JP2008230152A - Inkjet head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet head capable of handling either of an ink circulating type and an ink non-circulating type with a simple structure. <P>SOLUTION: The inkjet head 11 is provided with a pressure chamber 21, nozzles, a driving element, a first supplying part 14, a second supplying part 15, a discharging part 17, and a filter member 25. The inkjet head 11 is used on either of: a first using condition that an ink 16 supplied from the second supplying part 15 is ejected from the nozzles through the filter member 25 and the pressure chamber 21 under the condition that the first supplying part 14 and the discharging part 17 are closed; and a second using condition that a part of an ink 16 supplied from the first supplying part 14 is ejected from the nozzles through the pressure chamber 21 while a part of the ink is discharged outside from the discharging part 17 under the condition that the second supplying part 15 is closed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ink jet head that supports both ink circulation type and ink non-circulation type.

  For example, an ink jet head is known in which ink droplets can be ejected while ink is circulated in the head. The ink jet head has a plurality of fluid chambers, each fluid chamber being connected to a nozzle, an inlet manifold, and an outlet manifold. The ink jet head has members that create a fluid flow to the inlet manifold, each fluid chamber, and the outlet manifold.

  In this ink jet head, the flow of fluid through each chamber is sufficient to remove foreign substances contained in the fluid from the nozzle. Further, the flow resistance at the time from the inlet manifold to the outlet manifold changes by a small amount. For this reason, a significant difference is not brought about in the ejection characteristic of a droplet (for example, refer to patent documents 1).

On the other hand, ink jet heads that do not circulate ink within the head are well known. In this inkjet head, the ink supplied from the ink tank passes through the flow path in the inkjet head and is ejected as a small droplet from the nozzle.
JP-T-2002-533247

  The above-described conventional ink circulation type inkjet head is in high demand as a highly reliable inkjet head because of its high ejection reliability and high cleaning performance of the ink flow path. On the other hand, printing with a cheaper system, that is, an ink non-circulating ink jet head is also desired. For this reason, there is a situation that either the ink circulation type or the ink non-circulation type is selected according to the characteristics of the ink or the requirements of the printing apparatus. For this reason, there has been a demand for an ink jet head that can cope with both the ink circulation type and the ink non-circulation type. However, the above-described conventional ink jet head has no such idea or suggestion.

  An object of the present invention is to provide an ink jet head that has a simple structure and can cope with both ink circulation type and ink non-circulation type.

  In order to achieve the above object, an inkjet head according to an aspect of the present invention includes a pressure chamber filled with ink, a nozzle provided on one surface of the pressure chamber, the pressure chamber, and the pressure chamber. A drive element for discharging ink in the chamber from the nozzle, a first supply port and a second supply port for supplying the ink to the pressure chamber, and a discharge port for discharging the ink from the pressure chamber And a filter member provided between the second supply port and the pressure chamber, and supplied from the second supply port in a state where the first supply port and the discharge port are closed. The discharged ink is supplied from the first supply port through the filter and the pressure chamber, in a first use state where the ink is discharged from the nozzle and in a state where the second supply port is closed. Said a And the second use state in which a part is discharged from the nozzle and part thereof is discharged to the outside from the discharge port via the pressure chamber. The

  According to the present invention, it is possible to provide an ink jet head that has a simple structure and can cope with both ink circulation type and ink non-circulation type.

  Hereinafter, embodiments of the inkjet head of the present invention will be described with reference to the drawings. The ink jet head is used by being mounted on a so-called ink circulation type printing apparatus, but can also be used by being mounted on an ink non-circulation type printing apparatus.

  As shown in FIGS. 1 and 2, the inkjet head 11 includes a head main body 12, a pair of circuit boards 13 attached to the head main body 12, and a first ink supply for supplying ink 16 to the pressure chamber 21 of the head main body 12. The first supply unit 14 and the second supply unit 15, and a discharge unit 17 for discharging the ink 16 from the pressure chamber 21 of the head body 12 are provided. Each circuit board 13 has a head driving IC 18. The first supply unit 14 and the discharge unit 17 are used in a second use state in which the ink 16 is circulated. The second supply unit 15 is used in a first use state in which the ink 16 is not circulated.

  The first supply unit 14 has a first connection end 14A, and this first connection end 14A is used to connect to a circulation type ink tank when mounted on a printing apparatus (not shown). It is done. Similarly, the second supply unit 15 has a second connection end 15A, and the second connection end 15A is used to connect to a non-circulating ink tank of a printing apparatus (not shown). Yes. The discharge unit 17 has a third connection end 17A for returning to the ink 16 by connecting to the circulation type ink tank.

  As shown in FIGS. 2 and 3, the head body 12 includes a pressure chamber 21 formed therein, a plurality of through holes 22 communicating with the pressure chamber 21, and a drive element 23 provided in the pressure chamber 21. A nozzle plate 24 provided on one surface of the pressure chamber 21, a filter member 25 provided between the second supply unit 15 and the pressure chamber 21, a second supply unit 15 and the filter member 25. And a connecting portion 26 provided between the two. The head body 12 includes a first supply port 31 that communicates the pressure chamber 21 and the first supply unit 14, a second supply port 32 that communicates the connection unit 26 and the second supply unit 15, and a pressure. It has the discharge port 33 which makes the chamber 21 and the discharge part 17 communicate. When the inkjet head 11 is used, the ink 16 is filled in the pressure chamber 21.

  The plurality of through holes 22 include a plurality of central holes 22A for communicating the first supply unit 14 and the pressure chamber 21, and a plurality of both end holes 22B for communicating the discharge unit 17 and the pressure chamber 21. , Including. As shown in FIG. 5, the first supply unit 14 and the plurality of central holes 22 </ b> A are connected via a first communication channel 28. As shown in FIG. 6, the discharge portion 17 and the plurality of both end holes 22 </ b> B are connected via a second communication channel 29.

  The nozzle plate 24 has two nozzle rows 34 as shown in FIG. Each nozzle row 34 extends in a direction along the longitudinal direction of the inkjet head 11. Each nozzle row 34 includes a plurality of nozzles 35, but only one is shown in FIG. The nozzle diameter (diameter) of each nozzle 35 is 20-40 micrometers. Each nozzle 35 is provided on one surface of the pressure chamber 21.

  As shown in FIG. 4, the drive element 23 is formed by bonding together a first piezoelectric element 36 and a second piezoelectric element 37 whose polarization directions are opposed to each other. The drive element 23 further includes an electrode 38 for driving the first and second piezoelectric elements 36 and 37. The first piezoelectric element 36 and the second piezoelectric element 37 are each formed of, for example, a PZT (lead zirconate titanate) piezoelectric ceramic material. The electrode 38 is formed, for example, by electroless nickel plating on the surfaces of the first and second piezoelectric elements 36 and 37. The pressure chamber 21 is formed at a position between the drive elements 23. That is, the drive element 23 is provided facing the pressure chamber 21.

  The filter member 25 is a so-called electroformed filter. The hole diameter (diameter) of the filter member 25 is, for example, 1/2 to 1/3 the diameter of the nozzle 35.

  Next, with reference to FIGS. 3 and 4, a description will be given of a first use state in which the inkjet head 11 is mounted on a non-circulating printing apparatus and printing is performed. That is, in the first use state, ink droplet ejection driving is performed by a non-circulation method in which the ink 16 is not circulated in the inkjet head 11. The printing apparatus is configured by a known device (not shown), and includes, for example, an ink tank for supplying ink 16 to the inkjet head 11 and a control unit for controlling ink ejection of the inkjet head 11. Yes.

  In the first use state, the first supply unit 14 and the discharge unit 17 that are used in a circulating manner are not used. For this reason, for example, the first connecting end 14A provided in the first supply unit 14 and the third connecting end 17A provided in the discharge unit 17 are respectively sealed members as shown in FIG. The rubber plug 42 is sealed so that the pressure inside the head body 12 is constant. Further, the rubber plug 42 prevents the ink 16 in the head body 12 from leaking outside.

  As shown in FIG. 3, the ink 16 supplied from the second supply unit 15 is filled in the connection unit 26 via the second supply port 32. At this time, a meniscus is formed on the filter member 25. When a sufficient amount of ink 16 is filled in the connection portion 26 and the pressure in the connection portion 26 reaches the breaking pressure of the meniscus, the ink 16 is supplied to the pressure chamber 21 through the filter member 25. At this time, minute dust and particles contained in the ink 16 are removed by the filter member 25. As shown in FIG. 3, in the first use state, the ink 16 is supplied from the connection portion 26 to the pressure chamber 21 via the three rows of through holes 22.

  As shown in FIG. 4, when the user instructs the printing apparatus to start printing while the pressure chamber 21 is filled with the ink 16, the control unit of the printing apparatus sends a print signal to the inkjet head 11. Output to the driving IC 18. Upon receiving the print signal, the head drive IC 18 applies a drive pulse voltage to the drive element 23. Accordingly, as shown by a two-dot chain line in FIG. 4, the pair of left and right drive elements 23 are separated from each other so as to bend by performing shear mode deformation. Then, by returning these to the initial position and pressurizing the ink 16 in the pressure chamber 21, ink droplets are ejected from the nozzles 35 with vigorous force.

  Next, a second usage state in which the inkjet head 11 is mounted on a circulation type printing apparatus and printing is described with reference to FIGS. That is, in the second use state, ink droplets are driven to be ejected by a circulation method in which the ink 16 is circulated in the inkjet head 11. The printing apparatus is configured by a known device (not shown), for example, a circulation type ink tank for supplying ink 16 to the inkjet head 11, a control unit for controlling ink ejection of the inkjet head 11, A pump for circulating the ink 16 is included.

  In the second use state, the second supply unit 15 used in a non-circulation type is not used. For this reason, as shown in FIG. 9, in the second use state, the second connection end 15 </ b> A of the second supply unit 15 is provided with a rubber plug 42 as a sealing member. The rubber plug 42 keeps the pressure inside the head body 12 constant, and prevents the ink 16 inside the head body 12 from leaking outside.

  As shown in FIGS. 5 and 7, the ink 16 supplied from the first supply unit 14 is supplied to the pressure chamber 21 through the first supply port 31 and the plurality of central holes 22 </ b> A. That is, in the second use state, the ink 16 is not filtered by the filter member 25. In the pressure chamber 21, as shown in FIG. 4, when the driving element 23 is driven, ink droplets are ejected from the nozzle 35, which is the same as in the first use state described above. However, in the second use state, as shown in FIGS. 6 and 8, the ink 16 that has not been used in the pressure chamber 21 is discharged to the outside of the inkjet head 11 via the discharge port 33 and the discharge portion 17. And returned to the ink tank of the printing apparatus.

  As described above, the ink 16 is constantly circulated between the ink tank of the printing apparatus and the inkjet head 11. A series of printing processes is performed in a state where the ink 16 is circulated. For this reason, for example, even if the particles mixed in the ink 16 are fitted into the nozzle 35 and the nozzle 35 is not ejected, the particles are removed by the circulating flow of the ink 16 inside the head body 12.

  In the second use state, the ink 16 in the pressure chamber 21 and the through hole 22 is prevented from flowing over the filter member 25 to the connection portion 26.

  Hereinafter, this point will be specifically described. As shown in FIG. 9, air 27 is stored in the connection portion 26 in the second use state. Ink 16 is stored in the through hole 22 and the pressure chamber 21. The filter member 25 partitions the air 27 in the connection portion 26 and the ink 16 in the pressure chamber 21.

  The ink 16 in the vicinity of the central hole 22A sent from the first supply unit 14 is maintained at a positive pressure. Further, the ink 16 in the vicinity of both end holes 22B is maintained at a negative pressure. For this reason, the ink 16 inside the pressure chamber 21 in the middle of these is maintained at a weak negative pressure. For this reason, the ink 16 is prevented from leaking from the nozzle 35 when not intended.

  As shown in FIG. 9, an ink meniscus 51 that protrudes toward the connecting portion 26 is formed on the surface of the filter member 25 near the center hole, by leaking a small amount of ink 16. The filter member 25 of the present embodiment is designed so that the holding pressure of the ink meniscus 51 is higher than the pressure of the pressure chamber 21. For this reason, it is prevented that the ink 16 near the central hole 22A leaks out to the connecting portion 26 and the ink 16 does not circulate as originally. The holding pressure of the ink meniscus 51 is determined by, for example, the hole diameter of the filter member 25, the surface tension / contact angle of the ink meniscus 51, and the like.

  In addition, for some reason, the ink meniscus 51 may be destroyed, and the ink 16 may flow from the central hole 22A to the both end holes 22B via the connection portion 26. In the present embodiment, the filter member 25 is designed such that the flow path resistance inside thereof is larger than the flow path resistance of the pressure chamber 21. As a result, even if the ink 16 leaks into the connection portion 26 for some reason, the amount of the leaked ink 16 continues to flow in this path is small compared to the main flow (the circulation flow). It is like. In this case, the flow path resistance of the filter member 25 is determined by, for example, the filter hole diameter, the length of the pipeline, the viscosity of the ink, and the like. Further, since the amount of the ink 16 in the vicinity of the center hole 22A that flows through the inside of the filter member 25 to the both end holes 22B is small due to the flow path resistance of the filter member 25, the influence on the main flow can be ignored.

  As shown in FIG. 9, since the negative pressure is in the vicinity of both end holes 22B, an ink meniscus 52 that protrudes toward both end holes 22B is formed on the surface of the filter member 25. ing.

  The manufacturing process of the inkjet head 11 according to the present embodiment includes a cleaning process. Hereinafter, the cleaning process will be described. When cleaning the inside of the head body 12, for example, the cleaning liquid is supplied from the first supply unit 14 and the cleaning liquid is discharged from the discharge unit 17. Thereby, it is possible to perform cleaning with the cleaning liquid mainly on the structure on the downstream side of the filter member 25. In addition, since the inkjet head 11 of the present embodiment is based on a circulation type, the flow rate of the cleaning liquid is also appropriately maintained. For this reason, in the cleaning process, stagnation of the inside of the head main body 12 is prevented, and efficient cleaning is performed. The cleaning liquid may be fresh water or alcohol. Further, the cleaning step is not limited to the above, and it goes without saying that the upstream side of the filter member 25 can also be cleaned by flowing a cleaning liquid from the second supply unit 15.

  The above is the embodiment of the inkjet head 11. According to the present embodiment, the ink jet head 11 is configured such that the ink 16 supplied from the second supply unit 15 passes through the filter member 25 and the pressure chamber 21 with the first supply unit 14 and the discharge unit 17 closed. The ink 16 supplied from the first supply unit 14 in the first use state discharged from the nozzle 35 and the second supply unit 15 in the closed state passes through the pressure chamber 21, A part is discharged from the nozzle 35 and a part thereof is used in any one of the second usage state in which the part is discharged from the discharge part 17 to the outside.

  According to this configuration, the ink jet head 11 can be used both in the first use state in which the ink 16 is not circulated and in the second use state in which the ink 16 is circulated. Thereby, the inkjet head 11 which can respond to both an ink circulation type printing apparatus and an ink non-circulation type printing apparatus can be obtained. Further, the portion that cannot be cleaned by the normal non-circulating inkjet head 11, that is, the structure downstream of the filter member 25 can be efficiently cleaned by the inkjet head 11 of the present embodiment. As a result, the cleaning efficiency can be improved and the yield in manufacturing the inkjet head can be improved.

  In addition, the amount of particles allowed in the circulation type ink jet head is larger than the allowable amount of the non-circulation type ink jet head. This is based on the fact that, in an ink circulation type ink jet head, ink circulates even during the ejection operation, so that even if the nozzle is clogged with particles, the non-ejection state is eliminated by the ink flow. For this reason, in the circulation type ink jet head, the amount of particles such as dust allowed in the manufacturing process is relaxed compared to the non-circulation type. Since the inkjet head 11 of the present embodiment is based on a circulating inkjet head, the allowable particle conditions are also relaxed. Also from this point, the inkjet head 11 of this embodiment can improve a yield compared with a non-circulation inkjet head.

  In this case, it is provided between the second supply unit 15 and the filter member 25 and includes a connection unit 26 that stores the air 27 in the second use state, and the filter member 25 is in the second use state. The air 27 in the connection portion 26 and the ink 16 in the pressure chamber 21 are partitioned. According to this configuration, in the second use state, the filter member 25 that is not used can also serve as a part of the ink flow path. Thereby, in the second use state, it is not necessary to separately provide a wall portion for defining the flow path in the inkjet head 11, and the number of parts can be reduced and the inkjet head 11 can be reduced in size.

  In the second use state, an ink meniscus 51 is formed on the surface of the filter member 25 toward the connection portion 26, and the filter member 25 has a holding pressure of the ink meniscus 51 larger than the pressure in the pressure chamber 21. Have. According to this configuration, the ink meniscus 51 formed on the surface of the filter member 25 is not destroyed, and it is possible to prevent the ink circulation through the connection portion 26 that is not initially planned.

  In this case, the flow path resistance of the filter member 25 is larger than the flow path resistance of the pressure chamber 21. In general, the ink meniscus 51 formed on the surface of the filter member 25 is not destroyed, but the possibility that the ink meniscus 51 is destroyed under some conditions cannot be denied. According to this configuration, even if the ink 16 may flow from the first communication channel 28 to the second communication channel 29 via the connection portion 26, this flow is prevented from continuing. Then, the ink 16 is returned to the pressure chamber 21 having a low flow path resistance. Thereby, it is possible to prevent a situation where the ink 16 circulates in an unexpected direction.

  The present invention is not limited to the embodiment described above. Of course, various modifications can be made without departing from the scope of the invention.

1 is a perspective view showing an ink jet head according to a first embodiment. The perspective view which shows the head main body of the inkjet head shown in FIG. FIG. 5 is a cross-sectional view of the head main body shown in FIG. 2 taken along line F3-F3. Sectional drawing which shows the drive element of the head main body shown in FIG. FIG. 5 is a cross-sectional view taken along the line F5-F5 of the head body shown in FIG. FIG. 4 is a cross-sectional view taken along line F6-F6 of the head body shown in FIG. FIG. 6 is a cross-sectional view taken along line F7-F7 of the head body shown in FIG. Sectional drawing along F8-F8 line of the head main body shown in FIG. FIG. 6 is a cross-sectional view taken along line F9-F9 of the head body shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Inkjet head, 14 ... 1st supply part, 15 ... 2nd supply part, 16 ... Ink, 17 ... Discharge part, 21 ... Pressure chamber, 23 ... Drive element, 25 ... Filter member, 26 ... Connection part, 35 ... Nozzle, 51 ... Ink meniscus

Claims (4)

A pressure chamber filled with ink;
A nozzle provided on one surface of the pressure chamber;
A drive element that faces the pressure chamber and causes the ink in the pressure chamber to be ejected from the nozzle;
A first supply unit and a second supply unit for supplying the ink to the pressure chamber;
A discharge part for discharging the ink from the pressure chamber;
A filter member provided between the second supply unit and the pressure chamber;
Comprising
In a state where the first supply unit and the discharge unit are closed, the ink supplied from the second supply unit is discharged from the nozzle through the filter member and the pressure chamber. Usage state and
With the second supply part closed, the ink supplied from the first supply part passes through the pressure chamber, a part of which is ejected from the nozzle, and a part of the ink is supplied from the nozzle A second use state discharged from the discharge unit to the outside;
An inkjet head that is used in any one of the above. Provided between the second supply part and the filter member, and comprising a connection part for storing air in the second use state,
2. The inkjet head according to claim 1, wherein the filter member partitions the air in the connection portion and the ink in the pressure chamber in the second use state. In the second use state, an ink meniscus is formed on the surface of the filter member toward the connection portion.
The inkjet head according to claim 2, wherein the filter member has a holding pressure of the ink meniscus higher than a pressure of the pressure chamber.   The inkjet head according to claim 2, wherein a flow path resistance of the filter member is larger than a flow path resistance of the pressure chamber.

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