JP4816289B2 - Bubble capturing device, liquid transfer device, and ink jet recording device - Google Patents

Description

  The present invention relates to a bubble trapping device that traps bubbles in a liquid, a liquid transfer device that has a bubble trapping device and transports the liquid, and an ink jet recording apparatus that discharges ink from a nozzle to record an image or the like on a recording medium About.

  In an ink jet recording apparatus that applies pressure to ink in a pressure chamber communicating with a nozzle and ejects ink from the nozzle to record an image and / or characters on a recording medium, nozzle clogging or ink due to foreign matter mixed in the ink In order to prevent the recording quality from deteriorating due to the pressure variation in the pressure chamber due to the air bubbles inside, there is one in which a filter for capturing foreign matter and air bubbles mixed in the ink is provided in the ink flow path. In such an ink jet recording apparatus, bubbles trapped in the filter are discharged to the outside of the apparatus by purging the ink jet head when recording is not performed. However, if the wettability of the filter surface is low, the air bubbles are purged. However, bubbles remain on the surface of the filter and the filter may be clogged.

  In order to solve such a problem, in the ink jet recording apparatus disclosed in Technical Document 1 (corresponding to FIG. 6 of Japanese Patent Laid-Open No. 2004-114648), a filter is provided in a buffer tank that supplies ink to the manifold. In addition, the surface of the filter is subjected to plasma processing, and the wettability of the surface is increased. According to this, air bubbles hardly remain on the surface of the filter, and the air bubbles can be reliably discharged by purging the ink jet head.

JP 2004-114648 A (FIG. 6)

  However, in the ink jet recording apparatus described in Technical Document 1, since the wettability of the surface of the filter is high, bubbles are not easily attached to the filter even during recording, and the bubbles cannot be reliably captured during recording. There is a fear.

  An object of the present invention is to provide a liquid transfer device, an ink jet recording device, and a bubble trapping device provided with a filter that can reliably trap bubbles on the surface and can reliably remove bubbles attached to the surface. Is to provide.

Means for Solving the Problems and Effects of the Invention

According to the first aspect of the present invention, there is provided a bubble trapping device that includes a filter disposed in a liquid flow path, and traps bubbles included in the liquid flowing in the liquid flow path. A filter having a base material in which a conductive region having conductivity and a plurality of through-holes through which liquid passes are formed; a potential control mechanism for controlling a potential of the conductive region of the filter ; comprising a bubble capture mode that captures bubbles in the liquid at the surface of the filter, selectively a mode setting device for setting the bubble release mode to release the air bubbles trapped in the surface of the filter, the potential control mechanism Indicates the potential difference between the conductive region and the liquid flowing in the liquid flow path when the mode setting device is set to the bubble trapping mode. To be smaller than the potential difference between said conductive region and said liquid flowing through the liquid channel when it is set to bubble release mode, the bubble capture device that controls the electric potential of the conductive region Provided.

According to the first aspect of the present invention, the potential control mechanism indicates the potential difference between the conductive region and the liquid when the mode setting device is set in the bubble trapping mode, and the mode setting device enters the bubble release mode. to be smaller than the potential difference between the conductive region and the liquid when it is set, the potential of the conductive regions that are controlled. Therefore, by setting the mode setting device to the bubble capturing mode, the bubbles in the liquid are surely captured on the surface of the conductive region, so that the bubbles are prevented from flowing into the downstream side of the filter. On the other hand, by setting the mode setting device to the bubble release mode, an electrowetting phenomenon described later occurs, and the wettability of the surface of the conductive region is increased. As a result, bubbles attached to the surface of the conductive region are surely removed, and the filter is prevented from being clogged by the bubbles. Details of the electrowetting phenomenon are also described in Japanese Patent Laid-Open No. 2003-177219.

  The bubble trapping device of the present invention may further include an insulating layer that covers the conductive region of the substrate. In this way, by covering the conductive region with an insulating layer having low surface wettability (high liquid repellency), when the potential difference between the conductive region and the liquid is small, bubbles in the liquid can be reliably To the surface of the insulating layer. In addition, when a predetermined voltage is applied between the conductive region and the liquid, the surface of the insulating layer covering the conductive region to which the voltage is applied is wetted by an electrowetting phenomenon described later. Therefore, the attached bubbles can be reliably released. In addition, by covering the conductive region with the insulating layer, the current flowing between the conductive region and the liquid can be reduced when a predetermined voltage is applied between the conductive region and the liquid. Therefore, power consumption can be suppressed and the voltage applied to the conductive region can be increased.

  In the bubble trapping device of the present invention, the liquid may be a conductive liquid flowing in the liquid flow path, and the filter may trap bubbles contained in the conductive liquid. In this case, since the liquid has conductivity, the entire liquid can have the same potential.

  The liquid transfer device of the present invention may further include a constant potential holding mechanism that holds the liquid flowing in the liquid channel at a predetermined reference potential. According to this, since the potential of the liquid is always maintained at a constant reference potential, the potential control by the potential control mechanism is facilitated.

  In the bubble trapping device of the present invention, the liquid channel may be formed by a channel member including a conductive material, and the constant potential holding mechanism may include a grounding mechanism that grounds the channel member. According to this, since the potential of the liquid can be set to the ground potential without separately providing an electrode or the like in the liquid flow path, the configuration of the apparatus is simplified.

  In the bubble trapping device of the present invention, the potential control mechanism may be configured such that a potential difference between the potential of the conductive region and the reference potential when the mode setting device is set to the bubble release mode is the mode setting. The potential of the conductive region may be controlled to be larger than a potential difference between the potential of the conductive region and the reference potential when the apparatus is set to the bubble trapping mode. According to this, when the mode setting device is set to the bubble release mode, the wettability of the surface of the insulating layer is higher than when the mode is set to the bubble trapping mode. The bubbles trapped in can be reliably removed in the bubble release mode.

  In the bubble trapping device of the present invention, the potential control mechanism may be configured such that when the mode setting device is set to the bubble trapping mode, the conductive region of the filter and the reference potential are the same potential. When the mode setting device is set to the bubble release mode, the potential of the conductive region of the filter is different from the reference potential. The potential of the conductive region may be controlled. According to this, the potential control mechanism sets the conductive region to the reference potential when the mode setting device is set to the bubble trapping mode, and sets the conductive region to the reference potential when the mode setting device is set to the bubble release mode. Can be controlled so as to have different potentials, the potential can be easily controlled.

  In the bubble trapping device of the present invention, the base material may be formed of a metal material. According to this, the through hole can be easily formed by a method such as electroforming or pressing.

  In the bubble trapping device of the present invention, the base material includes an insulating member in which the plurality of through holes are formed, and an electrode that is formed on the surface of the insulating member to form the conductive region. You may do it. According to this, the through hole can be accurately formed in the insulating member by laser processing or the like.

  In the bubble trapping device of the present invention, the electrode may be formed on a surface that defines the through hole formed in the insulating member. According to this, by increasing the potential difference between the electrode and the liquid and increasing the wettability of the surface defining the through hole of the insulating member, the liquid in the liquid captured on the surface defining the through hole Since the bubbles can be reliably removed, the clogging of the through holes due to the bubbles can be reliably prevented.

  In the bubble trapping device of the present invention, the surface of the insulating member may be planar, and the electrode may be formed on the surface of the planar insulating member. According to this, since the surface on which the electrode is formed is planar, the electrode can be formed easily.

  In the bubble trapping device of the present invention, the cross-sectional area of the through hole may become smaller toward one side in the direction in which the through hole extends. According to this, for example, when one side in the direction in which the through hole extends is arranged toward the downstream side of the flow path, it is possible to reduce the backflow of liquid from the downstream side to the upstream side of the filter. .

  In the bubble trapping device of the present invention, the base material may be formed with the plurality of through holes that are uniformly distributed on the surface of the base material. According to this, bubbles can be efficiently captured on the entire surface of the substrate.

  In the bubble trapping device of the present invention, the insulating layer may be made of a fluororesin. By covering the conductive region of the substrate with an insulating layer made of fluororesin, when the voltage is not applied to the conductive region, the wettability of the surface of the insulating layer is sufficiently lowered, and a predetermined voltage is applied to the conductive region. When applied, the wettability of the surface of the insulating layer can be made sufficiently high.

  According to the second aspect of the present invention, there is provided a liquid transfer device including a liquid flow path through which a liquid flows and the bubble trapping device of the present invention. According to the second aspect of the present invention, bubbles contained in the liquid transferred by the liquid transfer device can be sufficiently removed. Moreover, since the air bubbles captured by the filter of the air bubble capturing device can be opened as necessary, there is no possibility that the filter is clogged by the air bubbles.

According to a third aspect of the present invention, an ink jet recording apparatus for ejecting ink, an ink supply which supplies the ink, and a plurality of ink discharge ports, and Common liquid chamber, said plurality of ink ejection A plurality of individual ink channels communicating with the outlet and the common liquid chamber, respectively, an energy application mechanism provided corresponding to each of the plurality of individual ink channels, and for applying ejection energy to the ink; An ink supply channel for supplying the ink from an ink supply source to the common liquid chamber, and a filter disposed in the ink supply channel, wherein a conductive region having conductivity is formed on a part of the surface. has a substrate, a filter having a plurality of through holes are formed to pass through the ink, the potential control mechanism which controls a potential of the conductive region of the filter, surface smell of the filter Comprising a bubble capture mode for capturing air bubbles in the ink, selectively and a mode setting device for setting the bubble release mode to release the air bubbles trapped in the surface of the filter, the electric potential control mechanism, the mode When the setting device is set to the bubble trapping mode, the mode setting device is set to the bubble release mode to determine the potential difference between the conductive region and the ink flowing in the ink supply channel. wherein such conductive region and smaller than the potential difference between the ink flowing through the ink supply channel when ink jet recording apparatus is provided that controls the potential of the conductive region.

According to the third aspect of the present invention, when recording is performed , the mode setting device is set to the bubble trapping mode so that the potential difference between the conductive region and the ink is reduced and the surface of the conductive region is By capturing the bubbles in the ink, the bubbles are prevented from flowing into the individual ink flow paths and the common liquid chamber, and variations in the ink discharge amount and discharge speed are reduced. Furthermore, when purging, by setting the mode setting device to the bubble release mode, the potential difference between the conductive region and the ink is increased to cause an electrowetting phenomenon. The trapped air bubbles can be removed, and after purging, the air bubbles hardly remain on the surface of the conductive material, and the filter is prevented from being clogged with air bubbles.

  In the ink jet recording apparatus of the present invention, the filter may further include an insulating layer that covers the conductive region of the substrate. When an insulating layer having low surface wettability is used, bubbles in the ink can be reliably captured on the surface of the insulating layer when the potential difference between the conductive region and the ink is reduced. In addition, when a predetermined voltage is applied between the conductive region and the liquid, the surface of the insulating layer covering the conductive region to which the voltage is applied is wetted by an electrowetting phenomenon described later. Therefore, the attached bubbles can be reliably released. Further, by covering the conductive region with an insulating layer, the current flowing between the conductive region and the liquid can be reduced when a predetermined voltage is applied between the conductive region and the liquid. Therefore, power consumption can be suppressed and the voltage applied to the conductive region can be increased.

  In the ink jet recording apparatus of the present invention, the inkjet recording apparatus further includes a suction device that sucks the ink and the bubbles, a purge mechanism having a cap that covers the ink discharge port, and a purge control device that controls the operation of the purge mechanism, When the purge control device controls and purges the purge mechanism, the mode setting device may be set to the bubble release mode. Furthermore, when the purge control device controls the purge mechanism to end the purge, the mode setting device may be set to the bubble trapping mode. In this way, by linking the mode setting device and the purge control device, the bubbles attached to the filter can be reliably removed during the purge operation, or when the purge operation is not performed, Air bubbles can be reliably attached to the filter.

  In the ink jet recording apparatus of the present invention, the minimum diameter of the inscribed circle that can be accommodated in the through hole may be smaller than the diameter of the inscribed circle that can be accommodated in the ejection port. According to this, it is possible to reliably remove foreign matter or bubbles in the ink of a size that cannot pass through the ink discharge port by the filter, and reliably prevent the ink discharge port from being clogged by foreign matter or bubbles. can do.

  In addition, in this application, an image contains a figure, a symbol, and a character.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. The present embodiment is an example in which the present invention is applied to an inkjet recording apparatus that records an image by ejecting ink from a nozzle onto a recording sheet as a droplet ejecting apparatus.

  As shown in FIG. 1, an ink jet recording apparatus 1 includes a carriage 2 that can move in a scanning direction (left and right direction in FIG. 1), and a serial type that is provided on the carriage 2 and discharges ink onto recording paper P. An inkjet head 3 and a transport roller 4 for transporting the recording paper P in the paper feed direction (front of FIG. 1) are provided. Ink is supplied from the ink tank 5 to the inkjet head 3 through the tube 6. The inkjet head 3 moves in the scanning direction integrally with the carriage 2 and from the ejection port 17a (see FIG. 3) of the nozzle 17 formed on the ink discharge surface 23a (see FIG. 3) on the lower surface thereof, the recording paper. Ink is ejected onto P to record an image on recording paper P. Further, the recording paper P on which an image is recorded by the ink jet head 3 is discharged by the transport roller 4 in the paper feeding direction.

  Further, the inkjet recording apparatus 1 includes the cap 7 that can come into contact with the ink ejection surface 23a so as to cover the emission ports 17a of the plurality of nozzles 17, and the cap 7 that is used for forcibly discharging the ink. A suction pump 8 is provided for sucking ink from the nozzles 17 in contact with the nozzle 17. In the ink jet recording apparatus 1, when the ejection nozzle 17 is clogged with foreign matters such as dust, or when air bubbles are mixed into the ink flow path of the ink jet head 3 and ink is not normally ejected from the nozzle 17, the cap 7. Is brought into contact with the ink discharge surface 23a, and the suction pump 8 is operated to perform purging to forcibly discharge the ink from the nozzles 17.

  Next, the inkjet head 3 will be described in detail with reference to FIGS. FIG. 2 is a plan view of the inkjet head 3 of FIG. 3 is a cross-sectional view taken along line III-III in FIG. However, the driver IC 60 (see FIG. 6) is not shown in FIGS.

  As shown in FIGS. 2 and 3, the inkjet head 3 includes a flow path unit 31 in which an individual ink flow path including the pressure chamber 10 is formed, and a piezoelectric actuator 32 disposed on the upper surface of the flow path unit 31. I have.

  2 and 3, the flow path unit 31 includes a cavity plate 20, a base plate 21, a manifold plate 22, and a nozzle plate 23. These four plates 20 to 23 are joined in a stacked state. ing. Among these, the cavity plate 20, the base plate 21, and the manifold plate 22 are stainless steel plates, and an ink flow path including a manifold flow path 11 and a pressure chamber 10 described later is etched in these three plates 20 to 22. It is formed by. Further, the nozzle plate 23 is made of, for example, a polymer synthetic resin material such as polyimide, and is bonded to the lower surface of the manifold plate 22. Alternatively, the nozzle plate 23 may also be formed of a metal material such as stainless steel, like the three plates 20 to 22.

  As shown in FIGS. 2 and 3, the cavity plate 20 is formed with a plurality of pressure chambers 10 (for example, 10) arranged along a plane, and the plurality of pressure chambers 10 are arranged in the paper feeding direction. They are arranged in two rows (vertical direction in FIG. 2). Each pressure chamber 10 is formed in a substantially oval shape that is long in the scanning direction (left-right direction in FIG. 2) in plan view.

  A communication hole 14 is formed in the base plate 21 at a position overlapping with an end portion on the side of the manifold channel 11 (described later) in the longitudinal direction (left and right direction in FIG. 2) of the pressure chamber 10 in a plan view. A communication hole 15 is formed at a position overlapping the other end portion in the longitudinal direction of the chamber 10 in plan view. The manifold plate 22 has a manifold channel 11 extending in the paper feeding direction. In FIG. 2, the manifold channel 11 is disposed so as to overlap the left half of the pressure chambers 10 arranged on the left side and the right half of the pressure chambers 10 arranged on the right side. The manifold channel 11 communicates with an ink supply port 12 formed in a vibration plate 40 to be described later. From the ink tank 5 (see FIG. 1), the manifold channel 11 passes through the tube 6 and the ink supply port 12. Ink is supplied to the path 11. A communication hole 16 that communicates with the communication hole 15 is formed at a position of the manifold plate 22 that overlaps with the end of the manifold plate 22 on the opposite side of the manifold channel 11 in the longitudinal direction of the pressure chamber 10.

  A nozzle 17 is formed at a position of the nozzle plate 23 that overlaps the communication hole 16 in plan view. As shown in FIGS. 2 and 3, the plurality of nozzles 17 overlap with the ends of the plurality of pressure chambers 10 arranged in two rows on the opposite side to the manifold channel 11, and the scanning direction of the inkjet head 3 is substantially the same. In the central portion, they are arranged in two rows at equal intervals in the paper feed direction. An ejection port 17a of the nozzle 17 having a diameter of about 30 to 40 μm is formed on the ink ejection surface 23a that is the lower surface of the nozzle plate 23. The discharge port 17a has a substantially circular shape in plan view. When the nozzle plate 23 is made of a synthetic resin material, the nozzle 20 can be formed by excimer laser processing or the like. Further, when the nozzle plate 23 is made of a metal material, it can be formed by press working or the like.

  As shown in FIG. 3, the manifold channel 11 communicates with each pressure chamber 10 via each communication hole 14, and each pressure chamber 10 communicates with each nozzle 17 via each communication hole 15, 16. Communicate. As described above, a plurality of individual ink channels from the manifold channel 11 to the nozzle 17 through the pressure chamber 10 are formed in the channel unit 31.

  Next, the piezoelectric actuator 32 will be described. As shown in FIG. 3, the piezoelectric actuator 32 includes a vibration plate 40 disposed on the upper surface of the flow path unit 31, a piezoelectric layer 41 formed on the upper surface of the vibration plate 40, and a plurality of piezoelectric layers 41 on the upper surface of the piezoelectric layer 41. And a plurality of individual electrodes 18 formed corresponding to the pressure chamber 10.

  The diaphragm 40 is a substantially rectangular metal plate in plan view, and is made of, for example, an iron-based alloy such as stainless steel, a copper-based alloy, a nickel-based alloy, or a titanium-based alloy. The diaphragm 40 is disposed on the upper surface of the cavity plate 20 so as to cover the plurality of pressure chambers 10, and is joined to the upper surface of the cavity plate 20. The conductive metal diaphragm 40 is connected to a driver IC 60 (shown in FIG. 6) and is always held at the ground potential, and an electric field is applied to the piezoelectric layer 41 sandwiched between the individual electrodes 18. It also serves as a common electrode that works. Further, the diaphragm 40 is formed with an ink supply port 12 having a substantially elliptical shape in plan view. The ink supply port 12 communicates with the manifold channel 11, and ink is supplied to the manifold channel 11 through the ink supply port 12.

  As shown in FIG. 2, lead titanate is formed on the upper surface of the vibration plate 40 except for a region where the ink supply port 12 is formed and a region extending from the ink supply port 12 in the scanning direction (left-right direction in FIG. 2). A piezoelectric layer 41 mainly composed of lead zirconate titanate (PZT), which is a solid solution with lead zirconate and is a ferroelectric, is disposed. As shown in FIGS. 2 and 3, the piezoelectric layer 41 is continuously formed across the plurality of pressure chambers 10. Here, the piezoelectric layer 41 can be formed by using, for example, an aerosol deposition method (AD method) in which very small particles of a piezoelectric material are sprayed onto a substrate to collide at high speed and are deposited on the substrate. Further, for example, it can also be formed by a sputtering method, a chemical vapor deposition method (CVD method), a sol-gel method, or a hydrothermal synthesis method. Alternatively, the piezoelectric layer 41 may be formed by cutting a piezoelectric sheet generated by firing a green sheet of PZT into a predetermined size and attaching the cut piezoelectric sheet to the vibration plate 40. .

  On the upper surface of the piezoelectric layer 41, a plurality of individual electrodes 18 that are slightly smaller than the pressure chamber 10 and have a substantially oval shape in plan view are formed. The plurality of individual electrodes 18 are respectively formed at positions overlapping the central portion of the corresponding pressure chamber 10 in plan view. The individual electrode 18 is made of a conductive material such as gold, copper, silver, palladium, platinum, or titanium. Furthermore, in the plurality of individual electrodes 18, from the end portions on the manifold flow path 11 side in the longitudinal direction of the plurality of individual electrodes 18, respectively, to portions extending in parallel with the longitudinal direction of the individual electrodes 18 (left and right direction in FIG. 2). A plurality of contacts 18a are formed. The plurality of individual electrodes 18 can be formed by, for example, screen printing, sputtering, or vapor deposition.

  A flexible printed circuit (FPC) (not shown) is joined to the plurality of contacts 18a from above the piezoelectric layer 41, and the plurality of contacts 18a are electrically connected to the driver IC 60 (see FIG. 6) via the FPC. It is connected. Then, the potentials of the plurality of individual electrodes 18 can be selectively controlled from the driver IC 60 via the contacts 18a.

  Next, an ink supply channel that communicates with the manifold channel 11 at the ink supply port 12 and supplies ink to the manifold channel 11 will be described with reference to FIGS. 4 and 5. FIG. 4 is an enlarged plan view of the vicinity of the ink supply port 12 of FIG. 5 is a cross-sectional view taken along line VV in FIG. As shown in FIG. 4, the diaphragm 40 is formed with an ink supply port 12 having a substantially elliptical shape in plan view. As shown in FIGS. 4 and 5, a step region 50 having a substantially elliptical shape that is slightly larger than the ink supply port 12 in a plan view is formed in a portion surrounding the ink supply port 12 at the top of the vibration plate 40. Has been. The step region 50 is provided with a filter 13 that is a substantially elliptical plate in plan view. The filter 13 is made of a conductive base material (conductive member) 52 made of metal such as flat nickel, and has low surface wettability such as a fluorine-based resin formed on the entire surface thereof (liquid repellent property). The insulating layer 53 is provided, and the plurality of through holes 13a are uniformly distributed over the entire surface of the filter 13 at equal intervals. The through-hole 13a is formed in a substantially circular shape in plan view, and the downstream area of the ink flow, that is, the flow path area becomes smaller toward the manifold flow path 11 side, and its minimum diameter is the ink discharge port 17a of the nozzle 17. It is about 8 to 10 μm which is smaller than the diameter. As will be described later, the insulating layer 53 has wettability such that bubbles in the ink attached to the surface of the filter 13 do not leave the surface due to the flow of ink when ink is ejected from the nozzle 17 to perform image recording. It is comprised with the material which has. Such a filter 13 can be manufactured as follows. First, a plurality of through-holes 13a are formed in a metal plate such as nickel by a method such as electroforming or pressing to produce the conductive substrate 52. Next, the insulating layer 53 is formed on the entire surface of the conductive substrate 52 by, for example, forming a fluorine-based resin layer having insulating properties by a CVD method or the like.

  The conductive base material 52 of the filter 13 is connected to the driver IC 60, and the potential of the conductive base material 52 can be controlled by the driver IC 60. A filter control unit (potential control mechanism) 64 described later of the driver IC 60 connected to the filter 13 and the conductive base material 52 of the filter 13 corresponds to the bubble trapping device according to the present invention.

  As shown in FIG. 5, a fixing member 51 in which a communication hole 51 a communicating with the ink supply port 12 is formed on a portion of the upper surface of the vibration plate 40 facing the ink supply port 12, and the filter 13 vibrates. The plate 40 and the fixing member 51 are sandwiched and fixed. A tube 6 communicating with the ink tank 5 is connected to the fixing member 51 on the side opposite to the vibration plate 40. An ink supply channel that communicates from the ink tank 5 to the manifold channel 11 via the tube 6, the communication hole 51 a, the plurality of through holes 13 a of the filter 13, and the ink supply port 12 is formed. The ink in the ink supply channel is in contact with the diaphragm 40 held at the ground potential, and is always held at the ground potential.

  In order to cause bubbles in the ink to adhere to the filter 13, the potential of the conductive substrate 52 of the filter 13 is set to the ground potential by using a filter control unit 64 described later. At this time, since the surface of the filter 13 is covered with the insulating layer 53 having high liquid repellency, bubbles are easily attached to the surface of the filter 13. This is because, in general, when the liquid repellency of the solid surface is high, it is more stable in terms of energy when the area where the liquid and the solid contact is reduced by increasing the area where the gas and the solid contact. Because it becomes. That is, compared to the case where bubbles are not attached to the surface of the filter 13, when the bubbles are attached to the surface of the filter 13, the area of the portion in contact with the ink on the surface of the filter 13 is reduced. This is because the energy is stable. Therefore, the bubbles contained in the ink can be attached to the surface of the filter 13 by setting the conductive substrate 52 of the filter 13 and the ink to the same potential.

  On the other hand, in order to release bubbles adhering to the surface of the filter 13, the potential of the conductive base material 52 of the filter 13 is set to a predetermined potential by using a filter control unit 64 described later. At this time, the liquid repellency of the insulating layer 53 decreases due to the electrowetting phenomenon. The electrowetting phenomenon is that when a voltage is applied between an electrode and a liquid when the electrode and the liquid having conductivity are insulated by an insulating film electrically connected to the electrode, This is a phenomenon in which the contact angle (wetting angle) between the surface of the insulating film and the liquid is smaller than when there is no potential difference between the electrode and the liquid. That is, when a voltage is applied between the electrode and the liquid, the liquid repellency on the surface of the insulating film is apparently reduced as compared with the case where there is no potential difference between the electrode and the liquid.

  In this way, when the liquid repellency of the surface of the filter 13 is lowered, bubbles are less likely to adhere to the surface of the filter 13. This is because, when the liquid repellency of the solid surface is low, it is more energetically stable to increase the area where the liquid and the solid contact by reducing the area where the gas and the solid contact. That is, compared with the case where bubbles are attached to the surface of the filter 13, the area where the bubbles are not attached to the surface of the filter 13 increases the area of the portion in contact with the ink on the surface of the filter 13. This is because it is stable. Therefore, the ink adhering to the surface of the filter 13 can be released by applying a predetermined voltage between the conductive substrate 52 of the filter 13 and the ink.

  Next, the driver IC 60 will be described with reference to FIG. FIG. 6 is a block diagram of the driver IC 60. The driver IC 60 controls various operations of the inkjet recording apparatus 1, and includes a mode setting unit 61, an actuator control unit 62, a purge control unit 63, a filter control unit 64, and a grounding unit 65, as shown in FIG. .

  The actuator controller 62 controls the operation of the piezoelectric actuator 32 by controlling the potentials of the plurality of individual electrodes 18 when ink is ejected from the nozzles 17 and recording is performed on the recording paper P. The purge control unit 63 controls the operation of the cap 7 and the suction pump 8 when purging to remove foreign matters and bubbles in the ink in the individual ink channel and the manifold channel 11.

  The mode instructing unit 61 captures bubbles in the filter 13 to prevent bubbles from flowing into the manifold channel 11 and the individual ink channels, and a bubble release mode in which the bubbles captured in the filter 13 are released. Set selectively. Here, in the purge operation described later, the mode setting unit 61 is set to the bubble release mode in conjunction with the purge control unit 63. Further, after the purge operation is completed, the mode setting unit 61 is set to the bubble trapping mode in conjunction with the purge control unit 63. As described above, since the mode setting unit 61 and the purge control unit 63 are interlocked with each other, it is possible to reliably release the bubbles attached to the surface of the filter 13 and to suck the bubbles during the purge. .

  The filter control unit 64 controls the potential of the conductive base material 52 of the filter 13 according to the mode set by the mode setting unit 61. Specifically, when the mode setting unit 61 is set to the bubble trapping mode, the filter control unit 64 sets the conductive base material 52 to the ground potential. When the mode setting unit 61 is set to the bubble release mode, the filter control unit 64 sets the conductive base material 52 to a predetermined potential (potential different from the reference potential) higher than the ground potential. The grounding unit 65 holds the diaphragm 40 at the ground potential. Note that the predetermined potential is a potential sufficient to improve the wettability of the surface of the insulating layer 53 by electrowetting phenomenon and purge the bubbles from the surface of the insulating layer 53 when purging described later.

  Next, a recording operation and a purge operation in the inkjet recording apparatus 1 will be described with reference to FIGS. 7A shows the state of the filter 13 when recording is performed in the inkjet recording apparatus 1, and FIG. 7B is an enlarged view of the surface of the filter 13 in FIG. 7A. . FIG. 8A shows the state of the filter 13 when purging in the inkjet recording apparatus 1, and FIG. 8B is an enlarged view of the surface of the filter 13 in FIG. 8A. . Note that “+” in FIG. 8A indicates a predetermined potential higher than the ground potential, and “GND” in FIGS. 7A and 8A indicates the ground potential. It shows that it has become.

  First, the operation at the time of recording in the inkjet recording apparatus 1 will be described. When recording, the mode setting unit 61 of the driver IC 60 is set to the bubble trapping mode. At this time, the filter control unit 64 controls the potential of the conductive base material 52 so that the potential of the conductive base material 52 becomes the ground potential as shown in FIG. As a result, the conductive substrate 52 and the ink in the ink supply channel have the same potential. In this case, for the reason described above, the wettability on the surface of the insulating layer 53 disposed between the ink and the conductive substrate 52 remains low (for example, the wetting angle θ is about 70 °). Air bubbles A in the ink are likely to adhere to the surface of the insulating layer 53.

  Then, the actuator control unit 62 selectively controls the potential of the desired individual electrode 18 to obtain a predetermined positive potential. At this time, a potential difference is generated between the diaphragm 40 as the common electrode held at the ground potential and the selected individual electrode 18. Thereby, in the piezoelectric layer 41, an electric field in the thickness direction is applied to a portion sandwiched between the individual electrode 18 and the diaphragm 40. At this time, when the polarization direction of the piezoelectric layer 41 is the same as the direction of the electric field, the piezoelectric layer 41 contracts in a horizontal direction orthogonal to the thickness direction that is the polarization direction. As the piezoelectric layer 41 contracts, the vibration plate 40 is deformed so as to protrude toward the pressure chamber 10. At this time, the volume in the pressure chamber 10 is reduced, pressure is applied to the ink in the pressure chamber 10, and ink is ejected from the nozzle 17 communicating with the pressure chamber 10.

  At this time, in the filter 13, since the bubbles A in the ink are likely to adhere to the surface of the insulating layer 53, the foreign matters and / or bubbles A in the ink are captured on the surface of the insulating layer 53 of the filter 13. It is prevented from flowing into the manifold channel 11. As a result, it is possible to prevent the recording quality from deteriorating due to the foreign matter and / or the bubbles A in the ink clogging the nozzles 17 or causing variations in the ink pressure in the pressure chamber 10. Furthermore, since the minimum diameter of the through-hole 13a of the filter 13 is smaller than the nozzle diameter, foreign matters and bubbles larger than the nozzle diameter are reliably prevented from flowing into the manifold channel 11 and the individual ink channels.

  Next, the purge operation in the inkjet recording apparatus 1 will be described. At the time of purging, the mode setting unit (mode instruction unit) 61 of the driver IC 60 is set to the bubble release mode. The bubble release mode is set according to the button operation by the user, or ink is not ejected from the nozzles 17 in the state set to the bubble capture mode (a predetermined positive potential is applied to the individual electrode 18). Is automatically set when a predetermined time has passed. At that time, the filter control unit 64 controls the potential of the conductive substrate 52 so that the potential of the conductive substrate 52 is a predetermined potential higher than the ground potential. Thereby, a potential difference is generated between the conductive substrate 52 of the filter 13 and the ink in the ink supply flow path. Therefore, the wettability on the surface of the insulating layer 53 disposed between the conductive substrate 52 and the ink is high (for example, the wetting angle θ is about 40 °) (electrowetting phenomenon), and the surface of the insulating layer 53 The bubbles A in the ink are less likely to adhere to the ink.

  Based on the control from the purge control unit 63, the cap 7 is brought into contact with the ink discharge surface 23a, and the suction pump 8 is driven in a state where the cap 7 is in contact with the ink discharge surface 23a. Ink in the flow path and the ink supply flow path is sucked from the cap 7 side and purged.

  At this time, since the surface of the insulating layer 53 of the filter 13 is in a state in which air bubbles are difficult to adhere, the air bubbles A in the ink adhering to the surface of the insulating layer 53 of the filter 13 are removed from the insulating layer 53 of the filter 13. , The ink supply flow path and the individual ink flow path are moved and discharged from the nozzle 17. In this way, since the bubble A attached to the surface of the filter 13 is reliably discharged by performing the purge, the bubble A remains in the through hole 13a of the filter 13, and the filter 13 is clogged by the bubble A. Can be prevented.

  According to the embodiment described above, when recording is performed in the inkjet recording apparatus 1, the mode setting unit 61 of the driver IC 60 is set to the bubble capturing mode, and the potential of the conductive substrate 52 of the filter 13 is set to the ground potential. Become. At this time, the wettability on the surface of the insulating layer 53 remains low, and bubbles in the ink tend to adhere to the surface of the filter 13. Therefore, when recording is performed, the bubbles in the ink can be reliably captured by the filter 13 and the bubbles can be prevented from flowing into the manifold channel 11. This prevents the nozzle 17 from being clogged by bubbles, and prevents the ink from being discharged normally from the nozzles 17 due to the bubbles flowing into the individual ink flow paths, thereby preventing the recording quality from deteriorating. Is done.

  Furthermore, when purging in the inkjet recording apparatus 1, the mode setting unit 61 of the driver IC 60 is set to the bubble release mode, and the potential of the conductive base material 52 of the filter 13 becomes a predetermined potential higher than the ground potential. . Due to the electrowetting effect described above, wettability on the surface of the insulating layer 53 is increased, and bubbles are less likely to adhere to the surface of the insulating layer 53 of the filter 13. Therefore, bubbles are prevented from remaining on the surface of the insulating layer 53 of the filter 13 when purging is performed. Thereby, clogging of the filter 13 due to bubbles remaining in the filter 13 can be prevented.

  Further, since the filter 13 has a structure in which an insulating layer 53 is formed on the surface of a metal conductive substrate 52 in which a plurality of through holes 13a are formed, electroforming or The filter 13 can be easily manufactured by forming the plurality of through holes 13a by a method such as pressing and forming the insulating layer 53 on the surface of the conductive substrate 52 by a method such as a CVD method.

  Further, since the ink in the ink supply channel is in contact with the vibration plate 40 held at the ground potential, the ink is held at the ground potential. When the potential of the conductive substrate 52 is set to a predetermined potential, a potential difference is surely generated between the conductive substrate 52 and the ink in the ink supply channel, so that the wettability of the surface of the insulating layer 53 is ensured. Can be high. Further, it is not necessary to provide a separate electrode or the like in the ink supply flow path in order to maintain the ink at the ground potential, and the configuration of the ink jet recording apparatus is simplified.

  Further, since the through hole 13a of the filter 13 has a smaller flow area toward the manifold flow path 11, the ink can be prevented from flowing back from the manifold flow path 11 to the ink supply flow path. Further, since the minimum diameter of the through-hole 13a is smaller than the diameter of the ink discharge port 17a of the nozzle 17, foreign matters and bubbles in the ink larger than the diameter of the ink discharge port 17a are surely removed in the filter 13, and the nozzle 17 Clogging can be further reliably prevented.

  Further, since the through holes 13a of the filter 13 are uniformly distributed in the conductive base material 52, the filter 13 can efficiently capture foreign matters and / or bubbles in the ink.

  Next, modified examples in which various changes are made to the present embodiment will be described. However, components having the same configuration as in the present embodiment are denoted by the same reference numerals, and description thereof is omitted as appropriate.

<First modification>
The filter is not limited to a filter in which an insulating layer is formed on the surface of a conductive base material in which a plurality of through holes are formed. For example, as in the filter 71 shown in FIG. 9, an insulating member 72 in which a plurality of through holes 71a are formed, a surface of the insulating member 72 opposite to the manifold channel 11 and a plurality of through holes 71a are defined. A metal electrode 73 formed on the inner surface of the electrode 73 and an insulating layer 74 formed on the surface of the electrode 73 may be provided. Here, the insulating member 72 and the insulating layer 74 are formed of an insulating material such as a fluororesin, but may be formed of the same material or different materials. The electrode 73 is connected to the driver IC 60 by a wiring (not shown).

  Even in this case, when the potential of the electrode 73 is the ground potential, the wettability on the surface of the insulating layer 74 remains low, so that bubbles easily adhere to the surface of the filter 71. When the potential of the electrode 73 becomes a predetermined potential, the wettability of the portion of the insulating layer 74 facing the electrode 73, that is, the surface of the filter 71 opposite to the manifold channel 11 and the inner surface defining the through hole 71a is increased. It becomes high and it becomes difficult for bubbles to adhere to this part. Therefore, bubbles can be reliably captured on the surface of the filter 71 when recording is performed, and bubbles attached to the through holes 71a are reliably discharged when purging is performed. Further, such a filter 71 has a predetermined surface, that is, a surface disposed on the side opposite to the manifold channel 11 after forming a plurality of through holes 71a by irradiating the insulating member 72 with an excimer laser or the like. In addition, an electrode 73 is formed on the inner surface defining the plurality of through holes 71a by vapor deposition or the like, and an insulating layer 74 is formed on the surface on which the electrode 73 is formed by the same method as in the embodiment. Can be produced. Thereby, the diameter of the through-hole 71a can be accurately formed by irradiating with an excimer laser or the like.

<Second modification>
Further, as in the filter 81 shown in FIG. 10, an electrode 82 is formed on the surface of the planar insulating member 72 on the side of the manifold channel 11, and an insulating layer 83 is formed so as to cover the entire insulating member 72 from above. It may be formed. In this case, since the surface on which the electrode 82 is formed is planar, the electrode 82 can be easily formed.

<Third modification>
An insulating layer may not be formed on the surface of the filter electrode. For example, the filter 91a illustrated in FIG. 11A includes a conductive base material 93a in which a plurality of through holes 92a are formed. The conductive base material 93a also serves as the electrode 94a. Here, the filter 91a has the same structure as the filter 13 of the above embodiment except that the insulating layer is not formed on the surface thereof. Alternatively, the filter 91b shown in FIG. 11B includes an insulating base material 93b in which a plurality of through holes 92b are formed, and the inner surface and base material of the base material 93b that define the through holes 92b. And a metal electrode 94b formed on one surface of 93b. Here, the filter 91b has the same structure as the filter 71 of the first modified embodiment except that an insulating layer is not formed on the surface of the electrode 94b. In either case, the electrodes 94a and 94b are connected to the driver IC 60 by wiring (not shown). In general, even when an insulating layer is not formed on the surface of the metal member, it is known that the wettability of the surface of the metal member is reduced by applying a voltage between the conductive liquid and the metal member. This phenomenon is also considered to be a kind of electrowetting phenomenon. Therefore, also in the filters 91a and 91b of this modified embodiment, when bubbles are attached to the surfaces of the electrodes 94a and 94b of the filters 92a and 92b, the electrodes 94a and 94b and the ink have the same potential. In order to open the bubbles attached to the filters 92a and 92b, a predetermined voltage is applied between the electrodes 94a and 94b and the ink. The filters 91a and 91b are insulated from the diaphragm 40 and the fixing member 51 by an insulating member (not shown).

  Further, in the present embodiment, the ink in the ink supply channel is held at the ground potential by the vibration plate 40, but an electrode separately held at the ground potential may be provided in the ink supply channel. .

  Further, when the mode setting unit 61 is set to the bubble release mode, the filter control unit 64 controls the potential of the conductive base material 52 to be a predetermined potential lower than the ground potential which is the reference potential. May be. Note that the predetermined potential in this case is also a potential sufficient to improve the wettability of the surface of the insulating layer 53 due to the electrowetting phenomenon and cause bubbles to separate from the surface of the insulating layer 53 when purging.

  Further, the through-hole 13a is not limited to the case where the flow passage area is smaller toward the manifold flow passage 11 side. For example, the through-hole 13a is formed perpendicular to the surface of the conductive substrate 52, and the flow passage area is constant. It may be.

  Further, the through holes 13 a may not be formed so as to be uniformly distributed in the conductive base material 52, but may be formed so as to be distributed only in a part of the conductive base material 52.

  Moreover, the through-hole 13a does not necessarily need to be formed in a substantially circular shape in plan view, and may be formed in a shape such as an ellipse, an ellipse, or a polygon. Further, the ink discharge port 17a may also be formed in a shape such as an ellipse, an ellipse, or a polygon in plan view. In this case, the minimum diameter of the through hole 13a (when the shape of the through hole 13a in plan view is not circular, the diameter of a circle inscribed in the shape of the through hole 13a in plan view) is set to the diameter of the ink discharge port 17a (ink discharge). In the case where the shape of the outlet is not circular, by forming it smaller than the diameter of the circle inscribed in the ink discharge port, the ink stagnates without passing through the ink discharge port 17a as in the above-described embodiment. Foreign matter and bubbles in the inside can be reliably removed by the filter 13, and clogging of the ink discharge port 17a can be reliably prevented.

  The location where the filter is installed is not limited to the location where the filter is installed in the above embodiment, for example, an ink flow path formed in the flow path unit or a tube connecting the ink tank and the flow path unit, It can be arranged at any position in the flow path through which the ink flows. Moreover, the diameter and shape of the through-hole formed in a filter can be set arbitrarily.

  The present invention can also be applied to a liquid transfer device that transfers liquids other than ink, such as reagents, biological solutions, wiring material solutions, electronic material solutions, refrigerants, and fuels, in addition to inkjet recording devices.

1 is a schematic perspective view of an ink jet recording apparatus according to an embodiment of the present invention. It is a top view of the inkjet head of FIG. It is the III-III sectional view taken on the line of FIG. FIG. 3 is an enlarged plan view around an ink supply port of FIG. 2. It is the VV sectional view taken on the line of FIG. FIG. 2 is a block diagram of a driver IC that controls the operation of the ink jet recording apparatus of FIG. 1. FIG. 7A is a diagram showing a state when recording is performed in the ink jet head of FIG. 2, and FIG. 7B is an enlarged view of the surface of the filter of FIG. 7A. FIG. 8A is a diagram showing a state in which purging is performed in the inkjet head of FIG. 2, and FIG. 8B is an enlarged view of the surface of the filter of FIG. 8A. It is sectional drawing equivalent to FIG. 5 of a 1st modification. It is sectional drawing equivalent to FIG. 5 of a 2nd modification. FIG. 11A is a cross-sectional view corresponding to FIG. 5 of the third modification, and FIG. 11B is a cross-sectional view corresponding to FIG. 9 of the third modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 3 Inkjet head 13 Filter 13a Through hole 40 Diaphragm 52 Conductive base material 53 Insulating layer 61 Mode setting unit 64 Filter control unit 65 Grounding unit 72 Insulating member 73 Electrode

Claims (20)

A bubble capturing device that includes a filter disposed in a liquid flow path and captures bubbles included in the liquid flowing in the liquid flow path,
A filter having a base material in which a conductive region having conductivity is formed on the surface and a plurality of through holes through which a liquid passes are formed;
A potential control mechanism for controlling the potential of the conductive region of the filter ;
A mode setting device for selectively setting a bubble capturing mode for capturing bubbles in the liquid on the surface of the filter and a bubble releasing mode for releasing bubbles captured on the surface of the filter ;
The potential control mechanism is configured to determine a potential difference between the conductive region and the liquid flowing in the liquid flow path when the mode setting device is set to the bubble trapping mode, and the mode setting device includes the bubble. It said to be smaller than the potential difference between the conductive region and said liquid flowing through the liquid channel when it is set to release mode, the bubble capture device that controls the electric potential of the conductive region.   Furthermore, the bubble capture | acquisition apparatus of Claim 1 provided with the insulating layer which covers the said electroconductive area | region of the said base material.   The gas capturing apparatus according to claim 1, wherein the liquid is a conductive liquid flowing in the liquid flow path, and the filter captures bubbles contained in the conductive liquid. The bubble trapping device according to claim 1 , further comprising a constant potential holding mechanism that holds the liquid flowing in the liquid channel at a predetermined reference potential. The bubble capturing apparatus according to claim 4 , wherein the liquid channel is formed by a channel member including a conductive material, and the constant potential holding mechanism includes a grounding mechanism that grounds the channel member. The potential control mechanism is configured such that a potential difference between the potential of the conductive region and the reference potential when the mode setting device is set to the bubble release mode is set by the mode setting device to the bubble trapping mode. The bubble trapping device according to claim 4 , wherein the potential of the conductive region is controlled to be larger than a potential difference between the potential of the conductive region and the reference potential when being performed. The potential control mechanism controls the potential of the conductive region so that the conductive region of the filter and the reference potential are the same potential when the mode setting device is set to the bubble trapping mode. When the mode setting device is set to the bubble release mode, the potential of the conductive region is controlled such that the potential of the conductive region of the filter is different from the reference potential. 5. The bubble trapping device according to 4 .   The bubble trapping device according to claim 1, wherein the base material is formed of a metal material.   The bubble trapping apparatus according to claim 1, wherein the base material includes an insulating member in which the plurality of through holes are formed, and an electrode that is formed on a surface of the insulating member and forms the conductive region. The bubble trapping apparatus according to claim 9 , wherein the electrode is formed on a surface that defines the through hole formed in the insulating member. The bubble trapping device according to claim 10 , wherein a surface of the insulating member is planar, and the electrode is formed on a surface of the planar insulating member.   The bubble trapping device according to claim 1, wherein a cross-sectional area of the through hole is reduced toward one side in a direction in which the through hole extends.   The bubble trapping device according to claim 1, wherein the plurality of through holes that are uniformly distributed on the surface of the substrate are formed in the substrate.   The bubble trapping device according to claim 2, wherein the insulating layer is made of a fluororesin.   A liquid transfer device comprising a liquid flow path through which a liquid flows and the bubble trapping device according to claim 1. An ink jet recording apparatus for discharging ink,
An ink supply source for supplying the ink;
A plurality of ink ejection openings ;
And Common liquid chamber,
A plurality of individual ink flow paths respectively communicating with the plurality of ink discharge ports and the common liquid chamber;
An energy application mechanism that is provided corresponding to each of the plurality of individual ink flow paths and that applies ejection energy to the ink;
An ink supply channel for supplying the ink from the ink supply source to the common liquid chamber;
A filter disposed in the ink supply flow path, having a base material in which a conductive region having conductivity is formed on a part of the surface, and having a plurality of through holes through which the ink passes. Filters,
A potential control mechanism for controlling the potential of the conductive region of the filter ;
A mode setting device for selectively setting a bubble capturing mode for capturing bubbles in the ink on the surface of the filter and a bubble releasing mode for releasing bubbles captured on the surface of the filter ;
The potential control mechanism is configured to determine a potential difference between the conductive region and the ink flowing in the ink supply channel when the mode setting device is set to the bubble trapping mode. so as to be smaller than the potential difference between the ink and the conductive region through the ink supply channel when it is set to bubble release mode, the ink jet recording apparatus that controls a potential of the conductive region . Furthermore, the said filter is provided with the insulating layer which covers the said electroconductive area | region of the said base material, The inkjet recording device of Claim 16 . And a purge mechanism having a suction device that sucks the ink and the bubbles and a cap that covers the ink discharge port, and a purge control device that controls the operation of the purge mechanism, wherein the purge control device includes the purge mechanism. The inkjet recording apparatus according to claim 16 , wherein the mode setting device is set to the bubble release mode when purging by control. 19. The inkjet recording apparatus according to claim 18 , wherein the mode setting device is set to the bubble trapping mode when the purge control device controls the purge mechanism to end the purge. The inkjet recording apparatus according to claim 16 , wherein a minimum diameter of an inscribed circle that fits in the through hole is smaller than a diameter of the inscribed circle that fits in the discharge port.

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