JP2005103758A - Inkjet printer and its buffer tank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress variations in liquid level of ink to the utmost by rapidly refilling a buffer tank with the ink when the liquid level of the ink in the buffer tank decreases. <P>SOLUTION: In the buffer tank 4 of an ink jet printer 1, an ink inlet passage 34 for allowing the ink I in an ink cartridge 3 to flow into the buffer tank 4 is equipped with an ink inlet pipe 36 which is provided in a top plate part 31 of the buffer tank 4 and which is elongated in a vertical direction, and a tube member 37 which has a larger diameter than the ink inlet pipe 36, which communicates with the ink inlet pipe 36 and which is extended from the top plate part 31 to a position below a lower end of the ink inlet pipe 36 and above a lower end of an air outlet passage 35. Thus, the buffer tank 4 can be rapidly refilled with the ink I when the air in the buffer tank 4 flows out into the ink cartridge 3 because of a decrease in the liquid level of the ink I. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ink jet printer capable of adjusting the back pressure of ink substantially constant, a buffer tank for adjusting the back pressure, and a buffer tank for adjusting the back pressure.

  In an ink jet printer that prints by ejecting ink from a nozzle toward a recording sheet, if the back pressure of the ink acting on the nozzle fluctuates due to the remaining amount of ink in the ink cartridge or the like, the fluctuation in the back pressure Affects the discharge accuracy. For this reason, ink jet printers are often provided with a mechanism for suppressing the back pressure fluctuation of the ink.

  As an example of such an ink jet printer, there is one provided with a buffer tank that suppresses fluctuations in back pressure acting on the nozzle by keeping the liquid level of the ink stored in the inside substantially constant (for example, Patent Documents). 1). As shown in FIGS. 7 and 8, in such a buffer tank 100, an ink inflow pipe 102 for allowing ink I to flow into the buffer tank 100 from the ink cartridge 101 and an atmosphere for causing the ink cartridge 101 to flow out of the atmosphere. An air outflow pipe 103 is provided on the top plate portion 104 of the buffer tank 100. In the buffer tank 100, the ink inflow tube 102 extends below the atmospheric outflow tube 103 and near the bottom. Here, when the ink cartridge 101 is attached to the buffer tank 100, the ink inflow pipe 102 and the atmospheric outflow pipe 103 pass through the two plug members 106 provided in the ink cartridge 101, respectively. The inflow pipe 102 and the atmospheric outflow pipe 103 are each formed into a thin hollow needle shape.

  As shown in FIG. 7, in a state where the ink I is not ejected from the nozzle, the ink I does not flow out from the buffer tank 100 to the nozzle, and the liquid level of the ink I is at a position near the lower end of the atmospheric outflow pipe 103. The ink is stopped and the ink has entered the inside of the lower end of the air outflow pipe 103. That is, in this state, the atmosphere does not enter the atmosphere outflow pipe 103 and the atmosphere does not flow out to the ink cartridge 101, so that the ink I does not flow into the buffer tank 100 from the ink cartridge 101. In this state, when the ink I is ejected from the nozzle, the ink I flows out from the ink supply port 105 formed at the bottom of the buffer tank 100 to the nozzle, and the liquid level of the ink I in the buffer tank 100 is lowered.

  Then, the liquid level of the ink I is separated from the lower end of the air outflow pipe 103, the air in the buffer tank 100 enters the air outflow pipe 103, and the air flows out to the ink cartridge 101. Then, the ink I flows from the ink cartridge 101 into the buffer tank 100 via the ink inflow tube 102 so as to be replaced with the atmosphere. When the liquid level of the ink I in the buffer tank 100 rises and reaches the vicinity of the lower end of the air outflow pipe 103, the air does not enter the air outflow pipe 103 again, and the air does not flow out to the ink cartridge 101. Inflow of the ink I into the tank 100 stops.

Japanese Patent Laying-Open No. 2002-307711 (FIG. 3)

  However, in the buffer tank as shown in FIGS. 7 and 8, the ink in the ink cartridge flows out into the buffer tank through the ink inflow tube, but the diameter of the ink inflow tube is small. Since the inflow pipe extends to the vicinity of the bottom of the buffer tank, the flow resistance when ink flows into the buffer tank increases. Therefore, when ink is ejected from the nozzle, the ink flows out to the nozzle, and the liquid level of the ink in the buffer tank is lowered, the ink is not replenished from the ink cartridge to the buffer tank quickly.

  In particular, when the viscosity of the ink is high due to a low temperature state or due to evaporation of moisture in the ink, the flow resistance further increases, and the replenishment of the ink to the buffer tank is delayed. Thus, if the replenishment of ink to the buffer tank is delayed, when the ink level drops, the lowered level does not immediately return to the original position (near the lower end of the atmospheric outflow pipe). The surface fluctuates, and the back pressure of the ink acting on the nozzle also fluctuates. Furthermore, there may be a case where ink is not supplied even when the ink level drops to near the bottom of the buffer tank. In this case, there is a possibility that bubbles are mixed into the ink supplied to the nozzle.

  An object of the present invention is to suppress the fluctuation of the ink liquid level as much as possible by configuring the buffer tank so that the ink is replenished immediately when the ink liquid level of the buffer tank decreases.

Means for Solving the Problems and Effects of the Invention

  According to a first aspect of the present invention, there is provided an ink jet printer comprising: a nozzle that ejects ink; and a buffer tank that holds ink flowing from an ink cartridge mounted above the ink tank and causes the ink to flow toward the nozzle. Is for causing the ink in the ink cartridge to flow into the buffer tank, and at least the ink inflow path including a portion extending downward from the top plate portion of the tank body in the buffer tank and the atmosphere from the outside. An atmosphere introduction port for introducing, and an atmosphere outflow path for allowing the atmosphere in the buffer tank to flow out to the ink cartridge, wherein the ink inflow path is provided in the top plate portion and extends vertically. A cylindrical member having a hollow cross-sectional area larger than that of the ink inflow pipe and communicating with the ink inflow pipe. It, is characterized in that a tubular member extending to a position below the lower end of and the air outlet passage at the lower than the ink inlet pipe from the top plate.

  In this ink jet printer, when the ink cartridge is mounted on the buffer tank, the atmosphere is introduced into the buffer tank through the atmosphere introduction port, and the atmosphere flows out from the atmosphere outflow path to the ink cartridge. Ink in the ink cartridge flows into the buffer tank from the ink inflow path so as to be replaced. Then, ink flows out from the buffer tank to the nozzle, and ink is ejected from the nozzle. Here, the ink inflow path includes an ink inflow pipe extending vertically and a cylindrical member communicating with the ink inflow pipe. The cylindrical member has a hollow cross-sectional area larger than that of the ink inflow pipe, and extends to a position below the lower end of the ink inflow pipe and above the lower end of the air outflow path.

  When ink is not ejected from the nozzles, ink does not flow out from the buffer tank to the nozzles, and the ink level in the buffer tank stops near the lower end of the air outflow path, and the air flows out of the air outflow path. The ink cartridge does not flow out. In this state, when the ink in the buffer tank flows out to the nozzle, the air in the buffer tank flows into the air outflow path, and the ink in the ink cartridge flows into the buffer tank through the ink inflow path instead of the air. To do. At this time, since the ink flows in the buffer tank in the cylindrical member having a cross-sectional area of the hollow portion larger than that of the ink inflow pipe, the flow resistance is reduced, so that the ink is quickly replenished to the buffer tank. . Therefore, it is possible to suppress the fluctuation of the ink level in the buffer tank as much as possible, and to reduce the fluctuation of the back pressure of the ink acting on the nozzle.

  An ink jet printer according to a second aspect is the ink jet printer according to the first aspect, wherein the ink inflow tube is provided in a vertically penetrating manner in the top plate portion, and the cylindrical member is formed from the top plate portion of the ink inflow tube. A portion extending into the tank body is inserted. Therefore, the ink that has flowed into the buffer tank from the ink cartridge through the ink inflow pipe flows in the large-diameter cylindrical member in the buffer tank, and the flow resistance is reduced.

  An ink jet printer according to a third invention is characterized in that, in the first or second invention, the top plate and the cylindrical member are integrally formed of a synthetic resin. Thus, by integrally forming the top plate portion and the cylindrical member with synthetic resin, it is possible to reduce the number of parts and the number of assembly steps.

  A buffer tank of an ink jet printer according to a fourth aspect of the present invention is a buffer tank for an ink jet printer that communicates with a nozzle that ejects ink and suppresses fluctuations in the back pressure of the ink that acts on the nozzle. An ink inflow pipe for covering the upper part of the tank main body and allowing the ink in the ink cartridge mounted on the upper side of the tank main body to flow into the tank main body and an air outflow pipe for allowing the air to flow out to the ink cartridge are respectively upper and lower. A cylindrical member in which a cross-sectional area of the hollow portion is larger than the ink inflow pipe and a portion of the ink inflow pipe extending from the top plate portion into the tank body is inserted, And a cylindrical member extending downward from the ink inflow pipe from the top plate portion.

  When ink flows out from the buffer tank to the nozzles and the ink level drops, the air in the buffer tank flows into the air outflow path and the air flows out to the ink cartridge. At the same time, the ink in the ink cartridge flows into the buffer tank from the ink inflow path so as to be replaced with the atmosphere. In the buffer tank, the ink passes through the cylindrical member whose hollow area is larger than the ink inflow pipe. Since it will flow, the flow resistance becomes small. Therefore, when the ink level drops, ink can be replenished quickly into the buffer tank, and fluctuations in the ink level can be suppressed as much as possible.

Embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, an ink jet printer 1 includes an ink jet head 2 having a nozzle 2a for ejecting ink I toward a recording paper P, and is connected to the ink jet head 2 via a supply tube 8 and above it. A buffer tank 4 that holds ink I flowing from the mounted ink cartridge 3, a carriage 5 that linearly moves the inkjet head 2 back and forth in one direction, a transport mechanism 6 that transports the recording paper P, and the inkjet head 2. A purge device 7 for sucking the air inside and the ink I having increased viscosity is provided.

  In this ink jet printer 1, ink I is supplied from the buffer tank 4 in which the ink cartridge 3 is mounted to the nozzle 2a of the ink jet head 2 through the supply tube 8, and the ink jet head 2 is driven by the carriage 5 in the direction perpendicular to the plane of FIG. The ink I is ejected from the nozzles 2a toward the recording paper P conveyed in the left-right direction in FIG. In order to prevent the ink I from leaking from the nozzle 2a when the ink I is not ejected from the nozzle 2a, the nozzle 2a is disposed at a position higher than the liquid level of the ink I in the buffer tank 4. ing.

  The purge device 7 sucks the ink I from the nozzle 2a and the purge cap 10 that can move in a direction approaching / separating from the ink discharge surface and that can be mounted on the inkjet head 2 so as to cover the ink discharge surface. A suction pump 11 is provided. When the ink jet head 2 is outside the printable range of the recording paper P, the suction pump 11 sucks the ink I, which has been mixed into the ink jet head 2 and evaporated to a high viscosity, from the nozzle 2a. Is possible.

  Next, the buffer tank 4 will be described. Before that, the ink cartridge 3 mounted above the buffer tank 4 will be briefly described. As shown in FIG. 1, the ink cartridge 3 includes a synthetic resin cartridge main body 20 that stores the ink I, and a synthetic resin lid member 21 that covers the lower portion of the cartridge main body 20. The cartridge body 20 is formed with two insertion holes 22 through which tips of an ink inflow pipe 36 and an atmospheric outflow pipe 38 described later are inserted. In addition, the cartridge body 20 is also formed with two cylindrical portions 23 that are connected to the upper ends of the two insertion holes 22 and extend into the cartridge body 20. In the two insertion holes 22, plug members 24 having elasticity (for example, made of rubber) for preventing ink leakage are press-fitted.

  The buffer tank 4 is for suppressing the fluctuation of the back pressure acting on the nozzle 2a by keeping the liquid level of the ink I held therein constant. As shown in FIGS. The ink cartridge 3 is mounted above the buffer tank 4, and the ink I in the ink cartridge 3 is configured to flow into the buffer tank 4. The buffer tank 4 includes a tank main body 30 that stores the ink I, and a top plate portion 31 that covers the upper portion of the tank main body 30. The tank main body 30 and the top plate portion 31 are each formed of a synthetic resin. Yes. The buffer tank 4 is formed with an air introduction port 32 for introducing air into the buffer tank 4. An ink outlet 33 is formed at the bottom of the tank body 30 to connect the supply tube 8 and allow the ink I to flow out to the nozzle 2a.

  Further, the buffer tank 4 causes the ink inflow path 34 through which the ink I in the ink cartridge 3 flows into the buffer tank 4 and the air in the buffer tank 4 introduced from the air introduction port 32 to flow out to the ink cartridge 3. And an atmospheric outflow passage 35 for the purpose.

  The ink inflow path 34 has an ink inflow pipe 36 provided in a vertically penetrating manner on the top plate portion 31, a diameter larger than the ink inflow tube 36, and the tank main body 30 from the top plate portion 31 of the ink inflow tube 36. It has the cylindrical member 37 (2nd cylindrical member) by which the part extended inward was inserted. On the other hand, the atmospheric outflow path 35 includes an atmospheric outflow pipe 38 provided in a vertically penetrating manner on the top plate portion 31, and a larger diameter than the atmospheric outflow pipe 38 and from the top plate portion 31 of the atmospheric outflow pipe 38 to the tank. A portion extending into the main body 30 has a cylindrical member 39 (first cylindrical member) inserted therein.

  The ink inflow pipe 36 and the atmospheric outflow pipe 38 are configured by hollow needle-shaped (cylindrical) metal members (for example, an inner diameter of 1.4 mm) having a sharp tip shape. Openings 36 a and 38 a are formed at the tip portions of the ink inflow pipe 36 and the atmospheric outflow pipe 38, respectively. The ink inflow pipe 36 and the atmospheric outflow pipe 38 are attached to the top plate 31 so as to protrude slightly downward from the top plate 31, and the lower ends of the ink inflow pipe 36 and the atmospheric outflow pipe 38 are at substantially the same position. Has been placed. Therefore, the ink inflow pipe 36 and the atmospheric outflow pipe 38 can be configured by the same hollow needle-like member.

  The two cylindrical members 37 and 39 are integrally formed with the top plate portion 31 made of synthetic resin. The cylindrical member 39 is formed in a cylindrical shape having a circular cross section, and has a larger diameter (for example, an inner diameter of about 6 mm) than the atmospheric outflow pipe 38, and the cross-sectional area of the hollow portion is that of the hollow portion of the atmospheric outflow pipe 38. It is larger than the cross-sectional area. A portion of the atmospheric outflow pipe 38 that extends from the top plate portion 31 into the tank body 30 is inserted into the cylindrical member 39 and communicates with the atmospheric outflow pipe 38. Further, the cylindrical member 39 is more than the atmospheric outflow pipe 38. It extends downward. Moreover, as shown in FIGS. 1-3, the protrusion part 39a which protrudes below partially in one place of the circumferential direction of the lower end part of the cylinder member 39 is formed, and in this protrusion part 39a, a cylinder member The separation distance from the lower end surface of 39 to the liquid surface of ink I is configured to be partially different.

  On the other hand, the cylindrical member 37 is formed in a cylindrical shape with a circular cross section, and has a larger diameter (for example, about 6 mm in inner diameter) than the ink inflow pipe 36, and the cross-sectional area of the hollow portion is hollow in the air outflow pipe 38. It is larger than the cross-sectional area of the part. A portion of the ink inflow pipe 36 that extends from the top plate portion 31 into the tank body 30 is inserted into the cylindrical member 37 and communicates with the ink inflow pipe 36. The cylindrical member 37 further includes the ink inflow pipe 36 and the cylinder. It extends below the member 39.

  When the ink cartridge 3 is mounted above the buffer tank 4 by passing the hollow needle-like ink inflow pipe 36 and the atmospheric outflow pipe 38 through the two plug members 24 of the ink cartridge 3, the opening of the atmospheric outflow pipe 38 is opened. The air flows out of the ink cartridge 3 from the air flow path 38a through the air outflow path 35, and the ink I in the ink cartridge 3 flows into the ink inflow pipe 36 from the opening 36a so as to be replaced with the air. Ink I flows into the buffer tank 4 via When the liquid level of the ink I in the buffer tank 4 rises and reaches the vicinity of the lower end of the cylindrical member 39 constituting the atmospheric outflow path 35, the ink I flows into the lower end of the cylindrical member 39 and the atmosphere is generated. Since the air does not enter the cylindrical member 39, the atmosphere does not flow out to the ink cartridge 3, and the ink I does not flow into the buffer tank 4 any more.

As described above, when the ink I is not discharged from the nozzle 2 a and the ink I does not flow out from the buffer tank 4 to the nozzle 2 a, the liquid level of the ink I in the buffer tank 4 is near the lower end of the cylindrical member 39. Has stopped. Here, as shown in FIG. 2, the distance h ₁ between the lower end of the cylindrical member 39 and the lower end of the atmospheric outflow pipe 38 breaks the meniscus formed in the atmospheric outflow pipe 38 due to the surface tension of the ink I. It is set to be larger than the water head difference h ₀ (see FIG. 8) necessary for this. As a specific example, when the surface tension of the ink I is 40 mN / m and the inner diameter of the atmospheric outflow pipe 38 is 1.4 mm, h ₀ is 9 mm. The distance h ₁ between the lower end of 39 and the lower end of the air outflow pipe 38 is 13 mm, which is larger than h ₀ .

Therefore, when the ink I is ejected from the nozzle 2 a and the ink I in the buffer tank 4 flows out to the nozzle 2 a, the liquid level of the ink I in the buffer tank 4 is lowered, but the ink I from the lower end of the atmospheric outflow pipe 38. for the distance to the liquid surface is always larger than h _0, the meniscus is not formed in the small air outlet tube 38 diameter, when the liquid surface of the ink I is separated from the lower end of the tubular member 39 decreases In addition, a meniscus is formed inside the lower end portion of the cylindrical member 39 by the surface tension of the ink I.

  Here, since the inner diameter of the cylindrical member 39 is larger than the inner diameter of the atmospheric outflow pipe 38 (for example, three times or more), the meniscus is formed in the atmospheric outflow pipe 38 like a conventional buffer tank as shown in FIG. Compared with the case where is formed, the water head difference (distance from the lower end surface of the cylindrical member 39 to the liquid surface of the ink I) necessary for breaking the meniscus is very small. For this reason, the meniscus of the cylindrical member 39 breaks and the atmosphere in the buffer tank 4 flows to the atmospheric outflow pipe 38 only when the liquid level of the ink I is slightly lowered.

  Furthermore, a protruding portion 39a that partially protrudes downward is formed at the lower end of the cylindrical member 39, and a portion having a different separation distance to the liquid surface of the ink I is formed by the protruding portion 39a. Become. Therefore, when the liquid level of the ink I is lowered, the balance of the surface tension of the meniscus formed on the cylindrical member 39 is easily lost, and the meniscus can be broken more easily. When the meniscus breaks, the ink I in the cylindrical member 39 is drawn into the buffer tank 4 along the protruding portion 39a by the surface tension of the ink I in the buffer tank 4, while the liquid of the ink I Atmosphere flows into the cylinder member 39 from the position on the left side in FIG. 2 at the lower end of the cylinder member 39 having a large separation distance from the surface, so that the ink I inside the cylinder member 39 instantaneously replaces the atmosphere. Therefore, when the liquid level of the ink I is lowered, the air can be quickly discharged to the ink cartridge 3.

  On the other hand, a portion of the ink inflow pipe 36 extending from the top plate portion 31 into the tank body 30 is inserted into a cylindrical member 37 having a diameter larger than that of the ink inflow pipe 36. The pipe 36 extends downward. Therefore, the ink I flowing into the buffer tank 4 from the ink cartridge 3 through the ink inflow path 34 flows in the large-diameter cylindrical member 37 in the buffer tank 4, and the flow resistance can be extremely reduced. Therefore, the atmosphere in the buffer tank 4 flows out to the ink cartridge 3 and the ink I in the ink cartridge 3 flows into the buffer tank 4 at the same time, so that the ink I is replenished to the buffer tank 4 quickly.

According to the inkjet printer 1 described above, the following effects can be obtained.
The top plate portion 31 of the buffer tank 4 is provided with a cylindrical member 39 having a diameter larger than that of the atmospheric outflow pipe 38 and communicating with the atmospheric outflow pipe 38. The cylindrical member 39 extends downward from the atmospheric outflow pipe 38. Yes. Therefore, when the liquid level of the ink I is lowered, no meniscus is formed in the small-diameter atmospheric outflow pipe 38, and a meniscus is formed in the lower end portion of the large-diameter cylindrical member 39. The formed meniscus is easily broken compared to the small-diameter atmospheric outflow pipe 38. Thereby, since the fluctuation amount of the liquid level of the ink I can be reduced as compared with the conventional buffer tank, the back pressure fluctuation of the ink I acting on the nozzle 2a can be suppressed smaller than that of the conventional one.

  Further, since a protruding portion 39a that protrudes partially downward is formed at the lower end of the cylindrical member 39, the balance of the surface tension of the meniscus formed on the cylindrical member 39 is likely to be lost, and the meniscus can be more easily removed. Can break. Accordingly, when the liquid level of the ink I is slightly lowered, the meniscus of the cylindrical member 39 is quickly broken, so that the atmosphere can be immediately discharged to the ink cartridge 3 through the atmosphere outflow path 35.

  The top plate portion 31 of the buffer tank 4 is also provided with a cylindrical member 37 having a diameter larger than that of the ink inflow pipe 36 and communicating with the ink inflow pipe 36. The cylindrical member 37 is also below the ink inflow pipe 36. It extends to. Therefore, the ink I that has flowed into the buffer tank 4 from the ink cartridge 3 flows in the large-diameter cylindrical member 37 in the buffer tank 4, and thus its flow resistance is reduced. Accordingly, when the atmosphere in the buffer tank 4 flows out to the ink cartridge 3 through the atmosphere outflow path 35, the ink I immediately flows into the buffer tank 4 from the ink inflow path 34, and the ink I enters the buffer tank 4. Since the ink is quickly replenished, fluctuations in the liquid level of the ink I in the buffer tank 4 can be suppressed, and fluctuations in the back pressure of the ink I acting on the nozzle 2a can be minimized.

  Since there is no need to make a difference between the positions of the lower ends of the ink inflow pipe 36 and the atmospheric outflow pipe 38 and the positions of the lower ends can be made the same, the ink inflow pipe 36 and the atmospheric outflow pipe 38 are formed in the same hollow needle shape. Therefore, the component cost can be reduced.

  Since the top plate portion 31 and the cylindrical members 37 and 39 are integrally formed of synthetic resin, the number of parts can be reduced and the number of steps for assembly can be omitted, so that the manufacturing cost can be reduced. .

Next, modified embodiments in which various modifications are made to the embodiment will be described. However, components having the same configurations as those of the above-described embodiment are denoted by the same reference numerals and description thereof is omitted as appropriate.
1] The shape of the lower end of the cylindrical member 39 communicating with the atmospheric outflow pipe 38 is preferably the shape shown in FIG. 3 described above, but is not necessarily limited to that shape. For example, as shown in FIG. 4, the lower end surface of the cylindrical member 39A may be formed in parallel with the liquid surface of the ink I. In this case, the balance of the surface tension of the meniscus is less likely to be lost compared with the shape of FIG. 3 described above, and the liquid level of the ink I is greatly reduced until the meniscus is broken. As compared with the case where the meniscus is formed in the atmospheric outflow pipe 38 having a small inner diameter as in the buffer tank, the meniscus break is remarkably facilitated. Further, the shape processing of the cylindrical member 39A becomes very easy. Furthermore, if the shape has a portion having a different separation distance from the lower end surface of the cylindrical member 39 and the liquid surface of the ink I, the meniscus can be easily broken as compared with the buffer tank of FIG. As shown, the balance of the surface tension of the meniscus may be easily broken by inclining the lower end surface of the cylindrical member 39B with a predetermined angle (for example, about 10 degrees) with respect to the liquid surface of the ink I.

2] It is not always necessary to integrally form the top plate portion 31 and the cylindrical members 37 and 39 with a synthetic resin, and each may be constituted by separate members.
3] In the above embodiment, the ink inflow pipe 36 and the atmospheric outflow pipe 38 penetrate the top plate portion 31 vertically, but as shown in FIG. 6, these ink inflow pipes 36 are provided in the buffer tank 4C. And the air outflow pipe 38 may project only upward without extending downward from the top plate portion 31 and communicate with the cylindrical members 37C and 39C, respectively. In this case, the distance from the lower end of the atmospheric outflow pipe 38 to the liquid level of the ink I can be made longer. Further, since the ink I flows only through the large-diameter cylindrical member 37C in the buffer tank 4C, the flow resistance when the ink I flows into the buffer tank 4C can be further reduced.
4] The cylindrical member 39 into which the atmospheric outflow pipe 38 is inserted has only to have a diameter larger than that of the atmospheric outflow pipe 38 at least at the lower end. For example, the cylindrical member 39 is formed in a so-called trumpet shape whose inner diameter increases toward the lower side. May be.

  5] In the above-described embodiment, the cylindrical members 37 and 39 are formed in a cylindrical shape. However, the cylindrical members 37 and 39 are not limited to these shapes. For example, the cylindrical members 37 and 39 may be formed in a polygonal prism shape. . That is, as long as the cross-sectional area of the hollow portion at least at the lower end of the cylindrical member 37 is configured to be larger than the cross-sectional area of the hollow portion of the ink inflow tube 36, the cylindrical member 37 has any cross-sectional shape compared to the conventional one. Thus, the flow resistance when the ink I flows into the buffer tank 4 can be reduced. In addition, as long as the cross-sectional area of the hollow portion at least at the lower end of the cylindrical member 39 is configured to be larger than the cross-sectional area of the hollow portion of the atmospheric outflow pipe 38, the cylindrical member 39 has any cross-sectional shape compared to the conventional one. The meniscus can be easily broken.

1 is a schematic configuration diagram of an inkjet printer according to an embodiment of the present invention. It is sectional drawing of a buffer tank. It is an enlarged view of the lower end part of a cylinder member. FIG. 4 is a diagram corresponding to FIG. 3 in a modified form. FIG. 6 is a diagram corresponding to FIG. 3 in another modified form. FIG. 6 is a view corresponding to FIG. 2 showing another modification. It is sectional drawing of the conventional ink cartridge and a buffer tank. It is sectional drawing of the conventional buffer tank.

Explanation of symbols

I Ink 1 Inkjet printer 2a Nozzle 3 Ink cartridges 4 and 4C Buffer tank 30 Tank body 31 Top plate portion 32 Atmospheric introduction port 34 Ink inflow path 35 Atmospheric outflow path 36 Ink inflow pipes 37 and 37C Cylindrical member

Claims (4)

A nozzle that ejects ink, and a buffer tank that holds ink flowing in from an ink cartridge mounted above and discharges ink toward the nozzle;
The buffer tank is
The ink in the ink cartridge is introduced into the buffer tank, and at least the ink inflow path including a portion extending downward from the top plate portion of the tank body in the buffer tank and the atmosphere is introduced from the outside. An atmosphere introduction port, and an atmosphere outflow passage for causing the atmosphere in the buffer tank to flow out to the ink cartridge,
The ink inflow path is
An ink inflow pipe provided on the top plate and extending vertically;
A cylindrical member having a hollow cross-sectional area larger than that of the ink inflow pipe and communicating with the ink inflow pipe, being below the ink inflow pipe from the top plate and below the lower end of the air outflow path A cylindrical member extending to the position of
An ink jet printer comprising:   The ink inflow tube is provided in a vertically penetrating manner in the top plate portion, and the cylindrical member is inserted into a portion of the ink inflow tube extending from the top plate portion into the tank body. Item 10. The inkjet printer according to Item 1.   The inkjet printer according to claim 1, wherein the top plate portion and the cylindrical member are integrally formed of a synthetic resin. A buffer tank of an ink jet printer that communicates with a nozzle that ejects ink and suppresses fluctuations in the back pressure of the ink that acts on the nozzle.
The tank body,
An ink inflow pipe for covering the upper part of the tank main body and allowing the ink in the ink cartridge mounted on the upper side of the tank main body to flow into the tank main body and an air outflow pipe for allowing the air to flow out to the ink cartridge are respectively A top plate that penetrates
A cylindrical member in which a cross-sectional area of the hollow portion is larger than that of the ink inflow pipe and a portion of the ink inflow pipe extending from the top plate portion into the tank main body is inserted, from the top plate portion to the ink inflow pipe A cylindrical member extending downward,
A buffer tank for an ink jet printer, comprising:

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