump, a diaphragm pump, a piston pump, etc. Choose the right one. The ink tank 2, the ink supply line 3, the print head 1, the ink reflux line 4, and the liquid feed pump 5 constitute an ink circulation system in which the ink 7 circulates in the direction indicated by the arrow in FIG. Yes.

In this case, in the embodiment of FIG. 1, the ink tank 2 is disposed below the ink discharge nozzle 10 of the print head 1, so that the liquid level of the ink 7 in the ink tank 2 and the nozzle member of the print head 1. Due to the height difference H from 9, negative water head pressure from the ink tank 2 is always applied to the ink discharge nozzle 10 of the nozzle member 9. Therefore, the ink 7 accommodated in the common liquid chamber 8 of the print head 1 can be prevented from flowing out naturally from each ink discharge nozzle 10 by the action of the negative water head pressure. Further, since capillary force acts on the ink discharge nozzles 10, air is not drawn into the ink discharge head 1 from the ink discharge nozzles 10 due to negative pressure.

Furthermore, by placing the ink tank 2 below the print head 1 and utilizing the negative head pressure generated in the print head 1, the negative pressure in the print head 1 is placed on the ink reflux line 4. There is no need to provide a special means for generating. Thereby, the flow path resistance of the ink 7 circulating between the ink tank 2 and the print head 1 is reduced, and the flow rate of the ink 7 in the print head 1 can be ensured. Therefore, even when a large amount of ink is ejected from a large number of ink ejection nozzles 10 in a short time when printing on recording paper with a so-called full line type print head 1 , a large amount of ink 7 is contained in the print head 1. Is suitable for a full-line type ink jet printer.

A filter 6 is provided on the ink reflux line 4 between the liquid feed pump 5 and the ink reflux port 18 of the ink tank 1. The filter 6 serves as a means for filtering foreign matter mixed in the ink 7 circulating between the print head 1 and the ink tank 2, and is made of, for example, a metal made of finely woven stainless fine fibers. A mesh filter is used. Specifically, the filter 6 is formed with a mesh smaller than the nozzle diameter so that the ink discharge nozzle 10 is not clogged. In the embodiment, the filtration accuracy is about 10 μm.

  Here, in order to filter the foreign matters mixed in the ink 7, it is ideal to arrange the filter 6 at a position immediately before the common liquid chamber 8 of the print head 1. When the air lock is performed, there is a problem that the ink 7 does not circulate. The air lock means that when air enters the filter 6, the meniscus of the ink 7 is formed in the mesh mesh, and the meniscus is not broken unless pressure higher than the surface tension is applied, and the ink 7 does not circulate. It is a phenomenon. In the filter 6 of the embodiment, the pressure for breaking the meniscus of the ink 7 is actually a water head pressure of 800 to 900 mm. Once the filter 6 is air-locked, the ink 7 is not applied unless a pressure higher than the above water head pressure is applied. It stops flowing.

Therefore, although not shown in the figure, when the filter 6 is disposed, for example, at a position immediately before the ink supply port 11 of the print head 1, a pressure higher than the water head pressure is applied to recover the air lock of the filter 6. In addition, if the ink 7 is circulated, the ink discharge nozzle 10 of the print head 1 has a weaker meniscus holding force than the filter 6, so the meniscus of the ink discharge nozzle 10 is destroyed and the ink discharge head 1 Then, air is drawn from each ink discharge nozzle 10 and the ink 7 cannot be circulated. At this time, for example, if the head cap 15 is in a completely sealed state, the air drawing from the ink discharge nozzle 10 can be minimized, so that the meniscus of the filter 6 can be destroyed and the air lock can be recovered. . However, in practice, the head cap 15 is provided with a small hole for venting air so as not to push air into the ink discharge nozzle 10 when the nozzle member 9 of the print head 1 is covered. Since it is not hermetically sealed, air is drawn into the ink discharge head 1 from each ink discharge nozzle 10 during ink circulation.

Therefore, in the present invention, as described above, the filter 6 is provided between the liquid feed pump 5 and the ink return port 18 of the ink tank 1. As a result, the ink 7 is circulated at a negative pressure within a range in which the meniscus of the ink 7 formed in the ink discharge nozzle 10 of the print head 1 is maintained, and dust mixed in the ink 7 and thickened and solidified. Foreign matter such as ink can be filtered. Further, in the case where the filter 6 has airlock, even when the ink 7 was circulated in the pump 5, as well as restore the airlock of the filter 6, the ink of that to the print head 1 the discharge nozzle 10 Air can be prevented from being drawn in.

  Next, an ink circulation operation for removing the bubbles 19 contained in the ink 7 in the thus configured ink jet printer will be described with reference to FIG. Such an ink circulation operation is executed when the ink jet printer is started (when power is turned on), before printing is started, every time a predetermined number of recording sheets are printed, or every predetermined time has elapsed.

  First, the liquid feed pump 5 provided in the middle of the ink reflux pipe 4 is driven. Then, the ink 7 in the ink reflux pipe 4 is sucked as indicated by an arrow A, and the ink 7 in the print head 1 is also sucked as indicated by an arrow B from the ink discharge port 12 at the other end of the print head 1. And flows toward the liquid feed pump 5. Then, by driving the liquid feeding pump 5, the ink 7 that has passed through the filter 6 is sent into the ink tank 2 from the ink reflux port 18. As a result, the ink 7 starts to flow from the ink discharge port 12 of the print head 1 toward the ink tank 2 through the ink reflux line 4.

  Next, the ink 7 flows out of the print head 1 in this way, so that the pressure in the common liquid chamber 8 decreases. Then, the ink 7 in the ink tank 2 flows in the ink supply conduit 3 as indicated by an arrow C, and flows into the print head 1 through the joint 13 attached to one ink supply port 11. Thus, by driving the liquid feed pump 5, the ink 7 in the print head 1 is sucked as indicated by the arrow A and flows to the ink tank 2 as indicated by the arrow B, and the ink 7 in the ink tank 2 is indicated by the arrow C. Thus, the ink 7 circulates between the print head 1 and the ink tank 2.

  At this time, since the ink flows in the print head 1 from the ink supply port 11 toward the ink discharge port 12, bubbles 19 existing in the common liquid chamber 8 of the print head 1 are discharged from the ink discharge port 12. Driven into the ink reflux line 4, enters the ink tank 2 through the ink return port 18 through the liquid feed pump 5 and the filter 6, and is released into the air from the air communication hole 16 formed in the top plate. . Thereby, the bubbles 19 included in the circulating ink 7 are removed.

  In this case, the ink circulation is a negative pressure method in which the ink 7 in the print head 1 is sucked by driving the liquid feed pump 5, and therefore, unlike the conventional positive pressure method in which the ink is injected into the print head, The ink 7 does not leak from the ink discharge nozzle 10 of the head 1. Therefore, it is possible to prevent the periphery of the nozzle from being stained with the ink 7 and to prevent the ink 7 from being wasted. Further, there is no need for means corresponding to the ink 7 leaking from the nozzle, and the apparatus can be downsized and the cost can be reduced.

  Here, in the negative pressure type ink circulation according to the present invention, if the suction pressure of the ink 7 driven by the liquid feed pump 5 is too strong, air is drawn from the ink discharge nozzles 10 of the print head 1 and bubbles 19 are mixed. Conversely, it may cause the cause of ink discharge failure. Therefore, the liquid feed pump 5 may be driven so as to generate a negative pressure within a range where the meniscus of the ink formed in each ink discharge nozzle 10 of the print head 1 is maintained.

Generally, when a liquid is stretched in a nozzle having a certain nozzle area, the pressure P at which the meniscus in the nozzle is held is:
P = Liquid surface tension × Nozzle circumference × cos (contact angle of liquid to inner wall of nozzle) ÷ Nozzle area. Assuming that the surface tension of the ink 7 is γ, the contact angle of the ink 7 to the inner wall of the nozzle is θ, and the nozzle diameter is d, the pressure P at which the meniscus in the ink discharge nozzle 10 of the print head 1 is held is
P = 4γ cos θ / d
It becomes.

For example, as an example, if the nozzle diameter d is 17 μm, the surface tension γ of the ink 7 is 30 mN / m, and the contact angle θ is about 5 °, the pressure P at which the meniscus is held is about 740 mmH 2 O. Become. In this case, in the meniscus in the ink discharge nozzle 10, if the negative pressure due to the driving of the liquid feeding pump 5 is about 740 mmH 2 O or less, the meniscus is not drawn and bubbles 19 are mixed in the print head 1. There is no.

Even if the negative pressure due to the driving of the liquid feeding pump 5 exceeds about 740 mmH 2 O, the pressure loss due to the flow path resistance of the ink path from the liquid feeding pump 5 to the ink discharge nozzle 10 of the print head 1 in FIG. Thus, if the meniscus holding pressure is not exceeded in the ink discharge nozzle 10, the meniscus is not broken and the bubbles 19 are not mixed into the print head 1.

  FIG. 2 is an explanatory diagram showing the flow of ink in a state where ink 7 is ejected from each ink ejection nozzle 10 of the print head 1 and printing is performed using the ink jet printer of the present invention. At the time of printing, the head cap 15 (see FIG. 1) is opened, and the lower surface of the nozzle member 9 of the print head 1 is exposed. 1, the ink 7 is supplied from the ink tank 2 to the print head 1 through the ink supply line 3 as shown by the arrow C, and the liquid corresponding to each ink discharge nozzle 10 is operated. .. Are ejected from the respective ink ejection nozzles 10 as ink droplets 20, 20,... By being driven by ejection driving means such as heating elements and piezoelectric elements installed in the chamber, and are printed on the recording paper. At this time, each time the ink droplet 20 is ejected from the ink ejection nozzle 10 of the print head 1, the pressure in the common liquid chamber 8 of the print head 1 decreases, and the ink 7 in the ink tank 2 supplies ink as indicated by an arrow C. It flows in the pipe 3 and flows into the print head 1.

  In the printing operation shown in FIG. 2, in order to prevent the ink 7 from flowing back from the liquid feed pump 5 side to the print head 1 side via the ink reflux line 4, the backflow of ink is prevented in the liquid feed pump 5. And a valve mechanism such as a check valve. If the check valve is not provided in the liquid feed pump 5, the check valve is omitted, but a check valve may be provided on the ink reflux line 4 between the liquid feed pump 5 and the print head 1. . The backflow prevention valve mechanism may use an electromagnetic valve or the like, or may use a mechanical valve that performs a passive opening / closing operation in accordance with the pressure of the ink 7 in the pipeline, such as a so-called duckbill valve. Good.

  The above-described backflow prevention valve mechanism is necessary particularly when the ink tank 2 is removed. During printing standby, the ink discharge nozzle 10 of the print head 1 is always subjected to a negative hydraulic head pressure due to the height difference H between the ink tank 2 and the print head 1, so that the ink 7 does not leak. When the ink tank 2 is removed, the connection port to the ink tank 2 (the portion of the ink recirculation port 18) is opened to the atmosphere and atmospheric pressure is applied. Therefore, unless the valve mechanism for preventing backflow is provided, the print head 1 This is because the ink 7 leaks from the ink discharge nozzle 10.

  FIG. 3 is a schematic view showing a second embodiment of the ink jet printer according to the present invention. In this embodiment, in the ink jet printer shown in FIG. 1, a replenishing liquid tank 21 storing predetermined ink 7 is connected to an ink replenishing conduit 36 provided in the middle of the ink reflux conduit 4, and this replenishing conduit is provided. The ink 7 in the liquid tank 21 is supplied to the ink tank 22 through the ink replenishment conduit 36 by the liquid feed pump 5. The replenishment ink tank 21 is a liquid tank that stores ink 7 to be replenished to the ink tank 22. The ink tank 21 accommodates the ink 7 in a highly airtight ink storage bag 21a, and the outside thereof is a resin tank. It is made of a housing. Further, the connecting portion 23 for connecting the replenishing ink tank 21 is of a needle type, and the replenishing ink tank 21 side is a rubber seal so that a hollow needle can be inserted into this to communicate with the outside. It has become.

  A check valve 24 and a first valve 25 are provided immediately after the connection portion 23 of the refill ink tank 21 and in the middle of the ink refill line 3. The check valve 24 is for preventing the ink 7 from spilling when the refill ink tank 21 is removed. Further, the first valve 25 is an electromagnetic valve, and in the embodiment, a type that is normally closed and opens when a current flows is used. Conversely, a type that is always open and closes when an electric current is passed can also be used. The refilling ink tank 21 can be omitted if the first valve 25 is always closed when the refilling ink tank 21 is removed.

  The ink tank 22 is formed in a box shape with a predetermined volume, is entirely molded of resin, and has an air communication hole 26 formed in the upper part thereof. An ink outlet 27 is formed near the bottom plate on the left side wall of the ink tank 22, and an ink return port 28 is formed near the top plate on the right side wall. The ink outlet 27 is connected to the joint 13 and the ink supply port 11 of the print head 1 through the ink supply pipe 3. The ink return port 28 is connected to the joint 14 and the ink discharge port 12 of the print head 1 through the ink return line 4, and the liquid feed pump 5 and the ink return line 4 are disposed in the middle of the ink return line 4. A filter 6 is provided, and a second valve 29 is provided. Like the first valve 25, the second valve 29 is an electromagnetic valve. In the embodiment, the second valve 29 is normally closed and opened when a current is supplied. Further, an electrode 30 for detecting the remaining amount of the ink 7 is provided inside the ink tank 22, and three levels of detection can be performed in this example. There are four electrodes 30. The longest electrode in the figure is a common electrode, and the other electrodes are electrodes corresponding to three levels. The level of the liquid level of the ink 7 can be determined based on whether or not a current flows between the common electrode and the other three electrodes.

As shown in FIG. 3, the ink tank 22 is disposed below the ink discharge nozzle 10 of the print head 1, so that the liquid level of the ink 7 in the ink tank 22 and the nozzle member 9 of the print head 1 The negative water head pressure from the ink tank 22 is always applied to the ink discharge nozzle 10 of the nozzle member 9 due to the height difference H. Therefore, the ink 7 accommodated in the common liquid chamber 8 of the print head 1 can be prevented from flowing out naturally from each ink discharge nozzle 10 by the action of the negative water head pressure. Further, since capillary force acts on the ink discharge nozzles 10, air is not drawn into the ink discharge head 1 from the ink discharge nozzles 10 due to negative pressure. In this case, the replenishment liquid tank 21 can be arranged at an arbitrary position. Accordingly, the degree of freedom in design is increased, and the replenishing liquid tank 21 can be made to have a large capacity.

  Next, the operation of the ink jet printer configured as described above will be described with reference to FIG. Here, at the beginning of use of the ink jet printer, the print head 1, the ink supply line 3, the ink tank 22, the liquid feed pump 5, and the ink reflux line 4 are not filled with the ink 7. In this state, the replenishment ink tank 21 is attached to the connection portion 23. Although there are various cases of the number of colors, in this embodiment, four colors of ink of yellow (Y), magenta (M), cyan (C), and black (K) are used. Hereinafter, the description will be made for one color.

  First, when the operation is started, the first valve 25 is opened, and the liquid feed pump 5 is driven to transfer the ink 7 from the replenishment ink tank 21 to the ink tank 22. The level of the liquid level of the ink 7 supplied into the ink tank 22 can be detected by the electrode 30. In this embodiment, the ink 7 is detected between the shortest electrode and the common electrode, and at the same time, the liquid feed pump 5 is stopped. Then, the first valve 25 is closed to stop the ink supply.

  Next, the second valve 29 is opened and the liquid feed pump 5 is driven to circulate the ink 7. When the liquid level of the ink 7 in the ink tank 22 drops to the level L indicated by the chain line, the liquid feed pump 5 is stopped. The level L of the ink 7 is such that the ink 7 in the ink tank 22 is supplied into the print head 1 via the ink supply line 3 and further to the liquid feed pump 5 via the ink reflux line 4. The position is set so that 7 is filled. As a result, the air bubbles 19 existing in the common liquid chamber 8 of the print head 1 are driven into the ink reflux pipe 4 and enter the ink tank 2 through the liquid feed pump 5 and the filter 6, and from the atmosphere communication hole 16. Since it is released into the air, the bubbles 19 contained in the ink 7 are removed. At this time, a negative head pressure corresponding to a height H from the liquid level of the ink 7 in the ink tank 22 to the ink discharge nozzle 10 is applied to the print head 1. Printing can be performed when the above operation is completed.

  Although not shown in the drawings, the head cap 15 is opened, and ink droplets are ejected from each ink ejection nozzle 10 of the print head 1. If printing is continued as it is, the pressure in the common liquid chamber 8 in the print head 1 decreases, so that the ink 7 in the ink tank 22 flows through the ink supply pipe 3 and into the print head 1. As a result, the ink 7 in the ink tank 22 decreases, and the electrode 30 does not detect the ink 7 at a certain time. In the present embodiment, the detection of the liquid level of the ink 7 by the electrode 30 is performed every time one sheet is printed.

  When the electrode 30 no longer detects the ink 7, as described above, the first valve 25 is opened and the second valve 29 is closed, and the liquid feed pump 5 is driven. As a result, the ink 7 is replenished from the replenishing ink tank 21 to the ink tank 22, and when the liquid level of the ink 7 in the ink tank 22 reaches a predetermined position, the liquid feed pump 5 is stopped and the first valve 25 is turned off. close. Then, the printing operation is started again. Further, by repeating the above-described operation, when the ink 7 is exhausted in the replenishment ink tank 21, the replenishment ink tank 21 is replaced with a new one. The remaining amount of ink 7 in the replenishment ink tank 21 can be grasped by how many times the ink has been replenished in the ink tank 22. The ink circulation operation is executed when the ink jet printer is started (when power is turned on), before printing starts, every time a predetermined number of recording sheets are printed, or every elapse of a predetermined time. Thereby, the bubbles 19 included in the circulating ink 7 are removed.

  FIG. 4 is a schematic view showing a third embodiment of the ink jet printer according to the present invention. In this embodiment, in the ink jet printer shown in FIG. 3, the print head 31 includes an ink supply port 32 at a substantially central portion of the upper surface thereof and ink discharge ports 33 at both ends. When the ink supply port 11 is provided at one end of the upper surface of the print head 1 and the ink discharge port 12 is provided at the other end as in the embodiment shown in FIGS. Occasionally, the negative pressure on the ink discharge port 12 side becomes larger than that on the ink supply port 11 side due to the effect of pressure loss in the common liquid chamber 8, which may cause a problem that the printing density is lowered. However, in the case shown in FIG. 4, the pressure loss as described above can be reduced to almost half by arranging the ink supply port 32 at the center of the common liquid chamber 8. As shown in FIG. 4, the supply pipe 34 that supplies the ink 7 to the ink supply port 32 in the substantially central portion of the print head 31 is connected to the joint 13 for connecting to the ink supply pipe 3. The discharge pipes 35 for discharging the ink 7 from the two ink discharge ports 33, 33 at both ends are connected to the joint 14 for joining and connecting to the ink reflux pipe 4. The length and thickness of the common liquid chamber 8 are adjusted so that the flow path resistances on the left and right sides of the print head 31 are equal, so that an equal ink flow rate can be obtained when the ink 7 is circulated. Is preferred.

  Next, an ink circulation operation in the ink jet printer configured as described above will be described. First, the liquid feeding pump 5 provided in the middle of the ink reflux pipe 4 is driven. Then, the ink 7 in the ink reflux line 4 is sucked as indicated by an arrow A, and the ink 7 in the print head 31 is sucked as indicated by an arrow B from the ink discharge ports 33 and 33 at both ends of the print head 31. The ink 7 flows toward the liquid feed pump 5, and the ink 7 is fed into the ink tank 2 through the liquid feed pump 5. Next, the ink 7 flows out of the print head 31 in this way, so that the pressure in the common liquid chamber 8 decreases. Then, the ink 7 in the ink tank 22 flows through the ink supply pipe 3 as indicated by the arrow C, flows through the supply pipe 34 as indicated by the arrow D, and passes through the ink supply port 32 at the central portion as indicated by the arrow E. It flows into 31. As a result, the ink 7 in the print head 31 is sucked by the driving of the liquid feed pump 5 and flows to the discharge pipe 35 as indicated by arrows F and B, and to the ink reflux line 4 as indicated by the arrow A. Flowing. Accordingly, the ink 7 circulates between the print head 31 and the ink tank 2.

  At this time, since the ink is circulated in the print head 31 from the central portion toward both ends, the air bubbles 19 existing in the print head 31 are discharged from the ink discharge ports 33 and 33 at both ends to the ink reflux line. 4 is expelled into the ink tank 22 and discharged into the air from the air communication hole 16 formed in the top plate. Thereby, the bubble 19 contained in the ink 7 is removed. In the above description, the print head 31 in which the ink supply port 32 is arranged in the central portion of the common liquid chamber 8 is applied to the ink jet printer shown in FIG. 4, but the present invention is not limited to this. The print head 31 may be applied to the ink jet printer shown in FIG.

  Further, the liquid discharge head of the liquid discharge apparatus according to the present invention is of a full line type in which the nozzle member 9 is formed to be long over the width of one side of the recording paper. However, the present invention is not limited to this, and the nozzle member The present invention can also be applied to a serial type in which 9 is formed shorter than the width of one side of the recording paper and reciprocates in the width direction of the recording paper.

  Further, in the above description, an example applied to an ink jet printer has been described. However, the present invention is not limited to this, and the liquid contained in the liquid chamber of the liquid ejection head is ejected as droplets from the liquid ejection nozzle. Anything can be used. For example, the present invention can be applied to a facsimile machine or a copying machine whose recording system is an inkjet system.

  The liquid ejected from the nozzles of the liquid ejection head of the liquid ejection apparatus is not limited to ink, and any other liquid ejection apparatus can be used as long as it can form a dot row or a dot by ejecting the liquid in the liquid chamber. Can be applied. For example, the present invention can be applied to a liquid discharge device for discharging a DNA-containing solution onto a pallet in DNA identification or the like, or a liquid discharge device for discharging a liquid containing conductive particles for forming a wiring pattern of a printed wiring board. Can do.

1 is a schematic diagram illustrating an embodiment of an inkjet printer as an example of a liquid ejection apparatus according to the present invention. It is explanatory drawing which shows the flow of the ink in the state which discharges ink from the ink discharge nozzle of the print head which comprises the said inkjet printer. It is a schematic diagram which shows 2nd Embodiment of the said inkjet printer. It is a schematic diagram which shows 3rd Embodiment of the said inkjet printer.

Explanation of symbols

1. Print head (liquid discharge head)
2. Ink tank (liquid tank)
3. Ink supply line (liquid supply line)
4 ... Ink reflux line (liquid reflux line)
5. Liquid feed pump (liquid circulation means)
6 ... Filter 7 ... Ink (liquid)
8 ... Common liquid chamber 9 ... Nozzle member 10 ... Ink discharge nozzle (liquid discharge nozzle)
11: Ink supply port (liquid supply port)
12 ... Ink discharge port (liquid discharge port)
DESCRIPTION OF SYMBOLS 13, 14 ... Joint 15 ... Cap member 16 ... Atmospheric communication hole 17 ... Ink outlet 18 ... Ink return port (liquid return port)
19 ... Bubbles 20 ... Ink drops 21 ... Replenishment ink tank (auxiliary liquid tank)
22 ... Ink tank (liquid tank)
23 ... Connection 24 ... Check valve (valve mechanism)
25, 29 ... Valve 26 ... Air communication hole 27 ... Ink outlet 28 ... Ink return port (liquid return port)
30 ... Electrode 31 ... Print head (liquid discharge head)
32. Ink supply port (liquid supply port)
33 ... Ink discharge port (liquid discharge port)
34 ... Supply piping 35 ... Discharge piping

Claims (9)

  1. A liquid discharge head for discharging a predetermined liquid from a plurality of liquid discharge nozzles formed on the nozzle surface;
    A liquid supply line for supplying liquid from a liquid tank storing liquid to be supplied to the liquid chamber in the liquid discharge head to the liquid discharge head;
    A liquid reflux line for returning liquid from the liquid discharge head to the liquid tank;
    A liquid circulating means disposed on the liquid reflux line for circulating the liquid between the liquid discharge head and the liquid tank;
    The liquid tank between the liquid ejection Rutotomoni provided to be arranged below the nozzle, the liquid recirculation opening of said liquid circulation means and the liquid tank by the liquid return pipe path of the liquid discharge head, the liquid discharge Provide a filter for filtering foreign matter mixed in the liquid circulating between the head and the liquid tank ,
    A liquid discharge apparatus characterized in that a negative pressure is generated in the liquid discharge head by driving the liquid circulation means to circulate the liquid between the liquid discharge head and the liquid tank.
  2.   The liquid discharge apparatus according to claim 1, wherein the liquid discharge head is detachably attached to the liquid discharge apparatus main body.
  3.   A replenishing liquid tank storing a predetermined liquid is connected in the middle of the liquid reflux pipe, and the liquid in the replenishing liquid tank is supplied to the liquid tank by the liquid circulating means. The liquid ejection device according to claim 1.
  4.   2. The liquid discharge apparatus according to claim 1, wherein the liquid circulation means is a liquid feed pump.
  5.   2. The liquid ejection apparatus according to claim 1, wherein the liquid circulation means generates a negative pressure within a range in which a meniscus of liquid formed in each liquid ejection nozzle of the liquid ejection head is maintained. .
  6.   2. The liquid ejection apparatus according to claim 1, wherein a valve mechanism for preventing a back flow of liquid from the liquid circulation means side to the liquid ejection head side is provided inside the liquid circulation means.
  7.   4. The liquid ejection apparatus according to claim 1, wherein a valve mechanism for preventing a back flow of liquid from the liquid circulation means side to the liquid ejection head side is provided on the liquid reflux conduit.
  8.   The liquid discharge apparatus according to claim 1, wherein the liquid discharge head includes a liquid supply port at one end and a liquid discharge port at the other end.
  9. The liquid discharge apparatus according to claim 1, wherein the liquid discharge head includes a liquid supply port at a substantially central portion thereof and a liquid discharge port at both ends.
JP2003364942A 2003-10-24 2003-10-24 Liquid ejection device Expired - Fee Related JP4433760B2 (en)

Priority Applications (1)

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Application Number Priority Date Filing Date Title
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JP4433760B2 true JP4433760B2 (en) 2010-03-17

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CN107264060B (en) * 2016-04-07 2018-12-28 东芝泰格有限公司 Ink circulation device, ink-jet recording apparatus

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