JP2018039135A - Inkjet head and inkjet recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet head which can efficiently remove residual air bubbles in a common ink chamber of the inkjet head, and to provide an inkjet recording device.SOLUTION: The inkjet head includes: a common ink chamber 41; an ink supply port 5a formed at the common ink chamber 41; an ink collection port 5b formed at the common ink chamber 41; at least one pressure chamber 23 which communicates with the common ink chamber 41 through an injection hole 31a and causes a volume variation by application of voltage; a nozzle 22 which communicates with the pressure chamber 23 and serves as a passage of an ink discharged from the interior of the pressure chamber 23 to the outside; and a distributor 41a which changes ink flow from the ink supply port 5a to the ink collection port 5b at the upper side in the common ink chamber 41. At least a part of the distributor 41a is disposed near the ink supply port 5a in the common ink chamber 41.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ink jet head and an ink jet recording apparatus, and more particularly to an ink jet head and an ink jet recording apparatus that can efficiently remove residual bubbles in a common ink chamber of the ink jet head.

  Some inkjet heads used in printers (inkjet recording apparatuses) have a common ink chamber for supplying ink to each pressure chamber. The common ink chamber is supplied with ink from an ink tank and communicates with each pressure chamber whose internal pressure is changed by driving a piezoelectric element, and supplies ink to each pressure chamber. If residual bubbles are present in the common ink chamber, the bubbles may enter the pressure chamber. When the bubbles enter the pressure chamber, there is a possibility that the ink ejection performance from the nozzle communicating with the pressure chamber may be affected.

  As an ink jet head capable of removing such residual bubbles, there has been proposed an ink jet head in which bubbles are removed from an inner wall of an ink flow path using a resonance phenomenon, and residual bubbles are removed by ink flow in a common ink chamber (patent) Reference 1). In addition, there has been proposed a technique in which the ceiling surface of the common ink chamber is inclined so that the ink discharge side is upward, and residual bubbles are removed using the buoyancy of bubbles (Patent Document 2).

JP 2008-087288 A JP 2009-126044 A

  By the way, in an inkjet head, the number of nozzles tends to increase due to demands for higher resolution and wider printing width. Therefore, the ink consumption per unit time also increases, the capacity of the common ink chamber increases, and the ink supply pressure to the common ink chamber tends to increase.

  In the ink-jet head described in Patent Document 1, when the capacity of the common ink chamber is increased, there is a possibility that an ink flow rate at which bubbles are sufficiently removed cannot be obtained in the common ink chamber. When the ink supply pressure to the common ink chamber is set to a high pressure such as 70 kPa, the ink flow in the common ink chamber is opposite to the ink supply port, that is, the ink supply port is located in the common ink chamber. If it is on the ceiling side, it concentrates on the bottom side, bubbles are not sufficiently removed on the ceiling side, and a lot of ink is discharged from the nozzles.

  In the ink jet head described in Patent Document 2, if the capacity is increased while the inclination angle of the ceiling surface of the common ink chamber is maintained, the height dimension of the common ink chamber is increased. If the height of the common ink chamber is maintained and the capacity is increased, the inclination angle of the ceiling surface is reduced, and the small residual bubbles cannot be sufficiently removed.

  Therefore, an object of the present invention is to provide an ink jet head and an ink jet recording apparatus that can efficiently remove residual bubbles in a common ink chamber of the ink jet head.

  Other problems of the present invention will become apparent from the following description.

  The above problems are solved by the following inventions.

1.
A common ink chamber;
An ink supply port formed in the common ink chamber and communicating with a flow path for supplying ink to the common ink chamber;
An ink recovery port formed in the common ink chamber and communicating with a flow path for recovering ink from the common ink chamber;
At least one pressure chamber that communicates with the common ink chamber via an injection hole and causes a volume variation by application of a voltage;
A nozzle communicating with the pressure chamber and serving as a flow path for ink discharged from the pressure chamber to the outside;
A rectifying plate that changes the flow of ink from the ink supply port to the ink recovery port on the upper side in the common ink chamber,
At least a part of the current plate is disposed in the vicinity of the ink supply port in the common ink chamber.
2.
2. The ink jet head according to claim 1, further comprising a discharge path communicating with the pressure chamber and discharging ink in the pressure chamber.
3.
3. The inkjet head according to claim 1 or 2, wherein the rectifying plate has a shape that guides ink flowing in the vicinity of the ink supply port to the upper side of the central portion in the common ink chamber.
4).
2. The ink jet head according to 1, 2, or 3, wherein two or more of the rectifying plates are arranged in the common ink chamber.
5.
The common ink chamber is characterized in that a ceiling surface is inclined with respect to a horizontal plane, and the ink recovery port is positioned higher than the ink supply port. Inkjet head.
6).
The inkjet head according to any one of 1 to 5, wherein the current plate is integrally connected to the common ink chamber via a vertical wall portion.
7).
The inkjet head according to any one of 1 to 6, wherein the current plate includes a curved surface portion that follows the flow of the ink in the common ink chamber.
8).
8. The ink jet head according to any one of 1 to 7, wherein a filter is provided inside the common ink chamber.
9.
The inkjet head according to any one of 1 to 8, wherein the rectifying plate is provided in a pressure attenuating unit disposed in the common ink chamber.
10.
The common ink chamber butt-joins at least a first member provided with the ink supply port and the ink recovery port and at least a second member provided with the mounting portion of the pressure chamber and the current plate. The inkjet head according to any one of 1 to 9, wherein the inkjet head is configured as described above.
11.
The inkjet head according to any one of 1 to 10;
An ink tank for storing ink transferred to the common ink chamber of the inkjet head;
An ink jet recording apparatus comprising: an ink transfer unit that transfers ink in the ink tank to the common ink chamber.
12
The inkjet head according to any one of 2 to 10, and
An ink tank for storing ink transferred to the inkjet head;
An ink transfer unit for transferring the ink in the ink tank to the inkjet head and collecting the ink transferred to the inkjet head;
The ink discharged from the pressure chamber through the discharge path is merged with the ink collected from the ink jet head.

  The present invention can provide an ink jet head and an ink jet recording apparatus that can efficiently remove residual bubbles in a common ink chamber of the ink jet head.

1 is a schematic configuration diagram of a main part showing an example of an ink jet recording apparatus of the present invention. Flow path diagram showing ink flow path in inkjet head An exploded perspective view schematically showing a head chip portion of an inkjet head The perspective view which shows embodiment of the flow volume adjustment member of an inkjet head The principal part longitudinal cross-sectional view which shows other embodiment of the baffle plate of an inkjet head The principal part longitudinal cross-sectional view which shows other embodiment of the baffle plate of an inkjet head Schematic configuration diagram of main parts showing another example of the ink jet recording apparatus of the present invention. The principal part longitudinal cross-sectional view which shows other embodiment of the baffle plate of an inkjet head Longitudinal sectional view showing another embodiment of the current plate of the ink jet head Longitudinal sectional view showing another embodiment of the current plate of the ink jet head A longitudinal sectional view showing an embodiment in which a filter is provided inside the common ink chamber A perspective view showing an embodiment provided with an external filter Disassembled perspective view of common ink chamber of inkjet head

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Inkjet recording device]
FIG. 1 is a schematic configuration diagram of a main part showing an example of an ink jet recording apparatus according to the present invention, and shows a partial cross section of an ink jet head.

  The ink jet recording apparatus 100 records an image by ejecting ink from the ink jet head 1 onto a recording medium transported in a certain direction (sub-scanning direction) by a transport unit (not shown). In a so-called one-pass ink jet recording apparatus, the ink jet head 1 is fixedly disposed, and ink is ejected from the nozzle toward the recording medium in the process of transporting the recording medium. In a so-called scanning ink jet recording apparatus, the ink jet head 1 is mounted on a carriage (not shown), and the nozzle moves from the nozzle toward the recording medium in the process of moving along the main scanning direction orthogonal to the sub scanning direction. Ink is ejected.

  In FIG. 1, only one inkjet head 1 is shown, but in general, an inkjet recording apparatus 100 is provided for each color ink such as yellow (Y), magenta (M), cyan (C), and K (black). A plurality of inkjet heads 1 are mounted. In the ink jet recording apparatus 100 shown in the present embodiment, an ink tank 101 for storing ink and a common ink chamber 41 of the ink jet head 1 are communicated by an ink transfer pipe 102 and an ink return pipe 103.

  A transfer pump 105 that is driven and controlled by the control unit 104 of the inkjet recording apparatus 100 is provided in the middle of the ink transfer tube 102. When the transfer pump 105 is driven, the ink in the ink tank 101 is transferred to the inkjet head 1 via the ink transfer pipe 102. Further, when the transfer pump 105 is driven, the ink (ink including bubbles) in the inkjet head 1 is returned to the ink tank 101 through the ink return pipe 103.

  In the inkjet recording apparatus 100, the ink transfer tube 102, the control unit 104, and the transfer pump 105 constitute an ink transfer unit that transfers the ink in the ink tank 101 to the inkjet head 1.

  The ink tank 101 is not particularly limited, but is preferably partitioned into an ink transfer chamber 101b and an ink return chamber 101c by a partition plate 101a that does not reach the bottom of the tank. In this case, one end of the ink transfer tube 102 is arranged in the ink transfer chamber 101b, and one end of the ink return tube 103 is arranged in the ink return chamber 101c. The partition plate 101a is provided in order to sufficiently degas the ink so that bubbles in the ink returned to the ink return chamber 101c do not flow into the ink transfer tube 102 again. Since the bubbles themselves have high buoyancy, the bubbles are restricted from flowing under the partition plate 101a and flowing into the ink transfer chamber 101b. Such an embodiment is a preferred embodiment when the ink is circulated.

[Inkjet head]
Next, a specific configuration of the inkjet head 1 according to the present invention shown in FIG. 1 will be described.

  The present invention can be applied to various ink jet heads such as a shear mode (edge (end) shooter, side shooter) type, a bend mode type, and a so-called MEMS type. That is, the inkjet head according to the present invention can be configured as these various inkjet heads.

  The inkjet head 1 shown in this embodiment is configured as a shear mode head. The ink jet head 1 is installed and used such that the ink discharge surface 1S faces downward in the vertical direction. In this specification, “upper” and “lower” mean “upper side in the vertical direction” and “lower side in the vertical direction”, and correspond to the upper side and the lower side in FIG. 1 (side view showing the use state). To do. However, the use state of the inkjet head of the present invention is not limited to the state in which the ink discharge surface 1S is directed downward in the vertical direction, and may be used while being inclined.

  As shown in FIG. 1, the ink jet head 1 includes an ink manifold 4 constituting a common ink chamber 41, a wiring board 3 bonded to a pressure chamber mounting portion 4 a of the ink manifold 4, and an ink sandwiching the wiring board 3. The head chip 2 is bonded to the opposite surface (lower surface) of the manifold 4. The wiring board 3 is a glass substrate, for example. On this wiring board 3, a wiring pattern (not shown) connected to a power supply circuit (not shown) via an FPC board is formed. The ink manifold 4 is formed of a synthetic resin material or the like in a horizontally long box shape having a pressure chamber mounting portion 4a that is an opening on the lower surface. The wiring board 3 is bonded to the ink manifold 4 so as to close the pressure chamber mounting portion 4a. The internal space of the ink manifold 4 serves as a common ink chamber 41 in which ink supplied from the ink tank 101 is stored.

  FIG. 2 is a flow path diagram showing the flow path of the ink in this ink jet head.

  As shown in FIGS. 1 and 2, the common ink chamber 41 is provided with an ink supply port 5a. An ink supply pipe 51a that forms a flow path for supplying ink into the common ink chamber 41 is connected to the ink supply port 5a. The ink supply port 5 a communicates the common ink chamber 41 outwardly above the common ink chamber 41. A connecting portion 7a is provided on the upper end side of the ink supply pipe 51a connected to the ink supply port 5a. The connecting portion 7a is detachably connected to the connecting portion 106a on the ink jet recording apparatus 100 side. The connecting portion 106 a on the ink jet recording apparatus 100 side communicates with the ink transfer tube 102. As a result, the ink jet head 1 can transfer ink from the ink jet recording apparatus 100.

  The common ink chamber 41 is provided with an ink recovery port 5b. The ink recovery port 5b is connected to an ink recovery pipe 51b that forms a flow path for recovering ink from the common ink chamber 41. The ink recovery port 5 b communicates the common ink chamber 41 outwardly above the common ink chamber 41. A connection portion 7b is provided on the upper end side of the ink recovery pipe 51b connected to the ink recovery port 5b. The connecting portion 7b is detachably connected to the connecting portion 106b on the ink jet recording apparatus 100 side. The connection part 106 b on the ink jet recording apparatus 100 side communicates with the ink return pipe 103. As a result, the ink jet head 1 can return ink to the ink jet recording apparatus 100.

  In the inkjet head 1, a flow path from the ink supply port 5a to a buffer space portion 6 to be described later in the middle of the ink recovery pipe 51b is a main flow path F1.

  It is preferable that the ink supply port 5 a and the ink recovery port 5 b are arranged apart from both ends in the longitudinal direction of the common ink chamber 41. In the present embodiment, the ink supply port 5a is disposed at the left end in FIG. 1 on the top surface of the ink manifold 4, and the ink recovery port 5b is on the right end in FIG. Is arranged. Thereby, the ink supplied from the ink supply port 5a to the common ink chamber 41 can be made to flow over the entire inside of the common ink chamber 41 toward the ink recovery port 5b. Accordingly, it is difficult to form a portion where the ink stays in the common ink chamber 41, and bubbles in the ink can be more efficiently eliminated.

  A rectifying plate 41a is provided in the ink manifold 4 as shown in FIG. The rectifying plate 41 a is formed integrally with the ink manifold 4. The rectifying plate 41a changes the flow of ink (main flow path F1) from the ink supply port 5a to the ink recovery port 5b on the upper side in the common ink chamber 41, and is configured as a horizontal plate in this embodiment. Has been. At least a part of the rectifying plate 41 a is disposed in the vicinity of the ink supply port 5 a in the common ink chamber 41. In this embodiment, the rectifying plate 41a is provided at a position extending from the side end of the common ink chamber 41 to directly below the ink supply port 5a. The rectifying plate 41 a does not extend from one end side to the other end side in the common ink chamber 41, and is disposed in only a part of the region in the longitudinal direction in the common ink chamber 41.

  Since at least a part of the rectifying plate 41a is located in the vicinity of the ink supply port 5a, when the ink flows from the ink supply port 5a, the flow rate of the ink is fast, so that the ink flow direction can be easily changed. The rectifying plate 41 a increases the flow rate of ink on the upper side of the common ink chamber 41 so that more ink flows on the upper side of the common ink chamber 41. As the ink flow rate is increased in this way, the residual bubbles in the common ink chamber 41 are quickly moved, and even when the ink pressure difference between the ink supply port 5a side and the ink recovery port 5b side is low, Residual bubbles can be efficiently removed. This rectifying plate 41a exhibits a more remarkable effect especially when the ink supply pressure to the common ink chamber 41 is increased. That is, the ink flow that tends to concentrate on the bottom surface side can be changed to the upper flow in the common ink chamber 41. Since the flow of ink can be changed to the flow on the upper side, a large amount of ink is not discharged from the nozzles.

  In the ink manifold 4, an ink discharge chamber 412 is provided adjacent to the common ink chamber 41. The ink discharge chamber 412 is separated from the common ink chamber 41 by a partition wall 45. The partition wall 45 is formed integrally with the ink manifold 4.

  FIG. 3 is an exploded perspective view schematically showing a head chip portion of the inkjet head.

  A plurality of pressure chambers 23 are formed in the head chip 2 as shown in FIG. These pressure chambers 23 are rectangular through-holes penetrating from the upper surface portion to the lower surface portion of the head chip 2, and the upper end side and the lower end side are open. The head chip 2 has a piezoelectric element corresponding to each pressure chamber 23.

  Each pressure chamber 23 communicates with the common ink chamber 41 through an injection hole 31 a formed in the wiring board 3. The ink in the common ink chamber 41 is injected into each pressure chamber 23 through the injection hole 31a. Each pressure chamber 23 undergoes volume fluctuation by application of a voltage to the piezoelectric element. Further, a nozzle plate 21 having a plurality of nozzles 22 corresponding to the respective pressure chambers 23 is bonded to the lower surface of the head chip 2. The nozzle 22 communicates with the pressure chamber 23 through an opening at the lower end of the pressure chamber 23, and communicates the pressure chamber 23 to the outside (downward). The lower surface portion of the nozzle plate 21 becomes the ink ejection surface 1S. The ink in each pressure chamber 23 is given a discharge pressure by the action of the piezoelectric element, and is discharged toward the external (lower) recording medium through the nozzle 22.

  Any specific means for applying discharge pressure to the ink in the pressure chamber 23 can be used, and any known means can be employed. In this embodiment, the adjacent pressure chambers 23 and 23 are separated by a drive wall 24 formed of a piezoelectric element. In the drive wall 24, a drive voltage of a predetermined voltage is applied to a drive electrode (not shown) formed on a surface facing the pressure chamber 23 from a power supply circuit (not shown) through a wiring pattern (not shown) formed on the FPC board and the wiring board 3. Is deformed by shearing. When the drive walls 24 and 24 on both sides of the pressure chamber 23 are subjected to shear deformation, the internal volume of the pressure chamber 23 expands or contracts. As a result, pressure is applied to the ink in the pressure chamber 23, and the ink is ejected through the nozzle 22.

  The number of the pressure chambers 23 formed in the head chip 2 is not particularly limited. In the head chip 2 shown in the present embodiment, a plurality of pressure chambers 23 are arranged in a plurality of rows along the X direction in FIG. 3 which is the longitudinal direction of the head chip 2.

  In this embodiment, no dummy channel is provided between the pressure chambers 23 and 23, and the adjacent pressure chambers 23 and 23 share one drive wall 24. Therefore, since each pressure chamber 23 cannot be driven (expanded or contracted) independently, so-called three-cycle driving is performed. When two drive walls 24, 24 are provided for each pressure chamber 23 and are formed as both wall portions of each pressure chamber 23, the pressure chamber 23 adjacent to the drive wall 24 constituting one pressure chamber 23 is provided. A gap between the drive wall 24 and the drive wall 24 is a dummy channel. In this case, each pressure chamber 23 can be driven (expanded or contracted) independently.

  An individual communication path 422 is formed at the side of each pressure chamber 23. The individual communication path 422 communicates with the side of the pressure chamber 23 (between the injection hole 31a and the nozzle 22). In the present embodiment, the individual communication path 422 is a groove formed on the upper surface of the nozzle plate 21 corresponding to the nozzle 22, and the head chip 2 is overlaid on the nozzle plate 21 to form a flow path. Yes.

  These individual communication paths 422 communicate with the common flow path 421 and merge with each other. The common flow path 421 is a tunnel formed in the side portion of the head chip 2 in the arrangement direction (X direction) of the pressure chambers 23. The end of the common flow path 421 is in communication with a discharge channel 424 formed in the head chip 2. The discharge channel 424 is formed on one end side in the longitudinal direction of the head chip 2 and is positioned below the ink discharge chamber 412. In this way, each pressure chamber 23 communicates with the exhaust channel 424.

  A part of the ink injected from the injection holes 31 a toward the pressure chambers 23 reaches the common flow path 421 through the individual communication paths 422. Then, the ink that has reached the common flow path 421 passes through the discharge channel 424, passes through the discharge hole 31 b formed in the wiring substrate 3, and reaches the ink discharge chamber 412.

  The individual communication path 422 and the common flow path 421 are not limited to the above modes. It is only necessary to form a flow path from each pressure chamber 23 to the discharge chamber 412 through the individual communication path 422, the common flow path 421, and the discharge channel 424. Therefore, the individual communication path 422 may be provided in, for example, the head chip 2 or a spacer member (not shown) provided between the head chip 2 and the nozzle plate 21. Further, the common flow path 421 may be provided, for example, in the nozzle plate 21 or a spacer member (not shown) provided separately between the head chip 2 and the nozzle plate 21.

  In this ink jet head 1, the nozzles are formed under this condition in consideration of the fact that a flow path from each pressure chamber 23 to each ink discharge chamber 412 through each individual communication path 422 and common flow path 421 is formed. The conditions such as the pressure applied by the transfer pump 105 are determined so that the meniscus break from 22 does not occur.

  As shown in FIGS. 1 and 2, the ink discharge chamber 412 is connected to an ink discharge pipe 51 c that forms a flow path for discharging ink from the ink discharge chamber 412. The upper end side of the ink discharge pipe 51c joins the ink recovery pipe 51b. The ink recovery pipe 51b and the ink discharge pipe 51c are joined together by being connected to the junction box 61.

  The junction box 61 is integrally formed of a synthetic resin material or a metal material, and has a buffer space 6 formed therein. First to third openings 48 a, 48 b, 48 c reaching the buffer space 6 are formed on the outer surface of the junction box 61. The flow path from the first opening 48a through the buffer space 6 to the third opening 48c is interposed in the middle of the ink recovery pipe 51b. In the mounting state, the ink collection pipe 51b is divided into an upstream side and a downstream side in the middle part, the upstream side is connected to the first opening 48a, and the downstream side is connected to the third opening 48c. An ink discharge pipe 51c is connected to the second opening 48b.

  In this inkjet head 1, the flow path from each individual communication path 422 to the buffer space 6 through the common flow path 421, the discharge channel 424, the discharge hole 31b, the ink discharge chamber 412 and the ink discharge pipe 51c is a discharge path. 423. The discharge path 423 is a flow path that communicates with each pressure chamber 23, discharges the ink in each pressure chamber 23, and joins the ink recovery pipe 51 b in the buffer space 6. Then, the passages 423 (the inlets from the individual communication passages 422 to the buffer space 6) through the injection holes 31a become the sub-flow passages F2 (see FIG. 2).

  By the way, since the discharge path 423 is formed as a flow path that passes through all of the individual communication paths 422 corresponding to the pressure chambers 23, the flow path resistance of the discharge path 423 as a whole increases as the pressure chambers 23 increase in density. It is getting bigger. Accordingly, even if the ink discharge pipe 51c is joined to the ink recovery pipe 51b, the flow rate of the main flow path F1 passing through the ink recovery pipe 51b from the ink supply port 5a is large, and the sub flow path F2 extending from each injection hole 31a to the discharge path 423. It is conceivable that they do not merge smoothly because of the low flow rate. In the ink jet head 1, the main flow path F1 and the sub flow path F2 are merged (merge between the ink discharge pipe 51c and the ink recovery pipe 51b) in the buffer space 6, and a flow rate adjusting member 9 described later or By using a suction pump, even if the flow rates of the main flow path F1 and the sub flow path F2 are different, they can be smoothly merged.

  According to the ink jet head 1 and the ink jet recording apparatus 100 including the ink jet head 1 as described above, by simply supplying ink from the ink supply port 5a, residual bubbles in the common ink chamber 41 pass through the main flow path F1 and the ink recovery pipe. It is discharged from 51b. At this time, since the flow rate of the ink on the upper side of the common ink chamber 41 is increased by the action of the rectifying plate 41a, the remaining bubbles in the common ink chamber 41 can be discharged well. Further, in the inkjet head 1, residual bubbles near the pressure chambers 23 can also be discharged from the ink discharge pipe 51c via the sub flow path F2. Therefore, the remaining bubbles in the entire ink manifold 4 (in the common ink chamber 41 and in the vicinity of each pressure chamber 23) can be efficiently removed.

  Further, according to the inkjet head 1 and the inkjet recording apparatus 100 including the inkjet head 1, when the ink is circulated between the ink tanks 101 during image recording, the ink in the vicinity of each pressure chamber 23 is also sublimated. It can be efficiently circulated through the flow path F2. For this reason, air bubbles drawn from the nozzles 22 during image recording can be quickly discharged. In addition, when using ink containing particles or pigments that easily settle, the sedimentation of particles or pigments in the individual communication paths 422 and the common flow path 421 during image recording is effectively suppressed. Ink density deviation can be suppressed.

[Pressure loss adjusting means]
The ink jet head 1 may be provided with pressure loss adjusting means for adjusting the relative relationship between the channel resistance of the main channel F1 and the channel resistance of the sub-channel F2.

  This pressure loss adjusting means applies a pressure loss ΔP corresponding to the difference in flow path resistance between the main flow path F1 and the sub flow path F2 to the main flow path F1. Alternatively, the pressure loss adjusting means reduces the flow resistance of the sub flow path F2 to correspond to the flow resistance of the main flow path F1.

   The channel resistance of the sub-channel F2 is determined by the channel diameter, the channel length, the number of bent portions, the flow velocity, etc. in the entire discharge channel 423 including all the injection holes 31a, all the individual communication channels 422 and the common channel 421. It is channel resistance. Since the individual communication path 422 and the common flow path 421 have a very small flow path diameter and a long flow path length, a large flow resistance is generated.

  In this ink jet head 1, the pressure loss adjusting means balances the flow resistance of the main flow path F1 and the flow resistance of the sub flow path F2 so that the ink pressure P0 in the ink supply pipe 51a can be easily adjusted. Ink can flow equally in both the main flow path F1 and the sub flow path F2.

  An example of the pressure loss adjusting means is shown in FIG. FIG. 4 is a perspective view showing a state in which the ink recovery pipe 51b provided with an example of the pressure loss adjusting means is partially broken.

  As the pressure loss adjusting means, for example, as shown in FIG. 4, a flow rate adjusting member 9 that partially narrows the flow path cross-sectional area of the ink recovery pipe 51b can be used. The flow rate adjusting member 9 is a member that is held in the ink recovery pipe 51b and partially narrows the inner diameter of the ink recovery pipe 51b. The flow rate adjusting member 9 of the present embodiment is integrally configured with a cylindrical portion 95 along the inner wall of the ink recovery pipe 51b and a disk portion 96 that closes one end of the cylindrical portion 95. A flow path hole 94 is formed in the center of the disk portion 96. The flow path of the ink recovery pipe 51b in the portion where the flow rate adjusting member 9 is disposed is only the flow path hole 94. Accordingly, the flow rate adjusting member 9 partially narrows the flow path cross-sectional area of the ink recovery pipe 51b by the flow path hole 94, and causes the pressure of the ink flowing in the ink recovery pipe 51b to be lost.

  The material of the flow rate adjusting member 9 is not particularly limited, and examples thereof include metals such as stainless steel, ceramics, and synthetic resins that are excellent in ink impermeability, easy to be inserted into the ink recovery tube 51b, and excellent in corrosion resistance against ink.

  In addition, by shortening the length of the flow path hole 94 of the flow rate adjusting member 9, it is possible to suppress fluctuations in flow path resistance when bubbles enter the flow path hole 94 and to suppress variations in flow velocity. The length of the flow path hole 94 of the flow rate adjusting member 9 shown in FIG. 4 is, for example, about 0.5 mm. By setting the length of the channel hole 94 to about 0.5 mm, it is possible to suppress variation in channel resistance due to bubbles.

  The pressure loss ΔP applied by the flow rate adjusting member 9 is a pressure loss ΔP corresponding to the difference in flow resistance between the main flow path F1 and the sub flow path F2, and is adjusted by the inner diameter of the flow path hole 94. The pressure loss ΔP balances the flow resistance of the main flow path F1 and the flow resistance of the sub flow path F2. That is, the ink pressure P0 in the ink supply pipe 51a is reduced to the pressure P1 immediately before the buffer space portion 6 of the main flow path F1, and becomes substantially equal to the pressure P2 immediately before the buffer space portion 6 of the sub flow path F2. . Further, the ink pressure P0 in the ink supply pipe 51a is substantially equal to the pressure applied by the transfer pump 105. The pressure P2 in the sub flow path F2 is set to be smaller than the pressure Px at which the meniscus break occurs so that the meniscus break from the discharge nozzle 22 does not occur. That is, [P1 = (P0−ΔP) = P2 <Px]. As a result, the ink pressure P0 in the ink supply pipe 51a allows the ink to flow evenly in both the main flow path F1 and the sub flow path F2.

  The ink pressure P0 can be measured by a manometer at the tip of the ink supply pipe 51a provided with a T-shaped branch. The pressure P1 can be measured with a manometer at the tip of the ink recovery pipe 51b (downstream from the flow rate adjusting member 9, upstream from the buffer space 6) where a T-shaped branch is provided. The pressure P2 can be measured with a manometer at the point where the ink discharge pipe 51c (upstream from the buffer space 6) is provided with a T-shaped branch.

  The specific inner diameter of the flow path hole 94 of the flow rate adjusting member 9 is determined so that the pressure loss of the ink recovery pipe 51b is a desired pressure loss in consideration of pressure loss due to pressure loss elements such as the individual communication path 422 and the common flow path 421. It adjusts suitably so that it may become. For example, the flow rate of the flow rate adjusting member 9 is set so that the ink flow rate recovered from the ink recovery tube 51b and the ink flow rate discharged from the ink discharge tube 51c through the individual communication paths 422 and the common flow path 421 are uniform. By adjusting the inner diameter of the passage hole 94, it is possible to make the ink flow evenly in both the main flow path F1 and the sub flow path F2. Accordingly, ink can be quickly stored in the ink storage chamber 41 (main flow path F1), the pressure chambers 23, the individual communication paths 422, and the common flow path 421 (sub-flow path F2). In particular, this is a preferred embodiment at the initial introduction of ink.

  By adjusting the inner diameter of the flow path hole 94 of the flow rate adjusting member 9, the ink flow rate (main flow path F1) recovered from the ink recovery pipe 51b and the ink discharge through each individual communication path 422 and the common flow path 421. The flow rate of ink discharged from the tube 51c (sub-flow path F2) can be made different. For example, the flow path resistance of the flow rate adjusting member 9 is increased, and the ink discharge pipe 51c passes through the individual communication paths 422 and the common flow path 421 rather than the ink flow rate (main flow path F1) recovered from the ink recovery pipe 51b. By increasing the discharged ink flow rate (sub-flow path F2) (increasing the flow rate of the sub-flow path F2), it is possible to more easily remove bubbles that are attached around the pressure chamber 23 and are difficult to remove. Conversely, the flow resistance of the flow rate adjusting member 9 can be lowered to increase the flow rate in the main flow path F1 (increase the flow rate of the main flow path F1) than in the sub flow path F2. In this case, it is possible to easily remove bubbles adhering to the ceiling surface and corners in the main channel F1. Further, in this case, even when a damper member (MF (Manifold) damper member) located above the pressure chamber 22 is provided in the ink manifold 4, bubbles easily remaining around the damper member are easily removed. can do.

  The flow rate adjusting member 9 may be provided in the junction box 61. If the flow rate adjusting member 9 is held in the junction box 61 in advance, a desired pressure loss can be applied to the ink recovery pipe 51b simply by interposing the junction box 61 to the ink recovery pipe 51b. Further, when it is desired to change or replace the flow rate adjusting member 9, the entire junction box 61 can be replaced, so that quick and easy replacement can be performed. Furthermore, even when foreign matter adheres to the vicinity of the flow rate adjusting member 9 and is contaminated, the neat state can be achieved quickly and easily by replacing the junction box 61.

  The ink discharge pipe 51c may be provided with a check valve 8 as shown in FIGS. The check valve 8 functions to allow ink to flow out from the ink discharge chamber 412 toward the buffer space 6 and to block the flow of ink in the opposite direction. For example, when the individual communication paths 422 and the common flow path 421 are clogged by contaminants contained in the ink and the pressure P2 of the sub flow path F2 decreases, the pressure P1 of the main flow path F1 in the common ink chamber 41 decreases. A pressure difference occurs between them. In this case, the ink recovered from the ink recovery tube 51b may flow back to the ink discharge tube 51c through the buffer space 6. By providing the check valve 8 in the ink discharge pipe 51c, it is possible to prevent air bubbles and impurities from returning to the common flow path 421 and the individual communication paths 422 due to the back flow of ink.

  Since the check valve 8 is also one of the pressure loss elements, the check valve cracking pressure (valve opening pressure) should be low, and the pressure Px (for example, about 5 kPa) at which the meniscus break from the nozzle 22 occurs. Must be low. Further, in order to reliably prevent meniscus breakage from the nozzle 22, the ink return pipe 103 is not pressurized by the transfer pump 105 (rather than the buffer space 6 between the ink recovery pipe 51b and the discharge flow path 423). A suction pump may be provided (on the downstream side), and the ink may be circulated only by the negative pressure generated by the suction pump.

  In the inkjet recording apparatus 100 of the embodiment described above, ink is circulated between the inkjet head 1 and the ink tank 101, but the present invention is not limited to this. Although not shown, the ink flowing out from the ink recovery pipe 51b and the ink discharge pipe 51c may be discharged to the waste ink tank without returning to the ink tank 101. The same applies to the case where an inkjet head 1 according to another embodiment described later is used.

[Other Embodiments of Rectification Plate]
FIG. 5 is a longitudinal sectional view of an essential part showing another embodiment of the current plate of the ink jet head.

  As shown in FIG. 5A, in the inkjet head 1, it is also preferable that the rectifying plate 41a is provided with the tip side inclined upward. In addition, if the front end side which is a part is arrange | positioned in the vicinity of the supply port 5a, the base end side may be separated from the supply port 5a. In this case, the ink that has flowed from the ink supply port 5a is blocked by the straightening flow path 41a by the straightening flow path 41a, changes its path toward the front end side of the straightening flow chart 41a, and the straightening flow chart 41a is inclined, so that the common ink It flows toward the upper side in the chamber 41. Accordingly, the upper ink flow rate in the common ink chamber 41 is increased and the flow velocity is increased, so that residual bubbles are efficiently discharged. Further, it is more preferable that the rectifying plate 41 a has a shape that guides the ink flowing from the ink supply port 5 a to the upper side of the central portion in the common ink chamber 41. For example, it is preferable that the rectifying plate 41 a is provided so as to be inclined so that the tip side is directed toward the upper side of the central portion in the common ink chamber 41. In this case, the ink that has flowed from the ink supply port 5 a flows toward the upper side of the central portion in the common ink chamber 41. Accordingly, since the flow path is wider than the vicinity of the ink supply port 5a and the vicinity of the ink recovery port 5b, the flow rate becomes slow and the ink flow rate near the center where bubbles tend to remain can be increased. Can be discharged.

  Further, the rectifying plate 41a may have a curved surface portion that follows the flow of ink in the common ink chamber 41, as shown in FIG. The rectifying plate 41a has a curved surface portion corresponding to the desired path in order to change the path of the ink flowing from the ink supply port 5a to the desired path. By providing a curved surface portion on the rectifying plate 41a, the ink path can be changed to a desired path without narrowing the flow path. By using this rectifying plate 41a, the ink flowing in from the ink supply port 5a is blocked by the straightening flow path by the rectifying plate 41a, and changes its path along the curved surface portion toward the front end side of the rectifying plate 41a. It flows toward the upper side of the central portion in the ink chamber 41. Accordingly, the upper ink flow rate in the common ink chamber 41 is increased and the flow velocity is increased, so that residual bubbles are efficiently discharged.

  FIG. 6 is a longitudinal sectional view of an essential part showing another embodiment of the rectifying plate of the ink jet head.

  As shown in FIG. 6, the rectifying plate 41 a may be provided on a damper member (MF (Manifold) damper) 81 that is a pressure damping means. The damper member 81 is disposed on the bottom surface of the common ink chamber 41 and is located above each pressure chamber 22. The damper member 81 buffers the pressure wave generated by the deformation of the pressure chamber 22 and returning to the common ink chamber 41, thereby preventing the pressure wave from affecting other pressure chambers 22 (crosstalk). . The rectifying plate 41 a protrudes integrally with the upper surface plate of the damper member 81. As described above, the rectifying plate 41a is inclined (see FIG. 6A) toward the upper side of the central portion of the common ink chamber 41, but is horizontal (FIG. 6B). Also good. In the inkjet head 1, it is possible to efficiently remove bubbles that are likely to remain around the damper member 81.

[Other Embodiments of Inkjet Head]
A plurality of discharge paths 423 may be provided in the ink manifold 4 as shown in FIG. FIG. 7 is a schematic configuration diagram showing a main part of another example of the ink jet recording apparatus according to the present invention, and shows a partial cross section of the ink jet head. Since the site | part of the same code | symbol as FIG. 1 is a site | part of the same structure, these description uses the said description and abbreviate | omits here.

  In the present embodiment, partition walls 45 and 45 are provided on one side and the other side in the longitudinal direction of the head chip 2 in the ink manifold 4, and two ink discharge chambers 412 and 412 are provided on both sides of the ink storage chamber 41. . Then, one and the other two discharge paths 423 and 423 that pass through the ink discharge chambers 412 and 412 are provided. One discharge path 423 is the same as the discharge path 423 in the above-described embodiment. The other discharge path 423 can also be configured similarly to the discharge path 423 in the above-described embodiment.

  That is, as described above, one ink discharge tube 51c that forms a flow path for discharging ink from the ink discharge chamber 412 is connected to one ink discharge chamber 412. Similarly, the other ink discharge chamber 412 is also provided with the other ink discharge pipe 51 c that forms a flow path for discharging ink from the ink discharge chamber 412.

  Then, the upper ends of the ink discharge pipes 51c and 51c are joined to the ink recovery pipe 51b, respectively. Each of the ink discharge pipes 51c and 51c and the ink recovery pipe 51b can be joined together by connecting to the junction box 61 as in the above-described embodiment.

First to fourth openings 48 a, 48 b, 48 c, 48 d reaching the buffer space 6 are formed on the outer surface of the junction box 61. The third through the buffer space 6 from the first opening 48a.
The flow path leading to the opening 48c is interposed in the middle of the ink recovery pipe 51b. In the mounting state, the ink collection pipe 51b is divided into an upstream side and a downstream side in the middle part, the upstream side is connected to the first opening 48a, and the downstream side is connected to the third opening 48c. One ink discharge pipe 51c is connected to the second opening 48b. The other ink discharge pipe 51c is connected to the fourth opening 48d.

  In the present embodiment, the discharge paths 423 and 423 are divided from the respective injection holes 31a through the respective pressure chambers 23 to one side and the other side in the longitudinal direction of the head chip 2, and the discharge holes 31b and 31b on both sides and the both sides are arranged. This is a path for ink to reach the buffer space 6 through the discharge channels 424 and 424. That is, the ink that reaches the common flow path 421 from the pressure chamber 23 is divided into one side and the other side in the longitudinal direction of the head chip 2, and reaches the discharge holes 31b and 31b through the discharge channels 424 and 424, respectively. The ink reaching the respective discharge holes 31b and 31b passes through the discharge holes 31b and 31b, passes through one and the other ink discharge chambers 412 and 412, and reaches one and the other ink discharge pipes 51c and 51c.

  When a plurality of discharge paths 423 are provided in this way, each pressure chamber 23 having a short distance to the discharge hole 31b can be increased, so that the flow path resistance of the entire discharge path 423 can be kept low. The channel resistance of the channel F2 can be kept low.

  FIG. 8 is a longitudinal sectional view of an essential part showing another embodiment of the rectifying plate of the inkjet head.

  As shown in FIG. 8, the rectifying plate 41 a in this embodiment is integrally connected to the common ink chamber 41 through a partition wall (vertical wall portion) 45. That is, the partition wall 45 and the rectifying plate 41 a that separate the common ink chamber 41 and the ink discharge chamber 412 are integrally connected to each other, and these are integrally connected to the common ink chamber 41. Since the partition wall 45 and the rectifying plate 41a are integrally connected to the common ink chamber 41, it is easy to manufacture and the rigidity and durability of the rectifying plate 41a can be improved.

  FIG. 9 is a longitudinal sectional view showing another embodiment of the current plate of the ink jet head.

  Two or more rectifying plates 41a may be arranged in the common ink chamber 41, and FIG. 9 is an example in which two rectifying plates 41a and 41b are arranged. In the common ink chamber 41, as shown in FIG. 9, the rectifying plate 41a described above is provided as the first rectifying plate 41a, and further, the second rectifying plate 41b is provided. The second rectifying plate 41b is located substantially at the center in the longitudinal direction in the common ink chamber 41, and is an inclined flat plate in which the upstream side of the ink flow in the common ink chamber 41 is located below and the downstream side is raised upward. It is formed in a shape. The second rectifying plate 41 b can be integrally provided in the common ink chamber 41.

  By this second rectifying plate 41b, the flow of ink bounced back against the ceiling surface of the common ink chamber 41 can be returned to the upper side again. Accordingly, the ink flow rate on the upper side of the common ink chamber 41 can be increased, and the flow velocity can be increased. Therefore, the residual bubbles above the common ink chamber 41 are efficiently discharged. When the common ink chamber 41 is elongated, it is preferable to further increase the number of second rectifying plates 41b according to the length of the common ink chamber 41. By increasing the number of the second rectifying plates 41b, the flow rate of the ink above the common ink chamber 41 can be maintained, and the residual bubbles above the common ink chamber 41 are efficiently discharged.

  FIG. 10 is a longitudinal sectional view showing another embodiment of the current plate of the inkjet head.

  As shown in FIG. 10, the partition wall 45 on the ink collection port 5 b side gradually collects ink from the bottom surface of the common ink chamber 41 in accordance with the direction of ink flow from the common ink chamber 41 toward the ink collection port 5 b. You may incline so that the mouth 5b may be approached.

  In each embodiment described above, the common ink chamber 41 may have the ceiling surface inclined with respect to the horizontal plane. That is, the ceiling surface is inclined so that the ink recovery port 5b is higher than the ink supply port 5a. Due to this inclination, the residual bubbles in the common ink chamber 41 move to the higher side along the ceiling surface, that is, to the ink recovery port 5b side. Can be discharged.

  FIG. 11 is a longitudinal sectional view showing an embodiment in which a filter is provided inside the common ink chamber.

  As shown in FIG. 11, a filter 71 may be provided inside the common ink chamber 41. The filter 71 is horizontally provided in the common ink chamber 41 at substantially the same height as the tip of the rectifying plate 41a, and divides the common ink chamber 41 into an upper side and a lower side. Unlike the rectifying plate 41 a, the filter 71 extends from one end side to the other end side in the common ink chamber 41. When the ink flowing from the upper side to the lower side in the common ink chamber 41 is transmitted, the filter 71 removes bubbles, sedimented particles, pigments, and the like contained in the ink. In this inkjet head 1, since the flow velocity of the ink on the upper side of the filter 71 is increased by providing the rectifying plate 41 a, the residual bubbles on the upper side of the filter 71 are efficiently discharged, and the nozzle 22 Fine bubbles generated by the filter 71 at the time of bubble entrainment can also be removed.

  FIG. 12 is a perspective view showing an embodiment in which an external filter is provided.

  As shown in FIG. 12, an external filter 72 can be used as a filter. The external filter 72 is installed outside the ink manifold 4 and in the middle of the ink collection pipe 51b so that the ink collected from the ink collection port 5b can pass therethrough. The ink that passes through the external filter 72 is freed of bubbles, precipitated particles, pigments, and the like contained in the ink, and returned to the ink tank 101.

[Common ink chamber embodiment]
FIG. 13 is an exploded perspective view of a common ink chamber of the inkjet head.

  In the inkjet head 1, the common ink chamber 41 can be configured by abutting and joining a first member 91 and a second member 92 as shown in FIG. 13. The first and second members 91 and 92 are integrally formed of a synthetic resin material.

  The first member 91 is provided with at least an ink supply port 5a and an ink recovery port 5b. The first member 91 has a flat canopy plate 93 that serves as a canopy portion of the common ink chamber 41, and an ink supply port 5 a and an ink recovery port 5 b are provided on both ends of the canopy plate 93. .

  The second member 92 is provided with at least a pressure chamber mounting portion 4a and a current plate 41a. Further, the second member 92 has a space portion that becomes the common ink chamber 41, and a rectifying plate 41 a is provided in the space portion. The open lower end of the space serving as the common ink chamber 41 is the pressure chamber mounting portion 4a. The second member 92 is provided with an ink discharge chamber 412 and an ink discharge pipe 51c.

  The first and second members 91 and 92 are abutted and joined to form the ink manifold 4, and a common ink chamber 41 is formed in the ink manifold 4.

  In this embodiment, the ink discharge chamber 412 and the ink discharge pipe 51c are provided on both sides of the ink manifold 4, respectively. That is, the discharge paths 423 and 423 are divided into one side and the other side in the longitudinal direction of the head chip 2 from the injection holes 31a through the pressure chambers 23, and the discharge holes 31b and 31b on both sides and the discharge channels 424 on both sides. It becomes an ink path to the buffer space 6 through 424. Accordingly, the ink that reaches the common flow path 421 from each pressure chamber 23 is divided into one side and the other side in the longitudinal direction of the head chip 2, and reaches the discharge holes 31b and 31b through the discharge channels 424 and 424, respectively. The ink reaching the respective discharge holes 31b and 31b passes through the discharge holes 31b and 31b, passes through one and the other ink discharge chambers 412 and 412, and reaches one and the other ink discharge pipes 51c and 51c.

  When a plurality of discharge paths 423 are provided in this way, the distance from each pressure chamber 23 to the discharge hole 31b can be shortened, so that the flow path resistance of the entire discharge path 423 can be kept low, and the side flow The flow path resistance of the path F2 can be kept low.

  The above-described embodiment is an example in which the inkjet head according to the present invention is configured as a shear mode head, but the present invention is not limited thereto, and any inkjet head having a common ink chamber in which bubbles can remain may be used. It can be applied to various inkjet heads.

1: Inkjet head 2: Head chip 21: Nozzle plate 22: Nozzle 23: Pressure chamber 24: Drive wall 24a: Piezoelectric element 3: Wiring board 31a: Injection hole 31b: Discharge hole 31c: Individual discharge hole 4: Ink manifold 41: Common ink chamber 412: Ink discharge chamber 421: Common flow path 422: Individual communication path 423: Discharge path 424: Discharge channel 45: Partition 46: Communication path 47: Separator 5a: Ink supply port 5b: Ink recovery port 51a: Ink Supply pipe 51b: Ink recovery pipe 51c: Ink discharge pipe 6: Buffer space 61: Junction box 71: Filter 72: External filter 8: Check valve 81: Damper member 9: Flow rate adjusting member F1: Main flow path F2: Subflow Path 100: Inkjet recording apparatus 101: Ink tank 102: Ink transfer pipe 103: In Return pipe 104: Control unit 105: Transfer pump

Claims (12)

A common ink chamber;
An ink supply port formed in the common ink chamber and communicating with a flow path for supplying ink to the common ink chamber;
An ink recovery port formed in the common ink chamber and communicating with a flow path for recovering ink from the common ink chamber;
At least one pressure chamber that communicates with the common ink chamber via an injection hole and causes a volume variation by application of a voltage;
A nozzle communicating with the pressure chamber and serving as a flow path for ink discharged from the pressure chamber to the outside;
A rectifying plate that changes the flow of ink from the ink supply port to the ink recovery port on the upper side in the common ink chamber,
At least a part of the current plate is disposed in the vicinity of the ink supply port in the common ink chamber.   2. The ink jet head according to claim 1, further comprising a discharge passage communicating with the pressure chamber and discharging ink in the pressure chamber.   3. The ink jet head according to claim 1, wherein the baffle plate has a shape for guiding the ink flowing in the vicinity of the ink supply port to the upper side of the central portion in the common ink chamber.   The inkjet head according to claim 1, wherein two or more of the current plates are arranged in the common ink chamber.   5. The common ink chamber has a ceiling surface inclined with respect to a horizontal plane, and the ink recovery port is higher than the ink supply port. 6. The inkjet head as described.   The inkjet head according to claim 1, wherein the rectifying plate is integrally connected to the common ink chamber via a vertical wall portion.   The ink jet head according to claim 1, wherein the current plate has a curved surface portion that follows the flow of the ink in the common ink chamber.   The inkjet head according to claim 1, further comprising a filter inside the common ink chamber.   The inkjet head according to claim 1, wherein the rectifying plate is provided in a pressure attenuating unit disposed in the common ink chamber. The common ink chamber butt-joins at least a first member provided with the ink supply port and the ink recovery port and at least a second member provided with the mounting portion of the pressure chamber and the current plate. The ink jet head according to claim 1, wherein the ink jet head is configured as described above. The inkjet head according to any one of claims 1 to 10,
An ink tank for storing ink transferred to the common ink chamber of the inkjet head;
An ink jet recording apparatus comprising: an ink transfer unit that transfers ink in the ink tank to the common ink chamber. An inkjet head according to any one of claims 2 to 10;
An ink tank for storing ink transferred to the inkjet head;
An ink transfer unit for transferring the ink in the ink tank to the inkjet head and collecting the ink transferred to the inkjet head;
The ink discharged from the pressure chamber through the discharge path is merged with the ink collected from the ink jet head.

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