WO2016136333A1 - Liquid discharge device and intermediate retaining body - Google Patents

Abstract

In the present invention, a liquid discharge device is provided with a discharge head that discharges a liquid, a liquid supply path that supplies the liquid to the discharge head, and an intermediate retaining body disposed in the liquid supply path. The intermediate retaining body comprises a first retaining chamber, a second retaining chamber disposed upstream of the first retaining chamber, an upper communication path that communicates between the first retaining chamber and the second retaining chamber, and a lower communication path that communicates between the first retaining chamber and the second retaining chamber below the upper communication path. The lower communication path has a lower communication opening that opens into the second retaining chamber, the upper communication path has an upper communication opening that opens into the second retaining chamber, and the lower communication opening is smaller than the upper communication opening.

Description

Liquid ejection device and intermediate reservoir

The present invention relates to a liquid ejection apparatus such as an ink jet printer and an intermediate storage body provided in the apparatus.

Generally, as a kind of liquid ejection device, an ink jet printer that performs printing by ejecting ink (liquid) from a nozzle opening of an ejection head to a medium is widely known. Some of such printers include a liquid introduction channel member that introduces ink of an ink cartridge into a head main body (ejection head) (see, for example, Patent Document 1).

This liquid introduction flow path member is provided with an ink introduction path for supplying ink to the nozzle openings. The ink introduction path includes a filter chamber, a pressure chamber disposed upstream of the filter chamber, a first communication path, and a second communication path. The first communication path has a bubble chamber extending vertically upward from the pressure chamber, and allows ink in the pressure chamber to flow into the filter chamber from the first communication path inlet of the pressure chamber. On the other hand, the second communication path causes ink in the pressure chamber to flow into the filter chamber from a second communication path inlet provided separately from the first communication path inlet below the first communication path inlet.

JP 2010-52210 A

By the way, in the printer of Patent Document 1, the second communication path inlet is disposed below the first communication path inlet. However, when bubbles are mixed in from the pressure chamber, the bubbles flow in from the second communication path inlet. The bubbles may flow into the filter chamber together with the ink via the second communication path. As a result, there is a problem that bubbles may enter the head body.

Such problems are not limited to ink jet printers that perform printing by ejecting ink from the nozzle openings of the ejection head, but are generally common to liquid ejection apparatuses that eject liquid from the nozzle openings of the ejection head. Yes.

An object of the present invention is to provide a liquid discharge device and an intermediate reservoir that can suppress bubbles from entering the discharge head.

A liquid discharge apparatus according to an aspect of the present disclosure includes a discharge head that discharges liquid from a nozzle to a medium, a liquid supply path that supplies the liquid stored in a liquid supply source to the discharge head, and the liquid supply An intermediate storage body that is provided in the path and can store the liquid. The intermediate storage body includes a first storage chamber capable of storing the liquid, a second storage chamber disposed upstream of the first storage chamber and capable of storing the liquid, the first storage chamber, An upper communication path that communicates with the second storage chamber, and a lower communication path that communicates the first storage chamber and the second storage chamber below the upper communication path, and the lower communication path The passage has a lower communication port that opens to the second storage chamber, the upper communication passage has an upper communication port that opens to the second storage chamber, and the lower communication port is more than the upper communication port. small.

According to this configuration, since the lower communication port is smaller than the upper communication port, bubbles can be prevented from flowing into the lower communication channel from the lower communication port. Therefore, it is possible to suppress bubbles from entering the ejection head.

In the liquid ejecting apparatus, it is preferable that the lower communication port is open upward.
According to this configuration, since the bubbles in the liquid are likely to float upward, the bubbles can be effectively prevented from flowing into the lower communication passage from the lower communication port.

In the liquid ejection apparatus, the lower communication path includes an upstream path extending from the lower communication port to a position lower than the lower communication port, and a downstream path extending upward from the downstream side of the upstream path. It is preferable to have.

According to this configuration, even when air bubbles flow into the lower communication path from the lower communication port, the upstream path extends from the lower communication port to a position lower than the lower communication port. Bubbles flowing into the lower communication path can be returned to the second storage chamber by the buoyancy. In addition, by forming the lower communication path with the upstream path and the downstream path, the flow resistance of the lower communication path is set high without increasing the distance between the first storage chamber and the second storage chamber. can do.

The liquid discharge device is provided in the first storage chamber, divides the first storage chamber into a downstream space connected to the discharge head and an upstream space connected to the second storage chamber, and the liquid passes therethrough. It is preferable that a filter having a possible hole is further provided, and the lower communication port is located above the filter.

According to this configuration, even when air bubbles flow into the lower communication path from the lower communication port, the air bubbles can be prevented from passing through the filter and entering the ejection head.
In the liquid ejection apparatus, the liquid supply path includes an inflow opening that opens into the second storage chamber, and the liquid supplied from the liquid supply source flows into the second storage chamber through the inflow port, The lower communication port is preferably located below the inflow port and opens in a direction different from the opening direction of the inflow port.

According to this structure, it can suppress that the bubble contained in the liquid which flows in into a 2nd storage chamber from an inflow port flows in into a lower communication path from a lower communication port.
In the liquid ejection apparatus, the upper communication port is an upper second communication port, and the upper communication channel further includes an upper first communication port that opens into the first storage chamber, and the lower communication port Is a lower second communication port, and the lower communication channel further includes a lower first communication port that opens to the first storage chamber, and the flow resistance and the upper side of the lower communication channel are The flow path resistance of the communication path is such that the liquid level of the intermediate reservoir is higher than the lower first communication port and the lower second communication port, and the upper first communication port and the upper second communication port. When the liquid is ejected from the ejection head to the medium in a steady state located below the mouth, the liquid level of the first storage chamber is set so as not to contact the filter. preferable.

According to this configuration, the liquid level (gas-liquid interface) of the liquid does not contact the filter when the liquid is discharged from the discharge head to the medium, so that the liquid supply capacity to the discharge head is reduced or bubbles pass through the filter. Thus, it is possible to suppress entry into the discharge head side.

The liquid ejecting apparatus further includes a discharge unit configured to execute a discharge operation of discharging the liquid from the nozzle, and the discharge unit discharges the liquid from the nozzle in the steady state. The filter is configured to execute a special discharge operation for bringing the liquid level of the first storage chamber into contact with the filter, and the hole of the filter causes the liquid to pass through the liquid supply path in accordance with the execution of the special discharge operation. It is preferable that the liquid meniscus formed in the hole of the filter is broken by a pressure difference between the downstream space and the upstream space when flowing.

According to this configuration, the bubbles staying in the second storage chamber can be discharged by performing the special discharge operation.
An intermediate reservoir according to an aspect of the present disclosure is provided in a liquid supply path that supplies the liquid stored in a liquid supply source to a discharge head that discharges liquid from a nozzle to a medium, and can store the liquid A first storage chamber capable of storing the liquid; a second storage chamber disposed upstream of the first storage chamber and capable of storing the liquid; and the first storage chamber. An upper communication path that communicates with the second storage chamber, and a lower communication path that communicates the first storage chamber and the second storage chamber below the upper communication path. The communication passage has a lower communication port that opens to the second storage chamber, the upper communication passage has an upper communication port that communicates with the second storage chamber, and the lower communication port is connected to the upper communication port. Is also small.

According to this configuration, since the lower communication port is smaller than the upper communication port, bubbles can be prevented from flowing into the lower communication channel from the lower communication port. Therefore, it is possible to suppress bubbles from entering the ejection head.

A liquid ejection apparatus according to a further aspect of the present disclosure includes: an ejection head that ejects liquid; a liquid supply path that supplies the liquid from a liquid storage unit that stores the liquid to the ejection head; and the liquid supply path And a filter part having a filter member for removing foreign substances in the liquid. The filter section includes a filter chamber in which the filter member is provided and an ink storage chamber in which the liquid is stored, and the filter chamber includes an upstream filter chamber and a downstream filter chamber partitioned by the filter member. The ink storage chamber and the upstream filter chamber are connected by a first communication pipe, a second communication pipe, and a ventilation pipe, and the first communication pipe includes the second communication pipe and the second communication pipe. Due to the pressure loss due to the first communication pipe below the vent pipe, a hydraulic head difference between the ink storage chamber and the upstream filter chamber is generated more than the length of the upstream filter chamber in the gravity direction. It is configured to be able to.

According to this configuration, the ink supplied to the ink storage chamber is transported to the upstream filter chamber through the first communication pipe, passes through the filter member, and is discharged to the ejection head side through the downstream filter chamber. At this time, air is present above the ink storage chamber and in the vent pipe. Since the air in each room can be moved back and forth by the vent pipe, the water level in each room changes according to the difference in water head.

When ink suction is performed from the discharge head side when the liquid level of the ink storage chamber is lower than the connection portion with the second communication pipe and the connection portion with the vent pipe, the ink storage chamber and the upstream filter are caused by the pressure loss of the first communication pipe. Since there is a water head difference between the chamber and the upstream filter chamber in the gravitational direction, the water level in the upstream filter chamber is lowered, and almost the entire filter member is covered with air. Since the ink flow is concentrated on the portion of the filter member not covered with air, the flow velocity is locally increased, and the pressure loss of the filter portion increases. As a result, a pressure equal to or higher than the bubble point is applied to the filter portion, and the air in the upstream filter chamber can be discharged downstream. Therefore, according to the above configuration, it is possible to obtain a liquid ejection device that can discharge bubbles accumulated in the filter unit with a simple and low-cost structure.

In the liquid ejecting apparatus, it is preferable that the second communication pipe has a shape protruding upward in the gravitational direction, and an uppermost part of the second communication pipe is lower than the uppermost part of the ink storage chamber. .

According to this configuration, since the second communication pipe has a shape protruding upward, the water level in the ink storage chamber rises to the top of the second communication pipe when bubbles are discharged by ink suction. After that, the water level decreases with the inflow of bubbles from the upstream, but ink continues to flow between the ink storage chamber and the filter chamber according to the siphon principle. Even if ink suction is performed in this state, most of the ink flows through the second communication pipe, so that the water level in the filter chamber does not decrease due to the pressure loss of the first communication pipe. That is, the discharge of bubbles is suppressed.

Since the ink flow in the second communication pipe is maintained until the water level in the ink storage chamber becomes equal to or lower than the connection part of the second communication pipe, the bubbles are not discharged until a certain amount of bubbles flow in. Therefore, this configuration has an advantage that the frequency of bubbles flowing into the ejection head during ink suction is reduced, and it becomes difficult to induce ejection failure.

In the liquid ejecting apparatus, it is preferable that the upper surface of the ink storage chamber is located above the upper surface of the upstream filter chamber in the direction of gravity.
According to this configuration, since the ink storage chamber is higher than the filter chamber, the residual air is stored mainly on the ink storage chamber side. As a result, the area of the filter member covered with air decreases, and the area of the filter member through which ink can pass increases. Therefore, this structure has an advantage that the utilization efficiency of the filter member is increased.

In the liquid ejecting apparatus, it is preferable that a flow path resistance of the first communication pipe is larger than a flow path resistance of the second communication pipe.
According to this configuration, since the flow resistance of the first communication pipe is larger than that of the second communication pipe, the head difference between the ink storage chamber and the filter chamber is smaller when ink is flowing through the second communication pipe. Therefore, when ink suction is performed in a state where ink is flowing through the second communication pipe, the water level in the upstream filter chamber is unlikely to decrease. Thereby, the discharge of bubbles is suppressed, and the bubbles are not discharged even if ink is sucked unless new bubbles are accumulated. Therefore, this configuration has an advantage that the frequency of bubbles flowing into the ejection head during ink suction is reduced, and it becomes difficult to induce ejection failure.

In the liquid ejecting apparatus, it is preferable that the vent pipe is connected to the ink storage chamber above the position of the second communication pipe connected to the ink storage chamber in the gravity direction.

According to this configuration, since the vent pipe is connected to the ink storage chamber at a position above the connection portion with the second communication pipe, it is above the connection portion with the second communication pipe in the ink storage chamber at the time of ink suction. Certain air can be exhausted through the vent tube. As a result, the water level in the ink storage chamber rises to a position above the connection portion with the second communication pipe, and the water level does not immediately fall below the connection portion with the second communication pipe even if a new bubble flows in thereafter. Since the bubble discharge operation is suppressed unless air inflow to the second communication pipe occurs, once the bubbles are discharged, the bubble discharge operation does not occur even if a certain amount of bubbles flow. Therefore, this configuration has an advantage that the frequency of bubbles flowing into the ejection head during ink suction is reduced, and it becomes difficult to induce ejection failure.

1 is a perspective view illustrating a schematic configuration of an ink jet printer according to a first embodiment. FIG. 2 is a schematic cross-sectional view showing an internal structure of the printer of FIG. 1. FIG. 2 is a schematic cross-sectional view illustrating an ink supply path in the printer of FIG. 1. FIG. 4 is a schematic cross-sectional view showing the structure of an intermediate reservoir in the ink supply path of FIG. 3. The schematic sectional drawing explaining operation | movement (initial filling state) of the intermediate | middle storage body of FIG. The schematic sectional drawing explaining operation | movement (after a long-term use) of the intermediate | middle storage body of FIG. The schematic sectional drawing explaining operation | movement (air discharge operation | movement 1) of the intermediate | middle storage body of FIG. FIG. 5 is a schematic cross-sectional view illustrating an operation (air discharge operation 2) of the intermediate storage body in FIG. FIG. 5 is a schematic cross-sectional view illustrating an operation (air discharge operation 3) of the intermediate storage body in FIG. FIG. 5 is a schematic cross-sectional view illustrating an operation (air discharge operation 4) of the intermediate storage body in FIG. The schematic sectional drawing explaining operation | movement (printing state) of the intermediate | middle storage body of FIG. The schematic sectional drawing which shows the structure (air discharge operation state) of the intermediate | middle storage body of 2nd Embodiment. The side view of the intermediate | middle storage body of 3rd Embodiment. FIG. 14 is a perspective view of the intermediate storage body of FIG. 13. FIG. 15 is a sectional view taken along line 15-15 in FIG. 14; FIG. 14 is a schematic cross-sectional view for explaining the operation (initial filling state) of the intermediate reservoir in FIG. 13. FIG. 14 is a schematic cross-sectional view for explaining the operation (after being left for a long time) of the intermediate reservoir in FIG. 13. FIG. 14 is a schematic cross-sectional view illustrating an operation (special discharge operation 1) of the intermediate reservoir in FIG. FIG. 14 is a schematic cross-sectional view illustrating an operation (special discharge operation 2) of the intermediate reservoir in FIG. The schematic diagram explaining the pressure which the meniscus formed in the hole of the filter of the intermediate storage body of FIG. 13 breaks. FIG. 14 is a schematic cross-sectional view illustrating an operation (special discharge operation 3) of the intermediate reservoir in FIG. FIG. 14 is a schematic cross-sectional view for explaining the operation (discharge operation) of the intermediate reservoir in FIG. 13. FIG. 14 is a schematic cross-sectional view illustrating the operation (printing state) of the intermediate reservoir in FIG. 13. Sectional schematic diagram which shows schematic structure of the inkjet printer of 4th Embodiment. FIG. 6 is a schematic cross-sectional view showing a main part of an ink jet printer of a modification example. FIG. 6 is a schematic cross-sectional view showing the main part of an ink jet printer according to another modification.

(First embodiment)
Hereinafter, a first embodiment in which a liquid ejection device is embodied in an ink jet printer will be described with reference to the drawings.

As shown in FIG. 1, an ink jet printer 1 as an example of a liquid ejection device has a substantially rectangular box shape. In the following description, when the ink jet printer 1 is installed, the upper surface of the two surfaces orthogonal to the direction of gravity is referred to as the upper surface, the lower side is referred to as the bottom surface, and the two surfaces in contact with the long sides of the upper surface and the bottom surface. One surface is referred to as a front surface, the surface opposite to the front surface is referred to as a back surface, and two surfaces in contact with the short sides of the top surface and the bottom surface are referred to as side surfaces.

As shown in FIG. 1, a front cover 2 and a plurality of operation buttons 4 are provided on the front surface of the ink jet printer 1. The front cover 2 is pivotally supported on the lower end side. When the front cover 2 is rotated so that the upper end side is tilted forward, an elongated paper discharge port 3 from which a printing paper 20 as an example of a medium is discharged appears.

The ink jet printer 1 has a paper feed tray (not shown) on the back side thereof. When the printing paper 20 is set in the paper feeding tray and the operation button 4 is operated, the printing paper 20 supplied from the paper feeding tray is changed. The printing paper 20 is conveyed by a predetermined amount, and after the image or the like is printed on the surface of the printing paper 20 inside, the printing paper 20 is discharged from the paper discharge port 3.

An upper surface cover 6 is provided on the upper surface side of the ink jet printer 1. The upper surface cover 6 is pivotally supported on the back side, and the front side cover 6 is lifted and opened so that the upper surface cover 6 is rotated, thereby confirming the internal state of the ink jet printer 1 or the ink jet printer 1. It is possible to perform repairs.

A tank case 7 having a rectangular box shape is provided on the side surface of the ink jet printer 1 via a pedestal 5. Four ink tanks 9 as an example of a liquid supply source are provided inside the tank case 7, and ink as liquid stored in these ink tanks 9 is supplied to the ink jet printer 1 and used for printing. It is supposed to be. In the ink jet printer 1 of this embodiment, a color image can be printed using four types of inks of cyan, magenta, yellow, and black, and an ink tank 9 is provided for each type of ink.

A confirmation window 8 is provided on the side surface of the tank case 7 (the surface far from the ink jet printer 1), and the four ink tanks 9 provided in the tank case 7 are visible. Further, since the ink tank 9 is formed of a transparent or translucent resin material, the remaining amount of ink in the ink tank 9 can be visually confirmed from the outside.

Next, the internal structure of the ink jet printer 1 will be described.
As shown in FIG. 2, the ink jet printer 1 includes a carriage 11 that reciprocates on a printing paper 20, an ejection head 12 that is mounted on the bottom side of the carriage 11 (the side on which the printing paper 20 is disposed), And an intermediate reservoir 30 mounted on the carriage 11. The intermediate reservoir 30 is connected to the ink tank 9 via the connection tube 10 and is connected to the ejection head 12 via the head connection tube 52 (see FIG. 3).

The intermediate reservoir 30 temporarily stores the ink supplied from the ink tank 9 through the connection tube 10 and removes foreign matters in the ink, and then discharges the ink through the head connection tube 52 (see FIG. 3). Supply to the head 12. In the present embodiment, the connection tube 10, the intermediate reservoir 30, and the head connection tube 52 are components of a liquid supply path that supplies ink stored in the ink tank 9 to the ejection head 12. That is, the intermediate reservoir 30 is provided in the middle of the liquid supply path.

Then, the ejection head 12 ejects the ink supplied from the ink tank 9 to the printing paper 20 as ink droplets from the nozzle 12a. In the ink jet printer 1 according to the present embodiment, four types of inks of cyan, magenta, yellow, and black are used. Therefore, the ejection head 12 mounted on the carriage 11 is provided for each ink type (color). A nozzle 12a is provided.

The carriage 11 is driven by a drive mechanism (not shown) and repeats reciprocating movement on the printing paper 20 while being guided by the guide rail 13. The ink jet printer 1 is also provided with a paper feeding mechanism (not shown) for transporting the printing paper 20, and the paper feeding mechanism transports the printing paper 20 little by little according to the movement of the carriage 11 reciprocatingly. An image or the like is printed on the printing paper 20 by ejecting ink from the nozzles 12a of the ejection head 12 in accordance with the movement of the carriage 11 reciprocatingly and the movement of the printing paper 20 being conveyed.

Four types of ink (cyan, magenta, yellow, and black) discharged from the nozzles 12a of the discharge head 12 are respectively stored in four ink tanks 9 provided in the tank case 7. The ink in each ink tank 9 is supplied to the ejection head 12 of the carriage 11 via the connection tube 10, the intermediate reservoir 30, and the head connection tube 52 (see FIG. 3) provided for each type of ink. . The intermediate reservoir 30 has a pressure damper function, and absorbs ink pressure fluctuations that occur during the operation of the carriage 11.

Further, an area called a home position is provided at a position where the carriage 11 is moved along the guide rail 13 to the outside of the printing paper 20 inside the ink jet printer 1. At the home position, a bottomed box-like cap 14 is provided, and this cap 14 can be moved in the vertical direction by an elevating mechanism (not shown).

While the ink jet printer 1 is not printing an image or the like, when the carriage 11 is moved to the home position and the cap 14 is raised, the cap 14 is moved to the bottom surface (surface on which the nozzle 12a is opened) of the ejection head 12. A closed space is formed so as to cover the nozzle 12a by being pressed. For this reason, it can suppress that the ink in the nozzle 12a (inside the discharge head 12) dries.

Further, a suction pump 16 is connected to the cap 14 via a suction tube 15. Then, the suction pump 16 is operated in a state where the cap 14 is pressed against the bottom surface side of the discharge head 12 to suck the inside of the cap 14 (closed space), thereby performing initial filling of the ink into the discharge head 12, It is also possible to perform normal cleaning (maintenance) for sucking out deteriorated ink (such as ink that has been dried and thickened) in the discharge head 12. In the present embodiment, the cap 14, the suction tube 15, and the suction pump 16 are components of the discharge unit 18 that can perform a discharge operation (normal cleaning) for sucking and discharging ink from the nozzle 12a.

Furthermore, a control unit 17 that controls the operation of the entire inkjet printer 1 is provided inside the inkjet printer 1. The control unit 17 sucks and discharges the ink from the nozzle 12a to maintain the normal printing, the operation of reciprocating the carriage 11, the operation of transporting the printing paper 20, the operation of discharging the ink from the nozzle 12a, and the normal printing. Controls the discharging operation (normal cleaning).

3 and 5, the ink tank 9 and the intermediate reservoir 30 are connected by a connection tube 10, and the intermediate reservoir 30 and the discharge head 12 are connected by a head connection tube 52. The intermediate storage body 30 as an example of the filter unit holds ink together with a certain amount of air inside an ink storage chamber 32 as an example of the ink storage chamber or the second storage chamber. Absorbs and mitigates pressure fluctuations.

When the printing paper 20 is printed, the ink in the connection tube 10 undergoes pressure fluctuation due to the water hammer effect as the carriage 11 accelerates and decelerates. It is possible to suppress the ink supply pressure to 12 from fluctuating rapidly, and to stabilize ink discharge from the discharge head 12.

Further, the intermediate reservoir 30 includes a filter 42 as an example of a filter member for removing foreign matter inside, and the filter 42 obstructs passage of foreign matter contained in the ink supplied from the ink tank 9. Thereby, the inflow of foreign matter to the ejection head 12 is suppressed, and clogging of the ejection head 12 and ink ejection failure from the ejection head 12 are reduced.

Since the filter 42 inhibits passage of not only foreign substances but also fine bubbles 54 (see FIG. 6), bubbles 54 flowing from upstream are accumulated on the upstream side of the filter 42. The accumulated bubbles 54 become large air masses, block the filter 42, and cause ejection failure of ink from the ejection head 12. Therefore, it is necessary to periodically discharge the bubbles 54. In the present embodiment, the bubbles 54 are discharged by sucking ink from the ejection head 12 side.

Next, the configuration of the intermediate reservoir 30 will be described in detail.
As shown in FIGS. 3 and 4, the intermediate reservoir 30 includes a filter chamber 34 as an example of a first storage chamber that can store ink, and an ink storage chamber 32 that can store ink. A filter 42 is provided in the filter chamber 34. In the present embodiment, the filter chamber 34 is partitioned along the vertical direction by the filter 42 and is divided into an upstream filter chamber 44 that forms an upstream space and a downstream filter chamber 46 that forms a downstream space. . An ink discharge port 50 is provided in the downstream filter chamber 46, and the ink discharge port 50 is connected to the ejection head 12 through a head connection tube 52.

The upstream filter chamber 44 is connected to the ink storage chamber 32 through a first communication pipe 36, a second communication pipe 38, which form a lower communication path, and a vent pipe 40, which forms an upper communication path. An ink inlet 48 is provided in the ink storage chamber 32, and the ink inlet 48 is connected to the ink tank 9 through the connection tube 10. The upper surface of the ink storage chamber 32 is disposed above the upper surface of the upstream filter chamber 44 in the gravity direction.

The first communication pipe 36 is disposed below the second communication pipe 38 and the vent pipe 40 in the direction of gravity, and the ink flow is always maintained. Since the first communication pipe 36 is formed of a thin pipe and has a function as a so-called orifice, a large pressure loss occurs when ink is sucked from the ejection head 12 side. This pressure loss is designed so that a water head difference between the ink storage chamber 32 and the upstream filter chamber 44 is greater than the length of the upstream filter chamber 44 in the gravitational direction. The flow resistance of the first communication pipe 36 is designed to be larger than the flow resistance of the second communication pipe 38.

The second communication pipe 38 is connected to the side surface of the ink storage chamber 32 and has a bent shape protruding upward in the direction of gravity. The uppermost part of the second communication pipe 38 is at a position below the uppermost part of the ink storage chamber 32 in the gravity direction. The second communication pipe 38 has a function as a so-called siphon, and once ink starts flowing, the ink can flow even when the water level in the ink storage chamber 32 is lower than the uppermost part of the second communication pipe 38. it can. The position where the vent pipe 40 and the ink storage chamber 32 are connected is higher in the gravity direction than the position where the second communication pipe 38 and the ink storage chamber 32 are connected. The uppermost part of the vent pipe 40 is arranged above the uppermost part of the second communication pipe 38 in the gravity direction.

Next, the operation of the intermediate reservoir 30 will be described.
<Initial filling state>
As shown in FIG. 5, in a state immediately after ink is filled into the intermediate reservoir 30 by ink suction from the ejection head 12 side, the filter chamber 34, the first communication pipe 36, and the second communication pipe 38 are completely closed. However, air remains in the upper part of the ink storage chamber 32 and the upper part of the vent pipe 40, respectively. This air produces a damper effect and suppresses ink pressure fluctuations.

<After long-term use>
As shown in FIG. 6, when the inkjet printer 1 is used for a long period of time, bubbles 54 may be generated in the connection tube 10. The bubbles 54 ride on the ink flow by printing and flow into the ink storage chamber 32 from the ink inlet 48. The inflowing bubbles 54 are stored integrally with the air in the upper part of the ink storage chamber 32. However, as the amount of inflow of the bubbles 54 increases, the water levels in the ink storage chamber 32 and the upstream filter chamber 44 decrease.

Then, when the water level in the upstream filter chamber 44 falls below a certain value, the filter 42 is blocked, causing discharge failure. Therefore, it is necessary to discharge air before the water level in the upstream filter chamber 44 falls below a certain value. Ink suction is used to discharge this air.

<Air discharge operation 1>
As shown in FIG. 7, when ink suction from the ejection head 12 side is performed in a state where the water level of the upstream filter chamber 44 is lowered, the ink in the ink storage chamber 32 passes through only the first communication pipe 36 and the upstream filter chamber 44. To flow. Due to the pressure loss generated in the first communication pipe 36 at this time, a water head difference H is generated between the ink in the ink storage chamber 32 and the ink in the upstream filter chamber 44. As a result, the air stored in the upper portion of the ink storage chamber 32 flows into the upstream filter chamber 44 through the vent pipe 40 and the second communication pipe 38.

<Air discharge operation 2>
As shown in FIG. 8, as the water level in the upstream filter chamber 44 decreases, the area of the filter wetted part 56 becomes very small. Then, since the ink flow is concentrated in a limited area, the ink flow is locally accelerated and a large pressure loss is caused by the filter 42. When this pressure loss becomes equal to or higher than the bubble point pressure of the filter 42, air can pass through the filter 42, and the air in the upstream filter chamber 44 is discharged into the downstream filter chamber 46 as bubbles 54. As the air is discharged, the water level in the ink storage chamber 32 rises.

<Air discharge operation 3>
As shown in FIG. 9, when the water level in the ink storage chamber 32 reaches the same height as the uppermost portion of the second communication pipe 38, ink begins to flow into the second communication pipe 38, so that the upstream filter chamber 44 rapidly Filled with ink. At this time, the air in the upstream filter chamber 44 flows into the ink storage chamber 32 through the vent pipe 40.

<Air discharge operation 4>
A part of the air stored in the ink storage chamber 32 through the above operation is discharged, and the water level in the intermediate storage body 30 returns to the state before the bubble accumulation as shown in FIG. In this state, the ink storage chamber 32 and the upstream filter chamber 44 are connected by the second communication pipe 38 with little pressure loss. For this reason, even if ink suction from the ejection head 12 side is performed again, no water head difference occurs between the ink in the ink storage chamber 32 and the ink in the upstream filter chamber 44, and bubble discharge does not occur.

The state where the bubbles are not discharged is maintained until the water level drops due to the bubble accumulation and the ink in the second communication pipe 38 becomes empty. With this mechanism, when ink suction that is not intended to discharge the air in the intermediate reservoir 30 is performed, the frequency of discharge of bubbles to the discharge head 12 is reduced, so that ink discharge from the discharge head 12 is unlikely to occur. Become.

<Printing status>
As shown in FIG. 11, when printing is performed, bubble discharge does not occur unlike when ink is sucked. This is because the water head difference H occurs between the ink in the ink storage chamber 32 and the ink in the upstream filter chamber 44 due to the ink flow velocity during printing, but the water level in the upstream filter chamber 44 is reduced by the bubble discharge because the ink flow velocity is slow. It is because it does not go down to the extent that it occurs. In order to realize a mechanism in which bubble discharge does not occur during printing, the pressure loss due to the first communication pipe 36 must be appropriately adjusted.

Specifically, the water level in the upstream filter chamber 44 does not drop to a level that causes a discharge failure at the flow rate during printing, and the amount of ink stored is greater than the length of the upstream filter chamber 44 in the gravity direction at the flow rate during ink suction. The pressure loss is required to cause a water head difference between the ink in the chamber 32 and the ink in the upstream filter chamber 44.

According to the first embodiment described in detail above, the following effects are exhibited.
(1) In the intermediate reservoir 30, the first communication pipe 36 is located below the second communication pipe 38 and the ventilation pipe 40 in the gravity direction, and the gravity of the upstream filter chamber 44 is caused by the pressure loss caused by the first communication pipe 36. The head difference between the ink in the ink storage chamber 32 and the ink in the upstream filter chamber 44 can be caused to exceed the length in the direction. For this reason, when ink is sucked, the length of the upstream filter chamber 44 in the gravity direction is between the ink in the ink storage chamber 32 and the ink in the upstream filter chamber 44 due to pressure loss caused by the first communication pipe 36. The above water head difference occurs. As a result, the water level in the upstream filter chamber 44 is lowered, and almost the entire surface of the filter 42 is covered with air. Then, since the ink flow is concentrated on the portion of the filter 42 that is not covered with air, the ink flow rate locally increases, and the pressure loss of the intermediate reservoir 30 increases. As a result, a pressure equal to or higher than the bubble point pressure is applied to the intermediate reservoir 30, and the air in the upstream filter chamber 44 can be discharged to the downstream filter chamber 46. Therefore, it is possible to realize the ink jet printer 1 that can discharge the bubbles 54 accumulated in the intermediate storage body 30 at a low cost without causing a complicated structure.

(2) The second communication pipe 38 has a bent shape protruding upward in the gravitational direction, and the uppermost part thereof is located below the uppermost part of the ink storage chamber 32 in the gravitational direction. For this reason, the water level of the ink storage chamber 32 rises to the top of the second communication pipe 38 when bubbles are discharged by ink suction. Thereafter, the water level of the ink storage chamber 32 decreases with the inflow of bubbles from the upstream, but the siphon is maintained while the water level of the ink storage chamber 32 is equal to or higher than the connection portion between the ink storage chamber 32 and the second communication pipe 38. The ink continues to flow between the ink storage chamber 32 and the filter chamber 34 according to the above principle. Even if ink suction is performed in this state, most of the ink flows through the second communication pipe 38, so that the water level in the filter chamber 34 does not decrease due to the pressure loss of the first communication pipe 36. That is, the discharge of the bubbles 54 is suppressed. For this reason, the flow of ink in the second communication pipe 38 is maintained until the water level of the ink storage chamber 32 becomes lower than the connection portion between the ink storage chamber 32 and the second communication pipe 38, so that the bubbles 54 are constant. The bubbles 54 are not discharged until an amount greater than that amount flows. Accordingly, since the frequency of the bubbles 54 flowing into the ejection head 12 is reduced when performing ink suction that is not intended to exhaust the air in the intermediate reservoir 30, the occurrence of ejection failure can be suppressed.

(3) Since the upper surface of the ink storage chamber 32 is above the upper surface of the upstream filter chamber 44 in the direction of gravity, the residual air is mainly stored on the ink storage chamber 32 side. For this reason, since the area covered with the air of the filter 42 decreases, the area of the filter 42 through which ink can pass increases. Therefore, the utilization efficiency of the filter 42 can be increased.

(4) Since the pressure loss of the second communication pipe 38 is smaller than the pressure loss of the first communication pipe 36, the ink in the ink storage chamber 32 and the filter chamber 34 are when the ink flows through the second communication pipe 38. The water head difference from the ink becomes smaller. For this reason, when ink suction is performed in a state where ink is flowing through the second communication pipe 38, the water level in the upstream filter chamber 44 is unlikely to drop. Thereby, since the discharge of the bubbles 54 is suppressed, the bubbles 54 are not discharged even if the ink is sucked unless the bubbles 54 are newly accumulated. Accordingly, the frequency of the bubbles 54 flowing into the ejection head 12 is reduced when performing ink suction that is not intended to discharge the air in the intermediate reservoir 30, thereby suppressing the occurrence of defective ink ejection from the ejection head 12. can do.

(5) Since the position of the vent pipe 40 connected to the ink storage chamber 32 is above the position of the second communication pipe 38 connected to the ink storage chamber 32 in the gravitational direction, the ink storage is performed during ink suction. Air above the connection portion of the chamber 32 with the second communication pipe 38 can be discharged through the vent pipe 40. As a result, the water level in the ink storage chamber 32 rises to a position above the connecting portion with the second communication pipe 38, so that the water level immediately reaches the second communication pipe 38 even if new bubbles 54 flow in thereafter. It will never go below the connection. Since the bubble discharge operation is suppressed unless air inflow to the second communication pipe 38 occurs, once the bubble 54 is discharged, the bubble discharge operation does not occur even if a certain amount of bubbles 54 flows. Accordingly, the frequency of the bubbles 54 flowing into the ejection head 12 is reduced when performing ink suction that is not intended to discharge the air in the intermediate reservoir 30, thereby suppressing the occurrence of defective ink ejection from the ejection head 12. can do.

(Second Embodiment)
Next, a second embodiment of the ink jet printer 1 will be described with reference to the drawings.
This 2nd Embodiment changes the intermediate | middle storage body 30 in the said 1st Embodiment into the intermediate | middle storage body 30a shown in FIG. Therefore, in 2nd Embodiment, the same code | symbol is used about the same member and the description which overlaps with 1st Embodiment is abbreviate | omitted.

As shown in FIG. 12, the intermediate reservoir 30 a has the same configuration as the intermediate reservoir 30 of the first embodiment, but is different in shape from the intermediate reservoir 30. That is, the upper space of the ink storage chamber 32a is expanded in the horizontal direction so as to extend right above the filter chamber 34a. The ventilation pipe 40a is connected to the lower surface of the upper space that protrudes directly above the filter chamber 34a in the ink storage chamber 32a. As a result, more air can be held in the upper part of the ink storage chamber 32a than in the intermediate storage body 30 of the first embodiment, so that the damper effect of the intermediate storage body 30a is intermediate between that of the first embodiment. This can be improved as compared with the reservoir 30.

Further, the filter chamber 34a is divided into two in the vertical direction along the horizontal direction by the filter 42a, and is divided into an upstream filter chamber 44a and a downstream filter chamber 46a. For this reason, even if the area of the filter 42a increases, the height of the upstream filter chamber 44a in the gravity direction does not increase. Therefore, the area of the filter 42a can be increased while keeping the pressure loss caused by the first communication pipe 36 low. In other words, the amount of foreign matter passing through the intermediate reservoir 30a can be increased without causing a decrease in ink ejection performance from the ejection head 12 due to an increase in pressure loss. The downstream filter chamber 46 a is provided with an ink discharge port 50 a, and the ink discharge port 50 a is connected to the ejection head 12 through the head connection tube 52.

Next, the operation of the intermediate reservoir 30a will be described.
Since the basic operation of the intermediate storage body 30 is the same as that of the intermediate storage body 30 of the first embodiment, here, the difference from the intermediate storage body 30 of the first embodiment is large <Air discharge operation 2>. I will explain.

<Air discharge operation 2>
As shown in FIG. 12, when the ink is sucked, the water level in the upstream filter chamber 44a is lowered, and the area of the filter wetted part 56a becomes very small. Since the ink flow concentrates in a limited area, the ink flow locally becomes faster and a large pressure loss occurs in the filter 42a. When the pressure loss becomes equal to or higher than the bubble point pressure of the filter 42a, air can pass through the filter 42a, so that the air in the upstream filter chamber 44a is discharged as bubbles 54 into the downstream filter chamber 46a. As the bubbles 54 are discharged, the water level in the ink storage chamber 32a rises.

As described above, the intermediate reservoir 30a can discharge bubbles by ink suction, similarly to the intermediate reservoir 30 of the first embodiment.
According to the second embodiment described in detail above, in addition to the effects (1) to (5), the following effects are exhibited.

(6) Compared with the first embodiment, the damper capacity can be improved and the amount of foreign matter passing prevention can be increased.
(Third embodiment)
Next, a third embodiment of the ink jet printer 1 will be described according to the drawings with a focus on differences from the first embodiment, and description of points that are common to the first embodiment will be omitted. In the third embodiment, the intermediate reservoir 30 is changed to the intermediate reservoir 60 shown in FIGS. 13 to 15 in the first embodiment.

As shown in FIGS. 13 and 14, the intermediate reservoir 60 has a substantially rectangular parallelepiped shape as a whole, and a plurality of recesses and grooves communicating with each other are formed on one side surface thereof. Then, as shown in FIG. 15, in a state where the filter 61 is provided inside the intermediate reservoir 60, the film sheet 62 is welded to one side surface of the intermediate reservoir 60 so as to close the recesses and grooves. As a result, various flow paths through which ink and air flow and various chambers in which ink is stored are formed in the intermediate reservoir 60. The intermediate reservoir 60 includes a filter 61 and a film sheet 62. However, in FIG. 13 and FIG. 14, the filter 61 and the film sheet 62 are omitted and the intermediate reservoir 60 is drawn.

As shown in FIGS. 13 and 14, the intermediate reservoir 60 includes a first reservoir chamber 63 and a second reservoir chamber 64 that can store ink. The first storage chamber 63 is formed from the central portion to the lower portion of the intermediate storage body 60. The second storage chamber 64 is formed on the ink tank 9 (see FIG. 3) side that is upstream of the first storage chamber 63. That is, the second storage chamber 64 is disposed in the upper part of the intermediate storage body 60 and on the upper side of the first storage chamber 63.

Further, the intermediate storage body 60 has an upper communication passage 65 communicating the first storage chamber 63 and the second storage chamber 64 in the upper part thereof, and a first storage chamber 63 below the upper communication passage 65. And a lower communication passage 66 that communicates with the second storage chamber 64. In the present embodiment, the upper communication passage 65 and the lower communication passage 66 are disposed on opposite sides of the first storage chamber 63 and the second storage chamber 64.

The lower communication passage 66 includes a lower second communication port 66a that is a communication port on the second storage chamber 64 side, and a lower first communication port 66b that is a communication port on the first storage chamber 63 side. Yes. On the other hand, the upper communication passage 65 has an upper second communication port 65a that is a communication port on the second storage chamber 64 side, and an upper first communication port 65b that is a communication port on the first storage chamber 63 side. . The lower second communication port 66a is designed to be smaller than the upper second communication port 65a.

A connection pipe 67 to which one end of the connection tube 10 (see FIG. 3) is connected is provided at the outer upper end of the intermediate reservoir 60. The other end of the connection tube 10 is connected to the ink tank 9 (see FIG. 3). On the upper side of the second storage chamber 64 in the intermediate storage body 60, a communication channel 68 that connects the connection pipe 67 and the second storage chamber 64 is formed. The communication flow path 68 extends from the connection pipe 67 so as to go around the second storage chamber 64 and is connected to the lower end portion of the second storage chamber 64.

The communication port on the second storage chamber 64 side in the communication channel 68 is an inlet 68 a through which ink supplied from the ink tank 9 (see FIG. 3) side flows into the second storage chamber 64. That is, the ink in the ink tank 9 (see FIG. 3) is supplied from the inlet 68a to the second storage chamber 64 via the connection tube 10 (see FIG. 3), the connection pipe 67, and the communication channel 68. The inflow port 68a opens from the side with respect to the second storage chamber 64. That is, the opening direction of the inflow port 68a coincides with the horizontal direction.

The lower second communication port 66a is located below the inflow port 68a and is disposed adjacent to the inflow port 68a. In the present embodiment, the lower second communication port 66a opens toward the second storage chamber 64 located above the lower second communication port 66a. Therefore, the opening direction of the lower second communication port 66a and the opening direction of the inflow port 68a intersect (orthogonal). That is, the lower second communication port 66a opens in a direction different from the opening direction of the inflow port 68a.

The lower communication path 66 includes an upstream path 66c extending from the lower second communication port 66a to a position lower than the lower second communication port 66a, and a downstream path 66d extending upward from the downstream side of the upstream path 66c. have. That is, the lower communication path 66 has a U-shaped curved portion 66e that curves downward at its lower end. Specifically, the upstream path 66c extends straight from the lower second communication port 66a toward the lower curved portion 66e, and the downstream path 66d extends straight upward from the curved portion 66e to the first. The storage chamber 63 communicates from the side. In the present embodiment, half of the curved portion 66e constitutes a part of the upstream path 66c, and the other half of the curved portion 66e constitutes a part of the downstream path 66d.

As shown in FIGS. 14 and 15, a connecting projection 69 connected to the discharge head 12 (see FIG. 3) side is integrally formed on the lower end surface of the intermediate reservoir 60. Therefore, in this embodiment, the connection convex part 69 comprises a part of liquid supply path instead of the head connection tube 52 (refer FIG. 3).

A filter 61 having a substantially pentagonal shape is provided in the lower part of the first storage chamber 63, and the filter 61 is provided on the downstream space 70 on the discharge head 12 (see FIG. 3) side and the second storage chamber 64 side. The first storage chamber 63 is partitioned into a certain upstream space 71. The downstream space 70 is configured by a space surrounded by a recess 74 that is recessed in a substantially pentagonal shape and the filter 61, and is narrower than the upstream space 71.

The filter 61 has a large number of holes 61a (see FIG. 20) that are eyes through which ink can pass. The downstream space 70 communicates with one end of the discharge channel 72 through the through hole 73 at the upper end portion thereof. The other end of the discharge channel 72 communicates with the connection convex portion 69. The lower second communication port 66 a is located above the filter 61.

Next, the filter 61 will be described.
As the filter 61, for example, a net-like body such as a wire net or a resin net, a porous body, or a metal plate in which fine through holes are formed can be used. Specific examples of the mesh include metal mesh filters and metal fibers. For example, a stainless steel (SUS) fine wire made of felt, or a compression sintered metal sintered filter, electro A forming metal filter, an electron beam processing metal filter, a laser beam processing metal filter, or the like can be used.

In particular, the filter 61 preferably has a bubble point pressure that is a pressure at which the meniscus formed by the hole 61a (opening portion) of the filter 61 does not vary, and is preferably a filter having a high-definition pore diameter. Further, the filter particle size of the filter 61 is smaller than the diameter (for example, 20 μm (0.020 mm)) of the opening of the nozzle 12a in order to prevent foreign matters in the ink from reaching the nozzle 12a (see FIG. 3). It is preferable to set to about 15 μm (0.015 mm).

When a stainless steel mesh filter is used as the filter 61, the filter 61 has a filtration particle size smaller than the diameter (for example, 20 μm) of the opening of the nozzle 12a in order to prevent foreign matters in the ink from reaching the nozzle 12a. It is preferable to set it as a tatami mat (filtration particle size 10um). In this case, the bubble point pressure generated in the ink (for example, the surface tension is about 28 mN / m) is 3 to 5 kPa. Further, the bubble point pressure generated in the ink when twill woven (filtering particle size 5 um) is employed is 10 to 15 kPa.

As the filter 61, a metal plate filter (for example, stainless steel or other flat metal plate (for example, 15 μm thick)) in which fine through holes are formed in a metal plate, and a large number of minute through holes (for example, inner diameter). If is the 15μm pores to adopt 1 cm ² tens of thousands holes) which was cut into a circle with bored), may be used having a diameter of, for example, about 8 ~ 9 mm of filter 61.

The inner diameter of this through hole is preferably set smaller than the diameter (for example, 20 μm) of the opening of the nozzle 12a. The through hole of the filter 61 may be a square or hexagonal hole. In this case, the length of the diagonal line of the through hole may be set smaller than the diameter of the opening of the nozzle 12a. In the hole 61a of the filter 61 of the present embodiment, the pitch of the adjacent holes 61a is set to about 4 μm.

Next, the operation of the intermediate reservoir 60 will be described.
<Initial filling state>
As shown in FIG. 16, in a state immediately after ink is filled into the intermediate reservoir 60 by ink suction from the ejection head 12 side by the discharge unit 18 (see FIG. 2), the downstream space 70 and the lower communication path 66 is completely filled with ink. In this case, the water level (liquid level) of the ink in the intermediate reservoir 60 is positioned above the lower first communication port 66b and the lower second communication port 66a in the lower communication passage 66 and in the upper communication passage 65. It is in the steady state which is a state located below the upper first communication port 65b and the upper second communication port 65a. In this state, air remains in the upper part of the first storage chamber 63, the upper part of the second storage chamber 64, and the upper communication path 65. This air produces a damper effect and suppresses ink pressure fluctuations.

<After leaving for a long time>
As shown in FIG. 17, when the inkjet printer 1 is left unused for a long period of time, air may enter the connection tube 10 to generate bubbles 54. The bubbles 54 flow into the second storage chamber 64 from the inflow port 68a through the connection pipe 67 and the communication channel 68 together with the ink. The inflowing bubbles 54 are stored integrally with the air in the upper part of the first storage chamber 63 and the air in the upper part of the second storage chamber 64, but the ink in the first storage chamber 63 increases as the amount of inflow of the bubbles 54 increases. And the water level of the ink in the second storage chamber 64 are lowered.

Then, when the water level of the ink in the first storage chamber 63 falls below a certain value, for example, the filter 61 is clogged with air, causing ink ejection failure from the ejection head 12. That is, the amount of bubbles 54 stored in the first storage chamber 63 and the second storage chamber 64 is limited. Therefore, it is necessary to discharge the bubbles 54 (air) before the water level of the ink in the first storage chamber 63 falls below a certain value. For the discharge of the bubbles 54, a special discharge operation (long-time cleaning) is performed.

In the present embodiment, the special discharging operation is to suck and discharge ink from the nozzles 12a by the discharging unit 18 (see FIG. 2) over a longer time than in the discharging operation (normal cleaning). In other words, the special discharge operation (long-time cleaning) is one in which the discharge operation (normal cleaning) is performed for a longer time than usual. In the special discharge operation (long-time cleaning), the ink suction force from the nozzles 12a is the same as the discharge operation (normal cleaning).

<Special discharge operation 1>
As shown in FIG. 18, when ink is sucked from the nozzle 12a by the discharge portion 18 (see FIG. 2) to perform a special discharge operation (long-time cleaning), the ink in the second storage chamber 64 is only in the lower communication path 66. To the upstream space 71 (first storage chamber 63). A water head difference H is generated between the ink in the upstream space 71 and the ink in the second storage chamber 64 due to the pressure loss generated in the lower communication path 66 at this time. That is, the water level of the ink in the upstream space 71 is lowered. Thereby, the air stored in the upper part of the second storage chamber 64 flows into the upstream space 71 through the upper communication passage 65.

<Special discharge operation 2>
As shown in FIG. 19, when ink is continuously sucked from the nozzle 12a by the discharge portion 18 (see FIG. 2), the water level of the ink in the upstream space 71 (first storage chamber 63) gradually decreases and eventually the filter 61 It drops to the lower end of the. Accordingly, the discharge unit 18 performs a special discharge operation for sucking and discharging ink from the nozzles 12a in a steady state, thereby filtering the water level (liquid level) of the ink in the upstream space 71 (first storage chamber 63). 61 can be contacted. That is, by performing a special discharge operation, the water level (liquid level) of the ink in the upstream space 71 (first storage chamber 63) is lowered from the steady state height to the height in contact with the filter 61. be able to.

Thereby, the area of the filter liquid contact portion 75 which is a contact portion with the ink on the upstream surface of the filter 61 becomes extremely small. Then, since the ink flow is concentrated in a limited area, the ink flow is locally accelerated, and a large pressure loss is caused by the filter 61. When this pressure loss becomes equal to or higher than the bubble point pressure of the filter 61, air can pass through the filter 61, and the air in the upstream space 71 is discharged into the downstream space 70 as bubbles 54. As the air is discharged from the upstream space 71 to the downstream space 70, the ink level in the second storage chamber 64 rises.

The hole 61a (see FIG. 20) of the filter 61 is formed by the pressure difference between the downstream space 70 and the upstream space 71 when ink flows through the intermediate reservoir 60 in accordance with the special discharging operation by the discharging unit 18. The ink meniscus formed in the hole 61a of the 61 is broken. That is, air cannot pass through the filter 61 unless the ink meniscus formed in the hole 61a of the filter 61 is broken.

Here, the pressure at which the meniscus of the ink formed in the hole 61a of the filter 61 is broken will be described with reference to FIG.
First, P is the pressure at the time of bubble generation (bubble point pressure), γ is the surface tension of the ink, ρ is the ink density, θ is the wetting angle, and D is the pore diameter of the filter 61.

Then, the pressure Pγ generated by the interfacial tension between the ink liquid surface and the filter 61 is Pγ = 4γcos θDπ / (πD ² ) = 4γcos θ / D. When bubbles are generated (when the meniscus formed by the hole 61a of the filter 61 is broken), the bubble point pressure P and the pressure Pγ are balanced. That is, since P = Pγ, P = Pγ = 4γcos θ / D.

<Special discharge operation 3>
As shown in FIG. 21, when the ink suction from the nozzle 12a by the discharge unit 18 (see FIG. 2) is completed, the discharge of the bubbles 54 (air) from the upstream space 71 to the downstream space 70 immediately stops. Ink continues to flow through the lower communication path 66 so that the ink level in the first storage chamber 63 and the ink level in the second storage chamber 64 are the same height. At this time, since the accumulated bubbles 54 have already been discharged, the water level (liquid level) of the ink in the intermediate reservoir 60 returns to the same height as in the steady state. Thereby, the special discharge operation is completed.

<Discharge operation>
As shown in FIG. 22, when ink is sucked from the nozzle 12a by the discharging unit 18 (see FIG. 2) to perform the discharging operation (normal cleaning), the discharging operation takes a suction time from the nozzle 12a as compared with the special discharging operation. Since it is short, the ink water level in the upstream space 71 (first storage chamber 63) does not drop to the filter 61.

That is, the discharging operation ends before the ink water level in the upstream space 71 (first storage chamber 63) drops to the filter 61. Accordingly, since the bubbles 54 in the upstream space 71 do not pass through the filter 61 and are discharged to the downstream space 70, the ink from the nozzles 12a of the ejection head 12 due to the bubbles 54 immediately after the discharge operation is discharged. Occurrence of ejection failure is suppressed.

In order to control whether or not the bubbles 54 are discharged from the nozzles 12a by properly using the discharging operation and the special discharging operation in which the suction time of the ink from the nozzles 12a by the discharging unit 18 (see FIG. 2) is different from each other, It is necessary to adjust the volume of the first storage chamber 63 appropriately. In the present embodiment, the ink level in the upstream space 71 does not drop down to the filter 61 in the discharge operation (normal cleaning), and the ink level in the upstream space 71 does not lower the lower end of the filter 61 in the special discharge operation (cleaning for a long time). The volume of the 1st storage chamber 63 is set so that it may fall to a part.

<Printing status>
As shown in FIG. 23, when printing is performed in a steady state, the bubbles 54 in the upstream space 71 do not pass through the filter 61 and are discharged into the downstream space 70. This is because a water head difference H occurs between the ink in the second storage chamber 64 and the ink in the upstream space 71 (first storage chamber 63) due to the ink flow speed during printing, but the ink flow speed is slower than the discharge operation. This is because the ink level in the upstream space 71 does not drop to the filter 61.

In order to realize a mechanism in which the bubbles 54 in the upstream space 71 do not pass through the filter 61 and are discharged into the downstream space 70 during printing, it is necessary to appropriately adjust the pressure loss due to the lower communication path 66. In this embodiment, the flow path resistance of the lower communication path 66 and the flow path resistance of the upper communication path 65 are the upstream side when ink is ejected from the ejection head 12 to the printing paper 20 in a steady state. The gas-liquid interface (liquid level) of the ink in the space 71 (first storage chamber 63) is set so as not to contact the filter 61.

According to the third embodiment described in detail above, the following effects are exhibited.
(7) In the intermediate reservoir 60, the lower second communication port 66a is smaller than the upper second communication port 65a. For this reason, it can suppress that the bubble 54 which flowed in into the 2nd storage chamber 64 from the inflow port 68a flows into the lower communication path 66 from the lower 2nd communication port 66a. Therefore, the bubbles 54 can be prevented from entering the ejection head 12.

(8) In the intermediate reservoir 60, the lower second communication port 66a is open upward. For this reason, it is possible to effectively prevent the bubbles 54 from flowing into the lower communication passage 66 from the lower second communication port 66a by utilizing the fact that the bubbles 54 in the ink easily float upward.

(9) In the intermediate reservoir 60, the lower communication path 66 includes an upstream path 66c extending from the lower second communication port 66a to a position lower than the lower second communication port 66a, and a downstream side of the upstream path 66c. And a downstream path 66d extending upward from the center. For this reason, even when the bubbles 54 flow into the lower communication path 66 from the lower second communication port 66a, the upstream path 66c extends from the lower second communication port 66a to the lower second communication port 66a. Since it extends to a low position, the bubbles 54 that have flowed into the lower communication passage 66 can be returned to the second storage chamber 64 by their buoyancy. In addition, since the lower communication path 66 has an upstream path 66c and a downstream path 66d, the lower communication path 66 is not increased without increasing the distance between the first storage chamber 63 and the second storage chamber 64. The flow path resistance can be set high.

(10) In the intermediate reservoir 60, the lower second communication port 66a is located above the filter 61. For this reason, even when the bubbles 54 flow into the lower communication passage 66 from the lower second communication port 66a, the bubbles 54 are filtered by utilizing the fact that the bubbles 54 in the ink are likely to rise upward. It is possible to suppress entry through the discharge head 12 through 61.

(11) In the intermediate reservoir 60, the lower second communication port 66a is located below the inflow port 68a and opens in a direction different from the opening direction of the inflow port 68a. For this reason, it can suppress that the bubble 54 contained in the ink which flows in into the 2nd storage chamber 64 from the inflow port 68a flows in into the lower side communication path 66 from the lower 2nd communication port 66a.

(12) In the intermediate reservoir 60, the flow resistance of the lower communication path 66 and the flow resistance of the upper communication path 65 are when the ink is ejected from the ejection head 12 to the printing paper 20 in a steady state. In addition, the gas-liquid interface (liquid level) of the ink in the first storage chamber 63 is set so as not to contact the filter 61. For this reason, at the time of printing, it is possible to suppress the ink supply capability to the ejection head 12 from being reduced, and the bubbles 54 (air) from passing through the filter 61 and entering the ejection head 12 side. Therefore, it is possible to suppress a decrease in print quality.

(13) In the intermediate reservoir 60, the hole 61 a of the filter 61 is caused by a pressure difference between the downstream space 70 and the upstream space 71 when ink flows through the intermediate reservoir 60 in accordance with the special discharge operation by the discharge unit 18. The ink meniscus formed in the hole 61a of the filter 61 is broken. For this reason, by performing the special discharge operation, the bubbles 54 retained in the second storage chamber 64 can be discharged from the upstream space 71 to the downstream space 70.

(Fourth embodiment)
Next, a fourth embodiment of the ink jet printer 1 will be described according to the drawings with a focus on differences from the third embodiment, and description of points that are common to the third embodiment will be omitted. In the fourth embodiment, as shown in FIG. 24, a pressure adjusting valve 80 for adjusting the pressure of the ink is provided between the intermediate reservoir 60 and the ejection head 12 in the third embodiment, and the ink tank 9 Instead, an ink cartridge 81 is employed as an example of a liquid supply source, and the ink of the ink cartridge 81 is configured to be pressurized and supplied to the ejection head 12 side.

As shown in FIG. 24, the ink jet printer 1 includes a mounting portion 82 on which an ink cartridge 81 as an example of a liquid supply source is detachably mounted, and a liquid supply path for supplying ink from the ink cartridge 81 to the ejection head 12. As an example, a supply path 83 is provided. The supply path 83 is provided with a supply pump 84 that causes ink to flow in the supply direction A, an intermediate reservoir 60 that can store ink, and a pressure adjustment valve 80 that adjusts the pressure of the ink.

The supply path 83 includes a first supply flow path 85 to a fourth supply flow path 88. Specifically, the first supply channel 85 connects the ink cartridge 81 and the supply pump 84, the second supply channel 86 connects the supply pump 84 and the intermediate reservoir 60, and the third supply channel 87. Connects the intermediate reservoir 60 and the pressure regulating valve 80, and the fourth supply flow path 88 connects the pressure regulating valve 80 and the discharge head 12.

The supply pump 84 includes a diaphragm pump 89 having a variable pump chamber volume, a suction valve 90 disposed upstream of the diaphragm pump 89, and a discharge valve 91 disposed downstream of the diaphragm pump 89. is doing. The suction valve 90 and the discharge valve 91 allow ink flow in the supply direction A from the ink cartridge 81 side toward the discharge head 12 side, and ink in the reverse flow direction from the discharge head 12 side toward the ink cartridge 81 side. It functions as a one-way valve that inhibits flow.

Accordingly, the supply pump 84 sucks ink from the ink cartridge 81 side through the suction valve 90 as the volume of the pump chamber of the diaphragm pump 89 increases, and discharges as the volume of the pump chamber decreases. Ink is ejected to the head 12 side via the ejection valve 91. The ejection head 12 to which the downstream end of the supply path 83 is connected is provided with an in-head filter 92 that captures bubbles and foreign matters in the ink.

The pressure regulating valve 80 includes a supply chamber 93 to which ink is supplied from the third supply channel 87, a pressure chamber 95 that communicates with the supply chamber 93 via the communication hole 94, and a space between the pressure chamber 95 and the supply chamber 93. And a biasing member 97 that biases the valve body 96 in the valve closing direction. The valve body 96 is inserted into the communication hole 94, and is configured to close the communication hole 94 by being biased by the biasing member 97. The pressure adjusting valve 80 constitutes a part of the liquid supply path.

A part of the wall surface of the pressure chamber 95 is constituted by a diaphragm 98 that can be bent and deformed along the urging direction of the urging member 97. The outer surface of the diaphragm 98 (left surface shown in FIG. 24) receives atmospheric pressure, while the inner surface of the diaphragm 98 (right surface shown in FIG. 24) receives ink pressure in the pressure chamber 95. Therefore, the diaphragm 98 is deflected and displaced according to a change in the differential pressure between the pressure in the pressure chamber 95 and the pressure received on the outer surface of the diaphragm 98.

The supply chamber 93 is held in a pressurized state by the ink sent by being pressurized from the ink cartridge 81. Then, ink is discharged from the nozzles 12a of the ejection head 12, the negative pressure in the pressure chamber 95 increases, and the differential pressure between the pressure in the pressure chamber 95 and the pressure received on the outer surface of the diaphragm 98 is a predetermined value (for example, 1000 Pa). When larger than this, the valve body 96 is urged in the valve opening direction against the urging force of the urging member 97, and the pressure chamber 95 and the supply chamber 93 communicate with each other.

On the other hand, when the pressure difference between the pressure in the pressure chamber 95 and the pressure applied to the outer surface of the diaphragm 98 reaches a predetermined value, the valve body 96 is urged in the valve closing direction by the urging member 97, and the pressure chamber 95 and the supply chamber are 93 is not in communication. In this way, the pressure adjustment valve 80 adjusts the pressure in the discharge head 12 that is the back pressure of the nozzle 12a, and the pressure of the ink supplied from the ink cartridge 81 to the discharge head 12 via the supply path 83. Adjust.

Also in the fourth embodiment, as in the third embodiment, by providing the discharge unit 18 and performing a special discharge operation by the discharge unit 18, bubbles staying in the second storage chamber 64 of the intermediate storage body 60. 54 can be discharged from the upstream space 71 to the downstream space 70.

Furthermore, in the fourth embodiment, by providing a valve opening mechanism for forcibly opening the valve body 96 of the pressure regulating valve 80, the valve body 96 is forcibly opened and pressurized by the supply pump 84. It is possible to perform pressure cleaning for discharging ink from the nozzles 12 a of the ejection head 12. Then, by performing this pressure cleaning, a special discharge by the discharge unit 18 in the third embodiment is performed using the pressure difference between the downstream space 70 and the upstream space 71 when the ink flows through the intermediate reservoir 60. Similarly to the operation, the bubbles 54 retained in the second storage chamber 64 of the intermediate storage body 60 may be discharged from the upstream space 71 to the downstream space 70.

Further, by performing a discharge operation using both the ink suction operation by the discharge portion 18 and the pressure cleaning by the supply pump 84, the second storage of the intermediate reservoir 60 is performed in the same manner as the special discharge operation by the discharge portion 18. The bubbles 54 retained in the chamber 64 may be discharged from the upstream space 71 to the downstream space 70.

According to the fourth embodiment described in detail above, the following effects are exhibited.
(14) Since the ink jet printer 1 includes the pressure adjustment valve 80 that adjusts the pressure of the ink between the intermediate reservoir 60 and the ejection head 12, the ink in the ink cartridge 81 is ejected by the supply pump 84. The pressure can be supplied to the side.

(15) By providing a valve opening mechanism for forcibly opening the valve body 96 of the pressure regulating valve 80, the discharge head discharges the ink pressurized by the supply pump 84 in a state where the valve body 96 is forcibly opened. The pressure cleaning discharged from the 12 nozzles 12a can be performed. Then, by performing this pressure cleaning, a special discharge by the discharge unit 18 in the third embodiment is performed using the pressure difference between the downstream space 70 and the upstream space 71 when the ink flows through the intermediate reservoir 60. Similarly to the operation, the bubbles 54 retained in the second storage chamber 64 of the intermediate storage body 60 can be discharged from the upstream space 71 to the downstream space 70.

(Example of change)
In addition, you may change each said embodiment as follows.
As shown in FIG. 25, in the fourth embodiment, an ink container 100 may be used as an example of a liquid supply source instead of the ink cartridge 81. In this case, the ink container 100 has an ink injection port 101, and ink can be replenished by injecting ink from the ink injection port 101. After refilling the ink container 100 with ink, the ink injection port 101 is closed by a lid (not shown).

As shown in FIG. 26, in the fourth embodiment, the ink cartridge 81 and the large-capacity ink tank 103 are connected by the ink supply tube 102, and the ink cartridge 81 is connected to the ink cartridge 81 via the ink supply tube 102. You may comprise so that ink may be supplied. In this case, the ink cartridge 81 functions as a sub tank that temporarily stores ink. Further, in this case, the large-capacity ink tank 103 has an ink injection port 104, and ink can be replenished by injecting ink from the ink injection port 104. After refilling the large capacity ink tank 103 with ink, the ink inlet 104 is closed by a lid (not shown). In this case, as shown in FIGS. 24 and 26, the large-capacity ink tank 103 is positioned such that its lower surface 103a is higher than the nozzle surface 12b on which the nozzle 12a of the ejection head 12 opens. Placed. In this way, the ink in the large-capacity ink tank 103 can be supplied to the ejection head 12 by the water head difference.

In the fourth embodiment, the supply pump 84 may be changed to a tube pump.
In the third embodiment, the ink suction force from the nozzles 12a by the discharge unit 18 in the special discharge operation (long-time cleaning) may be stronger than that in the discharge operation (normal cleaning). That is, in the special discharge operation, the amount of ink sucked per unit time may be larger than that in the discharge operation.

In the third embodiment, the shape of the filter 61 may be a circle, a horizontally long ellipse, a rectangle, a triangle, or the like. In this case, it is preferable to match the shape of the recess 74 with the shape of the filter 61.

-In 3rd Embodiment, when the wall surface of the 2nd storage chamber 64 of the intermediate | middle storage body 60 is formed with flexible members, such as a film, and the inside of the 2nd storage chamber 64 becomes a negative pressure, the 2nd storage chamber 64 You may comprise so that a flexible member may bend in the direction where the volume of becomes small. In this way, when the inside of the second storage chamber 64 becomes negative pressure, the bubbles in the second storage chamber 64 become flat, so that the bubbles can be easily moved downward. In this case, bubbles are more easily crushed by the flexible member by increasing the area of the flexible member and reducing the depth dimension of the second storage chamber 64.

In the first to third embodiments, the discharge unit 18 is configured by a pressurization mechanism (for example, a pressurization pump) that can pressurize the ink in the liquid supply path and discharge the ink from the nozzle 12a. Also good. Alternatively, the discharge unit 18 may be configured by both the pressurizing mechanism and a suction mechanism (cap 14, suction tube 15, and suction pump 16) that can suck and discharge ink from the nozzle 12a. .

In the third embodiment, the hole 61 a of the filter 61 is a hole due to a pressure difference between the downstream space 70 and the upstream space 71 when the ink flows through the intermediate reservoir 60 in accordance with the special discharging operation by the discharging unit 18. It is not always necessary that the ink meniscus formed on 61a is broken.

In the third embodiment, the flow resistance of the lower communication path 66 and the flow resistance of the upper communication path 65 are determined when ink is ejected from the ejection head 12 to the printing paper 20 in a steady state. It is not always necessary to set the gas-liquid interface (liquid level) of the ink in the first storage chamber 63 so as not to contact the filter 61.

In the third embodiment, the lower second communication port 66a does not necessarily need to be positioned below the inflow port 68a. Further, the lower second communication port 66a does not necessarily need to open in a direction different from the opening direction of the inflow port 68a. That is, the lower second communication port 66a may be positioned above the inlet 68a, for example, or may be opened in the same direction as the opening direction of the inlet 68a.

In the third embodiment, the lower second communication port 66a does not necessarily need to be positioned above the filter 61. That is, the lower second communication port 66a may be positioned below the filter 61, for example.

In the third embodiment, the lower communication path 66 includes an upstream path 66c extending from the lower second communication port 66a to a position lower than the lower second communication port 66a, and an upper side from the downstream side of the upstream path 66c. It is not always necessary to have the downstream path 66d extending in the direction. That is, the entire lower communication passage 66 may extend linearly, for example.

In the third embodiment, the lower second communication port 66a does not necessarily need to open upward. That is, the lower second communication port 66a may be opened downward, for example, or may be opened laterally.

In the third embodiment, the filter 61 may be omitted.
In each of the above embodiments, the ink jet printer 1 may be changed to a so-called line head type including a long and fixed droplet discharge unit corresponding to the entire width of the printing paper 20. In this case, the droplet discharge unit may be arranged so that the printing range covers the entire width of the printing paper 20 by arranging a plurality of unit head units on which nozzles are formed, or a single long head. By arranging a large number of nozzles so as to cover the entire width of the printing paper 20, the printing range may extend over the entire width of the printing paper 20.

In the above embodiments, the liquid ejecting apparatus may be a liquid ejecting apparatus that ejects liquid other than ink. Note that the state of the liquid ejected as a minute amount of liquid droplets from the liquid ejection device includes those in the form of particles, tears, and threads. The liquid here may be any material that can be discharged from the liquid discharge device. For example, it may be in a state in which the substance is in a liquid phase, such as a liquid with high or low viscosity, sol, gel water, other inorganic solvents, organic solvents, solutions, liquid resins, liquid metals (metal melts ). Further, not only a liquid as one state of a substance but also a substance in which particles of a functional material made of a solid such as a pigment or a metal particle are dissolved, dispersed or mixed in a solvent is included. Typical examples of the liquid include ink and liquid crystal as described in the above embodiment. Here, the ink includes general water-based inks and oil-based inks, and various liquid compositions such as gel inks and hot melt inks. Specific examples of the liquid ejection device include, for example, a liquid that contains materials such as electrode materials and color materials used in the manufacture of liquid crystal displays, EL (electroluminescence) displays, surface-emitting displays, color filters, and the like in a dispersed or dissolved form. There is a liquid ejection device that ejects water. Further, it may be a liquid ejecting apparatus for ejecting biological organic materials used for biochip production, a liquid ejecting apparatus for ejecting liquid as a sample used as a precision pipette, a printing apparatus, a micro dispenser, or the like. In addition, a transparent resin liquid such as UV curable resin is used to form a liquid ejection device that ejects lubricating oil pinpoint to precision machines such as watches and cameras, and micro hemispherical lenses (optical lenses) used in optical communication elements. It may be a liquid discharge device that discharges the liquid onto the substrate. Further, it may be a liquid discharge apparatus that discharges an etching solution such as acid or alkali in order to etch a substrate or the like.

Claims (13)

An ejection head for ejecting liquid from a nozzle to a medium;
A liquid supply path for supplying the liquid contained in the liquid supply source to the ejection head;
An intermediate storage body provided in the liquid supply path and capable of storing the liquid;
The intermediate reservoir is
A first storage chamber capable of storing the liquid;
A second storage chamber disposed upstream of the first storage chamber and capable of storing the liquid;
An upper communication path communicating the first storage chamber and the second storage chamber;
A lower communication path communicating the first storage chamber and the second storage chamber below the upper communication path,
The lower communication passage has a lower communication port that opens to the second storage chamber, the upper communication passage has an upper communication port that opens to the second storage chamber, and the lower communication port is the upper communication port. A liquid ejection device that is smaller than the communication port. The liquid ejection device according to claim 1, wherein the lower communication port is opened upward. The lower communication path has an upstream path extending from the lower communication port to a position lower than the lower communication port, and a downstream path extending upward from the downstream side of the upstream path. The liquid ejection apparatus according to claim 1 or 2. The first storage chamber is divided into a downstream space connected to the ejection head and an upstream space connected to the second storage chamber, and has a hole through which the liquid can pass. Further equipped with a filter,
The liquid ejection apparatus according to any one of claims 1 to 3, wherein the lower communication port is located above the filter. The liquid supply path has an inlet opening to the second storage chamber, and the liquid supplied from the liquid supply source flows into the second storage chamber through the inlet,
The liquid according to any one of claims 1 to 4, wherein the lower communication port is located below the inflow port and opens in a direction different from an opening direction of the inflow port. Discharge device. The upper communication port is an upper second communication port, and the upper communication channel further includes an upper first communication port that opens to the first storage chamber,
The lower communication port is a lower second communication port, and the lower communication channel further includes a lower first communication port that opens into the first storage chamber,
The flow resistance of the lower communication path and the flow resistance of the upper communication path are such that the liquid level of the liquid in the intermediate reservoir is higher than the lower first communication port and the lower second communication port. When the liquid is discharged from the discharge head to the medium in a steady state located below the upper first communication port and the upper second communication port, the liquid level of the first storage chamber is The liquid ejection apparatus according to claim 4, wherein the liquid ejection apparatus is set so as not to contact the filter. A discharge unit configured to execute a discharge operation of discharging the liquid from the nozzle;
The discharge unit is configured to execute a special discharge operation of bringing the liquid surface of the first storage chamber into contact with the filter by discharging the liquid from the nozzle in the steady state.
The hole of the filter is formed in the hole of the filter due to a pressure difference between the downstream space and the upstream space when the liquid flows through the liquid supply path in accordance with the execution of the special discharge operation. The liquid ejection device according to claim 6, wherein the liquid meniscus is configured to be broken. An intermediate storage body that is provided in a liquid supply path that supplies the liquid stored in a liquid supply source to a discharge head that discharges liquid from a nozzle to a medium, and can store the liquid.
A first storage chamber capable of storing the liquid;
A second storage chamber disposed upstream of the first storage chamber and capable of storing the liquid;
An upper communication path communicating the first storage chamber and the second storage chamber;
A lower communication path communicating the first storage chamber and the second storage chamber below the upper communication path,
The lower communication passage has a lower communication port that opens to the second storage chamber, the upper communication passage has an upper communication port that communicates with the second storage chamber, and the lower communication port is the upper communication port. An intermediate reservoir that is smaller than the communication port. An ejection head for ejecting liquid;
A liquid supply path for supplying the liquid from the liquid storage unit storing the liquid to the ejection head;
A liquid discharge device comprising: a filter unit disposed in the liquid supply path and having a filter member for removing foreign matter in the liquid,
The filter unit includes a filter chamber in which the filter member is provided and an ink storage chamber for storing the liquid,
The filter chamber has an upstream filter chamber and a downstream filter chamber partitioned by the filter member,
The ink storage chamber and the upstream filter chamber are connected by a first communication pipe, a second communication pipe, and a vent pipe,
The first communication pipe is located below the second communication pipe and the vent pipe in the direction of gravity, and the ink storage exceeds the length of the upstream filter chamber in the gravitational direction due to pressure loss caused by the first communication pipe. A liquid ejecting apparatus configured to generate a water head difference between a chamber and the upstream filter chamber. The second communication pipe has a shape protruding upward in the gravity direction,
10. The liquid ejection device according to claim 9, wherein the uppermost part of the second communication pipe is located below the uppermost part of the ink storage chamber in the direction of gravity. 10. The liquid ejection apparatus according to claim 9, wherein the upper surface of the ink storage chamber is above the upper surface of the upstream filter chamber in the direction of gravity. The liquid ejection device according to claim 9, wherein a flow path resistance of the first communication pipe is larger than a flow path resistance of the second communication pipe. 10. The liquid ejecting apparatus according to claim 9, wherein the vent pipe is connected to the ink storage chamber above the position of the second communication pipe connected to the ink storage chamber in a direction of gravity.

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