JP2013067032A - Ink supply device of inkjet recording apparatus and ink supply method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively remove visible size bubbles in ink.SOLUTION: An ink supply device of an inkjet recording apparatus includes: a first tank 81 which pools ink to be supplied to heads 3; a second tank 82 which is provided in a middle of a path to the heads from the first tank; a first liquid feed part 814 which feeds the ink to the second tank from the first tank; a second liquid feed part 829 which feeds the ink to the heads side from the second tank and a first ink flow path 811 which connects the first tank and the second tank. An end part of the second tank side of the first ink flow path is connected to the second tank so that the ink flows along an inner wall of the second tank, and the second liquid feed part feeds the ink from the lower part of the second tank.

Description

  The present invention relates to an ink supply apparatus and an ink supply method that are provided in an ink jet printer and supply ink to a head.

As a recording apparatus capable of forming an image on various recording media such as plain paper and plastic thin plate, there is an ink jet printer. The ink jet printer includes a head that ejects ink from nozzle holes. By ejecting ink as fine droplets from the nozzle holes of the head toward the recording medium, an image is formed on the recording medium.
The head is connected to a tank in which ink is stored, and ink is supplied from this tank to the head.
At that time, if a dissolved gas or air bubbles are mixed in the ink, in the case of a head that discharges droplets due to a change in the internal volume, it causes a discharge failure, so the conventional inkjet printer performs vacuum deaeration. A degassing module is provided between the ink tank and the head to remove the gas in the ink (see, for example, FIG. 11 of Patent Document 1).

JP 2011-079295 A

  However, the degassing module provided in the conventional ink jet printer described in Patent Document 1 described above can remove dissolved gas contained in the ink, but about bubbles of a size that can be visually confirmed. Could not be degassed, causing the bubbles to flow to the head side.

  An object of the present invention is to provide an ink jet recording apparatus capable of effectively removing bubbles of a visible size in ink and an ink supply method thereof.

  In order to solve the above problems, the present invention is provided in the middle of a first tank for storing ink to be supplied to a head for discharging ink to a recording medium, and a path from the first tank to the head. A second tank, a first liquid feeding section for sending ink from the first tank to the second tank, a second liquid feeding section for sending ink from the second tank to the head side, An ink jet recording apparatus comprising a first ink flow path connecting the first tank and the second tank, or an ink supply method thereof, the second tank side of the first ink flow path Is connected to the second tank so that the ink flows along the inner side wall surface of the second tank, and the second liquid feeding part is connected to the ink from the lower part of the second tank. It is characterized by feeding liquid.

  In the present invention, at least a portion of the inner side wall of the second tank to which ink is supplied from the first ink flow path may be inclined so that the ink flows on the inner wall surface. .

  Further, the present invention may be configured such that the second tank is formed in a funnel shape and ink is supplied so as to flow on the inner wall surface of the second tank from the first ink flow path.

  In addition, the present invention may include a connection switching unit that includes at least two or more of the first tanks and selectively switches the connection with the second tank from the respective first tanks. .

  In addition, the present invention may include a deaeration device that is provided in the middle of a path from the second tank to the head and that performs vacuum deaeration on ink.

In the present invention, a second tank is provided in the middle of the path from the first tank to the head, and ink flows from the first tank to the second tank along the inner side wall surface of the second tank. Thus, ink is supplied, and ink is fed from the lower part of the second tank to the head.
For this reason, since the ink supplied to the second tank flows along the inner wall surface, the generation of bubbles is reduced by flowing gently compared to the case where the ink is poured so as to collide with the liquid surface. Even if bubbles are already mixed, the bubbles in the ink gently poured into the second tank stay on the liquid level of the stored ink, and the ink is fed from the bottom of the second tank. As a result, only bubbles remain in the second tank, and the bubbles can be removed from the ink fed to the head side.
As a result, bubbles of a size that can be visually confirmed can be effectively removed from the ink, and a stable droplet discharge can be performed in the head.

In addition, since the ink supplied from the first ink flow path in the inner side wall of the second tank is inclined, the supplied ink flows more slowly and is poured, thereby preventing the generation of bubbles. Further, it is possible to further enhance the effect of preventing air bubbles from being mixed.
Furthermore, by making the second tank funnel-shaped, it is possible to flow ink along the inclined surface regardless of the position of ink supply to the inner side wall, and the first ink flow to the second tank. It becomes possible to easily adjust the ink supply position from the path.

  In addition, by providing two or more first tanks and, alternatively, supplying ink to the second tank, when the selected first tank runs out of ink, It is possible to switch quickly, avoiding interruption of the ink ejection operation, and realizing continuous image ejection.

  In addition, by providing a deaeration device in the middle of the path from the second tank to the head, it is possible to remove even fine bubbles and dissolved gas that cannot be visually recognized in the ink, making the head more stable. It is possible to discharge the droplets.

It is a perspective view of an inkjet recording device. It is a top view which shows arrangement | positioning of the head on a carriage. It is sectional drawing which shows the internal structure of a head. It is a schematic diagram which shows the outline of an ink supply apparatus. It is explanatory drawing which shows the connection state of a common flow path and each head. It is a block diagram which shows the control system of an inkjet recording device. It is a flowchart which shows liquid level monitoring control. It is a flowchart which shows head maintenance control. It is a flowchart which shows liquid feeding control. It is a flowchart which shows a negative pressure formation part back pressure adjustment control. It is a flowchart which shows wiping control. FIG. 12A and FIG. 12B are cross-sectional views showing other examples of sub-tanks, respectively.

  An ink jet recording apparatus 10 equipped with an ink supply apparatus according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a perspective view showing the entire inkjet recording apparatus 10.

The ink jet recording apparatus 10 includes a transport apparatus 2 that transports a recording medium along a horizontal direction, a carriage 4 that mounts a plurality of heads 3 (see FIG. 2) that eject ink from above onto the transported recording medium, and a carriage. Main scanning device 5 that transports 4 along a horizontal direction orthogonal to the transport direction of the recording medium, maintenance unit 7 that performs maintenance of each head 3 mounted on carriage 4, and each head 3 mounted on carriage 4. A nozzle moisturizing unit 6 for moisturizing the nozzle 311, an ink supply device 8 for supplying ink to each head 3 mounted on the carriage 4 (see FIG. 4), and a control device 9 for controlling these components (FIG. 6). And a frame 100 that supports the whole.
In the following description, the horizontal direction and the direction along the conveyance direction of the recording medium are the Y-axis direction, the horizontal direction and the direction along the conveyance direction of the carriage 4 are the X-axis direction or the main scanning direction, and the vertical direction. The vertical direction is referred to as the Z-axis direction.

[Conveyor]
The transport device 2 includes a drive roller 21 and a driven roller (not shown), a drive motor 22, and a transport belt 23.
The driving roller 21 and the driven roller are rotatably supported, and the driving roller 21 is disposed so as to extend in the main scanning direction X. The drive motor 22 is a drive source for rotationally driving the drive roller 21, and is attached to one end side of the drive roller 21.
The conveyor belt 23 is formed in an endless shape, and is stretched between the driving roller 21 and the driven roller. When the driving roller 21 rotates, the conveying belt 23 circulates between the driving roller 21 and the driven roller and conveys the recording medium placed on the upper surface thereof in the conveying direction F along the Y-axis direction. When the rotation of the roller 21 is stopped, the circulation between both rollers is stopped, and the conveyance of the recording medium is stopped.
When the head 3 completes one-way scanning along the X-axis direction under the control of the control device 90, the drive motor 22 rotates the drive roller 21 by a predetermined amount to transport the recording medium by a predetermined distance in the transport direction. When the head 3 starts scanning in the direction opposite to the main scanning direction X and finishes, the drive roller 21 is rotated again by a predetermined amount, and the recording medium is transported by a predetermined distance in the transport direction F and stopped. The recording medium is so-called intermittently conveyed.
As the recording medium, it is possible to use resin films, metals, etc. in addition to paper and fabric.

[flame]
As shown in FIG. 1, the frame 100 includes a rectangular main body portion 101 extending along the X-axis direction, a first base portion 102 that supports one end portion in the X-axis direction of the main body portion 101, and the main body portion 101. And the second base portion 103 that supports the other end portion in the X-axis direction.
The first base portion 102 supports one end portion of the main body portion 101 from below while storing and holding the maintenance portion 7 therein. In addition, the second base portion 103 supports the other end portion of the main body portion 101 from below while storing and holding the nozzle moisturizing portion 6 therein.
The main body 101 stores and holds a pair of carriage rails 51, 51 of the main scanning device 5, which will be described later, in the X-axis direction, and the carriage 4 extends in the X-axis direction inside the main body 101. Are transported.
Further, the first base portion 102 and the second base portion 103 are disposed on both sides in the X-axis direction with the above-described transport device 2 interposed therebetween, and the main body portion 101 is installed above the transport device 2. Thus, it is possible to form an image by ejecting ink from each head 3 mounted on the carriage 4 while transporting the carriage 4 in a direction orthogonal to the transport direction of the recording medium by the transport device 2.

[Main scanning device and carriage]
The main scanning device 5 includes a pair of bar-shaped carriage rails 51 and 51 supported so as to extend along the X-axis direction inside the main body 101 of the frame 100. The pair of carriage rails 51 and 51 are provided so as to straddle the upper portion of the conveyance belt 23 of the conveyance device 2. A box-shaped carriage 4 is supported on the carriage rails 51 and 51 so as to be reciprocally movable along the X-axis direction.

The carriage 4 is a substantially rectangular casing having an open top, and a plurality of heads 3 are mounted on the bottom plate. As shown in FIG. 1, the carriage 4 has arm portions 42 and 42 extending toward both sides in the Y-axis direction at the upper part of both side surfaces in the Y-axis direction, and the arm portions 42 and 42 are respectively linear guides. The carriage rails 51 and 51 are placed on the carriage rails 51 and 51 so that the carriage rails 51 and 51 can slide along the X-axis direction.
A linear motor is provided between the carriage rails 51 and 51 and the arm portions 42 and 42 of the carriage 4. That is, each carriage rail 51, 51 is equipped with a stator of a linear motor, each arm 42, 42 of the carriage 4 is equipped with a mover, and the carriage 4 is controlled by current control of the stator side coil. A transport operation along the X-axis direction is given.

FIG. 2 is a schematic explanatory view of the bottom plate 41 of the carriage 4 as viewed from above. In the inkjet recording apparatus 10, Y (yellow), Lm (light magenta), Or (orange), M (magenta), Bk (black), Bl (blue), Lk (light black), C (cyan), Lc Each of the nine colors (light cyan) includes nine heads 3, and a total of 81 heads 3 are attached to the bottom plate of the carriage 4.
As shown in the figure, the head groups of each color are arranged in the order of Y, Lm, Or, M, Bk, Bl, Lk, C, and Lc along the X-axis direction, and the nine heads 3 of each head group are arranged. Are arranged in a staggered manner along the Y-axis direction.
The bottom plate 41 is provided with a slit-shaped opening along the Y-axis direction for each mounting position of each head 3, and each head 3 attached to the bottom plate 41 from above is directly below the carriage 4 through the opening. Ink droplets can be ejected.
As described above, the nine heads 3 are arranged in a staggered manner for each color, so that the ink of each color can be placed at an arbitrary position within the range of almost the entire width in the Y-axis direction on the bottom plate 41 of the carriage 4. It is possible to perform discharge.

[head]
FIG. 4 is a cross-sectional view showing a schematic structure of the head 3. The head 3 includes a nozzle plate 31 on which a plurality of nozzles 311 for ejecting ink are formed, a plurality of channels 321 for guiding the ink to each nozzle 311, and a plurality of piezoelectrics for ejecting ink by changing the volume of the channels 321. A head chip 32 having elements 322, a wiring substrate 33 for applying a driving voltage to each piezoelectric element 322 of the head chip 32, and a manifold 34 for introducing ink to each channel 321 of the head chip 32 via a filter 343. And mainly.

The nozzle plate 31 is a rectangular flat plate. When the head 3 is mounted on the carriage 4, the flat plate surface is parallel to the XY plane, and the longitudinal direction thereof is parallel to the Y-axis direction.
Further, the nozzle plate 31 is formed with a plurality of through holes to be the nozzles 311 arranged in a line along the Y-axis direction.

  The head chip 32 is formed in a rectangular parallelepiped shape, and the nozzle plate 31 is attached to the bottom surface thereof. The head chip 32 has a plurality of channels 321 arranged in a line along the Y-axis direction in accordance with the arrangement of the nozzles 311 of the nozzle plate 31. Each channel 321 is an ink flow path that vertically penetrates the head chip 32, and can individually guide the ink in the manifold 34 to the nozzle 311. Further, each channel 321 is provided with a piezoelectric element 322 adjacent to each other, and when a voltage is selectively applied to any piezoelectric element 322, the piezoelectric element 322 expands or contracts. Ink can be ejected from the nozzle 311 that performs the operation.

A wiring substrate 33 is attached to the upper surface of the head chip 32. The wiring board 33 is connected to a head driving circuit (not shown) via a flexible board, and wiring for applying a driving voltage from the head driving circuit to each piezoelectric element 322 of the head chip 32 is provided. .
The wiring board 33 is attached to the manifold 34 so as to close the opened lower portion of the manifold 34, and the wiring board 33 has a rectangular shape so that the ink in the manifold 34 circulates to each channel 321 side of the head chip 32. An opening is formed.

The manifold 34 is an internal hollow rectangular parallelepiped arranged with its longitudinal direction along the Y-axis direction. As described above, the bottom part is open, but the wiring board 33 is fitted in the open part. It is blocked.
A cylindrical first port 341 and a second port 342 are formed in the upper portion of the manifold 34 in the Y-axis direction on the one end side and the other end side, respectively.
The inside of the manifold 34 is vertically divided into two by a filter 343 that filters out ink contaminants, the upper region is connected to the first port 341 and the second port 342, and the lower region is the head. It is connected to the chip 32. That is, the ink supplied from the outside into the manifold 34 by the first port 341 or the second port 342 is filtered by the filter 343, moves to the head chip 32 side, and is ejected from each nozzle 311.

[Maintenance Department]
The maintenance unit 7 performs maintenance of each head 3 during the non-recording operation. The maintenance unit 7 is provided on one end side of the carriage rails 51, 51 outside the transport device 2. That is, maintenance is performed in a state where the carriage 4 has moved to a position where the carriage rails 51 and 51 are opposed to the maintenance unit 7 at one end thereof.
The maintenance unit 7 includes a cleaning device that wipes off dirt on the lower surface of the nozzle plate 31 of each head 3, and an ink tray 71 (see FIG. 4) that serves as a tray when ink is ejected by the head 3 that is a maintenance target. I have.
The cleaning device mainly includes a cleaning roller that can rotate around a rotation axis along the X-axis direction that is in sliding contact with the lower surface of the nozzle plate 31, and a roller conveyance mechanism that conveys the cleaning roller along the Y-axis direction. The configured cleaning roller has a width in the X-axis direction so as to enable wiping of the three color head groups out of the nine color head groups mounted on the carriage 4. All the heads 3 are cleaned by a reciprocating half moving operation. This prevents clogging of the nozzle 311 due to the solidification of the ink.
Further, ink is ejected to the ink tray 71 at the time of maintenance, not by driving the piezoelectric element 322 of the head 3, but by the ink supply pressure of the ink supply device 8, thereby clogging the ink flow path in the head 3 and the like. Can be resolved.

[Nozzle moisturizer]
The nozzle moisturizing unit 6 is provided on the other end side of the carriage rails 51, 51 outside the transport device 2. That is, during the non-recording operation, the carriage 4 moves to a position facing the nozzle moisturizing unit 6 at the other end of the carriage rails 51 and 51, and in this state, the nozzle 311 of each head 3 is moisturized.
That is, the nozzle moisturizing unit 6 is in close contact with the nozzles 311 of the nozzle plate 31 so that the interior of each nozzle is connected to the moisturizing liquid storage unit. And its lifting mechanism.

[Ink supply device]
FIG. 4 is an explanatory diagram showing a schematic configuration of the ink supply device 8. The ink jet recording apparatus 10 includes the ink supply device 8 for each color.
The ink supply device 8 includes main tanks 81 and 81 as two first tanks for storing ink, a sub tank 82 as a second tank to which ink is supplied from each main tank 81 and 81, and a sub tank 82. A deaeration device 83 provided on the downstream side in the ink supply direction; an intermediate tank 84 provided on the downstream side in the ink supply direction of the deaeration device 83; and a downstream side in the ink supply direction of the intermediate tank 84; The negative pressure forming portion 86 provided in the head and the common flow path 87 in which the first ports 341 of the heads 3 are connected in parallel to supply ink to the heads 3 are mainly used. I have.
FIG. 4 also shows the ink tray 71 of the maintenance unit 7.

The main tanks 81 and 81 are containers whose upper portions are open to the atmosphere, and the two main tanks 81 and 81 are both detachable from the inkjet recording apparatus 10 so that they can be replaced when they become empty. ing. In addition, since there are two main tanks 81 and 81, ink can be supplied from the other main tank 81 even when one of the main tanks 81 is empty and when it is replaced, the recording operation of the inkjet recording apparatus 10 It is possible to avoid interruptions. The number of mounted solids in the main tank 81 may be increased.
Reference numeral 815 in FIG. 4 is a remaining amount sensor for detecting whether or not the ink in each of the main tanks 81 and 81 is empty.

Between the main tanks 81 and 81 and the sub tank 82, one end portion branches to the main tank 81 and 81 side, and the other end portion joins to the first ink flow path 811 reaching the sub tank 82. Is provided. In the vicinity of the main tanks 81 and 81 in the first ink flow path 811, tank valves 812 and 812 are provided as connection switching units that are electromagnetic valves that can switch the open / close state of the flow paths.
Further, a filter 813 for removing contaminants such as dust and dust from the ink is provided in the middle of the path on the sub tank 82 side in the first ink flow path 811, and further on the sub tank 82 side than the filter 813. A first liquid feed pump 814 is provided as a first liquid feed section that sends ink to the sub tank side.

The sub tank 82 has a funnel shape having a side wall portion 821 whose diameter decreases toward the lower side, and the upper portion is closed by a top plate 822.
The sub-tank 82 is connected to the second ink flow path 823 at the center of the bottom, so that the ink in the sub-tank 82 can be supplied to the deaerator 83 through the second ink flow path 823.
In addition, an air release pipe 824 for maintaining the inside of the sub tank 82 at atmospheric pressure is attached to the top plate 822 of the sub tank 82. The air release pipe 824 is equipped with a filter 825 for preventing intrusion of dust and dirt from the outside.

In addition, the top end of the first ink flow path 811 is connected to the top plate 822 of the sub tank 82 in a state of penetrating the top plate 822 and entering the inside.
The front end portion of the first ink flow path 811 extends to a position in contact with or just before the inner surface of the side wall 822 of the sub tank 82, and the ink supplied from the first ink flow path 811 passes through the side wall 822. Then, the liquid is poured into the liquid level in the sub tank 82.
The sub tank 82 has an upper limit position of the ink liquid level determined by liquid level monitoring control described later, and the tip of the first ink flow path 811 is positioned higher than the upper limit position of the ink liquid level. Ink is supplied to the side wall 822.

By setting the position of the front end portion of the first ink flow path 811 with respect to the sub tank 82 as described above, the ink supplied from the first ink flow path 811 always travels along the inner surface of the side wall portion 822 of the sub tank 82. Will be poured into the liquid surface. As a result, the ink gently flows along the inclined surface and is stored in the sub tank 82, so that bubbles of a visually recognizable size are mixed in the ink supplied from the first ink flow path 811. , The bubbles stay on the ink surface. In addition, since the ink gently flows along the inclined surface, it is possible to prevent new bubbles from being generated and mixed in the ink surface.
Further, since the ink in the sub tank 82 is fed from the bottom to the downstream side through the second ink flow path 823, it is possible to remove bubbles from the ink supplied to the downstream side of the sub tank 82.
That is, the sub tank 82 functions as a defoaming unit that defoams ink.

Further, in the sub tank 82, a first liquid level sensor 826 that defines the upper limit position of the ink liquid level in the liquid level monitoring control described later, and a second liquid level sensor 827 that defines the lower limit position of the ink liquid level. And are provided.
Each of these liquid level sensors 826 and 827 is a float type sensor provided with a float, and it is possible to detect whether the liquid level is above or below the upper limit position or the lower limit position from the height of the float. . The liquid level monitoring control will be described in detail later.

  Between the sub tank 82 and the deaerator 83, the above-described second ink flow path 823 is provided. In the middle of the second ink flow path 823, a check valve 828 for preventing the ink from returning from the deaeration device 83 to the sub tank 82, and a second liquid feed for sending ink from the sub tank 82 to the deaeration device 83. A second liquid feed pump 829 as a unit is provided.

The deaeration device 83 includes a deaeration module 831 to which the end of the second ink flow path 823 is connected, a vacuum pump 832 that evacuates the deaeration module 831, and pressure detection in the deaeration module 831. A vacuum pressure sensor 833 is provided, and a leak valve 834 that is an electromagnetic valve that opens the deaeration module 831 to atmospheric pressure.
The deaeration module 831 includes a vacuum container that is evacuated by a vacuum pump 832 and a hollow film that allows ink to pass inside the vacuum container, and the dissolved gas in the ink is removed by evacuation. It is structured to be sucked out through the hollow core membrane.
The vacuum pressure sensor 833 is detection means for measuring whether the pressure has been reduced to the target pressure during evacuation. The leak valve 834 is controlled to be opened by the control device 9 so that the deaeration module 831 is changed from a vacuum state to an atmospheric pressure state for maintenance of the deaeration module 831 when the power of the inkjet recording apparatus 10 is stopped. Done.

A third ink flow path 835 is provided between the deaeration module 831 and the intermediate tank 84. Ink is supplied to the intermediate tank 84 by the supply pressure of the second liquid feed pump 829 via the second and third ink flow paths 823 and 835.
The intermediate tank 84 is formed of a flexible bag, and expands / contracts when the amount of stored ink fluctuates.
The intermediate tank 84 is also provided with a liquid amount sensor 841 for detecting a state where a specified amount of ink is stored. When ink is supplied from the sub tank 82, ink is supplied by the second liquid feed pump 829 until the liquid amount sensor 841 detects that the specified amount has been reached.

  Between the intermediate tank 84 and the negative pressure forming portion 86, fourth to seventh ink flow paths 842 to 845 are provided, and ink is supplied through these. A first three-way switching valve 846, which is an electromagnetic switching valve, is interposed between the fourth ink channel 842 and the fifth ink channel 843, and the fifth ink channel 843 and the sixth ink channel. A second three-way switching valve 847 that is an electromagnetic switching valve is interposed between the flow path 844 and a sixth switching path that is an electromagnetic switching valve is provided between the sixth ink flow path 844 and the seventh ink flow path 845. Three three-way switching valves 848 are interposed.

  Further, a check valve 849 that allows only the flow in the direction from the first three-way switching valve 846 to the second three-way switching valve 847 and the check valve 849 allow the fifth ink flow path 843. And a relief valve 851 that returns ink to the sub-tank 82 when a prescribed pressure is exceeded on the downstream side of the third liquid feed pump 850. Is provided.

  The sixth ink channel 844 is connected to one end of the branch channel 852 in the middle thereof, and the other end of the branch channel 852 is connected to the first three-way switching valve 846. The first three-way switching valve 846 is controlled by the control device 9 so that the fifth ink channel 843 is connected to the fourth ink channel 842 and the fifth ink channel 843 is branched. It is possible to switch to the state connected to 852.

  The second three-way switching valve 847 is also connected to a return flow path 853 for returning ink to the sub tank 82, and the second three-way switching valve 847 is controlled by the control device 9 in accordance with the fifth It is possible to switch between a state in which the ink channel 843 is connected to the sixth ink channel 844 and a state in which the fifth ink channel 843 is connected to the return channel 853.

The first and second three-way switching valves 846 and 847 are combined and controlled by the control device 9 to be simultaneously switched, and the fourth, fifth and sixth ink flow paths 842, 843 and 844 are passed from the intermediate tank 84. After that, a supply connection state (white arrow in FIG. 4) in which ink is fed to the negative pressure forming unit 86 side, a branch channel 852, a fifth ink channel 843, and a return channel 853 from the negative pressure forming unit 86 side. Then, control is performed to switch the return connection state (black arrow in FIG. 4) in which ink is fed to the sub tank 82 side.
That is, using the delivery pressure of the third liquid feed pump 850, the supply of ink to the negative pressure forming unit 86 side and the recovery of ink from the negative pressure forming unit 86 side can be selectively performed. Is possible.

The third three-way switching valve 848 is also connected to a bypass flow path 854 that supplies ink to the head side without passing through the negative pressure forming portion 86, and the sixth ink flow path 844 is controlled by the control device 9. It is possible to switch between a state in which the seventh ink channel 845 is connected and a state in which the sixth ink channel 844 and the bypass channel 854 are connected.
That is, by this switching, a state where ink can be supplied and recovered to the negative pressure forming unit 86 and a state where ink can be supplied and recovered to the head 3 side (strictly, the common flow path 87). It is possible to switch between.

The negative pressure forming portion 86 includes a rectangular main body container 861 having a large opening on the front surface, a film member 862 made of a flexible resin film that closes the opening of the main body container 861, and the inside of the main body container 861 from the inside to the outside. It is mainly composed of a spring (not shown) that presses the center of the film member 862 toward the center.
The main body container 861 is connected to the aforementioned seventh ink flow path 845 and the eighth ink flow path 863 leading to the common flow path 87 to which all the first ports 341 of the nine heads 3 are connected in parallel. Yes.
Further, since the film member 862 is pressed outward by the center by a spring, the film member 862 is in a tension state with a shape that protrudes outward in a substantially conical shape.

Then, after the ink is filled in the main body container 861 at the same pressure as the atmospheric pressure, the first and second three-way switching valves 846 and 847 are returned to the connected state and the ink is collected from the main body container 861. The inside of each head 3 can be in a negative pressure state via the path. In this way, the inside of the head 3 is maintained at a negative pressure because, for example, if the inside of the nozzle 3 is at atmospheric pressure, the ink tends to leak from the nozzle 311 and the ink tends to adhere around the nozzle 311. This is to prevent discharge defects and dot diameter variations from occurring.
Note that the target pressure, which is a negative pressure, can be controlled by adjusting the amount of ink collected in the main body container 861.

  A communication pipe 864 that communicates with the inside of the main body container 861 and extends upward is provided on the upper part of the main body container 861 of the negative pressure forming portion 86. A liquid level sensor 865 is attached to the end of the communication pipe 864 on the main body container 861 side, and a pressure sensor 866 is attached to the upper end of the communication pipe 864. Further, a horizontally extending branch pipe 867 having one end opened to the atmosphere is connected to an intermediate portion of the communication pipe 864, and an opening valve 868 for opening and closing the branch pipe 867 and air are provided in the middle of the branch pipe 867. An air filter 869 for filtering is provided.

  These are structures used when supplying ink into the main body container 861 and controlling it to a predetermined negative pressure. That is, ink is supplied into the main body container 861 until the liquid level is detected by the liquid level sensor 865 with the open valve 868 opened, and then the open valve 868 is closed, and the pressure sensor 866 sets the target negative pressure. Ink is collected from the main body container 861 until the pressure is indicated. Thereby, the inside of each head 3 can be brought into a predetermined negative pressure state through the negative pressure forming portion 86.

  The eighth ink channel 863 extending from the negative pressure forming unit 86 joins the detour channel 854 described above and is connected to the common channel 87 on the way. In addition, a protective valve 871 that is a normally open electromagnetic valve is provided on the negative pressure forming part 86 side of the eighth ink flow path 863 from the junction with the bypass flow path 854.

  The common channel 87 has a flat internal hollow shape in which the shape in front view is a substantially isosceles triangle shape (precisely, a pentagonal shape formed by cutting off both ends of the base of the isosceles triangle along the vertical vertical direction). It is a container and is mounted on the carriage 4 so that its bottom portion faces the horizontal direction. In the common flow path 87, the eighth ink flow path 863 is connected to a portion corresponding to the apex of the isosceles triangle, and the ninth heads 3 of the same color are connected to the portion corresponding to the bottom side of the isosceles triangle. One port 341 is connected in parallel.

In the common flow path 87, the ink passes through an internal space in which a substantially triangular shape same as the external shape is three-dimensionalized. At that time, since the ink is supplied from the position of the apex, the ink is supplied evenly without causing a large deviation with respect to each head 3 connected to each part of the bottom side.
The common flow path 87 only needs to have a substantially isosceles triangle shape in the front view of the internal space to which ink is supplied, and the external shape does not have to be a substantially isosceles triangle shape.

  Further, a waste liquid flow path 872 communicating with a waste liquid tank (not shown) is connected near the apex position of the common flow path 87. The waste liquid flow path 872 is provided with a waste liquid valve 873 that is a normally closed electromagnetic valve. When the common flow path 87 is filled with ink, the waste liquid valve 873 is opened to discharge ink in order to discharge bubbles. It is a flow path for. Since the waste liquid flow path 872 is connected to the apex that is the upper end of the common flow path 87, bubbles are raised in the common flow path 87 by further supplying ink while the common flow path 87 is filled with ink. And is effectively discharged together with the ink. Thereby, bubbles that cause ink ejection failure can be removed, and stable ejection can be performed.

FIG. 5 is an explanatory diagram showing a connection state between the common flow path 87 and each head 3. As shown in FIGS. 4 and 5, the common flow path 87 is connected to the first port 341 of each head 3 via a recording operation valve 874 that is a normally open electromagnetic valve.
The second ports 342 of each head 3 are connected in parallel to the common waste liquid flow path 876 via a normally closed maintenance valve 875, respectively. The common waste liquid flow path 876 joins the waste liquid flow path 872 on the downstream side of the waste liquid valve 873 and is connected to the waste liquid tank.

[Control device]
FIG. 6 is a block diagram showing a control system of the ink supply device 8. The control device 9 shown in FIG. 6 controls the entire inkjet recording apparatus 10, but here, only the configuration of the ink supply device 8 is illustrated, and the other configurations are not shown. Further, only one of the plurality of configurations is illustrated.
The control device 9 not only controls the ink supply device 8 such as converting image data of an image to be recorded on a recording medium input from an external device into data corresponding to each nozzle 311 of the head 3, but also an ink jet recording device. The drive of each part of 10 is also controlled.
As shown in FIG. 6, the control device 9 is composed of a general-purpose computer in which a CPU 91, a ROM 92, a RAM 93, an input / output interface (not shown) and the like are connected to a bus.
The control device 9 includes first to third liquid feed pumps 814, 829, 850, a vacuum pump 832, a tank valve 812, a leak valve 834, and first to third three-way switching valves 846, 847, 848, open. A valve 868, a protection valve 871, a waste liquid valve 873, a recording operation valve 874, and a maintenance valve 875 are connected, and the control device 9 controls them.
Further, the remaining amount sensor 815, first and second liquid level sensors 826, 827, liquid amount sensor 841, liquid level sensor 865, vacuum pressure sensor 833, and pressure sensor 866 are connected to the control device 9, Various detection signals are input from these.
Further, an input operation unit 94 that performs support input such as execution of various operations from the operator, a display unit 95 that displays various information such as error information, and the like are also connected to the control device 9.
And the control apparatus 9 implements the liquid level monitoring control of the sub tank 82, the maintenance control of the head 3, etc. with respect to each said control object according to these detection information.

[Liquid level monitoring control]
The liquid level monitoring control of the sub tank 82 performed by the control device 9 will be described in detail based on the flowchart of FIG.
This liquid level monitoring control is a control for supplying ink from the main tank 81 of ink to the sub tank 82 and for maintaining a constant amount of ink in the sub tank 82, and is repeatedly performed at a predetermined cycle. The

This liquid level monitoring control is based on the premise that either one of the main tanks 81, 81 is opened and the other tank valve 812 is closed.
First, the control device 9 initializes a timer counter for determining whether or not the main tank 81 currently connected to the sub tank 82 is empty (step S1).
Next, it is determined by the first liquid level sensor 826 whether the level detected by the first liquid level sensor 826 indicating that the ink in the sub tank 82 is full is reached (step S3).
As a result, when it is detected that the ink has reached the detection level by the first liquid level sensor 826, since the ink in the sub tank 82 has reached the target amount, the control device 9 performs the liquid level monitoring. End control.

On the other hand, when it is detected that the ink has not reached the detection level by the first liquid level sensor 826, the timer starts to determine whether the main tank 81 is empty, and the first Is operated to supply ink from the main tank 81 to the sub tank 82 (step S5).
Next, the control device 9 determines whether or not the second liquid level sensor 827 has reached the detection level by the second liquid level sensor 827 indicating that the ink in the sub tank 82 is nearly empty (step S7). .
As a result, when it is detected that the ink has reached the detection level by the second liquid level sensor 827, the control device 9 has determined whether the time measured by the timer has passed the preset liquid feeding time It is determined whether or not (step S9).
If the time measured by the timer has not passed the preset liquid feeding time, the process returns to step S3 to determine whether or not the sub tank 82 is full.

The liquid feeding time in the determination in step S9 is set to a time sufficient to fill the sub tank 82 with the liquid feeding capacity of the first liquid feeding pump. That is, if the sub tank 82 is not full even after the liquid feeding time has elapsed, it is estimated that the main tank 81 is already empty.
Therefore, the control device 9 stops the driving of the first liquid feeding pump 814 (step S11), determines that the main tank 81 is empty (step S13), and closes the tank valve 812 that has been open until then. Then, the other tank valve 812 is opened to switch the main tank that supplies ink to the sub tank 82 (step S15). At this time, display control may be performed to notify the display unit 95 that one of the main tanks 81 is empty.
In addition, after switching the main tank 81, the control device 9 returns the process to step S1 again and restarts the ink supply to the sub tank 82.

  If the second liquid level sensor 827 detects that the sub tank 82 is empty in step S7 even though the first liquid feed pump 814 is feeding liquid (step S7: NO). ), The main tanks 81 and 81 are both in an empty state, indicating that all the ink in the main tanks 81 and 81 and the sub tank 82 is being used up. In order to prevent the occurrence of defects, all recording operations of the inkjet recording apparatus 10 are stopped during the recording operation. At this time, the display unit 95 may perform display control for executing a notification display indicating an error stop and a warning display indicating that the ink is empty.

[Maintenance control]
The maintenance control of the head 3 performed by the control device 9 will be described in detail based on the flowchart of FIG. Here, it is assumed that an ejection test is performed on all the heads 3 in advance to identify the heads 3 that require maintenance, and the heads 3 to be maintained have been input by the input operation unit 94.
Further, it is assumed that the carriage 4 stands by just above the maintenance unit 7.

First, the control device 9 switches the first and second three-way switching valves 846 and 847 to the supply connection state (connection indicated by white arrows in FIG. 4), and switches the third three-way switching valve 848 to the sixth ink flow path. It switches so that it may connect to the detour channel 854 from 844 (step S21).
Further, the control device 9 controls to open the waste liquid valve 873 of the common flow path 87, close the protective valve 871, and close the recording operation valves 874 of all the heads 3 (step S23).
Then, ink feeding control is executed (step S25).

Here, liquid feeding control will be described based on the flowchart of FIG.
At the time of liquid feeding, the control means activates the third liquid feeding pump 850 (step S251), determines whether the preset operating time T1 has elapsed (step S253), and continues until the operating time T1 has passed. The operation of the liquid feed pump 850 is continued.
By the operation of the third liquid feed pump 850, the ink in the intermediate tank 84 bypasses the negative pressure forming portion 86 and is directly supplied to the common flow path 87. At this time, the recording operation valves 874 of all the heads 3 are closed, and the maintenance valve 875 is a normally closed valve. Ink is filled. Further, when the common flow path 87 is filled with ink, excess ink is discharged from the waste liquid flow path 872. By continuing such supply for a certain period of time, the bubbles in the common flow path 87 rise to the top of the common flow path 87 and are discharged from the waste liquid flow path 872.
And if the operation time T1 passes, the 3rd liquid feeding pump 850 will be stopped (step S255), and it will wait until standby time T2 passes. As a result, bubbles generated by being poured into the common flow path 87 are floated and collected at the upper part in the common flow path 87.
When the standby time T2 has passed, the control device 9 determines whether or not the number of ink supply and standby repetitions has reached a preset target number N (step S259).
If the target number of times has not been reached, the process returns to step S251, and ink supply and standby are executed again.
The operating time T1, the standby time T2, and the target number N can be set in advance for the control device 9 by the input operation unit 94. The target number N of repetitions is desirably set at least twice so that the bubbles floating above the common flow path 87 due to standby can be discharged by the next ink supply.

Again, the description returns to FIG.
When the liquid feeding control is finished, the control device 9 controls to close the waste liquid valve 873 of the common flow path 87 (step S27) and open the recording operation valve 874 and the maintenance valve 875 of the head 3 to be maintained (step S27). S29).

And liquid feeding control is performed again (step S31). At this time, the operation time T1, the standby time T2, and the target number of times N may be the same as those in step S25 or may be set to different values.
In this case, ink is supplied from the common channel 87 into the maintenance target head 3 through the first port 341. Then, the supplied ink is discharged to the common waste liquid flow path 876 through the second port 342, and a part of the ink is discharged from the nozzle 311 of the head 3 to the ink tray 71.

When the second liquid feeding control is completed, the control device 9 closes the maintenance valve 875 of the head 3 to be maintained (step S33).
Then, the third liquid feeding control is executed (step S35). Also at this time, the operation time T1, the standby time T2, and the target number of times N may be set to the same value as step S25 or S31, or may be set to different values.
When supplying ink in this case, ink is supplied from the common flow path 87 into the head 3 to be maintained through the first port 341 and discharged from the nozzle 311 to the ink tray 71. At this time, all of the ink supply pressure acts on ejection from the nozzle 311, and therefore, for example, the nozzle 311 that has been clogged or the like can also push out foreign matter or the like to eliminate clogging.

When the third liquid feeding control is completed, the control device 9 opens all the recording operation valves 874 of all the heads 3 other than the head 3 to be maintained (step S37), and opens the protective valve 871. The third three-way switching valve 848 is switched to a state in which the sixth ink channel 844 and the seventh ink channel 845 are connected (step S39).
And the control apparatus 9 performs negative pressure formation part back pressure adjustment control (step S41), and also performs the wiping control of each head 3, and complete | finishes maintenance control (step S43).

Here, the negative pressure forming portion back pressure adjustment control will be described in detail based on the flowchart of FIG.
First, the control device 9 switches to open the open valve 868 and close the protective valve 871 (step S411).
Next, the current pressure of the pressure sensor 866 in the negative pressure forming unit 86 is set to atmospheric pressure (step S412).
Next, the operation of the third liquid feed pump 850 is started (step S413), and the liquid level sensor 865 in which the ink supplied into the main body container 861 of the negative pressure forming unit 86 is located at the upper end portion of the main body container 861. Is determined (step S414).
If the ink does not reach the upper end portion of the main body container 861, the ink supply to the main body container 861 is continued. If the ink reaches the upper end portion of the main body container 861, the third liquid feed pump 850 is stopped. (Step S415).
Thereafter, the control device 9 closes the opening valve 868 (step S416), and performs control to switch the first and second three-way switching valves 846, 847 to the return connection state (black arrow in FIG. 4) (step S417). .
When the third liquid feed pump 850 is operated again (step S418), the ink inside is discharged from the main body container 861 of the negative pressure forming unit 86. As a result, the internal pressure of the main body container 861 decreases.
A negative pressure value suitable for ink ejection of each head 3 is determined in advance, and when the pressure sensor 866 detects that the pressure has decreased to a negative pressure value suitable for ink ejection ( Step S419), the third liquid feed pump 850 is stopped (Step S420).
Then, the control device 9 opens the protective valve 871 (step S421), whereby the negative pressure forming portion 86 and each head 3 are connected via the eighth ink channel 863 and the common channel 87. For this reason, the inside of each head 3 becomes the same negative pressure as the inside of the negative pressure forming portion 86.
Thereafter, the control device 9 performs control to switch the first and second three-way switching valves 846 and 847 to the supply connection state (white arrow in FIG. 4) (step S422), and ends the negative pressure forming portion back pressure adjustment control. To do.

The wiping control will be described based on the flowchart of FIG. In the wiping control, all the heads 3 on the carriage 4 are wiped around the nozzles 311.
Each nozzle 311 is wiped by transporting a wiping roller that rotates around the rotation axis along the X-axis direction along the Y-axis direction while being in sliding contact with the lower surface of the nozzle plate 31. .
On the other hand, since this inkjet recording apparatus 10 has nine heads 3 mounted on the carriage 4 for each of the nine colors, the area for wiping is also very large. Therefore, if the wiping roller is to be completed by one-way conveyance, the wiping roller has to be lengthened in the direction of the rotation axis, so that bending or the like tends to occur, and effective wiping may not be performed.
Accordingly, the wiping roller has substantially the same size as the arrangement width of the heads 3 for the three colors in the X-axis direction, and performs wiping on the nozzles of all the heads 3 for nine colors in three times.
The operation control will be described below.

First, the control device 9 performs one-way (outward) conveyance from the standby position while rotating the wiping roller (step S431). Thereby, wiping with respect to the head 3 for three colors is performed.
Next, the carriage 4 is moved by the same distance as the X-axis direction width of the heads 3 for three colors (step S433), and the wiping roller is rotated, and the one-way (return) conveyance is executed (step). S435). Thereby, wiping is performed on the head 3 for the next three colors.
Further, the carriage 4 is moved by the same distance as the width of the heads 3 for the three colors in the X-axis direction (step S437), and the wiping roller is rotated and the one-way (outward) conveyance is executed (step S439). ). Thereby, wiping is performed on the head 3 for the last three colors.
Further, the wiping is repeatedly performed a preset number of times. Therefore, when the wiping for nine colors is completed, the control device 9 compares the current number of wiping executions with a preset number of repetitions (step S441). As a result, if the current number of executions has not reached the set number of repetitions, the process returns to S431, and the wiping operation is started again.
On the other hand, if the current number of executions matches the set number of repetitions, the wiping control is terminated.

[Technical effects in the embodiment of the invention]
The ink supply device 8 of the ink jet recording apparatus 10 is provided with a funnel-shaped sub tank 82 in the middle of the path from the main tank 81 to each head 3, and the inner side wall surface of the sub tank 82 inclined with respect to the sub tank 82 from the main tank 81. Ink is supplied so that the ink flows through the sub tank 82, and further, the ink is fed from the lower part of the sub tank 82 to each head 3 via the intermediate tank 84, the negative pressure forming part 86, the common flow path 87, and the like. .
For this reason, since the ink supplied to the sub tank 82 flows along the inclined inner wall surface, the generation of bubbles is reduced by flowing gently compared to the case where the ink is poured so as to collide with the liquid surface. Further, even when bubbles are already mixed, the bubbles in the ink gently poured into the sub tank 82 remain on the liquid level of the stored ink, and the ink is fed from the lower portion of the sub tank 82, Only the bubbles remain in the sub tank 82, and the bubbles can be removed from the ink fed downstream.
Thereby, bubbles of a size that can be visually confirmed can be effectively removed from the ink, and each head 3 can stably discharge droplets.

  Further, by providing two main tanks 81 and alternatively supplying ink to the sub tank 82, when the selected main tank 81 runs out of ink, the main tank 81 is quickly switched to the other main tank 81. Therefore, it is possible to avoid interruption of the ink discharge operation and realize continuous image discharge.

  Further, by providing the deaeration device 83 in the middle of the path from the sub tank 82 to each head 3, it is possible to remove even fine bubbles and dissolved gas that cannot be visually recognized in the ink. In this case, it is possible to discharge liquid droplets more stably.

[Others]
In the above embodiment, the funnel-shaped sub tank 82 is exemplified, but the structure is limited to the above example as long as the ink can flow from the first ink flow path 811 along the inner side wall surface of the sub tank. It is not something.
For example, as shown in the sub-tank 82A of FIG. 12A, the tank shape is a columnar shape or a rectangular parallelepiped shape, and the first ink flow path 811 is configured so that ink flows along the inner side wall surface along the vertical vertical direction. You may arrange | position a front-end | tip part to the proximity | contact or contact of the internal side wall surface of the sub tank 82A. In this case, since the ink flows along a vertical surface in the sub tank 82A, it flows at a speed higher than that of the inclined surface. However, the bubbles are sufficiently larger than the case where ink is poured directly onto the liquid surface. It is possible to remove the bubbles from the ink supplied downstream of the sub tank 82A while leaving the bubbles on the liquid surface.

  Further, as shown in the sub tank 82B of FIG. 12B, unlike the sub tank 82, the entire side wall surface is not inclined, but the portion where the ink supplied from the first ink flow path 811 flows is transmitted. Only the inclined surface is used, and the portion where ink does not flow through may be vertical. Also in this case, since the ink gently flows along the inclined surface in the sub tank 82, it is possible to obtain substantially the same effect as the sub tank 82.

3 Head 8 Ink supply device.
10 Inkjet recording device 81 Main tank (first tank)
82, 82A, 82B Sub tank (second tank)
83 Deaerator 811 First ink flow path 812 Tank valve (connection switching unit)
814 First liquid feeding pump (first liquid feeding unit)
829 Second liquid feeding pump (second liquid feeding unit)

Claims (10)

A first tank for storing ink to be supplied to a head for discharging ink to a recording medium;
A second tank provided in the middle of the path from the first tank to the head;
A first liquid feeding section for sending ink from the first tank to the second tank;
A second liquid feeding section for feeding ink from the second tank to the head side;
A first ink flow path connecting the first tank and the second tank;
The second tank side end of the first ink flow path is connected to the second tank so that ink flows along the inner side wall surface of the second tank,
The ink supply apparatus for an ink jet recording apparatus, wherein the second liquid supply section supplies ink from a lower portion of the second tank.   2. The portion of the inner side wall of the second tank, to which ink is supplied from at least the first ink flow path, is inclined so that the ink flows on the inner wall surface. Ink supply device for ink jet recording apparatus.   3. The ink jet recording apparatus according to claim 2, wherein the second tank is formed in a funnel shape and supplied from the first ink flow path so that ink flows on the inner wall surface of the second tank. Ink supply device. Including at least two of the first tanks;
4. The inkjet recording apparatus according to claim 1, further comprising a connection switching unit that selectively switches a connection with the second tank from each of the first tanks. 5. Ink supply device.   The inkjet according to any one of claims 1 to 4, further comprising a deaeration device that is provided in the middle of a path from the second tank to the head and that performs vacuum deaeration on the ink. Ink supply device of recording apparatus. A first tank that stores ink to be supplied to a head that discharges ink to a recording medium; a second tank that is provided in the middle of a path from the first tank to the head; and from the first tank A first liquid feeding section for sending ink to the second tank, a second liquid feeding section for sending ink from the second tank to the head side, the first tank and the second tank, An ink supply method for an ink jet recording apparatus comprising: a first ink flow path connecting
Ink is supplied to the second tank so that the ink flows from the end on the second tank side of the first ink flow path along the inner side wall surface of the second tank,
An ink supply method for an ink jet recording apparatus, wherein ink is supplied from a lower part of the second tank by the second liquid supply unit.   7. The ink supply is performed such that at least a portion of the side wall of the second tank to which ink is supplied from the first ink flow path is inclined so that the ink flows on the inner wall surface. An ink supply method for the ink jet recording apparatus according to claim 1.   8. The ink jet recording apparatus according to claim 7, wherein the second tank is formed in a funnel shape, and is supplied such that ink flows from the first ink flow path on the inner wall surface of the second tank. Ink supply method. Including at least two of the first tanks;
The ink supply method for an ink jet recording apparatus according to any one of claims 6 to 8, wherein ink is supplied to the second tank selectively from each of the first tanks.   10. The ink is supplied to the head by performing vacuum deaeration on the ink by a vacuum deaeration device in the middle of the path from the second tank to the head. An ink supply method for an ink jet recording apparatus according to one item.

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