JP4179220B2 - Inkjet recording device - Google Patents

Description

  The present invention relates to an ink jet recording apparatus that performs a printing operation by ejecting ink, and more particularly to a structure for removing bubbles in an ink flow path between an ink tank and a print head.

  Conventionally, as an ink jet recording apparatus that performs printing operation by ejecting ink based on an input signal, the ink is guided to an actuator of a print head, and the bending or heating of an actuator such as a piezoelectric element or an electrostrictive element according to the input signal. A device that ejects ink under pressure by utilizing local boiling of ink by an element is known.

  However, in some cases, bubbles may adhere to and accumulate on the wall surface in the ink flow path that guides ink to the actuator of the print head. When the bubbles enter the actuator, even if an attempt is made to increase the pressure in the actuator, the pressure is absorbed by the bubbles, the pressure cannot be increased sufficiently, and the ink is not ejected well. This is due to the fact that the bulk modulus of air is extremely smaller than that of ink, which adversely affects the print quality.

  For this reason, for example, Japanese Patent Application Laid-Open No. 56-75867 aims to remove bubbles by a simple operation and prevent them from entering the actuator when bubbles are attached to the inner wall surface of the ink flow path. As described in the official gazette, an ink tank and a manifold that distributes ink to an actuator of a print head are connected by a circulation flow path including an outward path and a return path, and the ink is forcibly circulated in the circulation path. Therefore, it is known to perform a circulation purge to remove bubbles adhering to the wall surface of the ink flow path.

JP-A-56-75867

  By the way, in such a case, in order to effectively remove bubbles adhering to the wall surface in the circulation flow path, it is desirable to increase the flow speed of the ink. The ink pressure in the flow path increases, and the increase in the pressure tends to break the meniscus formed by the surface tension of the ink in the nozzle holes of the print head, causing the ink to leak. For this reason, the flow rate of the ink cannot be increased to such an extent that the bubbles can be effectively removed, and the bubbles cannot be completely removed only by circulating the ink.

  SUMMARY An advantage of some aspects of the invention is that it provides an ink jet recording apparatus that can more effectively remove bubbles adhering to an ink flow path.

The present invention contains a head unit having a plurality of actuators that perform a printing operation by opening a plurality of nozzles on the nozzle surface and ejecting ink from each nozzle, and contains ink to be supplied to the plurality of actuators. Provided in the first ink flow path, an ink tank that collects ink, a first ink flow path and a second ink flow path that form an ink circulation flow path between the ink tank and the head unit. And circulating the ink in a circulation flow path comprising the ink tank, the first ink flow path, the head unit, and the second ink flow path to recover the bubbles in the circulation flow path into the ink tank. A circulation pump means for purging; a valve means provided in the second ink flow path for communicating and blocking the second ink flow path; and the head. A cap made of an elastic material that covers the nozzle surface of the unit; an opening / closing means that is connected to the suction cap and is closed and opened so that the inside of the cap covering the nozzle surface is a closed space; and the circulation pump means And a purge control means for controlling the valve means and the opening / closing means, and during the printing operation, the circulation pump means is stopped without closing the first ink flow path, and the valve means is the second means. The ink flow path is shut off, ink is supplied from the ink tank to the head unit via the first ink flow path, and the purge control means operates the circulation pump means to circulate the ink. When the circulation purge is performed, the valve means communicates the second ink flow path, the circulation pump means is driven, and the elastic material of the cap is compressed. Closing the switching means so as to closed space within the cap against the nozzle surface of the head unit so that the air within the closed space is, to remove air bubbles adhering to the circulation flow passage inside surface characterized in that so as to oppose the pressure by the flow rate of the circulation flow path.

  Preferably, a suction pump that sucks ink from the head unit in a state where the cap covers the nozzle surface of the head unit, and the opening and closing means is configured so that the purge control means enables driving of the suction pump. Open control. Further, when the cap covers the nozzle surface of the head unit, the opening / closing means is preferably closed simultaneously with or immediately after forming the closed space.

  Preferably, the head unit includes a print head having the plurality of actuators, an ink reservoir provided over all the actuators, and a manifold having an ink inflow portion and an ink outflow portion communicating with both ends of the ink reservoir. The first ink flow path and the second ink flow path are connected to the ink inflow portion and the ink outflow portion.

According to the present invention, during the printing operation, the circulation pump means is stopped without closing the first ink flow path, and the valve means shuts off the second ink flow path so that the first ink flow path is removed from the ink tank. Ink is supplied to the head unit through one ink flow path. When performing the circulation purge, by covering the nozzle surface of the head unit and to close the opening and closing means to form a closed space by compressing the resilient material of the cap, bubbles the ink flow rate circulating in performing the circulation purge Since the air in the closed space opposes the pressure , the purge efficiency can be improved.

  In addition, by connecting the cap to a suction pump and opening the opening / closing means, a special cap device that forms a closed space for circulation purge can be performed by suctioning ink in the head unit and performing suction purge. There is no need to provide it.

  Further, when the cap covers the nozzle surface of the head unit, the opening / closing means is closed at the same time as or immediately after forming the closed space, so that the air in the cap cannot be pushed into the nozzle when the cap moves forward.

  FIG. 1 shows a schematic configuration of an ink jet recording apparatus of a first reference example. As shown in FIG. 1, a head unit 2 including a print head 1 is mounted on a carriage 3. The operations of the print head 1 and the carriage 3 are controlled by a microcomputer (not shown). During the printing operation, the carriage 3 reciprocates in a print area for printing on a print medium (not shown), and the print head. 1 is that a plurality of actuators are selectively driven based on print data and ink is ejected to perform printing, while the carriage 3 moves into a recovery area outside the print area when printing is stopped. Yes. Like the normal print head, the print head 1 includes a plurality of pressure chambers to which ink is supplied from a manifold 11 to be described later, and applies ejection energy to the ink in the pressure chamber by an actuator. As known, an actuator that pressurizes and ejects ink by using bending of a piezoelectric element, an electrostrictive element or the like, or local boiling of ink by a heating element is used. An ejection port, that is, a nozzle hole of each pressure chamber opens to the lower surface (nozzle surface) of the print head 1.

  The head unit 2 includes a manifold 11 bonded to the upper surface of the print head 1, and a first head side in which one end is connected to the ink inlet 11a of the manifold 11 and a joint member 12 is provided at the other end. An ink tube 13 and a second head-side ink tube 16 having one end connected to the ink outlet 11b of the manifold 11 and a joint member 15 provided at the other end are provided. The ink inlet portion 11 a and the ink outlet portion 11 b of the manifold 11 are communicated with both ends of an ink reservoir portion 11 c provided across the pressure chambers of all the actuators of the print head 1. The ink outlet 11b and the joint member 12 are provided with filter members 14 and 17 for capturing dust in the ink.

  On the other hand, the carriage 3 is provided with a joint receiving member 18 that is detachably connected to the joint member 12 in a state where the head unit 2 is mounted.

  One end of a first tank side ink tube 23 is connected to the joint receiving member 18, and the other end of the tube 23 is connected to the ink tank 21. In the middle of the tube 23, an ink circulation pump 22 capable of forward and reverse rotation is provided. One end of a second tank side ink tube 26 is connected to the joint member 15, and the other end of the tube 26 is connected to the ink tank 21. An opening / closing valve 25 is provided in the middle of the tube 26.

  In the illustrated example, the ink circulation pump 22 has a tube 23 made of a flexible material, and a part of the tube is sequentially crushed in the longitudinal direction of the tube by a pressing member such as a plurality of rollers, whereby the ink flows. In addition, various known types are used. The on-off valve 25 is operated by an electromagnet, a motor or the like, and is closed when normal printing is performed, and is opened when the circulation pump 22 is driven.

  Both tank side tubes 23, 26 are opened away from each other at both ends of the bottom of the ink tank 21. A plurality of partitions 21a are provided in the ink tank 21 between the openings of the tubes 23 and 26, and the ink that has entered the ink tank 21 from the second tank side tube 26 bypasses the partition 21a. However, when meandering and flowing to the first tank side tube 23, the bubbles contained in the ink are separated by buoyancy. The ink tank 21 has an upper surface opened to the atmosphere, and can release separated bubbles.

  A suction purge device 31 that sucks ink in the print head 1 is provided in a recovery area on the side of the print area. The suction purge device 31 includes a suction cap 32 that covers the nozzle surface of the print head 1, a suction pump 34 connected to the suction cap 32 through a suction pipe 33, and the suction cap 32 to the nozzle surface of the print head 1. A known moving means (not shown) that moves in the approaching and separating directions is provided, and the nozzle face of the print head is covered with a suction cap 32 as in a known manner, and ink is sucked to perform purging.

  The ink circulation pump 22, the opening / closing valve 25 and the suction purge device 31 are linked to a purge control means 27 comprising a microcomputer. The purge control means 27 uses the ink circulation pump 22, the opening / closing valve 25 and the suction purge. The apparatus 31 is controlled to remove bubbles accumulated in the ink and ensure a good ink ejection state of the print head 1.

  With the above configuration, when the print head 1 is filled with ink, the suction cap 32 is moved forward by the moving means (not shown) under the control of the purge control means 27 so that the nozzle surface of the print head 1 is moved. The cover and the opening / closing valve 25 are opened, and the ink circulation pump 22 is driven to rotate. Thus, the ink is supplied from the ink tank 21 through the first tank-side ink tube 23 and the first head-side ink tube 13 to the ink reservoir 11 c of the manifold 11, and the second head-side ink tube 16. Then, the ink is returned to the ink tank 21 through the second tank-side ink tube 26. Thereafter, the open / close valve 25 is closed and the ink circulation pump 22 is stopped without closing the first tank-side ink tube 23. When the suction pump 34 is driven, the ink in the ink reservoir 11c is sucked through the suction cap 32, and the pressure chambers of the print head are filled with ink. During a printing operation, ink is supplied from the ink tank 21 through the first tank side ink tube 23 and the first head side ink tube 13 due to a pressure drop caused by ink ejection at the print head 1.

  Ink tank 21, first tank side ink tube 23, first head side ink tube 13, ink reservoir 11 c of manifold 11, second head side ink tube 16, second tank side ink tube 26, ink tank Bubbles adhering to the wall surface or the like of the circulation channel 21 are removed by forcibly flowing ink through the circulation channel.

  That is, when the circulation purge is performed, the ink circulation pump 22 is driven and the open / close valve 25 is opened under the control of the purge control means 27, and the first ink flow path is formed from the ink tank 21. Ink is supplied to the ink reservoir 11c of the manifold 11 through the first tank-side ink tube 23 and the first head-side ink tube 13, and a second ink flow path is formed from the ink reservoir 11c. The ink is collected in the ink tank 21 through the head-side ink tube 16 and the second tank-side ink tube 26. While the collected ink meanders through the partition 21a in the ink tank 21, bubbles contained in the ink rise and are released to the atmosphere. The ink with few bubbles is configured to be supplied to the print head 1 through the first tank-side ink tube 23.

  When the circulation purge is performed, in the first reference example, the rotation direction of the ink circulation pump 22 is changed only for a short time, and the ink flow in the ink tubes 23, 13, 16, 26 is changed by the change of the ink flow direction. The bubbles attached to the wall surface and the like are shaken, and the bubbles are easily removed by the flow of ink. Such control of the ink flow direction is performed by controlling the rotation direction of the ink circulation pump 22 by the purge control means 27. As an aspect of the control, for example, the ink circulation pump 22 (each 20 rotations in a forward direction in which normal ink flows, and 20 rotations in the forward direction, followed by one rotation in the reverse direction and then 20 rotations in the forward direction.

  In this way, by flowing ink in the direction opposite to the normal direction of flowing normal ink, the flow speed of the ink in the circulation flow path changes, and the flow speed of the ink greatly changes to form the ink flow path. The bubbles adhering to the inner wall surfaces of the ink tubes 13, 16, 23, and 26 are shaken and the bubbles are easily removed. In addition, since the ink is allowed to flow in the reverse direction only for a short time, the bubbles removed by the ink flow do not return or stagnate in the ink flow path, and the second is quickly performed. The ink channels 21 and 26 are carried to the ink tank 21.

  In particular, the ink circulation pump 22 provided in the first tank-side ink tube 23 is used to change the direction in which ink flows, so that the first tank-side ink tube 23 close thereto and the continuous ink tank 23 are continuous therewith. Air bubbles adhering to the wall surface or the like on the first head side ink tube 13 side are effectively shaken and are easily removed. That is, by using the ink circulation pump 22 as described above, it is advantageous to remove bubbles adhering to the wall surfaces in the ink tubes 23 and 13 on the ink supply side of the print head 1. .

  In addition, since the ink flow direction is changed to greatly change the ink flow velocity, the pressure in the ink flow path (ink tubes 13, 16, 23, 26) is not increased so much. Therefore, the ink meniscus formed in the nozzle holes of the print head 1 is not destroyed and the ink does not leak out.

  The suction purge unit 31 removes bubbles in the pressure chamber by bringing a suction cap 32 into close contact with the nozzle surface of the print head 1 and sucking ink from the pressure chamber of the print head, as is well known. The operation may be performed independently of the above-described circulation purge, or may be performed in association with the circulation purge as in a reference example described later.

  2 and 3 show a second reference example. The same parts as those in the reference example are denoted by the same reference numerals, and the description thereof is omitted.

  In this reference example, vibration applying means 41 for applying vibration to the circulated ink is provided. The vibration applying means 41 is provided on the downstream side of the ink circulation pump 22, and for example, as shown in FIG. 3, an operating member having a contact portion 42 a that contacts the ink tube 23, that is, a cam member 42 is used. 42, a pinion member 43 meshing with a gear portion (not shown) provided integrally with 42, and a step motor 44 as a driving means for rotationally driving the pinion member 43. The first tank-side ink tube 23 is formed of a flexible material so as to be easily vibrated by intermittent contact with the cam member 42.

  When the circulation purge is performed (for example, for about 1 minute), the vibration applying unit 41 is driven by the step motor 44 under the control of the purge control unit 41 after the start of the circulation purge. The contact portion 42a is rotated twice, and intermittently repels the ink tube 23 to give vibration, thereby giving vibration (swaying) to the circulating ink.

  In the circulation purge, the ink circulation pump 22 is driven and the open / close valve 25 is opened in the same manner as in the above-described reference example, and the ink tank 21, the first tank side ink tube 23, the first head side ink tube 13, Ink is forcedly circulated through a circulation flow path composed of the ink reservoir 11 c of the manifold 11, the second head side ink tube 16, the second tank side ink tube 26, and the ink tank 21. When performing the circulation purge, the cam member 42 intermittently contacts the flexible ink tube 23 on the downstream side of the ink circulation pump 22, vibrates the ink tube 23, and adheres to the wall surface or the like in the ink tube 23. The bubbles are shaken, and the bubbles are easily removed by the flow of ink. The bubbles removed by the ink flow are collected in the ink tank 21 together with the ink flow and separated.

  In particular, since vibration is applied to the first tank-side ink tube 23, the first tank-side ink tube 23 and the first head-side ink continuous with the first tank-side ink tube 23 on the ink supply side to the print head 1 are used. Air bubbles adhering to the wall surface or the like on the tube 13 side are effectively shaken and are easily removed. That is, by applying vibration on the downstream side of the ink circulation pump 22 in this way, bubbles attached to the wall surfaces and the like in the ink tubes 23 and 13 on the ink supply side of the print head 1 are effectively removed. And the bubbles can be collected through the ink tubes 16 and 26 on the return side. As a result, the bubbles in the ink supplied to the print head 1 during the printing operation can be extremely reduced, and the inability to print due to the bubbles can be eliminated.

  Further, since vibration is applied to the circulating ink so that the attached bubbles are shaken, the pressure in the ink flow path (ink tubes 13, 16, 23, 26) may be increased so much. Absent. Therefore, the meniscus formed in the nozzle hole of the print head 1 is not destroyed and the ink does not leak out.

  In this reference example, as the vibration applying means 41, a cam member 42 that is driven to rotate by a step motor 44 is used to apply vibration. It can also be made to oscillate in an angular range. In this way, the required space is reduced compared to the case of rotating, which is advantageous in saving space. It is also possible to provide a contact portion on the carriage without providing a cam member, and to move the carriage so that the ink tube is repelled at the contact portion and vibration is applied. Various types of vibrators can also be used.

  In the third reference example, the purge control means 27 executes the suction purge as well as the circulation purge, which is the same as that shown in FIG.

  When the circulation purge is performed while the carriage 3 is moved from the printing area to the recovery area at the time of printing suspension, the opening / closing valve 25 is opened by the control by the purge control means 27 as in the above-described reference example. At the same time, the ink circulation pump 22 is driven to rotate from the ink tank 21 to the first tank side ink tube 23, the first head side ink tube 13, the ink reservoir 11 c of the manifold 11, and the second head side. Ink is forced to flow back to the ink tank 21 through the ink tube 16 and the second tank side ink tube 26. The bubbles adhering to the inner wall surface of the tube are carried to the ink tank 21 together with the ink flow and separated.

  In addition to that, when the circulation purge is performed, the suction purge device 31 is driven for a predetermined time from the beginning of the circulation purge under the control of the purge control means 27, and the suction purge is performed in conjunction with the circulation purge. It becomes like this. That is, at the same time as the circulation purge is started, the suction cap 32 is advanced by a moving means (not shown) to cover the nozzle surface of the print head 1, and in this state, the suction pump 34 is driven and passed through the suction cap 32. Suction purge is performed to suck the air bubbles in the print head 1 together with the ink. Then, after a predetermined time has elapsed, the driving of the suction pump 34 is stopped and the suction cap 32 is retracted.

  Thus, by the control by the purge control means 27, the suction purge is used together for a fixed time from the beginning of the circulation purge, so that not only the inside of the circulation flow path but also the bubbles in the pressure chamber of the print head are removed. In addition, the flow velocity in the first tank side ink tube 23 and the first head side ink tube 13 is increased by the synergistic effect of the circulation purge and the suction purge. As the ink flow rate increases, bubbles attached to the inner wall surfaces of the ink tubes 13 and 23 are easily removed. When the carriage 3 returns to the print area, the nozzle surface of the print head 1 is wiped by a wiper member (not shown) in the same manner as when normal suction purge for recovery of defective ink ejection is completed. Then, an ink meniscus is formed in each nozzle of the print head 1.

  Therefore, a situation in which bubbles adhering on the first head side ink tube 13 and the first tank side ink tube 23 are supplied to the print head 1 is avoided, and a good printing state is secured.

  Further, the suction purge by the suction purge device 31 performed during the circulation purge is only performed for a certain period from the beginning of the circulation purge, and the amount of ink sucked is smaller than in the case of the normal suction purge. In addition, ink is not wasted by using the suction purge together. Furthermore, since the flow velocity is increased in the first part as described above, the bubbles are easily removed early, and the entire bubbles are removed in a short time.

  In this reference example, as the suction purge means used in combination with the circulation purge, the suction purge means for performing normal suction purge is used. However, the dedicated suction purge for performing only the suction purge for performing the circulation purge is used. The means can be provided separately from the normal suction purge means.

  FIG. 4 shows an embodiment of the present invention. In the present embodiment, a closed space is formed between the nozzle surface of the print head and the suction cap, so that the ink flow rate during the circulation purge can be increased.

  Specifically, the pipe 33 of the suction purge means 31 is provided with an opening / closing means such as a valve 35, and the suction purge device 31 and the opening / closing means 35 are linked to the purge control means 27 together with the ink circulation pump 22 and the opening / closing valve 25. ing. The purge control means 27 opens and closes when the suction cap 32 covers the nozzle surface of the print head, in addition to the normal purge operation performed in the case of ink ejection failure, and the circulation purge excluding bubbles in the circulation flow path. The means 35 is closed to form a closed space between the suction cap 32 and the nozzle surface.

  When the print head 1 is filled with ink as in the above-described reference example and when the ink in the pressure chamber of the print head is sucked, the purge control means 27 is used to make the suction pump 34 drive effective. Under the control, the opening / closing means 35 is opened.

  In order to remove bubbles adhering to the wall surfaces and the like in the ink tubes 23, 13, 16, and 26 (particularly the ink tubes 23 and 13 on the ink supply side), when the circulation purge is performed, first, the carriage 3 Is moved from the print area to the recovery area, and the print is suspended. Then, under the control of the purge control means 27, the ink circulation pump 22 is driven and the open / close valve 25 is opened. From the ink tank 21, the first tank side ink tube 23 and the first head side ink tube 13 are opened. The ink is forced to flow back to the ink tank 21 through the ink reservoir 11c of the manifold 11, the second head side ink tube 16 and the second tank side ink tube 26, and the inner wall surface of the tube Bubbles adhering to the ink are carried to the ink tank 21 together with the ink and removed.

  In addition to this, when the circulation purge is performed, the nozzle surface of the print head 1 is covered with the suction cap 32 of the suction purge device 31 and the opening / closing means 35 is closed under the control of the purge control unit 27, so that the nozzle surface and the suction cap are closed. The space between 23 is a sealed space. The opening / closing means 35 is preferably closed at the same time as or immediately after forming the sealed space so that the air inside the cap 23 is not pushed into the nozzles of the print head. As a result, even if the flow rate of the ink in the circulation channel is increased to such an extent that bubbles attached to the inner wall surfaces of the ink tubes 13, 16, 23, and 26 are easily removed, Since it opposes the pressure, the meniscus of the ink in the nozzle is not destroyed, and there is no possibility that the ink leaks. In particular, since the suction cap 23 is made of an elastic material such as rubber as is well known, the suction cap 23 is compressed by being slightly applied to the nozzle surface. Even if the ink flow rate is further increased, the ink meniscus is not destroyed.

  When the carriage 3 returns to the print area after the circulation purge, the nozzle surface of the print head 1 is wiped by a wiper member (not shown), unlike the case of the normal suction purge for recovery of defective ink ejection. This can be omitted.

  Therefore, a situation in which bubbles adhering on the first head side ink tube 13 and the first tank side ink tube 23 are supplied to the print head 1 is avoided, and a good printing state is secured.

  In addition, when performing the circulation purge, the suction purge device 31 does not perform the suction purge, but the suction cap 32 only covers the nozzle surface of the print head 1, so that ink is wasted to remove bubbles. It is never consumed.

  The fourth reference example uses a storage cap to form the above-described sealed space. Although not shown, the suction pump 34, the opening / closing means 35, and the pipe 33 are omitted in FIG. 4, and the suction cap 32 is replaced with a storage cap. As is well known, the storage cap is in close contact with the nozzle surface of the print head to prevent the ink in the nozzle hole from drying, and is suitable for forming the above-mentioned sealed space without air leakage. is there. In the circulation purge, substantially the same operation as that of the above embodiment is achieved except that the control of the opening / closing means 35 is lost.

  In the fifth reference example, the pressure in the circulation flow path is increased and air bubbles adhering to the wall surface of the first ink flow path or the pressure chamber of the print head are pushed out from the nozzle hole of the print head by the flow of ink. Is. The illustration is similar to FIG.

  The suction purge device 31 of the fifth reference example is linked to the purge control means 27 and is pushed out from the nozzle holes of the print head 1 in the auxiliary purge described later in addition to the suction purge operation performed in the case of ink ejection failure. Also functions to receive and discharge ink.

  That is, the auxiliary purge for driving the ink circulation pump 22 is performed with the open / close valve 25 closed at the stage before or after the completion of the circulation purge in the above-described embodiment and reference example. Thus, the pressure in the ink tubes 23 and 13 is increased so that the bubbles attached to the wall surface of the ink flow path are easily removed, and the removed bubbles are pushed out through the nozzle holes of the print head 1. ing. At that time, in order to prevent the surrounding contamination by the ink, the suction purge device 31 is driven to receive the pushed ink by the suction cap 32. In this case, the suction cap 32 does not need to be in close contact with the nozzle surface of the print head, and may simply be opposed.

  The operation of filling the print head 1 with ink and the suction purge for sucking ink in the pressure chamber of the print head are performed in the same manner as in the first reference example.

  When the circulation purge is performed at the time of the printing pause, the ink is forcibly caused to flow in the circulation flow path in the state where the carriage 3 is moved from the print area to the recovery area, and the circulation is performed. Bubbles in the path are carried to the ink tank 21 together with the ink and removed.

  In addition, the communication of the second ink tube 26 is blocked by the opening / closing valve 25 at a stage before the circulation purge is performed or after the circulation purge is completed, and in this state, the circulation pump 22 is driven for a certain period of time. A supplementary purge is performed. By this auxiliary purge, the pressure in the ink flow path of the first head side ink tube 13 and the first tank side ink tube 23 is increased, and bubbles adhering to the wall surface of the ink flow path perform the circulation purge. It is easier to remove than to do. As a result, the bubbles in the wall surface of the ink flow path and the pressure chamber are pushed out together with the ink from the nozzle holes of the print head 1. At this time, the nozzle surface of the print head 1 is covered with the suction cap 32, and the pushed ink is discharged from the suction cap 32 through the pipe 33. At this time, the suction pump 34 is driven to discharge ink from the suction cap 32.

  Thus, due to the synergistic effect of the circulation purge and the auxiliary purge, the first tank side ink tube 23, the inner wall surface of the first head side ink tube 13, the ink reservoir 11c of the manifold 11, and the pressure chamber of the print head are attached. The air bubbles are effectively removed, and the situation where the air bubbles block the pressure chamber of the print head 1 or absorb the pressure by the actuator is avoided, and a good printing state is ensured.

  It is also possible to repeat the auxiliary purge at a stage before the circulation purge is performed or after the circulation purge is completed. In other words, it is possible to perform the auxiliary purge at a stage after the circulation purge is completed and then perform the circulation purge again.

  In the above reference example, when the auxiliary purge is performed before the circulation purge is performed or after the circulation purge is completed, the communication of the second ink flow path is blocked by the open / close valve, and the circulation pump However, the sixth reference example is not limited to this, and if the pressure in the ink flow path is increased, bubbles attached to the wall surface and the like can be easily separated. For example, instead of the open / close valve, a valve circuit having a throttle portion is used, and when the auxiliary purge is performed, the flow of ink in the second ink flow path is throttled to suppress the flow of the second ink flow path. It is also possible to increase the pressure in the ink flow path. Even in this case, when performing the printing operation, the valve circuit needs to block the communication of the second ink flow path so that the printing operation is not hindered.

  In the sixth reference example, the suction purge means for performing normal suction purge is used as the capping means. However, at least the ink that has been pushed out is contaminated even if it is not actively suctioned. Therefore, a dedicated capping unit that covers the nozzle surface of the print head with a cap when performing the auxiliary purge can be provided separately from the normal suction purge unit. In addition, a storage cap means having a storage cap that covers the nozzle surface of the print head when printing is stopped or when printing is stopped, and prevents the nozzle surface from drying can be used. Even in those cases, a pump for discharging the ink in the cap is provided, and after the circulation pump is driven for a certain time, the pump is driven and the cap is used to discharge the leaked ink. It is also possible to discharge ink. Further, the ink pushed out from the nozzle may be directly received by a porous material, a container or the like.

  In the embodiment and the reference example described above, the carriage is applied to an ink jet recording apparatus that performs printing on the print medium while reciprocating along the print medium in the print area. It can also be applied to things that do not move.

  The ink tank 21 may be connected to a large-capacity main tank that replenishes ink as the ink in the ink tank decreases.

  The embodiment and the reference example can be implemented not only independently but also in any combination.

  As described above, according to the embodiment of the present invention, when the circulation purge is performed, the nozzle surface of the head unit is covered with the cap and the opening / closing means is closed to form a closed space. The pressure in the closed space against the pressure of the circulating ink acts on the nozzles of the head unit. Therefore, even if the ink flow rate is increased, the ink meniscus in the nozzle holes of the head unit is prevented from being destroyed and ink leakage is prevented. Therefore, the ink flow rate can be increased to improve the purge efficiency. it can. Further, the cap can be made of an elastic material and compressed when the nozzle surface of the head unit is covered to increase the pressure in the closed space, thereby further increasing the ink flow rate.

  In addition, by connecting the cap to a suction pump and opening the opening / closing means, a special cap device that forms a closed space for circulation purge can be performed by suctioning ink in the head unit and performing suction purge. There is no need to provide it. Further, when the cap covers the nozzle surface of the head unit, the opening / closing means is closed at the same time as or immediately after forming the closed space, so that the air in the cap cannot be pushed into the nozzle when the cap moves forward.

  In the first reference example, when the circulation purge is performed, the flow speed of the ink is changed by changing the flow direction of the ink, and the large change in the flow speed causes the ink to adhere to the inner wall surface in the ink flow path. The shaking bubbles are given to the bubbles, and the bubbles are easily removed by the flow of ink. The bubbles removed by the ink flow are collected in the ink tank and do not enter the actuator side. In this case, since the flow direction of the ink is changed to increase the flow velocity difference and the shaking is given, the pressure in the ink flow path is not so high compared to the case where the ink flow velocity is simply increased to give the shaking. Therefore, there is no problem that ink leaks from the nozzles of the head unit.

  Preferably, in the first reference example, the ink circulation means is an ink circulation pump provided in the first ink flow path and capable of rotating in the forward and reverse directions, and simple control of changing the rotation direction of the ink circulation pump. Therefore, the flow direction of the ink is easily changed in the circulation flow path, and shaking is given to the attached bubbles.

  Preferably, in the first reference example, when the circulation purge is performed, the ink is adhered by flowing the ink in a direction opposite to the forward direction for a shorter time than the time for flowing the normal ink in the forward direction. The bubbles removed by the flow of ink are quickly transported to the ink tank, and the removed bubbles return or stagnate in the ink flow path. Disappears.

  In the second reference example, when the circulation purge is performed, vibration is applied to the circulated ink by the vibration applying unit, and the vibration causes the ink to adhere to the inner wall surface in the ink flow path through the ink. The air bubbles are shaken and the air bubbles are easily removed by the flow of ink by the circulation purge. Therefore, the bubbles are removed by the ink flow and collected in the ink tank, and the bubbles do not enter the actuator side. In this case, since the vibration is only given to the circulated ink by shaking, the pressure in the ink flow path is increased as compared with the case where the air flow is simply increased to remove the bubbles. There is no need for this, so that no ink leaks from the nozzles of the head unit.

  In the second reference example, preferably, the vibration applying means is provided in the first ink flow path, so that vibration is applied to the first ink flow path and the second ink flow path is set during the circulation purge. Thus, the bubbles can be collected, the bubbles contained in the ink supplied to the head unit can be extremely reduced, and the inability to print due to the bubbles can be reduced.

  In the second reference example, preferably, the first or second ink flow path is configured by a flexible tube, and is circulated in the ink tube by applying vibration to the ink tube by the vibration applying unit. The ink that vibrates will vibrate, and the attached bubbles are shaken to effectively remove the bubbles.

  In the second reference example, preferably, the ink tube is provided with an ink circulation pump, and the ink tube is provided by an operation member provided on the downstream side of the ink circulation pump and intermittently contacting the ink tube. By vibrating, it is possible to apply vibration to the ink circulating inside.

  Further, in the second reference example, preferably, the operating member is a cam member that is rotationally driven, and is rotated once or twice after the start of the circulation purge so that the circulation of the ink is not impaired. Vibration can be applied.

  In the third reference example, when the circulation purge is performed, in addition to the circulation purge, the suction purge by the suction purge means is also performed. As a result, the synergistic effect of the circulation purge and the suction purge causes the ink to be discharged. From the tank, the flow velocity in the circulation flow path that returns to the ink tank through the first ink flow path, the manifold, and the second ink flow path increases, and bubbles attached to the wall surface of the ink flow path are easily removed. The removed bubbles are collected in the ink tank. As in a normal ink jet recording apparatus, when the suction purge is performed to recover the ejection failure, the nozzle surface of the head unit is wiped by the wiper member, so that an ink meniscus is formed in each nozzle. Since it is formed, the print quality is not affected.

  Preferably, in the third reference example, the purge control unit causes the suction purge unit to perform suction purge for a certain period of time in the circulation purge, so that the normal suction purge performed for recovery of ink ejection failure is performed. However, it is possible to avoid the unnecessary ink consumption, and the air bubbles attached not only to the ink flow path but also to the wall surface of the actuator are the same as the normal suction purge. Can be removed to a degree. In particular, by causing the suction purge means to perform the suction purge for a certain period from the beginning of the circulation purge, it is possible to effectively remove the bubbles over the entire ink flow path.

  In the fourth reference example, when the circulation purge is performed, the storage cap means covers the nozzle surface of the head unit to form a closed space, so that the flow rate of the ink is reduced as in the case of using the suction cap. The purge efficiency can be improved by speeding up. In particular, since the storage cap means for preventing the ink in the nozzle holes of the head unit from drying forms a closed space during the circulation purge, it is not necessary to provide a special cap device for forming the closed space. .

  In the fifth reference example, the ink is circulated between the ink tank and the manifold by circulation purge, and bubbles in the circulation flow path are removed. Before the circulation purge or after the circulation purge is completed, the circulation pump means is driven for a certain period of time with the valve means suppressing the flow of the second ink flow path under the control of the purge control means. Auxiliary purge is performed. Here, “the state in which the flow of the second ink flow path is suppressed” means not only that the flow of ink in the second ink flow path is completely blocked, but also the cross-sectional area of the ink flow path. It is also included to reduce the amount of ink flowing by narrowing down to a smaller value.

  According to the fifth reference example, in this auxiliary purge, since the valve means becomes a resistance for suppressing the ink flow in the second ink flow path, the inside of the circulation flow path including the first ink flow path is included. The pressure of is increased. As a result, bubbles adhering to the wall surface of the first ink flow path, the pressure chamber of the head unit, and the like are pushed out from the nozzle holes of the head unit by the flow of ink. After the operation, as in the case of performing the suction purge in a normal ink jet recording apparatus, the meniscus is formed in each nozzle by wiping the nozzle surface of the head unit with a wiper member or the like, and the subsequent printing Does not affect performance.

  Preferably, in the fifth reference example, a capping unit having a cap opposed to the nozzle surface of the head unit is provided, and when the auxiliary purging is performed by the control unit, the capping unit is driven to connect the cap to the nozzle surface. By facing each other, in the stage before performing the circulation purge or in the stage after the circulation purge is completed, the auxiliary purge allows the ink pushed out together with the air bubbles through the nozzle holes of the head unit to be received by the cap. Avoided.

  In the fifth reference example, preferably, the valve means is an open / close valve that shuts off the communication of the second ink flow path when the auxiliary purge is performed. Alternatively, at the stage after the circulation purge is completed, the communication of the second ink flow path is blocked by the opening / closing valve, and the pressure in the first ink flow path is efficiently increased by driving the circulation pump means for a certain period of time. It is done.

  Preferably, in the fifth reference example, the capping unit has a cap facing the nozzle surface of the head unit and a pump for discharging ink from the cap, and the control unit circulates when performing the auxiliary purge. Ink can be discharged from the cap by driving the pump in addition to driving the pump means. Here, it is only necessary to drive the pump as long as the ink can be discharged from the cap, and it is not always necessary to perform the pump while the circulating pump means is driven.

  Furthermore, in the fifth reference example, preferably, the capping unit has a cap facing the nozzle surface of the head unit and a pump for discharging ink from the cap, and the control unit circulates when performing the auxiliary purge. After driving the pump means for a certain period of time, the pressure in the first ink flow path is increased by driving the pump that discharges ink, and bubbles attached to the wall surface of the ink flow path are easily removed. And pushed out through the nozzle of the head unit. Thereafter, the pump is driven and ink is discharged from the cap. Here, the time for driving the pump is only a certain time immediately before the end of the auxiliary purge so that the ink is discharged from the cap.

  Preferably, in the fifth reference example, the capping unit is a storage cap unit having a storage cap that covers the nozzle surface of the head unit when printing is stopped or when printing is stopped, and prevents drying of ink in the nozzle holes. Therefore, it is not necessary to provide a cap means for the auxiliary purge.

  In the sixth reference example, in the circulation purge, the ink is circulated between the ink tank and the manifold to remove bubbles in the circulation flow path, and the second ink flow path is temporarily set by the valve means. In this state, the pressure in the ink flow path is increased, and bubbles adhering to the wall surface of the ink flow path, the pressure chamber of the head unit, and the like are pushed out from the nozzle together with the ink. When printing is performed, the communication of the second ink flow path is blocked by the valve means, ink is supplied through the first ink flow path, and the printing function is not impaired.

It is a figure which shows schematic structure of the inkjet recording device of the 1st, 3rd, 5th and 6th reference example of this invention. It is a figure which shows schematic structure of the inkjet recording device of the 2nd reference example. It is the figure which expanded the vibration provision means of the 2nd reference example. 1 is a diagram illustrating a schematic configuration of an ink jet recording apparatus according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Print head 2 Head unit 3 Carriage 11 Manifold 13 1st head side ink tube 16 2nd head side ink tube 21 Ink tank 22 Ink circulation pump 23 1st tank side ink tube 25 2nd tank side ink tube 26 Purge control means 31 Suction purge device 32 Suction cap

Claims (4)

A head unit having a plurality of actuators that perform a printing operation by opening a plurality of nozzles on the nozzle surface and ejecting ink from each nozzle;
An ink tank for containing ink to be supplied to the plurality of actuators and collecting bubbles together with the ink;
A first ink channel and a second ink channel that form an ink circulation channel between the ink tank and the head unit;
Air bubbles in the circulation flow path are provided in the first ink flow path, and the ink is circulated in the circulation flow path including the ink tank, the first ink flow path, the head unit, and the second ink flow path. Circulation pump means for performing a circulation purge for collecting the ink into the ink tank;
Valve means provided in the second ink flow path for communicating and blocking the second ink flow path;
A cap made of an elastic material covering the nozzle surface of the head unit;
Opening and closing means connected to the suction cap, closed and opened so as to make the inside of the cap covering the nozzle surface a closed space;
Purge control means for controlling the circulation pump means, valve means and opening / closing means,
In the printing operation, the circulation pump means is stopped without closing the first ink flow path, and the valve means shuts off the second ink flow path, and the first ink flow path is removed from the ink tank. Ink is supplied to the head unit through the ink flow path,
The purge control means operates the circulation pump means to perform the circulation purge for circulating ink, and the valve means communicates the second ink flow path and the circulation pump means is driven. The cap is applied to the nozzle surface of the head unit so that the elastic material is compressed, and the opening / closing means is closed so as to make the inside of the cap a closed space, and the air in the closed space is applied to the inner surface of the circulation channel. ink jet recording apparatus is characterized in that so as to oppose the pressure by the flow rate of the circulation flow path to remove air bubbles adhering.   A suction pump for sucking ink from the head unit in a state where the cap covers the nozzle surface of the head unit, and the purge control means controls the opening and closing means to enable the drive of the suction pump. The inkjet recording apparatus according to claim 1. 3. The ink jet recording apparatus according to claim 1, wherein when the cap covers the nozzle surface of the head unit, the opening / closing means is closed simultaneously with or immediately after forming the closed space.   The head unit includes a print head having the plurality of actuators, an ink reservoir provided over all the actuators, and a manifold having an ink inflow portion and an ink outflow portion communicating with both ends of the ink reservoir, The ink jet recording apparatus according to claim 1, wherein the ink flow path and the second ink flow path are connected to the ink inflow portion and the ink outflow portion.

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