JP3823885B2 - Inkjet recording device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a configuration of an ink jet recording apparatus such as a piezoelectric type, and more specifically, includes an apparatus for circulating ink between a print head and an ink tank and removing bubbles in the circulation path. It is about things.
[0002]
[Prior art]
Conventionally, in an ink jet recording apparatus that records ink by ejecting it onto a recording medium based on an input signal, the ink is guided from an ink tank to a plurality of ejection channels of a print head via an ink flow path, and a heating element and a piezoelectric element There is known an apparatus in which ink is ejected from the tip (nozzle) of an ejection channel by selectively driving such an actuator. Among them, as disclosed in, for example, JP-A-56-75867 and JP-A-2000-103084, the ink inflow side between the manifold chamber connected to the print head and the ink tank is provided. 1 ink flow path is connected to the second ink flow path on the discharge side, a circulation pump is provided in the middle of the second ink flow path, and ink is supplied to the ink tank → first ink flow path → manifold chamber → second ink. It is known to perform a circulation purge in which the air is circulated through a circulation path composed of a flow path and an ink tank, and bubbles contained in the ink are released into the atmosphere by the ink tank and removed.
[0003]
In the above publication, immediately after the circulation purge, the second ink flow path is closed to remove bubbles in the ejection channel of the print head, the nozzle face of the print head is covered with a suction cap, and the suction pump is driven. It is also known to perform a suction purge that sucks and removes bubbles together with the ink in the ejection channel.
[0004]
[Problems to be solved by the invention]
However, due to recent technological advances, the print head has been downsized, and the manifold chamber has also been downsized and its internal volume (ink storage volume) has been reduced. When introduced into the manifold chamber, the proportion of bubbles that accumulate in the manifold chamber increases, and the flexible tube constituting the first ink flow path that guides ink from the ink tank to the manifold chamber avoids air permeability. Instead, as time elapses, the air dissolves in the ink in the tube, and it becomes bubbles and flows into the manifold together with the ink. Since the manifold chamber is located immediately above the ejection channel of the print head, there is a problem that air bubbles are directly drawn into the ejection channel, resulting in ink ejection failure.
[0005]
In order to eliminate this inconvenience, a large-capacity buffer tank is disposed at a high position in front of the manifold chamber, and the buffer tank and the ink tank are connected by the first ink flow path and the second ink flow path. Then, it has been considered to provide a circulation pump in the second ink flow path to form a circulation purge between them.
[0006]
However, if the ceiling surface of the buffer tank is substantially horizontal and a discharge port (exit) to the second ink flow path is arranged in a part of the ceiling surface, the ink ( Even if the bubbles to be removed from the liquid) float up to the ceiling surface, it is difficult to move in the direction of the outlet, and there is a problem that the bubbles cannot be completely removed.
[0007]
By the way, the ink jet recording apparatus is generally placed on a placing surface such as a substantially horizontal table or shelf, but the ceiling surface of the buffer tank on the print head should be lowered on the outlet side. As described above, when the recording apparatus is placed on a slightly inclined placement surface, there is a problem in that bubbles are collected at the highest portion of the ceiling surface of the buffer tank and cannot be removed.
[0008]
The present invention has been made in order to solve such a problem, and an object of the present invention is to provide an ink jet recording apparatus that has a simple structure for discharging bubbles and can easily separate bubbles. It is.
[0009]
[Means for Solving the Problems]
In order to achieve this technical problem, an ink jet recording apparatus according to a first aspect of the present invention includes a print head having a plurality of ejection channels, a buffer tank for storing ink to be supplied to the print head, and an ink tank from the ink tank. A first ink channel for supplying ink to the buffer tank; a second ink channel for collecting ink from the buffer tank to the ink tank; the ink tank, the first ink channel, the buffer tank, and the second ink channel; In the ink jet recording apparatus provided with a pump that circulates ink between the two and removes bubbles, an outlet portion to the second ink flow path is provided at the highest position in the ceiling of the buffer tank. .
[0010]
According to a second aspect of the present invention, in the ink jet recording apparatus according to the first aspect of the present invention, substantially the entire ceiling surface of the buffer tank is positioned so that the outlet to the second ink flow path is at a high position. It is formed by an inclined surface having a predetermined inclination angle with respect to a horizontal plane.
[0011]
According to a third aspect of the present invention, in the ink jet recording apparatus according to the second aspect, an inclination angle of the ceiling surface with respect to a horizontal plane is set to 5 degrees or more.
[0012]
According to a fourth aspect of the present invention, there is provided the inkjet recording apparatus according to any one of the first to third aspects, wherein the inlet portion of the first ink flow path to the buffer tank is provided with the second ink flow. It is arrange | positioned in the position lower than the exit part to a road.
[0013]
Furthermore, the invention according to claim 5 is the ink jet recording apparatus according to any one of claims 1 to 4, further comprising suction purge means for sucking ink from an ink ejection side of the ejection channel of the print head. Is.
[0014]
A sixth aspect of the present invention is the ink jet recording apparatus according to any one of the first to fifth aspects, wherein the print head and the buffer tank are mounted on a movable carriage, and the ink tank is the carriage. The first ink channel and the second ink channel installed outside are flexible tubes that connect the buffer tank and the ink tank.
[0015]
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 schematically shows the ink jet recording apparatus according to the first embodiment. In the head unit 1, a print head 2 having a plurality of ejection channels (not shown) is disposed on the lower side, and a manifold body 3 having manifold chambers 3a communicating with all the ejection channels is disposed on the upper side. Both are bonded and fixed into a unit.
[0017]
The head unit 1 is fixedly mounted on the lower surface side of the carriage 4 with an adhesive or the like, and a buffer tank 5 is detachably fixed to the upper surface side thereof with mounting screws 6. The ink cartridge 30 as an ink supply source is connected to the bottom surface of the sub tank 32 via a flexible tube 31, and the ink in the ink cartridge 30 is replenished and supplied to the sub tank 32 by driving the first pump 33. A first ink flow path 34 made of a flexible tube is connected to the bottom surface of the sub tank 32 so as to supply ink to the ink inlet 8 of the buffer tank 5. A second ink flow path 35 made of a flexible tube is connected to the sub tank 32 to collect ink from the discharge port 9 of the buffer tank 5, and an ink circulation pump 36 is disposed in the middle of the second ink flow path 35. Yes. In that case, the sub tank 32 has an air release portion 32a on its upper surface, and bubbles mixed with ink recovered from the buffer tank 5 are also recovered in the sub tank 32 and discharged to the atmosphere.
[0018]
The ink cartridge 30 and the sub tank 32 are installed in a stationary part outside the carriage. The ink liquid level in the sub-tank 32 is disposed lower than the nozzle opening surface of the print head 2, and the pump 36 is stopped during the printing operation so that a negative pressure acts on the nozzle opening surface.
[0019]
Next, the print head 2 will be described. Since it has a known structure as disclosed in Japanese Patent Application Laid-Open No. 2000-103084 and the like, although not shown, nozzles communicating with a plurality of ejection channels are formed in rows on the lower surface. The ink droplets are ejected from the nozzles by driving the actuator, and two print heads 2 (only one is shown) are provided in parallel. On the upper surface of each print head 2, a manifold body 3 is provided in which a manifold chamber 3a is arranged to communicate with each ejection channel. The introduction pipes 12 and 12 projecting from the upper surfaces of the manifold chambers 3a and 3a (only one is shown in FIG. 1) are connected to the ink outlet 10 opened in the bottom plate 5a of the buffer tank 5 to be described later via the seal pipes 18 and 18. It is connected. As a configuration of the actuator, it is preferable that a side wall near the ejection channel is made of a piezoelectric material, and ink is ejected by deformation of the piezoelectric material.
[0020]
An ink inflow cylinder 8 hangs down from the ceiling wall 7 of the buffer tank 5 and opens near the bottom plate 5 a of the buffer tank 5. Further, the upper end of the ink inflow cylinder 8 protrudes upward from the ceiling wall 7. Further, a discharge port 9 serving as an outlet for discharging ink and bubbles is opened at a portion near one side of the ceiling wall 7, and the inner surface (ceiling surface) 7a of the ceiling wall 7 can be understood from FIG. In order to be able to do so, it is formed on an inclined surface having an appropriate inclination angle θ with respect to the horizontal plane so that it is generally low on the one hand and high on the discharge port 9 side. This inclination angle θ is approximately 5 degrees added to an allowable inclination angle (apparatus allowable inclination angle) when a main body (not shown) of a printer equipped with the ink jet recording apparatus of the present invention is placed on a mounting surface such as a table. In the embodiment, it is about 5 to 15 degrees, and more preferably about 10 degrees.
[0021]
A pair of ink outlets 10 and 10 projecting downward from the bottom plate 5a of the buffer tank 5 is provided with a filter 11 on the upper surface side (inside the buffer tank 5), so that bubbles in the ink or The foreign matter can be captured.
[0022]
The other end of the first flexible tube 13 whose one end is connected to the ink inflow cylinder 8 in the buffer tank 5 is connected to a connection member 14 provided on the substrate of the carriage 4, and the flexible tube 13 is connected to the first flexible tube 13. A part of the ink flow path 34 is formed. Further, the other end of the second flexible tube 15 having one end connected to a discharge port 9 as an outlet for ink and bubbles in the buffer tank 5 is connected to a connecting member 16 provided on the substrate of the carriage 4. The flexible tube 15 constitutes a part of the second ink flow path 35. Midway portions of the first flexible tube 13 and the flexible tube 15 are protected by a cover body 17 attached to the carriage 4.
[0023]
The carriage 4 on which the ink jet recording apparatus having the above-described configuration is mounted is reciprocating along a surface of a paper (not shown) as a recording medium and along a carriage movement direction orthogonal to the paper feeding direction. A suction cap 37 for suction purge is disposed at one end in the carriage movement direction so as to face the print head 2, and at the time of suction purge, the suction cap 37 is placed on the front surface (lower surface) of the print head 2. The nozzles close to each other so as to cover the nozzle opening surface, and are discharged to the drain tank 40 through the suction pipe 38 and the suction pump 39.
[0024]
With the above-described configuration, for example, when the ink cartridge 30 is first installed in the printer and the print head 2 is filled with ink, or when the ink cartridge 30 is replaced, the first pump 33 is first driven to drive the sub tank 32. A predetermined amount of ink is stored in Next, in a state where the nozzle opening surface of the print head 2 is covered with the suction cap 37, the ink circulation pump 36 is driven to make the inside of the buffer tank 5 have a negative pressure, and the ink in the sub-tank 32 is discharged to the first ink flow path 34. Then, the ink is supplied from the ink inflow cylinder 8 into the buffer tank 5. Thereafter, the suction pump 39 is driven to fill the ink in the buffer tank 5 into the ejection channel of the print head 2 from the ink outlet 10 through the introduction pipe 12 and the manifold chamber 3a.
[0025]
During the printing operation, the circulation pump 36 is stopped. When the ink in the buffer tank 5 decreases as the ink is ejected from the print head 2, the ink is replenished from the sub tank 3 through the first ink flow path 34 due to the pressure drop in the buffer tank 5.
[0026]
In the buffer tank 5, ink is stored such that the lower end of the ink inflow cylinder 8 is below the ink liquid level.
[0027]
Air dissolves in the ink from the wall surface of the flexible tube constituting the first ink flow path 34, and the air flows into the buffer tank 5 as air bubbles as time passes. Ink and bubbles are separated by gravity in the buffer tank 5. Most bubbles rise and accumulate on the ceiling. Further, since air bubbles are present in the ink or trapped on the inner surface of the buffer tank 5 or the location of the filter 11, the circulation pump 36 is periodically driven for a predetermined time to perform circulation purge. Execute.
[0028]
That is, when the ink is circulated through the circulation path of the sub tank 32 → the first ink flow path 34 → the buffer tank 5 → the second ink flow path 35 → the sub tank 32, the ink reduces the flow velocity in the sub tank 32 and the bubbles are buoyant. And are released into the atmosphere from the atmosphere opening portion 32a (circulation purge).
[0029]
In that case, the nozzle portion of the print head 2 is covered with the suction cap 37 and sealed, but the suction pump 39 is not operated. When the ejection channel or nozzle in the print head 2 is clogged due to ink drying or the like, the nozzle opening surface of the print head 2 is covered with the suction cap 37, and the clog is removed by suction purge by the suction pump 39. can do.
[0030]
When air bubbles in the buffer tank 5 are removed by the circulation purge, the inner surface 7a of the ceiling wall 7 of the buffer tank 5 is an inclined surface, and the discharge port 9 is provided at the highest portion of the inner surface 7a of the ceiling wall 7. As a result, when the entire interior of the buffer tank 5 is filled with ink, the bubbles are reliably transferred to the discharge port 9 as the outlet portion at the highest position along the inclined surface, and the second possible Shiwasei through the second ink flow path 35 such as a tube 15 and the connection member 1 6 is collected in the sub-tank 32 is able reliably discharged.
[0031]
When the ink inflow pipe 8 has an opening close to the bottom surface of the buffer tank 5 and the liquid level of the ink accumulated in the buffer tank 5 is higher than the opening, the buffer flows when the ink flows. There is an effect that the generation of bubbles can be suppressed as much as possible without involving the air in the tank 5.
[0032]
In the print head 2, instead of the above configuration, the ink is locally boiled and ejected by a known heat generating portion, and an electro-mechanical displacement converting means such as a piezoelectric element is opposed to a planarly arranged ejection channel. Can be applied. In these cases, the ink outlet of the buffer tank is connected to the manifold chamber that distributes the ink to the plurality of ejection channels.
[0033]
Further, the buffer tank 5 may be directly connected to the print head 2 without passing through the manifold body 3.
[0034]
The circulation pump 36 is provided in the second ink flow path 35, but may be provided in the first ink flow path 34. In any case, when the circulation pump is provided in the second ink flow path 35 by sealing the nozzle surface of the print head 2 with the suction purge means, the ejection channel of the print head 2 is started when the circulation pump 36 starts operating. However, when a circulation pump is provided in the first ink flow path 34, when the operation of the circulation pump 36 is started, the discharge channel of the print head 2 is not affected. Although positive pressure acts, ink does not leak from the ejection channel.
[0035]
In the reference example shown in FIG. 2, an air reservoir 5 b having a predetermined capacity protruding above the ceiling surface 7 a is formed on the ceiling surface of the buffer tank 5. The air reservoir 5 b is closed at the upper surface and side surfaces, and the lower surface is opened only into the buffer tank 5. Since other configurations in the reference example are the same as those in the first embodiment, the same parts and structures are denoted by the same reference numerals, and detailed description thereof is omitted. With the above configuration, air is always present in the air reservoir 5b even when the circulation pump 36 supplies ink to the buffer tank 5 and circulates the purge, so in the printing (recording) operation, As the print head 2 mounted on the carriage 4 moves, the ink in the first and second ink flow paths 34 and 35 moves due to inertia, and the buffer in the buffer tank 5 is subjected to pressure fluctuations. The pressure fluctuation is absorbed by the air remaining in the air reservoir 5b located at the uppermost part in the tank 5, and the ejection channel in the print head is not affected.
[0036]
Also in this reference example , since the discharge port 9 is provided at the upper part of the inclined ceiling surface 7a, the bubble generated from the ink can be effectively removed by executing the circulation purge, and the bubble enters the ejection channel. This can be prevented.
[0037]
The air reservoir 5b may be provided at the highest position of the inclined ceiling surface 7a as shown in FIG. 2 , but the same effect can be obtained even if it is provided at a low position.
[0038]
[Operation and effect of the invention]
As described above, the ink jet recording apparatus according to the first aspect of the present invention is a print head having a plurality of ejection channels, a buffer tank for storing ink to be supplied to the print head, and the buffer tank from the ink tank. A first ink flow path for supplying ink to the ink tank; a second ink flow path for collecting ink from the buffer tank to the ink tank; and between the ink tank, the first ink flow path, the buffer tank, and the second ink flow path. In the inkjet recording apparatus provided with a pump that circulates ink and removes bubbles, an outlet portion to the second ink flow path is provided at the highest position in the ceiling of the buffer tank.
[0039]
Accordingly, during the circulation purge in which the ink is circulated between the sub tank and the buffer tank by the first ink flow path and the second ink flow path and the pump in the middle thereof to remove bubbles in the ink from the buffer tank, Since the outlet to the second ink flow path is located at the highest position on the ceiling surface of the tank, bubbles do not remain in the buffer tank, and the bubbles can be reliably removed to the outside. There is an effect.
[0040]
According to a second aspect of the present invention, substantially the entire ceiling surface of the buffer tank is formed with an inclined surface having a predetermined angle with respect to a horizontal plane so that the outlet portion to the second ink flow path is at a high position. As a result, there is an effect that the bubbles can be discharged in a short time during the circulation purge for removing the bubbles in the ink from the buffer tank.
[0041]
According to a third aspect of the present invention, in the ink jet recording apparatus according to the second aspect, an inclination angle of the ceiling surface with respect to a horizontal plane is set to 5 degrees or more. If the inclination angle is set to such a level, the ceiling surface of the buffer tank is placed on the mounting surface having the inclination angle enough to guarantee the normal function of the ink jet recording apparatus. It is possible to ensure a degree of inclination such that the outlet to the second ink flow path is at a high position, and it is possible to reliably remove bubbles in the buffer tank.
[0042]
According to a fourth aspect of the present invention, in the ink jet recording apparatus according to any one of the first to third aspects, the inlet portion of the first ink flow path to the buffer tank is connected to the second ink flow path. Since it is arranged at a position lower than the outlet portion, when the ink in the buffer tank accumulates to a position higher than the inlet portion, the ink from the inlet portion jets into the ink liquid. At the time of the ink circulation purge, there is an effect that air in the buffer tank is not newly taken up, generation of bubbles is suppressed, and bubbles can be removed quickly.
[0043]
Furthermore, the invention according to claim 5 is the ink jet recording apparatus according to any one of claims 1 to 4, further comprising suction purge means for sucking ink from an ink ejection side of the ejection channel of the print head. since those, if sealing the nozzle surface of the print head by suction purge means during circulation purge, intrude bubbles in the injection channel of the printhead to availability and the ink leakage. In the unlikely event that nozzle clogging occurs, there is an effect that nozzle clogging can be quickly eliminated by operating the suction purge means.
[0044]
A sixth aspect of the present invention is the ink jet recording apparatus according to any one of the first to fifth aspects, wherein the print head and the buffer tank are mounted on a movable carriage, and the ink tank is the carriage. Since the first ink channel and the second ink channel, which are installed outside, are flexible tubes that connect the buffer tank and the ink tank, the air bubbles that have entered through the tubes are charged. The buffer tank of Item 1 can be effectively discharged, and stable ink ejection can be realized.
[0045]
[Brief description of the drawings]
FIG. 1 is a diagram of an ink jet recording apparatus according to a first embodiment of the present invention.
FIG. 2 is a diagram of an ink jet recording apparatus according to a reference example .
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 2 Print head 4 Carriage 5 Buffer tank 5a Bottom plate 5b Air pool 7 Ceiling wall 8 Ink inflow cylinder 9 Outlet 10 Ink outlet 11 Filter 13 1st flexible tube 14, 16 Connection member 15 2nd flexible tube 30 Ink Cartridge 31 Tube 32 Sub tank 33 First pump 34 First ink flow path 35 Second ink flow path 36 Ink circulation pump

Claims (6)

A print head having a plurality of ejection channels, a buffer tank for storing ink to be supplied to the print head, a first ink flow path for supplying ink from the ink tank to the buffer tank, and ink from the buffer tank to the ink tank In an inkjet recording apparatus comprising: a second ink flow path to be collected; and a pump that circulates ink between the ink tank, the first ink flow path, the buffer tank, and the second ink flow path to remove bubbles.
An ink jet recording apparatus, wherein an outlet to the second ink flow path is provided at a highest position in the ceiling of the buffer tank.   The substantially entire ceiling surface of the buffer tank is formed by an inclined surface having a predetermined inclination angle with respect to a horizontal plane so that an outlet portion to the second ink channel is at a high position. 2. An ink jet recording apparatus according to 1.   The inkjet recording apparatus according to claim 2, wherein an inclination angle of the ceiling surface with respect to a horizontal plane is set to 5 degrees or more.   The inflow port portion to the buffer tank of the first ink flow path is disposed at a position lower than the outlet portion to the second ink flow path. 2. An ink jet recording apparatus according to 1.   The ink jet recording apparatus according to claim 1, further comprising a suction purge unit that sucks ink from an ink ejection side of an ejection channel of the print head.   The print head and the buffer tank are mounted on a movable carriage, the ink tank is installed outside the carriage, and the first ink flow path and the second ink flow path include the buffer tank and the ink tank. 6. The ink jet recording apparatus according to claim 1, wherein the ink jet recording apparatus is a flexible tube to be connected.

Images