JP5397053B2 - Inkjet recording device - Google Patents

Description

  The present invention relates to an ink jet recording apparatus.

  2. Description of the Related Art Conventionally, ink jet recording apparatuses that record a predetermined image by ejecting ink onto a recording medium such as paper or a plastic thin plate have been proposed and put into practical use. The ink jet recording apparatus includes an ink jet head having nozzles (hereinafter sometimes referred to as a head), and ejects ink from the nozzle toward the recording medium while moving the ink jet head in a predetermined direction. A predetermined image is recorded on the recording medium.

  Incidentally, ink used in the ink jet recording apparatus may be supplied from an ink supply container to a head on a carriage through an 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 for such a phenomenon, a configuration in which a damper is arranged upstream of the head as shown in Patent Document 1 absorbs pressure fluctuations during ink supply. is there.

  Patent Document 1 discloses an ink jet recording apparatus in which an air chamber is provided in an ink inflow conduit and an ink outflow conduit to a head to provide a damper function.

  In addition, there is one in which an air chamber is disposed inside the head to provide a damper function (for example, see Patent Documents 2 to 4).

  Patent Document 2 discloses an ink jet head provided with a damper function by providing a plurality of air chambers adjacent to a common ink chamber of the head and holding gas inside. Patent Document 3 discloses an inkjet head having an air chamber that holds a gas that adjoins a common ink chamber of the head and absorbs pressure fluctuations transmitted through the ink in the common ink chamber. Patent Document 4 discloses an ink jet head having an air chamber that is adjacent to a common ink chamber of the head and communicates with the air port and an open / close valve that opens and closes the air port.

Japanese Patent Application Laid-Open No. 11-10911 JP-A-9-136415 JP-A-6-344558 JP 2006-315360 A

  However, in the structure in which air and ink are brought into contact with each other as disclosed in Patent Documents 1 to 3, it is not easy to stably keep air in such a place. Thus, there is a problem that the stable discharge is hindered by losing the effect of absorbing pressure fluctuations.

  In order to cope with such a problem, a throttle channel having a channel cross-sectional area smaller than that of the air chamber is provided, and an ink meniscus serving as a gas-liquid interface between ink and air flowing from the ink supply channel is formed in the throttle channel. Accordingly, it is possible to increase the holding force of the ink meniscus while securing the volume of the air chamber, and it is possible to suppress the outflow of air.

  However, since air is compressed when a purge operation is performed to pressurize the ink in the ink supply path, the ink meniscus moves from the inside of the restricting flow path to the air chamber side and enters the air chamber, and pressurizes. It was found that a part of the air remains even after the air pressure is returned, and the amount of air in the air chamber decreases due to the repetition of the purge operation, which causes a problem in stable discharge.

  None of the patent documents describes the invasion of ink into the air chamber by the purge operation, and there is no disclosure about the influence of this on the absorption effect of the pressure fluctuation.

  As disclosed in Patent Document 4, it is possible to reliably prevent ink from entering the air chamber by interposing a member such as an on-off valve at the interface between air and 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.

  The object of the present invention is to solve the above-mentioned problems, and to suppress the reduction of air from the air chamber due to the purge operation with a simple structure, and to reduce the supply pressure of the ink by the air held in the air chamber. An object of the present invention is to provide an ink jet recording apparatus capable of reducing fluctuations and improving ejection stability.

  The problems of the present invention are solved by the following configurations.

1. An inkjet head that ejects ink in the pressure chamber;
An ink supply path for supplying ink from an ink supply source to the pressure chamber of the inkjet head;
An air chamber capable of holding air;
One or more throttle channels having a smaller channel cross-sectional area than the air chamber;
Pressurizing means for pressurizing and discharging the ink in the ink supply path from the inkjet head,
The air chamber communicates with the ink supply path through the throttle channel,
The air in the throttle channel and the air in the throttle channel when the ink is pressurized by the pressurizing means in a state where a gas-liquid interface between ink and air flowing from the ink supply channel is formed. the amount of volume change, Ri total volume der following air in the throttle channel immediately before pressurized the pressurized,
At least a part of the ink supply path is constituted by an ink supply pipe;
The ink jet recording, wherein the air chamber and the throttle channel are formed between an air holding member inserted in a state where ink can communicate with the inside of the ink supply pipe and an inner surface of the ink supply pipe. apparatus.

  2. 2. The volume ratio of the air chamber to the total volume of the throttle channel is set so that the volume change amount of the air is equal to or less than the total volume of air of the throttle channel. Inkjet recording apparatus.

  3. 2. The ink jet recording apparatus according to 2, wherein the volume ratio is 1 or less.

  4). 3. The ink jet recording apparatus according to 2, wherein the volume ratio is 0.5 or less.

5. 3. The ink jet according to 1 or 2, wherein the pressure of the ink in the ink jet head when pressed by the pressurizing unit is 1.5 × 10 ⁵ Pa or more and 1.5 × 10 ⁶ Pa or less. Recording device.

6 . The ink jet recording apparatus according to any one of claims 1 to 5 , wherein a material of the air holding member is stainless steel.

7 . The ink jet recording apparatus according to any one of claims 1 to 5 , wherein a material of the air holding member is PTFE (polytetrafluoroethylene).

8 . An ink jet recording apparatus according to any one of claim 1 to 7, wherein the surface tension of the ink is 20 to 40 mN / m.

  According to the present invention, a decrease in air from the air chamber due to the purge operation can be suppressed with a simple structure, and fluctuations in ink supply pressure can be mitigated by the air held in the air chamber, thereby improving ejection stability. An ink jet recording apparatus that can be improved can be provided.

1 is a front view showing an outline of an ink jet recording apparatus according to an embodiment of the present invention. It is a block diagram of the ink supply system which concerns on embodiment of this invention. It is a disassembled perspective view of the inkjet head which concerns on embodiment of this invention. 1 is a perspective view of an inkjet head according to an embodiment of the present invention. 1A and 1B are schematic views of an air holding member according to an embodiment of the present invention, in which FIG. 1A is an enlarged perspective view, and FIG. is there. 4A and 4B are schematic views of an air holding member according to another embodiment of the present invention, in which FIG. 5A is an enlarged perspective view, and FIG. 5B is a perspective view illustrating a state where an ink supply pipe in which the air holding member is inserted is attached to an inkjet head. FIG.

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

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

  The ink jet recording apparatus 1 records ink on the recording medium P by ejecting ink onto the recording medium P. The ink jet recording apparatus 1 includes a transport unit (not shown). The transport unit transports the recording medium P in the sub-scanning direction orthogonal to the main scanning direction A while passing the recording area C in FIG. It has become.

  Above the recording area C, a carriage rail 2 extending along the main scanning direction A (horizontal direction) is arranged, and a carriage 3 guided by the carriage rail 2 is movable on the carriage rail 2. Is provided.

  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. In the present embodiment, the inkjet head 4 is installed such that main scanning is performed in the horizontal direction and the ink ejection direction from the nozzles is downward in the vertical direction.

  In the ink jet recording apparatus 1 according to the present embodiment, a total of four ink jet heads 4 are arranged on the carriage so as to eject ink of four colors of black (K), yellow (Y), magenta (M), and cyan (C). 3 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 ink jet head 4 is connected to an ink tank 5 for storing ink of each color of black, yellow, magenta and cyan by an ink supply pipe 6. Although not shown in FIG. 1, an intermediate tank 306, a pressurizing pump 314, etc. (see FIG. 2) are interposed between each ink jet head 4 and each ink tank 5, and the intermediate tank 306 is a carriage. 3 is installed.

  As shown in FIG. 2, ink is supplied to the inkjet head 4 from the intermediate tank 306 through an ink supply path inside the ink supply pipe 6. Details of the configuration of the ink supply system will be described later. In the present embodiment, the intermediate tank 306 functions as an ink supply source.

  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 caps 8 for covering the discharge surface 41S of the inkjet head 4 and receiving ink discharged from the nozzles by a purge operation, and a cleaning blade 9 for wiping off ink adhering to the discharge surface 41S. An ink receiver 10 for receiving ink ejected from the inkjet head 4 and a waste ink tank 12 are provided.

  The purge operation refers to an operation of recovering the ejection characteristics by discharging ink from the nozzles of the inkjet head 4 under pressure, for example, by discharging deteriorated ink or foreign matter in the inkjet head 4. Details of the purge operation will be described later.

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

  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 41S 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 41S of the four inkjet heads 4.

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

  Next, an ink supply system of the ink jet recording apparatus according to the present invention will be described with reference to FIG.

  FIG. 2 is a block diagram of an ink supply system of the black (K) ink jet head 4 among the four color ink jet heads 4 of black (K), yellow (Y), magenta (M), and cyan (C) of the present embodiment. FIG. In addition, since it is the same structure also about the inkjet head 4 of another color, these description is abbreviate | omitted.

  The inkjet head 4 is connected to the intermediate tank 306 by the ink supply pipe 6, and ink is supplied from the intermediate tank 306.

  The intermediate tank 306 is connected to the ink tank 5 via a valve 311 and a pressure pump 312. Further, the air can be communicated with the atmosphere via the valve 313. Further, it is connected to a pressurizing pump 314 via a valve 315. The pressure pump 314 functions as a purge unit.

  The back pressure of the inkjet head 4 is preferably determined by the intermediate tank 306. Below the ink tank 5, an intermediate tank 306 made of a flexible bag or a container having an air communication valve 313 as in this embodiment is provided via a valve 311 and a pressure pump 312. If the air communication valve 313 is opened and the valve 311 is closed, the ink in the intermediate tank 306 becomes atmospheric pressure. By placing the intermediate tank below the inkjet head 4 by a predetermined height, the ink in the head becomes a negative pressure by a predetermined water head value relative to the atmospheric pressure, and stable ejection can be realized.

  The remaining amount detection or empty detection is provided in the intermediate tank, and when the amount falls below a predetermined amount, the valve 311 is opened and the pressure pump 312 is operated to replenish ink from the ink tank 5 to the intermediate tank 306. If the intermediate tank 306 is not refilled even after a predetermined time has elapsed since the valve 311 was opened and the pressure pump 312 was operated, it can be detected that the ink tank 5 is empty.

  Compared to determining the back pressure directly at the position of the ink tank 5, there are advantages such as no influence of back pressure fluctuation due to fluctuations in the remaining amount of ink and empty detection of the ink tank 5. When the ink tank 5 is replaced, the replacement of the ink tank 5 and the image forming operation can be performed in parallel without interrupting the image forming operation with the ink remaining in the intermediate tank 306.

  In addition, a purge operation is necessary to stably eject ink. For this purpose, the intermediate tank 306 is connected to a pressure pump 314 via a valve 315. The pressurizing pump 314 functions as a pressurizing unit of the present invention.

  The pressurizing pump 314 includes a cylinder pump and a tube pump. The pressure pump 314 is operated with the cap 8 covering the discharge surface 41S and with the valve 315 opened to push out deteriorated ink and foreign matter in the inkjet head 4 from the nozzles of the inkjet head 4 together with the ink. Generate a pressure of.

  The valve 315 is closed except when the purge operation is performed, and when the purge operation is performed, the valve 315 is opened and the pressurizing pump 314 is operated so that the deteriorated ink and foreign matter together with the ink are put into the cap 8. Can be discharged.

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

  FIG. 3 is an exploded perspective view of the black (K) ink-jet head 4 of the four-color ink-jet heads 4 of black (K), yellow (Y), magenta (M), and cyan (C) according to this embodiment. FIG. 4 is a perspective view of the assembled state. In addition, since it is the same structure also about the inkjet head 4 of another color, these description is abbreviate | omitted.

The inkjet head 4 of the present embodiment is provided with two inkjet head chips (hereinafter referred to as “head chips”) 41 that discharge ink. The head chip 41 has a long outer shape, and a large number of nozzles (not shown) are arranged on the discharge surface 41S. (Hereinafter, the arrangement of nozzles is referred to as a “nozzle row”.)
The inkjet head 4 of the present embodiment is provided with two nozzle rows. 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.

  Thus, the head chip 41 is provided with a plurality of nozzles and a plurality of pressure chambers provided corresponding to the plurality of nozzles arranged in the arrow X direction. In the head chip 41, a surface extending along the arrangement direction of the pressure chambers is referred to as a side surface.

  In addition, a substantially rectangular ink supply port 43 is provided on the outer surface of each of the two stacked head chips 41, and the ink supply port 43 and the nozzle are formed in the head chip 41. It communicates via a discharge channel (not shown). A part of the ink discharge flow path forms a pressure chamber, and the pressure is changed by the action of a piezoelectric element (not shown) to discharge ink droplets from the nozzles. In the head chip 41, two sets of head drive substrates 46 and connectors 57 that transmit control signals from the control unit to the piezoelectric elements are connected to the piezoelectric elements via flexible wiring boards 47. ing.

  Two sets of manifolds 48 a and 48 b for supplying ink from the outside to the head chips 41 are attached to both sides of the two head chips 41. The manifolds 48a and 48b are made of a material excellent in ink resistance, and are formed with recesses for forming the common ink chambers 50a and 50b. At one end portions of the manifolds 48a and 48b, injection ports 481a and 481b through which ink flows into the common ink chambers 50a and 50b are provided.

  Reference numeral 60 denotes a cylindrical ink supply connection portion which is an ink introduction port attached to the side portion of the housing frame 54 and connected to the ink supply pipe 6, and a connecting portion 56 communicating with the injection ports 481a and 481b. Connected to.

  The connecting portion 56 is a U-shaped plate-like member, and a cylindrical connecting portion connected to the ink supply connecting portion 60 is provided on the side portion, and engages with the side portion of the housing frame 54. An ink supply path is formed inside.

  As shown in FIG. 2, a manifold 48a, a manifold 48b, and a holding plate 53 for holding the head chip 41 are attached to the lower portion of the head chip 41 so that the nozzle surface is exposed.

  Further, the inkjet head 4 is provided with a housing frame 54 to which the components of the inkjet head 4 such as the head chip 41, the manifold 48a, the manifold 48b, the head drive substrate 46, and the holding plate 53 are attached and fixed. The housing frame 54 is covered with a cover 52. A connector support portion 55 is attached to the upper portion of the housing frame 54.

  Next, the ink flow path when ink is introduced will be described.

  When ink is supplied from the intermediate tank 306 via the ink supply pipe 6, the ink first passes through the ink supply path 59 of the ink supply connecting portion 60 and flows into the connecting portion 56 in the inkjet head 4. The manifold 48a and the manifold 48b branch to the injection ports 481a and 481b and enter the common ink chambers 50a and 50b. The ink reaching the common ink chambers 50 a and 50 b enters the head chip 41 from the ink supply port 43.

  In order to stabilize the ink pressure applied to the ink jet head 4 as described above, an air chamber communicating with the ink supply path is provided, and between the ink supply path and the air chamber, a gas liquid of ink and air flowing from the ink supply path is provided. In this embodiment, an air holding member is inserted into the ink supply pipe 6 that connects the intermediate tank 306 and the inkjet head 4, and the inner surface of the ink supply pipe 6 is connected to the inner surface of the ink supply pipe 6. An air chamber and a throttle channel are formed between the air holding member.

  In the present embodiment, since the intermediate tank 306 is mounted on the carriage 3, the influence of fluctuations in ink pressure when the carriage 3 accelerates or decelerates can be suppressed. However, vibrations generated during carriage travel, motors, and pumps can be suppressed. Ink pressure fluctuation due to external vibration such as the above cannot be suppressed and density unevenness occurs, so an air chamber is provided as a countermeasure.

  With reference to FIG. 5, the air chamber and the throttle channel according to the present invention will be described.

  FIG. 5A is an enlarged perspective view of the air holding member 20A of this embodiment, and FIG. 5B shows the ink supply pipe 6 in which the air holding member 20A is inserted as the ink supply connecting portion of the inkjet head 4. FIG. 6 is a perspective view schematically showing a place where ink 26 is supplied after being attached to 60.

  As shown in FIG. 5B, an air holding member 20A is inserted into the ink supply pipe 6, and an air chamber 21 and a throttle channel are provided between the inner surface of the ink supply pipe 6 and the air holding member 20A. 22 is formed. As a result, the air held in the air chamber can alleviate fluctuations in the ink supply pressure due to external vibrations of the motor, pump, etc., carriage scanning, etc., and improve ejection stability.

  In addition, the air chamber and the throttle channel can be formed by simply inserting the air holding member into the ink supply pipe, and the ink supply pipe and the inkjet head can be used as they are, so that the air chamber and the throttle can be used without greatly changing the configuration of the inkjet recording apparatus. The flow path can be provided easily and at low cost.

  Specifically, the air holding member 20 </ b> A has a large-diameter portion 23 whose outer peripheral surface is in contact with the inner peripheral surface of the ink supply pipe 6, and is located closer to the pressure chamber than the large-diameter portion 23 and is integrated with the large-diameter portion 23. A small diameter portion 24 in which an annular air chamber 21 formed between the ink supply tube 6 and the inner peripheral surface of the ink supply tube 6 can be formed, and an inner surface of the ink supply tube 6 located on the pressure chamber side of the small diameter portion 24. The second large-diameter portion 29 is in contact with the second large-diameter portion 29.

  The second large-diameter portion 29 has ten groove portions 30 extending along the axial direction of the ink supply tube 6 on a part of the outer peripheral surface that contacts the inner surface of the ink supply tube 6. An air chamber 21 is formed between the small-diameter portion 24 and the throttle channel 22 is formed between the ten groove portions 30. The flow passage cross-sectional area (the cross-sectional area of the cross section perpendicular to the axial direction of the ink supply pipe) is smaller in each throttle flow path 22 than in the air chamber 21.

  A gas-liquid interface M between the ink 26 and air is formed in each throttle channel 22, and air is held in the entire air chamber 21 and a part of the throttle channel 22.

  The outer diameter of the second large diameter portion 29 is formed substantially the same as the outer diameter of the large diameter portion 23.

  Here, the inner diameter and the outer diameter mean the diameter when the shape is a circle, and when the shape is not a circle, the inner diameter and the outer diameter correspond to the diameter when the area is converted into a circle. Or the shape of a small diameter part and a large diameter part is not limited to circular.

  In this way, one air chamber 21 filled with air is provided, and the air chamber 21 has ten communication portions 101 through which substantially rectangular parallelepiped throttle channels 22 are parallel to the air holding member 20A. Ten pieces extend on the outer peripheral surface to reach the communication portion 102 with the ink supply path in the ink supply pipe 6. In the present embodiment, ten throttle channels 22 extend from one air chamber 21, but one or more throttle channels 22 may be used. For example, as shown in FIG. 6, one throttle channel 22 may be formed in a spiral shape around the axial direction of the ink supply pipe. In the air holding member 20 </ b> B of this embodiment, a spiral groove 31 extending along the axial direction of the ink supply pipe is formed on the outer peripheral surface of the second large-diameter portion 29. A space between the inner surface of the supply pipe 6 is a throttle channel 22.

Here, the channel cross-sectional area of one throttle channel 22 is preferably 0.01 mm ² or more and 0.5 mm ² or less from the viewpoint of ease of meniscus formation and prevention of clogging.

  In addition, the ratio of the channel cross-sectional area of one throttle channel 22 to the channel cross-sectional area of the air chamber 21 is preferably 0.5 or more and 2 or less from the viewpoint of enhancing the effect of preventing ink from flowing into the air chamber 21.

The volume of the air chamber 21 is preferably 15 mm ³ or more and 35 mm ³ or less from the viewpoint of enhancing the damping effect.

  The ink jet recording apparatus having the above configuration can hold the air holding member by the large-diameter portion that contacts the inner surface of the ink supply pipe 6 and can form an annular space formed between the small-diameter portion 24 and the air chamber. By using 21, the space inside the ink supply pipe can be used effectively.

  In addition, since the cross-sectional area of the flow path can be reduced by the throttle flow path 22 formed between the groove portion 30 or 31 and the ink supply pipe 6, the air and the ink 26 are maintained while maintaining a predetermined air volume in the air chamber 21. It is possible to reduce the contact area at the gas-liquid interface M in contact with.

  Here, the meniscus holding force at the gas-liquid interface M is proportional to the surface tension of the ink and inversely proportional to the diameter (corresponding to the contact area) of the gas-liquid interface. In this embodiment, since the meniscus holding force can be increased by reducing the contact area, the gas-liquid interface hardly moves against vibration and inclination, and the outflow of air can be suppressed with a simple structure.

  Further, when the purge operation is performed, the ink 26 is pressurized by the pressure pump 314 in a state where the gas / liquid interface M between the ink 26 flowing from the ink supply path inside the ink supply pipe 6 and the air is formed in the throttle channel 22. The volume change amount of air in the air chamber 21 and the throttle channel 22 when pressurized by the pressure is configured to be equal to or less than the total volume of air in the throttle channel 22 immediately before being pressurized. Therefore, as described later, even if the purge operation is repeatedly performed, the ink does not flow into the air chamber 21.

  The volume of air held in the air chamber 21 is set by the outer diameter, length, etc. of the small diameter portion 24 in the air holding member, and the volume of air held in the throttle channel 22 is the groove 30 in the air holding member, Since the cross-sectional area, length, number, etc. of 31 are set, air having different outer diameters or lengths of small-diameter parts and cross-sectional areas, lengths, numbers, etc. of the groove parts 30, 31 with respect to a single ink supply pipe By supplying the holding member, the volume ratio of the air chamber 21 to the throttle channel 22 can be easily changed. For example, it is not necessary to change the ink supply pipe and the ink jet head each time the volume ratio is changed when the pressure of the pump 314 is different, and the cost can be reduced.

  In the present embodiment, the air holding members 20A and 20B extend along the axial direction of the ink supply pipe 6 through the end surface of the large diameter portion 23 and the end surface of the second large diameter portion 29, and A hollow cylindrical body having a substantially circular cross-section in which a through hole 25 capable of communicating with ink is formed is used. Thereby, sufficient ink supply to an inkjet head is attained by a through-hole.

  The diameter of the through hole 25 may be different between the large diameter portion 23 and the small diameter portion 24, or may be the same. In the present embodiment, the diameter of the through hole 25 of the large diameter portion 23 is small. The diameter of the through hole 25 of the portion 24 is larger than that of the ink jet head 4 to achieve more sufficient ink supply.

  Further, since the large diameter portion 23 is located closer to the intermediate tank 306 than the small diameter portion 24 and the second large diameter portion 29, the surface of the air chamber 21 on the ink supply source (intermediate tank 306) side is closed. The surface on the pressure chamber side of the throttle channel 22 is open (communication portion 102). As a result, ink enters from the surface of the throttle channel 22 that is open on the pressure chamber side, but the surface of the air chamber 21 on the ink supply source side is closed to form a bag path, so that air is contained in the air chamber 21. Therefore, a space where ink does not enter can be easily secured. Since the direct ink entry from the upstream to the air chamber 21 is shielded, the position of the air chamber 21 where the air is held is a portion where the ink flow is small, and the outflow of air due to the ink flow is suppressed. The pressure fluctuation can be relaxed stably.

  Furthermore, it is preferable that the surface on the ink supply source side is positioned higher than the surface on the pressure chamber side in the posture when the ink jet recording apparatus is used. The air held in the air chamber can be made difficult to move, and the outflow of air from the air chamber 21 can be effectively prevented with a simple structure.

  In the ink jet recording apparatus 1 of the present embodiment, the ink jet recording apparatus 1 is installed and used in a substantially horizontal state. The surface on the ink supply source side of the air chamber 21 formed by the air holding members 20A and 20B is closed, the surface on the pressure chamber side of the throttle channel 22 is open, and the air holding members 20A and 20B are inserted. The ink supply pipe 6 is provided so that its axial direction is substantially vertical from the ink supply connection portion 60 of the inkjet head 4 upward. As described above, the closed surface of the air chamber 21 is positioned higher than the open surface of the throttle channel 22 in the posture during use of the ink jet recording apparatus.

  Specifically, in the actual use state, when the ink 26 is supplied from the intermediate tank 306, the ink from the upstream of the ink supply pipe 6 passes through the through hole 25 and the ink supply path 59 of the ink supply connection portion 60. Enter. Further, the ink enters from the surface (connecting portion 102) on the opening side of the throttle channel 22, but the air is contained in the air chamber 21 because the large diameter portion 23 forms a bag path, and the ink does not enter. Is secured.

  In addition, an air chamber 21 formed between the outer peripheral surface of the small-diameter portion 24 and the inner peripheral surface of the ink supply tube 6 facing the outer peripheral surface by the large-diameter portion 23 in contact with the inner peripheral surface of the ink supply tube 6. Direct ink entry from the upstream into the ink is shielded, and the ink flow during ink supply passes through the through hole 25 and is directed from top to bottom. Therefore, the position of the air chamber 21 where the air is held is a portion where there is little ink flow, and the outflow of air due to the ink flow can be suppressed, and the pressure fluctuation can be relieved stably.

  Thus, the ink is filled in the ink supply path from the ink tank 5 to the pressure chamber of the inkjet head 4 in a state where the air is contained in the air chamber 21 by the operation at the time of initial ink introduction.

  In the actual use state, as shown in FIG. 5B and FIG. 6B, when the nozzle is on the lower side, the ink 26 reaches the predetermined height of the throttle channel 22 (position near the communicating portion 102). It is filled and air is trapped at the top.

  Further, as shown in FIGS. 5B and 6B, the air holding members 20A and 20B can be inserted in the vicinity of the inkjet head 4 in the ink supply pipe 6 connected to the inkjet head at one end. preferable. Thereby, the pressure fluctuation which arises in the ink supply pipe | tube 6 of an upstream from the insertion position can be relieve | moderated more effectively.

  The ink supply pipe 6 connected at one end to the ink supply connection part 60 of the ink jet head 4 is fixed to the ink jet head 4, and the air holding members 20 </ b> A and 20 </ b> B are connected to the ink supply pipe 6 at one end. To the portion fixed by the fixing portion 27. The ink supply pipe 6 between the one end connected to the ink jet head 4 and the fixed portion 27 is restricted from moving along with the movement of the carriage 3, and vibrations are suppressed. Therefore, pressure fluctuation can be more effectively reduced.

  The ink supply pipe 6 may be fixed to the carriage 3 that is a mounting portion on which the inkjet head 4 is mounted.

  The air holding members 20A and 20B may be made of stainless steel or PTFE (polytetrafluoroethylene) which is excellent in ink impermeability, ease of insertion into the ink supply pipe 6 and resistance to ink corrosion. preferable. Thereby, even if it contacts directly with ink, a deformation | transformation, a quality change, etc. do not arise.

  In the present embodiment, a large-diameter portion 23 and a second large-diameter portion 29 are provided as contact portions that contact the inner surface of the ink supply pipe, and the air holding members 20A and 20B are made of stainless steel or PTFE. The ink supply tube 6 is composed of a stretchable ink supply tube made of a polymer resin material such as polyethylene, fluororesin or nylon, or a rubber material. The air holding members 20 </ b> A and 20 </ b> B are held inside the ink supply pipe 6 by being inserted from the large diameter part 23 side into the opening of the ink supply pipe 6 on the side connected to the ink supply connection part 60. Since the ink supply pipe 6 has elasticity, when the large diameter portion 23 is inserted into the opening of the ink supply pipe 6, the opening is smoothly expanded and elastically deformed, so that the ink supply pipe 6 can be easily inserted.

  Then, the ink supply pipe 6 is elastically restored and is in close contact with the outer peripheral surfaces of the large diameter part 23 and the second large diameter part 29, and the axial direction of the ink supply pipe 6 of the air holding members 20 </ b> A and 20 </ b> B by the elasticity of the ink supply pipe 6. Therefore, the air holding members 20A and 20B can be easily and reliably held inside the ink supply pipe without providing a fixing groove or the like in the ink supply pipe 6.

  In the present embodiment, the air holding members 20 </ b> A and 20 </ b> B have a tapered portion 28 that gradually decreases in diameter from the large diameter portion 23 toward the opposite direction to the small diameter portion 24. Thus, when the air holding member is inserted into the ink supply pipe, the large diameter portion does not come into contact with the inner surface of the ink supply pipe and is not caught and can be inserted smoothly.

  Thus, the tip of the large-diameter portion 23 is formed in one opening of the ink supply pipe 6 having both ends opened and an ink supply path formed therein, preferably on the opening connected to the ink supply connection portion 60. The air holding members 20A and 20B are inserted into the ink supply pipe 6 by the pressing force. Next, the ink supply pipe 6 is connected to the intermediate tank 306 and the ink supply connection portion 60.

  The ink supply tube 6 employs an ink supply tube made of the above-described polymer resin material such as polyethylene, fluororesin, nylon, or rubber material in consideration of ink resistance and elasticity.

  In consideration of elasticity and strength, the thickness of the ink supply tube 6 is preferably approximately 0.5 mm to 2 mm.

  The preferred inner diameter of the ink supply pipe 6 varies somewhat depending on the viscosity of the ink used, the ejection capability of the inkjet head, and the like, but the inner diameter (diameter) of the ink supply pipe 6 is preferably 1 to 6 mm.

  In addition, it is preferable that the ink supply pipe is transparent at least at a portion in contact with the air chamber. Since it is possible to detect whether or not air remains in the air chamber more than a predetermined amount, if it is less than the predetermined amount, an air replenishing mechanism for newly replenishing air may be provided (for example, a release valve) If the air is reintroduced by replacing it with new ink, it is possible to reliably maintain the state in which the air remains. Although a visual method may be used to detect whether or not air remains in a predetermined amount or more, for example, a mechanism for detecting whether or not air remains by measuring the light transmittance of an air chamber (for example, , A liquid level sensor) may be provided for automatic detection. If the amount is less than the predetermined amount, air may be replenished or reintroduced. Or you may make it alert | report to that.

  In the present embodiment, the entire ink supply pipe 6 is made of a transparent material. Note that “transparency” is sufficient to distinguish between air and ink, and can be achieved by employing an ink supply tube made of the above-described polymer resin material.

  The surface tension of the ink used in the ink jet recording apparatus is preferably 20 to 40 mN / m at the discharge temperature. If it is less than 20 mN / m, it may become difficult to spread and become difficult to be ejected when ejected, and if it exceeds 40 mN / m, it will be difficult to fill with ink. About discharge temperature, 20-60 degreeC is preferable and 25-50 degreeC is more preferable.

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

  When the power of the ink jet recording apparatus 1 is turned on, power is supplied to each part of the ink jet recording apparatus 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 cap 8 face each other. When the inkjet head 4 and the cap 8 face each other, the control unit controls the lifting motor to raise the maintenance unit 7 until the ejection surface 41S of the inkjet head 4 and the cap 8 are in close contact with each other.

  After completion of the raising of the maintenance unit 7, the control unit opens the valve 315 and controls the pressure pump 314 so that ink is pressurized and discharged for a predetermined time.

  The ink in the ink supply pipe 6 is pressurized by the operation of the pressure pump 314. Ink in the ink supply pipe 6 on the upstream side of the throttle channel 22 is also pressurized, and the ink 26 in the throttle channel 22 is pushed out to the air chamber 21 side.

  At this time, the air existing in the air chamber 21 and the throttle channel 22 shown in FIGS. 5B and 6B is compressed, and the gas-liquid interface M between the ink 26 and the air is drawn toward the air chamber 21 side. become.

  After the pressurization by the pressurization pump 314 is started, when the pressure rises and reaches a predetermined pressure (maximum value), the gas-liquid interface M drawn to the air chamber 21 side enters the air chamber 21. there's a possibility that. In this case, even if the purge operation is finished and the gas-liquid interface M returns to the original position, the ink remains in the air chamber 21 (step 100, etc.), and this residual ink gradually accumulates by repeating the purge operation. As a result, the amount of air is reduced.

  In other words, while the purge operation is performed by pressurizing the ink in the head 4 to a predetermined pressure, the gas-liquid interface M2 flows into the air chamber 21 without the ink flowing from the throttle channel 22 into the throttle flow. The volume change amount of the air in the air chamber 21 and the throttle channel 22 when the ink 26 is pressurized by the pressurizing pump 314 so as to be located in the channel 22 is the same as that of the throttle channel 22 immediately before being pressurized. It is necessary to make it less than the total volume of air.

  For this reason, the volume of the air chamber 21 with respect to the total volume of the throttle channel 22 is set so that the volume change amount of the air is equal to or less than the total volume of air of the one or more throttle channels 22 immediately before being pressurized. It is preferable to set the ratio. Accordingly, when performing the purge operation by pressurizing the ink with the pressurizing pump 314, it becomes easy to secure a predetermined pressure capable of recovering ejection as the pressure of the ink in the head 4.

  Next, a method for setting the volume ratio will be described.

  First, although the position of the gas-liquid interface M at the time of initial ink introduction depends on the physical properties of the ink, the channel cross-sectional area of the throttle channel, etc., the gas-liquid interface M is usually connected to the connecting portion 102 of the throttle channel 22. It becomes a position in the vicinity (a position slightly entering the throttle channel 22 from the connecting portion 102).

In this state, the atmospheric pressure in the throttle channel 22 and the air chamber 21 is 1 × 10 ⁵ Pa (1 atm).

The volume of air in the air chamber 21 is V1, and the total volume of air in one or more throttle channels 22 immediately before being pressurized, that is, one or more (10 in the air holding member 20A in FIG. 5). The total volume of air from the gas-liquid interface M immediately before pressurization in the throttle channel 22 to the connecting portion 101 is V2, the total volume of the one or more throttle channels 22, that is, one or more throttle channels. 22, the total volume from the connecting portion 102 to the connecting portion 101 is V3. The pressure (air pressure) in the throttle channel 22 and the air chamber 21 immediately before pressurization is P1 (= 1 × 10 ⁵ Pa), and the throttle channel 22 and the air chamber 21 at a predetermined pressure (maximum pressure) The atmospheric pressure (air pressure) is P2. The relationship with the volume change ΔV of air at a predetermined pressure is expressed by the following equation (1).

ΔV = (V1 + V2) (1− (P1 / P2)) (1)
If ΔV obtained from the equation (1) is the same as or smaller than the volume V2, that is, if the following equation (2) is satisfied, the gas-liquid interface M will remain in the air chamber even when pressurized by the purge operation. No entry into the 21.

ΔV = (V1 + V2) (1− (P1 / P2)) ≦ V2 (2)
Here, at the normal time, the position of the gas-liquid interface M immediately before pressurization is at the above-mentioned initial position, that is, the position in the vicinity of the connecting portion 102 of the throttle channel 22, so V2≈V3, and the expression (2) Becomes the following equation (3).

ΔV≈ (V1 + V3) (1− (P1 / P2)) ≦ V3 (3)
For example, when the atmospheric pressure P2 in the air chamber 21 is pressurized at a predetermined pressure that is 2 × 10 ⁵ Pa (2 atm), the volume change ΔV of air becomes (V1 + V3) / 2. That is, when the pressure of the ink is increased by the pump 314 so that the air pressure in the air chamber 21 becomes 2 × 10 ⁵ Pa, the air is compressed and its volume becomes half of the volume before pressurization. Further, when the ink is pressurized to 3 × 10 ⁵ Pa (3 atm), the volume change ΔV of air becomes 2 (V1 + V3) / 3, so that the volume becomes 1/3 of the volume before pressurization. Will be.

  When the volume change amount ΔV becomes larger than V3, the gas-liquid interface M enters the air chamber 21. Therefore, at a predetermined pressure required for maintenance, ΔV is calculated experimentally or by calculation using the above equation (3), so that ΔV is equal to or smaller than volume V3, that is, If the ratio of V1 and V3 is set so as to satisfy the expression (3), the gas-liquid interface M does not enter the air chamber 21 even when pressurized by the purge operation.

  Note that P2 may be measured by providing the air chamber 21 with a pressure sensor that measures the internal pressure. The pressure P2 at the time of the purge operation is not significantly different from the pressure of the ink in the head 4 when pressurized by the pump 314. Therefore, the volume ratio is set based on the pressure of the ink in the head 4 when pressurized by the pump. If set, there is no problem.

  The pressure of the ink in the head 4 may be measured by providing a pressure sensor for measuring the pressure inside the head 4 or in the vicinity thereof.

The pressure (maximum value) of the ink in the head 4 when pressurized by the pressure pump 314 is normally 1.5 × 10 ⁵ Pa or more and 1.5 × 10 ⁶ Pa or less, and 1.5 × 10 ^5. Pa to 3 × 10 ⁵ Pa is preferred. 1.5 × less than 10 5 ^Pa and hardly occurs ink discharged from the nozzle, there is a case where the ejection recovery can not, 3 × greater than 10 5 ^Pa when the strain on the structure member or the like of the ink-jet head and the ink supply path It is because there is a risk of taking.

Therefore, as a guideline for setting, for example, when the air pressure in the air chamber 21 is increased to 2 × 10 ⁵ Pa, as is apparent from the equation (3), the total volume of the throttle channel 22 is What is necessary is just to set so that the volume ratio of the air chamber 21, ie, V1 / V3, may become 1 or less. Moreover, what is necessary is just to set so that V1 / V3 may be set to 0.5 or less when the atmospheric pressure in the air chamber 21 is pressurized to 3 × 10 ⁵ Pa.

  In addition, when the gas-liquid interface M formed when the initial ink is introduced rises from the initial position due to dissolution of air or the like, the total volume of air in the throttle channel 22 when the gas-liquid interface M rises. Since V2 becomes small, ΔV calculated from the above-described equation (1) in consideration of the position of the gas-liquid interface M that has risen before pressurization (total volume of ink in the throttle channel 22: V3-V2) is obtained. It is considered that the volume V2 is equal to or smaller than V2, that is, V1 / V3 is set to be small so as to satisfy the above-described equation (2), and the influence of the rise of the gas-liquid interface M is considered. .

  Similarly, when the position of the gas-liquid interface M formed when the initial ink is introduced is at a position higher than the connecting portion 102, V1 / V3 is similarly reduced so as to satisfy the expression (2). To be considered and to eliminate the increased effect.

  The initial position and the rising position of the gas-liquid interface M may be obtained experimentally in advance by configuring the ink supply tube 6 with a transparent ink supply tube. The position of the gas-liquid interface M may be detected by providing a liquid level sensor that detects the position of the gas-liquid interface M visually.

  Further, a liquid level sensor for detecting the position of the gas-liquid interface M is provided, and the control unit is based on the position information of the gas-liquid interface M sent from the liquid level sensor immediately before performing the purge operation with the pressure pump 314. The data of the allowable critical position stored in the memory is called, and it is determined based on the data whether or not the gas-liquid interface M exists at a position where it does not enter the air chamber 21 during pressurization. The pressure pump 314 is driven to perform a purge operation.

  That is, at this time, the controller considers the allowable critical position so that the gas-liquid interface M does not enter the air chamber 21 during pressurization. That is, when the allowable critical position is exceeded due to the rise of the gas-liquid interface M, the control unit replenishes air or reintroduces air by the above-described air replenishment mechanism, and moves the gas-liquid interface M to the initial position. Alternatively, the purge operation is performed by returning to the vicinity and pressurizing.

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

  First, the following experiment was performed before recording with an inkjet recording apparatus.

As the ink jet recording apparatus, an apparatus having the configuration shown in FIG. 1 was used. An air holding member 20A or 20B (made of PTFE or stainless steel) is used as the air holding member, a polyethylene ink supply tube is used as the ink supply pipe 6, and ink is introduced into the head and the ink supply path and then added. The pressure of ink in the head 4 when pressurized by the pressure pump 314 (1.5 × 10 ⁵ Pa or more and 3 × 10 ⁵ Pa or less), the air chamber formed by the air holding members 20A and 20B, and the throttle channel The pressurizing pump 314 was driven under various combinations of volume ratios V1 / V3 (0.1 to 3), and the purge operation was repeated, and the presence or absence of inflow of ink into the air chamber 21 was examined.

  Here, the volume ratio is defined as V1 for the volume of the air chamber 21, V1 for the air holding member 20B, 10 for 20A, and V3 for the total volume from the connecting portion 102 to the connecting portion 101 in the ten restriction channels 22. V1 / V3 is changed by changing the length of the throttle channel 22 as constant.

  As the ink, a pigment dispersion ink having a surface tension of 30 mN / m was used. For the surface tension, the surface tension at 25 ° C. (discharge temperature) was measured using a vertical plate method (Wilhelmy method).

  In the ink jet recording apparatus of the present embodiment, the position of the gas-liquid interface M immediately before pressurization is in the vicinity of the connecting portion 102 of the throttle channel 22 (a position slightly entering the throttle channel 22 from the connecting portion 102). Therefore, V2≈V3 is satisfied, and if V1 / V3 is set so as to satisfy the above-described expression (3), ink does not flow into the air chamber 21 even if the purge operation is repeated.

Also in the experimental results, when the pressure of the ink in the head 4 is 2 × 10 ⁵ Pa, the purge operation is repeated 20 times or more if the volume ratio V1 / V3 is set to 1 or less. It was also confirmed that no ink flow into the air chamber 21 occurred.

Even when the ink pressure in the head 4 is increased to 3 × 10 ⁵ Pa, the purge operation may be repeated 20 times or more if V1 / V3 is set to 0.5 or less. It was confirmed that no ink flow into the air chamber 21 occurred.

As a comparative experiment, when the pressure of the ink in the head 4 is 2 × 10 ⁵ Pa and the volume ratio V1 / V3 is changed to be larger than 1, ΔV becomes larger than V3. Therefore, also in the experimental results, when the ink pressure in the head 4 is 2 × 10 ⁵ Pa, the purge operation is repeated 20 times if the volume ratio V1 / V3 is set to be greater than 1. It was confirmed that the inflow of the ink into the air chamber 21 occurred only by performing it.

When the ink pressure in the head 4 is set to 3 × 10 ⁵ Pa, the purge operation is repeated 20 times if the volume ratio V1 / V3 is set to be larger than 0.5. Thus, it was confirmed that the ink flow into the air chamber 21 occurred.

  Next, as in the actual use state, the ink was reciprocated to eject ink from the head onto the recording paper and output an image. As an image, a solid image was output and density unevenness was evaluated.

  Even in actual image recording, the volume ratio V1 / V3 is set so as to satisfy the above-described expression (3) with respect to the pressure of each ink, and no ink flows into the air chamber 21. The ink jet recording apparatus was capable of stable ejection even when image recording was performed after repeating the purge operation 20 times or more, and maintained a good recording state, and no density unevenness was observed.

  On the other hand, an ink jet recording apparatus according to a comparative example in which the volume ratio V1 / V3 not satisfying the above-described expression (3) is set with respect to the pressure of each ink and the inflow of ink into the air chamber 21 was observed is 20 When the image recording was performed after repeating the purge operation, a good recording state could not be maintained due to the instability of discharge due to pressure fluctuation, and density unevenness occurred.

  As described above, when the purge operation is performed in a state where the gas-liquid interface between the ink and air is formed in the throttle channel, the air in the air chamber and the throttle channel when the ink is pressurized by the pressure pump is used. In the ink jet recording apparatus of the present embodiment configured such that the volume change amount is equal to or less than the total volume of air in the throttle channel immediately before being pressurized, the purge operation is repeated at a predetermined pressure at which ejection can be recovered. Ink does not flow into the air chamber even if the operation is performed, and air can be held in the air chamber more stably even during the purging operation, so that a reduction in air from the air chamber can be suppressed with a simple structure. it can.

  In the above embodiment, the air holding member is inserted into the ink supply pipe connected to the ink jet head and the air chamber is installed. However, in the present invention, the pressure chamber of the ink jet head is supplied with the ink from the ink supply source. An air chamber communicating with an ink supply path for supplying ink may be installed. For example, an air chamber connected to an ink supply pipe constituting an ink supply path to the inkjet head may be separately provided or branched from the ink supply pipe. An air chamber may be provided.

  In the embodiment, one air holding member 20A is provided in one ink supply pipe 6, but the number is not particularly limited.

  In the embodiment, the present invention is applied to the ink jet recording apparatus provided with the sub tank, but the present invention can also be applied to an ink jet recording apparatus provided with only the main ink tank.

  In the embodiment, the present invention is applied to a serial type ink jet recording apparatus, but the present invention is also applicable to a line type ink jet recording apparatus. Even in the case of a line system in which the inkjet head is stationary, the ink supply pressure may fluctuate due to the influence of external vibrations such as a pump and a motor. According to the inkjet recording apparatus of the present invention, the ink supply It is possible to alleviate pressure fluctuations and improve ejection stability.

  In the embodiment, 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.

  In addition, the shape and positional relationship of the air holding member can be changed as appropriate. For example, various combinations of the annular portion, groove portion, and spiral portion of the space formed in each embodiment are possible. For example, a configuration in which the throttle channel is provided by using the groove portion and the spiral portion together is also possible. It is.

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 4 Inkjet head 6 Ink supply pipe 20A, 20B Air holding member 21 Air chamber 22 Restricted flow path 41 Head chip (inkjet head chip)
41S Discharge surface 48a, 48b Manifold P Recording medium X Nozzle row direction

Claims (8)

An inkjet head that ejects ink in the pressure chamber;
An ink supply path for supplying ink from an ink supply source to the pressure chamber of the inkjet head;
An air chamber capable of holding air;
One or more throttle channels having a smaller channel cross-sectional area than the air chamber;
Pressurizing means for pressurizing and discharging the ink in the ink supply path from the inkjet head,
The air chamber communicates with the ink supply path through the throttle channel,
The air in the throttle channel and the air in the throttle channel when the ink is pressurized by the pressurizing means in a state where a gas-liquid interface between ink and air flowing from the ink supply channel is formed. the amount of volume change, Ri total volume der following air in the throttle channel immediately before pressurized the pressurized,
At least a part of the ink supply path is constituted by an ink supply pipe;
The ink jet recording, wherein the air chamber and the throttle channel are formed between an air holding member inserted in a state where ink can communicate with the inside of the ink supply pipe and an inner surface of the ink supply pipe. apparatus.   The volume ratio of the air chamber to the total volume of the throttle channel is set so that the volume change amount of the air is equal to or less than the total volume of air of the throttle channel. 2. An ink jet recording apparatus according to 1.   The inkjet recording apparatus according to claim 2, wherein the volume ratio is 1 or less.   The inkjet recording apparatus according to claim 2, wherein the volume ratio is 0.5 or less. The pressure of the ink in the said inkjet head when it pressurizes by the said pressurization means is 1.5 * 10 < ⁵ > Pa or more and 1.5 * 10 < ⁶ > Pa or less, The Claim 1 or 2 characterized by the above-mentioned. Inkjet recording apparatus. An ink jet recording apparatus according to any one of claim 1 to 5, characterized in that the material of the air retaining member is stainless steel. An ink jet recording apparatus according to any one of claim 1 to 5, characterized in that the material of the air retaining member is a PTFE (polytetrafluoroethylene). An ink jet recording apparatus according to any one of claim 1 to 7, wherein the surface tension of the ink is 20 to 40 mN / m.

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