JP4946354B2 - Inkjet head and inkjet printer - Google Patents

Description

The present invention relates to an inkjet head and an inkjet printer .

  2. Description of the Related Art Conventionally, ink jet printers that record predetermined images by ejecting ink onto recording media such as paper and plastic thin plates have been proposed and put into practical use. The ink jet printer includes an ink jet head having nozzles, and records a predetermined image on the recording medium by ejecting ink from the nozzles toward the recording medium while moving the ink jet head in a predetermined direction. .

  Incidentally, the ink used in the ink jet printer may be supplied from the ink supply container to the head on the carriage through the ink supply tube.

  In this ink supply mechanism, since the carriage on which the head is mounted is scanned, the ink pressure supplied to the head varies due to acceleration / deceleration and vibration. In that case, there is a problem that the ink meniscus position of the nozzle of the head is shifted, resulting in uneven density, or in the worst case, the meniscus is broken and discharge becomes impossible.

  In addition, as a conventional solution to such a phenomenon, a damper is disposed upstream of the head as shown in Patent Documents 1, 6, and 7, and pressure fluctuation during ink supply is reduced. There is something to absorb. However, if there is a pipe between the damper and the head, there is a problem that the ink supply pressure fluctuates slightly due to mechanical vibration or acceleration / deceleration.

  For this reason, conventionally, there is a head provided with a damper function in order to prevent such a slight pressure fluctuation (see, for example, Patent Documents 2 to 5 and 8).

Japanese Patent Application Laid-Open No. H10-260260 discloses a device having a damper function by providing an air chamber having a sealed structure in a common ink chamber of a head. Patent Document 3 discloses a laminated head having a damper function using a thin plate. Patent Document 4 discloses that a groove is formed in a common ink chamber of a head and separated from an air chamber by a film to have a damper function. Patent Document 5 discloses a gas holding chamber formed adjacent to a common ink chamber of a head, and a bubble function is accumulated by electrolysis to provide a damper function. Patent Document 8 discloses a biochip head that can form a miniaturized pressure chamber when ink in a reservoir of the head is in contact with air.
JP 2000-158868 A JP 2001-130004 A JP 2004-114415 A JP 7-137262 A JP-A-7-323548 Japanese Patent Laid-Open No. 10-193646 JP-A-11-34349 JP 2004-226321 A

  As disclosed in Patent Documents 2, 3, and 4, it is possible to reliably prevent outflow of air from the air chamber by interposing a member such as a film at the interface between the air chamber and the ink. However, such a configuration requires new parts and manufacturing processes, and requires a special design due to the complicated structure, which may increase costs and reduce reliability.

  Further, in the structure in which air and ink are brought into contact with each other to form a gas-liquid interface as disclosed in Patent Documents 5 and 8, it is not easy to stably keep air in such a place. This causes a problem that the suction operation for preventing the clogging of the ink disappears.

  In particular, when air is introduced into the common ink chamber, since the air is not fixed in the common ink chamber and can move freely, it often enters the pressure chamber and often prevents ink ejection. There arises a problem that the air that has entered is exhausted.

  Further, the structure as disclosed in Patent Document 5 in which a gas holding chamber is formed adjacent to the common ink chamber of the head and air bubbles are accumulated by electrolysis to replenish air is complicated. In addition, complicated control such as timing for generating bubbles by electrolysis is required. Furthermore, there is also a problem that oil-based inks that do not generate gas by electrolysis do not function.

The object of the present invention is to solve the above-mentioned problems and to absorb the fluctuation of the ink supply pressure by the air chamber and maintain the ejection stability, and to easily discharge the air from the air chamber. It is an object of the present invention to provide an ink jet head that can be effectively prevented with a simple structure and an ink jet printer including the ink jet head.

The problems of the present invention are solved by the following configurations.
1.
An inkjet head chip having an ejection surface having a nozzle row and an ink supply port continuous with each nozzle on one side surface adjacent to the ejection surface ;
A manifold having a common ink chamber formed on one side of the inkjet head chip where the ink supply port is provided, and having a common ink chamber that guides ink to the ink supply port of the inkjet head chip;
A first ink flow path for guiding ink from the outside to the common ink chamber of the manifold ,
An inkjet head that records an image on the recording medium by being scanned along a main scanning direction orthogonal to the conveyance direction of the recording medium ,
A second ink channel branched from the middle of the first ink channel;
Arranged on the other side of the inkjet head chip adjacent to the ejection surface, connected to the second flow path, and supplied with ink from the second flow path, thereby containing air inside. And an air chamber that absorbs a change in pressure of the ink generated when the ink jet head is scanned and moved by a change in volume of the air .
2.
In the inkjet head according to 1 above,
An ink jet head, wherein a side surface of the ink jet head chip forms a part of a wall surface forming the air chamber.
3.
An inkjet head chip having an ejection surface having a nozzle row and an ink supply port continuous with each nozzle on both side surfaces adjacent to the ejection surface;
Two manifolds respectively disposed on both sides of the inkjet head chip where the ink supply port is provided, each having a common ink chamber formed to guide ink to the ink supply port of the inkjet head chip;
A first ink flow path for guiding ink from outside to the common ink chamber of the manifold,
An inkjet head that records an image on the recording medium by being scanned along a main scanning direction orthogonal to the conveyance direction of the recording medium,
A second ink channel branched from the middle of the first ink channel;
Each of the manifolds is disposed on a side opposite to the inkjet head chip, and is connected to the second flow path and supplied with ink from the second flow path, thereby containing air inside. And an air chamber that absorbs the pressure change of the ink generated when the ink jet head is moved by the volume change of the air .
4).
In the inkjet head according to any one of 1 to 3 ,
The ink jet head, wherein the first ink flow path includes an ink supply chamber, and the second ink flow path is branched from the ink supply chamber.
5.
In the inkjet head according to any one of 1 to 4 ,
The connecting portion of the second ink flow path and the air chamber, characterized in that said at wall surface forming the air chamber is formed at a position closer to the nozzle side of the ink supply port of said ink jet head chip An inkjet head.
6).
In the ink jet head according to any one of 1 to 5 ,
The inkjet head according to claim 1, wherein a resistance of the second ink flow path is smaller than a resistance of an ink flow path that constitutes a part of the first ink flow path and connects the branch portion and the manifold.
7).
A carriage on which the inkjet head according to any one of 1 to 6 is mounted;
Conveying means for conveying the recording medium along the sub-scanning direction;
Moving means for scanning and moving the carriage along a main scanning direction perpendicular to the conveyance direction of the recording medium;
An ink jet printer that performs image recording by discharging ink from the ink jet head onto the recording medium in the course of scanning movement of the carriage.

According to the present invention, since the second ink flow path branched from the middle of the first ink flow path that guides ink from the outside to the manifold and connected to the air chamber is provided, a gas-liquid interface is formed in the air chamber. By holding the air, it is possible to absorb the pressure fluctuation of the ink transmitted to the manifold when ink is ejected, and to stabilize the air in the air chamber during maintenance operation by ink suction operation from the nozzle. Therefore, the air chamber can absorb fluctuations in ink supply pressure and maintain ejection stability, and can effectively prevent the air from flowing out of the air chamber with a simple structure. It is possible to provide an inkjet head that can be used and an inkjet printer including the inkjet head.

  An embodiment of the present invention will be described below with reference to the drawings. However, the following is one embodiment of the present invention and does not limit the present invention.

  First, an overall configuration of an ink jet printer according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is an overall configuration diagram of an ink jet printer according to an embodiment of the present invention.

  The ink jet printer 1 ejects ink onto a recording medium P and records an image on the recording medium P. The ink jet printer 1 includes a transport unit (not shown), and the transport unit transports the recording medium P in the sub-scanning direction orthogonal to the main scanning direction A while passing through the recording area C in FIG. ing.

  Above the recording area C, a carriage rail 2 extending along the main scanning direction A is arranged. A carriage 3 guided by the carriage rail 2 is movably provided on the carriage rail 2. Yes.

  The carriage 3 is mounted with an inkjet head 4 that ejects ink onto the recording medium P, and moves in the direction of arrow A from the home position area B to the maintenance area D along the carriage rail 2.

  During this main scanning, the inkjet head 4 ejects ink d toward the recording medium P to form an image on the recording medium P. The ink jet head 4 is installed vertically so that the ink ejection direction from the nozzles is vertically downward.

  In the ink jet printer 1 according to the present embodiment, a total of four ink jet heads 4 are arranged in the carriage 3 so that four colors of ink of black (K), yellow (Y), magenta (M), and cyan (C) can be ejected. Is installed. In FIG. 1, three inkjet heads 4, 4, 4 are arranged in a line in the direction of arrow A, and the back of the inkjet head 4 at the center of the inkjet heads 4, 4, 4 aligned in the direction of arrow A is shown. Another ink jet head 4 (not shown) is arranged on the side (the back side in the direction perpendicular to the paper surface).

  Each of these inkjet heads 4 is connected to an ink tank 5 for storing black, yellow, magenta, and cyan inks via an ink supply pipe 6. That is, the ink in the ink tank 5 is supplied to each inkjet head 4 by the ink supply pipe 6.

  In the maintenance area D, a maintenance unit 7 that performs maintenance on the inkjet head 4 is provided. The maintenance unit 7 includes a plurality of suction caps 8 for covering the discharge surface 41a of the inkjet head 4 and sucking ink in the nozzles, a cleaning blade 9 for wiping off ink adhering to the discharge surface 41a, and an inkjet head. An ink receiver 10 that receives ink ejected from 4, a suction pump 11, and a waste ink tank 12 are provided.

  The suction cap 8 communicates with the waste ink tank 12 via the suction pump 11 and is raised during the maintenance operation so as to cover the ejection surface 41a of the inkjet head 4. Four suction caps 8, 8,... Are arranged so as to correspond to the respective ink-jet heads 4 so as to cover the ejection surfaces 41a of all the ink-jet heads 4 when raised as described above.

  The suction pump 11 includes a cylinder pump and a tube pump, and operates in a state where the suction cap 8 covers the discharge surface 41a. A suction force for suction is generated.

  In the present embodiment, a tube pump shown in FIG. As shown in FIG. 5, the suction pump 11 includes a tube 30, a pressure roller 32, two pressure rollers 33 and 34, and a tube holder 31. The suction side opening at the upper end of the tube 30 is connected to the suction cap 8. The discharge side opening at the lower end of the tube 30 is inserted into the waste ink tank 12. The intermediate portion of the tube 30 is corrected and held in a shape bent into an arc shape along the outer periphery of the pressure roller 32 so as to be sandwiched between the tube holder 31 and the pressure roller 32.

  The two pressure rollers 33 and 34 are attached to the outer periphery of the pressure roller 32. The two pressure rollers 33 and 34 protrude from the outer peripheral surface of the pressure roller 32 in the radial direction of the pressure roller 32 and are rotatably mounted. The two pressure rollers 33 and 34 are attached to each other at a position of 180 degrees around the central axis of the pressure roller 32. On the other hand, the tube holder 31 is formed so as to correct the tube 30 over an angle greater than 180 degrees, for example, about 210 degrees around the central axis of the pressure roller 32. The above angle is an example, and it is effective for providing a suction force to provide a period in which the tube 30 is simultaneously crushed by the two pressure rollers 33 and 34. Three or more pressure rollers may be provided. When three or more pressure rollers are provided, it is effective in order to exert a suction force that two of the pressure rollers are crushed at the same time during the rotation of the pressure roller 32.

  Now, the two pressure rollers 33 and 34 revolve with the rotation of the pressure roller 32. The two pressure rollers 33 and 34 move while crushing the tube 30 when passing through a portion of the tube 30 that has been corrected in the arc shape. After the pressure rollers 33 and 34 pass, the tube 30 is restored to its original shape due to its elasticity.

  The pressure roller 32 is driven by a motor (not shown) and rotates around its central axis. That is, the pressure roller 32 rotates and the distance from the tube holder 31 is constant during rotation.

  In order to exert the suction force, the pressure roller 32 is rotated in the direction of arrow E. When the pressure roller 32 is rotated in the direction of arrow E, the pressure rollers 33 and 34 revolve in the same direction of arrow E, and the position where the pressure rollers 33 and 34 crush the tube 30 moves. In this embodiment, the output of the suction pump 11 is controlled by adjusting the rotation speed of the pressure roller 32.

  In the home position area B, a moisturizing unit 13 for moisturizing the inkjet head 4 is provided. The moisturizing unit 13 is provided with four moisturizing caps 14 that moisturize the ink of the ink jet head 4 by covering the ejection surface 41a when the ink jet head 4 is in a standby state. These four moisturizing caps 14, 14,... Are arranged corresponding to the arrangement of the inkjet heads 4 so as to simultaneously cover the ejection surfaces 41a of the four inkjet heads 4.

  The control unit is configured to include a CPU (Central Processing Unit) and a memory, and controls each component of the inkjet printer 1. The memory stores image data to be formed on the recording medium P and a program for controlling each component of the inkjet printer 1, and controls each component based on the image data and program in the memory. A signal is transmitted.

  Next, the inkjet head 4 according to the present invention will be described with reference to FIGS.

  FIG. 2 is an exploded perspective view of the inkjet head 4 of the present embodiment, and FIG. 3 is a side view of the inkjet head 4 of the present embodiment. FIG. 4 is a schematic diagram showing the connection between the air chamber and manifold of the inkjet head 4 of this embodiment and the ink supply chamber.

  The inkjet head 4 of the present embodiment is provided with an inkjet head chip (hereinafter referred to as “head chip”) 41 that ejects ink. The head chip 41 has a long outer shape in the arrow X direction, and a large number of nozzles 42 are arranged in the arrow X direction on the discharge surface (tip surface) 41a. The row of nozzles 42 provided continuously in the arrow X direction is referred to as a nozzle row 42a. The inkjet head 4 of the present embodiment is provided with one nozzle row 42a. The inkjet head 4 is mounted on the carriage 3 so that the arrow X direction (nozzle row direction) and the main scanning direction A shown in FIG.

  As shown in FIG. 3, an ink supply port 43 is provided on one side surface of the head chip 41, and the ink supply port 43 and the nozzle 42 are connected via an ink flow path 44 formed inside the head chip 41. And are to continue. A part of the ink flow path 44 forms a pressure chamber, and has a structure in which an ink droplet is ejected from the nozzle 42 by changing the pressure by the action of a piezoelectric element (not shown).

  One manifold 48 that is connected to the ink supply port 43 and guides ink from the outside to the head chip 41 is bonded and fixed to one side of the head chip 41. The manifold 48 is made of a material excellent in ink resistance, and has a recess for forming the common ink chamber 480. An ink flow path 481 for allowing ink to flow into the common ink chamber 480 is integrally provided at one end of the manifold 48.

  In addition, an ink heater 49 is provided on the side of the manifold 48 between the manifold 48 and the housing frame 53 so as to contact the manifold 48 as shown in FIG. The ink heater 49 is provided to heat the ink introduced into the common ink chamber 480 of the manifold 48 to a predetermined temperature.

  Further, an adhesive is filled between the manifold 48 and the housing frame 53 so as to include at least the ink heater 49, whereby the housing frame 53, the ink heater 49, and the manifold 48 are bonded and fixed. Yes.

  In order to stabilize the ink pressure applied to the ink jet head 4, an air chamber forming member 58 is installed on the opposite side of the manifold 48 with the head chip interposed therebetween. The air chamber forming member 58 is made of a material excellent in ink resistance, and has a recess for forming the air chamber 580. An ink channel 581 (corresponding to the second ink channel in the present embodiment) for allowing ink to flow into the air chamber 580 is integrally provided at one end of the air chamber forming member 58.

  A manifold 48, an air chamber forming member 58, and a holding plate 51 that holds the head chip 41 are attached to the lower portion of the head chip 41 so that the discharge surface 41a is exposed. The ink supply chamber 52 that holds the ink flow path 481 of the manifold 48 and the ink flow path 581 of the air chamber forming member 58 at one end of the holding plate 51 and flows ink to the ink flow path 481 and the ink flow path 581. Is formed. The ink supply chamber 52 is disposed on one end side of the head chip 41 in the nozzle row direction, and is connected to the ink flow path 481 and the ink flow path 581. A connecting portion between the ink flow path 581 and the air chamber 580 is formed at a position closer to the nozzle 42 side than the ink inlet side of the head chip 41 on the wall surface forming the air chamber 580.

  Ink from the ink supply pipe 6 enters the ink supply chamber 52 through the frame ink flow path 55, and an ink flow path 481 that connects the ink supply chamber 52 and the manifold 48, an ink flow path that connects the ink supply chamber 52 and the air chamber 580. Branches to 581. The ink that has passed through the ink flow path 481 is supplied to the head chip 41 from the ink supply port 43 through the common ink chamber 480. The ink that has passed through the ink flow path 581 is supplied to the air chamber 580. When the ink 500 is filled from the frame ink channel 55, the air 501 is contained in the air chamber 580. In the actual use state, as shown in FIG. 4, when the nozzle 42 is on the lower side, the ink 500 is filled up to a predetermined height of the air chamber 580, and the air 501 is confined in the upper part thereof.

  In the present embodiment, the frame ink flow path 55, the ink supply chamber 52, and the ink flow path 481 that connects the ink supply chamber 52 and the manifold 48 constitute a first ink flow path. The ink supply chamber 52 that serves as an ink reservoir may not be provided.

  The air chamber 580 is branched from the first ink channel that guides ink from the outside to the manifold 48 by the ink channel 581, and the outflow of the air 501 from the air chamber 580 to the inkjet head chip 41 is suppressed. .

  Further, the connection portion between the ink flow path 581 and the air chamber 580 is formed at a position closer to the nozzle 42 side than the ink inlet side of the head chip 41 on the wall surface forming the air chamber 580, thereby changing the ink discharge direction. When placed vertically so as to be vertically downward, the air 501 can be easily held on the upper portion of the air chamber 580, and in particular, the air 501 is maintained during the suction of ink from the nozzles in the maintenance process described above. It is easy and preferable.

  The ink pressure change that occurs when the inkjet head 4 moves is transmitted from the ink flow path 581 of the air chamber forming member 58 to the air chamber 580 and is absorbed by the volume change of the air 501, and the ink pressure in the inkjet head 4. Is suppressed to such a small change that does not affect the ink ejection characteristics. In order to further improve the pressure absorption performance, the resistance of the ink flow path 581 that connects the ink supply chamber 52 and the air chamber 580 is greater than the resistance of the ink flow path 481 that connects the ink supply chamber 52 and the manifold 48. It is preferable to make it small. In order to reduce the resistance of the channel, the channel cross-sectional area may be increased.

  In this embodiment, in the configuration in which the manifold 48 is disposed on one side of the head chip 41, the air chamber 580 is disposed on the other side of the head chip 41, and the side surface of the head chip 41 is Since a part of the wall surface forming the air chamber 580 is formed, it is possible to reduce the size of the ink-jet head, and the vibration of the piezoelectric element of the head chip 41 during ink discharge causes the liquid in the air chamber 580 (ink 500). This is a preferable mode in which vibration can be absorbed and vibrations can be prevented from being transmitted to the outside.

  A head drive substrate 46 that transmits a control signal from the control unit to each piezoelectric element (not shown) of the head chip 41 is connected via a flexible wiring board 47. A heater circuit for supplying power to the ink heater 49 is formed on the head drive board 46, and a heating wire of the ink heater 49 is electrically connected to the heater circuit via an electric wire 50. Has been. Similarly, the temperature sensor 45 for detecting the temperature is electrically connected to the heater circuit by an electric wire (not shown). The temperature sensor 45 is disposed closer to the head chip 41 than the ink heater 49.

  The head drive board 46 is provided with a connector 461, to which an output terminal 62 of a flexible wiring board 60 having an input terminal 61 and an output terminal 62 is connected. A power source and a control unit (not shown) are electrically connected to the input terminal 61 of the flexible wiring board 60, and a control signal and power are supplied to the head drive substrate 46 via the flexible wiring board 60. It is like that.

  As shown in FIG. 2, the ink-jet head 4 is attached with the components of the ink-jet head 4 such as the head chip 41, the manifold 48, the air chamber forming member 58, the head driving substrate 46, and the holding plate 51, and accommodated therein. A fixed housing frame 53 and a cover 54 covering the housing frame 53 are provided. The casing frame 53 is provided with a frame ink channel 55 that supplies ink by being connected to the ink supply chamber 52 of the holding plate 51, and the ink supply pipe 6 is connected to the frame ink channel 55. It has come to be. A support beam 56 that supports the head drive substrate 46 is provided inside the housing frame 53.

  An opening 57 is provided in the upper part of the cover 54, and the input terminal 61 of the flexible wiring board 60 is exposed to the outside from the opening 57 after the ink jet head 4 is assembled.

  Next, the operation at the time of image formation by the inkjet printer 1 will be described.

  When the power of the ink jet printer 1 is turned on, power is supplied to each part of the ink jet printer 1.

  Thereafter, when an image recording start instruction is input, the carriage 3 starts reciprocating scanning, and the control unit transmits a control signal based on the image data to the head driving substrate 46 and other driving units. Start image recording. On the recording medium P conveyed to the conveying means, ink is ejected from the inkjet head 4 to form an image.

  When the maintenance timing for recovering the ejection state of the inkjet head 4 is reached, the control unit controls each unit to perform maintenance of the inkjet head 4. More specifically, the control unit controls the scanning motor in accordance with the maintenance timing, and moves the carriage 3 to a position where the inkjet head 4 and the suction cap 8 face each other. When the inkjet head 4 and the suction cap 8 face each other, the control unit controls the lifting motor to raise the maintenance unit 7 until the ejection surface 41a of the inkjet head 4 and the suction cap 8 are in close contact with each other.

  After completion of raising the maintenance unit 7, the control unit controls the suction pump 11 so that the inside of the suction cap 8 is sucked for a predetermined time.

  Here, with reference to FIG. 5, the movement form of the ink and the air in the maintenance process by suction of the inkjet head of this embodiment will be described.

  Due to the operation of the suction pump 11, the inside of the inkjet head 4 becomes negative pressure. The ink flow path 581 on the upstream side of the air chamber 580 also becomes negative pressure, and the ink stored in the air chamber 580 flows out from the ink flow path 581.

  At this time, the air 501 in the air chamber 580 expands, and the gas-liquid interface M between the ink 500 and the air 501 is drawn toward the ink flow path 581.

  In the ink jet head of the prior art, the ink is filled in the common ink chamber and the air is held in a normal use state, and the air held in the manifold is maintained during the maintenance operation for sucking the ink from the nozzle. In some cases, the ink may be discharged and replaced with ink. In such a case, as described above, the pressure fluctuation cannot be absorbed, and there is a possibility that the stable ejection may be disturbed.

  In the ink jet head according to the present embodiment, an ink flow path 581 that branches from the middle of the first ink flow path that guides ink from the outside to the manifold 48 and is connected to the air chamber 580 is provided. Since the air 501 can be stably held in the air chamber 580 during the maintenance operation, the outflow of the air 501 from the air chamber 580 can be effectively prevented with a simple structure.

  Further, the connection portion between the ink flow path 581 and the air chamber 580 is formed at a position closer to the nozzle 42 side than the ink inlet side of the head chip 41 on the wall surface forming the air chamber 580, thereby changing the ink discharge direction. When placed vertically so as to face vertically downward, the air 501 can be easily held on the upper portion of the air chamber 580, and the air 501 can be easily maintained when ink is sucked from the nozzles in the maintenance process.

  In FIG. 5, the distance between the gas-liquid interface M before suction and the air chamber upper wall surface is H1, the maximum distance between the gas-liquid interface M and air chamber upper wall surface during suction is H2, and the connecting portion of the ink flow path 581. If the suction pressure and H3 are set so that H2 is smaller than H3 when the distance between the upper end of the air chamber and the upper wall surface of the air chamber is H3, the outflow of the air 501 inside the air chamber 580 during suction is prevented. Is preferable because it is more reliable.

  When the negative pressure acting on the ink 500 in the air chamber 580 during suction is P1 (atmospheric pressure), the pressure of the air 501 is 1 (atmospheric pressure), so the relationship 1 / P1 = H2 / H1 is established. Therefore, as a guideline for setting, for example, if P1 is 0.5 (atmospheric pressure), H2 is twice H1, so that H3 may be set larger than this.

  For example, the air chamber forming member 58 is made of a translucent member so that the gas-liquid interface M in the air chamber can be visually confirmed, and experimentally, the suction pressure or H3 is set so that H2 becomes smaller than H3. Should be set.

  Next, the effect of absorbing pressure fluctuation during image recording will be described.

  First, the following experiment was performed before recording using the inkjet head 4.

  The inkjet head 4 provided with the air chamber 580 by the air chamber forming member 58 shown in FIGS. 2 to 4 and the inkjet head in the case of only the manifold 48 without the air chamber 580 are mounted on the inkjet printer 1 shown in FIG. When the head was reciprocated in the same manner as in actual use and the pressure fluctuation generated at the nozzle portion of the head was measured, it was as shown in FIG.

  In FIG. 6, the change of the pressure in the nozzle at the time of scanning is represented. The horizontal axis is time, and the vertical axis is the pressure P in the nozzle. The dotted line indicates the measurement data for the head without the air chamber 580, and the solid line indicates the measurement data for the head with the air chamber 580.

  Normally, pressure fluctuations occur due to acceleration during reciprocating scanning of the carriage, but (a) negative pressure in the nozzles occurs in the direction in which the inkjet head pulls the ink supply pipe during reciprocating scanning of the carriage. Further, (b) positive pressure is generated in the direction in which the ink jet head pushes the ink supply pipe during reciprocating scanning of the carriage.

  When there is no air chamber 580, the pressure change of about 2 kPa was shown on the negative pressure side and the positive pressure side corresponding to the above (a) and (b), whereas when the air chamber 580 was provided, There was almost no pressure change, and there was no problem in practical use.

  Even in actual image recording, the inkjet head 4 of the present embodiment was capable of stable ejection and was able to maintain a good recording state. On the other hand, the ink jet head in the case of only the manifold 48 without the air chamber 580 could not maintain a good recording state due to instability of ejection due to pressure fluctuation.

  Next, FIG. 7 shows another embodiment of the present invention. This example is different from the above-described embodiment in the following points. In the inkjet head 400 of the present embodiment, two nozzle rows 42a are provided.

  As shown in FIG. 7, ink supply ports 43 are provided on both side surfaces of the head chip 41, and the ink supply ports 43, the nozzles 42, and the like are connected via an ink flow path 44 formed inside the head chip 41. Has become continuous. A part of the ink flow path 44 forms a pressure chamber, and has a structure in which an ink droplet is ejected from the nozzle 42 by changing the pressure by the action of a piezoelectric element (not shown).

  Two manifolds 48 that are connected to the ink supply port 43 and guide the ink from the outside to the head chip 41 are bonded and fixed to both sides of the head chip 41. An ink flow path 481 for allowing ink to flow into the common ink chamber 480 is integrally provided at one end of the manifold 48.

  In order to stabilize the ink pressure applied to the ink jet head 400, two air chamber forming members 58 are installed on the side portions of the two manifolds 48.

  Ink from the ink supply pipe 6 enters the ink supply chamber 52 through the frame ink flow path 55, and the two ink flow paths 481, the ink supply chamber 52, and the two air chambers 580 connecting the ink supply chamber 52 and the two manifolds 48. Branches into two ink flow paths 581 connecting the two. The ink that has passed through the ink flow path 481 is supplied from the ink supply port 43 to the head chip 41 via the common ink chamber 480. The ink that has passed through the ink flow path 581 is supplied to the air chamber 580. When the ink 500 is filled from the frame ink channel 55, the air 501 is contained in the air chamber 580. In the actual use state, as shown in FIG. 7, the ink 500 is filled up to a predetermined height of the air chamber 580, and the air 501 is confined in the upper portion thereof.

  The air chamber 580 is branched from the first ink flow path that guides ink from the outside to the manifold 48 by the ink flow path 581, and the outflow of the air 501 from the air chamber 580 to the inkjet head chip 41 is suppressed. .

  The ink pressure change generated when the ink jet head 400 moves is transmitted from the ink flow path 581 of the air chamber forming member 58 to the air chamber 580 and absorbed by the volume change of the air 501, and the ink pressure in the ink jet head 400 is changed. Is suppressed to such a small change that does not affect the ink ejection characteristics. In order to further improve the pressure absorption performance, the resistance of the ink flow path 581 that connects the ink supply chamber 52 and the air chamber 580 is greater than the resistance of the ink flow path 481 that connects the ink supply chamber 52 and the manifold 48. It is preferable to make it small. In order to reduce the resistance of the flow path, the flow path cross section may be enlarged.

  Each of the two head drive substrates 46 that transmits a control signal from the control unit to each piezoelectric element (not shown) of the head chip 41 is connected via a flexible wiring board 47. A heater circuit for supplying power to the ink heater 49 is formed on the head drive board 46, and a heating wire of the ink heater 49 is electrically connected to the heater circuit via an electric wire 50. Has been. Similarly, the temperature sensor 45 for detecting the temperature is electrically connected to the heater circuit by an electric wire (not shown). The temperature sensor 45 is disposed closer to the head chip 41 than the ink heater 49.

  The two head drive boards 46 are each provided with a connector 461, and the output terminals 62 of the flexible wiring board 60 having one input terminal 61 and two output terminals 62 are connected to these connectors 461, respectively. Has been. A power source and a control unit (not shown) are electrically connected to the input terminal 61 of the flexible wiring board 60, and a control signal and power are supplied to the head drive substrate 46 via the flexible wiring board 60. It is like that.

  As described above, according to the ink jet head of the present embodiment, the ink jet head includes the second ink channel that branches from the middle of the first ink channel that guides the ink from the outside to the manifold and is connected to the air chamber. In addition, air can be held by forming a gas-liquid interface in the air chamber, and the pressure fluctuation of the ink transmitted to the manifold can be absorbed by the air when ink is ejected, and the maintenance operation by the ink suction operation from the nozzle Since air can be stably held in the air chamber at times, the air chamber can absorb fluctuations in ink supply pressure, maintain ejection stability, and prevent air from flowing out of the air chamber. An ink jet head that can be effectively prevented with a simple structure can be provided.

  The ink jet head and the ink jet printer according to the present invention are not limited to the above-described embodiments, and can be applied to other configurations.

  The ink jet head of the present invention can be applied not only to a so-called serial print type ink jet printer in which the head described above moves, but also to a line print type ink jet printer in which a large number of nozzles are arranged in parallel.

  In addition, the inkjet head is not limited to the configuration including the piezoelectric element in the head chip, and may be configured to include a heater, for example.

  Further, the shape and positional relationship of the manifold and the air chamber can be changed as appropriate.

  For example, in another embodiment of FIG. 7, the configuration in which the air chamber 580 is provided on each of the two manifold sides in the inkjet head 400 having two manifolds 48 has been described as an example. One air chamber 580 may be provided in any one of the manifolds 48, not necessarily.

  Furthermore, in the embodiment of FIG. 2, the air chamber 580 may be provided on the side of the manifold 48.

1 is a plan view illustrating an outline of an inkjet printer according to an embodiment of the present invention. 1 is an exploded perspective view of an inkjet head according to an embodiment of the present invention. It is a side view of the ink jet head concerning one embodiment of the present invention. It is a schematic diagram which shows the connection state of the air chamber and manifold of an inkjet head which concerns on one Embodiment of this invention, and an ink supply chamber. FIG. 5 is a schematic diagram for explaining a movement mode of ink and air in a maintenance process by suction of an inkjet head according to an embodiment of the present invention. It is a graph which shows the pressure fluctuation in the nozzle position in the inkjet head of this invention, and the conventional inkjet head. It is a side view of the inkjet head which concerns on other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet printer 4,400 Inkjet head 41 Head chip (inkjet head chip)
41a Discharge surface (tip surface)
42 Nozzle 42a Nozzle row 48 Manifold 49 Ink heater 53 Housing frame P Recording medium X Nozzle row direction

Claims (7)

An inkjet head chip having an ejection surface having a nozzle row and an ink supply port continuous with each nozzle on one side surface adjacent to the ejection surface ;
A manifold having a common ink chamber formed on one side of the inkjet head chip where the ink supply port is provided, and having a common ink chamber that guides ink to the ink supply port of the inkjet head chip;
A first ink flow path for guiding ink from the outside to the common ink chamber of the manifold ,
An inkjet head that records an image on the recording medium by being scanned along a main scanning direction orthogonal to the conveyance direction of the recording medium ,
A second ink channel branched from the middle of the first ink channel;
Arranged on the other side of the inkjet head chip adjacent to the ejection surface, connected to the second flow path, and supplied with ink from the second flow path, thereby containing air inside. And an air chamber that absorbs a change in pressure of the ink generated when the ink jet head is scanned and moved by a change in volume of the air . The inkjet head according to claim 1 ,
An ink jet head, wherein a side surface of the ink jet head chip forms a part of a wall surface forming the air chamber. An inkjet head chip having an ejection surface having a nozzle row and an ink supply port continuous with each nozzle on both side surfaces adjacent to the ejection surface;
Two manifolds respectively disposed on both sides of the inkjet head chip where the ink supply port is provided, each having a common ink chamber formed to guide ink to the ink supply port of the inkjet head chip;
A first ink flow path for guiding ink from outside to the common ink chamber of the manifold,
An inkjet head that records an image on the recording medium by being scanned along a main scanning direction orthogonal to the conveyance direction of the recording medium,
A second ink channel branched from the middle of the first ink channel;
Each of the manifolds is disposed on a side opposite to the inkjet head chip, and is connected to the second flow path and supplied with ink from the second flow path, thereby containing air inside. And an air chamber that absorbs the pressure change of the ink generated when the ink jet head is moved by the volume change of the air . The inkjet head according to any one of claims 1 to 3 ,
The ink jet head, wherein the first ink flow path includes an ink supply chamber, and the second ink flow path is branched from the ink supply chamber. The inkjet head according to any one of claims 1 to 4 ,
The connecting portion of the second ink flow path and the air chamber, characterized in that said at wall surface forming the air chamber is formed at a position closer to the nozzle side of the ink supply port of said ink jet head chip An inkjet head. The inkjet head according to any one of claims 1 to 5 ,
The inkjet head according to claim 1, wherein a resistance of the second ink flow path is smaller than a resistance of an ink flow path that constitutes a part of the first ink flow path and connects the branch portion and the manifold. A carriage on which the inkjet head according to any one of claims 1 to 6 is mounted;
Conveying means for conveying the recording medium along the sub-scanning direction;
Moving means for scanning and moving the carriage along a main scanning direction perpendicular to the conveyance direction of the recording medium;
An ink jet printer that performs image recording by discharging ink from the ink jet head onto the recording medium in the course of scanning movement of the carriage.

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