JP2014097616A - Ink tank of ink jet printer and circulation system of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable stirring an ink efficiently even in a vertical tank.SOLUTION: A sub-tank 100 comprises: a body 1 having a rectangular vertical thin box shape and being capable of storing an ink within it; and a rotation shaft 3 arranged near the central lower side in the thickness direction and protruding from the inside of the body 1 in the horizontal direction. The rotation shaft 3 has an impeller 5 provided with a plurality of blades 4 arranged radially from a bearing 7. The mounting of the impeller 5 on the rotation shaft 3 arranged in the horizontal direction makes the impeller 5 axis-supported in the vertical direction and rotates. When an ink is discharged from an ink discharge outlet 31 arranged in the lower side of the rotation shaft 3 of the body 1, the flow of the ink impinges on the blades 4 of the impeller 5 to rotate the impeller 5, and fine particles of the ink precipitated in the lower part of the body 1 are stirred.

Description

  The present invention relates to an ink tank of an ink jet printer that eliminates ink precipitation by stirring and a circulation system thereof.

  Conventionally, an ink tank as described in Patent Document 1 is known. FIG. 13 is a configuration diagram illustrating an example of a conventional ink tank. The ink tank 900 is provided with a stirrer chip 902 that stirs ink inside a container 901. A tapered portion 904 is provided on the bottom portion 903 of the container 901, and the stirrer chip 902 is disposed on the tapered portion 904. The stirrer chip 902 rotates in synchronization with the stirrer 905 provided on the lower side outside the container 901. An ink outlet 906 is provided at the bottom 903 of the container 901, and a head is provided at the tip of the ink outlet 906.

  In the ink tank 900, the stirrer chip 902 is rotated in synchronization with the rotating magnetic field generated by the stirrer 905, and the ink inside the container 901 is stirred.

JP 2004-74625 A

  In the conventional ink tank 900, since the stirrer 902 is rotated, there is a problem in that the stirrer 902 cannot be used in the case of the vertically arranged thin box-shaped ink tank because the area of the bottom surface is extremely small. It was. The same applies to a sub tank disposed between an ink tank and a printer head in a large printer.

  Accordingly, an object of the present invention is to enable efficient stirring of ink inside even a vertical tank.

  An ink tank of an ink jet printer according to the present invention includes a main body that stores ink therein, a rotation axis in a direction orthogonal to the gravity in the main body, and a plurality of blades that rotate substantially radially about the rotation axis. And an ink discharge port that discharges ink to the blades of the impeller.

  An impeller having a rotation shaft is provided in the thickness direction of the main body, and the impeller is rotated by discharging ink from the ink discharge port to the impeller blades. The ink in the main body is agitated by the rotation of the impeller, and the precipitated ink fine particles are uniformly mixed. According to such a configuration, all the upper and lower regions in the gravity direction of the ink tank can be stirred. The ink tank to which the present invention can be applied may be any tank that stores ink, and includes a so-called sub tank used as a damper. The rotating shaft may be constituted by a rotating shaft protruding from the main body and the impeller bearing, or the impeller rotating shaft may be inserted into a bearing on the inner wall of the main body. The blade may be a flat plate or a curved plate.

  Further, the ink discharge port may be positioned below the rotation shaft. In this way, air can be prevented from being caught by discharging ink from the lower side.

  Since the ink is discharged from the lower side of the impeller, the impeller can be rotated while the fine particles precipitated below the inside of the main body are blown off by the flow of the ink.

  Furthermore, an ink discharge port for discharging ink may be provided below the lowermost liquid surface of the ink on the inner wall of the main body.

  By disposing the ink discharge port below the lowermost liquid surface, the ink can be reliably discharged. Further, by discharging ink from a portion where the concentration of fine particles in the vicinity of the liquid surface is low, and discharging the ink from the ink discharge port, the thin liquid with a high concentration is supplied to the portion having a high concentration and is precipitated downward. By applying the ink flow directly to the fine particles and stirring the fine particles, the fine particles can be dispersed efficiently and uniformly.

  Furthermore, a bearing for inserting the rotating shaft may be provided in the impeller or the main body, and a play in which the impeller is movable may be provided between the rotating shaft and the bearing.

  The amount of movement of the impeller is determined by the amount of play between the rotating shaft and the bearing. Since play is provided between the rotating shaft and the bearing, the impeller can move freely by the amount of play to increase the range of stirring.For example, the impeller is impregnated by fine particles accumulated at the bottom of the main body at the initial stage of rotation of the impeller. Can be prevented from rotating.

  Furthermore, you may provide the float which covers the ink liquid level in the said main body.

  The float may be of a type that floats independently on the ink surface, or may be used as a float of a position sensor for detecting the liquid surface. By providing the float so as to cover the ink liquid level, it is possible to suppress the behavior of the liquid level, such as undulation, due to the rotation of the impeller. In addition, since the liquid surface can be prevented from being tilted during the high-speed movement and stop operation of the ink tank, the ink can be reliably discharged from the ink discharge port, and the ink can be stirred even during printing.

  Furthermore, a position sensor that detects the liquid level of the ink and a control unit that controls the liquid level to be maintained above the upper end of the impeller based on a signal from the position sensor may be provided.

  Thereby, it can prevent that the impeller blade | wing comes out from a liquid level and a bubble mixes from a liquid level.

  The circulation system of the ink jet printer according to the present invention includes a circulation system in which the ink discharge port and the ink discharge port of the ink tank are connected by a tube.

  Since such a circulation system is independent of the head between the ink discharge port and the ink discharge port, the ink can be stirred even during printing.

  Further, the circulation system of the ink jet printer according to the present invention has an ink take-out port through which the ink tank takes out ink from the head, and the ink take-out port and the ink discharge port are connected by a tube through the head. It has the system.

  By configuring such a circulation system, it is possible to eliminate the precipitation of ink in the head, so that the print quality is improved.

  According to the present invention, the ink inside can be efficiently stirred even in a vertical ink tank.

It is a block diagram which shows the sub tank which concerns on Embodiment 1 of this invention. It is explanatory drawing which expanded a part of sub-tank shown in FIG. It is a systematic diagram which shows the ink path | route of the inkjet printer using this subtank. It is explanatory drawing which shows operation | movement of a sub tank. FIG. 6 is a system diagram showing another ink path of the sub tank according to the first embodiment. FIG. 6 is still another ink system diagram of the sub tank according to the first embodiment. It is explanatory drawing which shows the subtank concerning Embodiment 2 of this invention. It is a partial block diagram which shows the subtank concerning Embodiment 3 of this invention. It is a block diagram which shows a part of sub tank which concerns on Embodiment 4 of this invention. It is explanatory drawing which shows operation | movement of this subtank. It is a block diagram which shows the subtank concerning Embodiment 5 of this invention. It is a block diagram which shows the modification of the subtank shown in FIG. It is a block diagram which shows an example of the conventional ink tank.

(Embodiment 1)
1A and 1B are configuration diagrams showing a sub tank according to Embodiment 1 of the present invention, in which FIG. 1A is a sectional view in a plane direction, and FIG. 1B is a sectional view in a thickness direction. FIG. 2 is an explanatory diagram in which a part of the sub tank shown in FIG. 1 is enlarged. FIG. 3 is a system diagram showing an ink path of an ink jet printer using this sub tank. The sub tank 100 functions as a damper disposed between the ink tank 50 and the head 51. The main body 1 of the sub-tank 100 has a rectangular vertical thin box shape that can store ink therein, and includes a main body 1 and a lid 2. The cover part 2 consists of a flat plate-shaped member made of synthetic resin. The main body 1 is similarly a box-shaped integrally molded body of synthetic resin, and has a structure in which the lid portion 2 is attached to the opening side. The main body 1 has a rotation shaft 3 in the vicinity of the center lower side in the vertical direction. The rotating shaft 3 protrudes from the inside of the main body 1 in a direction orthogonal to the direction of gravity, and the protruding length is substantially equal to the internal distance in the thickness direction inside the main body 1 (between the main body side surface 9 and the lid portion 2). equal.

  An impeller 5 provided with a plurality of blades 4 radially from a bearing 7 is rotatably mounted on the rotary shaft 3. By mounting the impeller 5 on the rotary shaft 3 provided in the horizontal direction, the impeller 5 is pivotally supported in the vertical direction. Each blade 4 is made of a curved plate member. By curving, the discharged ink can be received and easily converted into a rotational force. A substantially disc-shaped partition plate 6 is provided between the blades 4. The partition plate 6 has a diameter that is about half the diameter of the impeller 5, and is provided at the center of the impeller 5 in the thickness direction. A bearing 7 through which the rotary shaft 3 passes is provided at the center of the impeller 5. The bearing 7 and the rotary shaft 3 are loosely fitted. The impeller 5 is rotated with respect to the main body 1 by forming a lubricating layer with ink by inserting the rotating shaft 3 into the bearing 7.

  The bearing 7 slightly protrudes from both end edges of the blade 4 in the axial direction of the impeller 5, the protruding portion 8 contacts the main body side surface 9 and the lid portion 2, and the blade 4 contacts the lid portion 2 and the main body side surface 9. I'm not going to do that. If the protruding amount of the protruding portion 8 is large, the gap between the blade 4 and the lid portion 2 and the side surface 9 of the main body 9 is widened so that the ink flow hitting the blade 4 escapes in the gap direction and the force for rotating the impeller 5 is insufficient. This makes it difficult for the impeller 5 to rotate. On the other hand, if they are too close together, the impeller 5 contacts the main body side surface 9 and the lid portion 2, thereby impeding the rotation of the impeller 5. For this reason, it is necessary to set the protrusion amount of the protrusion 8 to an optimum value.

  The inner wall of the main body 1 is disposed close to the outer periphery of the impeller 5. In particular, the right wall 10 of the inner wall on the ink ejection side is curved and formed close to the tip of the blade 4 of the impeller 5. By forming close to the blades 4 of the impeller 5, the flow that has made one turn reaches the ink discharge port 31 again, so that the flow of ink discharged from the ink discharge port 31 is not disturbed. Further, the agitated ink can be easily discharged from the ink discharge port 32. Further, a step portion 11 is formed in the right wall 10 in the vicinity of the center of the main body 1 in the up-and-down direction, so that a later-described float 20 does not contact the impeller 5 and restricts downward movement. This prevents the float 20 from contacting the impeller 5 and not rotating when ink is ejected. The left wall 12, which is the inner wall on the side opposite to the ink ejection side, is formed slightly apart from the tip of the blade 4 of the impeller 5. Since the space between the impeller 5 and the left wall 12 has a relatively large volume, the ink is sufficiently mixed and stirred in the space.

  Further, an ink outlet 14 for taking out ink is provided on the lower wall 13 of the inner wall of the main body 1. By providing the ink outlet 14 on the lower wall 13 on the lower side of the impeller 5, the fine particles B precipitated on the lower side of the main body are strongly and reliably stirred by the impeller 5. It is possible to prevent the ink from being taken out from the ink outlet 14. Further, an ink discharge port 31, an ink opening 33, and an ink discharge port 32 are provided below the right wall 10 of the inner wall. The ink discharge port 31 is located below the rotation shaft 3. As a result, the ink is discharged from the lower side, and the fine particles B precipitated on the lower side of the main body can be stirred by the flow of discharge. Further, the disturbance of the liquid level due to ink ejection can be reduced. More preferably, the center line of the hole of the ink discharge port 31 is positioned substantially at the center of the blade 4 of the impeller 5. Thereby, the flow of the ejected ink hits the blades 4 of the impeller 5 from the front, and the ink flow is easily converted into rotation of the impeller 5.

  Further, as shown in FIG. 2, a flange-like portion 15 is formed around the ink discharge port 31. The hook-like portion 15 is formed by forming a curved inner surface below the right wall 10 of the inner wall. The hook-shaped portion 15 has a horizontal hook shape and faces the blade 4. The ink discharge port 31 is disposed below the rotating shaft 3 of the impeller 5 and provided above the lower end of the blade 4 of the impeller 5.

  Further, the hook-like portion 15 guides the flow of ink discharged from the ink discharge port 31 so as not to diverge to the surroundings, and restricts the ink flow to efficiently impinge on the blades 4. The partition plate 6 divides the space between the blade 4 and the blade 4 in order to prevent the energy of the ink discharged from the ink discharge port 31 from being lost in the space between the blade 4 and the blade 4. . By ejecting ink into these small areas, the energy of ejection can be efficiently transmitted to the impeller 5.

  A position sensor 17 is provided on the upper wall 16 of the inner wall of the main body 1. The position sensor 17 includes a magnet 18 provided at the upper end of a shaft 21 that moves up and down, a storage portion 19 that stores the magnet 18 and protrudes from the upper portion of the main body 1, and a float that is provided at the lower end of the shaft 21. 20. In this position sensor 17, the liquid surface position is measured by an electromotive force of a Hall element (not shown) accompanying the movement of the magnet 18 interlocked with the float 20. Moreover, the float 20 is a column-shaped long object, and one end part hits the step part 11 of the said right wall 10 when it moves below, and does not move below the said step part 11. FIG. For this reason, interference with the float 20 and the impeller 5 is prevented.

  The ink discharge port 32 is provided at a position substantially equal to the upper end position of the impeller 5 in the vertical direction of the main body 1. Thereby, the upper ink whose density is lowered can be discharged and returned to the ink tank 50. Further, the ink opening 33 may be used for introducing ink or may be used for discharging ink.

  Further, as shown in FIG. 3, a pump 36 is connected to the ink discharge port 31 of the sub tank 100 via a tube 35. An ink tank 50 is connected to the pump 36 by a tube 35. The tube 35 is provided with a switching valve 37. This switching valve 37 is connected to a tube 38 connected to the ink discharge port 32. The pump 36 and the switching valve 37 are controlled by the control unit 39 based on output signals from the position sensor 17 and the like. The upper wall 16 of the main body 1 is provided with an air hole for depressurizing the inside (not shown in FIG. 1), and this air hole is connected to the air control unit 41 by a tube 40. The air control unit 41 maintains the air pressure in the main body 1 at a constant negative pressure. An ink jet head 51 is connected to the ink outlet 14. In the ink path 30a shown in FIG. 3, the ink opening 33 is closed.

  Next, operations of the sub tank 100 and the ink path 30a will be described. FIG. 4 is an explanatory view showing the operation of the sub tank. When the ink is not used for a long time, the ink fine particles B are deposited below the main body 1. In order to eliminate this precipitation by stirring, first, the control unit 39 drives the pump 36 and switches the switching valve 37 so that the ink circulates, and the main body 1, the ink discharge port 32, the tube 35, the switching valve 37, and the pump 36. A circulation system that circulates between the ink discharge port 31 and the main body 1 is configured. In this state, as shown in FIG. 4A, ink is ejected from the ink ejection port 31 with a predetermined pressure. When ink is ejected into the main body filled with ink, the ink flow strikes the blades 4 of the impeller 5 and the impeller 5 rotates.

  The ink flow is well captured in the space partitioned by the partition plate 6 and efficiently transmitted to the blades 4, and the ejection energy is converted into the rotation of the impeller 5. By discharging the ink and the impeller 5, as shown in FIG. 4B, the ink fine particles B that have settled below the main body 1 roll up in the ink. Since the discharged ink is discharged from the ink discharge port 32 by the discharged amount, the liquid level in the main body 1 does not rise. The ink level is monitored by the position sensor 17 during the circulation operation. By continuing the ink ejection, the impeller 5 sufficiently stirs the ink.

  Further, since the clearance between the blade 4 and the side surface 9 of the main body and the lid portion 2 is defined to be minimum, the amount of ink that escapes from the clearance is reduced, and the force for rotating the impeller 5 can be secured. Thereby, the ink ejection energy can be efficiently converted into the rotational motion of the impeller 5. When the ink is circulated for a predetermined time, the circulation operation is stopped because the ink precipitation has been eliminated.

  When printing, the switching valve 37 is switched to form an ink path connecting the ink tank 50 and the pump 36. At this time, ink is not discharged from the ink discharge port 32. When the amount of ink in the main body 1 is reduced by printing, the position of the float 20 is lowered together with the liquid level. This is detected by a hall element (not shown) and a signal is transmitted to the control unit 39. The controller 39 drives the pump 36 to replenish ink in the main body 1. Further, the control unit 39 replenishes ink based on the output signal from the position sensor 17. Further, since the float 20 is not lowered from the step portion 11, the float 20 does not come into contact with the upper end of the impeller 5. The signal of the position where the float 20 comes into contact with the step portion 11 is at least the ink replenishment timing, so that the ink liquid level can always be above the upper end of the impeller 5. Thereby, it can prevent that the blade | wing 4 comes out of a liquid level and entrains air.

  In addition, when the ink tank is sufficiently refilled with a predetermined amount of ink, the switching valve 37 can be switched to constitute the ink circulation system independent of the head 51. Therefore, the ink circulation can be performed even during the ink printing operation. It can be carried out.

  As described above, according to the sub-tank 100, the fine ink particles B precipitated in the sub-tank 100 including the vertical thin box-shaped main body can be stirred. It should be noted that the present invention can be applied to any portion of the ink tank itself that stores ink such as head ink.

  FIG. 5 is a system diagram showing another ink path of the sub tank according to the first embodiment. In the case of this ink path 30 b, a tube 35 is connected to the ink discharge port 31, and this tube 35 is connected to the ink tank 50. A pump 36 is provided on the tube 35. Further, the ink outlet 14 is connected to the head 51 by a tube 42. Further, the head 51 is connected to the ink tank 50 by a tube 42, and a switching valve 37 is provided at a branch point with the tube 35. The pump 36 and the switching valve 37 are controlled by the control unit 39. The control unit 39 controls the pump 36 and the switching valve 37 based on signals from the position sensor 17 and the like.

  In the ink path 30b, when the ink is stirred, the switching valve 37 forms a circulation system of the main body 1, the ink outlet 14, the head 51, the switching valve 37, and the pump 36, and the pump 36 is driven at a predetermined flow rate. . In this circulation system, fine particles precipitated in the head 51 can be circulated together, so that the printing quality is further improved. Next, when printing is performed by the head 51, the ink tank 50 and the sub tank 100 are connected by the switching valve 37, and the return flow path from the head 51 is blocked.

  FIG. 6 is still another ink system diagram of the sub tank according to the first embodiment. In the case of this ink path 30 c, the ink discharge port 31 and the ink discharge port 32 are connected by a tube 43, and a pump 44 is provided in the tube 43. The ink opening 33 is connected to the ink tank 50 by a tube 45, and a pump 46 is provided on the tube 45. The pumps 44 and 46 are controlled by the control unit 39.

  In this ink path, when the ink is stirred, the pump 44 is driven to circulate the ink through the circulation system of the ink discharge port 31, the main body 1, the ink discharge port 32, and the pump 44. Further, when printing is performed by the head 51, printing is performed while the pump 46 is driven and ink in the ink tank 50 is supplied to the head 51. In this ink path 30c, since the ink circulation system is independent, the ink can be circulated even during the ink printing operation.

(Embodiment 2)
FIG. 7 is an explanatory view showing a sub tank according to Embodiment 2 of the present invention. The sub tank 200 has substantially the same configuration as the sub tank 100 according to the first embodiment, but the structure of the impeller 5 is different. Since other than that is the same as that of Embodiment 1, the same code | symbol is attached | subjected to the same component. The impeller 5 is provided with circular plates 201 at both end edges of the blades 4 instead of the partition plate 6. The diameter of the circular plate 201 is substantially the same as the diameter of the impeller 5. The circular plate 201 makes it difficult for the ink discharged between the blades 4 to escape to the left and right, and the discharge pressure is accumulated between the blades 4 and 4. Thereby, the ink ejection energy is efficiently transmitted to the impeller 5.

  At this time, it is necessary to determine the protrusion of the bearing 7 of the impeller 5 to be a predetermined amount, and to keep the gap between the circular plate 201 and the main body side surface 9 and the lid portion 2 at a constant amount. Moreover, you may provide stirring structures, such as an unevenness | corrugation, in the inner surface of the circular board 201 (illustration omitted). For example, a rod-shaped protrusion may be provided on the inner surface.

(Embodiment 3)
FIG. 8 is a partial configuration diagram showing a sub tank according to Embodiment 3 of the present invention. The sub tank 300 according to the third embodiment has substantially the same configuration as the sub tank 100 according to the first embodiment, but the structure of the impeller 5 is different. Since other than that is the same as that of Embodiment 1, the same code | symbol is attached | subjected to the same component. The sub tank 100 is characterized in that the right wall 10 and the left wall 12 of the main body 1 have a semicircular target shape, and a hose 301 is provided at the ink discharge port 31. A tip 302 of the hose 301 is cut obliquely, and the tip 302 is close to the tip of the blade 4 of the impeller 5. Specifically, the hose 301 is arranged so that the extension line 303 of the axis line is located at the approximate center of the blade 4. In this way, ink is ejected from the tip 302 of the hose 301 via the ink ejection port 31, and the ink flow efficiently strikes the blade 4.

(Embodiment 4)
FIG. 9 is a configuration diagram showing a part of a sub-tank according to Embodiment 4 of the present invention. The sub tank 400 has substantially the same configuration as the sub tank 300 according to the third embodiment, but the shaft support structure of the impeller 5 is different. The other components are the same as those in the third embodiment, and thus the same components are denoted by the same reference numerals. The sub-tank 400 is characterized in that the rotating shaft 403 of the impeller 5 is made smaller than the bearing 7 so that the impeller 5 can move freely within the range of play between the bearing 7 and the rotating shaft 403 while rotating. The amount of play is determined by the internal space of the body. For example, the diameter of the rotating shaft 403 is set to 1/2 to 1/3 of the diameter of the bearing 7.

  FIG. 10 is an explanatory diagram showing the operation of this sub tank. In the subtank 100, when the ink fine particles B are precipitated, the impeller 5 is located slightly on the lower side as shown in FIG. That is, the rotating shaft 403 is in contact with the upper side of the bearing 7 to support the impeller 5, and the blade 4 at the lower end of the impeller 5 is located close to the lower wall 13 of the main body 1. It enters a state of entering the precipitated fine particle B (indicated by dots in the figure) layer.

  Next, as shown in FIG. 10B, when ink is ejected from the ink ejection port 31, the ink flows against the blades 4 of the impeller 5. Thereby, since a certain play is provided between the rotating shaft 403 and the bearing 7, the impeller 5 is pushed and the whole impeller 5 moves diagonally upward. Further, ink pressure is applied to the blades 4 and the impeller 5 rotates while moving. Further, when the rotating shaft 403 rotates in the bearing 7, the ink existing in the bearing 7 enters between the rotating shaft 403 and the bearing 7 to form a lubricating layer, so that it rotates smoothly. Thereby, the blades 4 move so as to scrape the precipitated ink fine particles B, and the precipitated fine particles B are diffused.

  And as shown in FIG.10 (c), when the rotation of the impeller 5 continues, the position of the impeller 5 rotates, moving upwards. Then, the impeller 5 as a whole rotates while swinging due to fluctuations in the flow of the discharged ink, and stirs the ink in the sub tank 100. Next, when the ink discharge is stopped, as shown in FIG. 10A, the impeller 5 is lowered and the blade 4 is lowered.

  According to the above configuration, since the position of the impeller 5 is freely moved by the ink pressure by the amount of play between the bearing 7 and the rotary shaft 403, the range in which stirring is possible is widened. For this reason, not only the stirring of the fine particles B but also the retention of ink inside the main body 1 can be prevented. Further, by bringing the tip of the blade 4 of the impeller 5 close to the lower wall 13 when not stirring, the blade 4 can be positioned at a place where precipitation is likely to occur, and the ink deposited at the start of stirring can be strongly scraped.

(Embodiment 5)
FIG. 11 is a block diagram showing a sub tank according to Embodiment 5 of the present invention. The sub tank 500 has substantially the same configuration as the sub tank 100 according to the first embodiment, but the shape of the float 20 is different. Since other than that is the same as that of Embodiment 1, the same code | symbol is attached | subjected to the same component. In the sub tank 500, when the ink is stirred by the impeller 5, there is a possibility that the ink liquid surface rises or waves due to the stirring force of the impeller 5 and bubbles are mixed. For this reason, the shape of the float 520 is similar to the horizontal inner shape of the main body 1 and is characterized in that it is smaller than the inner shape. By covering most of the ink liquid level with the float 520, the liquid level does not swell or blow up due to the rotation of the impeller 5, and bubbles are prevented from being mixed.

  The shape of the float 520 may be an area that can cover most of the inner area in the horizontal direction, or only the area where blow-up or the like is generated by the rotation of the impeller 5 may be widened (not shown). . Further, by setting the area to cover most of the inner cross-sectional area in the horizontal direction, when the sub tank 500 moves at a high speed, the liquid level in the main body 1 can be prevented from tilting to one side, and the high-speed movement and stop can be performed. It is possible to prevent the liquid surface from undulating due to the operation. As a result, even if the impeller 5 is rotated during high-speed movement, the liquid level can be stirred without wobbling or wavy. In particular, when a plurality of colors of ink are contained in a plurality of sub tanks 500, stirring can be performed in the sub tanks 500 that are not used.

  In addition, as shown in FIG. 12, a curved portion 521 may be provided on the back surface of the float 520. Thereby, the flow of the ink stirred by the impeller 5 becomes smooth near the liquid surface, and disturbance and stagnation are reduced.

100 Sub tank 1 Body 2 Lid 3 Rotating shaft 4 Blade 5 Impeller 6 Partition plate 7 Bearing 31 Ink discharge port 32 Ink discharge port

Claims (8)

A main body for storing ink inside,
An impeller having a rotation axis in a direction orthogonal to the gravity in the main body and having a plurality of blades rotating substantially radially about the rotation axis;
An ink ejection port for ejecting ink to the impeller blades;
An ink tank for an ink jet printer, comprising:   The ink tank according to claim 1, wherein the ink discharge port is located below the rotation shaft.   The ink tank according to claim 1, further comprising an ink discharge port that discharges ink below the lowest liquid surface of the ink in the inner wall of the main body.   A bearing for inserting the rotating shaft is provided in the impeller or the main body, and a play in which the impeller can move is provided between the rotating shaft and the bearing. Ink tank.   The ink tank according to claim 1, further comprising a float that floats so as to cover an ink liquid level in the main body.   2. The apparatus according to claim 1, further comprising: a position sensor that detects a liquid level of the ink; and a control unit that controls the liquid level to be maintained above the upper end of the impeller based on a signal from the position sensor. The ink tank as described in any one of -5.   An ink tank circulation system comprising a circulation system in which the ink discharge port and the ink discharge port of the ink tank according to any one of claims 3 to 6 are connected by a tube.   A circulation system in which the ink tank according to any one of claims 1 to 6 has an ink take-out port for taking out ink from the head, and the ink take-out port and the ink discharge port are connected by a tube via the head. An ink tank circulation system comprising:

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